Method and apparatus for modulating HID ballast operating frequency using DC bus ripple voltage
AssigneeOsram Sylvania Inc.
InventorGrigoriy A. Trestman
Life of this patent
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Abstract
An apparatus and method to implement an electronic ballast for a high intensity discharge lamp having AC lamp current centered at approximately 300 kHz minimizes the ballast cost and utilizes modulation of the lamp current to avoid acoustic resonance. In order to minimize the number of additional components providing the modulation function, the ripple voltage produced by PFC circuit is fed through a capacitor to a FREQUENCY SET input of an inverter controller. The value of the capacitor can be chosen to produce the desired modulation range.
Claims20
A ballast circuit comprising:
- a DC power source producing a DC bus voltage having an AC ripple component;
- an inverter circuit electrically connected to the DC bus voltage, the inverter circuit comprising at least one switch;
- an inverter controller having a driver output electrically connected to each said at least one switch, the inverter controller having a frequency set input;
- wherein the frequency set input of the inverter controller is connected to a positive terminal of the DC bus voltage through a capacitor.
A ballast circuit comprising:
- a DC power source producing a DC bus voltage having an AC ripple component;
- an inverter circuit electrically connected to the DC bus voltage, the inverter circuit comprising at least one switch;
- a lamp connector connected to an output of the inverter circuit;
- and
- means for modulating a switching frequency of the inverter circuit at a frequency of the AC ripple component.
The ballast circuit of 11, wherein the modulating means comprises an oscillator having an input connected through a reactive component to a positive terminal of the DC bus voltage.
A method of operating a lamp ballast circuit comprising:
- a DC power source producing a DC bus voltage having an AC ripple component;
- an inverter circuit electrically connected to the DC bus voltage, the inverter circuit comprising at least one switch;
- and
- an inverter controller having a driver output electrically connected to each said at least one switch, the inverter controller having a frequency set input;
- the method comprising the steps of:
- providing an electrical connection between the DC bus voltage and the frequency set input of the inverter controller;
- using the electrical connection between the DC bus voltage and the frequency set input to modulate a switching frequency at which the inverter controller enables the at least one switch.
Dependencies are inferred from the claim text.