JP3106607B2 - Constant voltage 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 constant voltage circuit, and more particularly to a constant voltage circuit for obtaining a stable output voltage with respect to a change in temperature.

[0002]

2. Description of the Related Art A band gap zener circuit as shown in FIG. 5 has conventionally been used as a reference voltage circuit for generating an internal reference voltage for an IC (integrated circuit) or the like. The band gap zener circuit includes a current source CC ₃ , resistors R ₃₀ ... R ₃₂ ,
The transistors Q ₃₀ ... Q ₃₂ are provided so that a stable output voltage can be obtained between the output terminals 8 and 9 with respect to temperature fluctuation.

The present applicant has proposed a low-voltage reference voltage circuit in Japanese Patent Publication No. 55-18928 (FIG. 6 shows the principle circuit diagram). In the figure, reference numeral 10 denotes a differential amplifier circuit having transistors Q ₃₃ ... Q ₃₄ having different current densities, the output of which is supplied to the base of a control transistor Q ₃₈ , and It is controlled to be constant. The voltage across the resistor R ₃₄ is the differential amplifier circuit 1
0 is supplied to each input.

In the circuit of FIG. 6, the voltage Vre between the terminals 8 and 9 is
f the Vref by equal to the voltage Vgo corresponding to the semiconductor energy band gap of silicon or the like constituting the transistor Q ₃₉ is able to a temperature characteristic having a zero temperature coefficient, the Vref even if the temperature fluctuates The configuration was such that it could be kept stable.

[0005]

However, in the conventional constant voltage circuit, the output voltage Vref is stable against temperature fluctuation and is a good constant voltage power supply, but Vref is the energy band gap of the silicon constituting the transistor. Must be set to 1.2 V corresponding to Therefore, there is a disadvantage that it cannot cope with various devices operating at a low voltage of 1.2 V or less, which is increasing in recent years.

In view of the above, it is an object of the present invention to provide a constant voltage circuit that can set an output voltage having a zero temperature coefficient to a low voltage with a relatively simple circuit.

[0007]

In order to solve the above-mentioned problems, according to the present invention, a current source having an output current having a negative temperature characteristic and first and second current sources each having one end connected to one end of the current source. And the emitters are connected to the other ends of the first and second voltage drop elements, respectively, so that their current densities are different from each other. First and second transistors having the following temperature characteristics, and a first transistor which generates first and second divided voltages obtained by dividing an input voltage and supplies the first divided voltage via a first terminal. Voltage dividing means for applying the second divided voltage to the base of the second transistor via the second terminal, and applying the second divided voltage to the base of the second transistor. - a positive temperature characteristic voltage difference emitter voltage has, the more the current source One end of the current source supplies current s in the first and second voltage dropping element husband having a temperature characteristic and a first
And compensating by generating a voltage drop having a negative temperature characteristic between the emitter of each of the first and second transistors.

[0008]

According to the present invention having the above configuration, the negative current from the current source is
By supplying a current having a temperature characteristic to each of the first and second voltage drop elements, a voltage drop between one end of the current source and the emitter of each of the first and second transistors exhibits a negative temperature characteristic. Therefore, the voltage of the difference between the base-emitter voltage of each of the first and second transistors which has a positive temperature characteristic acts so as to be temperature-compensated by this, and the base-emitter of each of the first and second transistors becomes active. A voltage between the first terminal and the second terminal, which is a sum of the voltage of the difference between the voltages and the voltage drop generated between one end of the current source and the emitter of each of the first and second transistors. Acts to be temperature compensated.

[0009]

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

As shown in FIG. 1, a resistor R ₉ is connected to the collector of the transistor Q ₁ , and a resistor R ₁ ,
R ₂ are connected in series. These series circuits are connected via terminals 3 and 4 to both ends of a power supply voltage V _CC which is an input voltage, and _divide the power supply voltage V _CC . The current source CC ₁ between the transistors Q ₁ Nobesu and the terminal 3 are connected.

