Ignition circuit

Abstract

The present application relates to an ignition circuit. The ignition circuit includes: a synchronous buck control circuit for outputting an output voltage from its output terminal; a heating wire having a first end and a second end connected to the output voltage; and a feedback circuit connected between the second end of the heating wire and the feedback terminal of the synchronous buck control circuit for feeding back the synchronous buck control circuit based on the output current of the synchronous buck control circuit. In this way, by adopting the synchronous buck mode in combination with current feedback, the ignition operation can be achieved with constant current and constant voltage control, thereby effectively reducing the influence of the change in the resistance value of the heating wire on the ignition function and improving the reliability of ignition.

Description

Technical Field

[0001] This application relates to the field of circuit technologies, and more specifically, to an ignition circuit. Background Art

[0002] In a gas chromatograph, the most commonly used is the flame ionization detector (FID). Its outstanding advantages are high sensitivity, wide linear range, and response to almost all volatile organic compounds. Currently, the FID detector generally uses an electric heating wire for ignition. However, using electric heating wires of the same material usually causes difficult ignition of the FID due to differences in their length, connecting wires, and contact resistance. In addition, some electric heating wires will be oxidized after being used for a period of time, resulting in an increase in resistance value, which will also lead to difficult ignition.

[0003] Specifically, the currently widely used FID ignition circuit usually uses a transformer for power supply or a switching power supply for constant voltage power supply, with a fixed voltage. However, when using a transformer for power supply or a switching power supply for constant voltage power supply, the ignition voltage is fixed, and a high requirement is imposed on the consistency of the resistance value of the electric heating wire. Electric heating wires of different materials cannot be mixed. Even for electric heating wires of the same material, differences in length, connecting wires, and contact resistance will cause differences in the resistance value of the igniter load, resulting in the failure of some FIDs to ignite. In addition, after the FID operates normally for a period of time, some electric heating wires will be oxidized, causing an increase in resistance value and resulting in difficult re-ignition.

[0004] Therefore, it is desirable to provide an improved ignition circuit for a gas chromatograph. Summary of the Invention

[0005] An embodiment of this application provides an ignition circuit. By adopting a synchronous buck mode in cooperation with current feedback, it can achieve an ignition operation through constant current and constant voltage control, thereby effectively reducing the influence of changes in the resistance value of the electric heating wire on the ignition function and improving the reliability of ignition.

[0006] According to one aspect of this application, an ignition circuit is provided, including: a synchronous buck control circuit for outputting an output voltage from its output terminal; an electric heating wire having a first end and a second end connected to the output voltage; and a feedback circuit connected between the second end of the electric heating wire and the feedback terminal of the synchronous buck control circuit for feeding back the synchronous buck control circuit based on the output current of the synchronous buck control circuit.

[0007] In the above ignition circuit, the synchronous buck control circuit includes a TPS4005x series synchronous buck controller chip.

[0008] In the above ignition circuit, the feedback circuit includes: a sampling circuit for sampling the output current of the synchronous buck control circuit to obtain a sampling voltage; an operational amplifier circuit for amplifying the sampling voltage obtained by the sampling circuit to obtain an amplified voltage; and a comparison circuit for comparing the amplified voltage output by the operational amplifier circuit with a control voltage and feeding back the comparison result to the synchronous buck control circuit.

[0009] In the above ignition circuit, the amplification of the operational amplifier circuit is expressed as: VT1 = (1 + r2 / r1) * VT0, where VT1 is the amplified voltage value, VT0 is the input voltage value, and r1 and r2 are the first resistance value and the second resistance value for setting the amplification factor.

[0010] In the above ignition circuit, the circuit for generating the control voltage includes a first adjustable resistor connected between the control power supply and the ground, and the first adjustable resistor is used to adjust the range of the constant current value.

[0011] In the above ignition circuit, the adjustable range of the constant current value is 0.8A - 4A.

