Bo-Yuan Chen

Switching Control Technique of Phase-Shift-Controlled Full-Bridge Converter to Improve Efficiency Under Light-Load and Standby Conditions Without Additional Auxiliary Components

The main theme of this paper is to propose a switching method to reduce the loss of phase-shift-controlled full-bridge converter under light-load and standby conditions. It will be shown that the efficiency can be improved using the proposed switching control technique. The presented switching control technique controls the full-bridge converter by pulsewidth-modulated (PWM) switching mode under light-load condition and PWM switching with burst mode under standby condition. The transition point between phase-shift switching method and the proposed method is investigated and confirmed by experimental results. A field-programmable-gate-array-based digital-controlled experimental system has been set up. The specifications of the converter include: input voltage = 400 V, output voltage = 12 V, and output power = 400 W. Experimental results show that the efficiency improvement can be up to 26% under light-load condition and the standby power is less than 1 W. These results confirm the effectiveness of the proposed switching control technique.

New Digital-Controlled Technique for Battery Charger With Constant Current and Voltage Control Without Current Feedback

The main theme of this paper is to present a new digital-controlled technique for battery charger to achieve constant current and voltage control while not requiring current feedback. The basic idea is to achieve constant current charging control by limiting the duty cycle of charger. Therefore, the current feedback signal is not required and thereby reducing the cost of A/D converter, current sensor, and computation complexity required for current control. Moreover, when the battery voltage is increased to the preset voltage level using constant current charge, the charger changes the control mode to constant voltage charge. A digital-controlled charger is designed and implemented for uninterrupted power supply (UPS) applications. The charger control is based upon the proposed control method in software. As a result, the UPS control, including boost converter, charger, and inverter control can be realized using only one low cost MCU. Experimental results demonstrate that the effectiveness of the design and implementation.

Novel Random-Switching PWM Technique With Constant Sampling Frequency and Constant Inductor Average Current for Digitally Controlled Converter

A new 2-D random-switching pulsewidth modulation (PWM) technique is proposed to reduce the dominant harmonic clusters while retaining constant average inductor current and constant sampling frequency. The special feature of constant average inductor current can reduce the output voltage ripple. Moreover, the controller parameters of a digitally controlled power converter are not required to change, which is quite essential to digitally controlled systems. Current random PWM methods are discussed and compared with the proposed method in this paper. It will be shown that the merits of the presented method include random-switching frequency, constant sampling frequency, and constant average inductor current. An field-programmable-gate-array-based digitally controlled buck converter experimental system has been set up. The specifications of the converter include input voltage = 5 V, output voltage = 1.5 V, and switching frequency = 200 kHz. The proposed random-switching pattern is implemented by software. Experimental results demonstrate the effectiveness of the proposed random-switching pattern.

Bandwidth-based analysis and controller design of power factor corrector for universal applications

The purpose of this paper is to analyze and design the controllers of power factor corrector for universal applications. And present its implementation using field programmable gate array. For the controller design, the bandwidth of voltage loop as the input voltage changes for PFC with and without input voltage feedforward will be analyzed. It will be shown that for the PFC without input voltage feedforward, the bandwidth of voltage loop varies as the input voltage changes. And the bandwidth of voltage loop for low line input is significantly reduced as it is designed based upon the high line input model. In contrast, the bandwidth of voltage loop of PFC for high line input is increased as it is designed based upon the low line input model. For the PFC with feedforward input voltage, the bandwidth of voltage loop retains constant for both low line and high line inputs and therefore no additional gains are required for universal input applications. This analysis provides a guideline for the design of PFC for universal input applications. Moreover, to fully take the advantages of digital control, an FPGA is used for the realization of digital-controlled PFC for universal input applications. Experimental results derived from an FPGA-based digital-controlled universal PFC are presented to fully support the presented PFC.

Novel dual mode operation of phase-shifted full bridge converter to improve efficiency under light load condition

The main theme of this paper is to propose switching method to reduce the loss of phase-shift controlled full-bridge converter under light load and standby conditions. It will be shown that the efficiency can be improved using the proposed switching control technique. The presented switching control technique controls the full-bridge converter by PWM switching mode under light load condition and PWM switching with burst mode under standby condition. The transition point between phase-shift switching method and the proposed method is investigated and confirmed by experimental results. An FPGA-based digital-controlled experimental system has been set up. The specifications of the converter include: input voltage = 400 V, output voltage = 12V and output power = 400 W. Experimental results show that the efficiency improvement can be up to 26% under light load condition and the standby power is less than 1 W. These results confirm the effectiveness of the proposed switching control technique.

Novel random switching PWM technique with constant sampling frequency and constant inductor average current for digital-controlled converter

A new two-dimensional random switching PWM technique is proposed to reduce the dominant harmonic clusters while retaining constant average inductor current and constant sampling frequency. The special feature of constant average inductor current can reduce the output voltage ripple. And the controller parameters of digital-controlled power converter are not required to change which is quite essential to digital-controlled system. Current random PWM methods are discussed and compared with the proposed method in this paper. It will be shown that the presented method is with the merits of randomly changes switching frequency while keeping constant sampling frequency and average inductor current. An FPGA-based digital-controlled buck converter experimental system has been set up. The specifications of the converter includes: input voltage = 5 V, output voltage = 1.5 V and switching frequency = 200 kHz. The proposed random switching pattern is implemented by software. Experimental results demonstrate the effectiveness of the proposed random switching pattern.

Novel current limitation technique without current feedback for digital-controlled battery charger in UPS applications

The objective of this paper is to present a new current limitation technique without current feedback for digital-controlled battery charger in UPS applications. A control method is proposed to achieve constant current and constant voltage charging without current feedback. The basic idea is to keep constant charging current by limiting the duty of charger. As the battery voltage is increased after charge, constant voltage mode is achieved by voltage mode control. A digital-controlled charger is designed and implemented for UPS applications. A low cost MCU is used to realize the proposed control method in software. Experimental results demonstrate that the effectiveness of the design and implementation.

Corrections to “Switching Control Technique of Phase-Shift Controlled Full-Bridge Converter to Improve Efficiency Under Light Load and Standby Conditions Without Additional Auxiliary Components” [Apr 10 1001-1012]

This correspondence is to correct the errors in (31) and (32) in the above titled paper (ibid., vol. 25, no. 4, pp. 1001-1012, Apr. 2010).

Two-dimensional random PWM technique for full-bridge DC/DC converter

PWM techniques for full-bridge DC/DC converter are investigated and a new multi-dimension random PWM technique is proposed in this paper. Three PWM techniques with constant switching frequency are discussed and the related random PWM techniques are which spread the harmonic clusters and give constant average inductor current to reduce the output voltage ripple are discussed. The pros and cons of three constant switching frequency PWM techniques and the related random counterparts are investigated. Experimental results show there is significant efficiency drop of the random PWM technique due to significant increase of switching counts. Therefore, this paper presents a two-dimensional random PWM technique to significantly reduce the harmonic intensity while not causing relevant impact on the efficiency. An FPGA-based digital controlled isolated full-bridge DC/DC converter prototype is built to verify the performance of conventional and proposed PWM techniques. The specifications of the converter include: input voltage = 400 V, output voltage = 12 V, output power = 120 W and switching frequency = 100 kHz. Measured efficiency and Harmonic Spread Factor will be used for the evaluation of these PWM techniques.