Buck-boost converter

Abstract

The present application provides a buck-boost converter, which belongs to the technical field of current sampling. The buck-boost converter includes: an input, which includes a positive input terminal Vin+ and a negative input terminal Vin‑; an output, which includes a positive output terminal Vout+ and a negative output terminal Vout‑; a switch tube bridge arm, including a first switch tube Q1 and a second switch tube Q2, one end of the switch tube bridge arm is connected to the positive input terminal, and the other end is connected to the negative input terminal; an inductor and a resistor series branch, one end of the branch is connected to the midpoint end of the switch tube bridge arm, and the other end is connected to the negative output terminal; a first capacitor, connected across the positive input terminal and the negative input terminal; a second capacitor, connected across the positive output terminal and the negative output terminal; wherein the positive input terminal is directly connected to the positive output terminal, and the resistor is configured to be able to sample the current flowing through the inductor. High-precision and low-cost current sampling of parallel systems is achieved.

Description

Technical Field

[0001] The present application relates to the technical field of current sampling, and in particular to a buck-boost converter. Background Art

[0002] In power electronic systems, in order to ensure the stability and reliability of the system, it is necessary to accurately detect the current in the circuit. Current detection is usually used in power management, motor drive and other fields to achieve functions such as load balancing and fault diagnosis.

[0003] At present, for a single buck-boost converter, the common current detection method is to connect a sampling resistor in series between the switch tube and the filter capacitor, convert the current into a voltage signal through Ohm's law, and then send it to a microcontroller or other ADC conversion chip for analog-to-digital conversion through conditioning circuits such as operational amplifiers. In addition, when it is necessary to detect multiple parallel buck-boost converters at the same time, a Hall current sensor is usually used. This sensor is installed after the inductor and can independently detect the current value in each inductor.

[0004] Although the above-mentioned existing technical solutions can meet the current detection needs in different scenarios, it is found in actual application that the method based on sampling resistors is only applicable to a single buck-boost converter and is difficult to expand to multiple parallel systems; and although the solution based on Hall current sensors can realize simultaneous detection of multiple currents, its cost is much higher than that of the resistive sampling method in the scenario of high-precision detection in a large current range (between tens to thousands of amperes).

[0005] Therefore, there is an urgent need for a buck-boost converter with low cost, high sampling accuracy and adaptability to multiple buck-boosts in parallel. Summary of the invention

[0006] In order to solve the technical problem that the buck-boost converter in the prior art cannot simultaneously meet the requirements of low cost, high sampling accuracy, and adaptability to multiple buck-boosts, an embodiment of the present application provides a buck-boost converter.

[0007] In a first aspect, an embodiment of the present application provides a buck-boost converter, comprising: Input, which includes a positive input terminal Vin+ and a negative input terminal Vin-; Output, which includes a positive output terminal Vout+ and a negative output terminal Vout-; A switch tube bridge arm, comprising a first switch tube Q1 and a second switch tube Q2, wherein one end of the switch tube bridge arm is connected to the positive input end, and the other end is connected to the negative input end; An inductor and a resistor are connected in series, one end of the branch is connected to the midpoint end of the switch tube bridge arm, and the other end is connected to the negative output end; A first capacitor connected across the positive input terminal and the negative input terminal; A second capacitor connected across the positive output terminal and the negative output terminal; The positive input terminal is directly connected to the positive output terminal, and the resistor is configured to sample the current flowing through the inductor.

[0008] Optionally, the temperature coefficient of the resistor is less than or equal to 50 ppm.

[0009] Optionally, the buck-boost converter further includes a parallel sampling circuit; The parallel sampling circuit comprises at least one parallel switch tube bridge arm, the parallel switch tube bridge arm is a half-bridge structure, and the parallel switch tube bridge arm is connected in parallel with the switch tube bridge arm; The parallel sampling circuit also includes a sampling branch, which includes an inductor and a resistor; the resistor is connected in series downstream of the inductor, one end of the sampling branch is connected to the midpoint of the parallel switch bridge arm, and the other end of the sampling branch is connected to the negative output terminal.

