JP3089544B2 - Combustion control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control apparatus for a combustion apparatus having a fan motor for forcibly supplying an optimal amount of air to a combustion section at each time, as is recognized in, for example, a gas water heater or the like. In particular, it relates to an improvement in a power supply system of such a control device.

[0002]

2. Description of the Related Art In a combustion control apparatus for a combustion apparatus of this kind,
A switching power supply circuit is often used as the power supply. A switching power supply compared to the case of using a normal non-switching power supply circuit that directly transforms the input AC power supply voltage obtained from the commercial AC power supply according to the primary and secondary winding ratios of the transformer, rectifies and smoothes this This is because the transformer required for the circuit becomes considerably smaller, and thus the entire power supply circuit can be made smaller and lighter. FIG. 2 shows an overall schematic circuit configuration of the 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.

[0004] The output of the switching power supply circuit having the above-described component groups 12 to 18 is first supplied to the fan motor drive circuit 22.
The fan motor drive circuit 22 is also provided with a microcomputer (hereinafter simply referred to as a microcomputer) 31 which is often used as a main control circuit recently, as shown by a signal link line 36. And controls the fan motor 21 so that the required number of revolutions is obtained at each time.

On the other hand, if attention is paid to the microcomputer 31 which is a control circuit, a power supply is naturally required for this. Generally, this is achieved by adjusting the output voltage of the switching power supply circuit to a power supply voltage range suitable for the microcomputer 31 and stabilizing it. Through a dedicated microcomputer power supply 32. Microcomputer
31 also controls the other electrical loads 33 required for combustion control, as indicated by the signal link 35, this power also being obtained from a switching power supply circuit.

[0006]

In short, in a conventional control apparatus for a combustion apparatus, all power supplies of circuit elements included in or driven by the control apparatus are obtained from a single switching power supply circuit. . However, this causes various problems.

First, in the circuit of FIG. 2, the switching power supply circuit must have the ability to always rotate the fan motor 21 at the maximum rotation speed. However,
In a gas water heater or the like, especially in a summer or the like, when a large amount of combustion is not required to obtain a required tap water temperature, the fan motor drive circuit 22 is controlled by a command from the microcomputer 21 during the entire operation time. In many cases, control is performed to reduce the supply power to the fan motor 21 accordingly. Therefore, in such a case, the mounted switching power supply circuit has an excessively large capacity in many time ranges during the operation of the fan motor.

More specifically, even when combustion is stopped and the fan motor 21 does not need to be rotated in the first place, the switching power supply circuit itself must continue to operate because of the microcomputer 31 and other electric loads 33. . In addition, also at this time, the primary-side duty ratio is fixed, and the power of the maximum capacity can always be supplied. In other words, even in a situation where power needs to be supplied only to a microcomputer or other low power loads, that is, even in a very small power consumption situation,
In the conventional combustion control device, a large-capacity power supply circuit is always used.

Conversely, the switching power supply circuit used in the conventional circuit is the microcomputer 31 as described above.
And other electrical loads 33 controlled by it,
It is designed to have the capacity to operate all loads at once and always at maximum power supply. Therefore, the size can be reduced as compared with the case where a normal non-switching power supply circuit is used, but the size cannot be denied.

Moreover, such a large-capacity switching power supply circuit has a larger charging / discharging load on the smoothing capacitor 17 on the secondary winding side of the transformer than a normal non-switching power supply circuit comprising only a transformer and a rectifier, and has a longer life. Tends to be shorter. In the case of gas water heaters, at least the product life is required to be guaranteed about 10 years, but in order to satisfy this, it is necessary to allow more room for elements and components to be used, and this also makes the entire circuit more It will be large and expensive.

In addition, if a malfunction occurs in the switching power supply circuit 12 and the fan motor 21 stops or enters an abnormal rotation state, a dangerous situation may occur if the switching is not performed. You may not be able to do that. This is because the microcomputer is driven by the switching power supply circuit 12 in the first place.

The present invention has been made in view of the above circumstances, and has as its object to provide a combustion control device having a small and inexpensive power supply circuit in accordance with a rational operation principle.

