Power supply device and power supply control semiconductor device

Abstract

The present application provides a power supply device and a power supply control semiconductor device, which can control the rotation speed of a fan according to the ambient temperature without using a microcomputer. The power supply device includes a first DC power supply (11) that generates a DC voltage supplied to a device that becomes a load, and a second DC power supply (12) that generates a DC voltage supplied to a sensor that detects a predetermined physical quantity. In the power supply device, the first DC power supply is an output variable type power supply that generates a DC voltage that changes according to a signal from the sensor, and the second DC power supply is an output fixed type power supply that generates a DC voltage that is constant. Furthermore, the load is an air supply device, the sensor is a temperature detection unit, and the first DC power supply is configured to make the DC voltage supplied to the air supply device higher as the temperature detected by the sensor is higher based on the signal from the sensor.

Description

TECHNICAL FIELD

[0001] The present application relates to a power supply device capable of supplying direct current voltages of two systems, and particularly relates to a technology effective for a power supply device capable of generating a variable direct current voltage to be supplied to a load and a constant direct current voltage to be supplied to a sensor. BACKGROUND

[0002] At present, in an electronic device provided with a cooling air supply device (fan), a temperature sensor such as a thermistor is provided in the housing of the electronic device, a signal from the temperature sensor is input to a control device such as a microcomputer, and the control device linearly changes a voltage for driving a motor for rotating the fan in accordance with a detected temperature in the housing of the electronic device, thereby changing the air supply amount. Specifically, it is configured to control so that the higher the temperature, the faster the rotation speed of the cooling fan is made to increase the air supply amount, and the lower the temperature, the slower the rotation speed of the cooling fan is made to decrease the air supply amount (for example, refer to Patent Literature 1).

[0003] In addition, by a microcomputer (hereinafter referred to as a microcomputer), in accordance with a signal from the temperature sensor, an output voltage of a power supply device for generating a power supply voltage to be supplied to the air supply device is controlled to change the power supply voltage, thereby changing the rotation speed of the cooling fan in accordance with the detected temperature (for example, refer to Patent Literature 2).

[0004] However, the control device of the cooling fan described in Patent Literature 1 must convert the signal from the temperature sensor into a digital signal and input it to the microcomputer in order to control the rotation speed of the cooling fan by the microcomputer, and therefore an expensive microcomputer provided with an AD conversion circuit is required. In addition, there is a problem of requiring a DA conversion circuit that generates a signal for controlling the fan motor based on the processing result of calculating the rotation speed of the cooling fan in accordance with the temperature.

[0005] Furthermore, in the case of using a microcomputer, the fan and the microcomputer are often provided at a distant position, and therefore a relatively long wiring for connecting the fan, the temperature sensor, and the microcomputer is required, and a program of the microcomputer needs to be developed, and therefore there is a problem of causing an increase in cost.

[0006] In addition, a power supply voltage is required to be supplied to the temperature sensor, but a case where the power supply voltage is common to the power supply voltage to be supplied to the air supply device is also considered. However, in this case, as in the invention described in Patent Literature 2, if the power supply voltage to be supplied to the air supply device is changed by the microcomputer, there is a problem that the power supply voltage of the temperature sensor also changes, the temperature-voltage characteristic of the temperature sensor changes, and thus desired rotation speed control corresponding to the temperature cannot be performed.

[0007] Patent Literature 1: Japanese Patent Application Laid-Open (JP A) No. 2002-364583

[0008] Patent Literature 2: Japanese Patent Application Laid-Open (JP A) No. 2019-185732 SUMMARY

[0009] The present application has been made in view of the above-described problems, and has an object to provide a power supply device and a power supply control semiconductor device constituting the power supply device, which can control the rotation speed of a fan according to the ambient temperature without using a microcomputer and without causing a large increase in cost.

[0010] Another object of the present application is to provide a power supply device and a power supply control semiconductor device constituting the power supply device, which can control the rotation speed of a fan according to the ambient temperature without affecting the temperature-voltage characteristic of a temperature sensor.

