JP2015061406A - Power module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power module that allows achieving both reduction in switching loss and a recovery current in turn-on operation at the time of switching, and allows achieving low noise.SOLUTION: In a power module 100 according to the present invention, a driving circuit 11 includes an output switching circuit 12 for switching output signals supplied to a control terminal of a switching element 13. The output switching circuit 12 cycles a drive capability for an output signal to drive the switching element 13 from a first drive capability to a second drive capability to a third drive capability. The second drive capability is higher than the first drive capability, and the third drive capability is lower than the second drive capability.

Description

  The present invention relates to a power module, and more particularly to a power module including a switching element and a drive circuit for driving the switching element.

  Conventionally, in a drive circuit for driving a switching element, in order to achieve both suppression of switching loss of a switching element such as a MOSFET and suppression of recovery current, in the turn-on operation, the drive is driven with a relatively high driving ability at the initial turn-on, and A technique of driving with a relatively low driving capability has been used (see, for example, Patent Document 1).

JP 2012-147492 A

  However, the above prior art has the following problems to be solved. That is, since driving is performed with a relatively high driving capability at the beginning of turn-on, the rise of current becomes steep, and the time change (dv / dt) of the gate voltage becomes steep at this timing, so that the generation of electromagnetic noise increases. there were.

  The present invention has been made to solve the above-described problems, and in a turn-on operation at the time of switching, a power module that can suppress switching loss and suppress recovery current and can reduce noise. For the purpose of provision.

  A power module according to the present invention is a power module that includes a switching element and a drive circuit that drives the switching element, and the drive circuit includes an output switching circuit that switches an output signal applied to a control terminal of the switching element, The output switching circuit switches the driving ability of the output signal to drive the switching element when the switching element is turned on in the order of the first driving ability, the second driving ability, and the third driving ability. The third driving capability is higher than the first driving capability, and the third driving capability is lower than the second driving capability.

  According to the power module of the present invention, the switching element is driven with a relatively high driving capability in the middle period of the turn-on operation, and is driven with a relatively low driving capability in the final period, thereby suppressing the switching loss and the recovery current. It is possible to achieve both suppression. Further, by driving the switching element with a relatively low driving capability in the early stage of the turn-on operation, it is possible to moderate the time change (dv / dt) of the gate voltage and suppress the generation of electromagnetic noise.

2 is a functional block diagram of a power module according to Embodiment 1. FIG. FIG. 3 is a diagram showing an outline of the operation of the power module according to the first embodiment. 1 is a circuit diagram of a power module according to Embodiment 1. FIG. FIG. 3 is a diagram showing an operation sequence of the power module according to the first embodiment. 4 is a circuit diagram of a power module according to Embodiment 2. FIG. FIG. 10 is a diagram showing an operation sequence of the power module according to the second embodiment. 6 is a circuit diagram of a power module according to Embodiment 3. FIG. FIG. 10 is a diagram illustrating an operation sequence of a power module according to a third embodiment. FIG. 6 is a functional block diagram of a power module according to a fourth embodiment. It is a figure which shows the outline | summary of operation | movement of the power module which concerns on a premise technique.

<Prerequisite technology>
Prior to the description of the embodiments of the present invention, the technology that is the premise of the present invention will be described. FIG. 10 is a diagram showing an outline of the operation of the power module in the base technology. In FIG. 10, the gate voltage, drain current, and drain-source voltage of the switching element are denoted as VG, ID, and VDS, respectively. The threshold value of the gate voltage is expressed as Vth.

  As shown in FIG. 10, in the base technology, driving is performed with a relatively high driving capability at the initial turn-on, and switching is performed in a region indicated by A in FIG. Technology has been used. Thus, by performing the turn-on operation with the two-stage driving capability, both switching loss suppression and recovery current suppression are achieved.

  However, in the base technology, since driving is performed with a relatively high driving capability at the beginning of turn-on, the rise of current becomes steep, and the time change (dv / dt) of the gate voltage becomes steep at this timing. There was a problem that increased.

<Embodiment 1>
<Overview>
FIG. 1 is a functional block diagram of a power module 100 in the present embodiment. The power module 100 includes a switching element 13 and a drive circuit 11 that drives a control terminal (hereinafter referred to as a gate) of the switching element 13 based on an input signal. The switching element 13 is a MOSFET, and the drive circuit 11 is disposed in the IC chip. The output of the drive circuit 11 is connected to the gate of the switching element 13. The drive circuit 11 turns on and off the switching element 13 by changing the gate voltage (VG) based on the input signal (Vin).

