Patent Application
20240128712
The present disclosure claims the priority to the Chinese patent application with the filing No. 202110207122.8 filed with the Chinese Patent Office on Feb. 25, 2021, the contents of which are incorporated herein by reference in entirety for all purposes.
The present disclosure relates to the technical field of laser drive circuits, in particular to a constant current drive circuit for voltage-adaptive numerical-control laser and control method thereof.
Currently, the lasers have been widely used in daily life of people, industrial production, medical equipment, aerospace, special equipment or military weapons. LD semiconductor lasers are relatively common among lasers, and because of their mature production process and relatively low cost, they have been widely used in fields such as long-distance optical fiber communication, wireless communication, laser marking, laser ranging, laser radar, laser weapons.
LD lasers are generally driven by a constant current. Generally, the output current of the laser is a constant current or a current signal modulated by PWM, wherein the amplitude of the driving current thereof is generally constant. Ordinary lasers have poor ability to resist surge, when a large surge current or current overshoot is occurred during work, it is easy to reduce the lifespan of the laser or damage the laser.
In some special applications, such as laser marking, laser radar and laser weapons, it is always required that the pulse width of the driving constant current of the laser is controllable and that its current value can be regulated. In some other applications, it is required that the constant current drive circuit of the laser can be directly connected to different types of lasers for use, or that multiple lasers are used to be connected in series to increase the laser output power of the entire system, which requires that the circuit can use the operating voltage of different types of lasers, and can output adjustable current and pulse.
Products or solutions in the prior art involve constant current drive circuits for some lasers. For example, the patent CN109950790A “Laser Control Circuit, and Laser Device” proposes a constant current drive circuit to realize the operation of lasers with different junction voltages, but this solution can only output a constant current, and the power supply voltage is regulated through an external adjustable resistor; the patent CN111355121A “Double Pulse Laser Drive System, Drive Circuit and Drive Method” proposes a double-pulse LD laser constant current drive circuit and method thereof, but the power supply of this solution is not adjustable and this solution requires two input signals to control to generate double pulse, which limits its application; the patent CN110445011A “Laser Power Supply Constant Current Drive Circuit and Method thereof” mainly solves the problem of stability and lifespan of the laser in use, which does not take the operation efficiency of the laser and the application of PWM pulse width modulation into account; and the patent CN105208739B “Laser Light Source Constant Current Drive Device” proposes a constant current output laser drive circuit powered by a DC/DC power supply, which does not realize the regulation of the laser voltage and the PWM pulse width modulation of the laser.
The technical problem to be solved by the present disclosure is to provide a laser constant current drive circuit that has a PWM pulse width modulation output function, in which the operating voltage of the laser is self-adaptive. The circuit of the present disclosure adopts 4-way AD chips to collect the input power supply voltage, the positive voltage of the laser, the negative voltage of the laser and the voltage on the sampling resistor; then after passing through the voltage-follower and sampled by AD, the voltage is input to the MCU as a parameter for PID adjustment and the output voltage of controlling the switching power supply is feedback, so as to control the voltage drop of the power MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) in the constant current drive circuit, thereby reducing heat dissipation and achieving higher efficiency. At the same time, the analog switch chip is used as the control switch of the PWM signal, and the output voltage of multi-way DA conversion circuit is used as the reference value of the output current, and the MCU is used to realize the setting for pulse width and frequency, which can easily realize adjustment of strobing and step current.
In order to solve the above technical problems, the present disclosure further provides a voltage-adaptive laser drive circuit, including a switching power supply 1, a laser 2, a constant current drive circuit 3, a current setting circuit 4, a MCU control circuit 5, a voltage sampling circuit 6, and a voltage setting circuit 7.
The switching power supply 1 is respectively connected to the laser 2 and the voltage setting circuit 7, and configured to provide electric energy for the laser 2 and the voltage setting circuit 7.
The laser 2 is respectively connected to the switching power supply 1 and the constant current drive circuit 3 for generating light.
The constant current drive circuit 3 is respectively connected to the laser 2 and the current setting circuit 4, and configured to control the current passing through the laser 2 to be a constant current.
