A control method, control circuit and switching circuit of a four-switch buck-boost circuit

Abstract

The application discloses a control method, a control circuit and a switching circuit of a four-switch voltage-lifting and voltage-lowering circuit. The four-switch voltage-lifting and voltage-lowering circuit comprises a first switch tube, a second switch tube, a third switch tube and a fourth switch tube. The first switch tube and the second switch tube are connected in series, and the first switch tube is connected to an input end. The third switch tube and the fourth switch tube are connected in series, and the fourth switch tube is connected to an output end. The working mode of the four-switch voltage-lifting and voltage-lowering circuit is switched from a peak current mode to a valley current mode, or from the valley current mode to the peak current mode. The inductance current value in the working mode after the switching is calculated, and the inductance current sampling value is made to reach the corresponding value of the current value, and then the next switching period is entered. The application realizes smooth switching of the working mode in a wide input and output voltage range, and is stable in working and high in efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power electronics, and particularly relates to a control method, a control circuit and a switching circuit of a four-switch buck-boost circuit. BACKGROUND

[0002] A four-switch tube Buck-Boost step-up and step-down circuit topology structure is shown in the figure. Figure 1 The circuit includes a first switch tube S1, a second switch tube S2, a third switch tube S3, a fourth switch tube S4 and an inductor L, the first switch tube S1 and the second switch tube S2 are connected in series, the first switch tube S1 is connected to an input end, the second switch tube S2 is connected to the ground, the third switch tube S3 and the fourth switch tube S4 are connected in series, the fourth switch tube S4 is connected to an output end, and the third switch tube S3 is connected to the ground. The common end of the first switch tube S1 and the second switch tube S2 is a first node SW1, the common end of the third switch tube S3 and the fourth switch tube S4 is a second node SW2, and the inductor L is connected between the first node SW1 and the second node SW2.

[0003] When the input and output voltage difference is large, the system works in Buck mode or Boost mode. When the input and output voltage changes, the working mode switches, and when the working mode switches, generally a plurality of switching cycles are needed to enter a stable working state. During the switching process, there are many problems such as large switching loss and unstable work. SUMMARY

[0004] Therefore, the purpose of the present application is to provide a control method, a control circuit and a switching circuit of a four-switch buck-boost circuit to solve the problem that in the prior art, a plurality of switching cycles are needed to enter a stable working state when the working mode switches.

[0005] The technical solution of the present application is to provide a control method of a four-switch buck-boost circuit, the four-switch tube step-up and step-down circuit including 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 being connected in series, the first switch tube being connected to an input end, the second switch tube being connected to the ground, the third switch tube and the fourth switch tube being connected in series, the fourth switch tube being connected to an output end, and the third switch tube being connected to the ground, the control method including:

[0006] In the BUCK-BOOST working mode, the four-switch step-up and step-down circuit works in a peak or valley current mode;

[0007] In the BUCK working mode, the four-switch step-up and step-down circuit works in a peak or valley current mode;

[0008] In the BOOST working mode, the four-switch step-up and step-down circuit works in a peak or valley current mode;

[0009] The feedback voltage and the reference voltage are amplified to obtain a compensation voltage;

[0010] The working mode of the four-switch buck-boost circuit is switched from the peak current mode to the valley current mode or from the valley current mode to the peak current mode, the inductor current value in the switched working mode is calculated, and the inductor current sampling value reaches the corresponding value of the current value, and then the next switching period is entered;

[0011] The working mode is a BUCK working mode, a BOOST working mode, or a BUCK-BOOST working mode.

[0012] Optionally, the on time of the switch tube is a threshold on time, or the inductor current sampling value reaches a threshold voltage, which represents that the inductor current sampling value reaches the corresponding value of the inductor current value in the switched working mode.

[0013] Optionally, the threshold on time increases with the increase of the on time of the switch tube with the shortest on time among the first switch tube, the second switch tube, the third switch tube, and the fourth switch tube before the mode switching of the four-switch buck-boost circuit.

