Gate drive device and power conversion device

Abstract

A gate drive device for driving a gate drive type semiconductor element is provided with: a constant voltage circuit for discharging a gate of the semiconductor element at a constant voltage and terminating the discharge operation before a voltage between main terminals of the semiconductor element reaches a predetermined value; and a constant current circuit that starts to discharge the gate with a constant current after the constant voltage circuit starts to discharge with the constant voltage, and continues to discharge the gate with the constant current after the constant voltage circuit ends the discharge operation.

Description

Technical Field

[0001] This invention relates to gate driving devices and power conversion devices. Background Technology

[0002] In recent years, driver configurations have been reconsidered to reduce switching losses in power devices such as power semiconductors. As a result, drivers composed of constant voltage and constant current circuits, with the constant voltage circuit turning on and the constant current circuit turning off, can effectively reduce switching losses. However, in this configuration, if the constant current circuit is used directly, the turn-off time from the moment the semiconductor element's gate is turned off until it is completely turned off becomes longer. Consequently, the turn-off time of the gate increases, leading to increased conduction losses and deterioration of PWM (Pulse Width Modulation) controllability; therefore, it is necessary to shorten the turn-off time.

[0003] Previously, gate driving devices for driving the gates of power semiconductors included those using current mirror circuits and those using feedback. The current mirror circuit method allows a large current to flow through the gate of the semiconductor element at the moment of turn-off, enabling a phased reduction in the current. While the current mirror circuit method allows for high-speed operation, the cost of the integrated circuit (IC) constituting the gate driving device is high, and it is difficult to adjust the amount of current reduced from the gate. The feedback method, by feeding back the discharge current from the gate to an amplifier, allows switching of the control value. The feedback method is an easy and inexpensive way to adjust the discharge current from the gate, but it has a large operation delay until the discharge current is generated.

[0004] Patent Document 1 describes a configuration of a gate drive device that combines a constant voltage circuit and a constant current circuit. For example, Patent Document 1 describes a "gate drive device that can suppress the deviation in switching speed caused by the deviation of Vth and Miller voltage in multiple switching devices driven by the gate drive device, and can minimize the deviation in losses."

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2009-011049 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] In the gate driving device described in Patent Document 1, after the constant current circuit discharges from the gate with a constant current, the constant voltage circuit discharges from the gate with a constant voltage. The constant voltage circuit operates at high speed, but on the other hand, the constant current circuit operates at low speed, so it cannot shorten the turn-off time of the semiconductor element.

[0010] The present invention was made in view of the following situation, and its object is to shorten the turn-off time of a semiconductor element driven by a gate driving device.

[0011] Methods for solving problems

[0012] The gate driving device of the present invention drives a gate-driven semiconductor device. The gate driving device includes: a constant voltage circuit that discharges the gate of the semiconductor device with a constant voltage and ends the discharge operation before the voltage between the main terminals of the semiconductor device reaches a predetermined value; and a constant current circuit that, after the constant voltage circuit starts discharging with a constant voltage, starts discharging the gate with a constant current and continues to discharge the gate with a constant current after the constant voltage circuit ends the discharge operation.

[0013] The effects of the invention

[0014] According to the present invention, after a large amount of discharge current is output from the gate of the semiconductor element through a constant voltage circuit, a discharge current is output through a constant current circuit, thereby shortening the turn-off time of the semiconductor element.

[0015] Other issues, structures, and effects not mentioned above will be clarified through the following description of the implementation methods. Attached Figure Description

[0016] Figure 1 This is a diagram showing an example of the overall configuration of the gate driving device according to the first embodiment of the present invention.

[0017] Figure 2 This is a diagram illustrating an example of the discharge current from the gate of a semiconductor element according to the first embodiment of the present invention.

[0018] Figure 3 This is a timing diagram showing examples of the operating times of each part of the gate driving device according to the first embodiment of the present invention.

[0019] Figure 4 This is a graph showing the variation of the discharge current of the gate of the semiconductor element according to the first embodiment of the present invention.

[0020] Figure 5 This is a diagram illustrating an example of the operation of a conventional gate drive device.

[0021] Figure 6 This is a diagram illustrating an example of the operation of the gate driving device according to the first embodiment of the present invention.

[0022] Figure 7 This is a diagram illustrating an example of the use of Miller during the operation of the gate driving device according to the first embodiment of the present invention.

[0023] Figure 8This is a diagram illustrating an example of a time point when the gate voltage is less than a gate voltage threshold, where the moment during which the gate drive device of the first embodiment of the present invention switches from a constant voltage discharge period to a constant current discharge period is taken as the time point.

[0024] Figure 9 This is a diagram showing an example of the overall configuration of the gate driving device according to the second embodiment of the present invention.

[0025] Figure 10 This is a timing diagram showing examples of the operating times of each part of the gate driving device according to the second embodiment of the present invention.

[0026] Figure 11 This is a diagram illustrating an overall configuration example of the gate driving device according to the third embodiment of the present invention.

[0027] Figure 12 This is a timing diagram showing examples of the operating times of each part of the gate driving device according to the third embodiment of the present invention.

[0028] Figure 13 This is a diagram showing an overall configuration example of the gate driving device according to the fourth embodiment of the present invention.

[0029] Figure 14 This is a timing diagram of the gate driving device according to the fourth embodiment of the present invention.

[0030] Figure 15 This is a modified example of the timing diagram of the gate driving device according to the fourth embodiment of the present invention.

