Bridge circuit drive circuit, motor drive device using the same, and electronic device

Abstract

An output node of a high-side driver circuit 220 is connected to a gate of a high-side transistor MH. The high-side driver circuit 220 is operable in a first mode in which the high-side driver circuit 220 outputs a drive current IHG_ON of a first current amount in a first period after a high-side control signal HGCTL transitioned from off-level to on-level, and outputs, in a second period following the first period, a drive current of a second current amount less than the first current amount.

Description

[Technical Field]

[0001] The present disclosure relates to a drive circuit for a bridge circuit. [Background technology]

[0002] Half-bridge circuits, H-bridge circuits, and three-phase bridge circuits (hereinafter collectively referred to as bridge circuits) using 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 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 connected in parallel. The lower arm 14 includes a low-side transistor ML and a flywheel diode Di 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 be in a state φ1 where both the high-side transistor MH and the low-side transistor ML are off (high impedance state), a state φ2 where the high-side transistor MH is on and the low-side transistor ML is off (high output state), and a state φ3 where 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. OUT There is a current sink state (flowing to the left in the figure) that absorbs [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2018-82575 Summary of the Invention [Problem to be solved by the invention]

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

[0007] Consider the transition from the high impedance state φ1 to the high output state φ2 in the current source state. In the 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, where Vf is the forward voltage of the flywheel diode Di.

[0008] In the state φ2, the output current I of the bridge circuit 10 OUT flows through the high-side transistor MH. In addition, a reverse recovery current Irc flows from the cathode to the anode in the flywheel diode Di of the lower arm 14. 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 of the bridge circuit 10 OUT This causes instability and ringing, which is undesirable as it can cause unwanted radiation.

[0009] The present disclosure has been made in view of the above-mentioned problems, and one exemplary purpose of an embodiment thereof is to provide a drive circuit capable of suppressing shoot-through current and ringing caused by reverse recovery current of a flywheel diode. [Means for solving the problem]

[0010] One aspect of the present disclosure relates to a drive circuit for a bridge circuit. The bridge circuit has an upper arm including a high-side transistor and a flywheel diode connected in parallel between a power supply line and an output line, and a lower arm including a low-side transistor and a flywheel diode connected in parallel between the output line and a ground line. The drive circuit includes a high-side driver circuit having an output node connected to the gate of the high-side transistor and operable in a first mode to output a drive current of a first amount during a first period after a high-side control signal transitions from an off level to an on level, and to output a drive current of a second amount less than the first amount during a second period following the first period.

[0011] Another aspect of the present disclosure also relates to a drive circuit for a bridge circuit, including a low-side driver circuit having an output node connected to the gate of a low-side transistor, the low-side driver circuit being operable in a first mode to output a fourth amount of drive current during a fourth period after a low-side control signal transitions from an off level to an on level, and to output a fifth amount of drive current, which is less than the fourth amount of current, during a fifth period following the fourth period.

[0012] Another aspect of the present disclosure also relates to a drive circuit for a bridge circuit, including a high-side driver circuit having an output node connected to the gate of a high-side transistor and switchable between a first mode and a second mode in which the waveform of a drive current supplied to the gate of the high-side transistor is different.

[0013] Another aspect of the present disclosure also relates to a drive circuit for a bridge circuit, including a low-side driver circuit having an output node connected to the gate of a low-side transistor and switchable between a first mode and a second mode in which the waveform of the drive current supplied to the gate of the low-side transistor is different.

[0014] Any combination of the above components, or mutual substitution of the components or expressions of the present disclosure between methods, devices, systems, etc., are also valid aspects of the present invention. [Effects of the Invention]

[0015] According to an aspect of the present disclosure, it is possible to suppress shoot-through current caused by reverse recovery current of a flywheel diode. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a circuit diagram of a bridge circuit. [Figure 2] FIG. 2 is a circuit diagram of a switching circuit according to the embodiment. [Figure 3] FIG. 3 is a waveform diagram (simulation result) at the source rise of the switching circuit of FIG. [Figure 4] FIG. 4 is a waveform diagram (simulation results) in the comparative technology. [Figure 5] FIG. 5 is a waveform diagram (simulation result) at the source rise of the switching circuit of FIG. [Figure 6] FIG. 6 is a circuit diagram showing an example of the configuration of the periphery of the high-side driver circuit of the drive circuit. [Figure 7] FIG. 7 is a circuit diagram showing an example of the configuration of the periphery of the low-side driver circuit of the drive circuit. [Figure 8] FIG. 8 is a circuit diagram of a motor drive device including a switching circuit according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0017] (Outline of the embodiment) A summary of some exemplary embodiments of the present disclosure will be provided. This summary is intended to provide a basic understanding of one or more 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 refer to one embodiment (example or variant) or multiple embodiments (examples or variants) disclosed herein.

[0018] This summary is not an exhaustive overview of all possible embodiments, nor is it intended to identify key elements of all embodiments or 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.

