Driving and high-voltage biasing circuit applied to photoionization detector

Abstract

The invention discloses a driving and high-voltage biasing circuit applied to a photoionization detector, and relates to the field of photoionization detectors, and the circuit comprises a DC-DC chip, a transformer, an NMOS tube, a feedback loop and a rectification filter circuit. A pin 5 of the DC-DC chip is connected with the feedback loop, a pin 6 of the DC-DC chip is respectively connected with an S pole of the NMOS tube and the ground, a pin 8 of the DC-DC chip is connected with a G pole of the NMOS tube, a pin 9 of the DC-DC chip and a pin 1 of the transformer are both connected with the power supply, and a pin 10 of the DC-DC chip is connected with the single-chip microcomputer; the D pole of the NMOS tube is respectively connected with the pin 3 and the pin 4 of the transformer; a pin 6 of the transformer is connected with the rectification filter circuit. The feedback loop is also connected with the rectification filter circuit. The high-voltage bias electric field can be applied to the electrodes while the UV lamp can be efficiently driven, and the light intensity of the UV lamp is adjustable.

Description

Technical Field

[0001] The present application relates to the field of photoionization detectors, and in particular to a driving and high-voltage bias circuit applied to photoionization detectors. Background Art

[0002] For a photoionization detector to work properly, two necessary conditions are required. First, a certain high voltage is required to excite the ultraviolet (UV) lamp so that the UV lamp can emit photoions to ionize volatile organic compounds (VOC) gases; second, a certain high voltage bias electric field is required on the electrode to make the target gas ions form a signal current.

[0003] The current photoionization detector can only detect low-concentration VOC gas or very high-concentration VOC gas, and cannot be well compatible with high and low concentration full-range detection. The measurement of high and low concentration gases is achieved by adjusting the light intensity of the vacuum UV lamp. The current existing circuits have fixed driving currents and cannot adjust the UV light intensity. In addition, the existing UV lamp driving circuit needs to apply an additional square wave as an oscillation switch to drive the transformer to oscillate and boost, which occupies microcontroller resources and is inefficient.

[0004] In addition, the existing high-voltage bias circuit is a boost circuit with a very simple function, which requires a switch control circuit, which is complex to control and inefficient; or it is simply driven by a DC-DC chip and a transformer, and more peripheral components are added just for the bias electric field, resulting in a complex circuit structure. Summary of the invention

[0005] The purpose of the present application is to provide a driving and high-voltage bias circuit for a photoionization detector, which can efficiently drive a UV lamp while applying a high-voltage bias electric field to an electrode, and the UV lamp light intensity is adjustable.

[0006] To achieve the above-mentioned purpose, the present application provides a driving and high-voltage bias circuit for a photoionization detector, comprising: a DC-DC chip, a transformer, an NMOS tube, a feedback loop and a rectifier and filter circuit; pin 5 of the DC-DC chip is connected to the feedback loop, pin 6 of the DC-DC chip is respectively connected to the S pole and the ground of the NMOS tube, pin 8 of the DC-DC chip is connected to the G pole of the NMOS tube, pin 9 of the DC-DC chip and pin 1 of the transformer are both connected to a power supply, and pin 10 of the DC-DC chip is connected to a single-chip microcomputer; the D pole of the NMOS tube is respectively connected to pin 3 of the transformer and pin 4 of the transformer; pin 6 of the transformer is connected to the rectifier and filter circuit, and the feedback loop is also connected to the rectifier and filter circuit.

[0007] Optionally, the feedback loop includes a resistor R5, a digital potentiometer and a resistor R8; one end of the resistor R5 is connected to the rectifier and filter circuit, the other end of the resistor R5 is connected to one end of the ultraviolet lamp, the pin 7 of the digital potentiometer is respectively connected to the pin 5 of the DC-DC chip and the other end of the ultraviolet lamp, and the pin 2 of the digital potentiometer is connected to the power supply; one end of the resistor R8 is respectively connected to the pin 1 of the digital potentiometer and the pin 8 of the digital potentiometer, and the other end of the resistor R8 is grounded.