[0031] Figure 16 This is a diagram illustrating an overall configuration example of the motor drive inverter device according to the fifth embodiment of the present invention. Detailed Implementation

[0032] Hereinafter, embodiments for carrying out the present invention will be described with reference to the accompanying drawings. In this specification and the drawings, constituent elements having substantially the same function or structure are given the same reference numerals, and repeated descriptions are omitted. The present invention can be applied, for example, to inverter devices.

[0033] [First Implementation]

[0034] Figure 1 This diagram illustrates an overall configuration example of the gate driving device 501 according to the first embodiment. The gate driving device (gate driving device 501) drives a gate-driven semiconductor element (semiconductor element 301). In the following description, when the gate driving devices 501 are configured in pairs, they will drive... Figure 1 The gate driving device 501 of the semiconductor element 301 shown is referred to as the main arm, and the gate driving device 501 (not shown) that is paired with the main arm is referred to as the counterpart arm. Specific examples of the main arm and counterpart arm are described later. Figure 16 As shown.

[0035] Semiconductor element 301 is an example of a power semiconductor device used in inverters, etc. For example, an enhancement-mode N-channel MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor) is used as semiconductor element 301. Figure 1 The connection destinations of the drain and source of semiconductor element 301 are omitted. The gate 305 of semiconductor element 301 is connected to a circuit configured inside the gate driving device 501. The drain terminal of semiconductor element 301 is referred to as main terminal 302, and the source terminal is referred to as main terminal 303. The voltage applied between main terminals 302 and 303 is called the main terminal voltage Vds, and the current flowing through main terminals 302 and 303 is called the main terminal current Id.

[0036] The gate driving device 501 includes a semiconductor integrated circuit 502, a resistor 23, a transistor 42, and resistors 43 and 53. The semiconductor integrated circuit 502 is an example of the circuit constituting the gate driving device of the first embodiment. The semiconductor integrated circuit 502 includes a control circuit 21, a switch 22, a control circuit 31, a Miller clamp circuit 32, an operational amplifier 41, a selection circuit 44, a control circuit 51, a switch 52, and a comparator 54.

[0037] Switch 52 and resistor 53 constitute a constant voltage circuit 50 that discharges the gate 305 with a constant voltage. The constant voltage circuit (constant voltage circuit 50) discharges the gate (gate 503) of the semiconductor element (semiconductor element 301) with a constant voltage through resistor 53, and ends the discharge operation before the voltage between the main terminals of the semiconductor element (semiconductor element 301) reaches a predetermined value.

[0038] Control circuit 21 is connected to a control device (not shown) disposed outside the gate drive device 501. Control circuit 21 is connected to switch 22, control circuit 31, selection circuit 44, and control circuit 51. A control signal S1 is input to control circuit 21 to indicate whether semiconductor element 301 is turned on or off. When control signal S1 is input from the control device, control circuit 21 outputs control signal S21 to the gate of switch 22. Additionally, control circuit 21 outputs control signal S22 to control circuit 31, selection circuit 44, and control circuit 51. When control signal S1 indicates on, control circuit 21 outputs control signal S21 indicating on and control signal S22 indicating off. Conversely, when control signal S1 indicates off, control circuit 21 outputs control signal S21 indicating off and control signal S22 indicating on.

[0039] Switch 22 is, for example, a P-channel MOSFET, with its source grounded, drain connected to resistor 23, and gate connected to control circuit 21. Switch 22 is turned on when the control signal S1 output from control circuit 21 indicates an on state, and turned off when the control signal S1 indicates an off state. The on state of switch 22 maintains the semiconductor element 301 in the on state via resistor 23.

[0040] The control circuit 31 is connected to the gate 305 and the gate of the Miller clamp circuit 32. The control circuit 31 drives the Miller clamp circuit 32 according to the control signal S22.

[0041] The Miller clamping circuit 32 is, for example, an N-channel MOSFET, with its drain connected to the gate 305 and the output terminal of the Miller clamping circuit 32, its source grounded, and its gate connected to the control circuit 31. When the control signal S1 is enabled, the Miller clamping circuit 32 disconnects the Miller clamping action according to the output of the control circuit 31 based on the control signal S22. Conversely, when the control signal S1 is disabled, the Miller clamping circuit 32 can also perform the Miller clamping action according to the output of the control circuit 31 based on the control signal S22.

[0042] The constant current circuit 40 consists of an operational amplifier 41, a transistor 42, a resistor 43, and a selection circuit 44. After the constant voltage circuit (constant voltage circuit 50) begins discharging at a constant voltage, the constant current circuit (constant current circuit 40) begins discharging at a constant current to the gate (gate 503), and continues discharging at a constant current to the gate after the constant voltage circuit (constant voltage circuit 50) finishes discharging. For example, the constant current circuit 40 discharges at a constant current to the gate 305 through negative feedback.

[0043] Transistor 42 is, for example, an N-channel MOSFET, with its drain connected to its gate 305, its source grounded via resistor 43, and its gate connected to the output terminal of operational amplifier 41. Additionally, the emitter of transistor 42 is connected to the inverting input terminal of operational amplifier 41.

[0044] Selection circuit 44 switches the constant current output. The output terminal of selection circuit 44 is connected to the non-inverting input terminal of operational amplifier 41. Reference voltages V1 and V0 for negative feedback operation are input to selection circuit 44. Reference voltage V1 corresponds to the on of constant current operation, and reference voltage V0 corresponds to the off of constant current operation. Selection circuit 44 switches reference voltages V1 and V0 according to control signal S22 output from control circuit 21. When control signal S1 indicates on, selection circuit 44 selects reference voltage V0 as the output off level, and when control signal S1 indicates off, it selects reference voltage V1 as the specified level.