[0014] Optionally, the absolute value of the difference between the threshold voltage and the compensation voltage increases with the increase of the on time of the switch tube with the shortest on time among the first switch tube, the second switch tube, the third switch tube, and the fourth switch tube before the mode switching of the four-switch buck-boost circuit.

[0015] Optionally, in the BOOST working mode, the four-switch buck-boost circuit works in the peak current mode; and in the BUCK-BOOST working mode, the four-switch buck-boost circuit works in the valley current mode.

[0016] When the four-switch buck-boost circuit works in the BUCK-BOOST mode, when the simultaneous on time of the second switch tube and the fourth switch tube is less than a first time, and after the first switch tube and the third switch tube change from on to off, the second switch tube and the fourth switch tube change from off to on, and the on time is a first threshold on time, or the inductor current sampling value is less than a first threshold voltage, the second switch tube is turned off, the fourth switch tube remains on, the first switch tube changes from off to on, and the BOOST working mode is entered; the absolute value of the difference between the first threshold voltage and the compensation voltage increases with the increase of the first time; and the first threshold on time increases with the increase of the first time.

[0017] When the four-switch buck-boost circuit works in the BOOST mode, when the on-time of the third switch is less than the second time, in the next switching period, the on-time of the third switch is the second threshold on-time, or when the inductor current sampling value is greater than the second threshold voltage, the third switch is turned off and enters the BUCK-BOOST working mode; the absolute value of the difference between the second threshold voltage and the compensation voltage increases with the increase of the second time; the second threshold on-time increases with the increase of the second time.

[0018] As an option, when the four-switch buck-boost circuit works in the BUCK-BOOST mode, the time when the first switch and the fourth switch are turned on simultaneously is the third time.

[0019] As an option, when the four-switch buck-boost circuit works in the BUCK-BOOST mode, the clock signal changes from invalid to valid and starts timing, the second switch and the fourth switch are turned on, and the first switch and the third switch are turned off; when the detection value of the inductor current valley value is less than 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 timing reaches the fourth time, the second switch and the third switch are turned off, and the first switch and the fourth switch are turned on, and the sum of the third time and the fourth time is the switching period of the four-switch buck-boost circuit.

[0020] The application also provides a control circuit of a four-switch buck-boost circuit, the four-switch buck-boost circuit including a first switch, a second switch, a third switch, a fourth switch and an inductor, the first switch and the second switch being connected in series, the first switch being connected to an input terminal, the second switch being connected to ground, the third switch and the fourth switch being connected in series, the fourth switch being connected to an output terminal, and the third switch being connected to ground, and including a digital operation circuit and a logic control circuit, the digital operation circuit receiving the on-time of the first switch, the second switch, the third switch and the fourth switch, outputting a working mode and a switching voltage signal, and the logic control circuit receiving the output voltage of the digital operation circuit and a compensation voltage.

[0021] In the BUCK-BOOST working mode, the four-switch buck-boost circuit works in a peak or valley current mode.

[0022] In the BUCK working mode, the four-switch buck-boost circuit works in a peak or valley current mode.

[0023] In the BOOST working mode, the four-switch buck-boost circuit works in a peak or valley current mode.

[0024] The feedback voltage and the reference voltage are amplified to obtain a compensation voltage;

[0025] The working mode of the four-switch buck-boost circuit is switched from a peak current mode to a valley current mode or from the valley current mode to the peak current mode, the digital operation circuit calculates an inductor current value in the switched working mode, and the logic control circuit makes the inductor current sampling value reach a corresponding value of the current value and then enters a next switching period;

[0026] The working mode refers to a BUCK working mode, a BOOST working mode or a BUCK-BOOST working mode.

[0027] As an option, the digital operation circuit calculates a threshold conduction time, and the logic control circuit controls the conduction time of the switch tube to be the threshold conduction time; or the digital operation circuit calculates a threshold voltage, and the logic control circuit controls the inductor current sampling value to reach the threshold voltage, which represents that the inductor current sampling value reaches the corresponding value of the inductor current value in the switched working mode.

