JP2574200Y2 - Voltage comparison circuit - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage comparison circuit, and more particularly, to a voltage comparison circuit for switching an output according to an input voltage level.

[0002]

2. Description of the Related Art A voltage comparison circuit is used for a system reset for preventing a malfunction caused by an abnormal fluctuation of a power supply voltage or a battery checker for knowing a degree of consumption of a battery or the like. Generally, a reference voltage source and a comparator are used. It is composed of

FIG. 5 shows a circuit diagram of a conventional voltage comparison circuit. In FIG. 5 (A), between an input terminal 50 to the input voltage V _in is applied ground (GND) terminal 51, the comparator 52 is connected. Resistance R ₅₀ of the input voltage V _in, the divided voltage by R ₅₁ is input to one input terminal of the comparator 52, the other input terminal of the constant current source 53 and the Zener diode Z reference voltage by ₁ comparator 52 Is done. The output of comparator 52 is to bias the transistor Q ₅₀ for load drive output terminal 54 (V
_out ).

[0004] Such voltage comparator circuit includes a comparator 52 compares the divided voltage with the reference voltage above the resistor R _50, R _51, performs on and off operations of the voltage level of the input voltage V _in as a border it is intended to drive a load connected to the output terminal 54 by operating the transistor Q _50.

[0005] Further, it is desired to reduce the power consumption of the voltage comparison circuit, and a circuit as shown in FIG. 5B is known. In FIG. 5B, a comparator is constituted by transistors Q _{51 to} Q ₅₄ , and transistors Q ₅₅ and Q _55
56 constitutes a band gap circuit of a constant current source of the comparator. The transistor Q ₅₇ to Q ₅₉ amplifies the comparator output, transistor Q ₆₀ for a load driving
Is to operate.

In this case, the base-emitter voltage V _BE of transistor Q ₅₅ has a negative temperature characteristic, and the difference ΔV _BE between the base-emitter voltage of transistors Q ₅₁ and Q ₅₂ is equal to the resistance of resistor R ₅₃ . Appears at both ends and has positive temperature characteristics. Thus, a temperature change, V _BE and △ V varies with _BE are canceled, in particular the resistance R ₃ to be equal to the energy band gap voltage of silicon sum of both potential (components of the Torajisuta) , it is possible to obtain a zero temperature characteristic by setting the resistance value of R _4.

That is, a constant current is supplied to a comparator composed of transistors Q _{51 to} Q ₅₄ , and FIG.
(A) Constant current source 53 and Zener diode Z
₁ can be omitted to reduce power consumption.

In the circuit of FIG. 6, the voltage V between terminals T ₆ and T ₇
ref to can Vref by equal to the voltage Vgo corresponding to the energy band gap of silicon in the transistor Q ₁₄ is a temperature characteristic having a zero temperature coefficient, kept stably Vref even if the temperature fluctuates It was configured to be able to.

[0009]

However, in the conventional voltage comparison circuit, the reference voltage Vref is stable against temperature fluctuation and is a good constant voltage power supply. However, Vref is approximately equal to the energy band gap of silicon. Must be set to 1.2V. Therefore, it is increasing in recent years.
There is a problem that it cannot cope with various devices operating at a low voltage of less than V, and the circuit becomes complicated to operate at a low voltage of 1.2 V or less. .

The present invention has been made in view of the above points, and has as its object to provide a voltage comparison circuit which has a zero temperature coefficient with a relatively simple circuit and can freely set a reference voltage. .

[0011]

This invention SUMMARY OF THE INVENTION To solve the above issues, the input corresponding to the power supply voltage to the first input terminal
Voltage is supplied and the reference voltage is supplied to the second input terminal.
Output according to the comparison result between the input voltage and the reference voltage.
In a voltage comparison circuit having comparison means for inverting
Is connected in series with the input voltage to divide the power supply voltage
A bias circuit for generating the bias voltage Te, said via
The bias voltage generated by the bias circuit is supplied to the base.
Between the emitter and collector according to the bias voltage.
A predetermined voltage is generated, and the voltage is generated by the bias circuit.
A current corresponding to the generated bias voltage is supplied to the collector.
And the transistor to draw from, Kore of the transistor
Junction device connected between a power supply voltage and the power supply voltage
And the current drawn into the collector of the transistor
Current control means for detecting and outputting a current according to the detected current
If, converts the output current of the current control means to a voltage, the
Input voltage generation for generating the input voltage according to a power supply voltage
And a collector of the transistor and the
The second input of the comparing means is provided at a connection point with the PN junction element.
Input terminal to connect the current control means and the input voltage generation.
A first input terminal of the comparing means at a connection point with the first resistor;
Are connected.

