JP2000312142A - Intelligent power switch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To protect an intelligent power switch IPS by detecting overcurrent of the IPS and interrupting MOSFET(MOS-type field effect transistor) when an overcurrent flows. SOLUTION: The intelligent power switch IPS is provided with a power supply use overheat self-interrupt type semiconductor switch QA that switches power supplied from a power supply 4, a series circuit that consists of a reference use overheat self-interrupt type semiconductor switch QB, having the same voltage characteristic as that of the switch QA and a reference resistor Rr1 and is connected in parallel with the switch QA, a comparison circuit CMP1, that compares the difference (A-B) between the source voltage A of the switch QA and the source voltage B of the switch QB with a prescribed over-current criterion value C so as to discriminate whether this is an overcurrent and outputs a detection signal in response to the result of discrimination, and a drive circuit 2 that turns on/off the overheat self-interrupt type semiconductor switch QA with a control signal in response to the detection signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching circuit for selectively supplying power from a battery power supply to a plurality of types of loads such as headlights, particularly in an automobile. The present invention relates to an intelligent power switch device that protects a switching circuit from an abnormal state due to overheating.

[0002]

2. Description of the Related Art In recent years, switching circuits using semiconductor switching elements having advantageous characteristics have been proposed in place of relays operated by mechanical contacts. First, the applicant of the present application has determined that this type of switching circuit has an effect that an overcurrent flows through the switching circuit for some reason, and the overcurrent causes the element to overheat and damage the element. Has proposed an intelligent power switch device (hereinafter, referred to as IPS) having a self-protection function. This IPS detects a voltage value on the downstream side of the semiconductor switch device, detects an overcurrent flowing through the semiconductor switch device due to a short circuit of a load connected to the semiconductor switch device, and detects an undercurrent caused by opening (disconnection) of the load. It has functions such as detection, and is effective in protecting harnesses and system equipment.

As an example of the configuration of the IPS, for example, MOS
There is a type in which a semiconductor device using a field effect transistor (FET: Field Effect Transistor) of the (Metal Oxide Semiconductor) type as a switching element is connected to a load. This IPS applies a power supply voltage from an input terminal to the semiconductor device, and a MOS. Power is supplied to the load by performing on / off control of the type FET using an on / off output signal from a drive circuit (driver). Further, the IPS has, for example, an overvoltage detection circuit that detects an overvoltage when the power supply voltage is overvoltage, and outputs a voltage value based on a current value flowing between the drain and source of the MOS FET from the reference voltage generation circuit. And a temperature detection circuit for detecting overheating of the MOS FET, and the like. The detection signal output from each of the detection circuits is input to a logical OR circuit or the like, and the output signal from the logical OR circuit is applied to a drive circuit via a booster circuit (charge pump circuit). .

[0004] The charge pump circuit is a circuit necessary for boosting the gate of the MOS-type FET when the IPS-type MOS FET is connected to the upstream side of a load such as a headlight. That is, this charge pump circuit boosts the output voltage of the battery power supply and outputs it to the drive circuit as a drive voltage to operate the MOS FET. Usually, the charge pump circuit is I
A PS is provided for each of the MOS type FETs. The charge pump circuit is an IPS MOS type F.
The ET is generally used when provided on the upstream side of the load, and cannot be used when the IPS MOSFET is provided on the downstream side of the load. Therefore, there is a problem as to whether the charge pump circuit can be omitted when an IPS MOS FET is connected and used downstream of the load.

FIG. 5 does not use a charge pump circuit,
5 shows a conventional circuit example in which the IPS 20 is connected to the downstream low side of a load such as a headlight. That is, the load 6 is connected via the supply line 5 connected to the battery power supply 4. Downstream of the load 6, I
The input terminal of the PS 20 is connected, and the output terminal of the IPS 20 is grounded. The IPS 20 includes, as semiconductor switching elements, a main MOSFET 7A of, for example, a current mirror system, and a sub-reference MOSFET 7B for generating a reference voltage.
The load 6 is connected to the drain of the main MOS FET 7A, and the source is grounded. In this way, IP
By turning on the main MOSFET 7A of S20, the output voltage VB from the battery power supply 4 is supplied to the load 6 through the supply line 5, and the current flowing through the load 6 is reduced by the current of the main MOSFET 7A of the IPS 20. Flows to ground through drain and source.

The number of transistors constituting the main MOSFET 7A and the number of transistors constituting the reference MOSFET 7A
The ratio of the number of transistors constituting B is, for example, 1: 5
000. Therefore, the reference M
Assuming that a current of 10 A flows through the OS-type FET 7B, 1/5000 of the current flows through the main MOS-type FET 7A. Also, the main MOS type FET is connected by the resistor 8.
7A voltage of source terminal 7a and reference MOS type F
The voltage of the source terminal 7b of both FETs of the ET 7B is input to the comparator 9, and when a difference voltage is detected by the comparator 9 and an overcurrent flows through the main MOS FET 7A, the output of the comparator 9 is inverted, and the output of the comparator 9 is inverted. 9 outputs an OFF signal to the drive circuit 2, and the drive circuit 2 outputs a main MOS type FET.
7A is turned off.

[0007]

As described above, the conventional IPS 20 shown in FIG. 5 protects against abnormalities such as an excessive current by using a MOS-type FET of a current mirror type as a semiconductor switching element. I have.

[0008] Such a current mirror type MOS
The overcurrent protection method using a type FET limits a large current to interrupt overheating, or detects a shunt current due to a middle current with a microcomputer to protect it from overcurrent. For this reason, there is a problem that the shunt ratio, the reference voltage, and the resistance value vary.

An object of the present invention is to use a MOS type FET as a semiconductor switching element and to increase a boosted voltage to a MOS type FE.
Even if a charge pump circuit for applying a voltage to the gate of T is not used, the IPS is easily connected to the downstream side of the load to easily detect the overcurrent of the IPS.
The goal is to protect the IPS by blocking the type FET.

