A light source driving circuit and a gas analyzer

Abstract

This invention relates to a light source driving circuit and a gas analyzer. The light source driving circuit includes: a driving module comprising an inverter chip and a high-frequency transformer, wherein the inverter chip outputs A and B are square waves with a 180° phase difference, used to drive the high-frequency transformer to convert a DC voltage signal into an AC square wave signal; a DC voltage feedback control module, used to adjust the driving voltage of the primary coil of the high-frequency transformer according to the DC voltage feedback from the rectified AC square wave signal, and synchronously drive the light source with the AC square wave signal; and a timing control module, used to generate on or off signals through timing control to control the intermittent driving of the light source. The light source driving circuit of this invention uses automatic intermittent driving of the light source, which can greatly extend the life of the light source and eliminates the need for MCU control. The gas analyzer of this invention uses a light source driving circuit to drive the light source, resulting in stable light source operation and improved detection accuracy.

Description

Technical Field

[0001] This invention belongs to the field of gas analysis technology, specifically relating to a light source driving circuit and a gas analyzer. Background Technology

[0002] Gas analyzers, such as sulfur dioxide analyzers, use ultraviolet fluorescence for detection. An ultraviolet light source, a zinc lamp, generates ultraviolet light, which is then filtered by a filter and focused by a lens. The sulfur dioxide gas being measured passes through a hydrocarbon remover to remove carbon and hydrocarbon components before entering the gas chamber. There, it reacts with the ultraviolet light to produce fluorescence. A phototube receives the fluorescence signal, and the gas concentration is calculated using electrical signals. The driving mechanism of the ultraviolet light source is the core component of the gas analyzer and a key factor in ensuring the accuracy of the analysis. Current ultraviolet light source driving methods are constantly lit, such as the zinc lamp power supply device disclosed in patent document CN202276498U.

[0003] However, the constant-on driving method can affect the lifespan of the light source, and prolonged illumination leads to light energy decay, which in turn causes deviations in the detection results. Summary of the Invention

[0004] Based on the aforementioned shortcomings and deficiencies in the prior art, one of the objectives of this invention is to at least solve one or more of the aforementioned problems in the prior art. In other words, one of the objectives of this invention is to provide a light source driving circuit and a gas analyzer that meet one or more of the aforementioned requirements.

[0005] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0006] A light source driving circuit, comprising:

[0007] The drive module includes an inverter chip and a high-frequency transformer. The outputs A and B of the inverter chip are square waves with a phase difference of 180°, which are used to drive the high-frequency transformer to convert the DC voltage signal into an AC square wave signal to drive the light source.

[0008] The DC voltage feedback control module is used to adjust the drive voltage of the primary coil of the high-frequency transformer based on the DC voltage feedback from the rectified AC square wave signal.

[0009] The timing control module is used to generate on or off signals through timing control to control the intermittently driven light source.

[0010] As a preferred embodiment, the DC voltage feedback control module includes a SEPIC switching power supply topology and a DC voltage feedback branch. The SEPIC switching power supply topology adjusts the DC voltage output according to the DC voltage feedback from the DC voltage feedback branch, so as to adjust the driving voltage of the primary coil of the high-frequency transformer.

[0011] As a preferred embodiment, the SEPIC switching power supply topology includes a SEPIC controller, inductor L3, MOSFET Q6, capacitor C25, inductor L4, and diode D10. The RUN pin of the SEPIC controller is connected to the power supply. One end of inductor L3 is connected to the power supply and the VIN pin of the SEPIC controller, and the other end is connected to capacitor C25 and the drain of MOSFET Q6. The gate of MOSFET Q6 is connected to the GATE pin of the SEPIC controller through resistor R40, and the source of MOSFET Q6 is connected to the SENSE pin of the SEPIC controller and grounded through resistor R67. The other end of capacitor C25 is connected to the anode of diode D10 and grounded through inductor L4. The cathode of diode D10 is connected to the DC voltage output terminal for outputting DC voltage to the primary coil of the high-frequency transformer.

[0012] As a preferred embodiment, the DC voltage output terminal is grounded through a polarized capacitor CE4. The polarized capacitor CE4 is connected in parallel with resistors R63 and R65, which are connected in series. Resistor R63 is connected to the DC voltage output terminal, and resistor R65 is connected to the FB pin of the SEPIC type controller.

