CN210970721U

CN210970721U - Electric automobile and vehicle-mounted charger thereof

Info

Publication number: CN210970721U
Application number: CN201921427296.XU
Authority: CN
Inventors: 张信; 娄贺伟; 韩冰; 哈米德; 王春生
Original assignee: BYD Co Ltd
Current assignee: BYD Co Ltd
Priority date: 2019-08-28
Filing date: 2019-08-28
Publication date: 2020-07-10
Anticipated expiration: 2029-08-28

Abstract

The utility model discloses an electric automobile and on-vehicle machine that charges thereof, wherein, on-vehicle machine that charges includes: the alternating current end of the PFC circuit is connected with a power grid; the DC/AC conversion circuit, its direct-current end is connected with direct-current end of PFC circuit; the transformer comprises a primary coil, a first secondary coil, a second secondary coil and a third secondary coil, wherein the primary coil is connected with the alternating current end of the DC/AC conversion circuit; the alternating current end of the first AC/DC conversion circuit is connected with the first secondary coil, and the direct current end of the first AC/DC conversion circuit is connected with the power battery; and the first port and the second port of the alternating current end of the second AC/DC conversion circuit are correspondingly connected with one end of the second secondary coil and one end of the third secondary coil, the output end of the second AC/DC conversion circuit is connected with the first stage of the low-voltage storage battery, and the other ends of the second secondary coil and the third secondary coil are connected with the second pole of the low-voltage storage battery. The vehicle-mounted charger reduces the use of parts, thereby reducing the cost of the parts, reducing the volume of the parts and lightening the weight of the parts.

Description

Electric automobile and vehicle-mounted charger thereof

Technical Field

The utility model relates to the technical field of automobiles, especially, relate to an electric automobile and on-vehicle machine that charges thereof.

Background

With the development of new energy vehicles, the requirements of the OBC (On-board charger) and the On-board DC (direct current) On cost, volume, weight and the like are higher and higher, and the discrete OBC and the On-board DC cannot meet the development requirements of the new energy vehicles. At present, two-in-one scheme products for integrating OBC and vehicle-mounted DC exist in the market, but most schemes only realize integration through simple electrical connection of a bus, and the integration level is low.

SUMMERY OF THE UTILITY MODEL

The present invention aims at solving at least one of the technical problems in the related art to a certain extent. Therefore, an object of the utility model is to provide an electric automobile's on-vehicle machine that charges to reduce the use of spare part, reduce the cost of the on-vehicle machine that charges, reduce the volume of the on-vehicle machine that charges, alleviate the weight of the on-vehicle machine that charges.

In order to achieve the above object, the utility model discloses the first aspect provides an electric automobile's on-vehicle machine that charges, electric automobile includes power battery and low voltage battery, the on-vehicle machine that charges includes: a PFC (Power factor correction) circuit, wherein an AC end of the PFC circuit is connected with a power grid; the direct current end of the DC/AC conversion circuit is connected with the direct current end of the PFC circuit; the transformer comprises a primary coil, a first secondary coil, a second secondary coil and a third secondary coil, and the primary coil is connected with the alternating current end of the DC/AC conversion circuit; and a first port of an alternating current end of the first AC/DC conversion circuit is connected to one end of the second secondary winding, a second port of an alternating current end of the second AC/DC conversion circuit is connected to one end of the third secondary winding, an output end of the second AC/DC conversion circuit is connected to a first pole of the low-voltage battery, and the other end of the second secondary winding and the other end of the third secondary winding are both connected to a second pole of the low-voltage battery.

The utility model discloses an on-vehicle machine that charges through a transformer and a DC AC converting circuit, can realize giving power battery and low voltage battery with the energy transmission of electric wire netting to and through foretell transformer and two AC converting circuit, can realize that power battery supplies power for the low voltage battery, from this, the use of spare part has been reduced, thereby the cost of on-vehicle machine that charges has been reduced, the volume of on-vehicle machine that charges has been reduced, the on-vehicle machine weight that charges has alleviateed.

In order to achieve the above object, the utility model discloses the second aspect provides an electric automobile, electric automobile includes foretell electric automobile's on-vehicle machine that charges.

The utility model discloses electric automobile, on-vehicle machine that charges on it, through a transformer and a DC AC converting circuit, can realize giving power battery and low voltage battery with the energy transmission of electric wire netting to and through transformer and two AC DC converting circuit, can realize that power battery supplies power for low voltage battery, from this, reduced the use of spare part, make on-vehicle machine that charges cost reduction, volume reduction, weight reduction.

Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

Drawings

Fig. 1 is a block diagram of a vehicle-mounted charger of an electric vehicle according to an embodiment of the present invention;

fig. 2 is a schematic structural diagram of a first example of the vehicle-mounted charger of the present invention;

fig. 3 is a schematic diagram of energy transmission in the vehicle-mounted charger according to the first example of the present invention;

fig. 4 is a schematic diagram of energy transmission in a vehicle-mounted charger according to a second example of the present invention;

fig. 5 is a schematic diagram of energy transmission in a third example of the vehicle-mounted charger of the present invention;

fig. 6 is a schematic diagram of energy transmission in a fourth example of the vehicle-mounted charger of the present invention;

fig. 7 is a schematic structural diagram of a vehicle-mounted charger according to a second example of the present invention;

fig. 8 is a schematic structural diagram of a third example of the vehicle-mounted charger of the present invention;

fig. 9 is a block diagram of an electric vehicle according to an embodiment of the present invention.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are exemplary and intended to be used for explaining the present invention, and should not be construed as limiting the present invention.

The electric automobile and the vehicle-mounted charger thereof according to the embodiment of the present invention are described below with reference to the drawings.

Fig. 1 is a block diagram of a vehicle-mounted charger of an electric vehicle according to an embodiment of the present invention.

In this embodiment, the electric vehicle comprises a power battery P-battery and a low-voltage battery L-battery as shown in fig. 1, and the vehicle-mounted charger comprises a PFC circuit 10, a DC/AC conversion circuit 20, a transformer 30, a first AC/DC conversion circuit 40 and a second AC/DC conversion circuit 50.

Referring to fig. 1, an AC terminal of a PFC circuit 10 is connected to a power grid, a DC terminal of a DC/AC conversion circuit 20 is connected to a DC terminal of the PFC circuit 10, a transformer 30 includes a primary winding Np1, a first secondary winding Ns1, a second secondary winding Ns2, and a third secondary winding Ns3, the primary winding Np1 is connected to an AC terminal of the DC/AC conversion circuit 20, an AC terminal of the first AC/DC conversion circuit 40 is connected to the first secondary winding Ns1, the DC terminal of the first AC/DC conversion circuit 40 is connected to a P-battery, a first port of the AC terminal of the second AC/DC conversion circuit 50 is connected to one end of the second secondary winding Ns2, a second port of the AC terminal of the second AC/DC conversion circuit 50 is connected to one end of the third secondary winding Ns3, and an output terminal of the second AC/DC conversion circuit 50 is connected to one end of a positive pole (e.g., 12V) of a low-battery, such as a negative pole (Ns 3) of the second AC/DC conversion circuit 50 is connected to the other end of the second secondary winding Ns 3.

Specifically, referring to fig. 1, the present invention relates to a vehicle charger, which employs transformer magnetic integration (i.e. one or more magnetic devices are structurally integrated together, e.g. share a magnetic core), shares primary coil input of the transformer, outputs three secondary coils, wherein one secondary coil (i.e. the first secondary coil Ns1) output is connected to the power battery P-battery through the first AC/DC conversion circuit 40 on the power battery P-battery side, one end of the other two secondary coils (i.e. the second secondary coil Ns2, the third secondary coil Ns3) is connected to the low-voltage battery L-battery through the second AC/DC conversion circuit 50 on the low-voltage battery L-battery side, the other end of the other two secondary coils are both connected to the second pole of the low-voltage battery L-battery, and the vehicle DC/AC conversion circuit is shared by the OBC and the vehicle DC.

As an example, as shown in fig. 2, the PFC circuit 10 includes a first capacitor C1, a first inductor L, a first arm 11 and a second arm 12, one end of the first capacitor C1 is connected to the live wire L of the grid, the other end of the first capacitor C1 is connected to the neutral wire N of the grid, one end of the first inductor L is connected to one end of the first capacitor C25 and the live wire L of the grid, respectively, a midpoint of the first arm 11 is connected to the other end of the first inductor L, the first arm 11 includes a first switch tube Q1 and a second switch tube Q2 connected in series, a midpoint of the second arm 6312 is connected to the other end of the first capacitor C1 and the neutral wire N of the grid, and the second arm 12 is connected to the first arm 11 in parallel to form a first current sink end and a second current sink end, the first current sink end is connected to the first port of the DC/AC conversion circuit 20, the second arm 6312 is connected to the DC/AC conversion circuit 20 and the second arm 632 includes a fourth switch tube Q4 connected in series.

