JP3096553B2 - Drive unit for blower fan - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving device for a blower fan.

[0002]

2. Description of the Related Art In a water heater, for example, a microcomputer sets a combustion amount of a burner every moment based on a tapping temperature and a set temperature thereof, and blows combustion air to the burner in accordance with the set combustion amount. A device that controls the rotation speed of a blower fan is generally known. In this type, the required rotation speed of the blower fan is set by a microcomputer in accordance with the set combustion amount of the burner,
By grasping the actual rotation speed of the blower fan based on the detection signal of the speed sensor and the current supplied to the fan motor, the amount of power supplied to the blower fan is controlled by feedback so that the rotation speed matches the set rotation speed. The rotation speed of the blower fan is controlled.

More specifically, the control of the rotation speed of the blower fan as described above is performed using, for example, a circuit as shown in FIG.

In FIG. 1, a is a blower fan, b is a power supply circuit b for generating a DC power signal from a commercial power supply, and the blower fan a is connected to the power supply circuit b via a switching circuit c and a smoothing circuit d. . In this case, the switching circuit c is configured using, for example, a semiconductor switch element,
By applying a pulse signal to the control signal input unit, the DC power signal generated by the power circuit b is intermittently output to the smoothing circuit d. The smoothing circuit d includes a diode e, a coil f, and a capacitor g, and smoothes a power signal output intermittently from the switching circuit c into a power signal having a level corresponding to the duty and cycle of the intermittent. This is supplied to the blower fan a. Then, the blower fan a rotates at a rotation speed corresponding to the level of the power signal supplied from the smoothing circuit d.

Reference numeral h denotes a power supply control circuit for generating a pulse signal for switching the switching circuit c on and off and applying the pulse signal to the switching circuit c. The power supply control circuit h includes a blower fan a output from the microcomputer i. A rotation speed detector j comprising a set rotation speed signal indicating the set rotation speed of the fan, a speed sensor for detecting the rotation speed of the blower fan a, and a current sensor for detecting an energizing current corresponding to the rotation speed of the blower fan a. And an actual rotation speed signal indicating the actual rotation speed of the blower fan a output from the controller. Then, the power supply control circuit h generates a pulse signal in accordance with the deviation between the set rotation speed and the actual rotation speed of the blower fan a, applies the pulse signal to the switching circuit c, and causes the switching circuit c to be turned on and off. . In this case, the power supply control circuit h switches the switching circuit c on and off so that the actual rotation speed of the blower fan a matches the set rotation speed. For example, when the actual number of revolutions is smaller than the set number of revolutions, a pulse signal that shortens the OFF time of the switching circuit c is applied to the switching circuit c, and thereby applied to the smoothing circuit d per unit time. By increasing the DC power signal, the level of the power signal output from the smoothing circuit d to the blower fan a is increased, and the rotation speed of the blower fan a is increased.

Incidentally, in such a driving device of the blower fan a, if a current-carrying portion such as an armature coil of the blower fan a is disconnected, the actual rotation speed of the blower fan a decreases regardless of the set rotation speed. , For this, the blower fan a
The deviation between the set rotation speed and the actual rotation speed becomes large. For this reason, the power supply control circuit h controls the switching of the switching circuit c so as to shorten the OFF time of the switching circuit c in order to increase the amount of power supplied to the blower fan. For this reason, the voltage applied to the capacitor g of the smoothing circuit d increases to the level of the DC power signal generated by the power circuit b.

On the other hand, in this type of driving device for the blower fan a, generally, the maximum rated voltage of the condenser g is set to be equal to or slightly higher than the maximum rated voltage of the blower fan a. The rated voltage is lower than the level of the DC power signal generated by the power circuit b. That is, for example, in a water heater, the level of the DC power signal generated by the power supply circuit b from the commercial power supply is about one hundred and several tens of volts, whereas the blower fan a does not need a capacity corresponding to such a voltage, A maximum rated voltage of about several tens of volts is sufficient. Also, in the capacitor g of the smoothing circuit d for supplying power to the blowing fan a, a capacitor having a maximum rated voltage that is substantially equal to or slightly larger than the maximum rated voltage of the blowing fan a is sufficient, and the maximum rated voltage is more than necessary. It is not preferable to use the condenser g or the blower fan a having a large size, because it increases the size of the apparatus and increases the cost.

However, as described above, the blowing fan a
When the current-carrying part is disconnected, a large-level voltage close to the level of the DC power signal generated by the power supply circuit b is applied to the capacitor g of the smoothing circuit d, and the capacitor g may be broken. Was.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to improve a driving device of a blower fan. More specifically, the present invention relates to a method of connecting a power supply signal intermittently output from a switching circuit intermittently controlled by a power supply control circuit to a capacitor. It is an object of the present invention to provide a blower fan driving device that can protect a capacitor of a smoothing circuit from overvoltage in a blower fan drive device that supplies power to the blower fan after smoothing by a used smoothing circuit.

