US20020197068A1 - Speed control circuit of brushless DC fan motor - Google Patents

Speed control circuit of brushless DC fan motor Download PDF

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Publication number
US20020197068A1
US20020197068A1 US10/178,732 US17873202A US2002197068A1 US 20020197068 A1 US20020197068 A1 US 20020197068A1 US 17873202 A US17873202 A US 17873202A US 2002197068 A1 US2002197068 A1 US 2002197068A1
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United States
Prior art keywords
input terminal
differential amplifier
brushless
control circuit
speed
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
Application number
US10/178,732
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English (en)
Inventor
Junnan Xi
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Minebea Co Ltd
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Minebea Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Minebea Co Ltd filed Critical Minebea Co Ltd
Assigned to MINEBEA CO., LTD. reassignment MINEBEA CO., LTD. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: XI, JUNNAN
Publication of US20020197068A1 publication Critical patent/US20020197068A1/en
Priority to US10/782,809 priority Critical patent/US6879120B2/en
Abandoned legal-status Critical Current

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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P6/00—Arrangements for controlling synchronous motors or other dynamo-electric motors using electronic commutation dependent on the rotor position; Electronic commutators therefor
    • H02P6/08—Arrangements for controlling the speed or torque of a single motor

Definitions

  • the present invention relates to a brushless DC fan motor suitable for a fan radiating heat from a housing of an electronic appliance, and more particularly to a speed control circuit thereof.
  • a ventilation hole is provided in a wall or a ceiling of the housing, and a fan motor is mounted on the ventilation hole so as to radiate heat outside of the housing.
  • FIG. 2 shows a speed control circuit of a conventional brushless DC fan motor meeting this request.
  • numeral 21 denotes the speed control circuit of the brushless DC fan motor (circuit) 22 .
  • the two-phase motor 22 is employed here.
  • the brushless DC fan motor 22 comprises field coils L 1 and L 2 , switching elements SW 1 and SW 2 , Zener diodes ZD 1 and ZD 2 , resistors R 1 to R 4 , a diode D 1 and a drive circuit 22 a.
  • the field coils L 1 and L 2 are mounted on a stator (not shown) and electrified in an alternately switching manner to form the rotating magnetic field by the switching elements SW 1 and SW 2 alternately turning ON/OFF by the control signal from the drive circuit 22 a .
  • a rotor (not shown) is rotated by rotating a permanent magnet mounted thereon following the above rotating magnetic field.
  • the position signals S 1 and S 2 from a sensor to detect the position of rotation of the rotor are inputted in the drive circuit 22 a as the timing signal of switching and electrifying the field coils L 1 and L 2 .
  • the speed control circuit 21 comprises resistors R 5 to R 10 and an NPN transistor Q 1 .
  • the signal (PWM signal) in which the temperature in a housing for an OA appliance (not shown) is Pulse-Width Modulated (PWM), i.e., the signal in which the temperature in the above housing is converted into the pulse width (time) ratio on the H (High) and L (Low) levels of the voltage is inputted as the input signal in an input terminal IN of the speed control circuit 21 .
  • the inverted signal of the above input signal is outputted from an output terminal OUT of the speed control circuit 21 .
  • the speed control circuit 21 either validates or invalidates the control signal to the switching elements SW 1 and SW 2 of the motor 22 in the drive circuit 22 a by the voltage level of the output
  • the speed control circuit 21 validates the above control signal when the voltage Vb of the output terminal OUT (a control input terminal 22 b of the drive circuit 22 a ) is less than a predetermined value (the L-level). As a result, the switching elements SW 1 and SW 2 are alternately turned ON/OFF. When the voltage Vb is not less than the predetermined value (the H-level), the speed control circuit invalidates the above control signal, and turns off the switching elements SW 1 and SW 2 .
  • the driving force is given to the rotor by alternately electing the field coils L 1 and L 2 , or the driving force is not removed from the rotor by shutting off the electrification to the field coils L 1 and L 2 , and the rotational speed of the motor 22 is thus controlled.
  • the L-level time of the input voltage in the drive circuit 22 a i.e., the time in which the above control signal is valid is also increased, the time in which the driving force is continuously given to the rotor (not shown) is increased, and the rotational speed of the motor is thus increased.
  • the heat radiation effect is improved so as to decrease the temperature in the above housing.
  • the PWM signal in which the temperature in the housing is pulse-width modulated is set to be the input signal of the speed control circuit 21 , the drive circuit 22 a can be finely controlled by the ratio of the H-level to the L-level, the speed of the motor 22 can be accurately controlled such that the temperature in the housing can be efficiently adjusted.
  • the PWM signal has been used for the input signal for the following reason. That is, an operational point is established on the voltage level in a rise characteristic curve of the transistor Q 1 when the output voltage is taken out from a collector by using the voltage signal of the continuously changing level for the base input signal of the transistor Q 1 like the temperature detecting output voltage from a thermistor.
  • the transistor Q 1 has a steep but non-linear rinse characteristic, and is difficult to set the above operational point. Thus, it is difficult to improve the accuracy in controlling the speed by either validating or invalidating the control signal to the switching elements SW 1 and SW 2 with a predetermined temperature (the voltage level of the input signal) as a reference.