[0011] To achieve the above-described object, the present application is a power supply device including: a first direct-current power supply that generates a direct-current voltage supplied to a device that becomes a load; and a second direct-current power supply that generates a direct-current voltage supplied to a sensor that detects a predetermined physical quantity,

[0012] The first direct-current power supply is an output-variable type power supply that generates a direct-current voltage that varies according to a signal from the sensor,

[0013] The second direct-current power supply is an output-fixed type power supply that generates a direct-current voltage that is constant.

[0014] According to the power supply device having the above-described structure, the first direct-current power supply of the output-variable type can vary the output voltage according to the signal from the sensor and supply the output voltage to the device that becomes the load. Therefore, the direct-current voltage supplied to the device that becomes the load can be varied without using a microcomputer. In addition, the sensor can be supplied with the constant direct-current voltage generated by the second direct-current power supply. Therefore, the sensor can be supplied with the direct-current voltage that does not affect the temperature-voltage characteristic of the sensor, and the deviation due to the change in the ambient temperature can be suppressed.

[0015] Here, preferably, the load is a ventilation device, and the sensor is a temperature detection unit,

[0016] The first direct-current power supply is configured to supply the ventilation device with a higher direct-current voltage as the temperature detected by the sensor is higher based on the signal from the sensor.

[0017] According to the above-described structure, the rotation speed of the fan of the ventilation device can be controlled according to the ambient temperature, and the rotation speed of the fan is made higher as the temperature is higher to increase the cooling capacity, and the electronic device that becomes the target can be sufficiently cooled.

[0018] Further, it is preferable that the first DC power supply and the second DC power supply are constituted by linear voltage regulators.

[0019] According to this configuration, since the first DC power supply and the second DC power supply are linear voltage regulators of the same configuration, a part of the circuit can be shared, and thus the number of components can be reduced and the occupied area of the circuit can be reduced.

[0020] Further, it is preferable that the linear voltage regulator constituting the first DC power supply has a voltage control transistor connected between a voltage input terminal to which a DC voltage is input and an output terminal, a control circuit that controls the voltage control transistor based on a feedback voltage output, and an external terminal that inputs an output control signal supplied from the outside in order to control an output voltage,

[0021] The control circuit has:

[0022] a first error amplifier that outputs a voltage corresponding to a potential difference between a voltage divided by a first voltage dividing circuit that divides the output voltage of the output terminal and a predetermined reference voltage; and

[0023] an output voltage changing circuit that shifts the voltage divided by the first voltage dividing circuit input to the first error amplifier based on a voltage input to the external terminal, and thus changes the output voltage to a voltage corresponding to the output control signal.

[0024] According to the above configuration, the output voltage can be changed linearly by the output control signal input to the external terminal.

[0025] Further, since no external components are required, the output voltage is determined by the accuracy of the reference voltage and the ratio of the internal resistors, and thus the accuracy and temperature characteristics are good, and the variable input voltage range is large, and the accuracy of the deviation with respect to the input voltage is small.

[0026] Further, it is preferable that the output voltage changing circuit has:

[0027] a second voltage dividing circuit that divides the voltage input to the external terminal;

[0028] a first transistor and a resistor element connected in series between a node for taking out the voltage divided by the first voltage dividing circuit and a constant potential point; and

[0029] a second error amplifier that outputs a voltage corresponding to a potential difference between a voltage divided by the second voltage dividing circuit and a voltage converted from current to voltage by the resistor element,

[0030] the output of the second error amplifier is applied to a control terminal of the first transistor.

[0031] According to this configuration, since the output voltage is varied by displacement of the feedback voltage by voltage-current conversion of the error amplifier, a small-impact-of-power-supply-noise output variable DC power supply can be realized.

