Closed-loop current drive circuit and power tube output voltage slew rate control circuit and method

Abstract

The present application provides a closed-loop current driving circuit and a power tube output voltage slew rate control circuit and method, which are applied to the field of power tube driving technology, wherein the closed-loop current driving circuit includes: a closed-loop current module, the closed-loop current module includes a controlled current source, a sampling current source and a comparator; the controlled current source is connected in series between the first power supply and the gate of the power tube to be driven, the sampling current source is connected in series between the first power supply and an input end of the comparator, the other input end of the comparator is connected to a reference current, and the output end of the comparator is connected to the controlled end of the controlled current source. The output current of the controlled current source is sampled by the sampling current source according to a preset sampling ratio, and the comparator controls the controlled current source to generate a corresponding output current after comparing the sampling current and the reference current, so that the controlled current source can provide a current signal with fast response speed and stable adjustment, so that the power tube can quickly establish a working state under the action of the current signal, and the load slew rate is very small.

Description

Technical Field

[0001] The present application relates to the field of power tube driving technology, and in particular to a closed-loop current driving circuit for driving a power tube (such as a MOSFET or other type of power tube) and a power tube output voltage slew rate control circuit and method. Background Art

[0002] MOSFET or other types of power tubes, which are essential driving products for motors, usually require fast response, precise control and low electromagnetic radiation.

[0003] At present, there are two common types of power tube driving methods: switch mode and current mode. These two types have their own advantages and disadvantages. Among them, the switch drive method using a switch tube has the advantage of fast response speed, but it cannot accurately control the slope of the output voltage, which is not conducive to output voltage control, and the electromagnetic radiation is relatively large. Therefore, the more common method is current mode driving. However, the traditional current mode driving scheme is usually an open-loop architecture. Although it can roughly control the slope of the output voltage, the transient drive current has a large delay, slow response speed and poor anti-interference, and the transient output current is not constant enough.

[0004] Based on this, a new drive technology solution is needed. Summary of the invention

[0005] In view of this, the embodiments of the present specification provide a closed-loop current driving circuit and a power tube output voltage slew rate control circuit and method. Through the closed-loop current driving mode, the accuracy of the driving current can be improved and the response time can be shortened. The closed-loop current driving method has a fast response speed, precise output current control and strong anti-interference ability.

[0006] The embodiments of this specification provide the following technical solutions:

[0007] The embodiment of the present specification provides a closed-loop current driving circuit, including: a closed-loop current module, wherein the closed-loop current module includes a controlled current source, a sampling current source and a comparator; the controlled current source is connected in series between a first power supply and a gate of a power tube to be driven, the sampling current source is connected in series between the first power supply and an input terminal of the comparator, the other input terminal of the comparator is connected to a reference current, and the output terminal of the comparator is connected to the controlled terminal of the controlled current source;

[0008] Among them, the sampling current source is used to sample the output current of the controlled current source according to a preset sampling ratio, and output the corresponding sampling current to the comparator; the comparator is used to compare the sampling current output by the sampling current source with the reference current, and then control the controlled current source to generate the corresponding output current, so that the controlled current source provides an adjusted current signal to the gate of the power tube to be driven.

[0009] Preferably, the controlled current source includes a first transistor, the sampling current source includes a second transistor, and the comparator includes a third transistor; the gate and drain of the first transistor are connected, and the source of the first transistor is connected to the first power supply; the gate of the second transistor is connected to the gate of the first transistor, the source of the second transistor is connected to the first power supply, and the drain of the second transistor is connected to the gate of the third transistor; the source of the third transistor is connected to the drain of the first transistor, and the drain of the third transistor is connected to the gate of the power tube to be driven; the reference current is connected to the gate of the third transistor.

[0010] Preferably, the closed-loop current driving circuit further comprises a first switch, which is connected in series between the gate of the power tube to be driven and the ground, and is used to control the switching of the power tube to be driven between the on state and the off state.

[0011] Preferably, the closed-loop current driving circuit further includes a second switch, and the second switch is connected in series between the reference current source and the other input terminal of the comparator.

[0012] Preferably, the first switch comprises an electronic switch formed by a transistor.

[0013] Preferably, in the closed-loop current driving circuit described in any one of the embodiments, the closed-loop current driving circuit further includes a reference current source, which is connected in series between the input terminal of the comparator and the ground to provide a reference current.

