Vehicle-mounted charger

Abstract

The invention discloses a vehicle-mounted charger which comprises a primary side conversion circuit, a first secondary side conversion circuit, a second secondary side conversion circuit and a transformer. The primary side conversion circuit is connected with a primary side winding of the transformer, the first secondary side conversion circuit is connected with a first secondary side winding of the transformer, and the second secondary side conversion circuit is connected with a second secondary side winding of the transformer; the first secondary winding is used for supplying power to a power battery, and the second secondary winding is used for supplying power to other loads except the power battery; and the second secondary side conversion circuit is a first full-bridge conversion circuit. The vehicle-mounted charger provided by the invention comprises the transformer and the two independent secondary windings, so that the cost is low; and the second secondary side conversion circuit is a full-bridge circuit to realize soft switching control, and has the advantages of small output voltage stress, high efficiency, low heat and the like.

Description

Technical Field

[0001] The present invention relates to the field of power electronics technology, and particularly to an on-vehicle charger. Background Art

[0002] With the gradual popularization and application of new energy vehicles in the market, the on-vehicle charger, an important part of electric vehicles, has also received attention.

[0003] An on-vehicle charger generally has two output terminals. One output terminal is used to charge the power battery, and the other output terminal is used to supply power to the electrical equipment of the vehicle, such as air conditioners, headlights, etc.

[0004] The second secondary conversion circuit for supplying power to the electrical equipment adopts a full-wave rectification structure based on a center-tapped transformer. The full-wave rectification structure has defects such as large output current, low efficiency, and serious heating. Summary of the Invention

[0005] In order to solve the above technical problems existing in the prior art, the present invention provides an on-vehicle charger, and the second secondary conversion circuit can achieve advantages such as small output voltage stress, high efficiency, and low heating.

[0006] An embodiment of the present application provides an on-vehicle charger, including: a primary conversion circuit, a first secondary conversion circuit, a second secondary conversion circuit, and a transformer;

[0007] The primary conversion circuit is connected to the primary winding of the transformer, the first secondary conversion circuit is connected to the first secondary winding of the transformer, and the second secondary conversion circuit is connected to the second secondary winding of the transformer;

[0008] The first secondary winding is used to supply power to the power battery, and the second secondary winding is used to supply power to other loads other than the power battery;

[0009] The second secondary conversion circuit is a first full-bridge conversion circuit.

[0010] Preferably, it further includes: a controller;

[0011] The controller is configured to compare the output current Iout2 of the second secondary conversion circuit with the second reference current Iref2, perform loop compensation on the difference of the comparison to obtain a compensation value, take the smaller value of the obtained compensation value and the second preset voltage Vset2, take the smaller value as the second voltage loop reference value Vref2, compare the output voltage Vout2 of the second secondary conversion circuit with Vref2, perform loop compensation on the difference of the comparison to obtain a compensation value, and generate the positive wave time and negative wave time of the driving signal of the switching tube in the second secondary conversion circuit according to the compensation value.

[0012] Preferably, the second secondary conversion circuit further includes an output switch and a freewheeling switch;

[0013] The first terminal of the output switch is connected to the positive output terminal of the first full-bridge conversion circuit, and the second terminal of the output switch is connected to the negative output terminal of the first full-bridge conversion circuit through a freewheeling switch.

[0014] A controller, configured to compare and compensate Vout2 and Iout2 to obtain a compensation value, use the obtained compensation value as the chopping delay time T, add the positive wave starting time of the driving signal of the switching tube in the second secondary conversion circuit, the forward zero-crossing delay, and the chopping delay time as the conduction time of the output switch, and the output switch and the freewheeling switch act complementarily.

[0015] Preferably, the controller is specifically configured to compare Vout2 with Vref2, perform loop compensation on the difference of the comparison to obtain a compensation value, take the smaller value of the compensation value and the preset current loop preset value Iset2, and use the smaller value as the current loop reference value Iref2; compare Iout2 with Iref2, perform loop compensation on the difference of the comparison to obtain a compensation value, and the compensation value is T.

[0016] Preferably, the controller is further configured to obtain the zero-crossing moment of the primary conversion circuit from the input current Iin of the primary conversion circuit, and obtain the forward zero-crossing delay according to the wave starting time and the zero-crossing moment.

