Synchronous Timing Pulse Generation Circuit for Switching Power Supply CCM Prevention
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Solution Overview
Problem
Switching power supplies face challenges in maintaining constant output current and preventing inductor current from entering Continuous Conduction Mode (CCM), leading to magnetic core saturation, increased power loss, and reduced efficiency.
Innovation Solution
A synchronous timing pulse generation circuit that controls the pulse starting time of the pulse-width-modulation signal through a time delay unit, timing pulse regulation unit, and synchronization control unit, synchronized with the discharging time signal of the secondary side, to prevent inductor current from entering CCM.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the switching power supply uses conventional control without synchronous timing, then the circuit operation is simpler, but the inductor current enters CCM causing magnetic core saturation and increased power loss
Solution Approach 1:
The synchronous timing pulse generation circuit performs preliminary action by generating timing pulses in advance based on the discharging time signal of the secondary side. This allows the control circuit to proactively adjust the pulse starting time before CCM occurs, preventing magnetic core saturation and reducing power loss without requiring complex real-time detection and correction mechanisms.
Solution Approach 2:
The circuit employs feedback by using the discharging time signal of the secondary side as a reference to generate synchronous timing pulses. This feedback mechanism enables the control circuit to automatically adjust the pulse starting time based on the actual operating state, preventing CCM entry while maintaining relatively simple circuit structure through intelligent control.
2Reliability
If the pulse starting time is not synchronized with the discharging time signal, then the control circuit is simpler, but the output current cannot be kept constant and the converter efficiency decreases
Solution Approach 1:
The synchronous timing pulse generation circuit acts as an intermediary between the discharging time signal of the secondary side and the pulse-width modulation signal. It receives the discharging time signal, processes it through timing pulse generation, and outputs synchronized timing pulses that control the pulse starting time, thereby ensuring stable output current while maintaining relatively simple control circuitry through functional decomposition.
3Productivity
If the switching frequency is increased to improve power transfer efficiency, then the power transfer efficiency increases, but the risk of CCM and magnetic core saturation increases
Solution Approach 1:
The circuit implements dynamic control by adjusting the pulse starting time based on the discharging time signal of the secondary side. This dynamic adjustment allows the converter to operate stably at high switching frequencies by preventing CCM entry, thereby maintaining both high power transfer efficiency and converter stability through adaptive timing control rather than fixed frequency operation.
Data Source
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AI summary
A circuit regulator is used to generate a pulse-width-modulation signal, so as to control a power to be selectively input or not input to a primary side of a switching power supply. The circuit regulator includes a synchronous timing pulse generation circuit, outputs a starting pulse after performing signal process of time delay, timing pulse regulation, and synchronization control on a pulse-width-modulation signal and a discharging time signal of a secondary side, and accordingly effectively controls a pulse starting time of the pulse-width-modulation signal. Therefore, the synchronous timing pulse generation circuit can be applied to the circuit regulator, so as to further effectively prevent an inductor current of the switching power supply from entering a Continuous Conduction Mode (CCM).