Gate driver circuit, motor drive device using the same, and electronic device

Abstract

To restrain through-current and ringing caused by reverse recovery current of an opposite-side flywheel diode.SOLUTION: A voltage higher than the source of a high-side transistor MH is generated on a high-level line 412. A turn-on transistor SW1 sources a current IHG_ON to the gate of the high-side transistor MH. The turn-on transistor SW1 includes a plurality of transistors MP1 to MPn connected in parallel between the gate of the high-side transistor MH and the high-level line 412. When turning on the high-side transistor MH, a control circuit 210 controls the plurality of transistors MP1 to MPn such that the turn-on transistor SW1 has a first driving capability in a first period T1, has a second driving capability in a second period T2, and has a third driving capability in a third period.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to a gate driver circuit. [Background technology]

[0002] Half-bridge circuits, H-bridge circuits, and three-phase bridge circuits (hereinafter collectively referred to as bridge circuits) that use power transistors are widely used in motor driver circuits, DC / DC converters, power conversion devices, and the like.

[0003] 1 is a circuit diagram of a bridge circuit 10. The bridge circuit 10 includes an upper arm 12 and a lower arm 14 that are connected in series between a power supply terminal and a ground terminal. The upper arm 12 includes a high-side transistor MH and a flywheel diode Di that are connected in parallel. The lower arm 14 includes a low-side transistor ML and a flywheel diode Di that are connected in parallel. An inductor (coil) L1, which serves as a load, is connected to the output terminal of the bridge circuit 10.

[0004] The bridge circuit 10 can take a state φ1 in which both the high-side transistor MH and the low-side transistor ML are off (high impedance state), a state φ2 in which the high-side transistor MH is on and the low-side transistor ML is off (high output state), and a state φ3 in which the high-side transistor MH is off and the low-side transistor ML is on (low output state). OUT is discharged (flowing to the right in the figure), and the bridge circuit 10 is in a current source state where the current I OUT In the figure, there is a current sink state in which the current flows to the left. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2018-82575 A

[0006] [overview] As a result of examining the bridge circuit of FIG. 1, the present inventors have come to recognize the following problem.

[0007] Consider a transition from a high impedance state φ1 to a high output state φ2 in the current source state. In state φ1, the output current I OUT is supplied to the load via the flywheel diode Di of the lower arm 14 (current source). OUT is -Vf. Vf is the forward voltage of the flywheel diode Di.

[0008] In state φ2, the output current I OUT flows through the high-side transistor MH. A reverse recovery current Irc flows from the cathode to the anode in the flywheel diode Di of the lower arm 14 on the opposite side. Therefore, the high-side transistor MH receives the output current I OUT Both the reverse recovery current Irc and the through current Irc flow. This state is equivalent to a through current flowing. When a through current flows, the output voltage V OUT This causes instability and ringing, which is undesirable as it can lead to unwanted radiation.

[0009] The present disclosure has been made in view of the above problems, and one exemplary purpose of an embodiment of the present disclosure is to provide a gate driver circuit capable of suppressing shoot-through current and ringing caused by reverse recovery current of an opposite-side flywheel diode.

[0010] An embodiment of the present disclosure relates to a gate driver circuit that drives an N-type power transistor that constitutes a switching circuit. The gate driver circuit includes a high level line on which a voltage higher than the source of the power transistor occurs, a turn-on transistor configured to source a current to the gate of the power transistor, a turn-off transistor configured to sink a current from the gate of the power transistor, and a control circuit that controls the turn-on transistor and the turn-off transistor. The turn-on transistor includes a plurality of transistors connected between the gate of the power transistor and the high level line. When turning on the power transistor, the control circuit controls the on / off states of the plurality of transistors so that in a first period, the turn-on transistor has a first capability, in a second period, the turn-on transistor has a second capability lower than the first capability, and in a third period, the turn-on transistor has a third capability higher than the second capability.

[0011] Any combination of the above components, and mutual substitution of the components and expressions of the present disclosure between methods, devices, systems, etc. are also valid aspects of the present invention. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a circuit diagram of a bridge circuit. [Diagram 2] FIG. 2 is a circuit diagram of a switching circuit according to the embodiment. [Diagram 3] FIG. 3 is a circuit diagram of a gate driver circuit according to the embodiment. [Figure 4] FIG. 4 is an operational waveform diagram of the gate driver circuit of FIG. [Diagram 5] FIG. 5 is a circuit diagram of a drive circuit including a gate driver circuit. [Figure 6] FIG. 6 is a circuit diagram of a turn-on circuit according to the first modification. [Figure 7] FIG. 7 is a circuit diagram of a turn-on circuit according to the second modification. [Figure 8] FIG. 8 is a waveform diagram showing the operation (simulation results) of the turn-on circuit of FIG. [Figure 9] FIG. 9 is a circuit diagram of the drive circuit. [Figure 10] FIG. 10 is a circuit diagram of a motor drive device including a switching circuit according to an embodiment.

[0013] [Detailed Description] (Overview of the embodiment) A summary of some exemplary embodiments of the present disclosure will be described. This summary is intended to provide a simplified description of some concepts of one or more embodiments for the purpose of providing a basic understanding of the embodiments as a prelude to the detailed description that follows, and is not intended to limit the scope of the invention or disclosure. For convenience, the term "one embodiment" may be used to refer to one embodiment (example or variant) or multiple embodiments (examples or variants) disclosed in this specification.

