WO2023241396A1 - Digital isolator and sending circuit thereof - Google Patents

Abstract

Disclosed in the present invention are a digital isolator and a sending circuit thereof. The sending circuit comprises a digital sender, a high-side selection circuit and a low-side selection circuit, wherein the high-side selection circuit selects and outputs a digital signal to a power supply end of the digital sender, and the low-side selection circuit selects and outputs a common ground signal to a grounding end of the digital sender; and a high-side control circuit is configured to control, according to the digital signal and the common ground signal, the turning-on degree of a first high-side branch or a second high-side branch to be constant. The sending circuit provided in the present invention can adapt to a working environment having a bidirectional high-voltage signal input, such that the working of the circuit and the heating power can be kept stable.

Description

Digital isolator and its transmitting circuit

This application claims the priority of the Chinese patent application with the filing date of June 16, 2022, the application number is 202210677166.1, and the invention name is "Digital Isolator and Its Transmitting Circuit", the entire content of which is incorporated into this application by reference.

Technical field

The present invention relates to the field of isolation technology, and in particular to a digital isolator and its transmitting circuit.

Background technique

Digital isolators, also known as digital isolation units or digital isolation chips, are usually used in industrial factory environments to ensure the normal transmission of signals between two systems. In a specific working condition, it can be used to receive digital inputs from switches and sensors, and output them to the back end after processing and isolation. During this process, it is difficult for the digital isolator side to grasp and control the above-mentioned digital input conditions, especially the direction and voltage of the input. This will lead to the loss of the reverse digital input signal, increase the packaging cost, and make it difficult to adapt to higher voltages. Input requirements, as well as problems with system power accumulation and high heating power.

In the existing technology, the digital isolator can adapt to high-voltage input environments by limiting the voltage across the external sampling resistor. However, this technical solution is limited by circuit components and can only form a 1.2V band in the internal loop. The gap reference voltage has limited scope of application and beneficial effects, and it cannot take into account bidirectional high-voltage input. If rectifiers and other devices are added outside the digital isolator in the prior art to improve its adaptability to bidirectional high-voltage input, then on the one hand, the cost of internal component configuration will be increased; on the other hand, the multi-channel floating ground It is difficult to share terminals and more pins need to be set on the chip, thus increasing the cost of chip packaging.

Contents of the invention

One of the purposes of the present invention is to provide a transmitting circuit of a digital isolator to solve the technical problems in the prior art that digital isolation circuits are difficult to adapt to bidirectional high-voltage input environments, have high operating and heating power, and have high overall circuit costs.

One object of the present invention is to provide a digital isolator.

In order to achieve one of the above-mentioned objects of the invention, one embodiment of the present invention provides a transmission circuit of a digital isolator. The transmission circuit includes a digital transmitter, a high-side selection circuit and a low-side selection circuit; the high-side selection circuit selects and Output digital signals to the power supply end of the digital transmitter, and the low-side selection circuit selects and outputs a common ground signal to the ground end of the digital transmitter; the high-side selection circuit includes a high-side control circuit, and a The first high-side branch and the second high-side branch receive the digital signal and the common ground signal; the output end of the high-side control circuit is connected to the power supply end, and the control of the high-side control circuit The ends are respectively connected to the first high-side branch and the third Two high-side branches, and are configured to control the conduction degree of the first high-side branch or the second high-side branch to be constant according to the digital signal and the common ground signal.

As a further improvement of an embodiment of the present invention, the low-side selection circuit includes a low-side control circuit, and a first low-side branch and a second low-side branch respectively used to receive the digital signal and the common ground signal. path; the output end of the low-side control circuit is connected to the ground end, the control end of the low-side control circuit is connected to the first low-side branch and the second low-side branch respectively, and is configured to be according to the The digital signal and the common ground signal control the conduction degree of the first low-side branch or the second low-side branch to be constant.

As a further improvement of an embodiment of the present invention, the first high-side branch includes a first high-side switch tube, and the input end of the first high-side switch tube is connected to the power supply end and the first high-side switch. The output end of the tube is connected to the first input end, and the control end of the first high-side switch tube is connected to the high-side control circuit and the second input end respectively; the first input end is used to receive the digital signal and one of the common ground signal, and the second input terminal is used to receive the other one of the digital signal and the common ground signal.

As a further improvement of an embodiment of the present invention, the high-side control circuit includes a first high-side voltage regulator tube, and the input end of the first high-side voltage regulator tube is connected to the control end of the first high-side switch tube. , and the output end of the first high-side voltage regulator tube is connected to the power supply end and the first input end respectively.

As a further improvement of an embodiment of the present invention, the high-side control circuit further includes a first high-side driver tube, and the first high-side switch tube is connected to the high-side control circuit through the first high-side driver tube. The first high-side voltage regulator tube; the input end of the first high-side drive tube is connected to the control end of the first high-side switch tube and the power supply end, and the control end of the first high-side drive tube. The input end of the first high-side voltage regulator tube is connected, and the output end of the first high-side driver tube is connected to the second input end.

As a further improvement of an embodiment of the present invention, the first high-side branch further includes a first high-side diode parasitic on the first high-side switch tube, and the input end of the first high-side diode is connected to the a first input terminal, and an output terminal of the first high-side diode is connected to the power supply terminal.

As a further improvement of an embodiment of the present invention, the second high-side branch includes a second high-side switch tube, and the input end of the second high-side switch tube is connected to the power supply end and the second high-side switch. The output end of the tube is connected to the second input end, and the control end of the second high-side switch tube is connected to the high-side control circuit and the first input end respectively; the second high-side branch is also It includes a second high-side diode parasitic on the second high-side switch tube, the input end of the second high-side diode is connected to the second input end, and the output end of the second high-side diode is connected to the power supply end.

As a further improvement of an embodiment of the present invention, the high-side control circuit includes a second high-side voltage regulator tube, and the input end of the second high-side voltage regulator tube is connected to the control end of the second high-side switch tube. , and the second high-side regulator The output end of the tube is connected to the power supply end and the second input end respectively.

As a further improvement of an embodiment of the present invention, the high-side control circuit further includes a second high-side driver tube, and the second high-side switch tube is connected to the high-side control circuit through the second high-side driver tube. The second high-side voltage regulator tube; the input end of the second high-side drive tube is respectively connected to the control end of the first high-side switch tube and the power supply end, and the control end of the second high-side drive tube. The input end of the second high-side voltage regulator tube is connected, and the output end of the second high-side driving tube is connected to the first input end.

As a further improvement of an embodiment of the present invention, the first high-side switch tube is a P-channel field effect tube, and the input terminal of the first high-side switch tube is the source electrode of the P-channel field effect tube, and the The output terminal of the first high-side switch tube is the drain of the P-channel field effect transistor, and the control terminal of the first high-side switch tube is the gate of the P-channel field effect transistor.

As a further improvement of an embodiment of the present invention, the first low-side branch includes a first low-side switch, and the output end of the first low-side switch is connected to the ground terminal and the first low-side switch. The input end of the tube is connected to the first input end, and the control end of the first low-side switch tube is connected to the low-side control circuit and the second input end respectively; the first input end is used to receive the digital signal and one of the common ground signal, and the second input terminal is used to receive the other one of the digital signal and the common ground signal.

As a further improvement of an embodiment of the present invention, the first low-side switch tube is an N-channel field effect transistor, and the input end of the first low-side switch tube is the drain of the N-channel field effect tube, and the The output terminal of the first low-side switch tube is the source electrode of the N-channel field effect transistor, and the control terminal of the first low-side switch tube is the gate electrode of the N-channel field effect transistor.

