CN115603576A - Control method of Buck-Boost circuit - Google Patents

Abstract

The present application discloses a method for controlling a Buck-Boost circuit. The circuit includes a power input terminal, an inductor, a capacitor, a voltage output terminal, a first power transistor Q1, a second power transistor Q2, a third power transistor Q3, and a fourth power transistor. Q4, Q1 is connected to the positive pole of the power input terminal, Q2 is connected to the negative pole of the power input terminal, Q4 is connected to the positive pole of the voltage output terminal, and Q3 is connected to the negative pole of the voltage output terminal. When the input voltage is greater than the target output voltage, the output voltage is controlled by controlling the duty cycle of Q1 , control Q4 conduction, control Q2 and Q1 complementary conduction, control Q3 off, the duty cycle of Q1 is Vout/Vin; when the input voltage is less than the target output voltage, the output voltage is controlled by controlling the duty cycle of Q4, Q1 is controlled to be turned on, Q3 and Q4 are controlled to be turned on complementary, Q2 is controlled to be turned off, and the duty ratio of Q4 is Vin/Vout. Through the above control method, a better control effect is achieved.

Description

A control method of Buck-Boost circuit

technical field

The present application relates to the field of electronic technology, and more specifically, to a method for controlling a Buck-Boost circuit.

Background technique

The Buck-Boost circuit is a commonly used conversion circuit, and its output voltage can be lower than the input voltage or higher than the output voltage. In the Buck-Boost circuit, the output voltage is controlled by controlling the duty cycle of the power tube. .

However, in the current control of the Buck-Boost circuit, the control mode of the boost circuit and the step-down circuit makes the calculation of the duty cycle inconvenient, which leads to poor control effect of the circuit.

Contents of the invention

In view of this, the present application provides a Buck-Boost circuit control method, which is used to solve the problem of poor control effect of the circuit.

In order to achieve the above purpose, the proposed scheme is as follows:

A control method for a Buck-Boost circuit, the Buck-Boost circuit includes a power supply input terminal, an inductor, a capacitor, a voltage output terminal and four power transistors, the four power transistors are respectively the first power transistor Q1, the second power transistor Q1 Two power tubes Q2, a third power tube Q3 and a fourth power tube Q4, the Q1 is connected to the positive pole of the power input end, the Q2 is connected to the negative pole of the power input end, and the Q4 is connected to the positive pole of the voltage output end, The Q3 is connected to the negative pole of the voltage output terminal, the Q1 and the Q4 are in charge, the Q2 and the Q3 are synchronous rectifier tubes, the Q1 and the Q2 are complementary, and the Q3 and the Q4 are complementary , the method includes:

When the input voltage is greater than the target output voltage, the Buck-Boost circuit is in the Buck mode, and the output voltage is controlled by controlling the duty cycle of the Q1, the Q4 is controlled to be turned on, and the Q2 and the Q1 are controlled to be complementary Turning on, controlling the Q3 to turn off, wherein the duty ratio of the Q1 is Vout/Vin;

When the input voltage is less than the target output voltage, the Buck-Boost circuit is in the Boost mode, and the output voltage is controlled by controlling the duty cycle of the Q4, the Q1 is controlled to be turned on, and the Q3 and The Q4 is turned on complementary to control the Q2 to be turned off, wherein the duty cycle of the Q4 is Vin/Vout.

Optionally, the method also includes:

When the input voltage is equal to the target output voltage, by controlling the Q1 and the Q4 to perform synchronous actions based on the same duty cycle to control the output voltage, and controlling the complementary conduction of the Q3 and the Q4, Controlling the complementary conduction of the Q2 and the Q1.

Optionally, neither the duty cycle of Q1 nor the duty cycle of Q4 is 0.

Optionally, the method also includes:

If the output voltage after controlling the Q1 and the Q4 to perform synchronous actions based on the same duty ratio is lower than the target output voltage, then adjust the duty ratios of the Q1 and the Q4.

Optionally, the adjusting the duty cycle of the Q1 and the Q4 includes:

Increase the duty cycle of the Q1 and the Q4.

Optionally, the adjustment amount each time the duty cycle of the Q1 and the Q4 is adjusted is a fixed value or a variable value.

