class-E Rectifier Research Articles

Design and validation of a DC–DC converter-based inductive power transfer system with increased efficiency and reduced voltage stress across switches

Research in wireless power transfer(WPT) focuses on improving efficiency, reducing energy consumption, improving safety, and increasing sustainability. It prioritises developing more efficient transmission technologies, such as high-frequency switching and resonant coupling, to enhance the system’s overall performance. However, high voltage stress across the semiconductor devices during switching operations at high frequencies can result in increased switching loss, leading to decreased overall efficiency of the WPT system. The switching loss can be minimised by reducing voltage stress, resulting in higher efficiency and improved energy transfer performance. This leads to more cost-effective WPT solutions without compromising performance or reliability by using lower-rated components and reducing the need for elaborate voltage clamping and protection circuits. Lowering voltage stress across switches can also help WPT systems comply with industry standards and regulations related to electrical safety, electromagnetic compatibility (EMC), and energy efficiency. Meeting these standards is essential for ensuring the widespread adoption and commercial success of WPT technology. In this article, a class ø2 inverter and a modified class-E rectifier is integrated and applied in a WPT system. The benefits of a Resonant class ø2 inverter are zero voltage switching(ZVS) and lower switch voltage stress as compared to its predecessors. Also, a resonant class E/F3 rectifier inductively coupled in the receiving stage reduces the peak voltage stress across the diode. The system shown here is tuned to achieve maximum overall transfer efficiency. The proposed class ø2-E/F3 combined WPT system operating at 50 kHz simulated in PSIM software yielded a dc-dc efficiency of 94.56 percent, and the peak voltage stress across switches is found to reduced (2.4–2.7 times the input voltage as compared to the existing topologies where it surges upto 3.6–4 times the input voltage). These are also validated in Typhoon HIL’s Real-Time Emulator HIL402. In addition to that, a machine learning algorithm based on an Artificial Neural Network is used to generate a model to predict the switching frequency for a specified output voltage and efficiency.

Analysis and Design of a Self-Resonant Rectenna for Small-Size and Ultraloosely Coupled MHz Wireless Power Transfer Applications

Wireless power transfer (WPT) working at multimegahertz is widely considered a promising technology for a more compact and lighter system. Thanks to these features, the small-size megahertz (MHz) WPT systems are desired for the portable or implantable electronic devices. This article proposed a self-resonant rectenna for small-size and ultraloosely coupled MHz WPT applications. Different from the receiver using the Class-E rectifier, the rectenna can achieve the self-resonant operation without additional series compensation capacitor and bulky inductor, which helps to minimize the components count and receiver size. By the self-resonant operation and the corresponding design method, the rectenna also helps to achieve the high efficiency for the small-size MHz WPT systems when working at ultraloosely coupled conditions. A prototype of the self-resonant rectenna is built and tested in an example 6.78-MHz WPT system. The misalignment and the transfer distance of the prototype are up to 35 and 10 mm when the rectenna diameter is only 10 mm. The experimental results show that the self-resonant rectenna-based WPT system can achieve up to 21% dc–dc efficiency and 1.05-W output power when the mutual inductance coefficient <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$k$</tex-math></inline-formula> is ranging from 0.009 to 0.038, namely the ultraloosely coupled condition. In the same working condition, the traditional single-diode rectenna-based WPT system can only deliver 0.18-W output power with a 4.3% dc–dc efficiency.

Modelling and Compensation Design of Class-E Rectifier for Near-Resistive Impedance in High-Frequency Power Conversion

This article presents the investigation of circuit modelling, design, and optimization of the class-E rectifier to achieve a near-resistive impedance during a large load-range. Based on circuit modelling and impedance depiction, a circuit design concept of impedance compensation to achieve near-resistive impedance is proposed, and we selected the series inductor as the compensation network for class-E rectifiers. After an optimized design, a 6.78-MHz wireless power transfer prototype was built with applying the proposed concept and tested. The experimental results match well with the circuit modelling and validate the impedance shift can be optimized by the proposed circuit design concept. The experimental prototype achieves 87.2% dc-dc efficiency at the rated 220-W output and the phase angle shift is lower than 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> during the load decreasing from 220-W rated output to the 40-W light-load output. We also discuss the circuit design considerations and the hardware implementation of the prototype for the proposed design concept.

