JPS6312973A - Battery voltage detecting circuit - Google Patents

Abstract

PURPOSE:To detect with high accuracy whether a voltage of a battery is higher or lower than the set point decided by size ratio and resistance ratio of a MOSFET by generating the reference voltage decided by the size ratio and the resistance ratio of the MOSFET and composing the circuit comparing the reference voltage with the voltage of the battery by the use of a CMOSFET. CONSTITUTION:When the voltage of battery is high, a dividing voltage between resistances R3 and R4 which is the input to a voltage fluctuation detecting circuit 2 is higher than a comparison voltage V2 generated in a resistance R2 by a constant current outputted from the MOSFET P7, so that the MOSFET P4 of a differential amplifier 11, accordingly the MOSFET N3, N4 are conducting. The MOSFET P5, accordingly the MOSFET N5 are non-conducting too, and output of an inverter 3 consisting of the MOSFET P6, N5 is high level, consequently an output terminal 9 is low level. When the voltage of the battery drops and the dividing voltage between the resistance R3 and R4 is lower than the voltage V2, the FET P5 is conducting and FET P4, N3, N4 are non-conducting. Thus the output of the inverter 3 is low level, but the terminal 9 is high level, the voltage drop of the battery is thereby detected.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is applicable to watches, thermometers, etc. TT battery voltage detection voltage detection circuit.

(Prior Art) FIG. 3 is a circuit diagram of a conventional example of this type of battery voltage detection circuit.

The source of the P-channel MOS transistor Plfl is connected to the positive terminal f5 of the battery 4, the source of the N-channel MOS transistor NIB is connected to the negative terminal Y-6 of the battery 4, and its gate and drain are connected to the gate of the MOS transistor I'18. and connected to the drain, MO
An inverter 30 is configured by the S transistors PIO and NIR. The input of the inverter 30 is connected to the timing pulse input terminal 16, and the output of the inverter 30 is connected to the negative terminal 6 of the battery 4 via a resistor R9. The sources of P-channel MO3I-transistor P8 and N-channel MOS transistor N8 are connected to battery 4, respectively.
MOS transistors P8 and N8 constitute an inverter 13, whose gates and drains are connected to each other. The input of the inverter 13 is connected to the output of the inverter 30, and the output of the inverter 13 is connected to the output terminal: F9.

When a negative pulse approximately equal to the negative electrode potential of the battery 4 is applied to the timing pulse input terminal 16, the P channel MOS transistor pHl+ becomes conductive, and the divided voltage of the resistor R9 and the P channel MOS transistor P18 changes to the P channel transistor P.
8 and an N-channel transistor N8. Inverter 13 threshold? [The voltage is set to approximately % of the battery voltage.]

The on-resistance of the P-channel transistor P18 changes depending on the battery voltage. When the battery voltage is high, the on-resistance of the P-channel transistor P1[] is small, and when the battery voltage becomes low and the voltage applied to the P-channel transistor P18 decreases. On-resistance increases. Therefore, by appropriately setting the resistor R9, when the battery voltage drops to a predetermined voltage, the divided voltage of the P-channel transistor P18 and the resistor R9 becomes the same as the battery voltage, so that the inverter 13 is inverted. In this way, this battery voltage detection circuit detects the voltage of the battery 4 using the voltage dependence of the on-resistance of the P-channel transistor P18.

[The problem that the invention attempts to solve]

The conventional battery pressure detection circuit described above has large manufacturing variations in the on-resistance of the P-channel transistor PI.
It is necessary to measure the on-resistance of B and set the value of the resistor R9, which not only increases the number of external components but also increases measurement time and costs.

[Dingdan for solving problems]

