CN211656023U - Single-stage AC-DC converter with current isolation - Google Patents

Abstract

The utility model belongs to the technical field of power electronic soft switches, and discloses a single-stage AC-DC converter with current isolation, which comprises an AC-DC conversion unit and a DC-DC conversion unit; the AC-DC conversion unit comprises a first inductor, a second inductor, a third inductor, a first power switch tube, a second power switch tube, a third power switch tube, a fourth power switch tube, a first capacitor and a second capacitor; the input end of the DC-DC conversion unit is connected with the connecting line of the first power switch tube and the third power switch tube and the connecting line of the second power switch tube and the fourth power switch tube, and the output end of the DC-DC conversion unit is used for connecting a load. The power conversion and current isolation device is simple in design, has no bridge, only has four power switching tubes in a topological structure and is used for power conversion and current isolation, compared with the existing single-stage AC-DC converter, the number of the power switching tubes is obviously reduced, higher conversion efficiency can be generated, the peak current stress of components is small, the power conversion and current isolation device can be operated close to a unit input power factor, the control is simple, and the cost is low.

Description

A single-stage AC-DC converter with galvanic isolation

technical field

The utility model belongs to the technical field of power electronic soft switching, and relates to a single-stage AC-DC converter with galvanic isolation.

Background technique

Three-phase AC-DC converters with galvanic isolation are widely used in industrial applications, and the harmonic content of these converters is limited by regulatory agency harmonic standards, so the converters are implemented with some form of input power factor correction. Traditional converters are two-stage converters with a three-phase AC-DC stage at the input followed by a DC-DC stage containing an isolation transformer; however, two-stage converters require a large number of switches and are therefore expensive and bulky.

Some scholars have proposed simpler, lighter and cheaper single-stage AC-DC converters, which can convert three-phase AC voltage into isolated DC voltage, these converters use only one converter to perform three-phase AC-DC Conversion and DC-DC conversion: such as three-phase two-switch ZVS PFC DCM boost converter, but the input part of this converter is not controlled, so the input current is discontinuous and the current peak value is very high. Another example is a three-level integrated AC-DC converter, but this converter has an input diode bridge inside. When there is more current in the converter, the conduction loss of the high-power converter will increase. There is also a resonant converter, but it works by a combination of variable switching frequency control and pulse width modulation, so complex and non-standard converter-specific control methods must be used to operate the converter, which is difficult to implement .

Utility model content

The purpose of this utility model is to overcome the shortcomings of the existing single-stage AC-DC converters in the above-mentioned prior art, such as large number of switches, high current stress, high control complexity and discontinuous input current, and to provide a single-stage AC-DC converter with galvanic isolation. stage AC-DC converter.

In order to achieve the above object, the utility model adopts the following technical solutions to be realized:

A single-stage AC-DC converter with galvanic isolation, comprising an AC-DC conversion unit and a DC-DC conversion unit; the AC-DC conversion unit includes a first inductor, a second inductor, a third inductor, and a first power switch tube , the second power switch tube, the third power switch tube, the fourth power switch tube, the first capacitor and the second capacitor; the source of the first power switch tube is connected to the drain of the third power switch tube, and the drain is connected to the second power switch tube The drain electrode of the power switch tube; the source electrode of the second power switch tube is connected to the drain electrode of the fourth power switch tube; the source electrode of the third power switch tube is connected to the source electrode of the fourth power switch tube; one end of the first capacitor is connected to the drain electrode of the fourth power switch tube; The drain of a power switch tube and the drain of the second power switch tube, the other end is connected to one end of the second capacitor; the other end of the second capacitor is connected to the source of the third power switch tube and the source of the fourth power switch tube One end of the first inductor, the second inductor and the third inductor are respectively used to connect the three-phase input power supply, the other end of the first inductor is connected to the connecting line of the first power switch tube and the third power switch tube, and the other end of the second inductor One end is connected to the connection line of the second power switch tube and the fourth power switch tube, and the other end of the third inductor is connected to the connection line of the first capacitor and the second capacitor; the input end of the DC-DC conversion unit is connected to the first power switch tube and The connection line of the third power switch tube and the connection line of the second power switch tube and the fourth power switch tube are both connected, and the output end is used for connecting the load.

