JP2016093008A - Fan rotation number control circuit and power supply unit provided therewith - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fan rotation number control circuit, with which even when an input signal suddenly changes to a voltage level at which a fan rotates at a high speed, an abnormality is prevented from occurring to a power supply that supplies a current to the fan, and a compact and inexpensive power supply unit provided with the same.SOLUTION: When an input signal to a connector 6 that appears as a potential VA at a point A suddenly changes in a step-like manner from a high level instructing a lowest rotation number N of a fan 2 to a voltage level at a low level instructing a highest rotation number N, the change is converted by a smoothing circuit 9 into a gentle slope-like change of a smoothed voltage appearing on a potential VC at a point C. This gentle voltage change of the smoothed voltage is pulse-width modulated through comparison at a comparator 11 with a voltage level of a triangular wave outputted from a triangular wave generation circuit 10. Consequently, a control signal given to a CONTR terminal of the fan 2 changes in such a manner that a duty ratio d increases gradually.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a fan rotation speed control circuit that controls pulse width modulation (hereinafter referred to as PWM) of a fan rotation speed according to a duty ratio of an input signal, and a power supply unit including the fan rotation speed control circuit.

  2. Description of the Related Art Conventionally, for example, an automobile cooling device disclosed in Patent Document 1 that cools a radiator or the like mounted on an automobile is known. Cooling is performed by applying air to a radiator or the like with a fan, and the automotive cooling device is provided with a fan rotation speed control circuit that controls the rotation of the fan to a predetermined rotation speed. The fan is driven by an electric motor, and the rotational speed of the fan is controlled to a predetermined rotational speed by controlling the energization of the electric motor with a MOS transistor. An integration circuit composed of a resistor and a capacitor is provided at the gate of the MOS transistor. When the relay switch is turned on and the electric motor is started, the rise of the voltage applied to the gate of the MOS transistor is delayed by this integration circuit, and the inrush current generated when the electric motor is started is reduced.

  On the other hand, as disclosed in the same document, there is also known a fan rotation speed control circuit that performs PWM control of the fan rotation speed by controlling the duty ratio of the voltage applied to the electric motor. In this fan rotation speed control circuit, the inrush current generated at the start of the electric motor is reduced by gradually increasing the duty ratio of the PWM control signal at the start of the electric motor.

  As such a fan rotation speed control circuit that performs PWM control of the fan rotation speed, there is a power supply unit (power supply panel) 1 configured as shown in FIG. The fan 2 operates by receiving power supply from the DC-DC converter 3, and the rotation speed N is controlled by the PWM control signal S output from the device 4 to cool the device 4. A voltage is applied to the phototransistor Q0 constituting the photocoupler 5 from the DC-DC converter 3 by the resistors R1 and R2. The PWM control signal S output from the device 4 is applied to the photodiode D constituting the photocoupler 5 via the connector 6 and the resistor R3. When the potential VA at the point A becomes high level by the PWM control signal S, a current flows through the photodiode D, the phototransistor Q0 is turned on, and a current Id flows through the series circuit of the resistors R1 and R2. As the current Id flows through the resistor R2, a voltage is applied to the gate of the transistor Q1, and the transistor Q1 is turned on. When the transistor Q1 is turned on, the potential VE at the point E becomes low level. The potential VE at the point E is the same as the potential of the control (CONTR) terminal of the fan 2.

  The rotational speed N of the fan 2 is controlled by the duty ratio d of the signal at the point E given to the CONTR terminal as described above by the PWM control signal S, and the signal given to the CONTR terminal as shown in the timing chart of FIG. Increases as the duty ratio d increases. That is, the rotational speed N of the fan 2 is the lowest speed when the duty ratio d = 0 shown in FIG. 4A, and the duty ratio d = 0 as shown in FIGS. It increases as it becomes larger, .25, 0.5, 0.75. When the duty ratio d = 1, as shown in FIG.

