Sine pulse width modulation circuit and switching power supply

Abstract

The utility model discloses a sine pulse width modulation circuit and a switching power supply, and the circuit comprises a sine wave generation circuit which comprises a voltage division circuit, an RC oscillation circuit, a differential comparison amplification circuit, and a gating circuit; the voltage division circuit is used for carrying out voltage division processing on power supply voltage input by the input end of the sine pulse width modulation circuit and then outputting a direct-current voltage signal; the RC oscillating circuit is used for converting the direct-current voltage signal into an alternating-current oscillating signal and outputting the alternating-current oscillating signal; the differential comparison amplification circuit is used for comparing and amplifying the AC oscillation signal and the DC voltage signal and then outputting an AC voltage signal; the gating circuit is used for gating the AC voltage signal and then outputting a sine wave signal; the negative half-cycle rectifying circuit is used for overturning and rectifying a negative half-cycle signal in the sine wave signal and then outputting the negative half-cycle signal; and the positive half-cycle rectifying circuit is used for overturning and rectifying a positive half-cycle signal in the sine wave signal and then outputting the positive half-cycle signal. According to the utility model, the cost, volume and weight of the product can be reduced.

Description

TECHNICAL FIELD

[0001] The utility model relates to the field of switching converter, especially a sine pulse width modulation circuit and switching power supply. BACKGROUND

[0002] Due to the product application field of power industry is more and more wide, the localization, miniaturization, light weight of product are more and more high, and the miniaturization demand of inverter product is particularly important. Many inverter products use digital chips to control the whole sine pulse width modulation, but the digital chip is extremely easy to be disturbed, and the whole system control is complex, and the challenge to circuit and PCB layout is great, and too many resources are occupied in circuit size and cost, which is not conducive to the miniaturization and light weight of product, and the requirement of digital chip for the whole sine pulse width modulation control is extremely high, and most of the products on the market use expensive imported chips, so the localization is difficult.

[0003] The traditional low-power inverter power supply usually adopts analog chips to send frequency-adjustable sine waves, and then sends the sine waves to another analog chip for SPWM modulation after a series of signal conditioning circuits. This SPWM modulation method has a complex circuit, needs multiple analog chips for common control, has high cost, and has poor consistency. SUMMARY

[0004] Therefore, the utility model provides a sine pulse width modulation circuit and switching power supply, which can at least solve the above problems of the prior art to some extent.

[0005] As a first aspect of the utility model, the technical scheme of the embodiment of the provided sine pulse width modulation circuit is as follows:

[0006] A sine pulse width modulation circuit, comprising:

[0007] A sine wave generation circuit, comprising a voltage dividing circuit, an RC oscillation circuit, a differential comparison amplification circuit and a gating circuit. The input end of the voltage dividing circuit is connected to the input end of the sine pulse width modulation circuit, and is used to output a direct current voltage signal after dividing the power supply voltage input into the input end of the sine pulse width modulation circuit. The input end of the RC oscillation circuit is connected to the output end of the voltage dividing circuit, and is used to convert the direct current voltage signal into an alternating current oscillation signal output. One input end of the differential comparison amplification circuit is connected to the output end of the RC oscillation circuit, and the other input end is connected to the output end of the voltage dividing circuit, and is used to output an alternating current voltage signal after comparing and amplifying the alternating current oscillation signal and the direct current voltage signal. The input end of the gating circuit is connected to the output end of the differential comparison amplification circuit, and is used to output a sine wave signal after gating the alternating current voltage signal.

[0008] a negative half cycle rectifier circuit connected to the output end of the gating circuit, for outputting the negative half cycle signal in the sinusoidal signal after being inverted and rectified by the output end of the sinusoidal pulse width modulation circuit;

[0009] a positive half cycle rectifier circuit connected to the output end of the gating circuit, for outputting the positive half cycle signal in the sinusoidal signal after being inverted and rectified by the output end of the sinusoidal pulse width modulation circuit.

