Switching Power Supply Current Feedback for Stable LED Brightness
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Solution Overview
Problem
Existing switching power supplies primarily use constant voltage output, which fails to meet the need for consistent brightness and color consistency in LED lighting applications.
Innovation Solution
A switching power supply with a detection circuit generating two voltages, one representing output current, and a logic control chip comparing a summed feedback voltage with a reference voltage to control the turn-on time, ensuring constant current output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a switching power supply uses constant voltage output, then the power supply structure is simple and easy to manufacture, but the LED brightness consistency and color uniformity cannot be ensured
Solution Approach 1:
The patent changes the control parameter from voltage to current. The detection circuit generates a second voltage that represents the output current, and the logic control chip adjusts the turn-on time based on the feedback voltage (sum of first and second voltages) to maintain constant current output, ensuring LED brightness consistency while keeping the overall structure relatively simple
Solution Approach 2:
The patent implements a feedback mechanism where the detection circuit continuously monitors the output current (represented by the second voltage) and feeds it back to the logic control chip. The chip compares the feedback voltage with the reference voltage and adjusts the switching duty cycle accordingly, forming a closed-loop control system that maintains constant current output
2Device complexity
If a switching power supply uses constant voltage output, then the device complexity is low, but the LED chroma consistency cannot be ensured
Solution Approach 1:
The patent changes the controlled parameter from voltage to current. By using the second voltage to represent output current and adjusting the turn-on time based on current feedback rather than voltage feedback, the system ensures consistent LED chroma while maintaining relatively simple device complexity through the use of a detection circuit and standard logic control chip
3Manufacturing precision
If the switching power supply adjusts turn-on time to control output current, then the LED brightness and color consistency is improved, but the control system complexity increases
Solution Approach 1:
The patent implements feedback control where the detection circuit generates voltages representing output current, and the logic control chip continuously compares feedback voltage with reference voltage to adjust turn-on time. This closed-loop system maintains precise output current consistency while using standard electronic components to keep control system complexity manageable
Solution Approach 2:
The patent uses voltage signals as intermediaries to represent and control current. The detection circuit converts current information into voltage signals (first and second voltages), which are then processed by the logic control chip to adjust switching timing, providing an effective intermediary mechanism for current control
Data Source
AI summary
The application discloses a switching power supply with constant current output and a method for controlling constant current of a switching power supply, wherein the switching power supply comprises a detection circuit and a logic control chip, and the detection circuit is configured to output a feedback voltage. The feedback voltage is a sum voltage of a first voltage and a second voltage, and the second voltage represents output current of the switching power supply. The logic control chip is configured to receive the feedback voltage and compare the feedback voltage with a reference voltage. When the output current changes, the logic control chip changes turn on time of the switching power supply based on comparison result to control the output current constant. The reference voltage set by a switching power supply with constant voltage output is very high, while operating current requirement of constant current drive is very small, and the reference voltage is too high relative to the second voltage, so the first voltage is introduced to bear part of the reference voltage, so that constant current reference is lowered, so as to take into account needs of constant current drive and power consumption.