LED Drive Circuit Battery Voltage Compensation
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Solution Overview
Problem
Existing LED drive circuits in battery-powered devices fail to efficiently regulate current through LEDs as battery voltage drops, leading to reduced battery life due to maintaining constant brightness, which is aesthetically pleasing but shortens operation time.
Innovation Solution
A method and circuit that senses the current through an LED and adjusts the control signal for a power converter based on the power supply voltage, reducing the LED current as the battery voltage decreases, using a feedback circuit with an error amplifier to compare LED current feedback voltage to a reference voltage, offsetting the control signal in response to battery voltage changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If constant current is maintained through LED to maintain constant brightness, then LED brightness stability is improved, but battery life is reduced
Solution Approach 1:
The patent applies dynamics by transitioning from a static constant current regulation approach to a dynamic current regulation approach. The LED drive current is dynamically adjusted based on the battery voltage level, allowing the system to adapt its operation to extend battery life while maintaining acceptable brightness. The control circuit modifies the current setpoint continuously as battery voltage changes, rather than maintaining a fixed current value throughout discharge.
Solution Approach 2:
The patent changes the operating parameters of the LED driver based on battery voltage. Specifically, the current regulation setpoint is changed as a function of battery voltage, allowing the system to operate at lower currents when battery voltage drops. This parameter change enables extended battery life by reducing power consumption during the discharge phase, while still maintaining functional brightness levels.
2Duration of action of moving object
If battery voltage drops, then battery life is extended by reducing LED current, but LED brightness is reduced
Solution Approach 1:
The patent applies partial action by not maintaining full LED brightness throughout the entire battery discharge cycle. Instead, it accepts reduced brightness during the later discharge phase when battery voltage drops, in exchange for significantly extended battery life. This partial performance approach prioritizes operational duration over constant maximum brightness, allowing the device to remain functional for a longer period.
3Reliability
If specialized power converters are used to regulate LED current, then LED current regulation is improved, but device complexity is increased
Solution Approach 1:
The patent uses feedback by continuously monitoring battery voltage and using this information to adjust the LED drive current through the power converter control circuit. The feedback mechanism allows the system to automatically adapt its operation based on battery state, extending life without requiring complex additional hardware. The existing power converter's control loop is enhanced with voltage-dependent current setpoint adjustment.
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 extends the battery life by gradually reducing LED brightness as the battery discharges, allowing the device to operate for a longer period while maintaining functionality, as demonstrated by test results showing extended battery life with reduced LED current.
Implementation Method 1
an error amplifier for comparing an LED current feedback voltage and a reference voltage to produce a control signal
Implementation Method 2
the LED is driven by a power converter output
Implementation Method 3
light emitting diodes (LEDs) has become increasingly popular in small, portable, battery-powered electronics
Implementation Method 4
The control signal is then offset in response to the power supply voltage to reduce the current through the LED as the power supply voltage drops
Data Source
AI summary
In a method for producing a control signal for regulating a drive current for driving an LED, a current through the LED is sensed, wherein the LED is driven by a power converter output, and wherein an output voltage of the power converter is proportionately controlled by a control signal. Next, a power supply voltage is sensed. The control signal is produced for the power converter, wherein the control signal is proportional to a difference between a reference voltage and the current through the LED. The control signal is then offset in response to the power supply voltage to reduce the current through the LED as the power supply voltage drops.