# US 5,705,898 A · Lighting circuit for discharge lamp which restricts inversion of output voltage polarity > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,705,898 A - Document ID: US5705898A - Status: Granted - Kind: A - Application number: 08/645,408 - Filed: 1996-05-13 - Granted: 1998-01-06 - Earliest claimed: 1995-05-12 - Assignees: Koito Manufacturing Co., Ltd. - Inventors: Masayasu Yamashita; Atsushi Toda - Web page: https://patentgrep.com/patent/US5705898A ## CPC - H05B 41/2888: {the bridge being commutated at low frequency, e.g. 1kHz} - H05B 41/2883: {the controlled element being a DC/AC converter in the final stage, e.g. by harmonic mode starting} - H05B 41/388: {for a transition from glow to arc} - H05B 41/3922: {and measurement of the incident light} - Y02B 20/00: Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps - Y10S 315/05: Starting and operating circuit for fluorescent lamp - Y10S 315/07: Starting and control circuits for gas discharge lamp using transistors - H05B: ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL - Y02B: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS - Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS ## Abstract In a lighting circuit, a battery voltage is supplied via a DC booster circuit to a DC-AC converter where the voltage is converted to an AC voltage with a rectangular waveform. This AC voltage is supplied to a discharge lamp. At this time, the DC-AC converter controls the frequency of the rectangular wave output from the DC-AC converter in accordance with a signal sent to a bridge type driver from a frequency controller. A lighting detector is provided to detect if the discharge lamp has been lighted. Upon reception of a signal from the lighting detector, the frequency controller sets the frequency of the output voltage of the DC-AC converter in the pre-lighting period of the discharge lamp higher than the frequency of the output voltage of the DC-AC converter after the lighting of the discharge lamp and restricts the inversion of the polarity of the output voltage of the DC-AC converter until a predetermined time passes sfrom the point of the activation of the discharge lamp. ## Claims ### Claim 1 A lighting circuit for a discharge lamp having DC-AC converting means for converting a DC voltage to an AC voltage which is to be supplied to said discharge lamp via an inductive load, said lighting circuit comprising: lighting detection means for detecting if said discharge lamp is lighted; and frequency control means for, upon reception of a signal from said lighting detector, setting a frequency of an output voltage of said DC-AC converting means after activation of said discharge lamp higher than a frequency of said output voltage of said DC-AC converting means in a non-lighting period of said discharge lamp, and restricting inversion of a polarity of said output voltage of said DC-AC converting means until a predetermined time passes after a point of activation of said discharge lamp. ### Claim 2 (depends on 1) The lighting circuit according to claim 1, wherein said frequency control means executes polarity inversion at a lower frequency than said frequency of said output voltage of said DC-AC converting means in said non-lighting period of said discharge lamp during a period from a point of activation of said discharge lamp to passage of said predetermined time. ### Claim 3 (depends on 1) The lighting circuit according to claim 1, wherein said frequency control means generates different control signals in a first period in which said discharge lamp is lighted from beginning of activation of said discharge lamp, a second period from a point of lighting of said discharge lamp to a point of passage of a predetermined time and a third period subsequent to said second period. ### Claim 4 (depends on 2) The lighting circuit according to claim 2, wherein said frequency control means generates different control signals in a first period in which said discharge lamp is lighted from beginning of activation of said discharge lamp, a second period from a point of lighting of said discharge lamp to a point of passage of a predetermined time and a third period subsequent to said second period. ### Claim 5 (depends on 3) The lighting circuit according to claim 3, wherein said frequency control means generates a rectangular-wave signal with a low frequency in said first period, then generates a DC signal with a predetermined polarity in said second period, and generates and a rectangular-wave signal with a high frequency in said third period. ### Claim 6 (depends on 4) The lighting circuit according to claim 4, wherein said frequency control means generates a rectangular-wave signal with a low frequency in said first period, then generates a DC signal with a predetermined polarity in said second period, and generates and a rectangular-wave signal with a high frequency in said third period. ### Claim 7 (depends on 1) The lighting circuit according to claim 1, wherein said frequency control means comprises an oscillator for generating a clock signal with a basic frequency, and a frequency divider for frequency-dividing said clock signal from said oscillator. ### Claim 8 (depends on 2) The lighting circuit according to claim 2, wherein said frequency control means comprises an oscillator for generating a clock signal with a basic frequency, and a frequency divider for frequency-dividing said clock signal from said oscillator. ### Claim 9 (depends on 3) The lighting circuit according to claim 3, wherein said frequency control means comprises an oscillator for generating a clock signal with a basic frequency, and a frequency divider for frequency-dividing said clock signal from said oscillator. ### Claim 10 (depends on 4) The lighting circuit according to claim 4, wherein said frequency control means comprises an oscillator for generating a clock signal with a basic frequency, and a frequency divider for frequency-dividing said clock signal from said oscillator. ### Claim 11 (depends on 7) The lighting circuit according to claim 7, wherein said oscillator has a structure of an astable multivibrator. ### Claim 12 (depends on 8) The lighting circuit according to claim 8, wherein said oscillator has a structure of an astable multivibrator. ### Claim 13 (depends on 9) The lighting circuit according to claim 9, wherein said oscillator has a structure of an astable multivibrator. ### Claim 14 (depends on 10) The lighting circuit according to claim 10, wherein said oscillator has a structure of an astable multivibrator. ### Claim 15 (depends on 7) The lighting circuit according to claim 7, wherein said frequency divider has a counter, two D type flip-flops and a plurality of logic gates. ### Claim 16 (depends on 8) The lighting circuit according to claim 8, wherein said frequency divider has a counter, two D type flip-flops and a plurality of logic gates. ### Claim 17 (depends on 9) The lighting circuit according to claim 9, wherein said frequency divider has a counter, two D type flip-flops and a plurality of logic gates. ### Claim 18 (depends on 10) The lighting circuit according to claim 10, wherein said frequency divider has a counter, two D type flip-flops and a plurality of logic gates. ### Claim 19 (depends on 1) The lighting circuit as set forth in claim 1 wherein said detection means comprises a photo sensor for directly detecting the lighting of said lamp and a circuit responsive to the output of said photo sensor. ### Claim 20 A lighting circuit for a discharge lamp having DC-AC converting means for converting a DC voltage to an AC voltage which is to be supplied to said discharge lamp via an inductive load, said lighting circuit comprising: a lighting detector circuit for detecting whether said discharge lamp is lighted; and a frequency control circuit operative upon reception of a signal from said lighting detector to set a frequency of an output voltage of said DC-AC converting means after activation of said discharge lamp higher than a frequency of said output voltage of said DC-AC converting means in a non-lighting period of said discharge lamp, and causing inversion of a polarity of said output voltage of said DC-AC converting means a predetermined number of times during a predetermined period after a point of activation of said discharge lamp.