JPH0614300B2 - Constant voltage power supply circuit for vehicle electronic control system - Google Patents

Description

The present invention relates to a vehicle electronic control system, and more particularly, to a constant voltage suitable for use in a vehicle electronic control system including a microcomputer having a backup function. Regarding the power circuit.

[Prior art]

Conventionally, in this type of constant voltage power supply circuit, for example, a main constant voltage circuit that is supplied with power from a battery to generate a main constant voltage when an ignition switch of a vehicle is closed, and an auxiliary constant voltage that is constantly supplied with power from the battery. An auxiliary constant voltage circuit for generating the auxiliary constant voltage circuit is provided, and the auxiliary constant voltage is constantly applied to the above-mentioned microcomputer to keep the backup function of the microcomputer always valid, while the input / output interface connected to the microcomputer. There is one in which the main constant voltage is applied only when the ignition switch is closed to reduce unnecessary power consumption of the battery.

[Problems to be solved by the invention]

By the way, in such a configuration, when the ignition switch is closed, the power supply voltage of the microcomputer is ideally 5 ± 0.5 (V) standard in the case of a C-MOS type microcomputer. Moreover, the power supply voltage of the input / output interface is equal to the power supply voltage of the microcomputer because it becomes the voltage of the input / output port of the microcomputer. Therefore, the allowable input / output interface power supply voltage must be a voltage that can secure a high-level input voltage on the low side, and must be a voltage on which the microcomputer does not latch up on the high side. It costs. As a concrete example, the power supply voltage of the microcomputer is 5 ± 0.5.
When (V), the power supply voltage of the input / output interface is
(Power supply voltage of microcomputer +0.3 (V)) ~
It is in the range of (power supply voltage of microcomputer-0.5 (V)). However, if such a thing is always attempted to be realized with the ignition switch closed, fluctuations in the main constant voltage and the auxiliary constant voltage due to the load characteristics and temperature characteristics of the main constant voltage circuit and the auxiliary constant voltage circuit described above, etc. In order to absorb the voltage, a voltage compensating circuit and a temperature compensating circuit having a complicated circuit configuration must be adopted, and compensation and adjustment of these circuits must be performed as necessary.

Therefore, in order to deal with such a problem, the present invention always realizes the ideal relationship between the main constant voltage and the auxiliary constant voltage as described above in a vehicle electronic control system with a simple circuit configuration. The present invention intends to provide a constant voltage power supply circuit configured to do so.

[Means for solving problems]

In solving such problems, the structural features of the present invention are as follows.
In a vehicle electronic control system including a microcomputer having a backup function and an electronic circuit means connected to the microcomputer, a main constant voltage is generated by supplying power from a battery via an ignition switch of the vehicle to the electronic circuit means. Main constant voltage power supply to be given,
Connected to the auxiliary constant voltage power supply that is constantly fed from the battery and generates an auxiliary constant voltage lower than the main constant voltage, the main constant voltage power supply and the auxiliary constant voltage power supply, and The main constant voltage applied to the power supply circuit, comprising high voltage selection means for selecting a higher voltage of the main constant voltage and the auxiliary constant voltage from the auxiliary constant voltage power supply and applying the higher voltage to the power supply circuit. Of the auxiliary constant voltage and the auxiliary constant voltage, the power supply circuit is connected between the high voltage selecting means and the microcomputer, and an ignition switch is connected to the battery in order to apply the selected voltage to the microcomputer. I have connected without going through.

[Action effect]

By configuring the present invention in this way, when the main constant voltage power supply is supplied from the battery by the ignition switch, the main constant voltage power supply generates the main constant voltage. At this time, the auxiliary constant voltage power source is constantly supplied with power from the battery to generate the auxiliary constant voltage. Therefore, the high voltage selecting means selects the higher one of the main constant voltage and the auxiliary constant voltage to generate the selection voltage.
Therefore, the main constant voltage is applied to the electronic circuit means, while the selection voltage is applied to the microcomputer via the power supply circuit.

