JP3773245B2 - Fan drive control circuit - Google Patents

Fan drive control circuit Download PDF

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Publication number
JP3773245B2
JP3773245B2 JP2002270239A JP2002270239A JP3773245B2 JP 3773245 B2 JP3773245 B2 JP 3773245B2 JP 2002270239 A JP2002270239 A JP 2002270239A JP 2002270239 A JP2002270239 A JP 2002270239A JP 3773245 B2 JP3773245 B2 JP 3773245B2
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Japan
Prior art keywords
voltage
circuit
temperature
transistor
fan
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JP2002270239A
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JP2004112892A (en
Inventor
廣 東田
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ケル株式会社
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Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fan drive control circuit for a cooling fan used for heat generation countermeasures for electronic devices and the like.
[0002]
[Prior art]
With the advancement of information and communication technology, electronic devices using electronic circuits are used in all fields, but the amount of electric power used by electronic circuits is increasing with the improvement of processing capability. Low power consumption electronic elements and central processing units are being researched and developed, but as electronic devices become smaller and more dense, it is necessary to take measures against heat generated by electronic circuits to suppress the temperature rise of electronic devices. This is a very important problem for stable operation.
[0003]
Cooling fans are used as means for suppressing the heat generation of electronic devices, and many are operated with a DC voltage. Cooling fans rotate the propeller with a DC motor to create an air flow, circulate the air inside and outside the electronic equipment to exhaust heat, or generate heat due to high power consumption (central processing unit, etc.) The air is directly blown and cooled, but noise and vibration such as rotating sound and wind noise due to the rotation of the propeller are generated. Conventionally, many electronic devices have been installed in dedicated machine rooms, so this noise and vibration were not a problem. However, due to the widespread use of personal computers (hereinafter referred to as “PCs”) and communication devices, It has been installed in offices and homes, and noise and vibration countermeasures are required.
[0004]
Further, along with the downsizing of devices, portable electronic devices (for example, notebook personal computers) that are carried and used are increasing, and these electronic devices are configured to be driven by a battery. In this portable electronic device, a cooling fan is also used, and battery power is consumed by driving the cooling fan. However, since the battery can only store a limited amount of power, it is necessary to effectively use the battery power and extend the driving time. Therefore, the power consumption of the electronic circuit that constitutes the portable electronic device including the cooling fan. It is important to suppress this.
[0005]
  A cooling fan that operates with direct current voltage controls the speed of the propeller (rotation speed) when the voltage is controlled.AppliedIt has a property of changing in proportion to the generated voltage (when the rotational speed changes, the air volume generated by this propeller also changes in proportion thereto). For this reason, as a method to improve the quietness (suppress driving noise, wind noise and vibration) and energy saving (suppress power consumption) of the cooling fan using this property, it is supplied according to the temperature state inside the electronic equipment. A fan drive control circuit has been used in which the rotation speed of the cooling fan propeller is changed by controlling the voltage to be controlled or stopped when not necessary (see, for example, Non-Patent Document 1). Hereinafter, a conventional example of the fan drive control circuit will be described with reference to FIGS.
[0006]
FIG. 8 shows an example of the fan drive control circuit 50 that controls the voltage supplied to the cooling fan according to the temperature detected by the temperature detector to change the rotation speed of the propeller of the cooling fan 54. The fan drive control circuit 50 includes a temperature detector 51 that outputs a temperature-corresponding voltage Vt corresponding to the ambient temperature, a reference voltage circuit 52 that outputs a reference voltage Vref corresponding to a set temperature, a temperature-corresponding voltage Vt and a reference voltage Vref. And a first power supply 55 having an output voltage of + V1, and a second power supply 56 having an output voltage of + V2. Has been.
[0007]
The temperature detector 51 is configured such that the temperature-corresponding voltage Vt is low when the temperature is low, and the temperature-corresponding voltage Vt increases as the temperature rises. The reference voltage circuit 52 is configured in such a manner that the resistor R51 and the resistor R52 are connected in series in this order from the first power supply 55, and one end of the resistor R52 is grounded. The voltage + V1 of the first power supply 55 is supplied to the resistors R51, R51, The voltage is divided by R52, and the voltage of the resistor R52 is output as the reference voltage Vref corresponding to the set temperature from the output terminal at the connection point of the resistors R51 and R52.
[0008]
The amplifier circuit 53 includes an operational amplifier U51, an NPN transistor Q51, and resistors Rf50, R53, and R54. In the operational amplifier U51, the second power supply 56 is connected to the positive power supply terminal, the negative power supply terminal is grounded, and the output terminal is connected to the base of the transistor Q51 via the resistor R54. The transistor Q51 constitutes a grounded-emitter amplifier circuit in which the second power supply 56 is applied to the base by the resistor R53, and the collector is connected to the second power supply 56. Note that negative feedback is provided from the emitter of the transistor Q51 to the negative phase input terminal of the operational amplifier U51 via the resistor Rf. The temperature detector 51 is connected to the positive phase input terminal of the operational amplifier U51, the output terminal of the reference voltage circuit 52 is connected to the negative phase input terminal, and one end of the power supply terminal of the cooling fan 54 is connected to the emitter of the transistor Q51. And the other end of the power supply terminal of the cooling fan 54 is grounded.
[0009]
Since the transistor Q51 functions as an amplifier circuit for a current buffer for supplying the output of the amplifier circuit 53 as a driving power source for the cooling fan 54, a sufficient current output for the operational amplifier U51 to drive the cooling fan 54 is provided. If so, the amplifier circuit composed of the transistor Q51 and the resistor R53 and the operational amplifier U51 and the resistor R54 connecting the amplifier circuit are unnecessary. Therefore, the amplifier circuit 53 combines the operational amplifier U51 and the transistor Q51 to constitute a large output current type inverting amplifier, and supplies a voltage proportional to the change from the reference voltage Vref of the temperature-corresponding voltage Vt to the cooling fan 54. is doing.
