Single-inductor circuit genera

The single inductor and three Schottky diodes associated with this step-up converter derive +15V and -14V from a +5V source. The +15V output delivers as much as 200mA, with efficiencies up to 85% and about 44mV of output ripple. A similar version of this article appeared in the October 6, 2008 issue of EE Times magazine.Many circuit techniques can generate bipolar supply voltages from a single positive voltage, but most of them require multiple inductors. In Figure 1, a single inductor and three Schottky diodes derive +15V/-14V from a +5V source while reducing the circuit size and minimizing cost. The circuit is capable of meeting the demands of most analog circuitry, including audio, instrumentation, and industrial applications. It provides output currents up to 200mA with low output ripple (100mV_P-P), and drives several amplifiers drawing 5mA to 10mA each.Figure 4. These curves from Figure 1 show the output regulation for +15V, with 200mA load on -14V (a), and the output regulation for -14V, with 200mA load on +15V (b).