It is another object of the present invention to provide a blower fan drive device capable of protecting a capacitor of a smoothing circuit with a simple and inexpensive structure.

[0011]

In order to achieve the above object, the present invention provides a DC power supply using a rectifier circuit from an AC power supply.
A power supply circuit for generating a signal, at least the direct current and a switching circuit, the output of the switching circuit for intermittently outputting a DC power supply signal generated by the power supply circuit
The level of the original signal be a capacitor maximum rated voltage is small powers the wind fan feed to smooth, setting a smoothing circuit allowed to drive the air blowing fan, the rotational speed while monitoring the rotation speed of air blowing fan in the driving device of the blower fan which includes a power supply control signal for occupying performed intermittently in the switching circuit so as to match the speed and power supply control circuit to be applied to the switching circuit, the voltage of the capacitor of the smoothing circuit, wherein It may be approximately equal to the maximum rated voltage
Is characterized by comprising a power supply stopping means for stopping the power supply to the smoothing circuit when the voltage exceeds a predetermined overvoltage set to a value smaller than the maximum rated voltage .

The power supply stopping means includes a signal transmission path necessary for generating the power supply control signal in the power supply control circuit or a signal transmission path of the power supply control signal from the power supply control circuit to the switching circuit. A power supply to the smoothing circuit is stopped by interrupting the signal transmission path via the interrupting circuit, wherein the power supply to the smoothing circuit is stopped.

[0013] Alternatively, the power supply stopping means includes a cutoff circuit connected to a power supply path from the power supply circuit to the smoothing circuit so as to be able to cut off the power supply path, and cuts off the power supply path via the cutoff circuit. Thus, the power supply to the smoothing circuit is stopped.

Alternatively, there is provided a microcomputer for instructing the set number of revolutions to the power supply control circuit, and the microcomputer includes a voltage detecting circuit for generating a signal having a level corresponding to the voltage of the capacitor. And a rotation speed instruction unit for setting the set rotation speed to zero when the voltage of the capacitor grasped by the voltage grasping unit becomes equal to or higher than the overvoltage. It is characterized by the following.

Further, the power supply stopping means is connected to the capacitor, and generates a signal having a level corresponding to the voltage of the capacitor, and a signal necessary for generating the power supply control signal in the power supply control circuit. A switch circuit that is connected to the transmission path and cuts off the signal transmission circuit when a drive signal is applied; and a signal generated by the voltage detection circuit as an input signal, and a level of the input signal corresponds to the predetermined overvoltage. And a switch drive circuit for applying the drive signal to the switch circuit when the level exceeds the threshold level.

The power supply circuit generates a DC power supply signal from a commercial AC power supply using a rectifier circuit.

The switching circuit comprises a semiconductor switch element such as a transistor or an FET.

The smoothing circuit is composed of, for example, a diode and a coil connected in parallel to the output side of the switching circuit, and the capacitor connected to the coil in parallel with the blower fan.

Further, for example, an energizing current detecting circuit for detecting the energizing current of the blower fan as an actual rotational speed of the blower fan and generating a signal of a level corresponding to the energizing current, Power supply control circuit, for example, when a signal generated by the energizing current detection circuit and the set rotation speed signal generation circuit is input, A comparison circuit for generating a signal corresponding to the level deviation,
A pulse signal generation circuit that generates a pulse signal having a duty corresponding to the level of the signal generated by the comparison circuit as the power supply control signal. in this case,
When the signal transmission path in the power supply control circuit is cut off by the power supply stop means, for example, a signal transmission path from the comparison circuit to the pulse signal generation circuit is cut off.

Further, when the power supply stopping means is constituted by the voltage detection circuit, the switch circuit and the switch drive circuit, the voltage detection circuit is constituted by, for example, a divided resistor connected in parallel to the capacitor. Further, the switch circuit is configured by a semiconductor switch element such as a transistor. Further, the switch drive circuit includes:
For example, when the output of the voltage detection circuit and the input of the switch circuit are connected by a Zener diode, and the level of a signal generated at the output of the voltage detection circuit becomes equal to or higher than the level corresponding to the predetermined overvoltage. , A signal of a level necessary for driving the switch circuit is applied to an input portion of the switch circuit via a Zener diode.

[0021]

According to the present invention, when the blower fan is disconnected, the amount of power supplied from the power supply circuit to the smoothing circuit increases, and the voltage of the capacitor of the smoothing circuit increases. When the voltage of the capacitor becomes equal to or higher than a predetermined overvoltage, the power supply stopping means stops the power supply to the smoothing circuit, thereby preventing the voltage applied to the capacitor from being further increased. Protected from damage due to excessive voltage.

In this case, when the power supply to the smoothing circuit is stopped, a signal transmission path required for generating the power supply control signal in the power supply control circuit or the supply of the power supply control signal from the power supply control circuit to the switching circuit is performed. It is preferable to block the signal transmission path. With this configuration, the power supply control signal for interrupting the switching circuit is not provided to the switching circuit, so that the switching circuit is cut off, and thus the power supply from the power supply circuit to the smoothing circuit is stopped. Becomes In this case, since the signal level of the signal transmission path is relatively low, a circuit for cutting off the signal transmission path can be configured using small and inexpensive circuit elements.

