Drive circuit and switching power supply circuit

Abstract

The application provides a driving circuit and a switching power supply circuit. The circuit comprises an initial driving device, a first circuit on-off device and a capacitive driving device. When a control signal controls the conduction of a high-side power transistor, the initial driving device drives the high-side power transistor, so that the gate-source voltage of the high-side power transistor increases from 0 V to a voltage threshold, and part of the charging charge of the gate parasitic capacitance of the high-side power transistor comes from the initial driving device, avoiding the high-side power transistor directly taking electricity from the capacitive driving device. When the gate-source voltage of the high-side power transistor is the voltage threshold, the initial driving device stops driving the high-side power transistor. When the initial driving device stops driving the high-side power transistor, the first circuit on-off device connects the capacitive driving device and the high-side power transistor, so that the capacitive driving device charges the high-side power transistor. Thus, the charge of the integrated bootstrap capacitor is saved, the conduction loss of the high-side power transistor is reduced, and the working efficiency of the DC-DC converter is improved.

Description

Technical Field

[0001] This application relates to the field of integrated circuit technology, and in particular to a driving circuit and a switching power supply circuit. Background Technology

[0002] In direct-to-direct-current (DC-DC) converters, to reduce costs, the bootstrap capacitor is integrated inside the DC-DC converter. This bootstrap capacitor is called an integrated bootstrap capacitor. Generally, the capacitance value of an integrated bootstrap capacitor cannot be made too large, so the capacitance value is relatively small.

[0003] In traditional technology, the turn-on voltage in a DC-DC converter is obtained from an integrated bootstrap capacitor. After the upper transistor turns on, this results in a low voltage drop across the small-value integrated bootstrap capacitor, leading to a higher on-resistance of the upper transistor. This, in turn, increases the conduction loss of the upper transistor and reduces the operating efficiency of the DC-DC converter. Summary of the Invention

[0004] This application provides a drive circuit and a switching power supply circuit that can reduce the conduction loss of the upper transistor and improve the working efficiency of the DC-DC converter.

[0005] In a first aspect, this application provides a driving circuit applied in a switching power supply circuit, the switching power supply circuit including: a high-side power transistor and a low-side power transistor, the driving circuit including: an initial start driver, a first circuit switch and a capacitive driver.

[0006] The input terminals of the initial start driver and the capacitive driver are both used to receive control signals sent by the control circuit. The control signals are used to control the high-side power transistor to turn on or off. The output terminal of the capacitive driver is electrically connected to the first terminal of the first circuit switch. The second terminal of the first circuit switch is electrically connected to the control terminal of the high-side power transistor. The power supply terminal of the capacitive driver and the control terminal of the first circuit switch are both electrically connected to the first terminal of the high-side power transistor. The output terminal of the initial start driver is electrically connected between the second terminal of the first circuit switch and the control terminal of the high-side power transistor.

[0007] The initial start driver is used to drive the gate-source voltage of the high-side power transistor to increase from 0V when the control signal turns on the high-side power transistor, until the gate-source voltage of the high-side power transistor increases to the voltage threshold.

[0008] The first circuit switch is used to connect the capacitive driver and the high-side power transistor when the gate-source voltage of the high-side power transistor is a voltage threshold.

[0009] A capacitive driver is used to charge the high-side power transistor using a bootstrap capacitor in the capacitive driver after the capacitive driver and the high-side power transistor are connected.

[0010] The driving circuit provided in the first aspect is applied in a switching power supply circuit, which includes a high-side power transistor and a low-side power transistor. The driving circuit includes a start-up driver, a first circuit switch, and a capacitive driver. When the high-side power transistor is turned on by a control signal, the start-up driver can determine that the high-side power transistor has entered the turn-on process. Thus, the start-up driver can drive the high-side power transistor, causing its gate-source voltage to increase from 0V to a voltage threshold. As the gate-source voltage of the high-side power transistor continues to increase, when the gate-source voltage reaches the voltage threshold, the start-up driver stops driving the high-side power transistor. In this way, part of the charging charge of the gate parasitic capacitance of the high-side power transistor comes from the start-up driver, preventing the high-side power transistor from directly drawing power from the capacitive driver. When the start-up driver stops driving the high-side power transistor, the high-side power transistor is not turned on. At this time, the first circuit switch can connect the capacitive driver and the high-side power transistor, allowing the capacitive driver to charge the high-side power transistor. Thus, after the capacitive driver and the high-side power transistor are connected, the capacitive driver can charge the high-side power transistor using its bootstrap capacitor. This conserves the charge of the small-value integrated bootstrap capacitor, reduces the on-resistance of the high-side power transistor, and decreases its conduction losses. Consequently, the operating efficiency of the DC-DC converter is improved.

[0011] In one possible design, the start-up driver includes: a first power supply and a first transistor;

[0012] The first power supply is electrically connected to the first terminal of the first transistor, the control terminal of the first transistor is used to receive control signals, and the second terminal of the first transistor is electrically connected between the second terminal of the first circuit switch and the control terminal of the high-side power transistor.

[0013] In one possible design, the start-up driver also includes: a diode-connected transistor;

[0014] The first terminal of the diode-connected transistor is electrically connected to the second terminal of the first transistor. The control terminal of the diode-connected transistor is used to receive control signals. The second terminal of the diode-connected transistor is electrically connected between the second terminal of the first circuit switch and the control terminal of the high-side power transistor.

[0015] In one possible design, the capacitive driver includes: a second transistor, a third transistor, a first auxiliary capacitor, a first bootstrap capacitor, a first inverter, and a second inverter.

