Switch control circuit, switch control method thereof and switch power supply

Abstract

The invention provides a switching control circuit, a switching control method thereof and a switching power supply. The switch control circuit comprises a first error amplifying circuit, a second error amplifying circuit and a driving control circuit. The first input end of the first error amplification circuit is used for being coupled with a reference signal, the second input end of the first error amplification circuit is used for being coupled with a representation signal representing the output voltage of the switching power supply, and the output end of the first error amplification circuit is used for being coupled with a compensation capacitor. The first input end of the second error amplification circuit is used for being coupled with the compensation capacitor, and the second input end of the second error amplification circuit is used for receiving the preset voltage. The output end of the second error amplifying circuit is used for being coupled with the compensation capacitor. The input end of the driving control circuit is used for being coupled with the compensation capacitor to receive the compensation capacitor voltage, and the driving control circuit is used for outputting a driving signal according to the compensation capacitor voltage. According to the switching control circuit, the switching control method thereof and the switching power supply provided by the invention, the optimization of the load regulation rate is effectively realized.

Description

Technical Field

[0001] The present invention belongs to the field of power electronics, and relates to a switch control technology, and in particular to a switch control circuit and a switch control method thereof, and a switch power supply. Background Art

[0002] Switching power supplies are the main category of electronic power supplies. Due to their many advantages such as light weight, miniaturization, wide input voltage range, high power density and conversion efficiency, and low standby power consumption, they are widely used in most electronic devices such as consumer electronics and communication equipment.

[0003] For high-voltage buck circuits (i.e. step-down circuits) or buck-boost circuits (i.e. step-up and step-down circuits), Figure 1 As shown, the output voltage is usually when the second diode D2 is turned on, and the output voltage is fed back to the FB pin of the chip through the first diode D1. Then it is compared with the reference voltage Vref after passing through the voltage divider circuit, and the error amplifier circuit EA compensates to form the compensation capacitor voltage COMP. The compensation capacitor voltage COMP is controlled and processed by the frequency control circuit and the amplitude control circuit to finally output the switch control signal PWM. The chip controls the main switch tube to perform voltage regulation control. Therefore, the output voltage Vo of the switching power supply is Vo=Vref*k+VD1-VD2, where Vref is the reference voltage, k=(RF1+RF2) / RF2, RF1 is the resistance value of the first voltage divider resistor, RF2 is the resistance value of the second voltage divider resistor, VD1 is the forward voltage drop of the first diode D1 (referred to as the first voltage drop), and VD2 is the forward voltage drop of the second diode D2 (referred to as the second voltage drop). Due to the characteristics of the diode, affected by the parasitic internal resistance of the diode, the diode voltage drop VF changes with the current. From light load to full load, the current flowing through the first diode D1 is basically very small. It can be considered that the first voltage drop VD1 is basically unchanged, but the second voltage drop VD2 will increase with the increase of the current flowing through, thereby causing the output voltage to drop. Therefore, the load regulation rate becomes worse.

[0004] In view of this, it is necessary to provide a new structure or control method to solve at least part of the above problems. Summary of the invention

[0005] In view of one or more problems in the prior art, the present invention provides a switch control circuit and a switch control method thereof and a switch power supply.

[0006] According to one aspect of the present invention, a switch control circuit is disclosed. The switch control circuit is used to control a main switch tube in a switching power supply. The switch control circuit includes:

[0007] A first error amplifier circuit, wherein a first input terminal thereof is used to couple a reference signal, a second input terminal thereof is used to couple a characterizing signal characterizing an output voltage of the switching power supply, and an output terminal thereof is used to couple a compensation capacitor;

[0008] a second error amplifier circuit, whose first input terminal is coupled to the compensation capacitor, whose second input terminal is used to receive a preset voltage; whose output terminal is coupled to the compensation capacitor, or whose output terminal is coupled to an operation circuit, which is coupled to the first input terminal or the second input terminal of the first error amplifier circuit; and

[0009] The drive control circuit has an input terminal coupled to the compensation capacitor to receive the compensation capacitor voltage and is used to output a drive signal according to the compensation capacitor voltage to control the main switch tube.

[0010] In one embodiment, the second error amplifier circuit further includes a filter circuit, an input terminal of the filter circuit is coupled to the compensation capacitor, and an output terminal of the filter circuit outputs a filter signal. The second error amplifier circuit generates a compensation signal according to the filter signal and a preset voltage.

