Constant current protection circuit suitable for satellite laser communication

Abstract

The utility model provides a constant current protection circuit suitable for satellite laser communication. The constant current protection circuit comprises a filtering module, a protection starting module and a constant current driving module. The filtering module receives the PWM control signal, filters the PWM control signal and then outputs a control voltage signal to the constant-current driving module; the protection starting module receives the PWM control signal and controls the on-off of a triode according to the PWM control signal; when the triode is turned off, an enable signal is generated, and the constant current driving module receives the enable signal and outputs a grid driving voltage to softly start a load; and when the triode is switched on, the load is switched off. A protection starting module based on a triode is added in a traditional constant-current driving circuit, on-off of the triode and output of filtered control voltage are controlled at the same time through a PWM control signal, and dual protection of constant-current driving is achieved.

Description

TECHNICAL FIELD

[0001] The utility model relates to satellite laser communication field, concretely relates to a constant current protection circuit suitable for satellite laser communication. BACKGROUND

[0002] The traditional laser constant current drive circuit usually adopts the closed loop control structure that the operational amplifier, MOS tube and sampling resistance constitute. However, the prior art has the problem of insufficient power-on starting protection. At the system power-on moment, the MCU has not completed initialization, and its PWM output end can be in the high resistance state, at which time the positive input end voltage state of the operational amplifier is uncertain, and the situation that the voltage is higher than the negative input end voltage can appear. Under this condition, the operational amplifier outputs high level to drive the MOS tube to turn on, resulting in that the laser bears the large current impact at the power-on moment, which easily causes permanent damage of the laser, and seriously affects the reliability and service life of the equipment. SUMMARY

[0003] The utility model aims at solving the problem that the existing laser constant current drive circuit causes the large current impact at the power-on moment due to the non-initialization of the MCU, resulting in the damage of the laser.

[0004] The utility model provides a constant current protection circuit suitable for satellite laser communication, including filter module, protection starting module and constant current drive module;

[0005] The filter module receives the PWM control signal, filters and then outputs the control voltage signal to the constant current drive module; The protection starting module receives the PWM control signal, and controls the on-off of the triode according to the PWM control signal;

[0006] When the triode is off, the enable signal is generated, the constant current drive module receives the enable signal, and outputs the gate drive voltage to soft start the load; When the triode is on, the load is turned off.

[0007] Further, the filter module includes first stage filter and second stage filter, and the first stage filter includes first resistance and first capacitor; The second stage filter includes second resistance and second capacitor;

[0008] One end of the first resistance receives the PWM control signal, and the other end is connected with the first capacitor and one end of the second resistance respectively, the other end of the first capacitor is grounded, and the other end of the second resistance is connected with one end of the second capacitor and the input end of the protection starting module respectively, and the other end of the second capacitor is grounded;

[0009] One end of the third resistance is connected between the first resistance and the second resistance, and the other end of the third resistance is grounded.

[0010] Further, the protection starting module comprises a starting control unit and a voltage stabilizing unit; an input end of the starting control unit is connected with the filter module, and an output end thereof is connected with the voltage stabilizing unit; and an output end of the voltage stabilizing unit is connected with the constant current driving module.

[0011] The starting control unit is used for outputting the enable signal; and the voltage stabilizing unit is used for providing a stable voltage.

[0012] Further, the starting control unit comprises a triode and a fourth resistor; a collector of the triode is connected with the filter module, a base thereof is connected with one end of the fourth resistor, and an emitter thereof is grounded; and the other end of the fourth resistor is connected with an external power supply end.

[0013] Further, the voltage stabilizing unit comprises a diode, a fifth resistor and a sixth resistor; a negative electrode of the diode is connected with the constant current driving module, a positive electrode thereof is connected with one end of the fifth resistor, the sixth resistor is connected in series between the fourth resistor and the external power supply end, and the other end of the fifth resistor is connected between the fourth resistor and the sixth resistor.

