LED Control Device Segmented PWM for Accuracy and Responsivity
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Solution Overview
Problem
Existing LED driving circuits face challenges in achieving high accuracy PWM control without impairing responsivity, as increasing PWM bit gradations lengthens the PWM cycle, and high switching speed buck converters can cause unwanted radiation due to switching noise.
Innovation Solution
A control device and method that control an LED by obtaining a control value of n + m bits, where the number of switching element on times in a period is controlled by n higher-order bits and the ON time at one of these times is controlled by m lower-order bits, allowing for increased gradations without compromising responsivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If PWM bit gradations are increased to improve control accuracy, then manufacturing precision is improved, but the PWM cycle becomes longer and responsivity deteriorates
Solution Approach 1:
The patent segments the control of switching element operations into two independent dimensions: (1) the number of times the switching element is turned on within a PWM cycle, controlled by n higher-order bits, and (2) the ON time duration at each turning-on event, controlled by m lower-order bits. This segmentation allows the total control resolution to be (n+m) bits while maintaining a fixed PWM cycle length, thereby resolving the contradiction between control accuracy and responsivity.
2Speed
If switching speed is increased to improve responsivity, then speed is improved, but unwanted radiation due to switching noise increases
Solution Approach 1:
The patent introduces dynamic control of the switching element's ON time duration based on lower-order bits, allowing the ON time to be adjusted within each switching cycle without changing the overall switching frequency. This dynamic adjustment enables high-resolution control (m bits) while maintaining a fixed, optimized switching frequency that avoids radiation issues, thus resolving the contradiction between responsivity and switching noise radiation.
3Manufacturing precision
If the number of switching element on times is increased to improve control gradations, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The patent transitions from traditional one-dimensional PWM control (only varying duty cycle) to two-dimensional control by adding control over the ON time duration at each switching event. This dimensional expansion allows achieving (n+m) bit control resolution through independent control of two parameters (number of on-times and ON time duration), effectively increasing control gradations without proportionally increasing device complexity.
Data Source
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AI summary
A control device for controlling driving of an LED (11) includes: a driving section driving the LED (11), the driving section being formed including a switching element (12); a control value obtaining section (61) obtaining a control value of n + m bits; and a controlling section (21, 31, 34, 37, 36, 62-64) controlling the driving of the LED (11) by the driving section on a basis of the control value of the n + m bits obtained by the control value obtaining section (61) such that a number of times of turning on the switching element (12) in a predetermined period is controlled by a control value of n higher-order bits, an ON time at one of the times of turning on the switching element (12) is controlled by a control value of m lower-order bits, and ON times of the switching element (12) excluding the ON time at the one time of turning on the switching element (12) are a predetermined time.