Design of AC Inverter Based on UC2525

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First, the design needs

This power supply is applied to the front end of an AC voltage conversion. The input control signal is 4VAC (50HZ AC RMS variation range 2VAC-8VAC), and the input power supply is 350VDC (accuracy 0.5%). The output signal should be linearly proportional to the input signal (20 times magnification, accuracy 0.5%), and the phase error between the input control signal and the output signal is less than 20', and the power load is not less than 30VA.

Special requirements: The control signal input impedance is required to be greater than 500M.

Second, design analysis

The model of this power supply is an AC inverter power supply, but it provides a control signal and requires a linear proportional accuracy with the input signal. The accuracy requirements are quite high and have the same phase requirements. Therefore, this power supply is an AC signal amplifier in a certain sense.

The input power is 350VDC, which needs to be converted into an AC signal. The conversion method is to generate a square wave by SPWM, and then become a standard sine through LC. The SPWM is generated by using TI's UC2525 regulated pulse width modulator, and then controlling the on and off of the MOS transistor to generate a square wave. The input signal requires high impedance and can be isolated using an amplifier. Due to the output accuracy requirements, the amplifier's amplification factor needs to be adjusted to meet the design requirements. The processed signal is input to the UC2625 as a PWM duty control signal to obtain a correct output.

The design requirements have accuracy and phase requirements. In order to achieve the effect of closed-loop control, a small signal voltage transformer is added to the output as feedback.

Third, the implementation of the division

1 control signal input processing

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