[0014] Further, the constant current driving module comprises an operational amplifier.

[0015] A non-inverting input end of the operational amplifier is connected with the filter module, and an inverting input end thereof is connected with the protection starting module; and an output end of the operational amplifier is connected with a gate of a MOS tube after being connected in series with a seventh resistor; and a source of the MOS tube is grounded after being connected in series with an eighth resistor.

[0016] Further, a negative electrode of a laser is connected with a drain of the MOS tube, a positive electrode of the laser is connected with an external power supply end, the source of the MOS tube is also connected with one end of a ninth resistor, and the other end of the ninth resistor is connected with the inverting input end of the operational amplifier.

[0017] Compared with the prior art, the utility model at least has the following beneficial effects: through increasing the protection starting module based on the triode in the traditional constant current driving circuit, the triode on-off and the filtered control voltage output are controlled simultaneously by using the PWM control signal, so that the double protection of the constant current driving is realized, the safety and reliable work of the precision load such as the laser are ensured, and the stability of the system and the service life of the device are improved. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical scheme in the embodiments of the utility model or the prior art, the attached drawings needed to be used in the following embodiment or prior art description will be briefly introduced, and obviously, the attached drawings in the following description are only the embodiments of the utility model, and for the ordinary skilled in the art, other attached drawings can be obtained without paying the creative labor.

[0019] Figure 1 Figure 1 is a module diagram of an operational amplifier constant current source protection circuit based on a triode according to an embodiment of the present application;

[0020] Figure 2 Figure 1 is a schematic diagram of an operational amplifier constant current source protection circuit based on a triode according to an embodiment of the present application.

[0021] Wherein, C44-first capacitor; C45-second capacitor; R68-first resistor; R69-second resistor; R72-third resistor; R74-fourth resistor; R82-fifth resistor; R83-sixth resistor; R70-seventh resistor; R81-eighth resistor; R73-ninth resistor; VT5-triode; VQ5-MOS tube; VD1-diode; LED1-laser; N6C-operational amplifier. DETAILED DESCRIPTION

[0022] The application will be described in more detail with reference to the drawings, in which a preferred embodiment of the application is shown. It should be understood that the application is not limited to the embodiment described but can be modified in various ways without departing from the scope of the application. The following description is therefore to be understood as an illustration of the application and not as a limitation thereof.

[0023] It should be noted that the relative terms, such as first and second, and the like are used herein only to distinguish one entity or action from another, and do not necessarily require or imply any such actual relationship or order between such entities or actions. Moreover, the terms "comprising", "including", or any other variant thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements recited, but can also include other elements not expressly listed or inherent to such process, method, article, or apparatus.

[0024] The application will be described in more detail with reference to the drawings, in which a preferred embodiment of the application is shown. It should be understood that the application is not limited to the embodiment described but can be modified in various ways without departing from the scope of the application. The following description is therefore to be understood as an illustration of the application and not as a limitation thereof.

[0025] The present embodiment provides a constant current protection circuit suitable for satellite laser communication, please refer to Figure 1 and Figure 2 , comprising a filtering module, a protection starting module and a constant current driving module.

[0026] The filter module receives a PWM control signal and outputs a control voltage signal to the constant current drive module after filtering; the protection starting module receives the PWM control signal and controls the on-off of the triode VT5 according to the PWM control signal.

[0027] An enable signal is generated when the triode VT5 is off, and the constant current drive module receives the enable signal and outputs a gate drive voltage to soft-start the load; when the triode VT5 is on, the load is turned off.

[0028] Specifically, the filter module can be implemented by an RC filter circuit, and the specific parameters of the resistor and the capacitor can be adjusted according to the actual application scenario. The triode VT5 in the protection starting module can be of NPN type or PNP type, and the specific selection depends on the circuit design requirements. The operational amplifier N6C in the constant current drive module can be a general type or a precision type, and the MOS tube VQ5 connected to the output end thereof can be selected as an N-channel or a P-channel type, and the specific selection depends on the load characteristics.

