Coding and decoding methods for an analog optocoupler isolation amplifier using Σ-Δ modulation technology

Abstract

The present invention discloses a coding and decoding method for an analog optical isolated amplifier using Σ-Δ modulation technology. The analog optical isolated amplifier includes an encoder, a light source driver, a light source, a light sensor, and a decoder. The method includes: when an input digital signal generates an input pulse rising edge or an input pulse falling edge, generating a first pulse with a predetermined pulse width through the encoder; outputting a coded signal with a plurality of first pulses to the light source driver; driving the light source through the light source driver according to the plurality of first pulses of the coded signal to output a coded optical signal; sensing the coded optical signal through the light sensor to generate a sensing signal, and the sensing signal has a second pulse corresponding to the first pulse; and replicating the input digital signal of the encoder through the decoder according to the sensing signal with a plurality of second pulses.

Description

Technical Field

[0001] The present invention relates to an analog opto-isolated amplifier using Σ-Δ modulation technology, and particularly to a coding and decoding method for an analog opto-isolated amplifier, which can accurately recover the one-bit data stream generated by a Σ-Δ modulator after passing through an optical channel. Background Art

[0002] An opto-coupler component is a circuit component that uses light as a medium to transmit electrical signals. Its function is to provide electrical isolation between the input circuit and the output circuit, and when needed, it can transmit electrical signals through the electrical isolation layer.

[0003] Figure 1 Shown is a circuit block diagram of a traditional analog opto-isolated amplifier using Σ-Δ modulation technology. The analog input signal is converted into a high-speed serial one-bit data stream by a Σ-Δ modulator. It consists of a logic "1" potential and a logic "0" potential. The density of logic "1" in the data stream is proportional to the amplitude of the input analog signal. Then the data stream is encoded by an encoder, and the encoded data stream drives a light source to convert the encoded data signal into an optical signal. Then, through an optical detection and optical amplification circuit, the optical signal is converted into a data stream, then restored to a one-bit data stream by a decoder, and then converted into an analog signal by a digital-to-analog converter. Since the amplitude of the analog signal is proportional to the density of the logic "1" potential in the one-bit data stream, accurately recovering the one-bit stream after passing through the decoder becomes crucial in the design of the opto-isolated amplifier. As Figure 1 shown, a traditional analog opto-isolated amplifier 10 using Σ-Δ modulation technology includes a modulator 11, an encoder 12, a light source 13, a photosensor 14, and a decoder 15. The modulator 11 is an analog-to-digital modulator that can convert the input analog signal into a one-bit digital signal. The encoder 12 is electrically connected to the modulator 11, receives the digital signal, and encodes the digital signal. The light source 13 is electrically connected to the encoder 12, receives the encoded digital signal, and drives the light source 13 to output an optical signal with the encoded digital signal. The photosensor 14 senses the optical signal and converts the optical signal into a digital signal. The decoder 15 is electrically connected to the photosensor 14, receives the digital signal, and decodes and outputs an analog signal.

[0004] However, in the traditional analog opto-isolated amplifier 10 adopting Σ-Δ modulation technology, the analog input signal is converted into a high-speed serial one-bit data stream through the Σ-Δ modulator. When such a high-speed data stream passes through the optical channel composed of circuits such as an optical driver, a light source, a photodetector, and an optical amplifier, pulse deformation will occur, such as changes in the rising edge and the falling edge. If traditional encoding and decoding methods are adopted, it is impossible to accurately recover the one-bit stream generated by the Σ-Δ modulator after decoding. Figure 2 The waveform schematic diagram of the traditional analog opto-isolated amplifier adopting Σ-Δ modulation technology is shown as Figure 2 shown. The digital signal 21 of the modulator 11 will be converted into a coded digital signal 22 through the encoder 12. The pulse width of the coded digital signal 22 output by the encoder 12 is different from the output signal 23 of the decoder 11. That is to say, the density of logic "1" in the data stream has changed. These changes in the one-bit stream after decoding, after passing through the Σ-Δ digital-to-analog converter and being converted back into an analog signal, are converted into problems such as an increase in the offset voltage (Vos) of the opto-isolated amplifier, a decrease in the signal-to-noise ratio, or a decrease in linearity.

