JPH02188131A - Battery power supply circuit - Google Patents

Abstract

PURPOSE:To prevent overdischarge of a battery by detecting latch-up phenomenon through a current detecting circuit and turning a switching circuit OFF for a predetermined time. CONSTITUTION:Upon occurrence of latch-up phenomenon in a CPU 3, current supply from a battery 5 through a power source circuit 6 increases, and an overcurrent is detected through a current detecting circuit 11. Upon reception of a detection signal A, a one-shot multivibrator 12 brings the output B to High level and turns a transistor TR2 OFF for a predetermined time. Consequently, power supply to the CPU 3 is stopped during this interval and latch-up phenomenon is eliminated.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a battery power supply circuit that supplies power from a battery to electronic components, etc., and particularly relates to a battery power supply circuit that supplies power from a battery to electronic components. The present invention relates to a battery power supply circuit that prevents.

[Conventional technology]

Conventionally, this type of battery power supply circuit includes, for example,
There is one shown in the block diagram of FIG. 2 that is used in automobiles.

In the figure, each part CI, IC2, and a CPU 3 that centrally controls these are connected to each other by a bus 4, and power from a battery is constantly supplied to a power supply circuit 6 via VB and u terminals 5, and this power supply The circuit 6 constantly supplies a backup power supply voltage Va to various parts including the power supply terminal V of the CPU 3 and the like.

Further, the rise of the power supply voltage va is detected by a series circuit composed of a resistor R1 and a capacitor C1, and when the power supply voltage Va rises, a series circuit composed of a transistor TRI, resistors R2, R3, and a diode D1 is detected. A high-level potential is applied to the reset terminal R of the CPU 3 for a predetermined period of time by the switching circuit. Therefore, at the initial stage when the power supply circuit 6 is connected to the battery, the CPU 3 is reset, and the state of the boat terminal P1 is immediately read when the reset is applied. At this initial stage, the potential level of port terminal P1 is low level, so
The CPU 3 enters a power down mode, which is a low power consumption mode, and battery power is saved.

Further, when the ignition key switch is turned on, the ICP terminal 7 is connected to the battery, power is supplied from the battery to the power supply circuit 8, and the power supply circuit 8 outputs a stabilized voltage vb.

The rise of this voltage vb is caused by resistor R4 and capacitor C2.
is detected by a series circuit of transistor TR
1, resistors R3 and R5, and a diode D2, the CPU 3 is reset in the same manner as described above. When the reset is applied, the state of the port terminal P1 is immediately read, but since the voltage vb is output and the port terminal P1 is at a high level, the CPU 3 returns from the power down mode by this reset and starts executing the predetermined process. .

[Problem to be solved by the invention]

However, in the conventional circuit with the above configuration, CP
When a latch-up phenomenon occurs in U3, even if the ignition key switch is turned off and the power supply circuit 8 is disconnected from the battery, the power supply circuit 6 remains connected to the battery, so the power supply circuit 6 is disconnected from the battery via the power supply circuit 6. Power continues to be supplied to the CPU3. This latch-up phenomenon causes a large current to flow, so if this state continues for a while, the battery will be discharged, and the conventional circuit has had the problem that the vehicle cannot be restarted after that.

[Means to solve the problem]

The present invention has been made to solve these problems, and includes a current detection circuit that detects the output current of a power supply circuit that is constantly connected to a battery and outputs a signal when the current exceeds a predetermined current value, and A switching circuit that switches the output current of the power supply circuit supplied to the microprocessor via the circuit, and a power supply stop circuit that controls the switching circuit to be turned off for a predetermined time when an overcurrent is detected by the current detection circuit. It is something.

[Effect]

When a latch-up phenomenon occurs in the microprocessor, the current detection circuit detects an overcurrent, and the power supply stop circuit turns off the switching circuit for a predetermined period of time, thereby stopping power supply to the microprocessor for a predetermined period of time.

〔Example〕

Next, the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention, and the same or corresponding parts as in FIG. 2 are designated by the same reference numerals, and the explanation thereof will be omitted.

In the figure, the output of a backup power supply circuit 6 that is constantly connected to a battery is input to a current detection circuit 11,
This current detection circuit 11 measures the output current of the power supply circuit 6, and when it exceeds a predetermined current value,
The output signal A to the one-shot multivibrator 12 is set to high level. Further, the output current from the power supply circuit 6 via the current detection circuit 11 is input to the transistor TR2, and power for backup is supplied to the power supply terminal V of the CPU 3 via the emitter-collector circuit of the transistor TR2. ing. Further, the well-known one-shot multivibrator 12 outputs a pulse signal B, which is a high-level signal with a constant width, when the input signal A becomes high level, and operates by receiving power supply from the power supply circuit 6. It is something.

