Interleaved ZVS Flyback-Forward converter with reduced output voltage stress on secondary rectifier diodes
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In this paper, a novel active clamp Flyback-Forward converter is proposed for large voltage gain and high power applications. The interleaved configuration on the primary side is employed to handle the large input current. An improved voltage doubler configuration is adopted on the secondary side to make the output diodes sustain only half of the high output voltage. Furthermore, the output diode voltage stress can be auto-balanced due to the inherent series structure of the coupled inductors. Therefore, the low voltage stress diodes can be used to enhance the circuit performance. Moreover, the active clamp circuits can be employed to recycle the leakage energy and absorb the possible turn-off voltage spikes on the primary power devices. In addition, zero-voltage-switching (ZVS) soft switching operation is achieved for all the active switches during the switching transition. The output diode reverse-recovery problem is alleviated due to the leakage inductance, leading to a great reduction of switching losses. Finally, a 40 V-input 380 V-output 1 kW prototype is built to demonstrate the effectiveness of the theoretical analysis.Keywords:
Voltage doubler
Leakage inductance
Flyback diode
Voltage spike
Peak inverse voltage
Clamper
An active-clamp soft-switching step-up converter with high-voltage gain is proposed. By utilising the active-clamp circuit, the voltages across the power switches in the proposed converter are clamped and the zero-voltage switching of the power switches is achieved. To increase the voltage gain, two voltage doubler rectifiers are connected serially and stacked on top of the clamp capacitor. Therefore high-voltage gain is obtained and soft-switching characteristic is achieved. Also, the voltage stresses of the power switches and the output diodes are effectively reduced. Theoretical analysis and performance of the proposed converter are verified on a 110 W experimental prototype operating at 110 kHz switching frequency.
Voltage doubler
Clamper
Voltage multiplier
Voltage spike
High Voltage
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This paper presents a novel soft-switching bidirectional snubberless current-fed full-bridge voltage doubler. A novel secondary modulation technique is proposed to clamp the voltage across the primary side switches naturally with zero current commutation (ZCC). It, therefore, eliminates the necessity for active-clamping or passive snubbers to absorb the switch turn-off voltage spike, a major challenge in current-fed converters. Zero-current switching (ZCS) of primary side devices and zero-voltage switching (ZVS) of secondary side devices are achieved, which significantly reduce switching losses. Primary device voltage is clamped at low voltage, which enables the use of low voltage devices with low on-state resistance. Soft-switching and voltage-clamping is inherent and load independent. Analysis and design of proposed topology are presented. Simulation results using PSIM 9.0.4 are shown to verify the accuracy of the proposed analysis and design. A 250 W prototype has been tested to validate its performance.
Snubber
Voltage doubler
Commutation
Clamper
Voltage spike
Modulation (music)
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An RCD clamp circuit is usually used in flyback converters, in order to limit the voltage spikes caused by leakage transformer inductance. Oscillation ringing appears due to the clamp diode, which deteriorates the converter's power rate. This brief describes this ringing phenomenon and the use of an RC-RCD clamp circuit for damping the clamp diode's oscillation. This clamp circuit is capable for improving a flyback converter's power ratio.
Ringing
Flyback diode
Voltage spike
Clamper
Clamp
Snubber
Leakage inductance
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This paper introduces a zero voltage switching (ZVS) two-switch flyback pulse-width modulated (PWM) DC-DC converter along with the principle of circuit operation and steady-state analysis. The proposed converter topology is the result of incorporating an auxiliary circuit in place of the clamping diodes on the primary side of the conventional hard- switching two-switch flyback converter, resulting in a soft- switching two-switch flyback converter with reduced switch voltage stresses. The auxiliary circuit is an active-clamp circuit made up of two switches and a clamp capacitor. The active clamp circuit recycles the energy stored in the parasitic transformer leakage inductance, facilitates the ZVS operation of all active switches, and limits the voltage stresses of all the active switches to a value less than or equal to the DC input voltage V I . Circuit description, principle of operation, steady-state analysis, and simulation results of the proposed converter are presented.
Flyback diode
Leakage inductance
Clamper
Voltage spike
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Flyback derived power convertor topologies are attractive because of their relative simplicity when compared with other topologies used in low power applications. Incorporation of active-clamp circuitry into the flyback topology serves to recycle transformer leakage energy while minimizing switch voltage stress. The addition of the active-clamp circuit also provides a mechanism for achieving zero-voltage-switching (ZVS) of both the primary and auxiliary switches. ZVS also limits the turn-off di/dt of the output rectifier, reducing rectifier switching losses, and switching noise due to diode reverse recovery. This paper analyzes the behavior of the ZVS active-clamp flyback operating with unidirectional magnetizing current and presents design equations based on this analysis. Experimental results are then given for a 500 W prototype circuit illustrating the soft-switching characteristics and improved efficiency of the power converter. Results from the application of the active-clamp circuit as a low-loss turn-off snubber for IGBT switches is also presented.