[0014] This summary is not an exhaustive overview of all possible embodiments, nor is it intended to identify key elements of all embodiments or to delineate the scope of some or all aspects. Its sole purpose is to present some concepts of one or more embodiments in a simplified form as a prelude to the more detailed description that is presented later.

[0015] A gate driver circuit according to one embodiment drives an N-type power transistor constituting a switching circuit. The gate driver circuit includes a high level line on which a voltage higher than the source of the power transistor is generated, a turn-on transistor configured to source a current to the gate of the power transistor, a turn-off transistor configured to sink a current from the gate of the power transistor, and a control circuit that controls the turn-on transistor and the turn-off transistor. The turn-on transistor includes a plurality of transistors connected between the gate of the power transistor and the high level line. When turning on the power transistor, the control circuit controls the on / off states of the plurality of transistors so that in a first period, the turn-on transistor has a first capability, in a second period, the turn-on transistor has a second capability lower than the first capability, and in a third period, the turn-on transistor has a third capability higher than the second capability.

[0016] The current drive capability (also simply called drive capability or capability) of a turn-on transistor is the sum of the drive capabilities of the transistors that are in the on state among a plurality of transistors, and the drive capability of each transistor is determined by W / L (gate width / gate length). In the first to third periods, the current flowing through the turn-on transistor is determined by the drive capability of the turn-on transistor.

[0017] According to the above configuration, a first amount of drive current is supplied to the gate of the power transistor during a first period immediately before the power transistor is turned on, and the gate voltage is increased. Then, during a second period after the power transistor is turned on and during which a reverse recovery current may flow through the flywheel diode of the opposite arm, the drive current supplied to the gate of the power transistor is reduced to slowly turn on the power transistor while keeping the on-resistance of the power transistor large. This makes it possible to suppress shoot-through current and ringing caused by the reverse recovery current of the flywheel diode of the opposite arm. Next, during a third period during which the reverse recovery current is less likely to flow, the amount of current supplied to the gate is increased more than that of the second period, thereby shortening the turn-on time of the power transistor and reducing power consumption. Furthermore, during both the first and second periods, the first current mirror circuit operates and the amount of input current of the first current mirror circuit is switched, so that the current supplied to the gate changes slowly when switching to the second period. This makes it possible to further reduce power consumption.

[0018] In one embodiment, the third capability may be higher than the first capability. That is, the current supplied to the gate of the power transistor in the third period may be higher than the current supplied to the gate of the power transistor in the first and second periods. After the influence of the reverse recovery characteristic of the flywheel diode of the opposite arm becomes small, the on-resistance of the power transistor can be reduced in a short time by increasing the amount of current supplied to the gate of the power transistor, and the efficiency of the bridge circuit can be improved.

[0019] In one embodiment, at least one of the plurality of transistors may include a first transistor group assigned to the second period and a second transistor group assigned to the first period and the third period. The control circuit may fix the second transistor group to be off in the second period. In the second period, only the transistors included in the first transistor group can be turned on. As a result, when transitioning from the first period to the second period and from the second period to the third period, only one of the transistors being turned on and the transistors being turned off occurs, thereby suppressing discontinuity of current.

[0020] In one embodiment, the control circuit may control the on / off states of the plurality of transistors so that the turn-on transistor has a fourth capability higher than the third capability during the fourth period, thereby fixing the power transistor in the on state.

[0021] In one embodiment, the transistors may have the same size.

[0022] In one embodiment, the transistors may have binary weighted sizes.

[0023] In one embodiment, the gate driver circuit may further include a first sensor that compares the gate-source voltage of the power transistor with a first threshold voltage. The control circuit may transition to the second period in response to an output change of the first sensor in the first period. By monitoring the gate-source voltage of the power transistor, the magnitude of the drive current can be changed in conjunction with the transition of the power transistor from an off state to an on state. The first threshold voltage may be equal to, higher than, or lower than the gate threshold voltage of the MOSFET.

[0024] In one embodiment, the first sensor may be shared with a high-side off sensor that detects when the high-side transistor is turned off. This allows the drive current to be reduced before the high-side transistor is turned on. Also, an increase in the circuit area can be suppressed.

[0025] In one embodiment, the gate driver circuit may further include a second sensor that compares the output voltage of the switching circuit with a second threshold voltage. The control circuit may transition to a third period in response to a change in the output of the second sensor in the second period. By monitoring the output voltage, it is possible to detect that the effect of the reverse recovery characteristic of the flywheel diode of the opposite arm has become smaller.

[0026] In one embodiment, the gate driver circuit may further include a third sensor that compares the output voltage of the switching circuit with a third threshold voltage. The control circuit may transition to the fourth period in response to a change in the output of the third sensor during the third period.

[0027] In one embodiment, the gate driver circuit may be monolithically integrated on a single semiconductor substrate. "Monolithic integration" includes cases where all of the circuit components are formed on a semiconductor substrate, and cases where the main components of the circuit are monolithically integrated, and some resistors, capacitors, etc. may be provided outside the semiconductor substrate for adjusting the circuit constants. By integrating the circuit on a single chip, the circuit area can be reduced and the characteristics of the circuit elements can be kept uniform.

[0028] A motor drive circuit according to one embodiment includes a bridge circuit including a high-side transistor and a low-side transistor, a high-side driver which is any of the gate driver circuits described above that drives the high-side transistor as a power transistor, and a low-side driver which is any of the gate driver circuits described above that drives the low-side transistor as a power transistor.

[0029] An electronic device according to an embodiment includes a motor and the above-described motor drive device that drives the motor.

