JPH1163483A - Combustion control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To constitute a power supply system providing a reasonable operation and less amount of useless-operation in which a power supply circuit for a combustion control device for driving a plurality of fan motors having different ranges of voltage from each other is improved. SOLUTION: In the case that a first fan motor 20a having a larger maximum value of voltage range is controlled within a range of less than a set voltage, a micro-computer 31 sets a first operation control mode and controls a switching element 21a through a control circuit 22a for a first fan motor 20a while output voltages of the switching power supply circuits 12 to 18 are being fixed. In the case that the operation is controlled within a range exceeding a set voltage of the first fan motor 20a, the micro-computer 31 sets a second control mode and controls a rate of electrical energization at a primary winding of a transformer 14 for power supply circuits 12 to 18 while the switching element 21a of the first fan motor 20a is being kept as it is. The aforesaid set voltage is not less than a maximum value of a second fan motor 20b and lower than a maximum value of the first fan motor and a voltage control for the second fan motor is carried out by controlling the switching element 21b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention has separate combustion sections for hot water supply and for reheating of hot water in a bathtub, for example, as is recognized in recent gas water heaters and the like. The present invention relates to a control device for a combustion apparatus having a plurality of fan motors for forcibly supplying an optimal amount of air at each time, and particularly to an improvement in a power supply system thereof.

[0002]

2. Description of the Related Art As described above, a recent combustion apparatus has a plurality of fan motors having different application voltage ranges applied to rotation speed control because the required air supply amount to the combustion section is different. There is. FIG. 4 shows a conventional typical circuit configuration example of the combustion control device in such a case.

[0003] A switching control circuit 12 connected to a commercial AC power supply 11 controls on / off of a switching element 13 at a specific frequency to interrupt a primary current flowing through a primary winding of a transformer 14 at a fixed duty ratio. As a result, an output voltage corresponding to the fixed duty ratio appears on the secondary winding of the transformer 14, and this is rectified by an appropriate rectifying and smoothing circuit 15, 16, 17, and 18 to obtain a DC output. Diode in the case shown
The half-wave rectifier 15 is a choke input type having a choke coil 16, and its pulsating current output is smoothed by a smoothing capacitor 17. The diode 18 is a so-called flywheel diode, and passes the choke coil residual energy when the rectifier diode 15 is cut off to the smoothing capacitor 17.

The output voltage of the switching power supply circuit having the above-mentioned constituent elements 12 to 18 is supplied to the switching element 21a for the first and second fan motors 20a and 20b shown in FIG. , b. The switching elements 21a, b are, as shown by signal linking lines 36a, b,
Recently, the on / off state is controlled by on / off control circuits 22a and 22b controlled by a microcomputer (hereinafter, simply referred to as a microcomputer) 31 which is often used as a main control circuit.
The actual applied voltages to a and b are variably controlled, and the rotation of the fan motors 20a and b is controlled so that the required number of rotations is obtained at each time. The outputs of the switching elements 21a and 21b are smoothed by, for example, a smoothing circuit including a choke coil 24 and a smoothing capacitor 25, and a flywheel diode 23 is generally provided also in this portion.
Further, in the following, when the term “fan motor drive circuit” is used for convenience, the above-described circuit elements 21 to
Refers to the entire circuit, including 25.

On the other hand, paying attention to the microcomputer 31 which is a control circuit, a power supply is required of course. However, conventionally, generally, the output voltage of the switching power supply circuits 12 to 18 is adjusted to a power supply voltage range suitable for the microcomputer 31. It is obtained through a dedicated microcomputer power supply 32 that stabilizes and stabilizes. The microcomputer 31 also controls other electric loads 33 necessary for combustion control as indicated by a signal linking line 35, and this power is also usually obtained from a switching power supply circuit.

[0006]

However, regardless of whether the first and second fan motors 20a and 20b are fan motors having the same characteristics, as described above, separate fans are used for hot water supply and reheating. In the case of gas water heaters having a combustion section, these have different characteristics,
In particular, power consumption often differs greatly. Of course, the variable range of the voltage applied to each of the fan motors 20a and 20b is different,
Some have a large maximum applied voltage and some have a small maximum applied voltage. Devices using more than two fan motors are also conceivable, but often do so. Here, two cases will be described with reference to FIG. 4 for simplicity of description, but for convenience, it is assumed that the first fan motor 20a consumes larger power and has a larger maximum applied voltage. This is denoted as a fan motor (large) in the figure,
The other second fan motor 20b is referred to as a fan motor (small). The relationship between large and small does not necessarily depend on the size of the form, but generally, the form that consumes large power has a larger form.