Analysis and design of generalized class-E rectifier

Analysis and design of generalized class-E rectifier

A Prototype Based on Sensors with Power Factor Correction Rectification for Light Emitting Diode Street Lighting Systems

This paper introduced new topology of sensors signal based power factor correction for street lighting systems. This class-E rectifier based on zero-current switching, to increase the bridge diode current and reduced the current harmonics, furthermore the proposed converter reduced switching losses and its noise are also reduced by this proposed system. And important of the sensor-based this system used LDR sensor and a touch sensor that type of sensors used for street lighting systems. This proposed prototype topology has the minimum requirement of passive components and power switches, it has high power factor. Finally, Simple prototype hardware tested and verified.

Design Method of Self-Driving RF-DC Rectifier Based on Waveform-Guided Solutions to Passive Matching Network

The design of a self-driving RF-DC rectifier needs to synchronize the gate driving and RF power input. A waveform-based design method is proposed in this paper to get this synchronization through a direct network-parameter calculation of the coupling and matching circuit, other than introducing an adjustable phase shifter on its dual power amplifier prototype. In order to get a practical design at microwave band, nonlinear feedback capacitances, package parasitics, and device's I-V curves are considered in the large-signal RF-DC rectifier circuit analysis. The external passive matching network characterized by its Z -parameters can be determined in order to realize a specific high-efficiency operation mode, which is quantified by waveform distance. An RF-DC class-E rectifier example at 2.8 GHz is given to demonstrate this design method based on a modified GaN device model including negative drain voltages. Rectification efficiency of 70.8% is measured for a 10 W input power at 2.8 GHz.

Duty Cycle and Frequency Modulations in Class-E DC–DC Converters for a Wide Range of Input and Output Voltages

We present an operation scheme for a dc–dc converter consisting of a class-E inverter and a class-E rectifier to always achieve zero-voltage zero- $dv\text{/}dt$ switching at a wide range of input and output voltages. To cope with the high sensitivity due to load variations, previous approaches either forgo the zero- $dv\text{/}dt$ turn- on switching conditions or required additional components and topological changes. Instead, the proposed strategy modulates the duty cycles and switching frequencies depending on the input and output voltages to always achieve zero- $dv\text{/}dt$ turn- on switching and, thus, minimizes switching losses, while preserving the structural simplicity of the converter. Experiments demonstrate the prototype converter maintaining the desired soft-switching condition under 80–200-V input voltage and 5–20-V output voltage variations. In an additional prototype, we implemented a similar design with synchronous rectification that achieves a peak efficiency of 92.3% at an input voltage of 80 V, an output voltage of 12 V, and an output power of 26.9 W.

A Single-Stage LED Driver Based on ZCDS Class-E Current-Driven Rectifier as a PFC for Street-Lighting Applications

This paper presents a light-emitting diode (LED) driver for street-lighting applications that uses a resonant rectifier as a power-factor corrector (PFC). The PFC semistage is based on a zero-current and zero-derivative-switching (ZCDS) Class-E current-driven rectifier, and the LED driver semistage is based on a zero-voltage-switching (ZVS) Class-D LLC resonant converter that is integrated into a single-stage topology. To increase the conduction angle of the bridge-rectifier diodes current and to decrease the current harmonics that are injected in the utility line, the ZCDS Class-E rectifier is placed between the bridge-rectifier and a dc-link capacitor. The ZCDS Class-E rectifier is driven by a high-frequency current source, which is obtained from a square-wave output voltage of the ZVS Class-D LLC resonant converter using a matching network. Additionally, the proposed converter has a soft-switching characteristic that reduces switching losses and switching noise. A prototype for a 150-W LED street light has been developed and tested to evaluate the performance of the proposed approach. The proposed LED driver had a high efficiency (>91%), a high PF (>0.99), and a low total harmonic distortion (THD $_{i}$ ${{V}}_{{\rm{rms}}}$ . These experimental results demonstrate the feasibility of the proposed LED scheme.