The present application adopts a control method of a Buck-Boost circuit. The Buck-Boost circuit includes a power input terminal, an inductor, a capacitor, a voltage output terminal and four power transistors: the first power transistor Q1, the second power transistor Q2, the third power transistor Power tube Q3 and fourth power tube Q4, Q1 and Q4 are supervisors, Q2 and Q3 are synchronous rectifier tubes, Q1 and Q2 are complementary, Q3 and Q4 are complementary, Q1 is connected to the positive pole of the power input terminal, Q2 is connected to the negative pole of the power input terminal, and Q4 is connected to The positive pole of the voltage output terminal, Q3 is connected to the negative pole of the voltage output terminal. When the Buck-Boost circuit is in the step-down circuit mode, the output voltage is controlled by controlling the duty cycle of Q1, the direct connection of Q4 is controlled, and the complementary conduction of Q2 and Q1 is controlled. Q3 is turned off, and the duty cycle of Q1 is Vout/Vin; when the Buck-Boost circuit is in the boost circuit mode, the output voltage is controlled by controlling the duty cycle of Q4, Q1 is controlled to pass through, and Q3 and Q4 are controlled to be complementary to conduct , to control Q2 to turn off, and the duty ratio is Vin/Vout at this time. By changing the way of controlling the power tube, the calculation formula of the duty cycle in Buck mode is Vout/Vin, and the calculation formula of duty cycle in Boost mode is Vin/Vout. Only two parameters are involved in the calculation, and the calculation method is simple. It is convenient to calculate the duty ratio when performing circuit control, and achieve better circuit control effect.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only It is an embodiment of the present application, and those skilled in the art can also obtain other drawings according to the provided drawings without creative work.

Fig. 1 is a schematic circuit structure diagram of a Buck-Boost circuit provided by the present embodiment;

FIG. 2 is a flow chart of a control method for a Buck-Boost circuit provided in this embodiment;

FIG. 3 is a flow chart of another Buck-Boost circuit control method provided in this embodiment.

detailed description

The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all of them. Based on the embodiments in this application, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the scope of protection of this application.

A method for controlling a Buck-Boost circuit provided in an embodiment of the present application. As shown in FIG. 1, the Buck-Boost circuit includes a power input terminal Vin, an inductor L, capacitors Cin and Cout, a voltage output terminal Vout, and four power transistors , the four power tubes are the first power tube Q1, the second power tube Q2, the third power tube Q3 and the fourth power tube Q4, Q1 is connected to the positive pole of the power input terminal Vin, Q2 is connected to the negative pole of the power input terminal Vin, and Q4 Connect the positive pole of the voltage output terminal Vout, Q3 is connected to the negative pole of the voltage output terminal Vout, Q1 and Q4 are in charge, Q2 and Q3 are synchronous rectifier tubes, Q1 and Q2 are complementary, and Q3 and Q4 are complementary.

Among them, Vin is the output terminal of the power supply, Cin is the capacitor connected to the input terminal of the power supply, Vout is the output terminal of the voltage, Cout is the capacitor connected to the output terminal of the voltage, Q1, Q2, Q3 and Q4 are four power transistors, and L is the inductor device, and Gnd represents the grounding terminal of the wire.

Buck circuit, also known as step-down converter, is a single-tube non-isolated DC converter whose output voltage is lower than the input voltage. The Boost circuit, also known as a boost converter, is a single-tube non-isolated DC converter whose output voltage is higher than the input voltage. The Buck-Boost circuit, also known as a buck-boost converter, is a single-tube non-isolated DC converter whose output voltage can be lower than or higher than the input voltage, but the polarity of the output voltage is opposite to the input voltage. The Buck-Boost circuit can be regarded as a Buck circuit and a Boost circuit connected in series and a switch tube is combined. Setting Q2 and Q3 in the circuit can reduce the loss of Q1 and Q4.

The capacitor is composed of two conductors close to each other, and a layer of non-conductive insulating medium in the middle. When a voltage is applied between the two plates of the capacitor, the capacitor will store the charge. In the Buck-Boost circuit, when it is in the Buck circuit, the function of the capacitor is to store energy and reduce the pulsation of the output voltage. When it is in the Boost circuit, the function of the capacitor is mainly to control the output voltage within the specified range.

Inductors are components that convert electrical energy into magnetic energy and store it. Its structure is similar to a transformer. Inductors have a certain inductance, which only resists changes in current. If the inductor is in a state where no current is flowing, it will try to block the current from flowing through it when the circuit is on; if the inductor is in a state where current is passing, it will try to maintain the current when the circuit is off. In the Buck-Boost circuit, when in the Buck circuit, the inductance acts as a current limiter, especially at the moment when the main power is turned on, the capacitor has no voltage at the beginning, if the instantaneous main power directly charges the output capacitor, the charging current is very large, and the Blow up the capacitor. When in a Boost circuit, the inductance converts electric field energy and magnetic field energy into each other. When the switch is closed, the inductance converts the electric field energy into magnetic field energy and stores it. When the switch is closed, the inductance converts the stored magnetic energy into electric field energy. , provided to the load.