The differential amplifier circuit 5 includes a transistor Q_Two, ... Q
_Five, A first and second voltage drop element, a resistor R_Three,
R_Four, Current source CC_TwoCurrent source CC_TwoOne end is the end
Child 3. Tiger which is the first transistor
Transistor Q_TwoEmitter and current source CC_TwoBetween the other end of
Is the resistance R_ThreeIs the transistor that is the second transistor
Q _ThreeEmitter and current source CC_TwoBetween the other end of the resistor R
_FourIs connected.

[0012] across each resistor R ₁ s, through the terminals 1 and 2 are first and second terminals connected to each base over scan transistor Q _2, Q _3, the voltage across the resistor R ₁ is It is input to each base of the transistors Q ₂ and Q ₃ .

[0013] In addition, the collector output of the transistor Q ₃ is connected to the transistor Q ₆ total over vinegar, transistor Q
Collector output of ₆ is connected to the transistor Q ₁ total over the nest.

Incidentally, in FIG. 1, the transistors Q ₂ ,
The emitter junction area ratio of Q ₃ n _{1: 1} (although, n _1>
1), the current density ratio of the transistors Q ₂ and Q ₃ is weighted. The voltage and current of each part of the circuit are determined as shown, and the offset voltage of the difference between the base-emitter voltages of the transistors Q ₂ and Q ₃ is ΔV _BE .

Assuming that i _B6 << I _C3 , 1 << h _FE , the balance condition of the differential amplifier 5 is I _C2 = I _C3 = I _E2 = I _E3 (1).

[0016] When _{i B2 << I E1, i B3} << I E1, the voltage across V ₁ of the resistor R _{1 is, V 1 = R 1 I E1} (2) = ΔV BE + (R 4 I E3 −R ₃ I _E2 ) (3) = ΔV _BE + (R ₄ −R ₃ ) I _E2 (4)

[0017]

(Equation 1)

Here, if I ₂ (R ₄ −R ₃ ) / 2 = ΔV _R (6), then V ₁ = ΔV _BE + ΔV _R (7).

Here, ΔV _BE = (kT / q) ln (n ₁ ) (8) (where T is the operating temperature [K], k is the Boltzmann constant 1.380662 × 10 ⁻²³ [JK ⁻¹ ], and q is the electron since the charge amount 1.6021892 × 10 ^-19 [C]), the voltage across V ₁ of the resistor R ₁ is represented by _{V 1 = (kT / q)} ln (n 1) + ΔV R (9).

Here, the first term, ie, ΔV _BE is n ₁ > 1
Since there is a is a positive value, the second term [Delta] V _R becomes a negative value as described later. Therefore, by selecting the values of the resistors R ₃ and R ₄ according to the value of n _1, the value of V ₁ can be set to an arbitrary value.

Here, the temperature coefficient of the voltage V ₁ across the resistor R ₁ is obtained by partially differentiating both sides of the equation (9) with the temperature T.

[0022]

(Equation 2)

## EQU1 ##

To make the temperature coefficient of V ₁ zero, {V ₁ / ∂
From T = 0

[0025]

(Equation 3)

It is sufficient to set

[0027] That is, by selecting the values of resistors R _3, R ₄ as according to the value of the transistor Q _2, emitter junction ratio of Q ₃ n ₁ and the current I ₂ is [Delta] V _R, thereby satisfying the expression (12) ,
The temperature coefficient ∂V ₁ / ∂T of V ₁ may be zero. Here, since n ₁ > 1, (k / q) ln (n ₁ ) is a positive value.

Therefore, the temperature coefficient of ΔV _R ∂ΔV _R / ∂T
It was a negative value, if so the absolute value is equal to the value of (k / q) ln (n 1), the temperature coefficient of the voltage across V ₁ of the resistor R ₁ may be zero. Below, ΔV _R is (12)
The conditions for satisfying the expression will be described in detail.

FIG. 2 is a circuit diagram partially showing the first embodiment of the present invention in detail.

