Chien-Lan Huang

Interleaved ZVS Converter With Ripple-Current Cancellation

In this paper, an interleaved soft-switching converter with ripple-current cancellation is presented to achieve zero- voltage-switching (ZVS) turn-on and load current sharing. In order to achieve ZVS turn-on, an active snubber is connected in parallel with the primary winding of the transformer. The energy stored in the transformer leakage inductance and magnetizing inductance can be recovered so that the peak voltage stress of switching devices is limited. The resonance at the transition interval is used to realize ZVS turn-on of all switches. In order to achieve three-level pulsewidth-modulation (PWM) scheme, an addition fast-recovery diode is used in the converter. Three-level PWM scheme can reduce the ac ripple current on the output inductor such that the output inductor can be reduced. The current-doubler rectifier is adopted in the secondary side of the transformer to reduce the transformer secondary-winding current and output voltage ripple by canceling the current ripple of two output inductors. The output voltage is controlled at the desired value using the interleaved PWM scheme. These features make the proposed converter suitable for the dc-dc converter with high output current. The operation principles, steady state analysis, and design equations of the proposed converter are provided in detail. Finally, experiments based on a 600-W (12 V/50 A) prototype are provided to verify the effectiveness and feasibility of the proposed converter.

Analysis, Design, and Implementation of a Parallel ZVS Converter

A soft-switching converter is presented in this paper to achieve a zero-voltage-switching (ZVS) turn on for all switches. Two half-bridge converters with asymmetric pulsewidth-modulation scheme are connected in parallel to control the output voltage at the desired value and achieve load-current sharing. Based on the output capacitance of power switches and the resonant inductance, including the external inductance and the transformer leakage inductance, the resonance can be achieved at the transition interval of power switches. Therefore, the ZVS turn on of power switches can be realized. The peak voltage of the power switches is limited to input dc voltage. The center-tapped rectifier is adopted at the transformer secondary side to achieve a full-wave rectification. Operation principles, steady-state analysis, and design equations of the proposed converter are discussed in detail. Finally, experimental results based on a 240-W prototype are provided to verify the performance and the feasibility of the proposed converter.

Analysis of LLC converter with series-parallel connection

A parallel LLC resonant converter with series-connected in primary side and parallel-connected in secondary side is presented for server power supply systems. Based on the series resonant behavior, the power MOSFETs are turned on at zero voltage switching (ZVS) and the rectifier diodes are turned off at zero current switching (ZCS). Thus the switching losses on power semiconductors are reduced. In the proposed converter, the primary windings of two LLC converters are connected in series. Thus two converters have the same primary currents to ensure that two converters can supply the balance load current. In the output side of two LLC converters are connected in parallel to share the load current and to reduce the current stresses on the secondary windings and the rectifier diodes. In this paper, the principle of operation, steady state analysis and design consideration of the proposed converter are provided and discussed. Experiments with a laboratory prototype with 24V/21A output for server power supply were provided to verify the effectiveness of the proposed converter.

Analysis of the Two-Switch Forward Converter with Synchronous Current Doubler Rectifier

A soft switching two-switch forward converter is presented to achieve zero voltage switching turn-on of switching devices. In the adopted converter, a buck-boost type of active clamp is connected in parallel with the primary winding of transformer. The energy stored in the transformer leakage inductance and magnetizing inductance can be recovered so that the peak voltage stress of switching devices is limited. The resonance between the transient interval of two main and auxiliary switches is used to achieve ZVS turn-on of all switches. The current doubler synchronous rectifier is used in the secondary side of transformer to reduce the root mean square value of output inductor current, transformer secondary winding current and output voltage ripple by cancelling the current ripple of two output inductors. First the circuit configuration and principles of operation are analyzed in detail. The steady state analysis and design consideration are also presented. Finally, experimental results with a laboratory prototype based on a 380 V input and 12 V/30 A output were provided to verify the effectiveness of the proposed converter.

Analysis of a Zero Voltage Switching Cuk Converter

A boost type zero voltage switching (ZVS) isolated Cuk converter is presented in this paper to reduce the switching losses of main switch. An auxiliary switch and a clamp capacitor are connected in parallel with the main switch to absorb all the energy stored in the leakage inductance of the transformer. The ZVS operation of main switch is achieved by the resonance with the resonant inductor and output capacitor of main switch. The ZVS operation of auxiliary switch is achieved by the resonance with the resonant inductor and the clamp capacitor. Therefore both switches are turned on at ZVS. The principle of operation, system analysis and design consideration are presented Finally, experiments based on an 180 W (12 V/15 A) prototype are provided to demonstrate the effectiveness of the proposed converter.

