A semiconductor laser pulse driving circuit based on super capacitor

Abstract

The application discloses a kind of semiconductor laser pulse driving circuit based on super capacitor, belong to electronic circuit technical field.The circuit includes: at least one super capacitor, which is powered for vertical cavity surface emitting laser;Current control and sampling circuit controls the current flow and closes of vertical cavity surface emitting laser, while sampling and monitoring the discharge current of super capacitor through it, current control and sampling circuit and vertical cavity surface emitting laser and super capacitor are connected in series to form laser discharge loop;Charging circuit dynamically adjusts the voltage output by the sampling result of current sampling point, and then adjusts the voltage value of super capacitor.The application uses super capacitor to power vertical cavity surface emitting laser to realize millisecond level long pulse, large current driving current output, while using the duty cycle limit of practical application, reduce the average power requirement of circuit front-end power supply, and then reduce cost.

Description

Technical Field

[0001] This application relates to the field of electronic circuit technology, and in particular to a semiconductor laser pulse driving circuit based on a supercapacitor. Background Technology

[0002] High-power VCSEL (Vertical-Cavity Surface-Emitting Laser) chips, as a highly efficient and uniformly intense semiconductor laser source, are widely used in laser medical aesthetics, solid-state laser pumping, industrial heating, infrared illumination, and other fields. In laser medical aesthetics and other related fields, the operating state is limited to millisecond-level long pulses of 5-200ms, 1-10Hz, and a duty cycle ≤40%. Applications such as laser hair removal require high-power VCSEL chips to operate within these specified conditions.

[0003] To ensure stable optical power, semiconductor lasers are generally driven by constant current power supplies. Traditional constant current drive sources for semiconductor lasers mainly employ two methods: one directly maintains stable optical power through the principle of a constant current switching power supply, and the other uses MOSFET constant current modulation based on a constant voltage source to maintain stable optical power. For the first method, the output current of the power supply is sampled and fed back, and the output current is adjusted through a high-frequency switching circuit based on the feedback result, thereby achieving constant current output. For the second method, a high-power MOSFET is connected in series in the load circuit of the semiconductor laser, and the MOSFET is controlled to operate in the constant current region, thus achieving constant current power supply drive for the semiconductor laser.

[0004] In existing technologies, high-power VCSEL chips need to operate in long pulse states with pulse widths of 5-200ms. However, existing constant current source designs require the average power of the power supply to be no less than the peak power of the semiconductor laser load. Therefore, for long-pulse medical applications requiring low duty cycles, the driver power supply design has significant power redundancy, which also leads to unnecessary costs. Summary of the Invention

[0005] To address the issues of high power requirements and high duty cycles in existing technologies, this application primarily provides a semiconductor laser pulse driving circuit based on a supercapacitor.

[0006] To achieve the above objectives, the technical solution adopted in this application is: a semiconductor laser pulse driving circuit based on a supercapacitor, comprising: at least one supercapacitor for powering a vertical-cavity surface-emitting laser (VCSEL); a current control and sampling circuit that controls the current flow and shutdown of the VCSEL by controlling its switching state, and simultaneously sampling and monitoring the discharge current of the supercapacitor through a current sampling point; the current control and sampling circuit being connected in series with the VCSEL and the at least one supercapacitor to form a laser discharge circuit; and a charging circuit connected to the positive and negative terminals of the at least one supercapacitor and charging the at least one supercapacitor, wherein the charging circuit dynamically adjusts its output voltage based on the sampling results of the current sampling point of the laser discharge circuit, thereby adjusting the voltage value of the supercapacitor so that the supercapacitor provides a constant current to the VCSEL.

[0007] Optionally, the charging circuit charges at least one supercapacitor to a set voltage, and adjusts the voltage output of the charging circuit to at least one supercapacitor according to the sampling results of the capacitor voltage sampling point and the driving current of the vertical cavity surface emitter laser, so as to achieve the target driving current at the vertical cavity surface emitter laser, wherein the capacitor voltage sampling point is set on the outermost side of the supercapacitor.

[0008] Optionally, the device selection method for at least one supercapacitor is as follows: calculate the loop current value of the laser discharge circuit based on the preset open-circuit voltage of the supercapacitor, the loop internal resistance of the laser discharge circuit, the bandgap voltage of the vertical cavity surface-emitting laser, and the preset capacitance of the supercapacitor; and determine the device type of at least one supercapacitor based on the device selection criteria and the loop current value.

