JP2809840B2 - Battery power supply circuit - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a battery power supply circuit for supplying power from a battery to electronic components and the like, and more particularly, to discharging of a battery when an IC is latched up. The present invention relates to a battery power supply circuit for preventing the occurrence of power.

(Prior Art) Conventionally, as a battery power supply circuit of this type, there is a circuit shown in the block diagram of FIG. 2 for use in an automobile.

In the figure, the output current of the backup power supply circuit 6 constantly connected to the battery is supplied to the CPU 3 as a backup power supply via the current detection circuit 11 and the transistor TR2. The magnitude of the output current is detected by the current detection circuit 11, and when the magnitude of the output current exceeds a predetermined current value, the output signal to the terminal to which the resistor R11 is connected becomes "L" level.

Further, the power supply monitoring circuit 12 includes NAND (NAND) circuits 13 and 14 and a NOT
It is composed of circuits 15 and 16.

The output signal from the current detection circuit 11 to the resistor R11 is
The integrated signal A is integrated by an integrating circuit including the capacitor C3 and the integrated signal A is input to the NAND circuit 13 of the power supply monitoring circuit 12. On the other hand, the signal B output from the operating power supply circuit 8 is input to the NOT circuit 15.

The signals A and B thus input are output as signals C from the NOT circuit 16 in accordance with the truth table shown in Table 1 below.

The signal C output in this manner is input to the base of the transistor TR2 via the resistor R12 and
13 and input to an integrating circuit composed of a capacitor C4. The integrated signal is input to port terminal P2 of CPU3.

The collector of the transistor TR3 is connected to the reset terminal R of the CPU 3, and this terminal R is set to "H" for a predetermined time when the voltage Vb rises by the operating power supply circuit 8.
Level, and CPU3 is reset. R15 and R16 are a base resistance and a collector resistance, respectively.

In such a configuration, first, when a battery is connected to the backup power supply circuit 6, the power supply circuit 6 outputs a stabilized voltage Va of 5V. Also, the current detection circuit
The output signal to the 11th resistor R11 also becomes “H” level,
The signal A at the beginning of connection becomes "L" level due to the integration circuit of 11 and C3. This is for initial setting so that the output signal C of the monitoring circuit 12 becomes "H" level.

At this time, since the signal B is at the "L" level, the input state of the monitoring circuit 12 corresponds to the state shown in Table 1, and the signal C becomes the "H" level.

Thereafter, after a predetermined time, the signal A changes from the "L" level to the "H" level. Is off. Therefore, no current is supplied to the CPU 3 when the backup power supply circuit 6 is connected to the battery, and the current consumption of the battery is a small current consumed by the power supply monitoring circuit 12 and the like.

Next, when the ignition key switch is turned on after the backup power supply circuit 6 is connected to the battery, the operation power supply circuit 8 outputs a voltage Vb stabilized at 5 V and supplies it to IC1, IC2, and the like. Further, the input state of the monitoring circuit 12 becomes equivalent to the state shown in Table 1 by the rise of the voltage Vb, and the output signal C becomes "L" level, so that the transistor TR2 is turned on.

Therefore, a current is supplied to the CPU 3 from the battery via the backup power supply circuit 6 and the current detection circuit 11. At the same time, the output signal C is delayed by a predetermined time determined by the time constant of the integrating circuit including the resistor R13 and the capacitor C4, and the port terminal P2 of the CPU 3 is set to the "L" level.

The operating power supply circuit 8 is connected to a
When Vb is established, the transistor TR3 is turned on for a predetermined time determined by the time constant of the integrating circuit of the resistor 14 and the capacitor C5, and an “H” level signal is input to the reset terminal R of the CPU 3 for a predetermined time. Is done. The CPU 3 is reset by this “H” level signal, and then starts executing the stored program when it becomes “L” level. Note that the resistor R14,
The time constant of the integrating circuit formed by the capacitor C5 is set to be smaller than the time constant of the integrating circuit formed by the resistor R13 and the capacitor C4. Therefore, the reset to the reset terminal R of the CPU 3 is performed by changing the “L” level of the port terminal P2. Done earlier.

