| 摘要 |
PURPOSE:To enable to start completely even at a heavy load time and to extend the variation width of a load in a light load direction by flowing a starting current to the base of a switching transistor through a starting resistor of a small value at the time of starting the transistor. CONSTITUTION:When a light emitting diode LED1 of a power source controller 4 does not emit a light, a phototransistor Q3 is turned OFF, a switching transistor Q9 is not switched, and an output is not produced at the secondary side of a transformer T2. Then the diode LED1 emits a light, the transistor Q9 continues switching, and an output is presented at the secondary side of the transformer T2. The starting circuit of the transistor Q9 is formed of a transistor Q6 for flowing a starting current through a starting resistor R14 of small value to the base, and a transistor Q5 for turning OFF the transistor Q6 after starting. The transistor Q5 uses the output from an auxiliary coil L5 as a power. |
