JP2002188499A - Engine control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an engine control device capable of lessening the fluctuation in output voltage of a regulator, when a battery voltage is reduced. SOLUTION: This engine control device having the regulator for converting the battery voltage to the operation potential level of a calculation device has further a means for controlling the load of the regulator, when the battery voltage is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine control device, and more particularly to an engine control device capable of reducing fluctuations in the output voltage of a switching regulator when the voltage of a battery drops.

[0002]

2. Description of the Related Art A vehicle on which an engine is mounted is provided with various electronic devices such as an engine control device and the like. It is connected to the.

Here, in the engine control device, the heat generation of the circuit increases with the increase in the voltage of the battery, which makes it difficult to reduce the size and weight of the engine control device. There has been proposed a technology of an engine control device configured by connecting a regulator in series (for example, see Japanese Patent Application Laid-Open No. 5-79398). In addition, the applicant has a linear regulator that converts the voltage of the battery to the operating potential level of the arithmetic unit (CPU) of the engine control device. When the voltage of the battery drops, the output voltage of the linear regulator is monitored. An invention has been proposed in which the operation of the CPU is completely stopped based on the output voltage. As for another engine control device having a switching regulator, see Japanese Patent Laid-Open No. 5-381.
No. 38, JP-A-7-283797, JP-A-5
It has been proposed in, for example, JP-A-127765.

[0004]

In recent years, CPUs have been required to have higher functions and higher speeds due to the multi-functionality of the engine control device. Electricity is also increasing. Further, the engine control device is generally mounted in a vehicle compartment, but it is considered that a recent engine control device is mounted in an engine room in order to reduce a vehicle harness or the like.

However, considering the temperature environment in the engine room, the heat generated from the engine control device must be minimized. Therefore, in order to realize the mounting in the engine room of the engine control device while responding to the increase in the current consumption of the CPU, a switching regulator having higher efficiency and lower heat generation than the linear regulator is used as the regulator. Is desired.

On the other hand, when the engine is started, the voltage of the battery is greatly reduced, and the power supply in the engine control device using the voltage as a power supply is naturally reduced to be in an unstable state. In particular, since a large radiation noise is generated when the battery voltage drops, there is a problem that the use of this switching regulator makes the power supply in the engine control device more unstable.

That is, the present inventor has found that in an engine control apparatus having a switching regulator as a regulator for converting a battery voltage to an operating potential level of a CPU, there is some means for suppressing radiation noise when the battery voltage drops. New knowledge has been obtained that it is necessary to take measures and to reduce fluctuations in the output voltage from the switching regulator.

However, the prior art aims at miniaturizing an engine control device, preventing a malfunction of a CPU, or attenuating radiation noise due to switching with an electrolytic capacitor or the like. No particular consideration is given to reducing the load current and reducing the fluctuation of the output voltage of the switching regulator. The present invention has been made in view of such a problem, and an object of the present invention is to provide an engine control device capable of reducing a fluctuation in an output voltage of a switching regulator when a battery voltage decreases. It is in.

[0009]

In order to achieve the above object,
The engine control device of the present invention is basically an engine control device having a regulator that converts a voltage of a battery into an operation potential level of an arithmetic device, and the control device includes:
The power supply system further comprises means for controlling the load of the regulator when the voltage of the battery decreases.
In the engine control device according to the present invention configured as described above, the load current generated in the regulator is reduced by the means for controlling the load of the regulator when the voltage of the battery is low. Can be suppressed, noise can be suppressed, and processing by the arithmetic unit can be performed reliably.

In a specific aspect of the engine control device according to the present invention, the regulator is a switching regulator, or the means for controlling the load of the regulator outputs an output voltage from the regulator to the arithmetic device. Having another regulator for converting to an operating potential level, or means for controlling the load of the regulator, is provided for supplying the operating potential level to the arithmetic unit by the other regulator when the voltage of the battery decreases. To stop, or the control device, between the battery and the arithmetic device,
It is characterized in that it has a further regulator connected in parallel with the other regulator.

