# US 5,710,489 A · Overvoltage and thermally protected electronic ballast > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,710,489 A - Document ID: US5710489A - Status: Granted - Kind: A - Application number: 08/348,327 - Filed: 1994-12-02 - Granted: 1998-01-20 - Earliest claimed: 1982-08-25 - Inventors: Ole K. Nilssen - Web page: https://patentgrep.com/patent/US5710489A ## CPC - H05B 41/2855: {against abnormal lamp operating conditions} - H05B 41/2856: {against internal abnormal circuit conditions} - 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 An inverter-type electronic fluorescent lamp ballast has means to disable inverter operation in case of an overvoltage condition and/or in case its internal temperature were to exceed a safe level, thereby to provide automatic protection against damage that might otherwise result from excessive voltage and/or temperatures. ## Claims ### Claim 1 An arrangement comprising: a source operative to provide a DC voltage across a pair of DC terminals; a lamp holder having a pair of lamp sockets operative to receive and hold a gas discharge lamp; the lamp holder having a pair of socket terminals; and an assembly connected with the DC terminals and the socket terminals; the assembly being functional: (i) as long as the lamp is connected with the socket terminals, to deliver a lamp current thereto; and (ii) whenever the lamp is not so connected, to provide across the socket terminals a high frequency AC voltage that is amplitude-modulated at a low frequency; high frequency being defined as a frequency higher than 10 kHz; low frequency being defined as a frequency lower than 100 Hz; the assembly being further characterized by not including a thermal circuit breaker functional to make and break connection between two terminals by way of a thermally activated mechanical contactor means. ### Claim 2 (depends on 1) The arrangement of claim 1 wherein the assembly is further characterized by including a control sub-assembly operative, on receipt of a first control action at a control action input, to cause a substantial reduction of the magnitude of any voltage present across the socket terminals. ### Claim 3 (depends on 2) The arrangement of claim 2 wherein the assembly is still further characterized by including a restoring sub-assembly operative, whenever the magnitude of any voltage present across the socket terminals has remained below a certain low level for longer than a certain length of time, to cause a substantial increase in this magnitude. ### Claim 4 (depends on 1) The arrangement of claim 1 wherein the assembly is further characterized by including a control sub-assembly operative, on receipt of a control action at a control action input, to stop delivery of the lamp current even under a condition when the lamp is connected with its socket terminals. ### Claim 5 (depends on 4) The arrangement of claim 4 wherein the control sub-assembly is further characterized by including a temperature sensing sub-circuit operative to supply said control action in case a temperature associated with the assembly were to exceed a predetermined level. ### Claim 6 An arrangement comprising: a source operative to provide a DC voltage across a pair of DC terminals; a lamp holder having a pair of lamp sockets operative to receive and hold a gas discharge lamp; the lamp holder having a pair of socket terminals; and an assembly connected in circuit with the DC terminals and the socket terminals; the assembly being functional to provide an AC output voltage to the socket terminals; the assembly including a control sub-assembly connected in circuit therewithin and being operative to affect the RMS magnitude of the AC voltage in response to a control action received at a control action input; the assembly being further characterized by being operative, whenever the lamp is connected with the socket terminals, to cause a lamp current to flow through the lamp and to cause the RMS magnitude of the AC voltage to assume a first average level; and (ii) whenever the lamp is not connected with the socket terminals, to cause provision of said control action to the control action input, thereby to cause the RMS magnitude of the AC voltage to assume a second average level; the second average level being distinctly lower than the first average level. ### Claim 7 (depends on 6) The arrangement of claim 6 wherein the control sub-assembly is further characterized by causing, whenever the lamp is disconnected from the socket terminals, the AC voltage to be amplitude-modulated at a low frequency; the low frequency being lower than the frequency of the AC voltage by a factor higher than one hundred. ### Claim 8 (depends on 7) The arrangement of claim 7 wherein, whenever the lamp is disconnected from the socket terminals, the AC voltage comprises periodic bursts of high-frequency AC voltage; each burst of high-frequency AC voltage having a certain high-level RMS magnitude and being followed by a period during which the RMS magnitude of any voltage then present at the socket terminals is substantially lower than said high-level RMS magnitude. ### Claim 9 (depends on 8) The arrangement of claim 8 wherein the assembly is further characterized in that whenever the lamp is: (i) connected with the socket terminals, the AC voltage exhibits a first peak-to-peak magnitude; and (ii) not connected with the socket terminals, the AC voltage exhibits a second peak-to-peak magnitude; the second peak-to-peak magnitude being distinctly higher than the first peakto-peak magnitude. ### Claim 10 An arrangement comprising: source means operative to provide a DC voltage across a pair of DC terminals; a lamp holder having a pair of lamp sockets operative to receive and hold a gas discharge lamp; the lamp holder having a pair of socket terminals; and inverter power supply means connected in circuit between the DC terminals and the socket terminals; the inverter power supply means: (i) being operable to provide an inverter output voltage between the socket terminals; (ii) being operable to properly power