[0032] The other application of the present application is a power supply control semiconductor device comprising:

[0033] a voltage input terminal that inputs a DC voltage;

[0034] a first output terminal and a second output terminal;

[0035] a first voltage control transistor connected between the voltage input terminal and the first output terminal;

[0036] a first control circuit that controls the first voltage control transistor in accordance with a feedback voltage output from the first output terminal;

[0037] a second voltage control transistor connected between the voltage input terminal and the second output terminal;

[0038] a second control circuit that controls the second voltage control transistor in accordance with a feedback voltage output from the second output terminal; and

[0039] an external terminal that inputs an output control signal supplied from the outside in order to control the output voltage of the first output terminal,

[0040] the first control circuit comprises:

[0041] a first error amplifier that outputs a voltage corresponding to a potential difference between a voltage after voltage division of a first voltage division circuit that divides the output voltage of the first output terminal and a predetermined reference voltage; and

[0042] an output voltage changing circuit that displaces the reference voltage input to the first error amplifier or the voltage after voltage division of the first voltage division circuit in accordance with a voltage input to the external terminal, thereby changing the output voltage of the first output terminal to a voltage corresponding to the output control signal,

[0043] the second control circuit comprises a second error amplifier that outputs a voltage corresponding to a potential difference between a voltage after voltage division of a second voltage division circuit that divides the output voltage of the second output terminal and a predetermined reference voltage.

[0044] With the power supply control semiconductor device having the above structure, the first control circuit can linearly change the output voltage of the first output terminal by inputting a control signal to the external terminal, and the second control circuit can maintain the output voltage of the second output terminal constant, and by supplying the output voltage of the second output terminal to the sensor, the characteristics of the sensor can be prevented from changing due to temperature.

[0045] Further, it is preferable that the voltage input to the external terminal is a detection voltage from the temperature detection unit.

[0046] The first control circuit is configured to control the first voltage control transistor such that the higher the temperature detected by the temperature detection unit, the higher the output voltage of the first output terminal.

[0047] According to this structure, the temperature detection unit is provided inside the electronic device, and the output voltage of the first output terminal is supplied to the air blowing device, so that the rotation speed of the fan of the air blowing device can be controlled according to the internal temperature of the electronic device, the rotation speed of the fan is made higher as the temperature is higher to increase the cooling capacity, and the electronic device to be cooled can be cooled.

[0048] The power supply device and the power supply control semiconductor device according to the present application can control the rotation speed of the fan according to the ambient temperature without causing a large increase in cost. Further, according to the present application, it is possible to control the rotation speed of the fan according to the ambient temperature without affecting the temperature-voltage characteristics of the temperature sensor. BRIEF DESCRIPTION OF DRAWINGS

[0049] Figure 1 is a functional block diagram showing the structure of one embodiment of the power supply device of the present application and a system using the power supply device.

[0050] Figure 2 is a circuit structure diagram showing the structure of the power supply device (voltage regulator) of the first embodiment.

[0051] Figure 3 (A) of is a characteristic diagram showing the temperature characteristics of a thermistor used in the power supply device of the embodiment, Figure 3 (B) of is a characteristic diagram showing the relationship between the control voltage (thermistor voltage) and the output voltage in the voltage regulator constituting the power supply device of the embodiment.

[0052] Figure 4 is a circuit diagram showing a specific example of a control voltage generation circuit when an NTC thermistor is used.

[0053] Figure 5 is a circuit diagram showing a specific example of a control voltage generation circuit when a PTC thermistor is used. DETAILED DESCRIPTION

[0054] The preferred embodiment of the present application will be described below based on the drawings.

[0055] Figure 1 is a functional block diagram showing an example of the structure of an embodiment of the power supply device of the present application and a system using the power supply device.

[0056] As Figure 1 shown, the power supply device 10 of the present embodiment is provided with a first DC power supply circuit 11 that receives a DC voltage from a DC power supply 20 such as a battery, generates and outputs a power supply voltage for a driver 31 of a blower device 30 that is a load, and a second DC power supply circuit 12 that generates and outputs a power supply voltage for a temperature sensor (temperature detection unit) 21 such as a thermistor. The first DC power supply circuit 11 generates a DC power supply voltage that varies according to a signal from the temperature sensor 21, and the second DC power supply circuit 12 generates and outputs a constant DC power supply voltage.

[0057] The blower device 30 is composed of the driver 31, a fan motor 32 that is rotated by current drive through the driver, and an unillustrated fan that is rotated by the motor, and supplies air generated by rotation of the fan to an electronic device or equipment 40 that is a cooling target to perform cooling.

