JPH08130874A - Dc power supply - Google Patents

Abstract

PURPOSE: To step down the DC output and stop the operation of the object of power supply while avoiding the complication of a circuit and the use of an expensive switch. CONSTITUTION: This DC power supply is equipped with a switching circuit to which the voltage error of DC output 131 is fed back through a photocoupler 5, step down regulator 9, which steps down DC output 121 to a specified voltage and supplies it to a microcomputer 8, and a step down control circuit 7 which steps down the voltage supplied to a television circuit 10 to the voltage corresponding to waiting by controlling an error detection circuit 6 when the microcomputer 8 directs waiting. Moreover, the voltage of the DC output 121 supplied to the step down regulator 9 in waiting condition is made the voltage by which the step-down regulator 9 can supply the microcomputer 8 with specified voltage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device for supplying a DC output to a power supply target such as a television circuit. More specifically, the voltage of the DC output during standby is a standby state when a current flowing through the power supply target is in a standby state. The present invention relates to a DC power supply device that steps down the voltage to a value corresponding to.

[0002]

2. Description of the Related Art Televisions are provided with a television circuit which is a circuit relating to a video signal and a microcomputer for controlling main operations. In the standby mode in which no image is received, the power consumption is reduced, and the transition from the standby mode to the operation mode is controlled by the microcomputer.

FIG. 4 shows a first prior art of a power supply circuit for executing the above operation. That is, a main power supply 91 for operating the television circuit 94 and a sub power supply 92 for operating the microcomputer 93 are provided.
Equipped with seed power. Commercial power is supplied to the main power supply 91 via a switch S8 such as a relay whose connection is controlled by the microcomputer 93.
In the operation mode, by closing the connection of the switch S8, the main power supply 91 supplies a direct current output to the television circuit 94 to cause the television circuit 94 to perform a predetermined operation. Further, in the standby mode, the connection of the switch S8 is opened to stop the supply of the commercial power source to the main power source 91 to reduce the power consumption of the device.

FIG. 5 shows a second conventional technique, in which the microcomputer 93 and the television circuit 94 are
Both receive the DC output from the same power supply 95. Further, a switch S9 whose connection is controlled by the microcomputer 93 is provided. And the television circuit 94
Is configured to perform a predetermined operation when the connection of the switch S9 is closed, and to stop the horizontal oscillation operation when the connection of the switch S9 is opened. Therefore, the microcomputer 93 causes the television circuit 94 to perform a predetermined operation in the operation mode by closing the connection of the switch S9. In the standby mode, switch S9
The horizontal oscillation operation of the television circuit 94 is stopped by opening the connection. As a result, in the standby mode, the power consumption is reduced and the heater of the CRT is turned off.

[0005]

However, the first conventional technique requires two types of power sources 91 and 92. Therefore, there has been a problem that the circuit configuration of the power supply becomes complicated. Further, since the switch S8 is a switch such as a relay whose connection can be controlled by the microcomputer 93, there is a problem that the price becomes expensive.

On the other hand, in the second conventional technique, one power source 9 is used.
5 is used, and the switch S9 can be configured by a transistor that handles a very small amount of power, so that the circuit configuration of the power supply and the use of an expensive switch are avoided. However, the power supply 95
The operation is not performed by stopping the operation according to the voltage drop of the DC output of the above, but is performed by stopping the horizontal oscillation operation of the television circuit 94. That is, the DC output of the specified voltage is continuously applied to the television circuit 94 even in the standby mode. As a result, when shifting to the standby mode, the high voltage of 20 kV or more applied to the CRT is not discharged,
Since the voltage remains substantially the same, there is a problem that a CRT spot is likely to occur.

The present invention was conceived in order to solve the above problems. An object of the present invention is to maintain the voltage supplied to a microcomputer at a specified voltage while controlling the DC output voltage. By reducing the current flowing in the power supply target to a voltage that corresponds to the standby state, it is possible to reduce the power supply target by reducing the DC output even when the power supply circuit is not complicated and the use of expensive switches is avoided. It is to provide a DC power supply device that can stop the operation. Further, the object of the invention of claim 2 is to reduce the DC output by changing the voltage division ratio of the voltage dividing circuit.
It is an object of the present invention to provide a DC power supply device that can avoid complication of an error detection circuit of a switching power supply. It is another object of the present invention to provide a DC power supply device capable of preventing the occurrence of a CRT spot even when the complexity of the power supply circuit and the use of an expensive switch are avoided.

