JP7548092B2 - Switch overcurrent detection device - Google Patents

Description

The present invention relates to an overcurrent detection device for a switch.

As a device for detecting overcurrent in a switch, one that uses the DESAT method is known, as seen in, for example, Non-Patent Document 1. This device includes a voltage detection unit that detects the inter-terminal voltage generated between the main terminals of the corresponding switch, and a determination unit. The voltage detection unit detects the inter-terminal voltage via a diode whose cathode is connected to the high-potential terminal of the corresponding switch. If the determination unit determines that the inter-terminal voltage detected by the voltage detection unit exceeds the threshold voltage, it determines that an overcurrent is flowing in the corresponding switch.

"Smart Gate Driver Coupler DESAT Detection Circuit Design Hints," Toshiba Electronic Devices & Storage Corporation, 2019

The DESAT method requires a diode to detect the voltage between the terminals of the corresponding switch. If a diode is provided in an overcurrent detection device, the device will become larger, for example by increasing the size of the printed board on which the diode is mounted. There is still room for improvement in overcurrent detection devices to address this issue.

The present invention was made in consideration of the above problems, and its main objective is to provide a switch overcurrent detection device that can be made smaller.

The present invention relates to a semiconductor switch that is connected in parallel with one another and has a body diode;
When some of the plurality of semiconductor switches are used as sub-switches and the remaining semiconductor switches are used as main switches, a capacitor having a first electrode connected to an anode side of the body diode constituting the sub-switch and a second electrode connected to a low potential side terminal side of the main switch;
a voltage detection unit that detects a voltage between the terminals of the capacitor;
and an overcurrent determination unit that determines that an overcurrent is flowing through the main switch when the inter-terminal voltage detected while the main switch is in an on state is greater than an overcurrent threshold.

Multiple semiconductor switches each having a body diode may be connected in parallel to one another. When some of these multiple semiconductor switches are used as sub-switches and the remaining semiconductor switches are used as main switches, it is possible to provide a diode in addition to the multiple semiconductor switches in order to detect overcurrent in the main switch using the DESAT method. However, providing a diode in addition to the multiple semiconductor switches creates the problem of the device becoming larger.

In this invention, therefore, the body diode of the sub-switch is used to detect an overcurrent in the main switch. Specifically, a capacitor is provided having a first electrode connected to the anode side of the body diode of the sub-switch, and a second electrode connected to the low potential terminal side of the main switch. If the terminal voltage of the capacitor detected when the main switch is in the on state is greater than the overcurrent threshold, it is determined that an overcurrent is flowing in the main switch. This makes it possible to detect an overcurrent in the main switch using body diodes that are provided in advance in multiple semiconductor switches, and allows the device to be made more compact.

Overall system configuration diagram. FIG. 2 is a diagram showing a semiconductor module. FIG. 2 is a diagram showing a semiconductor module and each connection portion. FIG. FIG. FIG. 4 is a diagram showing the positional relationship between a semiconductor module and a control board. 4 is a flowchart of an overcurrent detection process. FIG. 13 is a diagram showing a control board of a modified example. FIG. 13 is a diagram showing a control board of a modified example.

The following describes a first embodiment of the switch overcurrent detection device according to the present invention, which is applied to an in-vehicle system 100, with reference to the drawings.

As shown in FIG. 1, the system 100 includes a rotating electric machine 10, an inverter 20, and a control device 50. In this embodiment, the rotating electric machine 10 is a brushless synchronous machine, for example a permanent magnet synchronous machine. The rotating electric machine 10 includes a three-phase armature winding 11.

The rotating electric machine 10 is connected to a battery 30 as a DC power source via an inverter 20. The inverter 20 has a series connection of an upper arm switch element unit 20H and a lower arm switch element unit 20L for each phase. The first end of the corresponding armature winding 11 is electrically connected (hereinafter simply connected) to the connection point of the upper and lower arm switch element units 20H, 20L of each phase via a conductive member 21. The second end of the armature winding 11 of each phase is connected at a neutral point PT.

