Negative voltage generator circuit, NE555 charge pump

Negative voltage generator circuit, NE555 charge pump

Keywords: NE555, charge pump circuit diagram

For sensor circuits or operational amplifier circuits, dual positive and negative power supplies are often required. However, for equipment such as vehicles that only have a single power supply, it is necessary to obtain the negative power supply from a single positive power supply. There are many methods, but using commercially available DC- DC converters are more convenient.

However, for situations where only a negative power supply is required to provide a small current, a charge pump circuit composed of a timing IC555 can be used. Although the output voltage changes to a certain extent with the output current, the circuit is simple and low-cost.

The circuit is shown in Figure 1. In theory, it can provide a negative voltage output equal to the 555 power supply voltage. However, in fact, the negative voltage output value is slightly lower than the absolute value of the power supply voltage. The reason is that diodes D1 and D2 have a forward voltage drop VF of about 0.6V.