Switching circuit for monitoring direct current circuits

  • Inventors:
  • Assignees: Bosch Gmbh Robert
  • Publication Date: April 18, 1973
  • Publication Number: GB-1314246-A


1314246 Lamp failure alarms ROBERT BOSCH GmbH 17 June 1970 [18 June 1969] 29327/70 Heading G4N [Also in Division H3] In a circuit for monitoring the current through a load 11, the inputs to a differential amplifier 16, 17 are connected via respective diodes 14, 15 to the ends of a monitoring resistor 12. The load 11 may be the flashing indicators or other lamps of a road vehicle. The ratio of resistors 23 to 19 should be equal to that of resistors 12 and 11. In the event of lamp failure, the current of transistor 17 is such as to turn on transistors 22 and 34 so as to operate a visual or audible alarm (not shown). The supply to the differential amplifiers 16, 17 is stabilized by a circuit 27 ... 33. A constant current circuit 24 ... 29 may be included in the common emitter lead, diode 26 having the same characteristics as the emitter/base diode of transistor 24 whilst diode 25 has the same characteristic as transistor 22 so as to provide temperature compensation. In Fig. 3 (not shown) a resistor is connected between a tapping on resistor 19 and the earth line 13, so as to provide adjustment of the operating point. The circuit may be formed together with a flasher unit as a single monolithic integrated circuit, complementary elements being arranged on isotherms of the semiconductor wafer.




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