The upper and lower arm switch element sections 20H and 20L each include a parallel connection of a first switch SW1 as a "main switch" and a second switch SW2 as a "sub-switch." In this embodiment, voltage-controlled semiconductor switching elements are used as the first and second switches SW1 and SW2, and more specifically, N-channel MOSFETs are used as SiC devices. A first body diode DA1 is connected in inverse parallel to the first switch SW1, and a second body diode DA2 is connected in inverse parallel to the second switch SW2.

The first switch SW1 and the second switch SW2 have the same voltage-current characteristics (drain-source voltage Vds and drain current Id) and are composed of several hundred semiconductor switching elements connected in parallel. The second switch SW2 is composed of several semiconductor switching elements that are a part of these semiconductor switching elements, and the first switch SW1 is composed of the remaining semiconductor switching elements. Therefore, the current capacity of the second switch SW2 is smaller than the current capacity of the first switch SW1.

As shown in FIG. 2, in each phase, the upper and lower arm switch element units 20H and 20L are housed in a body unit BD and integrated into a semiconductor module MS. In this embodiment, the body unit BD has a flat rectangular parallelepiped shape.

The semiconductor module MS has a switch high-voltage terminal TP, a switch low-voltage terminal TN, and an intermediate terminal TO. The switch high-voltage terminal TP, the switch low-voltage terminal TN, and the intermediate terminal TO are provided protruding from one surface CA of the main body portion BD. The switch high-voltage terminal TP is connected to the drain, which is the high-potential terminal of each switch SW1, SW2 in the upper arm switch element portion 20H. The switch low-voltage terminal TN is connected to the source, which is the low-potential terminal of the first switch SW1 in the lower arm switch element portion 20L, and is connected to the source of the second switch SW2 in the lower arm switch element portion 20L via the capacitor 51 shown in FIG. 4.

The intermediate terminal TO is connected to the source of the first switch SW1 in the upper arm switch element section 20H, and is also connected to the source of the second switch SW2 in the upper arm switch element section 20H via a capacitor 51. The intermediate terminal TO is also connected to the drains of the switches SW1 and SW2 in the lower arm switch element section 20L.

Furthermore, the semiconductor module MS has an anode terminal TA, a cathode terminal TK, a control terminal TS, a detection terminal TD, and a ground terminal TG. These terminals protrude from the face CB opposite the face CA of the main body portion BD, and are provided for each of the upper and lower arm switch element portions 20H and 20L. The method of connecting these terminals will be described in detail later.

As shown in FIG. 3, the switch high-voltage terminal TP of each semiconductor module MS is connected to the high-voltage conductive member BP via a conductive high-voltage connection part 30P. The high-voltage conductive member BP is connected to the positive terminal of the battery 30. In addition, the switch low-voltage terminal TN of each semiconductor module MS is connected to the low-voltage conductive member BN via a conductive low-voltage connection part 30N. The low-voltage conductive member BN is connected to the negative terminal of the battery 30. The intermediate terminal TO of each semiconductor module MS is connected to the first end of the armature winding 11.

In this embodiment, the system 100 includes a cooling device 40. As shown in FIG. 3, the cooling device 40 includes a pair of cooling pipes 41 and a plurality of cooling plates 42. The semiconductor module MS is sandwiched between the cooling plates 42. The cooling pipes 41 and the cooling plates 42 form a cooling passage through which a cooling fluid flows.

Returning to FIG. 1, the inverter 20 is provided with a smoothing capacitor 23 on its input side, which smoothes the input voltage of the inverter 20. The high-potential terminal of the smoothing capacitor 23 is connected to the positive terminal of the battery 30, and the low-potential terminal of the smoothing capacitor 23 is connected to the negative terminal of the battery 30.

