Method of starting DC/DC converter using synchronous freewheeling MOSFET
View Patent ↗A DC/DC converter including an inductor and a capacitor is started by connecting an input voltage to the inductor and shunting a current around the inductor so as to pre-charge the capacitor to a predetermined voltage.
1. A method of starting a DC/DC voltage converter, the converter comprising:
an inductor and a low-side switch connected in a series conduction path, a V x node being located in the series conduction path between the inductor and the low-side switch;
a freewheeling MOSFET connected in parallel with the inductor, a first body bias generator being connected between the source and drain terminals of the freewheeling MOSFET; and
an energy transfer switch connected between the V x node and an output terminal of the converter, the energy transfer switch comprising an energy transfer MOSFET and a second body bias generator connected between the source and drain terminals of the energy transfer MOSFET;
the method comprising:
closing the freewheeling MOSFET and the energy transfer switch while maintaining the low-side switch in an open condition;
while maintaining the freewheeling MOSFET and the energy transfer switch in a closed condition and maintaining the low-side switch in an open condition, applying a DC input voltage to a first terminal of the inductor; and
turning off the energy transfer MOSFET when a voltage at the output terminal reaches a predetermined level, the predetermined level being less than the DC input voltage.
2. The method of claim 1 further comprising connecting a diode across the freewheeling MOSFET when the voltage at the output terminal reaches the predetermined level.
3. The method of claim 1 further comprising determining whether the DC input voltage is greater than or less than the output voltage.