  3A shows an example of a change in the potential VA at the point A, and FIG. 3B shows an example of a change in the potential VE at the point E. As shown in FIGS. 9A and 9B, the potential VE at the point E is a potential obtained by inverting the potential VA at the point A by the PWM control signal S.

JP 11-229875 A

  However, an inrush current may also occur in the conventional fan speed control circuit as shown in FIG. 1 that performs PWM control of the speed N of the fan 2 as described above.

  For example, like the potential VA at point A shown in FIG. 3 (c), the PWM control signal S changes from a high level where the lowest speed N is commanded to a low level where the highest speed N is commanded. When changed, the potential VE at the point E, that is, the potential at the CONTR terminal, suddenly changes stepwise from a low level state with a duty ratio d = 0 to a high level state with a duty ratio d = 1, as shown in FIG. To do. The fan 2 consumes the current Id supplied from the DC-DC converter 3 as its rotational speed N increases. For this reason, the current Id rapidly increases as shown in FIG. 5E at the timing when the potential of the CONTR terminal is inverted and the rotation speed N changes from the lowest speed to the highest speed, and becomes an inrush current. The magnitude of the inrush current Id is about three times that in the steady state. Therefore, it is necessary to select a DC-DC converter 3 having a current capacity capable of supplying a current of that magnitude even when an inrush current Id is generated.

  Further, when the power supply unit 1 is removed from the device 4 and the connector 6 is disconnected, the command from the device 4 side is lost and the potential VA at the point A becomes low level. For this reason, since the photocoupler 5 does not operate, the transistor Q1 is turned off, and the potential of the CONTR terminal is rapidly changed to a high level state with a duty ratio d = 1 for commanding the highest speed at the timing when the power supply unit 1 is removed. Change. Therefore, also in this case, the current Id consumed by the fan 2 suddenly increases as shown in FIG. 3E, and becomes an inrush current.

  The DC-DC converter 3 generally includes an output overcurrent protection circuit, and at the time of overcurrent output, the output voltage is dropped to protect the internal circuit. Some output overcurrent protection circuits further have a protection function for stopping the power supply output when the drooping time elapses. Therefore, when the DC-DC converter 3 that cannot supply the current having the magnitude of the inrush current Id is used, the output voltage droops due to the output overcurrent protection circuit, and the power supply output stops in some cases. May occur. In order to prevent such an event from occurring, it is necessary to select a DC-DC converter 3 used for the power supply unit 1 having a large current capacity. Therefore, the external dimensions of the DC-DC converter 3 are increased, and the price thereof is expensive. For this reason, conventionally, it has been difficult to reduce the size and the price of the power supply unit 1.

The present invention has been made to solve such problems,
In the fan rotation speed control circuit that PWM controls the fan rotation speed in accordance with the duty ratio of the input signal,
A smoothing circuit that smoothes the voltage level of the input signal and converts the input signal to a smoothed voltage;
A triangular wave generating circuit that generates a triangular wave of the same frequency as the input signal with the same amplitude as the maximum voltage level of the smoothing voltage;
The fan rotation speed control circuit is configured by including a pulse width modulation circuit that compares the voltage level of the smoothing voltage with the voltage level of the triangular wave and modulates the smoothing voltage with a pulse width.

  According to this configuration, when the input signal changes to a voltage level that causes the fan speed to rotate rapidly from low speed to high speed, the change is converted into a gentle slope-like change in the smoothing voltage by the smoothing circuit. The This gentle voltage change of the smoothed voltage is pulse width modulated by comparing the voltage level of the triangular wave output from the triangular wave generating circuit with the pulse width modulating circuit. Therefore, the duty ratio of the PWM control signal given to the fan gradually changes as the voltage level of the input signal changes abruptly. For this reason, even if the voltage level of the input signal changes rapidly, the rotational speed of the fan does not change rapidly and gradually increases. Therefore, the current consumed by the fan also gradually increases, and the current for driving the fan does not become an inrush current that increases rapidly as in the prior art. As a result, an excessive load is not applied to the power supply that supplies current to the fan, and an event in which the output voltage of the power supply droops or the power supply output stops as in the conventional case does not occur.

