Buck-boost converter, control method, chip and electronic equipment

Abstract

The invention provides a buck-boost converter, a control method, a chip and electronic equipment. When the buck-boost converter is in a buck mode and a light load mode, the power supply control circuit controls the third power tube to be switched off all the time, controls the fourth power tube to be switched on all the time, and controls the first power tube and the second power tube to be switched between the switched-on state and the switched-off state, so that the inductor is switched between charging and discharging. And the power supply control circuit determines whether the current of the inductor during discharging crosses a zero point or not by detecting the voltage drop when the fourth power tube is switched on. And when the current of the inductor during discharging crosses a zero point, the power supply control circuit controls the third power tube to be switched on and the fourth power tube to be switched off, so that the voltage at the two ends of the inductor is zero, and the current of the inductor is maintained to be the current when discharging is stopped. Furthermore, when the inductor is recharged, the inductor current gradually increases from the current when the discharge is stopped. Therefore, the average current of the inductor in each switching period is kept unchanged, so that the buck-boost converter tends to be stable.

Description

Technical Field

[0001] The present application relates to the technical field of power management chips, and in particular to a buck-boost converter, a control method, a chip and an electronic device. Background Art

[0002] Buck-boost converter (Buck-Boost) is also referred to as peak-valley current mode. When the buck-boost converter in the related art is in buck mode and light-load mode, when the inductor in the buck-boost converter stops discharging in the current switching cycle, the inductor may still discharge at a higher slope, making the average current of the inductor in the next switching cycle lower, resulting in instability of the buck-boost converter. Buck mode refers to the buck-boost converter in this mode where the input voltage is greater than the output voltage, and light-load mode refers to the inductor current in this mode where the current in the inductor stops decreasing after decreasing to zero in each switching cycle, and zero point refers to the moment when the inductor current changes from a positive value to a negative value. Summary of the invention

[0003] The present application provides a buck-boost converter, a control method, a chip and an electronic device, which can keep the average current of the inductor in each switching cycle unchanged, so that the buck-boost converter tends to be stable.

[0004] In a first aspect, the present application provides a buck-boost converter, the buck-boost converter comprising: a power control circuit, a first power tube, a second power tube, a third power tube, a fourth power tube and an inductor;

[0005] The source end of the first power tube is used to access the input voltage of the buck-boost converter, the drain end of the first power tube is electrically connected to the first end of the inductor, the drain end of the second power tube is electrically connected between the drain end of the first power tube and the first end of the inductor, the second end of the inductor is electrically connected to the drain end of the fourth power tube, the drain end of the third power tube is electrically connected between the second end of the inductor and the drain end of the fourth power tube, the source end of the fourth power tube is used to output the output voltage of the buck-boost converter, the source end of the second power tube and the source end of the third power tube are both grounded, the first input end of the power control circuit is electrically connected to the drain end of the fourth power tube, the second input end of the power control circuit is electrically connected to the source end of the fourth power tube, and the output end of the power control circuit is electrically connected to the gate end of the first power tube, the gate end of the second power tube, the gate end of the third power tube and the gate end of the fourth power tube respectively;

[0006] In the case where the buck-boost converter is in buck mode and light load mode, wherein:

[0007] The power supply control circuit is used to control the third power tube to be always turned off, the fourth power tube to be always turned on, and control the first power tube and the second power tube to switch between being turned on or off, so that the inductor switches between charging and discharging;

[0008] The power supply control circuit is also used to determine whether the current of the inductor passes through zero when discharging by detecting the voltage drop when the fourth power tube is turned on, and when the current of the inductor passes through zero when discharging, control the third power tube to be turned on and the fourth power tube to be turned off, so that the voltage across the inductor is zero, so that the average current of the inductor in each switching cycle remains unchanged.

[0009] By means of the buck-boost converter provided in the first aspect, when the buck-boost converter is in the buck mode and the light load mode, the power control circuit can control the third power tube to be always off, the fourth power tube to be always on, and control the first power tube and the second power tube to switch between on or off, so that the inductor switches between charging and discharging. The power control circuit determines whether the current of the inductor during discharge passes through zero by detecting the voltage drop when the fourth power tube is turned on. When the current of the inductor during discharge passes through zero, the power control circuit can control the third power tube to be turned on and the fourth power tube to be turned off, so that the voltage across the inductor is zero, so that the current of the inductor is maintained at the current when the discharge stops. Furthermore, when the inductor is charged again, the current of the inductor gradually increases from the current when the discharge stops. Thus, the average current of the inductor in each switching cycle remains unchanged, so that the buck-boost converter tends to be stable.