When the execution of the program is started, the CPU 3 immediately reads the state of the port terminal P2. However, since the “L” level change of the signal C is delayed by the integration circuit as described above,
The CPU 3 reads "H" level. For this reason, CP
U3 determines that it is in the initial reset state immediately after the backup power supply circuit 6 is connected to the battery, and the internal RA of the CPU 3
After executing an initialization process for clearing M, the process proceeds to a predetermined process.

Next, when the ignition key switch is turned off, the connection between the operation 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 IC1, IC2, etc. stops. I do.

At this time, the input signal B of the monitoring circuit 12 becomes "L" level, but since the input signal A is at "H" level, the input state of the monitoring circuit 12 corresponds to the state shown in Table 1. Therefore, the output signal C remains at the “L” level without change, and the backup power supply to the CPU 3 is continuously performed.

The decrease in the voltage Vb is transmitted to the CPU 3 when the level of the port terminal P1 becomes “L” level.
When the level is detected, the operation mode is set to the power down mode which is a low power consumption mode. For this reason, the supply current from the battery is consumed only for holding the data in the internal RAM of the CPU 3, thereby saving the battery power.

Next, when the ignition key switch is turned on again, the voltage Vb is output again from the operating power supply circuit 8, and the power supply to IC1, IC2, etc. is restarted.
At this time, the input signals A and B both become "H" level, and the input state of the monitoring circuit 12 corresponds to the state shown in Table 1. Therefore, the output signal C does not change and remains at the “L” level. For this reason, the current is continuously supplied to the CPU 3 from the backup power supply circuit 6, and the data in the internal RAM is maintained.

Immediately after the ignition key switch is turned on, the CPU TR3 is turned on by the transistor TR3 as described above.
Is reset, the CPU 3 resumes operation from the power-down mode, starts operation, and reads the state to the port terminal P2. At this time, since the port terminal P2 is at the “L” level,
The CPU 3 determines that the transistor TR2 has been continuously turned on, and knows that the current operation of the ignition key switch is not the initial operation immediately after the backup power supply circuit 6 is connected to the battery.

For this reason, it is necessary to keep the state of the internal RAM data, and the internal RAM data is not initialized, and the internal RAM data is kept as it is, and a predetermined process is restarted.

The above operation is repeated by the subsequent on / off operation of the ignition key switch. In other words, when the key switch is turned off, the power supply to IC1, IC2, etc. is stopped, and the CPU 3 enters the power down mode.
Battery current consumption is reduced, and the internal RA
M data continues to be retained.

When the key switch is turned on, the CPU 3 executes a predetermined process using the held internal RAM data.

In such a state, if a latch-up phenomenon occurs in the CPU 3 due to some cause, for example, application of external noise, the supply current from the battery via the backup power supply circuit 6 increases, resulting in excessive current. Produce a current,
This overcurrent is detected by the current detection circuit 11. When the current detection circuit 11 detects this overcurrent, it changes the output signal to the resistor R11 to "L" level, and this "L" level change is delayed and transmitted to the signal A.

Note that, even if the latch-up phenomenon is detected and the signal A changes to the “L” level, the overcurrent continues to flow because the signal C maintains the “H” level. Since the alternator is generating sufficient power, the battery will not be discharged.

Then, when the ignition key switch is turned off, the voltage Vb output from the operating power supply circuit 8 decreases, and the input signal B becomes "L" level. Therefore, the input state of the monitoring circuit 12 at this time is as shown in Table 1, and the output signal C becomes "H" level. As a result, the TR2 is turned off, the power supply to the CPU 3 is cut off, the latch-up phenomenon of the CPU 3 is eliminated, and the supply current from the battery becomes small. Therefore, the battery is not discharged when the CPU 3 latches up.