[0005] Moreover, different signal pulse widths will have different signal deformations when passing through the optical channel composed of a light source driver and an optical sensor, such as different pulse rising edges, different pulse falling edges, or different delays. Therefore, the new one-bit data stream obtained through the decoder will be different from the one-bit data stream generated by the Σ-Δ modulator. We know that the analog input signal is converted into a one-bit data stream through the Σ-Δ modulator, and the density of "1" in this data stream is proportional to the amplitude of the input analog signal. Therefore, changes in pulse deformation, rising edge, and falling edge will cause changes in the density of "1" in the data stream passing through the optical channel. After passing through the Σ-Δ digital-to-analog converter, these changes are converted into problems such as an increase in the offset voltage (Vos) of the opto-isolated amplifier, a decrease in the signal-to-noise ratio, or a decrease in linearity.

[0006] Therefore, there is a need to find out how to accurately recover the one-bit data stream generated by the Σ-Δ modulator after passing through the optical channel through circuit design in the simulation opto-isolated amplifier. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a method of encoding and decoding in view of the deficiencies of the prior art. Such an encoder and decoder can accurately recover the one-bit stream generated by the Σ-Δ modulator after passing through the optical channel.

[0008] To solve the above technical problems, one of the technical solutions adopted by the present invention is to provide a coding and decoding method for an analog optocoupler isolation amplifier. The analog optocoupler isolation amplifier includes an encoder, a light source driver, a light source, a light sensor, and a decoder. The coding and decoding method includes: when an input digital signal generates an input pulse rising edge or an input pulse falling edge, a first pulse with a predetermined pulse width is generated by the encoder. The predetermined pulse width is 10% to 25% of the modulator clock, so as to ensure that the first pulse can effectively pass through the optical channel; an encoded signal with multiple first pulses is output to the light source driver; according to the multiple first pulses of the encoded signal, the light source is driven by the light source driver to output an encoded optical signal; the encoded optical signal is sensed by the light sensor to generate a sensed signal, and the sensed signal has multiple second pulses corresponding to the multiple first pulses of the encoded signal; according to the sensed signal with multiple second pulses, the decoder replicates the input digital signal of the encoder.

[0009] One of the beneficial effects of the present invention is that the coding and decoding method of the analog optocoupler isolation amplifier adopting the Σ-Δ modulation technology can improve the accuracy of the output signal of the optocoupler isolation amplifier, reduce the offset voltage (Vos) of the optical isolation amplifier, increase the signal-to-noise ratio, and improve the linearity of the analog optical isolation amplifier by means of the technical solution of setting a double-edge trigger signal generator in the encoder and a rising-edge trigger signal decoder in the decoder.

[0010] To enable a further understanding of the features and technical content of the present invention, please refer to the following detailed description and drawings of the present invention. However, the provided drawings are only for reference and illustration, and are not used to limit the present invention. Description of the Drawings

[0011] Figure 1 Showing the circuit block diagram of a traditional optocoupler isolation amplifier.

[0012] Figure 2 Showing the waveform schematic diagram of a traditional optocoupler isolation amplifier.

[0013] Figure 3 Being the block diagram of the optocoupler isolation amplifier of the present invention.

[0014] Figure 4 Being the flowchart of the coding and decoding method of the analog optocoupler isolation amplifier of the present invention.

[0015] Figure 5 Showing the waveform schematic diagram of the optocoupler isolation amplifier of the present invention.

[0016] Figure 6 Being the circuit schematic diagram of the decoder of the embodiment of the present invention.

