JP2013005231A - Drive device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for flexibly controlling a gate voltage of a voltage-driven element in a transition period of transition of the voltage-driven element between a driven state and a non-driven state.SOLUTION: A drive device 1 includes a voltage drive section 3 and a current drive section 4. In a local interval of a transition period of transition of a voltage-driven element 2 between a driven state and a non-driven state, control of a gate voltage Vg of the voltage-driven element 2 using the voltage drive section 3 is stopped and control of the gate voltage Vg of the voltage-driven element 2 using the current drive section 4 is executed.

Description

  The present invention relates to a driving device that drives a voltage-driven element.

  A voltage-driven element is an element that can exhibit a specific function using a driving voltage, and is widely used in various applications. As an example of a voltage driven element, a voltage driven element including a gate is known. The voltage-driven element controls a current value based on a gate voltage, and is used, for example, in an inverter device that converts a DC voltage into an AC voltage. An example of the voltage-driven element is a power semiconductor switching element including an IGBT (Insulated Gate Bipolar Transistor) and a MOSFET (Metal Oxide Semiconductor Field Effect Transistor).

  In order to drive such a voltage driven element, a driving device is connected to the voltage driven element. The drive device is configured to control the gate voltage of the voltage-driven element. For example, the driving device can control the gate voltage of the voltage-driven element based on a control signal that instructs on / off of the voltage-driven element. The driving device can also control the gate voltage based on a signal indicating the driving state of the voltage-driven element or a signal indicating the state of the external environment.

  As a driving method of such a driving device, voltage driving is widely used. In voltage driving, a predetermined voltage from a voltage source is applied to the gate of the voltage driven element to control the gate voltage of the voltage driven element.

  In Patent Document 1, the gate of a voltage-driven element is obtained by superimposing current driving on voltage driving in a part of a transition period when the voltage-driven element is transitioned between a driving state and a non-driving state. A technique for controlling the voltage with high accuracy is disclosed.

JP 2004-228768 A

  For example, when a voltage-driven element is turned on using voltage driving, the voltage applied to the gate of the voltage-driven element must be set between the gate threshold voltage of the voltage-driven element and the gate breakdown voltage. Don't be. When the voltage applied to the gate is lower than the gate threshold voltage, the voltage driven element is turned off. If the voltage applied to the gate is higher than the gate breakdown voltage, the gate will be damaged.

  For this reason, when a voltage-driven element is turned on using voltage driving, the voltage that can be applied to the gate is limited, and therefore the rate of increase in the gate voltage of the voltage-driven element is also limited. For example, in order to suppress surge current or ringing, there is a case where it is desired to control the rate of rise of the gate voltage of the voltage driven element to be slow. However, since there is a limit to the voltage that can be applied to the gate of the voltage-driven element, there is a limit to slowing down the gate voltage as long as voltage driving is used.

  According to the technique of Patent Document 1, the rising speed of the gate voltage can be finely adjusted by using the current drive superimposed on the voltage drive. However, in the technique of Patent Document 1, voltage driving is used throughout the entire transition period, and there is a limit to the reduction in the gate voltage increase rate.

  The present specification provides a technique for flexibly controlling the gate voltage of a voltage-driven element during a transition period when the voltage-driven element transitions between a driving state and a non-driving state.

  A driving apparatus disclosed in the present specification includes a voltage driving unit configured to be connectable to a gate of a voltage driving type element, and a current driving unit configured to be connectable to a gate of the voltage driving type element. ing. The driving device disclosed in the present specification is a voltage-driven element that uses a voltage driver in a part of a transition period when a voltage-driven element transitions between a driving state and a non-driving state. The gate voltage control is stopped, and the gate voltage control of the voltage-driven element using the current driver is executed. The driving device according to this aspect can change the gate voltage of the voltage driven element depending on a predetermined current from the current driving unit in a part of the transition period. The gate voltage can be controlled flexibly.

  In the driving device disclosed in this specification, in the first period of the transition period, the control of the gate voltage of the voltage driving element using the current driving unit is stopped, and the voltage driving element using the voltage driving unit is stopped. The gate voltage may be controlled to be executed. Further, in the driving device disclosed in this specification, in the second period of the transition period, the control of the gate voltage of the voltage driving element using the voltage driving unit is stopped, and the voltage driving using the current driving unit is performed. The gate voltage of the mold element may be controlled. According to the driving device of this aspect, the current driver is used only when flexible control is required, and the voltage driver is used when flexible control is not required. As a result, the gate voltage of the voltage-driven element can be flexibly controlled while suppressing an increase in power loss.

