CN118885044B - Closed-loop current drive circuit and power tube output voltage slew rate control circuit and method - Google Patents

Abstract

The 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 technical field of power tube driving, wherein the closed-loop current driving circuit comprises a closed-loop current module, a closed-loop current control module and a closed-loop control 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 grid electrode of the power tube to be driven, the sampling current source is connected in series between the first power supply and one input end of the comparator, the other input end of the comparator is connected with the reference current, and the output end of the comparator is connected with the controlled end of the controlled current source. The output current of the controlled current source is compared with the sampling current by the sampling current source according to a preset sampling proportion, and the comparator controls the controlled current source to generate a corresponding output current after comparing the sampling current with the reference current, so that the controlled current source can provide a current signal which is fast in response speed and stable to adjust, 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

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

Technical Field

The application relates to the technical field of power tube driving, in particular to a closed-loop current driving circuit for driving a power tube (such as a MOSFET or other types of power tubes), and a circuit and a method for controlling the slew rate of output voltage of the power tube.

Background

The driving products necessary for motors such as MOSFETs or other types of power tubes generally require fast response speed, precise control and small electromagnetic radiation.

At present, the driving mode of the power tube has two common types of a switch type and a current type, and each of the two types has advantages and disadvantages. The switch driving mode of the switch tube has the advantage of high response speed, but cannot accurately control the slope of the output voltage, is unfavorable for the control of the output voltage, and has larger electromagnetic radiation. Thus, the more common way is current mode driving. However, the conventional current mode driving scheme is usually an open loop architecture, and although the slope of the output voltage can be roughly controlled, the transient driving current has a large delay, the response speed is slow, the interference immunity is poor, and the transient output current is not constant enough.

Based on this, a new driving solution is needed.

Disclosure of Invention

In view of this, the embodiments of the present disclosure provide a closed-loop current driving circuit, a power transistor output voltage slew rate control circuit, and a method, which can improve the accuracy of driving current and shorten the response time through a closed-loop current driving mode, and the closed-loop current driving method has fast response speed, accurate output current control, and strong anti-interference capability.

The embodiment of the specification provides the following technical scheme:

The embodiment of the specification provides a closed-loop current driving circuit, which comprises 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 between a first power supply and a grid electrode of a power tube to be driven in series, the sampling current source is connected between the first power supply and one input end of the comparator in series, the other input end of the comparator is connected with a reference current, and the output end of the comparator is connected with the controlled end of the controlled current source;

The sampling current source is used for sampling the output current of the controlled current source according to a preset sampling proportion and outputting a corresponding sampling current to the comparator, and the comparator is used for controlling the controlled current source to generate a corresponding output current after comparing the sampling current output by the sampling current source with a reference current, so that the controlled current source provides an adjusted current signal for the grid electrode of the power tube to be driven.

Preferably, the controlled current source comprises a first transistor, the sampling current source comprises a second transistor, the comparator comprises a third transistor, the grid electrode and the drain electrode of the first transistor are connected, the source electrode of the first transistor is connected with a first power supply, the grid electrode of the second transistor is connected with the grid electrode of the first transistor, the source electrode of the second transistor is connected with the first power supply, the drain electrode of the second transistor is connected with the grid electrode of the third transistor, the source electrode of the third transistor is connected with the drain electrode of the first transistor, the drain electrode of the third transistor is connected with the grid electrode of the power transistor to be driven, and the reference current is connected to the grid electrode of the third transistor.

Preferably, the closed loop current driving circuit further comprises a first switch, wherein the first switch is connected in series between the grid electrode of the power tube to be driven and the ground, and is used for controlling the switching of the power tube to be driven between an on state and an off state.

Preferably, the closed loop current drive circuit further comprises a second switch connected in series between the reference current source and the other input terminal of the comparator.

Preferably, the first switch comprises an electronic switch constituted by a transistor.

Preferably, in the closed-loop current driving circuit according to any one of the embodiments, the closed-loop current driving circuit further includes a reference current source connected in series between the comparator input terminal and the ground, for providing the reference current.