[0008] Optionally, the rectifier and filter circuit includes a diode D1, a capacitor C5 and a capacitor C6; the positive electrode of the diode D1 is connected to the pin 6 of the transformer, the negative electrode of the diode D1 is respectively connected to one end of the resistor R5, one end of the capacitor C5 and one end of the capacitor C6, and the other end of the capacitor C5 and the other end of the capacitor C6 are both grounded.

[0009] Optionally, the driving and high-voltage bias circuit also includes: capacitor C2, capacitor C4 and capacitor C3, and the capacitor C2, capacitor C4 and capacitor C3 are all bypass capacitors of the DC-DC chip; one end of the capacitor C2 is connected to pin 9 of the DC-DC chip, and the other end of the capacitor C2 is grounded; one end of the capacitor C4 is connected to pin 4 of the DC-DC chip, and the other end of the capacitor C4 is grounded; one end of the capacitor C3 is connected to pin 1 of the DC-DC chip, and the other end of the capacitor C3 is grounded.

[0010] Optionally, the driving and high-voltage bias circuit further includes: a resistor R2, one end of the resistor R2 is connected to the pin 2 of the DC-DC chip, and the other end of the resistor R2 is grounded.

[0011] Optionally, the driving and high-voltage bias circuit also includes: a capacitor C7, which is a bypass capacitor of the digital potentiometer; one end of the capacitor C7 is connected to pin 2 of the digital potentiometer, and the other end of the capacitor C7 is respectively connected to pin 3 of the digital potentiometer and ground.

[0012] Optionally, the driving and high-voltage bias circuit further includes: a resistor R1, one end of the resistor R1 is connected to the single-chip microcomputer, and the other end of the resistor R1 is connected to a pin 10 of the DC-DC chip.

[0013] Optionally, the driving and high-voltage bias circuit further includes: a capacitor C1, one end of the capacitor C1 is grounded, and the other end of the capacitor C1 is connected to the pin 1 of the transformer.

[0014] Optionally, the driving and high-voltage bias circuit also includes: a resistor R3 and a resistor R4; one end of the resistor R3 is respectively connected to pin 6 of the DC-DC chip, the S pole of the NMOS tube and one end of the resistor R4, and the other end of the resistor R3 and the other end of the resistor R4 are both grounded.

[0015] Optionally, the driving and high-voltage bias circuit further includes: a resistor R6, one end of the resistor R6 is connected to the pin 5 of the DC-DC chip, and the other end of the resistor R6 is connected to the pin 7 of the digital potentiometer.

[0016] According to the specific embodiments provided by the present application, the present application has the following technical effects: the present application provides a driving and high-voltage bias circuit for a photoionization detector, including: a DC-DC chip, a transformer, an NMOS tube, a feedback loop, and a rectifier filter circuit; the current passing through the UV lamp can be adjusted through the feedback loop, and at the same time, the high voltage rectified by the rectifier filter circuit is supplied to the electrode sheet to form a high-voltage bias electric field. The circuit provided by the present application can apply a high-voltage bias electric field to the electrode while driving the UV lamp. The circuit structure is simple, which not only improves efficiency but also reduces costs. At the same time, the light intensity can be adjusted by adjusting the current of the UV lamp, so that the gas signal is always within the sampling range, thereby measuring VOC gases of different concentrations. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 A schematic diagram of the structure of a driving and high-voltage bias circuit applied to a photoionization detector provided in one embodiment of the present application. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0020] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0021] In an exemplary embodiment, Figure 1 As shown, a driving and high-voltage bias circuit for a photoionization detector is provided, including: a DC-DC chip U1, a transformer T1, an NMOS tube Q1, a feedback loop and a rectifier filter circuit.