[0045] The current value of the output current of the constant current circuit 40 is determined by the following formula (1).

[0046] (Reference voltage value selected by selection circuit 44) / (Resistance value of resistor 43) ... (1)

[0047] Switch 52 is, for example, an N-channel MOSFET, with its drain connected to the gate 305 via resistor 53, its source grounded, and its gate connected to control circuit 51. Switch 52 is part of a constant voltage circuit that discharges the gate 305 with a constant voltage. Comparator 54 compares the gate voltage of the gate 305 with the gate voltage threshold V2 (see below). Figure 3 The comparison is performed, and the output is given when the gate voltage is higher than the gate voltage threshold V2.

[0048] The control circuit 51 is an AND logic circuit that drives the gate of the switch 52 when the output of the comparator 54 and the control signal S22 are input. The action of the constant voltage circuit 50 starting to discharge at a constant voltage when the switch 52 is turned on is called pre-discharge.

[0049] Switch 52 is used to ensure that the voltage Vds between the main terminals of semiconductor element 301 reaches a predetermined value pd1 (see below) according to the operation of control circuit 51. Figure 3 This is a pre-discharge circuit that terminates the constant voltage discharge operation before the current discharge. Switch 52 is open when the control signal S1 is indicated to be on. On the other hand, switch 52 is turned on when the control signal S1 is indicated to be off and when the gate voltage is higher than the gate voltage threshold V2.

[0050] Figure 2 This is a diagram illustrating an example of the discharge current from the gate 305 of semiconductor element 301. Figure 2 This is an enlarged view of the constant voltage circuit 50 and the constant current circuit 40.

[0051] The discharge current Ig of gate 305 is calculated by adding the discharge currents I1 and I2. Discharge current I1 is generated when the constant voltage circuit 50 is in the ON state, and discharge current I2 is generated when the constant current circuit 40 is in the ON state.

[0052] Figure 3 This is a timing diagram showing examples of the operating times of each part of the gate driving device 501 in the first embodiment.

[0053] Time t0 represents the point in time when control signal S1 switches from an on indication to an off indication. At time t0, switch 22 switches from on to off, and remains off. At time t0, selection circuit 44 switches the reference voltage V0 to the reference voltage V1, and switch 52 switches from off to on. Through the actions of switches 22 and 52 and selection circuit 44, before the constant current circuit 40 begins constant current discharge through negative feedback, switch 52 begins discharging gate 305 with a constant voltage. Discharging gate 305 lowers its gate voltage.

[0054] Time t1 represents the point in time after the gate voltage is less than the gate voltage threshold V2. At time t1, the constant voltage discharge operation of the constant voltage circuit 50 ends when switch 52 is switched from on to off. That is, the constant voltage circuit (constant voltage circuit 50) ends the discharge operation based on the condition that the gate voltage of the semiconductor element (semiconductor element 301) is less than the gate voltage threshold. The period of pre-discharge with constant voltage is the constant voltage discharge period p1 from time t0 to time t1. By opening switch 52, the constant current discharge of the constant current circuit 40 begins from time t1.

[0055] Time t2 represents the point in time when the constant current discharge performed by the constant current circuit 40 ends. During the constant current discharge period p2 from time t1 to time t2, the voltage Vds between the main terminals increases and the current Id between the main terminals decreases due to the constant current discharge. Furthermore, as described later... Figure 4 As shown, the constant current discharge period is strictly equivalent to period p21, but for convenience, in this specification, a portion of period p21 that does not overlap with the constant voltage discharge period p1 is referred to as the constant current discharge period p2.

[0056] Time t3 represents the point in time after the gate voltage drops below the gate voltage threshold th1 and the Miller clamp circuit 32 is turned on. At time t3, the discharge of the constant current circuit 40 ends. At time t3, the Miller clamp circuit 32 turns on, thereby ending the turn-off operation of the semiconductor element 301. That is, the turn-off time of the semiconductor element 301 is from time t0 to time t3. When the turn-off operation of the semiconductor element 301 ends, the gate voltage remains at the off level until time t4.

[0057] Time t4 represents the point in time when control signal S1 switches from an off indication to an on indication. At time t4, switch 22 switches from off to on, and Miller clamp circuit 32 switches from on to off. Selection circuit 44 switches reference voltage V1 to reference voltage V0, and switch 52 remains off. Additionally, the gate voltage begins to rise.

[0058] Figure 4This is a graph showing the change in the gate discharge current of semiconductor element 301. Figure 4 The study focuses on the change in gate discharge current from time t0 to time t2.

[0059] The constant voltage circuit 50 starts discharging at a constant voltage from time t0 and continues discharging until time t1. During the constant voltage discharge period p1 during which the constant voltage circuit 50 discharges the discharge current I1, the discharge current I1 gradually decreases.

[0060] The constant current circuit 40 begins discharging a constant current from time t11 and continues discharging until time t2. Time t11 falls between time t0 and time t1. During the constant current discharge period p21 in which the constant current circuit 40 discharges the discharge current I2, the discharge current I2 is a fixed value. Here, the period p3 from time t11 to time t1 is the overlap period of the discharge of the constant voltage circuit 50 and the discharge of the constant current circuit 40.

[0061] The discharge current Ig of gate 305 is calculated by adding discharge current I2 to discharge current I1. The discharge period from gate 305 is the length of constant current discharge period p2, in which constant voltage discharge p1 of constant voltage circuit 50 discharges, plus constant current discharge period p2 in which constant current discharges the gate. The phenomenon of constant voltage circuit 50 discharging during constant voltage discharge period p1, including overlapping period p3, is called pre-discharge.

