Operating method of an electrical circuit

Abstract

Method for controlling an electrical circuit (1) comprising an electrical source (4) providing a chopped output voltage and an active electrical damper (8) connected to said electrical source (4) and capable of damping transient voltage peaks (12) or instabilities, said active damper (8) comprising a capacitor (8a), a diode (8b) and a switch (8c), said active damper (8) being capable of allowing the capacitor (8a) to charge in a first state of the switch (8c) when Vs > Vc + Vd where Vs is the output voltage of the electrical source (4), Vc is the voltage across the capacitor (8a) and Vd is the voltage of the diode (8b), said active damper (8) being capable of allowing the capacitor (8a) to discharge in a second state of the switch (8c), the output voltage Vs being a periodic voltage,alternating in each period between a high voltage level during a high portion (10) of said period and a low voltage level during a low portion (11) of said period, Figure of the abstract: Figure 1,

Description

Title of the invention: Method of operating an electrical circuit Technical field

[0001] The present invention relates to a method of operating an electrical circuit comprising an electrical source providing a chopped output voltage, and an active electrical damper connected to said electrical source and capable of damping transient voltage peaks or instabilities. Prior art

[0002] An active damper or snubber is an electronic device used in electrical circuits to mitigate unwanted surges, oscillations, or noise that may occur when switching electrical loads, including relays, electronic switches, or switching devices in general. Unlike a passive damper, which primarily uses passive components such as resistors and capacitors to mitigate these problems, an active damper incorporates active components, typically transistors or semiconductor devices, to provide a more dynamic and precise action.

[0003] The main purpose of an active snubber is to eliminate or reduce voltage spikes, excessive switching currents and oscillations that can damage circuit components or disrupt its normal operation.

[0004] In the case of a voltage source delivering a periodic voltage, for example in the form of a square wave signal, it is common to see voltage spikes, i.e. sudden and abrupt variations in the electrical voltage that occur during the transition from a low voltage level to a high voltage level or vice versa. These voltage spikes appear at the "flanks" of the square wave signal. They can be caused by the switching of electronic components such as transistors, relays or switches in a circuit. When these components open or close quickly, this can lead to rapid changes in the current and, consequently, voltage spikes.

[0005] There is a need to effectively and optimally attenuate such voltage spikes or instabilities. Summary

[0006] The present invention improves the situation.

[0007] To this end, the present invention relates to a method for controlling an electrical circuit comprising an electrical source providing a chopped output voltage, and an active electrical damper connected to said electrical source and capable of damping transient voltage peaks or instabilities, said active damper comprising a capacitor, a diode and a switch, said active damper being capable of allowing the capacitor to charge in a first state of the switch when Vs > Vc + Vd where Vs is the output voltage of the electrical source, Vc is the voltage across the capacitor and Vd is the voltage of the diode, said active damper being capable of allowing the capacitor to discharge in a second state of the switch, the output voltage Vs being a periodic voltage, alternating at each period between a high voltage level during a high portion of said period and a low voltage level during a low portion of said period,

[0008] said method comprising the steps of: - damping possible voltage peaks of the output voltage Vs by charging the capacitor during a respective first part of the high portion of at least one period, during a charging step, then discharging said capacitor during a second part of the high portion of said period or another period, located temporally after said charging step and called the discharging step, - monitor the voltage Vc across the capacitor terminals of said source, - depending on the said capacitor voltage Vc, adapt in such a way dynamic a duration of the discharge step and / or a frequency of repetition of the discharge step defining the periods during which the capacitor is discharged.

[0009] The chopped output voltage may have the form of a square signal whose period includes a high portion during which said voltage reaches a high level and a low portion during which said voltage reaches a low level. The low level and the high level may be positive voltages.

[0010] In this way, it is possible to adapt the discharge of the capacitor in order to limit the charge to the absorption of only the voltage peaks that may appear and to ensure a sufficient reduction of the capacitor voltage. The active damper thus makes it possible to suppress the parasitic voltage peaks while offering better efficiency than the damper of the prior art by minimizing the energy losses linked to the absorption of a part of the high portion of the period after an excessive discharge and the energy losses linked to an unnecessary or untimely closing of the switch.

[0011] The proposed method thus makes it possible to obtain a minimum capacitor voltage greater than the nominal square wave voltage plus the diode voltage, which makes it possible to avoid losses linked to a discharge / recharge of the capacitor between the square wave voltage and the square wave voltage plus the diode voltage.

[0012] The voltage across the capacitor can be evaluated directly or indi- directly.

