Gate driver circuit and motor driving device

Abstract

To provide a gate driver circuit capable of detecting an under voltage state of a bootstrap voltage.SOLUTION: An under voltage detection circuit 260 compares a potential difference ΔV between a bootstrap line 202 and an output line with a threshold voltage VUV. A first resistor R1 has a first end connected to the bootstrap line 202. A Zener diode ZD1 has a cathode connected to the bootstrap line 202 and has a parasitic capacitance between the cathode and a substrate. A first transistor M1 has a source connected to the output line, and also has a drain and a gate which are connected to a second end of the first resistor R1. A comparator 262 compares a voltage drop across a second resistor R2 with a threshold voltage Vth and generates an under voltage detection signal BSTUV.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] The motor drive circuit and power supply circuit include a switching circuit such as a single-phase inverter, a three-phase inverter, or an H-bridge circuit, and a gate driver circuit that drives the switching circuit.

[0003] When the high-side transistor is an N-type transistor, i.e., an N-channel MOSFET (Metal Oxide Semiconductor Field Effect Transistor), an NPN-type bipolar transistor, or an IGBT (Insulated Gate Bipolar Transistor), a bootstrap circuit is used.

[0004] To ensure that the high-side transistor is turned on, the potential difference between the output line connected to the source of the high-side transistor and the bootstrap line must be greater than or equal to the threshold voltage V GS(th) It needs to be higher than [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-087942

[0006] [overview] The present disclosure has been made in this situation, and one exemplary purpose of an embodiment thereof is to provide a gate driver circuit capable of detecting a low voltage state of a bootstrap voltage.

[0007] An embodiment of the present disclosure relates to a gate driver circuit for driving an N-type high-side transistor, the gate driver circuit including: an output line to be connected to a source of the high-side transistor; a bootstrap line to be connected to the high-side transistor via a bootstrap capacitor; a voltage source that applies a constant voltage to the bootstrap line; and a low-voltage detection circuit that compares a potential difference between the bootstrap line and the output line with a threshold voltage. the low voltage detection circuit includes a first resistor having a first end connected to the bootstrap line; a Zener diode having a cathode connected to the bootstrap line and a parasitic capacitance between the cathode and a substrate; an N-type first transistor having a source connected to the output line and a drain and a gate connected to a second end of the first resistor; an N-type second transistor having a source connected to the output line and a gate connected to a gate of the first transistor; an N-type third transistor having a source connected to a drain of the second transistor and a drain and a gate connected to an anode of the Zener diode; an N-type fourth transistor having a source connected to a source of the third transistor and a gate connected to a gate of the third transistor; a second resistor connected between the bootstrap line and a drain of the fourth transistor; and a comparator that compares a voltage drop across the second resistor with a threshold voltage.

[0008] Any combination of the above elements, or mutual substitution of elements or expressions between methods, devices, systems, etc., are also valid aspects of the present invention or the present disclosure. Furthermore, the description in this section (Means for Solving the Problems) does not describe all essential features of the present invention. For example, subcombinations of the described features may also constitute the present invention. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a circuit diagram of a switching circuit including a gate driver circuit according to an embodiment. [Figure 2] FIG. 2 is a circuit diagram of the low-voltage detection circuit according to the embodiment. [Figure 3] FIG. 3 is a diagram illustrating the operation of the low-voltage detection circuit. [Figure 4] FIG. 4 is a circuit diagram of a low-voltage detection circuit according to one embodiment. [Figure 5] FIG. 5 is a circuit diagram of the motor drive device according to the embodiment.

[0010] [Detailed explanation] A summary of some exemplary embodiments of the present disclosure is provided. This summary is intended to provide a simplified overview of some concepts of one or more embodiments in order to provide a basic understanding of the embodiments as a prelude to the more detailed description that follows. It is not intended to limit the scope of the invention or disclosure. Furthermore, this summary is not an exhaustive overview of all possible embodiments, nor does it limit essential elements of the embodiments. For convenience, the term "one embodiment" may refer to one embodiment (example or variant) or multiple embodiments (examples or variants) disclosed herein.