[0062] Here, refer to Figure 5 and Figure 6 The differences in operation between the existing gate driving device and the gate driving device of the first embodiment will be explained. The gate driving device disclosed in Patent Document 1 will be referred to as the existing gate driving device. The existing gate driving device includes a constant voltage circuit and a constant current circuit.

[0063] Figure 5 This is a diagram illustrating an example of the operation of a conventional gate drive device. Figure 5 Recorded Figure 3 The timing diagram shown is part of the project, with the addition of the constant voltage on-time.

[0064] exist Figure 5 The timing diagram shown illustrates that the PWM on this arm switches from on to off at time t101. The discharge current of the gate discharge of the semiconductor element driven by the conventional gate drive device discharges during the constant current discharge period p101, and then during the constant voltage discharge period p102, which switches to constant voltage discharge.

[0065] The gate voltage discharging from the existing semiconductor element begins to decrease during constant current discharge (p101) and becomes a fixed voltage (p102) during constant voltage discharge. That is, at time t102, when switching from constant current discharge (p101) to constant voltage discharge (p102), the constant voltage circuit changes the constant voltage from off to on (Lo level). Time t102 is also the time when the gate voltage is less than the threshold value th102.

[0066] During the constant current discharge period p101, the discharge current is fixed. Midway through p101, the inter-terminal voltage Vds of the semiconductor element driven by the conventional gate drive device rises. Conversely, midway through p101, the inter-terminal current Id begins to decrease. For example... Figure 5 As shown, in existing gate drive devices, there is no overlap between constant voltage and constant current. Furthermore, the sequence is constant current discharge followed by constant voltage discharge. As mentioned above, because the constant current circuit operates slowly, the turn-off time of the semiconductor element cannot be shortened in existing gate drive devices.

[0067] Figure 6 This is a diagram illustrating an example of the operation of the gate driving device 501 according to the first embodiment. Figure 6 Is it to remove Figure 3 The timing diagram shown is a portion of the diagram.

[0068] exist Figure 6 The timing diagram shows that the PWM on this arm switches from on to off at time t0. When the PWM on this arm is off, a discharge current Ig is generated from the gate 305, and the gate voltage decreases. Between time t0 and time t12, the inter-terminal current Id is a fixed value. The inter-terminal voltage Vds between the drain and source of semiconductor element 301 begins to rise near the transition from the constant voltage discharge period p1 to the constant current discharge period p2. That is, during the constant current discharge period p2 after the discharge action in the constant voltage discharge period p1 of the constant voltage circuit 50 ends the discharge action, the constant current circuit 40 discharges with a constant current. The overlapping period p3 of the constant voltage discharge and the constant current discharge ends before time t12, before the inter-terminal voltage Vds reaches the predetermined value pd1. Therefore, the constant voltage discharge performed by the constant voltage circuit 50 ends before the inter-terminal voltage Vds reaches the predetermined value pd1.

[0069] In the gate driving device 501 of the first embodiment, the constant voltage circuit 50 with a small delay begins to discharge before the constant current circuit 40 with a large delay starts discharging with a constant current. That is, by pre-discharging, the delay time until the gate 305 begins to discharge is shortened. Furthermore, by overlapping the discharge period of the constant voltage circuit 50 with the discharge start of the constant current circuit 40, the gate 305 is reliably discharged with a constant current at the end of the pre-discharge.

[0070] The gate drive device 501 solves the rise delay time problem by using a high-speed constant voltage circuit 50 during the period before the rise of the low-speed constant current circuit 40. Furthermore, the gate drive device 501 can reduce the switching losses of the semiconductor element 301 caused by constant current. Additionally, by shortening the turn-off time of the semiconductor element 301, the gate drive device 501 can suppress the conduction losses until turn-off.

[0071] Various variations can be conceived in the operation of the gate drive device 501. An example of the operation of the gate drive device 501 is described below.

[0072] Figure 7 This is a diagram illustrating an example of the use of Miller during the operation of the gate drive device 501.

[0073] The period during which the voltage Vds between the main terminals of the gate-driven semiconductor device 301 actually starts switching is called the Miller period. In the figure, the Miller period p4 is defined as the time from time t1 to time t13.

[0074] The gate drive device 501 ends the pre-discharge operation of the constant voltage circuit 50 before the moment when the voltage Vds between the main terminals rises and before the moment t1 when the Miller period p4 begins. That is, the constant voltage circuit (constant voltage circuit 50) ends the discharge operation before the start of the Miller period (Miller period p4) when the voltage Vds between the main terminals of the semiconductor element (semiconductor element 301) rises.

[0075] The gate drive device 501 ends the constant voltage discharge before the start of Miller period p4, thus shortening the actual switching start period of the semiconductor element 301, ensuring that it can discharge with a constant current during switching. Therefore, the gate drive device 501 can obtain the stable switching characteristics of the semiconductor element 301 brought about by the constant current discharge characteristic and the reduction effect of switching losses brought about by this switching characteristic.

[0076] Figure 8 This is a diagram illustrating an example of the time t1 when switching from constant voltage discharge period p1 to constant current discharge period p2, where the gate voltage is less than the gate voltage threshold V2.