[0010]
  According to such a configuration, the difference between the temperature-corresponding voltage Vt and the reference voltage Vref is amplified by the amplifier circuit 53 and supplied to the cooling fan 54, so that it is supplied to the cooling fan 54 in accordance with the ambient temperature of the temperature detector 51. Therefore, the rotation speed of the cooling fan 54 is controlled. Here, the resistors R51, R52, and Rf50 are connected to the cooling fan 54.AppliedIs used for setting a gain with respect to the offset of the applied voltage and a change in the temperature-corresponding voltage Vt output from the temperature detector 51, and the resistor R54 constituting the amplifier circuit 53 does not supply an excessive current to the base of the transistor Q51. At the same time, it is a current limiting resistor for limiting excessive current from flowing into the output of the operational amplifier U51.
[0011]
FIG. 9 shows a fan drive control circuit 60 that turns on / off the power supplied to the cooling fan 64 based on the temperature detected by the temperature detector 61. The fan drive control circuit 60 includes a temperature detector 61 that outputs a temperature-corresponding voltage Vt corresponding to the ambient temperature, a reference voltage circuit 62 that outputs a reference voltage Vref corresponding to a set temperature, a temperature-corresponding voltage Vt and a reference voltage Vref. And a power supply control circuit 63 for turning on / off the power supplied to the cooling fan 64, a first power supply 65 with an output voltage of + V1, and a second power supply 66 with an output voltage of + V2. . The temperature detector 61 and the reference voltage circuit 62 have the same configuration and operation as the temperature detector 51 and the reference voltage circuit 52 described above.
[0012]
The power supply control circuit 63 includes a comparator U61, a PNP transistor Q61, resistors R63 and R64, and a diode D62. In the comparator U61, the second power supply 66 is connected to the positive power supply terminal, the negative power supply terminal is grounded, and the output terminal is connected to the base of the transistor Q61 via the resistor R64. The transistor Q61 has a second power source 66 connected to the base by a resistor R63, and a second diode via a diode D62 whose emitter is connected in the forward direction (the emitter of the transistor Q61 is connected to the cathode of the diode D62). Is connected to a power source 66, and constitutes a collector grounded amplifier circuit. The output terminal of the reference voltage circuit 62 is connected to the positive phase input terminal of the comparator U61 of the power supply control circuit 63, the temperature detector 61 is connected to the negative phase input terminal, and the power supply of the cooling fan 64 is connected to the collector of the transistor Q61. One end of the supply terminal is connected, and the other end of the power supply terminal of the cooling fan 64 is grounded.
[0013]
  According to such a configuration, when the temperature-corresponding voltage Vt of the temperature detector 61 is lower than the reference voltage Vref (when the temperature is low), the output of the comparator U61 is a high voltage (at the positive power supply terminal).AppliedThe voltage + V2 of the second power supply 66 is approximately equal to or slightly lower than the voltage + V2 of the second power supply 66) and becomes the base of the transistor Q61.AppliedTherefore, the base current does not flow and the transistor Q61 is turned off, so that no current flows between the emitter and the collector, and no power is supplied to the cooling fan 64. Further, when the temperature-corresponding voltage Vt of the temperature detector 61 is equal to or higher than the reference voltage Vref (when the temperature is high), the output of the comparator U61 becomes a low voltage (almost 0 V because the negative power supply terminal is grounded). At the base of transistor Q61AppliedTherefore, the base current flows and the transistor Q61 is turned on, so that a current flows between the emitter and the collector, and power is supplied to the cooling fan 64. Thus, the transistor Q61 functions as a switch for turning on / off the power supplied to the cooling fan 64 by the output of the comparator U61.
[0014]
The resistor R64 is a current limiting resistor that prevents excessive current from flowing through the output of the comparator U61 and the base of the transistor Q61. Further, the resistor R63 may be omitted if the output of the comparator U1 is not open. The diode D62 is for adding an offset so that the output voltage of the comparator U61 becomes a base voltage that completely turns off the transistor Q61. The forward drop voltage of the diode D62 is added to the original base-emitter voltage of the transistor Q61. By using the added value as the base-emitter voltage of the transistor Q61 viewed from the comparator U61, the transistor Q61 can be completely turned off even when the output voltage of the comparator U61 is slightly lower than the output voltage + V2 of the second power supply 66. It is what you do. Therefore, if it is possible to output the output of the comparator U61 up to the output voltage + V2 of the second power supply 66 applied to the positive power supply terminal (if it is a Rail-to-Rail comparator), there is no diode D62. Alternatively, depending on the maximum output voltage characteristic of the comparator U61, it is necessary to increase the diode D62.
[0015]
FIG. 10 shows a fan drive control circuit 70 that controls the rotational speed of the cooling fan 74 in two stages of low-speed rotation and high-speed rotation based on the temperature detected by the temperature detector 71. The fan drive control circuit 70 includes a temperature detector 71 that outputs a temperature-corresponding voltage Vt corresponding to the ambient temperature, a reference voltage circuit 72 that outputs a reference voltage Vref corresponding to a set temperature, a temperature-corresponding voltage Vt and a reference voltage Vref. And a power supply control circuit 73 for controlling the output voltage of the driving power supply of the cooling fan 74 in two stages, a first power supply 75 having an output voltage of + V1, and a second power supply 76 having an output voltage of + V2. Has been. The temperature detector 71 and the reference voltage circuit 72 have the same configuration and operation as the temperature detector 51 and the reference voltage circuit 52 described above.
[0016]
The power supply control circuit 73 includes a comparator U71, a PNP transistor Q71, resistors R73 and R74, a diode D72, and a Zener diode Dz70. In the comparator U71, the second power supply 76 is connected to the positive power supply terminal, the negative power supply terminal is grounded, and the output terminal is connected to the base of the transistor Q71 via the resistor R74. The transistor Q71 has a second power source 76 applied to the base by a resistor R73, and the second through a diode D2 whose emitter is connected in the forward direction (the emitter of the transistor Q71 is connected to the cathode of the diode D2). Is connected to a power source 76, and constitutes a grounded amplifier circuit. A Zener diode Dz70 is connected between the collector and emitter of the transistor Q71 so that the collector side becomes the anode. The output terminal of the reference voltage circuit 72 is connected to the positive phase input terminal of the comparator U71 of the power supply control circuit 73, the temperature detector 71 is connected to the negative phase input terminal, and the power supply of the cooling fan 74 is connected to the collector of the transistor Q71. One end of the input terminal is connected, and the other end of the power input terminal of the cooling fan 74 is grounded.
