High-power high-repetition-frequency short pulse driving power supply system

Abstract

The invention belongs to the technical field of laser power supplies, and relates to a high-power high-repetition-frequency short pulse driving power supply system. The system comprises a DC-DC module, a pulse power generation module, an operation parameter detection module and a control module. The high-repetition-frequency pulse current is generated in a frequency synthesis mode, compared with a single power tube, the high-repetition-frequency pulse current can be achieved, the GaN power tube is adopted as the main power tube, and lower on resistance, higher switching frequency and faster turn-on time are achieved; in system feedback, an FPGA chip and a high-speed ADC are adopted for current sampling, and feedback control of high-repetition-frequency pulse current can be achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of laser power supplies, and relates to a short-pulse drive power supply system with high power and high repetition frequency. Background Art

[0002] With the development of modern technology, lidar is applied in more and more fields, such as unmanned driving, aerospace, military and other fields. The lidar drives a laser to generate laser light, and collects the time of the laser echo. By calculating the flight time of the laser, the distance between the laser emission position and the target is measured. Among them, the laser drive power supply is an important part of the lidar system. The power and repetition frequency of the laser are both controlled by the laser drive. A laser drive power supply with high repetition frequency and high power can enable the lidar to have better dynamic response time and longer detection distance. Therefore, the laser drive power supply has gradually become a research hotspot.

[0003] At present, there are many methods to generate ns-level pulse drives. The method of generating short-pulse drives through high-speed switching tubes is the most widely used. This method can generate pulses by controlling the on-off of the switching tubes. However, when the repetition frequency increases, the switching loss of the switching tubes also increases, which may even cause damage to the switching tubes. In addition, since the switching tubes can only be responsible for controlling the on-off of the circuit, it is also difficult to control the amplitude of the pulse current with this kind of circuit. There is also a part of applications that control the drive voltage of the switching tubes to make the switching tubes work in the linear region. In this way, the switching tubes can be equivalent to a variable resistor, and at this time, the output amplitude of the pulse current can be controlled. However, this method makes the switching tubes work in the linear region, and its power consumption also increases greatly. In high-power usage scenarios, it is very easy to cause damage to the switching tubes. And if larger-power switching tubes such as IGBTs are used, due to their slower switching speed, high-repetition-frequency applications cannot be achieved.

[0004] Secondly, the Marx generator circuit is also a common circuit module for generating short pulses. The Marx generator circuit generates short-time high-voltage pulses based on the principle of parallel charging and series discharging of capacitors. However, the Marx generator circuit is generally used to generate high-voltage pulses, and since it uses capacitors as energy storage devices, it is difficult to achieve long-term stability of the pulse amplitude. In addition, gas switches are also used as pulse power devices. These gas switches have the characteristics of large current and high voltage, but gas switches are extremely easy to damage and difficult to maintain. In addition, most gas switches are limited in high-repetition-frequency pulse power applications.

[0005] Finally, most short-pulse power supplies mostly adopt open-loop control. Since the pulse width of the short-pulse power supply is narrow and it is difficult to test the pulse amplitude, most short-pulse power supplies mostly adopt open-loop control. This may affect the stability and accuracy of the system. Summary of the Invention

[0006] The object of the present invention is to solve the problems existing in the prior art, and to provide a high-repetition-rate and high-power laser pulse power supply system with a short rise time. Moreover, this pulse power supply system can monitor the average current, output voltage and peak current, and implement the feedback control of the peak current.

[0007] The technical solution provided by the present invention is: a high-power and high-repetition-rate short-pulse driving power supply system, which includes a DC-DC module, a pulse power generation module, an operating parameter detection module and a control module; wherein, The DC-DC module is controlled by a synchronous buck-boost controller chip, and the current threshold pin and soft start pin of the synchronous buck-boost controller chip are connected to the output end of a multi-channel DAC; The pulse power generation module uses multiple parallel switch tubes as power devices; the on-off of the multiple parallel switch tubes is controlled by multiple signals with the same repetition frequency, and there is the same phase delay between each group of adjacent control signals; The operating parameter detection module includes a slow multi-channel ADC, a high-speed single-channel ADC, a sampling resistor and a differential amplifier; the sampling resistor is connected between the ground and the source of the parallel switch tubes; both ends of the sampling resistor are connected to the differential amplifier; the slow multi-channel ADC is connected to two functional pins of the synchronous buck-boost controller chip to measure the output voltage and average current of the DC-DC module respectively; The control module is responsible for the hardware drive of all functional devices; the control module interacts with the host computer with the sampled slow multi-channel ADC data at a set frequency; the pulse power generation module controls the peak current through a feedback control algorithm; the control module takes the peak current data sampled by the high-speed single-channel ADC and the set value as the input of the PI algorithm, and converts the obtained result into the control parameter of the DAC to control the output of the DC-DC module.

