具自適應外加斜坡控制之USB 傳輸線電感優先式混合型轉換器

Abstract

近年來，為因應輕薄化、高功率密度及低成本的需求，混合式轉換器在各類嵌入式電源系統中扮演著日益重要的角色。特別是在行動裝置、穿戴設備及 USB 供電（USB-PD）等應用領域，傳統電感式轉換器面臨體積限制與寄生效應問題，促使新型混合式架構逐漸受到關注。所謂的 Hybrid Converter（混合式轉換器）是結合兩種或多種電源轉換拓撲（如電感式與電容式、開關式與線性式等），以綜合各自優點的一種電源轉換架構。相較於傳統單一拓撲轉換器，混合式架構能在效率、功率密度、響應速度及成本間取得更佳平衡。 本文提出一種電感優先型混合式轉換器（inductor-first hybrid converter），專為 USB 供電應用設計。此架構利用電感與輸入電壓串聯的特性，可直接使用 USB 線路中的寄生電感作為直流轉換器的電感元件，且由於輸入電流連續，無需額外使用輸入電容來阻擋電磁干擾。藉由減少電感與電容元件的使用，大幅提升功率密度。然而，USB 線的寄生電感感值非固定，若採用傳統控制方式，可能導致迴路不穩定。為此，本文提出一種具自動追蹤斜率補償的谷底虛擬電感電流控制技術，能容忍感值及責任週期變異，使系統在不同感值及責任週期下仍維持相近的迴路增益，確保系統穩定運作。最終以下線晶片驗證搭配PCB板的設計，完成最高效率92%，能容忍變異的直流轉換器。由量測結果證實了使用USB Cable作為電感的可行性，以及整個系統的穩定。

In recent years, to meet the demands for slimmer profiles, higher power density, and lower cost, hybrid converters have played an increasingly important role in various embedded power systems. Especially in applications such as mobile devices, wearable electronics, and USB Power Delivery (USB-PD), traditional inductor-based converters face limitations in size and parasitic effects, driving growing interest in new hybrid architectures. A Hybrid Converter combines two or more power conversion topologies (e.g., inductive and capacitive, switching and linear) to leverage their respective advantages. Compared to conventional single-topology converters, hybrid architectures can achieve a better balance among efficiency, power density, transient response, and cost. This paper proposes an inductor-first hybrid converter designed specifically for USB power applications. Leveraging the series connection of the inductor and input voltage, the converter directly utilizes the parasitic inductance of the USB cable as the converter’s inductor. Furthermore, due to continuous input current, no additional input capacitor is needed to suppress electromagnetic interference (EMI). By reducing discrete inductors and capacitors, the power density is significantly improved. However, the parasitic inductance of USB cables is not fixed, and traditional control methods may cause loop instability. To address this, an automatic tracking slope compensation valley virtual-inductor-current (VIC) control technique is proposed, which tolerates inductance variation and maintains similar loop gain under different inductance values, ensuring stable system operation. Finally, the on-chip verification with the PCB design achieved a maximum efficiency of 92%, realizing a variation-tolerant DC-DC converter. The measurement results confirmed the feasibility of using a USB cable as the inductor and demonstrated the stability of the entire system.