[0010] In one possible design, the power control circuit includes: a feedback module, a differential amplifier, a voltage-to-current module, a clamping module, a current control delay module, a timing module, a logic control module, a first comparator, a second comparator, a first resistor, and a first capacitor;

[0011] The input end of the feedback module and the first input end of the timing module are both used to access the output voltage, the second input end of the timing module is used to access the input voltage, the output end of the timing module is electrically connected to the first input end of the logic control module, the output end of the feedback module is electrically connected to the negative input end of the differential amplifier, the positive input end of the differential amplifier is used to access the reference voltage, the output end of the differential amplifier is electrically connected to the input end of the voltage-to-current module, the first output end of the voltage-to-current module is electrically connected to the input end of the current control delay module, the output end of the current control delay module is electrically connected to the second input end of the logic control module, the second output end of the voltage-to-current module is electrically connected to the input end of the clamp module, and the The output end of the clamp module is electrically connected to the negative input end of the first comparator, the positive input end of the first comparator is used to collect the current when the second power tube or the third power tube is turned on, the output end of the first comparator is electrically connected to the third input end of the logic control module, the positive input end of the second comparator is electrically connected to the source end of the fourth power tube, the negative input end of the second comparator is electrically connected to the drain end of the fourth power tube, the output end of the second comparator is electrically connected to the fourth input end of the logic control module, the first end of the first resistor is electrically connected between the output end of the differential amplifier and the input end of the voltage-to-current module, the second end of the first resistor is electrically connected to the upper plate of the first capacitor, and the lower plate of the first capacitor is grounded;

[0012] The feedback module is used to transmit a feedback voltage to the differential amplifier, and the feedback voltage is used to characterize the change of the output voltage;

[0013] The differential amplifier is used to amplify the voltage difference between the feedback voltage and the reference voltage to obtain a first voltage, and transmit the first voltage to the voltage-to-current module via the first resistor and the first capacitor;

[0014] The voltage-to-current module is used to convert the first voltage into the first current, and transmit the first current to the clamping module and the current control delay module respectively;

[0015] The current control delay module is used to determine whether to change the delay time according to the magnitude of the first current to obtain a first pulse signal, and transmit the first pulse signal to the logic control module, wherein the first pulse signal is used to determine the switching period;

[0016] The clamping module is used to clamp the first current to obtain a second current, and transmit the second current to the first comparator;

[0017] The first comparator is used to compare the current when the second power tube is turned on with the second current to obtain a second pulse signal, and transmit the second pulse signal to the logic control module, wherein the second pulse signal is used to control the turning on or off of the power tube;

[0018] The timing module is used to obtain a third pulse signal according to the input voltage and the output voltage, and transmit the third pulse signal to the logic control module, wherein the third pulse signal is used to control the on-time of the buck-boost converter in the buck mode;

[0019] The logic control module is used to control the third power tube to be always turned off, the fourth power tube to be always turned on, and control the first power tube and the second power tube to switch between being turned on or off according to the first pulse signal, the second pulse signal and the third pulse signal;

[0020] The second comparator is used to detect the voltage drop when the fourth power tube is turned on by comparing the source terminal voltage and the drain terminal voltage when the fourth power tube is turned on, and transmit the zero-crossing signal to the logic control module when the current of the inductor passes through a zero point during discharge;

[0021] The logic control module is also used to control the third power tube to be turned on and the fourth power tube to be turned off according to the zero-crossing signal.

[0022] In one possible design, the feedback module includes: a second resistor and a third resistor;

[0023] The first end of the second resistor is used to access the output voltage, the second end of the second resistor is electrically connected to the first end of the third resistor, the negative input terminal of the differential amplifier is electrically connected between the second end of the second resistor and the first end of the third resistor, and the second end of the third resistor is grounded.

[0024] In one possible design, the power supply control circuit is specifically used to determine that the current of the inductor during discharge passes through zero when it is detected that the voltage drop when the fourth power tube is turned on is zero; or, when it is detected that the voltage drop when the fourth power tube is turned on is not zero, determine that the current of the inductor during discharge does not pass through zero.

[0025] In one possible design, the buck-boost converter further includes: an output capacitor and an output resistor;

[0026] The upper plate of the output capacitor and the first end of the output resistor are both electrically connected to the source end of the fourth power tube, and the lower plate of the output capacitor and the second end of the output resistor are both grounded.

[0027] In a possible design, the second power tube and the third power tube are N-type power tubes, and the first power tube and the fourth power tube are P-type power tubes.

[0028] In a second aspect, the present application provides a control method, which is performed by a synchronous rectification controller in the first aspect and each possible design of the first aspect, wherein the buck-boost converter includes: a power control circuit, a first power tube, a second power tube, a third power tube, a fourth power tube and an inductor;

[0029] The source end of the first power tube is used to access the input voltage of the buck-boost converter, the drain end of the first power tube is electrically connected to the first end of the inductor, the drain end of the second power tube is electrically connected between the drain end of the first power tube and the first end of the inductor, the second end of the inductor is electrically connected to the drain end of the fourth power tube, the drain end of the third power tube is electrically connected between the second end of the inductor and the drain end of the fourth power tube, the source end of the fourth power tube is used to output the output voltage of the buck-boost converter, the source end of the second power tube and the source end of the third power tube are both grounded, the first input end of the power control circuit is electrically connected to the drain end of the fourth power tube, the second input end of the power control circuit is electrically connected to the source end of the fourth power tube, and the output end of the power control circuit is electrically connected to the gate end of the first power tube, the gate end of the second power tube, the gate end of the third power tube and the gate end of the fourth power tube respectively; the method includes:

[0030] In the case where the buck-boost converter is in buck mode and light load mode, wherein:

[0031] The power supply control circuit controls the third power tube to be always turned off, the fourth power tube to be always turned on, and controls the first power tube and the second power tube to switch between being turned on or off, so that the inductor switches between charging and discharging;

[0032] The power supply control circuit determines whether the current of the inductor passes through zero when discharging by detecting the voltage drop when the fourth power tube is turned on, and when the current of the inductor passes through zero when discharging, controls the third power tube to be turned on and the fourth power tube to be turned off, so that the voltage across the inductor is zero, so that the average current of the inductor in each switching cycle remains unchanged.

