JP3325792B2 - Constant voltage generator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a constant voltage generating circuit capable of obtaining an output voltage which is extremely small due to a temperature change.

[0002]

2. Description of the Related Art A band gap reference circuit (hereinafter referred to as a BG circuit) is known as this kind of constant voltage generating circuit, and FIG. 5 is a circuit diagram showing one example thereof. This circuit comprises a first transistor Q1 and a second transistor Q1.
2. It is formed of a multi-emitter third transistor Q3, transistor Q4, transistor Q5, resistor R3, and resistor R4. Note that 1 is a power supply terminal to which the power supply voltage V _CC is applied, and N represents the number of emitters of the transistor Q3.

[0003] When the collector current of the transistor Q2 and the transistor Q3 are equal, band gap voltage V _G shown in the expression (1) as the output voltage is obtained at the output terminal 2. _{V G = V R3 + V BE1} = {R3 (V BE2 -V BE3) / R4} + V BE1 = {R3 · V T · Ln (N) / R4} + V BE1 (1) However, R3, R4 are each resistor R3 , R4, V
_BE1 , V _BE2 and V _BE3 are transistors Q1, Q2,
The base-emitter voltage of Q3, V _T is the thermal voltage, Ln is the natural logarithm, N is the number of the emitter of the transistor Q3. Temperature coefficient of thermal voltage V _T is positive in (0.085mV / ℃), since the temperature coefficient of the base-emitter voltage V _BE1 is negative extent (-2 mV / ° C.), the resistance value R3 in formula (1), R4
Bandgap voltage V _G not affected by temperature change can be obtained by selecting the appropriate.

[0004] However, precisely band gap voltage V _G when measured has received still the influence of the temperature change.
This is because the base-emitter voltage V _BE of the bipolar transistor is generally expressed by the equation (2). _{V BE = {1- (T /} T 0)} V GO + T · V BE0 / T 0 + (nkT / q) Ln (T 0 / T) + (kT / q) Ln (I C / I C0) ( 2) Equation (2) is obtained by substituting equation (4) into equation (3). _{V BE = (kT / q)} Ln (I C / I S) (3) I S = qAn i 2 D n / Q B (4) Here, in equation (4) from equation (2), q is the electronic charge, a is the emitter-base junction area, n _i is the intrinsic carrier concentration of silicon, D _n is the average effective value of the electron diffusion coefficient in the base, Q _B is the total amount of impurities per unit area in the base, k is Boltzmann's constant, I _C is the collector current, I _S
Is the saturation current, T is the absolute temperature, T ₀ is the reference temperature, V _BE0 and I _C0 are the base-emitter voltage and collector current at the reference temperature T ₀ , V _GO is the estimated value of the silicon bandgap voltage, and n is a constant It is.

In equation (2), the first two terms change while maintaining linearity with respect to temperature change, but the third and fourth terms change due to the square characteristic. The characteristics of such a base-emitter voltage V _BE is also occurs similarly in the base-emitter voltage V _BE1 of the transistor Q1 of FIG. 5 to obtain a band gap voltage. Then, it does not change linearly with the temperature coefficient of exactly due to the presence of the voltage V _BE1 is the square of the term (-2 mV / ° C.), the band gap voltage V _G can not be avoided still the influence of temperature change. Figure 6 is a characteristic diagram showing changes with respect to the temperature of the bandgap voltage V _G, it can be seen that cause a change of approximately 10mV between 100 ° C. from 0 ° C..

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a constant voltage generating circuit which obtains an output voltage using a sum of voltages having a positive temperature coefficient and a negative temperature coefficient such as a band gap voltage. An object of the present invention is to further reduce the influence of a temperature change on an output voltage.

[0007]

According to the present invention, an output voltage is obtained by using a sum of a voltage having a positive temperature coefficient and a voltage having a negative temperature coefficient obtained from an active element such as a transistor or a diode. In the voltage generation circuit, the negative temperature coefficient
A correction circuit that increases the current as the temperature decreases is connected to the active element that obtains the voltage .
In the temperature range where the output voltage decreases,
The voltage of the negative temperature coefficient is increased .

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Equation (5) is obtained by differentiating equation (2) with temperature, and equation (5) represents a temperature coefficient. _{dV BE / dT = - (V} GO / T 0) + V BE0 / T 0 + (nk / q) {Ln (T 0 / T) - (1 / T)} + (k / q) Ln (I C / I _C0 ) (5) The third and fourth terms of the square coefficient in the equation (5) have small values, and are ignored, and the voltage of the sum is calculated by focusing on the first and second terms of the linear coefficient. Improve properties. The bandgap voltage V _G falls as shown in Figure 6 is at a low temperature, (5) the absolute value of the magnitude is at a low temperature differential value due to the temperature of the base-emitter voltage V _BE1 of the transistor Q1, expressed like Formula Due to too much. This means that the value of the term corresponding to the first term with a minus sign in the equation (5) is too large, so that the term corresponding to the second term with a plus sign should be increased. I understand. That is, as the temperature decreases, the current of the transistor Q1 is increased to increase the base-emitter voltage of the transistor Q1 at the reference temperature corresponding to V _BE0 in the equation (5). Connect.

