| 摘要 |
PROBLEM TO BE SOLVED: To provide a switching mode electric power source which energizes a cold cathode fluorescent lamp(CCFL) is simple, and has high electric efficiency, high reliability and high cost performance. SOLUTION: A switching mode electric power source 100 for CCFL comprises a first semiconductor switch 102 connected in series with a primary winding of a voltage-raising transformer 112. The primary winding 108 and a secondary winding 132 having number of turns higher than that of the primary winding 108 are arranged in the surrounding of the magnetic core of the voltage transformer having linear magnetic permeability. A second semiconductor switch 124, connected in series and a capacitor 126, are connected in parallel with the primary winding 108 of the transformer. A controller circuit sends signals and turns switch on and off. The controller circuit turns on and off the first and the second semiconductor switches 102, 124 by a frequency higher than the resonance frequency of a resonator circuit constituted of the inductance of the transformer 112 and the capacitance of the capacitor 126. A decoupling capacitor 134 is connected in series with a first end part of a secondary winding 132 of the voltage transformer 112. A second terminal of the decoupling capacitor 134 and the second end part of the secondary winding provide an a.c. electric power output terminal for the switching mode electric power source with which the CCFL is to be connected. |
