JPH027117A - Reference voltage generating circuit - Google Patents

Abstract

PURPOSE:To generate a reference voltage stable for a power supply voltage fluctuation by controlling the current of a constant current circuit through a resistance based on the output voltage of a band gap reference circuit. CONSTITUTION:The title circuit is composed of a constant current circuit C2, a band gap reference circuit SV and a starter circuit ST. The constant current circuit C2 provides three transistors Q4-Q6, a resistance R8 is serially connected to the emitter side of a transistor Q6 and the base of the same Q6 is connected to the collector of a transistor Q3 of the reference circuit SV. The starter circuit ST assures the constant current action of the constant current circuit C2 at the time of turning on the power source. An output current I0 of the constant current circuit C2 goes to {(Vref-I3XR7)-Vbe}/Rs (in the expression, Vbe is the Vbe voltage of the transistor Q6) and the current I0 is kept constant regardless of a voltage Vcc.

Description

[Detailed Description of the Invention] [Summary] The present invention relates to a reference voltage generation circuit that can output a stable reference voltage despite changes in power supply voltage. A constant current circuit having a first transistor for outputting a constant current, and a second transistor for controlling the base current of the first transistor. , a multi-stage transistor type bandgap reference circuit to which a constant current is supplied from the constant current circuit, and a starter circuit that guarantees constant current operation when the constant current circuit is powered on, and the base current of the second transistor is The gist of this is a reference voltage generation circuit characterized in that the output reference voltage of a bandgap reference circuit is supplied to the final stage transistor of the bandgap reference circuit via a collector resistor inserted in series. be.

[Industrial application field]

The present invention relates to a reference voltage generation circuit that can output a stable reference voltage despite fluctuations in power supply voltage.

[Conventional technology]

As a reference voltage generating circuit often used in IC circuits, a combination of a constant current circuit and a bandgap reference circuit as shown in FIG. 3 is known. This reference voltage generation circuit generates a reference voltage Vr from a bandgap reference circuit SV connected to a power supply voltage Cc through a constant current source CI.
This is a circuit to obtain ef. The bandgap reference circuit Sv includes a series circuit of a resistor R1 and a transistor Q, a series circuit of a resistor R2, a transistor Q, and a resistor R3,
It consists of a parallel circuit with transistor Q3. The base of the transistor Q1 is connected to its own collector to form a diode connection, the base of the transistor Q2 is connected to the collector of the transistor Q1, and the base of the transistor Q3 is connected to the collector of the transistor Q2.

In the reference voltage generation circuit of FIG. 3, the output current I of the constant current source CI. It is well known that if Vref changes for some reason, the reference voltage Vref also changes.

Therefore, as a specific example of a practical reference voltage generating circuit, a circuit shown in FIG. 4, which is based on the circuit shown in FIG. 3, has been proposed. The feature of this circuit is in the constant current circuit C2,
The bandgap reference circuit S■ is no different from the one shown in FIG. 3. In this constant current circuit C2, a constant current I is supplied to the bandgap reference circuit SV. is transistor Q4
obtained through. In order to control the base current of transistor Q4, a series circuit of transistor Q5 and transistor Q6 and a series circuit of resistor R4 and transistor Q7 are connected in parallel to power supply voltage vcC. Transistor Q4 and transistor Q5 are PN
P type, transistor Q6 and transistor Q7
is of NPN type.

The base of transistor Q4 is connected to the base of transistor Q5, and transistor Q5 is diode-connected. Similarly, the base of transistor Q6 is connected to the base of transistor Q7, and transistor Q7 is diode-connected.

[Problem to be solved by the invention]

Here, the base-emitter voltage of transistor Q7 is V. , if the resistance value of the resistor R4 is R4, the output constant current I0 of the constant current circuit C2 is I = (Vcc-V, 8>/R, . . . (1).

As can be seen from equation (1), the current I. is the power supply voltage “cc”
changes, it changes accordingly. When the output constant current of the constant current circuit C2 changes, the reference voltage ref also changes. FIG. 5 shows how the reference voltage refC changes with respect to the change in the source voltage V.

Therefore, the present invention is capable of
It is an object of the present invention to provide a reference voltage generation circuit that can generate a more stable reference voltage.

[Means to solve the problem]

In order to achieve the above object, the reference voltage generation circuit of the present invention includes a first transistor (QA) for outputting a constant current.
, and a constant current circuit (C6) having a second transistor (C6) that controls the base current of the first transistor.
2) and a multi-stage transistor bandgap reference circuit (SV) to which a constant current is supplied from this constant current circuit (C2).
and a starter circuit (ST) that guarantees constant current operation when the constant current circuit (C2) is powered on, and the base current of the second transistor (C6) is controlled by the bandgap reference circuit (SV). The output reference voltage (Vref) is supplied to the final stage transistor (C3) of the bandgap reference circuit (SV) via a collector resistor that is not inserted in series.

[Effect]

In the reference voltage generation circuit configured as described above, the output current of the constant current circuit is determined by the reference voltage (V, . . . ).

Therefore, even if there is a fluctuation in the power supply voltage, the output current of the constant current circuit is not affected by the fluctuation in the power supply voltage, so a more stable reference voltage can be obtained.