The battery voltage detection circuit of the present invention comprises a first conductor 1"E" whose source is connected to a first electrode of the battery via a first resistor.
a first MOS transistor whose source is a battery, and a second MOS transistor whose source is a battery.
a first MOS transistor of a second conductivity type, whose gate and drain are connected to the electrode of the second conductivity type, whose connection point is connected to the drain of the first MOS transistor of the first conductivity type, and whose source is connected to the battery. a second MOS transistor of a second conductivity type whose drain and gate are connected to the second electrode of the second conductivity type and whose gate is connected to the gate of the first MOS transistor of the second conductivity type; A first MOS transistor whose connection point is connected to the drain of the second MOS transistor of the second conductivity type and the gate of the first MOS transistor of the first conductivity type, and whose source is connected to the first electrode of the battery. a reference voltage generation circuit having a second MOS transistor of a conductivity type, the output terminal being a connection point between the drain and gate of the first MOS transistor of the second conductivity type; and a battery voltage divider for dividing the battery voltage. circuit, a comparison voltage generation circuit that generates a voltage with which the divided battery voltages are compared; a third MOS transistor of a second conductivity type connected to the electrode of jIJ2 and whose gate is connected to the output of the reference voltage generation circuit; and a drain of the third MOS transistor of the second conductivity type and their respective sources; of the second conductivity type to which the fourth. 5th M
A differential amplifier circuit which has an OS transistor and receives the output of the battery voltage dividing circuit and the output of the comparison voltage generation circuit as input, and a fourth differential amplifier circuit whose gate and drain are connected and whose connection point is a second quaternary voltage type. a third Mo5) transistor of the first conductivity type connected to the drain of the MOS transistor and connected to the source or the first electrode of the battery, and a gate of the third Mo5) transistor of the first conductivity type; a current mirror circuit including a fourth MOS transistor of a first conductivity type, the drain of which is connected to the drain of a fifth MOS transistor of the second conductivity type, and the source of which is connected to the first electrode of the battery; , the sauce? a sixth MOS transistor of a second conductivity type, whose gate is connected to the second electrode of the battery, and whose source is connected to the first electrode of the battery, whose gate is connected to the output of the reference voltage generation circuit; a sixth MOS connected to the output of the dynamic amplifier circuit and having a drain of the second conductivity type;
The voltage fluctuation detection circuit includes an inverter circuit having a fifth MOS transistor of the first conductivity type connected to the drain of the transistor.

Now, the 1st guide of the 1st lead sparrow type. Letting the drain current of the second MOS transistor be Il+'2, +I = Ioo flat exp(Vc/(nu
t))exp(-VR/IT)・・・・・・・・・
(1) +7 = Ioo l1a2exp I'Jc/ (n
u t)) ・= ・= −(2) Here, the first is the gate-to-substrate voltage of each MOS transistor, VR is the voltage across the first resistor R1, n is the slope factor, and ■7 is kT/ q, -1 and -2 are the effective W/L of the first and second MOS transistors of the first conductivity type (W and L are the channel width and channel length, respectively), and too is the proportionality constant (of the MOS transistor). (current values showing the same value for the same process).

On the other hand, the first conductivity type of the second conductivity type. The drain currents of the second MOS transistors are respectively equal to I, , +2, and
Since the gate-source voltages of these MOS transistors are equal, the effective W/ of each MOS transistor is
If L is mμm and mβ2, 1+/IIm+ = 12/+11112
−・=−(3) From equations (+), (2), (3), Vu=lbJZn(k+ 42 / (Ila21
11m+))VR=0 nn1a41 m
s2 / (Ioo21h+))・・・・・・・・・
・(4) The voltage VR is a constant determined only by the size ratio of the MOS transistors. Hereinafter, the voltage VR will be used as a reference voltage for voltage comparison. 11 is I because it is strong in VR/R4, and 12 is a constant current determined by the size ratio of the MOS transistor and the resistance of the circuit.

Now, let R8 be the second MOS transistor of the second conductivity type, the sources of the MOS transistor P are connected to the second electrode of the battery, the gate is connected to the output of the quasi-voltage generating circuit, and the drain is connected to the second electrode of the battery. is connected to the first electrode of the battery through the load 2, the first MOS transistor 1 of the IA conductivity type and the second MOS transistor P of the second conductivity type of 'fJ2 are current. A mirror circuit is constructed, and the saturated drain current of two MOS transistors P is m# and I =□11 +nH.

It is. Here, 5m# is the second MOS of the second conductivity type.
This is the effective W/L of a transistor (hereinafter, α and β represent the first and second conductivity types, respectively). Formula (4
)1 As is clear from equation (5), the saturated drain current is a constant that depends only on the size ratio and resistance of the transistor.

The embodiment of the invention as set forth in claim 2 will be explained as follows.

