Parallel DC-DC Converter Drive Modes for Ripple and Efficiency Control
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Solution Overview
Problem
Existing DC-DC converter systems face challenges in optimizing power conversion efficiency and reducing ripple in output current, particularly when an odd number of devices are driven in parallel, as existing technologies do not effectively account for varying numbers of converters.
Innovation Solution
A power conversion device with N DC-DC converters connected in parallel, where N is 3 or more, utilizing a control device that assigns converters to first and second groups with different PWM switching controls based on carrier phases, allowing for dynamic adjustment of drive modes and output ratios to optimize efficiency and reduce ripple.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple DC-DC converters are driven in parallel to increase power output, then power conversion efficiency can be optimized, but output current ripple increases and becomes difficult to control
Solution Approach 1:
The patent applies periodic action by using multiple DC-DC converters with different switching frequencies or phase-shifted PWM signals. Each converter operates periodically with a staggered timing, causing their ripple currents to cancel each other out when combined. This periodic modulation approach transforms the harmful ripple effect into a beneficial cancellation mechanism, reducing total output ripple while maintaining high power output capability.
Solution Approach 2:
The control device dynamically adjusts the operating parameters of each DC-DC converter based on real-time conditions. By continuously monitoring output current and power demands, the system optimizes switching frequencies, duty cycles, and phase relationships to minimize ripple under varying load conditions. This dynamic control enables the system to maintain low ripple across different operating points while maximizing power conversion efficiency.
2Loss of energy
If the number of driven DC-DC converters is changed to optimize power conversion efficiency, then efficiency can be improved, but control complexity increases
Solution Approach 1:
The control device implements dynamic converter grouping that automatically adjusts which converters are active based on power demands and efficiency requirements. The system dynamically selects optimal converter combinations and adjusts their operating parameters in real-time, enabling efficient operation across varying load conditions without manual intervention. This dynamic approach simplifies control by automating the complexity of managing multiple converters with different efficiency characteristics.
Solution Approach 2:
The control system segments the fleet of DC-DC converters into functional groups based on their efficiency characteristics and operational states. By organizing converters into manageable segments or tiers, the control device can independently optimize each group's operation while coordinating their combined output. This segmentation strategy reduces overall control complexity by breaking down the management of multiple converters into smaller, more tractable control units.
3Object-generated harmful factors
If PWM switching control with different carrier phases is applied to converter groups, then output current ripple can be reduced, but switching control complexity increases
Solution Approach 1:
The patent implements periodic action by assigning phase-shifted PWM carriers to different converter groups. Each group uses a carrier wave with a specific phase offset (e.g., 0°, 120°, 240° for three groups), creating periodic ripple patterns that cancel each other when combined. This systematic phase distribution approach reduces output ripple through constructive interference cancellation while maintaining relatively simple individual converter control logic.
Solution Approach 2:
The control system applies local quality by tailoring the PWM carrier phase and frequency parameters specifically for each converter group's characteristics and position in the system. Rather than using a uniform control approach for all converters, each group receives optimized switching parameters suited to its specific operational context. This localized control strategy effectively reduces ripple while keeping individual group control complexity manageable through parameter specialization.
Data Source
AI summary
For connected-in-parallel N DC-DC converters (1 to N, where N is 3 or more), a first converter group on which PWM switching is performed with a first carrier, and a second converter group on which PWM switching is performed with a second carrier having a phase different from that of the first carrier, are provided. One or more of the DC-DC converters (1 to N) are assigned to each converter group. A plurality of drive modes in which the number of the DC-DC converters that are driven and the converter groups are set, are provided. The drive modes are switched through comparison between a preset threshold value and a total output of the N DC-DC converters (1 to N), and a ratio between total outputs in the first and second converter groups is set to fall within a predetermined range.