[0010] Optionally, the buck-boost converter further comprises: A second switch tube bridge arm includes a third switch tube Q3 and a fourth switch tube Q4, one end of the second switch tube bridge arm is connected to the positive input end, and the other end is connected to the negative input end; and The inductor and the resistor are connected in series to a second branch, one end of the second branch is connected to the midpoint end of the second switch tube bridge arm, and the other end is connected to the negative output end.

[0011] Optionally, the buck-boost converter further comprises: A third switch tube bridge arm, including a fifth switch tube Q5 and a sixth switch tube Q6, one end of the third switch tube bridge arm is connected to the positive input end, and the other end is connected to the negative input end; and The inductor and the resistor are connected in series to a third branch, one end of the third branch is connected to the midpoint end of the third switch tube bridge arm, and the other end is connected to the negative output end.

[0012] Optionally, the temperature coefficient of the resistor is less than or equal to 20 ppm.

[0013] Optionally, the input voltage of the buck-boost converter is: 3.0V to 4.2V, 12V to 16V or 200V to 800V.

[0014] Optionally, a capacitance value of the first capacitor is greater than or equal to 10 μF and less than or equal to 1000 μF.

[0015] Optionally, a capacitance value of the second capacitor is greater than or equal to 10 μF and less than or equal to 1000 μF.

[0016] Optionally, the accuracy of the resistor is greater than or equal to ±1%. The above technical solution provided by the present application has at least the following technical effects: The buck-boost converter provided in the embodiment of the present application creates a condition for current sampling on the low side by sharing the positive electrode between the positive input terminal and the positive output terminal, so that current sampling can be performed through a resistor, thereby avoiding the use of a Hall current sensor. In this way, the detection error of the Hall current sensor in a large current range is avoided, and the cost is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the background technology, the drawings required for use in the embodiments of the present application or the background technology will be described below.

[0018] Figure 1 An optional structural schematic diagram of a conventional buck-boost converter is shown; Figure 2 Another optional structural schematic diagram of a traditional buck-boost converter is shown; Figure 3 A schematic diagram of the structure of a buck-boost converter provided in an embodiment of the present application is shown. DETAILED DESCRIPTION

[0019] In order to enable people in the technical field to better understand the solution of this application, the technical solution in the embodiment of this application will be clearly and completely described below in conjunction with the drawings in the embodiment of this application. Obviously, the described embodiment is only a part of the embodiment of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0020] In the following description, many specific details are set forth to facilitate a full understanding of the present application, but the present application may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present application. Therefore, the present application is not limited to the specific embodiments disclosed below.

[0021] Figure 1 A conventional buck-boost converter is shown. Figure 1 , Figure 1The buck-boost circuit is sampled through a resistor. Figure 1 In the circuit, a resistor R1_1 is connected in series to the negative electrode between the switch tube Q1_2 and the filter capacitor C1_2. The current flowing through the resistor R1_1 is converted into a voltage signal by Ohm's law, and then sent to the main control chip or other analog-to-digital conversion chip (ADC) for analog-to-digital conversion through the operational amplifier conditioning circuit. Figure 1 The circuit in FIG. 1 can sample current through a resistor, but cannot sample current in a system with multiple buck-boost circuits in parallel.

[0022] Figure 2 Another conventional buck-boost converter is shown. Figure 2 , a Hall current sensor is connected in series at the back end of each of the two parallel buck-boost circuits, so that the current of each inductor can be collected. However, the price of Hall current sensors is much higher than that of resistors, and the peripheral circuit design of Hall current sensors is complex and occupies a large space. In addition, Hall current sensors include open-loop and closed-loop. Among them, open-loop Hall current sensors are suitable for large current measurement scenarios of hundreds to thousands of amperes, but the accuracy is not as good as closed-loop Hall current sensors. The closed-loop Hall current sensor has higher accuracy, but is only suitable for small current measurement scenarios of tens of amperes. Generally, the power electronic conversion accuracy of existing general Hall current sensors can reach an accuracy of less than or equal to 0.1%.FS, and higher-precision Hall current sensors can reach ≤0.05%.FS, or even ≤0.02%.FS. In addition, accuracy is also related to the range. For example, a 0-10A device can easily achieve an accuracy of 0.05%.FS, but if 0-100A wants to achieve 0.05%.FS, there is a certain degree of difficulty.

