Discharge lamp ballast with dimming
First Claim
1. A discharge lamp ballast comprising:
- a rectangular wave generating circuit that generates a rectangular wave signal of a predetermined frequency;
a driving signal generating circuit into which the rectangular wave signal and a dimmer signal of a PWM waveform of a frequency lower than that of the rectangular wave signal are input, and which outputs, as a driving signal, a signal obtained by extracting the rectangular wave signal for a period corresponding to a period in which the dimmer signal is on; and
a pulse transformer in which a rectangular wave voltage based on the driving signal is applied to a primary side, and the rectangular wave voltage is stepped up and applied to a discharge lamp;
wherein a rectangular wave reset circuit is provided so as to reset the operation of generating rectangular wave signal with the rectangular wave generating circuit at a rising of the dimmer signal, and the driving signal generating circuit extracts the rectangular wave signal for a period starting from the dimmer signal is turned on, until a time at which the dimmer signal and the rectangular wave signal are both off.
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Accused Products
Abstract
A ballast includes a rectangular wave generating circuit that generates a rectangular wave signal; a driving signal generating circuit supplied with the rectangular wave signal and a dimmer signal of a PWM waveform of a frequency lower than that of the rectangular wave signal and outputting a driving signal of an output obtained by extracting the rectangular wave signal for a period corresponding to “on” period of the dimmer signal; a pulse transformer which is supplied with a rectangular wave voltage based on the driving signal, step up the rectangular wave voltage and applying it to a discharge lamp. A rectangular wave reset circuit is provided so as to reset the generation of the rectangular wave signal at a rising of the dimmer signal. The driving signal generating circuit extracts the rectangular wave signal for a period starting from when the dimmer signal is turned on, until a time at which the dimmer signal and the rectangular wave signal are both off.
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Citations
12 Claims
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1. A discharge lamp ballast comprising:
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a rectangular wave generating circuit that generates a rectangular wave signal of a predetermined frequency;
a driving signal generating circuit into which the rectangular wave signal and a dimmer signal of a PWM waveform of a frequency lower than that of the rectangular wave signal are input, and which outputs, as a driving signal, a signal obtained by extracting the rectangular wave signal for a period corresponding to a period in which the dimmer signal is on; and
a pulse transformer in which a rectangular wave voltage based on the driving signal is applied to a primary side, and the rectangular wave voltage is stepped up and applied to a discharge lamp;
wherein a rectangular wave reset circuit is provided so as to reset the operation of generating rectangular wave signal with the rectangular wave generating circuit at a rising of the dimmer signal, and the driving signal generating circuit extracts the rectangular wave signal for a period starting from the dimmer signal is turned on, until a time at which the dimmer signal and the rectangular wave signal are both off. - View Dependent Claims (2, 3, 4, 5, 6)
a first differential circuit into which the dimmer signal is input; and
a first switching circuit that is driven by an output of the first differential circuit;
wherein a node between a capacitor and a resistor composing a CR oscillator in the rectangular wave generating circuit is connected to a ground potential via the first switching circuit.
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4. The discharge lamp ballast according to claim 1, wherein the rectangular wave generating circuit includes a timer circuit.
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5. The discharge lamp ballast according to claim 1, wherein the discharge lamp is an external electrode type dishcarge lamp, in which at least one electrode of the discharge lamp is provided at an outer surface of a arc tube.
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6. The discharge lamp ballast according to claim 5, wherein a discharge material of the discharge lamp includes a rare gas.
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7. A discharge lamp ballast comprising:
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a rectangular wave generating circuit that generates a rectangular wave signal of a predetermined frequency;
a driving signal generating circuit into which the rectangular wave signal and a dimmer signal of PWM waveform of a frequency lower than that of the rectangular wave signal input, and which outputs, as a driving signal, an output obtained by extracting the rectangular wave signal for a period corresponding to a period which the dimmer signal is on; and
a pulse transfer in which a rectangular wave AC voltage based on the driving signal is applied to a primary side, and the rectangular wave AC voltage is stepped up and applied a discharge lamp;
wherein an output reset circuit is provided so as to input a pulse voltage in phase with the rectangular wave AC voltage to the pulse transformer immediately after an end of the rectangular wave AC voltage in response to a completion of an ON period of the dimmer signal, a secondary side output of the pulse transformer being attenuated by application of the pulse voltage. - View Dependent Claims (8, 9, 10, 11, 12)
wherein by inputting an output of the switching elements to the pulse transformer, the rectangular wave AC voltage is applied to the pulse transformer, and wherein, the output reset circuit supplies an output reset signal that momentarily drives the switching element that was not being driven immediately prior to the end of the rectangular wave AC voltage.
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9. The discharge ballast according to claim 8, wherein the output reset circuit further comprises a second differential circuit into which the driving signal is input, and in which an output of the second differential circuit is supplied as an output reset signal.
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10. The discharge lamp ballast according to claim 8, wherein a pulse width of the output reset signal not greater than one-quarter of one cycle of a waveform of the driving signal.
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11. The discharge lamp ballast according to claim 7, wherein the rectangular wave generating circuit includes a timer circuit.
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12. The discharge lamp ballast according to claim 7, wherein the discharge lamp is an external electrode type discharge lamp, in which at least one electrode of the discharge lamp is provided at an outer surface of a arc tube.
Specification