[0028] Another technical solution of the present application is to provide a switching circuit.

[0029] Compared with the prior art, the circuit structure and method of the present application have the following advantages: the present application realizes smooth switching of the working mode in a wide input-output voltage range, and is stable and efficient. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 The four-switch tube Buck-Boost buck-boost circuit of the prior art;

[0031] Figure 2 Embodiments of the four-switch tube buck-boost circuit and its control circuit of the present application;

[0032] Figure 3 The inductor current i L , the first switch node SW1, the second switch node SW2 and the waveform diagram of the clock signal Clock;

[0033] Fig. 4(a) is a waveform diagram of the first node SW1, the second node SW2, the inductor current i L , the compensation voltage COMP, the driving voltage HDRV1 of the first switch tube, the driving voltage LDRV1 of the second switch tube, the driving voltage LDRV2 of the third switch tube and the driving voltage HDV2 of the fourth switch tube when the four-switch buck-boost circuit in an embodiment of the present application is switched from the BUCK-BOOST working mode to the BOOST working mode;

[0034] Fig. 4(b) is a waveform diagram of the first node SW1, the second node SW2, the inductor current iL, the compensation voltage COMP, the driving voltage of the first switch HDRV1, the driving voltage of the second switch LDRV1, the driving voltage of the third switch LDRV2 and the driving voltage of the fourth switch HDRV2 when the four-switch buck-boost circuit switches from the BUCK-BOOST mode to the BOOST mode according to another embodiment of the present application; L Fig. 4(b) is a waveform diagram of the first node SW1, the second node SW2, the inductor current iL, the compensation voltage COMP, the driving voltage of the first switch HDRV1, the driving voltage of the second switch LDRV1, the driving voltage of the third switch LDRV2 and the driving voltage of the fourth switch HDRV2 when the four-switch buck-boost circuit switches from the BUCK-BOOST mode to the BOOST mode according to another embodiment of the present application;

[0035] Figure 5 Fig. 4(b) is a waveform diagram of the first node SW1, the second node SW2, the inductor current iL, the compensation voltage COMP, the driving voltage of the first switch HDRV1, the driving voltage of the second switch LDRV1, the driving voltage of the third switch LDRV2 and the driving voltage of the fourth switch HDRV2 when the four-switch buck-boost circuit switches from the BUCK-BOOST mode to the BOOST mode according to another embodiment of the present application; L Fig. 4(b) is a waveform diagram of the first node SW1, the second node SW2, the inductor current iL, the compensation voltage COMP, the driving voltage of the first switch HDRV1, the driving voltage of the second switch LDRV1, the driving voltage of the third switch LDRV2 and the driving voltage of the fourth switch HDRV2 when the four-switch buck-boost circuit switches from the BUCK-BOOST mode to the BOOST mode according to another embodiment of the present application;

[0036] Figure 6 Fig. 4(b) is a waveform diagram of the first node SW1, the second node SW2, the inductor current iL, the compensation voltage COMP, the driving voltage of the first switch HDRV1, the driving voltage of the second switch LDRV1, the driving voltage of the third switch LDRV2 and the driving voltage of the fourth switch HDRV2 when the four-switch buck-boost circuit switches from the BUCK-BOOST mode to the BOOST mode according to another embodiment of the present application; L Fig. 4(b) is a waveform diagram of the first node SW1, the second node SW2, the inductor current iL, the compensation voltage COMP, the driving voltage of the first switch HDRV1, the driving voltage of the second switch LDRV1, the driving voltage of the third switch LDRV2 and the driving voltage of the fourth switch HDRV2 when the four-switch buck-boost circuit switches from the BUCK-BOOST mode to the BOOST mode according to another embodiment of the present application;

