JP2021116976A - Flame rod circuit, hydrogen generation device, fuel cell system and detection method - Google Patents

Abstract

To provide a technique useful for detecting a degree of a combustion state of a combustor.SOLUTION: A flame rod circuit 700 includes a combustor 710, a flame rod 720 and a signal generating circuit 400. The signal generating circuit 400 generates a detection signal. The signal generating circuit 400 includes an IV conversion circuit 100 and a VF conversion circuit 200. The IV conversion circuit 100 generates a conversion potential corresponding to an electric current flowing between the combustor 710 and the flame rod 720. The VF conversion circuit 200 sets frequency of the detection signal on the basis of the conversion potential.SELECTED DRAWING: Figure 2

Description

The present disclosure relates to frame rod circuits, hydrogen generators, fuel cell systems and detection methods.

Conventionally, various frame rod circuits have been proposed. The frame rod circuit is used for flame detection. In the frame rod circuit, the frame rod is placed in a position where it can be exposed to flames. When the frame rod is exposed to flame, a rectified current flows through the frame rod. When the frame rod is not exposed to flames, there is virtually no current flowing through the frame rod. The frame rod circuit utilizes such characteristics of the frame rod. Patent Document 1 discloses an example of a frame rod circuit.

JP-A-61-243217 Japanese Unexamined Patent Publication No. 2018-031547

The technique described in Patent Document 1 has room for improvement from the viewpoint of detecting the degree of combustion state of the combustor.

This disclosure is
Combustor and
With the frame rod
An IV conversion circuit that generates a detection signal and generates a conversion potential according to the current flowing between the combustor and the frame rod, and a frequency of the detection signal is set based on the conversion potential. A signal generation circuit including a VF conversion circuit for
Provides a frame rod circuit.

The technique according to the present disclosure is useful for detecting the degree of combustion state of a combustor.

FIG. 1 is a block diagram of a frame rod circuit. FIG. 2 is a circuit diagram of a frame rod circuit. FIG. 3 is a circuit diagram of an IV conversion circuit. FIG. 4A is an explanatory diagram of a current path. FIG. 4B is an explanatory diagram of the current path. FIG. 5A is an explanatory diagram of the conversion potential. FIG. 5B is an explanatory diagram of the conversion potential. FIG. 6 is a circuit diagram of a buffer circuit. FIG. 7 is a circuit diagram of a level setting circuit. FIG. 8 is an explanatory diagram of a threshold potential, a signal potential, and a comparative potential related to the comparator. FIG. 9 is a circuit diagram of a VF conversion circuit. FIG. 10A is an explanatory diagram of a current path. FIG. 10B is an explanatory diagram of the current path. FIG. 10C is an explanatory diagram of a triangular wave and a square pulse wave. FIG. 11 is an explanatory diagram of the detection signal. FIG. 12 is an explanatory diagram of the threshold value of the comparator when the frequency of the signal potential is low. FIG. 13 is an explanatory diagram of the threshold value of the comparator when the frequency of the signal potential is high. FIG. 14 is an explanatory diagram of the action of the feedback resistor. FIG. 15 is an explanatory diagram for improving the linearity by the feedback resistance. FIG. 16 is a circuit diagram of a VF conversion circuit. FIG. 17A is an explanatory diagram of a current path. FIG. 17B is an explanatory diagram of a current path. FIG. 17C is an explanatory diagram of a triangular wave and a square pulse wave. FIG. 18 is a circuit diagram of a control device and an insulation device. FIG. 19 is a circuit diagram of a frame rod circuit. FIG. 20A is an explanatory diagram of a current path. FIG. 20B is an explanatory diagram of the current path. FIG. 21A is an explanatory diagram of the conversion potential. FIG. 21B is an explanatory diagram of the conversion potential. FIG. 22 is an explanatory diagram of a threshold potential, a signal potential, and a comparative potential related to the comparator. FIG. 23 is a circuit diagram of the VF conversion circuit. FIG. 24 is a block diagram of the frame rod circuit. FIG. 25 is an explanatory diagram of the voltage and current applied between the combustor and the frame rod circuit.

Hereinafter, embodiments will be described with reference to the drawings. The disclosure is not limited by embodiments.

In embodiments, the first, second, third ... ordinal numbers may be used. If an element has an ordinal number, it is not essential that a younger element of the same type exists. The ordinal numbers can be changed as needed.

(Embodiment)
FIG. 1 is a block diagram of the frame rod circuit 700 according to the present embodiment. FIG. 2 is a circuit diagram of the frame rod circuit 700.

As shown in FIG. 1, the frame rod circuit 700 includes a combustor 710, a frame rod 720, a signal generation circuit 400, a control device 500, and an insulation device 600. The signal generation circuit 400 is connected to a control device 500, an insulation device 600, a combustor 710, and a frame rod 720. A voltage can be supplied to the frame rod circuit 700 from the power supply 770.

The power supply 770 outputs a DC voltage. The power supply system of the power supply 770 is not particularly limited. The power supply 770 includes a DCDC converter in one example, and includes a flyback type isolated DCDC converter in one specific example. The power supply 770 may include a converter that converts an AC voltage into a DC voltage. Specifically, the power supply 770 may include an AC power supply, a transformer, and a rectifier circuit.

The frame rod circuit 700 includes a first region 791 and a second region 792 having different reference potentials. The first region 791 and the second region 792 are separated by an insulating device 600. The control device 500 belongs to the first region 791. The combustor 710, the frame rod 720, and the signal generation circuit 400 belong to the second region 792.

The frame rod 720 is arranged at a position where it can be exposed to the flame generated by the combustor 710. The combustor 710 is, for example, a burner. As the frame rod 720, a known frame rod can be used.

In the state where the combustor 710 is burning, the frame rod 720 exhibits a rectifying characteristic in which a current is more likely to flow in the direction from the frame rod 720 to the combustor 710 than in the direction from the combustor 710 to the frame rod 720.

The reason why such a rectifying characteristic occurs is as follows. There are both cations and electrons in the flame. Electrons are easier to move than cations. The surface area A of the frame rod 720 is smaller than the surface area B of the combustor 710. When the potential of the frame rod 720 is lower than the potential of the combustor 710, it is difficult for immobile cations to reach the frame rod 720 with a small surface area. For this reason, it is relatively difficult for current to flow from the combustor 710 to the frame rod 720 (typically, it does not flow substantially). On the other hand, when the potential of the frame rod 720 is higher than the potential of the combustor 710, the cations reach the combustor 710 with a large surface area relatively easily, although they are difficult to move. Further, in this case, since the electrons are easy to move, they reach the frame rod 720 having a small surface area relatively easily. Therefore, a current is relatively easy to flow from the frame rod 720 to the combustor 710.

The ratio A / B is, for example, 1/4 or less. In one specific example, the ratio A / B is 1/10 to 1/4.

The signal generation circuit 400 generates the detection signal S _D. Specifically, the detection signal S _D are those corresponding to the current I _FR flowing between the combustor 710 and the frame rod 720. _{Hereinafter, the "current I FR} flowing between the combustor 710 and the frame rod 720" is abbreviated as the current I _FR flowing through the frame rod 720, the frame rod current I _FR , or the current I _FR. It may happen.

Specifically, the power supply 770 supplies a _{DC voltage V PS to the signal generation circuit 400.} Controller 500 supplies a control signal S _C to the signal generating circuit 400. Signal generating circuit 400 uses the DC voltage V _PS and a control signal S _C, generates a detection signal S _D.

In the present embodiment, the detection signal S _D is a DC signal or a square pulse signal. The expression "the detection signal S _D is a DC signal or a rectangular pulse signal" includes an embodiment in which the _{detection signal S D} is a DC signal in _{a certain period and the detection signal S D is a rectangular pulse signal in another period.} It is intended to be.

A DC signal is a signal having a frequency of zero. A square pulse signal is a signal having a frequency that is non-zero. Therefore, it can be explained that the DC signal and the rectangular pulse signal are signals having different frequencies.

As described above, the controller 500 transmits a control signal S _C to the signal generating circuit 400. Further, the control device 500 receives the _{detection signal S D from the signal generation circuit 400.}

Specifically, the control device 500 includes a switch 501 and a detector 502. Switch 501 transmits a control signal S _C to the signal generating circuit 400. The detector 502 receives the _{detection signal S D} from the signal generation circuit 400.

In this embodiment, the control device 500 is a digital device. The switch 501 is a digital device. The detector 502 is a digital device. A digital device refers to a device that processes a digital signal. For example, a digital device can be configured using a microcomputer.

Isolator 600, to insulate the transmission of the control signal S _C to the signal generating circuit 400 from the control device 500. Further, the insulation device 600 performs isolated transmission _{of the detection signal S D} from the signal generation circuit 400 to the control device 500.

Specifically, the insulating device 600, to insulate the transmission of the control signal S _C to the signal generating circuit 400 from switch 501. Further, the insulation device 600 performs isolated transmission _{of the detection signal S D} from the signal generation circuit 400 to the detector 502.

The frame rod circuit 700 can detect the combustion state of the combustor 710 and the state of insulation deterioration between the combustor 710 and the frame rod 720. The details of the detection method will be described later.

The combustion failure of the combustor 710 may be caused by a transient disorder of the balance between the supply amount of combustion fuel and the supply amount of combustion air.

Further, the deterioration of insulation between the combustor 710 and the frame rod 720 may be caused by thermal deformation of the combustor 710, the frame rod 720 and the like. Further, the insulation deterioration may be caused by the adhesion of soot to the combustor 710, the frame rod 720, and the like. The "deterioration of insulation between the combustor 710 and the frame rod 720" means that not only the combustor 710 and the frame rod 720 are completely short-circuited, but also the resistance between the combustor 710 and the frame rod 720 is zero. It is an expression intended to include a state of decline, although it has not reached.

The components of the signal generation circuit 400 will be described.

The signal generation circuit 400 includes an IV conversion circuit 100, a buffer circuit 300, a level setting circuit 350, and a VF conversion circuit 200. The IV conversion circuit 100 may also be referred to as a current-voltage conversion circuit 100. The VF conversion circuit 200 may also be referred to as a voltage-frequency conversion circuit 200.

The IV conversion circuit 100 generates a conversion potential _{VA corresponding to the current IF R} flowing between the combustor 710 and the frame rod 720.

Specifically, the power supply 770 supplies a _{DC voltage V PS to the IV conversion circuit 100.} Controller 500 supplies a control signal S _C to the IV conversion circuit 100. IV conversion circuit 100 uses the DC voltage V _PS and a control signal S _C, to produce a converted potential V _A.

The buffer circuit 300 is arranged on a path connecting the IV conversion circuit 100 and the level setting circuit 350. Further, the buffer circuit 300 is arranged on a path connecting the IV conversion circuit 100 and the VF conversion circuit 200. The buffer circuit 300 enhances the accuracy of detection by the frame rod circuit 700. Specifically, the frame rods circuit 700, the frame rod current I _FR is converted in the conversion potential V _A, it is detected based on the converted voltage V _A is made. According to the buffer circuit 300, the influence of the current flowing from the first line 111 through the second resistor 126 and the detection resistor 120 into the level setting circuit 350 and the VF conversion circuit 200 on the conversion potential _{VA is suppressed.} Therefore, the detection error due to this effect is reduced.

Level setting circuit 350 sets the size of A _S of the detection signal S _D. The magnitude _AS is a magnitude corresponding to the conversion potential V _A.

Here, the size A _S of the detection signal S _D, when the detection signal S _D is a DC signal, the magnitude of the DC signal. Size A _S of the detection signal S _D, when the detection signal S _D is a rectangular pulse signal, the amplitude of the rectangular pulse signal.

The VF conversion circuit 200 sets the frequency F _{S of the detection signal S D} based on the conversion potential V _A. Specifically, VF converter 200, when the rectangular pulse signal is generated as a detection signal S _D, the frequency F _S of the detection signal S _D, is set based on the conversion potential V _A.

In the present embodiment, the VF conversion by the VF conversion circuit 200 contributes to the detection of the combustion state of the combustor 710 by the frame rod circuit 700. Specifically, the frame rods circuit 700, a VF converter 200, a frequency F _S of the detection signal S _D, can be set based on the flame rod current I _FR. In this way, the frame rods circuit 700, the frequency F _S, can detect the degree of combustion status. Therefore, the frame rod circuit 700 can grasp the state when the combustor 710 is in the state immediately before the misfire. Therefore, in the system in which the frame rod circuit 700 is incorporated, it is possible to recover from the state immediately before the misfire to the normal combustion state, and it is possible to avoid the system stop due to the misfire. It should be noted that this restoration can be performed, for example, by increasing the amount of gas supplied to the combustor 710 or by appropriately sending air to the combustor 710.

Hereinafter, the components of the signal generation circuit 400 will be described in more detail.

[IV conversion circuit 100]
FIG. 3 shows the IV conversion circuit 100 of this embodiment.

The IV conversion circuit 100 includes a first line 111, a second line 112, a detection resistor 120, a reference point A, a first switching element 171 and a second switching element 172. In the example of FIG. 3, the potential of the reference point A is the conversion potential _VA .

A first DC potential V _DC1 is applied to the first line 111. A second DC potential V _DC2 is applied to the second line 112. The first DC potential V _DC1 is a relatively high potential, and the second DC potential V _DC2 is a relatively low potential. In other words, the first DC potential V _DC1 is higher than the second DC potential V _DC2. The combination of the first line 111 and the second line 112 is used to apply a voltage between the combustor 710 and the frame rod 720.

In the IV conversion circuit 100, the first period and the second period appear alternately. In the present embodiment, the first period and the second period are brought about by the switching of the first switching element 171 and the second switching element 172. Specifically, in the first period, the first switching element 171 is on and the second switching element 172 is off. In the second period, the first switching element 171 is off and the second switching element 172 is on.

In this embodiment, a single power source 770 can alternately apply positive and negative voltages to the frame rod 720 with reference to the combustor 710. Specifically, a positive voltage may be applied to the frame rod 720 in the first period, and a negative voltage may be applied to the frame rod 720 in the second period. In this way, a rectangular pulse voltage as schematically shown in FIG. 3 is applied to the frame rod 720. A method in which such a voltage is applied to the frame rod 720 can be referred to as a polarity switching DC method.

The ability to apply positive and negative voltages to the frame rod 720 relative to the combustor 710 with a single power source provides various benefits. For example, it is advantageous from the viewpoint of system cost reduction that only one power source is required. Further, when one power supply is connected in series, it is easy to use a component having a low rated voltage in the frame rod circuit 700.

In the present embodiment, if the combustor 710 is burning in the first period, a current flows between the combustor 710 and the frame rod 720. If insulation deterioration occurs between the combustor 710 and the frame rod 720 in the second period, a current flows between the combustor 710 and the frame rod 720.

By the way, in a typical example, the combustion failure of the combustor 710 occurs more frequently than the insulation deterioration between the combustor 710 and the frame rod 720. In this respect, in the present embodiment, the length of the first period is longer than the length of the second period. Therefore, the period during which combustion defects can be detected is longer than the period during which insulation deterioration can be detected. This is rational from the viewpoint of efficiently detecting the combustion failure of the combustor 710 and the deterioration of the insulation between the combustor 710 and the frame rod 720.

In the present embodiment, if the combustor 710 is combusted in the first period, current flows through the first line 111, the frame rod 720, the combustor 710, the first switching element 171 and the second line 112 in this order. Specifically, if the combustor 710 is burning in the first period, the first line 111, the detection resistor 120, the reference point A, the frame rod 720, the combustor 710, the first switching element 171 and the second line Current flows through 112 in this order. The state in which the current is flowing in this way is shown by a alternate long and short dash line in FIG. 4A. The frame rod circuit 700 detects the combustion state of the combustor 710 based on the potential of the reference point A in the first period.

In the present embodiment, if the insulation deterioration between the combustor 710 and the frame rod 720 occurs in the second period, the first line 111, the combustor 710, the frame rod 720, the second switching element 172, and the second line Current flows through 112 in this order. Specifically, if insulation deterioration occurs between the combustor 710 and the frame rod 720 in the second period, the first line 111, the combustor 710, the frame rod 720, the reference point A, the detection resistor 120, and the second A current flows through the two switching elements 172 and the second line 112 in this order. The state in which the current is flowing in this way is shown by a chain double-dashed line in FIG. 4B. The frame rod circuit 700 detects the state of insulation deterioration between the combustor 710 and the frame rod 720 based on the potential of the reference point A in the second period.

In the above context, "flowing current through the first line 111" means both a mode in which a current flows through a part of the first line 111 and a mode in which a current flows through the entire first line 111. It is an expression intended to include. The same applies to "flowing current through the second line 112". In the illustrated example, "flowing current through the first line 111" in the above context means that current flows through a part of the first line 111, and "flowing current through the second line 112 ..." in the above context. Corresponding to the case where "flowing current" means that current flows through a part of the second line 112.

Further, in FIG. 3, there is a character "FG" on the right side of the combustor 710. The word "FG" is also on the upper right side of the first switching element 171. "FG" indicates the potential of the combustor 710. In the example of FIG. 3, the combustor 710 and the first switching element 171 are connected to each other. Specifically, the combustor 710 and the first switching element 171 are connected at equal potentials.

In the illustrated example, the reference potential of the second region 792 is the second DC potential V _DC2 of the second line 112.

_{The conversion potential VA} in the first period and the second period will be further described with reference to FIGS. 5A and 5B. Note that FIGS. 5A and 5B are simple schematic views focusing on the current paths of FIGS. 4A and 4B and further showing the ON state of the switching element in a short-circuit state. This point is the same for FIGS. 21A and 21B described later.

As described above, if the combustor 710 is burning in the first period, the current IF _R flows as shown by FIG. 4A. In this case, as schematically shown in FIG. 5A, the current IF _R flows through the second resistor 126, the detection resistor 120, the frame rod 720, and the combustor 710 in this order. The conversion potential V _{A in} this case is given by the mathematical formula: V _A = V _DC1- (R ₁₂₆ + R ₁₂₀ ) × _{IF R.} In this formula, V _A is the potential value of the conversion potential V _{A , V DC 1} is the potential value of the first DC potential V _{DC 1} , R ₁₂₆ is the resistance value of the second resistance 126, and R ₁₂₀ is the detection resistance. The resistance value is 120, and I _FR is the current value of the current I _FR. In this embodiment, R ₁₂₆ is for sufficiently smaller than the R _120, are converted potential V _A, formula: can be approximated as _{V A ≒ V DC1 -R 120 ×} I FR. On the other hand, in the first period, when the current IF _R is not flowing, the conversion potential V _A is V _A = V _{DC 1} .

