Duty cycle conversion circuit, detection device and airbag detection system

Abstract

The present invention relates to a duty cycle conversion circuit, a detection device and an airbag detection system. A level conversion module converts a pulse whose voltage in a pulse to be tested is higher than a set voltage value to obtain a charging voltage, and outputs the charging voltage to the charging and discharging end of an energy storage module to charge the energy storage module, so that the voltage at the charging and discharging end of the energy storage module rises. Furthermore, a first level signal and a second level signal are obtained according to the voltage at the charging and discharging end through a discharge module and a threshold judgment module. If the duty cycle of the pulse to be tested changes, that is, the width of the pulse whose voltage in the pulse to be tested is higher than the set voltage value changes, the signal output by the threshold judgment module will change. Based on this, the pulse to be tested is converted into a first level signal and a second level signal, and whether the duty cycle of the pulse to be tested changes can be judged according to the transition between the first level signal and the second level signal, which effectively reduces the cost of software and hardware and improves convenience.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic circuits, and in particular to a duty cycle conversion circuit, a detection device and a safety airbag detection system. Background Art

[0002] Duty cycle refers to the ratio of the time occupied by a specific pulse to the period in a pulse cycle. Taking square wave as an example, the duty cycle can be the ratio of the duration of a high-level pulse to the square wave period, or the ratio of the duration of a low-level pulse to the square wave period. Among them, the change of duty cycle reflects the change of various pulse widths in a pulse cycle.

[0003] In traditional electronic circuit applications, it is often necessary to detect whether the duty cycle of the pulse to be tested has changed, or to use the change in duty cycle as a control condition for the subsequent circuit. For example, an MCU (Microcontroller Unit) that can detect changes in pulse width is used to determine whether the duty cycle of the pulse to be tested has changed, or a low-pass filter circuit or an integration circuit is used to convert the duty cycle change into an analog signal. However, the software implementation complexity and hardware cost of the MCU that can detect changes in pulse width are relatively high; using a low-pass filter circuit or an integration circuit to detect changes in duty cycle requires further analysis of the analog signal through corresponding hardware and software, which is not convenient for obtaining detection results and controlling costs.

[0004] In summary, the traditional method for detecting whether the duty cycle of the pulse to be tested has changed has the problems of high cost and poor convenience. Summary of the invention

[0005] Based on this, it is necessary to provide a duty cycle conversion circuit, a detection device and an airbag detection system to address the defects of the traditional method of detecting whether the duty cycle of the pulse to be tested has changed, which has high cost and poor convenience.

[0006] The embodiment of the present invention provides a duty cycle conversion circuit, including a level conversion module, an energy storage module, a discharge module and a threshold judgment module;

[0007] The level conversion module is used to access the pulse to be tested, and is also used to convert the pulse whose voltage in the pulse to be tested is higher than the set voltage value to obtain the charging voltage, and output the charging voltage to the charging and discharging end of the energy storage module;

[0008] The energy storage module is used to charge when the charging and discharging end is connected to the charging voltage, so that the voltage at the charging and discharging end increases;

[0009] The discharge module is connected to the charge and discharge end, and is used to discharge the energy storage module when the charge and discharge end is not connected to the charging voltage, so as to reduce the voltage of the charge and discharge end.

[0010] The threshold judgment module is used to output a first level signal when the voltage at the charge and discharge end is greater than a preset voltage threshold, and the threshold judgment module is used to output a second level signal when the voltage at the charge and discharge end is less than the preset voltage threshold.

[0011] In the above-mentioned duty cycle conversion circuit, the level conversion module obtains the charging voltage according to the pulse conversion in which the voltage in the pulse to be tested is higher than the set voltage value, and outputs the charging voltage to the charging and discharging end of the energy storage module to charge the energy storage module, so that the voltage at the charging and discharging end of the energy storage module rises. Furthermore, through the discharge module and the threshold judgment module, the first level signal and the second level signal are obtained according to the voltage at the charging and discharging end. If the duty cycle of the pulse to be tested changes, that is, the width of the pulse in which the voltage in the pulse to be tested is higher than the set voltage value changes, the signal output by the threshold judgment module will change. Based on this, the pulse to be tested is converted into the first level signal and the second level signal, and whether the duty cycle of the pulse to be tested has changed can be judged according to the transition between the first level signal and the second level signal, which effectively reduces the cost of software and hardware and improves convenience.

[0012] In one of the embodiments, the level conversion module includes a first switch unit;

[0013] The controlled end of the first switch unit is used to access the pulse to be tested, the first switch end of the first switch unit is used to access the logic high level, and the second switch end of the first switch unit is connected to the charging and discharging end of the energy storage module;

[0014] The first switch unit is used to turn on the first switch end and the second switch end of the first switch unit when the voltage of the controlled end of the first switch unit is higher than the set voltage value; in one embodiment, the logic high level is the charging voltage.

[0015] In one of the embodiments, the first switch unit includes a first controlled switch and a second controlled switch;

[0016] The controlled end of the first controlled switch is used to access the pulse to be tested, the first switch end of the first controlled switch is connected to the controlled end of the second controlled switch, and the second switch end of the first controlled switch is used to access the first switch signal; in one embodiment, the first controlled switch is used to conduct the first switch end and the second switch end of the first controlled switch when the voltage of the controlled end of the first controlled switch is higher than the set voltage value;

[0017] The first switch end of the second controlled switch is used to access a logic high level, and the second switch end of the second controlled switch is connected to the charging and discharging end of the energy storage module; in one embodiment, the second controlled switch is used to turn on the first switch end and the second switch end of the second controlled switch when the controlled end of the second controlled switch is connected to the first switch signal.

[0018] In one embodiment, the first controlled switch includes a first NPN transistor, and the second controlled switch includes a PNP transistor;

[0019] The base of the first NPN transistor is used to access the pulse to be tested, the collector of the first NPN transistor is connected to the base of the PNP transistor, and the emitter of the first NPN transistor is used to access the first switch signal; in one embodiment, the first switch signal is a logic low level;

[0020] The emitter of the PNP transistor is used to access the logic high level, and the collector of the PNP transistor is connected to the charging and discharging end of the energy storage module.