  • the temperature is expressed by the pulse width, i.e., the length on the time axis, and thus, the above operational point need not be finely set, and the setting thereof can be simplified. Accordingly, the conventional speed control circuit 21 has used the PWM signal for the input signal.
  • the conventional speed control circuit 21 requires an element to convert the original physical quantity used to control the speed, i.e., the temperature here into the electric signal for example, an expensive oscillator for PWM to convert the electric signal into the electric signal in addition to the thermistor, and there occurs a problem, in that the cost required for a circuit of the prestage is considerably increased.
  • an object of the present invention is to provide a speed control circuit of a brushless DC fan motor which can eliminate any expensive elements or circuits of the prestage, control the motor speed at a low cost with high accuracy, and efficiently adjust the temperature in a housing for an electronic appliance especially when applied for radiating heat outside of the housing.
  • a speed control circuit of a brushless DC fan motor driven by a drive circuit, and controlled in the rotational speed thereof by controlling the voltage of a control input terminal of the drive circuit and comprises a differential amplifier in which the voltage signal for controlling the speed is inputted in a first input terminal and the reference voltage signal is inputted in a second input terminal, wherein the differential amplifier is linear in the input-output characteristic, and can set a rise characteristic of a desired gradient, and give the voltage signal from the output terminal of the differential amplifier to the control input terminal of the drive circuit.
  • a speed control circuit of a brushless DC fan motor of the first aspect is characterized in that the reference voltage signal of the differential amplifier is given from a resistance voltage division point of a resistance voltage divider connected between a power source for driving the circuit and the ground, and the resistance of the resistance voltage divider is set to be an appropriate value in order to obtain a desired minimum rotational speed.
  • a speed control circuit of a brushless DC fan motor according to the first or second aspect of the present invention is characterized in that the voltage signal for controlling the speed is inputted in the first input terminal of the differential amplifier via a first resistor for setting the amplification degree, a second resistor for setting the amplification degree is connected between the first input terminal and the output terminal of the differential amplifier, a desired amplification degree is obtained for the differential amplifier by suitably setting the resistance of the first and second resistors for setting the amplification degree, and a desired rate of change in the rotational speed is set.
  • a speed control circuit of a brushless DC fan motor according to any one of the first to third aspects of the present invention is characterized in that the first input terminal and the second input terminal of the differential amplifier are grounded individually via a capacitor.
  • a speed control circuit of a brushless DC fan motor according to any one of the first to fourth aspects of the present invention is characterized in that the voltage signal from the output terminal of the differential amplifier is given to the control input terminal of the drive circuit via a resistor for finely adjusting the rotational speed.
  • a speed control circuit of a brushless DC fan motor according to any one of the first to fifth aspects of the present invention is characterized in that a voltage signal transmission line from the output terminal of the differential amplifier to the control input terminal of the drive circuit is grounded at a desired point via a capacitor.
  • FIG. 1 shows a speed control circuit of a brushless DC fan motor according to a first embodiment of the present invention
  • FIG. 2 shows a speed control circuit of a conventional brushless DC fan motor.
  • FIG. 1 shows a speed control circuit of a brushless DC fan motor according to a first embodiment of the present invention.
  • numeral 11 denotes a speed control circuit of a brushless DC fan motor (circuit) 22 .
  • a two-phase motor 32 is shown here.
  • Symbols +V and +Vcc denote a power source for driving the motor and the speed control circuit, respectively.
  • the above brushless DC fan motor 22 comprises field coils L 1 and L 2 , switching elements SW 1 and SW 2 , Zener diodes ZD 1 and ZD 2 , resistors R 1 to R 4 , a diode D 1 and a drive circuit 22 a.
  • the field coils L 1 and L 2 are mounted on a stator (not shown), and electrified in an alternately switching manner to form the rotating magnetic field by the switching elements SW 1 and SW 2 which are alternately turned ON/OFF by the control signal from the drive circuit 22 a .
  • a rotor (not shown) is rotated by rotating a permanent magnet mounted thereof following the above rotating magnetic field.
  • the position signals S 1 and S 2 from a sensor to detect the position of rotation of the above rotor (the permanent magnet), for example, a Hall element, are inputted in the drive circuit 22 a as the timing signal of switching and electrifying the field coils L 1 and L 2 .
  • the speed control circuit 21 comprises resistors R 11 to R 18 , capacitors C 1 -C 3 , and a differential amplifier AMP.
  • the speed control circuit 21 either validates or invalidates the control signal to the switching elements SW 1 and SW 2 of the motor 22 in the drive circuit 22 a by the voltage level of the output signal therefrom.
  • the speed control circuit 21 validates the above control signal when the voltage level Vb of the output terminal OUT (a control input terminal 22 b of the drive circuit 22 a ) is less than a predetermined value (the L-level). As a result, the switching elements SW 1 and SW 2 are alternately turned ON/OFF. When the voltage level Vb is not less than the predetermined value (the H-level), the speed control circuit invalidates the above control signal, and turns off the switching elements SW 1 and SW 2 .
  • the differential amplifier AMP is linear in the input-output characteristic and easy in setting the rise characteristic (the amplification degree) of a desired gradient, and comprises an operational amplifier.
