Deployment circuit of pyrotechnic equipment, corresponding integrated circuit, vehicle and method

Abstract

The invention relates to a deployment circuit of pyrotechnic equipment, a corresponding integrated circuit, a vehicle and a method. A deployment circuit for a pyrotechnic apparatus is provided. An example deployment circuit includes a driver circuit, a monitoring circuit, and a control circuit. The driver circuit energizes the pyrotechnic device by applying a voltage or current to the first and second terminals. A monitoring circuit measures a voltage across the first terminal and the second terminal, processes the measured voltage, and determines whether the processed voltage is greater than a threshold. The monitoring circuit asserts a comparison signal in response to the processed voltage being above a threshold. The control circuit receives an ignition request signal and a comparison signal. In response to the ignition request signal, the control circuit generates a control signal to energize the pyrotechnic device via the driver circuit and determines whether the comparison signal is asserted. In response to determining that the comparison signal is deasserted, the control circuit again energizes the pyrotechnic device.

Description

[0001] Cross-reference to related applications (one or more)

[0002] This application claims the benefit of priority of Italian Patent Application No. 102024000002019, filed on February 1, 2024, with the title "CIRCUITO DI INNESCO PER UN DISPOSITIVO PIROTECNICO, CORRISPONDENTE CIRCUITO INTEGRATO, VEICOLO E PROCEDIMENTO", which is incorporated herein by reference in its entirety to the maximum extent permitted by law. Technical field

[0003] The present disclosure relates to circuits for deploying electrically actuated pyrotechnic devices such as squibs, pyrotechnic fuses or pyrotechnic actuators, and corresponding methods. Background art

[0004] Electrically actuated pyrotechnic devices serve as indispensable components for delivering large amounts of energy within extremely short deployment windows and are thus very common in safety applications. Notably, this category includes squibs for airbag activation, pyrotechnic fuses designed to quickly disconnect electrical connections, such as disconnecting the connection of an electric vehicle (EV) battery in the event of a ground short circuit fault, and pyrotechnic actuators.

[0005] In the context of safety applications, various solutions have been proposed to monitor the correct connection of pyrotechnic devices to deployment circuits. For example, such solutions are disclosed in U.S. Patent Application Publication Nos. US 2018 / 0029554 A1 and US 2019 / 0302162 A1. Substantially, such solutions are based on the fact that pyrotechnic devices typically have a resistance value within a given tolerance range. Thus, by determining whether the resistance value between the terminals connected to the pyrotechnic device lies between a lower threshold and an upper threshold, the deployment circuit can determine whether the pyrotechnic device is correctly connected to the deployment circuit.

[0006] Conversely, the actual deployment of pyrotechnic devices is typically detected via auxiliary sensors. For example, such a solution is disclosed in U.S. Patent No. US10,029,640 B2 or JP 1002 / 144994 A in the context of airbag deployment detection. Summary of the invention

[0007] Given the mission-critical nature of the numerous applications in which pyrotechnic devices are employed, there is an urgent need for innovative solutions that enable real-time monitoring of deployment results.

[0008] According to one or more embodiments, this object can be achieved by means of a deployment circuit for a pyrotechnic device. Moreover, embodiments relate to related integrated circuits, vehicles, and methods.

[0009] The present disclosure is defined by the appended independent claims. The claims are an integral part of the technical teachings provided herein.

[0010] As previously mentioned, various embodiments of the present disclosure relate to a deployment circuit for a pyrotechnic device such as an explosive tube, a pyrotechnic fuse, or a pyrotechnic actuator for, for example, a vehicle, e.g., a deployment circuit integrated in an integrated circuit.

[0011] In various embodiments, the deployment circuit includes a first terminal and a second terminal configured to be connected to a pyrotechnic device, a driver circuit, a monitoring circuit, and a control circuit.

[0012] In various embodiments, the driver circuit is configured to power the pyrotechnic device by selectively applying a voltage or current to the first terminal and the second terminal according to at least one control signal. For example, in various embodiments, the driver circuit includes at least one electronic switch configured to selectively connect the first terminal and the second terminal to a supply voltage according to at least one control signal. Additionally, the driver circuit may include a current limiter connected in series with the first terminal and the second terminal to limit the current supplied to the first terminal and the second terminal to a maximum value. Alternatively, the driver circuit may be configured as a constant current source that directly provides the requested current. In various embodiments, the maximum value or the requested current can be set via at least one control signal.

[0013] In various embodiments, the monitoring circuit is configured to measure the voltage across the first terminal and the second terminal, process the measured voltage, and determine whether the processed voltage is greater than a threshold. In response to determining that the processed voltage is greater than the threshold, the monitoring circuit asserts a comparison signal.

[0014] Specifically, the processed signal should indicate whether the pyrotechnic device has been deployed.

[0015] For example, in various embodiments, the processed signal indicates the resistance value of the pyrotechnic device. For example, to this end, the monitoring circuit may also measure the current supplied via the first terminal and the second terminal and generate the processed voltage by calculating the ratio between the measured voltage and the measured current, such that the processed voltage indicates the resistance of the pyrotechnic device.

[0016] However, instead of directly measuring the resistance value of the pyrotechnic device, the monitoring circuit can also generate other processed signals that still indicate the resistance value of the pyrotechnic device or an increase in the resistance value of the pyrotechnic device. For example, to this end, the measurement circuit can generate a processed voltage by filtering the measured voltage with a low-pass filter or a band-pass filter. Alternatively, for example, when using a deployment cycle with a fixed duration, the monitoring circuit can generate a processed voltage by calculating the integral of the measured voltage. Alternatively, the monitoring circuit can generate a processed voltage by calculating the integral of the square of the measured voltage.

[0017] In various embodiments, the control circuit is configured to receive an ignition request signal and a comparison signal. In response to the ignition request signal, the control circuit generates at least one control signal to energize the pyrotechnic device via a driver circuit. For example, to this end, in response to the ignition request signal, the control circuit can start a timer and determine whether the timer reaches a time threshold. Thus, in response to determining that the timer reaches the time threshold, the control circuit can stop energizing the pyrotechnic device.

