Variable light-level production using different dimming modes for different light-output ranges
First Claim
1. A method of driving a gas discharge lamp to produce a variable light level in a range between a nominal light output level (LM) and a minimum light output level, comprising the steps of:
- generating an alternating lamp current (I) with a constant current amplitude;
when producing the nominal light output level (LM), constantly supplying the lamp with the alternating lamp current (I) at a nominal current amplitude (IM);
when producing light having a light output level in a first range below said nominal light output level (LM), supplying the lamp with spaced apart current bursts having a burst duration Tc and a burst repetition period T where, in each current burst, the lamp is constantly supplied with the alternating lamp current (I) at the nominal current amplitude (IM) and where, in the intervals between successive current bursts, substantially no current is supplied to the lamp, the light output level in the first range being varied by varying the burst duty cycle (Δ
), defined as Δ
=Tc/T, within a range between 100% and a minimum burst duty cycle value (Δ
T);
when producing light having a light output level in a second range below said first range, supplying the lamp with spaced apart current bursts where, in each current burst, the lamp is constantly supplied with the alternating lamp current (I) at a reduced current amplitude (IR) lower than the nominal current amplitude (IM) and where, in the intervals between successive current bursts, substantially no current is supplied to the lamp, the light output level being varied by varying the reduced current amplitude (IR) within a range between zero and the nominal current amplitude (IM) while keeping the burst duty cycle (Δ
) constant at said minimum burst duty cycle value (Δ
T).
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Accused Products
Abstract
A wake-up lighting device is described, comprising a gas discharge lamp (10) and a lamp driver (1; 2) comprising a power source (100) capable of generating spaced-apart current bursts (51) of alternating lamp current (I). The wake-up lighting device is capable of operating in an off-mode in which no lamp current is generated, and is adapted to switch from its off-mode to a wake-up mode in which the power source (100) operates to:—initially generate an alternating lamp current (I) with a minimum duty cycle value (ΔT) and a reduced current amplitude (IR) close to zero;—subsequently gradually increase the current amplitude while keeping the duty cycle (Δ) constant at the minimum duty cycle value (ΔT), until the current amplitude reaches a nominal current amplitude (IM);—subsequently gradually increase the duty cycle (Δ) while keeping the current amplitude constant at the nominal current amplitude (IM).
54 Citations
22 Claims
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1. A method of driving a gas discharge lamp to produce a variable light level in a range between a nominal light output level (LM) and a minimum light output level, comprising the steps of:
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generating an alternating lamp current (I) with a constant current amplitude; when producing the nominal light output level (LM), constantly supplying the lamp with the alternating lamp current (I) at a nominal current amplitude (IM); when producing light having a light output level in a first range below said nominal light output level (LM), supplying the lamp with spaced apart current bursts having a burst duration Tc and a burst repetition period T where, in each current burst, the lamp is constantly supplied with the alternating lamp current (I) at the nominal current amplitude (IM) and where, in the intervals between successive current bursts, substantially no current is supplied to the lamp, the light output level in the first range being varied by varying the burst duty cycle (Δ
), defined as Δ
=Tc/T, within a range between 100% and a minimum burst duty cycle value (Δ
T);when producing light having a light output level in a second range below said first range, supplying the lamp with spaced apart current bursts where, in each current burst, the lamp is constantly supplied with the alternating lamp current (I) at a reduced current amplitude (IR) lower than the nominal current amplitude (IM) and where, in the intervals between successive current bursts, substantially no current is supplied to the lamp, the light output level being varied by varying the reduced current amplitude (IR) within a range between zero and the nominal current amplitude (IM) while keeping the burst duty cycle (Δ
) constant at said minimum burst duty cycle value (Δ
T). - View Dependent Claims (2, 3, 4, 5, 6)
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7. A driver for driving a gas discharge lamp comprising a main power source for generating a lamp current (I) in spaced apart current bursts having a burst duration Tc and a burst repetition frequency 1/T where, in each current burst, the lamp current comprises an alternating current having a constant current frequency higher than the burst repetition frequency, a constant current amplitude, and a constant current duty cycle equal to 50%;
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the driver, in a first mode, varying the burst duty cycle (Δ
), defined as Δ
=Tc/T, within a range between 100% and a minimum burst duty cycle value (Δ
T) while keeping the current amplitude constant at a nominal current amplitude value (IM);and the driver, in a second mode, varying the current amplitude within a range between zero and the nominal current amplitude (IM) while keeping the burst duty cycle (Δ
) constant at said minimum burst duty cycle value (Δ
T). - View Dependent Claims (8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A wake-up lighting device comprising a gas discharge lamp and a lamp driver comprising a power source for generating spaced apart current bursts of alternating lamp current (I), the device being adapted to operate in an off-mode in which no lamp current is generated and in a wake-up mode in which the power source:
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initially generates an alternating a lamp current (I) with a minimum duty cycle value (Δ
T) and a reduced current amplitude (IR) close to zero;subsequently gradually increases the current amplitude while keeping the duty cycle (Δ
) constant at the minimum duty cycle value (Δ
T) until the current amplitude reaches a nominal current amplitude (IM);subsequently gradually increases the duty cycle (Δ
) while keeping the current amplitude constant at the nominal current amplitude (IM). - View Dependent Claims (22)
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Specification