ERICSSON type switching power supply circuit principle analysis - Power Circuit - Circuit Diagram

The circuit diagram for the mapping process is provided in the attached figure. This power supply system employs a self-excited oscillation circuit, where the transformer couples the buck output. Once the main power is activated, the 220V AC input is converted into approximately 260V DC high voltage via the D1-D4 bridge rectifier and C1 filter. This high voltage is then delivered to the load L1 and the b pole of the high-voltage switch transistor Q through resistors R3 and R5 (regulated by the voltage stabilizer and protected by diode D5). When Q is turned on, it generates a pulsed magnetic field through the primary winding L1 of the transformer T. This pulsed magnetic field induces a voltage of less than 9.5V in L3, which is then rectified by D8 and filtered by C5 to produce an approximate 8V DC output. On the other hand, the negative feedback voltage is connected to L2. This feedback voltage is applied to the base of Q via C2, R6, R4, and R5, causing Q to turn off. The high-voltage DC is reactivated by R3 and R5, and the pulse current is once again generated by L3. A new cycle of electromagnetic induction occurs, allowing the negative feedback current to follow its original path, turning Q back off. This continuous process ensures that the circuit oscillates repeatedly, with L3 consistently delivering DC power. In the case of using this switching power supply to provide power to a 6V recorder, the output circuit must include a 10Ω/8W wire-wound resistor and a 1500μF/16V electrolytic capacitor to create a filter before the power can be safely delivered. These components play a critical role in stabilizing the power supply, ensuring that the recorder receives a consistent and reliable power source. Without these additional elements, fluctuations in the power supply could damage the sensitive electronics within the device. Thus, the combination of the self-excited oscillation circuit, transformer coupling, and proper filtering guarantees both efficiency and safety in powering the 6V recorder.