[0018] Moreover, in various embodiments, the control circuit determines whether the comparison signal is asserted. For example, in various embodiments, the control circuit is configured to determine whether the comparison signal is asserted in response to determining that the timer reaches the time threshold.

[0019] Alternatively, in response to the ignition request signal, the control circuit can set the maximum value of the current limiter or the requested current to a first value for energizing the pyrotechnic device. Next, in response to determining that the timer reaches the time threshold, the control circuit can set the maximum value of the current limiter or the requested current to a second value, where the second value is less than the first value, thereby using a lower measurement current. Thus, in this case, once the maximum value of the current limiter is set to the second value, the control circuit can determine whether the comparison signal is asserted.

[0020] Thus, in various embodiments, when the comparison signal is asserted, the comparison signal indicates that the pyrotechnic device has been deployed. Thus, in various embodiments, in response to determining that the comparison signal is de-asserted, the control circuit can energize the pyrotechnic device again. In various embodiments, the control circuit can also wait for a predetermined amount of time before energizing the pyrotechnic device again.

[0021] For example, to energize the pyrotechnic device again, the control circuit can generate at least one control signal again to energize the pyrotechnic device via a driver circuit.

[0022] However, the deployment circuit may further include additional driver circuitry configured to energize the pyrotechnic device by selectively applying voltage or current to the first and second terminals in accordance with at least one additional control signal. Thus, in such a case, the control circuit may generate the at least one additional control signal to energize the pyrotechnic device via the additional driver circuitry. Generally, the control circuit may also be split into two parts, where a first control circuit manages the operation of the driver circuitry and the monitoring circuitry, and a second control circuit manages the operation of the additional driver circuitry. For example, in such a case, in response to determining that the comparison signal is de-asserted, the first control circuit may provide an additional ignition request signal to the second control circuit. Thus, in various embodiments, the first and second control circuits may have substantially the same structure, where the second control circuit and the additional driver circuitry operate as a redundant deployment circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Embodiments of the present disclosure will now be described with reference to the accompanying drawings, which are provided by way of non-limiting example only and in which:

[0024] Figure 1 a first embodiment of a circuit for deploying a pyrotechnic device in accordance with the present disclosure is shown;

[0025] Figure 2 a second embodiment of a circuit for deploying a pyrotechnic device in accordance with the present disclosure is shown;

[0026] Figure 3 a flowchart representing an embodiment of a method for deploying a pyrotechnic device is shown;

[0027] Figure 4 exemplary waveforms when using the Figure 3 method during a first deployment cycle are shown;

[0028] Figure 5 exemplary waveforms when using the Figure 3 method during a second deployment cycle are shown; and

[0029] Figure 6 an exemplary embodiment of a system including two daisy-chain deployment circuits in accordance with the present disclosure is shown. DETAILED DESCRIPTION

[0030] In the following description, numerous specific details are given to provide a thorough understanding of the embodiments. The embodiments may be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the embodiments.

[0031] References to "one embodiment" or "an embodiment" in the present specification mean that the particular features, structures, or characteristics described in connection with that embodiment are included in at least one embodiment. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" throughout the specification are not necessarily all referring to the same embodiment. Moreover, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0032] The headings provided herein are for convenience only and do not interpret the scope or meaning of the embodiments.

[0033] As previously mentioned, various embodiments of the present disclosure provide solutions for deploying pyrotechnic devices.

[0034] Figure 1 An embodiment of a deployment circuit 100 according to the present disclosure is shown.

[0035] In the embodiment under consideration, the deployment circuit 100 includes a first terminal 122a and a second terminal 122b configured to be connected to an electrically activated pyrotechnic device 101. For example, in various embodiments, the pyrotechnic device 101 may be an airbag squib, a seatbelt pretensioner initiator, a pyrotechnic switch, or a pyrotechnic fuse.

[0036] In the embodiment under consideration, the deployment circuit 100 further includes a driver circuit configured to selectively power the pyrotechnic device 101. Generally, the driver circuit is configured to apply a given voltage V PYRO to the terminals 122a and 122b or control the current I PYRO provided via the terminals 122a and 122b. In fact, from an electrical perspective, the pyrotechnic device 101 to be ignited mainly represents a resistive load.

[0037] For example, in Figure 1 the driver circuit is configured to selectively connect the terminals 122a and 122b to a supply voltage V IN . To this end, the driver circuit may include a first terminal 121 and a second terminal 123, for example, representing ground GND, configured to receive the supply voltage V IN . For example, the voltage V IN may be provided by, for example, a battery of a vehicle including, for example, pyrotechnic devices 101 associated with various airbags of the vehicle. Alternatively, the supply voltage V IN may be provided by one or more capacitors ( Figure 1 not shown in). For example, such (one or more) capacitors may be charged by additional electronic converters such as boost or buck converters.

[0038] Specifically, in Figure 1In the embodiment shown, the driver circuit includes a first electronic switch 104 configured to connect terminal 122a to terminal 121 according to a first drive signal 192a and / or a second electronic switch 103 configured to connect terminal 122b to terminal 123 according to a second drive signal 192b. For example, switches 103 and 104 can be field effect transistors (FETs), such as metal oxide semiconductor field effect transistors (MOSFETs). For example, each of switches 103 and 104 can be a normally open switch, such as a depletion mode MOSFET, which closes in response to the receipt of an asserted drive signal (192b or 192a).

[0039] Thus, when terminals 122a and 122b are connected to a supply voltage, for example, when electronic switches 103 and 104 are closed, voltage V IN is also applied to the pyrotechnic device 101 (neglecting possible parasitic resistances, such as the parasitic resistance of the cable), i.e., the voltage V at the pyrotechnic device 101 PYRO corresponds to voltage V IN so that current I PYRO flows through the pyrotechnic device 101.

[0040] Conversely, in Figure 2 the driver circuit is configured to selectively apply current to terminals 122a and 122b. For example, in the embodiment under consideration, the driver circuit includes a current source or current limiter 102 configured to set or limit the current provided via terminals 122a and 122b, respectively.

