Leak detection apparatus and associated power supply

Abstract

The invention relates to a leak detection device, said device comprising: a space intended to receive a part to be tested; at least two electrodes disposed on either side of the receiving space; a direct current power supply supplying an output voltage V S ; a current detector configured to measure the current resulting from the voltage difference between the electrodes. The power supply is a power supply comprising: a transformer (101) having a midpoint primary; a transistor (T) connected to the midpoint of the transformer; switches (M1 and M2) whose successive opening and closing have at least one duty cycle (a) and enable the transmission of energy through the transformer; at least one regulation circuit which regulates the value of the duty cycle (a) and supplies the voltage of the base of the transistor (T).

Description

Technical Field

[0001] This invention relates to a device for detecting leaks by highlighting electrical insulation defects, particularly by measuring current. More specifically, this invention relates to a power supply for this device. Background Technology

[0002] This leak detection device allows the detection of openings, voids, or homogeneous defects in the electrically insulating parts of an object (e.g., parts made of dielectric material). This type of device is particularly advantageous for verifying the integrity of batteries, such as lithium-ion batteries, Li-Po batteries, etc. In practice, this type of battery has an electrically insulating casing, typically made of a plastic material (or a derivative thereof), within which a cathode, anode, and an electrolyte generally in polymer form are housed.

[0003] In fact, such as Figure 1 As shown, the device 1 includes: a space 3 configured to receive a part 5 to be tested, such as the battery mentioned above; electrodes 7 and 9 disposed on either side of the part 5; a power supply 11 that supplies power to at least one of the electrodes 7; and a current measuring device 13 configured to measure the current flowing between the electrodes 7 and 9 (e.g., "through" the part to be tested).

[0004] More specifically, one of the electrodes, 7 (referred to as the injection electrode), is connected to the power supply 11 and supplied with a predetermined voltage, also referred to as the "test voltage," while the other electrode, 9, referred to as the receiving electrode, is connected to ground G and has a potential close to zero.

[0005] Therefore, there is a potential difference between the two electrodes 7 and 9, and an electric field is established between the electrodes 7 and 9 and the test object 5 to at least partially ionize the material, such as the constituent elements of air (e.g., molecular oxygen).

[0006] Therefore, as Figure 2 As demonstrated, air ionization occurs, generating charge carriers that move under the influence of an electric field. Therefore, if the part under test 5 has a defect or an opening 5a, the charge carriers then propel it upwards to the receiving electrode 9. In the case where the part under test 5 is a battery (i.e., the electrodes and electrolyte reservoir are surrounded by a layer of electrical insulation), and if the battery has a defect in its insulating layer, then part of the electrolyte is ionized, thereby generating an additional charge carrier current. Depending on the measured current, it is determined whether the battery has an insulation defect and is therefore defective.

[0007] The advantage of this method is that it can detect extremely small defects or openings in electrical insulation materials. Furthermore, because the measured current is low and limited, there is no risk of thermal or electrocution to the operator operating the device according to the invention.

[0008] The tested component may have an impedance ranging from 5 megohms (MΩ) to 5 gigaohms (GΩ) (5 megohms corresponds to the short-circuit resistance of the device). Significant variations in impedance are particularly relevant to the presence of defects in the dielectric material of the tested component. Furthermore, depending on the distance between the electrode and the component under test, the surrounding environment, etc., it is necessary to vary the test voltage supplied to the injection electrode between a few volts and one kilovolt. Therefore, considering the possible applications and the type of component under test, the current to be measured to determine the state of the component can thus vary in the range of several nanoamps to several milliamps.

[0009] Therefore, the value of the current to be measured is very low and can vary by about 10. 5 This requires a stable and low-noise power supply.

[0010] In practice, the power supply must be able to deliver a constant and variable test voltage, regardless of changes in load and / or impedance associated with the component being tested. Therefore, it is necessary to ensure that the servo control capable of adjusting the voltage is also stable.

[0011] In addition, the power supply must be low-noise; in fact, noise at the test voltage affects the quality of current-related measurements and thus the detection of defects on the tested parts. Furthermore, if the noise is kept at an acceptable level, this avoids additional signal processing for current measurements.

