Body diodes simplify UPS & energy recovery circuits
This Design Idea illustrates a way to make use of MOSFETs’ parasitic body diodes in a power circuit that can be used in UPS and energy-recovery (e.g., regenerative braking) designs.
The circuit can work in two modes: as a bridge rectifier, or a PWM DC/AC inverter.
In this mode, Q1 & Q2 are off and Q3 is on, enabling DC output U1.
When Mode is low, the circuit performs as a PWM DC/AC inverter. Q1 & Q2 get PWM from the control block, while D1 & D2 together with Zener D3 eliminate overvoltage spikes on the MOSFETs. D1 & D2 should therefore be fast, low capacitance parts. Also, Q3 and hence the DC output are off.
+Bat connects to battery circuitry, which could include a charge controller.
—Peter Demchenko studied math at the University of Vilnius and has worked in software development.