A switching power supply circuit and a control method thereof

Abstract

The embodiment of the application discloses a switching power supply circuit and a control method thereof, wherein the switching power supply circuit comprises a compensation comparison unit, a control unit, a current sampling unit and an output unit. The output current of the output unit is sampled by the current sampling unit to obtain a sampling current, and then the sampling current and the output voltage of the output unit are fed back to the compensation comparison unit. The compensation comparison unit performs voltage compensation operation based on the sampling current and the output voltage, and outputs a voltage compensation signal. Therefore, the control unit controls the output voltage of the output unit to be constant according to the voltage compensation signal. In the above manner, the compensation comparison unit can control the output of the output unit according to the output current information and the output voltage information, greatly simplifying the loop compensation characteristics and improving the transient response speed.

Description

Technical Field

[0001] This application relates to the field of power supply technology, and in particular to a switching power supply circuit and its control method. Background Technology

[0002] Compared to traditional DC power supplies, switching power supplies offer advantages such as small size, light weight, and high efficiency, making them widely used in communication equipment, industrial automation control, LED lighting, and other fields. Existing switching power supplies typically include inductors, with one end coupled to the switching circuit and the other end coupled to a parallel-connected electrolytic capacitor and the load. However, due to manufacturing limitations, electrolytic capacitors often have extremely low ESR values, and there is a phase difference between the inductor and capacitor, leading to stability issues such as multi-cycle output inductor current and a sharp increase in ripple. To achieve stability in switching power supplies, ripple compensation is necessary. Existing ripple compensation circuits typically generate a ramp using RC filtering when the P-power transistor is turned on, and introduce this ramp into the control loop for stabilization. However, introducing a ramp not only requires a large area, increasing manufacturing costs, but also necessitates continuous adjustment of the ramp amount based on application changes due to variations in input and output conditions, requiring extensive calculations and verification, consuming excessive time. Furthermore, different ramp amounts alter the loop output impedance, affecting the loop response speed. Summary of the Invention

[0003] This application provides a switching power supply circuit and its control method, which can greatly simplify loop compensation characteristics and improve transient response speed.

[0004] To address the aforementioned technical problems, this application provides a switching power supply circuit, including a compensation comparison unit, a control unit, a current sampling unit, and an output unit.

[0005] The output unit includes a control terminal, a first terminal for providing output current, and a second terminal for providing output voltage;

[0006] The input terminal of the current sampling unit is connected to the first terminal of the output unit to sample the output current and obtain the sampled current.

[0007] The first and second input terminals of the compensation comparison unit are respectively connected to the output terminal of the current sampling unit and the second terminal of the output unit. The third input terminal of the compensation comparison unit is connected to a reference voltage to perform voltage compensation calculation based on the sampled current, the output voltage and the reference voltage, and output a voltage compensation signal.

[0008] The input terminal of the control unit is connected to the output terminal of the compensation comparison unit. The first and second output terminals of the control unit are respectively connected to the control terminal of the current sampling unit and the control terminal of the output unit. The control unit is used to control the current sampling unit to perform current sampling or stop current sampling according to the voltage compensation signal, and to control the output voltage of the output unit to be constant.

[0009] In some embodiments, the compensation comparison unit includes a voltage compensation unit and a comparison unit;

[0010] The first and second input terminals of the voltage compensation unit serve as the first and second input terminals of the compensation comparison unit, respectively, and are connected to the output terminal of the current sampling unit and the second terminal of the output unit, respectively, for performing a summation operation on the sampled current and the output voltage to output a feedback voltage;

[0011] The first input terminal of the comparison unit serves as the third input terminal of the compensation comparison unit and is connected to the reference voltage. The second input terminal of the comparison unit is connected to the output terminal of the voltage compensation unit, used to compare the reference voltage and the feedback voltage, and output a voltage compensation signal according to the comparison result. The output terminal of the comparison unit is connected to the input terminal of the control unit.

[0012] In some embodiments, the voltage compensation unit includes a first resistor R1, the two ends of the first resistor R1 serving as the first input terminal and the second input terminal of the voltage compensation unit, respectively, to be connected to the output terminal of the current sampling unit and the second terminal of the output unit, respectively. The first input terminal of the voltage compensation unit also serves as the output terminal of the voltage compensation unit and is connected to the second input terminal of the comparison unit.

[0013] Alternatively, the voltage compensation unit includes a first switch Q1, a second switch Q2, a third switch Q3, a fourth switch Q4, a fifth switch Q5, a second resistor R2, a third resistor R3, and a fourth resistor R4; the first terminals of the first switch Q1 and the second switch Q2 are connected to the input voltage; the control terminal of the first switch Q1, the control terminal and the second terminal of the second switch Q2, and the first terminal of the fourth switch Q4 are connected; the second terminal of the first switch Q1 is connected to one end of the fourth resistor R4; and the other end of the fourth resistor R4, the first terminal of the third switch Q3, one end of the second resistor R2, and one end of the third resistor R3 are connected. The other end of the second resistor R2 serves as the second input terminal of the voltage compensation unit and is connected to the second terminal of the output unit. The other end of the third resistor R3, the second terminal of the third switch Q3, the second terminal of the fourth switch Q4, and the second terminal of the fifth switch Q5 are all grounded. The control terminals of the third switch Q3, the fourth switch Q4, and the fifth switch Q5 are connected to the first terminal of the fifth switch Q5. The first terminal of the fifth switch Q5 serves as the first input terminal of the voltage compensation unit and is connected to the output terminal of the current sampling unit. The second terminal of the first switch Q1 is the output terminal of the voltage compensation unit.

[0014] Alternatively, the voltage compensation unit includes a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, and a first amplifier; one end of the fifth resistor R5 is the second input terminal of the voltage compensation unit and is connected to the second terminal of the output unit; the other end of the fifth resistor R5, one end of the sixth resistor R6, and the first input terminal of the first amplifier are connected; the other end of the sixth resistor R6 is grounded; the second input terminal and the output terminal of the first amplifier are connected to one end of the seventh resistor R7; the other end of the seventh resistor R7 is the first input terminal of the voltage compensation unit and is connected to the output terminal of the current sampling unit; and the other end of the seventh resistor R7 is also the output terminal of the voltage compensation unit.

[0015] In some embodiments, the compensation comparison unit includes a voltage compensation unit and a comparison unit;

[0016] The first input terminal of the voltage compensation unit serves as the first input terminal of the compensation comparison unit and is connected to the output terminal of the current sampling unit. The second input terminal of the voltage compensation unit serves as the third input terminal of the compensation comparison unit and is connected to the reference voltage. It is used to perform a subtraction operation on the sampled current and the reference voltage to obtain the compensated reference voltage.