[0009] Optionally, the current control and sampling circuit consists of a MOSFET and a sampling resistor. The MOSFET is connected in series with the vertical cavity surface-emitting laser, and the MOSFET controls the current flow and shutdown of the vertical cavity surface-emitting laser by adjusting its switching state. The sampling resistor is connected in series with the MOSFET, and its other end is connected to an operational amplifier to amplify the voltage signal, which then serves as the current sampling point.

[0010] Optionally, the current sampling device of the current control and sampling circuit adopts a Hall effect current sensor, in which case the current sampling circuit is located at any position in the laser discharge circuit.

[0011] Optionally, the transient current value of the loop at any given time can be calculated based on the equivalence between the transient charge reduction of at least one supercapacitor and the transient charge increase of the loop, as well as the loop current value.

[0012] Optionally, based on the predetermined laser power fluctuation value and the transient current value at any time, it is determined whether the current fluctuation in the designed circuit meets the predetermined laser power fluctuation value, and the capacitance parameter of at least one supercapacitor is adjusted according to the determination result, and the larger the capacitance of the supercapacitor, the smaller the laser power fluctuation value.

[0013] Optionally, the laser power fluctuation of a vertical cavity surface-emitting laser is linearly related to its current.

[0014] Optionally, when the supercapacitor-based semiconductor laser pulse driving circuit includes multiple supercapacitors, the multiple supercapacitors are connected in series.

[0015] Optionally, when N supercapacitors are connected in series, a balancing and protection circuit is set at both ends of the electrodes of each supercapacitor, wherein N is not less than 2.

[0016] Optionally, at least one supercapacitor is connected to a discharge circuit at both ends to discharge the supercapacitor when the capacitor voltage needs to be reduced or when the entire system is shut down. The discharge circuit is generally composed of high-power resistors and switching devices (such as MOSFETs).

[0017] The beneficial effects of the technical solution of this application are: using a supercapacitor to power a vertical cavity surface-emitting laser, achieving millisecond-level long pulse and high current drive current output, and utilizing the duty cycle limitation of practical applications to reduce the average power of the circuit's front-end power supply, thereby significantly reducing costs, and meeting the requirements of medical devices for laser energy or peak power fluctuations. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the equivalent circuit of a high-power vertical-cavity surface-emitting laser chip in the prior art;

[0020] Figure 2 This is a comparison chart of the linear relationship between VCSEL and EEL;

[0021] Figure 3 This is a schematic diagram showing the relationship between the optical power and current of a vertical cavity surface-emitting laser within the normal junction temperature range.

[0022] Figure 4This is a schematic diagram of a specific embodiment of the semiconductor laser pulse driving circuit based on supercapacitors in this application;

[0023] Figure 5 This is a schematic diagram of the module connection of the semiconductor laser pulse driving circuit based on supercapacitor in this application;

[0024] Figure 6 This is a circuit diagram of the semiconductor laser pulse driving circuit based on supercapacitors in this application.

[0025] The accompanying drawings have illustrated specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to specific embodiments. Detailed Implementation

[0026] The preferred embodiments of this application will now be described in detail with reference to the accompanying drawings, so that the advantages and features of this application can be more easily understood by those skilled in the art, thereby providing a clearer and more definite definition of the scope of protection of this application.

[0027] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus that includes said element.

[0028] The basic principle of high-power semiconductor lasers is to use epitaxial growth to sequentially grow a reflective DBR (Distributed Bragg Reflector), a quantum well active region, and an output DBR in a direction perpendicular to the substrate, thereby forming a resonant cavity on the wavelength scale to achieve laser gain and output. The quantum well active region utilizes the recombination of electrons and holes in the P-region and N-region to achieve photon radiation and complete electro-optic conversion. Multiple vertical-cavity surface-emitting laser (VCSEL) dies are often arranged periodically and uniformly to form a high-power VCSEL array, i.e., a high-power VCSEL chip.

[0029] Figure 1This is a schematic diagram of the equivalent circuit of a high-power vertical-cavity surface-emitting laser (VCSEL) chip in the prior art. Without considering parasitic capacitance and high-frequency modulation, the equivalent circuit of the high-power VCSEL chip is as follows: Figure 1 As shown, the main impedance of the active region of a high-power vertical-cavity surface-emitting laser chip comes from the series resistance of the p-DBR and n-DBR, respectively. Other slight series impedances include those from the ohmic contacts of the chip's positive and negative electrodes and the substrate. The voltage drop in the active region is related to the different band gaps (Eg) of the active region. That is, Eg = 1.24 / λ, where λ is the laser wavelength (in μm). g The unit is eV.

