Electrical system with a voltage converter and an external converter control circuit.

Abstract

The invention relates to an on-board electrical system comprising at least one main battery (1), a primary network (VR1) directly supplied from the main battery, a voltage converter (3) supplying a secondary network (VR2), the voltage converter being supplied from the main battery by a first power line (2), the first power line comprising at least one smoothing filter (22), the system being characterized in that it comprises an external control circuit (4) for the converter, configured to selectively activate or deactivate the operation of the voltage converter, so as to minimize the voltage drop on the primary network at the time of the voltage converter's start-up. Abstract figure: Fig. 1

Description

Title of the invention: Electrical system with a voltage converter and an external converter control circuit.

[0001] The present invention relates to an electrical system with a voltage converter. The electrical system comprises a main battery and the voltage converter is powered from the main battery.

[0002] When the voltage converter is switched on, oscillations occur, resulting in a significant current draw from the main battery and leading to a voltage drop on the network supplied from the main battery. Voltage converters employ on / off switching to control the flow of current through one or more load inductors.

[0003] According to some known solutions, an inductive filter is placed at the output of the main battery to obtain a current smoothing effect and a reduction of the voltage drop phenomenon and oscillations induced by the chopped control prevailing in the voltage converter.

[0004] In the case of quasi-resonant voltage converters, the control switching exhibits a certain flexibility and is not operated according to a regular periodicity. The electromagnetic spectrum of possible disturbances produced by the choppy control of the resonant voltage converter is therefore relatively broad.

[0005] The switching and the resulting transients generally cause electromagnetic noise, in particular conducted disturbances throughout the on-board network, which degrades the performance from the point of view of the electromagnetic silence of the system including the voltage converter.

[0006] Some have tried to refine the inductive filtering solution placed between the main battery and the voltage converter, using a so-called "Pi filter". Such a Pi filter comprises an inductor mounted in series on the line and placed between a first upstream capacitor and a second downstream capacitor, each capacitor being interposed between the line and ground.

[0007] Such a Pi filter solution makes it possible to increase the transient reduction performance to some extent and over a wider frequency spectrum, but does not completely solve the problem.

[0008] The inventors sought to further improve the situation, in particular to reduce the voltage drop phenomenon and the oscillations induced by the chopped 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 battery main, a voltage converter supplying a secondary network, the voltage converter being supplied from the main battery by a first supply line, the first supply line comprising at least one smoothing filter, the system being characterized in that it comprises an external converter control circuit, configured to selectively activate or deactivate the operation of the voltage converter, so as to minimize the voltage drop on the primary network at the time of the voltage converter's start-up.

[0010] Thanks to these provisions, the selective activation control of the voltage converter allows it to be started up progressively, over the few hundred milliseconds between the start of the sequence and the full-speed operation of the voltage converter.

[0011] This results in a significant decrease in the voltage drop involved by the first current draw and a decrease in the amplitude of the oscillations and transients that follow.

[0012] Wherefore, it is also possible to reduce the size of the smoothing filter that is placed between the battery and the voltage converter.

[0013] Regarding the phrase "on-board electrical system", the qualifier "on-board" indicates that the electrical system is intended to be installed on a mobile vehicle or at least on a movable vehicle, without power supply from a general electricity network.

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

[0015] This limits the voltage drop on the supply line of the voltage converter. Advantageously, the impact on other consumers connected to the primary network, resulting from the voltage converter's start-up phenomenon, is reduced.

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

[0017] The converter is reactivated to continue the start-up sequence towards full-speed operation eventually.

[0018] We thus have an alternation between operation and non-operation, during the start-up phase of the voltage converter, said start-up phase being able to last a maximum of a few hundred milliseconds.

[0019] According to one embodiment, the external control circuit of the converter is a digital circuit. The use of a small microcontroller or a specific ASIC can fulfill the function to be performed here.

[0020] According to one embodiment, the external control circuit of the converter is formed in hardwired logic and includes a comparator with hysteresis.

[0021] Wherefore, a rustic, very reliable and simply designed solution is used, without having to develop specific software or digital circuit.