[0013] The diode may be arranged in parallel with the switch. The diode may be integrated into the switch. The switch and the diode may be formed by a transistor, for example a power transistor, for example a MOSFET.

[0014] The method may comprise:

[0015] - at least one adaptation according to a first type of adaptation in which one adapts one of the duration of the discharge step and the frequency of repetition of the discharge step, each adaptation according to the first type being followed by a capacitor charging step; then

[0016] - when the voltage Vc exceeds a predetermined threshold, at least one adaptation according to a second type of adaptation in which the other of the duration of the discharge step and the frequency of repetition of the discharge step are adapted, each adaptation according to the second type being followed by a capacitor charging step.

[0017] The output voltage may have the form of a square signal whose period includes a high portion during which said voltage reaches a high level and a low portion during which said voltage reaches a low level, possible peaks or voltage instabilities being able to appear in a first time window located at the start of the high portion, the discharge of the capacitor occurring in a second time window located in said high portion, after said first time window.

[0018] The second time window can be located exclusively in said upper portion. In other words, in such a case, the discharge of the capacitor during the lower portion of the period is avoided.

[0019] The period of a square wave signal is the total time required for one complete period of the signal to repeat. The high level is the average voltage value that the signal reaches during a portion of the period. During this first portion, called the high portion of the period, the signal remains at a substantially constant high level, except for voltage spikes or instabilities. The low level is the average voltage value that the signal reaches during the other portion of the period. During this second portion, called the low portion of the period, the signal remains at a substantially constant low level.

[0020] In operation, voltage spikes or bounces may appear in such a square wave signal, mainly at the beginning of the high portion, and are mainly due to the parasitic inductance and capacitance present in the circuit. They generally occur during rapid signal transitions, when the current or voltage changes abruptly.

[0021] For example, voltage peaks may appear during the first half of the high portion and the discharge of the capacitor may occur in the second half. of the said upper portion.

[0022] If the capacitor voltage at the end of the discharge step is lower than a first minimum threshold value VMINHYS, then the duration of the following discharge step can be reduced.

[0023] Such a reduction may be achieved by decrementing time, for example by reducing the expected duration by a decrement value of between 1 and 10% of the expected duration.

[0024] In an advantageous embodiment, if the capacitor voltage at the end of the discharge step is greater than a first maximum threshold value VMAXHYS, then the duration of the following discharge step is increased.

[0025] Such an increase may be achieved in time increments, for example by increasing the expected duration by an increment value of between 1 and 10% of the expected duration.

[0026] If the capacitor voltage is greater than a second maximum threshold value VMAX, then the repetition frequency of the discharge step is increased.

[0027] More particularly, when the voltage across the capacitor exceeds the maximum threshold value VMAX, a discharge step can be programmed to be carried out as soon as possible. This makes it possible to modulate the discharge frequency, upwards, but also downwards.

[0028] In other words, the discharge is only done when the need arises.

[0029] If the voltage peaks or instabilities decrease following a change in the operating point, the voltage continues to rise as long as the discharge is not activated, but more slowly than before. Thus, in such a case, the activation frequency decreases.

[0030] The second maximum threshold value VMAX may be greater than the first maximum threshold value VMAXHYS.

[0031] Thus, in operation, when the switch is in the first state and the capacitor is progressively charged by the voltage peaks, the voltage across the capacitor gradually increases until it exceeds the value VMAX. The switch is then switched to its second state, so that the capacitor is discharged during the discharge duration. This discharge preferably only occurs during the second part of said high portion of the period

[0032] If the capacitor voltage is greater than a third maximum value VSECU, then the electrical circuit can be placed in a safe state.

[0033] The third maximum threshold value VSECU may be greater than the second maximum threshold value VMAX.

[0034] In said safe state, the electrical source can be stopped and / or the capacitor can be discharged.

[0035] The precharge duration can be maintained between a minimum value and a value maximum.

[0036] Said minimum discharge duration value may be between 5 and 10% of a period. Said maximum discharge duration value may be between 10 and 20% of a period.

[0037] The voltage Vc can be determined during a period of time characterized by a low variation and a relative stability of this voltage.

[0038] The electrical source may comprise a transformer comprising a primary part and a secondary part.

[0039] The secondary part can be coupled to a full bridge capable of delivering said chopped output voltage.

[0040] Said electrical circuit may comprise a direct-direct voltage converter with a chopper (for example a half-bridge device), a transformer and a rectifier staged in this order, connected in use between a battery and an on-board network of a motor vehicle, the rectifier forming said electrical source providing a chopped output voltage.

