Driving circuit and power level circuit

Abstract

The utility model provides a drive circuit and a power level circuit, the drive circuit comprises a half-bridge circuit comprising an upper pull tube and a lower pull tube which are connected in series, and the lower pull tube is connected with a grid electrode and a source electrode of a high side power tube / a low side power tube; the detection circuit is used for detecting the voltage change rate at the joint of the high-side power tube and the low-side power tube; and the clamping circuit is used for controlling the grid electrode of the pull-down tube to be connected with the connection node of the pull-up tube and the pull-down tube when the voltage change rate is greater than a preset threshold value. According to the driving circuit provided by the utility model, when the voltage change rate of a connection node is greater than a preset threshold value, the pull-down tube is driven to be equivalent to a diode, so that the potential of the gate source parasitic capacitor of the high / low side power tube is clamped at the conduction voltage drop of the equivalent diode; therefore, the current of the gate-drain stray capacitor of the high / low side power tube flows through the pull-down tube and does not charge the gate-source capacitor of the high / low side power tube, thereby avoiding the direct connection between the high side power tube and the low side power tube.

Description

Technical Field

[0001] The utility model belongs to the technical field of power electronics, and in particular relates to a drive circuit and a power level circuit. Background Art

[0002] With the rapid development of power electronics technology, MOSFET is increasingly widely used, so the driving design of MOSFET has also received attention. Figure 1 and Figure 2 As shown in FIG. 1 , a half-bridge circuit is used to drive a high-side power tube or a low-side power tube in a power stage circuit. Figure 1 As shown in the figure, when the pull-down tube DRVN is turned on to drive the low-side power tube QL to turn off, the high-side power tube QH is turned on, which will cause a large dv / dt to be generated at the node SW. At this time, if the driving power supply is powered off or the logic is disturbed, the gate voltage of the pull-down tube DRVN cannot be reliably pulled up, which will cause the pull-down tube DRVN to be unable to discharge the gate-drain parasitic capacitance C of the low-side power tube. GD The current flowing to the gate of the low-side power tube makes the gate-source parasitic capacitance C of the low-side power tube GS It will be charged, which will cause the low-side power tube QL to be mis-conducted, and the high-side power tube QH and low-side power tube QL to be directly turned on. Figure 2 As shown, when the pull-down tube DRVN is turned on to drive the high-side power tube QH to turn off, the low-side power tube QL is turned on, which will also cause a large dv / dt to be generated at the node SW, and the high-side power tube QH and the low-side power tube QL will be directly connected.

[0003] Therefore, the existing MOSFET driving circuit needs to be improved to avoid the gate-source parasitic capacitance C when a large dv / dt is generated at the node SW. GS Charging, high-side power tube and low-side power tube are directly connected. Utility Model Content

[0004] In order to solve the technical problem that the driving circuit in the prior art cannot solve the direct connection between the high-side power tube and the low-side power tube in the power stage circuit, the utility model proposes a driving circuit and a power stage circuit, the driving circuit comprising:

[0005] A half-bridge circuit, comprising a pull-up tube and a pull-down tube connected in series, wherein the pull-up tube is connected to a high potential end, the pull-down tube is connected to a gate and a source of the high-side power tube, or the pull-down tube is connected to a gate and a source of the low-side power tube;

[0006] A detection circuit, detecting a voltage change rate of a first node, where the first node is a connection point between the high-side power tube and the low-side power tube;

[0007] A clamping circuit, when the voltage change rate is greater than a preset threshold, the clamping circuit controls the gate of the pull-down tube to connect the connection node of the pull-up tube and the pull-down tube.

[0008] Preferably, the clamping circuit comprises a first switch, and the first switch is connected between the gate of the pull-down tube and the connection node.

[0009] Preferably, the clamping circuit further includes a first resistor, and the first resistor is connected in series with the first switch.

[0010] Furthermore, it also includes a control circuit, which controls the on and off of the first switch. The control circuit controls the first switch to be turned on when the voltage change rate is greater than the preset threshold, and controls the first switch to be turned off when the voltage change rate is less than the preset threshold.