[0017]
  According to such a configuration, the relationship between the difference between the temperature-corresponding voltage Vt and the reference voltage Vref and the on / off state of the transistor Q71 is the same as that of the fan drive control circuit 60 described above. Therefore, when the temperature-corresponding voltage Vt is lower than the reference voltage Vref, the transistor Q71 is in an off state, and the cooling fan 74 is lower than the voltage + V2 of the second power supply 76 by the voltage drop of the diode D72 and the Zener diode Dz70. VoltageAppliedBecause it is, it rotates at a low speed. On the other hand, when the temperature-corresponding voltage Vt is equal to or higher than the reference voltage Vref, the transistor Q71 is on and the cooling fan 74 is turned on.AppliedThe voltage to be applied is a voltage lower than the voltage + V2 of the second power source 76 by the sum of the voltage drop of the diode D72 and the emitter-collector voltage of the transistor Q71, but when the transistor Q1 is in the on state, the emitter-collector voltage is Since it is small (ideally 0V), the cooling fan 74 rotates at a high speed. The uses of the resistors R73 and R74 are the same as in the above-described conventional example.
[0018]
[Non-Patent Document 1]
Intel Corporation, “NLX Electrical Design Suggestions Version 1.2”, USA, July 1998, p. 27
[0019]
[Problems to be solved by the invention]
As described above, in the conventional fan drive control circuit using the analog element, the fan drive control circuit 50 shown in FIG. 8 operates to change the rotation speed of the cooling fan in proportion to the temperature. The fan drive control circuit 60 shown in FIG. 10 operates to turn on / off the supply voltage to the cooling fan corresponding to the temperature, or the fan drive control circuit 70 shown in FIG. Since only the operation of switching the rotation speed of the fan in two stages of low speed and high speed is performed, there is only a circuit that performs any one of the operations, and fine control of the cooling fan cannot be performed. There is also a method of controlling the cooling fan in detail by configuring a fan drive control circuit with a digital circuit, but there is also a problem that the application range is limited because the circuit is complicated and the manufacturing cost increases.
[0020]
However, with the spread of electronic equipment, there is a growing demand for improvements in the cooling fan's quietness and energy savings, and it is necessary to turn off the power when cooling fan cooling is not necessary, and when necessary. It is necessary to provide a fan drive control circuit that performs control so as to perform a minimum operation at a low cost.
[0021]
The present invention has been made in view of such problems, and provides a fan drive control circuit that improves the quietness and energy saving of the cooling fan at a low cost by finely controlling the drive of the cooling fan. Objective.
[0022]
[Means for Solving the Problems]
  In order to solve the above problems, a fan drive control circuit according to the present invention has a temperature detection element (for example, the thermistor Rt in the embodiment) whose resistance value changes in accordance with the ambient temperature. A temperature detection circuit that outputs a temperature-corresponding voltage corresponding to the resistance value, a reference voltage circuit that outputs a reference voltage corresponding to the set temperature, a temperature-corresponding voltage and a reference voltageWhenAnd an amplifier circuit that amplifies the difference andDepending on outputFan (for example, cooling fan 5 in the embodiment)Is what drivesThe amplifier circuitThe output terminal of the temperature detection circuit and the output terminal of the reference voltage circuit are connected to the input terminals.Temperature response voltage and reference voltageWhenCompareThen, the difference is amplified and output from the output terminalAn operational amplifier toThe base is connected to the output terminal of the operational amplifier, the emitter is connected to the power source (for example, the second power source 7 in the embodiment), and the collector is connected to the fan.A transistor,A diode having an anode connected to the collector of the transistor and a cathode connected to the input terminal of the operational amplifier (for example, the diode D1 in the embodiment);TransistorFrom the collectorThe output of the operational amplifierInput terminalAnd a feedback circuit for negative feedback.
[0023]
  With such a configuration, the output of the operational amplifier turns off the transistor when the ambient temperature is lower than the set temperature.Disconnect the power supply and fan.WithSince the reverse voltage is applied to the diode and the feedback circuit is turned off, the output of the operational amplifier keeps the transistor off.. When the ambient temperature is higher than the set temperature, the operational amplifier output turns on the transistor.Connect the power supply and fanWithdiodeThe forward voltage isAppliedFeedback circuit is onBy beingNegative feedback worksKiThe fan circuit is proportional to the ambient temperature by the amplifier circuit.Applied voltageTherefore, the fan can be driven at a rotational speed proportional to the ambient temperature. Therefore, if the ambient temperature is low and it is not necessary to drive the fan, turn off the power supply and stop the fan. If the ambient temperature rises and the fan needs to be driven, supply power to the fan and And the rotation speed of the fan is controlled by adjusting the supply voltage so as to obtain an air volume corresponding to the temperature, so that silence and energy saving by driving the fan can be improved.
[0024]
  In addition,The reference voltage circuitPower supply to fan by amplifier circuitFrom powerIt is preferable to have a hysteresis circuit that lowers the set temperature by lowering the reference voltage when is supplied.According to such a configuration, the set temperature drops at the moment when the ambient temperature rises and the power is supplied to the fan. Can be supplied.
[0025]
  The feedback circuit preferably includes a Zener diode having a cathode connected to the cathode of the diode and an anode connected to the input terminal between the diode and the input terminal of the operational amplifier. With such a configuration, the voltage applied to the fan can be higher than the reference voltage by the breakdown voltage of the Zener diode, so even if the fan operating range specification is higher than the reference voltage, this fan Can be operated.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. First, the fan unit 12 to which the fan drive control circuit according to the present invention is applied will be described with reference to FIGS. FIG. 2 shows a board 10 on which a fan drive control circuit according to the present invention is mounted, a cooling fan 5 and a power cable 11 connected to the board 10. A fan drive control circuit, which will be described later, is mounted on the substrate 10, and only the thermistor Rt is shown in FIG. The board 10 is provided with a socket 10a for connecting to the power supply terminal 5a of the cooling fan 5 and a socket 10b for connecting to the terminal 11a of the power cable 11. In this embodiment, the thermistor Rt is arranged on the substrate 10, but it is also possible to arrange the thermistor Rt by pulling out leads to other measurement points.
