METHOD OF SHUTTING DOWN A HIGH PRESSURE DISCHARGE LAMP AND DRIVING UNIT FOR DRIVING A HIGH PRESSURE DISCHARGE LAMP
First Claim
1. A method of shutting down a high pressure discharge lamp (1) in which a pair of electrodes (2) is disposed in an arc tube (3), which method comprises reducing, upon receipt of a shut-down request (SR), the lamp power (P) towards a reduced power level (PR) required to sustain a long-term arc discharge between the electrodes (2), and driving the lamp (1) towards the reduced power level (PR) for a reduced power duration before completely shutting down the lamp power (P), whereby,prior to reducing the lamp power (P) towards the reduced power level (PR), the lamp power (P) is reduced to an undershoot power level (PU), which undershoot power level (PU) is lower than the reduced power level (PR) required to sustain a long-term arc discharge between the electrodes (2), and the lamp is driven at this undershoot power level (PU) for an undershoot power duration (tU) before increasing the lamp power (P) again to approach the reduced power level (PR).
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Abstract
The invention describes a method of shutting down a high pressure discharge lamp (1) in which a pair of electrodes (2) is disposed in an arc tube (3), which method comprises reducing, upon receipt of a shut-down request (SR), the lamp power (P) towards a reduced power level (PR) required to sustain a long-term arc discharge between the electrodes (2), and driving the lamp (1) towards the reduced power level (PR) for a reduced power duration before completely shutting down the lamp power (P), whereby, prior to reducing the lamp power (P) towards the reduced power level (PR), the lamp power (P) is reduced to an undershoot power level (Pu), which undershoot power level (Pu) is lower than the reduced power level (PR) required to sustain a long-term arc discharge between the electrodes (2), and the lamp is driven at this undershoot power level (Pu) for an undershoot power duration (tu) before increasing the lamp power (P) again to approach the reduced power level (PR). Moreover the invention describes an appropriate driving unit (4) for driving a high pressure discharge lamp (1) and an image rendering system (40), particularly a projector system, comprising such a driving unit (4).
14 Citations
10 Claims
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1. A method of shutting down a high pressure discharge lamp (1) in which a pair of electrodes (2) is disposed in an arc tube (3), which method comprises reducing, upon receipt of a shut-down request (SR), the lamp power (P) towards a reduced power level (PR) required to sustain a long-term arc discharge between the electrodes (2), and driving the lamp (1) towards the reduced power level (PR) for a reduced power duration before completely shutting down the lamp power (P), whereby,
prior to reducing the lamp power (P) towards the reduced power level (PR), the lamp power (P) is reduced to an undershoot power level (PU), which undershoot power level (PU) is lower than the reduced power level (PR) required to sustain a long-term arc discharge between the electrodes (2), and the lamp is driven at this undershoot power level (PU) for an undershoot power duration (tU) before increasing the lamp power (P) again to approach the reduced power level (PR).
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7. A driving unit (4) for driving a high pressure discharge lamp (1) in which a pair of electrodes (2) is disposed in an arc tube (3), which driving unit (4) comprises
a shut down request input (18) for receiving a shut down request (SR), and a lamp power control unit (10), which is configured in such a way that upon receiving the shut down request (SR), the lamp power (P) is reduced towards a reduced power level (PR) required to sustain a long-term arc discharge between the electrodes (2), and the lamp (1) is driven towards the reduced power level (PR) for a reduced power duration before completely shutting down the lamp power (P), and whereby, prior to reducing the lamp power (P) towards the reduced power level (PR), the lamp power (P) is reduced to an undershoot power level (PU), which undershoot power level (PU) is lower than the reduced power level (PR) required to sustain a long-term arc discharge between the electrodes (2), and the lamp is driven at this undershoot power level (PU) for an undershoot power duration (tU) before increasing the lamp power (P) again to approach the reduced power level (PR).
Specification