[0014] An embodiment of the present specification also provides a power tube output voltage slew rate control circuit, including: a power tube to be driven and a driving circuit, wherein the driving circuit is a closed-loop current driving circuit as described in any embodiment of the present application, and the driving circuit is used to provide an on signal or an off signal for the power tube to be driven, so that the power tube to be driven is turned on according to the on signal or turned off according to the off signal.

[0015] Preferably, the drain of the power tube to be driven is connected to the second power supply, and the source of the power tube to be driven is connected to the load.

[0016] Preferably, the power tube to be driven includes an NMOS power tube.

[0017] The embodiment of this specification also provides a power tube output voltage slew rate control method, which is applied to the power tube output voltage slew rate control circuit as described in any implementation of this application. The power tube output voltage slew rate control method includes:

[0018] Sampling the driving current to obtain a corresponding sampling current, wherein the driving current is an output current of a controlled current source and is used to drive the gate of the power tube to be driven;

[0019] The sampled current is compared with the reference current, and the controlled current source is controlled to generate a corresponding output current according to the comparison result, so as to form a closed-loop current to drive the power tube to be driven.

[0020] Compared with the prior art, the at least one technical solution adopted in the embodiments of this specification can achieve the following beneficial effects:

[0021] Driving according to the closed-loop current type circuit provided by the present invention can improve the driving current accuracy; and can quickly respond to load changes and system startup, reducing the time required to establish a stable current output, which enables the system to adapt to dynamic changes more quickly, shorten the response time and improve work efficiency; because the closed-loop control system can automatically correct deviations and errors, it has a stronger resistance to external interference and internal parameter changes, so the system has a stronger anti-interference ability; at the same time, precise control of the slope and stability of the output current helps to reduce the generation of electromagnetic radiation, which will reduce electromagnetic radiation to a certain extent. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0023] Figure 1 A conventional driving circuit structure diagram is shown in FIG;

[0024] Figure 2 The conventional open-loop current drive schematic diagram is shown in FIG.

[0025] Figure 3 FIG. 1 shows a schematic diagram of a closed-loop current drive proposed by the present invention;

[0026] Figure 4 A schematic diagram of a circuit implementation of a closed-loop current drive is shown in FIG.

[0027] Figure 5 The schematic diagram showing the comparison of the effects of open-loop and closed-loop current-type driving is shown in FIG.

[0028] Figure 6 A flow chart of a method for controlling the output voltage slew rate of a power tube is shown in FIG. DETAILED DESCRIPTION

[0029] The embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0030] The following describes the implementation methods of the present application through specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The present application can also be implemented or applied through other different specific implementation methods, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that, in the absence of conflict, the following embodiments and the features in the embodiments can be combined with each other. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work belong to the scope of protection of the present application.

[0031] It should be noted that various aspects of the embodiments within the scope of the appended claims are described below. It should be apparent that the aspects described herein can be embodied in a wide variety of forms, and any specific structure and / or function described herein is merely illustrative. Based on the present application, it should be understood by those skilled in the art that an aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number and aspect described herein can be used to implement the device and / or practice the method. In addition, other structures and / or functionalities other than one or more of the aspects described herein can be used to implement this device and / or practice this method.

[0032] It should also be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present application. The drawings only show components related to the present application rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0033] Additionally, in the following description, specific details are provided to facilitate a thorough understanding of the examples. However, it will be understood by those skilled in the art that the examples can be practiced without these specific details.

[0034] like Figure 1As shown, in the conventional scheme of using multiple switch tubes to drive power tubes, the power tubes are respectively marked as NMOS10-11, the power tubes are used to drive load 18, NMOS10 is used to pull up the output voltage VOUT, and NMOS11 is used to pull down VOUT; the switch tubes are respectively marked as switches K12-K15, K12 is respectively connected to the gate of NMOS10 and the VBOOT power supply, used to turn on NMOS10, K13 is connected to the gate of NMOS10 and the output VOUT, used to turn off NMOS10. K14 is connected to the gate of NMOS11 and the VDD power supply, used to turn on NMOS11, and K15 is connected to the gate of NMOS11 and the ground, used to turn off NMOS11. In addition, in order to reduce the electromagnetic radiation of VOUT, it is usually necessary to control the turn-on rate of NMOS10 and NMOS11, and the switch tubes K12 and K14 are often replaced by current sources I16 and I17 to form a current-type driving structure.