The further improvement of the present utility model is:

The DC-DC conversion unit is an FB-ZVS-PWM converter.

The DC-DC conversion unit includes a DC blocking capacitor, a leakage inductance, an isolation transformer, a first diode and a second diode; one end of the DC blocking capacitor is connected to the connecting line of the first power switch tube and the third power switch tube, The other end is connected to one end of the primary side of the isolation transformer through leakage inductance, and the other end of the primary side of the isolation transformer is connected to the connecting line of the second power switch tube and the fourth power switch tube; the secondary side of the isolation transformer is provided with a first tap, a second tap and The third tap, the second tap is located between the first tap and the third tap, the first tap is connected to the anode of the first diode, and the second tap is connected to the anode of the second diode; when in use: one end of the load is connected to the The cathode of one diode and the cathode of the second diode are both connected, and the other end is connected to the second tap.

The DC-DC conversion unit also includes a filter inductor and a filter capacitor; one end of the filter capacitor is connected to the cathode of the first diode and the cathode of the second diode through the filter inductor, and the other end is connected to the second tap; when in use: load in parallel with the filter capacitor.

The AC-DC conversion unit further includes a first auxiliary capacitor, a second auxiliary capacitor, a third auxiliary capacitor and a fourth auxiliary capacitor; the first auxiliary capacitor, the second auxiliary capacitor, the third auxiliary capacitor and the fourth auxiliary capacitor are respectively connected with the The first power switch tube, the second power switch tube, the third power switch tube and the fourth power switch tube are connected in parallel one by one.

Also includes a first freewheeling diode, a second freewheeling diode, a third freewheeling diode and a fourth freewheeling diode, the first freewheeling diode, the second freewheeling diode, the third freewheeling diode and the fourth freewheeling diode respectively It is connected in anti-parallel with the first power switch tube, the second power switch tube, the third power switch tube and the fourth power switch tube.

The first power switch tube, the second power switch tube, the third power switch tube and the fourth power switch tube are all MOSFET tubes.

Compared with the prior art, the utility model has the following beneficial effects:

A single-stage AC-DC converter is formed by setting an AC-DC conversion unit and a DC-DC conversion unit, wherein the AC-DC conversion unit is a four-switch three-phase AC-DC converter, consisting of three input inductors, one with four It consists of a power switch tube and a four-switch three-phase rectifier with a capacitor to perform power factor correction and absorb the required active power from the grid to power the load and store it in two capacitors on the intermediate DC bus. . At the same time, there are only four power switch tubes in the AC-DC converter topology for power conversion and current isolation, the design is simple, and there is no bridge arm design. Therefore, compared with the existing single-stage AC-DC converter, the power switch tube The number is significantly reduced, so it can produce higher conversion efficiency and reduce costs; because after the three-phase six-switch converter is converted into a three-phase four-switch converter, it is only necessary to change one of the gate signals of the two legs when generating the switch signal. It can be achieved by any control method used in a standard three-phase six-switch voltage source converter without changing the pulse width modulation mode, so it is easier to control; at the same time, the single-stage AC-DC converter has The input current is continuous, so the peak current stress of the components will not be too large, so it is safer and more reliable in use and has a wider range of use.

Further, setting the filter inductor and filter capacitor can filter out the unnecessary AC part of the voltage, so that the output DC voltage is smoother.

Further, four auxiliary capacitors are set, which are respectively connected in parallel with the four power switch tubes to ensure that the voltage of the power switch tubes does not suddenly reach the output voltage, thereby helping to reduce the turn-off loss.

Further, each power switch tube is connected in anti-parallel with a freewheeling diode. When the freewheeling diode is turned on before the power switch tube is turned on, the power switch tube works under the ZVS condition, which effectively reduces the switching loss.