[0012] In the above ignition circuit, the synchronous buck control circuit includes a second adjustable resistor at its output end for adjusting the range of the output voltage.

[0013] In the above ignition circuit, the adjustable range of the output voltage is 0.9V - 5V.

[0014] In the above ignition circuit, it further includes: a control circuit connected between the output end of the synchronous buck control circuit and the first end of the heating wire, and the control circuit controls the conduction and disconnection between the output end of the synchronous buck control circuit and the first end of the heating wire.

[0015] In the above ignition circuit, the control circuit is a single-pole double-throw relay controlled by a control circuit.

[0016] The ignition circuit provided by the embodiment of the present application can realize the ignition operation with constant current and constant voltage control by adopting the synchronous buck mode in cooperation with current feedback, thereby effectively reducing the influence of the change in the resistance value of the heating wire on the ignition function and improving the reliability of ignition. Description of the Drawings

[0017] By reading the detailed description in the following preferred specific embodiments, various other advantages and benefits of the present application will become clear to those of ordinary skill in the art. The accompanying drawings of the specification are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of the present application. Obviously, the following-described drawings are only some embodiments of the present application, and those of ordinary skill in the art can obtain other drawings based on these drawings without creative efforts. Moreover, throughout the drawings, the same reference numerals are used to represent the same components.

[0018] Figure 1 FIG. illustrates a schematic block diagram of an ignition circuit according to an embodiment of the present application.

[0019] Figure 2 FIG. illustrates an example of a TPS4005x series synchronous buck controller chip used in the ignition circuit according to an embodiment of the present application.

[0020] Figure 3 FIG. illustrates a schematic circuit diagram of a feedback circuit of the ignition circuit according to an embodiment of the present application.

[0021] Figure 4 FIG. illustrates a circuit diagram of a preferred example of the ignition circuit according to an embodiment of the present application. Specific Embodiments

[0022] Hereinafter, exemplary embodiments according to the present application will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. It should be understood that the present application is not limited by the exemplary embodiments described herein.

[0023] Figure 1 FIG. illustrates a schematic block diagram of an ignition circuit according to an embodiment of the present application.

[0024] As Figure 1 shown, the ignition circuit 100 according to an embodiment of the present application is composed of three parts, namely: a synchronous buck control circuit 110 for outputting an output voltage from its output terminal; a heating wire 120 having a first end and a second end connected to the output voltage; and a feedback circuit 130 connected between the second end of the heating wire and the feedback terminal of the synchronous buck control circuit for feeding back the synchronous buck control circuit based on the output current of the synchronous buck control circuit.

[0025] Specifically, the synchronous buck control circuit 110 may be a synchronous buck control circuit based on various synchronous buck controller chips. For example, the synchronous buck controller chip may be a TPS40055 chip, a TPS40077 chip, etc. for implementing synchronous buck. Figure 2Illustrated is an example of the TPS4005x series synchronous buck controller chip used in the ignition circuit according to an embodiment of the present application.

[0026] Here, the TPS4005x series synchronous buck controller chip is a high-voltage synchronous buck controller with a wide input voltage range (8V to 52V), which has a high degree of design flexibility and can provide a variety of user-programmable functions, including soft start, under-voltage lockout (UVLO), operating frequency, voltage feedforward, high-side current limit, and loop compensation.

[0027] Moreover, the TPS4005x series synchronous buck controller chip can use voltage feedforward control technology to provide good line regulation function within a wide input voltage (4:1) range and quickly respond to input line transients. The input-variable and approximately constant modulator gain simplifies loop compensation. The external programmable current limit function can provide pulse-by-pulse current limit, and at the same time, an internal fault counter is used to operate in discontinuous mode when the overload duration is long.

