Transformer Resonant Network for Power Converter Ripple Reduction
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Solution Overview
Problem
Single-stage power factor correction drivers for LED lighting applications suffer from output ripple issues, leading to flickering and potential device degradation, which are difficult to mitigate without increasing size, cost, or complexity.
Innovation Solution
A circuit incorporating a transformer with specific winding configurations and capacitance values, along with a resonant network, is used to reduce output ripple frequency, providing stable DC power to LED loads without large capacitors or dual-stage conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-stage power factor correction driver is used to achieve both voltage conversion and power factor correction, then device complexity is reduced, but output ripple increases causing flickering
Solution Approach 1:
The patent introduces an intermediary circuit between the power factor correction driver and the LED load. This intermediary circuit includes a capacitor connected in parallel with the LED string and a resistor connected in series with the capacitor, forming an RC network that filters the output ripple while maintaining the simplicity of the single-stage driver architecture.
2Object-generated harmful factors
If a large capacitance (at least 1000 μF) is provided at the output to reduce output power ripple, then output ripple is reduced, but device size and cost increase
Solution Approach 1:
The patent changes the parameters of the filtering circuit by using a smaller capacitance value (at least 10 μF but less than 1000 μF) combined with a specifically designed RC network. This parameter change allows achieving the same ripple reduction effect with a much smaller capacitor, thereby reducing device size and cost while maintaining effectiveness.
3Reliability
If power factor correction is increased to achieve higher than 90% power factor, then power factor is improved, but load current ripple increases to 90% of DC value
Solution Approach 1:
The patent uses an intermediary RC filtering network that is specifically designed to attenuate the ripple component of the load current while passing the DC component. The resistor and capacitor are selected with specific values to achieve the desired ripple reduction without affecting the power factor correction performance of the driver.
4Object-generated harmful factors
If two-stage conversion is used to reduce output ripple, then output ripple is reduced, but device size, cost, and complexity increase
Solution Approach 1:
The patent extracts the ripple reduction function from the main power conversion path and implements it as a separate, simple RC filtering network. This extraction allows the power factor correction driver to operate in a simple single-stage configuration while the ripple reduction is handled independently by the RC network, avoiding the need for complex two-stage conversion.
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 low-frequency output ripple in power converters, minimizing flickering and extending device lifespan while maintaining efficiency and simplicity.
Implementation Method 1
a first capacitor having a first capacitor terminal and a second capacitor terminal, the first capacitor terminal electrically coupled to the second primary terminal and the second secondary terminal of the transformer... the capacitance value (C) and the first inductance value (L) may satisfy: ω² = 1/(LC) where ω is the ripple frequency
Data Source
AI summary
Systems and methods for reducing low frequency (e.g., 100 Hz, 120 Hz) output ripple of a power converter which receives input power from an AC power source (e.g., AC mains). An output ripple reduction circuit is provided which is electrically coupled between an output of a power converter and a load (e.g., one or more LEDs). The output ripple reduction circuit comprises a transformer having a first winding and a second winding each wrapped around a core. The first winding has a first terminal electrically coupled to an output of the power converter and a second terminal coupled to a capacitor to form a first LC circuit. The second winding has a first terminal electrically coupled to a load and a second terminal coupled to the capacitor to form a second LC circuit.