| 摘要 |
<p>An LED lighting device includes a step-up chopper circuit (3) for increasing an input voltage (V2) to a prescribed DC voltage (Vdc1), a voltage detection circuit (5) for detecting the DC voltage (Vdc1), a step-down chopper circuit (4) for decreasing the DC voltage to apply it across a light source (7), a step-down chopper controlling circuit (41) for turning on and off a switching device (Q41) of the step-down chopper circuit (4) when the DC voltage (Vdc1) is a threshold voltage or more, and an inrush current preventing circuit (6) having a parallel circuit of a thyristor (Q61) and a thermistor (PTH61). When the DC voltage (Vdc1) is less than the threshold voltage, only the induced voltage obtained from the step-up chopper circuit (3) is employed as a drive power supply for the thyristor (Q61). When the DC voltage (Vdc1) is the threshold voltage or more, only the induced voltage obtained from the step-down chopper circuit (4) is employed as the drive power supply.</p> |