[0028] Therefore, considering that the igniter uses a DC ignition method, a low voltage and large current are required in the circuit. By using a synchronous buck controller (such as the TPS40055 chip), the design of a high-performance power supply can be simplified. And, the ignition circuit according to an embodiment of the present application can feedback a feedback signal based on the output current of the synchronous buck control circuit 110, such as a feedback voltage, back to the synchronous buck control circuit 110 through the feedback circuit 130, which can provide good line regulation function and quickly respond to input line transients to achieve the purpose of voltage regulation or current regulation. That is, while adopting the synchronous buck mode, it is combined with current detection and feedback to complete the ignition operation of the igniter through constant current and constant voltage control. In this way, even if the resistance value of the heating wire changes during use, since the ignition current is constant, it will not cause difficult ignition, and by adopting the synchronous buck circuit, the problem of large power loss in such low-voltage and large-current circuits is solved.

[0029] In an embodiment of the present application, the feedback circuit 130 may include a sampling circuit, an operational amplifier circuit, and a comparison circuit. The sampling circuit is used to sample the output current of the synchronous buck control circuit to obtain a sampling voltage. The operational amplifier circuit is used to amplify the sampling voltage obtained by the sampling circuit by a certain multiple to obtain an amplified voltage, and the comparison circuit is used to compare the amplified voltage output by the operational amplifier circuit with a control voltage to feedback the comparison result to the synchronous buck control circuit 110.

[0030] Figure 3 Illustrated is a schematic circuit diagram of the feedback circuit of the ignition circuit according to an embodiment of the present application. As Figure 3As shown, the feedback circuit includes a current sampling resistor R10, an operational amplifier circuit including an amplifier U2A, resistors R11, R12, and R13, and a comparison circuit including a comparator U2B, resistors R14, a potentiometer R15, resistors R16, R17, and a diode D1.

[0031] Specifically, the sampling resistor R10 is connected in series with the heating wire between the output voltage and the ground voltage of the synchronous buck control circuit. Therefore, the sampling resistor R10 samples the output current of the synchronous buck control circuit and outputs the sampling voltage across the sampling resistor R10.

[0032] The amplifier U2A amplifies the input signal VT0 by a certain multiple. The input signal, for example, the input voltage value VT0, is respectively connected to the non-inverting input of the amplifier U2A through the resistor R12 and to the power supply ground VSS through the current sampling resistor R10; both ends of the resistor R11 are connected to the inverting terminal of the amplifier and the power supply ground VSS; a resistor R13 is connected between the output terminal VT1 of the operational amplifier and the inverting input; the output signal of the amplifier U2A, for example, the output voltage value VT1, is input to the comparison circuit.

[0033] Moreover, the output signal of the amplifier U2A is connected to the non-inverting terminal of the comparator U2B. The power supply VAA is connected to the power supply ground VSS through resistors R16, R15, and R18. Both ends of the resistor R18 are respectively connected to the inverting terminal of the comparator U2B and the power supply ground VSS; the output of the comparator U2B is connected to the feedback terminal VFB of the synchronous buck controller U1 through the resistor R17 and the diode D1.

[0034] According to the "virtual short" and "virtual open" characteristics of the amplifier U2A, it can be obtained that:

[0035] VT1 = (1 + r2 / r1) * VT0

[0036] In the above formula, VT1 is the amplified voltage value, VT0 is the input voltage value, r2 and r1 are the resistance values of the resistors R13 and R11 in the figure respectively, and they can be selected according to the required amplification multiple. For example, the resistance value r2 of R13 can be selected as 40K, and the resistance value r1 of R11 can be selected as 10K, that is, the amplification multiple is 5, and VT1 = 5 * VT0.

[0037] In addition, the inverting input terminal VT2 of the comparator U2B is taken as the reference of the comparator. When the non-inverting input terminal VT1 > the inverting input terminal VT2, a high level, for example, 5V, is output. When the non-inverting input terminal VT1 < the inverting input terminal VT2, a low level, for example, 0V, is output.

