Cascade Dimming Circuit for LED Efficiency
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Solution Overview
Problem
Conventional dimming circuits for LED lights face efficiency decreases when adjusting LED driving current to low levels, leading to increased product costs due to inefficient operation of the DC-DC converter at the second stage.
Innovation Solution
A dimming circuit with a primary controlled flyback converter and a DC-DC converter in a cascade arrangement, where the control circuit adjusts the power switches based on a dimming signal to maintain the DC-DC converter within a predetermined state range, optimizing the output voltage and current control to improve efficiency and reduce production costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a DC-DC converter is used at the second stage to adjust LED driving current, then brightness adjustment capability is improved, but efficiency decreases when operating at low current levels
Solution Approach 1:
The patent dynamically adjusts the duty ratio of the DC-DC converter based on the LED driving current level. When LED current is high, a higher duty ratio is used; when LED current is low, a lower duty ratio is used. This dynamic adjustment ensures the converter operates in its efficient range across different dimming conditions, resolving the efficiency degradation at low current levels while maintaining full brightness adjustment capability
Solution Approach 2:
The patent changes the operating parameters (duty ratio) of the DC-DC converter according to the load conditions. By monitoring the LED driving current and adjusting the duty ratio accordingly, the converter maintains optimal efficiency across the full dimming range from 100% to 10% brightness, eliminating the efficiency loss that occurs with fixed parameter operation
2Adaptability or versatility
If multi-stage switching converters are used to adjust LED brightness, then dimming control is improved, but product cost increases
Solution Approach 1:
The patent makes the DC-DC converter perform multiple functions: it provides dimming control by adjusting LED driving current, maintains efficient operation across different power levels through duty ratio adjustment, and ensures stable voltage output. This multi-functionality eliminates the need for additional dedicated dimming control circuits, reducing overall system cost while maintaining full dimming control capability
Solution Approach 2:
The patent combines the dimming control function with the power conversion function in a single integrated DC-DC converter stage. By merging these functions, the patent reduces the number of separate components needed, simplifies the circuit structure, and lowers product cost while achieving effective brightness adjustment
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 configuration enhances the overall efficiency of the dimming circuit by allowing most power to be transferred directly through one stage, reducing device requirements and production costs while maintaining stable LED load operation across various dimming states.
Implementation Method 1
a transformer having a primary winding, a first secondary winding and a second secondary winding
Implementation Method 2
an LED load
Data Source
AI summary
A dimming circuit for adjusting the brightness of an LED load, can include: a primary controlled flyback converter having a primary-side circuit, a first secondary-side circuit, and a second secondary-side circuit; a DC-DC converter coupled in a cascade arrangement with the second secondary-side circuit, where an output node of the DC-DC converter is coupled in series to an output node of the first secondary-side circuit; a control circuit configured to control, according to a dimming signal that represents an expected output current of the dimming circuit, a power switch of the primary controlled flyback converter to adjust output voltages of the first and second secondary-side circuits, to adjust a power that is provided to the LED load; and the control circuit being configured to control a power switch of the DC-DC converter according to the dimming signal, such that the DC-DC converter operates within a predetermined state range.