JP5928417B2 - Semiconductor element module and gate drive circuit - Google Patents

Description

  The present invention relates to a semiconductor element module including a driving element made of a voltage-driven semiconductor element, and a gate driving circuit connected to the semiconductor element module and outputting a driving signal to the gate of the driving element.

  In the drive control of an IGBT (Insulated Gate Bipolar Transistor) which is a kind of voltage-driven semiconductor element, there is a technique of applying a gate voltage while monitoring a collector-emitter voltage in order to reduce a switching loss generated at the time of turn-off. . For example, in Patent Document 1, the gate 2a of the IGBT 2 is divided to provide a driving gate 2b and a detection gate 2c, and the collector voltage detection circuit 3 uses a parasitic capacitance Cgc between the detection gate 2c and the collector 2d. Thus, the voltage of the collector 2d is detected. According to this configuration, the collector voltage can be detected without connecting an element such as a resistance element or a capacitor to the collector outside the IGBT module.

JP 2011-103756 A

  However, in the configuration of Patent Document 1, the charge charged in the parasitic capacitance Cgc is moved to the capacitor 31 in the collector voltage detection circuit 3, and the change in the charge in the capacitor 31 is reflected in the output voltage of the operational amplifier 30, and the output thereof The voltage is output to the gate drive / control circuit 4. In such a configuration, while the switching operation of the IGBT 2 is performed, the driving state of the gate drive / control circuit 4 is changed by the voltage output from the collector voltage detection circuit 3 to suppress the surge voltage and reduce the switching loss. In order to reduce it, the response is not in time and it is practically difficult. Patent Document 1 also does not disclose a timing chart showing how the gate voltage of the IGBT 2 is changed by the action of the collector voltage detection circuit 3 and the gate drive / control circuit 4. Further, since the gate and the emitter are separated, there is a concern that the detection element may be erroneously turned on due to noise.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a conductor element module and a gate drive circuit that can reliably reduce switching loss that occurs when the drive element is turned off by a high-speed operation response. .

According to the semiconductor element module according to claim 1, the collector of the driving element composed of IGBT - provided a voltage change detection device likewise consisting of IGBT in order to detect the change in the emitter capacitor voltage, integral these elements It configures as the IC chip. The collector of the voltage change detecting device, connected to the collector of the driving element, connecting the gate to its emitter motor. Then, the emitter capacitor of the voltage change detecting device, a detecting terminal.

According to this structure, when the mirror effect by reducing the gate voltage reaches the region (mirror area) acting, driving element starts to turn off collector - emitter voltage rises. When the driving element is completely turned off, the collector potential becomes equal to the applied power supply voltage. In this process, a positive voltage change (dv / dt) occurs between the collector and the emitter, and this voltage change causes a parasitic capacitance existing between the collector and the gate of the voltage change detecting element and between the collector and the emitter. Thus, a current flows between the terminals.

  The current can be detected by arranging a current detection element such as a resistance element between the emitter of the voltage change detection element (detection terminal) and the emitter of the drive element. If the change in the emitter voltage of the current detection element is monitored, the change in the collector-emitter voltage in the process of turning off the driving element can be quickly grasped. Therefore, if the gate voltage of the drive element is changed in accordance with the change, the surge voltage that is generated in the collector at the time of turn-off can be reliably reduced. Further, since the gate of the voltage change detecting element is connected to its own emitter, it is possible to reliably prevent the voltage change detecting element from being turned on during the turn-off process.

  A gate driving circuit according to claim 4 is connected to the semiconductor element module according to any one of claims 1 to 3 and outputs a driving signal to a gate of the driving element. A switching speed variable means configured to change the speed is provided. Then, the switching speed control means sets the switching speed fast when the turn-off of the driving element is started, and detects that the terminal voltage of the detection resistance element has changed within the turn-off period. The switching speed variable means is controlled so as to slow down. As a result, the switching speed can be reduced and the surge voltage can be reduced within the period when the driving element is turned off.

The figure which is 1st Embodiment and shows the structure of a semiconductor element module and a gate drive circuit Timing chart showing each voltage waveform when the driving element is turned off FIG. 1 equivalent view showing the second embodiment The figure which is 3rd Embodiment and shows the structure of a semiconductor element module The figure which shows the result of having simulated each voltage waveform at the time of turn-off of a driving element FIG. 4 equivalent view showing the fourth embodiment

(First embodiment)
In FIG. 1, a semiconductor element module 1 includes a driving element 2 and a voltage change sensing element 3 (voltage change detection element). These are all IGBTs (voltage driven semiconductor elements), for example, and are configured as an integrated IC chip by the same process. Note that the size of the voltage change sensing element 3 is smaller than that of the driving element 2. Free wheel diodes 2D and 3D are formed between the collector and emitter of the driving element 2 and the voltage change sensing element 3, respectively.

