slua042DN-43 Design Note Simple Techniques to Generate a Negative Voltage Bias Supply from a Positive Input Voltage by Bill Andreycak Developing a low power negative supply voltage from a positive input supply can be accomplished using some very common PWM control ICs. Typical applications include generating a negative five through twelve volt (-5V to -12V) supply for analog function ICs (OP amps), RS-232 communication circuits, and MOSFET or IGBT gate drives at power levels below a few Watts. Many PWM ICs contain a high current totem pole output which goes high during the device’s ON-time or pulse width. The exact pulse width is modulated to regulate a converter’s output voltage during changes in input voltage and output current. The IC’s totem pole output can also be used as the main switch in……