the gas discharge lamp as long as this gas discharge lamp is indeed being held by the lamp sockets; and (iii) having control means functional to control the magnitude of the inverter output voltage such as to prevent its RMS magnitude from exceeding a predetermined level; the control means being further characterized by not including a thermal circuit breaker functional to make and break connection between two terminals by way of a thermally activated mechanical contactor means. ### Claim 11 An arrangement comprising: rectifier means adapted to connect with an ordinary electric utility power line and, when so connected, to provide a DC voltage at a DC output; self-oscillating inverter means connected with the DC output and, except after having been provided with a disable signal at a disable input, operable to convert the DC voltage to a high frequency voltage provided at an inverter output; connect and matching means connected with the inverter output and operative to connect with a gas discharge lamp means, thereby to properly power that lamp means; and temperature sensor means responsive to a temperature associated with the inverter means; the temperature sensor means being connected with the disable input and operative, whenever the temperature exceeds a predetermined level, to provide the disable signal; the temperature sensor means being further characterized by including an element whose electrical characteristics changes gradually but substantively as a result of gradual changes in said temperature; restart means connected with the inverter means and operative, after a predetermined period, to cause the inverter means to resume converting the DC voltage to the high frequency voltage; thereby, whenever the temperature has exceeded a predetermined level: (i) to disable the inverter means, therefore preventing it from converting the DC voltage to the high frequency voltage; (ii) substantially to cease supplying power to the lamp means; and (iii) substantially to stop the rectifier means from drawing power from the power line; and (iv) after the predetermined period, to cause the inverter means to attempt but fail to resume supplying power to the lamp means. ### Claim 12 An arrangement comprising: rectifier connected with an ordinary electric utility power line and operative to provide a DC voltage at a DC output; self-oscillating inverter connected with the DC output and, except after having been provided with a disable signal at a disable input, operative to provide a high frequency voltage at an inverter output; connect and matching means connected with the inverter output and operative to connect with a gas discharge lamp means, thereby to provide power to the lamp means; temperature sensor means responsive to a temperature associated with the inverter and operative whenever that temperature exceeds a predetermined level, to provide the disable signal, thereby to disable the inverter and to cease to provide power to the lamp means; the temperature sensor means being further characterized by including an element whose electrical characteristics changes gradually but substantively as a result of gradual changes in said temperature; and restart means connected in circuit with the inverter and operative to cause the inverter to re-start its operation some time after it has been disabled. ### Claim 13 An improvement for a power supply for a lamp; the power supply comprising self-oscillating inverter connected with a DC voltage and operable to convert the DC voltage to a high frequency voltage, therewith to power the lamp; the improvement comprising: disable means connected with the self-oscillating inverter; the disable means comprising an element whose electrical characteristics changes gradually but substantively as a result of gradual changes in a temperature associated with the inverter; the disable means being operable, whenever the temperature exceeds a predetermined level, to disable the self-oscillating inverter and thereby to prevent it from converting the DC voltage to the high frequency voltage; the disable means including automatic restart circuitry operative to cause the inverter to re-initiate its oscillation and to resume providing power to the lamp. ### Claim 14 An arrangement comprising: a source operative to provide a DC voltage of substantially constant magnitude across a pair of DC terminals; a lamp holder having a pair of lamp sockets operative to receive and hold a gas discharge lamp; the lamp holder having a pair of socket terminals; and an assembly connected in circuit with the DC terminals as well as with the socket terminals; the assembly being operative, whenever the lamp is not connected with the socket terminals, to provide thereacross an AC voltage amplitude-modulated at a frequency no higher than one hundredth that of the AC voltage; the assembly being further characterized by not including a thermal circuit breaker functional to make and break connection between two terminals by way of a thermally activated contactor means. ### Claim 15 An arrangement comprising: a source operative to provide a DC voltage of substantially constant magnitude across a pair of DC terminals; a lamp holder having a pair of lamp sockets operative to receive and hold a gas discharge lamp; the lamp holder having a pair of socket terminals; and an assembly connected in circuit with the DC terminals as well as with the socket terminals; the assembly being operative: (i) whenever the lamp is connected with the socket terminals, to supply to the lamp an alternating current of substantially constant amplitude; and (ii) whenever the lamp is not so connected, to provide across the socket terminals an AC voltage whose RMS magnitude varies periodically at a relatively low frequency; the frequency of the AC voltage being at least one hundred times higher than that of the relatively low frequency; the assembly being further characterized by not including a thermal circuit breaker functional to make and break connection between two terminals by way of a thermally activated contactor means.