Description of drawings

1 is a circuit diagram of a single-stage AC-DC converter of the present invention;

Fig. 2 is the equivalent circuit diagram of the 1st working mode of the utility model;

Fig. 3 is the equivalent circuit diagram of the 2nd kind of working mode of the present utility model;

Fig. 4 is the equivalent circuit diagram of the 3rd working mode of the utility model;

Fig. 5 is the equivalent circuit diagram of the 4th working mode of the present utility model;

Fig. 6 is the equivalent circuit diagram of the 5th working mode of the utility model;

Fig. 7 is the equivalent circuit diagram of the 6th working mode of the present invention;

Fig. 8 is the equivalent circuit diagram of the 7th working mode of the present utility model;

FIG. 9 is an equivalent circuit diagram of the eighth operating mode of the present invention.

Among them: e _a , e _b and e _c are three-phase input power supply; L is inductance; S ₁ -S ₄ are power switch tubes; C ₁ and C ₂ are capacitors; C _b is DC blocking capacitor; L _1k is leakage inductance ; D ₁ and D ₂ are diodes; L _o is the filter inductor; C _o is the filter capacitor; R _L is the load.

Detailed ways

In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described The embodiments are only some of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative work shall fall within the protection scope of the present invention.

It should be noted that the terms "first" and "second" in the description and claims of the present invention and the above drawings are used to distinguish similar objects, and are not necessarily used to describe a specific sequence or sequence. . It is to be understood that the data so used may be interchanged under appropriate circumstances so that the embodiments of the invention described herein can be practiced in sequences other than those illustrated or described herein. Furthermore, the terms "comprising" and "having" and any variations thereof, are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those expressly listed Rather, those steps or units may include other steps or units not expressly listed or inherent to these processes, methods, products or devices.

Below in conjunction with accompanying drawing, the utility model is described in further detail:

Referring to FIG. 1 , the present invention has a single-stage AC-DC converter with galvanic isolation, including an AC-DC conversion unit 1 and a DC-DC conversion unit 2 .

The AC-DC conversion unit 1 includes a first inductor, a second inductor, a third inductor, a first power switch S ₁ , a second power switch S ₂ , a third power switch S ₃ , and a fourth power switch S ₄ , a first capacitor _C1 and a _second capacitor C2; the source of the _first power switch S1 is connected to the drain of the _third power switch S3, and the drain is connected to the drain of the _second power switch S2; The source of the _second power switch S2 is connected to the drain of the _fourth power switch S4; the source of the _third power switch S3 is connected to the source of the _fourth power switch S4; _one end of the first capacitor C1 The drain of the _first power switch S1 and the drain of the _second power switch S2 are connected, and the other end is connected to one end of the _second capacitor C2 _; the other end of the second capacitor C2 is connected to the _third power switch S3 and the source of the _fourth power switch tube S4; one end of the first inductance, the second inductance and the third inductance are respectively used to connect the three-phase input power sources e _a , e _b and e _c , and the other end of the first inductance One end is connected to the connection line of the _first power switch S1 and the _third power switch S3, the other end of the second inductor is connected to the connection line of the _second power switch S2 and the _fourth power switch S4, the third inductor The other end is connected to the connection line of the first capacitor _C1 and the second capacitor C2; the input end of the DC-DC conversion unit ₂ is connected to the connection line of the _first power switch tube S1 and the _third power switch tube S3 and the second power switch tube S3. The connection lines of the power switch tube S ₂ and the fourth power switch tube 4 are both connected, and the output end is connected to the load _RL .

The first power switch S ₁ , the second power switch S ₂ , the third power switch S ₃ and the fourth power switch S ₄ are all MOSFETs.

The DC-DC conversion unit 2 is an FB-ZVS-PWM converter. Specifically, the DC-DC conversion unit 2 includes a DC blocking capacitor C _b , a leakage inductance L _1k , an isolation transformer, a first diode D ₁ and a second two pole tube D2 _; one end of the blocking capacitor _Cb is connected to the connecting line of the _first power switch tube S1 and the _third power switch tube S3, the other end is connected to one end of the primary side of the isolation transformer through the leakage inductance, and the other end of the primary side of the isolation transformer is connected One end is connected to the connecting line of the _second power switch tube S2 and the _fourth power switch tube S4; the secondary side of the isolation transformer is provided with a first tap, a second tap and a third tap, and the second tap is located at the first tap and the third tap. In between, the first tap is connected to the anode of the _first diode D1, and the second tap is connected to the anode of the _second diode D2; when in use: one end of the load is connected to the cathode of the _first diode D1 and the second _The cathodes of diode D2 are both connected, and the other end is connected to the second tap.

