A control method of a switching circuit, a control circuit, and a switching circuit

Abstract

The application discloses a control method and control circuit of a switching circuit and the switching circuit; output feedback and a reference voltage are subjected to operational amplification to obtain a compensation voltage; the switching circuit works in a valley current mode; when the off time of a main switch tube is less than or equal to a first off threshold, the compensation voltage is added to a bias voltage to obtain a bias compensation voltage; the main switch tube is off; when the inductor current sampling value drops to the bias compensation voltage, the main switch tube changes from off to on; the application realizes stable and reliable modulation of the output voltage of the switching converter under the condition of the limit duty ratio by a new control mode and modulation strategy of the switching circuit, and the output of the operational amplifier can be compared with the inductor current sampling value at any time.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of power electronics, in particular to a control method of a switching circuit, a control circuit and the switching circuit. BACKGROUND

[0002] The conventional switching circuit will have a duty cycle hitting the limit duty cycle when the input voltage and the output voltage are very close, so that the output of the operational amplifier cannot be reliably compared with the signal generating the duty cycle, resulting in the closed loop losing control of the output voltage.

[0003] The four-switch Buck-Boost step-up and step-down circuit topology is shown in Figure 1 The four-switch step-up and step-down circuit includes a first switch S1, a second switch S2, a third switch S3, a fourth switch S4 and an inductor L, the first switch S1 and the second switch S2 are connected in series, the common end of the first switch S1 and the second switch S2 is a first node SW1, the first switch S1 is connected to the input end VIN, the second switch S2 is connected to the ground, the third switch S3 and the fourth switch S4 are connected in series, the common end of the third switch S3 and the fourth switch S4 is a second node SW2, the fourth switch S4 is connected to the output end VOUT, the third switch S3 is connected to the ground, and the inductor L is connected between the first node SW1 and the second node SW2. When the four-switch step-up and step-down circuit works in BUCK-BOOST mode, the second switch S2 and the fourth switch S4 are turned on, and when the inductor current sampling value drops to the compensation voltage, the second switch S2 and the fourth switch S4 are turned off, and the first switch S1 and the third switch S3 are turned on. When the input voltage and the output voltage are very close, the duty cycle will hit the limit duty cycle, so that the output of the error amplifier cannot be compared with the signal generating the duty cycle, resulting in the closed loop losing control of the output voltage, and the boost working mode and the buck working mode are switched back and forth, and the inductor current waveform is shown in Figure 2 . SUMMARY

[0004] Therefore, the purpose of the present application is to provide a control method of a switching circuit, a control circuit and the switching circuit, to solve the problem that the existing technology has a duty cycle hitting the limit duty cycle when the input voltage and the output voltage are very close, so that the output of the operational amplifier cannot be compared with the signal generating the duty cycle, resulting in the closed loop losing control of the output voltage.

[0005] The technical solution of the present application is to provide a control method of a switching circuit, the switching circuit working in valley current mode:

[0006] The output feedback and the reference voltage are amplified by the operational amplifier to obtain a compensation voltage;

[0007] When the turn-off time of the main switch is less than or equal to the first turn-off threshold, the compensation voltage is added to the bias voltage to obtain a bias compensation voltage; and when the inductor current sample value drops to the bias compensation voltage, the main switch is turned on from being turned off.

[0008] As an option, the switching circuit is a four-switch boost-buck circuit; the four-switch boost-buck circuit comprises a first switch, a second switch, a third switch, a fourth switch and an inductor, the first switch and the second switch are connected in series, a common end of the first switch and the second switch is a first node, the first switch is connected to an input end, the second switch is connected to a ground, the third switch and the fourth switch are connected in series, a common end of the third switch and the fourth switch is a second node, the fourth switch is connected to an output end, the third switch is connected to the ground, and the inductor is connected between the first node and the second node; the four-switch boost-buck circuit works in a BUCK-BOOST mode, the second switch and the fourth switch are turned on, and when the inductor current sample value drops to a compensation voltage, the second switch and the fourth switch are turned off, and the first switch and the third switch are turned on.

[0009] When the time during which the second switch and the fourth switch are simultaneously turned on is less than or equal to the first turn-off threshold, the compensation voltage is added to the bias voltage to obtain a bias compensation voltage; and when the inductor current sample value drops to the bias compensation voltage, the second switch and the fourth switch are turned off, and the first switch and the third switch are turned on.

