Abstract-This paper presents a merged-two-stage circuit topology suitable for either wide-range dc input voltage or ac line voltage at low-to-moderate power levels (e.g., up to 30 W). This two-stage topology is based on a soft-charged switched-capacitor pre-regulator/transformation stage and a high-frequency magnetic regulator stage. Soft charging of the switched capacitor circuit, zero voltage switching of the high-frequency regulator circuit, and time-based indirect current control are used to maintain high efficiency, high power density, and high power factor. The proposed architecture is applied to an LED driver circuit, and two implementations are demonstrated: a wide input voltage range dc-dc converter and a line interfaced acdc converter. The dc-dc converter shows 88-96% efficiency at 30 W power across 25-200 V input voltage range, and the acdc converter achieves 88% efficiency with 0.93 power factor at 8.4 W average power. Contributions of this work include: 1) demonstration the value of a merged two-stage architecture to provide substantial design benefits in high input voltage, lowpower step down conversion applications, including both widerange-input dc-dc and line-input ac-dc systems; 2) introduction of a multi-mode soft-charged SC stage for the merged architecture that enables compression of an 8:1 input voltage range into a 2:1 intermediate range, along with its implementation, loss considerations and driving methods; and 3) merging of this topology with an resonant transition discontinuous-mode inverted buck stage and pseudo-current control to enable step-down power conversion (e.g., for LED lighting) operating at greatly increased frequencies and reduced magnetics size than with more conventional approaches.

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Abstract-The PowerChip research program is developing technologies to radically improve the size, integration, and performance of power electronics operating at up to grid-scale voltages (e.g., up to 200 V) and low-to-moderate power levels (e.g., up to 50 W) and demonstrating the technologies in a high-efficiency light-emitting diode driver, as an example application. This paper presents an overview of the program and of the progress toward meeting the program goals. Key program aspects and progress in advanced nitride power devices and device reliability, integrated highfrequency magnetics and magnetic materials, and high-frequency converter architectures are summarized.Index Terms-Gallium nitride, high frequency (HF), integrated magnetics, integrated power converter, light-emitting diode (LED) driver, PwrSoC.

Abstract-This paper presents a merged-two-stage circuit topology suitable for efficient LED drivers operating from either wide-range dc input voltage or ac line voltage. This two-stage topology is based on a soft-charged switched-capacitor preregulator/transformation stage and a high-frequency magnetic regulator stage. Soft charging of the switched capacitor circuit, zero voltage switching of the high-frequency regulator circuit, and time-based indirect scale current control are used to maintain high efficiency, high power density, and high power factor. Two implementations of the proposed architecture are demonstrated: a wide input voltage range dc-dc converter and a line interfaced ac-dc converter. The dc-dc converter shows 85-95% efficiency at 20 W power across 25-200 V input voltage range, and the ac-dc converter achieves 88% efficiency with 0.93 power factor at 8.4 W average power.