When signal B is output, this high level potential is applied to resistor R1.
2 to the base of the transistor TR2, the transistor TR2 is turned off, and the power supply to the CPU 3 is stopped. At the same time, the high level potential of signal B is transmitted to the base of transistor TR5 via resistor R19, transistor TR5 is turned on, and capacitor C5 is turned on.
The charges stored in the resistor R20 are discharged through the resistor R20.

The collector of the transistor TR3 is connected to the reset terminal R of the CPU 3, and this terminal R becomes high level for a predetermined period of time when the voltage Va from the power supply circuit 6 rises, and the CPU 3 is reset. That is, when the power supply voltage Va output from the power supply circuit 6 rises, a voltage is applied to the emitter of the transistor TR3, and a charging current begins to flow into the capacitor C5 via the resistor R14. However, since the terminal voltage of the capacitor C5 does not reach a high level immediately, a voltage is generated between the base and emitter of the transistor TR3, and a base current flows. Therefore, for a predetermined period of time, the transistor TR
3 is turned on, its collector potential level remains high for a predetermined period of time, and the CPU 3 is reset.

Note that R15 and R16 are a base resistance and a collector resistance, respectively.

Further, the output potential of the power supply circuit 8 is input to the boat terminal P1 of the CPU 3, and the state of power supply from the power supply circuit 8 to each ICI, IC2, etc. is monitored by the CPU 3.

The power supply circuit 8 is connected to the battery when the ignition key switch is turned on, and supplies a stabilized output voltage vb to various parts.The rise of this voltage vb is caused by a series circuit consisting of a capacitor C6 and a resistor R18. It is detected and transmitted to the base of transistor TR4 via resistor R17. Until the voltage vb is generated, the base potential of the transistor TR4 is kept at a low level by the resistor R18, but when the voltage vb rises, it becomes high level, a base current flows, and the transistor TR4 is turned on for a predetermined time.

When the transistor TR4 is turned on, the terminal of the capacitor C5 connected to the collector thereof is grounded, the charge is rapidly discharged, and the terminal voltage of the capacitor C5 decreases.

Then, due to this decrease in terminal voltage, the transistor TR
A potential difference is generated between the base and emitter of transistor TR3, and a base current flows, turning on transistor TR3, and resetting CPU3 for a predetermined time in the same manner as in the case described above.

In such a configuration, the operation of the present device will be described in detail below.

First, when a battery is connected to the power supply circuit 6, the 12V supply voltage output from the battery is converted to a stabilized voltage Va of 5V and output.

When the power supply voltage Va rises, the signal B output from the one-shot multivibrator 12 becomes low level, and the transistor TR2K is turned on.

Therefore, the power from the battery is supplied to the power supply circuit 6. The current is supplied to the CPU 3 via the current detection circuit 11 and the transistor TR2.

Further, the rise of voltage Va is detected by a series circuit of resistor R14 and capacitor C5, and transistor T
By turning on R3 for a predetermined period of time as described above, the CPU 3 is reset. C when reset occurs
The PU3 starts executing a predetermined process and immediately reads the state of the boat terminal P1, but since power is not being output from the power supply circuit 8, it knows that the boat terminal P1 is at a low level. For this reason, the CPU 3 changes its operating mode to a power down mode, which is a low power consumption mode, and the current supplied from the battery is consumed only for holding data in the internal RAM of the CPU 3, resulting in greater savings in battery power. It will be done.

Next, when the ignition key switch is turned on after connecting the power supply circuit 6 to the battery, power is supplied from the battery to the power supply circuit 8, and the voltage vb stabilized at 5V is output from the power supply circuit 8, and the ICI, Supplied to IC2 etc. Further, as described above, the rise of the voltage vb is detected by the series circuit of the capacitor C6 and the resistor R18, and the CPU 3 is reset by turning on the transistor TR4 for a predetermined time. When the reset is applied, the CPU 3 returns from the power down mode and starts executing predetermined processing.

Next, when the ignition key switch is turned off, the connection between the power supply circuit 8 and the battery is cut off, the voltage vb output from the power supply circuit 8 decreases, and the power supply to the ICI, IC2, etc. is stopped. In addition, the voltage vb decreases because the level of the boat terminal P1 becomes low level, so that the CP
When the CPU 3 detects this low level, the CPU 3 changes its operating mode to a power down mode, which is a low power consumption mode. Therefore, the current supplied from the battery is consumed only for holding data in the internal RAM of the CPU 3, thereby saving battery power.