As described above, if the insulation deterioration between the combustor 710 and the frame rod 720 occurs in the second period, the current IF _R flows as shown by FIG. 4B. In this case, as schematically shown in FIG. 5B, the current _IFR flows through the first resistor 125, the combustor 710, the frame rod 720, and the detection resistor 120 in this order. In this case, since in the present embodiment is sufficiently smaller than the resistance value R ₁₂₅ is the resistance R ₁₂₀ of the first resistor 125, the converted potential V _A, formula: as _{V A ≒ V DC2 + R 120} × I FR Can be approximated to. In this formula, V _DC2 is the potential value of the second DC potential V _DC2. On the other hand, in the second period, when the current IF _R is not flowing, the conversion potential V _A is V _A = V _{DC 2} .

In the present embodiment, the IV conversion circuit 100 can be described as follows. In the IV conversion circuit 100, the conversion potential _VA appears at the reference point A. The voltage drop in the detection resistor 120 that occurs in response to the _{current IF R} flowing between the combustor 710 and the frame rod 720 is reflected in the _{conversion potential VA.} Based on the conversion potential _VA , the combustion state of the combustor 710 and the insulation deterioration state between the combustor 710 and the frame rod 720 are detected.

_{Specifically, the current I FR} flowing between the combustor 710 and the frame rod 720 also flows to the detection resistor 120 and the reference point A, and the voltage drop generated in the detection resistor 120 by _{the current IF R} is reflected in the _{conversion potential VA.} NS. Strictly speaking, both the voltage drop that occurs in the first resistor 125 and the voltage drop that occurs in the second resistor 126 can be reflected.

_{More specifically, the voltage drop based on the frame rod current IF R} in the direction from the detection resistor 120 toward the reference point A, which may occur in the first period, lowers the conversion potential V _A with respect to the first DC potential V _{DC 1.} Acts on. _{On the other hand, the voltage drop based on the frame rod current IF R} in the direction from the reference point A toward the detection resistor 120, which may occur in the second period, acts to raise the conversion potential V _A with respect to the second DC potential V _{DC 2.}

In this embodiment, as shown in FIG. 3, the frame rod circuit 700 includes a first series circuit 181, a second series circuit 182, and a third series circuit 183. The main body including these is specifically a signal generation circuit 400, and more specifically, an IV conversion circuit 100.

In the first series circuit 181, the first line 111, the first connection point P1, the first switching element 171 and the second line 112 are arranged in this order. In the second series circuit 182, the first line 11, the second connection point P2, the second switching element 172, and the second line 112 are arranged in this order. In the third series circuit 183, the second connection point P2, the frame rod 720, the combustor 710, and the first connection point P1 are arranged in this order. In the third series circuit 183, in the third series circuit 183, the second connection point P2, the detection resistor 120, the reference point A, the frame rod 720, the combustor 710, and the first connection point P1 are arranged in this order. In this way, the current flow shown in FIGS. 4A and 4B can be realized.

In this embodiment, the frame rod circuit 700 includes a first resistor 125 and a second resistor 126. The main body including these is specifically a signal generation circuit 400, and more specifically, an IV conversion circuit 100.

The first resistor 125 is located between the first line 111 and the first connection point P1 in the first series circuit 181. The second resistor 126 is located between the first line 111 and the second connection point P2 in the second series circuit 182. The first resistor 125 and the second resistor 126 have an advantageous effect. This action will be described below.

It is assumed that the first resistor 125 is changed to the switching element J1 and the second resistor 126 is changed to the switching element J2. In this case, if the first switching element 171 and the switching element J1 are turned on at the same time, a current flows through these switching elements without limiting the current, and these switching elements may be destroyed by an overcurrent. Similarly, when the second switching element 172 and the switching element J2 are turned on at the same time, a current flows through these switching elements without limiting the current, and these switching elements may be destroyed by an overcurrent. In order to avoid such a situation, it is conceivable to set a dead time so that the switching elements 171 and J1 do not turn on at the same time, and set a dead time so that the switching elements 172 and J2 do not turn on at the same time. However, in order to do so, a circuit for providing a dead time is required.

On the other hand, according to the first resistor 125 and the second resistor 126, it is possible to prevent the first switching element 171 and the second switching element 172 from being destroyed by the overcurrent without providing a circuit for providing a dead time.

The present disclosure does not exclude the form in which the first resistor 125 is changed to the switching element J1 and the second resistor 126 is changed to the switching element J2 as described above. When this change is made, a dead time may be provided so that the switching elements 171 and J1 do not turn on at the same time, and a dead time may be provided so that the switching elements 172 and J2 do not turn on at the same time.

In this embodiment, the frame rod circuit 700 includes a third switching element 173. The main body including the third switching element 173 is specifically the signal generation circuit 400, and more specifically the IV conversion circuit 100.

In this embodiment, the first switching element 171 is a transistor. The first switching element 171 includes a current terminal 171a, a current terminal 171b, and a control terminal 171c.

Specifically, the first switching element 171 is a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor). More specifically, the first switching element 171 is an N-type MOSFET. The current terminal 171a is a drain terminal. The current terminal 171b is a source terminal. The control terminal 171c is a gate terminal. However, the first switching element 171 may be a bipolar transistor. In this case, a base resistor is typically connected to the base of the bipolar transistor.

In this embodiment, the second switching element 172 is a transistor. The second switching element 172 includes a current terminal 172a, a current terminal 172b, and a control terminal 172c.

Specifically, the second switching element 172 is a bipolar transistor. More specifically, the second switching element 172 is an NPN type bipolar transistor. The current terminal 172a is a collector terminal. The current terminal 172b is an emitter terminal. The control terminal 172c is a base terminal. However, the second switching element 172 may be a MOSFET.

In this embodiment, the third switching element 173 is a transistor. The third switching element 173 includes a current terminal 173a, a current terminal 173b, and a control terminal 173c.

Specifically, the third switching element 173 is a MOSFET. More specifically, the third switching element 173 is an N-type MOSFET. The current terminal 173a is a drain terminal. The current terminal 173b is a source terminal. The control terminal 173c is a gate terminal. However, the third switching element 173 may be a bipolar transistor. In this case, a base resistor is typically connected to the base of the bipolar transistor.

In the present embodiment, the control terminal 171c of the first switching element 171 and the control terminal 173c of the third switching element 173 are connected to each other so that the first switching element 171 and the third switching element 173 are turned on and off in synchronization. .. Further, the current terminal 173a of the third switching element 173 is connected to the control terminal 172c of the second switching element 172 so that the third switching element 173 and the second switching element 172 are turned on and off in a complementary manner.

Then, the control unit 500, a control signal S _C, is supplied to both the control terminal 173c of the control terminal 171c and the third switching element 173 of the first switching element 171. Specifically, the switch 501 makes such a supply. In this way, the first switching element 171 and the second switching element 172 can be turned on and off in a complementary manner.

Specifically, the control signal S _{for C} is supplied to both the control terminal 173c of the control terminal 171c and the third switching element 173 of the first switching element 171, first switching element 171 and the third switching element 173 is synchronized And turn it on and off. When the third switching element 173 is on, the current flowing through the third switching element 173 is supplied via the resistor 129, and the potential of the control terminal 172c of the second switching element 172 drops due to the voltage drop in the resistor 129. The switching element 172 is off. On the contrary, when the third switching element 173 is off, the current does not flow through the third switching element 173, so that the voltage drop does not occur, and the control terminal 172c of the second switching element 172 has the first DC potential V _DC1. A voltage obtained by dividing the voltage corresponding to the potential difference between the second DC potential V _DC2 by the resistor 129 and the resistor 130 is applied, whereby the second switching element 172 is turned on.

Note that the synchronous on / off of two switching elements is an expression intended that the period in which the two switching elements are on is the same and the period in which the two switching elements are off is the same. Complementary on / off of two switching elements means that the other switching element is off while one switching element is on and the other switching element is on while one switching element is off. It is an expression intended for.

In the present embodiment, the control signal S _C is the isolators 600 are insulated transmitted to the IV conversion circuit 100 from the control device 500.

Specifically, in the present embodiment, the insulating device 600 includes an insulating circuit 601 and an insulating circuit 603. Control signal S _C is the isolation circuit 603, and the switch 501 to the first switching element 171 and the third switching element 173 is insulated transmission.

In this embodiment, the insulation circuit 601 is a photocoupler. The insulation circuit 603 is a photocoupler.

In the present embodiment, the control signal S _C is a rectangular pulse wave. By alternately switching the level of the rectangular pulse wave, the first period and the second period can be switched alternately.

In this embodiment, the frame rod circuit 700 includes a voltage regulator 165, a capacitor 154, a capacitor 155, a resistor 127, a resistor 128, a resistor 129, and a resistor 130. The main body including these is specifically a signal generation circuit 400, and more specifically, an IV conversion circuit 100.

Voltage regulator 165, a DC voltage V _PS supplied from the power supply 770 shown in FIG. 1, is converted into a DC voltage of different sizes. Further, the voltage regulator 165 converts the _{DC potential V U} from the point U on the upstream side into the first DC potential V _DC1. The voltage regulator 165 is, in one example, a series regulator, and in one specific example, an LDO (Low Dropout).

The DC voltage V _PS before conversion corresponds to the potential difference between the DC potential V _U and the second DC potential V _{DC 2.} The converted DC voltage corresponds to the potential difference between the first DC potential V _DC1 and the second DC potential V _DC2.

In this embodiment, the converted DC voltage is smaller than _{the DC voltage V PS.}

The voltage regulator 165 is not essential. For example, the voltage regulator 165 may or may not be provided in consideration of the DC potential V _U , the potential that can be input to the buffer circuit 300 and the comparators 351 and 352 in the subsequent stage, and the like.

The capacitor 154 is provided after the voltage regulator 165 in the IV conversion circuit 100. The capacitor 154 is a decoupling capacitor (also referred to as a bypass capacitor). When a sudden load current fluctuation occurs, the capacitor 154 stabilizes the voltage by supplying a current. A capacitor similar to the capacitor 154 may be provided in front of the voltage regulator 165.

In this embodiment, a voltage divider circuit including a resistor 127 and a resistor 128 is configured. This voltage divider circuit connects the first line 111 and the second line 112, and generates a voltage divider voltage obtained by dividing the potential difference between _{the first DC potential V DC1} and the second DC potential V _DC2. Control signal S _C is supplied to a control terminal 171c of the first switching element 171 through the voltage divider circuit. Therefore, the control signal S _C is in a state of being biased by the divided voltage is supplied to the control terminal 171c of the first switching element 171.

In this embodiment, a voltage divider circuit including a resistor 129 and a resistor 130 is configured. This voltage divider circuit connects the first line 111 and the second line 112, and generates a voltage divider voltage obtained by dividing the potential difference between _{the first DC potential V DC1} and the second DC potential V _DC2. A potential reflecting this voltage dividing voltage is supplied to the control terminal 172c of the second switching element 172.

The resistors 128 and 130 are not essential. For example, the resistors 128 and 130 may or may not be provided in consideration of the first DC potential V _DC1 , the potential that can be input to the control terminals of the switching elements 171 and 172, and the like.

In the present embodiment, the first line 111 and the reference point A are connected via a capacitor 155. A capacitor 155 is suppressed and fine variation of the flame rod current I _FR, gradual variation in the flame rod current I _FR can be realized.

[Buffer circuit 300]
FIG. 6 shows the buffer circuit 300 of this embodiment.

As shown in FIG. 6, the buffer circuit 300 is connected to the IV conversion circuit 100. Specifically, the buffer circuit 300 is connected to the reference point A.

The buffer circuit 300 _{gives a potential corresponding to the conversion potential VA} to the level setting circuit 350. Further, the buffer circuit 300 gives the VF conversion circuit 200 a potential corresponding to _{the conversion potential VA.}

As shown in FIG. 6, in the present embodiment, the buffer circuit 300 includes the operational amplifier 301. The buffer circuit 300 is an operational amplifier circuit that constitutes a voltage follower.

In this embodiment, the buffer circuit 300 includes a resistor 311 and a capacitor 330. The operational amplifier 301 and the level setting circuit 350 are connected via a resistor 311. The operational amplifier 301, the resistor 311, the capacitor 330, and the second line 112 are connected in this order. The resistor 311 and the capacitor 330 constitute a low-pass filter. By this low-pass filter, the fine voltage fluctuation of the signal input to the comparators 351 and 352 of the level setting circuit 350 is suppressed, and the averaged signal can be input to the comparators 351 and 352. This can contribute to the prevention of false positives.

It is assumed that the buffer circuit 300 does not exist and the reference point A and the comparators 351 and 352 are connected without a buffer. In this case, it may be difficult to properly perform detection based on the _{frame rod current IFR} due to the influence of the current flowing into the comparators 351 and 352 (hereinafter, may be referred to as an input bias current). On the other hand, in the present embodiment, since the buffer circuit 300 exists, the above influence is suppressed, and high detection accuracy can be easily obtained. In the present embodiment, as the operational amplifier 301 of the buffer circuit 300, an operational amplifier whose input bias current is sufficiently smaller than that of the _{frame rod current IF R is selected.} However, the buffer circuit 300 is not essential. In some cases, such an action by the buffer circuit 300 is unnecessary.

[Level setting circuit 350]
FIG. 7 shows the level setting circuit 350 of this embodiment.

The frame rod circuit 700 includes a first comparator 351 and a second comparator 352. The main body including these is specifically the signal generation circuit 400, and more specifically the level setting circuit 350.

The first comparator 351 has a first threshold input unit 351a, a first signal input unit 351b, and a first signal output unit C. The second comparator 352 has a second threshold input unit 352a, a second signal input unit 352b, and a second signal output unit E.

In the present embodiment, the first threshold input unit 351a is a non-inverting input terminal. The first signal input unit 351b is an inverting input terminal. The first signal output unit C is an output terminal. However, a configuration in which the first threshold input unit 351a is an inverting input terminal and the first signal input unit 351b is a non-inverting input terminal can also be adopted.

In the present embodiment, the second threshold input unit 352a is an inverting input terminal. The second signal input unit 352b is a non-inverting input terminal. The second signal output unit E is an output terminal. However, a configuration in which the second threshold input unit 352a is a non-inverting input terminal and the second signal input unit 352b is an inverting input terminal can also be adopted.

The frame rod circuit 700 includes a first take-out circuit 381. The main body including the first extraction circuit 381 is specifically the signal generation circuit 400, and more specifically the level setting circuit 350.

The first take-out circuit 381 connects the first line 111 and the second line 112. The first take-out circuit 381 gives the first threshold input unit 351a a first threshold potential V _B having a _{second DC potential V DC2} or more and a first DC potential V _{DC1 or less.} In a typical example, the first threshold potential V _B is larger than the second DC potential V _{DC2 and} smaller than the first DC potential V _DC1 .

In this embodiment, the first take-out circuit 381 is a voltage divider circuit. Specifically, in this voltage divider circuit, the resistor 361 and the resistor 362 are connected in series. _{The first threshold potential V B} appears at the point B between the resistors 361 and 362 in this voltage divider circuit. Specifically, the first line 111, the resistor 361, the point B, the resistor 362, and the second line 112 are connected in this order by this voltage dividing circuit.

In this embodiment, the frame rod circuit 700 includes a capacitor 371. The main body including the capacitor 371 is specifically the signal generation circuit 400, and more specifically the level setting circuit 350.

A resistor 362 and a capacitor 371 are connected in parallel between the point B and the second line 112. The capacitor 371 stabilizes _{the first threshold potential V B} input to the first threshold input unit 351a of the first comparator 351.

The frame rod circuit 700 includes a second take-out circuit 382. The main body including the second extraction circuit 382 is specifically the signal generation circuit 400, and more specifically the level setting circuit 350.

The second take-out circuit 382 connects the first line 111 and the second line 112. The second extraction circuit 382 provides the second threshold input unit 352a with a second threshold potential V _D having a _{second DC potential V DC2} or more and a first DC potential V _{DC1 or less.} In a typical example, the second threshold potential V _D is larger than the second DC potential V _{DC2 and} smaller than the first DC potential V _DC1 .

In this embodiment, the second take-out circuit 382 is a voltage divider circuit. Specifically, in this voltage divider circuit, a resistor 363 and a resistor 364 are connected in series. _{A second threshold potential V D} appears at the point D between the resistors 363 and 364 in this voltage divider circuit. Specifically, the first line 111, the resistor 363, the point D, the resistor 364, and the second line 112 are connected in this order by this voltage dividing circuit.

In this embodiment, the frame rod circuit 700 includes a capacitor 372. The main body including the capacitor 372 is specifically the signal generation circuit 400, and more specifically the level setting circuit 350.

A resistor 364 and a capacitor 372 are connected in parallel between the point D and the second line 112. Capacitor 372 stabilizes the second threshold voltage V _D to be inputted to the second threshold value input section 352a of the second comparator 352.

The frame rod circuit 700 includes a first connection circuit 481. The main body including the first connection circuit 481 is specifically the signal generation circuit 400.

The first connection circuit 481 connects the reference point A and the first signal input unit 351b. The first connection circuit 481, the first signal input unit 351b, provides a signal potential V _S corresponding to the potential of the second DC potential V _DC2 or more and the first DC potential V _DC1 less and reference point A.

As described above, the potential of the reference point A is the same as the _{conversion potential VA. In this embodiment, the signal potential V S} is generated by averaging the conversion potential V _A by a low-pass filter with a resistor 311 and a capacitor 330.

Specifically, the reference point A, the buffer circuit 300, and the first signal input unit 351b are connected in this order by the first connection circuit 481. More specifically, the reference point A, the operational amplifier 301, and the first signal input unit 351b are connected in this order by the first connection circuit 481.

The frame rod circuit 700 includes a second connection circuit 482. The main body including the second connection circuit 482 is specifically the signal generation circuit 400.

The second connection circuit 482 connects the reference point A and the second signal input unit 352b. Second connection circuit 482, the second signal input unit 352b, provides a signal potential V _S.

Specifically, the reference point A, the buffer circuit 300, and the second signal input unit 352b are connected in this order by the second connection circuit 482. More specifically, the reference point A, the operational amplifier 301, and the second signal input unit 352b are connected in this order by the second connection circuit 482.

