JP2000222051A - Stabilized power unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the useless consumption of power and also to prevent a case where an IC circuit of a microcomputer or the like has a malfunction due to the deficient output voltage by stopping the operation of an output transistor when the input voltage is low than its prescribed level. SOLUTION: An output transistor Tr1 is placed in series between an input terminal 1 to which a battery power supply is connected and an output terminal 2 to which the load of a portable information terminal device or the like is connected. The input voltage Vin of the terminal 1 is divided by the voltage dividing resistances Ra and Rb and then the divided voltage is compared with the reference voltage Vref2 by a comparator circuit 4. When the voltage Vin is set lower than the prescribed input voltage Vin 1 that is previously decided, the output of the comparator circuit 4 is set at a low level. Thus, a control circuit cut-off transistor Tr3 and ten the Tr1 are turned off to stop the operation of a stabilized power circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stabilized power supply suitable for a charge-driven electronic device such as a mobile information terminal such as a mobile phone, and more particularly, it is impossible to stabilize the output due to a decrease in input voltage. The present invention relates to a stabilized power supply device having a function of stopping the operation of a circuit when the power supply circuit stops operating.

[0002]

2. Description of the Related Art Conventionally, a stabilized power supply circuit of an electronic device using a rechargeable battery such as a portable device has an output transistor provided in series between a rechargeable battery and a load circuit of the electronic device driven by the rechargeable battery. A detection circuit for detecting an output voltage supplied from the output transistor to the load circuit; and a feedback circuit for feeding back the output voltage detected by the detection circuit to the output transistor and controlling the output voltage to a predetermined output voltage. I have.

Accordingly, the detection circuit constantly detects the output voltage of the output transistor, and feeds back an error signal between the detected output voltage and a predetermined reference voltage to a control terminal of the transistor by a feedback circuit. A predetermined output voltage is derived from the output terminal.

[0004]

In recent years, mobile information communication technology has been developed and rechargeable battery-operated electronic devices such as mobile phones have become widespread. In such electronic devices, there is a demand for longer battery life. strong. In the above-mentioned conventional stabilized power supply circuit, when an input voltage which is larger than the sum of the output voltage of the stabilized power supply circuit and the voltage between the collector and the emitter of the output transistor is supplied to the input terminal, the stabilized power supply circuit Is controlled to the above-mentioned predetermined voltage, but if a sufficient voltage is not applied to the input terminal, the output voltage becomes larger than a value obtained by subtracting the collector-emitter voltage of the output transistor from the input voltage. The output voltage cannot be increased to the set value unless the input voltage is increased.

In a stabilized power supply circuit using a bipolar transistor, as shown in FIG. 11, an input voltage Vin is equal to a set output voltage Vo + collector of the bipolar transistor.
Until the emitter-to-emitter voltage Vi-o, the set output voltage Vo
Cannot be output, and a large circuit operation current as shown in FIG. 12 flows at the time of rising. Therefore, when the input voltage rises low, a large amount of useless current is consumed, and there is a problem in that the battery used as a power source is greatly consumed.

A microcomputer is usually used in an electronic device using the stabilized power supply circuit. However, when the input voltage to the microcomputer is reduced, the microcomputer operates as described above. A signal is required, and it is desired that the reset signal can be supplied from a stabilized power supply circuit.

According to the present invention, when the input voltage to the stabilized power supply circuit is low and the required output voltage cannot be obtained from the output circuit, the stabilized power supply circuit is turned off and the stabilized power supply circuit is turned off. An object of the present invention is to provide a stabilized power supply device capable of eliminating unnecessary power consumption and preventing an IC circuit such as a microcomputer from malfunctioning at an insufficient output voltage.

[0008]

According to the first aspect of the present invention, an output transistor is provided in series between an input terminal and an output terminal, and a voltage derived from the output terminal is detected. In a stabilized power supply device provided with a control feedback circuit for controlling the output transistor so that the output voltage is set to a predetermined value based on the detected voltage, an input voltage detection for detecting an input voltage supplied to the input terminal And a control circuit for stopping the operation of the output transistor when the voltage detected by the input voltage detection circuit is equal to or lower than a predetermined voltage.

The invention described in claim 2 is the first invention.
Wherein the control circuit cuts off the control transistor controlled by the output transistor and the control transistor when a voltage detected by the input voltage detection circuit is equal to or lower than a predetermined voltage. And a shut-off transistor to be turned on.

