OOK Signal Isolator Oscillator With Fast ON/OFF Carrier Switching
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Solution Overview
Problem
OOK-based signal isolators have inefficient designs, often requiring separate high-frequency oscillators and being power-hungry, which necessitates an improved transmitter architecture for efficient data exchange across galvanically isolated circuit systems.
Innovation Solution
The implementation of an oscillator circuit coupled with an isolator device, a control switch, and a quenching switch to accelerate transitions between ON and OFF states, along with a current injection circuit to facilitate faster signal generation and termination, reducing latency and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a separate high-frequency oscillator is used to generate the carrier signal, then the isolator can transmit data across galvanically isolated circuit systems, but the device complexity increases and power consumption increases
Solution Approach 1:
The patent combines the oscillator circuit with the isolator device into a single integrated unit. The oscillator generates the carrier signal and couples it directly to the isolation barrier through the control switch, eliminating the need for separate oscillator components and reducing overall device complexity while maintaining data transmission capability across galvanically isolated circuit systems
Solution Approach 2:
The oscillator circuit serves multiple functions: generating the carrier signal, coupling it to the isolation barrier, and working in conjunction with the control switch to enable OOK modulation. This multi-functional design reduces the number of separate components needed in the isolator architecture
2Reliability
If a separate high-frequency oscillator is used to generate the carrier signal, then the isolator can transmit data across galvanically isolated circuit systems, but the power consumption increases
Solution Approach 1:
The oscillator generates periodic carrier signals that are modulated using on-off keying (OOK). The control switch periodically connects and disconnects the oscillator output from the isolation barrier to encode binary data. This periodic action allows efficient power usage by only activating the oscillator when data transmission is required, rather than maintaining continuous signal generation
Solution Approach 2:
By integrating the oscillator with the isolator device and using the control switch to gate the oscillator output, the system reduces power consumption compared to separate oscillator designs that would require additional buffering and signal conditioning stages
3Device complexity
If the oscillator transitions between ON and OFF states slowly, then the oscillator circuit is simpler to design, but the signal transmission speed and throughput decrease
Solution Approach 1:
The control switch is positioned to directly connect the oscillator output to the isolation barrier, enabling rapid state transitions. The switch is designed to handle the full signal swing voltage, allowing it to quickly charge and discharge the oscillator output capacitance without requiring complex buffering stages that would slow down transitions
Solution Approach 2:
The control switch parameters are optimized for fast switching by selecting devices with appropriate capacitance and resistance characteristics. The switch resistance is minimized to enable fast charging of the oscillator output capacitance, while the switch capacitance is kept low to enable fast discharge during OFF transitions, achieving rapid signal transitions without complicating the oscillator circuit design
4Use of energy by moving object
If the oscillator transitions between ON and OFF states slowly, then the oscillator circuit has lower power consumption during transitions, but the data throughput and efficiency decrease
Solution Approach 1:
The oscillator operates in periodic ON/OFF cycles corresponding to the data being transmitted. By using OOK modulation where the oscillator is fully ON during logic 1 periods and fully OFF during logic 0 periods, the system achieves efficient power usage - the oscillator consumes power only when actively transmitting data, while maintaining high data throughput through rapid switching enabled by the control switch
Solution Approach 2:
The control switch maintains continuous control over the oscillator output, ensuring that the oscillator operates at full power during ON periods to maximize signal strength and data throughput, while completely shutting down during OFF periods to minimize power consumption. This continuous optimized operation balances power efficiency with high data transmission rates
Data Source
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Figure 4(a)~4(b)
AI summary
An oscillator for a signal isolator system includes a capacitor and an inductor connected in parallel, two pairs of cross-coupled switches and a control switch. The capacitor, the inductor and the cross-coupled switches form an oscillator. The control switch controls operation of the oscillator between an ON state and an OFF state in response to a data signal to be communicated across an isolation barrier. The inductor may be formed from a winding of an isolation transformer, which reduces component count as compared to a system that provides a separate inductor. Other embodiments may include a current-supplying kickstart circuit and a shorting transistor that can speed transition between the ON and OFF states.