[0017] Preferably, the controller is further configured to store a correspondence relationship. The output power of the primary conversion circuit is divided into multiple levels, and each level of output power corresponds to a correspondence relationship. Each correspondence relationship includes the correspondence relationship between the switching frequency of the switching tube and the forward zero-crossing delay; look up the forward zero-crossing delay corresponding to the switching frequency of the positive wave starting time according to the correspondence relationship corresponding to the current output power.

[0018] Preferably, the first secondary conversion circuit is a second full-bridge conversion circuit;

[0019] The controller is further configured to compare the output current Iout1 of the first secondary conversion circuit with the first reference current Iref1, perform loop compensation on the difference of the comparison to obtain a compensation value, take the smaller value of the obtained compensation value and the first preset voltage Vset1, and use the smaller value as the first voltage loop reference value Vref1, compare the output voltage Vout1 of the first secondary conversion circuit with the voltage loop reference value, perform loop compensation on the difference of the comparison to obtain a compensation value, and generate the positive wave starting time and the negative wave starting time of the driving signal of the switching tube in the second full-bridge conversion circuit according to the obtained compensation value.

[0020] Preferably, 2P2Z loop compensation is adopted for loop compensation.

[0021] Preferably, the primary conversion circuit is a third full-bridge conversion circuit.

[0022] Preferably, it further includes: a resonant capacitor and a resonant inductor;

[0023] The resonant capacitor and the resonant inductor are connected in series between the primary conversion circuit and the primary winding. The resonant inductor is an external inductor or the leakage inductance of a transformer.

[0024] Compared with the prior art, the present invention has at least the following advantages:

[0025] For the on-vehicle charger provided by the embodiment of the present application, both the first secondary conversion circuit and the second secondary conversion circuit adopt full-bridge conversion circuits. Since a full-bridge conversion circuit includes four controllable switching tubes, the voltage of two DC output terminals can be flexibly controlled, and thus, precise adjustment of the voltage can be achieved. Compared with the second secondary conversion circuit adopting a full-wave rectification circuit, the voltage stress can be small. Moreover, the transformer with a center tap is changed to a single transformer, and a magnetic integration scheme is adopted, which has high integration, low heat generation, low loss, and can reduce costs. Full-bridge rectification can achieve soft-switching operation, so the power conversion efficiency can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments recorded in the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0027] Figure 1 FIG. is a circuit schematic diagram of an on-vehicle charger provided by an embodiment of the present application;

[0028] Figure 2 FIG. is a schematic diagram of an on-vehicle charger in the prior art;

[0029] Figure 3 FIG. is a schematic diagram of another on-vehicle charger in the prior art. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] In order to enable those skilled in the art to better understand the solution of the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0031] Refer to Figure 1 , which is a circuit schematic diagram of an on-vehicle charger provided by an embodiment of the present application.

[0032] The on-vehicle charger provided by the embodiment of the present application includes: a primary conversion circuit, a first secondary conversion circuit, a second secondary conversion circuit, and a transformer; the primary conversion circuit is connected to the primary winding w1 of the transformer T1, the first secondary conversion circuit is connected to the first secondary winding w2 of the transformer T1, and the second secondary conversion circuit is connected to the second secondary winding w3 of the transformer T1.

[0033] For the on-vehicle charger provided by the embodiment of the present application, the primary conversion circuit, the first secondary conversion circuit, and the second secondary conversion circuit all adopt full-bridge conversion circuits. The primary conversion circuit includes Q1-Q4, and Q1-Q4 form an inverter circuit for converting direct current BT1 into alternating current and transmitting it to the primary winding w1 of the transformer T1. The primary conversion circuit has a first group of power switches Q1, Q4 and a second group of power switches Q2, Q3, and the switching actions of the two groups of power switches are opposite.

[0034] The direct current BT1 can come from a front-stage power factor correction (PFC) circuit.

[0035] The on-vehicle charger provided by the embodiment of the present application further includes: a resonant capacitor C1 and a resonant inductor L1;

[0036] The resonant capacitor C1 and the resonant inductor L1 are connected in series between the primary conversion circuit and the primary winding w1. The resonant inductor L1 is an external inductor or the leakage inductance of the transformer T1. The functions of the resonant capacitor C1 and the resonant inductor L1 are to improve the power conversion efficiency.

