Bidirectional converter

Abstract

The invention belongs to the technical field of power electronics, and discloses a bidirectional converter which comprises a capacitor C5, one end of the capacitor C5 is connected with one end of an inductor L1, the other end of the inductor L1 is connected with a drain electrode of an MOS tube Q1 and one end of a capacitor C1, and the other end of the capacitor C1 is connected with a pin 1 of a transformer T; and the other end of the capacitor C5 is connected with one end of a capacitor C6, a source electrode of the MOS tube Q1, a drain electrode of the MOS tube Q2, a pin 2 of the transformer T and a pin 3 of the transformer T. The three-level inversion DC / AC isolation belt midpoint balancing circuit has the advantages that in the application occasion of inputting or outputting high voltage, the circuit can use a low-voltage-resistant switch tube to achieve isolation bidirectional conversion, input and output ripple currents are reduced through coupling inductors, the midpoint tapped transformer is adopted, input and output can achieve automatic midpoint balancing, and the three-level inversion DC / AC isolation belt midpoint direct current circuit can be used as a three-level inversion DC / AC isolation belt midpoint direct current circuit.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronics, and in particular to a bidirectional converter. Background Art

[0002] A converter converts one form of electrical energy into another form of electrical energy that is suitable for the use scenario, such as the mutual conversion between AC and DC, and DC and DC, to meet different application requirements. In order to simplify the design, reduce the conversion links, reduce losses, and improve the overall efficiency, unidirectional converters are gradually transformed into bidirectional converters. An AC / DC converter is a circuit that converts AC power into DC power. Its power flow can be bidirectional. The power flow from the power source to the load is called rectification, and the power flow from the load back to the power source is called active inversion. In actual applications, there are also other bidirectional converters. Among the existing circuits, some have complex structures and high costs; some have simple structures and reduce costs, but their scope of use is limited. If the scope exceeds a certain range, the circuit will be unstable.

[0003] Therefore, it is necessary to provide a bidirectional converter with simple structure, stable operation and conducive to miniaturization design. Summary of the invention

[0004] The invention discloses a bidirectional converter, which can effectively solve the technical problems involved in the background technology.

[0005] To achieve the above object, the technical solution of the present invention is:

[0006] A bidirectional converter, comprising a capacitor C5, one end of the capacitor C5 is connected to one end of an inductor L1, the other end of the inductor L1 is connected to the drain of a MOS tube Q1 and one end of the capacitor C1, the other end of the capacitor C1 is connected to pin 1 of a transformer T, the other end of the capacitor C5 is connected to one end of a capacitor C6, the source of the MOS tube Q1, the drain of the MOS tube Q2, the pin 2 of the transformer T and the pin 3 of the transformer T, the other end of the capacitor C6 is connected to one end of the inductor L2, the other end of the inductor L2 is connected to the source of the MOS tube Q2 and one end of the capacitor C2, the other end of the capacitor C2 is connected to the transformer The pin 4 of the transformer T is connected to the pin 5 of the transformer T; the pin 5 of the transformer T is connected to one end of the capacitor C4, the other end of the capacitor C4 is connected to the source of the MOS tube Q4 and one end of the inductor L4, the other end of the inductor L4 is connected to one end of the capacitor C8, the pin 6 of the transformer T is connected to the pin 7 of the transformer T, the drain of the MOS tube Q4, the source of the MOS tube Q3, the other end of the capacitor C8 and one end of the capacitor C7, the pin 8 of the transformer T is connected to one end of the capacitor C3, the other end of the capacitor C3 is connected to the drain of the MOS tube Q3 and one end of the inductor L3, and the other end of the inductor L3 is connected to the other end of the capacitor C7.

[0007] As a preferred improvement of the present invention: one end of the capacitor C5 and the other end of the capacitor C6 are connected to a power supply, and the other end of the capacitor C7 and one end of the capacitor C8 are connected to a load.

[0008] As a preferred improvement of the present invention: the transformer T is a midpoint tapped transformer, pins 2 and 3 of the transformer T are the midpoints of the primary side, and pins 6 and 7 of the transformer T are the midpoints of the secondary side.