[0041] Specifically, in the embodiment shown in Figure 2 the driver circuit includes a current source or current limiter 102 connected between terminal 122a and terminal 121. In various embodiments, the current source or current limiter 102 can be configured to set the requested current or maximum current according to a reference signal 193, respectively. For example, circuit 102 can be implemented with a field effect transistor (FET). For example, this FET can correspond to the output stage of a current mirror.

[0042] In various embodiments, the driver circuit can also include Figure 1 the first electronic switch 104 and / or the second electronic switch 103 shown in Figure 2 For example, in PYRO the driver circuit includes an electronic switch 103 configured to connect terminal 122b to terminal 123 according to a second drive signal 192b. Thus, in the embodiment under consideration, the driver circuit is configured to regulate or at least limit the current I

[0043] flowing through the pyrotechnic device 101. For example, current source 102 can measure current IPYRO , such as the current flowing through electronic switches 104 and / or 103 (see Figure 1 ), wherein the driver circuit includes a closed-loop control circuit configured to regulate the measured current to a requested value by, for example, selectively connecting terminals 122a and 122b to voltage V via electronic switches 104 and 103 IN or disconnecting terminals 122a and 122b from voltage V IN .

[0044] Conversely, the driver circuit may implement current limiter 102 by connecting terminals 122a and 122b to voltage V when the measured current I PYRO is less than the maximum requested value and disconnecting terminals 122a and 122b from voltage V when the measured current I IN is greater than the maximum requested value. In various embodiments, the comparison may also include hysteresis, i.e., the driver circuit may be configured to disconnect terminals 122a and 122b from voltage V when the measured current I PYRO is greater than the maximum requested value and connect terminals 122a and 122b to voltage V when the measured current I IN is less than the minimum requested value. PYRO is greater than the maximum requested value and disconnecting terminals 122a and 122b from voltage V IN , and connecting terminals 122a and 122b to voltage V when the measured current I PYRO is less than the minimum requested value IN .

[0045] Thus, in various embodiments, deployment circuit 100 further includes control circuit 114 configured to generate one or more of signals 192a, 192b, and 193 in accordance with an ignition or deployment request signal 191. In various embodiments, signal 191 is generated by an external deployment control circuit.

[0046] For example, in the embodiment shown in Figure 1 , in response to detecting that the deployment request signal 191 indicates a request for ignition, e.g., when signal 191 is asserted, control circuit 114 asserts (high-side) drive signal 192a and (low-side) drive signal 192b.

[0047] Conversely, in the embodiment shown in Figure 2 , in response to detecting that the deployment request signal 191 indicates a request for ignition, e.g., when signal 191 is asserted, control circuit 114 asserts (low-side) drive signal 192b. In the case where current source or limiter 102 is configurable, control circuit 114 may also generate signal 193 to set current I PYRO to a given requested value or limit current I PYRO to a given maximum value. Alternatively, control circuit 114 may be configured to measure current I PYROand drive the electronic switches 103 and / or 104 based on the measured current, e.g., by implementing a closed-loop control of the current I PYRO or comparing it with one or more thresholds, such as a maximum current and a minimum current.

[0048] In various embodiments, the deployment circuit 100 is configured to monitor and analyze the voltages at terminals 122a and 122b.

[0049] In various embodiments, the deployment circuit 100 includes, for this purpose, an analog-to-digital converter (ADC) 110 that is connected to the terminals 122a and 122b of the pyrotechnic device 101, i.e., the ADC 110 is configured to receive the voltages at terminals 122a and 122b, i.e., the voltage V across the pyrotechnic device 101 PYRO and generate a digital signal 194 indicative of the voltage V PYRO For example, the ADC 110 can be a sigma-delta converter, but alternative embodiments using different ADC architectures, such as a flash ADC or a successive approximation ADC, are also possible.

[0050] In the considered embodiment, the digital signal 194 produced as an output by the analog-to-digital converter 110 is received by the processing circuit 111, which is configured to process the digital samples 194 of the voltage V PYRO Generally speaking, instead of using digital processing, the same operations can also be implemented via an analog processing circuit, i.e., the ADC 110 is entirely optional. Thus, generally speaking, the processing circuit 111 can be implemented with any analog or digital processing circuit or a combination thereof.

[0051] In various embodiments, the processing circuit 111 is configured to analyze the analog value of the voltage V PYRO or the digital samples provided by the ADC 110, which is hereinafter only indicated as the signal 194 for simplicity, and generate a processed signal 195. Thus, the processed signal 195 can also be an analog signal or a digital signal, respectively.

[0052] In various embodiments, the comparator 112 is configured to generate a deployment status signal 190a by comparing the processed signal 195 with a threshold 196. Specifically, in various embodiments, in response to determining that the processed signal 195 is greater than the threshold 196, the comparator 112 is configured to assert the deployment status signal 190a, e.g., set the signal 190a to high.

[0053] Thus, depending on whether the processed signal 195 is an analog or digital signal, the comparator can also be implemented as an analog or digital comparator, respectively. For example, in various embodiments, circuit 100 includes an ADC 110, digital processing circuit 111, and digital comparator 112, where signal 113 is a digital threshold 196, provided, for example, by register 113. For example, in various embodiments, processing circuit 111 and comparator 112 can be implemented using the same digital processing circuit, such as a microprocessor programmed via software instructions. For example, in such a case, ADC 110, as well as microprocessors 111 and 112, can be implemented using a microcontroller. In various embodiments, control circuit 114 can also be a digital control circuit and is implemented, for example, via software instructions executed by a microprocessor.

[0054] As previously mentioned, in various embodiments, processing circuit 111 is configured to process signal 194 and generate a processed signal 195. For example, in various embodiments, signal 195 can indicate the unit resistance specific energy i 2 t supplied to pyrotechnic device 101 and can be, for example, a resistance, voltage, or unit resistance specific energy. More details regarding the manner in which the acquired voltage 194 is processed into the processed data 195 will be provided hereinafter.