[0016] The first terminals of the second transistor and the third transistor are both electrically connected to the first terminal of the high-side power transistor. The second terminal of the second transistor is electrically connected to the upper plate of the first auxiliary capacitor. The control terminal of the third transistor is electrically connected between the second terminal of the second transistor and the upper plate of the first auxiliary capacitor. The second terminal of the third transistor is electrically connected to the upper plate of the first bootstrap capacitor. The lower plate of the first bootstrap capacitor is electrically connected to the first terminal of the second inverter. The control terminal of the second transistor is electrically connected between the second terminal of the third transistor and the upper plate of the first bootstrap capacitor. The second terminal of the second inverter is electrically connected to the first terminal of the first inverter. The lower plate of the first auxiliary capacitor is electrically connected between the second terminal of the second inverter and the first inverter.

[0017] A first circuit switch is used to connect the capacitive driver and the high-side power transistor when the upper and lower plates of the first bootstrap capacitor are simultaneously raised and the voltage on the upper plate of the first bootstrap capacitor is greater than the voltage on the control terminal of the first circuit switch.

[0018] In one possible design, the drive circuit also includes: a second circuit switch;

[0019] The input terminal of the second circuit switch is used to receive the control signal. The first terminal of the second circuit switch and the second terminal of the second circuit switch are both electrically connected between the second terminal of the first circuit switch and the control terminal of the high-side power transistor. The third terminal of the second circuit switch is electrically connected to the switching node, which is located between the second terminal of the high-side power transistor and the first terminal of the low-side power transistor.

[0020] The second circuit switch is used to connect the control terminal of the high-side power transistor to ground when the control signal controls the high-side power transistor to be turned off.

[0021] In one possible design, the second circuit switch includes: a third inverter, a fourth transistor, and a fifth transistor;

[0022] The input terminal of the third inverter is used to receive the control signal. The output terminal of the third inverter is electrically connected to the control terminal of the fourth transistor. The control terminal of the fifth transistor is electrically connected between the output terminal of the third inverter and the control terminal of the fourth transistor. The first terminal of the fourth transistor and the first terminal of the fifth transistor are both electrically connected between the second terminal of the first circuit switch and the control terminal of the high-side power transistor. The second terminal of the fourth transistor is electrically connected to the switching node, and the second terminal of the fifth transistor is grounded.

[0023] In one possible design, the initial start driver includes: a second power supply and a sixth transistor;

[0024] The second power supply is electrically connected to the control terminal of the sixth transistor. The first terminal of the sixth transistor is used to receive the control signal, and the second terminal of the sixth transistor is electrically connected between the third terminal of the first circuit switch and the control terminal of the high-side power transistor.

[0025] In one possible design, the capacitive driver includes: a first bootstrap unit and a fourth inverter;

[0026] The first terminal of the first bootstrap unit is electrically connected to the first terminal of the high-side power transistor, the second terminal of the first bootstrap unit is electrically connected to the first terminal of the first circuit switch, the third terminal of the first bootstrap unit is electrically connected to the output terminal of the fourth inverter, and the input terminal of the fourth inverter is used to receive control signals.

[0027] In one possible design, the drive circuit also includes: a fifth inverter;

[0028] The input terminal of the fifth inverter is used to receive the control signal, which is also used to control the turn-on or turn-off of the low-side power transistor. The output terminal of the fifth inverter is electrically connected to the control terminal of the low-side power transistor.

[0029] In a second aspect, this application provides a switching power supply circuit, which includes: a high-side power transistor, a low-side power transistor, a control circuit, and a driving circuit in the first aspect and any possible design of the first aspect.

[0030] The first terminal of the high-side power transistor is used to connect to the power supply voltage, and the second terminal of the low-side power transistor is grounded. The driving circuit is electrically connected to the control terminal of the high-side power transistor, the control terminal of the low-side power transistor, and the control circuit, respectively.

[0031] The beneficial effects provided in the second aspect and its various possible designs can be found in the first aspect and its various possible implementations, and will not be repeated here. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of a switching power supply circuit provided in one embodiment of the present application;

[0033] Figure 2 This is a schematic diagram of a driving circuit provided in one embodiment of this application;

[0034] Figure 3 This is a schematic diagram of a driving circuit provided in one embodiment of this application;

[0035] Figure 4 This is a schematic diagram of a driving circuit provided in an embodiment of this application. Detailed Implementation

[0036] In this application, "at least one" means one or more, and "more than one" means two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can mean: A alone, A and B simultaneously, or B alone, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one of a, b, or c alone can mean: a alone, b alone, c alone, a combination of a and b, a combination of a and c, a combination of b and c, or a, b, and c, where a, b, and c can be single or multiple. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0037] The terms “center,” “longitudinal,” “lateral,” “up,” “down,” “left,” “right,” “front,” and “rear,” etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0038] The terms "connected" and "connected" should be interpreted broadly. For example, in circuit structures, "connected" or "connected" can refer not only to physical connections but also to electrical or signal connections. This could be a direct connection (physical connection) or an indirect connection via at least one intermediate component, as long as the circuit is connected. It could also refer to the internal connection between two components. Similarly, a signal connection can refer to a connection via a circuit or a medium, such as radio waves. Those skilled in the art will understand the specific meaning of these terms in this application based on the specific circumstances.