[0021] In one of the embodiments, the first switch unit further includes a first current limiting resistor, a second current limiting resistor, a first bias resistor, a second bias resistor, a first pull-up resistor and a first output resistor;

[0022] The base of the first NPN transistor is used to access the pulse to be tested through the first current limiting resistor, the base of the first NPN transistor is connected to the emitter of the first NPN transistor through the first bias resistor, and the collector of the first NPN transistor is used to access the logic high level through the first pull-up resistor;

[0023] The base of the PNP transistor is connected to the collector of the first NPN transistor through the second current limiting resistor, the base of the PNP transistor is connected to the emitter of the PNP transistor through the second bias resistor, and the collector of the PNP transistor is connected to the charge and discharge end of the energy storage module through the first output resistor.

[0024] In one of the embodiments, the level conversion module further includes a first voltage stabilizing diode;

[0025] The cathode of the first voltage stabilizing diode is connected to the controlled end of the first switch unit, and the anode of the first voltage stabilizing diode is grounded.

[0026] In one of the embodiments, the level conversion module includes a second voltage stabilizing diode and a protection diode;

[0027] The positive electrode of the protection diode is used to connect the pulse to be tested, and the negative electrode of the protection diode is connected to the charging and discharging end of the energy storage module;

[0028] The cathode of the second voltage stabilizing diode is connected to the anode of the protection diode, and the anode of the second voltage stabilizing diode is grounded.

[0029] In one of the embodiments, the level conversion module further includes a first charging resistor, a second charging resistor and a third current limiting resistor;

[0030] The positive electrode of the protection diode is used to access the pulse to be measured through the third current limiting resistor;

[0031] One end of the first charging resistor is connected to the cathode of the protection diode, the other end of the first charging resistor is connected to the charging and discharging end of the energy storage module, and the other end of the first charging resistor is also used to be grounded through the second charging resistor.

[0032] In one of the embodiments, the threshold determination module includes a second switch unit;

[0033] The controlled end of the second switch unit is connected to the charging and discharging end, the first switch end of the second switch unit is used to access the logic high level, and the second switch end of the second switch unit is used to access the logic low level; the third switch end of the second switch unit is used to output the first level signal or the second level signal;

[0034] The second switch unit is used to turn on the first switch end and the third switch end of the second switch unit when the voltage at the controlled end of the second switch unit is greater than a preset voltage threshold, and the second switch unit is used to turn on the second switch end and the third switch end of the second switch unit when the voltage at the controlled end of the second switch unit is less than the preset voltage threshold; in one embodiment, the first level signal is a logic high level, and the second level signal is a logic low level.

[0035] In one of the embodiments, the second switch unit includes a third controlled switch, a fourth controlled switch and a second pull-up resistor;

[0036] The controlled end of the third controlled switch is connected to the charging and discharging end, the first switch end of the third controlled switch is connected to the controlled end of the fourth controlled switch, and the second switch end of the third controlled switch is used to access the second switch signal; in one embodiment, the third controlled switch is used to turn on the first switch end and the second switch end of the third controlled switch when the voltage of the controlled end of the third controlled switch is greater than a preset voltage threshold;

[0037] The first switch end of the fourth controlled switch is used to access a logic high level through a second pull-up resistor, and the second switch end of the fourth controlled switch is used to access a logic low level; in one embodiment, the first switch end and the second switch end of the fourth controlled switch are normally closed, and the fourth controlled switch is used to disconnect the first switch end and the second switch end of the fourth controlled switch when the controlled end of the fourth controlled switch is connected to the second switch signal; the first switch end of the fourth controlled switch is used to output a logic high level or a logic low level.

[0038] In one embodiment, the third controlled switch includes a second NPN transistor, and the fourth controlled switch includes a third NPN transistor;

[0039] The base of the second NPN transistor is connected to the charging and discharging terminal, the collector of the second NPN transistor is connected to the base of the third NPN transistor, and the emitter of the second NPN transistor is used to access the second switch signal; in one embodiment, the second switch signal is a logic low level;

[0040] The collector of the third NPN transistor is used to access a logic high level, and the emitter of the third NPN transistor is used to access a logic high level; in one embodiment, the collector of the third NPN transistor is used to output a logic high level or a logic low level.

[0041] In one of the embodiments, the second switch unit further includes a third pull-up resistor and a third bias resistor;

[0042] The collector of the second NPN transistor is used to access the logic high level through the third pull-up resistor, and the base of the third NPN transistor is connected to the emitter of the base of the third NPN transistor through the third bias resistor.

[0043] In one embodiment, the discharge module includes a first discharge resistor and a second discharge resistor;

[0044] The charging and discharging ends of the energy storage module are used to be grounded through a first discharge resistor and a second discharge resistor in sequence.

[0045] In one of the embodiments, the charging and discharging ends of the energy storage module are connected to the threshold judgment module via a first discharge resistor.

[0046] In one embodiment, the energy storage module includes a charging capacitor;

[0047] One end of the charging capacitor is the charging and discharging end of the energy storage module, and the other end of the charging capacitor is used for grounding.

[0048] An embodiment of the present invention further provides a duty cycle detection device, comprising a first MCU and a duty cycle conversion circuit of any of the above embodiments;

[0049] The first MCU is used to access the first level signal or the second level signal output by the threshold judgment module, and is used to detect whether the signal output by the threshold judgment module changes, and to determine whether the duty cycle of the pulse to be tested changes when the signal output by the threshold judgment module changes.

[0050] In the above-mentioned duty cycle detection device, the first MCU is connected to the first level signal or the second level signal output by the threshold judgment module, and the first MCU can detect whether the signal output by the threshold judgment module changes, and determine whether the duty cycle of the pulse to be measured changes when the signal output by the threshold judgment module changes. Based on this, there is no need to select an MCU that supports detection of pulse width changes, and only the first MCU that can detect level changes can be selected to detect duty cycle changes, which can effectively reduce software complexity and hardware costs.

[0051] An embodiment of the present invention further provides an airbag detection system, comprising a second MCU and a duty cycle conversion circuit of any of the above embodiments;

[0052] The pulse to be tested is a pulse signal output by the airbag controller;

[0053] The second MCU is used to access the first level signal or the second level signal output by the threshold judgment module, and is used to determine that the airbag explodes when the signal output by the threshold judgment module changes from the first level signal to the second level signal.

