Fast Acting Electronic Circuitbreakers

Related Circuit - Electronic Circuit Breaker (2010)

  Most of the circuit breakers on this page make use of the Zetex - ZXCT1009 "High Side Current Monitor' integrated circuit. The circuits have variable trip current settings and are designed for low current DC applications.

Zetex - ZXCT1009 "High Side Current Monitor'

  The current sensing IC is placed in the supply side of the circuit ahead of the isolation device. This allows the COMMON side of the circuit to be free of voltage dropping resistances.

  For information on the operation of the ZXCT1009 current monitor itself, please refer to the manufacturers data sheet at - ZETEX - ZXCT1009 Data Sheet (PDF)

  Three circuitbreaker designs are shown; The first has its power isolation device on the Low or common side of the circuit while the second and third have their isolation device on the High or supply side of the circuit. All circuits use MOSFET transitors or ICs to isolate the supply from the load.

  The overload detection and trip system is completely electronic and therefore has a very fast response time (1/120th of a second or less for a full wave DC supply). This allows the load to be disconnected almost instantaneously when an over current condition is detected.

Also see: 10 Amp Fast Electronic Circuit Breaker

- Low Side Isolation Circuit Breaker -

  This circuit has its isolation device, Q1, on the Low or common side of the circuit. The disadvantage of this method is that the breaker cannot easily be used in typical circuit configurations that share a low side or negative common.

  The method is simple to implement however and a wide range of output devices can be used. The transistor used to test this circuit was a IRL520 MOSFET

Low Side Circuit Breaker

Circuit Controls and Indicators

- High Side Isolation Circuit Breaker -

  This circuit has its isolation device, IC 3, on the High or Supply side of the circuit. This allows the circuit breaker to be easily used in typical circuit configurations that share a LOW side or negative common.

  IC 3 is a PROFET® BTS409L1 - 'Smart High Side power Switch' from INFINEON.

High Side Circuit Breaker #1

Circuit #1 Controls and Indicators

  LED - D3 is optional and is connected to the internal diagnostics system of the BTS409L1 and will turn ON to indicate various fault conditions. These are listed in the BTS409L1 data sheet.

  The second HIGH Side circuitbreaker uses an IRL9520 MOSFET as the isolation device.

High Side Circuit Breaker #2

Very - Basic Operation Of All Circuitbreakers

  1.   As the current through RSENSE increases the voltage across resistors ROUT - MAX and ROUT - ADJ increases proportionally.

  2.   When the voltage at the MINUS input of IC 2A rises above the voltage at the PLUS input its OUTPUT will go LOW.

  3.   When the OUTPUT of IC 2A goes LOW it causes the Flip-Flop formed IC 2B to change states, producing a LOW condition at it's OUTPUT.

  4.   Depending on the circuit used, a LOW at the output of IC 2B causes the Gate of Q1 or the Input Terminal of IC 3 to go LOW. This will cause Q1 or IC 3 to turn OFF and open the downstream circuit.

High Side Circuit Breaker With LM317 Voltage Regulator Output

Circuit Breaker Page Notes


Other Similar Circuits

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  If you use any of these circuit ideas, ask your parts supplier for a copy of the manufacturers data sheets for any components that you have not used before. These sheets contain a wealth of data and circuit design information that no electronic or print article could approach and will save time and perhaps damage to the components themselves. These data sheets can often be found on the web site of the device manufacturers.

  Although the circuits are functional the pages are not meant to be full descriptions of each circuit but rather as guides for adapting them for use by others. If you have any questions or comments please send them to the email address on the Circuit Index page.

04 September, 2012