JP3397655B2 - 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, and more particularly to a constant voltage generator that obtains a constant voltage output based on V _CC .

[0002]

2. Description of the Related Art The structure and problems of a conventional constant voltage generator will be described with reference to FIGS. As shown in FIG. 2, the conventional constant voltage generator is provided with a constant voltage circuit on the V _CC power supply side via a constant current source on the ground (hereinafter referred to as GND) side, and a constant voltage with reference to V _CC is provided. There is something to output. Such a constant voltage generator has an advantage that a stable voltage can be obtained with a relatively small circuit scale.

However, in the constant voltage generator shown in FIG.
Since the stabilized output voltage V _REF itself is provided on the V _CC side, noise and electromagnetic interference (EMI; Electro-Magnetic I
There is a problem that the output voltage malfunctions due to the influence of the interference) and the stable voltage is not maintained.

In order to avoid these problems, the output V _REF of the GND-based constant voltage circuit is set to a voltage gain of 1 as shown in FIG.
Through the operational amplifier, and a constant current circuit for supplying a constant current I ₁₀ by entering the base of the transistor Q _10, since it is substantially equal to I ₁₀ and I _20, at both ends of R ₂₀ R ₂₀ × I A constant voltage generator is known which outputs a constant voltage V ₂₀ with a V _CC reference equal to ₂₀ . However, since an operational amplifier is used, the circuit scale is large, and the operational amplifier itself is easily affected by noise and the like, so that good results have not always been obtained.

Since the output voltage V ₂₀ is smaller than V _REF, it is necessary to increase the resistance ratio of R ₂₀ / R ₁₀ to boost the output voltage. There was a problem that it would be affected.

[0006]

In the conventional constant voltage generating device as described above SUMMARY OF THE INVENTION Problem to ## those of the circuit form of taking out the stabilized voltage V _CC criteria, the constant voltage circuit and the constant voltage circuit to V _CC side Since the output voltage is provided on the V _CC side, there is a problem that the circuit scale is small but it is easily affected by noise and EMI.

Further, a constant voltage circuit is provided on the GND side, the stabilized voltage is taken out with GND as a reference, and is input to the constant current circuit of the transistor through an operational amplifier, and the load resistance of the transistor provided on the V _CC side is applied to V _CC. The circuit type which takes out the reference output has a problem that the resistance value varies and the operational amplifier itself is easily affected by noise and EMI, and thus a good result cannot always be obtained.

The present invention has been made to solve the above problems, and it is an object of the present invention to provide a constant voltage generator which is not easily affected by noise and EMI and which can obtain a stable output voltage based on V _CC. Has an aim.

[0009]

A constant voltage generator according to the present invention is characterized in that a current mirror circuit is used to output a GND reference constant voltage as a Vcc reference constant voltage. Specifically, in the constant voltage generator of the present invention, a constant voltage circuit that outputs a ground-referenced constant voltage, an emitter is grounded, and a collector is connected to an output terminal of the constant voltage circuit via a first load resistor. Yes first and transistor other that is, the emitter is grounded, the collector is the first load resistor and resistance equal
The second through the load resistor is connected to the Vcc power supply for, based
Connected to the base and collector of the first transistor.
The connected second transistor and collector have the Vcc voltage.
Connected to the source of the second load resistor and the base of the second load resistor and the second load resistor.
It is connected to the connection point of the transistor and from the emitter to the Vcc
A third transistor that generates a constant voltage based on the power supply
And is provided .