[0033] The beneficial effects of the methods provided in the above-mentioned second aspect and each possible design of the above-mentioned second aspect can be referred to the beneficial effects brought about by the above-mentioned first aspect and each possible implementation method of the first aspect, and will not be repeated here.

[0034] In a third aspect, the present application provides a chip, comprising: the buck-boost converter in the above-mentioned first aspect and each possible design of the above-mentioned first aspect.

[0035] In a fourth aspect, the present application provides an electronic device, comprising: the chip in the third aspect above.

[0036] The above description is only an overview of the technical solution of the embodiment of the present application. In order to more clearly understand the technical means of the embodiment of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the embodiment of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions of the embodiments of the present application, a brief introduction will be given below to the drawings required for use in the description of the embodiments. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0038] Figure 1 A schematic diagram of the working timing of a buck-boost converter in the related art;

[0039] Figure 2 A schematic diagram of a current waveform of an inductor in a buck-boost converter in the related art;

[0040] Figure 3 A schematic diagram of the structure of a buck-boost converter provided in one embodiment of the present application;

[0041] Figure 4 A flow chart of a control method provided in one embodiment of the present application;

[0042] Figure 5 A schematic diagram of the working timing of a buck-boost converter provided in one embodiment of the present application;

[0043] Figure 6 A schematic diagram of a current waveform of an inductor in a buck-boost converter provided in one embodiment of the present application. DETAILED DESCRIPTION

[0044] In this application, "at least one" means one or more, and "plurality" means two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone, where A and B can be singular or plural. The character " / " generally indicates that the associated objects before and after are in an "or" relationship. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, at least one of a, b, or c alone can represent: a, b, c, a and b, a and c, or a, b, and c, where a, b, and c can be single or multiple. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0045] The directions or positional relationships indicated by terms such as "center", "longitudinal", "lateral", "up", "down", "left", "right", "front", and "back" are based on the directions or positional relationships shown in the accompanying drawings and are only for the convenience of describing the present application and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present application.

[0046] The terms "connected" and "connected" should be understood in a broad sense. For example, the "connected" or "connected" of a circuit structure can refer to not only physical connection, but also electrical connection or signal connection. For example, it can be directly connected, that is, physically connected, or indirectly connected through at least one intermediate element, as long as the circuit is connected, or it can be the internal connection of two elements; signal connection can refer to signal connection through a circuit or through a media medium, such as radio waves. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0047] First, the professional terms involved in the embodiments of the present application are explained.

[0048] Buck mode refers to the buck-boost converter mode in which the input voltage is greater than the output voltage.

[0049] Boost mode refers to the buck-boost converter in which the input voltage is less than the output voltage.

[0050] Buck-boost mode refers to the buck-boost converter in which the input voltage is close to the output voltage.

[0051] The light load mode means that in this mode, the current of the inductor drops to zero in each switching cycle and then stops decreasing.

[0052] Heavy load mode means that in this mode the current of the inductor changes linearly with the load.

[0053] The zero point is the moment when the inductor current changes from a positive value to a negative value.

[0054] In light load mode, the buck-boost converter uses pulse frequency modulation (PFM), which is a technique for controlling the output signal by adjusting the frequency of the pulse signal.

[0055] In heavy load mode, the buck-boost converter uses pulse width modulation (PWM), which is a technique for controlling the output signal by adjusting the duty cycle of a pulse signal.

[0056] The buck-boost converter may include: power tube A', power tube B', power tube C', power tube D' and inductor IND'. The power tube A', power tube B', power tube C' and power tube D' are alternately turned on and off in a certain sequence, so that the output voltage of the buck-boost converter remains constant, and energy is transferred from the input voltage to the output voltage through the inductor IND'.

[0057] When the input voltage is much greater than the output voltage, the power tube D' is always on, the power tube C' is always off, and the power tube A' and the power tube B' are alternately on and off. At this time, the buck-boost converter is in buck mode. In the buck mode, the buck-boost converter is in valley current mode.

[0058] When the input voltage is much lower than the output voltage, the power tube A' is always on, the power tube B' is always off, and the power tube C' and the power tube D' are alternately on and off. At this time, the buck-boost converter is in boost mode. In the boost mode, the buck-boost converter is in peak current mode.

[0059] When the input voltage is close to the output voltage, the power tubes A', B', C' and D' are turned on and off alternately according to a specific timing sequence. At this time, the buck-boost converter is in the buck-boost mode.