The control device 50 performs switching control of each switch SW1, SW2 constituting the inverter 20 to control the control amount of the rotating electric machine 10 to a command value in order to perform drive control of the rotating electric machine 10. The control amount is, for example, torque. The control device 50 outputs drive commands SA corresponding to the upper and lower arm switches to drive circuits Dr individually provided for each switch element unit 20H, 20L so that the switch included in the upper arm switch element unit 20H and the switch included in the lower arm switch element unit 20L are alternately turned on with dead time DT in between. The drive command SA is either an on command or an off command.

The drive circuit Dr performs switching control to control the drive state of the first switch SW1 of the first and second switches SW1 and SW2 based on the drive command SA input from the control device 50. The drive circuit Dr also detects overcurrent in the first switch SW1 using the DESAT method. The configuration of the drive circuit Dr will be described below with reference to FIG. 4.

Figure 4 shows the configuration of the drive circuit Dr corresponding to the upper and lower arm switch element parts 20H and 20L. First, the drive circuit Dr corresponding to the upper arm switch element part 20H will be described. The drive circuit Dr includes a capacitor 51, a comparator 52, a constant voltage power supply 53, a control circuit 54, and a constant current source 55. The constant current source 55 is connected to the first electrode of the capacitor 51, and outputs a charging current to the capacitor 51 in order to detect an overcurrent by the DESAT method. In this embodiment, the charging current of the constant current source 55 is prevented from becoming large, and specifically, the charging current is, for example, several hundred μA. The second electrode of the capacitor 51 is connected to the source of the first switch SW1 and the conductive member 21.

The anode of the second body diode DA2 is connected to the first electrode of the capacitor 51. The cathode of the second body diode DA2 is connected to the drain of the first switch SW1. In other words, the second body diode DA2 is connected so that the forward direction is from the capacitor 51 to the drain of the first switch SW1. Therefore, as shown in (Equation 1), a determination voltage Vjd, which is the sum of the drain-source voltage Vds of the first switch SW1 and the forward voltage Vf of the second body diode DA2, is applied as a terminal voltage to the capacitor 51.

Vjd=Vds+Vf...(Formula 1)
A first electrode of the capacitor 51 is connected to a non-inverting input terminal 52A of a comparator 52. An inverting input terminal 52B of the comparator 52 is connected to a positive terminal of a constant voltage power supply 53. A negative terminal of the constant voltage power supply 53 is connected to a positive terminal of the constant voltage power supply 53. , is connected to the source of the first switch SW1. The constant-voltage power supply 53 outputs a voltage that is higher than the source of the first switch SW1 by the overcurrent threshold Vth to the inverting input terminal 52B of the comparator 52. The comparator 52 The determination voltage Vjd inputted from a pair of input terminals 52A, 52B is compared with an overcurrent threshold Vth, and a signal indicating which is larger or smaller is outputted from an output terminal 52C.

The control circuit 54 is connected to the gate of the first switch SW1 via the control line LS. The gate of the second switch SW2 is connected to the source of the first switch SW1. Therefore, the second switch SW2 is always maintained in the off state. The control circuit 54 is also connected to the source of the first switch SW1. Furthermore, the control circuit 54 is connected to the output terminal 52C of the comparator 52, and detects an overcurrent in the first switch SW1 based on the signal output from the output terminal 52C.

In this embodiment, the semiconductor module MS is provided with a temperature sensing diode DK that detects the temperature of the switches SW1 and SW2 in each arm switch element portion 20H and 20L. The control circuit 54 is connected to the anode and cathode of the corresponding temperature sensing diode DK.

The configuration of the drive circuit Dr corresponding to the lower arm switch element unit 20L is the same as the configuration of the drive circuit Dr corresponding to the upper arm switch element unit 20H, and a duplicated explanation will be omitted. In the drive circuit Dr corresponding to the lower arm switch element unit 20L, the second electrode of the capacitor 51 is connected to the source of the first switch SW1 and the negative terminal of the battery 30.

