TWI752628B - Encoding and decoding method for optical isolated amplifier employing sigma-delta modulation technology - Google Patents

Abstract

A coding and decoding method for optical isolated amplifier employing Sigma-Delta modulation technology is disclosed and the amplifier includes an encoder, an optical driver, a light source, a light sensor and a decoder. The method includes: generating a first pulses with a predetermined pulse width by the encoder when an input digital signal has an input pulse rising edge or an input pulse falling edge; outputting an encoding signal having first pulses to the optical driver; driving the light source by the optical driver to output an encoding optical signal according to the first pulses; sensing the optical light signal to output a sensing signal and the sensing signal includes second pulses corresponding to the first pulses of the encoding signal; and duplicating the input digital signal of the encoder by the decoder according to the second pulses of the sensing signal.

Description

Encoding and decoding method of analog optocoupler isolation amplifier using sigma-delta modulation technology

The present invention relates to an analog optocoupler isolation amplifier adopting sigma-delta modulation technology, in particular to a coding and decoding method of an analog optocoupler isolation amplifier, which can make a one-bit data stream generated by a sigma-delta modulator pass through optical After the channel is restored accurately.

The photoelectric coupling element is a circuit element that transmits electrical signals through light as a medium. Its function is to provide electrical isolation between the input circuit and the output circuit. When necessary, the electrical signal can be transmitted through the electrical isolation layer.

Figure 1 shows a circuit block diagram of a conventional analog opto-isolated amplifier using sigma-delta modulation technology. The analog input signal is converted into a high-speed serial one-bit data stream through a sigma-delta modulator, which is composed of a logic "1" potential and a logic "0" potential. The logic "1" in the data stream "The density is proportional to the amplitude of the input analog signal, and then the data flows through the encoder for encoding, and the encoded data stream drives the light source to convert the encoded data signal into an optical signal, and then converts the optical signal into an optical signal through an optical detection and optical amplifier circuit. The data stream is then restored to a one-bit data stream by a decoder, and then converted to an analog signal by a digital-to-analog converter. Since the amplitude of the analog signal is proportional to the density of logic "1" potentials in the one-bit data stream, it is critical to accurately recover the one-bit data stream after passing through the decoder in the design of optical isolation amplifiers. As shown in FIG. 1 , the conventional analog optocoupler isolation amplifier 10 using sigma-delta modulation technology includes a modulator 11 , an encoder 12 , a light source 13 , a photo sensor 14 and a decoder 15 . The modulator 11 is an analog digital modulator, which can convert the input analog signal into a one-bit digital signal. The encoder 12 is electrically connected to the modulator 11, which 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 the optical signal with the encoded digital signal. The light sensor 14 senses the light signal and converts the light signal into a digital signal. The decoder 15 is electrically connected to the light sensor 14, receives the digital signal, and decodes and outputs an analog signal.

However, in the traditional analog optocoupler isolation amplifier 10 using the sigma-delta modulation technology, the analog input signal is converted into a high-speed serial one-bit data stream through the sigma-delta modulator. This high-speed data flow When passing through an optical channel composed of circuits such as an optical driver, a light source, a photodetector, and an optical amplifier, pulse deformation, changes in the rising and falling edges, etc. will occur. If traditional encoding and decoding methods are used, the one-bit data stream generated by the sigma-delta modulator cannot be accurately recovered after decoding. Figure 2 shows a schematic diagram of the waveform of a traditional analog optocoupler isolation amplifier using sigma-delta modulation technology. As shown in Figure 2, the digital signal 21 of the modulator 11 will be converted into an encoded digital signal 22 by the encoder 12. The pulse width of the coded digital signal 22 output by 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. The Δ digital-to-analog converter, after converting back to the analog signal, translates into problems such as increased offset voltage (Vos), decreased signal-to-noise ratio or decreased linearity of the optical isolation amplifier.

