JP2022149223A - Switch overcurrent detection device - Google Patents

Abstract

To provide a switch overcurrent detection device capable of miniaturizing the device.SOLUTION: A switch overcurrent detection device includes a plurality of semiconductor switches SW1 and SW2 connected in parallel with each other and having body diodes, a capacitor 51 having a first electrode connected to the anode side of a body diode constituting a sub-switch and a second electrode connected to the low-potential side terminal side of a main switch when some semiconductor switches among the plurality of semiconductor switches are used as the sub switch SW2 and the remaining semiconductor switches are used as the main switch SW1, a voltage detection unit 54 that detects the voltage between the terminals of the capacitor, and an overcurrent determination unit 54 that determines that an overcurrent is flowing through the main switch when the voltage between the terminals detected when the main switch is in the ON state is greater than an overcurrent threshold.SELECTED DRAWING: Figure 4

Description

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

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

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

The DESAT scheme requires a diode to detect the voltage across the corresponding switch. If a diode is provided in the overcurrent detection device, the size of the device increases, for example, the size of the printed board on which the diode is mounted increases. With respect to such problems, there is still room for improvement in overcurrent detection devices.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and a main object thereof is to provide an overcurrent detection device for a switch that can be downsized.

The present invention comprises a plurality of semiconductor switches connected in parallel with each other and having body diodes;
a first electrode connected to an anode side of the body diode constituting the sub-switches, when some of the plurality of semiconductor switches are sub-switches and the remaining semiconductor switches are main switches; a capacitor having a second electrode connected to the low potential side terminal of the main switch;
a voltage detection unit that detects a voltage between terminals of the capacitor;
an overcurrent determination unit that 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.

Multiple semiconductor switches with body diodes may be connected in parallel with each other. When some of these semiconductor switches are used as sub-switches and the remaining semiconductor switches are used as main switches, in order to detect overcurrent in the main switches by the DESAT method, the semiconductor switches are It is conceivable to provide a separate diode. However, if diodes are provided separately from the plurality of semiconductor switches, there arises a problem that the size of the device increases.

Therefore, in the present invention, the body diode of the sub-switch is used to detect the overcurrent of the main switch. Specifically, a capacitor having a first electrode connected to the anode side of the body diode of the sub switch and a second electrode having a second electrode connected to the low potential side terminal side of the main switch is provided. . Then, when the voltage across the terminals of the capacitor detected when the main switch is turned on is greater than the overcurrent threshold, it is determined that overcurrent is flowing through the main switch. As a result, overcurrent in the main switch can be detected using body diodes provided in advance in the plurality of semiconductor switches, and the size of the device can be reduced.

Overall configuration diagram of the system. The figure which shows a semiconductor module. FIG. 4 is a diagram showing a semiconductor module and each connecting portion; The figure which shows a drive circuit. The figure which shows a control board. FIG. 4 is a diagram showing a positional relationship between a semiconductor module and a control board; 4 is a flowchart of overcurrent detection processing; The figure which shows the control board of a modification. The figure which shows the control board of a modification.

A first embodiment in which an overcurrent detection device for a switch according to the present invention is applied to an in-vehicle system 100 will be described below 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. As shown in FIG. In this embodiment, the rotating electric machine 10 is a brushless synchronous machine, such as a permanent magnet synchronous machine. A rotating electric machine 10 includes a three-phase armature winding 11 .

Rotating electric machine 10 is connected to battery 30 as a DC power supply via inverter 20 . The inverter 20 includes a series connection body of an upper arm switch element portion 20H and a lower arm switch element portion 20L for each phase. A first end of the corresponding armature winding 11 is electrically connected (hereinafter simply connected) to a connection point between the upper and lower arm switch element portions 20H and 20L of each phase via a conductive member 21. . A second end of the armature winding 11 of each phase is connected at a neutral point PT.

The upper and lower arm switch element units 20H and 20L are provided with a parallel connection body 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 as SiC devices are used. A first body diode DA1 is anti-parallel connected to the first switch SW1, and a second body diode DA2 is anti-parallel connected to the second switch SW2.

The first switch SW1 and the second switch SW2 have the same voltage-current characteristics of the drain-source voltage Vds and the drain current Id, and are composed of several hundred semiconductor switching elements connected in parallel with each other. A second switch SW2 is composed of several semiconductor switching elements which are a part of these semiconductor switching elements, and a 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 portions 20H and 20L are accommodated in the body portion BD and integrated as a semiconductor module MS. In this embodiment, the body portion 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. A switch high-voltage terminal TP, a switch low-voltage terminal TN, and an intermediate terminal TO are provided so as to protrude from one surface CA of the body portion BD. The switch high-voltage terminal TP is connected to drains, which are high-potential terminals of the switches SW1 and SW2 in the upper arm switch element section 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 section 20L, and is connected to the second switch terminal TN in the lower arm switch element section 20L via the capacitor 51 shown in FIG. It is connected to the source of switch SW2.