[0011] A gate driver circuit according to one embodiment drives an N-type high-side transistor and includes an output line (also referred to as a switching line) to be connected to the source of the high-side transistor, a bootstrap line to be connected to the high-side transistor via a bootstrap capacitor, a voltage source that applies a constant voltage to the bootstrap line, and an undervoltage (UV) detection circuit that compares the potential difference between the bootstrap line and the output line with a threshold voltage. the low voltage detection circuit includes a first resistor having a first end connected to the bootstrap line; a Zener diode having a cathode connected to the bootstrap line and a parasitic capacitance between the cathode and a substrate; an N-type first transistor having a source connected to the output line and a drain and a gate connected to a second end of the first resistor; an N-type second transistor having a source connected to the output line and a gate connected to a gate of the first transistor; an N-type third transistor having a source connected to a drain of the second transistor and a drain and a gate connected to an anode of the Zener diode; an N-type fourth transistor having a source connected to a source of the third transistor and a gate connected to a gate of the third transistor; a second resistor connected between the bootstrap line and a drain of the fourth transistor; and a comparator that compares a voltage drop across the second resistor with a threshold voltage.

[0012] With this configuration, the parasitic capacitance of the Zener diode exists between the bootstrap line and the substrate, so fluctuations in the voltage levels of the bootstrap line and output line caused by switching do not affect the operating point of the low-voltage detection circuit. This enables accurate low-voltage detection even during switching operations. Furthermore, the current consumption of the low-voltage detection circuit can be made extremely small.

[0013] In one embodiment, the first resistor and the second resistor may be the same type. In another embodiment, the first resistor and the second resistor may be arranged adjacent to each other. This can improve the relative accuracy of the resistance values ​​of the first resistor and the second resistor and reduce variations in the low voltage detection threshold.

[0014] In one embodiment, the comparator may include a fifth P-type transistor having a source connected to the bootstrap line and a gate connected to the drain of the fourth transistor, and a third resistor connected between the drain of the fifth transistor and ground.

[0015] In one embodiment, the first to fourth transistors may be floating MOS transistors.

[0016] In one embodiment, the first resistor and the second resistor may be formed on a well connected to the bootstrap line.

[0017] A motor drive device according to an embodiment may include any of the gate driver circuits described above.

[0018] (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.

[0019] 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.

[0020] 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.

[0021] 1 is a circuit diagram of a switching circuit 100 including a gate driver circuit 200 according to an embodiment. The switching circuit 100 includes a bridge circuit 110 and a gate driver circuit 200. Although only the configuration of one phase of the switching circuit 100 is shown here, the switching circuit 100 may be a single-phase circuit, a three-phase circuit, or an H-bridge circuit.

[0022] 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) DH connected in parallel. The lower arm 114 includes a low-side transistor ML and a flywheel diode DL 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 diodes DH and DL. Depending on the application, a shunt resistor for current detection may be inserted between the low-side transistor ML and the ground line 106.

[0023] The gate driver circuit 200 receives a control signal S CTRL The high-side transistor MH and the low-side transistor ML of the bridge circuit 110 are controlled based on the control signal S CTRL can take three states φ1 to φ3.

[0024] The first state φ1 is a high output state (VOUT =V IN ) is the state that indicates

[0025] The second state φ2 is a low output state (V OUT = 0V).

[0026] The third state φ3 is a high-impedance state (V OUT =HiZ).

[0027] The gate driver circuit 200 is a functional IC integrated on a single semiconductor substrate, and includes a control circuit 210, a high-side driver 220, a level shifter 224, a low-side driver 230, a regulator 240, a charging circuit 250, and a low-voltage detection circuit 260. The gate driver circuit 200 may be a gate driver IC (Integrated Circuit), or may be part of a motor driver IC or a controller IC for a DC / DC converter.

[0028] The high-side gate pin HG of the gate driver circuit 200 is connected to the gate of the high-side transistor MH, and the low-side gate pin LG is connected to the gate of the low-side transistor ML. The ground pin GND is connected to the source of the low-side transistor ML. The switching pin (output pin) OUT is connected to the output line 104. A bootstrap capacitor C is connected between the bootstrap pin BST and the switching pin OUT. BST is attached externally.