In the illustrated example, the first connection circuit 481 and the second connection circuit 482 partially overlap.

The first comparator 351, by comparing the first threshold potential V _B and the signal potential V _S, may output a first comparison potential V _C. Specifically, the first comparator 351, the first signal output station C, a may output a first comparison potential V _C. More specifically, the first comparison potential V _C is generated by the first comparator 351, then, it is subjected to generate a composite output later.

The second comparator 352 can output the second comparative potential V _E by comparing the second threshold potential V _D and the signal potential V _S. Specifically, the second comparator 352, the second signal output unit E, can output a second comparison potential V _E. Specifically, the second comparative potential _VE is generated by the second comparator 352 and then used to generate the combined output described later.

In this embodiment, the first comparison potential V _C takes a value of high or low. Specifically, when the signal potential V _S is larger than the first threshold potential V _B , the first comparative potential V _C takes a low level value. On the other hand, when the signal potential V _S is smaller than the first threshold potential V _B , the first comparative potential V _C takes a high level value.

In this embodiment, the second comparative potential _VE takes a high level or a low level value. Specifically, when the signal potential V _S is larger than the second threshold potential V _D , the second comparative potential V _E takes a high level value. On the other hand, when the signal potential V _S is smaller than the second threshold potential V _D , the second comparative potential V _E takes a low level value.

In the present embodiment, the low level of the first comparison potential V _C corresponds to the reference potential of the second region 792. Low level of the second comparison potential V _E corresponds to the reference potential of the second region 792.

In the present embodiment, the first signal output unit C and the second signal output unit E are connected to each other. Level setting circuit 350 generates a combined output of the first comparison potential V _C and a second comparison potential V _E.

Specifically, when both the first comparative potential V _C and the second comparative potential V _E are at a high level, a combined output having a high level potential is generated. When both the first comparative potential V _C and the second comparative potential V _E are at low levels, a combined output with low level potentials is produced. When one is at a high level the other of the first comparison potential V _C and a second comparison potential V _E is at the low level, a low-level potential combined output is generated. The low level potential corresponds to the reference potential of the second region 792.

The configuration for generating the combined output that has a high level potential or a low level potential as described above is not particularly limited. In the present embodiment, the first comparator 351 has a first output circuit (not shown). The first output circuit is of the open drain type. The first output circuit is connected to the first signal output unit C. The second comparator 352 has a second output circuit (not shown). The second output circuit is of the open drain type. The second output circuit is connected to the second signal output unit E. A wired or is configured by connecting the first signal output unit C connected to the first output circuit of the open drain type and the second signal output unit E connected to the second output circuit of the open drain type. Therefore, the above-mentioned composite output is obtained.

In the present embodiment, both the first signal output unit C and the second signal output unit E are connected to the point G. The above composite output propagates to the point G.

FIG. 8 schematically shows the relationship between the threshold potential, the signal potential, and the comparative potential according to the comparator of the present embodiment. In the example of FIG. 8, the signal potential V _S is the same as the conversion potential V _A. Therefore, in FIG. 8, _{the notation "VA} " is used. This point is the same for FIGS. 12 and 22 described later.

Hereinafter, the upper left box of FIG. 8 may be referred to as “column 1-1”. The box on the upper right of FIG. 8 may be referred to as "column 1-2". The lower left box in FIG. 8 may be referred to as "column 2-1". The lower right box in FIG. 8 may be referred to as "column 2-2".

Column 1-1 in FIG. 8 shows the relationship between _{the first threshold potential V B} , the conversion potential V _A, and the first comparative potential V _{C in the first period.} Column 1-2 of FIG. 8 shows the relationship between _{the second threshold potential V D} , the conversion potential V _A, and the second comparative potential V _{E in the first period.} In addition, column 1-1 and column 1-2 of FIG. 8 represent a situation in which insulation deterioration between the combustor 710 and the frame rod 720 has not occurred.

During combustion of the combustor 710, the frame rod current _IFR in the first period is larger than that during non-combustion. Therefore, the voltage drop in the detection resistor 120 based on the frame rod current IF _{R is also relatively large.} In the first period, this voltage drop acts to lower the _{conversion potential VA.} Therefore, as shown in columns 1-1 and 1-2 of FIG. 8, the conversion potential _VA is at a relatively low level.

When the combustor 710 is not combusted, the frame rod current _IFR in the first period is substantially zero. Therefore, the voltage drop in the detection resistor 120 based on the frame rod current IF _{R is also substantially zero.} Therefore, as shown in columns 1-1 and 1-2 of FIG. 8, the conversion potential _VA is at a relatively high level.

As shown in column 1-1 of FIG. 8, the first threshold potential V _B is larger than the above-mentioned relatively low-level conversion potential V _A and the above-mentioned relatively high-level conversion potential V _A. Smaller than Therefore, when the combustor 710 is switched from the burning state to the non-burning state, _{the level of the conversion potential V A} rises across the first threshold potential V _B. Therefore, as shown in column 1-1 in FIG 8, this switching, the first comparison potential V _C falls from the high level to the low level.

On the other hand, as shown in column 1-2 of FIG. 8, the second threshold potential V _D is not only smaller than the above-mentioned relatively high-level conversion potential _VA , but also the above-mentioned relatively low-level conversion. It is smaller than the _{potential VA.} Therefore, even if the combustor 710 is switched from the burning state to the non-burning state, _{the level of the conversion potential V A} does not change across the second threshold potential V _D. Therefore, as shown in column 1-2 in FIG. 8, even if the switching occurs, no second comparison potential V _E changes.

Column 2-1 of FIG. 8 shows the relationship between _{the first threshold potential V B} , the conversion potential V _A, and the first comparative potential V _{C in the second period.} Column 2-2 of FIG. 8 shows the relationship between _{the second threshold potential V D} , the conversion potential V _A, and the second comparative potential V _{E in the second period.} In addition, column 2-1 and column 2-2 of FIG. 8 represent both the situation where the combustor 710 is burning and the situation where it is not burning.

When the insulation deterioration between the combustor 710 and the frame rod 720 occurs, the frame rod current _IFR in the second period is larger than when the insulation deterioration does not occur. Therefore, the voltage drop in the detection resistor 120 based on the frame rod current IF _{R is also relatively large.} In the second period, this voltage drop acts to increase the _{conversion potential VA.} Therefore, as shown in columns 2-1 and 2-2 of FIG. 8, the conversion potential _VA is at a relatively high level.

_{The frame rod current IF R} in the second period is substantially zero when there is no insulation degradation between the combustor 710 and the frame rod 720. Therefore, the voltage drop in the detection resistor 120 based on the frame rod current IF _{R is also substantially zero.} Therefore, as shown in columns 2-1 and 2-2 of FIG. 8, the conversion potential _VA is at a relatively low level.

As shown in column 2-2 of FIG. 8, the second threshold potential V _D is larger than the above-mentioned relatively low-level conversion potential _VA and the above-mentioned relatively high-level conversion potential _VA. Smaller than Therefore, when a state in which insulation deterioration does not occur changed to the condition insulation deterioration has occurred, the level of conversion potential V _A is raised across the second threshold potential V _D. Therefore, as shown in column 22 of FIG. 8, by the switches, the second comparison potential V _E rises from the low level to the high level.

On the other hand, as shown in column 2-1 of FIG. 8, the first threshold potential V _B is not only larger than the above-mentioned relatively low-level conversion potential _VA , but also the above-mentioned relatively high-level conversion. Greater than the potential _VA. Therefore, even when switched to a state in which insulation deterioration has not insulation degradation from a state which occurs occurs, the level of conversion potential V _A is, does not change across a first threshold potential V _B. Therefore, as shown in column 2-1 in FIG. 8, even if the switching occurs, not the first comparison potential V _C changes.

Flame rod circuit 700, based on the first comparison potential V _C, to detect the combustion state of the combustor 710. Flame rod circuit 700, based on the second comparison potential V _E, for detecting the insulation deterioration state between the combustor 710 and the frame rod 720. Details of these detection methods will be described later.

The following description can be made with respect to the comparator 351 or 352 of the present embodiment. The frame rod circuit 700 includes a comparator 351 or 352, an extraction circuit 381 or 382, and a connection circuit 481 or 482. The comparator 351 or 352 has a threshold input unit 351a or 352a and a signal input unit 351b or 352b. The take-out circuit 381 or 382 connects the first line 111 and the second line 112. The extraction circuit 381 or 382 provides the threshold input unit 351a or 352a with a threshold potential V _B or V _D having a _{second DC potential V DC2} or more and a first DC potential V _{DC1 or less.} Connecting circuit 481 or 482, the signal input section 351b or 352b, depending on the current I _FR flowing between the second DC potential V _DC2 or more and not more than the first DC potential V _DC1 combustor 710 and the frame rods 720 give the signal potential V _S. The comparator 351 or 352 generates a comparative potential V _C or V _{E by comparing the threshold potential V B} or V _D with the signal potential V _S. Flame rod circuit 700, based on the comparison potential V _C, or V _E, for detecting the combustion state or insulation degradation condition.

Specifically, the connection circuit 481 or 482 connects the reference point A and the signal input unit 351b or 352b. The connection circuit 481 or 482, the signal input section 351b or 352b, provides a signal potential V _S corresponding to the potential of the second DC potential V _DC2 or more and the first DC potential V _DC1 less and reference point A.

The comparator 351 or 352 of the present embodiment contributes to the detection of the combustion state or the insulation deterioration state.

By the way, the above-mentioned Patent Document 1 describes a DC type frame rod circuit using two positive and negative power supplies. The positive and negative dual power supplies include a positive power supply that applies a positive voltage to the frame rod and a negative power supply that applies a negative voltage to the frame rod. In Patent Document 1, the positive voltage and the negative voltage are applied to the comparator. However, the total voltage of the positive voltage and the negative voltage described above often exceeds the rated voltage of a general comparator. Comparators with high rated voltages are often special and expensive. In this respect, it is not essential to use the comparators 351 and 352 of the present embodiment having a high rated voltage. Specifically, since the first DC potential V _DC1 and the second DC potential V _DC2 can be obtained by a single power source 770, the potential difference between them can be suppressed. Below this potential difference, the potential difference that may occur between the threshold input unit 351a and the signal input unit 351b of the comparator 351 can be suppressed, and the potential difference that may occur between the threshold input unit 352a and the signal input unit 352b of the comparator 352 can be suppressed. The power supply voltage of the comparator 351 and the power supply voltage of the comparator 352 need only be slightly larger than the potential difference. Therefore, it is not essential to use the comparators 351 and 352 of the present embodiment having a high rated voltage. Therefore, this embodiment is advantageous from the viewpoint of cost reduction.

In this embodiment, as shown in FIG. 7, the comparator 351 and the comparator 352 are housed in one package PAC. _{A DC potential V U} is supplied to the package PAC from a point U on the upstream side of the voltage regulator 165. _{The DC potential V U} supplied in this way is given to the positive power supply terminals (not shown) of the comparator 351 and the comparator 352. The DC potential V _U is higher than the first DC potential V _{DC 1. Further, the second DC potential V DC2} is supplied to the package PAC from the second line 112. The second DC potential V _DC2 supplied in this way is given to the negative power supply terminals (not shown) of the comparator 351 and the comparator 352. Thus, the package PAC, the DC potential V _U and the power supply voltage corresponding to the potential difference of the second DC potential V _DC2 is supplied, the power supply voltage, a first DC potential V _DC1 than the potential difference of the second DC potential V _DC2 Is also big.

In the comparator, an input terminal to which a potential in phase with that of the positive power supply terminal is applied is referred to as a positive in phase input terminal. In the example of FIG. 7, the first threshold input unit 351a and the second signal input unit 352b correspond to the positive in-phase input terminals. In general, the upper limit of the input potential to the positive in-phase input terminal (hereinafter, may be referred to as the upper limit of the common-mode input range) for proper operation of the comparator is higher than the potential of the positive power supply terminal. It is a little small value. The "slightly small value" is, for example, a value as low as 1 to 1.5 V. In this embodiment, it is assumed that the comparators 351 and 352 are such general comparators. However, as the comparators 351 and 352, it is also possible to use a comparator whose upper limit of the common mode input range is the same as the potential of the positive power supply terminal. In that case, the first DC potential V _DC1 may be applied to the positive power supply terminal.

Further, the following description can be made with respect to the comparator 351 or 352 of the present embodiment. The signal generation circuit 400 includes a comparator 351 or 352. Comparator 351 or 352, and the threshold voltage V _B or V _D, by comparing a signal potential corresponding to the converted voltage V _A, setting the size A _S of the detection signal S _D.

The following description can be made with respect to the buffer circuit 300 and the like of the present embodiment. The connection circuit 481 or 482 has a buffer circuit 300. In the illustrated example, the reference point A, the buffer circuit 300, and the signal input unit 351b or 352b are connected in this order.

Further, it is not essential to use an expensive buffer circuit 300 having a high rated voltage. Specifically, as described above, since the first DC potential V _DC1 and the second DC potential V _DC2 can be obtained by a single power source 770, the potential difference between them can be suppressed. This is advantageous from the viewpoint of suppressing the input voltage to the buffer circuit 300. Therefore, this embodiment is advantageous from the viewpoint of cost reduction.

Specifically, in this embodiment, the buffer circuit 300 includes an operational amplifier 301. The rated voltage of a general-purpose operational amplifier is not high, and an operational amplifier with a high rated voltage is often expensive. In this respect, the present embodiment is advantageous from the viewpoint of suppressing the power supply voltage of the operational amplifier 301.

_{Although not shown, in the present embodiment, the DC potential V U} is supplied to the positive power supply terminal of the operational amplifier 301 from the point U on the upstream side of the voltage regulator 165. _{Further, the second DC potential V DC2} is supplied from the second line 112 to the negative power supply terminal of the operational amplifier 301. Thus, the operational amplifier 301, the DC potential V _U and the power supply voltage corresponding to the potential difference of the second DC potential V _DC2 is supplied, the power supply voltage, a first DC potential V _DC1 than the potential difference of the second DC potential V _DC2 Is also big. However, as with the comparators 351 and 352, an operational amplifier whose upper limit of the common mode input range is slightly smaller than the potential of the positive power supply terminal may be used as the operational amplifier 301, and an operational amplifier whose upper limit is the same as the potential of the positive power supply terminal is used. You may. In the latter case, the first DC potential V _DC1 may be applied to the positive power supply terminal of the operational amplifier 301.

[VF conversion circuit 200]
FIG. 9 shows the VF conversion circuit 200 of this embodiment. The VF conversion circuit 200 includes an integrating circuit 210, a comparison circuit 240, and a transistor 260. A power supply 257 is connected to the VF conversion circuit 200. The power supply 257 is a DC power supply. Specifically, the power supply 257 outputs _{the first DC potential V DC1.}

_A potential corresponding to the conversion potential VA is input to the integrator circuit 210. In the present embodiment, "potential corresponding to the converted voltage V _A" is the same as the conversion potential V _A. However, "potential in accordance with the conversion potential V _A" may be different from the conversion potential V _A.

The integrator circuit 210 includes a first operational amplifier 211 and a negative feedback circuit 239. The first operational amplifier 211 includes a non-inverting input terminal 211a, an inverting input terminal 211b, and an output terminal 211c. The negative feedback circuit 239 includes a feedback capacitor 235. The negative feedback circuit 239 connects the output terminal 211c and the inverting input terminal 211b. The feedback capacitor 235 may be referred to as a time constant capacitor.

In this embodiment, the integrating circuit 210 includes a resistor 221 and a resistor 222 and a resistor 223. The buffer circuit 300, the resistor 221 and the point M, and the non-inverting input terminal 211a are connected in this order. The buffer circuit 300, the resistor 222, and the inverting input terminal 211b are connected in this order. The point M, the resistor 223, and the power supply 257 are connected in this order.

The comparison circuit 240 includes a second operational amplifier 241 and a positive feedback circuit 259. The second operational amplifier 241 includes a non-inverting input terminal 241a, an inverting input terminal 241b, and an output terminal 241c. The positive feedback circuit 259 includes a feedback resistor 253. The positive feedback circuit 259 connects the output terminal 241c and the non-inverting input terminal 241a.

In the present embodiment, the comparison circuit 240 comprises a voltage divider circuit including a resistor 251 and a resistor 252. A point S between the resistor 251 and the resistor 252 in this voltage divider circuit is connected to the non-inverting input terminal 241a. This voltage divider circuit is connected to the power supply 257. In the illustrated example, this voltage divider circuit is connected to the reference potential of the second region 792. Specifically, the power supply 257, the resistor 251 and the resistor 252, and the reference potential of the second region 792 are connected in this order by this voltage dividing circuit.

The transistor 260 includes a control terminal 260c, a first current terminal 260a, and a second current terminal 260b.

In this embodiment, the transistor 260 is a MOSFET. Specifically, the transistor 260 is a P-type MOSFET. The first current terminal 260a is a source terminal. The second current terminal 260b is a drain terminal. The control terminal 260c is a gate terminal. However, the transistor 260 may be a bipolar transistor, and specifically, a PNP type bipolar transistor. In that case, the first current terminal 260a is an emitter terminal. The second current terminal 260b is a collector terminal. The control terminal 260c is a base terminal.

In this embodiment, the VF conversion circuit 200 includes a resistor 261 and a resistor 262. The resistors 261 and 262 are arranged in this order on the path connecting the output terminal 241c of the second operational amplifier 241 and the power supply 257. A point T between the resistors 261 and 262 in this path is connected to the control terminal 260c of the transistor 260.

In this embodiment, the VF conversion circuit 200 includes a resistor 263. The second current terminal 260b of the transistor 260 and the inverting input terminal 211b of the first operational amplifier 211 are connected via a resistor 263.

In this embodiment, the VF conversion circuit 200 includes a diode 269. The point G, the anode of the diode 269, the cathode of the diode 269, and the output terminal 241c of the second operational amplifier 241 are connected in this order.

The VF conversion circuit 200 is configured so that the first phenomenon, the second phenomenon, and the third phenomenon appear when a DC potential is input to the VF conversion circuit 200. Specifically, when the output of the buffer circuit 300 is a DC potential, the DC potential is input to the VF conversion circuit 200. Hereinafter, the DC potential input to the VF converter 200, sometimes referred to as the DC potential V _in. In this embodiment, the DC potential V _in is the potential input to the integration circuit 210.