[0027]
FIG. 3 shows a case where the board 10 on which the fan drive control circuit according to the present invention is mounted is mounted on the fan unit 12. As shown in FIG. 3 (A), the fan unit 12 has a substrate 10, a cooling fan 5 and a power cable 11 arranged integrally. As shown in FIG. 3 (B), the fan unit 12 is mounted on a rack 13, for example. used. In FIG. 3A, the power cable 11 is provided with a unit attaching / detaching connector 11b, and when mounted on a rack or the like, power is supplied from the unit attaching / detaching connector 11b to the fan unit 12. FIG. 3B shows a case where four sets of fan units 12 (12 a to 12 d) are mounted on the rack 13. In the present embodiment, the case where the fan drive control circuit according to the present invention is applied to the fan unit 12 to be mounted on the rack 13 has been described, but the present invention is not limited to this form.
[0028]
【Example】
Next, an embodiment of the fan drive control circuit will be described with reference to the drawings.
[0029]
[First embodiment]
FIG. 1 is a circuit diagram showing a configuration of a first embodiment of a fan drive control circuit according to the present invention. The fan drive control circuit 1 includes a temperature detection circuit 2 that outputs a temperature-corresponding voltage Vt corresponding to the ambient temperature, a reference voltage circuit 3 that outputs a reference voltage Vref corresponding to a set temperature, a temperature-corresponding voltage Vt and a reference voltage Vref. And a first power source 6 having an output voltage + V1 and a second power source 7 having an output voltage + V2, and the output of the amplifier circuit 4 is cooled as a power source. It is supplied to the fan 5.
[0030]
The temperature detection circuit 2 is configured by connecting a thermistor Rt and a resistor Rb in series, one end of the thermistor Rt is connected to the first power supply 6, one end of the resistor Rb is grounded, and the thermistor Rt and the resistor Rb are connected. Is connected to the output terminal 2a, and the voltage of the resistor Rb is output from the output terminal 2a as a temperature-corresponding voltage Vt corresponding to the ambient temperature of the thermistor. A thermistor is a semiconductor made by combining several oxides of manganese, cobalt, etc. and baking at a high temperature of about 1500 ° C. The temperature of the thermistor is measured using the property that the resistance value of this semiconductor changes greatly with temperature. An element used in a circuit or the like. In general, a negative resistance thermistor whose resistance value decreases with increasing temperature is used, and it can be handled in the same manner as a resistor and is easy to handle.
[0031]
Here, the temperature-corresponding voltage Vt output from the temperature detection circuit 2 will be described with reference to FIG. 4A is the same as the temperature detection circuit 2 shown in FIG. 1, and the output voltage Vs when the output terminal 2a of the temperature detection circuit 2 is opened and the resistance Rs of the circuit viewed from the output terminal 2a. Is expressed by the following equations (1) and (2).
[0032]
[Expression 1]
Vs = + V1 · Rb / (Rt + Rb) (1)
Rs = Rt · Rb / (Rt + Rb) (2)
[0033]
Therefore, according to Thevenin's theorem, the temperature detection circuit 2 in FIG. 4A can be replaced with the equivalent circuit 2 ′ in FIG. 4B. When the above-described negative resistance thermistor is used as the thermistor Rt, the temperature is When the temperature rises, the resistance value of the thermistor Rt falls and Vs rises according to the equation (1). Therefore, the temperature detection circuit 2 can be obtained in which the temperature corresponding voltage Vt rises when the temperature rises. If the thermistor Rt and the resistor Rb of the temperature detection circuit 2 are interchanged, the temperature-corresponding voltage Vt can be decreased when the temperature rises, and a fan drive control circuit corresponding to the temperature detection circuit having such a configuration can be realized. Needless to say. In this embodiment, the thermistor Rt is used to configure the temperature detection circuit 2. However, the present invention is not limited to this element, and an element or output whose resistance value changes according to a change in temperature. Any circuit that changes voltage can be used as the temperature detection circuit 2.
[0034]
The reference voltage circuit 3 is configured by connecting a resistor R1 and a resistor R2 in series, one end of the resistor R1 is connected to the first power source 6, one end of the resistor R2 is grounded, and the resistors R1, R2 Is connected to the output terminal 3a. The voltage + V1 of the first power supply 6 is divided by the resistors R1 and R2, and the voltage of the resistor R2 is output from the output terminal 3a as the reference voltage Vref. The voltage Vr when the output terminal 3a of the reference voltage circuit 3 is opened and the resistance Rr viewed from the output terminal 3a are expressed by the following equations (3) and (4). It can be replaced with an equivalent circuit by Vr and resistor Rr (not shown).
[0035]
[Expression 2]
Vr = + V1 · R2 / (R1 + R2) (3)
Rr = R1 · R2 / (R1 + R2) (4)
[0036]
The reference voltage Vref output from the reference voltage circuit 3 is a voltage corresponding to the temperature at which the cooling fan 5 is started or stopped in the fan drive control circuit 1. In the following, it is referred to as “set temperature”) by adjusting the values of the resistors R1 and R2 so that the temperature corresponding voltage Vt of the temperature detection circuit 2 and the reference voltage Vref have the same value.
[0037]
The amplifier circuit 4 includes an operational amplifier U1, a PNP transistor Q1, resistors Rf, R3, R4, a capacitor Cf, diodes D1, D2, and a Zener diode Dz. The operational amplifier U1 has a positive power supply terminal connected to the second power supply 7 and a negative power supply terminal grounded. The output terminal 3a of the reference voltage circuit 3 is connected to the positive phase input terminal of the operational amplifier U1, the output terminal 2a of the temperature detection circuit 2 is connected to the negative phase input terminal, and the output terminal is connected to the resistor R4. To the base of the transistor Q1. A capacitor Cf is connected by connecting the negative phase input terminal and the output terminal of the operational amplifier U1. Here, the resistor R4 is a current limiting resistor for preventing an excessive current from flowing through the output terminal of the operational amplifier U1 and the base of the transistor Q1, and the capacitor Cf has a phase around by a combination of the operational amplifier U1 and the transistor Q1. This is a phase compensation capacitor for performing phase compensation when an oscillation phenomenon occurs. The operational amplifier U1 has a sufficient phase margin, and the capacitor Cf may be omitted as long as the feedback does not result in oscillation around the phase of the transistor Q1.