[0010] Further, the invention according to claim 3 is based on claim 1.
Wherein the power supply cutoff circuit for cutting off the supply of power to the control circuit when the voltage detected by the input voltage detection circuit is equal to or lower than a predetermined voltage is provided. And According to a fourth aspect of the present invention, in the stabilized power supply according to any one of the first to third aspects, the control circuit controls an operation of the output transistor based on a voltage detected by the input voltage detection circuit. Is characterized in that the operation stop voltage has a hysteresis characteristic.

The invention described in claim 5 is the first invention.
5. The stabilized power supply device according to any one of 1 to 4, wherein a signal for forcibly stopping the operation of the output transistor is supplied to the control circuit when an input voltage is insufficient to generate a stabilized output voltage. A control signal input terminal is provided.

According to a sixth aspect of the present invention, an output transistor is provided in series between an input terminal and an output terminal, a voltage derived from the output terminal is detected, and the output voltage is determined by the detected voltage. In a stabilized power supply device provided with a control feedback circuit for controlling the output transistor so that the output transistor has a value, when the input voltage supplied to the input terminal is equal to or higher than a predetermined value, the output transistor is turned off. A control circuit for causing the output transistor to stop operating when the input voltage falls below the predetermined value, and a reset signal when the input voltage falls below the predetermined value. Is provided.

According to a seventh aspect of the present invention, an output transistor is provided in series between an input terminal and an output terminal, a voltage derived from the output terminal is detected, and the output voltage is determined by the detected voltage. In the stabilized power supply device provided with a control feedback circuit for controlling the output transistor so as to obtain the value of the first output transistor, a first divided voltage obtained by dividing an input voltage supplied to the input terminal is obtained. Voltage divider circuit,
A second voltage dividing circuit for deriving a second divided voltage lower than the first divided voltage obtained by dividing the input voltage; and the second divided voltage is equal to or less than a predetermined voltage. A control circuit for stopping the operation of the output transistor; and a reset signal generating circuit for generating a reset signal when the first divided voltage is equal to or lower than a predetermined voltage.

[0014]

Therefore, according to the stabilized power supply device of the first aspect, the input voltage supplied from the power supply such as a battery to the input terminal is detected by the input voltage detection circuit, and the detected voltage is set to a predetermined predetermined value. When the voltage becomes lower than the voltage of the output terminal, the operation of the output transistor is stopped by the control circuit, and the supply of the voltage to the output terminal is cut off. As a result, unnecessary large current consumption of the stabilized power supply device when the input voltage decreases can be suppressed.

According to the stabilized power supply device of the present invention, when the input voltage detected by the input voltage detection circuit falls below a predetermined voltage, the operation of the output transistor is controlled by the control circuit cut-off transistor. As a result, the output transistor is turned off and the supply of voltage to the output terminal is interrupted.

According to the stabilized power supply device of the third aspect, when the input voltage detected by the input voltage detection circuit becomes equal to or lower than a predetermined voltage, the power supply cutoff circuit supplies power to the control circuit. Cut off. As a result, the output transistor is turned off by the control circuit, and the supply of the voltage to the output terminal is cut off.

Further, according to the stabilized power supply device of the present invention, when the voltage of the input terminal detected by the input voltage detection circuit falls below a predetermined value, the control output for turning off the output transistor of the control circuit. Is provided with a hysteresis characteristic, it is possible to prevent the ON / OFF control of the output transistor by the control circuit from becoming unstable due to vibration such as chattering near the predetermined voltage.

According to the stabilized power supply device of the fifth aspect, a control input terminal is provided, and if the input voltage to the input terminal becomes insufficient to generate a stabilized output voltage,
Since a control signal for forcibly stopping the operation of the output transistor can be input to the control circuit from the control input terminal, when the input voltage decreases, the stabilized power supply device can be reliably turned off. .

According to the stabilized power supply device of the present invention, when the input voltage becomes equal to or less than a predetermined value,
The operation of the output transistor is stopped by the control circuit, and a reset signal for resetting the load circuit connected to the output terminal is generated by the reset signal generation circuit.

