CN111525808A

CN111525808A - Isolated charging power supply

Info

Publication number: CN111525808A
Application number: CN202010307720.8A
Authority: CN
Inventors: 卓廷厚; 张维娜
Original assignee: Xiamen Xinguang Runze Technology Co ltd
Current assignee: Xiamen Xinguang Runze Technology Co ltd
Priority date: 2020-04-17
Filing date: 2020-04-17
Publication date: 2020-08-11

Abstract

An isolated charging power supply comprising: an alternating current power supply for supplying alternating current power; a first rectifying circuit for rectifying alternating-current power supplied from the alternating-current power supply; the at least two conversion circuits are connected in parallel, and the input of each conversion circuit is connected with the output of the first rectifying circuit; the input of one isolation transformer is correspondingly connected with the output of one conversion circuit; the input of one second rectifying circuit is correspondingly connected with the output of one isolation transformer; and the switching circuit is connected between two adjacent second rectifying circuits and is used for switching the connection structure between the second rectifying circuits between a series connection structure and a parallel connection structure. The output voltage range of the isolation charging power supply is expanded.

Description

Isolated charging power supply

Technical Field

The invention relates to the field of charging power supplies, in particular to an isolated charging power supply.

Background

With the national large-scale popularization of new energy automobiles, the popularization degree of the new energy automobiles is higher and higher. The new energy automobile is different from a fuel automobile and can be refueled at a gas station, but a charging pile is needed to charge. Along with the popularization of new energy vehicles, the demand of charging piles is also rapidly increasing.

At present, common charging piles are divided into alternating current charging piles and direct current charging piles. Because the charging power of alternating-current charging stake is less, be difficult to satisfy new energy automobile quick charge's requirement, consequently more and more the direct-current charging stake of the more and more trend of electric pile of filling of new installation. The basic function of the direct current charging pile is to isolate alternating current and convert the alternating current into direct current to directly charge the battery.

With the development of battery technology, in order to improve the power of a new energy automobile, on one hand, the current capacity of a battery is larger and larger, and on the other hand, the voltage of the battery is higher and higher. The battery voltage has reached over 800V from the first 300V to now. This means that the battery voltage of present new energy automobile 300V ~ 800V all has, and corresponding electric pile that fills is as charging source, also must satisfy the charging voltage range of at least 200V ~ 800V. However, the existing charging power supply cannot meet the design requirement of the charging pile.

Disclosure of Invention

The invention solves the problem of providing an isolated charging power supply, so that the charging power supply can have a wider output range.

To solve the above problems, the present invention provides an isolated charging power supply, comprising: an alternating current power supply for supplying alternating current power; a first rectifying circuit for rectifying alternating-current power supplied from the alternating-current power supply; the at least two conversion circuits are connected in parallel, and the input of each conversion circuit is connected with the output of the first rectifying circuit; the input of one isolation transformer is correspondingly connected with the output of one conversion circuit; the input of one second rectifying circuit is correspondingly connected with the output of one isolation transformer; and the switching circuit is connected between two adjacent second rectifying circuits and is used for switching the connection structure between the second rectifying circuits between a series connection structure and a parallel connection structure.

Optionally, the number of the conversion circuit, the isolation transformer and the second rectification circuit is two; the switching circuit comprises a first switching tube, a second switching tube and a third switching tube; the first end of the first switching tube is connected with the positive end of the first second rectifying circuit; the second end of the first switching tube is connected with the positive end of a second rectifying circuit; the first end of the second switching tube is connected with the positive end of the second rectifying circuit; the second end of the second switching tube is connected with the ground end of the first second rectifying circuit; the first end of the third switching tube is connected with the ground end of the first second rectifying circuit; the second end of the third switching tube is connected with the ground end of the second rectifying circuit; and the third end of the first switching tube, the third end of the second switching tube and the third end of the third switching tube are connected with a control unit.

Optionally, the first switching tube, the second switching tube and the third switching tube are NMOS tubes;

the first end of the first switch tube is a drain electrode, the second end of the first switch tube is a source electrode, and the third end of the first switch tube is a grid electrode;

the first end of the second switch tube is a drain electrode, the second end of the second switch tube is a source electrode, and the third end of the second switch tube is a grid electrode;

the first end of the third switching tube is a drain electrode, the second end of the third switching tube is a source electrode, and the third end of the third switching tube is a grid electrode.

