Voltage regulated DC supply with intermediate transistor chopper - which is modulated to reduce frequency disturbance to connected load

摘要

The power supply finds application in telecommunication equipment. The object is to reduce interference from the chopper stage especially when the power supply is feeding frequency sensitive or selective equipment. The supply alternating voltage (1) is rectified and smoothed (2) and applied to the primary winding (5) of a transistor (4) controlled chopper (3). The chopper output is rectified (7) and applied to the load (9), for example an active filter. The rectified voltage is fed back as the control signal (15) to adjust the mark-space ratio of an impulse generator (13) in order to keep the chopper output constant. A modulating generator (16) slowly changes the impulse frequency in a sinusoidal manner. This sinusoidal modulation spreads the disturbing frequencies due to the chopper action over a wider band and, importantly, also reduces the energy content of each frequency. The disturbing effect on the load is thus greatly reduced from the value which would exist without modulation.