Flame detection device and gas device

Abstract

The present invention provides a flame detection device and a gas device, the flame detection device comprising: a detection circuit, comprising a fire detection pin and a third resistor connected to the fire detection pin; the other end of the third resistor is connected to the housing, and also comprises a power supply terminal for accessing a power supply; an amplifier circuit, comprising an operational amplifier, the two input ends of the operational amplifier are connected to the two ends of the first resistor, and the output end outputs a detection signal. In such a design, the voltage drop across the third resistor in the detection circuit is amplified by the amplifier circuit, and the presence and size of the flame can be detected by outputting the detection signal through the output end of the amplifier circuit, thereby detecting the combustion condition of the prototype in real time.

Description

Technical Field

[0001] The present invention relates to the technical field of household appliances, and in particular to a flame detection device and a gas device. Background Art

[0002] In gas water heaters, gas stoves, gas heating furnaces and other products, flame combustion conditions are the key factors to ensure the core performance indicators such as product combustion performance, efficiency, flue gas emission safety, and environmental protection. Especially in the high-end technical fields of forced combustion technology, premixed (including semi-premixed) combustion technology, condensing combustion heat exchange technology and other such products, monitoring of flame combustion conditions is also the key to ensuring that the core performance indicators such as product combustion performance, efficiency, flue gas emission safety, and environmental protection meet the product standard requirements.

[0003] The detection of existing flame combustion conditions is achieved through a specially set fire detection device. Fire detection devices can be divided into strong current flame detection and weak current flame detection by type. Although strong current flame detection is low in cost, it must be within a reasonable voltage range to work stably and is easily affected by mains power fluctuations. Weak current flame detection is supplied by a switching power supply, so the power supply voltage is not affected by mains power fluctuations, and its working stability is very good. Therefore, weak current fire detection is widely used in high-end models due to its high cost.

[0004] However, in the prior art, whether it is strong current fire detection or weak current fire detection, it can only detect the presence of flame, but not the size of flame. Detecting the size of flame can often reflect the combustion situation inside the appliance, and can more accurately judge the combustion state inside the appliance. Summary of the invention

[0005] Therefore, the technical problem to be solved by the present invention is that the prior art can only detect the presence or absence of flame but cannot detect the size of flame.

[0006] To achieve the above object, the present invention provides a flame detection device, comprising:

[0007] The detection circuit includes a fire detection pin and a third resistor connected to the fire detection pin; the other end of the third resistor is connected to the housing, and also includes a power supply terminal for connecting to a power supply;

[0008] The amplifier circuit comprises an operational amplifier, wherein two input terminals of the operational amplifier are connected to two terminals of the first resistor, and an output terminal outputs a detection signal.

[0009] Optionally, a power supply circuit is included, and the power supply circuit includes a power supply end that outputs a pulse voltage to the power supply end, and the pulse voltage is not less than the breakdown voltage of the flame.

[0010] Optionally, the power supply circuit includes a pulse transformer and a transistor, the pulse transformer includes a primary winding and a first secondary winding and a second secondary winding cooperating with the primary winding; the emitter of the transistor is connected to the input voltage of the power supply circuit, the collector is connected to the primary winding, the first secondary winding is connected to the power supply end, and the second secondary winding is connected to the base to form self-excited oscillation.

[0011] Optionally, the other end of the primary winding is grounded, and the second secondary winding is grounded through a seventh resistor.

[0012] Optionally, the power supply circuit includes a MOS switch or a high-frequency transformer.

[0013] Optionally, the amplifier circuit is an inverting amplifier circuit, the housing is grounded, the non-phase input terminal of the operational amplifier is grounded, a fourth resistor is arranged between the inverting input terminal and the third resistor, and a fifth resistor is arranged between the inverting input terminal and the output terminal.

[0014] Optionally, the housing is grounded through a sixth resistor and then connected to the third resistor.

[0015] Optionally, the output end is grounded via a second filter capacitor.

[0016] Optionally, a first filter capacitor is connected in parallel across both ends of the third resistor.

[0017] Optionally, the amplifier circuit is a common-phase amplifier circuit; its inverting input terminal and the housing are grounded.

[0018] Optionally, the amplifier circuit is a multi-stage amplifier circuit composed of a plurality of operational amplifiers.

[0019] Optionally, the detection circuit is further connected in series with at least one current limiting resistor.

