Switching converter and driving circuit therefor

Abstract

Disclosed in the present invention are a switching converter and a driving circuit therefor. The driving circuit comprises: a logic control circuit, configured to generate a first control signal on the basis of an output voltage and perform an edge delay on the first control signal to obtain a second control signal, wherein the second control signal is used for controlling the on and off of a main switching transistor; a main switching transistor driving circuit, connected to a control end of the main switching transistor and configured to drive the on and off of the main switching transistor on the basis of the second control signal; a bootstrap capacitor, connected between a bootstrap node and a switching node, wherein the bootstrap node is used for supplying power to the main switching transistor driving circuit; and a charge pump circuit, connected to the bootstrap node and configured to charge the bootstrap capacitor. The edge delay refers to an edge delay for controlling the on of the main switching transistor, the delay time is a set time, and the charge pump circuit also pre-charges the bootstrap capacitor within the set time. In this way, it is ensured that the bootstrap node can normally supply power to the main switching transistor driving circuit when the main switching transistor is switched from an off state to an on state.

Description

Switching converter and driving circuit thereof Cross-reference to related applications

[0001] This application claims priority to the Chinese Patent Application No. 202411366032.3, filed on September 27, 2024, and entitled “Switching converter and driving circuit thereof”, the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present application relates to the technical field of integrated circuits, and in particular to a switching converter and a driving circuit thereof. BACKGROUND

[0003] For a Buck converter using NMOS transistors as the main switch and the synchronous switch, a bootstrap capacitor is usually needed to form a bootstrap voltage to supply power for the main switch.

[0004] In order to make the switching converter work normally when the input voltage Vin is close to the output voltage Vout, a charge pump circuit needs to be integrated inside the switching converter to charge the bootstrap capacitor when the voltage difference between the two plates of the bootstrap capacitor is lower than a preset value or the main switch is always on. When the bootstrap capacitor is charged to the preset value, the charge pump circuit will enter a dormant state. However, in the prior art, when the input voltage Vin is low, in the no-load or light-load mode, especially in the case of high-temperature leakage, the main switch needs to be frequently turned off to start the charge pump circuit to charge the bootstrap capacitor, which generates a large loss and affects the light-load efficiency. In addition, the voltage detection circuit for detecting the voltage difference between the two plates of the bootstrap capacitor also needs to work all the time, which also causes a certain loss.

[0005] Therefore, a new switching converter needs to be proposed to solve the above problems. SUMMARY

[0006] In view of the above problems, the purpose of the present application is to provide a switching converter and a driving circuit thereof, so as to ensure that when the main switch is switched from off to on, the bootstrap node can normally supply power for the main switch driving circuit.

[0007] According to an aspect of the present application, there is provided a driving circuit of a switching converter, the switching converter comprising a main switch connected between an input and a switching node, the main switch being configured to control the transmission of electric energy from the input to an output to convert an input voltage into an output voltage, the driving circuit comprising a logic control circuit configured to generate a first control signal according to the output voltage and to perform an edge delay on the first control signal to obtain a second control signal, the second control signal being configured to control the on and off time of the main switch; a main switch driving circuit connected to the control terminal of the main switch and configured to drive the on and off of the main switch according to the second control signal; a bootstrap capacitor connected between a bootstrap node and the switching node, the bootstrap node being configured to supply power to the main switch driving circuit; and a charge pump circuit connected to the bootstrap node and configured to charge the bootstrap capacitor, wherein the edge delay refers to the edge delay of the control signal for turning on the main switch, the time of the delay being a set time, and the charge pump circuit is further configured to pre-charge the bootstrap capacitor within the set time.

[0008] Optionally, the charge pump circuit comprises a charge pump capacitor; the charge pump circuit has a charging state for charging the charge pump capacitor and a pumping state for charging the bootstrap capacitor, in a first sub-period of the set time, the charge pump circuit is in the pumping state, and in a second sub-period of the set time, the charge pump circuit is in the charging state; when the main switch is turned on, the charge pump circuit is in the pumping state.