[0019] A drive circuit according to one embodiment drives a bridge circuit having an upper arm including a high-side transistor and a flywheel diode connected in parallel between a power supply line and an output line, and a lower arm including a low-side transistor and a flywheel diode connected in parallel between the output line and a ground line. The drive circuit includes a high-side driver circuit having an output node connected to the gate of the high-side transistor, the high-side driver circuit being operable in a first mode to output a drive current of a first amount during a first period after a high-side control signal transitions from an off level to an on level, and to output a drive current of a second amount less than the first amount during a second period following the first period.

[0020] With this configuration, during a first period immediately before the high-side transistor turns on, a drive current of a first amount is supplied to the gate of the high-side transistor to raise the gate voltage. Then, during a second period after the high-side transistor turns on, during which reverse recovery current may flow through the flywheel diode in the lower arm, the drive current supplied to the gate of the high-side transistor is reduced to maintain a high on-resistance of the high-side transistor and slowly turn it on. This suppresses shoot-through current and ringing caused by the reverse recovery current of the flywheel diode in the lower arm.

[0021] In one embodiment, the drive circuit may further include a first sensor that compares the gate-source voltage of the high-side transistor with a first threshold voltage. The high-side drive circuit may transition to the second period in response to a change in the output of the first sensor during the first period. By monitoring the gate-source voltage of the high-side transistor, the magnitude of the drive current can be changed in conjunction with the transition of the high-side transistor from the OFF state to the ON state. The first threshold voltage may be equal to, higher than, or lower than the gate threshold voltage of the MOSFET.

[0022] 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, and also prevents an increase in circuit area.

[0023] In one embodiment, the high-side driver circuit may output a drive current of a third current amount greater than the second current amount during a third period following the second period. After the influence of the reverse recovery characteristics of the flywheel diode of the lower arm becomes smaller, the output current of the high-side driver circuit can be increased to quickly reduce the on-resistance of the high-side transistor and improve the efficiency of the bridge circuit.

[0024] In one embodiment, the drive circuit may further include a second sensor that compares the output voltage of the output line with an upper threshold voltage. The high-side driver circuit may transition to a third period in response to a change in the output of the second sensor during the second period. By monitoring the output voltage, it is possible to detect that the influence of the reverse recovery characteristics of the lower-arm flywheel diode has decreased.

[0025] In one embodiment, the high-side driver circuit may operate in a first mode when the high-side transistor and the low-side transistor are off and the high-side transistor is turned on from sourcing current through the flywheel diode of the lower arm.

[0026] In one embodiment, the high-side driver circuit may include a first switch connected between the gate and source of the high-side transistor and turned on after the state transition of the bridge circuit is completed. By turning on the first switch, the high-side transistor can be fixed in the on state.

[0027] In one embodiment, the high-side driver circuit may be operable in a second mode in addition to the first mode. In the second mode, the high-side driver circuit outputs a constant amount of drive current greater than the second current amount from when the high-side control signal transitions from an off level to an on level until the state transition of the bridge circuit is complete. The transition, which starts from an initial state in which no current flows through the flywheel diode of the lower arm, is not affected by the reverse recovery current. In this case, by selecting the second mode, which has a higher drive capability, rather than the first mode, the on-resistance of the high-side transistor can be reduced in a short period of time, thereby improving efficiency.

[0028] In one embodiment, the high-side driver circuit may operate in a second mode when turning on the high-side transistor from a state in which the high-side transistor is off and the low-side transistor is on and sinking current through the low-side transistor.

[0029] A drive circuit according to one embodiment further includes a low-side driver circuit operable in a first mode, the low-side driver circuit having an output node connected to the gate of the low-side transistor, outputting a drive current of a fourth amount of current for a fourth period after the low-side control signal transitions from an off level to an on level, and outputting a drive current of a fifth amount of current less than the fourth amount of current for a fifth period following the fourth period.

[0030] With this configuration, during a fourth period immediately before the low-side transistor turns on, a fourth amount of drive current is supplied to the gate of the low-side transistor to raise the gate voltage. Then, during a fifth period after the low-side transistor turns on, during which reverse recovery current may flow through the flywheel diode in the lower arm, the drive current supplied to the gate of the low-side transistor is reduced to maintain a high on-resistance of the low-side transistor and slowly turn it on. This suppresses shoot-through current and ringing caused by the reverse recovery current of the flywheel diode in the upper arm.

[0031] In one embodiment, the drive circuit may further include a third sensor that compares the gate-source voltage of the low-side transistor with a third threshold voltage. The low-side driver circuit may transition to a fifth period in response to a change in the output of the third sensor during the fourth period. By monitoring the gate-source voltage of the low-side transistor, the magnitude of the drive current can be changed in conjunction with the transition of the low-side transistor from an OFF state to an ON state. The second threshold voltage may be equal to, higher than, or lower than the gate threshold voltage of the MOSFET.

