Center-tapped Rectifier Research Articles

Analysis and implementation of soft switching converter with series-connected transformers

The system analysis and design consideration of a zero voltage switching (ZVS) converter with series-connected transformers are presested. Based on the operational behaviour, each transformer in the adopted converter can be operated as an inductor or a transformer. Therefore no output filter inductor is needed in the adopted converter. To reduce the voltage stress of the switching device in the conventional forward converter, an active snubber based on a clamp switch and a clamp capacitor is used to recycle the energy stored in the transformer leakage. During the transition interval, the resonance based on the junction capacitance of switches and transformer leakage inductance can achieve ZVS operation of switches. The centre-tapped rectifier is used at the secondary side to achieve full-wave rectification. The operating principles, steady-state analysis and design equations of the proposed converter are provided. Finally, experimental results for a 100 W (5 V/20 A) prototype circuit are provided to verify the converter performance.

Analysis and implementation of ZVS forward converter with centre-tapped rectifier

The system analysis and circuit implementation of a ZVS forward converter with centre-tapped rectifier are presented. To reduce the voltage stress of the active switch in the forward converter, one auxiliary switch and one clamp capacitor are used in the adopted converter to recycle the energy stored in the transformer leakage. The resonant circuit based on the output capacitance of switches and leakage inductance of the transformer will achieve zero-voltage-switching turn-on for both switches in the adopted converter to increase the total circuit efficiency. The centre-tapped rectifier is used at the secondary side to achieve full-wave rectifier. In high output current applications, the synchronous rectifier can be used in the secondary side to further reduce the conduction losses of rectifier diodes. The operating principles of the adopted ZVS forward converter with centre-tapped rectifier are analysed in detail. The design consideration and circuit example of the ZVS forward converter are presented. Finally, experimental results based on a ZVS forward converter with 5 V/16 A output load are provided to verify the effectiveness of the adopted converter compared with the asymmetrical half-bridge converter

Analysis, design and implementation of active clamp zero voltage switching converter with output ripple current cancellation

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

Resonant dc/dc converter with class DE tuned power oscillator

AbstractIn this paper, we propose a new resonant dc/dc converter with a class DE tuned power oscillator and a center‐tapped rectifier. The proposed converter uses a class DE tuned power oscillator as a dc/ac inverter. The MOSFET is used as a switch, which does not require any external drive circuits. Thus, compared to conventional inverters, the proposed circuits is effective in downsizing. Since the proposed circuit satisfies the class E switching operating condition, that is, the switching turns on and off instantaneously at zero voltage and zero slope of the voltage, highly efficient operation is possible at high frequencies. The proposed circuit is analyzed theoretically and is verified experimentally. The measured maximum dc/dc conversion efficiency is 75.8% at 2 MHz and 2.5 W. © 2001 Scripta Technica, Electron Comm Jpn Pt 1, 84(12): 61–69, 2001

Frequency-controlled series-resonant converter with synchronous rectifier

This paper presents an analysis and experimental results for a frequency-controlled series-resonant dc-dc converter that consists of a Class-D zero-voltage-switching (ZVS) series-resonant inverter and a center-tapped synchronous rectifier. If the dc output voltage is low, the efficiency of the converter is dominated by the efficiency of the rectifier. Low on-resistance metal-oxide-semiconductor field-effect transistors (MOSFETs) are used in the rectifier instead of diodes because the forward voltage drop across the rectifying device is low, resulting in a high efficiency. The dc output voltage is regulated against variations in the load resistance and the dc input voltage by varying the operating frequency. Experimental results are presented for a converter with a dc input voltage of 150 V, an output voltage of 5 V, and a dc load resistance ranging from 0.5 to 5.5 R. The measured efficiency was 86% for a 50 W output and 89% for a 25 W output. The theoretical results were in good agreement with the measured results.