The embodiment of the specification also provides a power tube output voltage slew rate control circuit which comprises a power tube to be driven and a driving circuit, wherein the driving circuit is the closed loop current driving circuit according to any one of the embodiments of the application, and the driving circuit is used for providing an opening signal or a closing signal for the power tube to be driven, so that the power tube to be driven is opened according to the opening signal or closed according to the closing signal.

Preferably, the drain electrode of the power tube to be driven is connected with the second power supply, and the source electrode of the power tube to be driven is connected with the load.

Preferably, the power tube to be driven comprises an NMOS power tube.

The embodiment of the 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 according to any one of the embodiments of the application. The power tube output voltage slew rate control method comprises the following steps:

Sampling the driving current to obtain a corresponding sampling current, wherein the driving current is the output current of a controlled current source and is used for driving the grid electrode of the power tube to be driven;

Comparing the sampling current with a reference current, and controlling 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.

Compared with the prior art, the beneficial effects that above-mentioned at least one technical scheme that this description embodiment adopted can reach include at least:

the closed loop current type circuit provided by the invention can drive, so that the driving current precision can be improved, the load conversion and the system start can be responded quickly, the time required for establishing stable current output is reduced, the system can adapt to dynamic change more quickly, the response time is shortened, the working efficiency is improved, the closed loop control system can correct deviation and error automatically, has stronger resistance to external interference and internal parameter change, has stronger anti-interference capability, and meanwhile, the slope and stability of the output current are controlled accurately, so that the generation of electromagnetic radiation is reduced, and the electromagnetic radiation is reduced to a certain extent.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings can be obtained according to these drawings without inventive effort for a person skilled in the art.

A conventional driving circuit configuration diagram is shown in fig. 1;

a schematic diagram of a conventional open loop current type drive is shown in fig. 2;

a schematic diagram of a closed loop current drive proposed by the present invention is shown in fig. 3;

A schematic diagram of a closed loop current driven circuit implementation is shown in fig. 4;

a comparative schematic of the effects of open-loop and closed-loop current mode driving is shown in fig. 5;

fig. 6 shows a flow chart of a method for controlling slew rate of output voltage of a power tube.

Detailed Description

Embodiments of the present application will be described in detail below with reference to the accompanying drawings.

Other advantages and effects of the present application will become apparent to those skilled in the art from the following disclosure, which describes the embodiments of the present application with reference to specific examples. It will be apparent that the described embodiments are only some, but not all, embodiments of the application. The application may be practiced or carried out in other embodiments that depart from the specific details, and the details of the present description may be modified or varied from the spirit and scope of the present application. It should be noted that the following embodiments and features in the embodiments may be combined with each other without conflict. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.

It is noted that various aspects of the embodiments are described below within the scope of the following claims. It should be apparent that the aspects described herein may be embodied in a wide variety of forms and that any specific structure and/or function described herein is merely illustrative. Based on the present disclosure, one skilled in the art will appreciate that one aspect described herein may be implemented independently of any other aspect, and that two or more of these aspects may be combined in various ways. For example, apparatus may be implemented and/or methods practiced using any number and aspects set forth herein. In addition, such apparatus may be implemented and/or such methods practiced using other structure and/or functionality in addition to one or more of the aspects set forth herein.

It should also be noted that the illustrations provided in the following embodiments merely illustrate the basic concept of the present application by way of illustration, and only the components related to the present application are shown in the drawings and are not drawn according to the number, shape and size of the components in actual implementation, and the form, number and proportion of the components in actual implementation may be arbitrarily changed, and the layout of the components may be more complicated.

In addition, in the following description, specific details are provided in order to provide a thorough understanding of the examples. However, it will be understood by those skilled in the art that the present invention may be practiced without these specific details.

As shown in fig. 1, in the conventional scheme of driving power transistors by using a plurality of switching transistors, the power transistors are respectively denoted as NMOS10 to 11, the power transistors are used for driving a load 18, the NMOS10 is used for pulling up an output voltage VOUT, the NMOS11 is used for pulling down VOUT, the switching transistors are respectively denoted as switches K12 to K15, and K12 are respectively connected to the gate of the NMOS10 and the VBOOT power supply, and are used for opening the NMOS10, and K13 is connected to the gate of the NMOS10 and the output VOUT, and is used for closing the NMOS 10. K14 connects the gate of NMOS11 and the VDD power supply for turning on NMOS11, and K15 connects the gate of NMOS11 and ground for turning off NMOS11. In addition, to reduce the electromagnetic radiation of VOUT, it is generally necessary to control the turn-on rates of NMOS10 and NMOS11, and switching transistors K12 and K14 are often replaced with current sources I16 and I17 to form a current-driven structure.