[0010] Preferably, the voltage dividing circuit comprises a resistor R2, a resistor R6, a capacitor C3 and a capacitor C5, one end of the resistor R2 and one end of the capacitor C3 are connected together as the input end of the voltage dividing circuit, the other end of the resistor R2, the other end of the capacitor C3, one end of the resistor R6 and one end of the capacitor C5 are connected together as the output end of the voltage dividing circuit, and the other end of the resistor R6 and the other end of the capacitor C5 are connected together as the ground end of the voltage dividing circuit for grounding.

[0011] Preferably, the RC oscillation circuit comprises a resistor R3, a resistor R1, a capacitor C1 and a capacitor C2, one end of the resistor R3 and one end of the capacitor C1 are connected together as the input end of the RC oscillation circuit, the other end of the resistor R3, the other end of the capacitor C1 and one end of the resistor R1 are connected together as the output end of the RC oscillation circuit, the other end of the resistor R1 is connected to one end of the capacitor C2, and the other end of the capacitor C2 is connected to the output end of the differential comparison amplification circuit.

[0012] Preferably, the differential comparison amplification circuit comprises an operational amplifier U1B, a resistor R4 and a resistor R7, the non-inverting input end of the operational amplifier U1B is one input end of the differential comparison amplification circuit, one end of the resistor R4 is another input end of the differential comparison amplification circuit, the other end of the resistor R4 and one end of the resistor R7 are simultaneously connected to the inverting input end of the operational amplifier U1B, and the output end of the operational amplifier U1B and the other end of the resistor R7 are connected together as the output end of the differential comparison amplification circuit.

[0013] Preferably, the gating circuit comprises a capacitor C4, one end of the capacitor C4 is the input end of the gating circuit, and the other end of the capacitor C4 is the output end of the gating circuit.

[0014] Preferably, the gating circuit further comprises a resistor R5, the other end of the capacitor C4 is connected to one end of the resistor R5, and the other end of the resistor R5 is the output end of the gating circuit.

[0015] Preferably, the negative half-wave rectifier circuit comprises a resistor R9, a resistor R11 and an operational amplifier U3B, one end of the resistor R11 is the input end of the negative half-wave rectifier circuit, the other end of the resistor R11 is connected to the inverting input end of the operational amplifier U3B and one end of the resistor R9 at the same time, the non-inverting input end of the operational amplifier U3B is connected to ground, the other end of the resistor R9 and the output end of the operational amplifier U3B are connected together as the output end of the negative half-wave rectifier circuit, and the output end of the sine pulse width modulation circuit is connected.

[0016] Preferably, the positive half-wave rectifier circuit comprises a resistor R8, a resistor R10, a diode D1, a diode D2, an operational amplifier U2B, a resistor R9 and an operational amplifier U3B, one end of the resistor R8, the cathode of the diode D1 and the inverting input end of the operational amplifier U2B are connected together as the input end of the positive half-wave rectifier circuit, the non-inverting input end of the operational amplifier U2B is connected to ground, the anode of the diode D1 and the cathode of the diode D2 are connected to the output end of the operational amplifier U2B at the same time, the other end of the resistor R8 and the anode of the diode D2 are connected to one end of the resistor R10 at the same time, the other end of the resistor R10 and one end of the resistor R9 are connected to the inverting input end of the operational amplifier U3B at the same time, the non-inverting input end of the operational amplifier U3B is connected to ground, the other end of the resistor R9 and the output end of the operational amplifier U3B are connected together as the output end of the negative half-wave rectifier circuit, and the output end of the sine pulse width modulation circuit is connected.

[0017] Preferably, the voltage dividing circuit comprises a resistor R2, a resistor R6, a capacitor C3 and a capacitor C5, one end of the resistor R2 and one end of the capacitor C3 are connected together as the input end of the voltage dividing circuit, the other end of the resistor R2, the other end of the capacitor C3, one end of the resistor R6 and one end of the capacitor C5 are connected together as the output end of the voltage dividing circuit, and the other end of the resistor R6 and the other end of the capacitor C5 are connected together as the input end of the differential comparison amplification circuit connected to ground.

