| 摘要 |
PURPOSE:To eliminate improper rise of a switching power source at low temperature time by detecting the temperature of a switching transistor and thereby controlling a base current. CONSTITUTION:An AC input from an AC power source 1 is rectified, smoothed and converted to a DC via a diode bridge D1 and a capacitor C1. The DC voltage is converted to an AC via a switching transistor Q1 and a transformer T1, the AC is rectified and smoothed via diodes D2, D3, a coil L1 and a capacitor C4 to becomes a desired output voltage. A controller 2 switches the transistor Q1 at a suitable ON.OFF ratio of the prescribed period. A thermistor TH connected in parallel with a resistor R2 supplies sufficient base current at low temperature when the DC amplification factor hfe of the transistor Q1 is low to accelerate the rising speed of the power source. |