[0009] Optionally, the charge pump circuit comprises a first diode, the anode of which is connected to the input voltage of the switching converter; a second diode, the anode of which is connected to the cathode of the first diode and the cathode of which is connected to the bootstrap node; a first switch, the charge pump capacitor and the first switch being connected in sequence between the cathode of the first diode and a ground terminal; and a second switch, connected between the input voltage of the switching converter and a common node of the charge pump capacitor and the first switch.

[0010] Optionally, the charge pump circuit further comprises a switch control unit configured to control the working state of the charge pump circuit by controlling the on and off of the first switch and the second switch, wherein when the switch control unit controls the first switch to be off and the second switch to be on, the charge pump circuit is in the pumping state to charge the bootstrap capacitor through the second diode by the charge pump capacitor; and when the switch control unit controls the first switch to be on and the second switch to be off, the charge pump circuit is in the charging state to charge the charge pump capacitor by the input voltage.

[0011] Optionally, the switch control unit comprises a timer, the switch control unit starts the timer when the first control signal appears at the edge of controlling the main switch tube to be turned on, and controls the charge pump circuit to be in the pumping state; and when the time of the timer reaches a first sub-time, the switch control unit controls the charge pump circuit to switch to the charging state, and when the time of the timer reaches the set time, the switch control unit controls the charge pump circuit to switch to the pumping state again, wherein the time interval between the set time and the first sub-time is the second sub-time.

[0012] Optionally, the switch control unit comprises a timer, the switch control unit starts the timer when the first control signal appears at the edge of controlling the main switch tube to be turned on, and controls the charge pump circuit to be in the pumping state; and when the time of the timer reaches a first sub-time, the switch control unit controls the charge pump circuit to switch to the charging state, and when the second control signal appears at the edge of controlling the main switch tube to be turned on, the switch control unit controls the charge pump circuit to switch to the pumping state again, wherein the time interval between the edge of controlling the main switch tube to be turned on and the first sub-time is the second sub-time.

[0013] Optionally, the logic control circuit comprises a comparator for comparing a feedback voltage of the switch converter output voltage with a reference voltage to output a pulse width modulation signal according to a comparison result; a logic control unit for receiving the pulse width modulation signal and outputting the first control signal; and a delay unit for performing edge delay on the first control signal to obtain a second control signal.

[0014] Optionally, the main switch tube driving circuit comprises a voltage detection circuit for detecting a voltage difference between the bootstrap node and the switch node and outputting a detection signal according to a comparison result of the voltage difference and a first threshold voltage; and a driving unit connected with a control end of the main switch tube for driving the main switch tube to be turned on and turned off, wherein the voltage detection circuit is turned on when the main switch tube is turned on and is turned off when the main switch tube is turned off, and an initial value of the detection signal is a first level, and the detection signal is flipped to a second level when the voltage detection circuit detects that the voltage difference is reduced to be less than the first threshold voltage.

[0015] Optionally, the driving circuit further comprises a logic unit for performing AND operation on the detection signal and a second control signal to obtain a third control signal; and the driving unit receives the third control signal or the second control signal and outputs a driving signal to drive the main switch tube to be turned on and turned off.

[0016] According to another aspect of the present application, a switching converter is provided, comprising a main switch connected between an input terminal and a switching node; a synchronous switch connected between the switching node and a ground terminal; an inductor connected between the switching node and an output terminal; and the driving circuit as described above.

[0017] The switching converter and the driving circuit thereof provided by the present application comprise a logic control circuit, which is configured to generate a first control signal according to an output voltage, and to perform a rising edge delay on the first control signal to obtain a second control signal, the second control signal being configured to control the on and off time of the main switch; a main switch driving circuit, which is connected to the control terminal of the main switch and configured to drive the on and off of the main switch according to the second control signal; a bootstrap capacitor, which is connected between a bootstrap node and the switching node, the bootstrap node being configured to supply power to the main switch driving circuit; and a charge pump circuit, which is connected to the bootstrap node and configured to charge the bootstrap capacitor, wherein the delay time is a set time, and the charge pump circuit is further configured to pre-charge the bootstrap capacitor within the set time, so as to ensure that the bootstrap node can normally supply power to the main switch driving circuit when the main switch is switched from off to on.