In another specific aspect of the engine control device of the present invention, the means for controlling the load of the regulator includes a means for outputting an interrupt signal to the arithmetic unit based on an output signal from the regulator. Means for outputting a reset signal to the arithmetic device based on an output signal from the means for outputting the interrupt signal, and outputting a standby signal to the arithmetic device based on an output signal from the means for outputting the reset signal. Means, or means for outputting an interrupt signal to the arithmetic device, has a threshold of a voltage smaller than a ripple voltage generated in the regulator, and based on the threshold and an output voltage from the regulator. Means for outputting an interrupt signal to the arithmetic unit or controlling the load of the regulator, Apparatus based on an output signal from the means for outputting an interrupt signal to, is characterized by outputting a signal for stopping the supply of operating potential level to the computing device to the other regulators. Further, the control device is disposed in an engine room of the vehicle.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of an engine control device according to the present invention will be described in detail with reference to the drawings. FIG.
1 shows the overall configuration of an engine control system including the engine control device 1 of the present embodiment. The engine control device 1 includes a switching regulator 10, a computing device (CPU) 11, and the like, and is arranged in an engine room of a vehicle.

The engine control device 1 includes at least a rotation signal 2a from an engine rotation sensor 2 for detecting the number of rotations of the engine 6, and an air amount signal 3a from an air flow sensor 3 for detecting the amount of air taken into the cylinder of the engine 6. , The CPU 11 calculates at least the fuel injection amount and the ignition timing supplied to the engine 6, and based on the result, the fuel injection device 4 and the ignition device 5
Control.

The output voltage of the battery 7 for supplying power to the engine control device 1 and the starter motor 8 is generally 14 V, but the I / O interface of the CPU 11 set in the engine control device 1 is 5 V. Therefore, in the engine control device 1, the switching regulator 10 converts the battery voltage 14V to the operating potential level 5V of the CPU 11, as described later.

The switching regulator 10 has higher efficiency and lower heat generation than the conventional linear regulator in order to cope with the fact that the engine control device 1 is mounted in the engine room and the power consumption of the CPU 11 increases. It is. That is, considering the loss in the conventional linear regulator, the battery voltage 14
When generating the 5V output for use in the engine control device 1 from V, when the load current 500mA, loss P _R of the linear regulator is as shown in equation (1).

[0016]

P _R = (14V−5V) × 500mA = 4.5W (1) Therefore, when the heat resistance of the heat radiating portion is 10 ° C./W, the calorific value ΔT _R is expressed by the following equation (2). It is.

[0017]

[Number 2] _{ΔT R = 4.5W × 10 ℃ /} W = 45 ℃ (2) Therefore, when operating in an environment of ambient temperature Ta = 95 ° C., the temperature _{T R} of the linear regulator, the formula It is shown as (3).

[0018]

T _R = Ta + ΔT _R = 95 ° C. + 45 ° C. = 140 ° C. (3) Therefore, the semiconductor chip junction temperature Tj = 150
It can be seen that there is almost no room for ° C.

Therefore, it is understood that the engine control device 1 can be arranged in the engine room by employing the switching regulator 10 which can realize a loss of generally 10 to 20% as compared with the linear regulator.

On the other hand, when the engine 6 is started, the starter motor 8 powered by the battery voltage signal 7a is started, and the voltage of the battery 7 is greatly reduced. As the voltage decreases, the 5V power supply in the engine control device 1 that uses the voltage of the battery 7 as a power supply naturally decreases. That is, the engine control device 1 enters an unstable state.

In order to prevent this, even if the voltage of the battery 7 drops, it is necessary to minimize the fluctuation of the 5V power supply in the engine control device 1. However, a switching regulator 10 having radiation noise due to switching is used. As a result, the effect of the battery voltage drop is greater than that of the conventional linear regulator. Therefore, in the engine control device 1 according to the present embodiment, as described later, the fluctuation of the 5V power supply is minimized to achieve the stabilization. When the voltage of the battery 7 decreases, the voltage is supplied via the switching regulator 10 and another regulator 13.
3V system voltage is stopped.