  The gate (conduction control terminal), collector (conduction terminal), and emitter (reference potential side conduction terminal) of the driving element 2 are connected to the external terminals G, C, and E of the semiconductor element module 1, respectively. The collector of the voltage change sense element 3 is connected to the external terminal C, and the gate is connected to the external terminal S (detection terminal) of the semiconductor element module 1 together with its emitter.

  Outside the semiconductor element module 1, a resistance element R1 (detection resistance, voltage change detection element) is connected between the external terminal S and the external terminal E '. Since the external terminal E ′ is substantially the same terminal as the external terminal E, it is not necessarily provided independently. The external terminal S is connected to the inverting input terminal of the comparator 4, and the reference voltage Vref is applied to the non-inverting input terminal of the comparator 4. The reference potential of the reference voltage Vref is the external terminal E ′ (circuit ground).

  The output terminal of the comparator 4 is connected to the input terminal of the turn-off control unit 6 (switching speed control means) via the delay circuit 5. Between the external terminal G and the external terminal E ′ of the semiconductor element module 1, a series circuit (switching speed varying means) of the resistance element R2 and the switch 7 and a series circuit of the resistance element R3 and the switch 8 (variable switching speed). Means) are connected in parallel.

When the drive signal (gate control signal) of the drive element 2 is given to the turn-off control unit 6 and the drive signal is low level and the output voltage of the comparator 5 is high level, the switches 7 and 8 are simultaneously turned on. Turn on. If the drive signal is at a low level and the output voltage of the comparator 5 is at a low level, only the switch 7 is turned on. In the above description, the gate drive circuit 9 is configured except for the semiconductor element module 1.
The gate driving circuit 9 shows only a component for turning off the driving element 2. When the driving element 2 is turned on, a high level signal is sent to the external terminal G through a signal path (not shown). Applied (at this time, both switches 7 and 8 are turned off).

  Next, the operation of this embodiment will be described. 2 shows (a) a gate-emitter voltage VGE, (b) a collector-emitter voltage VCE, and (c) a sense terminal S-emitter voltage VSE when the driving element 2 of the semiconductor element module 1 is turned off. Show. In the middle of changing the voltage VGE from the high level to the low level, the voltage waveform becomes substantially flat in the mirror region. Thereafter, the driving element 2 starts to turn off, the voltage VCE increases, and finally reaches the power supply voltage (system voltage) applied to the collector.

  In the above process, if it is consistently a parallel circuit of the resistance elements R2 and R3 that is connected between the terminals GE ′ of the semiconductor element module 1, the voltage VCE changes as indicated by a solid line, When the driving element 2 is going to be completely turned off, a surge voltage is generated in the collector due to an inductance component.

  On the other hand, a positive voltage change (dv / dt) occurs between the collector and the emitter in the process of increasing the voltage VCE by the gate drive circuit 9. Due to this voltage change, a current flows between the two terminals via the parasitic capacitance existing between the collector and gate of the voltage change sense element 3 and between the collector and emitter, and this current further flows to the gate of the voltage change sense element 3. The current flows from the emitter through the terminal S to the resistance element R1. Thereby, when the terminal voltage of the resistance element R1 rises and exceeds the reference voltage Vref, the output voltage of the comparator 4 changes to a low level. Then, the turn-off control unit 6 turns off the switch 8, and thereafter, the gate of the driving element 2 is discharged only through the resistance element R2.

  That is, in the middle of turning off the driving element 2, the resistance value in the path for discharging the gate increases, and the switching speed decreases. By this action, the gradient at which the voltage VGE decreases becomes gentle and the change in the voltage VCE is relaxed, so that the amplitude of the surge voltage is reduced as shown by the broken line. As a result, the falling slope of the waveform of the voltage VSE also changes gently as shown by the broken line. Note that the delay time provided by the delay circuit 5 is effective for switching the gate resistance value immediately after the output voltage of the comparator 4 changes to the low level and immediately before the voltage VCE reaches the power supply voltage. It is set in consideration of the time for suppression.

  As described above, according to the present embodiment, the voltage change sense element 3 is provided to detect the change in the collector-emitter voltage of the drive element 2, and the collector of the voltage change sense element 3 is connected to the drive element 2. Connect to the collector and connect the gate to your emitter. The emitter of the voltage change sense element 3 is used as the detection terminal S of the semiconductor element module 1. With this configuration, the drive element 2 starts to turn off by lowering the gate voltage, and in the process in which the collector-emitter voltage increases, a positive voltage change (dv / dt) between the collector and emitter. As a result of this voltage change, a current flows between the two terminals via the parasitic capacitance existing between the collector and gate of the voltage change sensing element 3 and between the collector and emitter.

