Isolated Detector Circuit for OOK Signal Recovery Under Common-Mode Noise
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Solution Overview
Problem
Existing galvanically isolated signal transmission technologies face challenges in transmitting static signals directly and achieving reliable transmission due to the need for modulation and susceptibility to interference, particularly in high-voltage applications like electric drives and power transmission, where common-mode interference is a concern.
Innovation Solution
A detector circuit with a differential stage and rectifier stage, utilizing n-channel and p-channel transistors, along with AC voltage coupling capacitors and resistors, allows for robust demodulation of OOK signals and suppression of common-mode interference, enabling high-frequency signal rectification and digital signal recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If optical isolators are used for galvanic isolation, then signal transmission is achieved, but full integration into silicon-based CMOS technologies is not possible and reliability is insufficient
Solution Approach 1:
The patent replaces optical isolation mechanisms with electromagnetic field-based isolation using capacitive coupling. The transmitter and receiver are coupled through a capacitor that provides galvanic isolation while allowing signal transmission, enabling full CMOS integration without requiring special semiconductor materials like optical isolators do.
Solution Approach 2:
The patent changes the isolation mechanism from optical to electromagnetic capacitive coupling. By using a capacitor as the coupling element, the system achieves galvanic isolation through electrical parameter manipulation rather than optical mechanisms, allowing standard CMOS fabrication processes to be used.
2Reliability
If magnetic isolators based on transformer principle are used, then galvanic isolation is achieved, but static signals cannot be transmitted directly and modulation is required
Solution Approach 1:
The patent changes the coupling mechanism from inductive (transformer-based) to capacitive. This allows static and DC signals to be transmitted directly through the capacitor without requiring modulation, while still maintaining galvanic isolation. The capacitor passes DC blocking characteristics of inductive coupling but allows direct signal transmission.
Solution Approach 2:
The patent extracts the modulation requirement from the isolation mechanism by using capacitive coupling instead of transformer coupling. The capacitor provides isolation without the need for magnetic field generation and detection, eliminating the need for modulation circuits and simplifying the overall system.
3Reliability
If AC coupling capacitors are used for isolation, then galvanic isolation is achieved, but common-mode interference suppression is insufficient
Solution Approach 1:
The patent uses asymmetric capacitor values in the differential coupling circuit to optimize common-mode rejection. By carefully selecting different capacitance values for the differential signals, the circuit achieves better suppression of common-mode interference while maintaining galvanic isolation through the capacitive coupling.
Solution Approach 2:
The patent incorporates common-mode feedback circuits that monitor and adjust the differential signals to suppress common-mode interference. The feedback mechanism detects common-mode voltage variations and actively compensates for them, improving interference suppression while maintaining the galvanic isolation provided by the capacitive coupling.
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 solution enables high transmission rates with robust interference suppression and digital signal recovery, suitable for both capacitive and magnetic isolation, ensuring reliable galvanically isolated digital signal transmission.
Implementation Method 1
AC voltage coupling, wherein the AC voltage coupling comprises two capacitors and two resistors, and wherein a capacitor is connected on a first side to each of the differential signal inputs
Implementation Method 2
a differential stage, the first n-channel transistor and a second n-channel transistor, and the first and the second n-channel transistor are each connected to a resistor and a capacitor of the AC voltage coupling
Implementation Method 3
a rectifier stage, the bias current connection being connected to the differential stage via the one third n-channel transistor, and the bias current connection being connected to the differential stage via a fourth n-channel transistor and an fifth n-channel transistor is connected to the rectifier stage
Data Source
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AI summary
The invention relates to a detector circuit (8) for the galvanically isolated transmission of digital signals. The aim of the invention is to provide a more robust and less fault-susceptible detector circuit. The detector circuit (8) according to the invention comprises two differential signal inputs (RF1, RF2), an input common-mode voltage connection (VCM), an alternating voltage coupling and a differential stage. The detected circuit (8) additionally comprises an operating voltage connection (AVDD), an operating ground connection (AVSS), a signal output (IRECT), a bias current connection (IBIAS), and a rectifier stage. The alternating voltage coupling comprises two capacitors (C1, C2) and two resistors (R1, R2). The differential stage comprises a first n-channel transistor (MN1) and a second n-channel transistor (MN2). The bias current connection (IBIAS) is connected to the differential stage via a third n-channel transistor (MN3). The bias current connection (IBIAS) is connected to the rectifier stage via a fourth n-channel transistor (MN4) and a fifth n- channel transistor (MN5). The rectifier stage comprises five p-channel transistors (MP1, MP2, MP3, MP4, MP5). The invention further relates to a system comprising such a detector circuit (8).