JPH11312021A - Regulator circuit and method for adjusting output voltage of the same circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an accurate output voltage by adjusting a resistance value by using zapping. SOLUTION: This regulator circuit is provided with a current supplying means 1, output terminal 2 connected with the current supplying means for generating a constant voltage, first and second resistances 3 and 4 to which currents from the current supplying means are supplied, control transistor 5 for adjusting the voltage of the output terminal 2 according to the voltage of the connection middle point A of the first and second resistances, first resistance value adjusting means 6 in which a third resistance 7 and a first Zener diode 8 are serially connected which is connected with the first resistance 3 in parallel, and second resistance value adjusting means 9 in which a fourth resistance 10 and a second Zener diode 11 are serially connected which is connected with the second resistance 4 in parallel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a regulator circuit for generating a constant DC voltage and a method for adjusting the output voltage thereof, and more particularly to a regulator circuit using zapping and a method for adjusting the output voltage thereof.

[0002]

2. Description of the Related Art A regulator circuit for generating a constant DC voltage is known. There are various types of regulator circuits.

For example, a method of using two series-connected resistors and setting the output voltage by the voltage at the midpoint of the connection can be considered.

There is also a type in which a comparator compares a level between a reference voltage and an output voltage and adjusts the output voltage according to the difference.

[0005]

However, in each of the conventional devices, the accuracy of the output voltage is at most about ± 3%. It has been difficult to reduce the output voltage accuracy to ± 3% or less due to variations in the current amplification factor and resistance value of the transistor inside the IC.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and comprises a current supply means, an output terminal connected to the current supply means for generating a constant voltage, and First and second resistors to which a current is supplied from a supply means, a control transistor for adjusting the voltage at the output terminal according to the voltage at the connection midpoint between the first and second resistors, a third resistor and a third resistor. A first resistance value adjusting means connected in series with one Zener diode, and a fourth resistance and a second Zener diode connected in series with the first resistance; And a second resistance value adjusting means connected in parallel.

The present invention also provides a current supply means, an output terminal connected to the current supply means for generating a constant voltage, first and second resistors supplied with current from the current supply means,
A control transistor for adjusting the voltage of the output terminal according to the voltage at the midpoint of connection of the first and second resistors, a third resistor and a first Zener diode are connected in series, and are connected in parallel to the first resistor. A first resistance value adjusting means connected to the second resistor, a fourth resistor and a second zener diode connected in series,
A second resistance adjusting means connected in parallel with the resistor, wherein when the voltage of the output terminal fluctuates, the first
Alternatively, the voltage of the output terminal is adjusted by destroying the Zener diode of the second resistance value adjusting means.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A regulator circuit according to the present invention and a method for adjusting an output voltage thereof will be described with reference to FIG. 1 is a current source (may be a resistor) that operates as current supply means,
2 is an output terminal connected to the current source 1 for generating a constant voltage;
Reference numerals 3 and 4 denote first and second resistors to which the current from the current source 1 is supplied. Reference numeral 5 denotes a control transistor for adjusting the voltage of the output terminal 2 in accordance with the voltage at the connection point A. Reference numeral 6 denotes a third resistor 7. And a first Zener diode 8 connected in series, a first resistance value adjusting means 9 connected in parallel to the first resistor 3, a fourth resistor 10 and a second Zener diode 11 connected in series, The second resistance adjusting means is connected in parallel with the second resistance.

The voltage of the output terminal 2 is, for example, about 3.5 V.

This voltage is determined according to the resistance ratio of the first and second resistors. For example, when the resistance value of the second resistor 4 decreases, the voltage at the point A decreases. When the voltage at the point A decreases, the emitter voltage of the transistor 12 decreases, and the voltage at the point B decreases.

When the voltage at the point B decreases, the collector current of the control transistor 5 decreases. When the collector current of the control transistor 5 decreases, the voltage at the output terminal 2 increases.

Conversely, when the resistance value of the first resistor 3 decreases, the voltage at the point A increases. When the voltage at point A increases,
The emitter voltage of the transistor 12 increases, and the voltage at the point B increases.

When the voltage at the point B increases, the collector current of the control transistor 5 increases. When the collector current of the control transistor 5 increases, the voltage of the output terminal 2 decreases, so that the voltage of the output terminal 2 is determined according to the resistance ratio between the first and second resistors 3 and 4.