[0038]
  A second power supply 7 is connected to the base of the transistor Q1 via a resistor R3, a second power supply 7 is connected to the emitter via a diode D2, and a collector is connected to one end of a power supply input terminal of the cooling fan 5. And with these elementsEmitterA grounded amplifier is formed. The other end of the power input terminal of the cooling fan 5 is grounded, and the diode D2 is arranged in such a direction that its cathode is connected to the emitter of the transistor Q1. Here, the resistor R3 is for bias applied to the base of the transistor Q1, and may be omitted if the output of the operational amplifier U1 is not open. The diode D2 is for adding an offset so that the output voltage of the operational amplifier U1 becomes a base voltage for completely turning off the transistor Q1, and the forward direction of the diode D2 is added to the original base-emitter voltage of the transistor Q1. By adding the voltage drop to the base-emitter voltage of the transistor Q1 viewed from the operational amplifier U1, the transistor Q1 can be turned on even when the output voltage of the operational amplifier U1 is slightly lower than the voltage + V2 of the second power supply 7. It can be turned off. Therefore, if the output of the operational amplifier U1 can output up to the voltage + V2 of the second power supply 7 applied to the positive power supply terminal (if it is a Rail-to-Rail operational amplifier), the diode D2 The diode D2 may need to be increased depending on the characteristics of the maximum output voltage of the operational amplifier U1.
[0039]
  The feedback circuit 4a is connected so as to connect the collector of the transistor Q1 and the positive phase input terminal of the operational amplifier U1. The feedback circuit 4a includes a diode D1, a resistor Rf, and a Zener diode Dz in order from the collector side of the transistor Q1. Connected in series. The diode D1 is connected so that the direction in which the output of the transistor Q1 is fed back to the positive phase input terminal of the operational amplifier U1 is the forward direction (the anode of the diode D1 is connected to the collector of the transistor Q1). Has an anode connected to the positive phase input terminal of the operational amplifier U1. PNP transistor Q1EmitterSince it is configured as a grounded amplifier, by operating the base voltage of the transistor Q1 to turn on / off the transistor Q1, the transistor Q1 is operated as a switch for turning on / off the power supplied to the cooling fan 5, and at the same time When Q1 is in the on state, its output is a current buffer that acts as an amplifier whose phase is inverted, similar to an inverting amplifier. Accordingly, the amplifier circuit 4 (the output from the collector of the transistor Q1) is negatively fed back to the positive phase input terminal of the operational amplifier U1 by the feedback circuit 4a, so that the amplifier circuit 4 has a large combination of the operational amplifier U1 and the transistor Q1. Since it operates as an output current type inverting amplifier, when the transistor Q1 is on and power is supplied to the cooling fan 5, it is proportional to the difference between the temperature-corresponding voltage Vt of the temperature detector 2 and the reference voltage Vref. The voltage output with the amplification set by the resistors R1, R2, and Rf is supplied to the cooling fan 5.
[0040]
  In the fan drive control circuit 1 configured as described above, when the ambient temperature of the thermistor Rt is lower than the set temperature, the difference between the temperature-corresponding voltage Vt and the reference voltage Vref is positive, so the output of the operational amplifier U1 is high. Voltage (positive power supply terminalAppliedOutput voltage + V2 of the second power supply 7 that is approximately equal to or slightly lower than the output voltage + V2 of the second power source 7) and the base of the transistor Q1AppliedTherefore, the potential difference between the base and emitter of the transistor Q1 disappears, no current flows through the base of the transistor Q1, and the transistor Q1 is turned off. For this reason, no current flows between the emitter and the collector, and power is not supplied to the cooling fan 5, so that it is stopped.(That is, the second power supply 7 and the cooling fan 5 are disconnected). When the transistor Q1 is in an off state, no current flows through the feedback circuit 4a, so negative feedback via the feedback circuit 4a does not work, and the operational amplifier U1 operates as a so-called comparator. The output maintains the high voltage described above. Further, the diode D1 of the feedback circuit 4a prevents a current from flowing from the reference voltage circuit 3 toward the cooling fan 5 because a reverse voltage is applied to the diode D1 when the transistor Q1 is off. The power supply from the reference voltage circuit 3 to the cooling fan 5 via the feedback circuit 4a is prevented. Further, in the absence of the diode D1, when a current flows through the feedback circuit 4a, the output voltage Vref of the reference voltage circuit 3 fluctuates and cannot be used as a reference voltage. It is also inserted to prevent fluctuations in Vref.
[0041]
  When the ambient temperature of the thermistor Rt rises and becomes equal to the set temperature, the difference between the temperature-corresponding voltage Vt and the reference voltage Vref becomes 0V, so that the output voltage of the operational amplifier U1 decreases and the same voltage as the reference voltage Vref is output. For this reason, a potential difference is generated between the base and emitter of the transistor Q1, a current flows through the base of the transistor Q1 to turn on, and a current also flows between the emitter and collector to supply power to the cooling fan 5.(That is, the second power source 7 and the cooling fan 5 are connected). When the transistor Q1 is turned on, a forward voltage is applied to the diode D1, so that a current also flows through the feedback circuit 4a, and the amplifier circuit 4 operates as an inverting amplifier as described above. Therefore, when the ambient temperature of the thermistor Rt is equal to or higher than the set temperature and the difference between the temperature-corresponding voltage Vt and the reference voltage Vref is 0 V or negative, the temperature is amplified in proportion to the difference between the temperature-corresponding voltage Vt and the reference voltage Vref. Since the voltage is supplied to the cooling fan 5, the cooling fan 5 can be operated at a rotational speed proportional to the ambient temperature of the thermistor Rt.