[0032] In one embodiment, the third sensor may be shared with a low-side off sensor that detects when the low-side transistor is turned off. This allows the drive current to be reduced before the low-side transistor is turned on, and also prevents an increase in the circuit area.

[0033] In one embodiment, the low-side driver circuit may output a drive current of a sixth current amount, which is greater than the fifth current amount, during a sixth period following the fifth period. After the influence of the reverse recovery characteristics of the flywheel diode in the upper arm becomes smaller, the output current of the low-side driver circuit can be increased to quickly reduce the on-resistance of the low-side transistor and improve the efficiency of the bridge circuit.

[0034] In one embodiment, the drive circuit may further include a fourth sensor that compares the output voltage of the output line with a lower threshold voltage. The low-side driver circuit may transition to a sixth period in response to a change in the output of the fourth sensor during the fifth period. By monitoring the output voltage, it is possible to detect that the influence of the reverse recovery characteristics of the upper arm flywheel diode has decreased.

[0035] In one embodiment, the low-side driver circuit may operate in a first mode when the high-side transistor and the low-side transistor are off and the low-side transistor is turned on from a state where it is sinking current through the flywheel diode of the upper arm.

[0036] In one embodiment, the low-side driver circuit may include a second switch connected between the gate and source of the low-side transistor and turned on after the state transition of the bridge circuit is completed. By turning on the second switch, the low-side transistor can be fixed in the on state.

[0037] In one embodiment, the low-side driver circuit may be operable in a second mode in addition to the first mode. In the second mode, the low-side driver circuit outputs a constant drive current greater than the fifth current amount from when the low-side control signal transitions from an off level to an on level until the state transition of the bridge circuit is complete. The reverse recovery current is not affected by the transition, which starts from a state in which no current flows through the upper-arm flywheel diode. In this case, by selecting the second mode, which has a higher drive capability, instead of the first mode, the on-resistance of the low-side transistor can be reduced in a short time, thereby improving efficiency.

[0038] In one embodiment, the low-side driver circuit may operate in a second mode when the low-side transistor is turned on from a state in which the high-side transistor is on and the low-side transistor is off and sourcing current through the high-side transistor.

[0039] (Embodiment) Preferred embodiments will be described below with reference to the drawings. The same or equivalent components, parts, and processes shown in each drawing will be designated by the same reference numerals, and redundant descriptions will be omitted where appropriate. Furthermore, the embodiments are merely examples and do not limit the invention, and all features and combinations thereof described in the embodiments are not necessarily essential to the invention.

[0040] 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 between them or that do not impair the function or effect achieved by their connection.

[0041] Similarly, "a state in which component C is provided between component A and component B" includes not only cases in which components A and C, or components B and C, are directly connected, but also cases in which they are indirectly connected via other components that do not substantially affect the electrical connection state between them or impair the functions or effects achieved by their combination.

[0042] 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.

[0043] 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.

[0044] 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 both the upper arm 112 and the lower arm 114 are 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. The output current I OUT The direction of current flow from the output line 104 of the bridge circuit 110 to the inductor L1, which is the load, is taken as positive, and the opposite direction is taken as negative. OUT is positive (current source), and the output current I OUT is negative (current sink), and states φ1B to φ3B are present.

[0045] 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 corresponding to each of 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.

[0046] 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. 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 , turning off the high-side transistor MH.

[0047] The high-side driver circuit 220 can select one of several 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 supplied to the gate of the high-side transistor MH according to the state of the bridge circuit 110. HG_ON is changed in multiple stages.

[0048] In the first mode, the high-side driver circuit 220 controls the driving current I of the first current amount I1 during a first period T1 after the high-side control signal HGCTL transitions from the off level to the on level. HG_ON During a second period T2 following the first period T1, a driving current I2 having a second current amount I2 smaller than the first current amount I1 is output. HG_ON Then, in a third period T3 following the second period T2, a driving current I of a third current amount I3 that is greater than the second current amount I2 is output. HG_ON The third current amount I3 may be smaller than the first current amount I1, may be equal to the first current amount I1, or may be larger than the first current amount I1.

[0049] 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 is different from that of the first mode. 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.

[0050] 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. 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.

[0051] Similar to 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.

[0052] In the first mode, the low-side driver circuit 260 controls the driving current I to be supplied to the gate of the low-side transistor ML according to the state of the bridge circuit 110. LG_ON is changed in multiple stages.

[0053] In the first mode, the low-side driver circuit 260 controls the driving current I of the fourth current amount I4 during a fourth period T4 after the low-side control signal LGCTL transitions from the off level to the on level. LG_ON During a fifth period T5 following the fourth period T4, a driving current I of a fifth current amount I5 that is less than the fourth current amount I4 is output. LG_ON Then, in a sixth period T6 following the fifth period T5, a driving current I LG_ON The sixth current amount I6 may be smaller than the fourth current amount I4, may be equal to the fourth current amount I4, or may be larger than the fourth current amount I4.