Further, according to the stabilized power supply device of the present invention, the large divided voltage is derived from the large divided voltage circuit obtained by dividing the input voltage, and the second divided voltage is derived from the second divided voltage circuit. Derive a second divided voltage lower than the first divided voltage, and when the second divided voltage falls below a predetermined voltage, the control circuit stops the operation of the output transistor, When the divided voltage becomes equal to or lower than a predetermined voltage, a reset signal for resetting the load circuit is generated by the reset signal generation circuit.

[0021]

<First Embodiment> FIG. 1 is a circuit diagram of a first embodiment of the present invention. Battery power (not shown)
Input terminal 1 for connecting to a personal digital assistant (not shown)
An output transistor Tr1 is provided in series between output terminals 2 for connecting a load such as. The output terminal 2 has a voltage dividing resistor Rc
And Rd are provided in series, and a comparison circuit 3 comprising a differential amplifier for comparing a divided voltage by the voltage dividing resistors Rc and Rd with a predetermined reference voltage Vref1 is provided, and an output of the comparison circuit 3 is output by the output transistor. The output transistor Tr1 connected to the control terminal of Tr1 is connected to the control terminal of a control transistor Tr2 for controlling the output transistor Tr1. Tr3 is a control circuit cut-off transistor connected in series with the control transistor Tr2.

On the other hand, the input terminal 1 has voltage dividing resistors Ra and Rb for dividing the input voltage VIN supplied to the input terminal 1.
And a comparison circuit 4 composed of a differential amplifier for comparing the divided voltage divided by the dividing resistors Ra and Rb with a predetermined reference voltage Vref2, and outputting the output of the comparison circuit 4 to the control circuit Connected to the control terminal of the blocking transistor Tr3. In this case, the reference voltage Vref1 is output from the output terminal 2
Output voltage VOUT is a predetermined output voltage VOU
A voltage divided by the voltage dividing resistors Rc and Rd at the time of T1 is set, and the reference voltage Vref2 is set to the output terminal 2
Of the output transistor T
The voltage VI obtained by adding the base-emitter voltage VEB of r1
N1 is set to a divided voltage divided by the dividing resistors Ra and Rb.

Therefore, the output voltage VOUT at the output terminal 2 is divided by the voltage dividing resistors Rc and Rd, input to one terminal of the comparison circuit 3, and compared with the reference voltage Vref1. As a result, when the output voltage VOUT of the output terminal 2 is lower than a predetermined output voltage VOUT1, a high signal is output from the comparison circuit 3, and when it is higher, a low signal is output. Is turned on and off, and accordingly, the output transistor is turned on and off, and a predetermined voltage VOUT is applied to the output terminal 2.
1 is output.

On the other hand, the input voltage VIN of the input terminal 1 is divided by the voltage dividing resistors Ra and Rb, and the divided voltage is compared with the reference voltage Vref2 by the comparison circuit 4. As a result, when the input voltage VIN is higher than the predetermined input voltage VIN1, the output of the comparison circuit 4 becomes High, the transistor Tr3 for turning off the control circuit is turned on, and the output transistor Tr1 is kept on. , The stabilized power supply operates normally, and a predetermined stable output voltage VO is output from the output terminal.
Outputs UT1. However, when the input voltage VIN becomes lower than the predetermined input voltage VIN1, the comparison circuit 4
Becomes low, and the control circuit shut-off transistor T
r3 is turned off and the output transistor Tr1 is turned off
And the operation of the stabilized power supply circuit is stopped.

<Embodiment 2> FIG. 2 is a circuit diagram of a second embodiment of the present invention. 2, parts corresponding to those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. FIG. 2 differs from FIG. 1 in that the polarity of the input terminal of the comparison circuit 4 in FIG. 1 is reversed, and when the input voltage VIN1 is higher than a predetermined voltage VIN1 (= Vref2). Is set to Low, and when the output is low, the output of the comparison circuit 4 is set to High. Then, the control circuit cutoff transistor Tr3 that operates at the output of the comparison circuit 4 in FIG. 1 is removed, and a control circuit cutoff transistor Tr4 that operates at the output of the comparison circuit 4 is provided at the input terminal of the control transistor Tr2 instead.