[0022] According to one option, the first and second comparator thresholds are defined relative to a smoothed average value of the first supply line. Whereby, instead of using absolute values, the upper and lower thresholds are defined relative to a relative value obtained by averaging over a sliding window. The use of threshold values ​​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 an output of an RC filter which 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 an output of an RC filter which filters the instantaneous voltage of the first supply line.

[0024] This average value can be obtained very simply by using an analog RC low-pass filter, which will be described later. A cutoff frequency of approximately 1 kHz for this filter is suitable.

[0025] According to one embodiment, the voltage converter is a quasi-resonant voltage converter. The modulated control provided by the external control circuit makes it possible to reduce the amplitude of the oscillations regardless of the control logic implemented in the voltage converter, and this applies to a wide range of possible disturbance frequencies.

[0026] It is also noted that the control modulated by the external control circuit can be applied to any type of voltage converter.

[0027] The present invention also relates to a method implemented in an on-board electrical system as described above, the method providing for selectively activating and deactivating the voltage converter from an inactive state to a steady-state operating state, the method comprising:

[0028] - disable the operation of the voltage converter if a voltage value instantaneous voltage of the first supply line falls below a first threshold, - reactivate the operation of the voltage converter if the value of the instantaneous voltage of the first supply line rises above a second threshold.

[0029] This results in an alternation between operation and non-operation during the start-up phase of the voltage converter. The start-up phase can last a few hundred milliseconds, or even less than 100 ms in some cases.

[0030] As already mentioned, the first threshold and the second threshold can be, according to one option, fixed thresholds or, according to another option, thresholds defined relative to an average voltage of the primary network.

[0031] The present invention also relates to a vehicle comprising at least one on-board electrical system as described above.

[0032] The invention will be further detailed by describing non-limiting embodiments, and based on the accompanying figures illustrating variants of the invention, in which: - [Fig.l] schematically illustrates an example of an electrical circuit of the proposed system; - [Fig.2] illustrates an example of a chronogram illustrating the proposed process.

[0033] In the various figures, the same reference numerals designate identical or similar elements. For the sake of clarity, some elements are not necessarily shown to scale.

[0034] In [Fig.1], an on-board electrical system is illustrated which includes a main battery 1 and a voltage converter 3 supplied from the main battery by a first power line 2.

[0035] The voltage converter 3 is referred to in the jargon as "DCDC". In a typical configuration, the voltage converter has a lower output voltage value than its input ("step-down DCDC"), however, the reverse configuration ("step-up DCDC") is not excluded.

[0036] In the present context, the invention described below is particularly relevant in the case of a quasi-resonant voltage converter. A quasi-resonant voltage converter is a known piece of equipment and therefore not described in detail here; the reader may refer, for example, to US patent 5903448.

[0037] The main battery 1 can be, for example, a traction battery capable of powering a vehicle in zero-emission mode. The vehicle can be a light vehicle, a recreational vehicle, a passenger vehicle, a commercial vehicle; there is no limit to the type of vehicle that can be considered. The nominal voltage of the main battery can typically be 12 or 24 volts on a conventional vehicle or greater than 50 volts, most often greater than 100 volts, for an electric vehicle.

[0038] A primary network VR1 is powered directly from the main battery; it carries the voltage Vsup of the main battery 1. The first power supply line, labeled 2, is part of the primary network VR1. Other loads can be connected to the primary network VR1.

[0039] A secondary network VR2 is powered directly from output 32 of the voltage converter 3. The secondary network VR2 may include an auxiliary battery with a nominal voltage corresponding to the nominal voltage of the secondary network. The secondary network VR2 can power a plurality of auxiliary loads.

[0040] The first supply line 2 includes an inductance 21 denoted L2 and a smoothing filter 22. The smoothing filter 22 is a Pi filter, with a series inductance L1, a first upstream capacitance Cl and a second downstream capacitance C2. Each capacitance C1,C2 is interposed between the supply line and ground.

[0041] The current entering the input 31 of the voltage converter is denoted Is. On the timing diagram of [Fig.2], the mid-height curve shows the evolution of the current Is consumed by the voltage converter.

