| 摘要 |
<P>PROBLEM TO BE SOLVED: To eliminate the need of making a PFC circuit to be a step-up type in a DC power supply device for illumination, in which LED is made as a load, since a step-down DC-DC converter is installed in a rear step of a step-up PFC circuit for driving the LED load at low voltage in a conventional DC power supply device. <P>SOLUTION: A DC power supply device includes: a step-down converter where a switching element Q1 and a reactor L1 are connected in series to an output of a rectifier DB; current detecting means R1 detecting a current of the reactor at a time constant longer than a voltage period of an input AC voltage AC1; critical current detecting means CP2 detecting a timing when regenerative electric current flowing in the reactor becomes zero; triangular wave generating means (CC1, Ct, 3) raising a voltage signal at a prescribed inclination when the regenerative electric current becomes zero and resetting it when the regenerative electric current flowing in the reactor becomes zero; and gate signal output means turning on the switching element when the regenerative electric current becomes zero and turns off the switching element when the voltage signal Vct generated in the triangular wave generating means exceeds a current detection signal Vcfb. <P>COPYRIGHT: (C)2012,JPO&INPIT |