[0011] In one embodiment, the second error amplifier circuit includes a second transconductance amplifier, a non-inverting input terminal of the second transconductance amplifier is coupled to the compensation capacitor, an inverting input terminal of the second transconductance amplifier is coupled to a preset voltage, and an output terminal of the second transconductance amplifier is used to couple to the compensation capacitor.

[0012] In one embodiment, the second error amplifier circuit includes an error amplifier, a non-inverting input terminal of the error amplifier is coupled to the compensation capacitor, an inverting input terminal of the error amplifier is coupled to a preset voltage, and an output terminal of the error amplifier is coupled to the operation circuit.

[0013] In one embodiment, the first error amplifying circuit includes a first transconductance amplifier, and the transconductance of the second error amplifying circuit is selected according to the internal resistance value of the second diode and the transconductance of the first transconductance amplifier.

[0014] In one embodiment, the switch control circuit includes an operation circuit, the operation circuit includes an adding circuit, a first input terminal of the adding circuit receives a reference signal, a second input terminal of the adding circuit is coupled to an output terminal of an error amplifier, and an output terminal of the adding circuit is coupled to a first input terminal of a first error amplifier circuit.

[0015] In one embodiment, the switch control circuit includes an operation circuit, the operation circuit includes a subtraction circuit, a first input terminal of the subtraction circuit receives a characterization signal, a second input terminal of the subtraction circuit is coupled to an output terminal of an error amplifier, and an output terminal of the subtraction circuit is coupled to a second input terminal of the first error amplifier circuit.

[0016] In one embodiment, the drive control circuit comprises:

[0017] A frequency control circuit, whose input terminal is coupled to the compensation capacitor, for controlling the driving signal according to the compensation capacitor voltage; and

[0018] The amplitude control circuit has an input terminal coupled to the compensation capacitor and is used to control the driving signal according to the compensation capacitor voltage.

[0019] According to another aspect of the present invention, a switching power supply is disclosed. The switching power supply includes a switch control circuit as described in any one of the above items. The switch control circuit generates a drive signal to control a main switch tube.

[0020] According to another aspect of the present invention, a switch control method is disclosed. The switch control method is used to generate a drive signal to control a main switch in a switching power supply. The switch control method includes:

[0021] Performing error amplification according to a reference signal and a characterizing signal characterizing an output voltage of the switching power supply to generate a first current to charge and discharge the compensation capacitor;

[0022] Amplifying the error between the preset voltage and the compensation capacitor voltage of the compensation capacitor to generate a compensation current to charge and discharge the compensation capacitor, thereby compensating the compensation capacitor voltage; and

[0023] A driving signal is output according to the compensation capacitor voltage to control the main switch tube.

[0024] According to another aspect of the present invention, a switch control method is also disclosed. The switch control method is used to generate a drive signal to control a main switch in a switching power supply. The switch control method includes:

[0025] Performing error amplification according to a reference signal and a characterizing signal characterizing an output voltage of the switching power supply to generate a first current to charge and discharge the compensation capacitor;

[0026] Amplifying the error between the preset voltage and the compensation capacitor voltage of the compensation capacitor to generate a compensation voltage, and performing a compensation operation on the reference signal according to the compensation voltage; and

[0027] A driving signal is output according to the compensation capacitor voltage to control the main switch tube.

[0028] The present invention proposes a switch control circuit and a switch control method thereof and a switch power supply. The switch control circuit is used to control the main switch tube in the switch power supply. The switch control circuit includes a first error amplifier circuit, a second error amplifier circuit and a drive control circuit. The first input end of the first error amplifier circuit is used to couple a reference signal, the second input end of the first error amplifier circuit is used to couple a characterization signal characterizing the output voltage of the switch power supply, and the output end of the first error amplifier circuit is used to couple a compensation capacitor. The first input end of the second error amplifier circuit is used to couple the compensation capacitor, and the second input end of the second error amplifier circuit is used to receive a preset voltage. The output end of the second error amplifier circuit is used to couple the compensation capacitor, or the output end of the second error amplifier circuit is coupled to an operation circuit, and the operation circuit is coupled to the first input end or the second input end of the first error amplifier circuit. The input end of the drive control circuit is used to couple the compensation capacitor to receive the compensation capacitor voltage, and the drive control circuit is used to output a drive signal according to the compensation capacitor voltage to control the main switch tube. The switch control circuit and the switch control method thereof and the switch power supply proposed by the present invention effectively optimize the load regulation rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The accompanying drawings are used to provide a further understanding of the present invention and are used together with the description to explain the embodiments of the present invention, but do not constitute a limitation of the present invention. In the accompanying drawings:

