Gate driver circuits, motor drive devices, electronic equipment

Abstract

To provide a gate driver circuit that can operate more stably. [Solution] The bootstrap switch SW1 has one end connected to the bootstrap terminal BST and the other end connected to a constant voltage V REG The first sensor 280 receives a change in the electrical state of the high-side transistor MH or the low-side transistor ML based on its gate voltage, and asserts a first detection signal Sdet1. In response to the assertion of the first detection signal Sdet1, the control circuit 210 turns on the bootstrap switch SW1.

Description

[Technical Field]

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

[0002] The output stage of a motor driver circuit consists of switching circuits such as an H-bridge circuit or a three-phase inverter.

[0003] A switching circuit leg comprises an upper arm located between the input line IN and the output line OUT, and a lower arm located between the output line OUT and the ground line. When the transistor in the upper arm is an N-type transistor, i.e., an N-channel FET (Field-Effect Transistor), an NPN bipolar transistor, or an IGBT, a bootstrap circuit is used.

[0004] A bootstrap circuit comprises a bootstrap capacitor with one end connected to the output line, and a rectifier element (diode) that applies a constant voltage to the other end of the bootstrap capacitor. The other end of the bootstrap capacitor is set to a voltage higher than the output voltage (switching voltage) generated on the output line. REG - Bootstrap voltage V is only higher than Vf. BST This will occur. V BST =V OUT +V REG -Vf

[0005] As the switching frequency increases, or as the duty cycle increases, V OUT The low-output period, where the voltage is 0V, becomes shorter. This means the charging time for the bootstrap capacitor is reduced, and it becomes impossible to store sufficient charge in the bootstrap capacitor. If the charging voltage is insufficient, the power transistor on the upper arm cannot be turned on, which disrupts the circuit's operation. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2023-003900 [Patent Document 2] U.S. Patent Application Publication No. 2023 / 0040189

[0007] [overview] This disclosure has been made in view of the aforementioned problems, and one exemplary objective of a certain aspect thereof is to provide a gate driver circuit that can operate more stably.

[0008] A part of the present disclosure relates to a gate driver circuit for driving a switching circuit having an N-type high-side transistor and a low-side transistor in response to an input signal. The gate driver circuit includes a bootstrap terminal to which one end of a bootstrap capacitor is connected, a high-side gate terminal to which the gate of a high-side transistor is connected, a low-side gate terminal to which the gate of a low-side transistor is connected, a switching terminal to which the output line of the switching circuit is connected, a bootstrap switch with one end connected to the bootstrap terminal and the other end receiving a constant voltage, a high-side driver with an upper power supply terminal connected to the bootstrap terminal and a lower power supply terminal connected to the switching terminal that generates a high-side gate voltage at the high-side gate terminal in response to a high-side control signal, a low-side driver that generates a low-side gate voltage at the low-side gate terminal in response to a low-side control signal, a first sensor that asserts a first detection signal when it detects a change in the electrical state of the high-side transistor or low-side transistor based on its gate voltage, and a control circuit that generates a high-side control signal and a low-side control signal in response to an input signal and turns on the bootstrap switch in response to the assertion of the first detection signal.

[0009] Furthermore, any combination of the above components, or in which components or expressions are mutually substituted among methods, apparatus, systems, etc., are also valid embodiments of the present invention. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a circuit diagram of a switching circuit related to the comparative technology. [Figure 2] Figure 2 is a waveform diagram illustrating the operation of the switching circuit shown in Figure 1. [Figure 3] Figure 3 is a circuit diagram of a switching circuit according to an embodiment. [Figure 4] Figure 4 is a waveform diagram illustrating the operation of the switching circuit according to the embodiment. [Figure 5] Figure 5 illustrates a modified example of bootstrap switch control. [Figure 6] Figure 6 is a circuit diagram of a motor drive device according to an embodiment.