[0017] The first input terminal of the comparison unit serves as the second input terminal of the compensation comparison unit and is connected to the second terminal of the output unit. The second input terminal of the comparison unit is connected to the output terminal of the voltage compensation unit and is used to compare the output voltage with the compensated reference voltage to output a voltage compensation signal. The output terminal of the comparison unit is connected to the input terminal of the control unit.

[0018] In some embodiments, the voltage compensation unit includes a second amplifier, a sixteenth switch Q16, a seventeenth switch Q17, an eighteenth switch Q18, a nineteenth switch Q19, an eighth resistor R8, and a ninth resistor R9.

[0019] The first terminals of the sixteenth switch Q16 and the seventeenth switch Q17 are connected to the input voltage. The control terminals of the sixteenth switch Q16 and the seventeenth switch Q17 are connected to the output terminal of the second amplifier. The second terminal of the sixteenth switch Q16 and one end of the eighth resistor R8 are connected to the first input terminal of the second amplifier. The second terminal of the seventeenth switch Q17, one end of the ninth resistor R9, and the first terminal of the eighteenth switch Q18 are connected and serve as the output terminal of the voltage compensation unit for outputting the compensated reference voltage. The control terminals of the eighteenth switch Q18, the nineteenth switch Q19, and the first terminal of the nineteenth switch Q19 are connected and serve as the first input terminal of the voltage compensation unit, which is connected to the output terminal of the current sampling unit. The other ends of the eighth resistor R8, the ninth resistor R9, the second terminals of the eighteenth switch Q18, and the nineteenth switch Q19 are grounded. The second input terminal of the second amplifier serves as the second input terminal of the voltage compensation unit and is connected to the reference voltage.

[0020] In some embodiments, the current sampling unit includes a sixth switch Q6, a seventh switch Q7, an eighth switch Q8, a ninth switch Q9, a tenth switch Q10, an eleventh switch Q11, a twelfth switch Q12, a thirteenth switch Q13, a fourteenth switch Q14, and a fifteenth switch Q15.

[0021] The first terminals of the sixth switch Q6, the seventh switch Q7, the eighth switch Q8, and the tenth switch Q10 are all connected to the input voltage. The second terminal of the sixth switch Q6 is connected to the control terminal, the control terminal of the seventh switch Q7, and the first terminal of the thirteenth switch Q13. The second terminal of the seventh switch Q7, the control terminal of the ninth switch Q9, the control terminal of the eleventh switch Q11, and the first terminal of the fourteenth switch Q14 are connected. The second terminal of the eighth switch Q8 is connected to the control terminal, the first terminal of the ninth switch Q9, and the control terminal of the tenth switch Q10. The second terminal of the tenth switch Q10 is connected to the first terminal of the eleventh switch Q11. The connection is as follows: the second terminal of the eleventh switch Q11 is the output terminal of the current sampling unit; the second terminals of the ninth switch Q9, the fourteenth switch Q14, and the first terminal of the fifteenth switch Q15 are connected; the control terminal of the fifteenth switch Q15 is the control terminal of the current sampling unit; the second terminal of the fifteenth switch Q15 is the input terminal of the current sampling unit; the first terminal and control terminal of the twelfth switch Q12, the control terminal of the thirteenth switch Q13, and the control terminal of the fourteenth switch Q14 are connected; the second terminals of the twelfth switch Q12 and the thirteenth switch Q13 are grounded; and the first terminal of the twelfth switch Q12 is connected to the input current.

[0022] In some embodiments, the output unit has two control terminals, and the control unit has two second output terminals, which are respectively connected to the two control terminals of the output unit; the output unit includes a PMOS transistor, an NMOS transistor, an inductor L, an output capacitor C, and a load R. L ;

[0023] The control terminals of the PMOS transistor and the NMOS transistor are respectively the two control terminals of the output unit. The two second output terminals of the control unit are respectively connected to the control terminals of the PMOS transistor and the NMOS transistor to drive the PMOS transistor and the NMOS transistor to be turned on or off.

[0024] The source of the PMOS transistor, the drain of the NMOS transistor, and one end of the inductor L are connected, and the connection node is the first terminal of the output unit. The drain of the PMOS transistor is connected to the input voltage, and the source of the NMOS transistor is grounded. The other end of the inductor L, one end of the output capacitor C, and the load R are connected. L One end of the output capacitor is connected to the second end of the output unit, and the other end of the output capacitor and the other end of the load are grounded.

[0025] In some embodiments, the control unit includes a conduction mode control module, a logic module, a drive module, and a zero-crossing detection module;

[0026] The logic module is used to control the current sampling unit to perform current sampling or stop current sampling based on the voltage compensation signal output by the compensation comparison unit, the conduction mode signal output by the conduction mode control module, and the zero-crossing detection signal output by the zero-crossing detection module, and to control the driving module to drive the PMOS transistor and NMOS transistor to turn on or off.

[0027] The conduction mode signal includes one of a fixed conduction time control signal, a fixed peak current control signal, and a fixed turn-off time control signal;

[0028] The zero-crossing detection module is used to detect the current flowing through the NMOS transistor and outputs a zero-crossing detection signal when the current flowing through the NMOS transistor gradually decreases from a positive current to zero.

[0029] This application also provides a control method for a switching power supply circuit, including:

[0030] The output current of the output unit is sampled by the current sampling unit to obtain the sampled current;

[0031] The compensation comparison unit performs compensation calculations based on the reference voltage, the sampling current, and the output voltage of the output unit, and outputs a voltage compensation signal.

[0032] The voltage compensation signal is used to control the current sampling unit to perform current sampling or stop current sampling, and to control the output voltage of the output unit to remain constant.

[0033] In some embodiments, the step of performing compensation calculations by the compensation comparison unit based on the reference voltage, the sampling current, and the output voltage of the output unit, and outputting a voltage compensation signal, specifically includes:

[0034] The voltage compensation unit in the compensation comparison unit performs a summation operation on the sampled current and the output voltage to output a feedback voltage;

[0035] The reference voltage and the feedback voltage are compared by the comparison unit in the compensation comparison unit, and a voltage compensation signal is output according to the comparison result.

[0036] Alternatively, the compensation comparison unit performs compensation calculations based on the reference voltage, the sampled current, and the output voltage of the output unit, and outputs a voltage compensation signal, specifically including:

[0037] The voltage compensation unit in the compensation comparison unit performs a subtraction operation between the sampled current and the reference voltage to obtain the compensated reference voltage.

[0038] The output voltage of the output unit is compared with the compensated reference voltage by the comparison unit in the compensation comparison unit to output a voltage compensation signal.