[0030] Figure 1 A schematic diagram of the circuit structure of a prior art step-down switching power supply is shown;

[0031] Figure 2 A schematic diagram of the circuit structure of a switch control circuit according to an embodiment of the present invention is shown;

[0032] Figure 3 A schematic diagram of the circuit structure of a step-down switching power supply according to an embodiment of the present invention is shown;

[0033] Figure 4 A schematic diagram of the circuit structure of a step-down switching power supply according to another embodiment of the present invention is shown;

[0034] Figure 5 A characteristic curve diagram of a diode in the prior art is shown;

[0035] Figure 6 shows a characteristic curve of a diode according to an embodiment of the present invention and a linear fitting schematic diagram;

[0036] Figure 7 A schematic diagram of signal waveforms of a prior art step-down switching power supply is shown;

[0037] Figure 8A schematic diagram of signal waveforms of a step-down switching power supply according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0038] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0039] The description in this section is only for several typical embodiments, and the present invention is not limited to the scope of the embodiments. The combination of different embodiments, the mutual replacement of some technical features in different embodiments, and the mutual replacement of the same or similar prior art means with some technical features in the embodiments are also within the scope of the description and protection of the present invention.

[0040] "Coupled" or "connected" in the specification includes both direct connection and indirect connection. Indirect connection is a connection through an intermediate medium, such as a connection through an electrically conductive medium such as a conductor, wherein the electrically conductive medium may contain parasitic inductance or parasitic capacitance, or a connection through an intermediate circuit or component described in the embodiments in the specification; an indirect connection may also include a connection through other active or passive devices on the basis of achieving the same or similar functions, such as a connection through circuits or components such as switches, signal amplification circuits, and follower circuits. "Multiple" or "many" means two or more. In addition, in the present invention, words such as first and second are mainly used to distinguish one technical feature from another technical feature, and do not necessarily require or imply that there is a certain actual relationship or order between these technical features.

[0041] An embodiment of the present invention discloses a switch control circuit, which is used to control a main switch in a switch power supply. The switch control circuit controls the output voltage of the switch power supply by controlling the switch state of the main switch. The switch state includes an on state and an off state. Figure 2As shown, the switch control circuit includes a first error amplifier circuit 10, a second error amplifier circuit 20 and a drive control circuit 30. The first input terminal of the first error amplifier circuit 10 is used to receive a reference signal, the second input terminal of the first error amplifier circuit 10 is used to receive a characterization signal Vd that characterizes the output voltage of the switching power supply, and the output terminal of the first error amplifier circuit 10 is used to couple the compensation capacitor Cz. In one embodiment, the characterization signal Vd is positively correlated with the output voltage of the switching power supply. In another embodiment, the characterization signal Vd is proportional to the output voltage of the switching power supply. The first error amplifier circuit 10 is used to perform error amplification according to the reference signal and the characterization signal Vd to generate a first current. The first error amplifier circuit 10 controls the charging and discharging of the compensation capacitor Cz through the first current, thereby adjusting the compensation capacitor voltage of the compensation capacitor Cz. The first input terminal of the second error amplifier circuit 20 is coupled to the compensation capacitor Cz to obtain the compensation capacitor voltage Vcomp, the second input terminal of the second error amplifier circuit 20 is used to receive a preset voltage, the output terminal of the second error amplifier circuit 20 is used to couple the compensation capacitor, and the second error amplifier circuit 20 is used to perform error amplification according to the compensation capacitor voltage and the preset voltage to generate a compensation current. In another embodiment, the first input terminal of the second error amplifier circuit 20 is coupled to the compensation capacitor Cz to obtain the compensation capacitor voltage Vcomp, the second input terminal of the second error amplifier circuit 20 is used to receive a preset voltage, and the output terminal of the second error amplifier circuit 20 is coupled to the operation circuit, and the operation circuit is coupled to the first input terminal or the second input terminal of the first error amplifier circuit. The second error amplifier circuit 20 is used to generate a compensation voltage by performing error amplification according to the compensation capacitor voltage and the preset voltage. Figure 2 As shown, the input terminal of the drive control circuit 30 is used to couple the compensation capacitor Cz to receive the compensation capacitor voltage Vcomp, and the drive control circuit 30 is used to output a drive signal according to the compensation capacitor voltage to control the main switch. The switch control circuit proposed by the present invention can effectively optimize the load regulation rate.