[0058] The temperature sensor 21 is disposed in the vicinity of the electronic device or equipment 40, for example, in the housing of the device, detects the temperature in the housing, and inputs a detection signal to the first DC power supply circuit 11, which is configured to variably control the output voltage according to the detection signal of the sensor.

[0059] Figure 2 is a circuit structure diagram showing a specific example of the power supply device 10. Further, in Figure 2 , the portion enclosed by the single-dot chain line is formed as a semiconductor integrated circuit (power supply control IC) on a semiconductor chip such as single-crystal silicon. The power supply control IC is provided with a voltage input terminal IN to which a DC input voltage Vin is applied, a variable voltage regulator that is the output voltage of the first DC power supply circuit 11 that outputs a DC voltage to a load such as the blower device 30 shown in Figure 1 , a constant voltage DC regulator that is the second DC power supply circuit 12 that outputs a stable DC voltage to a thermistor Rt that is a temperature sensor, and output terminals OUT1, OUT2 corresponding to each DC power supply. Capacitors Co1, Co2 are connected to the output terminals OUT1, OUT2, respectively, whereby the DC power supply that is an output stable DC voltage functions.

[0060] In the power supply device 10 of the present embodiment, as Figure 2As shown, voltage control transistors Q1, Q2 composed of PNP bipolar transistors are connected between the voltage input terminal IN and the output terminals OUT1, OUT2, respectively, and error amplifiers (error amplifying circuits) AMP1, AMP2 that control the base terminals of the control transistors Q1, Q2, respectively, are provided inside the IC.

[0061] Further, series resistors R11, R12 and R21, R22 that divide the output voltages Vout1, Vout2, respectively, are connected between the output terminals OUT1, OUT2 and a ground line (ground point) to which the ground potential GND is applied.

[0062] Further, the voltage of the connection node N1 of the output dividing resistors R11, R12 is input as a feedback voltage VFB1 to the non-inverting input terminal of the error amplifier AMP1, and the voltage of the connection node N2 of the dividing resistors R21, R22 is input as a feedback voltage VFB2 to the non-inverting input terminal of the error amplifier AMP2.

[0063] In addition, a predetermined reference voltage Vref is input to the inverting input terminals of the error amplifiers AMP1, AMP2, and the error amplifiers AMP1, AMP2 generate voltages corresponding to the potential difference between the output feedback voltages VFB1, VFB2 and the reference voltage Vref and supply the voltages to the gate terminals of the voltage control transistors Q1, Q2 to control Q1, Q2, so that the output voltages Vout1, Vout2 become desired potentials, respectively. That is, the first and second DC power supply circuits 11, 12 are constituted as low saturation type linear voltage regulators (LDOs) of the series regulator type.

[0064] In addition, in the voltage regulator IC of the present embodiment, a reference voltage source 15 that generates a reference voltage Vref based on an input voltage Vin, a bias circuit 16 that generates an operating current for the reference voltage source 15 and the error amplifiers AMP1, AMP2, and an on-off control terminal CNT as an external terminal that inputs an on-off control signal ON / OFF for on-off control of the bias circuit 16 are provided, and the voltage regulator IC is constituted so that when the on-off control signal ON / OFF of low level (0 V) is input to the on-off control terminal CNT, the bias circuit 16 stops supplying the operating current to the reference voltage source 15 and the error amplifiers AMP1, AMP2, and the operation of these circuits is stopped.

[0065] Also, in the voltage regulator IC of the present embodiment, the output control terminal ADJ as an external terminal of the input control signal Vadj and the control voltage generation circuit 17 that corrects the feedback voltage VFB1 to the error amplifier AMP1 according to the control signal Vadj are provided, and the output voltage Vout1 from the output terminal OUT1 is changed by correcting the feedback voltage VFB1 input to the error amplifier AMP1.

[0066] In addition, the resistance Rs and the thermistor Rt are connected in series between the output terminal OUT2 and the ground, and the potential (hereinafter referred to as the thermistor voltage) VT of the connection node of the resistance Rs and the thermistor Rt is input to the output control terminal ADJ of the voltage regulator IC as the control signal Vadj. Thereby, the output voltage Vout1 is changed according to the characteristic of the thermistor Rt. The resistance Rs is an adjustment resistance for correcting the non-linear temperature characteristic of the thermistor Rt so that the change of the thermistor voltage VT is close to a straight line.