[0011] Preferably, when the pull-down tube is connected to the high-side power tube, the detection circuit includes a first capacitor, the control circuit includes a comparator, a first control tube, a second control tube and a third control tube, the negative electrode of the first capacitor is connected to the first node, the positive electrode is connected to the positive input end of the comparator, the output end of the comparator is connected to the gate of the third control tube, the drain of the third control tube is connected to the gates of the first control tube and the second control tube, and the gates of the first control tube and the second control tube are connected to a power supply, the source of the first control tube is connected to the source of the first switch, the drain is connected to the gate of the first switch, the drain of the second control tube is connected to the drain of the first control tube, the source is connected to the first node, the source of the first switch is sequentially connected to the first resistor and the connection node, and the drain is connected to the gate of the pull-down tube.

[0012] Preferably, when the pull-down tube is connected to the low-side power tube, the detection circuit includes a first capacitor, and the control circuit includes a first control tube and a second control tube. The positive electrode of the first capacitor is connected to the first node, and the negative electrode is connected to the gates of the first control tube and the second control tube. The source of the first control tube is connected to the source of the first switch, and the drain is connected to the gate of the first switch. The drain of the second control tube is connected to the drain of the first control tube, and the source is grounded. The source of the first switch is connected to the first resistor and the connection node in sequence, and the drain is connected to the gate of the pull-down tube.

[0013] Furthermore, when the voltage change rate is greater than the preset threshold, the second control tube and the first switch are turned on; when the voltage change rate is less than the preset threshold, the first control tube and the third control tube are turned on, and the first switch is turned off.

[0014] Furthermore, when the voltage change rate is greater than the preset threshold, the second control tube and the first switch are turned on; when the voltage change rate is less than the preset threshold, the first control tube is turned on and the first switch is turned off.

[0015] Furthermore, the pull-up tube is a PMOS, the pull-down tube is an NMOS, the source of the pull-up tube is connected to the high potential end, the drain of the pull-up tube is connected to the drain of the pull-down tube, the drain of the pull-down tube is connected to the gate of the high-side power tube, and the source is connected to the first node, or the drain of the pull-down tube is connected to the gate of the low-side power tube, and the source is grounded.

[0016] A power stage circuit includes a high-side power tube and a low-side power tube, and includes the driving circuit described above.

[0017] In the driving circuit proposed by the utility model, when the high-side power tube / low-side power tube in the power stage circuit is turned on, causing the voltage change rate of the first node to be greater than a preset threshold value, the clamping circuit will make the pull-down tube equivalent to a diode, so the potential of the gate-source parasitic capacitance of the high-side power tube / low-side power tube will be clamped at the conduction voltage drop of the equivalent diode, and the current of the gate-drain parasitic capacitance of the high-side power tube / low-side power tube will all flow into the pull-down tube, so no current will flow through the gate-source parasitic capacitance of the high-side power tube / low-side power tube, thereby avoiding the situation where the high-side power tube and the low-side power tube are directly connected. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A driving circuit for a low-side power tube in the prior art;

[0019] Figure 2 A driving circuit for a high-side power tube in the prior art;

[0020] Figure 3 This is a structural block diagram of the driving circuit of the low-side power tube proposed by the utility model;

[0021] Figure 4 The specific circuit of the driving circuit of the low-side power tube proposed by the utility model;

[0022] Figure 5 This is a structural block diagram of the driving circuit of the high-side power tube proposed by the utility model;

[0023] Figure 6 This is a specific circuit of the driving circuit of the high-side power tube proposed by the utility model. DETAILED DESCRIPTION

[0024] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively with reference to the relevant drawings. The drawings provide preferred embodiments of the present invention. However, the present invention can be implemented in different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0025] The driving circuit in the prior art cannot solve the problem of direct connection between the high-side power tube and the low-side power tube when driving the high-side power tube / low-side power tube in the power stage circuit. Based on this problem, the utility model proposes a driving circuit, including:

