Flame detection device

Abstract

To provide a flame detection device that enables transformerless operation by using a novel power supply circuit that directly connects capacitors and resistors to the primary power line of the AC power supply. [Solution] The flame detection device 1 using a flame rod 11 is equipped with a flame rod power supply circuit 2 that connects a capacitor C1 in parallel to the primary line L of a commercial AC power supply 10 and a resistor R1 to line N, then connects line L and line N, connects a capacitor C2 to the connected power supply line, and applies an AC voltage to the flame rod 11 through the capacitor C2.

Description

Technical Field

[0001] The technology disclosed in the present application relates to a flame detection device using a flame sensor used in a combustion control device for controlling ignition, extinguishing, etc. of a combustion means.

Background Art

[0002] Conventionally, a flame detection device using a frame rod, which is one of the flame sensors, has been disclosed in Patent Document 1 and the like.

[0003] Patent Document 1 discloses a frame rod type flame detection device that insulates the primary side and the secondary side of an AC power supply by an insulating transformer and applies an AC voltage to the frame rod through a capacitor connected to the secondary side of the insulating transformer.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Disclosure of the Invention

Problems to be Solved by the Invention

[0005] In a conventional frame rod type flame detection device, an insulating transformer has been adopted in a power supply circuit for applying an AC voltage to the frame rod. However, recently, the price of the insulating transformer has soared, resulting in an increase in manufacturing cost. In addition, there is also a problem that the size of the insulating transformer itself is large and it is difficult to reduce the size of the flame detection device. Furthermore, there is also a problem that the power consumption due to the no-load loss of the insulating transformer cannot be ignored.

[0006] The technology disclosed in the present application has been proposed in view of the above problems, and an object thereof is to provide a flame detection device that enables transformerless operation by using a novel power supply circuit in which a capacitor and a resistor are directly connected to the power supply line on the primary side of an AC power supply. [Means for solving the problem]

[0007] To achieve the above objective, the flame detection device according to claim 1 is a flame detection device using a flame rod, characterized in that it comprises a power supply circuit that connects a first capacitor in parallel to one of the two power lines on the primary side of a commercial AC power supply, a resistor in parallel to the other power line, then connects the one power line and the other power line, connects a second capacitor to the connected power line, and applies an AC voltage to the flame rod through the second capacitor. [Effects of the Invention]

[0008] In the flame detection device according to claim 1, a first capacitor is connected in parallel to one of the two power lines on the primary side of a commercial AC power supply, and a resistor is connected in parallel to the other power line. Then, the two power lines are connected, and a second capacitor is connected to the connected power lines. An AC voltage is then applied to the flame rod through the second capacitor. Even with a power supply circuit using the primary side of such a power line, it is possible to apply a flame-detectable AC voltage to the flame rod. Furthermore, since the second capacitor provides insulation between the primary side of the power line and the flame detection circuit including the flame rod, it becomes possible to apply an AC voltage to the flame rod using only the primary side of the commercial AC power supply without using an isolation transformer as in the conventional method. Therefore, it becomes possible to assemble a power supply circuit for the flame rod without a transformer, providing a low-cost and space-saving flame detection device. In addition, because it is transformerless, power consumption due to no-load losses of the isolation transformer, as in the conventional method, can also be reduced. [Brief explanation of the drawing]

[0009] [Figure 1] This is a circuit diagram of a flame detection device, which is one embodiment of the present invention. [Figure 2] Figure 1 is a circuit diagram showing the power supply circuit for the frame rod when the power plug is connected in reverse. [Figure 3] Figure 1 shows the circuit diagram of the flame detection device when the frame ground of the enclosure is not connected to earth. [Figure 4] This is a circuit diagram of a flame detection device that uses a switching power supply that is not connected to ground in its control circuit. [Modes for carrying out the invention]

[0010] First, a flame detection device 1, which is one embodiment of the present invention, will be described with reference to the drawings.

[0011] Figure 1 shows the circuit of a flame detection device 1, which is one embodiment of the present invention. The flame detection device 1 consists of a flame rod power supply circuit 2 that applies an AC voltage to a flame rod 11, which is a flame detection sensor, a flame circuit 3, a filter circuit 4, a flame detection circuit 5, and a control circuit (not shown) that controls the flame detection circuit 5 and the like.