[0054] The above-mentioned airbag detection system can obtain the pulse signal output by the airbag controller and convert the pulse signal output by the airbag controller into a first level signal or a second level signal. Further, when the second MCU detects that the signal output by the threshold judgment module changes from the first level signal to the second level signal, it is determined that the airbag has exploded. Based on this, only the second MCU that can detect the level change is needed to detect whether the airbag has exploded, which reduces the functional requirements for the second MCU, facilitates the simplification of software implementation and reduces hardware costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 is a structural diagram of a duty cycle conversion circuit module according to an implementation method;

[0056] Figure 2 is a schematic diagram of a level conversion module according to an implementation method;

[0057] Figure 3 is a structural diagram of a level conversion module according to an implementation method;

[0058] Figure 4 A circuit diagram of a level conversion module according to an embodiment;

[0059] Figure 5 A circuit diagram of a level conversion module according to another embodiment;

[0060] Figure 6 is a schematic diagram of a threshold determination module in one implementation mode;

[0061] Figure 7 is a structural diagram of a threshold determination module in one implementation mode;

[0062] Figure 8 A circuit diagram of a threshold determination module according to an implementation mode;

[0063] Fig. 9 A duty cycle conversion circuit diagram of a specific application example;

[0064] Fig.10 is a voltage waveform diagram based on a specific application example;

[0065] Fig.11 is a module structure diagram of a duty cycle detection device according to an embodiment;

[0066] Fig.12 A module structure diagram of an airbag detection system according to an embodiment;

[0067] Fig.13 Output pulse waveform for airbag controller. DETAILED DESCRIPTION

[0068] In order to better understand the purpose, technical solution and technical effect of the present invention, the present invention is further explained below in conjunction with the accompanying drawings and embodiments. At the same time, it is stated that the embodiments described below are only used to explain the present invention and are not used to limit the present invention.

[0069] An embodiment of the present invention provides a duty cycle conversion circuit.

[0070] Figure 1 FIG. 1 is a block diagram of a duty cycle conversion circuit according to an embodiment of the present invention. Figure 1 As shown, a duty cycle conversion circuit of an embodiment includes a level conversion module 100, an energy storage module 101, a discharge module 102 and a threshold judgment module 103;

[0071] The level conversion module 100 is used to access the pulse S1 to be tested, and is also used to convert the pulse whose voltage in the pulse S1 to be tested is higher than the set voltage value to obtain the charging voltage, and output the charging voltage to the charging and discharging end of the energy storage module 101;

[0072] In the process of converting the level conversion module 100 to obtain the charging voltage, assuming that the pulse width higher than the set voltage value in one cycle T of the pulse S1 to be tested is t1, then in one cycle T of the pulse S1 to be tested, there is a charging voltage with a duration of t1. That is, in one cycle T of the pulse S1 to be tested, the energy storage module 101 is charged with a duration of t1, and the energy storage module 101 is in a discharge state during the remaining time (T-t1). In one embodiment, the charging voltage is a fixed voltage, and the voltage value of the fixed voltage is equal to the set voltage value or other voltage values ​​of corresponding set magnitudes.

[0073] In one embodiment, if the duty cycle of the pulse S1 to be tested changes, the pulse width higher than the set voltage value changes from t1 to t2. That is, in a period T of the pulse S1 to be tested, the energy storage module 101 is charged for a duration of t2, and the energy storage module 101 is in a discharge state during the remaining time (T-t2).

[0074] In one embodiment, Figure 2 Schematic diagram of a level conversion module according to an implementation method, Figure 2 As shown, a level conversion module 100 according to an embodiment includes a first switch unit 200;

[0075] The controlled end of the first switch unit 200 is used to access the pulse to be tested S1, the first switch end of the first switch unit 200 is used to access the logic high level U1, and the second switch end of the first switch unit 200 is connected to the charging and discharging end of the energy storage module 101;

[0076] In one embodiment, the level conversion module 100 can use a steady-state circuit or an integration circuit to directly process the pulse S1 to obtain a charging voltage. Figure 2 In the level conversion module 100 of one embodiment shown, the first switch unit 200 is a switch circuit, which uses the pulse S1 to be tested as the conduction trigger condition of the switch circuit, and outputs the logic high level U1 to the charging and discharging end of the energy storage module 101 to charge the energy storage module 101.

[0077] The first switch unit 200 is used to turn on the first switch end and the second switch end of the first switch unit 200 when the voltage at the controlled end of the first switch unit 200 is higher than the set voltage value; wherein the logic high level U1 is the charging voltage.

[0078] After the controlled end of the first switch unit 200 is connected to the pulse S1 to be tested, a pulse signal with a voltage higher than the set voltage value appears in the pulse S1 to be tested, and the voltage of the controlled end of the first switch unit 200 is higher than the set voltage value. At this time, the first switch end of the first switch unit 200 is connected to the second switch end, and the logic high level U1 is output to the charging and discharging end of the energy storage module 101. In one embodiment, the first switch unit 200 can use modular switch circuits or switch elements such as electronic switch chips and semiconductor switches. Through the switch circuit or switch element, when the first switch unit 200 meets the conduction trigger condition, the logic high level U1 is indirectly output as a charging voltage, without processing the pulse S1 to be tested to directly obtain the charging voltage, which is conducive to ensuring the stability of the charging voltage.

[0079] As a preferred implementation method, Figure 3 FIG. 1 is a structural diagram of a level conversion module according to an embodiment of the present invention. Figure 3 As shown, the first switch unit 200 includes a first controlled switch 300 and a second controlled switch 301;

[0080] The controlled end of the first controlled switch 300 is used to access the pulse to be tested S1, the first switch end of the first controlled switch 300 is connected to the controlled end of the second controlled switch 301, and the second switch end of the first controlled switch 300 is used to access the first switch signal K1; in one embodiment, the first controlled switch 300 is used to conduct the first switch end and the second switch end of the first controlled switch 300 when the voltage at the controlled end of the first controlled switch 300 is higher than the set voltage value;

[0081] The first switch end of the second controlled switch 301 is used to access the logic high level U1, and the second switch end of the second controlled switch 301 is connected to the charging and discharging end of the energy storage module 101; in one embodiment, the second controlled switch 301 is used to turn on the first switch end and the second switch end of the second controlled switch 301 when the controlled end of the second controlled switch 301 is connected to the first switch signal K1.

