SINEWAVE DIMMER CONTROL METHOD

摘要

An input line filter (28) separates an ac sinusoidal power source (22) from a power switching stage (26) having a series switching section (44) and a clamp switching section (46). Both the series switching section (44) and the clamp switching section (46) include complementary pairs (68-70 and 86-88) of high power and high speed MOSFETs. The series switching section (44) is connected in series between the input line filter (28) and the inductor (42) of an output load filter (38) between the power switching stage (26) and a load (24). The clamp switching section (46) is connected to shunt the inductor (42) and load (24). Synchronous operation is achieved by alternately operating the series (44) and clamp (46) switching sections to conductive conditions at a high pulse width modulation frequency. The duty cycle is selected to provide a sinusoidal output waveform with a desired amplitude. A microprocessor based programmable controller (56) provides control signals (102, 106) for alternate conduction of the series (44) and clamp (46) switching sections. A dead time interval (110, 112) stored in memory in the controller (56) separates the control signals (102, 106) for reliable and efficient operation. The dead time interval (110, 112) may be constant, or may be varied in accordance with load power variations.