Now, the value of the load 13 becomes smaller and the output terminal 2
Is lowered from 3.5V. Then, the voltage at the point A also decreases. When the voltage at the point A decreases, the collector current of the control transistor 5 decreases as in the above-described operation. When the collector current of the control transistor 5 decreases, the voltage at the output terminal 2 increases.

Therefore, the voltage of the output terminal 2 is going to return to 3.5V.

Conversely, it is assumed that the value of the load 13 increases and the voltage of the output terminal 2 increases from 3.5V. Then, the voltage at point A also increases. When the voltage at the point A increases, the collector current of the control transistor 5 increases similarly to the above operation. When the collector current of the control transistor 5 increases, the voltage at the output terminal 2 decreases.

Therefore, the voltage of the output terminal 2 tries to return to 3.5V.

As described above, according to the circuit of FIG. 1, a constant voltage can be obtained from the output terminal 2.

In the present invention, a more accurate constant voltage is obtained from the output terminal 2. Therefore, in the present invention, the first
A first resistance value adjusting means 6 connected in parallel with the resistor 3 and a second resistance value adjusting means 9 connected in parallel with the second resistor 4 are provided.

This resistance value adjusting means is used after it is confirmed that a desired voltage is not generated from the output terminal 2.

The first Zener diode 8 of the first resistance adjusting means 6 can be destroyed from outside the IC by zapping technique. Although the circuit of FIG.
Reference numerals 4, 15, and 16 are pad terminals of the IC. Various signals for the purpose of inspection, measurement, and adjustment can be applied to the pad terminals before molding in the IC manufacturing process. As the signal, a pulse of the reverse polarity which destroys the Zener diode by the zapping technique is applied.

For example, when a high-level pulse is applied to the terminal 14 and a low-level pulse is applied to the terminal 15 between the terminals 14 and 15, the first Zener diode 8 is destroyed. When the first Zener diode 8 is destroyed,
Since the impedance becomes almost zero, the first resistor 3
, A third resistor 7 is connected in parallel, and its combined impedance is reduced. When the combined impedance decreases, the voltage at the point A increases, and the voltage at the output terminal 2 can be reduced.

On the contrary, when the second Zener diode 11 is destroyed, the fourth resistor 10 is connected in parallel to the second resistor 4, and the combined impedance is reduced. When the combined impedance decreases, the voltage at the point A decreases, and the voltage at the output terminal 2 can increase.

In the embodiment of FIG. 1, the first Zener diode 8 and the second Zener diode 11 are described.
A plurality of Zener diodes may be connected in parallel as shown in FIG. In this way, the selectable resistance value can be increased by that amount.

[0025]

According to the present invention, the first resistance value adjusting means is provided in parallel with the first resistance of the first and second resistances for determining the output voltage of the regulator circuit, and the first resistance value adjusting means is provided for the second resistance. Since the second resistance value adjusting means is provided and the resistance value is adjusted by zapping, a very accurate voltage can be obtained as the output voltage.

[Brief description of the drawings]

FIG. 1 is a regulator circuit of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Current source 2 Output terminal 3 1st resistance 4 2nd resistance 5 Control transistor 6 1st resistance value adjustment means 9 2nd resistance value adjustment means

Claims (2)

[Claims] An output terminal connected to the current supply means for generating a constant voltage; first and second resistors to which a current is supplied from the current supply means; A control transistor for adjusting the voltage of the output terminal according to the voltage at the midpoint of connection of the two resistors, a third resistor and a first Zener diode connected in series, and a first transistor connected in parallel to the first resistor A regulator circuit comprising: a resistance value adjusting means; and a second resistance value adjusting means in which a fourth resistor and a second Zener diode are connected in series and connected in parallel with the second resistor. 2. A current supply means, an output terminal connected to the current supply means for generating a constant voltage, first and second resistors supplied with current from the current supply means, and the first and second resistors. A control transistor for adjusting the voltage of the output terminal according to the voltage at the midpoint of connection of the two resistors, a third resistor and a first Zener diode connected in series, and a first transistor connected in parallel to the first resistor And a second resistance adjusting means in which a fourth resistor and a second Zener diode are connected in series and connected in parallel to the second resistor. The method of adjusting the output voltage of the regulator circuit, wherein, if any, the voltage of the output terminal is adjusted by destroying the Zener diode of the first or second resistance adjusting means.