[0082] The first controlled switch 300 and the second controlled switch 301 can both be modular switch circuits or switch elements such as electronic switch chips and semiconductor switches. In one embodiment, the conduction triggering condition of the first controlled switch 300 is that a pulse signal with a voltage higher than a set voltage value appears in the pulse to be measured S1, and the conduction triggering condition of the second controlled switch 300 is that the controlled end of the second controlled switch 300 receives the first switch signal K1. Based on this, the working logic of the first switch unit 200 is realized by the cooperation of the first controlled switch 300 and the second controlled switch 301. At the same time, through the design of the two switches, the influence of the discharge of the energy storage module 101 on the pulse to be measured S1 or the previous circuit is reduced when the pulse to be measured S1 is lower than the set voltage value.

[0083] As a preferred implementation method, Figure 4 is a circuit diagram of a level conversion module according to an implementation mode, such as Figure 4 As shown, both the first controlled switch 300 and the second controlled switch 301 are semiconductor switches, that is, the first controlled switch 300 includes a first NPN transistor Q1, and the second controlled switch 301 includes a PNP transistor Q2;

[0084] The base of the first NPN transistor Q1 is used to access the pulse S1 to be tested, the collector of the first NPN transistor Q1 is connected to the base of the PNP transistor Q2, and the emitter of the first NPN transistor Q1 is used to access the first switch signal K1; in one embodiment, the first switch signal K1 is a logic low level;

[0085] The emitter of the PNP transistor Q2 is used to access the logic high level U1 , and the collector of the PNP transistor Q2 is connected to the charging and discharging end of the energy storage module 101 .

[0086] In one embodiment, the set voltage value is greater than or equal to the conduction voltage of the first NPN transistor Q1. As a preferred implementation, the set voltage value is equal to the conduction voltage of the first NPN transistor Q1. Accordingly, the difference between the logic high level U1 and the first switch signal K1 is also greater than the conduction voltage of the PNP transistor Q2. As one implementation, in this specific implementation, the logic low level is the ground level. Figure 4As shown, when a pulse S1 to be tested that is higher than the set voltage value appears, the first NPN transistor Q1 is turned on, and the first switch signal K1 is transmitted to the PNP transistor Q2, turning on the PNP transistor Q2, and transmitting the logic high level U1 to the charge and discharge end of the energy storage module 101.

[0087] It should be noted that, under the condition that the switching logic of the first controlled switch 300 and the second controlled switch 301 can be realized, the first controlled switch 300 and the second controlled switch 301 can also use other types of semiconductor switching elements. The first controlled switch 300 is the first NPN transistor Q1 and the second controlled switch 301 is the PNP transistor Q2, which does not represent the only selection limitation for the first controlled switch 300 and the second controlled switch 301.

[0088] In one embodiment, if Figure 4 As shown, the first switch unit 200 further includes a first current limiting resistor R1, a second current limiting resistor R2, a first bias resistor R3, a second bias resistor R4, a first pull-up resistor R5 and a first output resistor R6;

[0089] The base of the first NPN transistor Q1 is used to access the pulse to be tested S1 through the first current limiting resistor R1, the base of the first NPN transistor Q1 is connected to the emitter of the first NPN transistor Q1 through the first bias resistor R3, and the collector of the first NPN transistor Q1 is used to access the logic high level U1 through the first pull-up resistor R5;

[0090] The base of the PNP transistor Q2 is connected to the collector of the first NPN transistor Q1 through the second current limiting resistor R2, the base of the PNP transistor Q2 is connected to the emitter of the PNP transistor Q2 through the second bias resistor R4, and the collector of the PNP transistor Q2 is connected to the charging and discharging end of the energy storage module 101 through the first output resistor R6.

[0091] In one embodiment, the first current limiting resistor R1 and the second current limiting resistor R2 play the role of base current limiting; the first bias resistor R3 provides a bias voltage for the first NPN transistor Q1, and the second bias resistor R4 provides a bias voltage for the PNP transistor Q2; the first pull-up resistor R5 is used to pull the collector of the first NPN transistor Q1 to a high level. The first output resistor R6 is used to send the logic high level U1 to the charging and discharging end of the energy storage module 101.

[0092] In one embodiment, if Figure 4 As shown, the level conversion module 100 further includes a first voltage stabilizing diode D1;

[0093] The cathode of the first zener diode D1 is connected to the controlled end of the first switch unit 200 , and the anode of the first zener diode D1 is grounded.

[0094] In one embodiment, if Figure 4 As shown, the cathode of the first voltage stabilizing diode D1 is connected to the controlled end of the first switch unit 200, and is used to stabilize the level of the controlled end of the first switch unit 200. In one embodiment, the cathode of the first voltage stabilizing diode D1 can be connected to the base of the first NPN transistor Q1. In another embodiment, the cathode of the first voltage stabilizing diode D1 can be connected to the first current limiting resistor R1 for accessing one end of the pulse S1 to be measured.

[0095] In one embodiment, Figure 5 FIG. 4 is a circuit diagram of a level conversion module according to another embodiment of the present invention. Figure 5 As shown, the level conversion module 100 includes a second voltage stabilizing diode D2 and a protection diode D3;

[0096] The positive electrode of the protection diode D3 is used to connect to the pulse S1 to be tested, and the negative electrode of the protection diode D3 is connected to the charging and discharging end of the energy storage module 101;

[0097] The cathode of the second voltage stabilizing diode D2 is connected to the anode of the protection diode D3 , and the anode of the second voltage stabilizing diode D2 is grounded.

[0098] In one embodiment, the second voltage stabilizing diode D2 is used to stabilize the pulse S1 to be tested which is higher than the set voltage value into a charging voltage, and the charging voltage is equal to the stable voltage value of the second voltage stabilizing diode D2. The protection diode D3 is used to prevent the discharge of the energy storage module 101 from affecting the pulse S1 to be tested or the previous circuit.