Conventionally, however, the switching power supply circuits 12 to 18 must always operate at an output voltage capable of rotating the first fan motor (large) 20a at the maximum speed. FIG. 3 is a characteristic diagram used later for describing the present invention. As shown in FIG.
If the maximum value of the voltage range to be applied to is Vmax (a), the fixed output voltage of the switching power supply circuits 12 to 18 is also
As shown by the thick broken line in FIG. 3, this value is fixed to Vmax (a) (however, the voltage drop in the power supply line from the switching power supply circuit to the fan motor is, for convenience of explanation,
Ignored).

In other words, in other words, the voltage applied to the second fan motor (small) 20b is fixed even when the maximum voltage Vmax (b) is applied to the second fan motor 20b. Output voltage (= Vmax
From the viewpoint of (a)), this must be lowered considerably, and this amount (= Vmax (a) -Vmax (b)) must be consumed by the fan motor drive circuit including the switching element 21b. This is pretty wasteful. Furthermore, in general, since the second fan motor 20b must rotate at a low rotation speed, the waste of power consumption increases and the heat generated by the switching element 21b increases as the second fan motor 20b must rotate at a low rotation speed. Become. In addition, the fact that such a large voltage drop must be generated means that the switching element 20b and other related circuit elements must be large, which hinders miniaturization and cost reduction of the device. It is. Even if the first fan motor 20a having a large capacity is used, if it is sufficient that the first fan motor 20a rotates at a low speed, the load for the voltage drop at the switching element 21a in the fan motor drive circuit also becomes large, and Problem arises.

The present invention has been made in view of such circumstances, and in a combustion control device which needs to drive a plurality of fan motors having different applied voltage ranges from each other, the power supply circuit thereof has been particularly improved to make it more rational and wasteful. It is intended to construct a small power supply system.

[0010]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a plurality of fan motors having different applied voltage ranges for controlling the number of rotations because the required air supply to the combustion section is different. And a common power supply circuit provided to supply operating power to the plurality of fan motors, and a transformer for generating an output voltage of a magnitude corresponding to the duty factor of the primary winding in the secondary winding. A switching power supply circuit including the switching power supply circuit, a switching element individually inserted between the switching power supply circuit and each of the plurality of fan motors, and an on / off state of each switching element controlled based on a command from the control circuit. An on / off control circuit for individually and variably controlling the applied voltage to the fan motor connected to each of the switching elements; Data of two specific fan motors that have a magnitude relationship with the maximum value of the applied voltage range, the one with the largest maximum value is the first fan motor and the smaller one is the second fan motor. When the applied voltage to be applied to the first fan motor is variably controlled within the range from the set voltage to the lower voltage or less than the set voltage, the control circuit enters the first control mode, and the primary winding of the transformer of the switching power supply circuit is turned on. The on / off state of the switching element is variably controlled via an on / off control circuit relating to the first fan motor while maintaining the output voltage at a fixed value corresponding to the set voltage while keeping the duty ratio constant; When the applied voltage to be applied is variably controlled in a range exceeding or exceeding the set voltage, the control circuit enters a second control mode, and controls on / off of the first fan motor. While variably controlling the duty ratio of the primary winding of the transformer of the switching power supply circuit while keeping the switching element in the ON state through the path; setting the above set voltage to the maximum value of the applied voltage range of the second fan motor or more. The voltage applied to the second fan motor is controlled to be less than the maximum value of the applied voltage range of the first fan motor; the variable control of the applied voltage to the second fan motor is performed through an on / off control circuit for the second fan motor throughout the applied voltage range. The present invention proposes a combustion control apparatus characterized in that the control is performed by controlling on / off of a switching element.

Here, when the set voltage is set to the maximum value of the applied voltage range of the second fan motor, as described above, the variable control of the applied voltage to the second fan motor uses the on / off control circuit. Under the condition that the on / off of the switching element is controlled by way of the switch, the efficiency is highest.