[0022] Pin 5 of the DC-DC chip U1 is connected to the feedback loop, pin 6 of the DC-DC chip U1 is respectively connected to the S pole of the NMOS tube Q1 and the ground, pin 8 of the DC-DC chip U1 is connected to the G pole of the NMOS tube Q1, pin 9 of the DC-DC chip U1 and pin 1 of the transformer T1 are both connected to the power supply, and pin 10 of the DC-DC chip U1 is connected to the single-chip microcomputer; the D pole of the NMOS tube Q1 is respectively connected to pin 3 of the transformer T1 and pin 4 of the transformer T1; pin 6 of the transformer T1 is connected to the rectifier and filter circuit, and the feedback loop is also connected to the rectifier and filter circuit.

[0023] The NMOS tube Q1 is an external NMOS tube, and its G pole is connected to the DC-DC chip U1. An oscillation signal is generated through pin 8 of the DC-DC chip U1 to switch the D pole and the S pole of the NMOS tube Q1, thereby causing the transformer T1 to oscillate.

[0024] In a specific embodiment, Figure 1 As shown, the feedback loop includes a resistor R5, a digital potentiometer U2, and a resistor R8. One end of the resistor R5 is connected to the rectifier filter circuit, the other end of the resistor R5 is connected to one end of the ultraviolet lamp, the pin 7 of the digital potentiometer U2 is respectively connected to the pin 5 of the DC-DC chip U1 and the other end of the ultraviolet lamp, and the pin 2 of the digital potentiometer U2 is connected to the power supply; one end of the resistor R8 is respectively connected to the pin 1 of the digital potentiometer U2 and the pin 8 of the digital potentiometer U2, and the other end of the resistor R8 is grounded.

[0025] Resistor R8 and digital potentiometer U2's R BW (The resistance of the B terminal and the W terminal of U2) is connected in series to form the lower limit resistance in the feedback loop. BW When adjusted to the minimum, the resistor R8 can prevent the lower limit resistor from being grounded, that is, the lower limit resistor in the feedback loop can be adjusted by the digital potentiometer U2, thereby adjusting the current I through the UV lamp. UV , the formula is: UV =V FB / (R BW +R8), V FB is the feedback voltage of pin 5 of U1. Resistor R9 is the address selection resistor of digital potentiometer U2.

[0026] In a specific embodiment, Figure 1As shown, the rectifier filter circuit includes a diode D1, a capacitor C5 and a capacitor C6. The anode of the diode D1 is connected to the pin 6 of the transformer T1, the cathode of the diode D1 is connected to one end of the resistor R5, one end of the capacitor C5 and one end of the capacitor C6 respectively, and the other end of the capacitor C5 and the other end of the capacitor C6 are both grounded.

[0027] The high voltage rectified by the rectifying and filtering circuit is supplied to the electrode sheet through the current limiting resistor R7 to form a high voltage bias electric field.

[0028] In a specific embodiment, Figure 1 As shown, capacitors C2, C4 and C3 are bypass capacitors of the DC-DC chip U1; capacitor C7 is a bypass capacitor of the digital potentiometer U2; capacitor C1 is an energy storage capacitor with an input voltage of 5V, and can also filter the input voltage of the transformer T1.

[0029] One end of capacitor C2 is connected to pin 9 of DC-DC chip U1, and the other end of capacitor C2 is grounded; one end of capacitor C4 is connected to pin 4 of DC-DC chip U1, and the other end of capacitor C4 is grounded; one end of capacitor C3 is connected to pin 1 of DC-DC chip U1, and the other end of capacitor C3 is grounded.

[0030] One end of the capacitor C7 is connected to the pin 2 of the digital potentiometer U2, and the other end of the capacitor C7 is connected to the pin 3 of the digital potentiometer U2 and the ground respectively.

[0031] One end of the capacitor C1 is grounded, and the other end of the capacitor C1 is connected to the pin 1 of the transformer T1.

[0032] In a specific embodiment, Figure 1 As shown, the driving and high-voltage bias circuit further includes: a resistor R2, a resistor R1, a resistor R3, a resistor R4, and a resistor R6.

[0033] One end of the resistor R2 is connected to pin 2 of the DC-DC chip U1, and the other end of the resistor R2 is grounded. The resistor R2 can adjust the oscillation frequency f of the DC-DC chip U1, and the formula is f=5×10 10 / R2, usually f is 100KHz~500KHz.

