Auxiliary power module with ultra-wide voltage range

Abstract

An improved auxiliary power module for use with an electric vehicle is provided. The auxiliary power module includes a reconfigurable dual active bridge converter for providing a voltage feed input or a current feed input to the primary side full bridge. The auxiliary power module also includes a current feed output port that integrates an interleaved step-down stage and presents an ultra-wide voltage coverage. The auxiliary power module implements a low switching current on the secondary side of the dual active bridge converter with a low current stress on the output port that reduces loss and transformer turns ratio when compared to conventional topologies.

Description

Technical Field

[0001] The present invention relates to an auxiliary power module, and more particularly to an auxiliary power module for an electric vehicle having a reconfigurable battery pack. Background Art

[0002] Auxiliary power modules are an integral aspect of modern electric vehicles (EVs). The auxiliary power module bridges the high-voltage propulsion system and the low-voltage auxiliary system by stepping down the high-voltage DC bus voltage (e.g., 400V) to a low-voltage DC bus voltage (e.g., 12V) to power non-propulsion loads and charge the low-voltage battery. As the demand for fast battery charging increases, high-voltage propulsion systems are increasingly being designed for 800V rather than 400V. To accommodate this trend, auxiliary power modules also face the challenge of accepting a much wider voltage range, particularly in EVs with reconfigurable battery packs (i.e., battery packs that can operate at two or more voltages, e.g., 400V and 800V).

[0003] In addition to the challenges associated with accepting a wide range of input voltages, modern auxiliary power supply systems must provide high output current. Due to the lower output voltage, typically 6V to 16V, the auxiliary power module experiences high current stress on the low-voltage side of the internal step-down transformer. For example, a 3.5kW output at 12V represents an output current of up to 300A. For common topologies such as LLC converters and DAB converters, high-current loads imply high switching currents or impractically high voltage gains. Although efforts have been made to implement two-stage converters that provide high power and wide voltage gain, these converters have proven to be complex and expensive.

[0004] Accordingly, there remains a continuing need for a low-cost auxiliary power module for use with reconfigurable batteries. In particular, there remains a need for an auxiliary power module that provides high power output over a wide range of input voltages, has improved voltage gain on the low-voltage side, and low switching current stress. Summary of the Invention

[0005] An improved auxiliary power module for an electric vehicle is provided. The auxiliary power module includes a reconfigurable dual-active bridge converter for providing a voltage-fed input or a current-fed input to a primary-side full bridge. The auxiliary power module further includes a current-fed output port that integrates an interleaved buck stage and exhibits an ultra-wide voltage coverage range. The auxiliary power module achieves low switching current on the secondary side of the dual-active bridge converter and has low current stress at the output port, which reduces losses when compared to conventional topologies.

[0006] In one embodiment, the auxiliary power module includes a switch connected between the input port of the dual-active bridge converter and the primary-side full bridge. The switch can move between a first switch state and a second switch state based on the input voltage and / or the output voltage. The switch is optionally a double-throw relay configured to couple the input port to a first terminal or a second terminal corresponding to the first switch state and the second switch state, respectively. The primary-side full bridge receives a voltage-fed input when the switch is in the first switch state and a current-fed input when the switch is in the second switch state. The primary-side full bridge is connected in parallel to the input port in the first switch state to provide a voltage-fed input to the primary-side full bridge.

[0007] In another embodiment, the auxiliary power supply includes a low-pass filter, and the low-pass filter includes first and second smoothing inductors. Both smoothing inductors can be coupled inductors. The first smoothing inductor is connected between the second terminal of the double-throw relay and the first branch of the primary-side full bridge, and the second smoothing inductor is connected between the second terminal of the double-throw relay and the second branch of the primary-side full bridge. The auxiliary power supply includes a high-voltage clamp capacitor connected in parallel to the primary-side full bridge.

[0008] In yet another embodiment, the auxiliary power module includes a low-voltage clamp capacitor and a secondary-side low-pass filter. The clamp capacitor is connected in parallel to the secondary-side full bridge. The low-pass filter includes a filter capacitor and first and second smoothing inductors connected between the secondary-side full bridge and the output port. The secondary side of the dual-active bridge converter is functionally a combined full bridge and interleaved boost stage. When in the voltage-fed mode, the voltage applied to the high-voltage winding of the step-down transformer is determined by both the input voltage and the primary-side duty cycle, while when in the current-fed mode, the voltage applied to the high-voltage winding of the step-down transformer is determined only by the input voltage.