[0013] As a preferred embodiment, the timing control module includes resistor R80, capacitor C29, operational amplifier U7B, resistors R81 and R83, transistors Q9 and Q10, and resistor R76. The INV INPUT pin of the inverter chip is connected to the output of operational amplifier U7B through resistor R80. Resistor R80 and the INV INPUT pin of the inverter chip are also grounded through capacitor C29. The inverting input of operational amplifier U7B is connected to a reference voltage through resistor R79, and the non-inverting input of operational amplifier U7B is connected to the base of transistor Q9, the emitter of transistor Q10, and the N1 pin of the inverter chip through resistor R81. The INPUT pin connects the base of transistor Q10 to the comparator output pin of the inverter chip via resistor R76. The emitter of transistor Q10 is connected to the power supply, the emitter of transistor Q9 is connected to the reference voltage, and the collector of transistor Q9 is connected to the FB pin of the SEPIC controller. Resistor R83 is connected between the INPUT pin of the inverter chip and resistor R81.

[0014] Among them, transistor Q9 is a PNP transistor, and transistor Q10 is an NPN transistor.

[0015] As a preferred embodiment, the resistor R83 is also connected to the reference voltage via resistor R82 between the inverter chip and the NI INPUT pin.

[0016] As a preferred embodiment, the DC voltage feedback branch includes a rectifier bridge, an operational amplifier U7A, and a resistor R73. The input of the rectifier bridge is connected to the secondary coil of the high-frequency transformer, the output of the rectifier bridge is connected to the non-inverting input of the operational amplifier U7A, the inverting input of the operational amplifier U7A is connected to the reference voltage through a resistor R71, and the output of the operational amplifier U7A is connected to the FB pin of the SEPIC controller through a resistor R73.

[0017] As a preferred embodiment, the output A of the inverter chip is connected to the gate of the field-effect transistor Q8 through a resistor R74, the source of the field-effect transistor Q8 is grounded, and the drain of the field-effect transistor Q8 is connected to the primary coil of the high-frequency transformer.

[0018] The output B of the inverter chip is connected to the gate of the field-effect transistor Q7 through resistor R69. The source of the field-effect transistor Q7 is grounded, and the drain of the field-effect transistor Q7 is connected to the primary coil of the high-frequency transformer.

[0019] The present invention also provides a gas analyzer, including a light source and a detector, wherein the light source is driven by a light source driving circuit as described in any of the above embodiments.

[0020] As a preferred embodiment, the current signal collected by the detector is converted into a voltage signal by a high-frequency logarithmic amplifier.

[0021] Compared with the prior art, the beneficial effects of this invention are:

[0022] The light source driving circuit of the present invention adopts an automatic intermittent driving light source, which can greatly extend the life of the light source and eliminate the need for MCU control.

[0023] The gas analyzer of the present invention uses a light source driving circuit to drive the light source, which is stable and helps to improve detection accuracy. Moreover, its detector is equipped with a high-frequency logarithmic amplifier, which can improve the detection range without affecting the signal quality, thereby improving the detection limit. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the light source driving circuit according to an embodiment of the present invention;

[0025] Figure 2 This is a circuit diagram of the driving module according to an embodiment of the present invention;

[0026] Figure 3 This is a circuit diagram of the DC voltage feedback control module according to an embodiment of the present invention;

[0027] Figure 4 This is a circuit diagram of the timing control module according to an embodiment of the present invention;

[0028] Figure 5 This is a circuit diagram of a detector configured with a high-frequency logarithmic amplifier according to an embodiment of the present invention;

[0029] Figure 6 This is a configuration diagram of the detection end of the gas analyzer according to an embodiment of the present invention. Detailed Implementation

[0030] To more clearly illustrate the embodiments of the present invention, specific implementation methods will be described below with reference to the accompanying drawings. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings and other implementation methods can be obtained based on these drawings without any creative effort.

[0031] The light source driving circuit of this invention will be described in detail using the driving of a zinc lamp as an example.

[0032] like Figure 1 As shown, the light source driving circuit of this embodiment includes a driving module, a DC voltage feedback control module, and a timing control module.

[0033] Specifically, the drive module includes an inverter chip and a high-frequency transformer. The inverter chip's outputs A and B are square waves with a 180° phase difference, used to drive the high-frequency transformer to convert the DC voltage signal into an AC square wave signal, which synchronously drives the zinc lamp with the drive voltage of the high-frequency transformer's primary coil. The DC voltage feedback control module adjusts the drive voltage of the high-frequency transformer's primary coil based on the DC voltage feedback from the rectified AC square wave signal. The timing control module generates on / off signals through timing control to control the intermittently driven zinc lamp light source.

