TWI517710B - A receiver circuit for processing differential-mode and common-mode signals concurrently - Google Patents

Description

Receiving circuit capable of simultaneously processing differential mode signals and common mode signals

The present invention relates to a differential mode signal and a common mode signal processing technique for differential signaling, and more particularly to a HEAC receiving circuit.

In the technical field of analog message processing and delivery, the commonly used method is differential message transmission, and the differential amplifier can be said to be one of the most important components. The differential amplifier itself suppresses the interference of its input differential signal to its common mode component (or common mode signal), and only processes the differential mode component (or differential mode signal), and most of them Mode signal interference is only environmental noise, and its impact is limited; therefore, the circuit composed of the differential amplifier usually has good performance. However, when the interference caused by the common mode signal is too large, the differential amplifier must have a high Common-Mode Rejection Ratio (CMRR) to resist this common mode signal interference.

In the special application of HEAC (HDMI Ethernet & Audio return Channel) (HDMI is the abbreviation of High-Definition Multimedia Interface), the common mode signal of the differential signal pair is used to transmit ARC (Audio Return Channel). The sound source signal, and the intensity of the sound source signal is much larger than the general environmental noise, which will cause the differential amplifier circuit to seriously interfere with each other and the common mode signal, so that the differential mode signal of the HEC (HDMI Ethernet Channel) end The performance is severely attenuated; at this time, the common mode rejection capability of the differential amplifier circuit must be increased, but the manufacturing cost is also increased. Therefore, in order to balance the differential mode signal and the common mode signal of the differential message transmission, it is necessary to further develop a new differential amplifying circuit technology.

According to an aspect of the present invention, an embodiment provides a differential signal that can be processed simultaneously And a receiving circuit for transmitting the differential mode signal and the common mode signal, comprising: a first input end receiving a first signal; a second input end receiving a second signal, wherein the first and second signals are mutually a complementary signal for the differential message; a differential amplifier having an inverting input and a non-inverting input, the inverting input being coupled to the first input, and the non-inverting input coupled to the second And a common mode compensation unit configured to detect a common mode signal generated by the first and second signals, and adjust an input signal of the input terminals of the differential amplifier accordingly. The receiving circuit can be applied to the reception of HEAC signals.

In addition, the common mode compensation unit includes: a common mode extraction unit for extracting the common mode signal; and a compensation control unit configured to generate first and second compensation signals according to the common mode signal, respectively providing the difference The inputs of the operational amplifier are used to reduce the common mode component of the first and second signals entering the differential amplifier.

100‧‧‧ receiving circuit

101‧‧‧ first input

102‧‧‧second input

103‧‧‧ Output

110‧‧‧Differential Amplifier

111‧‧‧Inverting input

112‧‧‧ non-inverting input

120‧‧‧Common mode compensation unit

130‧‧‧Common mode extraction unit

131‧‧‧Splicing point

140‧‧‧Compensation Control Unit

145‧‧‧ comparator

1 is a block diagram of a differential message passing and receiving circuit in accordance with an embodiment of the present invention.

Fig. 2 is a detailed circuit diagram of the receiving circuit of the embodiment.

3 is a circuit diagram of a voltage to current amplifier of the comparator of the embodiment.

In order to provide a further understanding and understanding of the features, objects and functions of the present invention, the present invention will be described in detail with reference to the drawings. In all of the specification and drawings, the same component numbers will be used to designate the same or similar components. For the convenience and clarity of the description, the thickness or size of each element in the drawings is expressed in an exaggerated or omitted or schematic manner, and the size of each element is not completely the actual size.

For differential messaging technology, the message is transmitted by two complementary signals V ⁺ and V ^- (or called differential signal pairs) on two pairs of wires (or differential line pairs ( In the differential pair)), the differential mode component of the differential signal pair is (V ⁺ -V ^- ), that is, the differential mode signal V _d of the differential signal pair, and the common mode component of the differential signal pair It is (V ⁺ +V ^- )/2, which is the common mode signal V _{c of} the differential signal pair. When the differential signal pair passes through a differential amplifier, its output signal V _o can be expressed as V _o =A _d (V ⁺ -V ^- )+A _c (V ⁺ +V ^- )/2=A _d ×V _d + A _c × V _c where A _d is the differential mode gain and A _c is the common mode gain. In addition, since differential signaling technology usually transmits signals by differential mode signals, common mode signals are usually not used to transmit messages. Therefore, it is desirable that the differential mode gain A _{d is} large and the common mode gain A _{c is} small, and the differential amplifier is measured. The parameter that suppresses the ability of the common mode signal is the common mode rejection ratio (CMRR = A _d / A _c ).

