Switching Power Supply Resonance Current Control
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Solution Overview
Problem
Existing switching power-supply devices face challenges in suppressing off-resonance and protecting switching elements during large load variations, which can lead to through-current and potential damage.
Innovation Solution
A switching power-supply device with a transformer, rectifying-and-smoothing circuit, series resonance circuit, and a control unit that alternately turns on and off switching elements with dead time, using a resonance current detection unit to invert the switching state based on threshold levels of resonance current to prevent off-resonance and through-current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the lower-limit frequency of the switching frequency is set close to the resonance frequency to widen the output voltage control range, then the control range is widened, but off-resonance may occur when variation exists in element characteristics
Solution Approach 1:
The control unit detects the resonance current and compares its absolute value with thresholds to determine whether the switching frequency is in the normal control range. When off-resonance is detected, the control unit returns the switching frequency to the normal control range, creating a feedback mechanism that maintains frequency stability while allowing wide output voltage control range
Solution Approach 2:
The system dynamically adjusts the switching frequency based on real-time resonance current detection. The control unit continuously monitors the resonance current and modifies the switching frequency to maintain it within the normal control range, enabling the system to adapt to element characteristic variations while preventing off-resonance
2Adaptability or versatility
If the time to turn off the switching element is extended to handle load variation, then load adaptation is improved, but regenerative current flows through the body diode and through-current may damage the switching element
Solution Approach 1:
The control unit detects when the absolute value of resonance current exceeds a threshold, indicating upcoming regenerative current flow. It preemptively inverts the turn on-and-off state of the switching element before the regenerative current can cause damage, preventing through-current while maintaining load adaptation capability
Solution Approach 2:
The system applies preliminary anti-action by detecting the condition that would lead to regenerative current flow and inverting the switching state in advance. This counteracts the harmful effect before it occurs, protecting the switching element from through-current damage while allowing the system to handle load variations
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
Effectively suppresses off-resonance and through-current, enhancing the reliability of switching elements by optimizing switching control in response to load variations, thereby preventing damage and maintaining efficiency.
Implementation Method 1
a transformer (T) comprising a primary winding (P1) and a secondary winding (S1, S2) magnetically coupled to the primary winding (P1)
Implementation Method 2
a series resonance circuit comprising a capacitor (Cri) and a primary winding (P1)
Data Source
AI summary
A switching power-supply device which includes a control unit configured to perform a switching control; and a resonance current detection unit configured to detect the resonance current flowing through the series resonance circuit.When an absolute value level of the resonance current exceeds a second threshold greater than a first threshold, the control unit inverts the turn on-and-off state of the first switching element or the second switching element at the time when the absolute value level reaches a third threshold between the first threshold and the second threshold. When the absolute value level of the resonance current exceeds the first threshold and does not exceed the second threshold, the control unit inverts the turn on-and-off state of the first switching element or the second switching element at the time when the absolute value level reaches the first threshold.