[0009] These and other features and advantages of the present invention will become apparent from the following description of the present invention when considered in conjunction with the accompanying drawings and the appended claims.

[0010] Before explaining embodiments of the present invention in detail, it is to be understood that the present invention is not limited to the operating details or the arrangement and structure details of components set forth in the following description or illustrated in the drawings. The present invention can be implemented in various other embodiments and can be practiced or carried out in alternative ways not explicitly disclosed herein. Further, it is to be understood that the language and terminology used herein are for the purpose of description and should not be regarded as restrictive. The use of "including" and "comprising" and their variants means including the items listed thereafter and their equivalents as well as additional items and their equivalents. Additionally, listings can be used in the description of various embodiments. Unless otherwise explicitly stated, the use of listings should not be construed as limiting the present invention to any particular order or number of components. The use of listings should also not be construed as excluding any additional steps or components that may be combined with or incorporated into the listed steps or components from the scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 is a circuit diagram of a reconfigurable dual-active-bridge converter for an auxiliary power module in voltage-fed mode.

[0012] Figure 2 is a circuit diagram of a reconfigurable dual-active-bridge converter for an auxiliary power module in current-fed mode.

[0013] Figure 3 includes Figure 1-2 voltage and current waveforms of the reconfigurable dual-active-bridge converter.

[0014] Figure 4 includes graphs depicting high-voltage switch current and low-voltage switch current as a function of low-voltage duty cycle.

[0015] Figure 5 includes waveforms of a working example of a reconfigurable current-fed dual-active-bridge converter at 600V input voltage and 16V output voltage.

[0016] Figure 6 includes graphs illustrating the efficiency of a reconfigurable current-fed dual-active-bridge converter over a wide range of input and output voltages.

[0017] Figure 7 is a circuit diagram of a reconfigurable dual-active-bridge converter for an auxiliary power module having a low-voltage switch in voltage-fed mode.

[0018] Figure 8 is Figure 7Circuit diagram of a reconfigurable dual active bridge converter, where the low voltage switches are in current-fed mode. Detailed implementation

[0015] As discussed herein, an auxiliary power module according to one embodiment includes a reconfigurable dual active bridge converter to cover an ultra-wide input and output voltage range. Depending on the input voltage and / or output voltage, the reconfigurable dual active bridge converter can operate in voltage-fed mode and current-fed mode. Although described below for an auxiliary power module for an EV, the reconfigurable dual active bridge converter is not limited to EVs and can be used in other applications as needed.

[0016] Now refer to Figure 1-2 , the auxiliary power module is illustrated and generally designated as 10. The auxiliary power module 10 includes a high voltage input port 12, a low voltage output port 14, and a reconfigurable dual active bridge converter 16 therebetween. The input port 12 is configured to receive a high voltage DC input from a high voltage battery, such as an input voltage between 180V and 900V from a rechargeable lithium-ion battery pack for an EV. The output port 14 is configured to provide a low voltage DC output to a low voltage bus, such as an output voltage between 6V and 20V for charging a low voltage battery.

[0017] The dual active bridge converter 16 includes a primary side full bridge 18, a secondary side full bridge 20, and a step-down transformer 22 therebetween. The primary side full bridge 18 includes switches P1 - P4 (distributed along first and second branches 24, 26) and is electrically coupled to the primary side winding 28 via an inductor Lp. The inductor Lp can be an independent inductor or the leakage inductance on the primary side of the transformer. Similarly, the secondary side full bridge 20 includes switches S1 - S4 (distributed along third and fourth branches 30, 32) and is electrically coupled to the secondary side winding 34 via an inductor Ls. The inductor Ls can be an independent inductor or the leakage inductance on the secondary side of the transformer. A high voltage clamping capacitor Chv is connected in parallel to the primary side full bridge 18, and a low voltage clamping capacitor Clv is connected in parallel to the secondary side full bridge 20. A filter capacitor Cinh is also connected in parallel to the input port 12.