[0011] [Detailed explanation] (Summary of the embodiment) This section outlines some exemplary embodiments of the present disclosure. This outline is intended to provide a basic understanding of the embodiments and to simplify some concepts of one or more embodiments, serving as a prelude to the more detailed descriptions that follow. It is not intended to limit the scope of the invention or disclosure. This outline is not a comprehensive overview of all possible embodiments, nor is it intended to identify essential elements of all embodiments or to delineate the scope of some or all aspects. For convenience, “one embodiment” may be used to refer to one or more embodiments (examples or variations) disclosed herein.

[0012] A gate driver circuit according to one embodiment drives a switching circuit having an N-type high-side transistor and a low-side transistor in response to an input signal. The gate driver circuit includes a bootstrap terminal to which one end of a bootstrap capacitor is connected, a high-side gate terminal to which the gate of the high-side transistor is connected, a low-side gate terminal to which the gate of the low-side transistor is connected, a switching terminal to which the output line of the switching circuit is connected, a bootstrap switch with one end connected to the bootstrap terminal and the other end receiving a constant voltage, a high-side driver with an upper power supply terminal connected to the bootstrap terminal and a lower power supply terminal connected to the switching terminal that generates a high-side gate voltage at the high-side gate terminal in response to a high-side control signal, a low-side driver that generates a low-side gate voltage at the low-side gate terminal in response to a low-side control signal, a first sensor that asserts a first detection signal when it detects a change in the electrical state of the high-side transistor or low-side transistor based on its gate voltage, and a control circuit that generates a high-side control signal and a low-side control signal in response to an input signal and turns on the bootstrap switch in response to the assertion of the first detection signal.

[0013] In a gate driver circuit, there is a delay between the change in the input signal and the change in the gate voltage of the high-side or low-side transistor, and there is an even further delay before the output voltage of the switching circuit changes. If the bootstrap switch is controlled using the input signal when the output voltage transitions from high voltage to low voltage, the bootstrap switch will turn on even though the output voltage is high, causing the bootstrap capacitor to discharge. This unnecessary discharge leads to a voltage deficiency in the bootstrap capacitor, preventing the high-side transistor from turning on.

[0014] In the above embodiment, by providing a first sensor and waiting for the electrical state of the high-side transistor or low-side transistor to actually change before turning on the bootstrap switch, the period during which the charge from the bootstrap capacitor discharges can be shortened, and the high-side transistor can be reliably turned on.

[0015] In one embodiment, the gate driver circuit may further include a second sensor that asserts a second detection signal when it detects a change in the electrical state of a high-side or low-side transistor based on its gate voltage. The control circuit may turn off a bootstrap switch in response to the assertion of the second detection signal.

[0016] When the output voltage transitions from low to high voltage, if the bootstrap switch is controlled using the input signal, the bootstrap switch will turn off even though the output voltage is low. This means that the bootstrap capacitor will not be charged even though it is in a state where it can be charged.

[0017] In the above embodiment, by providing a second sensor and waiting for the electrical state of the high-side transistor or low-side transistor to actually change before turning off the bootstrap switch, the charging period of the bootstrap capacitor can be extended as much as possible, and the high-side transistor can be reliably turned on.

[0018] In one embodiment, the first sensor may compare the gate-source voltage of the low-side transistor with a first threshold voltage.

[0019] In one embodiment, the second sensor may compare the gate-source voltage of the low-side transistor with a second threshold voltage.

[0020] In one embodiment, the first sensor may compare the gate-source voltage of the high-side transistor with a first threshold voltage.

[0021] In one embodiment, the second sensor may compare the gate-source voltage of the high-side transistor with a second threshold voltage.

[0022] In one embodiment, the first sensor may compare the drain-source voltage of the low-side transistor with a first threshold voltage.

[0023] In one embodiment, the second sensor may compare the drain-source voltage of the low-side transistor with a second threshold voltage.

[0024] In one embodiment, the first sensor may compare the drain-source voltage of the high-side transistor with a first threshold voltage.

[0025] In one embodiment, the second sensor may compare the drain-source voltage of the high-side transistor with a second threshold voltage.

[0026] A motor drive device according to one embodiment may include a switching circuit including a high-side transistor and a low-side transistor, and any of the above-described gate driver circuits for driving the switching circuit.

[0027] An electronic device according to one embodiment may include a motor and the motor drive device described above for driving the motor.

