AC-Side LED Control Circuit Using Ferro-Resonant Current Stabilization
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Solution Overview
Problem
Existing LED lighting systems face challenges with high initial transient currents due to electrolytic capacitors and the expense of high-voltage semiconductors, leading to increased complexity and circuit failure risks, particularly when transitioning from HID lamps to LED installations.
Innovation Solution
A control circuit that includes an AC control circuit with a capacitor in series with an inductive winding of a magnetic component, utilizing ferro-resonance to stabilize the DC current supplied to LED lamps, allowing for a simpler and cost-effective conversion from HID to LED installations while reducing variations in AC current and maintaining constant DC current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electrolytic capacitors with high capacitance are used in LED control circuits, then filtering of rectifier output is improved, but very high initial transient currents occur at starting
Solution Approach 1:
The patent removes electrolytic capacitors from the LED control circuit entirely, replacing them with a resistor-inductor network that provides filtering without generating high transient currents. The inductor L1 and resistor R1 combination filters rectifier ripple while avoiding the capacitor charging surge problem.
Solution Approach 2:
The patent uses simple, inexpensive components (resistors and inductors) instead of expensive electrolytic capacitors. These passive components are more reliable and have longer operational life without suffering from capacitor degradation issues.
2Power
If high voltage semiconductors are used in LED driver circuits, then power delivery is improved, but cost and complexity increase significantly
Solution Approach 1:
Instead of using high-voltage semiconductors to handle the full LED string voltage, the patent inverts the approach by using low-voltage components in a series configuration. Multiple low-voltage LED strings are connected in series, each with its own simple current-limiting resistor, avoiding the need for high-voltage semiconductor switches.
Solution Approach 2:
The patent divides the LED lighting system into multiple separate LED strings (first LED string, second LED string, etc.), each operating at low voltage with simple current control. This segmentation allows the use of inexpensive low-voltage components while achieving the required total voltage and power output.
3Ease of manufacture
If multiple driver systems are used to avoid high voltage semiconductors, then cost is reduced, but the number of control wires and complexity increase
Solution Approach 1:
The patent merges multiple LED strings into a single series circuit configuration, sharing common current paths and power supply connections. This reduces the number of separate control wires needed compared to multiple independent driver systems, while still using only low-voltage, inexpensive components.
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 reduces current variations and eliminates the need for multiple driver systems, simplifying the conversion process, reducing costs, and enhancing the reliability of LED lighting installations by using existing cabling and control gear, while providing stable and efficient power delivery to LED lamps.
Implementation Method 1
an AC control circuit including a capacitor in series with an inductive winding of a magnetic component having a magnetically permeable core that at least part of which in operation is at least partially saturated by ferro-resonance
Data Source
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AI summary
The present invention discloses a lighting installation having an LED lamp (19), normally consisting of a series string of individual LED's (18), which is supplied by a rectifier (20, 200). A control circuit (23, 23 & C1) is interposed between the rectifier and the AC supply which powers the rectifier. Various circuits for filtering, power factor control, multi-phase operation and dimming, for example by phase switching, are disclosed. In particular, the control carried out by the control circuit takes place on the AC side of the rectifier. Also disclosed are the control circuit per se and a method of converting a High Intensity Discharge (HID) lamp installation into a Light Emitting Diode (LED) installation. The control circuit can take the form of an inductor, an inductor and series capacitor, a shunt inductor, a leakage reactance transformer, a constant current transformer, an autotransformer, an isolation transformer or a ferro-resonant transformer.