[0018] As described above, the auxiliary power module 10 can operate in voltage-fed mode and current-fed mode. To achieve this versatility, the auxiliary power module 10 includes a switch SW connected between the input port 12 and the dual active bridge converter 16. The switch SW is optionally a double-throw relay that connects the input port 12 to a first terminal S1 or to a second terminal S2. As Figure 1As shown, when the switch SW connects the input port 12 to the first terminal S1, the dual-active-bridge converter 16 receives a voltage-fed input from the input port 12. As Figure 2 As shown, when the switch SW connects the input port to the second terminal S2, the dual-active-bridge converter 16 receives a current-fed input from the input port 12.

[0019] More specifically, the switch SW may include a double-throw relay that can move between a first switch state and a second switch state. In the first switch state, the input port 12 is connected in parallel to the high-voltage clamping capacitor Chv and the primary-side full bridge 18. In the second switch state, the input port 12 is connected to the first and second branches 24, 26 of the primary-side full bridge 18 via the first and second smoothing inductors Lin1, Lin2. The first smoothing inductor Lin1 is coupled to the node between the serially connected switches P1 and P2, and the second smoothing inductor Lin2 is coupled to the node between the serially connected switches P3 and P4.

[0020] As described above, the auxiliary power module 10 integrates a full bridge and an interleaved buck stage. As Figure 1-2 As shown, the low-voltage clamping capacitor Clv is connected in parallel to the secondary-side full bridge 20. The low-pass filter 36 includes the first and second smoothing inductors Lo1, Lo2 and the filtering capacitor Col coupled between the secondary-side full bridge 20 and the output port 14. The first smoothing inductor Lo1 is electrically connected to the third branch 30 between the switches S1 and S2, and the second smoothing inductor Lo1 is electrically connected to the fourth branch 32 between the switches S3 and S4.

[0021] By switching the relay SW to the positions S1 or S2 respectively, the dual-active-bridge converter 16 can be reconfigured as a voltage-fed DC / DC converter or a current-fed DC / DC converter. The voltage-fed mode covers the main input and output voltage ranges, and the current-fed mode can be used as needed for extreme input and output voltages. The output port 14 always operates in the current-fed mode to reduce the RMS current of the low-voltage winding 34 of the transformer. As Figure 1 As shown, when the switch SW is in the voltage-fed switch state, the voltage applied to the high-voltage winding 28 is determined only by the input voltage Vinh. As Figure 2 As shown, when the switch SW is in the current-fed switch state, the voltage applied to the high-voltage winding 28 is determined by both the input voltage Vinh and the primary-side duty cycle Dh. Figure 3 Exemplary voltage waveforms (Vhv, Vlv) and current waveforms (Ihv, Ilv) are shown. Figure 3 The primary-side duty cycle (Dh) and the secondary-side duty cycle (Dl) of the primary-side full bridge 18 and the secondary-side full bridge 20 are also shown respectively. However, the control of the dual-active-bridge converter 16 is not limited toFigure 3 The waveforms or duty cycles in Figure 3 the waveforms or duty cycles in are provided for illustrative purposes and are not intended to be limiting.

[0022] Whether the primary - side full - bridge 18 is voltage - fed or current - fed is mainly a function of the input voltage Vinh and the output voltage Vol, and the input voltage Vinh and the output voltage Vol directly determine the zero - voltage - switching (ZVS) current. When the relay SW is in the first switching state S1, the ZVS current (Izvs hv ) is set forth in Equation (1) below, where Nt is the transformer turns ratio, and Lp and Ls represent the primary - side and secondary - side leakage inductances respectively: According to Equation (1) above, for a high - voltage duty cycle Dh that satisfies Equation (2) below, zero - voltage switching can be ensured, where Dh is physically limited to be less than 0.5: The output power Pout is given in Equation (3), where Ps represents the time delay between the mid - points of Dh and Dl, as Figure 3 shown in, where Ps is less than Dh–Dl. As a result, the power output Pout can be controlled only by the phase shift generated by a proportional - integral (PI) controller. In addition, the switching current Ihv can be optimized as a function of the duty cycles Dh and Dl. For example, Figure 4 the high - voltage switching current Ihv is plotted as a function of the low - voltage duty cycle Dl, and the low - voltage switching current Ilv is plotted as a function of the low - voltage duty cycle Dl, where Vinh = 700V and Vol = 14V. The high - voltage side achieves the minimum switching current at Dl opt_hv = 0.11, and the low - voltage side achieves the minimum switching current at Dl opt_lv = 0.25. Therefore, to achieve the minimum total loss, the optimal duty cycle Dl opt is determined by Equation (4) below, where Eoff_hv and Eoff_lv are the switching energies of the high - voltage switches (P1 - P4) and the low - voltage switches (S1 - S4):