[0018] The RC oscillation circuit comprises a resistor R3, a resistor R1, a capacitor C1 and a capacitor C2, one end of the resistor R3 and one end of the capacitor C1 are connected together as the input end of the RC oscillation circuit, the other end of the resistor R3, the other end of the capacitor C1 and one end of the resistor R1 are connected together as the output end of the RC oscillation circuit, the other end of the resistor R1 is connected to one end of the capacitor C2, and the other end of the capacitor C2 is connected to the output end of the differential comparison amplification circuit.

[0019] The differential comparison amplification circuit comprises an operational amplifier U1B, a resistor R4 and a resistor R7; one input end of the differential comparison amplification circuit is the noninverting input end of the operational amplifier U1B, the other input end of the differential comparison amplification circuit is one end of the resistor R4, the other end of the resistor R4 and one end of the resistor R7 are connected to the inverting input end of the operational amplifier U1B at the same time, and the output end of the operational amplifier U1B and the other end of the resistor R7 are connected together to be the output end of the differential comparison amplification circuit;

[0020] The gating circuit comprises a capacitor C4 and a resistor R5; one end of the capacitor C4 is the input end of the gating circuit, the other end of the capacitor C4 is connected to one end of the resistor R5, and the other end of the resistor R5 is the output end of the gating circuit.

[0021] The negative half-wave rectification circuit comprises a resistor R9, a resistor R11 and an operational amplifier U3B; one end of the resistor R11 is the input end of the negative half-wave rectification circuit, the other end of the resistor R11 is connected to the inverting input end of the operational amplifier U3B and one end of the resistor R9 at the same time, the noninverting input end of the operational amplifier U3B is connected to ground, and the other end of the resistor R9 and the output end of the operational amplifier U3B are connected together to be the output end of the negative half-wave rectification circuit and connected to the output end of the sinusoidal pulse width modulation circuit.

[0022] The positive half-wave rectification circuit comprises a resistor R8, a resistor R10, a diode D1, a diode D2, an operational amplifier U2B, the resistor R9 and the operational amplifier U3B; one end of the resistor R8, the cathode of the diode D1 and the inverting input end of the operational amplifier U2B are connected together to be the input end of the positive half-wave rectification circuit, the noninverting input end of the operational amplifier U2B is connected to ground, the anode of the diode D1 and the cathode of the diode D2 are connected to the output end of the operational amplifier U2B at the same time, the other end of the resistor R8 and the anode of the diode D2 are connected to one end of the resistor R10 at the same time, the other end of the resistor R10 and one end of the resistor R9 are connected to the inverting input end of the operational amplifier U3B at the same time, the noninverting input end of the operational amplifier U3B is connected to ground, and the other end of the resistor R9 and the output end of the operational amplifier U3B are connected together to be the output end of the negative half-wave rectification circuit and connected to the output end of the sinusoidal pulse width modulation circuit.

[0023] As a second aspect of the utility model, the embodiment technical scheme of the switching power supply is as follows:

[0024] A switching power supply, wherein: comprising the sinusoidal pulse width modulation circuit of any one of the first aspect.

[0025] Compared with the prior art, the utility model has the following beneficial effects:

[0026] The sine pulse width modulation circuit of the utility model embodiment generates high-frequency sine wave through RC oscillation circuit in sine wave generating circuit, generates direct current steamed bun wave signal after processing through negative half cycle rectifier circuit and positive half cycle rectifier circuit, finally gives single-chip microcomputer to carry out sine pulse width modulation, realizes sine pulse width hardware modulation function, realizes sine pulse width modulation function with very low cost, circuit applicability is extensive, can be applicable to all low -power inverter power supply product, can greatly reduce product's cost, volume and weight, improves product's reliability, and can realize 100% localization. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 It is a specific circuit schematic diagram of the sine pulse width modulation circuit of the first embodiment of the utility model. DETAILED DESCRIPTION

[0028] In order to make the above-mentioned purpose, features and advantages of the utility model more apparent, obvious and easy to understand, the specific embodiment of the utility model is described in detail below with the drawings, obviously, the described embodiment is a part of the embodiment of the utility model, rather than all the embodiments. Based on the embodiment in the application, all other embodiments obtained by the person skilled in the art without making creative labor should belong to the protection scope of the application.