[0017] Figure 7 Schematic diagram of the circuit of the encoder according to an embodiment of the present invention. Detailed implementation manners

[0018] The following are specific embodiments to illustrate the implementation manners of the present invention regarding "encoding and decoding methods of an analog optocoupler isolation amplifier using Σ-Δ modulation technology". Those skilled in the art can understand the advantages and effects of the present invention from the content disclosed in this specification. The present invention can be implemented or applied through other different specific embodiments, and various details in this specification can also be modified and changed based on different viewpoints and applications without departing from the concept of the present invention. Additionally, the drawings of the present invention are only simple schematic illustrations and are not depicted according to actual sizes, hereby declared in advance. The following implementation manners will further elaborate on the related technical content of the present invention, but the disclosed content is not used to limit the protection scope of the present invention.

[0019] It should be understood that although terms such as first, second, and third may be used herein to describe various components or signals, these components or signals should not be limited by these terms. These terms are mainly used to distinguish one component from another, or one signal from another. Additionally, the term "or" used herein should, depending on the actual situation, possibly include any one or a combination of multiple of the associated listed items.

[0020] For clarity of explanation, in some cases, the present technology may be presented as including independent functional blocks containing functional blocks, steps or routes in methods implemented in devices, device components, software, or combinations of hardware and software.

[0021] Devices implementing the methods according to these disclosures may include hardware, firmware, and / or software, and may take any various forms. Typical examples of such forms include laptop computers, smart phones, small personal computers, personal digital assistants, and so on. The functions described herein may also be implemented in peripheral devices or built-in cards. By further example, such functions may also be implemented on different chips or circuit boards of different programs executed on a single device.

[0022] The instruction, the medium for transmitting such an instruction, the computing resources for executing it, or other structures for supporting such computing resources are means for providing the functions described in these disclosures.

[0023] Embodiment of the present invention

[0024] Figure 3 Is a block diagram of the analog optocoupler isolation amplifier of the present invention, Figure 4 Is a flowchart of the encoding and decoding methods of the analog optocoupler isolation amplifier using Σ-Δ modulation technology of the present invention, Figure 5This is a waveform schematic diagram of the analog optocoupler isolation amplifier of the present invention. As Figure 3 shown, the analog optocoupler isolation amplifier 30 of the present invention at least includes: a modulator 31, an encoder 32, a light source driver 33, a light source 34, a photosensor 35, a decoder 36, a digital-to-analog converter 37, and a low-pass filter 38.

[0025] Please refer to Figure 3 , Figure 4 and Figure 5 , in step S401, the input analog signal Sia is converted into an input digital signal Si by the modulator 31. The modulator 31 is preferably an integrating-differentiating modulator, also known as a Sigma-Delta (Σ-Δ) modulator or a Pulse Density Modulation (PDM) modulator. The integrating-differentiating modulator is a circuit for digital-to-analog conversion that can convert an analog signal into a digital signal, that is, sample the analog signal and convert it into a one-bit digital signal. Its advantage is that it can shape the noise and effectively suppress the quantization noise, having a high signal-to-noise ratio (SNR). The ΔΣ modulation circuit composed of a differentiator and an integrator will have a high-pass filtering effect on the quantization noise due to its differentiating characteristics. The principle of the integrating-differentiating modulator is well known to those skilled in the art and will not be elaborated here. In a preferred embodiment of the present invention, the input signal is an input analog signal Sia, and the input analog signal Sia is transmitted to the modulator 31, and the modulator 31 converts the input analog signal Sia into an input one-bit digital signal Si.

[0026] In step S402, when an input digital signal Si generates an input pulse rising edge or an input pulse falling edge, an encoded signal S having a plurality of first pulses coded_pulses is generated by the encoder 32, and each first pulse coded_pulse has a predetermined pulse width. The encoder 32 is electrically connected to the modulator 31, and the encoder 32 can be used to encode the input digital signal Si transmitted from the modulator 31. Further, the encoder 32 can detect the input pulse rising edge or the input pulse falling edge of the input digital signal Si generated by the modulator 31, and generate the first pulses coded_pulses with a predetermined pulse width according to the input pulse rising edge or the input pulse falling edge of the input digital signal Si.

