JP6371713B2 - Constant voltage device and reference voltage generation circuit - Google Patents

Description

  The present invention relates to a constant voltage device that generates an output voltage having a constant voltage value, and a reference voltage generation circuit included in the constant voltage device.

  Currently, a constant voltage circuit capable of generating an output voltage with a constant voltage value based on a power supply voltage has been proposed (see, for example, Patent Document 1). This constant voltage circuit is provided with a field effect transistor that outputs an output voltage via its own source or drain. A first circuit in which a first diode, a first resistor and a second resistor are connected in series, and a third resistor and a second diode are connected in series to the source or drain of the field effect transistor. The second circuit is connected in parallel. Furthermore, in such a constant voltage circuit, the comparison result obtained by comparing the voltage at the connection point between the first and second resistors with the voltage at the connection point between the third resistor and the second diode. Comparing means is provided for applying a signal to the gate of the field effect transistor.

  In the constant voltage circuit, when the second and third resistors have the same resistance value and the output voltage output from the field effect transistor is equal to the desired voltage value, the current flowing through the first and second circuits is The resistance value of the first resistor is set to be the same. Therefore, when the output voltage does not match the desired voltage value, the amount of current flowing in each of the first and second circuits changes, and accordingly, the voltage at the connection point between the first and second resistors is There is a difference between the third resistor and the voltage at the connection point between the diodes. At this time, the field effect transistor operates so that the difference between the voltage at the connection point between the first and second resistors and the voltage at the connection point between the third resistor and the diode becomes zero. As a result, the output voltage is maintained at a desired constant voltage value.

JP-A-10-171545

  However, the above-described configuration has a problem that fluctuations in output voltage due to changes in environmental temperature cannot be suppressed.

  Therefore, an object of the present invention is to provide a constant voltage device that can suppress fluctuations in output voltage due to temperature fluctuations, and a reference voltage generation circuit included in the constant voltage device.

  A constant voltage device according to the present invention is a constant voltage device that outputs an output voltage via an output line, and a power supply voltage is applied to one end of a source end and a drain end, and the source end and the drain end An output transistor having the other end of the output line connected to the output line, a voltage dividing circuit for dividing the voltage of the output line to obtain a divided voltage, and a drain end having a gate end connected to the drain A reference voltage generating transistor in which a ground potential is applied to one of the end and the source end, and a source / drain in a boundary region between a saturated region and a non-saturated region of the reference voltage generating transistor based on a voltage of the output line A voltage application unit that applies a voltage having an inter-voltage value as a reference voltage to the other end of the drain end and the source end of the reference voltage generating transistor A reference voltage generation circuit including a differential amplifier that supplies an output voltage control signal having a level corresponding to a difference value between the voltage value of the divided voltage and the voltage value of the reference voltage to the gate terminal of the output transistor; The reference voltage generation transistor has a threshold voltage within a voltage range equal to the voltage range of the source-drain voltage in the boundary region.

  The reference voltage generation circuit according to the present invention is a reference voltage generation circuit that generates a reference voltage based on a supply voltage, and has a drain terminal connected to a gate terminal and a drain terminal and a source terminal. A reference voltage generating transistor having a ground potential applied to one end thereof, and a voltage having a source-drain voltage value in a boundary region between a saturated region and a non-saturated region of the reference voltage generating transistor based on the supply voltage. A voltage applying unit that applies a voltage to the other end of the drain end and the source end of the reference voltage generating transistor, and the reference voltage generating transistor has a voltage range of a source-drain voltage in the boundary region; Have a threshold voltage within an equal voltage range.

  In the present invention, a diode-connected transistor for generating a reference voltage has a threshold voltage within a voltage range equal to the voltage range of the source-drain voltage in the boundary region between the saturation region and the non-saturation region of the transistor. Use. Then, a reference voltage is generated by applying a voltage having a source-drain voltage value in a boundary region between the saturated region and the non-saturated region of the reference voltage generating transistor to the reference voltage generating transistor.