[0030] In FIG. 2, the transistors Q _7, ... Q ₁₁ and resistors R _5, ... by R _8, current source CC _1, CC in Figure 1
_Make up _two . The transistors Q ₁₀ and Q ₁₁ constitute a multi-collector transistor, and are weighted by the current density ratio. The collector of the transistor Q ₁₀ is the resistance R _3, R ₄
A common connection point to supply current I _2, the collector of the transistor Q ₁₁ is supplying current I ₁ to the transistor Q ₁ Total chromatography scan of.

[0031] In FIG. 2, the transistors Q _7, ... Q ₁₁ and resistors R _5, ... by R _8, current source CC _1, CC in Figure 1
_Make up _two . The transistors Q ₁₀ and Q ₁₁ constitute a multi-collector transistor, and are weighted by the current density ratio. The collector of the transistor Q ₁₀ is the resistance R _3, R ₄
A common connection point to supply current I _2, the collector of the transistor Q ₁₁ is supplying current I ₁ to the transistor Q ₁ Total chromatography scan of.

FIG. 2 shows the voltage and current of each part of the circuit.
Set as shown. I_C8Is the resistance R _Five, R₆, R₇And
Transistor Q₇, Q₈To a constant current.
You. Transistor Q₉, Q_Ten, Q₁₁DC current gain h_FE
H_FE>> 1 and I_C8h_FE<< I_B8Then I_E10= V_BE9/ R₈ (13) In addition, I_E10= I₁+ I_Two (14) Therefore, the transistor Q_Ten, Q₁₁Collector junction surface
Product ratio n_Two: 1 and I_Two= I_E10n_Two/ (1 + n_Two) (15)

Here, assuming that n ₂ / (1 + n ₂ ) = n ₃ and substituting equation (13) into equation (15), I ₂ = I _E10 n ₃ = n ₃ V _BE9 / R ₈ (16) Become.

Therefore, from equation (5),

[0035]

(Equation 4)

## EQU1 ##

By the way,

[0038]

(Equation 5)

The base-emitter voltage V _BE9 of the transistor Q ₉ shows a negative temperature coefficient as is well known.
Therefore, since a negative temperature coefficient current I ₂ from equation (16), [Delta] V _R indicates a negative temperature coefficient.

Here, Vgo is a voltage (1.) corresponding to the energy band gap of silicon constituting the transistor.
12 to 1.17 [eV]), T is the operating temperature (K), T ₀ is the operating temperature to be a reference (K), V _BE09 is between transistors Q ₉ Nobesu emitter when the T = T ₀ Voltage [V].

Here, the equations (8) and (18) are replaced with the equations (17)
Substituting into the expression,

[0042]

(Equation 6)

By partially differentiating both sides of equation (19) with temperature T,

[0044]

(Equation 7)

Is as follows.

Here, ΔV ₁ / ΔT = 0, that is,

[0047]

(Equation 8)

[0048] and if the resistor R _3, sets the value of R ₄ such that it is possible to zero the temperature coefficient of V _1.

[0049] (22) a n _1> 1 in formula, also because it is _{Vgo-V BE09> 0 (23} ), the right side has a positive value.

Therefore, R ₄ > R _3, and n is set so that the absolute value | R ₄ −R ₃ | of the difference is equal to the value on the right side.
By setting the values of the resistors R ₃ and R ₄ according to the values of ₁ and n ₄ , V ₁
The temperature coefficient of the can be zero, the resistance R ₃ is may be omitted.

That is, when the resistor R ₃ is omitted,

[0052]

(Equation 9)

[0053] As will be, by setting the value of the resistor R ₄ in accordance with the value of n _1, n _3, it is possible to zero the temperature coefficient of V _1.

[0054] Incidentally, the collector current of the transistor Q ₁ is made a constant current, also across the voltage V ₂ of the resistor R _2, the resistance R ₁
Voltage V ₃ between the top and ground, the voltage across V ₉ of the resistor R ₉
Are respectively V ₂ = V ₁ R ₂ / R ₁ (25)

[0055]

(Equation 10)

Is as follows.