[0029] It should be noted that the terms "include" and "have" and their any variants described in the specification and claims of the application are intended to cover the non-exclusive inclusion, for example, a series of components, unit circuits or control time sequences described in the specification and claims of the application are not limited to the clearly listed components, unit circuits or control time sequences, but can include the components, unit circuits or control time sequences not clearly listed or inherent to the circuit.

[0030] In addition, the embodiments in the application and the features in the embodiments can be combined with each other without conflict.

[0031] It should be understood that, in the specification and claims, when describing that an element is "connected" to another element, the element can be "directly connected" to the other element, or "connected" to the other element through a third element, when describing that a step is connected to another step, the step can be directly connected to the other step, or connected to the other step through a third step.

[0032] First embodiment

[0033] The utility model discloses a sine pulse width modulation circuit, wherein, including:

[0034] The sine wave generating circuit comprises a voltage dividing circuit, an RC oscillation circuit, a differential comparison amplification circuit and a gating circuit; the input end of the voltage dividing circuit is connected with the input end of the sine pulse width modulation circuit, and is used for outputting a direct current voltage signal after voltage dividing treatment of the power supply voltage inputted by the input end of the sine pulse width modulation circuit; the input end of the RC oscillation circuit is connected with the output end of the voltage dividing circuit, and is used for converting the direct current voltage signal into an alternating current oscillation signal and outputting the alternating current oscillation signal; one input end of the differential comparison amplification circuit is connected with the output end of the RC oscillation circuit, and the other input end is connected with the output end of the voltage dividing circuit, and is used for comparing and amplifying the alternating current oscillation signal and the direct current voltage signal and outputting an alternating current voltage signal; the input end of the gating circuit is connected with the output end of the differential comparison amplification circuit, and is used for gating the alternating current voltage signal and outputting a sine wave signal;

[0035] The negative half cycle rectification circuit is connected with the output end of the gating circuit, and is used for inverting and rectifying the negative half cycle signal in the sine wave signal and outputting the negative half cycle signal from the output end of the sine pulse width modulation circuit;

[0036] The positive half cycle rectification circuit is connected with the output end of the gating circuit, and is used for inverting and rectifying the positive half cycle signal in the sine wave signal and outputting the positive half cycle signal from the output end of the sine pulse width modulation circuit.

[0037] Figure 1 For the specific circuit principle diagram of the sine pulse width modulation circuit of the first embodiment of the utility model, please refer to Figure 1 , wherein:

[0038] The voltage dividing circuit comprises a resistor R2, a resistor R6, a capacitor C3 and a capacitor C5, one end of the resistor R2 and one end of the capacitor C3 are connected together as the input end VCC of the voltage dividing circuit, the other end of the resistor R2, the other end of the capacitor C3, one end of the resistor R6 and one end of the capacitor C5 are connected together as the output end of the voltage dividing circuit, and the other end of the resistor R6 and the other end of the capacitor C5 are connected together as the input ground end of the voltage dividing circuit for grounding;

[0039] The RC oscillation circuit comprises a resistor R3, a resistor R1, a capacitor C1 and a capacitor C2, one end of the resistor R3 and one end of the capacitor C1 are connected together as the input end of the RC oscillation circuit, the other end of the resistor R3, the other end of the capacitor C1 and one end of the resistor R1 are connected together as the output end of the RC oscillation circuit, the other end of the resistor R1 is connected with one end of the capacitor C2, and the other end of the capacitor C2 is connected with the output end of the differential comparison amplification circuit;

[0040] The differential comparison amplification circuit comprises an operational amplifier U1B, a resistor R4 and a resistor R7; the non-inverting input terminal of the operational amplifier U1B is an input terminal of the differential comparison amplification circuit, one end of the resistor R4 is another input terminal of the differential comparison amplification circuit, the other end of the resistor R4 and one end of the resistor R7 are connected to the inverting input terminal of the operational amplifier U1B, and the output terminal of the operational amplifier U1B and the other end of the resistor R7 are connected together to form an output terminal of the differential comparison amplification circuit;

[0041] The gating circuit comprises a capacitor C4; one end of the capacitor C4 is an input terminal of the gating circuit, and the other end of the capacitor C4 is an output terminal of the gating circuit.