  Further, the present invention controls a fan speed by a fan for cooling the apparatus, a power supply for supplying power to the fan, a connector for inputting a PWM control signal output from the apparatus, and a PWM control signal input from the connector. A power supply unit including the above-described fan rotation speed control circuit is configured.

  According to this configuration, the power supply unit inputs a PWM control signal from the apparatus via the connector. Then, the input PWM control signal is converted into a smoothed voltage in a fan rotation speed control circuit, and the converted smoothed voltage is compared with a triangular wave voltage to perform pulse width modulation. The fan is driven by a current supplied from a power supply, and the number of rotations is controlled by a control signal pulse-modulated by a fan rotation number control circuit to cool the device. Therefore, when a command for a PWM control signal that causes the fan to rotate rapidly from low speed to high speed comes from the device side, or when the power supply unit is removed from the device and the connector is disconnected from the device, the fan from the connector Even if the level of the voltage input to the rotation speed control circuit suddenly changes to the highest voltage level, the current consumed by the fan gradually increases as described above and suddenly increases as before. There is no current. For this reason, there is no need to select a power supply with a current capacity that takes into account the inrush current as the power supply provided in the power supply unit, and a power supply with a current capacity that can supply a steady-state current is used. it can. As a result, the power supply provided in the power supply unit can be reduced in size and price, and therefore the power supply unit can be reduced in size and price.

The present invention also provides:
The smoothing circuit is composed of an integrating circuit consisting of a capacitor and a resistor.
The triangular wave generating circuit is composed of a Schmitt circuit that outputs a square wave, and an integrating circuit that integrates the square wave output from the Schmitt circuit and outputs a triangular wave.
The pulse width modulation circuit includes a comparator that compares the voltage level of the smoothed voltage output from the smoothing circuit and the voltage level of the triangular wave output from the triangular wave generation circuit.

  According to this configuration, the voltage level of the signal input to the fan rotation speed control circuit is smoothed by the integrating circuit including the capacitor and the resistor, and the input signal is converted into a smoothed voltage. Further, the triangular wave whose voltage level is compared with the smoothed voltage is generated by integrating the square wave output from the Schmitt circuit by the integrating circuit. The smoothed voltage is pulse width modulated by comparing the triangular wave and the voltage level by a comparator, and a control signal subjected to the pulse width modulation is supplied to the fan, and the rotational speed of the fan is PWM-controlled.

  According to the present invention, even if the signal for controlling the rotation speed of the fan changes from a low speed rotation to a voltage level that causes the fan to rapidly rotate at a high speed, the output voltage of the power source that supplies current to the fan drops or the power output Therefore, it is possible to provide a fan rotation speed control circuit that does not cause an event that causes the motor to stop. In addition, by providing the fan rotation speed control circuit in the power supply unit, the power supply unit can be reduced in size and price.

It is a circuit diagram of a conventional fan rotation speed control circuit and a conventional power supply unit including the same. It is a timing chart figure which shows that the rotation speed of a fan is controlled by the duty ratio of a control signal. FIG. 2 is a timing chart showing a voltage change and a current change in each part of the circuit shown in FIG. 1. It is a perspective view which shows the usage example of the power supply unit by one Embodiment of this invention. FIG. 5 is a circuit diagram of a power supply unit and a fan rotation speed control circuit provided in the power supply unit according to the embodiment shown in FIG. 4. FIG. 6 is a timing chart showing a voltage change in each part of the circuit shown in FIG. 5 when a signal input to the fan rotation speed control circuit according to an embodiment changes in a normal voltage. FIG. 6 is a timing chart showing a voltage change and a current change in each part of the circuit shown in FIG. 5 when a signal input to the fan rotation speed control circuit according to an embodiment has a voltage change that rapidly increases the fan rotation speed. .

  Next, a fan rotation speed control circuit and a power supply unit including the same according to an embodiment of the present invention will be described.