[0028] (Embodiment) Preferred embodiments will be described below with reference to the drawings. The same or equivalent components, members, and processes shown in each drawing will be denoted by the same reference numerals, and redundant descriptions will be omitted as appropriate. Furthermore, the embodiments are illustrative and not limiting to the invention, and not all features or combinations thereof described in the embodiments are necessarily essential to the invention.

[0029] In this specification, "member A connected to member B" includes not only cases where member A and member B are directly connected physically, but also cases where member A and member B are indirectly connected via other members that do not substantially affect their electrical connection or impair the functions or effects produced by their combination.

[0030] Similarly, "the state in which member C is provided between member A and member B" includes not only cases where member A and member C, or member B and member C, are directly connected, but also cases where they are indirectly connected via other members that do not substantially affect their electrical connection state or impair the functions or effects produced by their combination.

[0031] In this specification, the vertical and horizontal axes of the waveform diagrams and time charts have been enlarged or reduced as appropriate for ease of understanding, and the waveforms shown have also been simplified, exaggerated, or emphasized for ease of understanding.

[0032] Before describing the gate driver according to the embodiment, we will explain the problems that occur in gate driver circuits by referring to comparative techniques.

[0033] Figure 1 is a circuit diagram of a switching circuit 100R relating to the comparative technology. The switching circuit 100R comprises a bridge circuit 110 and a gate driver circuit 200R. Here, only the configuration of one phase of the switching circuit 100 is shown, but the switching circuit 100 may be a three-phase circuit or an H-bridge circuit.

[0034] The bridge circuit 110 includes a high-side transistor MH located between the power line (input line) 102 and the output terminal (output line) 104, and a low-side transistor ML located between the output line 104 and the ground line 106. The input line 102 is connected to the input voltage V Mis supplied. In this embodiment, the high-side transistor MH and the low-side transistor ML are N-channel MOSFETs, and their respective body diodes also serve as freewheeling diodes.

[0035] The gate driver circuit 200R drives the high-side transistor MH and the low-side transistor ML of the bridge circuit 110.

[0036] A bootstrap capacitor C is connected between the bootstrap pin BST and the output line 104. BST The high-side gate pin HG is connected to the gate of the high-side transistor MH. The switching pin SW is connected to the source of the high-side transistor MH and the drain of the low-side transistor ML. The low-side gate pin LG is connected to the gate of the low-side transistor ML.

[0037] The bootstrap line 202 is connected to the bootstrap pin BST. The bootstrap line 202 is provided with a bootstrap switch SW1 that can be switched on and off according to the control signal SWCTRL.

[0038] During the period when the bootstrap switch SW1 is on, a fixed voltage V is applied to the bootstrap line 202. REG The bootstrap switch SW1 and the bootstrap capacitor C form a bootstrap circuit, and keep the voltage V of the bootstrap line 202 at V + V - V. V is the voltage drop of the bootstrap switch SW1. BST BST OUT REG ON ON

[0039] ​​​​​​The gate driver circuit 200R is a functional IC integrated on a single semiconductor substrate, comprising the control circuit 210R, high-side driver 220, and low-side driver 250. The high-side driver 220 has its upper power supply terminal connected to the bootstrap line 202 and its lower power supply terminal connected to the switching line 204, and in response to its input, the high-side control signal HCTRL, it applies a high voltage V BST or low voltage V OUT Outputs.

[0040] The low-side driver 250 has its upper power terminal connected to the constant voltage line 206 and its output power terminal connected to the ground line 208, and in response to its input, the low-side control signal LCTRL, a high voltage V REG or low voltage V SS Outputs.