Further, when the ignition key switch is turned on again, the latch-up phenomenon of the CPU 3 has been eliminated, so that the CPU 3 starts operating in the same manner as in the initial state when the backup power supply circuit 6 is connected to the battery, and the predetermined operation is started. Processing will be performed.

According to such a configuration, the latch-up phenomenon of the CPU 3 is detected as an overcurrent by the current detection circuit 11, and when the ignition key switch is subsequently turned off, the output of the operation power supply circuit 8 decreases, and the transistor TR2 is turned off. Turned off.

Therefore, when a latch-up phenomenon occurs in the CPU 3, the current supply from the battery to the CPU 3 is cut off, and the battery does not discharge due to the latch-up phenomenon.

(Problems to be Solved by the Invention) In the above-described conventional technology, the circuit configuration becomes complicated because the current detection circuit 11 requires at least components such as a current detection resistor, a differential amplifier, and a comparison circuit. There is a problem that it is difficult to reduce the size and increase the reliability.

Furthermore, since the power supply monitoring circuit 12 also requires a large number of digital ICs, there is a problem that this hinders miniaturization and high reliability of the device.

An object of the present invention is to solve the above-mentioned problems and to provide a highly reliable battery power supply circuit with a small and simple configuration.

(Means for Solving the Problems) In order to achieve the above object, according to the present invention, a backup power supply circuit for outputting a backup current, a series connection between the backup power supply circuit and the microprocessor, and a control signal A switching means that is closed in response to the power supply, a resistor that is connected in series between the backup power supply circuit and the microprocessor, reduces the output voltage according to the backup current, and is connected to the battery by turning on an ignition key switch. An operation power supply circuit for outputting a current from a battery to a microprocessor and its peripheral circuit device; a means for adding a current corresponding to an output voltage of the resistor to an output current from the operation power supply circuit; Control signal generating means for generating the control signal when the sum current is equal to or greater than a predetermined value. Wherein the control signal generating means stops generating a control signal when the sum current is less than a predetermined value, opens the switching means, and inhibits supply of a backup current to the microprocessor. There are features.

(Operation) According to the above configuration, when a large backup current flows due to a latch-up phenomenon occurring in the microprocessor, a current corresponding to the output voltage of the resistor becomes substantially zero due to a voltage drop by the resistor.

Therefore, when the ignition key switch is subsequently turned off, the sum current becomes substantially zero, so that the control signal generation means stops outputting the control signal and inhibits the supply of the backup current from the backup power supply circuit to the microprocessor. I do.

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

FIG. 1 is a block diagram showing an embodiment of the present invention.
Since the same reference numerals as those in FIG. 2 indicate the same or equivalent parts, the description thereof will be omitted.

In the figure, the output current of the backup power supply circuit 6 constantly connected to the battery is input to the transistor TR2 via the resistor R20 as the emitter current. The collector current of the transistor TR2 is supplied to the CPU 3 as a backup current, while the diode D2 and the resistor R2
The signal is supplied to the base of the transistor TR4 via 1.

The output current of the operating power supply circuit 8 is further supplied to the base of the transistor TR4 via the diode D1 and the resistor R22, and the collector of the transistor TR2 is supplied to the collector of the transistor TR4.
Is input.

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

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

At this time, since the output voltage of the operating power supply circuit 8 is 0 V, no base current is supplied to the transistor TR4, and the transistor TR4 is off. Unless the transistor TR4 is turned on, the base potential of the transistor TR2 is maintained at the "H" level. Since no potential difference occurs between the base and the emitter, the transistor TR2 is off. Therefore, when the backup power supply circuit 6 is connected to the battery, the CPU 3
Is not supplied with power, and the current consumption of the battery is very small.

Next, when the ignition key switch is turned on after the backup power supply circuit 6 is connected to the battery, power is supplied from the battery to the operation power supply circuit 8, and the voltage Vb stabilized at 5 V is output from the power supply circuit 8. Being IC1, I
Supplied to C2 etc.

Also, the rise of the voltage Vb causes the diode D1,
Since the base current is supplied to the transistor TR4 via the resistor R22, the transistor TR4 is turned on. Therefore, the transistor T
The base potential of R2 drops, causing a potential difference between the base and the emitter, causing a base current to flow, turning on the transistor TR2.