[0060] In order to improve the efficiency of the buck-boost converter at light load, the buck-boost converter is usually designed with the function of automatically entering the light load mode. When the load is heavy, the buck-boost converter operates in continuous conduction mode (CCM). When the load is reduced to a certain level, the buck-boost converter automatically enters the light load mode.

[0061] Among them, in the continuous conduction mode, the operating frequency of the buck-boost converter, that is, the switching period, remains unchanged. The buck-boost converter achieves output voltage stability by adjusting the duty cycle of the power tube. In this mode, the current of the inductor changes linearly with the load.

[0062] Among them, in the light load mode, the power stage circuit composed of power tube A', power tube B', power tube C', power tube D' and inductor IND' maintains the stability of the output voltage through intermittent operation. In this mode, the current of the inductor will not continue to decrease after it drops to zero in each switching cycle.

[0063] Reference Figure 1 , Figure 1 for Figure 1 FIG. 1 is a schematic diagram of the working timing of a buck-boost converter in the related art. Figure 1 As shown, in the buck-boost converter in the related art, the power tube C' remains off in the buck mode. When the signal PWM' is at a high level, the power tubes A' and D' are turned on, the power tube B' is turned off, and the inductor is charged. When the signal PWM' is at a low level, the power tubes B' and D' are turned on, the power tube A' is turned off, and the inductor is discharged. When the current of the inductor passes through zero, the signal ZCD' becomes a high level, the power tube B' continues to be turned on, the power tube A' and D' are turned off, and the inductor stops discharging.

[0064] The delay time of the signal T3 ′ being at a high level determines the switching cycle, that is, the next switching cycle is triggered by the signal T3 ′.

[0065] When the signal T3' changes from high level to low level, the signal PWM' changes to high level, so that the buck-boost converter starts the next switching cycle. At the same time, when the signal T3' is set to high level, the buck-boost converter starts the next delay timing.

[0066] Reference Figure 2 , Figure 2 FIG. 1 is a schematic diagram of the current waveform of the inductor in the buck-boost converter in the related art. Figure 2As shown, since the buck-boost converter in the related art has high requirements for the zero-crossing detection accuracy of the inductor current. Therefore, when the zero-crossing detection current I_ZAD' is high, the current of the inductor will continue to discharge through the parasitic diodes of the power tube B' and the power tube D'. In this way, when the inductor is discharged, the voltage across the inductor is the sum of the output voltage and the voltage drop of the parasitic diode, so that when the inductor stops discharging at time t1, the current of the inductor may still discharge at a higher slope. Furthermore, because the conduction time of the power tube A' and the power tube D' is fixed, that is, the charging time of the inductor is fixed, the current of the inductor when charging starts in the next switching cycle is lower than the current when charging starts in the previous switching cycle. In other words, the current of the inductor at time t2 is lower than the current of the inductor at time t1. In this way, the average current of the inductor in the next switching cycle is lower than the average current in the previous switching cycle, so that the loop of the buck-boost converter needs to reduce the delay time t1-t2 when the signal T3' is high. As a result, the buck-boost converter is prone to instability when entering the light load mode.

[0067] The voltage drop of the parasitic body diode is, for example, 0.7V.

[0068] In order to solve the above problems, the present application provides a buck-boost converter, a control method, a chip and an electronic device.

[0069] The buck-boost converter may be a chip or a circuit module.

[0070] In this application, electronic devices may include, but are not limited to: portable electronic devices, power management systems, automotive electronics, and household appliances.

[0071] Reference Figure 3 , Figure 3 Schematic diagram of a buck-boost converter according to an embodiment of the present application. Figure 3 As shown, the buck-boost converter 100 may include: a power control circuit 110, a first power tube A, a second power tube B, a third power tube C, a fourth power tube D and an inductor IND.

[0072] The source end of the first power tube A is used to connect to the input voltage VIN of the buck-boost converter 100, the drain end of the first power tube A is electrically connected to the first end of the inductor IND, the drain end of the second power tube B is electrically connected between the drain end of the first power tube A and the first end of the inductor IND, the second end of the inductor IND is electrically connected to the drain end of the fourth power tube D, the drain end of the third power tube C is electrically connected between the second end of the inductor IND and the drain end of the fourth power tube D, the source end of the fourth power tube D is used to output the output voltage VOUT of the buck-boost converter 100, the source end of the second power tube B and the source end of the third power tube C are both grounded, the first input end of the power control circuit 110 is electrically connected to the drain end of the fourth power tube D, the second input end of the power control circuit 110 is electrically connected to the source end of the fourth power tube D, and the output end of the power control circuit 110 is electrically connected to the gate end of the first power tube A, the gate end of the second power tube B, the gate end of the third power tube C, and the gate end of the fourth power tube D, respectively.

[0073] Among them, the power control circuit 110, the first power tube A, the second power tube B, the third power tube C, the fourth power tube D and the inductor IND can be set separately or integrated, and the embodiment of the present application does not make specific limitations on this.