[0035] like Figure 2 As shown, a conventional open-loop current-type drive structure is formed by using multiple switch tubes (such as K21, K24, and K25 marked in the figure) and current sources (input current source I26, proportional current mirror composed of PMOS22 and PMOS23) to drive external load 27. Among them, the input current source I26 is connected to the drain and gate of PMOS23 to form a current bias; the gate of PMOS22 is connected to the gate of PMOS23 through the switch tube K25 to form a matching current mirror with PMOS23; the switch tube K24 is connected to the gate of PMOS22 and the VBOOT power supply. When the switch K24 is closed and K25 is opened, PMOS22 is turned off and stops driving the power tube NMOS20. When the switch K25 is closed and K24 is opened, PMOS22 is turned on and drives the power tube NMOS20 according to the input current source I26 and the current mirror ratio. The switch K21 connects the gate of the power tube and the ground to turn off the power tube NMOS20. This method is an open-loop current driving method. When the switch tubes K24 and K25 are switched, the gate voltage of PMOS22 will fluctuate, making its output driving current unstable. In addition, it takes a long time for the gate of PMOS22 to be opened from closed to opened.

[0036] In addition, the prior art has also made some attempts to address the slew rate problem of the power tube output voltage. For example, Document 1 (Chinese application number: 201210549722.3) discloses an interface circuit for limiting the output voltage slew rate and its implementation method; Document 2 (Chinese application number: 201410624465.4) discloses a slew rate limiting driver.

[0037] In summary, the traditional switch drive circuit and the current open-loop drive circuit each have their own advantages and disadvantages, and there is still room for improvement in the voltage slew rate problem when the power tube drives the load.

[0038] Based on this, the embodiment of this specification proposes a closed-loop current driving architecture solution: Figure 3 As shown, a closed-loop driving module 31 is used to replace the traditional open-loop current driving architecture, wherein the closed-loop driving module 31 includes a controlled current source I32 for driving the power tube, and its output end is connected to the gate of the power tube NMOS30 to be driven, so as to drive NMOS30; the sampling current source I33 is used to sample the output current of the controlled current source I32 according to a certain ratio, and its sampled output current is connected to the reference current source I35 and the input end of the comparator 34, and the output end of the comparator controls the output current size of the controlled current source I32 to form a closed-loop feedback structure.

[0039] The connection relationship between each circuit unit and the function of each circuit are shown as follows: the closed-loop current module includes a controlled current source I32, a sampling current source I33 and a comparator 34; the controlled current source I32 is connected in series between the first power supply (denoted as VBOOT) and the gate of the power tube to be driven (denoted as the power tube NMOS30), the sampling current source I33 is connected in series between the first power supply and an input end of the comparator 34, the other input end of the comparator is connected to a reference current (for example, a reference current provided by a high-precision current reference standard (i.e., a reference current source)), and the output end of the comparator 34 is connected to the controlled current source I32; wherein the sampling current source is used to sample the output current of the controlled current source according to a preset sampling ratio, and output the corresponding sampling current to the comparator; the comparator is used to control the controlled current source to generate a corresponding output current after comparing the sampling current output by the sampling current source with the reference current, so that the controlled current source provides an adjusted current signal to the gate of the power tube to be driven.

[0040] The principle of rapid current response and adjustment is as follows: when the output current of the controlled current source I32 is too large, the sampling current of the sampling current source I33 also follows it and becomes larger, and thus the output of the comparator is controlled after being compared with the reference current of the reference current source I35, thereby reducing the output current of the controlled current source I32, thereby forming a closed-loop control current; when the output current of the controlled current source I32 is too small, the sampling current of the sampling current source I33 also follows it and becomes smaller, and thus the output of the comparator is controlled after being compared with the reference current of the reference current source I35, thereby increasing the output current of the controlled current source I32, thereby forming a closed-loop control current.

[0041] In practice, the output current of the stabilized controlled current source I32 can be set as follows: Iout = Iref*k, where Iref is the input current of the reference current source I35, and k is the current ratio of the driving stage and the current sampling stage. Therefore, by setting Iref, k, etc., the closed-loop current can meet the application scenarios of different driving currents, and Iref and k are both configurable constants, so that an output current Iout with fast response speed and high precision can be obtained under closed-loop control.