[0041] The control circuit 210R controls the high-side driver 220 and the low-side driver 250 in response to the input signal IN. When the input signal IN is at a first level (e.g., high), the control circuit 210R controls the high-side driver 220 to a high voltage (V BST The high-side control signal HCTRL is generated to output ) and the low-side driver 250 outputs a low voltage (ground voltage V SS A low-side control signal LCTRL is generated to output (=0V). This turns on the high-side transistor MH and off the low-side transistor ML, and the bridge circuit 110 enters a high output state (output voltage V). OUT =V M )

[0042] When the input signal IN is at the second level (low), the control circuit 210R lowers the high-side driver 220 to a low voltage (V OUT The high-side control signal HCTRL is generated to output ) and the low-side driver 250 is set to high voltage (V REG A low-side control signal LCTRL is generated to output (V). This turns off the high-side transistor MH and on the low-side transistor ML, and the bridge circuit 110 enters a low output state (output voltage V).OUT =V SS )

[0043] When the input signal IN transitions from the first level (high) to the second level (low), the control circuit 210R operates the high-side driver 220 in current sink mode, and the gate-source voltage V of the high-side transistor MH is reduced. GS(H) The voltage is reduced towards 0V, turning off the high-side transistor MH. When the turn-off of the high-side transistor MH is detected, the low-side driver 250 is operated in current source mode, and the gate-source voltage of the low-side transistor ML is reduced to V GS(L) Increase the voltage and turn on the low-side transistor ML.

[0044] Conversely, when the input signal IN transitions from the second level (low) to the first level (high), the control circuit 210R operates the low-side driver 250 in current sink mode, and the gate-source voltage V of the low-side transistor ML is reduced. GS(L) The voltage is reduced towards 0V, turning off the low-side transistor ML. Upon detecting that the low-side transistor ML has turned off, the high-side driver 220 is operated in current source mode, and the gate-source voltage of the high-side transistor MH is reduced to V GS(H) Increase the voltage and turn on the high-side transistor MH.

[0045] In the comparative technique, the control circuit 210R controls the bootstrap switch SW1 in response to the input signal IN. Specifically, it generates a control signal SWCTRL such that when the input signal IN is at the first level (high), the bootstrap switch SW1 is turned off, and when the input signal IN is at the second level (low), the bootstrap switch SW1 is turned on.

[0046] The above describes the configuration of the switching circuit 100R related to the comparative technology. Next, the operation of the switching circuit 100R will be explained.

[0047] Figure 2 shows the operating waveform of the switching circuit 100R in Figure 1. Here, we will explain the operation of the switching circuit 100 in current source mode, that is, when it sources current from the bridge circuit 110 to the load.

[0048] Before time t0, the input signal IN is at the first level (high), the high-side transistor MH is on, the low-side transistor ML is off, and the output voltage V OUT High voltage V M This is the state (high output state HOUT).

[0049] At time t0, the input signal IN changes from the first level (high) to the second level (low). Due to the control delay in the control circuit 210R and the propagation delay of the high-side driver 220, the gate voltage V of the high-side transistor MH is reduced at time t1, which is τd1 after time t0. HG The gate-source voltage V begins to decrease. GS(H) The gate-source voltage V decreases. GS(H) When the voltage drops, the voltage drop across the high-side transistor MH increases, so the output voltage V OUT It decreases over time.

[0050] At time t2, the gate-source voltage V of the high-side transistor MH GS(H) The gate threshold voltage V of the MOSFET GS(th) When the impedance drops further, the high-side transistor MH turns off. At this point, the bridge circuit 110 enters a high-impedance state (HiZ, or dead time).

[0051] When the turn-off of the high-side transistor MH is detected, the gate voltage V of the low-side transistor ML is turned off. GS(L) The voltage increases, and at time t3, the gate voltage V GS(L) The gate threshold voltage V GS(th) The unit turns on when the threshold is exceeded. After time t3, it enters the low output state LOUT.

[0052] At time t4, the input signal IN changes from the second level (low) to the first level (high). Due to the control delay in the control circuit 210R and the propagation delay of the low-side driver 250, at time t5, τd2 after time t4, the gate voltage V of the low-side transistor ML changes. LG (i.e., gate-source voltage V GS(L) ) begins to decline.

[0053] At time t6, the gate-source voltage V of the low-side transistor ML GS(L) The gate threshold voltage V of the MOSFET GS(th) When the impedance drops further, the low-side transistor ML turns off. At this point, the bridge circuit 110 enters a high-impedance state (HiZ).

