Switching power supply circuit using MC44603P

Switching power supply circuit using MC44603P

Shown is a switching power supply circuit using MC44603P. The switching pulse
signal generated by MC44603P with switching oscillation and voltage stabilization control is output from the @ pin to drive the switching field effect inversion transistor. The AC 220 V voltage is converted into an unregulated DC voltage of about 300 V through the bridge rectifier stack, which is applied
to the primary winding of the switching transformer T801, and then added to the drain (D) of the switching field effect transistor through the primary winding. After the power is turned on, the AC
220V voltage passes through R2 to provide the starting voltage for pin ①, causing IC 801 to start vibrating and start working. The secondary output of the switching transformer T801 is rectified and
filtered to output a variety of DC voltages.
    The voltage stabilizing circuit is composed of error sampling amplifier IC803, photocoupler IC802 and other parts. The error sampling circuit is set in the +150 V
output circuit. The voltage dividing points of R23 and R22 are used as error sampling points, and their voltages are added to The error voltage input terminal of IC803, the
error signal amplified by IC803 is fed back to the ⑩ pin of IC 801 through the photocoupler IC802 for voltage stabilization control.