[0037] Figure 7 Fig. 4(b) is a waveform diagram of the first node SW1, the second node SW2, the inductor current iL, the compensation voltage COMP, the driving voltage of the first switch HDRV1, the driving voltage of the second switch LDRV1, the driving voltage of the third switch LDRV2 and the driving voltage of the fourth switch HDRV2 when the four-switch buck-boost circuit switches from the BUCK-BOOST mode to the BOOST mode according to another embodiment of the present application; L Fig. 4(b) is a waveform diagram of the first node SW1, the second node SW2, the inductor current iL, the compensation voltage COMP, the driving voltage of the first switch HDRV1, the driving voltage of the second switch LDRV1, the driving voltage of the third switch LDRV2 and the driving voltage of the fourth switch HDRV2 when the four-switch buck-boost circuit switches from the BUCK-BOOST mode to the BOOST mode according to another embodiment of the present application. DETAILED DESCRIPTION

[0038] The preferred embodiments of the present application will be described in detail with reference to the drawings, of which:

[0039] For the public to have a thorough understanding of the present application, specific details are described in the following preferred embodiments of the present application, but the present application can be fully understood without these details.

[0040] The invention is described in more detail below by way of example with reference to the accompanying drawings. It should be noted that the drawings are in a simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of the invention.

[0041] This invention provides a control circuit for a four-switch buck-boost circuit. Please refer to [the relevant documentation]. Figure 2 The diagram illustrates an embodiment of the four-switch buck-boost circuit and its control circuit of the present invention. It 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 first switch S1 is connected to the 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 fourth switch S4 is connected to the output terminal VO. The third switch S3 is connected to ground. The circuit includes a digital arithmetic circuit and a logic control circuit. The digital arithmetic circuit receives the on-time of the first switch S1, the second switch S2, the third switch S3, and the fourth switch S4, and outputs the operating mode and switching voltage signals. The logic control circuit receives the output voltage and the compensation voltage COMP from the digital arithmetic circuit. In the BUCK-BO... In OST mode, the four-switch buck-boost circuit operates in peak or valley current mode; in BUCK mode, the four-switch buck-boost circuit operates in peak or valley current mode; in BOOST mode, the four-switch buck-boost circuit operates in peak or valley current mode; the feedback voltage and reference voltage are amplified operationally to obtain the compensation voltage; the operating mode of the four-switch buck-boost circuit switches from peak current mode to valley current mode, or vice versa. The digital operation circuit calculates the inductor current value in the switched operating mode, and the logic control circuit makes the inductor current sampling value reach the corresponding value of this current value before entering the next switching cycle; the operating mode refers to BUCK mode, BOOST mode, or BUCK-BOOST mode.

[0042] Optionally, the digital processing circuit calculates a threshold conduction time, and the logic control circuit controls the conduction time of the switching transistor to be the threshold conduction time; or the digital processing circuit calculates a threshold voltage, and the logic control circuit controls the inductor current sampling value to reach the threshold voltage, which indicates that the inductor current sampling value has reached the corresponding value of the inductor current value in the switched operating mode.

[0043] In one embodiment, the threshold conduction time increases as the conduction time of the switch with the shortest conduction time among the first, second, third, and fourth switches in the four-switch buck-boost circuit increases before mode switching.

[0044] In one embodiment, the absolute value of the difference between the threshold voltage and the compensation voltage increases with the increase of the conduction time of the switch with the shortest conduction time among the first switch, the second switch, the third switch and the fourth switch before the mode switching of the four-switch buck-boost circuit.

