Ballast with adaptive end-of-lamp-life protection
AssigneeOsram Sylvania Inc.
InventorHimamshu V. Prasad
Life of this patent
Estimating the term…
Abstract
A ballast (100) having an inverter (110,120,122) and a direct current blocking capacitor (130) coupled in series with a ballast output (108) includes a control circuit (140) for providing adaptive end-of-lamp-life protection. During operation, control circuit executes the steps of measuring (208) and storing (210) a reference value for the voltage across the DC blocking capacitor (130), monitoring (308,310) the voltage across the DC blocking capacitor (130), and protecting (312) the inverter and lamp sockets in response to the voltage across the DC blocking capacitor departing from the reference value by more than a predetermined threshold amount.
Claims12
A ballast for powering at least one gas discharge lamp, comprising:
- a pair of input connections adapted to receive a source of alternating current;
- first and second output connections adapted for connection to the gas discharge lamp;
- an inverter operably coupled between the input connections and the first output connection, the inverter including an inverter drive circuit for providing inverter switching at a predetermined operating frequency, the inverter drive circuit having a protection input and being operable, in response to application of a fault signal at the protection input, to take protective action;
- a direct current (DC) blocking capacitor coupled between the second output connection and circuit ground;
- a control circuit having a control input operably coupled to the DC blocking capacitor, and a control output coupled to the protection input of the inverter drive circuit, wherein the control circuit is operable:
- (i) following initial application of power to the ballast, to measure the voltage across the DC blocking capacitor and to store that voltage as a reference value;
- and
- (ii) following each subsequent application of power to the ballast:
- (a) to monitor the voltage across the DC blocking capacitor;
- and
- (b) in response to the voltage across the DC blocking capacitor departing from the reference value by more than a predetermined threshold amount, to provide the fault signal at the control output.
A control circuit for providing end-of-lamp-life protection in an electronic ballast having an inverter and a direct current (DC) current blocking capacitor coupled in series with a ballast output, the protection circuit being operable to execute the following steps:
- (i) measuring a reference value for the voltage across the DC blocking capacitor;
- (ii) storing the reference value;
- (iii) monitoring the voltage across the DC blocking capacitor;
- and
- (iv) protecting the inverter and lamp sockets in response to the voltage across the DC blocking capacitor departing from the reference value by more than a predetermined threshold amount.
Dependencies are inferred from the claim text.