JPH0637017U - Power supply circuit for air bag system control - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a control power supply circuit for an airbag system, which is capable of coping with an abnormal vehicle battery voltage and having improved reliability. A control power supply circuit in an airbag system 3, the airbag system 3 boosts a battery voltage received from a battery 1 and makes it a constant voltage to supply operating energy to a squib 8 and the battery. The booster circuit 9 includes a first constant voltage circuit 21 that lowers the voltage and supplies a constant voltage to the control circuit 10.
If the battery voltage is below a predetermined lower limit value or above a predetermined upper limit value between the output side of the first constant voltage circuit 21 and the output side of the first constant voltage circuit 21,
The second constant voltage circuit 2 that reduces the output voltage of the booster circuit 9 and supplies the constant voltage to the control circuit 10 instead of the constant voltage circuit 21.
2 is provided.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a power supply circuit for controlling an airbag system, which is a vehicle occupant protection device.

[0002]

[Prior art]

 A specific example of a conventional control power supply circuit for this type of airbag system will be described with reference to FIG. FIG. 3 is a circuit diagram showing the entire airbag system including the control power supply circuit. In FIG. 3, 1 is an in-vehicle battery, 2 is an ignition switch, and 3 is an airbag system. A booster circuit 9 that receives a voltage from the vehicle-mounted battery 1 through the ignition switch 2 to boost it to a constant voltage, a backup capacitor 13 that is charged through a resistor 12 and discharged at the time of ignition, and a reverse current blocking diode 14. Constitutes the energy source for squib 8 ignition. The squib 8 is a heat-generating coil that generates heat when energized to ignite the gas generator 7 and generate gas to inflate the airbag 6. The acceleration sensor 5 is composed of a piezoelectric element, a semiconductor, or the like, detects a collision, and outputs a signal to the control circuit 10. When the control circuit 10 receives the signal, the semiconductor switch 4, which is a normally open contact, is turned on and the squib 8 is energized to ignite.

Next, the constant voltage circuit 11 is a power source of the control circuit 10 and supplies the constant voltage to the control circuit 10 by stabilizing and stabilizing the voltage of the vehicle-mounted battery 1 (usually about 8 to 16V) to about 5V. It is a stabilized power supply. The control circuit 10 has a function (not shown) for diagnosing a circuit abnormality of the airbag system 3 in addition to the control of the semiconductor switch 4 described above, and requires a constant voltage. Further, since the airbag system operates to protect an occupant in the event of a vehicle collision, the power supply for the control circuit of the airbag system is required to have high reliability so as not to be inoperable.

[0004]

[Problems to be Solved by the Invention] The voltage of the on-vehicle battery 1 fluctuates due to charging / discharging, and is usually within the range of 8 to 16 V, but it may become higher due to a jumper start or the like in winter. . In such a case, the constant voltage circuit 11 has a large potential difference to be stepped down, which increases the load and the internal heat generation amount. As a result, a failure may occur or the life may be shortened. On the contrary, when the ignition switch 2 is turned on, the battery voltage decreases, but when the voltage is, for example, 5 V or less, the constant voltage circuit 11 cannot raise it. Further, when the on-vehicle battery 1 is disconnected, the ignition energy can be supplied by the back-up capacitor 13, but the control circuit 10 cannot be supplied with voltage.

The present invention has been made in view of the above problems of the conventional technology, and an object of the present invention is to be able to cope with an abnormal in-vehicle battery voltage, and It is to provide a power supply circuit for controlling an airbag system with improved reliability.

[0006]

[Means for Solving the Problems]

 In order to solve the above problems, the present invention relates to a control power supply circuit for an airbag system, which boosts a battery voltage received from a battery and makes it a constant voltage to supply operating energy to a squib. And a first constant voltage circuit for stepping down the battery voltage and supplying a constant voltage to the control circuit, and a battery voltage is provided between the output side of the booster circuit and the output side of the first constant voltage circuit. A second constant voltage circuit which supplies a constant voltage to the control circuit by stepping down the output voltage of the step-up circuit in place of the first constant voltage circuit at a predetermined lower limit value or above or a predetermined upper limit value or above is provided. is there.

[0007]

[Action]

 When the battery voltage exceeds a predetermined upper limit value, the voltage of the booster circuit is stepped down by the second constant voltage circuit and the constant voltage is supplied to the control circuit. Further, even when the battery voltage becomes equal to or lower than the predetermined lower limit value, the voltage boosted by the booster circuit is stepped down by the second constant voltage circuit and supplied to the control circuit. Further, when the battery is broken due to a vehicle collision or the like, a voltage which is almost equal to the output voltage of the booster circuit from the backup capacitor is stepped down by the second constant voltage circuit and supplied to the control circuit.

[0008]

【Example】

 Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a control power supply circuit of the air bag system of the present invention. Note that, in FIG. 1, portions having the same operations as those in FIG. 3 are denoted by the same reference numerals, and description thereof will be omitted.

