JP2004100493A - Acoustic equipment equipped with cooling fan motor voltage control circuit, and other instrument - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize complete starting and remove an adverse effect due to wind noises, in acoustic equipment equipped with a cooling fan motor voltage control circuit, and other instruments. <P>SOLUTION: A resistor for current detection is connected in series to a cooling fan motor. The formation of a bypass circuit of a voltage limit element connected to the cooling fan motor is controlled based on a voltage drop value generated by the resistor for current detection. At the time of starting, the bypass circuit is formed because of a large voltage drop to supply high voltage to the cooling fan motor. After the starting, no bypass circuit is formed because of a small voltage drop to supply the reduced voltage to the cooling fan motor. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an acoustic device and a device having a cooling fan motor voltage control circuit for driving a cooling fan.
[0002]
[Prior art]
In recent years, recorders using a small-sized and large-capacity hard disk drive for recording a video signal are becoming widespread. However, since a hard disk drive generates a large amount of heat, a cooling fan must be provided in the recorder body. However, in a recorder that reproduces an audio signal, the wind noise of the cooling fan causes noise to the user. In particular, the reproduction of music signals is an extremely large obstacle. Therefore, during steady-state rotation, a low voltage equal to or lower than the rated voltage is supplied to eliminate the generation of wind noise, and a high voltage is supplied at the time of startup to ensure smooth startup. Such measures for preventing the generation of wind noise are considered not only for the recorder but also for various devices.
[0003]
For this reason, as described in, for example, Japanese Patent Application Laid-Open No. 6-189586 (first related art), in a device such as a printer, there is little need for cooling during idling, so that the cooling fan is operated at a low speed. The system is operated to eliminate wind noise and to operate at high speed during operation. In addition, a technique has been proposed in which the necessity of cooling is detected by using a temperature sensor to control the supply voltage to a cooling fan motor.
[0004]
Further, for example, as described in JP-A-6-335285 (second related art), a high voltage required for startup is supplied when the cooling fan is started, and thereafter, a voltage required for at least steady rotation is supplied. To achieve smooth startup and low noise. As the control, a technique has been proposed in which an integration circuit having a predetermined time constant including a capacitor and a resistor is provided in a power supply circuit, and a high voltage is supplied only when the cooling fan is started.
[0005]
Furthermore, for example, as described in Japanese Patent Application Laid-Open No. 8-126361 (third conventional example), a voltage for reliable start-up is supplied when the power is turned on, and no wind noise is generated during the subsequent steady operation. The voltage has been reduced to ensure reliable startup and low noise. As the control, a technique has been proposed in which a high voltage is supplied to the cooling fan motor only at the time of starting using a pulse generating circuit formed of, for example, a monostable multivibrator triggered at power-on, and thereafter a low voltage is supplied.
[0006]
[Problems to be solved by the invention]
In the first prior art, the ambient temperature is detected by a temperature sensor to perform high-speed operation and low-speed operation of the cooling fan, and cannot be employed in, for example, audio equipment that gives priority to measures against wind noise. That is, in this conventional example, if the temperature rises for some reason during use of the audio equipment, there is a problem that the cooling fan rotates at a high speed and suddenly generates a wind noise. Further, smooth start-up is not considered, and there is a problem that the cost is increased due to the provision of the temperature sensor.
[0007]
Further, in the second prior art, wind noise countermeasures and startup countermeasures, which are problems of the first prior art, are improved. However, since the starting characteristics of the cooling fan motor vary, the set time constant of the integrating circuit must be large enough to absorb all the variations. For this reason, a device to which such a cooling fan is applied has a problem that high-speed rotation is performed for a while after the power is turned on, and the wind noise cannot be eliminated early. That is, in this conventional example, there is a problem that a wind noise is inevitably generated during the first period of starting use of the device.
[0008]
Further, in the third conventional example, the measures against wind noise and starting are improved as described above, but a high voltage is supplied by using a pulse generating circuit for generating a pulse having a constant pulse width. Therefore, a sufficiently large pulse width is required in consideration of variations in the starting characteristics of the cooling fan motor, as in the second conventional technique. Therefore, the high-speed rotation is performed for a while after the power is turned on, and there is a problem that the wind noise cannot be eliminated early. That is, even in this conventional example, there is a problem that a wind noise is inevitably generated during the first period of starting use of the device.
[0009]
SUMMARY OF THE INVENTION The present invention solves the problems of the prior art described above, reliably eliminates the adverse effects of wind noise on users of audio equipment and other equipment, and provides a low-cost acoustic fan having a cooling fan motor voltage control circuit. The purpose is to provide equipment and other equipment.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a hard disk drive, a power supply circuit, and an audio device having a heat source such as a circuit board, wherein a DC voltage is supplied to a DC power supply via a power switch and a voltage limiting element. A cooling fan motor for driving the connected cooling fan, a current detecting resistor connected in series with the cooling fan motor, and a detecting device for detecting a value of a voltage drop generated in the current detecting resistor. An acoustic device including a cooling fan motor voltage control circuit including a transistor and a bypass transistor connected in parallel with the voltage limiting element and controlled to be turned on and off by a detection output of the detection transistor.