[0041] The electrical circuit may comprise a passive electrical damper connected to said electrical source, in parallel with the active damper, said passive damper comprising a capacitor and a resistor arranged in series.

[0042] The passive damper can allow intervention on dynamics or phenomena different from the active damper, thus allowing more margin to be given to the active damper.

[0043] The voltage Vd across the diode can be between 0.2 and 1 Volt.

[0044] The threshold VMAXHYS can be between 2 Volts and 4 Volts more than Vs. The VMAX threshold can be between 3 Volts and 5 Volts higher than Vs. VMINHYS threshold can be between 1 Volt and 2 Volts higher than Vs. VMIN threshold can be a value slightly higher than Vd + Vs. VSECU can be lower than the maximum voltage supported by the capacitor, for example 10 Volts lower than this maximum voltage.

[0045] The invention also relates to a device comprising: - an electrical circuit comprising an electrical source capable of providing a chopped output voltage, and an active electrical damper connected to said electrical source and capable of damping transient voltage peaks or instabilities, said active damper comprising a capacitor, a diode and a switch, said active damper being capable of allowing the capacitor to discharge in a second state of the switch, and capable of allowing the capacitor to charge in a first state of the switch when Vs > Vc + Vd where Vs is the output voltage of the electrical source, Vc is the voltage across the capacitor and Vd is the voltage of the diode, said damper active being capable of allowing the discharge of the capacitor in a second state of the switch, - means of monitoring the Vc voltage, - a computer capable of receiving information relating to the voltage Vc and of providing a control signal for the switch, so as to implement the method according to the invention. The invention also relates to a vehicle equipped with a device of the aforementioned type. Brief description of the drawings

[0046] Other characteristics, details and advantages will appear on reading the detailed description below, and on analyzing the attached drawings, in which:

[0047] [Fig-1] is a schematic of an electrical circuit of the device according to the invention,

[0048] [Fig.2] schematically represents the active damper,

[0049] [Fig.3] illustrates the variation of the output voltage Vs,

[0050] [Fig.4] illustrates the high portion of the period of the voltage Vs,

[0051] [Fig.5] is a diagram illustrating the operation of the device according to the invention,

[0052] [Fig.6] schematically illustrates a first mode of operation of the electrical circuit,

[0053] [Fig.7] schematically illustrates a second mode of operation of the electrical circuit,

[0054] [Fig.8] schematically illustrates a third mode of operation of the electrical circuit. Description of the embodiments

[0055] [Fig.l] schematically illustrates an electrical circuit 1 comprising a DC-DC voltage converter with a chopper 2, a transformer 3 and a rectifier 4 staged in this order, connected in use between a battery 5 and an on-board network 6 of a motor vehicle, the rectifier 4 forming an electrical source providing a chopped output voltage. A passive damper 7 and an active damper 8 are located upstream of the on-board network.

[0056] The passive damper 7 (optional) comprises a resistor 7a and capacitor 7b arranged in series. The active damper 8, also illustrated in [Fig.2], comprises a capacitor 8a, a diode 8b and a switch 8c, said active damper 8 being capable of allowing the passive charging of the capacitor 8a in a first state of the switch 8c when Vs > Vc + Vd where Vs is the output voltage of the electrical source 4, Vc is the voltage across the capacitor 8a and Vd is the voltage of the diode 8b, said active damper 8 being capable of allowing the active discharging of the capacitor 8a in a second state of the switch 8b.

[0057] Diode 8b can be integrated into switch 8c. Switch 8c and diode 8b can be formed by a transistor, for example a power transistor, for example a MOSFET.

[0058] As illustrated in Figures 3 and 4, the output voltage Vs is a periodic chopped voltage, alternating at each period between a high voltage level during a high portion 10 of said period and a low voltage level during a low portion 11 of said period, both voltage levels being positive. At each period, any voltage peaks or instabilities 12 of the output voltage Vs are at the start of the high portion 10. In [Fig.4], a second time window 110 is also shown, located in said high portion 10, and during which the possible discharge of the capacitor 8a occurs. The second time window 110 is located after a first time window receiving the voltage peaks or instabilities 12 of greater amplitude.

[0059] Switch 8c is controlled so as to:

[0060] - dampen possible peaks or voltage instabilities 12 of the output voltage Vs in charging the capacitor 8a during a respective first part of the high portion 10 of at least one period, during a charging step, then discharging said capacitor 8a during a second part of the high portion 10 of said period or another period, situated temporally after said charging step and called discharging step,

[0061] - monitor the voltage Vc across the capacitor 8a of said source 4,

[0062] - depending on said voltage Vc of the capacitor 8a, dynamically adapt a duration of the discharge step and / or a frequency of repetition of the discharge step defining the periods during which the capacitor 8a is discharged.