[0034] like Figure 2 As shown, the inverter chip U6 is model SG2525AP. Its CT pin is grounded to GND through capacitor C28, its DISCHARGE pin is grounded to GND through resistor R62 and capacitor C28 in sequence, its SOFT-START pin is grounded through capacitor C27, its RT pin is grounded through resistor R66, its VREF pin is connected to the reference voltage VREF, its +VI pin and VC pin are connected to the power supply VCC, and its GROUND pin and SHUTDOWN pin are grounded.

[0035] The A output of inverter chip U6 is connected to the gate of MOSFET Q8 via resistor R74. The source of MOSFET Q8 is grounded, and the drain of MOSFET Q8 is connected to the primary coil of the high-frequency transformer. Conversely, the B output of inverter chip U6 is connected to the gate of MOSFET Q7 via resistor R69. The source of MOSFET Q7 is grounded, and the drain of MOSFET Q7 is connected to the primary coil of the high-frequency transformer. This outputs a square wave with a 180° phase difference to drive the high-frequency transformer, converting the DC voltage signal into an AC square wave signal, thereby driving zinc lamp J3. Resistors R69 and R74 are used to ensure the integrity of the drive signal when driving the MOSFETs.

[0036] like Figure 3 As shown, the DC voltage feedback control module includes a SEPIC switching power supply topology and a DC voltage feedback branch. The SEPIC switching power supply topology adjusts the DC voltage output according to the DC voltage feedback from the DC voltage feedback branch, so as to adjust the drive voltage of the primary coil of the high-frequency transformer.

[0037] Specifically, the SEPIC switching power supply topology includes a SEPIC controller U5, inductor L3, MOSFET Q6, capacitor C25, inductor L4, and diode D10, wherein the SEPIC controller U5 is model LTC1871EMS-7. The advantage of the SEPIC switching power supply topology in this embodiment of the invention is that it can achieve step-up and step-down voltage adjustments, facilitating the adjustment of the drive voltage for the high-frequency transformer.

[0038] The RUN pin of the SEPIC controller U5 is connected to the power supply VCC. The ITH pin of the SEPIC controller U5 is grounded to GND through resistor R31 and capacitor C26 in sequence. The FREQ pin of the SEPIC controller U5 is grounded to GND through resistor R64. The INTVCC pin of the SEPIC controller U5 is shorted to the MODE / SYNC pin. The GND pin of the SEPIC controller U5 is grounded.

[0039] One end of inductor L3 is connected to the power supply VCC and the VIN pin of the SEPIC controller U5, and the other end is connected to capacitor C25 and the drain of MOSFET Q6. The gate of MOSFET Q6 is connected to the GATE pin of SEPIC controller U5 through resistor R40, and the source of MOSFET Q6 is connected to the SENSE pin of SEPIC controller U5 and grounded through resistor R67. The other end of capacitor C25 is connected to the anode of diode D10 and grounded through inductor L4. The cathode of diode D10 is connected to the DC voltage output terminal (referred to as DC voltage output) and is used to output DC voltage to the primary coil of the high-frequency transformer.

[0040] The MOSFET Q6 is model IRFR3410TRPBF. Resistor R67 is a current sampling resistor used to protect Q6; resistor R64 is a frequency setting resistor.

[0041] In addition, the DC voltage output terminal is grounded through the polarized capacitor CE4. The polarized capacitor CE4 is connected in parallel with the series resistors R63 and R65. Resistor R63 is connected to the DC voltage output terminal. Resistor R63 and resistor R65 are connected to the FB pin of the SEPIC type controller. Resistor R65 is grounded.

[0042] like Figure 4 As shown, the timing control module includes resistor R80, capacitor C29, operational amplifier U7B, resistors R81 and R83, transistors Q9 and Q10, and resistor R76. The INV INPUT pin of inverter chip U6 is connected to the output of operational amplifier U7B through resistor R80. Resistor R80 and the INV INPUT pin of inverter chip U6 are also grounded through capacitor C29. The inverting input of operational amplifier U7B is connected to the reference voltage VREF through resistor R79, and the non-inverting input of operational amplifier U7B is connected to the base of transistor Q9, the emitter of transistor Q10, and the N1 pin of inverter chip U7B through resistor R81. The INPUT pin connects the base of transistor Q10 to the comparator output pin (COMP pin) of the inverter chip via resistor R76. The emitter of transistor Q10 is connected to the power supply. The emitter of transistor Q9 is connected to the reference voltage VREF. The collector of transistor Q9 is connected to the FB pin of the SEPIC controller. The emitter and base of transistor Q9 are connected via resistor R75. Additionally, resistor R78 connects the base of transistor Q9 to resistor R81, and resistor R83 connects the NI INPUT pin of the inverter chip to resistor R81. Resistor R83 is grounded (GND) via resistor R85.