[0034] One end of the resistor R1 is connected to the single chip microcomputer, and the other end of the resistor R1 is connected to the pin 10 of the DC-DC chip U1. The resistor R1 is a current limiting resistor connecting the single chip microcomputer and the DC-DC chip U1, and is used to control the opening and closing of the DC-DC chip U1.

[0035] One end of the resistor R3 is connected to the pin 6 of the DC-DC chip U1, the S pole of the NMOS tube Q1 and one end of the resistor R4, and the other end of the resistor R3 and the other end of the resistor R4 are both grounded. The resistors R3 and R4 can adjust the output current of the transformer T1.

[0036] One end of the resistor R6 is connected to pin 5 of the DC-DC chip U1, and the other end of the resistor R6 is connected to pin 7 of the digital potentiometer U2. R6 is a current limiting resistor in the feedback loop to prevent high voltage from impacting the DC-DC chip U1.

[0037] The detailed working process of the driving and high-voltage bias circuit applied to the photoionization detector provided in the present application is as follows: First, the power supply is turned on, and the single-chip microcomputer controls pin 10 of the DC-DC chip U1, so that U1 starts to work. U1 controls the NMOS tube Q1 to switch through the oscillation output of pin 8, so that the transformer T1 starts to oscillate, and the oscillating high voltage is output through pin 6 of T1, and then rectified and filtered by diode D1, capacitors C5 and C6 to obtain a stable DC high voltage. This DC high voltage can provide a high-voltage bias electric field to the electrode. At the same time, this DC high voltage passes through resistor R5, UV lamp, digital potentiometer U2, resistor R8 and resistor R6, and the feedback loop forms a closed loop with the DC-DC chip U1. Here, the UV lamp is connected in series in the feedback loop, so it can drive the UV lamp to light up, and the current of the entire feedback loop can be adjusted by adjusting the resistance of the digital potentiometer U2 through the single-chip microcomputer. The current of this feedback loop is also the current of the UV lamp, thereby adjusting the light intensity of the UV lamp.

[0038] By means of the driving and high-voltage bias circuit applied to the photoionization detector provided by the present application, it is possible to simultaneously drive the UV lamp and apply a high-voltage bias electric field to the electrode, which not only improves efficiency but also reduces costs. At the same time, the current of the UV lamp can be adjusted to adjust the light intensity so that the gas signal is always within the sampling range, thereby measuring VOC gases of different concentrations. For example, the light intensity of the UV lamp of this circuit is set to 0.8 mA when it leaves the factory. This light intensity corresponds to a VOC gas curve of several hundred ppm. When encountering a relatively small concentration (below 100 ppm) of VOC gas, the signal induced by the light intensity of 0.8 mA is relatively small, and the accuracy is not achieved. At this time, the UV lamp current is adjusted to 1 mA. This light intensity corresponds to a VOC gas curve of less than 100 ppm, and the signal will also increase accordingly, falling within a reasonable sampling interval. Similarly, when encountering a relatively large concentration (several thousand ppm) of VOC gas, the UV lamp current is adjusted to 0.6 mA. This light intensity corresponds to a VOC gas curve of several thousand ppm. At this time, the gas signal will become smaller, thereby being able to measure a wider range of VOC gas concentrations.

[0039] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0040] This article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and core ideas of this application. At the same time, for those skilled in the art, according to the ideas of this application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. A driving and high voltage bias circuit for a photoionization detector, characterized in that: include: DC-DC chip, transformer, NMOS tube, feedback loop and rectifier filter circuit; Pin 5 of the DC-DC chip is connected to the feedback loop, pin 6 of the DC-DC chip is respectively connected to the S pole and the ground of the NMOS tube, pin 8 of the DC-DC chip is connected to the G pole of the NMOS tube, pin 9 of the DC-DC chip and pin 1 of the transformer are both connected to the power supply, and pin 10 of the DC-DC chip is connected to the single-chip microcomputer; The D pole of the NMOS tube is connected to the pin 3 of the transformer and the pin 4 of the transformer respectively; the pin 6 of the transformer is connected to the rectifier and filter circuit, and the feedback loop is also connected to the rectifier and filter circuit.

