Isolated power conversion system

An isolated power conversion system, comprising:

• a rectifying unit for converting an AC power into a DC power;
• a transformer comprising a primary coil, an auxiliary coil and a secondary coil, the primary coil receiving the DC power, the auxiliary coil generating an auxiliary induced current by induction of a current flowing through the primary coil, the auxiliary induced current flowing through a serial resistor and generating an auxiliary signal, the secondary coil generating a secondary induced current by induction of the current flowing through the primary coil;
• a switching transistor implemented by a MOS (metal-oxide-semiconductor) transistor with a drain, a gate and a source or a BJT (bipolar junction transistor) with a collector, a base and an emitter, the drain or the collector connected to the primary coil, the gate or the base connected to an end of a sensing resistor, another end of the sensing resistor grounded, the source or the emitter generating a sensing signal;
• an output unit comprising an output transistor, an output diode and an output capacitor, a positive end of the output diode connected to a drain of the output transistor and an end of the output capacitor, a negative end of the output diode connected to a source of the output transistor, another end of the output capacitor connected to the secondary coil, the output capacitor connected to a load in parallel for generating an output power;
• a first Pulse Width Modulation (PWM) controller having a first end, a second end, a third end, a fourth end, a transmit end and a receive end, the first end floating, the second end connected to the gate or the base of the switching transistor through a driving serial resistor, the third end receiving the auxiliary signal, the fourth end connected to the source or the emitter of the switching transistor through a sensing serial resistor for receiving the sensing signal;
• a second PWM controller having a first end, a second end, a third end, a fourth end, a transmit end and a receive end, the first end connected to the negative end of the output diode, the second end connected to the gate of the output transistor, the third end connected to the positive end of the output diode, the fourth end connected to the load;
• and
• a signal blocking unit connected between the first and second PWM controllers, and implemented by a signal sensing coil provided in the transformer to perform bi-directional signal communication for the primary and secondary coils,
• wherein the first PWM controller performs a first control process based on the sensing signal and the auxiliary signal and electrical signal from the receive end to generate a driving signal with a PWM feature, the second end of the first PWM controller transmits the driving signal to the gate or the base of the switching transistor to drive the switching transistor, the first PWM controller generates a first digital output signal, the transmit end of the first PWM controller transmits the first digital output signal to the receive end of the second PWM controller through the signal blocking unit, the second PWM controller performs a second control process based on electrical signals from the first, third, fourth ends and receive end of the second PWM controller so as to generate a secondary coil adjust signal, the second end of the second PWM controller transmits the secondary coil adjust signal to the gate of the output transistor, the second PWM controller generates a second digital output signal, the transmit end of the second PWM controller transmits the second digital output signal to the receive end of the first PWM controller through the signal blocking unit, and connection interface provided for the signal blocking unit to communicate with the first and second PWM controllers is operated by signals in a digital form.