[0054] When the turn-off of the low-side transistor MH is detected, the gate voltage V of the high-side transistor MH is turned off. GS(H) The voltage increases, and at time t7, the gate voltage V GS(H) The gate threshold voltage V GS(th) The unit turns on when the threshold is exceeded. After time t7, it enters the high-power state HOUT.

[0055] Next, we will explain the control of the bootstrap switch SW1. In the comparative technique, the bootstrap switch SW1 is controlled in conjunction with the input signal IN. That is, when the input signal IN is at the first level (high), the bootstrap switch SW1 is off, and when the input signal IN is at the second level (low), the bootstrap switch SW1 is on.

[0056] Let's focus on the period t0 to t2. During this period, the output voltage V OUT High voltage V M Therefore, V REG <V BST The following relationship holds. In the comparative technique, since the bootstrap switch SW1 is on during this period t0~t2, the bootstrap capacitor C is connected via the bootstrap switch SW1. BSTThis causes the bootstrap capacitor C to discharge. In situations where the switching frequency is high or the duty cycle is large, the unnecessary discharge over the period t0 to t2 results in a loss of power. BST This leads to a voltage shortage, preventing the high-side transistor MH from turning on.

[0057] Let's focus on the period t4 to t6. During this period, the output voltage V OUT Low voltage V SS (=0V). Therefore, this section is essentially a bootstrap capacitor C. BST It is possible to charge the bootstrap capacitor C. However, in the comparative technology, the bootstrap switch SW1 is turned off during this period t4 to t6, and no charging occurs. In situations where the switching frequency is high or the duty cycle is large, the non-charging period from t4 to t6 affects the bootstrap capacitor C. BST This leads to a voltage shortage, preventing the high-side transistor MH from turning on.

[0058] The above summarizes the problems that arise in the comparative technology. Next, the switching circuit 100 according to the embodiment will be described.

[0059] Figure 3 is a circuit diagram of the switching circuit 100 according to the embodiment. The gate driver circuit 200 according to the embodiment includes a first sensor 280 and a second sensor 282 in addition to the gate driver circuit 200R shown in Figure 1.

[0060] The first sensor 280 monitors the electrical state of the monitored transistor (first transistor), which is either the high-side transistor MH or the low-side transistor ML, based on its gate voltage. When the first sensor 280 detects a change in the electrical state, it asserts the first detection signal Sdet1. The electrical state based on the gate voltage of a transistor can be the gate-source voltage or the drain-source voltage of that transistor.

[0061] The second sensor 282 monitors the electrical state of the monitored transistor (referred to as the second transistor), which is either a high-side transistor ML or a low-side transistor ML, based on its gate voltage. When the second sensor 282 detects a change in the electrical state, it asserts the second detection signal Sdet2.

[0062] The first transistor monitored by the first sensor 280 and the second transistor monitored by the second sensor 282 may be the same transistor or they may be different transistors.

[0063] The control circuit 210 turns on the bootstrap switch SW1 in response to the assertion of the first detection signal Sdet1 after the input signal IN changes from the first level to the second level.

[0064] Furthermore, the control circuit 210 turns off the bootstrap switch SW1 in response to the assertion of the second detection signal Sdet2 after the input signal IN changes from the second level to the first level.

[0065] In one embodiment, both the first transistor monitored by the first sensor 280 and the second transistor monitored by the second sensor 282 are low-side transistors ML.

[0066] The first sensor 280 is the gate-source voltage V of the low-side transistor ML. GS(L) The first threshold voltage V TH1 Compared with V GS(L) >V TH1 Therefore, the first detection signal Sdet1 is asserted.

[0067] The second sensor 282 measures the gate-source voltage V of the low-side transistor ML. GS(L) The second threshold voltage V TH2 Compared with V GS(L) <V TH2 Therefore, the second detection signal Sdet2 is asserted. First threshold voltage V TH1 and the second threshold voltage VTH2 They may be defined as equal, in which case the first sensor 280 and the second sensor 282 can be shared.

[0068] Figure 4 is an operating waveform diagram of the switching circuit 100 according to the embodiment. Except for the control of the bootstrap switch SW1, it is the same as in Figure 2.

