JP3340345B2 - 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 generator suitable as a temperature compensated reference voltage generator provided inside an integrated circuit device.

[0002]

2. Description of the Related Art A stabilized power supply that is less affected by fluctuations in input power supply voltage and temperature is indispensable as a reference voltage for various electronic circuits. Conventionally, a bandgap reference voltage source shown in FIG. 3 has been widely used as a reference voltage generating circuit provided inside such an integrated circuit element. This bandgap reference voltage source is connected to the emitters of the output transistor Q6 and the transistors Q7, Q8 and the resistors R5, R6, R7.
It is composed of Further, capacitors C1 and C2 for preventing oscillation and suppressing high-frequency noise are provided. By optimizing the values of the respective resistors of these transistor sizes and adjusting the distribution of current flowing through the transistor group, silicon (S
A constant voltage value close to the band gap voltage of i) is output. This bandgap reference voltage source basically includes a negative temperature coefficient of a diode voltage between the base and the emitter of the transistor Q5 driven by a constant current, and a transistor Q7, Q8 and resistors R5, R6, R
This is realized based on the principle of canceling with a positive temperature coefficient of the voltage drop of the resistor R5 determined by S7.

[0003] Such a circuit is an excellent circuit system in which an output voltage can have a positive temperature coefficient or a negative temperature coefficient by adjusting elements such as transistors and resistors.

However, as apparent from FIG. 3, the current injected into the circuit, which affects the output voltage, is determined by the power supply voltage, the output voltage, the transistor Q6 and the resistor R40, and corresponds to the power supply voltage fluctuation. The fluctuation can be easily inferred.

For this reason, the generated voltage fluctuates and the temperature stability deteriorates at the same time. In fact, as shown in FIG. 5, in a typical operation characteristic example when the power supply voltage is 3.3 V, 10
The output fluctuation with respect to a temperature change of 0 ° C. is as small as 2 mV or less, whereas the fluctuation in power supply is about 10 mV for a change of 10%.
Is observed.

In order to improve such characteristics, as an attempt to stabilize the current injected into the bandgap reference voltage source, resistors R1 and R2 shown in FIG.
4, R20 and transistors Q1 and Q4. The circuit of FIG. 4 has slightly improved characteristics as compared with the circuit example of FIG. 3, but the reference voltage of the constant current generator is Q-connected in series with R1.
1 is a voltage generated at both ends and is still sensitive to fluctuations in the power supply voltage.

The sensitivity to power supply fluctuation is relatively small when the input power supply voltage is higher than the generated reference voltage. However, in a situation where the operating voltage has been reduced as in a recent integrated circuit element, it cannot be ignored. is there. Especially 3.3V
In the case of the following power supply, the sensitivity to power supply fluctuation in the circuit of FIG. 4 reaches 1%, and the stability is often insufficient for use as a reference voltage.

When the circuit shown in FIG. 4 is applied to a circuit requiring high stability, a multi-stage stabilization is performed by installing a preliminary stabilizing circuit in the preceding stage even when the power supply voltage is 5 V or more. Therefore, there is a problem that a complicated circuit is required, an occupied area is increased, and power consumption is increased.

[0009]

As described above, the conventional bandgap reference voltage source does not have sufficient stability against temperature fluctuations and input power supply voltage fluctuations, or it is necessary to ensure the stability. It required a complicated circuit.

An object of the present invention is to provide a constant voltage generating circuit which occupies almost the same area as the conventional circuit and consumes low power by merely adding a few transistors and resistors to the conventional circuit. Is to do.

[0011]

According to another aspect of the present invention, there is provided a constant voltage generating circuit including a plurality of transistors and a plurality of resistors, and configured to generate a constant voltage corresponding to a bandgap voltage of silicon. Consists of the gap constant voltage generator and the input stage of this band gap constant voltage generator
Having a first transistor and a second transistor
And a constant current generator including a current source circuit.
The constant current generator is located before the current source circuit.
A third transistor connected in series to the second transistor
And a diode connected to the base of the third transistor.
And a power supply and the fourth transistor.
A first resistor connected between the transistor and a base of the transistor;
A second resistor connected between the third transistor and ground;
It is characterized by including.