[0042] In summary, in this closed-loop current drive architecture, the current source and the comparator in the closed-loop drive module are connected end to end to form a closed-loop feedback control circuit, forming a closed-loop control current, and the driving current of the main drive is controlled by the comparator, which can make the circuit respond quickly, the output current control is precise and the anti-interference ability is strong, so that the driving power tube obtains a very stable driving current, effectively reducing the output fluctuation and slew rate of the power tube.

[0043] In some embodiments, the circuit forms such as the current source and comparator in the above-mentioned architecture can be existing mature integrated circuits, or transistor currents, or an implementation method using transistor circuits in the following examples of this application, that is, a closed-loop current-driven transistor circuit implementation method can be provided in the following examples of this application.

[0044] refer to Figure 4 As shown, PMOS41, PMOS42 and PMOS43 are used to form the above-mentioned closed-loop current sampling architecture, wherein PMOS41 is used as the first transistor to form the core circuit of the controlled current source, PMOS42 is used as the second transistor to form the core circuit of the sampling current source, and PMOS43 is used as the third transistor to form the core circuit of the current comparator.

[0045] The circuit connection relationship and working principle are shown as follows: the gate and drain of PMOS41 are connected together and connected to the source of PMOS43, and the drain of PMOS43 is connected to the gate of the power tube NMOS40. At this time, the driving current will pass from PMOS41 through PMOS43 to drive the power tube NMOS40 to turn on. The gate of PMOS42 is connected to the gate of PMOS41, which is used to sample the driving current according to a certain ratio. The drain of PMOS42 is connected to the input current source I44 (i.e., the reference current source) and is connected to the gate of PMOS43. Therefore, after comparing the sampling current with the current of the input current source I44, the gate voltage of PMOS43 is controlled, and then the gate voltage of PMOS41 is controlled, thereby controlling the output current of the main drive.

[0046] In some embodiments, a first switch K45 and / or a second switch K46 may be provided to control the connection or disconnection of each circuit through the switch.

[0047] For example, the first switch K45 is used to control the switching of the power tube between the on state and the off state. Specifically, the first switch K45 connects the gate of the power tube NMOS40 and the ground. When the first switch K45 is disconnected, the power tube NMOS40 is allowed to be turned on; when the first switch K45 is closed, the power tube NMOS40 is turned off.

[0048] For example, the second switch K46 is used to control the connection or disconnection of the input current source I44. Specifically, the second switch K46 is connected in series in the connection branch of the input current source I44. When the second switch tube K46 is closed, the input current 44 controls the PMOS 43 to turn on quickly, start driving, and the loop is quickly established and stabilized.

[0049] In some examples, the switch may be an electronic switch composed of a transistor, so that the advantage of the fast switching speed of the transistor can be used to achieve high-speed connection or disconnection of the circuit, which is conducive to the circuit quickly establishing a stable state.

[0050] Based on the same inventive concept, the present application also provides a power tube output voltage slew rate control circuit, so that the output voltage provided by the power tube to the load has a good slew rate characteristic.

[0051] Refer to the above Figure 3 or Figure 4 The schematic circuit of the power tube output voltage slew rate control circuit may include: a power tube to be driven and a driving circuit, wherein the driving circuit is a closed-loop current driving circuit as described in any of the above embodiments. The driving circuit is used to provide an on signal or an off signal to the power tube to be driven, so that the power tube to be driven is turned on according to the on signal or turned off according to the off signal.

[0052] Therefore, since the driving circuit can provide a very stable on or off signal, the power tube can supply power to the load (LOAD) (such as Figure 3 The first load 37 is shown, or Figure 4 The second load 47) shown provides a stable output voltage with a very good voltage slew rate.

[0053] For example, refer to Figure 5 The waveform effect is shown in the figure, which shows the actual effect comparison of the voltage change waveform formed at the load end by the open-loop circuit driving scheme (the original scheme) and the closed-loop current type driving scheme (the scheme provided by this application). Specifically, when EN is enabled (for example Figure 4After the second switch K46 shown in the figure is closed), the traditional main drive output current (Icharge_prior) has a slow response time, and the establishment time of the current rise and fall is long, resulting in a slow drive output response and uncontrollable slope. After adopting the closed-loop current control scheme proposed in the present application, the new drive current (Icharge_new) is significantly established quickly and remains stable during the driving process, achieving precise output control and low external electromagnetic radiation.

[0054] In some examples, the power tube may drive the load by drain driving or source driving. The following example of the present application provides an example of a power tube source driving the load. In implementation, the drain of the power tube to be driven is connected to the second power supply (marked as VM), and the source of the power tube to be driven is connected to the load.

