Extreme's Blog :Return to Blog
Dual Supply From Single Battery Source
Timer IC NE555 is configured as a free-running oscillator. It produces around 100kHz frequency. An audio system would not pick up this frequency as it is above the audible range. Therefore a Villard cascade voltage multiplier is used as the voltage booster. The boosted voltage is made ripple-free and regulated to -9V by negative-voltage regulator LM7909.
The frequency of the squarewave generator depends on the values of C1, R1 and R2. The frequency of the signal may slightly change with the temperature variation but the change in frequency does not affect the output voltage of the circuit. Capacitors C3, C4, C5 and C6 and diodes D1, D2, D3 and D4 form the Villard cascade voltage multiplier. The output voltage from the Villard cascade voltage multiplier is fed to linear negative-voltage regulator IC2 to eliminate ripples and get accurate -9V DC. Capacitors C7 and C8 provide additional noise-filtering.
The output from voltage regulator IC2 is -9V. Assemble the circuit on a general-purpose PCB and enclose in a suitable cabinet. Fix the 9V battery inside the cabinet. At the front panel, connect three terminals for outputs. EFY note. This power supply can be used only for low-power applications.