  FIG. 4 is a perspective view showing an example of how the power supply unit 21 according to this embodiment is used, and FIG. 5 is a circuit diagram showing its internal circuit configuration. 4 and 5, the same or corresponding parts as those in FIG.

  As shown in FIG. 4, the power supply unit 21 is detachably provided on the device 4 such as a personal computer, and supplies a direct current (DC) 48V input via the cable 8 and the connector 7 to the device 4, as well as a fan. 2 to cool the inside of the device 4. FIG. 5 shows a circuit configuration in which the power supply unit 21 is attached to the device 4, and the power supply unit 21 is connected to the device 4 via the connector 6.

  Smoothing circuit 9, triangular wave generation circuit 10 and comparator 11 constitute a fan rotation speed control circuit according to the present embodiment. The power supply unit 21 includes a fan 2 that cools the device 4, a DC-DC converter 3 that is a power source that supplies power to the fan 2, a connector 6 that receives a PWM control signal S output from the device 4, and a connector 6. The fan rotational speed control circuit that controls the rotational speed of the fan 2 according to the input PWM control signal S is provided.

  The fan rotation speed control circuit takes in the PWM control signal S to the photocoupler 5 via the connector 6 and controls the rotation speed of the fan 2 according to the duty ratio of the PWM control signal S. A resistor R3 is connected in series to the photodiode D that constitutes the photocoupler 5. When the potential VA at the point A becomes high level by the PWM control signal S that is an input signal, a current flows through the photodiode D, The phototransistor Q0 constituting the photocoupler 5 is turned on. A voltage obtained by dividing DC12V output from the DC-DC converter 3 by the resistor R14 and the resistor R13 is applied between the collector and the emitter of the phototransistor Q0. Therefore, when the phototransistor Q0 is turned on, a current flows between the collector and emitter of the phototransistor Q0, and the capacitor C4 connected in series with the phototransistor Q0 is charged.

  FIG. 6 is a timing chart showing a voltage change in each part of the circuit shown in FIG. When the potential VA at the point A is changed by the PWM control signal S as shown in FIG. 6A, for example, the potential VB at the point B is changed as shown in FIG.

  The smoothing circuit 9 includes, in addition to the resistor R13 and the capacitor C4, a first integrating circuit including a resistor R12 and a capacitor C3, a voltage follower 12, a resistor R6, and a capacitor C1. 2 integrating circuits. The potential VB at the point B shown in FIG. 6B is smoothed by the first and second integrating circuits, converted into the smoothed voltage shown in FIG. 6C, and converted to the potential VC at the point C. Become. That is, the smoothing circuit 9 smoothes the voltage level of the PWM control signal S shown in FIG. 6A and converts it to the smoothed voltage shown in FIG. At this time, the voltage follower 12 prevents the element constants of the resistor R6 and the capacitor C1 constituting the second integration circuit from being affected by the first integration circuit due to the high input impedance.

  The triangular wave generation circuit 10 includes a Schmitt circuit including an operational amplifier 13 that outputs a square wave, an integration circuit including a resistor R7, a capacitor C2, and an operational amplifier 14 that integrates the square wave output from the Schmitt circuit and outputs a triangular wave. Consists of A voltage obtained by dividing DC12V output from the DC-DC converter 3 by the resistor R10 and the resistor R11 is applied to the inverting input terminal of the operational amplifier 13 and the non-inverting input terminal of the operational amplifier 14 as the reference voltage e0.

