LED buck driver with only partial power conversion

Abstract

This paper proposes an LED driver circuit that requires only partial power conversion. This driver consists of a buck converter. The LED current is regulated by controlling the duty cycle of the power switch. While over 70% of the power required by the LED string is directly provided by the DC power source, the buck converter only needs to convert 30% of the power to maintain a constant LED current. The input and output of the proposed buck converter are both low voltage with minimizing the voltage stress on all components. This allows the circuit to adopt the lower voltage and current rating of components, which then reduces cost and size. Since both input and output voltages are within 5V, the components such as the power switch, diode, and resistor can be integrated into an integrated circuit, further reducing overall circuit size and cost. This article provides the circuit operating principle and analysis. A simulation circuit is also designed for an LED lamp consisting of three LEDs. The simulation results verify the feasibility of the proposed LED driver circuit.