The current setting circuit 4 is respectively connected to the constant current drive circuit 3 and the MCU control circuit 5, and configured to correspondingly output an analog voltage according to the output current of the constant current drive circuit 3.
The MCU control circuit 5 is respectively connected to the current setting circuit 4, the voltage sampling circuit 6, and the voltage setting circuit 7, and configured to realize the numerical-control adjustment of the voltage-adaptive laser drive circuit.
The voltage sampling circuit 6 collects the output voltage of the switching power supply 1, the input voltage of the laser 2, the output voltage of the laser 2, and the voltage of the sampling resistor in the constant current drive circuit 3, and then provides them for the MCU control circuit 5 for collecting analog voltage to realize digital control.
The voltage setting circuit 7 is respectively connected to the MCU control circuit 5 and the switching power supply 1, and configured to output voltage to the switching power supply 1 to realize linear adjustment for the output voltage.
Preferably, the current setting circuit 4 further includes a digital-control analog-voltage setting-and-selecting output circuit. The current setting circuit 4 further includes a multi-channel DA chip and a multi-channel analog switch chip, wherein the DA chip outputs voltage to the analog switch chip.
Preferably, the constant current drive circuit 3 is a current series-connection negative feedback structure. The voltage of the current sampling resistor is applied to the input negative terminal of the operational amplifier. The output signal of the current setting circuit 4 is transmitted to one terminal of the current limiting resistor, and the other terminal of the current limiting resistor is connected to the input positive terminal of the operational amplifier, and the output signal of the operational amplifier is transmitted to the grid of the power MOSFET.
Preferably, the constant current drive circuit 3 is a current parallel-connection negative feedback structure, wherein one terminal of the parallel resistor is connected to the input negative terminal of the operational amplifier, and the other terminal is connected to the input terminal of the current sampling resistor. One terminal of the current limiting resistor receives the output signal of the analog switch chip, the other terminal of the current limiting resistor is connected to the input negative terminal of the operational amplifier, the positive terminal of the operational amplifier is connected to the output terminal of the reference voltage chip, and the output signal of the operational amplifier is transmitted to the gate of the power MOSFET.
Preferably, the MCU control circuit 5 is further configured to perform PID setting on the output voltages of the voltage setting circuit 7 and the switching power supply 1.
Preferably, the switching power supply 1 further includes an input voltage VCC, an output voltage OUT, a reset signal RESET and a voltage regulation pin FB.
Preferably, the laser 2 is a laser driven by a constant current.
Preferably, the constant current drive circuit 3 is set in a linear constant current control mode, wherein its topological structure is a current series-connection negative feedback structure, or a current parallel-connection negative feedback structure.
Preferably, the voltage setting circuit 7 further includes a DA conversion circuit, wherein the output terminal of the DA conversion circuit is connected to one terminal of the voltage setting resistor, and the other terminal of the voltage setting resistor is connected to the switching power supply 1.
Preferably, the laser 2 is replaced with an LED light source.
In order to solve the above-mentioned technical problems, the present disclosure also provides a control method for the voltage-adaptive laser drive circuit, including the following steps:
Step 1, after starting up, setting the input voltage VFB of the switching power supply 1 to be 0V, and at this time, setting the output voltage Vout of the switching power supply 1 to be the maximum value;
Step 2, according to the value of step current set by the user, selecting the maximum output step current Imax of the step current passing through the laser 2, and controlling the output voltage during this period;
Step 3, acquiring, by the voltage sampling circuit 6, the input voltage VLD+ of the laser 2, the output voltage VLD− of the laser 2, and the voltage VRS of the sampling resistor of the constant current drive circuit 3, and calculating the operating voltage VLD at two terminals of the laser 2;
Step 4, calculating the power heat dissipation of the MOSFET in the constant current drive circuit 3;
Step 5, according to the preset value PH of the power heat dissipation of the MOSFET in the constant current drive circuit 3, determining the voltage drop VDS across the drain and the source of the MOSFET;
Step 6, calculating the output voltage Vout of the switching power supply 1;
Step 7, calculating the numerical value of the output voltage VT of the DA chip of the voltage setting circuit 7, and then controlling the output voltage VT of the DA chip of the voltage setting circuit 7 by gradually increasing VT via the MCU control circuit 5; and
Step 8, controlling the voltage sampling circuit 6 by the MCU control circuit 5 to sample the operating voltage of each point again, according to the output voltage Vout of the switching power supply 1 and the value of the VT of the DA chip of the voltage setting circuit 7, comparing the actual power consumption of the MOSFET with the preset power consumption, to realize the closed-loop control of PID of output voltage value.