As shown in fig. 2, a conventional open loop current type driving structure is formed by using a plurality of switching transistors (such as K21, K24, K25 labeled in the figure) and a current source (a proportional current mirror formed by an input current source I26, a PMOS22, and a PMOS 23) to drive an external load 27. The input current source I26 is connected with the drain electrode and the grid electrode of the PMOS23 to form a current bias, the grid electrode of the PMOS22 is connected with the grid electrode of the PMOS23 through the switch tube K25 to form a matched current mirror with the PMOS23, and the switch tube K24 is connected with the grid electrode of the PMOS22 and the VBOOT power supply. When the switch K24 is closed and the switch K25 is opened, the PMOS22 is closed, and the driving of the power transistor NMOS20 is stopped. When the switch K25 is closed and the switch K24 is opened, the PMOS22 is opened, and the power tube NMOS20 is driven according to the input current source I26 and the current mirror ratio. The switch K21 is connected with the grid electrode of the power tube and the ground and is used for turning off the NMOS20 of the power tube. The method is an open loop current driving method, when the switching transistors K24 and K25 are switched, the voltage of the grid electrode of the PMOS22 is fluctuated, so that the output driving current is unstable, and the grid electrode of the PMOS22 needs a long establishment time from being closed to being opened.

In addition, aiming at the slew rate problem of the output voltage of the power tube, some attempts are made in the prior art, for example, a first document (China application number: 201210549722.3) discloses an interface circuit for limiting the slew rate of the output voltage and an implementation method thereof, and a second document (China application number: 201410624465.4) discloses a slew rate limiting driver.

In summary, the conventional switch-mode driving circuit and current open-loop driving circuit have advantages and disadvantages, and the problem of slew rate of the power tube when driving the load is still to be improved.

Based on this, the embodiment of the present disclosure proposes a closed-loop current driving architecture scheme, as shown in fig. 3, in which a closed-loop driving module 31 is used to replace a conventional open-loop current driving architecture, where the closed-loop driving module 31 includes a controlled current source I32 for driving a power tube, an output end of the controlled current source I32 is connected to a gate of a power tube NMOS30 to be driven, so as to drive the NMOS30, a sampling current source I33 is used to sample an output current of the controlled current source I32 according to a certain proportion, a sampling output current of the sampling current source I33 is connected to a reference current source I35 and an input end of a comparator 34, and an output end of the comparator controls an output current of the controlled current source I32, so as to form a closed-loop feedback structure.

The connection relation among the circuit units and the circuit functions are shown as follows, the closed loop current module comprises a controlled current source I32, a sampling current source I33 and a comparator 34, the controlled current source I32 is connected in series between a first power supply (shown as VBOOT) and the grid electrode of a power tube to be driven (shown as a power tube NMOS 30), the sampling current source I33 is connected in series between the first power supply and one input end of the comparator 34, the other input end of the comparator is connected with a reference current (such as a reference current provided by a high-precision current reference standard (namely the reference current source)) and the output end of the comparator 34 is connected with the controlled current source I32, wherein the sampling current source is used for sampling the output current of the controlled current source according to a preset sampling proportion and outputting a corresponding sampling current to the comparator, and the comparator is used for controlling the controlled current source to generate a corresponding output current after comparing the sampling current outputted by the sampling current and the reference current, so that the controlled current source provides an adjusted current signal to the grid electrode of the power tube to be driven.

The current quick response and adjustment principle is that when the output current of the controlled current source I32 is overlarge, the sampling current of the sampling current source I33 is also larger, so that the output of the comparator is controlled after the comparison with the reference current of the reference current source I35, the output current of the controlled current source I32 is further reduced, and thus a closed-loop control current is formed, when the output current of the controlled current source I32 is smaller, the sampling current of the sampling current source I33 is also smaller, so that the output of the comparator is controlled after the comparison with the reference current of the reference current source I35, and the output current of the controlled current source I32 is further increased, thus forming the closed-loop control current.