The first phenomenon is that the on / off of the transistor 260 is switched according to the output potential of the comparison circuit 240, so that the charging period in which the current flows in the feedback direction RD through the feedback capacitor 235 and the current in the direction opposite to the feedback direction RD in the feedback capacitor 235. It is a phenomenon that the discharge period in which the current flows alternately appears. The feedback direction RD is a direction in which the negative feedback circuit 239 travels from the output terminal 211c of the first operational amplifier 211 toward the inverting input terminal 211b.

The second phenomenon is a phenomenon _in which a triangular wave having a frequency corresponding to the DC potential Vin is output from the integrating circuit 210. Specifically, such a triangular wave is output from the output terminal 211c of the first operational amplifier 211.

The third phenomenon is a phenomenon in which a rectangular pulse wave having the same frequency as the triangular wave is output from the comparison circuit 240. Specifically, such a rectangular pulse wave is output from the output terminal 241c of the second operational amplifier 241.

According to the VF conversion circuit 200 configured so that the first phenomenon, the second phenomenon, and the third phenomenon appear, a rectangular pulse wave having a frequency corresponding _{to the conversion potential VA is utilized by utilizing the charge / discharge of the feedback capacitor 235.} Can be generated.

With reference to FIG. 10C from FIG. 10A, the current I _C flowing through the feedback capacitor 235, the triangular wave TW and the rectangular pulse wave SW, further described. In the following description, it is specified that the transistor 260 is a P-type MOSFET.

In FIG. 10A, the current flowing through the VF conversion circuit 200 during the charging period is represented by the alternate long and short dash line DL1. During the charging period
· Rectangular pulse wave SW, the potential of the gate terminal 260c in high level · P-type MOSFET260 is higher · P-type MOSFET260, in the off state and the current, a feedback capacitor 235 as the current I _C in the feedback direction RD Flows, then flows through resistor 222 towards buffer circuit 300-Triangle wave TW level rises

In FIG. 10B, the current flowing through the VF conversion circuit 200 during the discharge period is represented by the alternate long and short dash line DL2. During the discharge period
-The rectangular pulse wave SW is at a low level.-The potential of the gate terminal 260c of the P-type MOSFET 260 is low.-The P-type MOSFET 260 is in the ON state.-Current flows through the P-type MOSFET 260 from the power supply 257 to the resistor 263. some of-the current flowing through the P-type MOSFET260 is, as the current I _C, and a feedback capacitor 235 feedback direction RD level in the opposite direction to the flow-triangular wave TW decreases in the discharge period, through the P-type MOSFET260 Another portion of the current flows through the resistor 222 towards the buffer circuit 300.

When the VF conversion circuit 200 shows the behavior shown in FIGS. 10A and 10B during the charging period and the discharging period, the triangular wave TW and the rectangular pulse wave SW as shown in FIG. 10C can be obtained. In FIG. 10C, the horizontal axis is time t.

The VF conversion circuit 200 cooperates with the level setting circuit 350 to generate a _{detection signal S D which is a rectangular pulse signal.} Specifically, in this way the rectangular pulse signal generated has an amplitude A _S which is set by the level setting circuit 350, a frequency F _S which is set by the VF converter 200. The frequency F _S corresponds to the frequencies of the triangular wave TW and the square pulse wave SW.

As described above, in the present embodiment, a rectangular pulse voltage as schematically shown in FIG. 3 is applied to the frame rod 720. That is, in this embodiment, the polarity switching DC method is adopted. In the frame rod circuit 700 of the present embodiment in which the polarity switching DC method is adopted and the VF conversion circuit 200 is provided, the frequency F increases as the absolute value _{of the frame rod current IFR increases in the first period. S} becomes high. On the other hand, in the second period, the larger the absolute value _{of the frame rod current IF R,} the lower the frequency F S. The flame rod frequency F _S is dependent on the absolute value of the current I _FR is flame rod current I _FR is reflected in the potential of the reference point A, the potential corresponding to the potential of the reference point A is inputted to the VF converter 200 Because.

The combustion state of the fuel device 710 and the insulation state between the fuel device 710 and the frame rod 720 _{are reflected in the displacement voltage VA} , and the VF conversion circuit 200 generates a rectangular pulse wave having a frequency corresponding to the _{displacement voltage VA. When the displacement voltage V A} fluctuates due to the combustion state and / or the insulation state, the VF conversion circuit 200 generates a rectangular pulse wave having a frequency corresponding _{to the fluctuating displacement voltage V A.}

_{The detection signal S D} generated when the level setting circuit 350 operates according to the example shown in FIG. 8 will be described with reference to FIG.

Pulse waveform shown in the column 11 of FIG. 11 are those that would be obtained if the first comparison potential V _C of the column 11 of FIG. 8 is pulsed by VF converter 200 temporarily. Pulse waveform shown in the column 1-2 in FIG. 11 are those that would be obtained if the second comparison potential V _E column 1-2 in FIG. 8 is pulsed by VF converter 200 temporarily. Pulse waveform shown in the column 1-3 in FIG. 11, by the combined output of the first comparison potential V _C and a second comparison potential V _E at the first period is pulsed by VF converter 200, it is actually produced It is a thing.

Pulse waveform shown in the column 2-1 in FIG. 11 are those that would be obtained if the first comparison potential V _C of column 2-1 of Figure 8 is pulsed by VF converter 200 temporarily. Pulse waveform shown in the column 22 of FIG. 11 are those that would be obtained if the second comparison potential V _E column 22 of FIG. 8 is pulsed by VF converter 200 temporarily. Pulse waveform shown in the column 2-3 in FIG. 11, by the combined output of the first comparison potential V _C and a second comparison potential V _E at the second period is pulsed by VF converter 200, it is actually produced It is a thing.

Specifically, as described above, in the present embodiment, the first signal output unit C connected to the first output circuit of the open drain type and the second signal output connected to the second output circuit of the open drain type. A wired or is formed by being connected to the portion E. Therefore, when both the first comparative potential V _C and the second comparative potential V _E are at a high level, the combined output of the level setting circuit 350 becomes a high level potential. When at least one of the first comparative potential V _C and the second comparative potential V _E is at a low level, the combined output of the level setting circuit 350 becomes a low level potential. When the combined output of the level setting circuit 350 is a high level potential, a pulse is transmitted from the VF conversion circuit 200 to the point G via the diode 269. On the other hand, when the combined output of the level setting circuit 350 is a low level potential, the pulse from the VF conversion circuit 200 is not transmitted to the point G due to the presence of the diode 269.

When the combustor 710 is burned and the insulation between the combustor 710 and the frame rod 720 is deteriorated, the combined output of the level setting circuit 350 becomes a high level potential. Therefore, the frame rod current IF _R flowing at these times is converted into a pulse. In the present embodiment, the detector 502 can know the _{frame rod current IFR} by the inverse transformation from the period of the pulse.

In the case of isolated transmission of an analog signal, the isolated transmission circuit tends to be large-scale or expensive. In this regard, in the present embodiment, the frame rod current _IFR , which is an analog signal, is once converted into a pulse, which is a digital signal. As a result, the information of the frame rod current IF _R can be isolated and transmitted to the detector 502 relatively easily and inexpensively. There is an advantage of performing VF conversion.

_{In the first period, the detection signal S D,} which is a rectangular pulse wave as shown in column 1-3 of FIG. 11, may appear at the point G. _{Further, in the second period, the detection signal S D,} which is a rectangular pulse wave as shown in column 2-3 of FIG. 11, may appear at the point G.

In this embodiment, the negative feedback circuit 239 includes a feedback resistor 231 connected in series with the feedback capacitor 235. The feedback resistor 231 can enhance the linearity of the change in the frequency of the square pulse wave with respect to the change in the _{conversion potential VA.}

Hereinafter, a situation in which the linearity deteriorates and a mechanism in which the linearity is improved by the feedback resistor 231 will be described.

The operational amplifier may be configured such that the signal output from the output terminal is switched when the magnitude relationship between the signal potential input to one input terminal and the threshold potential input to the other input terminal is switched. However, strictly speaking, the operational amplifier has a response delay. Therefore, the output is switched at a timing delayed from the timing at which the magnitude relationship of the input is switched. The delay becomes apparent when the frequency of the signal potential is high. In other words, even if the threshold potential is actually constant, it seems as if the threshold potential deviates significantly from the actual value as the frequency increases.

In the comparison circuit 240 shown in FIG. 9, the potential of the output terminal 241c of the second operational amplifier 241 is high level in the first period and low level in the second period. The potential of the output terminal 241c is positively fed back to the non-inverting input terminal 241a via the positive feedback circuit 259. Therefore, the potential of the non-inverting input terminal 241a acting as a threshold is relatively high level in the first period and relatively low level in the second period.

FIG. 12 shows the above threshold value added to FIG. 10C. In FIG. 12, the upper alternate long and short dash line is the threshold at the high level. The lower dash-dotted line is the threshold at the low level. FIG. 12 assumes a situation in which the feedback resistor 231 is removed from the configuration of FIG. 9, but the response delay of the second operational amplifier 241 can be ignored because the frequencies of the triangular wave TW and the square pulse wave SW are low.

FIG. 13 assumes a situation in which the feedback resistor 231 is removed from the configuration of FIG. 9, as in FIG. However, FIG. 13 assumes a situation in which the frequencies of the triangular wave TW and the square pulse wave SW are higher than those in the state of FIG.

It is assumed that the second operational amplifier 241 has no response delay. In that case, in FIG. 13, as in FIG. 12, the triangular wave TW bends at the positions of the upper one-dot chain line and the lower one-dot chain line, and the level of the rectangular pulse wave SW is switched at the same timing.

However, in reality, the second operational amplifier 241 has a response delay. The response delay becomes apparent when the frequencies of the triangular wave TW and the square pulse wave SW increase due to the increase _{in the} DC potential Vin input to the integrating circuit 210. As a result, the position where the triangular wave TW bends on the upper side shifts to the position of the upper two-dot chain line above the upper one-dot chain line. The upper block arrow schematically represents this deviation. Further, the position where the triangular wave TW bends on the lower side shifts to the position of the lower two-dot chain line below the lower one-dot chain line. The lower block arrow schematically represents this deviation.

In this way, the apparent threshold shifts. Specifically, this deviation acts to lengthen one cycle of the triangular wave TW and the square pulse wave SW as compared with the case where the response delay can be ignored. That is, it acts to lower the frequencies of the triangular wave TW and the square pulse wave SW.

Such an unintended decrease in the frequencies of the triangular wave TW and the square wave SW can be suppressed by the feedback resistor 231 for the following reasons.
- When the DC potential V _in increases, which is input to the integration circuit 210, the absolute value becomes large, the charging period of the current I _C flowing through the feedback capacitors 235 in the charging period and the discharging period, the feedback resistor 231 by a current I _C A voltage (hereinafter referred to as the first offset voltage) V _off1 is generated, and the _{level of the triangular wave at the start of the charging period rises by} the amount of the first offset voltage V off1, and as a result, the level of the triangular wave is at the upper two points from the start of the charging period. effect that the time is shortened up to the chain line is obtained, the absolute value becomes large as the first offset voltage V _off1 increases this effect becomes larger and discharging period of the current I _C, a feedback resistor by a current I _C A voltage (hereinafter referred to as a second offset voltage) V _off2 is generated at 231 and the level of the triangular wave at the start of the discharge period is lowered by the amount of the second offset voltage V _off2 , and as a result, the level of the triangular wave is lowered from the start of the discharge period. effect that the time is shortened up to the two-dot chain line is obtained, and these effects by the current I _C of the absolute value becomes large as the second offset voltage V _off2 increases, the feedback resistor 231 this effect becomes larger In combination, as the DC potential V _in input to the integrating circuit 210 increases, the frequency raising action of the triangular wave TW and the rectangular pulse wave SW played based on the feedback resistance 231 increases. As a result, the second operational capacitor 241 The frequency lowering action of the triangular wave TW and the rectangular pulse wave SW caused by the deviation of the apparent threshold due to the response delay of 231 is at least partially canceled by the frequency raising action of the feedback resistor 231.

In (a) of FIG. 14 shows a time chart showing the relation between the current I _C and the triangular wave TW when there is no feedback resistor 231. In (b) of FIG. 14 shows a time chart showing the relation between the current I _C and the triangular wave TW when there is a feedback resistor 231. Upper (a) and (b) of FIG. 14 represents the time variation of the current I _C. The lower part of FIGS. 14A and 14B shows the time change of the level of the triangular wave TW. In FIG. 14, the horizontal axis is time t. From FIG. 14, it can be seen that the frequency can be adjusted appropriately by setting the value of the feedback resistor 231 _{appropriately and adjusting the offset voltages V off 1} and V off _{2 appropriately.}

FIG. 15 schematically shows how the linearity is improved by the feedback resistor 231. The horizontal axis of FIG. 15 is the DC potential V _in input to the integrating circuit 210. The vertical axis represents the frequency F _S. As described above, the frequency F _S is the frequency of the rectangular pulse signal constituting the detection signal S _D , and corresponds to the frequencies of the triangular wave TW and the rectangular pulse wave SW. The solid line is a graph showing the relationship between the _{input DC potential V in} and the frequency F _S when the feedback resistor 231 is present. Dotted line, when there is no feedback resistor 231 is a graph showing the relationship between the input DC potential V _in and the frequency F _S.

In the example of FIG. 9, in the feedback circuit 239, the feedback resistor 231 and the feedback capacitor 235 are arranged in this order in the feedback direction RD. However, in the feedback circuit 239, the feedback capacitor 235 and the feedback resistor 231 may be arranged in this order in the feedback direction RD.

[VF conversion circuit 290 according to a modified example]
A modified example of the VF conversion circuit will be described with reference to FIG. Hereinafter, the description of the same portion as that of the VF conversion circuit 200 of FIG. 9 may be omitted.

The VF conversion circuit 290 shown in FIG. 16 includes an inverting amplifier circuit 270, an integrating circuit 210, a comparison circuit 240, and a transistor 265. A power supply 257 and a power supply 275 are connected to the VF conversion circuit 290. The power supply 275 is a DC power supply.

_A potential corresponding to the conversion potential VA is input to the inverting amplifier circuit 270. In this modification, "potential corresponding to the converted voltage V _A" is the same as the conversion potential V _A. However, "potential in accordance with the conversion potential V _A" may be different from the conversion potential V _A.

A power supply 275 is connected to the inverting amplifier circuit 270. The inverting amplifier circuit 270 includes an operational amplifier 276 and a negative feedback circuit 279. The operational amplifier 276 includes a non-inverting input terminal 276a, an inverting input terminal 276b, and an output terminal 276c. The negative feedback circuit 279 includes a feedback resistor 277. The negative feedback circuit 279 connects the output terminal 276c and the inverting input terminal 276b.

In this modification, the inverting amplifier circuit 270 constitutes a voltage dividing circuit including a resistor 271 and a resistor 272. A point K between the resistors 271 and 272 in this voltage divider circuit is connected to the non-inverting input terminal 276a. This voltage divider circuit is connected to the power supply 275. In the illustrated example, this voltage divider circuit is connected to the reference potential of the second region 792. Specifically, the power supply 275, the resistor 271, the resistor 272, and the reference potential of the second region 792 are connected in this order by this voltage dividing circuit. In this example, the reference potential of the second region 792 is the second DC potential V _DC2 . The power supply 275 outputs the first DC potential V _DC1.

本変形例では、Ｒ₂₇₁＝Ｒ₂₇₂＝Ｒ₂₇₃＝Ｒ₂₇₇である。これを考慮すると、上記の数式は、以下のようになる。

さらに、Ｖ_DC2＝０Ｖと扱えば、以下の数式が得られる。

The following relational expression holds between the potential V _{in input to the inverting amplifier circuit 270 and the potential V w} output from the inverting amplifier circuit 270. In the following relational expression, V _K is the potential of the point K. R ₂₇₁ is the resistance value of the resistor 271. R ₂₇₂ is the resistance value of the resistor 272. R ₂₇₃ is the resistance value of the resistor 273. R ₂₇₇ is the resistance value of the resistor 277. V _DC2 is the value of the second DC potential V _DC2. V _DC1 is the value of the first DC potential V _DC1.

In this modification, R ₂₇₁ = R ₂₇₂ = R ₂₇₃ = R ₂₇₇ . Considering this, the above formula becomes as follows.

Further, if V _DC2 = 0V is treated, the following mathematical formula can be obtained.

Inverting amplifier circuit 270 according to this modification, the potential signal to decrease the flame rod current I _FR with respect to the first DC potential V _DC1 is increased, increase flame rod current I _FR a second DC potential V _DC2 with respect It can be converted into a rising potential signal. This conversion can be referred to as conversion _{from a V DC1} reference signal to a V _{DC2 reference signal.} Specifically, the inverting amplifier circuit 270 can perform such a conversion according to the above mathematical formula.

The integrator circuit 210 of the modified example shown in FIG. 16 includes the same elements as the integrator circuit 210 of the example of FIG. In this modification, the output terminal 276c of the operational amplifier 276, the resistor 221 and the point M, and the non-inverting input terminal 211a are connected in this order. The output terminal 276c of the operational amplifier 276, the resistor 222, and the inverting input terminal 211b are connected in this order. The point M, the resistor 223, and the reference potential of the second region 792 are connected in this order.

The comparison circuit 240 of the modified example shown in FIG. 16 includes the same elements as the comparison circuit 240 of the example of FIG.

In this modification, the transistor 265 is a MOSFET. Specifically, the transistor 265 is an N-type MOSFET. The first current terminal 265a is a drain terminal. The second current terminal 265b is a source terminal. The control terminal 265c is a gate terminal. However, the transistor 265 may be a bipolar transistor, or specifically, an NPN type bipolar transistor. In that case, the first current terminal 265a is a collector terminal. The second current terminal 265b is an emitter terminal. The control terminal 265c is a base terminal.

In this modification, the output terminal 241c of the second operational amplifier 241 and the control terminal 265c of the transistor 265 are connected via a resistor 261. Further, the control terminal 265c of the transistor 265 and the reference potential of the second region 792 are connected via the resistor 262.