[0099] In one embodiment, if Figure 5 As shown, the level conversion module 100 further includes a first charging resistor R7, a second charging resistor R8 and a third current limiting resistor R9;

[0100] The positive electrode of the protection diode D3 is used to connect the pulse S1 to be measured through the third current limiting resistor R9;

[0101] One end of the first charging resistor R7 is connected to the cathode of the protection diode D3 , the other end of the first charging resistor R7 is connected to the charging and discharging end of the energy storage module 101 , and the other end of the first charging resistor R7 is also used to be grounded through the second charging resistor R8 .

[0102] In one embodiment, a first charging resistor R7 and a second charging resistor R8 are included to divide the stable voltage value of the second voltage stabilizing diode D1 to adjust the size of the charging voltage.

[0103] The energy storage module 101 is used to charge when the charging and discharging end is connected to the charging voltage, so that the voltage of the charging and discharging end increases;

[0104] The energy storage module 101 is used to charge when the charging and discharging terminals are connected to a charging voltage, and the charging is characterized by a rise in the voltage at the charging and discharging terminals; the energy storage module 101 is used to discharge when the charging and discharging terminals are not connected to a charging voltage, and the discharging is characterized by a drop in the voltage at the charging and discharging terminals. In one embodiment, the energy storage module 101 can use a component with charging and discharging characteristics such as a charging capacitor.

[0105] The discharge module 102 is connected to the charge and discharge end. The discharge module 102 is used to discharge the energy storage module 101 when the charge and discharge end is not connected to the charging voltage, so as to reduce the voltage of the charge and discharge end.

[0106] The discharge module 102 is used to discharge the electric energy of the energy storage module 101 to reduce the voltage of the charge and discharge end. In one embodiment, the discharge module 102 can be a discharge element such as a discharge resistor or a discharge tube.

[0107] The threshold judgment module 103 is used to output a first level signal S2 when the voltage at the charge and discharge end is greater than a preset voltage threshold, and the threshold judgment module 103 is used to output a second level signal S3 when the voltage at the charge and discharge end is less than the preset voltage threshold.

[0108] The first level signal S2 and the second level signal S3 output by the threshold judgment module 103 are used to indicate the change in the duty cycle of the pulse S1 to be measured. If the signal output by the threshold judgment module 103 changes from the first level signal S2 to the second level signal S3, or from the second level signal S3 to the first level signal S2, it indicates that the duty cycle of the pulse S1 to be measured has changed.

[0109] In one embodiment, the threshold determination module 103 may use a comparison circuit or a switch circuit, and output a first level signal S2 when it is determined that the voltage at the charge / discharge end is greater than a preset voltage threshold, and output a second level signal S3 otherwise.

[0110] In one embodiment, Figure 6 Schematic diagram of a threshold determination module according to an implementation mode, Figure 6 As shown, the threshold determination module 103 includes a second switch unit 400;

[0111] The controlled end of the second switch unit 400 is connected to the charging and discharging end, the first switch end of the second switch unit 400 is used to access the logic high level U1, and the second switch end of the second switch unit 400 is used to access the logic low level U2; the third switch end of the second switch unit 400 is used to output the first level signal S2 or the second level signal S3;

[0112] In one embodiment, the logic low level U2 includes a ground level.

[0113] The second switch unit 400 is used to turn on the first switch end and the third switch end of the second switch unit 400 when the voltage at the controlled end of the second switch unit 400 is greater than a preset voltage threshold, and the second switch unit 400 is used to turn on the second switch end and the third switch end of the second switch unit 400 when the voltage at the controlled end of the second switch unit 400 is less than the preset voltage threshold; in one embodiment, the first level signal S2 is a logic high level U1, and the second level signal S3 is a logic low level U2.

[0114] It should be noted that if the pulse width higher than the set voltage value is greater than the pulse width of the set voltage value, the charging time of the energy storage module 101 is greater than the discharging time, and the voltage at the charging and discharging end of the energy storage module 101 is greater than the preset voltage threshold; if the pulse width lower than the set voltage value is less than the pulse width of the set voltage value, the discharging time of the energy storage module 101 is greater than the charging time, and the voltage at the charging and discharging end of the energy storage module 101 is less than the preset voltage threshold.

[0115] In one embodiment, the controlled end of the second switch unit 400 is connected to the charging and discharging end, that is, the voltage of the controlled end of the second switch unit 400 changes synchronously with the voltage of the charging and discharging end. When the voltage of the charging and discharging end is greater than the preset voltage threshold, the second switch unit 400 turns on the first switch end and the third switch end, and the threshold judgment module 103 outputs the first level signal S2; when the voltage of the charging and discharging end is less than the preset voltage threshold, the second switch unit 400 turns on the second switch end and the third switch end, and the threshold judgment module 103 outputs the second level signal S3. In one embodiment, the second switch unit 400 can select an electronic switch chip or switch element with a single-pole multi-throw switch function. The second switch unit 400 outputs the external logic high level U1 and the logic low level U2 as signals, so that the subsequent circuit only needs to judge the level change, and can judge the change of the pulse S1 to be measured without complex processing capabilities.

[0116] In one embodiment, Figure 7 is a structural diagram of a threshold determination module according to an implementation mode, such as Figure 7 As shown, the second switch unit 400 includes a third controlled switch 500, a fourth controlled switch 501 and a second pull-up resistor R10;

[0117] The controlled end of the third controlled switch 500 is connected to the charging and discharging end, the first switch end of the third controlled switch 500 is connected to the controlled end of the fourth controlled switch 501, and the second switch end of the third controlled switch 500 is used to access the second switch signal K2; in one embodiment, the third controlled switch 500 is used to turn on the first switch end and the second switch end of the third controlled switch 500 when the voltage of the controlled end of the third controlled switch 500 is greater than a preset voltage threshold;

[0118] The first switch end of the fourth controlled switch 501 is used to access the logic high level U1 through the second pull-up resistor R10, and the second switch end of the fourth controlled switch 501 is used to access the logic low level U2; in one embodiment, the first switch end and the second switch end of the fourth controlled switch 501 are normally closed, and the fourth controlled switch 501 is used to disconnect the first switch end and the second switch end of the fourth controlled switch 501 when the controlled end of the fourth controlled switch 501 is connected to the second switch signal; the first switch end of the fourth controlled switch 501 is used to output the logic high level U1 or the logic low level U2.