[0045] In one embodiment, the digital operation circuit calculates the threshold conduction time, and the logic control circuit controls the conduction time of the switch to be the threshold conduction time; in the BOOST mode, the four-switch buck-boost circuit works in the peak current mode; in the BUCK-BOOST mode, the four-switch buck-boost circuit works in the valley current mode, and the time when the first switch and the fourth switch are simultaneously turned on is the third time. Please refer to Figure 3 Fig. 2 shows the inductor current i L Fig. 1 shows the waveform diagram of the first node SW1, the second node SW2 and the clock signal Clock. The first node SW1 is the common terminal of the first switch S1 and the second switch S2; the second node SW2 is the common terminal of the third switch S3 and the fourth switch S4. When the clock signal changes from invalid to valid, the timing starts, the second switch S2 and the fourth switch S4 are turned on, and the first switch S1 and the third switch S3 are turned off, which is the first time T BUCK_OFF When the detected value of the inductor current valley is less than 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, which is the second time T BOOST_ON When the timing reaches the fourth time, the second switch S2 and the third switch S3 are turned off, and the first switch S1 and the fourth switch S4 are turned on, and the sum of the third time and the fourth time is the switching period T SW As a preferred embodiment, the third time is 70% of the switching period. Please refer to Fig. 4(a) which shows the waveform diagram of the first node SW1, the second node SW2, the inductor current i L, a waveform diagram of the compensation voltage COMP, the driving voltage of the first switch tube HDRI, the driving voltage of the second switch tube LDRVI, the driving voltage of the third switch tube LDRV2 and the driving voltage of the fourth switch tube HDRI2, when the four-switch buck-boost circuit works in the BUCK-BOOST working mode, when the simultaneous conduction time of the second switch tube and the fourth switch tube is less than the first time, after the third switch tube S3 and the first switch tube SI change from conduction to cut-off, the second switch tube S2 and the fourth switch tube S4 change from cut-off to conduction, the conduction time is the first threshold conduction time, the second switch tube S2 is cut off, the fourth switch tube S4 remains conduction, the first switch tube SI changes from cut-off to conduction, and enters the BOOST working mode; the first threshold conduction time increases with the increase of the first time; when the last period of the BUCK-BOOST mode, T BOOST_ON After the end, a BUCK_OFF pulse is inserted, that is, the second switch tube S2 and the fourth switch tube S4 are conduction, the first switch tube SI and the third switch tube S3 are cut off, and the width is D BUCK_OFF_PULSE *T SW , enters the BOOST working mode, wherein,

[0046]

[0047]

[0048] D BUCK_OFF0 is the duty ratio of the second switch tube S2 and the fourth switch tube S4 before the working mode is switched, and the first switch tube SI and the third switch tube S3 are cut off;

[0049] △D is the fourth time;

[0050] T SW is the switching period.

[0051] By setting a BUCK_OFF pulse at the switching time, the four-switch buck-boost circuit can be stably switched from the BUCK-BOOST working mode to the BOOST working mode in one switching period.

[0052] In another embodiment, please refer to Fig. 4(b), which shows the first node SW1, the second node SW2, the inductor current i L, the waveform diagram of the compensation voltage COMP, the driving voltage of the first switch tube HDRI, the driving voltage of the second switch tube LDRV1, the driving voltage of the third switch tube LDRV2 and the driving voltage of the fourth switch tube HDRI2. When the four-switch buck-boost circuit works in the BUCK-BOOST mode, when the simultaneous conduction time of the second switch tube and the fourth switch tube is less than the first time, the second switch tube and the fourth switch tube change from conduction to cut-off, the third switch tube S3 and the first switch tube SI change from cut-off to conduction, when the simultaneous conduction time of the third switch tube and the first switch tube reaches the fourth time, the third switch tube S3 changes from conduction to cut-off, the fourth switch tube changes from cut-off to conduction, when the simultaneous conduction time of the first switch tube and the fourth switch tube reaches the third time, the first switch tube changes from conduction to cut-off, the second switch tube changes from cut-off to conduction, the conduction time is the third threshold conduction time, the second switch tube S2 is cut-off, the fourth switch tube S4 remains conduction, the first switch tube SI changes from cut-off to conduction, and enters the BOOST mode. The third threshold conduction time increases with the increase of the first time.

