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In this paper, a quasi-resonant (QR) flyback primary-side regulation (PSR) converter with adaptive frequency control is proposed. The converter adopts the PSR scheme to detect load information through the auxiliary winding. The converter employs the QR control scheme to switch in the valley mode either in CV or CC operation, which greatly reduces the switching loss. In addition, according to the load condition, the converter adaptively reduces the switching frequency and realize valley switching, which achieves better light-load efficiency in the CV mode. The proposed QR converter was implemented using the HHGRACE 0.35 μm BCD process and verified in a 5 V/1A circuit prototype. Experimental results show that the light-load power efficiency of the proposed converter is improved by up to 4.0% when compared to the conventional QR controller. In addition, the valley switching is realized under different load conditions, which improves the system efficiency in the entire range of output load. [ABSTRACT FROM AUTHOR]

In this paper, based on the combination scheme of dual-sampling and adaptive predictive PID control, a digital controller for improving the transient performance of Buck DC–DC converters is designed. Due to the inherent loop delay in analog-to-digital (A/D) conversion, the calculation process of the digital controller and digital pulse width modulator (DPWM) of conventional digitally-controlled Buck DC–DC converters limits the system bandwidth and this makes the transient response lower. The designed digital controller can reduce the delay time in analog-to-digital converter (ADC), the digital controller and DPWM of digitally-controlled Buck DC–DC converters. Adaptive predictive control is used to eliminate the delay time of ADC and the digital controller, while dual-sampling scheme is used to reduce the delay time of DPWM in this paper. These are two new control schemes, and they show better performance in improving the transient response than other existing control schemes. Both simulation and experimental results demonstrate that the designed digital controller based on dual-sampling and adaptive predictive PID control is effective in improving the transient performance of Buck DC–DC converters. During experimental verification, for a load step between 0.5 A and 1.0 A, the fastest transient recovery time and the overshoot voltage are found to be 102 μ s and 120 mV, respectively. Compared with the conventional digital PID controller, the transient recovery time and the overshoot voltage of the digital controller designed in this paper are decreased by 40.0% and 27.3%, respectively. [ABSTRACT FROM AUTHOR]

A primary-side regulation (PSR) constant current (CC) output and constant voltage (CV) output AC–DC converter is proposed and an adaptive high-precision closed-loop constant current control scheme is put forward in this paper. In the CC mode, the converter adopts the closed-loop control strategy to realize that the switching period adaptively converges to twice the demagnetization time, which realizes the CC output. In addition, exactly detecting the demagnetization time is a prerequisite for obtaining a high-precision output current. Therefore, a demagnetization time detection circuit is designed to provide accurate and reliable demagnetization information. The control IC was fabricated with the Nuvoton 0.5um BCD process, and a 5 V/2 A prototype circuit was implemented to verify its performance. Experimental results show that the CC deviation is within ± 1.4%, which is lower than the target value of ± 2.0%. Under different loads and AC inputs, the conversion efficiency in the CC mode varies between 76.3% and 80.7%. [ABSTRACT FROM AUTHOR]

To balance the output stability and maximum efficiency of a system, an efficiency optimization method based on adaptive frequency control is proposed. In this paper, load transmission is carried out using a DC–DC converter at the receiving end. When the load changes, controlling the rectified output voltage is carried out to realize the maximum efficiency point tracking. Meanwhile, the duty cycle of the rear stage DC–DC converter is changed to keep the output voltage constant. The sampled rectified voltage is compared with the estimated value and the resulting error data are sent to the system transmitter through ASK modulation wireless communication. Then the transmitter demodulation communication information through PID algorithm control is used to achieve the frequency of the adaptive adjustment. The feasibility of the proposed method has been verified by the simulation and experimental results. When the output voltage is 5 V, the constant voltage accuracy is within ± 1%, the maximum efficiency is up to 79.2%, and the dynamic response time is only 160 ms. [ABSTRACT FROM AUTHOR]