  In the drive device disclosed in this specification, the first period may be the first half of the transition period, and the second period may be the second half of the transition period. For example, the second half of the turn-on transition period is a section that easily affects surge current or ringing. Further, the latter half of the turn-off transition period is a section that easily affects the surge voltage. In the driving device disclosed in this specification, the gate voltage of the voltage-driven element can be flexibly controlled in the latter half of the transition period.

  The current driver may be configured to be capable of adjusting the change rate of the gate voltage of the voltage-driven element to a plurality of levels. The current driver may be configured to be able to adjust the change rate of the gate voltage of the voltage-driven element to an arbitrary level. According to these embodiments, it becomes possible to actively drive the gate voltage of the voltage-driven element.

  The current driver may be configured to be able to adjust the rate of change of the gate voltage of the voltage driven element according to the driving state of the voltage driven element.

  The driving device disclosed in the present specification can change the gate voltage of the voltage driven element depending on a predetermined current from the current driving unit in a part of the transition period. The gate voltage of the driving element can be flexibly controlled.

FIG. 1 shows an outline of the driving apparatus of the first embodiment. FIG. 2 shows an outline of a modification of the drive device of the first embodiment. FIG. 3 shows details of the driving apparatus of the first embodiment. FIG. 4 shows a timing chart of the driving apparatus of the first embodiment. FIG. 5 shows details of a timing chart during the turn-on transition period. FIG. 6 shows an outline of the driving apparatus of the second embodiment. FIG. 7 shows details of the driving apparatus of the second embodiment.

First, the features of the drive device disclosed in this specification will be summarized.
(First Feature) A voltage-driven element is an element that can exhibit a specific function using a driving voltage. The voltage-driven element may be a voltage-driven switching element having an insulated gate, in particular a power semiconductor switching element.
(Second Feature) The voltage driven element may be formed of a wand band gap semiconductor material. For example, the voltage driven element may be formed of a compound semiconductor such as silicon carbide or gallium nitride. In the voltage drive type element formed of such a wide band gap semiconductor material, it is desired to solve the problem of surge and ringing. The drive device disclosed in this embodiment is useful in solving such problems.
(Third feature) The transition period when the voltage driven element is transitioned between the driving state and the non-driving state includes both a transition period when the voltage driven element is turned on and a transition period when the voltage driven element is turned off. . The turn-on transition period is from the start of rising of the gate voltage of the voltage-driven element to the steady state. The turn-off transition period is from the start of the fall of the gate voltage of the voltage-driven element to the steady state.
(Fourth feature) In the driving device disclosed in this specification, there is at least a section in which voltage driving is stopped when current driving is executed. As a result, the gate voltage of the voltage driven element can be controlled with high accuracy.

  Embodiments will be described below with reference to the drawings. In addition, about the component which is common in each Example, a common code | symbol is attached | subjected and the description is abbreviate | omitted.

  FIG. 1 shows an outline of a driving apparatus 1 that drives a voltage-driven element 2 of an n-type MOSFET. As shown in FIG. 1, a reflux diode is connected in parallel to the voltage driven element 2. The voltage-driven element 2 may be used as, for example, a power semiconductor switching element that constitutes the upper and lower arms of the inverter device.

  The driving device 1 is configured to switch between a driving state (ON state) and a non-driving state (OFF state) of the voltage-driven element 2, and includes a gate resistor Rg, a pair of switches SW1 and SW2, and a voltage driving unit. 3, a current driver 4, a controller 5, a signal generator 6, and a voltage source 7. In this example, a configuration in which voltage driving and current driving are switched in a transition period in which the voltage driven element 2 is turned on is illustrated, but if necessary, in a transition period in which the voltage driven element 2 is turned off, A configuration that switches between voltage driving and current driving may be employed.

  The gate resistance Rg is a fixed resistance element connected to the gate of the voltage driven element 2. The gate resistance Rg determines the charging speed and discharging speed of the gate current of the voltage driven element 2.

  The first switch SW <b> 1 has one end connected to the gate resistance Rg and the other end connected to the positive polarity of the voltage source 7 via the voltage driving unit 3 and the current driving unit 4. The second switch SW2 has one end connected to the gate resistance Rg and the other end connected to the negative polarity of the voltage source 7.

