JP2005301439A - Voltage regulator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent overshoot in output voltage, even if input voltage is changed with a comparatively small circuit scale without the need of an output transistor section or a change circuit which become a large circuit scale. <P>SOLUTION: A differential amplification circuit 31 compares the inputted feedback voltage with reference voltage. As a result of comparison of the divided and feedback voltage with the reference voltage from a reference voltage circuit 11, when the feedback voltage is lower than the reference voltage, differential amplification circuit 31 is high and the transistor M20 is off. When the overshoot of the output voltage is carried out, and the feedback voltage becomes higher than the reference voltage, the output of the differential amplification circuit 31 is low and the transistor M20 turns on. As the result, an output driver transistor M10 is turned off and overshoot becoming larger can be prevented. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a voltage regulator that is configured as, for example, an IC (Integrated Circuit) or the like and stably supplies a voltage.

A conventional voltage regulator circuit is shown in FIG.
The reference voltage is input to the inverting input terminal of the differential amplifier circuit 21, the output of the differential amplifier circuit 21 is input to the gate of the output driver transistor M10, the drain of the output driver transistor M10 is the resistor R1 at the output terminal VOUT of the voltage regulator. The feedback voltage divided by the voltage dividing circuit composed of R2 is input to the non-inverting input terminal of the differential amplifier circuit 21.

In the voltage regulator disclosed in Patent Document 1, the output transistor section controlled by the output of the error amplifier circuit includes two or more transistors having different switchable driving capabilities, and these transistors are selectively used by using a switching circuit. Therefore, an attempt is made to reduce the overshoot generated in the output terminal voltage.
JP 2001-282371 A

However, in the voltage regulator of 5V output having the configuration shown in FIG. 10 described above, when the input voltage VIN changes suddenly from 0V to 16V as shown in FIG. 2, the output voltage VOUT rises as shown in FIG. Overshooted to about 5.7V.
Further, when the input voltage fluctuates from 2V to 12V as shown in FIG. 5, the output voltage has overshooted to about 5.5V at the time of rising as shown in FIG.

Generally, microcomputers used in portable devices, home appliances, in-vehicle devices, etc. operate with 5V input, and the absolute maximum rating value is 5V ± 10%. For this reason, if the voltage regulator has an overshoot as shown in FIG. 3, the microcomputer connected to the output terminal of the voltage regulator may be destroyed.
Also, in the state where mobile devices, home appliances, in-vehicle devices, etc. are actually used, there are various fluctuations in the input voltage, not limited to 0V → 16V shown in FIG. 2, and overshooting can be prevented in that case as well. Was desired.

  Further, the above-mentioned Patent Document 1 requires a large circuit as the above-described output transistor unit, and also requires a large circuit as a switching circuit for switching a plurality of transistors.

  The present invention has been made in view of such a situation, and does not require an output transistor section or a switching circuit having a large circuit scale, and is a case where the input voltage fluctuates while having a relatively small circuit scale. Another object of the present invention is to provide a voltage regulator that can prevent overshoot in the output voltage.

  In order to achieve this object, a voltage regulator according to the present invention includes a reference voltage supply unit, a feedback obtained by dividing an output voltage as a voltage regulator, and a first differential amplification unit that receives an input of the reference voltage supply unit. A voltage regulator comprising a driver transistor unit having an output from the first differential amplifying unit connected to a gate, the same feedback and reference voltage supply as the first differential amplifying unit described above A second differential amplifying unit that receives the input of the first part, and a transistor unit having an output from the second differential amplifying unit connected to the gate and a drain connected to the gate of the driver transistor unit It is characterized by.

It is preferable that the above-described second differential amplifier has an offset.
It is preferable that the above-described offset can be adjusted by laser trimming.

  The driver transistor section is composed of a P-channel transistor. In the first differential amplifier section, the reference voltage supply section is connected to the inverting input terminal and the feedback is connected to the non-inverting input terminal. In the second differential amplification unit, it is preferable that a feedback is connected to the inverting input terminal and a reference voltage supply unit is connected to the non-inverting input terminal.