[0077] Figure 7The gate voltage of semiconductor element 301 in Miller period p4 shown is determined based on the voltage threshold and Vgs-Id characteristics set for the gate voltage of semiconductor element 301, and the inverter device for motor drive (see below). Figure 16 The gate voltage is determined by the output current of the semiconductor element 301 in Miller period p4. During Miller period, the gate voltage of semiconductor element 301 is lower than the gate voltage that keeps semiconductor element 301 in the ON state (e.g., the gate voltage at time t0). Therefore, a gate voltage threshold V2 is set between the gate voltage when semiconductor element 301 is ON and the gate voltage in Miller period p4. Gate drive device 501 ends pre-discharge at the point when the gate voltage is less than the gate voltage threshold V2.

[0078] exist Figure 8 The figure illustrates an example of setting a gate voltage threshold V2. As described above, the time point when the gate voltage of semiconductor element 301 is less than the gate voltage threshold V2 is defined as time t1. Arrow a1 in the figure indicates that at the time point when the gate voltage is less than the gate voltage threshold V2, the constant voltage discharge period p1 ends. Therefore, the constant voltage discharge period p1 only switches to the constant current discharge period p2 at time t1.

[0079] By setting the pre-discharge end time t1 according to the gate voltage threshold V2, it is possible to ensure that the gate 305 is discharged with a constant current when the voltage Vds between the main terminals changes. Therefore, it is possible to reduce the switching losses caused by the constant current circuit 40 and suppress the occurrence of power surges caused by the constant voltage circuit 50 not being turned on.

[0080] In the gate drive device 501 of the first embodiment described above, a high-speed constant voltage circuit 50 is used during the period before the rise of the low-speed constant current circuit 40, and an overlapping period p3 is set between the start of constant voltage discharge and constant current discharge. Furthermore, the gate drive device 501 ends the constant current discharge after the constant voltage discharge ends. Therefore, the problem of the rise delay time of the constant current circuit 40 can be solved.

[0081] Furthermore, since a constant voltage drive can be set during the concurrent period at the start of the turn-off of the semiconductor element 301, the turn-off time is shortened. As a result, the switching losses caused by constant current can be reduced, and the turn-off time of the semiconductor element 301 can be shortened, suppressing conduction losses until turn-off. In addition, the gate drive device 501 is an inexpensive component and can improve PWM controllability.

[0082] [Second Implementation]

[0083] Below, refer to Figure 9 and Figure 10The following describes a configuration example and an operation example of the gate driving device according to the second embodiment of the present invention. In the gate driving device of the second embodiment, the constant voltage discharge of the gate stops when the voltage between the main terminals is above the voltage threshold between the main terminals.

[0084] Figure 9 This is a diagram showing an overall configuration example of the gate driving device 501A according to the second embodiment.

[0085] The gate driving device 501A includes the semiconductor integrated circuit 502A of the second embodiment. The semiconductor integrated circuit 502A is an example of a semiconductor integrated circuit used to implement the gate driving device 501A. The circuitry of the gate driving device 501A other than the semiconductor integrated circuit 502A is... Figure 1 The gate driving device 501 shown in the first embodiment is the same, so a detailed description is omitted. The gate driving device 501A differs from the gate driving device 501 of the first embodiment in that it includes a diode 56, a resistor 57a, and a resistor 57b.

[0086] The cathode of diode 56 is connected to the drain terminal 302 of semiconductor element 301. The anode of diode 56 is connected to the midpoint of resistors 57a and 57b and the non-inverting input terminal of comparator 54A. Diode 56, resistors 57a and 57b are interfaces used to connect the voltage Vds between the main terminals of semiconductor element 301 to diode 56, limiting the maximum value of the input voltage without directly applying the voltage level of a battery (not shown) to comparator 54A.

[0087] The anode of diode 56 is connected to one input terminal (non-inverting input terminal) of comparator 54A, and a threshold voltage V3 is input to the other input terminal (inverting input terminal). Comparator 54A compares the voltage Vx supplied from the drain terminal 302 with the gate voltage threshold V3 input from the other input terminal. If the voltage Vx is greater than the threshold voltage V3, a positive voltage is output to the control circuit 51.

[0088] Figure 10 This is a timing diagram showing examples of the operating times of each part of the gate driving device 501A in the second embodiment.

[0089] Switch 52 is turned off when control signal S1 is on. Then, when the control signal changes from on to off at time t0, switch 52 turns on again. Switch 52 turns off again when control signal S1 is off and voltage Vx is above the threshold voltage V3. The time point from turn-on to turn-off of switch 52 is defined as time t21.

[0090] Time t21 is also the point at which, after the voltage Vds between the main terminals of semiconductor element 301 begins to rise, the voltage Vx becomes above the threshold voltage V3, and the voltage Vds between the main terminals becomes above the threshold voltage th2. The constant voltage circuit (constant voltage circuit 50) ends the discharge operation when the voltage Vds between the main terminals of semiconductor element (semiconductor element 301) becomes above the threshold voltage th2.

[0091] Next, from time t21 to time t2, the voltage Vds between the main terminals shifts due to the constant current discharge of the constant current circuit 40. As a result, in the gate drive device 501A of the second embodiment, the effect of reducing switching losses can also be obtained.

[0092] In the gate drive device 501A of the second embodiment described above, the pre-discharge ends at the point when the actual start of the switch to turn off the semiconductor element 301 is detected and the voltage Vds between the main terminals begins to rise. Therefore, the gate drive device 501A, through the combined effect of the constant current circuit and the pre-discharge, can achieve a high-speed rise with deviation but low loss until the middle of the switch. In addition, the gate drive device 501A achieves a stable switching operation with constant current after the pre-discharge ends, thus suppressing surge occurrence and minimizing switching losses.