[0042] The voltage converter is provided with an activation input, designated 33. In the illustrated example, when the activation input is low, the converter is activated and operates, whereas conversely, when the activation input is high, the converter is deactivated and its operation is stopped. The response to the activation input is immediate.

[0043] Advantageously, the system according to the present invention includes an external control circuit 4 of the converter, configured to selectively activate or deactivate the operation of the voltage converter.

[0044] In the illustrated example, a wired analog circuit is used. More specifically, in this case, the external control circuit 4 includes a comparator with hysteresis, labeled 43.

[0045] The hysteresis comparator 43 includes a positive input 42 (also called the positive terminal), a negative input 41 (also called the negative terminal) and an output 44.

[0046] The positive input 42 is connected to the first supply line and consequently receives the instantaneous voltage Vsup which prevails on the first supply line 2.

[0047] The output 44 of the voltage converter is connected to a control line CL4 which directly activates the activation input 33 of the voltage converter.

[0048] The negative input 41 receives a voltage denoted VFm.

[0049] This voltage VFm represents the output of a low-pass filter, for example an RC filter.

[0050] More specifically, a resistor R4 is provided, the upper terminal of which is connected to the first power line and the lower terminal is connected to the negative input 41 of the comparator. In addition, a capacitor C4 is connected on one side to the negative input 41 of the comparator and on the other side to ground.

[0051] Components R4 and C4 thus form a classic analog low-pass filter. The capacitance and resistance values ​​can be chosen to obtain a time constant on the order of 0.16 milliseconds, corresponding to a cutoff frequency of 1 kHz. The midpoint between components R4 and C4 constitutes the filter output.

[0052] The operating principle is as follows.

[0053] The external control circuit 4 of the converter disables the operation of the voltage converter if a value of the instantaneous voltage Vsup of the first supply line falls below a first threshold VsLo.

[0054] The first threshold VsLo can be a predefined voltage value. The first threshold VsLo can be a function of a value obtained by a sliding window average, 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.

[0055] The external control circuit 4 of the converter reactivates the operation of the voltage converter if a value of the instantaneous voltage Vsup of the first supply line goes above a second threshold VsHi.

[0056] Similar to the first, the second threshold VsHi can be a predefined voltage value or can be a value based on a value obtained from a sliding window average as in the case of the output of the RC filter discussed above.

[0057] On [Fig.2], the voltage Vsup which prevails in the first supply line 2 is initially at the value VsupO before any current demand by the voltage converter.

[0058] Using a dotted line, the average voltage VFm by the R4-C4 filter has been represented.

[0059] Between times t1 and t2 we have a first phase of activation of the voltage converter. At time t1, the comparator 43 receives a logic command via its supply line 40.

[0060] The current passing through the resistor R4 is zero, therefore the positive input 42 and the negative input 41 are substantially at the same voltage and the output of the comparator 44 is in the low state.

[0061] From the instant tl, the current Is consumed by the converter increases and the voltage Vsup decreases.

[0062] At time t2, the positive input 42 becomes significantly lower than the negative input 41 and the comparator output goes low. The converter then stops operating (CL4 is OFF in logic).

[0063] From time t2, the voltage Vsup increases. Thanks to the R4-C4 filter and the comparator hysteresis, the comparator output 44 remains low until time t3.

[0064] At time t3, the negative input 41 becomes significantly lower than the positive input 42 and the comparator output goes high, which reactivates the operation of the converter which draws current again (CL4 is in the "ON" state in logic).

[0065] From time t3, the current Is consumed by the converter increases and the voltage Vsup decreases.

[0066] At time t4, the positive input 42 becomes significantly lower than the negative input 41 and the comparator output goes low. The converter then stops operating.

[0067] From time t4, the voltage Vsup increases. Thanks to the R4-C4 filter and the comparator hysteresis, the comparator output 44 remains low until time t5.

[0068] At time t5, the negative input becomes significantly lower than the positive input and the comparator output goes high, which reactivates the operation of the converter which draws current again.

[0069] From time t5, the current Is consumed by the converter increases and the voltage Vsup decreases.

