Switching converter and driving circuit thereof

Abstract

The invention discloses a switching converter and a driving circuit thereof, and the driving circuit comprises a logic control circuit which is used for generating a first control signal according to an output voltage, and carrying out the edge delay of the first control signal to obtain a second control signal, and the second control signal is used for controlling the on and off of a main switching tube; the main switch tube driving circuit is connected with the control end of the main switch tube and is used for driving the main switch tube to be switched on and switched off according to the second control signal; the bootstrap capacitor is connected between a bootstrap node and the switch node, and the bootstrap node is used for supplying power to the main switch tube driving circuit; the charge pump circuit is connected with the bootstrap node and is used for charging the bootstrap capacitor, the edge delay refers to edge delay for controlling conduction of the main switch tube, the delay time is set time, and the charge pump circuit also pre-charges the bootstrap capacitor within the set time to ensure that when the main switch tube is switched from turn-off to turn-on, the bootstrap capacitor is switched to turn-on from turn-off to turn-on. The bootstrap node can normally supply power to the main switch tube driving circuit.

Description

Technical Field

[0001] The present invention relates to the technical field of integrated circuits, and in particular to a switching converter and a driving circuit thereof. Background Art

[0002] For a buck converter in which both the main switch tube and the synchronous switch tube use NMOS tubes, a bootstrap capacitor is usually required to form a bootstrap voltage to power the main switch tube.

[0003] In order to make the switching converter work normally when the input voltage Vin is close to the output voltage Vout, it is necessary to integrate a charge pump circuit 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 tube is normally open. When the bootstrap capacitor is charged to the preset value, the charge pump circuit will enter a dormant state. However, the switching converter of the prior art needs to frequently turn off the main switch tube to start the charge pump circuit to charge the bootstrap capacitor when the input voltage Vin is low, in no-load or light-load mode, especially when the high-temperature leakage is large, resulting in large losses and affecting the light-load efficiency. In addition, the voltage detection circuit that detects the voltage difference between the two plates of the bootstrap capacitor also needs to work all the time, which will also cause certain losses.

[0004] Therefore, a new switching converter is needed to solve the above problems. Summary of the invention

[0005] In view of the above problems, an object of the present invention is to provide a switching converter and a driving circuit thereof, so as to ensure that when the main switch tube is switched from off to on, the bootstrap node can normally supply power to the main switch tube driving circuit.

[0006] According to one aspect of the present invention, a driving circuit of a switching converter is provided, wherein the switching converter comprises a main switch connected between an input terminal and a switch node, the main switch being used to control the transmission of electric energy from the input terminal to the output terminal so as to convert an input voltage into an output voltage, the driving circuit comprising a logic control circuit for generating a first control signal according to the output voltage, and performing an edge delay on the first control signal to obtain a second control signal, the second control signal being used to control the on and off moments of the main switch; a main switch driving circuit connected to the control terminal of the main switch and used to drive the on and off moments of the main switch according to the second control signal; a bootstrap capacitor connected between a bootstrap node and the switch node, the bootstrap node being used to supply power to the main switch driving circuit; and a charge pump circuit connected to the bootstrap node and used to charge the bootstrap capacitor, wherein the edge delay refers to the edge delay for controlling the on-state of the main switch, the delay time is a set time, and the charge pump circuit is further used to pre-charge the bootstrap capacitor within the set time.

[0007] Optionally, the charge pump circuit includes 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 a pumping state, and in a second sub-time period of the set time, the charge pump circuit is in a charging state; when the main switch tube is turned on, the charge pump circuit is in a pumping state.

[0008] Optionally, the charge pump circuit includes a first diode, whose anode is connected to the input voltage of the switching converter; a second diode, whose anode is connected to the cathode of the first diode and whose cathode is connected to the bootstrap node; a first switch, wherein the charge pump capacitor and the first switch are connected in sequence between the cathode of the first diode and the ground terminal; and a second switch, connected between the input voltage of the switching converter and a common node between the charge pump capacitor and the first switch.

[0009] Optionally, the charge pump circuit also includes a switch control unit, which controls 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 turned off and the second switch to be turned on, the charge pump circuit is in a pumping state so that the charge pump capacitor charges the bootstrap capacitor through the second diode; 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 a charging state so that the input voltage charges the charge pump capacitor.