Referring to fig. 2, the vehicle-mounted charger further includes: a second capacitor C2 and a second capacitor C2 are connected between the PFC circuit 10 and the DC/AC conversion circuit 20, one end of the second capacitor C2 is connected to the first bus terminal, and the other end of the second capacitor C2 is connected to the second bus terminal. The second capacitor C2 functions as a dc bus capacitor and filters the dc power output by the PFC circuit 10.

Referring to fig. 2, the DC/AC conversion circuit 20 includes: third leg 21 and fourth leg 22. The middle point of the third bridge arm 21 is connected with one end of the primary coil Np1, and the third bridge arm 21 comprises a fifth switching tube Q5 and a sixth switching tube Q6 which are connected in series; the midpoint of the fourth bridge arm 22 is connected to the other end of the primary coil Np1, the fourth bridge arm 22 is connected to the third bridge arm 21 in parallel to form a third junction end and a fourth junction end, the third junction end is connected to the first port of the dc end of the PFC circuit 10, the fourth junction end is connected to the second port of the dc end of the PFC circuit 10, and the fourth bridge arm 22 includes a seventh switching tube Q7 and an eighth switching tube Q8 connected in series to each other.

Referring to fig. 2, the first AC/DC conversion circuit 40 includes: fifth leg 41, sixth leg 42, and third capacitor C3. The middle point of the fifth bridge arm 41 is connected with one end of the first secondary coil Ns1, and the fifth bridge arm 42 comprises a ninth switching tube Q9 and a tenth switching tube Q10 which are connected in series; the middle point of the sixth bridge arm 42 is connected with the other end of the first minor edge coil Ns1, the sixth bridge arm 42 is connected with the fifth bridge arm 41 in parallel to form a fifth junction end and a sixth junction end, the fifth junction end is connected with the first pole of the power battery P-battery, the sixth junction end is connected with the second pole of the power battery P-battery and grounded, and the sixth bridge arm comprises an eleventh switching tube and a twelfth switching tube which are connected in series; one end of the third capacitor C3 is connected to the fifth bus terminal and the first pole of the power battery P-battery, and the other end of the third capacitor C3 is connected to the sixth bus terminal and the second pole of the power battery P-battery, and is grounded.

The first pole of the power battery P-battery can be a positive pole, and the second pole of the power battery P-battery is a negative pole.

Referring to fig. 2, the second AC/DC conversion circuit 50 includes a thirteenth switching tube Q13, a fourteenth switching tube Q14, a second inductor L2, a third inductor L, and a fourth capacitor C4, a source of the thirteenth switching tube Q13 is connected to one end of a second sub-boundary coil Ns2, a source of a fourteenth switching tube Q14 is connected to one end of the third sub-boundary coil Ns3, one end of a second inductor L is connected to a drain of the thirteenth switching tube Q13, the other end of the second inductor L is connected to a first pole of the low-voltage battery L-battery, one end of the third inductor L is connected to a drain of the fourteenth switching tube Q14, the other end of the third inductor L3 is connected to the first pole of the low-voltage battery L-battery and the other end of the second inductor L, one end of a fourth capacitor C4 is connected to the other end of the second inductor L, the third inductor 363, the other end of the second sub-battery L-battery 867, the second sub-battery 36867, and the second sub-battery 8672.

The first pole of the low-voltage battery L-battery can be a positive pole, and the second pole of the low-voltage battery L-battery can be a negative pole.

The second AC/DC conversion circuit 50 uses a full-wave rectification circuit to split an original single filter inductor in the full-wave rectification circuit into two independent filter inductors (i.e., the second inductor L2 and the third inductor L3), and the discrete inductors can improve the heat dissipation of components, reduce the consumption of inductors, and improve the efficiency of the system.

Referring to fig. 2, the vehicle-mounted charger further includes a fourth inductor L4 and a fifth capacitor C5., wherein one end of the fourth inductor L4 is connected to the midpoint of the third leg 21, the other end of the fourth inductor L4 is connected to one end of the primary coil Np1, one end of the fifth capacitor C5 is connected to the midpoint of the fourth leg 22, and the other end of the fifth capacitor C5 is connected to the other end of the primary coil Np1, and the fourth inductor L4, the fifth capacitor C5 and the primary coil Np1 are connected in series to form a resonant circuit.