[0012] These noise and stability constraints are accompanied by the fact that the power supply must be variable, compact, robust, and inexpensive to manufacture. Summary of the Invention

[0013] Therefore, the present invention aims to overcome at least one of the aforementioned disadvantages and relates to a leak detection device, the leak detection device comprising:

[0014] -At least two electrodes;

[0015] - A space designed to receive the parts to be tested;

[0016] - A DC power supply that supplies power to at least one of the electrodes;

[0017] - A current detector, configured to measure the current flowing through the part under test when the part under test is exposed to a voltage difference;

[0018] The power supply is characterized by being a variable power supply including the following:

[0019] - A transformer with a neutral primary;

[0020] - A transistor connected to the midpoint of the transformer;

[0021] - A switch, whose continuous opening and closing has at least one duty cycle α and enables energy transfer through a transformer;

[0022] - At least one regulating circuit that regulates the value of the duty cycle α and the voltage supplied to the base of the transistor (T).

[0023] In particular, the device according to the invention has the advantages of being compact and inexpensive, especially through the use of a transformer with a midpoint and a system for generating a DC voltage with minimal noise, which is suitable for measuring the impedance variables of objects tested by the device according to the invention thanks to the regulating circuit. Therefore, the device according to the invention includes a power supply with high stability criteria and low noise, insensitive to a wide range of load variations in the value of the test voltage.

[0024] According to possible features, the power supply includes a first regulating circuit that regulates the supply to the base of the transistor and a second regulating circuit that regulates the value of the duty cycle α.

[0025] In particular, the duty cycle α and the regulation of the power supply to the base of the transistor vary with the reference voltage V. ref and / or a test voltage V applied to at least one of the electrodes S The value of the load (or the value of the impedance to be tested) varies.

[0026] More specifically, the adjustment of each operation in the first and second circuits allows for 102 power and 10 respectively. 3 Dynamics (dynamics should be understood as the range between the maximum and minimum values ​​of the actual quantity being considered).

[0027] Therefore, it is particularly advantageous to use a transformer with a midpoint at the primary and to reconstruct a sine wave, as this is less costly and more compact than a sine wave generator or another type of transformer. More specifically, this architecture has better energy efficiency than the oscillator associated with a linear amplifier, especially for implementing power, and it also allows for a smaller heatsink (and thus less energy dissipation). Furthermore, the device according to the invention is particularly capable of using non-ideal power supplies, and is therefore especially suitable for industrial applications.

[0028] According to another possible feature, the second circuit is based on the reference voltage and the output voltage V. S and having frequency f osc The duty cycle value is adjusted by the modulation signal.

[0029] According to another possible feature, the second regulating circuit includes circuitry for controlling the opening and closing of the switch.

[0030] According to another possible feature, the transformer is a step-up voltage transformer.

[0031] According to another possible feature, the device includes rectifier and filter circuitry configured to rectify an AC signal derived from the secondary winding of a transformer and then apply the signal to at least one electrode.

[0032] According to another possible feature, the device further includes a compensation circuit configured to compensate for the value of the voltage actually delivered by the transformer at the output when the impedance of the part under test changes, and at least one input of the compensation circuit is placed at the output of the rectification and filtering circuit.

[0033] The present invention also relates to a DC power supply for a leakage detection device according to one of the foregoing embodiments.

[0034] According to a possible feature of at least one embodiment, the power supply includes:

[0035] - A transformer with a neutral primary;

[0036] - A transistor connected to the midpoint of the primary winding of the transformer;

[0037] - A switch, whose continuous opening and closing has at least one duty cycle α and enables energy transfer through a transformer;

[0038] - At least one regulating circuit that regulates the value of the duty cycle α and the voltage supplied to the base of the transistor.

[0039] According to a possible feature of at least one embodiment, the power supply includes a resistor disposed between the midpoint of the transistor and the primary of the transformer.

[0040] According to a possible feature of at least one embodiment, the power supply includes a rectification and filtering circuit at the secondary side of a transformer, the rectification and filtering circuit being configured to rectify and filter an AC signal at the secondary side of the transformer, which is then supplied to the injection electrodes.