  The square-wave + side saturation voltage (+ ES) output from the operational amplifier 13 is input to the inverting input terminal of the operational amplifier 14 via the resistor R7 and integrated, and the output voltage e2 of the operational amplifier 14 quickly decreases. However, since the voltage eR obtained by dividing the difference between the output voltages e1 and e2 of the operational amplifiers 13 and 14 by the resistors R8 and R9 is applied to the non-inverting input terminal of the operational amplifier 13, the output voltage e2 of the operational amplifier 14 is As the voltage decreases, the voltage eR applied to the non-inverting input terminal of the operational amplifier 13 also decreases. When the voltage eR applied to the non-inverting input terminal of the operational amplifier 13 drops to the reference voltage e0 applied to the inverting input terminal, the output voltage e1 of the operational amplifier 13 becomes a square-wave-side saturation voltage (-ES). At the same time, the voltage eR applied to the non-inverting input terminal of the operational amplifier 13 is greatly reduced to the minus side. When the output voltage e1 of the operational amplifier 13 is inverted, the operational amplifier 14 integrates the square-wave-side saturation voltage (-ES), so that the output voltage e2 of the operational amplifier 14 starts to rise. Therefore, the voltage eR applied to the non-inverting input terminal of the operational amplifier 13 also rises, and when the reference voltage e0 is reached, the output voltage e1 of the operational amplifier 13 is inverted again to the square-wave + side saturation voltage (+ ES). . Since this operation is repeated, a triangular wave is obtained from the output of the operational amplifier 14.

  The amplitude of the triangular wave is adjusted by the absolute value of the saturation voltage ES of the square wave and the values of the resistors R8, R9, and the frequency of the triangular wave is adjusted by the values of the resistors R7, R8, R9 and the capacitor C2. The triangular wave generation circuit 10 according to the present embodiment generates a triangular wave having the same magnitude as the maximum voltage level of the smoothed voltage appearing at the point C and the same frequency as the PWM control signal S, for example, as shown in FIG. Then, the potential VD at point D is used.

  The comparator 11 constitutes a pulse width modulation circuit, compares the voltage level of the smoothed voltage output from the smoothing circuit 9 with the voltage level of the triangular wave output from the triangular wave generation circuit 10, and pulses the smoothed voltage. Modulate width. The resistors R4 and R5 provided at the input terminals of the comparator 11 are for setting the input impedances of the input terminals of the comparator 11 to be equal. For example, the comparator 11 compares the voltage level of the smoothed voltage indicated by the solid line in FIG. 6C and indicated by the dotted line in FIG. 6D with the voltage level of the triangular wave as shown in FIG. Then, the smoothing voltage is subjected to pulse width modulation. The output voltage of the comparator 11 is divided by the resistors R1 and R2, and the divided voltage is applied to the base of the transistor Q1.

  Accordingly, the conduction of the transistor Q1 is controlled by the output of the comparator 11, and the potential VE at the point E, that is, the potential of the CONTR terminal of the fan 2 changes as shown in FIG. This potential change becomes a PWM control signal delayed by a certain time from the PWM control signal S by inverting the PWM control signal S shown in FIG. The fan 2 is PWM-controlled as shown in FIG. 2 in accordance with the duty ratio d of this control signal input to the CONTR terminal. Therefore, the fan rotation speed control circuit controls the rotation speed N of the fan 2 according to the duty ratio d of the control signal input to the CONTR terminal, that is, according to the duty ratio of the PWM control signal S. .

  In such a fan rotational speed control circuit, the input signal to the connector 6 that appears as the potential VA at the point A starts from a high level commanding the minimum rotational speed N of the fan 2 as shown in FIG. In the case of a sudden stepwise change to a low level voltage level commanding the highest rotational speed N, the change is caused by the smoothing circuit 9 via the potential VB at point B shown in FIG. 7 (c) is converted into a gentle slope-like change in the smoothing voltage indicated by the potential VC at point C. This gentle voltage change of the smoothing voltage is compared with the voltage level of the triangular wave shown in FIG.

  Therefore, the control signal applied to the CONTR terminal of the fan 2 is such that the signal level input to the fan rotation speed control circuit is steeply stepped from the lowest high level shown in FIG. 7A to the highest low level. As shown in FIG. 7 (e), the duty ratio d is gradually increased. For this reason, even if the potential VA at the point A changes suddenly, the rotational speed of the fan 2 does not change rapidly and gradually increases. Therefore, the current Id consumed by the fan 2 gradually increases as shown in FIG. 7 (f), and the current Id for driving the fan 2 increases rapidly like the conventional inrush current. Never become. As a result, an excessive load is not applied to the DC-DC converter 3 that supplies the current Id to the fan 2, so that the output voltage of the DC-DC converter 3 drops or the power supply output stops as in the prior art. No more events will occur.

