TW486901B - Low-power level shift compensation circuit - Google Patents

Abstract

A kind of low-power level shift compensation circuit includes a buffer, which is connected to the second coil terminal of the transformer of the network receiver, and an equalizer, which is connected to the output terminal of a buffer. In addition, the present invention uses a current compensation circuit located between the front terminal of the equalizer and the buffer output terminal for compensating the level shift of input signal of the equalizer. Additionally, a baseline extractor is connected to the output terminal of the equalizer, and a digital feedback circuit is connected to the output terminal of the baseline extractor for generating a digital signal representing the shift amount. At last, a digital/analog converting circuit is used to convert the digital signal into an analog signal in order to control the current compensation circuit.

Description

486901 V. Description of the invention (1) 5-1 Field of invention: The present invention relates to a base 1 inewander compensation circuit, especially a low power compensation circuit using a digital feedback circuit. 0 5-2 BACKGROUND OF THE INVENTION: In a network system, such as a 10 ca 1 area network (LAN), the receiving circuit usually requires a transformer to isolate different power sources. However, the low-frequency response of the transformer is usually very poor, which leads to quasi-bit drift of the DC component of the signal (b a s e 1 i n e wander). This drift may exceed the common-mode input signal reception range of the equalizer, or the low-frequency gain of the equalizer may amplify this low-frequency component, resulting in missing digital signals or detection errors. The first figure shows a signal with level drift, and the DC component of the component 11 drifts. In addition, the inductance component of a general transformer usually causes the level of the initial end of the received signal to be missed, so that the correct digital signal cannot be detected. Many people have proposed solutions to the above problems. One of the traditional methods is to directly compensate the input signal; although this method is simple, it requires large current consumption, and it is often difficult to really properly set the common-mode bias voltage of the differential signal. Another way is to wait after the J Dagger

486901 V. Description of the invention (2) Line compensation; however, this method cannot prevent the equalizer input signal from exceeding its common mode range. Furthermore, in terms of compensation control, some people have proposed a compensation method that enables the analog feedback circuit. Although it can achieve continuous time level compensation, because the use of the analog feedback circuit requires a large capacitor to effectively control it. The loop bandwidth and stability make the circuit size too large and increase the cost. In view of the many shortcomings of the traditional methods mentioned above, many shortcomings need to be improved, so it is urgent to propose a low power level drift compensation circuit, which can immediately compensate for signal level drift, avoiding the large area and complexity of traditional analog feedback circuits The problem of power consumption and power consumption can also avoid the use of large capacitor values to control the loop bandwidth and stability, which can greatly reduce the required current and reduce the difficulty of the bias circuit design. 5-3 Purpose and Summary of the Invention: In view of the above-mentioned backgrounds of the invention, the conventional level drift compensation circuit has many shortcomings. The present invention provides a level drift compensation circuit using a digital feedback control method. Adjust the level drift to solve the problem of DC level distortion caused by the signal on the transmission line (especially the signal of the local network) after being transformed by the transformer. One of the objectives of the present invention is to avoid feedback in a digitally controlled manner to avoid

Description of the invention (3) 咦 is larger than required by the feedback circuit, and can also avoid the meaning of your post-hybridity and power consumption. Use a large capacitor value to control the loop bandwidth and stability.

Yet another object of the present invention is to # M ^ spoon is to add a buffer in the transformer and motor compensation circuit, equalize 5 | Ximen, go to $ 丨 丄 ^, and look at the Chinese electric power and drop Handle between # π, to achieve a significant reduction in the required current, and to reduce the difficulty of & bias. According to the above-mentioned object, the present invention provides a level drift compensation circuit, which has a primary winding connected to a local network and a secondary winding connected to, buffer. An equalizer is connected to the output of the buffer to restore the signal attenuated by the transmission line. Furthermore, the present invention uses a current compensation circuit located between the front end of the equalizer and the buffer output end to compensate the voltage level of the electronic signal. A base 1 ine extraction circuit (base 1 ine ex tract or) is connected to the output terminal of the equalizer to obtain the level signal of the electronic signal. In addition, a digital feedback circuit is connected to the output terminal of the quasi-bit extraction circuit to generate a digital signal representing the drift of the electronic signal. Finally, a digital conversion analog circuit is connected to the digital signal of the digital feedback circuit to convert the digital signal into an analog signal to control the current compensation circuit.