[0053] In another embodiment, referring to Figure 5 , the first node SW1, the second node SW2, the inductor current i L , the waveform diagram of the compensation voltage COMP, the driving voltage of the first switch tube HDRI, the driving voltage of the second switch tube LDRV1, the driving voltage of the third switch tube LDRV2 and the driving voltage of the fourth switch tube HDRI2. When the four-switch buck-boost circuit works in the BOOST mode, when the conduction time of the third switch tube is less than the second time, in the next switching period, the conduction time of the third switch tube is the second threshold conduction time, or when the inductor current sampling value is greater than the second threshold voltage, the third switch tube is cut-off, and enters the BUCK-BOOST mode. The absolute value of the difference between the second threshold voltage and the compensation voltage increases with the increase of the second time. As a preferred, the second threshold conduction time is

[0054]

[0055] The mode switching in other working states can be switched in the above-mentioned similar manner, for example, Figure 6 and Figure 7 , the first node SW1, the second node SW2, the inductor current i LFig. 1 is a waveform diagram of the voltage of the input terminal, the voltage of the output terminal, the voltage of the feedback terminal, the voltage of the reference terminal, the voltage of the compensation terminal, the driving voltage of the first switch tube, the driving voltage of the second switch tube, the driving voltage of the third switch tube, and the driving voltage of the fourth switch tube.

[0056] Another technical solution of the present application is to provide a control method of a four-switch buck-boost circuit, the four-switch buck-boost circuit comprising 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 being connected in series, the first switch tube being connected to an input terminal, the second switch tube being connected to a ground terminal, the third switch tube and the fourth switch tube being connected in series, the fourth switch tube being connected to an output terminal, the third switch tube being connected to the ground terminal, the control method comprising:

[0057] In the BUCK-BOOST operation mode, the four-switch buck-boost circuit operates in a peak current mode or a valley current mode.

[0058] In the BUCK operation mode, the four-switch buck-boost circuit operates in a peak current mode or a valley current mode.

[0059] In the BOOST operation mode, the four-switch buck-boost circuit operates in a peak current mode or a valley current mode.

[0060] The feedback voltage and the reference voltage are amplified to obtain a compensation voltage.

[0061] The operation mode of the four-switch buck-boost circuit is switched from a peak current mode to a valley current mode or from a valley current mode to a peak current mode, the inductor current value in the switched operation mode is calculated, and the inductor current sampling value reaches the corresponding value of the inductor current value, and then the next switching period is entered.

[0062] The operation mode is a BUCK operation mode, a BOOST operation mode, or a BUCK-BOOST operation mode.

[0063] Optionally, the on time of the switch tube is a threshold on time, or the inductor current sampling value reaches a threshold voltage, which represents that the inductor current sampling value reaches the corresponding value of the inductor current value in the switched operation mode.

[0064] Optionally, the threshold on time increases with the increase of the on time of the switch tube with the shortest on time among the first switch tube, the second switch tube, the third switch tube, and the fourth switch tube before the mode switching of the four-switch buck-boost circuit.

[0065] As an option, the absolute value of the difference between the threshold voltage and the compensation voltage increases with the increase of the conduction time of the switch tube with the shortest conduction time among the first switch tube, the second switch tube, the third switch tube and the fourth switch tube before the mode switching of the four-switch buck-boost circuit.

[0066] As an option, the four-switch buck-boost circuit works in peak current mode in BOOST mode; the four-switch buck-boost circuit works in valley current mode in BUCK-BOOST mode.

[0067] When the four-switch buck-boost circuit works in BUCK-BOOST mode, when the simultaneous conduction time of the second switch tube and the fourth switch tube is less than a first time, after the first switch tube and the third switch tube change from conduction to non-conduction, the second switch tube and the fourth switch tube change from non-conduction to conduction, the conduction time is a first threshold conduction time, or the inductor current sampling value is less than a first threshold voltage, the second switch tube is turned off, the fourth switch tube remains in conduction, the first switch tube changes from non-conduction to conduction, and enters BOOST mode; the absolute value of the difference between the first threshold voltage and the compensation voltage increases with the increase of the first time; the first threshold conduction time increases with the increase of the first time.