[0039] In traditional technology, after the upper transistor is turned on, the integrated bootstrap capacitor shares charge with the gate parasitic capacitance of the upper transistor, resulting in a lower voltage drop across the small-value integrated bootstrap capacitor. In other words, the gate-source voltage of the upper transistor is lower. This increases the on-resistance of the upper transistor and its conduction losses. This is especially problematic in applications where integrated bootstrap capacitors are most suitable, namely low-voltage applications with large duty cycles. Consequently, this reduces the operating efficiency of the DC-DC converter.

[0040] To solve the above-mentioned technical problems, this application provides a switching power supply circuit, referring to... Figure 1 , Figure 1 This is a schematic diagram of a switching power supply circuit provided in one embodiment of this application. Figure 1 As shown, the switching power supply circuit includes: a high-side power transistor HS, a low-side power transistor LS, a control circuit 200, and a drive circuit 100.

[0041] The first terminal of the high-side power transistor HS is used to connect to the power supply voltage Vin, and the second terminal of the low-side power transistor LS is grounded. The driving circuit 100 is electrically connected to the control terminal of the high-side power transistor HS, the control terminal of the low-side power transistor LS, and the control circuit 200, respectively.

[0042] The high-side power transistor HS is the upper transistor, and the low-side power transistor LS is the lower transistor.

[0043] The control circuit 200 can send the control signal HON_IN to the drive circuit 100.

[0044] The control signal HON_IN is used to control the high-side power transistor HS to turn on or off.

[0045] The control signal HON_IN is also used to control the turn-on or turn-off of the low-side power transistor LS.

[0046] The drive circuit 100 can turn on the high-side power transistor HS by first driving the high-side power transistor HS with the initial start driver 110, and then continuing to charge the high-side power transistor HS with the capacitive driver 130 when the initial start driver 110 stops driving the high-side power transistor HS.

[0047] This saves charge on small-value integrated bootstrap capacitors and increases their voltage drop. In other words, it increases the gate-source voltage of the high-side power transistor HS.

[0048] Furthermore, this reduces the on-resistance of the high-side power transistor HS, thereby reducing its conduction loss.

[0049] This improves the operating efficiency of the DC-DC converter.

[0050] The implementation of the drive circuit 100 will be described in detail below.

[0051] Reference Figure 2 , Figure 2 This is a schematic diagram of a driving circuit provided in one embodiment of this application. Figure 2 As shown, the drive circuit 100 may include: a start driver 110, a first circuit switch 120, and a capacitive driver 130.

[0052] The input terminals of the initial start driver 110 and the capacitive driver 130 are both used to connect to the control signal HON_IN sent by the control circuit 200. The control signal HON_IN is used to control the high-side power transistor HS to turn on or off. The output terminal of the capacitive driver 130 is electrically connected to the first terminal of the first circuit switch 120. The second terminal of the first circuit switch 120 is electrically connected to the control terminal of the high-side power transistor HS. The power supply terminal of the capacitive driver 130 and the third terminal of the first circuit switch 120 are both electrically connected to the first terminal of the high-side power transistor HS. The output terminal of the initial start driver 110 is electrically connected between the second terminal of the first circuit switch 120 and the control terminal of the high-side power transistor HS.

[0053] Figure 2 In the diagram, the input terminal of the initial start driver 110 is denoted as 1, the output terminal of the initial start driver 110 is denoted as 2, the input terminal of the capacitive driver 130 is denoted as 1, the output terminal of the capacitive driver 130 is denoted as 2, the power supply terminal of the capacitive driver 130 is denoted as 3, the first terminal of the first circuit switch 120 is denoted as 1, the second terminal of the first circuit switch 120 is denoted as 2, and the third terminal of the first circuit switch 120 is denoted as 3.

[0054] The initial start driver 110, the first circuit switch 120, and the capacitive driver 130 can be configured separately or integrated.

[0055] For ease of understanding, the first circuit switch 120 in the following embodiment is described using a P-channel metal-oxide-semiconductor (PMOS) transistor as an example.

[0056] Specifically, when the control signal HON_IN controls the high-side power transistor HS to turn on, for example, when the control signal HON_IN is at a high level, the high-side power transistor HS is in the process of switching from off to on. When the control signal HON_IN controls the high-side power transistor HS to turn off, for example, when the control signal HON_IN is at a low level, the high-side power transistor HS is in the process of switching from on to off.

[0057] The start-up driver 110 can drive the high-side power transistor HS when the control signal HON_IN turns it on. This allows the gate-source voltage Vgs of the high-side power transistor HS to increase from 0V. When the gate-source voltage Vgs of the high-side power transistor HS increases to a voltage threshold, the start-up driver 110 can stop driving the high-side power transistor HS.

[0058] The voltage threshold can be the maximum supply voltage of the initial start driver 110.

[0059] In the initial stage of turning on the high-side power transistor HS, the voltage at the second terminal of the high-side power transistor HS and the voltage at the control terminal of the high-side power transistor HS are relatively low. Therefore, the control terminal of the high-side power transistor HS can directly draw power from the start-up driver 110. In other words, the start-up driver 110 can drive the high-side power transistor HS.

[0060] When the voltage at the control terminal of the high-side power transistor HS exceeds the voltage threshold, the start-up driver 110 can stop driving the high-side power transistor HS.

[0061] When the initial start-up driver 110 stops driving the high-side power transistor HS, the first circuit switch 120 can be turned on, connecting the capacitive driver 130 and the high-side power transistor HS. Therefore, after the capacitive driver 130 and the high-side power transistor HS are connected, the bootstrap capacitor in the capacitive driver 130 can charge the high-side power transistor HS. In this way, the gate-source voltage Vgs of the high-side power transistor HS can increase from the voltage threshold.

