JPH0145233Y2 - - Google Patents

Description

[Detailed Description of the Invention] Technical Field of the Invention The present invention relates to a power supply device for an automobile control device equipped with a RAM for data retention.

Conventional technology and problems When microcomputers are used as in-vehicle control equipment, it is possible to achieve various types of control that were not possible before, and to improve their accuracy.In particular, in order to aim for higher-grade technology, microcomputers are equipped with a learning function that takes into account changes in various data over time. In some cases, rewritable memory (RAM) is required. However, since RAM is volatile, standby current must be supplied from the backup power supply even after the ignition switch is turned off.

Figure 1 is a configuration diagram of a conventional power supply device for automotive control equipment, where 1 is a microprocessor (MPU) for controlling the engine, 2 is a regulator that creates the stabilized power supply Vcc, and 3 is a normally-off main relay. , 4 is a battery, 5 is a fuse, and 6 is an ignition switch. The engine control unit (ECU) is integrated on the right side of the dashed line in the figure, and is installed in a separate location from the power supply block PSU on the left side. The two are connected by various wires, but conventionally, the first wire +B is connected to the contact 3a of the relay 3, the second wire MARL is connected to the coil 3b, and the ignition wire switch 6
In addition to the third wire IGSW, which is connected to the IGSW, there is a fourth wire STBY dedicated to standby. In this case, the ground line GND is used as the body ground, so there is no need to lay it as a wire.

The general operation will be explained. When the ignition switch 6 is turned on, a base current flows to the npn type driver transistor Tr ₂ through the diode D ₁ and the resistor R ₁ . As a result, when the transistor Tr ₂ is turned on, current flows from the battery 4 to the coil 3b of the relay 3, turning on the contact 3a. When this contact 3a turns on, the PNP transistor Tr ₁ of the regulator 2
Normal operating power is supplied to the MPU 1 through the MPU 1.
When MPU1 starts, resistor R ₄ is applied from its output port.
It starts sending a signal to turn on the transistor Tr ₂ through the transistor Tr2, and also starts operating according to a predetermined control program. This operation is, for example, engine speed control, but one of them is the built-in data storage.
This includes the ability to appropriately modify control data in RAM using a learning function.

Eventually, when the ignition switch 6 is turned off to stop the engine, the on signal of the transistor Tr ₂ from the wire IGSW disappears.
The MPU 1 monitors this change from the input port through the resistor R ₃ and the inverter 7, and after performing certain processing, stops the ON signal (for the transistor Tr ₂ ) at the output port. As a result, the transistor Tr ₂ is turned off, the relay 3 is turned off and its contact 3a is opened, and the power supply Vcc to the MPU 1 is also turned off. However, a backup current (several tens of μA) is applied directly to the standby terminal (STBY) of MPU1 via the standby wire STBY.
~ mA) is supplied, so the data in the data retention RAM described above is saved without being lost.
Note that C ₁ to _{C 3} are capacitors for noise removal, VS is a varistor for surge absorption, and D ₂ and D ₃ are Zener diodes.

By the way, with the above-mentioned power supply device, it is necessary to install a dedicated standby wire STBY, which complicates the wiring harness, increases the chance of wires getting caught and disconnected, and reduces system reliability. There is.

Purpose of the invention The present invention aims to simplify the wiring harness by omitting the standby-only wire, and to improve the reliability of the system accordingly.

Structure of the invention The present invention includes a battery, an ignition switch and a main relay for extracting current from the battery in two systems on the power supply block side, a microprocessor for control, a regulator for its operating power supply, and a main relay. The driver transistor for the relay is installed on the automotive control equipment block side,
A first wire connects the contacts of the main relay and the regulator, a second wire connects the coil of the relay and the drive end of the driver transistor, and a second wire connects the contacts of the main relay and the regulator. A third wire connects the control input terminal of the driver transistor and the control input switch to the driver transistor so that the transistor can also be driven from the output port of the microprocessor, and the potential habit of the third wire is changed. In the power supply device for an automobile control device, the ignition switch is monitored at an input port of the processor to detect whether the ignition switch is turned off, the OR circuit extracting the highest potential of the first to third wires; A capacitor charged by the output of the OR circuit is provided on the control equipment block side, and a standby current for backup memory is supplied from a connection point between the capacitor and the OR circuit to the standby terminal of the microprocessor. This will be described in detail below with reference to the illustrated embodiments.

Embodiment of the Invention FIG. 2 is a circuit diagram showing an embodiment of the invention, in which the same parts as in FIG. 1 are given the same reference numerals. This example differs from FIG. 1 in three points. The first is that the standby dedicated wire (STBY in Figure 1) has been abolished, and the second is that the remaining three wires IGSW,
MARL, +B to MPU1 standby terminal
An OR circuit is configured with diodes D ₄ to _{D 6} to supply standby current to STBY.
The third is a Zener diode (first
This is the point where D ₂ ) in the figure has been omitted. In this case, diodes D ₄ and D ₆ can be replaced with resistors,
Also, transistor Tr ₁ and regulator 2
If there is a function to prevent leakage from the MPU1 side (especially its internal RAM), diode _D5 can also be replaced with a resistor.

