# US 2014/0152179 A1 · Preheating circuit for electronic ballast > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0152179 A1 - Document ID: US20140152179A1 - Status: Published application - Kind: A1 - Application number: 14/070,641 - Filed: 2013-11-04 - Published: 2014-06-05 - Earliest claimed: 2012-11-30 - Assignees: General Electric Company - Applicants: General Electric Company - Inventors: Fanbin WANG; Youmin Zhang; Hongbin Wei - Web page: https://patentgrep.com/patent/US20140152179A1 ## CPC - H01J 61/526: {heating or cooling of electrodes} - H05B 41/14: Circuit arrangements - H05B 41/295: with semiconductor devices and specially adapted for lamps with preheating electrodes, e.g. for fluorescent lamps - H01J: ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS (spark-gaps H01T; electric arc lamps H05B31/00; particle accelerators H05H) - H05B: ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL ## Abstract A filament preheat module for preheating a filament of a lamp powered by a power circuit including an inverter, the inverter comprising an inductively coupled conductor, an inductively coupled conductor of the filament preheat module magnetically coupled to the inductively coupled conductor of the inverter to power the filament during preheating, and a switching circuit configured to electrically connect the power from the inductively coupled conductor of the filament preheat module to the filament. The switching module is configured to cutoff the power to the filament from the filament preheat module after a predetermined time period during preheating. ## Claims ### Claim 1 A filament preheat module for preheating a filament of a lamp that is powered by a power circuit comprising an inverter for powering the lamp, the inverter comprising an inductively coupled conductor, the filament preheat module comprising: an inductively coupled conductor, the inductively coupled conductor of the filament preheat module magnetically coupled to the inductively coupled conductor of the inverter, to power the filament during preheating; and a switching circuit configured to electrically connect the power from the inductively coupled conductor of the filament preheat module to the filament, wherein the switching module is configured to cutoff the power to the filament from the filament preheat module after a predetermined time period during the preheating. ### Claim 2 (depends on 1) The filament preheat module of claim 1, wherein the switching circuit comprises: a first switch coupled to the filament and configured to enable a current flow through the filament from the inductively coupled conductor of the filament preheat module in a conducting state; a second switch configured to control a state of the first switch between the conducting state and a non-conducting state; and a delay circuit coupled to the second switch and configured to control a state of the second switch between a conducting and a non-conducting state. ### Claim 3 (depends on 2) The filament preheat module of claim 2, wherein each of the first switch and the second switch is a MOSFET device or a BJT device. ### Claim 4 (depends on 2) The filament preheat module of claim 2, wherein the conducting state of the first switch is a filament preheating stage of the filament preheating circuit and the non-conducting state of the first switch is a cutoff stage. ### Claim 5 (depends on 1) The filament preheat module of claim 1, wherein a delay circuit is configured to enable a conducting state of the second switch at the end of the predetermined period of time during the preheating. ### Claim 6 (depends on 1) The filament preheat module of claim 1, wherein during the preheating the switching circuit enables a preheating state of the filament preheat module. ### Claim 7 (depends on 1) The filament preheat module of claim 1, wherein the switching device comprises a first switching device configured to control flow of current through the filament and a second switching device configured to control the first switching device, a control of the second switching device electrically coupled to a delay circuit configured to switch the second switching device to a conducting state at the end of the predetermined time period. ### Claim 8 (depends on 7) The filament preheat module of claim 7, wherein the first switching device and the second switching device are MOSFET or BJT devices, and the second switching device switches to the conducting state when a gate-to-source voltage of the second switching device exceeds a pre-determined threshold voltage supplied by the delay circuit. ### Claim 9 (depends on 1) The filament preheat module of claim 1, further comprising a preheating inductor coupled to the switching circuit and configured to be magnetically coupled to an inductively coupled conductor of another lamp to power the another lamp. ### Claim 10 (depends on 9) The filament preheat module of claim 9, wherein the preheating inductor is electrically coupled across the filament of the lamp. ### Claim 11 (depends on 9) The filament preheat module of claim 9, wherein the preheating inductor is electrically coupled between the switching circuit and the filament of the lamp. ### Claim 12 (depends on 11) The filament preheat module of claim 11, further comprising a capacitor device electrically coupled in series between the switching circuit and the preheating inductor. ### Claim 13 A circuit for preheating a filament of a lamp, the circuit comprising: a filament preheating circuit electrically coupled to the filament; a resonant inverter comprising a resonant inductor or a transformer magnetically coupled to the filament preheating circuit to provide electrical power to the filament; and a switching device configured to enable power to flow from the filament preheating circuit to the filament in a preheating stage. ### Claim 14 (depends on 13) The circuit of claim 13, wherein the switching device comprises: a first switch coupled to the filament and configured to enable a current flow through filament in a conducting state; a second switch configured to control a state of the first switch between the conducting state and a non-conducting state; a delay circuit coupled to the second switch and configured to control a state of the second switch between a conducting state and a non-conducting state. ### Claim 15 (depends on 14) The circuit of claim 14, wherein the delay circuit is configured to switch the state of the second switch to the conducting state at the end of a predetermined time period and interrupt the flow of power from the first switch through the filament. ### Claim 16 (depends on 13) The circuit of claim 13, further comprising a transformer winding, the transformer winding magnetically coupled to a winding of the resonant inverter, wherein the switching device comprises a first switch, the transformer winding configured to provide electrical power to the filament in a conducting state of the first switch. ### Claim 17 (depends on 16) The circuit of claim 16, wherein the resonant inverter comprises a resonant inductor and the transformer winding is magnetically coupled to the resonant inductor. ### Claim 18 (depends on 16) The circuit of claim 16, wherein the switching device further comprises a second switch configured to interrupt an electrical connection between the first switch and the filament in a conducting state of the second switch. ### Claim 19 (depends on 18) The circuit of claim 18, wherein the delay circuit is further configured to enable the conducting state of the second switch after a pre-determined time period. ### Claim 20 A ballast for driving a gas discharge lamp, the ballast comprising: an inverter configured to generate a lamp supply voltage signal; and a filament preheat circuit electrically coupled to the inverter and the gas discharge lamp, the filament preheat circuit configured to preheat a filament of the gas discharge lamp, the filament preheat circuit comprising: inductively coupled winding magnetically coupled to the inverter, the inductively coupled winding configured to provide electrical power to the filament during preheating; and a switching circuit configured to electrically connect the power from the inductively coupled conductor of the filament preheat module to the filament, wherein the switching module is configured to enable power to the filament during preheating and cutoff the power to the filament from the filament preheat module after a predetermined time period during preheating.