This paper proposes a capacitive power transfer (CPT) system to supply power to multiple loads, which uses a Class-E inverter as the power transmission unit. The proposed system has a relay unit consisting of compensating inductors, a compensating capacitor, and two CPT coupling units to provide a constant voltage (CV) output to multiple loads simultaneously. In addition, ZVS is achieved by using a Class-E inverter to reduce switching losses. Simulation and circuit experiments were performed. From the results of the experiment, the measured total output power of two loads was 0.40 W with the power conversion efficiency of 86.8% at frequency of 1 MHz.

In this research, we propose a variable-gain load-independent class-E rectifier with fixed input reactance for wireless power transfer (WPT) system. Featuring an adjusting network, the proposed rectifier can adjust its voltage gain to maintain a constant output voltage against load variations and coil misalignment, eliminating the need for additional regulators. Based on equations derived from circuit analysis, we present a design method to achieve the zero-voltage switching (ZVS) condition, ensuring high efficiency even at multi-MHz frequencies. Additionally, the input reactance of the proposed rectifier remains fixed, which is beneficial for maintaining ZVS of the inverter. To validate the design method, a WPT system at 6.78 MHz was built. The experimental results confirmed the successful voltage-gain adjustment to compensate for coil misalignment. Furthermore, load-independent ZVS and fixed input reactance were achieved, demonstrating the effectiveness of the proposed rectifier.

This paper proposes a new capacitive isolated inverter in which the output end of the load independent class E-1inverter with shunt capacitance is isolated by two capacitors. This circuit has the advantage of maintaining Zero-Voltage Switching (ZVS) and the constant amplitude of the output voltage over a wide range of the load resistance. In this paper, we introduce the configuration and the theoretical operation of the proposed circuit. Then, the equivalent circuit transformation is shown, and based on it, the designing method is described in detail. A prototype circuit was built and tested under the specifications of the output power 2.00 W, the operating frequency 2.00 MHz, and the rated load resistance$\mathbf{100}\ \Omega$. The circuit operation maintaining ZVS and the constant output voltage amplitude against the load resistance variation were confirmed.

This paper proposes a HERIC based transformerless inverter for grid connected PV system. The proposed circuit consists of a symmetrical boost chopper and a HERIC inverter. The common mode voltage, therefore, is always kept at a constant value, and hence the proposed circuit can reduce the leakage current. Furthermore, a partial sinewave tracking dual mode control is adopted. The symmetrical boost chopper operates only when a boost operation is required. Compared to the conventional PV inverter, which always operates the boost chopper at high frequency, the proposed circuit reduces the switching loss. This paper shows the operation principle, theoretical equations for common mode voltage, and the experimental results.

A new Class E oscillator is proposed. The proposed circuit is based on the voltage-source parallel resonant Class E inverter, which has a parallel resonant tank and no choke inductor or dc blocking capacitor. The proposed oscillator was designed and built using 2SJ681 Pch MOSFET. An experimental circuit oscillated at 786.4 kHz with the output power 1.056W, and the dc to ac power conversion efficiency was 89.49%.

This paper proposes a common ground five-level inverter using switched capacitor. The main features of the proposed inverter are the common ground structure, multilevel output, and step-up input voltage. Because of the common ground structure, it can eliminate leakage current. Therefore, it is expected to operate more safely and enhance power conversion efficiency. Furthermore, a multilevel topology reduces the device voltage stresses and improves quality of the output voltage which downsizes the output filter. Also, switched capacitor structure boosts input voltage without using magnetic elements. In this paper, operation principle, modes of proposed inverter are described and its operation is validated by a small-scale circuit experiment.

This paper proposes a voltage-source parallel resonant Class DE inverter with shunt capacitor. The proposed inverter achieves both zero voltage switching (ZVS) and zero voltage derivative switching (ZVDS) conditions. Thus, the proposed circuit archives high power conversion efficiency under high operating frequency. The proposed circuit has shunt capacitors in parallel to the switching devices, which reduce the influence of parasitic capacitance with the switching devices. The property of achieving ZVS as the resistance value increases is suitable for the application such as the battery charge. Also, the voltage stress on switching devices is limited to the input voltage. This paper shows the theoretical equations, design equations, simulation waveforms, and experimental results. A theoretical waveform, simulation, and circuit experiments were matched well. Measured power conversion efficiency was 92.4 % at the switching frequency 1.00 MHz and the output power 1.59 W.