[0010] Optionally, the switch control unit includes a timer, and when the first control signal appears an edge that controls the main switch tube to be turned on, the switch control unit starts timing the timer and controls the charge pump circuit to be in a pumping state; and when the timing time of the timer reaches a first sub-time, the charge pump circuit is controlled to switch to a charging state, and when the timing time of the timer reaches the set time, the charge pump circuit is controlled to switch to a pumping state again, wherein the time interval between the set time and the first sub-time is the second sub-time.

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

[0012] Optionally, the logic control circuit includes a comparator for comparing the feedback voltage of the output voltage of the switching converter with a reference voltage to output a pulse width modulation signal according to the 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.

[0013] Optionally, the main switch tube driving circuit includes a voltage detection circuit, which is used to detect the voltage difference between the bootstrap node and the switch node, and output a detection signal according to the comparison result of the voltage difference and the first threshold voltage; a driving unit, which is connected to the control end of the main switch tube, and is used to drive the main switch tube to be turned on and 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, the initial value of the detection signal is a first level, and when the voltage detection circuit detects that the voltage difference is reduced to less than the first threshold voltage, the detection signal is flipped to a second level.

[0014] Optionally, the driving circuit also includes: a logic unit, used to perform an AND operation on the detection signal and the 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 off.

[0015] According to another aspect of the present invention, a switching converter is provided, comprising a main switch tube connected between an input terminal and a switch node; a synchronous switch tube connected between the switch node and a ground terminal; an inductor connected between the switch node and an output terminal; and a drive circuit as described above.

[0016] The switching converter and its driving circuit provided by the present invention include a logic control circuit, which is used to generate a first control signal according to an output voltage, and delay the rising edge of the first control signal to obtain a second control signal, wherein the second control signal is used to control the on and off moments of the main switch tube; a main switch tube driving circuit, which is connected to the control end of the main switch tube, and is used to drive the on and off of the main switch tube according to the second control signal; a bootstrap capacitor, which is connected between a bootstrap node and a switch node, and the bootstrap node is used to supply power to the main switch tube driving circuit; a charge pump circuit, which is connected to the bootstrap node, and is used to charge the bootstrap capacitor, wherein the delay time is a set time, and the charge pump circuit is also used to pre-charge the bootstrap capacitor within the set time to ensure that when the main switch tube is switched from off to on, the bootstrap node can supply power to the main switch tube driving circuit normally.

[0017] In a preferred embodiment, by putting the charge pump circuit in a pumping state in the first sub-time period within the set time, putting the charge pump circuit in a charging state in the second sub-time period within the set time, and putting the charge pump circuit in a pumping state when the main switch tube is turned on, the power-off speed of the bootstrap capacitor can be reduced, the continuous conduction time of the main switch tube can be increased, and the light-load efficiency of the switching converter can be improved.

[0018] In a preferred embodiment, the main switch tube driving circuit includes a voltage detection circuit. The voltage detection circuit is turned on only when the main switch tube is turned on, which can reduce the power consumption of the switching converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The above and other objects, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

[0020] Figure 1 A schematic structural diagram of a switching converter is shown;

[0021] Figure 2 Shows Figure 1 The circuit diagram of the switching converter shown;

[0022] Figure 3 A circuit diagram of a switching converter according to an embodiment of the present invention is shown;

[0023] Figure 4 FIG. 4 shows a timing diagram of a switching converter according to an embodiment of the present invention. DETAILED DESCRIPTION

[0024] Various embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. In each of the accompanying drawings, the same elements or modules are represented by the same or similar reference numerals. For the sake of clarity, the various parts in the accompanying drawings are not drawn to scale.

[0025] It should be understood that in the following description, a "circuit" may include a single or multiple combined hardware circuits, programmable circuits, state machine circuits, and / or elements capable of storing instructions executed by programmable circuits. When an element or circuit is said to be "connected to" another element or an element or circuit is said to be "connected between" two nodes, it may be directly coupled or connected to another element or there may be an intermediate element, and the connection between the elements may be physical, logical, or a combination thereof. Conversely, when an element is said to be "directly coupled to" or "directly connected to" another element, it means that there is no intermediate element between the two.

[0026] At the same time, certain words are used in this patent specification and claims to refer to specific components. It should be understood by those skilled in the art that hardware manufacturers may use different terms to refer to the same component. This patent specification and claims do not use differences in names as a way to distinguish components, but rather use differences in components' functions as the criteria for distinction.

[0027] In addition, it should be noted that, in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or equipment. In the absence of more restrictions, the elements defined by the statement "comprise one..." do not exclude the existence of other identical elements in the process, method, article or equipment including the elements.

