Circuit for protecting against reverse polarity

摘要

A circuit for protecting an electric load against reverse polarity is provided by using a MOSFET (metal oxide semiconductor field-effect transistor), wherein: the circuit is connected on the input side to a voltage supply and on the output side to the load; the source connection of the MOSFET is connected to the voltage supply; the drain connection of the MOSFET is connected to the load; the circuit has dynamic behavior similar to a diode and at the same time low power loss; the gate of the MOSFET is connected to the collector of a first bipolar transistor; the source of the MOSFET is connected to the emitter of the first bipolar transistor; the base of the first bipolar transistor is controlled by a control current; and the control current is derived from the voltage at the drain of the MOSFET.

主权项

1. A circuit for the protection of an electrical consumer against polarity reversal, said circuit comprising:
a metal oxide semiconductor field effect transistor (MOSFET) (T1); a first diode; a second diode; and a resistor (R4) arranged between the first diode and a drain of the MOSFET (T1), wherein:
the circuit is connected to a voltage supply on its input, and to the consumer on its output;the source terminal of the MOSFET (T1) is connected to the voltage supply;the drain terminal of the MOSFET (T1) is connected to the consumer;the gate of the MOSFET (T1) is connected to the collector of a first bipolar transistor (T3);the source of the MOSFET (T1) is connected to the emitter of the first bipolar transistor (T3);the base of the first bipolar transistor (T3) is controlled by means of a control current;the control current is derived from the voltage at the drain of the MOSFET (T1);the first diode is configured for tapping the control current from the voltage of the drain of the MOSFET (T1);the resistor (R4) is configured to control the voltage drop across the MOSFET (T1); andthe MOSFET (T1) is an n-channel enhancement MOSFET;the first diode is formed by the base-emitter path of a second bipolar transistor (T2); the second diode is arranged between the emitter and the base of the second bipolar transistor (T2); andthe second diode being configured to prevent an excessively high voltage flowing backward between the emitter and the base in the event of a reversal in polarity or of an interruption in the supply voltage.