A 100-V Battery Charger Voltage Extender IC With 97% Efficiency at 4-A and ±0.5% Voltage Accuracy

This paper presents an IC that extends the voltage capability of a low voltage battery charger to 100V for accurately and reliably charging lithium ion (Li-Ion) battery stacks of up to 18 cells. The IC interfaces with a buck converter battery charger that utilizes external nFET control and an external inductor current sensing resistor. The voltage extender IC provides voltage level translation for the nFET control signals and the current sensing function while supporting an input power supply voltage of up to 100V and output battery voltage of up to 80V. The inductor current sense voltage is translated with a ping-pong amplifier capable of driving a bi-directional input voltage to a fully differential output with a maximum load current of 10 mA at 20 MHz bandwidth and less than 500 μV offset. The combined system of the voltage extender IC and battery charger achieved 97% efficiency at a 4-A charging current. The battery charging voltage accuracy was better than ± 0.5% at 80V.