turns off in fig2 the switching frequency is determined by the capacitance c 2 when the phototransistor tr 2 turns on the switching frequency is determined by the capacitances c 2 and c 3 since the capacitance at the ct terminal of the pwm ic 135 increases by parallel connections between the capacitors c 2 and the c 3 the switching frequency decreases the voltage induced to the second coil of the power transforming part 150 is rectified and smoothed at the first and second power outputting parts 160 and 170 respectively the first power outputting part 160 outputs a first dc voltage va as a first output voltage and the second power outputting part 170 outputs a second dc voltage vb as a second output voltage the switching power supply apparatus may alternatively include a greater number of power outputting parts the second power outputting part 170 includes coils l 1 and l 2 i e inductances diodes d 2 through d 5 capacitors c 4 and c 5 resistances r 2 through r 6 and a transistor tr 3 the coil l 2 is used for a forward converter and is charged with a current when a high voltage is supplied to the first coil of the power transforming part 150 when a low voltage is supplied to the first coil of the power transforming part 150 the current charged at the coil l 2 flows through the capacitor c 5 and the diode d 4 and the current charged at the coil.