Method for operating a DC-DC voltage converter for a motor vehicle, computer program, data processing device, and motor vehicle

Abstract

The invention relates to a method (100) for operating a DC voltage converter (210) for a motor vehicle (200), comprising a primary full-bridge rectifier (211) and a secondary synchronous rectifier (212), comprising: detecting (110) an input voltage (UI) of the synchronous rectifier (212), an output voltage (UO) of the synchronous rectifier (212) and an output power (PO) of the synchronous rectifier (212); determining (120) a switching event (300) as a signal edge (310) of a respective switching element (S3) of the DC voltage converter (210) and a switching element (S67) of the synchronous rectifier (212) drops; ascertaining (130) a delay (315) of a drop of a signal edge (310) of a switching element (S67) of the synchronous rectifier (212) by means of the input voltage (UI), the output voltage (UO) and the output power (PO); and output (140) a control signal for shifting a signal edge (310 ') of a switching element (S67) of the synchronous rectifier (212) according to the delay (315).

Description

Field of the Invention

[0001] The present disclosure relates to a method for operating a DC voltage converter for a motor vehicle having a primary full-bridge rectifier and a secondary synchronous rectifier, and a data processing device designed to at least partially execute the method. Additionally, a motor vehicle having the data processing device is provided. Additionally or alternatively, a computer program is provided, including instructions that cause the computer to at least partially execute the method when the program is executed by the computer. Additionally or alternatively, a computer-readable medium is provided, including instructions that cause the computer to at least partially execute the method when the instructions are executed by the computer. Background Art

[0002] DE102007001673A1 discloses a vehicle electrical system for a motor vehicle, including: a high-voltage energy storage device for providing a high-voltage power grid for powering one or more high-voltage loads; and a first conversion device for converting the high voltage of the high-voltage power grid to a predetermined low voltage of a low-voltage power grid for powering one or more low-voltage loads. There is a second conversion device, which is connected in parallel with the first conversion device and at least temporarily inputs predetermined energy into the low-voltage power grid via the second conversion device.

[0003] The DC voltage converter according to the prior art has an LC filter as an output stage. Here, the coil decouples the switching element of the synchronous rectifier from the capacitor or capacitance. This results in an overshoot of the output voltage (drain voltage) of the switching element. This overshoot is caused by the resonance of the DC voltage converter. Here, the reverse recovery charge (Qrr) of the body diode assigned to the switching element further enhances this overshoot. The voltage during the overshoot causes the output voltage overshoot to exceed the threshold voltage at which the switching element operates reliably. The overshoot of the voltage causes accelerated aging of the switching element. Summary of the Invention

[0004] Against the background of this prior art, the task of the present disclosure is to provide an improved method that is suitable for enriching the prior art. The specific design of the present disclosure can solve the following task, that is, to avoid the overshoot of the output voltage, enable improved operation of the switching element, and reduce the aging of the switching element.

[0005] This task is solved by the features of the independent claims. The dependent claims have the disclosed optional further expansions as content.

[0006] Accordingly, this task is solved by a method for operating a DC voltage converter for a motor vehicle having a primary full-bridge rectifier and a secondary synchronous rectifier, wherein the method has: detecting the input voltage, the output voltage, and the output power of the synchronous rectifier; determining a switching event as the signal edges of a respective switching element of the DC voltage converter and of the switching element of the synchronous rectifier fall; ascertaining the delay of the falling signal edge of the switching element of the synchronous rectifier by means of the input voltage, the output voltage, and the output power; and outputting a control signal for shifting the signal edge of the switching element of the synchronous rectifier according to the delay.

[0007] It has been recognized here that the DC voltage converter causes an excessive overshoot of the voltage of the switching element of the synchronous rectifier without proper control of the switching element. In order to be able to reduce the overshoot, an adaptation of the logic switching signal is used to control the switching of the switching element of the synchronous rectifier. Here, the signal edge of the switching element of the synchronous rectifier can be shifted relative to the signal edge of the switching element of the full-bridge rectifier. In other words, the signal edge of the switching element of the synchronous rectifier falls later than the signal edge of the switching element of the full-bridge rectifier. It has been recognized here that the time period defined by the delay between the falling signal edge of the switching element of the full-bridge rectifier and the falling signal edge of the switching element of the synchronous rectifier causes a current drop in the switching element of the synchronous rectifier.