  Further, the power supply unit 21 receives the PWM control signal S from the device 4 through the connector 6 as described above. Then, the input PWM control signal S is converted into a smoothed voltage as described above in the fan rotational speed control circuit, and the converted smoothed voltage is compared with a triangular wave voltage and subjected to pulse width modulation. The fan 2 is driven by the current Id supplied from the DC-DC converter 3, and the rotational speed N is controlled by a control signal that is input to the CONTR terminal and is pulse-width modulated by the fan rotational speed control circuit, whereby the device 4 Cool down.

  Therefore, when the command of the PWM control signal S that causes the fan 2 to rotate rapidly from low speed to high speed comes from the apparatus 4 side, or the power supply unit 21 is removed from the apparatus 4 and the connection of the connector 6 to the apparatus 4 is disconnected. In this case, as shown in FIG. 7A, the voltage input from the connector 6 to the fan rotation speed control circuit is abruptly changed stepwise from the lowest high level to the highest low level. However, the current Id consumed by the fan 2 gradually increases as described above, and does not become an inrush current that rapidly increases as in the conventional case. For this reason, the DC-DC converter 3 included in the power supply unit 21 does not need to select a DC-DC converter 3 having a current capacity of a magnitude that takes into account the inrush current as in the prior art, and a current that can supply the steady-state current Id. You can use one with capacity. As a result, the DC-DC converter 3 included in the power supply unit 21 can be reduced in size and price, and therefore, the power supply unit 21 can be reduced in size and price.

  In the above embodiment, the case where the triangular wave generation circuit 10 is configured by the Schmitt circuit including the operational amplifier 13 and the integration circuit including the operational amplifier 14 has been described. However, the triangular wave generation circuit 10 is not limited to this configuration. . For example, the triangular wave generating circuit may be configured by an integrating circuit composed of a resistor and a capacitor without using an operational amplifier. Even with such a configuration, the same effects as the above-described embodiment can be obtained.

2 ... Fan 3 ... DC-DC converter (power supply)
DESCRIPTION OF SYMBOLS 4 ... Apparatus 5 ... Photocoupler 6, 7 ... Connector 8 ... Cable 9 ... Smoothing circuit 10 ... Triangular wave generation circuit 11 ... Comparator 12 ... Voltage follower 13, 14 ... Operational amplifier 21 ... Power supply unit

Claims (3)

In the fan rotation speed control circuit that performs pulse width modulation control of the fan rotation speed according to the duty ratio of the input signal,
A smoothing circuit that smoothes the voltage level of the input signal and converts the input signal into a smoothed voltage;
A triangular wave generating circuit that generates a triangular wave of the same frequency as the input signal with the same amplitude as the maximum voltage level of the smoothing voltage;
A fan rotation speed control circuit comprising: a pulse width modulation circuit that compares the voltage level of the smoothed voltage with the voltage level of the triangular wave and modulates the smoothed voltage with a pulse width.   The fan for cooling the device, a power supply for supplying power to the fan, a connector for inputting a pulse width modulation control signal output from the device, and the pulse width modulation control signal input from the connector A power supply unit comprising the fan rotation speed control circuit according to claim 1 that controls a rotation speed. The smoothing circuit is constituted by an integrating circuit composed of a capacitor and a resistor,
The triangular wave generating circuit includes a Schmitt circuit that outputs a square wave, and an integrating circuit that integrates the square wave output from the Schmitt circuit and outputs a triangular wave.
The pulse width modulation circuit includes a comparator that compares the voltage level of the smoothed voltage output from the smoothing circuit and the voltage level of the triangular wave output from the triangular wave generation circuit. The fan rotational speed control circuit according to claim 1 or the power supply unit according to claim 2.

Images