  In the present embodiment, the drive circuit 11 includes an output switching circuit 12 that switches an output signal applied to the gate of the switching element 13. The output switching circuit 12 switches the driving ability for driving the switching element 13 in the order of the first driving ability, the second driving ability, and the third driving ability when the switching element 13 is turned on. In the present embodiment, the driving capability is an output voltage output from the driving circuit 11.

  In the present embodiment, the second driving capability is higher than the first driving capability, and the third driving capability is lower than the second driving capability. Here, the output voltage in the first driving capability is the first voltage (V1), the output voltage in the second driving capability is the second voltage (V2), and the output voltage in the third driving capability is the third voltage (V3). In other words, the second voltage (V2) is larger than the first voltage (V1), and the third voltage (V3) is smaller than the second voltage (V2).

  FIG. 2 is a diagram showing an outline of the operation of the power module 100 in the present embodiment. FIG. 2 shows temporal changes in the waveforms of the gate voltage (VG), drain current (ID), and drain-source voltage (VDS) of the switching element 13 during the turn-on operation. The drive circuit 11 first drives with the first drive capability, and exceeds the gate threshold value (Vth) at time t1. Thereafter, the drive circuit 11 switches from the first drive capability to the second drive capability at time t2, and performs driving until time t3. Further, at time t3, driving is performed by switching from the second driving capability to the third driving capability.

  In FIG. 2, attention is paid to the time change of VG and ID before and after the regions indicated by B and C in FIG. 2. It can be seen that the time change from time t2 to time t3 is steeper than the time change from time t1 to time t2. This is because before and after the region indicated by B in FIG. 2, the first drive capability is switched to the second drive capability having a higher drive capability. Also, it can be seen that the time change from time t3 to time t4 is more gradual than the time change from time t2 to time t3. This is because before and after the region indicated by C in FIG. 2, the second drive capability is switched to the third drive capability having a lower drive capability.

  As described above, the driving circuit 11 in the present embodiment drives the switching element 13 with a relatively low driving capability in the initial stage (time t1 to t2) and the final stage (time t3 to t4) of the turn-on operation. On the other hand, in the middle period (time t2 to t3) of the turn-on operation, the switching element 13 is driven with a relatively high driving capability.

<Configuration>
FIG. 3 is a circuit diagram of power module 100 in the present embodiment. Moreover, FIG. 4 is a figure which shows the operation | movement sequence of the power module 100 in this Embodiment.

  As shown in FIG. 3, the drive circuit 11 includes n-channel MOSFETs 1 and 2 connected in series. A NOT element 5 is inserted before the gate of the n-channel MOSFET 2 on the sink side. In response to the high level / low level pulse of the input signal (Vin), the output voltage (VrOut) of the variable voltage circuit 4 is switched to the high level / low level via the input circuit 3, whereby the n-channel MOSFET 1 on the drive side. And the n-channel MOSFET 2 on the sink side is alternately turned on and off, and the gate of the switching element 13 is driven. Here, the input circuit 3 is a circuit that amplifies the input signal (Vin). The variable voltage circuit 4 will be described later.

  The drive circuit 11 further includes an output switching circuit 12. The output switching circuit 12 feeds back the gate voltage (VG) of the switching element 13 to which the output signal is given and compares it with a predetermined voltage value, and switches the driving capability based on the comparison result of the comparison circuit. And a circuit to perform (that is, variable voltage circuit 4).

  The comparison circuit includes comparators 10A and 10B. A gate voltage (VG) is input to the non-inverting input of the comparator 10A, and a predetermined voltage value is input to the inverting input. Here, the predetermined voltage value is a voltage that determines the timing (time t2 in FIG. 4) at which the driving capability is switched from the first driving capability to the second driving capability. When VG exceeds a predetermined voltage value, the output of the comparator 10A is switched from the low level to the high level.

  The gate voltage (VG) is input to the non-inverting input of the comparator 10B, and a predetermined voltage value is input to the inverting input. Here, the predetermined voltage value is a voltage that determines a timing (time t3 in FIG. 4) at which the driving capability is switched from the second driving capability to the third driving capability. When VG exceeds a predetermined voltage value, the output of the comparator 10B is switched from the low level to the high level. The outputs of the comparators 10A and 10B are input to the variable voltage circuit 4.