The working principle of the vehicle-mounted charger according to the embodiment of the present invention is described below with reference to fig. 3 to 6:

the vehicle-mounted charger works in a first mode, namely a power grid charges a low-voltage storage battery L-battery, before a power battery P-battery is charged, the power grid firstly charges the low-voltage storage battery L-battery when the SOC value of the low-voltage storage battery L-battery is lower than a first set value, after the power battery P-battery is charged, the SOC value of the low-voltage storage battery L-battery is judged again, when the SOC value of the low-voltage storage battery L-battery is lower than a second set value, the low-voltage storage battery L-battery is charged until the SOC value is 100%, and the charging of a whole vehicle is judged to be finished, in the first mode, referring to fig. 3, the energy on the side of the power grid charges the low-voltage storage battery through a PFC circuit 10, a DC/AC conversion circuit 20, a fourth inductor L4, a primary coil Np1, a fifth capacitor C5, a second secondary coil 2 of a transformer 30 and a second AC/DC conversion circuit Ns/DC conversion circuit L-battery on the side of the low-battery L-battery.

The values of the first set value and the second set value can be the same or different.

After the SOC value of the low-voltage storage battery L-battery is judged to be larger than a third set value, referring to fig. 4, the energy on the grid side charges the power battery P-battery through a PFC circuit 10, a DC/AC conversion circuit 20, a fourth inductor L4, a primary coil Np1 of a transformer 30, a fifth capacitor C5, a first secondary coil Ns1 of the transformer 30 and a first AC/DC circuit 40 on the power battery P-battery side.

The third set value is larger than the first set value and the second set value.

Referring to fig. 5, the energy of the power battery P-battery sequentially passes through the first AC/DC circuit 40 at the power battery P-battery side, the first secondary coil Ns1 of the transformer 30, the primary coil Np1 of the transformer 30, the fourth inductor L4, the fifth capacitor C5, the DC/AC conversion circuit 20 and the PFC circuit 10 to discharge outside the vehicle, such as 220V/50 Hz.

In the mode, referring to fig. 6, the energy of the power battery P-basic is discharged to the low-voltage load and the low-voltage storage battery L-basic through a first AC/DC conversion circuit 40 at the side of the power battery P-basic, a first secondary coil Ns1 of a transformer 30, a second secondary coil Ns2 of the transformer 30, a third secondary coil Ns3 of the transformer 30 and a second AC/DC conversion circuit 50 at the side of the storage battery L-basic.

The fourth setting value may be greater than or equal to the first setting value.

As an example, as shown in fig. 7, the second AC/DC conversion circuit 50 further includes a fifteenth switch Q15, a source of the fifteenth switch Q15 is connected to the other end of the second secondary winding Ns2 and the other end of the third secondary winding Ns3, respectively, and a drain of the fifteenth switch Q15 is connected to the other end of the fourth capacitor C4 and the second pole of the low-voltage battery L-battery, respectively, and is grounded.

In the example, the output voltage of the low-voltage storage battery L-battery side can be modulated by the newly added fifteenth switching tube Q15, if the voltage of the low-voltage storage battery L-battery side is not required to be controlled during the operation of the system, the fifteenth switching tube Q15 is kept in a normally closed state, and if the voltage of the low-voltage storage battery L-battery side is required to be controlled during the operation of the system, the fifteenth switching tube Q15 operates in a PWM modulation state.

As an example, as shown in fig. 8, the second AC/DC conversion circuit 50 includes a thirteenth switching tube Q13, a fourteenth switching tube Q14, a second inductor L2, and a fourth capacitor C4. the source of the thirteenth switching tube Q13 is connected to one end of the second sub-boundary coil Ns2, the source of the fourteenth switching tube Q14 is connected to one end of the third sub-boundary coil Ns3, the drain of the fourteenth switching tube Q14 is connected to the drain of the thirteenth switching tube Q13, one end of the second inductor L is connected to the drain of the thirteenth switching tube Q13 and the drain of the fourteenth switching tube Q14, the other end of the second inductor L is connected to the first pole of the low-voltage battery L-battery, one end of the fourth capacitor C4 is connected to the other end of the second inductor L and the first pole of the low-voltage battery L-battery, and the other end of the fourth capacitor C3584 is connected to the second sub-boundary coil Ns L of the low-battery, the second sub-battery 3 and the third sub-boundary coil Ns 3.