As described above, the divided voltages V ₂ , V ₃ , and V ₉ divided by the ratio of the resistance values of the resistors R ₁ , R ₂ , and R ₉ can be constant voltages. Can be set to zero. Therefore, by selecting the resistance ratio of the resistors R ₁ , R ₂ , and R ₉ , it is possible to obtain a temperature-compensated low-voltage reference voltage, which cannot be obtained by the conventional band gap zener circuit. As described above, in this embodiment, the current source CC ₂ having a negative temperature coefficient is provided to the emitters of the transistors Q ₂ and Q ₃ in which the current ratio is unbalanced and the base-emitter voltage has an offset voltage. supplying a current through the more resistant R _3, R _4, by the temperature corrected by the positive resistance of the offset voltage indicative of the temperature coefficient R _3, the voltage drop across the R ₄ (indicating a negative temperature coefficient), and configured to the voltage across the resistor R ₁ and zero temperature coefficient.

FIG. 3 is a circuit diagram of a second embodiment of the present invention. This example basic structure is the same as the first embodiment, an example of changing the method of controlling the current I _1. In other words, the current mirror pair transistor Q ₁₂ in the transistor Q _6,
Drives the Q _13, thereby configured to control the transistor Q ₁ which is a PNP type.

FIG. 4 is a circuit diagram of a third embodiment of the present invention. This embodiment is an example in which n ₁ > 1 is set in the first embodiment, the resistor R ₃ is omitted, and the circuit configuration of the current sources CC ₁ and CC ₂ is changed.

[0060] That is, the transistors Q _14, ... Q ₁₆ and resistors R _10, ... by the current source CC ₁ 'consisting of R ₁₂ to drive the transistors Q _1, transistors Q _17, ... Q _19, resistors R _13, ... R ₁₇ Current source CC ₂ ′ composed of
Thus, a current is supplied to the transistors Q ₂ and Q ₃ . Further, a current mirror circuit including the transistors Q ₂₁ and Q ₂₂ was connected between the collector of the transistor Q ₁ and the terminal 7.

According to this embodiment, the operating voltage range can be expanded as compared with the first and second embodiments, and a constant current can be obtained from the terminal 7.

[0062]

As described above, according to the present invention, the voltage between the first terminal and the second terminal is the first voltage having a positive temperature characteristic.
And the voltage of the sum of the difference between the base-emitter voltages of the respective second transistors and the voltage drop showing a negative temperature characteristic between one end of the current source and the respective emitters of the first and second transistors. Therefore, when the divided voltage from the voltage dividing means is set to a low voltage, a low voltage reference voltage stable to the temperature can be obtained.

[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 partially showing the first embodiment of the present invention in detail.

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

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

FIG. 5 is a circuit diagram of an example of a conventional constant voltage circuit.

FIG. 6 is a circuit diagram of another example of a conventional constant voltage circuit.

[Explanation of symbols]

1 terminal (first terminal) 2 terminal (second terminal) Q ₂ transistor (first transistor) Q ₃ transistor (second transistor) R ₃ resistor (first voltage dropping element) R ₄ resistance (the second voltage dropping _{element) CC 1, CC 2, CC} 1 ', CC 2' current source V _CC input voltage

Claims (1)

(57) [Claims] 1. A current source having an output current having a negative temperature characteristic, and first and second terminals each having one end connected to one end of the current source.
And the other ends of the first and second voltage drop elements are connected to respective emitters, and are configured to have different current densities. Generates first and second transistors having a positive temperature characteristic, and first and second divided voltages obtained by dividing the input voltage,
The first divided voltage is applied to the base of the first transistor via a first terminal, and the second divided voltage is applied to the base of the second transistor via a second terminal. Voltage dividing means for applying a positive temperature characteristic of a voltage difference between a base-emitter voltage of each of the first and second transistors to the current source.
The current having a negative temperature characteristic is supplied to each of the first and second voltage drop elements, and a negative temperature characteristic is provided between one end of the current source and the emitter of each of the first and second transistors. A constant voltage circuit configured to compensate by generating a voltage drop having the following.