The switching of the control mode between the first and second control modes in the control circuit can be performed based on the data of the set voltage stored in the nonvolatile memory, or separately from the control circuit. , The applied voltage actually applied to the first fan motor is detected, and the comparison between the detected voltage and the set voltage can be made based on the detection result of a voltage detection circuit which can be made by the user. Further, the control circuit can be configured to include a microcomputer, which is normal in recent technical circumstances.

Further, the present invention can be applied to a combustion apparatus having three or more fan motors having substantially different applied voltage ranges. That is, in the two fan motors selected in combination of taking two out of the three or more fan motors, the larger one of the maximum values of the applied voltage range is the first fan motor, and the smaller one is the second one. What is necessary is just to apply the above-mentioned gist structure of this invention to a fan motor. In such a case, the present invention can be applied to any one, some, or all of the plurality of possible combinations.

For example, regarding the maximum value of the applied voltage range,
Suppose there are three fan motors in a large, medium, and small relationship. In this case, when the present invention is applied focusing on the fan motor (large) and the fan motor (middle), a configuration in which the first applied voltage, preferably the maximum applied voltage of the fan motor (middle) is preferably set as the first set voltage. is there. According to the above configuration,
The control circuit switches the control mode on the basis of the first set value. In addition, attention is further paid to the fan motor (large) and the fan motor (small), and if the present invention is applied between them, it is preferable that the fan motor (small) be used.
There is a configuration in which the control circuit switches the control mode with the maximum applied voltage as a set value. Similarly, pay attention to the fan motor (middle) and the fan motor (small), and set the set value between them. And the configuration of the present invention can be applied. In such a case, there are two or three set values when viewed as a whole of the combustion equipment, and depending on the operating condition required for each fan motor at each time, the control circuit controls the first control mode and the second control mode for each set value. The control mode is switched between the control modes. However, even in such a case, the present invention is applied to the combustion equipment in duplicate for each combination of two fan motors that are basically in a combined relationship.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a first embodiment of a combustion control device for a combustion apparatus constituted according to the present invention. Elements denoted by the same reference numerals as the circuit elements in the conventional configuration described above indicate elements that may be the same or similar, and the description thereof will be omitted with reference to the preceding description. is there.

Further, as described above, the present invention can be basically applied to a combustion apparatus having three or more fan motors having different applied voltage ranges, but here, the first fan motor having a large maximum applied voltage range. 20a (shown as "fan motor (large)" in the figure) and a smaller second fan motor 20b (also called "fan motor (small)") for combustion equipment having two fan motors. An application example is shown. Therefore, it is easy to compare with the conventional example already described with reference to FIG.

In the illustrated embodiment, this is not directly relevant to the present invention, but preferably has two separate power supply circuits. One is a switching power supply circuit according to the switching method already described, and the specific circuit configuration itself may be arbitrary, but in the case shown in the figure, similarly to the conventional example described above, it operates by receiving operation power from the commercial AC power supply 11. A switching element 13 for intermittently switching the primary current of the transformer 14 in accordance with the control of the switching control circuit 12, a half-wave rectifier circuit having a diode 15 for rectifying the secondary AC output of the transformer 14,
Choke coil 16 and smoothing capacitor to smooth the output
17, and a flywheel diode 18. The switching power supply circuit
20a, b are driven.

However, what is different from the conventional circuit shown in FIG. 4 is that the switching control circuit 12 for controlling the ON / OFF of the switching element 13 always performs the ON / OFF control at a fixed transformer primary winding duty ratio as in the prior art. Rather, as will be described in detail later, the signal linking line is controlled by a command from the microcomputer 31 used as a main control circuit in the illustrated case.
Under the control of the primary winding, the duty ratio of the primary winding may be varied.

Another power supply circuit is a non-switching circuit having a transformer 41 for transforming the voltage of the commercial AC power supply 11 only according to a turn ratio between the primary winding and the secondary winding, and a rectifying circuit 42 for rectifying the output. Power supply circuit. Although the specific circuit configuration itself may be arbitrary, the rectifier circuit is constituted by a full-wave rectifier (so-called bridge rectifier) 42 in the illustrated case, and the rectified pulsating current output is smoothed by the smoothing capacitor 43.