[0010]

According to the first aspect of the present invention, there is provided an intelligent power switch device connected between a load connected to a power supply and a ground, and supplying power from the power supply to the ground. A power supply overheating self-interrupting semiconductor switch, and a series circuit consisting of a reference overheating self-interrupting semiconductor switch having the same voltage characteristics as the power supply overheating self-interrupting semiconductor switch and a reference resistor. A reference circuit connected in parallel with the overheating semiconductor switch, and a difference (AB) between a source voltage A of the overheating semiconductor switch for power supply and a source voltage B of the overheating semiconductor switch for reference. A comparison is made with a predetermined overcurrent determination value C to determine whether or not the current is an overcurrent. A comparator circuit for outputting a detection signal,
A drive circuit for turning on and off the power supply overheating self-interruption type semiconductor switch with a control signal corresponding to the detection signal, and continuously operate the power supply overheating self-interruption type semiconductor switch while the current is normal. When the overcurrent is detected in this state, the overheating self-interrupting semiconductor switch for power supply is turned off, and the normal current is detected after the overheating self-interrupting semiconductor switch for power supply is once turned off. Then, control is performed to turn on the power supply overheating self-interruptible semiconductor switch again. According to the first aspect of the present invention, a MOS-type FET is used as a semiconductor switching element.
The overcurrent of the IPS can be easily detected by connecting the IPS to the downstream side of the load without using the charge pump circuit that applies the boosted voltage to the gate of the MOS FET. IPS by cutting off MOS FET
Can be protected.

In order to achieve the above object, an intelligent power switch device according to a second aspect of the present invention is configured such that an output signal is changed from a Hi signal when an overcurrent flows through a power supply overheating self-interrupting semiconductor switch. It is constituted by a comparator which inverts to a Low signal and outputs the signal to the drive circuit. According to the second aspect of the present invention, a MOS-type FET is used for the semiconductor switching element, and a charge pump circuit for applying a boosted voltage to the gate of the MOS-type FET is not required. , The IPS is connected to the downstream side of the load to easily detect the overcurrent of the IPS.
The IPS can be protected by blocking the OS-type FET.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the intelligent power switch device according to the present invention will be described below. 1 to 4 show an embodiment of the intelligent power switch device according to the present invention.

In FIG. 1, an intelligent power switch device is used in a vehicle such as an automobile to load each load 6 such as a headlight from a battery power supply 4 via a power supply line 5.
, And is configured as one chip. Reference numeral 1 denotes a power supply device, which is used to supply a current from a battery power supply 4 to a load 6 by switching.
It is configured as one semiconductor chip. One end of the power supply device 1 is connected to the downstream side of the load 6,
One end of the power supply device 1 is grounded. The power supply device 1 has a function capable of operating with a small voltage without using a charge pump circuit for boosting the power supply voltage that applies a boosted power supply voltage to the gate of a built-in semiconductor switch. . In this power supply device 1, a connection terminal for connecting an external element is indicated by a circle.

An input terminal A of the power supply 1 is connected to one end of a load 6 such as a headlight via a supply line 5, and the other end of the load 6 is connected to a battery power supply 4. ing. The output terminal B is grounded. On the other hand, a switch SW1 whose one end is grounded and the other end is connected to the battery VB via the resistor R4 is connected to the switching terminal C. Also, the input side terminal A
The drain side terminal DA of the power supply overheating self-interruption type semiconductor switch QA is connected, and the output side terminal B is connected to the source side terminal SA of the power supply overheating self-interruption type semiconductor switch QA. In addition, the power supply overheat self-interruption type semiconductor switch QA is provided with a gate terminal GA. The power supply overheat self-interrupting semiconductor switch QA is connected to the battery power supply 4 through the supply line 5.
Are connected in series between the load 6 and the ground.

The power supply overheat self-interrupting semiconductor switch QA has a configuration as shown in FIG. That is, the drain of the main FET Q1 is connected to the drain terminal DA, and the source terminal SA is connected to the source of the main FET Q1. This main FET Q
One gate is connected to a gate terminal GA via an internal resistor RA (for example, 10 kΩ). The temperature detection circuit 30 is connected between the gate terminal GA and the source terminal SA. The temperature detection circuit 30 is for detecting the temperature of the main FET Q1, and a latch circuit 31 is connected to the temperature detection circuit 30.
Then, the temperature detection circuit 30 outputs an ON signal to the latch circuit 31 when the temperature of the main FET Q1 reaches a predetermined temperature (abnormal temperature). The latch circuit 31 has a function of receiving a signal from the temperature detection circuit 30 and continuously outputting an ON signal. The output terminal of the latch circuit 31 is connected to the gate of the overheat cutoff FET Q2.
When the temperature detection circuit 30 detects that the main FET Q1 is overheated, the overheat cutoff FET Q2 is turned on by the ON signal output via the latch circuit 31, and the main F
The main FET Q1 is cut off by lowering the gate voltage of ETQ1.

On the other hand, the source side terminal SA of the power supply overheat self-interrupting semiconductor switch QA is grounded via the output side terminal B. The power supply to the load 6 is performed by the main FET of the power supply overheat self-interruption type semiconductor switch QA.
This is performed by turning on / off Q1. Thus, the power supply overheated self-interrupting semiconductor switch Q
A is the main FET when both ends of the load 6 are short-circuited.
In order to prevent overcurrent from flowing through Q1 and overheating and destruction of the main FET Q1, when the temperature of the main FET Q1 rises above a prescribed value, a self-heating self-cutoff function forcibly turning off (cutting) by its own action is provided. Have. The main FET Q1 constituting the power supply overheat self-interruption type semiconductor switch QA is constituted by an NMOSFET having a DMOS structure. The power supply overheat self-interruption type semiconductor switch QA is connected to the downstream side of the load 6. That is, the load 6 is connected to the drain side terminal DA of the main FET Q1 of the power supply overheating self-interruption type semiconductor switch QA. Therefore, a current flows from the battery power supply 4 to the load 6 by turning on the main FET Q1 of the power supply overheating self-interrupting semiconductor switch QA. Therefore, the load 6 serves as a current limiting resistor for the main FET Q1 of the power supply overheat self-interruption type semiconductor switch QA, and the battery voltage VB drops by the load 6 on the drain side of the main FET Q1. The applied voltage is applied.