[0055] Thus, in various embodiments, deployment circuit 100 includes a comparator circuit 112 that is configured to compare signal 195 with a (programmable) deployment threshold 196 and, if signal 195 is greater than (or equal to) the programmable deployment threshold 196, then generate a good ignition signal 190a as an output. More details regarding the physical quantity represented by the processed signal 195 will be provided hereinafter.

[0056] In various embodiments, control circuit 114 is coupled to timer circuit 115. In various embodiments, timer 115 can also be implemented via software instructions executed by a microprocessor that implements control circuit 114 and / or processing circuit 111.

[0057] Specifically, in various embodiments, in response to receiving an ignition request signal 191, control circuit 114 resets timer circuit 115 by sending a reset signal 187, i.e., instructing timer circuit 115 to reset its contents and start counting from zero. The elapsed time can be stored in a register provided within timer circuit 115 and is accessible by control circuit 114. Control circuit 114 is also configured to repeatedly compare the ongoing time 188 with a time threshold t TIMEOUT indicating the maximum time that the deployment operation may take during the deployment operation. In response to determining that time 188 exceeds time threshold t TIMEOUT, the control circuit 114 interrupts the deployment of the pyrotechnic device. Thus, in various embodiments, the control circuit 114 is configured to drive the pyrotechnic device 101 within a given maximum time in response to the ignition request signal 191.

[0058] Similarly, as previously mentioned, in Figure 2 the embodiment shown, the driver circuit is configured to selectively apply current to terminals 122a and 122b. For example, in the embodiment under consideration, the driver circuit includes current sources or current limiters 102 configured to set or limit the current provided via terminals 122a and 122b, respectively. In various embodiments, the current sources or current limiters 102 may be configured to set the requested current or maximum current according to the reference signal 193, respectively.

[0059] Moreover, the driver circuit may include a first electronic switch 104 configured to connect terminal 122a to terminal 121 according to the first drive signal 192a and / or a second electronic switch 103 configured to connect terminal 122b to terminal 123 according to the second drive signal 192b.

[0060] Thus, in Figure 2 the embodiment shown, the deployment circuit 100 further includes a control circuit 114 configured to generate one or more of the signals 192a, 192b, and 193 according to the ignition or deployment request signal 191. For example, Figure 2 an additional timer circuit 115 is also shown, which may be used to drive the pyrotechnic device 101 only within a given maximum time.

[0061] Thus, in this embodiment, the deployment circuit 100 may also monitor and analyze the voltage V at terminals 122a and 122b PYRO . For example, in Figure 2 the optional ADC 110, processing circuit 111, comparator 112, and threshold signal generator 113 are shown again.

[0062] Possible embodiments of the operation of the deployment circuit 100 will now be described with respect to Figure 3 and Figure 1 and Figure 2 .

[0063] Specifically, Figure 3 the start step 300 is shown, which is initiated when the deployment circuit 100, such as the control circuit 114, determines that the ignition request signal 191 is asserted.

[0064] As in Figure 1 and Figure 2As shown, control circuit 114 may also receive an optional ignition inhibition signal 190b. For example, such an ignition inhibition signal 190b allows for daisy-chaining of two or more instances of the pyrotechnic device deployment circuit 100, to allow for a configuration with redundant deployment circuits 100, i.e., the ignition inhibition signal 190b may be received from another instance of the deployment circuit 100, as Figure 6 shown. In this way, a deployment with a primary / first deployment circuit 100a may be attempted, and if the first deployment fails, then a second deployment attempt may be made with the aid of a backup / second deployment circuit 100b. Conversely, if the first deployment attempt is successful, then the backup deployment circuit 100b will not fire because the ignition inhibition signal 190b received from the primary deployment circuit 100a is asserted. More details regarding such a configuration will be provided below.

[0065] This is also shown in Figure 3 where the deployment circuit 100, e.g., the control circuit 114, is configured to verify in step 301 whether the ignition inhibition signal 190b is asserted or de-asserted.

[0066] Specifically, in response to determining that the ignition inhibition signal 190b is de-asserted (output “Y” of verification step 301), the deployment circuit 100, e.g., the control circuit 114, may proceed to step 302 to start a deployment cycle. Conversely, in response to determining that the ignition inhibition signal 190b is asserted (output “N” of verification step 301), the deployment circuit 100, e.g., the control circuit 114, may stop the deployment request at stop step 310, and thus the method terminates.

[0067] Thus, in the absence of the ignition inhibition signal 190b and the corresponding verification step 301, the method may proceed directly to step 302.

[0068] Specifically, in various embodiments, the deployment circuit 100, e.g., the control circuit 114, is configured to drive a driver circuit to power the pyrotechnic device 101, thereby starting a deployment cycle. According to various embodiments, the pyrotechnic device 101 may be powered by applying a deployment voltage V PYRO to terminals 122a and 122b, as Figure 1 performed in the exemplary embodiment shown, or by providing a deployment current I PYRO to terminals 122a and 122b, as Figure 2 performed in the exemplary embodiment shown.

[0069] Thus, in various embodiments, the deployment circuit 100, such as the control circuit 114, may generate one or more of the drive signals 192a and / or 192b for switches 104 and 103, and / or the reference signal 193 for the current source or current limiter 102.

[0070] In various embodiments, this step 302 may be performed after a predetermined time delay t DELAY which will be counted by means of the timer circuit 115. In particular, a configuration such as the system shown in DELAY may require a non-zero time delay t during powering the pyrotechnic device using the standby deployment circuit 100b. Figure 6 This time delay inherently allows the system, such as the one shown, to perform a first deployment attempt using the main deployment circuit 100a as soon as an ignition request 191 is received, and in the case of a failed first deployment attempt, to perform a second deployment attempt using the standby deployment circuit 100b after the time delay t DELAY has elapsed. As previously specified, if the standby driver 100b receives the ignition inhibition signal 190b from the corresponding daisy-chain master driver 100a, then the standby driver 100b stops executing the deployment routine, indicating that this master driver has successfully deployed the pyrotechnic device 101 and thus no second deployment attempt is required. DELAY

[0071] As previously mentioned, in various embodiments, the deployment circuit 100 limits the time of the deployment cycle to a given maximum time. For example, in various embodiments, the deployment circuit 100, such as the control circuit 114, starts the timer circuit 115 in step 303, e.g., by programming a given initial value into the timer 115 and enabling the timer circuit 115. In general, the timer circuit 115 may be started immediately before or after step 302, or in parallel with step 302.