[0062] When the gate-source voltage Vgs of the high-side power transistor HS is greater than the turn-on threshold voltage of the high-side power transistor HS, the high-side power transistor HS turns on. Thus, the voltage at the second terminal of the high-side power transistor HS, that is, the voltage at the switching node SW, gradually increases.

[0063] Thus, part of the charge on the gate parasitic capacitance of the high-side power transistor HS comes from the start-up driver 110, and the remaining charge on the gate parasitic capacitance of the high-side power transistor HS comes from the capacitive driver 130.

[0064] Furthermore, this saves the charge of the small-value integrated bootstrap capacitor in the capacitive driver 130, reduces the on-resistance of the high-side power transistor HS, and decreases the conduction loss of the high-side power transistor HS. This, in turn, improves the operating efficiency of the DC-DC converter.

[0065] The driving circuit provided in this application embodiment is applied in a switching power supply circuit. When the high-side power transistor is turned on by a control signal, the initial start-up driver can determine that the high-side power transistor has entered the turn-on process. Thus, the initial start-up driver can drive the high-side power transistor, causing its gate-source voltage to increase from 0V to a voltage threshold. As the gate-source voltage of the high-side power transistor continues to increase, when the gate-source voltage reaches the voltage threshold, the initial start-up driver can stop driving the high-side power transistor. In this way, part of the charging charge of the gate parasitic capacitance of the high-side power transistor comes from the initial start-up driver, preventing the high-side power transistor from directly obtaining power from the capacitive driver. When the initial start-up driver stops driving the high-side power transistor, the high-side power transistor is not turned on. At this time, the first circuit switch can connect the capacitive driver and the high-side power transistor, allowing the capacitive driver to charge the high-side power transistor. Thus, after the capacitive driver and the high-side power transistor are connected, the capacitive driver can use its bootstrap capacitor to charge the high-side power transistor. This saves charge on the small-value integrated bootstrap capacitor, reduces the on-resistance of the high-side power transistor, and decreases the conduction loss of the high-side power transistor. Consequently, the operating efficiency of the DC-DC converter is improved.

[0066] Based on the description of the above embodiments, the driving circuit 100 can be implemented in a variety of feasible ways.

[0067] As a feasible implementation of the drive circuit 100, refer to Figure 3 , Figure 3 This is a schematic diagram of a driving circuit provided in one embodiment of this application. Figure 3 As shown, the initial start driver 110 may include: a first power supply PVDD1 and a first transistor M1.

[0068] The first power supply PVDD1 is electrically connected to the first terminal of the first transistor M1. The control terminal of the first transistor M1 is used to receive the control signal HON_IN. The second terminal of the first transistor M1 is electrically connected between the second terminal of the first circuit switch 120 and the control terminal of the high-side power transistor HS.

[0069] Among them, the first power supply PVDD1 is an internal power supply.

[0070] For ease of understanding, the first transistor M1 in this embodiment is described using an N-channel metal-oxide-semiconductor (NMOS) transistor as an example.

[0071] When the control signal HON_IN is high, the first transistor M1 is turned on. Thus, the first power supply PVDD1 can drive the high-side power transistor HS. When the voltage at the control terminal of the high-side power transistor HS exceeds the maximum voltage provided by the first power supply PVDD1, that is, when the gate-source voltage Vgs of the high-side power transistor HS is the maximum supply voltage of the startup driver 110, the first transistor M1 is turned off. Consequently, the first power supply PVDD1 stops charging the high-side power transistor HS.

[0072] Therefore, the initial start driver can drive the high-side power transistor when the control signal is high, and stop driving the high-side power transistor when the gate-source voltage of the high-side power transistor is at the voltage threshold.

[0073] In addition, Figure 3 Based on the structure shown, the initial driver 110 may also include a diode-connected transistor M2.

[0074] The first terminal of diode-connected transistor M2 is electrically connected to the second terminal of first transistor M1. The control terminal of diode-connected transistor M2 is used to receive the control signal HON_IN. The second terminal of diode-connected transistor M2 is electrically connected between the second terminal of first circuit switch 120 and the control terminal of high-side power transistor HS.

[0075] Among them, the diode-connected transistor M2 and the first transistor M1 have the same structure.

[0076] When the control signal HON_IN is high, the first transistor M1 is turned on, allowing the current supplied by the first power supply PVDD1 to flow from the positive terminal to the negative terminal. At this time, the diode-connected transistor M2 is turned off. This prevents the current supplied by the first power supply PVDD1 from flowing from the negative terminal to the positive terminal, thus preventing reverse current flow.

[0077] In summary, using a diode-connected transistor enables a capacitive driver to have a reverse current protection function.

[0078] Continue to combine Figure 3 The capacitive driver 130 may include: a second bootstrap unit 131, a first inverter INV1, a delay unit Delay, and an AND gate device.

[0079] The first terminal of the second bootstrap unit 131 is electrically connected to the first terminal of the high-side power transistor HS. The second terminal of the second bootstrap unit 131 is electrically connected to the first terminal of the first circuit switch 120. The third terminal of the second bootstrap unit 131 is electrically connected to the first terminal of the first inverter INV1. The second terminal of the first inverter INV1 is electrically connected to the output terminal of the AND gate device AND. The first input terminal of the AND gate device AND and the first terminal of the delay device Delay are both used to input the control signal HON_IN. The second input terminal of the AND gate device AND is electrically connected to the second terminal of the delay device Delay.