In the above, VFB is the input voltage of the switching power supply 1; Vout is the output voltage of the switching power supply 1; Imax is the maximum output step current in the step current passing through the laser 2; VLD+ is the input voltage of the laser 2; VLD− is the output voltage of the laser 2; VRS is the voltage of the sampling resistor of the constant current drive circuit 3; VLD is the operating voltage at two terminals of the laser 2; VDS is the voltage drop across the drain and source of the MOSFET in the constant current drive circuit 3; and VT is the output voltage of the DA chip of the voltage setting circuit 7.
Preferably, realizing the closed-loop control of PID of output voltage value further includes controlling, by the MCU control circuit 5, the switching power supply 1, the laser 2, the constant current drive circuit 3, the voltage sampling circuit 6, and the voltage setting circuit 7 for voltage output, to realize the circuit adjustment.
Preferably, the laser 2 is replaced with an LED light source.
The present disclosure includes the following beneficial effects.
In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure or the prior art, the following will briefly introduce the drawings required in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only part of the embodiments or the prior art. For those ordinarily skilled in the art, other similar or related drawings can also be obtained according to these drawings without inventive effort.
The present disclosure is described in detail below in conjunction with embodiments. In order to make the purpose, technical solutions and advantages of the present disclosure clearer and more explicit, the present disclosure will be further described in detail below, but the present disclosure is not limited to these embodiments.
The present disclosure relates to a constant current drive circuit for voltage-adaptive numerical-control laser, including a switching power supply 1, a laser 2, a constant current drive circuit 3, a current setting circuit 4, an MCU control circuit 5, a voltage sampling circuit 6, and a voltage setting circuit 7, wherein the MCU control circuit 5 realizes the numerical-control adjustment for the system, the voltage sampling circuit 6 is a digital-control 4-channel analog-voltage sampling circuit, the current setting circuit 4 provides an output voltage for the constant current drive circuit to realize the constant current output, and the voltage setting circuit 7 outputs a voltage to the switching power supply to realize self-adaptive adjustment according to the characteristics of the operating voltage of the laser. In the present disclosure, the PID adjustment of the voltage sampling circuit and the voltage setting circuit is accomplished by the MCU control circuit, so as to realize the self-adaptive change of the output voltage of the switching power supply according to the working state of the laser and the constant current circuit, and the PWM high-speed strobing function is realized by regulating the current setting circuit through the MCU control circuit.
The voltage sampling circuit 6 collects the output voltage of the switching power supply 1, the input voltage of the laser 2, the output voltage of the laser 2, and the voltage of the sampling resistor in the constant current drive circuit 3, and provides them for the MCU control circuit 5 for collecting analog voltage to realize digital control.
As shown in
The switching power supply supplies power to the laser. The switching power supply can be realized through many ways, which can adopt a non-isolated topological structure or an isolated switching power supply topological structure. The characteristic of the switching power supply is that the external performance of the switching power supply should include input voltage VCC, output voltage OUT, reset signal RESET and voltage regulation pin FB.
The laser is an LD laser or other types of lasers driven by constant current. The laser can also be in the form of an external terminal, and the user can access the desired laser according to the needs.
The constant current drive circuit controls the current passing through the laser to be a constant current, wherein the constant current drive circuit adopts a linear constant current control method, and its topological structure can be a current series-connection negative feedback structure or a current parallel-connection negative feedback structure.
The current setting circuit is a digital-control analog-voltage setting-and-selecting output circuit, wherein the current setting circuit is composed of a multi-channel DA chip and a multi-channel analog switch. The output voltage of the DA chip is provided for the input of the analog switch chip. The number of output channels of the DA chip should correspond to the number of input channels of the analog switch chip, and the current setting circuit is communicatively controlled by the MCU.