When the saturated drain current 17 of the seventh MO3I-transistor of the second conductivity type is loaded on the second resistor R2, the voltage across the resistor R2 is from equation (5). therefore,
Let the electromotive force of the battery be E, and the output of the battery voltage divider circuit be xE
(x is the voltage division ratio), the output of the differential amplifier circuit is 2
The threshold value is the battery voltage at which the two inputs are equal, and changes rapidly in response to changes in battery voltage. Therefore, Ezh is a constant determined by the size ratio of the transistor and the resistance ratio.

Next, an embodiment of the present invention as set forth in claim 3 will be described.

In the present embodiment, the first The fifth MO of conductivity type
The saturated drain currents INS of the S transistors N are compared.

Now, assuming that the fifth resistor is R5, the differential amplifier circuit inputs the output xE of the battery voltage divider circuit and sets the fifth resistor of the first conductivity type so that the voltage across the resistor R1 is equal to xE. 6
A negative feedback operation is performed through the MOS transistor N.

Therefore, the current flowing through the resistor R5, that is, the drain current of N MOS transistors is IN 6 =
). On the other hand, MO5! - The transistor N6 and the fifth MO5I transistor N of the first conductivity type have the same gate-source voltage, so the saturated drain current of the MOSI transistor N5 is. Therefore, the output of the inverter circuit is Is,
=lI)6 ・・・・・・・・・(10)
The battery voltage Eth determined by is set as a threshold value, and changes in accordance with fluctuations in the battery voltage. +llb is given by equation (5). Therefore, it becomes a constant determined only by the resistance ratio and size ratio of the MOS transistor.

In this way, by making the battery check voltage (the voltage that checks whether the battery voltage is higher or lower than that voltage) determined by the transistor size ratio and resistance ratio, the battery voltage can be controlled with high accuracy. It is possible to provide a battery voltage detection circuit which can be checked by the battery voltage and which can be built into an LSI with low power consumption by configuring most of the circuit with CMOS transistors.

〔Example〕

Next, practical examples of the present invention will be explained with reference to the drawings.

i<1 is a circuit diagram of a first embodiment of the battery voltage detection circuit of the present invention.

The source of the first N-channel MOS transistor N is connected to the low potential end 8 via a resistor R1. The source of the first P-channel MOS transistor P1 is connected to the high potential end 7, the gate and drain are connected, and the connection point thereof is connected to the drain of the first N-channel MOS transistor N1. P-channel second MOS)
The source of the transistor P2 is connected to the high potential end 7, and the gate is connected to the drain of the MOS transistor PI. N-channel second MOSl-transistor N2
The source of is connected to the low potential terminal 8, its drain and source are connected, and the connection point is the MOS transistor
connected to the drain of P2, and the MOS transistor N
, connected to the gate. MOS transistor Nl
A loop formed by +PINP2+N2 constitutes a reference voltage generation circuit 1, and its output terminal 10 is the output terminal (drain) of a MOS transistor N.

The source of the third P-channel MOS transistor P3 is connected to the high potential terminal 7, and the gate is connected to the output terminal IO of the reference voltage generating circuit 1. P channel 4th. Fifth
The sources of the MOS transistors P4+P5 are connected to each other, and the connection point thereof is connected to the drain of the third P-channel MOS transistor P3. As a result, M.O.
S transistor p4. Differential amplifier circuit I+ by p5
The source circuit thereof is a constant current circuit formed by the third MOS transistor P3. The source of the third N-channel MOS transistor N3 is connected to the low potential end 8, the gate and drain are connected, and the connection point thereof is connected to the drain of the MOS transistor P4. Further, the gate of the fourth N-channel MOS transistor N4 is connected to the gate of the MOS transistor N3, and the drain thereof is connected to the drain of the MOS transistor P5, so that a current mirror circuit 12 is configured by the MOS transistors N3+N4. . The source of the P-channel seventh MOS transistor Pl is connected to the high potential terminal 7, and the gate is connected to the output terminal IO of the reference voltage generating circuit 1. One end of the second resistor R2 is connected to the low potential end 8, and the other end is connected to the drain of the MOS transistor Pl. As a result, MOS transistor P and resistor R7 cause MOS1-transistor P7 to
Comparison voltage generation circuit 1 whose output terminal is the connection point between R2 and resistor R2.
3 are made up. Third. Resistance RA of Trj4, R,
One end of each is a high potential end 7. connected to the low potential end 8;
The other ends are connected to each other, and the resistors RM and R4 constitute a battery voltage dividing circuit 14 whose output terminal is the connection point of the resistors R, . . . R4. The output terminals of the comparison voltage generation circuit 13 and the battery voltage division circuit 14 are each connected to a MOS transistor p4. p, is connected to the gate of p.