In a preferred embodiment, the above _- mentioned DC-DC conversion unit 2 of the single-stage AC-DC converter with galvanic isolation further includes a filter inductor L _o and a filter capacitor C _{o ;} The cathode of _a diode D1 and the cathode of the _second diode D2, and the other end is connected to the second tap; in use state: the load is connected in parallel with the filter capacitor C _o . By setting the filter inductor L _o and the filter capacitor C _o , the unnecessary AC part of the voltage can be filtered out, so that the output DC voltage is smoother.

In a preferred embodiment, the above-mentioned AC-DC conversion unit 1 with a galvanically isolated single-stage AC-DC converter further includes a first auxiliary capacitor, a second auxiliary capacitor, a third auxiliary capacitor and a fourth auxiliary capacitor; the first auxiliary capacitor The auxiliary capacitor, the second auxiliary capacitor, the third auxiliary capacitor and the fourth auxiliary capacitor are respectively connected with the first power switch S ₁ , the second power switch S ₂ , the third power switch S ₃ and the fourth power switch S ₄ One by one in parallel. By setting the auxiliary capacitor, it is ensured that the voltage of the power switch tube does not suddenly reach the output voltage, thereby helping to reduce the turn-off loss.

In a preferred embodiment, the above-mentioned AC-DC conversion unit 1 with a galvanically isolated single-stage AC-DC converter further comprises a first freewheeling diode, a second freewheeling diode, a third freewheeling diode and a fourth freewheeling diode diodes, the first freewheeling diode, the second freewheeling diode, the third freewheeling diode and the fourth freewheeling diode are respectively connected with the first power switch tube S ₁ , the second power switch tube S ₂ , and the third power switch tube S ₃ In anti-parallel with the _fourth power switch tube S4, when the freewheeling diode is turned on before the power switch tube is turned on, the power switch tube works under the ZVS condition, which effectively reduces the switching loss.

The working principle and process of the single-stage AC-DC converter with galvanic isolation of the present utility model are described below:

AC-DC conversion unit 1 is a four-switch pulse width modulated voltage source, this part performs power factor correction and absorbs the required active power from the grid, powers the load _RL and stores it in the first on the intermediate DC bus capacitor _C1 and the _second capacitor C2. In order to perform these operations, the AC-DC conversion unit 1 should apply appropriate three-phase balanced voltages at the converter terminals A, B and C, and since only two branches of the AC-DC conversion unit 1 have active switches, the two an active branch, i.e. the phase difference between the voltages of phase A and phase B is 60° instead of 120°. The DC-DC conversion unit 2 is a traditional FB-ZVS-PWM converter, and its strobe signal can be generated in the SPWM mode. The single-stage AC-DC converter has 8 continuous operating modes in one switching cycle. In working mode as shown:

Before the first working mode starts, it is assumed that the _first power switch S1 and the _second power switch S2 are turned on, and there is a dead zone between switching transitions.

The first working mode: Referring to FIG. 2 , at the beginning of this mode, the _second power switch S2 is turned off, and the primary current I _pri of the isolation transformer begins to flow through the anti-parallel diode of the _fourth power switch S4. V _AB is equal to the bus voltage V _PN , and I _pri increases linearly. In this mode, the _fourth power switch S4 can be turned on through the zero-voltage switch ZVS before I _pri reaches zero. In this mode, V _sec1 and V _sec2 are both zero, the current I _Lo of the filter inductor _Lo flows through the first diode D ₁ and the second diode D ₂ on the secondary side, this is the freewheeling mode, No energy is transferred from the primary side of the isolation transformer to the secondary side, i.e. no energy is transferred to the output.