[0067] Figure 3 (A) of FIG. 8 shows the relationship between the thermistor voltage VT and the ambient temperature Ta when the NTC (Negative Temperature Coefficient) type thermistor is used, and (B) of FIG. 8 shows the relationship between the control signal Vadj input to the output control terminal ADJ, that is, the NTC thermistor voltage VT, and the output voltage Vout1 of the output variable voltage regulator REG1. Figure 3

[0068] As is apparent from (A) of FIG. 8, the higher the ambient temperature Ta, the lower the thermistor voltage VT, and as is apparent from (B) of FIG. 8, the lower the control signal Vadj, that is, the thermistor voltage VT, the higher the output voltage Vout1. Figure 3 Figure 3 As is apparent from (A) of FIG. 8, the higher the ambient temperature Ta, the lower the thermistor voltage VT, and as is apparent from (B) of FIG. 8, the lower the control signal Vadj, that is, the thermistor voltage VT, the higher the output voltage Vout1.

[0069] Therefore, according to the power supply device of the present embodiment, it is possible to control the rotation speed of the fan without the control of the microcomputer. In addition, the output voltage Vout2 of the second DC power supply circuit 12 applied to the temperature detection unit composed of the resistance Rs and the thermistor Rt is constant regardless of the temperature, and thus it is possible to prevent the temperature characteristic of the thermistor voltage VT from changing due to the change of the power supply voltage.

[0070] As the thermistor Rt, it is also possible to use one having a characteristic different from that of the thermistor Rt of the temperature detection unit 10. Figure 3 ​​of the temperature characteristics of (A) a PTC (Positive Temperature Coefficient) type thermistor. In this case, the resistance Rs and the thermistor Rt are connected in an inverse relationship. Figure 2

[0071] Next, a specific example of the control voltage generation circuit 17 will be described. In addition, the same applies to Figure 4 and Figure 5 A specific example of the control voltage generation circuit 17 will be described. In addition, the same applies to Figure 4 and Figure 5 Only the portion of the regulator IC shown in FIG. 1, which is the output variable voltage regulator that constitutes the first DC power supply circuit 11, is extracted and illustrated. Figure 2 The circuit other than the control voltage generation circuit 17 is the same structure as that shown in FIG. 1. In addition, Figure 2 A circuit example of the control voltage generation circuit when using an NTC type as the thermistor is shown in FIG. 2, Figure 4 A circuit example of the control voltage generation circuit when using a PTC type as the thermistor is shown in FIG. 3. Figure 5

[0072] Figure 4 The control voltage generation circuit shown in FIG. 1 is provided with a current mirror circuit 17A composed of transistors Trl, Tr2 that have their base terminals connected to each other, and an output voltage changing circuit 17B having an error amplifier 17b that applies an output control signal Vadj input from an external terminal ADJ to a non-inverting input terminal. The emitter terminals of the transistors Trl, Tr2 that constitute the current mirror circuit 17A are connected to a voltage input terminal IN, and the collector terminal of the transistor Tr2 is connected to a connection node Nl of output dividing resistors Rll, R12. In addition, the output voltage changing circuit 17B is provided with a transistor Q2 connected in series with the transistor Trl of the current mirror circuit 17A, and a resistor R4.

[0073] The output terminal of the error amplifier 17b is connected to the base terminal of the transistor Q2, and the voltage V4 of the connection node N4 of the transistor Q2 and the resistor R4 is input to the inverting input terminal of the error amplifier 17b, thereby applying a negative feedback, driving the transistor Q2 by the action of a virtual short circuit, so that the voltage V4 of the node N4 causes the same current as the output control signal Vadj input from the external terminal ADJ to flow through the resistor R4.