  Therefore, if the resistance element R1 is arranged between the detection terminals S and E ′, the current can be detected. Therefore, if the change in the terminal voltage of the resistance element R1 is monitored, the collector in the process in which the driving element 2 is turned off. -The change in the voltage between the emitters can be caught quickly. Therefore, if the gate voltage of the drive element 2 is changed in accordance with the change, the surge voltage that is generated in the collector at the time of turn-off can be reliably reduced.

  Here, the IGBT 2 in Patent Document 1 has a structure in which only the gate 2a is divided into two gates 2b and 2c. It can be said that the two are separated from each other. In the present embodiment, such an element structure is adopted, and the gate of the voltage change sensing element 3 is connected to its emitter. Therefore, it is possible to reliably prevent the voltage change sense element 3 from being turned on in the turn-off process.

  Then, the turn-off control unit 6 of the gate driving circuit 9 sets the gate resistance value to be lower and sets the switching speed faster at the stage when the turn-off is started, and the terminal voltage of the resistance element R1 has changed during the turn-off period. When detected, the gate resistance value was increased to reduce the switching speed. As a result, the switching speed can be reduced and the surge voltage can be reduced within the period in which the driving element 2 is turned off.

(Second Embodiment)
Hereinafter, the same parts as those of the first embodiment are denoted by the same reference numerals, description thereof is omitted, and only different parts will be described. As shown in FIG. 3, in the gate drive circuit 11 of the second embodiment, the series circuit of the resistance element R2 and the switch 7 and the series circuit of the resistance element R3 and the switch 8 are deleted, and can be changed instead. A constant current source 12 (switching speed variable means) is arranged.

  Further, the turn-off control unit 13 (switching speed control means) that replaces the turn-off control unit 6 has, for example, an output signal at a low level if the drive signal of the driving element 2 is at a low level and the output voltage of the comparator 5 is at a high level. To. At this time, the constant current value supplied by the variable constant current source 12 is set to be large, the gate of the driving element 2 is rapidly discharged, and the switching speed becomes relatively fast. If the drive signal is at a low level and the output voltage of the comparator 5 is at a low level, the turn-off control unit 13 sets the output signal to a high level. At this time, the constant current value supplied by the variable constant current source 12 is set to be small, the gate of the driving element 2 is slowly discharged, and the switching speed is relatively slow.

  According to the second embodiment configured as described above, the gate driving circuit 11 changes the switching speed when turning off the driving element 2 by changing the constant current value that the variable constant current source 12 flows. Therefore, the same effect as the first embodiment can be obtained.

(Third embodiment)
A semiconductor element module 21 shown in FIG. 4 is obtained by adding a current sense element 22 (current detection element) to the semiconductor element module 1. The current sensing element 22 is connected in parallel to the voltage change sensing element 3, and the gate is connected to the gate of the driving element 2. Some semiconductor element modules incorporating an IGBT also incorporate a current sensing element for detecting a collector current flowing through the IGBT as a driving element. In general, a collector current obtained by diverting a collector current flowing through the driving element to about one thousandth of the current flows in the current sense element. However, the current sense element 22 of the third embodiment is similar to a general current sense element. It is the composition.

  In the case of a semiconductor element module including a current sense element, the detection terminal S is provided as a terminal for detecting a current flowing through the drive element via the current sense element. Therefore, the semiconductor element module 21 has a form in which the voltage change sensing element 3 is added to the semiconductor element module having the above-described general configuration.

  Any one of the gate drive circuits 9 and 11 of the first and second embodiments may be connected to the semiconductor element module 21. However, for example, a general circuit for detecting overcurrent is required separately. The overcurrent detection is performed based on the terminal voltage of the resistance element R1 during the period in which the driving element 2 is turned on, and thus can be performed independently of the gate voltage control at the time of turn-off.

  FIG. 5 is a simulation of each voltage waveform when the driving element 2 of the semiconductor element module 1 is turned off. The gate-emitter voltage VGE, the collector-emitter voltage VCE, and the sense terminal S-emitter voltage VSE are shown in FIG. Show. In the middle of changing the voltage VGE from the high level to the low level, after the voltage waveform becomes flat in the mirror region, the driving element 2 starts to turn off, and the voltage VCE rises. Reach power supply voltage. Note that the generation of the surge voltage is not reflected in the waveform of the voltage VCE.

  If the voltage change sensing element 3 does not exist, a substantially constant current flows through the resistance element R1 through the current sensing element 22 while the driving element 2 is turned on in the process of increasing the voltage VCE. The VSE is consistently flat. On the other hand, when the voltage change sense element 3 is present, the current flowing through the voltage change sense element 3 is also superimposed on the resistance element R1. As a result, as indicated by a broken line in the figure, the level of the voltage VSE rises in a pulse manner. Therefore, the change in the voltage VCE can be detected by setting the reference voltage Vref during the increase of the voltage VSE.

