JPH06112878A - Reset circuit for radio equipment - Google Patents

Abstract

PURPOSE:To obtain a reset circuit of a radio equipment in which a battery is not over-discharged even when the battery is left as it is if the battery is worn out. CONSTITUTION:A circuit is provided with a transmission reception circuit 11, a system control use microcomputer 11 controlling the transmission reception circuit 11, a voltage detection circuit 31 detecting whether or not a voltage of the power supply battery 21 is a specified voltage or over, a monostable multivibrator 35 of edge trigger type receiving a detection output of the voltage detection circuit 31. The monostable multivibrator 31 is triggered by the detection output when it is detected that the voltage of the battery 21 is a specified value or over. An output pulse of the monostable multivibrator 35 is fed to the microcomputer 15 as its reset voltage. The microcomputer 15 is reset for a period of the output pulse.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reset circuit for a microcomputer in a wireless device such as a cordless telephone.

[0002]

2. Description of the Related Art Rechargeable batteries include nickel-cadmium batteries and lead batteries. However, nickel-cadmium batteries have a reduced capacity due to memory effects. That is, if the battery is repeatedly charged before it becomes empty, the battery will gradually deteriorate and its capacity will decrease.

In cordless telephone handsets, mobile telephones and the like, it is inevitable that the battery is charged before the battery becomes empty in consideration of the usage pattern, and therefore the decrease in the battery capacity due to the memory effect can be avoided. Absent. For this reason,
For cordless handsets, mobile phones, etc.,
Lead batteries are effective as batteries.

On the other hand, in cordless telephone handsets and mobile phones, the built-in battery can be charged during standby, but when a long call is made or a call is frequently made. , It may be necessary to replace the empty battery with a charged battery.

When the battery is replaced, the microcomputer for system control needs to be reset. Immediately after the replacement of the battery, the clock formation (clock oscillation) in the microcomputer is not stable, so the clock is not stable. It is necessary to keep the reset state until it stabilizes, and release the reset when the clock stabilizes.

For this reason, the reset circuit and its peripheral circuits of cordless telephone handsets and portable telephones are constructed as shown in FIG. 3, for example.

That is, in FIG. 3, 10 is a cordless telephone handset, 11 is a transmission / reception circuit thereof, 12 is a transmitter, 13 is a receiver, and 14 is a transmission / reception antenna.
Further, reference numeral 15 denotes a microcomputer for system control.
Is controlled, and the entire operation of the child device 10 is controlled.

It should be noted that the microcomputer 15 is reset when it is a level trigger and is reset when it is "H".

Further, reference numeral 21 denotes a lead battery for power supply, and this battery 21 is detachable from the slave unit 10.
The output voltage of the battery 21 is supplied to the transmission / reception circuit 11, the microcomputer 15, and circuits 23, 24, 30 described later as their operating voltages, and the battery 21 is connected to the charging terminal 22.

Further, 23 is a battery voltage detection circuit, 24 is a charge detection circuit, and 30 is a reset circuit. This reset circuit 30 includes a voltage detection circuit 31, a time constant circuit 32, and an inverter 33 which also functions as a waveform shaping circuit. It is configured.

In this case, the detection circuit 31 includes, for example, as shown in FIG. 4, a FET (Q1), a voltage comparison circuit Q2, a constant current source Q3, a reference voltage forming circuit Q4, and voltage dividing resistors R1 and R.
It is composed of 2 etc. and is integrated into a single-chip IC. The input voltage is the specified value V31 (for example, 2V)
When the input voltage is lower than the specified value V31, VB =
It becomes "L".

When the battery 21 is replaced with a charged battery 21 due to a decrease in the voltage of the battery 21 (the battery 21 has become empty) or the like, the reset circuit 3
0 resets the microcomputer 15 once.

That is, when the old battery 21 is removed from the slave 10 and a new battery 21 is set, the voltage VA of the power supply line rises rapidly from the time t1 when the new battery 21 is set, as shown in FIG. 5A.

Then, when VA ≥V31 at the time t2 during the rising of the voltage VA, this is detected by the detection circuit 3.
1 and the detection output VB becomes "H" from the time point t2, as shown in FIG. 5B. Then, this detection output VB is supplied to the time constant circuit 32, and as shown in FIG. 5C, the voltage VC whose waveform is blunt is taken out, and this voltage VC is fed through the inverter 33 to the microcomputer 1
5 as its reset voltage.