[0030] If we define the series impedance of the p-DBR and n-DBR as R, the driving current as I, and the active region bandgap voltage as g, then the voltage across the high-power vertical-cavity surface-emitting laser chip is: V = I R+g= I R+Eg / e. For example, when the required laser wavelength is 810nm (i.e., λ=0.81um), the band gap of the high-power vertical cavity surface-emitting laser chip is Eg=1.24 / 0.81=1.53eV, and the theoretical voltage drop of its active region is g=Eg / e=1.53V.

[0031] In fact, a better linear relationship can be obtained by regression analysis of the measured VCSEL voltage and current experimental data through experimental methods. Figure 2 This is a comparison chart of the linear relationship between VCSEL and EEL, such as... Figure 2 As shown, the slope coefficient of the VCSEL is 0.0082, meaning the equivalent series resistance R (in milliohms) of the VCSEL is 0.0082, while 1.5912 is an approximation of the active region voltage drop (in V). It is evident that the presence of relatively large and stable internal resistances in the p-DBR and n-DBR results in a superior linear relationship between the voltage and current of the VCSEL. Furthermore, since the VCSEL does not have an optical damage threshold limitation, it can withstand instantaneous surges and overshoots. These factors make constant current driving of the VCSEL possible. In contrast, traditional edge-emitting semiconductor lasers (EELs), whose equivalent internal resistance is mainly composed of ohmic contacts and substrate resistance, have relatively small resistance values. Moreover, the resistance of the ohmic contacts is not very stable due to the influence of the manufacturing process, resulting in a less linear regression curve than the VCSEL. Slight voltage fluctuations can lead to large current fluctuations, and the device damage threshold is low, making it unable to withstand instantaneous current overshoots and surges. Therefore, a strictly constant current power supply must be used for driving them.

[0032] Figure 3 This is a schematic diagram showing the relationship between the optical power and current of a vertical-cavity surface-emitting laser within its normal junction temperature range, as shown below. Figure 3As shown, within the normal junction temperature range and above the emission threshold, the injection current received by a vertical-cavity surface-emitting laser (VCSEL) is linearly related to the number of radiated photons. This linear relationship is often expressed by the slope efficiency (SE), which typically ranges from 0.8 to 1.2 W / A, meaning that the output optical power corresponding to each ampere of current is usually 0.8 to 1.2 W / A. Based on these characteristics of VCSELs, in practical applications, constant current power supplies are generally used to drive them to ensure stable optical power.

[0033] Therefore, this application proposes a semiconductor laser pulse driving circuit based on a supercapacitor, which further ensures the stability of the laser emitted by the vertical cavity surface emitter by guaranteeing the stability of the current received by the vertical cavity surface emitter.

[0034] The technical solutions of this application and how they solve the aforementioned technical problems will be described in detail below with specific embodiments. The specific embodiments described below can be combined with each other to form new embodiments. The same or similar ideas or processes described in one embodiment may not be repeated in other embodiments. The embodiments of this application will now be described with reference to the accompanying drawings.

[0035] Figure 4 This paper illustrates one embodiment of a semiconductor laser pulse driving circuit based on a supercapacitor according to this application.

[0036] Figure 4 The supercapacitor-based semiconductor laser pulse driving circuit shown includes: at least one supercapacitor 401, which powers a vertical-cavity surface-emitting laser.

[0037] The current control and sampling circuit 402 controls the current flow and shutdown of the vertical cavity surface-emitting laser by controlling its switching state. At the same time, it has a current sampling point to sample and monitor the discharge current of the supercapacitor. The current control and sampling circuit is connected in series with the vertical cavity surface-emitting laser and at least one supercapacitor to form a laser discharge circuit.

[0038] The charging circuit 403 is connected to the positive and negative terminals of at least one supercapacitor and charges the at least one supercapacitor. The charging circuit dynamically adjusts its output voltage based on the sampling results of the current sampling point, thereby adjusting the voltage value of the supercapacitor so that the supercapacitor provides a constant current to the vertical cavity surface emitter laser.