The non-switching power supply circuits 41 to 43 are connected to a microcomputer 31 via a microcomputer power supply circuit 32 which is a dedicated stabilized power supply.
When the combustion equipment is provided with other electric loads 33 such as an electric ignition device, an electromagnetic valve, and various electric sensors, the other loads 33 are also driven. These other loads
33 may be controlled by the microcomputer 31 as indicated by the signal linking line 35, and may provide the microcomputer 31 with information necessary for combustion control. Since these points are not related to the present invention, detailed description will be omitted.

The output voltages of the switching power supply circuits 12 to 18 are smoothed by a smoothing circuit including, for example, a choke coil 24 having a flywheel diode 23 and a smoothing capacitor 25, similarly to the above-described conventional example. It is applied to fan motors 20a, b. The switching elements 21a and 21b are inserted in series in the power supply lines to the individual fan motors 20a and 20b, respectively.
On / off states of a and b are controlled by on / off control circuits 22a and b, respectively. The on / off control circuits 22a and 22b also
As shown by the signal link lines 36a and 36b, the microcomputer 31 is controlled by a control circuit. Each switching element 21a, b
The higher the on / off duty ratio, that is, the longer the on-time within a unit cycle, the higher the voltage applied to each assigned fan motor 20a, b. However, according to the present invention, this point is completely different from the conventional example,
As described later, the switching element 21a for the first fan motor may be subjected to ON / OFF control, or may be left ON, instead.

Hereinafter, a characteristic control mode in the combustion control device of the present invention will be described. FIG. 3 shows a characteristic example of the first and second fan motors 20a and 20b in which the minimum applied voltage at the minimum air supply amount and the maximum applied voltage at the maximum air supply amount are different.
Although the maximum applied voltage of the first fan motor 20a is indicated by Vmax (a) and that of the second fan motor 20b by Vmax (b), the microcomputer 31 specifies the voltage to be applied to the first fan motor 20a. If the voltage is equal to or less than the set voltage Vs (for convenience, "less than" here), the control operation is performed in the first control mode, and if the voltage exceeds or exceeds the set voltage Vs (here, " ) Is the control operation in the second control mode. As will be understood from the following description, the set voltage Vs is set at a value equal to or higher than the maximum applied voltage Vmax (b) of the second fan motor 20b and lower than the maximum applied voltage Vmax (b) of the first fan motor 20a. Even if it is set, the effect of using the present invention is recognized as compared with the conventional example, but in this embodiment, the set voltage Vs is the maximum applied voltage Vmax (b ). The value Vs is stored in a non-volatile memory (not shown) attached to the microcomputer 31 in this embodiment.

The microcomputer 31 calculates the applied voltage corresponding to the required number of revolutions of the fan motor for the amount of combustion at each time. The calculation result of the voltage to be applied to the first fan motor 20a is calculated by a nonvolatile memory (not shown). As long as the voltage does not reach the set voltage Vs stored in the memory, the microcomputer 31 operates in the first control mode. In this first control mode, the microcomputer
31 acts on a switching control circuit 12 of a switching power supply circuit 12 to 18 which is a large power supply circuit common to both fan motors 20a, b via a signal linking line 34, and its output voltage corresponds to a set voltage Vs. The switching element 13 is controlled at a fixed duty ratio so as to have a fixed value. As described above, the set voltage Vs is at least equal to or higher than the maximum applied voltage Vmax (b) of the second fan motor 20b, and in response to this, the voltage to be actually output from the switching power supply circuits 12 to 18 is the fan motor The value Vs + α is obtained by adding the voltage drop α in the power supply line up to 20a, b. In the summary of the present application, “fixed value according to the set voltage” has such a meaning.
However, since the point of adding the voltage drop α is a common sense in circuit design, such a voltage drop α will be ignored hereafter, and the switching power supply circuits 12 to 18 will set the set voltage under the first control mode. Vs is output.

