AC/DC Converter Control Circuit for LED Current Ripple Limiting
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Solution Overview
Problem
Conventional single stage LED controllers with power factor correction suffer from significant line frequency ripple in the output current due to small DC bus capacitance, which can shorten component lifespan and cause flickering.
Innovation Solution
A high power factor control circuit for AC/DC converters that includes a rectification module, a conversion module with an inductive element and a switching element, and a control circuit with a peak limiting signal generator and switching element control module to regulate the output current within a limit value, reducing ripple by controlling the switching element based on sample signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a small DC bus capacitance is used in single stage LED controllers with power factor correction, then the circuit architecture is streamlined and cost effectiveness is improved, but significant line frequency ripple appears in the output current
Solution Approach 1:
The control circuit performs preliminary action by predicting the peak inductor current and proactively limiting it before the ripple becomes excessive. The peak limiting signal generator creates a reference signal that anticipates the current peak and prevents overcurrent conditions, thereby reducing output current ripple while maintaining the streamlined circuit architecture with small DC bus capacitance.
Solution Approach 2:
The control circuit implements feedback by continuously monitoring the inductor current through the sense resistor and comparing it against the peak limiting reference signal. The switching element control module adjusts the switching element based on this feedback to maintain the inductor current below the peak limit, effectively controlling the output current ripple while preserving the simplified circuit design.
2Object-generated harmful factors
If the inductor current peak value is reduced to control output current ripple, then the ripple is kept within reasonable range, but the power factor correction performance may be affected
Solution Approach 1:
The control circuit employs dynamic adjustment by varying the peak limiting reference signal based on the instantaneous operating conditions. The reference signal is generated dynamically during each switching cycle, allowing the system to adapt the current limit to match the required power factor correction performance while maintaining acceptable output current ripple levels. This dynamic approach enables optimal balance between ripple control and power factor.
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 solution effectively reduces output current ripple, extending component lifespan and mitigating LED flickering, while allowing for a smaller output capacitor, thus reducing costs.
Implementation Method 1
The rectification module is configured to receive AC power and to rectify it into a DC current
Implementation Method 2
The conversion element includes an inductive element
Implementation Method 3
the switching element is configured to regulate a current flowing through the load
Data Source
AI summary
A high power factor control circuit is disclosed, which is used in an AC/DC converter. The converter includes a rectification module, a conversion module and a load. The rectification module receives AC power and rectifies it into a DC current, and the conversion module converts the DC current to drive power as desired by the load and provides it to the load. The conversion module includes a conversion element including an inductive element and a switching element. The control circuit includes a peak limiting signal generator and a switching element control module. The peak limiting signal generator receives a reference signal and produces at least one peak limiting signal from a sample signal. The switching element control module is configured to control switching of the switching element so that, within at least half a line-frequency period, a value of the ripple in the output current flowing through the load is not greater than a limit value.