| 摘要 |
A power supply is arranged to generate less heat, by producing an intermediate value (+30 volts) direct voltage from the mains supply, generating oscillations from it which are used to chop the direct voltage, smoothing the chopped voltage with an inductor (11) and using the back emf comprising current spikes appearing upstream of the inductor (11) by flywheel effects during the zero voltage intervals in the chopped supply. The current spikes are supplied to a reservoir capacitor (16) downstream of the inductor (11) in order to supplement that supplied through the inductor (11). A further supply (-24 volts) is derived by shunt zeners (42) which normally dissipate substantial heat but which are bypassed by means of a triac (48) when the further supply is unwanted, eg temporarily while a thermo-switch is operative. The heat dissipated is then only that developed in a resistor (49) in the feed to the triac (48). |