[0074] The first power tube A, the second power tube B, the third power tube C and the fourth power tube D may include but are not limited to metal-oxide semiconductor field effect transistors and gallium nitride transistors.

[0075] Below, refer to Figure 4 , Figure 4 A flowchart of a control method provided in one embodiment of the present application.

[0076] S101, the power control circuit controls the third power tube to be always turned off, the fourth power tube to be always turned on, and controls the first power tube and the second power tube to switch between on and off, so that the inductor switches between charging and discharging.

[0077] S102, the power supply control circuit determines whether the current of the inductor passes through zero when discharging by detecting the voltage drop when the fourth power tube is turned on, and when the current of the inductor passes through zero when discharging, controls the third power tube to be turned on and the fourth power tube to be turned off, so that the voltage across the inductor is zero, so that the average current of the inductor in each switching cycle remains unchanged.

[0078] Combine the following Figure 5 and Figure 6 , Figure 5 A schematic diagram of the working timing of a buck-boost converter provided in one embodiment of the present application is shown in FIG. Figure 6A schematic diagram of a current waveform of an inductor in a buck-boost converter provided in an embodiment of the present application is provided, which describes in detail the working contents of the buck-boost converter when the buck-boost converter 100 is in the buck mode BUCK and the light load mode.

[0079] The power control circuit 110 can control the third power tube C to be always off and the fourth power tube D to be always on. In addition, the power control circuit 110 can control the first power tube A and the second power tube B to switch between on and off. Figure 5 During the T0-T1 period, the power control circuit 110 can control the first power tube A to be turned on, the second power tube B to be turned off, the inductor IND to be charged, and the current IL of the inductor IND to gradually increase. Figure 5 During the period T1-T2, the power control circuit 110 can control the first power tube A to turn off, the second power tube B to turn on, the inductor IND to discharge, and the current IL of the inductor IND to gradually decrease. Figure 5 During the period T3-T4, the power control circuit 110 can control the first power tube A to be turned on, the second power tube B to be turned off, the inductor IND to be charged, and the current IL of the inductor IND to gradually increase. Figure 5 During the period T4-T5, the power control circuit 110 can control the first power tube A to be turned off, the second power tube B to be turned on, the inductor IND to be discharged, and the current IL of the inductor IND to be gradually reduced. In this way, the inductor IND is switched between charging and discharging.

[0080] The power control circuit 110 determines whether the current of the inductor IND during discharge passes through zero by detecting the voltage drop when the fourth power tube D is turned on. When it is detected that the voltage drop when the fourth power tube D is turned on is zero, the power control circuit 110 can determine that the current of the inductor IND during discharge passes through zero. When it is detected that the voltage drop when the fourth power tube D is turned on is not zero, the power control circuit 110 can determine that the current of the inductor IND during discharge does not pass through zero.

[0081] In this way, Figure 5 At time T2 and time T4, when the current of the inductor IND passes through the zero point during discharge, the power control circuit 110 can control the third power tube C to be turned on and the fourth power tube D to be turned off, so that the voltage across the inductor IND is zero, that is, the current of the inductor IND remains unchanged. Figure 5 The current at time T3 is maintained at Figure 5 The current when the inductor stops discharging at time T2 in the figure. Then, the inductor IND is Figure 5 When charging is performed during the T3-T5 period, the current of the inductor IND will also stop discharging from the previous switching cycle (i.e., Figure 5 The current at time T2 in the figure gradually increases. Figure 6As shown, the average current IL_AVG of the inductor IND in each switching cycle remains constant, so that the buck-boost converter 100 tends to be stable.

[0082] In some examples, the second power tube B and the third power tube C are N-type power tubes, and the first power tube A and the fourth power tube D are P-type power tubes.

[0083] The buck-boost converter provided by the present application, when the buck-boost converter is in the buck mode and the light load mode, the power control circuit can control the third power tube to be always turned off, the fourth power tube to be always turned on, and control the first power tube and the second power tube to switch between on or off, so that the inductor switches between charging and discharging. The power control circuit determines whether the current of the inductor during discharge passes through zero by detecting the voltage drop when the fourth power tube is turned on. When the current of the inductor during discharge passes through zero, the power control circuit can control the third power tube to be turned on and the fourth power tube to be turned off, so that the voltage across the inductor is zero, so that the current of the inductor is maintained at the current when the discharge stops. Furthermore, when the inductor is charged again, the current of the inductor gradually increases from the current when the discharge stops. Thus, the average current of the inductor in each switching cycle remains unchanged, so that the buck-boost converter tends to be stable.

[0084] Based on the description of the above embodiment, a possible implementation of the power control circuit 110 is exemplified. Figure 3 As shown, the power control circuit 110 may include: a feedback module 111, a differential amplifier 112, a voltage-to-current module 113, a clamping module 114, a current control delay module 115, a timing module 116, a logic control module 117, a first comparator 118, a second comparator 119, a first resistor R1 and a first capacitor C1.