[0042] Further, the gating circuit further comprises a resistor R5; the other end of the capacitor C4 is connected to one end of the resistor R5, and the other end of the resistor R5 is the output terminal of the gating circuit.

[0043] The negative half-cycle rectification circuit comprises a resistor R9, a resistor R11 and an operational amplifier U3B; one end of the resistor R11 is an input terminal of the negative half-cycle rectification circuit, the other end of the resistor R11 is connected to the inverting input terminal of the operational amplifier U3B and one end of the resistor R9, the non-inverting input terminal of the operational amplifier U3B is connected to ground, the other end of the resistor R9 and the output terminal of the operational amplifier U3B are connected together to form an output terminal of the negative half-cycle rectification circuit, and the output terminal of the sine pulse width modulation circuit is connected.

[0044] The positive half-cycle rectification circuit comprises a resistor R8, a resistor R10, a diode D1, a diode D2, an operational amplifier U2B, a resistor R9 and an operational amplifier U3B; the resistor R9 and the operational amplifier U3B are shared by the negative half-cycle rectification circuit; one end of the resistor R8, the cathode of the diode D1 and the inverting input terminal of the operational amplifier U2B are connected together to form an input terminal of the positive half-cycle rectification circuit, the non-inverting input terminal of the operational amplifier U2B is connected to ground, the anode of the diode D1 and the cathode of the diode D2 are connected to the output terminal of the operational amplifier U2B, the other end of the resistor R8 and the anode of the diode D2 are connected to one end of the resistor R10, the other end of the resistor R10 and one end of the resistor R9 are connected to the inverting input terminal of the operational amplifier U3B, the non-inverting input terminal of the operational amplifier U3B is connected to ground, the other end of the resistor R9 and the output terminal of the operational amplifier U3B are connected together to form an output terminal of the negative half-cycle rectification circuit, and the output terminal of the sine pulse width modulation circuit is connected.

[0045] Figure 1 The working principle of the circuit is as follows:

[0046] The voltage dividing circuit divides the power supply voltage inputted from the input end of the sinusoidal pulse width modulation circuit, and outputs a direct current voltage signal. Since the sinusoidal pulse width modulation circuit is single-capacitor power supply, the voltage dividing circuit needs to provide two power supplies by voltage division of the capacitors C3 and C5. However, the voltage division effect of the capacitors is poor, and therefore each capacitor needs to be connected in parallel with a voltage division resistor to achieve a better voltage division effect.

[0047] The input end of the RC oscillation circuit is connected to the output end of the voltage dividing circuit. The direct current voltage signal generated by the output end of the voltage dividing circuit charges the capacitors C1 and C2. The charging path is: the input end of the RC oscillation circuit→the capacitor C1→the resistor R1→the capacitor C2→the ground terminal inside the operational amplifier U1B (the pin 7 of the operational amplifier U1B can form a current loop according to the internal structure of the operational amplifier), and the voltage across the capacitor C1 gradually increases. When the capacitor C1 is fully charged, the capacitor C1 is discharged and reset through the resistor R3. Since the non-inverting input terminal and the inverting input terminal of the operational amplifier U1B are virtually shorted, the capacitor C2 is discharged and reset through the resistor R1. The charging and discharging of the capacitors C1 and C2 are alternately performed, so that an alternating current oscillation signal is generated at the output end of the RC oscillation circuit. The signal is related to the charging and discharging curve of the capacitor C1, is similar to a triangular wave, and is sinusoidal to a certain extent. The amplitude and frequency of the signal can be designed by selecting the parameters of the capacitors C1 and C2, the resistor R1 and the resistor R3. The resistor R1 has the same resistance value as the third resistor R3, and the capacitor C1 has the same capacitance value as the capacitor C2.

