Electricity: motive power systems – Reciprocating or oscillating motor – Energizing winding circuit control
Reexamination Certificate
2002-02-21
2004-03-09
Duda, Rina I. (Department: 2837)
Electricity: motive power systems
Reciprocating or oscillating motor
Energizing winding circuit control
C318S434000, C318S254100, C388S800000, C388S806000, C388S815000, C388S821000, C388S822000, C388S915000
Reexamination Certificate
active
06703803
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a fan motor driving circuit and more particularly to a driving circuit for a brushless fan motor.
2. Description of the Prior Art
FIG. 6
shows a conventional driving circuit for a DC brushless fan motor having coils separated by 180 degrees from each other to form a two-phase winding. Reference numerals
1
and
2
denote bias resistors for a hall element
3
for detecting a magnetic pole position of a rotor magnet,
4
denotes a differential amplifier for amplifying an output of the hall element
3
,
5
denotes a conducting current signal generating circuit for receiving an output of the differential amplifier
4
and a signal from a rotary speed varying means
30
, and generating a conducting current signal other than conducting current signals of two phases separated by 180° from each other,
6
and
7
denote buffer resistors,
8
and
9
denotes transistors which receive outputs of the conducting current signal generating circuit
5
and are conducted alternately, and
10
and
11
denote stator windings.
The rotary speed varying means
30
is composed of a rotary pulse generating circuit
31
, a time constant circuit
40
, a comparator
34
, and a rotary speed instructing means
91
composed of a resistor
33
and a variable resistor
32
.
The time constant circuit
40
is composed of a resistor
41
, a capacitor
42
, and a transistor
43
. The rotary speed varying means
30
shapes the output of the differential amplifier
4
into a signal in a shape of rectangular wave and then generates a discharge pulse during a short period of time. The time constant circuit
40
generates a voltage of saw tooth wave form across the capacitor
42
according to a time constant determined by the resistor
41
and the capacitor
42
. This voltage is divided by the resistors
32
and
33
. The comparator
34
operates the conducting current signal generating circuit
5
to energize the stator windings
10
and
11
, when the divided voltage reaches a reference voltage. That is, the conducting current signal generating circuit
5
interrupts the conducting current during a predetermined period of time, when an output of the hall element
3
is generated, so that an effective conducting current is reduced, and that the rotary speed of the fan motor is controlled according to the current interruption time.
In the conventional driving circuit, however, the rotary speed of the fan motor is varied according to the voltage variation of the power source, because no feedback circuit of the rotary speed of the motor is provided, though it is possible to vary the rotary speed of the motor by the variable resistor
32
of the rotary speed instructing means
91
.
The power consumption is increased in proportion to the square of the rotor speed, the temperature becomes high, and the noise is increased remarkably, especially when the voltage of the power source is elevated over the rated voltage.
In order to solve the above problems, it is considered to control the variation of the rotary speed by the speed feed back, however, the circuit becomes complicated and the space and the cost for installing the electronic parts are increased.
SUMMARY OF THE INVENTION
An object of the invention is to provide a fan motor driving circuit which solves the above problems.
Another object of the present invention is to provide a fan motor driving circuit comprising means for detecting a power source voltage and outputting a voltage in proportion to a difference between the power source voltage and a predetermined rated voltage when the power source voltage is elevated over the rated voltage, and means for controlling a rotary speed of a fan motor to a predetermined value by varying an elementary signal for determining the rotary speed of the fan motor according to an output voltage of the power source voltage detecting means automatically when the power source voltage is elevated over a predetermined value.
A further object of the present invention is to provide a brushless fan motor driving circuit comprising means for detecting a position of a permanent magnet of a rotor, a conducting current signal generating circuit for generating a conducting current signal according to an output of the position detecting means, a conducting current control element for energizing stator windings of the motor according to the conducting current signal, means for varying a rotary speed of a fan motor, means for generating a rotary speed instructing voltage, means for detecting a power source voltage and outputting a voltage in proportion to a difference between the power source voltage and a rated voltage when the power source voltage is elevated over a predetermined rated voltage, and means for controlling a rotary speed of a fan motor to a predetermined value by varying the rotary speed instructing voltage by an output voltage of the power source voltage detecting means automatically when the power source voltage is elevated over the predetermined rated voltage, the rotary speed varying means comparing a saw-tooth wave signal generated in a saw-tooth wave generating circuit including a time constant circuit consisting of a resistor and a capacitor with the rotary speed instructing voltage so as to vary an energizing time of the stator windings.
Yet further object of the present invention is to provide a brushless fan motor driving circuit comprising means for detecting a position of a permanent magnet of a rotor, a conducting current signal generating circuit for generating a conducting current signal according to an output of the position detecting means, a conducting current control element for energizing stator windings of the motor according to the conducting current signal, means for varying a rotary speed of a fan motor, the rotary speed varying means comparing a saw-tooth wave signal generated in a saw-tooth wave generating circuit including a time constant circuit consisting of a resistor and a capacitor with the rotary speed varying voltage so as to vary an energizing time of the stator windings, means for generating a rotary speed instructing voltage for setting a rotary speed of a brushless fan motor to a predetermined value, means for detecting a power source voltage and outputting a voltage in proportion to a difference between the power source voltage and a rated voltage when the power source voltage is elevated over a predetermined rated voltage, and means for controlling a rotary speed of the fan motor to a predetermined value by varying an inclined angle of the saw-tooth wave of the rotary speed varying means according to an output voltage of the power source voltage detecting means automatically when the power source voltage is elevated over the predetermined rated voltage.
A still further object of the present invention is to provide a brushless fan motor driving circuit comprising means for detecting a position of a permanent magnet of a rotor, a conducting current signal generating circuit for generating a conducting current signal according to an output of the position detecting means, a conducting current control element for energizing stator windings of the motor according to the conducting current signal, means for detecting a power source voltage and outputting a voltage in proportion to a difference between the power source voltage and a rated voltage when the power source voltage is elevated over a predetermined rated voltage, means for detecting a current from the conducting current control element, a comparator for comparing an output of the conducting current detecting means with an output of the power source voltage detecting means, and means for controlling a rotary speed of a fan motor to a predetermined value by controlling the conducting current signal generating circuit automatically when the power source voltage is elevated over the predetermined rated voltage, an output of the comparator being supplied to the conducting current signal generating circuit.
A still further object of the present invention is to
Ohiwa Shoji
Otsuka Motoi
Duda Rina I.
Japan Servo Co. Ltd.
Patterson Thuente Skaar & Christensen P.A.
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