[0043] Among them, resistor R83 is connected to the reference voltage via resistor R82 between it and the NI INPUT pin of the inverter chip; resistor R82 is used to provide an initial voltage for the non-inverting input to ensure that the circuit can operate normally when it is first powered on.

[0044] In this embodiment of the invention, transistor Q9 is a PNP transistor and transistor Q10 is an NPN transistor.

[0045] The DC voltage feedback branch of this embodiment includes a rectifier bridge, an operational amplifier U7A, and a resistor R73. The rectifier bridge is composed of diodes D11, D12, D13, and D14. The input of the rectifier bridge is connected to the secondary coil of the high-frequency transformer, and the output of the rectifier bridge is connected to the non-inverting input of the operational amplifier U7A. The inverting input of the operational amplifier U7A is connected to a reference voltage through resistor R71, and the output of the operational amplifier U7A is connected to the FB pin of the SEPIC controller through resistor R73. The rectifier bridge is grounded through resistor R68. The rectifier bridge rectifies the AC signal driving the zinc lamp into a DC voltage, thereby controlling the DC voltage driving the primary coil of the high-frequency transformer and ensuring the stability of the zinc lamp output.

[0046] The aforementioned op-amps U7A and U7B are model numbers LM258DR.

[0047] The principle of intermittent driving in the light source driving circuit of this invention is as follows:

[0048] When the initial state of the non-inverting input is low, transistor Q9 is turned on, and the control DC voltage circuit (i.e., the SEPIC switching power supply topology) is turned off. Simultaneously, the voltage of the non-inverting input is amplified by operational amplifier U7B, and then, after being delayed by resistor R80 and capacitor C29, the voltage of the inverting input slowly decreases. The delay time is determined by the values ​​of resistor R80 and capacitor C29. When the voltage of the inverting input drops to a level lower than that of the non-inverting input, the comparator output goes high, the inverter chip stops working, the voltage of the non-inverting input immediately becomes high, transistor Q9 is turned off, and the control DC voltage circuit (i.e., the SEPIC switching power supply topology) is shut down. When the C-type switching power supply topology is turned on, the voltage value of the primary coil of the high-frequency transformer T6 is controlled by acquiring the current signal of the zinc lamp to maintain the stable operation of the zinc lamp. At the same time, the voltage input in the same direction is amplified by the operational amplifier U7B, and then the voltage input in the reverse direction is slowly increased after being delayed by resistor R80 and capacitor C29. The delay time is determined by the values ​​of resistor R80 and capacitor C29. When the voltage input in the reverse direction rises to a higher value than the voltage input in the same direction, the comparator output is pulled low, and the inverter chip starts to work. This cycle is repeated to form a period. The time when the zinc lamp is on and off is determined by the values ​​of resistor R80 and capacitor C29.

[0049] like Figure 5 and 6 As shown, the gas analyzer of this embodiment includes a light source, a detector, a high-frequency logarithmic amplifier, and an ADC for acquisition. The light source is driven by the aforementioned light source driving circuit, and the current signal IN acquired by the detector is converted into a voltage signal V by the high-frequency logarithmic amplifier. out The data is acquired via an ADC for subsequent data processing to obtain the gas concentration. For the specific structure of the aforementioned high-frequency logarithmic amplifier, please refer to [link to relevant documentation]. Figure 5 This will not be elaborated upon here, but existing technologies may be consulted.

[0050] The transformation formula for the high-frequency logarithmic amplifier is: V out =150mV*log(IN)+1.23V.

[0051] The detector in this embodiment of the invention, when paired with a high-frequency logarithmic amplifier, can improve the detection range and thus the detection limit without affecting signal quality.

[0052] The light source driving circuit described in this embodiment of the invention can also be applied to the driving of other types of light sources according to actual needs, thereby being applied to gas analyzers for different gas detection.

[0053] The above description is merely a detailed explanation of preferred embodiments and principles of the present invention. For those skilled in the art, there may be changes in specific implementation methods based on the ideas provided by the present invention, and these changes should also be considered within the scope of protection of the present invention.