[0030] (Embodiment) Preferred embodiments will be described below with reference to the drawings. The same or equivalent components, parts, and processes shown in each drawing are given the same reference numerals, and duplicated descriptions will be omitted as appropriate. In addition, the embodiments are illustrative and do not limit the invention, and all features and combinations thereof described in the embodiments are not necessarily essential to the invention.

[0031] In this specification, "a state in which component A is connected to component B" includes not only a case in which component A and component B are directly physically connected to each other, but also a case in which component A and component B are indirectly connected to each other via other components that do not substantially affect the electrical connection state between them or that do not impair the function or effect achieved by their combination.

[0032] Similarly, "a state in which component C is provided between components A and B" includes not only the case in which components A and C, or components B and C, are directly connected to each other, but also the case in which they are indirectly connected to each other via other components that do not substantially affect the electrical connection between them or that do not impair the functions or effects achieved by their combination.

[0033] 2 is a circuit diagram of a switching circuit 100 according to an embodiment. The switching circuit 100 includes a bridge circuit 110 and a drive circuit 200. Although only the configuration of one phase of the switching circuit 100 is shown here, the switching circuit 100 may be a three-phase circuit or an H-bridge circuit.

[0034] The bridge circuit 110 includes an upper arm 112 provided between a power supply line (input line) 102 and an output terminal (output line) 104, and a lower arm 114 provided between the output line 104 and a ground line 106. The upper arm 112 includes a high-side transistor MH and a flywheel diode (freewheel diode) Di connected in parallel. The lower arm 114 includes a low-side transistor ML and a flywheel diode Di connected in parallel. In this embodiment, the high-side transistor MH and the low-side transistor ML are N-channel MOSFETs, and their respective body diodes also function as the flywheel diode Di.

[0035] The drive circuit 200 controls the upper arm 112 and the lower arm 114 of the bridge circuit 110. The drive circuit 200 switches between three states: a high impedance state φ1 in which the upper arm 112 and the lower arm 114 are both off, a high output state φ2 in which the upper arm 112 is on and the lower arm 114 is off, and a low output state φ3 in which the upper arm 112 is off and the lower arm 114 is on. OUT The direction of current I from the output line 104 of the bridge circuit 110 to the load, the inductor L1, is taken as positive, and the opposite direction is taken as negative. OUT is positive (current source), and the output current I OUT In this case, there are states φ1B to φ3B in which the input is negative (current sink).

[0036] The drive circuit 200 is a functional IC that includes a control circuit 210, a high-side driver circuit 220, and a low-side driver circuit 260, and is integrated on a single semiconductor substrate. The control circuit 210 selects one of states φ1 to φ3 according to the load state of the bridge circuit 110, and generates control signals HGCTL and LGCTL according to each of the states φ1 to φ3. In state φ1, the high-side control signal HGCTL and the low-side control signal LGCTL are both at an off level (for example, low). In state φ2, the high-side control signal HGCTL is at an on level (for example, high), and the low-side control signal LGCTL is at an off level. In state φ3, the high-side control signal HGCTL is at an off level, and the low-side control signal LGCTL is at an on level.

[0037] The high-side driver circuit 220 receives a high-side control signal HGCTL at an input node IN, and an output node OUT is connected to the gate of the high-side transistor MH via a high-side gate pin HG. When the high-side control signal HGCTL transitions from an off level to an on level, the high-side driver circuit 220 supplies a driving current I HG_ON and supplies the gate-source voltage V of the high-side transistor MH. GS When the high-side control signal HGCTL transitions from an ON level to an OFF level, the high-side driver circuit 220 supplies a driving current I HG_OFF Pull out the gate-source voltage V GS This causes the high-side transistor MH to turn off.

[0038] The high-side driver circuit 220 can select a number of operation modes when the high-side transistor MH is turned on, one of which is referred to as a first mode. In the first mode, the high-side driver circuit 220 controls the drive current I HG_ON is changed in multiple stages.

[0039] In the first mode, the high-side driver circuit 220 controls the driving current I HG_ON During a second period T2 following the first period T1, a driving current I HG_ON Then, in a third period T3 following the second period T2, a driving current I HG_ON Output.

[0040] The high-side driver circuit 220 is configured to be operable in a second mode in addition to the first mode. In the second mode, the driving current I HG_ON The waveform of the driving current I HG_ON is a constant amount Ic that is greater than the second current amount I2 from when the high side control signal HGCTL transitions from the off level to the on level until the state transition of the bridge circuit 110 is completed. The constant amount Ic may be greater than any of the first current amount I1 to the third current amount I3.

[0041] The low-side driver circuit 260 receives a low-side control signal LGCTL at an input node IN, and an output node OUT is connected to the gate of the low-side transistor ML via a low-side gate pin LG. When the low-side control signal LGCTL transitions from an off level (for example, low) to an on level (high), the low-side driver circuit 260 supplies a driving current I LG_ON and supplies the gate-source voltage V of the low-side transistor ML. GS When the low-side control signal LGCTL transitions from an ON level to an OFF level, the low-side driver circuit 260 supplies a driving current I LG_OFF Pull out the gate-source voltage V GS , turning off the low-side transistor ML.

[0042] Like the high-side driver circuit 220, the low-side driver circuit 260 is configured to be switchable between a first mode and a second mode.

[0043] In the first mode, the low-side driver circuit 260 controls the driving current I LG_ON is changed in multiple stages.