[0020] The present invention also provides a gas device, comprising the above-mentioned flame detection device.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] An embodiment of the present invention provides a flame detection device, which is designed such that the voltage drop across the third resistor in the detection circuit is amplified by an amplifier circuit, and the presence and size of the flame can be detected by outputting a detection signal through the output end of the amplifier circuit, thereby detecting the combustion condition of the prototype in real time. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 The schematic diagram of the flame detection device of this embodiment is shown. DETAILED DESCRIPTION

[0025] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] like Figure 1 As shown, an embodiment of the present invention provides a flame detection device. The flame detection device includes a power supply circuit, a detection circuit and an amplification circuit.

[0027] The power supply circuit is used to provide a continuous pulse voltage for the detection circuit, and the pulse voltage should be no less than the breakdown power of the flame. Specifically, the power supply circuit includes a pulse transformer T1 and a transistor Q1. The pulse transformer includes a primary winding, a first secondary winding and a second secondary winding that cooperate with the primary winding. The emitter of the transistor Q1 is connected to the input voltage, the collector is connected to the primary winding, the first secondary winding is the power supply end for external power supply, and the second secondary winding is connected to the base. The other end of the primary winding is grounded, and the second secondary winding is grounded through the seventh resistor R7.

[0028] The power supply circuit first plays a role in boosting voltage, and by utilizing the characteristics of saturated conduction and cutoff of transistor Q1, the pulse transformer T1 continuously generates a self-excited oscillation pulse voltage signal under the action of transistor Q1, and the pulse voltage signal is an AC voltage pulse signal. In this embodiment, a 5V voltage is input, and an AC pulse output of about 250V can be obtained at the power supply end. The power supply circuit is designed in this way, and the self-excited oscillation principle of the pulse transformer T1 is utilized to realize the weak current boosting function, thereby realizing the use of weak current to detect flames, and effectively eliminating the poor fire detection phenomenon caused by the instability of strong electricity itself.

[0029] In the detection circuit, the fire detection pin J, the first resistor R1, the first secondary winding, the second resistor R2, the third resistor R3, the sixth resistor R6 and the housing PE are connected in series. The third resistor R3 and the sixth resistor R6 are grounded through a wire. The first resistor R1 and the second resistor R2 are current limiting resistors that play a current limiting role. The size can be set according to the actual circuit parameters. One, multiple, or no resistors can be set. The first secondary winding is used to connect the high-voltage pulse voltage generated by the power supply circuit to the power supply end of the detection circuit. Between the first resistor R1 and the second resistor R2 is the power supply end for connecting to the power supply.

[0030] In this embodiment, the amplifier circuit is an inverting amplifier circuit. Specifically, the non-phase input terminal of the operational amplifier L2-A is grounded, the inverting input terminal is connected to the third resistor R3, a fourth resistor R4 is arranged between the inverting input terminal and the third resistor R3, a fifth resistor R5 is arranged between the inverting input terminal and the output terminal, the output terminal is connected to the output interface FIRE-AD, and the output terminal and the output interface are grounded through the second filter capacitor C2. The first filter capacitor C1 for filtering is connected in parallel at both ends of the third resistor R3.

[0031] The working principle of the flame detection device is:

[0032] The power supply circuit outputs a continuous high voltage pulse voltage.

[0033] When there is no flame, the flame detection pin J does not form a loop with the housing PE, the detection circuit does not form a closed loop, and there is no voltage drop across the third resistor R3. The output voltage calculated by the amplifier circuit is 0V, indicating that no flame is detected.

[0034] When there is flame, the flame will be equivalent to a current limiting resistor and a unidirectional conducting diode. The flame detection pin J is connected to the casing PE through the flame, the detection circuit is in a conducting state, and there is a voltage drop across the third resistor R3.

[0035] By detecting the voltage change across the third resistor R3, the state change of the flame can be understood. Specifically, since the flame ion concentration and flame impedance of different flame sizes are different: the smaller the flame, the greater the flame impedance, the smaller the current in the detection circuit, and the smaller the voltage drop across the third resistor R3; the larger the flame, the smaller the flame impedance, the greater the current in the detection circuit, and the greater the voltage drop across the third resistor R3. Therefore, the detection circuit can detect the size of the flame in real time through the change of the voltage drop across the third resistor R3.

[0036] Since a fourth resistor R4 is provided between the inverting input terminal of the operational amplifier L2-A and the third resistor R3, and a fifth resistor R5 is provided between the inverting input terminal and the output terminal, and according to the virtual short principle in the operational amplifier circuit, the voltage at the pin 1 of the fourth resistor R4 is the same as the voltage at the pin 1 of the third resistor R3, both of which are equal to the ground terminal voltage of 0. Therefore, the voltage U across the third resistor R3 is 3 and the voltage U across the fourth resistor R4 4 Since the pin 2 of the fifth resistor R5 is connected to the pin 1 of the fourth resistor R4, the voltage across the fifth resistor R5 is equal to the output voltage U 0 Since the third resistor R 3 grounded, so the third resistor R3 is a negative voltage, and the fourth resistor R 4 It is also a negative voltage.