In this example, the low-voltage battery L-battery side adopts a full-wave rectification circuit, and compared with the example shown in fig. 2, the example combines the second inductor L2 and the third inductor L3 of the example shown in fig. 2 into one filter inductor, so that the use of electrical components is reduced, and the cost is saved.

It should be noted that each of the switch tubes may be a MOS (Metal-Oxide-Semiconductor field effect Transistor) tube or an IGBT (Insulated Gate Bipolar Transistor), and referring to fig. 2 to 8, each of the switch tubes is connected in parallel with a freewheeling diode, and the above operation modes of the vehicle-mounted charger are realized by controlling the on or off of the switch tube.

The utility model discloses electric automobile's on-vehicle machine that charges, adopt transformer magnetism integrated technology, with OBC and on-vehicle DC's isolation transformer integrated design, reduce a transformer in the physical structure, OBC and on-vehicle DC share the primary transform circuit of transformer and EMC filter circuit simultaneously, the use of spare part has been reduced, thereby the cost of on-vehicle machine that charges has been reduced, the volume of on-vehicle machine that charges has been reduced, the weight of on-vehicle machine that charges has been alleviateed, in addition, low voltage battery L-battery output side adopts current doubling circuit, it takes a percentage to make the transformer secondary not have the center, the design degree of difficulty of transformer has been reduced, and simultaneously, set up two filter inductance in the current doubling circuit, be favorable to filter inductance's heat dissipation design, power efficiency has been promoted.

As shown in fig. 9, the electric vehicle 1000 includes the vehicle-mounted charger 100 of the electric vehicle of the above embodiment.

The utility model discloses electric automobile, electric automobile's on-vehicle machine that charges on it, the spare part that uses is few, and is with low costs, small, light in weight, and the design degree of difficulty of transformer, power efficiency is high.

In addition, other structures and functions of the electric vehicle according to the embodiment of the present invention are known to those skilled in the art, and are not described herein for reducing redundancy.

In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", and the like, indicate the orientation or positional relationship indicated based on the drawings, and are only for convenience of description and simplicity of description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore, should not be construed as limiting the present invention.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.

In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," and "fixed" are to be construed broadly and may, for example, be fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meaning of the above terms in the present invention can be understood according to specific situations by those skilled in the art.

In the present application, unless expressly stated or limited otherwise, the first feature may be directly on or directly under the second feature or indirectly via intermediate members. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.

Although embodiments of the present invention have been shown and described, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art without departing from the scope of the present invention.

Claims

1. The utility model provides an electric automobile's on-vehicle machine that charges, electric automobile includes power battery and low-voltage battery, its characterized in that, on-vehicle machine that charges includes:

the alternating current end of the PFC circuit is connected with a power grid;

the direct current end of the DC/AC conversion circuit is connected with the direct current end of the PFC circuit;

the transformer comprises a primary coil, a first secondary coil, a second secondary coil and a third secondary coil, and the primary coil is connected with the alternating current end of the DC/AC conversion circuit;

the alternating current end of the first AC/DC conversion circuit is connected with the first secondary coil, and the direct current end of the first AC/DC conversion circuit is connected with the power battery;

and a first port of an alternating current end of the second AC/DC conversion circuit is connected with one end of the second secondary coil, a second port of the alternating current end of the second AC/DC conversion circuit is connected with one end of the third secondary coil, an output end of the second AC/DC conversion circuit is connected with a first pole of the low-voltage storage battery, and the other end of the second secondary coil and the other end of the third secondary coil are both connected with a second pole of the low-voltage storage battery.

2. The vehicle-mounted charger of the electric vehicle according to claim 1, wherein the PFC circuit comprises:

one end of the first capacitor is connected with a live wire of the power grid, and the other end of the first capacitor is connected with a zero line of the power grid;

one end of the first inductor is respectively connected with one end of the first capacitor and a live wire of the power grid;

the middle point of the first bridge arm is connected with the other end of the first inductor, and the first bridge arm comprises a first switching tube and a second switching tube which are connected in series;

and the midpoint of the second bridge arm is respectively connected with the other end of the first capacitor and a zero line of the power grid, the second bridge arm and the first bridge arm are connected in parallel to form a first bus end and a second bus end, the first bus end is connected with a first port of a direct current end of the DC/AC conversion circuit, the second bus end is connected with a second port of the direct current end of the DC/AC conversion circuit and is grounded, and the second bridge arm comprises a third switching tube and a fourth switching tube which are connected in series.

