| 摘要 |
PROBLEM TO BE SOLVED: To increase a power factor at low costs by providing a control circuit turning on/off a switching element on the side agreeing with a voltage polarity at that time in an alternating current power source. SOLUTION: A controller 59 for a lighting device turns on/off either of switching elements 51, 52 agreeing with a voltage polarity at that time in an alternating current power source 21. When a voltage of the alternating current power source 21 shows a positive polarity, an on-off signal is supplied to the switching element 51 agreeing with the voltage polarity so as to give a command for turning on/off the element 51. During this process, the other switching element 52 is kept in an OFF state. When the voltage of the alternating current power source 21 shows a negative polarity, an on-off signal is fed to the switching element 52 agreeing with the voltage polarity. During this process, the other switching element 51 is kept in an OFF state. The voltage of the alternating current power source 21 charges an arm capacitor 11 or 12 initially via a chopper inductor 22 and a flywheel diode 41 or 42. Under this condition, an inverter action is started. |
