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This paper studies ON/OFF control of a dc-dc system that contains multiple active-clamp LLC resonant modules operating in parallel. The architecture and the ON/OFF control method yield high overall efficiency and fast transient responses. Two converter models are introduced: 1) a high-frequency model to determine a gate timing sequence that enables fast ON/OFF control, and 2) an averaged model to assist in the system control loop design. The models and the ON/OFF control method are verified by experiments on a prototype consisting of two 1-MHz, 24-3.3-V, 5-W active-clamp LLC modules. The performance of PI and PID system controllers is compared, and capacitor size is analyzed by simulations on systems containing up to 20 modules. [ABSTRACT FROM AUTHOR]

This paper presents an alternative modulation approach for digitally controlled dc–dc switching converters, which exploits the natural jittering activity of a digital hysteretic feedback loop in order to provide an effective increase in resolution. The proposed structure replaces conventional high-resolution digital pulsewidth modulators (DPWMs) or sigma–delta-based (ΣΔ-DPWM) solutions with a single, fully digital block featuring reduced complexity, high resolution, improved noise performance, and small-signal characteristics, enabling the design of accurate, high-bandwidth digital feedback loops with minimum hardware resources. A stochastic modeling approach is developed for the proposed structure, which allows the derivation of a simple and effective switching frequency-control criterion. Analysis, simulation, and experimental tests are shown to validate the properties of the proposed digital hysteretic modulator. [ABSTRACT FROM AUTHOR]

This paper describes design and implementation of a digitally controlled dc/dc converter that provides a dynamically adjustable supply voltage for a radio frequency power amplifier (RFPA). The techniques employed in the design include a combination of constant-frequency continuous conduction mode (CCM) and a variable-frequency discontinuous conduction mode to achieve very high converter efficiency over a wide range of output power levels. The variable-frequency converter control is accomplished using a current-estimator circuit, which eliminates the need for current sensing. A field-programmable gate array (FPGA)-based digital controller implementation allows programmability of the mode transition and other controller parameters. In the complete experimental system, which consists of the digitally controlled dc/dc converter and a class-E RFPA operating at 10 GHz, experimental results show that the overall system efficiency is significantly improved over a wide range of RFPA output power levels. [ABSTRACT FROM AUTHOR]

This paper describes the design, implementation, and characterization of a high-efficiency 10-GHz amplifier with dynamic drain bias control that maintains high efficiency over a range of output power levels. The power amplifier (PA) operates in class-E switched mode with 67% drain efficiency at an output power of 20.3 dBm, 0.7 dB less than the specified maximum power for the device. A coupler and detector at the output of the PA provide a feedback signal to the drain-bias controller based on a 96% efficient Buck dc-dc converter. When compared with a PA with constant drain bias (4 V), the average efficiency of the PA with dynamic biasing is improved by a factor of 1.4. Over an output power between 15-20 dBm, the drain bias varies from 2 to 4 V, and the efficiency improves from 22% to 65% at the lower power level. The efficiency includes the losses in the dc-dc converter. [ABSTRACT FROM AUTHOR]