JP3460116B2 - Fan drive control circuit - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fan drive control circuit for driving a fan for forced air cooling or the like. In order to suppress the temperature rise of various equipment, a configuration in which cooling is performed by rotating a fan is adopted. In this case, the cooling action can be efficiently performed by detecting the temperature and controlling the rotational speed of the fan. In such a configuration, it is desired to improve the starting characteristic.

[0002]

2. Description of the Related Art FIG. 5 is an explanatory view of a conventional example. FAN is a fan, M is a DC fan drive motor, Q1 is a transistor, R1 and R2 are resistors, TH1 is a thermistor, and M1.
Is a shunt regulator, and T1 and T2 are terminals. The fan driving motor M is driven by a DC voltage of several V to several tens V, and can control the rotation speed according to the applied voltage.

Further, the thermistor TH1 is arranged so as to detect the temperature of various electronic devices and detection sites such as ventilation paths, and the thermistor TH1 and the resistor R2 are connected in series, and this series circuit is connected to a fan driving motor. Connect in parallel with M. The divided voltage by the resistor R2 and the thermistor TH1 is used as the control voltage of the shunt regulator M1 that constitutes the transistor control circuit. The shunt regulator M1 has a characteristic that the equivalent impedance becomes low when the control voltage is high, and conversely becomes high when the control voltage is low.

A resistor R1 and a shunt regulator M1 are connected in series between terminals T1 and T2 for applying a power supply voltage, and the base of a transistor Q1 is connected to the connection point. Therefore, when the power supply voltage is applied, the base current flows through the resistor R1, and the voltage is applied to the fan driving motor M through the transistor Q1 to rotate the fan driving motor M.

When the temperature drops, the thermistor T
Since the impedance of H1 increases and the divided voltage increases accordingly, the equivalent impedance of the shunt regulator M1 decreases, the base current of the transistor Q1 decreases, the applied voltage of the fan driving motor M decreases, and the rotation speed increases. The number decreases and the air volume decreases. On the contrary, when the temperature rises, the impedance of the thermistor TH1 decreases, and the divided voltage decreases accordingly, and the shunt regulator M1
, The base current of the transistor Q1 rises, the voltage applied to the fan driving motor M rises, the rotation speed rises, and the air volume increases.

The shunt regulator M1 described above includes a comparator for comparing the voltage applied to its control terminal, that is, the divided voltage of the series circuit with the reference voltage, and a transistor controlled by the output of the comparator. Is common,
Therefore, when the divided voltage of the series circuit increases, the output signal of the comparator increases and the current flowing through the transistor increases, that is, the impedance decreases. On the contrary, when the divided voltage of the series circuit becomes low, the current flowing through the transistor decreases, that is, the impedance increases. Therefore,
When it is acceptable to reduce the cooling action of the temperature detection portion due to the temperature decrease, the rotation speed of the fan can be decreased to reduce noise due to fan rotation.

[0007]

The fan FAN for forced air cooling has a problem of noise. This fan FAN
The noise due to the rotation can be reduced by reducing the rotation speed. Therefore, like the above-mentioned conventional example,
The temperature of the temperature detection portion is detected by the thermistor TH1, and when the temperature decreases, the rotation speed of the fan FAN is automatically decreased to bring about a low noise state.

However, when the temperature of the fan driving motor M is low when the temperature is low, the impedance of the thermistor TH1 becomes high, so that the divided voltage by the series circuit of the resistor R2 and the thermistor TH1 becomes high. This lowers the equivalent impedance of the shunt regulator TH1,
The base current of the transistor Q1 may not be sufficiently flowed. In that case, there has been a problem that a voltage required for starting cannot be applied to the fan driving motor M via the transistor Q1.

Even during the rotation of the fan FAN, the temperature of the thermistor TH1 is greatly lowered and its impedance is reduced, so that the voltage applied to the fan driving motor M through the transistor Q1 is lowered, and the fan driving motor M is driven. The motor M sometimes stopped. For example, a fan drive motor having a rating of 12V has a usable voltage of about 8 to 16V, and stops when the applied voltage drops to 6 to 7V. Moreover, at the time of starting, 8 V or more is required. Also, a fan driving motor with a rating of 24V has a usable voltage of about 12 to 30V,
Therefore, when the applied voltage drops to 11 V or less, it stops, and 12 V or more is required at the time of starting. It is an object of the present invention to enable the fan driving motor to be started and continued to rotate even if the temperature is lowered.