Therefore, power is supplied to the CPU 3 from the battery via the backup power supply circuit 6 and the resistor 20. At this time, if the resistance value is set so that the voltage drop caused by the resistor R20 is, for example, about 0.1 V, the operating voltage of the CPU 3 is ensured, and no inconvenience occurs in the operation.

At this time, a collector current flows through TR4.
The port terminal P2 of CPU3 is delayed by a predetermined time determined by the time constant of the integrating circuit by the resistor R13 and the capacitor C4.
Becomes “L” level.

The operating power supply circuit 8 is connected to a
When Vb is established, the transistor TR3 is turned on for a predetermined time determined by the time constant of the integrating circuit of the resistor 14 and the capacitor C5, and an “H” level signal is input to the reset terminal R of the CPU 3 for a predetermined time. Is done.

When detecting the "H" level signal, the CPU 3 starts executing the stored program. The time constant of the integrating circuit formed by the resistor R14 and the capacitor C5 is set to be smaller than the time constant of the integrating circuit formed by the resistor R13 and the capacitor C4. This is performed earlier than the “L” level change.

When the execution of the program is started, the CPU 3 immediately reads the state of the port terminal P2. However, since the change in the “L” level of the collector potential of the transistor TR4 has been delayed by the integration circuit as described above, the CPU 3 "The level will be read. For this reason, the CPU 3 determines that it is in the initial reset state immediately after the backup power supply circuit 6 is connected to the battery, executes an initialization process for clearing the internal RAM of the CPU 3, and then proceeds to a predetermined process.

Next, when the ignition key switch is turned off, the connection between the operation 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 IC1, IC2, etc. stops. I do.

At this time, since the transistor TR2 is on, the base current continues to be supplied to the transistor TR4 via the diode D2 and the resistor R21, so that the transistor TR4 remains on. Therefore, the transistor TR2 also maintains the ON state, and the backup power supply to the CPU 3 is continuously performed.

The decrease in the voltage Vb is transmitted to the CPU 3 when the level of the port terminal P1 becomes “L” level.
When the level is detected, the operation mode is set to the power down mode which is a low power consumption mode. For this reason, the supply current from the battery is consumed only for holding the data in the internal RAM of the CPU 3, thereby saving the battery power.

Next, when the ignition key switch is turned on again, the connection between the operation power supply circuit 8 and the battery is restored, and the voltage Vb is output again from the power supply circuit 8, and the voltage to the IC1, IC2, etc. Power supply is resumed.

At this time, the base current is supplied again to the transistor TR4 via the diode D1 and the resistor R22, but the transistor T4
Since the base current was continuously supplied to R4 via the diode D2 and the resistor R21, TR4 maintained the on state, and C
Power is continuously supplied to the PU3 from the backup power supply circuit 6, and the data in the internal RAM is held.

Immediately after the ignition key switch is turned on, the CPU TR3 is turned on by the transistor TR3 as described above.
Is reset, the CPU 3 resumes operation from the power-down mode, starts operation, and reads the state of the port terminal P2. At this time, since the port terminal P2 is at the “L” level, the CPU3
Determines that the transistor TR4 has been continuously turned on, and knows that the current operation of the ignition key switch is not the initial operation immediately after the backup power supply circuit 6 is connected to the battery.

For this reason, it is necessary to keep the state of the internal RAM data, and the internal RAM data is not initialized, and the internal RAM data is kept as it is, and a predetermined process is restarted.

The above operation is repeated by the subsequent on / off operation of the ignition key switch. In other words, when the key switch is turned off, the power supply to IC1, IC2, etc. is stopped, and the CPU 3 enters the power down mode.
Battery current consumption is reduced, and the internal RA
M data continues to be retained.

When the key switch is turned on, the CPU 3 executes a predetermined process using the held internal RAM data.

