DIMMABLE INSTANT START BALLAST

摘要

A ballast for dimming a lamp is provided. The ballast includes an inverter circuit to energize the lamp via a lamp current and a dim interface for receiving an input indicating a selected lighting level. A control circuit is connected to the dim interface for generating a pulse width modulated (PWM) signal having a duty cycle corresponding to the selected lighting level. A switching network is connected to the control circuit, receives the PWM signal, and operates between a conductive state and a nonconductive state as a function of the PWM signal. An impedance device is connected across the switching network and is configured for connecting in series with the lamp so that it receives the lamp current when the switching network is operating in the nonconductive state and the lamp current bypasses the capacitor when the switching network is operating in the conductive state.