Starting fluorescent lamps with a voltage fed inverter
AssigneeGeneral Electric Company
InventorLouis Robert Nerone
Life of this patent
Estimating the term…
Abstract
A lamp ballast includes an inverter circuit, a resonant circuit, a control circuit, and a startup circuit. When the DC bus reaches its final value, a capacitor in the startup circuit charges to a predetermined voltage, at which point a pulse is sent to start a gate drive circuit in the inverter. Additionally, a gate in the control circuit is initially OFF, allowing full power to the lamp, and a capacitor in the control circuit charges to a predetermined voltage, at which point a gate is turned ON. When the gate is ON, power to the lamp is reduced. The control circuit capacitor is selected so that it charges for a sufficient period to allow the lamp to complete a glow phase of startup before turning on the gate and reducing power as the lamp transitions into an arc phase.
Claims20
A lamp ballast, comprising:
- a resonant circuit with a high-frequency bus coupled to at least one lamp;
- a control circuit, coupled to the high-frequency bus;
- an inverter circuit with first and second gate drive circuits that generate a waveform input for the resonant circuit;
- a bias voltage supply that supplies voltage to a power factor correction (PFC) circuit coupled to the ballast;
- and
- a startup circuit, coupled to the second gate drive circuit by a switch, and having a first capacitor that is charged by the PFC circuit during startup;
- wherein the second gate drive circuit is turned on when the first capacitor reaches a predetermined threshold voltage, causing the switch to send a pulse to the second gate drive circuit.
A startup system for a fluorescent lamp ballast, comprising:
- a voltage-fed inverter circuit having first and second gate drive circuits, and a bias voltage supply;
- a resonant circuit, coupled to the inverter circuit and to at least one fluorescent lamp;
- a control circuit that is coupled to the inverter circuit and the resonant circuit;
- and
- a startup circuit, hardwired to the inverter circuit, with a first capacitor that charges when the bias voltage supply supplies voltage to the startup circuit through a PFC circuit.
A startup circuit, comprising:
- a diode with an anode connected to a positive terminal and a cathode connected to a first node;
- a capacitor connected to the first node, and a second node;
- a first resistor connected in parallel with the capacitor;
- and
- a second resistor connected to the first node and to a switch;
- wherein the second node is coupled to a negative terminal and to ground;
- and
- wherein the startup circuit sends a pulse, via the switch, to start a gate drive circuit.
Dependencies are inferred from the claim text.