Light source driving circuit of high-voltage gas particle counter

Abstract

A kind of light source driving circuit of high pressure gas particle counter, based on closed-loop negative feedback control system of operational amplifier, by real-time monitoring laser diode output optical power, dynamic adjustment driving current, realize the high stability control of light power.System core uses photodiode (PD) as the feedback of light illumination power, with high-precision operational amplifier to build error comparison and voltage regulation circuit, effectively suppresses the light power fluctuation caused by temperature drift, aging and other factors.Experiments show that, under normal use conditions, the system can improve the light power stability to within ±1%, significantly better than the traditional open-loop driving scheme, and has the advantages of fast response, low cost, easy integration.

Description

Technical Field

[0001] This utility model relates to laser diode optical power control technology, and in particular to a light source driving circuit for a high-pressure gas particle counter. Background Technology

[0002] High-pressure gas particle counters are widely used in environmental monitoring, electronics manufacturing, and biomedicine. HPGP (USA) uses a laser reference voltage, which is a measurement of the passive cavity laser power. Therefore, this voltage must be maintained at a certain level to ensure sufficient signal-to-noise ratio and accurate dimensional precision. When the actual laser voltage deviates from the reference voltage, dimensional accuracy cannot be guaranteed, requiring repair or even scrapping. Laser diodes (LDs), as the core light source of modern optoelectronic systems, directly affect system performance due to the stability of their output power. However, the inherent temperature sensitivity of laser diodes leads to a serious problem: under constant drive current, for every 1°C increase in junction temperature, the output optical power decreases by approximately 0.5% to 1.0% (typical value). This drift is particularly significant during long-term operation or when the ambient temperature changes, and the power decrease leads to reduced measurement accuracy and increased counting errors.

[0003] Existing traditional solutions include open-loop temperature compensation: predicting the amount of current compensation through temperature sensors (such as thermistors), but with limited compensation accuracy; active temperature control (TEC): using thermoelectric coolers to stabilize the LD temperature, but with high energy consumption, large size, and slow response; and constant power (APC) modules: integrating PD and driver ICs, but with low flexibility and high cost.

[0004] Therefore, there is an urgent need for a high-precision, fast-response, low-cost, and easily integrated optical power stabilization control scheme to solve the power fluctuation problem of laser diodes in complex environments. Utility Model Content

[0005] To address the issue of unstable optical power in existing laser diodes due to factors such as temperature drift and aging, this invention proposes a light source driving circuit for a high-pressure gas particle counter. Based on a discrete scheme using a general-purpose operational amplifier, it dynamically adjusts the laser diode's driving current by comparing the deviation between the target optical power and the actual optical power in real time through negative feedback. This design combines high precision, fast response, and low cost, making it suitable for laboratory equipment, industrial sensors, and small-to-medium power laser modules.

[0006] The technical solution of this utility model is as follows:

[0007] A light source driving circuit for a high-pressure gas particle counter is characterized by comprising a light power sampling unit, an I / V (current-voltage) conversion unit, a feedback adjustment unit, and a current adjustment unit connected in sequence to form a closed-loop negative feedback control system.

[0008] The optical power sampling unit includes a laser diode (LD) and its built-in photodiode (PD) for receiving laser output and generating a photocurrent proportional to the optical power.

[0009] The I / V conversion unit includes a transimpedance amplifier U3, whose inverting input terminal is connected to the anode of the PD via a wire, and whose forward input terminal is grounded together with the cathode of the PD; its output terminal is connected to the feedback adjustment unit via a wire, and together with the feedback network, they form an inverting proportional transimpedance amplifier to convert the photocurrent signal into a voltage signal.

[0010] The feedback adjustment unit includes an adjustable resistor R3 and a metal film resistor R4 connected between a -5V reference power supply and ground. By superimposing the PD voltage with a set voltage, the drive current of the laser diode is controlled through the current-limiting resistor.