[0072] In a subsequent step 304, the deployment circuit 100, such as the processing circuit 111, obtains the signal 194, i.e., the voltage V PYRO across the pyrotechnic device 101 or the corresponding digital sample provided by the ADC 110.

[0073] In a subsequent step 305, the deployment circuit 100, such as the processing circuit 111, processes the voltage measurement 194 in order to generate a processed signal 195. In general, by processing the voltage V PYRO , the signal 195 may represent different physical quantities.

[0074] In this regard, Figure 4 shows the current I PYRO and voltage V of the pyrotechnic device 101 during the deployment cyclePYRO and the resistor R PYRO The deployment cycle starts at time t0 and ends at time t2 as the resistance R and current I evolve over time. For example, as previously described, the deployment cycle may start at step 302 (time t0) and may end when the timer circuit 115 reaches a given maximum time (time t2).

[0075] As previously described, during the deployment cycle, the drive circuit supplies voltage V and current I to the pyrotechnic device 101 via terminals 122a and 122b, PYRO and current I PYRO thereby biasing the pyrotechnic device 101.

[0076] Specifically, due to parasitic inductance and / or capacitance, the voltage and current supplied to the pyrotechnic device 101 typically do not increase in a stepwise fashion but increase gradually as shown in Figure 4 . Moreover, in the embodiment shown in Figure 2 , the current I PYRO may be limited to a given maximum value.

[0077] In this regard, as previously described, the pyrotechnic device 101 essentially represents a resistive load, whereby the voltage V PYRO and current I PYRO are related to each other based on Ohm's law, i.e., V PYRO = I PYRO ∙ R PYRO , where R PYRO corresponds to the resistance of the pyrotechnic device 101.

[0078] Specifically, during the deployment cycle, the resistor R PYRO initially remains substantially constant, which is typical of an undeployed pyrotechnic device. During this time period, the chemical reaction that causes ignition of the pyrotechnic device has not been triggered, indicating that the structure and composition of the pyrotechnic device initiator do not change when the deployment current I PYRO flows through the pyrotechnic device initiator.

[0079] Subsequently, at time t1, the pyrotechnic device 101 starts to ignite. Specifically, the inventors observed that the ignition causes a sudden increase in the resistance R PYRO . Further, this increase in the resistance R PYRO results in a decrease in the deployment current I PYRO and an increase in the voltage V PYRO .

[0080] Finally, at time t2, the ignition of the pyrotechnic device 101 is complete. Accordingly, the deployment current I PYRO stops decreasing, and the resistor R PYRO stabilizes to a higher value, which is typical of a successfully deployed pyrotechnic device. Consequently, the voltage VPYRO to a higher value that is closer to the supply voltage. Subsequently, the pyrotechnic device deployment circuit 100 detects the successful deployment of the pyrotechnic device and outputs an asserted ignition good signal 190a.

[0081] Thus, the inventors observed that the correct deployment can be achieved by determining the resistance R PYRO to detect the increase.

[0082] Specifically, to measure the resistance R PYRO , the deployment circuit 100 may be configured to provide a (small) measurement current I via terminals 122a and 122b. MEAS And the value of the signal 194 is evaluated, for example, via the processing circuit 111 and the comparator. In fact, when the pyrotechnic device 101 is in the non-deployed condition, the resistor R PYRO Should have a first value R PYRO1 Specifically, this first value R PYRO1 For example, this behavior can be used to periodically determine whether the pyrotechnic device 101 is correctly connected to the terminals 122a and 122b, i.e., in the absence of an ignition request, the deployment circuit 100 can be configured to periodically:

[0083] − Apply a measurement current I to terminals 122a and 122b via the driver circuit MEAS ;

[0084] − Monitor the voltage V via the processing circuit 112 PYRO And determine the indicating resistance R PYRO Signal 195; and

[0085] − It is determined via the comparator 112 whether the signal 195 lies between a lower threshold and an upper threshold.

[0086] For example, in this case, in response to determining that signal 195 is not within a threshold, deployment circuit 100 may signal a malfunction of pyrotechnic device 101 .

[0087] Thus, similarly, once the deployment cycle is complete, the deployment circuit 100 can be configured to measure the current I MEAS For resistor R PYRO A new measurement is performed and a determination is made as to whether signal 195 is greater than threshold 196. Specifically, in this case, when signal 195 is greater than threshold 196, pyrotechnic device 101 has been correctly deployed.

[0088] However, the inventors also observed that during the deployment period the (higher) deployment current I PYRO It can be used to determine the resistance R PYRO In this regard, Figure 4As shown, during the deployment cycle, the current I PYRO is not typically constant. However, the inventors have observed that once the pyrotechnic device 101 is deployed at time t2, the voltage V PYRO exhibits a significant increase. Thus, in various embodiments, the deployment circuit 100 is configured to analyze the voltage V PYRO during the deployment cycle, i.e., simultaneously with the deployment of the pyrotechnic device 101, and optionally measure and also consider the current I PYRO .

[0089] Specifically, in a first embodiment, the deployment circuit 100, such as the processing circuit 111 and the comparator 112, is configured to detect an increase in the voltage V PYRO , i.e., the signal 195 corresponds to the signal 194 indicative of the voltage V PYRO (and preferably is proportional thereto).

[0090] Specifically, in a second embodiment, the deployment circuit 100, such as the processing circuit 111, is configured to generate the signal 195 by filtering the signal 194 in step 305, thereby generating a signal 195 indicative of the filtered voltage V PYRO' . Specifically, in various embodiments, the processing circuit 111 implements a low-pass or band-pass filter. For example, this allows avoiding glitches and other undesired effects caused by transient spikes or more generally by electrical noise that may affect the voltage measurement. For example, in various embodiments, the digital processing circuit 111 may be configured as a digital low-pass filter, such as a finite impulse response (FIR) or infinite impulse response (IIR) filter, which is configured to receive the digital voltage measurement 194 and return the filtered voltage measurement 195. For example, suppression of the interference affecting the voltage measurement may be performed by means of an averaging filter or a moving average. In various embodiments, the filtering operation starts at time t0.