[0041] According to a possible feature of at least one embodiment, the power supply includes a short-circuit resistor to limit the current injected at the electrode. Attached Figure Description

[0042] The invention will be better understood from the following description of specific embodiments of the invention, given only by way of illustration and not limitation, in which other objects, details, features, and advantages of the invention will become clearer, wherein:

[0043] [ Figure 1 [Illustration] is a specific schematic diagram of the leak detection device according to the present invention;

[0044] [ Figure 2 ]yes Figure 1 A specific schematic diagram of the electrodes of the device during the testing of the part;

[0045] [ Figure 3 ]yes Figure 1 A specific schematic diagram of the power supply for the device;

[0046] [ Figure 3a [ ] is a detailed schematic diagram of the rectification and filtering circuit according to an embodiment of the present invention;

[0047] [ Figure 4 ]yes Figure 3 Detailed view of the second regulating circuit for power supply;

[0048] [ Figure 5 ]yes Figure 3 A detailed view of the first regulating circuit for the power supply;

[0049] [ Figure 6 ]yes Figure 1 Schematic and detailed views of a variant embodiment of the circuit;

[0050] [ Figure 7 ]yes Figure 3 The simplified equivalent circuit of the transformer for power supply;

[0051] [ Figure 8 ] indicates specific to Figure 3 An example of a signal regulating circuit;

[0052] [ Figure 9 ] indicates by Figure 3 The power supply is supplied by the switch receiving signals and the output signals at the secondary winding of the transformer. Detailed Implementation

[0053] therefore, Figure 1 This is a specific schematic diagram of a leak detection device 1 according to the present invention, the leak detection device comprising:

[0054] - Space 3, which is designed to receive the part to be tested 5;

[0055] - Two electrodes, 7 and 9;

[0056] - A DC power supply 11 supplies power to at least one of the electrodes 7, and the electrode supplied by the power supply 11 is referred to as the injection electrode;

[0057] - Current measuring device 13, such as a transimpedance operational amplifier type ammeter, is configured to measure the current flowing through the tested part 5 when the tested part 5 is exposed to a voltage difference.

[0058] More particularly, especially shown in Figure 3 The power supply 11 mentioned above includes:

[0059] - Transformer 101, which has a neutral primary;

[0060] - Transistor T, which is connected to the midpoint of the primary winding of the transformer 101;

[0061] - Switches M1 and M2, whose continuous opening and closing have at least one duty cycle α and realize energy transfer through transformer 101;

[0062] - At least one regulating circuit 105 and regulating circuit 103, which regulate the value of the duty cycle α and the voltage supplied to the base of the transistor T.

[0063] It should be noted that, such as Figure 3 As shown, the power supply 11 may also include a resistor R disposed between the midpoint of the transistor T and the primary of the transformer 101. P This can have the advantage of limiting the intensity of the current at the primary stage.

[0064] It should also be noted that, as shown in the detailed embodiment, the power supply 11 may include a rectification and filtering circuit 107 at the secondary side of the transformer 101, which is configured to rectify and filter the AC signal at the secondary side of the transformer 101, and then supply this signal to the injection electrode 7. The power supply 11 may also include a resistor R, referred to as a short-circuit resistor. S (especially in) Figure 7 (as shown in the figure) to limit the current injected at the electrode.

[0065] In this article, especially in Figure 3a The rectifier and filter circuit 107 shown includes two diodes D1 and D2, and two capacitors C1 and C2, which are arranged to form a Schenkel-type voltage multiplier. This type of mounting allows for both rectification and filtering of the AC voltage present at the secondary side of the transformer T.

[0066] The power supply 11 may also include a voltage divider bridge disposed at the output of the rectifier and filter circuit 107. This type of installation allows, for example, the acquisition of a test voltage V. S The image, the voltage of which is referred to below as V' S And (for example) in Figure 3a and Figure 4As shown in the image.

[0067] More specifically, the voltage divider bridge includes two resistors, R1 and R2, with the voltage at the terminal of resistor R2 being the image voltage V'. S According to the following formula, the voltage V' of this image is... S Related to load voltage Vs:

[0068]

[0069] Therefore, k is a factor that depends on resistors R1 and R2.