[0048] One input end of the differential comparison amplification circuit is connected to the output end of the RC oscillation circuit, and the other input end is connected to the output end of the voltage dividing circuit. The differential comparison amplification circuit is used to compare and amplify the alternating current oscillation signal and the direct current voltage signal inputted from the two input ends, and outputs an alternating current voltage signal. The resistor R4 is a sampling resistor, and the resistor R7 is a feedback resistor. The resistor R4 and the resistor R7 are set to make the operational amplifier U1B form a reverse proportional amplifier, so that the signal outputted from the operational amplifier U1B is a reverse amplified signal of the difference between the two input ends, i.e. an alternating current voltage signal.

[0049] The gating circuit includes the capacitor C4. The capacitor C4 selects the alternating current voltage signal outputted from the output end of the differential comparison amplification circuit by using the characteristic of passing alternating current and blocking direct current, so that the output end of the gating circuit outputs a pure alternating current voltage signal. The resistor R5 functions as a current limiter.

[0050] When the selected gating circuit outputs the negative half cycle voltage signal, diode D1 and diode D2 are turned off, so that the current is forced to pass through the branch with resistor R11 and the branch with resistor R8 and resistor R10, resistor R11 is a sampling resistor, resistor R9 is a feedback resistor, the negative voltage signal output by the gating circuit is inverted negatively by operational amplifier U3B, and a positive voltage signal is generated at the output end of operational amplifier U3B; when the gating circuit outputs the positive half cycle voltage signal, the 6th pin of operational amplifier U2B is positive voltage, so that the 7th pin outputs negative voltage, so that the anode potential of diode D2 is higher than the cathode, diode D2 is turned on, the anode potential is pulled down to the voltage at the 7th pin of operational amplifier U2B, and after sampling by resistor R10, the voltage is sent to U3B, inverted negatively by operational amplifier U3B, and a positive voltage signal is generated at the output end of operational amplifier U3B, wherein resistor R10 functions as an isolation resistor in the process of rectifying the positive and negative alternating voltage signals, otherwise the positive and negative rectification paths do not exist.

[0051] It can be known from the working principle that the sine pulse width modulation circuit generates a high-frequency sine wave through the RC oscillation circuit in the sine wave generation circuit, generates a direct current steamed bun wave signal after being processed by the negative half cycle rectifier circuit and the positive half cycle rectifier circuit, and finally sends the signal to the single-chip microcomputer for sine pulse width modulation, so that the sine pulse width hardware modulation function is realized. Figure 1 The specific circuit is very simple, and the components are all conventional components, and 100% localization can be realized.

[0052] Second embodiment

[0053] The switching power supply provided in the embodiment comprises any one of the sine pulse width modulation circuits in the first embodiment, so that the cost, size and weight of the product can be greatly reduced, the reliability of the product is improved, and 100% localization can be realized.

[0054] The above is only the preferred embodiment of the utility model, and more equivalent modifications or replacements can be added on this basis, which also belongs to the protection scope of the patent. It should be noted that the above preferred embodiment should not be regarded as a limitation of the utility model, and some improvements and refinements can be made by those skilled in the art without departing from the spirit and scope of the utility model, and these improvements and refinements should also be regarded as the protection scope of the utility model, which will not be described in detail here, and the protection scope of the utility model should be limited by the scope defined in the claims.

Claims

1. A sinusoidal pulse width modulation circuit, characterized by, The application relates to a sine wave generating circuit. The sine wave generating circuit comprises a voltage dividing circuit, an RC oscillation circuit, a differential comparison amplification circuit and a gating circuit; the input end of the voltage dividing circuit is connected with the input end of the sine pulse width modulation circuit, and the voltage dividing circuit is used for dividing the voltage supplied by the input end of the sine pulse width modulation circuit and outputting a direct current voltage signal; the input end of the RC oscillation circuit is connected with the output end of the voltage dividing circuit, and the RC oscillation circuit is used for converting the direct current voltage signal into an alternating current oscillation signal and outputting the alternating current oscillation signal; one input end of the differential comparison amplification circuit is connected with the output end of the RC oscillation circuit, and the other input end of the differential comparison amplification circuit is connected with the output end of the voltage dividing circuit, and the differential comparison amplification circuit is used for comparing and amplifying the alternating current oscillation signal and the direct current voltage signal and outputting an alternating current voltage signal; the input end of the gating circuit is connected with the output end of the differential comparison amplification circuit, and the gating circuit is used for gating the alternating current voltage signal and outputting a sine wave signal. The negative half cycle rectification circuit is connected with the output end of the gating circuit, and is used for inverting and rectifying the negative half cycle signal in the sine wave signal and outputting the negative half cycle signal from the output end of the sine pulse width modulation circuit. The positive half cycle rectification circuit is connected with the output end of the gating circuit, and is used for inverting and rectifying the positive half cycle signal in the sine wave signal and outputting the positive half cycle signal from the output end of the sine pulse width modulation circuit.

