Discharge lamp ballast having an auto-transformer for high voltage detection
First Claim
1. A discharge lamp ballast comprising:
- a power supply circuit further comprising an inverter circuit configured to convert a DC voltage obtained from a DC power source into a voltage having a determined frequency, and further configured to supply the converted voltage to a discharge lamp inserted between a pair of output ends of the inverter circuit;
a resonant circuit further comprising an auto-transformer and a resonant capacitor, the resonant circuit configured for supplying an output voltage corresponding to a frequency of the converted voltage of the power supply circuit to the discharge lamp;
a voltage detection circuit for detecting an output voltage of the resonant circuit based on a potential of the resonant capacitor; and
a control circuit having a startup control mode wherein the control circuit is configured to determine the frequency of the converted voltage based on the detected voltage from the voltage detection circuit, wherein the output voltage of the resonant circuit exceeds a starting voltage of the discharge lamp.
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Accused Products
Abstract
A lamp ballast is provided requiring less size and cost for powering a discharge lamp. An inverter circuit converts a DC voltage from a DC power source into a voltage having a determined frequency, and supplies the converted voltage to the discharge lamp inserted between a pair of output ends of the inverter. A resonant circuit includes an auto-transformer and a resonant capacitor, and supplies an output voltage corresponding to a frequency of the rectangular wave voltage of the power supply circuit to the discharge lamp. A voltage detection circuit detects an output voltage of the resonant circuit based on a potential of the resonant capacitor. A control circuit has a startup control mode to set the frequency of the rectangular wave voltage based on the detected voltage from the voltage detection circuit, wherein the output voltage of the resonant circuit exceeds a starting voltage of the discharge lamp.
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Citations
22 Claims
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1. A discharge lamp ballast comprising:
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a power supply circuit further comprising an inverter circuit configured to convert a DC voltage obtained from a DC power source into a voltage having a determined frequency, and further configured to supply the converted voltage to a discharge lamp inserted between a pair of output ends of the inverter circuit; a resonant circuit further comprising an auto-transformer and a resonant capacitor, the resonant circuit configured for supplying an output voltage corresponding to a frequency of the converted voltage of the power supply circuit to the discharge lamp; a voltage detection circuit for detecting an output voltage of the resonant circuit based on a potential of the resonant capacitor; and a control circuit having a startup control mode wherein the control circuit is configured to determine the frequency of the converted voltage based on the detected voltage from the voltage detection circuit, wherein the output voltage of the resonant circuit exceeds a starting voltage of the discharge lamp. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A discharge lamp ballast comprising:
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a power supply circuit further comprising an inverter circuit configured to convert a DC voltage obtained from a DC power source into a voltage having a determined frequency, and to supply the converted voltage to a discharge lamp inserted between a pair of output ends of the inverter circuit, a step-down inductor coupled between a first output end of the inverter circuit and the discharge lamp, and a step-down capacitor coupled to a connection point of the step-down inductor and the discharge lamp; a resonant circuit for supplying an output voltage corresponding to a frequency of the voltage of the power supply circuit to the discharge lamp, the resonant circuit further comprising an auto-transformer coupled between the second output end of the inverter circuit and the discharge lamp, and a resonant capacitor coupled to an intermediate tap of the resonant inductor; a voltage detection circuit for detecting an output voltage of the resonant circuit based on a potential of the resonant capacitor; and a control circuit having a startup control mode wherein the control circuit is configured to determine the frequency of the rectangular wave voltage based on the detected voltage from the voltage detection circuit, wherein the output voltage of the resonant circuit exceeds a starting voltage of the discharge lamp. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17)
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18. A discharge lamp ballast comprising:
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an inverter circuit having two pairs of switches arranged in a full bridge configuration for converting a DC voltage obtained from a DC power source into a voltage having a determined frequency, the inverter circuit further arranged to supply the converted voltage to a discharge lamp coupled between a pair of output ends located between the pairs of switches; a resonant circuit comprising an auto-transformer and a resonant capacitor, the auto-transformer coupled between a first output end of the inverter circuit and the discharge lamp, and the resonant capacitor coupled to an intermediate tap of the auto-transformer, the resonant circuit configured to supply an output voltage corresponding to the determined frequency of the converted voltage of the power supply circuit to the discharge lamp; a voltage detection circuit coupled to the intermediate tap of the auto-transformer for detecting an output voltage of the resonant circuit; and a control circuit having a startup control mode wherein the control circuit is configured to sweep the frequency of the converted voltage from the power supply circuit through a predetermined frequency range so that the frequency of the converted voltage approaches a target frequency, wherein the output voltage of the resonant circuit exceeds a starting voltage of the discharge lamp, and a steady-state mode wherein the control circuit is configured after ignition of the discharge lamp to alternately switch on and off the pairs of switches in the inverter circuit at a low frequency relative to the determined frequency of the startup control mode. - View Dependent Claims (19, 20, 21, 22)
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Specification