In such a circuit, the constant voltage output from the bandgap voltage generator is connected to the first voltage connected to the power supply.
A diode-connected fourth transistor is connected via a resistor. The voltage at the connection point between the first resistor and the fourth transistor is input to the base of a third transistor for generating a constant current, and a second resistor is connected between the emitter of the third transistor and ground. With this circuit configuration, the voltage applied to both ends of the second resistor has a constant value regardless of temperature fluctuation and power supply fluctuation. Therefore, the current output from the collector of the common-base third transistor becomes constant. This output current is received by a load in which a diode-connected complementary second transistor of the bandgap voltage generator and a resistor are connected in series, and is converted into a voltage. Further, using this voltage as a reference voltage, a current is generated in a circuit comprising a complementary first transistor of the same size and a resistor of the same value.

The current generated in this way has a mirror-inverted value with respect to the above current, and becomes a temperature-compensated constant current. As a result, the current injected into the bandgap voltage generator becomes constant irrespective of the operating environment such as temperature fluctuation and power supply voltage fluctuation.

Therefore, the temperature dependence of the output voltage can be minimized by finally adjusting the element value of the bandgap voltage generating section, whereby a stabilized voltage can be generated. In the present invention, based on the output of the hour and minute
The bias current of the operation circuit is controlled, but the first resistor and
Start-up current flows through the fourth transistor
Therefore, the operation circuit of this principle often
Trapped at a problematic abnormal stable point
The fear of not being able to do so can also be avoided.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A constant voltage generating circuit according to an embodiment of the present invention will be described below with reference to FIG. The constant voltage generation circuit according to the present invention includes a bandgap constant voltage generation unit 100.
And a constant current generator. The circuit in FIG. 1 is an example of a constant voltage generation circuit that generates a positive reference constant voltage. The circuit of this embodiment is basically the same as the conventional example shown in FIG. 4 except that two transistors Q2 and Q3 having the same size and a resistor R3
Is a circuit to which is added. The transistor Q3 has a collector and a base connected to each other and operates equivalently to a diode. The collector of the transistor Q3 is connected to the power supply voltage Vcc via the resistor R3, and the emitter is connected to the reference voltage output Vout. A value obtained by subtracting Vout and the forward drop voltage of the diode from the power supply voltage Vcc and dividing by a current value Ib desired to flow through the diode is selected as the resistance value of the resistor R3.

In this case, the value of the resistor R3 can be sufficiently larger than the differential resistance of the diode. Further, the resistance R
2 is selected so as to be Vout / Ib, and when a voltage equal to or higher than the base voltage is applied to the collector of the transistor Q2, the voltage difference between both ends of the resistor R2 is Vout regardless of the temperature and the fluctuation of the power supply voltage. Will be kept.

As a result, a constant temperature-compensated current Ib flows into the collector of transistor Q2. N used for the band gap constant voltage generator and the constant current generator
The pn transistor is a complementary pnp transistor Q1
And the transistor Q4 are transistors of the same size,
By setting the resistors R1 and R4 to have the same value, a constant temperature-compensated current Ib similarly flows from the collector of the transistor Q4 and is injected into the band gap constant voltage generator. In this state, the element value of the bandgap constant voltage generator is adjusted so that the output voltage has a minimum temperature dependency.

As a result, it is possible to simultaneously generate a constant voltage stabilized with respect to power supply voltage fluctuation. As can be seen from the characteristic example of FIG. 2, the output fluctuation due to the power supply fluctuation is almost the same as the fluctuation due to the temperature change, and an improvement of about one digit is realized as compared with FIG.