[0093] [Third Implementation]

[0094] Below, refer to Figure 11 and Figure 12 The following describes a configuration example and an operation example of the gate driving device according to the third embodiment of the present invention. In the gate driving device of the third embodiment, the constant voltage discharge of the gate stops before the gate voltage is lower than the voltage threshold V2.

[0095] Figure 11 This is a diagram showing an overall configuration example of the gate driving device 501B according to the third embodiment.

[0096] The gate driving device 501B includes the semiconductor integrated circuit 502B of the second embodiment. The semiconductor integrated circuit 502B is an example of a semiconductor integrated circuit used to implement the gate driving device 501B. The circuitry of the gate driving device 501B other than the semiconductor integrated circuit 502B is... Figure 1 The gate driving device 501 shown in the first embodiment is the same, so detailed description is omitted.

[0097] Semiconductor integrated circuit 502B includes a pulse generation circuit 58 on one input side of control circuit 51, that is, on an input side different from the input side where the output of comparator 54 is received. Pulse generation circuit 58 receives control signal S22 from control circuit 21. When control signal S22 switches from an off indication to an on indication, pulse generation circuit 58 generates the pulse signal (described later). Figure 12 The pulse has a specified time width tp. The pulse generated by the pulse generation circuit 58 is input to the control circuit 51. The constant voltage circuit (constant voltage circuit 50) terminates the discharge operation after a certain time (a certain time tc) has elapsed since the start of the discharge operation.

[0098] When control circuit 51 receives both the output of comparator 54 and the pulse from pulse generation circuit 58, it turns on switch 52. Switch 52 is turned off when control signal S1 indicates on. Additionally, switch 52 turns on at moment t0 when control signal S1 switches from on to off. On the other hand, switch 52 turns off when the gate voltage is less than the gate voltage threshold V2, or when a certain time tc has elapsed since switch 52 was turned on. The certain time tc is set to be the same as or longer than the specified time width tp, but not excessively long.

[0099] Figure 12 This is a timing diagram showing an example of the operating times of each part of the gate driving device 501B in the third embodiment. Figure 12 right Figure 3 The timing diagram shown includes the operation time of the pulse generation circuit 58.

[0100] The time point t31 is defined as the elapsed time tc after switch 52 is turned on. Even if the gate voltage is not less than the threshold voltage V2 at time t31, the semiconductor integrated circuit 502B turns off switch 52. Therefore, in addition to the constant voltage discharge termination operation described in the first and second embodiments, the constant voltage circuit 50 also terminates the constant voltage discharge operation after a certain time tc has elapsed since the start of the discharge operation. The process of the constant voltage circuit 50 terminating the discharge operation after a certain time tc has elapsed since the start of the discharge operation is used in conjunction with the process of the gate drive device terminating the discharge operation in the first and second embodiments.

[0101] In the gate drive device 501B of the third embodiment described above, the constant voltage discharge ends even after a certain time tc has elapsed since the start of operation of the constant voltage circuit 50. For example, even if the gate voltage becomes abnormally high due to a fault in the semiconductor integrated circuit 502B, the switch 52 will turn off at a certain time tc after being turned on. Therefore, the switching elements such as the switch 52 will not be damaged, and the switching elements will be safely stopped.

[0102] Alternatively, the inter-terminal voltage Vds in the second embodiment can also be combined to form the inter-terminal voltage threshold th2. Figure 10 The above-mentioned process of stopping constant voltage discharge is the same as the process of ending constant voltage discharge in the third embodiment when a certain time tc has elapsed since the start of operation of constant voltage circuit 50.

[0103] Furthermore, in cases such as abnormal current flowing beyond the normal operating range, the gate voltage during the Miller period may exceed the gate voltage threshold V2, or an abnormality may occur in the voltage detection circuit (not shown). Even in such cases, since the constant voltage discharge of the constant current circuit 40 stops after a certain time tc, surges from the constant voltage circuit 50 can be suppressed.

[0104] [Fourth Implementation]

[0105] Below, refer to Figures 13 to 15 The configuration and operation examples of the gate driving device according to the fourth embodiment of the present invention will be described.

[0106] Figure 13 This is a diagram showing an example of the overall configuration of the gate driving device 501C according to the fourth embodiment.

[0107] The gate driving device 501C includes the semiconductor integrated circuit 502C of the fourth embodiment. The semiconductor integrated circuit 502C is an example of a semiconductor integrated circuit used to implement the gate driving device 501C. The circuitry of the gate driving device 501C other than the semiconductor integrated circuit 502C is... Figure 1 The gate driving device 501 shown in the first embodiment is the same, so detailed description is omitted.

[0108] Semiconductor integrated circuit 502C includes a control circuit 45 that limits the conditions under which the selection circuit 44 selects the reference voltage V1. For example, the control circuit 45 is constructed from a logic product circuit. One input terminal of the control circuit 45 receives a control signal S22, and the other input terminal receives the output of the control circuit 31 inverted. Based on the output of the control circuit 45, the selection circuit 44 selects the reference voltage V1 when the control signal S1 is off and the Miller clamp circuit 32 is off. The constant current circuit (constant current circuit 40) ends the discharge operation before the semiconductor element (semiconductor element 301) begins charging its gate (gate 305) again.

[0109] Figure 14 This is the timing diagram of the gate drive device 501C. Figure 14 It is recorded in the middle. Figure 13The timing of the local arm-side PWM, the opposite arm-side PWM, the gate discharge current, the gate voltage LG of transistor 42, the local arm-side gate voltage, the Miller clamp circuit 32, and the opposite arm-side gate voltage in the gate drive device 501C shown.