The second working mode: refer to Fig. 3, at the beginning of this mode, I _pri becomes positive, flows through the first power switch S ₁ and the fourth power switch S ₄ , V _AB is equal to the bus voltage V _PN , the isolation transformer The primary voltage of is positive, when V _sec1 is positive and the first diode D ₁ conducts, the energy from the first capacitor C ₁ and the second capacitor C ₂ is transferred to the output.

The third working mode: referring to FIG. 4 , at the beginning of this mode, the _first power switch S1 is turned off, and I _pri flows through the anti _- parallel diode of the first power switch S3. The voltage at both ends of V _AB is zero, the voltage V _Cb of the blocking capacitor C _b is applied to the primary side winding of the isolation transformer, and I _pri decreases linearly. In this mode, the energy will not be transferred from the primary side to the secondary side of the isolation transformer, the output current is circulated through the _first diode D1 and the _second diode D2, and the first power switch S3 can be _combined with ZVS opens together.

The 4th working mode: refer to Figure 4, at the beginning of this mode, I _pri becomes negative, flows through the anti-parallel diodes of the _third power switch S3 and the _fourth power switch S4, and V _Cb is applied to the isolation transformer Primary side winding. In this mode, V _sec2 is a positive value, which is equal to the reflection value of V _Cb , and at the same time the second diode D ₂ is turned on, and the current I _Lo of the filter inductor L _o at the output increases. Capacitor _Cb is passed to the output.

The fifth working mode: referring to FIG. 6 , at the beginning of this mode, the _first power switch S1 is turned on, and this mode is the same as the first working mode.

The sixth operating mode: see Figure 7, at the beginning of this mode, the direction of I _pri changes. This mode is the same as the second working mode. At the end of this mode, the _fourth power switch S4 is turned off, and I _pri flows through the anti-parallel diode of the _second power switch S2.

The seventh working mode: refer to Figure 8, at the beginning of this mode, the _second power switch S2 is turned on through ZVS, the voltage across V _AB is zero, V _Cb is applied to the primary side winding of the isolation transformer, and Ipri decreases linearly. In this mode, energy is not transferred from the input to the output, and the output current circulates through the _first diode D1 and the _second diode D2.

The eighth working mode: refer to Figure 9, at the beginning of this mode, Ipri becomes a negative value, flows through the first power switch S ₁ and the second power switch S ₂ , V _Cb is applied to the primary side winding of the isolation transformer, The voltage and current in the isolation transformer and secondary coil are the same as in the 4th operating mode. It can be seen that the working mode of the AC-DC converter is relatively simple, and several modes are the same, so it is compatible with the design and application, and the energy cannot be transmitted to the output end in individual modes, achieving the effect of galvanic isolation.

The utility model has a single-stage AC-DC converter with galvanic isolation, and has simple design, no bridge, and only four power switch tubes in the topology structure for power conversion and current isolation. Compared with the existing single-stage AC-DC converter, the utility model has the advantages of: The number of power switch tubes is significantly reduced, so higher conversion efficiency can be generated; since the three-phase six-switch converter is converted into a three-phase four-switch converter, only the gate signals of two legs need to be changed when generating the switch signal The phase relationship between PWM and PWM can be achieved with any control method used in standard three-phase six-switch voltage source converters without changing the pulse width modulation mode, so it is easier to control; while the single-stage AC-DC converter The input current is continuous, so the peak current stress of the components will not be too large, so it is safer and more reliable in use and has a wider range of use; When the freewheeling diode is turned on before it is turned on, the power switch tube works under the ZVS condition, which effectively reduces the switching loss; therefore, compared with similar structures, it is the simplest and cheapest three-phase single-stage AC current isolation. -DC converter.

The above content is only to illustrate the technical idea of the present utility model, and cannot limit the protection scope of the present utility model. Any changes made on the basis of the technical solution according to the technical idea proposed by the present utility model fall into the scope of the present utility model. within the scope of protection of the claims.