[0028] Figure 1 A circuit diagram of a switching converter is shown. Figure 1The switching converter 100 includes a power circuit and a driving circuit. The power circuit includes a main switch tube HS and a synchronous switch tube 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 tube HS and the synchronous switch tube LS, that is, a switch 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 an input voltage Vin, and the output terminal provides an output voltage Vout.

[0029] In addition, the switching converter 100 further includes a voltage divider network composed of resistors R1 and R2 , which is used to obtain a feedback voltage Vfb of the output voltage Vout.

[0030] The driving circuit includes 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 .

[0031] The comparator 160 is used to compare the feedback voltage Vfb with the reference voltage Vref to obtain the pulse width modulation signal PWM according to the comparison result. The logic control circuit 110 is used to receive the pulse width modulation signal PWM and the detection signal ctrl_bst, and provide the control signal ctrl_hs and the control signal ctrl_ls. The driving unit 120 is connected between the bootstrap node BST and the switch node SW, and is used to generate the driving signal hs_on according to the control signal ctrl_hs to control the on and off of the main switch tube HS. The driving unit 130 is connected between the power supply voltage Vdd and the ground terminal, and is used to generate the driving signal ls_on according to the control signal ctrl_ls to control the on and off of the synchronous switch tube LS. In each switching cycle, the main switch tube HS and the synchronous switch tube LS are alternately turned on and off, and the inductor L is charged and discharged, thereby providing a DC output voltage Vout at the output terminal.

[0032] The bootstrap capacitor Cbst is connected between the bootstrap node BST and the switch node SW. The voltage detection circuit 140 is used to detect the voltage difference between the bootstrap node BST and the switch node SW, and compare the voltage difference with a first threshold voltage and a second threshold voltage, so as to output a detection signal ctrl_bst according to the comparison result, wherein when the voltage difference between the bootstrap node BST and the switch node SW increases to be greater than the second threshold voltage, the detection signal ctrl_bst flips to a first level, and when the voltage difference between the bootstrap node BST and the switch node SW decreases to be less than the first threshold voltage, the detection signal ctrl_bst flips to a second level, and the second threshold voltage is greater than the first threshold voltage. When the detection signal ctrl_bst is at the second level, the logic control circuit 110 outputs a control signal ctrl_hs at the second level to turn off the main switch tube HS, and outputs a control signal ctrl_ls at the first level to turn on the synchronous switch tube LS.

[0033] The charge pump circuit 150 is used to charge the bootstrap capacitor Cbst when the main switch HS is turned off.

[0034] Figure 2 Shows Figure 1 The circuit diagram of the switching converter is shown in Figure 1. Figure 2 The logic control circuit 110 , the resistor R1 , the resistor R2 , and the comparator 160 are not shown.

[0035] See also Figure 2 The charge pump circuit 150 includes 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 between the cathode of the diode D2 and the ground terminal in sequence, and the switch S2 is connected between the input voltage Vin and the intermediate node between the charge pump capacitor Cpunp and the switch S1.

[0036] When the main switch tube HS is turned off, the switch S1 is turned off and the switch S2 is turned on to pump up 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 tube HS is turned on, the switch S1 is turned on and the switch S2 is turned off to charge the charge pump capacitor Cpunp through the input voltage Vin.

[0037] When the input voltage Vin of the switching converter 100 is relatively low, in no-load or light-load mode, especially when the high-temperature leakage is large, the main switch tube HS needs to be frequently turned off to start the charge pump circuit 150 to charge the bootstrap capacitor Cbst, resulting in large 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.

[0038] Figure 3 A circuit diagram of a switching converter according to an embodiment of the present invention is shown.

[0039] See also Figure 3 The switching converter 200 includes a power circuit and a driving circuit. The power circuit includes a main switch tube HS and a synchronous switch tube 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 tube HS and the synchronous switch tube LS, that is, a switch 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 an input voltage Vin, and the output terminal provides an output voltage Vout. The main switch tube HS is used to control the transmission of electric energy from the input terminal to the output terminal to convert the input voltage Vin into an output voltage Vout.

[0040] In addition, the switching converter 200 further includes a voltage divider network composed of resistors R1 and R2, which is used to obtain a feedback voltage Vfb of the output voltage Vout.