As a further improvement of an embodiment of the present invention, the digital transmitter includes a current loop, the current loop includes a reference branch and a sensing branch; the sensing branch is provided at the power supply end and the Between the output sides of the digital transmitter, it is configured to generate an original transmission signal according to the input of the power supply terminal; the reference branch is connected to the power supply terminal and is configured to control the sensor according to the reference signal in the digital transmitter. The operating current on the measuring branch is constant.

As a further improvement of an embodiment of the present invention, the current loop includes a first operational amplifier, a sensing resistor and a reference resistor; after the inverting input terminal and output terminal of the first operational amplifier are connected, they are connected to the sensing resistor. The resistor is connected to form the sensing branch; the non-inverting input end of the first operational amplifier is connected to the reference resistor to form the reference branch.

As a further improvement of an embodiment of the present invention, the digital transmitter includes a bandgap reference source for generating and outputting the reference signal; the first reference input end of the bandgap reference source is connected to the sensing branch. The first node between the circuit and the output side of the digital transmitter, the second reference input terminal of the bandgap reference source is connected to the ground terminal, and the first reference output terminal of the bandgap reference source is connected to the Describe the reference branch.

As a further improvement of an embodiment of the present invention, the bandgap reference source includes an interconnected bandgap voltage source and a signal conversion circuit, the bandgap voltage source is configured to generate a bandgap reference voltage, and the signal conversion circuit is configured To convert the bandgap reference voltage into the reference signal; the reference signal is a reference current signal corresponding to the bandgap reference voltage.

As a further improvement of an embodiment of the present invention, the signal conversion circuit includes a second operational amplifier, a conversion transistor and an adjustment resistor; the drain of the conversion transistor is connected to the reference branch, and the gate of the conversion transistor is connected to the reference branch. The output terminal of the second operational amplifier, and the source of the conversion transistor is connected to the inverting input terminal of the second operational amplifier; both ends of the adjustment resistor are respectively connected to the inverting input terminal of the second operational amplifier. and the ground terminal; the non-inverting input terminal of the second operational amplifier is connected to the bandgap voltage source and forms a second node.

As a further improvement of an embodiment of the present invention, the digital transmitter further includes an isolation comparison circuit and a transmission drive circuit; the first comparison input terminal of the isolation comparison circuit is connected to the first node and the ground terminal respectively. The second comparison input end of the isolation comparison circuit is connected to the second node, and the comparison output end of the isolation comparison circuit is connected to the drive enable end of the transmission drive circuit; the drive input end of the transmission drive circuit is connected to the The first node is configured to receive a first oscillation signal generated according to the voltage of the first node.

As a further improvement of an embodiment of the present invention, an oscillation generating circuit is further included between the drive input terminal and the first node, configured to output the first oscillation signal; the sending drive circuit is configured to output the first oscillation signal according to the first node. An oscillation signal generates a first clock signal.

As a further improvement of an embodiment of the present invention, the isolation comparison circuit includes a hysteresis comparator; the transmission drive circuit includes an AND gate, an inverter and a buffer; the input end of the inverter and the buffer The input terminal is connected to the output terminal of the AND gate.

In order to achieve one of the above-mentioned objects of the invention, one embodiment of the present invention provides a digital isolator, which includes a receiving circuit, an isolation capacitor, and a transmitting circuit of the digital isolator described in any of the above technical solutions.

As a further improvement of an embodiment of the present invention, the digital isolator includes a first transmission circuit provided in the first transmission channel, and a second transmission circuit provided in the second transmission channel; the first transmission circuit is connected to the first transmission circuit The input terminal is to receive the first digital signal, and the first transmitting circuit is connected to the second input terminal to receive the common ground signal; the second transmitting circuit is connected to the third input terminal to receive the second digital signal, and the A second sending circuit is connected to the second input terminal to receive the common ground signal.

Compared with the existing technology, the transmitting circuit of the digital isolator provided by the present invention sets a high-side selection circuit and a low-side selection circuit at the power supply end and the ground end of the digital transmitter respectively, so that the received digital signal and the common ground After the signal is selected, always keep the digital signal and the public ground signal corresponding to the input power supply terminal and the ground terminal, which can adapt to the working environment of bidirectional signal input; by setting up a high-side control circuit in the high-side selection circuit to limit the high-side selection The degree of conduction of the two branches in the circuit can adapt to the working environment of high-voltage signal input, so that the components working on it will not be damaged or overloaded, and due to the restriction on the degree of conduction, it can also ensure the operation of the circuit And the heating power is stable; since the bidirectional signal is not rectified or otherwise transformed, the circuit can adapt to the requirement of unified ground level for multiple channels and can reduce the overall cost of the circuit.

Description of the drawings

Figure 1 is a schematic structural diagram of a digital isolator in an embodiment of the present invention.

FIG. 2 is a circuit structure diagram of a high-side selection circuit of a transmitting circuit in an embodiment of the present invention.

FIG. 3 is a circuit structure diagram of a low-side selection circuit of a transmitting circuit in an embodiment of the present invention.

FIG. 4 is a circuit structure diagram of a digital transmitter of a transmitting circuit in an embodiment of the present invention.

FIG. 5 is a circuit structure diagram of a high-side selection circuit of a transmitting circuit in another embodiment of the present invention.

FIG. 6 is a circuit structure diagram of a low-side selection circuit of a transmitting circuit in another embodiment of the present invention.

Detailed ways

The present invention will be described in detail below with reference to the specific embodiments shown in the accompanying drawings. However, these embodiments do not limit the present invention. Structural, method, or functional changes made by those of ordinary skill in the art based on these embodiments are all included in the protection scope of the present invention.

It should be noted that the term "comprising" or any other variation thereof is intended to cover a non-exclusive inclusion, such that a process, method, article or apparatus including a list of elements not only includes those elements, but also includes those not expressly listed other elements, or elements inherent to the process, method, article or equipment. Furthermore, the terms "first," "second," etc. are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

One embodiment of the present invention provides a digital isolator 100 as shown in Figure 1 for realizing isolation and signal transmission between two systems. The above two systems can be, for example, electromechanical systems at a detection site, and, for example, industrial systems. The control system of the controller can protect the two sides with different working environment requirements and ensure the normal progress of signal transmission and control. The digital isolator 100 provided by the present invention includes a receiving circuit 12, an isolation capacitor 11, and a transmitting circuit 13 of a digital isolator. Among them, the sending circuit 13 is used to receive the input signal from the electromechanical system side, the isolation capacitor 11 is used to prevent the electromechanical system from being directly coupled to the control system, and the receiving circuit 12 is used to receive the input signal from the sending circuit 13 and the isolation capacitor 11. Signal, realize communication and transmit the signal to the control system side.

In an embodiment where the digital isolator 100 is provided with a data transmission channel, the digital isolator 100 may include at least a first transmission channel and a second transmission channel. The digital isolator 100 further includes at least a first transmitting circuit disposed on the first transmission channel, and a second transmitting circuit disposed on the second transmission channel. When the first transmitting circuit and the second transmitting circuit are configured as the circuit structure of the transmitting circuit of the digital isolator provided by the present invention, they can be specifically configured as follows: the first transmitting circuit is connected to the first input terminal 131 to receive the first number word signal Input, and the first sending circuit is connected to the second input terminal 132 to receive the common ground signal COM; the second sending circuit is connected to the third input terminal to receive the second digital signal, and the second sending circuit is connected to The second input terminal 132 is used to receive the common ground signal COM. In this way, multiple channels can receive multiple digital signal inputs, but the effect of multiplexing the same common ground signal terminal (the second input terminal 132) can greatly improve the cost problem under the condition of multiple data transmission channels. It can be understood that the above "circuit structure of the transmitting circuit of the digital isolator provided by the present invention" will be described in detail below, and the relevant technical effects can also be formed in the technical solution of the digital isolator 100 provided by the present invention, here No longer.

