LED Driver Circuit Digital Current Retention
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Solution Overview
Problem
Existing semiconductor light source lighting circuits for LEDs are large due to the need for capacitors to retain current values in an analog manner, which is inconvenient and inefficient for PWM light dimming applications.
Innovation Solution
A semiconductor light source lighting circuit that uses a switching regulator and a control circuit with a comparator, up/down counter, digital/analog converter, and drive circuit to digitally retain the drive current during inactive states, allowing for PWM light dimming without the need for large capacitors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If capacitors are used to retain current values in an analog manner, then the current value can be maintained during stop periods, but the circuit size becomes unnecessarily large
Solution Approach 1:
The patent replaces the analog capacitor-based retention system with a digital retention system using a register or memory element. The analog manner of retaining current values through capacitors is substituted with a digital representation where the current value is converted to a digital signal and stored in a register during the stop period, eliminating the need for large capacitors and reducing circuit size while maintaining reliable value retention.
Solution Approach 2:
The patent changes the parameter representation from analog continuous voltage levels stored in capacitors to digital discrete values stored in registers. By converting the analog current value to a digital parameter and storing it in a digital memory element, the system achieves the same retention function with significantly reduced component size and improved precision.
2Illumination intensity
If PWM light dimming method is adopted, then color shift is avoided and brightness can be adjusted, but the circuit requires digital processing components increasing complexity
Solution Approach 1:
The control circuit is designed to perform multiple functions: it generates PWM signals for brightness adjustment, converts analog current values to digital signals, stores digital values in registers, and controls the switching element. By integrating these functions into a single control circuit, the patent avoids the need for separate dedicated circuits for each function, thereby reducing overall circuit complexity while maintaining full PWM dimming capability.
Solution Approach 2:
The patent merges the analog-to-digital conversion, digital value storage, and PWM generation functions into a single integrated control circuit. Instead of having separate circuits for each function, the design combines these operations into one unified control unit that manages the switching element directly, simplifying the overall circuit architecture while enabling precise brightness control through PWM.
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 circuit size while maintaining adjustable LED brightness through PWM light dimming, using digital retention of control values to simplify the circuit and improve efficiency.
Implementation Method 1
a switching regulator that has a switching element and produces a drive current for driving the semiconductor light source by using the switching element
Implementation Method 2
a comparator that compares the magnitude of the drive current and the target value
Implementation Method 3
an up/down counter that is configured to perform a counting operation, in which a digital value is incremented or decremented based on a result of comparison performed by the comparator
Implementation Method 4
a digital/analog converter that converts the digital value into an analog signal
Data Source
AI summary
A semiconductor light source lighting circuit includes a switching regulator that produces a drive current ILED with a switching element, and a control circuit that controls turning on and off of the switching element so that the magnitude of the drive current ILED approaches a target value. The control circuit includes an error comparator that compares the drive current ILED and the target value, an up/down counter that performs a counting operation, in which the control digital value is incremented or decremented based on the result of the comparison, a D/A converter that converts the control digital value into an analog duty ratio setting signal S4, and a drive circuit that controls the turning on and off of the switching element based on the signal S4. The up/down counter stops the counting operation when the switching regulator is brought into the inactive state.