Moreover, different signal pulse widths will have different signal deformations when passing through the optical channel composed of the light source driver and the light sensor, such as different pulse rising edges, different pulse falling edges or different delays. The resulting new one-bit data stream will be different from the one-bit data stream generated by the sigma-delta modulator. We know that the analog input signal is converted into a one-bit data stream by a sigma-delta modulator, and the density of "1" in this data stream is proportional to the amplitude of the input analog signal. Therefore, the change of pulse deformation, rising edge and falling edge, etc., will cause the density of "1" in the data flow through the optical channel to change. This change is converted into optical isolation after passing through the sigma-delta digital-to-analog converter. Problems such as increased offset voltage (Vos), decreased signal-to-noise ratio, or decreased linearity of the amplifier.

Therefore, there is a need for how to accurately restore the one-bit data stream generated by the Σ-Δ modulator in the analog optocoupler isolation amplifier through the optical channel through circuit design.

The technical problem to be solved by the present invention is to provide a method for encoding and decoding in view of the deficiencies of the prior art. The encoder and decoder can make the one-bit data stream generated by the sigma-delta modulator pass through the optical channel after passing through the optical channel. can be recovered precisely.

In order to solve the above-mentioned technical problems, one of the technical solutions adopted by the present invention is to provide an encoding 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 The optical sensor and a decoder, the encoding and decoding methods include: when an input digital signal generates a rising edge of an input pulse or a falling edge of the input pulse, a first pulse with a predetermined pulse width is generated by the encoder, and the predetermined pulse width is It is 10%-25% of the modulator clock to ensure that the first pulse can effectively pass through the optical channel; output an encoded signal with multiple first pulses to the light source driver; according to multiple first pulses of the encoded signal, pass The light source driver drives the light source to output an encoded optical signal; the encoded optical signal is sensed by the optical sensor to generate a sensing signal, and the sensing signal has multiple second pulses corresponding to multiple first pulses of the encoded signal Pulse; according to the sensing signal with a plurality of second pulses, the input digital signal of the encoder is reproduced through the decoder.

One of the beneficial effects of the present invention is that the present invention provides an encoding and decoding method for an analog optocoupler isolation amplifier using Σ-Δ modulation technology, which can be achieved by setting a double edge trigger signal generator in the encoder and a decoder in the decoder. Set up the technical scheme of the rising edge trigger signal decoder to improve the output signal accuracy 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.

For a further understanding of the features and technical content of the present invention, please refer to the following detailed descriptions and drawings of the present invention. However, the drawings provided are only for reference and description, and are not intended to limit the present invention.

The following are specific specific examples to illustrate the implementation of the "encoding and decoding method of an analog optocoupler isolation amplifier using sigma-delta modulation technology" disclosed in the present invention, and those skilled in the art can refer to the content disclosed in this specification. Learn about the advantages and effects of the present invention. 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. In addition, the drawings of the present invention are merely schematic illustrations, and are not drawn according to the actual size, and are stated in advance. The following embodiments will further describe the related technical contents of the present invention in detail, but the disclosed contents are not intended to limit the protection scope of the present invention.

It should be understood that although terms such as "first", "second" and "third" may be used herein to describe various elements or signals, these elements or signals should not be limited by these terms. These terms are primarily used to distinguish one element from another element, or a signal from another signal. In addition, the term "or", as used herein, should include any one or a combination of more of the associated listed items, as the case may be.

[Embodiment of the present invention]

FIG. 3 is a block diagram of the analog optocoupler isolation amplifier of the present invention, FIG. 4 is a flowchart of the encoding and decoding method of the analog optocoupler isolation amplifier using the sigma-delta modulation technology in the present invention, and FIG. 5 is the analog optocoupler isolation amplifier of the present invention. The waveform diagram of the coupled isolation amplifier. As shown in FIG. 3 , 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 light sensor 35 , and a decoder 36 , a digital-to-analog converter 37 and a low-pass filter 38 .

Please refer to FIG. 3 , FIG. 4 and FIG. 5 , in step S401 , the input analog signal Sia is converted into the input digital signal Si by the modulator 31 . The modulator 31 is preferably an integral-differential modulator, or called a Sigma-Delta (Σ-Δ) modulator or a Pulse Density Modulation (PDM) modulator. The integral-differential modulator is a digital-to-analog conversion circuit that can convert analog signals into digital signals, that is, convert analog signal samples into one-bit digital signals. It can effectively suppress the quantization noise and has a high signal-to-noise ratio (SNR). The effect of high-pass filtering. The principle of the integrator-derivative modulator is well known to those skilled in the art, and will not be repeated here. In a preferred embodiment of the present invention, the input signal is an input analog signal Sia, 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.