[0054] In the second mode, the driving current I generated by the low-side driver circuit 260 LG_ON The waveform of the driving current I is different from that of the first mode. LG_ON is a constant amount Id that is greater than the fifth amount of current I5 from when the low-side control signal LGCTL transitions from the off level to the 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 amount of current I4 to the sixth amount of current I6.

[0055] The above is the configuration of the switching circuit 100. Next, the operation will be described.

[0056] 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.

[0057] Specifically, the high-side driver circuit 220 is configured such that the high-side transistor MH and the low-side transistor ML are off and the current I flows through the flywheel diode Di of the lower arm 114. OUT The transistor MH operates in the first mode when it is turned on (source rise) from the state φ1A in which the transistor MH is sourced.

[0058] In addition, the high-side driver circuit 220 is configured such that the high-side transistor MH is off and the low-side transistor ML is on, and a current I OUT The second mode is activated when the high-side transistor MH is turned on (sink rise) from a state where the current is sinking.

[0059] 3 is a waveform diagram (simulation result) of the source rise of the switching circuit 100 of FIG. 2. In FIG. 3, the current I LO , the drive current I HG_ON , output voltage V OUT , the gate voltage V of the high-side transistor MH HG , the gate-source voltage V of the high-side transistor MH GS , the gate voltage V of the low-side transistor ML LG is shown.

[0060] Before time t0, the low-side control signal LGCTL is at an on level (high), and the gate voltage V LG is high (for example, 12 V), and the low-side transistor ML is on.

[0061] At this time, the current I flowing through the lower arm 114 LO is negative. Negative current I LO flows from the ground line 106 through the lower arm 114 to the output line 104, and the output current I OUT Indicates the state in which the source is being sourced.

[0062] At time t0, the low-side control signal LGCTL goes to the off level (low). The low-side driver circuit 260 supplies a driving current I HG_OFF (not shown in FIG. 3) and generates the gate voltage V LG Decreases.

[0063] At time t1, the gate voltage V LG is the MOSFET threshold voltage V GS(th) When the voltage Vcc becomes lower than t1, the low-side transistor ML is turned off. After t1, the state becomes a high impedance state φ1 in which both the high-side transistor MH and the low-side transistor ML are off.

[0064] At time t2, the high-side control signal HGCTL transitions to the on level (high). At this time, the negative lower arm current I LO flows through the flywheel diode Di of the lower arm 114. Therefore, a reverse recovery current may occur. In this situation, the high-side driver circuit 220 operates in the first mode.

[0065] Specifically, during a first period T1 from t2 to t3, the high-side driver circuit 220 supplies a driving current I HG_ON This outputs the gate-source voltage V of the high-side transistor MH. GS (=V HG -V OUT ) rises at a first slope (first slew rate).

[0066] During a second period T2 from t3 to t4, the high-side driver circuit 220 generates a driving current I HG_ON to the second current amount I2. As a result, the gate-source voltage V of the high-side transistor MHGS The slope of the curve becomes very small. As a result, the on-resistance of the high-side transistor MH slowly decreases. The large on-resistance of the high-side transistor MH at this time acts as a brake on the reverse recovery current.

[0067] time t p The end t4 of the second period T2 is the time t p During a third period T3 from t4 to t5, the high-side driver circuit 220 generates a driving current I HG_ON The current I2 is increased from the second current amount I2 to the third current amount I3. This increases the driving capability of the high-side driver circuit 220, accelerating the turn-on of the high-side transistor MH. This reduces the on-resistance of the high-side transistor MH, turning it completely on, and increasing the output voltage V OUT is the high-level voltage (for example, V IN After the transition is completed (t5~), a high-level voltage (for example, 12 V) is applied directly to the gate of the high-side transistor MH, and the gate-source voltage V GS is fixed to a high level voltage.

[0068] The above is the operation of the switching circuit 100. This switching circuit 100 can prevent shoot-through caused by reverse recovery current. As a result, as shown in FIG. 3, the output voltage V OUT No ringing occurs.

[0069] The advantages of the switching circuit 100 become clear when compared with a comparative technique, in which the high-side driver circuit 220 outputs a constant current in the source-rise mode, as in the second mode.

[0070] 4 is a waveform diagram (simulation result) in the comparative technique. In the comparative technique, the high-side driver circuit 220 supplies a constant current Ia to the gate of the high-side transistor MH. In this case, the output current I OUTThe reverse recovery current of the flywheel diode of the low-side transistor ML rises sharply, and its peak current rises to about 13A. OUT Large ringing also occurs.

[0071] In contrast, in this embodiment, by operating in the first mode in the sync rise mode, the current I LO The peak of the output current I OUT The peak of the output voltage V can be reduced from 13A in Figure 4 to 4.5A in Figure 3. OUT The ringing is also suppressed.

[0072] In the transition from the initial state where no current flows through the flywheel diode of the lower arm, there is no influence of the reverse recovery current. In this case, the high-side driver circuit 220 can reduce the on-resistance of the high-side transistor MH in a short time and improve efficiency by selecting the second mode, which has a higher driving capability, rather than the first mode.