[0042]
  The Zener diode Dz of the feedback circuit 4a is connected to the cooling fan 5 when the temperature is higher than the set temperature.AppliedThis is to make the initial value of the applied voltage higher than the reference voltage Vref. This is because the Zener diode Dz is connected in the direction opposite to the feedback direction of the feedback circuit 4a, and the voltage at which current flows to the feedback circuit 4a is applied to the cooling fan 5.AppliedThis is because the applied voltage is higher than the reference voltage Vref by the breakdown voltage (zener voltage) of the Zener diode Dz. Therefore, the Zener diode Dz is added when the specification of the operating range of the cooling fan 5 is too low for the reference voltage Vref due to various settings. If the reference voltage Vref is within the operating range of the cooling fan 5, there is no May be.
[0043]
  The transistor Q1 constituting the amplifier circuit 4 uses a PNP type, which is for increasing the supply voltage to the cooling fan 5 to widen the operating range. In this fan drive control circuit 1, an NPN type transistor can be used as the transistor Q1, but in this case, the voltage supplied to the cooling fan 5 is applied to the base of the transistor Q1.AppliedThe voltage from the applied voltage (the output voltage of the operational amplifier U1) to a voltage lower by the base-emitter voltage of the transistor Q1 is supplied. However, when a PNP type is used as in this embodiment, the voltage supplied to the cooling fan 5 is the second power supply when the Rail-to-Rail operational amplifier U1 that does not require the diode D2 is used. 7 to the voltage obtained by subtracting the collector-emitter saturation voltage from the voltage + V2, and the operating range of the cooling fan 5 can be widened.
[0044]
As described above, since the fan drive control circuit 1 according to the first embodiment can finely control the drive of the cooling fan 5, the quietness and energy saving performance of the cooling fan 5 are improved, and this fan drive is performed. All of the components constituting the control circuit 1 are generally widely available analog elements that are easily available, and the circuit configuration is simple, so that they can be manufactured at low cost.
[0045]
[Second embodiment]
FIG. 5 is a circuit diagram showing a second embodiment of the fan drive control circuit according to the present invention. The fan drive control circuit 1a according to the second embodiment has the fan drive control circuit 1 according to the first embodiment as a basic circuit, and a hysteresis circuit 3b is added to the reference voltage circuit 3 of the fan drive control circuit 1 as the basic circuit. The switch circuit 8 is added. Therefore, the description of the temperature detection circuit 2, the amplifier circuit 4, and the feedback circuit 4a which are the same as those in the first embodiment is omitted. In the fan drive control circuit 1a, the resistor RI connected in parallel to the cooling fan 5 is inserted so that the power supply end to the cooling fan 5 is securely grounded when the cooling fan 5 is not connected. The basic circuit is unnecessary and may be omitted.
[0046]
The hysteresis circuit 3b includes an NPN transistor Q2 and resistors Rh, R5, and R6. The resistors R5 and R6 are connected in series, one end of R5 is connected to the collector of the transistor Q1, and one end of R6 is grounded. The connection point of the resistors R5 and R6 is connected to the base of the transistor Q2. The collector of the transistor Q2 is connected to the connection point (output terminal) 3a of the resistor R1 and the resistor R2 so as to be in parallel with the resistor R2 of the reference voltage circuit 3 via the resistor Rh. The emitter is grounded.
[0047]
  According to such a configuration, as described in the first embodiment, when the ambient temperature of the thermistor Rt is lower than the set temperature, the transistor Q1 is in an off state, so that no power is supplied to the cooling fan 5, The voltage is also applied to the base of the transistor Q2 of the hysteresis circuit 3b.AppliedSince there is no potential difference between the base and emitter of the transistor Q2, no base current flows. Therefore, the transistor Q2 is in the off state, and no current flows between the collector and the emitter of the transistor Q2, so that no current flows through the resistor Rh. Therefore, the reference voltage circuit 3 is divided by the resistors R1 and R2, and the resistor Rh The voltage of R2 is output as the reference voltage Vref.
[0048]
When the ambient temperature of the thermistor Rt rises and exceeds the set temperature, the transistor Q1 is turned on, so that power is supplied to the cooling fan 5, thereby generating a potential difference between the base and emitter of the transistor Q2, and resistance. A current flows into the base of the transistor Q2 via R5, and the transistor Q2 is turned on. Note that the resistor R6 is used for protecting the base of the transistor Q2, but it is not necessary for the circuit operation. When the transistor Q2 is turned on, a current flows between the collector and the emitter of the transistor Q2, and as a result, a current flows from the first power supply 6 to the resistor Rh via the resistor R1. Since the resistor Rh is connected in parallel with the resistor R2 of the reference voltage circuit 3, the reference voltage Vref corrected by the resistor Rh is divided by the resistor R1, the resistors R2 and Rh, and a parallel circuit of the resistors R2 and Rh. However, since the combined resistance of the resistors R2 and Rh connected in parallel has a value smaller than that of the resistor R2, the corrected reference voltage Vref is lower than the reference voltage Vref before correction. Lowering the reference voltage Vref means lowering the set temperature at which power supply to the cooling fan 5 is stopped. Note that the transistor Q2 operates as a switch that causes a current to flow through the resistor Rh when power is supplied to the cooling fan 5 as described above. Therefore, the transistor Q2 can also be realized using other components. It is.
[0049]
  In FIG.Round numbers 1-4The figure showing the relationship of the supply voltage to the cooling fan 5 when raising and lowering the ambient temperature of the thermistor Rt in this order is shown. Thus, the temperature when the temperature rises and the power is supplied to the cooling fan 5 becomes the reference voltage determined by the resistors R1 and R2, but when the power is supplied to the cooling fan 5, the resistors R1, R2, and R2 are supplied. Since the reference voltage is determined by Rh, the set temperature isFallingThe relationship between the temperature and the voltage supplied to the cooling fan 5 forms a hysteresis loop. Since the voltage supplied to the cooling fan 5 is the output voltage + V2 supplied from the second power supply 7, a voltage higher than that is supplied to the cooling fan 5.Applied(In reality, there is a voltage drop due to the diode D2, the transistor Q1, etc., so the value is smaller than the voltage + V2.)