Claims

1. A light source driving circuit, characterized by comprising: The application relates to a driving module, a direct-current voltage feedback control module and a time sequence control module. The driving module comprises an inverter chip and a high-frequency transformer, the output A and the output B of the inverter chip are square waves with a phase difference of 180 degrees, and the high-frequency transformer is used for converting a direct-current voltage signal into an alternating square wave signal. The direct-current voltage feedback control module is used for adjusting the driving voltage of the primary coil of the high-frequency transformer according to the rectified direct-current voltage feedback of the alternating square wave signal and synchronously driving the light source with the alternating square wave signal. The time sequence control module is used for generating an opening or closing signal through time sequence control to control the intermittent driving of the light source. The direct-current voltage feedback control module comprises a SEPIC switching power supply topology and a direct-current voltage feedback branch, the SEPIC switching power supply topology adjusts the direct-current voltage output according to the direct-current voltage feedback of the direct-current voltage feedback branch to adjust the driving voltage of the primary coil of the high-frequency transformer. The SEPIC switching power supply topology comprises a SEPIC controller, an inductor L3, a field effect tube Q6, a capacitor C25, an inductor L4 and a diode D10, the RUN pin of the SEPIC controller is connected to a power supply; one end of the inductor L3 is connected to the power supply and the VIN pin of the SEPIC controller, and the other end is connected to the capacitor C25 and the drain of the field effect tube Q6; the gate of the field effect tube Q6 is connected to the GATE pin of the SEPIC controller through the resistor R40, the source of the field effect tube Q6 is connected to the SENSE pin of the SEPIC controller and grounded through the resistor R67; the other end of the capacitor C25 is connected to the positive pole of the diode D10 and grounded through the inductor L4; and the negative pole of the diode D10 is connected to a direct-current voltage output end for outputting the direct-current voltage to the primary coil of the high-frequency transformer. The direct-current voltage output end is grounded through a polarity capacitor CE4, the polarity capacitor CE4 is connected in parallel with the series connection of a resistor R63 and a resistor R65, the resistor R63 is connected to the direct-current voltage output end, and the resistor R65 is connected to the FB pin of the SEPIC controller. The time sequence control module comprises a resistor R80, a capacitor C29, an operational amplifier U7B, a resistor R81, a resistor R83, a triode Q9, a triode Q10 and a resistor R76, the INV INPUT pin of the inverter chip is connected to the output end of the operational amplifier U7B through the resistor R80, the resistor R80 and the INV INPUT pin of the inverter chip are further grounded through the capacitor C29, the reverse input end of the operational amplifier U7B is connected to a reference voltage through the resistor R79, the same direction input end of the operational amplifier U7B is connected to the base of the triode Q9, the emitter of the triode Q10 and the NI INPUT pin of the inverter chip through the resistor R81, the base of the triode Q10 is connected to the comparator output pin of the inverter chip through the resistor R76, the emitter of the triode Q10 is connected to a power supply, the emitter of the triode Q9 is connected to a reference voltage, the collector of the triode Q9 is connected to the FB pin of the SEPIC controller, and the resistor R83 is connected between the NI INPUT pin of the inverter chip and the resistor R81. The triode Q9 is a PNP triode, and the triode Q10 is an NPN triode.

2. A light source driving circuit according to claim 1, characterized in that The resistance R83 is also connected to the reference voltage through the resistance R82 between the NI INPUT pin of the inverter chip.

3. A light source driving circuit according to any one of claims 1-2, characterized in that, The direct current voltage feedback branch includes a rectifier bridge, an operational amplifier U7A and a resistance R73, the input of the rectifier bridge is connected to the secondary coil of the high-frequency transformer, the output of the rectifier bridge is connected to the same input end of the operational amplifier U7A, the opposite input end of the operational amplifier U7A is connected to the reference voltage through the resistance R71, and the output end of the operational amplifier U7A is connected to the FB pin of the SEPIC type controller through the resistance R73.

4. A light source driving circuit according to any one of claims 1-2, characterized in that The output A of the inverter chip is connected to the gate connection of the field effect transistor Q8 through the resistance R74, the source of the field effect transistor Q8 is grounded, and the drain of the field effect transistor Q8 is connected to the primary coil of the high-frequency transformer. The output B of the inverter chip is connected to the gate connection of the field effect transistor Q7 through the resistance R69, the source of the field effect transistor Q7 is grounded, and the drain of the field effect transistor Q7 is connected to the primary coil of the high-frequency transformer.

5. A gas analyser comprising a light source and a detector, characterised in that, The light source is driven by the light source driving circuit according to any one of claims 1-4.

6. A gas analyzer according to claim 5, characterized in that The current signal collected by the detector is converted into a voltage signal by a high-frequency logarithmic amplifier.

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