[0029] The bootstrap line 202 is connected to the bootstrap pin BST, the switching line 204 is connected to the switching pin OUT, and the ground line 206 is connected to the GND pin. REG Generates a constant voltage V REGis the threshold voltage V of the high-side transistor MH and the low-side transistor ML GS(th) For example, the constant voltage V REG is about 12V.

[0030] The bootstrap line 202 is supplied with a constant voltage V REG is applied to the rectifying element 208 and the bootstrap capacitor C BST forms a bootstrap circuit, and the voltage (switching voltage) V of the switching line 204 is applied to the bootstrap line 202 by utilizing the switching operation of the bridge circuit 110. OUT The bootstrap voltage V is higher than the BST When the forward voltage of the rectifying element 208 is Vf, ΔV=V REG It becomes -Vf.

[0031] The control circuit 210 outputs the control signal S CTRL When the first state φ1 is in the first state, the high-side transistor MH is turned on, the low-side transistor ML is turned off, and the control signal S CTRL is in the second state φ2, the control signal S is set to turn off the high-side transistor MH and turn on the low-side transistor ML. CTRL is in the third state φ3, the high-side control signal HCTRL and the low-side control signal LCTRL are generated so that the high-side transistor MH is turned off and the low-side transistor ML is turned off.

[0032] The high-side control signal HCTRL generated by the control circuit 210 is level-shifted up by the level shifter 224 and supplied to the high-side driver 220. The high-side driver 220 adjusts the gate voltage V of the high-side transistor MH in response to the level-shifted high-side control signal HCTRL. HG The upper power supply node 221 of the high-side driver 220 is connected to the bootstrap line 202 and controls the bootstrap voltage V BSTThe lower power supply node 222 is connected to the switching line 204 and is supplied with a switching voltage V OUT The high-side driver 220 supplies a high gate voltage V BST , gate low voltage V OUT One of these is output to the high-side gate pin HG.

[0033] The high-side driver 220 may be configured so that its driving capability is controllable. The high-side driver 220 may be configured as a current-driven or voltage-driven type. In the case of a current-driven high-side driver, its driving capability can be understood as the amount of current sourced to the gate of the high-side transistor MH or the amount of current sunk from the gate. In the case of a voltage-driven high-side driver, its driving capability can be understood as the output impedance. In short, the high-side driver 220 controls the gate voltage V generated at the high-side gate pin HG. HG The slope (slew rate) of the signal may be switchable.

[0034] The low-side driver 230 controls the gate voltage V of the low-side transistor ML in response to the low-side control signal LCTRL. LG The upper power supply node 231 of the low-side driver 230 is connected to a power supply voltage V DD is supplied to the low-side power supply node 232 of the low-side driver 230, and the ground voltage is supplied to the low-side power supply node 232 of the low-side driver 230.

[0035] The low-side driver 230 may also be configured to have a controllable driving capability, similar to the high-side driver 220, and the gate voltage V LG The tilt of the light source 10 may be switchable.

[0036] The switching circuit 100 supports an operating mode in which the high-side transistor MH is clamped on with a duty cycle of 100%. When the high-side transistor MH is clamped on, the bootstrap capacitor C BSTIn this mode of operation, the charging circuit 250 is active and drives the bootstrap line 202 to the input voltage V IN The configuration of the charging circuit 250 is not limited, but may include, for example, a charge pump circuit 252 and a constant current source 254.

[0037] The power supply voltage V supplied to the gate driver circuit 200 CC The power supply voltage V CC is the constant voltage V REG When the voltage drops below the target level (for example, 12V), the constant voltage V REG becomes lower than the target level. REG is the threshold voltage V of the high-side transistor MH. GS(th) If the voltage V is lower than the threshold voltage V, the high-side transistor MH cannot be turned on. UV Detects lower undervoltage conditions.

[0038] 2 is a circuit diagram of a low-voltage detection circuit 260 according to an embodiment. The low-voltage detection circuit 260 includes a first resistor R1, a second resistor R2, a first transistor M1, a second transistor M2, a third transistor M3, and a fourth transistor M4, which are NMOS transistors, a Zener diode ZD1, and a comparator 262.

[0039] A first end of the first resistor R1 is connected to the bootstrap line 202. A cathode of the Zener diode ZD1 is connected to the bootstrap line 202. The Zener diode ZD1 has a parasitic capacitance Czd1 between the cathode and the semiconductor substrate (SUB).