[0011] The current regulation unit includes an adjustable voltage regulator U2 and R5 (5.1Ω). Its adjustment terminal is connected to the output terminal of U3 through a wire, and its output terminal is connected to the anode of LD through a wire via a current-limiting resistor R5. It is used to dynamically adjust the driving current of the laser diode according to the error control signal so that the optical power is stabilized at the set value.

[0012] Furthermore, the I / V conversion unit also includes a feedback resistor R1 and a compensation capacitor C1 connected in parallel between the inverting input terminal and the output terminal of the transimpedance amplifier U3, forming a transimpedance gain network with high-frequency noise suppression function.

[0013] Compared with the prior art, the present invention has the following technical effects:

[0014] 1. The laser diode optical power feedback adjustment system reduces the impact of temperature drift by more than 20 times and significantly improves anti-interference capability.

[0015] 2. The laser diode optical power feedback adjustment system can effectively ensure that the optical power is stably output at a certain value, thereby improving data accuracy and equipment durability. Attached Figure Description

[0016] Figure 1 This is the core circuit design diagram of the automatic adjustment system for stable control of laser diode optical power of this utility model. Detailed Implementation

[0017] The present invention will be further described below with reference to the accompanying drawings and embodiments, but this should not be construed as limiting the scope of protection of the present invention.

[0018] A light source driving circuit for a high-pressure gas particle counter includes an optical power sampling unit, an I / V conversion unit, a feedback adjustment unit, and a current adjustment unit. The optical power sampling unit includes a laser diode, resistors R3 (10kΩ) and R4 (2kΩ), and generates photocurrent using the laser diode's built-in photodiode (PD). The I / V conversion unit includes a transimpedance amplifier, resistor R1 (510kΩ), and capacitor C1 (10pF), and converts the photocurrent I into a voltage V(pd) using the transimpedance amplifier (TIA). The feedback adjustment unit controls the driving current of the laser diode by superimposing V(pd) with a set voltage V(ref) and passing it through a current-limiting resistor. The current adjustment unit includes an LM317 adjustable voltage regulator, capacitors C2 and C3, resistors R2 (1kΩ) and R5 (5.1Ω), and uses the laser diode to control the voltage, increasing / decreasing I until V(pd) = V(ref).

[0019] The working process of the light source driving circuit of the high-pressure gas particle counter of this invention is as follows:

[0020] The circuit uses an inverting proportional operational amplifier circuit built with U3. R3 (10kΩ adjustable) and R4 (2kΩ) form a voltage divider to provide the base voltage to the inverting input of U3. U3, as an inverting proportional op-amp, amplifies the input voltage in reverse through a feedback network of R1 (510kΩ) and C1 (10pF), ultimately outputting the corresponding positive voltage from pin 1. The PD generates current when irradiated by the laser power, flowing into the inverting input of U3. This current is then converted to a voltage signal by a transimpedance amplifier (utilizing the high impedance of the op-amp to convert the current signal into a voltage signal). If the laser diode power decreases, the PD current decreases, and the output voltage of U3 increases in the reverse direction. U2 (LM317 adjustable regulator) receives the output voltage signal from U3 and, combined with the feedback from R2 (1kΩ), adjusts the laser diode's supply current through a current-limiting resistor R5 (5.1Ω). When the output of U3 increases due to a decrease in laser power, the output voltage of U2 rises, providing a higher current to the laser diode to compensate for the power loss (the drive current changes accordingly, eventually bringing the laser power back to the preset value). During normal use, R3 is adjusted to a fixed optical power. When the PD stabilizes, the feedback current is adjusted, U3 outputs the corresponding voltage, and U2 provides a stable power supply to the laser diode. When the temperature rises, causing the optical power to decrease, the PD receives less light, resulting in a smaller current. This causes the voltage at the op-amp output to increase, leading to a higher output voltage. Consequently, the drive current supplying the laser diode through the current-limiting resistor R5 increases, and the optical power rises to the preset power.