〔Example〕

FIG. 1 shows an embodiment of the invention.

This embodiment is basically constructed on the basis of the reference voltage generating circuit shown in FIG. 6, and the same or equivalent circuit components are denoted by the same reference numerals.

This reference voltage generation circuit includes a constant current circuit C2, a bandgap reference circuit S2, and a starter circuit ST.

The constant current circuit C2 includes three transistors Q4, Q5. Q
6, and the connections between them are the same as in the case of FIG. However, a resistor R9 is connected in series to the emitter side of the transistor Q, and the base of the transistor Q6 is connected to the collector of the transistor Q3 of the bandgap reference circuit Sv.

The bandgap reference circuit Sv is substantially similar to that of FIG. 4, the only difference being that a resistor R7 is connected in series to the collector side of the transistor Q.

The starter circuit ST is provided to ensure constant current operation of the constant current circuit C2 when the power is turned on, and
During steady operation, it is not involved in the reference voltage generation operation at all.
This starter circuit ST includes a series circuit of a resistor R9, a transistor Q, and a transistor Q9, which are provided for the power supply voltage V
and a transistor Q1° connected between the base C and the transistor Q6 of the constant current circuit C2. The bases of Q9 are each connected to its own collector. Transistor Q1o
The base of is connected to the connection point between resistor R9 and transistor Q8.

The output current I0 of the constant current circuit C2 in the circuit of FIG.・If the emitter voltage is V and the resistance value of resistor R8 is R8, then ・R) Vb, 1/R6 l0=((vref-I3 7... (2) However, I = I + 12 + 13 ■ = constant : I = constant: l3 = - constant.

Therefore, the current I. is constant regardless of the voltage vcc. For this voltage cc. FIG. 2 shows the relationship between the reference voltage vref.

As is clear from Figure 2, the power supply voltage vCo is ±10%
It can be seen that when the reference voltage vref changes, the change in the reference voltage vref is only ±0.2%. By the way, in the case of the circuit shown in FIG. 4 under the same conditions, the reference voltage V. .

The change in value reaches as much as ±3%.

Next, the operation of the starter circuit ST will be explained.

At power-on, the base of transistor Q1o is connected to resistor R9 and transistor Q8. Due to the action of the voltage divider consisting of Q9, the transistor Q1 is positively biased with a base-emitter voltage twice the rated value "be", and the transistor Q1 is turned on, supplying base current to the transistor Q6 to turn it on.

As a result, the constant current circuit C2 operates, and the bandgap reference circuit Sv also operates to generate a constant reference voltage V (for example, about ef 1.25V).

Next, during steady state, the base of transistor Q1o is positively biased with a base-emitter voltage vbo that is twice the rated value, and the emitter of transistor Q1o (=base of transistor Q6) has a bow) (vref −R73 A voltage of the magnitude is applied.Here, 2·V −
(V-R-I)<Vb.

be ref 7 3 ...(3) If the circuit is designed so that the transistor Q1
゜ is off during normal operation.

〔Effect of the invention〕

As described above, according to the present invention, the current control of the constant current circuit is performed via the resistor based on the output voltage of the bandgap reference circuit, so even if there is a fluctuation in the power supply voltage, It is possible to generate an extremely stable reference voltage with almost no fluctuations.

[Brief explanation of the drawing]

FIG. 1 is a circuit connection diagram showing an embodiment of the present invention, FIG. 2 is an explanatory diagram showing voltage fluctuation characteristics of the circuit in FIG. 1, FIG. 3 is a diagram of a conventional first reference voltage generation circuit, and FIG. FIG. 4 is a connection diagram showing a second example of a conventional reference voltage generation circuit, and FIG. 5 is an explanatory diagram showing voltage fluctuation characteristics of the circuit shown in FIG. 4. CC...constant current circuit, RV...bandgap reference circuit, ST...starter circuit, R1, R2, R3, R4, R5, R6, R7, R8...
・Resistance, Ql, Q2, Q3. Q4. Q5. Q6. Q7. Q8. Q9. Qlo-1-rangister. Power supply voltage Vcc (%) Fig. 1 An explanatory diagram showing the characteristics of the circuit shown in Fig. 2 A circuit connection diagram showing an embodiment of this research Fig. 1 A conventional first reference voltage generation circuit diagram Fig. 3 A conventional circuit diagram 2. Power supply voltage Vcc (%) -

Claims (1)

[Claims] First transistor (Q_A) for outputting constant current
, and a constant current circuit (C_2) having a second transistor (Q_6) that controls the base current of this first transistor, and a multistage transistor type bandgap to which a constant current is supplied from this constant current circuit (C_2). The circuit includes a reference circuit (SV) and a starter circuit (ST) that guarantees constant current operation when the constant current circuit (C_2) is powered on, and controls the base current of the second transistor (Q_6) according to the bandgap. Output reference voltage (V_r_e_f) of the reference circuit (SV)
), the reference voltage generating circuit is characterized in that the voltage is supplied via a collector resistor inserted in series to the final stage transistor (Q_3) of the bandgap reference circuit (SV).