[0073] 5 is a waveform diagram (simulation result) of the source rise of the switching circuit 100 of FIG. 2. In FIG. 5, the driving current I HG_ON The amount of current I3 in the second period T2 is smaller than the amount of current I2 in the second period T2.

[0074] If the current amount I3 in the third period T3 is reduced, the efficiency will deteriorate, but the ringing will be suppressed. In other words, the output voltage V OUT It is possible to adjust the waveform of the drive current I in the third period T3. In addition, when I3=I2, it is equivalent to controlling in two stages. In other words, in the control of FIG. 3, the drive current I HG_ON By setting the current amount I3 to a third current amount I3 that is greater than the second current amount I2, the on-resistance of the high-side transistor MH can be reduced in a short time, and the efficiency of the bridge circuit 110 can be improved.

[0075] Next, the operation of the low-side driver circuit 260 will be described.

[0076] 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.

[0077] Specifically, the low-side driver circuit 260 is configured such that the high-side transistor MH and the low-side transistor ML are off and the current I flows through the flywheel diode Di of the upper arm 112. OUT In a state where the low-side transistor ML is turned on from a state φ1B where the current is being sinked (sink fall), the inverter operates in the first mode.

[0078] In addition, the low-side driver circuit 260 is configured such that 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.

[0079] Next, configuration examples of the high-side driver circuit 220 and the low-side driver circuit 260 will be described.

[0080] FIG. 6 is a circuit diagram showing an example of the configuration of the periphery of the high-side driver circuit 220 of the drive circuit 200. As shown in FIG.

[0081] The drive circuit 200 includes a first sensor 202 and a second sensor 204. The first sensor 202 detects the gate-source voltage V of the high-side transistor MH. GS the first threshold voltage V TH1 The first threshold voltage V TH1 is the threshold voltage of the MOSFET, V GS(th) You should decide based on that.

[0082] 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 a control circuit 210 (not shown in FIG. 6). The control circuit 210 monitors the output of the high-side off sensor, and after the high-side transistor MH is reliably turned off, transitions the low-side control signal LGCTL to the on level. This prevents the high-side transistor MH and the low-side transistor ML from being turned on simultaneously, preventing a through current.

[0083] If the drive 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.

[0084] In the first period T1, when the output of the first sensor 202 changes, that is, when the gate-source voltage V of the high-side transistor MH 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 threshold voltage of the MOSFET, V GS(th) If the response delay is large, the high-side driver circuit 220 enters the second period T2 simultaneously with the turn-on of the high-side transistor MH or with a slight delay therebetween.

[0085] Gate-source voltage V of high-side transistor MH GS By monitoring the drive current I HG_ON The size of can be changed.

[0086] The second sensor 204 detects the output voltage V OUT the upper threshold voltage V THHIn response to the change in the output of the second sensor 204 during 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 characteristics of the flywheel diode Di of the lower arm 114 has become smaller.

[0087] The drive circuit 200 has an output voltage V OUT To detect the completion of the 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 voltage with a threshold voltage that is a predetermined voltage width lower may be provided. In this case, the voltage monitoring circuit may also be used as the second sensor 204, thereby preventing an increase in the circuit area.

[0088] Next, we will explain a specific configuration example of the high-side driver circuit 220. The high-side driver circuit 220 includes a logic circuit 222, current sources 224 and 226, and switches SW1 and SW2.

[0089] A first current source 224 and a first switch SW1 are provided in association with turning on the high-side transistor MH. The first current source 224 is a variable current source, and its output current I HG_ON can be controlled in multiple stages (I1, I2, I3, Ic). The configuration of the first current source 224 is not particularly limited, and may include multiple current sources that can be switched on and off. Alternatively, the first current source 224 may be a current DAC (D / A converter). The first switch SW1 connects the gate of the high-side transistor MH to the high-level voltage V H (>V IN ) is provided between the power supply lines 201 to which the

[0090] A second current source 226 and a second switch SW2 are provided in association with turning off the high-side transistor MH. The second current source 226 is a constant current source or a variable current source, and supplies a current I HG_OFF The second switch SW2 is provided between the gate and source of the high-side transistor MH.

[0091] The logic circuit 222 controls the current sources 224, 226 and the switches SW1, SW2 based on the high-side control signal HGCTL, the mode control signal MODE, and the outputs of the first sensor 202 and the second sensor 204. When the high-side control signal HGCTL is at an ON level, the logic circuit 222 operates the first current source 224 and the first switch SW1 to turn on the high-side transistor MH. When the high-side control signal HGCTL is at an OFF level, the logic circuit 222 operates the second current source 226 and the second switch SW2 to turn off the high-side transistor MH.