[0069] In this embodiment, at time t8, the gate-source voltage V of the low-side transistor ML is GS(L) The first threshold voltage V TH1 When it exceeds this value, the bootstrap switch SW1 turns on. Also, at time t9, the gate-source voltage V of the low-side transistor ML GS(L) The second threshold voltage V TH2 When the temperature drops further, the bootstrap switch SW1 turns off.

[0070] The above describes the operation of the switching circuit 100. With this switching circuit 100, the timing at which the bootstrap switch SW1 turns on is delayed compared to the comparative technology. Specifically, the output voltage V OUT After the voltage drops to low, the bootstrap switch SW1 turns on, causing the bootstrap capacitor C to... BST This can suppress the discharge.

[0071] Furthermore, with this switching circuit 100, the timing at which the bootstrap switch SW1 turns off is delayed compared to the comparative technology. As a result, the bootstrap capacitor C BST It can be charged for a longer period compared to other technologies.

[0072] Next, we will explain a modified version of the control of the bootstrap switch SW1.

[0073] Figure 5 illustrates a modified example of the control of the bootstrap switch SW1.

[0074] This section explains a variation regarding the turn-on timing of the bootstrap switch SW1.

[0075] (i) Variant 1 The first sensor 280 monitors the voltage V between the drain and source of the high - side transistor MH DS(H) and when V DS(H) >V TH1 it may assert the first detection signal Sdet1. In other words, the first sensor 280 monitors the output voltage V OUT and when V OUT <V M -V TH1 it may assert the first detection signal Sdet1.

[0076] (ii) Variant 2 The first sensor 280 monitors the voltage V between the drain and source of the low - side transistor ML DS(L) and when V DS(L) <V TH1 it may assert the first detection signal Sdet1. In other words, the first sensor 280 monitors the output voltage V OUT and when V OUT <V TH1 it may assert the first detection signal Sdet1.

[0077] (iii) Variant 3 The first sensor 280 monitors the voltage V between the gate and source of the high - side transistor MH GS(H) and when V GS(H) <V TH1 it may assert the first detection signal Sdet1.

[0078] A variant regarding the turn - off timing of the bootstrap switch SW1 will be described.

[0079] (iv) Variant 4 The second sensor 282 monitors the voltage V between the drain and source of the high - side transistor MH DS(H) and when V DS(H) <V TH2 it may assert the second detection signal Sdet2. In other words, the second sensor 282 monitors the output voltage V OUT and when VOUT <V M -V TH2 When this occurs, the second detection signal Sdet2 may be asserted.

[0080] (v) Variant 5 The second sensor 282 monitors the drain-source voltage V of the low-side transistor ML DS(L) and when V DS(L) > V TH2 occurs, the second detection signal Sdet2 may be asserted. In other words, the second sensor 282 monitors the output voltage V OUT and when V OUT > V TH2 occurs, the second detection signal Sdet2 may be asserted.

[0081] (vi) Variant 6 The second sensor 282 monitors the gate-source voltage V of the high-side transistor MH GS(H) and when V GS(H) > V TH2 occurs, the second detection signal Sdet2 may be asserted.

[0082] The control of the turn-on and turn-off of the bootstrap switch SW1 can be arbitrarily combined with those described in the embodiments and variants.

[0083] (Application) Next, the application of the switching circuit 100 will be described. The switching circuit 100 can be suitably used for a motor drive circuit.

[0084] FIG. 6 is a circuit diagram of a motor drive device 300 according to an embodiment. The motor drive device 300 drives a three-phase motor 302 as a load and controls its rotational state.

[0085] The motor drive device 300 includes a bridge circuit 310 and a gate driver circuit 400. The bridge circuit 310 is a three-phase inverter and has legs for the U-phase, V-phase, and W-phase, and each phase leg has a high-side transistor MH and a low-side transistor ML.

[0086] The gate driver circuit 400 includes a control circuit 410 and high-side drivers 420U~420W and low-side drivers 450U~450W. The control circuit 410 generates control signals that indicate the state of the six arms constituting the bridge circuit 310 based on the state of the load, which is a three-phase motor 302.