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 via the capacitor 51 to the source of the second switch SW2 in the upper arm switch element section 20H. The intermediate terminal TO is 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 a surface CB of the body portion BD facing the surface CA, and are provided for each of the upper and lower arm switch element portions 20H and 20L. A 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 a high-voltage conductive member BP via a conductive high-voltage connection 30P. The high voltage conductive member BP is connected to the positive terminal of the battery 30 . Also, the switch low-voltage terminal TN of each semiconductor module MS is connected to a low-voltage conductive member BN via a conductive low-voltage connection portion 30N. The low voltage conductive member BN is connected to the negative terminal of the battery 30 . An intermediate terminal TO of each semiconductor module MS is connected to the first end of the armature winding 11 .

Note that the system 100 includes a cooling device 40 in this embodiment. The cooling device 40 includes a pair of cooling pipes 41 and a plurality of cooling plates 42, as shown in FIG. Semiconductor module MS is provided in a state of being sandwiched between cooling plates 42 . The cooling pipe 41 and the cooling plate 42 constitute a cooling passage through which cooling fluid flows.

Returning to FIG. 1, the inverter 20 has a smoothing capacitor 23 on its input side for smoothing the input voltage of the inverter 20 . A high potential side terminal of the smoothing capacitor 23 is connected to the positive terminal of the battery 30 , and a low potential side terminal of the smoothing capacitor 23 is connected to the negative terminal of the battery 30 .

In order to drive and control the rotary electric machine 10, the control device 50 performs switching control of the switches SW1 and SW2 forming the inverter 20 in order to control the control amount of the rotary electric machine 10 to a command value. The controlled variable is, for example, torque. The control device 50 corresponds to the upper and lower arm switches so as to alternately turn on the switches included in the upper arm switch element section 20H and the switches included in the lower arm switch element section 20L while interposing the dead time DT. A drive command SA for switching is output to a drive circuit Dr provided individually for each of the switch element units 20H and 20L. The drive command SA takes either an ON command or an OFF command.

The driving circuit Dr performs switching control for controlling the driving state of the first switch SW1 out of the first and second switches SW1 and SW2 based on the driving command SA input from the control device 50 . Further, the drive circuit Dr detects overcurrent of the first switch SW1 by the DESAT method. The configuration of the drive circuit Dr will be described below with reference to FIG.

FIG. 4 shows the configuration of the drive circuit Dr corresponding to the upper and lower arm switch element sections 20H and 20L. First, the drive circuit Dr corresponding to the upper arm switch element section 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 . A 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 overcurrent by the DESAT method. In this embodiment, the charging current of the constant current source 55 is suppressed from becoming a large current, and specifically, the charging current is several hundred μA, for example. A second electrode of the capacitor 51 is connected to the source of the first switch SW1 and the conductive member 21 .

A first electrode of the capacitor 51 is connected to an anode of the second body diode DA2. The cathode of the second body diode DA2 is connected to the drain of the first switch SW1. That is, the second body diode DA2 is connected so that the direction from the capacitor 51 to the drain of the first switch SW1 is the forward direction. Therefore, as shown in (Equation 1), the capacitor 51 receives a determination voltage Vjd, which is a voltage obtained by adding the forward voltage Vf of the second body diode DA2 to the drain-source voltage Vds of the first switch SW1. applied as a voltage between

Vjd=Vds+Vf (Formula 1)
A first electrode of the capacitor 51 is connected to a non-inverting input terminal 52A of the comparator 52 . The inverting input terminal 52B of the comparator 52 is connected to the positive terminal of the constant voltage power supply 53 . A negative 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 to the inverting input terminal 52B of the comparator 52 a voltage that is higher than the source of the first switch SW1 by the overcurrent threshold value Vth. The comparator 52 compares the determination voltage Vjd input from the pair of input terminals 52A and 52B with the overcurrent threshold Vth, and outputs a signal indicating the magnitude relationship between them from the output terminal 52C.

The control circuit 54 is connected to the gate of the first switch SW1 via the control wiring 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 kept off. Also, the control circuit 54 is 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 overcurrent of the first switch SW1 based on the signal output from the output terminal 52C.

In this embodiment, the semiconductor module MS is provided with temperature-sensitive diodes DK for detecting the temperature of the switches SW1 and SW2 in the respective arm switch element portions 20H and 20L. The control circuit 54 is connected to the anode and cathode of the corresponding temperature sensitive diode DK.