[0092] The mode control signal MODE is generated by a control circuit (not shown in FIG. 6). In the first mode, the logic circuit 222 transitions in order from a first period T1 to a second period T2 to a third period T3 in accordance with the outputs of the first sensor 202 and the second sensor 204, and controls the amount of current of the current source 224. After the transition of the bridge circuit 110 is completed, the logic circuit 222 turns on the first switch SW1 and connects the gate of the high-side transistor MH to the high voltage V H Secure it in place.

[0093] The function of the logic circuit 222 may be provided to the control circuit 210 in FIG.

[0094] 7 is a circuit diagram showing an example of the configuration of the periphery of the low-side driver circuit 260 of the drive circuit 200. The drive circuit 200 includes a third sensor 206 and a fourth sensor 208. The third sensor 206 detects the gate-source voltage V GS the second threshold voltage V TH2 Compare with the second threshold voltage V TH2 is the threshold voltage of the MOSFET, V GS(th) You should decide based on that.

[0095] The drive circuit 200 is often provided with a low-side off sensor that detects when the low-side transistor ML is turned off. The output of the low-side off sensor is referenced by the control circuit 210. The control circuit 210 monitors the output of the low-side off sensor, and after the low-side transistor ML is reliably turned off, transitions the high-side control signal HGCTL to the on level. This prevents the high-side transistor MH and the low-side transistor ML from being turned on simultaneously, thereby preventing a shoot-through current.

[0096] If the drive circuit 200 includes a low-side off sensor, the third sensor 206 can be shared with the low-side off sensor, thereby reducing the circuit area.

[0097] In the fourth period T4, when the output of the third sensor 206 changes, that is, when the gate-source voltage V GS is the second threshold voltage V TH2 When the second threshold voltage V exceeds the threshold voltage V, the fifth period T5 begins. TH2 is the threshold voltage of the MOSFET, V GS(th) If the response delay is set lower, the low-side driver circuit 260 can be shifted to the fifth period T5 before the low-side transistor ML is turned on. If the response delay is large, the low-side driver circuit 260 shifts to the fifth period T5 simultaneously with the turn-on or with a slight delay thereafter.

[0098] Gate-source voltage V of low-side transistor ML GS By monitoring the drive current I LG_ON The size of can be changed.

[0099] The fourth sensor 208 detects the output voltage V OUT The lower threshold voltage V THLIn response to the change in the output of the fourth sensor 208 during the fifth period T5, the low-side driver circuit 260 transitions to the sixth period T6. OUT By monitoring this, it is possible to detect that the influence of the reverse recovery characteristics of the flywheel diode Di of the upper arm 112 has become smaller.

[0100] The drive circuit 200 has an output voltage V OUT To detect the completion of the low-to-high transition of the output voltage V OUT With a threshold voltage that is higher than the ground voltage (0 V) by a predetermined voltage step, a sensor (voltage monitoring circuit) may be provided. In this case, the voltage monitoring circuit may also serve as the fourth sensor 208, thereby preventing an increase in the circuit area.

[0101] The low-side driver circuit 260 includes a logic circuit 262, current sources 264 and 266, and switches SW3 and SW4.

[0102] A third current source 264 and a third switch SW3 are provided in association with turning on the low-side transistor ML. The third current source 264 is a variable current source, and its output current I LG_ON can be controlled in multiple stages (I4, I5, I6, Id). The configuration of the third current source 264 is not particularly limited, and may include multiple current sources that can be switched on and off. Alternatively, the third current source 264 may be a current DAC (D / A converter). The third switch SW3 connects the gate of the low-side transistor ML to the gate of the power supply voltage V DD The power supply line 203 is connected to the power supply line 203.

[0103] In connection with turning off the low-side transistor ML, a fourth current source 266 and a fourth switch SW4 are provided. The fourth current source 246 is a constant current source or a variable current source, and outputs a current I LG_OFF The fourth switch SW4 is provided between the gate and source of the low-side transistor ML.

[0104] The logic circuit 262 controls the current sources 264, 266 and the switches SW3, SW4 based on the low-side control signal LGCTL, the mode control signal MODE, and the outputs of the third sensor 206 and the fourth sensor 208. When the low-side control signal LGCTL is at an ON level, the logic circuit 262 operates the third current source 264 and the third switch SW3 to turn on the low-side transistor ML. When the low-side control signal LGCTL is at an OFF level, the logic circuit 262 operates the fourth current source 266 and the fourth switch SW4 to turn off the low-side transistor ML.

[0105] The mode control signal MODE is generated by the control circuit 210 (not shown in FIG. 6). In the first mode, the logic circuit 262 transitions in order from a fourth period T4 to a fifth period T5 to a sixth period T6 in accordance with the outputs of the third sensor 206 and the fourth sensor 208, and controls the amount of current of the current source 264. After the transition of the bridge circuit 110 is completed, the logic circuit 262 turns on the third switch SW3, and connects the gate of the low-side transistor ML to the power supply voltage V DD Secure it in place.

[0106] Next, we will explain the applications of the switching circuit 100. The switching circuit 100 can be suitably used in a motor drive circuit.

[0107] 8 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.

[0108] 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.