  • the voltage signal Vi for controlling the rotational speed of the motor which is inputted in an input terminal IN is inputted in an inverting input terminal ⁇ of the differential amplifier (the operational amplifier) AMP via the resistor R 13 .
  • the reference voltage signal Va with the voltage level set by the resistance voltage dividers (the resistors R 11 and R 12 ) connected between the above power source +Vcc and the ground is inputted in a non-inverting input terminal + of the differential amplifier AMP via the resistor R 14 .
  • the above control voltage signal Vi is the voltage signal with the level thereof continuously changed according to the temperature in a housing of an OA appliance, for example, the temperature detecting output voltage signal by a thermistor (not shown).
  • the reference voltage signal Va is the voltage corresponding to the preset temperature of detection, in other words, the voltage corresponding to the minimum rotational speed, and the minimum rotational speed of the motor 22 corresponding to the predetermined temperature of detection is set by the set value of this voltage.
  • the resistor R 15 is a resistor to set the amplification degree (the gradient of the rise characteristic) of the differential amplifier AMP, in other words, the rate of change of the rotational speed of the motor 22 together with the resistor R 13 , and connected by the inverting input terminal ⁇ and the output terminal of the differential amplifier AMP.
  • the resistors R 16 and R 17 are resistors to set the voltage of the control input terminal 22 b of the drive circuit 22 a at a predetermined voltage level.
  • the output signal Vo of the speed control circuit 21 controls the voltage level Vb of the output terminal OUT in a predetermined range with the voltage set by the above resistors R 16 and R 17 as the reference.
  • the resistors R 13 and R 14 are set to be the same resistance. Symbols R 13 and R 14 also denote each resistance thereof, and symbols Vi and Va also denote each voltage level) thereof.
  • Vo ⁇ ( Vi ⁇ Va ) ⁇ ( R 13/ R 15) ⁇ (1)
  • Vb ⁇ Va ( R 13/ R 15) ⁇ Vi+Va ( R 13/ R 15) (2)
  • the resistor R 18 is inserted between an output terminal o of the differential amplifier AMP and the above control input terminal 22 b in order to finely adjust the voltage level Vb of the control input terminal 22 b of the drive circuit 22 a , and is valid in finely adjusting the rotational speed of the motor.
  • the capacitor C 1 and the capacitor C 2 are capacitors for removing noise which are inserted between the inverting input terminal ⁇ of the differential amplifier AMP and the ground, and between the non-inverting input terminal + of the differential amplifier AMP and the ground, respectively, and are effective to obtain the stable rotational speed.
  • the capacitor C 3 is a smoothing capacitor connected between the control input terminal 22 b of the drive circuit 22 a and the ground.
  • the capacitor C 3 is not essential in the speed control circuit 11 in accordance with the present invention.
  • the PWM signal can be used for the input signal if this capacitor is added to the speed control circuit.
  • the differential amplifier AMP outputs the voltage signal which is obtained by amplifying the difference in the voltage level between the control voltage signal Vi and the reference voltage signal Va at the amplification degree set by the resistors R 13 and R 15 .
  • the output voltage Vo of the differential amplifier AMP is reverse in polarity to the control voltage signal Vi (refer to the formula (1) above).
  • the switching elements SW 1 and SW 2 of the motor 22 are alternately turned ON/OFF, the field coils L 1 and L 2 are alternately electrified, and the driving force is given to the rotor (not shown).
  • the motor 22 is started or accelerated, and the radiation of heat in the housing is started or increased so as to drop the temperature in the housing.
  • the switching elements SW 1 and SW 2 of the motor 22 are turned off, the electrification to the field coils L 1 and L 2 is shut off, and the driving force on the rotor is removed.
  • the rotor is subjected to the inertial rotation, i.e., the decelerated rotation, the radiation of heat in the housing is gradually reduced, and soon, the rotor is stopped, and the heat radiation is completed.
  • the field coils L 1 and L 2 are alternately electrified, and the driving force is given to the rotor, and the rotor is started or accelerated. As a result, heat is started to be radiated outside of the housing, or the radiation is increased, and the temperature in the housing is dropped. These operations are repeated to efficiently adjust the temperature in the housing to be within a predetermined range.
  • the speed of the motor 22 can be accurately controlled without using any PWM signal for the input signal, and the temperature in the housing can be efficiently adjusted.
  • the above embodiment describes a case in which the speed of the brushless DC fan motor is controlled by detecting the temperature, but the brushless DC fan motor may be controlled by other physical quantities including the humidity and the concentration of the smoke or the gas.
  • the speed control circuit of the brushless DC fan motor in accordance with the present invention has advantages in that any expensive elements or circuits of the presage are unnecessary, the motor speed can be controlled at a low cost with high accuracy, and the temperature in the housing can be efficiently adjusted particularly when the speed control circuit is used for radiating the heat in electronic appliances.
  • the minimum rotational speed, the rate of change of the rotational speed, the fine adjustment of the rotational speed, and the stable rotational speed can be realized by a simple means by adding resistors and/or capacitors, or setting these values.
  • the PWM signal can be used for the input signal.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Control Of Motors That Do Not Use Commutators (AREA)
  • Control Of Positive-Displacement Air Blowers (AREA)
US10/178,732 2001-06-25 2002-06-25 Speed control circuit of brushless DC fan motor Abandoned US20020197068A1 (en)