[0018] In a preferred embodiment, the charge pump circuit is in a pumping state within a first sub-time period of the set time, is in a charging state within a second sub-time period of the set time, and is in the pumping state when the main switch is on, so that the power-down speed of the bootstrap capacitor can be reduced, the on time of the main switch can be prolonged, and the light load efficiency of the switching converter can be improved.

[0019] In a preferred embodiment, the main switch driving circuit comprises a voltage detection circuit, which is only turned on when the main switch is on, so that the power consumption of the switching converter can be reduced. BRIEF DESCRIPTION OF DRAWINGS

[0020] The above and other objects, features and advantages of the present application will become more apparent from the following description when taken in conjunction with the accompanying drawings, in which:

[0021] FIG. 1 shows a structural schematic diagram of a switching converter;

[0022] FIG. 2 shows a circuit schematic diagram of the switching converter shown in FIG. 1;

[0023] FIG. 3 shows a circuit schematic diagram of a switching converter according to an embodiment of the present application;

[0024] FIG. 4 shows a timing schematic diagram of a switching converter according to an embodiment of the present application. DETAILED DESCRIPTION

[0025] Various embodiments of the present application will be described in more detail below with reference to the accompanying drawings. In the drawings, like reference numerals refer to like elements or modules throughout. The drawings are not drawn to scale for the sake of clarity.

[0026] It should be understood that, in the following description, "circuitry" can include a single or multiple components or a combination of hardware circuitry, programmable circuitry, state machine circuitry, and / or elements storing instructions for execution by a programmable circuit. When an element or circuit is referred to as being "connected to" another element or "connected between" two nodes, it can be directly coupled or connected to the other element or there can be intervening elements between the elements, the connection between elements can be physical, logical, or a combination thereof. In contrast, when an element is referred to as being "directly coupled to" or "directly connected to" another element, it implies that the two are connected without any intervening elements.

[0027] Also, certain terms have been used herein for the purpose of reference only and thus are not intended to be limiting. For example, terms such as "upper", "lower", "above", and "below" refer to the patent drawings and are solely for the purpose of illustration and do not limit the items described to or from a particular spatial orientation.

[0028] In addition, it should also be noted that, in the present context, terms such as first and second should only be used to differentiate one entity or operation from another entity or operation, and do not necessarily imply or suggest any such actual relationship or order between the entities or operations. Moreover, the terms "comprising", "including", or any other variant thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements recited, but can also include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising a" does not exclude the presence of additional identical elements in the process, method, article, or apparatus that includes the element.

[0029] FIG. 1 shows a circuit schematic of a switching converter. Referring to FIG. 1, the switching converter 100 includes a power circuit and a drive circuit. The power circuit includes a main switch HS and a synchronous switch LS connected in series between an input voltage Vin and a ground terminal, an inductor L connected between a common node of the main switch HS and the synchronous switch LS, i.e., a switching node SW, and an output terminal, a load RL connected between the output terminal and the ground terminal, and an output capacitor Cout connected in parallel with the load RL. The input terminal of the power circuit receives the input voltage Vin, and the output terminal provides an output voltage Vout.

[0030] In addition, the switching converter 100 further comprises a voltage dividing network composed of resistors R1 and R2, which is used to obtain a feedback voltage Vfb of the output voltage Vout.

[0031] The driving circuit comprises a logic control circuit 110, a driving unit 120, a driving unit 130, a bootstrap capacitor Cbst, a voltage detection circuit 140, a charge pump circuit 150, and a comparator 160.

[0032] The comparator 160 is configured to compare the feedback voltage Vfb with a reference voltage Vref to obtain a pulse width modulation signal PWM according to a comparison result. The logic control circuit 110 is configured to receive the pulse width modulation signal PWM and a detection signal ctrl_bst, and provide a control signal ctrl_hs and a control signal ctrl_ls. The driving unit 120 is connected between a bootstrap node BST and a switching node SW, and is configured to generate a driving signal hs_on according to the control signal ctrl_hs to control the turn-on and turn-off of a main switch HS. The driving unit 130 is connected between a power supply voltage Vdd and a ground terminal, and is configured to generate a driving signal ls_on according to the control signal ctrl_ls to control the turn-on and turn-off of a synchronous switch LS. In each switching cycle, the main switch HS and the synchronous switch LS are alternately turned on and turned off to charge and discharge the inductor L, so as to provide a direct current output voltage Vout at the output terminal.