[0042] In one embodiment, the switching power supply is a buck switching power supply. In another embodiment, the switching power supply may also be a buck-boost switching power supply. Figure 3 As shown, the step-down switching power supply includes a step-down conversion circuit and a switch control circuit. The step-down conversion circuit includes a main switch tube, a second diode D2, an inductor L and an output capacitor. The first end of the main switch tube is coupled to the input voltage end, the cathode of the second diode D2 is coupled to the second end of the main switch tube, and the anode of the second diode D2 is coupled to the ground. The first end of the inductor L is coupled to the second end of the main switch tube. The first end of the output capacitor is coupled to the second end of the inductor L, and the second end of the output capacitor is coupled to the anode of the second diode D2. In one embodiment, the main switch tube is built into the switch control circuit. In another embodiment, the main switch tube is external to the switch control circuit. As shown in FIG. Figure 3As shown, the pins provided in the switch control circuit include a drain pin DRAIN, a ground pin GND and a feedback pin FB. The feedback pin FB is coupled to the cathode of the first diode D1, and the anode of the first diode D1 is coupled to the first end of the output capacitor. The switch control circuit includes a first error amplifier circuit, a second error amplifier circuit 21 and a drive control circuit. The first error amplifier circuit includes a first transconductance amplifier, the non-inverting input terminal of the first transconductance amplifier is coupled to the reference voltage Vref, and the inverting input terminal of the first transconductance amplifier receives the characterization signal Vd. In one embodiment, the characterization signal Vd is a divided voltage of the feedback voltage VFB, and the feedback voltage VFB is proportional to the output voltage Vo of the switching power supply. The voltage divider circuit includes a first voltage divider resistor RF1 and a second voltage divider resistor RF2. The first end of the first voltage divider resistor RF1 is coupled to the feedback pin FB, the first end of the second voltage divider resistor RF2 is coupled to the second end of the first voltage divider resistor RF1, and the second end of the second voltage divider resistor RF2 is coupled to the chip ground. The inverting input terminal of the first transconductance amplifier is coupled to the first end of the second voltage divider resistor RF2. The output terminal of the first transconductance amplifier is coupled to the compensation capacitor Cz. In another embodiment, a first resistor Rz is also coupled between the first transconductance amplifier and the compensation capacitor, that is, the output end of the first transconductance amplifier is coupled to the first end of the first resistor, and the second end of the first resistor is coupled to the first end of the compensation capacitor Cz. At this time, the compensation capacitor voltage Vcomp is the terminal voltage of the first end of the first resistor.

[0043] like Figure 3In one embodiment shown, the second error amplifier circuit 21 includes a filter circuit 212 and a second transconductance amplifier 211. The input end of the filter circuit 212 is coupled to the compensation capacitor Cz, and the output end of the filter circuit 212 outputs a filter signal. The in-phase input end of the second transconductance amplifier 211 is coupled to the output end of the filter circuit 212, the inverting input end of the second transconductance amplifier 211 is coupled to the preset voltage, and the output end of the second transconductance amplifier 211 is used to couple the compensation capacitor. The second transconductance amplifier 211 generates a compensation signal according to the filter signal and the preset voltage, and the compensation signal is a compensation current. The preset voltage can be a chip ground voltage, that is, the GND voltage of the switch control circuit; the preset voltage can also be other preset values ​​that meet the design requirements. The second error amplifier circuit charges and discharges the compensation capacitor through the compensation current, thereby compensating the compensation capacitor voltage to optimize the load regulation rate. In one embodiment, the transconductance of the second transconductance amplifier is selected according to the internal resistance value of the second diode and the transconductance of the first transconductance amplifier. The drive control circuit includes a frequency control circuit, an amplitude control circuit, a comparison circuit, an RS trigger circuit and a driver. The input end of the frequency control circuit is coupled to the compensation capacitor Cz, and the frequency control circuit is used to adjust the switching frequency according to the compensation capacitor voltage. The input end of the amplitude control circuit is coupled to the compensation capacitor Cz, and the amplitude control circuit is used to control the amplitude according to the compensation capacitor voltage. The first input end of the comparison circuit is coupled to the sampling resistor Rcs to obtain the sampling signal, and the second input end of the comparison circuit is coupled to the output end of the amplitude control circuit. The set end of the RS trigger circuit is coupled to the output end of the frequency control circuit, and the reset end of the RS trigger circuit is coupled to the output end of the comparison circuit. The input end of the driver is coupled to the output end of the RS trigger circuit, and the driver outputs a driving signal PWM to drive the main switch tube.