The VF conversion circuit 290 is configured so that the first phenomenon, the second phenomenon, and the third phenomenon appear when a DC potential is input to the VF conversion circuit 290. Specifically, when the output of the buffer circuit 300 is a DC potential, the DC potential is input to the VF conversion circuit 290. Hereinafter, the DC potential input to the VF conversion circuit 290 may be referred _{to as a DC potential V in.} In this modification, the DC voltage V _in is the potential input to the inverting amplifier circuit 270.

The first phenomenon is that the on / off of the transistor 265 is switched according to the output potential of the comparison circuit 240, so that the charging period in which the current flows in the feedback direction RD through the feedback capacitor 235 and the current in the direction opposite to the feedback direction RD in the feedback capacitor 235. It is a phenomenon that the discharge period in which the current flows alternately appears. The feedback direction RD is a direction in which the negative feedback circuit 239 travels from the output terminal 211c of the first operational amplifier 211 toward the inverting input terminal 211b.

The second phenomenon is a phenomenon _in which a triangular wave having a frequency corresponding to the DC potential Vin is output from the integrating circuit 210. Specifically, such a triangular wave is output from the output terminal 211c of the first operational amplifier 211.

The third phenomenon is a phenomenon in which a rectangular pulse wave having the same frequency as the triangular wave is output from the comparison circuit 240. Specifically, such a rectangular pulse wave is output from the output terminal 241c of the second operational amplifier 241.

According to the VF conversion circuit 290 configured so that the first phenomenon, the second phenomenon, and the third phenomenon appear, a rectangular pulse wave having a frequency corresponding _{to the conversion potential VA is utilized by utilizing the charge / discharge of the feedback capacitor 235.} Can be generated.

With reference to Figure 17C from FIG. 17A, the current I _C flowing through the feedback capacitor 235, the triangular wave TW and the rectangular pulse wave SW, further described. In the following description, it is specified that the transistor 265 is an N-type MOSFET.

In FIG. 17A, the current flowing through the VF conversion circuit 290 during the charging period is represented by the alternate long and short dash line DL1. During the charging period
· Rectangular pulse wave SW, the potential of the gate terminal 265c in high level · N type MOSFET265 is higher · N type MOSFET265, in the ON state and current is, the feedback capacitor 235 as the current I _C in the feedback direction RD Flows, then flows through the reference potentials of the resistor 263, N-type MOSFET 265 and the second region 792 in this order. ・ The level of the triangular wave TW rises.

In FIG. 17B, the current flowing through the VF conversion circuit 290 during the discharge period is represented by a chain double-dashed line. During the discharge period
-The square pulse wave SW is at a low level.-The potential of the gate terminal 265c of the N-type MOSFET 265 is low.-The N-type MOSFET 265 is in the off state.-The current flows so as to move the resistor 222 away from the inverting amplifier circuit 270. , then the level in the opposite direction to the flow-triangular wave TW decreases the feedback direction RD feedback capacitor 235 as the current I _C

By the VF conversion circuit 290 showing the behavior shown in FIGS. 17A and 17B during the charging period and the discharging period, the triangular wave TW and the rectangular pulse wave SW as shown in FIG. 17C can be obtained. In this way, the VF conversion circuit 290 can perform VF conversion in the same manner as the VF conversion circuit 200. In FIG. 17C, the horizontal axis is time t.

In the present embodiment, when the combustion intensity of the frame rod 720 decreases in the first period, _{the absolute value of the frame rod current IF R} decreases, and the conversion potential V _A approaches the first DC potential V _{DC 1.} Both the VF conversion circuit 200 in the example of FIG. 9 and the VF conversion circuit 290 in the example of FIG. 16 are configured so that _{the frequency F S} of the output pulse decreases as the _{conversion potential V A} approaches the first DC potential V _{DC 1.} Has been done. Specifically, the VF conversion circuits 200 and 290 are rectangular pulses output from the VF conversion circuits 200 and 290 when _{the frame rod current IF R} is zero and the conversion potential _VA is the first DC potential V _DC1. The frequency of the wave SW is configured to be zero.

As can be understood from the explanation using FIG. 13, in the region where the frequency of the square pulse wave SW is low, it is difficult for the deviation of the “apparent threshold” to become apparent. The frequency of the square pulse wave SW becomes low when the combustion intensity of the frame rod 720 is low and the absolute value of the _{frame rod current IF R is small.} Therefore, when the VF conversion circuits 200 and 290 are configured as described above, the detection accuracy is ensured in the region where _{the combustion intensity of the frame rod 720 is low and the absolute value of the frame rod current IFR is small in the first period.} easy. To give a specific example, it is easy to accurately detect the situation where the flame of the frame rod 720 is about to extinguish for some reason.

Specifically, in the VF conversion circuit 200 of the example of FIG. 9, in the first period, the integrating circuit 210 _{utilizes the first DC potential V DC1} derived from the power supply 257 and changes based on the first DC potential V _DC1. The conversion potential _VA is pulsed in cooperation with the comparison circuit 240. The VF converter 200, In this manner, configuration combustion intensity of the flame rod 720 to output the low frequency F _S when low is realized.

On the other hand, in the example of the VF converter 290 in FIG. 16, in the first period, the inverting amplifier circuit 270, a potential signal to decrease the flame rod current I _FR with respect to the first DC potential V _DC1 is increased, a second direct current position the V _DC2 as a reference into a potential signal rises flame rod current I _FR increases. _{Then, the integrating circuit 210 utilizes the second DC potential V DC2} connected to the second current terminal 265b, and transfers the signal obtained by the conversion, that is, the signal that _{changes based on the second DC potential V DC2} reference to the comparison circuit 240. Collaborate to pulse. The VF converter 290, In this manner, configuration combustion intensity of the flame rod 720 to output the low frequency F _S when low is realized. According to the example of FIG. 16, an N-type MOSFET can be used as the transistor 265.

As can be understood from the above description, in the frame rod circuit 700, if the combustor 710 is burning, a first period in which a current flows between the combustor 710 and the frame rod 720 appears. In the examples of FIGS. 9 and 16, in the first period, the _{smaller the absolute value of the current IFR} flowing between the combustor 710 and the frame rod 720, the lower the frequencies of the triangular wave TW and the rectangular pulse wave SW, whereby the frequency of the triangular wave TW and the rectangular pulse wave SW becomes smaller. When the detection signal S _D is a rectangular pulse signal, the frequency F _{S of the detection signal S D} becomes smaller. This is suitable for accurately detecting the combustion state when the combustion intensity of the frame rod 720 is low. To give a specific example, this is suitable for accurately detecting the situation where the flame of the frame rod 720 is about to extinguish.

[Detection]
Returning to FIG. 2, as described above, the frame rod circuit 700 includes a detector 502. Specifically, the control device 500 includes a detector 502.

_{The detection signal S D} generated in the signal generation circuit 400 is supplied to the detector 502. The detector 502 detects the combustion state of the combustor 710 and the insulation deterioration state 720 between the combustor 710 and the frame rod 720 by using the _{detection signal SD} input to the detector 502. In the example of FIG. 2, the detection signal S _D is based on the current I _FR flowing between the combustor 710 and the frame rod 720. Specifically, the detector 502 uses a portion based on the current I _FR flowing between the combustor 710 and the frame rod 720 in the first period of the detection signal S _D inputted to the detector 502, the combustion Detect the state. The detector 502 detects the insulation deterioration state by using the portion of _{the detection signal S D} input to the detector 502 _{based on the current IFR} flowing between the combustor 710 and the frame rod 720 in the second period. ..

In the example of FIG. 2, it can be said that the detection signal S _D is based on the potential of the reference point A. Specifically, the detector 502 detects _{the combustion state by using the portion of the detection signal S D} input to the detector 502 based on the potential of the reference point A in the first period. _{The detector 502 detects the insulation deterioration state by using the portion of the detection signal S D} input to the detector 502 based on the potential of the reference point A in the second period.

Specifically, in the example of FIG. 2, the detector 502 is a digital device. Hereinafter, the detector 502, which is a digital device, may be referred to as a digital detector 502.

<Distinguishing the combustion state of the combustor 710>
In the present embodiment, as can be understood from the explanation with reference to columns 1-3 of FIG. 11, the frequency F _{S of the detection signal S D} in the first period is the first state, the second state, and the third state. And different. The first state is a state in which the combustor 710 is not burning. The second state is a state in which the combustion intensity of the combustor 710 is relatively weak. The third state is a state in which the combustion intensity of the combustor 710 is relatively strong. The "state in which the combustion intensity of the combustor 710 is relatively weak" in the second state does not include the state in which the combustion intensity of the combustor 710 is zero (that is, the second state is the first state). To be distinguished from). In addition, "combustor intensity of combustor 710 is relatively weak" regarding the second state and "combustion intensity of combustor 710 is relatively weak" regarding the third state are the combustor in the second state than in the third state. This expression is intended to mean that the combustion intensity of 710 is weak.

The first state corresponds to “non-combustion” in column 1-3 of FIG. The second state corresponds to the region where the rectangular pulse signal exists in the “transient time” in columns 1-3 of FIG. The third state corresponds to "during combustion" in column 1-3 of FIG.

As described above, in the present embodiment, the frequency F _{S of the detection signal S D} in the first period differs between the first state and the third state. This can contribute to discriminating between the situation where the combustor 710 is not burning and the situation where the combustor is burning 710 normally.

Further, in the present embodiment, the frequency F _{S of the detection signal S D} in the first period is different from the first state and the third state in the second state. This can be useful for detecting a situation in which the combustor 710 has not misfired, but the combustion intensity of the combustor 710 is weak and the combustor is misfired.

In the present embodiment, the detection signal _SD in the first period is a DC signal in the first state and a square pulse signal in the second and third states. In this way, the detector 502 can easily distinguish the first state from the second state and the third state by the _{detection signal SD in the first period.} Therefore, it is easy to secure the detection accuracy of the first state in which the combustor 710 is not burning.

In the present embodiment, the size A _S of the detection signal S _D in the first period is in the first state is different from the second state and third state. In this way, even if the function of generating the _{pulsed detection signal S D} is lost due to a failure of the VF conversion circuit 200 or the like, the detector 502 has a large _{detection signal S D in the first period.} is the a _S, the first state can be distinguished from the second state and third state.

Specifically, as understood from the description with reference to column 1-3 of Figure 11, the magnitude A _S of the detection signal S _D in the first period is in the first state is a low level. The magnitude _AS is at a high level in the second and third states.

In the present embodiment, the detector 502 determines the combustion state of the combustor 710 based on the magnitude _AS and the frequency F _{S of the detection signal S D in the first period.} Specifically, in the detector 502, the frequency F _{S of the detection signal S D} is zero (that is, the detection signal S _D is a DC signal), and the magnitude A _{S of the detection signal S D} is low level. In the case, it is determined that it is in the first state. The detector 502 determines that the combustor 710 is in the second state when the frequency F _S of the detection signal S _{D is not zero but is relatively low.} When the frequency F _S of the detection signal S _D is relatively high, it is determined that the combustor 710 is in the third state.

Further, in the present embodiment, when the detection signal S _D is a DC signal and its magnitude A _S in the first period is different from the first state, the detector 502 includes an abnormal circuit occurs decision do. Specifically, in the example of columns 1-3 of FIG. 11, when the detection signal S _D in the first period is a DC signal and its magnitude _AS is high level, the detector 502 is a circuit. Judge that an abnormality has occurred.

<Differentiation of insulation deterioration state between combustor 710 and frame rod 720>
In the present embodiment, as understood from the description with reference to column 2-3 of Figure 11, the frequency F _S of the detection signal S _D in the second period is different between the fourth state, the fifth state. The fourth state is a state in which the insulation resistance between the combustor 710 and the frame rod 720 is relatively high. The fifth state is a state in which the insulation resistance is relatively low. "The insulation resistance between the combustor 710 and the frame rod 720 is relatively high" for the fourth state and "the insulation resistance is relatively low" for the fifth state are the insulation resistances in the fourth state than in the fifth state. It is an expression intended to be high.

The fourth state corresponds to "normal time" in column 2-3 of FIG. The fifth state corresponds to “at the time of insulation deterioration” in column 2-3 of FIG. It should be noted that the region in which the rectangular pulse signal does not exist in the “transient time” in columns 2-3 of FIG. 11 can also be considered to belong to the fourth state. Further, it can be considered that the region in which the rectangular pulse signal exists in the “transient time” in columns 2-3 of FIG. 11 also belongs to the fifth state.

As described above, in the present embodiment, the frequency F _{S of the detection signal S D} in the second period is different between the fourth state and the fifth state. This contributes to discriminating between the situation where the insulation between the combustor 710 and the frame rod 720 is properly secured and the situation where the insulation deterioration between the combustor 710 and the frame rod 720 has progressed. obtain.

In the present embodiment, the detection signal _SD in the second period is a DC signal in the fourth state and a rectangular pulse signal in the fifth state.

In the present embodiment, _{the magnitude of the detection signal SD} in the second period is different in the fifth state from that in the fourth state. In this way, even if the function of generating the _{pulsed detection signal S D} is lost due to a failure of the VF conversion circuit 200 or the like, the detector 502 has a large _{detection signal S D in the second period.} is the a _S, the fifth state can be distinguished from the fourth state.

Specifically, as understood from the description with reference to column 2-3 of Figure 11, the magnitude A _S of the detection signal S _D in the second period, in the fourth state, a low level. The magnitude _AS is at a high level in the fifth state.

In a variant, the size A _S of the detection signal S _D in the second period, the fourth state is a high level. The magnitude _AS is low level in the fifth state. This modification can be realized, for example, by exchanging the connection between the second threshold input unit 352a and the second signal input unit 352b of the second comparator 352.

In the present embodiment, the detector 502, based on the frequency F _S of the detection signal S _D in the second period, to determine the insulation degradation state of the combustor 710. Specifically, the detector 502 determines that the insulation deterioration state is in the fourth state when the frequency F _{S of the detection signal S D is relatively low.} When the frequency F _S of the detection signal S _D is relatively high, the detector 502 determines that the insulation deterioration state is in the fifth state.

In the above context regarding the second period, "when the frequency F _{S of the detection signal S D} is relatively low" is an expression intended to include the case where _{the frequency F S is zero.} Therefore, the determination mode of the fourth state and the fifth state described above is when the frequency F _{S of the detection signal S D} is zero (that is, the detection signal) as shown in column 2-3 of FIG. When S _D is a DC signal), it is determined that the insulation deterioration state is in the fourth state, and when the frequency F _{S of the detection signal S D} is non-zero, it is determined that the insulation deterioration state is in the fifth state. Includes aspects.

It is also possible to distinguish the fifth state into a 5-1 state in which the insulation resistance between the combustor 710 and the frame rod 720 is relatively high and a 5-2 state in which the insulation resistance is relatively low. be. In the present embodiment, when distinguished in this way, the frequency F _{S of the detection signal S D} in the second period differs between the 5-1st state and the 5-2nd state. It is also possible to configure the detector 502 so that the degree of progress of insulation deterioration can be discriminated and detected by utilizing this difference.

The detector 502 can also be configured to determine the insulation deterioration state of the combustor 710 based on the magnitude _AS and frequency F _S of the detection signal S _{D in the second period.} Specifically, in this configuration example according to column 2-3 of FIG. 11, in the detector 502, the frequency F _{S of the detection signal S D} in the second period is zero (that is, the detection signal S _D is a DC signal). If its size _AS is low level, it is determined that it is in the fourth state. The detector 502 determines that the detection signal S _D is in the fifth state when the frequency F _S of the detection signal S D in the second period is not zero and its magnitude _{AS is high level.} Further, the detector 502 determines that a circuit abnormality has occurred when the frequency F _{S of the detection signal S D} in the second period is zero and the magnitude A _{S is high level.} It is also possible to configure.

The technique for determining the insulation state of deterioration of the combustor 710 on the basis of the magnitude A _S and the frequency F _S of the detection signal S _D in the second period, the magnitude A _S of the detection signal S _D in the second period is fourth state It is also possible to adopt an example combined with a modified example which is a high level in. In this combination example, the detector 502 determines that the detection signal S _D is in the fifth state when the frequency F _S of the detection signal S D in the second period is zero and the magnitude _{AS is low level.} The detector 502 determines that the detection signal S _D is in the fourth state when the frequency F _S of the detection signal S D in the second period is not zero and its magnitude _{AS is high level.} Further, the detector 502 determines that a circuit abnormality has occurred when the frequency F _{S of the detection signal S D} in the second period is zero and the magnitude A _{S is high level.} It is also possible to configure.

In a typical example, even if there is no insulation deterioration between the combustor 710 and the frame rod 720, if the combustor 710 is burning, the frame rod current IF _{R in the second period will be} It will not be completely zero. In this case, it is also possible to detect the insulation deterioration state in consideration of the minute frame rod current _{IFR in the second period.} Specifically, when no insulation deterioration has occurred, both the frame rod current _IFR in the first period and the minute frame rod current _IFR in the second period fluctuate according to the degree of combustion of the combustor 710. However, there is a correlation in the way they fluctuate. Therefore, the detector 502 according to a specific example determines the degree of insulation deterioration with reference to the frequency F _{S of the detection signal S D in the first period.} As a result, the detector 502 knows to what extent the combustion-derived component of the combustor 710 _{of the frame rod current IF R} in the second period affects the frequency F _{S of the detection signal S D in the second period.} Can be done. Then, the detector 502, by subtracting the influence component from the frequency F _S in the second period, it is possible to detect the insulation deterioration state with high accuracy.

As can be understood from the above description, in the frame rod circuit 700 according to the present disclosure, a first period and a second period appear. If the combustor 710 is burning in the first period, a current flows between the combustor 710 and the frame rod 720. If insulation deterioration occurs between the combustor 710 and the frame rod 720 in the second period, a current flows between the combustor 710 and the frame rod 720. The frequency F _S of the detection signal S _D in the first period is the first state in which the combustor 710 is not burning, the second state in which the combustion intensity of the combustor 710 is relatively weak, and the combustion intensity of the combustor 710. It differs from the relatively strong third state. The frequency F _S of the detection signal S _D in the second period differs between the fourth state in which the insulation resistance between the combustor 710 and the frame rod 720 is relatively high and the fifth state in which the insulation resistance is relatively low. .. Typically, the first period and the second period alternate.

In the frame rod circuit 700, the detection signal S _D is a DC signal or a rectangular pulse signal. DC signals and square pulse signals are easy to detect by digital devices. Actually, in the present embodiment, the DC signal and the detection signal _SD which is a rectangular pulse are detected by the digital detector 502.