[0074] ​​Then, the current of the transistor Q2 is copied by the current mirror circuit 17A, and the copied current flows into the connection node Nl of the resistors Rl l, R12, whereby the voltage of the node Nl is shifted, and the shifted potential is inputted to the non-inverting input terminal of the error amplifier AMPl which controls the base terminal of the voltage control transistor Ql as the feedback voltage VFB 1. Thus, the output voltage Voutl corresponding to the output control signal Vadj is outputted to the output terminal OUTl of the voltage regulator (11). Therefore, the control voltage generating circuit 17 which changes the output voltage Voutl to the voltage corresponding to the output control signal Vadj is constituted by the current mirror circuit 17A and the output voltage changing circuit 17B.

[0075] The output voltage Voutl of the voltage regulator (11) of the control voltage generating circuit when the NTC thermistor is used as the thermistor is represented by the following equation: Figure 4

[0076] Voutl = ((Rl l + R12) / R12) x Vref - (V4 / R4) x Rl l = ((Rl l + R12) / R12) x Vref - (Vadj / R4) x Rl l.

[0077] According to the above equation, the detection voltage Vt of the temperature detection unit (Rs, Rt) is inputted as the output control signal Vadj, whereby the output voltage Voutl is changed in correspondence with the detection voltage Vt of the temperature detection unit. The variable range of the output voltage Voutl is Vref ~ Vin.

[0078] The output voltage Voutl of the voltage regulator (11) of the control voltage generating circuit when the PTC thermistor is used as the thermistor is represented by the following equation: Figure 5 The control voltage generating circuit 17 shown in the drawing is provided with: a voltage dividing circuit 17a which is constituted by the resistors R2, R3 connected in series between the external terminal ADJ and the ground, and which divides the output control signal Vadj; a transistor Q2 and a resistor R4 which are connected in series between the connection node Nl of the output dividing resistors Rl l, R12 and the ground.

[0079] Further, the error amplifier 17b which controls the base terminal of the transistor Q2 is provided in the control voltage generating circuit 17, and the voltage V3 of the node N3 divided by the above voltage dividing circuit 17a is inputted to the error amplifier 17b.

[0080] The error amplifier 17b applies negative feedback by applying the voltage V4 of the connection node N4 of the transistor Q2 and the resistor R4 which is the control object to the inverting input terminal, and drives the transistor Q2 by the action of virtual short circuit, so that the same current as the voltage V3 of the node N3 flows in the resistor R4 by the voltage V4 of the node N4.

[0081] ​Further, the voltage V3 of the node N3 is shifted by the current flowing through the resistor R4, and the shifted potential is inputted to the non-inverting input terminal of the error amplifier AMP1 which controls the base terminal of the transistor Ql as a feedback voltage VFB1. Thus, the output voltage Voutl corresponding to the output control signal Vadj is outputted to the output terminal OUTl of the voltage regulator 11. Therefore, the control voltage generating circuit 17 which changes the output voltage Voutl to the voltage corresponding to the output control signal Vadj is constituted by the voltage dividing circuit 17a, the error amplifier 17b, the transistor Q2 and the resistor R4.

[0082] Figure 5 The output voltage Voutl of the voltage regulator 11 is represented by the following equation (1) :

[0083] Voutl = ((Rll + R12) / R12) x Vref + (V4 / R4) x Rll... (1)

[0084] The voltage V3 of the node N3 is represented by the following equation (2) :

[0085] V3 = (R3 / (R3 + R4)) x Vadj... (2).

[0086] Here, since V4 = V3, Voutl is represented by the following equations (1), (2) :

[0087] Voutl = ((Rll + R12) / R12) x Vref + ((R3 x Rll) / R4 x (R2 + R3)) x Vadj... (3).

[0088] According to the above equation (3), the detection voltage Vt of the temperature detecting unit (Rs, Rt) is inputted as the output control signal Vadj, and thus the output voltage Voutl is changed in correspondence with the detection voltage Vt of the temperature detecting unit. The variable range of the output voltage Voutl is Vref ~ Vin.