[0080] When the control signal HON_IN is high, and when the initial start driver 110 stops driving the high-side power transistor HS, the control signal HON_IN is transmitted to the second input terminal of the AND gate device AND and the first input terminal of the AND gate device AND through the delay timer Delay. Under the action of the first inverter INV1, the control signal HON_IN becomes low. This makes the voltage at the second terminal of the second bootstrap unit 131 Vin + VDD. That is, the voltage at the first terminal of the first circuit switch 120 is Vin + VDD. At this time, the voltage at the third terminal of the first circuit switch 120 is Vin. Therefore, the first circuit switch 120 is turned on. Thus, the capacitive driver 120 can drive the high-side power transistor HS.

[0081] VDD is the power supply voltage for the inverter.

[0082] When the control signal HON_IN is low, it is transmitted to the second input of the AND gate device and the first input of the AND gate device via the Delay timer. Under the action of the first inverter INV1, the control signal HON_IN becomes high. This sets the voltage at the second terminal of the second bootstrap unit 131 to Vin. That is, the voltage at the first terminal of the first circuit breaker 120 is Vin. At this time, the voltage at the third terminal of the first circuit breaker 120 is Vin. Consequently, the first circuit breaker 120 is turned off. Thus, the capacitive driver 130 stops driving the high-side power transistor HS.

[0083] In summary, after the capacitive driver and the high-side power transistor are connected, the capacitive driver can use the bootstrap capacitor in the capacitive driver to charge the high-side power transistor.

[0084] Based on the description of the above embodiments, an exemplary possible implementation of the second bootstrap unit 131 is as follows: Figure 3As shown, the second bootstrap unit 131 may include: a second transistor M3, a third transistor M4, a first auxiliary capacitor C_ASS1, a first bootstrap capacitor C_BST1, and a second inverter INV2.

[0085] The first terminals of the second transistor M3 and the third transistor M4 are both electrically connected to the first terminal of the high-side power transistor HS. The second terminal of the second transistor M3 is electrically connected to the upper plate of the first auxiliary capacitor C_ASS1. The control terminal of the third transistor M4 is electrically connected between the second terminal of the second transistor M3 and the upper plate of the first auxiliary capacitor C_ASS1. The second terminal of the third transistor M4 is electrically connected to the upper plate of the first bootstrap capacitor C_BST1. The lower plate of the first bootstrap capacitor C_BST1 is electrically connected to the first terminal of the second inverter INV2. The control terminal of the second transistor M3 is electrically connected between the second terminal of the third transistor M4 and the upper plate of the first bootstrap capacitor C_BST1. The second terminal of the second inverter INV2 is electrically connected to the first terminal of the first inverter INV1. The lower plate of the first auxiliary capacitor C_ASS1 is electrically connected between the second terminal of the second inverter INV2 and the first terminal of the first inverter INV1.

[0086] Among them, the first bootstrap capacitor C_BST1 is a small-value integrated bootstrap capacitor.

[0087] When the control signal HON_IN is low, the first auxiliary capacitor C_ASS1 is charging, and the voltage across its upper plate changes from Vin to Vin+VDD. At this time, the third transistor M4 is turned on, and the first bootstrap capacitor C_BST1 is charging, changing its upper plate voltage from zero to Vin. In other words, the voltage at the second terminal of the second bootstrap unit 131 is Vin. Thus, the first circuit switch 120 is turned off.

[0088] When the control signal HON_IN is high, and when the initial start driver 110 stops driving the high-side power transistor HS, the first auxiliary capacitor C_ASS1 is discharging. Therefore, the voltage at the upper plate of the first auxiliary capacitor C_ASS1 changes from Vin+VDD to zero, and the first bootstrap capacitor C_BST1 is charging. Therefore, the voltage at the upper plate of the first bootstrap capacitor C_BST1 changes from Vin to Vin+VDD. That is, the voltage at the second terminal of the second bootstrap unit 131 is Vin+VDD. At this time, both the second transistor M3 and the first circuit switch 120 are turned on. Thus, the first auxiliary capacitor C_ASS1 is charging. Consequently, the voltage at the upper plate of the first auxiliary capacitor C_ASS1 is Vin.

[0089] In summary, the second bootstrap unit can charge the first bootstrap capacitor according to the aforementioned charging and discharging cycle when the control signal is low or high, causing the voltage at the second terminal of the bootstrap unit to change from Vin to Vin+VDD. Therefore, when the initial start-up driver stops driving the high-side power transistor, the first circuit switch is turned on, connecting the capacitive driver and the high-side power transistor.

[0090] Based on the description of the above embodiments, in Figure 3 Based on the structure shown, the drive circuit 100 may further include: a second circuit switch 140.

[0091] The input terminal of the second circuit switch 140 is used to receive the control signal HON_IN. The first terminal and the second terminal of the second circuit switch 140 are both electrically connected between the second terminal of the first circuit switch 120 and the control terminal of the high-side power transistor HS. The third terminal of the second circuit switch 140 is electrically connected to the switching node SW, which is located between the second terminal of the high-side power transistor HS and the first terminal of the low-side power transistor LS.

[0092] The second circuit switch 140 can be turned on when the control signal HON_IN is low, connecting the control terminal of the high-side power transistor HS to ground.

[0093] This causes the voltage at the control terminal of the high-side power transistor HS to drop. Consequently, the gate-source voltage Vgs of the high-side power transistor HS drops to zero.

[0094] Therefore, when the control signal is low, the second circuit switch 140 connects the control terminal of the high-side power transistor to ground.

[0095] The second circuit switch 140 can be implemented in various ways.

[0096] In some examples, such as Figure 3 As shown, the second circuit switch 140 may include: a third inverter INV3, a fourth transistor M5, and a fifth transistor M6.