[0050]
When power is turned on to the electronic device on which the fan drive control circuit 1a according to the second embodiment is mounted and the ambient temperature of the thermistor Rt rises and reaches a set temperature, power is supplied to the cooling fan 5 and the cooling fan 5 Since it is driven, an air flow is generated, and the ambient temperature of the thermistor Rt is lowered. Without this hysteresis circuit 3b, the cooling fan 5 may stop as soon as the ambient temperature of the thermistor Rt decreases, and the ambient temperature may increase repeatedly, so that it is supplied to the cooling fan 5 near the set temperature. The power supply is frequently turned on / off, the operation becomes unstable, and there is a possibility that the life of the fan drive control circuit 1a and the cooling fan 5 is shortened and the power consumption is increased. On the other hand, when the hysteresis circuit 3b is mounted, the set temperature decreases when the temperature reaches the set temperature and the cooling fan 5 is turned on. Does not repeat the on / off operation, and can perform a stable operation.
[0051]
Similarly, when the ambient temperature drops and the power supply to the cooling fan 5 stops, the transistor Q2 of the hysteresis circuit 3b is turned off, and the set temperature becomes the original value (value determined by the resistors R1 and R2 of the reference voltage circuit 3). Therefore, the power supply of the cooling fan 5 is not repeatedly turned on / off in the vicinity of the temperature at which the power supply is cut off. The advantage of the hysteresis circuit 3b is that the hysteresis circuit 3b is added to the negative feedback side instead of being configured to affect the output of the temperature detection circuit 2 by feeding back to the terminal that becomes the positive feedback. The function can be added without affecting the basic circuit shown. With this configuration, the temperature-corresponding voltage Vt, which is the output of the temperature detection circuit 2, is output only corresponding to the change in the resistance value of the thermistor Rt, so that this output can be used for other circuits without any problem. Is possible.
[0052]
  The switch circuit 8 including a transistor (P-channel MOSFET) Q3, resistors R7 and R8, and a switch 8a is a circuit for directly supplying power supplied to the cooling fan 5 from the second power supply 7. It is added if necessary as an emergency operation. The source of the transistor Q3 of the switch circuit 8 is connected to the second power supply 7 (the substrate is connected to the source), and the power supply input terminal of the cooling fan 5 to which the collector of the transistor Q1 is connected is connected to the power supply input terminal of the transistor Q3. The drain is connected. The resistors R7 and R8 are connected in series, one end of the resistor R7 is connected to the second power supply 7, one end of the resistor R8 is connected to the switch 7a, and the connection point between the resistors R7 and R8 is the transistor Q3. Connected to the gate. When the switch 8a is turned on in an emergency or when it is not necessary to control the voltage supplied to the cooling fan 5 by controlling the transistor Q1, the voltage + V2 of the second power source 7 is divided by the resistors R7 and R8. The voltage of the resistor R8 is applied to the gate of the transistor Q3.AppliedTherefore, the transistor Q3 is turned on, and the second power supply 7 is directly supplied to the cooling fan 5. Since the transistor Q1 is a PNP type, the switch circuit 8 switches the transistor Q1 to the transistor Q1.AppliedThere is no need to consider the reverse breakdown voltage due to the applied voltage.
[0053]
As described above, similarly to the first embodiment, the fan drive control circuit 10 according to the second embodiment can finely control the driving of the cooling fan 5, and even if the ambient temperature of the thermistor Rt is near the set temperature, By adding the hysteresis circuit 3b to the reference voltage circuit 3, it is possible to operate stably. In addition, since the components constituting the fan drive control circuit 10 are generally composed of widely used analog elements and the circuit configuration is simple, the fan drive control circuit 10 can be manufactured at low cost.
[0054]
In the first and second embodiments described above, the first and second power sources 6 and 7 are separate power sources, but can be supplied from the same power source. However, since the noise due to the rotation of the cooling fan 5 has a low frequency component and a large value, the noise is supplied to the temperature detection circuit 2 and the reference voltage circuit 3 in order to operate the fan drive control circuit 1 stably. The first power source 6 is preferably separated as a noise-free power source via a stabilization circuit or the like.
[0055]
  When the first and second power sources 6 and 7 are supplied from the same power source, a three-terminal regulator U2 is connected as shown in FIG.AppliedIt is also possible not to do so. The three-terminal regulator U2 is an element that acts to keep the output voltage constant even when the input voltage or the output current changes. FIG. 7A shows the fan drive control circuit 1 shown in the first embodiment. FIG. 7B shows an example of a fan drive control circuit 1b configured by connecting a terminal regulator U2, and FIG. 7B shows a fan drive configured by connecting a three-terminal regulator U2 to the fan drive control circuit 1a shown in the second embodiment. It is an example of the control circuit 1c. In any case, the second power supply 7 as a power supply to be supplied to the cooling fan 5 is connected to the IN terminal of the three-terminal regulator, the first power supply 6 is connected to the OUT terminal of the three-terminal regulator U2, and the GND terminal Is grounded, and power is supplied from the second power source 7. The three-terminal regulator is available at low cost, and the fan drive control circuit according to the present invention can be manufactured at low cost.
[0056]
Conventionally, when controlling such a cooling fan, a relatively expensive fan unit with a sensor has been used. However, the fan drive control circuit according to the present invention as shown in the first embodiment or the second embodiment is used. Since it can be realized by combining with a normal cooling fan, it is advantageous in terms of cost, availability, and the like.
[0057]
【The invention's effect】
The fan drive control circuit according to the present invention includes a temperature detection element whose resistance value changes according to the ambient temperature, and outputs a temperature-corresponding voltage corresponding to the resistance value of the temperature detection element. The circuit includes a reference voltage circuit that outputs a reference voltage corresponding to the set temperature, and an amplifier circuit that compares and amplifies the difference between the temperature-corresponding voltage and the reference voltage. The amplifier circuit compares the temperature-corresponding voltage with a reference voltage and amplifies the difference, a transistor that amplifies the output of the operational amplifier, and a feedback that negatively feeds back the output of the transistor to the input of the operational amplifier. And a rectifier connected so that the direction of feedback to the feedback circuit is the forward direction, the fan is stopped when the ambient temperature of the temperature detection element is lower than the set temperature. When the temperature is equal to or higher than the set temperature, the fan is driven, and the rotation speed of the fan can be controlled in proportion to the temperature. Therefore, by finely controlling the drive control of the fan, quietness and energy saving can be improved, the circuit configuration is simple, and analog elements that are generally widely used can be used, so it is easy to obtain, It can be provided at low cost.