[0013]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention first improves a combustion control device having a function of controlling a fan motor for forced air supply to a combustion section. The power supply circuit that supplies the operating power to the motor is a switching power supply circuit having a transformer that generates an output voltage having a magnitude corresponding to the duty factor of the primary winding in the secondary winding; and controls the rotation speed of the fan motor. The power supply circuit that supplies the operating power to the control circuit is a power supply circuit that is separate from the switching power supply circuit described above.
A non-switching power supply circuit that transforms only the secondary winding ratio and then rectifies it; control of the fan motor speed by the control circuit is performed by controlling the primary winding duty of the transformer in the switching power supply circuit. To do.

[0014] In addition to satisfying this basic configuration, the present invention further provides the above-described control circuit which stops the operation of the switching power supply circuit itself when it is not necessary to drive the fan motor. In order to prevent the smoothing capacitor provided at the output of the switching power supply from being discharged even when the operation of the switching power supply circuit is stopped, a charging circuit for charging the smoothing capacitor with the output of the non-switching power supply circuit is provided.

According to yet another aspect of the present invention,
A combustion control device in which an electric load other than the fan motor is driven by the non-switching power supply circuit is also proposed. Of course, the control circuit can generally be configured to include a microcomputer.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a circuit configuration of a combustion control device for a combustion apparatus constructed 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 for those elements, the above description is referred to, and the description in this section may be omitted. is there.

The combustion control device of the present invention 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 interrupting the primary current of a transformer 14 in accordance with the control of the switching control circuit 12, a half-wave rectifier circuit having a diode 15 for rectifying a secondary AC output of the transformer 14, and a choke coil for smoothing the output. The switching power supply circuit drives a fan motor 21. The switching power supply circuit 16 includes a smoothing capacitor 16, a flywheel diode 18, and a flywheel diode 18.

However, what is different from the conventional circuit shown in FIG. 2 is that the switching control circuit 12 for controlling the on / off of the switching element 13 always performs on / off control at a fixed transformer primary winding duty ratio as in the prior art. Instead, as will be described later, the duty ratio of the primary winding can be changed by a command from the microcomputer 31 used as a main control circuit in the case shown in the drawing, and more preferably, the completeness of the switching power supply circuit can be reduced. The configuration is such that a stop state (continuous OFF state of the switching element 13) can be realized.

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 circuit drives the microcomputer 31 via a microcomputer power supply circuit 32, which is a dedicated stabilized power supply, and desirably supplies an electric ignition device, a solenoid valve, various electric sensors, etc. to the combustion equipment. If other electric loads 33 are provided, those other loads 33 are also driven.

The microcomputer 31 has a signal connection line 34,
Acts on the switching control circuit 12 so that the required air supply amount should be obtained according to the combustion amount at that time, and controls the on / off duty of the switching element 13 so that the primary winding of the transformer 14 is energized. The rate is variably controlled, and the voltage value to be supplied to the fan motor 21 at each time, that is, the supplied power is controlled.

Therefore, unlike the conventional control method in which the output of the switching power supply that can always operate at the maximum capacity by operating at the fixed primary winding duty ratio is controlled in the direction in which the fan motor drive circuit 22 reduces the output, Since only the power required for the power supply can be supplied to the fan motor, the switching power supply circuit itself can be made smaller. Further, when the fan motor 21 may be stopped, the switching power supply circuit can be completely stopped by controlling the switching element 13 to be kept in a completely off state. In combination with this, the power consumption over time of the entire device can be greatly suppressed, and the life of the switching power supply circuit is extended.

However, according to the present invention, the non-switching power supply circuit always operates. However, compared to the fan motor 21 which continues to consume large power, the microcomputer 31
Needless to say, the other loads 33 also operate with sufficiently small power. Therefore, a considerably small transformer 41 for the non-switching power supply circuit can be used, which more than compensates for the disadvantage of using two transformers. Reducing the size of the fan motor drive power supply leads, above all, to reducing the size and cost of this type of apparatus as a whole. Other effects described below also demonstrate the benefits of the present invention.

