Discharge lamp fast preheat circuit independent of type of ballast
AssigneeU.S. Philips Corporation
InventorsHubertus M. J. Chermin, Ronald Siepkes
Life of this patent
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Abstract
A circuit arrangement for preheating electrodes of a discharge lamp connected in series with a ballast by means of a supply voltage of alternating polarity. The circuit arrangement is provided with a switching element (S) which shunts the lamp and which is operated by means of a control signal. A circuit portion (II) adjusts both the phase and the frequency of the control signal in dependence on whether the ballast is inductive or capacitive. The electrodes of the lamp are preheated in a short period both for an inductive ballast and for a capacitive ballast.
Claims18
A circuit arrangement for preheating electrodes of a discharge lamp connected in series with a ballast by means of a supply voltage of alternating polarity, comprising;
- a branch circuit for connection to the electrodes of the discharge lamp, which branch circuit comprises a switching element,
- a control circuit coupled to a control electrode of the switching element for generating a control signal to render the switching element conductive during preheating in each cycle of the supply voltage,
- a first circuit coupled to the control circuit for governing the control signal in dependence on whether the ballast is inductive or capacitive, and wherein the first circuit comprises a second circuit for adjusting both the phase and the frequency of the control signal.
A circuit for preheating the electrodes of a discharge lamp adapted for connection to a source of AC supply voltage via a series connected ballast having an inductive or a capacitive characteristic, set circuit comprising:
- a branch circuit for connection to the lamp electrodes and which includes a controlled semiconductor switching element arranged to conduct a lamp electrode preheat current,
- a control circuit coupled to a control electrode of the semiconductor switching element for supplying thereto a control signal that governs conduction of the semiconductor switching element during a preheating period in each cycle of the AC supply voltage,
- a first circuit coupled to the control circuit and including means for modifying both the phase and the frequency of the control signal dependent on whether the ballast has an inductive or a capacitive characteristic, and wherein said first circuit further comprises means for detecting whether the series connected ballast has a capacitive or an inductive characteristic and for indicating same to said control signal modifying means.
Dependencies are inferred from the claim text.