Class-E Rectifiers and Power Converters: The Operation of the Class-E Topology as a Power Amplifier and a Rectifier with Very High Conversion Efficiencies

In the late 1970s, interest in reducing the value and size of reactive components motivated power supply specialists to operate dc-to-dc converters at hundreds of kilohertz or even megahertz frequencies. Passive energy storage (mainly magnetics) is the dominant factor in the size of power electronics and also limits its cost, reliability, and dynamic response. With the goals of miniaturization and improved control bandwidth, researchers had to face the frequency-dependent turn-on and turn-off losses associated with the use of rectangular waveforms in the hard-switched topologies of that time. Similar to approaches for RF/microwave power amplifiers (PAs), the introduction of resonant circuits allowed shaping either a sinusoidal voltage or current, with parasitic reactive elements absorbed by the topology in the neighborhood of the switching frequency. The resulting resonant power converters, obtained by cascading a dc-to-ac resonant inverter with a high-frequency rectifier, first transform the dc input power into controlled ac power and then convert it back into the desired dc output [1].

Class-E Half-Wave Zero dv/dt Rectifiers for Inductive Power Transfer

This paper analyses and compares candidate zero dv / dt half-wave Class-E rectifier topologies for integration into multi-MHz inductive power transfer (IPT) systems. Furthermore, a hybrid Class-E topology comprising advantageous properties from all existing Class-E half-wave zero dv / dt rectifiers is analyzed for the first time. From the analysis, it is shown that the hybrid Class-E rectifier provides an extra degree of design freedom that enables optimal IPT operation over a wider range of operating conditions. Furthermore, it is shown that by designing both the hybrid and the current-driven rectifiers to operate below resonance provides a low deviation input reactance and inherent output voltage regulation with duty cycle allowing efficient IPT operation over wider dc load range than would otherwise be achieved. A set of case studies demonstrated the following performances: First, for a constant dc load resistance, a receiving end efficiency of 95% was achieved when utilizing the hybrid rectifier, with a tolerance in required input resistance of 2.4% over the tested output power range (50–200 W). Second, for a variable dc load in the range of 100–10%, the hybrid and current-driven rectifiers presented an input reactance deviation less than 2% of the impedance of the magnetizing inductance of the inductive link respectively and receiving end efficiencies greater than 90%. Third, for a constant current in the receiving coil, both the hybrid and the current-driven rectifier achieve inherent output voltage regulation in the order of 3% and 8% of the nominal value, respectively, for a variable dc load range from 100% to 10%.

A 2.4-GHz CMOS Class-E Synchronous Rectifier

A class-E synchronous rectifier has been designed and implemented using 0.13- $\mu {\text {m}}$ CMOS technology. A design methodology based on the theory of time-reversal duality has been used where a class-E amplifier circuit is transformed into a class-E rectifier circuit. The methodology is distinctly different from other CMOS RF rectifier designs which use voltage multiplier techniques. Power losses in the rectifier are analyzed including saturation resistance in the switch, inductor losses, and current/voltage overlap losses. The rectifier circuit includes a 50- $\Omega $ single-ended RF input port with on-chip matching. The circuit is self-biased and completely powered from the RF input signal. Experimental results for the rectifier show a peak RF-to-dc conversion efficiency of 30% measured at a frequency of 2.4 GHz.

Transmission Line Resistance Compression Networks and Applications to Wireless Power Transfer

Microwave-to-dc rectification is valuable in many applications, including RF energy recovery, dc–dc conversion, and wireless power transfer. In such applications, it is desired for the microwave rectifier system to provide a constant RF input impedance. Consequently, variation in rectifier input impedance over varying incident power levels can hurt system performance. To address this challenge, we introduce multiway transmission line resistance compression networks (TLRCNs) for maintaining near-constant input impedance in RF-to-dc rectifier systems. A development of TLRCNs is presented, along with their application to RF-to-dc conversion and wireless power transfer. We derive analytical expressions for the behavior of TLRCNs, and describe two design methodologies applicable to both single and multistage implementations. A 2.45-GHz four-way TLRCN network is implemented and applied to create a 4-W resistance compressed rectifier system that has narrow-range resistive input characteristics over a 10-dB power range. It is demonstrated to improve the impedance match to mostly resistive but variable input impedance class-E rectifiers over a 10-dB power range. The resulting TLRCN plus rectifier system has >50% RF-to-dc conversion efficiency over a >10-dB input power range at 2.45 GHz (peak efficiency 70%), and standing wave ratio <1.1 over a 7.7-dB range, despite a nonnegligible reactive component in the rectifier loads.