[0010] As an option, the bias voltage is related to the inductor current slope and the turn-off time of the main switch, and when the switching circuit is a four-switch boost-buck circuit, the turn-off time of the main switch corresponds to the time during which the second switch and the fourth switch are simultaneously turned on.

[0011] As an option, the bias voltage is equal to Vin / L*Toff*K-Vcclamp, wherein Vin is an input voltage, L is an inductance value, Toff is the turn-off time of the main switch, K is a ratio of the compensation voltage to the inductor current, and Vcclamp is the lowest clamping voltage of the compensation voltage; when the switching circuit is a four-switch boost-buck circuit, the turn-off time of the main switch corresponds to the time during which the second switch and the fourth switch are simultaneously turned on.

[0012] The application also discloses a control circuit of a switching circuit, the control circuit comprising a comparison circuit and an operational amplifier circuit; the switching circuit works in a valley current mode, and the operational amplifier circuit receives output feedback and a reference voltage, and outputs a compensation voltage after operational amplification.

[0013] When the turn-off time of the main switch tube is less than or equal to a first turn-off threshold, the compensation voltage is added to the bias voltage to form a bias compensation voltage; the comparison circuit receives a sampling value of an inductor current, the compensation voltage and the bias voltage; when the sampling value of the inductor current drops to the bias compensation voltage, the main switch tube changes from turn-off to turn-on.

[0014] As an option, the switching circuit is a four-switch tube boost-buck circuit; the four-switch tube boost-buck circuit comprises a first switch tube, a second switch tube, a third switch tube, a fourth switch tube and an inductor, the first switch tube and the second switch tube are connected in series, the common end of the first switch tube and the second switch tube is a first node, the first switch tube is connected to an input end, the second switch tube is connected to the ground, the third switch tube and the fourth switch tube are connected in series, the common end of the third switch tube and the fourth switch tube is a second node, the fourth switch tube is connected to an output end, the third switch tube is connected to the ground, and the inductor is connected between the first node and the second node; the four-switch tube boost-buck circuit works in a BUCK-BOOST mode, the second switch tube and the fourth switch tube are turned on, and when the sampling value of the inductor current drops to the compensation voltage, the second switch tube and the fourth switch tube are turned off, and the first switch tube and the third switch tube are turned on.

[0015] When the time when the second switch tube and the fourth switch tube are simultaneously turned on is less than or equal to a first turn-off threshold, the compensation voltage is added to the bias voltage to form a bias compensation voltage; the second switch tube and the fourth switch tube are turned on, and when the sampling value of the inductor current drops to the bias compensation voltage, the second switch tube and the fourth switch tube are turned off, and the first switch tube and the third switch tube are turned on.

[0016] As an option, the bias voltage is related to the inductor current slope and the turn-off time of the main switch tube, and when the switching circuit is a four-switch tube boost-buck circuit, the turn-off time of the main switch tube corresponds to the time when the second switch tube and the fourth switch tube are simultaneously turned on.

[0017] As an option, the bias voltage is equal to Vin / L*Toff*K-Vcclamp, wherein Vin is an input voltage, L is an inductance value, Toff is a main switch tube off time, when the switching circuit is a four switch tube Buck-Boost circuit; the main switch tube off time corresponds to a time when the second switch tube and the fourth switch tube are simultaneously turned on, K is a ratio of a compensation voltage and an inductance current, and Vcclamp is a lowest clamping voltage of the compensation voltage.

[0018] The application discloses a control circuit of a switching circuit, the control circuit comprising a comparison circuit and an operational amplifier circuit; the switching circuit works in a peak current mode, the operational amplifier circuit receives an output feedback and a reference voltage, and outputs a compensation voltage after operational amplification; when a turn-on time of a main switch tube is less than or equal to a first turn-on threshold, the compensation voltage is added with a bias voltage to form a bias compensation voltage; the comparison circuit receives a sampling value of an inductance current, the compensation voltage and the bias voltage; the main switch tube is turned on, and when the sampling value of the inductance current rises to the bias compensation voltage, the main switch tube is turned off to be turned on.

[0019] Another technical solution of the application is to provide a switching circuit.