Next, when the ignition key switch is turned on again, the connection between the power supply circuit 8 and the battery is restored, the voltage vb is output again from the power supply circuit 8, and the IC
Power supply to I, IC2, etc. is resumed. Immediately after the ignition key switch is turned on, the transistors TR3 and TR4 turn on the CP as described above.
Since U3 is reset, the CPU 3 recovers from the power down mode and resumes processing operations using the stored internal RAM data.

Then, turn on the ignition key switch,
The above operation is repeated by the off operation. In other words,
ICI when the key switch is off.

The power supply to the IC 2 and the like is stopped, and the CPU 3 enters the power down mode, the current consumption of the battery is reduced, and the internal RAM data of the CPU 3 continues to be held. Furthermore, when the key switch is turned on, the CPU 3 executes predetermined processing using the retained internal RAM data.

In such a state, if a latch-up phenomenon occurs in the CPU 3 due to some reason, for example, noise applied from the outside, the current supplied from the battery via the power supply circuit 6 increases, causing an overcurrent. is detected by the current detection circuit 11. When the current detection circuit 11 detects this overcurrent, it changes the output signal A to a high level and notifies the one-shot multivibrator 12 that an overcurrent has occurred.

When the one-shot multi-by-break 12 receives the signal A, it outputs the signal B having a predetermined time width. The high level change in signal B is transmitted to the base of transistor TR2 via resistor R12, transistor TR2 is turned off, and power supply from the battery to CPU3 is stopped. As a result, the rough lump phenomenon occurring in the CPU 3 is eliminated. Further, the power supply stop time corresponds to the high level time of the signal B output from the one-shot multivibrator 12, and the signal B returns to the low level after a predetermined time elapses. When the signal B becomes low level, the transistor TR2 is turned on and power is again supplied from the battery to the CPU3.

In parallel to this, the high level change of signal B is caused by the resistance R
19 to the transistor TR5, and the transistor TR5 is turned on. When the transistor TR5 is turned on, the charge stored in the capacitor C5 is transferred to the resistor R2.
0 and the collector of transistor TR5 is discharged through the emitter circuit. After a predetermined time determined by this resistor R20 and capacitor C5, that is, the CPU
When power supply to C3 is resumed, capacitor C5
The terminal voltage of is sufficiently reduced, and transistor TR3 is turned on. This on operation causes the voltage Va from the power supply circuit 6 to
The CPU 3 is reset in the same way as at the time of startup, the CPU 3 is initialized, and the same operation as when the power supply circuit 6 is connected to the battery is repeated.

According to this embodiment, when latch-up occurs in the CPU 3, the power supply to the CPU 3 is automatically cut off.
The latch-up phenomenon is eliminated.

Therefore, unlike the conventional case, the battery does not discharge due to latch-up.

Furthermore, since the power supply to the CPU 3 is automatically resumed, the driver of the car does not need to take any precautions and is free from any inconvenience.

〔Effect of the invention〕

As explained above, the present invention includes a current detection circuit that detects the output current of a power supply circuit that is constantly connected to a battery, and outputs a signal when the current exceeds a predetermined current value, and a current detection circuit that outputs a signal when the current exceeds a predetermined current value. It is equipped with a switching circuit that switches the output current of the supplied power supply circuit, and a power supply stop circuit that turns off the switching circuit for a predetermined period of time when an overcurrent is detected by the current detection circuit. When the power-up phenomenon occurs, the current detection circuit detects an overcurrent, and the power supply stop circuit turns off the switching circuit for a predetermined period of time, thereby stopping power supply to the microprocessor for a predetermined period of time.

Therefore, even if a latch-up phenomenon occurs in the microprocessor, the conventional problem of the battery being discharged and the electronic equipment not operating when the vehicle is restarted can be solved.

Furthermore, the power supply to the microprocessor is automatically resumed, so there is no need for the driver of the car to take any precautions.
It also has the effect of being hassle-free.

TR2...Transistor.

Patent Applicant Honda Motor Co., Ltd. Representative Patent Attorney Yoshiki Hase
Fumiaki Terashima

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a circuit configuration according to an embodiment of the present invention, and FIG. 2 is a block diagram showing a conventional circuit configuration.

Claims (1)

[Claims] A current detection circuit that detects the output current of a backup power supply circuit that is constantly connected to the battery and outputs a signal when the current exceeds a predetermined current value, and the power supply circuit that supplies the microprocessor with the current through this current detection circuit. A battery power supply circuit comprising: a switching circuit that switches the output current of the battery; and a power supply stop circuit that controls the switching circuit to be turned off for a predetermined time when the current detection circuit detects an overcurrent.