[0040] Let's look at Zener diode ZD1. The cathode of Zener diode ZD1 is adjacent to the sub-substrate, which increases the parasitic capacitance between the cathode and the substrate. The voltage between the anode and cathode is approximately 5.2V.

[0041] The source of the first transistor M1 is connected to the switching line 204, and the drain and gate are connected to the second end of the first resistor R1. The source of the second transistor M2 is connected to the switching line 204, and the gate of the second transistor M2 is connected to the gate of the first transistor M1. The first transistor M1 and the second transistor M2 constitute a current mirror circuit CM1.

[0042] The source of the third transistor M3 is connected to the drain of the second transistor M2, and the drain and gate of the third transistor M3 are connected to the anode of the Zener diode ZD1. The source of the fourth transistor M4 is connected to the source of the third transistor M3, and the gate of the fourth transistor M4 is connected to the gate of the third transistor M3. The third transistor M3 and the fourth transistor M4 constitute a current mirror circuit CM2.

[0043] The second resistor R2 is connected between the bootstrap line 202 and the drain of the fourth transistor M4. The comparator 262 compares the voltage drop V R2 across the second resistor R2 with the threshold voltage Vth, and negates the low voltage detection signal BSTUV when V R2 > Vth, and asserts the low voltage detection signal BSTUV when V R2 < Vth.

[0044] It is desirable that the first resistor R1 and the second resistor R2 be of the same type (same structure). Further, it is desirable that the first resistor R1 and the second resistor R2 be arranged adjacent to each other in a common well. This can suppress the relative variation in the resistance values of the first resistor R1 and the second resistor R2.

[0045] Furthermore, it is desirable that all of the first transistor M1 to the fourth transistor M4 are configured as floating NMOS transistors. By connecting the floating well, which has low impedance, to a power supply line based on the switching line 204, the influence of switching is reduced to a signal system, which has high impedance, specifically, the input signal (V B ) or the output signal (BSTUV).

[0046] The above is the configuration of the low voltage detection circuit 260. Next, the operation of the low voltage detection circuit 260 will be described.

[0047] The gate-source voltage of the first transistor M1 is V GS Then, the current I1 flowing through the first resistor R1 and ΔV=V BST -V OUT The relationship between them is expressed by equation (1). I1=(ΔV-V GS ) / R1 …(1)

[0048] The Zener voltage of Zener diode ZD1 is V ZD , the gate-source voltage of the third transistor M3 is V GS ΔV>V ZD +V GS When V, the Zener diode ZD1 is conductive. ZD +V GS is the threshold voltage V of the low voltage detection circuit 260 UV This is the voltage equivalent to

[0049] ΔV>V UL At this time, a current I2 proportional to the current I1 flows through the second transistor M2. Because the third transistor M3 and the fourth transistor M4 form a current mirror circuit CM2, currents I3 and I4 flow through the third transistor M3 and the fourth transistor M4 in a ratio that depends on their size parameters (W / L). W is the gate width, and L is the gate length. For example, when the size parameters W / L of the third transistor M3 and the fourth transistor M4 are equal, I3 = I4 = I2 / 2.

[0050] When current I4 flows, a voltage drop V occurs across the second resistor R2. R2 =I4×R2 occurs. The threshold voltage Vth of the comparator 262 is set when the Zener diode ZD1 is conductive, that is, when ΔV>V UL When this holds, the voltage drop V R2 Therefore, the low voltage detection signal BSTUV is negated.

[0051] ΔV <V ZD +V GS At this time, the Zener diode ZD1 is cut off. At this time, the current I2 does not flow through the second transistor M2, and the current does not flow through the third transistor M3 and the fourth transistor M4 either. As a result, the voltage drop V across the second resistor R2 R2 becomes zero, V R2 <Vth Therefore, the low voltage detection signal BSTUV is asserted.

[0052] 3 is a diagram illustrating the operation of the low voltage detection circuit 260. The horizontal axis represents the potential difference ΔV between the bootstrap line 202 and the switching line 204. Here, V OUT = 0V, that is, the switching of the bridge circuit 110 is stopped. BST , output voltage V OUT , the drain voltage V of the second transistor M2 A , the drain voltage V of the fourth transistor M4 B is shown. Voltage V BST and V B The potential difference is the voltage drop V of the second resistor R2. R2 is.