In addition, in an embodiment that includes multiple data transmission channels, the isolation capacitor 11 can be provided with multiple isolation branches, and each isolation branch is connected in series with at least one isolator. The isolator can be a capacitor or an inductor. , transformer or other electromagnetic components sufficient to form an isolation channel.

Continuing as shown in Figure 1, one embodiment of the present invention provides a transmitting circuit 13 of a digital isolator, which can be mounted in the above-mentioned digital isolator 100, can also be mounted in other industrial controllers, or can be installed anywhere between two systems. Used in components to achieve isolation and digital signal transmission. The sending circuit 13 may specifically include a high-side selection circuit 200, a digital transmitter 300 and a low-side selection circuit 400. Among them, the high-side selection circuit 200 is used to select and output the digital signal Input to the power supply terminal 301 of the digital transmitter 300 , and the low-side selection circuit 400 is used to select and output the common ground signal COM to the ground terminal 302 of the digital transmitter 300 . Therefore, the digital transmitter 300 can generate an appropriate signal according to the digital signal Input and the common ground signal COM and output it to the rear-side components, thereby realizing isolated transmission of digital signals.

The high-side selection circuit 200 and the low-side selection circuit 400 can be configured as needed, for example, multiple selection branches can be provided to cooperate with single or multiple corresponding switching devices. The high-side selection circuit 200 and the low-side selection circuit 400 may adopt corresponding circuit structure configurations, or may adopt mutually different circuit structure configuration schemes. In one embodiment, preferably, the high-side selection circuit 200 and the low-side selection circuit 400 have corresponding circuit structures, and in addition to selecting the input signal, they also have the function of adjusting the input signal to adapt to the digital isolator 100 and/or the functional configuration required by the working environment of the back-side circuit structure (for example, the isolation capacitor 11, the receiving circuit 12 and/or the control system or electromechanical system connected to the receiving circuit 12).

Further, the high-side selection circuit 200 includes a first high-side branch 21 and a second high-side branch 22 for receiving the digital signal Input and the common ground signal COM respectively, and a high-side control circuit 23 . Among them, the first high-side branch 21 and the second high-side branch 22 are used to select the digital signal Input and output the digital signal Input to the power supply terminal 301 . The output terminal of the high-side control circuit 23 is connected to the power supply terminal 301, and the control terminals of the high-side control circuit 23 are respectively connected to the first high-side branch 21 and the second high-side branch 22, and the high-side control circuit 23 is configured as follows: according to the digital The signal Input and the common ground signal COM control the conduction degree of the first high-side branch 21 or the second high-side branch 22 to be constant.

In this way, adaptive selection of the digital signal Input and the common ground signal COM can be achieved to ensure that the digital transmitter 300 receives signals in the correct direction, realizing adaptation to bidirectional signal input, and a high-side control circuit 23 is provided on the signal receiving side of the digital transmitter 300 to adapt to the working environment of high-voltage signal input by limiting the degree of conduction. The combination of these beneficial effects enables the sending circuit 13 and the digital isolator 100 equipped with the sending circuit 13 and other devices to adapt to the working conditions of high-voltage bidirectional signal input, avoiding packaging problems caused by adding a rectifier circuit or simply clamping the voltage. Problems such as increased cost and uncontrollable heating power.

The degree of conduction can be further explained as: the opening of the switching device on the first high-side branch 21 or the second high-side branch 22 . Based on this, the transmitting circuit 13 of the digital isolator provided by the present invention can improve the self-damage, overload or circuit damage caused by the opening of the switching device on the high-side branch increasing with the increase of the input signal (digital signal Input). Working in abnormal conditions.

On the one hand, in an embodiment in which the low-side selection circuit 400 and the high-side selection circuit 200 are configured to have the same or corresponding circuit structure, the low-side selection circuit 400 may further include a low-side control circuit 43, and a circuit for receiving The first low-side branch 41 and the second low-side branch 42 of the digital signal Input and the common ground signal COM. Among them, the first low-side branch 41 and the second low-side branch 42 are used to select the common ground signal COM and output the common ground signal COM to the ground terminal 302 . The output terminal of the low-side control circuit 43 is connected to the ground terminal 302, and the control terminals of the low-side control circuit 43 are respectively connected to the first low-side branch 41 and the second low-side branch 42, and the low-side control circuit 43 is configured as: according to the digital The signal Input and the common ground signal COM control the conduction degree of the first low-side branch 41 or the second low-side branch 42 to be constant. Therefore, there are limits on the degree of conduction on both sides of the power supply terminal 301 and the ground terminal 302 of the digital transmitter 300. On the basis of supporting bidirectional signal input, the stability of the overall working state of the transmitting circuit 13 is ensured, and the circuit itself is adaptively adjusted. Signal parameters enable it to adapt to more complex and harsh working conditions.

Of course, in other embodiments, since the level selected by the low-side selection circuit 400 is a low level, the low-side selection circuit 400 can also be simply configured as a switch selection circuit, and some of the low-side control circuits can be canceled or retained. 43 settings. The present invention does not limit other alternative configurations of the above technical solutions by those skilled in the art. Any alternative configurations that do not deviate from the above scope fall within the protection scope of the present invention.

In addition, it can be understood that the inputs of the digital signal Input and the common ground signal COM should correspond to the same on both sides of the high-side selection circuit 200 and the low-side selection circuit 400 . In one implementation, the ends of the high-side selection circuit 200 and the low-side selection circuit 400 used to receive the digital signal Input can be connected to each other and uniformly connected to a terminal before the sending circuit 13; the high-side selection circuit 200 and the low-side selection circuit One end of the circuit 400 for receiving the common ground signal COM can be connected to each other and uniformly connected to the other end before the sending circuit 13 .

At the same time, any relative relationship definitions such as "connected to" and "connected to" in the present invention do not necessarily refer to direct electrical connections. They can also be indirect connections, and specifically they can be connected through other circuit components or through circuits. Other parts are connected. For the part involving signal transmission, it can also be a connection method such as communication connection. The present invention relates to "assembly For the limitations of relative relationships such as "", the connection relationship implied by it can also follow the above explanation. The above content will not be repeated below.

On the other hand, the configuration of the internal components of the high-side selection circuit 200 and the control of the conduction degree of the first high-side branch 21 or the second high-side branch 22 by the high-side control circuit 23 can be adopted on the high-side branch. An adjustable current-limiting device is provided, and the high-side control circuit 23 is connected to the current-limiting adjustment terminal of the adjustable current-limiting device and outputs level signals of different sizes to dynamically adjust the opening degree and opening frequency of the adjustable current-limiting device. parameter. In a preferred embodiment, as shown in Figures 1 and 2, the first high-side branch 21 in the present invention may include a first high-side switch tube 211, and the input end 2111 of the first high-side switch tube is connected to The power supply terminal 301 and the output terminal 2112 of the first high-side switch are connected to the first input terminal 131, and the control terminal 2113 of the first high-side switch are connected to the high-side control circuit 23 and the second input terminal 132 respectively. The first input terminal 131 is used to receive one of the digital signal Input and the common ground signal COM, and the second input terminal 132 is used to receive the other of the digital signal Input and the common ground signal COM.

In this way, the high-side control circuit 23 can be used to affect the conduction degree of the first high-side switch 211 by controlling the control terminal 2113 of the first high-side switch, thereby affecting the connection between the input terminal 2111 and the output terminal 2112. The degree of conduction is high or low to achieve the technical effect of controlling the degree of conduction to be constant. Furthermore, although in the case shown in FIG. 2 , the first input terminal 131 is configured to receive the digital signal Input and the second input terminal 132 is configured to receive the common ground signal COM, in the case of signals having opposite directions During input, the signal input diagram in Figure 2 can be adjusted accordingly, which should be understood by those skilled in the art.

In a preferred embodiment, in order to further simplify the circuit structure, the high-side control circuit 23 does not use integrated control chips and other devices that increase packaging difficulty and cost, but uses a voltage regulator tube (or Zener diode) to achieve the corresponding technical effects. Of course, the present invention does not exclude the use of the former integrated control chip implementation. Based on this, the high-side control circuit 23 includes a first high-side voltage regulator tube 231. The input terminal of the first high-side voltage regulator tube 231, serving as at least one of the control terminals of the high-side control circuit 23, is connected to the first high-side voltage regulator tube 231. The control terminal 2113 of a high-side switch is connected to the second input terminal 132 . The output terminals of the first high-side voltage regulator tube 231 are connected to the power supply terminal 301 and the first input terminal 131 respectively.

In this way, the first high-side voltage regulator tube 231 can be used to adaptively conduct or shield the first high-side branch 21 , and the first high-side voltage regulator tube 231 can be used to form a conductive degree to the first high-side switch tube 211 . limit. Specifically, when the first input terminal 131 receives the digital signal Input and the second input terminal 132 receives the common ground signal COM, if the voltage of the digital signal Input is high and the first high-side voltage regulator tube 231 is reversely broken down, Then, the first high-side voltage regulator tube 231 limits the voltage of the control terminal 2113 of the first high-side switch tube, thereby limiting the conduction degree of the first high-side switch tube 211 and stabilizing its conduction degree. When the first input terminal 131 receives the common ground signal COM and the second input terminal 132 receives the digital signal Input, the first high-side voltage regulator tube 231 conducts forward to shield the first high-side branch 21 .

In a preferred embodiment, in order to further simplify the circuit wiring, the first high-side branch 21 includes a first high-side diode 212 parasitic on the first high-side switch 211, or the first high-side switch 211 configuration There is a first high-side diode 212 for internal parasitics. The input terminal of the first high-side diode 212 is connected to the first input terminal 131 , and the output terminal of the first high-side diode 212 is connected to the power supply terminal 301 . In this way, the conduction directions of the first high-side diode 212 and the first high-side switch tube 211 are opposite, and the output terminal of the first high-side voltage regulator tube 231 is connected to the first input terminal through the input terminal 2111 of the first high-side switch tube. 131. When the digital signal Input is input to the first input terminal 131 and the common ground signal COM is input to the second input terminal 132, the first high-side switch 211 is turned on, and at the same time, the high-level digital signal Input is added through the first high-side diode 212. At the output end of the first high-side voltage regulator tube 231, when the digital signal Input voltage is high, the first high-side voltage regulator tube 231 is reversely broken down; at the first input terminal 131, the common ground signal COM is input, and the second When the digital signal Input is input to the input terminal 132, the first high-side switch tube 211 is turned off, and the first high-side voltage regulator tube 231 is forward-conducted. Preferably, in order to limit current and divide voltage, a protection resistor may also be included between the first high-side voltage regulator tube 231 and the second input terminal 132 .

Correspondingly, in order to achieve a constant branch conduction degree when the digital signal Input and the common ground signal COM are connected in reverse, the second high-side branch 22 may have any of the above-mentioned first high-side branch 21 The structural configuration is the same. Of course, other existing schemes for controlling the conduction degree or frequency can also be used. Regarding the former, in the embodiment provided in FIG. 2 , the second high-side branch 22 specifically includes a second high-side switch 221 . The input terminal 2211 of the second high-side switch is connected to the power supply terminal 301 . The second high-side switch The output terminal 2212 of the tube is connected to the second input terminal 132, and the control terminal 2213 of the second high-side switch tube is connected to the high-side control circuit 23 and the first input terminal 131 respectively. In this way, when a high-level digital signal Input is input to the second input terminal 132, the first high-side branch 21 is turned off, the second high-side branch 22 is turned on, and the second high-side circuit 21 is connected to the second high-side circuit 22 through the high-side control circuit 23. The control of the control terminal 2213 of the side switch tube forms a control over the conduction degree of the second high side branch 22 .

The second high-side branch 22 also includes a second high-side diode 222 parasitic on the second high-side switch transistor 221 , or the second high-side switch transistor 221 is configured to have the second high-side diode 222 parasitic inside. Similar to the first high-side branch 21 , the above two can be interpreted as referring to the same solution, or they can be interpreted as referring to two different solutions of separate arrangement and integrated arrangement respectively. The input terminal of the second high-side diode 222 is connected to the second input terminal 132 , and the output terminal of the second high-side diode 222 is connected to the power supply terminal 301 , thereby forming a current conduction direction opposite to that of the second high-side switch tube 221 . In this way, the high-side control circuit 23 is connected to the output terminal of the second high-side diode 222 and the input terminal 2211 of the second high-side switch tube by connecting the terminal on the side of the power supply terminal 301, so that the high-side switch tube can be controlled according to the second high-side switch tube. The level conditions of the control terminal 2213 and the input terminal 2211 of the second high-side switch tube control the degree of conduction of the second high-side branch 22.

Preferably, the high-side control circuit 23 specifically includes a second high-side voltage regulator tube 232, which uses the reverse breakdown property to stabilize the voltage between the control terminal 2213 of the second high-side switch tube and its input terminal 2211, thereby forming a pair. its degree of conduction limit. The input terminal of the second high-side voltage regulator tube 232, as at least one of the control terminals of the high-side control circuit 23, is connected to the control terminal 2213 of the second high-side switch tube, and thereby connected to the first input terminal 131; The output terminal of the second high-side voltage regulator tube 232 is connected to the power supply terminal 301 and is connected to the second input terminal 132 through the output terminal of the second high-side diode 222 . In this way, the conduction degree of the second high-side switch transistor 221 can be limited to ensure that the conduction degree of the second high-side switch transistor 221 does not increase as the digital signal input voltage increases.

Regarding the specific component selection of the above-mentioned first high-side switch transistor 211, it can be preferably configured as a P-channel field effect transistor to meet the needs of high-side driving and avoid the cost increase caused by insufficient driving force and the addition of a charge pump. Of course, the present invention does not exclude the technical solution of combining N-channel field effect transistors and driving elements. Based on this, the input terminal 2111 of the first high-side switch is the source of the P-channel field effect transistor, and the output terminal 2112 of the first high-side switch is the drain of the P-channel field effect transistor. , and the control terminal 2113 of the first high-side switch transistor is the gate electrode of the P-channel field effect transistor. Correspondingly, the second high-side switch transistor 221 can also be configured as a P-channel field effect transistor, so that its input terminal 2211, its output terminal 2212 and its control terminal 2213 can correspond to the P-channel field effect transistor. source, drain and gate. In this way, the voltage regulator tube is used to control it to always work in the constant current area to prevent the degree of conduction from greatly increasing as the input voltage increases.

Regarding the configuration of the internal components of the low-side selection circuit 400, in an embodiment in which the low-side selection circuit 400 is configured to include the first low-side branch 41, the second low-side branch 42, and the low-side control circuit 43, the same can be This is achieved by setting an adjustable current-limiting device on the low-side branch and adjusting the opening degree, opening frequency and other parameters of the adjustable current-limiting device. Preferably, the low-side selection circuit 400 may have a structural configuration as shown in FIGS. 1 and 3 . Among them, the first low-side branch 41 includes a first low-side switch 411. The output terminal 4111 of the first low-side switch is connected to the ground terminal 302, and the input terminal 4112 of the first low-side switch is connected to the first input terminal 131. , and the control terminal 4113 of the first low-side switch tube is connected to the low-side control circuit 43 and the second input terminal 132 respectively. Correspondingly, the first input terminal 131 is used to receive one of the digital signal Input and the common ground signal COM, and the second input terminal 132 is used to receive the other of the digital signal Input and the common ground signal COM.

In this way, when the high-level digital signal Input passes through the first input terminal 131 and the common ground signal COM passes through the second input terminal 132, the first low-side switch 411 is turned off. When the high-level digital signal Input passes into the second input terminal 132 and the common ground signal COM passes into the first input terminal 131, the first low-side switch 411 is turned on and connects the common ground signal COM to the ground terminal 302. , and the low-side control circuit 43 controls the conduction degree of the first low-side switch transistor 411 to be constant.

Preferably, the low-side control circuit 43 includes a first low-side voltage regulator tube 431, and the output end of the first low-side voltage regulator tube 431, serving as at least one of the control terminals of the low-side control circuit 43, is connected to the first The control terminal 4113 of a low-side switch is connected to the second input terminal 132 . The input terminals of the first low-side voltage regulator tube 431 are respectively connected to the ground terminal. 302 and the first input terminal 131.

Preferably, the first low-side branch 41 includes a first low-side diode 412 parasitic on the first low-side switch 411 , or the first low-side switch 411 is configured to have the first low-side diode 412 parasitic inside. The output terminal of the first low-side diode 412 is connected to the first input terminal 131 , and the input terminal of the first low-side diode 412 is connected to the ground terminal 302 .

Correspondingly, the second low-side branch 42 may include a second low-side switch 421 , the output terminal 4211 of the second low-side switch is connected to the ground terminal 302 , and the input terminal 4212 of the second low-side switch is connected to the ground terminal 302 . The second input terminal 132 and the control terminal 4213 of the second low-side switch are connected to the low-side control circuit 43 and the first input terminal 131 respectively.

Preferably, the second low-side branch 42 further includes a second low-side diode 422 parasitic on the second low-side switch tube 421, or the second low-side switch tube 421 is configured to have the second low-side diode 422 parasitic inside. . The output terminal of the second low-side diode 422 is connected to the second input terminal 132 , and the input terminal of the second low-side diode 422 is connected to the ground terminal 302 .

Further, the low-side control circuit 43 specifically includes a second low-side voltage regulator tube 432 . Among them, the output terminal of the second low-side voltage regulator tube 432, serving as the control terminal of at least one of the low-side control circuits 43, is connected to the control terminal 4213 of the second low-side switch tube, thereby being connected to the first input terminal. 131. The input terminal of the second low-side voltage regulator tube 432 is connected to the ground terminal 302 , and the input terminal of the second low-side diode 422 is connected to the second input terminal 132 .

In this way, two low-side branches that are symmetrically arranged and conduct in both directions can be used, and the two low-side voltage regulator tubes can be used to control the voltage between the gate and the source, so as to maintain a constant conduction level of the branches at least when high voltage is input. .

Preferably, the first low-side switch transistor 411 can be configured as an N-channel field effect transistor to meet the requirements of low-side driving and avoid the cost increase caused by insufficient driving force and the addition of a charge pump. Of course, the present invention does not exclude the technical solution of using a combination of P-channel field effect transistors and driving elements. Based on this, the output terminal 4111 of the first low-side switch is the source of the N-channel field effect transistor, and the input terminal 4112 of the first low-side switch is the drain of the N-channel field effect transistor. , and the control terminal 4113 of the first low-side switch transistor is the gate electrode of the N-channel field effect transistor. Correspondingly, the second low-side switch transistor 421 can also be configured as an N-channel field effect transistor, so that its output terminal 4211, its input terminal 4212 and its control terminal 4213 can correspond to the N-channel field effect transistor. source, drain and gate. In this way, the voltage regulator tube is used to control it to always work in the constant current region, preventing the conduction degree of the branch from greatly increasing as the input voltage increases.

As shown in Figures 1 and 4, an embodiment of the present invention further provides a digital transmitter 300, which can be independently installed in the transmission circuit of any digital isolator, or can be combined with the above-mentioned high-side selection circuit 200 and low-side At least one of the selection circuits 400 is connected to realize corresponding functional configuration. It can be understood that for the latter, the digital transmitter 300 can establish a connection relationship with the high-side selection circuit 200 through the power supply terminal 301, and/or establish a connection relationship with the low-side selection circuit 400 through the ground terminal 302.

The digital transmitter 300 in this embodiment includes a current loop 31, which specifically may include It includes a reference branch 311 and a sensing branch 312. The sensing branch 312 is disposed between the power supply terminal 301 and the output side 303 of the digital transmitter, and the sensing branch 312 is configured to generate an original transmission signal according to the input of the power supply terminal 301 . The reference branch 311 is connected to the power supply end 301 , and the reference branch 311 is configured to control the operating current on the sensing branch 312 to be constant according to the reference signal in the digital transmitter 300 . In this way, the operating current on the power supply terminal 301 can be limited from the side of the digital transmitter 300, and the operating current can be adjusted to adapt to various operating conditions by adjusting the reference signal in the digital transmitter 300. Combined with the configuration of the high-side selection circuit 200, restrictions on the sensing branch 312 and the power supply end 301 can be formed from two aspects: operating current and branch conduction level, which can better maintain the stability of the circuit operation. At the same time, compared with the technical solution that limits the operating voltage on the sensing branch 312 to be constant, the above solution provided by the present invention does not require frequent adjustment of the circuit structure of the sensing branch 312 and can adapt to a wider range of voltage inputs.

Further, the current loop 31 preferably includes a first operational amplifier 313, a sensing resistor 3120, and a reference resistor 3110. Specifically, after the inverting input terminal of the first operational amplifier 313 is connected to the output terminal of the first operational amplifier 313, it is connected to the sensing resistor 3120 to form the above-mentioned sensing branch 312; the non-inverting input terminal of the first operational amplifier 313 It is connected with the reference resistor 3110 and forms the above-mentioned reference branch 311. In this way, by configuring the first operational amplifier 313 as a follower connection, the currents on the reference branch 311 and the sensing branch 312 are equal, so that the reference signal input to the reference branch 311 can be controlled to form a sensing pair. Control of operating current on branch 312.

Preferably, the digital transmitter 300 further includes a bandgap reference source 32 for generating and outputting said reference signal. The first reference input terminal 321 of the bandgap reference source 32 is connected to the first node N1 between the sensing branch 312 and the output side 303 of the digital transmitter, and the second reference input terminal 322 of the bandgap reference source 32 is connected to the ground terminal. 302, and the first reference output terminal 323 of the bandgap reference source 32 is connected to the reference branch 311. In this way, the bandgap reference source 32 can be used to generate the reference signal that is independent of temperature, and combined with the configuration of the current loop 31 , temperature drift during circuit signal transmission can be eliminated. Furthermore, when the current loop 31 is configured with the first operational amplifier 313 in a follower connection, the temperature drift problem can be solved from the current level. Compared with the voltage or current mirror configuration, the reference branch 311 and the sensing branch can be achieved There is no temperature drift effect on 312, so that the accuracy of the adjustment of the reference branch 311 and the response of the sensing branch 312 is simultaneously improved.

Specifically, the bandgap reference source 32 may include a bandgap voltage source 5 and a signal conversion circuit 6 connected to each other. Wherein, the bandgap voltage source 5 is configured to generate a bandgap reference voltage Vref, and the signal conversion circuit 6 is configured to convert the bandgap reference voltage Vref into the reference signal. Preferably, the reference signal is a reference current signal Iref corresponding to the bandgap reference voltage Vref. In this way, the bandgap reference voltage Vref is converted into a temperature-independent reference current signal Iref, and the reference current signal Iref is used as the reference signal to adjust the power-on signal of the sensing branch 312 even without replacing the sensing resistor 3120 or other components. In the case of the structure of the sensing branch 312, it can also achieve zero temperature drift and wide range adjustment of the original transmission signal, and can cope with high-voltage signal input.

Preferably, the signal conversion circuit 6 includes a second operational amplifier 61 , a conversion transistor 62 and an adjustment resistor 63 . The drain of the conversion transistor 62 is connected to the reference branch 311 , the gate of the conversion transistor 62 is connected to the output terminal of the second operational amplifier 61 , and the source of the conversion transistor 62 is connected to the inverting input terminal of the second operational amplifier 61 . Preferably, switching transistor 62 is an N-type transistor. The two ends of the adjustment resistor 63 are respectively connected to the inverting input terminal and the ground terminal 302 of the second operational amplifier 61 . The non-inverting input terminal of the second operational amplifier 61 is connected to the bandgap voltage source 5 and forms the second node N2. In this way, not only can the cooperation of the second operational amplifier 61 and the conversion transistor 62 be utilized, but when the value of the bandgap reference voltage Vref is appropriate, the bandgap reference voltage Vref is added to both ends of the adjustment resistor 63 , thereby configuring the adjustment resistor 63 The resistance value, according to Ohm's law, forms a suitable reference current signal Iref and inputs it to the reference branch 311, so that the sensing branch 312 also generates a suitable, adjustable, zero temperature drift, sufficient to adapt to a wide range of adjustment and sufficient to cope with high voltage input. electrical signal.

Preferably, the bandgap voltage source 5 may be specifically composed of a first low dropout linear regulator (LDO, Low Dropout Regulator) 52 and a bandgap reference voltage source 51 which are connected in series with each other.

Continuing, the digital transmitter 300 may also include an isolation comparison circuit 33 and a transmission driving circuit 34. Among them, the first comparison input terminal 331 of the isolation comparison circuit 33 is connected to the first node N1 and the ground terminal 302, the second comparison input terminal 332 of the isolation comparison circuit 33 is connected to the second node N2, and the comparison output terminal 333 of the isolation comparison circuit 33 Connect the drive enable terminal 341 of the sending drive circuit 34. Therefore, based on the comparison result between the potential of the first node N1 and the potential of the ground terminal 302 and the potential of the second node N2 (bandgap reference voltage Vref), the transmission driving circuit 34 can be selectively enabled to output the voltage corresponding to the required voltage. The output transmit signal of the original transmit signal.

Correspondingly, the driving input terminal 342 of the sending driving circuit 34 is connected to the first node N1 and is used to receive the first oscillation signal generated according to the voltage of the first node N1 (or the original sending signal). Therefore, according to the first oscillation signal and the output of the isolation comparison circuit 33, according to the preset operation logic, an output transmission signal is generated and sent from the output side 303 of the digital transmitter to the back-end components.

The first oscillation signal may be generated by an oscillation generating circuit 7. The oscillating generating circuit 7 is disposed between the driving input terminal 342 and the first node N1, and is configured to generate the oscillation generating circuit 7 according to the voltage of the first node N1. The first oscillation signal. Correspondingly, the transmission driving circuit 34 is configured to generate a first clock signal according to the first oscillation signal as the output transmission signal. Specifically, the first clock signal may be a differential high-frequency clock, and the oscillation generating circuit 7 may be configured to include a second low-voltage linear regulator 72 and an oscillator (OSC, Oscillator) 71 .

Regarding the specific configuration of components, on the one hand, the isolation comparison circuit 33 may include a hysteresis comparator 330. Based on this, the first comparison input terminal 331 may be the non-inverting input terminal of the hysteresis comparator 330, and the second comparison input terminal 332 may be The inverting input terminal and the comparison output terminal 333 of the hysteresis comparator 330 may be the output terminal of the hysteresis comparator 330 . Therefore, the isolation comparison circuit 33 can jointly set a threshold through its front-end circuit structure. When the digital signal Input meets the threshold requirement, an enable signal is output to cause the transmission driving circuit 34 to operate. On the other hand, the sending driving circuit 34 may include an AND gate 343, a buffer 344 and an inverter 345, wherein the input terminals of the buffer 344 and the inverter 345 are connected to the output terminal of the AND gate 343, and the two terminals of the AND gate 343 The input terminals serve as the above-mentioned driving enable terminal 341 and the driving input terminal 342 respectively. Thereby, the original transmission signal (or the first oscillation signal output by the oscillation generating circuit 7) is finally formed through the first node N1, the output of the inverter 345 is adjusted, and the output of the buffer 344 is adjusted by the level of the ground terminal 302. Technical solutions.

The above technical solutions respectively provide parts of the transmitting circuit 13 of the digital isolator, and the combination of the above technical solutions can form a better transmitting circuit 13 . In order to further improve the driving speed and driving capability so that the transmitting circuit 13 can be applied to a working environment with higher input voltage requirements, the present invention further provides another implementation as shown in Figures 5 and 6.

As further shown in FIG. 1 , in this other embodiment, the high-side selection circuit 200' further includes a first high-side driving transistor 24. The first high-side switching transistor 211 on the first high-side branch 21 passes through the first high-side switching transistor 211. A high-side driver tube 24 is connected to the first high-side voltage regulator tube 231 of the high-side control circuit. The input terminal 241 of the first high-side driver tube is connected to the control terminal 2113 and the power supply terminal 301 of the first high-side switch tube respectively. The control terminal 243 of the first high-side driver tube is connected to the input terminal of the first high-side voltage regulator tube 231. And the output terminal 242 of the first high-side driver tube is connected to the second input terminal 132 . In this way, the conduction degree of the first high-side driving tube 24 can be controlled through the first high-side voltage stabilizing tube 231, so that the first high-side switching tube 211 can be stably driven. Preferably, the first high-side driver transistor 24 is a P-channel field effect transistor, and its corresponding input terminal 241, output terminal 242 and control terminal 243 may be the source, drain and gate of the P-channel field effect transistor. Preferably, a protection resistor may also be included between the input terminal 241 of the first high-side driver tube and the power supply terminal 301.

Taking the digital signal Input to the first input terminal 131 and the common ground signal COM to the second input terminal 132 as an example, the high-level digital signal Input passes through the parasitic third parasitic signal inside the first high-side switch 211 . A high-side diode 212 is added to the input terminal 241 of the first high-side driver tube and the output terminal of the first high-side voltage regulator tube 231, causing the first high-side driver tube 24 to conduct, and causing the first high-side voltage regulator tube to conduct. 231 reverse breakdown to control the current on the first high-side driver tube 24 to be constant. After the first high-side driver tube 24 is turned on, the control terminal 2113 of the first high-side switch tube is connected to the second input terminal 132, so that it can The common ground signal COM is turned on, and the digital signal Input of the first input terminal 131 is connected to the power supply terminal 301 . At the same time, under the joint action of the restriction of the first high-side voltage regulator tube 231 and the driving of the first high-side driving tube 24, the first high-side switch tube 211 has an appropriate and stable conduction degree.

