# US 5,710,488 A · Low-frequency high-efficacy electronic ballast > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,710,488 A - Document ID: US5710488A - Status: Granted - Kind: A - Application number: 07/859,616 - Filed: 1992-03-23 - Granted: 1998-01-20 - Earliest claimed: 1986-12-22 - Inventors: Ole K. Nilssen - Web page: https://patentgrep.com/patent/US5710488A ## CPC - H05B 41/3922: {and measurement of the incident light} - H05B 41/28: using static converters - Y10S 315/04: Dimming circuit for fluorescent 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 - Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS ## Abstract A bridge rectifier is connected with a 277Volt/60 Hz power line and provides full-wave-rectified unfiltered DC voltage to a series-combination of: i) an inductor, ii) a full bridge inverter switched in synchronism with the 60 Hz power line voltage, and iii) an electronic switching device. A fluorescent lamp is connected with the inverter's output and receives 60 Hz current of exceptionally low crest-factor, thereby operating at an exceptionally high efficacy. The electronic switching device is normally in a fully conductive state. However, it is controlled--by a photo sensor responsive to the light output of the fluorescent lamp--in such a manner that whenever the instantaneous light output exceeds a certain adjustably predetermined upper level, it switches into a non-conductive state where it remains until the instantaneous light output level diminishes to a certain adjustably predetermined lower level. Whenever the electronic switching device is switched off while current flows through the inductor, a flywheel diode shunts the current away from the switching device and into an energy-storing capacitor, the DC voltage on which is used for filling-in the valleys between the individual 120 Hz DC pulses on the unfiltered power supply. ## Claims ### Claim 1 An arrangement comprising: a source operative to provide an AC voltage at a pair of AC terminals; and a circuit connected with the AC terminals and operable to power a gas discharge lamp; the circuit being characterized by: (i) providing a conditioned voltage at a pair of terminals; and (ii) including a transistor conducting intermittently at a time-varying switching frequency, thereby to maintain the absolute magnitude of the conditioned voltage substantially constant. ### Claim 2 (depends on 1) The arrangement of claim 1 wherein the switching frequency is: (i) many times higher than the frequency of the AC voltage; and (ii) time-varying at a frequency equal to twice the frequency of the AC voltage. ### Claim 3 (depends on 1) The arrangement of claim 1 wherein the source is an ordinary electric utility power line. ### Claim 4 (depends on 1) The arrangement of claim 1 wherein the conditioned voltage is: (i) an alternating voltage; and (ii) of frequency substantially lower than the switching frequency. ### Claim 5 An arrangement comprising: a source operative to provide an AC voltage at a pair of AC terminals; and a circuit connected with the AC terminals and operable to power a gas discharge lamp; the circuit being characterized by: (i) providing a conditioned voltage at a pair of terminals; and (ii) including a transistor conducting intermittently with a time-varying duty-cycle at a switching frequency, thereby being operative to maintain the absolute magnitude of the conditioned voltage substantially constant. ### Claim 6 (depends on 5) The arrangement of claim 5 wherein: (i) the switching frequency is many times higher than the frequency of the AC voltage; and (ii) the duty-cycle varies at a frequency equal to twice the frequency of the AC voltage. ### Claim 7 (depends on 5) The arrangement of claim 5 wherein the conditioned voltage is: (i) an alternating voltage; and (ii) of frequency substantially lower than the switching frequency. ### Claim 8 An arrangement comprising: a source providing an AC voltage at a pair of AC terminals; and an assembly of electrical components connected with the AC terminals and characterized by: (i) including a gas discharge lamp; (ii) providing an output voltage from a pair of output terminals; and (iii) including a transistor conducting intermittently at a time-varying switching frequency, thereby to maintain the absolute magnitude of the output voltage substantially constant. ### Claim 9 (depends on 8) The arragement of claim 8 wherein an electrical conduction path exists, at least at certain times, between one of the output terminals and one of the AC terminals. ### Claim 10 (depends on 8) The arrangement of claim 8 wherein the assembly is additionally characterized by including an energy-storing inductor. ### Claim 11 (depends on 8) The arrangement of claim 8 wherein the gas discharge lamp is a fluorescent lamp operating at a substantially constant level of ionization. ### Claim 12 An arrangement comprising: a source providing an AC voltage at a pair of AC terminals; and an assembly of electrical components and parts connected with the AC terminals and characterized by: (i) including a gas discharge lamp; (ii) being operable to power the gas discharge lamp at a substantially constant level of ionization, thereby causing the lamp to emit a substantially constant level of light output; (iii) providing an output voltage at a pair of output terminals; and (iv) including a transistor conducting intermittently at a time-varying switching frequency, thereby to maintain the absolute magnitude of the output voltage substantially constant.