[0027] In step S403, an encoded signal Se having a plurality of first pulses coded_pulses is output to the light source driver 33. Specifically, the encoder 32 is preferably a double-edge triggered signal encoder. The double-edge triggered signal encoder receives the input digital signal Si of the modulator 31. According to the input digital signal Si of the modulator 31, the double-edge triggered signal encoder generates a first pulse coded_pulses having a predetermined pulse width when the rising edge or the falling edge of the input pulse of the input digital signal Si occurs. In other words, when the double-edge triggered signal encoder detects the rising edge or the falling edge of the input pulse of the input digital signal Si of the modulator 31, a first pulse coded_pulses having a predetermined pulse width is generated. Each first pulse coded_pulses has the same pulse width, and a plurality of first pulses coded_pulses having a predetermined pulse width are combined into an encoded signal Se.

[0028] In step S404, according to the plurality of first pulses coded_pulses of the encoded signal Se, the light source 34 is driven by the light source driver 33 to output an encoded optical signal Sp. The light source driver 33 is electrically connected to the encoder 32 and the light source 34, receives the encoded signal Se having a plurality of first pulses coded_pulses output by the encoder 32, and according to the encoded signal Se having a plurality of first pulses coded_pulses, the light source driver 33 can drive the light source 34 to output the encoded optical signal Sp. The light source 34 is preferably a light emitting diode (LED), but in different embodiments, the light source 34 can also be composed of different light emitting bodies, which is not limited herein. The light source driver 33 receives the encoded signal Se having a plurality of first pulses coded_pulses output from the encoder 32 to drive the light source 34 to emit light, and then outputs an encoded optical signal Sp. In other words, the encoded optical signal Sp output by the light source 34 corresponds to the encoded signal Se.

[0029] Next, in step S405, the encoded optical signal Sp is sensed by the optical sensor 35 to generate a sensing signal S, and the sensing signal S has a plurality of second pulses sensing_pulses corresponding to the plurality of first pulses coded_pulses of the encoded signal Se. After the light source driver 33 drives the light source 34 to generate the encoded optical signal Sp according to the encoded signal Se having a plurality of first pulses coded_pulses, the optical sensor 35 senses the encoded optical signal Sp and generates a sensing signal S having a plurality of second pulses sensing_pulses with distortion, as Figure 5 shown, the signal distortion magnitude of each second pulse sensing_pulses is related to the pulse width of each first pulse coded_pulse.

[0030] Specifically, the optical sensor 35 is disposed at a position corresponding to the light source 34, that is to say, the setting position of the optical sensor 35 is on the light transmission path of the light source 34. The optical sensor 35 is used to sense the encoded optical signal Sp output by the light source 34 to generate a sensing signal S. The sensing signal S generated by the optical sensor 35 has a plurality of second pulses sensing_pulses corresponding to a plurality of first pulses coded_pulses of the encoded signal Se. The pulse width of each second pulse sensing_pulse is related to the signal width of the first pulse coded_pulse. By sensing the encoded optical signal Sp, the optical sensor 35 can form the sensing signal S by generating a plurality of second pulses sensing_pulse.

[0031] In step S406, according to the sensing signal S having a plurality of second pulses sensing_pulse, the input digital signal Si of the encoder 31 is restored by the decoder 36. The decoder 36 is electrically connected to the optical sensor 35 and is used to receive the sensing signal S generated by the optical sensor 35. According to the sensing signal S having a plurality of second pulses sensing_pulse, the decoder 36 restores the input digital signal Si of the encoder 31. Further, the decoder 36 is preferably a rising edge triggered decoder. When the decoder 36 detects the rising edge of each second pulse sensing_pulse, the output state of the decoder 36 changes once. For example, assume that the current output of the decoder 36 is a high level (1). When the decoder 36 detects the rising edge of the first second pulse sensing_pulse, the output state will change to a low level (0), and when the decoder 36 detects the rising edge of the second second pulse sensing_pulse, the output state will further change to a high level. In other words, when the rising edge is detected for the first time, a high level is output and maintained at the high level, and when the rising edge is detected for the second time, it will change from the high level to the low level, and vice versa. Therefore, when the decoder 36 receives two consecutive second pulses sensing_pulse, an output pulse will be generated, and the pulse width of the output pulse is determined by the rising edges of the two consecutive second pulses sensing_pulse and the time interval between them. The output digital signal So is composed of a plurality of output pulses. Since the pulse width of the first pulse is the same, when the first pulse passes through the optical channel, the generated second pulses have very similar deformations or delays, so as to ensure that the output digital signal So can accurately reproduce the input digital signal Si of the encoder 31.

