CN108352781B

CN108352781B - Method and system for dissipating a determined amount of energy stored in a capacitor

Info

Publication number: CN108352781B
Application number: CN201680065532.0A
Authority: CN
Inventors: Y.蒙德特; Y.勒让德
Original assignee: Valeo Japan Co Ltd
Current assignee: Valeo Japan Co Ltd
Priority date: 2015-11-16
Filing date: 2016-11-14
Publication date: 2021-04-13
Anticipated expiration: 2036-11-14
Also published as: JP2018537939A; FR3043863B1; FR3043863A1; CN108352781A; WO2017085607A1

Abstract

The invention relates to a method for dissipating a determined amount of energy stored in a capacitor connected to at least one branch comprising a first switch and a second switch, each having a parasitic capacitor, the method comprising alternately repeating the steps of: a) opening the first switch and simultaneously closing the second switch, and b) closing the first switch and simultaneously opening the second switch to alternately charge and discharge parasitic capacitors of the first switch and the second switch until the determined amount of energy is dissipated.

Description

Method and system for dissipating a determined amount of energy stored in a capacitor

Technical Field

The present invention relates to a method and a system for dissipating a determined amount of energy stored in a capacitor connected to at least one branch comprising a first switch and a second switch, each having a parasitic capacitance.

Background

It is known to use converters, more particularly power inverters, in motor vehicles.

For example, a power inverter may be used in an electric compressor having an integrated power inverter and intended for a motor vehicle. Such an electric compressor with an integrated power inverter is generally equipped with a housing containing the electric motor of the compressor, as well as a compression mechanism, and a power inverter contained within the housing. The power inverter is adapted to convert direct current generated by the high-voltage power supply into three-phase alternating current, and supply the three-phase alternating current to an electric motor of the compressor via insulated glass terminals. The insulating glass terminal makes it possible to provide the electric motor of the compressor while ensuring the tightness of the cooling circuit in which the electric motor is integrated.

In air conditioning systems of vehicles, in particular motor vehicles, power inverters are commonly used to control the rotational speed of the motor of the compressor, allowing for variable coolant flow rates, and in order to regulate the temperature within the air conditioned passenger compartment.

The power inverter comprises a plurality of electronic components, in particular an electronic board of the printed circuit type (known as "printed circuit board", abbreviated to "PCB"). The electronic system of the power inverter includes a filter capacitor. A determined amount of energy may be stored in the filter capacitor.

The use of a power inverter including a filter capacitor may also prove useful for providing current to a traction electric motor in an electric or hybrid vehicle.

Unfortunately, the filter capacitors described above, while necessary for operation of the power inverter, are potentially dangerous. For example, a dangerous situation may arise if, for some reason, a user touches the filter capacitor or an electronic circuit connected to the filter capacitor. This may occur, for example, when the power inverter is turned on within the scope of maintenance and/or equipment replacement operations.

In view of this problem, systems have been developed that aim to dissipate a determined amount of energy stored in a capacitor (e.g., a filter capacitor). One of the systems includes a parallel resistor adapted to dissipate an amount of energy stored in a capacitor in the form of heat (converting the energy into heat in the resistor). However, one inherent disadvantage of this type of system is the relatively long period of time required to dissipate energy in the form of heat (which is dissipated in the resistor). During this time period (in the order of a few minutes), there is still a risk of electrocution.

Furthermore, another drawback of the above-mentioned prior art systems comprising parallel resistors adapted to dissipate a certain amount of energy (in the form of heat) stored in the capacitor is the need to provide and install such systems in addition to the existing systems, which leads in particular to complications of the systems and higher production costs.

Furthermore, other solutions to the above-mentioned problems have been developed, including solutions capable of dissipating the energy stored in a capacitor in a motor vehicle directly into the motor phase of said vehicle. Unfortunately, this solution also proves to be disadvantageous, since it can damage the electrical components used for energy dissipation. Furthermore, this type of system may also lead to potentially dangerous situations, in which the dissipation of energy into the motor phase of the motor vehicle causes the electric motor to rotate in an undesired (and uncontrolled) manner, eventually leading to an accidental and potentially dangerous (collision, etc.) movement of the motor vehicle.

