JPH0775456B2 - Power supply device for electronic equipment mounted on automobile - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is equipped with an electronic device such as a one-chip microcomputer, and a power supply for an electronic device mounted on a vehicle in which a backup power supply is set in the microcomputer or the like. Regarding the device.

[Prior Art] An automobile is equipped with various electronic control devices for various driving control or traveling control, and the electronic device is, for example, a device configured by using a one-chip microcomputer. Is often used.

In general, electronic devices mounted on a vehicle are supplied with power in a state where an ignition switch is turned on. However, in the one-chip microcomputer, in order to supply power to the built-in backup RAM, the auxiliary power supply circuit connected directly from the battery is set without passing through the ignition switch,
Power is supplied from this auxiliary power supply circuit to the power supply terminal of the microcomputer.

When the auxiliary power supply is set in this way, for example, if the power supply is momentarily cut off at the connection terminal of the battery, the power supply of the microcomputer and its peripheral devices will start up at the same time when the power supply is restored. However, the power supply for the peripheral device rises substantially quickly, and the power supply voltage for the peripheral device becomes higher than the input voltage of the microcomputer at a certain point.

Then, when the input voltage of the peripheral device becomes higher than the input voltage of the microcomputer by exceeding a predetermined value (for example, 0.3 V), a latch-up phenomenon occurs, which causes a failure in the microcomputer.

[Problems to be Solved by the Invention] The present invention has been made in view of the above points, and has a problem that an input voltage of a peripheral device becomes higher than an input voltage of a microcomputer due to a momentary interruption of a battery power source or the like. It is intended to provide a power supply device for an electronic device mounted on a vehicle, which solves the above problem and ensures that a microcomputer and the like can be protected without causing a latch-up phenomenon even if there is a momentary interruption in the battery power supply. is there.

[Means for Solving the Problems] In the power supply device for an automobile-mounted electronic device according to the present invention, the first power supply circuit is set so as to be directly connected to the battery without an ignition switch, and A second power supply circuit is set so as to be connected to the battery via the ignition switch, and power is supplied from the first power supply circuit to the microcomputer. Then, when the output voltage from the second power supply circuit rises above the set value of the output voltage of the first power supply circuit, the output voltage of the second power supply circuit is controlled. There is.

[Operation] In the power supply device configured as described above, the voltage applied to the peripheral device is higher than the voltage applied to the microcomputer when the power supply is restored due to a momentary interruption of the battery power supply or the like. If the voltage exceeds the set voltage and becomes high, the output voltage of the second power supply circuit is prevented from rising greatly exceeding the output voltage of the first power supply circuit. Therefore, the occurrence of the latch-up phenomenon is surely prevented, the failure of the microcomputer is easily and surely prevented, and the reliability of the vehicle-mounted electronic device can be further improved. Like

[Embodiment of the Invention] An embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 shows the circuit configuration, in which a first power supply circuit 12 is directly connected to a battery 11 mounted in an automobile, and a second power supply circuit 14 is further connected via an ignition switch 13. Are connected.

The first power supply circuit 12 is connected in series to the first power supply line 121, and the transistor 122 that constitutes the first voltage adjusting means for adjusting the voltage of the first voltage V _S to the power supply line 121.
And a transistor 1 controlled by an output from an operational amplifier 123 that receives the voltage of the first power supply line 121 as an input.
The transistor 122 is controlled by 24. The operational amplifier 123 is supplied with the voltage signal from the operational amplifier 126 set by the reference power supply 125. And
The power supply of the first power supply voltage V _S generated by the first power supply circuit is supplied to the one-chip microcomputer 15 as the input power supply V _DD .

The second power supply circuit 14 includes a transistor 142 that is connected in series to the second power supply line 141 and that constitutes a second voltage adjusting unit that adjusts the second voltage V _M on the power supply line 141. Then, the transistor 142 controlled by the operational amplifier 143 that detects the voltage of the second power supply line 141 controls the transistor 142 so that the second power supply voltage V _M is obtained. The voltage V of this second power supply line 141
_M is supplied as a power source to the peripheral device of the microcomputer 16.

The microcomputer 15 is used, for example, for engine control, and a detection signal from sensors 16 such as an intake air amount sensor, a rotation speed sensor, a throttle opening sensor, an air-fuel ratio sensor, and a cooling water temperature sensor is stored in the buffer 17. The control signal which is arithmetically processed based on these input data is supplied to the engine control means 19 through the buffer 18.

The second power supply line 141 is connected to the data input line and output line of the microcomputer 15 via pull-up resistors 20 and 21, respectively, and is also connected to the buffer 18 as a power supply.

A voltage control circuit 22 is provided for such first and second power supply circuits 12 and 14. This voltage control circuit 22
In, the operational amplifiers 221 and 222 and the resistors R1 to R4 form a differential amplifier circuit. And operational amplifier
The second power supply voltage V _M is input to the non-inverting input terminal of 221 and the predetermined voltage V _R is input to the non-inverting input terminal of the operational amplifier 222,
The voltages V _M and V _R are differentially amplified. Therefore, the output V _O from the operational amplifier 221 becomes V _O = 2 × (V _M −V _R ), and this voltage V _O is divided into 1/2 by the resistors R5 and R6 having the same value, and the inverted value of the comparator 223 is inverted. Supply to the input terminal.

The first power supply voltage V _S is input to the non-inverting input terminal of the comparator 223 to form a voltage state detecting means. The output of the comparator 223 is V _M −V _R > V _S. It will be set to "L" level.

The output signal from the comparator 223 controls the base of the transistor 144 of the second power supply circuit 14 and controls to reduce the output voltage from the second power supply circuit 14.