Two-stage interleaved dc-dc converter with input-parallel output-series connection is proposed. The proposed circuit has a cascaded configuration composed of an interleaved boost converter with input-parallel output-series connection (IBCIPOS) and a three-level boost (TLB) converter. Thus, the voltage conversion ratio of the proposed converter is high and the voltage stress of the semiconductor devices is low. Furthermore, by fixing the duty ratio of the IBCIPOS stage at 0.5, the input current ripple becomes theoretically zero, which reduces input capacitance. Circuit operation of the proposed circuit has been confirmed in reduced scale circuit experiment.

This paper proposes a class D series-resonant DC/DC converter using switch-controlled capacitor (SCC) with ON-OFF feedback control. The proposed class D inverter can control the output voltage by using the ON-OFF control in the switch-controlled capacitor. Impedance variation owing to the SCC maintains the output voltage at a constant value when load fluctuation occurs at a fixed switching frequency. The SCC is turned on when the voltage difference between the two capacitors becomes zero to prevent inrush current between the capacitors. This paper also provides a design example of the proposed class D series-resonant DC/DC converter using switch-controlled capacitor with feedback control. Experimental results show the proposed method can control the output voltage between 6.08 V and 7.43 V. It is also confirmed that the proposed ON-OFF feedback control kept the constant output voltage after a 20% load fluctuation. The experimental results verify the relevance of the proposed method.

A thermoelectric generator (TEG) which generates electric power from the temperature difference is expected to be applied to a wireless sensor node as a power source. This study proposes a wireless sensor node driving system using thermoelectric energy harvesting, which is composed of a bridgeless boost rectifier, a self-start-up circuit, and a control circuit. The bridgeless boost rectifier accepts bipolar output voltage of the TEG, and a maximum power point tracking (MPPT) operation is available. The proposed system starts autonomously at a low output voltage of the TEG regardless of the polarity of the TEG, then switched to the normal operation mode with MPPT. The system operation has been confirmed in circuit experiments.

A half-wave Class DE low dvldt rectifier using common-grounded controlled shunt capacitor (CSC) is proposed. Since all switches are common-grounded, no high side gate driver is needed. In addition, using the proposed design approach, more number of outputs can be obtained than conventional design method. A prototype circuit with three CSCs was designed, analyzed, built, and experimented. In the experimental results, 12.1 V, 5.82 V, 3.81 V, 2.80 V, 1.72 V, 1.38 V, 1.14 V, and 0.956 V were obtained by variation of CSCs.

In this paper, a single-input dual-output rectifier for piezoelectric energy harvesting is proposed. An energy harvester often needs to feed multiple devices. The proposed rectifier provides dual outputs and the number of circuit components in the current path is reduced compared with conventional circuits. Furthermore, with this rectifier, the internal capacitance of the piezoelectric element is charged in a shorter time, which results in higher output power. Experimental results show that the proposed circuit increases the output power up to 114 % of the conventional one.

This paper proposes full-wave voltage doubling type series-synchronized switch harvesting on inductor (S-SSHI) circuit for piezoelectric energy harvesting. A conventional circuit is composed of a full-bridge rectifier circuit and SSHI circuit to increase the output power. In the proposed circuit, a full-wave voltage doubling rectifier is chosen and the SSHI circuit is included in the rectifier circuit. Therefore, number of diodes and conduction losses of the diodes become smaller than the conventional circuit. Thereby, the maximum output power of the proposed circuit is larger than the conventional circuit, which has been confirmed in the simulation and in the experiment. In the experiment, the maximum output power with the PEH in the proposed circuit was 3.63 times larger than that in the conventional circuit.