[0029] By introducing the protection starting module, the problem of current impact caused by uncertain PWM control signal at the moment of power-on of the traditional laser driver circuit is effectively solved. Specifically, at the initial stage of system power-on, the protection starting module generates an enable signal through the off state of the triode VT5, so that the constant current drive module enters a soft-start mode, thereby avoiding that the load bears excessive current. Compared with the prior art, the reliability and safety of the circuit are improved, and it is especially suitable for load protection sensitive to current.

[0030] Further, the filter module includes first-stage filtering and second-stage filtering, the first-stage filtering includes a first resistor R68 and a first capacitor C44, and the second-stage filtering includes a second resistor R69 and a second capacitor C45.

[0031] One end of the first resistor R68 receives the PWM control signal, and the other end is connected to the first capacitor C44 and one end of the second resistor R69, respectively. The other end of the first capacitor C44 is grounded, and the other end of the second resistor R69 is connected to one end of the second capacitor C45 and an input end of the protection starting module, respectively. The other end of the second capacitor C45 is grounded.

[0032] One end of a third resistor R72 is connected between the first resistor R68 and the second resistor R69, and the other end of the third resistor R72 is grounded.

[0033] Specifically, the first-stage filtering is composed of the first resistor R68 and the first capacitor C44, which is used to preliminarily filter the PWM control signal and filter out high-frequency noise. The second-stage filtering is composed of the second resistor R69 and the second capacitor C45, which is used to further filter the signal and improve the signal quality. The third resistor R72 acts as a voltage dividing resistor, which limits the maximum working current of the laser LED1 when the duty ratio of the PWM control signal reaches 100%.

[0034] As a preferred embodiment, the resistance values of the first resistor R68 and the second resistor R69 can be the same or different, which is selected according to actual needs. In the present embodiment, the first resistor R68 and the second resistor R69 are both resistors with a resistance value of 12k. The capacitance values of the first capacitor C44 and the second capacitor C45 can also be adjusted according to the filtering needs, for example, the first capacitor C44 can be a ceramic capacitor, and the second capacitor C45 can be an electrolytic capacitor, so as to achieve different frequency band filtering effects. In the present embodiment, the first capacitor C44 is 0.1μF, and the second capacitor C45 is 0.47μF.

[0035] By setting the two-stage filtering structure, the noise interference in the PWM control signal can be effectively filtered out, and the stability of the control signal can be improved. Among them, the first-stage filtering mainly filters out high-frequency noise, and the second-stage filtering further smooths the signal. Compared with the prior art, a more stable control voltage signal can be provided, and the misoperation caused by signal interference can be avoided, thereby improving the overall reliability of the circuit. Specifically, by reasonably selecting the resistance and capacitance parameters, effective suppression of different frequency noises can be realized, and stable control signals can be obtained for the constant current driving module.

[0036] Further, the protection starting module includes a starting control unit and a voltage stabilizing unit; the input end of the starting control unit is connected to the filtering module, and the output end is connected to the voltage stabilizing unit; the output end of the voltage stabilizing unit is connected to the constant current driving module.

[0037] The starting control unit is used to output the enable signal; and the voltage stabilizing unit is used to provide a stable voltage.

[0038] The starting control unit can be realized by discrete components or integrated circuits. In the embodiment, a transistor VT5 is used as a switching element, and a current limiting resistor is used to form a basic control loop. In specific implementation, when the PWM control signal is low, the transistor VT5 is cut off, and a high level enable signal is output at the collector; when the PWM control signal is high, the transistor VT5 is turned on, and the enable signal is pulled low. The voltage stabilizing unit can be realized by a Zener diode VD1 or a low dropout linear regulator, the input end of which is connected to the output end of the starting control unit, and the output end is connected to the enable end of the constant current driving module. As a preferred embodiment, the voltage stabilizing unit can be composed of a diode VD1 and a voltage dividing resistor network, wherein the negative electrode of the diode VD1 is connected to the constant current driving module, the positive electrode is connected to the ground through the voltage dividing resistor, and the voltage dividing node is connected to the external power supply.