In this embodiment, the signal generation circuit 400 is an analog circuit. The detection signal S _D is generated by the analog circuit and detected by the digital detector 502. DC signals and square pulse signals are suitable as signals generated by analog circuits and detected by digital detector 502.

In the present embodiment, the detection signal S _D generated by the frame rod circuit 700 is insulated and transmitted to the detector 502 via the insulation circuit 601. _{The detection signal S D,} which is a DC signal or a square pulse signal, is easily isolated and transmitted.

Specifically, in the present embodiment, the frame rod circuit 700 includes a first region 791 and a second region 792 having different reference potentials from each other. The frame rod circuit 700 includes a photocoupler as an insulation circuit 601. The detector 502 belongs to the first region 791. The combustor 710, the frame rod 720 and the signal generation circuit 400 belong to the second region 792. The detection signal S _D is isolated and transmitted from the signal generation circuit 400 to the detector 502 via the photocoupler 601.

Insulated transmission of a signal is generally performed by a method using an isolated amplifier, a method of converting a digital signal into a digital signal by an A / D converter, and then transmitting the digital signal by a digital isolator. However, in the frame rod circuit 700, the temporal change of the current flowing through the frame rod 720 is often gradual. In that case, the rectangular pulse wave reflecting the current can be a rectangular pulse wave in a low frequency range. Such a square pulse wave can be isolated and transmitted by a general-purpose photocoupler (specifically, a transistor output photocoupler). In addition, DC waves can also be insulated and transmitted with a general-purpose photocoupler. For this reason, according to the present embodiment, by making good use of the properties of the current flowing through the frame rod 720, an inexpensive insulated transmission means is configured by combining a _{detection signal SD which can be a square pulse wave and a photocoupler.} can.

The frequency F _S of the detection signal S _D is, for example, 0 Hz to 5 kHz, and may be 0 Hz to 3 kHz. When the frequency F _S is in this range, hard distortion of the detection signal S _D in isolating transfer of the detection signal S _D with a general purpose photocoupler occurs. In one specific example, the upper limit of the frequency F _{S of the detection signal S D} is limited by the characteristics of the photocoupler and the influence of peripheral components connected to the photocoupler.

[Control device 500 and insulation device 600]
Hereinafter, the control device 500 and the insulation device 600 will be further described with reference to FIG.

The frame rod circuit 700 includes a resistor 731, a resistor 733, and a resistor 735.

The control device 500, the resistor 735, and the insulation circuit 603 are connected in this order. Specifically, the switch 501, the resistor 735, and the insulation circuit 603 are connected in this order.

As described above, in this embodiment, the insulation circuit 603 is a photocoupler. The photocoupler 603 includes a light emitting diode 603d and a phototransistor 603t. The light emitting diode 603d is connected to the first region 791. The resistor 735, the light emitting diode 603d, and the reference potential of the first region 791 are connected in this order. The phototransistor 603t is connected to the second region 792.

The control device 500, the point Y, and the insulation circuit 601 are connected in this order. Specifically, the detector 502, the point Y, and the insulation circuit 601 are connected in this order.

As described above, in the present embodiment, the insulation circuit 601 is a photocoupler. The photocoupler 601 includes a phototransistor 601t and a light emitting diode 601d. The phototransistor 601t is connected to the first region 791. The point Y, the phototransistor 601t, and the reference potential of the first region 791 are connected in this order. The light emitting diode 601d is connected to the second region 792. The first line 111, the resistor 731, the light emitting diode 601d, and the point G are connected in this order.

The power supply 750, the resistor 733, and the point Y are connected in this order. The power supply 750 is a DC power supply.

In the present embodiment, the control device 500 determines the combustion state of the combustor 710 in the first period. The control device 500 determines the state of insulation deterioration between the combustor 710 and the frame rod 720 in the second period. Specifically, the main body of these determinations is the detector 502.

In the present embodiment, a certain period from the switching from the first period to the second period is set as the wait time. Further, a certain period from the switching from the second period to the first period is set as the wait time. During the wait time, the control device 500 does not determine the combustion state and the insulation deterioration state. By doing so, it is easy to prevent erroneous determination.

The length of the wait time is 100 to 1000 msec in one example and 200 to 600 msec in one specific example.

As described above, in the present embodiment, one control device 500 transmits a control signal S _C, receives the detection signal S _D. Therefore, the control device 500 _{can easily grasp whether a certain part of the detection signal SD} belongs to the first period or the second period.

In one specific example, the control device 500 includes a microcomputer and a transistor with a built-in resistor. The transistor with built-in resistor is connected to the power supply. The control device 500 includes a microcomputer and a switch 501 including a transistor with a built-in resistor. Specifically, built-in resistors transistors by microcomputer in a state of being controlled in an ON state, a power supply with built-in resistor transistor outputs a control signal S _C cooperate. Further, the control device 500 includes a detector 502 including a microcomputer. It is also possible to use a MOSFET instead of a transistor with a built-in resistor.

[Configuration example shown in FIG. 19]
The frame rod circuit may have the configuration shown in FIG. The example of FIG. 19 is different from the example of FIG. 2 in the position of the reference point A, the position of the detection resistor 120, and the position of the capacitor 155. Specifically, the frame rod 720, the reference point A, and the detection resistor 120 are connected in this order. Further, in the example of FIG. 19, a VF conversion circuit 299 is provided instead of the VF conversion circuit 200 (see FIG. 23).

In the frame rod circuit 799 of FIG. 19, the potential “FG” of the frame rod 720 corresponds to the _{conversion potential VA.} In the example of FIG. 19, the combustor 710 and the first switching element 171 are connected via a detection resistor 120. Specifically, the combustor 710 and the first switching element 171 are connected via a parallel circuit of the detection resistor 120 and the capacitor 155.

In FIG. 19, the character "FX" is located below the detection resistor 120. The word "FX" is also on the upper right side of the first switching element 171. “FX” indicates the potential of the end of the detection resistor 120 opposite to the reference point A. In the example of FIG. 3, the end portion and the first switching element 171 are connected to each other. Specifically, the end portion and the first switching element 171 are connected at equipotential.

In the frame rod circuit 799 of FIG. 19, similarly to the frame rod circuit 700 of FIG. 2, if the combustor 710 is combusted in the first period, the first line 111, the frame rod 720, the combustor 710, and the first switching are performed. Current flows through the element 171 and the second line 112 in this order. However, in the frame rod circuit 799 of FIG. 19, unlike the example of the frame rod circuit 700 of FIG. 2, if the combustor 710 is combusted in the first period, the first line 111, the frame rod 720, and the combustor A current flows through the 710, the reference point A, the detection resistor 120, the first switching element 171 and the second line 112 in this order. The state in which the current is flowing in this way is shown by a alternate long and short dash line in FIG. 20A. The frame rod circuit 799 detects the combustion state of the combustor 710 based on the potential of the reference point A in the first period.

In the frame rod circuit 799 of FIG. 19, similarly to the frame rod circuit 700 of FIG. 2, if the insulation deterioration between the combustor 710 and the frame rod 720 occurs in the second period, the first line 111 and the combustor 710 , The frame rod 720, the second switching element 172, and the second line 112, the current flows in this order. However, in the frame rod circuit 799 of FIG. 19, unlike the example of the frame rod circuit 700 of FIG. 2, if the insulation deterioration between the combustor 710 and the frame rod 720 occurs in the second period, the first line Current flows through 111, the detection resistor 120, the reference point A, the combustor 710, the frame rod 720, the second switching element 172, and the second line 112 in this order. The state in which the current is flowing in this way is shown by a chain double-dashed line in FIG. 20B. The frame rod circuit 799 detects the state of insulation deterioration between the combustor 710 and the frame rod 720 based on the potential of the reference point A in the second period.

According to the frame rod circuit 799 of FIG. 19, positive voltage and negative voltage are alternately applied to the frame rod 720 as in the frame rod circuit 700 of FIG. According to the frame rod circuit 799 of FIG. 19, positive voltage and negative voltage can be alternately applied to the frame rod 720 by a single power supply 770 as in the frame rod circuit 700 of FIG. Then, through the application of such a voltage, the combustion state of the combustor 710 and the insulation deterioration state between the combustor 710 and the frame rod 720 can be detected.

_{The conversion potential VA} in the first period and the second period and the potential applied to the frame rod 720 will be further described with reference to FIGS. 21A and 21B.

As described above, if the combustor 710 is burning in the first period, the current IF _R flows as shown by FIG. 20A. In this case, as schematically shown in FIG. 21A, the current _IFR flows through the second resistor 126, the frame rod 720, the combustor 710, and the detection resistor 120 in this order. In this case, since sufficiently smaller than the resistance value R ₁₂₆ to the resistance value R ₁₂₀ in this example, the conversion potential V _A, formula: can be approximated as _{V A ≒ V DC2 + R 120} × I FR. On the other hand, in the first period, when the current IF _R is not flowing, the conversion potential V _A is V _A = V _{DC 2} .

As described above, if the insulation deterioration between the combustor 710 and the frame rod 720 occurs in the second period, the current IF _R flows as shown by FIG. 20B. In this case, as schematically shown in FIG. 21B, the current _IFR flows through the first resistor 125, the detection resistor 120, the combustor 710, and the frame rod 720 in this order. The conversion potential V _{A in} this case is given by the mathematical formula: V _A = V _DC1- (R ₁₂₅ + R ₁₂₀ ) × _{IF R.} In this example, R ₁₂₅ is for sufficiently smaller than the R _120, are converted potential V _A, formula: can be approximated as _{V A ≒ V DC1 -R 120 ×} I FR. On the other hand, in the second period, when the current IF _R is not flowing, the conversion potential V _A is V _A = V _{DC 1} .

In the first and second periods, the conversion potential _VA described with reference to FIGS. 21A and 21B appears at reference point A. In this way, positive voltage and negative voltage are alternately applied to the frame rod 720. That is, a rectangular pulse voltage is applied to the frame rod 720. Also in this example, the polarity switching DC method is realized.

In the example of FIG. 19, the conversion potential _VA appears at the reference point A as in the example of FIG. The voltage drop in the detection resistor 120 that occurs in response to the _{current IF R} flowing between the combustor 710 and the frame rod 720 is reflected in the _{conversion potential VA. Specifically, the current I FR} flowing between the combustor 710 and the frame rod 720 also flows to the detection resistor 120 and the reference point A, and the voltage drop generated in the detection resistor 120 by _{the current IF R} is reflected in the _{conversion potential VA.} NS. Strictly speaking, both the voltage drop that occurs in the first resistor 125 and the voltage drop that occurs in the second resistor 126 can be reflected.

_{However, in the example of FIG. 19, unlike the example of FIG. 2, the voltage drop based on the frame rod current IFR} in the direction from the reference point A toward the detection resistor 120, which may occur in the first period, is the second DC potential V _DC2. It acts to raise the conversion potential _{VA. On the other hand, the voltage drop based on the frame rod current IF R} in the direction from the detection resistor 120 toward the reference point A, which may occur in the second period, acts to lower the conversion potential V _A with respect to the first DC potential V _{DC 1.}

In the example of FIG. 19, as in the example of FIG. 2, in the third series circuit 183, the second connection point P2, the frame rod 720, the combustor 710, and the first connection point P1 are arranged in this order. However, in the example of FIG. 19, in the third series circuit 183, the second connection point P2, the frame rod 720, the combustor 710, the reference point A, the detection resistor 120, and the first connection point P1 are arranged in this order. In this way, the current flow shown in FIGS. 20A and 20B can be realized.

In the frame rod circuit 799, the capacitor 155 is connected in parallel with the detection resistor 120. Also in the example of FIG. 19, as in the example of FIG. 2, the capacitor 155 is suppressed and fine variation of the flame rod current I _FR, gradual variation in the flame rod current I _FR can be realized.

FIG. 22 schematically shows the relationship between the threshold potential, the signal potential, and the comparative potential related to the comparator in the frame rod circuit of FIG.

Column 1-1 in FIG. 22 shows the relationship between _{the first threshold potential V B} , the conversion potential V _A, and the first comparative potential V _{C in the first period.} Column 1-2 of FIG. 22 shows the relationship between _{the second threshold potential V D} , the conversion potential V _A, and the second comparative potential V _{E in the first period.} In addition, column 1-1 and column 1-2 of FIG. 22 represent a situation in which insulation deterioration between the combustor 710 and the frame rod 720 has not occurred.

During combustion of the combustor 710, the frame rod current _IFR in the first period is larger than that during non-combustion. Therefore, the voltage drop in the detection resistor 120 based on the frame rod current IF _{R is also relatively large.} In the first period, this voltage drop acts to raise the _{conversion potential VA.} Therefore, as shown in columns 1-1 and 1-2 of FIG. 22, the conversion potential _VA is at a relatively high level.

When the combustor 710 is not combusted, the frame rod current _IFR in the first period is substantially zero. Therefore, the voltage drop in the detection resistor 120 based on the frame rod current IF _{R is also substantially zero.} Therefore, as shown in columns 1-1 and 1-2 of FIG. 22, the conversion potential _VA is at a relatively low level.

As shown in column 1-2 of FIG. 22, the second threshold potential V _D is larger than the above-mentioned relatively low-level conversion potential _VA and the above-mentioned relatively high-level conversion potential _VA. Smaller than Therefore, when the combustor 710 is switched from the burning state to the non-burning state, _{the level of the conversion potential V A} drops across the second threshold potential V _D. Therefore, as shown in column 1-2 in FIG. 22, this switching, the second comparison potential V _E falls from the high level to the low level.

On the other hand, as shown in column 1-1 of FIG. 22, the first threshold potential V _B is not only larger than the above-mentioned relatively low-level conversion potential _VA , but also the above-mentioned relatively high-level conversion. Greater than the potential _VA. Therefore, even when switched to a state that is not burned in the state where the combustor 710 is burning, the level of conversion potential V _A is, does not change across a first threshold potential V _B. Therefore, as shown in column 11 of FIG. 22, even this switching occurs, not the first comparison potential V _C changes.

Column 2-1 of FIG. 22 shows the relationship between _{the first threshold potential V B} , the conversion potential V _A, and the first comparative potential V _{C in the second period.} Column 2-2 of FIG. 22 shows the relationship between _{the second threshold potential V D} , the conversion potential V _A, and the second comparative potential V _{E in the second period.} In addition, column 2-1 and column 2-2 of FIG. 22 represent both the situation where the combustor 710 is burning and the situation where it is not burning.

When the insulation deterioration between the combustor 710 and the frame rod 720 occurs, the frame rod current _IFR in the second period is larger than when the insulation deterioration does not occur. Therefore, the voltage drop in the detection resistor 120 based on the frame rod current IF _{R is also relatively large.} In the second period, this voltage drop acts to lower the _{conversion potential VA.} Therefore, as shown in columns 2-1 and 2-2 of FIG. 22, the conversion potential _VA is at a relatively low level.

_{The frame rod current IF R} in the second period is substantially zero when there is no insulation degradation between the combustor 710 and the frame rod 720. Therefore, the voltage drop in the detection resistor 120 based on the frame rod current IF _{R is also substantially zero.} Therefore, as shown in columns 2-1 and 2-2 of FIG. 22, the conversion potential _VA is at a relatively high level.

As shown in column 2-1 of FIG. 22, the first threshold potential V _B is larger than the above-mentioned relatively low-level conversion potential _VA and the above-mentioned relatively high-level conversion potential _VA. Smaller than Therefore, when a state in which insulation deterioration does not occur changed to the condition insulation deterioration has occurred, the level of conversion potential V _A is lowered across the first threshold potential V _B. Therefore, as shown in column 2-1 in FIG. 22, this switching, the first comparison potential V _C rises from the low level to the high level.

On the other hand, as shown in column 2-2 of FIG. 22, the second threshold potential V _D is not only larger than the above-mentioned relatively high-level conversion potential _VA , but also the above-mentioned relatively low-level conversion. It is smaller than the _{potential VA.} Therefore, even if the state in which the insulation deterioration has not occurred is switched to the state in which the insulation deterioration has occurred, the level of the _{conversion potential V A} does not change across _{the second threshold potential V D.} Therefore, as shown in column 22 of FIG. 22, even this switching occurs, no second comparison potential V _E changes.

In the example of FIG. 19, unlike the example of FIG. 2, the frame rods circuit 799, based on the first comparison potential V _C, to detect insulation degradation state between the combustor 710 and the frame rod 720. Flame rod circuit 799, based on the second comparison potential V _E, for detecting the combustion state of the combustor 710. That is, in the example of FIG. 2, the first comparator 351 is used for detecting the combustion state, and the second comparator 352 is used for detecting the insulation deterioration state. On the other hand, in the example of FIG. 19, the second comparator 352 is used for detecting the combustion state, and the first comparator 351 is used for detecting the insulation deterioration state.

In the example of FIG. 19, as in the example of FIG. 2, the first signal output unit C connected to the first output circuit of the open drain type and the second signal output unit connected to the second output circuit of the open drain type are also used. A wired or is configured by being connected to E. As a result, the combined output of the first comparison potential V _C and a second comparison potential V _E in the example of FIG. 19 is the same as the synthesized output in the example of FIG.

The VF conversion circuit 299 of FIG. 19 is obtained by omitting the inverting amplifier circuit 270 from the VF conversion circuit 290 of FIG. FIG. 23 shows an enlarged view of the VF conversion circuit 299.

The DC potential to be inputted to the VF converter 299 in FIG. 23, may be referred to as the DC potential V _in. In this example, the DC potential V _in is the potential input to the integration circuit 210.

As described above, in the example of the VF converter 290 in FIG. 16, in the first period, the inverting amplifier circuit 270, a potential signal to decrease the flame rod current I _FR with respect to the first DC potential V _DC1 is increased, the 2 DC potential V _DC2 as a reference into a potential signal rises flame rod current I _FR increases. Then, the potential signal obtained by the conversion is input to the integrating circuit 210.

In contrast, as described above, in the example of FIG. 19, in the first period, the conversion potential V _A, a potential signal rises second DC voltage V _DC2 with reference flame rod current I _FR increases. In the example of FIG. 19, the potential signal is input to the integrating circuit 210 of the VF conversion circuit 299. Therefore, in the example of FIG. 19, the VF conversion circuit 299 can generate the same output as the VF conversion circuit 290 of FIG. 16 without the inverting amplifier circuit 270.