[0033] The bootstrap capacitor Cbst is connected between the bootstrap node BST and the switching node SW. The voltage detection circuit 140 is configured to detect a voltage difference between the bootstrap node BST and the switching node SW, and compare the voltage difference with a first threshold voltage and a second threshold voltage to output the detection signal ctrl_bst according to a comparison result, wherein the detection signal ctrl_bst is flipped to a first level when the voltage difference between the bootstrap node BST and the switching node SW rises to be greater than the second threshold voltage, and the detection signal ctrl_bst is flipped to a second level when the voltage difference between the bootstrap node BST and the switching node SW falls to be less than the first threshold voltage, and the second threshold voltage is greater than the first threshold voltage. The logic control circuit 110 outputs the control signal ctrl_hs of the second level to turn off the main switch HS and outputs the control signal ctrl_ls of the first level to turn on the synchronous switch LS when the detection signal ctrl_bst is of the second level.

[0034] The charge pump circuit 150 is configured to charge the bootstrap capacitor Cbst when the main switch HS is turned off.

[0035] FIG. 2 shows a circuit schematic diagram of the switching converter shown in FIG. 1. For the convenience of description, the logic control circuit 110, the resistor R1, the resistor R2, and the comparator 160 are not shown in FIG. 2.

[0036] Referring to FIG. 2, the charge pump circuit 150 comprises diodes D1-D2, a charge pump capacitor Cpunp and switches S1-S2. The anode of the diode D2 is connected to the input voltage Vin, the cathode of the diode D2 is connected to the anode of the diode D1, and the cathode of the diode D1 is connected to the bootstrap node BST. The charge pump capacitor Cpunp and the switch S1 are connected in sequence between the cathode of the diode D2 and the ground terminal, and the switch S2 is connected between the input voltage Vin and the intermediate node of the charge pump capacitor Cpunp and the switch S1.

[0037] When the main switch HS is off, the switch S1 is off and the switch S2 is on to pump the first plate voltage of the charge pump capacitor Cpunp to the input voltage Vin, so that the charge pump capacitor Cpunp charges the bootstrap capacitor Cbst; when the main switch HS is on, the switch S1 is on and the switch S2 is off to charge the charge pump capacitor Cpunp by the input voltage Vin.

[0038] The switching converter 100 needs to frequently turn off the main switch HS to start the charge pump circuit 150 to charge the bootstrap capacitor Cbst when the input voltage Vin is relatively low, in the no-load or light-load mode, especially in the case of high temperature leakage, resulting in high power consumption of the switching converter 100 and affecting the light-load efficiency. In addition, the voltage detection circuit 150 of the switching converter 100 also needs to work all the time, further increasing the power consumption of the switching converter 100.

[0039] FIG. 3 shows a circuit schematic diagram of a switching converter according to an embodiment of the present application.

[0040] Referring to FIG. 3, the switching converter 200 comprises a power circuit and a driving circuit. The power circuit comprises a main switch HS and a synchronous switch LS connected in series between an input voltage Vin and a ground terminal, an inductor L connected between a common node of the main switch HS and the synchronous switch LS, i.e. a switching node SW, and an output terminal, a load RL connected between the output terminal and the ground terminal, and an output capacitor Cout connected in parallel with the load RL. The input terminal of the power circuit receives the input voltage Vin, and the output terminal provides an output voltage Vout. The main switch HS is used to control the transmission of electrical energy from the input terminal to the output terminal to convert the input voltage Vin into the output voltage Vout.

[0041] In addition, the switching converter 200 further comprises a voltage dividing network composed of resistors R1 and R2, which is used to obtain a feedback voltage Vfb of the output voltage Vout.