[0119] The third controlled switch 500 and the fourth controlled switch 501 can both use modular switch circuits or switch elements such as electronic switch chips and semiconductor switches. In one embodiment, the on-trigger condition of the third controlled switch 500 is that the voltage of the controlled end of the third controlled switch 500 is greater than the preset voltage threshold; the off-trigger condition of the fourth controlled switch 501 is that the controlled end of the fourth controlled switch 501 receives the second switch signal K2. When the third controlled switch 500 is on, the second switch signal K2 causes the fourth controlled switch 501 to change from on to off. In one embodiment, when the fourth controlled switch 501 is on, its first switch end outputs a logic low level U2; when the fourth controlled switch 501 is off, its first switch end outputs a logic high level U1 based on the first pull-up resistor R10. Based on this, the working logic of the second switch unit 400 is realized through the cooperation of the third controlled switch 500 and the fourth controlled switch 501.

[0120] As a preferred implementation method, Figure 8 is a circuit diagram of a threshold judgment module according to an implementation mode, such as Figure 8 As shown, the third controlled switch 500 includes a second NPN transistor Q3, and the fourth controlled switch 501 includes a third NPN transistor Q4;

[0121] The base of the second NPN transistor Q3 is connected to the charging and discharging end, the collector of the second NPN transistor Q3 is connected to the base of the third NPN transistor Q4, and the emitter of the second NPN transistor Q3 is used to access the second switch signal K2; in one embodiment, the second switch signal K2 is a logic low level U2;

[0122] The collector of the third NPN transistor Q4 is used to access the logic high level U1, and the emitter of the third NPN transistor Q4 is used to access the logic high level U1; in one embodiment, the collector of the third NPN transistor Q4 is used to output the logic high level U1 or the logic low level U2.

[0123] In one embodiment, the preset voltage threshold is greater than or equal to the turn-on voltage of the second NPN transistor Q3. As a preferred implementation, the preset voltage threshold is equal to the turn-on voltage of the second NPN transistor Q3.

[0124] It should be noted that, under the condition that the switching logic of the third controlled switch 500 and the fourth controlled switch 501 can be realized, the third controlled switch 500 and the fourth controlled switch 501 can also use other types of semiconductor switching elements. The third controlled switch 500 is the second NPN transistor Q3 and the fourth controlled switch 501 is the third NPN transistor Q4, which does not represent the only selection limitation for the third controlled switch 500 and the fourth controlled switch 501.

[0125] In one embodiment, if Figure 8 As shown, the second switch unit 400 further includes a third pull-up resistor R11 and a third bias resistor R12;

[0126] The collector of the second NPN transistor Q3 is used to access the logic high level U1 through the third pull-up resistor R11, and the base of the third NPN transistor Q4 is connected to the emitter of the base of the third NPN transistor Q4 through the third bias resistor R12.

[0127] In one embodiment, if Figure 8 As shown, the second switch unit 400 further includes a fourth current limiting resistor Ri. The collector of the second NPN transistor Q3 is connected to the base of the third NPN transistor Q4 through the fourth current limiting resistor Ri.

[0128] In one embodiment, the third pull-up resistor R11 is used to pull up the collector of the second NPN transistor Q3 to a logic high level U1. The third bias resistor R12 is used to provide a bias voltage for the third NPN transistor Q4.

[0129] In one embodiment, Fig. 9 FIG. 1 is a duty cycle conversion circuit diagram of a specific application example. Fig. 9 As shown, the level conversion module 100 uses the first switch unit 200, and the threshold judgment module 103 uses the second switch unit 400. The energy storage module 101 includes a charging capacitor C1, one end of the charging capacitor C1 is the charging and discharging end of the energy storage module 101, and the other end of the charging capacitor C1 is used for grounding. The discharge module 102 includes a first discharge resistor R13 and a second discharge resistor R14, and the charging and discharging end of the energy storage module 101 is used to be grounded through the first discharge resistor R13 and the second discharge resistor R14 in sequence.

[0130] like Fig. 9 As shown, the voltage at the charging and discharging end of the energy storage module 101 is U o1 The level signal output by the threshold judgment module 103 is Uo2 . Fig.10 is a voltage waveform diagram based on a specific application example, such as Fig.10 As shown, the pulse S1 to be tested takes the square wave Ui as an example. When the pulse S1Ui to be tested is in a normal state, the width Ta of the high level is greater than the width Tb of the low level. After the pulse S1Ui to be tested changes to an abnormal state, the width Tc of the high level is less than the width Td of the low level. In one embodiment, the high levels Ta and Tc can keep the charging capacitor C1 in a charging state.

[0131] Under normal conditions, the charge and discharge terminal voltage U o1 The minimum voltage is Ua; in abnormal state, the charge and discharge terminal voltage U o1 The maximum voltage of the second NPN transistor Q3 is Ub. In one embodiment, Ua is greater than Ub. At the same time, under normal conditions, after Ua is divided by the first discharge resistor R13 and the second discharge resistor R14, the base voltage of the second NPN transistor Q3 is still greater than the preset voltage threshold or the conduction voltage U BE(on) , the level signal U output by the threshold judgment module 103 o2 In an abnormal state, after Ub is divided by the first discharge resistor R13 and the second discharge resistor R14, the base voltage of the second NPN transistor Q3 is less than the preset voltage threshold, and the level signal U output by the threshold judgment module 103 is o2 U2 is at logic low level, that is, ground CND. Fig.10 As shown, when the pulse to be tested S1Ui changes from a normal state to an abnormal state, the level signal U o2 Generates a falling edge interrupt signal.

[0132] In one embodiment, based on Fig. 9 In the specific application example shown, each component should satisfy the following relationships (1) to (5):

[0133]

[0134]

[0135]

[0136]

[0137]

[0138] In the duty cycle conversion circuit of any of the above embodiments, the level conversion module 100 converts the pulses whose voltage in the pulse S1 to be tested is higher than the set voltage value to obtain the charging voltage, and outputs the charging voltage to the charging and discharging end of the energy storage module 101 to charge the energy storage module 101, so that the voltage at the charging and discharging end of the energy storage module 101 rises. Further, through the discharge module 102 and the threshold judgment module 103, the first level signal S2 and the second level signal S3 are obtained according to the voltage at the charging and discharging end. If the duty cycle of the pulse S1 to be tested changes, that is, the width of the pulse whose voltage in the pulse S1 to be tested is higher than the set voltage value changes, the signal output by the threshold judgment module 103 will change. Based on this, the pulse S1 to be tested is converted into the first level signal S2 and the second level signal S3, and it can be judged whether the duty cycle of the pulse S1 to be tested has changed according to the transition between the first level signal S2 and the second level signal S3, which effectively reduces the cost of software and hardware and improves convenience.