Page 6 5. Description of the Invention (4) is as follows. However, in addition to implementing the following embodiments in other applications, which will be described in detail with preferred embodiments of the present invention, the present invention can also be widely used. That is, 'the scope of the present invention is not limited, and the scope of subsequent patents shall prevail. The second figure shows a signal according to the present invention ^ ^ r 4-. ≪ Ethernet (Ethernet) area network transmission β (transceiver). 2 1 part circuit. In this example of the car ’s driver Gabe, the local network from

At 糸 is 1 0 0 based-Ethernet, but other types of sad Ethernet, even 5 # a 7 _, can be selected to other networks, signal transmission or non-network electronic circuits, as long as it will happen Anyone who is in a situation of baseiine wander can be applied in accordance with the spirit of the present invention. In the second picture, the foremost point 2 2 of the 'receiver 21 1 receives a signal from the Ethernet circuit (not shown in the figure), and the received signal is transformed to' 2 4 to isolate its DC component. The transformer 24 has a primary winding 26 connected to the local area network, and has a secondary winding 28. Generally, two ends of the second coil 28 of the transformer 24 are connected with a terminal (t e r m i n a t i n g) resistor 25 to match the impedance. In addition, the second coil 2 8 of the transformer 24 is further connected to a set of buffers 3 0 to reduce the influence caused by its subsequent load, which can greatly reduce the current consumption of the circuit of the receiver 21 and make the circuit easy to apply. Bias (bias)

486901 V. Description of the invention (5), and then ′ is connected to the output terminal of the buffer 30 with the equalizer 3 2 for the original loss of the transmission medium. At the input of these equalizers 32, the DC voltage needs to be biased even when there is no level drift. The circuit of the equalizer 32 is a well-known technology, so its details are not disclosed here. The output end of the equalizer 32 is connected to a basel extraction circuit 34 to obtain a level value of the electronic signal. Usually, the peak detection circuit (Peakdetector) is used to implement this level detection circuit. 34 The peak detector is a low-pass filter circuit that can detect the peak or wave seal of the L number of the electron ( envel〇pe). Then, the output terminal of the level picking circuit 34 is connected to a digital feedback control. The circuit 36 is used to generate a ^ bit signal representing the drift of the received electronic signal. The third figure shows a detailed circuit embodiment of the digital feedback control circuit M in the present invention. Although the present invention uses the circuit of the third figure as a preferred embodiment of the feedback circuit, other equivalent changes are equally applicable to the overall receiving circuit of the present invention. The digital feedback control circuit 3 6 mainly includes a group of comparators 5 2 ′, which are general analog comparators, which are mainly used to respectively separate the level signal 54 and a preset upper limit signal (value) 5β and 1 'Pre-μ lower limit signal (value) 58 is compared. Then, a logic circuit composed of an exclusive-exclusive OR (exciusi: OR) logic gate 60, a D-type flip-flop gate 62 and an up-down counter 63 is received. The 'output' is used to generate a digital signal representing the amount of drift of the electronic signal.

Page 486901 V. Description of the invention (6) Because the digital feedback control circuit 36 is used in the present invention, the power consumption can be smaller than the traditional analog feedback control circuit. It can also control the feedback speed and stabilize the feedback system by selecting the clock signal frequency of the flip-flop. Referring again to the second figure, a digital conversion analog circuit 3 8 converts the digital signal of the feedback control circuit 36 into an analog signal, and its output is connected to and controls a current compensation circuit 39, which is located at the equalizer 3 2 Between the front end and the 30 output end of the buffer, to compensate for the level drift of the electronic signal of the local network. In the embodiment of the present invention, as shown in the second figure, a replica biasing can also be included. ) Circuit, which generates a reference voltage connected to the second coil 28 of the transformer 24 to provide a bias voltage at the output of the transformer 24, and makes this voltage pass through the buffer 30 to be equal to the equalizer 32. Required input common-mode bias. According to the description of the above embodiments, the level drift compensation circuit in the digital feedback control method of the present invention can adjust the level drift in real time, and solve the problem of the signal on the transmission line (especially the signal of the local network) after receiving The problem of DC level distortion caused by the converter's conversion; moreover, this digital control feedback method can avoid the problems of large area, complexity and power consumption required by traditional analog feedback circuits, and can also avoid Use large capacitor values to control loop bandwidth and stability. In addition, in the embodiment of the present invention,

486901 V. Description of the invention (7) The punch between the transformer and the current compensation circuit and the equalizer can greatly reduce the current required for level drift compensation and bias, and reduce the difficulty of controlling the bias. The above are merely preferred embodiments of the present invention, and are not intended to limit the scope of patent application for the present invention; all other equivalent changes or modifications made without departing from the spirit disclosed by the present invention shall be included in the following Within the scope of patent application.

Page 10 486901 Brief description of the diagram The first diagram shows a signal waveform diagram with level drift. The DC component of the signal drifts after passing through the transformer. The second figure is a circuit diagram of a signal receiver of an Ethernet local area network receiver (t r a n s c e i v e r) according to the present invention. The third figure shows a circuit embodiment of a digital feedback control circuit in the present invention.