[0008]

In order to solve the above-mentioned problems, a direct-current power supply device according to the invention of claim 1 is provided with one direct-current output or a plurality of direct-current outputs, and the direct-current output of the direct-current output is provided via a photo coupler. By feeding back the voltage error to the primary side, a switching power supply that supplies the stabilized DC output to the power supply target, and an output obtained by stepping down the DC output to a predetermined voltage are supplied to a microcomputer that controls the operation of the power supply target. When the step-down regulator to be supplied and the microcomputer instruct the standby, the switching power supply is controlled so that the voltage of the DC output supplied to the power supply target is the standby current value flowing in the power supply target. And a step-down control circuit for stepping down the voltage to a voltage corresponding to the step-down control circuit in the standby state. The voltage of the DC power supplied to the regulator, the Buck regulator is a voltage that can be supplied to the predetermined voltage to the microcomputer. According to a second aspect of the present invention, in the DC power supply device, the step-down control circuit is provided in an error detection circuit that detects the voltage error when the microcomputer instructs standby, and the DC output device The voltage of the DC output is reduced by dividing the voltage and reducing the voltage division ratio of the voltage dividing circuit in which the divided voltage is compared with the reference voltage. In the DC power supply device according to the invention of claim 3, the power supply target is a television circuit.

[0009]

The operation of the invention according to claim 1 will be described below. In the standby state in which the voltage of the DC output supplied to the power supply target is reduced by the step-down control circuit, the value of the current flowing through the power supply target decreases and the operation of the power supply target stops. At this time, the value of the current flowing through the power supply target is a value corresponding to the standby state (eg, a value near 0). In the standby state, the DC output voltage supplied to the step-down regulator also drops. However, the voltage of the DC output supplied to the step-down regulator in the standby state is a voltage at which the step-down regulator can supply a predetermined voltage to the microcomputer. From the above, in the standby state, the power supply target stops the operation and consumes a small current. Further, a direct-current output of a predetermined voltage is supplied to the microcomputer from the step-down regulator. Therefore, the microcomputer executes the predetermined operation even in the standby state. That is, in the standby state, only the microcomputer executes the predetermined operation,
The power supply target is in a state of low current consumption.

The operation of the invention according to claim 2 will be described below.
The error detection circuit detects a difference between the divided voltage and the reference voltage and amplifies the detected difference. Therefore, if the voltage dividing ratio of the voltage dividing circuit or the reference voltage is changed, the voltage of the DC output changes in accordance with this change. That is, when the voltage division ratio is reduced, the divided voltage rises, so that the voltage of the DC output is controlled to decrease. When the reference voltage is lowered, it is determined that the divided voltage has increased, so
DC output voltage drops. However, in the case of changing the reference voltage, it is necessary to have a configuration including two elements having different reference voltages and a switching circuit that switches the output of each element, or to add a switching circuit that changes the reference voltage. There is. On the other hand, in the case of changing the voltage division ratio of the voltage dividing circuit, the voltage dividing circuit for dividing the DC output only needs to have a configuration capable of dividing the voltage with two types of voltage dividing ratios.

The operation of the invention according to claim 3 will be described below.
The voltage of the DC output changes continuously when the operating state shifts to the standby state. In the standby state,
The voltage supplied to the power supply target is a voltage at which the operation stops. Therefore, the accelerating voltage applied to the CRT is discharged by the high voltage generating circuit in the transition from the operating state to the standby state, and the voltage value decreases.

[0012]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an electrical configuration of a television using an embodiment of a DC power supply device according to the present invention.