[0068] When the four-switch buck-boost circuit works in BOOST mode, when the conduction time of the third switch tube is less than a second time, in the next switching period, the conduction time of the third switch tube is a second threshold conduction time, or when the inductor current sampling value is greater than a second threshold voltage, the third switch tube is turned off, and enters BUCK-BOOST mode; the absolute value of the difference between the second threshold voltage and the compensation voltage increases with the increase of the second time; the second threshold conduction time increases with the increase of the second time.

[0069] As an option, when the four-switch buck-boost circuit works in BUCK-BOOST mode, the simultaneous conduction time of the first switch tube and the fourth switch tube is a third time.

[0070] As an option, when the four-switch buck-boost circuit works in BUCK-BOOST mode, the clock signal changes from invalid to valid, starts timing, the second switch tube and the fourth switch tube are in conduction, and the first switch tube and the third switch tube are in non-conduction; when the detection value of the inductor current valley is less than the compensation voltage, the second switch tube and the fourth switch tube are turned off, the first switch tube and the third switch tube are in conduction, when the timing reaches a fourth time, the second switch tube and the third switch tube are turned off, the first switch tube and the fourth switch tube are in conduction, and the sum of the third time and the fourth time is the switching period of the four-switch buck-boost circuit.

[0071] Another technical solution of the present application is to provide a switching circuit including the control circuit of the four-switch buck-boost circuit or using the control method of the four-switch buck-boost circuit.

[0072] In addition, although the above embodiments are described and explained separately, the technologies involved in some parts are common, and can be replaced and integrated between the embodiments according to the ordinary skill in the art. If the content not explicitly recorded in one of the embodiments is referred to, another embodiment recorded can be referred to.

[0073] The above-described embodiments do not constitute a limitation on the protection scope of the technical solutions. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the above-described embodiments shall be included in the protection scope of the technical solutions.

Claims

1. A control method of a four-switch buck-boost circuit, the four-switch buck-boost circuit including a first switch, a second switch, a third switch, a fourth switch, and an inductor, the first switch and the second switch being connected in series, the first switch being connected to an input terminal, the second switch being connected to a ground terminal, the third switch and the fourth switch being connected in series, the fourth switch being connected to an output terminal, the third switch being connected to the ground terminal, the control method comprising: determining whether a voltage of the output terminal is higher than a voltage of the input terminal; and controlling the first switch, the second switch, the third switch, and the fourth switch based on the determination result. The control method comprises: In the BUCK-BOOST mode, the four-switch buck-boost circuit works in the peak or valley current mode; In the BUCK mode, the four-switch buck-boost circuit works in the peak or valley current mode; In the BOOST mode, the four-switch buck-boost circuit works in the peak or valley current mode; The feedback voltage and the reference voltage are amplified to obtain a compensation voltage; The working mode of the four-switch buck-boost circuit is switched from the peak current mode to the valley current mode or from the valley current mode to the peak current mode, the inductor current value in the switched working mode is calculated, the inductor current sampling value reaches the corresponding value of the inductor current value, and the next switching period is entered; The working mode refers to the BUCK mode, the BOOST mode or the BUCK-BOOST mode.

2. The control method of the four-switch buck-boost circuit according to claim 1, characterized by: When the on time of the switch tube is the threshold on time or the inductor current sampling value reaches the threshold voltage, the inductor current sampling value reaches the corresponding value of the inductor current value in the switched working mode.

3. The control method of the four-switch buck-boost circuit according to claim 2, characterized by: The threshold on time increases with the increase of the on time of the switch tube with the shortest on time among the first switch tube, the second switch tube, the third switch tube and the fourth switch tube before the mode switching of the four-switch buck-boost circuit.

4. The control method of the four-switch buck-boost circuit according to claim 2, characterized by: The absolute value of the difference between the threshold voltage and the compensation voltage increases with the increase of the on time of the switch tube with the shortest on time among the first switch tube, the second switch tube, the third switch tube and the fourth switch tube before the mode switching of the four-switch buck-boost circuit.