Then, in this case, as shown in FIG. 5, the voltage VC exceeds the input threshold level V33 of the inverter 33 at the time t3, which is a little later than the time t2. Therefore, as shown in FIG. The output voltage VD of the inverter 33 becomes a voltage having a waveform that rises at time t1 and falls at time t3.

Since this voltage VD is supplied to the microcomputer 15 as a reset voltage, the microcomputer 15
It is reset during the period of D = "H", that is, the period t2 to t3, and the reset is released at the time point t3. Therefore, in the microcomputer 15, the period t2 to t
The clock becomes stable at 3, and the operation of the microcomputer 15 is started from the time point t3. Thereafter, a predetermined operation is performed and the handset 10 enters the standby state.

Further, after the time t3, the voltage of the battery 21 is lowered by using the slave unit 10, that is,
At time t4, when the voltage VA of the power supply line drops from its steady value (for example, 4 V) to the specified value V23 (for example, 3.3 V), this is detected by the detection circuit 23, and it is detected that the voltage of the battery 21 has dropped. Circuit 23 to microcomputer 15
Will be notified.

Then, the LED 16 is turned on by the microcomputer 15, the replacement or charging of the battery 21 is requested, and the microcomputer 15 enters the stop mode. Further, as a result, the transmission / reception circuit 11 is also stopped, and the handset 10 becomes unusable.

Therefore, the user replaces the battery 21 with the new battery 2
When it is replaced with 1, the operation from the above-mentioned time point t1 is executed again, and the handset 10 enters the standby state.

When the slave unit 10 is set in a charging device (not shown), the battery 21 is charged from the charging device through the terminal 22. At this time, the charging voltage is detected by the detection circuit 24, and the detection output is supplied to the microcomputer 24. As a result, the microcomputer 14
From the stop mode until then to the operation mode, the handset 10
Becomes standby again. Further, the LED 16 is changed from lighting of the charging request to blinking during charging. Then, when charging is completed, the LED 16 is turned off.

Thus, in this reset circuit,
When the voltage of the battery 21 drops, the microcomputer 15 is stopped and the child device 10 cannot be used. When the battery 21 is replaced with a new battery 21, the microcomputer 15 is reset,
After restarting, the child device 10 can be used.

In general, when the lead battery becomes over-discharged, it becomes unchargeable and cannot be used anymore. However, in the above-mentioned cordless handset 10, after the time t4, the cordless handset 10 is stopped and the battery 21 is discharged. Therefore, a lead battery can be used as the battery 21. Since the lead battery does not have the memory effect unlike the nickel-cadmium battery, the battery 21 can be always fully charged.

[0023]

However, in the above reset circuit, when the voltage of the battery 21 drops,
There is no problem in replacing the battery 21 with a new battery 21 or charging the battery 21, but if the voltage of the battery 21 drops, leaving the battery 21 as it is causes a problem.

That is, in FIG. 5, when the voltage of the battery 21 drops to the specified value V23 at time t4, the microcomputer 15 enters the stop mode and the slave unit 10 cannot be used as described above. After time t4, no current should be taken out.

However, actually, the microcomputer 15 consumes a current of several μA even in the stop mode. Further, as is clear from FIG. 3, the circuits 23, 24, 31, 33 are
Even if the microcomputer 15 is directly connected to the battery 21 and the microcomputer 15 enters the stop mode, the operating current flows through the circuits 23, 24, 31, and 33 (actual circuits 23 to 33 are composed of C-MOS. Therefore, the current consumption is very small).

Therefore, if the battery 21 is left as it is after the time point t4, the voltage VA of the power supply line gradually decreases after the time point t4 as shown in FIG. 5A.

At time t5, VA <V31, which is detected by the detection circuit 31 and VB = "L" as shown in FIG. 5B. Then, as shown in FIG. 5C, the voltage VC also starts to drop from the time point t5,
At time t6, which is slightly delayed from time t5, VC <
V33, and as shown in FIG. 5D, from time t6 VD =
It becomes "H".

Then, the microcomputer 15 is reset by this VD = "H", so that the microcomputer 15 returns from the stop mode to the operation mode and the current consumption of the microcomputer 15 increases to near the steady value. As a result, as shown in FIG. 5A, the voltage VA of the power supply line, that is,
After the time t6, the voltage of the battery 21 decreases at a speed faster than the period t4 to t6, and eventually the battery 21
Will be over-discharged.