[0139] The embodiment of the present invention also provides a duty cycle detection device.

[0140] Fig.11 FIG. 1 is a module structure diagram of a duty cycle detection device according to an embodiment of the present invention. Fig.11 As shown, a first MCU 600 of a duty cycle detection device according to an implementation manner and a duty cycle conversion circuit 601 of any of the above embodiments;

[0141] The first MCU600 is used to access the first level signal S2 or the second level signal S3 output by the threshold judgment module 103, and is used to detect whether the signal output by the threshold judgment module 103 changes, and when the signal output by the threshold judgment module 103 changes, it determines that the duty cycle of the pulse S1 to be tested changes.

[0142] In one embodiment, the first MCU 600 is an MCU capable of detecting high and low level changes.

[0143] In the duty cycle detection device of any of the above embodiments, the first MCU 600 is connected to the first level signal S2 or the second level signal S3 output by the threshold judgment module 103. At the same time, the first MCU 600 can detect whether the signal output by the threshold judgment module 103 changes, and determine whether the duty cycle of the pulse S1 to be tested changes when the signal output by the threshold judgment module 103 changes. Based on this, there is no need to select an MCU that supports detection of pulse width changes, and only the first MCU 600 that can detect level changes can be selected to detect duty cycle changes, which can effectively reduce software complexity and hardware costs.

[0144] The embodiment of the present invention also provides an airbag detection system.

[0145] Fig.12The structural diagram of the airbag detection system module for an embodiment is as follows: Fig.12 As shown, the airbag detection system of an embodiment includes a second MCU 700 and the duty cycle conversion circuit 701 of any of the above embodiments;

[0146] The pulse S1 to be measured is the pulse signal output by the airbag controller;

[0147] The second MCU 700 is used to access the first level signal S2 or the second level signal S3 output by the threshold judgment module 103, and is used to determine that the airbag has exploded when the signal output by the threshold judgment module 103 changes from the first level signal S2 to the second level signal S3.

[0148] Fig.13 The pulse waveform diagram output by the airbag controller is as follows: Fig.13 As shown, before and after the airbag explodes, the duty cycle of the pulse waveform output by the airbag controller changes. Among them, before the airbag explodes, the high-level time is Ta, the low-level time is Tb, and Ta > Tb; after the airbag explodes, the high-level time is Tc, the low-level time is Td, and Tc < Td. After the airbag explodes, it will trigger a waveform change of N cycles.

[0149] The airbag detection system of any of the above embodiments can obtain the pulse signal output by the airbag controller, convert the pulse signal output by the airbag controller into the first level signal S2 or the second level signal S3, and further, when the second MCU 700 detects that the signal output by the threshold judgment module 103 changes from the first level signal S2 to the second level signal S3, it determines that the airbag has exploded. Based on this, only the second MCU 700 that can detect the level change is required to detect whether the airbag has exploded, which reduces the functional requirements for the second MCU 700 and is convenient for simplifying software implementation and reducing hardware costs.

[0150] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as these combinations of technical features do not conflict, they should all be considered as the scope described in this specification.

[0151] The above embodiments only represent several implementation manners of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several deformations and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the invention patent should be subject to the appended claims.

Claims

1. A duty cycle conversion circuit, characterized in that: It includes a level conversion module, an energy storage module, a discharge module and a threshold judgment module; The level conversion module is used to access the pulse to be tested, and is also used to convert the pulse whose voltage in the pulse to be tested is higher than the set voltage value to obtain the charging voltage, and output the charging voltage to the charging and discharging end of the energy storage module; wherein the charging voltage is a fixed voltage; The energy storage module is used to charge when the charging and discharging end is connected to the charging voltage, so that the voltage of the charging and discharging end increases; The discharge module is connected to the charge and discharge end, and is used to discharge the energy storage module when the charge and discharge end is not connected to the charging voltage, so that the voltage of the charge and discharge end decreases; The threshold judgment module is used to output a first level signal when the voltage at the charge and discharge end is greater than a preset voltage threshold, and the threshold judgment module is used to output a second level signal when the voltage at the charge and discharge end is less than a preset voltage threshold.

2. The duty cycle conversion circuit according to claim 1, characterized in that: The level conversion module includes a first switch unit; The controlled end of the first switch unit is used to access the pulse to be tested, the first switch end of the first switch unit is used to access a logic high level, and the second switch end of the first switch unit is connected to the charging and discharging end of the energy storage module; The first switch unit is used to turn on the first switch end and the second switch end of the first switch unit when the voltage of the controlled end of the first switch unit is higher than the set voltage value; wherein the logic high level is the charging voltage.

3. The duty cycle conversion circuit according to claim 2, characterized in that: The first switch unit includes a first controlled switch and a second controlled switch; The controlled end of the first controlled switch is used to access the pulse to be tested, the first switch end of the first controlled switch is connected to the controlled end of the second controlled switch, and the second switch end of the first controlled switch is used to access the first switch signal; wherein the first controlled switch is used to conduct the first switch end and the second switch end of the first controlled switch when the voltage of the controlled end of the first controlled switch is higher than the set voltage value; The first switch end of the second controlled switch is used to access the logic high level, and the second switch end of the second controlled switch is connected to the charging and discharging end of the energy storage module; wherein the second controlled switch is used to turn on the first switch end and the second switch end of the second controlled switch when the controlled end of the second controlled switch is connected to the first switch signal.

4. The duty cycle conversion circuit according to claim 3, characterized in that: The first controlled switch includes a first NPN transistor, and the second controlled switch includes a PNP transistor; The base of the first NPN transistor is used to access the pulse to be tested, the collector of the first NPN transistor is connected to the base of the PNP transistor, and the emitter of the first NPN transistor is used to access the first switch signal; wherein the first switch signal is a logic low level; The emitter of the PNP transistor is used to access the logic high level, and the collector of the PNP transistor is connected to the charging and discharging end of the energy storage module.