The drain side terminal DA of the power supply overheating self-interruption type semiconductor switch QA is connected to the drain side terminal DB of the reference overheating self-interruption type semiconductor switch QB.
Is connected to the drain side terminal DC of the reference overheating self-interruption type semiconductor switch QC. The output side terminal E is connected to the source side terminal SB of the reference overheating self-interruption type semiconductor switch QB, and the output side terminal F is connected to the source side terminal SC of the second reference overheating self-interruption type semiconductor switch QC. Is connected. The reference overheating self-interruption type semiconductor switch QB is provided with a gate-side terminal GB, and the second reference overheating self-interruption type semiconductor switch QC is provided with a gate-side terminal GC.

The reference overheating self-interruption type semiconductor switch QB has a configuration as shown in FIG.
Has the same configuration as the power supply overheat self-interruption type semiconductor switch QA shown in FIG. That is, the drain of the main FET Q3 is connected to the drain terminal DB, and the source terminal SB is connected to the source of the main FET Q3. The gate of the main FET Q3 is connected to the gate terminal GB via an internal resistor RB (for example, 10 kΩ). The temperature detection circuit 40 is connected between the gate side terminal GB and the source side terminal SB. This temperature detection circuit 40 is connected to the main FET Q
3 for detecting the temperature of the temperature detecting circuit 4.
The latch circuit 41 is connected to 0. The temperature detection circuit 40 has a function of outputting an ON signal to the latch circuit 41 when the temperature of the main FET Q3 becomes equal to or higher than a predetermined temperature (abnormal temperature) due to a current larger than a predetermined current flowing through the main FET Q3. Have. The latch circuit 41 has a function of receiving a signal from the temperature detection circuit 40 and continuously outputting an ON signal.
Further, the output terminal of the latch circuit 41 is connected to the gate of the overheat cutoff FET Q4. When the temperature detection circuit 40 detects that the main FET Q3 is overheated, the output is output via the latch circuit 41. The overheat cutoff FET Q4 is turned on by the ON signal, and the main FET is turned on.
The main FET Q3 is cut off by lowering the gate voltage of Q3.

On the other hand, the output side terminal E is connected to the source side terminal SB of the reference overheating self-interruption type semiconductor switch QB.
Is connected to the reference resistor Rr1, and the other end of the reference resistor Rr1 is grounded. The main FET Q3 and the reference resistor Rr1
A reference circuit is constituted by these. This reference circuit is connected in parallel to a series circuit of a load 6 and a main FET Q1 of a power supply overheat self-interruption type semiconductor switch QA. This reference circuit is a main FE of a power supply overheat self-interrupt type semiconductor switch QA.
By turning on TQ1, a current flows from the battery power supply 4 to the load 6, and when the current is flowing normally to the load 6, the source (source side) of the main FET Q1 of the power supply overheat self-interrupting semiconductor switch QA Terminal SA)
The same voltage (reference voltage) as the voltage generated at the main FET of the overheat self-interruption type semiconductor switch QB for reference
It has the function of constantly generating the source of Q3 (source side terminal SB). That is, the source (source terminal SB) of the main FET Q3 of the reference overheating self-interruption type semiconductor switch QB has the state of the load 6 connected to the drain side terminal DA of the power supply overheating self-interruption type semiconductor switch QA. A constant source voltage is always generated irrespective of a change (a change in which the value of the load increases or decreases). Main FET Q3 of this reference overheat self-interruption type semiconductor switch QB
Is excessively applied to the load 6 when compared with the source voltage generated at the source (source terminal SA) of the main FET Q1 when the current flows excessively to the main FET Q1 of the power supply overheating self-interruption type semiconductor switch QA. This is a first reference voltage for detecting that a current has flowed.

As described above, in the reference overheating self-interruption type semiconductor switch QB, an overcurrent flows through the main FET Q3 of the reference overheating self-interruption type semiconductor switch QB due to a short circuit of the reference resistor Rr1 connected to the source of the main FET Q3. Sometimes this main FET
In order to prevent the Q3 from being overheated and destroyed, the main FET Q3 is provided with an overheating self-interruption function of forcibly turning off (interrupting) by its own action when the temperature of the main FET Q3 rises above a specified value. The main FET Q3 constituting the reference overheat self-interruption type semiconductor switch QB is a DMOS
It is composed of an NMOSFET having a structure.

The second reference overheating self-interruption type semiconductor switch QC has a configuration as shown in FIG. 4, and the second reference overheating self-interruption type semiconductor switch QC is shown in FIG. The configuration is the same as that of the power supply overheat self-interruption type semiconductor switch QA. That is, the drain of the main FET Q5 is connected to the drain terminal DC, and the source of the main FET Q5 is
The source terminal SC is connected. This main FET
The gate of Q5 is connected to a gate terminal GC via an internal resistor RC (for example, 10 kΩ). A temperature detection circuit 50 is connected between the gate terminal GC and the source terminal SC. The temperature detection circuit 50 is for detecting the temperature of the main FET Q5, and a latch circuit 51 is connected to the temperature detection circuit 50. The temperature detection circuit 50 is connected to the main FET Q
5 has a function of outputting an ON signal to the latch circuit 51 when the temperature of the main FET Q5 becomes equal to or higher than a predetermined temperature (abnormal temperature) due to a current larger than a predetermined current flowing through the latch circuit 51. The latch circuit 51 has a function of receiving a signal from the temperature detection circuit 50 and continuously outputting an ON signal. Further, the output terminal of the latch circuit 51 is connected to the gate of the overheat cutoff FET Q6.
When the temperature detection circuit 50 detects that the main FET Q5 is overheated, the overheat cutoff FET Q6 is turned on by an ON signal output via the latch circuit 51,
Drop the gate voltage of the main FET Q5 to reduce the main FET
Turn off Q5.

On the other hand, a second reference resistor Rr2 is connected to the source-side terminal SC of the second reference overheat self-interruption-type semiconductor switch QC via an output-side terminal F. The other end of Rr2 is grounded. The main FET Q5 and the second
And the reference resistor Rr2 constitute a second reference circuit. The second reference circuit is connected in parallel to a series circuit of a load 6 and a main FET Q1 of a power supply overheat self-interruption type semiconductor switch QA. This second reference circuit allows a current to flow from the battery power supply 4 to the load 6 by turning on the main FET Q1 of the power supply overheating self-interruption type semiconductor switch QA. Sometimes the same voltage (reference voltage) as the voltage generated at the source (source side terminal SA) of the main FET Q1 of the power supply overheating self-interruption type semiconductor switch QA is applied to the main of the second reference overheating self-interruption type semiconductor switch QC. FETQ
5 (source side terminal SC). That is, the source (source side terminal SC) of the main FET Q5 of the second reference overheating self-interruption type semiconductor switch QC is connected to the load 6 connected to the drain side terminal DA of the power supply overheating self-interruption type semiconductor switch QA. Changes in the state of the
Irrespective of the change of the source voltage), a constant source voltage is always generated.