In step S402, when an input digital signal Si generates a rising edge of an input pulse or a falling edge of an input pulse, a coded signal S with a plurality of first pulses coded_pulses is generated by the encoder 32, and each first pulse coded_pulse has a predetermined value Pulse Width. The encoder 32 is electrically connected to the modulator 31 , and the encoder 32 can be used for encoding the input digital signal Si transmitted from the modulator 31 . Further, the encoder 32 can detect the rising edge of the input pulse or the falling edge of the input pulse of the input digital signal Si generated by the modulator 31, and according to the rising edge of the input pulse of the input digital signal Si Or the falling edge of the input pulse generates the first pulse coded_pulses with a predetermined pulse width.

In step S403 , a coded signal Se with a plurality of first pulses coded_pulses is output to the light source driver 33 . In detail, the encoder 32 is preferably a dual-edge-triggered signal encoder, and the dual-edge-triggered signal encoder receives the input digital signal Si of the modulator 31 , and according to the input digital signal Si of the modulator 31 , the dual-edge-triggered signal The encoder will generate a first pulse coded_pulses with a predetermined pulse width when the rising edge of the input pulse or the falling edge of the input pulse of the input digital signal Si occurs. In other words, when the dual edge trigger signal encoder detects the rising edge of the input pulse or the falling edge of the input pulse of the input digital signal Si of the modulator 31, it will generate the first pulse coded_pulses with a predetermined pulse width. The pulse widths of the first pulses coded_pulses are the same, and a plurality of first pulses coded_pulses having predetermined pulse widths are combined into an encoded signal Se.

In step S404, according to the plurality of first pulses coded_pulses of the coded signal Se, the light source 34 is driven by the light source driver 33 to output a coded optical signal Sp. The light source driver 33 is electrically connected to the encoder 32 and the light source 34, and receives the coded signal Se with a plurality of first pulses coded_pulses output by the encoder 32. According to the coded signal Se with a plurality of first pulses coded_pulses, the light source driver 33 can drive the light source 34. The encoded optical signal Sp is output. The light source 34 is preferably a light emitting diode (LED), but in different embodiments, the light source 34 may also be composed of different light sources, which is not limited herein. The light source driver 33 receives the encoded signal Se with 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 optical signal Sp. Signal Se.

Next, in step S405, the coded 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 coded 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 light sensor 35 senses the encoded optical signal Sp to generate a plurality of second pulses with distortion sensing_pulses. As shown in FIG. 5 , the signal distortion of each second pulse sensing_pulses is related to the pulse width of each first pulse coded_pulse.

In detail, the light sensor 35 is arranged at a position corresponding to the light source 34 , that is to say, the arrangement position of the light sensor 35 is on the light transmission route of the light source 34 , and the light sensor 35 is used for sensing the output of the light source 34 . The encoded optical signal Sp is generated to generate a sensing signal S. The sensing signal S generated by the light sensor 35 has a plurality of second pulses sensing_pulses corresponding to the plurality of first pulses coded_pulses of the coded signal Se, and the pulse width of each second pulse sensing_pulse is the same as the signal width of the first pulse coded_pulse Relatedly, by sensing the encoded light signal Sp, the light sensor 35 may form a sensing signal S by generating a plurality of second pulses sensing_pulse.

In step S406, the input digital signal Si of the encoder 31 is restored by the decoder 36 according to the sensing signal S having a plurality of second pulses sensing_pulse. The decoder 36 is electrically connected to the light sensor 35 for receiving the sensing signal S generated by the light 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, assuming 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, it will change the output state to a low level (0), When the decoder 36 detects the rising edge of the second second pulse sensing_pulse, it further changes the output state to a high level. In other words, when a rising edge is detected for the first time, the output is high and remains high, and when a rising edge is detected for the second time, the output will change from high to low, 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 It is determined that 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 pulse of the second pulse generated has a very similar deformation or delay, which ensures that the output digital signal So can accurately replicate the encoder 31 The input digital signal Si.

