CN111176359B - Digital current control method and device - Google Patents
Digital current control method and device Download PDFInfo
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- CN111176359B CN111176359B CN202010009723.3A CN202010009723A CN111176359B CN 111176359 B CN111176359 B CN 111176359B CN 202010009723 A CN202010009723 A CN 202010009723A CN 111176359 B CN111176359 B CN 111176359B
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
- G05F1/00—Automatic systems in which deviations of an electric quantity from one or more predetermined values are detected at the output of the system and fed back to a device within the system to restore the detected quantity to its predetermined value or values, i.e. retroactive systems
- G05F1/10—Regulating voltage or current
- G05F1/46—Regulating voltage or current wherein the variable actually regulated by the final control device is dc
- G05F1/56—Regulating voltage or current wherein the variable actually regulated by the final control device is dc using semiconductor devices in series with the load as final control devices
Abstract
According to the digital current control method and device, after the digital peak current value is calculated, the digital peak current value is used as a reference current value and is input to the reference end of the analog comparator, the other end of the analog comparator in the analog loop collects the current value of the analog loop in real time, and when the current value reaches the digital peak current value, a control signal is output to control the current period of the analog loop to be closed so as to limit the maximum current value of the analog loop. According to the method, the maximum power value is pre-specified and is used for preventing the maximum power value of overload; the input voltage, the output voltage, the compensation voltage value and the switching period of the analog loop are all known quantities, and real-time sampling is carried out simultaneously to ensure that the maximum current value of each switching period in the analog loop does not exceed the digital peak current value, so that the reliability of the analog loop can be greatly improved.
Description
Technical Field
The present disclosure relates to control circuits, and particularly to a digital current control method and apparatus.
Background
At present, most of pre-controlled circuits are controlled by adopting an analog technology, namely, peak current control is required to be carried out by depending on an analog chip, however, because the analog chips of each manufacturer are different, the control modes of the peak current are different, and when a control circuit is required to be added for carrying out the peak current control, a chip with a corresponding function needs to be selected in advance, so that the reliability of an analog loop is reduced.
Disclosure of Invention
The application provides a digital current control method and a digital current control device, and aims to solve the problem of how to improve the reliability of an analog loop.
In order to achieve the above object, the present application provides the following technical solutions:
a digital current control method is applied to a digital controller, and comprises the following steps:
acquiring an output signal of the analog loop in each switching cycle, the output signal comprising: a compensation voltage, an input voltage and an output voltage;
calculating a digital peak current value through a preset calculation formula according to a preset maximum power value, the compensation voltage, the input voltage and the output voltage;
inputting the digital peak current value as a reference value to a reference end of an analog comparator in the analog loop;
and acquiring the current value of the analog loop in real time, and outputting a control signal by the analog comparator when the current value reaches the digital peak current value to control the current period of the analog loop to be closed so as to limit the maximum current value of the analog loop.
Preferably, the step of calculating the digital peak current value according to the preset maximum power value, the compensation voltage, the input voltage, and the output voltage by using a preset calculation formula specifically includes:
calculating the average current value of the analog loop according to a first preset formula according to the preset maximum power value, wherein the first preset formula is
Wherein Pin _ max is a preset maximum power value, and Vin is an input voltage;
superposing a triangular wave current on the average current value of the analog loop, and calculating the inductive current of the triangular wave current according to a second preset formula, wherein the second preset formula is as follows:
wherein, Δ I is an inductive current of a triangular wave current, Vout is an output voltage, L is an inductance of the analog loop, and Ton is a turn-on time of the switching tube;
calculating the digital peak current value by the preset calculation formula
Namely:
wherein, Ipk is the digital peak current value, Period is the PWM switching Period, and Comp is the compensation voltage.
Preferably, the compensation voltage is obtained by a digital loop calculation formula through the output voltage.
Preferably, the sampling range of the output signal is smaller than the sampling range of the digital controller.
A digital current control device is applied to a digital controller, and comprises:
a collection unit for collecting an output signal of the analog loop in each switching cycle, the output signal comprising: a compensation voltage, an input voltage and an output voltage;
the calculation unit is used for calculating a digital peak current value through a preset calculation formula according to a preset maximum power value, the compensation voltage, the input voltage and the output voltage;
an input unit for inputting the digital peak current value as a reference value to a reference terminal of an analog comparator in the analog loop;
and the control unit is used for acquiring the current value of the analog loop in real time, and when the current value reaches the digital peak current value, the analog comparator outputs a control signal to control the current cycle of the analog loop to be closed so as to limit the maximum current value of the analog loop.
Preferably, the computing unit is specifically configured to:
calculating the average current value of the analog loop according to a first preset formula according to the preset maximum power value, wherein the first preset formula is
Wherein Pin _ max is a preset maximum power value, and Vin is an input voltage;
superposing a triangular wave current on the average current value of the analog loop, and calculating the inductive current of the triangular wave current according to a second preset formula, wherein the second preset formula is as follows:
wherein, Delta I is the inductive current of the triangular wave currentVout is output voltage, L is inductance of the analog loop, and Ton is conduction time of the switching tube;
calculating the digital peak current value by the preset calculation formula
Namely:
wherein, Ipk is the digital peak current value, Period is the PWM switching Period, and Comp is the compensation voltage.
