An app note from Alpha and Omega Semiconductor on using their AOZ1016 buck regulator to generate negative voltage. Link here (PDF)
The negative voltage source is widely used in various applications such as computing systems, LCD panels, audio amplifiers, etc. Using the additional secondary winding of a transformer is the widely used approach to generate the negative voltage source for computing systems, but it requires isolation transformer which may not be possible in other applications, and regulation is also bad. The LCD panels usually employs the charge pump to generate the negative voltage due to low cost, but the drawback is obvious: power delivery is limited and regulation is very bad and changes with input voltage since charge pump can only generate the integral times input voltage. In some high-end audio amplifier applications, the text-book method – buck boost – is applied. The lack of dedicated commercial buck-boost controllers, and the essential control difficulty of buck-boost (right plate zero) prevent the method from being widely used. And thus, designing a high qualify negative voltage source is always the challenge in system applications.
This article illustrates how to use buck converter to generate negative voltage source. The basic operation theory is introduced, and one practical example is presented.