[0041] The driving circuit includes a logic control circuit 210, a main switch tube driving circuit 220, a driving unit 230, a bootstrap capacitor Cbst and a charge pump circuit 240. The logic control circuit 210 is used to generate a control signal ctrl_hs1 according to the output voltage Vout, and edge delay the control signal ctrl_hs1 to obtain a control signal ctrl_hs, and the control signal ctrl_hs is used to control the on and off moments of the main switch tube, wherein the delay time is the set time t1. The main switch tube driving circuit 220 is connected to the control end of the main switch tube HS, and is used to drive the main switch tube HS to be turned on and off according to the control signal ctrl_hs. The bootstrap capacitor Cbst is connected between the bootstrap node BST and the switch node SW, and the bootstrap node BST is used to power the main switch tube driving circuit 220. The charge pump circuit 240 is connected to the bootstrap node BST and is used to charge the bootstrap capacitor Cbst. The charge pump circuit 240 is also used to pre-charge the bootstrap capacitor Cbst within a set time t1.

[0042] The charge pump circuit 240 has a charging state and a pumping state. In the first sub-period of the set time t1, the charge pump circuit 240 is in the pumping state. In the second sub-period of the set time t1, the charge pump circuit 240 is in the charging state. When the main switch tube HS is turned 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.

[0043] The logic control circuit 210 includes a comparator 211, a logic control unit 212, and a delay unit 213. The comparator 211 is used to compare the feedback voltage Vfb of the output voltage Vout with the reference voltage Vref to obtain a pulse width modulation signal PWM according to the comparison result. The logic control unit 212 is used to receive the pulse width modulation signal PWM, and provide a control signal ctrl_hs for controlling the main switch tube HS to be turned on and off and a control signal ctrl_ls for controlling the synchronous switch tube LS to be turned on and off, wherein the control signal ctrl_hs and the control signal ctrl_ls are, for example, pulse width modulation signals. The control signal ctrl_hs, for example, controls the main switch tube HS to be turned on at a first level, and controls the main switch tube HS to be turned off 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, and when the first level is a low level, the second level is a high level. In the following, the embodiment of the present invention is described by taking the first level as a high level and the second level as a low level as an example. The input end of the delay unit 213 receives the control signal ctrl_hs1, and the output end provides the control signal ctrl_hs. The delay unit 213 is used to perform edge delay on the control signal ctrl_hs1 to obtain the control signal ctrl_hs, wherein the delay time is the set time t1, and the edge delay refers to the edge delay for controlling the main switch tube HS to be turned on. When encountering the edge for controlling the main switch tube HS to be turned off, the delay unit 213 directly outputs the control signal ctrl_hs1 as the control signal ctrl_hs. For example, the edge delay for controlling the main switch tube HS to be turned on is the rising edge, and the edge delay is the rising edge delay.

[0044] The driving unit 230 is connected between the power supply voltage Vdd and the ground terminal, and is used to generate a driving signal ls_on according to the control signal ctrl_ls to drive the synchronous switch tube LS to turn on and off. The control signal ctrl_ls, for example, controls the synchronous switch tube LS to turn on when it is at a first level. In each switching cycle, the main switch tube HS and the synchronous switch tube LS are alternately turned on and off to charge and discharge the inductor L, thereby providing a DC output voltage Vout at the output terminal.

[0045] The charge pump circuit 240 includes a charge pump unit and a switch control unit 241. The charge pump unit includes 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 between the cathode of the diode D2 and the ground terminal in sequence, 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.

[0046] The switch control unit 241 controls the operation 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 turned off and the switch S2 to be turned on, the charge pump circuit 240 is in a pumping state to bootstrap the charge pump capacitor Cpunp, so that the charge pump capacitor Cpunp charges the bootstrap capacitor Cbst through the diode D1; and when the switch control unit 241 controls the switch S1 to be turned on and the switch S2 to be turned off, the charge pump circuit 240 is in a charging state to charge the charge pump capacitor Cbump through the input voltage Vin.

[0047] Optionally, the switch control unit 241 controls the working state of the charge pump circuit 240 only according to the control signal ctrl_hs1. 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 has a rising edge, and controls the charge pump circuit 240 to be in a pumping state; and when the timing time of the timer reaches the first sub-time, the charge pump circuit 240 is controlled to switch to a charging state, and when the timing time of the timer reaches the set time t1, the charge pump circuit 240 is controlled to switch to a pumping state again, wherein the time interval between the set time t1 and the first sub-time is the second sub-time.

