JPH0574706B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a memory backup circuit for a vehicle internal combustion engine control device using a microcomputer that operates by receiving power from a battery.

(Prior Art) In order to electronically control the operation of a vehicle internal combustion engine, a vehicle internal combustion engine control device configured using a microcomputer is widely used. Conventional control devices of this type are configured to receive power from the battery installed in the vehicle via the ignition switch, and therefore the random access memory ( The data stored in RAM will be lost when the ignition switch is turned off. However, it is often necessary to retain data stored in RAM for a long period of time, regardless of whether the ignition switch is turned on or off.

For this reason, in the past, in order to constantly store the necessary data in the microcomputer, a RAM for memory backup was installed separately, and the RAM for memory backup was There is a known memory backup circuit which realizes a memory backup function by controlling the memory retention terminal of RAM with a separate circuit (for example, Japanese Patent Laid-Open No. 158419/1983) reference).

(Problem to be solved by the invention) However, in the conventional circuit described above, a RAM for memory backup is required, and even when the battery voltage fluctuates greatly, an appropriate drive voltage is supplied to this RAM. In order to be able to do this, a separate, expensive power supply circuit that uses many active elements is required, which makes the circuit configuration complicated and increases the price. .

Therefore, an object of the present invention is to use a microcomputer having a power saving mode terminal to
To provide a memory backup circuit for a vehicle internal combustion engine control device that is simple in configuration and highly economical, without providing a RAM and requiring a simple backup power source.

(Means for Solving the Problems) The configuration of the present invention for achieving the above object includes a battery, a switch connected to the battery,
The first power supply circuit is connected to the battery through the switch and supplies power at a predetermined rated voltage, and has a configuration that can be operated in a power saving mode by an external signal, and includes a random access memory (RAM). and a microcomputer that operates upon receiving power from the first power supply circuit, wherein the microcomputer directly connected to the battery is omitted. a second power supply circuit with a small power capacity for supplying the power necessary to operate in the power mode;
selection means responsive to each output voltage from the power supply circuit to selectively supply the higher level output voltage to the microcomputer; The present invention is characterized in that it includes a switching means for switching the microcomputer to a power saving mode when the power becomes lower than the power saving mode.

(Function) When the switch is closed and the specified voltage is supplied from the battery to the first power supply circuit,
The output voltage of the first power supply circuit is a required rated voltage. As a result, the microcomputer is switched to normal mode by the switching means. In this state, the power consumption of the microcomputer is large, so even if the output voltage of the second power supply circuit is supplied to the microcomputer, the level of the output voltage will drop due to its small capacity. Therefore, the output voltage from the first power supply circuit is selected by the selection means, and the microcomputer operates by receiving power from the first power supply circuit.

If the level of the output voltage of the first power supply circuit decreases due to deterioration of the battery performance or the switch is opened, and it becomes impossible to continue the normal operation of the microcomputer, the switching means is activated and the microcomputer is switched to power saving mode. In this case, of course, the output voltage from the second power supply circuit is higher than the output voltage from the first power supply circuit, so the microcomputer is maintained in its operating state by the output voltage from the second power supply circuit. . Therefore, even if the switch is turned off, the data in the RAM in the microcomputer is retained by the output voltage from the second power supply circuit, and the memory backup function is realized.

(Embodiment) The drawings show a block diagram of an embodiment of a memory backup circuit for a vehicle internal combustion engine control device according to the present invention. Reference numeral 1 indicates a microcomputer that is one of the main components of a vehicle internal combustion engine control device (not shown).
This microcomputer 1 is equipped with a random access memory (RAM) 2 inside and is configured to operate in a power saving mode depending on the level of the voltage applied to its input terminal 3. In the illustrated embodiment, when the level of the input terminal 3 is "L", the microcomputer 1 operates in the normal operation mode in which it operates at the rated power consumption,
On the other hand, when the level of the input terminal 3 is "H", the microcomputer 1 operates in the power saving mode.

Battery 4 mounted on a vehicle (not shown)
The negative pole is grounded, and the positive pole is connected to the main power supply circuit 6 via the ignition switch 5. The main power supply circuit 6 is a circuit that outputs a predetermined constant voltage stabilized based on the input voltage supplied from the battery 4 when the ignition switch 5 is formed. The output voltage V ₁ from the main power supply circuit 6 is supplied as a power supply voltage to the microcomputer 1 via a selection circuit 11 which will be described later.

When the ignition switch 5 is opened and the power supply from the main power supply circuit 6 to the microcomputer 1 is stopped, the RAM2 memory To perform the backup, the microcomputer 1 is equipped with a memory backup circuit according to the invention. The memory backup circuit is designated by the symbol 1 in the drawing.
0, it has a backup power supply circuit 12 to which the voltage of the battery 4 is directly applied so that the backup voltage can be supplied to the microcomputer 1 regardless of whether the ignition switch 5 is opened or closed. are doing. The backup power supply circuit 12 is made up of a constant voltage diode 13 and a resistor 14 connected as shown in the figure, and the constant voltage output generated across the constant voltage diode 13 is outputted as the output voltage V ₂ of the backup power supply circuit 12 and selected. applied to circuit 11.