Accordingly, when the input voltage VIN of the input terminal 1 is higher than the predetermined input voltage VIN1, the output of the comparison circuit 4 becomes low, and the control circuit cut-off transistor Tr4 is turned off. Tr
1 performs a normal operation, and outputs a predetermined output voltage VOUT1 to the output terminal 2. Also, the input voltage VI
When N becomes lower than the predetermined input voltage VIN1, the output of the comparison circuit 4 becomes High and the control circuit cut-off transistor Tr4 is turned on.
r2 is turned off, and the output transistor Tr1 is turned off.

<Embodiment 3> FIG. 3 is a circuit diagram of a third embodiment of the present invention. 3, parts corresponding to those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. 3 is different from FIG. 1 in that power supply control transistors Tr5 and Tr6 for controlling the power supply of a control circuit composed of the control transistor Tr2, the comparison circuit 3, the voltage dividing resistors Rc and Rd, and the reference voltage Vref1 in FIG. That is, The transistor Tr6 is provided in series between the input terminal 1 and the ground via the resistor R1, and supplies the reference voltage Vref1 of the comparison circuit 3 to the input terminal using the voltage between both terminals of the resistor R1 as the power supply voltage of the control circuit. A resistor R2 for generating the reference voltage Vref1 is provided between the input terminal and the ground. Then, a transistor Tr5 is provided at the control terminal of the transistor Tr6,
5 is connected to the output terminal of the comparison circuit 4.

Therefore, when the input voltage VIN is higher than the predetermined input voltage VIN1, the output of the comparison circuit 4 becomes Hi.
gh, the transistor Tr5 is turned on, the transistor Tr6 is turned on, power is supplied from the input terminal 1 to the comparison circuit 3 of the control circuit, and the output transistor Tr1 is operated. When the input voltage VIN becomes lower than the input voltage VIN1, the output of the comparison circuit 4 becomes Low, the transistors Tr5 and Tr6 are turned off, and the supply of power to the comparison circuit 3 constituting the control circuit is cut off. as a result,
The output transistor Tr1 turns off.

<Embodiment 4> FIG. 4 is a circuit diagram of a fourth embodiment of the present invention. 4, parts corresponding to those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. 4 differs from FIG. 1 in the control circuit of the control circuit cut-off transistor Tr3. Output voltage VO of output terminal 2
Voltage dividing resistors Re and Rf for dividing the UT, and a divided voltage of the output voltage VOUT divided by the voltage dividing resistors Re and Rf;
The divided voltage of the input voltage VIN to the input terminal 1 by the resistors Ra and Rb provided at the input terminal 1 is referred to as a reference voltage Vr.
ef2 is supplied to the first and second input terminals of a comparison circuit 5 composed of a differential amplifier for comparison. The output terminal of the comparison circuit 5 is connected to the control circuit cut-off transistor Tr3.
To the control terminal.

In this case, the voltage dividing resistors Ra, Rb, R
The values of e and Rf are determined as follows. Output voltage VO
When the UT is not output (VOUT = 0), the predetermined input voltage required to operate the stabilized power supply circuit is set to VI.
When N1 is set, the values of the resistors Ra and Rb are determined so that the voltage divided by the resistors Ra and Rb of VIN1 becomes VIN1 * Rb / (Ra + Rb) = Vref2.

When the output voltage VOUT is at a predetermined output voltage VOUT1, a stabilizing power supply circuit is turned from ON to OFF when the input voltage VIN is at a predetermined input voltage VIN2. Switch to. In this case, VIN1> VIN2, and the value of VIN1−VIN2 is set to such an extent that vibration due to ON / OFF of a circuit such as chattering does not occur in VIN1.

Therefore, it is set so that VIN2 * Rb * (Ra + Rb) = VIN1 * Rb * (Ra + Rb) -VOUT1 * Rf * (Re + Rf). On the other hand, since VIN1 * Rb * (Ra + Rb) = Vref2, VOUT1 * Rf * (Re + Rf) = Vref2-VIN2 * Rb * (Ra + Rb). Is determined.

Then, the divided voltage of the input voltage VIN and the output voltage VOUT by the voltage dividing resistors Ra and Rb and Re and Rf determined as described above is supplied to the comparison circuit 5,
The comparison circuit 5 compares the voltage with the reference voltage Vref2. Now, in a state where the output voltage VOUT is not output, the input voltage VIN
Gradually rises, and the output of the comparison circuit 5 holds Low until it reaches VIN1, but when the input voltage exceeds VIN1, the output of the comparison circuit 5 is inverted to High, and the transistors Tr3 and Tr2 are turned ON. A predetermined output voltage VOUT1 is output to the output terminal 2.