[0039] By setting an independent protection starting module, the problem of mis-triggering of the MOS transistor VQ5 caused by uncertain voltage at the input end of the operational amplifier N6C in the power-on stage is effectively improved. The starting control unit monitors the state of the PWM control signal in real time, and immediately cuts off the enable signal when an abnormal signal is detected, preventing the constant current driving module from malfunctioning. The voltage stabilizing unit provides a stable operating voltage for the subsequent circuit, ensuring reliable transmission of the protection signal. Through the hardware circuit, fast response protection is realized, without relying on the software initialization process, avoiding damage to the laser caused by power-on impact.

[0040] Further, the starting control unit comprises a transistor VT5 and a fourth resistor R74, the collector of the transistor VT5 is connected to the filter module, the base is connected to one end of the fourth resistor R74, and the emitter is grounded; the other end of the fourth resistor R74 is connected to an external power supply end.

[0041] Specifically, the transistor VT5 is an NPN transistor, and the collector is connected to the second stage filter output end of the filter module through a wire. The resistance value of the fourth resistor R74 is preferably in the range of 10kΩ to 100kΩ, which is used to limit the base current. The external power supply end provides a working voltage of 5V to 12V as the bias power supply of the transistor VT5. As a preferred embodiment, the model of the transistor VT5 can be selected from general-purpose small power transistors such as 2N3904 or BC547. The fourth resistor R74 can be a metal film resistor or a thick film resistor. The emitter of the transistor VT5 is reliably grounded through a conductive copper foil, and the base is connected to the fourth resistor R74 through a gold-plated pin to ensure reliable contact.

[0042] Thus, by the cooperation of the triode VT5 and the fourth resistor R74, accurate detection and fast response of the PWM control signal are realized. When the control voltage output by the filtering module reaches the conduction threshold of the triode VT5, the triode VT5 is immediately turned on and the emitter potential is pulled down, thereby generating an effective enable signal. Compared with the traditional comparator scheme, this structure has the advantages of fast response speed, simple circuit and low cost. Especially at the power-on moment, it can effectively avoid the misoperation caused by abnormal PWM control signal, and ensure the safe start of the constant current driving module. The resistance value selection of the fourth resistor R74 directly affects the switching speed of the triode VT5, which needs to be optimized and designed according to the response requirements of the actual application scene.

[0043] Further, the voltage stabilizing unit comprises a diode VD1, a fifth resistor R82 and a sixth resistor R83; the negative electrode of the diode VD1 is connected to the constant current driving module, the positive electrode is connected to one end of the fifth resistor R82, the sixth resistor R83 is connected in series between the fourth resistor R74 and the external power supply end, and the other end of the fifth resistor R82 is connected between the fourth resistor R74 and the sixth resistor R83.

[0044] Specifically, the diode VD1 is used to prevent reverse current impact, the fifth resistor R82 and the sixth resistor R83 constitute a voltage dividing circuit for adjusting the output voltage. The sixth resistor R83 serves as a pull-up resistor for the MU_EN end, ensuring that the base of VT5 is high during MCU reset, and the MOS tube is turned off. As a preferred embodiment, the diode VD1 can use a Schottky diode VD1 to reduce the forward voltage drop; the fifth resistor R82 and the sixth resistor R83 can use metal film resistors with an accuracy of 1% to ensure the voltage dividing accuracy. Further, the resistance value range of the fifth resistor R82 can be 1kΩ-10kΩ, and the resistance value range of the sixth resistor R83 can be 2kΩ-20kΩ, thereby forming a stable voltage dividing ratio.