Although the above description has been made on the assumption that the transistor has a sufficiently large current amplification factor and the base current can be neglected, actual devices often deviate from ideal characteristics. . However, even in such a case, as described above, the bandgap constant voltage generator can adjust the temperature coefficient to either positive or negative by adjusting the circuit element value, so that the deviation from the ideal characteristic can be compensated. In particular, the present invention is characterized in that the characteristics can be adjusted by slightly shifting the value of the resistor R2 and the relative values of the resistors R1 and R4 from 1, and that there is much room for adjustment.

In this embodiment, the circuit of FIG.
Only the number of elements is increased, and the circuit scale hardly changes.
Therefore, the area required on the integrated circuit element is slightly increased, which can contribute to downsizing.

Further, the current flowing through the transistor Q3 only reduces the supply current required for the circuit operation from the transistor Q6, and can keep the total current consumption unchanged. As a result, there is no increase in power consumption. For this reason, like the array circuit, the reference voltage is incorporated independently,
Even when it is desired to ensure isolation, it is possible to minimize the increase in chip area and power consumption.

Further, in the present invention, the bias current of the operation circuit is controlled based on its own output.
Since the starting current flows through the transistor 3 and the transistor Q3, it is possible to avoid the possibility that the operation circuit of such a principle is trapped at an abnormal stable point which often becomes a problem and does not enter a normal operation. . Further, temperature compensation such as base-emitter voltage can be achieved by np
Since n transistors or pnp transistors function independently, npn transistors and pnp transistors
It is also characterized in that phase correction of complete characteristics is not required between the transistor and the p transistor.

The circuit for generating a positive reference voltage has been described above. However, when a negative reference voltage is to be generated, it can be realized by turning over the npn transistor and the pnp transistor. In addition, the transistor is not limited to Si as long as it is a bipolar type, and SiGe, G
Needless to say, the present invention can be applied to HBT such as aAs and InP.

[0024]

As described above, the present invention provides a plurality of transistors.
Bandgap of silicon, including
Band gap constant voltage that generates a constant voltage equivalent to the voltage
Generator and the input stage of this band gap constant voltage generator.
It has a first transistor and a second transistor to constitute
Constant current generator including a constant current source circuit
In the raw circuit, the constant current generating section may include the current source circuit
A third transistor connected in series to the second transistor
And a resistor connected to the base of the third transistor.
An ion connection type fourth transistor, a power supply and the fourth
A first resistor connected between the transistor and the base of the transistor;
A second resistor connected between the third transistor and ground.
A constant voltage generation circuit that occupies almost the same area as the conventional circuit and consumes low power by only adding a few transistors and resistors to the conventional circuit by including the resistor. Can be provided.

[Brief description of the drawings]

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

FIG. 2 is a characteristic diagram showing an output fluctuation with respect to a power fluctuation in the embodiment.

FIG. 3 is a circuit diagram showing a bandgap reference voltage generation circuit.

FIG. 4 is a band gap reference voltage generation circuit to which a constant current generation circuit is added.

FIG. 5 is a characteristic diagram showing output fluctuation with respect to power supply fluctuation in FIG. 4;

[Explanation of symbols]

R1 to R7, R20, R40 ... resistance, Q1, Q4 ... pn
p transistor, Q2, Q3, Q5 to Q8 ... npn transistor, C1, C2 ... capacity, Vcc ... power supply voltage, Ve
e: ground, Vout: voltage output

Claims (1)

(57) [Claims] 1. A bandgap constant voltage generator including a plurality of transistors and a plurality of resistors for generating a constant voltage corresponding to a bandgap voltage of silicon, and a first unit forming an input stage of the bandgap constant voltage generator.
Current source circuit having one transistor and second transistor
And a constant current generator including a constant current circuit.
The constant current generator is connected in series to the second transistor of the current source circuit.
And a diode connected to the base of the third transistor
A connection type fourth transistor, connected between a power supply and a base of the fourth transistor;
A first resistor and a second resistor connected between the third transistor and ground.
Constant voltage generating circuit, characterized in that it comprises an anti-city.