[0044] In the first mode, the low-side driver circuit 260 outputs a driving current I of a fourth current amount I4 during a fourth period T4 after the low-side control signal LGCTL transitions from an off level to an on level. LG_ON During a fifth period T5 following the fourth period T4, a driving current I LG_ON Then, in a sixth period T6 following the fifth period T5, a driving current I LG_ON Output.

[0045] In the second mode, the driving current I LG_ON The waveform of the driving current I LG_ON is a constant amount Id greater than the fifth current amount I5 from when the low-side control signal LGCTL transitions from an off level to an on level until the state transition of the bridge circuit 110 is completed. The constant amount Id may be greater than any of the fourth current amount I4 to the sixth current amount I6.

[0046] The above is the configuration of the switching circuit 100. Next, the operation will be described.

[0047] First, we will explain the operation of the high-side driver circuit 220. The high-side driver circuit 220 operates in a first mode when a reverse recovery current of the flywheel diode of the lower arm 114 may occur, and operates in a second mode when a reverse recovery current of the flywheel diode of the lower arm 114 does not occur.

[0048] Specifically, in the high-side driver circuit 220, the high-side transistor MH and the low-side transistor ML are off, and a current I OUT When the high-side transistor MH is turned on (source rise) from the state φ1A in which the current is sourced, the device operates in the first mode.

[0049] In addition, in the high-side driver circuit 220, the high-side transistor MH is off and the low-side transistor ML is on, and a current I OUT The input current flows through the high-side transistor MH and the high-side transistor MH is turned on (sink rise). This causes the input current to flow through the high-side transistor MH. The input current flows through the high-side transistor MH and the high-side transistor MH is turned on (sink rise). This causes the input current to flow through the high-side transistor MH and the high-side transistor MH to turn on (sink rise).

[0050] 3 is a circuit diagram of a gate driver circuit 400 according to an embodiment. Here, the gate driver circuit 400 is the high-side driver circuit 220 in FIG 2, and drives an N-type high-side transistor MH that forms the upper arm.

[0051] The turn-on circuit 410 supplies an on-current I to the gate of the high-side transistor MH, which is an N-type power transistor. HG_ON The turn-off circuit 420 is configured to source a current I from the gate of the high-side transistor MH. HG_OFF The device is configured to sink

[0052] The turn-on circuit 410 includes a turn-on transistor SW1. The turn-on transistor SW1 is configured to have a variable driving capability S. Specifically, the turn-on transistor SW1 includes a plurality of n transistors MP1 to MPn connected in parallel. The plurality of transistors MP1 to MPn are configured to be independently switchable on and off. The driving capability S of the turn-on transistor SW1 is adjustable according to the number of transistors that are in an on state among the plurality of transistors MP1 to MPn.

[0053] The drive capability of the i-th (i=1, 2, ... n) transistor MPi is determined by the aspect ratio W / L of the gate width W and gate length L. Therefore, the drive capability of the turn-on transistor SW1 is the sum of the drive capabilities of the transistors that are on.

[0054] In this embodiment, the W / L, i.e., the driving capabilities, of the multiple transistors MP1 to MPn are all equal. Therefore, when m out of n transistors (1≦m≦n) are on, the driving capability of the turn-on transistor SW1 is m times that of one transistor.

[0055] The control circuit 210 generates a control signal HGCTL that indicates the states of the turn-on transistor SW1 and the turn-off transistor SW2. Specifically, the control circuit 210 is configured to control the on / off states of the multiple transistors MP1 to MPn with respect to the turn-on transistor SW1.

[0056] In the first mode, the control circuit 210 operates in the following sequence including a first period T1 to a fourth period T4 in response to an instruction to turn on the high-side transistor MH.

[0057] The capability of the turn-on transistor SW1 is determined so that the turn-on transistor SW1 operates in a saturation region during the first period T1 to the third period T3. During the fourth period T4, the turn-on transistor SW1 is considered to operate in a linear region.

[0058] (i) First Period T1 In the first period T1, the capacity of the turn-on transistor SW1 is set to a first capacity S1. Therefore, the current flowing through the turn-on transistor SW1 does not depend on the drain-source voltage, but is determined by the gate-source voltage and the current capacity. In the first period T1, a current I of a first current amount I1 flows to the gate of the high-side transistor MH. HG_ON is supplied.

[0059] (ii) Second Period T2 In the second period T2, the capability of the turn-on transistor SW1 is set to a second capability S2 lower than the first capability S1. In the second period T2, a current I2 having a second current amount I2 smaller than the first current amount I1 is supplied to the gate of the high-side transistor MH. HG_ON is supplied.

[0060] (iii) Third Period T3 In the third period T3, the capability of the turn-on transistor SW1 is set to a third capability S3 higher than the second capability S2. The third capability S3 may be higher or lower than the first capability S1, but is assumed to be higher here. In the third period T3, a current I of a third current amount I3, which is higher than the first current amount I1 and the second current amount I2, is supplied to the gate of the high-side transistor MH. HG_ON is supplied.

[0061] (iv) 4th period T4 In a fourth period T4, the capability of the turn-on transistor SW1 is set to a fourth capability S4 higher than the first capability S1, the second capability S2, and the third capability S3.

[0062] For example, when n=5, control can be performed such that m=2 in the first period T1, m=1 in the second period, m=4 in the third period, and m=5 in the fourth period.