In addition, as shown in FIG. 6 , in a preferred embodiment of the present invention, the encoder 32 may be composed of a mutually exclusive OR gate (XOR GATE) 321 and a plurality of delay units 322 . The plurality of delay units 322 can generate a quarter of the clock delay of the input signal, and the output digital signal Si of the modulator 31 is transmitted to the input end A of the first delay unit 322 and is connected by five inverting gates ( The first input terminal 324 of the mutually exclusive OR gate 321 composed of the NAND Gate) 323, and the output terminal YN of the last delay unit 322 is connected to the second input terminal 325 of the mutually exclusive OR gate 321. The first pulse coded_pulse is output from the output terminal 326 of the exclusive OR gate 321 . The first pulse coded_pulse having a predetermined signal width is generated by the signal rising edge or the signal falling edge of the input digital signal Si of the encoder 32 of the present invention. It should be noted here that the above encoder 32 is composed of a plurality of delay units 322 and mutually exclusive OR gates 321, but in different embodiments, the encoder 32 may also be composed of different logic units. Without limitation, those with ordinary knowledge in the art can design the encoder 32 composed of different elements according to different requirements. After generating the first pulse coded_pulse with a predetermined signal width, the encoder 32 of the present invention outputs a coded signal Se having a plurality of first pulses coded_pulse.

FIG. 7 is a schematic circuit diagram of a decoder according to an embodiment of the present invention. As shown in FIG. 7 , further, the decoder 35 is also called a dual-edge-triggered decoder, which is a D-edge-triggered flip-flop (D Flip Flop ) 351 and an inverter 352, a plurality of sensing signals S of the second pulse sensing_pulse with a predetermined signal width are transmitted to the clock input terminal clk of the flip-flop 351, and the output terminal YN of the inverter 352 is electrically connected The data input terminal data of the flip-flop 351 and the input terminal A of the inverter 352 are connected to the output terminal Q of the flip-flop 351, and the output digital signal So is output from the other output terminal QN of the flip-flop 351. The decoding circuit composed of the inverter 351 and the inverter 352 can decode a plurality of second pulses sensing_pulse with the same signal width to generate an output signal. In addition, it should be noted here that, in the preferred embodiment of the present invention, the dual-edge trigger decoder is composed of a flip-flop 351 and an inverter 352, but in different embodiments, the dual-edge trigger decoder is The decoder can also be composed of other different logic units, which is not limited here.

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 passing through a low-pass filter (Low Pass Filter). ) 38, filtering the noise in the output analog signal. 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 the output analog signal Sa, so as to restore 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 signal with less noise. The analog signal Sa is output.

It can be clearly seen from FIG. 5 that in the optocoupler isolation amplifier 30 of the present invention, the encoder 32 can output a plurality of predetermined pulses when the input pulse rising edge or the input pulse falling edge of the input digital signal Si is generated. The coded signal Se of the first pulse coded_pulse of the width can accurately know the start and end times of the signal pulse of the input digital signal Si. After Se with the same pulse width passes through the optical channel at the same time, they experience the same pulse deformation, the same rising edge and falling edge, and through the circuit design of the present invention, due to the multiple second pulses with predetermined pulse widths, multiple second pulses with predetermined pulse widths can be completely replicated. A first pulse with a predetermined pulse width, even if the sensing signal S is delayed and deformed after passing through the optical channel, after the decoding of the present invention, the output digital signal So can accurately restore the input digital signal Si at the time of input, thereby improving the optical isolation Problems such as increased offset voltage (Vos), decreased signal-to-noise ratio, or decreased linearity of the amplifier.

[Advantageous effects of the embodiment]

One of the beneficial effects of the present invention is that the optocoupler isolation amplifier provided by the present invention can pass the double-edge-triggered signal encoder and the technical solution of setting the upper-edge-triggered signal decoder in the upper-edge-triggered signal decoder, To improve the output signal accuracy of the optocoupler isolation amplifier.