[0044] In yet another embodiment, Figure 4 As shown, the switch control circuit includes a first error amplifier circuit, a second error amplifier circuit 22 and a drive control circuit. The second error amplifier circuit 22 includes a filter circuit 222 and an error amplifier 221. The input end of the filter circuit 222 is coupled to the compensation capacitor Cz to obtain the compensation capacitor voltage, and the output end of the filter circuit 222 outputs the filter signal. The non-inverting input end of the error amplifier 221 is coupled to the output end of the filter circuit 222, the inverting input end of the error amplifier 221 is coupled to the preset voltage, and the output end of the error amplifier 221 is used to couple the operation circuit. The error amplifier 221 performs error amplification according to the filter signal and the preset voltage to generate a compensation signal, and the compensation signal is a compensation voltage. As shown in Figure 4In one embodiment shown, the operation circuit includes an adding circuit, a first input terminal of the adding circuit receives a reference voltage Vref, a second input terminal of the adding circuit is coupled to the output terminal of the error amplifier 221, and the output terminal of the adding circuit is coupled to the first input terminal of the first error amplifier circuit. In another embodiment, the operation circuit includes a subtracting circuit, a first input terminal of the subtracting circuit receives a characteristic signal Vd, a second input terminal of the subtracting circuit is coupled to the output terminal of the error amplifier 221, and the output terminal of the subtracting circuit is coupled to the second input terminal of the first error amplifier circuit.

[0045] In one embodiment, Figure 5 It is the VF-IF characteristic curve of the diode, VF is the voltage drop of the diode, and IF is the current flowing through the diode. Figure 6 In the figure, the solid line is the characteristic curve of the current IF at 0.15-0.35A, and the dotted line is the linear fitting line of the current IF at 0.15-0.35A. Figure 3 , the output voltage is V o =V ref *k+V D1 -V D2 , where k = (RF1 + RF2) / RF2, RF1 is the resistance value of the first voltage-dividing resistor, RF2 is the resistance value of the second voltage-dividing resistor, VD1 is the forward voltage drop of the first diode D1 (referred to as the first voltage drop), and VD2 is the forward voltage drop of the second diode D2 (referred to as the second voltage drop). We can get ΔV o =ΔV ref *k+Δ(V D1 -V D2 ), ΔV o is the change in output voltage under different loads, ΔV ref is the change of reference voltage under different loads, Δ(V D1 -V D2 ) is the change value of the difference between the first voltage drop and the second voltage drop under different loads. The first diode D1 is a feedback diode, and the first voltage drop VD1=0.52V. The second diode D2 is a rectifier diode, which can be linearly fitted to the second voltage drop VD2=RD*Ipk+1 through a curve. RD is the internal resistance of the second diode, which is approximately 1ohm, and Ipk is the peak current of the switching power supply. In one embodiment, Ipk is the current flowing through the second diode, or is positively correlated or proportional to the current flowing through the second diode. When Ipk changes, Δ(V D2 -V D1 )=R d ΔI pk . Considering ideal compensation, ΔV o =0, then the compensation amount required for Vref is: From the above formula, we can know that the compensation amount of reference voltage V ref_addThe peak current change ΔI pk , is related to the internal resistance of the second diode.