[0039] This specific implementation utilizes a supercapacitor to power the vertical cavity surface-emitting laser, achieving millisecond-level long pulses and high-current drive current output. Furthermore, by leveraging the duty cycle limitations of practical applications, the average power of the circuit's front-end power supply is reduced, thereby lowering costs and meeting the requirements of medical devices for laser energy or peak power fluctuations.

[0040] Specifically, for driving a vertical-cavity surface-emitting laser (VCSEL), controlling its current is crucial. Therefore, this application utilizes the voltage across a supercapacitor to further control the VCSEL current. Furthermore, by determining the loop current in the laser discharge circuit, the output voltage of the supercapacitor can be determined. To ensure the accuracy of the voltage released by the supercapacitor, a charging circuit regulates its output voltage. To further ensure the accuracy of this regulation, the charging circuit acquires current sampling point information in real time. Changes in the capacitance within the circuit can regulate current fluctuations. The VCSEL can also be other types of semiconductor lasers.

[0041] Figure 5 This is a schematic diagram of the module connection of the semiconductor laser pulse driving circuit based on supercapacitors in this application, as shown below. Figure 5As shown, a vertical-cavity surface-emitting laser (VCSEL), a supercapacitor, and a current control and sampling circuit are connected in series to form the laser discharge circuit. The current control and sampling circuit is divided into a current control circuit that controls the operation of the VCSEL and a sampling circuit that samples relevant information from the laser discharge circuit. The current control circuit typically uses a MOSFET; the operation of the VCSEL is controlled by adjusting the MOSFET's state. The sampling circuit samples and monitors the discharge current of the supercapacitor, thus acquiring the magnitude of the VCSEL's drive current. Each of the at least one supercapacitor is connected to a balancing and protection circuit as well as a discharge circuit. A charging circuit is connected to the positive and negative terminals of at least one supercapacitor, and a capacitor voltage sampling point is set across each supercapacitor to monitor its capacitance. The charging circuit adjusts its charging voltage to the supercapacitor based on the sampled current, ensuring the discharge circuit current reaches the target set value. The charging circuit obtains power through an external circuit. The capacitor discharge circuit is used to discharge energy when it is necessary to reduce the voltage of at least one supercapacitor and to release residual energy stored in the capacitor when the power system is off. Vertical-cavity surface-mount lasers (VCSELs) operate by being driven by a specific current to achieve a specific optical power output. Simultaneously, the laser pulse width and frequency are controlled by switching the discharge circuit. In medical applications, the control of optical power and pulse width allows for the control of the laser's single-pulse output energy. This application describes one or more VCSELs, which can be connected in parallel, series, or series-parallel configurations. The control circuit provides power to its various functional modules according to a predetermined operating mode, supplying a stable current to the VCSEL.

[0042] In one specific embodiment of this application, the charging circuit charges at least one supercapacitor to a set voltage, and adjusts the voltage output of the charging circuit to at least one supercapacitor according to the sampling results of the capacitor voltage sampling point and the driving current of the vertical cavity surface emitter laser, so as to achieve the target driving current at the vertical cavity surface emitter laser. The capacitor voltage sampling point is set at both ends of at least one supercapacitor.

[0043] Specifically, the voltage across the supercapacitor is set by the capacitor charging circuit. The charging circuit monitors the voltage across the capacitor in real time. After charging at least one supercapacitor to the set voltage, the charging circuit adjusts the voltage output to the supercapacitor based on the sampling results of the capacitor voltage sampling points and the drive current of the vertical-cavity surface-emitting laser (VCSEL). If the voltage of the supercapacitor is detected to be lower than the preset value, charging is quickly initiated; if the voltage exceeds the preset value, charging is stopped, thus achieving the target drive current at the VCSEL. In other words, after charging at least one supercapacitor to the set voltage, the sampling results of the capacitor voltage sampling points are monitored in real time. When it is necessary to reduce the voltage of at least one supercapacitor, accurate voltage discharge processing is performed based on the sampling results of the capacitor voltage sampling points, so that the voltage of the discharged capacitor reaches the predetermined value.

[0044] In particular, voltage detection has a dynamic voltage during discharge and an open-circuit voltage when not discharging. The former is lower than the latter, but there is a corresponding relationship between the two.

[0045] This specific implementation ensures the stability of the discharge current across the supercapacitor by monitoring and maintaining the preset voltage across the supercapacitor, thereby ensuring the target driving current is achieved at the vertical cavity surface-emitting laser.

