Mini Inverter. Design Note 41


Here is a simple Mini Inverter circuit to light 11 Watts CFL from 12 volt battery. It is an ideal gadget to check the vehicle engine or electrical circuit in night. It can be hooked in the vehicle’s battery and the CFL will light. It can also be used in home as emergency lamp using the 12 volt UPS battery. An AC socket provision is also added to charge Mobile phone or other low watt gadgets while travelling. The 12 volt DC can be tapped from the Cigarette lighter socket of the car. The Inverter has maximum 18 Watts power.

It is a Mini Inverter that converts 12 volt DC to 230 volt AC. Two high power NPN transistors
T1 and T2 acts as a simple oscillator to generate the frequency. The oscillating pulses are fed to the inverter transformer and from its secondary winding, AC will be available.


The 12 volt DC from the battery first passes through the 330 uH choke that eliminates noise from the circuit during the switching of the inverter transformer. Resistor R1 biases T1 directly and T2 through the winding of transformer. So with C1, Transistors T1 and T2 oscillate and the oscillations are fed to the winding of transformer with a center tap that gets DC from the battery through the choke. So the oscillations of T1 and T2 induce AC current in the secondary of transformer which lights the CFL.


Assemble the circuit on a common PCB. Use ready made inverter transformer and 330 uH inductor with ferrite rod. Enclose in a shock proof plastic case with a holder for CFL and AC socket for charging purpose.

15 Watts CFL Lights in 12 volt battery using the circuit



Pin connection of CTC 880. Its equivalent is D 880


Inverter Transformer



downloadCaution: The circuit generates high volt AC at the output. So do not touch on the PCB when it is connected to the battery, Do not trouble shoot when the circuit is powered. It can give a fatal shock if handled carelessly.