However, when the switching power supply circuits 12 to 18 are configured to be able to be completely stopped as described above, when the power supply circuit is restarted from the completely stopped state, it is assumed that the smoothing capacitor 17 has already been completely discharged. , A considerable rush current (rush current) occurs at the time of initial charging,
If this is repeated many times, the life of the capacitor 17 may be significantly shortened. Therefore, in the circuit shown in the figure, a part of the rectified output of the non-switching power supply circuit that is always operating is supplied to the smoothing capacitor 17 via the current control resistor 52 and the backflow prevention diode 51, and the switching power supply circuit 12 The necessary amount of charge is charged to the smoothing capacitor 17 even when the motor is stopped. Of course, since the fan motor 21 is not driven through this bypass current path, the power consumption for this is small. Rather, the resistance value and the like are designed so that the leakage current to the fan motor 21 is reduced.

[0025] With such a contrivance, the switching power supply circuit can be reduced in size, and the power consumption of the entire device can be largely suppressed by driving the switching power supply circuit only when necessary without shortening the life of the switching power supply circuit. Although it is possible to obtain a small and inexpensive device, in the case of the circuit shown in the figure, as can be understood from the fact that the signal linking line 34 is a double-headed arrow, the microcomputer 31 controls the state of the switching control circuit 12, for example, It is possible to take in the current value or voltage value of the main part, and to know the short-circuit state of the circuit element. Therefore, even if an abnormality occurs in the switching power supply circuit, since the microcomputer 31 is driven by another non-switching power supply circuit, the microcomputer 31 can maintain a normal operation state, and can know occurrence of the abnormality. it can. Of course, when the occurrence of an abnormality is recognized, according to the existing technology, for example, a fuel flow control valve (not shown) is forcibly closed.
Safety measures can be taken.

[0026]

According to the present invention, the drive power of the fan motor consuming a large amount of power can be reduced in size and cost, and power can be supplied according to the required rotational speed of the fan motor. The power consumption of the entire combustion equipment including the device can be suppressed. In addition, since the switching power supply circuit for driving the fan motor can be completely stopped when it is unnecessary, the power consumption is further reduced. Furthermore, since the non-switching power supply circuit is configured to charge the switching power supply circuit smoothing capacitor at this time,
It is also possible to avoid the problem of the shortening of the life of the smoothing capacitor, which may occur in some cases, and to enjoy only the advantages of reducing the size of the device while reducing the power consumption.

[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 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 15 Rectifier diode for switching power supply circuit 16 Choke coil for switching power supply circuit 17 Smoothing capacitor for switching power supply circuit 21 Fan motor 31 Control circuit (microcomputer) 33 Other Electrical load 41 Transformers for non-switching power supply circuits 42 Rectifier circuits for non-switching power supply circuits 43 Smoothing capacitors for non-switching power supply circuits

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-8-251986 (JP, A) JP-A-6-58606 (JP, A) JP-A-9-42656 (JP, A) 114390 (JP, U) Actual opening 63-124088 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) F23L 5/00 F04D 27/00-27/02 H02M 3/00- 3/44 F24F 11/04

Claims (3)

(57) [Claims] 1. A combustion control device having a function of controlling a fan motor for forced air supply to a combustion section; a power supply circuit for supplying operating power to the fan motor corresponds to a duty ratio of a primary winding. A switching power supply circuit having a transformer for generating an output voltage of a magnitude in a secondary winding; a power supply circuit for supplying operating power to a control circuit for controlling the rotation speed of the fan motor is separate from the switching power supply circuit; Power supply circuit, the input AC voltage to the primary of the transformer,
A non-switching power supply circuit that transforms only by a secondary winding ratio and then rectifies; controlling the rotation speed of the fan motor by the control circuit controls a duty ratio of a primary winding of the transformer in the switching power supply circuit; The control circuit stops the operation of the switching power supply circuit itself when it is not necessary to drive the fan motor; and outputs the output of the switching power supply even when the operation of the switching power supply circuit is stopped. A combustion circuit for charging the smoothing capacitor with the output of the non-switching power supply circuit to avoid discharging the provided smoothing capacitor; 2. The combustion control device according to claim 1, wherein an electric load other than the fan motor used in the combustion equipment is driven by the non-switching power supply circuit. apparatus. 3. The combustion control device according to claim 1, wherein the control circuit includes a microcomputer.