Communications: electrical – Condition responsive indicating system – Specific condition
Reexamination Certificate
2002-09-13
2004-03-16
Hofsass, Jeffery (Department: 2636)
Communications: electrical
Condition responsive indicating system
Specific condition
C324S166000, C415S118000, C388S806000, C318S808000
Reexamination Certificate
active
06707385
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to DC motor rotation speed alarm circuitry, and more particularly, to alarm circuitry that is able to accurately display alarm signals even if the rotation speed of the motor changes.
BACKGROUND OF THE INVENTION
In modern society, a great amount of electronic data is broadcasted and processed so that information and knowledge are exchanged rapidly. Technological developments accelerate at a faster pace, and people's lives are greatly enriched. Take notebook computers for instance. When processing a large amount of data, the central processing unit becomes overheated. Hence the notebook computer usually has a control circuit to modulate the operating speed of the radiator to resolve the heat dissipation problem, and alarm circuitry to feed back alarm signals to the computer system to indicate whether the computer system is functioning properly.
Refer to
FIGS. 1 and 2
for the heat dissipation procedures of a conventional radiator
10
for a central processing unit (CPU)
12
, and a simple circuit diagram of the driving circuit
16
and the alarm circuit
20
shown in FIG.
1
. As shown in
FIG. 1
, the radiator
10
includes a DC motor
14
, a driving circuit
16
electrically connected to the DC motor
14
, and a radiation fan
18
electrically connected to the DC motor
14
. When the radiator
10
performs a heat dissipation procedure to the CPU
12
, the driving circuit
16
first transmits a rotation signal to control the rotation of the DC motor
14
. The rotation signal is usually a current signal. Then the radiation fan
18
is driven to rotate by the DC motor
14
to perform heat dissipation processes to the CPU
12
. Finally, the CPU
12
feeds back signals indicating the result and operating conditions of the heat dissipation procedure, and also whether to modulate the rotation speed of the DC motor
14
to the driving circuit
16
. The alarm circuit
20
receives the operating conditions of the CPU
12
transmitted from the driving circuit
16
, and outputs an alarm signal to the computer system (not shown in the drawings).
Referring to
FIG. 2
, the driving circuit
16
includes an n-p-n bipolar junction transistor (BJT) functioning as a switch component
17
, which has an emitter connected to the ground GND and a collector electrically connected to the alarm circuit
20
. The alarm circuit
20
is connected to a constant voltage power supply Vcc
2
. In addition, the driving circuit
16
has one node connected to a voltage power supply Vcc
1
with a voltage greater than or equal to the voltage of Vcc
2
.
In order to facilitate description of the operating principle of the alarm circuit
20
, the alarm signals described below are represented by digital signals ‘0’ and ‘1’. ‘0’ indicates that the CPU
12
is in a normal operating condition while ‘1’ indicates that the CPU
12
is not operating or is operating abnormally. Another assumption is that the voltage of the first voltage power supply Vcc
1
is 12 V (Volts) while the voltage of the second voltage power supply Vcc
2
is 6 V.
When the CPU
12
is in a normal operating condition, the DC motor
14
maintains a selected rotation speed, and the current generated by the voltage power supply Vcc
1
passes through the switch component
17
and flows to the ground node G through the emitter of the n-p-n BJT
17
. In such a condition, there is no electric potential difference between the emitter of the BJT
17
and the ground GND. Hence the voltage received by the alarm circuit
20
is approximately 0 V, and the indication of the alarm signal output by the alarm circuit
20
is ‘0’. This means that the CPU
12
is functioning normally. When the CPU
12
is not functioning, the DC motor
14
does not rotate. The first voltage power supply Vcc
1
does not provide power to the switch component
17
(i.e. the BJT
17
does not conduct electrically). The voltage received by the alarm circuit
20
is 6 V (i.e. the voltage provided by the second voltage power supply Vcc
2
). Then the alarm signal outputted by the alarm circuit
20
indicates ‘1’, meaning that the CPU
12
is not functioning or is functioning improperly.
When data processing volume in the CPU
12
increases, the driving circuit
16
accelerates the rotation speed of the DC motor
14
. In such a condition, there is a floating voltage between the driving circuit
16
and the ground GND (i.e. the transistor
17
and the ground GND). The faster the DC motor
14
rotates, the greater the floating voltage becomes. Assuming that the rotation speed of the DC motor
14
increases to a preset level and the floating voltage between the driving circuit
16
and the ground GND is 3 V, the voltage received by the alarm circuit
20
is 3 V. In such a condition, the alarm circuit
20
cannot output the correct alarm signals. When the floating voltage is 6 V (i.e. same as the voltage of the second voltage power supply Vcc
2
), the alarm signal outputted by the alarm circuit
20
indicates ‘1’. However, the overall computer system is in fact in a normal operating condition, but is processing or transmitting a large amount of data. Therefore, the system could mistakenly judge the situation and cause a system shutdown because of the error signals.
SUMMARY OF THE INVENTION
The object of the invention is therefore to provide DC motor rotation speed alarm circuitry that is simply designed with a smaller number of electronic components and can accurately display alarm signals for motor operating conditions even if the rotation speed of the motor has changed, thus enabling the whole system to maintain normal operation.
The foregoing, as well as additional objects, features and advantages of the invention will be more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings.
REFERENCES:
patent: 4028686 (1977-06-01), Wilson et al.
Birch & Stewart Kolasch & Birch, LLP
Delta Electronics , Inc.
Hofsass Jeffery
Stone Jennifer
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