Claims (7)

1. A single-stage AC-DC converter with galvanic isolation, characterized by comprising an AC-DC conversion unit (1) and a DC-DC conversion unit (2);

the AC-DC conversion unit (1) comprises a first inductor, a second inductor, a third inductor, a first power switch tube, a second power switch tube, a third power switch tube, a fourth power switch tube, a first capacitor and a second capacitor;

the source electrode of the first power switch tube is connected with the drain electrode of the third power switch tube, and the drain electrode of the first power switch tube is connected with the drain electrode of the second power switch tube; the source electrode of the second power switch tube is connected with the drain electrode of the fourth power switch tube; the source electrode of the third power switch tube is connected with the source electrode of the fourth power switch tube; one end of the first capacitor is connected with the drain electrode of the first power switch tube and the drain electrode of the second power switch tube, and the other end of the first capacitor is connected with one end of the second capacitor; the other end of the second capacitor is connected with a source electrode of the third power switch tube and a source electrode of the fourth power switch tube; one end of the first inductor, one end of the second inductor and one end of the third inductor are respectively used for connecting a three-phase input power supply, the other end of the first inductor is connected with a connecting wire of the first power switch tube and a connecting wire of the third power switch tube, the other end of the second inductor is connected with a connecting wire of the second power switch tube and a connecting wire of the fourth power switch tube, and the other end of the third inductor is connected with a connecting wire of the first capacitor and the second capacitor;

the input end of the DC-DC conversion unit (2) is connected with the connecting line of the first power switch tube and the third power switch tube and the connecting line of the second power switch tube and the fourth power switch tube, and the output end of the DC-DC conversion unit is used for connecting a load.

2. Single-stage AC-DC converter with galvanic isolation according to claim 1, characterized in that the DC-DC conversion unit (2) is a FB-ZVS-PWM converter.

3. The single-stage AC-DC converter with galvanic isolation according to claim 1, characterized in that the DC-DC conversion unit (2) comprises a DC blocking capacitance, a leakage inductance, an isolation transformer, a first diode and a second diode;

one end of the blocking capacitor is connected with a connecting line of the first power switch tube and the third power switch tube, the other end of the blocking capacitor is connected with one end of the primary side of the isolation transformer through leakage inductance, and the other end of the primary side of the isolation transformer is connected with a connecting line of the second power switch tube and the fourth power switch tube; the secondary side of the isolation transformer is provided with a first tap, a second tap and a third tap, the second tap is positioned between the first tap and the third tap, the first tap is connected with the anode of the first diode, and the second tap is connected with the anode of the second diode;

when in use state: one end of the load is connected with the cathode of the first diode and the cathode of the second diode, and the other end of the load is connected with the second tap.

4. Single-stage AC-DC converter with galvanic isolation according to claim 3, characterized in that the DC-DC conversion unit (2) further comprises a filter inductance and a filter capacitance;

one end of the filter capacitor is connected with the cathode of the first diode and the cathode of the second diode through the filter inductor, and the other end of the filter capacitor is connected with a second tap; when in use state: the load is connected in parallel with the filter capacitor.

5. The single-stage AC-DC converter with galvanic isolation according to claim 1, characterized in that the AC-DC conversion unit (1) further comprises a first auxiliary capacitance, a second auxiliary capacitance, a third auxiliary capacitance and a fourth auxiliary capacitance;

the first auxiliary capacitor, the second auxiliary capacitor, the third auxiliary capacitor and the fourth auxiliary capacitor are respectively connected with the first power switch tube, the second power switch tube, the third power switch tube and the fourth power switch tube in parallel one by one.

6. The single-stage AC-DC converter with galvanic isolation of claim 1, further comprising a first freewheeling diode, a second freewheeling diode, a third freewheeling diode, and a fourth freewheeling diode, the first freewheeling diode, the second freewheeling diode, the third freewheeling diode, and the fourth freewheeling diode being anti-parallel to the first power switch tube, the second power switch tube, the third power switch tube, and the fourth power switch tube, respectively.

7. The single-stage AC-DC converter with galvanic isolation of claim 1, wherein the first power switch, the second power switch, the third power switch and the fourth power switch are all MOSFET transistors.

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