[0010]

A fan drive control circuit according to the present invention will be described with reference to FIG. 1. (1) Fan FA
A thermistor TH1 that detects the temperature of a portion where cooling or ventilation is performed by rotation of N, and a transistor Q1 that is connected in series with a fan driving motor M that rotates a fan FAN.
When, a series circuit of a thermistor TH1 connected in parallel with the fan drive motor M and the resistor R2 to R4, and applies the divided voltage by the series circuit, the divided voltage is decreased by reduction of the impedance of the thermistor TH1 At the same time, the fan drive control circuit includes a transistor control circuit CNT that raises the applied voltage of the fan drive motor M via the transistor Q1, and the thermistor TH due to an increase in impedance of the thermistor TH1 due to a temperature decrease.
1 and the resistors R2 to R4 connected in series increase the divided voltage .
Diode D which conducts to suppress the divided voltage to a predetermined value
1, D2 or a Zener diode is connected in parallel to the thermistor TH1.

(2) The thermistor TH1 for detecting the temperature of a portion for cooling or ventilation by rotating the fan FAN.
, A transistor Q1 connected in series with a fan driving motor M for rotating the fan FAN, a thermistor TH1 connected in parallel with the fan driving motor M, and resistors R2 to R.
A series circuit of a 4, the divided voltage is applied by the series circuit, the transistor control for increasing the voltage applied to the motor M for the fan drive via a transistor Q1 when the divided voltage is lowered by lowering the impedance of the thermistor TH1 a fan drive control circuit that includes a circuit CNT, conductive by increasing the divided voltage <br/> series circuit of the thermistor TH1 and the resistor R2~R4 when the impedance of the thermistor TH1 by temperature decrease is increased The transistor control circuit C with a Zener diode for preventing the applied voltage of the fan driving motor M from decreasing via the transistor Q1.
It can be provided in NT.

(3) In the fan drive control circuit, a capacitor that is charged through the resistance and diode of the series circuit and reduces the divided voltage of the series circuit only when the fan drive motor M is started. C1 can be connected.

(4) In the fan drive control circuit, the transistor control circuit CNT connects a series circuit of a shunt regulator, a Zener diode and a resistor, which lowers impedance when the divided voltage of the series circuit is high, to a power supply voltage. A structure in which the connection point between the Zener diode and the resistor is connected to the base of the transistor Q1 can be formed by connecting between the application terminals.

[0014]

1 is an explanatory view of a first embodiment of the present invention, in which FAN is a fan, M is a fan driving motor, Q1 is a transistor, R1 to R4 are resistors, and D1 to D1.
D4 is a diode, C1 is a capacitor, TH1 is a thermistor, M1 is a shunt regulator, CNT is a transistor control circuit, and T1 and T2 are terminals. Also fan FA
A part for detecting temperature such as an electronic device such as a large-scale integrated circuit cooled by N and a ventilation path is not shown in the drawing, and a thermistor TH1 is provided at this temperature detecting part.

A resistor R1 and a shunt regulator M1 are connected in series between the terminals T1 and T2, and the connection point is connected to the base of the transistor Q1 to form a transistor control circuit CNT. This shunt regulator M1
As described above, when the control voltage is high, the equivalent impedance is low, and conversely, when the control voltage is low, the equivalent impedance is high. Then, when the equivalent impedance of the shunt regulator M1 is high, the base current of the transistor Q1 becomes large, and the applied voltage of the fan driving motor M becomes high. On the contrary, when the equivalent impedance is low, the base current of the transistor Q1 becomes small and the voltage applied to the fan driving motor M becomes low.

Further, in the series circuit of the resistors R2 to R4 and the thermistor TH1, a divided voltage is applied as a control voltage of the shunt regulator M1 of the transistor control circuit CNT from the connection point of the resistors R3 and R4. Also the thermistor TH1
And diodes D1 and D2 are connected in parallel with. in this case,
The diodes D1 and D2 have a forward polarity with respect to the terminal voltage of the thermistor TH1. That is, the diodes D1 and D
The forward voltage of 2 clamps the thermistor TH1 so that the terminal voltage of the thermistor TH1 does not rise at a low temperature. Therefore, the number of diodes connected in series can be set in accordance with the impedance characteristic of the thermistor TH1 and the divided voltage output characteristic of the series circuit.

