Synchronous Rectification Switching Power Supply Circuit Stabilization
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Solution Overview
Problem
Conventional switching power supply circuits experience unstable switching control and output voltage undulations due to small ripple components in the output voltage, especially when using capacitors with low ESR or high switching frequencies, leading to deviations in timing and unstable output voltage.
Innovation Solution
Incorporating a differential amplification stage, current information detection and holding means to adjust the timing of the set signal based on real-time current information, effectively increasing the difference voltage and stabilizing the switching action by delaying or advancing the rise of the set signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a capacitor with low ESR is used or switching frequency is increased, then power supply efficiency and response speed are improved, but the ripple component of output voltage becomes small causing unstable switching control and output voltage undulations
Solution Approach 1:
The patent introduces a feedback mechanism where the coil current detection signal is fed back to the differential amplification stage. This feedback allows the system to sense the actual current state and adjust the switching control accordingly, ensuring stable operation even when ripple voltage is small due to low ESR capacitors or high switching frequencies.
Solution Approach 2:
The patent uses coil current detection as an intermediary parameter to control the switching elements. Instead of relying solely on output voltage ripple for control, the system detects coil current and uses this information to generate control signals, providing a more reliable control mechanism that works effectively with low ESR capacitors and high switching frequencies.
2Loss of energy
If ripple component of output voltage is small, then power loss is reduced, but the difference voltage for flip-flop circuit setting becomes insufficient causing timing deviations
Solution Approach 1:
The patent replaces the voltage-based control mechanism with a current-based control mechanism. Instead of using output voltage ripple to trigger the flip-flop circuit, the system uses detected coil current information to control switching, providing more precise and reliable timing signals even when voltage ripple is minimal.
3Productivity
If synchronous rectification mode is used with alternately turning on main and subordinate switching elements, then rectification efficiency is improved, but unstable switching control causes output voltage undulations
Solution Approach 1:
The patent implements feedback control by detecting coil current and feeding this information back to the control circuit. This allows the synchronous rectification mode to maintain stable operation by continuously monitoring the actual current state and adjusting switching control accordingly, preventing output voltage undulations while maintaining high rectification efficiency.
Data Source
AI summary
A switching power supply circuit comprises: a differential amplification stage for outputting an error signal representing a difference voltage between a preset reference voltage and a voltage based on an output voltage; an ON-time generation circuit for defining a period of time during which a main switching element is kept ON; a flip-flop circuit which is set by a set signal based on the error signal and reset by a reset signal being an output of the ON-time generation circuit; current information means for detecting current information representing a current flowing to a subordinate switching element; current information detecting means for supplying a current information detecting signal, which makes an adjustment based on the current information so as to delay the timing of the rise of the set signal, to the output side or the interior of the differential amplification stage; and current information holding means for holding the current information detected by the current information means at a moment when the subordinate switching element is turned on, and supplying a current information holding signal, which makes an adjustment so as to advance the timing of the rise of the set signal, to the output side or the interior of the differential amplification stage.