JPH067375Y2 - Output voltage temperature compensated stabilized DC power supply - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a stabilized DC power supply which converts an unstable DC voltage into a required stable DC voltage and supplies the same to devices and circuits.

[Conventional technology]

Conventionally, in this type of stabilized DC power supply, as shown in FIG. 4, the reference voltage E is usually made by a Zener diode D1 (V1 is an input voltage, R5 is a Zener diode current setting resistor), It is input to the non-inverting input terminal, and the output voltage V ₀ is divided by resistors R1 and R2, and then the operational amplifier I
It is input to the inverting input terminal of C, and after the voltage is amplified by the operational amplifier IC, it is input to the base of the transistor Q and the negative feedback is applied to stabilize the output voltage V ₀ .

[Problems to be solved by the invention]

In the conventional stabilized DC power supply described above, when the voltage across the Zener diode D1 fluctuates due to temperature fluctuation, the output V ₀ fluctuates by (R1 + R2) / R1 times, and in a normal circuit, it is about twice or more. Therefore, there is a drawback that the output voltage V ₀ cannot be highly stabilized.

An object of the present invention is to provide a stabilized DC power supply that uses a Zener diode to compensate for temperature fluctuations of a reference voltage and highly stabilizes an output voltage.

[Means for solving problems]

The stabilized DC power supply of the present invention has an input terminal, an output terminal,
An operational amplifier, an anode is connected to ground, a cathode is connected to a non-inverting input terminal of the operational amplifier, and a Zener diode for reference voltage is connected between the input terminal and the cathode of the Zener diode for reference voltage. A current setting resistor, a transistor whose collector, emitter, and base are connected to the input terminal, the output terminal, and the output terminal of the operational amplifier, and a first feedback voltage dividing resistor whose one end is connected to the output terminal; Second feedback voltage dividing resistor whose one end is connected to the other end of the feed voltage dividing resistor, and output voltage compensation in which the cathode is connected to the other end of the second feedback voltage dividing resistor and the anode is connected to the ground. Zener diode connected in series between the connection point of the first and second feedback voltage dividing resistors and ground Is, connection points has a third, and a fourth feedback voltage dividing resistor connected to the inverting input terminal of the operational amplifier.

〔Example〕

Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram of an embodiment of the stabilized DC current of the present invention. In FIG. 1, the same symbols as in FIG. 4 indicate the same things.

This embodiment is different from the conventional circuit of FIG. 4 in that an output voltage compensating Zener diode D2 is provided between the feedback voltage dividing resistor R2 and the ground, and the connection point of the feedback voltage dividing resistors R1 and R2 is connected to the ground. Connected in series between
The connection point is provided with feedback voltage dividing resistors R3 and R4 connected to the inverting input terminal of the operational amplifier IC.

2 is a block diagram of the embodiment shown in FIG. 1, and FIG.
The figure is a graph of the Zener voltage temperature variation ΔV _z with respect to the Zener current I _z of a general Zener diode.

When the voltage across the Zener diode D2 is V, the base-emitter voltage V _{BE of} the transistor Q, and the gain of the operational amplifier IC are A, the output voltage V ₀ is expressed by the following equation (1).

Since the gain A is extremely large (usually about 10,000 times), the equation (1) is as shown in the following equation (2).

Therefore, when the reference voltage E is .DELTA.e, the voltage V across changes Delta] v, the variation [Delta] V ₀ of the output voltage V ₀ is as shown in the following equation (3).

Here, Δe is set to the operating point where ΔV _z becomes the minimum in FIG. Next, if the resistors R1 and R2 are adjusted so that the value of (R2 / R1) is not changed and Δv is set to the optimum value, Δv ₀ can be made zero.

Strictly speaking, in FIG. 2, the coefficients applied to the voltages V ₀ and V are kR ₂ and kR ₁ , respectively.

_{k = (R 3 + R 4} ) / R 1 R 2 + (R 1 + R 2) (R 3 + R 4).

However, when actually configuring the circuit, the resistors R ₁ and R ₂ are for setting the operation of the diode D ₂ , and the resistors R ₃ and R ₄ are for adjusting the output voltage. You need to keep it. Thus resistors R _3, R ₄ the resistance R _1, so as not to affect the diode operating current value by R _2, must be set to a sufficiently large value for resistor R _1, R _2, Under such conditions, the coefficients applied to the voltages V ₀ and V may be R ₂ / (R ₁ + R ₂ ), R ₁ / (R ₁ + R ₂ ).

After all, by adding the Zener diode D2 and setting the operating point of the Zener diode D2 to the optimum value, the fluctuation of the output voltage V ₀ due to the temperature fluctuation Δe of the reference voltage E can be eliminated.

[Effect of device]

As described above, the present invention eliminates the fluctuation of the output voltage with respect to the temperature fluctuation of the reference voltage by inserting the Zener diode at the feedback side of the stabilized DC power supply, the resistance dividing point, and the return side. This has the effect of being able to supply a stabilized output voltage to devices and circuits.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment of the stabilized DC power supply of the present invention,
FIG. 2 is a block diagram of the circuit of FIG. 1, FIG. 3 is a graph of a Zener current of a general Zener diode vs. temperature change of Zener voltage, and FIG. 4 is a circuit diagram of a conventional example. R1 to R4 …… Resistor for feedback voltage division, R5 …… Zener diode D1 current setting resistance, D1 …… Reference voltage Zener diode, D2 …… Output voltage compensation Zener diode, IC …… Operational amplifier, Q… ... dropper transistor from the input voltage to the output voltage, E ...... reference voltage, V ...... voltage across the zener diode D2, V ₀ ...... output voltage, the base-emitter voltage of V _BE ...... transistor Q, a ... … Gain of operational amplifier IC, I _z …… Zener current, ΔV _z …… Zener voltage change with temperature.

Claims (1)

[Scope of utility model registration request] 1. An input terminal, an output terminal, an operational amplifier,
Zener diode for reference voltage whose anode is connected to ground and whose cathode is connected to the non-inverting input terminal of the operational amplifier, and Zener diode current setting resistor connected between the input terminal and the cathode of the Zener diode for reference voltage. , A transistor whose collector, emitter, and base are connected to the input terminal, the output terminal, and the output terminal of the operational amplifier, a first feedback voltage dividing resistor whose one end is connected to the output terminal, and a first feed voltage. A second feedback voltage dividing resistor having one end connected to the other end of the dividing resistor, and an output voltage compensating zener diode having a cathode connected to the ground at the other end of the second feedback voltage dividing resistor. Is connected in series between the connection point of the first and second feedback voltage dividing resistors and ground, and the connection point Third, the output voltage temperature compensation stabilized DC power source and a fourth feedback voltage dividing resistor connected to the inverting input terminal of the operational amplifier.