[0091] In a third embodiment, instead of explicitly calculating an average, the processing circuit 111 is configured to generate a signal 195 corresponding to the integral of the signal 194.

[0092] In a fourth embodiment, the processing circuit 111 is configured to generate a signal 195 corresponding to the integral of the square of the signal 194. Thus, in this embodiment, the processing circuit 111 produces as output the processed data 195 containing the value .

[0093] In a fifth embodiment, the processing circuit 111 may also measure the current I PYRO, for example, by monitoring the voltage drop across a shunt resistor connected in series with the pyrotechnic device 101 via the ADC 110, or directly monitoring the voltage drop across the electronic switches 103 or 104. In this case, the processing circuit 111 may be configured to determine a signal 195 indicative of the resistance R PYRO =V PYRO / I PYRO based on Ohm's law, i.e., R PYRO (and preferably proportional thereto).

[0094] Still in this case, instead of using the instantaneous value of the resistance R PYRO , the processing circuit 111 may also process the resistance R PYRO , for example, by applying a low-pass filter to the resistance R PYRO or calculating the integral of the resistance R PYRO to generate the signal 195.

[0095] Thus, in step 306, the deployment circuit 100, e.g., the comparator 112, is configured to compare the processed value 195 with a reference value 196, which indicates a minimum threshold of, for example, the instantaneous value, the filtered value, or the integrated value of the voltage V PYRO or the resistance R PYRO , and this minimum threshold indicates the correct deployment of the pyrotechnic device 101. In various embodiments, the threshold 196 is programmable or at least adjustable.

[0096] For example, the value 196 may be a voltage value V DEPLOY above which the pyrotechnic device is considered to have been successfully deployed. Specifically, the voltage V DEPLOY represents the minimum threshold of the voltage characterizing the successfully deployed device, and this minimum threshold is expected to be approximately the supply voltage V IN provided by the supply rail 121. As explained previously, the resistance of a successfully deployed pyrotechnic device is significantly greater than that of an undeployed pyrotechnic device, and thus, the voltage drop across the deployed device is expected to be greater than that across the undeployed device. On the other hand, the undeployed device is characterized by a lower resistance. Therefore, for example, if the measured voltage drop across a pyrotechnic fuse is V PYRO = 11.5V and the minimum threshold V DEPLOY is set to 6V, i.e., half of the bias voltage V IN = 12V, then it can be assumed that this pyrotechnic fuse has been correctly deployed because V PYRO ≥V DEPLOY . Thus, in various embodiments, the threshold signal 196 may be selected or even automatically determined based on the value of the voltage V IN . For example, the threshold 196 may be selected within a range between 50% and 95% of the voltage V IN , preferably between the voltage VIN between 70% and 90%. For example, to this end, the deployment circuit 100 can also measure the voltage V via the ADC 110, for example. IN .

[0097] Alternatively, the value 196 can be the resistance value R DEPLOY , above which the pyrotechnic device is considered to have been successfully deployed. Specifically, the resistance R DEPLOY represents the minimum threshold of the resistance of the device characterizing successful deployment, and the resistance of a successfully deployed device is expected to be significantly greater than that of an undeployed pyrotechnic device. Thus, for example, if the resistance R PYRO of the pyrotechnic fuse determined by measurement is equal to 155 ohms and the minimum resistance characteristic R DEPLOY declared by the pyrotechnic fuse manufacturer for successful deployment is equal to 100 ohms, then it can be assumed that this pyrotechnic fuse has been correctly deployed because R PYRO ≥R DEPLOY .

[0098] Thus, in response to determining that the signal 195 exceeds (or is at least equal to) the threshold (output "Y" of the verification step 306), the deployment circuit 100 can detect the correct deployment of the pyrotechnic device 101 at step 307 and assert the good ignition signal 190a, for example, corresponding to the output signal of the comparator 112. Generally speaking, once the correct deployment is detected, the deployment cycle can be immediately terminated by proceeding to the stop step 310, where the drive circuit is deactivated, or the deployment circuit 100 can wait for the timer circuit 115 to reach the corresponding time threshold in any case.

[0099] Conversely, in response to determining that the signal 195 does not exceed the threshold (output "N" of the verification step 306), the deployment circuit 100 proceeds to step 308. In step 308, the deployment circuit 100, such as the control circuit 114, verifies whether the timeout condition is met, that is, whether the time t tracked by the timer circuit 115 is greater than or equal to the time limit t TIMEOUT .

[0100] In various embodiments, the time limit t TIMEOUT can be constant or settable, for example programmable. In various embodiments, the control circuit can also be configured to adapt the predetermined time limit t PYRO based on the value or the evolving measurement of the current I TIMEOUT .

[0101] In response to determining that the maximum time t TIMEOUT has not been reached (output "N" of the verification step 308), the deployment circuit 100 returns to step 304, thereby performing further measurements on the voltage V PYRO and then continuing with the subsequent steps as described above.

[0102] Conversely, in response to determining that the maximum time t has been reached TIMEOUT (verifying the output "Y" of verification step 308), the deployment circuit 100 may verify in an optional step 309 whether another deployment cycle should be initiated. For example, step 309 may be useful for performing a given maximum number of deployment cycles.

[0103] Thus, in the embodiment under consideration, when a deployment is detected at step 307 before the timeout condition is reached, the deployment is considered successful. In this case, a possible ignition of the backup deployment circuit can be inhibited, for example, by asserting an ignition inhibition signal for the backup deployment circuit. Conversely, when the timeout condition is reached, another deployment cycle can be initiated with the same deployment circuit or the backup deployment circuit.

[0104] For example, in various embodiments, the deployment circuit 100, such as the control circuit 114, is configured to determine whether the ongoing deployment attempt is the first deployment attempt.

