| 摘要 |
PURPOSE: A power supply unit for signal lamp is provided to supply the stable power to a remaining time indicator by preventing damages of circuits due to counter electromotive force. CONSTITUTION: A power supply unit includes two bridge diodes(BD1,BD2), the first and the second constant-voltage circuits(110,140), a battery(130), and a plurality of diodes(D1,D2,D3). The bridge diodes(BD1,BD2) are used for rectifying the flickering power for flickering a red lamp and a green lamp. An arrester is connected to both input terminals of the bridge diodes(BD1,BD2). A switching mode power supply(100) is connected to both output terminals of the bridge diodes(BD1,BD2) in order to convert AC flickering power to DC power. The first constant-voltage circuit(110) and the diode(D1) are connected to an output terminal of the switching mode power supply(100). The first constant-voltage circuit(110) is used for supplying the output power of the switching mode power supply(100) to the battery(130). The second constant-voltage circuit(110) is used for supplying the output power of the switching mode power supply(100) or the output power of the battery(130) to a remaining time indicator.
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