In the first control mode, when a constant output voltage Vs is being output from the switching power supply circuits 12 to 18, the voltage should be applied to the first fan motor 20a according to the amount of combustion at each time. The microcomputer 31 acts on the on / off control circuit 22a via the signal link line 36a to control the switching element 21a to turn on and off so that the voltage becomes the voltage. Therefore, when it is sufficient to apply a voltage equal to or lower than the set voltage Vs also to the first fan motor 20a, it is not necessary to cause a large voltage drop from the maximum applied voltage Vmax (a) as in the conventional case, and the set voltage Vs Therefore, power consumption is reduced and the load on the switching element 21a is also reduced. Further, the second fan motor whose maximum applied voltage Vmax (b) is smaller than that of the first fan motor 20a.
Regarding 20b, the power consumption of the switching element 21b for supplying a voltage thereto can be greatly reduced as compared with the conventional example, greatly contributing to the miniaturization and cost reduction of the circuit.

As is apparent, the switching power supply circuit 12
18 output a set voltage Vs at least equal to or higher than Vmax (b) (Vmax (b) = Vs in this embodiment). Therefore, regarding the second fan motor 20b, when the microcomputer 31 is in the above-described first control mode. Also, in the second control mode described below, the microcomputer 31 operates the on / off control circuit 22b via the signal connection line 36b to control the switching element 21b to turn on and off the second fan motor. Controls the applied voltage to 20b.

However, the microcomputer 31 calculates the applied voltage corresponding to the required number of revolutions of the fan motor for the amount of combustion at each time. As a result, the calculation result of the voltage to be applied to the first fan motor 20a becomes the set voltage. If Vs or more, the microcomputer 31 changes the control mode from the first control mode to the second control mode. In the second control mode, first, the microcomputer 31 keeps the switching element 21a included in the fan motor drive circuit for the first fan motor 20a in the on state via the on / off control circuit 22a. Then, in the first control mode, the switching power supply circuits 12 to
Instead of controlling the 18 to output the fixed output voltage Vs, the microcomputer 31 acts on the switching control circuit 12 of the switching power supply circuits 12 to 18 via the signal connection line 34,
By variably controlling the duty ratio of the primary winding of the transformer 14 (variably controlling the duty ratio of the switching element 13 for the switching power supply circuit to an appropriate value), the output voltage of the first fan A voltage value required for the motor 20a is set.

Therefore, in this situation, the power consumption of the switching element 21a in the individual fan motor drive circuit for the first fan motor 20a is minimized, and the burden is also reduced. In addition, even if the fan motor drive circuit of the second fan motor 20b is used, the first fan motor 20a
Compared with the conventional example in which a voltage drop from the maximum application voltage Vmax (a) is required, the width of the voltage drop can be reduced, and the power consumption here is also reduced.

As described above, according to the present invention, the switching power supply circuits 12 to 18 always output a voltage corresponding to the maximum applied voltage Vmax (a) for the first fan motor 20a, as compared with the conventional example. Individual fan motor drive circuits 21 to 25
Can significantly reduce power consumption in the economy,
Not only is it reasonable, but also smaller and less expensive elements can be used for the fan motor drive circuit.
The same can be said because the switching power supply circuits 12 to 18 themselves do not always need to operate at the maximum power. In general, a capacitor used for an output smoothing unit of a voltage variable circuit by this type of switching control tends to have a short life due to a large charge / discharge load. However, according to the present invention, this is also alleviated, and eventually, the capacitor is used. It also increases the reliability of the equipment.

As is apparent, even if the set voltage Vs is higher than Vmax (b) in the above-described embodiment, if the set voltage Vs is at least lower than the maximum applied voltage Vmax (a) for the first fan motor 20a, this set voltage Vs By switching the control mode at the voltage Vs, it is possible to expect a reduction in power consumption as compared with the related art. However, in other words, the second fan motor 20 that always controls the applied voltage only by turning on and off the switching element 21b in the fan motor drive circuit.
b, the maximum applied voltage Vmax (b)
The fact that Vs is set is most important for switching element 21.
The burden on b is small and effective.

FIG. 2 shows another embodiment according to the present invention. Since the basic operation itself is the same as that described with reference to FIG. 1, only the changed points will be described. The same reference numerals as those in FIG. 1 are used for the reference numerals in FIG. What has been changed in the present embodiment is a setting voltage Vs that determines a control switching point between the first control mode and the second control mode,
This is for comparison with the voltage actually applied to the first fan motor 20a.