<Operation>
As shown in FIG. 4, in the variable voltage circuit 4, when the input signal (Vin) is at a high level and the output signals (CompA, CompB) from the comparators 10A and 10B are at a low level (time t1 to t2), V1 is output as VrOut.

  At time t2, when VG exceeds the above-described predetermined voltage, the output signal (CompA) of the comparator 10A changes to a high level. Then, the variable voltage circuit 4 outputs V2 having a voltage higher than V1 as VrOut. Further, when VG exceeds the predetermined voltage described above at time t3, CompB changes to a high level. Then, the variable voltage circuit 4 outputs V3 having a voltage smaller than V2 as VrOut.

  As described above, the drive circuit 11 provided in the power module 100 according to the present embodiment feeds back the gate voltage (VG) of the switching element 13 to obtain a predetermined voltage value in the comparison circuit (that is, the comparators 10A and 10B). The comparison is performed, and the driving ability is switched based on the comparison result. Since the drive circuit 11 switches the drive capability at time t2 and time t3, the drive circuit 11 can drive the switching element 13 with three stages of drive capability.

  In the present embodiment, the driving capability is the output voltage output from the drive circuit 11. However, when the current is assumed as the output signal to be supplied to the control terminal of the switching element 13, the drive circuit 11 outputs the output voltage. The output current to be used may be the driving capability.

<Effect>
The power module 100 in the present embodiment is a power module that includes a switching element 13 and a drive circuit 11 that drives the switching element 13, and the drive circuit 11 outputs an output signal to be supplied to a control terminal of the switching element 13. The output switching circuit 12 includes an output switching circuit 12. The output switching circuit 12 includes a first driving capability, a second driving capability, and a third driving capability for driving the switching device 13 with an output signal when the switching device 13 is turned on. The second driving capability is higher than the first driving capability, and the third driving capability is lower than the second driving capability.

  Therefore, in the present embodiment, the drive circuit 11 performs control to switch the driving capability for driving the switching element 13 in three steps in the order of low, high, and low at the time of turn-on. Therefore, it is possible to achieve both switching loss suppression and recovery current suppression by driving with a relatively high driving capability in the middle period of the turn-on operation and driving with a relatively low driving capability in the final period. Further, by performing driving with a relatively low driving capability in the early stage of the turn-on operation, it is possible to moderate the time change (dv / dt) of the gate voltage and suppress the generation of electromagnetic noise.

  Further, in the power module 100 according to the present embodiment, the output switching circuit 12 feeds back the voltage at the control terminal of the switching element 13 to which the output signal is given and compares it with a predetermined voltage value (that is, a comparator). 10A, 10B) and a circuit (that is, variable voltage circuit 4) for switching the driving capability based on the comparison result of the comparison circuit.

  Accordingly, in the comparison circuit including the two comparators 10A and 10B, the voltage of the control terminal of the switching element 13 fed back is compared with a predetermined voltage value, and the variable voltage circuit 4 switches the driving capability based on the comparison result. By doing so, it is possible to switch the driving capability to three stages. Further, by feeding back the gate voltage of the switching element 13, it is possible to switch the driving capability corresponding to the gate voltage.

  In the present embodiment, the switching element 13 is a MOSFET. Accordingly, since the MOSFET has a sharp rise in current at turn-on, the present invention for controlling the switching speed is effective.

<Embodiment 2>
FIG. 5 is a circuit diagram of power module 200 in the present embodiment. FIG. 6 is a diagram showing an operation sequence of the power module 200 in the present embodiment.

  In the present embodiment, the output switching circuit 12A includes a timer circuit 14 that operates based on an input signal to the driving circuit 11, and a circuit that switches the driving capability based on the output of the timer circuit 14 (that is, the variable voltage circuit 4). ).

  The timer circuit 14 includes comparators 20A and 20B. The non-inverting inputs of the comparators 20A and 20B are connected between the source of the timer switching element 50 and the timer capacitor 40. An input signal (Vin) is input to the control terminal of the timer switching element 50 via the input circuit 3.