[0009]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram showing an embodiment of a constant voltage generating circuit according to the present invention. The same parts as those in FIG. 5 are denoted by the same reference numerals. In FIG.
Transistor Q1 to transistor Q5 and resistor R
3. The connection of the resistor R4 is almost the same as that of FIG. 5, and forms a BG circuit. Diode-connected transistor Q
2 and the emitter of the multi-emitter transistor Q3
Connected to each other via a resistor R4 and grounded,
Base comrades are also connected. The transistors Q4 and Q5 form a current mirror circuit, and the emitters of both transistors are connected to the power supply terminal 1.
The collector of the transistor Q4 is connected to the collector of the transistor Q2, and the collector of the diode-connected transistor Q5 is connected via a resistor R3 to the base of the transistor Q1 whose collector and emitter are grounded.

A correction circuit is connected to the collector of the transistor Q1. This correction circuit includes transistors Q8 and Q9 forming a first current mirror circuit, transistors Q6 and Q7 forming a second current mirror circuit, a transistor Q10 forming an emitter follower circuit, a resistor R5, a bias current circuit. , And a diode row DM1. The emitter follower circuit is connected to the input side of the first current mirror circuit, and the input side of the second current mirror circuit is connected to the output side of the first current mirror circuit. The collector of the transistor Q10 of the emitter follower circuit is connected to the power supply terminal 1 and the base is connected to the power supply terminal 1 via the resistor R6. The base is a diode array DM
1 is grounded. The collector of the diode-connected input transistor Q9 of the first current mirror circuit is connected to the emitter of the transistor Q10 via the resistor R5, and the collector of the output transistor Q8 is diode-connected to the second current mirror circuit. Connected to the collector of transistor Q7 on the input side. The collector of the transistor Q6 on the output side of the second current mirror circuit is connected to the collector of the first transistor Q1. The emitters of the transistors Q8 and Q9 of the first current mirror circuit are grounded, and the emitters of the transistors Q6 and Q7 of the second current mirror circuit are connected to the power supply terminal 1.

In the constant voltage generating circuit thus configured, the voltage of the negative temperature coefficient is applied to the first transistor Q1.
And the voltage having a positive temperature coefficient is the base-emitter voltage V _BE of the second transistor Q2.
_BE2 and so obtained from the difference between the base-emitter voltage V _BE3 of the third transistors Q3, bandgap voltage V _G is obtained at the output terminal 2 and satisfied formula (1). However, the influence of the temperature change of the connection of the correction circuit to the bandgap voltage V _G can be further reduced. This is because the collector current I _C1 shown in the equation (6) flows through the transistor Q1. I _C1 = (V _DM1 −V _BE10 −V _BE9 ) / R5 (6) where V _DM1 is the voltage between both ends of the diode string DM1, V
_BE10 and V _BE9 are the base-emitter voltages of the transistors Q10 and Q9, respectively, and R5 is the resistance value of the resistor R5. The current I _C1 is equal to the resistance R of the emitter follower circuit.
5 equal to the current flowing through it.

In equation (6), the voltage V _DM1 ,
Since the emitter-to-emitter voltages V _BE10 and V _BE9 both increase with a decrease in temperature, the current I _C1 also increases with a decrease in temperature. By increasing the current I _C1 , V
_Since the base-emitter voltage of the transistor Q1 at the reference temperature corresponding to _BE0 also increases, the value of the expression (5), that is, the negative temperature coefficient is not increased even if the temperature is lowered, and the positive temperature coefficient is changed. It can be adjusted to just cancel out. Therefore, it is possible to obtain a band-gap voltage V _G was more reduce the influence of temperature variation to the output terminal 2.

FIG. 2 is a circuit diagram showing another embodiment of the constant voltage generating circuit of the present invention, and the same parts as those in FIG. 1 are denoted by the same reference numerals. The emitters of the second transistor Q2 forming the differential pair and the multi-emitter third transistor Q3 are grounded via a current source S1, and the bases are connected via a resistor R8. The emitters of the transistors Q11 and Q12 forming the current mirror circuit are connected to the output terminal 2, and the diode-connected transistor Q
The collector of the transistor 11 is connected to the collector of the transistor Q3, and the collector of the transistor Q12 is connected to the collector of the transistor Q2. The transistor Q13 has a base connected to the collector of the transistor Q12, a collector connected to the amplifier circuit 3, and an emitter connected to the output terminal 2.