[0063] In this way, it is possible to adapt the charging and discharging of the capacitor 8a in order to limit such charging to the absorption of only the voltage peaks or instabilities 12 which may appear and in order to ensure sufficient discharging of the capacitor 8a. The active damper 8 thus makes it possible to suppress the parasitic voltage peaks while offering better efficiency than the damper of the prior art by minimizing the energy losses linked to damping.

[0064] The method may comprise:

[0065] - at least one adaptation according to a first type of adaptation in which one adapts one of the duration of the discharge step and the frequency of repetition of the discharge step, each adaptation according to the first type being followed by a step of charging the capacitor 8a; then

[0066] - when the voltage Vc exceeds a predetermined threshold, at least one adaptation according to a second type of adaptation in which the other of the duration of the discharge step and the frequency of repetition of the discharge step are adapted, each adaptation according to the second type being followed by a step of charging the capacitor 8a.

[0067] [Fig.5] illustrates, using a diagram, the method of controlling the electrical circuit.

[0068] During an acquisition step E1, the voltage Vc of the capacitor 8a is determined. Then, during a step E2, it is determined whether the switch 8c is activated (i.e. closed). If so, it is determined whether Vc is less than a threshold VMINHYS during a step E3. If so, the activation duration Te of the switch 8c is reduced during a step E4. Conversely, if not, it is determined during a step E5 whether Vc is greater than a threshold VMAXHYS. If so, Te is increased during a step E6. Conversely, if not, Te is unchanged (step E7).

[0069] At the end of steps E4, E6 or E7, or in the negative in step E2, it is then determined whether Vc is greater than a threshold VSECU. If so, the electrical circuit is interrupted and Te is assigned to its maximum value during a step E9 and the switch 8c is activated during a step E10, the activation of the switch 8c inducing a discharge of the capacitor 8a. Conversely, if not, it is determined whether Vc is greater than a threshold VMAX during a step E11. If so, the switch 8c is activated during a step E12, the duration of the switching being equal to Te (step E13). Conversely, if not, the switch 8c is deactivated during a step E14, no activation being provided (step E15).

[0070] [Fig.6] illustrates a first mode of operation of the electrical circuit 1 during which the capacitor 8a is gradually charged.

[0071] The upper part of the diagram in [Fig.6] illustrates the evolution over time of the voltage Vsec, which is the voltage across the secondary terminals of transformer 3. As described previously, it can be seen that this voltage has the form of a square signal and includes peaks or voltage instabilities at the start of each high portion of the period.

[0072] The lower part of the diagram in [Fig.6] illustrates the evolution over time of the voltage Vc across the terminals of the capacitor 8a, as well as the thresholds VMAX, VMAXHYS and VMINHYS.

[0073] At each period, the voltage peaks and instabilities 12 exceeding Vc + Vd are absorbed by the capacitor 8a, until the voltage Vc across the capacitor 8a exceeds the threshold VMAX. In such a case, the switch 8c is activated or closed for the expected duration Te, which causes a discharge of the capacitor 8a, and therefore a drop in the voltage VC. The capacitor 8a is then gradually charged again during the following periods, until Vc exceeds VMAX again.

[0074] It will be noted that, in the case illustrated in [Fig.6], during the first discharge of the capacitor 8a, Vc is reduced to a value lower than VMINHYS, which has to reduce the activation time Te of the switch 8c, for the next activation. In fact, the second discharge of the capacitor 8a is of a shorter or shorter duration than the first, and we also note that the voltage Vc then no longer falls below the threshold VMINHYS, but falls to a value between VMINHYS and VMAXHYS.

[0075] [Fig.7] illustrates a second mode of operation in which the voltage Vc increases progressively and is then discharged at each period, for several periods, until the value Vc falls back below the threshold VMINHYS. It will be noted that the duration Te is progressively increased during the first four discharges of the capacitor 8a illustrated, because Vc remains greater than VMAXHYS. During the following discharges, Vc falls back to a value between VMINHYS and VMAXSYS, so that Te remains unchanged.

[0076] [Fig.8] illustrates a third operating mode in which the voltage Vc exceeds the threshold VSECU. As seen previously, in such a case, the electrical circuit 1 is placed in a safety state where the battery 5 is disconnected from the circuit 1 and the capacitor 8a is discharged.