In this embodiment, the constant current source 55, capacitor 51, comparator 52, constant voltage power supply 53, and control circuit 54 that constitute the drive circuit Dr are configured as a semiconductor integrated circuit IC integrated into a single chip. As shown in FIG. 5, the semiconductor integrated circuit IC is mounted on the mounting surface CD of the control board KS. In this embodiment, the mounting surface CD corresponds to the "board surface."

The mounting surface CD of the control board KS is provided with a plurality of through-hole electrodes connected to the anode terminal TA, cathode terminal TK, control terminal TS, detection terminal TD, and ground terminal TG of the semiconductor module MS. The plurality of through-hole electrodes include an anode hole HA, a cathode hole HK, a control hole HS, a detection hole HD, and a ground hole HG. The anode hole HA is connected to the anode terminal TA, and is connected to the anode of the temperature-sensing diode DK via the anode terminal TA. The cathode hole HK is connected to the cathode terminal TK, and is connected to the cathode of the temperature-sensing diode DK via the cathode terminal TK.

The control hole HS is connected to the control terminal TS and is connected to the gate of the first switch SW1 via the control terminal TS. The detection hole HD is connected to the detection terminal TD and is connected to the source of the second switch SW2 (the anode of the second body diode DA2) via the detection terminal TD. The ground terminal TG is connected to the ground terminal TG and is connected to the source of the first switch SW1 via the ground terminal TG.

Moreover, the mounting surface CD of the control board KS is provided with a plurality of connection wirings that connect these through-hole electrodes to the semiconductor integrated circuit IC. The plurality of connection wirings include an anode wiring LA, a cathode wiring LB, a control wiring LS, a detection wiring LD, and a ground wiring LG. The anode wiring LA connects the anode hole HA to the semiconductor integrated circuit IC. The cathode wiring LB connects the cathode hole HK to the semiconductor integrated circuit IC. The control wiring LS connects the control hole HS to the semiconductor integrated circuit IC. The detection wiring LD connects the detection hole HD to the semiconductor integrated circuit IC. The ground wiring LG connects the ground hole HG to the semiconductor integrated circuit IC.

On the mounting surface CD of the control board KS, the anode wiring LA, cathode wiring LB, control wiring LS, detection wiring LD, and ground wiring LG are arranged in this order and parallel to one another. Electronic components DB such as chip resistors or chip capacitors are arranged on or between these paths.

As shown in FIG. 6, in this embodiment, the semiconductor module MS and the control board KS are arranged so as to be perpendicular to each other and are connected to each other. Specifically, each terminal of the semiconductor module MS is inserted into a corresponding through-hole electrode of the control board KS so as to intersect with the mounting surface CD of the control board KS and is connected to the mounting surface CD. As a result, the semiconductor module MS and the control board KS are arranged at a distance from each other. The "overcurrent detection device" of this embodiment is constituted by the semiconductor module MS and the control board KS.

Next, a method for determining an overcurrent in the control circuit 54 will be described. When no overcurrent flows through the first switch SW1, when the first switch SW1 is switched to the on state, the drain-source voltage Vds of the first switch SW1 is reduced to and held at the saturation voltage. Here, the saturation voltage refers to the voltage at which the drain-source voltage Vds stops decreasing when the drain current Id flowing through the first switch SW1 is increased. When no overcurrent flows through the first switch SW1, the drain-source voltage Vds is held at the saturation voltage, and therefore the determination voltage Vjd is held at a value smaller than the overcurrent threshold Vth.

On the other hand, if an overcurrent equal to or greater than the threshold current flows through the first switch SW1 due to a short circuit between the upper and lower arms, the drain-source voltage Vds does not decrease to the saturation voltage. Therefore, the determination voltage Vjd becomes greater than the overcurrent threshold Vth, and the control circuit 54 determines that an overcurrent is flowing through the first switch SW1.