[0110] At time t0, the PWM on the opposite arm remains off, while the PWM on the local arm switches from on to off. The gate voltage LG of transistor 42 begins to rise. The gate voltage on the local arm (the voltage of gate 305) decreases. The gate voltage on the opposite arm (the gate voltage of the semiconductor element disposed on the opposite arm, not shown) remains unchanged.

[0111] As described above, constant voltage discharge and constant current discharge occur from time t0 to time t3. After time t3, the PWM on the opposite arm side is activated at time t41. Therefore, the gate voltage on the opposite arm side begins to rise. Additionally, at time t3, the Miller clamp circuit 32 is activated, becoming the ground voltage Lo.

[0112] At time t42, the gate voltage LG of transistor 42 decreases. Time t42 is the point in time before the next cycle begins charging of the gate. The constant current circuit 40 ends the discharge operation before the semiconductor element 301 begins charging the gate again. After time t42, transistor 42 enters the state of discharge operation completed (gate off). The state of discharge operation completed (gate off) continues during period p11.

[0113] At time t43, the PWM on the opposite arm switches from on to off, and the gate voltage on the opposite arm begins to decrease. The point at which the gate voltage on the opposite arm completely decreases is designated as time t44. After time t44, at time t45, the PWM on this arm turns on, and the Miller clamp circuit 32 turns off. Additionally, the gate voltage on this arm begins to rise. The point at which the gate voltage on this arm exceeds the voltage threshold th3 is designated as time t46. From time t44 to time t46, neither the semiconductor element 301 on this arm nor the semiconductor element on the opposite arm (not shown) performs any substantial operation; therefore, this period is referred to as the dead time period p13.

[0114] After time t46, the point at which the gate voltage on this arm reaches its maximum value is designated as time t47. The period from the time t45 when the gate voltage on this arm begins to rise to the time t47 when the gate voltage on this arm reaches its maximum value is called the turn-on time p12. The turn-on time p12 represents the time required for the semiconductor element 301 on this arm to substantially operate.

[0115] In the gate drive device 501C of the fourth embodiment described above, the current path of the constant current circuit 40 is cut off until the start of the next gate charge (time t46). Therefore, the on-time p12 and dead time p13 of the semiconductor element 301 in the next cycle are shortened, and the loss in the dead time can be reduced.

[0116] Figure 15 yes Figure 14 The timing diagram shown is a variation.

[0117] The gate voltage LG of transistor 42 decreases at time t3 immediately after the constant current discharge, which serves as the gate discharge current, has ended. Alternatively, the gate voltage LG may decrease after time t3, as shown by the dashed line LG2. Figure 3 As shown, time t3 is the moment when the gate voltage is less than the gate voltage threshold th1. That is, at time t3 when the gate voltage is less than the gate voltage threshold th1, the gate voltage LG of transistor 42 begins to decrease, and the Miller clamp circuit 32 changes from off to on.

[0118] The Miller clamp circuit (Miller clamp circuit 32) maintains the gate voltage at a low level when the gate voltage of the semiconductor element (semiconductor element 301) is less than the gate voltage threshold (gate voltage threshold th1). The Miller clamp circuit 32 disconnects at the moment t51 when the PWM is turned on on this arm side. As the operation of the Miller clamp circuit (Miller clamp circuit 32) begins, the constant current circuit (constant current circuit 40) ends its discharge operation.

[0119] exist Figure 15 In this configuration, the on-time p12A of the semiconductor element 301 on this arm side is set to the period from when the PWM on this arm side is turned on at time t51 to when it is turned off at time t52. Therefore, the on-time p12A continues until the gate voltage begins to decrease after the gate voltage reaches its maximum value. The gate off-time p11A, where the gate becomes off after the gate discharge operation ends, is from time t3 to time t52. Since the constant current circuit 40 ends its discharge operation after the Miller clamp circuit 32 starts operating, the current path of the constant current circuit 40 can be reliably cut off before the next gate charging begins.

[0120] [Fifth Implementation]

[0121] Next, refer to Figure 16 Examples of configuration and operation of a power conversion device having the gate driving device of the first to fourth embodiments of the present invention will be described.

[0122] Figure 16This diagram illustrates an example of the overall configuration of the motor drive inverter device 200. The motor drive inverter device 200 is an example of the power conversion device according to the fifth embodiment. The power conversion device (motor drive inverter device 200) includes a gate drive device (gate drive device 501) that drives a gate drive type semiconductor element (semiconductor element 301), and converts the power supplied to the load (motor 900) according to the operation of the semiconductor element (semiconductor element 301).

[0123] The motor drive inverter device 200 includes a current sensor 201, a motor control controller 210, a gate drive circuit 220, a voltage sensor 230, a voltage smoothing capacitor 240, and a power semiconductor module 300 as main components. The motor control controller 210 controls the motor 900. The current sensor 201 monitors the output current of the motor drive inverter device 200. The voltage smoothing capacitor 240 smooths the applied voltage that fluctuates during power conversion input to the motor drive inverter device 200. The power semiconductor module 300 is a power semiconductor device modularized from multiple semiconductor elements 301.

[0124] A battery 901 and a contactor 902 are connected to the motor drive inverter device 200. The contactor 902 controls the connection or disconnection between the motor drive inverter device 200 and the battery 901.