[0023] When faced with the scenario of full-range measurement of large current range (from tens of amperes to thousands of amperes), Hall current sensors are difficult to meet. Figure 2 The circuit in the figure is high-side current sampling. Different from low-side current sampling, high-side current sampling requires the addition of isolation components to prevent high voltage from entering the weak current circuit and breaking down other components.

[0024] In view of this, the present application provides a buck-boost converter. Figure 3 As shown, the buck-boost converter provided in the embodiment of the present application includes: Input, which includes a positive input terminal Vin+ and a negative input terminal Vin-; Output, which includes a positive output terminal Vout+ and a negative output terminal Vout-; The switch tube bridge arm includes a first switch tube Q1 and a second switch tube Q2, one end of the switch tube bridge arm is connected to the positive input end, and the other end is connected to the negative input end; An inductor and a resistor are connected in series in a branch, one end of the branch is connected to the midpoint end of the switch bridge arm, and the other end is connected to the negative output end; A first capacitor is connected across the positive input terminal and the negative input terminal; A second capacitor is connected across the positive output terminal and the negative output terminal; Among them, the positive input terminal is directly connected to the positive output terminal, and the resistor is configured to sample the current flowing through the inductor. The current passing through the resistor is converted into voltage through Ohm's law, and then sent to the main control chip or other analog-to-digital conversion chip through the operational amplifier conditioning circuit to achieve current sampling.

[0025] The input / output voltage range provided in the embodiment of the present application is determined by the design requirements and application scenarios, and there is no special restriction. For example, when applied to lithium battery-powered devices (such as smart phones, tablet computers, portable electronic devices), the input voltage range is 3.0V (volts) to 4.2V. For another example, when applied to the high-voltage system of new energy vehicles (such as the main drive motor, battery management system), the input voltage range is 200V to 800V. For another example, the input voltage range is 12V to 16V for the low-voltage system (such as interior lighting, entertainment system, etc.) of new energy vehicles. Exemplarily, the output voltage of the buck-boost converter provided in the embodiment of the present application is 3.V to 5V in the low-voltage output scenario, 5V to 12V in the medium-voltage output scenario, 12V to 48V in the high-voltage output scenario, and 200V to 1000V in the high-voltage and high-current scenario.

[0026] It should be noted that the traditional buck-boost circuit (such as Figure 1 and Figure 2 The output negative electrode and the input negative electrode are directly connected without an intermediate element, but the positive input terminal and the positive output terminal of the buck-boost converter of the present application are directly connected without an intermediate element, that is, a common positive electrode. This creates conditions for current sampling on the low side, and thus creates conditions for current sampling through a resistor.

[0027] According to the implementation of the present application, optionally, the switch tube bridge arm is a half-bridge structure, wherein the first switch tube Q1 is an upper bridge arm switch tube connected to the positive electrode; the second switch tube Q2 is a lower bridge arm switch tube connected to the negative electrode. When the first switch tube Q1 is turned on, the current flows from the positive electrode to the load through the first switch tube; when the second switch tube Q2 is turned on, the current flows from the load to the negative electrode through the second switch tube.

[0028] Optionally, the switching tube provided in the embodiment of the present application includes a metal oxide semiconductor field effect transistor (MOSFET), an insulated gate bipolar transistor (IGBT), a silicon carbide field effect transistor (SiC MOSFET, SiCMetal Oxide Semiconductor Field Effect Transistor), a gallium nitride field effect transistor (GaNFET, GaN Field Effect Transistor), and a bipolar transistor (BJT, Bipolar Junction Transistor).

[0029] According to an embodiment of the present application, the first capacitor C1 is used for bus energy storage and filtering. According to an embodiment of the present application, the second capacitor C2 is used for output end energy storage and filtering. Exemplarily, the capacitance value of the first capacitor is greater than or equal to 10μF and less than or equal to 1000μF. Exemplarily, the capacitance value of the second capacitor is greater than or equal to 10μF and less than or equal to 1000μF. Exemplarily, the withstand voltage value of the first capacitor or the second capacitor is greater than or equal to 1.5 times the output voltage.