The source voltage of the main FET Q5 of the second reference overheated self-interruption type semiconductor switch QC is applied to the load 6 despite the fact that the main FET Q1 of the power supply overheating self-interruption type semiconductor switch QA is on. When a current does not flow or an excessively small current flows (in the case of a load disconnection or the like), the amount of current flowing through the main FET Q1 of the power supply overheat self-interrupting semiconductor switch QA has flowed below a second predetermined value. At this time, it is the second reference voltage for detecting that the current has excessively flowed into the load 6 as compared with the source voltage of the main FET Q1.

As described above, the second reference overheated self-interruption type semiconductor switch QC is formed by short-circuiting the second reference resistor Rr2 connected to the source of the main FET Q5. In order to prevent the main FET Q5 from overheating and being destroyed when an overcurrent flows through the main FET Q5, when the temperature of the main FET Q5 rises above a specified value, it is forcibly turned off (cut off) by its own action. )). The main FET Q5 constituting the second reference overheat self-interrupting semiconductor switch QC is constituted by an NMOSFET having a DMOS structure.

A main FET Q1 of a power supply overheating self-interruption type semiconductor switch QA, a main FET Q3 of a reference overheating self-interruption type semiconductor switch QB,
Second reference overheat self-interruption type semiconductor switch Q
The C main FET Q5 is composed of a plurality of transistors, and the main FET Q1, the main FET Q3,
The ratio of the number of transistors constituting the main FET Q5 is: main FET Q1> main FET Q3 main FET Q1> main FET Q5. Specifically, for example, the main FET Q1 of the power supply overheating self-interruption type semiconductor switch QA, the main FET Q3 of the reference overheating self-interruption type semiconductor switch QB, and the main FET Q1 of the power supply overheating self-interruption type semiconductor switch QA Main FET Q5 of reference 2 overheating self-interruption type semiconductor switch QC
Are set to 1000: 1.

With this configuration, the reference circuit and the second reference circuit can be made small, and the area occupied on the chip can be reduced. In addition, by manufacturing the overheated self-interrupting semiconductor switch QA for power supply, the overheated self-interrupting semiconductor switch QB for reference, and the second overheated self-interrupting semiconductor switch QC for reference on the same chip in the same process, lot-to-lot variation. And the effect of temperature drift can be removed, and the detection accuracy of overcurrent and undercurrent can be improved.

When a load current (drain current) of 5 A flows through the main FET Q1 of the power supply overheating self-interruption type semiconductor switch QA, for example, the reference heating self-interruption type semiconductor switch Qr is turned on.
A drain current of 5 mA flows through the main FET Q3 of B, and the main F of the overheat self-interruption type semiconductor switch QA for power supply.
The same drain / drain as the drain-source voltage Vds of ETQ1
The source-to-source voltage is set to a value so as to be generated between the drain and the source of the main FET Q3 of the reference overheating self-interruption type semiconductor switch QB. Further, for example, when a 5 A load current (drain current) flows through the main FET Q1 of the power supply overheating self-interruption type semiconductor switch QA, the second reference overheating self-interruption type semiconductor switch QC Main FE
A drain current of 5 mA flows through TQ5, and the same drain-source voltage Vds as the drain-source voltage Vds of the main FET Q1 of the power supply overheating self-interruption type semiconductor switch QA is applied to the second reference overheating self-interruption type semiconductor switch Q.
The value is set so as to be generated between the drain and source of the C main FET Q5.

Therefore, the gate-source voltage of the main FET Q1 of the power supply overheating self-interruption type semiconductor switch QA and the gate-source voltage of the main FET Q3 of the reference overheating self-interruption type semiconductor switch QB are:
As long as the load 6 connected to the drain-side terminal DA of the main FET Q1 of the power supply overheat self-interruption type semiconductor switch QA is normal, the values are the same. Similarly, the main FET Q1 of the power supply overheat self-interruption type semiconductor switch QA
And the gate-source voltage of the main FET Q5 of the second reference overheating self-interruption type semiconductor switch QC are the drain side terminal DA of the main FET Q1 of the power supply overheating self-interruption type semiconductor switch QA.
Are the same as long as the load 6 connected to is normal.

The gate of the main FET Q1 of the power supply overheating self-interruption type semiconductor switch QA, the gate of the main FET Q3 of the reference overheating self-interruption type semiconductor switch QB, and the main of the second reference overheating self-interruption type semiconductor switch QC. The gate of the FET Q5 is a resistor R
7 and a resistor R8 are connected to the drive circuit 2 via a series circuit. The gate signal output from the drive circuit 2 causes the main FET Q1 of the power supply overheat self-interruption type semiconductor switch QA and the reference overheat self-interruption. FET Q3 of the solid-state semiconductor switch QB and the main FE of the second reference overheat self-interruption type semiconductor switch QC
TQ5 is turned on and off at the same time.

An anode of a Zener diode ZD1 is connected to the source of the main FET Q1 of the power supply overheating self-interruption type semiconductor switch QA. A connection point of the resistor R7 and the resistor R8 is connected to a cathode of the Zener diode ZD1. Is connected. The source of the main FET Q1 of the power supply overheat self-interruption type semiconductor switch QA is connected via a resistor R5 to the (+) side input terminal of a comparator CMP1 composed of a comparator and a comparator CMP2 composed of a comparator. (−) Side input terminals are connected to each other. The source (source side terminal SA) of the main FET Q1 of the power supply overheat self-interruption type semiconductor switch QA is connected to the (+) side input terminal of the comparison circuit CMP1 composed of this comparator via the resistor R5. The (-) side input terminal is connected to a reference overheat self-interruption type semiconductor switch QB via a resistor R6.
Of the main FET Q3 (source side terminal SB) is connected.