[0020] Compared with the prior art, the circuit structure and the method have the following advantages: the output of the operational amplifier can be compared with the sampling value of the inductance current at any time by using a new control mode modulation strategy of the switching circuit, and stable and reliable modulation of the output voltage of the switching converter under the condition of the limit duty ratio is realized. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 The four switch tube Buck-Boost circuit is a prior art;

[0022] Figure 2 The inductance current waveform diagram of the four switch tube Buck-Boost circuit when switching between the boost working mode and the buck working mode;

[0023] Figure 3 The waveform schematic diagram of the inductance current sampling value, the compensation voltage, the bias voltage and the bias compensation voltage in the valley current mode of the embodiment of the application;

[0024] Figure 4 The control circuit is one embodiment of the application;

[0025] Figure 5 The bias voltage generation circuit is one embodiment of the application;

[0026] Figure 6Fig. 1 shows the waveform of the inductor current sampling value, the compensation voltage, the bias voltage and the bias compensation voltage in the peak current mode according to an embodiment of the present application. DETAILED DESCRIPTION

[0027] The preferred embodiments of the present application will be described in detail with reference to the drawings, but the present application is not limited to these embodiments. The present application encompasses any alternatives, modifications, equivalents, and variations of the preferred embodiments within the spirit and scope of the present application.

[0028] In order to make the public thoroughly understand the present application, the specific details are described in the following preferred embodiments of the present application, and the present application can be fully understood without these details by those skilled in the art.

[0029] The present application will be described in more detail with reference to the following examples. It should be understood that the drawings are only schematic and are non-to-scale for purposes of illustration only. The specific embodiments of the present application are shown in these drawings, which are presented as illustrative and not restrictive in nature.

[0030] The present application discloses a control circuit of a switching circuit, which comprises a comparison circuit and an operational amplifier circuit. The switching circuit works in the valley current mode, and the operational amplifier circuit receives an output feedback and a reference voltage, and outputs a compensation voltage after operational amplification. Please refer to Fig. 1, which shows the waveform of the inductor current sampling value, the compensation voltage, the bias voltage and the bias compensation voltage in the valley current mode according to an embodiment of the present application. When the off time of the main switch tube is less than or equal to the first off threshold, the compensation voltage is added to the bias voltage to form the bias compensation voltage. The comparison circuit receives the inductor current sampling value, the compensation voltage and the bias voltage. When the inductor current sampling value drops to the bias compensation voltage, the main switch tube changes from off to on. By using a new control mode of the switching circuit, the output of the operational amplifier can be compared with the inductor current sampling value at any time, so that the output voltage of the switching converter under the condition of the limit duty ratio can be stably and reliably modulated. Figure 3 As an option, the first off threshold is the minimum off time. Please refer to Fig. 1.

[0031] Figure 4 Fig. 2 shows an embodiment of the control circuit of the present application. It should be noted that since the comparison circuit generally has a bias terminal, the bias value of the comparison value can be set. In this embodiment, the comparison circuit receives the inductor current sampling value, the compensation voltage and the bias voltage, and outputs the comparison result of the inductor current sampling value and the bias compensation voltage. Alternatively, the compensation voltage and the bias voltage can pass through an adder or a subtractor to output the bias compensation voltage, and the comparison circuit receives the bias compensation voltage and the inductor current sampling value, and outputs the comparison result of the inductor current sampling value and the bias compensation voltage. ​

[0032] As an option, when the switching circuit is a four-switch boost-buck circuit; please refer to Figure 1 Fig. 1 shows a circuit diagram of a four-switch boost-buck circuit, which includes a first switch S1, a second switch S2, a third switch S3, a fourth switch S4 and an inductor L. The first switch S1 and the second switch S2 are connected in series, and the common terminal of the first switch S1 and the second switch S2 is a first node SW1. The first switch S1 is connected to an input terminal VIN, and the second switch S2 is connected to ground. The third switch S3 and the fourth switch S4 are connected in series, and the common terminal of the third switch S3 and the fourth switch S4 is a second node SW2. The fourth switch S4 is connected to an output terminal VOUT, and the third switch S3 is connected to ground. The inductor L is connected between the first node SW1 and the second node SW2. The four-switch boost-buck circuit operates in a BUCK-BOOST mode. When the inductor current sampling value decreases to a compensation voltage, the second switch S2 and the fourth switch S4 are turned off, and the first switch S1 and the third switch S3 are turned on.

[0033] In one embodiment, the bias voltage is related to the inductor current slope and the main switch turn-off time, when the switching circuit is a four-switch boost-buck circuit. The main switch turn-off time corresponds to the time when the second switch S2 and the fourth switch S4 are turned on simultaneously.