  Therefore, the reference voltage generation transistor operates at a voltage whose threshold voltage does not fluctuate even when a temperature change occurs, that is, a voltage within the voltage range of the source-drain voltage in the boundary region between the saturated region and the unsaturated region of the transistor. Thus, it is possible to obtain a reference voltage and an output voltage having a constant voltage value excluding temperature dependency.

1 is a circuit diagram showing a constant voltage device 100 according to the present invention. It is a figure which shows the current voltage characteristic showing the saturation area | region and non-saturation area | region of the reference voltage generation transistor QR. It is a circuit diagram which shows the modification of the constant voltage apparatus 100 which concerns on this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a circuit diagram showing an example of a constant voltage device 100 according to the present invention. The constant voltage device 100 outputs an output voltage VT having a constant voltage value CV. As shown in FIG. 1, the output transistor 10, the voltage dividing circuit 11, the reference voltage generating circuit 12, and the differential amplifier 13 are output. Have

  The output transistor 10 is, for example, a p-channel MOS (Metal-Oxide-Semiconductor) type transistor, and a power supply voltage VDD is applied to a source terminal thereof. A voltage dividing circuit 11 and a reference voltage generating circuit 12 are connected to the drain terminal of the output transistor 10 via an output line LL. An output voltage control signal CS output from the differential amplifier 13 is supplied to the gate terminal of the output transistor 10. The output transistor 10 generates the above-described output voltage VT based on the power supply voltage VDD, and supplies the output voltage VT to the voltage dividing circuit 11 and the reference voltage generation circuit 12 via the output line LL.

  The voltage dividing circuit 11 includes resistors Ra and Rb connected in series. One end of the resistor Ra is connected to the output line LL, and the other end is connected to one end of the resistor Rb. A ground potential GND is applied to the other end of the resistor Rb.

  With this configuration, the voltage dividing circuit 11 supplies the divided voltage DV obtained by dividing the output voltage VT with the resistors Ra and Rb to the inverting input terminal of the differential amplifier 13.

  The resistance values of the resistors Ra and Rb are such that when the voltage value of the output voltage VT matches the voltage value CV, the voltage value of the divided voltage DV matches the voltage value of the reference voltage RV described later. The resistance value is set.

  The reference voltage generation circuit 12 includes a series resistance group RG including resistors R1 to R4 connected in series, an n-channel MOS type reference voltage generation transistor QR, and n-channel MOS type first to third transistors Q1 to Q1. Q3.

  One end of the series resistor group RG, that is, one end of the resistor R1 is connected to the output line LL. The other end of the resistor R1 is connected to one end of the resistor R2. The other end of the resistor R2 is connected to one end of the resistor R3. The other end of the resistor R3 is connected to one end of the resistor R4. The other end of the series resistor group RG, that is, the other end of the resistor R4 is connected to the non-inverting input terminal of the differential amplifier 13 and the drain terminal of the reference voltage generating transistor QR.

  The drain end of the transistor Q1 is connected to the connection point between the resistors R1 and R2, and the drain end of the transistor Q2 is connected to the connection point between the resistors R2 and R3. The drain end of the transistor Q3 is connected to the connection point between the resistors R2 and R3.

  The drain end and the gate end of the first transistor Q1 are connected to each other, and the ground potential GND is applied to the source end. The drain terminal and gate terminal of the second transistor Q2 are connected to each other, and the ground potential GND is applied to the source terminal. The drain end and the gate end of the third transistor Q3 are connected to each other, and the ground potential GND is applied to the source end.

  The drain end and the gate end of the reference voltage generating transistor QR are connected to each other, and the ground potential GND is applied to the source end.

  That is, the reference voltage generating transistor QR and the transistors Q1 to Q3, each of which is diode-connected, are provided between a ground line (not shown) for supplying the ground potential GND and the series resistance group RG.

