Maintenance of Repeated Breakdown of Rectification Diode in HY-U19 Electromagnetic Stove for Little Swan 2

Under the mutual inductance of T1 transformer, an induced electromotive force is also generated in the secondary winding, with a polarity of up negative and down positive. This potential is fed back to the base of U1 (13005) through R6 and C3, causing U1 to quickly saturate and conduct. When U1 saturates and conducts, its collector current no longer increases, and the polarity of T1 primary potential changes and is fed back to the base of UI through C3 and R6, causing a decrease in Ul collector current. The induced potential in T1 winding decreases, causing Ul to quickly cut off. The above process repeats itself, thus forming self-excited oscillation. In the process of self-excited oscillation, the conduction time of U1 diode (13005) is determined by the charging time of C3, while the cutoff time of U1 (13005) is determined by the discharging time of C3. The charging and discharging time of C3 is determined by the time constant composed of R6 and C3. Therefore, if there is a parameter change in C3 or R6, the time constant will change, which in turn changes the conduction time and cutoff time of U1 (i.e. changes the duty cycle of the switch pulse), and the rectified output voltage of D4 (RF107) will change. At the beginning of self-excited oscillation (when U1 is just turned on), due to the polarity of the induced potential of the secondary winding being negative at the upper end and positive at the lower end, the D4 (RF104) rectifier diode is turned off, and there is no output at+18V. However, when U1 is turned off, the polarity of the induced potential changes to positive at the upper end and negative at the lower end, so D4 (RF107) is turned on, and its conduction current charges the VD2 (470wF/25V) electrolytic capacitor on one hand, and supplies power to the load on the other hand. Therefore, the switch stabilized power supply composed of U1 and T1 is a reverse excitation power supply method. That is, when U1 is turned off, the magnetic field energy stored in the primary winding of T1 is discharged diode through the load of the secondary winding, which is rectified and supplied by D4 (RF107). When U1 is conducting, the electric field energy stored in CD2 (470wF/25V) is discharged through the load, that is, CD2 (470wF/25V) discharges and supplies power. At this time, D4 is in the cut-off state.