Optionally, the isolation charging power supply further includes an input filter capacitor, and the input filter capacitor is located at the front end of the conversion circuit.

Optionally, each of the isolation transformers further has a resonant inductor at an input terminal thereof.

Optionally, the inverter circuit is a full bridge circuit.

Optionally, the isolation charging power supply further includes an output filter capacitor, and the output filter capacitor is located at the rear end of the second rectifying circuit.

Optionally, one of the conversion circuits, the corresponding one of the resonant inductors, one of the isolation transformers, one of the second rectification circuits, and the output filter capacitor form a full-bridge LLC circuit or a full-bridge CLLC circuit.

Optionally, an MOS transistor or an IGBT transistor is used as the switching transistor in the full bridge circuit of the inverter circuit.

Optionally, the ac power supply is a three-phase ac power supply, and when the three-phase ac power supply is connected to the first rectifying circuit (110), each phase has an inductor (L1/L2/L3) on its corresponding line.

In one aspect of the technical scheme of the invention, the isolation charging power supply performs series-parallel switching on the second rectifying circuit through the switching circuit, so that the output voltage can be adjusted among multiple times of the lowest output voltage, and therefore, the adjustment range of the output voltage can be expanded.

Drawings

FIG. 1 is a circuit diagram of a topology provided by an embodiment of the present invention;

FIG. 2 is a circuit diagram of a topology according to another embodiment of the present invention;

fig. 3 is a circuit diagram of a topology according to another embodiment of the present invention.

Detailed Description

In the existing charging power supply, after an alternating current power supply enters a circuit, the alternating current power supply converts alternating current into direct current. The dc power is then converted to ac power that can be passed through an isolation transformer. The converted power supply passes through an isolation transformer and then is converted into a direct current power supply through a rectifying circuit to charge the battery pack.

Because the charging current of the charging pile is very large, the conversion circuit can adopt a full-bridge LLC circuit. When the battery is charged, the voltage of the battery rises from a low voltage to a rated voltage, so that the output voltage of the LLC circuit also rises from a low voltage to a high voltage. According to the principles of LLC circuits, the output voltage is generally regulated by adjusting the operating frequency of the conversion circuit. The specific principle is as follows: when the battery voltage is low, the switching frequency of the LLC is high. As the battery voltage rises, the charging voltage of the charging circuit decreases; the switching frequency of the LLC is reduced, so that the output voltage of the power supply is improved, and further the charging current is increased to reach the rated charging current of the charging pile; the LLC circuit does not increase the charging frequency to reduce the charging current until the battery voltage reaches the maximum charging voltage, and does not turn off the output until the charging current is zero.

According to the above principle, the voltage output range of a charging pile depends on the voltage output range of the LLC circuit. The wider the output voltage range is, the lower the efficiency of the LLC circuit will be, and the output voltage range is typically around 2:1 and not more than 3: 1. Due to the characteristic property of the LLC circuit, the existing charging scheme improved by the LLC circuit is difficult to meet the requirement of the charging pile. Therefore, the problem that the output voltage range is narrow exists in the current charging pile LLC charging circuit scheme.

Therefore, the invention provides a novel isolated charging power supply to solve the existing defects.

For a more clear presentation, the invention is described in detail below with reference to the accompanying drawings.

An embodiment of the invention provides an isolated charging power supply, please refer to fig. 1. The isolated charging power supply includes:

an ac power source (not separately labeled, as shown by lines a, B, and C connected to the leftmost end of fig. 1) for supplying ac power;

a first rectifier circuit 110, the first rectifier circuit 110 rectifying ac power supplied from an ac power supply;

the two conversion circuits are respectively a conversion circuit 121 and a conversion circuit 122, the conversion circuit 121 and the conversion circuit 122 are connected in parallel, and the input of the conversion circuit 121 and the input of the conversion circuit 122 are both connected with the output of the first rectification circuit 110; the conversion circuit 121 and the conversion circuit 122 convert the output from the rectifier circuit 110 into an alternating current;

the input of the isolation transformer T1 is correspondingly connected to the output of the conversion circuit 121, and the input of the isolation transformer T2 is correspondingly connected to the output of the conversion circuit 122; the isolation transformer is connected between the conversion circuit and other subsequent circuits, so that the other subsequent circuits are electrically insulated from the alternating current power supply;