[0009] As a preferred improvement of the present invention: Pin 1 and Pin 2 of the transformer T share a coil, Pin 3 and Pin 4 of the transformer T share a coil, Pin 5 and Pin 6 of the transformer T share a coil, and Pin 7 and Pin 8 of the transformer T share a coil.

[0010] As a preferred improvement of the present invention: the gates of the MOS transistor Q1 , the MOS transistor Q2 , the MOS transistor Q3 and the MOS transistor Q4 are all connected to the MCU.

[0011] As a preferred improvement of the present invention: the inductor L1 and the inductor L2 are coupled inductors, the inductor L3 and the inductor L4 are coupled inductors, one end of the inductor L1 and one end of the inductor L3 are like-named ends, and the other end of the inductor L2 and the other end of the inductor L4 are like-named ends.

[0012] As a preferred improvement of the present invention: pin 6 of the transformer T is connected to the drain of the MOS tube Q4 and the other end of the capacitor C8, and is connected to the other end of the inductor L3 and the other end of the capacitor C7 through a switch S1; pin 7 of the transformer T is connected to the source of the MOS tube Q3 and one end of the capacitor C7, and is connected to pin 6 of the transformer T through a switch S2; and one end of the capacitor C8 is connected to pin 7 of the transformer T through a switch S3.

[0013] The beneficial effects of the present invention are as follows:

[0014] In applications where high voltage is input or output, the circuit can use a lower withstand voltage switch tube to achieve isolated bidirectional conversion and wide voltage range bidirectional conversion, which improves the utilization rate of the inductor core and is conducive to miniaturization design. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work, among which:

[0016] Figure 1 is a circuit diagram of an existing converter;

[0017] Figure 2 A schematic diagram of a bidirectional converter according to the present invention;

[0018] Figure 3 The circuit principle of the present invention is shown in FIG. Figure 1 ;

[0019] Figure 4 The circuit principle of the present invention is shown in FIG. Figure 2 ;

[0020] Figure 5 This is a schematic diagram of Embodiment 1 of the present invention. DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the present invention will be described clearly and completely below in combination with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0023] In addition, in the present invention, descriptions such as "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0024] In the present invention, unless otherwise clearly specified and limited, the terms "connection", "fixation", etc. should be understood in a broad sense. For example, "fixation" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0025] In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that ordinary technicians in the field can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0026] See also Figure 1 As shown, Figure 1 It is a converter circuit, C13 is used as the input filter capacitor, and C14 is used as the output filter capacitor. The steady-state working process is as follows: when Q11 is turned on and Q12 is turned off, the current of inductor L11 increases, capacitor 11 is connected in parallel with the primary side of transformer T1, and the voltage of capacitor C11 is superimposed on the voltage of capacitor C12 through transformer T1. After being filtered by L12 and C14, power is supplied to the load. When Q11 is turned off, the current of inductor L11 decreases. At this time, the inductor voltage commutates, and the primary voltage of transformer T1 increases from the negative maximum to the positive maximum. The body diode of Q12 is turned on due to forward bias. At this time, Q12 is turned on, L12 enters the freewheeling stage, the current decreases, the voltage reverses, and continues to charge C14. V C14 =-L12dL12 / dt. Vs transformer secondary voltage, when Vs+V C12 -V C14 When it drops to zero and becomes negative, the inductor current L12 starts to drop from the maximum. When the inductor current L12 is close to zero, Q11 is turned on, the inductor current L12 starts to rise, and the transformer turns ratio is equal to 1:n. When Q11 is turned off, the current of the inductor L11 drops, and the voltage across it changes direction. The voltage stress across the switch tube is V C13 -L11di L11 / dt, greater than the input voltage V C13 When Q12 is turned off, the voltage stress across it is Vc 14 +L12di L12 / dt, greater than the output voltage V C14 When the switch tubes Q11 and Q12 are turned off, the voltage stress is greater than the input voltage and the output voltage, and the isolated DC output or the output cannot be directly connected to the commonly used three-level inverter circuit DC / AC.