[0042] The driving circuit comprises a logic control circuit 210, a main switch driving circuit 220, a driving unit 230, a bootstrap capacitor Cbst and a charge pump circuit 240. The logic control circuit 210 is configured to generate a control signal ctrl_hs1 according to an output voltage Vout, and perform edge delay on the control signal ctrl_hs1 to obtain a control signal ctrl_hs, the control signal ctrl_hs being used to control the on and off time of the main switch, wherein the delay time is a set time t1. The main switch driving circuit 220 is connected to the control end of the main switch HS, and is configured to drive the on and off of the main switch HS according to the control signal ctrl_hs. The bootstrap capacitor Cbst is connected between a bootstrap node BST and a switch node SW, and the bootstrap node BST is used to supply power for the main switch driving circuit 220. The charge pump circuit 240 is connected to the bootstrap node BST, and is configured to charge the bootstrap capacitor Cbst, wherein the charge pump circuit 240 is also configured to pre-charge the bootstrap capacitor Cbst within the set time t1.

[0043] The charge pump circuit 240 has a charging state and a pumping state. In a first sub-period of the set time t1, the charge pump circuit 240 is in the pumping state, and in a second sub-period of the set time t1, the charge pump circuit 240 is in the charging state. When the main switch HS is on, the charge pump circuit 240 is in the pumping state. The sum of the first sub-period and the second sub-period is the set time t1.

[0044] The logic control circuit 210 comprises a comparator 211, a logic control unit 212 and a delay unit 213. The comparator 211 is configured to compare a feedback voltage Vfb of the output voltage Vout with a reference voltage Vref to obtain a pulse width modulation signal PWM according to a comparison result. The logic control unit 212 is configured to receive the pulse width modulation signal PWM and provide a control signal ctrl_hs for controlling the main switch HS to turn on and turn off and a control signal ctrl_ls for controlling the synchronous switch LS to turn on and turn off. The control signal ctrl_hs and the control signal ctrl_ls are, for example, pulse width modulation signals. The control signal ctrl_hs is configured to control the main switch HS to turn on when the control signal ctrl_hs is at a first level and control the main switch HS to turn off when the control signal ctrl_hs is at a second level. The first level can be a high level or a low level. When the first level is a high level, the second level is a low level. When the first level is a low level, the second level is a high level. In the following, the first level is a high level and the second level is a low level are taken as an example for illustration. The delay unit 213 receives the control signal ctrl_hs1 at an input terminal and provides the control signal ctrl_hs at an output terminal. The delay unit 213 is configured to perform an edge delay on the control signal ctrl_hs1 to obtain the control signal ctrl_hs. The delay time is a set time t1. The edge delay is, for example, a rising edge delay. When a falling edge of the control signal ctrl_hs1 is encountered, the delay unit 213 directly outputs the control signal ctrl_hs1 as the control signal ctrl_hs.

[0045] The drive unit 230 is connected between the power supply voltage Vdd and the ground terminal and configured to generate a drive signal ls_on according to the control signal ctrl_ls to drive the synchronous switch LS to turn on and turn off. The control signal ctrl_ls is configured to control the synchronous switch LS to turn on when the control signal ctrl_ls is at a first level. In each switching cycle, the main switch HS and the synchronous switch LS are alternately turned on and turned off to charge and discharge the inductor L, thereby providing a direct current output voltage Vout at the output terminal.

[0046] The charge pump circuit 240 comprises a charge pump unit and a switch control unit 241. The charge pump unit comprises diodes D1-D2, a charge pump capacitor Cpump and switches S1-S2. An anode of the diode D2 is connected to the input voltage Vin, a cathode of the diode D2 is connected to an anode of the diode D1, and a cathode of the diode D1 is connected to the bootstrap node BST. The charge pump capacitor Cpump and the switch S1 are connected in sequence between a cathode of the diode D2 and the ground terminal, and the switch S2 is connected between the input voltage Vin and an intermediate node of the charge pump capacitor Cpump and the switch S1.