[0026] A half-bridge circuit, wherein the half-bridge circuit includes a pull-up tube and a pull-down tube connected in series, wherein the pull-up tube is connected to a high potential end, and the pull-down tube is connected to a low potential end, wherein the pull-down tube is connected between the gate and the source of the high-side power tube in the power stage circuit to drive the high-side power tube to turn on and off, or the pull-down tube is connected between the gate and the source of the low-side power tube in the power stage circuit to drive the low-side power tube to turn on and off;

[0027] A detection circuit detects a voltage change rate at a connection node between the high-side power tube and the low-side power tube, and the connection node between the high-side power tube and the low-side power tube is recorded as a first node;

[0028] The clamping circuit controls the gate of the pull-down tube to connect the connection node of the pull-up tube and the pull-down tube when the voltage change rate is greater than a preset threshold value, so that the pull-down tube is equivalent to a diode, so as to control the potential of the gate-source parasitic capacitance of the high-side power tube / low-side power tube to be clamped at the conduction voltage drop of the equivalent diode.

[0029] It can be seen from this that when the high-side power tube / low-side power tube in the power stage circuit is turned on, causing the voltage change rate of the first node to be greater than the preset threshold value, the clamping circuit will make the pull-down tube equivalent to a diode, so the potential of the gate-source parasitic capacitance of the high-side power tube / low-side power tube will be clamped at the conduction voltage drop of the equivalent diode, and the current of the gate-drain parasitic capacitance of the high-side power tube / low-side power tube will all flow into the pull-down tube, so no current will flow through the gate-source parasitic capacitance of the high-side power tube / low-side power tube, thereby avoiding the situation where the high-side power tube and the low-side power tube are directly connected.

[0030] Furthermore, the simplest design of the clamping circuit is that the clamping circuit only includes a first switch, and the first switch is connected between the gate of the pull-down tube, the connection node of the pull-up tube and the pull-down tube. When the voltage change rate is greater than a preset threshold, the first switch is turned on to connect the gate of the pull-down tube, the connection node of the pull-up tube and the pull-down tube. When the voltage change rate is less than the preset threshold, the first switch is turned off to avoid energy consumption by the internal resistance of the wire and the internal resistance of the first switch.

[0031] Furthermore, in order to adjust the conduction voltage drop when the pull-down tube is equivalent to a diode, the clamping circuit also includes a first resistor, which is connected in series with the first switch. The series-connected first resistor and the first switch are connected between the gate of the pull-down tube, the connection node of the pull-up tube and the pull-down tube. When the voltage change rate is greater than a preset threshold, the first switch is turned on to connect the gate of the pull-down tube, the connection node of the pull-up tube and the pull-down tube. When the voltage change rate is less than the preset threshold, the first switch is turned off to avoid the first resistor consuming energy.

[0032] Correspondingly, the driving circuit also includes a control circuit, and the detection circuit controls the first switch to be turned on when the voltage change rate is greater than a preset threshold value, so as to control the gate of the pull-down tube to connect the connection node of the pull-up tube and the pull-down tube, so that the pull-down tube is equivalent to a diode to reduce the potential of the gate-source parasitic capacitance of the high-side power tube / low-side power tube to the conduction voltage drop of the equivalent diode. The detection circuit controls the first switch to be turned off when the voltage change rate is less than the preset threshold value to avoid additional energy consumption.

[0033] The driving circuit proposed by the utility model will be further explained and illustrated in conjunction with specific embodiments below.