A capacitor C1 is connected to a connection point of the resistors R2 and R3 of the series circuit via a diode D3. That is, the capacitor C1 is connected so as to be charged via the resistor R2 and the diode D3. Also this capacitor C1
The diode D4 for discharging the charged electric charge is connected.

When a DC voltage is applied to the terminals T1 and T2 from the power source, the transistor Q1 is turned on and the DC voltage is applied to the fan driving motor M. At that time, the resistance R
Since the capacitor C1 is charged via 2 and the diode D3, the voltage drop due to the resistor R2 becomes large and the divided voltage of the DC circuit becomes low. Therefore, the shunt regulator M1 of the transistor control circuit CNT has a high equivalent impedance, and the voltage applied to the base of the transistor Q1 also increases, so that the voltage applied to the fan driving motor M increases. Thereby, the fan driving motor M can be started by applying a DC voltage of the rated voltage.

After the fan driving motor M is started, the charging voltage of the capacitor C1 rises according to the time constant of the resistor R2 and reaches the potential at the connection point of the resistors R2 and R3. Therefore, the voltage is applied, so that the circuit is disconnected from the series circuit.
When the DC voltage applied to the terminals T1 and T2 is turned off,
The capacitor C1 discharges the charge to the fan driving motor M and the series circuit of the resistors R2 to R3 and the thermistor TH1 via the diode D4, and can be prepared for the next start.

Further, if the temperature of the temperature detecting portion of an electronic device such as a large-scale integrated circuit forcibly cooled by the fan FAN or an electronic device controlling the air flow rate according to the ambient temperature is low, the impedance of the thermistor TH1 becomes high. As a result, the divided voltage of the series circuit increases. But,
Since the diodes D1 and D2 are connected in parallel with the thermistor TH1, even if the impedance of the thermistor TH1 becomes high and the voltage across the thermistor TH1 becomes high, it will not rise above the forward voltage of the diodes D1 and D2. . That is, the divided voltage of the series circuit can be controlled so as not to rise above a predetermined value.

Therefore, when the thermistor TH1 has a high equivalent impedance at the time of start-up or during operation and the divided voltage of the series circuit is about to rise, the diode D
Since the voltage across both ends of the thermistor TH1 is clamped so as not to rise above the forward voltage of 1, D2, the rise of the divided voltage of the series circuit is suppressed, and the applied voltage of the fan drive motor M is suppressed via the transistor Q1. It can be controlled so as not to drop below the minimum. That is, the capacitor C
Even when 1 is not provided, the starting characteristic can be improved, and by providing the capacitor C1, the starting characteristic can be further improved.

FIG. 2 is a characteristic explanatory view at the time of starting of the first embodiment of the present invention. FIG. 2A shows a change in the applied voltage of the fan driving motor M at the time of starting with a curve (a). , Curve (b) shows the change in impedance of the thermistor TH1. Also, (B) shows a change in the voltage applied to the fan driving motor M at the time of start-up by a curve (c), and a change in the terminal voltage of the capacitor C1 by a curve (d).

When the fan driving motor M is started, for example, when the temperature of the temperature detecting portion is low and the thermistor TH1 has a small impedance, the fan driving motor M is applied with the rated voltage V1 or higher voltage V1. . Then, the temperature detection portion is cooled by the rotation of the fan FAN, and due to the temperature decrease, the impedance of the thermistor TH1 becomes larger than that at the start-up as shown in the curve (b) of (A), and after the time t1, the transistor Q1 The voltage applied to the fan driving motor M via the motor decreases, and the rotation speed of the fan FAN decreases, resulting in a low noise state.

Then, after the time t2, the thermistor TH1
When the impedance of the thermistor becomes larger, the thermistor T
Since the voltage across H1 is clamped by the diodes D1 and D2, the voltage applied to the fan driving motor M via the transistor Q1 is
Is controlled so that the voltage does not drop below the minimum voltage V2 required for the operation. Therefore, even if the temperature detection portion becomes low in temperature, the fan operation continues even though it is rotating at a low speed. As described above, since the voltage can be controlled so as not to drop below the voltage V2, the fan driving motor M can be started even in the case where the capacitor C1 is omitted.

