Partial Smoothing Circuit for LED Lighting Ripple Reduction
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Solution Overview
Problem
Conventional LED illumination systems face issues with ripple components in load current, power factor deterioration, and increased noise due to high-frequency switching circuits, which complicate the circuit configuration and require large capacitors or high-current components, leading to increased costs and sizes.
Innovation Solution
A light emitting element lighting device with a partial smoothing circuit that includes capacitors connected in series during charging and parallel during discharging, along with a resistor in the charging path, and a control unit that adjusts the switching frequency and operating mode to reduce the peak input current and improve power factor, while maintaining a constant load current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the capacitance value of the input capacitor is increased to reduce ripple component, then the ripple component of load current is reduced, but the power factor deteriorates and the conduction angle becomes narrow
Solution Approach 1:
The patent divides the smoothing function into two separate circuits: an input capacitor for voltage smoothing and a partial smoothing circuit for ripple reduction. This segmentation allows each circuit to perform its specific function optimally without the negative effects of over-smoothing, maintaining both low ripple and good power factor.
Solution Approach 2:
The patent introduces a partial smoothing circuit as an intermediary between the input capacitor and the load. This intermediate circuit selectively smooths only the low voltage periods of the ripple voltage, acting as a mediator that reduces ripple without causing the power factor deterioration associated with full smoothing.
2Use of energy by moving object
If a power factor correction circuit is added to improve power factor, then the power factor is improved, but noise increases and circuit configuration becomes complicated
Solution Approach 1:
The patent makes the input capacitor serve multiple functions: it acts as both the main voltage smoothing element and, through its interaction with the partial smoothing circuit, contributes to ripple reduction. This multi-functionality eliminates the need for a separate power factor correction circuit, simplifying the overall configuration.
Solution Approach 2:
The input capacitor and partial smoothing circuit work together in a self-regulating manner where the capacitor naturally provides power factor improvement while the partial smoothing circuit handles ripple reduction, making the system self-sufficient without requiring additional active power factor correction components.
3Object-affected harmful factors
If a partial smoothing circuit is used to reduce ripple component, then the ripple component is reduced and power factor is improved, but the peak value of input current increases
Solution Approach 1:
The patent applies partial smoothing only to the low voltage periods of the ripple voltage rather than smoothing the entire waveform. This partial action is sufficient to eliminate the harmful effects of ripple on load current while avoiding the excessive current peaks that would result from attempting to smooth the entire voltage waveform.
Solution Approach 2:
The partial smoothing circuit is designed to act locally on specific portions of the voltage waveform (only the low voltage periods), applying smoothing where it is most needed to prevent load current ripple while leaving the rest of the waveform untouched to avoid increasing peak input current.
4Power
If large current withstanding capability parts are used to handle steep charging current, then the peak input current is withstood, but the thickness of wire and capacity of switch or breaker must be increased, causing increase in cost or size
Solution Approach 1:
By applying partial smoothing only to low voltage periods rather than the entire waveform, the patent avoids creating steep charging currents that would require oversized components. The partial action is sufficient for ripple reduction while keeping current peaks within normal limits.
Solution Approach 2:
The patent uses standard-rated components with normal current withstanding capabilities rather than expensive, oversized components designed for peak currents. This approach allows the use of conventional, cost-effective parts that are sufficient for the actual operating conditions created by the partial smoothing circuit.
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 the ripple component of the load current, improves the power factor, and decreases noise, achieving these results with a simpler circuit configuration and reducing the peak input current, thereby minimizing the need for high-current components and enhancing the reliability and efficiency of the lighting device.
Implementation Method 1
a rectifying unit which rectifies an AC voltage outputted from a power supply
Implementation Method 2
a smoothing unit which smoothes a ripple voltage outputted from the rectifying unit
Data Source
AI summary
A light emitting element lighting device includes: a rectifying unit which rectifies an AC voltage; a smoothing unit which smoothes a ripple voltage from the rectifying unit; a power supply unit having a switching element; and a control unit which controls on/off of the switching element. Further, the smoothing unit servers as a partial smoothing circuit for partially smoothing a low voltage period of the ripple voltage outputted from the rectifying unit. The power supply unit supplies a lighting power to a light source unit including one or more light emitting elements. The control unit controls a switching frequency of the switching element to decrease as the output voltage of the smoothing unit decreases.