[0039] The switching power supply circuit provided in this application sample the output current of the output unit through a current sampling unit to obtain a sampled current. Then, the sampled current and the output voltage of the output unit are fed back to the compensation comparison unit. The compensation comparison unit performs voltage compensation calculation based on the sampled current and the output voltage and outputs a voltage compensation signal. The control unit controls the output voltage of the output unit to be constant according to the voltage compensation signal. Therefore, this solution directly introduces the output voltage and output current as feedback signals into the control loop to achieve stability. It does not require the use of RC filtering to generate ramp waves to achieve stability. Compared with the existing method, it can greatly simplify the loop compensation characteristics and improve the transient response speed. Attached Figure Description

[0040] The technical solution and its beneficial effects will become apparent from the following detailed description of specific embodiments of this application, in conjunction with the accompanying drawings.

[0041] Figure 1 This is a schematic diagram of the overall structure of the switching power supply circuit provided in the embodiments of this application;

[0042] Figure 2 This is a schematic diagram of a specific structure of the switching power supply circuit provided in an embodiment of this application;

[0043] Figure 3 This is a circuit diagram of a voltage compensation unit provided in an embodiment of this application;

[0044] Figure 4 This is another circuit diagram of the voltage compensation unit provided in the embodiments of this application;

[0045] Figure 5 This is another circuit structure diagram of the voltage compensation unit provided in the embodiments of this application;

[0046] Figure 6 This is a circuit diagram of a current sampling unit provided in an embodiment of this application;

[0047] Figure 7 This is a timing waveform diagram of the switching power supply circuit provided in the embodiment of this application in DCM mode;

[0048] Figure 8 This is another timing waveform diagram of the switching power supply circuit provided in the embodiment of this application in DCM mode;

[0049] Figure 9This is a timing waveform diagram of the switching power supply circuit provided in the embodiment of this application in CCM mode;

[0050] Figure 10 This is another timing waveform diagram of the switching power supply circuit provided in the embodiment of this application in CCM mode;

[0051] Figure 11 This is a waveform diagram of the output voltage of the switching power supply circuit provided in the embodiment of this application as a function of load;

[0052] Figure 12 This is another specific structural schematic diagram of the switching power supply circuit provided in the embodiments of this application;

[0053] Figure 13 yes Figure 12 The circuit diagram shown is a circuit structure diagram of the voltage compensation unit of the switching power supply circuit.

[0054] Figure 14 This is a flowchart of the control method for the switching power supply circuit provided in the embodiments of this application. Detailed Implementation

[0055] Please refer to the diagrams, where the same component symbols represent the same components. The principles of this application are illustrated by example in a suitable computing environment. The following description is based on the specific embodiments of this application exemplified, and should not be construed as limiting other specific embodiments not detailed herein.

[0056] See Figure 1 In a switching power supply circuit provided in this application embodiment, the switching power supply circuit includes a compensation comparison unit 11, a control unit 12, a current sampling unit 13, and an output unit 14.

[0057] The output unit 14 includes a control terminal, a first terminal for providing output current, and a second terminal for providing output voltage Vout. The input terminal of the current sampling unit 13 is connected to the first terminal of the output unit 14 to sample the output current, thereby obtaining the sampled current Isense. The first and second input terminals of the compensation comparison unit 11 are respectively connected to the output terminal of the current sampling unit 13 and the second terminal of the output unit 14. The third input terminal of the compensation comparison unit 11 is connected to a reference voltage Vref to perform voltage compensation calculations based on the sampled current Isense, the output voltage Vout, and the reference voltage Vref, and output a voltage compensation signal. The input terminal of the control unit 12 is connected to the output terminal of the compensation comparison unit 11. The first and second output terminals of the control unit 12 are respectively connected to the control terminal of the current sampling unit 13 and the control terminal of the output unit 14, for controlling the current sampling unit 13 to perform current sampling or stop current sampling according to the voltage compensation signal, and controlling the output voltage Vout of the output unit 14 to remain constant.

[0058] Therefore, in the switching power supply circuit of this application, the sampling current Isense and the output voltage Vout of the output current are provided to the compensation comparison unit 11 for voltage compensation calculation, and the calculated voltage compensation signal is output to the control unit 12 so that the control unit 12 can drive according to the voltage compensation signal. That is, by incorporating the output current information and the output voltage information into the loop feedback, the loop stability is achieved by using the dual feedback signals of output voltage Vout and sampling current Isense. This not only enables the switching power supply circuit to output a stable voltage, but also eliminates the need to use RC filtering to generate ramp waves to achieve stability. Compared with the existing methods, this greatly simplifies the loop compensation characteristics and can greatly improve the transient response speed.

[0059] See Figure 2 In some embodiments of the switching power supply of this application, the compensation comparison unit 11 specifically includes a voltage compensation unit 111 and a comparison unit 112. The first and second input terminals of the voltage compensation unit 111 serve as the first and second input terminals of the compensation comparison unit 11, and are respectively connected to the output terminal of the current sampling unit 13 and the second terminal of the output unit 14, for performing a summation operation on the sampled current Isense and the output voltage Vout to output a feedback voltage Vfb.

[0060] The first input terminal of the comparison unit 112 is connected to the reference voltage Vref, which serves as the third input terminal of the compensation comparison unit 11. The second input terminal of the comparison unit 112 is connected to the output terminal of the voltage compensation unit 111, and is used to compare the reference voltage Vref and the feedback voltage Vfb, and output a voltage compensation signal CTL1 based on the comparison result. The output terminal of the comparison unit 112 is connected to the input terminal of the control unit 12.

[0061] The output unit 14 has two control terminals, and the control unit 12 has two second output terminals, which are respectively connected to the two control terminals of the output unit 12. Further, the output unit 14 may include a PMOS transistor, an NMOS transistor, an inductor L, an output capacitor C, and a load R. L .

[0062] The control terminals of the PMOS and NMOS transistors are the two control terminals of the output unit 14, respectively. The two second output terminals of the control unit 12 are connected to the control terminals of the PMOS and NMOS transistors to drive them to turn on or off. The source of the PMOS transistor, the drain of the NMOS transistor, and one end of the inductor L are connected together, and the connection node is the first terminal of the output unit 14. This connection node is denoted as LXSW, that is, the first terminal of the output unit 14 is... Figure 2 The connection node LXSW is shown. The drain of the PMOS transistor is connected to the input voltage Vin, the source of the NMOS transistor is grounded, and the other end of the inductor L, one end of the output capacitor C, and the load R are connected. L One end of the output capacitor is connected to the second end of the output unit 14, and the other end of the output capacitor and the other end of the load are grounded.

