| 摘要 |
PURPOSE: A constant power type ballast circuit is provided to constantly maintain power supplied to a lamp by using a choke coil to control the power supplied to the lamp. CONSTITUTION: A constant power type ballast circuit is comprised of a relay driving circuit(100), a choke coil(200), a lamp(300), a no-load and short state sensing circuit(400), a timer circuit(500), and a constant output circuit(600). An AC input terminal(10) generates a voltage of 220 ± 22 V that is difference between a first pole and a second pole(12). The relay driving circuit includes a first capacitor(101), a first diode(102), a second diode(103), a first zener diode(104), a first relay(105), and a second capacitor(106). The choke coil includes a first coil, a second coil, and a third coil. A lamp is connected between the second pole of the AC input terminal and the third coil of the choke coil. The no-load and short state sensing circuit is electrically between the third coil of the choke coil and the lamp and senses the no-load and short state of the lamp. The timer circuit breaks one pole of the AC input terminal by driving the relay driving circuit when the no-load and short state of the lamp is sensed. The constant output circuit decreases power supplied to the lamp by changing the winding ratio of the chock coil when the voltage of the AC input terminal rise. |
