LED Mains Voltage Measurement Using Current Mirror
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Solution Overview
Problem
Existing measurement circuits for solid-state lighting (SSL) devices struggle to accurately measure input voltage across a wide range of voltage values, which is essential for reliable dimming control and compatibility with different mains voltage levels.
Innovation Solution
A measurement circuit utilizing a current mirror configuration with adjustable ratios, coupled with a resistor divider, allows for accurate digital measurement of input voltage by adjusting the current mirror ratio to maintain the sensed voltage within a predetermined range, regardless of input voltage variations, using auxiliary transistors and an offset current source.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed voltage divider is used to measure input voltage, then the circuit is simple, but the measurement accuracy deteriorates across wide voltage ranges
Solution Approach 1:
The patent applies the dynamics principle by making the voltage divider ratio adjustable through current mirror circuitry with selectable current mirror ratios. The measurement circuit dynamically adapts to different input voltage ranges by switching between different current mirror ratios, allowing accurate measurements across wide voltage ranges (e.g., 90V-264V) while maintaining reasonable circuit complexity.
2Device complexity
If the current mirror ratio is fixed, then the circuit is simpler, but the ability to adapt to different voltage levels is reduced
Solution Approach 1:
The patent implements dynamic adaptability by providing multiple selectable current mirror ratios through auxiliary transistors and switches. The controller can select appropriate current mirror ratios based on detected input voltage levels, enabling the same circuit to accurately measure both 110V and 230V mains voltages as well as intermediate voltages, thereby achieving high versatility with moderate complexity increase.
Solution Approach 2:
The patent changes the electrical parameters of the current mirror circuitry by adjusting the current mirror ratio according to the input voltage level. This parameter adjustment allows the measurement circuit to maintain optimal operating conditions across different voltage ranges, improving both adaptability and measurement accuracy without requiring completely different circuits for each voltage level.
3Measurement precision
If high-resolution ADC is used to cover wide voltage range, then measurement accuracy is improved, but cost increases
Solution Approach 1:
The patent uses dynamic range adaptation through adjustable current mirror ratios to map different input voltage ranges to a standardized ADC input range. This allows the use of lower-resolution, lower-cost ADCs while maintaining effective measurement precision across wide voltage ranges, thereby reducing manufacturing cost without sacrificing measurement capability.
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 enables precise and cost-effective measurement of input voltage across a wide range, enhancing dimming control accuracy and reducing ADC costs by adapting to varying input voltages, while being robust against voltage spikes and transients.
Implementation Method 1
The current mirror circuitry is configured to translate an input current at the input of the current mirror circuitry into an output current at an output of the current mirror circuitry, such that the output current is proportional to the input current by a current mirror ratio
Implementation Method 2
the first resistor and the current mirror circuitry may be implemented in series with respect to one another... the input current of the current mirror circuitry corresponds to the current through the first resistor
Data Source
AI summary
Measurement circuits which are configured to measure wide ranges of the input voltage using a sensed input voltage of the driver circuits for solid state lighting (SSL) devices are presented. The measurement circuit comprises a first resistor which is coupled at a first side to the input voltage. The measurement circuit comprises current mirror circuitry coupled at an input to a second side of the first resistor, and which translates an input current at the input of the current mirror circuitry into an output current at an output of the current mirror circuitry, such that the output current is proportional to the input current by a current mirror ratio. The measurement circuit comprises a second resistor coupled to the output of the current mirror circuitry and to provide the sensed input voltage, when the input voltage is coupled to the first side of the first resistor.