This paper proposes a current-source parallel resonant Class E inverter with low peak switch current. The proposed circuit consists of two switches, a parallel resonant circuit, a capacitor, an inductor, a choke inductor, and a DC voltage source. The peak current flowing through the switches is no more than the input current, which reduces the current stress of the switching devices. Zero-voltage switching (ZVS) and zero-voltage derivative switching (ZVDS) are maintained, therefore, high power conversion efficiency is achieved under high operating frequency. Moreover, both the source pins of the switches are grounded, so that no complex gate drive circuit is needed. A circuit analysis, simulation, and circuit experiment were carried out. The simulation results and the experimental results were in good agreement. Measured power conversion efficiency was over 91.3 % with the output power 2.6 W and the input voltage 10 V at the operating frequency 500 kHz.

In recent years, thermoelectric generator (TEG) is expected as a power supply source for wireless sensor nodes. An open circuit voltage of TEG is proportional to a temperature difference between each side of TEG. TEG has a maximum power point (MPP) because of the large internal resistance. Therefore, maximum power point tracking (MPPT) control is needed to track the MPP against temperature variation. Temperature difference between a room and outside air changes depending on the season and time. Therefore, polarity of output voltage of TEG can be reversed. This paper proposes a thermoelectric power generation system which is composed of a bridgeless boost/buck-boost rectifier and a microcontroller. The bridgeless boost/buck-boost rectifier is used as a bipolar input DC-DC converter. The MPPT algorithm based on the open circuit voltage method is installed. The circuit operation has been confirmed by circuit experiment.

Energy storage cells have been widely used in many applications. Depending on the application, energy storage cells are connected in series to match the voltage requirement. Each the energy storage cell has individual differences such as internal impedance and self-discharging, which cause cell voltage imbalance. This paper proposes a switched capacitor voltage equalizer. The proposed equalizer combines a double-tiered switched capacitor voltage equalizer with a modularized switched capacitor voltage equalizer. The time to make the cell voltages equal of the proposed equalizer is less affected by the voltage difference than either that of the double-tired switched capacitor voltage equalizer or that of the modularized switched capacitor voltage equalizer. The simulation and the circuit experiments are presented.

A new hybrid nine-level inverter with small number of components is proposed. Applying series/parallel conversion technique used in switched capacitors, the proposed inverter outputs a nine-level voltage waveform. The capacitor voltages are self-balanced without any voltage sensors or complex controls. The circuit configuration, the operation principle, the modulation method, and the simulation and experimental results are indicated. The results of the simulation and the experiment are well agreed with the theory.

An ac/dc power conversion using Class DE voltage driven low dv/dt rectifier can perform in high efficiency by satisfying switching conditions zero-voltage-derivative-switching and zero-voltage-switching when the diodes turn off. The output voltage of the Class DE voltage driven low dv/dt rectifier is determined by the capacitance when the load resistance and the input voltage are fixed. In this paper, the Class DE voltage driven low dv/dt rectifier with switch-controlled capacitor (SCC) is proposed. The proposed circuit is composed of the Class DE voltage driven low dv/dt rectifier and SCC which is a series circuit of an active switch and a capacitor. The output voltage is variable by changing the states of the active switches. In the circuit experiments, the output voltage was regulated from 2.92 V to 4.88 V at the four steps.

This paper proposes a bridgeless buck AC-DC converter for piezoelectric energy harvesting. A conventional circuit for this purpose consists of a full-bridge rectifier and a buck converter. The proposed circuit has the same functions as the conventional one and achieves better efficiency. In the circuit, the internal capacitance of the piezoelectric element and inductors used for the step-down operation form a resonant circuit, which plays a central role for reducing energy losses. Our experimental results show that the maximum output power of the proposed circuit is about 1.5 times higher than that of the conventional one.

This paper proposes a new structure of cell voltage equalizer combining two conventional circuits, a chain structure of switched capacitor and a modularized switched capacitor. The equalization time and efficiency of the proposed circuit are less affected by the initial voltage variation. Also, a new structure of a bidirectional switch is proposed, which reduces 3N/2 MOSFETs with driving circuit in N-cell string. Characteristics of the equalization performance with two conventional structures and with two proposed ones are compared in simulation and circuit experiment.

