Electrical system having voltage converter and external control circuit for controlling converter

Abstract

An electrical system having a voltage converter and an external control circuit for controlling the converter is disclosed. The invention relates to an in-vehicle electrical system comprising at least one main battery (1), a primary network (VR1) directly supplied with power from the main battery, a voltage converter (3) supplying power to a secondary network (VR2), the voltage converter being supplied with power from the main battery via a first supply line (2) comprising at least one smoothing filter (22), the system is characterized in that it comprises an external control circuit (4) for controlling the converter, the circuit being configured to selectively activate or disable the operation of the voltage converter in order to minimize the voltage drop across the primary network when the voltage converter is activated.

Description

[0001] This invention relates to an electrical system having a voltage converter. The electrical system includes a main battery, and the voltage converter is supplied with power from the main battery.

[0002] When the voltage converter starts up, the main battery oscillates and experiences a large inrush current, which causes a voltage drop on the network that is being powered from the main battery. In the voltage converter, an on-off switch is used to control the current flow through one or more load inductors.

[0003] According to specific known solutions, an inductor filter is placed at the output of the main battery to smooth the current and reduce voltage drop and oscillations caused by chopper control used in the voltage converter.

[0004] In the case of a quasi-resonant voltage converter, the control switches have a certain degree of flexibility and are not executed at regular intervals. Therefore, the electromagnetic spectrum of potential interference generated by the chopper control of the resonant voltage converter is relatively broad.

[0005] Switching operations and the resulting transients generally cause electromagnetic noise, especially interference conducted throughout the vehicle network, which degrades performance from the perspective of the electromagnetic compatibility of systems including voltage converters.

[0006] Some researchers have attempted to improve the inductive filtering solution placed between the main battery and the voltage converter by using a filter known as a Pi filter. Such a Pi filter consists of an inductor connected in series on the line and placed between an upstream first capacitor and a downstream second capacitor, with each capacitor inserted between the line and ground.

[0007] Such solutions involving Pi filters allow for some improvement in transient reduction performance, and even across a wider frequency spectrum, but do not completely solve the problem.

[0008] The inventors have sought to further improve the aforementioned situation, and in particular to reduce voltage drop and oscillations caused by the chopper control of the voltage converter.

[0009] To this end, an on-board electrical system is proposed, comprising: at least one main battery; a primary network directly powered from the main battery; and a voltage converter powering a secondary network, the voltage converter being powered from the main battery via a first supply line including at least one smoothing filter. The system is characterized by including external control circuitry for controlling the converter, the external control circuitry being configured to selectively activate or disable the operation of the voltage converter to minimize voltage drop on the primary network when the voltage converter is activated.

[0010] With these arrangements, selective control for activating the voltage converter makes it possible to progressively turn on the converter over hundreds of milliseconds between the start of the sequence and the full-load operation of the voltage converter.

[0011] This results in a significant reduction in the voltage drop caused by the first inrush current, as well as a reduction in the amplitude of subsequent oscillations and transients.

[0012] In this way, it is possible to incidentally reduce the size of the smoothing filter placed between the battery and the voltage converter.

[0013] Regarding the expression "vehicle-mounted electrical system," the qualifier "vehicle-mounted" indicates that the electrical system is intended to be installed on a mobile machine, or at least on a mobile machine, and is not supplied with power by the main power grid.

[0014] According to one embodiment, an external control circuit for controlling the converter is configured to disable the operation of the voltage converter if the instantaneous voltage value of the first supply line drops below a first threshold.

[0015] Therefore, the voltage drop on the supply line of the voltage converter is limited. Advantageously, this reduces the impact on other electrical devices connected to the primary network caused by the activation of the voltage converter.

[0016] According to one embodiment, the external control circuit for controlling the converter is configured to reactivate the operation of the voltage converter if the instantaneous voltage value of the first supply line rises above a second threshold.

[0017] The converter's operation is reactivated to continue the startup sequence, eventually reaching full-load operation.

[0018] Therefore, there is an alternation between operation and non-operation during the startup phase of the voltage converter, which lasts for a maximum of several hundred milliseconds.

[0019] According to one embodiment, the external control circuitry used to control the converter is a digital circuit. In this case, a small microcontroller or a dedicated ASIC can be used to achieve the desired functionality.

[0020] According to one embodiment, the external control circuitry for controlling the converter is in the form of wired logic and includes a hysteresis comparator.

[0021] As a result, a highly reliable and simple-to-design basic solution is used, without the need to develop specific digital circuits or software.