[0012]

According to the present invention, the reference voltage is obtained from the connection point between the PN junction element and the transistor. Therefore, the reference voltage is a voltage corresponding to the difference between the junction voltage of the PN junction element and the voltage between the transistors. If both the PN junction element and the tiger <br/> down di Star has a temperature coefficient substantially the same,
The difference voltage between the junction voltage of the PN junction element and the junction voltage of the transistor does not change due to the temperature change. Therefore, a stable output with respect to temperature can be obtained.
Further, the output voltage can be varied by changing the bias voltage of the bias circuit to change the junction voltage of the transistor. Since the input voltage is obtained by obtaining a current corresponding to the current flowing through the PN junction element, detection at a zero temperature coefficient is possible.

[0013]

FIG. 1 is a block diagram showing an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a bias circuit which is formed by connecting resistors R ₁ and R ₂ in series. Bias circuit 1 is connected to the DC power source 2 via the resistor R _3.

Q ₁ is a current control transistor, which is NPN
Is a transistor, the collector is connected to the transistor Q ₂ to which a PN junction element, the base is connected to the connection point between the resistor R ₁ which constitutes a bias circuit 1 and the resistor R _2, the emitter power 2 and the bias circuit 1 Is connected to the connection point. Transistor Q _{2 which} is a PN junction element is PN
Formed of a P transistor, is connected to the base and the collector are short-circuited, the base and collector of the transistor Q ₂ to a connection point between the collector connected, the emitter is connected to the connection point of the bias circuit 1 and the resistor R ₃ You. The reference voltage is generated by the transistor Q _1, Q ₂ and the bias circuit 1, a reference voltage transistor Q ₁ and the transistor Q
Taken out from a connection point between ₂ and is supplied to a comparator 4 consisting of transistors Q ₄ to Q ₁₃ and resistors R ₆ to R ₈ as shown in FIG.

Reference numeral 3 denotes a detecting means, which comprises a PNP transistor Q ₃ and a resistor R ₄ . The emitter of the transistor Q ₃ are connected to the connection point of the bias circuit 1 and the resistor R _3, the base collector connected to the base of the transistor Q ₂ is through a resistor R ₄ to the connection point of the bias circuit 1 and the power supply 2 Connected. Becomes a connection point of the transistor Q ₃ and the resistor R ₄ is output, a signal corresponding to the power supply voltage is output and supplied to the comparator 4.

Next, the operation of the circuit will be described. In Figure 1, the voltage V _CC power source 2, a current flowing through the resistor R ₃ I ₁ resistor R ₁ current flowing through the I _2, the current flowing through the resistor R ₂ When _{I 3, V CC = R 3} I 1 + R ₁ I ₂ + R ₂ I ₃ (1) Further, when the base-emitter voltage of the transistor Q ₁ and V _BE2, a _{I 3 = V BE2 / R 2} ... (2). In addition, the base current of the transistor Q ₁ i _B2
I ₂ = I ₃ + i _B2 (3) where i _B3 ≪I ₃ , I ₂ I ₃ (4) Therefore, V _CC = R ₃ I ₁ + (R ₁ + R ₂ ) I ₃ (5) Therefore, the voltage V ₁ applied to the bias circuit 1 is V ₁ = V _BE2 · (1+ (R ₁ / R ₂ )) (6) Further, the transistors Q ₁ and Q ₂ and the transistor Q ₁ a transistor Q ₃ of n ₁ the junction area ratio of the emitter: 1, and 1: When n _2, the reference voltage V _S is _{V S = △ V bE + (} R 1 / R 2) · V BE2 ... (7) However, ΔV _BE is V _BE2 −V _BE .

[0017] △ V _BE is represented by the general to _{△ V BE = (KT / q} ) 1n n 1 ... (8). In addition, V _BE2

[0018]

(Equation 1)

## EQU1 ## Here Vgo the voltage corresponding to the energy band gap of silicon in the transistor Q ₁ (about 1.2V), T is the temperature, T ₀ and serving as a reference operating temperature, transistor when the V _BE0 is T = T ₀ it is the base-emitter voltage of Q _1.

