| 摘要 |
PROBLEM TO BE SOLVED: To provide a power supply that practically sufficiently improves an input power factor from an AC power supply Vs, can drive a small number of LEDs with an efficiently stable electric current, and is small and inexpensive. SOLUTION: A pulse width of a PWM signal for switching on/off a switching element Q of a step-down chopper circuit directly connected to a pulsating output terminal of a full-wave rectifier DB without using a smoothing capacitor is feed-forward-controlled according to a phase of a pulsating voltage and feed-back-controlled according to a current detecting signal from a light-emitting diode 3, and only one light-emitting diode 3 is used or the number of light-emitting diodes 3 in series is limited so that an input current waveform of the full-wave rectifier DB conforms to a class C higher harmonic wave regulation. Alternatively, using a step-up/step-down chopper circuit or a flyback converter instead of a step-down chopper circuit, the pulse width of the PWM signal for switching on/off the switching element is feed-forward-controlled according to the phase of the pulsating voltage and feed-back-controlled according to the current detecting signal of the light-emitting diode. COPYRIGHT: (C)2010,JPO&INPIT |
