JP2008217203A - Regulator circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a regulator circuit which normally operates even at high temperature while suppressing power consumption in order to solve the problem that output voltage cannot be stabilized due to increase of leak current of an output stage transistor at high temperature in the regulator circuit. <P>SOLUTION: In this regulator circuit 20, a resister series connection body comprising resistors R<SB>1</SB>, R<SB>2</SB>and a bypass transistor Tr<SB>2</SB>are connected in parallel between a ground potential and a drain of the output stage transistor Tr<SB>1</SB>whose gate potential is controlled by an operational amplifier 22. The Tr<SB>2</SB>and the Tr<SB>1</SB>have a same kind, size, structure, production process or the like, and is configured such that OFF leak current having the same temperature dependence and the same magnitude flows. By bypassing the leak current of the Tr<SB>1</SB>by the Tr<SB>2</SB>, current flowing through the R<SB>1</SB>, the R<SB>2</SB>is kept constant even at high temperature, and the regulator circuit 20 maintaining output voltage V<SB>OUT</SB>to a setting value is normally controlled. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a regulator circuit that converts an input voltage into a predetermined output voltage, and more particularly to stabilization of operation at a high temperature.

The regulator circuit can basically output a constant voltage regardless of fluctuations in the input voltage and fluctuations in the output load current, and has been widely used in electronic circuits. FIG. 2 is a circuit diagram of a conventional regulator circuit. This regulator circuit includes an output stage transistor 2, resistors R ₁ and R ₂ , an operational amplifier 4, and a reference voltage circuit 6. In the output stage transistor 2, the input voltage _VIN is applied to the source, and the output voltage of the operational amplifier 4 is applied to the gate. The resistors R ₁ and R ₂ are connected in series between the drain of the output stage transistor 2 and the ground potential GND. The inverting input terminal of the operational amplifier 4 is applied with the reference voltage V _REF from the reference voltage circuit 6, and the non-inverting input terminal is connected to the connection point N _R between R ₁ and R ₂ . The connection point between the drain of the output stage transistor 2 and the resistor R ₁ becomes the output terminal N _{OUT of the} regulator circuit, from which the output voltage _{VOUT of the} regulator circuit is taken out.

In this configuration, the potential at the connection point N _R is basically set to V _REF due to a virtual short circuit between the two input terminals of the operational amplifier 4. Thus, the value of the current I _R flowing through R _1, R ₂ is basically given by the following equation. Normally order to reduce power consumption, the R ₂ as a high resistance, I _R is set to a small value.
I _R = V _REF / R ₂ (1)

In a state where the output terminal N _OUT no load, the source of the output stage transistor 2 - drain current I _D is controlled so as to match the I _R expressed by equation (1). At this time, the output stage transistor 2 is basically in an off state, and a leak current (off leak current) I _LEAK that flows in an off state between the source and drain occupies a part of _ID .

The open loop gain of the operational amplifier 4 is A,
β = R ₂ / (R ₁ + R ₂ ) (2)
Then,
V _OUT = V _REF · A / {β (1 + A)} (3)
And when A is sufficiently larger than 1, V _OUT is
V _OUT = V _REF / β (3 ')
Given in.
JP 2006-330869 A

At higher temperatures, increased off leak current _{I LEAK} of the output stage transistor 2 becomes larger than the value represented by _{I R} is (1), no longer function feedback control through an operational amplifier _{4, V OUT} is according to _{V REF} The value set by the Leakage current increases exponentially with increasing temperature, and _VOUT can rise to _VIN as the temperature increases. Thus, there is a problem that the regulator circuit does not operate normally at high temperatures. Also, the leakage current increases with the size of the transistor. Therefore, for example, in a regulator circuit in which the size of the output stage transistor is increased to increase the load current supply capability, the above problem can be significant. Here, there is a limit in increasing power consumption in order to solve the above problem by setting _IR large.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a regulator circuit capable of operating normally even at high temperatures while suppressing power consumption.

  The regulator circuit according to the present invention includes an output transistor having an input voltage applied to a source, a first resistor and a second resistor connected in series between a drain of the output transistor and a ground potential, and a first difference. The reference voltage is applied to the dynamic input terminal, the potential at the connection point between the first resistor and the second resistor is applied to the second differential input terminal, and the gate of the output transistor is connected to the output terminal. An operational amplifier and a bypass transistor diode-connected between the drain and the ground potential in parallel with the first resistor and the second resistor, and an output voltage corresponding to the reference voltage Is output from a connection point between the drain and the first resistor, and the bypass transistor has an off-leakage current having a magnitude corresponding to an off-leakage current of the output transistor. It is be one.

According to the present invention, an off-leakage current flows through the output transistor whose drain is connected to the output terminal of the regulator circuit and the bypass transistor connected to the output terminal. For example, when the temperature rises, the off-leakage current of the output transistor generally increases, but at this time, the off-leakage current of the bypass transistor also increases. The off-leakage currents of both transistors are opposite to each other when viewed from the output terminal of the regulator circuit. That is, at least a portion of the off-leak current of the output transistor, it is possible to offset the off-leakage current of the bypass transistor, the I _R the current flowing through the first resistor and the second resistor is represented by (1) It can suppress exceeding. As a result, an increase in the output voltage _VOUT of the regulator circuit can be avoided, and the regulator circuit can operate normally even at high temperatures. This effect is particularly preferably realized when the temperature dependence of the off-leakage current of both transistors is made equal. Furthermore, minute off-leakage current is canceled out, can be the set value I _R of the current flowing through the first resistor and the second resistor to decrease, power consumption can be reduced.