[0085] The input end of the feedback module 111 and the first input end of the timing module 116 are both used to access the output voltage VOUT, the second input end of the timing module 116 is used to access the input voltage VIN, the output end of the timing module 116 is electrically connected to the first input end of the logic control module 117, the output end of the feedback module 111 is electrically connected to the negative input end of the differential amplifier 112, the positive input end of the differential amplifier 112 is used to access the reference voltage VREF, the output end of the differential amplifier 112 is electrically connected to the input end of the voltage-to-current module 113, the first output end of the voltage-to-current module 113 is electrically connected to the input end of the current control delay module 115, the output end of the current control delay module 115 is electrically connected to the second input end of the logic control module 117, the second output end of the voltage-to-current module 113 is electrically connected to the positive input end of the clamp module 114 The input end is electrically connected, the output end of the clamp module 114 is electrically connected to the negative input end of the first comparator 118, the positive input end of the first comparator 118 is used to collect the current when the second power tube B or the third power tube C is turned on, the output end of the first comparator 118 is electrically connected to the third input end of the logic control module 117, the positive input end of the second comparator 119 is electrically connected to the source end of the fourth power tube D, the negative input end of the second comparator 119 is electrically connected to the drain end of the fourth power tube D, the output end of the second comparator 119 is electrically connected to the fourth input end of the logic control module 117, the first end of the first resistor R1 is electrically connected between the output end of the differential amplifier 112 and the input end of the voltage-to-current module 113, the second end of the first resistor R1 is electrically connected to the upper plate of the first capacitor C1, and the lower plate of the first capacitor C1 is grounded.

[0086] In the buck mode BUCK, the positive input terminal of the first comparator 118 is used to collect the current when the second power tube B is turned on. In the boost mode BOOST, the positive input terminal of the first comparator 118 is used to collect the current when the third power tube C is turned on.

[0087] In some examples, the feedback module 111 may include: a second resistor R2 and a third resistor R3 .

[0088] The first end of the second resistor R2 is used to connect to the output voltage VOUT, the second end of the second resistor R2 is electrically connected to the first end of the third resistor R3, the negative input end of the differential amplifier 112 is electrically connected between the second end of the second resistor R2 and the first end of the third resistor R3, and the second end of the third resistor R3 is grounded.

[0089] The feedback module 111 can transmit the feedback voltage VFB to the differential amplifier 112 , so that the differential amplifier 112 can obtain the feedback voltage VFB.

[0090] The feedback voltage VFB is used to characterize the change of the output voltage VOUT.

[0091] The differential amplifier 112 can amplify the voltage difference between the feedback voltage VFB and the reference voltage VREF to obtain the first voltage VC. Furthermore, the differential amplifier 112 can transmit the first voltage VC to the voltage-to-current module 113 via the first resistor R1 and the first capacitor C1, so that the voltage-to-current module 113 can obtain the first voltage VC.

[0092] The first voltage VC decreases as the load decreases.

[0093] The voltage-to-current module 113 can convert the first voltage VC into the first current I1. Furthermore, the voltage-to-current module 113 can transmit the first current I1 to the clamping module 114 and the current-controlled delay module 115 respectively, so that the clamping module 114 and the current-controlled delay module 115 can obtain the first current I1.

[0094] The first current I1 input to the current-controlled delay module 115 may also be represented by letters IPFM.

[0095] The current control delay module 115 can determine whether to change the delay time according to the magnitude of the first current I1 to obtain the first pulse signal T3. In addition, the current control delay module 115 can transmit the first pulse signal T3 to the logic control module 117 so that the logic control module 117 can obtain the first pulse signal T3.

[0096] The first pulse signal T3 is used to determine the switching period.

[0097] The delay time increases as the first current I1, i.e., the first current IPFM, decreases. In the light load mode, the first current I1 decreases due to the decrease in the first voltage VC, so that the delay time increases. Thus, the switching period determined by the first pulse signal T3 is greater than the switching period determined by the first pulse signal T3, so that the switching period is determined by the first pulse signal T3.

[0098] The clamping module 114 can clamp the first current I1 to obtain the second current IC. Furthermore, the clamping module 114 can transmit the second current IC to the first comparator 118 so that the first comparator 118 can obtain the second current IC.

[0099] When the first current I1 is greater than the preset current set by the clamping module 114, the second current IC is equal to the first current I1. When the first current I1 is less than the preset current set by the clamping module 114, the second current IC is equal to the preset current. Since the first current I1 is clamped to the preset current by the clamping module 114 in the light load mode, the second current IC is equal to the preset current, so that the current of the inductor in each switching cycle does not continue to decrease after the current decreases to zero.

[0100] The first comparator 118 can compare the current when the second power tube B is turned on with the second current IC to obtain the second pulse signal PWM. In addition, the first comparator 118 can transmit the second pulse signal PWM to the logic control module 117 so that the logic control module 117 can obtain the second pulse signal PWM.

[0101] The second pulse signal PWM is used to control the on or off of the power tube.

[0102] The timing module 116 can monitor the input voltage VIN and the output voltage VOUT to obtain the third pulse signal T1. In addition, the timing module 116 can transmit the third pulse signal T1 to the logic control module 117 so that the logic control module 117 can obtain the third pulse signal T1.