[0070] At time t6, the positive input becomes significantly lower than the negative input and the comparator output goes high. From then on, the converter's operation is stopped.

[0071] From time t6, the voltage Vsup increases. Thanks to the R4-C4 filter and the comparator hysteresis, the comparator output 44 remains low until time t7.

[0072] At time t7, the negative input 41 becomes significantly lower than the positive input 42 and the comparator output goes high, which reactivates the operation of the converter which draws current again.

[0073] Following the same logic, at time t8, the operation of the converter is stopped.

[0074] It is reactivated at time t9, from which point the voltage Vsup no longer falls back down. below the first threshold, first threshold VsLo.

[0075] The converter start-up sequence is then complete.

[0076] As an alternative to the hardwired logic solution, it may be provided that the circuit of external control is based on a microcontroller and a digital solution which can remain quite simple, by performing digital filtering and digital comparison to deliver the output sent on the CL4 command line.

[0077] In [Fig. 1], a solution with a single comparator is illustrated. It is also possible to use a solution with two comparators: a first comparator to compare Vsup to a low switching threshold VsLo and a second comparator to compare Vsup to a high switching threshold VsHi. An AND gate and / or an OR gate can be provided at the output of the two comparators to activate the CL4 control line.

[0078] 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.

[0079] Similarly, depending on a particular configuration of interest, the positive and negative terminals can be reversed according to the desired control polarity of the converter.

[0080] Thanks to the selective activation logic of the voltage converter proposed here, it is possible to size the series inductance 21 and the pi filter 22 as accurately as possible, which makes it possible to reduce the cost of these power components, and to optimize the overall cost of the solution while improving its performance in electromagnetic silence.

Claims

Demands

1. On-board electrical system comprising at least one main battery (1), a primary network (VR1) directly supplied from the main battery, a voltage converter (3) supplying a secondary network (VR2), the voltage converter being supplied from the main battery by a first supply line (2), the first supply line comprising at least one smoothing filter (22), the system being characterized in that it comprises an external control circuit (4) of the converter, configured to selectively activate or deactivate the operation of the voltage converter, so as to minimize the voltage drop on the primary network at the time of the voltage converter's start-up.

2. On-board electrical system according to claim 1, wherein the external control circuit (4) of the converter is configured to disable the operation of the voltage converter if a value of the instantaneous voltage (Vsup) of the first supply line falls below a first threshold (VsLo).

3. On-board electrical system according to claim 2, wherein the external control circuit (4) of the converter is configured to reactivate the operation of the voltage converter if the instantaneous voltage value (Vsup) of the first supply line goes above a second threshold (VsHi).

4. On-board electrical system according to any one of claims 1 to 3, wherein the external control circuit (4) of the converter is a digital circuit.

5. On-board electrical system according to any one of claims 1 to 3, wherein the external control circuit (4) of the converter is formed in hardwired logic and includes a comparator with hysteresis.

6. On-board electrical system according to claim 5, wherein the first and second thresholds (VsLo, VsHi) are defined with respect to an averaged smoothed value (VFm) of the first power line.

7. On-board electrical system according to claim 5, wherein the positive terminal of the hysteresis comparator is connected to the instantaneous voltage (Vsup) of the first supply line and the terminal negative of the hysteresis comparator is connected to an output of an RC filter that filters the instantaneous voltage (Vsup) of the first supply line, or 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 an output of an RC filter that filters the instantaneous voltage (Vsup) of the first supply line.

8. On-board electrical system according to any one of claims 1 to 7, wherein the voltage converter is a quasi-resonant voltage converter.

9. A method implemented in an on-board electrical system according to claim 1, the method comprising selectively activating and deactivating the voltage converter from an inactive state to an established operating state, the method comprising: - deactivating the operation of the voltage converter if a value of the instantaneous voltage (Vsup) of the first supply line falls below a first threshold (VsLo), - reactivating the operation of the voltage converter if the value of the instantaneous voltage (Vsup) of the first supply line rises above a second threshold (VsHi).

10. Vehicle comprising at least one on-board electrical system according to any one of claims 1 to 8.

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