Electronic Fuse DC and AC

You can use either direct current (up to 2 A and 20 Vdc) as alternating current (up to 3.5 A AC and 15 VDC). Replaces conventional fuses.

electronic fuse

Component Type-Value
D1, D4 1N5404
D5 RED 5mm
T1 TIP41 - Transistor
T2 BC337/2A - Transistor
T3 BC548/2A - Transistor
R1, R2 1 Kohm - Resistor
R3 10 Kohms - Resistor
R4 33 Kohms - Resistor
R5 47 Kohms - Resistor(see note)
C1 4,7 nF - Capacitor
L Heatsink L type


The circuit values are calculated for a voltage of 20 volts. The R5 value depends of max current used.

  • 600 mA R5=47 Kohms
  • 1,8 A R5=56 Kohms
  • 3,3 A R5=68 Kohms