[0022] According to one option, the comparator's first and second thresholds are defined with respect to the average smoothed value of the first supply line. In this way, instead of using absolute values, the high and low thresholds are defined with respect to relative values ​​obtained by averaging over a sliding window. Using thresholds based on a relative reference allows for better adaptation to the situation and the current state of charge of the main battery.

[0023] According to one embodiment, the positive terminal of the hysteresis comparator is connected to the instantaneous voltage of the first supply line, and the negative terminal of the hysteresis comparator is connected to the output of an RC filter that filters the instantaneous voltage of the first supply line; or the negative terminal of the hysteresis comparator is connected to the instantaneous voltage of the first supply line, and the positive terminal of the hysteresis comparator is connected to the output of an RC filter that filters the instantaneous voltage of the first supply line.

[0024] It is possible to obtain this average value very simply by using an analog RC low-pass filter, which will be described below. A cutoff frequency on the order of 1 kHz may be suitable for this filter.

[0025] According to one embodiment, the voltage converter is a quasi-resonant voltage converter. Modulation control performed by external control circuitry allows for reduction of the oscillation amplitude, regardless of the control logic implemented in the voltage converter, and this applies to a wide range of possible interference frequencies.

[0026] Furthermore, it will be noted that control modulated by an external control circuit can be applied to any type of voltage converter.

[0027] The present invention also relates to a method implemented in the vehicle electrical system described above, the method specifying the selective activation and deactivation of a voltage converter from an inactive state to a stable operating state, the method comprising:

[0028] - If the instantaneous voltage value of the first supply line drops below a first threshold, the operation of the voltage converter is disabled.

[0029] -If the instantaneous voltage value of the first supply line rises above the second threshold, the operation of the voltage converter is reactivated.

[0030] Therefore, during the startup phase of the voltage converter, there is an alternation between operation and non-operation. The startup phase can last for hundreds of milliseconds, or in some cases even less than 100 milliseconds.

[0031] As already mentioned, according to one option, the first threshold and the second threshold can be fixed thresholds, or according to another option, the first threshold and the second threshold can be thresholds that are relatively defined with respect to the average voltage of the primary network.

[0032] The present invention also relates to a vehicle comprising at least one of the on-board electrical systems described above.

[0033] The present invention will be further described in detail by way of a description of non-limiting embodiments and based on the accompanying drawings, which illustrate variations of the invention, and in the accompanying drawings:

[0034] [ Figure 1 An example of the circuitry for the proposed system is illustrated schematically.

[0035] [ Figure 2 The illustration shows an example of a timing diagram illustrating the proposed method.

[0036] The same reference labels are used throughout the figures to indicate the same or similar elements. For clarity, some elements may not be shown to scale.

[0037] Figure 1 The diagram illustrates an onboard electrical system, which includes a main battery 1 and a voltage converter 3, the voltage converter 3 being powered from the main battery via a first supply line 2.

[0038] In industry terminology, voltage converter 3 is referred to as a DC-DC converter. In a typical configuration, the voltage converter has an output voltage lower than its input voltage (buck DC-DC converter), however, the opposite configuration (boost DC-DC converter) is not excluded.

[0039] In this context, the invention presented below is particularly relevant in the case of a quasi-resonant voltage converter. A quasi-resonant voltage converter is a known device in itself and therefore will not be described in detail here. The reader may refer, for example, to document US5903448.

[0040] By way of example, the main battery 1 can be a traction battery, which enables the vehicle to move in zero-emission mode. The vehicle can be a light vehicle, recreational vehicle, passenger vehicle, or multi-purpose vehicle; there are no restrictions on the types of vehicles that can be considered. For conventional vehicles, the nominal voltage of the main battery can typically be 12 or 24 volts, or for electric vehicles, the nominal voltage of the main battery can typically be greater than 50 volts, and most often greater than 100 volts.

[0041] Primary network VR1 is powered directly from the main battery and carries the voltage Vsup of main battery 1. The first supply line, labeled 2, forms part of primary network VR1. Other electrical devices can be connected to primary network VR1.

[0042] The secondary network VR2 is powered directly from the output 32 of the voltage converter 3. The secondary network VR2 may include an auxiliary battery having a nominal voltage corresponding to the nominal voltage of the secondary network. The secondary network VR2 can supply power to multiple auxiliary electrical devices.

[0043] The first supply line 2 includes an inductor 21 and a smoothing filter 22. The inductor 21 is designated L2. The smoothing filter 22 is a Pi filter having a series inductor L1, an upstream first capacitor C1, and a downstream second capacitor C2. Each capacitor C1, C2 is inserted between the supply line and ground.

