Inverse Buck Driving Circuit Voltage Compensation for LED Current Stability
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Solution Overview
Problem
Conventional inverse buck driving circuits experience significant variations in average output current due to fluctuations in input and output voltages, affecting the stability and efficiency of LED string driving.
Innovation Solution
A driving circuit incorporating a switching element, inductor, switch, current sensing element, and control module, where the control module compensates sensed voltage based on input and output voltages to generate a compensated signal, switching the switch from ON to OFF state when the signal exceeds a reference threshold for a delay time, thereby stabilizing the output current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional inverse buck driving circuit is used to drive LED string, then the circuit structure is simple, but the average output current varies greatly depending on input voltage and output voltage
Solution Approach 1:
The patent implements a feedback mechanism where the control module continuously monitors the output voltage across the LED string and adjusts the duty cycle of the switching element accordingly. This closed-loop feedback system compensates for voltage variations, maintaining stable average output current despite changes in input voltage or LED forward voltage, thus resolving the contradiction between simple circuit structure and output current stability
Solution Approach 2:
The control module dynamically changes the duty cycle parameter of the switching element based on detected voltage conditions. By adjusting this key parameter in response to input voltage and output voltage variations, the system maintains consistent output current characteristics without requiring a fundamentally complex circuit architecture
2Speed
If the switch is turned OFF immediately when sensed voltage exceeds reference threshold, then the response speed is fast, but the output current becomes unstable due to voltage fluctuations
Solution Approach 1:
The control module performs preliminary assessment of voltage conditions before triggering the switch OFF state. By evaluating whether the sensed voltage exceeds the reference threshold for a predetermined time duration, the system prepares and validates the switching condition in advance, preventing premature or erroneous switch transitions that would cause output current instability while maintaining fast response to genuine overvoltage conditions
Solution Approach 2:
The patent introduces a time delay mechanism that acts as a cushioning buffer before the switch transitions to OFF state. This delay period absorbs transient voltage spikes and fluctuations, preventing them from causing immediate switch transitions that would destabilize the output current, thus protecting the system stability while preserving rapid response to sustained overvoltage conditions
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 variations in the average output current, maintaining stability and efficiency across varying input and output voltage conditions, with deviations within a tolerance of ±5.0% as shown in the embodiments.
Implementation Method 1
The current sensing element senses a current flowing through the switch to generate a sensed voltage
Implementation Method 2
The inductor has a first terminal coupled to the second terminal of the switching element, and a second terminal
Data Source
AI summary
A driving circuit includes: a switching element having a first terminal to receive an input voltage, and a second terminal; an inductor coupled to the second terminal of the switching element; a switch and a current sensing element coupled in series to the second terminal of the switching element; and a control module compensating a voltage sensed by the current sensing element based on at least one of the input voltage and an output voltage across the switching element and the inductor to generate a compensated signal, and switching the switch from an ON state to an OFF state when the compensated signal exceeds a reference threshold for a delay time.