Analysis of integrated buck-flyback ZVS converter

This paper presents the system analysis and circuit implementation of a soft switching converter based on buck-flyback topology to have a large voltage step-down between the output and input sides. Compared with the conventional buck converter, the proposed converter has wide turn-on period so that the lower output voltage can be achieved. An active snubber circuit is connected in parallel with the main switch to achieve zero voltage switching (ZVS). The resonance is based on the output capacitance of power switch and resonant inductance at the transition interval between the main and auxiliary switches. Therefore, the turn-on switching losses of power switch are reduced. The circuit configuration, system analysis, and design consideration of the proposed converter are presented in detail. Finally, experimental results based on a laboratory prototype with 240 W rated power are provided to verify the effectiveness of the proposed converter.

Analysis of a Soft Switching PWM Active Clamp Cuk Converter

A soft switching pulse-width modulation (PWM) Cuk converter with boost type of active clamp is proposed. Active clamp circuit can help the switching devices in the Cuk converter to be operated at zero voltage switching (ZVS) turn-on. Therefore this converter is suitable for high frequency operation to reduce the size of reactive components. The clamp capacitor and auxiliary switch are connected in parallel with the primary switch. When main switch is turned off, the positive inductor current will flow through the anti-parallel diode of auxiliary switch. At this instant, the auxiliary switch can turn on at ZVS. On the other hand, the resonance between the resonant inductor and output capacitor of main switch will create a ZVS condition for main switch. The principle of operation, system analysis, and design consideration are presented in this paper. Experimental results for a laboratory prototype rated at 400 W, input voltage of 150 V~300 V, output voltage of 200 V, and operating at 105 kHz are given to demonstrate the effectiveness of the proposed converter.

Analysis and Design of Half-Bridge Converter with Two Current Doubler Rectifiers

A new half bridge converter with two current doubler rectifiers is proposed. Two transformers are used in the proposed converter. The primary windings of two transformers are connected in series to reduce the voltage stress across the magnetizing inductor. Two current doubler rectifiers at the secondary sides are connected in parallel to reduce the current stress of secondary winding and rectifier diodes. The asymmetrical pulse-width modulation technique is used in the proposed converter to regulate the dc output voltage and improve the duty cycle utilization. The transformer leakage inductance and the output capacitance of switching switches are used to resonant during the transition interval between two switches in order to achieve zero voltage switching (ZVS). The operation principle and design considerations of the proposed converter are provided. Experimental results for a 100 W (5 V/20 A) prototype are presented to verify the theoretical analysis and circuit performance

Implementation of a ZVS Half-Bridge Converter with Current Doubler Rectifier

This paper presents the system analysis and circuit implementation of a zero voltage switching (ZVS) half-bridge converter with current doubler rectifier. The asymmetrical pulse-width modulation technique is used in the adopted power converter to regulate the DC output voltage and improve the duty cycle utilization. The transformer leakage inductance and the output capacitance of power switches are used to achieve ZVS operation during the transition interval between two switches. The operation principle of the converter is analyzed and explained. The design consideration of the ZVS half- bridge converter with current doubler rectifier is provided. Finally experimental results are provided to verify the theoretical analysis and circuit performance.

Step-UP ZVS converter with bi-transformer

In this paper, a step-up active-clamp SEPIC with bi-transformer is presented for battery sourcing application. Two voltage double circuits are connected in series at secondary side, thus, the output voltage could be increase compared with the conventional isolated SEPIC converter. The voltage double circuit at secondary side provides high voltage gain and limits the voltage spike on output diodes. The interleaved operation in output side reduces ripple current and output capacitance. The active-clamp technique is used to reduce voltage stresses on switches and achieve ZVS for main and auxiliary switches and recycle the stored energy of resonant inductance and magnetizing inductance. The leakage inductance of the transformer and additional resonant inductance are used to achieve ZVS during the dead time. Therefore, high conversion efficiency can be obtained. The analysis and design consideration of the proposed converter are shown in detail. Experimental results are shown to prove prototype with input 48V and 200V / 2A output.