[0032] In addition, as Figure 6As shown, in a preferred embodiment of the present invention, the encoder 32 may be composed of an exclusive OR gate (XOR GATE) 321 and a plurality of delay units 322. The plurality of delay units 322 can cause a quarter-frequency delay of the input signal. The output digital signal Si of the modulator 31 is transmitted to the input terminal A of the first delay unit 322 and the first input terminal 324 of the exclusive OR gate 321 composed of five NAND gates. The output terminal YN of the last delay unit 322 is connected to the second input terminal 325 of the exclusive OR gate 321. A plurality of first pulses coded_pulse with a predetermined signal width are output from the output terminal 326 of the exclusive OR gate 321. Through the rising edge or falling edge of the input digital signal Si of the encoder 32 of the present invention, a first pulse coded_pulse with a predetermined signal width is generated. It should be noted here that the above encoder 32 is composed of a plurality of delay units 322 and an exclusive OR gate 321. However, in different embodiments, the encoder 32 may also be composed of different logic units, which is not limited here. Those skilled in the art can design an encoder 32 composed of different components according to different requirements. After the encoder 32 of the present invention generates a first pulse coded_pulse with a predetermined signal width, it outputs a coded signal Se with a plurality of first pulses coded_pulse.

[0033] Figure 7 Schematic diagram of the circuit of the decoder according to an embodiment of the present invention, as Figure 7 shown. Further, the decoder 35 is also called a double-edge triggered decoder, which is composed of a D edge-triggered flip-flop (D Flip Flop) 351 and an inverter 352. The sensing signal S of a plurality of second pulses sensing_pulse with a predetermined signal width is transmitted to the frequency input terminal clk of the flip-flop 351. The output terminal YN of the inverter 352 is electrically connected to the data input terminal data of the flip-flop 351. The input terminal A of the inverter 352 is connected to the output terminal Q of the flip-flop 351. The output digital signal So is output from the other output terminal QN of the flip-flop 351. Through the above decoding circuit composed of the flip-flop 351 and the inverter 352, a plurality of second pulses sensing_pulse with the same signal width can be decoded to generate an output signal. In addition, it should be noted here that in a preferred embodiment of the present invention, the double-edge triggered decoder is composed of a flip-flop 351 and an inverter 352. However, in different embodiments, the double-edge triggered decoder may also be composed of other different logic units, which is not limited here.

[0034] In addition, in the encoding and decoding method of the analog optocoupler isolation amplifier of the present invention, it may further include converting the output digital signal into an output analog signal through a digital-to-analog converter 37, and then filtering the noise in the output analog signal through a low-pass filter (Low Pass Filter) 38. The digital-to-analog converter 37 is electrically connected to the decoder 36, receives the output digital signal So of the decoder 36, and converts the output digital signal So into an output analog signal Sa, so as to achieve the purpose of restoring the original input analog signal Sia of the optocoupler isolation amplifier 30. In a preferred embodiment of the present invention, the low-pass filter 38 of the digital-to-analog converter 37 can be used to filter the noise generated when the output digital signal So is converted into the output analog signal Sa, and finally output the output analog signal Sa with less noise.

