A negative voltage generator with 4-stage configurable parallel switching for smart window film applications

A negative voltage generator was developed that can be used in the drivers of smart window films (SWF), which have typical operating voltages of ±8 to ±10 V. It consists of four Negative Charge Pump (NCP) stages and a 4-phase non-overlapping Clock Generator (CG), where the 4 NCP stages are configurable by external digital signals. This generates a wide output voltage range necessary to control different SWF modes, such as opaque, transparent, and tinted modes. TSMC 0.18-μm HV BCD (High-Voltage Bipolar-CMOS-DMOS) process was used to fabricate the proposed negative voltage generator on silicon. Measurement results demonstrate that at switching frequency (fsw) = 20 MHz, supplied voltage (VDD) = 4.5 V and Vin = GND, it generates a wide output voltage range of −3.9 to −14.0 V, achieving the widest voltage range among the prior works, which covers the required negative voltage range for SWF usage. The peak efficiency is measured on silicon to be 58.08% .