However, in order to detect an overcurrent in the first switch SW1 in the DESAT method, a diode is required, and it is possible to provide a diode in addition to the first and second switches SW1 and SW2 and the first and second body diodes DA1 and DA2. In this case, the diode needs to be mounted on the control board KS, which causes the problem of the control board KS becoming larger. In addition, since the diode used in the DESAT method is connected to the drain, which is the high-potential terminal of the second switch SW2, it is necessary to ensure an insulation distance between the diode in the control board KS and other electronic components DB, which causes a problem of reduced artworkability of the control board KS.

In this embodiment, the second body diode DA2 of the second switch SW2 is used to detect an overcurrent in the first switch SW1. Therefore, there is no need to mount a diode on the control board KS. As a result, the device can be made smaller while improving the artwork.

Next, the overcurrent detection process performed by the control circuit 54 will be described with reference to FIG. 7. This process is repeatedly executed at a predetermined control period.

In step S10, the first switch SW1 is switched to the on state. In the following step S11, the comparator 52 is used to detect the judgment voltage (hereinafter, simply the judgment voltage) Vjd of the first switch SW1, and the process proceeds to step S12. In this embodiment, the process of step S12 corresponds to the "voltage detection unit."

In step S12, it is determined whether the determination voltage Vjd detected in step S11 is greater than the overcurrent threshold Vth. Specifically, the control circuit 54 determines whether the determination voltage Vjd is greater than the overcurrent threshold Vth based on the signal output from the output terminal 52C of the comparator 52.

If no overcurrent is flowing through the first switch SW1, the judgment voltage Vjd is equal to or lower than the overcurrent threshold Vth, and a negative judgment is made in step S12. In this case, the overcurrent detection process ends. On the other hand, if the first switch SW1 of the opposing arm switch element unit has a short circuit failure and an overcurrent is flowing through the first switch SW1, the judgment voltage Vjd becomes greater than the overcurrent threshold Vth, and a positive judgment is made in step S12. In this case, proceed to step S13.

In step S13, it is determined that an overcurrent is flowing through the first switch SW1. In the following step S14, the first switch SW1 is switched to the off state, and the overcurrent detection process is terminated. In this embodiment, the processes of steps S12 and S13 correspond to the "overcurrent determination unit", and the processes of steps S10 and S14 correspond to the "state control unit".

The present embodiment described above provides the following advantages:

To detect an overcurrent in the first switch SW1 using the DESAT method, a diode is required. In this embodiment, the second body diode DA2 of the second switch SW2 is used to detect an overcurrent in the first switch SW1. This eliminates the need to provide diodes in addition to the first and second switches SW1 and SW2, making it possible to miniaturize the device.

In this embodiment, the semiconductor module MS and the control board KS are arranged so as to be perpendicular to each other and spaced apart from each other. Therefore, by mounting the semiconductor integrated circuit IC and electronic component DB on the control board KS, these can be arranged at a distance from the second body diode DA2 of the second switch SW2, and there is no need to ensure an insulation distance in the control board KS. This allows the device to be made more compact and the artworkability of the control board KS to be improved.

When the second body diode DA2 of the second switch SW2 is used to detect an overcurrent in the first switch SW1, when switching control of the second switch SW2 is performed to control the drive of the rotating electric machine 10, an unintended current flows between the anode and cathode of the second body diode DA2 via the second switch SW2. This reduces the accuracy of detecting an overcurrent in the first switch SW1. In this embodiment, the gate of the second body diode DA2 is connected to the source of the first switch SW1, and the second switch SW2 is constantly maintained in the off state. As a result, it is possible to improve the accuracy of detecting an overcurrent in the first switch SW1.

When the second body diode DA2 of the second switch SW2 is used to detect an overcurrent in the first switch SW1, the switching function of the second switch SW2 is lost. In this embodiment, the current capacity of the second switch SW2 is set smaller than the current capacity of the first switch SW1. This makes it possible to protect the first switch SW1 from an overcurrent using the second body diode DA2 of the second switch SW2, which has a small current capacity, while ensuring the switching function of the first switch SW1, which has a large current capacity.