The source of the sixth P-channel MOS transistor P6 is connected to the high potential terminal 7, and the gate is connected to the output terminal l of the reference voltage generation circuit 1.
The source of the N-channel fifth MOS transistor N5 is connected to the low potential terminal 8, the gate is connected to the drain of the MOS transistor P, the drain is connected to the drain of the MOS transistor R6, and the MOS transistor l'61 is connected to the drain of the MOS transistor R6. ``l constitutes the first inverter 3.

The voltage fluctuation detection circuit 2 has a comparison voltage generation circuit 13 and a battery voltage division circuit 14 as input circuits, a differential amplifier circuit 11 having a current mirror circuit 12 as a load circuit, and the output of the differential amplifier circuit I+. First inverter 3 as input
It is made up of.

A second inverter 15 that receives the output of the first inverter 3 is configured by the P-channel eighth MOS transistor P8 and the N-channel eighth MOS transistor N8, and outputs a signal via the output terminal 9. has been done.

The drain of the seventh N-channel MOS transistor N7 is connected to the low potential terminal 8, the source is connected to the negative electrode of the battery 4 via the battery negative terminal 6, and the gate is connected to the timing pulse input terminal 16 to receive the timing pulse. When it is at a high level, the IZ terminal 8 is connected to the negative electrode of the battery, and when it is at a low level, it is disconnected. .

Further, the substrate gates of all the P-channel MOS transistors used are connected to the high potential terminal 7, and the substrate gates of all the N-channel MOS transistors used, except for MOS transistor N7, are connected to the high potential terminal 7. The substrate gate of the MOS transistor N7 is connected to the low potential terminal 8, and the substrate gate of the MOS transistor N7 is connected to the negative electrode of the battery 4.

Next, the operation of this embodiment will be explained.

Timing pulse input terminal 16 when measuring battery voltage
A positive pulse is input. As a result, the MOS transistor N7 becomes conductive, and the reference voltage generation circuit 1, voltage fluctuation detection circuit 2, and second inverter 15 each operate.

When the source-drain current 11 of the MOS transistor N1 increases, the drain current I2 of the MOS transistor P2 increases according to equation (3), and as seen from equation (2), the gate substrate voltage Vc increases logarithmically, and the MOS transistor
Positive feedback is given to the gate of Sl-transistor N1. However, since the resistor R and the MOS transistor N's source voltage increase in proportion to the drain current (and thus in proportion to 12), the gate-source voltage &
As s decreases, the increase in current 11 is compensated and the current 11 is kept constant.

When the battery voltage is high, the divided voltage of resistors R3 and R4, which is the input of the voltage fluctuation detection circuit 2, is applied to the MOS transistor P7.
differential amplifier circuit 1.
One MOS transistor P is conductive, and four MOS transistors N3+N4 are also conductive. In addition, MOS transistor P is non-conductive, so MOS transistor N5 is also non-conductive, and MOS transistor P&
+N's, the output of the first inverter 3 is at a high level, and as a result, the output terminal 9 is at a low level.

As the battery voltage decreases, the divided voltage between resistor R3 and the island becomes the comparison voltage V.
When the voltage drops below 2, MOS transistor P becomes conductive and MOS transistor P becomes conductive.
The S transistor '4+N3+N4 becomes non-conductive, the output of the first inverter 3 becomes a low level, and the output terminal 9 becomes a high level, and it is detected that the battery voltage has dropped. Therefore, the voltage ET of the battery at which the output terminal 9 becomes high level is determined by substituting into equation (7) / (1la2 mβ1)) River...
・It becomes (13). Equation (13) shows that the battery detection voltage is given by the resistance ratio and the transistor size ratio, and since the variation is small within the same chip, a highly accurate battery detection circuit can be realized.

FIG. 2 is a circuit diagram of a second embodiment of the battery voltage detection circuit of the present invention.

The voltage fluctuation detection circuit 20 of this embodiment is shown in FIG.
The input circuit of the differential amplifier circuit II of the voltage fluctuation detection circuit 2 is changed, and a new inverter is added to the front stage of the inverter 15.

