LED Load Driving Apparatus Using Segmented Integer-Fractional Signals
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Solution Overview
Problem
Conventional light-emitting diode (LED) driving apparatuses face challenges in reducing electromagnetic interference (EMI) and maintaining performance, particularly when increasing dimming frequency or duration, which can lead to audible sounds and increased current consumption.
Innovation Solution
A load driving apparatus that generates a driving signal through a combination of integer and fractional signals, allowing for precise control of switch-on and switch-off durations without increasing frequency, thereby reducing EMI and enhancing overall performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the frequency of the dimming clock is increased to increase the dimming order of the LED, then the dimming resolution is improved, but the EMI phenomenon becomes more severe and current consumption increases
Solution Approach 1:
The patent segments the dimming control into multiple independent signal lines, each carrying a specific bit of the dimming code. Instead of using a single high-frequency PWM signal, the system divides the dimming control into multiple lower-frequency signal lines that are combined at the LED driver stage, thereby achieving high resolution without high frequency PWM signals that cause EMI
Solution Approach 2:
The patent transitions from time-domain PWM dimming to a spatial/dimensional approach by using multiple parallel signal lines for dimming control. The dimming resolution is achieved through the combination of multiple signal lines rather than through high-frequency temporal modulation, effectively moving the solution from one dimension (time/frequency) to another (spatial/parallel lines)
2Measurement precision
If the duration of the dimming period is increased to increase the dimming order, then the dimming resolution is improved, but the dimming frequency is reduced below 20 kHz generating audible sound
Solution Approach 1:
The dimming control is segmented into multiple independent signal lines, each operating at a higher frequency than the overall dimming period. This allows the individual signal lines to maintain frequencies above the audible range while the overall dimming resolution is determined by the combination of multiple lines, preventing audible noise while achieving high dimming order
Solution Approach 2:
The system uses more signal lines than the minimum required for the desired dimming resolution. By employing multiple signal lines with amplitudes that are fractions of each other (e.g., 1/2, 1/4, 1/8), the system achieves the required precision while maintaining each individual line's frequency above the audible threshold
3Measurement precision
If the frequency of the PWM signal is increased to improve dimming control precision, then the dimming resolution is improved, but the EMI phenomenon becomes more severe
Solution Approach 1:
The high-precision dimming control is achieved by segmenting the control into multiple lower-frequency signal lines rather than using a single high-frequency PWM signal. Each signal line operates at a lower frequency that minimizes EMI, while the combined precision of all lines achieves the desired control accuracy
Solution Approach 2:
The patent introduces an intermediary encoding/decoding stage that converts the dimming control requirement into multiple parallel signal lines. This intermediary layer allows the system to achieve high precision control without directly using high-frequency PWM signals, effectively mediating between the control requirement and the EMI constraint
Data Source
AI summary
A load driving apparatus is disclosed. The load driving apparatus includes a driving signal generator and a controller. The driving signal generator is used for providing a driving signal to a load. The controller is used for generating and providing a control signal to the driving signal generator. The driving signal generator generates N integer signals and M fractional signals in a driving period to form the driving signal according to the control signal. N and M are positive integers, and an amplitude of the integer signals is greater than an amplitude of each of the fractional signals.