When the common mode signal also plays the role of transmitting messages in the differential message transmission, the strength of the common mode signal may be much larger than that of the general environmental noise, which will cause a larger difference to the differential mode signal originally used to transmit the message. Interference, so the differential amplifier used must have a larger common mode rejection ratio to account for. For the HEAC technology, the differential mode signal of the differential signal pair used is used to transmit the HEC data signal, and the common mode signal is used to transmit the ARC sound source signal, which is one of the objects to be processed in this embodiment.

1 is a block diagram of a differential message transmitting and receiving circuit 100 according to an embodiment of the present invention, in which a differential signal pair and a common mode signal are used to transmit a message, which is also required by the receiving circuit 100. signal. The differential signal pair includes a first signal V ⁺ and a second signal V ⁻ that are complementary to each other. As shown in FIG. 1, the receiving circuit 100 has a first input terminal 101 and a second input terminal 102, and includes a differential amplifier 110 and a common mode compensation unit 120. The first input terminal 101 receives the first A signal V ⁺ , the second input 102 receives the second signal V ⁻ .

The differential amplifier 110 has an inverting input terminal 111 connected to the first input terminal 101 and a non-inverting input terminal 112 connected to the second input terminal 102. The differential amplifier 110 is configured to amplify the differential mode signal V _d (=V ⁺ -V ^- ) of the differential signal pair to extract the differential mode signal V _d and the message carried by the differential mode signal.

The common mode compensation unit 120 is configured to detect a common mode signal Vc of the differential signal pair (=(V ⁺ +V ^- )/2); in other words, the common mode compensation unit 120 is also connected to the first and second inputs. The terminals 101 and 102 respectively receive the first and second signals V ⁺ and V ⁻ and take out the common mode signal V _c and the message carried by the same. In addition, the common mode compensation unit 120 adjusts the input signals of the input terminals 111 and 112 of the differential amplifier 110 according to the detected common mode signal V _c .

In order to describe the operation of the embodiment in more detail, FIG. 2 illustrates a circuit diagram of the receiving circuit 100. The common mode compensation unit 120 includes a common-mode extraction unit 130, and a compensation control unit 140; wherein the common mode extraction unit 130 for taking out the common mode signal V _C, the compensation control unit 140 is configured in accordance with the common mode signal V when entering the differential amplifier 110 ^- _c generates a first and a second compensation signal are supplied to the input terminal of the differential amplifier 110 such 111 and 112, so as to reduce the first signal and the second signal V ⁺ V Common mode composition.

The common mode extraction unit 130 can obtain the common mode signal V _c by means of voltage division; for example, as shown in FIG. 2, the common mode extraction unit 130 can be formed by connecting two identical resistors R _{c in} series, and 131 taken by the concatenation point first and second signals V ⁺ and V ^- average value of the common mode signal V _c; but the present invention is not limited to. The compensation control unit 140 can include a comparator 145 for comparing the common mode signal V _c and a reference voltage V _ref taken by the common mode extraction unit 130 and generating a compensation signal for providing to the differential amplifier 110. The input signals of the inputs 111 and 112 of the differential amplifier 110 are adjusted.