[0046] In one specific embodiment of this application, the current control and sampling circuit consists of a MOSFET and a sampling resistor. The MOSFET is connected in series with the vertical cavity surface-emitting laser, and the MOSFET controls the current flow and shutdown of the vertical cavity surface-emitting laser by adjusting its switching state. The sampling resistor is connected in series with the MOSFET, and its end away from the MOSFET is at a relative ground level. Its other end is connected to an operational amplifier to amplify the voltage signal and then serve as a current sampling point.

[0047] In one specific embodiment of this application, the current sampling line is a Hall-effect current sensor, and when the current sampling line is a Hall-effect current sensor, the current sampling line is located at any position in the laser discharge circuit.

[0048] Specifically, the current control circuit typically uses a MOSFET to control the current flow and shutdown of the vertical-cavity surface-emitting laser. The current sampling circuit can be a circuit consisting of a sampling resistor and an operational amplifier connected in series, and then the low-voltage signal collected in this circuit is amplified to a high-voltage signal for detection to obtain sampling information. Alternatively, it can use a Hall effect current sensor with its own amplifier to detect the magnetic field of the current and thus detect the current magnitude.

[0049] Specifically, Figure 6 This is a circuit diagram of the semiconductor laser pulse driving circuit based on supercapacitors, as described in this application. Figure 6As shown, when the current sampling circuit consists of a MOSFET and a sampling resistor, the negative terminal of the vertical-cavity surface-emitting laser (VCSEL) is connected to the source of the MOSFET, and the drain of the MOSFET is connected to the sampling resistor (for high-current sampling, a high-power zero-ohm resistor is commonly used as the sampling resistor). When the supercapacitor-based semiconductor laser pulse drive circuit contains multiple supercapacitors, the multiple supercapacitors are connected in series, and the series capacitor group is connected in parallel with the circuit consisting of the VCSEL, MOSFET, and sampling resistor connected in series. That is, multiple supercapacitors are first connected in series, and the series-connected supercapacitors are then connected in parallel with the circuit consisting of the VCSEL, MOSFET, and sampling resistor. The charging circuit is also connected in parallel with the circuit consisting of the series-connected supercapacitors. The other end of the sampling resistor can be connected to an operational amplifier to amplify the voltage signal, which is then used as the current sampling point for current sampling. The control section controls whether the VCSEL operates, whether it performs discharge processing, and whether voltage regulation is required.

[0050] Furthermore, the MOSFET controlling the VCSEL current switch operates in a switching state rather than a constant current region, reducing heat dissipation requirements and energy loss. The circuit design described above enables long pulses and high current output, allowing the vertical-cavity surface-emitting laser to generate stable laser light. Additionally, the low average power consumption of the front-end power supply in this application reduces wasted power supply costs.

[0051] When the current sampling circuit is a Hall-effect current sensor, the Hall-effect current sensor can be located anywhere in the laser discharge circuit. The remaining operation and function of the Hall-effect current sensor in the semiconductor laser pulse drive circuit are similar to or the same as those of the circuit composed of a MOSFET and a sampling resistor, and will not be elaborated further here.

[0052] In one specific embodiment of this application, the transient current value of the loop at any given time is calculated based on the equivalence between the transient decrease in charge of at least one supercapacitor and the transient increase in charge of the loop, as well as the loop current value.

[0053] Specifically, when the current sampling circuit consists of a MOSFET and a sampling resistor, the loop current value of the vertical-cavity surface-emitting laser (VCSEL) during operation is calculated based on the series impedance of the CCSEL, the internal resistance of the MOSFET, the internal resistance of the sampling resistor, the DC internal resistance of the capacitor, the bandgap voltage of the CCSEL, and the capacitance and voltage of at least one supercapacitor. Then, based on the equivalence between the transient charge reduction of at least one supercapacitor and the transient charge increase of the loop, and the loop current value, the transient current value of the loop at any given time is calculated.

[0054] When the current sampling circuit uses a Hall effect current sensor, the loop current value of the vertical-cavity surface-emitting laser (VCSEL) during operation is calculated based on the internal resistance of the CCSEL, the internal resistance of the Hall effect current sensor, the DC internal resistance of the capacitor, the bandgap voltage of the CCSEL, and the capacitance and voltage of at least one supercapacitor. Then, based on the equivalence between the transient charge reduction of at least one supercapacitor and the transient charge increase of the loop, and the loop current value, the transient current value of the loop at any given time is calculated.

