PURPOSE: To realize a short circuit preventing circuit of a transistor which prevent the transistor from the breakdown due to a short circuit, by connecting a resistor for detection of current in series to a load and turning on a protecting transistor with the voltage at the both ends of the resistor.
CONSTITUTION: When a short circuit occures across a load 1, the current flowing through a resistance 14 increases. When this current exceeds the Zener voltage of a Zener diode 17, the base current flows to a transistor (TR)15. As a result, a large current is poured to the base of a TR5 through a resistance 18. This increases the collector current of a TR4. At the same time, the base current increases more than the short circuit current. As a result, the TR4 keeps the saturated state even after the occurrence of a short circuit to reduce the loss caused within the TR4. Meanswhile a fuse 13 is fused to prevent the breakdown of the TR4.
ICHIISHI TSUNEO
YODA MIKIO
SHINOHARA YASUSHI
ISHIYAMA FUMIO
Next Patent: CONTROL METHOD OF SEMICONDUCTOR BREAKER