In the figure, a rectifying / smoothing circuit 1 is a block including a bridge diode, a smoothing capacitor, etc., rectifies and smoothes a commercial power source, and outputs a smoothed output to a switching circuit 2. The switching circuit 2 is
The block is provided with a switching transistor, a control transistor that limits the base current of the switching transistor, and the like. Then, based on the coupling action of the primary coil 31 and the base coil 32 wound around the transformer 3,
By performing self-excited oscillation, the current flowing through the primary coil 31 is switched.

The rectifying / smoothing circuit 12 is a block for rectifying and smoothing the switching output generated in the secondary coil 34. The DC output 121 obtained by the rectifying / smoothing is supplied to the step-down regulator 9 and the television circuit. 10 and supply. In addition, the voltage of the DC output 121 is a voltage of 20V, and serves as an operating power source for the audio signal circuit of the television circuit 10. The rectifying / smoothing circuit 13 is a block that rectifies and smoothes the switching output generated in the secondary coil 35, and supplies the DC output 131 obtained by the rectifying and smoothing to the television circuit 10. DC output 1
31 is sent to the error detection circuit 6. In addition, DC output 13
The voltage of 1 is a voltage of about 100 V and serves as an operating power supply for the horizontal oscillation circuit of the television circuit 10.

The error detection circuit 6 is a block including a voltage dividing circuit for dividing the DC output 131, a reference voltage generating circuit, a circuit for detecting a difference between the divided voltage and the reference voltage, and the like. Then, the voltage error between the divided voltage of the DC output 131 and the reference voltage is detected, and the photocoupler 5 is driven by the current corresponding to the detected voltage error. The voltage control circuit 4 is
It is a block including a control circuit for controlling the base current of the control transistor in the switching circuit 2.
Then, by controlling the switching operation of the switching circuit 2 based on the error output given from the error detection circuit 6 via the photocoupler 5, the DC output 121,
The voltage of 131, ... Is stabilized.

A rectifying / smoothing circuit is connected to the secondary coil 33, and a direct current output (having a voltage of about 12 V) output from the rectifying / smoothing circuit is applied to the television circuit 10. However, in the same figure, for simplicity of the drawing, the illustration of the block connected to the secondary coil 33 is omitted. As described above, the switching power supply according to the present embodiment has eight blocks 1 to 6, 12,
13 and a block (not shown) connected to the secondary coil 33, which is a self-excited switching power supply known as a prior art.

The step-down regulator 9 has a DC output 121.
Is reduced to a predetermined voltage such as 5V, and the reduced output 91 is supplied to the microcomputer 8. Specifically, it is a three-terminal regulator that outputs 5V. The microcomputer 8 is a block for controlling the operation of the television circuit 10 and receives an instruction from a remote controller or an instruction from a switch on the operation panel. Therefore, the microcomputer 8 is in an operating state even when no image is received. It is a block that is required to exist.

Since the step-down control circuit 7 stops image reception,
When the microcomputer 8 gives an instruction for standby, the DC output 121, 131 is set so that the value of the current flowing through the television circuit 10 becomes a value corresponding to standby by reducing the voltage division ratio of the voltage dividing circuit of the error detection circuit 6. It is a block that lowers the voltage of ... The TV circuit 10
It is a circuit known as a prior art, and receives a video signal and C
The RT11 is driven and the like.

FIG. 2 shows the error detection circuit 6 and the step-down control circuit 7.
It is a circuit diagram which shows the detailed electrical connection with.

The error detecting circuit 6 includes a transistor Q1,
A Zener diode D1, six resistors R1 to R6, and a capacitor C1 are provided, and the three resistors R4 to R6 are connected in series. One of the terminals of the resistor R4 is connected to the DC output 131, and one of the terminals of the resistor R6 is grounded. That is, the three resistors R4 to R6 form a voltage dividing circuit 62 that outputs a divided voltage from the connection point of the resistors R5 and R6.

