LED Driver Switching PWM and Current Control for Efficiency
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Solution Overview
Problem
LED driving apparatuses face inefficiencies in controlling luminous power, leading to increased power consumption and heating issues due to varying luminous efficiency with driving current values, particularly when using current value control and PWM control methods.
Innovation Solution
An LED driving apparatus that switches between current value control and PWM control based on a target luminous power value, using PWM control when the target is below a predetermined value for maximum efficiency and switching to current value control when the target is above this value to minimize power consumption and heating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If current value control is used to achieve target luminous power, then luminous power control flexibility is improved, but luminous efficiency deteriorates when target value does not correspond to maximum efficiency current
Solution Approach 1:
The patent applies dynamics by making the control method adaptive rather than static. The control section dynamically selects between PWM control and current value control based on the target luminous power value. When target value is below a predetermined threshold, PWM control is used to maintain high efficiency; when above the threshold, current value control is used to achieve the required luminous power. This dynamic adaptation resolves the contradiction between control flexibility and energy efficiency.
Solution Approach 2:
The patent changes the control parameter based on the operating condition. For low luminous power requirements (below predetermined value), PWM control varies the duty cycle while maintaining constant current. For high luminous power requirements (above predetermined value), current value control directly adjusts the current magnitude. This parameter change strategy ensures optimal luminous efficiency across different operating ranges while maintaining the ability to achieve any target luminous power.
2Ease of operation
If PWM control is used with constant current value, then control simplicity is improved, but luminous efficiency deteriorates when constant current does not correspond to maximum efficiency current
Solution Approach 1:
The patent makes the control approach dynamic by selecting between PWM control and current value control based on the target luminous power. This dynamic selection ensures that PWM control (with its simplicity) is used only when appropriate (target value below predetermined value), while current value control is used when needed (target value above predetermined value), thus maintaining both ease of operation and luminous efficiency.
Solution Approach 2:
The patent changes the control parameter (duty cycle for PWM, current magnitude for current value control) based on the target luminous power requirement. This parameter adaptation allows the system to maintain high luminous efficiency across different operating conditions while preserving the simplicity of PWM control where applicable.
3Use of energy by moving object
If LED is driven with low luminous efficiency, then power consumption increases, but device miniaturization is hindered due to increased heating
Solution Approach 1:
The patent applies dynamics by dynamically selecting the control method based on target luminous power. This dynamic selection ensures the LED operates at or near maximum luminous efficiency for all target values, thereby minimizing power consumption and heat generation. The adaptive control prevents the LED from being driven with low luminous efficiency, thus enabling device miniaturization by reducing thermal management requirements.
4Loss of energy
If target luminous power value is below predetermined value, then PWM control maintains high efficiency, but if target value is above predetermined value, then current value control is needed which may reduce efficiency
Solution Approach 1:
The patent segments the luminous power control range into two regions: a low power region (target value below predetermined value) where PWM control is used for high efficiency, and a high power region (target value above predetermined value) where current value control is used for sufficient luminous power output. This segmentation allows each control method to operate in its optimal range, resolving the contradiction between efficiency and control range.
Solution Approach 2:
The patent changes the control parameter strategy based on the target luminous power level. For low target values, PWM duty cycle is adjusted while maintaining constant current. For high target values, current magnitude is directly adjusted. This parameter change approach ensures high luminous efficiency is maintained across the entire luminous power control range by adapting the control method to the operating region.
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 approach allows the LED to be driven with the highest luminous efficiency possible while minimizing power consumption and heat generation, thereby enabling device miniaturization.
Implementation Method 1
Another is to implement pulse width modulation (PWM) control with keeping a driving current level constant
Implementation Method 2
backlights employing light emitting diodes (LEDs), which consume less power
Data Source
AI summary
A light emitting diode (LED) driving apparatus includes a drive section for driving an LED to emit light, and a control section that controls a driving current supplied from the drive section to the LED. The control section implements luminous power control by controlling an ON/OFF ratio of the driving current if a target value of luminous power of the LED is smaller than a predetermined value. The control section implements luminous power control by controlling a level of the driving current if the target value is equal to or larger than the predetermined value.