[0087] The high-side drivers 420U to 420W are constructed using the same architecture as the high-side driver 220 described above. The low-side drivers 450U to 450W are constructed using the same architecture as the low-side driver 250 described above.

[0088] Here, a three-phase motor is used as an example, but a single-phase motor can also be used. In this case, the bridge circuit 310 becomes an H-bridge circuit.

[0089] Next, the applications of the motor drive unit 300 will be explained. The motor drive unit 300 can be used to control the spindle motor of a hard disk, or to control the lens drive motor of an imaging device. Alternatively, it can be used to drive the head drive motor or paper feed motor of a printer. Alternatively, the motor drive unit 300 can be used to drive motors in electric vehicles and hybrid vehicles.

[0090] The embodiments are illustrative, and it will be understood by those skilled in the art that various modifications are possible in combinations of their components and processing steps, and that such modifications also fall within the scope of this disclosure or the present invention. Such modifications will be described below.

[0091] (Variation 1) In this embodiment, the bridge circuit 110 is composed of discrete components, but it is not limited to that, and the bridge circuit 110 may be integrated into the gate driver circuit 200.

[0092] (Modification 2) The upper and lower arms may be composed of IGBTs (Insulated Gate Bipolar Transistors).

[0093] (Variation 3) The applications of the switching circuit 100 are 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, and so on. Therefore, the switching circuit 100 can be used in consumer electronics including electronic devices and home appliances, automobiles and in-vehicle components, industrial vehicles and industrial machinery.

[0094] The embodiments described using specific terminology 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.

[0095] (Note) This specification discloses the following technologies:

[0096] (Item 1) A gate driver circuit that drives a switching circuit having an N-type high-side transistor and a low-side transistor in response to an input signal, The bootstrap terminal to which one end of the bootstrap capacitor should be connected, The high-side gate terminal to be connected to the gate of the aforementioned high-side transistor, The low-side gate terminal to be connected to the gate of the aforementioned low-side transistor, A switching terminal to be connected to the output line of the switching circuit, A bootstrap switch is connected to the bootstrap terminal at one end and receives a constant voltage at the other end. The upper power terminal is connected to the bootstrap terminal, and the lower power terminal is connected to the switching terminal. A high-side driver generates a high-side gate voltage at the high-side gate terminal in accordance with the high-side control signal. A low-side driver that generates a low-side gate voltage at the low-side gate terminal in response to a low-side control signal, A first sensor that asserts a first detection signal when it detects a change in the electrical state of the high-side transistor or the low-side transistor based on its gate voltage, A control circuit generates the high-side control signal and the low-side control signal in response to the input signal, and turns on the bootstrap switch in response to the assertion of the first detection signal, A gate driver circuit equipped with the following features.

[0097] (Item 2) The system further includes a second sensor that, upon detecting a change in the electrical state of the high-side transistor or the low-side transistor based on its gate voltage, asserts a second detection signal. The gate driver circuit according to item 1, wherein the control circuit turns off the bootstrap switch in response to the assertion of the second detection signal.

[0098] (Item 3) The first sensor is a gate driver circuit according to item 1 or 2, which compares the gate-source voltage of the low-side transistor with a first threshold voltage.

[0099] (Item 4) The second sensor is a gate driver circuit as described in item 2, which compares the gate-source voltage of the low-side transistor with a second threshold voltage.

[0100] (Item 5) The first sensor is a gate driver circuit according to item 1 or 2, which compares the gate-source voltage of the high-side transistor with a first threshold voltage.

[0101] (Item 6) The second sensor is a gate driver circuit as described in item 2, which compares the gate-source voltage of the high-side transistor with a second threshold voltage.

[0102] (Item 7) The first sensor is a gate driver circuit according to item 1 or 2, which compares the drain-source voltage of the low-side transistor with a first threshold voltage.

[0103] (Item 8) The second sensor is a gate driver circuit as described in item 2, which compares the drain-source voltage of the low-side transistor with a second threshold voltage.