Analysis and design of a current-driven two-inductor ZCS low di/sub D//dt full-wave rectifier

An analysis and experimental verification of a current-driven two-inductor zero-current-switching (ZCS) low di/sub D//dt full-wave rectifier are given. The design equations are derived using the time-domain analysis and Fourier series technique. The rectifier operates as a full-wave rectifier with two diodes and a one-secondary winding transformer overcoming the limitations of class D current-driven full-bridge and center-tapped rectifiers and preserving their advantages. The rectifier operates with lower conduction losses than the center tapped rectifier. Moreover, the diodes turn on at zero di/sub D//dt, low d/spl nu//sub D//dt, and turn off at low di/sub D//dt. As a consequence, switching losses are reduced and this rectifier is suitable for a high-frequency and high-efficiency operation. Integrated inductors can be used to reduce the size, volume, and cost of the circuit. A breadboard of the rectifier was designed and tested for a constant output voltage V/sub 0/=12 V, and an output current I/sub 0/ ranging from no-load to 12 A. The rectifier was driven by an off-line AC-AC converter operated at an input r.m.s. voltage varying from 176-270 V and a minimum frequency of 550 kHz. The predicted results are in good agreement with those measured. A full-load efficiency of 89.4% was achieved for the entire AC-DC converter.

Class D current-driven transformer center-tapped controllable synchronous rectifier

We present analysis and experimental results for a phase-controlled, synchronous, transformer center-tapped rectifier. The rectifier is driven by a resonant inverter. A digital control adjusts the phase in the driver of the rectifier MOSFET's. The output voltage is regulated while maintaining a 94% maximum and a 80% minimum efficiency for a 30% line swing, and 50% efficiency for a load swing of 400% from full power. Experimental results are presented for a 10 W rectifier with an output voltage of 3.3 V. Theoretical calculations agreed well with the experimental results, with certain deviations due to the nonidealities of the transformer. The center-tapped topology allows for high efficiency even at 3.3 V and simplifies the control design, providing simple regulation.

Phase-controlled series-parallel resonant converter

A constant-frequency, phase-controlled, series-parallel resonant DC-DC converter is introduced, analyzed in the frequency domain, and experimentally verified. To obtain the DC-DC converter, two identical series-parallel resonant inverters are paralleled and the resulting phase-controlled resonant inverter is loaded by a voltage-driven rectifier. The converter can regulate the output voltage at a constant switching frequency in the range of load resistance from full-load resistance to infinity while maintaining good part-load efficiency. The efficiency of the converter is almost independent of the input voltage. For switching frequencies slightly above the resonant frequency, power switches are always inductively loaded, which is very advantageous if MOSFETs are used as switches. Experimentally results are given for a converter with a center-tapped rectifier at an output power of 52 W and a switching frequency of 127 kHz. The measured current imbalance between the two inverters was as low as 1.2:1. >

Single-capacitor phase-controlled series resonant converter

A new phase-controlled series resonant, DC/DC converter is described, analyzed, and experimentally verified. The circuit comprises a phase-controlled inverter and a Class D current-driven rectifier. The phase-controlled inverter consists of two switching legs, two resonant inductors, and a single resonant capacitor connected in series with an AC load. The phase shift between the voltages that drive the MOSFETs is varied to control the AC current of the inverter and thereby regulate the DC output voltage of the converter. A frequency-domain analysis is used to derive basic equations which govern the circuit operation. An important advantage of the converter is that the operating frequency can be maintained constant. For operation at a switching frequency greater than 1.15 resonant frequency, the load of each switching leg is inductive. The proposed converter has an excellent full-load and part-load efficiency. An experimental prototype of the converter with a center-tapped rectifier was built and extensively tested at an output power of 78 W and a switching frequency of 200 kHz. The theoretical and experimental results were in good agreement. >

Class E DC/DC converters with an inductive impedance inverter

The analysis, design equations, and experimental verification are presented for a class E DC/DC switching-mode high-efficiency resonant DC/DC converter with a transformer center-tapped rectifier. The analysis is performed at a constant current through the DC-feed choke and using the high Q/sub 1/ assumption (Q/sub 1/>or=5). The converter can operate under safe conditions for load resistances ranging from a full load to an open circuit. This feature has been obtained by using an inductive impedance inverter. The results of the analysis are then generalized for the entire family of class E DC/DC converters. Experimental results show good agreement with the theoretical predictions. The measured total efficiency was 89% at 1 MHz with 15 W output power. A narrowband FM regulation ( delta f/f=12%) of the DC output voltage was achieved as the load was varied from a minimum resistance (full load) to an open circuit. >