When the power supply to the smoothing circuit is stopped, a power supply path from the power supply circuit to the smoothing circuit may be cut off. Even in this case, when the voltage of the capacitor becomes equal to or higher than a predetermined overvoltage, the power supply to the smoothing circuit is stopped, and the capacitor is protected.

When a microcomputer for instructing the set number of revolutions to the power supply control circuit is provided, the microcomputer may be provided with the voltage grasping unit and the number of revolutions instructing unit as the power supply stopping means. Good. In this case, when the voltage of the capacitor becomes equal to or higher than the overvoltage, the set number of revolutions given to the power supply control circuit from the revolution number instruction unit of the microcomputer becomes zero, so that the power supply control circuit turns off the switching circuit. The state is controlled so that the power supply to the smoothing circuit is stopped.

When the power supply stopping means is constituted by the voltage detection circuit, the switch circuit, and the switch drive circuit, when the voltage of the capacitor becomes equal to or higher than the overvoltage, the drive signal is transmitted from the switch drive circuit to the switch circuit. The switch circuit blocks a signal transmission path necessary for generating the power supply control signal in the power supply control circuit. For this reason, the power supply control circuit does not generate a power supply control signal for interrupting the switching circuit, and accordingly, the switching circuit
In the state F, the power supply to the smoothing circuit is stopped. With such a configuration of the power supply stopping means, the power supply stopping means can be simply configured using a small and inexpensive circuit element such as a resistor or a semiconductor switch element. It is possible to quickly cut off the signal transmission path of the control circuit and quickly stop the power supply to the smoothing circuit.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram of the apparatus of the present embodiment.

In FIG. 1, reference numeral 1 denotes a power supply circuit for generating a DC power supply signal from a commercial AC power supply 2, and 3 denotes an intermittent DC power supply signal generated by the power supply circuit 1 by applying a pulse signal to a control input unit. Switching circuit to output to
Reference numeral 4 denotes a smoothing circuit for smoothing the output of the switching circuit 3 by the diode D, the coil 5 and the capacitor 6 to supply power to the blower fan 7, and 8 generates a signal (actual speed signal) corresponding to the actual rotational speed of the blower fan 7. A rotation speed detector 9 for generating a signal indicating a set rotation speed of the blower fan 7 (a set rotation speed signal); and 10 a switching circuit 3 which receives the actual rotation speed signal and the set rotation speed signal as inputs. Is a power supply control circuit that generates a pulse signal (power supply control signal) for interrupting the power supply. Power supply circuit 1, switching circuit 3,
The configurations of the smoothing circuit 4, the blower fan 7, the rotation speed detector 8, and the power supply control circuit 10 and their connection configurations are described in FIG.
Are the same as those shown in FIG. In addition, the rotation speed setting device 9
As in the case of FIG. 6, a microcomputer may be used, or a set rotation speed signal may be manually generated using a variable resistor or the like.

The basic operation of the apparatus of this embodiment is shown in FIG.
And a pulse having a duty or frequency corresponding to a deviation between the actual rotation speed of the blower fan 7 indicated by the actual rotation speed signal and the set rotation speed of the blower fan 7 indicated by the set rotation speed signal. By providing a signal from the power supply control circuit 10 to the switching circuit 3,
The switching circuit 3 is turned on and off. At this time, power is supplied to the blower fan 7 from the power supply circuit 1 via the switching circuit 3 and the smoothing circuit 4 so as to eliminate the deviation between the actual rotation speed and the set rotation speed. Is feedback-controlled so as to match the set rotation speed.

On the other hand, the apparatus of this embodiment includes a power supply stopping means 11 for stopping the power supply from the power supply circuit 1 to the smoothing circuit 4 when the voltage of the capacitor 6 of the smoothing circuit 4 becomes equal to or higher than a predetermined overvoltage. ing.

The power supply stopping means 11 receives a voltage of the capacitor 6 and generates a signal having a level corresponding to the voltage, and a signal necessary for the power supply control circuit 10 to generate the pulse signal. And a shutoff circuit 13 connected to a signal transmission path (not shown) inside the power supply control circuit 10 for performing transmission.
When the level of the signal generated by the voltage detection circuit 12 becomes equal to or higher than a level corresponding to a predetermined overvoltage set in advance in the capacitor 6, the power supply control circuit 1
The signal transmission path inside the power supply control circuit 10 is interrupted so as to stop the generation of the pulse signal due to 0. The set value of the overvoltage of the capacitor 6 is about the maximum rated voltage of the capacitor 6 or slightly lower.

