Single-stage PFC converter with constant voltage and constant current

A power supply circuit comprising:

• a bridge rectifier coupled to input of the power supply circuit;
• a transformer coupled to the bridge rectifier;
• a power device coupled to the transformer for switching the transformer to product an output of the power supply circuit;
• a switching controller receiving a feedback signal for generating a switching signal coupled to drive the power device, wherein an input circuit of the switching controller is coupled to the transformer to sample an input signal for generating the feedback signal, and the input signal is correlated to the output of the power supply circuit;
• and
• a capacitor coupled to the switching controller to provide frequency compensation for a feedback loop of the power supply circuit;
• wherein the bridge rectifier is developed by high speed diodes, output of the bridge rectifier is without an electrolytic capacitor, and a maximum output current of the power supply circuit is a constant current;
• wherein the input circuit further generates a voltage-feedback signal and a demagnetizing-time signal according to the input signal, and enabling of the demagnetizing-time signal indicates that the transformer is fully demagnetized;
• and
• wherein the switching controller comprises:
• an integrator generating a current-feedback signal according to the input signal and the demagnetizing-time signal;
• a first error amplifier comparing the voltage-feedback signal with a first reference signal;
• a second error amplifier comparing the current-feedback signal with a second reference signal, wherein outputs of the first and second error amplifiers are coupled to the capacitor to generate a compensated signal;
• and
• a PWM circuit receiving the compensated signal and the demagnetizing-time signal and generating the switching signal according to the compensated signal and the demagnetizing-time signal.