Thus, in the above-mentioned reset circuit, when the voltage of the battery 21 is lowered, if the battery 21 is left as it is, the battery 21 is over-discharged and cannot be charged and cannot be used thereafter. I will end up.

The present invention is intended to solve such a problem.

[0031]

Therefore, in the present invention, when the reference numerals of the respective parts correspond to the embodiments described later, the transmitter / receiver circuit 11 and the system control microcomputer 15 for controlling the transmitter / receiver circuit 11 are described.
A voltage detection circuit 31 for detecting whether the voltage of the battery 21 for power supply is equal to or higher than a specified value, and the voltage detection circuit 3
An edge-trigger type monostable multivibrator 35 to which the detection output 1 is supplied is provided. When the voltage detection circuit 31 detects that the voltage of the battery 21 is the specified value or more, the monostable multivibrator 35
Triggered by the detection output, the output pulse of the monostable multivibrator 35 is supplied to the microcomputer 15 as its reset voltage, and the microcomputer 15 is kept in the reset state during the period of the output pulse.

[0032]

When the power is turned on by replacing the battery 21 or the like, the monostable multivibrator 35 is triggered according to the detection output of the voltage detection circuit 31, and the output pulse of the monostable multivibrator 35 resets the microcomputer 15. However, even if the voltage of the battery 21 drops, the monostable multivibrator 35 is not triggered and therefore the microcomputer 15 is not reset.

[0033]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, a reset circuit 30 comprises a voltage detection circuit 31 and a monostable multivibrator 35. Then, the voltage VA of the power supply line is supplied to the detection circuit 31, and the output voltage VB thereof is supplied to the input terminal B of the rising edge trigger type monostable multivibrator 35. The output pulse from the output terminal Q of the monostable multivibrator 35 is supplied to the reset terminal R of the system control microcomputer 15 as the reset voltage VD.

The elements C35 and R35 are capacitors and resistors for the time constant of the monostable multivibrator 35. By setting the time constant, the pulse width of the output pulse of the monostable multivibrator 35 is determined by the microcomputer. 1
5 is sufficient for the clock to stabilize. Further, the microcomputer 15 is reset when the reset is a level trigger and is "H".

According to this structure, when the old battery 21 is removed from the slave 10 and a new battery 21 is set,
As shown in FIG. 2A, the voltage VA of the power supply line rises rapidly from the time t1 when a new battery 21 is set.

Then, when VA ≥V31 at the time t2 during the rising of the voltage VA, this is detected by the detection circuit 3
1 and the detection output VB becomes "H" from the time point t2, as shown in FIG. 2B. Then, the detection output VB is supplied to the monostable multivibrator 35, and the monostable multivibrator 35 outputs the detection output VB.
Since it is triggered by the rising edge of B, the monostable multivibrator 35 outputs the time t as shown in FIG. 2C.
The pulse voltage VD rising to 2 and falling to time t3 after a period determined by the time constants of the elements C35 and R35 is taken out.

Since this pulse voltage VD is supplied to the microcomputer 15 as its reset voltage, the microcomputer 15 has a period of VD = "H", that is, the period t2.
The reset is released at t3, and the reset is released at time t3. Therefore, in the microcomputer 15,
The clock becomes stable during the period t2 to t3, the operation of the microcomputer 15 is started from the time point t3, and thereafter, a predetermined operation is performed and the slave unit 10 enters the standby state.

Further, after the time t3, the voltage of the battery 21 decreases by using the slave unit 10, and at the time t4, when the voltage VA of the power supply line decreases from its steady value to the specified value V23, this is detected. The detection by the circuit 23 notifies the microcomputer 15 that the voltage of the battery 21 has dropped.

Then, the LED 16 is turned on by the microcomputer 15, the replacement or charging of the battery 21 is requested, and the microcomputer 15 enters the stop mode. Further, as a result, the transmission / reception circuit 11 is also stopped, and the handset 10 becomes unusable.

Then, the user replaces the battery 21 with the new battery 2
When it is replaced with 1, or when the cordless handset 10 is set in the charging device (not shown), the same operation as in the case of FIG. 3 is performed, and the cordless handset 10 is ready to be used again.