2. The sinusoidal pulse width modulation circuit of claim 1, wherein: The voltage dividing circuit comprises a resistor R2, a resistor R6, a capacitor C3 and a capacitor C5; one end of the resistor R2 and one end of the capacitor C3 are connected together to serve as the input end of the voltage dividing circuit; the other end of the resistor R2, the other end of the capacitor C3, one end of the resistor R6 and one end of the capacitor C5 are connected together to serve as the output end of the voltage dividing circuit; the other end of the resistor R6 and the other end of the capacitor C5 are connected together to serve as the ground end of the voltage dividing circuit.

3. The sinusoidal pulse width modulation circuit of claim 1, wherein: The RC oscillation circuit comprises a resistor R3, a resistor R1, a capacitor C1 and a capacitor C2; one end of the resistor R3 and one end of the capacitor C1 are connected together to serve as the input end of the RC oscillation circuit; the other end of the resistor R3, the other end of the capacitor C1 and one end of the resistor R1 are connected together to serve as the output end of the RC oscillation circuit; the other end of the resistor R1 is connected with one end of the capacitor C2; the other end of the capacitor C2 is connected with the output end of the differential comparison amplification circuit.

4. The sinusoidal pulse width modulation circuit of claim 1, wherein: The differential comparison amplification circuit comprises an operational amplifier U1B, a resistor R4 and a resistor R7; the non-inverting input end of the operational amplifier U1B serves as one input end of the differential comparison amplification circuit; one end of the resistor R4 serves as the other input end of the differential comparison amplification circuit; the other end of the resistor R4 and one end of the resistor R7 are connected with the inverting input end of the operational amplifier U1B; the output end of the operational amplifier U1B and the other end of the resistor R7 are connected together to serve as the output end of the differential comparison amplification circuit.

5. The sinusoidal pulse width modulation circuit of claim 1, wherein: The gating circuit comprises a capacitor C4; one end of the capacitor C4 serves as the input end of the gating circuit; the other end of the capacitor C4 serves as the output end of the gating circuit.

6. The sinusoidal pulse width modulation circuit of claim 5, wherein: The gate circuit further comprises a resistor R5, one end of the resistor R5 is connected to the other end of the capacitor C4, and the other end of the resistor R5 is an output end of the gate circuit.

7. The sinusoidal pulse width modulation circuit of claim 1, wherein: The negative half-wave rectification circuit comprises a resistor R9, a resistor R11, and an operational amplifier U3B, one end of the resistor R11 is an input end of the negative half-wave rectification circuit, the other end of the resistor R11 is connected to the inverting input end of the operational amplifier U3B and one end of the resistor R9, the non-inverting input end of the operational amplifier U3B is grounded, the other end of the resistor R9 and the output end of the operational amplifier U3B are connected together to be an output end of the negative half-wave rectification circuit, and the output end of the sine pulse width modulation circuit is connected.

8. The sinusoidal pulse width modulation circuit of claim 1, wherein: The positive half-wave rectification circuit comprises a resistor R8, a resistor R10, a diode D1, a diode D2, an operational amplifier U2B, a resistor R9, and an operational amplifier U3B, one end of the resistor R8, the cathode of the diode D1, and the inverting input end of the operational amplifier U2B are connected together to be an input end of the positive half-wave rectification circuit, the non-inverting input end of the operational amplifier U2B is grounded, the anode of the diode D1 and the cathode of the diode D2 are connected to the output end of the operational amplifier U2B, the other end of the resistor R8 and the anode of the diode D2 are connected to one end of the resistor R10, the other end of the resistor R10 and one end of the resistor R9 are connected to the inverting input end of the operational amplifier U3B, the non-inverting input end of the operational amplifier U3B is grounded, the other end of the resistor R9 and the output end of the operational amplifier U3B are connected together to be an output end of the negative half-wave rectification circuit, and the output end of the sine pulse width modulation circuit is connected.