In this paper, the ripple free operating method of two-stage boost type dc-dc converter is proposed which is suitable for PV and fuel cell systems. The ripple free two-stage boost type dc-dc converter (RFTSBC) is composed of a conventional interleaved boost converter and a cascade boost type chopper. The primary stage is driven at a fixed duty ratio to make the input current ripple of the RFTSBC close to zero. The second stage moreover boosts the voltage, and controls the output voltage. In addition, the two inductors in the primary stage can be miniaturized within continuous current mode (CCM) by adjusting the switching frequency. As a result, the equivalent series resistance (ESR) of the inductors in the primary stage can be reduced. The operation of the RFTSBC has been confirmed by reduced scale circuit experiment.

Vibration energy harvesting is attracting attention as a driving power supply for wireless sensor nodes. Piezoelectric elements are used for piezoelectric energy harvesting (PEH). Because piezoelectric elements provide AC power, a full bridge rectifier is used to obtain DC power. However, a parasitic capacitor of the piezoelectric elements causes a power loss in conventional PEH circuits. Synchronized switch harvesting on inductor (SSHI) circuit was proposed in order to solve this problem. Output power of a rectifier used in a PEH circuit has a maximum power point (MPP). The MPP varies with the amplitude and the frequency of the vibration. Therefore, the maximum power point tracking (MPPT) control is needed. The open circuit voltage method is commonly used as the MPPT algorithm for PEH circuits, even if it takes a long time, of which the output voltage reaches the open circuit voltage in a SSHI circuit. In this study, low-capacitance filter capacitors are used to reduce the time to reach the open circuit voltage of a SSHI circuit. Thereby, the SSHI circuit is operated by the MPPT algorithm based on the open circuit voltage method. The circuit operation was confirmed by simulations and circuit experiments.

A new type of Class DE inverter is proposed. The proposed circuit consists of two switches, a parallel resonant circuit, and a capacitor connected in series with the parallel resonant circuit. The proposed circuit shows two features mainly. First, the voltage stress of the switching devices is low. Second, the switch voltage and its derivative are zero at the switch turning on, therefore, the proposed circuit reduces switching losses. In the circuit experiments of the proposed circuit, the measured efficiency of the dc/ac power conversion was 93.2 % at the loaded quality factor Q = 5, the switching frequency 500 kHz, and the output power 0.336 W. The experimental results show good agreement with the theoretical performance.

The dc-dc converters which are suitable for the fuel cell need high boost ability, low input current ripple, and small size. As one of the dc-dc converters having the three characteristics, interleaved soft-switching multilevel boost converter is proposed. This circuit is composed of two multilevel boost converter parts and an auxiliary inductor. By the auxiliary inductor, the switches can achieve low voltage switching. However, this circuit has a disadvantage of employing many circuit component. This paper proposes interleaved soft-switching multilevel boost converter with coupled inductor. The proposed circuit reduces the number of circuit components by coupling the two inductors in interleaved soft-switching multilevel boost converter. Additionally, since the leakage inductance takes a role as the auxiliary inductor of the conventional circuit, the proposed circuit realizes the smaller size and the lower cost. Furthermore, the proposed circuit achieves half the input current ripple of the conventional circuit. The operational principle of the proposed circuit has been confirmed by analysis and reduced scale circuit experiment in steady-state.

This paper proposes high step-up DC-DC converter using transformer with intrinsic voltage-doubler. The proposed converter has following advantages: 1) raised voltage gain by not only duty ratio but also increasing transformer turn ratio; 2) lower voltage stress of the switches; and 3) less number of elements compared to conventional high step-up converters. The circuit configuration, operation, and theoretical analysis of the proposed converter are described. The circuit operation has been confirmed by reduced scale circuit experiment.

When a photovoltaic (PV) string is in partial shading condition, its I-V curve has multi steps and the P-V curve has multiple maxima. Conventional MPPT (Maximum Power Point Tracking) methods could fail to track the global MPP (Maximum Power Point) in this condition. Therefore, partial shading compensating circuits which resolve this issue were proposed. In this paper, effects of blocking diodes and bypass diodes on PV strings with a partial shading compensating circuit using voltage equalizer is studied. As a partial shading compensating circuit, resonant switched-capacitor converter is chosen. P-V curves of PV string and loci of operation points were obtained by simulation with PSIM and circuit experiment. These results show that blocking diodes prevent power consumption of shaded PV modules around open circuit voltage. However, the effect of the bypass diodes were not observed.