[0063] In this embodiment, the voltage compensation unit 14 can be implemented in several ways, such as the following three methods:

[0064] The first type: such as Figure 3 As shown, the voltage compensation unit 111 includes a first resistor R1. One end of the first resistor R1 serves as the first input terminal of the voltage compensation unit 111 and is connected to the output terminal of the current sampling unit 13, thereby transmitting the sampled current Isense to that end of the first resistor R1. This end also serves as the output terminal of the voltage compensation unit 111, used to output the feedback voltage Vfb. The other end of the first resistor R1 serves as the second input terminal of the voltage compensation unit 111 and is connected to the second terminal of the output unit 14, thereby transmitting the output voltage Vout to that other end of the first resistor R1.

[0065] In this method, the feedback voltage Vfb = Vout + Isense * R1.

[0066] The second type: such as Figure 4 As shown, the voltage compensation unit 111 includes a first switch Q1, a second switch Q2, a third switch Q3, a fourth switch Q4, a fifth switch Q5, a second resistor R2, a third resistor R3, and a fourth resistor R4.

[0067] In this circuit, the first terminals of the first switch Q1 and the second switch Q2 are connected to the input voltage Vin. The control terminal of the first switch Q1, the control terminal and the second terminal of the second switch Q2, and the first terminal of the fourth switch Q4 are connected together. The second terminal of the first switch Q1 is connected to one end of the fourth resistor R4. The other end of the fourth resistor R4, the first terminal of the third switch Q3, one end of the second resistor R2, and one end of the third resistor R3 are connected together. The other end of the second resistor R2 is the second input terminal of the voltage compensation unit 111, which is connected to the second terminal of the output unit 14. The other end of the third resistor R3, the second terminal of the third switch Q3, the second terminal of the fourth switch Q4, and the second terminal of the fifth switch Q5 are all grounded. The control terminals of the third switch Q3, the fourth switch Q4, and the fifth switch Q5 are connected to the first terminal of the fifth switch Q5. The first terminal of the fifth switch Q5 serves as the first input terminal of the voltage compensation unit 111 and is connected to the output terminal of the current sampling unit 13. The second terminal of the first switch Q1 is the output terminal of the voltage compensation unit 111, used to output the feedback voltage Vfb.

[0068] Among them, the first switch Q1 and the second switch Q2 can be, for example, P-type field-effect transistors, and the third switch Q3, the fourth switch Q4 and the fifth switch Q5 can be, for example, N-type field-effect transistors. The first terminal of the first switch Q1 to the fifth switch Q5 is the drain and the second terminal is the source.

[0069] In this method, the feedback voltage Vfb = Vout*(R2+R3) / R3+Isense*R4.

[0070] The third type: such as Figure 5 As shown, the voltage compensation unit 111 includes a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, and a first amplifier.

[0071] Among them, one end of the fifth resistor R5 is the second input terminal of the voltage compensation unit 111, which is connected to the second terminal of the output unit 14. The other end of the fifth resistor R5, one end of the sixth resistor R6, and the first input terminal of the first amplifier are connected. The other end of the sixth resistor R6 is grounded. The second input terminal and the output terminal of the first amplifier are connected to one end of the seventh resistor R7. The other end of the seventh resistor R7 is the first input terminal of the voltage compensation unit 111, which is connected to the output terminal of the current sampling unit 13. At the same time, the other end of the seventh resistor R7 is also the output terminal of the voltage compensation unit 111, which is used to output the feedback voltage Vfb.

[0072] In this method, the feedback voltage Vfb = Vout*(R5+R6) / R6+Isense*R7.

[0073] Therefore, in this embodiment, the voltage compensation unit 111 can be implemented in various ways, and the circuit structure is simple and easy to implement, which greatly saves chip area and helps to reduce power consumption.

[0074] See Figure 6 , combined Figure 2 In this embodiment, the current sampling unit 13 includes a sixth switch Q6, a seventh switch Q7, an eighth switch Q8, a ninth switch Q9, a tenth switch Q10, an eleventh switch Q11, a twelfth switch Q12, a thirteenth switch Q13, a fourteenth switch Q14, and a fifteenth switch Q15.

[0075] In this circuit, the first terminals of the sixth switch Q6, the seventh switch Q7, the eighth switch Q8, and the tenth switch Q10 are all connected to the input voltage Vin. The second terminal of the sixth switch Q6 is connected to the control terminal, the control terminal of the seventh switch Q7, and the first terminal of the thirteenth switch Q13. The second terminal of the seventh switch Q7, the control terminal of the ninth switch Q9, the control terminal of the eleventh switch Q11, and the first terminal of the fourteenth switch Q14 are connected. The second terminal of the eighth switch Q8 is connected to the control terminal, the first terminal of the ninth switch Q9, and the control terminal of the tenth switch Q10. The second terminal of the tenth switch Q10 is connected to the first terminal of the eleventh switch Q11. The second terminal of the eleventh switch Q11 is the output terminal of the current sampling unit 13, used to output the sampled data. The current Isense is connected to the second terminal of the ninth switch Q9, the second terminal of the fourteenth switch Q14, and the first terminal of the fifteenth switch Q15. The control terminal of the fifteenth switch Q15 is the control terminal of the current sampling unit 13 and is connected to the first output terminal of the control unit 12. The second terminal of the fifteenth switch Q15 is the input terminal of the current sampling unit 13 and is connected to the first terminal of the output unit 14. That is, the second terminal of the fifteenth switch Q15 is connected to the connection node LXSW of the output unit 14. The first terminal and control terminal of the twelfth switch Q12, the control terminal of the thirteenth switch Q13, and the control terminal of the fourteenth switch Q14 are connected. The second terminals of the twelfth switch Q12 and the second terminals of the thirteenth switch Q13 are grounded. The first terminal of the twelfth switch Q12 is connected to the input current ib.

[0076] In the aforementioned current sampling unit 13, the sixth switch Q6 to the eleventh switch Q11 are all P-type field-effect transistors, and the twelfth switch Q12 to the fifteenth switch Q15 are all N-type field-effect transistors. The first terminal of the sixth switch Q6 to the fifteenth switch Q15 is the drain, and the second terminal is the source.

[0077] Continue reading Figure 2In the embodiments of this application, the control unit 12 further includes a conduction mode control module 121, a logic module 122, a drive module 123, and a zero-crossing detection module 124.

[0078] The logic module 122 generates two control signals, namely control signal CTL2 and control signal CTL5, based on the voltage compensation signal CTL1 output by the comparison unit 112, the conduction mode signal CTL3 output by the conduction mode control module 121, and the zero-crossing detection signal CTL4 output by the zero-crossing detection module 124. Control signal CTL2 is output to the drive module 123, which drives the PMOS and NMOS transistors to turn on or off according to the control signal. Control signal CTL5 is output to the current sampling unit 13, specifically to the control terminal of the fifteenth switch Q5 of the current sampling unit 13, so as to control the current sampling unit 13 to perform current sampling or stop working.