[0034] In one embodiment, the bias voltage is equal to Vin / L*Toff*K-Vcclamp, where Vin is the input voltage, L is the inductance value, Toff is the main switch turn-off time, when the switching circuit is a four-switch boost-buck circuit. The main switch turn-off time Toff corresponds to the time when the second switch S2 and the fourth switch S4 are turned on simultaneously. K is the ratio of the compensation voltage to the inductor current, and Vcclamp is the lowest clamping voltage of the compensation voltage.

[0035] Please refer to Figure 5 Fig. 2 shows an embodiment of the bias voltage generation. The switch M OFFSET and the capacitor C OFFSET are connected in parallel, and the bias current I OFFSET is connected to the switch MOFFSET and capacitor C OFFSET in parallel, capacitor C OFFSET The voltage on capacitor C OFFSET is bias voltage. Switch M OFFSET is off, bias current I OFFSET charges capacitor C OFFSET When the bias voltage reaches the required voltage, bias current I OFFSET stops charging capacitor C OFFSET . When the bias voltage is not needed, bias enable signal is high, switch M OFFSET is on, and bias voltage is zero.

[0036] The application discloses a control circuit of a switching circuit, which comprises a comparison circuit and an operational amplifier circuit; the switching circuit works in a peak current mode; the operational amplifier circuit receives output feedback and a reference voltage, and outputs a compensation voltage after operational amplification; please refer to Figure 6 for a waveform diagram of an inductor current sampling value, a compensation voltage, a bias voltage and a bias compensation voltage in the peak current mode of an embodiment of the application. When the on time of a main switch is less than or equal to a first on threshold, the compensation voltage is added to the bias voltage to form a bias compensation voltage; the comparison circuit receives the inductor current sampling value, the compensation voltage and the bias voltage; the main switch is on, and when the inductor current sampling value rises to the bias compensation voltage, the main switch changes from off to on. Optionally, the first on threshold is a minimum on time. For an embodiment of the control circuit of the application, please refer to Figure 4 .

[0037] When the switching circuit is a four-switch boost-buck circuit; please refer to Figure 1 for a circuit diagram of the four-switch boost-buck circuit. The four-switch boost-buck circuit works in a BUCK-BOOST mode; the first switch S1 and the third switch S3 are on, and when the inductor current sampling value rises to the compensation voltage, the first switch S1 and the third switch S3 are off, and the second switch S2 and the fourth switch S4 are on; when the time during which the first switch S1 and the third switch S3 are on simultaneously is less than or equal to a first on threshold, the compensation voltage is added to the bias voltage to form a bias compensation voltage; the first switch S1 and the third switch S3 are on, and when the inductor current sampling value rises to the bias compensation voltage, the first switch S1 and the third switch S3 are off, and the second switch S2 and the fourth switch S4 are on.

[0038] In one embodiment, the bias voltage and the inductor current slope are related to the main switch tube conduction time, and when the switching circuit is a four-switch tube boost-buck circuit; the main switch tube conduction time corresponds to the time when the first switch tube S1 and the third switch tube S3 are simultaneously turned on.

[0039] The technical solution of the present application is to provide a control method of a switching circuit, the switching circuit working in a valley current mode, the control method comprising: outputting feedback and reference voltage through an operational amplifier to obtain a compensation voltage; when the off time of a main switch tube is less than or equal to a first off threshold, the compensation voltage is added with a bias voltage to obtain a bias compensation voltage; and when the inductor current sampling value drops to the bias compensation voltage, the main switch tube is turned on from off.

[0040] As an option, the switching circuit is a four-switch tube boost-buck circuit; the four-switch tube boost-buck circuit comprises a first switch tube, a second switch tube, a third switch tube, a fourth switch tube and an inductor, the first switch tube and the second switch tube are connected in series, the common end of the first switch tube and the second switch tube is a first node, the first switch tube is connected to an input end, the second switch tube is connected to the ground, the third switch tube and the fourth switch tube are connected in series, the common end of the third switch tube and the fourth switch tube is a second node, the fourth switch tube is connected to an output end, the third switch tube is connected to the ground, the inductor is connected between the first node and the second node, the four-switch boost-buck circuit works in a BUCK-BOOST mode, the second switch tube and the fourth switch tube are turned on, and when the inductor current sampling value drops to the compensation voltage, the second switch tube and the fourth switch tube are turned off, and the first switch tube and the third switch tube are turned on.