The dual circuit of Cockcroft-Walton (CW) circuit is proposed as the multistage Class DE current driven low di/dt rectifier. The dual circuit of CW circuit naturally satisfies Class E switching condition. The equations of diodes and inductors waveforms are obtained at any diode on-duty ratio using the same scheme for Class DE rectifier. Moreover, the simulation and the experimental results are presented. Theoretical, simulation, and experimental results were in good agreement. The proposed circuit is suitable for low voltage and large current power sources.

Electric Vehicle (EV) and Hybrid EV (HEV) require higher voltage than what a single storage cell can output, so a large number of cells are needed to be connected in series. For the series connected storage cells, the voltage equalizer is required. In this paper, modularized LC resonant switched capacitor cell voltage equalizer is proposed. By means of modularizing and Zero Current Switching (ZCS), the proposed equalizer reduces the equalization time and switching losses.

This paper proposes bidirectional cascaded quasi-Z-source dc-dc converter (BC-qZSC). Compared to the traditional cascaded quasi-Z-source network (C-qZSN), the diodes in C-qZSN are replaced by active switches with a parallel diode. BC-qZSC has the higher boost ability and the lower input current ripple than those of the bidirectional quasi-Z-source dc-dc converter (B-qZSC). In this paper, the operational principle, analysis, and experiment results of BC-qZSC are shown. Also, those of the voltage-fed B-qZSC in the regeneration mode are shown in order to compare BC-qZSC with B-qZSC.

Class DE current driven low di/dt rectifier is proposed and analyzed. The Class DE current driven low di/dt rectifier has advantages of low diode current stresses, diodes' turning on at zero di/dt and low absolute value of dv/dt, and turning off at low absolute value of di/dt. Therefore, the rectifier reduces switching losses, switching noises, and reverse recovery effect. The equations of diodes and inductor waveforms and current transfer function are obtained at any diode on-duty ratio. Moreover, the simulation and the experimental results are presented. Theoretical, simulation and experimental results were in good agreement.

This paper proposes a design method for Z-source network based on inductor current. In Z-source inverter, when the variation of the output current from the Z-source network is large, the variation of the inductor current and the capacitor voltage increase in the Z-source network. Therefore, discontinuous current mode (DCM) condition transiently occurs in the Z-source network inductors. DCM condition affects the operation of the Z-source inverter. Against the problem, this paper proposes a new design method of the Z-source inverter to maintain continuous current mode (CCM) condition. The proposed method is confirmed by simulation results with PSIM and circuit experiments.

Recently, the technology on electric vehicle (EV) is more and more focused. In order to control the motor driving, power conversion circuits are applied, and as the energy storage, rechargeable battery and electric double layer capacitor (EDLC) are generally used. The energy storage is composed of series connected cells to get high output voltage, therefore cell voltage unbalance occurs by means of the unequal characteristic of each cell. To avoid the voltage unbalance, several voltage equalizing circuits have been proposed. In this paper, motor driving circuit using hybrid energy storage is proposed. This circuit has two sets of energy storages, and enables cell voltage equalization and energy transfer among energy storages. In proposed circuit, flyback transformer is connected to each energy storage cell. The circuit operation has been confirmed by reduced scale circuit experiment.

The three-level (TL) dc-dc converter have advantages of low voltage stress of the switches and diodes, and reduction of filter size. However, in order to achieve high step-up voltage gain, very high duty ratio of switches is required because their output voltage gain is the same as the traditional dc-dc converters. This paper proposes a new type of TL buck-boost dc-dc converter. The proposed converter is a transformerless dc-dc converter with a double self-lift switched-inductor cell inserted to the nonisolated TL buck-boost converter, which increases the voltage gain in the boost operation without very high duty ratio of switches. The proposed converter achieves high step-up and down voltage gain with maintaining advantages of the TL buck-boost converter. The operational principles and steady-state analysis have been verified by PSIM simulation and circuit experiments.