[0053] In this example, the threshold voltage V UV is around 5.5V, and ΔV <V UV Then, current stops flowing through the Zener diode ZD1, and the voltage drop V across the second resistor R2 R2 becomes lower than the threshold voltage Vth of the comparator 262.

[0054] In this way, the low voltage detection circuit 260 can detect a low voltage state of the potential difference ΔV.

[0055] In the low voltage detection circuit 260, the cathode of the Zener diode ZD1 is connected to the bootstrap line 202, and the influence of the parasitic capacitance Czd1 on the electrical signal generated in the low voltage detection circuit 260, specifically the voltage V A ,V B , V R2 , the influence on the currents I1, I2, I3, and I4 flowing through the low voltage detection circuit 260 is extremely small. Therefore, accurate low voltage detection is possible even during the switching operation of the bridge circuit 110.

[0056] Another advantage of the low voltage detection circuit 260 is that it consumes little current. The circuit disclosed in Patent Document 1 (JP 2020-087942 A) requires a current consumption of more than 50 μA, but the low voltage detection circuit 260 in FIG. 2 can reduce the current consumption to 10 μA or less.

[0057] 4 is a circuit diagram of a low-voltage detection circuit 260A according to one embodiment. In this embodiment, the comparator 262A includes a third resistor R3 and a fifth transistor M5, which is a PMOS transistor. The source of the fifth transistor M5 is connected to the bootstrap line 202, and the gate is connected to the drain of the fourth transistor M4. The third resistor R3 is connected between the drain of the fifth transistor M5 and ground. The threshold voltage Vth of this comparator 262A is calculated by dividing the threshold voltage Vth of the fifth transistor M5 by the threshold voltage Vth of the fifth transistor M5. GS(th) In other words, the voltage drop V across resistor R2 R2 is the threshold voltage V GS(th) When the voltage V is greater than the threshold voltage V, the fifth transistor M5 is turned on and the low voltage detection signal BSTUV is high (negated). R2 is the threshold voltage V GS(th) If it is smaller, the fifth transistor M5 is turned off and the low voltage detection signal BSTUV goes low.

[0058] Next, we will explain the applications of the switching circuit 100. The switching circuit 100 can be suitably used in a motor drive circuit.

[0059] 5 is a circuit diagram of a motor driving device 300 according to an embodiment. The motor driving device 300 drives a three-phase motor 302, which is a load, and controls the rotation state.

[0060] The motor drive device 300 includes a bridge circuit 110 and a gate driver circuit 200, and is a three-phase configuration of the above-described switching circuit 100. The 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.

[0061] The gate driver circuit 200 includes a control circuit 210, high-side drivers 220U to 220W, and low-side drivers 230U to 230W. 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.

[0062] 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.

[0063] 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.

[0064] 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 the respective treatment processes, and that such modifications are also within the scope of the present disclosure and the present invention. Such modifications will be described below.

[0065] (Variation 1) The configuration of the comparator 262 is not limited to the configuration of FIG. 4, and a voltage comparator using a differential amplifier may be used.

[0066] (Variation 2) 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.

[0067] Although the embodiments of the present disclosure have been described using specific terms, this description is merely an example to facilitate understanding and does not limit the scope of the present disclosure or the claims. The scope of the present invention is defined by the claims, and therefore, embodiments, examples, and modifications not described herein are also included in the scope of the present invention.

[0068] (Addendum) The present specification discloses the following techniques.