According to the digital current control method and device, after the digital peak current value is calculated, the digital peak current value is used as a reference current value and is input to a reference end of an analog comparator in an analog loop, the other end of the analog comparator in the analog loop collects the current value of the analog loop in real time, and when the current value reaches the digital peak current value, the analog comparator outputs a control signal to control the current period of the analog loop to be closed so as to limit the maximum current value of the analog loop.
As can be seen from the above calculation formula of the digital peak current value, the maximum power value is pre-specified and is used for preventing the maximum power value of overload; the input voltage, the output voltage, the compensation voltage and the switching period of the analog loop are all known quantities, and real-time sampling is carried out simultaneously to ensure that the maximum current value of each switching period in the analog loop does not exceed the digital peak current value, so that the reliability of the analog loop can be greatly improved.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a Buck topology circuit diagram provided in an embodiment of the present application;
fig. 2 is a schematic diagram illustrating a relationship between an inductor current iL and a switching period according to an embodiment of the present disclosure;
FIG. 3 is a flow chart of a digital current control method according to an embodiment of the present disclosure;
fig. 4 is a schematic structural diagram of a digital current control device according to an embodiment of the present disclosure.
Detailed Description
The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
The embodiment of the application is not limited to the topological mode of sampling by the control circuit: buck, Boost, Cuk, isolated or non-isolated topologies, and the like. The following discussion takes the Buck topology as an example, as shown in fig. 1, and the inductor current iL versus the switching period is shown in fig. 2.
As shown in fig. 3, a flowchart of a method for calculating a digital peak current provided in an embodiment of the present application is applied to a digital controller, and the method specifically includes the following steps:
s301: acquiring an output signal of the analog loop in each switching cycle, the output signal comprising: compensation voltage, input voltage and output voltage.
In this embodiment, a digital control chip, such as a 16-bit, 32-bit or 8-bit DSP, MCU, DSC, etc., may be used, and the output signal of the analog loop is acquired in real time in each switching period, where the output signal includes: compensation voltage (COMP voltage), input voltage Vin, and output voltage Vout.
It should be noted that the sampling range of the output signal in the embodiment of the present application is smaller than the sampling range of the digital controller.
S302: and calculating the digital peak current value through a preset calculation formula according to the preset maximum power value, the compensation voltage, the input voltage and the output voltage.
It should be noted that, the above calculating the digital peak current value according to the preset maximum power value, the compensation voltage, the input voltage, and the output voltage by using a preset calculation formula specifically includes:
calculating the average current value of the analog loop according to a first preset formula according to the preset maximum power value, wherein the first preset formula is
Wherein Pin _ max is a predetermined maximum power value, and Vin is an input voltage.
Superposing a triangular wave current on the average current value of the analog loop, and calculating the inductive current of the triangular wave current according to a second preset formula, wherein the second preset formula is as follows:
wherein Δ I is an inductive current of the triangular wave current, Vout is an output voltage, L is an inductance of the analog loop, and Ton is a turn-on time of the switching tube.
Calculating the digital peak current value by the preset calculation formula
Namely:
wherein, Ipk is the digital peak current value, Period is the PWM switching Period, and Comp is the compensation voltage.
In the embodiment of the present application, the on-time Ton of the switching tube is limited, that is: ton is less than Ton/,
the compensation voltage Comp is obtained from the output voltage by means of a digital loop calculation equation, Comp ═ 2P2Z (c.f.)Formula) ((Vref-Vout), where Comp is the actual compensation voltage value, Vref is the reference voltage value, and Vout is the output voltage.
It should be noted that, in a pure digital control system, the compensation voltage value is not necessarily sampled, and may also be calculated by the sampled output voltage Vout through algorithms such as PID, 2P2Z, 3P3Z, and the like; for a semi-digital control system, the compensation voltage must be sampled to obtain the loop output information.
It should be noted that the PID, 2P2Z, 3P3Z and other algorithms belong to the prior art, and specific contents can be referred to the description of related contents, which is not described herein again in detail.
S303: and inputting the digital peak current value as a reference value to a reference end of an analog comparator in the analog loop.
S304: and acquiring the current value of the analog loop in real time, and outputting a control signal by the analog comparator when the current value reaches the digital peak current value to control the current period of the analog loop to be closed so as to limit the maximum current value of the analog loop.
According to the embodiment of the application, after the digital peak current value is calculated, the digital peak current value is used as a reference current value and is input to the reference end Vref of the analog comparator in the analog loop, the other end of the analog comparator in the analog loop collects the current value of the analog loop in real time, and when the current value reaches the digital peak current value, the analog comparator outputs a control signal to control the current cycle of the analog loop to be closed so as to limit the maximum current value of the analog loop.