FIG. 2 shows that the terminal of the battery 11 is instantaneous (for example, several hundreds).
For example, the behavior of the first power supply voltage V _S and the second power supply voltage V _M in the case of contact failure due to vehicle vibration or the like and a momentary disconnection during msec) is shown.

First, it is assumed that the battery 11 is momentarily disconnected at time t1 in FIG. 2A, a contact failure occurs during the period t2, and then the battery 11 is restored. Here, when the resistance of the load to which the second power supply voltage is supplied is smaller than that of the load to which the first power supply voltage is supplied, the capacitance of the capacitor to be inserted between these power supplies and the ground point. And the load resistance, the first and second power supply voltages perform discharging and charging operations. That is, the first and second power supply voltages V _S and V _M varies as shown in of FIG. 2 (B), in the portion shown in this figure by hatching, than the first power supply voltage difference V _S The second power supply voltage V _M becomes higher.

In such a state, the microcomputer 15 will be lower than the power supply voltage of the one-chip microcomputer 15.
The input signal voltage of is increased and a latch-up phenomenon occurs. Therefore, the power consumption of the microcomputer 15 suddenly increases, and the microcomputer 15
The problem occurs that 15 is destroyed by heat.

However, in the apparatus shown in the embodiment, as shown in of FIG. 2 (C) than the first supply voltage V _S second
When the power supply voltage V _M becomes high, the second power supply voltage is controlled to lower the second power supply voltage. Then, the latch-up phenomenon is prevented from occurring.

Here, the latch-up phenomenon is a mode in which a power supply and a ground point are generally close to a short-circuited state, and one of the causes is a state in which the input voltage is higher than the power-supply voltage of the microcomputer, for example. Then, it is likely to occur. Then, once the latch-up phenomenon occurs, this state continues until the current of the microcomputer is turned off, and the microcomputer eventually fails due to heat generation.

That is, in the voltage control circuit 22 of the power supply device shown in FIG. 1, assuming that the operational amplifiers 221 and 222 form a differential amplifier circuit and the resistance values of the resistors R1 to R4 are all the same value, this differential The output from the amplifier circuit is
The difference between the “input voltage of 221” and the “input voltage of operational amplifier 222” is doubled.

Therefore, when the second power supply voltage V _M is supplied to the input terminal of the operational amplifier 221 and a predetermined voltage (for example, 0.3 V) is input to the input terminal of the operational amplifier 222, 2 × (second power supply voltage V _M −0.3 V) Is output and this output voltage is divided by resistors R5 and R6
It will be divided into two. Therefore, the comparator 223
The voltage obtained by subtracting 0.3 V from the second power supply voltage V _M is input to the inverting input terminal of.

The non-inverting input terminal of the comparator 223, in which the first power supply voltage V _S is input, therefore V _M -V _S> When the 0.3V state, the output of the comparator 223 is "L" level It is said that

Therefore, the base potential of the transistor 144 of the second power supply circuit 14 is set to the low level, the transistor 144 is turned off, and the second power supply voltage is lowered. That is, as shown in of FIG. 2 (C), is as a second power supply voltage is V _M is prevented to be raised higher than the first power supply voltage V _S, the microcomputer 15
Is surely protected.

[Effects of the Invention] As described above, according to the power supply device for an on-vehicle electronic device of the present invention, even if the terminal portion of the battery is loosened due to vibration of the vehicle body or the like, the power supply is momentarily cut off. , The power supply voltage from the second power supply circuit supplied to the peripheral equipment of the microcomputer becomes higher than necessary than the power supply voltage from the first power supply circuit constantly supplied to the microcomputer. Is certainly prevented. Therefore, the occurrence of the latch-up phenomenon is surely prevented, and the reliability of the vehicle-mounted electronic device is surely improved.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram for explaining a power supply device for an automobile-mounted electronic device according to an embodiment of the present invention, and FIG. 2 is a diagram for explaining behavioral states of first and second power supply voltages in this kind of power supply device. It is a figure. 11 ... Battery, 12 ... First power supply circuit, 13 ... Ignition switch, 14 ... Second power supply circuit, 15 ... Microcomputer (one chip), 16 ... Sensors, 19
...... Engine control means, 22 ...... Voltage control circuit.

Claims (2)

[Claims] 1. A battery mounted on an automobile is directly connected to the vehicle, and is configured to include a first voltage adjusting means for adjusting an output voltage from the battery, and a first voltage adjusting means. Is connected to the battery via an ignition switch and a second power supply circuit for controlling the output voltage from the battery. A second power supply circuit configured to include a voltage adjusting means and the second voltage adjusting means, controlling the second voltage adjusting means to supply power to the peripheral circuit section of the computer; and the first power supply circuit. The output voltage from the power supply circuit is compared with the output voltage from the second power supply circuit, and the output voltage of the second power supply circuit is set to a value set by the output voltage from the first power supply circuit. Over Voltage state detecting means for detecting a high voltage state, and the output voltage of the second power supply circuit is set to be higher than the output voltage of the first power supply circuit based on the detection signal from the voltage state detecting means. And a voltage control means for suppressing the output voltage from the second power supply circuit by controlling the second voltage adjusting means so as not to become higher than the predetermined value. Power supply. 2. The voltage state detecting means includes a voltage value setting means for setting the set value, and the voltage control means controls the output voltage of the first power supply circuit and the second power supply circuit. 2. The power supply device for an on-vehicle electronic device according to claim 1, wherein a state in which a difference between the output voltage and the output voltage exceeds the value set by the voltage value setting means is detected.