  A predetermined voltage value is input to the inverting input of the comparator 20A. Here, the predetermined voltage value is a voltage that determines a timing (time t2 in FIG. 6) at which the driving capability is switched from the first driving capability to the second driving capability. When the voltage at the non-inverting input exceeds the voltage at the inverting input, the output of the comparator 20A is switched from the low level to the high level. A predetermined voltage value is input to the inverting input of the comparator 20B. Here, the predetermined voltage value is a voltage that determines the timing (time t3 in FIG. 6) at which the driving capability is switched from the second driving capability to the third driving capability. When the voltage of the non-inverting input exceeds the voltage of the inverting input, the output of the comparator 20B is switched from the low level to the high level. As in the first embodiment, the outputs of the comparators 20A and 20B are input to the variable voltage circuit 4. Since other configurations are the same as those of the first embodiment (FIG. 3), description thereof is omitted.

<Operation>
As shown in FIG. 6, when the input signal Vin is at a high level and the output signals (DelyA, DelyB) from the comparators 20A and 20B are at a low level (time t1 to t2), the variable voltage circuit 4 is set as VrOut. V1 is output. At the same time, the high-level input signal Vin turns on the timer switching element 50, whereby charging of the timer capacitor 40 is started.

  As the charging of the timer capacitor 40 proceeds, when the non-inverting input of the comparator 20A exceeds the predetermined voltage value described above at time t2, the output signal (DelyA) of the comparator 20A changes to a high level. Then, the variable voltage circuit 4 outputs V2 having a voltage higher than V1 as VrOut.

  Further, as the charging of the timer capacitor 40 proceeds, when the non-inverting input of the comparator 20B exceeds the above-described predetermined voltage value at time t3, the output signal (DelyB) of the comparator 20B changes to a high level. Then, the variable voltage circuit 4 outputs V3 having a voltage smaller than V2 as VrOut.

  As described above, the driving circuit 11 provided in the power module 200 according to the present embodiment switches the driving capability based on the high level signal output by the timer circuit 14 that operates based on the input signal to the driving circuit 11 with a time difference. I do. Since the drive circuit 11 switches the drive capability at time t2 and time t3, the drive circuit 11 can drive the switching element 13 with three stages of drive capability.

<Effect>
In the power module 200 according to the present embodiment, the output switching circuit 12A includes a timer circuit 14 that operates based on an input signal to the driving circuit 11 and a circuit that switches driving capability based on the output of the timer circuit 14 (that is, And a variable voltage circuit 4).

  Accordingly, in each of the two comparators 20A and 20B provided in the timer circuit 14, a voltage that rises due to charging of the timer capacitor 40 is compared with a predetermined voltage value. Then, the variable voltage circuit 4 switches the driving capability based on the output of the timer circuit 14, so that the driving capability can be switched in three stages as in the first embodiment. In addition, by controlling the driving capability switching timing using the timer circuit 14, it is possible to switch the driving capability without depending on the variation in the characteristics of the switching element 13.

<Embodiment 3>
FIG. 7 is a circuit diagram of power module 300 in the present embodiment. FIG. 8 is a diagram showing an operation sequence of the power module 300 in the present embodiment.

  As shown in FIG. 7, in the present embodiment, the switching element 13 includes a sense terminal 15. In the present embodiment, the output switching circuit 12B includes a comparison circuit that feeds back the sense current of the sense terminal 15 and compares it with a predetermined voltage value, and a circuit that switches the drive capability based on the comparison result of the comparison circuit ( That is, a variable voltage circuit 4) is provided.

  The comparison circuit includes comparators 30A and 30B. A voltage (hereinafter referred to as a sense voltage) generated when a sense current flows through the resistance element 16 is input to the non-inverting input of the comparator 30A, and a predetermined voltage value is input to the inverting input. Here, the predetermined voltage value is a voltage that determines the timing (time t2 in FIG. 8) at which the driving capability is switched from the first driving capability to the second driving capability. When the sense voltage exceeds a predetermined voltage, the output of the comparator 30A is switched from the low level to the high level.

  Similarly to the comparator 30A, a sense voltage is input to the non-inverting input of the comparator 30B, and a predetermined voltage value is input to the inverting input. Here, the predetermined voltage value is a voltage that determines the timing (time t3 in FIG. 8) at which the driving capability is switched from the second driving capability to the third driving capability. When the sense voltage exceeds a predetermined voltage, the output of the comparator 30B is switched from the low level to the high level. As in the first embodiment, the outputs of the comparators 30A and 30B are input to the variable voltage circuit 4. Since other configurations are the same as those of the first embodiment (FIG. 3), description thereof is omitted.