[0070] More specifically, the at least one adjustment circuit 105 and adjustment circuit 103 have the following at the input end:

[0071] -Reference voltage or reference voltage V ref Reference voltage V ref The value of the test voltage V that should be obtained at the output terminal S Proportional;

[0072] -Image voltage V' S Its output voltage V S The image, this image shows the voltage V' S This can be achieved, for example, by using a voltage divider bridge;

[0073] - Modulation signal S M The duty cycle α is determined by the circuit; therefore, the power supply 11 includes a first regulating circuit 105 that regulates the supply to the base of the transistor T, and a second regulating circuit 103 that regulates the value of the duty cycle α. Specifically, the adjustment of the duty cycle α is based on a reference voltage V. ref Values ​​of load voltage V S The value (indirectly via voltage V) S Image voltage V' S ) and modulation signal S M The value is used to determine the outcome.

[0074] Especially in Figure 5 The first adjustment circuit 105 shown includes an operational amplifier AO5 associated with two resistors R4 and R5, the operational amplifier being configured to receive a reference voltage V at its input. ref The non-inverting amplifier (e.g., resistors R4 and R5 have equal values). The first adjustment circuit 105 is configured to adjust the injection voltage V at the injection electrode 7. S When there is no load, the regulation operated by the first circuit 105 is dominant, that is, when there is no load, the circuit 105 via transistor T is dominant in setting the value of the injection voltage.

[0075] Therefore, transistor T:

[0076] -A DC voltage V is supplied at the collector. alim ;

[0077] - Its base is connected to the output of the first regulating circuit 105, the output being based on the voltage V derived from the first circuit 105. AO5 This allows for voltage variations at the primary winding of transformer 101.

[0078] The transistor's emitter delivery is between kV ref The voltage value between the reference voltage V and zero (where k equals 1 + R5 / R4) is determined based on the reference voltage V. ref Adjustments were made.

[0079] According to the reference voltage V ref The variable adjustment circuit 105 allows adjustment of the voltage at the midpoint of the primary winding and thus obtains the desired voltage at the secondary winding, and thus also obtains the output voltage V. S .

[0080] More specifically, the regulation of the voltage delivered by transistor T thus allows the test voltage to be servo-controlled to a reference voltage requested by the operator, while the second regulation circuit 103 activates to compensate for the test voltage and maintain the test voltage in the event of load changes (i.e., changes in the insulation resistance of the tested part). Each of the regulation circuits 105 and 103 acts as a means to allow the test voltage V to be adjusted. S A servo that allows for finer adjustments within a wide range of values.

[0081] Especially in Figure 4 The second adjustment circuit 103 shown includes:

[0082] - Shaping circuit 103a, which includes operational amplifier AO3, which is mounted as a comparator-integrator associated with capacitor C3 and resistor R3.

[0083] - Control circuit 103b, which has the output of operational amplifier AO3 as input and voltage V osc The modulation signal S m and frequency f osc The modulation signal S m The control circuit 103b is configured to generate a PWM signal (representing "pulse width modulation") using a duty cycle α to control the opening and closing of switches M1 and M2.

[0084] Therefore, operational amplifier AO3 receives the image voltage V' at its input terminal. S and reference voltage V ref And the resulting voltage V delivered at the output terminal is in the following formAO3 :∫(V ref -V′ S )dt.

[0085] Subsequently, the control circuit 103b (more particularly visible in) Figure 4 (in Chinese) includes:

[0086] - Operational amplifier AO4, which is mounted as a comparator, receives a frequency f at its input. osc The modulation signal S M and the output voltage V of operational amplifier AO3 AO3 ;

[0087] Two logic gates, P1 and P2, are phase-shifted by π relative to each other, such that the closing and opening of switches M1 and M2 are performed in a phase-relative manner.

[0088] More specifically, the operational amplifier AO4 therefore transforms the output voltage V of the shaping circuit 103a. AO3 With modulation signal S M The voltage V (e.g., ramp or sawtooth type) osc Compare the modulator's frequency f. osc It is a fixed value that roughly corresponds to the resonant frequency of the power supply 11 (i.e., the inductance of the primary and the capacitance present in the secondary winding returning to the primary).