[0023] A working example of the auxiliary power supply according to an exemplary embodiment will now be described. The auxiliary power supply includes four C3M0032120K SiC switches P1 - P4 from Wolfspeed, Inc. (formerly Cree, Inc.) and four IRFF100P219 Si switches S1 - S4 from Infineon Technologies AG. The transformer has a turns ratio of 12:1. Figure 5 and Figure 6 show the test results for a 600V input voltage and a 16V output voltage, and the efficiency curves at different input and output voltages, respectively. The tested waveforms (Vhv, Vlv) and switch currents (Ihv, Ilv) show a strong correlation with the computer model, and a peak efficiency of 95.3% was obtained for a 600V input and 16V output at 3kW. This working example demonstrates the ability to cover an ultra - wide input and output voltage range, where Figure 6 depicts an input voltage range from 180V to 700V and an output voltage range from 6V to 16V. Input voltages and output voltages outside these ranges are also possible. The auxiliary power module achieves low switching current on the low - voltage side and low current stress at the output port, which reduces losses when compared to traditional topologies.

[0024] Now referring to Figure 7-8 , a reconfigurable dual - active - bridge converter according to an additional embodiment is illustrated. Figure 7-8 The converter of Figure 1-2 is structurally and functionally similar to the converter of Figure 7-8 , except that the converter of Figure 1-2 includes a low - voltage switch SW2 in addition to the high - voltage switch SW1 that appears in Figure 7 . The low - voltage switch SW2 is connected between the secondary - side full - bridge 20 and the low - voltage output port 14 and provides multiple operating states to the low - voltage output port 14. As shown in Figure 8 , when the low - voltage switch SW2 connects the output port 14 to the first terminal S3, the output port 14 receives a voltage - fed output. As shown in Figure 7 , when the low - voltage switch SW2 connects the output port 14 to the second terminal S4, the output port 14 receives a current - fed output. More specifically, the low - voltage switch SW2 is optionally a double - throw relay that can move between two positions. In the first position, as shown in Figure 8In the second position shown, output port 14 is a current feeding port via smoothing inductors Lo1, Lo2. In this regard, output port 14 can provide either a voltage feeding output or a current feeding output, regardless of the position of high voltage switch SW1, which, as described above, provides either a voltage feeding input or a current feeding input to the primary side full bridge 18 of converter 10.

[0025] The foregoing description is of the presently contemplated embodiments of the invention. While certain features of a putter grip are functional, they may be implemented in different aesthetic configurations. Various changes and variations may be made without departing from the spirit and broader aspects of the invention as defined in the appended claims, which are to be interpreted in accordance with the principles of patent law, including the doctrine of equivalents. This disclosure is presented for purposes of illustration and should not be construed as an exhaustive description of all embodiments of the invention or as limiting the scope of the claims to the specific elements illustrated or described in connection with these embodiments. The invention is not limited to those embodiments that include all of these features or provide all of the benefits described, unless expressly set forth otherwise in the issued claims. Any reference to an element in the singular, for example, using the articles "a," "an," "the," or "said," is not to be construed as limiting the element to the singular.

Claims

1. An auxiliary power module, comprising: A dual-active bridge converter, the dual-active bridge converter including a primary full bridge, a secondary full bridge, and a step-down transformer therebetween, the step-down transformer having a first winding electrically connected to the primary full bridge and a second winding electrically connected to the secondary full bridge; Wherein the primary full bridge is electrically connected to an input port, and wherein the secondary full bridge is electrically connected to an output port, the dual-active bridge converter being adapted to convert a high voltage at the input port into a low voltage at the output port; and Wherein the dual-active bridge converter further includes a switch electrically connected between the input port and the primary full bridge, the switch being capable of moving between a first switch state and a second switch state, wherein when the switch is in the first switch state, the primary full bridge receives a voltage-fed input, and wherein when the switch is in the second switch state, the primary full bridge receives a current-fed input.

2. The auxiliary power module according to claim 1, wherein The switch is capable of moving between the first switch state and the second switch state based on an input voltage at the input port.

3. The auxiliary power module according to claim 1, wherein The switch is a double-throw relay configured to couple the input port to a first terminal or a second terminal corresponding to the first switch state and the second switch state, respectively.