two second rectifying circuits, namely a second rectifying circuit 131 and a second rectifying circuit 132, wherein the input of one second rectifying circuit is correspondingly connected with the output of one isolation transformer, specifically, the input of the second rectifying circuit 131 is correspondingly connected with the output of the isolation transformer T1, and the input of the second rectifying circuit 132 is correspondingly connected with the output of the isolation transformer T2; the second rectifying circuit rectifies the output of the isolation transformer and is used for outputting the output to a corresponding battery BA to be charged;

a switching circuit 140, the switching circuit 140 is connected between two adjacent second rectification circuits, that is, between the second rectification circuit 131 and the second rectification circuit 132 in this embodiment, and the switching circuit 140 is configured to switch the connection structure between the second rectification circuit 131 and the second rectification circuit 132 between a series connection structure and a parallel connection structure.

After passing through the switching circuit, the isolated charging power supply may be used to charge the corresponding battery BA to be charged, as shown in fig. 1.

As can be seen from the above structure, in this embodiment, the input terminals of the two isolation transformers (the isolation transformer T1 and the isolation transformer T2) are connected in parallel through the converting circuit (the converting circuit 121 and the converting circuit 122), the output terminals of the two isolation transformers (the isolation transformer T1 and the isolation transformer T2) are respectively connected to one rectifying circuit (the isolation transformer T1 is connected to the second rectifying circuit 131, the isolation transformer T2 is connected to the second rectifying circuit 132), and the two rectifying circuits (the second rectifying circuit 131 and the second rectifying circuit 132) are connected together through the switching circuit 140. This kind of structure makes the isolation charging power supply of this embodiment can realize the output voltage scope of broad to satisfy new energy automobile to filling the requirement of electric pile.

In this embodiment, the input terminals of the isolation transformer are connected in parallel through the transformation circuit, that is, the input terminals of the isolation transformer T1 and the isolation transformer T2 are connected in parallel and then connected to the output terminals of the corresponding transformation circuit 121 and transformation circuit 122, respectively.

It should be noted that the switching circuit of the present invention is connected between two adjacent second rectification circuits, where the meaning that the switching circuit is connected between two adjacent second rectification circuits means that if there are K (K is an integer greater than or equal to 2) second rectification circuits, there may be K-1 switching circuits, but there may also be an integrated switching circuit, and in this case, the integrated switching circuit is a circuit in which K-1 individual switching circuits are unified. In short, the switching circuit is used for ensuring that the switching between the series connection structure and the parallel connection structure can be realized between different second rectifying circuits.

Referring to fig. 1, in the present embodiment, the switching circuit 140 includes a first switch Q23, a second switch Q24 and a third switch Q25. A first end of the first switching tube Q23 is connected to the positive terminal of the second rectifying circuit 131. A second end of the first switch Q23 is connected to the positive end of the second rectifying circuit 132. A first end of the second switching tube Q24 is connected to the positive end of the second rectifying circuit 132. A second end of the second switching tube Q24 is connected to the ground end of the second rectifying circuit 131. A first end of the third switching tube Q25 is connected to the ground end of the second rectifying circuit 131. A second end of the third switching tube Q25 is connected to the ground end of the second rectifying circuit 132.

Although not shown in the drawings, the connection control unit for the third terminal of the first switch Q23, the third terminal of the second switch Q24 and the third terminal of the third switch Q25 may be a processor (not shown) for isolating the charging power supply.

Referring to fig. 1, in the present embodiment, the first switch Q23, the second switch Q24, and the third switch Q25 are all NMOS transistors (N-channel MOS transistors). The first switch Q23 has a first terminal serving as a drain (D), a second terminal serving as a source (S), and a third terminal serving as a gate (G).

Similarly, the second switch Q24 has a first terminal serving as a drain, a second terminal serving as a source, and a third terminal serving as a gate. The third switch Q25 has a first terminal serving as a drain, a second terminal serving as a source, and a third terminal serving as a gate.

In other embodiments, the first switching transistor Q23, the second switching transistor Q24, and the third switching transistor Q25 may also be PMOS transistors. At this time, other device structures of the overall topology of fig. 1 may be replaced accordingly according to the replacement of the device.

In this embodiment, the isolated charging power supply further includes an input filter capacitor C1, and the input filter capacitor C1 is located at the front ends of the converting circuit 121 and the converting circuit 122.

In this embodiment, each isolation transformer has a resonant inductor at its input terminal. Specifically, the isolation transformer T1 further has a resonant inductor L4 at its input terminal, and the isolation transformer T2 further has a resonant inductor L5 at its input terminal.

