Rotary Encoder Debouncing Circuit for Quadrature Signal Bounce
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Solution Overview
Problem
Existing rotary encoders, particularly those with mechanical sensors, suffer from bouncing effects that affect the decoding of quadrature waveforms, leading to inaccurate signal processing and increased costs due to the need for complex debouncing circuits.
Innovation Solution
A debouncing circuit and method that uses an edge detector, pulse skip and reset circuit, and sampling circuit to process quadrature signals, adapting the debouncing period to pulse changes without requiring a timer, ensuring fast and efficient signal cleaning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mechanical sensors are used in rotary encoders, then the encoder can detect angular position changes, but bouncing effects occur that affect signal decoding accuracy
Solution Approach 1:
The debouncing circuit performs preliminary signal cleaning by detecting edges and generating pulses only during stable periods when the quadrature signal is de-asserted. This preliminary action removes bouncing effects before the signal reaches the decoder, ensuring accurate angular position detection without compromising measurement precision
Solution Approach 2:
The patent introduces an intermediary debouncing circuit between the mechanical sensor and the decoder. This intermediary component processes the raw quadrature signals by skipping pulses during unstable periods and resetting the signal state, thereby mediating between the noisy mechanical sensor output and the decoder requiring clean input signals
2Reliability
If complex debouncing circuits are used to eliminate bouncing effects, then signal decoding accuracy improves, but device complexity and cost increase
Solution Approach 1:
The debouncing circuit operates autonomously using only the existing quadrature signals A and B. The circuit self-regulates by detecting when signal B is de-asserted and automatically generating reset pulses without external control or complex timing mechanisms. This self-service approach eliminates bouncing effects while maintaining simple circuit architecture
Solution Approach 2:
The patent extracts only the essential debouncing functionality needed to eliminate bouncing effects, removing unnecessary complex components. The solution uses a minimal set of logic elements that detect edges and generate pulses based on simple conditions, extracting the core debouncing action from complex circuitry
3Reliability
If traditional debouncing circuits are used, then bouncing effects are reduced, but the debouncing period is fixed and cannot adapt to varying encoder speeds
Solution Approach 1:
The debouncing circuit dynamically adapts to varying encoder speeds by using the actual quadrature signal transitions to determine when to generate reset pulses. The circuit responds to real-time signal conditions rather than operating with a fixed timing mechanism, allowing it to effectively debounce signals across different rotation speeds and frequencies
Solution Approach 2:
The patent changes the operational parameters of the debouncing circuit based on the input signal characteristics. The circuit monitors the state of quadrature signal B and adjusts its pulse generation accordingly, changing its behavior from a fixed debouncing period to a variable period that adapts to the encoder's current speed and signal frequency
Data Source
AI summary
A first input node receives a first input signal and a second input node receives a second input signal. The first and second input signals are in phase quadrature. An edge detector circuit senses the first input signal and produces a pulsed signal indicative of edges detected in the first input signal. A pulse skip and reset circuit senses the pulsed signal and the second input signal, and produces a reset signal indicative of pulses detected in the pulsed signal while the second input signal is de-asserted. A sampling circuit senses the second input signal and the reset signal, and produces an output signal that is deasserted in response to assertion of the second input signal and is asserted in response to a pulse being detected in the reset signal.