[0079] The conduction mode signal CTL3 includes one of a fixed conduction time control signal, a fixed peak current control signal, and a fixed turn-off time control signal. That is, the control unit 12 of this application can be applied to multiple control modes, such as a fixed conduction time control mode, a fixed peak current control mode, or a fixed turn-off time control mode.

[0080] The zero-crossing detection module 124 is used to detect the current flowing through the NMOS transistor and outputs a zero-crossing detection signal, namely CTL4, when the current flowing through the NMOS transistor gradually decreases from a positive current to zero. After the CTL4 is processed by the logic module 122, the drive module 123 controls the NMOS transistor to turn off.

[0081] The following will combine Figure 2 Further explanation of the working principle of the switching power supply circuit in this application:

[0082] The first scenario: The switching power supply circuit is in DCM mode. In DCM mode, there is current in the inductor L for a period of time and no current for a period of time.

[0083] When the load R L Under light load, the sampling current Isense = Il / K, where K is the sampling coefficient. In this stage, Il = Inmos, where Inmos is the current flowing through the NMOS transistor. The voltage compensation unit 111 is illustrated using the first implementation method described above, i.e., the feedback voltage Vfb = Vout + Isense * R1. The specific implementation circuit of the current sampling unit 13 is as follows: Figure 6 The circuit shown in the figure has the following timing waveforms for this stage of operation: Figure 7 As shown.

[0084] Combination Figure 7The waveform shown is shown in the figure, where Iload is the load R. L The current, Ipeak, is the reference current. When the signal CTL1 output by the comparator unit 112 has a rising edge, it triggers the PMOS transistor to turn on, thereby charging the inductor L. When the current Il of the inductor L increases from zero, the current sampling unit 13 does not work, and Isense = 0, while the feedback voltage Vfb = Vout + Isense * R1 = Vout. When the current Il reaches a fixed peak value or the PMOS transistor reaches a fixed on time, the PMOS transistor turns off and the NMOS transistor turns on. The current sampling unit 13 starts to sample the current flowing through the NMOS transistor to obtain the sampled current Isense. At this time, the feedback voltage Vfb = Vout + Isense * R1, thus the feedback voltage Vfb contains both output voltage and output current information.

[0085] At this stage, due to the load R L The current Iload is relatively small. During the PMOS transistor's on-state (i.e., during the rising edge of Il), the output voltage Vout is sufficient, and the CTL1 signal transitions from 1 (high level) to 0 (low level). However, during this phase, the current Il has not reached its fixed peak value or the PMOS transistor has not reached its fixed on-time, so the current Il will continue to rise. After the current Il reaches its fixed peak value or the PMOS transistor reaches its fixed on-time, the PMOS transistor turns off, the NMOS transistor turns on, and the current Il enters the freewheeling phase, continuously outputting to the load R. L And the output capacitor C. It can be understood that the current Il reaches or does not reach the fixed peak value, where the fixed peak value refers to the reference current Ipeak.

[0086] Because there is a phase difference between the inductor L and the output capacitor C, i.e. Figure 7 As shown, during the rising edge phase of Il, when Iload = Il, the output voltage drops to a minimum, and the output voltage Vout reaches its lowest value. Afterward, the output voltage Vout gradually increases, reaching its maximum value when the inductor current Il falls to equal Iload. During the rising edge phase of Il, Isense = 0, and Vfb = Vout. When the NMOS transistor is turned on, the sampling current Isense follows the change in inductor current Il, making Vfb = Vout + Isense * R1. After the inductor current Il becomes 0, Isense = 0, and Vfb = Vout.

[0087] Since the output voltage Vout is sufficient, the signal CTL1 output by the comparator unit 112 remains at 0, and the output voltage Vout is maintained due to the load R. LAs power consumption continues to decrease, when it drops below the reference voltage Vref, CTL1 changes from 0 to 1, resulting in a rising edge on CTL1, which causes the PMOS transistor to turn on again, thereby charging the inductor L, and repeating the above process.

[0088] Optionally, in some other embodiments, when the PMOS transistor is turned on, the sampling current Isense can be set to a fixed value. In this case, the operating timing waveform of the switching power supply circuit is as follows: Figure 8 As shown, in this method, with Figure 7 The only difference between the embodiments shown is the sampling current Isense and the feedback voltage Vfb, which are equivalent to the following when the PMOS transistor is turned on: Figure 7 Add a DC level to the existing level; for example, you can... Figure 6 Based on the current sampling unit shown, a DC power supply is connected to the Isense terminal via a switch. When the PMOS transistor is turned on, the switch is turned on, thus outputting a DC level at the Isense terminal. When the PMOS transistor is turned off, the switch is also in the off state. It is understandable that... Figure 8 The embodiments shown are only in Figure 7 Based on the above, a DC level is added. The other structures and working principles are the same, so they will not be described in detail here.

[0089] The second scenario: The switching power supply circuit is in CCM mode. In CCM mode, there is a continuous current in the inductor L, such as the reference current Ipeak = 120mA and the turn-off current Ivalley = 60mA.

[0090] When the load R L Under heavy load, the timing waveform of the switching power supply circuit is as follows: Figure 9 As shown. Figure 9 As shown, when the signal CTL1 output by the comparator unit 112 has a rising edge, it triggers the PMOS transistor to turn on, thereby charging the inductor L. When the current Il of the inductor L increases from zero, the current sampling unit 13 does not work, and Isense = 0. At this time, the feedback voltage Vfb (taking the first voltage compensation unit implementation method mentioned above as an example) = Vout + Isense * R1 = Vout. When the current Il reaches a fixed peak value or the PMOS transistor reaches a fixed on time, the PMOS transistor turns off and the NMOS transistor turns on. The current sampling unit 13 starts to sample the current flowing through the NMOS transistor to obtain the sampled current Isense. At this time, the feedback voltage Vfb = Vout + Isense * R1. Thus, the feedback voltage Vfb contains both the output voltage information and the output current information.

[0091] At this stage, due to the load R LThe current Iload is relatively large. During the PMOS transistor's on-state (i.e., during the rising edge of Il), the output voltage Vout has not reached the preset value, and the CTL1 signal remains at 1 (high level). When the current Il reaches a fixed peak value or the PMOS transistor reaches a fixed on-time, the PMOS transistor turns off, the NMOS transistor turns on, and the current Il enters the freewheeling phase. During the freewheeling phase, when Il decreases, CTL1 flips from 1 (high level) to 0 (low level), and the inductor current Il is continuously output to the load R. L and output capacitor C.