[0046] In one embodiment, the reference voltage compensation Vref_add is realized by the transconductance gm_add of the second transconductance amplifier. The compensation capacitor voltage Vcomp is filtered by the filter circuit and then connected to the second transconductance amplifier to output the compensation current. This part of the current is equivalent to the gm transconductance. The change in Vref required is ΔV cs_pk ΔV is the peak voltage change from light load to full load, and the peak voltage corresponds to the peak current. cs_pk =R cs ΔI pk , ΔI pk is the peak current change from light load to full load, that is, the absolute value of the difference between the peak current of the switching power supply in light load state and the peak current in full load state. Therefore, the transconductance of the second transconductance amplifier required for compensation can be deduced as:

[0047]

[0048] Wherein, RD is the internal resistance of the second diode, Rcs is the sampling resistor, k is the voltage division coefficient, and gm_EA is the transconductance of the first transconductance amplifier. In another embodiment, the compensation amount Vref_add of the reference voltage passes through an operation circuit, and the operation circuit compensates the reference voltage according to the compensation voltage output by the second error amplifier circuit.

[0049] like Figure 7 FIG. 1 is a schematic diagram of a signal waveform of a conventional step-down switching power supply. When the output current Iout changes from 5mA to 200mA, the output voltage Vout changes by 183mV. Figure 8 FIG. 1 is a schematic diagram of a signal waveform of a step-down switching power supply according to an embodiment of the present invention. Figure 7 The circuit structure is optimized. When the output current Iout changes from 5mA to 200mA, the output voltage Vout changes by 54mV. By comparison, it can be seen that it is optimized by 129mV. Therefore, the switch control circuit and the switch control method and the switch power supply proposed by the present invention effectively optimize the load regulation rate.

[0050] Another embodiment of the present invention further discloses a switching power supply, the switching power supply includes a switch control circuit as described in any one of the above items, the switch control circuit generates a drive signal to control the switch state of the main switch tube. The switch control circuit controls the output voltage of the switching power supply by controlling the switch state of the main switch tube. In one embodiment, the switch control circuit includes the main switch tube. In another embodiment, the main switch tube is external to the switch control circuit.

[0051] Another embodiment of the present invention further discloses a switch control method, which is used to generate a drive signal to control a main switch in a switching power supply. The switch control method comprises the following steps:

[0052] Performing error amplification according to a reference signal and a characterizing signal characterizing an output voltage of the switching power supply to generate a first current to charge and discharge the compensation capacitor;

[0053] Amplifying the error between the preset voltage and the compensation capacitor voltage of the compensation capacitor to generate a compensation current to charge and discharge the compensation capacitor, thereby compensating the compensation capacitor voltage; and

[0054] A driving signal is output according to the compensation capacitor voltage to control the main switch tube.

[0055] The present invention also discloses another switch control method, which is used to generate a drive signal to control a main switch in a switch power supply. The switch control method includes:

[0056] Performing error amplification according to a reference signal and a characterizing signal characterizing an output voltage of the switching power supply to generate a first current to charge and discharge the compensation capacitor;

[0057] Amplifying the error between the preset voltage and the compensation capacitor voltage of the compensation capacitor to generate a compensation voltage, and performing a compensation operation on the reference signal according to the compensation voltage; and

[0058] A driving signal is output according to the compensation capacitor voltage to control the main switch tube.

[0059] Those skilled in the art should know that the logic controls such as "high level" and "low level", "set" and "reset", "AND gate" and "OR gate", "non-inverting input terminal" and "inverting input terminal" in the logic controls involved in the specification or drawings can be interchanged or changed with each other, and the same function or purpose as the above embodiment can be achieved by adjusting the subsequent logic controls.

[0060] The description and application of the present invention here are illustrative, and it is not intended to limit the scope of the present invention to the above-mentioned embodiments. The effects or advantages involved in the specification may not be reflected in the actual experimental examples due to the uncertainty of specific condition parameters or other factors, and the effects or advantages are not used to limit the scope of the invention. The deformation and change of the embodiments disclosed here are possible, and the replacement of the embodiments and the various equivalent parts are well known to those of ordinary skill in the art. It should be clear to those skilled in the art that the present invention can be implemented in other forms, structures, arrangements, proportions, and with other components, materials and parts without departing from the spirit or essential features of the present invention. Other deformations and changes can be made to the embodiments disclosed here without departing from the scope and spirit of the present invention.

