| 摘要 |
PROBLEM TO BE SOLVED: To decrease the number of components of a primary-side circuit of an auxiliary converter and minimize the mounting face on a printed board, by using an IC circuit which is made by mounting a main converter control circuit, an auxiliary converter circuit, and an auxiliary switching element on one chip. SOLUTION: A PWM control IC 50 is made by mounting a main converter control circuit 52, an auxiliary converter control circuit 54, and an auxiliary switching element Q3 on one chip. The auxiliary converter circuit 54 sends an on/off control signal to the auxiliary switching element Q3 so as to stabilize the voltage Vcc of an auxiliary power supply detected by a primary-side rectifying and smoothing circuit to a specified reference voltage. The auxiliary switching element Q3 has the source grounded and the drain connected to a primary winding n3 . By allowing a frequency generator to be jointly used by the main converter control circuit 52 and the auxiliary converter control circuit 54, there is no difference between a switching frequency of a main converter section 20 and that of an auxiliary converter section 40, thereby easily eliminating problems such as noise. |