In the case of the embodiment shown in FIG. 1, data of the set voltage Vs is written in a nonvolatile memory attached to the microcomputer 31, and the voltage determined by the microcomputer 31 to be applied to the first fan motor 20a at each time. The value is compared with the value, and the first control mode or the second control mode is determined according to the magnitude relation. On the other hand, in the embodiment shown in FIG.
A voltage detection circuit capable of detecting the voltage value actually applied to 20a and detecting whether or not the voltage value has reached the set voltage by itself is used.

In the case of this embodiment, the voltage detection circuit includes a zener diode 26, a resistor 27, and a digital transistor 28 that substantially performs an inverter operation.
The Zener voltage of the Zener diode 26 corresponds to the set voltage Vs. That is, when the voltage applied to the first fan motor 20a becomes the set voltage Vs corresponding to the Zener voltage of the Zener diode 26, a detection output is generated in the output of the voltage detection circuit, and in the case shown, the output of the digital transistor 28 is inverted. And it goes low. Accordingly, the on / off control circuit 22a uses this detection output to function to keep the switching element 21a in the on state. Then, such a circuit state is fed back to the microcomputer 31 via the signal linking line 36a, and based on this information, the microcomputer 31 acts on the switching control circuit 12 to perform variable control of the on / off state of the switching element 13, and The second control mode for variably controlling the duty ratio of the primary winding of the heater 14 is entered.

Although the embodiments of the present invention and the advantages thereof have been described above, in the illustrated embodiment, a power supply circuit for supplying operating power to the microcomputer 31 and a power supply circuit for supplying operating power to each fan motor are separately provided. Therefore, there is also the following advantage (although such a configuration itself has been separately filed by the present applicant). First, when the fan motors 20a and 20b may be stopped, the microcomputer 31 controls the switching element 13 to be completely turned off so that the switching power supply circuits 12 to 18 can be completely stopped. it can. Since the microcomputer 31 is also supplied with power by a separate non-switching power supply circuit at this time, such control is possible. In the case of the conventional example shown in FIG. 4, if the power of the switching power supply circuits 12 to 18 is turned off, the microcomputer 31 cannot operate. However, to put it the other way around, the non-switching power supply circuits 41 to 43 always operate. However, compared to the fan motors 20a and 20b that consume large amounts of power, not only the microcomputer 31 but also the other loads 33 operate with sufficiently small power, so that the transformer 41 for the non-switching power supply circuit is equivalent to the transformer 41. A small one can be used. On the other hand, since the switching power supply circuit tends to be large, the fact that the switching power supply circuit can be reduced in size as the power consumption is reduced more than compensates for the disadvantage of using two transformers. The reliability of the device is also improved and the life is extended.

However, the present invention can naturally be applied to a combustion apparatus having three or more fan motors having different applied voltage ranges. When the present invention is applied to only two of the three, the embodiment is substantially the same as the above-described embodiment, but two or more or all of the combinations of two of the three The present invention can be applied to combinations.

For example, as described above, it is assumed that there are three fan motors having a large, medium, and small relationship with respect to the maximum value of the applied voltage range. These values are set as Vmax (a), Vmax (b), and Vmax (c) in the order of large, medium, and small, respectively. In such a case, when the present invention is applied focusing on the fan motor (large) and the fan motor (middle), first, the first set voltage Vs is preferably set as the maximum applied voltage Vm of the fan motor (middle).
There is a configuration in which ax (b) is set to the set value Vs, which corresponds to the above-described embodiment itself. In addition to this, attention is paid to the fan motor (large) and the fan motor (small), and if the present invention is applied between them, it is preferable that the fan motor (small) be used.
There is a configuration in which the control circuit switches the control mode on the basis of the maximum applied voltage Vmax (c) as the second set value Vs,
Similarly, attention is also paid to the fan motor (middle) and the fan motor (small), and a set value is provided between these, so that the set voltage Vs is also the smallest maximum applied voltage Vmax (c). is there.