[0041] When the time when the second switch tube and the fourth switch tube are simultaneously turned on is less than or equal to a first off threshold, the compensation voltage is added with a bias voltage to obtain a bias compensation voltage; the second switch tube and the fourth switch tube are turned on, and when the inductor current sampling value drops to the bias compensation voltage, the second switch tube and the fourth switch tube are turned off, and the first switch tube and the third switch tube are turned on.

[0042] As an option, the bias voltage and the inductor current slope are related to the main switch tube off time, and when the switching circuit is a four-switch tube boost-buck circuit; the main switch tube off time corresponds to the time when the second switch tube and the fourth switch tube are simultaneously turned on.

[0043] As an option, the bias voltage is equal to Vin / L*Toff*K-Vcclamp, wherein Vin is an input voltage, L is an inductance value, Toff is a main switch tube off time, when the switch circuit is a four switch tube step-up and step-down circuit; the main switch tube off time corresponds to a time when the second switch tube and the fourth switch tube are simultaneously turned on, K is a ratio of a compensation voltage and an inductance current, and Vcclamp is a lowest clamping voltage of the compensation voltage.

[0044] Another technical solution of the present application is to provide a control method of a switch circuit, the switch circuit working in a peak current mode, an output feedback and a reference voltage being subjected to operational amplification to obtain a compensation voltage; when a turn-on time of a main switch tube is less than or equal to a first turn-on threshold, the compensation voltage is added with a bias voltage to be a bias compensation voltage; the main switch tube is turned on, and when an inductance current sampling value rises to the bias compensation voltage, the main switch tube is changed from being turned on to being turned off.

[0045] When the switch circuit is a four switch tube step-up and step-down circuit; please refer to Figure 1 Fig. 1, which is a circuit diagram of a four switch tube step-up and step-down circuit, the four switch tube step-up and step-down circuit working in a BUCK-BOOST mode, the first switch tube S1 and the third switch tube S3 being turned on, when an inductance current sampling value rises to a compensation voltage, the first switch tube S1 and the third switch tube S3 being turned off, and the second switch tube S2 and the fourth switch tube S4 being turned on; when a time when the first switch tube S1 and the third switch tube S3 are simultaneously turned on is less than or equal to a first turn-on threshold, the compensation voltage is added with a bias voltage to be a bias compensation voltage; the first switch tube S1 and the third switch tube S3 are turned on, and when the inductance current sampling value rises to the bias compensation voltage, the first switch tube S1 and the third switch tube S3 are turned off, and the second switch tube S2 and the fourth switch tube S4 are turned on.

[0046] In one embodiment, the bias voltage is related to a main switch tube turn-on time, when the switch circuit is a four switch tube step-up and step-down circuit; the main switch tube turn-on time corresponds to a time when the first switch tube S1 and the third switch tube S3 are simultaneously turned on.

[0047] Still another technical solution of the present application is to provide a switch circuit.

[0048] In addition, although the above embodiments are separately explained and described, the technical contents involved in the parts in common can be replaced and integrated between the embodiments, and the contents not explicitly recorded in one of the embodiments can be referred to the other recorded embodiment.

[0049] The above-described embodiments do not constitute a limitation on the protection scope of the technical solutions. Any modification, equivalent replacement and improvement made within the spirit and principle of the above-described embodiments should be included in the protection scope of the technical solutions.

Claims

1. A method for controlling a switching circuit, the switching circuit being a four-switch boost-buck converter; the four-switch boost-buck converter comprising a main switch and an inductor, the main switch comprising a first switch, a second switch, a third switch and a fourth switch, the first switch and the second switch being connected in series, a common terminal of the first switch and the second switch being a first node, the third switch and the fourth switch being connected in series, a common terminal of the third switch and the fourth switch being a second node, the inductor being connected between the first node and the second node, the switching circuit operating in a valley current mode, the method comprising: obtaining a compensation voltage by operating an amplifier with an output feedback and a reference voltage; when a turn-off time of the main switch is less than or equal to a first turn-off threshold, adding a bias voltage to the compensation voltage to obtain a bias compensation voltage; turning off the first switch and the third switch, and turning on the second switch and the fourth switch; when the inductor current sample value decreases to the bias compensation voltage, turning on the first switch and the third switch, and turning off the second switch and the fourth switch; the turn-off time of the main switch corresponding to a time when the second switch and the fourth switch are turned on simultaneously. when the time when the second switch and the fourth switch are turned on simultaneously is less than or equal to the first turn-off threshold, adding the bias voltage to the compensation voltage to obtain the bias compensation voltage; turning on the second switch and the fourth switch, and turning off the first switch and the third switch; when the inductor current sample value decreases to the bias compensation voltage, turning off the second switch and the fourth switch, and turning on the first switch and the third switch. the bias voltage being related to the turn-off time of the main switch and a slope of the inductor current. the bias voltage being equal to Vin / L*Toff*K-Vcclamp, wherein Vin is an input voltage, L is an inductance value, Toff is the turn-off time of the main switch, K is a ratio of the compensation voltage to the inductor current, and Vcclamp is a lowest clamping voltage of the compensation voltage.