In such a case, the main constant voltage is set to be equal to or higher than the auxiliary constant voltage, but the main constant voltage becomes the auxiliary constant voltage according to the load characteristics or temperature characteristics of the main constant voltage power supply and the auxiliary constant voltage power supply. Even if it fluctuates, the high voltage selection means generates the higher voltage, that is, the auxiliary constant voltage as the selection voltage. Therefore, the relationship between the power supply voltage of the microcomputer and the power supply voltage of the electronic circuit means is changed. You can always keep it right. Further, since such an operation effect can be achieved only by adopting the high voltage selecting means, this kind of constant voltage power supply circuit can be provided at a low cost with a simple circuit configuration.

Further, when the main constant voltage power supply is cut off from the battery by the ignition switch, the main constant voltage from the main constant voltage power supply disappears. However, since the auxiliary constant voltage power source is still generating the auxiliary constant voltage, the high-voltage selecting means replaces the main constant voltage with the auxiliary constant voltage as the selection voltage and supplies the auxiliary constant voltage to the microcomputer via the power supply circuit. Give. Therefore, this microcomputer effectively exhibits its backup function based on the selected voltage. The electronic circuit means is deactivated by the disappearance of the main constant voltage.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.
The figure shows an example in which the constant voltage power supply circuit Ps according to the present invention is applied to a vehicle electronic control system. The electronic control system includes various sensors 10, an input buffer circuit 20 connected to each sensor, and an input buffer circuit 2
0 and the output buffer circuit 40 connected to the microcomputer 30.
And various actuators 50 connected to the output buffer circuit 40, the various sensors 10 detect the driving state of the vehicle. The input buffer circuit 20 gives the detection results of the various sensors 10 to the microcomputer 30 as buffer outputs. In such a case, the proper power supply voltage of the input buffer circuit 20 is within the range of 5 ± 0.25 (V).

The microcomputer 30 is a microcomputer having a backup function, and in this embodiment, a HD6301V type microcomputer manufactured by Hitachi, Ltd. is adopted as the microcomputer 30. In such a case, the backup power supply voltage of the microcomputer 30 required to maintain only the backup function of the microcomputer 30 is 2 (V).
That is all. The normal power supply voltage required for normal operation of the microcomputer 30 is within the range of 5 ± 0.5 (V). Then, the microcomputer 30 operates under the normal power supply voltage and performs the arithmetic processing necessary for controlling the various actuators 50 according to the buffer output from the input buffer circuit 20. Also, the microcomputer 3
0 exhibits a backup function under the backup power supply voltage.

The output buffer circuit 40 uses the calculation processing result of the microcomputer 30 as a buffer output for various actuators 5.
Assign to 0. In such a case, the proper power supply voltage of the output buffer circuit 40 is within the range of 5 ± 0.25 (V). The various actuators 50 are for driving various operating devices of the vehicle.

The constant voltage power supply circuit Ps includes a main constant voltage circuit 60 and an auxiliary constant voltage circuit 70. The main constant voltage circuit 60 has its power supply terminal 61 at the ignition switch I of the vehicle.
It is connected to the positive side terminal of the battery B via G, and at the output terminal 62 thereof, the power supply terminal 2 of the input buffer circuit 20.
1 and the power supply terminal 41 of the output buffer circuit 40. Then, the main constant voltage circuit 60 receives the DC voltage from the battery B under the closing of the ignition switch IG to generate the main constant voltage Vm, and generates the main constant voltage Vm.
And to the output buffer circuit 40 as the proper power supply voltage. In such a case, the main constant voltage Vm is 5 ± 0.25
(V). The main constant voltage circuit 60 is cut off from the battery B by opening the ignition switch IG to reduce the main constant voltage Vm to 0 (V).

The auxiliary constant voltage circuit 70 is composed of a Zener diode and a resistor, and the power supply terminal 71 of the auxiliary constant voltage circuit 70 is directly connected to the positive terminal of the battery B. Therefore, the auxiliary constant voltage circuit 70 is constantly supplied with the DC voltage from the battery B and generates the auxiliary constant voltage Va at the output terminal 72. In such a case, the auxiliary constant voltage Va is a voltage that is equal to or higher than the voltage that can be backed up and does not exceed the main constant voltage Vm even if variations in elements and temperature characteristics are included, and is 4 ± 0. It becomes 5 (V).