The resistors R2 and R3 are connected in series, and one terminal of the resistor R2 is connected to the DC output 131. Further, the cathode of the Zener diode D1 is
One of the terminals of the resistor R3 is connected, and the anode is grounded. Further, the connection point of the resistors R5 and R6 is led to the base of the transistor Q1, the cathode of the Zener diode D1 is connected to the emitter, and the cathode of the light emitting diode D5 of the photocoupler 5 is connected to the collector. ing. The connection point between the resistors R2 and R3 is led to one terminal of the resistor R1, and the anode of the light emitting diode D5 is connected to the other terminal of the resistor R1. The capacitor C1 connected between the collector and the base of the transistor Q1 is a phase correction capacitor.

The step-down control circuit 7 is provided with two transistors Q2 and Q3, two diodes D2 and D3, and three resistors R7 to R9. The DC output 131 is connected to one of the terminals of the resistor R7. The other terminal of the resistor R7 is connected to the base of the transistor Q2, the anodes of the diodes D2 and D3 are connected to the emitter, and the DC output 131 is connected to the collector. The cathode of the diode D2 is led to the connection point between the resistors R2 and R3, and the cathode of the diode D3 is led to the connection point between the resistors R4 and R5. An output 81 from the microcomputer 8 is led to the base of the transistor Q3 via the resistor R8. The base of the transistor Q2 is connected to the collector of the transistor Q3, and the emitter is grounded. The base of the transistor Q3 is grounded via the resistor R9.

FIG. 3 is a timing chart showing waveforms of main signals when the operating state shifts to the standby state. The operation of the embodiment will be described below with reference to FIG.

In the operating state, the output 81 of the microcomputer 8 is at the H level and the transistor Q3 is turned on, so the transistor Q2 is in the off state. That is, the error detection circuit 6 is separated from the step-down control circuit 7. Therefore, the voltage dividing circuit 62 is

## EQU1 ## R6 / (R4 + R5 + R6) ... The DC output 131 is divided according to the voltage division ratio expressed by the following equation. As a result, the voltage of the DC output 131 is about 100V,
The voltage of the DC output 121 is controlled to 20V, which is a predetermined voltage, and the television circuit 10 performs a predetermined image receiving operation. The microcomputer 8 is supplied with stabilized 5V by the step-down regulator 9.

When the image reception is stopped, the microcomputer 8 gives a standby instruction to the step-down control circuit 7 by setting the output 81 to the L level (see FIG. 3). As a result, the transistor Q3 turns off and the transistor Q2
Is turned on, and a voltage substantially equal to the voltage of the DC output 131 is applied to the connection point between the resistors R4 and R5. Therefore, the voltage dividing circuit 62 is

## EQU00002 ## R6 / (R5 + R6) ... The DC output 131 is divided with a voltage division ratio represented by the following equation, that is, a voltage division ratio smaller than the operating state. Then, the divided voltage is output to the base of the transistor Q1.

The partial pressure ratio represented by the above equation 1 is 1 /
If a and the partial pressure ratio shown by the equation 2 is 1 / b,

[Formula 3] a: b≈4: 1. As a result, as shown in FIG. 3, the voltage of the DC output 131 becomes about 1/4 of the voltage in the operating state, and drops to about 20V. DC output 1
The voltage of 21 drops to about 7V (diode D
2 prevents the current value of the light emitting diode D5 from decreasing in the standby state in which the voltage of the DC output 131 decreases).

Therefore, in the television circuit 10, the DC output 1
Along with the voltage drop of 31, the horizontal oscillation circuit
The oscillation operation is stopped while reducing the high-voltage acceleration voltage applied to. The other circuits in the television circuit 10 also stop operating. As a result, the current consumed by the television circuit 10 becomes a current near zero. Further, since the acceleration voltage is lowered, all the rasters are quickly erased from the screen of the CRT 11.

On the other hand, since the voltage of the DC output 121 in the standby state is about 7V, the step-down regulator 9
The microcomputer 8 is in a state capable of outputting the required 5V. For this reason, the microcomputer 8 has the configuration shown in FIG.
As indicated by reference numeral 91, since 5V is supplied even in the standby state, the microcomputer 8 executes the operation required in the standby state without any trouble. When the image reception is started again, the output 81 is set to the H level and the transistor Q2 is turned off to raise the DC outputs 121, 131, ... To a predetermined voltage.