[0038] As Figure 4As shown, in the embodiment of the present application, the circuit for generating the control voltage may include a first adjustable resistor connected between the control power supply, i.e., VAA5 and ground, i.e., R15 shown in the figure, for adjusting the control range of the constant current value. For example, based on Figure 4 As shown by the specific parameter values, the adjustment range of the constant current value can be 0.8A - 4A. Figure 4 The figure shows a circuit diagram of a preferred example of the ignition circuit according to the embodiment of the present application.

[0039] In addition, as Figure 4 shown, in the embodiment of the present application, the synchronous buck control circuit 110 may include a second adjustable resistor at its output end, i.e., R8 shown in the figure, for adjusting the VOUT output voltage value. For example, based on Figure 4 As shown by the specific parameter values, the VOUT adjustment range is 0.9V - 5V.

[0040] In this way, when the ignition circuit according to the embodiment of the present application is powered in the constant voltage and constant current mode, the magnitudes of the voltage and current can be set by the adjustable resistor, so as to adapt to heating wires of different materials.

[0041] Next, taking the specific example of the ignition circuit shown in Figure 4 as an example, the circuit adjustment process when the constant current source is 2A is described as follows:

[0042] (1) When I = 2A, VT0 = 0.2V, VT1 = 5 * VT0 = 1V;

[0043] (2) Adjust the potentiometer R15 to make the VT2 voltage 1V;

[0044] (3) When the current in the loop is greater than 2A, VT0 increases, VT1 increases, VT1 > VT2, VT3 outputs 5V, the input voltage of VFB increases, and due to the closed-loop regulation effect of U1, the output voltage VOUT decreases, and the current I also decreases accordingly;

[0045] (4) When the current in the loop is less than 2A, VT1 < VT2, VT3 outputs 0V. Due to the existence of the diode D1, VT3 has no influence on VFB. The output is in the constant voltage mode, and VOUT is determined by R7, R8, and R9;

[0046] (5) If VOUT causes the load current to be greater than 2A, then return to (3), and finally the load 2 current is stabilized at 2A;

[0047] (6) If VOUT causes the load current to be less than 2A, then maintain the constant voltage output state.

[0048] In addition, as Figure 4As shown, in the ignition circuit according to an embodiment of the present application, a control circuit connected between the output terminal of the synchronous buck control circuit and the first end of the heating wire may be further included, and the control circuit controls the conduction and disconnection between the output terminal of the synchronous buck control circuit and the first end of the heating wire. For example, it may be implemented in the form of a single-pole double-throw switch in a circuit as shown in Figure 4 In addition, it may also be implemented as a control MOS that can control conduction and cut-off.

[0049] That is, by controlling the switch of the output voltage to the heating wire, when the ignition action is not performed, the heating wire is directly connected to VSS, and the collection of the FID micro-current signal will not be interfered. When the ignition action is performed, the output voltage is output to the heating wire, and current passes through the heating wire. In this way, the influence of the ignition voltage on the FID ion current can be effectively reduced, the FID noise can be reduced, and the FID sensitivity can be improved.

[0050] In summary, when the ignition circuit according to an embodiment of the present application is used for, for example, an FID igniter, since the ignition voltage is fixed, a high requirement is imposed on the consistency of the resistance value of the heating wire, so that heating wires of different materials cannot be mixed. Even for heating wires of the same material, due to differences in length or connection wires and contact resistance, differences in the load resistance of the igniter will be caused, resulting in some FIDs not being able to ignite. The ignition circuit according to an embodiment of the present application is powered in a constant voltage and constant current mode, and the magnitudes of the voltage and current are set by a potentiometer, which can adapt to heating wires of different materials.

[0051] In addition, after the FID operates normally for a period of time, some heating wires will be oxidized, resulting in an increase in resistance value, making it difficult to ignite again. In the ignition circuit according to an embodiment of the present application, even if the resistance value of the heating wire changes during use, since the ignition current is constant, it will not cause difficulty in ignition.