FIG. 2 shows the CPU 1 in the engine control device 1.
1 is shown. The engine control device 1 basically includes a switching regulator 10 that converts the voltage of the battery 7, a CPU 11 that operates at the converted potential level, and a switching regulator 10 that operates when the voltage of the battery 7 decreases. And a load control means 12 for controlling a load. The load control means 12 outputs the output voltage from the switching regulator 10 to the CPU 1.
It has another regulator 13 for converting the operating potential level to one. Further, the engine control device 1 has another regulator 17 connected in parallel between the battery 7 and the CPU 11 to the other regulator 13. The 14 V voltage of the battery 7 is supplied to the 5 V power signal 10 a via the switching regulator 10.
Is converted to a 3.3V power signal 13a via the regulator 13, and then transmitted to the CPU 11. That is, the CPU 11
Has a two power supply configuration of 5V power supply and 3.3V power supply in view of reduction in power consumption and reduction in breakdown voltage due to chip shrink.

Then, the engine control device 1 of the present embodiment
Converts the 14 V voltage of the battery 7 into a 3.3 V power signal 17 a by the regulator 17 and sends it to the CPU 11. The 3.3 V power signal 17
a and 3.3V power signal 13 by the regulator 13
“a” is appropriately switched based on a signal from the load control means 12.

The load control means 12 includes, in addition to the other regulator 13, a means 14 for outputting an interrupt signal NMI to the CPU 11 based on an output signal from the switching regulator 10, and a means 1 for outputting the interrupt signal.
4 for outputting a reset signal RES to the CPU 11 based on an output signal 14a from the CPU 4 and a CP based on an output signal 15a from the means 15 for outputting the reset signal.
Means for outputting a standby signal STBY to U11.

Means 14 for outputting interrupt signal NMI
Has a threshold of a voltage smaller than a ripple voltage generated in the switching regulator 10 while detecting the output voltage VCC from the switching regulator 10 in order to prevent a malfunction of the CPU 11 due to a voltage drop of the 5V power supply 10a. An interrupt signal 14a is output to the CPU 11 based on the threshold and the output voltage VCC.

The means 15 for outputting the reset signal RES stops the operation program group of the CPU 11 such as the fuel injection amount and the ignition timing.
The means 16 for outputting BY sets the mechanical equipment of the CPU 11 in a low power consumption state.
6a is output to the regulator 13 which outputs the 3.3V power signal 13a.

That is, the engine control device 1 of the present embodiment
When the voltage of the battery 7 decreases, that is, when the 5 V output voltage VCC of the switching regulator 10 decreases, the CPU 11 is configured to synchronize the regulator 13 of the 3.3 V power supply with the means 16 for outputting the standby signal STBY. At the same time as the standby state, the supply from the regulator 13 to the CPU 11 is stopped, and the output is switched from the 3.3 V power supply regulator 17 to the CPU 11 so that the load current generated in the switching regulator 10 is reduced. The output voltage VCC of the switching regulator 10 is prevented from lowering. More specifically, when the voltage of the battery 7 decreases due to the start of the starter motor 8, radiation noise may be generated, but the operation of the CPU 11 is temporarily stopped, and the regulator 17 of the other 3.3V power supply is used. The operation of the CPU 11 is restarted after the voltage is supplied to the CPU 11 to secure the 3.3V system voltage.
The power supply voltage generated by the engine control device 1, ie,
The 5V system voltage VCC output from the switching regulator 10 is secured, and radiation noise that can be generated in the switching regulator 10 due to the reduction of the voltage VCC can be reduced.