In the apparatus according to the present embodiment, when a current-carrying portion such as an armature coil of the blower fan 7 is disconnected, the blower fan 7 indicated by the actual rotation speed signal of the rotation speed detector 8 is used.
Since the actual rotation speed of the power supply becomes lower or becomes “0” with respect to the set rotation speed, the power supply control circuit 10 controls the switching of the switching circuit 3 to increase the amount of power supply to the blower fan 7. For this reason, the DC power supply signal applied from the power supply circuit 1 to the smoothing circuit 4 also increases, and the voltage of the capacitor 6 rapidly increases.

However, in the power supply stopping means 11, when the voltage of the capacitor 6 exceeds a predetermined overvoltage,
Since the level of the signal generated by the voltage detection circuit 12 is equal to or higher than the level corresponding to the overvoltage of the capacitor 6, the cutoff circuit 13 cuts off the signal transmission path inside the power supply control circuit 10. For this reason, the power supply control circuit 10
The switching circuit 3 is turned off, and the power supply from the power supply circuit 1 to the smoothing circuit 4 is stopped. This prevents the voltage of the capacitor 6 from rising above the overvoltage, and prevents the capacitor 6 from being destroyed by the overvoltage.

In this case, the signal level for generating the pulse signal in the power supply control circuit 10 is generally lower than the level of the power supply signal from the power supply circuit 1 to the smoothing circuit 4 and the blower fan 7. Therefore, the cutoff circuit 13 of the power supply stopping means 11 only needs to cut off a low-level signal transmission path. Therefore, the cutoff circuit 13 can be configured using a relatively inexpensive and small switch element or the like. .

In this embodiment, the signal transmission path inside the power supply control circuit 10 is interrupted.
As shown by the imaginary line a in FIG.
Connected to a signal transmission path for transmitting the set rotation speed signal to the power supply control circuit 10 or a virtual line b in FIG.
As shown in FIG.
May be connected to a signal transmission circuit for applying the pulse signal, and these signal transmission paths may be cut off by the cutoff circuit 13 in the same manner as described above. Even in this case, when the voltage of the capacitor 6 of the smoothing circuit 4 becomes equal to or higher than the overvoltage, the power supply control circuit 10 does not generate the pulse signal or the pulse signal is not applied to the switching circuit 3. 3 is OF
In the state F, the power supply from the power supply circuit 1 to the smoothing circuit 4 is stopped. This prevents the voltage of the capacitor 6 from rising above the overvoltage, and prevents the capacitor 6 from being destroyed by the overvoltage.

Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 2 is a block diagram of the apparatus of the present embodiment. In the following description, components having the same configuration as that of the first embodiment are denoted by the same reference numerals, and detailed description is omitted.

The basic configuration of the device of this embodiment is the same as that of the first embodiment, and includes a power supply circuit 1, a switching circuit 3, a smoothing circuit 4 having a capacitor 6, a blower fan 7, a rotation speed detector. 8, rotation speed setting device 9, power supply control circuit 1
0, and a power supply stopping means 11 comprising a voltage detection circuit 12 and a cutoff circuit 14. In this case, the cutoff circuit 1
Reference numeral 4 is connected to a power supply path from the switching circuit 3 to the smoothing circuit 4, and is not shown when the level of a signal generated by the voltage detection circuit 12 becomes equal to or higher than a level corresponding to a predetermined overvoltage of the capacitor 6. The power supply path from the switching circuit 3 to the smoothing circuit 4 is cut off by a switch element or the like.

According to the apparatus of this embodiment, when the blower fan 7 is disconnected and the voltage of the capacitor 6 of the smoothing circuit 4 increases and becomes higher than a predetermined overvoltage, the power supply stopping means 11
Of the switching circuit 3 to the smoothing circuit 4
Cut off the power supply path leading to. As a result, the power supply from the power supply circuit 1 to the smoothing circuit 4 is stopped, and the voltage of the capacitor 6 is prevented from rising above the overvoltage, and the capacitor 6 is not destroyed by the overvoltage.

In this embodiment, the power supply path from the switching circuit 3 to the smoothing circuit 4 is cut off.
For example, as shown by an imaginary line c in FIG. 2, a cutoff circuit 14 is connected to a power supply path from the power supply circuit 1 to the switching circuit 3, and the power supply path from the power supply circuit 1 to the switching circuit 3 is cut off by the cutoff circuit 14. You may. Even in such a case, when the voltage of the capacitor 6 becomes equal to or higher than the overvoltage, power is not supplied to the smoothing circuit 4, so that the capacitor 6 is protected from the overvoltage.

Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 3 is a block diagram of the apparatus of the present embodiment. In the following description, components having the same configuration as that of the first embodiment are denoted by the same reference numerals, and detailed description is omitted.