[0008] The method has the following advantages: the reverse recovery charge can be avoided or reduced by the current drop, the voltage overshoot can be reduced and thus premature aging of the switching element of the synchronous rectifier can be resisted.

[0009] The ascertainment of the delay can be carried out by means of equations that are linearly related to the input voltage, the output voltage, and the output power, respectively. In other words, the delay is ascertained by means of a linearized model having the three variables of the input voltage, the output voltage, and the output power. The linearized model can be analyzed efficiently and takes into account the variables related to the delay and the avoidance of overshoot. In other words, the equation for the delay has the form t = a*iV + b*oV + c*oP, with the delay t, the input voltage UI, the output voltage UO, the output power PO, and the coefficients a, b, and c.

[0010] The ascertainment of the delay can be carried out by means of a simulation of the DC voltage converter. Here, in particular, the non-linear characteristics of the capacitance of the synchronous rectifier (Coss) can be modeled for the simulation. Here, the functional model for the capacitance of the synchronous rectifier can be implemented by fitting a non-linear function to the data points of the capacitance of the synchronous rectifier, such as the data points in a data sheet. The non-linear function can be used to model and simulate the DC voltage converter in order to efficiently model the oscillation characteristics and in particular the overshoot.

[0011] The simulation can simulate a DC voltage converter for each of an input voltage range, an output voltage range, and an output power range. Thus, the simulation can simulate a DC voltage converter for typical operating points.

[0012] The simulation can simulate a DC voltage converter in non-intermittent operation (current conduction mode or continuous current mode, CCM). Thus, the DC voltage converter can be modeled in a situation where the output current of the DC voltage converter never becomes zero, so as to efficiently simulate the DC voltage converter.

[0013] The determination of the delay can be implemented such that the switching current of the switching element involving the synchronous rectifier is reduced below a threshold value and / or reduced to 0 A. Thus, it can be ensured that the switching current is reduced in such a way that no reverse recovery charge occurs or only an insignificant reverse recovery charge that does not contribute to excessive aging occurs, and thus excessive overshoot can be avoided.

[0014] The switching event can be defined by pulse width modulation. Thus, the switching event can be efficiently controlled. By defining the switching event by pulse width modulation, an efficient determination of the switching event can be achieved.

[0015] Furthermore, a computer program is provided, which includes instructions that cause the computer to at least partially execute or implement the above method when the program is executed by the computer.

[0016] The program code of the computer program can exist in any code, especially in a code suitable for controlling a motor vehicle.

[0017] What has been described above regarding the method similarly applies to the computer program and vice versa.

[0018] Furthermore, a data processing device for an automated motor vehicle, such as a controller, is provided, wherein the data processing device is designed to at least partially execute or implement the above method. Thus, the method is a computer-implemented method.

[0019] The data processing device can be part of or form part of a driving assistance system. The data processing device can be, for example, an electronic control unit (ECU = electronic control unit in English). The electronic controller can be an intelligent processor-controlled unit, which can communicate with other modules via a central gateway (CGW) for example, and which can form a vehicle on-board electrical network with a telematics controller via a field bus (such as CAN bus, LIN bus, MOST bus, and FlexRay) or via automotive Ethernet if necessary.

[0020] What has been described above for the method and computer program applies analogously to a data processing device and vice versa.

[0021] Furthermore, a motor vehicle is provided, which includes the above-described data processing device.

[0022] The motor vehicle can be a sedan, in particular an automobile. Optionally, the automated motor vehicle can be an electrically drivable motor vehicle. The motor vehicle can for this purpose include an electric drive device, which can be loaded with electrical energy provided by an energy storage device to drive the motor vehicle. Optionally, the automated motor vehicle can be designed to at least partially and / or at least temporarily assume longitudinal guidance and / or lateral guidance during automated driving of the motor vehicle. The automated driving can be carried out in such a way that the progress of the motor vehicle takes place (to a large extent) autonomously. The automated driving can be controlled at least partially and / or temporarily by the data processing device. The motor vehicle can be a motor vehicle with an automation level from 0 to 5.