[0048] 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 has a rising edge, and controls the charge pump circuit 240 to be in a pumping state; and when the timing time of the timer reaches a first sub-time, the charge pump circuit 240 is controlled to switch to a charging state, and when the control signal ctrl_hs has a rising edge, the charge pump circuit 240 is controlled to switch to a pumping state again, wherein the time interval between the time when the control signal ctrl_hs has a rising edge and the first sub-time is a second sub-time.

[0049] The switch control unit 241 controls the on and off of the switches S1 and S2 respectively by generating a clock signal Φ1 and a clock signal Φ1_b, thereby controlling the working state of the charge pump circuit 240. The clock signal Φ1 and the clock signal Φ1_b are in anti-phase.

[0050] Optionally, the switch control unit 241 may not be arranged in the charge pump circuit 240 , and may be arranged separately or inside the logic control circuit 210 .

[0051] Optionally, the delay unit 213 may not be arranged inside the logic control circuit 210 , and may be arranged separately or in the charge pump circuit 240 .

[0052] The main switch tube 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 used to generate a driving signal hs_on according to the control signal ctrl_hs to drive the main switch tube HS to turn on and off. The voltage detection circuit 221 is used to detect the voltage difference between the bootstrap node BST and the switch node SW, and compare the voltage difference with the first threshold voltage to output a detection signal ctrl_bst according to the comparison result. Among them, the initial level of the detection signal ctrl_bst is the first level. When it is detected that the voltage difference between the bootstrap node BST and the switch node SW is reduced to less than the first threshold voltage, the detection signal ctrl_bst is flipped to the second level.

[0053] Furthermore, the voltage detection circuit 221 is turned on and off by the control signal ctrl_hs, and is turned on when the control signal ctrl_hs is at the first level (i.e., the main switch tube HS is turned on), and is turned off when the control signal ctrl_hs is at the second level (i.e., the main switch tube HS is turned off), thereby reducing the power consumption of the switching converter 200. The voltage detection circuit 221 is turned on and off, for example, by a switch.

[0054] Further, the logic control unit 212 also receives the detection signal ctrl_bst. When the detection signal ctrl_bst is at the second level, the logic control unit 212 outputs the control signal ctrl_hs1 at the second level to control the main switch tube HS to be turned off, and outputs the control signal ctrl_ls at the first level to control the synchronous switch tube LS to be turned on. 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 tube HS to be turned on and off. Specifically, when the control signal ctrl_hs is at the first level, the main switch tube HS is turned on, and when the control signal ctrl_hs is at the second level, the main switch tube HS is turned off.

[0055] Further, the main switch tube driving circuit 220 also includes a logic unit 222. The logic unit 222 is used to perform an AND operation on the detection signal ctrl_bst and the control signal ctrl_hs to obtain the control signal ctrl_hs_a. The logic unit 260 is implemented, for example, by an AND gate. 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, that is, the driving unit 223 receives the control signal ctrl_hs_a and outputs the driving signal hs_on to drive the main switch tube HS to be turned on and off. Specifically, when the control signal ctrl_hs_a is at a first level, the main switch tube HS is turned on, and when the control signal ctrl_hs_a is at a second level, the main switch tube HS is turned off.

[0056] Figure 4 FIG. 4 shows a timing diagram of a switching converter according to an embodiment of the present invention.

[0057] See also Figure 4, when the feedback voltage Vfb decreases from greater than the reference voltage Vref to 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 setting time t1 than the rising edge of the control signal ctrl_hs1. After the control signal ctrl_hs1 has a rising edge, within the setting time t1 before the control signal ctrl_hs has a rising edge, the clock signal Φ1 first flips to a low level to control the charge pump circuit 240 to be in a pumping state in the first sub-time period, and then the clock signal Φ1 flips to a high level to control the charge pump circuit 240 to be in a 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 a low level again to control the charge pump circuit 240 to be in a 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, and at this time, the clock signal Φ1 flips to a high level to control the charge pump circuit 240 to be in a charging state.

[0058] The switching converter 200 provided in the embodiment of the present invention delays the rising edge of the control signal ctrl_hs1 by the set time t1 and outputs it 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 off to on, the bootstrap node BST can normally supply power to the main switch tube driving circuit 220.

[0059] Furthermore, within the set time t1, the bootstrap capacitor Cbst is charged first, and then the charge pump capacitor Cbump is charged to raise the voltages of both. Thereafter, when the rising edge of the control signal ctrl_hs appears, the bootstrap capacitor Cbst is charged again, so that when the main switch tube HS is turned on, the bootstrap capacitor Cbst will still be charged through the charge pump capacitor Cbump during the power-off process, which can reduce the power-off speed of the bootstrap capacitor Cbst, increase the continuous conduction time of the main switch tube HS, reduce the turn-on frequency of the voltage detection circuit 240 and the start-up frequency of the charge pump circuit 250, and improve the light load efficiency.