[0097] The input terminal of the third inverter INV3 is used to receive the control signal HON_IN. The output terminal of the third inverter INV3 is electrically connected to the control terminal of the fourth transistor M5. The control terminal of the fifth transistor M6 is electrically connected between the output terminal of the third inverter INV3 and the control terminal of the fourth transistor M5. The first terminal of the fourth transistor M5 and the first terminal of the fifth transistor M6 are both electrically connected between the second terminal of the first circuit switch 120 and the control terminal of the high-side power transistor HS. The second terminal of the fourth transistor M5 is electrically connected to the switching node SW, and the second terminal of the fifth transistor M6 is grounded.

[0098] When the control signal HON_IN is low, it goes high under the action of the third inverter INV3. At this time, the fifth transistor M6 turns on, causing the voltage at the control terminal of the high-side power transistor HS to drop. Then, the fourth transistor M5 turns on, causing the voltage at the control terminal of the high-side power transistor HS to continue to drop. This further reduces the gate-source voltage Vgs of the high-side power transistor HS to zero. Consequently, the control terminal of the high-side power transistor HS is grounded.

[0099] In summary, the second circuit switch can connect the control terminal of the high-side power transistor to ground when the control signal is low.

[0100] Based on the description of the above embodiments, in Figure 3 Based on the structure shown, the driving circuit 100 may further include: a first buffer BUF1, a second buffer BUF2, a third buffer BUF3, a fourth buffer BUF4, and a fifth buffer BUF5.

[0101] The first terminal of the first buffer BUF1, the first terminal of the second buffer BUF2, and the first terminal of the fifth buffer BUF5 are all used to receive the control signal HON_IN. The second terminal of the first buffer BUF1 is electrically connected to the first terminal of the initial start driver 110 and the first terminal of the delay timer Delay, respectively. The second terminal of the second buffer BUF2 is electrically connected to the first input terminal of the AND gate device AND. The first terminals of the third buffer BUF3 and the fourth buffer BUF4 are both electrically connected to the output terminal of the third inverter INV3. The second terminal of the third buffer BUF3 is electrically connected to the control terminal of the fourth transistor M5. The second terminal of the fourth buffer BUF4 is electrically connected to the control terminal of the fifth transistor M6. The second terminal of the fifth buffer BUF5 is electrically connected to the control terminal of the low-side power transistor LS.

[0102] As another feasible implementation of the drive circuit 100, refer to Figure 4 , Figure 4 This is a schematic diagram of a driving circuit provided in one embodiment of this application. Figure 4 As shown, the initial start driver 110 may include: a second power supply PVDD2 and a sixth transistor M7.

[0103] The second power supply PVDD2 is electrically connected to the control terminal of the sixth transistor M7. The first terminal of the sixth transistor M7 is used to receive the control signal HON_IN, and the second terminal of the sixth transistor M7 is electrically connected between the third terminal of the first circuit switch 120 and the control terminal of the high-side power transistor HS.

[0104] Among them, the second power supply PVDD2 is an internal power supply.

[0105] For ease of understanding, the sixth transistor M7 in this embodiment is described using an NMOS transistor as an example.

[0106] When the control signal HON_IN is low, the voltage at the first terminal of the sixth transistor M7 is zero. This pulls the voltage at the control terminal of the high-side power transistor HS down to zero. At this time, the high-side power transistor HS is in the off state.

[0107] When the control signal HON_IN changes from low to high, the voltage at the first terminal of the sixth transistor M7 rises from zero to VDD, and the sixth transistor M7 switches to a diode connection, turning on. Thus, the second power supply PVDD2 can drive the high-side power transistor HS. The voltage at the control terminal of the high-side power transistor HS is pulled up by the sixth transistor M7, and the voltage at the control terminal of the high-side power transistor can be pulled up to a maximum of VDD - Vth_M7. Here, Vth_M7 is the turn-on threshold voltage of the sixth transistor. That is, when the gate-source voltage Vgs of the high-side power transistor HS is the maximum supply voltage of the initial start driver 110, the sixth transistor M7 turns off to prevent the capacitive driver 120 from back-feeding to the first terminal of the sixth transistor M7. Consequently, the second power supply HON_IN stops charging the high-side power transistor HS.

[0108] Therefore, the initial start driver can drive the high-side power transistor when the control signal is high, and stop driving the high-side power transistor when the gate-source voltage Vgs of the high-side power transistor HS is at the voltage threshold.

[0109] Based on the description of the above embodiments, in Figure 4 Based on the structure shown, the initial start driver 110 may also include: a sixth buffer BUF6.

[0110] The first terminal of the sixth buffer BUF6 is used to receive the control signal HON_IN, and the second terminal of the sixth buffer BUF6 is electrically connected to the first terminal of the sixth transistor M7.

[0111] Continue to combine Figure 4 The capacitive driver 130 may include a first bootstrap unit 132 and a fourth inverter INV4.

[0112] The first end of the first bootstrap unit 132 is electrically connected to the first end of the high-side power transistor HS. The second end of the first bootstrap unit 132 is electrically connected to the first end of the first circuit switch 120. The third end of the first bootstrap unit 132 is electrically connected to the output end of the fourth inverter INV4. The input end of the fourth inverter INV4 is used to input the control signal HON_IN.