[0047] The switch control unit 241 controls the working state of the charge pump circuit 240 by controlling the on and off of the switches S1 and S2. Specifically, the switch control unit 241 receives the control signal ctrl_hs1, and generates the clock signal Φ1 and the clock signal Φ1_b according to the control signal ctrl_hs1 to control the on and off of the switches S1 and S2, respectively. When the switch control unit 241 controls the switch S1 to be off and the switch S2 to be on, the charge pump circuit 240 is in the pumping state to bootstrap the charge pump capacitor Cbump, so that the bootstrap capacitor Cbst is charged by the charge pump capacitor Cbump through the diode D1; and when the switch control unit 241 controls the switch S1 to be on and the switch S2 to be off, the charge pump circuit 240 is in the charging state to charge the charge pump capacitor Cbump by the input voltage Vin.

[0048] Optionally, the switch control unit 241 controls the working state of the charge pump circuit 240 according to the control signal ctrl_hs1 only. The switch control unit 241 includes a timer. The switch control unit 241 controls the timer to start timing when the control signal ctrl_hs1 rises, and controls the charge pump circuit 240 to be in the pumping state; and controls the charge pump circuit 240 to switch to the charging state when the timing time of the timer reaches the first sub-time, and controls the charge pump circuit 240 to switch to the pumping state again when the timing time of the timer reaches the set time t1, wherein the time interval between the set time t1 and the first sub-time is the second sub-time.

[0049] Optionally, the switch control unit 241 controls the working state of the charge pump circuit 240 according to the control signal ctrl_hs1 and the control signal ctrl_hs. The switch control unit 241 includes a timer. The switch control unit 241 controls the timer to start timing when the control signal ctrl_hs1 rises, and controls the charge pump circuit 240 to be in the pumping state; and controls the charge pump circuit 240 to switch to the charging state when the timing time of the timer reaches the first sub-time, and controls the charge pump circuit 240 to switch to the pumping state again when the control signal ctrl_hs rises, wherein the time interval between the time when the control signal ctrl_hs rises and the first sub-time is the second sub-time.

[0050] The switch control unit 241 controls the working state of the charge pump circuit 240 by generating the clock signal Φ1 and the clock signal Φ1_b to control the on and off of the switches S1 and S2, respectively. The clock signal Φ1 and the clock signal Φ1_b are opposite.

[0051] Optionally, the switch control unit 241 can also not be arranged in the charge pump circuit 240, and can be arranged separately or in the logic control circuit 210.

[0052] Optionally, the delay unit 213 can also not be arranged inside the logic control circuit 210, and can be arranged separately or in the charge pump circuit 240.

[0053] The main switch driving circuit 220 includes a voltage detection circuit 221 and a driving unit 223. The driving unit 223 is connected between the bootstrap node BST and the switch node SW, and is configured to generate a driving signal hs on according to a control signal ctrl hs to drive the main switch HS to turn on and turn off. The voltage detection circuit 221 is configured to detect a voltage difference between the bootstrap node BST and the switch node SW, and compare the voltage difference with a first threshold voltage to output a detection signal ctrl bst according to a comparison result. An initial level of the detection signal ctrl bst is a first level, and the detection signal ctrl bst flips to a second level when the voltage difference between the bootstrap node BST and the switch node SW is detected to be lower than the first threshold voltage.

[0054] Further, the turning on and turning off of the voltage detection circuit 221 is controlled by the control signal ctrl hs, and the voltage detection circuit 221 turns on when the control signal ctrl hs is the first level (i.e., the main switch HS turns on), and turns off when the control signal ctrl hs is the second level (i.e., the main switch HS turns off), thereby reducing the power consumption of the switching converter 200. The turning on and turning off of the voltage detection circuit 221 is achieved by, for example, a switch.

[0055] Further, the logic control unit 212 also receives the detection signal ctrl bst, and outputs a control signal ctrl hs1 of the second level to control the main switch HS to turn off, and outputs a control signal ctrl ls of the first level to control the synchronous switch LS to turn on when the detection signal ctrl bst is the second level. At this time, the driving unit 223 receives the control signal ctrl hs, and outputs the driving signal hs on to drive the main switch HS to turn on and turn off. Specifically, the main switch HS turns on when the control signal ctrl hs is the first level, and the main switch HS turns off when the control signal ctrl hs is the second level.

