Relative Error Voltage Detection Circuit Using Current Mirrors
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Solution Overview
Problem
Traditional comparator circuits for detecting relative voltage differences are limited by precision and process cost, especially when the required difference is less than 100 mV, and are not suitable for high voltage fields due to the need for additional processing layers, which increases costs and limits input signal range.
Innovation Solution
A detection circuit comprising a first and second current mirror, a third current mirror, and resistors R1, R2, and R3, where the current sink converts double-ended currents to single-ended voltage signals, allowing for improved precision and voltage range without increasing process cost, using zero-temperature coefficient reference voltage and variable resistors for adjustable ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional grid-input comparator circuits are used to detect relative voltage differences, then the circuit structure is simple, but the detection precision deteriorates when the required difference value is less than 100 mV due to Corner (process deviation) changes
Solution Approach 1:
The patent transforms the voltage comparison problem into a current comparison problem by using current mirrors. The input voltages V1 and V2 are converted to currents through resistors R2 and R3, then mirrored through multiple current mirror stages. This parameter transformation (voltage→current) enables higher precision detection because current mirrors provide better matching characteristics and are less sensitive to process deviations than direct voltage comparators, thereby resolving the contradiction between detection precision and reliability under process deviation.
Solution Approach 2:
The patent introduces current mirrors as intermediary elements between the input voltage signals and the comparison operation. Instead of directly comparing voltages, the circuit uses current mirrors to convert and transfer the voltage information into current form, which is then compared. This intermediary transformation improves precision while maintaining stability against process variations, as current mirrors are inherently more robust to Corner effects than direct voltage comparison circuits.
2Adaptability or versatility
If gate-source devices bearing high voltage are used for high voltage input signals, then the input signal range is expanded, but the process cost increases due to the extra process layer required
Solution Approach 1:
The patent segments the high voltage handling function from the comparison function. The input stage uses standard low-voltage transistors for the current mirror operation, while the high voltage is handled only by the input resistors R2 and R3 and the voltage sources themselves. The sensitive comparison operation is performed on converted current signals at lower voltage levels. This segmentation allows the circuit to accept high voltage inputs without requiring expensive high-voltage process layers, as only passive components need to withstand the high voltage.
Solution Approach 2:
The patent uses current mirrors as intermediaries to transfer signal information from high voltage domain to low voltage domain. The input voltages V1 and V2 (which can be high voltage) are converted to currents through resistors, then processed by low-voltage current mirror circuits. This intermediary current conversion stage isolates the expensive low-voltage CMOS circuitry from the high voltage stress, enabling high voltage input capability using standard process technology.
3Measurement precision
If traditional comparator circuits are used for precise relative difference detection, then the circuit structure is simple, but the precision deteriorates when the required difference value is less than 100 mV
Solution Approach 1:
The patent replaces the direct voltage comparison mechanism with a current mirror-based comparison mechanism. Instead of using a traditional voltage comparator that directly compares V1 and V2, the circuit uses current mirrors to convert voltages to currents, perform the comparison in the current domain, and then convert back to voltage for output. This substitution of comparison mechanism (voltage→current→voltage) achieves superior precision for small voltage differences while the increased complexity is confined to the current mirror transistor stages.
Data Source
AI summary
A detection circuit for a relative error voltage, including: a first current mirror, a second current mirror, a third current mirror, a current sink and resistors R1, R2 and R3. A voltage signal to be detected V1 accesses the first current mirror via the resistor R2, and a voltage signal to be detected V2 accesses the second current mirror via the resistor R3; a mirrored-end of the first current mirror is connected to the current sink, and a mirroring-end thereof is connected to a mirrored-end of the third current mirror; a mirrored-end of the second current mirror is connected to the current sink, and a mirroring-end thereof is connected to a mirroring-end of the third current mirror; the current sink is grounded via the resistor R1; and the third current mirror converts double-ended currents of the first and the second current mirrors to single-ended currents to output as voltage signals.