The switched capacitor equalizer is one of the simplest voltage equalizing methods. However this equalizer has disadvantages which are prolonged equalization time and large difference of equalization time caused by the position of problematic energy storage cell. This paper proposes novel switched capacitor equalizer which has the advantages of the switched capacitor with chain structure and the double-tiered switched capacitor. The proposed circuit has many paths of charge exchange, which reduces the equalization time and constantly keeps the performance above a certain level regardless of the position of the problematic cell. The performance of the proposed circuit was confirmed with simulation and circuit experiments.

In this paper, a voltage multiplier cell applied to high-step-up dc-dc converter with ripple free input current is proposed. The voltage multiplier cell is inserted in the conventional interleave boost converter with cascade Three-Level (TL) boost converter, which offers high voltage transfer function. The voltage multiplier cell and TL converter makes the voltage stress of all the semiconductor devices lower than the output voltage of each step. Furthermore, the input current ripple closes to zero when the interleave converter's duty ratio is 0.5. The circuit configuration and operation of the proposed converter are described. The circuit operation has been confirmed by circuit experiments.

Multilevel DC-DC boost converter which consists of an inductor based boost circuit and a switched capacitor circuit has high voltage gain and flexible output voltage. It is suitable for a low voltage power source such as fuel cells. However, in high switching frequency, multilevel DC-DC boost converter's power conversion efficiency is reduced by switching loss. Against the problem, this paper proposes an interleaved soft-switching multilevel DC-DC converter. The efficiency of the proposed converter is improved compared with the conventional soft switching converter in high boost ratio. The operation of the proposed converter has been confirmed by circuit experiments and simulations.

Quasi-Z-source dc-dc converter has a unique LC impedance network that can output positive polar boost voltage and negative polar buck-boost voltage. Quasi-Z-source dc-dc converter has following advantages; 1) continuous input current, 2) low voltage stress on capacitors, and 3) sharing the input and output grounds. However, the input current ripple is higher than that of the traditional dc-dc converters, and the voltage gain is the same as that of the traditional Z-source dc-dc converter. This paper proposes quasi-Z-source dc-dc converter with voltage-lift technique. In the proposed circuit, one capacitor, one inductor, and two diodes are added to the conventional quasi-Z-source network. Compared with Quasi-Z-source dc-dc converter, the proposed circuit reduces the input current ripple and the voltage stress on capacitors, and has high boost voltage conversion ability. The operational principle of the proposed circuit has been confirmed by analysis and circuit experiment in steady-state.

This paper introduces a zero current switching (ZCS) type Class DE rectifier, along with design procedure, simulation and experimental results. The feature of ZCS type Class DE rectifier is that the diodes maintain ZCS and zero current derivative switching (ZCDS), therefore, switching losses and switching noise are reduced. The measured efficiency was 80.6% at 100 kHz. The experimental results show good agreement with the simulation results with PSIM. Moreover, the proposed circuit always satisfies ZCS and ZCDS even when the input voltage, the operating frequency, and the output resistance are changed.

A novel circuit topology of the Z-source dc/dc converter, 'Common grounded Z-source buck-boost converter' is proposed. The proposed converter realizes the buck gain in addition to the boost gain in the positive output voltage range, which was only realized in the negative output voltage range in the previous research. Furthermore, the proposed topology provides a common ground for the input voltage source and for the load resistance even though a Z-source network is installed. The theoretical approach for the circuit operation, the simulation results, and the experimental results are introduced.

A novel switched-capacitor inverter is proposed. The proposed inverter outputs larger voltage than the input voltage by switched capacitors in series and in parallel. The maximum output voltage is decided by the number of the capacitors. The proposed inverter, which does not need any inductors, can be smaller than a conventional unit which consists of a boost converter and an inverter. Its output harmonics is reduced compared to the conventional single phase inverter. The proposed inverter is driven by the multicarrier PWM method. In this paper, the circuit configuration, the theoretical operation, the simulation results with MATLAB/SIMULINK and the experimental results are shown. The experimental results accorded with the theoretical calculation and the simulation results.

