| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a lighting circuit with a stable operation, an illumination device, and an illumination system.SOLUTION: According to an embodiment, there is provided a lighting circuit comprising a power conversion unit, a current adjustment circuit, and a control unit. The power conversion unit is connected to a dimmer via a power supply path and to an illumination load, converts a phase-controlled AC voltage supplied from the dimmer to a DC voltage, and supplies the DC voltage to the illumination load. The current adjustment unit switches a conduction state in which a part of current flowing in the power supply path is applied to a branch path to a non-conduction state in which it is not applied or vice versa. When a detection voltage of the AC voltage becomes less than a first threshold voltage, the control unit puts the current adjustment unit into the conduction state. When the detection voltage becomes more than or equal to the first threshold voltage, the control unit puts the current adjustment unit into the non-conduction state, and delays the timing of switching the current adjustment unit to the non-conduction state till the detection voltage becomes more than or equal to a second threshold voltage in the range in which the detection voltage changes from the minimum value to the maximum value.</p> |