The comparison circuit CMP1 comprises a voltage induced at the source (source terminal SA) of the main FET Q1 of the power supply overheating self-interruption type semiconductor switch QA and the main FE of the reference overheating self-interruption type semiconductor switch QB.
The load 6 connected to the drain-side terminal DA of the main FET Q1 of the power supply overheat self-interruption type semiconductor switch QA is compared with a voltage induced at the source (source-side terminal SB) of the TQ3. The purpose of this is to detect the flow of an excessive current through the circuit. That is, the output of the comparison circuit CMP1 is the source voltage (source S) of the main FET Q1 of the power supply overheat self-interruption type semiconductor switch QA.
A potential on the A side) and a source voltage (source S) of the main FET Q3 of the reference overheat self-interruption type semiconductor switch QB.
B) and the difference is equal to or less than the overcurrent determination value (overheating self-interrupting semiconductor switch QA for power supply).
Hi is output while the potential of the source of the main FET Q1 is equal to or higher than the potential of the source of the main FET Q3 of the reference overheating self-interruption type semiconductor switch QB, and when the difference becomes larger than the overcurrent determination value (overheating for power supply). When the potential of the source of the main FET Q1 of the self-interruption type semiconductor switch QA becomes smaller than the potential of the source of the main FET Q3 of the reference overheating self-interruption type semiconductor switch QB), the output is inverted and Low is output, and it is determined that an excessive current has flowed.

The comparison circuit CMP2 is connected to the voltage induced at the source (source side terminal SA) of the main FET Q1 of the power supply overheating self-interruption type semiconductor switch QA and the second reference overheating self-interruption type semiconductor switch QC. By comparing the voltage induced at the source (source side terminal SC) of the main FET Q5, whether a predetermined amount of current is flowing through the main FET Q1 of the power supply overheat self-interruption type semiconductor switch QA (whether the current is not too small). Is to be detected. That is, the output of the comparison circuit CMP2 is output to the main F of the overheating self-interruption type semiconductor switch QA for power supply.
The source voltage (potential on the source SA side) of the ETQ1 is compared with the source voltage (potential on the source SC side) of the main FET Q5 of the second reference overheat self-interruption type semiconductor switch QC, and the difference is equal to or less than the undercurrent determination value. (The main FE of the overheat self-interruption type semiconductor switch QA for power supply)
Hi is output while the source voltage of TQ1 is lower than the source voltage of the main FET Q5 of the second reference overheat self-interruption type semiconductor switch QC (Hi), and when the difference becomes larger than the undercurrent determination value (power supply). When the source voltage of the main FET Q1 of the overheating self-interruption type semiconductor switch QA becomes higher than the source voltage of the main FET Q5 of the second reference overheating self-interruption type semiconductor switch QC), it is inverted and Low is output, and it is determined that an undercurrent occurs. I do. The (-) side input terminal of the comparison circuit CMP1 is connected to the source of the main FET Q3 of the reference overheating self-interruption type semiconductor switch QB via a resistor R6. Furthermore, the source of the main FET Q5 of the second reference overheat self-interruption type semiconductor switch QC is
The (+) side input terminal of the comparison circuit CMP2 is connected.

On the other hand, the emitter of the PNP transistor Tr1 is connected to the input terminal A of the power supply device 1, and the collector of the PNP transistor Tr1 is
A series circuit of a resistor R1, a resistor R3 and a resistor R2 is connected, and the other end of the resistor R2 is grounded. The (+) side input terminal of the comparison circuit CMP1 is connected to the resistor R1 and the resistor R1.
3 is connected via a diode D1 to a connection point,
The (−) input terminal of the comparison circuit CMP1 is connected to a connection point between the resistors R3 and R2 via a diode D2. Therefore, a voltage (for example, 5 V) obtained by stepping down the battery voltage VB of the battery power supply 4 by the load 6 is applied to the (+) side input terminal of the comparison circuit CMP1 by the resistor R1, the combined resistance of the resistor R3 and the resistor R2. The divided voltage is supplied to the (−) side input terminal of the comparison circuit CMP1 by a resistor R.
1 and a voltage divided by the resistor R2 and the combined resistor of the resistor R3 and the resistor R3.
This PNP transistor Tr1, a resistor R1, and a resistor R
3. After the main FET Q1 of the power supply overheating self-interruption type semiconductor switch QA is turned off from on due to an abnormality such as a short circuit due to the resistor R2, the diode D1, and the diode D2, the power supply overheating self-interruption type semiconductor switch. A return circuit for returning the main FET Q1 of QA to ON is configured. This return circuit includes a PNP transistor Tr1 having an emitter connected to an output terminal on the battery VB side, a base connected to an input terminal on the switch SW1 side via a resistor R10, and a resistor connected in series between its collector and ground. R1, resistor R3, resistor R2
And the current flowing through the resistor R1 is compared with (+) of the comparison circuit CMP1.
It is composed of a diode D1 passing to the terminal side and a diode D2 passing current flowing through the resistors R1 and R3 to the minus terminal side of the comparison circuit CMP1.

The resistor R1 which is a component of the return circuit
Is turned on when the switch SW1 is turned on.
When the NP transistor Tr1 is turned on, the potential V1 at the connection point of the resistors R1 and R3 is about 60 to 80% of the battery, and the potential of the source-side terminal SA of the power supply overheat self-interruption type semiconductor switch QA is the resistor R5. Is set to a value larger than the voltage V3 (cathode-side potential of the diode D1) reduced by the voltage drop.

Further, an anode of a diode D3 is connected to a (+) side input terminal of the comparison circuit CMP1 via a resistor R9, and a gate signal output terminal of the drive circuit 2 is connected to a cathode of the diode D3. Have been. The output terminal of the comparison circuit CMP1 is connected to the drive circuit 2, and the result of the determination by the comparison circuit CMP1 is input to the drive circuit 2. An input terminal of the power supply device 1 is connected to an input terminal of the drive circuit 2.
A voltage VG (for example, VP = 5 V) obtained by stepping down the battery voltage VB of the battery power supply 4 by the load 6 is applied from the input terminal A of the power supply device 1 to the input terminal of the drive circuit 2. This voltage VG is the main FET Q1 of the power supply overheating self-interruption type semiconductor switch QA and the main FET of the reference overheating self-interruption type semiconductor switch QB.
Q3 is a gate voltage of the main FET Q5 of the second reference overheat self-interruption type semiconductor switch QC.

