Sine Wave Pulse Width Modulation Study for Improving Vehicle Lighting Control

Vehicle lighting has become more demanding with different load requirements, strict Electromagnetic Compatibility (EMC) requirements, accuracy requirements, and power consumption requirements. These requirements are all under the constraint of ever shrinking PCB’s driving up the cost of PCB real estate. Pulse width modulation (PWM) is used to control the interior and exterior lighting in vehicles and meet all these requirements. One or more electronic control units in the body domain of a vehicle contain a number of integrated circuits that drive loads using PWM signals. In addition to driving loads, PWM signals are used for things such as dimming and diagnostic functions. In current technology the PWM signal is usually composed of a trapezoidal wave or rounded wave which control bulbs and light emitting diodes (LED) loads in a vehicle. The trapezoidal or rounded wave may not be the most efficient way to meet requirements in the automotive industry due to their sharp rising edges so different methods have been developed to improve functionality and reduce cost. Using PWM with sine wave control could be an improvement over the current technology. This study looks at two integrated circuits that use each control method, the rounded wave and the sine wave. Both control methods are studied with the same PCB layout and environmental conditions then compared through testing such as radiated emissions testing and thermal testing. The comparison is used to determine which method is more beneficial for use in controlling automotive lighting. Other methods in recent literature are also reviewed along with future outlooks on controlling lighting loads in the automotive industry.