The configuration of the drive circuit Dr corresponding to the lower arm switch element section 20L is the same as the configuration of the drive circuit Dr corresponding to the upper arm switch element section 20H, and redundant description will be omitted. In the drive circuit Dr corresponding to the lower arm switch element section 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, the capacitor 51, the comparator 52, the constant voltage power source 53 and the control circuit 54 that constitute the drive circuit Dr are configured by a single-chip semiconductor integrated circuit IC. As shown in FIG. 5, the semiconductor integrated circuit IC is mounted on the mounting surface CD of the control board KS. In addition, in this embodiment, the mounting surface CD corresponds to the “board surface”.

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

A plurality of connection wirings for connecting these through-hole electrodes and the semiconductor integrated circuit IC are provided on the mounting surface CD of the control substrate KS. The plurality of connection wirings include anode wirings LA, cathode wirings LB, control wirings LS, detection wirings LD and ground wirings LG. The anode wiring LA connects the anode hole HA and the semiconductor integrated circuit IC. The cathode wiring LB connects the cathode hole HK and the semiconductor integrated circuit IC. The control wiring LS connects the control hole HS and the semiconductor integrated circuit IC. The detection wiring LD connects the detection hole HD and the semiconductor integrated circuit IC. The ground wiring LG connects the ground hole HG and the semiconductor integrated circuit IC.

On the mounting surface CD of the control substrate KS, the anode wiring LA, cathode wiring LB, control wiring LS, detection wiring LD and ground wiring LG are arranged in this order so as to be parallel to each other. 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 connected to each other while being arranged so as to be orthogonal to each other. Specifically, each terminal of the semiconductor module MS is inserted into a corresponding through-hole electrode of the control substrate KS so as to cross the mounting surface CD of the control substrate KS, and is connected to the mounting surface CD. As a result, each of the semiconductor module MS and the control board KS is arranged apart from each other. The semiconductor module MS and the control board KS constitute the "overcurrent detection device" of the present embodiment.

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 turned on, the drain-source voltage Vds of the first switch SW1 is kept reduced to the saturation voltage. Here, the saturation voltage is the voltage when 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, so 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 higher than the overcurrent threshold Vth, and the control circuit 54 determines that an overcurrent is flowing through the first switch SW1.

By the way, in order to detect the overcurrent of the first switch SW1 in the DESAT method, a diode is required. can be considered. In this case, it is necessary to mount the diode on the control board KS, which causes a problem of increasing the size of the control board KS. Also, since the diode used in the DESAT method is connected to the drain, which is the high-potential side terminal of the second switch SW2, an insulating distance is secured between the diode on the control board KS and the other electronic component DB. Therefore, there arises a problem that the artwork property of the control board KS is deteriorated.

In this embodiment, the overcurrent of the first switch SW1 is detected using the second body diode DA2 of the second switch SW2. Therefore, it is not necessary to mount a diode on the control board KS. As a result, it is possible to improve artwork quality while downsizing the device.

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

In step S10, the first switch SW1 is turned on. In the subsequent step S11, the comparator 52 is used to detect the determination voltage (hereinafter simply referred to as the determination voltage) Vjd of the first switch SW1, and the process proceeds to step S12. It should be noted that in the present embodiment, the process of step S12 corresponds to the "voltage detector".

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

If no overcurrent is flowing through the first switch SW1, the determination voltage Vjd is equal to or less than the overcurrent threshold Vth, and a negative determination is made in step S12. In this case, the overcurrent detection process ends. On the other hand, when the first switch SW1 of the opposing arm switch element section is short-circuited and an overcurrent is flowing through the first switch SW1, the determination voltage Vjd becomes larger than the overcurrent threshold Vth, and an affirmative determination is made in step S12. In this case, the process proceeds to step S13.

In step S13, it is determined that overcurrent is flowing through the first switch SW1. In the subsequent step S14, the first switch SW1 is switched to the OFF state, and the overcurrent detection process ends. In this embodiment, the processing of steps S12 and S13 corresponds to the "overcurrent determination unit", and the processing of steps S10 and S14 corresponds to the "state control unit".

According to this embodiment detailed above, the following effects can be obtained.

A diode is required to detect the overcurrent of the first switch SW1 in the DESAT method. In this embodiment, the overcurrent of the first switch SW1 is detected using the second body diode DA2 of the second switch SW2. Therefore, it is not necessary to provide diodes separately from the first and second switches SW1 and SW2, and the size of the device can be reduced.

