Comprehensive modulation strategy for DAB-LLC bidirectional isolated converter with wide input voltage range

In this paper, a three-phase current-fed dual-active-bridge (DAB) bidirectional DC-DC converter is presented. Compared to the voltage source DAB converter, the proposed converter allows low RMS current and maintains zero voltage switching (ZVS) in the whole operating range by keeping the ratio between primary side and secondary side DC-link voltage constant, leading to high efficient energy conversion over a wide input voltage range. In addition, the ZVS conditions can be maintained using small DC inductors and the input current ripple still remains small because of high DC inductor current ripples being alleviated by three-phase interleaving structure. Furthermore, the proposed topology with Y-Y connected transformers is proven to have better current sharing capability compared with other three-phase topologies with different transformer connections. The operation mode analysis, soft switching conditions, and hardware design guidelines are derived in this paper. A 6-kW hardware prototype with input voltage range of 24~48 V and rated 288 V output voltage is developed and tested in the laboratory. The experimental results verified that the proposed converter could maintain high efficiency over a wide input voltage and power range.

High frequency power electronic technology is an important development tendency for future power supplies. ON-OFF control is widely adopted in high frequency applications up to multi-megahertz. A detailed analysis of the high frequency Class E dc-dc converter with ON-OFF control over wide input voltage range is performed in this paper. It is revealed that with the increase of input voltage, the soft switching realization become easier and the output power capacity is enhanced; concurrently, the voltage/current stresses of the power components are all increases. Based on this, design considerations of the Class E dc-dc converter with wide input voltage range are given. It is pointed out that, to help achieve soft switching and rated output power requirements over the whole input voltage range, the converters' parameters should be designed at the minimum input voltage; on the other hand, to avoid electrical damage of the power components, the voltage and current stresses of the components should be considered at the maximum input voltage. A design example of 20 MHz, 10 W Class E dc-dc converter are given with 9–18 V inputs. The experimental results are presented to verify the necessity and feasibility of the proposed design considerations.

A high input voltage converter with a wide input voltage range is crucially required in long-distance submarine power system. However, the concise implementation of high input voltage and wide input voltage ranges remains a challenge for existing converter. In this article, a serial hybrid-clamped three-level half-bridge <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> resonant converter is proposed. The proposed converter can withstand high input voltage by connecting two hybrid-clamped three-level half-bridges in series. All the operating states of the converter are analyzed, five modulation modes are presented, four of which are controlled by pulse frequency modulation, and the other is controlled by changing the equivalent phase shift angle. The five modulation modes cover different voltage gain ranges, and can be combined to achieve wide input voltage regulation while maintaining soft switching of switching devices. The experimental prototype with 1 kW power level and 250 V–2 kV input voltage range is built to verify the wide voltage regulation rang soft-switching performance of the proposed converter.

A charge pump (CP) with reconfigurable multi-ratio is proposed for wireless energy harvesting system, which has almost eight ratios with small step to suit for wide input or output voltage range applications. Six flying capacitors are adopted to generate different conversion ratios (CRs) from ×0.25 to ×2 with step of 0.25. The CR of the CP is determined by input voltage and on-chip control unit. Thus, an almost constant output voltage is obtained in a wide input voltage range. Besides, the MOS switches of the CP are driven by a two-phase non-overlapping clock to reduce quiescent current and improve the power conversion efficiency (PCE). As a result, a configurable CP is achieved by using a standard 0.35 μm CMOS process with 1.7 mm2 die area (include PADs.) The output voltage of the CP can be kept almost constant at 3.6 V when Vin varies from 1.77 V to 4.80 V. The PCE is over 80% no matter which CR is, and the maximum PCE of 93.8% is achieved when Vin=3.6 and CR=1 @ 1.2 KΩ load resistance. The wide input/output voltage range and PCE of the proposed CP shows its good practicality for DC-DC converter of wireless energy harvesting system.

