DC Offset Cancellation Circuit for Time-Variant Encoder Signals
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Solution Overview
Problem
Conventional DC offset cancellation circuits in servo motor systems fail to effectively eliminate DC offsets in time variant signals from optical encoders, leading to inaccurate position and speed control of servo motors.
Innovation Solution
A DC offset cancellation circuit that includes a superposing unit, current-to-voltage converters, a differential amplifier, a processing unit, and a current digital-to-analog converter, which generates and superposes DC currents with sensing currents to equalize their offsets, allowing the differential amplifier to cancel common mode signals and eliminate DC offsets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional DC offset cancellation circuits are used, then the circuit structure is simple, but the DC offsets in time variant signals cannot be effectively eliminated
Solution Approach 1:
The patent applies dynamics by making the DC current adjustable and adaptive rather than fixed. The DC current is dynamically adjusted based on the actual DC offset of the time variant signal through feedback control, allowing the circuit to adapt to changing signal conditions and effectively cancel DC offsets in time variant signals.
Solution Approach 2:
The patent implements feedback control where the output signal is processed to detect the DC offset component, and this detected DC offset is fed back to adjust the DC current generated by the digital-to-analog converter. This closed-loop feedback mechanism ensures continuous optimization of DC offset cancellation effectiveness.
2Measurement precision
If DC offsets are not canceled, then the circuit operation is simple, but position and speed control accuracy deteriorates
Solution Approach 1:
The patent applies preliminary action by generating and superposing the DC current onto the sensing current before the signal enters the main processing path. This preliminary DC offset compensation ensures that the differential amplifier receives already-balanced signals, improving position and speed control accuracy from the outset.
Solution Approach 2:
The patent introduces a DC current as an intermediary element to bridge the imbalance between positive and negative sensing currents. This DC current acts as a mediator that equalizes the DC offsets of different sensing currents before they are processed further, thereby improving measurement precision.
3Reliability
If DC current is adjusted to match signal variations, then DC offset cancellation effectiveness is improved, but control complexity increases
Solution Approach 1:
The patent implements self-service by designing a system where the DC current automatically adjusts itself based on the detected DC offset of the input signal. The feedback loop enables the circuit to self-regulate and maintain optimal DC offset cancellation without requiring external manual adjustment or complex control mechanisms.
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 circuit successfully cancels DC offsets in photoelectronic signals, ensuring accurate rotation speed and position control of servo motors by equalizing the DC offsets between the A+ and A− sensing currents, thereby improving the precision and reliability of servo motor systems.
Implementation Method 1
The superposing unit is used for generating a first DC current and a second DC current. After the first DC current and the first sensing current are superposed with each other by the superposing unit, a first superposed current is generated. After the second DC current and the second sensing current are superposed with each other by the superposing unit, a second superposed current is generated.
Implementation Method 2
The first current-to-voltage converter is used for converting the first superposed current into a first voltage signal. The second current-to-voltage converter is for converting the second superposed current into a second voltage signal.
Implementation Method 3
allowing the differential amplifier to cancel common mode signals and eliminate DC offsets
Data Source
AI summary
A DC offset cancellation circuit is provided. A first DC current and a first sensing current are superposed with each other to generate a first superposed current. A second DC current and a second sensing current are superposed with each other to generate a second superposed current. The first superposed current is converted into a first voltage signal. The second superposed current is converted into a second voltage signal. After the first voltage signal and the second voltage signal are received by a differential amplifier, an output signal is generated. The output signal is processed into a DC value. The DC value is converted into a DC current signal. The superposing unit generates the first DC current and the second DC current according to the DC current signal, so that the first superposed current and the second superposed current have the same DC offset.