9. The sine pulse width modulation circuit according to claim 1, wherein: The voltage dividing circuit comprises a resistor R2, a resistor R6, a capacitor C3, and a capacitor C5, one end of the resistor R2 and one end of the capacitor C3 are connected together to be an input end of the voltage dividing circuit, the other end of the resistor R2, the other end of the capacitor C3, one end of the resistor R6, and one end of the capacitor C5 are connected together to be an output end of the voltage dividing circuit, and the other end of the resistor R6 and the other end of the capacitor C5 are connected together to be a ground end for grounding; The RC oscillation circuit comprises a resistor R3, a resistor R1, a capacitor C1, and a capacitor C2, one end of the resistor R3 and one end of the capacitor C1 are connected together to be an input end of the RC oscillation circuit, the other end of the resistor R3, the other end of the capacitor C1, and one end of the resistor R1 are connected together to be an output end of the RC oscillation circuit, the other end of the resistor R1 is connected to one end of the capacitor C2, and the other end of the capacitor C2 is connected to the output end of the differential comparison amplification circuit. The differential comparison amplification circuit comprises an operational amplifier U1B, a resistor R4 and a resistor R7; one input end of the differential comparison amplification circuit is the non-inverting input end of the operational amplifier U1B, the other input end of the differential comparison amplification circuit is one end of the resistor R4, the other end of the resistor R4 and one end of the resistor R7 are connected to the inverting input end of the operational amplifier U1B, and the output end of the operational amplifier U1B and the other end of the resistor R7 are connected together to form the output end of the differential comparison amplification circuit; The gating circuit comprises a capacitor C4 and a resistor R5; one end of the capacitor C4 is the input end of the gating circuit, the other end of the capacitor C4 is connected to one end of the resistor R5, and the other end of the resistor R5 is the output end of the gating circuit; The negative half-wave rectification circuit comprises a resistor R9, a resistor R11 and an operational amplifier U3B; one end of the resistor R11 is the input end of the negative half-wave rectification circuit, the other end of the resistor R11 is connected to the inverting input end of the operational amplifier U3B and one end of the resistor R9, the non-inverting input end of the operational amplifier U3B is connected to ground, and the other end of the resistor R9 and the output end of the operational amplifier U3B are connected together to form the output end of the negative half-wave rectification circuit and are connected to the output end of the sinusoidal pulse width modulation circuit; The positive half-wave rectification circuit comprises a resistor R8, a resistor R10, a diode D1, a diode D2, an operational amplifier U2B, the resistor R9 and the operational amplifier U3B; one end of the resistor R8, the cathode of the diode D1 and the inverting input end of the operational amplifier U2B are connected together to form the input end of the positive half-wave rectification circuit, the non-inverting input end of the operational amplifier U2B is connected to ground, the anode of the diode D1 and the cathode of the diode D2 are connected to the output end of the operational amplifier U2B, the other end of the resistor R8 and the anode of the diode D2 are connected to one end of the resistor R10, the other end of the resistor R10 and one end of the resistor R9 are connected to the inverting input end of the operational amplifier U3B, the non-inverting input end of the operational amplifier U3B is connected to ground, the other end of the resistor R9 and the output end of the operational amplifier U3B are connected together to form the output end of the negative half-wave rectification circuit and are connected to the output end of the sinusoidal pulse width modulation circuit.

10. A switching power supply characterized by comprising: The sinusoidal pulse width modulation circuit comprises the differential comparison amplification circuit, the gating circuit, the negative half-wave rectification circuit and the positive half-wave rectification circuit. The sinusoidal pulse width modulation circuit comprises the differential comparison amplification circuit, the gating circuit, the negative half-wave rectification circuit and the positive half-wave rectification circuit.

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