PANASONIC KX-FP320G
Manual de Servicio

KX-FP320G / KX-FM330G

The following shows the operation of this circuit with the simple circuit. The circuit in the previous page, when the transistor Q101 is ON, secondary rectifier diode D201 is OFF and the energy is charged in the transformer T101. Q101 continues being ON while the voltage is generated by control winding (B). Q101 is tuned OFF by control circuit, then each windings of T101 changes the polarity and rectifier diode D201 truns ON. The charged energy of T101 supplies power through D201 to output load. And the voltage of control winding is decreased and Q101 contines being OFF state. When all energy is discharged through D201, Q101 is turned ON again and it makes the polarity of each windings of T101 in reverse and goes to self oscillation. When input voltage Ei is high, the operation frequency is stopped up, and when load current is high, the operation frequency is stopped down.

Because of the repetition of this operation, the voltage, which is stepped down by winding ratio of transformer, is produced at the secondary side of transformer. And after rectified, it´s supplied as a DC voltage. [Control Circuit And Error Detecting Circuit] Error detection circuit compares 24V output with the internal reference voltage, and transmits this error signal to control circuit of primary side through PC101. The control circuit drives the main transistor Q101 and controls the ON period according to the error signal in order to keep stability of output.This is shown as follows. When the output voltage of 24V circuit steps up, the current of photo coupler PC101 increases, the pulse width of gate signal of Q101 and the ON period of Q101 becomes shorter. [Over Current Limiter (O.C.L.)] IC101 rectifiers the highest voltage with resistors R105 detecting the current in the primary side. When the current is supplied higher then the highest voltage, it switches to latch mode which stops oscillating.

182