Snubber
Flyback diode
Clamper
Voltage spike
Insulated-gate bipolar transistor
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The system analysis and circuit implementation of an active clamp converter with current doubler rectifier to reduce the voltage stress of the switching device and the current stress of the transformer secondary winding is presented. An active clamp circuit based on one auxiliary switch and one clamp capacitor is used to recycle the energy stored in the transformer leakage in order to minimise the spike voltage at the transformer primary side and reduce the voltage stress of the switching devices. The resonant behaviour, based on the output capacitance and leakage inductance of the transformer during the transition interval between the main and auxiliary switches in the proposed converter, is used to achieve zero voltage switching. Therefore the switching losses of the switching devices are reduced. For the output stage, the current doubler rectifier offers ripple current cancellation at the output capacitor and reduces the current stress of the transformer secondary winding. The winding turns of the current doubler rectifier are also reduced compared with the center-tapped rectifier. The circuit configuration and operating principle of the proposed converter are analysed and discussed. The design considerations of the circuit are presented. Finally experimental results for a 150 W (5 V/30 A) prototype are presented to verify the theoretical analysis and circuit performance.
Voltage doubler
Leakage inductance
Clamper
Voltage spike
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Voltage doubler
Peak inverse voltage
Rectifier (neural networks)
Precision rectifier
Voltage multiplier
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In this paper, a novel active clamp Flyback-Forward converter is proposed for large voltage gain and high power applications. The interleaved configuration on the primary side is employed to handle the large input current. An improved voltage doubler configuration is adopted on the secondary side to make the output diodes sustain only half of the high output voltage. Furthermore, the output diode voltage stress can be auto-balanced due to the inherent series structure of the coupled inductors. Therefore, the low voltage stress diodes can be used to enhance the circuit performance. Moreover, the active clamp circuits can be employed to recycle the leakage energy and absorb the possible turn-off voltage spikes on the primary power devices. In addition, zero-voltage-switching (ZVS) soft switching operation is achieved for all the active switches during the switching transition. The output diode reverse-recovery problem is alleviated due to the leakage inductance, leading to a great reduction of switching losses. Finally, a 40 V-input 380 V-output 1 kW prototype is built to demonstrate the effectiveness of the theoretical analysis.
Voltage doubler
Leakage inductance
Flyback diode
Voltage spike
Peak inverse voltage
Clamper
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Citations (6)
Novel zero-voltage switching(ZVS) flyback-boost converter with a voltage-double rectifier(VDR) has been proposed. By integrating the common part of a flyback converter and a boost converter, the proposed circuit can provide a switch voltage clamping and a high step-up ratio. An auxiliary switch instead of a boost diode enables to turn all switches on under ZVS conditions. The VDR can extend a step-up ratio as well as clamp the voltage of secondary rectifiers. The operational principle and theoretical analysis are presented. Experimental results based on a 42V input, 400V/0.5A output and 50㎑/100㎑ prototype are shown to verify the proposed scheme.
Voltage doubler
Peak inverse voltage
Flyback diode
Rectifier (neural networks)
Buck converter
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A wide range active clamp two-switch converter with current doubler rectifier (CDR) is presented in this paper. An active clamp circuit based on two clamp switches and one clamp capacitor are used to recycle the energy stored in the transformer leakage inductor to minimize the spike voltage at the transformer primary side and reduce the voltage stress of switching devices. The resonant behavior based on the output capacitance and leakage inductance of the transformer during the transition interval between the main and clamp switches in the proposed converter is used to achieve ZVS operation of main switching devices. The duty ratio of main switching devices in the proposed converter can be more than 50% of the conventional forward converter. In the output stage of the proposed converter, the CDR circuit offers the ripple current cancellation at the output capacitor and reduces the current stress of transformer secondary winding. The winding turn of the current doubler rectifier is also reduced compared with the winding turn of the center-tapped rectifier. The circuit configuration and the principle of operation are analyzed and discussed. The design considerations of the proposed converter are provided. Finally, the characteristics of the proposed converter are verified on a 130 V -350 V input and 5 V/20 A output experimental prototype.
Voltage doubler
Leakage inductance
Clamper
Voltage spike
Snubber
Duty cycle
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