| 摘要 |
PROBLEM TO BE SOLVED: To provide a switching mode power source with power factor correction at low cost and with simple configuration, by constituting a control device with a switching timing means and an on-time control means. SOLUTION: A switching element 44 is periodically turned on and off by the control circuit consisting of elements 60 and 71. The timing for turning on of the switching element 44 occurs in synchronous manner just after the voltage induced to the coil of a transformer 42 drops to zero. The duration of an time of the switching element 44 is adjusted so that the value of an output voltage V0 is maintained to a specified level, according to the value of output voltage V0 . Due to the control method, the switching frequency of the switching element 44 typically changes, instead of being fixed, in the range from 50 to 300kHz. Thus, at low cost and with a simple configuration, well adjusted d.c. output is supplied. |
