One of the important issues in modern electronic equipment is providing higher peak power while preserving high energy density. Hybrid power sources composed of fuel cells and batteries combine the high-energy capabilities of fuel cells with the high-power capabilities of batteries. DC/DC power converters can appropriately control the power flow shared between the fuel cell and battery system. In this paper, we propose a new implementation of hybrid fuel cell/battery systems. A 50-W isolated power electronic interface system for a hybrid solid-oxide fuel cell (SOFC)/Li-ion battery portable power supply is designed and implemented. The control strategy presented in this paper is able to regulate the output current of the fuel cell, the charging current of the battery, and the output voltage of the power supply. The control strategy is implemented in a DSP and tested by simulation and experiments. Experimental results present the flexibility and generality of the control strategy.

Digital Control of an Isolated Active Hybrid Fuel Cell/Li-Ion Battery Power Supply

Optocouplers are widely used in isolated power supplies to transfer the feedback signal from the secondary to the primary side. In many power supplies, the feedback amplifier is supplied from the output voltage that creates additional feedback path which should be taken into account in the control design. The paper presents a detailed analysis and control design for each of the two possible feedback loops that can be identified. In addition, dynamic limitations of the TL431 shunt regulator and of the optocoupler are discussed. Practical guidelines for the error amplifier design and a design example are presented for both voltage-mode and current-mode controls.

Small-signal analysis and control design of isolated power supplies with optocoupler feedback

This paper presents performance comparison of continuous conduction mode (CCM) and discontinuous conduction mode (DCM) flyback converters The comparison is conducted through experiment on the 5 V/25 W, 50 kHz prototype CCM and DCM flyback converters, which have been designed and built with similar circuit layouts, components, and power ratings Aspects to be compared are component stress, output voltage regulation and transient response due to a step-load, and efficiency The pros and cons for each mode of operation are discussed based on the experimental results

Performance comparison of continuous conduction mode (CCM) and discontinuous conduction mode (DCM) flyback converters

In switch mode power supplies(SMPS), flyback converters are very popular because of, design simplicity, low cost, multiple isolated outputs, high output voltages and high efficiency. They are preferred especially for low power applications (150W). In this work, flyback converters are analyzed, mathematical modeled, designed with given parameters, tested with simulation software and practically results.

Design and implementation of flyback converters

In this paper, a new single-stage half-bridge (HB) resonant $LLC$ converter additionally employing one resonant capacitor and two relays with one package is proposed, compared with a single-stage HB $LLC$ converter. Moreover, a center-tapped transformer is replaced with a coupled transformer. Since the proposed converter changes the turns ratio of the coupled transformer using a relay according to low- or high-input-voltage range, it can decrease the range of its needed voltage gain. It means that the proposed converter can be designed with large transformer magnetizing inductance compared with the conventional single-stage HB $LLC$ converter. As a result, the primary conduction and turn-off losses are reduced. Moreover, in low input voltage range, it has smaller total primary wire resistance of the transformer due to parallel connection of the coupled transformer, which decreases its conduction loss. In addition, additionally employed small-sized components can be inserted to the conventional system. To confirm the operation, features, and validity of the proposed converter, universal input with low line and high line and 16.5 V/60 W output laboratory prototype targeting laptop adapters with wide-input-voltage range is built and tested.

High-Efficiency Single-Stage LLC Resonant Converter for Wide-Input-Voltage Range

The accurate dynamic modeling and quantitative controller design for an isolated converter with optocoupler isolation in its feedback loop are considered to be difficult issues, since the transfer characteristics of some blocks are highly nonlinear and difficult to be modeled analytically. First a current-mode controlled flyback converter with an optically isolated feedback path is designed. Then the equivalent control system block diagram is constructed, and its block transfer functions are found. To increase the accuracy, the dynamic models of some critical blocks are estimated from measurements. In order to facilitate the controller design, the model simplification is further made. Finally, based on the reduced dynamic model, a quantitative design procedure is derived to find the parameters of the voltage controller to meet the prescribed regulating specifications. Validity of the estimated dynamic model and the proposed controller design approach is demonstrated by some simulation and experimental results.

W.L. Lin

Papers

Dynamic modeling and controller design of flyback converter