The constant voltage power supply circuit Ps serves as a high voltage selection circuit 80 connected to the main constant voltage circuit 60 and the auxiliary constant voltage circuit 70, and a power supply circuit connected between the high voltage selection circuit 80 and the microcomputer 30. And a voltage-follower circuit 90. The high voltage selection circuit 80 includes a pair of operational amplifiers 81 and 82 and a pair of diodes 83 and 84.
And a resistor 85, and an operational amplifier 81
Is connected to the output terminal 62 of the main constant voltage circuit 60 at its non-inverting input terminal, while the operational amplifier 82 is connected to the output terminal 72 of the auxiliary constant voltage circuit 70 at its non-inverting input terminal. .

Diode 83 has its anode connected to the output terminal of operational amplifier 81, while diode 84 has its anode connected to the output terminal of operational amplifier 82. The cathodes of the diodes 83 and 84 are both connected to the inverting input terminals of the operational amplifiers 81 and 82, and are grounded via the resistor 85. Therefore, in the high voltage selection circuit 80, the main constant voltage Vm from the main constant voltage circuit 60 is changed to the auxiliary constant voltage Va from the auxiliary constant voltage circuit 70.
When the voltage is higher than the above, the main constant voltage Vm is selected according to both actions of the operational amplifier 81 and the diode 83, and is generated as the selection voltage Vs from the common terminal 86 (hereinafter referred to as the output terminal 86) of the diode 83 and the resistor 85. On the other hand, when the auxiliary constant voltage Va is higher than the main constant voltage Vm, the high voltage selection circuit 80 selects the auxiliary constant voltage Va according to the actions of the operational amplifier 82 and the diode 84 and generates it as the selected voltage Vs from the output terminal 86. To do. Here, since the selected voltage Vs has a low voltage value and cannot be input to the microcomputer as it is, it is necessary to input it to the voltage follower circuit 90 serving as a power feeding circuit to increase the voltage value.

The voltage follower circuit 90 includes an operational amplifier 91,
The operational amplifier 91 is connected to the output terminal 86 of the high voltage selection circuit 80 at its non-inverting input terminal. Also transistor 92
Is connected at its base to the output terminal of the operational amplifier 91. The collector of the transistor 92 is connected to the positive terminal of the battery B, while the emitter of the transistor 92 is connected to the inverting input terminal of the operational amplifier 91. It is connected to the power supply terminal 31 of the microcomputer 30. Then, the voltage follower circuit 90 generates the selection voltage Vs from the high voltage selection circuit 80 from the emitter of the transistor 92 according to the operations of the operational amplifier 91 and the transistor 92, and applies it to the microcomputer 30. In such a case, when the ignition switch IG is closed, the selection voltage Vs functions as the normal power supply voltage (which is the main constant voltage Vm in terms of voltage setting), and when the ignition switch IG is open, the selection voltage Vs is the backup power supply voltage. Function as.

In the embodiment configured as described above, the vehicle is started by closing the ignition switch IG, and the DC voltage V from the battery B is applied to the constant voltage power supply circuit Ps.
When b (see b1 in FIG. 2) is applied, the main constant voltage circuit 60 of the constant voltage power supply circuit Ps receives a DC voltage from the battery B via the ignition switch IG and the main constant voltage Vm (see FIG. 2). Input buffer circuit 20, output buffer circuit 40 and high voltage selection circuit 8
Assign to 0.

Then, the input buffer circuit 20 and the output buffer circuit 4
0 receives the main constant voltage Vm from the main constant voltage circuit 60 as the proper power supply voltage and becomes the operating state. Also, at this time,
The auxiliary constant voltage circuit 70 keeps the direct current voltage Vb from the battery B at all times.
In response to this, the auxiliary constant voltage Va is generated. Therefore, the high voltage selection circuit 80 selects the higher one of the main constant voltage Vm from the main constant voltage circuit 60 and the auxiliary constant voltage Va from the auxiliary constant voltage circuit 70 as the selection voltage Vs (reference numeral in FIG. 2). (Refer to S1) and is applied as the normal power supply voltage to the microcomputer 30 via the voltage follower circuit 90.