[0063] 4 is an operation waveform diagram of the gate driver circuit 400 of FIG. 3. The control signal CTRL is a logic signal that indicates the state of the bridge circuit 110. LGS is the gate voltage (gate-source voltage) of the low-side transistor ML. V HG is the gate voltage of the high-side transistor MH, and V OUT V is the source voltage of the high-side transistor MH, i.e., the output voltage. HGS is the gate-source voltage of the high-side transistor MH, and V HG and V OUT is the potential difference.

[0064] Before time t0, the control signal CTRL is at a low level, the high-side transistor MH is off, the low-side transistor ML is on, and the output voltage V OUT is set to low voltage (0V).

[0065] FIG. 4 shows the operation of the current source mode. Before time t0, a negative current I ML is flowing.

[0066] At time t0, the control signal CTRL transitions to a high level. As a result, the low-side driver circuit 260 controls the gate voltage V LG , turning off the low-side transistor ML.

[0067] At time t1, the gate voltage V of the low-side transistor ML LG When the voltage Vth1 falls below the fourth threshold voltage Vth4, the high-side driver circuit 220 becomes active.

[0068] In the first period T1, m=2 transistors are turned on, and the turn-on transistor SW1 has a first capability S1. At this time, a current I HG_ON is supplied to the gate of the high-side transistor MH.

[0069] Then, at time t2, the gate-source voltage V of the high-side transistor MH HGS When the first threshold voltage Vth1 is exceeded, the second period T2 begins. In the second period T2, m=1 transistors are turned on, and the turn-on transistor SW1 has the second capability S2. At this time, the current I HG_ON is supplied to the gate of the high-side transistor MH. Since the second current amount I2 is smaller than the first current amount I1, the gate-source voltage V HGS The rate of increase in the first period T1 is slower than that in the first period T2.

[0070] Then, at time t3, the output voltage V OUTWhen m exceeds the second threshold voltage Vth2, the third period T3 begins. In the third period T3, m=4 transistors are turned on, and the turn-on transistor SW1 has a third capability S3. At this time, a current I HG_ON is supplied to the gate of the high-side transistor MH. The third current amount I3 is greater than the first current amount I1 and the second current amount I2, and the gate-source voltage V HGS The rate of increase becomes faster.

[0071] Then, at time t4, the output voltage V OUT is the input voltage V IN When the third threshold voltage Vth3 determined in the vicinity of m is exceeded, the fourth period T4 begins. In the fourth period T4, m=5 transistors are turned on, the turn-on transistor SW1 has the maximum fourth capability S4, and the turn-on transistor SW1 is in a fully-on state. When the turn-on transistor SW1 is in a fully-on state, the gate voltage V of the high-side transistor MH HG is fixed to a high level voltage, and the high-side transistor MH is strongly fixed to the on state.

[0072] The operation of the switching circuit 100 has been described above.

[0073] According to the switching circuit 100, a driving current I of a first current amount I1 is supplied to the gate of the high-side transistor MH during a first period T1 until just before the high-side transistor MH is turned on. HG_ON and gate voltage V HG Then, during a second period T2 during which a reverse recovery current can flow through the flywheel diode of the lower arm after the high-side transistor MH is turned on, the drive current I HG_ON to the second current amount I2, the high-side transistor MH is turned on gradually while maintaining a large on-resistance. This makes it possible to suppress shoot-through current and ringing caused by the reverse recovery current of the flywheel diode in the arm opposite to the upper arm that is the driving target of the drive circuit 200, i.e., the lower arm.

[0074] Next, in the third period T3 in which the reverse recovery current is unlikely to flow, the drive current I HG_ON to a third current amount I3 that is greater than the second period T2, the turn-on time of the high-side transistor MH can be shortened, and power consumption can be reduced.

[0075] Furthermore, in the third period T3, the driving current I HG_ON is greater than the first current amount I1 in the first period T1. This allows the on-resistance of the high-side transistor MH to be reduced in a short period of time, thereby further improving the efficiency of the bridge circuit.

[0076] Next, a configuration example of the turn-off circuit 420 will be described.

[0077] 5 is a circuit diagram of the drive circuit 200A including a gate driver circuit 400A. The gate driver circuit 400A includes a turn-on circuit 410A and a turn-off circuit 420A.

[0078] The configuration of the turn-on circuit 410A is the same as that in FIG.

[0079] The turn-off circuit 420A includes a turn-off transistor SW2. The turn-off transistor SW2 includes a plurality of transistors MN1 to MNn connected in parallel. The number n of transistors MN constituting the turn-off transistor SW2 may be the same as or different from the number n of transistors MP constituting the turn-on transistor SW1.

[0080] The plurality of transistors MN1 to MPN are configured to be able to be switched on and off independently. The driving capability S of the turn-off transistor SW2 is adjustable according to the number of transistors that are in the on state among the plurality of transistors MN1 to MNn.

[0081] According to this turn-off circuit 420A, when turning off the high-side transistor MH, the drive current I HG_OFF The drive current I HG_ON Similarly, it can be changed in stages.

[0082] Next, a modification of the turn-on circuit 410 will be described.

[0083] (Variation 1) FIG. 6 is a circuit diagram of a turn-on circuit 410 according to the first modification.

[0084] The capabilities (sizes) of the multiple transistors MP1 to MPn that configure the turn-on transistor SW1 may be binary weighted. Specifically, the W / L ratios of the transistors MP1, MP2, ..., MPn may satisfy the following relationship: 1:2:…:2 n-1

[0085] When n=5, the W / L ratios of the five transistors MP1 to MP5 are as follows: 1:2:4:8:16

[0086] An example of control in this case will be described below. (i) First Period T1 MP1=OFF MP2=ON MP3=OFF MP4=OFF MP5=OFF The capacity of the turn-on transistor SW1 in the first period T1 is W / L=2.

