Lighting circuit for discharge lamp
First Claim
1. A lighting circuit for a discharge lamp having a DC power supply section to be supplied with a voltage from a DC power supply and supplies an output voltage, based on the output voltage of said DC power supply section, to said discharge lamp, said lighting circuit comprising:
- (1) lighting detection means for detecting if said discharge lamp is lighted;
(2) input-voltage monitor means for detecting an input voltage to said DC power supply section and checking if said input voltage lies within an allowable range, said input-voltage monitor means having input-voltage comparing means for detecting said input voltage to said DC power supply section and comparing said input voltage with a first threshold value or a second threshold value, and threshold changing means for changing said first or second threshold value; and
(3) power-supply allowing/inhibiting means for allowing or inhibiting power supply to said discharge lamp in accordance with a signal from said input-voltage monitor means,whereby when said input voltage to said DC power supply section is less than said first threshold value at a time said input-voltage monitor means receives a signal indicative of a light-OFF state of said discharge lamp from said lighting detection means, said input-voltage monitor means sends a signal to said power-supply allowing/inhibiting means to cut off power supply to said discharge lamp and when said input voltage to said DC power supply section exceeds said second threshold value, said input-voltage monitor means sends a signal to said power-supply allowing/inhibiting means to supply power to said discharge lamp, andwhereby when said signal from said lighting detection means indicates said light-OFF state of said discharge lamp, said threshold changing means sets said first threshold value in said input-voltage monitor means smaller than said first threshold value in a light-ON state of said discharge lamp and/or sets said second threshold value in said input-voltage monitor means smaller than said second threshold value in said light-ON state of said discharge lamp.
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Accused Products
Abstract
A lighting circuit supplies an input voltage from a battery to a discharge lamp after the input voltage has been sent via a DC power supply section to a DC-AC converter. This lighting circuit comprises a lighting detector for detecting if the discharge lamp is lighted, an input-voltage monitor circuit for detecting the input voltage to the DC power supply section and checking if the input voltage lies within an allowable range, and a stable power supply circuit and a switch section for supplying power to the discharge lamp or inhibiting the power supply thereto in accordance with a signal from the input-voltage monitor circuit. The input-voltage monitor circuit performs variable control on a reference value to be compared with the input voltage, in accordance with a signal from the lighting detector.
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Citations
20 Claims
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1. A lighting circuit for a discharge lamp having a DC power supply section to be supplied with a voltage from a DC power supply and supplies an output voltage, based on the output voltage of said DC power supply section, to said discharge lamp, said lighting circuit comprising:
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(1) lighting detection means for detecting if said discharge lamp is lighted; (2) input-voltage monitor means for detecting an input voltage to said DC power supply section and checking if said input voltage lies within an allowable range, said input-voltage monitor means having input-voltage comparing means for detecting said input voltage to said DC power supply section and comparing said input voltage with a first threshold value or a second threshold value, and threshold changing means for changing said first or second threshold value; and (3) power-supply allowing/inhibiting means for allowing or inhibiting power supply to said discharge lamp in accordance with a signal from said input-voltage monitor means, whereby when said input voltage to said DC power supply section is less than said first threshold value at a time said input-voltage monitor means receives a signal indicative of a light-OFF state of said discharge lamp from said lighting detection means, said input-voltage monitor means sends a signal to said power-supply allowing/inhibiting means to cut off power supply to said discharge lamp and when said input voltage to said DC power supply section exceeds said second threshold value, said input-voltage monitor means sends a signal to said power-supply allowing/inhibiting means to supply power to said discharge lamp, and whereby when said signal from said lighting detection means indicates said light-OFF state of said discharge lamp, said threshold changing means sets said first threshold value in said input-voltage monitor means smaller than said first threshold value in a light-ON state of said discharge lamp and/or sets said second threshold value in said input-voltage monitor means smaller than said second threshold value in said light-ON state of said discharge lamp. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification