Anti-backflow circuit, bidirectional level converter and integrated circuit

Abstract

A transistor backflow prevention circuit is connected to a signal terminal, comprising: a driving transistor, a gate connected to a driving signal, a high potential terminal connected to a power supply, and a low potential terminal connected to the signal terminal; an anti-backflow module, electrically connected to the pull-up power supply, the signal terminal, and the substrate of the driving transistor, configured to load the power supply voltage on the substrate of the driving transistor when the power supply is powered on, and to load the voltage of the signal terminal on the substrate of the driving transistor when the pull-up power supply is powered off. The substrate voltage of the transistor tube can be adjusted to follow the change of the signal terminal level, so that the low potential voltage of the transistor will not be higher than the substrate voltage, effectively preventing the tube from burning out due to current backflow.

Description

Technical Field

[0001] The present invention belongs to the technical field of integrated circuits, and in particular relates to an anti-backflow circuit, a bidirectional level converter and an integrated circuit. Background Art

[0002] At present, data transmission technology is widely used in people's daily life. However, when designing electronic circuits, the design becomes more and more complex. In the design of circuits with complex internal transmission structures, the most basic problem is to solve the conversion problem between two different levels. Among them, the most widely used is the bidirectional level converter.

[0003] However, there are certain risks in the practical application of traditional level converters. The traditional bidirectional level converter structure has two input and output ports, and two power supply voltages are loaded on the two ports respectively, and the substrates of the pull-up drive tubes on the two ports are connected to the power supply voltages. When one of the power supply voltages has no voltage, the corresponding pull-up drive tube substrate voltage is no longer high. At this time, the pull-up drive tube may have a current backflow phenomenon, which may cause the tube to burn out. Summary of the invention

[0004] In view of this, the embodiments of the present invention provide a transistor backflow prevention circuit, a bidirectional level converter and an integrated circuit, aiming to solve the problem that the pull-up drive tube of the traditional level converter may have current backflow, thereby burning the tube.

[0005] A first aspect of an embodiment of the present invention provides a transistor backflow prevention circuit connected to a signal terminal, comprising:

[0006] A driving transistor, wherein the gate is connected to a driving signal, the high potential terminal is connected to a power supply, and the low potential terminal is connected to the signal terminal;

[0007] The anti-backflow module is electrically connected to the pull-up power supply, the signal terminal and the substrate of the driving transistor, and is configured to load the power supply voltage on the substrate of the driving transistor when the power supply is powered on, and to load the voltage of the signal terminal on the substrate of the driving transistor when the pull-up power supply is powered off.

[0008] A second aspect of an embodiment of the present invention provides a bidirectional level converter, including a first signal terminal, a second signal terminal, a first power supply, a second power supply, a first pull-up driving tube connected to the first signal terminal, a first pull-down driving tube connected to the first signal terminal, a second pull-up driving tube connected to the second signal terminal, a second pull-down driving tube connected to the second signal terminal, a driving circuit, a first anti-current backflow circuit connected to the first pull-up driving tube, and a second anti-current backflow circuit connected to the second pull-up driving tube, wherein the first anti-current backflow circuit and the second anti-current backflow circuit are the transistor anti-current backflow circuits described above.

[0009] A fourth aspect of the embodiments of the present invention provides an integrated circuit, comprising the above-mentioned transistor backflow prevention circuit and / or the above-mentioned bidirectional level converter.

[0010] The above transistor backflow prevention circuit design can adjust the substrate voltage of the transistor tube so that it follows the change of the signal terminal level, so that the low potential voltage of the transistor will not be higher than the substrate voltage, effectively preventing the tube from burning out due to current backflow. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0012] Figure 1 A module diagram of a bidirectional level converter provided by an embodiment of the present invention;

[0013] Figure 2 A schematic diagram of a transistor backflow prevention circuit provided by an embodiment of the present invention;

[0014] Figure 3 for Figure 1 The second signal terminal circuit applies a schematic diagram of a transistor backflow prevention circuit;

[0015] Figure 4 A circuit schematic diagram of the backflow prevention module provided in an embodiment of the present invention;

[0016] Figure 5 for Figure 1 When the bidirectional level converter works normally, the substrate voltage Vsub follows the changing waveform of VCCB;

[0017] Figure 6 for Figure 1When the VCCB power supply of the bidirectional level converter is powered off, Vsub follows the change waveform of the input level of the second signal terminal 12. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0019] See also Figure 1 , a module diagram of a bidirectional level converter provided in an embodiment of the present invention, for the sake of convenience of explanation, only the part related to the present embodiment is shown, which is described in detail as follows:

[0020] The bidirectional level converter includes a first signal terminal 11, a second signal terminal 12, a first power supply VCCA, a second power supply VCCB, a first pull-up driving tube connected to the first signal terminal 11, a first pull-down driving tube connected to the first signal terminal 11, a second pull-up driving tube connected to the second signal terminal 12, a second pull-down driving tube connected to the second signal terminal 12, two driving circuits, a first current backflow prevention circuit connected to the first pull-up driving tube, and a second current backflow prevention circuit connected to the second pull-up driving tube, wherein the connection relationship of each component is as follows Figure 1 As shown, the first current backflow prevention circuit and the second current backflow prevention circuit are transistor backflow prevention circuits.

[0021] During design, it is only necessary to add a transistor anti-backflow circuit to each of the first signal terminal 11 and the second signal terminal 12 to ensure that when the voltage at either end of the first power supply VCCA or the second power supply VCCB is 0, the pull-up drive tubes at both ends will not be burned out. During the design process, the tube structure and parameters can be appropriately adjusted according to the actual power supply voltage at both ends, so that when the power supply voltage at one end is low, the substrate potential of the drive tube at that end will accurately track the change of the input voltage.

[0022] See also Figure 2 , the principle diagram of the transistor backflow prevention circuit provided by the embodiment of the present invention, for the convenience of explanation, only the part related to the present embodiment is shown, and the details are as follows:

[0023] The transistor backflow prevention circuit includes a driving transistor T1 and an backflow prevention module 13, wherein the gate of the driving transistor T1 is connected to a driving signal, the high potential terminal of the driving transistor T1 is connected to a power supply VCCB, and the low potential terminal of the driving transistor T1 is connected to a signal terminal 12; the backflow prevention module 13 is electrically connected to the power supply VCCB, the signal terminal 12 and the substrate of the driving transistor T1, and is configured such that when the power supply VCCB is powered on, the voltage of the power supply VCCB is loaded on the substrate of the driving transistor T1, and when the power supply VCCB is powered off, the voltage of the signal terminal 12 is loaded on the substrate of the driving transistor T1.

[0024] If the power supply is not powered on normally, there is no voltage at the high potential end of the driving transistor T1, and the voltage at the low potential end follows the level change of the signal terminal 12. If the substrate voltage of the driving transistor T1 continues to follow the power supply VCCB voltage, there is no voltage on the substrate of the transistor T1. The driving transistor T1 may be burned out because the low potential voltage is higher than the substrate voltage. To avoid this phenomenon, the anti-backflow module 13 in the circuit solves the problem of current backflow that may occur during the level conversion process by adjusting the substrate potential of the driving transistor T1. It has the advantages of simple circuit structure, low cost, low power consumption, and high reliability. The effect is particularly obvious in bidirectional level conversion circuits, and the invention can also be cited in other circuits where current backflow may occur.

[0025] See also Figure 1 and Figure 3 , taking the second signal terminal 12 circuit as an example, there are two driving circuits to drive the level converter to work, namely a weak driving circuit and a one-shot circuit. DRIVER is the driving signal generated by the weak driving circuit, UP_PULL and DN_PULL are the driving signals generated by the one-shot circuit, the driving transistor T1 is a PMOS tube, and its high potential end and low potential end are respectively the drain and the source. In other embodiments, the driving transistor T1 is an NMOS tube, and the driving transistor T1 and the NMOS tube T2 are the pull-up and pull-down driving tubes of the weak driving circuit; the PMOS tube T3 is the pull-up driving tube of the one-shot driving circuit, and the NMOS tubes T4, T5, T6, and T7 (one can be replaced) are the pull-down driving tubes of the one-shot driving circuit. When the level signal is transmitted from the first signal terminal 11 to the second signal terminal 12, the weak drive circuit and the one-shot circuit drive their respective pull-up drive tubes and pull-down drive tubes. When the circuit works normally, that is, VCCA and VCCB are powered normally, the substrate voltage Vsub of T1 and T3 is high under the action of the anti-backflow module 13. Since the power supply VCCB voltage is high under normal working conditions, T1 and T3 can work as pull-up tubes.

[0026] When the signal is transmitted from the second signal terminal 12 to the first signal terminal 11, the principle of normal operation is the same as that of the signal from the first signal terminal 11 to the second signal terminal 12. If the second power supply VCCB of the second signal terminal 12 is not normally powered on when the signal is transmitted from the second signal terminal 12 to the first signal terminal 11, the source of the pull-up transistors T1 and T3 has no voltage, and the drain voltage follows the input level change of the second signal terminal 12. If the substrate voltage of the pull-up transistors T1 and T3 continues to follow the second power supply VCCB, the substrate has no voltage, and the pull-up transistors T1 and T3 may be burned out due to the drain voltage being higher than the substrate voltage. To avoid this phenomenon, the design of the anti-backflow module 13 in the circuit can adjust the substrate voltage Vsub of the pull-up transistors T1 and T3 to follow the change of the input level of the second signal terminal 12, so that the drain voltage of the pull-up transistors T1 and T3 will never be higher than the substrate voltage, effectively preventing the tube from being burned out due to current backflow. Similarly, the anti-backflow module 13 circuit in the first signal terminal 11 circuit has the same function.

[0027] See also Figure 2 and Figure 4 The backflow prevention module 13 includes a first transistor T12, a second transistor T13, a third transistor T14 and a first diode D1.

[0028] The gate of the first transistor T12 and the second transistor T13 are connected to the second power supply VCCB, the drain of the first transistor T12 is connected to the substrate of the driving transistor, the source of the second transistor T13 is connected to the second signal terminal 12, the source of the first transistor T12, the drain of the second transistor T13, the gate of the third transistor T14 and the second signal terminal 12 are connected in common, the drain of the third transistor T14 is connected to the power supply, the source of the third transistor T14 is connected to the substrate of the driving transistor, the anode of the first diode D1 is connected to the second power supply VCCB, and the cathode of the first diode D1 is connected to the substrate of the driving transistor.

[0029] In other embodiments, the backflow prevention module 13 further includes transistors T1-T11, and the connection relationship of the transistors T1-T11 is as follows: Figure 4 The first transistor T12, the second transistor T13, the third transistor T14 and the first diode D1 are PMOS transistors, and in other embodiments they may be NMOS transistors.

[0030] Combination Figures 1 to 4 The specific principle is explained by using a bidirectional level converter in a transistor backflow prevention circuit. The specific function of the transistor backflow prevention circuit is: when the level conversion circuit works normally, the substrate voltage Vsub of the pull-up driver is equal to the power supply voltage VCCB. When the input power supply voltage VCCB has no voltage, the substrate voltage Vsub of the pull-up driver is equal to the drain voltage.

[0031] When the circuit works normally, the level signal is transferred from the first signal terminal 11 to the second signal terminal 12. Figure 4 When the second power supply VCCB in is at a high level, the first transistor T12 and the second transistor T13 are turned off, so that the input level of the second signal terminal 12 cannot be transmitted to the substrate of the pull-up driving tube. At the same time, the third transistor T14 is turned off, and the voltage of the second power supply VCC second signal terminal 12 is transmitted to the substrate through the diode D1. Figure 5 As shown, the substrate voltage Vsub changes with VCCB, so that the substrate potential of the pull-up driving tube of the level converter is high, and the level can be converted normally.