  As shown in FIG. 2, the reference voltage generating transistor QR is a threshold voltage within a voltage range that can be taken as the drain-source voltage Vds in the boundary region between the saturated region and the non-saturated region of the reference voltage generating transistor QR. A material having Vth is used. That is, the reference voltage generating transistor QR has a gate width or a gate length so that the threshold voltage Vth is equal to a voltage value within a voltage range that can be taken as a drain-source voltage in the boundary region between the saturated region and the non-saturated region. This is a set MOS transistor.

  With this configuration, the reference voltage generation circuit 12 supplies the voltage at the connection point between the resistor R4 and the reference voltage generation transistor QR to the non-inverting input terminal of the differential amplifier 13 as the reference voltage RV. At this time, the reference voltage RV is equal to or higher than the threshold voltage Vth of the reference voltage generation transistor QR, and, as shown in FIG. 2, between the drain and the source in the boundary region between the saturation region and the non-saturation region of the reference voltage generation transistor QR. It has a voltage value within a possible voltage range as the voltage Vds.

  The differential amplifier 13 obtains a difference value between the voltage value of the divided voltage DV and the voltage value of the reference voltage RV, and outputs an output voltage control signal CS having a level corresponding to the difference value to the gate of the output transistor 10. Supply to the end.

  The operation of the constant voltage device 100 having the configuration shown in FIG. 1 will be described below.

  First, when the voltage value of the output voltage VT becomes higher than the voltage value CV, for example, with the fluctuation of the power supply voltage VDD, the voltage value of the divided voltage DV becomes higher than the voltage value of the reference voltage RV. As a result, the level of the output voltage control signal CS output from the differential amplifier 13 becomes higher than a predetermined level, and the gate voltage of the output transistor 10 becomes higher. Therefore, at this time, the drain-source resistance of the output transistor 10 increases, and the voltage value of the output voltage VT decreases. That is, the voltage value of the output voltage VT is controlled so as to approach the voltage value CV.

  On the other hand, when the voltage value of the output voltage VT becomes lower than the voltage value CV, the voltage value of the divided voltage DV becomes lower than the voltage value of the reference voltage RV. As a result, the level of the output voltage control signal CS output from the differential amplifier 13 becomes lower than a predetermined level, and the gate voltage of the output transistor 10 becomes lower. Therefore, at this time, the drain-source resistance of the output transistor 10 decreases, and the voltage value of the output voltage VT increases. That is, the voltage value of the output voltage VT is controlled so as to approach the voltage value CV.

  With the above-described operation, in the constant voltage device 100, the voltage value of the output voltage VT is kept constant regardless of the fluctuation of the voltage value of the power supply voltage VDD.

  Hereinafter, temperature compensation operations in the voltage dividing circuit 11 and the reference voltage generating circuit 12 in the constant voltage device 100 shown in FIG. 1 will be described.

  In the voltage dividing circuit 11, the resistance values of the resistors Ra and Rb change with temperature variation, but the resistance values change at the same rate. Therefore, the divided voltage DV generated by the resistors Ra and Rb does not vary in voltage value due to temperature variation.

  On the other hand, in the reference voltage generation circuit 12, when the output voltage VT is applied to the output line LL, the transistors Q1 to Q3 and the reference voltage generation transistor QR are turned on, and each of these transistors is connected via the resistors R1 to R4. A current flows through (Q1 to Q3, QR). Therefore, the voltage V1 at the connection point between the resistor R1 and the resistor R2 is lower than the output voltage VT, and the voltage V2 at the connection point between the resistor R2 and the resistor R3 is lower than the voltage V1. Further, the voltage V3 at the connection point between the resistor R3 and the resistor R4 is lower than the voltage V2, and the reference voltage RV is lower than the voltage V3.

