FEEDBACK DIMMING CONTROL CIRCUIT

摘要

PROBLEM TO BE SOLVED: To hold a light output constant even if input voltage and load requirements fluctuate by providing a feedback circuit which performs control functions. SOLUTION: A multiplier 30 produces an output voltage by multiplying a feedback current passed through a resonant tank 28 by an input voltage to the tank 28. The output voltage is subtracted from a reference voltage and is input to a subtractor circuit 34 via an error amplifier 22 and an inverter 24. The circuit 34 subtracts the input voltage from an inverted output signal and applies the result to an oscillator 26. An oscillation output is applied to the multiplier and the lamp 32 via the tank 28 as a feedback current. The frequency of the tank 28 is controlled using the frequency of the oscillation output, to adjust the feedback current to enable optimum feedback control.