[0104] (Item 9) The first sensor is a gate driver circuit according to item 1 or 2, which compares the drain-source voltage of the high-side transistor with a first threshold voltage.

[0105] (Item 10) The second sensor is a gate driver circuit as described in item 2, which compares the drain-source voltage of the high-side transistor with a second threshold voltage.

[0106] (Item 11) A switching circuit including a high-side transistor and a low-side transistor, A gate driver circuit according to any one of items 1 to 10 for driving the switching circuit, A motor drive device equipped with the following features.

[0107] (Item 12) Motor and, A motor drive device as described in item 11 for driving the motor, An electronic device equipped with the following features. [Explanation of Symbols]

[0108] 100 Switching Circuits 102 input lines 104 output lines 106 Grounding line 110 Bridge Circuit MH High-Side Transistor ML Low-Side Transistor 200 Gate Driver Circuit 202 Bootstrap Line 204 Switching Line 208 Grounding line 210 Control circuits 220 High-Side Driver 250 Low-Side Driver SW1 Bootstrap Switch 280 First Sensor 282 Second Sensor HCTRL High-Side Control Signal LCTRL Low-side control signal 300 Motor drive unit 302 Three-phase motor 310 Bridge Circuit 400 Gate Driver Circuit 410 Control Circuit 420 High-Side Driver 450 Low-Side Driver

Claims

1. A gate driver circuit that drives a switching circuit having an N-type high-side transistor and a low-side transistor in response to an input signal, The bootstrap terminal to which one end of the bootstrap capacitor should be connected, The high-side gate terminal to be connected to the gate of the aforementioned high-side transistor, The low-side gate terminal to be connected to the gate of the aforementioned low-side transistor, A switching terminal to be connected to the output line of the switching circuit, A bootstrap switch is connected to the bootstrap terminal at one end and receives a constant voltage at the other end. The upper power terminal is connected to the bootstrap terminal, and the lower power terminal is connected to the switching terminal. A high-side driver generates a high-side gate voltage at the high-side gate terminal in accordance with the high-side control signal. A low-side driver that generates a low-side gate voltage at the low-side gate terminal in response to a low-side control signal, A first sensor that asserts a first detection signal when it detects a change in the electrical state of the high-side transistor or the low-side transistor based on its gate voltage, A control circuit generates the high-side control signal and the low-side control signal in response to the input signal, and turns on the bootstrap switch in response to the assertion of the first detection signal, A gate driver circuit equipped with the following features.

2. The system further includes a second sensor that, upon detecting a change in the electrical state of the high-side transistor or the low-side transistor based on its gate voltage, asserts a second detection signal. The gate driver circuit according to claim 1, wherein the control circuit turns off the bootstrap switch in response to the assertion of the second detection signal.

3. The gate driver circuit according to claim 1 or 2, wherein the first sensor compares the gate-source voltage of the low-side transistor with a first threshold voltage.

4. The gate driver circuit according to claim 2, wherein the second sensor compares the gate-source voltage of the low-side transistor with a second threshold voltage.

5. The gate driver circuit according to claim 1 or 2, wherein the first sensor compares the gate-source voltage of the high-side transistor with a first threshold voltage.

6. The gate driver circuit according to claim 2, wherein the second sensor compares the gate-source voltage of the high-side transistor with a second threshold voltage.

7. The gate driver circuit according to claim 1 or 2, wherein the first sensor compares the drain-source voltage of the low-side transistor with a first threshold voltage.

8. The gate driver circuit according to claim 2, wherein the second sensor compares the drain-source voltage of the low-side transistor with a second threshold voltage.

9. The gate driver circuit according to claim 1 or 2, wherein the first sensor compares the drain-source voltage of the high-side transistor with a first threshold voltage.

10. The gate driver circuit according to claim 2, wherein the second sensor compares the drain-source voltage of the high-side transistor with a second threshold voltage.

11. A switching circuit including a high-side transistor and a low-side transistor, A gate driver circuit according to claim 1 or 2 for driving the switching circuit, A motor drive device equipped with the following features.

12. Motor and, A motor drive device according to claim 11 for driving the motor, An electronic device equipped with the following features.

Images