[0012] Normally, of the two lines L and N of a commercial power supply (AC100V) 10, line N is grounded to Earth. The flame detection device 1 according to the present invention is equipped with a flame rod power supply circuit 2 that applies an AC voltage to the flame rod 11 using the commercial power supply (AC100V) 10. Lines L and N of the commercial power supply (AC100V) 10 are connected to the flame rod power supply circuit 2 of the flame detection device 1 through a power plug CN1. In the flame rod power supply circuit 2, a capacitor C1 is connected in parallel to line L and a resistor R1 is connected to line N as shown in Figure 1. After connecting lines L and N, line F is connected to the flame rod 11 of the flame circuit 3 through a capacitor C2. Capacitor C2 and the flame circuit 3 are connected by a connector CN2. Because it is connected to the flame circuit 3, filter circuit 4, and flame detection circuit 5 through capacitor C2, the flame rod power supply circuit 2, which is generated using commercial power supply (AC100V) 10, can be isolated from the flame circuit 3, filter circuit 4, and flame detection circuit 5. Therefore, by employing the flame rod power supply circuit 2 according to the present invention, an AC voltage isolated from the commercial power supply 10 can be applied to the flame rod without using an isolation transformer as in the conventional method.

[0013] In the flame circuit 3, the flame rod 11 is inserted into the flame 12, and a flame current (hereinafter referred to as "flame current") flows from the flame rod 11 according to the state of the flame 12. The circuit consisting of a resistor and a diode enclosed by the dotted line is the equivalent circuit of the flame 12. The flame 12 is generated from a burner 13 that is grounded to earth (EARTH). The earth (EARTH) connected to the burner 13 is connected to the GND of the filter circuit 4 and the flame detection circuit 5 through resistor R2.

[0014] In the flame circuit 3, the flame current flowing through the flame rod 11 flows to the flame detection circuit 5 through a filter circuit 4, which consists of resistors R3 and R4 and capacitors C3 and C4, which are low-pass filter circuits. As mentioned above, filter circuit 4 is a low-pass filter circuit, so only the DC component of the flame current flowing from the flame rod 11 flows to the flame detection circuit 5.

[0015] The flame detection circuit 5 consists of an input resistor R5, an operational amplifier U1, a feedback resistor R6, a feedback capacitor C5, and a calculation unit 14. Although not shown in the diagram, the calculation unit 14 incorporates an A / D converter, a CPU, and other components. The flame current flowing from the filter circuit 4 through the input resistor R5 is input to the negative (-) input of the operational amplifier U1. The positive (+) input of the operational amplifier U1 is connected to GND, and the feedback resistor R6 and feedback capacitor C5 are connected in parallel between the negative (-) input and the output of the operational amplifier U1. With this circuit configuration, the circuit consisting of the operational amplifier U1, feedback resistor R6, and feedback capacitor C5 functions as a current / voltage conversion amplifier circuit.

[0016] Furthermore, in the flame detection device 1 according to the present invention, since the operational amplifier U1 employs an operational amplifier with a low bias current in the pA range, the difference between the current flowing through the input resistor R5 and the current flowing through the feedback resistor R6 can be suppressed to a negligible degree. Therefore, the output voltage (measured value) inverted and amplified by the operational amplifier U1 is output as the product of the feedback resistor R6 and the flame current flowing through the feedback resistor R6. In other words, the measured value of the flame current output by the flame detection circuit (output voltage of operational amplifier U1) is proportional to the resistance value of the feedback resistor R6, so there are fewer factors for measurement error, and highly accurate measured values ​​can be input to the calculation unit 14. In addition, the current / voltage conversion amplifier circuit used in the flame detection circuit 5 can measure current with high sensitivity, making it possible to detect even minute current signals, and even when the AC voltage applied to the flame rod 11 is low, the flame can be detected from the flame current.

[0017] Figure 2 is a circuit diagram of the flame detection device 100 when the power plug CN1 is connected in reverse phase as in Figure 1. In this case, as shown in the flame rod power supply circuit 20 in Figure 2, a resistor R1 is connected to line L of the commercial power supply (AC100V) 10 and a capacitor C1 is connected to line N. Thus, even when the power plug CN1 is connected in reverse phase, a flame rod power supply circuit 20 similar to the flame rod power supply circuit 2 in Figure 1 can be used.

[0018] Next, the flame rod power supply circuits 2 and 20, which are features of the present invention, will be described in detail. In Figure 1, as an example, if the value of resistor R1 is 60kΩ and the value of capacitor C1 is 0.047μF, the AC voltage applied from capacitor C2 to the flame rod 11 will be approximately 73V if the commercial power supply 10 is AC100V, 60Hz, and approximately 66V if the commercial power supply 10 is AC100V, 50Hz. Furthermore, even in the case of reverse phase as shown in Figure 2, if resistor R1 and capacitor C1 are the same, the voltage will be approximately 68V if the commercial power supply 10 is AC100V, 60Hz, and approximately 75V if the commercial power supply 10 is AC100V, 50Hz. Therefore, with isolation from the primary side of the commercial power supply 10, the flame rod power supply circuits 2 and 20 of the flame detection devices 1 and 100 according to the present invention can output an AC voltage of 65V or more. Note that the values ​​of resistor R1 and capacitor C1 mentioned above are just examples, and the values ​​of resistor R1 and capacitor C1 should be set appropriately according to the frame rod used and the target AC voltage (applied to the frame rod).