[0034] In the first embodiment, if Figure 3 and Figure 4 As shown, the driving circuit is used to drive the low-side power tube QL in the power stage circuit. Figure 4As shown, the half-bridge circuit in the driving circuit includes a pull-up tube DRVP and a pull-down tube DRVN, the pull-up tube DRVP and the pull-down tube DRVN are connected in series, the pull-up tube DRVP is a PMOS tube, and the pull-down tube DRVN is an NMOS tube, the source of the pull-up tube DRVP is connected to the power supply VDD, and the drain is connected to the drain of the pull-down tube DRVN, the source of the pull-down tube DRVN is connected to the source of the low-side power tube QL, and the drain (the connection node LO of the pull-up tube DRVP and the pull-down tube DRVN) is connected to the gate of the low-side power tube QL, and the gates of the pull-up tube DRVP and the pull-down tube DRVN receive a PWM driving signal. The PWM driving signal in the effective state controls the pull-up tube DRVP to be turned on and the pull-down tube DRVN to be turned off, so as to drive the low-side power tube QL to be in the on state; the PWM driving signal in the invalid state controls the pull-up tube DRVP to be turned off and the pull-down tube DRVN to be turned on, so as to drive the low-side power tube QL to be in the off state. The detection circuit in the driving circuit includes a first capacitor C1, the clamping circuit in the driving circuit includes a first switch M1 and a first resistor R1, and the control circuit in the driving circuit includes a first control tube MOS1 and a second control tube MOS2. The positive electrode of the first capacitor C1 is connected to the first node SW, the negative electrode of the first capacitor C1 is connected to the gates of the first control tube MOS1 and the second control tube MOS2, the source of the second control tube MOS2 is connected to the source of the first switch M1, the drain of the first control tube MOS1 is connected to the gate of the first switch M1, the source of the first switch is connected to the first resistor and the gate of the low-side power tube QL in sequence, the drain of the second control tube is connected to the drain of the first control tube MOS1, and the source of the second control tube is grounded.

[0035] The specific working principle is as follows: when the PWM driving signal in the invalid state drives the pull-down tube DRVN to turn on to drive the low-side power tube QL to turn off, if the high-side power tube QH is controlled to turn on, the first capacitor will detect that the voltage of the node SW rises rapidly. When the first capacitor C1 detects that the voltage change rate of the first node SW exceeds the preset threshold, the first capacitor C1 will pull up the gate voltage of the second control tube to turn on the second control tube, thereby lowering the gate voltage of the first switch M1 to turn on the first switch M1. Therefore, the gate and drain of the pull-down tube DRVN are connected and equivalent to a diode, so that the potential of the gate-source parasitic capacitance of the low-side power tube QL is clamped at the conduction voltage drop of the equivalent diode. When the first capacitor C1 detects that the voltage change rate of the first node SW does not exceed the preset threshold, the first capacitor C1 pulls down the gate voltage of the first control tube MOS1 to turn on the first control tube, thereby connecting the gate and source of the first switch M1 to turn off the first switch M1, avoiding the first resistor R1 and the conduction internal resistance of the first switch M1 to consume energy.

[0036] In summary, when the high-side power tube in the power stage circuit is turned on and causes the voltage change rate of the first node to be greater than the preset threshold value, the pull-down tube is equivalent to a diode, so the potential of the gate-source parasitic capacitance of the low-side power tube will be clamped at the conduction voltage drop of the equivalent diode, and the current of the gate-drain parasitic capacitance of the low-side power tube will all flow into the pull-down tube, and no current will flow through the gate-source parasitic capacitance of the low-side power tube, thereby avoiding the situation where the high-side power tube and the low-side power tube are directly connected.

