A digital optimal battery charger capable of detecting the
fault within one switching cycle is presented in the paper.
The charger enables a smooth and stable transition from CC
to CV without the need of any extra switch or control loop.
The carrier for the hysteretic comparator is generated (in
FPGA) from the sensed converter voltage waveforms (output
voltage and switch node voltage) without the need of direct
inductor current sensing. This facilitates immediate fault
detection (within one switching cycle) in case of the main
switch (TOP FET) failure of the converter. Simulation and
experimental results are presented for 20 W prototype. The
proposed digital modulator is validated for charging of a real
6 V-4.5 Ah lead acid battery as well.