In this post we discuss a few miniature inverter circuits that can convert 1.5 V to 220 V or 3 V to 220 V or 6 V to 220 V. All the designs employ a single PNP transistor and transformer, connected in the feedback mode for generating the oscillations.
1.5 V to 220 V Inverter Circuit
The mini inverter circuit demonstrated in the following figure can produce a highest AC output of 220 volts if it is powered through any battery between 1.5 V and 6 V battery. It employs a TIP2955 power transistor forming a Hartley type oscillator with the transformer.
The center tapped 6.3 v winding of a small iron core transformer (T1) works like a center feedback type of coil for this oscillator. With a 6 V battery (B1), the highest current drain is around 80 ma. The 50k 10 watt wirewound potentiometer (R1) adjusts the no-load DC output between 2 V and 220 V volts.
In this inverter design if R1 is substituted by a 200 ohm 10 watt wirewound pot and R2 replaced with a 20 ohm, 1 watt resistor, battery B1 specifications could be minimized to 1.5 V., and then the circuit work like a 1.5 V to 220 V inverter circuit.
The maximum drain from the battery at 1.5 V supply will be roughly around 100 ma. R1 will alter the DC output between 60 and 80 volts, in the absence of a load.
3 V to 220 V Inverter Circuit
The next 3 V to 220 V inverter circuit is designed to work in a blocking oscillator mode having an operating frequency set at around 400 Hz. The transistor used can be any PNP power transistor.
The center tap transformer can be any standard step down transformer. This transformer provides the feedback and the voltage boosting both together.
The connections of the two low voltage windings of T1 must be configured correctly with the transistor, otherwise the inverter may fail to work, and begin heating up. The 50 K potentiometer is a wirewound variable resistor (R1) which must be appropriately set to get reliable oscillation and the maximum voltage output. This 3 V to 220 V inverter circuit may draws around 70 ma from the 3 V battery (B1).
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