4. The auxiliary power module according to claim 3, wherein, When the switch is in the first switch state, the primary full bridge is connected in parallel to the input voltage at the input port.

5. The auxiliary power module according to claim 3, further comprising a primary-side low-pass filter, the primary-side low-pass filter including first and second smoothing inductors, the first smoothing inductor being connected between the second terminal of the double-throw relay and a first branch of the primary full bridge, and the second smoothing inductor being connected between the second terminal of the double-throw relay and a second branch of the primary full bridge.

6. The auxiliary power module according to claim 1 further includes: A high-voltage clamping capacitor connected in parallel to the primary full bridge; And a low-voltage clamping capacitor connected in parallel to the secondary full bridge.

7. The auxiliary power module according to claim 1, further comprising a secondary-side low-pass filter, the secondary-side low-pass filter including a filter capacitor and first and second smoothing inductors connected between the secondary full bridge and the output port.

8. The auxiliary power module according to claim 1, wherein Each of the first winding and the second winding includes an energy storage circuit, the energy storage circuit including an independent inductor.

9. The auxiliary power module according to claim 1, wherein, Each of the first winding and the second winding includes an energy storage circuit, the energy storage circuit including a leakage inductance.

10. The auxiliary power module according to claim 1, wherein, The dual-active bridge converter is adapted to convert a first DC voltage between 180V and 900V into a second DC voltage between 6V and 20V.

11. The auxiliary power module according to claim 1, further comprising a low-voltage switch connected between the secondary full bridge and the output port, the low-voltage switch being operable to switch between a voltage-fed output and a current-fed output at the output port.

12. An auxiliary power module, comprising: An input port adapted to be coupled to a first battery of an electric vehicle; An output port adapted to be coupled to a second battery of an electric vehicle; And A DC / DC converter electrically connected between the input port and the output port, the DC / DC converter comprising: A primary-side full bridge, A secondary-side full bridge, A primary-side smoothing inductor coupled between the input port and the primary-side full bridge, A secondary-side smoothing inductor coupled between the output port and the secondary-side full bridge, A step-down transformer operatively coupled between the primary-side full bridge and the secondary-side full bridge, and A switch electrically connected between the input port and the primary-side full bridge, the switch being movable between a first switch state and a second switch state, wherein the primary-side full bridge receives a voltage-fed input from the input port when the switch is in the first switch state and receives a current-fed input from the input port when the switch is in the second switch state.

13. The auxiliary power module according to claim 12, wherein, The switch is movable between the first switch state and the second switch state based on an input voltage at the input port.

14. The auxiliary power module according to claim 12, wherein, The switch is a double-throw relay configured to couple the input port to a first terminal or a second terminal corresponding to the first switch state and the second switch state, respectively.

15. The auxiliary power module according to claim 14, wherein, When the switch is in the first switch state, the primary-side full bridge is connected in parallel to the input voltage at the input port.

16. The auxiliary power module according to claim 14, wherein The primary-side smoothing inductor includes a first smoothing inductor connected between the second terminal of the double-throw relay and a first branch of the primary-side full bridge, and includes a second smoothing inductor connected between the second terminal of the double-throw relay and a second branch of the primary-side full bridge.

17. The auxiliary power module according to claim 12, wherein, The DC / DC converter further includes a low-pass filter, the low-pass filter including a filter capacitor and the secondary-side smoothing inductor connected between the secondary-side full bridge and the output port.

18. The auxiliary power module according to claim 12 further includes: A high-voltage clamping capacitor connected in parallel to the primary-side full bridge; And a low-voltage clamping capacitor connected in parallel to the secondary-side full bridge.

19. The auxiliary power module according to claim 12, wherein The transformer includes a first winding electrically connected to the primary-side full bridge and a second winding electrically connected to the secondary-side full bridge, wherein each of the first winding and the second winding includes all or a part of an energy storage circuit.

20. The auxiliary power module according to claim 12, wherein The primary-side full bridge, the secondary-side full bridge and the transformer include a dual-active-bridge converter.

21. The auxiliary power module according to claim 12, wherein, The DC / DC converter is adapted to convert a first voltage between 180V and 900V into a second voltage between 6V and 20V.

22. The auxiliary power module according to claim 12, further comprising a low-voltage switch connected between the secondary-side full bridge and the output port, the low-voltage switch being operable to switch between a voltage-fed output and a current-fed output at the output port.

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