Method and apparatus for single-ended conversion of DC to AC power for driving discharge lamps
First Claim
1. An apparatus for converting a direct current (DC) signal into an alternating current (AC) signal, comprising:
- a network of one switch for generating an AC signal from a DC signal, the AC signal being generated by the one switch of the network periodically opening and closing;
filtering means being coupled between said network of the one switch and a load, said filtering means filtering the AC signal delivered to said load, wherein said filtering means includes;
a transformer having at least one primary winding that receives the AC signal from said network of at least one switch and having a secondary winding that is coupled to said load;
a diode being connected to the at least one primary winding of said transformer;
at least one capacitor being in series with the at least one primary winding of said transformer, wherein the at least one capacitor is operable to store energy to be delivered to the secondary winding of said transformer; and
impedance means being in series with the second winding of said transformer, wherein the impedance is operable to resonate to the at least one primary winding of said transformer and said network of at least one switch.
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Abstract
The present disclosure introduces a simple method and apparatus for converting DC power to AC power, and, specifically, to single-ended inverter circuits for driving discharge lamps such as a Cold Cathode Fluorescent Lamp (CCFL) or an External Electrode Fluorescent Lamp (EEFL). Among other advantages, these circuits offer nearly symmetrical voltage waveform to drive discharge lamps when the duty cycle is close to 50%. They also eliminate the high current and high voltage resonant capacitor on the primary side, and reduce the voltage rating of a primary switch to twice the input voltage without the need for snubber circuits. The recommended inverters can be used to efficiently drive discharge lamps at low cost, particularly for applications with a narrow input voltage range. The lamp current can be regulated through the duty cycle modulation of the main switch.
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Citations
33 Claims
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1. An apparatus for converting a direct current (DC) signal into an alternating current (AC) signal, comprising:
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a network of one switch for generating an AC signal from a DC signal, the AC signal being generated by the one switch of the network periodically opening and closing; filtering means being coupled between said network of the one switch and a load, said filtering means filtering the AC signal delivered to said load, wherein said filtering means includes; a transformer having at least one primary winding that receives the AC signal from said network of at least one switch and having a secondary winding that is coupled to said load; a diode being connected to the at least one primary winding of said transformer; at least one capacitor being in series with the at least one primary winding of said transformer, wherein the at least one capacitor is operable to store energy to be delivered to the secondary winding of said transformer; and impedance means being in series with the second winding of said transformer, wherein the impedance is operable to resonate to the at least one primary winding of said transformer and said network of at least one switch. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. An apparatus for converting a direct current (DC) signal into an alternating current (AC) signal for operating at least one electrical discharge lamp, comprising:
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a single-ended network of one switch for generating an AC signal from a DC input signal, said AC signal being generated by the one switch of the network periodically opening and closing; filtering means being coupled between said network of the one switch and a load, said filtering means filtering said AC signal delivered to said load, wherein said filtering means includes a transformer having two primary windings and a secondary winding that is coupled to said load; a first capacitor being in parallel with said load; and a second capacitor being in between said two primary windings of said transformer, wherein the second capacitor is operable to store energy to be delivered to the secondary winding of said transformer. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25)
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26. A method of converting a direct converting a direct current (DC) signal into an alternating current (AC) signal for operating at least one electrical discharge lamp, comprising:
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receiving a DC signal; opening and closing a single switching device; chopping said DC input signal by the opening and closing of said switching device; generating an alternating signal in at least one primary windings of a transformer by chopping the DC signal, wherein a capacitor is coupled to at least one primary winding of the transformer; stepping up said alternating signal of the at least one primary winding of the transformer into its secondary winding and deriving a stepped-up alternating signal; filtering said stepped-up alternating signal and deriving a filtered signal through a filter; and supplying said filtered signal to said electrical discharge lamp. - View Dependent Claims (27, 28, 29, 30, 31, 32, 33)
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Specification