2. The control method of the switching circuit according to claim 1, characterized by: 5.A control circuit for a switching circuit, the switching circuit being a four-switch boost-buck converter; the four-switch boost-buck converter comprising a main switch and an inductor, the main switch comprising a first switch, a second switch, a third switch and a fourth switch, the first switch and the second switch being connected in series, a common terminal of the first switch and the second switch being a first node, the third switch and the fourth switch being connected in series, a common terminal of the third switch and the fourth switch being a second node, the inductor being connected between the first node and the second node, the control circuit comprising a comparison circuit and an operational amplifier circuit; the switching circuit operating in a valley current mode, the control circuit comprising: ​ 3. The control method of the switching circuit according to claim 1, characterized by: ​ 4. The control method of the switching circuit according to claim 1, characterized by: ​ ​ The operational amplifier circuit receives output feedback and reference voltage, and performs operational amplification, and outputs compensation voltage; When the turn-off time of the main switch is less than or equal to a first turn-off threshold, the compensation voltage is added to the bias voltage to form a bias compensation voltage; the comparison circuit receives the sampling value of the inductor current, the compensation voltage and the bias voltage; the first switch and the third switch are turned off, and when the sampling value of the inductor current decreases to the bias compensation voltage, the first switch and the third switch are turned on. The turn-off time of the main switch corresponds to the time when the second switch and the fourth switch are turned on simultaneously.

6. The control circuit of the switching circuit according to claim 5, characterized in that: The four-switch buck-boost circuit works in a BUCK-BOOST mode, the second switch and the fourth switch are turned on, and when the sampling value of the inductor current decreases to the compensation voltage, the second switch and the fourth switch are turned off, and the first switch and the third switch are turned on. When the time when the second switch and the fourth switch are turned on simultaneously is less than or equal to a first turn-off threshold, the compensation voltage is added to the bias voltage to form a bias compensation voltage; the second switch and the fourth switch are turned on, and when the sampling value of the inductor current decreases to the bias compensation voltage, the second switch and the fourth switch are turned off, and the first switch and the third switch are turned on.

7. The control circuit for the switching circuit of claim 5, wherein: The bias voltage is related to the turn-off time of the main switch and the slope of the inductor current.

8. The control circuit for the switching circuit of claim 5, wherein: The bias voltage is equal to Vin / L*Toff*K-Vcclamp, wherein Vin is the input voltage, L is the inductance value, Toff is the turn-off time of the main switch, K is the ratio of the compensation voltage to the inductor current, and Vcclamp is the lowest clamping voltage of the compensation voltage.

9. A control circuit of a switching circuit, the switching circuit being a four-switch buck-boost circuit; the four-switch buck-boost circuit comprising a main switch and an inductor, the main switch comprising a first switch, a second switch, a third switch and a fourth switch, the first switch and the second switch being connected in series, the common terminal of the first switch and the second switch being a first node, the third switch and the fourth switch being connected in series, the common terminal of the third switch and the fourth switch being a second node, the inductor being connected between the first node and the second node, the control circuit comprising a comparison circuit and an operational amplifier circuit; the switching circuit working in a peak current mode, characterized in that: The operational amplifier circuit receives output feedback and reference voltage, and performs operational amplification, and outputs compensation voltage; When the on-time of the main switch is less than or equal to a first on-time threshold, the compensation voltage is added to the bias voltage to form a bias compensation voltage; the comparison circuit receives a sample value of the inductor current, the compensation voltage and the bias voltage; the first switch and the third switch are turned on, and when the sample value of the inductor current rises to the bias compensation voltage, the second switch and the fourth switch are turned on from off; the on-time of the main switch corresponds to the time when the first switch and the third switch are simultaneously turned on.

10. A switching circuit, characterized by: The control circuit comprises the control circuit according to any one of claims 5 to 8, or the control method comprises the control method according to any one of claims 1 to 4.

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