<Operation>
As shown in FIG. 8, in the variable voltage circuit 4, when the input signal (Vin) is at a high level and the output signals (CompA, CompB) from the comparators 30A and 30B are at a low level (time t1 to t2), V1 is output as VrOut.

  When the sense voltage exceeds the predetermined voltage value described above at time t2, the output signal (CompA) of the comparator 30A changes to a high level. Then, the variable voltage circuit 4 outputs V2 having a voltage higher than V1 as VrOut. Further, when the sense voltage exceeds the predetermined voltage value described above at time t3, CompB changes to high level. Then, the variable voltage circuit 4 outputs V3 having a voltage smaller than V2 as VrOut.

  As described above, the drive circuit 11 provided in the power module 300 according to the present embodiment feeds back the sense current of the switching element 13 to perform comparison in the comparison circuit (that is, the comparators 30A and 30B), and based on the comparison result. Switch the driving capacity. Since the drive circuit 11 switches the drive capability at time t2 and time t3, the drive circuit 11 can drive the switching element 13 with three stages of drive capability.

<Effect>
In the power module 300 in the present embodiment, the switching element 13 includes a sense terminal, and the output switching circuit 12B feeds back the sense current of the sense terminal 15 and compares it with a predetermined voltage value (that is, comparators 30A and 30B). ) And a circuit (that is, variable voltage circuit 4) for switching the driving ability based on the comparison result of the comparison circuit.

  Accordingly, in the comparison circuit including the two comparators 30A and 30B, the current of the sense terminal 15 of the switching element 13 is fed back and compared with a predetermined voltage value, and the variable voltage circuit 4 switches the driving capability based on the comparison result. By performing the above, it is possible to switch the driving capability to three stages. Further, by feeding back the sense current of the switching element 13, it is possible to switch the driving capability corresponding to the variation in characteristics of the switching element 13.

<Embodiment 4>
FIG. 9 is a functional block diagram of power module 400 in the present embodiment. Although the MOSFET is used as the switching element 13 in the first to third embodiments, the IGBT 21 is used as the switching element 13 in the present embodiment. In particular, IGBTs having a relatively low collector impurity concentration have been widely used for inverter applications in recent years for the purpose of reducing loss by shortening the time required for switching.

  Such an IGBT has a steep current rise as compared with a conventional IGBT and has a turn-on waveform similar to that of a MOSFET. Therefore, the effect of applying the present invention can be obtained more remarkably. Note that other types of switching elements may be used as long as the waveform at turn-on is similar to that of the MOSFET.

  It should be noted that the present invention can be freely combined with each other within the scope of the invention, and each embodiment can be appropriately modified or omitted.

  1, 2 n-channel MOSFET, 3 input circuit, 4 variable voltage circuit, 5 NOT element, 10A, 10B, 20A, 20B, 30A, 30B comparator, 11 drive circuit, 12, 12A, 12B output switching circuit, 13 switching element, 14 timer circuit, 15 sense terminal, 16 resistance element, 21 IGBT, 40 timer capacitor, 50 timer switching element, 100, 200, 300, 400 power module.

Claims (6)

A power module including a switching element and a drive circuit for driving the switching element,
The drive circuit includes an output switching circuit that switches an output signal applied to a control terminal of the switching element,
The output switching circuit switches the driving ability of the output signal to drive the switching element when the switching element is turned on in the order of a first driving ability, a second driving ability, and a third driving ability;
The second driving capability is higher than the first driving capability, and the third driving capability is lower than the second driving capability.
Power module. The output switching circuit is
A comparison circuit that feeds back a voltage of the control terminal of the switching element to which the output signal is applied and compares it with a predetermined voltage value;
A circuit for switching the driving capability based on a comparison result of the comparison circuit;
Characterized by comprising,
The power module according to claim 1. The output switching circuit is
A timer circuit that operates based on an input signal to the drive circuit;
A circuit for switching the driving capability based on the output of the timer circuit;
Characterized by comprising,
The power module according to claim 1. The switching element includes a sense terminal;
The output switching circuit is
A comparison circuit that feeds back a sense current of the sense terminal and compares it with a predetermined voltage value;
A circuit for switching the driving capability based on a comparison result of the comparison circuit;
Characterized by comprising,
The power module according to claim 1. The switching element is a MOSFET,
The power module according to claim 1. The switching element is an IGBT,
The power module according to claim 1.

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