[0105] In response to determining that the ongoing deployment attempt is the first (verifying the output "Y" of verification step 309), the deployment circuit 100 returns to step 302, thereby performing a second deployment attempt and subsequent steps in the order described previously. For example, the timer circuit 115 is restarted in step 302, and then the subsequent steps are performed according to the description mentioned above. In various embodiments, instead of directly returning to step 302, the deployment circuit 100 may first disable the drive circuit for a given period of time.

[0106] Conversely, in response to determining that the ongoing deployment attempt is not the first (verifying the output "N" of verification step 309), the deployment circuit 100 stops further deployment attempts, and the method terminates at the stop step 310 without asserting the ignition good signal 190a, thereby indicating a failure in the deployment of the pyrotechnic device.

[0107] Thus, in the embodiment under consideration, step 309 enables the pyrotechnic device deployment circuit 100 to perform one or more additional deployment attempts in the case of a failure in the first deployment attempt without the intervention of an external circuit such as a microcontroller unit, thereby providing a faster and more robust solution.

[0108] For example, Figure 5 shows a graph of the current I PYRO 、voltage V PYRO and resistance R PYRO of the pyrotechnic device 101 over time, where two deployment cycles are performed.

[0109] Specifically, at the first moment t0, the deployment operation starts. Thus, the pyrotechnic device 101 is biased by the deployment circuit 100, so the deployment current I PYRO and the deployment voltage V PYRO start to increase, while the resistance R PYRO remains constant at its initial value, which is a characteristic of the undeployed pyrotechnic device. Similar to the example shown in Figure 4 , during this time period, since the resistance R PYRO remains (substantially) at a constant value, the chemical reaction that causes the ignition of the pyrotechnic device has not been triggered yet, indicating that when the deployment current I PYRO flows through the pyrotechnic device initiator, the structure and composition of the pyrotechnic device initiator do not change.

[0110] Thus, different from the example shown in Figure 4 , in this deployment attempt, the pyrotechnic device initiator fails. In particular, due to, for example, insufficient triggering temperature or contaminated reagent, the chemical reaction that enables the initiator to ignite may not be triggered. Thus, the timeout condition is reached at the moment t2.

[0111] At the moment t2, the pyrotechnic device deployment circuit 100 thus detects the failure of the ongoing deployment attempt and therefore interrupts the biasing of the pyrotechnic device. Thus, the voltage V PYRO and the current I PYRO drop to zero. Then, the deployment circuit 100 arranges a second deployment attempt for the same pyrotechnic device.

[0112] After waiting for a predetermined stabilization time, the second deployment attempt starts at the moment t3, and thus the pyrotechnic device 101 is re-biased.

[0113] At the moment t4, the pyrotechnic device 101 ignites, causing the resistance R PYRO to suddenly increase while the current I PYRO decreases. At this moment, as indicated by the significant increase in the resistance R PYRO , the chemical reaction that enables the pyrotechnic device initiator to ignite has been successfully triggered.

[0114] Finally, at the moment t5, the ignition of the pyrotechnic device 101 is completed. Thus, the deployment current I PYRO stops decreasing, and the resistance R PYRO stabilizes to a higher value, which is typical of a successfully deployed pyrotechnic device. Thus, the voltage V PYRO increases to a higher value closer to the supply voltage. Subsequently, the pyrotechnic device deployment circuit 100 detects the successful deployment of the pyrotechnic device and outputs an asserted ignition good signal 190a.

[0115] To provide a deeper understanding of a configuration that employs more than one deployment circuit 100, Figure 6The figure illustrates a system 200 including two daisy-chain deployment circuits 100.

[0116] Specifically, the system 200 includes a battery pack 197, a load 198, a deployment control circuit 199, and two deployment circuits 100a and 100b respectively coupled to a pyrotechnic device 101. This system can represent a scenario where, for example, the battery pack powers one or more electric traction motors provided in, for example, a battery electric vehicle (BEV).

[0117] When the system 200 operates correctly, a load current I LOAD is drawn from the power supply 197 and absorbed by the load 198, while a voltage V LOAD is applied across the load 198. Moreover, the deployment control circuit 199 is generally configured to monitor whether the load 198 is operating properly and, in the event of an anomaly, assert an ignition request signal 191 to disconnect the battery pack 197 from the load 198.

[0118] In an alternative embodiment, such a deployment control circuit 199 can be connected to one or more external sensors, such as, for example, an accelerometer, and can assert the ignition request signal 191 based on readings obtained from the one or more external sensors. This can represent a scenario where the pyrotechnic device to be deployed is, for example, an airbag or a seatbelt pretensioner.

[0119] In any case, the deployment control circuit 199 can assert the ignition request signal 191 when requested. Thus, the asserted ignition request signal 191 is received by the main deployment circuit 100a and the standby deployment circuit 100b respectively.

[0120] The main deployment circuit 100a is configured to immediately start a deployment operation in accordance with the teachings of the present solution (e.g., according to a method). In contrast, the standby deployment circuit 100b is configured to start a deployment operation after a predetermined time period t DELAY unless it receives an asserted ignition inhibition signal 190b from the main deployment circuit 100a.

[0121] Specifically, in this configuration, the main deployment circuit 100a performs a first deployment attempt, and subsequently, if this first attempt is unsuccessful, then the standby deployment circuit 100b is used to perform a second deployment attempt. In the case where the first deployment attempt performed by the main deployment circuit 100a is successful, the main deployment circuit 100a asserts an ignition good signal 190a, which is subsequently received by the standby deployment circuit 100b as an input to the ignition inhibition signal 190b. Thus, the standby deployment circuit 100b does not perform a second deployment attempt. In contrast, if the standby deployment circuit 100b reaches a time threshold t DELAYIf the ignition inhibition signal 190b has not been received previously, then a second deployment attempt is performed. Each deployment circuit 100a, 100b may be able to wait for a predetermined amount of time before initiating a deployment attempt by means of the control circuit 114 and the timer circuit 115, and the control circuit 114 and the timer circuit 115 provide various embodiments of the deployment circuit 100.

