Solar Garden Light Control Circuit Voltage Drop Reduction
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Solution Overview
Problem
Conventional solar-powered garden lights face inefficiencies due to voltage drops from diodes, increased power requirements from continuously powered comparators, and complex pulse width modulation circuitry, leading to higher costs and reduced efficiency.
Innovation Solution
A control circuit that includes a battery charging circuit using a p-channel charging transistor to maximize charging voltage, a driver circuit with a driver enable circuit to reduce power consumption, and a low voltage disable circuit to prevent deep discharge, all integrated on a semiconductor device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a diode or diode-connected transistor is used to charge the battery from the solar cell, then the battery charging operation can be enabled, but a voltage drop of about 0.7 Volts occurs which reduces charging efficiency
Solution Approach 1:
The patent removes the diode component from the charging circuit entirely. Instead of using a diode or diode-connected transistor to prevent reverse current flow, the invention employs a controller with control circuitry that actively manages the charging process through pulse width modulation (PWM) of a switching element. This extraction of the diode eliminates the inherent 0.7V voltage drop and associated power loss while maintaining battery protection through electronic control.
Solution Approach 2:
The patent replaces the passive mechanical/diode-based current blocking mechanism with an active electronic control system. The controller uses PWM signals to switch a transistor on and off, precisely controlling current flow to the battery. This substitution of diode-based passive protection with active electronic switching achieves the same protective function without the voltage drop penalty, improving charging efficiency.
2Ease of operation
If a comparator is used to compare battery voltage with photo resistor voltage to control LED power, then the LED power decision can be made, but the comparator requires continuous power from the battery which increases power requirements and reduces charging efficiency
Solution Approach 1:
The patent replaces the continuously operating comparator with a periodic sensing and control mechanism. The controller periodically samples the battery voltage and ambient light conditions, then adjusts the LED power delivery accordingly through PWM control. This periodic operation eliminates the need for continuous power consumption by a comparator, reducing overall system power requirements while maintaining effective LED power management.
Solution Approach 2:
The controller integrates multiple functions including voltage sensing, light sensing, and power management into a single self-sufficient unit. Rather than requiring separate powered components like a comparator and photo resistor, the controller performs all decision-making internally by monitoring system conditions and autonomously adjusting power delivery to the LED based on battery state and ambient light levels.
3Ease of operation
If photo resistor is used for voltage comparison with battery, then the LED power decision can be made, but the photo resistor increases system costs
Solution Approach 1:
The patent combines the functions of voltage comparison, light sensing, and power management into a single integrated controller. The controller incorporates internal sensing capabilities that eliminate the need for external photo resistors and separate comparison circuits. This merging of functions reduces the total component count, simplifies the bill of materials, and lowers overall system cost while maintaining the ability to make informed LED power decisions based on both battery voltage and ambient light conditions.
4Ease of operation
If complex pulse width modulation circuitry is used to control LED current by varying clock signal phase width, then LED power can be controlled, but the circuitry is fairly complex and results in significant power consumption
Solution Approach 1:
The patent extracts and removes the complex dedicated PWM circuitry from the system. Instead of using specialized pulse width modulation circuits with multiple timing components and phase control mechanisms, the invention implements a simplified switching control approach where a controller generates PWM signals using a single switching element. This extraction of complex modulation circuitry reduces device complexity while maintaining effective LED current control through straightforward on/off switching based on timing intervals.
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
The solution enhances the efficiency of solar-powered garden lights by minimizing voltage drops, reducing power consumption, and preventing deep discharge, resulting in a more efficient and cost-effective system.
Implementation Method 1
a battery charging circuit using a p-channel charging transistor to maximize charging voltage
Implementation Method 2
The LED was typically powered by charging an inductor during one phase of a clock signal, and then discharging the inductor to supply current to the LED during another phase of the clock signal
Implementation Method 3
A capacitor often typically was connected in parallel with the LED, such that the capacitor was charged during the time that the inductor discharged to power the LED
Data Source
AI summary
In one exemplary embodiment, a control circuit includes a comparator circuit that compares a solar cell voltage and a battery voltage and responsively activates a charging control signal if the solar cell voltage is greater than the battery voltage. If the solar cell voltage is not greater than the battery voltage, the comparator circuit deactivates the charging control signal.