A new wide voltage operation range isolated battery charger, which is composed of an asymmetric T‐type AC–DC power rectifier and a modified re‐configurable half bridge DC–DC power converter, is proposed in this paper. The asymmetric T‐type rectifier adopts different modulation strategies under different AC bus voltage amplitudes and different battery voltages for increasing power conversion efficiency. As the isolated DC–DC power stage, a modified re‐configurable half bridge converter applies a three‐winding transformer to achieve a wide output operation range. The proposed battery charger operates over a wide AC input voltage range and wide DC output voltage range. A 3.2 kW hardware battery charger prototype is built to adapt AC voltage between 85 and 265 V. Both constant current and constant voltage modes are implemented experimentally to charge the battery up to 6.5 A from 50 to 500 V. The experimental results prove that the proposed asymmetric T‐type rectifier adopts different modulation strategies under different AC bus voltage amplitudes and different battery voltages can increase the power conversion efficiency, the proposed DC–DC converter can output the DC voltage from 50 to 500 V and the proposed battery charger can achieve around 94% efficiency.

Power factor correction (PFC) is widely used in ac–dc converters to improve power quality. The current-source charge pump (CS-CP) PFC converter has the advantages of simple structure, easy control, and low cost, but it can only obtain a high power factor (PF) over a narrow input range. The operation principle of the CS-CP PFC converter and the input voltage range are analyzed in this article. In order to obtain a high PF over a wide input voltage range, in this article, a variable turn ratio CS-CP PFC converter is proposed. By adjusting the turn ratio according to the variation of the input voltage, the proposed converter can obtain a high PF over a wide input voltage range, reduce the voltage stress of the bus capacitor, and solve the problem of insufficient voltage gain at low input voltage. The operating modes and the wide input voltage range of the proposed converter are analyzed, and the relevant parameters are given. A 40-W experimental prototype operating with the input voltage range of 100–242 Vac is built to verify the theoretical analysis. The proposed converter obtains the PF of 0.946–0.991 and its total harmonic distortion of current can satisfy the IEC 61000-3-2-2020 Class-C Standard in the whole input voltage.

Conventional resonant DC-DC converters are typically limited to a narrow range of operating input voltage. In this paper, a multimode high-frequency LLC resonant DC-DC converter designed to operate with a wide range of input voltage, is proposed. The converter has three operating modes. It can provide a variable and wide voltage gain conversion via mode switching. Besides, this converter can attain a constant switching frequency operation, as well as ZVS operation for its switches and ZCS operation for its rectifier diodes. A 200 W prototype is constructed. Experiments are conducted to verify its features. Results show that the converter is functional over a wide range of input voltage (25 V-200 V) to provide a fixed output voltage of 200 V, while maintaining the ZVS and ZCS operations and high-efficiency power conversion.

Traditional phase-shift full-bridge converters are popular in industrial applications due to the advantages of simple design, fixed-frequency control and soft switching. However, a large duty cycle variation range is required in applications with a wide input voltage range, which can cause loss of soft switching range, excessive circulating currents and output current ripple. This article introduces a three-leg converter that is a hybrid combination of two full-bridges. The current and power of the two transformers in the converter are shared automatically by adopting the symmetrical structure and modulation, and output current ripple is suppressed by the superposition of the two transformer voltages. The circulating current is minimized in the proposed converter that the conduction loss is reduced. By adding two auxiliary switches on the secondary side, zero-voltage switching and zero-current switching of all switches can be achieved to maintain high efficiency in a wide range. An experimental prototype rated at 1 kW is designed to convert 220–460 V input to 100 V output. The experimental results show that the proposed converter can achieve high efficiency over a wide input voltage and load range.

The four-switch buck-boost (FSBB) converter effectively reduces the average inductance current of FSBB when the input and output voltage is close to each other by using the four-mode operation, which alleviates the problem of limited duty cycle and low efficiency in the traditional control modes. However, the steady-state duty cycle mutation of FSBB with four-mode control will occur during mode switching, resulting in output voltage fluctuation. We analyzed the mechanism of duty cycle sudden change of four-mode control FSBB during mode switching, explored its influencing factors and governing laws, and proposed to use input voltage feedforward control to improve the smoothness of four-mode switching, so as to improve the response speed of output voltage when input voltage changes suddenly. The simulation results showed that after the input voltage feedforward control method was adopted, the four working modes can be switched smoothly in a wide input voltage range, the output voltage can be adjusted quickly, and the full load peak efficiency can reach 98%.