When the capacitor C1 is provided, the terminal voltage of the capacitor C1 is almost zero in the initial stage of startup as shown in the curve (d) of (B), and rises according to the time constant with the resistor R2 after startup. However, after time t4, the thermistor TH
The potential rises to the potential V4 at the connection point of the resistors R2 and R3 corresponding to the impedance of 1, and becomes constant. Therefore, the potential at the connection point between the resistors R2 and R3 in the initial stage of the startup changes according to the terminal voltage of the capacitor C1, and the initial value is low in the initial stage.
The divided voltage of the series circuit also becomes low.

As a result, the transistor control circuit CNT
The equivalent impedance of the shunt regulator M1 becomes large, and the voltage applied to the fan driving motor M via the transistor Q1 is the rated voltage or higher in the initial stage of startup as shown by the curve (c) in (B). Voltage V1
Becomes Then, for example, after the time t3, the divided voltage rises corresponding to the rise of the terminal voltage of the capacitor C1, so that the applied voltage of the fan drive motor M gradually decreases,
After time t4, the voltage becomes V3 corresponding to the impedance of the thermistor TH1. That is, since the capacitor C1 is connected at the initial stage of activation, the voltage V1 sufficient for activation can be applied to the fan driving motor M, so that the fan can be activated reliably.

FIG. 3 is an explanatory view of the second embodiment of the present invention. The same reference numerals as those in FIG. 1 indicate the same parts, ZD1 is a Zener diode, and R5 is a resistor. In this embodiment, the Zener voltage of the Zener diode ZD1
The terminal voltage of the thermistor TH1 is clamped, and the fan driving motor M can continue to rotate even if the temperature detection portion is at a low temperature. The resistor R5 is for discharging the capacitor C1 and can reliably discharge the electric charge charged in the capacitor C1 even when the fan driving motor M is disconnected.

FIG. 4 is an explanatory view of the third embodiment of the present invention. The same symbols as those in FIG. 1 indicate the same parts, and ZD2 is a Zener diode. In this embodiment, instead of clamping the terminal voltage of the thermistor TH1, the Zener diode ZD2 maintains a minimum base potential of the transistor Q1 to ensure a minimum applied voltage of the fan driving motor M. Is.

For example, when the temperature of the temperature detecting portion decreases, the impedance of the thermistor TH1 increases, and the divided voltage of the series circuit increases, the shunt regulator M1 is generated.
Since the equivalent impedance of the
The base potential of 1 becomes low. For example, when the equivalent impedance of the shunt regulator M1 becomes substantially zero, the base potential of the transistor Q1 also becomes substantially zero and the transistor Q1 shifts to the off state. However, the Zener diode ZD2 causes the base potential of the transistor Q1 to become substantially zero. Can be prevented. Therefore, the voltage applied to the fan driving motor M via the transistor Q1 can be maintained at the minimum value required to continue the rotation.

The capacitor C1 is charged via the resistor R2 and the diode D3 at the time of starting, and the resistor R2
It is possible to lower the divided voltage of the series circuit of ~ R4 and the thermistor TH1, increase the equivalent impedance of the shunt regulator M1, and increase the voltage applied to the fan driving motor M through the transistor Q1. Therefore, the starting characteristic of the fan driving motor M can be improved regardless of the magnitude of the equivalent impedance of the thermistor TH1.

The present invention is not limited to the above-described embodiments, but various additions and modifications can be made. For example, the transistor control circuit CNT can be configured by a transistor circuit or the like whose equivalent impedance is controlled by the divided voltage of the series circuit, similarly to the shunt regulator M1 connected in series with the resistor R1. Although the transistor Q1 is shown as a bipolar transistor, it is a field effect transistor (FE).
It is also possible to select T), and it can be selected in consideration of the output capacity of the fan driving motor M and the like. Also in the embodiment shown in FIG. 4, a discharging resistor may be connected in parallel with the capacitor C1 charged through the diode D3 at the time of start-up, and the discharging diode D4 may be omitted. . As the fan driving motor M, various DC motors whose rotation speed is controlled by applied voltage can be applied.