[0045] By the cooperation of the diode VD1 and the voltage dividing resistor, stable voltage output can be provided during the starting process. When the enable signal is output by the starting control unit, the voltage stabilizing unit can quickly establish a stable voltage to avoid the influence of voltage fluctuation on the constant current driving module. Compared with the prior art, the problem of unstable voltage at the power-on moment is effectively improved, and a reliable voltage stabilizing function is realized through a hardware circuit, thereby protecting the subsequent circuit from the influence of voltage mutation.

[0046] Further, the constant current driving module comprises an operational amplifier N6C.

[0047] The non-inverting input terminal of the operational amplifier N6C is connected to the filter module, and the inverting input terminal is connected to the protection starting module. The output terminal of the operational amplifier N6C is connected to the gate of the MOS tube VQ5 after being connected in series with the seventh resistor R70. The source of the MOS tube VQ5 is connected to the ground after being connected in series with the eighth resistor R81.

[0048] Specifically, the operational amplifier N6C is used to compare the voltage difference between the non-inverting input terminal and the inverting input terminal, and output the corresponding control signal. The seventh resistor R70 is used to limit the output current of the operational amplifier N6C, preventing the MOS tube VQ5 from being damaged due to excessive driving current. The eighth resistor R81 is used to sample the working current of the laser LED1, and its resistance value determines the working current of the laser LED1. The ninth resistor R73 is used to form a negative feedback loop to improve the stability of the circuit. As a preferred embodiment, the resistance value of the seventh resistor R70 ranges from 100Ω to 1kΩ, the eighth resistor R81 is a sampling resistor, and its resistance value ranges from 1Ω to 10Ω. The resistance value of the ninth resistor R73 ranges from 1kΩ to 10kΩ.

[0049] To this end, through the cooperation of the operational amplifier N6C, the MOS tube VQ5, and the resistor network, precise control of the load current is achieved. Among them, the operational amplifier N6C acts as a comparator, which can quickly respond to changes in input voltage and maintain stable output through a negative feedback loop. The MOS tube VQ5 acts as a power switch, which can withstand large currents and achieve soft start function through the gate resistor network. Thus, this scheme effectively improves the current impact problem caused by the uncertainty of the PWM control signal at the power-on moment of the traditional laser driver circuit, and improves the reliability and service life of the circuit.

[0050] Further, the drain of the MOS tube VQ5 is connected to the negative electrode of the laser LED1, and the positive electrode of the laser LED1 is connected to the external power supply terminal. The source of the MOS tube VQ5 is also connected to one end of the ninth resistor R73, and the other end of the ninth resistor R73 is connected to the inverting input terminal of the operational amplifier N6C.

[0051] Specifically, the ninth resistor R73 acts as a feedback resistor, which is used to feed back the gate voltage of the MOS tube VQ5 to the inverting input terminal of the operational amplifier N6C to form a closed-loop control. Among them, the resistance value of the ninth resistor R73 can be adjusted according to actual needs, for example, selecting a resistance value within the range of 1kΩ to 10kΩ. As a preferred embodiment, the ninth resistor R73 can use a metal film resistor with an accuracy of 1% to ensure the stability of the feedback signal. Further, the laser LED1 acts as a load, and its working current is controlled by the conduction state of the MOS tube VQ5, thereby realizing constant current driving of the load.

[0052] The sixth resistor R83, the fifth resistor R82, the diode VD1, the ninth resistor R73 and the eighth resistor R81 form a loop. After voltage division, it is ensured that the negative input of the operational amplifier is greater than the positive input when the negative feedback has not been established, and at this time, the voltage of the positive input is determined by the voltage division of the first resistor R68 and the third resistor R72, so that the MOS transistor VQ5 can be ensured to be not turned on even when the PWM duty ratio is 100%.