On the other hand, even if the voltage VA of the battery 21 drops to the specified value V23 at the time t4, if it is left as it is, the microcomputer 15 enters the stop mode as described above, but the circuits 23, 24, 31 are used. , 35, the operating current continues to flow, and as shown in FIG.
Gradually decreases.

At time t5, VA <V31, which is detected by the detection circuit 31 and VB = "L" as shown in FIG. 2B.

However, even if VB = “L”, the output voltage VD of the monostable multivibrator 35 does not change and remains “L” because the monostable multivibrator 35 is of a type triggered by the rising edge. To the microcomputer 15
Is not reset and the microcomputer 15 returns to the time point t5.
After that, the stop mode is continued and a large normal operating current is not consumed.

Therefore, when the voltage of the battery 21 drops, it is possible to prevent the battery 21 from being over-discharged even if the slave 10 is left as it is.

[0045]

According to the present invention, in a cordless telephone handset, a mobile telephone, or the like, when the power is turned on, the detection output VB is supplied to an edge trigger type monostable multivibrator 35, and its output pulse is output. Voltage V
The microcomputer 15 for system control is reset by D.

Therefore, when the voltage of the battery 21 for power supply drops and the microcomputer 15 enters the stop mode, the stop mode of the microcomputer 15 is not released even if it is left as it is, and the microcomputer 15 operates normally. Since no current flows, the battery 21 will not be over-discharged.

Since the battery 21 does not become over-discharged, a lead battery can be used as the battery 21, and the lead battery has no memory effect.
1 can be kept in a fully charged state at all times and can talk at any time.

[Brief description of drawings]

FIG. 1 is a system diagram showing an example of the present invention.

FIG. 2 is a waveform diagram for explaining the present invention.

FIG. 3 is a system diagram for explaining the present invention.

FIG. 4 is a circuit diagram showing a part of FIG.

FIG. 5 is a waveform diagram for explaining the circuit of FIG.

[Explanation of symbols]

 10 Handset 11 Transmitter / receiver circuit 15 Microcomputer 21 Battery 22 Charging terminal 23 Battery voltage detection circuit 24 Charge detection circuit 30 Reset circuit 31 Voltage detection circuit 35 Monostable multivibrator

Claims (4)

[Claims] 1. A transmission / reception circuit, a system control microcomputer for controlling the transmission / reception circuit, a voltage detection circuit for detecting whether or not a voltage of a battery for a power source is a specified value or more, and a voltage detection circuit for the voltage detection circuit. It has an edge trigger type monostable multivibrator to which a detection output is supplied, and this monostable multivibrator, when the voltage detection circuit detects that the voltage of the battery is the specified value or more, Triggered by the detection output, the output pulse of the monostable multivibrator is supplied to the microcomputer as its reset voltage, the microcomputer, during the period of the output pulse,
The reset circuit of the radio set to the reset state. 2. A transmission / reception circuit, a system control microcomputer for controlling this transmission / reception circuit, and a voltage detection circuit whose detection output is "H" when the voltage of the battery for the power supply is equal to or higher than a specified value. And a rising edge trigger type monostable multivibrator to which the detection output of the voltage detection circuit is supplied, wherein the microcomputer has a reset terminal in a reset state for a predetermined level. The output pulse of the multivibrator is supplied to the microcomputer as its reset voltage, and the microcomputer outputs the period of the output pulse,
The reset circuit of the radio set to the reset state. 3. A radio device having a transmitter / receiver circuit and a system control microcomputer for controlling the transmitter / receiver circuit, wherein the power supply is a battery, and detects whether or not the voltage of the battery is a specified value or more. , This detection output is supplied to an edge trigger type monostable multivibrator, and the monostable multivibrator is triggered by the detection output when it is detected that the voltage of the battery is equal to or higher than the specified value. A reset circuit for a wireless device, wherein the microcomputer causes the microcomputer to be in a reset state during the period of the output pulse by the output pulse of the stable multivibrator. 4. A radio device having a transmitter / receiver circuit and a system control microcomputer for controlling the transmitter / receiver circuit, wherein the power supply is a battery, and becomes “H” when the voltage of the battery is a specified value or more. The detection output is obtained, and this detection output is supplied to the rising edge trigger type monostable multivibrator, and the output pulse of this monostable multivibrator is supplied to the microcomputer as its reset voltage. The duration of the pulse,
The reset circuit of the radio set to the reset state.