  The voltage driver 3 is configured to be connectable to the gate resistor Rg of the voltage driven element 2 via the first switch SW1. The voltage driving unit 3 is configured to apply a predetermined voltage to the gate of the voltage driving type element 2. Further, the gate voltage Vg of the voltage driven element 2 is input to the voltage driver 3. The voltage driving unit 3 applies a predetermined voltage to the gate of the voltage driven element 2 (a state where voltage driving is performed) and does not apply a voltage (a voltage driving is performed) according to the gate voltage Vg of the voltage driven element 2. The state of stopping) can be switched. As will be described later, when voltage driving by the voltage driving unit 3 is being executed, current driving by the current driving unit 4 is stopped, and when voltage driving by the voltage driving unit 3 is stopped, current driving is performed. The unit 4 is configured to execute current driving.

  The current driver 4 is configured to be connectable to the gate resistor Rg of the voltage driven element 2 via the first switch SW1. The current driver 4 is configured to supply a predetermined current to the gate of the voltage driven element 2. The command signal Vord from the signal generator 6 is input to the current driver 4. In addition, the current driver 4 can adjust the gate current value supplied to the gate of the voltage driven element 2 in accordance with the command signal Vord.

  In response to a PWM signal from an electronic control unit (ECU) (not shown), the control unit 5 outputs a first control signal V1 to the first switch SW1 and outputs a second control signal V2 to the second switch SW2. The controller 5 can switch the driving state (ON state) and the non-driving state (OFF state) of the voltage-driven element 2 by alternately switching the first switch SW1 and the second switch SW2 on and off. .

  The signal generator 6 generates a command signal Vord that is input to the current driver 4. The command signal Vord can be set according to the conditions of element current, element voltage, and element temperature, and an example thereof is shown in FIG. In the example of FIG. 2, the drain current of the voltage driven element 2 detected using the current detection circuit 8 is input to the signal generation unit 6, and the drain-source voltage of the voltage driven element 2 is also input. ing. The signal generator 6 can generate the command signal Vord by using these drain current and drain-source voltage. For example, the signal generator 6 may set the command signal Vord to be turned on next time based on the state of change in the drain current (surge current, ringing, etc.). Further, the signal generator 6 may set the command signal Vord for the next turn-on based on the state of change of the drain-source voltage (change speed or the like), for example.

  Next, with reference to FIG. 3, the detail of a structure of the drive device 1 is demonstrated. The voltage driver 3 includes a first transistor Tr1 and a gate voltage detection circuit 3a. In the first transistor Tr1, the drain is connected to the positive polarity of the voltage source 7, the source is connected to the first switch SW1, and the gate is connected to the gate voltage detection circuit 3a. The gate voltage detection circuit 3a receives the gate voltage Vg of the voltage driven element 2, and compares the gate voltage Vg with the switching threshold voltage. The switching threshold voltage is set to have a timing suitable for switching from voltage driving to current driving in order to effectively suppress surge current and ringing when the voltage driven element 2 is turned on. Typically, the switching threshold voltage is set to a timing at which the gate voltage Vg of the voltage driven element 2 is in the mirror period. The gate voltage detection circuit 3a turns on the first transistor Tr1 when the gate voltage Vg of the voltage driven element 2 is equal to or lower than the switching threshold voltage, and when the gate voltage Vg of the voltage driven element 2 exceeds the switching threshold voltage. The first transistor Tr1 is configured to be turned off. The gate voltage detection circuit 3a may be configured using, for example, a comparator.

  The current driver 4 includes a current mirror circuit 4a and a current control circuit 4b. The current mirror circuit 4a includes a pair of pnp transistors Tr2 and Tr3, the second transistor Tr2 is disposed on the output side, and the third transistor Tr3 is disposed on the input side. The current control circuit 4b is connected to the input side of the current mirror circuit 4a, and includes an npn-type fourth transistor Tr4, an operational amplifier OP1, and a fixed resistance element R1.

