Yueshi Guan

A Single-Stage LED Driver Based on BCM Boost Circuit and

In this paper, a single-stage LED driver is proposed for a street lighting system. Two boost circuits that share a single inductor are formed by integrating the switches of a half-bridge LLC resonant converter. Both boost circuits operate in the boundary conduction mode, which realizes a power-factor correction function. Because the input voltage of the LED driver is divided by two capacitors, the bus voltage is considerably reduced to almost the input peak voltage, rendering the novel single-stage LED driver to work suitably under high-input-voltage conditions. The soft-switching characteristics of the half-bridge LLC resonant circuit are not affected by the integration of the switches; thus, the converter has a low cost and a high efficiency. A 100-W prototype was developed, and the efficiency was determined to be as high as 91.1% in a full-load state under a 220-V ac input.

LLC

A single-stage LED driver based on an interleaved buck-boost circuit and an LLC resonant converter is proposed. The buck-boost circuit and the LLC resonant converter are integrated by sharing switches, which can decrease the system cost and improve the system efficiency. The input voltage of the buck-boost circuit is half of the rectified voltage, and two buck-boost circuits are formed with the two half-bridge switches and corresponding diodes. The two buck-boost circuits work in interleaved mode and the inductor current is in discontinuous conduction mode, both helping to achieve the power factor (PF) correction. A half-bridge LLC resonant converter is adopted here, and the soft switching characteristic of the LLC resonant converter is not changed by the switch integration. The primary-side switches still work in zero voltage switching (ZVS) mode, and the secondary diodes still work in ZCS mode, which both reduce the switching losses and improve the efficiency of the system. The design process is described in detail this paper, and a 100-W LED street lighting prototype is proposed, with a PF of 0.995, a total harmonic distortion of 5.7%, and an efficiency of 91.6% at full load.

Converter for Street Lighting System

A CLCL resonant dc/dc converter has been proposed and analyzed in this paper for two-stage light-emitting diode (LED) drivers. The circuit performs zero-voltage-switching (ZVS) turn-on and quasi-zero-current-switching (ZCS) turn-off. Then, a two-stage system has been designed using a power factor correction circuit before the proposed converter. Optimum input impedance angle, dead time, and components parameters have been achieved after thoughtful design, thus obtaining good soft-switching performance and reduced voltage stress. A 100-W prototype has been realized and tested demonstrating its high feasibility and efficiency at full load and during dimming operations.

A Single-Stage LED Driver Based on Interleaved Buck–Boost Circuit and LLC Resonant Converter

A single-stage light-emitting diode (LED) driver has been developed integrating a single-ended primary-inductor converter with a half-bridge LLC resonant converter. The proposed topology reduces systems cost, enhancing reliability. Because the LLC resonant part maintains soft-switching characteristics, switching losses are relatively low. Due to careful parameters selection, the system bus voltage can be kept low as needed in high-power LED drive designs. Some experiments using a 100-W prototype were performed to validate theoretical analysis. The obtained power factor was as high as 0.99, and due to soft-switching operations efficiency was up to 92% at full load.

A CLCL Resonant DC/DC Converter for Two-Stage LED Driver System

A novel single-stage light-emitting diode (LED) driver with high voltage gain for LED automobile headlight is proposed in the paper. The converter is made up of two parts, which are the boost cell and double LLC cell, and the two parts are integrated by sharing the switch. Since the number of the system components is reduced by integrating the switches, the cost decreases. The boost circuit works in the continuous conduction mode with double voltage gain, and the double LLC cell connected in series can decrease the peak current and increase the efficiency of the system. A 30-W prototype is proposed in the lab, with 30 high-brightness LEDs connected in series. The experimental results well confirm the theoretical prediction, and the efficiency of the system for the full load is higher than 92%.

A Single-Stage LED Driver Based on SEPIC and LLC Circuits

With the increasing demand of low-profile, high-power density for power electronics system, the planar magnetics (inductors and transformers) begin to be adopted in many fields. The copper tracks on printed circuit board (PCB) are mostly adopted as the windings of the planar magnetics which cannot be changed flexibly once the PCB is produced. So the design method of planar magnetics is an important issue. In this paper, the Response Surface Method (RSM) is adopted to design the planar inductor. The method can exactly obtain the inductance and resistance by the formulas obtained from experimental or simulation test results which can simplifying the design process. For the planar transformer, the Modular Layer Model (MLM) is adopted to build the final equivalent model of the transformer, by which the magnetizing inductance, leakage inductance and resistance can be calculated. The proposed design methods of planar inductor and planar transformer are verified by a resonant converter prototype.

A Single-Stage LED Driver Based on Double LLC Resonant Tanks for Automobile Headlight With Digital Control

With the development of high frequency converters, driving circuits have gained more and more attention. Self-driven methods can effectively simplify system design and reduce components’ number. A basic self-driven circuit can be achieved by adding a series resonant inductor at the switch gate; however the losses of driving circuit are high. To reduce the corresponding losses, a high efficiency self-driven network with an additional parallel branch is proposed, which can significantly improve the system efficiency. A 13 MHz prototype is built to verify the feasibility of the proposed self-driven circuit. The system efficiency can be improved from 80% to 83.9%.

Analysis and design of planar inductor and transformer for resonant converter

In this paper, two resistive matching networks are proposed, which can maintain the resistive transferring property under different load conditions. The high-frequency converter based on the resistive network can adequately achieve the soft-switching characteristics within a large load variation range, which helps to reduce switching losses and improve system efficiency. At the same time, a detailed design method for planar spiral inductor is described. In addition, the quality factor characteristics of different winding structures are analyzed. A 20-MHz high-frequency dc/dc converter based on the T-type matching network and circular spiral inductor is designed in this paper. The experimental results verify the advantages of the proposed resistive matching network and spiral inductor.

High-Efficiency Self-Driven Circuit With Parallel Branch For High Frequency Converters

In this paper, a high step up converter consisting of an integrated quadratic-boost converter and a voltage doubler is proposed. The integration of the quadratic-boost converter makes the system easier to lift up its voltage gain through slightly increasing the duty ratio of the single switch. The voltage doubler further increases the voltage gain of the system as the turn ratio rises. The voltage stresses on the switch and the diodes are decreased for such cascaded topology. Different operation modes are analyzed and mathematical analysis of the converter is presented in detail. The leakage inductance contributes to realizing zero current switching of the diodes in the second boost stage and the doubler and the energy can be recycled to the load. A 38-W prototype is built to work as a vehicle LED driver. Experiments are conducted to verify the advantages of the proposed converter and the efficiency is 90% at the nominal operating point.

Analysis and Design of High-Frequency Converter With Resistive Matching Network and Spiral Inductor

A CLCL resonant DC/DC converter based on the transformer leakage inductance is proposed in this paper. With the adoption of leakage inductance, the system volume and magnetic losses can be greatly reduced. The optimal design method of the proposed converter is analyzed in detail. Also, the advantages of the CLCL converter are depicted compared with LLC circuit. The design of variable width winding planar magnetics is depicted in detail, which can reduce the winding losses and parasitic capacitance. A 1-MHz prototype using gallium nitride FETs is built to verify the feasibility of the proposed resonant converter and design method.