[0092] Because there is a phase difference between the inductor L and the output capacitor C, i.e. Figure 9 As shown, during the rising edge phase of Il, when Iload = Il, the output voltage drops to a minimum, and the output voltage Vout reaches its lowest value. Afterward, the output voltage Vout gradually increases, reaching its maximum value when the inductor current Il falls to equal Iload. During the rising edge phase of Il, Isense = 0, and Vfb = Vout. When the NMOS transistor is turned on, the sampling current Isense follows the change in inductor current Il, resulting in Vfb = Vout + Isense * R1.

[0093] The output voltage Vout is due to the load R L The power consumption decreases continuously. When it drops below the reference voltage Vref, CTL1 changes from 0 to 1, resulting in a rising edge on CTL1, which causes the PMOS transistor to turn on again, thereby charging the inductor L, and repeating the above process.

[0094] Optionally, in some other embodiments, when the PMOS transistor is turned on, the sampling current Isense can be set to a fixed value. In this case, the operating timing waveform of the switching power supply circuit is as follows: Figure 10 As shown, in this method, with Figure 9 The only difference between the embodiments shown is the sampling current Isense and the feedback voltage Vfb, which are equivalent to the following when the PMOS transistor is turned on: Figure 9 Based on the above, add a DC level, and everything else is the same, so it will not be described again here.

[0095] Therefore, by combining the timing waveforms of the switching power supply circuit in DCM and CCM modes, we can obtain the output voltage Vout of the switching power supply circuit as a function of the load R across the entire range. L The changing waveform, such as Figure 11As shown, when the load current Iload is relatively small, the operating frequency of the switching power supply circuit is low, most of the energy is stored in the capacitor, and the ripple is relatively large. As the load current Iload increases, some energy is sent to the load terminal, and the rest is stored in the output capacitor C. In DCM mode, by increasing the number of PMOS transistor turn-on times, i.e., increasing the switching frequency to provide sufficient load, the ripple is reduced accordingly. As the load current Iload continues to increase, after entering CCM mode, the sampling current Isense of the NMOS transistor introduces an offset in the loop, making the output voltage Vout slightly lower than the set value, and its ripple is further reduced, thereby achieving stable output of the switching power supply circuit.

[0096] In the switching power supply circuits of the above embodiments, by making the feedback signal include output voltage information and output current information, and then providing the feedback signal to the compensation comparison unit, the compensation comparison unit can drive the PMOS and NMOS transistors in the output unit to turn on and off according to the feedback signal carrying the output voltage information and output current information, so as to achieve a constant output voltage of the output unit. This can greatly simplify the loop compensation characteristics and improve the transient response speed. Moreover, the conduction mode signal CTL3 of this application can be one of a fixed conduction time control signal, a fixed peak current control signal, and a fixed turn-off time control signal. Therefore, the switching power supply circuit of this application can be applied to a variety of control modes, such as a fixed conduction time control mode, a fixed peak current control mode, or a fixed turn-off time control mode. Furthermore, there are multiple ways to implement the voltage compensation unit, which is simple and easy to implement, and helps to reduce the cost of IC chips.

[0097] See Figure 12 This application also provides another embodiment of the switching power supply circuit, which differs from the above embodiment mainly in that the compensation operation of the compensation comparison unit 11 is different. Other structures, such as the control unit 12, the current sampling unit 13 and the output unit 14, can be implemented with reference to the above embodiment.

[0098] In this embodiment, the first input terminal of the voltage compensation unit 111 of the compensation comparison unit 11 is connected to the output terminal of the current sampling unit 13, and the second input terminal of the voltage compensation unit 111 is connected to the reference voltage Vref as the third input terminal of the compensation comparison unit 11. This is used to perform a subtraction operation on the sampled current Isense and the reference voltage Vref to obtain the compensated reference voltage Vref', thereby the compensated reference voltage Vref' carries the output current information.

[0099] The first input terminal of the comparison unit 112 serves as the second input terminal of the compensation comparison unit 11 and is connected to the second terminal of the output unit 14. The second input terminal of the comparison unit 112 is connected to the output terminal of the voltage compensation unit 111 and is used to compare the output voltage Vout with the compensated reference voltage Vref' to output a voltage compensation signal. The output terminal of the comparison unit 112 is connected to the input terminal of the control unit 12, so that the control unit 12 controls the output of the output unit 14 according to the voltage compensation signal, thereby achieving constant regulation of the output voltage.

[0100] Among them, such as Figure 13 As shown, in this embodiment, the voltage compensation unit 112 includes a second amplifier, a sixteenth switch Q16, a seventeenth switch Q17, an eighteenth switch Q18, a nineteenth switch Q19, an eighth resistor R8, and a ninth resistor R9.

[0101] The first terminals of the sixteenth switch Q16 and the seventeenth switch Q17 are connected to the input voltage Vin. The control terminals of the sixteenth switch Q16 and the seventeenth switch Q17 are connected to the output terminal of the second amplifier. The second terminal of the sixteenth switch Q16 and one end of the eighth resistor R8 are connected to the first input terminal of the second amplifier. The second terminal of the seventeenth switch Q17, one end of the ninth resistor R9, and the first terminal of the eighteenth switch Q18 are connected and serve as the output terminal of the voltage compensation unit 112 for outputting the compensated reference voltage Vref'. The control terminals of the eighteenth switch Q18, the nineteenth switch Q19, and the first terminal of the nineteenth switch Q19 are connected and serve as the first input terminal of the voltage compensation unit 112, which is connected to the output terminal of the current sampling unit 13. The other ends of the eighth resistor R8, the other ends of the ninth resistor R9, the second terminals of the eighteenth switch Q18 and the nineteenth switch Q19 are grounded. The second input terminal of the second amplifier serves as the second input terminal of the voltage compensation unit 112 and is connected to the reference voltage Vref.

[0102] Among them, the sixteenth switch Q16 to the nineteenth switch Q19 can all be P-type field-effect transistors, with the first terminal of each switch being the drain and the second terminal being the source.

[0103] The main difference between this embodiment and the above embodiments lies in the different compensation comparison units. Other structures and working principles can be implemented with reference to the above embodiments. For example, the current sampling unit 13 in this embodiment can adopt... Figure 6 The sampling circuit shown is used to implement this, and the working principle of the control unit and output unit can also be referred to the above embodiment, which will not be described in detail here.

[0104] In this embodiment, the output voltage and output current information are also fed back to the compensation comparison unit to drive the power transistor, thus achieving the following: Figure 2 The technical effects of the illustrated embodiments.

