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US 5,550,437 AGranted
Electronic dimmable gas tube power supply with overvoltage protection
AssigneeFrance/Scott Fetzer Company
InventorsWilliam T. Hopkins, Alan M. Smith
Life of this patent
Estimating the term…
Abstract
A ballast for driving a gas discharge tube light with overvoltage protection and dimming. A clamp winding coupled to the internal DC power source prevents overvoltage of the secondary terminals by permitting induced current flow in the clamp winding if the clamp winding voltage exceeds that of the internal DC power source. The transformer core includes a shunt leg which supports a dimmer control winding. When the dimmer control winding is open-circuited, magnetic flux is shunted away from the secondary winding, reducing the light intensity; when the dimmer control winding is short-circuited, currents induce in the dimmer control winding prevent substantial of magnetic flux density and increase the light intensity.
Claims17
A ballast for supplying power to a light, comprising
- a core of magnetically permeable material defining a window therethrough for providing a closed path for magnetic field flux around said window,
- a primary winding comprising a primary conductor extending between two primary terminals and wound onto said core through said window such that magnetic field flux produced by current in said primary conductor is channeled into said closed path;
- an oscillator coupled between said primary terminals and bi-directionally electrically stimulating said primary winding via said primary terminals to produce bi-directional magnetic flux in said core;
- a secondary winding comprising a secondary conductor extending between two secondary terminals and wound onto said core through said window such that magnetic field flux travelling along said closed path couples to said secondary winding and electrically stimulates said light coupled between said secondary terminals;
- a clamp winding comprising a conductor extending between two clamp terminals and wound onto said core through said window such that magnetic field flux travelling along said closed path couples to said clamp winding and produces a voltage between said clamp terminals, said clamp winding being wound onto said core directly adjacent to said secondary winding to produce a low leakage flux coupling between said secondary winding and said clamp winding;
- and
- a clamping circuit having two clamping terminals, said clamping circuit absorbing energy through said clamping terminals whenever a voltage in excess of a given clamp voltage is applied between said clamping terminals;
- said clamp terminals of said clamp winding being connected to said clamping terminals of said clamping circuit;
- whereby said clamping circuit absorbs energy from said clamp winding by permitting a current to be induced in said clamp winding whenever a voltage in excess of said clamp voltage is produced between said clamp terminals, such that said clamp winding produces magnetic flux in said closed path tending to oppose magnetic flux produced by said primary winding and thereby limits voltage produced between said secondary terminals.
6 more elements
A ballast for supplying power to a light, comprising
- a core of magnetically permeable material defining first and second windows therethrough for providing first and second closed paths for magnetic field flux around said windows,
- a primary winding comprising a primary conductor extending between two primary terminals and wound onto said core through at least one of said windows such that magnetic field flux produced by current in said primary conductor is channeled into said closed paths;
- an oscillator coupled between said primary terminals and bi-directionally electrically stimulating said primary winding via said primary terminals to produce bi-directional magnetic flux in said core;
- a secondary winding comprising a secondary conductor extending between two secondary terminals and wound onto said core through said first window such that magnetic field flux travelling along said first closed path couples to said secondary winding and electrically stimulates said light coupled between said secondary terminals;
- a dimmer control winding comprising a dimmer conductor extending between two dimmer terminals and wound onto said core through said second window such that magnetic field flux travelling along said second closed path couples to said dimmer control winding;
- and
- a variable impedance element coupled between said dimmer terminals for selectably permitting or inhibiting current flow through said dimmer conductor,
- whereby said variable impedance element selectably permits current to be induced in said dimmer control winding, such that said dimmer control winding produces magnetic flux in said second closed path tending to oppose magnetic flux produced by said primary winding, thereby increasing magnetic flux coupled to said secondary winding and increasing light intensity produced by said light.
5 more elements
Dependencies are inferred from the claim text.