[0023] What has been described above for the method, data processing device and computer program also applies analogously to the motor vehicle and vice versa.

[0024] Furthermore, a computer-readable medium, in particular a computer-readable storage medium, is provided. It includes instructions which, when executed by a computer program, cause the computer to at least partially execute the above method.

[0025] That is to say, a computer-readable medium including the computer program defined above can be provided. The computer-readable medium can be any digital data storage device, such as a USB flash drive, hard disk, optical disc, SD card or SSD card. The computer program does not have to be stored on such a computer-readable storage medium in order to be provided to the motor vehicle, but can also be obtained via the Internet or other external means.

[0026] What has been described above for the method, data processing device, computer program and automated motor vehicle also applies analogously to the computer-readable medium and vice versa. Description of the Drawings

[0027] Embodiments are described below with reference to the drawings.

[0028] Figure 1 A motor vehicle according to one aspect of the present disclosure is schematically shown;

[0029] Figure 2 A DC voltage converter for a motor vehicle according to one aspect of the present disclosure is shown;

[0030] Figure 3 A schematic diagram of a switching element for switching a DC voltage converter for a motor vehicle according to one aspect of the present disclosure is shown;

[0031] Figure 4 Schematically show the voltage, current, and switching signal with respect to time of the switching element of a synchronous rectifier according to the prior art, respectively;

[0032] Figure 5 Schematically show the switching element voltage, current, and switching signal with respect to time of the switching element of a synchronous rectifier of a DC voltage converter for a motor vehicle according to an aspect of the present disclosure, respectively; and

[0033] Figure 6 Schematically show a flowchart of a method according to an aspect of the present disclosure. Detailed Description of the Invention

[0034] Figure 1 Schematically show a motor vehicle 200 according to an aspect of the present disclosure. The motor vehicle 200 is, for example, a hybrid vehicle and / or an electric vehicle. The motor vehicle 200 has a traction battery (not shown) as a high-voltage energy storage device. The motor vehicle 200 also has a low-voltage power grid (not shown), such as an on-vehicle power grid. In order to enable the low-voltage power grid to be charged with electrical energy or operated through the high-voltage energy storage device, the motor vehicle includes a DC voltage converter 210 and a data processing device 250. The DC voltage converter 210 is designed to convert the high-voltage voltages HV+ and HV- into low-voltage voltages LV+ and LV-. The data processing device 250 is designed to control and / or regulate the DC voltage converter 210. The data processing device 250 is designed to implement the method 100 described with reference to Figure 6 For this purpose, the data processing device 250 is designed to detect by measuring the input voltage UI, the output voltage UO, and the output power PO and to define switching events 300 through pulse width modulation and to cause switching events by outputting corresponding control signals. Refer to Figure 2 , Figure 3 and Figure 5 The DC voltage converter 210 is described in more detail.

[0035] Figure 2 Show a DC voltage converter 210 for a motor vehicle 200 according to an aspect of the present disclosure. Refer to Figure 1 This motor vehicle 200 is described.

[0036] According to Figure 2The DC voltage converter 210 includes a primary full-bridge rectifier 211 and a secondary synchronous rectifier 212. The full-bridge rectifier 211 is designed to be loaded with high voltages HV+ and HV- and has four switching elements S1, S2, S3, S4. Each of these switching elements S1, S2, S3, S4 is configured as a MOSFET and is connected in parallel with body diodes D1, D2, D3, D4. Capacitors C1, C2, C3, C4 as output stages are connected downstream of each of these switching elements S1, S2, S3, S4.

[0037] The full-bridge rectifier 211 and the synchronous rectifier 212 are coupled to each other via an oscillation circuit 213.