In this embodiment, the first rectifying circuit 110 includes corresponding bridge rectifying circuits, specifically including an upper arm, a middle arm, and a lower arm. The upper arm is provided with a switching tube Q1 and a switching tube Q2 which are respectively connected in series, the middle arm is provided with a switching tube Q3 and a switching tube Q4 which are respectively connected in series, and the lower arm is provided with a switching tube Q5 and a switching tube Q6 which are respectively connected in series.

Meanwhile, the corresponding ac power supply in this embodiment is a three-phase ac power supply, and when the three-phase ac power supply is connected to the first rectification circuit 110, each phase has an inductor on the corresponding line, as shown in fig. 1, the three-phase ac power supply is divided into a line a, a line B, and a line C, which are respectively connected to an inductor L1, an inductor L2, and an inductor L3. The line A, the line B and the line C are respectively connected to the middle of the upper arm, the middle arm and the lower arm.

In this embodiment, the first rectifying circuit 110 is made of various NMOS transistors, and can simultaneously realize the function of a pfc (power Factor correction) circuit to perform power Factor correction.

In this embodiment, the inverter circuit 121 and the inverter circuit 122 are full bridge circuits. As shown in fig. 1, the full bridge circuit of the inverter circuit 121 includes a switch Q7, a switch Q8, a switch Q11, and a switch Q12. The full bridge circuit of the inverter circuit 122 includes a switch transistor Q9, a switch transistor Q10, a switch transistor Q13 and a switch transistor Q14.

In this embodiment, the full-bridge circuits of the inverter circuit 121 and the inverter circuit 122 use silicon carbide MOS transistors as the corresponding switching transistors. Namely, the switching tube Q7, the switching tube Q8, the switching tube Q11, the switching tube Q12, the switching tube Q9, the switching tube Q10, the switching tube Q13 and the switching tube Q14 all adopt silicon carbide MOS tubes, and specifically adopt NMOS tubes. Furthermore, a silicon carbide MOS tube with 1200V voltage can be adopted as a switching tube of the conversion circuit.

In other embodiments, the full bridge circuits of the inverter circuit 121 and the inverter circuit 122 may be configured by a gan MOS transistor or the like. On the aspect of high-frequency rectification characteristics, the silicon carbide MOS tube and the gallium nitride MOS tube are superior to the silicon MOS tube. In other embodiments, however, silicon MOS transistors or IGBT transistors may be used for these full-bridge circuits.

As described above, when each switching transistor of the converting circuit 121 is an NMOS transistor, the drain of the switching transistor Q8, the source of the switching transistor Q7, the source of the switching transistor Q11, and the drain of the switching transistor Q12 in the converting circuit 121 are connected to the primary side of the isolation transformer T1 (i.e., the input terminal of the isolation transformer T1), that is, the output terminal of the converting circuit 121 is connected to the input terminal of the isolation transformer T1.

As described above, when each switching transistor of the converting circuit 122 is an NMOS transistor, the drain of the switching transistor Q10, the source of the switching transistor Q9, the source of the switching transistor Q13, and the drain of the switching transistor Q14 in the converting circuit 122 are connected to the primary side of the isolation transformer T2 (i.e., the input terminal of the isolation transformer T2), that is, the output terminal of the converting circuit 122 is connected to the input terminal of the isolation transformer T2.

In this embodiment, the second rectifying circuit 131 and the second rectifying circuit 132 are bridge rectifying circuits, each of which includes two upper and lower arms connected in parallel, each of the upper and lower arms includes 2 rectifying elements connected in series, and in this embodiment, the rectifying elements are diodes. The upper arm of the second rectifier circuit 131 includes a diode D1 and a diode D3, and the lower arm of the second rectifier circuit 131 includes a diode D2 and a diode D4. The output of the isolation transformer T1 is connected between the upper arm and the lower arm of the second rectifier circuit 131. The upper arm of the second rectifier circuit 132 includes a diode D5 and a diode D7, and the lower arm of the second rectifier circuit 132 includes a diode D6 and a diode D8. The output of the isolation transformer T2 is connected between the upper arm and the lower arm of the second rectifier circuit 132.

In this embodiment, the isolated charging power supply further includes an output filter capacitor C5, and the output filter capacitor C5 is located at the rear ends of the second rectifying circuit 131 and the second rectifying circuit 132.

