An isolated transmission circuit based on on-chip transformer

Abstract

The present invention relates to an isolated transmission circuit based on an on-chip transformer, wherein the transmission circuit comprises an encoding module, a decoding module, a driving module and two groups of transformers, wherein TA / GND1-RA / RX form one group of transformers, and TB / GND1-RB / RX form another group of transformers; the solution greatly reduces the cost of the solution, reduces the volume, and the on-chip hollow transformer has the advantages of high coupling coefficient, low power consumption, high transmission rate and integration.

Description

Technical Field

[0001] The invention relates to a transmission circuit, in particular to an isolation transmission circuit based on an on-chip transformer, and belongs to the technical field of integrated circuits. Background Art

[0002] In order to ensure safety or for other reasons, the input and output of electronic products need to be isolated. In the application scheme, in order to make the input and output signals linked, an isolated communication mechanism must exist. Traditional isolated communication uses discrete component design, such as the optocoupler + TL431 components commonly used in ACDC switching power supply applications. The use of discrete components increases the cost of the solution on the one hand, and limits the volume of the solution on the other hand, which is not conducive to the trend of miniaturization. Although technicians in this field have been trying new solutions, the results are not ideal. Summary of the invention

[0003] The present invention is aimed at the problems existing in the prior art and provides an isolated transmission circuit based on an on-chip transformer. The solution involves a circuit system for isolated transmission based on an air-core transformer manufactured on a silicon chip, which can replace the traditional isolated transmission of discrete components, greatly reducing the cost and volume of the solution. The on-chip air-core transformer has the advantages of high coupling coefficient, low power consumption, high transmission rate and integration.

[0004] In order to achieve the above-mentioned purpose, the technical solution of the present invention is as follows: an isolated transmission circuit based on an on-chip transformer, characterized in that the transmission circuit includes an encoding module, a decoding module, a driving module and two groups of transformers, wherein TA / GND1-RA / RX constitutes one group of transformers, TB / GND1-RB / RX constitutes another group of transformers, the primary side of the transformer, and the secondary side of the transformer on the right side of the dotted line. The illustrated architecture includes a total of four parts. The encoding module uses an oscillator and a logic gate combination to generate a series of pulse signals; the encoding module encodes the input square wave received by the IC into a series of pulses, and the pulses are transmitted to the primary end of the transformer after being driven and amplified. The series of pulse signals will be coupled at the secondary end of the transformer. After the signal is decoded by the decoding module, a square wave signal similar to the IC input square wave is obtained again.

[0005] As an improvement of the present invention, the decoding module includes an attenuation unit, an amplification unit, and a decoding unit. The attenuation unit is the input part, mainly attenuating unnecessary clutter so that it cannot be detected. The amplification unit is used to amplify the signals that are not filtered out by the attenuation unit. The decoding unit logically combines the useful signals and decodes them into signals that can be processed by subsequent IC modules; the very low serial pulses received by the attenuation unit RA or RB are filtered out, and only high serial pulses need to be transmitted. The function of the amplification unit is to amplify the analog signals output by the attenuation module into digital signals, and the function of the decoding unit is to decode the serial pulses into the final square wave signal PWM2.

[0006] As an improvement of the present invention, the purpose of the attenuation unit is to attenuate unnecessary relatively low interference pulses and only retain pulses with relatively high pulses. The attenuation unit is an operational amplifier with an amplification factor less than 1. The input of the operational amplifier is RA / RB, two triodes connected in series in a diode connection method. The output of the operational amplifier is triodes Q1 / Q2. Q1 / Q2 will generate current pulses, thereby changing the voltage at the lower end of the load resistor to obtain the outputs VA / VB. This module has high precision requirements, and the two inputs and two outputs need to be highly matched. With this design, the relatively high level received on RA / RB will result in a voltage difference reflected on the outputs VA / VB; while the relatively low level (interference signal) received on RA / RB cannot generate an obvious voltage difference on the outputs VA / VB after attenuation, and thus is filtered out.