[0038] The synchronous rectifier 212 is designed to provide low voltages LV+ and LV- and has four switching elements S58, S67. Each of these switching elements S58, S67 is configured as a MOSFET and is connected in parallel with body diodes D58, D67. Capacitors C58, C67 as output stages are connected downstream of each of these switching elements S58, S67.

[0039] The switching elements S1, S2, S3, S4, S58, S67 are switched by a switching signal SS. Thus, the switching of the switching elements S1, S2, S3, S4, S58, S67 is controlled by a data processing device 250. For this purpose, the data processing device 250 applies a switching signal SS defined by pulse width modulation to these switching elements S1, S2, S3, S4, S58, S67. Figure 3 A schematic diagram for switching these switching elements S1, S2, S3, S4, S58, S67 according to such a signal is shown.

[0040] Figure 3 A schematic diagram for switching the switching elements S1, S2, S3, S4, S58, S67 of the DC voltage converter 210 for a motor vehicle 200 according to an aspect of the present disclosure is shown. Refer to Figure 1 and Figure 2 for description Figure 3 .

[0041] In particular, Figure 3 a switching signal SS for switching these switching elements S1, S2, S3, S4, S58, S67 with respect to time t is shown. Here, the switching signal SS is plotted in arbitrary units, and the switching signals SS of the switching elements S1, S2, S3, S4, S58, S67 are plotted overlapping each other, wherein each switching signal SS for one of the switching elements S1, S2, S3, S4, S58, S67 is described using a zero line marked with 0 as a reference and for orientation.

[0042] The switching signal SS includes a plurality of switching events 300. In each switching event 300, the switching signal SS of one of the switching elements S1, S2, S3, S4, S58, S67 changes in a stepwise manner. In particular, the switching may include a switching edge 310 dropping to the zero line.

[0043] The vertically arranged dashed lines depict that, according to the prior art, the switching of one of the switching elements S1, S2, S3, S4 of the full - bridge rectifier 311 and the switching of one of the switching elements S58, S67 of the synchronous rectifier 312 occur simultaneously. Thus, there is no dead time (delay) between the switching of one of the switching elements S1, S2, S3, S4 of the full - bridge rectifier 311 and the dropping of the switching edge 310 when one of the switching elements S58, S67 of the synchronous rectifier 312 switches.

[0044] By simultaneously switching one of the switching elements S1, S2, S3, S4 of the full - bridge rectifier 311 and one of the switching elements S58, S67 of the synchronous rectifier 312, the relationship over time between the voltage US, the current IS, and the switching signal SS as described with reference to Figure 4 is generated.

[0045] Figure 4 Schematically shown are the voltage US, the current IS, and the switching signal SS over time for the switching elements S58, S67 of the synchronous rectifier 311 according to the prior art or for the diodes, i.e., the body diodes D58, D59, connected in parallel with the switching elements S58, S67.

[0046] The switching signal SS (gate signal, PWM signal) describes the switching of the switching elements S58, S67. Here, the signal edge 310 drops at the defined switching time point indicated by the vertical dotted line. Before switching, a negative current IS (MOSFET current, solid line) flows through the switching elements S58, S67. At the time of switching, the current IS through the switching elements S58, S67 becomes zero, and the current IS is instead conducted through the body diodes D58, D67 (no load, "body diode current", dashed line). When the current IS reaches zero, the current IS flowing through the body diodes D58, D67 causes reverse recovery charge (RRC). The reverse recovery charge causes an overshoot and damped oscillation of the voltage US ("drain - source voltage") of the switching elements S58, S67. In addition, this causes further losses in the DC - voltage converter 210 due to the voltage drop across the body diodes D58, D67.

[0047] Figure 5Schematically shown are the voltage, current, and switching signal over time of the switching elements S58 and S67 of the synchronous rectifier 311 of the DC voltage converter 210 for a motor vehicle 200 according to one aspect of the present disclosure. Refer to Figures 1 to 4 Description Figure 5 In particular, described herein is Figure 4 and Figure 5 the difference.