[0087] (ii) Second Period T2 MP1=ON MP2=OFF MP3=OFF MP4=OFF MP5=OFF The capability of the turn-on transistor SW1 in the second period T2 is W / L=1.

[0088] (iii) Third Period T3 MP1=OFF MP2=OFF MP3=OFF MP4=OFF MP5=ON The capacity of the turn-on transistor SW1 in the third period T3 is W / L=16.

[0089] (iii) Fourth Period T4 MP1=ON MP2=ON MP3=ON MP4=ON MP5=ON The capacity of the turn-on transistor SW1 in the fourth period T4 is W / L=31.

[0090] (Variation 2) FIG. 7 is a circuit diagram of a turn-on circuit 410 according to the second modification.

[0091] The capabilities (sizes) of the multiple transistors MP1 to MPn that make up the turn-on transistor SW1 are weighted in binary. In this example, n=5, and the W / L ratios of the transistors MP1, MP2, ..., MP5 may satisfy the following relationship: 1:2:2:4:8

[0092] Of the multiple transistors MP1 to MP5, MP1 and MP2 are assigned to a first transistor group, and MP3 to MP5 are assigned to a second transistor group. The state of the first transistor group is fixed over a first period T1 to a third period T3. For example, MP1 is fixed to off, and MP2 is fixed to on. A second current amount I2 in the second period T2 can be set by combining the states of the two transistors MP1 and MP2. In the second period T2, the transistors MP3 to MP5 included in the second transistor group are all fixed to off.

[0093] In the first period T1, the third period T3, and the fourth period T4, the transistors MP3 to MP5 included in the second transistor group are switched on and off.

[0094] An example of control in this case will be described below. (i) First Period T1 MP1=OFF MP2=ON MP3=OFF MP4=ON MP5=OFF The capacity of the turn-on transistor SW1 in the first period T1 is W / L=6.

[0095] (ii) Second Period T2 MP1=OFF MP2=ON MP3=OFF MP4=OFF MP5=OFF The capacity of the turn-on transistor SW1 in the second period T2 is W / L=2.

[0096] (iii) Third Period T3 MP1=OFF MP2=ON MP3=OFF MP4=OFF MP5=ON The capacity of the turn-on transistor SW1 in the third period T3 is W / L=10.

[0097] (iii) Fourth Period T4 MP1=OFF MP2=ON MP3=ON MP4=ON MP5=ON The capacity of the turn-on transistor SW1 in the fourth period T4 is W / L=16.

[0098] FIG. 8 is a waveform diagram showing the operation (simulation results) of turn-on circuit 410 of FIG.

[0099] In this configuration, the second current amount I2 in the second period T2 can be set in three stages.

[0100] In addition, when the first period T1 transitions to the second period T2, no transistors are turned on, only turned off, and when the second period T2 transitions to the third period T3, no transistors are turned off, only turned on.

[0101] When the first period T1 changes to the second period T2, or when the second period T2 changes to the third period T3, if there are both turn-ons and turn-offs, discontinuity in the current may occur if the timing of these events is not aligned. Modification 2 can solve this problem.

[0102] In the fourth period T4, the transistor MP1 may be turned on.

[0103] 9 is a circuit diagram of the drive circuit 200. The drive circuit 200 may include a first sensor 202, a second sensor 204, a third sensor 206, and a low side off sensor 208.

[0104] The low-side off sensor 208 detects the turn-off of the low-side transistor ML. The low-side off sensor 208 compares the gate-source voltage of the low-side transistor ML with a fourth threshold voltage Vth4. When the control circuit 210 detects the turn-off of the low-side transistor ML based on the output of the low-side off sensor 208, the control circuit 210 transitions to the first period t1.

[0105] The first sensor 202 detects the gate-source voltage V GS is compared with a first threshold voltage Vth1. The first threshold voltage Vth1 is the threshold voltage V GS(th) You can decide based on that.

[0106] The drive circuit 200 is often provided with a high-side off sensor that detects when the high-side transistor MH is turned off. The output of the high-side off sensor is referenced by the control circuit 210. The control circuit 210 monitors the output of the high-side off sensor, and after the high-side transistor MH is definitely turned off, transitions the low-side control signal LGCTL to the on level. This makes it possible to prevent the high-side transistor MH and the low-side transistor ML from being turned on simultaneously, thereby preventing a shoot-through current.

[0107] When the driving circuit 200 includes a high-side off sensor, the first sensor 202 can be shared with the high-side off sensor, thereby reducing the circuit area.

[0108] In the first period T1, when the output of the first sensor 202 changes, that is, when the gate-source voltage V GS is the first threshold voltage V TH1 When the first threshold voltage V exceeds the threshold voltage V, the second period T2 begins. TH1 is the MOSFET threshold voltage V GS(th) If it is set lower, the high-side driver circuit 220 can be shifted to the second period T2 before the high-side transistor MH is turned on. If the response delay is large, the high-side driver circuit 220 shifts to the second period T2 simultaneously with the turn-on or slightly later.

[0109] Gate-source voltage V of high-side transistor MH GS By monitoring the drive current I HG_ON The size of can be changed.

[0110] The second sensor 204 detects the output voltage V OUT The high-side driver circuit 220 compares the output voltage V with the second threshold voltage Vth2. In response to the output change of the second sensor 204 in the second period T2, the high-side driver circuit 220 transitions to the third period T3.OUT By monitoring this, it is possible to detect that the influence of the reverse recovery characteristic of the flywheel diode Di of the lower arm 114 has become smaller.