The voltage E of the battery 4 is divided by a battery voltage dividing circuit 4 constituted by series resistors R3 and R4, and the divided voltage output is input to the gate of a P-channel MOS transistor P4. N-channel sixth MOS transistor N
6 has a source connected to the low potential end 8, a gate connected to the gate of the MOS transistor N3, a drain connected to the high potential end 7 via the fifth resistor R5, and a connection between the drain and the resistor R5. The point is connected to the gate of the P-channel MO3I transistor P, forming a negative feedback circuit, and the MOS transistor N6 and resistor R5 constitute a comparison voltage generation circuit 23 that uses the voltage across the resistor R5 as a comparison voltage. has been done. MOS transistor N5
The gate of (input terminal of inverter 3) is connected to the drain of MOS transistor P4. Inverter circuit 2
5, a P channel M is installed before the second inverter 15.
A CMOS inverter consisting of an OS transistor P and an N-channel MO5I-run transistor N9 is provided.

The output of the first inverter 3 is the CM of the 114 stages.
It is input to the OS inverter, and the output of the CMOS inverter at the previous stage is input to the second inverter 15 at the rear stage. Further, a capacitor C is connected between the input end of the second inverter 15 and the low potential end 8.

When the voltage of the battery 4 changes and, as a result, the voltage across the resistor R3 changes, the differential amplifier circuit 11 connects the MOS transistor P through the MOS transistor N6.

A negative feedback operation is performed so that the gate voltages of P5 are equalized. The output of the MOS transformer P of the differential amplifier circuit 11 is input to the first inverter 3. If the threshold voltage is Eth, the output of the first inverter 3 is as follows: 1: = E th When th, the transfer state, E>
When Eth, the state is low, and when E<Eth, the state is high. Ei
h can be determined from formula (I 1).

Capacitor C is provided to remove unnecessary signals caused by the rising edge transient characteristics of reference voltage generation circuit 1 and voltage fluctuation detection circuit 20. As is clear from equation (11), in this embodiment as well, the threshold voltage Eth is determined by the resistance ratio and the size ratio of the transistors, so the accuracy is improved.

〔Effect of the invention〕

As explained above, the present invention generates a reference voltage determined by the size ratio and resistance ratio of MOS transistors,
By configuring the circuit that compares the reference voltage and battery voltage using CMOS transistors, the battery voltage can be compared with MOS transistors without changing circuit constants to deal with variations in characteristics caused by the manufacturing process as in conventional circuits. It is possible to detect with high accuracy that the value is below or above the set value determined by the size ratio and resistance ratio of the transistor, and the LSI
It is possible to provide a battery voltage detection circuit which has a great advantage in terms of production cost because it can be built into the battery.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of an embodiment of the battery voltage detection circuit 1 of the present invention, Fig. 2 is a circuit diagram of a second embodiment of the battery voltage detection circuit of the present invention, and Fig. 3 is a circuit diagram of a battery voltage detection circuit 1 of the present invention. FIG. 2 is a circuit diagram of a conventional example of a circuit. 1.-, 1, t, quasi-voltage generation circuit, 2.20... voltage fluctuation detection circuit, 3... first inverter, 4... battery, 5... battery positive terminal, 6... -Battery negative terminal, 7...High potential end, 8...Low potential end, 9...Output terminal, IO...Reference voltage generation circuit output terminal, 11...Differential amplifier circuit, 12. ...Current mirror circuit, ml, 23-...Comparison voltage generation circuit, 14...Battery 'ε pressure dividing circuit, +5-...Second inverter, l6...Timing pulse input terminal, 25...・Inverter circuit, N1, N2, N3, N4, N5, N6, N7, N
8. N. ...N-channel Os transistor, Pl/R2/R
3・R4・R5・P6+ R7・R8・R9...P channel Mos transistor, RI+ R2+ R3+
R4, R5...Resistance, C...Capacitor. Patent applicant Japan 7 "Ki Co., Ltd. ff13 figure

Claims (1)