After analyzing systems and devices developed in the prior art, such as those described above, applicants have demonstrated a need for improvements in such systems and apparatus to minimize or eliminate the risks associated with mechanisms for dissipating energy stored in capacitors within vehicles, such as motor vehicles. These improvements are intended to ensure the best safety for the user of this type of vehicle, but also for the mechanic who must work on the vehicle.

Disclosure of Invention

It is therefore an object of the present invention to provide a method and system for dissipating a determined amount of energy stored in a capacitor in complete safety.

Therefore, a first subject of the invention relates to a method for dissipating a determined amount of energy stored in a capacitor connected to at least one branch comprising a first switch and a second switch, each having a parasitic capacitance, the method comprising alternately repeating the steps of:

a) opening the first switch and simultaneously closing the second switch, an

b) Closing the first switch and simultaneously opening the second switch,

so as to alternately charge and discharge the parasitic capacitances of the first and second switches until the determined amount of energy is dissipated.

According to an embodiment of this first subject matter of the present invention, said capacitor is connected to at least two branches or to at least three branches, each branch comprising a first switch and a second switch, said first switch and said second switch each having a parasitic capacitance, said method comprising alternately repeating the steps of:

a) all of the first switches are opened simultaneously and all of the second switches are closed simultaneously, an

b) Simultaneously closing all the first switches and simultaneously opening all the second switches,

so as to alternately charge and discharge the parasitic capacitances of all first switches and of the second switches until the determined amount of energy is dissipated.

According to an embodiment of this first subject matter of the present invention, the phase of the first switch and the second switch is 50%.

In other words, the first switch and the second switch are turned on for 50% of the time during a period defined by the alternation of charging and discharging.

According to other embodiments, it is conceivable that the first switch and the second switch are conducting for a time in the range of 30% to 70% within a period defined by the alternation of charging and discharging.

According to an embodiment of this first subject matter of the invention, the frequency for alternately opening and closing the first switch and the second switch is in the range of 1kHz to 1MHz, preferably in the range of 10kHz to about 50kHz, preferably in the range of 10kHz to 50 kHz.

According to one embodiment of this first subject of the present invention, the opening and closing of the switch is commanded by command means adapted to provide a command signal of said switch, said command means comprising a trigger element adapted to generate an instruction to activate said method of dissipating a determined amount of energy stored in the capacitor, said method comprising:

-receiving a signal in the command device to trigger a method for dissipating a determined amount of energy stored in the capacitor, preferably by a sensor connected to the command device,

-performing an acknowledge filtering of the trigger signal before starting the method for dissipating a determined amount of energy stored in the capacitor, and in case of an acknowledge,

-initiating a method for dissipating a determined amount of energy stored in said capacitor.

A second subject of the invention relates to a system for dissipating a determined quantity of energy stored in a capacitor, wherein said capacitor is connected to at least one branch comprising a first switch and a second switch, each having a parasitic capacitance, said system comprising command means adapted to provide a command signal for said switches, said command means being adapted to alternately emit:

-a command signal SC1 for opening the first switch and simultaneously for closing the second switch, and

a command signal SC2 for closing the first switch and simultaneously for opening the second switch,

According to one embodiment of this second subject of the present invention, said capacitor is connected to at least two branches or to at least three branches, each branch comprising a first switch and a second switch, each having a parasitic capacitance, said command means being adapted to alternately emit:

a command signal SC1 for opening all the first switches and for closing all the second switches simultaneously, and

a command signal SC2 for closing all first switches and for opening all second switches simultaneously,

According to an embodiment of this second subject matter of the present invention, the phase of the first switch and the second switch is 50%.