Analysis of a Broadband High-Efficiency Switch-Mode $\Delta \Sigma $ Supply Modulator Based on a Class-E Amplifier and a Class-E Rectifier

<?Pub Dtl=""?> In this paper, a broadband high-efficiency supply modulator is proposed. This modulator, with a node controlled by <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$\Delta \Sigma $</tex></formula> modulator's output, consists of a conventional Class-E amplifier and a Class-E rectifier. The configurations and operation principles of this modulator are introduced to explain the envelope reconstruction process. The performance of this modulator in steady state is analyzed to show the reason for high-efficiency operations assisted by a shunt diode, especially for short-circuited load resistance. Its performance for broadband envelopes amplification is analyzed using numerical difference equations. The results show that efficiency degradation and nonlinearity of this modulator are inevitable due to transient responses. The most significant factors related to the performance degradation, such as switch loss and conduction loss, are determined and verified by numerical simulations. The simulations for one-carrier wavelength code-division multiple-access (WCDMA) envelopes show that over 80% average efficiency and normalized mean square error (NMSE) of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$-\hbox{16 dB}$</tex> </formula> can be obtained in numerical examples even considering the nonidealities. An experimental supply modulator is given to verify the proposed modulator. In this experiment, 48.6% average efficiency and NMSE of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$-\hbox{15.9 dB}$</tex></formula> are measured for WCDMA envelopes of 6.1-dB peak-to-average-power ratio.

An RF–DC Converter with Wide-Dynamic-Range Input Matching for Power Recovery Applications

An improved RF-dc converter based on a class-E rectifier with wide-dynamic-range input matching is presented. The input impedance is controlled by two varactor diodes to compensate for impedance changes with RF input power and dc loading conditions. The RF-dc converter achieved a peak efficiency of 60% and an <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> less than - 20 dB over an input RF power range of 12 dB and an operating battery voltage of 2.5-4.2 V at 800 MHz. An analytical model for input impedance and efficiency was developed and shown to match simulation and measurement results.

Resonant DC&amp;#8211;DC Converter With Class-E Oscillator

This paper presents a new free-running-oscillation resonant DC-DC converter with the Class-E oscillator and the Class-E rectifier, along with its design procedure and design curves for any conditions. The proposed converter is a free-running-oscillation system and has no gate-drive circuit to drive the MOSFET. Therefore, the structure of the proposed converter is simpler than that of class E2 dc-dc converter. The proposed converter is suitable for a constant voltage and constant power operation under the fixed designed condition. The proposed converter has the ability to achieve a high power-conversion efficiency and low noises under high-frequency operation because of Class-E switching at both the oscillator and the rectifier. We investigate operations of the proposed converter by circuit experiments and show the validity of the design curves. This paper denotes two experimental results. One achieves 79.3% power-conversion efficiency under 1.54-W output power at an operating frequency 2.00 MHz. The other does 80.5% under 1.60-W output power at an operating frequency 1.98 MHz

Phase control for resonant DC-DC converter with class-DE inverter and class-E rectifier

In this paper, a phase control scheme for Class-DE-E dc-dc converter is proposed and its performance is clarified. The proposed circuit is composed of phase-controlled Class-DE inverter and Class-E rectifier. The proposed circuit achieves the fixed frequency control without frequency harmonics lower than the switching frequency. Moreover, it is possible to achieve the continuous control in a wide range of the line and load variations. The output voltage decreases in proportion to the increase of the phase shift. The proposed converter keeps the advantages of Class-DE-E dc-dc converter, namely, a high power conversion efficiency under a high-frequency operation and low switch-voltage stress. Especially, high power conversion efficiency can be kept for narrow range control. We present numerical calculations for the design and the numerical analyses to clarify the characteristics of the proposed control. By carrying out circuit experiments, we show a quantitative similarity between the numerical predictions and the experimental results. In our experiments, the measured efficiency is over 84% with 2.5 W output power for 1.0-MHz operating frequency at the nominal operation. Moreover, the output voltage is regulated from 100% to 39%, keeping over 57% power conversion efficiency by using the proposed control scheme.