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Application Number Priority Date Filing Date Title
US10/782,809 US6879120B2 (en) 2001-06-25 2004-02-23 Speed control circuit of brushless DC fan motor

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2001-191385 2001-06-25
JP2001191385A JP2003003990A (ja) 2001-06-25 2001-06-25 ブラシレス直流ファンモータの速度制御回路

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US20040165869A1 (en) * 2003-02-24 2004-08-26 Sunonwealth Electric Machine Industry Co., Ltd. Speed control circuit for a brushless dc motor
US20060074575A1 (en) * 2004-09-24 2006-04-06 Meng-Chih Liu Control circuit of a DC fan motor for start with high voltage and high rotational speed with low voltage
US20060091837A1 (en) * 2004-10-30 2006-05-04 Hon Hai Precision Industry Co., Ltd. Self-startup circuit for DC fan
CN102996485A (zh) * 2012-11-30 2013-03-27 杭州顿力电器有限公司 外转子电子控制式风机的隔离特性调速电路及调速方法
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Cited By (11)

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US20030173916A1 (en) * 2000-05-03 2003-09-18 Horton Inc. Brushless DC ring motor cooling system
US6912353B2 (en) * 2000-05-03 2005-06-28 Horton, Inc. Brushless DC ring motor cooling system
US20050254800A1 (en) * 2000-05-03 2005-11-17 Horton, Inc. Control system for brushless DC ring motor cooling fan
US20040165869A1 (en) * 2003-02-24 2004-08-26 Sunonwealth Electric Machine Industry Co., Ltd. Speed control circuit for a brushless dc motor
US6828748B2 (en) 2003-02-24 2004-12-07 Sunonwealth Electric Machine Industry Co., Ltd. Speed control circuit for a brushless dc motor
US20060074575A1 (en) * 2004-09-24 2006-04-06 Meng-Chih Liu Control circuit of a DC fan motor for start with high voltage and high rotational speed with low voltage
US7089128B2 (en) * 2004-09-24 2006-08-08 Asia Vital Component Co., Ltd. Control circuit of a DC fan motor for start with high voltage and high rotational speed with low voltage
US20060091837A1 (en) * 2004-10-30 2006-05-04 Hon Hai Precision Industry Co., Ltd. Self-startup circuit for DC fan
US7205733B2 (en) * 2004-10-30 2007-04-17 Hong Fu Jin Precision Industry (Shenzhen) Co., Ltd. Self-startup circuit for DC fan
CN102996485A (zh) * 2012-11-30 2013-03-27 杭州顿力电器有限公司 外转子电子控制式风机的隔离特性调速电路及调速方法
WO2024141929A1 (en) * 2022-12-28 2024-07-04 Atomberg Technologies Private Limited A regulator detection system for a bldc fan and method thereof

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JP2003003990A (ja) 2003-01-08
US6879120B2 (en) 2005-04-12
EP1271759A3 (en) 2003-12-17
EP1271759A2 (en) 2003-01-02
US20040164692A1 (en) 2004-08-26
CN1407711A (zh) 2003-04-02

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