The constant voltage generator of the present invention is a constant voltage generator comprising first to fifth transistors, first to fourth resistors, an operational amplifier and a GND-based constant voltage circuit, A first transistor having an emitter grounded and a base connected to a collector, one terminal connected to the collector of the first transistor, and the other terminal connected to an output terminal of the GND-referenced constant voltage. First
A second resistor whose one terminal is grounded; a second transistor whose emitter is connected to the other terminal of the second resistor and whose base is connected to the base of the first transistor; A third resistor, one terminal of which is connected to the collector of the second transistor and the other terminal of which is connected to the output terminal of the GND-based constant voltage circuit, the emitter is grounded, and the base is the second resistor. A third transistor connected to the base of the transistor, a fourth resistor having one terminal connected to the collector of the third transistor and the other terminal connected to the V _CC power supply terminal, and an emitter connected to the fourth resistor. 1, the fourth connected to the other terminal of the third resistor
Transistor, first and second inputs are connected to the collectors of the first and second transistors, respectively, and an output is connected to the base of the fourth transistor, and an emitter is the fourth transistor. A fifth transistor connected to the collector of the transistor, the base of which is connected to one terminal of the fourth resistance, and the collector of which is connected to the V _CC power supply terminal; and the resistance of the first and fourth resistances. by equalizing the value, the constant voltage output of a ground reference between the other terminal of said the GND first resistor, the V _CC reference from between the emitters of the V _CC power supply terminal and said fifth transistor constant It is characterized by being output as a voltage output.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing a circuit configuration of a constant voltage generator of the present invention. Constant voltage source shown in Fig. 1
Output voltage _{V BG} from the constant voltage circuit of the raw device GND reference
And a current mirror circuit for returning this to the V _CC side and outputting it as V _REF .

The constant voltage generator of the present invention comprises npn transistors Q _{1 to} Q ₅ , resistors R _{1 to} R _4, and an operational amplifier. The GND-based constant voltage output V _{BG in} FIG. 1 is V _BG = V
It is represented by ₁ + V _BE (Q ₁ ). Where V ₁ is V ₁ = (I
_It is expressed as ₁ + I ₄ ) × R ₁ . V _BE (Q ₁ ) is the voltage between the base and emitter of the transistor Q ₁ .

[0013] By configuring the current mirror circuit with the transistor _{Q 1, Q 2, Q 3} , the current I ₁ flowing through the circuit including the transistor Q ₁ is, the transistor Q ₃
Can be made substantially equal to the current I ₃ flowing through the circuit including. Therefore, if R ₁ = R ₄ , the voltage V ₁ generated across R ₁ becomes substantially equal to the voltage V ₂ generated across R ₄ .

If V _BE (Q ₁ ) is added to the voltage V ₁ , V _BG
Is equal to, and if V _BE (Q ₅ ) is added to V ₂ , V
_Since it becomes equal to _REF , if V _BE of Q ₁ and Q ₅ are equal, V _{BG = V REF} , and the folding of V _{BG to} the V _CC side can be easily realized.

Next, the GND-based constant voltage output V _BG and V _CC
Regarding the relationship with the reference output voltage V _REF , the above Q ₁ , Q
_It will be described in more detail including the difference in V _BE in ₅ .
An error voltage may be generated between V _BG and V _REF based on the following two reasons.

First, the emitter currents I ₇ and Q of Q ₅ are
The difference in the _first emitter current _{I 1 + I B (Q 1} ), Q 5
And Q ₁ V _BE has a difference. Where I _B (Q ₁ ) is Q
It is a base current of ₁ . Assuming that the difference between V _BE is ΔV _BE , κ is a constant determined by the emitter sizes of Q ₁ and Q ₅ , and is given by the following equation.

[0017]

[Equation 1] Becomes

Since the difference in V _BE caused by the difference in the base currents is usually smaller than that caused by the difference in the emitter currents shown in equation (2), ΔV _BE shown in equation (2) is mainly used as the error voltage. Just think. Further, since ΔV _BE is determined by the current ratio of I ₁ and I ₂ from the equation (2), ΔV _BE
It can be seen that _BE is not affected by temperature changes.

For example, in the present invention, the circuit constants are selected as follows, and the error in folding back V _{BG to} the V _CC side is evaluated as follows. R ₁ = R ₄ = 6.8 kΩ, R
₂ = 2.27 kΩ, R ₃ = 31.05 kΩ, V _BG = 1.
If 24V, I ₁ = 86.8 μA and I ₂ = 8.3 μA, ΔV _BE = 2.36 mV. This error corresponds to about 0.5% of the output voltage value and can be ignored.

