| 摘要 |
<p>An interface circuit for a lamp ballast includes first and second input power lines, L 1 and. L2, with first and second respective switches, and a neutral power line N, all coupled to a diode bridge. Closing one of the first or second input power lines L1 or L2 causes a photodiode in an opto-isolator coupled to the diode bridge to turn ON. which in turn causes a MOSFET in a control circuit to be in an open state. When in the open state, a first resistor coupled to the source of the MOSFET is included in the control circuit and causes a lamp attached thereto to operate in a dimmed state. When both input power line switches are closed. L 1 and L2 are both coupled to the diode bridge and thereby cause the phototransistor to be in an OFF state, which causes the MOSFET to close, thereby including a second resistor, coupled to the drain of the MOSFET. in the control circuit in parallel with the first resistor. This in turn causes the lamp to operate at full intensity.</p> |