Correspondingly, the high-side selection circuit 200' also includes a second high-side driver tube 25. The second high-side switch tube 221 on the second high-side branch 22 is connected to all the switches through the second high-side driver tube 25. The second high side of the high side control circuit Voltage regulator tube 232. The input terminal 251 of the second high-side driver tube is connected to the control terminal 2213 and the power supply terminal 301 of the second high-side switch tube respectively, and the control terminal 253 of the second high-side driver tube is connected to the input terminal of the second high-side voltage regulator tube 232. And the output terminal 252 of the second high-side driver tube is connected to the first input terminal 131 . Preferably, the second high-side driver transistor 25 is a P-channel field effect transistor, and its corresponding input terminal 251, output terminal 252 and control terminal 253 may be the source, drain and gate of the P-channel field effect transistor. Preferably, a second high-side diode 222 is parasitic inside the second high-side switch tube 221. There may also be a protection resistor between the input terminal 251 of the second high-side driver tube and the power supply terminal 301.

Regarding the ground terminal 302 side, in another embodiment, the low-side selection circuit 400' further includes a first low-side driver tube 44, and the first low-side switch tube 411 on the first low-side branch 41 is connected through the first low-side switch tube 411. A low-side driver tube 44 is connected to the first low-side voltage regulator tube 431 of the low-side control circuit. The output terminal 441 of the first low-side driver tube is connected to the control terminal 4113 and the ground terminal 302 of the first low-side switch tube respectively. The control terminal 443 of the first low-side driver tube is connected to the output terminal 431 of the first low-side voltage regulator tube. , and the input terminal 442 of the first low-side driver tube is connected to the second input terminal 132 . In this way, the conduction degree of the first low-side driving tube 44 can be controlled through the first low-side voltage stabilizing tube 431, so that the first low-side switching tube 411 can be stably driven. Preferably, the first low-side driver transistor 44 is an N-channel field effect transistor, and its corresponding output terminal 441, input terminal 442 and control terminal 443 may be the source, drain and gate of the N-channel field effect transistor. Preferably, a protection resistor may also be included between the output terminal 441 of the first low-side driver tube and the ground terminal 302.

Taking the common ground signal COM as an example, the common ground signal COM is applied to the first input terminal 131 and the digital signal Input is applied to the second input terminal 132. The low-level common ground signal COM is parasitic inside the first low-side switch transistor 411. The first low-side diode 412 is added to the output terminal 441 of the first low-side driver tube and the input terminal of the first low-side voltage regulator tube 431 to conduct the first low-side driver tube 44 and enable the first low-side voltage regulator. The tube 431 reversely breaks down to control the current on the first low-side driving tube 44 to be constant. After the first low-side driving tube 44 is turned on, the control terminal 4113 of the first low-side switching tube is connected to the second input terminal 132, causing it to After obtaining the digital signal Input, it is turned on, and the common ground signal COM of the first input terminal 131 is connected to the ground terminal 302 . At the same time, under the joint action of the restriction of the first low-side voltage regulator tube 431 and the driving of the first low-side driving tube 44, the first low-side switch tube 411 has an appropriate and stable conduction degree.

Correspondingly, the low-side selection circuit 400' also includes a second low-side drive tube 45. The second low-side switch tube 421 on the second low-side branch 42 is connected to all the switches through the second low-side drive tube 45. The second low-side voltage regulator tube 432 of the low-side control circuit. The output terminal 451 of the second low-side driver tube is connected to the control terminal 4213 and the ground terminal 302 of the second low-side switch tube respectively, and the control terminal 453 of the second low-side driver tube is connected to the output terminal of the second low-side voltage regulator tube 432. And the input terminal 452 of the second low-side driver tube is connected to the first input terminal 131 . Preferably, the second low-side driver transistor 45 is an N-channel field effect transistor, and its corresponding output terminal 451, input terminal 452 and control terminal 453 may be the source, drain and gate of the N-channel field effect transistor. Preferably, the second low-side switch transistor 421 has a second low-side diode 422 internally parasitized. There may also be a protection resistor between the output terminal 421 of the low-side driver tube and the ground terminal 302.

It is worth emphasizing that due to the existence of the low-side selection circuit 400 (or the low-side selection circuit 400'), the ground terminal 302 is always connected to the common ground signal COM, and the digital isolator 100 is provided with more transmitting circuits 13 and/or components. In the implementation of more data transmission channels, the ground terminal 302 of each circuit and/or channel can be uniformly connected to a common ground signal COM, thereby saving the pin configuration of the chip. In this way, the above-mentioned circuit configuration of the present invention is repeatedly arranged to form more derivative technical solutions, and any technical effects that can be imagined based on the circuit configuration of the present invention are included in the protection scope of the present invention.

In summary, the transmitting circuit of the digital isolator provided by the present invention selects the received digital signal and the common ground signal by setting a high-side selection circuit and a low-side selection circuit at the power supply end and the ground end of the digital transmitter respectively. , always keep the digital signal and the public ground signal corresponding to the input power supply terminal and the ground terminal, and can adapt to the working environment of bidirectional signal input; by setting up a high-side control circuit in the high-side selection circuit, it is used to limit the two The degree of conduction of the branch can adapt to the working environment of high-voltage signal input, and due to the restriction on the degree of conduction of the branch, it can also ensure the stability of the circuit's operation and heating power; since the bidirectional signal is not rectified or otherwise transformed, Therefore, the circuit can adapt to the requirement of unified ground level for multiple channels and can reduce the overall cost of the circuit.

It should be understood that although this specification is described in terms of implementations, not each implementation only contains an independent technical solution. This description of the specification is only for the sake of clarity. Persons skilled in the art should take the specification as a whole and understand each individual solution. The technical solutions in the embodiments can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

The series of detailed descriptions listed above are only specific descriptions of feasible implementations of the present invention. They are not intended to limit the protection scope of the present invention. Any equivalent implementations or implementations that do not deviate from the technical spirit of the present invention are not intended to limit the protection scope of the present invention. All changes should be included in the protection scope of the present invention.

Claims (20)

1. A transmitting circuit of a digital isolator, characterized in that the transmitting circuit includes a digital transmitter, a high-side selection circuit and a low-side selection circuit;

   The high-side selection circuit selects and outputs a digital signal to the power supply terminal of the digital transmitter, and the low-side selection circuit selects and outputs a common ground signal to the ground terminal of the digital transmitter;

   The high-side selection circuit includes a high-side control circuit, and a first high-side branch and a second high-side branch respectively used to receive the digital signal and the common ground signal;

   The output end of the high-side control circuit is connected to the power supply end, the control end of the high-side control circuit is connected to the first high-side branch and the second high-side branch respectively, and is configured according to the The digital signal and the common ground signal control the conduction degree of the first high-side branch or the second high-side branch to be constant.
2. The transmitting circuit of a digital isolator according to claim 1, characterized in that the low-side selection circuit includes a low-side control circuit, and a first low-side circuit for receiving the digital signal and the common ground signal respectively. branch and second low side branch;