As can be seen from the above calculation formula of the digital peak current value Ipk, the maximum power value Pin _ max is a pre-specified maximum power value for preventing overload; the input voltage Vin, the output voltage Vout, the compensation voltage Comp value and the switching Period of the analog loop are all known quantities, and real-time sampling is carried out to ensure that the maximum current value of each switching Period in the analog loop does not exceed the digital peak current value Ipk, so that the reliability of the analog loop can be greatly improved.
Referring to fig. 4, based on the digital current control method disclosed in the foregoing embodiment, the present embodiment correspondingly discloses a digital current control apparatus, which is applied to a digital controller, and the apparatus specifically includes: acquisition unit 401, calculation unit 402, input unit 403 and control unit 404, wherein:
an acquisition unit 401, configured to acquire an output signal of the analog loop in each switching cycle, where the output signal includes: compensation voltage, input voltage and output voltage.
A calculating unit 402, configured to calculate a digital peak current value according to a preset calculation formula according to a preset maximum power value, the compensation voltage, the input voltage, and the output voltage.
An input unit 403, configured to input the digital peak current value as a reference value to a reference terminal of an analog comparator in the analog loop.
And the control unit 404 is configured to acquire a current value of the analog loop in real time, and when the current value reaches the digital peak current value, the analog comparator outputs a control signal to control a current cycle of the analog loop to be closed so as to limit a maximum current value of the analog loop.
Preferably, the calculating unit 402 is specifically configured to:
calculating the average current value of the analog loop according to a first preset formula according to the preset maximum power value, wherein the first preset formula is
Wherein Pin _ max is a preset maximum power value, and Vin is an input voltage;
superposing a triangular wave current on the average current value of the analog loop, and calculating the inductive current of the triangular wave current according to a second preset formula, wherein the second preset formula is as follows:
wherein Δ I is an inductive current of the triangular wave current, Vout is an output voltage, L is an inductance of the analog loop, and Ton is onClosing the tube and conducting time;
calculating the digital peak current value by the preset calculation formula
Namely:
wherein, Ipk is the digital peak current value, Period is the PWM switching Period, and Comp is the compensation voltage.
It is further noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that an article or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such article or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other like elements in an article or device that comprises the element.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (4)
1. A digital current control method, applied to a digital controller, the method comprising:
acquiring an output signal of the analog loop in each switching cycle, the output signal comprising: a compensation voltage, an input voltage and an output voltage;
according to the preset maximum power value, the compensation voltage, the input voltage and the output voltage, calculating a digital peak current value through a preset calculation formula, specifically: calculating the average current value of the analog loop according to a first preset formula according to the preset maximum power value, wherein the first preset formula is
Wherein Pin _ max is a preset maximum power value, and Vin is an input voltage;
superposing a triangular wave current on the average current value of the analog loop, and calculating the inductive current of the triangular wave current according to a second preset formula, wherein the second preset formula is as follows:
wherein, Δ I is an inductive current of a triangular wave current, Vout is an output voltage, L is an inductance of the analog loop, and Ton is a turn-on time of the switching tube;
calculating the digital peak current value by the preset calculation formula
Namely:
wherein, Ipk is a digital peak current value, Period is a PWM switching Period, and Comp is a compensation voltage;
inputting the digital peak current value as a reference value to a reference end of an analog comparator in the analog loop;
and acquiring the current value of the analog loop in real time, and outputting a control signal by the analog comparator when the current value reaches the digital peak current value to control the current period of the analog loop to be closed so as to limit the maximum current value of the analog loop.
2. The method of claim 1, wherein the compensation voltage is derived from the output voltage by a digital loop calculation formula.
3. The method of claim 1, wherein a sampling range of the output signal is less than a sampling range of the digital controller.
4. A digital current control apparatus, applied to a digital controller, the apparatus comprising:
a collection unit for collecting an output signal of the analog loop in each switching cycle, the output signal comprising: a compensation voltage, an input voltage and an output voltage;
a calculating unit, configured to calculate a digital peak current value according to a preset calculation formula according to a preset maximum power value, the compensation voltage, the input voltage, and the output voltage, and specifically configured to: calculating the average current value of the analog loop according to a first preset formula according to the preset maximum power value, wherein the first preset formula is
Wherein Pin _ max is a preset maximum power value, and Vin is an input voltage;
superposing a triangular wave current on the average current value of the analog loop, and calculating the inductive current of the triangular wave current according to a second preset formula, wherein the second preset formula is as follows:
wherein, Δ I is an inductive current of a triangular wave current, Vout is an output voltage, L is an inductance of the analog loop, and Ton is a turn-on time of the switching tube;
calculating the digital peak current value by the preset calculation formulaThe preset calculation formula is
Namely:
wherein, Ipk is a digital peak current value, Period is a PWM switching Period, and Comp is a compensation voltage;
an input unit for inputting the digital peak current value as a reference value to a reference terminal of an analog comparator in the analog loop;
and the control unit is used for acquiring the current value of the analog loop in real time, and when the current value reaches the digital peak current value, the analog comparator outputs a control signal to control the current cycle of the analog loop to be closed so as to limit the maximum current value of the analog loop.
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