In this embodiment, the output filter capacitor C5 is further installed at the rear end of the switching circuit 140, that is, the output filter capacitor C5 is located between the battery BA to be charged and the

second rectifying circuit

131 and 132.

In this embodiment, a full-bridge LLC circuit is formed by one conversion circuit, a corresponding resonant inductor, an isolation transformer, a second rectification circuit, and an output filter capacitor C5. Specifically, the conversion circuit 121, the corresponding resonant inductor L4, the isolation transformer T1, the second rectifying circuit 131, and the output filter capacitor C5 form a full bridge LLC circuit. The conversion circuit 122, the corresponding resonant inductor L5, the isolation transformer T2, the second rectifying circuit 132 and the output filter capacitor C5 form a full bridge LLC circuit. The full-bridge LLC circuit has higher power density and is suitable for high-power occasions. In other embodiments, a full-bridge CLLC circuit may be further formed by adding a capacitor to a conversion circuit and a corresponding resonant inductor, an isolation transformer, a second rectification circuit, and the output filter capacitor C5, and the full-bridge CLLC circuit may implement bidirectional voltage output.

In this embodiment, the turns ratios of the primary coil and the secondary coil of the isolation transformer T1 and the isolation transformer T2 may be 2.5: 1.

in other embodiments, the winding turns ratio of the isolation transformer may be other values.

The principle of the isolated charging power supply provided by the embodiment for realizing the wide output range is as follows:

two different connection configurations are implemented by the switching circuit 140;

in the first connection structure, the first switch Q23 and the third switch Q25 are turned on, the second switch Q24 is turned off, and at this time, the second rectification circuit 131 and the second rectification circuit 132 output in parallel, that is, if the maximum output voltage range output in one way is 3:1, calculating that the output voltage is still 3 after parallel connection: 1;

in the second connection structure, the second switching tube Q24 is turned on, the first switching tube Q23 and the third switching tube Q25 are turned off, and at this time, the second rectifying circuit 131 and the second rectifying circuit 132 output in series, that is, if the maximum output voltage range output in one way is 3:1, the output voltage becomes 6: 1, it is clear that the range of the output voltage of the series arrangement is significantly broadened.

Therefore, the topological structure provided by the invention can effectively widen the output voltage range and can provide at least more than two different output voltage ranges.

As mentioned above, in this embodiment, the conversion circuit 121, the corresponding resonant inductor L4, the isolation transformer T1, the second rectifying circuit 131, and the output filter capacitor C5 form a full bridge LLC circuit; the conversion circuit 122, the corresponding resonant inductor L5, the isolation transformer T2, the second rectifying circuit 132 and the output filter capacitor C5 form a full bridge LLC circuit. On the basis of the circuit structure, when a 380V three-phase alternating current power supply is input and the full-bridge LLC circuit of the embodiment enters full resonance, the output voltage of the single-path second rectifying circuit is about 256V-360V. And the working frequency of the full-bridge LLC circuit is adjusted to realize the gain of 2 times of change, and the output voltage of the single-path second rectifying circuit is 192V-450V.

At this time, when the isolated charging power supply is switched to the first connection structure, the whole charging power supply provides two paths of charging outputs, and in each path of charging output, the charging voltage range output by the second rectifying circuit is 192V-450V; on the contrary, when the isolated charging power supply is switched to the second connection structure, the rectifying circuit and the series circuit output a charging voltage in the range of 384V to 900V.

Therefore, the output voltage range of the isolated charging power supply is improved to 192V-900V by different switch controls of the switching circuit 140 and the frequency modulation control of the LLC circuit and the bus voltage regulation control of the PFC circuit. Compared with the output voltage range of 192V to 450V when the output circuits are directly connected in parallel, the charging output voltage range of the present embodiment is expanded by 2.74 times, that is, (900-.

In summary, the output voltage of the LLC circuit is generally adjusted in a range of only about 1:3 (e.g., 450/192 is 2.34 in the previous example), so that the maximum output voltage of the rectified output circuit is only about 3 times the minimum output voltage. However, when the isolated charging power supply provided in this embodiment is switched to connect the second rectifying circuits in series, the corresponding output voltage may be about 2 to 6 times (e.g., 900/192-4.69 in the foregoing example) the single lowest voltage. Therefore, the isolated charging power supply provided by the embodiment switches the second rectifying circuit in series and parallel through the switching circuit 140, so that the output voltage can be adjusted between 1-6 times of the lowest output voltage, and therefore, the adjustment range of the output voltage can be expanded.