The basic configuration of the apparatus of this embodiment is the same as that of the first embodiment, and includes a power supply circuit 1, a switching circuit 3, a smoothing circuit 4 having a capacitor 6, a blower fan 7, a rotation speed detector. 8, rotation speed setting device 9, power supply control circuit 1
0 and power supply stopping means 11. In this case, the rotation number setting device 9 is constituted by a microcomputer 9a. The microcomputer 9a includes a rotation speed instruction unit 1 that outputs the set rotation speed signal to the power supply control circuit 10.
5 and digital data obtained by A / D converting a signal of a level corresponding to the voltage of the capacitor 6 generated by the voltage detection circuit 12 having the same configuration as that of the first embodiment by the A / D converter 16. And a voltage grasping unit 17 for grasping the voltage of the capacitor 6 is functionally provided as the power supply stopping unit 11. The rotation speed instruction unit 15 determines that the voltage of the capacitor 6 grasped by the voltage grasping unit 17 is equal to or higher than the overvoltage. Is set to "0", the power supply control circuit 1
0 is designated.

According to the apparatus of the present embodiment, when the blower fan 7 is disconnected and the voltage of the capacitor 6 of the smoothing circuit 4 increases and becomes higher than a predetermined overvoltage, this becomes the voltage detection circuit 12 and the A / D converter. At this time, the rotation speed instructing unit 15 of the microcomputer 9a sets the set rotation speed to “0” and sets the set rotation speed corresponding to the set rotation speed to “0”. The signal is output to the power supply control circuit 10. Therefore, the power supply control circuit 10 controls the switching circuit 3 so as to stop the switching circuit 3 from being turned on and off so as to turn the switching circuit 3 off, and thereby the smoothing circuit 4
The power supply to is stopped. Therefore, the voltage of the capacitor 6 is prevented from rising above the overvoltage, and the capacitor 6 is not destroyed by the overvoltage.

In this embodiment, the A / D converter 1
The A / D conversion by the microcomputer 6 and the arithmetic processing by the microcomputer 9a require some time from when the voltage of the capacitor 6 exceeds the overvoltage until the set number of revolutions becomes "0". It is preferable that the set value of the overvoltage of the capacitor 6 for stopping the power supply is set to be smaller than in the case of the first embodiment and the second embodiment.

Next, as a particularly preferred embodiment of the present invention, a more specific embodiment of the first embodiment will be described with reference to FIGS.
This will be described with reference to FIG. FIG. 4 is a circuit configuration diagram of the device of this embodiment.

In FIG. 4, the power supply circuit 1 includes a rectifier circuit 18 composed of a diode bridge circuit for rectifying an AC power supply signal of the commercial AC power supply 2 (for example, 100 V), and an output of the rectifier circuit 18. A smoothing circuit 21 having a capacitor 20 for smoothing to a constant level DC power signal is output from the smoothing circuit 21 to the switching circuit 3 at a substantially constant level (for example, 140 V).

The switching circuit 3 is constituted by an FET 22 which is a semiconductor switch element.
Is connected to the smoothing circuit 21 of the power supply circuit 1. The FET 22 applies a pulse signal between its gate terminal G and the drain terminal D, so that the source terminal S and the drain terminal D are turned on / off in accordance with the pulse signal. The applied DC power signal is output to the drain terminal D side.

The smoothing circuit 4 including the diode 23, the coil 5 and the capacitor 6 has the coil 5 connected to the drain terminal D of the FET 22, and the capacitor 6 and the fan motor 7 a of the blower fan 7 are provided downstream of the coil 5. They are connected in parallel. The diode 23 is for a flywheel, and is for supplying power to the coil 5 via the ground of the fan motor 7a when the FET 22 is OFF. In this embodiment, the capacitor 6 has a maximum rated voltage of 63 V, for example, and the fan motor 7 a of the blower fan 7 is a DC motor, for example, having a maximum rated voltage of 50 V.

The rotation speed detector 8 comprises an energization current detection circuit 24 for detecting the energization current to the fan motor 7a as corresponding to the actual rotation speed of the blower fan 7. The energizing current detection circuit 24 includes a resistor 25 connected to an energizing portion of the fan motor 7a so as to apply an energizing current to the fan motor 7a, and outputs a voltage signal generated in the resistor 25 at a level proportional to the energizing current. It outputs to the power supply control circuit 10 as a signal indicating the current supplied to the motor 7a, in other words, as an actual speed signal indicating the actual speed of the blower fan 7.

The rotation number setting device 9 serving as a setting rotation number signal generating circuit generates a pulse signal having a duty corresponding to the setting rotation number of the blower fan 7, and the microcomputer 26 generates the pulse signal. A smoothing circuit 28 that receives the pulse signal via the photocoupler 27. The smoothing circuit 28 converts the pulse signal received from the microcomputer 26 via the photocoupler 27 into a level corresponding to the duty, in other words, A voltage signal having a level corresponding to the set rotation speed of the blower fan 7 is smoothed and output to the power supply control circuit 10 as a set rotation speed signal indicating the set rotation speed.