  Hereinafter, embodiments of the present invention (hereinafter referred to as embodiments) will be described with reference to the drawings.

FIG. 1 is a schematic circuit diagram of a regulator circuit according to an embodiment. The regulator circuit 20 is an integrated circuit (IC) formed on one semiconductor chip, and includes an output stage transistor Tr ₁ , resistors R ₁ and R ₂ , an operational amplifier 22, a bypass transistor Tr ₂ , and a reference voltage circuit 24. Consists of.

Output stage transistor Tr ₁ has a source connected to the input terminal _{N IN} of the regulator circuit 20 is applied an input voltage _{V IN} from the terminal _{N IN.} The drain of Tr ₁ is connected to one end of R ₁ , and this connection point becomes the output terminal N _OUT of the regulator circuit 20. The gate of Tr ₁ is connected to the output terminal of the operational amplifier 22 and its output voltage is applied. Tr ₁ supplies current to the load connected to N _OUT . For example, in the present circuit 20, Tr ₁ is composed of a P-channel MOS transistor (pMOS).

The resistors R ₁ and R ₂ are connected in series between the drain of Tr ₁ and the ground potential GND.

The operational amplifier 22 has an inverting input terminal connected to the output terminal of the reference voltage circuit 24, and the reference voltage V _REF is applied from the reference voltage circuit 24. On the other hand, the non-inverting input terminal of the operational amplifier 22 is connected to a connection point N _R between R ₁ and R ₂ . The output terminal of the operational amplifier 22 is connected to the gate of Tr ₁ as already described.

The reference voltage circuit 24 operates based on, for example, _VIN and GND, generates a temperature-compensated reference voltage V _REF , and applies it to the inverting input terminal of the operational amplifier 22.

In this configuration, the operational amplifier 22 detects and compares V _REF and the output voltage _VOUT divided by R ₁ and R ₂ to control the output voltage _VOUT . Incidentally, V _OUT is given by the above equation (3) or (3 ′).

The bypass transistor Tr ₂ is diode-connected to N _OUT in parallel with a series connection of resistors composed of R ₁ and R ₂ . Specifically, the source and gate of Tr ₂ are connected to N _OUT and the drain is connected to GND.

Tr ₂ is configured such that the off-leakage current I _LRAK2 has the same magnitude as the off-leakage current I _LEAK1 of Tr ₁ . Furthermore, the magnitude of the off-leakage current of both transistors is configured to be the same regardless of the temperature. That is, both transistors are configured so that the temperature dependence of off-leakage current is the same. This can be realized, for example, by configuring Tr ₁ and Tr ₂ as a common transistor with respect to type, size, structure, manufacturing process, and the like. For example, in this circuit 20, Tr ₂ is also composed of pMOS, corresponding to the fact that Tr ₁ is composed of pMOS.

The present regulator circuit 20 and is connected in series with the bypass transistor Tr ₂ to the output stage transistor Tr _1, the off-leakage current _{I leak1} flowing through the Tr ₁ to the output terminal _{N OUT} in a state where a load is not connected, Tr ₂ can be bypassed. That, _{I LEAK} of Tr _{1 flows} into the _{N IN} to _{N OUT,} the amount of Tr ₂ of _{I LEAK2} corresponding thereto flows out to the GND from _{N OUT.} Thus, the source of Tr ₁ due to an increase in _{I leak1} due to temperature rise - increment of drain current _{I D is} offset by an increase in _{I LEAK2,} resistors _R 1, current flowing in _{R 2 I R} is (1 ) Can be maintained. That is, the regulator circuit 20 is normally controlled by the operational amplifier 22 even at a high temperature, and can keep the _VOUT favorably at the set value represented by the equation (3) or (3 ′).

Note that I _LEAK1 of the source-drain current I _D of Tr ₁ is bypassed by Tr ₂ regardless of the temperature. That is, in the configuration in which no bypass due Tr _2, I _R is had to be set to a value which gave a degree margin to allow absorption of I _leak1 at room temperature or the like, in this configuration, I _R may not absorb _{I leak1,} correspondingly, it is possible to set small _{I R.}

1 is a schematic circuit diagram of a regulator circuit according to an embodiment of the present invention. It is a circuit diagram of the conventional regulator circuit.

Explanation of symbols

20 regulator circuit, 22 operational amplifier, 24 reference voltage circuit, R ₁ , R ₂ resistance, Tr ₁ output stage transistor, Tr ₂ bypass transistor.

Claims (2)

An output transistor with an input voltage applied to the source;
A first resistor and a second resistor connected in series between the drain of the output transistor and a ground potential;
A reference voltage is applied to the first differential input terminal, a potential at a connection point between the first resistor and the second resistor is applied to the second differential input terminal, and the gate of the output transistor is connected to the output terminal. A connected operational amplifier;
A bypass transistor diode-connected between the drain and the ground potential in parallel with the first resistor and the second resistor;
A regulator circuit that outputs an output voltage corresponding to the reference voltage from a connection point between the drain and the first resistor,
The bypass transistor flows an off-leakage current having a magnitude corresponding to the off-leakage current of the output transistor,
Regulator circuit characterized by. The regulator circuit according to claim 1,
The output transistor and the bypass transistor have the same temperature dependence of the off-leakage current;
Regulator circuit characterized by.

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