[0069] (Item 1) A gate driver circuit that drives an N-type high-side transistor, an output line to be connected to the source of the high-side transistor; a bootstrap line to be connected to the high-side transistor via a bootstrap capacitor; a voltage source that applies a constant voltage to the bootstrap line; a low voltage detection circuit that compares the potential difference between the bootstrap line and the output line with a threshold voltage; Equipped with The low voltage detection circuit a first resistor having a first end connected to the bootstrap line; a Zener diode having a cathode connected to the bootstrap line and having a parasitic capacitance between the cathode and a substrate; a first N-type transistor having a source connected to the output line and a drain and a gate connected to the second end of the first resistor; a second N-type transistor having a source connected to the output line and a gate connected to the gate of the first transistor; a third N-type transistor having a source connected to the drain of the second transistor and a drain and gate connected to the anode of the Zener diode; a fourth transistor of N-type, the source of which is connected to the source of the third transistor and the gate of which is connected to the gate of the third transistor; a second resistor connected between the bootstrap line and the drain of the fourth transistor; a comparator that compares the voltage drop across the second resistor with a threshold voltage; a gate driver circuit including:

[0070] (Item 2) Item 2. The gate driver circuit of item 1, wherein the first resistor and the second resistor are of the same type.

[0071] (Item 3) 3. The gate driver circuit of item 1 or 2, wherein the first resistor and the second resistor are arranged adjacent to each other.

[0072] (Item 4) The comparator a fifth transistor of P type, the source of which is connected to the bootstrap line and the gate of which is connected to the drain of the fourth transistor; a third resistor connected between the drain of the fifth transistor and ground; 4. The gate driver circuit of any one of items 1 to 3, comprising:

[0073] (Item 5) 5. The gate driver circuit of any one of items 1 to 4, wherein the first to fourth transistors are floating MOS transistors.

[0074] (Item 6) 6. The gate driver circuit of any one of items 1 to 5, wherein the first resistor and the second resistor are formed on a well connected to the bootstrap line.

[0075] (Item 7) 7. A motor circuit comprising the gate driver circuit according to any one of items 1 to 6. [Explanation of symbols]

[0076] 100 Switching Circuit 102 Power Line 104 output lines 106 Ground Line 110 Bridge Circuit 112 Upper Arm 114 Lower Arm MH high-side transistor ML low-side transistor DH,DL Flywheel diode 200 Gate driver circuit 210 Control circuit 220 High Side Driver 224 Level Shifter 230 Low Side Driver 240 Regulator 250 charging circuit 252 Charge pump circuit 254 constant current source 260 Low voltage detection circuit R1 First resistor R2 2nd resistor R3 3rd resistor M1 First transistor M2 Second transistor M3 Third transistor M4 4th transistor ZD1 Zener diode 262 Comparator 300 Motor drive unit 302 Three-phase motor 202 Bootstrap Line 204 Switching Line

Claims

1. A gate driver circuit for driving an N-type high-side transistor, an output line to be connected to the source of the high-side transistor; a bootstrap line to be connected to the high-side transistor via a bootstrap capacitor; a voltage source that applies a constant voltage to the bootstrap line; a low voltage detection circuit that compares the potential difference between the bootstrap line and the output line with a threshold voltage; Equipped with The low voltage detection circuit a first resistor having a first end connected to the bootstrap line; a Zener diode having a cathode connected to the bootstrap line and having a parasitic capacitance between the cathode and a substrate; a first N-type transistor having a source connected to the output line and a drain and a gate connected to the second end of the first resistor; a second N-type transistor having a source connected to the output line and a gate connected to the gate of the first transistor; a third N-type transistor having a source connected to the drain of the second transistor and a drain and gate connected to the anode of the Zener diode; a fourth N-type transistor having a source connected to the source of the third transistor and a gate connected to the gate of the third transistor; a second resistor connected between the bootstrap line and the drain of the fourth transistor; a comparator for comparing the voltage drop across the second resistor with a threshold voltage; a gate driver circuit including:

2. The gate driver circuit of claim 1 , wherein the first resistor and the second resistor are of the same type.

3. The gate driver circuit according to claim 1 , wherein the first resistor and the second resistor are disposed adjacent to each other.

4. The comparator a fifth transistor of P type, the source of which is connected to the bootstrap line and the gate of which is connected to the drain of the fourth transistor; a third resistor connected between the drain of the fifth transistor and ground; 3. The gate driver circuit of claim 1, comprising:

5. 3. The gate driver circuit according to claim 1, wherein the first to fourth transistors are floating MOS transistors.

6. 3. The gate driver circuit according to claim 1, wherein the first resistor and the second resistor are formed on a well connected to the bootstrap line.

7. A motor driving device comprising the gate driver circuit according to claim 1 or 2.

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