[0037] Among them, the first secondary conversion circuit includes Q5-Q8, and Q5-Q8 form a first secondary rectification circuit for converting the alternating current coupled by the first secondary winding w2 of the transformer T1 into direct current to supply power to the power battery.

[0038] The second secondary conversion circuit includes Q9-Q12, and Q9-Q12 form a second secondary rectification circuit for converting the alternating current coupled by the second secondary winding w3 of the transformer T1 into direct current to supply power to other loads except the power battery, such as an air conditioner or a vehicle lamp.

[0039] The second secondary conversion circuit has a first group of rectification switches Q10, Q11 and a second group of rectification switches Q9, Q12, and the switching actions of the two groups of rectification switches are opposite.

[0040] C2 is the resonant capacitor in the first secondary conversion circuit. C2 can resonate with the first secondary winding w1. C3 is the filter capacitor in the first secondary conversion circuit. L2, C4, and C5 are the filter inductor and filter capacitors in the second secondary conversion circuit.

[0041] In addition, the second secondary conversion circuit provided by the embodiments of the present application further includes an output switch Q13 and a freewheeling switch Q14.

[0042] The on-vehicle charger provided by the embodiments of the present application further includes: a controller MCU; the MCU can control the switching states of Q1-Q14, that is, the MCU outputs drive signals to Q1-Q14. Specifically, the MCU generates drive signals according to the input voltage Vin, input current Iin of the primary conversion circuit, and the output voltage Vout1, output current Iout1 of the first secondary conversion circuit, and the output voltage Vout2, output current Iout2 of the second secondary conversion circuit. It should be understood that the on-vehicle charger provided by the embodiments of the present application further includes a sampling circuit for collecting the above voltages and currents.

[0043] Among them, R1 and R2 respectively correspond to the loads of the first secondary conversion circuit and the second secondary conversion circuit.

[0044] For the on-vehicle charger provided by the embodiments of the present application, both the first secondary conversion circuit and the second secondary conversion circuit adopt full-bridge conversion circuits. Since the full-bridge conversion circuit includes four controllable switch tubes, the voltages at the two DC output terminals can be flexibly controlled, and thus precise voltage adjustment can be achieved. Compared with the second secondary conversion circuit adopting a full-wave rectification circuit, the voltage stress can be reduced. Moreover, the transformer with a center tap is changed to a single transformer, and a magnetic integration scheme is adopted, which has high integration, low heat generation, low loss, and can reduce costs. Full-bridge rectification can achieve soft-switching operation, so the power conversion efficiency can be improved.

[0045] Next, continue to combine Figure 1 to introduce in detail the working principle of the on-vehicle charger provided by the embodiments of the present application.

[0046] For the on-vehicle charger provided by the embodiments of the present application, the controller MCU is used to compare the output current Iout2 of the second secondary conversion circuit with the second reference current Iref2, perform loop compensation on the difference obtained by the comparison to obtain a compensation value, take the smaller value of the obtained compensation value and the second preset voltage Vset2, that is, take the smaller value between the compensation value and Vset2 as the second voltage loop reference value Vref2, compare the output voltage Vout2 of the second secondary conversion circuit with Vref2, perform loop compensation on the difference obtained by the comparison to obtain a compensation value, and generate the positive wave time and negative wave time of the drive signal of the switch tube in the second secondary conversion circuit according to the compensation value.

[0047] That is, for the control of the second secondary conversion circuit, the MCU provided in the embodiments of the present application adopts a dual-loop control of a voltage loop and a current loop, uses the control result of the current loop as the reference value of the voltage loop for voltage control, and finally generates the drive signal of the switching tube of the second secondary conversion circuit according to the control result of the voltage loop, so as to achieve precise closed-loop control.

[0048] In addition, the first end of the output switch Q13 is connected to the positive output end of the first full-bridge conversion circuit, and the second end of the output switch Q13 is connected to the negative output end of the first full-bridge conversion circuit through the freewheeling switch Q14; the output switch Q13 and the freewheeling switch Q14 act complementarily.

[0049] To precisely control the conduction time of the switching tube in each cycle, specifically, the switching tube in the second secondary conversion circuit is controlled according to the wave generation moment of the switching tube of the primary conversion circuit.