[0011]
On the other hand, the present invention relates to a power supply circuit, a device having a heat source such as a circuit board, for driving a cooling fan connected so that a DC voltage is supplied to a DC power supply via a power switch and a voltage limiting element. A cooling fan motor, a current detecting resistor connected in series with the cooling fan motor, a detecting unit for detecting a value of a voltage drop generated by the current detecting resistor, and a parallel connection with the voltage limiting element. And a bypass fan controlled by the detection output of the detection means.
[0012]
The present invention also drives a cooling fan connected to a DC power supply such that a DC voltage is supplied via a power supply slitch and a voltage limiting element in a device having a heat source such as a power supply circuit and a circuit board. A cooling fan motor, a current detection resistor connected in series with the cooling fan motor, a detection transistor for detecting a value of a voltage effect generated by the current detection resistor, and the voltage limiting element. An apparatus provided with a cooling fan motor voltage control circuit including a bypass transistor that is connected in parallel and is turned on and off by a detection output of the detection transistor.
[0013]
Here, the current detection resistor is a device including a cooling fan motor voltage control circuit including a variable resistor whose value can be variably set.
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0014]
FIG. 1 is a block diagram of a cooling fan motor voltage control circuit according to an embodiment of the present invention. Reference numeral 1 denotes a cooling fan motor, which is provided in an audio equipment main body (not shown) such as a recorder, for example. Reference numeral 2 denotes a DC power supply, and 3 denotes a power switch. Reference numeral 4 denotes a voltage limiting element composed of a Zener diode connected in series with the cooling fan motor 1, and reference numeral 5 denotes a current detecting resistor also connected in series with the cooling fan motor 1. The cooling fan motor 1 is supplied with the voltage of the DC power supply reduced by the voltage limiting element 4. The reduced voltage is set so that the cooling fan motor 1 rotates to such an extent that the fan does not generate wind noise. Reference numeral 6 denotes a bypass transistor which constitutes bypass means connected in parallel with the voltage limiting element 4 and is composed of a PNP transistor whose emitter is connected to the cathode side of a Zener diode which constitutes the voltage limiting element 4 and whose collector is Is connected to the anode side of the Zener diode, and is switched from off to on due to a decrease in the base potential, thereby forming a bypass circuit. 7 is a bias resistor connected between the emitter and the base.
[0015]
Numeral 8 denotes a detecting transistor which constitutes detecting means for detecting the value of the voltage drop generated by the current detecting resistor 5, which is composed of an NPN type transistor, the emitter of which is connected to the negative side of the DC power supply 2; The base is connected to the negative side of the DC power supply 2 via the current detecting resistor 5, and the collector is connected to the base of the bypass transistor via the resistor 9. Reference numeral 10 denotes a bias resistor connected to the collector of the detection transistor 8, and when a current of a predetermined value or more flows through the current detection resistor 5, the detection transistor 8 is turned on from off by a voltage value corresponding to the current. It is about to change. The on-operation of the detection transistor 8 turns on the bypass transistor 6.
[0016]
Next, the operation of the cooling fan motor voltage setting circuit according to the embodiment of the present invention will be described.
[0017]
With the start of use of the device, the power switch 3 is closed and a DC voltage is supplied to the cooling fan motor 1. At the start of the supply of the DC voltage, a current larger than the steady state flows through the cooling fan motor 1 and starts to rotate. Therefore, a large current also flows through the current detection resistor 5, and the value of the voltage drop there increases. Due to this large voltage drop, the base potential of the detection transistor 8 is greatly displaced in the plus direction, and the detection transistor 8 which is off in the steady state is turned on. Then, the base potential of the bypass transistor 6 is displaced in the negative direction, and in a steady state, it is turned on from an off state to form a bypass circuit. By forming this bypass circuit, a high DC voltage that is not limited by the voltage limiting element 4 is supplied to the cooling fan motor 1.
[0018]
Therefore, the cooling fan motor 1 generates a high torque and immediately rotates toward the high-speed rotation. When the rotation is sufficient, the load on the cooling fan motor 1 is reduced, and the flowing current is rapidly reduced. When the current decreases, the value of the voltage drop across the current detection resistor 5 decreases, and the detection transistor 8 switches from on to off. By the switching to the off state, the bypass transistor 6 is again switched off, and the bypass circuit is not formed. Therefore, the voltage supplied to the cooling fan motor 1 is a value at which the fan reduced by the voltage limiting element 4 does not generate wind noise.
[0019]
Here, the period during which a bypass is formed at the time of startup and a high voltage is supplied to the cooling fan motor 1 is achieved by setting in advance the timing of turning on and off the detection transistor 8.