The operation will be explained below with reference to the time chart shown in FIG. The circuit shown in Figure 2 is intended to supply standby current from the IGSW line while the ignition switch 6 is on, and from the +B line or MARL line when the switch is turned off. However, in reality, it is predicted that there will be a state in which no current is applied from any of the diodes D ₄ to D ₆ during a part of the period T ₁ and T ₅ , so the capacitance of the capacitor C ₂ is increased to cover that part. I need to get through it.
According to actual measurements, C ₂ =47 μF is sufficient. _T1 is the period during which chatter occurs in the IGSW line after the switch 6 is turned on manually until the potential stabilizes.
Variations occur in the timing at which power is applied to the MARL line. Therefore, period T ₁ is line MARL,
There is a possibility that both IGSW will be de-energized (+B is originally de-energized). The following period T ₂ is a time delay from when the coil 3b of the relay 3 is energized until the contact 3a is made, and during this period, the diode D ₄
Current is supplied from the IGSW line to the standby terminal STBY. During the next period _T3 , the contact 3a is completely closed, so a standby current flows from the +B line through the diode _D5 or from the IGSW line through the diode _D4 to the terminal STBY.

Eventually, when ignition switch 6 is turned off, a chattering effect appears on the IGSW line, and then the current from diode D ₄ disappears.
Since the MPU 1 continues to output the ON signal of the transistor Tr ₂ for the duration T ₄ , the relay 3 continues to be ON, and a standby current is supplied from the +B line to the terminal STBY through the diode D ₅ . period after this
At _T5 , the same state as energized continues for a while due to the surge current when relay 3 is off, but on the other hand, there is a period in which there is a delay in the coercive force of relay 3 and the break of contact 3a.
It is predicted that a state in which all lines will not be energized again will occur during the overlap period with _T6 . These two non-conducting periods are each compensated for by discharging capacitor _C2 . After this the diode
Standby current is supplied from the MARL line through _D6 . In this case, the current is passed through the coil 3b of the relay 3, but the standby current is on the order of less than mA, so the resistance of the coil 3b (several 10
~100Ω) can be ignored.

In addition, the back electromotive force (several 100 V) of main relay 3 is
Since it is applied between the collector and emitter of transistor Tr ₂ (withstand voltage: 10V) through the MARL line, in Figure 1, a Zener diode D ₂ is connected between the collector and base of transistor Tr ₂ to absorb this. In this example, the path from the MARL line to the varistor VS is formed by the diode D ₆ , so the surge caused by the main relay 3 is absorbed by the varistor VS, and the Zener diode D ₂ as shown in Figure 1 is not necessary. It will no longer be.

Effects of the invention As described above, according to the invention, a wire dedicated to standby RAM is no longer required by simply adding a simple circuit element, which simplifies the wiring harness and reduces the incidence of disconnections. system reliability. Additionally, the addition of the above-mentioned circuit elements has the advantage that a dedicated Zener diode for absorbing main relay surges is not required.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a conventional automobile control device and its power supply device, FIG. 2 is a circuit diagram showing an embodiment of the present invention, and FIG. 3 is an operating waveform diagram thereof. In the figure, 1 is a microprocessor equipped with data retention RAM, 2 is a regulator, 3 is a main relay, 3a is its contact, 3b is a coil, 4 is a battery, 6 is an ignition switch, Tr ₂ is a driver transistor, STBY is the standby terminal, C ₂
is a capacitor, D ₄ to _{D 6} are diodes for the OR circuit, and +B, MARL, and IGSW are each wire.

Claims (1)

[Claims for Utility Model Registration] A battery, an ignition switch and a main relay for extracting current from the battery in two systems are provided on the power supply block side, and a microprocessor for control, a regulator for its operating power supply, and a A driver transistor for the main relay is provided on the side of the automobile control equipment block, and a first wire connects the contacts of the main relay and the regulator, and a coil of the relay and a drive end of the driver transistor are connected. between the second
A third wire connects the ignition switch and a control input terminal of the driver transistor, and the transistor can also be driven from an output port of the microprocessor; Further, in the power supply device for an automobile control device, the potential change of the third wire is monitored at the input port of the processor to detect whether the ignition switch is turned off. An OR circuit for extracting the highest potential and a capacitor charged by the output of the OR circuit are provided on the control equipment block side, and a connection point between the capacitor and the OR circuit is connected to the standby terminal of the microprocessor for backup memory. A power supply device for automotive control equipment, characterized in that it supplies a standby current of .