The emitter of the first transistor Q1 is grounded through a series connection of a resistor R7, a resistor R8 and a diode string DM2, and the collector is connected to the output terminal 2. The output terminal 2 is connected to the power supply terminal 1 via the resistor R9, and is grounded via the resistors R1 and R2. Resistance R1
A connection point P1 between the resistor and the resistor R2 is connected to the base of the transistor Q1. The correction circuit is connected between the output terminal 2 and a connection point P2 between the diode row DM2 and the resistor R8.

This correction circuit includes transistors Q8 and Q9 forming a first current mirror circuit, transistors Q6 and Q7 forming a second current mirror circuit, a transistor Q10 forming an emitter follower circuit, a resistor R5, It is composed of a resistor R6 forming a bias current circuit and a diode array DM1, and has the same configuration as that of FIG. The constant voltage generating circuit having this arrangement, it is possible to obtain the connection point P1 of the voltages V ₁ represented by the equation (7). V ₁ = V _DM2 + V _BE1 + (R7 + R8) · I _R8 (7) I _R8 = (1 / R8) · (kT / q) · Ln (N) (8) The output terminal 2 is represented by the formula (9). Output voltage V _OUT can be obtained. V _OUT = (R1 + R2) · V ₁ / R2 (9) The collector current I _C6 of the transistor Q6 flowing from the correction circuit into the diode array DM2 is expressed by the equation (10) in the same manner as the collector current I _{C1 of the} equation (6). It is represented by I _C6 = (V _DM1 −V _BE10 −V _BE9 ) / R5 (10) In the equations (7) to (9), V _DM2 is a voltage between both ends of the diode string DM2, and I _R8 is a current of the resistor R8. ,
R7 and R8 are resistance values of the resistors R7 and R8, respectively.

This constant voltage generating circuit is based on the difference between the voltage of the negative temperature coefficient obtained from the diode string DM2 and the transistor Q1 and the voltage between the base and the emitter of the transistor Q2 and the transistor Q3 as shown by the equation (7). voltage V ₁ of the sum of the voltages of the positive temperature coefficient obtained by use of (9)
The output voltage V _OUT shown in the equation is obtained at the output terminal 2.
(7) Also in the voltage V ₁ of the formula, the temperature coefficient of the voltage having a negative temperature coefficient is larger than the temperature coefficient of the voltage having a positive temperature coefficient when the temperature decreases. Therefore, a current I _C6, which increases with a decrease in temperature, is caused to flow through a correction circuit through a diode array DM 2 which is a part of an active element that obtains a voltage having a negative temperature coefficient.

The current I _C6 increases as the temperature decreases, as is apparent from equation (10). The voltage between the terminals of each diode of the diode row DM2 is expressed by the equation (2), and the temperature coefficient is expressed by the equation (5). Therefore, since the second term in the individual diodes of the diode line DM 2 of (5) increases with decreasing temperature, the negative temperature coefficient decreases. As a result, the negative temperature coefficient of the diode array DM2 at the voltage V _DM2 in the equation (7) also decreases, and the value of the total negative temperature coefficient of the voltage (V _DM2 + V _BE1 ) also decreases in the third term of the equation (7). The temperature coefficient of a voltage having a positive temperature coefficient can be made small enough to just cancel out. And
It is possible to obtain a small voltage V ₁ of the effect of temperature changes to the connection point P1. It goes without saying that the output voltage V _OUT obtained from the voltage V ₁ is similarly less affected by temperature changes.

FIG. 3 is a circuit diagram further embodying the circuit of FIG. 2, and the same parts as those of FIG. 2 are given the same reference numerals.
In FIG. 3, a second transistor Q forming a differential pair
Between the transistors Q11 and Q12 forming a current mirror circuit with the second and multi-emitter third transistors Q3, transistors Q16 and Q17 whose bases are connected to each other to prevent the Early effect are connected. The amplifier circuit 3 of FIG. 2 connected to the transistor Q13 includes Darlington-connected transistors Q18, Q19, Q20, and a resistor R1.
It is formed by a common-emitter amplifier circuit consisting of zero.

Transistors Q21, Q22, Q23, Q
The current mirror circuit composed of 24 forms a constant current source S1 and a current source of a common emitter amplifier circuit. The diode-connected transistors Q25 and Q26 and the diode-connected transistors Q27, Q28 and Q29 form the diode rows DM2 and DM1, respectively, of FIG. Further, the current mirror circuit including the transistors Q14 and Q15 supplies current to the current mirror circuit including the first transistor Q1 and the transistors Q21, Q22, Q23 and Q24.