Representative symbols of the main parts:

11 Signal level drift 21 Network signal receiver 22 End point of external LAN 24 Transformer 25 Termination resistance 26 Transformer main coil 28 Transformer second coil 29 Bias setting circuit 30 Buffer 32 Equalizer 34 Level taking circuit 36 Feedback control circuit 38 Digital to analog converter 39 Current compensation circuit

Page 11 486901 Brief description of the diagram 5 2 Voltage comparator 5 4 Level signal 56 Upper limit signal 58 Lower limit signal 60 Mutex OR gate 62 Flip-flop 6 3 Up-down counter Page 12

Claims (1)

486901 486901 six —89116912 Circuit except for b'aseline wander 'This circuit contains at least • "· I. AC voltage transformer' The transformer has a primary coil (primary w 1 η 1 ng) connected to a local area network, And has a second coil (=: =: Wlnding), the transformer is used to isolate the DC component of the electronic signal from the road; $ 网 、 '爰 冲 杰' is connected to the second of the transformer, if used to isolate The input transmission cage is specialized in the suppression of ^^, friend-impact system loads ... It can reduce the input signal from the subsequent I-connector, connected to the output of the buffer; a current compensation circuit, located in Xisheng叩 ,, between the outgoing ends, to compensate ... f "the financial end and the buffer wheel are a standard extraction circuit (baseU position you move; the output end of the adapter is used for 楫 + e ^^ extractor), Connected to the-digital return level signal; to generate a digital signal representing the output of the electric: circuit to output the analog signal of the digital feedback circuit to control the analog signal, the product 2 · If the circuit of the first scope of the patent application Complex ... Ethernet (Ethernet) local area network. "The above-mentioned local area network is used as a standard to obtain electricity. 3. For example, the circuit in the scope of patent application No. 1 in which the above page 13 486901: No. 89116912. VI. Applying for a correction circuit includes a peak detector. 4 · If the circuit of the scope of patent application item (1), the above digital feedback circuit includes at least: a set of comparators for comparing the level signal with a preset signal respectively; and a logic circuit for receiving The output of the comparators is used to generate a digital signal representing the drift of the electronic 彳 § number. 5. The circuit of item 1 of the patent application scope further includes a replica biasing circuit that generates a reference voltage and is connected to a second coil of the transformer to provide a bias voltage of the transformer. 6. The circuit of item (1) of the scope of patent application, further comprising a terminating resistor, the two ends of which are respectively connected to the two ends of the second coil of the transformer. 7. A type of 'basel ine wander' circuit, the circuit contains at least: • 夂 L " Hai Mai pressure has a primary winding, receives the electronic signal, and has a The second coil (secondary Windl " S ") is used to isolate the direct current component of the electronic signal; specialized device, connected to the second coil of the transformer; The front end of the device and the second coil 486901 One question: _ pet ^ to compensate the level drift of the electronic signal; ------ Baseline extracting device, connected to the output end of the clothing set, to obtain the electronic signal The level is used as the number. • The production device is connected to the input of the level acquisition device: the digital signal representing the drift of the electronic signal is used, and the number = conversion analog device is connected to the input feedback control Digital of the circuit: The digital signal is converted into an analog signal, and the generated analog signal output is used to control the current compensation device. The circuit in item 7 of the scope further includes a buffer, which is connected to the second coil of 忒 and AC voltage. Shi Shiwang ^ A receiving circuit used in a local area network system to eliminate level drift (ase "= wander), the receiving circuit contains at least · • d a% voltage /, the transformer has a primary coil (primary -Connected to the local area network and has a second coil ($ 11 + ϋηάιη8). The transformer is used to isolate the DC component of the electronic signal from the local area network. F, connected to the second side of the transformer Coil; a thunder = state ^ connected to the output end of the buffer; the output stage: the compensation circuit is located at the front end of the adapter and the buffer input is one or two to compensate the accuracy of the electronic signal of the local network Bit drift; 哭 哭: a circuit extractor, connected to the output of the wheel-to get the level signal of the electronic signal; _ Case No. 89116912 Modified name _, where, the circuit 'is connected to the round-out of the level-taking circuit. # = The level-signal is compared with a preset limit signal, and the electron is represented by a dagger. Digital signal of signal drift, a digital conversion analog circuit, connected to the digital signal input to the digital feedback circuit, to convert the digital signal into an analog signal, the resulting full ratio 彳 5 5 Tiger output To control the current compensation circuit; and a replica biasing circuit, whose Yansheng reference voltage is connected to the second coil of the transformer to provide the bias voltage of the transformer Page 16