[0052] Here, those skilled in the art can understand that the ignition circuit according to an embodiment of the present application can be used not only for FID igniters but also for other igniters, such as FPD detectors, that is, Flame Photometric Detectors (FPD), etc.

[0053] The basic principles of the present application have been described above in conjunction with specific embodiments. However, it should be noted that the advantages, advantages, effects, etc. mentioned in the present application are only examples and not limitations, and it cannot be considered that these advantages, advantages, effects, etc. are essential for each embodiment of the present application. In addition, the above-disclosed specific details are only for the purposes of illustration and easy understanding, rather than limitations, and the above details do not limit the present application to necessarily adopt the above specific details to be implemented.

[0054] The block diagrams of the devices, apparatuses, equipment, and systems involved in the present application are merely illustrative examples and are not intended to require or imply that they must be connected, arranged, and configured in the manner shown in the block diagrams. As those skilled in the art will recognize, these devices, apparatuses, equipment, and systems can be connected, arranged, and configured in any manner. Words such as "including", "comprising", "having", etc. are open-ended terms that mean "including but not limited to" and can be used interchangeably with each other. The word "or" and "and" used herein refer to the phrase "and / or" and can be used interchangeably with it, unless the context clearly indicates otherwise. The phrase "such as" used herein refers to the phrase "such as but not limited to" and can be used interchangeably with it.

[0055] It should also be noted that in the apparatuses, equipment, and methods of the present application, each component or each step can be decomposed and / or recombined. These decompositions and / or recombinations should be regarded as equivalent solutions of the present application.

[0056] The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use the present application. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein can be applied to other aspects without departing from the scope of the present application. Therefore, the present application is not intended to be limited to the aspects shown herein, but rather to the broadest scope consistent with the principles and novel features disclosed herein.

[0057] The above description has been given for purposes of illustration and description. In addition, this description is not intended to limit the embodiments of the present application to the forms disclosed herein. Although several example aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations thereof.

Claims

1. An ignition circuit, characterized in that, it includes: A synchronous buck control circuit for outputting an output voltage from its output terminal; A heating wire having a first end and a second end connected to the output voltage; And A feedback circuit connected between the second end of the heating wire and the feedback terminal of the synchronous buck control circuit for feeding back the synchronous buck control circuit based on the output current of the synchronous buck control circuit; wherein, the synchronous buck control circuit includes a TPS4005x series synchronous buck controller chip; The feedback circuit includes: A sampling circuit for sampling the output current of the synchronous buck control circuit to obtain a sampling voltage; An operational amplifier circuit for amplifying the sampling voltage obtained by the sampling circuit to obtain an amplified voltage; and A comparison circuit for comparing the amplified voltage output by the operational amplifier circuit with a control voltage to feedback the comparison result to the synchronous buck control circuit; wherein, the circuit for generating the control voltage includes a first adjustable resistor connected between a control power supply and ground, and the first adjustable resistor is used to adjust the range of the constant current value; wherein, the synchronous buck control circuit includes a second adjustable resistor at its output terminal for adjusting the range of the output voltage.

2. The ignition circuit according to claim 1, wherein, The amplification of the operational amplifier circuit is expressed as: VT1 = (1 + r2 / r1) * VT0 wherein, VT1 is the amplified voltage value, VT0 is the input voltage value, and r1 and r2 are the first resistance value and the second resistance value for setting the amplification factor.

3. The ignition circuit according to claim 1, wherein, The adjustment range of the constant current value is 0.8A - 4A.

4. The ignition circuit according to claim 1, wherein, The adjustment range of the output voltage is 0.9V - 5V.

5. The ignition circuit according to claim 1, further includes: A control circuit connected between the output terminal of the synchronous buck control circuit and the first end of the heating wire, and the control circuit controls the conduction and disconnection between the output terminal of the synchronous buck control circuit and the first end of the heating wire.

6. The ignition circuit according to claim 5, wherein, The control circuit is a single - pole double - throw relay controlled by a control circuit.

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