The drive circuit 2 receives the Hi signal output from the comparison circuit CMP1 and the ON signal input from the switch side when the switch SW1 is turned on, and the source-side transistor 2a of the drive circuit 2
Turns on, the sink-side transistor 2b turns off, and the voltage V
The G drive signal (gate voltage) is applied to the gate of the main FET Q1 of the power supply overheating self-interruption type semiconductor switch QA via the resistors R8 and R7, and thereby the mains of the power supply overheating self-interruption type semiconductor switch QA is applied. FET
Q1 is turned on. Similarly, drive circuit 2
Overheating self-interruption type semiconductor switch QB for reference by drive signal (gate voltage) of voltage VG output from
And the main FET Q5 of the second reference overheat self-interruption type semiconductor switch QC is also turned on. The driving circuit 2 includes a comparison circuit CMP
While the signal from 1 to Hi is being input (unless a Low signal is output), the main FET Q1 of the power supply overheating self-interruption type semiconductor switch QA (the main FET Q3 of the reference overheating self-interruption type semiconductor switch QB, the second FET) QC for overheating self-interruption type semiconductor switch for reference
Of the main FET Q5). In the drive circuit 2, when the comparison circuit CMP1 is inverted and a Low signal is input from the comparison circuit CMP1, the source-side transistor 2a of the drive circuit 2 is turned off, the sink-side transistor 2b is turned on, and the input terminal of the drive circuit 2 The supply of the voltage VG (for example, VP = 5V) obtained by reducing the battery voltage VB of the battery power supply 4 applied from the input terminal A of the power supply device 1 by the load 6 to the gate output terminal of the drive circuit 2 is stopped. Is grounded, so that the output from the drive circuit 2 is reliably Low. Due to the low level of the output from the drive circuit 2, the gate voltage is not applied to the gate of the main FET Q1 of the power supply overheat self-interruption type semiconductor switch QA (OFF signal is output),
Main FET Q1 of power supply overheating self-interruption type semiconductor switch QA (Main FET Q3 of reference overheating self-interruption type semiconductor switch QB, main FET Q5 of second reference overheating self-interruption type semiconductor switch QC)
Turn off. The output terminal of the comparison circuit CMP2 is connected to the output terminal G to the outside, and the comparison circuit CMP2
Is output from the output terminal H (for example, as a monitor signal) and used by a circuit connected to the output terminal H (for example, a circuit for turning on or blinking an alarm lamp to warn the outside). .

At start-up, when the switch SW1 is turned on, P
The NP transistor Tr1 turns on, and the power supply voltage VB (12
V) is reduced by the load 6 to the voltage (5 V)
1 and [the resistance R3 + the resistance R2], the voltage value (for example, 60% to 80% of the step-down voltage) is compared with the comparison circuit CM.
The voltage is applied to the (+) side terminal of P1. The voltage value (for example, 20% to 40% of the step-down voltage) divided by the [resistance R1 + the resistance R3] and the resistance R2 is applied to the (−) side terminal of the comparison circuit CMP1. . This resistor R3 has a small resistance value, and the resistance value of the resistor R1 and [resistance R3 + resistance R2]
Are slight differences.

When the switch SW1 is turned on and the PNP transistor Tr1 is turned on, the voltage (5V) obtained by stepping down the power supply voltage VB (12V) by the load 6 is divided by the resistor R1 and [the resistor R3 + the resistor R2]. It is applied to the (+) side input terminal of the comparison circuit CMP1 and the (−) side input terminal of the comparison circuit CMP1. At this time, the comparison circuit C
Since the voltage applied to the (+) side input terminal of MP1 is higher than the voltage applied to the (−) side input terminal of the comparison circuit CMP1, the output of the comparison circuit CMP1 becomes Hi and drives the drive circuit 2, The drive circuit 2 outputs a gate drive signal Hi
Is output. The gate drive signal Hi is supplied to the main FET Q1 of the power supply overheat self-interruption type semiconductor switch QA.
To turn on the main FET Q1. The gate drive signal is simultaneously supplied to the main FET Q3 and the second
The main FET Q5 of the reference overheat self-interruption type semiconductor switch QC is turned on.

The output of the comparison circuit CMP1 is connected to the main FET Q of the overheat self-interruption type semiconductor switch QA for power supply.
1 is used to determine that an overcurrent has flown. Now, when a dead short circuit such as a short circuit at both ends of the load 6 occurs, the voltage Vd between the drain and the source of the main FET Q1 of the overheat self-interrupting semiconductor switch QA for power supply.
s increases (the voltage between the drain and the source increases as long as the main FET Q1 of the power supply overheating self-interruption type semiconductor switch QA is on), and the main FET Q1 of the power supply overheating self-interruption type semiconductor switch QA turns on. It stabilizes where it is determined by the resistance and the short-circuit current. Main FET of overheating self-interruption type semiconductor switch QB for reference
If the source of Q3 is normally on in the continuous ON state, and if it is normal, the source of the main FET Q1 of the power supply overheating self-interruption type semiconductor switch QA is compared with the source of the main FET Q3 of the reference overheating self-interruption type semiconductor switch QB. Since the reference resistor Rr1 is set so that the source is higher, the source of the main FET Q1 of the overheat self-interrupting semiconductor switch QA for power supply is lower. When the switch is normally on, the drain of the main FET Q1 of the power supply overheat self-interruption type semiconductor switch QA
Since the source-to-source voltage Vds (about 0.5 V), the main FET of the power supply overheat self-interruption type semiconductor switch QA is smaller than the voltage divided by the resistors R1, R3, and R2.
Both the source of Q1 and the source of the main FET Q3 of the reference overheating self-interruption type semiconductor switch QB are high (close to the power supply voltage). The voltage divided by the resistors R1, R3, and R2 is cut by the diodes D1 and D2, and the (+) of the comparator CMP1 is cut off.
It becomes irrelevant to the side input terminal and the (−) side input terminal. That is, the value of the source of the main FET Q1 of the power supply overheating self-interruption type semiconductor switch QA and the source of the main FET Q3 of the reference overheating self-interruption type semiconductor switch QB are directly input to the (+) side input terminal of the comparison circuit CMP1, (− ) Side input terminal.