Regarding the selection of the four power transistors Q1, Q2, Q3 and Q4, you can choose a diode or a MOS transistor.

As shown in Figure 2, the control method of the Buck-Boost circuit may include:

S10. Determine the relationship between the input voltage and the target output voltage. If the input voltage is greater than the target output voltage, perform step S11. If the input voltage is less than the target output voltage, perform step S12;

S11. Control the output voltage by controlling the duty ratio of Q1, control Q4 to conduct, control Q2 and Q1 to conduct complementary conduction, and control Q3 to turn off;

S12 , controlling the duty cycle of Q4 to control the output voltage, controlling Q1 to be turned on, controlling Q3 and Q4 to be complementary turned on, and controlling Q2 to be turned off.

Among them, when performing circuit control of the Buck-Boost circuit, firstly determine which mode the Buck-Boost circuit is in, and determine the mode of the Buck-Boost circuit by comparing the required target output voltage with the input voltage. If the input voltage If the output voltage is greater than the target output voltage, the Buck-Boost circuit needs to be controlled in the boost circuit mode, that is, in the Buck mode. At this time, the output voltage is controlled by controlling the duty cycle of Q1. At this time, the calculation formula of the duty cycle of Q1 Vout/Vin, the states of Q3 and Q4 do not change during the entire control process of the circuit, and the state of Q2 changes according to the state of Q1; if the input voltage is less than the target output voltage, the Buck-Boost circuit needs to be controlled in the step-down Circuit mode, that is, in Boost mode. At this time, the output voltage is controlled by controlling the duty cycle of Q4. At this time, the calculation formula of the duty cycle of Q4 is Vin/Vout, and the states of Q1 and Q2 are in the whole control process of the circuit. No change occurs in Q3, the state of Q3 changes according to the state of Q4.

In this embodiment, through a control method of Buck-Boost circuit, by replacing the control power tube, the formula for calculating the duty cycle in Buck mode is Vout/Vin, and the formula for calculating the duty cycle in Boost mode is Vin/Vin Vout, only two parameters are involved in the calculation, and the calculation method is simple, it is convenient to calculate the duty cycle when performing circuit control, and achieve a better circuit control effect.

As shown in FIG. 3, in a method for controlling a Buck-Boost circuit provided according to an embodiment of the present application, the method shown in FIG. 2 may further include:

If the input voltage is equal to the target output voltage, execute step S13;

S13 , by controlling Q1 and Q4 to perform synchronous actions based on the same duty ratio to control the output voltage, control Q3 and Q4 to be turned on complementary, and control Q2 and Q1 to be turned on complementary.

Among them, in the Buck-Boost circuit, when the input voltage is equal to the target output voltage, the output voltage is controlled by simultaneously controlling Q1 and Q4, that is, during the entire control process of the Buck-Boost circuit, the states of Q1 and Q4 are the same, which can It can be turned off at the same time, and it can also be turned on at the same time. When the output voltage is controlled by controlling Q1 and Q4, the state of Q2 changes according to the state of Q1, and the state of Q3 changes according to the state of Q4.

In a control method for a Buck-Boost circuit provided according to an embodiment of the present application, neither the duty cycle of Q1 nor the duty cycle of Q4 is 0.

Among them, Q1 and Q4 are synchronously controlled, that is, the duty ratios of Q1 and Q4 are the same, if the duty ratios of Q1 and Q4 are both 0, then Q2 and Q1 are complementary, Q3 and Q4 are complementary, and the power output terminal is directly connected to the power input The capacitor at the terminal is charged, and the capacitor is likely to fail. If the capacitor does not fail, but because the capacitor communicates with AC and blocks DC, the capacitor does not supply energy, and there is no current in the circuit, resulting in the voltage at the voltage output terminal being 0.

In a method for controlling a Buck-Boost circuit provided according to an embodiment of the present application, the method may further include:

If the output voltage after synchronous operation based on the same duty ratio is lower than the target output voltage by controlling Q1 and Q4, then adjust the duty ratios of Q1 and Q4.

