555 Negative Voltage Power Supply Circuit
A negative supply can be generated by a “Charge-Pump” circuit created with a 555, diodes and capacitors.
Another advantage of this circuit is that, the negative voltage together with the original positive supply can be used to simulate a dual supply.
This circuit diagram shows how to obtain a negative voltage from a positive voltage supply.
| PARTS LIST | |
| C1 | 0.1µF (104) |
| C2 | 0.022µF (223) |
| C3 | 22µF 25V |
| C4 | 33µF 25V |
| C5 | 100µF 25V |
| R1 | 4.7kΩ |
| R2 | 33kΩ |
| D1 | 1N4002 |
| D2 | 1N4002 |
| IC1 | NE555 |
The 555 is connected as an astable multivibrator operating at around 1KHz. During the timer output at pin 3 goes positive, the series C3 capacitor charges through the diode D1. When the output switches to ground, the C3 cap discharges through the D2 and charges the C4 capacitor to a negative voltage. As a result of this the voltage at the junction of the anode of D2 and cathode of C4 will be always negative with respect to the ground.
The output will deliver about 50mA.
 |
 |
Please send your ideas, which are very important for our success…
#1 by RamsaPhil on June 19th, 2012
Can I increase current deliver up to 100-200Ma?
#2 by Neel Mehta on April 26th, 2011
What would the output voltage be if you feed in a 15V DC supply? My guess is that through the internal resistance of the IC, resistors and the capacitors, there will be a great loss of Power. When you specify that the max input voltage 15V is, then the output will be more than -15V. How would you manage to get a output Voltage supply of exactly -15V?
#3 by Monex Investigation on December 14th, 2010
With DC and positive voltage signals the current goes from source to ground now with AC you have negative voltage how does current travel then? Current also travels from the ground to the source thru a positive voltage except it is the negative current. So to your question a negative voltage can have either negative current or positive current flowing thru it.