The selection circuit 11 is made up of diodes 15 and 16 connected as shown, and output voltages V ₁ and V ₂ are applied to the anodes of the diodes 15 and 16, respectively. The cathodes of the diodes 15 and 16 are connected in common to the power input terminal 7 of the microcomputer 1. Microcomputer 1
The other power supply input terminal 8 is connected to the output common line 17 of the main power supply circuit 6 . Therefore, the selection circuit 11 selects the output voltage with a higher level and supplies it to the microcomputer 1.

In order to detect that the level of the output voltage V ₁ has decreased for some reason and has fallen below a predetermined level La at which normal operation of the microcomputer 1 cannot be guaranteed, a voltage is applied to the output side of the main power supply circuit 6. is provided with a level detector 18 that operates in response to the output voltage _V1 , and when the level of the output voltage _V1 falls below the above-mentioned level La, the level detector 18 detects the level of the output line 18a. is set to the "H" level. Output line 1
8a is connected to the microcomputer 1, and the microcomputer 1 responds to the change in the level of the output line 18a from "L" to "H", that is, when the level of the output voltage _V1 becomes lower than the level La. The output line 9
change the level from "L" to "H".

Output line 9 is an R-S flip-flop (F/
F) is connected to the set input terminal S of 19.
The reset input terminal R of the R-S flip-flop 19 is connected to the output side of the ignition switch 5, and the level of the reset input terminal R changes when the ignition switch 5 is switched from the off state to the on state. changes from "L" to "H" and the R-S flip-flop 19 is reset. Thereafter, when the level of the reset input terminal S changes from "L" to "H", the R-S flip-flop 19 is set, and the level of the output voltage _VQ of the Q output terminal changes from "L" to "H". H”. The output voltage V _Q is applied to the input terminal 3 of the microcomputer 1. Therefore, when the R-S flip-flop 19 is set, the level of the input terminal 3 is held at "H", and the microcomputer 1 is It will be latched into power saving mode.

When the microcomputer 1 enters the power saving mode, its power consumption is small, and therefore, the microcomputer is in a state where its operating state can be maintained by the output voltage V ₂ from the backup power supply circuit 12 having a small power capacity.

Next, the memory backup circuit 1 shown in the drawing is
The operation of 0 will be explained.

When the key switch 5 is turned on, the main power circuit 6
Since power is supplied from the battery 4, the output voltage _V1 is output, and is applied to the selection circuit 11 to which the output voltage _V2 is applied regardless of whether the switch 5 is open or closed. At this time, in response to the ON operation of switch 5, R-S flip-flop 1
9 is reset, the level of the output voltage _VQ is "L", and therefore the microcomputer 1 is in the normal mode. As a result,
Since the power consumption of the microcomputer 1 is larger than the power supply capacity of the second power supply circuit 12, if the battery 4 and the main power supply circuit 6 are normal, the output voltage
V ₁ is higher than the output voltage V ₂ , so the microcomputer 1 operates by receiving power from the main power supply circuit 6 .

In the above state, when the level of the output voltage _V1 decreases to below the predetermined level La due to the switch 5 being opened, etc., the level of the output line 18a becomes "H" and the R-S flip-flop 19 becomes "H". is set, and the microcomputer 1 is switched to the power saving mode. In this case, V ₂ >V ₁ , and therefore, the output voltage V ₂ is selected by the selection circuit 11, and the microcomputer 1 operates in the power saving mode using the output voltage V ₂ . As a result, even if the main power circuit 6 becomes inoperable,
The stored contents of RAM2 are backup power supply circuit 1
2, the data in the RAM 2 can be reliably retained regardless of whether the key switch 5 is opened or closed.

(Effects) According to the present invention, by using a microcomputer that can be switched to operate in a power saving mode,
When the output voltage level from the main power supply falls below a predetermined level, the microcomputer is put into power saving mode and continues to operate using a small power capacity backup power supply directly connected to the battery. Therefore, there is no need to provide backup RAM outside the microcomputer as in the past, and the backup power supply has a simple configuration, greatly reducing manufacturing costs without compromising the reliability of the device. It has an excellent effect in that it can be gradually reduced.

[Brief explanation of the drawing]

The drawing is a block diagram showing an embodiment of a memory backup circuit for a vehicle internal combustion engine control device according to the present invention. 1...Microcomputer, 2...RAM,
4... Battery, 5... Ignition switch, 6... Main power supply circuit, 10... Memory backup circuit, 11... Selection circuit, 12... Backup power supply circuit, 18... Level detector, 19... …
R-S flip-flop, V ₁ , V ₂ ...output voltage.

Claims (1)

[Claims] 1 A battery, a switch connected to the battery, a first power supply circuit connected to the battery via the switch and supplying power at a predetermined rated voltage, and operated in a power saving mode by an external signal. In the memory backup circuit for a vehicle internal combustion engine control device, the memory backup circuit includes a microcomputer that is configured to have a random access memory and is operated by receiving power from the first power supply circuit. a second power supply circuit directly connected to the microcomputer and having a small power capacity for supplying the power necessary for the microcomputer to operate in a power saving mode, and responsive to each output voltage from the first and second power supply circuits. selecting means for selecting an output voltage with a higher level and supplying the selected output voltage to the microcomputer; 1. A memory backup circuit for a vehicle internal combustion engine control device, comprising: switching means for switching the engine to a power saving mode.