[0021] like Figure 1As shown, the light source driving circuit of the high-pressure gas particle counter of this invention uses the PD built into the laser diode to generate photocurrent; the transimpedance amplifier (TIA) converts the photocurrent I into voltage V(pd); V(pd) is superimposed with the set voltage V(ref), and the driving current of the laser diode is controlled by the current limiting resistor; the laser diode is used to control the voltage, increasing / decreasing I until V(pd) = V(ref).

[0022] The circuit uses an inverting proportional operational amplifier circuit built with U3. R3 (10kΩ adjustable) and R4 (2kΩ) form a voltage divider to provide the base voltage to the inverting input (pin 4) of U3. U3, as an inverting proportional op-amp, amplifies the input voltage in reverse through a feedback network of R1 (510kΩ) and C1 (10pF), ultimately outputting the corresponding positive voltage from pin 1. The PD generates current when irradiated by the laser power, flowing into the inverting input of U3. This current is then converted to a voltage signal by a transimpedance amplifier (utilizing the high impedance of the op-amp to convert the current signal into a voltage signal). If the laser diode power decreases, the PD current decreases, and the output voltage of U3 increases in the reverse direction. U2 (LM317 adjustable regulator) receives the output voltage signal from U3 and, combined with the feedback from R2 (1kΩ), adjusts the laser diode's supply current through a current-limiting resistor R5 (5.1Ω). When the output of U3 increases due to a decrease in laser power, the output voltage of U2 rises, providing a higher current to the laser diode to compensate for the power loss (the drive current changes accordingly, eventually bringing the laser power back to the preset value). During normal use, R3 is adjusted to a fixed optical power. When the PD stabilizes, the feedback current is adjusted, U3 outputs the corresponding voltage, and U2 provides a stable power supply to the laser diode. When the temperature rises, causing the optical power to decrease, the PD receives less light, resulting in a smaller current. This causes the voltage U3 at the op-amp output to increase, leading to an increase in the output voltage of U2. Consequently, the voltage across the laser diode increases, and the drive current, controlled by the current-limiting resistor R5 (5.1Ω), increases, raising the optical power to the preset level.

Claims

1. A light source driving circuit for a high-pressure gas particle counter, characterized in that, It includes an optical power sampling unit, a current-to-voltage (I / V) conversion unit, a feedback regulation unit, and a current regulation unit connected in sequence, forming a closed-loop negative feedback control system; The optical power sampling unit includes a laser diode (LD) and its built-in photodiode (PD) for receiving laser output and generating a photocurrent proportional to the optical power; The I / V conversion unit includes a transimpedance amplifier U3, whose inverting input terminal is connected to the anode of the PD via a wire, and whose forward input terminal is grounded together with the cathode of the PD; its output terminal is connected to the feedback adjustment unit via a wire, and together with the feedback network, they form an inverting proportional transimpedance amplifier to convert the photocurrent signal into a voltage signal. The feedback adjustment unit includes an adjustable resistor R3 and a metal film resistor R4 connected between the -5V reference power supply and ground. By superimposing the PD voltage with the set voltage, the driving current of the laser diode is controlled through the current limiting resistor. The current regulation unit includes an adjustable voltage regulator U2 and R5 (5.1Ω). Its adjustment terminal is connected to the output terminal of U3 through a wire, and its output terminal is connected to the anode of LD through a wire via a current-limiting resistor R5. It is used to dynamically adjust the driving current of the laser diode according to the error control signal so that the optical power is stabilized at the set value.

2. The light source driving circuit for the high-pressure gas particle counter according to claim 1, characterized in that, The I / V conversion unit also includes a feedback resistor R1 and a compensation capacitor C1 connected in parallel between the inverting input terminal and the output terminal of the transimpedance amplifier U3, forming a transimpedance gain network with high-frequency noise suppression function.

Images