[0105] See Figure 14 This application also provides a control method for a switching power supply circuit, wherein the switching power supply circuit can be any of the switching power supply circuits described in the above embodiments. As shown in the figure, the control method includes the following steps:

[0106] Step S1401: Sample the output current of the output unit through the current sampling unit to obtain the sampled current.

[0107] Step S1402: The compensation comparison unit performs compensation calculations based on the reference voltage, the sampling current, and the output voltage of the output unit, and outputs a voltage compensation signal.

[0108] Step S1403: Control the current sampling unit to perform current sampling or stop current sampling according to the voltage compensation signal, and control the output voltage of the output unit to be constant.

[0109] There are two ways to perform the compensation operation. For example, in some implementations, the compensation comparison unit performs the compensation operation based on the reference voltage, the sampled current, and the output voltage of the output unit to output a voltage compensation signal. This can include the following steps: the voltage compensation unit in the compensation comparison unit performs a sum operation on the sampled current and the output voltage to output a feedback voltage; the comparison unit in the compensation comparison unit compares the reference voltage and the feedback voltage and outputs a voltage compensation signal based on the comparison result.

[0110] Alternatively, in some other implementations, the compensation comparison unit performs compensation calculations based on the reference voltage, the sampled current, and the output voltage of the output unit to output a voltage compensation signal. This may include the following steps: subtracting the sampled current and the reference voltage using the voltage compensation unit in the compensation comparison unit to obtain the compensated reference voltage; and comparing the output voltage with the compensated reference voltage using the comparison unit in the compensation comparison unit to output a voltage compensation signal.

[0111] In the control method of this embodiment, loop stabilization is achieved by using the dual feedback signals of the output voltage and the output current of the output unit. This not only enables the switching power supply circuit to output a stable voltage, but also eliminates the need to generate ramp waves using RC filtering to achieve stability. Compared with existing methods, this greatly simplifies the loop compensation characteristics and significantly improves the transient response speed.

[0112] The foregoing has provided a detailed description of a switching power supply circuit and its control method according to the embodiments of this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A switching power supply circuit, characterized in that, It includes a compensation comparison unit, a control unit, a current sampling unit, and an output unit; The output unit includes a control terminal, a first terminal for providing output current, and a second terminal for providing output voltage; The input terminal of the current sampling unit is connected to the first terminal of the output unit to sample the output current and obtain the sampled current. The first and second input terminals of the compensation comparison unit are respectively connected to the output terminal of the current sampling unit and the second terminal of the output unit. The third input terminal of the compensation comparison unit is connected to a reference voltage to perform voltage compensation calculation based on the sampled current, the output voltage and the reference voltage, and output a voltage compensation signal. The input terminal of the control unit is connected to the output terminal of the compensation comparison unit, and the first and second output terminals of the control unit are respectively connected to the control terminal of the current sampling unit and the control terminal of the output unit, for controlling the current sampling unit to perform current sampling or stop current sampling according to the voltage compensation signal, and controlling the output voltage of the output unit to be constant. The compensation comparison unit includes a voltage compensation unit and a comparison unit; The first input terminal of the voltage compensation unit serves as the first input terminal of the compensation comparison unit and is connected to the output terminal of the current sampling unit. The second input terminal of the voltage compensation unit serves as the third input terminal of the compensation comparison unit and is connected to the reference voltage. It is used to perform a subtraction operation on the sampled current and the reference voltage to obtain the compensated reference voltage. The first input terminal of the comparison unit serves as the second input terminal of the compensation comparison unit and is connected to the second terminal of the output unit. The second input terminal of the comparison unit is connected to the output terminal of the voltage compensation unit and is used to compare the output voltage with the compensated reference voltage to output a voltage compensation signal. The output terminal of the comparison unit is connected to the input terminal of the control unit.

2. The switching power supply circuit according to claim 1, characterized in that, The compensation comparison unit includes a voltage compensation unit and a comparison unit; The first and second input terminals of the voltage compensation unit serve as the first and second input terminals of the compensation comparison unit, respectively, and are connected to the output terminal of the current sampling unit and the second terminal of the output unit, respectively, for performing a summation operation on the sampled current and the output voltage to output a feedback voltage; The first input terminal of the comparison unit serves as the third input terminal of the compensation comparison unit and is connected to the reference voltage. The second input terminal of the comparison unit is connected to the output terminal of the voltage compensation unit, used to compare the reference voltage and the feedback voltage, and output a voltage compensation signal according to the comparison result. The output terminal of the comparison unit is connected to the input terminal of the control unit.

3. The switching power supply circuit according to claim 2, characterized in that, The voltage compensation unit includes a first resistor R1. The two ends of the first resistor R1 serve as the first input terminal and the second input terminal of the voltage compensation unit, respectively, to be connected to the output terminal of the current sampling unit and the second terminal of the output unit. The first input terminal of the voltage compensation unit also serves as the output terminal of the voltage compensation unit and is connected to the second input terminal of the comparison unit. Alternatively, the voltage compensation unit includes a first switch Q1, a second switch Q2, a third switch Q3, a fourth switch Q4, a fifth switch Q5, a second resistor R2, a third resistor R3, and a fourth resistor R4; the first terminals of the first switch Q1 and the second switch Q2 are connected to the input voltage; the control terminal of the first switch Q1, the control terminal and the second terminal of the second switch Q2, and the first terminal of the fourth switch Q4 are connected; the second terminal of the first switch Q1 is connected to one end of the fourth resistor R4; and the other end of the fourth resistor R4, the first terminal of the third switch Q3, one end of the second resistor R2, and one end of the third resistor R3 are connected. The other end of the second resistor R2 serves as the second input terminal of the voltage compensation unit and is connected to the second terminal of the output unit. The other end of the third resistor R3, the second terminal of the third switch Q3, the second terminal of the fourth switch Q4, and the second terminal of the fifth switch Q5 are all grounded. The control terminals of the third switch Q3, the fourth switch Q4, and the fifth switch Q5 are connected to the first terminal of the fifth switch Q5. The first terminal of the fifth switch Q5 serves as the first input terminal of the voltage compensation unit and is connected to the output terminal of the current sampling unit. The second terminal of the first switch Q1 is the output terminal of the voltage compensation unit. Alternatively, the voltage compensation unit includes a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, and a first amplifier; one end of the fifth resistor R5 is the second input terminal of the voltage compensation unit and is connected to the second terminal of the output unit; the other end of the fifth resistor R5, one end of the sixth resistor R6, and the first input terminal of the first amplifier are connected; the other end of the sixth resistor R6 is grounded; the second input terminal and the output terminal of the first amplifier are connected to one end of the seventh resistor R7; the other end of the seventh resistor R7 is the first input terminal of the voltage compensation unit and is connected to the output terminal of the current sampling unit; and the other end of the seventh resistor R7 is also the output terminal of the voltage compensation unit.