In such a state, if a latch-up phenomenon occurs in the CPU 3 due to some cause, for example, application of external noise, the supply current from the battery via the backup power supply circuit 6 increases and becomes excessive. Produce a current,
Due to this overcurrent, a large voltage drop occurs in the resistor 20.
As a result, the emitter potential and the collector potential of the transistor TR2 become almost 0 V, and the diode D2,
The base current supply to the transistor TR4 via the resistor R21 will not be performed.

When the ignition key switch is turned off, the voltage Vb output from the operating power supply circuit 8 decreases, and the transistor TR4 via the diode D1 and the resistor 22 is turned off.
The base current supply to the power supply is not performed.

Therefore, when the transistor TR4 is turned off and the base potential of the transistor TR2 becomes "H" level, the transistor TR2 is turned off and the power supply to the CPU 3 is cut off. As a result, the latch-up phenomenon of the CPU 3 is eliminated, and the supply current from the battery becomes small, so that the battery is not discharged when the CPU 3 latches up.

Further, when the ignition key switch is turned on again, the latch-up phenomenon of the CPU 3 has been eliminated, so that the CPU 3 starts the operation in the same manner as in the initial stage of connecting the backup power supply circuit 6 to the battery, and performs the predetermined operation. Processing will be performed.

In the embodiment described above, the resistor R20 is described as being connected between the backup power supply circuit 6 and the transistor TR2. However, the present invention is not limited to this. However, it may be connected to the TR2 side from the branch point to the diode D2.

(Effects of the Invention) As is clear from the above description, according to the present invention, a highly reliable battery power supply circuit with a small and simple configuration can be provided.

[Brief description of the drawings]

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 circuit configuration of the prior art. 3 ... CPU, 6 ... Backup power supply circuit, 8 ... Operation power supply circuit, TR2, TR3, TR4 ... Transistor, D1, D
2 …… Diode

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H02J 9/00-9/06

Claims (3)

(57) [Claims] A backup power supply circuit which is always connected to a battery and outputs a backup current; a switching means which is connected in series between the backup power supply circuit and the microprocessor and is closed in response to a control signal; A resistor connected in series between the power supply circuit and the microprocessor for reducing the output voltage according to the backup current, and connected to the battery by turning on the ignition key switch, the current from the battery is transferred to the microprocessor and its surroundings. An operation power supply circuit that outputs to the circuit device; a unit that adds a current corresponding to an output voltage of the resistor to an output current from the operation power supply circuit; and that the added sum current is greater than or equal to a predetermined value. Control signal generating means for generating the control signal, wherein the control signal generating means The sum current stops the generation of the control signal is less than a predetermined value to open said switching means, battery power supply circuit and inhibits the supply of the backup current to the microprocessor. 2. A backup power supply circuit which is always connected to a battery and outputs a backup current, a backup power supply circuit is connected to an emitter, a microprocessor is connected to a collector, and an emitter / collector is responsive to a base current. A first transistor having a conductive state between the first and second transistors, a resistor connected in series between the backup power supply circuit and the microprocessor, for reducing an output voltage according to the backup current, and a battery connected to the battery by turning on an ignition key switch. An operating power supply circuit that is connected and outputs a current from a battery to a microprocessor and its peripheral circuit device; and a unit that adds a current corresponding to an output voltage of the resistor to an output current from the operating power supply circuit; The emitter is grounded and the collector is connected to the base of the first transistor. A second transistor having the added sum current as a base current, wherein the second transistor conducts between the emitter and the collector when the base current is equal to or more than a predetermined value, and the first transistor A battery, wherein when the current is less than a predetermined value, the emitter-collector state is cut off, the base current flow is inhibited, and the emitter-collector state of the first transistor is cut off. Power supply circuit. 3. The resistance value of the resistor is such that the output voltage dropped by the backup current when the microprocessor is normal is sufficient to back up the microprocessor, and the microprocessor drops by the backup current when latched up. 3. The battery power supply circuit according to claim 1, wherein a current corresponding to the output voltage is set to be less than the predetermined value.