[0050] The MCU provided in the embodiments of the present application is used to compare and compensate Vout2 and Iout2 to obtain a compensation value, use the obtained compensation value as the chopping delay time T, and add the positive wave generation moment of the drive signal of the switching tube in the second secondary conversion circuit, the positive zero-crossing delay, and the chopping delay time as the conduction time of the output switch.

[0051] The following introduces a method for obtaining the chopping delay time.

[0052] The MCU is specifically used to compare Vout2 with Vref2, perform loop compensation on the comparison difference to obtain a compensation value, take the smaller value of the compensation value and the preset current loop preset value Iset2, and use the smaller value as the current loop reference value Iref2; compare Iout2 with Iref2, perform loop compensation on the comparison difference to obtain a compensation value, and the compensation value is T.

[0053] The following introduces a method for obtaining the positive zero-crossing delay.

[0054] The MCU is further used to obtain the zero-crossing moment of the primary conversion circuit from the input current Iin of the primary conversion circuit, and obtain the positive zero-crossing delay according to the wave generation moment and the zero-crossing moment of the primary conversion circuit.

[0055] The positive zero-crossing delay provided above is controlled according to the parameters of the primary conversion circuit. In addition, the correspondence relationship can be calculated in advance, and the positive zero-crossing delay can be obtained according to the current output power, which is more time-saving and has a faster response speed.

[0056] The controller MCU is also used to store the comparison relationships. The output power of the primary conversion circuit is divided into multiple levels, and each level of output power corresponds to a comparison relationship, that is, multiple comparison relationships are stored, and each level of power corresponds to a comparison relationship. Each comparison relationship includes the corresponding relationship between the switching frequency of the switching tube and the positive zero-crossing delay; the positive zero-crossing delay corresponding to the switching frequency at the positive wave generation moment is found according to the comparison relationship corresponding to the current output power.

[0057] In addition, for the on-vehicle charger provided in the embodiment of the present application, the first secondary conversion circuit is a second full-bridge conversion circuit;

[0058] The controller MCU is also used to compare the output current Iout1 of the first secondary conversion circuit with the first reference current Iref1, perform loop compensation on the difference obtained by the comparison to obtain a compensation value, take the smaller value between the obtained compensation value and the first preset voltage Vset1, and use the smaller value as the first voltage loop reference value Vref1. The output voltage Vout1 of the first secondary conversion circuit is compared with the voltage loop reference value, loop compensation is performed on the difference obtained by the comparison to obtain a compensation value, and the positive wave generation moment and negative wave generation moment of the drive signal of the switching tube in the second full-bridge conversion circuit are generated according to the obtained compensation value.

[0059] The embodiment of the present application does not specifically limit the control method adopted for the above loop compensation. For example, in a possible implementation manner, the loop compensation can adopt 2P2Z loop compensation.

[0060] See Figure 2 , this figure is a schematic diagram of a traditional on-vehicle charger.

[0061] In the traditional technology, generally two transformers are used, or, as Figure 2 shown, they are T1 and T2 of two transformers, and the second secondary circuit adopts a full-wave rectifier circuit including Q9 and Q10. In this way, the transformer cost is high, and the voltage stress of the full-wave rectification is large. Soft-switching action cannot be achieved, and the power consumption is also large.

[0062] See Figure 3 , this figure is a schematic diagram of another traditional on-vehicle charger.

[0063] In the traditional technology, generally a transformer T1 with a center tap is used, and the second secondary circuit adopts a full-wave rectifier circuit including Q9 and Q10. In this way, the transformer cost is high, and the voltage stress of the full-wave rectification is large. Soft-switching action cannot be achieved, and the power consumption is also large.

[0064] The on-vehicle charger provided in the embodiment of the present application can flexibly control the DC voltages output by the two secondary conversion circuits with one MCU, has accurate voltage regulation and strong anti-interference ability; at the same time, it has the advantages of small output voltage stress, low loss, small heat generation and high efficiency.

