Load Driving Apparatus Feedback Control for Constant Current
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Solution Overview
Problem
Existing load driving apparatuses face challenges in accurately supplying constant current to loads due to temperature dependencies and varying load types, leading to increased costs and consumption current, especially when trying to improve driving speed and flexibility.
Innovation Solution
A load driving apparatus incorporating a shunt resistor and a driver circuit with feedback control, utilizing a reference voltage source and operational amplifier to adjust the constant current, and a Darlington circuit configuration with sensing resistors and switches to enhance accuracy and flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a PNP transistor is used to supply constant current to the load, then the current can be controlled, but the current accuracy deteriorates due to temperature dependencies of gain and forward voltage
Solution Approach 1:
The patent employs feedback control by detecting the voltage at the first end of the shunt resistor and comparing it with a reference voltage through an operational amplifier. The operational amplifier adjusts the shunt current based on the voltage difference, creating a closed-loop feedback system that compensates for temperature dependencies and maintains accurate constant current supply to the load.
Solution Approach 2:
The patent introduces a shunt resistor as an intermediary element to convert the constant current into a measurable voltage signal. This voltage is then used by the feedback control circuit to regulate the current, providing an accurate reference that is independent of transistor parameter variations.
2Adaptability or versatility
If the gate driver circuit is designed for the load that needs the maximum constant current, then all loads can be driven, but the cost increases
Solution Approach 1:
The patent implements dynamic current adjustment capability through the feedback control circuit. The operational amplifier continuously adjusts the shunt current based on the actual load requirements, allowing the circuit to adapt to different load types and current demands without being fixed to a maximum current design, thereby reducing cost while maintaining versatility.
Solution Approach 2:
The patent enables parameter changes in the constant current magnitude through feedback control. By varying the reference voltage or feedback ratio, the circuit can adjust the constant current level to match different load requirements, eliminating the need to design for maximum current and reducing overall circuit cost.
3Speed
If two NPN transistors are connected in Darlington configuration to increase driving speed, then the driving speed improves, but the consumption current increases
Solution Approach 1:
The patent uses feedback control to precisely regulate the constant current supplied to the load. This allows the circuit to provide high current only when needed for fast switching, and reduce current during steady-state operation, thereby achieving high driving speed while minimizing overall consumption current compared to Darlington configurations that continuously draw high current.
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 ensures accurate and flexible constant current supply to loads, reduces consumption current, and improves driving speed by using feedback control and Darlington configurations, allowing for adaptable current capability without considering maximum load current.
Implementation Method 1
The driver circuit adjusts the magnitude of the constant current by performing a feedback-control of the magnitude of the shunt current in such a manner that a first voltage corresponding to the reference voltage becomes equal to a second voltage corresponding to a voltage at the first end of the shunt resistor
Implementation Method 2
A shunt current corresponding to the constant current flows through the shunt resistor
Data Source
AI summary
A load driving apparatus for driving a load with a constant current includes a shunt resistor and a driver circuit. A shunt current corresponding to the constant current flows though the shunt resistor. The driver circuit is connected to a first end of the shunt resistor to supply the constant current corresponding to the shunt current to the load. The driver circuit includes a reference voltage source for generating a predetermined reference voltage. The driver circuit adjusts the magnitude of the constant current by performing a feedback-control of the magnitude of the shunt current in such a manner that a first voltage corresponding to the reference voltage and a second voltage corresponding to a voltage at the first end of the shunt resistor become equal to each other.