PWM Controller for Flyback Converter Using Auxiliary Winding Valley Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Flyback converters face challenges in accurately controlling output voltage and current due to noise effects and resonance phenomena, particularly when using primary-side regulation methods, which can lead to inefficient power supply in portable electronic devices.
Innovation Solution
A Pulse-Width Modulation (PWM) controlling apparatus that includes a valley detector, output voltage controller, output current controller, and gate controller, utilizing averaging and sampling methods to accurately control the auxiliary winding voltage and current, thereby minimizing noise effects and improving regulation accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If primary side control method is used to simplify circuit structure and reduce cost, then device complexity is reduced, but regulation precision deteriorates due to indirect feedback and diode voltage drop influence
Solution Approach 1:
The patent applies preliminary action by detecting the valley of auxiliary winding voltage before resonance occurs. The valley detector identifies the timing when the auxiliary winding voltage reaches its minimum point before the resonance phenomenon begins, allowing the control system to sample the voltage at the optimal moment when the signal is still clean and accurate, thus maintaining regulation precision while using primary side control
Solution Approach 2:
The patent implements skipping by rapidly switching between different control modes (peak current mode and average current mode) depending on the operating conditions. When resonance is detected or predicted, the system skips the problematic sampling period and transitions to alternative control strategies, thereby avoiding the degradation of regulation precision while maintaining the simplicity of primary side control
2Productivity
If peak current mode PWM method is used for output current control, then productivity is improved, but reliability deteriorates due to operation failures from switching noise
Solution Approach 1:
The patent applies dynamics by making the control mode adaptable and changeable based on real-time operating conditions. The system dynamically switches between peak current mode PWM (for high productivity when conditions are favorable) and average current mode PWM (for high reliability when noise is present). This dynamic adaptation allows the system to maintain both productivity and reliability by selecting the appropriate control mode for each operating scenario
Solution Approach 2:
The patent implements feedback by continuously monitoring the auxiliary winding voltage and detecting resonance conditions. The valley detector provides feedback about the timing and presence of resonance, which feeds back to the control system to determine whether to continue using peak current mode or switch to average current mode. This feedback mechanism ensures reliability by detecting problematic conditions and triggering appropriate corrective actions
3Loss of information
If auxiliary winding voltage is sampled during resonance phenomenon, then measurement is obtained, but measurement precision deteriorates due to resonance distortion
Solution Approach 1:
The patent applies preliminary action by detecting the valley of auxiliary winding voltage before resonance occurs. The valley detector identifies the timing when the auxiliary winding voltage reaches its minimum point before the resonance phenomenon begins, allowing the control system to sample the voltage at the optimal moment when the signal is still clean and accurate, thus maintaining measurement precision while obtaining necessary voltage information
Solution Approach 2:
The patent implements preliminary anti-action by taking preventive measures against resonance distortion. The system detects the approaching resonance condition through valley detection and takes countermeasures by switching to average current mode control or adjusting sampling timing before the resonance fully develops and corrupts the voltage signal, thereby preventing measurement precision deterioration
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
The proposed solution effectively reduces the likelihood of operation failures and enhances the accuracy of output voltage and current control, improving the overall functionality and efficiency of flyback converters.
Implementation Method 1
A flyback converter is a buck-boost converter with the inductor split to form a transformer
Implementation Method 2
An opto-coupler uses light to transfer signals between otherwise isolated circuits
Implementation Method 3
The auxiliary winding voltage in this example generates a resonance phenomenon through an inductance of a primary side transformer and series parasitic inductances
Data Source
AI summary
A Pulse-Width Modulation (PWM) controlling apparatus includes a valley detector configured to detect a valley of an auxiliary winding voltage of a flyback converter, an output voltage controller configured to output a first PWM control signal by performing averaging and sampling of the auxiliary winding voltage, an output current controller configured to output a second PWM control signal by performing an average current mode method on a current signal (CS) voltage, a latch configured to output a gate control signal after being supplied with the result of a logical OR operation of the first PWM control signal output by the output voltage controller and the second PWM control signal output by the output current controller, or an output signal of the valley detector, and a gate controller configured to perform a turning-on or turning-off operation of a first switch based on the gate control signal.