[0055] In some examples, the power tube to be driven may include an NMOS power tube, so that the NMOS transistor is used to provide a large operating current for the load.

[0056] Based on the same inventive concept, the present application also provides a power tube output voltage slew rate control method. Through the current closed-loop control in the power tube output voltage slew rate control circuit of any embodiment of the present application, the slew rate of the power tube output voltage can be effectively changed.

[0057] refer to Figure 6 In the embodiment, a method for controlling the output voltage slew rate of a power tube may include the following steps:

[0058] Step S202, sampling the driving current to obtain a corresponding sampling current, wherein the driving current is an output current of a controlled current source, wherein the output current is used to drive a gate of a power tube to be driven;

[0059] Step S204: compare the sampled current with the reference current, and control the controlled current source to generate a corresponding output current according to the comparison result, so as to form a closed-loop current to drive the power tube to be driven.

[0060] In this specification, the same or similar parts between the various embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the embodiments described later, the description is relatively simple, and the relevant parts can be referred to the partial description of the previous embodiments.

[0061] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A closed-loop current driving circuit, characterized in that: include: A closed-loop current module, wherein the closed-loop current module comprises a controlled current source, a sampling current source and a comparator; the controlled current source is connected in series between the first power supply and the gate of the power tube to be driven, the sampling current source is connected in series between the first power supply and an input end of the comparator, the other input end of the comparator is connected to a reference current, and the output end of the comparator is connected to the controlled end of the controlled current source; The sampling current source is used to sample the output current of the controlled current source according to a preset sampling ratio, and output the corresponding sampling current to the comparator; The comparator is used to control the controlled current source to generate a corresponding output current after comparing the sampling current output by the sampling current source with the reference current, so that the controlled current source provides an adjusted current signal to the gate of the power tube to be driven, wherein the drain of the power tube to be driven is connected to the second power supply, and the source of the power tube to be driven is connected to the load; The controlled current source includes a first transistor, the sampling current source includes a second transistor, and the comparator includes a third transistor; the gate and drain of the first transistor are connected, and the source of the first transistor is connected to the first power supply; the gate of the second transistor is connected to the gate of the first transistor, the source of the second transistor is connected to the first power supply, and the drain of the second transistor is connected to the gate of the third transistor; the source of the third transistor is connected to the drain of the first transistor, and the drain of the third transistor is connected to the gate of the power tube to be driven; the reference current is connected to the gate of the third transistor.

2. The closed-loop current driving circuit according to claim 1, characterized in that: The closed-loop current driving circuit also includes a first switch, which is connected in series between the gate of the power tube to be driven and the ground, and is used to control the switching of the power tube to be driven between the on state and the off state.

3. The closed-loop current driving circuit according to claim 1, characterized in that: The closed-loop current driving circuit also includes a second switch, which is connected in series between the reference current source and the other input terminal of the comparator.

4. The closed-loop current driving circuit according to claim 1, characterized in that: The first switch includes an electronic switch formed by a transistor.

5. The closed-loop current driving circuit according to any one of claims 1 to 4, characterized in that: The closed-loop current driving circuit also includes a reference current source, which is connected in series between the input terminal of the comparator and the ground to provide a reference current.

6. A power tube output voltage slew rate control circuit, characterized in that: include: A power tube to be driven and a driving circuit, wherein the driving circuit is a closed-loop current driving circuit as described in any one of claims 1 to 5, and the driving circuit is used to provide an on signal or an off signal for the power tube to be driven, so that the power tube to be driven is turned on according to the on signal or turned off according to the off signal.

7. The power tube output voltage slew rate control circuit according to claim 6, characterized in that: The drain of the power tube to be driven is connected to the second power supply, and the source of the power tube to be driven is connected to the load.

8. The power tube output voltage slew rate control circuit according to claim 7, characterized in that: The power tube to be driven includes an NMOS power tube.

9. A method for controlling the output voltage slew rate of a power tube, characterized in that: Applied to the power tube output voltage slew rate control circuit according to any one of claims 6 to 8, the method comprising: Sampling the driving current to obtain a corresponding sampling current, wherein the driving current is an output current of a controlled current source and is used to drive the gate of the power tube to be driven; The sampled current is compared with the reference current, and the controlled current source is controlled to generate a corresponding output current according to the comparison result, so as to form a closed-loop current to drive the power tube to be driven.

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