In this embodiment, the charging current of the constant current source 55 is suppressed so as not to become large in response to the relatively small current capacity of the second switch SW2. This improves the accuracy of detecting an overcurrent of the first switch SW1.

Other Embodiments
Each of the above embodiments may be modified as follows.

- In the above embodiment, an example was described in which the anode wiring LA, cathode wiring LB, control wiring LS, detection wiring LD, and ground wiring LG are arranged in this order and parallel to one another on the mounting surface CD of the control board KS. However, the order in which these wirings are arranged is not limited to the above. In this case, the ground wiring LG may be arranged between the control wiring LS and the detection wiring LD.

The detection wiring LD is connected to the second body diode DA2 and capacitor 51 used for overcurrent detection by the DESAT method. Therefore, the detection wiring LD has a high impedance and is prone to noise due to signal switching in adjacent wiring. Therefore, as shown in FIG. 5, if the control wiring LS and the detection wiring LD are arranged adjacent to each other, there is a risk of erroneous detection of an overcurrent due to the drive signal input to the gate of the first switch SW1 being switched between an on voltage and an off voltage.

As shown in FIG. 8, the terminal arrangement in the semiconductor integrated circuit IC may be changed so that the ground wiring LG is disposed between the control wiring LS and the detection wiring LD. This can prevent erroneous detection of overcurrent.

When the terminal arrangement in the semiconductor module MS can be changed, the arrangement of the through-hole electrodes in the control substrate KS may be changed as shown in FIG. 9. Specifically, a ground hole HG may be arranged between the control hole HS and the detection hole HD. This makes it possible to appropriately prevent erroneous detection of overcurrent. It is also possible to prevent the control substrate KS from becoming larger due to the routing of the paths between the through-hole electrodes and the semiconductor integrated circuit IC.

- In the above embodiment, three or more switches may be connected in parallel to each of the arm switch element sections 20H and 20L.

51: Capacitor, 54: Control circuit, SW1: First switch, SW2: Second switch.

Claims (5)

a main switch (SW1) which is a semiconductor switch having a drain, a source, a gate and a first body diode (DA1);
a sub-switch (SW2) which is a semiconductor switch having a drain, a source, a gate and a second body diode (DA2);
a capacitor (51) having a first electrode connected to the anode side of the second body diode and a second electrode connected to the source side of the main switch;
A voltage detection unit (54) that detects a voltage between the terminals of the capacitor;
a constant current source (55) connected to a first electrode of the capacitor;
An overcurrent determination unit (54),
The drain of the sub switch is connected to the drain of the main switch,
The sub-switch is always maintained in an off state,
The overcurrent determination unit determines that an overcurrent is flowing through the main switch when the inter-terminal voltage detected when the main switch is in an on state is greater than an overcurrent threshold . a semiconductor module (MS) having a body (BD) in which the main switch and the sub switch are housed, and a control terminal (TS) electrically connected to a gate of the main switch and protruding from the body;
a control board (KS) having a plate surface to which the control terminal is connected;
Equipped with
the control terminal is connected to a plate surface of the control board so as to intersect with the plate surface,
2. The switch overcurrent detection device according to claim 1, wherein the capacitor, the voltage detection section, and the overcurrent determination section are provided on a surface of the control board. A state control unit (54) is provided on a surface of the control board and controls the driving state of the main switch,
The control board includes:
A control line (LS) that connects a gate of the main switch and the state control unit;
a detection wiring (LD) connecting an anode side of the second body diode and a first electrode of the capacitor;
a ground wiring (LG) connected to a source side of the main switch;
the control wiring, the detection wiring, and the ground wiring are arranged in parallel with each other on the control substrate,
The switch overcurrent detection device according to claim 2 , wherein the ground wiring is disposed between the control wiring and the detection wiring on the control board. 4. The switch overcurrent detection device according to claim 1, wherein a gate of the sub switch is connected to a source side of the main switch. The switch overcurrent detection device according to any one of claims 1 to 4, wherein the sub-switch has a smaller current capacity than the main switch.

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