JP4623248B2 - IC for series regulator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a series regulator, and more particularly, to a series regulator that can cope with a wide range of ESR values of capacitors connected to an output side.
[0002]
[Prior art]
Currently, there are a wide variety of capacitors connected to the output side of series regulators. On the other hand, it is also known that the ESR value (equivalent series resistance) varies depending on the type of capacitor. For example, although an electrolytic capacitor changes with frequency and temperature, it has an ESR value of about 0.1-100, and a tantalum capacitor has an ESR value of 0.01-1. In addition, ceramic capacitors that have rapidly spread in recent years have ESR values of 0.001 to 0.1.
[0003]
Here, it should be noted that oscillation occurs if the relationship between the phase compensation range of the series regulator and the ESR value of the capacitor connected to the series regulator is not appropriate. In particular, IC-based general series regulators are designed with a phase compensation range targeting an ESR value of several tens of ohms to 0.01 ohms, so they themselves support ceramic capacitors with low ESR values. There are things you can't do.
[0004]
In order to prevent this oscillation, when the ESR value of the capacitor is conventionally within the phase compensation range of the series regulator, the output terminal of the series regulator and the capacitor are directly connected, while the ESR value of the capacitor is the series. When it is not within the phase compensation range of the regulator, a resistor for preventing oscillation was inserted between the output terminal of the series regulator and the capacitor.
[0005]
The conventional method will be described in detail with reference to FIG. 5. For example, when the capacitor C is a ceramic capacitor having a low ESR value, one end of an oscillation preventing resistor R ₅ is connected to the output terminal V _o of the series regulator 20. And the capacitor C is connected to the other end of the resistor R ₅ . In contrast, for example, when the capacitor C is such as tantalum capacitors, without inserting a resistor R ₅ for preventing oscillation, was connected to one end of the capacitor C directly to an output terminal V _o.
[0006]
[Problems to be solved by the invention]
However, as described above, the problem is that the series regulator itself cannot cope with a ceramic capacitor having a low ESR value. For example, in terms of cost, a tantalum capacitor is more than twice as large as a ceramic capacitor. On the other hand, in order to expand the range of the series regulator itself, it is necessary to avoid a complicated circuit configuration and an increase in the element size of the series regulator.
[0007]
In addition, when the conventional method is followed, if the series regulator itself cannot handle it, an external resistor must be connected between the capacitor and the output terminal of the series regulator. This is equivalent to increasing the element size.
[0008]
In view of these circumstances and problems, the present invention provides a series regulator that can cope with a wide variety of capacitor ESR by itself, by making a change with as little influence as possible to the conventional series regulator. For the purpose.
[0009]
[Means for Solving the Problems]
The present invention provides series regulators listed below as specific means for solving the above-described problems.
[0010]
According to the present invention, as the first series regulator, the output terminal (V _o ) connected to the output line and the adjustment resistor (or adjustment wiring: aluminum wiring as the resistance) connected to the output line at one end. (R ₆ ) and an adjustment terminal (V _o ′) connected to the other end of the adjustment resistor (R ₆ ) and operating as an additional output terminal, a series regulator is obtained. It is done.
[0011]
Further, according to the present invention, as the second series regulator, the series regulator is an IC, and the connection between the adjustment resistor (R ₆ ) and the output line is performed inside the IC. The characteristic first series regulator is obtained.
[0012]
Furthermore, according to the present invention, as the third series regulator, the resistance value of the adjustment resistor (R ₆ ) is substantially 1 to 0.1 ohm, Is obtained.
[0013]
Further, according to the present invention, as the fourth series regulator, the third series regulator can be obtained, wherein the adjustment resistor (R ₆ ) is formed by routing a wiring inside the IC. .
[0014]
Furthermore, according to the present invention, as a fifth series regulator, a series regulator as a three-terminal regulator further provided with an input terminal (V _IN ) and a ground terminal (GND),
The IC has a total of four terminals, that is, an input terminal (V _IN ) and a ground terminal (GND) of the series regulator, and an output terminal and (V _o ) and an adjustment terminal (V _o ′). The second series regulator is obtained in a 4-pin package.
[0015]
In the above description, reference numerals in parentheses given when enumerating specific solution means are inserted for convenience in order to facilitate understanding of the means. However, the present invention is not limited to the embodiments described later.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a series regulator according to an embodiment of the present invention will be described with reference to the drawings.
[0017]
The series regulator 10 according to this embodiment, as shown in FIG. 1, the input terminal V _IN, a ground terminal GND, and the deformation of the three-terminal regulator having an output terminal V _o, further comprising an adjustment terminal V _o ' Is. In particular, the illustrated series regulator is a small package (MMP, SOT), and the adjustment terminal V _o ′ is connected to one end of a resistor R ₆ provided inside the IC package as an adjustment resistor. The other end of the resistor R ₆ is connected to an output terminal V _o , more specifically, a lead line (output line) of the output terminal V _o . The resistance value of the adjustment resistor R ₆ is about 0.1 to 1Ω. Such an adjustment resistor R ₆ is formed by, for example, routing an Al wiring or a diffusion resistor inside the IC.
[0018]
When using such a series regulator 10, the user can select either the capacitor C output terminal V _o or the adjustment terminal V _o ′ depending on the ESR value of the capacitor C.
[0019]
More specifically, the series regulator 10 according to the present embodiment includes resistors R _{1 to} R ₄ and R ₆ , a Zener diode D _z , an operational amplifier OP, and first and second transistors Tr ₁ and Tr _2. ing.
[0020]
Among these, the resistor R ₁ and the Zener diode D _z operate as a reference voltage source for supplying a reference voltage to the non-inverting input terminal (+) of the operational amplifier OP. On the other hand, the second and third resistors R ₂ and R ₃ divide the voltage appearing at the output terminal V _o (that is, the output voltage), and change the voltage that changes according to the output voltage to the inverting input terminal ( Operates as a circuit for supplying to-). The operational amplifier OP operates as a comparator, compares the reference voltage supplied to the non-inverting input terminal with the voltage input to the inverting input terminal, and outputs a voltage corresponding to the difference between the output voltage and the reference voltage. Is. The first transistor Tr ₁ and the resistor R ₄ amplify the output of the operational amplifier OP. The second transistor Tr ₂ is a so-called output transistor or control transistor, and is controlled by the collector output of the first transistor Tr ₁ and operates as a variable resistor. In FIG. 1, the output current I _o flows from an external load.
[0021]
FIG. 2 is a graph showing the relationship between the output current _Io and the ESR value, and is for checking the stability of the IC with respect to the output current _Io . When a ceramic capacitor having a low ESR value is used, if the capacitor C is directly connected to the output terminal V _o , the ESR value may enter an unstable region shown in the lower side of FIG. In such a case, as shown in FIG. 3, the capacitor C is connected not to the output terminal V _o but to the adjustment terminal V _o ′ so that the ESR value enters the stable region (the middle stage in FIG. 2). adjust. On the other hand, in the case of a capacitor C whose ESR value belongs to the stable region shown in the middle part of FIG. 2 even when directly connected to the output terminal V _o , such as a tantalum capacitor, the unstable region when connected to the adjustment terminal V _o ′ since there is a fear that enters (FIG. 2 upper), such capacitor C, as shown in FIG. 4, it is connected to the output terminal V _o.
[0022]
As described above, the series regulator 10 according to the present embodiment is a small package such as an MMP or SOT. Here, normally, only 4 pins are provided in a small package, and the conventional 3 terminal series regulator package is provided with a control terminal for turning on / off the series regulator. There is no free space. Therefore, in the series regulator according to the present embodiment, the control terminal is omitted and an adjustment terminal is added. However, if there is no problem in design, the control terminal may be left and an adjustment terminal may be added to form a 5-pin package.
[0023]
The concept of the present invention has been described in detail above with reference to the embodiment, but the concept of the present invention is not limited to this. For example, in the above-described embodiment, the control transistor (second transistor Tr ₂ ) is a pnp transistor, and the amplifying transistor (first transistor Tr ₁ ) is an npn transistor. The circuit design may be changed within the range, and transistors having different polarities may be used. Further, the control transistor may be a Darlington connection of a plurality of transistors. In that case, the amplifying transistor may be further omitted.
[0024]
【The invention's effect】
As described above, according to the present invention, an adjustment resistor is provided inside an IC of a conventional series regulator and is pulled out as an adjustment terminal, so that the series regulator itself can cope with various capacitors. .
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing a schematic configuration of a series regulator according to an embodiment of the present invention.
FIG. 2 is a diagram showing a relationship between an output current of a series regulator and an ESR value.
FIG. 3 is a diagram showing an example of how to use the series regulator according to the embodiment of the present invention.
FIG. 4 is a diagram showing another example of how to use the series regulator according to the embodiment of the present invention.
FIG. 5 is a diagram for explaining a conventional ESR value adjusting method;
[Explanation of symbols]
10 series regulator 20 series regulator