The contents disclosed above are only preferred feasible embodiments of the present invention, and are not intended to limit the scope of the present invention. Therefore, any equivalent technical changes made by using the contents of the description and drawings of the present invention are included in the application of the present invention. within the scope of the patent.

10: Optocoupler isolation amplifier 11: Modulator 12: Encoder 13: Light source 14: Sensor 15: Decoder 21: digital signal 22: Encoded digital signal 23: output signal 30: Analog optocoupler isolation amplifier 31: Modulator 32: Encoder 321: mutex or gate 322: Delay unit 323: Reverse and gate 324: first input 325: the second input 326: output terminal Sia: Input analog signal Si: Input digital signal Se: encoded signal coded_pulse: first pulse Sp: encoded optical signal S: sensing signal Sensing_pulse: Second pulse So: output digital signal Sa: output analog signal 33: Light source driver 34: Light source 35: Light sensor 351: Edge-triggered D flip-flop 352: Inverter 36: Decoder 37: Digital to Analog Converters 38: Low Pass Filter S401-S406: Steps A: Input terminal clk: clock signal YN: output terminal Q, QN: output terminal data: data input

Figure 1 shows the circuit block diagram of a conventional optocoupler isolation amplifier.

Figure 2 shows the waveform diagram of a conventional optocoupler isolation amplifier.

FIG. 3 is a block diagram of the optocoupler isolation amplifier of the present invention.

FIG. 4 is a flow chart of the encoding and decoding method of the analog optocoupler isolation amplifier of the present invention.

FIG. 5 is a schematic waveform diagram of the optocoupler isolation amplifier of the present invention.

FIG. 6 is a schematic circuit diagram of a decoder according to an embodiment of the present invention.

FIG. 7 is a schematic circuit diagram of an encoder according to an embodiment of the present invention.

S401-S406: Steps

Claims (8)

An encoding and decoding method of an analog optocoupler isolation amplifier using Σ-Δ modulation technology, the analog optocoupler isolation amplifier includes an encoder, a light source driver, a light source, a light sensor and a decoder, and the The encoding and decoding method includes: when an input digital signal generates a rising edge of an input pulse or a falling edge of an input pulse, generating an encoded signal with a plurality of first pulses by the encoder, each of the first pulses having a a predetermined pulse width; outputting the encoded signal having a plurality of the first pulses to the light source driver; according to the plurality of the first pulses of the encoded signal, the light source driver is driven to drive the light source, and output a coded optical signal; the coded optical signal is sensed by the optical sensor to generate a sensing signal, and the sensing signal has a plurality of first pulses corresponding to a plurality of the first pulses of the coded signal two pulses; and replicating the input digital signal of the encoder by the decoder according to the sensed signal having a plurality of the second pulses; wherein before the step of generating the first pulses , further comprising converting an input analog signal into the input digital signal through an integral-differential (Sigma-Delta) modulator; wherein, among the plurality of first pulses generated by the encoder, all The width of the predetermined pulse width is the same, and the range of the predetermined pulse width is 10% to 25% of the clock pulse of the integral-derivative modulator. The encoding and decoding method according to claim 1, wherein after the encoded signal with a plurality of the first pulses passes through the light source driver and the light source, the sensor will generate a plurality of distorted The sensing signal of the second pulse, the distortion size of each of the second pulses is related to the pulse width of each of the first pulses. The encoding and decoding method of claim 1, wherein the pulse width of each of the second pulses is equal to or close to the pulse width of the first pulse. The encoding and decoding method of claim 1, wherein the decoder is a rising edge triggered decoder, and when the decoder senses that the second pulse of the sensing signal is a rising edge of the pulse , its output state changes from high level 1 to low level 0 or from low level 0 to high level 1. The encoding and decoding method of claim 1, wherein when the decoder receives two consecutive second pulses, the decoder generates 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 intervals are determined. The encoding and decoding method of claim 5, further comprising outputting an output digital signal having a plurality of the output pulses through the decoder. The encoding and decoding method of claim 6, further comprising converting the output digital signal into an output analog signal through a digital-to-analog converter. The encoding and decoding method of claim 7, further comprising passing a low-pass filter to filter noise generated when the output signal is converted into the output analog signal.

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