Resonant Isolated LED Converter Snubber for Off-Time Oscillation Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing converters for LED-based loads experience resonant current oscillations during off-time periods, particularly when dimming via high-frequency PWM switching, which are inefficient and costly to suppress.
Innovation Solution
An isolated converter with a transformer, snubber circuit, and snubber switch controlled by a control unit, activated during off-time periods of LF PWM to dissipate oscillation energy, using an RC snubber circuit and an ASIC for efficient control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If high-frequency PWM switching is used for LED dimming, then dimming performance is improved, but resonant current oscillations occur during off-time periods
Solution Approach 1:
The patent applies preliminary anti-action by activating the snubber circuit before the harmful oscillations can fully develop. The snubber circuit is enabled during off-time periods to preemptively dampen resonant current oscillations before they propagate through the circuit, thereby preventing the harmful effects while maintaining LED dimming performance
Solution Approach 2:
The snubber circuit acts as an intermediary element between the switching circuit and the LED load. It provides a controlled path for resonant currents during off-time periods, mediating the energy dissipation in a way that suppresses oscillations without directly interfering with the LED dimming operation during on-time periods
2Object-generated harmful factors
If snubber circuit is continuously activated to suppress oscillations, then oscillation suppression is improved, but energy efficiency deteriorates
Solution Approach 1:
The patent implements periodic action by activating the snubber circuit only during off-time periods when oscillations occur, and deactivating it during on-time periods when the switch is closed. This periodic activation pattern ensures oscillation suppression is applied exactly when needed, avoiding continuous energy dissipation and maintaining overall system efficiency
Solution Approach 2:
The snubber circuit's operation is made dynamic through PWM-controlled switching. The control unit adjusts the snubber circuit activation based on the switching state, enabling it during off-time and disabling it during on-time. This dynamic control optimizes the balance between oscillation suppression and energy efficiency by adapting the snubber's presence to the actual circuit conditions
3Object-generated harmful factors
If snubber circuit is activated during on-time periods, then oscillation suppression is improved, but LED dimming control deteriorates
Solution Approach 1:
The patent uses periodic action to activate the snubber circuit only during off-time periods when the switch is open and oscillations occur, while keeping it inactive during on-time periods when the switch is closed and LED dimming control is active. This temporal separation ensures that oscillation suppression does not interfere with LED dimming operation
Solution Approach 2:
The control unit dynamically manages the snubber circuit based on the switching waveform phase. During on-time periods, the snubber remains disabled to preserve full LED dimming control authority. During off-time periods, the snubber is enabled to suppress oscillations. This dynamic, phase-dependent control ensures both LED dimming precision and oscillation suppression are optimized without mutual interference
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
Effectively reduces or eliminates resonant current oscillations during dimming, enhancing efficiency and reducing costs by selectively activating the snubber circuit during off-time periods.
Implementation Method 1
the snubber circuit or the corresponding elements thereof, respectively, dissipate the oscillation energy
Implementation Method 2
a transformer defining a primary side and a secondary side of the converter
Data Source
Figure 1
Figure 2
AI summary
A converter (10) for supplying an LED-based load is provided. Said converter (10) is an isolated converter (10) having a transformer (11) defining a primary side (12a) and a secondary side (12b) of the converter (10). Said converter (10) further comprises at least one switch (13a, 13b) and a resonance circuitry (14) on the primary side (12a) of the converter (10). Said converter (10) further comprising a snubber circuit (15), preferably a RC snubber circuit. Said snubber circuit (15) has an ancillary winding (16) on the secondary side (12b) of the transformer (11), and a snubber switch (17) arranged for enabling and/or disabling the operation of the snubber circuit (15), the snubber switch (17) being controlled via a signal from a control unit (18) arranged on the primary side (12a) of the converter (10).