5. The control method of the four-switch buck-boost circuit according to claim 2, characterized in that: In the BOOST mode, the four-switch buck-boost circuit works in the peak current mode; in the BUCK-BOOST mode, the four-switch buck-boost circuit works in the valley current mode; When the four-switch buck-boost circuit works in the BUCK-BOOST mode, when the simultaneous on time of the second switch tube and the fourth switch tube is less than the first time, after the first switch tube and the third switch tube change from on to off, the second switch tube and the fourth switch tube change from off to on, the on time is the first threshold on time, or the inductor current sampling value is less than the first threshold voltage, the second switch tube is off, the fourth switch tube remains on, the first switch tube changes from off to on, and the BOOST mode is entered; the absolute value of the difference between the first threshold voltage and the compensation voltage increases with the increase of the first time; the first threshold on time increases with the increase of the first time; When the four-switch buck-boost circuit works in the BOOST mode, when the on-time of the third switch is less than the second time, in the next switching period, the on-time of the third switch is the second threshold on-time, or when the inductor current sampling value is greater than the second threshold voltage, the third switch is turned off, and the BUCK-BOOST mode is entered; the absolute value of the difference between the second threshold voltage and the compensation voltage increases with the increase of the second time; the second threshold on-time increases with the increase of the second time.

6. The control method of the four-switch buck-boost circuit according to claim 5, characterized by: When the four-switch buck-boost circuit works in the BUCK-BOOST mode, the time when the first switch and the fourth switch are turned on simultaneously is the third time.

7. The control method of the four-switch buck-boost circuit according to claim 6, characterized by: When the four-switch buck-boost circuit works in the BUCK-BOOST mode, the clock signal changes from invalid to valid, and the timing starts, the second switch and the fourth switch are turned on, and the first switch and the third switch are turned off; when the detection value of the inductor current valley value is less than the compensation voltage, the second switch and the fourth switch are turned off, the first switch and the third switch are turned on, and when the timing reaches the fourth time, the second switch and the third switch are turned off, the first switch and the fourth switch are turned on, and the sum of the third time and the fourth time is the switching period of the four-switch buck-boost circuit.

8. A control circuit of a four-switch buck-boost circuit, the four-switch buck-boost circuit comprising a first switch, a second switch, a third switch, a fourth switch and an inductor, the first switch and the second switch being connected in series, the first switch being connected to an input, the second switch being connected to ground, the third switch and the fourth switch being connected in series, the fourth switch being connected to an output, the third switch being connected to ground, Characterized in that, comprising a digital operation circuit and a logic control circuit, the digital operation circuit receives the on-time of the first switch, the second switch, the third switch and the fourth switch, outputs the working mode and the switching voltage signal, and the logic control circuit receives the output voltage of the digital operation circuit and the compensation voltage; In the BUCK-BOOST working mode, the four-switch buck-boost circuit works in the peak or valley current mode; In the BUCK working mode, the four-switch buck-boost circuit works in the peak or valley current mode; In the BOOST working mode, the four-switch buck-boost circuit works in the peak or valley current mode; The feedback voltage and the reference voltage are amplified to obtain the compensation voltage; When the working mode of the four-switch buck-boost circuit switches from the peak current mode to the valley current mode, or from the valley current mode to the peak current mode, the digital operation circuit calculates the inductor current value in the switched working mode, and the logic control circuit makes the inductor current sampling value reach the corresponding value of the current value, and then enters the next switching period; The working mode refers to the BUCK working mode, the BOOST working mode or the BUCK-BOOST working mode.

9. The control circuit of the four-switch buck-boost circuit according to claim 8, characterized in that: The digital operation circuit calculates the threshold on-time, and the logic control circuit controls the on-time of the switch to be the threshold on-time; or the digital operation circuit calculates the threshold voltage, and the logic control circuit controls the inductor current sampling value to reach the threshold voltage, which represents that the inductor current sampling value reaches the corresponding value of the inductor current value in the switched working mode.

10. A switching circuit, characterized by: The control circuit according to any one of claims 8-9 or the control method according to any one of claims 1-7.

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