[0007] As an improvement of the present invention, the amplification unit includes two voltage comparators. These two comparators are hysteresis comparators with the same structure and have two output terminals. For example, for CMP1, its functions are: 1. When VA <= VB, Y1 is at a low level and Y2 is at a high level; 2. When VA > VB, Y1 is at a high level and Y2 is at a low level.

[0008] As an improvement of the present invention, the decoding module mainly processes the voltage relationship between VA and VB. If VA < VB, OUT1 is at a low level, OUT2 is at a high level, and PWM2 is at a low level; if VA > VB, OUT1 is at a high level, OUT2 is at a low level, and PWM2 is at a high level, and PWM2 has a latching function. The purpose is to attenuate unnecessary relatively low interference pulses and only retain pulses with relatively high pulses. The decoding module consists of three groups of latches, which store the serial high and low levels output by the amplification module to obtain the PWM square wave signal.

[0009] As an improvement of the present invention, since the on-chip transformer is only wound with a metal layer, the inductance is usually between several nH and tens of nH. Therefore, the encoding module needs to have a built-in oscillator, usually with a frequency of several MHz to tens of MHz, so as to ensure that the time for driving the primary inductance of the transformer is short and prevent the transformer from being magnetically saturated. Usually, the high-level time of the high-frequency series of pulses obtained after encoding is between several ns and tens of ns. The on-chip transformer mentioned in this article refers to: the transformer is made on a silicon wafer, and the transformer is formed by winding coils of the bottom metal and the top metal.

[0010] Compared with the prior art, the present invention has the following advantages: 1) The on-chip transformer isolation transmission of this technical solution has the advantages of high coupling coefficient, low power consumption, high transmission rate and integration; 2) The ingenious encoding and decoding modules in this solution ensure the accurate transmission of the transformer; 3) The decoding module in this solution adopts interference signal attenuation and effective signal amplification, which well ensures the normal transmission of signals on both sides of the transformer; 4) This technical solution is integrated on chip, which greatly reduces the cost; the withstand voltage between the metal layers of the silicon wafer can improve the withstand voltage of both ends of the transformer, and the transmission speed is fast. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0012] Figure 2 It is a schematic diagram of waveform relationship;

[0013] Figure 3 It is a schematic diagram of the decoding module;

[0014] Figure 4 It is a logical relationship diagram. DETAILED DESCRIPTION

[0015] In order to deepen the understanding of the present invention, the present embodiment is described in detail below with reference to the accompanying drawings.