[0037] In the second embodiment, if Figure 5 and Figure 6 As shown, the driving circuit is used to drive the high-side power tube QH in the power stage circuit. The driving circuit includes: a half-bridge circuit, a detection circuit, a clamping circuit and a control circuit. Figure 6As shown, the half-bridge circuit includes a pull-up tube DRVP and a pull-down tube DRVN, the pull-up tube DRVP and the pull-down tube DRVN are connected in series, the pull-up tube DRVP is a PMOS tube, and the pull-down tube DRVN is an NMOS tube, the source of the pull-up tube DRVP is connected to the power supply VDD, and the drain is connected to the drain of the lower power N tube DRVP, the source of the pull-down tube DRVN is connected to the source of the high-side power tube QH, and the drain (the connection node HO of the pull-up tube DRVP and the pull-down tube DRVN) is connected to the gate of the high-side power tube QH, and the gates of the pull-up tube DRVP and the pull-down tube DRVN receive a PWM drive signal. The PWM drive signal in the effective state controls the pull-up tube DRVP to be turned on and the pull-down tube DRVN to be turned off, so as to drive the high-side power tube QH to be in the on state; the PWM drive signal in the invalid state controls the pull-up tube DRVP to be turned off and the pull-down tube DRVN to be turned on, so as to drive the high-side power tube QH to be in the off state. The detection circuit includes a first capacitor C1, the clamping circuit includes a first switch M1 and a first resistor R1, the detection circuit includes a first capacitor C1, and the control circuit includes a comparator COMP, a first control tube MOS1, a second control tube MOS2 and a third control tube MOS3. The negative electrode of the first capacitor C1 is connected to the first node SW, the positive electrode of the first capacitor C1 is connected to the positive input terminal of the comparator COMP, the negative input terminal of the comparator CMOP receives the reference voltage VREF, the output terminal of the comparator COMP is connected to the gate of the third control tube MOS3, the drain of the third control tube MOS3 is connected to the gates of the first control tube MOS1 and the second control tube MOS2, the source of the third control tube MOS3 is grounded, the source of the first control tube MOS1 is connected to the source of the first switch M1, the drain of the first control tube MOS1 is connected to the gate of the first switch M1, the gate of the first control tube MOS1 is connected to the power supply, the drain of the second control tube MOS2 is connected to the drain of the first control tube MOS1, the source of the second control tube MOS2 is connected to the first node SW, the gate of the second control tube MOS2 is connected to the power supply, the source of the first switch M1 is connected to the first resistor R1 and the gate of the high-side power tube QH in sequence, and the drain of the first switch M1 is connected to the gate of the pull-down tube DRVN.

[0038] The specific working principle is as follows: when the PWM driving signal in the invalid state drives the pull-down tube DRVN to turn on to drive the high-side power tube QH to turn off, if the low-side power tube QL is controlled to turn on, the first capacitor will detect that the voltage of the first node SW drops rapidly. When the voltage change rate of the first node SW is greater than the preset threshold, the voltage at the positive input terminal of the comparator COMP is less than the voltage at the reverse input terminal. The output of the comparator COMP pulls down the gate voltage of the third control tube MOS3 to turn off the third control tube MOS3, pulls up the gate voltages of the first control tube MOS1 and the second control tube MOS2 to turn off the first control tube MOS1 and turn on the second control tube MOS2, thereby pulling down the gate voltage of the first switch M1 to turn on the first switch M1. Therefore, the gate and drain of the pull-down tube DRVN are connected and are equivalent to a diode, and the potential of the gate-source parasitic capacitance of the high-side power tube QH is clamped to the conduction voltage drop of the equivalent diode. When the voltage change rate of the first node SW is less than the preset threshold, the voltage at the positive input terminal of the comparator COMP is greater than the voltage at the reverse input terminal, and the output of the comparator COMP pulls up the gate voltage of the third control tube MOS3 to turn on the third control tube MOS3, and pulls down the gate voltages of the first control tube MOS1 and the second control tube MOS2 to turn on the first control tube MOS1 and turn off the second control tube MOS2, so that the gate of the first switch M1 is connected to the source, that is, the first switch M1 is turned off.

[0039] In summary, when the low-side power tube in the power stage circuit is turned on and causes the voltage change rate of the first node to be greater than the preset threshold value, the pull-down tube is equivalent to a diode, so the potential of the gate-source parasitic capacitance of the high-side power tube will be clamped at the conduction voltage drop of the equivalent diode, so the current of the gate-drain parasitic capacitance of the high-side power tube will all flow into the pull-down tube, and no current will flow through the gate-source parasitic capacitance of the high-side power tube, thereby avoiding the direct connection between the high-side power tube and the low-side power tube.

[0040] The utility model also proposes a power stage circuit, which includes a high-side power tube and a low-side power tube, and also includes the driving circuit proposed above, which is used to drive the high-side power tube / low-side power tube to be turned on and off to avoid the situation where the high-side power tube and the low-side power tube are directly turned on.

