Power balance control algorithm for input-series-output-parallel structure LLC converters

Hyeong-Jin Lee; Seung-Woo Baek; Hae-in Kim; Jae-Ha Hwang; Kwan-Yuhl Cho; Hag-Wone Kim

Power balance control algorithm for input-series-output-parallel structure LLC converters

Vol. 26, No. 4, pp. 749-765, Apr. 2026

10.1007/s43236-026-01309-0

Input-series-output-parallel modular converter

Input voltage sharing

LLC converter

Power Balancing

Abstract

This paper presents a power balance control algorithm that employs duty control for input-series-output-parallel (ISOP) LLC resonant converters. With increasing demands for power capacity and system reliability, modular power converters are being widely adopted, particularly in high-voltage, high-current applications where ISOP structures are prevalent. In LLC converters, voltage gain is governed by the resonant tank parameters. Therefore, parameter mismatches among modules may result in power imbalances. Conventional power balance control methods compensate for input voltage discrepancies by allowing independent switching frequencies per module. However, in frequency-controlled LLC converters, such approaches can cause mismatches in current cycles, leading to increased output voltages and current ripples that degrade power quality. To overcome this limitation, the proposed method synchronizes the switching frequency across all modules while individually adjusting the duty ratios to achieve power sharing. The proposed algorithm is validated through PSIM simulations and experimentally verified via hardware-in-the-loop simulation.

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Cite this article

[IEEE Style]

H. Lee, S. Baek, H. Kim, J. Hwang, K. Cho, H. Kim, "Power balance control algorithm for input-series-output-parallel structure LLC converters," Journal of Power Electronics, vol. 26, no. 4, pp. 749-765, 2026. DOI: 10.1007/s43236-026-01309-0.

[ACM Style]

Hyeong-Jin Lee, Seung-Woo Baek, Hae-in Kim, Jae-Ha Hwang, Kwan-Yuhl Cho, and Hag-Wone Kim. 2026. Power balance control algorithm for input-series-output-parallel structure LLC converters. Journal of Power Electronics, 26, 4, (2026), 749-765. DOI: 10.1007/s43236-026-01309-0.