Claims

Claims

1. Method for controlling an electrical circuit (1) comprising an electrical source (4) providing a chopped output voltage, and an active electrical damper (8) connected to said electrical source (4) and capable of damping transient voltage peaks (12) or instabilities, said active damper (8) comprising a capacitor (8a), a diode (8b) and a switch (8c), said active damper (8) being capable of allowing the capacitor (8a) to charge in a first state of the switch (8c) when Vs > Vc + Vd where Vs is the output voltage of the electrical source (4), Vc is the voltage across the capacitor (8a) and Vd is the voltage of the diode (8b), said active damper (8) being capable of allowing the capacitor (8a) to discharge in a second state of the switch (8c), the output voltage Vs being a periodic voltage,alternating at each period between a high voltage level during a high portion (10) of said period and a low voltage level during a low portion (11) of said period, said method comprising the steps of:, - damping possible voltage peaks (12) of the output voltage Vs by charging the capacitor (8a) during a respective first part of the high portion (10) of at least one period, during a charging step, then discharging said capacitor (8a) during a second part of the high portion (10) of said period or another period, located temporally after said charging step and called discharging step, - monitor the voltage Vc across the capacitor (8a) of said source (4), - depending on said voltage Vc of the capacitor (8a), dynamically adapting a duration of the discharge step and / or a repetition frequency of the discharge step defining the periods during which the capacitor (8a) is discharged.

2. Method according to claim 1, characterized in that it comprises: - at least one adaptation according to a first type of adaptation in which one of the duration of the discharge step and the frequency of repetition of the discharge step, each adaptation according to the first type being followed by a step of charging the capacitor (8a); then - when the voltage Vc exceeds a predetermined threshold, at least one adaptation according to a second type of adaptation in which the other of the duration of the discharge step and the frequency of repetition of the discharge step is adapted, each adaptation according to the second type being followed by a step of charging the capacitor (8a).

3. Method according to claim 1 or 2, in which the output voltage has the form of a square signal whose period includes a high portion (10) during which said voltage reaches a high level and a low portion during which said voltage reaches a low level, possible peaks or voltage instabilities (12) being able to appear in a first time window located at the start of the high portion (11), the discharge of the capacitor (8a) occurring in a second time window located in said high portion (11), after said first time window.

4. Method according to the preceding claim, in which, if the voltage of the capacitor (8a) at the end of the discharge step is lower than a first minimum threshold value VMINHYS, then the duration of the following discharge step is reduced.

5. Method according to one of the preceding claims, in which, if the voltage of the capacitor (8a) at the end of the discharge step is greater than a first maximum threshold value VMAXHYS, then the duration of the following discharge step is increased.

6. A method according to claim 5, wherein, if the voltage of the capacitor (8a) is greater than a second maximum threshold value VMAX, then the repetition frequency of the discharging step is increased.

7. Method according to claim 6, wherein, if the voltage of the capacitor (8a) is greater than a third maximum value VSECU, then the electrical circuit (1) is placed in a safe state.

8. Method according to one of the preceding claims, in which the precharge duration is maintained between a minimum value and a maximum value.

9. Method according to one of the preceding claims, in which the electrical source (4) comprises a transformer (3) comprising a primary part and a secondary part.

10. Method according to claim 1, characterized in that said electrical circuit (1) comprises a DC-DC voltage converter with a chopper (2), a transformer (3) and a rectifier (4) staged in this order, connected in use between a battery (5) and an on-board network (6) of a motor vehicle, the rectifier (4) forming said electrical source (4) providing a chopped output voltage.

11. Method according to one of the preceding claims, in which the electrical circuit (1) comprises a passive electrical damper (7) connected to said electrical source (4), in parallel with the active damper (8), said passive damper (7) comprising a capacitor (7a) and a resistor (7b) arranged in series.

12. Device comprising: - an electrical circuit (1) comprising an electrical source (4) capable of providing a chopped output voltage, and an active electrical damper (8) connected to said electrical source (4) and capable of damping transient voltage peaks (12) or instabilities, said active damper (8) comprising a capacitor (8a), a diode and a switch (8c), said active damper (8) being capable of allowing the capacitor (8a) to discharge in a second state of the switch (8c), and capable of allowing the capacitor (8a) to charge in a first state of the switch (8c) when Vs > Vc + Vd where Vs is the output voltage of the electrical source (4), Vc is the voltage across the capacitor (8a) and Vd is the voltage of the diode (8b), said active damper (8) being capable of allowing the capacitor (8a) to discharge in a second state of the switch (8c), - means for monitoring the voltage Vc,- a computer capable of receiving information relating to the voltage Vc and of providing a control signal for the switch (8c), so as to implement the method according to one of the preceding claims.,

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