Claims (4)

An input terminal to which power is supplied, an output terminal connected to the output line, an adjustment resistor connected to one end of the output line, and an additional output terminal connected to the other end of the adjustment resistor An adjustment terminal and a ground terminal, which are integrated into an IC, and the connection between the adjustment resistor and the output line is an IC for a series regulator that is performed inside the IC,
A reference voltage source for generating a reference voltage from the power source between the input terminal and the ground terminal;
A voltage dividing circuit that divides an output voltage appearing between the output terminal and the ground terminal and outputs the divided voltage;
An operational amplifier that compares the reference voltage with the divided voltage and outputs a voltage corresponding to a difference between the output voltage and the reference voltage;
Receiving an output from the operational amplifier, an emitter connected to the input terminal, a collector connected to the output terminal, an output transistor,
The series regulator IC, wherein the IC is a 4-pin package in which a total of four terminals including the input terminal, the ground terminal, the output terminal, and the adjustment terminal are drawn out . 2. The series regulator IC according to claim 1, wherein a resistance value of the adjusting resistor is substantially about 1 to 0.1 ohm. 3. The series regulator IC according to claim 2 , wherein the adjustment resistor is a resistance formed by routing a wiring inside the IC . 3. The series regulator IC according to claim 2 , wherein the adjusting resistor is formed by a diffused resistor inside the IC .

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