The present invention is not limited to the above embodiment,
Although the case where the present invention is applied to a television has been described, other devices such as a video-integrated television can be similarly applied.

[0030]

The DC power supply device according to the present invention has one DC output or a plurality of DC outputs, and returns the voltage error of the DC output to the primary side via the photocoupler. A switching power supply that supplies a stabilized DC output to the power supply target, a step-down regulator that supplies the output that has reduced the DC output to a predetermined voltage to a microcomputer that controls the operation of the power supply target, and the microcomputer instructs standby. In some cases, the switching power supply is controlled to include a step-down control circuit that steps down the voltage of the DC output supplied to the power supply target to a voltage at which the value of the current flowing through the power supply target becomes a value corresponding to standby. . In addition, the voltage of the DC output supplied to the step-down regulator in the standby state is set to a voltage that enables the step-down regulator to supply a predetermined voltage to the microcomputer. Therefore, the voltage supplied to the microcomputer is maintained at the predetermined voltage even in the standby state,
Moreover, since the voltage of the DC output drops to a voltage at which the current flowing to the power supply target corresponds to the standby state, the DC output voltage is reduced even when the power supply circuit is prevented from becoming complicated and the use of expensive switches is avoided. It is possible to stop the operation of the power supply target by reducing the voltage.

According to the second aspect of the present invention, in the DC power supply device, the step-down control circuit is provided in the error detection circuit for detecting a voltage error when the microcomputer instructs standby, and the voltage of the DC output is provided. Is divided and the divided voltage is compared with the reference voltage to reduce the voltage division ratio of the voltage dividing circuit, thereby reducing the voltage of the DC output. Therefore, a voltage divider circuit that divides the DC output is
Since it suffices that the voltage can be divided by the two voltage dividing ratios, it is possible to avoid complication of the error detection circuit of the switching power supply.

In the DC power supply device according to the third aspect of the present invention, the power supply target is a television circuit. Therefore, in the television circuit, in the transition from the operating state to the standby state, the accelerating voltage of the raster is discharged by the high voltage generating circuit and the voltage value decreases, so that the power supply circuit is not complicated and the use of expensive switches is avoided. Even in such a case, it is possible to prevent the CRT spot from being generated.

[Brief description of drawings]

FIG. 1 is a block diagram showing an electrical configuration of a television using an embodiment of a DC power supply device according to the present invention.

FIG. 2 is a circuit diagram showing a detailed electrical connection between an error detection circuit and a step-down control circuit.

FIG. 3 is a timing chart showing waveforms of main signals when the operating state shifts to the standby state.

FIG. 4 is a block diagram showing a configuration of a conventional technique.

FIG. 5 is a block diagram showing a configuration of a conventional technique.

[Explanation of symbols]

 2 switching circuit 4 voltage control circuit 5 photocoupler 6 error detection circuit 7 step-down control circuit 8 microcomputer 9 step-down regulator 10 TV circuit 62 voltage dividing circuit

Claims (3)

[Claims] 1. A direct current output or a plurality of direct current outputs is provided, and the stabilized direct current output is supplied to a power supply target by feeding back a voltage error of the direct current output to a primary side via a photocoupler. A switching power supply, a step-down regulator that supplies an output obtained by stepping down the DC output to a predetermined voltage to a microcomputer that controls the operation of the power supply target, and when the microcomputer instructs standby,
By controlling the switching power supply, a step-down control circuit that steps down the voltage of the DC output supplied to the power supply target to a voltage at which the current value flowing to the power supply target becomes a value corresponding to the standby, A DC power supply device, wherein the voltage of the DC output supplied to the step-down regulator in the standby state is a voltage that enables the step-down regulator to supply the predetermined voltage to the microcomputer. 2. The step-down control circuit is provided in an error detection circuit for detecting the voltage error when a standby instruction is given from the microcomputer, and divides the voltage of the DC output and divides the divided voltage. The DC power supply device according to claim 1, wherein the voltage of the DC output is stepped down by reducing the voltage division ratio of the voltage dividing circuit compared with the reference voltage. 3. The DC power supply device according to claim 1, wherein the power supply target is a television circuit.