[0122] Thus, for example, if the deployment control circuit 199 in the system 200 detects an anomaly on the load 198, such as a short circuit, then it asserts the ignition request signal 191. Consequently, the primary deployment circuit 100a receives the ignition request 191 and begins the first deployment attempt. If the first deployment attempt is successful, then the primary deployment circuit 100a asserts the ignition good signal 190a, and the redundant deployment circuit 100b subsequently receives it as the ignition inhibition signal 190b. Thus, the redundant deployment circuit 100b does not initiate a second deployment attempt because it has received confirmation of the first successful deployment.

[0123] Conversely, if the first deployment attempt is unsuccessful, then the primary deployment driver 100a does not assert the ignition good signal 190a. Thus, the redundant deployment circuit 100b waits for a predetermined amount of time t DELAY , and then begins the second deployment attempt. Finally, if the second deployment attempt is successful, then the redundant deployment circuit 100b outputs the asserted ignition good signal 190a to confirm the successful deployment of the pyrotechnic device.

[0124] It is clear that such a system 200 has the advantage of being able to schedule a second deployment attempt in the event of a first attempt failure, without the intervention of an external controller such as, for example, the deployment control circuit 199. Thus, by employing a system according to the solution described herein, the delays that may occur during the deployment attempt of a pyrotechnic device can be reduced, thereby obtaining a system with a faster response.

[0125] Thus, the embodiments disclosed herein relate to a new solution for driving a pyrotechnic device. The solution described performs the deployment of a given pyrotechnic device while monitoring relevant quality factors, namely, current, voltage, and resistance, in order to determine whether the deployment is successful. Additionally, if the deployment is unsuccessful, then the solution described can schedule a second deployment attempt of the same pyrotechnic device, or, alternatively, if the first deployment attempt is confirmed as failed, then the second deployment of the pyrotechnic device can be performed as soon as possible without waiting for a response from an external control circuit.

[0126] Of course, without prejudice to the principles of the present disclosure, the details of the construction and the embodiments can vary widely with respect to what has been described and illustrated herein only by way of example, without departing from the scope of the present disclosure as defined by the appended claims.

Claims

1. A deployment circuit for a pyrotechnic device, comprising: - A first terminal and a second terminal, the first terminal and the second terminal being configured to be connected to the pyrotechnic device; - A driver circuit configured to power the pyrotechnic device by selectively applying a voltage or current to the first terminal and the second terminal according to at least one control signal; - A monitoring circuit configured to: - Measure the voltage across the first terminal and the second terminal, - Process the measured voltage, - Determine whether the processed voltage is greater than a threshold, and - Assert a comparison signal in response to determining that the processed voltage is greater than the threshold; And - A control circuit configured to: - Receive an ignition request signal and the comparison signal, - Generate the at least one control signal in response to the ignition request signal to power the pyrotechnic device via the driver circuit, - Determine whether the comparison signal is asserted, - Power the pyrotechnic device again in response to determining that the comparison signal is de-asserted.

2. The deployment circuit according to claim 1, wherein The driver circuit includes: - At least one electronic switch configured to selectively connect the first terminal and the second terminal to a supply voltage according to the at least one control signal.

3. The deployment circuit according to claim 2, wherein The driver circuit further includes: - A current limiter configured to limit the current supplied to the first terminal and the second terminal to a maximum value.

4. The deployment circuit according to claim 3, wherein, The maximum value can be set via the at least one control signal.

5. The deployment circuit according to claim 1, wherein The control circuit is further configured to: - Start a timer in response to the ignition request signal, - Determine whether the timer reaches a time threshold, and - Stop powering the pyrotechnic device via the driver circuit in response to determining that the timer reaches the time threshold.

6. The deployment circuit according to claim 5, wherein The control circuit is further configured to determine whether the comparison signal is asserted in response to determining that the timer reaches the time threshold.

7. The deployment circuit according to claim 4, wherein The control circuit is further configured to: - Set the maximum value of the current limiter to a first value in response to the ignition request signal, - Set the maximum value of the current limiter to a second value in response to determining that the timer reaches the time threshold, where the second value is less than the first value, and - Then determine whether the comparison signal is asserted.

8. The deployment circuit according to claim 1, wherein Processing the measured voltage includes: - Generating the processed voltage by filtering the measured voltage with a low-pass filter or a band-pass filter; or - Generating the processed voltage by calculating the integral of the measured voltage.

9. The deployment circuit according to claim 1, wherein Processing the measured voltage includes: - Generating the processed voltage by calculating the integral of the square of the measured voltage.

10. The deployment circuit according to claim 1, wherein The monitoring circuit is further configured to measure the current supplied via the first terminal and the second terminal, and wherein processing the measured voltage includes: - Generating the processed voltage by calculating the ratio between the measured voltage and the measured current, whereby the processed voltage indicates the resistance of the pyrotechnic device.

11. The deployment circuit according to claim 1, Among them, Re - energizing the pyrotechnic device includes regenerating the at least one control signal to energize the pyrotechnic device via the driver circuit; or wherein, the deployment circuit includes an additional driver circuit configured to energize the pyrotechnic device by selectively applying a voltage or current to the first terminal and the second terminal according to at least one additional control signal, and wherein re - energizing the pyrotechnic device includes generating the at least one additional control signal to energize the pyrotechnic device via the additional driver circuit.

12. An integrated circuit comprising the deployment circuit according to claim 1.

13. A vehicle comprising the deployment circuit according to claim 1.

14. A method of operating the deployment circuit according to claim 1, comprising: Providing an ignition request signal to the deployment circuit, including: - Measuring the voltage across the first terminal and the second terminal with the monitoring circuit, - Processing the measured voltage with the monitoring circuit, - Determining with the monitoring circuit whether the processed voltage is greater than a threshold, and - Responsive to determining that the processed voltage is greater than the threshold, asserting a comparison signal with the monitoring circuit; and - Receiving the ignition request signal and the comparison signal with the control circuit, - Responsive to the ignition request signal, generating the at least one control signal with the control circuit to energize the pyrotechnic device via the driver circuit, - Determining with the control circuit whether the comparison signal is asserted, - Responsive to determining that the comparison signal is de - asserted, re - energizing the pyrotechnic device with the control circuit again.

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