[0089] It should be noted that, Figure 6 In the variations shown in the middle section, the image voltage V is not derived simply and directly from the voltage divider bridge as previously explained. S '.

[0090] More specifically, like this Figure 6 As shown, in addition to resistors R1 and R2 of the voltage divider bridge, there is a shunt resistor R1 located between the rectifier and filter circuit 107 and resistor R2. SH Therefore, the power supply 11 includes a load change compensation circuit 109, which has a shunt resistor R. SH The terminals serve as input terminals, and the output voltage V of the voltage divider bridge formed by resistors R1 and R2 is... S Therefore, when the impedance of the object being tested changes, for example, decreases, the efficiency of the transformer decreases, and the compensation circuit 109 then allows compensation for the value of the voltage actually delivered by the transformer at the output.

[0091] Therefore, the measurement power can be increased while maintaining the same current measurement accuracy.

[0092] Therefore, the compensation circuit 109 includes:

[0093] - The first operational amplifier AO6 has its input connected to the shunt resistor R. SH The terminal is to which a predetermined gain G is applied, so that a voltage related to the value of the current flowing in the secondary winding of the transformer 101 exists at the output of the operational amplifier AO6.

[0094] - The second operational amplifier AO7 adds the voltage value derived from the voltage divider bridge and operational amplifier AO6.

[0095] Therefore, the voltage drop across the secondary winding is represented by V at the output of circuit 109. S The image of the voltage, the image of the voltage V S Next, the input value of the second adjustment circuit 103 is used.

[0096] Furthermore, the closing and opening frequencies f of the switches M1 and M2, which are in phase relative to each other, are... osc The choice of this option thus allows a sinusoidal signal to be reconstructed at the secondary winding of transformer 101. In particular, this allows for maximizing energy transfer through transformer 101 by limiting noise generation on the current delivered by the secondary winding of transformer 101.

[0097] In fact, Figure 3 The power supply section can be simplified by modeling the equivalent circuit. This simplified equivalent circuit is particularly useful in... Figure 7 As shown in the diagram. Therefore, from a primary perspective, the circuit can be considered an RLC circuit, which includes a voltage source E; resistors R corresponding to the generator's internal resistance (and short-circuit resistance), the resistance of the primary winding, and the resistance connected to the midpoint of transformer 101, respectively. S Resistor R B Resistor R P ; Inductance L corresponding to the primary magnetization inductance MAG And the capacitance C corresponding to the capacitance present at the terminals of the two primary sets. P It should be noted that the resistance of a transistor allows for the acquisition of an equivalent variable voltage regulator.

[0098] In this case, the resistance of the primary winding can be ignored compared to the values ​​of other resistors.

[0099] Therefore, the natural ripple ω0 of this RLC circuit is as follows:

[0100]

[0101] In the same way, we can determine the reduced damping coefficient m as follows:

[0102]

[0103] Therefore, in the pseudo-periodic mode, a pseudo-pulsation ω can be defined. P , so that:

[0104]

[0105] However, when the modulator frequency f osc When the frequency is equal to (or approximately equal to) that of the equivalent circuit, especially in sustained subcritical mode, m is much less than 1 and ω≈ω0.

[0106] The voltage U delivered by the transformer M Then it forms a U M ≈λαE, where α is the duty cycle of the first adjustment circuit 103 and λ is a coefficient that depends on the transfer function of the PWM control circuit.

[0107] Therefore, as Figure 8 As shown, the shaping circuit 103a integrates the image voltage V' S With reference voltage V ref The difference between them, and therefore the output DC voltage V AO3 Therefore, this voltage V AO3 With modulation voltage V osc Comparison is performed, and the generation of a square wave signal S is allowed. PWM Therefore, the duty cycle α of the square wave signal is modified according to the change in load current. More specifically, if the reference voltage V... ref If it increases, then the voltage V will follow. AO3 The value decreases, and the resulting square wave signal S PWM The duty cycle α increases. In fact, when the resistance (or load) of the component being tested decreases, the duty cycle α increases to maintain the test voltage.