  In addition, the driver transistor unit described above includes an N-channel transistor, and in the first differential amplifier unit described above, a feedback is connected to the inverting input terminal and a reference voltage supply unit is connected to the non-inverting input terminal. In the second differential amplification unit, the reference voltage supply unit may be connected to the inverting input terminal and the feedback may be connected to the non-inverting input terminal.

  As described above, according to the present invention, there is no need for an output transistor section or a switching circuit having a large circuit scale, and even when the input voltage fluctuates while the circuit scale is relatively small, Overshoot can be prevented.

  Next, an embodiment in which the voltage regulator according to the present invention is applied to a voltage regulator using a Pch (P channel) transistor as an output driver will be described in detail with reference to the drawings.

  As shown in FIG. 1, the voltage regulator according to this embodiment includes a reference voltage circuit (reference voltage supply unit) 11 connected to an input voltage VIN, and a differential amplifier circuit 21 (to which the reference voltage circuit 11 is connected). A first differential amplifier section), a differential amplifier circuit 31 (second differential amplifier section), a driver transistor M10 whose output from the differential amplifier circuit 21 is connected to the gate, and a differential amplifier circuit 31. Is configured as a circuit including a transistor M20 whose output is connected to the gate, and resistors R1 and R2 that divide the output from the driver transistor M10.

  That is, the voltage regulator according to this embodiment is configured by adding the differential amplifier circuit 31 and the gate voltage control transistor M20 of the output driver transistor M10 to the conventional voltage regulator shown in FIG.

  In the differential amplifier circuit 21, a feedback obtained by dividing the output voltage as a voltage regulator by resistors R1 and R2 is connected to a non-inverting input terminal, and a reference voltage circuit 11 is connected to an inverting input terminal. The output is connected to the gate of the driver transistor M10.

In the differential amplifier circuit 31, the same feedback as that input to the differential amplifier circuit 21 is connected to the inverting input terminal, and the reference voltage circuit 11 is connected to the non-inverting input terminal. The output is connected to the gate of the transistor M20.
The drain of the transistor M20 is connected to the gate of the driver transistor M10.

The differential amplifier circuit 31 compares the input feedback voltage with a reference voltage.
As a result of comparing the divided and fed back voltage with the reference voltage from the reference voltage circuit 11, when the feedback voltage is lower than the reference voltage, the differential amplifier circuit 31 is HIGH and the transistor M20 is OFF.
When the output voltage overshoots and the feedback voltage becomes higher than the reference voltage, the output of the differential amplifier circuit 31 is LOW and the transistor M20 is turned on. As a result, the output driver transistor M10 is turned off, and further overshoot can be prevented from increasing.

When the differential amplifier circuit 31 has an offset, the balance between the feedback voltage and the reference voltage when the output of the differential amplifier circuit 31 becomes LOW can be controlled.
Even if there is no offset, it can operate normally and the output voltage can be made constant.

  FIG. 4 shows the fluctuation of the output voltage when the input voltage changes as shown in FIG. 2 with respect to the voltage regulator of this embodiment. The overshoot is clearly smaller than the fluctuation of the output voltage shown in FIG. 3 by the above-described conventional voltage regulator.

FIG. 5 shows an example of an input waveform when the input voltage is changed from 2 V to 12 V, and FIG. 7 shows a rising waveform of the output voltage by the voltage regulator of this embodiment when the input is made.
Also in this case, in the voltage regulator as the present embodiment, the overshoot is obviously improved to be smaller than the rising waveform of the output voltage shown in FIG. 6 by the above-described conventional voltage regulator.

  Next, means for giving an offset to the differential amplifier circuit 31 will be described with reference to an example shown in FIG. FIG. 8 shows a general differential amplifier circuit. By making the size ratio of the transistors M41 and M42 not 1: 1, the differential amplifier circuit can be offset. Also, the differential amplifier circuit can be offset by making the size ratio of the transistors M51 and M52 not 1: 1.

Further, by preparing a plurality of transistors as input transistors in advance as the transistors M51 and M52 and selecting them by laser trimming in a later process, an optimum offset can be set for each IC.
This offset adjustment by laser trimming can also be performed by preparing a plurality of transistors as input transistors as the transistors M41 and M42 and selecting them by laser trimming in a later step.