4. The switching power supply circuit according to claim 1, characterized in that, The voltage compensation unit includes a second amplifier, a sixteenth switch Q16, a seventeenth switch Q17, an eighteenth switch Q18, a nineteenth switch Q19, an eighth resistor R8, and a ninth resistor R9. The first terminals of the sixteenth switch Q16 and the seventeenth switch Q17 are connected to the input voltage. The control terminals of the sixteenth switch Q16 and the seventeenth switch Q17 are connected to the output terminal of the second amplifier. The second terminal of the sixteenth switch Q16 and one end of the eighth resistor R8 are connected to the first input terminal of the second amplifier. The second terminal of the seventeenth switch Q17, one end of the ninth resistor R9, and the first terminal of the eighteenth switch Q18 are connected and serve as the output terminal of the voltage compensation unit for outputting the compensated reference voltage. The control terminals of the eighteenth switch Q18, the nineteenth switch Q19, and the first terminal of the nineteenth switch Q19 are connected and serve as the first input terminal of the voltage compensation unit, which is connected to the output terminal of the current sampling unit. The other ends of the eighth resistor R8, the ninth resistor R9, the second terminals of the eighteenth switch Q18, and the nineteenth switch Q19 are grounded. The second input terminal of the second amplifier serves as the second input terminal of the voltage compensation unit and is connected to the reference voltage.

5. The switching power supply circuit according to any one of claims 2-4, characterized in that, The current sampling unit includes a sixth switch Q6, a seventh switch Q7, an eighth switch Q8, a ninth switch Q9, a tenth switch Q10, an eleventh switch Q11, a twelfth switch Q12, a thirteenth switch Q13, a fourteenth switch Q14, and a fifteenth switch Q15. The first terminals of the sixth switch Q6, the seventh switch Q7, the eighth switch Q8, and the tenth switch Q10 are all connected to the input voltage. The second terminal of the sixth switch Q6 is connected to the control terminal, the control terminal of the seventh switch Q7, and the first terminal of the thirteenth switch Q13. The second terminal of the seventh switch Q7, the control terminal of the ninth switch Q9, the control terminal of the eleventh switch Q11, and the first terminal of the fourteenth switch Q14 are connected. The second terminal of the eighth switch Q8 is connected to the control terminal, the first terminal of the ninth switch Q9, and the control terminal of the tenth switch Q10. The second terminal of the tenth switch Q10 is connected to the first terminal of the eleventh switch Q11. The connection is as follows: the second terminal of the eleventh switch Q11 is the output terminal of the current sampling unit; the second terminals of the ninth switch Q9, the fourteenth switch Q14, and the first terminal of the fifteenth switch Q15 are connected; the control terminal of the fifteenth switch Q15 is the control terminal of the current sampling unit; the second terminal of the fifteenth switch Q15 is the input terminal of the current sampling unit; the first terminal and control terminal of the twelfth switch Q12, the control terminal of the thirteenth switch Q13, and the control terminal of the fourteenth switch Q14 are connected; the second terminals of the twelfth switch Q12 and the thirteenth switch Q13 are grounded; and the first terminal of the twelfth switch Q12 is connected to the input current.

6. The switching power supply circuit according to any one of claims 2-4, characterized in that, The output unit has two control terminals, and the control unit has two second output terminals, which are respectively connected to the two control terminals of the output unit. The output unit includes a PMOS transistor, an NMOS transistor, an inductor L, an output capacitor C, and a load R. L ; The control terminals of the PMOS transistor and the NMOS transistor are respectively the two control terminals of the output unit. The two second output terminals of the control unit are respectively connected to the control terminals of the PMOS transistor and the NMOS transistor to drive the PMOS transistor and the NMOS transistor to be turned on or off. The drains of the PMOS transistor and the NMOS transistor are connected to one end of the inductor L, and the connection node is the first terminal of the output unit. The source of the PMOS transistor is connected to the input voltage, and the source of the NMOS transistor is grounded. The other end of the inductor L, one end of the output capacitor C, and the load R are connected. L One end of the output capacitor is connected to the second end of the output unit, and the other end of the output capacitor and the other end of the load are grounded.

7. The switching power supply circuit according to claim 6, wherein the control unit includes a conduction mode control module, a logic module, a drive module, and a zero-crossing detection module; The logic module is used to control the current sampling unit to perform current sampling or stop current sampling based on the voltage compensation signal output by the compensation comparison unit, the conduction mode signal output by the conduction mode control module, and the zero-crossing detection signal output by the zero-crossing detection module, and to control the driving module to drive the PMOS transistor and NMOS transistor to turn on or off. The conduction mode signal includes one of a fixed conduction time control signal, a fixed peak current control signal, and a fixed turn-off time control signal; The zero-crossing detection module is used to detect the current flowing through the NMOS transistor and outputs a zero-crossing detection signal when the current flowing through the NMOS transistor gradually decreases from a positive current to zero.

8. A control method for a switching power supply circuit, characterized in that, include: The output current of the output unit is sampled by the current sampling unit to obtain the sampled current; The compensation comparison unit performs compensation calculations based on the reference voltage, the sampling current, and the output voltage of the output unit, and outputs a voltage compensation signal. The voltage compensation signal is used to control the current sampling unit to perform current sampling or stop current sampling, and to control the output voltage of the output unit to remain constant. The compensation comparison unit includes a voltage compensation unit and a comparison unit; The voltage compensation unit is used to perform a subtraction operation on the sampled current and the reference voltage to obtain the compensated reference voltage; The comparison unit is used to compare the output voltage with the compensated reference voltage to output the voltage compensation signal.

9. The control method according to claim 8, characterized in that, The compensation comparison unit performs compensation calculations based on the reference voltage, the sampled current, and the output voltage of the output unit, and outputs a voltage compensation signal, specifically including: The voltage compensation unit in the compensation comparison unit performs a summation operation on the sampled current and the output voltage to output a feedback voltage; The reference voltage and the feedback voltage are compared by the comparison unit in the compensation comparison unit, and a voltage compensation signal is output according to the comparison result. Alternatively, the compensation comparison unit performs compensation calculations based on the reference voltage, the sampled current, and the output voltage of the output unit, and outputs a voltage compensation signal, specifically including: The voltage compensation unit in the compensation comparison unit performs a subtraction operation between the sampled current and the reference voltage to obtain the compensated reference voltage. The output voltage of the output unit is compared with the compensated reference voltage by the comparison unit in the compensation comparison unit to output a voltage compensation signal.

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