The power supply control circuit 10 controls the deviation between the level of the actual rotation speed signal applied from the energizing current detection circuit 24 and the level of the set rotation speed signal applied from the rotation speed setting device 9, in other words, A comparison circuit 29 for generating a voltage signal having a level corresponding to the deviation between the actual rotation speed of the fan 7 and the set rotation speed, and a pulse signal (power supply) having a duty corresponding to the level of the voltage signal output from the comparison circuit 29 And a pulse signal generating circuit 30 for generating a control signal) and applying the control signal to the gate terminal G of the FET 22 of the switching circuit 3.

The comparison circuit 29 is constituted by using an operational amplifier 31 which receives the actual rotational speed signal and the set rotational speed signal as inputs. The operational amplifier 31 has a voltage of a level corresponding to the level difference between the two input signals. The signal is output to the pulse signal generation circuit 30. In this case, in this embodiment, the OP amplifier 31
The capacitor 32 and the resistors 33 and 34 for mitigating the output change with respect to the input change are connected to the OP amplifier 31.

The pulse signal generating circuit 30 generates an oscillating circuit 35 for generating a triangular wave signal having a constant period and a constant peak level.
And a comparator 36 that receives and outputs the output signal of the comparison circuit 29 and the output signal of the oscillation circuit 35 to generate and output a pulse signal having a duty corresponding to the level of the output signal of the comparison circuit 29, and the output of the comparator 36 ( A switching transistor 37 which is turned on / off in accordance with a pulse signal), and a transformer 38 having a primary coil connected to the switching transistor. The secondary coil of the transformer 38 is connected between the gate terminal G and the drain terminal D of the FET 22 via resistors 39 and 40, and the pulse signal generating circuit 3 is connected to the middle point of the primary coil.
0 or the power supply voltage VD (for example, 12 V) of the comparison circuit 29 is applied.

With this configuration, the pulse signal generation circuit 3
0 indicates that the comparator 36 generates a pulse signal having a duty corresponding to the level of the output signal of the comparison circuit 29, in other words, the deviation between the actual rotation speed and the set rotation speed, and outputs the pulse signal to the gate of the FET 22 through the transformer 38. A power supply control signal is applied between the terminal G and the drain terminal D.

In this embodiment, the comparison circuit 29
And the level of the output signal of the comparator 36 of the pulse signal generation circuit 30 are at most about 5V.

The power supply stopping means 11 comprises the voltage detection circuit 12 and the cutoff circuit 13.
Is an NPN type switching transistor 4 which is a semiconductor switch element having a collector connected to a signal transmission path 41 from the comparison circuit 29 to the pulse signal generation circuit 30.
2 and a switch drive circuit 44 that generates a drive signal for driving the transistor 42 of the switch circuit 43.

The voltage detecting circuit 12 is composed of divided resistors 45 and 46 connected in parallel to the capacitor 6 of the smoothing circuit 4, and outputs a voltage signal having a level corresponding to the voltage of the capacitor 6 to the divided resistors 45 and 46. Output from the midpoint.

The emitter of the transistor 42 of the switch circuit 43 is grounded. When a drive signal of a predetermined level (for example, 0.6 V) or more is applied to the base of the transistor 42, the transistor 42 conducts between the emitter and the collector. The signal transmission path 41 is grounded (maintained at no signal level).

The switch drive circuit 44 includes the voltage detection circuit 1
A constant voltage zener diode 47 connected between the midpoint of the split resistors 45 and 46 which are the output points of the second and the base of the transistor 42; a resistor 48 connected between the base of the transistor 42 and the ground side; It consists of. In this configuration, when a voltage equal to or higher than the breakdown voltage of the Zener diode 47 is generated at the midpoint between the dividing resistors 45 and 46, the Zener diode 47 conducts, and the midpoint between the dividing resistors 45 and 46 according to the voltage of the capacitor 6. Is applied to the base of the transistor 42 by stepping down the voltage generated at the time by the breakdown voltage of the Zener diode 47. In this case, the breakdown voltage of the Zener diode 47 and the resistance 48
When the voltage of the capacitor 6 becomes equal to or higher than the predetermined overvoltage (for example, 50 V), the transistor 42
Is set so that a voltage (a voltage of 0.6 V or more) that turns on the transistor 42 is applied to the base of.

Next, the operation of the apparatus of this embodiment will be described.

The basic operation of the device of this embodiment is as described above. The power supply control circuit 10 switches the switching circuit 3 on and off so as to eliminate the deviation between the actual rotation speed and the set rotation speed of the blower fan 7. Do it.

More specifically, for example, when the actual rotation speed is larger than the set rotation speed, the duty of the pulse signal generated by the pulse signal generation circuit 30 of the power supply control circuit 10 decreases, so that the switching is performed. FET22 of circuit 3
Is turned on per unit time is shortened. Therefore, the amount of power supply from the power supply circuit 1 to the smoothing circuit 4 decreases, and accordingly, the amount of power supply to the fan motor 7a of the blower fan 7 also decreases. Thus, the actual rotation speed of the blower fan 7 decreases so as to approach the set rotation speed.