According to an embodiment of this second subject matter of the present invention, said command means are adapted to provide a command signal of said switch such that said command signal SC1 and said command signal SC2 alternate with a frequency in the range of about 10kHz to about 50kHz, preferably in the range of 10kHz to 50 kHz.

According to one embodiment of this second subject of the present invention, said command means comprise a triggering element adapted to generate a method for activating a means for dissipating a determined amount of energy stored in said capacitor, said triggering element being connected to a sensor adapted to sense a signal triggering said energy dissipation means.

According to one embodiment of this second subject of the invention, said command means are provided with an acknowledgement filter adapted to perform an acknowledgement filtering of said signal to trigger an energy dissipation method before activating the method for dissipating a determined amount of energy stored in said capacitor.

A third subject of the invention relates to a power inverter comprising a system according to the second subject of the invention (see above).

A fourth subject of the invention relates to an electric compressor with integrated power inverter and suitable for equipping a vehicle such as a motor vehicle, said electric compressor comprising a power inverter according to the third subject of the invention (see above).

A fifth subject of the invention relates to a computer program product storing executable code for performing the method according to the first subject of the invention.

Drawings

The objects, subject matter, and features of the present invention, as well as advantages thereof, will become more apparent upon reading of the present description of various embodiments of the invention, in which:

fig. 1 shows a schematic diagram of a part of an electronic circuit comprising at least one filter capacitor and three branches, each branch comprising a switch;

fig. 2 shows a part of the circuit according to fig. 1 during a first phase of a method for dissipating a determined amount of energy stored in a filter capacitor; and

fig. 3 shows a part of the circuit according to fig. 1 during a second phase of the method for dissipating a determined amount of energy stored in the storage capacitor.

Detailed Description

The following detailed description is intended to explain the invention in a fully clear and complete manner, and in particular with reference to figures 1 to 3, but in no way should be considered to limit the scope of protection to the embodiments specifically described below.

Fig. 1 shows an electronic circuit 1, which electronic circuit 1 comprises at least one capacitor 2 and a component consisting of a first branch 10, a second branch 20 and a third branch 30. The first branch 10 comprises a first switch 11 and a second switch 12. The second branch 20 comprises a first switch 21 and a second switch 22. The third branch 30 comprises a first switch 31 and a second switch 32.

The electronic circuit 1 shown in fig. 1 is, for example, adapted to be integrated in an electronic circuit of a power inverter, in which the capacitor 2 is a filter capacitor. In this embodiment, the set of

branches

10, 20 and 30 form a three-phase power inverter bridge, wherein each of the

branches

10, 20 and 30 is connected to one of the phases of a three-phase electric motor.

During use of the electronic circuit 1, a determined amount of energy may be stored in the capacitor 2, as shown in fig. 1. In the example of a compressor with an integrated power inverter, the filter capacitor may store a certain amount of energy that may exceed expected safety limits: safety constraints expected in the case of contact of the capacitor 2 with a human being, such as a user or a mechanic.

For safety reasons it is important that a determined amount of energy stored in the capacitor 2 can be dissipated in a relatively short time interval in order to minimize or eliminate any risk of electric shock for a person (user or mechanic) making direct or indirect contact with the capacitor 2. For example, in case of an accident, an electric shock hazard may occur when the connector is disconnected and/or when certain parts of the device need to be handled for maintenance or replacement reasons.

In order to control the dissipation of a determined amount of energy stored in the capacitor 2, each

switch

11, 12, 21, 22, 31 and 32 has a parasitic capacitance in accordance with the invention, in which a relatively small determined amount of energy can be stored.

According to the invention, a determined quantity of energy stored in the capacitor 2 is dissipated in a controlled manner by simultaneously opening the

first switches

11, 21 and 31, while simultaneously closing the second switches 12, 22 and 32, and vice versa. In other words, at a given instant ("instant t"), for each of the

branches

10, 20 and 30, the first switch is open and the second switch is closed, and vice versa.

