Constant-frequency active filter controlled by a peak current control mode

A constant-frequency active filter controlled by a peak current control mode, the constant-frequency active filter comprising:

• a voltage step-up unit comprising a transistor used as an active switch to adjust a waveform of an input current to form a sine wave, wherein the voltage step-up unit comprises:
• a power supply arranged to provide an input voltage and the input current;
• a voltage step-up inductor connected to the power supply;
• a bridge rectifier connected to the voltage step-up inductor and to a first diode;
• a current transformer having a primary coil connected to the bridge rectifier and to the transistor;
• two series-connected capacitors connected to the first diode;
• and
• a second diode connected to the two series-connected capacitors and to the first diode;
• a current control unit connected to the voltage step-up unit, wherein the current control unit comprises a PWM controller that outputs a clock signal to control a photocoupler connected to an output of the PWM controller so as to control the transistor connected to the photocoupler to be selectively activated and deactivated;
• and
• a voltage control unit connected to the current control unit, wherein the voltage control unit comprises a microprocessor for providing a current command to control the clock signal outputted by the PWM controller.