[0060] According to the embodiments of the present invention, as described above, these embodiments do not describe all the details in detail, nor do they limit the invention to specific embodiments. Obviously, many modifications and changes can be made based on the above description. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can make good use of the present invention and the modified use based on the present invention. The scope of protection of the present invention shall be based on the scope defined by the claims of the present invention and their equivalents.

Claims

1. A driving circuit of a switching converter, the switching converter comprising a main switch connected between an input terminal and a switch node, the main switch being used to control the transmission of electric energy from the input terminal to the output terminal so as to convert an input voltage into an output voltage, the driving circuit comprising: A logic control circuit, used for generating a first control signal according to the output voltage, and performing 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 timings of the main switch tube; a main switch tube driving circuit, connected to the control end of the main switch tube, and used for driving the main switch tube to be turned on and off according to the second control signal; A bootstrap capacitor connected between a bootstrap node and the switch node, the bootstrap node being used to supply power to the main switch tube drive circuit; a charge pump circuit connected to the bootstrap node and configured to charge the bootstrap capacitor, The edge delay refers to the edge delay for controlling the conduction of the main switch tube, the delay time is a set time, and the charge pump circuit is also used to pre-charge the bootstrap capacitor within the set time.

2. The driving circuit according to claim 1, wherein: The charge pump circuit includes 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, the charge pump circuit is in the pumping state in a first sub-period of the set time, and the charge pump circuit is in the charging state in a second sub-period of the set time; When the main switch tube is turned on, the charge pump circuit is in a pumping state.

3. The driving circuit according to claim 2, wherein: 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, an anode of which is connected to the cathode of the first diode, and a cathode of which is connected to the bootstrap node; A first switch, wherein the charge pump capacitor and the first switch are sequentially connected between the cathode of the first diode and a ground terminal; The second switch is connected between the input voltage of the switching converter and a common node between the charge pump capacitor and the first switch.

4. The driving circuit according to claim 3, wherein: The charge pump circuit further includes: a switch control unit, controlling the operating 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 turned off and the second switch to be turned on, the charge pump circuit is in a pumping state, so that the charge pump capacitor charges the bootstrap capacitor through the second diode; 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 a charging state, so that the input voltage charges the charge pump capacitor.

5. The driving circuit according to claim 4, wherein: The switch control unit includes a timer, and when the first control signal has an edge that controls the main switch tube to be turned on, the switch control unit starts timing the timer and controls the charge pump circuit to be in a pumping state; and when the timing time of the timer reaches a first sub-time, the charge pump circuit is controlled to switch to a charging state, and when the timing time of the timer reaches the set time, the charge pump circuit is controlled to switch to a pumping state again, wherein the time interval between the set time and the first sub-time is the second sub-time.

6. The driving circuit according to claim 4, wherein: The switch control unit includes a timer, and when the first control signal has an edge that controls the main switch tube to be turned on, the switch control unit starts timing the timer and controls the charge pump circuit to be in a pumping state; and when the timing time of the timer reaches a first sub-time, the charge pump circuit is controlled to switch to a charging state, and when the second control signal has an edge that controls the main switch tube to be turned on, the charge pump circuit is controlled to switch to a pumping state again, wherein the time interval between the time when the edge that controls the main switch tube to be turned on appears and the first sub-time is the second sub-time.

7. The driving circuit according to claim 4, wherein: The logic control circuit comprises: A comparator, used for comparing a feedback voltage of the output voltage of the switching converter with a reference voltage, so as 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 is used to perform edge delay on the first control signal to obtain a second control signal.

8. The driving circuit according to 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 to the control end of the main switch tube and used to drive the main switch tube to be turned on and off, In which, 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. The initial value of the detection signal is a first level. When the voltage detection circuit detects that the voltage difference is reduced to less than the first threshold voltage, the detection signal flips to a second level.

9. The driving circuit according to claim 8, further comprising: a logic unit, configured to perform an AND operation on the detection signal and the second control signal to obtain a third control signal; 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 off.

10. A switching converter, comprising: A main switch tube connected between the input terminal and the switch node; A synchronous switch tube connected between the switch node and the ground terminal; an inductor connected between the switch node and the output terminal; as well as A drive circuit as claimed in any one of claims 1 to 9.

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