JP3024222B2 - 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 whose output voltage does not fluctuate with temperature.

[0002]

2. Description of the Related Art The present applicant has proposed a constant voltage circuit shown in FIG. 5 in Japanese Patent Publication No. 55-18928. In the figure, a power supply 1 is connected to terminals T ₁ and T ₂ , a differential amplifier circuit 3 composed of transistors having different current densities, the output of which is amplified by a PNP transistor Q ₅ and connected to an output terminal T _3. ing. The voltage across the resistor R ₇ are respectively supplied to the two inputs of the differential amplifier circuit 3. In this circuit, by making the output voltage V _S between the terminals T ₃ and T ₂ equal to the voltage V _g01 corresponding to the silicon _band cap forming the NPN transistor Q ₄ , V _S has a temperature characteristic having a zero temperature coefficient. V _S can be kept stable even when the temperature fluctuates.

FIG. 6 shows a circuit diagram of another example. The same parts as those in FIG. 5 are denoted by the same reference numerals, and description thereof will be omitted. NPN
The output of the transistor Q ₆ is connected to the output terminal T ₃ is amplified by the NPN transistor Q ₇ and Q _8. Voltage V _{g0 1} In this circuit corresponding to the band gap of silicon constituting the NPN transistor Q ₈ output voltage V _S
And V _S by equal be a temperature characteristic having a zero temperature coefficient, the same effect as the circuit of FIG.

[0004]

[SUMMARY OF THE INVENTION] However, the output V _S of the circuit in the conventional constant voltage circuit is a stable good constant voltage power supply for variations in temperature, V _S is equivalent to the band gap of silicon Must be set to about 1.1V. Therefore, there has been a problem that the circuit of FIG. 5 or FIG. 6 cannot cope with various devices operating at a low voltage of 1.1 V or less, which is increasing in recent years.

The present invention has been made in view of the above points, and has a zero temperature coefficient which is equal to or lower than a voltage (about 1.1 V in the case of silicon) corresponding to a band cap of a semiconductor constituting a transistor. It is an object of the present invention to provide a constant voltage circuit capable of obtaining an output voltage.

[0006]

According to the present invention, there is provided a constant voltage circuit comprising:
A constant current source, a diode to which a constant current from the constant current source is supplied, and a collector connected to the cathode of the diode,
Base connected to the anode of the diode, the voltage corresponding to that from the collector-emitter and a transistor for outputting a constant voltage V _S, metal and semiconductor Shiyottoki barrier values constituting a diode or semiconductor bandgap,

[0007]

(Equation 3)

_However , a diode different from the voltage V _g01 corresponding to the band cap of the transistor is used.

Further, the voltage V _g01 and

[0010]

(Equation 4)

The current density ratio of the diode to the transistor is set such that the difference is substantially equal to the voltage V _S. Furthermore, a resistor is inserted between the cathode of the diode and the collector of the transistor, or a first resistor is inserted between the anode of the diode and the base of the transistor, and the base of the transistor is connected to the emitter of the transistor. A second resistor is connected between them.

[0012]

Next, the principle and operation of the present invention will be described. In the constant voltage circuit having the above configuration, the output voltage V _S obtained between the collector and the emitter of the transistor is equal to the anode voltage of the diode. It is expressed as a voltage difference between the voltage V _FD1 between the cathode and the voltage V _BE1 between the base and the emitter of the transistor.

Further, the voltage V _FD1 is the absolute temperature T during operation,

[0014]

(Equation 5)

[0015] and has a function of voltage V _{F0 D1} between the anode and the cathode of the diode at a reference temperature T _0, the voltage V _BE1 is the absolute temperature T during operation, the voltage V _{g0 1} and reference It is a function of the base-emitter voltage V _BE01 of the transistor at the voltage T ₀ .

Therefore, V represented by the above function
_The output voltage V _S represented by the difference between _FD1 and V _BE1 is T,

[0017]

(Equation 6)

It becomes a function of V _g01 , V _F0D1 , V _BE01 ,
_{It is possible to set S} to a voltage _{equal to} or lower than the voltage V _g01 corresponding to the band cap of the semiconductor constituting the transistor. In addition, in order to make the temperature coefficient of the output voltage V _S zero, the values of V _F0D1 and V _BE01 are set so that the equation obtained by partially differentiating the equation of V _S with T becomes zero, that is, By setting the current density ratio of the diode to the transistor, the output voltage V _S is set to V _g01

[0019]

(Equation 7)

The difference can be set so as to be equal to or less than the voltage V _g01 corresponding to the band gap of the semiconductor constituting the transistor, and to have a zero temperature coefficient.