Further, for example, when disconnection of the energizing portion of the fan motor 7a of the blower fan 7 occurs, the energizing current detecting circuit 24
No current flows through the resistor 25 of the power supply control circuit 1.
A signal of the “0” level is input to the 0 comparison circuit 29 as an actual rotation speed signal.

As a result, the deviation between the level of the actual speed signal and the level of the set speed signal becomes large, and the comparison circuit 2
9 finally outputs the maximum level voltage signal to the comparator 36 of the pulse signal generation circuit 30. When such a high-level signal is input, the comparator 36 generates and outputs a pulse signal with a large duty,
Therefore, the time during which the FET 22 is turned on per unit time becomes longer.

Accordingly, the amount of power supplied from the power supply circuit 1 to the smoothing circuit 4 increases, and the voltage of the capacitor 6 of the smoothing circuit 4 increases.

However, when the voltage of the capacitor 6 rises and becomes equal to or higher than the overvoltage, the Zener diode 47 of the power supply stopping means 11 conducts as described above, and at this time, the transistor 42 A drive signal having a level for turning ON the switch 42 is given. As a result, the emitter-collector of the transistor 42 conducts, and the signal transmission path 41 from the comparison circuit 29 to the pulse signal generation circuit 30 is forcibly grounded.
Becomes "0" level. For this reason, the pulse signal generation circuit 30 does not generate a pulse signal that causes the FET 22 to be turned on and off, thereby turning off the FET 22 and stopping the power supply to the smoothing circuit 4. Is further prevented from rising above the overvoltage. And
The electric charge accumulated in the capacitor 6 is divided by the divided resistors 45,
Discharge through 46.

As described above, according to the apparatus of this embodiment, when the voltage of the capacitor 6 becomes higher than the overvoltage, the power supply to the smoothing circuit 4 is stopped, so that the capacitor 6 is surely protected from being destroyed by the overvoltage. be able to. When the voltage of the capacitor 6 exceeds the overvoltage, the switch circuit 4
Since a drive signal for turning on the transistor 42 is instantaneously applied to the transistor 42 via the zener diode 47, the signal transmission path 41 of the power supply control circuit 10 is quickly cut off. Can be quickly stopped. Further, the signal level of the signal transmission path 41 which is cut off (grounded) by the transistor 42 of the switch circuit 43 is extremely lower than the power supply level to the blower fan 7.
And the switch drive circuit 44 using a small and inexpensive transistor 4
2 and a circuit element such as a Zener diode 47.

The following is a modification of this embodiment.

That is, in the present embodiment, the signal transmission path 4 from the comparison circuit 29 to the pulse signal generation circuit 30
4, the collector of the switch circuit 43 is connected to the signal transmission path on the output side of the comparator 36 of the pulse signal generation circuit 30 to cut off the output of the comparator 36, as shown by the imaginary line in FIG. You may make it confuse.

Further, in the present embodiment, the switch circuit 43 is constituted by using only the transistor 42. However, as shown in FIG. 5, for example, the polarity of the input side of the comparator 36 of the pulse signal generation circuit 30 is changed as shown in FIG. The switching circuit 43 may be configured using a set of switching transistors 49 and 50 in the opposite case. In this case, the signal transmission path 41 from the comparison circuit 29 to the comparator 36 of the pulse signal generation circuit 30 is held at the high level when the voltage of the capacitor 6 becomes higher than the overvoltage. No signal is generated.

Further, in this embodiment, the switch circuit 43 is configured using the transistor 42 as a semiconductor switch element. However, the switch circuit 43 may be configured using a switch element such as a relay.

In this embodiment, the switch driving circuit 44 is constituted by using the Zener diode 47. For example, the output voltage of the voltage detecting circuit 12 is
May be compared with the level corresponding to the overvoltage by the comparator, and the comparator may apply a drive signal to the transistor 42 of the switch circuit 43.

In this embodiment, the blower fan 7
The actual rotation speed of the blower fan 7 may be detected directly by using an appropriate speed sensor or the like, instead of detecting the actual rotation speed of the blower fan 7 by using the supplied current.

The current supplied to the blower fan 7 is detected and input to the power supply control circuit 10, and the actual rotation speed is detected by the speed sensor and input to the microcomputer 26, which then outputs. The set speed signal may be corrected by the actual speed detected by the speed sensor. This way,
For example, even if the rotation speed of the blower fan 7 fluctuates due to an exhaust gas blockage or the like in the water heater, it can be maintained at the target rotation speed.