[0065] The above are only the preferred embodiments of the present invention and do not impose any form of limitation on the present invention. Although the present invention has been disclosed above with the preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can, without departing from the scope of the technical solution of the present invention, make many possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above, or modify it into equivalent embodiments with equivalent changes. Therefore, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A vehicle-mounted charger, characterized in that: include: A primary side conversion circuit, a first secondary side conversion circuit, a second secondary side conversion circuit and a transformer; The primary conversion circuit is connected to the primary winding of the transformer, the first secondary conversion circuit is connected to the first secondary winding of the transformer, and the second secondary conversion circuit is connected to the second secondary winding of the transformer; The first secondary winding is used to supply power to the power battery, and the second secondary winding is used to supply power to other loads other than the power battery; The second secondary side conversion circuit is a first full-bridge conversion circuit.

2. The vehicle-mounted charger according to claim 1, characterized in that: Also includes: Controller; The controller is used to compare the output current Iout2 of the second secondary conversion circuit with the second reference current Iref2, perform loop compensation on the comparison difference to obtain a compensation value, take the smaller of the obtained compensation value and the second preset voltage Vset2, and take the smaller value as the second voltage loop reference value Vref2, compare the output voltage Vout2 of the second secondary conversion circuit with the Vref2, perform loop compensation on the comparison difference to obtain a compensation value, and generate the positive wave transmission moment and the negative wave transmission moment of the drive signal of the switch tube in the second secondary conversion circuit according to the compensation value.

3. The vehicle-mounted charger according to claim 2, characterized in that: The second secondary side conversion circuit also includes an output switch and a freewheeling switch; The first end of the output switch is connected to the positive output end of the first full-bridge conversion circuit, and the second end of the output switch is connected to the negative output end of the first full-bridge conversion circuit through the freewheeling switch; The controller is used to compare and compensate the Vout2 and the Iout2 to obtain a compensation value, and use the obtained compensation value as the chopping delay time T, and use the positive wave emission moment of the driving signal of the switch tube in the second secondary side conversion circuit plus the positive zero crossing delay and the chopping delay time as the conduction time of the output switch, and the output switch and the freewheeling switch act complementary to each other.

4. The vehicle-mounted charger according to claim 3, characterized in that: The controller is specifically used to compare the Vout2 with the Vref2, perform loop compensation on the comparison difference to obtain a compensation value, take the smaller of the compensation value and the preset current loop preset value Iset2, and take the smaller value as the current loop reference value Iref2; compare the Iout2 with the Iref2, perform loop compensation on the comparison difference to obtain a compensation value, and the compensation value is the T.

5. The vehicle-mounted charger according to claim 3 or 4, characterized in that: The controller is also used to obtain the zero-crossing time of the primary-side conversion circuit using the input current Iin of the primary-side conversion circuit, and obtain the positive zero-crossing delay according to the wave-generating time and the zero-crossing time.

6. The vehicle-mounted charger according to claim 3 or 4, characterized in that: The controller is also used to store a comparison relationship. The output power of the primary side conversion circuit is divided into multiple levels, and each level of output power corresponds to a comparison relationship. Each comparison relationship includes a corresponding relationship between the switching frequency of the switch tube and the positive zero-crossing delay. The positive zero-crossing delay corresponding to the switching frequency at the positive wave moment is searched in the comparison relationship corresponding to the current output power.

7. The vehicle-mounted charger according to claim 2, characterized in that: The first secondary side conversion circuit is a second full-bridge conversion circuit; The controller is also used to compare the output current Iout1 of the first secondary conversion circuit with the first reference current Iref1, perform loop compensation on the comparison difference to obtain a compensation value, take the smaller of the obtained compensation value and the first preset voltage Vset1, and take the smaller value as the first voltage loop reference value Vref1, compare the output voltage Vout1 of the first secondary conversion circuit with the voltage loop reference value, perform loop compensation on the comparison difference to obtain a compensation value, and generate the positive wave transmission moment and the negative wave transmission moment of the drive signal of the switch tube in the second full-bridge conversion circuit according to the obtained compensation value.

8. The vehicle-mounted charger according to any one of claims 2 to 7, characterized in that: The loop compensation adopts 2P2Z loop compensation.

9. The vehicle-mounted charger according to claim 1, characterized in that: The primary side conversion circuit is a third full-bridge conversion circuit.

10. The vehicle-mounted charger according to claim 1, characterized in that: Also includes: Resonant capacitor and resonant inductor; The resonant capacitor and the resonant inductor are connected in series and connected between the primary conversion circuit and the primary winding. The resonant inductor is an external inductor or a leakage inductance of the transformer.

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