  As described above, according to the voltage regulator of this embodiment, the differential amplifier circuit for monitoring the output voltage overshoot is provided, and the output driver transistor of the voltage regulator is installed at the moment when the output voltage overshoot is detected. Since it can be turned off, the overshoot in the output voltage can be kept small.

In addition, since the differential amplifier circuit for monitoring the overshoot of the output voltage has an offset, the amount of overshoot to be detected can be controlled and adjusted according to the specifications and characteristics of the voltage regulator. it can.
Furthermore, an optimum offset can be set for each IC by performing laser trimming in a later process.

In the above, one embodiment in which the voltage regulator according to the present invention is applied to a voltage regulator using a Pch (P channel) transistor as an output driver has been described. However, the type of transistor is not limited to this, for example, The present invention can be similarly applied even when an Nch (N-channel) transistor is used for the output driver.
In this case, the circuit configuration is illustrated in FIG. 9, but the functions of the respective units and the operations for obtaining the effects according to the present invention are the same as those in the above-described embodiment.

The above-described embodiment is a preferred embodiment of the present invention, and various modifications can be made without departing from the spirit of the present invention.
For example, the present invention can be similarly applied to an output voltage limiting circuit of a high withstand voltage voltage regulator and an output voltage limiting circuit of a large current voltage regulator.

It is a circuit diagram showing an example of a voltage regulator as an embodiment of the present invention. It is a wave form diagram which shows the example of the input voltage which changes rapidly. It is a wave form diagram which shows the example of an output voltage in the conventional voltage regulator with respect to the input voltage shown in FIG. It is a wave form diagram which shows the output voltage example in the voltage regulator of this embodiment with respect to the input voltage shown in FIG. It is a wave form diagram which shows the example of an input voltage at the time of making it fluctuate from 2V to 12V. FIG. 6 is a waveform diagram showing an output voltage example in a conventional voltage regulator with respect to the input voltage shown in FIG. 5. FIG. 6 is a waveform diagram showing an output voltage example in the voltage regulator of the present embodiment with respect to the input voltage shown in FIG. It is a circuit diagram which shows the example of the differential amplifier circuit which gave the offset. It is a circuit diagram which shows one Example at the time of using an Nch transistor. It is a circuit diagram which shows an example of the conventional voltage regulator.

Explanation of symbols

11, 12 Reference voltage circuit (reference voltage supply unit)
21, 22 Differential amplifier circuit (first differential amplifier)
31, 32 differential amplifier circuit (second differential amplifier)
M10, M12 Driver transistor M20, M22 Transistor

Claims (5)

A reference voltage supply unit; a first differential amplification unit that receives an input of the reference voltage supply unit and a feedback obtained by dividing an output voltage as a voltage regulator; and an output from the first differential amplification unit to a gate A voltage regulator composed of a circuit having a driver transistor section connected thereto,
A second differential amplifier that receives the same feedback as the first differential amplifier and an input of the reference voltage supply unit;
A voltage regulator comprising: a transistor unit having an output from the second differential amplifier unit connected to a gate and a drain connected to a gate of the driver transistor unit.   The voltage regulator according to claim 1, wherein the second differential amplifier has an offset.   The voltage regulator according to claim 2, wherein the offset can be adjusted by laser trimming. The driver transistor unit is a P-channel transistor,
In the first differential amplification unit, the reference voltage supply unit is connected to an inverting input terminal and the feedback is connected to a non-inverting input terminal,
4. The second differential amplifier unit according to claim 1, wherein the feedback is connected to an inverting input terminal and the reference voltage supply unit is connected to a non-inverting input terminal. Voltage regulator described in 1. The driver transistor unit is an N-channel transistor,
In the first differential amplification unit, the feedback is connected to an inverting input terminal and the reference voltage supply unit is connected to a non-inverting input terminal,
4. The second differential amplifier unit according to claim 1, wherein the reference voltage supply unit is connected to an inverting input terminal and the feedback is connected to a non-inverting input terminal. Voltage regulator described in 1.

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