A switched-capacitor (SC) DC-DC boost converter suitable for energy harvesting in IoT sensor systems with varying harvesting source and battery voltages is presented in this paper. Unlike the conventional multi-staged SC DC-DC converters, where efficiency is optimized only for a few topology-dependent conversion ratios, soft-charging-based SC conversion is adopted to achieve conversion-ratio-insensitive high efficiency. With soft-charging flying capacitors with small voltage steps, charge redistribution loss is minimized and evenly high conversion efficiency can be achieved for a wide range of input and output voltages. The proposed converter exhibited evenly high efficiency by achieving a peak efficiency of 85.3% and an average efficiency of 83.6% for generating regulated 1.8V output from a wide range of input voltages (0.9-1.8V). It also achieved a peak efficiency of 88.9% and an average efficiency of 87.6% for harvesting energy from a 1.2V source with a wide battery voltage range (3.0-4.2V).

A novel circuit design technique for realizing a linear CMOS transconductance element, consisting of an adaptively biased source-coupled differential pair using a quadritail cell, is proposed. In the circuitry, the quadritail cell, which provides an output current proportional to the square of a differential input voltage, cancels a nonlinear term of the source-coupled differential pair. The circuit have a superior linearity and a wide linear input voltage range compared with the conventional linear CMOS transconductance elements because the transconductance characteristic is theoretically linear over wide input voltage range when all the MOS field-effect transistors (MOSFETs) are operating in the saturation region and the MOSFETs' behaviors are according to the relation based on the square-law characteristic. The proposed adaptively biased source-coupled differential pair was verified by using transistor-arrays and discrete components on a breadboard.

Aiming at the problem of traditional LLC resonant converters in wide input voltage range, an improved variable mode hybrid modulation strategy combining frequency modulation and asymmetric PWM is proposed. When the input voltage is lower than the switching voltage, the frequency modulation strategy is used to implement the boosting; when the input voltage is higher than the switching voltage, the asymmetric PWM modulation strategy is used to implement the step-down. In this paper, the working principle and circuit characteristics of LLC resonant DC/DC converters with two modulation strategies are analyzed in detail. Finally, the experiment results prove the correctness of the theoretical analysis and the feasibility of the circuit scheme.

It has been proposed that the main battery voltage of electric vehicles should be increased to increase the driving distance and decrease the charging time. Thus, a low-voltage dc/dc converter (LDC) with high and wide input voltage range is required for electronic loads. This article proposes a two-mode LDC and the entire input range is divided into two low and high input voltage ranges. The converter has two operating modes corresponding to these input voltage ranges. In the low input voltage range, it operates as a three-switch double-ended active clamp forward converter. In the high input voltage range, it operates as an asymmetric half-bridge converter. Changing the operating mode according to the input voltage, the proposed converter can have low-voltage stresses on the switches and a low dc offset current of the transformer resulting in high efficiency for the entire input voltage range. In order to confirm the validity of the proposed converter, a 600 W prototype is implemented and experimented.

A novel approach is presented by which the switching frequency of a two-transistor zero-voltage-switched multiresonant converter (ZVS-MRC) is controlled in proportion to input voltage changes in order to maintain essentially constant efficiency over the input voltage range with a switching variation of only +or-10%. It is shown that a buck topology constant frequency (CF) ZVS-MRC can be accurately modeled using a spreadsheet-hosted design aid on a personal computer. Guidelines are presented for designing a buck CF ZVS-MRC, and component values are determined using the computer design aid. It is shown that if a buck CF ZVS-MRC is required to regulate over a wide input voltage range, its efficiency will be severely reduced when operating near maximum input voltage. The computer simulations are verified with experimental results.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

This paper introduces a fully integrated switched-capacitor (SC) DC-DC boost converter suitable for energy harvesting in miniature sensor systems with varying harvesting source and battery voltages. Unlike the conventional SC DC-DC boost converters, where efficiency is optimized only for a few topology-dependent voltage conversion ratios (VCRs), the proposed soft-charging-based SC converter achieved VCR-insensitive evenly high efficiency for a wide range of input and output voltages. A test chip was fabricated in 180nm process, and the measured peak efficiency and average efficiency are 85.3% and 83.6%, respectively, for 1.8V regulated output voltage and a wide range of input voltages (0.95–1.8 V). Also, a peak efficiency of 88.9% and average efficiency of 87.6% are achieved for a wide range of battery output voltages (3.0–4.2 V) and a 1.2V harvesting source input voltage.