[0113] When the control signal HON_IN is high, and when the initial start-up driver 110 stops driving the high-side power transistor HS, the third terminal of the first bootstrap unit 132 is low under the action of the fourth inverter INV4. Thus, the voltage at the second terminal of the first bootstrap unit 132 is Vin + VDD. That is, the voltage at the first terminal of the first circuit breaker 120 is Vin + VDD. At this time, the voltage at the third terminal of the first circuit breaker 120 is Vin, and the first circuit breaker 120 is turned on. Therefore, the capacitive driver 130 can charge the high-side power transistor HS.

[0114] When the control signal HON_IN is low, it becomes high under the action of the fourth inverter INV4, meaning the third terminal of the first bootstrap unit 132 is high. Consequently, the voltage at the second terminal of the first bootstrap unit 132 is Vin. This means the voltage at the first terminal of the first circuit breaker 120 is Vin. At this time, the voltage at the third terminal of the first circuit breaker 120 is Vin, and the first circuit breaker 120 is turned off. Therefore, the capacitive driver 130 stops charging the high-side power transistor HS.

[0115] In summary, after the capacitive driver and the high-side power transistor are connected, the capacitive driver can charge the high-side power transistor.

[0116] The first bootstrap unit 132 can be implemented in various ways.

[0117] In some examples, such as Figure 4 As shown, the first bootstrap unit 132 may include: a seventh transistor M8, an eighth transistor M9, a second auxiliary capacitor C_ASS2, a second bootstrap capacitor C_BST2, and a sixth inverter INV6.

[0118] The first terminal of the seventh transistor M8 and the first terminal of the eighth transistor M9 are both electrically connected to the first terminal of the high-side power transistor HS. The second terminal of the seventh transistor M8 is electrically connected to the upper plate of the second auxiliary capacitor C_ASS2. The control terminal of the eighth transistor M9 is electrically connected between the second terminal of the seventh transistor M8 and the upper plate of the second auxiliary capacitor C_ASS2. The second terminal of the eighth transistor M9 is electrically connected to the upper plate of the second bootstrap capacitor C_BST2. The lower plate of the second bootstrap capacitor C_BST2 is electrically connected to the first terminal of the sixth inverter INV6. The control terminal of the seventh transistor M8 is electrically connected between the second terminal of the eighth transistor M9 and the upper plate of the second bootstrap capacitor C_BST2. The second terminal of the sixth inverter INV6 is electrically connected to the first terminal of the fourth inverter INV4. The lower plate of the second auxiliary capacitor C_ASS2 is electrically connected between the second terminal of the sixth inverter INV6 and the first terminal of the fourth inverter INV4.

[0119] Among them, the second bootstrap capacitor C_BST2 is a small-value integrated bootstrap capacitor.

[0120] When the control signal HON_IN is low, the second auxiliary capacitor C_ASS2 is charging, and the voltage across its upper plate changes from Vin to Vin+VDD. At this time, the eighth transistor M9 is turned on, and the second bootstrap capacitor C_BST2 is charging, changing its upper plate voltage from zero to Vin. In other words, the voltage at the second terminal of the first bootstrap unit 132 is Vin. Consequently, the first circuit switch 120 is turned off.

[0121] When the control signal HON_IN is high, and when the initial start driver 110 stops driving the high-side power transistor HS, the second auxiliary capacitor C_ASS2 is discharging. Therefore, the voltage at the upper plate of the second auxiliary capacitor C_ASS2 changes from Vin+VDD to zero, and the second bootstrap capacitor C_BST2 is charging. Therefore, the voltage at the upper plate of the second bootstrap capacitor C_BST2 changes from Vin to Vin+VDD. That is, the voltage at the second terminal of the first bootstrap unit 132 is Vin+VDD. At this time, both the seventh transistor M8 and the first circuit switch 120 are turned on. Thus, the second auxiliary capacitor C_ASS2 is charging. Consequently, the voltage at the upper plate of the second auxiliary capacitor C_ASS2 is Vin.

[0122] In summary, when the control signal is low or high, the first bootstrap unit can charge the second auxiliary capacitor according to the aforementioned charging and discharging cycle, causing the voltage at the second terminal of the bootstrap unit to change from Vin to Vin+VDD. Therefore, when the initial start-up driver stops driving the high-side power transistor, the first circuit switch is turned on, connecting the capacitive driver and the high-side power transistor.

[0123] Based on the description of the above embodiments, in Figure 3 and Figure 4 Based on the structure shown, the driving circuit may also include: a fifth inverter INV5.

[0124] The input terminal of the fifth inverter INV5 is used to receive the control signal HON_IN. The control signal HON_IN is also used to control the on or off of the low-side power transistor LS. The output terminal of the fifth inverter INV5 is electrically connected to the control terminal of the low-side power transistor LD.

[0125] When the control signal HON_IN is low, it goes high under the action of the fifth inverter INV5. This turns on the low-side power transistor LS.

[0126] When the control signal HON_IN is high, it goes low under the action of the fifth inverter INV5. This turns off the low-side power transistor LS.

[0127] In summary, the control signal can control the low-side power transistor to turn on or off via the fifth inverter.

