Optical Coupling Pulse Width Distortion Measurement
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Solution Overview
Problem
Semiconductor devices with optically-coupled insulating circuits face challenges in transmitting analog signals with high integrity due to noise immunity issues and signal distortion, particularly when using delta-sigma conversion circuits and pulse width modulation, which can lead to demodulation errors.
Innovation Solution
A semiconductor device with an analog/digital conversion unit, pulse width modulation unit, and reference signal generation unit that allows for the selection between transmission and reference signals, enabling the measurement of pulse width distortion and ensuring transmission margin by using a fixed pulse pattern for testing, thereby reducing demodulation errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the clock frequency of the AD conversion is increased to transmit analog signals with high integrity, then the transmission quality improves, but pulse width distortion increases causing demodulation errors
Solution Approach 1:
The patent applies preliminary action by measuring the pulse width distortion of the optical coupling unit in advance during a test phase before actual signal transmission. The controller determines whether the measured distortion is within a predetermined range, and only when it is acceptable does the system proceed to transmit analog signals. This prevents demodulation errors from occurring in the first place by ensuring the optical coupling unit is suitable for the intended clock frequency.
Solution Approach 2:
The patent inverts the conventional approach by not directly transmitting analog signals at high clock frequencies, but instead first transmitting test signals to measure pulse width distortion. The system works backward from the observed distortion to determine whether the transmission parameters are acceptable, rather than directly attempting transmission and hoping for successful demodulation.
2Productivity
If a modulation circuit superimposes sampling clock and digital data into one signal series, then the optical transmission efficiency improves, but pulse width distortion occurs reducing transmission margin
Solution Approach 1:
The patent applies preliminary action by measuring the pulse width distortion caused by the modulation circuit and optical coupling unit before actual signal transmission. The controller uses the measured distortion to determine whether the combined modulation and optical transmission system maintains sufficient transmission margin, ensuring reliable operation before committing to actual data transmission.
3Object-affected harmful factors
If IC output-type photocouplers are used to transmit digital signals, then noise immunity improves, but analog signal transmission integrity deteriorates
Solution Approach 1:
The patent applies parameter changes by converting the operating parameters of the photocoupler from digital signal transmission mode to analog signal transmission mode. This involves changing the modulation scheme and carefully controlling the clock frequency based on measured pulse width distortion characteristics, allowing the same hardware to operate in analog mode while maintaining the noise immunity benefits of optical 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 effectively suppresses demodulation errors and ensures high-integrity signal transmission by measuring and compensating pulse width distortion, ensuring the transmission margin of the optical coupling unit, thus enabling reliable analog signal digitization.
Implementation Method 1
a light emitting element drive unit that outputs a drive current for the light emitting element, and a light emitting element that emits light based on the transmission signal or the reference signal
Implementation Method 2
an optical receiving unit that converts a photocurrent of a light receiving element receiving the optical signal into a voltage signal
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
According to an embodiment, a semiconductor device includes an analog/digital conversion unit (3), a pulse width modulation unit (5) outputting a transmission signal, the transmission signal being a pulse pattern corresponding to a digital signal output from the analog/digital conversion unit (3), a reference signal generation unit (7) generating a reference signal, the reference signal being a fixed pulse pattern. The device includes a first control unit (13) selecting one of the transmission signal and the reference signal, a light emitting element drive unit (9) outputting a drive current based on the transmission signal or the reference signal, a light emitting element (15) driven by the light emitting element drive unit (9). The device includes an optical receiving unit (21) converting the optical signal into a voltage signal, and a demodulation unit (25) demodulating the voltage signal into a digital signal based on the transmission signal or the reference signal.