In practice, the output current of the stabilized controlled current source I32 may be set by iout=iref×k, 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 occasions of different driving currents, and Iref, k are settable constants, so that the output current Iout with high response speed and high precision can be obtained under the closed-loop control.

In summary, in the closed-loop current driving architecture, a current source and a comparator in a closed-loop driving module are connected end to form a closed-loop feedback control circuit, so that closed-loop control current is formed, and the comparator is used for controlling driving current of a main drive, so that the circuit response speed is high, the output current is accurately controlled, the anti-interference capability is high, the driving power tube obtains very stable driving current, and the output fluctuation and the slew rate of the power tube are effectively reduced.

In some embodiments, the current source, the comparator and the like in the architecture can be in the form of an existing mature integrated circuit, or can be transistor current, or can be implemented by using a transistor circuit in the following examples, namely, the following examples can provide a closed loop current driven transistor circuit implementation.

Referring to fig. 4, the closed loop current sampling architecture is formed by using PMOS41, PMOS42 and PMOS43, wherein PMOS41 forms a core circuit of a controlled current source as a first transistor, PMOS42 forms a core circuit of a sampling current source as a second transistor, and PMOS43 forms a core circuit of a current comparator as a third transistor.

The circuit connection relation and the working principle are shown as follows, the grid electrode and the drain electrode of the PMOS41 are connected together and connected with the source electrode of the PMOS43, the drain electrode of the PMOS43 is connected with the grid electrode of the power tube NMOS40, and at the moment, the driving current is started and driven from the PMOS41 to the power tube NMOS40 through the PMOS 43. The gate of PMOS42 is connected to the gate of PMOS41 for sampling the drive current according to a certain ratio. The drain of PMOS42 is connected to input current source I44 (i.e., the reference current source) and to the gate of PMOS 43. Accordingly, the sampling current is compared with the current of the input current source I44, and then the gate voltage of the PMOS43 is controlled, and the gate voltage of the PMOS41 is controlled, thereby controlling the output current of the main drive.

In some embodiments, a first switch K45 and/or a second switch K46 may also be provided, through which the switching on or off of the respective circuits is controlled.

For example, the first switch K45 is used to control switching of the power transistor between an on state and an off state. Specifically, the first switch K45 connects the gate of the power tube NMOS40 with ground, when the first switch K45 is turned off, the power tube NMOS40 is allowed to turn on, and when the first switch K45 is turned off, the power tube NMOS40 is turned off.

For example, the second switch K46 is used to control the switching on or off 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, and after the second switch tube K46 is closed, the input current 44 controls the PMOS43 to be opened quickly, starting to drive and the loop is built up and stabilized quickly.

In some examples, the switch may be an electronic switch formed by a transistor, so that the transistor may be used to realize high-speed connection or disconnection of a circuit, which is beneficial to quickly establishing a stable state of the circuit.

Based on the same inventive concept, the 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 good slew rate characteristics.

Referring to the schematic circuit of fig. 3 or fig. 4, the power tube output voltage slew rate control circuit may include a power tube to be driven and a driving circuit, where the driving circuit is a closed loop current driving circuit according to any one of the foregoing embodiments. The driving circuit is used for providing an opening signal or a closing signal for the power tube to be driven, so that the power tube to be driven is opened according to the opening signal or closed according to the closing signal.

Therefore, since the driving circuit can provide a very stable on or off signal, the power transistor provides a stable output voltage to a LOAD (LOAD) (such as the first LOAD 37 illustrated in fig. 3 or the second LOAD 47 illustrated in fig. 4), and the slew rate of the voltage is very good.

For example, referring to fig. 5, a waveform effect is illustrated, which illustrates a comparison of actual effects of voltage variation waveforms formed at a load side by an open loop circuit driving scheme (original scheme) and a closed loop current driving scheme (scheme provided by the present application). Specifically, after EN is enabled (e.g., the second switch K46 illustrated in fig. 4 is closed), the conventional main driving output current (icharge_priority) has a slow response time, and the setup time of current rise and fall is long, resulting in slow driving output response and uncontrollable slope. After the closed-loop current control scheme provided by the application is adopted, the new driving current (Icharge_new) is obviously and rapidly established and is kept stable in the driving process, so that the accurate control of output is realized and the outward electromagnetic radiation is small.