[0128] Finally, it should be noted that the above embodiments are merely specific implementations of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions within the technical scope disclosed in this application should be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A driving circuit, applied in a switching power supply circuit, the switching power supply circuit comprising: The high-side power transistor and the low-side power transistor are characterized in that the driving circuit includes: an initial start driver, a first circuit switch, and a capacitive driver. The input terminals of the initial start driver and the capacitive driver are both used to receive control signals sent by the control circuit. The control signals are used to control the high-side power transistor to turn on or off. The output terminal of the capacitive driver is electrically connected to the first terminal of the first circuit switch. The second terminal of the first circuit switch is electrically connected to the control terminal of the high-side power transistor. The power supply terminal of the capacitive driver and the control terminal of the first circuit switch are both electrically connected to the first terminal of the high-side power transistor. The output terminal of the initial start driver is electrically connected between the second terminal of the first circuit switch and the control terminal of the high-side power transistor. The initial start driver is used to drive the gate-source voltage of the high-side power transistor to increase from 0V until the gate-source voltage of the high-side power transistor increases to a voltage threshold when the control signal controls the high-side power transistor to be turned on. The first circuit switch is used to connect the capacitive driver and the high-side power transistor when the gate-source voltage of the high-side power transistor is the voltage threshold. The capacitive driver is used to charge the high-side power transistor using a bootstrap capacitor in the capacitive driver after the capacitive driver and the high-side power transistor are connected.

2. The circuit according to claim 1, characterized in that, The startup driver includes: a first power supply and a first transistor; The first power supply is electrically connected to the first terminal of the first transistor, the control terminal of the first transistor is used to receive the control signal, and the second terminal of the first transistor is electrically connected between the second terminal of the first circuit switch and the control terminal of the high-side power transistor.

3. The circuit according to claim 2, characterized in that, The initial start driver also includes: a diode-connected transistor; The first terminal of the diode-connected transistor is electrically connected to the second terminal of the first transistor. The control terminal of the diode-connected transistor is used to receive the control signal. The second terminal of the diode-connected transistor is electrically connected between the second terminal of the first circuit switch and the control terminal of the high-side power transistor.

4. The circuit according to claim 2, characterized in that, The capacitive driver includes: a second transistor, a third transistor, a first auxiliary capacitor, a first bootstrap capacitor, a first inverter, and a second inverter; The first terminal of the second transistor and the first terminal of the third transistor are both electrically connected to the first terminal of the high-side power transistor. The second terminal of the second transistor is electrically connected to the upper plate of the first auxiliary capacitor. The control terminal of the third transistor is electrically connected between the second terminal of the second transistor and the upper plate of the first auxiliary capacitor. The second terminal of the third transistor is electrically connected to the upper plate of the first bootstrap capacitor. The lower plate of the first bootstrap capacitor is electrically connected to the first terminal of the second inverter. The control terminal of the second transistor is electrically connected between the second terminal of the third transistor and the upper plate of the first bootstrap capacitor. The second terminal of the second inverter is electrically connected to the first terminal of the first inverter. The lower plate of the first auxiliary capacitor is electrically connected between the second terminal of the second inverter and the first terminal of the first inverter. The first circuit switch is used to connect the capacitive driver and the high-side power transistor when the upper and lower plates of the first bootstrap capacitor are simultaneously raised and the voltage on the upper plate of the first bootstrap capacitor is greater than the voltage on the control terminal of the first circuit switch.

5. The circuit according to claim 2, characterized in that, The driving circuit further includes: a second circuit switch; The input terminal of the second circuit switch is used to receive the control signal. The first terminal and the second terminal of the second circuit switch are both electrically connected between the second terminal of the first circuit switch and the control terminal of the high-side power transistor. The third terminal of the second circuit switch is electrically connected to the switching node, which is located between the second terminal of the high-side power transistor and the first terminal of the low-side power transistor. The second circuit switch is used to connect the control terminal of the high-side power transistor to ground when the control signal controls the high-side power transistor to be turned off.

6. The circuit according to claim 5, characterized in that, The second circuit switch includes: a third inverter, a fourth transistor, and a fifth transistor; The input terminal of the third inverter is used to receive the control signal. The output terminal of the third inverter is electrically connected to the control terminal of the fourth transistor. The control terminal of the fifth transistor is electrically connected between the output terminal of the third inverter and the control terminal of the fourth transistor. The first terminal of the fourth transistor and the first terminal of the fifth transistor are both electrically connected between the second terminal of the first circuit switch and the control terminal of the high-side power transistor. The second terminal of the fourth transistor is electrically connected to the switching node. The second terminal of the fifth transistor is grounded.

7. The circuit according to claim 1, characterized in that, The initial start driver includes: a second power supply and a sixth transistor; The second power supply is electrically connected to the control terminal of the sixth transistor. The first terminal of the sixth transistor is used to receive the control signal, and the second terminal of the sixth transistor is electrically connected between the second terminal of the first circuit switch and the control terminal of the high-side power transistor.

8. The circuit according to claim 7, characterized in that, The capacitive driver includes: a first bootstrap unit and a fourth inverter; The first end of the first bootstrap unit is electrically connected to the first end of the high-side power transistor, the second end of the first bootstrap unit is electrically connected to the first end of the first circuit switch, the third end of the first bootstrap unit is electrically connected to the output end of the fourth inverter, and the input end of the fourth inverter is used to receive the control signal.

9. The circuit according to any one of claims 1-8, characterized in that, The driving circuit further includes: a fifth inverter; The input terminal of the fifth inverter is used to receive the control signal, which is also used to control the turn-on or turn-off of the low-side power transistor. The output terminal of the fifth inverter is electrically connected to the control terminal of the low-side power transistor.

10. A switching power supply circuit, characterized in that, The switching power supply circuit includes: a high-side power transistor, a low-side power transistor, a control circuit, and a drive circuit as described in any one of claims 1-9; The first terminal of the high-side power transistor is used to connect to the power supply voltage, the second terminal of the low-side power transistor is grounded, and the driving circuit is electrically connected to the control terminal of the high-side power transistor, the control terminal of the low-side power transistor, and the control circuit, respectively.

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