In this embodiment, the comparator 145 can be a voltage-to-current amplifier, and the circuit diagram can be as shown in FIG. 3. The voltage-to-current amplifier can be implemented by using a symmetrical type of transistor amplifier stage circuit with a current mirror. , while the common mode voltage V _c and the difference between the reference voltage V _ref for the current signal into a compensation signal in the form of, e.g., a first and a second compensation current source I _c1 and I _c2. The input terminals 111 and 112 of the differential amplifier 110 are respectively charged or discharged by the first and second compensation current sources I _c1 and I _c2 , so that the input signals of the input terminals 111 and 112 can be subjected to the common mode signal V _c increment / decrement adjustments or reverse compensation to offset or reduce the common mode interference due to common mode signal V _c and the message carrying the differential mode signal V _d caused. In addition, in order to facilitate the above charging/discharging, the two resistors R _x may be respectively disposed between the input terminals 111 and 112 of the differential amplifier 110 and the input terminals 101 and 102 of the receiving circuit 100.

In addition, in order to simplify the circuit of the voltage-to-current amplifier, in the present embodiment, the first compensation current source I _c1 and the second compensation current source I _c2 are the same size each other; however, the invention is not limited thereto. In addition, if the present embodiment is applied to the reception of the HEAC signal, the HEC data signal can be taken out by the output terminal 103 of the receiving circuit 100, and the ARC sound source signal can be taken out by the resistance string contact 131 of the common mode extraction unit 130.

The above is only the preferred embodiment of the invention, and the scope of the invention is not limited thereto. It is to be understood that the scope of the present invention is not limited by the spirit and scope of the present invention, and should be considered as a further embodiment of the present invention.

100‧‧‧ receiving circuit

101‧‧‧ first input

102‧‧‧second input

110‧‧‧Differential Amplifier

111‧‧‧Inverting input

112‧‧‧ non-inverting input

120‧‧‧Common mode compensation unit

Claims (8)

A receiving circuit for simultaneously processing a differential mode signal and a common mode signal in differential signaling, comprising: a first input receiving a first signal; and a second input receiving a a second signal, wherein the first and second signals are mutually complementary signals for differential signal transmission; a differential amplifier having an inverting input and a non-inverting input, the inverting input being coupled to the first An input terminal, wherein the non-inverting input terminal is connected to the second input end; and a common mode compensation unit configured to detect a common mode signal generated by the first and second signals, and adjust the differential amplifier according to the The input signal of the input terminal; wherein the common mode compensation unit comprises: a common mode extraction unit for extracting the common mode signal; and a compensation control unit for generating the first and second signals according to the common mode signal Compensating signals are respectively supplied to the input terminals of the differential amplifier, thereby reducing a common mode component when the first and second signals enter the differential amplifier; wherein the compensation control unit includes a comparator The first and second compensation signals to compare the common mode signal and a reference voltage, and the generated current signal. The receiving circuit of claim 1, wherein the common mode extracting unit comprises at least one resistor, and the common mode signal is taken out by voltage division. The receiving circuit of claim 1, wherein the first and second compensation signals are identical to each other. The receiving circuit of claim 1, wherein the comparator comprises a voltage-to-current amplifier for converting a voltage difference between the common mode signal and the reference voltage into first and second compensation signals of the current form. . A HEAC (HDMI Ethernet & Audio return Channel) receiving circuit includes: a first input terminal receiving a first signal; a second input terminal receiving a second signal, wherein the first and second signals are mutually a complementary signal for differential signal transmission; a differential amplifier having an inverting input and a non-inverting input, the inverting input being coupled to the first input, and the non-inverting input coupled to the second input And a common mode compensation unit for detecting a common mode signal generated by the first and second signals, and adjusting an input signal of the input terminals of the differential amplifier; wherein the common mode compensation The unit includes: a common mode extraction unit for extracting the common mode signal; and a compensation control unit for generating first and second compensation signals according to the common mode signal, respectively providing the input to the differential amplifier End, wherein the common mode component of the first and second signals entering the differential amplifier is reduced; wherein the compensation control unit includes a comparator for comparing the common mode signal with a reference voltage, and the generated The first and second compensation signals are current signals. The HEAC receiving circuit of claim 5, wherein the common mode extracting unit comprises at least one resistor, and the common mode signal is taken out by voltage division. The HEAC receiving circuit of claim 5, wherein the first and second compensation signals are identical to each other. The HEAC receiving circuit of claim 5, wherein the comparator comprises a voltage to current amplifier for converting the voltage difference between the common mode signal and the reference voltage into the first and second compensations of the current form. signal.