Further, by inserting a resistor between the cathode of the diode and the collector of the transistor, when the constant current source fluctuates, the variation width of the base-emitter voltage of the transistor can be reduced by the anode of the diode. A fluctuation which appears in the output voltage obtained between the collector and the emitter of the transistor due to the fluctuation width of the voltage between the cathodes can be corrected by a voltage drop of the resistor.

Further, a first resistor is inserted between the anode of the diode and the base of the transistor, and a second resistor is connected between the base and the emitter of the transistor, so that the collector and the collector of the transistor are connected. Fine adjustment of the setting of the output voltage obtained between the emitters becomes possible.

[0023]

FIG. 1 is a circuit diagram of a first embodiment of the present invention.
In FIG.₁, T_TwoPower supply 1 is connected between
T_Three, T_TwoOutput voltage V_SIs taken out. Terminal
T₁, T_TwoConstant current source 2 and Schottky barrier die between
Aether D₁, NPN transistor Q₁Collector of Emi
Are connected in series. Transistor Q₁Bee
Are constant current source 2 and Schottky barrier diode D₁of
It is connected to the connection point with the anode. Schottky
Rear diode D₁Cathode and transistor Q ₁No
The connection point with the collector is terminal T_ThreeIt is connected to the. Same circuit
Then transistor Q₁Base-emitter voltage V_BE1
And Schottky barrier diode D₁Anode Caso
Voltage V between nodes_FD1And the difference voltage V_SIs the output voltage
You.

In the circuit shown in FIG. 1, the voltage V _FD1 between the anode and the cathode of the Schottky barrier diode D _{1 at} the operating temperature (absolute temperature) T is equal to the reference voltage D ₁ at the operating temperature T ₀ . V between anode and cathode
_F0D1, the voltage corresponding to the metal-semiconductor Schottky barrier values constituting D ₁

[0025]

(Equation 8)

Then, it is expressed by the following equation.

[0027]

(Equation 9)

The base-emitter voltage V _{BE1 at} the operating temperature (absolute temperature) T of the NPN transistor Q _1
Assuming that the base-emitter voltage of Q _{1 at} the reference operating temperature T ₀ is V _BE01 , and the voltage corresponding to the band gap of the semiconductor constituting Q ₁ is V _g01 , the following equation is given.

[0029]

(Equation 10)

The output voltage taken out between the terminals T ₃ and T ₂ , that is, the collector-emitter voltage V _S of the NPN transistor Q ₁ is expressed by the following equation.

V _S = V _BE1 −V _FD1 (3) Therefore, when Equations (1) and (2) are substituted into Equation (3), V _S
Is represented by the following equation.

[0032]

[Equation 11]

Next, in order to make the temperature coefficient of the output voltage V _S zero, the equation (4) is partially differentiated with respect to T.

[0034]

(Equation 12)

Where

[0036]

(Equation 13)

If the constant is set so as to satisfy, the temperature coefficient of V _S becomes zero. That is, from equations (5) and (6),

[0038]

[Equation 14]

V _BE01 −V _F0D1 may be set so that Next, a method of setting V _BE01 -V _F0D1 will be described.

NP of Schottky barrier diode D ₁
Assuming that the current density ratio (or the area ratio of the junction) to the N transistor Q ₁ is n, the Boltzmann constant is K, and the electron charge is q

[0041]

(Equation 15)

By setting n, V _BE01 −
V _F0D1 can be set. The value of V _S at T = T ₀ is expressed by the following equation by substituting equation (7) into equation (4).

[0043]

(Equation 16)

Further, since the temperature coefficient is zero, V
_S is represented by the following equation.

[0045]

[Equation 17]

From this,

[0047]

(Equation 18)

_Depending on the selection method, a zero temperature coefficient can be realized even when V _S is lower than V _g01 (up to 1.1 V).

For example, in the case of a combination of an NPN transistor Q ₁ made of silicon (Si) and a Schottky barrier diode D _{1 formed} by a Schottky junction of silicon (Si) and aluminum (Al), V _g01 is about 1 .1V, said

[0050]

[Equation 19]

Is about 0.72 V, V _S becomes (1
From equation 0)

[0052]

(Equation 20)

Is as follows. As described above, according to the present embodiment, the temperature coefficient can be made zero even at a voltage (about 1.1 V) or less corresponding to the band gap of the semiconductor (here, silicon), and the temperature coefficient is stable without being affected by the low voltage temperature. A voltage is obtained.

FIG. 2 shows a circuit example of the constant current source 2 shown in FIG. 1. The same reference numerals are given to the same parts as those in FIG. 1, and the description thereof will be omitted. The configuration of the circuit corresponding to the constant current source 2 is as follows.
The high-potential-side power supply terminal T ₁ is connected to the low-potential-side power supply terminal T ₂ via the emitter and collector of the PNP transistor Q ₂ and two resistors R ₁ and R ₂ in series. The base of transistor Q ₂ is connected to the connection point of the resistors R _1, R _2. Also connected the emitter of the PNP transistor Q ₃ to the power supply terminal T _1, the collector of the transistor Q ₃ is connected to a connection point between the base of the Schottky barrier diode D ₁ of the anode and the transistor Q _1. The base of the transistor Q ₃ are connected to the connection point between the collector of the transistor Q ₂ and a resistor R _1.