A difference from FIG. 3 is that a second constant voltage circuit 22 is provided between the output side of the booster circuit 9 and the output side of the first constant voltage circuit 21, and the first constant voltage circuit 21 and the second constant voltage circuit 21 are provided. That is, the voltage circuit 22 is a stabilized power supply including an input voltage monitoring function. That is, the first constant voltage circuit 21 turns off when the voltage of the vehicle-mounted battery 1 supplied to the first constant voltage circuit 21 is below a predetermined lower limit value or above a predetermined upper limit value. On the other hand, the second constant voltage circuit 22 monitors the voltage of the vehicle-mounted battery 1 supplied to the first constant voltage circuit 21 to turn it on or below a predetermined lower limit value or a predetermined upper limit value or more. As the predetermined values, the upper limit value and the lower limit value of the normal voltage fluctuation range of the vehicle-mounted battery 1 are set. Normally, this voltage fluctuation range is about 8V to 16V, and hereinafter, a predetermined upper limit value of 16V and a predetermined lower limit value of 8V will be described. There are various known methods for switching between the first constant voltage circuit 21 and the second constant voltage circuit 22, and the method described above is an example, and the method is not limited to this method.

In the circuit having the above-mentioned configuration, when the voltage of the on-vehicle battery 1 fluctuates to 16 V or more, the first constant voltage circuit 21 is turned off and the second constant voltage circuit 22 is turned on. Then, the second constant voltage circuit 22 reduces the voltage of the booster circuit 9 and supplies the constant voltage to the control circuit 10. The step-up circuit 9 is a step-up type stabilized power source normally composed of a DC / DC converter or the like in order to ensure the ignition of the squib 8 in FIG. 3, and its output voltage is constant at about 28V, for example. is there. Therefore, although the second constant voltage circuit 22 has a large potential difference to be stepped down from 28V to 5V, the second constant voltage circuit 22 operates only in the abnormal state, and therefore the operating time in actual use (life) is short, which makes it a little unreasonable. You can use it without any problem. Further, since the input voltage range to be covered by the first constant voltage circuit 21 is also reduced, the amount of internally generated heat can be reduced. As a result, reliability in actual use is improved. Next, even when the voltage of the on-vehicle battery 1 becomes 8 V or less, the first constant voltage circuit 21 is turned off and the second constant voltage circuit 22 is turned on, and the voltage boosted by the booster circuit 9 is changed to the second constant voltage. The voltage is reduced by the circuit 22 and supplied to the control circuit 10. In this case, the lower limit voltage of the in-vehicle battery 1 that can be handled is determined by the booster circuit 9, but is usually about 4V. Further, even if the in-vehicle battery 1 is disconnected, a voltage that is substantially equal to the output voltage of the booster circuit 9 is supplied from the back-up capacitor 13 to the second constant voltage circuit 22 through the resistor 12, and this is supplied to the second constant voltage circuit 22. The voltage can be stepped down and supplied to the control circuit 10.

FIG. 2 shows a configuration in which a common third constant voltage circuit is provided on the output side of the first constant voltage circuit 21 and the second constant voltage circuit 22 in FIG. In FIG. 2, the output voltage of the first constant voltage circuit 24 and the second constant voltage circuit 25 is about 6V, and the third constant voltage circuit 26 steps this down to 5V. With such a configuration, the load on the first constant voltage circuit 24 and the second constant voltage circuit 25 is reduced, and the amount of internally generated heat is reduced, so that the reliability can be further improved and the control voltage can be increased. It is also possible to improve the accuracy of.

[0012]

[Effect of device]

 As described above, the control power supply circuit for the airbag system of the present invention supplies a constant voltage from the constant voltage circuit when the vehicle battery voltage is normal by using the booster circuit when there is an abnormality. Since the constant voltage circuit is provided, it is possible to deal with the case where the vehicle battery voltage becomes abnormal, and it is possible to constantly supply the constant voltage to the control circuit. Moreover, since the load on each constant voltage circuit can be reduced, the amount of internally generated heat can be reduced, and failure and thermal deterioration can be prevented, and reliability in actual use can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram of a control power supply circuit of an airbag system of the present invention.

FIG. 2 is a block diagram of an embodiment of the present invention.

FIG. 3 is a circuit diagram of a conventional airbag system.

[Explanation of symbols]

 1 Car Battery 3 Airbag System 8 Squib 9 Booster Circuit 10 Control Circuit 21 First Constant Voltage Circuit 22 Second Constant Voltage Circuit

Claims (2)

[Scope of utility model registration request] 1. A power supply circuit for control in an airbag system, wherein the airbag system boosts a battery voltage received from a battery and makes it a constant voltage to supply operating energy to a squib, and lowers the battery voltage. To supply a constant voltage to the control circuit
A constant voltage circuit is provided, and between the output side of the booster circuit and the output side of the first constant voltage circuit, when the battery voltage is below a predetermined lower limit value or above a predetermined upper limit value, boosting is performed in place of the first constant voltage circuit. A power supply circuit for controlling an air bag system, comprising a second constant voltage circuit for stepping down an output voltage of the circuit and supplying a constant voltage to the control circuit. 2. The power supply circuit for controlling an airbag system according to claim 1, wherein a common third constant voltage circuit is provided on an output side of the first constant voltage circuit and the second constant voltage circuit.