[0103] The third pulse signal T1 is used to control the on-time of the buck-boost converter 100 in the buck mode BUCK.

[0104] The timing module 116 can monitor the input voltage VIN and the output voltage VOUT to obtain the fourth pulse signal T2 for controlling the buck-boost converter 100 in the boost mode BOOST. Since the fourth pulse signal T2 does not work in the buck mode BUCK, it is not Figure 3 It is reflected in.

[0105] The logic control module 117 can control the third power tube C to be always off and the fourth power tube D to be always on according to the first pulse signal T3, the second pulse signal PWM and the third pulse signal T1, and control the first power tube A and the second power tube B to switch between on and off.

[0106] The second comparator 119 can detect the voltage drop when the fourth power tube D is turned on by comparing the source terminal voltage and the drain terminal voltage when the fourth power tube D is turned on. In addition, when the current of the inductor IND passes through the zero point during discharge, the second comparator 119 can obtain the zero-crossing signal ZCD and transmit the zero-crossing signal ZCD to the logic control module 117, so that the logic control module 117 can obtain the zero-crossing signal ZCD.

[0107] In this way, the logic control module 117 can control the third power tube C to be turned on and the fourth power tube D to be turned off according to the zero-crossing signal ZCD. Therefore, when the current of the inductor IND passes through the zero point during discharge, the power control circuit 110 can control the third power tube C to be turned on and the fourth power tube D to be turned off. The fourth power tube D is turned off so that the current of the inductor IND does not become a negative value, and the third power tube C is turned on so that the voltage across the inductor IND is zero.

[0108] Based on the description of the above embodiment, a possible implementation of the buck-boost converter 100 is exemplified. Figure 3 As shown, the buck-boost converter 100 may further include: an output capacitor Cout and an output resistor Rout.

[0109] The upper plate of the output capacitor Cout and the first end of the output resistor Rout are both electrically connected to the source end of the fourth power tube D, and the lower plate of the output capacitor Cout and the second end of the output resistor Rout are both grounded.

[0110] Finally, it should be noted that the above embodiments are only specific implementation methods of the present application, but the protection scope of the present application is not limited thereto, and any changes or substitutions within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A buck-boost converter, characterized in that: The buck-boost converter comprises: a power control circuit, a first power tube, a second power tube, a third power tube, a fourth power tube and an inductor; The source end of the first power tube is used to access the input voltage of the buck-boost converter, the drain end of the first power tube is electrically connected to the first end of the inductor, the drain end of the second power tube is electrically connected between the drain end of the first power tube and the first end of the inductor, the second end of the inductor is electrically connected to the drain end of the fourth power tube, the drain end of the third power tube is electrically connected between the second end of the inductor and the drain end of the fourth power tube, the source end of the fourth power tube is used to output the output voltage of the buck-boost converter, the source end of the second power tube and the source end of the third power tube are both grounded, the first input end of the power control circuit is electrically connected to the drain end of the fourth power tube, the second input end of the power control circuit is electrically connected to the source end of the fourth power tube, and the output end of the power control circuit is electrically connected to the gate end of the first power tube, the gate end of the second power tube, the gate end of the third power tube and the gate end of the fourth power tube respectively; In the case where the buck-boost converter is in buck mode and light load mode, wherein: The power supply control circuit is used to control the third power tube to be always turned off, the fourth power tube to be always turned on, and control the first power tube and the second power tube to switch between being turned on or off, so that the inductor switches between charging and discharging; The power supply control circuit is also used to determine whether the current of the inductor passes through zero when discharging by detecting the voltage drop when the fourth power tube is turned on, and when the current of the inductor passes through zero when discharging, control the third power tube to be turned on and the fourth power tube to be turned off, so that the voltage across the inductor is zero, so that the average current of the inductor in each switching cycle remains unchanged.