[Claims] 1. A first MOS transistor of a first conductivity type, the source of which is connected to a first electrode of a battery via a first resistor, and the source of which is connected to a second electrode of a battery. a first M, whose gate and drain are connected and whose connection point is of the first conductivity type;
a first MOS transistor of a second conductivity type connected to the drain of the OS transistor; and a first MOS transistor whose source is connected to a second electrode of the battery and whose gate is of the second conductivity type.
a second MOS transistor of a second conductivity type connected to the gate of the S transistor; and a second MOS transistor of the second conductivity type whose drain and gate are connected and whose connection point is the drain of the second conductivity type and the first conductivity type connected to the gate of the S transistor. a second MOS transistor of a first conductivity type connected to the gate of the first MOS transistor of the second conductivity type and whose source is connected to the first electrode of the battery; A reference voltage generation circuit whose output terminal is a connection point between the drain and gate of a MOS transistor, a battery voltage division circuit which divides a battery voltage, and a comparison voltage generation circuit which generates a voltage with which the divided battery voltages are compared. , a third MOS transistor of a second conductivity type, whose source is connected to the second electrode of the battery and whose gate is connected to the output of the reference voltage generation circuit; and a third MOS transistor of the second conductivity type. A differential amplifier circuit having fourth and fifth MOS transistors of a second conductivity type whose drains and respective sources are connected, and whose inputs are the output of the battery voltage dividing circuit and the output of the comparison voltage generation circuit. and a third MOS transistor of the first conductivity type whose gate and drain are connected, whose connection point is connected to the drain of the fourth MOS transistor of the second conductivity type, and whose source is connected to the first electrode of the battery. M of
an OS transistor and a third M whose gate has the first conductivity type;
a fourth MOS transistor of the first conductivity type, which is connected to the gate of the OS transistor, whose drain is connected to the drain of the fifth MOS transistor of the second conductivity type, and whose source is connected to the first electrode of the battery; a sixth MOS transistor of a second conductivity type whose source is connected to the second electrode of the battery and whose gate is connected to the output of the reference voltage generation circuit; and a sixth MOS transistor whose source is connected to the first electrode of the battery. a fifth MOS transistor of the first conductivity type, the gate of which is connected to the output of the differential amplifier circuit, and the drain of which is connected to the drain of the sixth MOS transistor of the second conductivity type;
A battery voltage detection circuit having a voltage fluctuation detection circuit including an inverter circuit having an OS transistor. 2. The comparison voltage generation circuit of the voltage fluctuation detection circuit includes a second resistor whose one end is connected to the first electrode of the battery, and whose source is connected to the second electrode of the battery and whose gate generates the reference voltage. a seventh MOS transistor of a second conductivity type connected to the output of the circuit and having a drain connected to the other end of the second resistor, and a drain of the seventh MOS transistor of the second conductivity type; The connection point with the second resistor is the output terminal, and the battery voltage dividing circuit of the voltage fluctuation detection circuit is connected to the third and fourth electrodes connected in series between the first and second electrodes of the battery. It has a resistor, and the connection point of the resistor is the output terminal, and the output of the comparison voltage generation circuit is connected to the fourth MO of the second conductivity type.
The output of the battery voltage dividing circuit is input to the gate of the S transistor, and the output of the battery voltage dividing circuit is input to the gate of the fifth MOS transistor of the second conductivity type, and the drain of the fifth MOS transistor of the second conductivity type is input to the gate of the fifth MOS transistor of the second conductivity type. The battery voltage detection circuit according to claim 1, wherein the battery voltage detection circuit is connected to the gate of the fifth conductive type MOS transistor. 3. The comparison voltage generation circuit of the voltage fluctuation detection circuit includes a fifth resistor whose one end is connected to the second electrode of the battery, and a fifth resistor whose source is connected to the first electrode of the battery and whose drain is connected to the fifth resistor. a third M whose gate is connected to the other end and whose gate is of the first conductivity type;
A sixth MOS transistor of the first conductivity type is connected to the gate of the OS transistor, and the connection point between the fifth resistor and the drain of the sixth MOS transistor of the first conductivity type is connected to the output terminal. The battery voltage dividing circuit of the voltage fluctuation detection circuit has third and fourth resistors connected in series between the first and second electrodes of the battery, and the connection point of the resistors is The output terminal of the comparison voltage generation circuit is the fifth MOS of the second conductivity type.
The output of the voltage dividing circuit is input to the gate of the transistor, the output of the voltage dividing circuit is input to the fourth MOS transistor of the second conductivity type, and the gate of the fifth MOS transistor of the first conductivity type is input to the gate of the fifth MOS transistor of the second conductivity type. 4. The battery voltage detection circuit according to claim 1, wherein the battery voltage detection circuit is connected to the drain of the MOS transistor No. 4.