Synchronous High Step-Down Ratio Non-Isolated LED Constant Current Driver Based on Improved Watkins-Johnson Topology

Abstract

In the field of non-isolated light-emitting diode (LED) driver, the omnipresent buck-based LED constant current driver shows poor efficiency in occasions of high step-down ratio due to the marginal operating duty cycle. In order to overcome such drawback and to provide an alternative topological scheme for an LED driver, a Watkins-Johnson topology-based solution is proposed in this paper, by improving the original circuit structure into a dual low-side power switch version and introducing a feedback network for regulating the output current to a constant level. Theoretical analysis, including accurate model construction, steady-state analysis, dynamic analysis, and design consideration, is conducted. Also, an experimental prototype is realized to drive all kinds of LED arrays for acquiring electrical parameters and evaluating performance. The innovative points include invoking the low-side-ize approach to realize the power circuit transformation, and furthermore, the Watkins-Johnson topology is first applied to the constant current power supply. The proposed LED driver holds salient features of low-terminal current ripple, ease of driving, highvoltage conversion ratio tolerance, and inherent energy recovery functionality. The application scope covers low-voltage dc input or automotive lighting use.INDEX TERMS Constant current, LED driver, synchronous control, Watkins-Johnson topology.

Multi-Objective Design of Output LC Filter for Buck Converter via the Coevolving-AMOSA Algorithm

“…As an example, capacitors of ECA1JM series of Panasonic [31] are selected in Fig. 10, in which statistical R 2 is close to 1, validating the linear relationship between Vol C and C. With ( 9) and ( 10), the total volume V tot to be minimized is shown in (11), and is linearly related to the inductance L and capacitance C. The design objective 3 is to minimize the volume V tot in (11) for a compact Buck converter.…”

“…The design specifications are listed in Table 2. Three objectives with respects to L and C can be analyzed with (1) to (11), and are summarized as the following:…”

“…1, airplanes, satellites and electric vehicles demand high-efficiency products [10]. Battery adapter, rooftop PV, digital camera and LED, which have limited space, prefer more compact electronic devices [11]. And the LC filter with smaller cut-off frequency in Buck converter displays better filtering capability, which is suitable for audio amplifier or MP3 player with strict requirements on the ripple reduction [6].…”

A single‐stage bridgeless LLC resonant converter with constant frequency control based LED driver

“…Moreover, unlike conventional lighting sources, LEDs have a superior long lifetime, environmental friendliness, and cooler temperatures. For these reasons, LEDs will gradually replace fluorescent lamps and high-intensity discharge lamps in the future [4][5][6][7]. To ensure the high performance of LEDs, an especially designed circuit supply called an LED driver with constant current output is absolutely necessary.…”

Linear current module adaptive to wide operating voltage range based on automatic series/parallel conversion

“…The adaptive conversion of connection of current branches and load branches is controlled by a switch array. LED driver is one of the main applications of constant current source [23,24,26,27,28,29,30,31]. Based on the proposed linear current module, a four-segment LED driver is designed and experimentally verified.…”