[0016] Example 1: See Figure 1 The core architecture of the on-chip transformer isolation communication provided by the present invention is as follows: Figure 1As shown, the left side of the dashed line is the primary part of the transformer, and the right side of the dashed line is the secondary part of the transformer. The illustrated architecture includes a total of four parts: an encoding module, a decoding module, a driving module, and two sets of transformers. Among them, TA / GND1 - RA / RX form a set of transformers, and TB / GND1 - RB / RX form another set of transformers. The encoding module uses a combination of an oscillator and logic gates to generate a series of pulse signals; the encoding module encodes the input square wave received by the IC into a series of pulses. After being amplified by the driver, the pulses are transmitted to the primary end of the transformer. At the secondary end of the transformer, a series of pulse signals will be coupled. After being decoded by the decoding module, a square wave signal similar to the IC input square wave is obtained again. The decoding module includes an attenuation unit, an amplification unit, and a decoding unit. The attenuation unit is the input part, mainly attenuating unnecessary clutter so that it cannot be detected; the amplification unit is used to amplify the signals that are not filtered out by the attenuation unit; the decoding unit logically combines the useful signals and decodes them into signals that can be processed by the subsequent modules of the IC; the very low series of pulses received by the attenuation unit RA or RB are filtered out, and only high series of pulses need to be transmitted; the function of the amplification unit is to amplify the analog signal output by the attenuation module into a digital signal, and the function of the decoding unit is to decode the series of pulses into the final square wave signal PWM2. The purpose of the attenuation unit is to attenuate unnecessary relatively low interference pulses and only retain pulses with relatively high pulses. The attenuation unit is an operational amplifier with an amplification factor less than 1. The input of the operational amplifier is RA / RB, two triodes connected in series in the diode connection method. The output of the operational amplifier is the triodes Q1 / Q2. Q1 / Q2 will generate current pulses, thereby changing the voltage at the lower end of the load resistor to obtain the outputs VA / VB. This module has high precision requirements, and the two inputs and two outputs need to be highly matched. With this design, a higher level received on RA / RB will result in a voltage difference reflected on the outputs VA / VB; while a lower level (interference signal) received on RA / RB cannot generate an obvious voltage difference on the outputs VA / VB after attenuation and is thus filtered out. The amplification unit includes two voltage comparators, and these two comparators are hysteresis comparators of the same structure and have two output terminals. For example, for CMP1, its functions are as follows: 1. When VA <= VB, Y1 is at a low level and Y2 is at a high level; 2. When VA > VB, Y1 is at a high level and Y2 is at a low level. The decoding module mainly processes the voltage relationship between VA and VB. If VA < VB, OUT1 is at a low level, OUT2 is at a high level, and PWM2 is at a low level; if VA > VB, OUT1 is at a high level, OUT2 is at a low level, and PWM2 is at a high level. And PWM2 has a latching function. Reference Figure 3. The purpose is to attenuate unnecessary relatively low interference pulses and only retain relatively high pulses. The decoding module is composed of three groups of latches. The series of high and low levels output by the amplification module are stored in the latches to obtain a PWM square wave signal. Since the on-chip transformer is only wound with a metal layer, the usual inductance is between a few nH and tens of nH. Therefore, the encoding module needs to have a built-in oscillator, usually with a frequency of a few MHz to tens of MHz, to ensure that the final drive time of the primary inductance of the transformer is short to prevent the transformer from being magnetically saturated. Usually, the high-level time of the high-frequency series of pulses obtained after encoding is between a few ns and tens of ns. The on-chip transformer mentioned in this article refers to: the transformer is made on a silicon wafer, and the transformer is formed by winding coils on the bottom metal and the top metal. In Figure 1 In the figure, the transformer symbol is used to represent it vividly.

[0017] Working principle: The encoder encodes the input PWM square wave signal into a high-frequency series of pulse signals. The high-frequency series of pulse signals are driven and amplified and directly sent to the primary side of the transformer winding. The secondary winding of the transformer will sense the high-frequency series of pulse signals, which are decoded by the decoding module to finally obtain the PWM square wave signal. Since the on-chip transformer is only wound with a metal layer, the inductance is usually between a few nH and tens of nH. Therefore, the encoding module needs to have a built-in oscillator, usually with a frequency of several MHz to tens of MHz, so as to ensure that the final driving time of the primary inductance of the transformer is short to prevent the transformer from magnetic saturation. Usually, the high-level time of the high-frequency series of pulses obtained after encoding is between a few ns and tens of ns.

[0018] Figure 2 The waveform relationship of each major signal is shown. The waveform relationship from PWM1 square wave to TA / TB can be easily obtained through the logic function of the encoding module, and the waveform relationship from RA / RB to PWM2 needs to be decoded by the decoding module. And the figure shows that when RA is a series of high pulses, RB will have a series of low pulses due to interference or parasitic reasons, which requires the decoding module to have a filtering function for such low series of pulses.

[0019] Figure 3 The structure of the display decoding module includes three functions: attenuation, amplification, and decoding. Figure 2 The very low series of pulses received by RA or RB in the module are filtered out, and only high series of pulses need to be transmitted; the amplification function refers to amplifying the analog signal output by the attenuation module into a digital signal, and the decoding function refers to decoding the series of pulses into the final square wave signal PWM2.