Among them, when the input voltage is equal to the target output voltage, the output voltage is adjusted by synchronously controlling the duty cycle of Q1 and Q4. In the adjustment process, it is not a one-time adjustment to the output accuracy of the output voltage, but it is necessary to adjust the duty cycle of Q1 and Q4 several times to adjust to the output accuracy of the output voltage.

According to a method for controlling a Buck-Boost circuit provided in an embodiment of the present application, adjusting the duty ratios of Q1 and Q4 may include:

Increase the duty cycle of Q1 and Q4.

Wherein, after the duty ratios of Q1 and Q4 increase synchronously, the duty ratio of Q3 changes, causing the output voltage to change to a certain extent at the same time, so as to ensure that the output voltage is within the output accuracy.

In a control method for a Buck-Boost circuit provided according to an embodiment of the present application, the adjustment amount each time the duty cycle of Q1 and Q4 is adjusted is a fixed value or a variable value.

Among them, the adjustment amount is determined according to the gap between the current output voltage and the target output voltage. If the adjustment amount is a fixed value, it means that the output voltage can be guaranteed to be within the output accuracy through one-time adjustment; if the adjustment amount is a variable value, It means that the output voltage cannot be guaranteed within the output accuracy through one-time adjustment, and multiple adjustments are required to ensure the output voltage within the output accuracy.

Finally, it should also be noted that in this text, relational terms such as first and second etc. are only used to distinguish one entity or operation from another, and do not necessarily require or imply that these entities or operations, any such actual relationship or order exists. Furthermore, the term "comprises", "comprises" or any other variation thereof is intended to cover a non-exclusive inclusion such that a process, method, article or apparatus comprising a set of elements includes not only those elements, but also includes elements not expressly listed. other elements of or also include elements inherent in such a process, method, article, or device. Without further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article or apparatus comprising said element.

Each embodiment in this specification is described in a progressive manner, each embodiment focuses on the difference from other embodiments, and the same and similar parts of each embodiment can be referred to each other.

The above 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 general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the application. Therefore, the present application will not 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 (6)

1. the control method of a kind of Buck-Boost circuit is characterized in that, described Buck-Boost circuit comprises power supply input terminal, inductor, capacitor, voltage output terminal and four power tubes, and described four power tubes are respectively the first A power tube Q1, a second power tube Q2, a third power tube Q3 and a fourth power tube Q4, the Q1 is connected to the positive pole of the power input end, the Q2 is connected to the negative pole of the power input end, and the Q4 is connected to the The positive pole of the voltage output terminal, the Q3 is connected to the negative pole of the voltage output terminal, the Q1 and the Q4 are in charge, the Q2 and the Q3 are synchronous rectifier tubes, the Q1 and the Q2 are complementary, the Q3 and said Q4 are complementary, and said method comprises: When the input voltage is greater than the target output voltage, the Buck-Boost circuit is in the Buck mode, and the output voltage is controlled by controlling the duty cycle of the Q1, the Q4 is controlled to be turned on, and the Q2 and the Q1 are controlled to be complementary Turning on, controlling the Q3 to turn off, wherein the duty cycle of the Q1 is Vout/Vin; When the input voltage is less than the target output voltage, the Buck-Boost circuit is in the Boost mode, and the output voltage is controlled by controlling the duty cycle of the Q4, the Q1 is controlled to be turned on, and the Q3 and The Q4 is turned on complementary to control the Q2 to be turned off, wherein the duty ratio of the Q4 is Vin/Vout. 2. The method according to claim 1, characterized in that the method further comprises: When the input voltage is equal to the target output voltage, by controlling the Q1 and the Q4 to perform synchronous actions based on the same duty cycle to control the output voltage, and controlling the complementary conduction of the Q3 and the Q4, Controlling the complementary conduction of the Q2 and the Q1. 3. The method according to claim 2, wherein neither the duty cycle of the Q1 nor the duty cycle of the Q4 is 0. 4. The method according to claim 2 or 3, characterized in that the method further comprises: If the output voltage after controlling the Q1 and the Q4 to perform synchronous actions based on the same duty ratio is lower than the target output voltage, then adjust the duty ratios of the Q1 and the Q4. 5. The method according to claim 4, wherein said adjusting the duty cycle of said Q1 and said Q4 comprises: Increase the duty cycle of the Q1 and the Q4. 6 . The method according to claim 5 , wherein the adjustment amount each time the duty cycle of the Q1 and the Q4 is adjusted is a fixed value or a variable value.

Images