[0048] The switching signal SS (gate signal, PWM signal) describes the switching of the switching elements S58 and S67. Herein, refer to Figure 4 the described switching signal SS is shown by a dashed line (“PWM signal: typical”) in Figure 5 , while the switching signal SS according to the method 100 according to one aspect of the present disclosure is shown by a solid line (“PWM signal: adapted”). The difference in the switching signal SS lies in the falling of the signal edges 310 and 310'. The falling of the signal edge 310 according to the prior art is deliberately shifted by a delay 315 in order to achieve the falling of the signal edge 310' according to the method 100 according to one aspect of the present disclosure.

[0049] The delay 315 is additionally described by a dotted line in Figure 3 . It can be seen here that the switching of the primary full-bridge converter 311 remains unchanged, and only the switching of the switching elements S58 and S67 of the synchronous rectifier 312 during disconnection is shifted according to the delay 315 relative to the switching of the switching elements S1, S2, S3, and S4 of the full-bridge converter 311.

[0050] As Figure 5 shown, the current IS drops to zero until the signal edge 310' falls. The formation of no-load and reverse recovery charge (RRC) of the diodes D58 and D67 is avoided. Herein, refer to Figure 4 the described current IS is shown by a weak dotted line (“body diode current: typical”) and a strong dotted line (“MOSFET current: typical”) in Figure 5 , and the current IS according to the method 100 according to one aspect of the present disclosure is shown by a solid line (“body diode current: adapted”) and a dashed line (“MOSFET current: adapted”). Therefore, the overshoot of the voltage US (“drain-source voltage: adapted”, solid line) of the switching elements S58 and S67 can be reduced by 40% relative to the prior art (“drain-source voltage: typical”, dotted line). In addition, further losses due to the voltage drop across the body diodes D58 and D67 in the DC voltage converter 210 can be avoided.

[0051] Figure 6A flowchart of a method 100 according to one aspect of the present disclosure is schematically shown. The method 100 is a method for operating a DC voltage converter 210 having a primary full-bridge rectifier 211 and a secondary synchronous rectifier 212 for a motor vehicle 200. Reference is made to Figure 1 such a motor vehicle 200 is described. Reference is made to Figure 2 such a DC voltage converter 210 is described.

[0052] According to Figure 6 the method 100 has: detecting 110 the input voltage UI, the output voltage UO, and the output power PO of the synchronous rectifier 212. The detection 110 of the input voltage UI, the output voltage UO, and the output power PO can be achieved by measurements using a measuring device (not shown) connected to a data processing device 250 (see Figure 1 ).

[0053] Determining 120 a switching event 300 as the signal edge 310 of a corresponding switching element S3 of the DC voltage converter 210 and the switching element S67 of the synchronous rectifier 212 falls. The switching event 300 is defined by pulse width modulation. Thus, the determination 120 of the switching event 300 can be determined by the data processing device 250 by means of pulse width modulation.

[0054] Ascertaining 130 the delay 315 of the signal edge 310 of the switching element S67 of the synchronous rectifier 212 by means of the input voltage UI, the output voltage UO, and the output power PO. The ascertaining 130 of the delay 315 can be carried out by means of a simulation of the DC voltage converter 210. Here, the DC voltage converter 210 is simulated in the operating range. For this purpose, the simulation simulates the DC voltage converter 210 for one interval each of the input voltage UI, the output voltage UO, and the output power PO. The simulation simulates the DC voltage converter 210 in non-intermittent operation, i.e., in the operation where the DC voltage converter 210 outputs a voltage at all times. The ascertaining 130 of the delay 315 is ascertained by means of equations that are linearly related to the input voltage UI, the output voltage UO, and the output power PO respectively. In other words, the delay is given as a linear combination of the input voltage UI, the output voltage UO, and the output power PO. The ascertaining 130 of the delay 315 is carried out such that the switching current IS of the switching element 67 of the synchronous rectifier 322 is reduced below a threshold value and / or reduced to 0 A. For this purpose, the three variables of the input voltage UI, the output voltage UO, and the output power PO are optimized according to the reduction of the switching current IS in order to achieve a local minimum or a global minimum of the switching current IS according to the input voltage UI, the output voltage UO, and the output power PO in the delay 315. The ascertaining 130 of the delay 315 is carried out by the data processing device 250.

