| 摘要 |
In an a.c. to d.c. converter comprising a rectifier (3) which feeds a reservoir capacitor (13) and a load (14) a choke (9) is interposed in the current path between the a.c. supply (1) and the capacitor (13), and a switching transistor (10) connected across the capacitor is repeatedly switched at a frequency appreciably greater than the supply frequency, so that current is alternately drawn from the supply when the transistor conducts to store energy in the choke (even when the instantaneous supply voltage is lower than the capacitor voltage) and transferred to the capacitor when the transistor is not conducting. The duty ratio of the switching transistor is controlled such that the supply current (i) substantially follows the supply voltage (v). Feedback from a comparator (19) to vary the duty ratio of the switching transistor may be provided via opto- coupler (20, 8) to regulate the output voltage. <IMAGE> |