[0125] When a host controller (not shown) provides a torque or rotation command, or other command for driving the motor, to the motor control controller 210, the motor control controller 210 provides a PWM signal corresponding to the command to the gate drive circuit 220. The gate drive circuit 220 controls the switching of the power semiconductor module 300 according to the PWM signal. The motor drive inverter device 200 has the following function: by controlling the switching of the power semiconductor module 300, when the contactor 902 is closed, it converts the DC voltage supplied from the battery 901 into an AC voltage for driving the motor 900.

[0126] In the gate drive circuit 220, a gate drive device 501 is provided for each of the plurality of semiconductor elements 301 configured in the power semiconductor module 300. Using the timing diagram described above, the gate drive device 501 that operates at the time of interest is referred to as the local arm-side gate drive device 501_1. The gate drive devices 501 used in pairs with the local arm-side gate drive device 501_1 are referred to as the opposite arm-side gate drive devices 501_2. In addition, a power supply 510 for supplying drive voltage to the motor control controller 210 is provided in the gate drive circuit 220.

[0127] In the motor drive inverter device 200, a voltage sensor 230 composed of multiple resistors is provided as a safety measure component. The voltage divided by the voltage sensor 230 is input to the motor control controller 210 to monitor the voltage. The motor drive inverter device 200 controls the torque and rotational speed of the motor 900 based on information from the motor drive rotation sensor 910, the current sensor 20, and the voltage sensor 10. When the motor 900 is driven, and the contactor 902 is disconnected according to the instruction of the upper controller, the motor drive inverter device 200 is electrically disconnected from the battery 901.

[0128] Semiconductor element 301 is divided into upper arm semiconductor element 301u and lower arm semiconductor element 301d. Motor control controller 210 controls the switching on and off of upper arm semiconductor element 301u and lower arm semiconductor element 301d through gate drive circuit 220. Voltage smoothing capacitor 240 absorbs the voltage ripple generated when the upper arm semiconductor element 301u and lower arm semiconductor element 301d are switched.

[0129] The motor drive inverter device 200 of the fifth embodiment described above, by incorporating the gate drive device of the first to fourth embodiments, can improve the power efficiency of the power semiconductor module 300. Furthermore, it can also reduce the switching losses of the upper arm semiconductor element 301u and the lower arm semiconductor element 301d of the power semiconductor module 300. Therefore, the overall power efficiency of the motor drive inverter device 200 can be improved.

[0130] Furthermore, the present invention is not limited to the above-described embodiments. As long as it does not depart from the spirit of the present invention as described in the claims, various other application examples and modifications may also be adopted.

[0131] For example, the above embodiments have been described in detail and specifically to illustrate the structure of the apparatus for ease of understanding of the present invention, and are not necessarily limited to having all the described structures. Furthermore, a portion of the structure of the embodiments described herein may be replaced with the structure of other embodiments, and the structure of other embodiments may be added to the structure of a certain embodiment. Additionally, for a portion of the structure of each embodiment, other structures may be added, deleted, or replaced.

[0132] Furthermore, control lines and information lines refer to lines deemed necessary in the specifications, but not all control lines and information lines may be represented on the product. In reality, almost all components can be considered interconnected.

[0133] Symbol Explanation

[0134] 21…control circuit, 22…switch, 32…Miller clamping circuit, 40…constant current circuit, 50…constant voltage circuit, 301…semiconductor element, 305…gate, 501…gate drive device, 502…semiconductor integrated circuit.

Claims

1. A gate drive device that drives a semiconductor element of a gate drive type, the gate drive device characterized by comprising: a constant voltage circuit that discharges a gate of the semiconductor element at a constant voltage, and ends a discharge operation before a voltage between main terminals of the semiconductor element reaches a prescribed value; and a constant current circuit that starts discharging the gate at a constant current after the constant voltage circuit starts discharging the gate at a constant voltage, and continues discharging the gate at a constant current after the constant voltage circuit ends the discharge operation.

2. The gate drive device according to claim 1, characterized in that the constant voltage circuit ends the discharge operation before a Miller period in which the voltage between the main terminals of the semiconductor element rises starts.

3. The gate drive device according to claim 1, characterized in that the constant voltage circuit ends the discharge operation based on a case where a gate voltage of the semiconductor element has become less than a gate voltage threshold value.

4. The gate drive device according to claim 2, characterized in that the constant voltage circuit ends the discharge operation in a case where a certain time has passed after the discharge operation starts.

5. The gate drive device according to claim 1, characterized in that the constant voltage circuit ends the discharge operation based on a case where the voltage between the main terminals of the semiconductor element has become a main terminal voltage threshold value or more.

6. The gate drive device according to claim 5, characterized in that the constant voltage circuit ends the discharge operation in a case where a certain time has passed after the discharge operation starts.

7. The gate drive device according to claim 1, characterized in that the constant current circuit ends the discharge operation before the semiconductor element next starts charging the gate.

8. The gate drive device according to claim 1, characterized by comprising a Miller clamp circuit that holds a gate voltage of the semiconductor element at a low level when the gate voltage is less than a gate voltage threshold value, the constant current circuit ends the discharge operation in conjunction with the start of an operation of the Miller clamp circuit.

9. A power conversion device that comprises a gate drive device that drives a semiconductor element of a gate drive type, and converts power supplied to a load in accordance with an operation of the semiconductor element, the power conversion device characterized in that the gate drive device comprises: a constant voltage circuit that discharges a gate of the semiconductor element at a constant voltage, and ends a discharge operation before a voltage between main terminals of the semiconductor element reaches a prescribed value; and a constant current circuit that starts discharging the gate at a constant current after the constant voltage circuit starts discharging the gate at a constant voltage, and continues discharging the gate at a constant current after the constant voltage circuit ends the discharge operation. ​

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