FIG. 4 is a characteristic diagram of the circuit of FIG. 3, in which the horizontal axis represents temperature, and the vertical axis represents the output voltage V _OUT of the output terminal 2. FIG.
The power supply voltage V _CC in is 7V. The characteristic curve at a temperature of around 35 ° C. or lower is divided into three of CH1, CH2, and CH3, which can be obtained by changing the value of the resistor R5. When the value of the resistor R5 is decreased, the resistance R5 moves upward as indicated by the characteristic curve CH1, and when the resistance R5 increases, the resistance R5 moves downward as indicated by the characteristic curve CH3. Therefore, by setting the value to an appropriate value, the influence of the temperature change on the output voltage V _OUT can be extremely reduced as shown by the characteristic curve CH2. In FIG. 4, the resistance R5 is 150 KΩ,
Characteristic curves CH1 and C at 200KΩ and 250KΩ respectively
H2 and CH3 were shown. In the characteristic curve CH2, -40 ° C
It can be seen from FIG. 4 that the output voltage V _OUT changes only by about 2 mV in a temperature range of 100 ° C., indicating that extremely good temperature characteristics are exhibited. Although the correction circuit in the embodiment is mainly configured using a current mirror circuit and an emitter follower circuit, another circuit may be used as long as the current increases as the temperature decreases. Further, the correction circuit can be constituted only by the emitter follower circuit, excluding the current mirror circuit in the embodiment.

[0021]

As described above, the constant voltage generating circuit of the present invention utilizes the sum of the positive temperature coefficient voltage and the negative temperature coefficient voltage obtained from an active element such as a transistor or a diode. A correction circuit is connected so that the current of the active element having a negative temperature coefficient increases as the temperature decreases. And the temperature characteristic especially on the low temperature side can be improved. By increasing the current of the active element having a negative temperature coefficient with decreasing temperature,
The temperature coefficient of the active element becomes smaller at a low temperature, and the temperature coefficient of the active element having a positive temperature coefficient just cancels out. Thus, it is possible to provide a practical constant voltage generating circuit capable of obtaining an output voltage which is extremely small in the influence of a temperature change in a wide temperature range.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of a constant voltage generation circuit according to the present invention.

FIG. 2 is a circuit diagram showing another embodiment of the constant voltage generating circuit of the present invention.

FIG. 3 is a circuit diagram further embodying the circuit diagram of FIG. 2;

4 is a characteristic diagram of the constant voltage generation circuit shown in FIG.

FIG. 5 is a circuit diagram of a conventional constant voltage generation circuit.

FIG. 6 is a characteristic diagram of a conventional constant voltage generation circuit.

[Explanation of symbols]

 Reference Signs List 1 power supply terminal 2 output terminal 3 amplifier circuit Q1 first transistor Q2 second transistor Q3 third transistor

Claims (5)

(57) [Claims] 1. A constant voltage generating circuit for obtaining a voltage and a negative voltage output voltage using the sum of the voltage of the temperature coefficient of the positive temperature coefficient obtained from the active element, the negative temperature coefficient of the voltage
Is connected to a correction circuit that increases the current as the temperature decreases , and the current of the correction circuit
In the temperature range where the output voltage decreases,
A constant voltage generation circuit characterized by increasing the voltage of the negative temperature coefficient . 2. A constant voltage generating circuit for obtaining an output voltage using the voltage of the sum of the voltage of the voltage and the negative temperature coefficient of the positive temperature coefficient obtained from the active element, the voltage of the negative temperature coefficient plurality A correction circuit for increasing the current with a decrease in temperature is connected to at least a part of the active elements , and the output of the output is determined by the current of the correction circuit.
In the temperature range where the voltage decreases, the negative
A constant voltage generating circuit characterized by increasing the voltage of the temperature coefficient . 3. The base and emitter of a first transistor
Using the sum of the voltage of the negative temperature coefficient obtained from the voltage between the transistors and the voltage of the positive temperature coefficient obtained from the difference between the base-emitter voltages of the second and third transistors having different emitter current densities. in the constant voltage generating circuit for obtaining an output voltage, connected to the correction circuit to increase the current as the temperature decreases to the collector of the first transistor, conductivity of the correction circuit
Current in the temperature range where the output voltage drops
A voltage of the negative temperature coefficient is increased as the voltage decreases . 4. A voltage between a base and an emitter of a first transistor, an emitter of the first transistor , and a ground.
Positive temperature obtained from the difference between the voltage of the negative temperature coefficient obtained from the terminal voltage of the provided diode, the base-emitter voltage of the second and the third transistor of emitter current densities different in series between the In a constant voltage generation circuit that obtains an output voltage by using the voltage of the sum of the coefficient voltages, a correction circuit that increases the current with a decrease in temperature is connected to the diode, and the output voltage decreases due to the current of the correction circuit. Do
In the temperature range, the negative temperature coefficient
A constant voltage circuit characterized by increasing the pressure . 5. The constant voltage generating circuit according to claim 1, wherein said correction circuit comprises an emitter follower circuit whose current increases as the temperature decreases.