[0030] Furthermore, if Figure 3 As shown, the buck-boost converter provided in the embodiment of the present application also includes a parallel sampling circuit. The parallel sampling circuit includes at least one parallel switch tube bridge arm, and the parallel switch tube bridge arm is a half-bridge structure. The parallel switch tube bridge arm is connected in parallel with the switch tube bridge arm. The parallel sampling circuit also includes a sampling branch, and the sampling branch includes an inductor and a resistor; the resistor is connected in series to the rear end of the inductor, one end of the sampling branch is connected to the midpoint of the parallel switch tube bridge arm, and the other end of the sampling branch is connected to the negative output terminal.

[0031] For example, Figure 3 As shown, the buck-boost converter provided in the embodiment of the present application also includes: a second switch tube bridge arm, including a third switch tube Q3 and a fourth switch tube Q4; one end of the second switch tube bridge arm is connected to the positive input terminal, and the other end is connected to the negative input terminal; and, an inductor and a resistor are connected in series to a second branch, one end of the second branch is connected to the midpoint end of the second switch tube bridge arm, and the other end is connected to the negative output terminal.

[0032] For example, Figure 3As shown, the buck-boost converter provided in the embodiment of the present application also includes: a third switch tube bridge arm, including a fifth switch tube Q5 and a sixth switch tube Q6, one end of the third switch tube bridge arm is connected to the positive input terminal, and the other end is connected to the negative input terminal; and, an inductor and a resistor are connected in series to a third branch, one end of the third branch is connected to the midpoint end of the third switch tube bridge arm, and the other end is connected to the negative output terminal.

[0033] It should be noted that in the buck-boost converter of the embodiment of the present application, due to the design of the common positive electrode, it is possible to construct at least one parallel switch tube bridge arm and sampling branch in parallel on the basis of the existing switch tube bridge arm, inductor and resistor series branch. It is not difficult to understand that the number of parallel buck-boost circuits in the embodiment of the present application is not limited, and the corresponding sampling branch is also not limited.

[0034] Specifically, Figure 3 As shown, the drain of the upper bridge arm switch tube (such as Q1, Q3 or Q5) in the half-bridge structure provided by the embodiment of the present application is connected to the positive electrode of the bus, and the source and the drain of the lower bridge arm switch tube (such as Q2, Q4 or Q6) are electrically connected as the midpoint of the bridge arm. In addition, the source of the lower bridge arm switch tube is connected to the negative electrode of the bus.

[0035] According to the implementation mode of the present application, the upper bridge arm switch tube and the lower bridge arm switch tube of the half-bridge structure provided in the embodiment of the present application are alternately turned on in a switching cycle to provide a pulse square wave voltage for the subsequent circuit. In order to prevent the bridge arm from being directly turned on, a certain dead time is usually inserted between the turn-on moments of the upper bridge arm tube and the lower bridge arm tube, so that the lower bridge arm tube is turned on with a delay after the upper bridge arm switch tube is turned off.

[0036] According to the implementation mode of the present application, other performance requirements of the resistor, such as temperature coefficient, accuracy, temperature drift, operating range and maximum operating voltage, need to be selected according to the actual sampling current requirements. Optionally, the resistor used for sampling in the embodiment of the present application is preferably a resistor with a low temperature coefficient. Optionally, a resistor with low linearity is preferred in the embodiment of the present application. More advantageously, the temperature coefficient of the resistor is less than or equal to 50ppm / °C to ensure that the measurement accuracy is greater than that of the Hall current sensor in the full range of scenarios with a large current range (tens to thousands of amperes). Furthermore, the temperature coefficient of the resistor is less than or equal to 20ppm / °C. Exemplarily, the accuracy of the resistor is greater than or equal to ±1%.

