UV-C Sterilizer for the Wireless Powerlizer

Abstract

The effectiveness of ultraviolet (UV) irradiation for disinfection has been well-known for more than a century. Recent advances in light­-emitting diode (LED) technology have brought UV LEDs to the consumer market. These offer many advantages over traditional gas­-discharge lamps, allowing UV radiation to be generated with higher reliability in a much smaller form factor. In this thesis, the design of a portable battery­-powered sterilizer based on UV LEDs is described. The sterilizer is intended for the sterilization of personal items such as mobile phones, face masks, and keys.

The design of the sterilizer consisted of two parts: the LED array and the LED driver. For their design, a model­-based approach was taken to ensure high performance and low cost. For the LED array, a radiometric model was developed and applied in an optimization procedure. The design of the LED driver was based on an analytical loss model in MATLAB and LTspice simulations.

The UV LED array provides a radiant power of 113 mW to the disinfection area, resulting in an irradiation dose of 195 μW/cm2. This allows for more than 99.9% disinfection in less than 15 min. The LED driver is a boost converter operating at 750 kHz in the discontinuous conduction mode. This converter supplies the array with a nominal input power of 4.3 W at a simulated efficiency of 91%.

The design of the LED driver is verified with a prototype. Measurements show efficiencies around 83% at 4.1 W output power. Incorporating several improvements over the prototype, efficiencies between 85–87% can be expected for the LED driver in the sterilizer.