[0035] From Figure 5 It can be clearly seen that in the optocoupler isolation amplifier 30 of the present invention, through the encoder 32, when the rising edge or falling edge of the input pulse of the input digital signal Si is generated, an encoded signal Se of a plurality of first pulses coded_pulse with a predetermined pulse width can be output, whereby the start and end times of the signal pulse of the input digital signal Si can be accurately known. At the same time, after Se with the same pulse width passes through the optical channel, they experience the same pulse deformation, the same rising edge and falling edge, and through the circuit design of the present invention, since a plurality of second pulses with a predetermined pulse width can completely replicate a plurality of first pulses with a predetermined pulse width, even if the sensed signal S has a delay and deformation after passing through the optical channel, after decoding by the present invention, the output digital signal So can accurately restore the input digital signal Si at the time of input, thereby improving problems such as an increase in the offset voltage (Vos), a decrease in the signal-to-noise ratio, or a decrease in linearity of the optical isolation amplifier.

[0036] One of the beneficial effects of the present invention is that the optocoupler isolation amplifier provided by the present invention can improve the accuracy of the output signal of the optocoupler isolation amplifier through the technical solutions of a double-edge-triggered signal encoder and a rising-edge-triggered signal decoder with a rising-edge-triggered signal decoder.

[0037] The content disclosed above is only a preferred feasible embodiment of the present invention, and does not limit the protection scope of the claims of the present invention. Therefore, all equivalent technical changes made by using the content of the specification and drawings of the present invention are included in the protection scope of the claims of the present invention.

Claims

1. A coding and decoding method for an analog optocoupler isolation amplifier using Σ-Δ modulation technology, characterized in that, The analog optocoupler isolation amplifier includes an encoder, a light source driver, a light source, a light sensor, and a decoder. The encoding and decoding method includes: When an input digital signal generates an input pulse rising edge or an input pulse falling edge, an encoded signal with a plurality of first pulses is generated by the encoder, and each of the first pulses has a predetermined pulse width; Output the encoded signal with the plurality of first pulses to the light source driver; According to the plurality of first pulses of the encoded signal, drive the light source through the light source driver to output an encoded optical signal; Sense the encoded optical signal through the light sensor to generate a sensed signal, and the sensed signal has a plurality of second pulses corresponding to the plurality of first pulses of the encoded signal; and According to the sensed signal with the plurality of second pulses, replicate the input digital signal of the encoder through the decoder; Wherein, before the step of generating the first pulse, it further includes converting an input analog signal into the input digital signal through an integrating-differentiating modulator; wherein, among the plurality of first pulses generated by the encoder, the widths of all the predetermined pulse widths are the same, and the range of the predetermined pulse width is 10% to 25% of the frequency of the integrating-differentiating modulator.

2. The encoding and decoding method according to claim 1, characterized in that, After the encoded signal with the plurality of first pulses passes through the light source driver and the light source, the sensor will generate a sensed signal with a plurality of distorted second pulses, and the distortion magnitude of each second pulse is related to the pulse width of each first pulse.

3. The encoding and decoding method according to claim 1, characterized in that, The pulse width of each second pulse is equal to or close to the pulse width of the first pulse.

4. The encoding and decoding method according to claim 1, characterized in that, The decoder is a rising-edge triggered decoder. When the decoder senses that the second pulse of the sensed signal is a pulse rising edge, its output state changes from high level 1 to low level 0 or from low level 0 to high level 1.

5. The encoding and decoding method according to claim 1, wherein When the decoder receives two consecutive second pulses, the decoder will generate an output pulse, and the pulse width of the output pulse is determined by the rising edges of the two consecutive second pulses and their time interval.

6. The encoding and decoding method according to claim 5, characterized in that, It further includes outputting an output digital signal with a plurality of the output pulses through the decoder.

7. The encoding and decoding method according to claim 6, characterized in that, It further includes converting the output digital signal into an output analog signal through a digital-to-analog converter.

8. The encoding and decoding method according to claim 7, wherein It further includes filtering the noise generated when the output digital signal is converted into the output analog signal through a low-pass filter.

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