The output voltage VOUT is a predetermined output voltage VOU
When the value of the input voltage VIN decreases while T1 is being output, VIN lower than the input voltage VIN1
Until the output becomes 2, the output of the comparison circuit 5 holds High,
When the input voltage becomes lower than VIN2, the output of the comparison circuit 5 is inverted to Low. As a result, the transistor Tr3,
Tr2 is turned off, the output transistor Tr1 is turned off, and the stabilized power supply circuit stops operating.

Therefore, the operation characteristics of the output transistor Tr1 turning on and off with respect to the fluctuation of the input voltage include the characteristics shown in FIG.
As shown in the figure, the output voltage VOUT can be output or output even when the input voltage VIN fluctuates when the input voltage is near a predetermined input voltage VIN1 (VIN VIN1). It is possible to prevent the unstable output voltage from oscillating.

<Fifth Embodiment> FIG. 6 is a circuit diagram of a fifth embodiment of the present invention. 6, portions corresponding to those in FIG. 2 are denoted by the same reference numerals, and description thereof will be omitted. 6 differs from FIG. 2 in that a control terminal 8 is provided at a voltage dividing point of a voltage dividing circuit composed of voltage dividing resistors Ra and Rb provided at the input terminal 1.

Therefore, when the input voltage to the input terminal 1 is lower than the predetermined input voltage VIN1, the divided voltage of the input voltage VIN by the resistors Ra and Rb is equal to the reference voltage V1.
ref2, the output of the comparison circuit 4 is High.
The control terminal of the transistor Tr4 for shutting off the control circuit is set to High, and the transistors Tr2 and Tr1 are turned off.
FF is performed to shut off the stabilized power supply circuit. When the input voltage to the input terminal 1 becomes higher than the input voltage VIN1, the divided voltage by the resistors Ra and Rb becomes equal to the reference voltage Vre.
Beyond f2, a low signal is supplied from the comparison circuit 4 to the control terminal of the transistor Tr4. As a result, the transistor Tr4 is turned off, and the transistors Tr2 and Tr3 are turned off.
Is turned on to operate the stabilized power supply circuit.

On the other hand, when control is performed by inputting a control signal from the control terminal 8, a high active circuit is used.
When a low signal is supplied from the control terminal 8, the output of the comparison circuit 4 becomes high, and the transistor Tr4 is turned off.
N, the transistors Tr2 and Tr1 are turned off, and the stabilized power supply circuit can be forcibly turned off.

<Embodiment 6> FIG. 7 is a circuit diagram of a sixth embodiment of the present invention. 7, parts corresponding to those in FIG. 2 are denoted by the same reference numerals, and description thereof will be omitted. 7 differs from FIG. 2 in the control circuit of the control circuit cut-off transistor Tr4.

This control circuit is configured as follows. A series circuit of a resistor R5 and a transistor Tr7 is provided between the input terminal 1 and the ground, and a resistor R4 is provided between the voltage dividing point of the voltage dividing resistors Ra 'and Rb' provided between the input terminal 1 and the ground and the input terminal of the transistor Tr7. And a series circuit of a diode D. Further, the output terminal of the transistor Tr7 is connected to the input terminal of the control circuit shut-off transistor Tr4. Further, a control terminal 9 connected to the voltage dividing point of the voltage dividing resistors Ra 'and Rb' is provided.

When the value of the voltage dividing resistors Ra 'and Rb' reaches the predetermined input voltage VIN1 when the value of the input terminal VIN becomes a predetermined value, the divided voltage becomes the diode D
And the base-emitter voltage of the transistor Tr7.

Therefore, according to the above configuration, the input voltage V
When IN is lower than a predetermined input voltage VIN1, the potential of the voltage dividing point of the voltage dividing circuit by the voltage dividing resistors Ra ′ and Rb ′ cannot exceed the threshold of the diode D and the transistor Tr7, The transistor Tr7 is turned off. As a result, the control circuit cut-off transistor Tr4 is turned on and the transistor Tr4 is turned off.
2. Turn off Tr1 to shut off the stabilized power supply circuit.