  The fourth transistor Tr4 of the current control circuit 4b has a collector connected to the collector of the third transistor Tr3 of the current mirror circuit 4a, and an emitter connected to the fixed resistance element R1. In the operational amplifier OP1, the command signal Vord is input to the inverting input terminal, the connection point P1 of the fourth transistor Tr4 and the fixed resistance element R1 is connected to the non-inverting input terminal, and the output is the control terminal of the fourth transistor Tr4. It is connected to the. The current control circuit 4b controls the fourth transistor Tr4 so that the voltage at the connection point P1 becomes equal to the command signal Vord. For this reason, when the command signal Vord is low, the value of the current flowing through the fourth transistor Tr4 is also controlled to be small, and as a result, the output current of the current mirror circuit 4a is also controlled to be small. On the other hand, when the command signal Vord is high, the value of the current flowing through the fourth transistor Tr4 is also controlled to be high, and as a result, the output current of the current mirror circuit 4a is also controlled to be high. Thus, the current drive unit 4 can generate an arbitrary drive current according to the command signal Vord.

  Next, an outline of the operation when the voltage driven element 2 is turned on will be described with reference to FIG. At timing t2, the first control signal V1 rises and the second control signal V2 falls. As a result, the first switch SW1 is turned on and the second switch SW2 is turned off. Prior to the timing t2, the command signal Vord is input to the operational amplifier OP1 at the timing t1.

  At the timing t2, since the gate voltage Vg is equal to or lower than the switching threshold voltage, the gate voltage detection circuit 3a controls the first transistor Tr1 to be on. Therefore, when the switch SW1 is turned on at the timing t2, a positive voltage is applied from the voltage source 7 to the gate of the voltage-driven element 2 via the voltage driver 3, and the gate voltage Vg increases. At this time, since the first transistor Tr1 of the voltage driver 3 is on, the current mirror circuit 4a does not operate, and the current supply from the current mirror circuit 4a to the gate of the voltage driven element 2 is stopped. For this reason, the gate voltage Vg of the voltage driven element 2 is controlled only through the voltage driver 3.

  When the gate voltage Vg of the voltage-driven element 2 rises and the gate voltage Vg exceeds the switching threshold voltage at timing t3, the gate voltage detection circuit 3a controls the first transistor Tr1 to turn off. When the first transistor Tr1 is turned off, current supply from the current mirror circuit 4a to the gate of the voltage driven element 2 is started. The gate voltage Vg of the voltage driven element 2 rises due to current driving, and reaches a steady state at timing t4.

  Here, the turn-on transition period will be described in more detail with reference to FIG. As shown in FIG. 5, timings t2 to t4 are turn-on transition periods. As described above, until the gate voltage Vg of the voltage driven element 2 reaches the switching threshold voltage Va (until timing t3), the gate voltage Vg of the voltage driven element 2 increases using the voltage driver 3. At this time, the current drive using the current drive unit 4 is stopped. After the gate voltage Vg of the voltage driven element 2 exceeds the switching threshold voltage Va (after timing t3), the gate voltage Vg of the voltage driven element 2 rises using the current driver 4. At this time, the current drive via the voltage driver 3 is stopped.

  As described above, the current supplied from the current driver 4 can be arbitrarily set according to the command signal Vord. Therefore, as shown by the broken line in FIG. 5, when the command signal Vord is set low, the rising speed of the gate voltage Vg of the voltage driven element 2 is relatively slow, and the command signal Vord is set high. If so, the rising speed of the gate voltage Vg of the voltage-driven element 2 becomes relatively high. As described above, in the current driving using the current driving unit 4, the rising speed of the gate voltage Vg of the voltage driven element 2 can be arbitrarily set according to the command signal Vord. The second half of the period when the voltage driven element 2 is turned on is a section that easily affects the surge current and ringing. The driving device 1 of the present embodiment can control the rising speed of the gate voltage Vg of the voltage driven element 2 to an arbitrary magnitude and with high accuracy in the latter half section when the voltage driven element 2 is turned on. . Further, it is known that the surge current and the ringing depend on the variation of the voltage driven element 2. The driving device 1 of the present embodiment can set the optimum rising speed of the gate voltage Vg for each voltage-driven element 2 by appropriately changing the command signal Vord, so that such variation is easy. Can deal with.

  Returning to FIG. When the gate voltage of the voltage-driven element 2 reaches a steady state, the input of the command signal Vord is stopped at the timing t5. Thereby, in a steady state, the current mirror circuit 4a in the current driver 4 is stopped, and an increase in loss generated in the third transistor Tr3, the fourth transistor Tr4, and the fixed resistance element R1 is suppressed.