[0027] See also Figure 2 As shown, based on Figure 1In order to solve the problem in the invention, a bidirectional converter is provided. In the application occasion of inputting or outputting high voltage, the circuit can use a relatively low withstand voltage switch tube to realize isolated bidirectional conversion. The converter circuit comprises a capacitor C5, one end of the capacitor C5 is connected to one end of an inductor L1, the other end of the inductor L1 is connected to the drain of a MOS tube Q1 and one end of the capacitor C1, the other end of the capacitor C1 is connected to pin 1 of a transformer T, the other end of the capacitor C5 is connected to one end of a capacitor C6, the source of the MOS tube Q1, the drain of the MOS tube Q2, the pin 2 of the transformer T and the pin 3 of the transformer T, the other end of the capacitor C6 is connected to one end of an inductor L2, the other end of the inductor L2 is connected to the drain of the MOS tube Q2, and the other end of the capacitor C6 is connected to one end of the inductor L2. The source and one end of the capacitor C2, the other end of the capacitor C2 is connected to the pin 4 of the transformer T; the pin 5 of the transformer T is connected to one end of the capacitor C4, the other end of the capacitor C4 is connected to the source of the MOS tube Q4 and one end of the inductor L4, the other end of the inductor L4 is connected to one end of the capacitor C8, the pin 6 of the transformer T is connected to the pin 7 of the transformer T, the drain of the MOS tube Q4, the source of the MOS tube Q3, the other end of the capacitor C8 and one end of the capacitor C7, the pin 8 of the transformer T is connected to one end of the capacitor C3, the other end of the capacitor C3 is connected to the drain of the MOS tube Q3 and one end of the inductor L3, and the other end of the inductor L3 is connected to the other end of the capacitor C7. In this embodiment, one end of the capacitor C5 and the other end of the capacitor C6 are connected to the power supply, and the other end of the capacitor C7 and one end of the capacitor C8 are connected to the load. The gates of the MOS tubes Q1, Q2, Q3 and Q4 are all connected to the MCU. The inductor L1 and the inductor L2 are coupled inductors, the inductor L3 and the inductor L4 are coupled inductors, one end of the inductor L1 and one end of the inductor L3 are the same end, and the other end of the inductor L2 and the other end of the inductor L4 are the same end.

[0028] As an implementation mode, the transformer T is a midpoint tapped transformer, pins 2 and 3 of the transformer T are the midpoints of the primary side, and pins 6 and 7 of the transformer T are the midpoints of the secondary side. Or, pins 1 and 2 of the transformer T share a coil, pins 3 and 4 of the transformer T share a coil, pins 5 and 6 of the transformer T share a coil, and pins 7 and 8 of the transformer T share a coil. It should be further explained that the use of other components to achieve the above-mentioned effects should all fall within the inventive concept of the present invention and should fall within the protection scope of the present invention.

[0029] Working principle:

[0030] When Q1 and Q2 are turned on at the same time, the current of inductors L1 and L2 increases. Capacitors C1 and C2 are connected in parallel with the primary side of transformer T, and the voltage of capacitors C1 and C2 is superimposed on the voltage of capacitors C3 and C4 through transformer T. After being filtered by L3, C7, L4, and C8, power is supplied to the load. Voltage stress of Q3 and Q4: V Q3DS +V Q4DS =L3di L3 / dt+L4di L4 / dt-V C7 -V C8 .

[0031] Inductors L1, L2, L3, and L4 are coupled inductors. Figure 2 When Q1 and Q2 are turned on at the same time, the currents of inductors L1, L2, L3, and L4 increase. Due to coupling, the ripple current in the inductors decreases. Q4 voltage stress: V Q3DS +V Q4DS =L3di L3 / dt+L4di L4 / dt-V C7 -V C8 .

[0032] Since the average voltage of the inductor and transformer is zero, V C1 =V C5 , V C6 =V C2 , V C3 =V C7 , V C4 =V C8 If V C7 With V C8 When a deviation occurs, the transformer with a center tap will automatically balance the voltage deviation and achieve voltage balance. This is connected to a three-level DC / AC inverter circuit to achieve single-phase, column-phase and three-phase AC inversion to adapt to unbalanced AC loads.

[0033] Embodiment 1

[0034] Series-parallel switching Figure 5 shown.