When the input terminal VIN becomes higher than a predetermined input voltage VIN1, the voltage at the voltage dividing point of the voltage dividing resistors Ra 'and Rb' exceeds the threshold voltage of the diode D and the transistor Tr7, and the voltage of the transistor Tr7
To ON. As a result, the control circuit cut-off transistor Tr4 is turned off, and the transistors Tr2 and Tr1 are turned off.
N to bring the stabilized power supply circuit into an operating state.

On the other hand, when control is performed by inputting a control signal from the control terminal 9, a high active circuit is used.
When a High signal is input from the outside through the control terminal 9, the transistor Tr7 is turned on beyond the threshold voltage, and as a result, the stabilized power supply circuit is turned off in the same manner as described above.

<Embodiment 7> FIG. 8 is a circuit diagram of a seventh embodiment of the present invention. 8, parts corresponding to those in FIG. 7 are denoted by the same reference numerals, and description thereof will be omitted. 8 differs from FIG. 7 in that a resistor R7 is externally connected between the control terminal 9 and the input terminal 1.

Therefore, the voltage at the voltage dividing point between the voltage dividing resistors Ra 'and Rb' can be switched by connecting the resistor R7. As a result, the potential of the voltage dividing point of the voltage dividing circuit with respect to the predetermined input voltage VIN1 can be adjusted, and depending on the type or state of the battery connected to the input terminal 1 and the load connected to the output terminal 2, It is possible to adjust the value of the desired input voltage VIN1 at the switching point at which the stabilized power supply circuit is switched between the cutoff state and the operation state to an optimum value.

<Eighth Embodiment> FIG. 9 is a circuit diagram of an eighth embodiment of the present invention. 9, parts corresponding to those in FIG. 2 are denoted by the same reference numerals, and description thereof will be omitted. 9 differs from FIG. 2 in that the input voltage VIN of the input terminal 1 is different.
, The reset signal supplied to the load circuit connected to the stabilized power supply circuit is simultaneously output.

In FIG. 9, reference numeral 6 denotes a comparison circuit for comparing the potential of the voltage dividing point by the voltage dividing resistors Ra and Rb connected to the input terminal 1 with a predetermined reference voltage Vref2. Connects the input terminal of the transistor Tr9, and provides a series circuit of the transistor Tr9 and the resistor R7 between the terminal 11 of the power supply Vcc and the ground. Reference numeral 12 denotes a reset signal output terminal connected to the collector of the transistor Tr9.

Therefore, when the input voltage VIN of the input terminal 1 becomes higher than a predetermined value, the transistor Tr1 is turned on and the stabilized power supply circuit is activated, as in the case of FIG. Also, at this time, the output terminal of the comparison circuit 6 becomes high similarly to the comparison circuit 4, and the transistor Tr9 is turned on. Therefore, the reset signal output terminal 1
The reset signal output from 2 goes low.

On the other hand, when the input voltage VIN of the input terminal 1 becomes lower than a predetermined value, the transistor Tr1 is turned off as in the case of FIG. 2, and the stabilizing circuit is turned off. At this time, the comparison circuit 6 outputs Low, opposite to the comparison circuit 4, and turns off the transistor Tr9. Therefore, the reset signal output terminal 12 becomes High level. As described above, when the input level of the input terminal 1 falls below a predetermined input voltage VIN1 or more, the stabilized power supply circuit is shut off, and the output terminal 2 of the stabilized power supply circuit is turned off. A reset signal for resetting the load circuit connected to the terminal is output from a reset signal output terminal 12.

<Embodiment 9> FIG. 10 is a circuit diagram of an eighth embodiment of the present invention. 10, parts corresponding to those in FIG. 9 are denoted by the same reference numerals, and description thereof will be omitted. FIG.
9 is different from FIG. 9 in that the output timing of the reset signal is shifted from the ON / OFF switching timing of the stabilized power supply circuit.

In FIG. 10, a voltage dividing circuit composed of resistors Ri and Rj and a voltage dividing circuit composed of resistors Rk and Rl are provided between the input terminal 1 and the ground, and the voltage dividing point of the voltage dividing circuit composed of the resistors Ri and Rj is determined. The reference voltage Vref2 is connected to the + input terminal of the comparison circuit 7 connected to the-input terminal, and the resistance R
k, Rl is divided by a reference voltage Vref
2 is connected to the negative input terminal of the comparison circuit 4 connected to the positive input terminal. Then, the comparison circuits 4 and 7
Are connected to the input terminals of the transistors Tr4 and Tr9, respectively, as in the eighth embodiment shown in FIG.