Single-stage electronic ballast with class-E rectifier as power-factor corrector

A single-stage high-power-factor electronic ballast with a Class-E rectifier as a power-factor corrector is proposed. A Class-E rectifier is inserted between the front-end bridge rectifier and the bulk filter capacitor to increase the conduction angle of the bridge-rectifier diode current for obtaining low line-current harmonics. The Class-E rectifier is driven by a high-frequency sinusoidal current source, which is obtained from the square-wave output voltage of the Class-D inverter through an LC series resonant circuit. A high-frequency transformer is used for impedance matching. The experimental results for a 32-W prototype ballast are given. The switching frequency was 61.3 kHz. At full power, the power factor was 0.992 and the total ballast efficiency was 88.3%. The lamp-current crest factor was about 1.36. The simulated and experimental results were in very good agreement.

Class-E rectifier using thinned-out method

A new control method of a class-E rectifier is presented, which regulates the output voltage or power with elimination of the voltage pulse of the rectifier at a constant rate. When the class-E rectifier controlled by this method is used in a class-E DC/DC power converter, both the inverter and rectifier operate under zero-voltage-switching conditions. Since the rectifier is controlled by a synchronized switch, it achieves the following advantages: (1) power efficiency for low-output voltage is improved; (2) output voltage and power are controllable at a fixed operating frequency; and (3) switching noise can be reduced. Additionally, this method is suitable for applications in which the output voltage or power are changed immediately because the output voltage and power are controlled by means of replacements of pulse patterns. The output characteristics of the rectifier are analyzed under a condition that the amplitude of the input current is constant. Experimental results show good agreement with the theoretical results.

Class E low dv/dt synchronous rectifier with controlled duty ratio and output voltage

A class-E high-frequency low-dv/dt synchronous rectifier/DC regulator is analyzed. The circuit is derived from a class-E rectifier by replacing a diode with a controllable switch. It can then both rectify and regulate the rectified output against variations in DC load and amplitude of the AC input voltage. The switch consists of a transistor and an antiparallel diode or a series diode. The DC output voltage of the rectifier is regulated by varying the ON duty ratio of the switch. The AC input voltage can be at a constant or varying frequency. The controllable switch turns on and off at zero voltage with low dv/dt, reducing switching losses, stresses, and noise. Equations governing the circuit operation are derived. Experimental results at 0.5 MHz were in good agreement with the theoretical predictions. The rectifier can be used in high-frequency-power-density multiple-output power supplies, all of whose outputs are regulated. The frequency need not be varied to regulate the DC output.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Analysis and design of class-E/sup 2/ DC/DC converter

A family of class-E/sup 2/ DC/DC power converters is introduced. Their analysis and design are presented and experimentally verified. The converters are composed of class-E inverters and class-E rectifiers. Zero-voltage switching (with low dv/dt) of the transistor and zero-current switching (with low di/dt) of the rectifier diode reduce switching losses in both stages of the converters, making them especially suitable for high-frequency operation. Because of the high loaded quality factor of the resonant circuit, the range of frequency required for output-voltage regulation is as narrow as 5.46% for load resistances from a full load of 100 Omega to an open circuit. The full-load overall efficiency is 80.36% at 1 MHz. The converters can also operate at a fixed frequency if synchronous rectifiers are applied. The reduction of class-E/sup 2/ converters to lower order converters is presented. Many multiresonant converter topologies are created in this way. The class-E/sup 2/ converters can be utilized to build highly efficient high-power-density switching power supplies.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>