[0035] When S1 and S2 are closed and S3 is open, the outputs of C7 and C8 are connected in parallel. When S1 and S2 are open and S3 is closed, the outputs of C7 and C8 are connected in series. When Q1 and Q2 are turned on, the current of inductors L1 and L2 increases. The voltage of capacitors C1 and C2 is superimposed on C3 and C4 through the transformer, and the load is supplied with power through inductors L3, L4, capacitors C7 and C8. When Q1 and Q2 are turned off, the current of inductors L1 and L2 decreases, and capacitors C1 and C2 are charged. The body diodes of Q1 and Q2 are turned on, and the output circuit continues to flow.

[0036] In applications where the input or output voltage is high, the circuit can use lower withstand voltage switching tubes to achieve isolated bidirectional conversion, and the coupled inductor can reduce the input and output ripple current. By using a midpoint tap transformer, the input and output can achieve automatic midpoint balance, and can be used as a DC circuit at the midpoint of the isolation zone of a three-level inverter DC / AC.

[0037] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the embodiments. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the illustrations shown and described herein.

Claims

1. A bidirectional converter, characterized in that: It includes a capacitor C5, one end of which is connected to one end of an inductor L1, the other end of which is connected to the drain of a MOS tube Q1 and one end of the capacitor C1, the other end of which is connected to pin 1 of a transformer T, the other end of which is connected to one end of a capacitor C6, the source of the MOS tube Q1, the drain of the MOS tube Q2, pin 2 of the transformer T and pin 3 of the transformer T, the other end of which is connected to one end of an inductor L2, the other end of which is connected to the source of the MOS tube Q2 and one end of the capacitor C2, and the other end of which is connected to pin 4 of the transformer T; Pin 5 of the transformer T is connected to one end of the capacitor C4, the other end of the capacitor C4 is connected to the source of the MOS tube Q4 and one end of the inductor L4, the other end of the inductor L4 is connected to one end of the capacitor C8, pin 6 of the transformer T is connected to pin 7 of the transformer T, the drain of the MOS tube Q4, the source of the MOS tube Q3, the other end of the capacitor C8 and one end of the capacitor C7, pin 8 of the transformer T is connected to one end of the capacitor C3, the other end of the capacitor C3 is connected to the drain of the MOS tube Q3 and one end of the inductor L3, and the other end of the inductor L3 is connected to the other end of the capacitor C7.

2. A bidirectional converter according to claim 1, characterized in that: One end of the capacitor C5 and the other end of the capacitor C6 are connected to a power source, and the other end of the capacitor C7 and one end of the capacitor C8 are connected to a load.

3. A bidirectional converter according to claim 1, characterized in that: The transformer T is a midpoint tapped transformer, pins 2 and 3 of the transformer T are the midpoints of the primary side, and pins 6 and 7 of the transformer T are the midpoints of the secondary side.

4. A bidirectional converter according to claim 1, characterized in that: Pin 1 and pin 2 of the transformer T share a coil, pin 3 and pin 4 of the transformer T share a coil, pin 5 and pin 6 of the transformer T share a coil, and pin 7 and pin 8 of the transformer T share a coil.

5. A bidirectional converter according to claim 1, characterized in that: The gates of the MOS transistor Q1 , the MOS transistor Q2 , the MOS transistor Q3 and the MOS transistor Q4 are all connected to the MCU.

6. A bidirectional converter according to claim 1, characterized in that: The inductor L1 and the inductor L2 are coupled inductors, the inductor L3 and the inductor L4 are coupled inductors, one end of the inductor L1 and one end of the inductor L3 are the same end, and the other end of the inductor L2 and the other end of the inductor L4 are the same end.

7. A bidirectional converter according to claim 1, characterized in that: Pin 6 of the transformer T is connected to the drain of the MOS tube Q4 and the other end of the capacitor C8, and is connected to the other end of the inductor L3 and the other end of the capacitor C7 through a switch S1. Pin 7 of the transformer T is connected to the source of the MOS tube Q3 and one end of the capacitor C7, and is connected to pin 6 of the transformer T through a switch S2. One end of the capacitor C8 is connected to pin 7 of the transformer T through a switch S3.

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