[0108] Therefore, the square wave signal S PWM This is the output signal of control circuit 103b, which controls the opening and closing of switches M1 and M2. Square wave signal S PWM Having a constant frequency f osc Therefore, the opening and closing of switches M1 and M2 alternately supply each of the primary portion of transformer 101 with a phase shift of π.

[0109] like Figure 9 As shown, the closing and opening of each of the switches M1 and M2 thus allows the reconstruction of the fundamental harmonic of the square wave signal, i.e., by defining the signal S generated by the parallel resonant oscillator operating in a forced weakly damped mode. sec Therefore, modifying the duty cycle α allows for an increase in the amount of energy transmitted and thus the alternating current signal S acting on the secondary side of transformer 101. sec The value of the voltage.

Claims

1. A leak detection device, the device comprising: - A space designed to receive the parts to be tested; - At least two electrodes are disposed on either side of the receiving space; - A DC power supply that supplies an output voltage V to at least one of the electrodes. S ; - A current detector configured to measure the current generated by the voltage difference between the electrodes; The power supply (11) includes the following: - Transformer (101), which has a neutral primary; - A transistor (T) connected to the midpoint of the transformer; - Switches (M1 and M2), whose continuous opening and closing have at least one duty cycle (α) and energy transfer is achieved through the transformer; - At least one regulating circuit that regulates the value of the duty cycle (α) and the voltage supplied to the base of the transistor (T); The power supply (11) is characterized in that it includes a first regulating circuit (105) for regulating the power supply of the base of the transistor and a second regulating circuit (103) for regulating the duty cycle (α).

2. The apparatus according to claim 1, characterized in that, The second adjustment circuit (103) adjusts the value of the duty cycle (α) according to the reference voltage Vref, the output voltage VS and the modulation signal having a frequency fosc.

3. The apparatus according to claim 1, characterized in that, The first regulating circuit (105) regulates the voltage delivered by the transistor (T) to the primary of the transformer according to the reference voltage Vref.

4. The apparatus according to claim 1, characterized in that, The frequency at which the switches (M1 and M2) are opened and closed is constant.

5. The apparatus according to claim 1, characterized in that, The opening and closing frequencies of the switches (M1 and M2) have values ​​that set the circuit to underdamped mode.

6. The apparatus according to claim 5, characterized in that, The second regulating circuit (103) includes a circuit (103a) for shaping the value of the reference voltage Vref and the value of the output voltage VS, and a circuit (103b) for controlling the opening and closing of the switches (M1 and M2).

7. The apparatus according to claim 6, characterized in that, The transformer (101) is a step-up voltage transformer.

8. The apparatus according to claim 1, characterized in that, The power supply (11) includes a rectifier and filter circuit (107) configured to rectify an AC signal derived from the secondary of the transformer (101) and then apply the signal to at least one electrode (7).

9. The apparatus according to claim 8, characterized in that, The power supply (11) further includes a compensation circuit (109) configured to compensate for the value of the voltage actually delivered by the transformer at the output when the impedance of the part under test changes, and at least one input of the compensation circuit (109) is placed at the output of the rectification and filtering circuit (107).

10. A DC power supply for use in the leak detection device according to any one of claims 1 to 9.

11. The power supply according to claim 10, characterized in that, The power supply includes: - Transformer (101), which has a neutral primary; - A transistor (T) connected to the midpoint of the primary winding of the transformer (101); - Switches (M1 and M2), which continuously open and close with at least one duty cycle (α) and realize energy transfer through the transformer (101); - At least one regulating circuit (105) and regulating circuit (103) which regulate the value of the duty cycle (α) and the voltage supplied to the base of the transistor (T).

12. The power supply according to claim 11, characterized in that, The power supply includes a resistor (R) disposed between the midpoint of the primary winding of the transistor (T) and the transformer (101). P ).

13. The power supply according to claim 12, characterized in that, The power supply includes a rectification and filtering circuit (107) at the secondary of the transformer (101), which is configured to rectify and filter the AC signal at the secondary of the transformer (101), and then supply this signal to the injection electrode (7).

14. The power supply according to claim 10, characterized in that, The power supply (11) includes a short-circuit resistor (R) S This is to limit the current injected at the electrode.

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