Then, a resistor R constituting one voltage dividing circuit
When the input voltage VIN of the input terminal 1 becomes larger than a predetermined input voltage VIN1, the resistance R
It is set so that the divided voltage of the voltage dividing circuit by i and Rj can exceed the reference voltage Vref2. Also, the values of the resistors Rk and Rl constituting the other voltage dividing circuit are
When the input voltage VIN of the input terminal 1 becomes higher than a predetermined input voltage VIN2, a setting is made so that the divided voltage of the voltage dividing circuit by the resistors Rk and Rl can exceed the reference voltage Vref2. In this case, the relationship between the predetermined input voltages VIN1 and VIN2 is V
IN1> VIN2.

Therefore, when the input voltage VIN is higher than the predetermined input voltage VIN1, the output of the comparison circuit 4 becomes Low, turning off the transistor Tr4 to put the stabilized power supply circuit into an operating state. The output of the comparison circuit 7 is set to High, and the reset signal output terminal 1
2 is at the low level, and the reset signal is not output. The input voltage VIN is a predetermined input voltage VI
When the voltage is between N1 and VIN2, the output of the comparison circuit 4 goes low and the stabilized power supply circuit is activated as described above. However, the output of the comparison circuit 7 also goes low and the transistor Tr9 is turned off. And reset signal output terminal 12
Is set to High, and a reset signal is output. When the input voltage VIN becomes lower than the predetermined input voltage VIN2, the output of the comparison circuit 4 is inverted to High, the stabilized power supply circuit is turned off, and the output of the comparison circuit 7 is changed to Low. , The reset signal output terminal 12 is set to Hi.
gh, and outputs a reset signal.

Therefore, when the input voltage VIN is VIN> VIN
In 1, the stabilized power supply circuit operates normally and no reset signal is output. However, VIN1>VIN> VIN
When the value becomes 2, the stabilized power supply circuit operates, and at the same time, a reset signal is output, so that appropriate measures such as protecting the load circuit can be taken. Further, when VIN <VIN2, a reset signal is output, but at the same time, the stabilized power supply circuit is turned off.

[0056]

According to the present invention, when the input voltage becomes lower than a predetermined value in the input voltage detection circuit, the operation of the output transistor is stopped and the stabilized power supply is shut off. Since the state is set, consumption of a large current supplied to the stabilized power supply device when the input voltage decreases can be eliminated, and the life of the battery power supply connected to the input terminal can be extended.

According to the present invention, when the input voltage detection circuit detects that the input voltage becomes lower than the predetermined value, the control transistor is driven by the control circuit cut-off transistor, and the output transistor is turned off. Therefore, the circuit current at the time of low input voltage of the stabilized power supply device can be eliminated with a simple circuit configuration, and the consumption of the battery power supply connected to the input terminal can be suppressed.

According to the third aspect, when the input voltage to the input terminal becomes lower than a predetermined value, the supply of power to the control circuit is cut off. In this case, the consumption of the circuit current can be suppressed.

According to the fourth aspect, when the input voltage is in the vicinity of a predetermined voltage, the ON / OFF control of the output transistor has a hysteresis characteristic when the input voltage rises and falls. It is possible to suppress an unstable operation in which the output transistor repeatedly turns ON and OFF around the predetermined voltage.

According to the present invention, a control signal for forcibly turning off the output transistor can be input to the control circuit from the control signal input terminal. The device can be reliably turned off.

According to the present invention, when the input voltage becomes lower than a predetermined value, the control circuit turns off the output transistor to prevent consumption of the circuit current and to reduce the power consumption of the battery power supply connected to the input terminal. A reset signal can be generated to prevent wear and to prevent a malfunction due to a voltage drop of a load circuit connected to the output terminal with a decrease in the input voltage.

According to the seventh aspect, the first input voltage
When the divided voltage becomes lower than a predetermined voltage, a reset signal is derived, and when the divided voltage becomes lower than a second divided voltage lower than the first divided voltage, the stabilized power supply circuit is shut off. Therefore, even if the input voltage drops from the normal operation state of the stabilized power supply circuit, a reset signal is generated before the circuit is shut off.
By using this reset signal, it is possible to take measures to protect the load circuit during the operation of the load circuit before the shutdown of the stabilized power supply circuit.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a first embodiment of the present invention.