  At timing t6, when the first control signal V1 falls and the second control signal V2 rises, the first switch SW1 is turned off and the second switch SW2 is turned on. As a result, the charge accumulated in the gate of the voltage driven element 2 is discharged, and the voltage driven element 2 is turned off.

Hereinafter, the characteristics of the drive device 1 of this embodiment will be summarized.
(1) In normal voltage-driven switching, the gate voltage signal is determined by the CR time constant determined by the gate input capacitance and the gate resistance of the voltage-driven element 2. In this case, it is possible to suppress surge and ringing by changing the CR time constant by switching the gate resistance in the middle of the switching transition. However, the effect is limited in actual operation due to variations in gate input capacitance, gate resistance, element temperature, element current, and the like of the voltage driven element 2. In order to provide robustness, it is conceivable to provide a plurality of gate resistance values to be switched, but the circuit scale becomes large and is not suitable for practical use. On the other hand, in the driving device 1 of the present embodiment, the rate of increase of the gate voltage Vg can be increased with high accuracy by switching to the current driving in which the gate current amount can be set to an arbitrary value from the middle of the switching transition. Can be controlled.

(2) In the present embodiment, current driving is stopped and only voltage driving is executed in the first half of the transition period. In the first half of the transition period, it is relatively less necessary to accurately control the gate voltage increase rate. As a result, it is possible to drive the voltage driven element 2 while suppressing an increase in power loss.

  FIG. 6 shows an outline of the driving apparatus 10 of the second embodiment, and FIG. 7 shows the details thereof. In the drive device 10, the voltage drive unit 13 is different from the drive device 1 of the first embodiment. The voltage driver 13 includes a fixed resistance element R2, a Zener diode ZD1, and a pnp-type fifth transistor Tr5. The fixed resistance element R2 is connected between the emitter and base of the fifth transistor Tr5. The Zener diode ZD1 has a cathode connected to the base of the fifth transistor Tr5 and an anode connected to the collector of the fifth transistor Tr5.

  While the gate voltage Vg of the voltage driven element 2 is low, the Zener diode ZD1 breaks down, and thereby the fifth transistor Tr5 is turned on. When the gate voltage Vg of the voltage driven element 2 rises and the Zener diode ZD1 becomes non-conductive, the fifth transistor Tr5 is also turned off. In this way, the voltage driver 13 can be switched according to the gate voltage Vg. Other operations are the same as those of the driving device 1 of the first embodiment. The voltage driving unit 13 of the second embodiment is advantageous in terms of cost because it can switch between voltage driving and current driving using a simple configuration.

Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.
The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or the drawings can achieve a plurality of objects at the same time, and has technical usefulness by achieving one of the objects.

1: Drive device 2: Voltage-driven element 3: Voltage drive unit 4: Current drive unit 5: Control unit 6: Signal generation unit 7: Voltage source

Claims (6)

A driving device for driving a voltage-driven element,
A voltage driver configured to be connectable to a gate of the voltage-driven element;
A current drive unit configured to be connectable to a gate of the voltage-driven element,
Control of the gate voltage of the voltage-driven element using the voltage driver is stopped in a part of the transition period when the voltage-driven element is transitioned between the driving state and the non-driving state. A driving device configured to control the gate voltage of the voltage-driven element using the current driving unit. In the first period of the transition period, control of the gate voltage of the voltage-driven element using the current driver is stopped, and control of the gate voltage of the voltage-driven element using the voltage driver is stopped. Configured to run,
In the second period of the transition period, control of the gate voltage of the voltage driven element using the voltage driver is stopped, and control of the gate voltage of the voltage driven element using the current driver is not performed. The drive device according to claim 1, wherein the drive device is configured to be executed. The first section is a first half section of the transition period;
The driving apparatus according to claim 2, wherein the second section is a latter half section of the transition period.   The driving device according to claim 1, wherein the current driving unit is configured to be capable of adjusting a change rate of a gate voltage of the voltage-driven element to a plurality of levels.   The driving device according to claim 4, wherein the current driving unit is configured to be capable of adjusting a change speed of a gate voltage of the voltage-driven element to an arbitrary level. The driving device according to claim 4, wherein the current driving unit is configured to be capable of adjusting a change speed of a gate voltage of the voltage driven element according to a driving state of the voltage driven element.

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