Isolation type power conversion method based on demagnetization iteration control and power conversion circuit

An isolation type power conversion method based on demagnetization iteration control, characterized by comprising a plurality of steps, wherein:

• step 1, a high-frequency transformer circuit of a power conversion circuit comprising a high -frequency transformer, at a beginning of power-on, a secondary side control circuit of the high -frequency transformer maintains a turn-off state, a primary side control circuit of the high-frequency transformer comprising an oscillator module, a one-out-of-two selector and an adaptive turn-on time control circuit, the oscillator module in the primary side control circuit triggering the adaptive turn-on time control circuit through a ‘0’ input end of the one-out-of-two selector, the adaptive turn-on time control circuit controlling a primary side power tube in a power switch tube circuit electrically connected with the adaptive turn-on time control circuit to be turned on so as to enable the high -frequency transformer to enter an excitation stage, the high-frequency transformer charging a secondary side power supply capacitor in a charging capacitor circuit electrically connected to a secondary side of the high-frequency transformer in the excitation stage through a power supply unit in the secondary side control circuit, a positive electrode end of the secondary side power supply capacitor being electrically connected to a secondary side positive output end of the high-frequency transformer in the excitation stage through the power supply unit, and a negative electrode end of the secondary side power supply capacitor being electrically connected to a negative electrode of a secondary side load output end in a demagnetization stage;
• step 2, when the adaptive turn-on time control circuit controls the primary side power tube in the power switch tube circuit to be turned off, the high-frequency transformer entering the demagnetization stage, the high-frequency transformer charging an output capacitor in the charging capacitor circuit electrically connected to the secondary side of the high-frequency transformer in the demagnetization stage, wherein, the secondary side control circuit still maintains the turn -off of a secondary side synchronous rectifier tube electrically connected with the secondary side of the high-frequency transformer so as to prevent a primary side and the secondary side of the high -frequency transformer from being turned on at a same time;
• step 3, after a plurality of continuous excitation stages under a control of the oscillator module and the adaptive turn-on time control circuit are completed, and a charging voltage of the secondary side power supply capacitor reaches a set threshold value, the secondary side control circuit sending a pulse communication signal to the primary side control circuit through a high-voltage capacitor isolation circuit by using a control signal modulation circuit located in the secondary side control circuit in order to establish a communication handshake with the primary side control circuit in the demagnetization stage, the one-out-of-two selector in the primary side control circuit selecting a demodulated communication signal obtained by a ‘1’ input end to trigger the adaptive turn-on time control circuit only after the communication handshake is successful, therefore, a turn-on and turn-off of the secondary side synchronous rectifier tube and the primary side power tube controlled by the adaptive turn-on time control circuit being both only controlled by the secondary side control circuit, under a condition that the primary side control circuit does not receive a communication handshake signal of the secondary side control circuit, and after the primary side control circuit controls the primary side power tube for dozens of switching cycles by using the oscillator module, a logic circuit which is arranged in the oscillator module and functions as a microcontroller controlling the oscillator module to stop outputting a signal so as to cause the primary side control circuit to be automatically turned off, and repeating Step 1 to restart the demagnetization iteration control;
• step 4, summing a feedback voltage value of an output feedback circuit of the secondary side of the high-frequency transformer and an output signal of a ripple injection module, comparing an obtained summed voltage value with a reference voltage value of a reference voltage circuit in the secondary side control circuit, and when two conditions that, the summed voltage value is smaller than the reference voltage value of the reference voltage circuit, and the demagnetization time of the current cycle is greater than or equal to the difference between a demagnetization time of a previous cycle and an iteration error amount, namely Tdemn≥Tdemn−1−ΔTdem, wherein
• Tdemn is a demagnetization time of an nth switching with a unit being microsecond;
• Tdemn−1 is a demagnetization time of an (n−1) switching with a unit being microsecond;
• ΔTdem is the iteration error amount with a unit being nanosecond;
• are met, a demagnetization time iteration control unit in the secondary side control circuit turning off the secondary side synchronous rectifier tube through a secondary side turn-off/turn-on unit in the secondary side control circuit, and sending a TX turn-on signal to the primary side control circuit through the control signal modulation circuit located in the secondary side control circuit after delaying for several nanoseconds;
• a signal being coupled by the high-voltage capacitor isolation circuit and demodulated by a control signal demodulation circuit in the primary side control circuit to generate an RX signal, the RX signal being input into the adaptive turn-on time control circuit located in the primary side control circuit, the adaptive turn-on time control circuit controlling the primary side power tube to be turned on, and the high-frequency transformer obtaining excitation storage energy;
• the adaptive turn-on time control circuit calculating the turn-on time of the primary side power tube according to a primary side bus voltage VIN parameter of the high-frequency transformer and automatically turning off the primary side power tube after the turn-on time is reached, so as to enable the high-frequency transformer to enter the demagnetization stage to output energy to the secondary side;
• the secondary side control circuit turning on the secondary side synchronous rectifier tube through the secondary side turn-off/turn-on unit comprised in the secondary side control circuit, thereby ensuring that a load end of the secondary side of the high-frequency transformer obtains an energy supply;
• and
• step 5, detecting a feedback voltage of the output feedback circuit at the load end of the secondary side of the high-frequency transformer in real time, and repeating Step 4 to realize energy transfer after power conversion from the primary side of the high-frequency transformer to the secondary side of the high-frequency transformer.