  That is, the voltage application unit including the resistors R1 to R4 and the transistors Q1 to Q3 reduces the voltage (VT) of the output line LL, thereby draining the boundary region between the saturation region and the non-saturation region of the reference voltage generation transistor QR. A voltage within a voltage range that can be taken as a source-to-source voltage is generated and applied to the reference voltage generating transistor QR. At this time, the voltage generated at the connection point between the series resistance group RG and the reference voltage generating transistor QR is obtained as the reference voltage RV.

  By the way, the threshold voltage of the MOS transistor decreases as the temperature increases in the saturation region of the transistor, but increases as the temperature increases in the non-saturation region. At this time, the threshold voltage does not vary with the temperature change in the boundary region between the saturated region and the non-saturated region of the transistor.

  Therefore, in the reference voltage generation circuit 12, as the reference voltage generation transistor QR, a voltage within the voltage range in which the voltage value of its own threshold voltage Vth can be taken as the drain-source voltage in the boundary region between the saturated region and the non-saturated region. The one constructed to be equal to the value is used. The reference voltage RV is obtained by operating the reference voltage generating transistor QR at a voltage within a voltage range that can be taken as a drain-source voltage in the boundary region between the saturated region and the non-saturated region.

  Therefore, the reference voltage generation transistor operates at a voltage whose threshold voltage does not fluctuate even when a temperature change occurs, that is, a voltage within the voltage range of the source-drain voltage in the boundary region between the saturated region and the unsaturated region of the transistor. Thus, it is possible to obtain a reference voltage and an output voltage having a constant voltage value excluding temperature dependency.

  Therefore, according to the constant voltage device 100 shown in FIG. 1, it is possible to output the output voltage VT having a constant voltage value CV even when not only the power supply voltage varies but also the temperature varies. .

  In the above embodiment, a p-channel MOS transistor is employed as the output transistor 10, but an n-channel MOS transistor may be employed.

  Further, in the reference voltage generating transistor QR and the transistors Q1 to Q3, a p-channel MOS type transistor may be employed as shown in FIG. 3 instead of the n-channel MOS type transistor.

  At this time, when the p-channel MOS type is adopted as the reference voltage generating transistor QR and the transistors Q1 to Q3, as shown in FIG. 3, the drain end and the gate end of each transistor (QR, Q1 to Q3) are grounded. While applying a potential, each source end is connected to a connection point between the resistors (R1 to R4) of the series resistor group RG. The configuration shown in FIG. 3 is the same as that shown in FIG. 1 except for the reference voltage generation transistor QR and the transistors Q1 to Q3.

  In short, as the constant voltage device 100 shown in FIG. 1, any device including the following output transistor (10), voltage dividing circuit (11), reference voltage generation circuit (12), and differential amplifier (13) may be used. It ’s good. That is, the power supply voltage is applied to one end of the source end and the drain end of the output transistor, and the output line (LL) is connected to the other end of the source end and the drain end. The voltage dividing circuit divides the voltage of the output line to obtain a divided voltage (DV). The reference voltage generation circuit includes a reference voltage generation transistor (QR) and voltage application units (R1 to R4, Q1 to Q3).

  The drain end and the gate end of the reference voltage generating transistor are connected to each other, and a ground potential (GND) is applied to one end of the drain end and the source end. The voltage application unit uses the voltage having the source-drain voltage (Vds) in the boundary region between the saturation region and the non-saturation region of the reference voltage generation transistor based on the voltage of the output line as a reference voltage (RV). Applied to the other end of the drain end and the source end. The differential amplifying unit supplies an output voltage control signal (CS) having a level corresponding to the difference value between the voltage value of the divided voltage and the voltage value of the reference voltage to the gate terminal of the output transistor.

  As the reference voltage generating transistor described above, a transistor having a threshold voltage within a voltage range equal to the voltage range of the source-drain voltage in the boundary region between the saturated region and the non-saturated region of the reference voltage generating transistor is adopted. is there.

