subject: Self-regulating, no load protected electronic ballast system [print this page] Self-regulating, no load protected electronic ballast system
This invention is directed to an electronic ballast system for fluorescent or gas discharge tubes. In particular, this invention relates to automatic gain controlled ballast systems for fluorescent tubes. Still further, this invention relates to an electronic ballast system which limits the voltage output to fluorescent or gas discharge tubes when the output voltage of the power source increases. This invention limits the output voltage of the electronic ballast system and substantially reduces such when the gas discharge tube or fluorescent tube is electrically removed from the overall circuit. More in particular, this invention pertains to a no load protection transformer being series coupled to an induction circuit for preventing the generation of voltages above a predetermined value when the gas discharge or fluorescent tube is electrically removed from the circuit. More in particular, this invention relates to an electronic ballast system where a primary winding of a no load protection transformer forms a variable inductance which is inversely proportional to the magnitude of power delivered to the gas discharge or fluorescent tube.
Still further, this invention directs itself to a transistor switching mechanism which is feedback coupled to an induction circuit for establishing a regulated current for a gas discharge tube independent of the gain of a transistor used in a particular ballast system unit. Additionally, this invention pertains to an electronic ballast system where there is provided a transistor switching network including a regulation control circuit for maintaining the power output of a gas discharge or fluorescent tube at a predetermined and substantially constant value.
Further, this invention directs itself to an electronic ballast system having a toroidal transformer to provide a predetermined variable inductance for regulating a power output to the gas discharge or fluorescent tube. Still further, this invention relates to an electronic ballast system which is transistorized and where the current gain of various transistors range over a wide value range from one system unit to another and provides for electrical circuitry which will maintain the gas discharge tube light output fluctuation to a minimum tolerance value.
Electronic ballast systems for gas discharge or fluorescent tubes are known in the art. However, in some prior art electronic ballast systems, removal of the gas discharge or fluorescent tube from the ballast circuit causes excessive voltage outputs to the gas discharge or fluorescent tubes. This condition can have a deleterious effect to the operating life of the particular tube or set of tubes utilized in a particular ballast system.
Other prior art systems do not provide for a no load protection transformer being coupled to an induction circuit of such electronic ballast systems for preventing the generation of voltages above predetermined values when the gas discharge or fluorescent tubes are electrically decoupled from the ballast circuit. Such prior art systems do not have the capability of providing a variable inductance which is inversely proportional to the magnitude of the power delivered to the gas discharge or fluorescent tubes. Thus, such prior art systems do not allow a limited voltage to be generated by control of the collector current of the ballast transistor responsive to load conditions, as is seen in the subject invention concept.
In other prior art electronic ballast systems, the light output of the gas discharge tubes are highly dependent upon the gain of the transistors used in the circuits. In such prior art systems, where the transistor gains between one unit and another vary over a large value, the light output from the gas discharge tube may fluctuate by excessive amounts. In such prior art systems, additional circuitry must be added A self-regulating, no load protected electronic ballast system having a power source for actuating at least one gas discharge tube with a regulated current and limited voltage to maintain the gas discharge tube input and output power at predetermined values. The electronic ballast system includes a filter circuit connected to the power source for (1) maintaining a substantially smooth direct current voltage signal, and (2) suppressing harmonic frequencies generated by the electronic ballast system. Additionally, the self-regulating, no load protected electronic ballast system includes induction circuitry coupled to the filter circuit having a tapped primary winding providing an auto-transformer configuration for establishing the frequency of the regulated current. The induction circuit includes a trigger control winding for generating a controlled current and further includes a no-load protection circuit for generating a voltage across the gas discharge tube responsive to the regulated current and for maintaining the output voltage at a predetermined value when the gas discharge tube is decoupled from the electronic ballast system. Switching circuitry is feedback coupled to the induction circuit for establishing the regulated current. The switching circuit includes regulation circuitry for maintaining the power output of the gas discharge tube at a predetermined and substantially constant value. The regulation circuit includes a toroidal transformer having (1) a first winding coupled in series relation with the trigger control winding and the switching circuitry for modifying the control current, and, (2) a second winding coupled to the tapped primary winding of the induction circuit and the filter circuit in series relation for feedback to the first winding of the toroidal transformer.
Although this invention has been described in connection with specific forms and embodiments thereof, it will be appreciated that various modifications other than those discussed above may be resorted to without departing from the spirit or scope of the invention, for example, equivalent elements may be substituted for those specifically shown and described, certain features may be used independently of other features, and in certain cases, particular location of elements may be reversed or interposed, all without departing from the spirit or scope of the invention as defined in the appended claims.