[0055] In one specific embodiment of this application, based on a predetermined laser power fluctuation value and a transient current value at any given time, it is determined whether the current fluctuation in the designed circuit meets the predetermined laser power fluctuation value, and the capacitance parameter of at least one supercapacitor is adjusted according to the determination result, wherein the larger the capacitance of the supercapacitor, the smaller the laser power fluctuation value.

[0056] In one specific embodiment of this application, the laser power fluctuation value of the vertical cavity surface-emitting laser is linearly related to its current.

[0057] Specifically, the laser power fluctuation of a vertical-cavity surface-emitting laser (VCSEL) has a linear relationship with its current. Therefore, when it is necessary to generate laser pulses with large pulse width, small duty cycle and stable optical power, the power supply that provides current to the VCSEL also has high requirements. This application utilizes a supercapacitor to provide a large current drive for the VCSEL, which enables the VCSEL to operate in the required state while reducing the average power requirement of the front-end power supply, thereby reducing manufacturing costs.

[0058] In one specific embodiment of this application, the device selection method for at least one supercapacitor is as follows: the loop current value of the laser discharge circuit is calculated based on the preset open-circuit voltage of the supercapacitor, the loop internal resistance of the laser discharge circuit, the bandgap voltage of the vertical cavity surface-emitting laser, and the preset capacitance and voltage of the supercapacitor; and the device type of at least one supercapacitor is determined based on the device selection criteria and the loop current value.

[0059] Specifically, supercapacitors are capacitors with low operating voltage, high capacitance, and low internal resistance. Preferably, supercapacitors are farad capacitors, which are capacitors made of a special material and typically have a capacitance in the farad (F) range. Furthermore, to ensure that each capacitor avoids uneven charging and overcharging problems caused by differences in impedance and capacitance during the charging process, balancing and protection circuits can be set at both ends of each capacitor to ensure timely discharge in case of overcharging and prevent device damage.

[0060] In one specific embodiment of this application, when a supercapacitor-based semiconductor laser pulse driving circuit includes multiple supercapacitors, the multiple supercapacitors are connected in series.

[0061] In one specific embodiment of this application, at least one supercapacitor is connected to a discharge circuit at both ends, which discharges the supercapacitor when the capacitor voltage needs to be reduced or when the entire system is shut down.

[0062] Specifically, for the circuit supplying power to the VCSEL, since the VCSEL needs to operate under long pulse width and high current conditions to excite high laser energy, its current source is usually directly provided by the front-end power supply, or a large-capacity capacitor is used for discharge to power the VCSEL. In this application, multiple supercapacitors connected in series are used to power the VCSEL, and a capacitor voltage sampling point is set at the outermost periphery of the series supercapacitors. This allows for timely adjustment of the supercapacitor voltage when the output voltage of the charging circuit is inconsistent with the voltage across the supercapacitor. That is, when the capacitor voltage is insufficient, the charging circuit is activated to charge the supercapacitor; if the capacitor voltage exceeds a preset value, a bypass circuit is activated to discharge the supercapacitor. The discharge circuit is generally composed of high-power resistors and switching devices (such as MOSFETs).

[0063] In one specific embodiment of this application, in a practical application scenario, such as a home-use semiconductor laser hair removal system, assuming the electro-optical efficiency of the VCSEL is 40%, if a 10J light pulse needs to be generated within 100ms, then at least 25J of electrical injection is required into the VCSEL. Using the existing method of directly supplying power with a switching power supply, the output power of the switching power supply needs to be designed to be at least 25J / 100ms = 250W. In this case, if the VCSEL operating voltage is 2V, the discharge current provided by the switching power supply to the circuit is 125A.

[0064] Furthermore, in practical applications, VCSELs require relatively low operating voltage but high operating current. When a large-capacity capacitor is used to discharge and power the VCSEL, the energy storage capacity formula E=CU is applied. 2 / 2, under the same application conditions as described above, requires a capacitor with a capacitance in the joule range. However, traditional electrolytic capacitors often have smaller capacitances and are more suitable for energy storage at high voltages. Therefore, in applications requiring low voltage and high capacitance, supercapacitors with a voltage of 2.7-3.0V, a capacitance in the hundreds of farads, and an internal resistance in the milliohms range can be used to power the VCSEL. By using supercapacitors with low operating voltage, high capacitance, and low internal resistance to power the VCSEL, long pulses and large currents can be provided, reducing the power required for VCSEL operation and generating high-energy pulsed lasers with low duty cycles.

