Inverter circuit for energizing and dimming gas discharge lamps

摘要

An illumination control system for gas discharge lamps which can be dimmed is provided in which a central inverter produces a sinusoidal output voltage at about 23 kHz. The amplitude of the inverter output is adjustable to dim the lamps. A transmission line consisting of spaced wires having respective thick insulation sheaths distributes the high frequency power to remotely located assemblies of ballasts and lamps. The ballasts consist of passive linear components. A high power factor rectifier network is disclosed for providing a d-c input to the inverter from the 50/60 Hz mains. The inverter circuit is provided with novel controls for gradual start-up and turn-off and is protected against load fault currents and internal fault currents. Automatic and manual resets are provided for internal fault current and load fault current, respectively. The basic inverter circuit consists of two alternately conducting controllably conductive power switching devices. Each is in parallel with a respective oppositely poled diode. The input d-c power line is connected in series with the series-connected power switching devices. A single series tuned circuit is connected in series with an output circuit element and is connected across one of the power switching devices. The amplitude of the inverter output is controlled by adjusting the phase at which the power switching devices turn on. In another embodiment, a single power switching device is used for the inverter circuit.