The frame rod circuits of FIGS. 2 and 19 can be described as follows. That is, the frame rod circuit includes a combustor 710, a frame rod 720, a first switching element 171 and a second switching element 172. The first period and the second period appear alternately. In the first period, when the first switching element 171 is turned on, a positive voltage is applied to the frame rod 720 with reference to the combustor 710. In the second period, when the second switching element 172 is turned on, a negative voltage is applied to the frame rod 720 with reference to the combustor 710. The combustion state of the combustor 710 is detected based on the _{current IFR} flowing between the combustor 710 and the frame rod 720 while flowing through the first switching element 171 in the first period. In the second period, the insulation deterioration state between the combustor 710 and the frame rod 720 is detected based on the _{current IFR} flowing between the combustor 710 and the frame rod 720 as well as flowing through the second switching element 172.

According to such a frame rod circuit, a single power source can apply a positive voltage and a negative voltage to the frame rod 720 with reference to the combustor 710. Specifically, two switching elements 171 and 172 contribute to make this possible.

Further, in the frame rod circuit of FIGS. 2 and 19, a conversion potential _{VA corresponding to the current IF R} flowing between the combustor 710 and the frame rod 720 appears. In one of the first and second periods, the conversion potential _{VA when the current IF R} flowing between the combustor 710 and the frame rod 720 is zero is higher than in the other of the first and second periods. On the one hand of the first period and the second period _{, the conversion potential VA} decreases as the absolute value of the _{current IF R flowing between the combustor 710 and the frame rod 720 increases. In the other of the first and second periods, the conversion potential VA} increases as the absolute value of the _{current IF R} flowing between the combustor 710 and the frame rod 720 increases. In the examples of FIGS. 2 and 19, the frame rod circuit detects the combustion state based on the _{conversion potential VA in the first period.} The frame rod circuit detects the insulation deterioration state based on the _{conversion potential VA in the second period.} In the examples of FIGS. 2 and 19, the conversion potential _VA is the potential of the reference point A.

Specifically, in the frame rod circuit of FIG. 2, the above "one of the first period and the second period" is the first period, and "the other of the first period and the second period" is the second period. .. On the other hand, in the frame rod circuit of FIG. 19, the above "one of the first period and the second period" is the second period, and "the other of the first period and the second period" is the first period.

Further, the frame rod circuit of FIGS. 2 and 19 includes a detection resistor 120. The voltage drop in the detection resistor 120 that occurs in response to the _{current IF R} flowing between the combustor 710 and the frame rod 720 is reflected in the _{conversion potential VA.} In the examples of FIGS. 2 and 19, the frame rod circuit detects the combustion state based on the _{conversion potential VA in the first period.} The frame rod circuit detects the insulation deterioration state based on the _{conversion potential VA in the second period.} In the examples of FIGS. 2 and 19, the conversion potential _VA is the potential of the reference point A.

Specifically, in the examples of FIGS. 2 and 19, the current _IFR flowing between the combustor 710 and the frame rod 720 also flows to the detection resistor 120. _{Therefore, the above-mentioned "voltage drop in the detection resistor 120 caused by the current IF R} flowing between the combustor 710 and the frame rod 720" is a voltage drop caused in the detection resistor 120 due to the current IF _R flowing in the detection resistor 120. Is.

[Configuration example not the polarity switching DC method: Configuration example shown in FIG. 24]
As a method of the frame rod circuit, there is also a method other than the polarity switching DC method. It is also possible to use the VF conversion circuit 200 in a frame rod circuit that operates by a method other than the polarity switching DC method. This point is the same for the VF conversion circuit described with reference to FIGS. 16 to 17C and 23. More generally, as long as there is no contradiction, the techniques of the non-polarity switching DC scheme can be combined with the various techniques according to the present disclosure.

FIG. 24 shows a configuration in which the VF conversion circuit 200 is incorporated in the AC type frame rod circuit.

The frame rod circuit 800 of FIG. 24 includes a combustor 710, a frame rod 720, a signal generation circuit 880, a detector 502, an insulation circuit 601 and a resistor R9. The signal generation circuit 880 is connected to a detector 502, an insulation circuit 601, a combustor 710 and a frame rod 720. Voltages can be supplied to the frame rod circuit 800 from the power supply 801 and the power supply 802 and the power supply 803.

The power supply 801 is an AC power supply. An AC voltage can be applied between the combustor 710 and the frame rod 720 by the AC power supply 801. The frequency of the AC output by the AC power supply 801 is, for example, 50 Hz or 60 Hz. The power supply 802 and the power supply 803 are DC power supplies.

The frame rod circuit 800 includes a first region 891 and a second region 892 having different reference potentials. The first region 891 and the second region 892 are separated by an insulating circuit 601.

In the example of FIG. 24, the detector 502 belongs to the first region 891. The combustor 710, the frame rod 720, and the signal generation circuit 880 belong to the second region 892.

The signal generation circuit 880 generates the detection signal S _D. Specifically, the detection signal S _D are those corresponding to the current I _FR flowing between the combustor 710 and the frame rod 720.

The insulation circuit 601 performs isolated transmission _{of the detection signal S D} from the signal generation circuit 880 to the detector 502.

The components of the signal generation circuit 880 will be described.

The signal generation circuit 880 includes an IV conversion circuit 860, a level setting circuit 850, and a VF conversion circuit 200.

The IV conversion circuit 860 generates a conversion potential _{VA corresponding to the current IF R} flowing between the combustor 710 and the frame rod 720. Specifically, the IV conversion circuit 860 uses the voltages supplied from the power supply 801 and the power supply 802 to generate the _{conversion potential VA.}

Level setting circuit 850 sets the size of A _S of the detection signal S _D. The magnitude _AS is a magnitude corresponding to the conversion potential V _A.

The VF conversion circuit 200 sets the frequency F _{S of the detection signal S D} based on the conversion potential V _A. Specifically, VF converter 200, when the rectangular pulse signal is generated as a detection signal S _D, the frequency F _S of the detection signal S _D, is set based on the conversion potential V _A.

Hereinafter, the components of the signal generation circuit 880 will be described in more detail.

[IV conversion circuit 860]
The frame rod circuit 800 includes a filter unit 820, a resistor R1, a resistor R2, a resistor R5, a detection resistor R6, and a capacitor C1. The main body including these is specifically a signal generation circuit 880, and more specifically, an IV conversion circuit 860.

The AC power supply 801 is connected to the input unit 820i of the filter unit 820 via the resistor R1 and the capacitor C1. Further, the AC power supply 801 is connected to the frame rod 720 via a resistor R1, a capacitor C1 and a resistor R2.

The resistor R1 and the resistor R2 are current limiting resistors for circuit protection. The capacitor C1 is provided to cut the direct current from the AC power supply 801.

The filter unit 820 has a resistor R3, a resistor R4, a capacitor C2, a capacitor C3, an input section 820i, and an output section 820о. The resistor R3 and the capacitor C2 form a first RC filter. The resistor R4 and the capacitor C3 form a second RC filter. In this way, in the filter unit 820, a two-stage RC filter is configured by the first RC filter and the second RC filter. However, the filter unit 820 may be a one-stage RC filter.

The input unit 820i of the filter unit 820 is connected to the frame rod 720 via the resistor R2. The output unit 820о of the filter unit 820 is connected to the reference point A via the resistor R5. Filter unit 820 according to the current I _FR flowing between the combustor 710 and the frame rods 720, the reference point A give conversion potential V _A.

The DC power supply 802, the detection resistor R6, and the reference point A are connected in this order. When the combustor 710 is not burned, it converted potential V _A which is the potential of the reference point A converge to a pull-up potential. The pull-up potential is a potential determined by the DC power supply 802. The conversion potential _VA becomes lower than the pull-up potential due to the power supply from the AC power supply 801 to the signal generation circuit 880 when the combustor 710 is burning.

[Level setting circuit 850]
The frame rod circuit 800 includes a resistor R7, a resistor R8, and a comparator 810. The main body including these is specifically a signal generation circuit 880, and more specifically, a level setting circuit 850.

The resistor R7 and the resistor R8 form a voltage dividing circuit. The DC power supply 802, the resistor R7, the point Z, the resistor R8, and the reference potential of the second region 892 are connected in this order. At point Z, a fixed potential appears in which the potential difference between the DC power supply 802 and the reference potential is divided by the resistors R7 and R8. Hereinafter, this fixed potential may be referred to as a threshold potential.

The comparator 810 has a threshold input unit 810a, a signal input unit 810b, and a signal output unit 810c. In the example of FIG. 24, the threshold input unit 810a is a non-inverting input terminal. The signal input unit 810b is an inverting input terminal. However, a configuration in which the signal input unit 810b is a non-inverting input terminal and the threshold value input unit 810a is an inverting input terminal can also be adopted.

The signal input unit 810b is connected to the output unit 820o of the filter unit 820 via the reference point A and the resistor R5 in this order. In the example of FIG. 24, the signal input section 810b, converts the potential V _A which is the potential of the reference point A is inputted. The threshold input unit 810a is connected to the point Z of the voltage dividing circuit by the resistor R7 and the resistor R8. The signal output unit 810c is connected to the point G.

[VF conversion circuit 200]
The VF conversion circuit 200 is the same as that of FIG. For example, the VF conversion circuit 200 may have the configuration described with reference to FIG. 9 and the like.

_{A potential corresponding to the conversion potential VA} , which is the potential of the reference point A, is input to the VF conversion circuit 200. In the example of FIG. 24, "potential corresponding to the converted voltage V _A" is the same as the conversion potential V _A. However, "potential in accordance with the conversion potential V _A" may be different from the conversion potential V _A. Specifically, the conversion potential _VA is input to the integrating circuit 210 of the VF conversion circuit 200.

The VF conversion circuit 200 includes a diode 269. The anode of diode 269 is connected to point G. A pulse is transmitted from the VF conversion circuit 200 to the point G via the diode 269.

[Insulation circuit 601 and detector 502]
The insulation circuit 601 is similar to that of FIG. In the example of FIG. 24, the insulation circuit 601 is a photocoupler. The photocoupler 601 includes a phototransistor 601t and a light emitting diode 601d.

The DC power supply 803, the resistor R9, the light emitting diode 601d, the point G, and the anode of the diode 269 are connected in this order.

The detector 502 is similar to that of FIG. For example, the detector 502 may be included in the control device 500. The detector 502 can be a digital device.

The detector 502, the phototransistor 601t, and the reference potential of the first region 891 are connected in this order.

[Operation of frame rod circuit 800]
Hereinafter, the operation of the frame rod circuit 800 of FIG. 24 will be described with reference to FIG. 25.

In FIG. 25, the dotted line shows _{the voltage V FR} of the frame rod 720 with respect to the combustor 710. The solid line shows the _{current IF R} flowing between the combustor 710 and the frame rod 720.

FIG. 25 shows a situation in which the combustor 710 is burning and the insulation deterioration between the combustor 710 and the frame rod 720 has not substantially occurred. In this situation, the absolute value of the current I _{FR is large during the period when the voltage V FR} of the frame rod 720 with respect to the combustor 710 is positive. On the other hand, in the period when the voltage of the frame rod 720 with reference to the combustor 710 is negative, the current IF _R is small, specifically, substantially zero.

The filter unit 820, the current I _FR and the voltage V _FR of the period in which the voltage V _FR is positive average current I _FR of negative and it period is reflected in the conversion potential V _A of the reference point A. In the situation of FIG. 25, _{the average of the currents IF R} for both periods is positive (that is, from the frame rod 720 to the combustor 710), and the conversion potential _VA that reflects this positive average current is referenced. Appears at point A. The positive mean current acts to convert potential V _A of the reference point A to decrease from the pull-up potential. _{The conversion potential VA} that appears in this way is substantially direct current.

If the combustor 710 is not burning and there is substantially no insulation degradation between the combustor 710 and the frame rod 720, the voltage V _FR of the frame rod 720 relative to the combustor 710 will be _{The current IF R} is virtually zero for both positive and negative periods. Therefore, the above average current is substantially zero, and the conversion potential VA at the reference point _A is substantially a pull-up potential.

If there is insulation deterioration between the combustor 710 and the frame rod 720, _{in both the period when the voltage V FR} of the frame rod 720 with respect to the combustor 710 is positive and the period when it is negative. The absolute value of the current IF _{R is large.} Therefore, the above average current is substantially zero, and the conversion potential VA at the reference point _A is substantially a pull-up potential.

As described above, the filter unit 820 _{converts the frame rod current IF R} into the conversion potential _VA . For details of the behavior of the current and voltage appearing in the filter unit 820 during this conversion, refer to, for example, Patent Document 2.

The frame rod circuit 800 of FIG. 24 includes a detection resistor R6 like the frame rod circuit of FIGS. 2 and 19. Voltage drop across the detection resistor R6 generated according to the current I _FR flowing between the combustor 710 and the frame rod 720 is reflected to the conversion voltage V _A. In the example of FIG. 24, the conversion potential _VA is the potential of the reference point A.

Specifically, a current corresponding to the current I _FR flows in the detection resistor R6. The above "the voltage drop across the detection resistor R6 generated according to the current I _FR flowing between the combustor 710 and the frame rod 720" occurs in the detection resistor 120 by a current corresponding to the current I _FR in the detection resistor 120 flows It is a voltage drop.

In the comparator 810, a signal potential corresponding _{to the conversion potential VA is input to the signal input unit 810b.} Specifically, in the example of FIG. 24, this signal potential is the conversion potential _VA . On the other hand, as described above, at the point Z, a threshold potential obtained by dividing the potential difference between the DC power supply 802 and the reference potential by the resistors R7 and R8 appears. The threshold potential is input to the threshold input unit 810a.

The comparator 810 can output the comparative potential by comparing the threshold potential and the signal potential. Specifically, the comparator 810 can output a comparative potential from the signal output unit 810c.

In the example of FIG. 24, the comparative potential takes a high level or a low level value. Specifically, when the signal potential is larger than the threshold potential, the comparative potential takes a low level value. On the other hand, when the signal potential is smaller than the threshold potential, the comparative potential takes a high level value.

In the example of FIG. 24, the low level of the comparative potential corresponds to the reference potential of the second region 892.

In the example of FIG. 24, when the combustor 710 is burning and there is substantially no insulation deterioration between the combustor 710 and the frame rod 720, the conversion potential _VA is small and the comparative potential is high. Can be a level. On the other hand, when the combustor 710 is not burning and the insulation deterioration between the combustor 710 and the frame rod 720 is substantially not caused, the conversion potential _VA becomes large and the comparative potential can be at a low level. .. Even when insulation deterioration occurs, the conversion potential _VA becomes large and the comparative potential can be at a low level.

In the example of FIG. 24, the signal output unit 810c is connected to the point G. The above comparative potential propagates to the point G. In this way, the detection signal S _D having a magnitude A _S which is set by the level setting circuit 850 is generated.

_A signal potential corresponding to the conversion potential VA is input to the integration circuit 210 of the VF conversion circuit 200. Specifically, in the example of FIG. 24, "potential corresponding to the converted voltage V _A" is converted potential V _A. However, "potential in accordance with the conversion potential V _A" may be different from the conversion potential V _A.

The operation of the VF conversion circuit 200 is as described with reference to FIGS. 9 to 15.

When the comparative potential output by the comparator 810 is a high level potential, a pulse is transmitted from the VF conversion circuit 200 to the point G via the diode 269. On the other hand, when the comparative potential is a low level potential, the pulse from the VF conversion circuit 200 is not transmitted to the point G due to the presence of the diode 269.

In the example of FIG. 24, when the combustor 710 is burning and there is substantially no insulation deterioration between the combustor 710 and the frame rod 720, the comparative potential becomes a high level potential, and the VF conversion circuit 200 A pulse can be transmitted to the point G via the diode 269. On the other hand, when the combustor 710 is not burning and the insulation deterioration between the combustor 710 and the frame rod 720 is substantially not caused, the comparative potential becomes a low level potential, and the presence of the diode 269 causes the VF. The voltage of the pulse from the conversion circuit 200 to the point G can be blocked. Even when insulation deterioration occurs, the comparative potential becomes a low-level potential, and the presence of the diode 269 can block the voltage of the pulse from the VF conversion circuit 200 to the point G.

By pulse is transmitted to the point G from the VF converter 200 in the manner described above, the detection signal S _D having a frequency F _S which is set by the VF converter 200 is generated.

The detection signal S _D is isolated and transmitted to the detector 502 via the insulation circuit 601.

As described above, in the AC type frame rod circuit 800 of FIG. 24, the frame reflecting the combustion state of the combustor 710 during the period _{when the voltage V FR of the frame rod 720 with respect to the combustor 710 is positive.} Rod current IF _R flows. _{On the other hand, during the period when the voltage V FR} of the frame rod 720 with respect to the combustor 710 _{is negative, the frame rod current I FR} reflecting the insulation deterioration state between the combustor 710 and the frame rod 720 flows. These currents I _FR and converting potential V _A where these conditions are reflected by the detection resistor R6, appearing at the reference point A. Then, the detection signal S _D corresponding to the conversion potential _VA is generated.

The signal generation circuit 880 of FIG. 24 generates the detection signal S _{D in the same} manner as the signal generation circuits of FIGS. 2 and 19. The signal generation circuit 880 includes an IV conversion circuit 860 and a VF conversion circuit 200. The IV conversion circuit 860 generates a conversion potential _{VA corresponding to the current IF R} flowing between the combustor 710 and the frame rod 720. The VF conversion circuit 200 sets the frequency F _{S of the detection signal S D} based on the conversion potential V _A.

In the example of FIG. 24, as in the examples of FIGS. 2 and 19, the detection signal _SD is a DC signal or a square pulse signal.

In the example of FIG. 24, as in the examples of FIGS. 2 and 19, the frame rod circuit 800 includes a first region 891 and a second region 892 having different reference potentials, and a photocoupler 601. The first region 891 has a detector 502. The second region 892 includes a combustor 710, a frame rod 720, and a signal generation circuit 880. The detection signal S _D is isolated and transmitted from the signal generation circuit 880 to the detector 502 via the photocoupler 601.

In the example of FIG. 24, as in the example of FIGS. 2 and 19, a comparator 810, a threshold potential, by comparing a signal potential corresponding to the converted voltage V _A, the detection signal S _D of size A _S To set.

In the AC type frame rod circuit 800 of FIG. 24, the VF conversion circuit 200 may be changed to the VF conversion circuit 290 of FIG.