By the way, the selection voltage Vs to the power supply terminal 31 of the microcomputer 30 and the main constant voltage Vm to the power supply terminals 21 and 41 of the input buffer circuit 20 and the output buffer circuit 40, respectively.
Between and, for example, when ΔV = 0.3 (V),
Vs−0.5 ≦ Vm ≦ Vs + ΔV must be satisfied. Therefore, the main constant voltage circuit 60 and the auxiliary constant voltage circuit 7
Each set voltage of 0 is 5 ± 0.2, respectively, as described above.
It is set to 5 (V) and 4 ± 0.5 (V), and even if the temperature characteristics of each constant voltage circuit are taken into consideration, the voltage of the main constant voltage circuit is always higher, so the selection voltage Vs = main The constant voltage Vm results in an ideal power supply circuit. Moreover, since such an effect is achieved only by employing the high voltage selection circuit 80 and the voltage follower circuit 90 serving as a power supply circuit, the load characteristics of the main constant voltage power supply and the auxiliary constant voltage power supply,
This kind of constant voltage power supply circuit Ps is used without using a complicated compensating circuit for absorbing an output voltage fluctuation due to temperature characteristics or the like.
Can be provided at a low cost with a simple configuration.

As described above, when the main constant voltage Vm from the main constant voltage circuit 60 is applied to the input buffer circuit 20 and the output buffer circuit 40, and the selection voltage Vs from the voltage follower circuit 90 is applied to the microcomputer 30, The input buffer circuit 20 gives the detection results of the various sensors 10 as a buffer output to the microcomputer 30, and the output buffer circuit 40 causes the microcomputer 30 to output.
The calculation processing result of 1 is given to the various actuators 50 as a buffer output.

After that, when the vehicle is stopped and the ignition switch IG is opened, the main constant voltage V from the main constant voltage circuit 60 is increased.
m disappears and becomes 0 (V) (each symbol b2, m in FIG. 2)
2). Therefore, both the input buffer circuit 20 and the output buffer circuit 40 become inactive in response to Vm = 0 (V). Further, since the auxiliary constant voltage circuit 70 constantly generates the auxiliary constant voltage Va, the high voltage selection circuit 80 replaces the auxiliary constant voltage Va with the main constant voltage Vm = 0 (V) and selects the selected voltage Vs (second It is generated as a reference numeral S2 in the figure) and applied to the microcomputer 30 through the voltage follower circuit 90. In such a case, Vs = Va> 2
(V) Therefore, the selection voltage Vs functions as a backup power supply voltage of the microcomputer 30. As a result, the microcomputer 30 causes the ignition switch I
The stored data immediately before the opening of G is stored as it is even after the opening of the ignition switch IG.

Further, the circuit configuration of the high voltage selection circuit 80 may be appropriately changed and implemented as necessary.

[Brief description of drawings]

FIG. 1 is an electronic circuit diagram showing an embodiment of the present invention, and FIG.
The figure is an input / output waveform diagram of the main constituent elements in FIG. Explanation of symbols B …… Battery, IG …… Ignition switch, P
s: constant voltage power supply device, 20: input buffer circuit, 3
0 ... Microcomputer, 40 ... Output buffer circuit, 60 ... Main constant voltage circuit, 70 ... Auxiliary constant voltage circuit,
80: High voltage selection circuit.

Claims (1)

[Claims] 1. An electronic control system for a vehicle comprising a microcomputer having a backup function and electronic circuit means connected to the microcomputer, wherein a main constant voltage is generated by supplying power from a battery via an ignition switch of the vehicle. A main constant voltage power source applied to the electronic circuit means, an auxiliary constant voltage power source that is constantly fed from the battery and generates an auxiliary constant voltage lower than the main constant voltage, the main constant voltage power source and the auxiliary constant voltage source. Connected to the power supply,
A high voltage selecting means for selecting a higher voltage of the main constant voltage from the main constant voltage power supply and the auxiliary constant voltage from the auxiliary constant voltage power supply and giving it to the power supply circuit; The power supply circuit is connected between the high voltage selecting means and the microcomputer in order to apply the higher selected voltage of the applied main constant voltage and the auxiliary constant voltage to the microcomputer. A constant voltage power supply circuit for an electronic control system for a vehicle, characterized in that the battery is connected to the battery without an ignition switch.