A Class E low dv/dt rectifier, which is a counterpart of a class E zero-voltage-switching (ZVS) inverter, is suitable for high-frequency and high-efficiency rectification with low noise. In the Class E low dv/dt rectifier, the junction capacitance of the diode is included in the shunt capacitor, which has been regarded as a constant capacitance. However, some kinds of Class E rectifiers have a MOSFET instead of a diode to regulate the output power or to reduce the power dissipation. The junction capacitance of a MOSFET is generally larger than the junction capacitance of a diode. Therefore, depending on the value of the shunt capacitor, the nonlinear behavior of the junction capacitance cannot be ignored. In this paper, the influence of the nonlinear behavior of the junction capacitance on the switch voltage waveform of the Class E low dv/dt rectifier with MOSFET is verified and discussed based on the results with numerical analysis and circuit experiments.

Applying the delta-sigma modulated driving patterns, Class D zero-current-switching (ZCS) series resonant inverter driven at 200 kHz outputs the 50-Hz sinusoidal envelope waveform. In this study, the load impedance which was limited to a purely resistive load is expanded to an inductive load. The waveforms observed in experiments and simulations have well agreed. The Class D inverter outputs the 50-Hz sinusoidal envelope waveform with maintaining ZCS under the condition of an inductive load. The measured power conversion efficiency was 70.2 % at the switching frequency 193 kHz, 2.6 W in reduced-scale circuit experiments.

This paper presents a class DE inverter with asymmetric shunt capacitors. Generally the shunt capacitors of class DE inverter are equally given to the two switching devices. The input current from the dc power source flows into the upper shunt capacitor during the dead time. Therefore, the minimization of the upper shunt capacitor leads to the reduction of ac components of the input current, which reduces the reverse power flow and the power loss occurring in the internal resistance of the dc power source and line impedance. In this paper, a circuit model of class DE inverter with considering each equivalent series resistance (ESR) is given. Based on the circuit model, the circuit equations are built, and the state equations are drawn in each state. The power loss caused by the input current is numerically calculated from the state equations. The waveforms and power conversion efficiencies are confirmed in circuit experiments. The asymmetric shunt capacitors, especially minimizing the upper shunt capacitor, offer the highest power conversion efficiency

The output envelope waveforms of the delta-sigma modulated class D series resonant inverter is analyzed, compared, and discussed based on the simulation results with Matlab Simulink simulator. The class D inverter operating at 200 kHz generates 50 Hz envelope waveform through the additional switching legs. Firstly, the relationship between the feed-back gain of the delta-sigma modulator and the output envelope waveforms is clarified. Secondly, the variable parameters are expanded to the loaded Q-factor QL. For QL= 10 to 10000, the output waveforms are analyzed. The simulation results show that THD is held under 3 % from QL= 50 to 100. The obtained envelope waveform is highly qualified as an ac power source

Class E switches have many advantages in comparison with PWM switches. Their low switching losses allow for high-efficiency operation at high frequency. They can operate with low electro-magnetic interference (EMI). In addition, class E synchronous rectifier has the advantage of low power dissipation in the devices. So it is effective especially in low power circuits. On the other hand, thinned-out method can regulate the output voltage easily by adding a simple logic circuit to the drive circuit. In this paper, we propose to apply the thinned-out method to a class E synchronous rectifier. The experimental circuit is Class E/sup 2/ resonant dc/dc converter composed of a basic class E inverter and a class E synchronous rectifier. The circuit can regulate the output voltage by controlling (thinning-out) the drive voltage waveforms of the MOSFET in the synchronous rectifier. Some experimental results are shown, and compared with other circuits. At low output power less than 0.4 W, it was maintained over 60 percent for varying the output voltage from 3.0 V to 2.1 V. The maximum measured efficiency is 78 percent.

A new class D type tuned power amplifier is proposed. It can operate at a far higher frequency (above 1 MHz) than a conventional class D one. This can be realized by applying the class E switching conditions to each switch. This circuit is very similar to class D amplifier but has a shunt capacitor in each switch device. The analysis, design procedure and experimental results are given. The measured efficiency was over 96 percent at 1 MHz.>