Therefore, the constant voltage generator of the present invention is
Since the constant voltage output V _{REF based} on V _CC is obtained from the constant voltage output V _{BG based on} GND, it is strong against disturbances such as noise and EMI.
Further, it is possible to output a stable constant voltage V _{REF based} on V _CC with a small number of elements.

The present invention is not limited to the above embodiment. For example, the current mirror circuit is not necessarily limited to the circuit shown in FIG. 1, and the same purpose can be achieved by using other types of current mirror circuits. Other various modifications can be implemented without departing from the scope of the present invention.

[0022]

As described above, according to the present invention, a GND-based constant voltage output can be converted into a V _{CC -based} constant voltage output with a relatively small number of elements. Further, since the constant voltage generator of the present invention is based on the constant voltage output of the GND standard, it is possible to provide the constant voltage output of the V _CC standard which is strong against disturbances such as noise and EMI.

[Brief description of drawings]

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

FIG. 2 is a block diagram showing a configuration of a conventional constant voltage circuit.

FIG. 3 is a block diagram showing the configuration of another conventional constant voltage circuit.

[Explanation of symbols]

_{Q 1 ~Q 5, Q 10 ...} npn transistor _{R 1 ~R 4, R 10,} R 20 ... output voltage V ₁ of the constant voltage V _REF ... constant voltage circuit of the resistor V _BG ... GND reference, V _2, V ₂₀ ... Voltages I _{1 to} I ₇ , I ₁₀ , I ₂₀ of each part of the constant voltage circuit ... Currents of each part of the constant voltage circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-233084 (JP, A) JP-A-9-265330 (JP, A) JP-A-61-182118 (JP, A) JP-A-5- 241672 (JP, A) JP 64-20708 (JP, A) JP 3-273319 (JP, A) JP 3-123917 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/822 H01L 27/04 H03F 3/343 H05F 3/26 H05F 1/56

Claims (2)

(57) [Claims] 1. A constant voltage circuit for outputting a ground-referenced constant voltage, a first transformer having an emitter grounded and a collector connected to an output terminal of the constant voltage circuit through a first load resistor. /> and Soo motor, the emitter is grounded, the load resistor and the collector of the first
It is connected to the Vcc power supply through a second load resistor having the same resistance value, and the base is the base of the first transistor.
And a second transistor connected to the collector, a collector connected to the Vcc power supply, and a base connected to the second
Connected to the connection point between the load resistance of and the second transistor,
Generates a constant voltage based on the Vcc power source from the emitter
That the third transistor and a constant voltage generator device characterized by comprising a. 2. A constant voltage generator for outputting a ground-referenced constant voltage comprising first to fifth transistors, first to fourth resistors, and an operational amplifier, wherein an emitter is grounded and a base is connected. A first transistor having a collector connected thereto; a first resistor having one terminal connected to the collector of the first transistor and the other terminal connected to the ground-referenced constant-voltage output terminal; A second resistor having one terminal grounded; a second transistor having an emitter connected to the other terminal of the second resistor and a base connected to the base of the first transistor; and one terminal Is connected to the collector of the second transistor, the other terminal is connected to the ground-referenced constant voltage output terminal, and the emitter is grounded, and the base is connected to the second transistor. A third transistor connected to the base; a fourth resistor having one terminal connected to the collector of the third transistor and the other terminal connected to the V _CC power supply terminal; A fourth transistor connected to the other terminal of the third resistor, first and second inputs connected to the collectors of the first and second transistors, respectively, and an output of the fourth transistor. A fifth transistor having an operational amplifier connected to the base, an emitter connected to the collector of the fourth transistor, a base connected to one terminal of a fourth resistor, and a collector connected to the V _CC power supply terminal. By equalizing the resistance values of the first and fourth resistors, the ground-referenced constant voltage output between the ground and the other terminal of the first resistor is set to the V _CC power supply terminal and the first resistor. 5 Constant voltage generator, characterized in that output as a constant voltage output of V _CC reference from between the emitter of the transistor.