[0058]
In addition, when power is supplied to the fan, the fan is turned on / off by adding a hysteresis circuit that reduces the set temperature by lowering the reference voltage output from the reference voltage circuit to the reference voltage circuit. The operation of the drive control circuit can be made more stable. Of course, the fan drive control circuit to which this hysteresis circuit has been added has a simple circuit configuration and can be easily obtained because it can be configured by analog elements that are generally widely used, and can be provided at low cost.
[Brief description of the drawings]
FIG. 1 is a circuit diagram of a first embodiment of a fan drive control circuit according to the present invention.
FIG. 2 is a diagram showing a board on which a fan drive control circuit according to the present invention is mounted.
FIG. 3 is a configuration example of a fan unit equipped with a fan drive control circuit according to the present invention, (A) is a plan view of the fan unit, and (B) is a case where the fan unit is mounted on a rack. FIG.
4A and 4B are diagrams for explaining the operation of the temperature detection circuit. FIG. 4A is a circuit diagram of the temperature detection circuit according to the present invention, and FIG. 4B is an equivalent circuit thereof.
FIG. 5 is a circuit diagram of a second embodiment of the fan drive control circuit according to the present invention.
FIG. 6 is a graph showing a change in fan supply voltage when the temperature is changed in the second embodiment of the fan drive control circuit according to the present invention;
7 is a circuit diagram when the same power is supplied to the fan drive control circuit according to the present invention, and FIG. 7A is a circuit diagram showing a case where a three-terminal regulator is added to the first embodiment; B) is a circuit diagram showing a case where a three-terminal regulator is added to the second embodiment.
FIG. 8 is a circuit diagram of a conventional fan drive control circuit that changes the rotational speed of the fan according to temperature.
FIG. 9 is a circuit diagram of a conventional fan drive control circuit for turning on / off a fan according to temperature.
FIG. 10 is a circuit diagram of a conventional fan drive control circuit that switches the rotational speed of the fan to two stages of low speed and high speed depending on the temperature.
[Explanation of symbols]
1 Fan drive control circuit
2 Temperature detection circuit
3 Reference voltage circuit
3b Hysteresis circuit
4 Amplifier circuit
4a Feedback circuit
5 Cooling fan (fan)
Rt thermistor (temperature detection element)
D1 Diode (rectifier)
U1 operational amplifier
Q1 transistor

Claims (3)

  1. A temperature detection circuit that has a temperature detection element whose resistance value changes corresponding to the ambient temperature and outputs a temperature corresponding voltage corresponding to the resistance value of the temperature detection element, and a reference that outputs a reference voltage corresponding to the set temperature a voltage circuit, is composed of an amplifying circuit for amplifying the difference by comparing the reference voltage and the temperature-dependent voltage, a fan drive control circuit for driving the fan by the output of the amplifier circuit,
    The amplifier circuit is
    Is connected to the output terminal of the output end and the reference voltage circuit of the temperature detection circuit to the input terminal, an operational amplifier for outputting from the output terminal to amplify the difference by comparing the reference voltage and the temperature-dependent voltage,
    A PNP type transistor having a base connected to the output terminal of the operational amplifier, an emitter connected to a power source, and a collector connected to the fan ;
    A feedback having a diode having an anode connected to the collector of the transistor and a cathode connected to the input terminal of the operational amplifier, and negatively feeding back an output from the collector of the transistor to the input terminal of the operational amplifier Circuit and
    When the ambient temperature is lower than the set temperature, the output of the operational amplifier turns off the transistor to disconnect the power source and the fan, and a reverse voltage is applied to the diode to turn off the feedback circuit. Therefore, the state where the output of the operational amplifier keeps the transistor off,
    When the ambient temperature is equal to or higher than the set temperature, the output of the operational amplifier turns on the transistor to connect the power supply and the fan, and a forward voltage is applied to the diode to turn on the feedback circuit. -out negative feedback work by being, fan drive control circuit, characterized in that changing the voltage applied to the fan in proportion to the ambient temperature by the amplifier circuit.
  2. The said reference voltage circuit has a hysteresis circuit which lowers | hangs the said reference voltage and reduces the said preset temperature, when the electric power is supplied to the said fan from the said power supply by the said amplifier circuit. Fan drive control circuit.
  3. The feedback circuit includes a Zener diode having a cathode connected to the cathode of the diode and an anode connected to the input terminal between the diode and the input terminal of the operational amplifier. 3. The fan drive control circuit according to 1 or 2.
JP2002270239A 2002-09-17 2002-09-17 Fan drive control circuit Expired - Fee Related JP3773245B2 (en)

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US7202624B2 (en) * 2004-04-30 2007-04-10 Minebea Co., Ltd. Self calibrating fan
CN100462896C (en) * 2004-05-19 2009-02-18 鸿富锦精密工业(深圳)有限公司 CPU working voltage adjustment system
JP4703141B2 (en) * 2004-07-22 2011-06-15 株式会社荏原製作所 Polishing apparatus, substrate processing apparatus, and substrate jumping detection method
CN100380340C (en) * 2005-04-30 2008-04-09 华硕电脑股份有限公司 Temperature detecting and control circuit
JP5060422B2 (en) * 2008-08-05 2012-10-31 キヤノン株式会社 Printed wiring board and apparatus having the printed wiring board
CN102042250B (en) * 2009-10-20 2015-04-15 淮南东正电子科技有限公司 Fan control system
JP2013135984A (en) * 2013-04-11 2013-07-11 Fujishoji Co Ltd Game machine
CN103982455B (en) * 2014-05-25 2016-08-31 姜智康 The fan temperature control speed governing circuit of operating point easy to set up

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