  Moreover, in the said Example, the operation | movement was demonstrated using the serial resistance group RG which consists of four resistance R1-R4 connected in series, and three transistors Q1-Q3 as a voltage application part. However, the number of stages of resistors connected in series in the series resistor group RG is not limited to four, and the number of transistors connected to the connection point between these resistors is not limited to three.

  In short, the series resistor group may be any one in which the first to nth (n is an integer of 2 or more) resistors are connected in series. At this time, an output line is connected to one end of the first to nth resistors, or a supply voltage is applied, and the other end of the first to nth resistors has a reference The other end of the drain end and the source end of the voltage generating transistor QR is connected. Furthermore, the voltage application unit is provided with first to (n−1) th transistors in which one end of each drain end and source end is connected to each connection point of the first to nth resistors. ing. At this time, each of the first to (n-1) th transistors has the ground potential applied to the other end of the drain end and the source end, and the drain end and the gate end of the transistor are connected to each other. Has been.

10 output transistor 11 voltage dividing circuit 12 reference voltage generating circuit
13 Differential amplifiers Q1-Q3 Transistors Ra, Rb, R1-R4 Resistance

Claims (4)

A constant voltage device that outputs an output voltage via an output line,
An output transistor in which a power supply voltage is applied to one end of a source end and a drain end and the output line is connected to the other end of the source end and the drain end;
A voltage dividing circuit that divides the voltage of the output line to obtain a divided voltage;
A reference voltage generating transistor having a gate terminal connected to the drain terminal and a ground potential applied to one of the drain terminal and the source terminal; and a saturation region of the reference voltage generating transistor based on the voltage of the output line And a reference voltage including a voltage application unit that applies a voltage having a source-drain voltage value in a boundary region between the unsaturated regions to the other end of the drain end and the source end of the reference voltage generating transistor as a reference voltage A generation circuit;
A differential amplifier for supplying an output voltage control signal having a level corresponding to a difference value between the voltage value of the divided voltage and the voltage value of the reference voltage to the gate terminal of the output transistor;
The reference voltage generating transistor has a threshold voltage within a voltage range equal to a voltage range of a source-drain voltage in the boundary region. The voltage application unit includes:
First to nth (n is an integer of 2 or more) resistors are connected in series, and the output line is connected to one end of the first to nth resistors, and the first A series resistor group in which the other end of the drain end and the source end of the reference voltage generating transistor is connected to the other end of the first to nth resistors;
First to (n-1) th transistors, each having a drain end and a source end connected to each connection point of the first to nth resistors,
In each of the first to (n-1) th transistors, a ground potential is applied to the other end of the drain end and the source end, and the drain end and the gate end are connected. The constant voltage device according to claim 1. A reference voltage generation circuit that generates a reference voltage based on a supply voltage,
A reference voltage generating transistor having a gate terminal connected to the drain terminal and a ground potential applied to one end of the drain terminal and the source terminal;
Based on the supply voltage, a voltage having a source-drain voltage value in a boundary region between a saturation region and a non-saturation region of the reference voltage generation transistor is used as the reference voltage, and the drain end and the source end of the reference voltage generation transistor A voltage application unit to be applied to the other end,
The reference voltage generation circuit, wherein the reference voltage generation transistor has a threshold voltage within a voltage range equal to a voltage range of a source-drain voltage in the boundary region. The voltage application unit includes:
First to nth (n is an integer of 2 or more) resistors are connected in series, and the supply voltage is applied to one end of the first to nth resistors. A series resistor group in which the other end of the drain end and the source end of the reference voltage generating transistor is connected to the other end of the first to nth resistors;
First to (n-1) th transistors, each having a drain end and a source end connected to each connection point of the first to nth resistors,
Each of the first to (n-1) th transistors has a ground potential applied to the other end of its drain end and source end, and the drain end and the gate end are connected. The reference voltage generation circuit according to claim 3.

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