On the other hand, a circuit including a resistor R9 and a diode D3 is connected to the (+) side input terminal of the comparison circuit CMP1, and the cathode of the diode D3 of this circuit is connected to the gate signal output terminal. When the wiring is normal,
Since the gate of the main FET Q1 of the power supply overheat self-interruption type semiconductor switch QA is turned on, this diode D
The cathode of No. 3 is at a considerably high voltage. Therefore, the diode D3 is cut off, and no current flows through the series circuit of the resistor R9 and the diode D3. Therefore, no current flows through the resistors R5 and R6, and the main F of the overheat self-interruption type semiconductor switch QA for power supply.
The source voltage of the ETQ1 and the source voltage of the main FET Q3 of the reference overheating self-interruption type semiconductor switch QB are directly input to the (+) input terminal and the (-) input terminal of the comparison circuit CMP1. At this time, if the load 6 is normal (not a dead short circuit in which both ends of the load 6 are connected), the reference overheating self-interruption type semiconductor switch is compared with the source of the main FET Q1 of the power supply overheating self-interruption type semiconductor switch QA. Since the reference resistor Rr1 is set so that the source of the QB main FET Q3 is small, the output of the comparison circuit CMP1 is Hi.

In this state, when both ends of the load 6 are connected and short-circuit occurs between both ends of the load 6 (between loads), the limiting resistance by the load 6 is eliminated, and the power supply heating A large current flows to the main FET Q1 side of the cut-off type semiconductor switch QA, and the main FET Q of the power supply overheat self-cut-off type semiconductor switch QA
A large current is applied to the ON resistance of No. 1 and the potential difference between the drain and the source increases. However, the drain of the main FET Q3 of the overheated self-interruption type semiconductor switch QB for reference
Since the potential difference between the sources is fixed by the reference resistor Rr1, it remains constant. Therefore, the source voltage of the main FET Q3 of the reference overheating self-interruption type semiconductor switch QB is compared with the main FET Q of the power supply overheating self-interruption type semiconductor switch QA.
The source voltage of 1 decreases.

The source voltage of the main FET Q1 of the power supply overheating self-interruption type semiconductor switch QA decreases, and the main F of the reference overheating self-interruption type semiconductor switch QB decreases.
When the source voltage of the ETQ3 becomes lower than the overcurrent determination value and becomes lower than the overcurrent determination value, the output of the comparison circuit CMP1 is inverted from Hi to Low, and a Low signal is output to the drive circuit 2. When a Low signal is input from the comparison circuit CMP1 to the drive circuit 2, the source-side transistor 2a of the drive circuit 2 is turned off, the sink-side transistor 2b is turned on, and the output from the drive circuit 2 is changed from Hi to Low, resulting in power consumption. An off signal is output to the gate of the main FET Q1 of the power supply overheating self-interruption type semiconductor switch QA to try to shut off the main FET Q1 of the power supply overheating self-interruption type semiconductor switch QA. The low FE signal from the drive circuit 2 causes the main FE of the reference overheating self-interruption type semiconductor switch QB to be turned on.
An off signal is also input to the gate of TQ3 and the gate of the main FET Q5 of the second reference overheating self-interruption type semiconductor switch QC, and the gate of the main FET Q3 of the reference overheating self-interruption type semiconductor switch QB and the second reference overheating self-interruption semiconductor switch QB. The main FET Q5 of the cutoff type semiconductor switch QC is also cut off.

When trying to cut off the main FET Q1 of the power supply overheating semiconductor switch QA, the transistor 2a on the source side of the drive circuit 2 is turned off and the transistor 2b on the sink side is turned on. Therefore, since the cathode side of the diode D3 of the series circuit of the resistor R9 and the diode D3 is grounded, the resistor R9 and the diode D3
A current flows through the series circuit of No. 3. This current is supplied to the main FET Q1 of the overheat self-interruption type semiconductor switch QA for power supply.
Flows from the source side terminal SA through the resistor R5, through the resistor R9, and through the diode D3 to the ground. Then, a current flows through the resistor R5, causing a voltage drop by the resistor R5.
Because of this voltage drop, the (+) side input terminal of the comparison circuit CMP1 is connected to the power supply overheat self-interrupt type semiconductor switch Q.
The source voltage of the main FET Q1 of A is lower by the voltage drop of the resistor R5. This is hysteresis.

The overheating semiconductor switch QA for power supply is compared with the voltage of the source side terminal SB of the main FET Q3 of the overheating semiconductor switch QB for reference.
Once the voltage of the source side terminal SA of the main FET Q1 becomes lower, the comparator CMP1 is inverted and the driving circuit 2
Is input, and the drive circuit 2 is turned off. Once the drive circuit 2 is stopped, the transistor 2a on the source side of the drive circuit 2 is turned off and the transistor 2b on the sink side is turned on.
A current flows through the series circuit No. 3 and the (+) input terminal of the comparison circuit CMP1 has a voltage lower than the actual source of the main FET Q1 of the overheating self-interrupting semiconductor switch QA for power supply. Therefore, even if the source of the main FET Q1 of the power supply overheat self-interruption type semiconductor switch QA rises slightly and fluctuates, the comparison circuit CMP1 is stably turned off. That is, the resistor R9 and the diode D3
Constitute a hysteresis circuit.

In this state, since the drive circuit 2 is turned off, the main FET Q1 of the power supply overheating self-interruption type semiconductor switch QA and the main FET Q3 of the reference overheating self-interruption type semiconductor switch QB shift to the off direction. . First, the voltage between the drain and the source gradually increases in both cases. As the drain-source voltage increases, the capacitance of the CGD in the gate is charged by being pulled by it, and is pulled while being charged, and the main FET Q of the power supply overheat self-interrupting semiconductor switch QA is charged.
1. Reference overheated self-interrupting semiconductor switch QB
, The voltage between the true gate and source of the main FET Q3 increases, and the current temporarily increases. However, the source voltage of the main FET Q1 of the power supply overheating self-interruption type semiconductor switch QA and the source voltage of the main FET Q3 of the reference overheating self-interruption type semiconductor switch QB do not become infinitely large, so that the power supply voltage VB (12 V) is loaded. Saturation occurs when the voltage slightly exceeds the voltage (5 V) reduced by step 6, and the pulling effect is lost any more. The main FET Q1 of the power supply overheating self-interruption type semiconductor switch QA and the reference overheating self-interruption at the gate discharge circuit. The gate charge of the main FET Q3 of the type semiconductor switch QB comes off rapidly, and the gate voltage with respect to the source drops. For this purpose, the main FET Q1 of the power supply overheating self-interruption type semiconductor switch QA and the main FE of the reference overheating self-interruption type semiconductor switch QB are used.
At the same time as the current of TQ3 decreases, the voltage between the drain and the source of the main FET Q1 of the overheating self-interrupting semiconductor switch QA for power supply and the main FET Q3 of the overheating self-interrupting semiconductor switch QB for reference also increase steadily.