[0037] The buck-boost converter provided in the embodiment of the present application creates the condition for current sampling on the low side by sharing the positive pole with the positive input terminal and the positive output terminal, so that current sampling can be performed through a resistor, thereby avoiding the use of a Hall current sensor. Thereby, the detection error of the Hall current sensor under a large current range is avoided, and the cost is reduced. The buck-boost converter provided in the embodiment of the present application creates conditions for current sampling on the low side by directly connecting the positive pole of the input terminal and the positive pole of the output terminal, thereby sampling multiple parallel buck-boost circuits through resistors, and the current of each inductor must pass through a resistor and a conditioning circuit to converge, thereby achieving current sampling of each inductor. Through resistor sampling, the cost of current sampling is reduced, the space occupied by the sampling circuit is reduced, and it is adapted to a wider range of application scenarios.

[0038] The above is only a specific implementation of the embodiment of the present application, but the protection scope of the embodiment of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or replacements within the technical scope disclosed in the embodiment of the present application, which should be included in the protection scope of the embodiment of the present application. Therefore, the protection scope of the embodiment of the present application shall be based on the protection scope of the claims.

Claims

1. A buck-boost converter, characterized in that: include: Input, which includes a positive input terminal Vin+ and a negative input terminal Vin-; Output, which includes a positive output terminal Vout+ and a negative output terminal Vout-; A switch tube bridge arm, comprising a first switch tube Q1 and a second switch tube Q2, wherein one end of the switch tube bridge arm is connected to the positive input end, and the other end is connected to the negative input end; An inductor and a resistor are connected in series, one end of the branch is connected to the midpoint end of the switch tube bridge arm, and the other end is connected to the negative output end; A first capacitor connected across the positive input terminal and the negative input terminal; A second capacitor connected across the positive output terminal and the negative output terminal; The positive input terminal is directly connected to the positive output terminal, and the resistor is configured to sample the current flowing through the inductor.

2. The buck-boost converter according to claim 1, characterized in that: The temperature coefficient of the resistor is less than or equal to 50 ppm / °C.

3. The buck-boost converter according to claim 1, characterized in that: The buck-boost converter also includes a parallel sampling circuit; The parallel sampling circuit comprises at least one parallel switch tube bridge arm, the parallel switch tube bridge arm is a half-bridge structure, and the parallel switch tube bridge arm is connected in parallel with the switch tube bridge arm; The parallel sampling circuit also includes a sampling branch, which includes an inductor and a resistor; the resistor is connected in series to the rear end of the inductor, one end of the sampling branch is connected to the midpoint of the parallel switch bridge arm, and the other end of the sampling branch is connected to the negative output end.

4. The buck-boost converter according to claim 3, characterized in that: The buck-boost converter further comprises: A second switch tube bridge arm includes a third switch tube Q3 and a fourth switch tube Q4, one end of the second switch tube bridge arm is connected to the positive input end, and the other end is connected to the negative input end; and The inductor and the resistor are connected in series to a second branch, one end of the second branch is connected to the midpoint end of the second switch tube bridge arm, and the other end is connected to the negative output end.

5. The buck-boost converter according to claim 1, characterized in that: The buck-boost converter further comprises: A third switch tube bridge arm, including a fifth switch tube Q5 and a sixth switch tube Q6, one end of the third switch tube bridge arm is connected to the positive input end, and the other end is connected to the negative input end; and The inductor and the resistor are connected in series to a third branch, one end of the third branch is connected to the midpoint end of the third switch tube bridge arm, and the other end is connected to the negative output end.

6. The buck-boost converter according to claim 2, characterized in that: The temperature coefficient of the resistor is less than or equal to 20 ppm / °C.

7. The buck-boost converter according to any one of claims 1 to 4, characterized in that: The input voltage of the buck-boost converter is 3.0V to 4.2V, 12V to 16V or 200V to 800V.

8. The buck-boost converter according to any one of claims 1 to 4, characterized in that: The capacitance value of the first capacitor is greater than or equal to 10 μF and less than or equal to 1000 μF.

9. The buck-boost converter according to any one of claims 1 to 4, characterized in that: The capacitance value of the second capacitor is greater than or equal to 10 μF and less than or equal to 1000 μF.

10. The buck-boost converter according to any one of claims 1 to 4, characterized in that , the accuracy of the resistor is greater than or equal to ±1%.

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