| 摘要 |
PURPOSE:To automatically restart a steady power feed when an overcurrent condition is released while protecting a power feed transistor, by stopping the power feed while continuing detection of an overcurrent on the basis of an alarm signal by the overcurrent. CONSTITUTION:An overcurrent is allowed to flow in a load 1, when an overcurrent detecting resistor RD1 increases its both end voltages, a transistor (Tr)Q2 is turned on, and an alarm signal obtains an L level because a phototransistor Tr in a photocoupler PH1 is turned on. This alarm signal turns on a transistor TrQ3 as the signal of H level through a gate G. Then a phototransistor Tr in a photocoupler PH2 is turned on, turning off a power feeder transistor TrQ1, and the overcurrent is allowed to flow in a route of power source VBB load 1 overcurrent detecting resistor RD1 current limiting resistor RD2. Accordingly, the power feed transistor TrQ1 prevents its power consumption from exceeding the rated value by the overcurrent. When an overcurrent condition is released, the alarm signal obtains an H level, and again turning on the power feed transistor TrQ1, a steady power feed is automatically restarted. |