In this embodiment, the semiconductor module MS and the control board KS are arranged so as to be orthogonal to each other and are arranged apart from each other. Therefore, by mounting the semiconductor integrated circuit IC and the electronic component DB on the control board KS, they can be spaced apart from the second body diode DA2 of the second switch SW2. need not be ensured. As a result, the apparatus can be made more compact, and the artwork of the control board KS can be further improved.

When the overcurrent of the first switch SW1 is detected using the second body diode DA2 of the second switch SW2, when the switching control of the second switch SW2 is performed to control the driving of the rotary electric machine 10, the second An unintended current flows between the anode and cathode of the second body diode DA2 via the switch SW2. As a result, the overcurrent detection accuracy of the first switch SW1 is lowered. In this embodiment, the gate of the second body diode DA2 is connected to the source of the first switch SW1 so that the second switch SW2 is always kept off. As a result, the overcurrent detection accuracy of the first switch SW1 can be improved.

If the second body diode DA2 of the second switch SW2 is used to detect overcurrent in the first switch SW1, the switching function in the second switch SW2 is lost. In this embodiment, the current capacity of the second switch SW2 is made smaller than the current capacity of the first switch SW1. As a result, the first switch SW1 can be protected from overcurrent by using the second body diode DA2 of the second switch SW2 with a small current capacity while ensuring the switching function of the first switch SW1 with a large current capacity. .

In the present embodiment, the charging current of the constant current source 55 is suppressed so as not to become a large current, corresponding to the relatively small current capacity of the second switch SW2. Therefore, it is possible to improve the detection accuracy of the overcurrent of the first switch SW1.

(Other embodiments)
It should be noted that each of the above-described embodiments may be modified as follows.

In the above embodiment, the anode wiring LA, the cathode wiring LB, the control wiring LS, the detection wiring LD, and the ground wiring LG are arranged parallel to each other in this order on the mounting surface CD of the control substrate KS. explained. However, the arrangement order of these wirings 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 the capacitor 51 used for overcurrent detection by the DESAT method. Therefore, the detection wiring LD has high impedance, and noise is likely to occur due to switching of signals in adjacent wirings. Therefore, as shown in FIG. 5, when the control wiring LS and the detection wiring LD are arranged adjacent to each other, the drive signal input to the gate of the first switch SW1 is switched between the ON voltage and the OFF voltage. , there is a risk of erroneous detection of overcurrent.

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

If the terminal layout in the semiconductor module MS can be changed, the layout of the through-hole electrodes in the control substrate KS may be changed as shown in FIG. Specifically, the ground hole HG may be arranged between the control hole HS and the detection hole HD. As a result, erroneous detection of overcurrent can be properly suppressed. In addition, it is possible to suppress an increase in the size of the control substrate KS due to routing of 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 elements 20H and 20L.

51...capacitor, 54...control circuit, SW1...first switch, SW2...second switch.

Claims (5)

a plurality of semiconductor switches (SW1, SW2) connected in parallel with each other and having body diodes;
When some of the plurality of semiconductor switches are used as sub-switches (SW2) and the remaining semiconductor switches are used as main switches (SW1), the body diodes constituting the sub-switches are connected to the anode side of the body diodes. a capacitor (51) having a first electrode and a second electrode connected to the low-potential terminal side of the main switch;
a voltage detection unit (54) for detecting a voltage between terminals of the capacitor;
an overcurrent determination unit (54) that 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; An overcurrent detector for a switch comprising: A semiconductor module (MS) having a main body (BD) housing a plurality of semiconductor switches connected in parallel and a control terminal (TS) electrically connected to the gate of the main switch and protruding from the main body (MS). When,
a control board (KS) having a plate surface to which the control terminals are connected;
with
The control terminal is connected to the plate surface of the control board so as to intersect with the plate surface,
2. The overcurrent detection device for a switch according to claim 1, wherein said capacitor, said voltage detection section, and said overcurrent determination section are provided on a board surface of said control board. A state control unit (54) provided on the plate surface of the control board for controlling the driving state of the main switch,
The control board is
a control wiring (LS) connecting the gate of the main switch and the state control unit;
a detection wiring (LD) that connects the anode side of the body diode and the first electrode of the capacitor that constitute the sub-switch;
a ground wiring (LG) connected to the low-potential side terminal 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;
3. The overcurrent detection device for a switch according to claim 2, wherein said ground wiring is disposed between said control wiring and said detection wiring on said control board. 4. The switch overcurrent detection device according to claim 1, wherein the gate of the sub-switch is connected to the low-potential side terminal of the main switch. 5. The switch overcurrent detection device according to claim 1, wherein the sub-switch has a current capacity smaller than that of the main switch.

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