For the sake of clarity and readability, fig. 2 and 3 schematically show an electronic circuit 1 provided with only branches 10. Obviously, the reader will readily understand that the explanations given below regarding the operation of the switches 11 and 12 of the branch 10 apply analogously also to the

switches

21 and 22 of the second branch 20 (see fig. 1) and to the

switches

31 and 32 of the third branch 30 (see also fig. 1).

A determined amount of energy stored in the capacitor 2 is indicated by reference numeral 50 in fig. 2. In the first phase of the energy dissipation method shown in fig. 2, the first switch 11 is closed and the second switch 12 is open.

After a relatively short determined period of time has elapsed, the situation shown in fig. 2 ("first phase") is reversed and the situation shown in fig. 3 ("second phase") is obtained, i.e. the first switch 11 is closed and the second switch 12 is open. In turn, after a relatively short determined period of time, the situation represented in fig. 3 ("second phase") is changed to the situation shown in fig. 2 ("first phase") by alternately opening and closing the switches 11, 12, and so on, until the determined/desired amount of energy has been sufficiently dissipated.

Referring to fig. 2 and 3, during the alternating opening and closing of the switches 11, 12, a certain amount of energy is stored in the parasitic filter capacitance of each switch 11, 12. As mentioned above, by alternately opening and closing the switches 11, 12, a determined amount of energy 50 stored in the capacitor 2 is dissipated as a small amount of energy (which is stored in the parasitic capacitances of the switches 11 and 12), schematically indicated by means of

reference numerals

52 and 53.

Advantageously, the energy dissipation method (also called "energy discharge") is performed by alternately opening and closing the

switches

11, 21, 31 on the one hand and the

switches

12, 22, 32 on the other hand at a frequency in the range of 10 to 50 kHz. In this way, a relatively large amount of energy can be dissipated/discharged in a relatively short period of time, which has proven to be particularly advantageous and desirable as explained in the preamble of the present patent application. As an example, over a period of about two seconds, a determined amount of energy may be dissipated, which initially corresponds to a potential in the range of 350V to 450V, so that finally a residual potential of 60V is obtained. This rate of dissipation of the energy stored in the capacitor makes it possible to greatly limit the situation of potential danger in terms of electric shock risk (as represented in fig. 1) for the user/mechanic who has touched the circuit 1.

In order to activate and control the energy dissipation phase (change from the first phase shown in fig. 2 to the second phase shown in fig. 3 and vice versa), the system according to the invention can advantageously be provided with control/command means connected to the

switches

11, 21, 31 and 12, 22, 32 and adapted to provide signals intended to alternately open and close said switches. This type of command means may be adapted to receive a signal to trigger the energy dissipation method, i.e. intended to activate it, in which case the instruction may be associated with the detection of the opening of the "interlock". In order to optimize the system according to the invention, the command device may be equipped with a filter, so that the filtering may be triggered upon receipt of a signal relating to the energy dissipation method, so that the need to activate the energy dissipation method may be confirmed or rejected.

The advantages of the energy dissipation method and system according to the invention are manifold. First of all, it may be noted that the energy dissipation method and system according to the invention may be used for all types of converters, such as DC/DC, DC/AC or AC/DC type converters.

Another technical advantage is associated with the fact that the method and system according to the invention do not require the installation of additional circuits or components and therefore never complicate and prove inexpensive to existing electronic installations. The energy dissipation method can be performed, for example, by means of command means intended to open and close the

various switches

11, 21, 31 and 12, 22, 32 within the "normal use" range of the electronic circuit, i.e. during which a certain amount of energy stored in the capacitor is not required/not required to be dissipated. It is however clear that in this figurative case it does require modification of the item(s) of software that operate this type of command device.