[0032] When the level signal is transmitted from the second signal terminal 12 to the first signal terminal 11, if the second power supply voltage VCCB of the second signal terminal 12 becomes 0, the second signal terminal 12 port has a normal input level, the first transistor T12 and the second transistor T13 are turned on, and the input level of the second signal terminal 12 port is transmitted to the substrate, which can prevent the backflow of current in the external pull-up drive tube and ensure that the drive tube is not burned. The substrate voltage Vsub changes with the input voltage of the second signal terminal 12 port as shown in Figure 6 shown.

[0033] Since the structures of the circuit of the first signal terminal 11 and the circuit of the second signal terminal 12 of the bidirectional level converter are the same, the circuit of the first signal terminal 11 also has the same transistor backflow prevention circuit structure. At this time, if the input level is converted from the second signal terminal 12 to the first signal terminal 11, the substrate voltage of the pull-up and pull-down drive tubes of the first signal terminal 11 follows the change of the first power supply VCCA, and the circuit works normally; when the input level is converted from the first signal terminal 11 to the second signal terminal 12, if the voltage of the first power supply VCCA of the first signal terminal 11 becomes 0, then due to the effect of the transistor backflow prevention circuit of the first signal terminal 11, the substrate voltage Vsub of the pull-up drive tube follows the level change of the first signal terminal 11, thereby avoiding the current backflow of the pull-up drive tube in the circuit of the first signal terminal 11.

[0034] Therefore, in the bidirectional level converter, only one transistor anti-backflow circuit needs to be added to each of the first signal terminal 11 and the second signal terminal 12 circuits to effectively prevent the current backflow phenomenon caused by power failure.

[0035] The present invention adopts a special circuit structure to adjust the potential of the substrate of the driving tube, thereby solving the problem of current backflow that may occur during the level conversion process. It has the advantages of simple circuit structure, low cost, low power consumption, high reliability, etc. The effect is particularly obvious in the bidirectional level conversion circuit, and the invention can also be used in other circuits where current backflow may occur.

[0036] In addition, an integrated circuit is provided, comprising the transistor backflow prevention circuit and / or the bidirectional level converter. It is understandable that the transistor backflow prevention circuit can also be used in other discrete circuits.

[0037] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A transistor backflow prevention circuit connected to a signal terminal, characterized in that: include: A driving transistor, wherein the gate is connected to a driving signal, the high potential terminal is connected to a power supply, and the low potential terminal is connected to the signal terminal; an anti-backflow module, electrically connected to the power supply, the signal terminal and the substrate of the driving transistor, and configured to load the power supply voltage on the substrate of the driving transistor when the power supply is powered on, and to load the voltage of the signal terminal on the substrate of the driving transistor when the power supply is powered off; The anti-backflow module includes a first transistor, a second transistor, a third transistor and a first diode, wherein: The gate of the first transistor and the second transistor are connected to the power supply in common, the drain of the first transistor is connected to the substrate of the driving transistor, the source of the second transistor is connected to the signal terminal, the source of the first transistor, the drain of the second transistor, the gate of the third transistor and the signal terminal are connected in common, the drain of the third transistor is connected to the power supply, the source of the third transistor is connected to the substrate of the driving transistor, the anode of the first diode is connected to the power supply, and the cathode of the first diode is connected to the substrate of the driving transistor.

2. A bidirectional level converter, characterized in that: It includes a first signal terminal, a second signal terminal, a first power supply, a second power supply, a first pull-up driving tube connected to the first signal terminal, a first pull-down driving tube connected to the first signal terminal, a second pull-up driving tube connected to the second signal terminal, a second pull-down driving tube connected to the second signal terminal, a driving circuit, a first anti-current backflow circuit connected to the first pull-up driving tube and a second anti-current backflow circuit connected to the second pull-up driving tube, the first anti-current backflow circuit and the second anti-current backflow circuit are the transistor anti-current backflow circuits according to claim 1.

3. An integrated circuit, characterized in that: It includes the transistor backflow prevention circuit according to claim 1 and / or the bidirectional level converter according to claim 2.

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