[0032]

As described above, according to the present invention, the divided voltage of the series circuit of the thermistor TH1 and the resistors R2 to R4 provided in the temperature detecting portion is input to the transistor control circuit to detect the temperature of the temperature detecting portion. Is a fan drive control circuit for controlling the voltage applied to the fan drive motor M in accordance with
Even if the impedance of the thermistor TH1 at a low temperature is high, the voltage across the thermistor TH1 or the divided voltage should not exceed a predetermined value.
1, D2 or the Zener diode ZD2 is provided, whereby it is possible to improve the starting characteristics and prevent the fan driving motor M from stopping during operation.

Further, by providing the capacitor C1 which is charged via the diode D3 at the time of starting, the divided voltage of the series circuit is lowered at the time of starting, thereby controlling the transistor Q1 from the transistor control circuit CNT. Since the voltage applied to the fan driving motor M can be increased, there is an advantage that the fan driving motor M can be reliably started even when the temperature detection portion is at a low temperature.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a first embodiment of the present invention.

FIG. 2 is a characteristic explanatory diagram at the time of startup according to the first embodiment of this invention.

FIG. 3 is an explanatory diagram of a second embodiment of the present invention.

FIG. 4 is an explanatory diagram of a third embodiment of the present invention.

FIG. 5 is an explanatory diagram of a conventional example.

[Explanation of symbols]

M fan drive motor Fan fan Q1 transistor TH1 thermistor M1 shunt regulator C1 capacitor R1 to R4 resistance D1-D4 diode CNT transistor control circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-10-97327 (JP, A) JP-A-62-290386 (JP, A) JP-A-58-18718 (JP, A) Sankaihei 3- 18697 (JP, U) Actual development 61-201118 (JP, U) (58) Fields surveyed (Int.Cl. ⁷ , DB name) G05F 1/00-1/70 G05D 23/00-23/32 H05K 7/20 H02P 1/00-1/58 H02P 5/04-5/26 H02P 7/04-7/34 H02M 3/00-3/44 F04D 27/00-27/02

Claims (4)

(57) [Claims] 1. A thermistor for detecting a temperature of a portion for cooling or ventilation by rotating a fan, a transistor connected in series with a fan driving motor for rotating the fan, and a transistor connected in parallel with the fan driving motor. A series circuit of the thermistor and a resistor, and a divided voltage by the series circuit is applied, and when the divided voltage is lowered due to a decrease in impedance of the thermistor, the applied voltage of the fan drive motor is increased through the transistor. In a fan drive control circuit including a transistor control circuit for causing the divided voltage to rise due to an increase in the divided voltage of the series circuit of the thermistor and the resistor due to an increase in impedance of the thermistor due to a temperature decrease, the divided voltage in parallel to the thermistor suppressing diode or Zener diode to a predetermined value Fan drive control circuit, characterized in that connection was. 2. A thermistor for detecting a temperature of a portion for cooling or ventilation by rotating a fan, a transistor connected in series with a fan driving motor for rotating the fan, and a transistor connected in parallel with the fan driving motor. A series circuit of the thermistor and a resistor, and a divided voltage by the series circuit is applied, and when the divided voltage is lowered due to a decrease in impedance of the thermistor, the applied voltage of the fan drive motor is increased through the transistor. In a fan drive control circuit including a transistor control circuit for controlling the resistance of the thermistor, when the impedance of the thermistor increases due to a temperature decrease, the divided voltage of the series circuit of the thermistor and the resistor increases to conduct the transistor. Zener die for preventing a decrease in applied voltage of the fan drive motor via a Fan drive control circuit, characterized in that a chromatography de to said transistor control circuit. 3. The method for starting the fan driving motor
The divided voltage by the series circuit of the thermistor and the resistor
Connect a capacitor that charges via a diode that conducts
The fan drive control circuit according to claim 1, wherein the fan drive control circuit continues . Wherein said transistor control circuit, the Sir
The divided voltage of the series circuit of the mister and the resistor is the control voltage.
And it is applied, the impedance is low when the control voltage is high
A series circuit of a shunt regulator, a zener diode, and a resistor to be connected is connected between application terminals of a power supply voltage, and a connection point of the zener diode and the resistor is connected to a base of the transistor. The fan drive control circuit according to claim 2.