[0053] Through the above technical solution, the inverting input of the operational amplifier N6C can monitor the change of the gate voltage of the MOS transistor VQ5 in real time, and compare it with the control voltage signal of the non-inverting input, so as to accurately adjust the conduction degree of the MOS transistor VQ5. Therefore, at the power-on moment of the system, even if the PWM control signal is in an uncertain state, the operational amplifier N6C can quickly and stably output through the feedback loop, so as to avoid the MOS transistor VQ5 from being mis-triggered to be turned on. Thus, the laser does not bear a large current impact at the power-on moment, and the problem of insufficient start protection in the prior art is effectively solved. Compared with the prior art, the feedback loop composed of the ninth resistor R73 is introduced, so that the response speed and stability of the circuit are improved, and the peripheral circuit design is simplified.

[0054] The above application of specific examples is used to describe the utility model, which is only used to help understand the utility model, and does not limit the utility model. According to the idea of the utility model, those skilled in the art of the utility model can make several simple deductions, deformations or substitutions.

Claims

1. A constant current protection circuit suitable for satellite laser communication, characterized in that, The filter module, the protection starting module and the constant current drive module are included. The filter module receives a PWM control signal, filters the PWM control signal and outputs a control voltage signal to the constant current drive module; the protection starting module receives the PWM control signal and controls the on-off of a triode according to the PWM control signal; An enable signal is generated when the triode is turned off, and the constant current drive module receives the enable signal and outputs a gate drive voltage to soft-start a load; the load is turned off when the triode is turned on.

2. The constant current protection circuit suitable for satellite laser communication according to claim 1, wherein, The filter module includes a first-stage filter and a second-stage filter, the first-stage filter includes a first resistor and a first capacitor, and the second-stage filter includes a second resistor and a second capacitor. One end of the first resistor receives the PWM control signal, the other end of the first resistor is connected to the first capacitor and one end of the second resistor respectively, the other end of the first capacitor is grounded, the other end of the second resistor is connected to one end of the second capacitor and an input end of the protection starting module respectively, and the other end of the second capacitor is grounded. One end of a third resistor is connected between the first resistor and the second resistor, and the other end of the third resistor is grounded.

3. The constant current protection circuit for satellite laser communication according to claim 1, wherein, The protection starting module includes a starting control unit and a voltage stabilizing unit; an input end of the starting control unit is connected to the filter module, an output end of the starting control unit is connected to the voltage stabilizing unit, and an output end of the voltage stabilizing unit is connected to the constant current drive module. The starting control unit is configured to output the enable signal, and the voltage stabilizing unit is configured to provide a stable voltage.

4. The constant current protection circuit suitable for satellite laser communication according to claim 3, wherein, The starting control unit includes a triode and a fourth resistor; a collector of the triode is connected to the filter module, a base of the triode is connected to one end of the fourth resistor, and an emitter of the triode is grounded; and the other end of the fourth resistor is connected to an external power supply end.

5. The constant current protection circuit suitable for satellite laser communication according to claim 4, wherein, The voltage stabilizing unit includes a diode, a fifth resistor and a sixth resistor; a negative electrode of the diode is connected to the constant current drive module, a positive electrode of the diode is connected to one end of the fifth resistor, the sixth resistor is connected in series between the fourth resistor and the external power supply end, and the other end of the fifth resistor is connected between the fourth resistor and the sixth resistor.

6. The constant current protection circuit suitable for satellite laser communication according to claim 1, wherein, The constant current drive module includes an operational amplifier. A non-inverting input end of the operational amplifier is connected to the filter module, an inverting input end of the operational amplifier is connected to the protection starting module, and an output end of the operational amplifier is connected to a gate of a MOS tube after being connected in series with a seventh resistor; a source of the MOS tube is connected to ground after being connected in series with an eighth resistor.

7. The constant current protection circuit suitable for satellite laser communication according to claim 6, wherein, A drain of the MOS tube is connected to a negative electrode of a laser, a positive electrode of the laser is connected to an external power supply end, and the source of the MOS tube is further connected to one end of a ninth resistor, and the other end of the ninth resistor is connected to the inverting input end of the operational amplifier.

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