[0020]

(Equation 2)

## EQU1 ## Next, I _S = I ₄ + I ₅ (11). From the junction area ratio of Q ₁ and Q ₃ , I ₅ = n ₂ I ₄ ... (12) Therefore, the equation (11) is given by I _S = (1 + n ₂ ) I _4, so that I ₄ = I _S / (1 + n ₂₎ ) (13) I ₅ = (n ₂ / (1 + n ₂ )) · I _s (14) Therefore, V _0ut = R ₄ I ₅ = R ₄ · (n ₂ / (1 + n ₂ )) (15) If I ₂ , I ₃ ≪I _S , then I _S ≒ I ₁ = I ₄ + I ₅ .

From this, the equation (15) is obtained by the following equation: V _out ≒ (n ₂ / (1 + n ₂ )) · R ₄ · I ₁ (16)

[0023]

(Equation 3)

From this

[0025]

(Equation 4)

From equations (16) and (18),

[0027]

(Equation 5)

[0028] The comparison voltage V _in the comparator 4 (7),
From equation (19)

[0029]

(Equation 6)

When V _BE2 and ΔV _BE are rewritten,

[0031]

(Equation 7)

To make the temperature coefficient of V _in zero

[0033]

(Equation 8)

If it is set so that V _CC at zero temperature coefficient
Can be detected. When T = T ₀ , V _OUT is

[0035]

(Equation 9)

From this

[0037]

(Equation 10)

And V _out = V _S ,

[0039]

[Equation 11]

That is, V _CC that satisfies the expression (26) becomes the threshold voltage. FIG. 2 shows a block diagram of a second embodiment of the present invention. In the figure, the same components as those of FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.

[0041] The resistor R ₅ between the transistor Q _1, the transistor Q ₂ is provided in this embodiment, it is obtained a reference voltage from the connection point between the resistor R ₅ and the transistor Q _1. Also, by adding a resistor R _11.

[0042] Thus, reduced voltage characteristic with the same effect as in the first embodiment can be obtained by providing the resistor R ₅ can be improved.

FIG. 4 is a circuit diagram of a third embodiment of the present invention. In the figure, the same components as those in FIGS. 1 and 2 are denoted by the same reference numerals, and description thereof will be omitted. As shown in FIG.
The resistors R ₃ and R ₉ are provided at both ends of the bias circuit 1, and the detecting means 3 is composed of a PNP transistor Q ₁₄ , a PNP transistor Q ₁₅ and a resistor R ₁₀ .

With such a configuration, the same effects as in the first embodiment can be obtained. In the first to third embodiments, the configuration can be such that the polarity of the transistor is reversed.

[0045]

As described above, according to the present invention, the transistor is connected in series to the PN junction element, and the reference voltage is obtained from the connection point between the PN junction element and the current control transistor. Since the voltage becomes a voltage corresponding to the difference voltage between the PN junction element and the transistor, if the PN junction element and the transistor have the same temperature coefficient, a stable reference voltage with respect to a temperature change can be obtained. The output voltage can be set freely by changing the difference voltage between the PN junction element and the transistor. Further, since the input signal is generated from a current corresponding to the current flowing through the PN junction element, it has a feature that the power supply voltage can be detected at a zero temperature coefficient.

[Brief description of the drawings]

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

FIG. 2 is a block diagram of a second embodiment of the present invention.

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

FIG. 4 is a block diagram of a third embodiment of the present invention.

FIG. 5 is a block diagram of an example of the related art.

[Description of Signs] 1 Bias circuit 2 DC power supply 3 Detecting means Q ₁ , Q ₂ transistor

Claims (1)

(57) [Scope of request for utility model registration] An input corresponding to a power supply voltage is input to a first input terminal.
Voltage is supplied and the reference voltage is supplied to the second input terminal.
Output according to the comparison result between the input voltage and the reference voltage.
A voltage comparison circuit having a comparison means for inverting the power supply voltage, the voltage comparison circuit being connected in series with the input voltage and dividing the power supply voltage.
Base bias circuit for generating the bias voltage Te, the bias voltage generated by the bias circuit
To the emitter and the emitter-core in accordance with the bias voltage.
A predetermined voltage is generated between the
Current corresponding to the bias voltage generated by the
A transistor drawn from the collector, and a contact between the collector of the transistor and the power supply voltage.
Detects current drawn into the connected PN junction element and the collector of the transistor
Current control means for outputting a current corresponding to the detected current; and converting the output current of the current control means into a voltage,
An input voltage generating resistor for generating the input voltage according to a voltage;
Comprising an anti-city, contact between the collector and the PN junction element of said transistor
Connecting the second input terminal of the comparing means to a continuation point;
At the connection point between the current control means and the input voltage generating resistor.
A voltage comparison circuit configured to connect the first input terminal of the comparison means .