Isolated DC-DC Converter Transient Response Control
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Solution Overview
Problem
Transformer core saturation in isolated DC-DC converters during transient load conditions is a challenge that existing technologies address either by oversizing the transformer core or limiting the duty cycle, leading to suboptimal performance and increased costs.
Innovation Solution
The method involves switching primary side devices at a fixed first switching period and variable duty cycle during non-transient conditions, and at a second switching period during transient conditions to avoid saturation, with shorter energy circulation intervals, allowing for miniaturization without degrading transient performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the transformer core is oversized to avoid saturation during transient load conditions, then transformer core saturation is prevented, but the size and cost of the converter increases
Solution Approach 1:
The patent applies dynamics by switching between two different control modes: a first control mode for steady-state operation and a second control mode for transient load conditions. During transients, the controller dynamically adjusts the duty cycle of primary side switching devices to prevent transformer core saturation, allowing the use of a smaller transformer core while maintaining reliability during both steady-state and transient operations.
2Reliability
If the maximum duty cycle is limited as a function of input voltage to avoid transformer core saturation, then transformer core saturation is prevented, but transient response is degraded
Solution Approach 1:
The patent changes the control parameter from a fixed duty cycle limit to a dynamic duty cycle adjustment based on detected transient conditions. When a transient load condition is detected, the controller modifies the duty cycle of primary side switching devices to prevent transformer core saturation while maintaining fast transient response, avoiding the need to limit the maximum duty cycle as a function of input voltage.
3Reliability
If the switching frequency is constrained by linear loop limits, then transformer core saturation is avoided, but transient response performance is suboptimal
Solution Approach 1:
The patent implements feedback by detecting transient load conditions and adjusting the duty cycle of primary side switching devices accordingly. This feedback mechanism allows the controller to prevent transformer core saturation during transients without being constrained by linear loop limits on switching frequency, thereby achieving optimal transient response performance while maintaining reliability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach prevents transformer core saturation while maintaining fast transient response and minimizing transformer size and cost, achieving optimal performance without linear loop constraints on switching frequency.
Implementation Method 1
a transformer having a core, the transformer coupling the primary side switching devices to the secondary side rectifying devices
Data Source
AI summary
A method of controlling an isolated DC-DC converter includes switching the primary side switching devices of the converter at a fixed first switching period and variable duty cycle during non-transient load conditions so as to transfer energy across the transformer of the converter during first energy transfer intervals separated by energy circulation intervals, such that the ratio of each first energy transfer interval to the first switching period is less than unity. The method also includes switching the primary side switching devices at a second switching period different than the first switching period during a transient load condition so as to transfer energy across the transformer during second energy transfer intervals of a duration determined so as to avoid saturation of the transformer core, and such that any energy circulation interval separating the second energy transfer intervals is shorter than the energy circulation intervals separating the first energy transfer intervals.