5. The duty cycle conversion circuit according to claim 4, characterized in that: The first switch unit further includes a first current limiting resistor, a second current limiting resistor, a first bias resistor, a second bias resistor, a first pull-up resistor and a first output resistor; The base of the first NPN transistor is used to access the pulse to be tested through the first current limiting resistor, the base of the first NPN transistor is connected to the emitter of the first NPN transistor through the first bias resistor, and the collector of the first NPN transistor is used to access the logic high level through the first pull-up resistor; The base of the PNP transistor is connected to the collector of the first NPN transistor through the second current limiting resistor, the base of the PNP transistor is connected to the emitter of the PNP transistor through the second bias resistor, and the collector of the PNP transistor is connected to the charging and discharging end of the energy storage module through the first output resistor.

6. The duty cycle conversion circuit according to claim 2, characterized in that: The level conversion module also includes a first voltage stabilizing diode; The cathode of the first voltage stabilizing diode is connected to the controlled end of the first switch unit, and the anode of the first voltage stabilizing diode is grounded.

7. The duty cycle conversion circuit according to claim 1, characterized in that: The level conversion module includes a second voltage stabilizing diode and a protection diode; The positive electrode of the protection diode is used to access the pulse to be tested, and the negative electrode of the protection diode is connected to the charging and discharging end of the energy storage module; The cathode of the second voltage stabilizing diode is connected to the anode of the protection diode, and the anode of the second voltage stabilizing diode is grounded.

8. The duty cycle conversion circuit according to claim 7, characterized in that: The level conversion module also includes a first charging resistor, a second charging resistor and a third current limiting resistor; The positive electrode of the protection diode is used to access the pulse to be tested through the third current limiting resistor; One end of the first charging resistor is connected to the cathode of the protection diode, the other end of the first charging resistor is connected to the charging and discharging end of the energy storage module, and the other end of the first charging resistor is also used to be grounded through the second charging resistor.

9. The duty cycle conversion circuit according to claim 1, characterized in that: The threshold determination module includes a second switch unit; The controlled end of the second switch unit is connected to the charging and discharging end, the first switch end of the second switch unit is used to access a logic high level, and the second switch end of the second switch unit is used to access a logic low level; the third switch end of the second switch unit is used to output the first level signal or the second level signal; The second switch unit is used to turn on the first switch end and the third switch end of the second switch unit when the voltage at the controlled end of the second switch unit is greater than a preset voltage threshold, and the second switch unit is used to turn on the second switch end and the third switch end of the second switch unit when the voltage at the controlled end of the second switch unit is less than a preset voltage threshold; wherein the first level signal is the logic high level and the second level signal is the logic low level.

10. The duty cycle conversion circuit according to claim 9, characterized in that: The second switch unit includes a third controlled switch, a fourth controlled switch and a second pull-up resistor; The controlled end of the third controlled switch is connected to the charging and discharging end, the first switch end of the third controlled switch is connected to the controlled end of the fourth controlled switch, and the second switch end of the third controlled switch is used to access the second switch signal; wherein the third controlled switch is used to conduct the first switch end and the second switch end of the third controlled switch when the voltage of the controlled end of the third controlled switch is greater than a preset voltage threshold; The first switch end of the fourth controlled switch is used to access the logic high level through the second pull-up resistor, and the second switch end of the fourth controlled switch is used to access the logic low level; wherein the first switch end and the second switch end of the fourth controlled switch are normally closed, and the fourth controlled switch is used to disconnect the first switch end and the second switch end of the fourth controlled switch when the controlled end of the fourth controlled switch is connected to the second switch signal; the first switch end of the fourth controlled switch is used to output the logic high level or the logic low level.

11. The duty cycle conversion circuit according to claim 10, characterized in that: The third controlled switch includes a second NPN transistor, and the fourth controlled switch includes a third NPN transistor; The base of the second NPN transistor is connected to the charging and discharging end, the collector of the second NPN transistor is connected to the base of the third NPN transistor, and the emitter of the second NPN transistor is used to access the second switch signal; wherein the second switch signal is a logic low level; The collector of the third NPN transistor is used to access the logic high level, and the emitter of the third NPN transistor is used to access the logic high level; wherein the collector of the third NPN transistor is used to output the logic high level or the logic low level.

12. The duty cycle conversion circuit according to claim 11, characterized in that: The second switch unit further includes a third pull-up resistor and a third bias resistor; The collector of the second NPN transistor is used to access the logic high level through the third pull-up resistor, and the base of the third NPN transistor is connected to the emitter of the third NPN transistor through the third bias resistor.

13. The duty cycle conversion circuit according to any one of claims 1 to 12, characterized in that: The discharge module includes a first discharge resistor and a second discharge resistor; The charging and discharging ends of the energy storage module are used to be grounded through the first discharge resistor and the second discharge resistor in sequence.

14. The duty cycle conversion circuit according to claim 13, characterized in that: The charging and discharging ends of the energy storage module are connected to the threshold judgment module through the first discharge resistor.

15. The duty cycle conversion circuit according to any one of claims 1 to 12, characterized in that: The energy storage module includes a charging capacitor; One end of the charging capacitor is the charging and discharging end of the energy storage module, and the other end of the charging capacitor is used for grounding.

16. A duty cycle detection device, characterized in that: comprising a first MCU and a duty cycle conversion circuit as claimed in any one of claims 1 to 15; The first MCU is used to access the first level signal or the second level signal output by the threshold judgment module, and to detect whether the signal output by the threshold judgment module changes, and to determine whether the duty cycle of the pulse to be measured changes when the signal output by the threshold judgment module changes.

17. An airbag detection system, characterized in that: comprising a second MCU and a duty cycle conversion circuit as claimed in any one of claims 1 to 15; The pulse to be tested is a pulse signal output by the airbag controller; The second MCU is used to access the first level signal or the second level signal output by the threshold judgment module, and is used to determine that the airbag explodes when the signal output by the threshold judgment module changes from the first level signal to the second level signal.

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