FIG. 3 is a circuit diagram of the switching regulator 10. The switching regulator 10
The switching device 20, the coil 21, the freewheeling diode 22, and the capacitors 23 and 24 have a basic configuration. The switching element 20 is connected to the voltage signal 7 of the battery 7.
a, the ON voltage of the switching element 20 increases, the output voltage VCC of the switching regulator 10 increases.
The output voltage VCC decreases as the N Duty decreases. The output voltage VCC is stabilized by adjusting the ON duty. The output voltage VC
C is represented as in equation (4).

[0029]

## EQU4 ## VCC = Vin × Ton / (Ton + Toff)
(4) Here, Vin is the voltage of the battery 7, Ton is the ON time of the switching element 20, and Toff is the OFF time of the switching element 20.

The coil 21 is connected to the switching element 2
When the switching element 20 is turned off, the freewheeling diode 22 stores the voltage supplied from the battery voltage signal 7a as energy.
The energy stored in 1 is circulated as electric current. That is, the current flowing through the coil 21 when the switching element 20 is ON is
Since the current cannot be changed instantaneously at the time of FF, current is supplied through the freewheeling diode 22.

Further, the capacitor 23 serves to reduce the change in the output voltage VCC when the load current fluctuates. When the load current increases, the load is supplied from the electric charge stored in the capacitor 23 so that the load is supplied. Prevents an increase in current, that is, a decrease in output voltage VCC,
When the load current decreases, the charge is stored in the capacitor 23 to reduce the load current, that is, the output voltage VC.
C is prevented from rising and stabilizing.

The capacitor 24 reduces noise generated at the time of switching of the switching element 20, and draws an input current flowing when the switching element 20 is turned on from the capacitor 24 arranged closer to the battery 7. The battery line 7a
To prevent the potential from dropping.

However, in order to keep the output voltage VCC constant in the equation (4), when the starter motor 8 starts at the start of the engine 6 and the voltage of the battery 7 decreases, the ON duty (To) of the switching element 20 is reduced.
n) needs to be large. If the ON duty becomes large, the required input current cannot be covered by the electric charge stored in the capacitor 24, and the battery 7
Will draw current from it. As a result, the potential of the vehicle harness connecting the engine control device 1 to the battery 7 is reduced, and this component is radiated from the harness as noise. Here, the average input current signal 7
If the amount of b is Iin and the amount of the load current signal 10b is ILOAD, the following equation (5) is established.

[0034]

Iin = ILOAD × Ton / (Ton + Toff) (5) Therefore, the amount of current 7b drawn from the battery voltage signal 7a is reduced, that is, the load current ILOAD of the switching regulator 10 is reduced, thereby superimposing on the battery line 7a. It can be seen that the occurrence of noise is minimized.

FIG. 4 shows the waveform of each signal of the switching regulator 10. As shown by the dotted line 31, when the drive voltage signal 20a is applied to the switching element 20, the switching element 20 is turned on. With the rise of the ON signal, the amount of current flowing through the coil 21 and the capacitor 23 increases, and the signal line 1
The output voltage VCC of 0a increases. Further, the input current Iin also increases due to the increase in the amount of current flowing through the output circuit of the switching regulator 10, and the input current Iin draws current from the battery line 7a, so that the potential Vin of the battery line 7a decreases.

Next, as shown by the dotted line 32, if the switching element 20 is turned off after the switching element 20 is turned on for the time Ton, the current flowing through the coil 21 cannot be changed instantaneously. However, the flowing current gradually decreases, and the output voltage VCC also decreases. Switching element 20
Is OFF, no current is drawn from the battery line 7a, so there is no potential drop and the battery potential V
in returns to its original state as indicated by the dotted line 33.

By repeating the above, a ripple voltage Vrpl having a waveform is generated in the output voltage VCC of the switching regulator 10, and a ripple current Irpl is generated in the current flowing through the coil 21. The load control means 12 of the engine control device 1 outputs the ripple voltage V by the means 14 for outputting the interrupt signal NMI.
Since a threshold smaller than rpl is provided, the supply of the 3.3 V power from the regulator 13 is stopped, and the supply of the 3.3 V power from the regulator 17 is performed based on the output voltage VCC and the threshold. The average output voltage VCC of the switching regulator 10 can be maintained at a constant level.