In summary, the present embodiment provides an isolated charging power supply with a wide output range, and when the input voltage of the isolated charging power supply is 380V of ac power, the final rectified output bus dc voltage range may be 640V-900V through the three-phase PFC structure provided in the present embodiment.

Referring to fig. 2, the structure of the isolated charging power supply of the present embodiment is substantially the same as that of the isolated charging power supply shown in fig. 1.

The difference between this embodiment and fig. 1 is that in this embodiment, the second rectification circuit 131 includes a switching tube Q15, a switching tube Q16, a switching tube Q19 and a switching tube Q20, which are not diodes, and are specifically corresponding NMOS tubes; the second rectifying circuit 132 includes a switch Q17, a switch Q18, a switch Q21 and a switch Q22, which are not diodes, and are specifically NMOS transistors.

In the second rectifying circuit 131, the drain of the switching tube Q16, the source of the switching tube Q15, the source of the switching tube Q19, and the drain of the switching tube Q20 are connected to the secondary side of the isolation transformer T1 (i.e., the output terminal of the isolation transformer T1), and the output terminal of the second rectifying circuit 131 is connected to the switching circuit 140.

In the second rectifying circuit 132, the drain of the switching tube Q18, the source of the switching tube Q17, the source of the switching tube Q21, and the drain of the switching tube Q22 are connected to the secondary side of the isolation transformer T2 (i.e., the output terminal of the isolation transformer T1), and the output terminal of the second rectifying circuit 132 is connected to the switching circuit 140.

In this embodiment, the second rectifying circuit 131 and the second rectifying circuit 132 are implemented by using NMOS switching transistors, so as to achieve better rectifying effect, and the average value and polarity of the dc voltage output by the rectifying circuit can be adjusted by controlling the conduction status of the element.

Referring to fig. 3, the structure of the isolated charging power supply of the present embodiment is substantially the same as that of the isolated charging power supply shown in fig. 2.

The present embodiment is different from fig. 2 in that the present embodiment includes three conversion circuits, that is, a conversion circuit 123 in addition to the conversion circuit 121 and the conversion circuit 122.

The present embodiment is different from fig. 2 in that, correspondingly, the present embodiment includes three isolation transformers, that is, in addition to the transformer T1 and the isolation transformer T2, the present embodiment further includes a transformer T3.

The present embodiment is different from fig. 2 in that, correspondingly, the present embodiment includes three second rectification circuits, that is, includes a second rectification circuit 133 in addition to the second rectification circuit 131 and the second rectification circuit 132.

The difference between this embodiment and fig. 2 is that, correspondingly, this embodiment includes two switching circuits, that is, a switching circuit 150 is further included in addition to the switching circuit 140.

That is, the isolated charging power supply of the present embodiment adds a circuit, and at the same time, adds the corresponding switching circuit 150, and the switching circuit 150 associates the circuit with other circuits to form a switchable structure that can be adjusted to be connected in series or in parallel.

The switching circuit 150 added in the present embodiment includes a fourth switching tube Q23, a fifth switching tube Q24 and a sixth switching tube Q25, and the connection relationship between the fourth switching tube Q23, the fifth switching tube Q24 and the sixth switching tube Q25 and the second rectifying circuit 132 and the second rectifying circuit 133 can refer to fig. 3, and can refer to the corresponding content of the foregoing embodiments (refer to the corresponding content of the first switching tube Q23, the second switching tube Q24 and the third switching tube Q25).

The second rectifying circuit 133 added in this embodiment includes a switching tube Q31, a switching tube Q32, a switching tube Q35 and a switching tube Q36, and reference may be made to the corresponding contents of the second rectifying circuit 131 and the second rectifying circuit 132.

The additional converting circuit 123 of this embodiment includes a switching tube Q29, a switching tube Q30, a switching tube Q33 and a switching tube Q34, and it can refer to the corresponding contents of the converting circuit 121 and the converting circuit 122.

In this embodiment, the input terminal of the isolation transformer T3 further has a resonant inductor L6.

In this embodiment, the conversion circuit 123, the corresponding resonant inductor L6, the isolation transformer T3, the second rectification circuit 133, and the output filter capacitor C5 also form a full bridge LLC circuit. Reference may be made to another two full-bridge LLC circuits formed by other structures, and reference may be made to the corresponding contents in the foregoing embodiments.