[0056] Further, the main switch tube driving circuit 220 further comprises a logic unit 222. The logic unit 222 is configured to perform AND operation on the detection signal ctrl_bst and the control signal ctrl_hs to obtain a control signal ctrl_hs_a. The logic unit 260 is implemented by an AND gate for example. By setting the logic unit 260, it can be ensured that the main switch tube HS is turned on only after the voltage detection circuit 221 is turned on, thereby improving the reliability of the circuit. At this time, the driving unit 223 no longer receives the control signal ctrl_hs, but receives the control signal ctrl_hs_a, i.e., the driving unit 223 receives the control signal ctrl_hs_a and outputs the driving signal hs_on to drive the turn-on and turn-off of the main switch tube HS. Specifically, when the control signal ctrl_hs_a is at the first level, the main switch tube HS is turned on, and when the control signal ctrl_hs_a is at the second level, the main switch tube HS is turned off.

[0057] FIG. 4 shows a timing diagram of the switching converter according to an embodiment of the present application.

[0058] Referring to FIG. 4, when the feedback voltage Vfb is reduced from being greater than the reference voltage Vref to being less than the reference voltage Vref, the control signal ctrl_hs1 has a rising edge, and the rising edge of the control signal ctrl_hs is delayed by a set time t1 from the rising edge of the control signal ctrl_hs1. Within the set time t1 after the control signal ctrl_hs1 has the rising edge and before the control signal ctrl_hs has the rising edge, the clock signal Φ1 first flips to the low level to control the charge pump circuit 240 to be in the pumping state in the first sub-time period, and then the clock signal Φ1 flips to the high level to control the charge pump circuit 240 to be in the charging state in the second sub-time period. After the rising edge of the control signal ctrl_hs arrives, the clock signal Φ1 flips to the low level again to control the charge pump circuit 240 to be in the pumping state, and after the falling edge of the control signal ctrl_hs1 arrives, the falling edge of the control signal ctrl_hs arrives synchronously, at which time the clock signal Φ1 flips to the high level to control the charge pump circuit 240 to be in the charging state.

[0059] The switching converter 200 provided by the embodiment of the present application delays the rising edge of the control signal ctrl_hs1 by the set time t1 to output as the control signal ctrl_hs, and pre-charges the bootstrap capacitor Cbst within the set time t1 to ensure that when the main switch tube HS is switched from being turned off to being turned on, the bootstrap node BST can normally supply power to the main switch tube driving circuit 220.

[0060] Further, in the setting time t1, the bootstrap capacitor Cbst is charged first, and then the charge pump capacitor Cbump is charged, so that the voltages of the two are both charged high. Then, when the rising edge of the control signal ctrl_hs appears, the bootstrap capacitor Cbst is charged again, so that when the main switch HS is turned on, the bootstrap capacitor Cbst is still charged through the charge pump capacitor Cbump in the power-off process. The power-off speed of the bootstrap capacitor Cbst can be reduced, the time of the main switch HS being turned on continuously can be increased, the opening frequency of the voltage detection circuit 240 and the starting frequency of the charge pump circuit 250 can be reduced, and the light load efficiency can be improved.

[0061] In accordance with the embodiments of the present application as described above, the embodiments do not describe all the details and are not limited to the specific embodiments. It is obvious that many modifications and changes can be made according to the above description. The embodiments are selected and specifically described in this specification in order to better explain the principles and practical applications of the present application, so that those skilled in the art can well utilize the present application and make modifications and uses based on the present application. The protection scope of the present application should be defined by the claims of the present application and the equivalent scope thereof.