[0111] The drive circuit 200 has an output voltage V OUT To detect the completion of a low-to-high transition of the output voltage V OUT is the input voltage V IN In some cases, a sensor (voltage monitoring circuit) that compares the threshold voltage with a threshold voltage that is a predetermined voltage width lower may be provided. In this case, the voltage monitoring circuit may be used as the second sensor 204 to prevent an increase in the circuit area.

[0112] The third sensor 206 outputs an output voltage V OUT , the input voltage V IN The control circuit 210 compares the output of the third sensor 206 with a third threshold voltage Vth3 determined to be in the vicinity of V OUT When exceeds Vth3, the fourth period T4 begins.

[0113] Next, a description will be given of the configuration and operation of the low-side driver circuit 260. The low-side driver circuit 260 can be configured in the same manner as the high-side driver circuit 220.

[0114] The low-side driver circuit 260 operates in a first mode in a situation where a reverse recovery current of the flywheel diode of the upper arm 112 may occur, and operates in a second mode in a situation where a reverse recovery current of the flywheel diode of the upper arm 112 does not occur.

[0115] Specifically, in the low-side driver circuit 260, the high-side transistor MH and the low-side transistor ML are off, and a current I OUT In a situation where the low-side transistor ML is turned on from a state φ1B in which the current is being sinked (sink fall), the inverter operates in the first mode.

[0116] In addition, in the low-side driver circuit 260, the high-side transistor MH is on and the low-side transistor ML is off, and a current I OUT In the situation where the low-side transistor ML is turned on from the sourcing state (source fall), the device operates in the second mode.

[0117] (Application) Next, we will explain the applications of the switching circuit 100. The switching circuit 100 can be suitably used in a drive circuit for a motor.

[0118] 10 is a circuit diagram of a motor driving device 300 including a switching circuit 100 according to an embodiment. The motor driving device 300 drives a three-phase motor 302, which is a load, and controls the rotation state.

[0119] Motor driving device 300 includes a bridge circuit 110 and a driving circuit 200. Bridge circuit 110 is a three-phase inverter and has U-phase, V-phase, and W-phase legs, and each phase leg has an upper arm and a lower arm.

[0120] The drive circuit 200 includes a control circuit 210, high-side driver circuits 220U to 220W, and low-side driver circuits 260U to 260W. The control circuit 210 generates control signals indicating the states of the six arms that constitute the bridge circuit 110 based on the state of a three-phase motor 302, which is a load.

[0121] The high-side driver circuits 220U to 220W are configured with the architecture of the above-mentioned high-side driver circuit 220. The low-side driver circuits 260U to 260W are configured with the architecture of the above-mentioned low-side driver circuit 260.

[0122] Although a three-phase motor is used as an example here, a single-phase motor may also be used, in which case the bridge circuit 110 becomes an H-bridge circuit.

[0123] Next, applications of the motor drive device 300 will be described. The motor drive device 300 can be used to control the spindle motor of a hard disk, or the lens drive motor of an imaging device. Alternatively, the motor drive device 300 can be used to drive a printer head drive motor, or a paper feed motor. Alternatively, the motor drive device 300 can be used to drive a motor in an electric vehicle, a hybrid vehicle, or the like.

[0124] The embodiments are merely examples, and it will be understood by those skilled in the art that various modifications are possible in the combination of each component and each processing step, and that such modifications are also within the scope of the present disclosure or the present invention. Such modifications will be described below.

[0125] (Variation 1) In the embodiment, the bridge circuit 110 is configured with discrete components, but this is not a limitation, and the bridge circuit 110 may be integrated into the drive circuit 200.

[0126] (Variation 2) The upper arm 112 and the lower arm 114 may be configured with an IGBT (Insulated Gate Bipolar Transistor).

[0127] (Variation 3) In the embodiment, both the high-side driver circuit 220 and the low-side driver circuit 260 are capable of selecting a plurality of modes, but only one of them may be configured to be mode controllable.

[0128] (Variation 4) The application of the switching circuit 100 is not limited to the motor drive device 300. For example, the switching circuit 100 can be suitably used in switching regulators (DC / DC converters), various power conversion devices (inverters and converters), inverters for lighting discharge lamps, digital audio amplifiers, etc. Therefore, the switching circuit 100 can be used in consumer devices including electronic devices and home appliances, automobiles and in-vehicle parts, industrial vehicles and industrial machines.

[0129] The embodiments described using specific terms merely illustrate the principles and applications of the present invention, and many modifications and changes in arrangement are permitted in the embodiments without departing from the spirit of the present invention as defined in the claims.

