US 5,422,546 A · Dimmable parallel-resonant electric ballast

Abstract

A pre-converter is connected with AC power line voltage and provides DC voltage across a pair of DC terminals. A current-limiting inductor, a self-oscillating parallel-resonant inverter, and a periodically activated FET switch are series-connected with one another across the DC terminals. The inverter provides a high-frequency (e.g., 20-30 kHz) substantially sinusoidal output voltage across its output terminals. Each of plural rapid-start fluorescent lamps is connected across the output terminals by way of a current-limiting capacitor. The magnitude of the resulting lamp current depends on the RMS magnitude of the output voltage. In turn, for a given load condition, this RMS magnitude depends on the average magnitude of the unidirectional current drawn by the inverter from the DC terminals; which average magnitude is determined by the ON/OFF duty-cycle of the FET switch. The FET switch is turned ON/OFF at twice the frequency of the inverter's output voltage. By adjusting the ON/OFF-ratio, the average magnitude of the unidirectional current supplied to the inverter is correspondingly adjusted, thereby resulting in a corresponding adjustment in the magnitude of the lamp current.

Claims61

Dependent claims

An arrangement comprising:

a DC source operative to provide a DC voltage at a pair of DC output terminals;
a ballasting circuit having DC input terminals and AC output terminals;
a fluorescent lamp having thermionic cathodes and being connected in circuit with the AC output terminals, thereby to be properly powered with an AC lamp current as long as a unidirectional current is being supplied to the DC input terminals;
the AC lamp current having a period not shorter than 100 micro-seconds;
the ballasting circuit including circuitry functional to prevent unidirectional current from being supplied from the AC output terminals;
and
electronic circuitry connected with the DC output terminals as well as with the DC input terminals;
the circuitry being functional to cause the DC voltage to be intermittently applied to the DC input terminals, thereby to cause said unidirectional current to be supplied.

5 more elements

An arrangement comprising:

a power source providing a power line voltage at a pair of power line terminals;
a gas discharge lamp having lamp terminals;
and
an assembly of interconnected electrical component parts having a pair of power input terminals connected with the power line terminals and power output terminals connected with the lamp terminals, thereby to supply an AC tamp current to the gas discharge lamp;
the AC lamp current having a period not shorter than 100 micro-seconds;
the assembly including circuitry functional to prevent unidirectional current from being supplied from the power output terminals;
the assembly being further characterized by including:
(i) a first pair of terminals across which exists a first unidirectional voltage having a substantially constant magnitude, (ii) a second pair of terminals across which exists a second unidirectional voltage having a magnitude that alternates, at a first repetition frequency, between being substantially zero and being substantially equal to said substantially constant magnitude, and (iii) a pair of AC terminals across which exists an AC voltage having a fundamental frequency substantially higher than the frequency of the power line voltage.

5 more elements

An arrangement comprising:

a power source providing a power line voltage at a pair of power line terminals;
a gas discharge lamp having lamp terminals;
and
an electronic ballasting circuit having a pair of power input terminals connected with the power line terminals and power output terminals connected with the lamp terminals, thereby to supply an AC lamp current to the gas discharge lamp;
the electronic ballasting circuit being characterized by:
(i) having a first pair of DC terminals across which exists a first unidirectional voltage having a substantially constant magnitude, (ii) having a second pair of DC terminals across which exists a second unidirectional voltage having a certain average magnitude and consisting of unidirectional voltage pulses having a certain repetition frequency, (iii) having a pair of AC terminals across which exists an AC voltage having a fundamental frequency substantially higher than the frequency of the power line voltage, (iv) having a parallel-tuned L-C circuit connected in circuit with the AC terminals, and (v) having a pair of control terminals responsive to a control voltage, thereby to permit the RMS magnitude of the AC lamp current to be controlled by applying a control voltage of adjustable magnitude to the control terminals;
the parallel-tuned L-C circuit having a natural resonance frequency about equal to the fundamental frequency of the AC voltage.

4 more elements

An arrangement comprising:

a power source providing a power line voltage at a pair of power line terminals;
a gas discharge lamp having lamp terminals;
and
an electronic ballasting circuit having a pair of power input terminals connected with the power line terminals and power output terminals connected with the lamp terminals, thereby to supply an AC lamp current to the gas discharge lamp;
the electronic ballasting circuit being further characterized by including:
(i) a first pair of DC terminals across which exists a first unidirectional voltage having a certain substantially constant magnitude;
(ii) a second pair of DC terminals across which exists a second unidirectional voltage having a certain average magnitude and consisting of unidirectional voltage pulses having a certain repetition frequency, each unidirectional voltage pulse being shaped approximately like a complete half-cycle of a sinusoidal voltage;
the second pair of DC terminals drawing electric power from the first pair of DC terminals;
and (iii) a pair of AC terminals across which exists an AC voltage having a fundamental frequency substantially higher than the frequency of the power line voltage.

6 more elements

An arrangement comprising:

a power source providing a power line voltage at a pair of power line terminals;
a number of gas discharge lamp, each lamp having lamp terminals;
and
an electronic ballasting circuit having a pair of power input terminals connected with the power line terminals and power output terminals connectable with the lamp terminals, thereby to supply an AC lamp current to each gas discharge lamp connected with the power output terminals;
the electronic ballasting circuit being further characterized by including:
(i) two DC terminals across which exists a substantially constant DC supply voltage having an absolute magnitude distinctly higher than the peak absolute magnitude of the power line voltage;
(ii) an inductor means;
(iii) a connecting means;
and (iv) a circuit assembly having two assembly input terminals and two assembly output terminals;
the two assembly input terminals being connected with the two DC terminals by way of the inductor means and the connecting means;
a unidirectional voltage existing across the two assembly input terminals;
an AC voltage existing across the two assembly output terminals;
an LC circuit being connected with the two assembly output terminals;
the LC circuit having a natural resonance frequency approximately equal to the fundamental frequency of the AC voltage;
the two assembly output terminals being connected with the power output terminals via a matching sub-circuit.

12 more elements

Dependencies are inferred from the claim text.

Dimmable parallel-resonant electric ballast

Life of this patent

Dimmable parallel-resonant electric ballast

Life of this patent

Abstract

Claims61