[0020]
According to an example of the embodiment of the present invention, when the power switch 3 is closed at the start of use of the device, a large current flows through the cooling fan motor 1. In this state, the voltage drop in the current detection resistor 5 can be directly detected by the detection transistor 8. Then, the bypass transistor 6 is turned on to form a bypass circuit, and a high voltage is supplied to the cooling fan motor 1 to achieve the start-up in a short time. When the cooling fan motor 1 is started, the load is reduced and the current is sharply reduced, so that the detection transistor 8 is turned off and the bypass transistor 6 is turned off. By this switching to off, the bypass circuit is not formed, and the cooling fan motor 1 is supplied with the voltage reduced by the voltage limiting element 4, so that the cooling fan motor 1 does not generate wind noise and operates with a certain rotation of the cooling effect. . In this way, the cooling fan motor can be started quickly so that wind noise does not occur during the substantial use of the device main body. In particular, the effect is great for audio equipment that handles audio signals.
[0021]
Next, another example of the embodiment of the present invention will be described with reference to FIG. 2, but the same parts as those of the example of the embodiment in FIG. 1 described above are denoted by the same reference numerals, and the description thereof will be omitted.
[0022]
In this other example, a resistor whose value can be variably set is connected as a current detecting resistor 11 in series with the cooling fan motor 1. Further, detection transistors 8 forming detection means are connected to both ends thereof.
[0023]
According to such another example of the embodiment of the present invention, the ON / OFF switching timing of the detection transistor 8 can be finely adjusted. Therefore, the minimum period necessary for starting the cooling fan motor 1 can be set, and the influence of wind noise can be reliably eliminated. In addition, in the case of mass production and various kinds of production, even if a cooling fan motor 1 with a different standard is adopted by using a common substrate for the voltage control circuit, the cooling fan motor 1 can be set to an optimum state, so that there is an effect of reducing costs.
[0024]
According to the present invention, the zener diode is used for the voltage limiting element 4 in one example and other examples of the embodiment, but the present invention is not limited to this, and a diode, a resistor, or the like may be used.
[0025]
【The invention's effect】
As described above, according to the first aspect of the present invention, a change in current flowing through the cooling fan motor can be directly detected by the detection transistor in the current detection resistor connected in series with the cooling fan motor. The high voltage is supplied only for a minimum period required for the start, the start is completed, and there is an effect that it is possible to provide an acoustic device substantially free from the influence of wind noise generated from the cooling fan. In addition, since the configuration only requires the use of a detection transistor, a bypass transistor, and the like, there is an effect that the object can be achieved at low cost.
[0026]
Further, according to the second aspect of the present invention, a change in the current flowing through the cooling fan motor can be directly detected by the detecting means in the current detecting resistor connected in series with the cooling fan motor. There is an effect that a high voltage is supplied only for a minimum period to complete the start-up, and a device substantially free of the influence of wind noise generated from the cooling fan can be provided.
[0027]
Furthermore, according to the third aspect of the present invention, a change in the current flowing through the cooling fan motor can be directly detected by the detection transistor in the current detecting resistor connected in series with the cooling fan motor, so that the cooling fan motor can be started up. There is an effect that a high voltage is supplied only for a necessary minimum period to complete the start-up, and an apparatus can be provided in which the influence of wind noise generated from the cooling fan is substantially eliminated. In addition, since the configuration only requires the use of a detection transistor, a bypass transistor, and the like, there is an effect that the object can be achieved at low cost.
[0028]
Further, according to the third aspect of the present invention, since the value of the current detection resistor connected in series with the cooling fan motor is variable, the detection state of the detection transistor or the detection means is finely adjusted. This has the effect of reliably starting up and eliminating the adverse effects of wind noise.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating an example of an embodiment of the present invention.
FIG. 2 is a block diagram showing another example of the embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Cooling fan motor 4 Voltage limiting element 5 Current detection resistor 6 Bypass transistor 8 Detection transistor

Claims (4)

In an acoustic device having a heat source such as a hard disk drive, a power supply circuit, and a circuit board, a cooling fan motor for driving a cooling fan connected to a DC power supply via a power switch and a voltage limiting element, and the cooling fan motor A current detection resistor connected in series, a detection transistor for detecting a value of a voltage drop generated by the current detection resistor, and a voltage limiting element, which are connected in parallel with the detection output and are turned on by a detection output of the detection transistor. An acoustic device including a cooling fan motor voltage control circuit including a bypass transistor that is controlled to be off. In a device having a heat source such as a power supply circuit and a circuit board, a cooling fan motor for driving a cooling fan connected so that a DC voltage is supplied to a DC power supply via a power switch and a voltage limiting element, A current detection resistor connected in series with the cooling fan motor, detection means for detecting a value of a voltage drop generated by the current detection resistance, and detection of the detection means connected in parallel with the voltage limiting element A device equipped with a cooling fan motor voltage control circuit that functions as bypass means controlled by the output. In a device having a heat source such as a power supply circuit and a circuit board, a cooling fan motor for driving a cooling fan connected so that a DC voltage is supplied to a DC power supply via a power switch and a voltage limiting element, A current detection resistor connected in series with the cooling fan motor, a detection transistor for detecting a value of a voltage drop generated in the current detection resistor, and the detection transistor connected in parallel with the voltage limiting element. A cooling fan motor voltage control circuit comprising a bypass transistor that is turned on and off by a detection output of the cooling fan motor. 4. An apparatus comprising a cooling fan motor voltage control circuit according to claim 2, wherein said current detection resistor comprises a variable resistor whose value can be variably set.

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