FIG. 5 is an operation flowchart of the engine control device 1. In step 1, when the engine 6 starts, the starter motor 8 is driven, and the engine control device 1
Is supplied with the voltage of the battery 7, and the power generation of the switching regulator 10 starts in step 2, and the output voltage VCC of the switching regulator 10 follows the rise of the voltage of the battery 7.

In step 3, the output voltage VCC of the switching regulator 10 is detected by the means 14 for outputting the interrupt signal NMI of the load control means 12, and the output voltage VCC is supplied to the hardware operable voltage VS of the CPU 11.
It is determined whether it is larger than TBYH. When the output voltage VCC is higher than the hardware operable voltage VSTBYH, that is, when the determination is YES, the process proceeds to step 4, the means 14 for outputting the interrupt signal NMI rises, and the standby signal S
The means 16 for outputting TBY rises, the hard standby mode of the CPU 11 is released, and the clock of the CPU 11 starts oscillating.

In step 5, when the time (Ton) for stabilizing the clock oscillation elapses, the means 15 for outputting the reset signal RES rises, the CPU 11 is released from the software standby mode, and
Starts. On the other hand, when the output voltage VCC is lower than the hardware operable voltage VSTBYH in step 3, this determination operation is repeated, and the CPU 11 remains in the hardware standby mode.

In step 6, it is determined whether or not the voltage of the battery 7 has dropped due to the start of the starter motor 8, and if the voltage of the battery 7 has dropped, that is, the output voltage VCC of the switching regulator 10 has begun to drop. That is, if YES, the process proceeds to step 7, and if it has not started decreasing, a series of operations is ended.

In step 7, the output voltage VCC of the switching regulator 10 is detected by the means 14 for outputting the interrupt signal NMI, and it is determined whether or not the output voltage VCC is lower than the interrupt signal generation voltage VNMIL which is the threshold value. judge. When output voltage VCC is lower than interrupt signal generation voltage VNMIL, that is, when YE
In the case of S, the process proceeds to step 8 where the interrupt signal NMI
Output means 14 falls, an interrupt to the CPU 11 is generated, and the routine proceeds to step 9. The output voltage VC
When C is higher than the interrupt signal generation voltage VNMIL, this determination operation is repeated, and no interrupt to the CPU 11 occurs.

In step 9, when an interrupt to the CPU 11 occurs, the means 15 for outputting the reset signal RES falls based on the number of soft steps and the clock of the CPU 11, and the software operation of the CPU 11 is stopped. Here, the time TRES from the generation of the interrupt signal to the fall of the reset signal is expressed by Expression (6).

[0044]

TRES ≧ number of soft steps required for NMI processing × CPU step time (6) In step 10, the means 16 for outputting the standby signal STBY falls in synchronization with the fall of the reset signal RES. The operation enters the hard standby mode and proceeds to step 11.

In step 11, the 3.3 V power supply is synchronized with the standby signal STBY, that is, the standby signal SBY.
The TBY output unit 16 outputs the standby signal 16 a to the regulator 13 that outputs the 3.3 V power supply, stops the supply from the regulator 13, and starts the supply from the regulator 17. As described above, in step 12, the load current of the switching regulator 10 is reduced, the fluctuation of the output voltage VCC of the switching regulator 10 due to the decrease in the voltage of the battery 7 is reduced, and the radiation noise is suppressed. The operation of is ended.

As described above, the embodiment of the present invention has the following functions by using the above configuration. That is, in the engine control device 1 of the present embodiment, the load control unit 12 synchronizes the regulator 13 of the 3.3 V power supply with the unit 16 that outputs the standby signal STBY,
When the output voltage VCC of the switching regulator 10 starts to decrease, the CPU 11 is temporarily set in a standby state, and the supply from the regulator 13 to the CPU 11 is switched to the supply from the 3.3 V power supply from the regulator 17, and then the standby state is set. Has been canceled,
Even when the voltage of the battery 7 decreases due to the start of the starter motor 8, the switching regulator 10
, The 5V output voltage VCC can be prevented from lowering, the radiation noise that can be generated in the switching regulator 10 can be suppressed, and the CPU 11
And the reliability of the engine control device 1 can be improved. Further, according to the configuration of the engine control device 1 of the present embodiment,
The engine control device 1 can be mounted in an engine room of a vehicle, and it is possible to cope with multifunctional control devices and low manufacturing costs.