In this case, there are two or three set values when viewed as a whole of the combustion equipment, and according to the operating condition required for each fan motor at each time, the control circuit determines the set value for each set value. The control mode is switched between the one control mode and the second control mode. However, in the end, such a combustion apparatus basically only applies the present invention redundantly for each combination of two fan motors in a combination relationship, and follows the gist configuration of the present invention. .

[0037]

As described above, in a combustion apparatus having a plurality of fan motors having different applied voltage ranges, a switching power supply circuit which always outputs the maximum value of the fan motor having the largest maximum applied voltage range is used. In addition, the power consumption is extremely large, and the device life tends to be short.
On the other hand, according to the present invention, the output voltage of the switching power supply circuit can be switched and used according to the required voltage value to be applied to the fan motor at each time, so that the power supply circuit can be made significantly smaller and consume less power. Can be. Smoothing circuit section,
In particular, the load on the smoothing capacitor and the switching element in each fan motor drive circuit is reduced, so that not only a small one can be used, but also the life is extended and the reliability of the entire device is improved.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram of an embodiment of a combustion control device configured according to the present invention.

FIG. 2 is a circuit configuration diagram in another embodiment of the combustion control device configured according to the present invention.

FIG. 3 is an explanatory diagram of a control operation in the combustion control device of the present invention.

FIG. 4 is a typical circuit configuration diagram of a conventional combustion control device.

[Explanation of symbols]

 11 Commercial AC power supply 12 Switching control circuit 13 Switching element 14 Transformer for switching power supply circuit 17 Smoothing capacitor for switching power supply circuit 20a, b Fan motor 21a, b Switching element 22a, b On / off control circuit 25 Smoothing capacitor 26 Zener diode 28 Digital transistor 31 Control circuit (microcomputer) 33 Other electrical loads 41 Non-switching power supply circuit transformer

Claims (5)

[Claims] The present invention relates to a plurality of fan motors having different application voltage ranges to be applied to rotation speed control due to a difference in a required amount of air supply to a combustion section, and to supply operating power to the plurality of fan motors. A switching power supply circuit including a transformer for generating an output voltage of a magnitude corresponding to the duty factor of the primary winding in the secondary winding, the switching power supply circuit and the plurality of switching power supplies. A switching element individually inserted between each of the fan motors, and an on / off state of each of the switching elements is controlled based on a command from a control circuit, and the voltage applied to the fan motor connected to each of the switching elements is controlled. A combustion control device comprising: an on / off control circuit for individually variably controlling a voltage; wherein the plurality of fan motors have a maximum value within the applied voltage range. When two of the specific two fan motors having a larger maximum value are the first fan motor and the smaller one is the second fan motor, an applied voltage to be applied to the first fan motor. Is variably controlled within a range of not more than a set voltage and less than a set voltage, the control circuit enters a first control mode in which the duty ratio of the primary winding of the transformer of the switching power supply circuit is kept constant and the switching power supply circuit is controlled. Variably controls the on / off state of the switching element via the on / off control circuit for the first fan motor while maintaining the output voltage of the first fan motor at a fixed value corresponding to the set voltage; When variably controlling the applied voltage to exceed or exceed the set voltage, the control circuit enters a second control mode, and the control circuit enters the second control mode. While variably controlling the duty ratio of the primary winding of the transformer of the switching power supply circuit while maintaining the switching element in an on state via an on / off control circuit; Above the maximum value of the applied voltage range and less than the maximum value of the applied voltage range of the first fan motor; the variable control of the applied voltage to the second fan motor is controlled by the second fan motor. Controlling the on / off of the switching element through the on / off control circuit for the second fan motor in the entire range of the applied voltage range; 2. The combustion control device according to claim 1, wherein:
The combustion control device, wherein the set voltage is a maximum value of the applied voltage range of the second fan motor. 3. The combustion control device according to claim 1, wherein the control mode switching between the first and second control modes in the control circuit is stored in a nonvolatile memory. The combustion control device is based on data of a set voltage. 4. The combustion control device according to claim 1, wherein switching of the control mode between the first and second control modes in the control circuit is provided separately from the control circuit. Detecting the applied voltage actually applied to the first fan motor, and performing the detection based on a detection output of a voltage detection circuit capable of comparing the detected voltage with the set voltage. Combustion control device. 5. The combustion control device according to claim 1, wherein the control circuit includes a microcomputer.