2. The driving and high voltage bias circuit for a photoionization detector according to claim 1, characterized in that: The feedback loop includes a resistor R5, a digital potentiometer and a resistor R8; One end of the resistor R5 is connected to the rectifier and filter circuit, the other end of the resistor R5 is connected to one end of the ultraviolet lamp, the pin 7 of the digital potentiometer is respectively connected to the pin 5 of the DC-DC chip and the other end of the ultraviolet lamp, and the pin 2 of the digital potentiometer is connected to the power supply; one end of the resistor R8 is respectively connected to the pin 1 of the digital potentiometer and the pin 8 of the digital potentiometer, and the other end of the resistor R8 is grounded.

3. The driving and high voltage bias circuit for a photoionization detector according to claim 2, characterized in that: The rectification and filtering circuit includes a diode D1, a capacitor C5 and a capacitor C6; The anode of the diode D1 is connected to the pin 6 of the transformer, the cathode of the diode D1 is respectively connected to one end of the resistor R5, one end of the capacitor C5 and one end of the capacitor C6, and the other end of the capacitor C5 and the other end of the capacitor C6 are both grounded.

4. The driving and high voltage bias circuit for a photoionization detector according to claim 1, characterized in that: The driving and high-voltage bias circuit further includes: a capacitor C2, a capacitor C4 and a capacitor C3, wherein the capacitor C2, the capacitor C4 and the capacitor C3 are all bypass capacitors of the DC-DC chip; One end of the capacitor C2 is connected to the pin 9 of the DC-DC chip, and the other end of the capacitor C2 is grounded; One end of the capacitor C4 is connected to the pin 4 of the DC-DC chip, and the other end of the capacitor C4 is grounded; One end of the capacitor C3 is connected to the pin 1 of the DC-DC chip, and the other end of the capacitor C3 is grounded.

5. The driving and high voltage bias circuit for a photoionization detector according to claim 1, characterized in that: The driving and high-voltage bias circuit further includes: a resistor R2, one end of the resistor R2 is connected to the pin 2 of the DC-DC chip, and the other end of the resistor R2 is grounded.

6. The driving and high voltage bias circuit for a photoionization detector according to claim 2, characterized in that: The driving and high-voltage bias circuit further includes: a capacitor C7, which is a bypass capacitor of the digital potentiometer; One end of the capacitor C7 is connected to the pin 2 of the digital potentiometer, and the other end of the capacitor C7 is connected to the pin 3 of the digital potentiometer and the ground respectively.

7. The driving and high voltage bias circuit for a photoionization detector according to claim 1, characterized in that: The driving and high-voltage bias circuit further includes: a resistor R1, one end of the resistor R1 is connected to the single-chip microcomputer, and the other end of the resistor R1 is connected to the pin 10 of the DC-DC chip.

8. The driving and high voltage bias circuit for a photoionization detector according to claim 1, characterized in that: The driving and high-voltage bias circuit further includes: a capacitor C1 , one end of which is grounded, and the other end of which is connected to the pin 1 of the transformer.

9. The driving and high voltage bias circuit for a photoionization detector according to claim 1, characterized in that: The driving and high-voltage bias circuit also includes: a resistor R3 and a resistor R4; one end of the resistor R3 is respectively connected to the pin 6 of the DC-DC chip, the S pole of the NMOS tube and one end of the resistor R4, and the other end of the resistor R3 and the other end of the resistor R4 are both grounded.

10. The driving and high voltage bias circuit for a photoionization detector according to claim 2, characterized in that: The driving and high-voltage bias circuit further includes: a resistor R6, one end of the resistor R6 is connected to the pin 5 of the DC-DC chip, and the other end of the resistor R6 is connected to the pin 7 of the digital potentiometer.

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