[0044] The current entering input 31 of the voltage converter is denoted as Is. Figure 2 In the timing diagram, the middle curve shows the change in the current Is consumed by the voltage converter.

[0045] An activation input, designated as 33, is provided on the voltage converter. In the illustrated example, when the activation input is low, the converter is activated and operates, while conversely, when the activation input is high, the converter is disabled and its operation is stopped. The response to the activation input is instantaneous.

[0046] Advantageously, the system according to the invention includes an external control circuit 4 for controlling the converter, the external control circuit 4 being configured to selectively activate or disable the operation of the voltage converter.

[0047] In the illustrated example, a wired analog circuit is used. More specifically, in this case, the external control circuit 4 includes a hysteresis comparator designated as 43.

[0048] The hysteresis comparator 43 includes a positive input 42 (also referred to as the positive terminal), a negative input 41 (also referred to as the negative terminal), and an output 44.

[0049] Positive input 42 is connected to the first supply line and thus receives the instantaneous voltage Vsup present in the first supply line 2.

[0050] The output 44 of the voltage converter is connected to the control line CL4, which directly activates the activation input 33 of the voltage converter.

[0051] The negative input 41 receives the voltage, which is denoted as VFm.

[0052] The voltage VFm represents the output of a low-pass filter (such as an RC filter).

[0053] More specifically, a resistor R4 is provided, the upper terminal of which is connected to the first supply line, and the lower terminal of which is connected to the negative input 41 of the comparator. Furthermore, a capacitor C4 is connected to the negative input 41 of the comparator on one side and to ground on the other.

[0054] Therefore, components R4 and C4 form a conventional analog low-pass filter. The capacitor and resistor values ​​can be selected to obtain a time constant on the order of 0.16 milliseconds, resulting in a cutoff frequency of 1 kHz. The midpoint between components R4 and C4 forms the filter's output.

[0055] The operating principle is as follows.

[0056] If the instantaneous voltage Vsup of the first supply line drops below the first threshold VsLo, the external control circuit 4 used to control the converter disables the operation of the voltage converter.

[0057] The first threshold VsLo can be a predefined voltage value. The first threshold VsLo can also be a value that is a function of the value produced by averaging via a sliding window, as in the case of the output of the RC filter discussed above. In this case, the first threshold VsLo can be said to be floating.

[0058] If the instantaneous voltage Vsup of the first supply line rises above the second threshold VsHi, the external control circuit 4 used to control the converter will reactivate the operation of the voltage converter.

[0059] Similar to the first threshold, the second threshold VsHi can be a predefined voltage value, or it can be a value that is a function of the value generated by the sliding window averaging, as in the case of the output of the RC filter discussed above.

[0060] exist Figure 2 In the first supply line 2, the voltage Vsup is initially at the value Vsup0 before any current is drawn by the voltage converter.

[0061] The average voltage VFm obtained by the filter R4-C4 is shown by the dashed line.

[0062] There is a first activation phase for the voltage converter between times t1 and t2. At time t1, comparator 43 receives a logic command via its supply line 40.

[0063] The current flowing through resistor R4 is zero, and as a result, positive input 42 and negative input 41 are at essentially the same voltage, and the output of comparator 44 is low.

[0064] Starting from time t1, the current Is consumed by the converter increases, and the voltage Vsup decreases.

[0065] At time t2, the positive input 42 becomes significantly lower than the negative input 41, and the comparator output changes to a low state. Therefore, the converter operation is stopped (CL4 is in the logic OFF state).

[0066] From time t2, the voltage Vsup increases. Thanks to the hysteresis of filters R4-C4 and the comparator, the comparator output 44 remains low until time t3.

[0067] At time t3, the negative input 41 becomes significantly lower than the positive input 42, and the comparator output changes to a high state, which reactivates the operation of the converter, and the converter draws current again (CL4 is in the logic ON state).

[0068] Starting from time t3, the current Is consumed by the converter increases, and the voltage Vsup decreases.

[0069] At time t4, the positive input 42 becomes significantly lower than the negative input 41, and the comparator output changes to a low state. Therefore, the converter operation is stopped.

[0070] From time t4, the voltage Vsup increases. Thanks to the hysteresis of filters R4-C4 and the comparator, the comparator output 44 remains low until time t5.

[0071] At time t5, the negative input becomes significantly lower than the positive input, and the comparator output changes to a high state, which reactivates the converter's operation, and the converter draws current again.