[0065] For example, assuming a VCSEL operates at a current of 125A and a voltage of 2V, if a 400F supercapacitor with a maximum voltage of 3V, a DC resistance of 3.2mΩ, and dimensions of approximately D35x60mm is used to power the VCSEL, the required voltage drop across its internal impedance will be 3.2mΩ when its discharge current is 125A. 125A = 0.32V. If the internal resistance of the MOSFET in the circuit is 1mΩ and the resistance of the zero-ohm resistor used for sampling is 1mΩ, the allowable voltage margin for supplying power to the VCSEL is 3 - 0.32 - 125. (0.001 + 0.001) = 2.35V. This voltage exceeds the 2V operating voltage required for VCSEL operation. In other words, the supercapacitor can provide sufficient supply voltage and current to the VCSEL.

[0066] For applications such as laser medical treatment, the laser power fluctuation is generally required to be no more than + / - 20%. Since VCSEL current and optical power are essentially linearly related, to ensure the laser power fluctuation meets requirements, the drive current fluctuation must also be no more than + / - 20%. For example, when the VCSEL's emission threshold current is 15A, taking the initial discharge current of 125A as a baseline, the current provided by the supercapacitor at the end of the discharge cycle should not be lower than (125-15). 80% + 15 = 103A.

[0067] Assuming the open-circuit voltage of the series-connected supercapacitor is U, the total internal resistance of the loop is R (including the internal resistance of the VCSEL, MOSFET, sampling resistor, and the DC internal resistance of the supercapacitor), the bandgap voltage of the VCSEL is g, and the capacitance of the supercapacitor is C, then when the MOSFET is turned on, the average circuit current I in the loop satisfies: U = I R+g.

[0068] Because there is an equivalent relationship between the transient decrease in charge of a supercapacitor and the transient increase in charge of the loop, i.e., I dt=-C If dU, then substituting the average circuit current I=(Ug) / R in the loop into the equivalent relation, we get (Ug) / R dt=-C dU, i.e., dt = -RC / (Ug) dU, for dt = -RC / (Ug) Integrating both sides of the equation dU, we get t = -RC ln(Ug).

[0069] Then, when the discharge time t starts from time 0 and ends at time T of the first discharge pulse, it satisfies the following restrictions:

[0070] T=RC [ln(U0-g)-ln(U1-g)], where U1-g=I1 R

[0071] Therefore, the transient loop current at time T can be obtained as: I1 = EXP[ln(U0-g)-T / (RC)] / R

[0072] If the preset laser power fluctuation value requirement is (I1-I th ) / (I0-I th )≤1-δ, where δ is the error standard, which can take values ​​of 5%, 10%, 20%, etc., and based on the loop transient current at time T and the preset laser power fluctuation requirement, we can know that:

[0073] {EXP[ln(U0-g)-T / (RC)] / RI th} / [(U0-g) / RI th ≤1-δ

[0074] The above calculation results are based on the bandgap width of a single VCSEL. If the circuit loop contains n VCSELs connected in series, then:

[0075] {EXP[ln(U0-n g)-T / (RC)] / RI th} / [(U0-n g) / RI th ≤1-δ.

[0076] When the parameters of the designed supercapacitor can make the VCSEL meet the above requirements, the parameters of the designed supercapacitor can be optimized, or the current parameters can be used as the final result. If the parameters of the designed supercapacitor cannot make the VCSEL meet the above requirements, the parameters of the supercapacitor should be modified until the VCSEL meets the constraints.

[0077] For example, when the internal resistance of the VCSEL satisfies (2-1.53) / 125=3.76mΩ, where 2 is the operating voltage of the VCSEL, 125A is the operating current of the VCSEL, and 1.53 is the bandgap value of the VCSEL, the total impedance of the circuit R=3.76+3.2+1+1=0.00896Ω. If U0=2.65V, C=400F, and g=1.53V at this time, then at T=0.1s, the transient current of the circuit is:

[0078] I1=EXP[ln(U0-g)-RC / T] / R=121.56A

[0079] At this time, if the VCSEL's light emission threshold current I th If the amplitude is 15A, the optical power decrease is 1-(121.56-15) / (125-15)=3.13%, which is much smaller than the usual requirements for optical power fluctuation.