3. The vehicle-mounted charger according to claim 2, further comprising:

and the second capacitor is connected between the PFC circuit and the DC/AC conversion circuit, one end of the second capacitor is connected with the first bus bar end, and the other end of the second capacitor is connected with the second bus bar end.

4. The vehicle-mounted charger according to claim 1, wherein the DC/AC conversion circuit comprises:

the middle point of the third bridge arm is connected with one end of the primary coil, and the third bridge arm comprises a fifth switching tube and a sixth switching tube which are connected in series;

the middle point of the fourth bridge arm is connected with the other end of the primary coil, the fourth bridge arm and the third bridge arm are connected in parallel to form a third bus end and a fourth bus end, the third bus end is connected with a first port of a direct current end of the PFC circuit, the fourth bus end is connected with a second port of the direct current end of the PFC circuit and is grounded, and the fourth bridge arm comprises a seventh switch tube and an eighth switch tube which are connected in series.

5. The vehicle-mounted charger according to claim 1, wherein the first AC/DC conversion circuit comprises:

the middle point of the fifth bridge arm is connected with one end of the first secondary coil, and the fifth bridge arm comprises a ninth switching tube and a tenth switching tube which are connected in series;

the middle point of the sixth bridge arm is connected with the other end of the first secondary coil, the sixth bridge arm and the fifth bridge arm are connected in parallel to form a fifth junction end and a sixth junction end, the fifth junction end is connected with the first pole of the power battery, the sixth junction end is connected with the second pole of the power battery and is grounded, and the sixth bridge arm comprises an eleventh switching tube and a twelfth switching tube which are connected in series;

and one end of the third capacitor is connected with the fifth bus end and the first pole of the power battery respectively, and the other end of the third capacitor is connected with the sixth bus end and the second pole of the power battery respectively and grounded.

6. The vehicle-mounted charger according to claim 1, wherein the second AC/DC conversion circuit comprises:

a thirteenth switching tube, wherein a source electrode of the thirteenth switching tube is connected with one end of the second secondary coil;

a fourteenth switching tube, a source of which is connected to one end of the third secondary winding;

one end of the second inductor is connected with the drain electrode of the thirteenth switching tube, and the other end of the second inductor is connected with the first pole of the low-voltage storage battery;

one end of the third inductor is connected with the drain electrode of the fourteenth switching tube, and the other end of the third inductor is respectively connected with the first pole of the low-voltage storage battery and the other end of the second inductor;

and one end of the fourth capacitor is connected with the other end of the second inductor, the other end of the third inductor and the first pole of the low-voltage storage battery respectively, and the other end of the fourth capacitor is connected with the second pole of the low-voltage storage battery, the other end of the second secondary coil and the other end of the third secondary coil respectively and is grounded.

7. The vehicle-mounted charger according to claim 6, wherein the second AC/DC conversion circuit further comprises:

and a source electrode of the fifteenth switching tube is respectively connected with the other end of the second secondary coil and the other end of the third secondary coil, and a drain electrode of the fifteenth switching tube is respectively connected with the other end of the fourth capacitor and the second pole of the low-voltage storage battery and is grounded.

8. The vehicle-mounted charger according to claim 1, wherein the second AC/DC conversion circuit comprises:

a source electrode of the fourteenth switching tube is connected with one end of the third secondary side coil, and a drain electrode of the fourteenth switching tube is connected with a drain electrode of the thirteenth switching tube;

one end of the second inductor is connected with the drain electrode of the thirteenth switching tube and the drain electrode of the fourteenth switching tube respectively, and the other end of the second inductor is connected with the first pole of the low-voltage storage battery;

and one end of the fourth capacitor is connected with the other end of the second inductor and the first pole of the low-voltage storage battery respectively, and the other end of the fourth capacitor is connected with the second pole of the low-voltage storage battery, the other end of the second secondary side coil and the other end of the third secondary side coil respectively and is grounded.

9. The vehicle-mounted charger according to claim 4, further comprising:

one end of the fourth inductor is connected with the midpoint of the third bridge arm, and the other end of the fourth inductor is connected with one end of the primary coil;

and one end of the fifth capacitor is connected with the midpoint of the fourth bridge arm, and the other end of the fifth capacitor is connected with the other end of the primary coil.

10. An electric vehicle, characterized in that it comprises an on-board charger for electric vehicles according to any one of claims 1 to 9.