CONSTANT-VOLTAGE POWER SOURCE DEVICE

PURPOSE:To obtain sufficient ripple suppression and rising characteristic with a less number of elements, by rectifying and smoothing AC electric power supplied from the secondary winding of a power transformer so as to make the AC power to become a constant current and supplying the constant current to a constant-voltage diode. CONSTITUTION:AC electric power produced in the 2nd winding 18 of a power transformer 1 is converted into a direct current by means of a diode 15 for rectifying and capacitor 16 for smoothing and supplied to the drain of a field effect transistor 17. The transistor 17 acts as a constant-current source since its gate is short-circuited with its source, and a constant current having little ripple components is obtained as a drain current. The constant current is supplied to a constant-voltage diode 10 and the base of a transistor 13 for control is driven by a DC voltage containing no ripple produced across both ends of the diode 10. DC electric power obtained by rectifying by means of diodes 3 and 4 for rectifying and smoothing by means of capacitors 5 and 6 for smoothing the AC electric power supplied from the secondary winding 2 is outputted after its voltage is made constant.