The MCU control circuit can be a microprocessor circuit, a CUP circuit, an ARM circuit or an FPGA circuit.
The voltage sampling circuit is a digital-control 4-channel analog-voltage sampling circuit. The 4-way AD chip collects the input power supply voltage, the positive voltage of the laser, the negative voltage of the laser and the voltage on the sampling resistor. The voltage is applied to the MCU as a parameter for PID adjustment. The output voltage of the switching power supply is subjected to feedback control. The adjustment for PID feedback signal is realized by software, so as to control the voltage drop of the MOSFET in the constant current drive circuit, thereby reducing heat dissipation and achieving higher efficiency.
The MCU communicatively controls output voltage of voltage setting circuit, which is applied to the switching power supply, thereby controlling the output voltage of the switching power supply to perform linear adjustment.
As shown in
The constant current drive circuit is of a current series-connection negative feedback structure, wherein the linear constant current power tube is M1, the current sampling resistor is R31, the voltage of the sampling resistor is applied to the input negative terminal of the operational amplifier U11, the output signal of the analog switch circuit 4 is transmitted to one terminal of the resistor R14, the other terminal of the resistor R14 is connected to the input positive terminal of the operational amplifier U11, and the output signal of the operational amplifier U11 is transmitted to the gate of the power MOSFET. At this time, the calculation formula of the output current is:
In Formula 1, VD is the voltage at the connection point between the resistor R14 and the analog switch circuit, and RS is the resistance value of the sampling resistor R31.
The core chip of the current setting circuit adopts 8-way 12-bit DA chip, wherein the output voltage signals are Vout0, Vout1, Vout2, Vout3, Vout4, Vout5, Vout6, and Vout7. The current setting circuit uses SPI interface to communicate with MCU, wherein the communication signals are SCLK, SYNC, SDI, SDO, LDAC and RESET, wherein SCLK, SYNC, SDI and SDO are respectively connected in series with resistors R17, R20, R22 and R24 and then connected to the MCU. The analog switch chip adopts an single 8-channel analog switch, and the channel-selection control signals are 3-bit A2, A1 and A0 signals, which are respectively connected in series with resistors R30, R29 and R28 and connected to the control terminals of the MCU; the 8-channel signal input terminals S8, S7, S6, S5, S4, S3, S2 and S1 of the analog switch chip are respectively connected to the output signal of the DA chip; and the output signal terminal of the analog switch chip is D, wherein the output signal is provided for the constant current drive circuit.
The MCU control circuit can be selected to be connected to the display circuit, communication circuit, and control circuit. The display circuit is used to display the working status and output condition of the circuit. The communication circuit is used to communicate with the upper machine or perform remote control. The control circuit is used to configure the working status and output value.
The signal pins P06, P07 and P10 of the MCU control circuit are respectively connected in series to the resistors R30, R29, and R28 to be connected to the signal-selection terminals A2, A1, and A0 of the analog switch circuit; the signal pins P00, P01 are respectively connected to LDAC and RESET of the current setting circuit; the signal pins P02, P03, PO4, P05 are respectively connected to SDO, SDI, SYNC and SCLK of the current setting circuit through resistors R24, R22, R20, R17; the signal pins P11, P12, P13, P14 are connected to CONVST, ALERT, SDA and SCL of the voltage sampling circuit; and the signal pins P15, P16, and P17 are connected with A0, SCL and SDA pins of the voltage setting circuit.
The voltage sampling circuit adopts the 4-way DA voltage conversion chip U6 with I2C interface. The signals SCL, SDA, ALERT, and CONVEST of U6 are connected to the terminals P14, P13, P12, and P11 of the MCU control circuit, and the signal pins SCL, SDA, and ALERT are pulled up to 3.3V voltage via resistors R6, R7, R8.
Resistors R26 and R27 obtain the sampling resistor voltage VRS of constant current drive circuit and divide the voltage, wherein the signal after dividing the voltage is provided for the operational amplifier U12 for following and then input to Vin1 of U6.
Resistors R11 and R12 obtain the negative voltage VLED− of the LED light source and divide the voltage, wherein the signal after voltage division is provided for the operational amplifier U8 for following and then input to Vin2 of U6.