[0109] 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 make up the bridge circuit 110 based on the state of a three-phase motor 302, which is a load.

[0110] The high-side driver circuits 220U to 220W are configured with the architecture of the above-described high-side driver circuit 220. The low-side driver circuits 260U to 260W are configured with the architecture of the above-described low-side driver circuit 260.

[0111] 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.

[0112] Next, we will explain the uses of motor drive device 300. 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. It can also be used to drive a printer head drive motor or a paper feed motor. Motor drive device 300 can also be used to drive motors in electric vehicles, hybrid vehicles, etc.

[0113] 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 the respective components and processing steps, and that such modifications are also within the scope of the present disclosure and the present invention. Such modifications will be described below.

[0114] (Variation 1) In the embodiment, the bridge circuit 110 is configured with discrete components, but this is not limiting, and the bridge circuit 110 may be integrated into the drive circuit 200.

[0115] (Variation 2) The upper arm 112 and the lower arm 114 may be configured by an IGBT (Insulated Gate Bipolar Transistor).

[0116] (Variation 2) In the embodiment, both the high-side driver circuit 220 and the low-side driver circuit 260 are configured to be able to select a plurality of modes, but only one of them may be configured to be mode controllable.

[0117] (Variation 3) 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 on-board components, industrial vehicles and industrial machinery.

[0118] 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 as long as they do not deviate from the spirit of the present invention as defined in the claims. [Industrial Applicability]

[0119] The present disclosure relates to a drive circuit for a bridge circuit. [Explanation of symbols]

[0120] 100 Switching Circuit 102 input lines 104 output lines 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 Third Sensor 208 4th Sensor 210 Control circuit 220 High-side driver circuit 222 Logic Circuits 224 1st current source 226 Second current source SW1 First switch SW2 Second switch 260 Low-side driver circuit 262 Logic Circuits 264 Third current source 266 4th current source SW3 Third switch SW4 4th switch 300 Motor drive unit 302 Three-phase motor

Claims

1. A drive circuit for driving a bridge circuit having an upper arm including a high-side transistor and a flywheel diode connected in parallel between a power supply line and an output line, and a lower arm including a low-side transistor and a flywheel diode connected in parallel between the output line and a ground line, a high-side driver circuit having an output node connected to a gate of the high-side transistor, the high-side driver circuit outputting a drive current of a first amount during a first period after a high-side control signal transitions from an off level to an on level, and outputting the drive current of a second amount less than the first amount during a second period following the first period; a first sensor that compares a gate-source voltage of the high-side transistor with a first threshold voltage; Equipped with The high-side driver circuit transitions to the second period in response to a change in the output of the first sensor during the first period.

2. The drive circuit according to claim 1 , wherein the first sensor is shared with a high-side off sensor that detects that the high-side transistor is turned off.

3. The drive circuit according to claim 1 , wherein the high-side driver circuit outputs the drive current of a third current amount greater than the second current amount during a third period following the second period.

4. A drive circuit for driving a bridge circuit having an upper arm including a high-side transistor and a flywheel diode connected in parallel between a power supply line and an output line, and a lower arm including a low-side transistor and a flywheel diode connected in parallel between the output line and a ground line, a high-side driver circuit having an output node connected to a gate of the high-side transistor, the high-side driver circuit outputting a drive current of a first current amount during a first period after a high-side control signal transitions from an off level to an on level, and outputting the drive current of a second current amount less than the first current amount during a second period following the first period; The high-side driver circuit outputs the drive current of a third current amount greater than the second current amount during a third period following the second period.

5. a second sensor for comparing the output voltage of the output line with an upper threshold voltage; 5. The drive circuit according to claim 3, wherein the high-side driver circuit transitions to the third period in response to a change in the output of the second sensor during the second period.

6. 5. The drive circuit of claim 1, wherein the high-side driver circuit operates in the first mode when the high-side transistor is turned on from a state in which the high-side transistor and the low-side transistor are off and a current is sourced through the flywheel diode of the lower arm.

7. 5. The drive circuit according to claim 1, wherein the high-side driver circuit is operable in, in addition to the first mode, a second mode in which the high-side driver circuit outputs a constant amount of drive current that is greater than the second current amount from when the high-side control signal transitions from an off level to an on level until a state transition of the bridge circuit is completed.

8. 8. The drive circuit of claim 7, wherein the high side driver circuit operates in the second mode when turning on the high side transistor from a state in which the high side transistor is off, the low side transistor is on, and the high side driver circuit is sinking current through the low side transistor.

9. 5. The drive circuit according to claim 1, wherein the high-side driver circuit includes a first switch connected between a gate and a source of the high-side transistor and turned on after completion of a state transition of the bridge circuit.

10. 5. The drive circuit according to claim 1, further comprising: a low-side driver circuit operable in a first mode having an output node connected to a gate of the low-side transistor, the low-side driver circuit outputting a fourth amount of drive current during a fourth period after a low-side control signal transitions from an off level to an on level, and outputting a fifth amount of drive current less than the fourth amount of current during a fifth period following the fourth period.