As described above, since the current flowing through the main FET Q1 of the power supply overheating self-interruption type semiconductor switch QA decreases, the source side of the main FET Q1 of the power supply overheating self-interruption type semiconductor switch QA becomes close to ground. Go. Then, the source voltage of the main FET Q1 of the overheating self-interrupting semiconductor switch QA for power supply, and the main FET Q of the overheating self-interrupting semiconductor switch QB for reference.
The source voltage of No. 3 is lower than a voltage obtained by dividing the power supply voltage by the resistors R1, R3 and R2. As a result, the source voltage of the main FET Q3 of the reference overheating self-interruption type semiconductor switch QB and the source voltage of the main FET Q3 of the reference overheating self-interruption type semiconductor switch QB are the (−) side input terminal of the comparison circuit CMP1, the comparison circuit C
A signal cannot be sent to the (+) side input terminal of MP1.

In such a state, the voltage obtained by dividing the power supply voltage by the resistors R1, R3 and R2 is applied to the (+) side input terminal of the comparison circuit CMP1 and the comparison circuit CMP1.
(-) Side input terminal. Then
The voltage divided by the resistors R1, R3, and R2 applied to the (+) input terminal of the comparison circuit CMP1 is equal to the resistances R1, R3, and R2 applied to the (−) input terminal of the comparison circuit CMP1. Is higher by the voltage drop of the resistor R3 than the divided voltage by the comparator circuit CMP1.
Is inverted and surely becomes Hi. This comparison circuit CM
When the output Hi of P1 is reached, the drive circuit 2 is turned on again, and the gate signal is supplied to the power supply overheating self-interrupting semiconductor switch Q
A is sent to the gate of the main FET Q1 to turn on the main FET Q1 of the power supply overheat self-interruption type semiconductor switch QA. As a result, a current flows through the load 6. Such repetition is performed.

As described above, according to the present embodiment, even if the input voltage to the drive circuit 2 is about 5 V or less than 5 V, it is turned on / off with good responsiveness, which is very effective for protection of system equipment. It is. That is, even if the main FET Q1 of the overheat self-interruption type semiconductor switch QA for power supply is connected to the downstream side of the load 6, even if the IPS is not provided with the charge pump circuit 3 for boosting the gate, an overcurrent or an undercurrent is generated. A protection function can be provided when an abnormality occurs.

[0049]

According to the first aspect of the present invention, the IPS can be loaded without using a MOS-type FET as the semiconductor switching element and without using a charge pump circuit for applying a boosted voltage to the gate of the MOS-type FET. The overcurrent of the IPS can be easily detected by connecting to the downstream side of the IPS, and the IPS can be protected by shutting off the MOSFET when an overcurrent flows through the IPS.

According to the second aspect of the present invention, the IPS can be connected downstream of the load without using a charge pump circuit for applying a boosted voltage to the gate of the MOS FET by using a MOS FET as the semiconductor switching element. Connected to the side
The overcurrent of the PS can be easily detected, and when an overcurrent flows through the IPS, the MOS type FET can be cut off to protect the IPS.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of an intelligent power switch device according to the present invention.

FIG. 2 is a detailed circuit diagram of the power supply overheat self-interruption type semiconductor switch QA shown in FIG. 1;

FIG. 3 is a detailed circuit diagram of the reference overheat self-interruption type semiconductor switch QB shown in FIG. 1;

FIG. 4 is a detailed circuit diagram of a second reference overheat self-interruption type semiconductor switch QC shown in FIG. 1;

FIG. 5 is a circuit diagram of a conventional intelligent power switch in which an IPS is connected downstream of a load.

[Explanation of symbols]

1 Power supply device 2 Drive circuit 4 Battery power supply 5 Supply line 6 …………………………………… Load CMP1 ………………… Comparison circuit CMP2 ………………………… Comparison circuit QA ……………………………………………………………………………………………………………………………………………………………. ... Second reference resistor

Claims (2)

[Claims] An overheat self-interrupting semiconductor switch for power supply, which is connected between a load connected to a power supply and ground and switches the supply of power from the power supply, the same as the overheat self-interrupting semiconductor switch for power supply. A reference circuit composed of a series circuit comprising a reference overheating self-interruption semiconductor switch having a voltage characteristic and a reference resistor and connected in parallel to the power supply overheating self-interruption semiconductor switch; and the power supply overheating self-interruption semiconductor. A difference (A−B) between a source voltage A of the switch and a source voltage B of the reference overheating self-interruption type semiconductor switch is compared with a predetermined overcurrent determination value C to determine whether the current is an overcurrent. And a comparison circuit that outputs a detection signal corresponding to the determination result, and the power supply overheating is performed by a control signal corresponding to the detection signal. And a drive circuit for turning on and off the self-interrupting type semiconductor switch. While the current is a normal current, the power supply overheating self-interrupting type semiconductor switch is maintained in a continuous ON state. Is detected, the power supply overheating self-interruption type semiconductor switch is turned off, and after the power supply overheating self-interruption type semiconductor switch is once turned off, when the normal current is detected, the power supply overheating self-interruption type semiconductor switch is turned off. An intelligent power switch device that performs control to turn on a cut-off semiconductor switch again. 2. The comparator circuit according to claim 1, wherein said comparator circuit inverts an output signal from a Hi signal to a Low signal and outputs the signal to said drive circuit when an overcurrent flows through said power supply overheating self-interrupting semiconductor switch. The intelligent power switch device according to claim 1, wherein the intelligent power switch device is configured.