Patent ID: 8300433

Claim:
An isolated primary circuit regulator, applied to a primary side of a transformer, the isolated primary circuit regulator comprising: a discharge time detector, connected to the transformer, for detecting a discharge time of a switching current generated at a secondary side of the transformer, and outputting a discharge time signal and an inverse discharge time signal; an oscillator, for generating an oscillation signal; a control circuit, connected to the discharge time detector, for performing signal processing of output current waveform reconstruction, filtering, amplification and comparison on a critical voltage according to the discharge time signal and the inverse discharge time signal, and outputting an adjustment signal, wherein the critical voltage is corresponding to a peak value of a switching voltage signal generated at the primary side of the transformer; and a pulse width modulator, comprising a first input terminal and a second input terminal, wherein the first input terminal is connected to the control circuit, the second input terminal is connected to the oscillator, the pulse width modulator outputs a switching signal, the switching signal has a duty cycle and a frequency corresponding to the oscillation signal and the adjustment signal, and the adjustment signal is used for resetting the pulse width modulator, wherein the control circuit comprises: an output current waveform reconstruction circuit, for outputting a square wave signal according to the discharge time signal, the inverse discharge time signal, the switching signal and the critical voltage, wherein the square wave signal has an amplitude corresponding to the critical voltage, the square wave signal occurs in synchronization to the discharge time signal, and the square wave signal has a waveform corresponding to a waveform of an output current; a low-pass filter, for filtering the square wave signal to output a direct current (DC) signal; an error amplifier, for amplifying the DC signal into the critical voltage; and a comparator, connected between the error amplifier and the pulse width modulator, for comparing the critical voltage to the switching voltage signal to generate the adjustment signal.