[0055] In the constant current source of the configuration, it varies the current in the resistance R ₁ is when the supply voltage fluctuates, the current of Q ₃ by controlling the base voltage of the transistor Q _3, i.e. variation of the load current is obstructed Can be

FIGS. 3 and 4 are circuit diagrams of the second and third embodiments of the present invention, respectively. In these circuit diagrams, the same parts as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.

[0057] The second embodiment of Figure 3 to a connection point resistor R ₃ is inserted between the circuit in the Schottky barrier diode D ₁ and a transistor to Q ₁ Figure 1, when the current of the constant current source 2 fluctuates The variation in the output voltage V _S due to the variation in the base-emitter voltage of the transistor Q _{1 being} larger than the variation in the anode-cathode voltage of the Schottky barrier diode D ₁ is reduced by the voltage drop of the resistor R ₃ . Has the effect of compensating.

[0058] The third embodiment of Figure 4 resistor R ₄ is inserted between the base of the connection point between the transistors to Q ₁ the anode and a constant current source 2 of the Schottky barrier diode D ₁ of the circuit of Figure 1, Q resistor R ₅ is connected between the _first base and the emitter.

According to the present embodiment, the output voltage V _S is set by setting R ₄ and R ₅ so that the base current I _B1 of the transistor Q ₁ is much smaller than the current I ₁ flowing through the resistor R _4. Is

[0060]

(Equation 21)

Is obtained. Substituting equations (1) and (2) into equation (11) and performing partial differentiation with T,

[0062]

(Equation 22)

By setting a constant so that
Temperature coefficient of V _S is zero. Ie

[0064]

(Equation 23)

V _BE01 -V _F0D1 may be set so that Accordingly, fine adjustment of the setting of the output voltage V _S becomes possible by adding the resistors R ₄ and R _{5 as} compared with the circuit of FIG.

An embodiment combining the second embodiment and the third embodiment is also possible. It should be noted that the present invention is not limited to the above-described embodiments. In addition, for example, a combination of a silicon transistor and a germanium diode, a combination of a silicon transistor and a Schottky barrier diode made of various semiconductors and metals. For example, a transistor having a different voltage corresponding to the band gap of a semiconductor forming a transistor and a voltage corresponding to a Schottky barrier value (or a semiconductor band gap) of a metal and a semiconductor forming a Schottky barrier diode (or a PN junction element). And Schottky barrier diode (or PN
(Junction elements), and various combinations of output voltages can be set by these combinations. Table 1 shows voltages (unit: V) corresponding to Schottky barrier values of various metals and semiconductors.

[0067]

[Table 1]

[0068]

As described above, the constant voltage circuit according to the present invention has a zero temperature of not more than the voltage (about 1.1 V in the case of silicon) corresponding to the band gap of the semiconductor constituting the transistor with a relatively simple circuit configuration. It can supply a stable low voltage with a coefficient, can meet the demand for a low voltage reference power supply that is expanding with the increase of battery-operated electric products, and can more easily integrate into an integrated circuit. Therefore, it is advantageous in terms of reliability and economy.

[Brief description of the drawings]

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

FIG. 2 shows a circuit example of a constant current source in the circuit of FIG.

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 constant voltage circuit proposed by the present applicant.

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

[Explanation of symbols]

1 power supply 2 constant current source Q ₁ NPN transistor D ₁ Schottky barrier diode R ₃ to R ₅ resistance

Claims (4)

(57) [Claims] 1. A constant current source, a diode to which a constant current is supplied from the constant current source, a collector connected to a cathode of the diode, a base connected to an anode of the diode, and a collector-emitter A transistor that outputs a more constant voltage V _S , and a voltage corresponding to a Schottky barrier value of a metal and a semiconductor constituting the diode or a band gap of the semiconductor. Is the voltage V corresponding to the band gap of the transistor.
A constant voltage circuit using a diode different from _g01 . 2. The voltage V _g01 and: 2. The constant voltage circuit according to claim 1, wherein a current density ratio of the diode to the transistor is set so that a difference between the two is substantially equal to the voltage V _S. 3. The constant voltage circuit according to claim 1, wherein a resistor is inserted between a cathode of said diode and a collector of said transistor. 4. A transistor according to claim 1, wherein a first resistor is inserted between an anode of said diode and a base of said transistor, and a second resistor is connected between a base and an emitter of said transistor. The constant voltage circuit as described.