[0073]

As is apparent from the above description, according to the present invention, the power supply stopping means for stopping the power supply to the smoothing circuit when the voltage of the capacitor of the smoothing circuit exceeds a predetermined overvoltage. By this, it is possible to prevent the voltage of the capacitor of the smoothing circuit from excessively rising when a disconnection or the like occurs in the energizing portion of the blower fan that is controlled so that the actual rotational speed matches the set rotational speed. , The capacitor can be protected from overvoltage. When the power supply to the smoothing circuit is stopped, the power supply control circuit cuts off a signal transmission path necessary for generating a power supply control signal for interrupting the switching circuit or a signal transmission path from the power supply control circuit to the switching circuit. Alternatively, when the power supply path from the power supply circuit to the smoothing circuit is shut off, or when the set rotation speed of the blower fan is set by a microcomputer, the microcomputer instructs the power supply control circuit to set the rotation speed to zero. Although there are various aspects such as, in any of the aspects,
The capacitor of the smoothing circuit can be easily protected from overvoltage. In particular, when the signal transmission path of the power supply control circuit or the signal transmission path from the power supply control circuit to the switching circuit is interrupted, the signal transmission at a relatively low level may be interrupted. The configuration can be easily configured using small and inexpensive circuit elements.

Further, when the signal transmission path of the power supply control circuit is interrupted to stop the power supply to the smoothing circuit, a circuit for performing such interruption is constituted by a voltage detection circuit, a switch circuit, and a switch drive circuit. In such a case, each circuit can be configured using a resistor, a switching element such as a switching transistor, an extremely inexpensive and small circuit element such as a zener diode, and the voltage of the capacitor of the smoothing circuit is equal to or higher than the overvoltage. In such a case, the power supply to the smoothing circuit can be quickly stopped, and therefore, the power supply stop means capable of reliably and quickly protecting the capacitor from overvoltage is made inexpensive, small, and simple. be able to.

[Brief description of the drawings]

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

FIG. 2 is a block diagram of a second embodiment of the present invention.

FIG. 3 is a block diagram of a third embodiment of the present invention.

FIG. 4 is a circuit configuration diagram showing a specific circuit configuration of the device of FIG. 1;

FIG. 5 is a circuit configuration diagram showing a modification of the device of FIG. 4;

FIG. 6 is a block diagram of a conventional driving device for a blower fan.

[Explanation of symbols]

1: power supply circuit, 3: switching circuit, 4: smoothing circuit,
6 condenser, 7 blower fan, 9a microcomputer, 10 power supply control circuit, 11 power supply stop means,
12: voltage detection circuit, 13, 14: cutoff circuit, 15: voltage grasping unit, 17: rotation speed instruction unit, 43: switch circuit,
44 ... Switch drive circuit.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H02P 5/00-5/26 H02P 7/00 H02P 7/34 F04D 27/00 H02M 7/217

Claims (5)

(57) [Claims] 1. A DC power supply signal from an AC power supply using a rectifier circuit.
A power supply circuit which generates a No., a switching circuit for intermittently outputting a DC power supply signal generated by the power supply circuit,
An output of the switching circuit is connected to at least the DC power signal.
Level to power the air fan feed smoothed using a capacitor maximum rated voltage is less than the issue, setting rotation and smoothing circuit allowed to drive the air blowing fan, the rotational speed while monitoring the rotation speed of air blowing fan in the driving device of the blower fan and a power supply control circuit to be applied to the switching circuit power supply control signal for occupying performed intermittently in the switching circuit so as to match the number, the voltage of the capacitor of the smoothing circuit, said maximum It is approximately equal to the rated voltage or
A drive device for a blower fan, comprising: a power supply stop means for stopping power supply to the smoothing circuit when the voltage exceeds a predetermined overvoltage set to a value smaller than the maximum rated voltage . 2. The power supply stopping device according to claim 1, wherein the power supply control circuit includes a signal transmission path necessary for generating the power supply control signal or a signal transmission path of the power supply control signal from the power supply control circuit to the switching circuit. 2. The blower fan according to claim 1, further comprising: a cutoff circuit connected so as to be able to cut off a transmission path, and stopping the power supply to the smoothing circuit by cutting off the signal transmission path via the cutoff circuit. Drive. 3. The power supply stopping means includes a cutoff circuit connected to a power supply path from the power supply circuit to the smoothing circuit so as to be able to cut off the power supply path, and cuts off the power supply path via the cutoff circuit. 2. The blower fan driving device according to claim 1, wherein the power supply to the smoothing circuit is stopped. 4. A microcomputer for instructing the power supply control circuit of the set number of revolutions, the microcomputer comprising a voltage detecting circuit for generating a signal having a level corresponding to the voltage of the capacitor. And a rotation speed instruction unit for setting the set rotation speed to zero when the voltage of the capacitor grasped by the voltage grasping unit becomes equal to or higher than the overvoltage. The driving device for a blower fan according to claim 1, wherein: 5. The power supply stopping means is connected to the capacitor, and generates a signal having a level corresponding to the voltage of the capacitor, and a signal necessary for generating the power supply control signal in the power supply control circuit. Connected to the transmission path,
A switch circuit that cuts off the signal transmission circuit when a predetermined level of the drive signal is applied; and a signal generated by the voltage detection circuit as an input signal, the level of the input signal corresponding to the predetermined overvoltage. The drive device for a blower fan according to claim 1, further comprising: a switch drive circuit that applies the drive signal to the switch circuit.