[0037] In summary, according to the virtual disconnection principle in the operational amplifier circuit, we can get:

[0038] , , so the output voltage U 0 and the third resistor R 3 Voltage Directly proportional.

[0039] Therefore, the output voltage U 0 When there is no flame, according to the above detection circuit, there is no voltage drop across the third resistor R3, that is, U 3 is 0, so the output voltage U 0 When there is a flame, the larger the flame, the greater the voltage drop across the third resistor R3, so the output voltage U 0 The larger the flame, the smaller the voltage drop across the third resistor R3, so the output voltage U 0 The smaller.

[0040] This arrangement can solve the problem that the prior art can only detect the presence of flames but not the size of flames. By detecting the size of flames, the burning condition of flames can be better reflected. 0 Determine the presence and size of flame to save chip resources.

[0041] As an alternative implementation, the power supply circuit may use a MOS switch or a high-frequency transformer, or other components or circuits that can convert a low-voltage input into a high-voltage pulse output.

[0042] As an alternative implementation, strong electricity can be used as the input voltage in the power supply circuit, and a voltage stabilizing device can be added to stabilize the AC power fluctuations to solve the problem of AC power fluctuations affecting the stability of fire detection.

[0043] As an alternative implementation, the amplifier circuit may use a common-mode amplifier circuit, a differential amplifier circuit, or other circuits that can linearly amplify the input voltage difference. Those skilled in the art may make adaptive improvements to the amplifier circuit based on actual conditions, for example, whether the third resistor R3 is grounded.

[0044] The embodiment of the present invention also provides a gas-burning device, which includes the flame detection device in the above embodiment.

[0045] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A flame detection device, characterized in that: include: The detection circuit comprises a fire detection pin (J) and a third resistor (R3) connected to the fire detection pin (J); the other end of the third resistor (R3) is connected to the housing (PE), and also comprises a power supply terminal for connecting to a power supply; an amplifying circuit, comprising an operational amplifier (L2-A), wherein two input terminals of the operational amplifier (L2-A) are connected to two terminals of the third resistor (R3), and an output terminal outputs a detection signal; The amplifier circuit is an inverting amplifier circuit, the housing (PE) is grounded, the non-inverting input terminal of the operational amplifier is grounded, a fourth resistor (R4) is arranged between the inverting input terminal and the third resistor (R3), and a fifth resistor (R5) is arranged between the inverting input terminal and the output terminal; The detection signal is an output voltage, and the presence or absence of flame and the size of the flame are determined by the output voltage. When there is no flame, the output voltage is 0. When there is flame, the larger the flame, the larger the output voltage, and the smaller the flame, the smaller the output voltage.

2. The flame detection device according to claim 1, characterized in that: The invention comprises a power supply circuit, wherein the power supply circuit comprises a power supply terminal for outputting a pulse voltage to the power supply terminal, and the pulse voltage is not less than the breakdown voltage of the flame.

3. The flame detection device according to claim 2, characterized in that: The power supply circuit comprises a pulse transformer (T1) and a transistor (Q1), wherein the pulse transformer (T1) comprises a primary winding and a first secondary winding and a second secondary winding matched with the primary winding; the emitter of the transistor (Q1) is connected to the input voltage of the power supply circuit, the collector is connected to the primary winding, the first secondary winding is connected to the power supply end, and the second secondary winding is connected to the base to form self-excited oscillation.

4. The flame detection device according to claim 3, characterized in that: The other end of the primary winding is grounded, and the second secondary winding is grounded via a seventh resistor (R7).

5. The flame detection device according to claim 2, characterized in that: The power supply circuit includes a MOS switch or a high-frequency transformer.

6. The flame detection device according to claim 1, characterized in that: The housing (PE) is grounded through a sixth resistor (R6) and then connected to the third resistor (R3).

7. The flame detection device according to claim 1, characterized in that: The output end is grounded via a second filtering capacitor (C2).

8. The flame detection device according to claim 1, characterized in that: A first filter capacitor (C1) is connected in parallel across both ends of the third resistor (R3).

9. The flame detection device according to any one of claims 1 to 5, characterized in that: The amplifier circuit is a multi-stage amplifier circuit composed of a plurality of operational amplifiers.

10. The flame detection device according to claim 1, characterized in that: The detection circuit is further connected in series with at least one current limiting resistor.

11. A gas device, characterized in that: The flame detection device comprises the flame detection device according to any one of claims 1 to 10.

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