POWER UNIT PROTECTION CIRCUIT
PROBLEM TO BE SOLVED: To prevent a trouble where a transistor TR is abnormally heated to emit smoke or take fire by controlling the TR that manages the open/close state of the power rectification output by making use of the voltage drop that is applied to the load in a load short circuit mode. SOLUT...
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Zusammenfassung: | PROBLEM TO BE SOLVED: To prevent a trouble where a transistor TR is abnormally heated to emit smoke or take fire by controlling the TR that manages the open/close state of the power rectification output by making use of the voltage drop that is applied to the load in a load short circuit mode. SOLUTION: The DC voltage is acquired from the secondary winding of a power transformer T via a rectifier diode D1 and a smoothing capacitor C1 and then applied to the emitter of a PNP TR Q1 which opens and closes the power rectification output. The collector of the IR Q1 is connected to the load RL and a smoothing capacitor C2. At the same time, a diode D2 is connected between the collector of the TR Q1 and the base of a control TR Q2 in the direction where the load RL absorbs the base voltage of the TR Q2 in a short circuit mode of the load RL. Thus the TR Q2 which manages the open/close state of the power rectification output is set in a non-conductive state. Then the TR Q2 conducts in a normal state when the load RL has no short circuit. As a result, both TR Q1 and Q2 can be prevented from being abnormally heated to emit smoke or take fire. |
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