In the isolated charging power supply provided by this embodiment, three circuit structures capable of performing series-parallel connection are included, so that, compared with the power supplies of the two embodiments, the power supply provided by this embodiment can further provide three different output voltage ranges. Still using the corresponding conditions of the foregoing embodiments, three different output voltage ranges, such as 192V to 450V, 384V to 900V and 576V to 1350V, can be further provided in this embodiment, i.e., a charging voltage range of 192V to 1350V can be provided.

As can be seen from analysis of other principles of the foregoing embodiment, the isolated charging power supply provided in this embodiment switches the second rectification circuits in series and parallel through the switching circuit 140 and the switching circuit 150, so that the output voltage can be adjusted between 1 to 9 times of the lowest output voltage, and therefore, the adjustment range of the output voltage can be expanded.

Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be effected therein by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. An isolated charging power supply, comprising:

an alternating current power supply for supplying alternating current power;

a first rectifying circuit (110) for rectifying alternating-current power supplied from the alternating-current power supply;

at least two inverter circuits (121/122, 121/122/123), the inverter circuits being connected in parallel with each other, the inputs of the inverter circuits being connected to the first rectifier circuit outputs;

at least two isolation transformers (T1/T2, T1/T2/T3), wherein the input of one isolation transformer is correspondingly connected with the output of one conversion circuit;

at least two second rectifying circuits (131/132, 131/132/133), wherein the input of one second rectifying circuit is correspondingly connected with the output of one isolation transformer;

a switching circuit (140, 140/150) connected between adjacent two of the second rectification circuits, the switching circuit being for switching a connection structure between the second rectification circuits between a series structure and a parallel structure.

2. The isolated charging power supply of claim 1, wherein:

the conversion circuit (121/122), the isolation transformer (T1/T2) and the second rectifying circuit (131/132) are all two;

the switching circuit (140) comprises a first switching tube (Q23), a second switching tube (Q24) and a third switching tube (Q25);

the first end of the first switching tube (Q23) is connected with the positive end of the first second rectifying circuit (131);

the second end of the first switching tube (Q23) is connected with the positive end of a second rectifying circuit (132);

the first end of the second switching tube (Q24) is connected with the positive end of a second rectifying circuit (132);

a second end of the second switching tube (Q24) is connected with the ground end of a first second rectifying circuit (131);

a first end of the third switching tube (Q25) is connected with the ground end of the first second rectifying circuit (131);

a second end of the third switching tube (Q25) is connected with the ground end of a second rectifying circuit (132);

the third end of the first switching tube (Q23), the third end of the second switching tube (Q24) and the third end of the third switching tube (Q25) are connected with a control unit.

3. The isolated charging power supply of claim 2, wherein:

the first switching tube (Q23), the second switching tube (Q24) and the third switching tube (Q25) are all NMOS tubes;

the first end of the first switching tube (Q23) is a drain electrode, the second end is a source electrode, and the third end is a grid electrode;

the first end of the second switching tube (Q24) is a drain electrode, the second end is a source electrode, and the third end is a grid electrode;

the first end of the third switching tube (Q25) is a drain electrode, the second end is a source electrode, and the third end is a grid electrode.

4. The isolated charging power supply of claim 3, further comprising an input filter capacitor (C1), the input filter capacitor (C1) being located at a front end of the conversion circuit (121/122).

5. The isolated charging power supply of claim 4, wherein each of said isolation transformers (T1/T2) further has a resonant inductor (L4/L5) at its input.

6. The isolated charging power supply of claim 5, wherein said conversion circuit (121/122) is a full bridge circuit.

7. The isolated charging power supply of claim 6, further comprising an output filter capacitor (C5), the output filter capacitor (C5) being located at a rear end of the second rectification circuit (131/132).

8. The isolated charging power supply of claim 7, wherein one of said transforming circuits (121/122) and a corresponding one of said resonant inductor (L4/L5), one of said isolation transformer (T1/T2), one of said second rectifying circuit (131/132), and said output filter capacitor (C5) form a full bridge LLC circuit or a full bridge CLLC circuit.

9. The isolated charging power supply of claim 6, wherein a MOS transistor or an IGBT transistor is adopted as a switch transistor in a full bridge circuit of the conversion circuit (121/122).

10. The isolated charging power supply of claim 1, wherein the ac power supply is a three-phase ac power supply, and when the three-phase ac power supply is connected to the first rectifying circuit (110), each phase has an inductor (L1/L2/L3) on its corresponding line.