A simple high voltage generator circuit is explained here which can be used to step up any DC level to about 20 times or depending upon the transformer secondary rating.
As can be visualized in the shown high voltage generator circuit diagram, it employs a standard transistor blocking oscillator configuration for generating the required stepped up voltage across the output winding of the transformer.
The circuit may be understood as follows:
The transistor conducts and drives the associated winding of the transformer via its collector/emitter the moment power is applied to the center of the transformer.
The upper half of the transformer winding simply provides a feedback to the base of the transistor via C2 such the T1 stays locked on to the conduction mode until C2 charges fully, breaking the latch and forcing the transistor to begin the conduction cycle afresh.
R1 which is a 1K resistor is positioned to limit the base drive for T1 to safe limits while VR1 which is a 22k preset may be adjusted for obtaining an efficiently pulsating T1 frequency.
C2 may be also fine tuned by trying other values until the highest possible output is attained at the trafo output
The transformer could be any iron-cored step down transformer (500mA) normally used in transformer type AC/DC adapter units.
The output right across the transformer output would be at the rated secondary level, for example if it is a 220V secondary, then the output could be expected to be at this level.
The above level could be further amplified or stepped up through the attached diode, capacitor charge pump network akin to cockroft-walton generator network.
The network raises the 220V level to many hundreds of volts which may be forced to spark across an appropriately positioned end terminals of the charge pump circuit.
The circuit can be also used in mosquito swatter bat application by replacing the iron cored transformer with a ferrite core counterpart.