Resistors R2 and R3 obtain the input voltage VCC of the switching power supply and divide the voltage, wherein the signal after voltage division is provided for the operational amplifier U2 for following and then input to Vin3 of U6.
Resistors R9 and R10 obtain the positive voltage VLED+ of the LED light source and divide the voltage, wherein the signal after voltage division is provided for the operational amplifier U4 for following and then input to Vin4 of U6.
The voltage setting circuit adopts a single-way DA chip, the input control signal adopts I2C interface, and the signal pins are SCL and SDA. The input signals are transmitted to the communication pins of the MCU, which are pulled up by the resistors R4 and R5 respectively. The output signal is connected to one terminal of the resistor R1, and the other terminal of the resistor R1 is connected to the FB pin of the switching power supply.
The drive circuit in the present disclosure can be used to drive the laser, and can also be used to drive the LED light source.
As shown in
In Formula 2, VD is the voltage at the connection point between the resistor R14 and the analog switch chip, RS is the resistance value of the sampling resistor R31, VREF is the reference voltage value of the positive terminal of the operational amplifier U11, and K1 is the ratio of the resistor R32 to the resistor R14.
As shown in
V
out=(K2+K3+1)·VFB−K3·VT Formula 3.
In Formula 3, Vout is the output voltage of the switching power supply; VT is the output voltage of the DA conversion circuit in the voltage setting circuit; VFB is the input voltage of the switching power supply circuit, which is the reference pin of the output voltage Vout, and also known as the output feedback pin, which is connected to the input terminal of the internal error amplifier to set the output voltage; K2 is the ratio of the resistor R13 to the resistor R16; and K3 is the ratio of the resistor R13 to the resistor R1.
As shown in
Step 1, after starting up, setting the output voltage VFB of the voltage setting circuit to be 0, and Vout to be the maximum value;
Step 2, selecting the maximum output step current Imax in the step current according to the step current value configured by the user, and controlling the output voltage in this cycle;
Step 3, collecting the output voltages VLD+, VLD−, VRS by the voltage sampling circuit, and calculating the operating voltage VLD at two terminals of the LD light source as:
V
LD
=V
LD+
−V
LD− Formula 4;
Step 4, at this time, calculating the power consumption of the MOSFET as:
P=I
max×(VLD−−VRS) Formula 5;
Step 5, according to the preset value PH of the power heat dissipation of the MOSFET, determining the voltage drop VDS across the drain and source of the power MOSFET:
V
DS
=P
H
/I
max Formula 6;
Step 6, calculating the output voltage Vout:
V
out
=V
DS
+V
LD
+V
RS Formula 7;
Step 7, calculating the value of VT according to Formula 3 and Formula 7, and then controlling the output voltage VT of the voltage setting circuit 7 through the MCU control circuit 5 by the way of gradually increasing VT; and
Step 8, sampling the operating voltage of each point again by controlling the voltage sampling circuit through the MCU, and comparing the actual power consumption of the MOSFET with the preset power consumption Ph according to the values of Vout and VT, so as to realize the closed-loop control of PID of the output voltage value.
In the above, VFB is the input voltage of the switching power supply 1; Vout is the output voltage of the switching power supply 1; Imax is the maximum output step current in the step current passing through the laser 2; VLD+ is the input voltage of the laser 2; VLD− is the output voltage of the laser 2; VRS is the voltage of the sampling resistor of the constant current drive circuit 3; VLD is the operating voltage at two terminals of the laser 2; VDS is the voltage drop between the drain and the source of the MOSFET in the constant current drive circuit 3; and VT is the output voltage of the DA chip of the voltage setting circuit 7.
The above contents are only a few embodiments of the present disclosure, and do not limit the present disclosure in any way. Although the present disclosure is disclosed above by the preferred embodiments, but it is not intended to limit the present disclosure. For any person skilled in the art, without departing from the scope of the technical solution of the present disclosure, using the above revealed technical content to make minor changes or modifications is equivalent to the equivalent implementation, which are all within the scope of protection of the technical solution of the present disclosure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202110207122.8 | Feb 2021 | CN | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CN2021/129992 | 11/11/2021 | WO |