[0089] Further, with respect to the output voltage Voutl when the output control signal Vadj is 0V, it is known that the second term of the above equation (3) becomes "0", and thus it is set by the ratio of the resistors Rll and R12 and the reference voltage Vref. Specifically, for example, in the case where the reference voltage Vref is 1.5V, by setting the ratio of Rll and R12 to 1:1, the output voltage Vout can be set to 3V by Vadj = 0V. Thus, for example, in the case where a power supply device which supplies a power supply voltage to a motor which operates at a minimum voltage of 3V or more is designed, the motor can be reliably operated, and when the detection voltage Vt of the sensor becomes high due to temperature rise, the rotation speed of the motor can be increased.

[0090] The voltage regulator IC according to the above-described embodiment can realize a variable output voltage type DC power supply that eliminates external components of the IC and changes the output voltage Voutl only by a control signal Vadj input to the output control terminal ADJ. In addition, the output voltage is determined by the accuracy of the reference voltage and the ratio of the internal resistors, so the accuracy and temperature characteristics become good, and the variable input voltage range is large, and the deviation accuracy with respect to the input voltage becomes small. In addition, because it is a structure that changes the output voltage by displacing the feedback voltage through voltage-current conversion by the error amplifier, a variable power supply device with little influence of power supply noise can be realized.

[0091] In the voltage regulator IC of the above-described embodiment ( Figure 2 ), an on / off control terminal CNT that inputs an on / off signal for stopping the operation of the IC is provided, but a structure in which the on / off control terminal CNT is omitted can also be used. In the case where the on / off control terminal CNT is omitted, because the voltage regulator IC can be constituted by five terminals, space saving and cost reduction can be realized by the miniaturization of the package.

[0092] In addition, in the power supply device of the above-described embodiment, a case where the first DC power supply and the second DC power supply are each constituted by a linear regulator of a series regulator type is described, but a regulator of a shunt regulator type can also be used instead of the series regulator type, and the first DC power supply can also be constituted by a DC-DC converter of a switching control type. In addition, a voltage source using a Zener diode can also be used as the reference voltage source 15.

[0093] The above describes the invention made by the present inventors based on the embodiments, but the present invention is not limited to the above-described embodiments. For example, in the above-described embodiment, it is shown that the control voltage generation circuit 17 is provided at the non-inverting input terminal of the error amplifier AMP1 for voltage control, but the control voltage generation circuit 17 can also be provided at the inverting input terminal of the error amplifier AMP1 as disclosed in Patent Literature 2. In addition, the structure of the second embodiment or the modified example described in Patent Literature 2 can also be applied.

[0094] In addition, in the voltage regulator IC of the above-described embodiment, a case where a thermistor is used as the temperature detection unit to linearly change the output voltage is described, but a temperature sensor IC can also be used instead of the thermistor. In addition, a temperature sensor IC having a temperature sensor that switches a flag when the ambient temperature exceeds a predetermined temperature can be used to configure the power supply device to change the output voltage in stages by inputting a signal corresponding to the state of the flag to the output control terminal ADJ using such a sensor.

[0095] Also, in the voltage regulator IC of the above embodiment, a case where a PNP bipolar transistor is used as the voltage control transistor Ql and the transistor Q2 constituting the control voltage generation circuit 17 is shown, but a MOS transistor (insulated gate type field effect transistor) can be used instead of the bipolar transistor. In this case, the voltage control transistor is constituted by a P-channel MOS transistor, but it can also be a structure using an N-channel MOS transistor. Also, with respect to the bipolar transistor, an NPN can be used instead of the PNP.

[0096] Also, in the above embodiment, an example where the application is applied to a system in which the sensor is a temperature detecting sensor and the load is an air blowing device is explained, but it can also be applied to a system in which a humidity sensor, a pressure sensor, a photoelectric sensor, an acceleration sensor, or the like, which detects a physical quantity other than temperature, is used as the sensor.

[0097] Explanation of Reference Numerals

[0098] 10: power supply device (voltage regulator IC), 11: first direct current power supply, 12: second direct current power supply, 15: reference voltage source, 16: bias circuit, 17: control voltage generation circuit, 17A: current mirror circuit, 17B: output voltage changing circuit, 17a: voltage dividing circuit, 17b: error amplifier, 21: temperature detecting unit, 30: air blowing device (load), Ql: voltage control transistor, AMP1, AMP2: error amplifier, ADJ: output control terminal, CNT: on-off control terminal.

