Hysteresis Controlled DC-DC Converter Current Regulation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing DC-DC converters face challenges in maintaining a constant output current due to rapid changes in load impedance, leading to over- or undercurrents and flickering light issues, especially with LED groups, as traditional current controllers react slowly and are costly to compensate.
Innovation Solution
A hysteresis control method that measures and compares the output current to first and second reference values, introducing a time delay based on the difference between these times to balance periods of excess and deficit current, using only two comparators and digital components for cost-effective implementation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional PI controllers are used for current regulation, then slow effects like temperature and aging can be compensated, but rapidly changing loads cannot be handled effectively, leading to over- or undercurrents and flickering light
Solution Approach 1:
The patent replaces the traditional analog PI controller with a digital control system that uses an microcontroller to implement hysteresis control. This substitution enables much faster response times (microsecond range) compared to analog controllers, allowing the system to track rapidly changing LED loads effectively while maintaining current regulation stability
Solution Approach 2:
The patent implements a feedback mechanism where the actual LED current is continuously measured and compared with the target current. Based on this comparison and the hysteresis window, the control algorithm dynamically adjusts the PWM duty cycle to maintain accurate current regulation even during rapid load transitions
2Speed
If hysteresis control is used to respond quickly to load changes, then current regulation improves, but the switching time depends on output voltage and other parameters causing the current to exceed or fall below limits
Solution Approach 1:
The patent implements dynamic hysteresis window adjustment where the hysteresis range is not fixed but adapts based on operating conditions such as output voltage and load characteristics. This dynamic adjustment compensates for parameter variations and keeps the current accurately within the hysteresis range despite changes in switching timing
Solution Approach 2:
The control algorithm dynamically changes the hysteresis window parameters based on the measured output voltage and current conditions. By adjusting the hysteresis range and switching thresholds in real-time, the system compensates for voltage fluctuations and parameter variations, maintaining precise current control
3Manufacturing precision
If analog circuits with four amplifier circuits are used to compensate for current deviations quickly, then current accuracy improves, but manufacturing costs increase compared to uncompensated circuits
Solution Approach 1:
The patent replaces complex analog compensation circuits with a digital control implementation using an microcontroller. The current deviation compensation is achieved through software algorithms that calculate and apply corrective PWM adjustments, eliminating the need for multiple expensive analog amplifier circuits while maintaining high current accuracy
Solution Approach 2:
The patent uses a cost-effective digital approach with a single microcontroller and minimal additional components instead of expensive analog amplifier circuits. The digital compensation algorithm provides accurate current control at a fraction of the cost of analog solutions, making the system economically viable for mass production
Data Source
Figure 1~3
Figure 4
Figure 5
AI summary
Method and apparatus for controlling the hysteresis of an output current from a DC-DC converter (3) to a default value (19) for an average output current and within a hysteresis range (11), wherein the output current (6) is measured and is compared with a first reference value and a second reference value, wherein a switch (7) of the DC-DC converter (3) is changed over at the limits of the hysteresis range (11) on the basis of a first reference time (20), at which the output current (6) reaches the first reference value, and a second reference time (24), at which the output current reaches the second reference value, wherein the switch (7) is changed over with a time delay after the second reference time (24), and wherein the time delay is selected on the basis of a time difference between the first reference time (20) and the second reference time (24) in such a manner that a period of time, during which the output current (6) is higher than the default value (19), and a period of time, during which the output current (6) is lower than the default value (19), are compensated for.