11. a third sensor that compares a gate-source voltage of the low-side transistor with a third threshold voltage; The drive circuit according to claim 10 , wherein the low-side driver circuit transitions to the fifth period in response to a change in the output of the third sensor in the fourth period.

12. The drive circuit according to claim 11 , wherein the third sensor is shared with a low-side off sensor that detects that the low-side transistor is turned off.

13. The drive circuit according to claim 10 , wherein the low-side driver circuit outputs the drive current of a sixth current amount greater than the fifth current amount during a sixth period following the fifth period.

14. a fourth sensor for comparing the output voltage of the output line with a lower threshold voltage; The drive circuit according to claim 13 , wherein the low-side driver circuit transitions to the sixth period in response to a change in the output of the fourth sensor in the fifth period.

15. 11. The drive circuit of claim 10, wherein the low-side driver circuit operates in the first mode when the low-side transistor is turned on from a state in which the high-side transistor and the low-side transistor are off and sinking current through the flywheel diode of the upper arm.

16. 11. The drive circuit according to claim 10, wherein the low-side driver circuit is operable in, in addition to the first mode, a second mode in which a constant amount of drive current greater than the fifth current amount is output from a time when the low-side control signal transitions from an off level to an on level until a state transition of the bridge circuit is completed.

17. 17. The drive circuit of claim 16, wherein the low side driver circuit operates in the second mode when the low side transistor is turned on from a state in which the high side transistor is on, the low side transistor is off, and the low side driver circuit is sourcing current through the high side transistor.

18. The drive circuit according to claim 10 , wherein the low-side driver circuit includes a second switch connected between the gate and source of the low-side transistor and turned on after the state transition of the bridge circuit is completed.

19. A drive circuit for driving a bridge circuit having an upper arm including a high-side transistor and a flywheel diode connected in parallel between a power supply line and an output line, and a lower arm including a low-side transistor and a flywheel diode connected in parallel between the output line and a ground line, a low-side driver circuit operable in a first mode, the low-side driver circuit having an output node connected to a gate of the low-side transistor, the low-side driver circuit outputting a fourth amount of drive current during a fourth period after a low-side control signal transitions from an off level to an on level, and outputting a fifth amount of drive current less than the fourth amount of current during a fifth period following the fourth period; a third sensor that compares the gate-source voltage of the low-side transistor with a third threshold voltage; Equipped with The low-side driver circuit transitions to the fifth period in response to a change in the output of the third sensor in the fourth period.

20. The drive circuit according to claim 19 , wherein the third sensor is shared with a low-side off sensor that detects that the low-side transistor is turned off.

21. The drive circuit according to claim 19 , wherein the low-side driver circuit outputs the drive current of a sixth current amount greater than the fifth current amount during a sixth period following the fifth period.

22. A drive circuit for driving a bridge circuit having an upper arm including a high-side transistor and a flywheel diode connected in parallel between a power supply line and an output line, and a lower arm including a low-side transistor and a flywheel diode connected in parallel between the output line and a ground line, a low-side driver circuit having an output node connected to a gate of the low-side transistor, the low-side driver circuit outputting a fourth amount of drive current during a fourth period after a low-side control signal transitions from an off level to an on level, and outputting a fifth amount of drive current less than the fourth amount of current during a fifth period following the fourth period; The low-side driver circuit outputs the drive current of a sixth current amount, which is greater than the fifth current amount, during a sixth period following the fifth period.

23. a fourth sensor for comparing the output voltage of the output line with a lower threshold voltage; 23. The drive circuit according to claim 21, wherein the low-side driver circuit transitions to the sixth period in response to a change in the output of the fourth sensor in the fifth period.

24. 23. The drive circuit of claim 19, wherein the low-side driver circuit operates in the first mode when the low-side transistor is turned on from a state in which the high-side transistor and the low-side transistor are off and sinking current through the flywheel diode of the upper arm.

25. 23. The drive circuit according to claim 19, wherein the low-side driver circuit is operable in, in addition to the first mode, a second mode in which a constant amount of drive current greater than the fifth current amount is output from a time when the low-side control signal transitions from an off level to an on level until a state transition of the bridge circuit is completed.

26. 26. The drive circuit of claim 25, wherein the low side driver circuit operates in the second mode when the low side transistor is turned on from a state in which the high side transistor is on, the low side transistor is off, and the low side driver circuit is sourcing current through the high side transistor.

27. 23. The drive circuit according to claim 19, wherein the low-side driver circuit includes a second switch connected between the gate and source of the low-side transistor and turned on after completion of the state transition of the bridge circuit.

28. a bridge circuit including a high-side transistor and a low-side transistor; a drive circuit according to any one of claims 1 to 4 and 19 to 22, which drives the bridge circuit; A motor drive device comprising:

29. A motor; a motor drive device according to claim 28 for driving the motor; An electronic device comprising:

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