Although one embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and various designs may be made without departing from the spirit of the invention described in the claims. Can be changed. For example, in the engine control device of the present embodiment, the fluctuation of the output voltage from the switching regulator is reduced. However, the present invention needs to suppress the fluctuation of the output voltage from the regulator when the voltage of the battery decreases. The same effects can be obtained in this case as well.

[0048]

As can be understood from the above description, the engine control apparatus of the present invention can reduce the load current of the regulator even when the battery voltage is reduced, and can suppress the fluctuation of the output voltage of the regulator.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of an engine control system including an engine control device of the present embodiment.

FIG. 2 is a control block diagram of the engine control device of FIG. 1;

FIG. 3 is a circuit configuration diagram of the switching regulator of FIG. 1;

FIG. 4 is a waveform diagram of each signal of the switching regulator of FIG. 1;

FIG. 5 is an operation flowchart of the engine control device of FIG. 1;

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 engine control device 7 battery 10 switching regulator 11 arithmetic device (CPU) 12 means for controlling load of regulator 13 other regulator 14 means for outputting interrupt signal to arithmetic device 15 means for outputting reset signal to arithmetic device 16 arithmetic device Means for outputting a standby signal to another 17 Still another regulator

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Shoji Sasaki 2520 Oji Takaba, Hitachinaka-shi, Ibaraki F-term in the Automotive Equipment Group, Hitachi, Ltd. 3G084 BA00 DA11 EB04 FA03 5H730 AA16 AS01 AS05 BB13 BB57 BB84 DD04 FG05

Claims (9)

[Claims] 1. An engine control device having a regulator for converting a voltage of a battery to an operation potential level of an arithmetic device, wherein the control device has means for controlling a load of the regulator when the voltage of the battery decreases. An engine control device, characterized in that: 2. The engine control device according to claim 1, wherein the regulator is a switching regulator. 3. The engine according to claim 1, wherein the means for controlling the load of the regulator includes another regulator for converting an output voltage from the regulator to an operating potential level of the arithmetic unit. Control device. 4. The method according to claim 1, wherein the control of the load of the regulator stops the supply of the operating potential level to the arithmetic unit by the other regulator when the voltage of the battery decreases. Item 4. The engine control device according to item 3. 5. The engine according to claim 3, wherein the control device further includes another regulator connected between the battery and the arithmetic device in parallel with the another regulator. Control device. 6. A means for controlling a load of the regulator, comprising: means for outputting an interrupt signal to the arithmetic unit based on an output signal from the regulator; and means for outputting an interrupt signal based on an output signal from the means for outputting the interrupt signal. 6. The device according to claim 3, further comprising: means for outputting a reset signal to the arithmetic device; and means for outputting a standby signal to the arithmetic device based on an output signal from the means for outputting the reset signal. The engine control device according to claim 1. 7. The means for outputting an interrupt signal to the arithmetic unit has a threshold value of a voltage smaller than a ripple voltage generated in the regulator, and the arithmetic unit outputs the interrupt signal based on the threshold value and an output voltage from the regulator. 7. The engine control device according to claim 6, wherein an interrupt signal is output to the device. 8. A means for controlling a load of said regulator stops supply of an operating potential level to said arithmetic device to said another regulator based on an output signal from means for outputting an interrupt signal to said arithmetic device. The engine control device according to claim 6, wherein a signal for causing the engine control device to output is output. 9. The engine control device according to claim 1, wherein the control device is disposed in an engine room of a vehicle.