In some examples, the manner in which the power tube drives the load may be drain driving, or source driving. Examples of power tube source drive loads are provided in the following examples of the application. In implementation, the drain electrode of the power tube to be driven is connected with a second power supply (marked as VM), and the source electrode of the power tube to be driven is connected with a load.

In some examples, the power transistors to be driven may include NMOS power transistors, thereby providing a large operating current to the load with NMOS transistors.

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

Referring to fig. 6, a method for controlling slew rate of output voltage of a power tube may include the following steps:

Step S202, sampling the driving current to obtain a corresponding sampling current, wherein the driving current is the output current of a controlled current source, and the output current is used for driving the grid electrode of a power tube to be driven;

and step S204, comparing the sampling current with a reference current, and controlling 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.

In this specification, identical and similar parts of the embodiments are referred to each other, and each embodiment focuses on the differences from the other embodiments. In particular, the description is relatively simple for the embodiments described later, and reference is made to the description of the foregoing embodiments for relevant points.

The foregoing is merely illustrative of the present application, and the present application is not limited thereto, and any changes or substitutions easily contemplated by those skilled in the art within the scope of the present application should be included in the present application. Therefore, the protection scope of the application is subject to the protection scope of the claims.

Claims (9)

1. The closed-loop current driving circuit is characterized by comprising 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 between a first power supply and a grid electrode of a power tube to be driven in series, the sampling current source is connected between the first power supply and one input end of the comparator in series, the other input end of the comparator is connected with a reference current, and the output end of the comparator is connected with the controlled end of the controlled current source;

The comparator is used for comparing the sampling current output by the sampling current source with a reference current and controlling the controlled current source to generate a corresponding output current so that the controlled current source provides an adjusted current signal for the grid electrode of the power tube to be driven, wherein the drain electrode of the power tube to be driven is connected with a second power supply, and the source electrode of the power tube to be driven is connected with a load;

The controlled current source comprises a first transistor, the sampling current source comprises a second transistor, the comparator comprises a third transistor, the grid electrode and the drain electrode of the first transistor are connected, the source electrode of the first transistor is connected with a first power supply, the grid electrode of the second transistor is connected with the grid electrode of the first transistor, the source electrode of the second transistor is connected with the first power supply, the drain electrode of the second transistor is connected with the grid electrode of the third transistor, the source electrode of the third transistor is connected with the drain electrode of the first transistor, the drain electrode of the third transistor is connected with the grid electrode of the power transistor to be driven, and the reference current is connected to the grid electrode of the third transistor.

2. The closed loop current driving circuit according to claim 1, further comprising a first switch connected in series between the gate of the power transistor to be driven and ground for controlling switching of the power transistor to be driven between an on state and an off state.

3. The closed loop current drive circuit of claim 1 further comprising a second switch connected in series between the reference current source and the other input of the comparator.

4. The closed loop current drive circuit of claim 1 wherein the first switch comprises an electronic switch comprised of a transistor.

5. The closed loop current drive circuit of any one of claims 1-4, further comprising a reference current source connected in series between the comparator input and ground for providing a reference current.

6. The power tube output voltage slew rate control circuit is characterized by comprising a power tube to be driven and a driving circuit, wherein the driving circuit is the closed loop current driving circuit as claimed in any one of claims 1-5, and the driving circuit is used for providing an opening signal or a closing signal for the power tube to be driven, so that the power tube to be driven is opened according to the opening signal or closed according to the closing signal.

7. The power tube output voltage slew rate control circuit of claim 6 where the drain of the power tube to be driven is connected to a second power source and the source of the power tube to be driven is connected to a load.

8. The power tube output voltage slew rate control circuit of claim 7 where the power tube to be driven comprises an NMOS power tube.

9. A power tube output voltage slew rate control method applied to the power tube output voltage slew rate control circuit of any one of claims 6-8, the method comprising:

Sampling the driving current to obtain a corresponding sampling current, wherein the driving current is the output current of a controlled current source and is used for driving the grid electrode of the power tube to be driven;

Comparing the sampling current with a reference current, and controlling 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.