[0041] Finally, it should be noted that: Obviously, the above embodiments are only examples for clearly explaining the present invention, and are not intended to limit the implementation methods. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from this are still within the scope of protection of the present invention.

Claims

1. A driving circuit for driving the on and off of a high-side power tube or a low-side power tube in a power stage circuit, characterized in that: include: A half-bridge circuit, comprising a pull-up tube and a pull-down tube connected in series, wherein the pull-up tube is connected to a high potential end, the pull-down tube is connected to a gate and a source of the high-side power tube, or the pull-down tube is connected to a gate and a source of the low-side power tube; A detection circuit, detecting a voltage change rate of a first node, where the first node is a connection point between the high-side power tube and the low-side power tube; A clamping circuit, when the voltage change rate is greater than a preset threshold, the clamping circuit controls the gate of the pull-down tube to connect the connection node of the pull-up tube and the pull-down tube.

2. The driving circuit according to claim 1, characterized in that: The clamping circuit includes a first switch connected between the gate of the pull-down tube and the connection node.

3. The driving circuit according to claim 2, characterized in that: The clamping circuit further includes a first resistor connected in series with the first switch.

4. The driving circuit according to claim 2 or 3, characterized in that: It also includes a control circuit, which controls the on and off of the first switch. The control circuit controls the first switch to be turned on when the voltage change rate is greater than the preset threshold, and controls the first switch to be turned off when the voltage change rate is less than the preset threshold.

5. The driving circuit according to claim 4, characterized in that: When the pull-down tube is connected to the high-side power tube, the detection circuit includes a first capacitor, the control circuit includes a comparator, a first control tube, a second control tube and a third control tube, the negative electrode of the first capacitor is connected to the first node, the positive electrode is connected to the positive input end of the comparator, the output end of the comparator is connected to the gate of the third control tube, the drain of the third control tube is connected to the gates of the first control tube and the second control tube, and the gates of the first control tube and the second control tube are connected to a power supply, the source of the first control tube is connected to the source of the first switch, the drain is connected to the gate of the first switch, the drain of the second control tube is connected to the drain of the first control tube, the source is connected to the first node, the source of the first switch is sequentially connected to the first resistor and the connection node, and the drain is connected to the gate of the pull-down tube.

6. The driving circuit according to claim 4, characterized in that: When the pull-down tube is connected to the low-side power tube, the detection circuit includes a first capacitor, and the control circuit includes a first control tube and a second control tube. The positive electrode of the first capacitor is connected to the first node, and the negative electrode is connected to the gates of the first control tube and the second control tube. The source of the first control tube is connected to the source of the first switch, and the drain is connected to the gate of the first switch. The drain of the second control tube is connected to the drain of the first control tube, and the source is grounded. The source of the first switch is sequentially connected to the first resistor and the connection node, and the drain is connected to the gate of the pull-down tube.

7. The driving circuit according to claim 5, characterized in that: When the voltage change rate is greater than the preset threshold, the second control tube and the first switch are turned on; when the voltage change rate is less than the preset threshold, the first control tube and the third control tube are turned on, and the first switch is turned off.

8. The driving circuit according to claim 6, characterized in that: When the voltage change rate is greater than the preset threshold, the second control tube and the first switch are turned on; when the voltage change rate is less than the preset threshold, the first control tube is turned on and the first switch is turned off.

9. The driving circuit according to claim 1, characterized in that: The pull-up tube is a PMOS, the pull-down tube is an NMOS, the source of the pull-up tube is connected to the high potential end, the drain of the pull-up tube is connected to the drain of the pull-down tube, the drain of the pull-down tube is connected to the gate of the high-side power tube, and the source is connected to the first node, or the drain of the pull-down tube is connected to the gate of the low-side power tube, and the source is grounded.

10. A power stage circuit, comprising a high-side power tube and a low-side power tube, characterized in that: A driving circuit comprising any one of claims 1 to 9.

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