Absolutely usable switching power supply: Hitachi A1PM8C power supply

Hitachi A1PM8C movement color motor models include: Hitachi 25M8C, 25M8C-041, 25M8C-042, 29M8C, etc. The power supply can adapt to 90V-260V grid voltage.

During the oscillation process,
the 220V AC voltage is full-wave rectified, and a DC voltage of about 300V is generated on C906, which is added to pin (3) of IC901 through the L1 winding of T901. At the same time, the 220V is rectified by half-wave, and then added through R942, R903, and R904. At pin (2) of IC901, the internal switch tube of IC901 begins to conduct, the current in L1 in T901 increases, and a positive feedback voltage is induced in winding L2. This voltage is added to pin (2) of IC901 through Q901, D905, and L907, so The internal switching tube of IC901 is quickly saturated.
During the conduction period of the switch tube, the L2 winding charges C905 through R906 and R907 on the one hand, and charges C909 through R909 on the other hand. The result of C909 charging is that the potential of IC901 (1) pin gradually decreases. When (1) pin voltage ratio ( 4) When the pin voltage is about 0.7V lower, the internal transistor is turned on, shunting the B pole of the switch tube, causing the switch tube to exit the saturated state, causing the polarity of the induced voltage of the L1 and L2 windings to reverse, and the result of positive feedback causes the switch tube to Quick deadline. During the conduction period of the switch tube, T901 stores magnetic field energy.
During the cut-off period of the switch tube, C505 discharges through the internal transistor of IC901, C909 discharges through D906 and R907, and the magnetic field energy stored in T901 is released to the load, forming a voltage of 111V on C911 and a voltage of 15V on C912. As T901 energy is released and C909 is discharged through D906 and R907, the potential of IC901 (2) pin gradually rises, and the internal switch tube will be turned on again to start a new round of oscillation.
The function of the series voltage stabilizing circuit composed of Q901, R930, ZD904, D916 and other components is to keep the voltage of pole B (i.e. pin (2) of IC901) stable when the switch tube is turned on.

Voltage
stabilizing circuit The voltage stabilizing circuit consists of components such as pins (1) and (5) of IC904, IC902, and IC901. When the output voltage fluctuates, IC904 detects it, controls the conduction degree of IC902 (optocoupler), and then controls the current of pins (1) and (5) of IC901. By controlling the conduction time of the switch tube internally in IC901, stability can be achieved. pressure.

The protection circuit
is omitted.