   The output terminal of the low-side control circuit is connected to the ground terminal, the control terminals of the low-side control circuit are respectively connected to the first low-side branch and the second low-side branch, and are configured to operate according to the digital signal. and the common ground signal to control the conduction degree of the first low-side branch or the second low-side branch to be constant.
3. The transmitting circuit of the digital isolator according to claim 2, characterized in that the first low-side branch includes a first low-side switch tube, and the output end of the first low-side switch tube is connected to the ground end. , the input terminal is connected to the first input terminal, and the control terminal is connected to the low-side control circuit and the second input terminal respectively; the first input terminal is used to receive one of the digital signal and the common ground signal, The second input terminal is used to receive the other one of the digital signal and the common ground signal.
4. The transmitting circuit of the digital isolator according to claim 1, characterized in that the first high-side branch includes a first high-side switch tube, and the input end of the first high-side switch tube is connected to the power supply end. , the output end of the first high-side switch tube is connected to the first input end, and the control end of the first high-side switch tube is connected to the high-side control circuit and the second input end respectively; the first input The second input terminal is used to receive one of the digital signal and the common ground signal, and the second input terminal is used to receive the other of the digital signal and the common ground signal.
5. The transmitting circuit of a digital isolator according to claim 4, wherein the high-side control circuit includes a first high-side voltage regulator tube, and the input end of the first high-side voltage regulator tube is connected to the third voltage regulator tube. The control terminal of a high-side switch tube, and the output terminal of the first high-side voltage regulator tube are respectively connected to the power supply terminal and the first input terminal.
6. The transmitting circuit of the digital isolator according to claim 5, characterized in that the high-side control circuit The circuit also includes a first high-side driving tube, and the first high-side switching tube is connected to the first high-side voltage regulator tube of the high-side control circuit through the first high-side driving tube;

   The input terminal of the first high-side driver tube is connected to the control terminal of the first high-side switch tube and the power supply terminal respectively, and the control terminal of the first high-side driver tube is connected to the first high-side voltage regulator. The input end of the tube, and the output end of the first high-side driver tube is connected to the second input end.
7. The transmitting circuit of a digital isolator according to claim 4, wherein the first high-side branch further includes a first high-side diode parasitic on the first high-side switch tube, and the first high-side The input terminal of the side diode is connected to the first input terminal, and the output terminal of the first high-side diode is connected to the power supply terminal.
8. The transmitting circuit of the digital isolator according to claim 7, characterized in that the second high-side branch includes a second high-side switch tube, and the input end of the second high-side switch tube is connected to the power supply end. The output terminal of the second high-side switch tube is connected to the second input terminal, and the control terminal of the second high-side switch tube is connected to the high-side control circuit and the first input terminal respectively;

   The second high-side branch further includes a second high-side diode parasitic on the second high-side switch tube, the input terminal of the second high-side diode is connected to the second input terminal, and the second high-side diode is connected to the second input terminal. The output terminal of the high-side diode is connected to the power supply terminal.
9. The transmitting circuit of a digital isolator according to claim 8, characterized in that the high-side control circuit includes a second high-side voltage regulator tube, and the input end of the second high-side voltage regulator tube is connected to the third voltage regulator tube. The control terminals of the two high-side switching tubes, and the output terminals of the second high-side voltage regulator tubes are respectively connected to the power supply terminal and the second input terminal.
10. The transmitting circuit of the digital isolator according to claim 9, characterized in that the high-side control circuit further includes a second high-side drive tube, and the second high-side switch tube passes through the second high-side drive tube. a second high-side voltage regulator tube connected to the high-side control circuit;

    The input terminal of the second high-side driver tube is connected to the control terminal and the power supply terminal of the first high-side switch tube respectively, and the control terminal of the second high-side driver tube is connected to the second high-side voltage regulator. The input end of the tube, and the output end of the second high side driver tube is connected to the first input end.
11. The transmitting circuit of a digital isolator according to claim 1, characterized in that the digital transmitter includes a current loop, and the current loop includes a reference branch and a sensing branch;

    The sensing branch is disposed between the power supply end and the output side of the digital transmitter, and is configured to generate an original transmission signal according to the input of the power supply end;

    The reference branch is connected to the power supply end and is configured to control the operating current on the sensing branch to be constant according to the reference signal in the digital transmitter.
12. The transmitting circuit of the digital isolator according to claim 11, characterized in that the current loop Includes a first operational amplifier, sensing resistor and reference resistor;

    After the inverting input terminal and the output terminal of the first operational amplifier are connected, they are connected to the sensing resistor and form the sensing branch;

    The non-inverting input terminal of the first operational amplifier is connected to the reference resistor and forms the reference branch.
13. The transmitting circuit of a digital isolator according to claim 11, wherein the digital transmitter includes a bandgap reference source for generating and outputting the reference signal;

    The first reference input terminal of the bandgap reference source is connected to a first node between the sensing branch and the output side of the digital transmitter, and the second reference input terminal of the bandgap reference source is connected to The ground terminal is connected to the ground terminal, and the first reference output terminal of the bandgap reference source is connected to the reference branch.
14. The transmitting circuit of a digital isolator according to claim 13, wherein the bandgap reference source includes a bandgap voltage source and a signal conversion circuit connected to each other, and the bandgap voltage source is configured to generate a bandgap reference voltage. , the signal conversion circuit is configured to convert the bandgap reference voltage into the reference signal; the reference signal is a reference current signal corresponding to the bandgap reference voltage.
15. The transmitting circuit of a digital isolator according to claim 14, characterized in that the signal conversion circuit includes a second operational amplifier, a conversion transistor and an adjustment resistor;

    The drain of the conversion transistor is connected to the reference branch, the gate of the conversion transistor is connected to the output terminal of the second operational amplifier, and the source of the conversion transistor is connected to the inverting terminal of the second operational amplifier. Input terminal; both ends of the adjustment resistor are respectively connected to the inverting input terminal of the second operational amplifier and the ground terminal; the non-inverting input terminal of the second operational amplifier is connected to the bandgap voltage source and forms a third Two nodes.
16. The transmitting circuit of a digital isolator according to claim 15, characterized in that the digital transmitter further includes an isolation comparison circuit and a transmission drive circuit; the first comparison input terminals of the isolation comparison circuit are respectively connected to the first The node is connected to the ground terminal and the second comparison input terminal of the isolation comparison circuit is connected to the second node, and the comparison output terminal of the isolation comparison circuit is connected to the driving enable terminal of the transmission driving circuit; the transmission driving circuit The driving input terminal is connected to the first node for receiving a first oscillation signal generated according to the voltage of the first node.
17. The transmitting circuit of a digital isolator according to claim 16, wherein an oscillation generating circuit is further included between the driving input terminal and the first node, configured to output the first oscillation signal; The driving circuit is configured to generate a first clock signal based on the first oscillation signal.
18. The transmission circuit of the digital isolator according to claim 16, characterized in that the isolation comparison circuit includes a hysteresis comparator; the transmission drive circuit includes an AND gate, an inverter and a buffer; the inverter The input terminal and the input terminal of the buffer are connected to the output terminal of the AND gate.
19. A digital isolator, characterized by comprising a receiving circuit, an isolation capacitor, and a transmitting circuit of the digital isolator according to any one of claims 1-18.
20. The digital isolator according to claim 19, characterized in that the digital isolator includes a first transmitting circuit disposed on a first transmission channel and a second transmitting circuit disposed on a second transmission channel; the first The sending circuit is connected to a first input terminal to receive a first digital signal, and the first sending circuit is connected to a second input terminal to receive the common ground signal; the second sending circuit is connected to a third input terminal to receive a second digital signal. signal, and the second sending circuit is connected to the second input terminal to receive the common ground signal.