  As described above, according to the third embodiment, the semiconductor element module 21 has a collector and a gate connected to the collector and gate of the driving element 2 and a current sensing element whose emitter is connected to the detection terminal S, respectively. 22. In this case, since the voltage change sense element 3 is added to the semiconductor element module including the current sense element 22, the change in the voltage VCE can be detected using the terminal S already provided for current detection.

  In this case, since the current sensing element 22 is present, a substantially constant current flows through the resistance element R1 while the driving element 2 is turned on, so that the terminal voltage of the resistance element R1 is also at a substantially constant level. Is shown. This is a state in which a surge voltage is more likely to occur during turn-off. When the driving element 2 is turned off, a voltage corresponding to the current flowing through the voltage change sensing element 3 is generated in a form added to the level. Therefore, it is possible to more quickly detect that the voltage VCE has changed, and to switch the switching speed at a faster timing.

(Fourth embodiment)
The semiconductor element module 31 of the fourth embodiment includes the current sense element 22 as in the third embodiment, but its emitter is not commonly connected to the emitter of the voltage change sense element 3. The emitter of the voltage change sensing element 3 is connected to an external terminal VS (detection terminal) of the semiconductor element module 31, and the emitter of the current sensing element 22 is connected to an external terminal IS provided separately. A resistance element R4 for current detection is connected between the terminals IS and E ′.

  That is, in the semiconductor element module 31, the terminal IS for performing current detection by the current sense element 22 and the terminal VS for detecting change of the voltage VCE by the voltage change sense element 3 are separated. If both terminals are integrated as described in the third embodiment, it is possible to more quickly detect that the voltage VCE has changed. However, in that case, it is necessary to set the reference voltage Vref to be applied to the comparator 4 in the gate drive circuits 9 and 11 in consideration of the voltage difference in each state. On the other hand, if the terminal VS is separated from the terminal IS as in the fourth embodiment, since the normal potential of the terminal VS is at the zero level, the reference voltage Vref can be easily set. Further, the resistance values of the resistance elements R1 and R4 can be easily selected.

The present invention is not limited to the embodiments described above or shown in the drawings, and the following modifications or expansions are possible .
In the first embodiment, for example, the resistance value of the resistance element R2 is set low and the resistance value of the resistance element R3 is set high, and only the resistance element R2 is connected at the start of turn-off. You may control to switch the connection.

  In the drawings, 1 is a semiconductor element module, 2 is a driving element, 3 is a voltage change sensing element (voltage change detection element), 6 is a turn-off control unit (switching speed control means), and 7 and 8 are switches (switching speed variable). Means), 9 is a gate drive circuit, R1 is a resistance element (detection resistance, voltage change detection element), and R2 and R3 are resistance elements (switching speed variable means).

Claims (6)

Both are configured as an integrated IC chip including a driving element (2) made of IGBT (Insulated Gate Bipolar Transistor) and a voltage change detecting element (3) ,
The voltage change detecting element, collector of the driving element - provided for detecting a change in the emitter capacitor voltage, the collector is connected to the collector of the driving element, the gate of its own emitter is connected to the other,
Semiconductor element module emitter capacitor of the voltage change detecting device, characterized in that provided as a detection terminal (S) (1,21,31). Consists IGBT, collector及 beauty gate is connected to the collector及 beauty gates of the driving element, further comprising a current detecting element for emitting data are connected to the detection terminal (22) 2. The semiconductor element module (21) according to claim 1, characterized in that: Consists IGBT, collector及 beauty gate is connected to the collector及 beauty gates of the driving element, further comprising a current detecting element for emitting data are connected to the current detecting terminal (IS) The semiconductor element module (31) according to claim 1, characterized in that: A gate drive circuit connected to the semiconductor element module according to any one of claims 1 to 3 and outputting a drive signal to a gate of the drive element,
Wherein a detection terminal, the detecting resistor element connected between the emitter motor of the driving element (R1),
Switching speed variable means (7, 8, R2, R3, 12) configured to change the switching speed of the driving element;
When the turn-off of the driving element is started, the switching speed is set fast, and when the change of the terminal voltage of the detection resistance element is detected within the turn-off period, the switching speed is slowed down. And a switching speed control means (6, 13) for controlling the switching speed variable means.   5. The gate drive circuit (9) according to claim 4, wherein the switching speed variable means changes the switching speed by changing a gate resistance value of the driving element.   The gate drive circuit (11) according to claim 4, wherein the switching speed variable means changes the switching speed by changing an amount of current that discharges a gate of the driving element.

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