[0130] (Additional Note) The present specification discloses the following techniques:

[0131] (Item 1) A gate driver circuit for driving an N-type power transistor constituting a switching circuit, a high level line on which a voltage higher than the source of the power transistor is generated; a turn-on transistor configured to source a current to a gate of the power transistor; a turn-off transistor configured to sink current from the gate of the power transistor; a control circuit for controlling the turn-on transistor and the turn-off transistor; Equipped with the turn-on transistor includes a plurality of transistors connected between the gate of the power transistor and the high level line; When turning on the power transistor, the control circuit During a first period, the turn-on transistor has a first driving capability; In a second period, the turn-on transistor has a second driving capability lower than the first driving capability; In a third period, the turn-on transistor has a third driving capability higher than the second driving capability. A gate driver circuit that controls the on / off states of the plurality of transistors. (Item 2) 2. The gate driver circuit of claim 1, wherein the third driving capability is higher than the first driving capability. (Item 3) At least one of the plurality of transistors includes a first transistor group assigned to the second period and a second transistor group assigned to the first period and the third period; 3. The gate driver circuit of claim 1, wherein the control circuit fixes the second group of transistors to an off state during the second period. (Item 4) The control circuit includes: 4. The gate driver circuit of any one of items 1 to 3, wherein in a fourth period, the on / off states of the plurality of transistors are controlled so that the turn-on transistor has a fourth driving capability higher than the third driving capability. (Item 5) 5. The gate driver circuit of any one of items 1 to 4, wherein the plurality of transistors have the same size. (Item 6) 5. The gate driver circuit of any of items 1 to 4, wherein the plurality of transistors have binary weighted sizes. (Item 7) a first sensor for comparing a gate-source voltage of the power transistor with a first threshold voltage; 7. The gate driver circuit of any one of items 1 to 6, wherein the control circuit transitions to the second period in response to a change in the output of the first sensor in the first period. (Item 8) a second sensor for comparing the output voltage of the switching circuit to a second threshold voltage; 8. The gate driver circuit of any one of items 1 to 7, wherein the control circuit transitions to the third period in response to a change in the output of the second sensor in the second period. (Item 9) a third sensor for comparing an output voltage of the switching circuit with a third threshold voltage; 5. The gate driver circuit of item 4, wherein the control circuit transitions to the fourth period in response to a change in the output of the third sensor during the third period. (Item 10) 10. A gate driver circuit according to any one of items 1 to 9, monolithically integrated on a single semiconductor substrate. (Item 11) a bridge circuit including a high-side transistor and a low-side transistor; A high-side driver, which is a gate driver circuit according to any one of items 1 to 9, for driving the high-side transistor as the power transistor; A low-side driver, which is a gate driver circuit according to any one of items 1 to 9, for driving the low-side transistor as the power transistor; A motor drive device comprising: (Item 12) A motor; A motor drive device according to item 11 for driving the motor; An electronic device comprising: [Explanation of symbols]

[0132] 100 Switching Circuits 102 Power Line 104 Output Line 106 Ground Line 110 Bridge Circuit 112 Upper Arm 114 Lower Arm MH High Side Transistor ML Low Side Transistor Di Flywheel Diode 200 Drive circuit 202 First Sensor 204 Second Sensor 206 3rd Sensor 208 Low side off sensor 210 Control circuit 220 High-side driver circuit 260 Low-side driver circuit 300 Motor drive unit 302 Three-phase motor 400 Gate driver circuit 410 Turn-on circuit 412 High Level Line SW1 turn-on transistor SW2 turn-off transistor 420 Turn-off circuit

Claims

1. A gate driver circuit for driving an N-type power transistor constituting a switching circuit, a high level line on which a voltage higher than the source of the power transistor is generated; a turn-on transistor configured to source a current to a gate of the power transistor; a turn-off transistor configured to sink current from the gate of the power transistor; a control circuit for controlling the turn-on transistor and the turn-off transistor; Equipped with the turn-on transistor includes a plurality of transistors connected between the gate of the power transistor and the high level line; When turning on the power transistor, the control circuit During a first period, the turn-on transistor has a first driving capability; In a second period, the turn-on transistor has a second driving capability lower than the first driving capability; In a third period, the turn-on transistor has a third driving capability higher than the second driving capability. A gate driver circuit that controls the on / off states of the plurality of transistors.

2. The gate driver circuit according to claim 1 , wherein the third driving capability is higher than the first driving capability.

3. At least one of the plurality of transistors includes a first transistor group assigned to the second period and a second transistor group assigned to the first period and the third period; The gate driver circuit according to claim 1 , wherein the control circuit fixes the second group of transistors to an off state during the second period.

4. The control circuit includes:

4. The gate driver circuit according to claim 1, further comprising: a gate driver circuit configured to control, in a fourth period, the on / off states of the plurality of transistors so that the turn-on transistor has a fourth driving capability higher than the third driving capability.

5. The gate driver circuit of claim 1 , wherein the plurality of transistors have the same size.

6. 4. The gate driver circuit of claim 1, wherein the plurality of transistors have binary weighted sizes.

7. a first sensor for comparing a gate-source voltage of the power transistor with a first threshold voltage; 4. The gate driver circuit according to claim 1, wherein the control circuit transitions to the second period in response to a change in the output of the first sensor during the first period.

8. a second sensor for comparing the output voltage of the switching circuit to a second threshold voltage; 4. The gate driver circuit according to claim 1, wherein the control circuit transitions to the third period in response to a change in the output of the second sensor during the second period.

9. a third sensor for comparing the output voltage of the switching circuit with a third threshold voltage; The gate driver circuit according to claim 4 , wherein the control circuit transitions to the fourth period in response to a change in the output of the third sensor during the third period.

10. 4. The gate driver circuit according to claim 1, which is monolithically integrated on a single semiconductor substrate.

11. a bridge circuit including a high-side transistor and a low-side transistor; a high-side driver that is a gate driver circuit according to claim 1 , which drives the high-side transistor as the power transistor; a low-side driver that is a gate driver circuit according to claim 1 , which drives the low-side transistor as the power transistor; A motor drive device comprising:

12. A motor; A motor drive device according to claim 11 that drives the motor; An electronic device comprising:

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