Claims

1. A switch control circuit for controlling a main switch in a switching power supply, characterized in that: The switch control circuit comprises: A first error amplifier circuit, wherein a first input terminal thereof is used to couple a reference signal, a second input terminal thereof is used to couple a characterizing signal characterizing an output voltage of the switching power supply, and an output terminal thereof is used to couple a compensation capacitor; a second error amplifier circuit, whose first input terminal is coupled to the compensation capacitor, whose second input terminal is used to receive a preset voltage; whose output terminal is coupled to the compensation capacitor, or whose output terminal is coupled to an operation circuit, which is coupled to the first input terminal or the second input terminal of the first error amplifier circuit; and The drive control circuit has an input terminal coupled to the compensation capacitor to receive the compensation capacitor voltage and is used to output a drive signal according to the compensation capacitor voltage to control the main switch tube.

2. The switch control circuit according to claim 1, characterized in that: The second error amplifying circuit further comprises a filter circuit, an input end of the filter circuit is coupled to the compensation capacitor, and an output end of the filter circuit outputs a filter signal; The second error amplifier circuit generates a compensation signal according to the filtered signal and a preset voltage.

3. The switch control circuit according to claim 1, characterized in that: The second error amplifier circuit includes a second transconductance amplifier, a non-inverting input terminal of the second transconductance amplifier is coupled to the compensation capacitor, an inverting input terminal of the second transconductance amplifier is coupled to a preset voltage, and an output terminal of the second transconductance amplifier is coupled to the compensation capacitor.

4. The switch control circuit according to claim 1, characterized in that: The second error amplifier circuit includes an error amplifier. A non-inverting input terminal of the error amplifier is coupled to a compensation capacitor. An inverting input terminal of the error amplifier is coupled to a preset voltage. An output terminal of the error amplifier is coupled to an operation circuit.

5. The switch control circuit according to claim 3, characterized in that: The first error amplifying circuit includes a first transconductance amplifier, and the transconductance of the second error amplifying circuit is selected according to the internal resistance value of the second diode and the transconductance of the first transconductance amplifier.

6. The switch control circuit according to claim 4, characterized in that: The switch control circuit includes an operation circuit, which includes an adding circuit. The first input terminal of the adding circuit receives a reference signal, the second input terminal of the adding circuit is coupled to the output terminal of the error amplifier, and the output terminal of the adding circuit is coupled to the first input terminal of the first error amplifier circuit.

7. The switch control circuit according to claim 4, characterized in that: The switch control circuit includes an operation circuit, which includes a subtraction circuit. The first input terminal of the subtraction circuit receives the characterization signal, the second input terminal of the subtraction circuit is coupled to the output terminal of the error amplifier, and the output terminal of the subtraction circuit is coupled to the second input terminal of the first error amplifier circuit.

8. The switch control circuit according to claim 1, characterized in that: The drive control circuit comprises: A frequency control circuit, an input end of which is coupled to a compensation capacitor, for controlling a driving signal according to a voltage of the compensation capacitor; as well as The amplitude control circuit has an input terminal coupled to the compensation capacitor and is used to control the driving signal according to the compensation capacitor voltage.

9. A switching power supply, characterized in that: The switching power supply comprises a switching control circuit as claimed in any one of claims 1 to 8, and the switching control circuit generates a driving signal to control a main switching tube.

10. A switch control method for generating a drive signal to control a main switch in a switch power supply, characterized in that: The switch control method comprises: Performing error amplification according to a reference signal and a characterizing signal characterizing an output voltage of the switching power supply to generate a first current to charge and discharge the compensation capacitor; Amplifying the error between the preset voltage and the compensation capacitor voltage of the compensation capacitor to generate a compensation current to charge and discharge the compensation capacitor, thereby compensating the compensation capacitor voltage; and A driving signal is output according to the compensation capacitor voltage to control the main switch tube.

11. A switch control method for generating a drive signal to control a main switch in a switch power supply, characterized in that: The switch control method comprises: Performing error amplification according to a reference signal and a characterizing signal characterizing an output voltage of the switching power supply to generate a first current to charge and discharge the compensation capacitor; Amplifying the error between the preset voltage and the compensation capacitor voltage of the compensation capacitor to generate a compensation voltage, and performing a compensation operation on the reference signal according to the compensation voltage; and A driving signal is output according to the compensation capacitor voltage to control the main switch tube.

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