Claims

1. A driving circuit of a switching converter, the switching converter comprising a main switch connected between an input and a switching node, the main switch being configured to control the transfer of electrical energy from the input to an output to convert an input voltage to an output voltage, the driving circuit comprising: a logic control circuit configured to generate a first control signal based on the output voltage and to perform an edge delay on the first control signal to obtain a second control signal, the second control signal being configured to control the turn-on and turn-off time of the main switch; a main switch driving circuit connected to a control terminal of the main switch and configured to drive the turn-on and turn-off of the main switch according to the second control signal; a bootstrap capacitor connected between a bootstrap node and the switching node, the bootstrap node being configured to supply power to the main switch driving circuit; a charge pump circuit connected to the bootstrap node and configured to charge the bootstrap capacitor, wherein the edge delay refers to a delay on an edge of the first control signal that controls the turn-on of the main switch, the delay time being a set time, and the charge pump circuit is further configured to pre-charge the bootstrap capacitor within the set time. The charge pump circuit comprises a charge pump capacitor. The charge pump circuit has a charging state for charging the charge pump capacitor and a pumping state for charging the bootstrap capacitor, in a first sub-time period of the set time, the charge pump circuit is in the pumping state, and in a second sub-time period of the set time, the charge pump circuit is in the charging state. In the turn-on of the main switch, the charge pump circuit is in the pumping state. The charge pump circuit comprises: a first diode having an anode connected to an input voltage of the switching converter; a second diode having an anode connected to a cathode of the first diode and a cathode connected to the bootstrap node; a first switch connected between a cathode of the first diode and a ground in sequence with the charge pump capacitor; and a second switch connected between the input voltage of the switching converter and a common node of the charge pump capacitor and the first switch. The charge pump circuit further comprises: a switch control unit configured to control the working state of the charge pump circuit by controlling the turn-on and turn-off of the first switch and the second switch, wherein when the switch control unit controls the first switch to be turned off and the second switch to be turned on, the charge pump circuit is in the pumping state to charge the bootstrap capacitor through the second diode by the charge pump capacitor; and when the switch control unit controls the first switch to be turned on and the second switch to be turned off, the charge pump circuit is in the charging state to charge the charge pump capacitor by the input voltage.

2. The drive circuit of claim 1, wherein, ​ ​ ​ 3. The drive circuit of claim 2, wherein, ​ ​ ​ ​ ​ 4. The drive circuit of claim 3, wherein, ​ ​ ​ ​ 5. The drive circuit of claim 4, wherein, The switch control unit comprises a timer, the switch control unit controls the timer to start timing when the first control signal appears at the edge of controlling the main switch tube to be turned on, and controls the charge pump circuit to be in a pumping state; and controls the charge pump circuit to switch to a charging state when the timing time of the timer reaches a first sub-time, controls the charge pump circuit to switch to the pumping state again when the timing time of the timer reaches the set time, wherein the time interval between the set time and the first sub-time is the second sub-time.

6. The drive circuit of claim 4, wherein, The switch control unit comprises a timer, the switch control unit controls the timer to start timing when the first control signal appears at the edge of controlling the main switch tube to be turned on, and controls the charge pump circuit to be in a pumping state; and controls the charge pump circuit to switch to a charging state when the timing time of the timer reaches a first sub-time, controls the charge pump circuit to switch to the pumping state again when the timing time of the timer reaches the set time, wherein the time interval between the set time and the first sub-time is the second sub-time.

7. The drive circuit of claim 4, wherein, The logic control circuit comprises: a comparator, configured to compare a feedback voltage of the switch converter output voltage with a reference voltage to output a pulse width modulation signal according to a comparison result; a logic control unit, configured to receive the pulse width modulation signal and output the first control signal; a delay unit, configured to perform edge delay on the first control signal to obtain a second control signal.

8. The drive circuit of claim 7, wherein, The main switch tube driving circuit comprises: a voltage detection circuit, configured to detect a voltage difference between the bootstrap node and the switch node, and output a detection signal according to a comparison result of the voltage difference and a first threshold voltage; a driving unit, connected with a control end of the main switch tube, configured to drive the main switch tube to be turned on and turned off, wherein the voltage detection circuit is turned on when the main switch tube is turned on, and is turned off when the main switch tube is turned off, an initial value of the detection signal is a first level, and the detection signal is flipped to a second level when the voltage detection circuit detects that the voltage difference is reduced to be less than the first threshold voltage.

9. The driving circuit of claim 8, further comprising: a logic unit, configured to perform AND operation on the detection signal and a second control signal to obtain a third control signal; wherein the driving unit receives the third control signal or the second control signal, and outputs a driving signal to drive the main switch tube to be turned on and turned off.

10. A switch converter, comprising: a main switch tube, connected between an input end and a switch node; a synchronous switch tube, connected between the switch node and a ground end; an inductor, connected between the switch node and an output end; and the driving circuit of any one of claims 1-9. ​

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