Claims

1. A power supply device, comprising: a first DC power supply that generates a DC voltage supplied to a device that becomes a load; and a second DC power supply that generates a DC voltage supplied to a sensor that detects a predetermined temperature, characterized in that the first DC power supply is an output variable type power supply that generates a DC voltage that varies in accordance with a signal from the sensor, the second DC power supply is an output fixed type power supply that generates a constant DC voltage, and the first DC power supply is configured to make the DC voltage supplied to the device that becomes a load higher as the temperature detected by the sensor is higher based on the signal from the sensor.

2. The power supply device according to claim 1, characterized in that the load is an air blowing device.

3. The power supply device according to claim 1 or 2, characterized in that the first DC power supply and the second DC power supply are constituted by linear voltage regulators.

4. A power supply device, comprising: a first DC power supply that generates a DC voltage supplied to a device that becomes a load; and a second DC power supply that generates a DC voltage supplied to a sensor that detects a predetermined physical quantity, characterized in that the first DC power supply is an output variable type power supply that generates a DC voltage that varies in accordance with a signal from the sensor, the first DC power supply includes: a voltage control transistor connected between a voltage input terminal that inputs a DC voltage and an output terminal; a control circuit that controls the voltage control transistor in accordance with a feedback voltage output; and an external terminal that inputs an output control signal supplied from the outside in order to control an output voltage, the second DC power supply is an output fixed type power supply that generates a constant DC voltage, and the control circuit includes: a first error amplifier that outputs a voltage corresponding to a potential difference between a voltage that a first voltage dividing circuit that divides the output voltage of the output terminal divides and a predetermined reference voltage; and an output voltage changing circuit that shifts the voltage that the first voltage dividing circuit of the first error amplifier divides or the reference voltage in accordance with a voltage input to the external terminal, thereby changing the output voltage to a voltage corresponding to the output control signal.

5. The power supply device according to claim 4, characterized in that the output voltage changing circuit includes: a second voltage dividing circuit that divides a voltage input to the external terminal; a first transistor and a resistance element that are connected in series between a node for taking out a voltage that the first voltage dividing circuit divides and a constant potential point; and a second error amplifier that outputs a voltage corresponding to a potential difference between a voltage that the second voltage dividing circuit divides and a voltage that is current-voltage converted by the resistance element, and is configured to apply an output of the second error amplifier to a control terminal of the first transistor.

6. The power supply device according to claim 4, characterized in that the second DC power supply is constituted by a linear voltage regulator. comprising: a voltage input terminal that inputs a DC voltage; a first output terminal and a second output terminal; ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 7. A semiconductor device for power control, characterized in that, ​ ​ ​ a first voltage control transistor connected between the voltage input terminal and the first output terminal; a first control circuit that controls the first voltage control transistor in accordance with a feedback voltage of an output of the first output terminal; a second voltage control transistor connected between the voltage input terminal and the second output terminal; a second control circuit that controls the second voltage control transistor in accordance with a feedback voltage of an output of the second output terminal; and an external terminal that inputs an output control signal supplied from the outside in order to control an output voltage of the first output terminal, the first control circuit includes: a first error amplifier that outputs a voltage corresponding to a potential difference between a voltage after a first voltage dividing circuit that divides an output voltage of the first output terminal is divided and a predetermined reference voltage; and an output voltage changing circuit that shifts the reference voltage input to the first error amplifier or a divided voltage of the first voltage dividing circuit in accordance with a voltage input to the external terminal, thereby changing the output voltage of the first output terminal to a voltage corresponding to the output control signal, the second control circuit is configured to include a second error amplifier that outputs a voltage corresponding to a potential difference between a voltage after a second voltage dividing circuit that divides an output voltage of the second output terminal is divided and a predetermined reference voltage.

8. The power supply control semiconductor device according to claim 7, wherein the voltage input to the external terminal is a detection voltage from a temperature detection unit, the first control circuit controls the first voltage control transistor such that the higher the temperature detected by the temperature detection unit, the higher the output voltage of the first output terminal. ​

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