[0080] In the several embodiments provided in this application, it should be understood that the disclosed apparatus can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative. For instance, the division of the units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed.

[0081] The above description is merely an embodiment of this application and does not limit the patent scope of this application. Any equivalent structural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A semiconductor laser pulse driving circuit based on a supercapacitor, characterized in that, include: At least one supercapacitor that powers a vertical-cavity surface-emitting laser; The current control and sampling circuit controls the current flow and shutdown of the vertical cavity surface-emitting laser by controlling its switching state. At the same time, it is equipped with a current sampling point to sample and monitor the discharge current of the supercapacitor. The current control and sampling circuit is connected in series with the vertical cavity surface-emitting laser and at least one supercapacitor to form a laser discharge circuit. A charging circuit is connected to the positive and negative terminals of at least one of the supercapacitors and charges at least one of the supercapacitors. The charging circuit dynamically adjusts its output voltage based on the sampling results of the current sampling point, thereby adjusting the voltage value of the supercapacitor so that the supercapacitor provides a constant current to the vertical cavity surface emitter laser. The charging circuit charges at least one supercapacitor to a set voltage, and adjusts the voltage output to at least one supercapacitor based on the sampling results of the capacitor voltage sampling point and the driving current of the vertical cavity surface emitter laser. The capacitor voltage sampling point is located on the outermost side of the supercapacitor. The charging circuit adjusts its charging voltage to the supercapacitor according to the magnitude of the sampling current so that the current value of the discharge circuit reaches the target set value.

2. The semiconductor laser pulse driving circuit based on supercapacitor according to claim 1, characterized in that, The device selection method for the at least one supercapacitor is as follows: Based on the preset open-circuit voltage of the supercapacitor, the loop resistance of the laser discharge circuit, the bandgap voltage of the vertical-cavity surface-emitting laser, and the preset capacitance of the supercapacitor, the loop current value of the laser discharge circuit is calculated; and... The device type of the at least one supercapacitor is determined based on the device selection criteria and the loop current value.

3. The semiconductor laser pulse driving circuit based on supercapacitor according to claim 1, characterized in that, The current control and sampling circuit consists of a MOSFET and a sampling resistor. The MOSFET is connected in series with the vertical cavity surface-emitting laser (VCSEL), and the MOSFET controls the current flow and shutdown of the VCSEL by adjusting its switching state. The sampling resistor is connected in series with the MOSFET, and its other end is connected to an operational amplifier to amplify the voltage signal, which then serves as the current sampling point.

4. The semiconductor laser pulse driving circuit based on supercapacitor according to claim 1, characterized in that, The current control and sampling circuit is a Hall effect current sensor, and when the current sampling circuit is a Hall effect current sensor, the current sampling circuit is located at any position in the laser discharge circuit.

5. The semiconductor laser pulse driving circuit based on supercapacitor according to claim 1, characterized in that, Based on the equivalence between the transient decrease in charge of at least one of the supercapacitors and the transient increase in charge of the loop, and the loop current value, the transient current value of the loop at any given time is calculated.

6. The semiconductor laser pulse driving circuit based on supercapacitor according to claim 5, characterized in that, Based on the predetermined laser power fluctuation value and the transient current value at any given time, it is determined whether the current fluctuation in the designed circuit meets the predetermined laser power fluctuation value, and the capacitance parameter of at least one of the supercapacitors is adjusted according to the determination result, and the larger the capacitance of the supercapacitor, the smaller the laser power fluctuation value.

7. The semiconductor laser pulse driving circuit based on supercapacitor according to claim 1, characterized in that, The laser power fluctuation of the vertical cavity surface-emitting laser is linearly related to its current.

8. The semiconductor laser pulse driving circuit based on supercapacitor according to claim 1, characterized in that, When a supercapacitor-based semiconductor laser pulse driving circuit includes multiple supercapacitors, the multiple supercapacitors are connected in series.

9. The semiconductor laser pulse driving circuit based on supercapacitor according to claim 1, characterized in that, When N supercapacitors are connected in series, a balancing and protection circuit is provided at both ends of the electrodes of each supercapacitor, wherein N is not less than 2.

10. The semiconductor laser pulse driving circuit based on supercapacitor according to claim 1, characterized in that, At least one of the supercapacitors is connected to a discharge circuit at both ends to discharge the supercapacitor when the capacitor voltage needs to be reduced or the entire system is shut down.

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