Flyback Control Loop Ripple Attenuation
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Solution Overview
Problem
Conventional PWM controllers for flyback power converters face challenges in maintaining constant current regulation across varying input voltages and loads, particularly in attenuating ripple performance without requiring complex filtering or altering cycle-to-cycle update processes.
Innovation Solution
A modified primary side sensing control loop that calculates on-time based on the product of on-time, reset-time, and instantaneous input voltage, allowing for cycle-by-cycle compensation and attenuation of ripple voltage without filtering, ensuring stable current limit across a wide input voltage range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional PWM controllers are used for constant current regulation, then current control can be achieved, but ripple performance deteriorates and requires complex filtering
Solution Approach 1:
The controller performs preliminary calculation of the on-time value based on the desired current limit and instantaneous input voltage before the switching cycle begins. This pre-calculated on-time value is then used to control the switch, allowing the system to proactively compensate for input voltage variations and prevent ripple generation rather than reacting to it afterward
Solution Approach 2:
The system implements a feedback mechanism where the actual on-time is measured and used to update the on-time calculation for the next cycle. This cycle-by-cycle feedback ensures that the controller continuously adapts to changing conditions while maintaining constant current regulation and minimizing ripple
2Object-generated harmful factors
If filtering is added to reduce ripple, then ripple performance improves, but device complexity increases
Solution Approach 1:
Instead of treating ripple as a harmful effect that requires filtering, the invention converts the ripple issue into a benefit by using the instantaneous input voltage information to pre-calculate the on-time. This approach transforms what would be a problematic ripple condition into a useful signal for precise current control, eliminating the need for additional filtering components
3Object-generated harmful factors
If cycle-to-cycle update process is altered to attenuate ripple, then ripple performance improves, but control responsiveness deteriorates
Solution Approach 1:
The on-time value is calculated in advance before each switching cycle based on the desired current limit and the instantaneous input voltage. This preliminary calculation allows the system to prepare the control signal ahead of time, ensuring both ripple attenuation and maintained responsiveness without altering the cycle-to-cycle update process
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 effectively maintains constant current regulation and reduces ripple performance by compensating for input voltage variations and load changes, ensuring stable and efficient power supply operation in Constant Current mode without the need for a loop filter.
Implementation Method 1
The energy is stored in the transformer core gap when the switch is on, and is transferred to the load circuit when the switch is off
Data Source
AI summary
A modification of a control loop of a primary side sensing power control system that uses a different and unique relationship to accomplish the constant current control while attenuating the affects of a ripple voltage.