[Various other changes]
Various changes can be applied to the frame rod circuit according to the above description. For example, the level setting circuit can be omitted.

In the frame rod circuit according to the first modification, the level setting circuit is omitted. In this case, _{a signal in which the conversion potential VA} is pulsed by the VF conversion circuit can be input to the detector 502 as a detection signal. The detector 502 can detect the combustion state of the combustor 710 and the insulation deterioration state between the combustor 710 and the frame rod 720 based on the detection signal.

Further, the frame rod circuit may detect the combustion state of the combustor 710, but may not detect the insulation deterioration state between the combustor 710 and the frame rod 720. The frame rod circuit does not have to have an element for detecting the state of insulation deterioration.

[Application to hydrogen generators and fuel cell systems]
A hydrogen generating apparatus including the frame rod circuit according to the above description can be configured. In addition, a fuel cell system including a frame rod circuit can be configured.

In one embodiment, the hydrogen generator comprises a reformer and a frame rod circuit. The reformer reforms the raw material gas containing a hydrocarbon component to generate a reformed gas containing hydrogen. The combustor 710 of the frame rod circuit heats the reformer by burning a flammable raw material containing a hydrocarbon component.

In one embodiment, the fuel cell system comprises a reformer, a fuel cell, and a frame rod circuit. The reformer reforms the raw material gas containing a hydrocarbon component to generate a reformed gas containing hydrogen. The fuel cell uses reformed gas to generate electricity. The combustor 710 of the frame rod circuit heats the reformer by burning a flammable raw material containing a hydrocarbon component.

[effect]
As described above, the frame rod circuit according to the first aspect of the present disclosure is
Combustor and
With the frame rod
An IV conversion circuit that generates a detection signal and generates a conversion potential according to the current flowing between the combustor and the frame rod, and a frequency of the detection signal is set based on the conversion potential. A signal generation circuit having a VF conversion circuit and a signal generation circuit having the same VF conversion circuit is provided.

The technique according to the first aspect is suitable for detecting the degree of combustion state of the combustor.

In the second aspect of the present disclosure, for example, in the frame rod circuit according to the first aspect,
The detection signal may be a DC signal or a rectangular pulse signal.

DC signals or square pulse signals are easy to detect by digital devices.

In the third aspect of the present disclosure, for example, the frame rod circuit according to the second aspect may include a first region and a second region having different reference potentials, and a photocoupler.
The first region may have a detector.
The second region may include the combustor, the frame rod, and the signal generation circuit.
The detection signal may be isolated and transmitted from the signal generation circuit to the detector via the photocoupler.

According to the third aspect, an inexpensive insulated transmission means can be constructed by making good use of the property of the current flowing through the frame rod.

In the fourth aspect of the present disclosure, for example, in the frame rod circuit according to any one of the first to third aspects.
The VF conversion circuit
Integrator circuit and
Comparison circuit and
May include transistors,
The integrator circuit
With the first operational amplifier
A negative feedback circuit connected to the first operational amplifier, which may include a negative feedback circuit including a feedback capacitor.
The comparison circuit
With the second operational amplifier
It may include a positive feedback circuit connected to the second operational amplifier.
The VF conversion circuit is used when a DC potential is input to the VF conversion circuit.
By switching the on / off of the transistor according to the output potential of the comparison circuit, the charging period in which the current flows in the feedback direction of the feedback capacitor and the discharge period in which the current flows in the direction opposite to the feedback direction of the feedback capacitor are set. Appear alternately,
A triangular wave having a frequency corresponding to the DC potential is output from the integrating circuit.
The comparison circuit may be configured to output a rectangular pulse wave having the same frequency as the triangular wave.

According to the VF conversion circuit of the fourth aspect, it is possible to generate a rectangular pulse wave having a frequency corresponding to the conversion potential by utilizing the charging / discharging of the feedback capacitor.

In the fifth aspect of the present disclosure, for example, in the frame rod circuit according to the fourth aspect,
The negative feedback circuit may include a feedback resistor connected in series with the feedback capacitor.

The feedback resistor of the fifth aspect can enhance the linearity of the change in the frequency of the square pulse wave with respect to the change in the conversion potential.

In the sixth aspect of the present disclosure, for example, in the frame rod circuit according to the fourth or fifth aspect.
If the combustor is burning, a first period in which a current flows between the combustor and the frame rod may appear.
In the first period, the smaller the absolute value of the current flowing between the combustor and the frame rod, the smaller the frequencies of the triangular wave and the square pulse wave, whereby the detection signal is a square pulse signal. In some cases, the frequency of the detection signal may be reduced.

The sixth aspect is suitable for accurately detecting the combustion state when the combustion intensity of the frame rod is low.

In the seventh aspect of the present disclosure, for example, in the frame rod circuit according to any one of the first to sixth aspects.
If the combustor is burning, a first period in which a current flows between the combustor and the frame rod may appear.
The frequency of the detection signal in the first period is relative to the first state in which the combustor is not burning, the second state in which the combustion intensity of the combustor is relatively weak, and the combustion intensity of the combustor. It may be different from the third state, which is strong against.

The technique according to the seventh aspect is suitable for detecting the degree of combustion state of the combustor.

In the eighth aspect of the present disclosure, for example, in the frame rod circuit according to the seventh aspect,
The detection signal in the first period may be a DC signal in the first state, or may be a rectangular pulse signal in the second state and the third state.

According to the eighth aspect, it is easy to secure the detection accuracy of the first state in which the combustor is not burning.

In the ninth aspect of the present disclosure, for example, in the frame rod circuit according to the seventh or eighth aspect.
The magnitude of the detection signal in the first period may be different from the second state and the third state in the first state.

According to the ninth aspect, even if the function of generating the pulsed detection signal is lost due to some kind of failure or the like, the detector determines the first state depending on the magnitude of the detection signal in the first period. It can be distinguished from the second state and the third state.

In the tenth aspect of the present disclosure, for example, in the frame rod circuit according to any one of the first to ninth aspects,
If the insulation deteriorates between the combustor and the frame rod, a second period in which a current flows between the combustor and the frame rod may appear.
The frequency of the detection signal in the second period differs between the fourth state in which the insulation resistance between the combustor and the frame rod is relatively high and the fifth state in which the insulation resistance is relatively low. You may.

The technique according to the tenth aspect is suitable for detecting the state of insulation deterioration between the combustor and the frame rod.

In the eleventh aspect of the present disclosure, for example, in the frame rod circuit according to the tenth aspect,
The detection signal in the second period is
It may be a DC signal in the fourth state, or may be a rectangular pulse signal in the fifth state.

According to the eleventh aspect, it is easy to secure the detection accuracy of the fifth state in which the insulation resistance is relatively low.

In the twelfth aspect of the present disclosure, for example, in the frame rod circuit according to the tenth aspect or the eleventh aspect.
The magnitude of the detection signal in the second period may be different in the fifth state from the fourth state.

According to the twelfth aspect, even if the function of generating the pulsed detection signal is lost due to some kind of failure or the like, the detector determines the fifth state depending on the magnitude of the detection signal in the second period. It can be distinguished from the fourth state.

In the thirteenth aspect of the present disclosure, for example, in the frame rod circuit according to any one of the first to the twelfth aspects.
If the combustor is burning, a first period in which a current flows between the combustor and the frame rod, and if insulation deterioration between the combustor and the frame rod occurs, the combustor and the frame The second period in which the current flows between the rods may appear alternately.

The thirteenth aspect is a specific example of how the first period and the second period appear.

In the fourteenth aspect of the present disclosure, for example, in the frame rod circuit according to any one of the first to thirteenth aspects,
If the combustor is burning, a first period in which a current flows between the combustor and the frame rod, and if insulation deterioration between the combustor and the frame rod occurs, the combustor and the frame A second period, in which current flows between the rods, may appear,
The length of the first period may be longer than the length of the second period.

The fourteenth aspect is rational from the viewpoint of efficiently detecting the combustion failure of the combustor and the deterioration of the insulation between the combustor and the frame rod.

In the fifteenth aspect of the present disclosure, for example, in the frame rod circuit according to any one of the first to the fourteenth aspects.
The IV conversion circuit may include a detection resistor.
The voltage drop in the detection resistor generated in response to the current flowing between the combustor and the frame rod may be reflected in the conversion potential.

According to the detection resistor of the fifteenth aspect, the current flowing between the combustor and the frame rod can be converted into a conversion potential.

In the 16th aspect of the present disclosure, for example, in the frame rod circuit according to any one of the 1st to 15th aspects,
The signal generation circuit may include a comparator.
The comparator may set the magnitude of the detection signal by comparing the threshold potential with the signal potential corresponding to the conversion potential.

According to the comparator of the 16th aspect, the magnitude of the detection signal can be set.

The hydrogen generating apparatus according to the 17th aspect of the present disclosure is
A reformer that reforms the raw material gas containing hydrocarbon components to generate a reformed gas containing hydrogen,
A frame rod circuit according to any one of the first to sixteenth aspects, wherein the combustor burns a flammable raw material containing a hydrocarbon component to heat the reformer. , Equipped with.

According to the seventeenth aspect, it is possible to realize a hydrogen generating device that achieves the effect of the first aspect.

The fuel cell system according to the eighteenth aspect of the present disclosure is
A reformer that reforms the raw material gas containing hydrocarbon components to generate a reformed gas containing hydrogen,
A fuel cell that generates electricity using the reformed gas and
A frame rod circuit according to any one of the first to sixteenth aspects, wherein the combustor burns a flammable raw material containing a hydrocarbon component to heat the reformer. , Equipped with.

According to the eighteenth aspect, it is possible to realize a fuel cell system that achieves the effect of the first aspect.

The detection method according to the 19th aspect of the present disclosure is
It is a detection method that detects the state of the combustor using a frame rod.
To generate a conversion potential according to the current flowing between the combustor and the frame rod,
It includes setting the frequency of the detection signal based on the conversion potential.

According to the nineteenth aspect, the same effect as that of the first aspect can be obtained.

The VF conversion circuit according to the 20th aspect of the present disclosure is
Integrator circuit and
Comparison circuit and
Including transistors
The integrator circuit
With the first operational amplifier
A negative feedback circuit connected to the first operational amplifier, including a negative feedback circuit including a feedback capacitor and a feedback resistor connected in series with each other.
The comparison circuit
With the second operational amplifier
Includes a positive feedback circuit connected to the second operational amplifier.
The VF conversion circuit is used when a DC potential is input to the VF conversion circuit.
By switching the on / off of the transistor according to the output potential of the comparison circuit, the charging period in which the current flows in the feedback direction of the feedback capacitor and the discharge period in which the current flows in the direction opposite to the feedback direction of the feedback capacitor are set. Appear alternately,
A triangular wave having a frequency corresponding to the DC potential is output from the integrating circuit.
The comparison circuit is configured to output a rectangular pulse wave having the same frequency as the triangular wave.

According to the VF conversion circuit according to the twentieth aspect, the potential information can be converted into the frequency information. Such a VF conversion circuit is useful for detecting the degree of combustion state of the combustor.

The frame rod circuit according to the 21st aspect of the present disclosure is
Combustor and
With the frame rod
An IV conversion circuit that generates a conversion potential according to the current flowing between the combustor and the frame rod.
A VF conversion circuit according to a twentieth aspect, which is a frequency of the detection signal and sets a frequency corresponding to the conversion potential.
A detector for detecting the combustion state of the combustor based on the output of the VF conversion circuit is provided.

The techniques of the 20th and 21st aspects and the techniques of the 1st to 19th aspects can be appropriately combined. It is also possible to change the twentieth aspect and the twenty-first aspect to the aspect of the method.

The frame rod circuit according to the present disclosure can be used for a hydrogen generator, a fuel cell system, and the like.

100,860 IV conversion circuit 111,112 Line 120, 125,126,127,128,129,130,221,222,223,231,253,261,262,263,271,272,273,277,311, 361, 362, 363, 364, 731, 733, 735, R1, R2, R3, R4, R5, R6, R7, R8, R9 Resistance 154,155,235,330,371,372, C1, C2, C3 Capacitor 165 Voltage regulators 171, 172, 173 Switching elements 171a, 171b, 171c, 172a, 172b, 172c, 173a, 173b, 173c, 211a, 211b, 211c, 241a, 241b, 241c, 251,252, 260a, 260b, 260c, 265a, 265b, 265c, 276a, 276b, 276c, terminals 181,182,183 Series circuit 269 Diode 200, 290 VF conversion circuit 210 Integrator circuit 211,241,276,301 Operational amplifier 239,259,279 Feedback circuit 240 Comparison circuit 257 , 275,750,770,801,802,803 Power supply 260,265 Transistor 270 Inversion amplifier circuit 300 Buffer circuit 350,850 Level setting circuit 351,352,810 Comparer 351a, 351b, 352a, 352b Input unit C, E Output unit 381,382 Extraction circuit 400,880 Signal generation circuit 481,482 Connection circuit 500 Control device 501 Switcher 502 Detector 600 Insulation device 601,603 Insulation circuit 601d, 603d Light emitting diode 601t, 603t Phototransistor 700,800 Frame rod circuit 710 , 901b Combustor 720 Frame rod 791,792,891,892 Area 820 Filter part 820i Input part 820o Output part A, B, D, G, K, S, T, U, Y, Z, P1, P2 points DL1 One point Chain line DL2 Two-point chain line SW Rectangular pulse wave TW Triangular wave PAC Package RD Feedback direction

Claims (19)

Combustor and
With the frame rod
An IV conversion circuit that generates a detection signal and generates a conversion potential according to the current flowing between the combustor and the frame rod, and a frequency of the detection signal is set based on the conversion potential. A signal generation circuit including a VF conversion circuit for
Frame rod circuit. The detection signal is a DC signal or a rectangular pulse signal.
The frame rod circuit according to claim 1. The frame rod circuit includes a first region and a second region having different reference potentials, and a photocoupler.
The first region has a detector and
The second region includes the combustor, the frame rod, and the signal generation circuit.
The detection signal is isolated and transmitted from the signal generation circuit to the detector via the photocoupler.
The frame rod circuit according to claim 2. The VF conversion circuit
Integrator circuit and
Comparison circuit and
Including transistors
The integrator circuit
With the first operational amplifier
A negative feedback circuit connected to the first operational amplifier, including a negative feedback circuit including a feedback capacitor.
The comparison circuit
With the second operational amplifier
Includes a positive feedback circuit connected to the second operational amplifier.
The VF conversion circuit is used when a DC potential is input to the VF conversion circuit.
By switching the on / off of the transistor according to the output potential of the comparison circuit, the charging period in which the current flows in the feedback direction of the feedback capacitor and the discharge period in which the current flows in the direction opposite to the feedback direction of the feedback capacitor are set. Appear alternately,
A triangular wave having a frequency corresponding to the DC potential is output from the integrating circuit.
A rectangular pulse wave having the same frequency as the triangular wave is output from the comparison circuit.
The frame rod circuit according to any one of claims 1 to 3. The negative feedback circuit includes a feedback resistor connected in series with the feedback capacitor.
The frame rod circuit according to claim 4. If the combustor is burning, a first period in which a current flows between the combustor and the frame rod appears.
In the first period, the smaller the absolute value of the current flowing between the combustor and the frame rod, the smaller the frequencies of the triangular wave and the square pulse wave, whereby the detection signal is a square pulse signal. In some cases, the frequency of the detection signal becomes smaller.
The frame rod circuit according to claim 4 or 5. If the combustor is burning, a first period in which a current flows between the combustor and the frame rod appears.
The frequency of the detection signal in the first period is relative to the first state in which the combustor is not burning, the second state in which the combustion intensity of the combustor is relatively weak, and the combustion intensity of the combustor. Different from the third state, which is strong against
The frame rod circuit according to any one of claims 1 to 6. The detection signal in the first period is a DC signal in the first state, and is a rectangular pulse signal in the second state and the third state.
The frame rod circuit according to claim 7. The magnitude of the detection signal in the first period is different from the second state and the third state in the first state.
The frame rod circuit according to claim 7 or 8. If the insulation deteriorates between the combustor and the frame rod, a second period in which a current flows between the combustor and the frame rod appears.
The frequency of the detection signal in the second period differs between the fourth state in which the insulation resistance between the combustor and the frame rod is relatively high and the fifth state in which the insulation resistance is relatively low.
The frame rod circuit according to any one of claims 1 to 9. The detection signal in the second period is a DC signal in the fourth state and a square pulse signal in the fifth state.
The frame rod circuit according to claim 10. The magnitude of the detection signal in the second period is different from that of the fourth state in the fifth state.
The frame rod circuit according to claim 10 or 11. If the combustor is burning, a first period in which a current flows between the combustor and the frame rod, and if insulation deterioration between the combustor and the frame rod occurs, the combustor and the frame The second period, in which current flows between the rods, appears alternately.
The frame rod circuit according to any one of claims 1 to 12. If the combustor is burning, a first period in which a current flows between the combustor and the frame rod, and if insulation deterioration between the combustor and the frame rod occurs, the combustor and the frame The second period, when current flows between the rods, appears,
The length of the first period is longer than the length of the second period.
The frame rod circuit according to any one of claims 1 to 13. The IV conversion circuit includes a detection resistor.
The voltage drop in the detection resistor generated in response to the current flowing between the combustor and the frame rod is reflected in the conversion potential.
The frame rod circuit according to any one of claims 1 to 14. The signal generation circuit includes a comparator.
The comparator sets the magnitude of the detection signal by comparing the threshold potential with the signal potential corresponding to the conversion potential.
The frame rod circuit according to any one of claims 1 to 15. A reformer that reforms the raw material gas containing hydrocarbon components to generate a reformed gas containing hydrogen,
The frame rod circuit according to any one of claims 1 to 16, wherein the combustor burns a flammable raw material containing a hydrocarbon component to heat the reformer. , A hydrogen generator. A reformer that reforms the raw material gas containing hydrocarbon components to generate a reformed gas containing hydrogen,
A fuel cell that generates electricity using the reformed gas and
The frame rod circuit according to any one of claims 1 to 16, wherein the combustor burns a flammable raw material containing a hydrocarbon component to heat the reformer. , Equipped with a fuel cell system. It is a detection method that detects the state of the combustor using a frame rod.
To generate a conversion potential according to the current flowing between the combustor and the frame rod,
Including setting the frequency of the detection signal based on the conversion potential.
Detection method.

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