2. The buck-boost converter according to claim 1, characterized in that: The power control circuit includes: a feedback module, a differential amplifier, a voltage-to-current module, a clamping module, a current control delay module, a timing module, a logic control module, a first comparator, a second comparator, a first resistor and a first capacitor; The input end of the feedback module and the first input end of the timing module are both used to access the output voltage, the second input end of the timing module is used to access the input voltage, the output end of the timing module is electrically connected to the first input end of the logic control module, the output end of the feedback module is electrically connected to the negative input end of the differential amplifier, the positive input end of the differential amplifier is used to access the reference voltage, the output end of the differential amplifier is electrically connected to the input end of the voltage-to-current module, the first output end of the voltage-to-current module is electrically connected to the input end of the current control delay module, the output end of the current control delay module is electrically connected to the second input end of the logic control module, the second output end of the voltage-to-current module is electrically connected to the input end of the clamp module, and the The output end of the clamp module is electrically connected to the negative input end of the first comparator, the positive input end of the first comparator is used to collect the current when the second power tube or the third power tube is turned on, the output end of the first comparator is electrically connected to the third input end of the logic control module, the positive input end of the second comparator is electrically connected to the source end of the fourth power tube, the negative input end of the second comparator is electrically connected to the drain end of the fourth power tube, the output end of the second comparator is electrically connected to the fourth input end of the logic control module, the first end of the first resistor is electrically connected between the output end of the differential amplifier and the input end of the voltage-to-current module, the second end of the first resistor is electrically connected to the upper plate of the first capacitor, and the lower plate of the first capacitor is grounded; The feedback module is used to transmit a feedback voltage to the differential amplifier, and the feedback voltage is used to characterize the change of the output voltage; The differential amplifier is used to amplify the voltage difference between the feedback voltage and the reference voltage to obtain a first voltage, and transmit the first voltage to the voltage-to-current module via the first resistor and the first capacitor; The voltage-to-current module is used to convert the first voltage into the first current, and transmit the first current to the clamping module and the current control delay module respectively; The current control delay module is used to determine whether to change the delay time according to the magnitude of the first current to obtain a first pulse signal, and transmit the first pulse signal to the logic control module, wherein the first pulse signal is used to determine the switching period; The clamping module is used to clamp the first current to obtain a second current, and transmit the second current to the first comparator; The first comparator is used to compare the current when the second power tube is turned on with the second current to obtain a second pulse signal, and transmit the second pulse signal to the logic control module, wherein the second pulse signal is used to control the turning on or off of the power tube; The timing module is used to obtain a third pulse signal according to the input voltage and the output voltage, and transmit the third pulse signal to the logic control module, wherein the third pulse signal is used to control the on-time of the buck-boost converter in the buck mode; The logic control module is used to control the third power tube to be always turned off, the fourth power tube to be always turned on, and control the first power tube and the second power tube to switch between being turned on or off according to the first pulse signal, the second pulse signal and the third pulse signal; The second comparator is used to detect the voltage drop when the fourth power tube is turned on by comparing the source terminal voltage and the drain terminal voltage when the fourth power tube is turned on, and transmit the zero-crossing signal to the logic control module when the current of the inductor passes through a zero point during discharge; The logic control module is also used to control the third power tube to be turned on and the fourth power tube to be turned off according to the zero-crossing signal.

3. The buck-boost converter according to claim 2, characterized in that: The feedback module includes: a second resistor and a third resistor; The first end of the second resistor is used to access the output voltage, the second end of the second resistor is electrically connected to the first end of the third resistor, the negative input terminal of the differential amplifier is electrically connected between the second end of the second resistor and the first end of the third resistor, and the second end of the third resistor is grounded.

4. The buck-boost converter according to claim 1, characterized in that: The power supply control circuit is specifically used to determine that the current of the inductor during discharge passes through zero when it is detected that the voltage drop when the fourth power tube is turned on is zero; or, when it is detected that the voltage drop when the fourth power tube is turned on is not zero, determine that the current of the inductor during discharge does not pass through zero.

5. The buck-boost converter according to any one of claims 1 to 4, characterized in that: The buck-boost converter also includes: an output capacitor and an output resistor; The upper plate of the output capacitor and the first end of the output resistor are both electrically connected to the source end of the fourth power tube, and the lower plate of the output capacitor and the second end of the output resistor are both grounded.

6. The buck-boost converter according to any one of claims 1 to 4, characterized in that: The second power tube and the third power tube are N-type power tubes, and the first power tube and the fourth power tube are P-type power tubes.

7. A control method, characterized in that: The method is performed by a buck-boost converter, the buck-boost converter comprising: a power control circuit, a first power tube, a second power tube, a third power tube, a fourth power tube and an inductor; The source end of the first power tube is used to access the input voltage of the buck-boost converter, the drain end of the first power tube is electrically connected to the first end of the inductor, the drain end of the second power tube is electrically connected between the drain end of the first power tube and the first end of the inductor, the second end of the inductor is electrically connected to the drain end of the fourth power tube, the drain end of the third power tube is electrically connected between the second end of the inductor and the drain end of the fourth power tube, the source end of the fourth power tube is used to output the output voltage of the buck-boost converter, the source end of the second power tube and the source end of the third power tube are both grounded, the first input end of the power control circuit is electrically connected to the drain end of the fourth power tube, the second input end of the power control circuit is electrically connected to the source end of the fourth power tube, and the output end of the power control circuit is electrically connected to the gate end of the first power tube, the gate end of the second power tube, the gate end of the third power tube and the gate end of the fourth power tube respectively; the method includes: In the case where the buck-boost converter is in buck mode and light load mode, wherein: The power supply control circuit controls the third power tube to be always turned off, the fourth power tube to be always turned on, and controls the first power tube and the second power tube to switch between being turned on or off, so that the inductor switches between charging and discharging; The power supply control circuit determines whether the current of the inductor passes through zero when discharging by detecting the voltage drop when the fourth power tube is turned on, and when the current of the inductor passes through zero when discharging, controls the third power tube to be turned on and the fourth power tube to be turned off, so that the voltage across the inductor is zero, so that the average current of the inductor in each switching cycle remains unchanged.

8. A chip, characterized in that: include: A buck-boost converter as claimed in any one of claims 1 to 6.

9. An electronic device, characterized in that: include: The chip as claimed in claim 8.

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