This paper presents a multioutput converter using an asymmetrical pulsewidth modulation half-bridge flyback topology employing a parallel-series-connected transformer. Compared to conventional multioutput topologies, the proposed converter operates using a single-output controller without the need for additional control loops and devices. In order to solve the cross-regulation problem, the output stages of the proposed converter are stacked in series. In addition, the voltage regulation of the proposed multioutput converter is improved through the analysis of its resonant characteristics under load variations and minimizing the secondary conduction loss. The proposed multioutput converter shows excellent performance in terms of its output regulation from no-load to full-load conditions and good cross regulation under high output currents. The design methodology and performance of the proposed converter have been verified through experimentation employing a 110-W (3.3 V/16 A, 5 V/12 A) prototype converter.

Analysis and Design of a Multioutput Converter Using Asymmetrical PWM Half-Bridge Flyback Converter Employing a Parallel–Series Transformer

This paper presents a new topology named zero-voltage switching (ZVS) resonant reset dual switch forward dc-dc converter, which, compared with resonant reset single switch forward dc-dc converter, maintains the advantage that duty cycle can be more than 50%, at the same time disadvantages of high voltage stress for main switches and low efficiency are overcome. In addition, ZVS is achieved for all switches of the presented topology. Therefore, this proposed topology is very attractive for high voltage input, wide range, and high efficiency applications. In this paper, the operation principle and characteristic of this topology are analyzed in detail. Next, the design consideration is presented. Finally, the advantages mentioned above are verified by experimental results

A Novel ZVS Resonant Reset Dual Switch Forward DC–DC Converter

Multi-output LLC resonant topologies with asymmetrical structures dedicating to multi-output power supply systems, having limitation of lowest load, are presented in this paper. According to output power level, different configuration of secondary output end can be flexibly adapted. Consequently, the presented topology is a favorable candidate for such application as whose outputs are not symmetrical, i.e. compared with auxiliary output, power level of main output is comparatively higher. In addition, all switches of the very topology operate under the condition of ZVS and therefore it is applicable to such occasion as high frequency, high power density. Asymmetrical operating principle and ZVS operation are analyzed in detail, moreover key parameter design considerations are presented. Finally, the analysis above is verified both by simulation and experiment.

A simple structure of LLC resonant DC-DC converter for multi-output applications

An accurately regulated multiple-output zero-voltage switching (ZVS) DC-DC converter is proposed. The converter is composed of three outputs altogether. The first and second outputs are regulated through the duty cycle control of two asymmetrical half bridge converters, while the third output is regulated through the phase shift of the two asymmetrical half bridge converters. The characteristic of this multiple-output dc-dc converter is analyzed and design process is investigated. ZVS is realized for all the main switches. Therefore this multiple-output dc-dc converter can operate with higher efficiency at higher switching frequency. The operation stages, ZVS condition and control detail are also presented. A 400 V input, 48 V/10 A, 5 V/20 A, 12 V/5 A outputs prototype is built to verify the design. The efficiency at rated input voltage full load is 93.36%.

Design and Implementation of an Accurately Regulated Multiple Output ZVS DC–DC Converter

The flyback converter is one of the most attractive isolated converters in small power applications because of its simple structure. However, it suffers from a high device stress and a large transformer size. To relieve these drawbacks, a high-efficient pulsewidth modulation resonant single-switch isolated converter is proposed. The proposed converter derives the power using the resonance between transformer leakage inductor and secondary capacitor without a large filter inductor. Therefore, the switch turn-off loss and snubber loss are reduced by a sinusoidal-shaped current. Moreover, it has a reduced voltage stress on the secondary diodes without a dissipative snubber and a smaller transformer size. Therefore, it features a simple structure, low cost, and high efficiency. The operational principle and characteristics of the proposed converter are presented and verified experimentally with a 300~400 Vdc input, 70 Vdc/1.5 A output prototype converter.

PWM Resonant Single-Switch Isolated Converter

In this paper, a new magamp technique for flyback converters is proposed. The operation principle of the proposed approach is described and design guidelines are provided. Experimental verifications on a 50 W two-output flyback converter are conducted. Recordings show that the proposed approach is effective and voltage regulation of the auxiliary output is excellent.

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Magamp post regulation for flyback converter

The present invention discloses flyback power converter. The flyback power converter includes a transformer for transferring an input voltage from a primary side to a secondary side. The secondary side includes a main output voltage loop and at least one auxiliary output loop connected with a magnetic amplifier. A pulse width modulation (PWM) controller controls a switch on the primary side of the transformer for turning on the switch and turning off the main output voltage loop and the auxiliary output voltage loop for storing a magnetizing energy on windings of the secondary side. The PWM controller further turns off the switch and turning on the main output voltage loop for providing a main voltage output and for magnetizing the magnetic amplifier connected to the auxiliary output voltage loop. The magnetic amplifier functioning as an auxiliary-loop switch for turning on the auxiliary output voltage loop when the magnetic amplifier is saturated with magnetization and turning off the main voltage output voltage loop for providing an auxiliary output voltage. A time-shared energy transfer mechanism is provided between the main output voltage loop and the auxiliary output voltage loop to fully utilize the entire duty cycle.

Auxiliary output voltage control circuit of flyback power converter with a magnetic amplifier

The present invention discloses forward power converter. The power converter includes a transformer for transferring an input voltage from a primary side to a secondary side. The secondary side includes a main output voltage loop and at least one auxiliary output loop connected with a magnetic amplifier. A pulse width modulation (PWM) controller controls a switch on the primary side of the transformer for turning on the switch and turning off the main output voltage loop and the auxiliary output voltage loop for storing a magnetizing energy on windings of the secondary side. The magnetic amplifier includes a first and a second magnetization windings controlled by a first and a second control circuits respectively for providing a positive and negative magnetization current to carrying out a bi-directional magnetization process to achieve expanded load range operable for the forward power converter.

Auxiliary output voltage control implemented with a bi-directionally magnetizing magnetic amplifier

Auxiliary output voltage control realized using idirectional magnetization magnetic amplifier

An auxiliary output voltage control circuit for feedback power transformer with magnetic amplifier is disclosed. Said feedback power transformer is composed of a transformer whose secondary side has a primary output voltage circuit and at least one auxiliary output voltage circuit connected with magnetic amplifier, a PWM controller for controlling the switch at the primary side of transformer foraccumulating the energy in the primary winding, and a magnetic amplifier connected with the auxiliary output voltage circuit to provide the auxiliary output voltage while open the primary output voltage circuit.

Chen Wei

Papers

Magamp post regulation for flyback converter

Auxiliary output voltage control circuit of flyback power converter with a magnetic amplifier

Auxiliary output voltage control implemented with a bi-directionally magnetizing magnetic amplifier

Auxiliary output voltage control realized using idirectional magnetization magnetic amplifier

Auxiliary output voltage control circuit of feedback power convertor prossessing magnetic amplifier