As mentioned above, when a determined amount of energy is dissipated by means of the method and system according to the invention, said energy is dissipated as a plurality of small amounts of energy. This makes it possible to avoid exposing the various components of the electronic circuit to high energy levels that may impair its correct operation. In other words, the components are used within their normal operating range, which further prevents their premature aging. Furthermore, there is no local stress, i.e. no "hot" spots are formed on the electronic components for energy dissipation. The

switches

11, 21, 31 and 12, 22, 32 for this energy dissipation purpose do not need to be of any over-size. The

switches

11, 21, 31 and 12, 22, 32 are used in their normal capacity without the risk of premature ageing.

In case the phase of the first switch (es) 11, 21, 31 and the second switch (es) 12, 22, 32 is 50%, it is important to avoid possible energy dissipation/discharge in the electric motor phase, which may lead to operation of the motor, more particularly if the motor is a traction motor, such as the traction motor of an electric vehicle.

Claims

1. A method for dissipating a determined amount of energy stored in a capacitor connected to at least one branch comprising a first switch and a second switch, each of the first switch and the second switch having a parasitic capacitance, the method comprising alternately repeating the steps of:

a) opening the first switch and simultaneously closing the second switch, an

b) Closing the first switch and simultaneously opening the second switch,

2. The method of claim 1, the capacitor being connected to at least two branches or at least three branches, each branch comprising a first switch and a second switch, each of the first and second switches having a parasitic capacitance, the method comprising alternately repeating the steps of:

so as to alternately charge and discharge the parasitic capacitances of all the first and second switches until said determined amount of energy is dissipated.

3. The method of claim 2, wherein the phase of the first switch and the second switch is 50%.

4. The method of any one of the preceding claims, wherein steps a) and b) alternate at a frequency in the range of 1kHz to 1 MHz.

5. A method according to any one of claims 1 to 3, wherein the opening and closing of the switch is commanded by a command device adapted to provide a command signal for the switch, the command device comprising a trigger element adapted to generate an instruction to activate a method for dissipating a determined amount of energy stored in a capacitor, the method comprising:

receiving a signal in the command device to trigger a method for dissipating a determined amount of energy stored in the capacitor through a sensor connected to the command device,

prior to starting the method for dissipating a determined amount of energy stored in the capacitor, an affirmative filtering of the trigger signal is performed, and in case of an acknowledgement,

a method for dissipating a determined amount of energy stored in the capacitor is initiated.

6. A system for dissipating a determined amount of energy stored in a capacitor, wherein the capacitor is connected to at least one branch comprising a first switch and a second switch, each of the first switch and the second switch having a parasitic capacitance, the system comprising command means adapted to provide a command signal for the switches, the command means being adapted to alternately issue:

a command signal SC1 for opening the first switch and simultaneously for closing the second switch, an

7. The system of claim 6, wherein the capacitor is connected to at least two branches or at least three branches, each branch comprising a first switch and a second switch, each of the first and second switches having a parasitic capacitance, the command means being adapted to issue alternately:

a command signal SC1 for opening all the first switches and for closing all the second switches simultaneously, an

A command signal SC2 for closing all first switches, and simultaneously for opening all second switches,

8. The system of claim 7, wherein the first switch and the second switch are 50% in phase.

9. The system of any one of claims 6 to 8, wherein said command means are adapted to provide a command signal of said switch such that said command signal SC1 and said command signal SC2 alternate at a frequency, said frequency being in the range of 10kHz to 50 kHz.

10. A system according to any one of claims 6 to 8, wherein said command means comprises a trigger element adapted to generate a method of initiating a process for dissipating a determined amount of energy stored in said capacitor, said trigger element being connected to a sensor adapted to sense a signal triggering said energy dissipation process.

11. The system of claim 10, wherein the command device is provided with an acknowledgement filter adapted to perform an acknowledgement filtering of the signal to trigger an energy dissipation method prior to initiating the method for dissipating a determined amount of energy stored in the capacitor.

12. A power inverter comprising a system as claimed in any one of claims 6 to 11.

13. An electric compressor adapted to equip a vehicle, the electric compressor comprising the power inverter of claim 12.