[0055] Output a control signal 140 according to a delay 315 for shifting a signal edge 310' of a switching element S67 of the synchronous rectifier 212. To this end, the data processing device 250 outputs a correspondingly adapted switching signal SS to adjust the switching event 300 of the synchronous rectifier 212 and delay it with respect to the switching event 300 of the full-bridge rectifier 211.

[0056] List of reference numerals

[0057] 100 Method

[0058] 110 Detect input voltage, output voltage and output power

[0059] 120 Determine switching event

[0060] 130 Ascertain delay

[0061] 140 Output control signal

[0062] 200 Motor vehicle

[0063] 210 DC voltage converter

[0064] 211 Full-bridge rectifier

[0065] 212 Synchronous rectifier

[0066] 213 Oscillation circuit

[0067] 250 Data processing device

[0068] 300 Switching event

[0069] 310 Signal edge

[0070] 310’ Signal edge

[0071] 315 Delay

[0072] C1, C2, C3, C4, C58, C67 Capacitors

[0073] D1, D2, D3, D4, D58, D67 Body diodes

[0074] IS Current of the switching element of the synchronous rectifier

[0075] LV+, LV- Low-voltage

[0076] HV+, HV- High-voltage

[0077] PO Output power

[0078] S1, S2, S3, S4, S58, S67 Switching elements

[0079] t time

[0080] UI Input voltage

[0081] US Voltage of switching element of synchronous rectifier

[0082] UO Output voltage

Claims

1. A method (100) for operating a DC voltage converter (210) having a primary full-bridge rectifier (211) and a secondary synchronous rectifier (212) for a motor vehicle (200), wherein, The method (100) has: detecting (110) an input voltage (UI) of the synchronous rectifier (212), an output voltage (UO) of the synchronous rectifier (212), and an output power (PO) of the synchronous rectifier (212); determining (120) a switching event (300) as the signal edge (310) of a respective switching element (S3) of the DC voltage converter (210) and a switching element (S67) of the synchronous rectifier (212) falls; ascertaining (130) a delay (315) of the signal edge (310) of the switching element (S67) of the synchronous rectifier (212) by means of the input voltage (UI), the output voltage (UO), and the output power (PO); and outputting (140) a control signal for shifting the signal edge (310') of the switching element (S67) of the synchronous rectifier (212) according to the delay (315).

2. The method (100) according to claim 1, wherein The ascertaining (130) of the delay (315) is effected by means of an equation that is linearly dependent on the input voltage (UI), the output voltage (UO), and the output power (PO) respectively.

3. The method (100) according to claim 1 or 2, wherein, The ascertaining (130) of the delay (315) is effected by means of a simulation of the DC voltage converter (210).

4. The method (100) according to claim 3, wherein, The simulation simulates the DC voltage converter (210) for one interval each of the input voltage (UI), the output voltage (UO), and the output power (PO).

5. The method (100) according to claim 3 or 4, wherein The simulation simulates the DC voltage converter (210) in non-intermittent operation.

6. The method (100) according to any one of the preceding claims, wherein, The ascertaining (130) of the delay (315) is effected such that a switching current (IS) of the switching element (67) of the synchronous rectifier (322) is reduced below a threshold and / or reduced to 0 A.

7. The method (100) according to any one of the preceding claims, wherein, The switching event (300) is defined by pulse width modulation.

8. A computer program and / or a computer-readable medium, the computer program and / or the computer-readable medium including instructions that, when the program or the instructions are executed by a computer, cause the computer to perform the method (100) according to any one of claims 1 to 7 and / or the steps of the method (100).

9. A data processing device (250) for a motor vehicle (200), wherein, The data processing device (250) is designed to perform the method (100) according to any one of claims 1 to 7.

10. A motor vehicle (200), the motor vehicle including the data processing device (250) according to claim 9.

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