[0020] In the attenuation module, the structures of RA, RB, and RX with respect to ground are both composed of two BE junctions plus a resistor. Therefore, at static state, the voltages of RA, RB, and RX are equal. For RA and RB, their structures with respect to VDD are the same. Thus, at static state, the voltages of VA and VB are equal. Suppose at a certain moment, RA receives a high pulse, which will trigger Q1 to generate a large current, thereby pulling down the voltage of VB. At this time, the voltage of VA will be greater than the voltage of VB. Similarly, when RB receives a high pulse, the voltage of VA will be less than the voltage of VB. When RA or RB returns to the static state after receiving the pulse, the voltages of VA and VB will be equal again. As Figure 2 , during normal operation, when RA receives a series of high pulses and RB receives a series of low pulses, after the processing of the attenuation module, the interference of the series of low pulses will be shielded.

[0021] The amplification module consists of two voltage comparators. As shown in the figure, these two comparators are hysteresis comparators with the same structure and have two output terminals. For example, for CMP1, its functions are as follows: 1. When VA <= VB, Y1 is at a low level and Y2 is at a high level; 2. When VA > VB, Y1 is at a high level and Y2 is at a low level.

[0022] The decoding module mainly processes the voltage relationship between VA and VB. If VA < VB, OUT1 is at a low level, OUT2 is at a high level, and PWM2 is at a low level; if VA > VB, OUT1 is at a high level, OUT2 is at a low level, and PWM2 is at a high level. And PWM2 has a latching function. The logical relationships of RA, RB, OUT1, OUT2, and PWM2 are as Figure 4 shown.

[0023] It should be noted that the above embodiments are not used to limit the protection scope of the present invention. Any equivalent transformation or substitution made on the basis of the above technical solutions falls within the protection scope of the claims of the present invention.

Claims

1. An isolation transmission circuit based on an on-chip transformer, characterized in that: The transmission circuit includes an encoding module, a decoding module, a driving module, and two groups of transformers. Among them, TA / GND1-RA / RX form a group of transformers, and TB / GND1-RB / RX form another group of transformers. The encoding module uses a combination of an oscillator and logic gates to generate a series of pulse signals; The encoding module encodes the input square wave received by the IC into a series of pulses. After the pulses are amplified by driving, they are transmitted to the primary end of the transformer. At the secondary end of the transformer, a series of pulse signals will be coupled. After this signal is decoded by the decoding module, a square wave signal identical to the IC input square wave is obtained again; The decoding module includes an attenuation unit, an amplification unit, and a decoding unit. The very low series of pulses received by the attenuation unit RA or RB are filtered out, and only the high series of pulses need to be transmitted. The function of the amplification unit is to amplify the analog signal output by the attenuation module into a digital signal. The function of the decoding unit is to decode the series of pulses into the final square wave signal PWM2; The attenuation unit is set as an operational amplifier with an amplification factor less than 1. The input of the operational amplifier is RA / RB, and two triodes connected in series in a diode configuration. The output of the operational amplifier is triodes Q1 / Q2. Q1 / Q2 will generate current pulses, thereby changing the voltage at the lower end of the load resistor to obtain the outputs VA / VB; The amplification unit includes two voltage comparators. These two comparators are hysteresis comparators with the same structure and have two output terminals; The decoding module processes the voltage relationship between VA and VB. If VA < VB, OUT1 is at a low level, OUT2 is at a high level, and PWM2 is at a low level; if VA > VB, OUT1 is at a high level, OUT2 is at a low level, and PWM2 is at a high level, and PWM2 has a latching function; The decoding module consists of three groups of latches. The series of high and low levels output by the amplification module are stored by the latches to obtain the PWM square wave signal; The on-chip transformer is wound with a metal layer, and the inductance is between a few nH and dozens of nH. Therefore, the encoding module needs to have an internal oscillator with a frequency between a few MHz and dozens of MHz to ensure that the time for finally driving the primary inductance of the transformer is short, prevent transformer magnetic saturation, and the high-level time of the high-frequency series of pulses obtained after encoding is between a few ns and dozens of ns.

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