Multi-Op-Amp Current Generator for Precise Car Lamp LED Modes
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Solution Overview
Problem
Current generators in car lamp systems fail to provide precise currents for both brake light and running light modes, with existing circuits only achieving 99% and 40% of target currents, respectively, due to significant differences in current requirements.
Innovation Solution
A current generating circuit comprising multiple operational amplifiers, semiconductor switches, and a control unit, where each operational amplifier receives a reference voltage and controls a corresponding semiconductor switch to output precise currents to LEDs, mitigating errors caused by offset voltages and allowing for precise current generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single operational amplifier circuit is used to generate both high and low currents, then the circuit complexity is reduced, but the current precision deteriorates significantly for low current modes
Solution Approach 1:
The patent divides the current generation function into separate operational amplifiers for different current modes. Specifically, it uses one operational amplifier for high current generation and another for low current generation, allowing each amplifier to be optimized for its specific current range and thereby maintaining high precision in both modes without compromising circuit complexity excessively.
Solution Approach 2:
The patent implements dynamic switching between different operational amplifiers based on the required current mode. The control unit dynamically selects which operational amplifier to activate depending on whether high current or low current is needed, enabling the system to adapt its precision characteristics to the specific operating conditions.
2Measurement precision
If the reference voltage is increased to compensate for offset voltage errors, then low current precision improves, but high current generation becomes excessive
Solution Approach 1:
The patent applies different reference voltage levels to different operational amplifiers according to their specific requirements. The high current operational amplifier receives a reference voltage appropriate for high current generation, while the low current operational amplifier receives a lower reference voltage that provides sufficient margin to overcome offset voltage errors without causing excessive current in high current mode.
Solution Approach 2:
The patent changes the reference voltage parameter based on the operating mode. By providing different reference voltage levels to different operational amplifiers optimized for different current ranges, the system achieves high precision in low current mode without generating excessive current in high current mode.
3Device complexity
If a single transistor is used for both high and low current output, then the device structure is simplified, but the transistor size must be large to handle high current, increasing overall device size
Solution Approach 1:
The patent segments the current output function into separate transistors for different current modes. It uses one transistor for high current output and another for low current output, allowing each transistor to be sized appropriately for its specific current requirement. This eliminates the need for an oversized transistor that would be required if a single transistor had to handle both high and low current modes.
Data Source
AI summary
A current generating circuit for providing one or more than one load current is provided. The current generating circuit includes: one or more than one operational amplifier, coupled to a reference voltage source, wherein each positive input end of the one or more than one operational amplifier receives the reference voltage source;one or more than one semiconductor switch, used for controlling the output of the one or more than one load current, wherein each semiconductor switch is respectively coupled to a corresponding operational amplifier and a load, and the semiconductor switch operates according to signals outputted from the output end of the corresponding operational amplifier to output the corresponding load current; and a control unit, coupled to the one or more than one operational amplifier, for outputting a control signal to control the operation of the one or more than one operational amplifier.