Secondary-Side Ripple Control Using Voltage-Controlled Resistor
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Solution Overview
Problem
Existing LED driver systems face challenges in achieving stable luminous output without flicker, as they are sensitive to drive current changes, and feedback control delays lead to power factor and harmonic distortion issues, along with increased system complexity and cost due to the need for optocouplers for communication between isolated circuits.
Innovation Solution
A power supply system with a secondary-side ripple controller and voltage threshold controller, utilizing a voltage-controlled resistor (VCR) dynamically adjusts resistance to compensate for ripples in the drive signal, reducing the need for optocouplers and minimizing power losses by lowering voltage headroom at the secondary side.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a feedback loop is used to measure and control output ripple, then ripple control is achieved, but system complexity and cost increase due to optocoupler requirements
Solution Approach 1:
The invention extracts the ripple control function from the primary side feedback loop and implements it independently on the secondary side. The ripple controller is separated from the main power conversion control, allowing ripple compensation without requiring communication across the isolation barrier. This extraction eliminates the need for optocouplers while maintaining effective ripple control.
Solution Approach 2:
The secondary side ripple controller performs self-service by directly sensing and compensating for output ripple without external feedback from the primary side. The controller uses local sensing elements and adjusts the output stage components to compensate for ripple, making the system self-regulating for ripple control purposes.
2Reliability
If feedback control is implemented from secondary to primary side, then ripple control is achieved, but power factor and harmonic distortion deteriorate due to control delays
Solution Approach 1:
The invention extracts the ripple control function from the primary side feedback loop and implements it independently on the secondary side. The ripple controller is separated from the main power conversion control, allowing ripple compensation without requiring communication across the isolation barrier. This extraction eliminates the need for optocouplers while maintaining effective ripple control.
Solution Approach 2:
The ripple controller on the secondary side performs preliminary action by compensating for ripple at the source before it affects the output. By acting locally and immediately on the secondary side, the controller eliminates ripple without the delays inherent in primary-side feedback loops, thus maintaining power factor and minimizing harmonic distortion.
3Reliability
If optocouplers are used for communication between isolated circuits, then feedback control is enabled, but system cost increases
Solution Approach 1:
The invention extracts the ripple control function from the primary side feedback loop and implements it independently on the secondary side. The ripple controller is separated from the main power conversion control, allowing ripple compensation without requiring communication across the isolation barrier. This extraction eliminates the need for optocouplers while maintaining effective ripple control.
Solution Approach 2:
The invention uses secondary side sensing elements that create local copies of the output signal for ripple detection. Instead of transmitting feedback signals across isolation barriers, the system uses replicated sensing functionality on the secondary side, eliminating the need for expensive optocoupler-based communication.
4Ease of operation
If voltage headroom is maintained at the secondary side, then converter operation is simplified, but power losses increase due to ripple controller
Solution Approach 1:
The invention implements dynamic resistance adjustment in the ripple controller rather than using fixed resistance components. The ripple controller dynamically adapts its impedance characteristics based on operating conditions, allowing it to minimize power losses while maintaining effective ripple compensation. This dynamic approach reduces the voltage headroom requirement compared to static designs.
Solution Approach 2:
The invention changes the resistance parameter of the ripple controller dynamically to optimize performance. By adjusting the resistance value based on operating conditions, the system minimizes power losses (P=I²R) while maintaining effective ripple control, thereby reducing the required voltage headroom at the secondary side.
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 solution enables quick and efficient ripple correction, reduces system complexity and cost, and minimizes power losses while maintaining stable LED output with improved power factor and reduced harmonic distortion.
Implementation Method 1
a voltage-controlled resistor (VCR) coupled to a secondary-side of the converter and configured to dynamically adjust a resistance of the VCR to compensate for ripples in the drive signal
Implementation Method 2
an operational amplifier configured to receive the reference signal and the sensed drive signal, and to generate a gate control signal based on a difference between the reference signal and the sensed drive signal
Implementation Method 3
a rectifier configured to rectify an input signal to generate a rectified signal having a single polarity
Data Source
AI summary
A power supply system includes a rectifier configured to rectify an input signal to generate a rectified signal having a single polarity, a converter configured to generate a drive signal for powering a light source, and a ripple control system including a voltage-controlled resistor (VCR) coupled to a secondary-side of the converter and configured to dynamically adjust a resistance of the VCR to compensate for ripples in the drive signal.