[0072] Starting from time t5, the current Is consumed by the converter increases, and the voltage Vsup decreases.

[0073] At time t6, the positive input becomes significantly lower than the negative input, and the comparator output changes to a high state. Therefore, the converter operation is stopped.

[0074] From time t6, the voltage Vsup increases. Thanks to the hysteresis of filters R4-C4 and the comparator, the comparator output 44 remains low until time t7.

[0075] At time t7, the negative input 41 becomes significantly lower than the positive input 42, and the comparator output changes to a high state, which reactivates the converter's operation, and the converter draws current again.

[0076] Following the same logic, the converter operation is stopped at time t8.

[0077] It is reactivated at time t9, and from time t9 onwards, the voltage Vsup no longer drops below the first threshold VsLo.

[0078] Then, the converter's startup sequence was completed.

[0079] As an alternative to wired logic solutions, an external control circuit based on a microcontroller can be specified, and a relatively simple digital solution can be maintained to perform digital filtering and digital comparison to deliver the output sent on control line CL4.

[0080] Figure 1 The diagram illustrates a solution with a single comparator. It is also possible to use a solution with two comparators: a first comparator for comparing Vsup with the low switching threshold VsLo, and a second comparator for comparing Vsup with the high switching threshold VsHi. AND and / or OR gates can be provided at the outputs of both comparators to activate control line CL4.

[0081] Regarding the activation and deactivation logic of the voltage converter and the output logic of the comparator, it may be necessary to add an inverter gate between the output of the comparator and the activation input of the voltage converter.

[0082] Similarly, depending on the specific configuration of interest, the positive and negative terminals can be reversed depending on the desired control polarity of the converter.

[0083] With the selective activation logic of the voltage converter presented herein, it is possible to determine the dimensions of the series inductor 21 and the Pi filter 22 as accurately as possible, thereby reducing the cost of these power components and optimizing the overall cost of the solution, while improving its performance in terms of electromagnetic compatibility.

Claims

1. An on-board electrical system, comprising: At least one main battery (1); a primary network (VR1) that is directly powered from the main battery; A voltage converter (3) supplies power to a secondary network (VR2), the voltage converter being powered from a main battery via a first supply line (2), the first supply line including at least one smoothing filter (22), the system being characterized in that it includes an external control circuit (4) for controlling the converter, the circuit being configured to selectively activate or disable the operation of the voltage converter in order to minimize the voltage drop on the primary network when the voltage converter is activated, and wherein a first threshold (VsLo) and a second threshold (VsHi) are defined with respect to an average smoothing value (VFm) of the first supply line, the average smoothing value (VFm) representing the signal output from the smoothing filter (22), wherein the external control circuit (4) for controlling the converter is configured to disable the operation of the voltage converter if the instantaneous voltage (Vsup) of the first supply line drops below the first threshold (VsLo), and wherein the external control circuit (4) for controlling the converter is configured to reactivate the operation of the voltage converter if the instantaneous voltage (Vsup) of the first supply line rises above the second threshold (VsHi).

2. The vehicle electrical system according to claim 1, wherein the external control circuit (4) for controlling the converter is a digital circuit.

3. The vehicle electrical system according to any one of claims 1 and 2, wherein the external control circuit (4) for controlling the converter is in the form of wired logic and includes a hysteresis comparator.

4. The vehicle electrical system of claim 3, wherein the positive terminal of the hysteresis comparator is connected to the instantaneous voltage (Vsup) of the first supply line, and the negative terminal of the hysteresis comparator is connected to the output of an RC filter that filters the instantaneous voltage (Vsup) of the first supply line. Alternatively, the negative terminal of the hysteresis comparator is connected to the instantaneous voltage (Vsup) of the first supply line, and the positive terminal of the hysteresis comparator is connected to the output of an RC filter that filters the instantaneous voltage (Vsup) of the first supply line.

5. The vehicle electrical system according to any one of claims 1 to 4, wherein the voltage converter is a quasi-resonant voltage converter.

6. A method implemented in an on-board electrical system according to claim 1, the method specifying the selective activation and disabling of a voltage converter from an inactive state to a stable operating state, the method comprising: - If the instantaneous voltage (Vsup) of the first supply line drops below a first threshold (VsLo), then the operation of the voltage converter is disabled. - If the instantaneous voltage (Vsup) of the first supply line rises above the second threshold (VsHi), the operation of the voltage converter is reactivated.

7. A vehicle comprising at least one on-board electrical system according to any one of claims 1 to 6.

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