[0019] As described above, since the flame rod power supply circuit 2 of the flame detection device 1 and flame detection device 100 (with the power supply reversed in phase in flame detection device 1) according to the present invention does not use an isolation transformer, a low-cost and space-saving flame detection device can be provided. Furthermore, because it is transformerless, power consumption due to no-load losses of the isolation transformer, as in conventional devices, can also be reduced. In addition, while conventional flame detection circuits have employed comparators, the flame detection device 1 (and flame detection device 100) according to the present invention employs a current / voltage conversion amplifier circuit using an operational amplifier, as in the flame detection circuit 5. As mentioned above, such a current / voltage conversion amplifier circuit can measure current with high sensitivity, so ignition can be determined even when the AC voltage applied to the flame rod 11 is lower and the flame current is small.

[0020] Here, the flame detection devices 1 and 100 are examples of flame detection devices, the frame rod 11 is an example of a frame rod, the commercial AC power supply 10 is an example of a commercial AC power supply, the lines L and N are examples of two power lines, the capacitor C1 is an example of a first capacitor, the resistor R1 is an example of a resistor, the capacitor C2 is an example of a second capacitor, and the power supply circuit 2 for the frame rod is an example of a power supply circuit.

[0021] As described above in detail for the embodiments of the present invention, these are merely examples, and the present invention is not to be construed as being limited in any way by the specific descriptions in such embodiments. It can be implemented in various modified, corrected, and improved forms based on the knowledge of those skilled in the art. It should be understood that any such embodiments are included within the scope of the present invention as long as they do not depart from the spirit of the present invention.

[0022] For example, as shown in FIG. 3, even when the frame ground of the housing is not connected to the ground, a simple modification can be made to form a power supply circuit for the frame rod. When the frame ground of the housing is not connected to the ground, as in the power supply circuit 21 for the frame rod shown in (A) of FIG. 3, the capacitor C10 is directly connected to the line N of the commercial power supply 10 and connected to the frame ground FL-GND of the housing in the flame circuit 30 through the capacitor 10. Or, as in the power supply circuit 22 for the frame rod shown in (B) of FIG. 3, the capacitor C10 is directly connected to the line L of the commercial power supply 10 and connected to the frame ground FL-GND of the housing in the flame circuit 30 through the capacitor 10. Then, for the flame detection device 110 shown in (A) of FIG. 3 and the flame detection device 120 shown in (B) of FIG. 3, similar to the case of the flame detection device 1 shown above, the power supply circuits 21 and 22 for the frame rod that apply voltage to the frame rod 11 can be configured.

[0023] Figure 4 is a circuit diagram of a flame detection device 130 that employs a switching power supply not connected to ground in the control circuit. Although not shown in Figures 1 to 3, control circuits are included. However, in the control circuits of Figures 1 to 3, the primary AC power supply is isolated, and the isolated power supply includes a low-frequency transformer. However, when using the control circuit 6 shown in Figure 4, the need for a low-frequency transformer is eliminated, and even in circuits that use a flame rod that uses an AC power supply for the flame power supply, a circuit configuration using only a switching power supply is possible, as shown in the control circuit 6 of Figure 4. Figure 4 is considered with the control circuit 6 including the switching power supply. [Explanation of Symbols]

[0024] 1, 100, 110, 120, 130... Flame detection device 2, 20, 21, 22... Power supply circuit for frame rod 3...Flame circuit 4. Filter Circuit 5. Flame detection circuit 6. Power supply circuit for control circuit 10. Commercial power supply (AC100V) 11. Frame Rod 12. Flame 13. Burner 14... Arithmetic section R1, R2, R3, R4, R5, R6...Resistance C1, C2, C3, C4, C5, C10, C20, C21, C22... Capacitors D1 Diode U1 op-amp

Claims

[Claim 1] A flame detection device using a flame rod, A flame detection device characterized by comprising a power supply circuit that connects a first capacitor in parallel to one of the two primary power lines of a commercial AC power supply, a resistor in parallel to the other power line, then connects the first power line and the other power line, connects a second capacitor to the connected power line, and applies an AC voltage to the flame rod through the second capacitor.

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