FIG. 2 is a circuit diagram according to a second embodiment of the present invention.

FIG. 3 is a circuit diagram of a third embodiment of the present invention.

FIG. 4 is a circuit diagram according to a fourth embodiment of the present invention.

FIG. 5 is an operation explanatory diagram of a fourth embodiment of the present invention.

FIG. 6 is a circuit diagram according to a fifth embodiment of the present invention.

FIG. 7 is a circuit diagram according to a sixth embodiment of the present invention.

FIG. 8 is a circuit diagram according to a seventh embodiment of the present invention.

FIG. 9 is a circuit diagram of an eighth embodiment of the present invention.

FIG. 10 is a circuit diagram of a ninth embodiment of the present invention.

FIG. 11 is an operation explanatory diagram of a conventional example.

FIG. 12 is an operation explanatory diagram of a conventional example.

[Explanation of symbols]

1 input terminal 2 output terminal 3, 4, 5, 6, 7 comparison circuit 8, 9, 10 control terminal 11 power supply terminal 12 control terminal Ra, Rb, Rc, Rd, Re, Rf, Ri, Rj, R
k, Rl, Ra ', Rb' resistance R1, R2, R3, R4, R5, R6, R7 resistance Tr1, Tr2, Tr3, Tr4, Tr5, Tr6, T
r7, Tr8, Tr9 transistor

Claims (7)

[Claims] An output transistor is provided in series between an input terminal and an output terminal, detects a voltage derived from the output terminal, and sets the output voltage to a predetermined value based on the detected voltage. A stabilized power supply device provided with a control feedback circuit for controlling the input voltage, wherein an input voltage detection circuit for detecting an input voltage supplied to the input terminal, and a voltage detected by the input voltage detection circuit is a predetermined predetermined value. A stabilized power supply device comprising a control circuit for stopping the operation of the output transistor when the voltage is lower than the voltage. 2. A control transistor for controlling the output transistor by the control circuit, and a cutoff for setting the control transistor to a cutoff state when a voltage detected by the input voltage detection circuit is equal to or lower than a predetermined voltage. 2. The stabilized power supply device according to claim 1, wherein the stabilized power supply device comprises: 3. A power supply shutoff circuit for shutting off power supply to said control circuit when a voltage detected by said input voltage detection circuit is equal to or lower than a predetermined voltage. 2. The stabilized power supply device according to 1. 4. The control circuit according to claim 1, wherein an operation stop voltage of said control circuit for controlling an operation of said output transistor based on a voltage detected by said input voltage detection circuit has a hysteresis characteristic. A stabilized power supply according to any one of the above. 5. A control signal input terminal for supplying a signal for forcibly stopping the operation of the output transistor to the control circuit when an input voltage is insufficient to generate a stabilized output voltage. The stabilized power supply device according to any one of claims 1 to 4, wherein: 6. An output transistor is provided in series between an input terminal and an output terminal, detects a voltage derived from the output terminal, and sets the output voltage to a predetermined value based on the detected voltage. In a stabilized power supply device provided with a control feedback circuit for controlling the output transistor, when the input voltage supplied to the input terminal is equal to or higher than a predetermined value, the output transistor is turned on, and the input voltage is increased. A control circuit for stopping the operation of the output transistor when the voltage falls below a predetermined value; and a reset signal generating circuit for generating a reset signal when the input voltage falls below the predetermined value. A stabilized power supply device. 7. An output transistor is provided in series between an input terminal and an output terminal, detects a voltage derived from the output terminal, and sets the output voltage to a predetermined value based on the detected voltage. A stabilized power supply device provided with a control feedback circuit for controlling the input voltage; a first voltage dividing circuit for deriving a first divided voltage obtained by dividing an input voltage supplied to the input terminal; A second voltage dividing circuit for deriving a second divided voltage lower than the first divided voltage obtained by dividing the voltage, and outputting the output when the second divided voltage is equal to or less than a predetermined voltage. A stabilized power supply device comprising: a control circuit for stopping operation of a transistor; and a reset signal generation circuit for generating a reset signal when the first divided voltage is equal to or lower than a predetermined voltage.