| 摘要 |
Provided is improvement in efficiency of a light emitting diode (LED) driving circuit for illumination that uses a constant-current circuit at a load side of the LED driving circuit. The LED driving circuit having an efficiency improvement function, the LED driving circuit being connected to an alternating current (AC) power supply, includes: a rectifier circuit that rectifies the AC power supply; a control circuit connected to an output of the rectifier circuit; an LED load and a constant-current circuit that are connected to an output of the control circuit in series; a capacitor that is connected in parallel to the LED load and the constant-current circuit that are connected in series to each other, the capacitor smoothing the output of the rectifier circuit; and a detection circuit that detects whether the rectified voltage exceeds a predetermined particular voltage value that is equal to or greater than the sum of a voltage applied to the LED load when the LED load is turned on and a voltage applied to the constant-current circuit at a time when the LED load starts being turned on, wherein, if, as a result of detection of the detection circuit, the rectified voltage does not exceed the particular voltage value, the control circuit controls the output of the rectifier circuit to be passed, and if the rectified voltage exceeds the particular voltage value, the control circuit controls so that a first operation of blocking the output of the rectifier circuit and a second operation of passing the output of the rectifier circuit are repeatedly performed. |