[0008] Preferably, the output of the DC-DC module is connected to a MOS field effect transistor and a series resistor; the MOS field effect transistor is used to quickly reduce the output voltage of the DC-DC module.

[0009] Preferably, the parallel switch tubes are GaN switch tubes, and the number is eight.

[0010] Preferably, it further includes a host computer, which communicates with the FPGA control module and is responsible for the initialization, parameter setting and operation monitoring of the system; the parameter setting includes the setting of pulse width, repetition frequency and amplitude.

[0011] The high-power and high-repetition-frequency short-pulse drive power supply system provided by the present invention generates high-repetition-frequency pulsed current by means of frequency synthesis. Compared with a single power transistor, it can achieve higher-repetition-frequency pulsed current. It uses a GaN power transistor as the main power transistor, which has a lower on-resistance, a higher switching frequency, and a faster turn-on time compared with MOS transistors. In the system feedback, an FPGA and a high-speed ADC are used for current sampling to achieve feedback control of high-repetition-frequency pulsed current. Description of the Drawings

[0012] Figure 1 It is a schematic structural diagram of the high-power and high-repetition-frequency short-pulse drive power supply system provided in the embodiment of the present invention; Figure 2 It is a schematic diagram of the internal modules of the lt8390 chip; Figure 3 It is a schematic diagram of the frequency synthesis technology; Figure 4 is a schematic diagram of the current sampling and processing circuit; in the figure, 1 is a differential amplifier; 2 is an operational amplifier; Figure 5 It is a schematic diagram of the sampling principle of the pulsed peak current with a high repetition frequency; Figure 6 It is a schematic diagram of the selection of actual sampling points. Detailed Embodiments

[0013] For the convenience of understanding the present invention, the present invention will be described in more detail below in conjunction with the drawings and specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described in this specification. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosed content of the present invention more thorough and comprehensive.

[0014] The high-power and high-repetition-frequency short-pulse drive power supply system provided by the present invention includes a DC-DC module, a pulse power generation module, an operating parameter detection module, and a control module. Among them, the control module uses an FPGA chip to perform feedback control of voltage and current by collecting the average output current of the buckboost (synchronous buck-boost controller chip). And according to user requirements, it can achieve control of the pulse width, repetition frequency, and output current.

[0015] For the synchronous buck-boost control chip of the DC-DC module, a commercial LT8390 chip is selected. This chip is a synchronous 4-switch buck-boost DC-DC controller. The chip has an input voltage range of 4 - 60 V and an output voltage capability of 0 - 60 V. The chip has a current output control pin Ctrl, and the maximum output current of the DC current can be controlled by controlling the voltage of the Ctrl pin. In the present invention, the conventional usage of LT8390 is changed. By connecting the Ctrl pin and the SS pin of the chip to the output of a multi-channel DAC, the output voltage and current of the DC-DC module can be controlled by controlling the output voltage of the DAC.

[0016] The SS pin of the LT8390 chip is originally a soft-start pin. Initially, the SS pin is hardware-connected to the ground. When the voltage of the SS pin is less than 0.2 V, it enters the initialization state. In the initial state, SS is pulled low, and after waiting for 10 us until SS is completely pulled low, it enters the PRE state. After waiting for another 10 us, the SS pin is connected to an internal current source of 12.5 uA to charge the external capacitor. When the voltage of the SS pin is greater than 1.75 V, the chip enters the normal working state. At this time, the value of the internal error comparator is set to 1 V, and the voltage of the Vfb pin is compared with 1 V, thus achieving the effect of controlling the output voltage. As Figure 2 shown, when the chip is in the normal working state, the internal current source 3 of the LT8390 chip charges the external capacitor of the SS pin. When the capacitor voltage reaches the reference voltage Vref, the chip reaches the preset voltage. In the invention, the SS pin is connected to the output of the multi-channel DAC. When the system enters the RUN state, since the input current of the multi-channel DAC is greater than the internal current source, the voltage of the SS pin is now controlled by the DAC, and the voltage of the SS pin will not exceed 1.75 V. At this time, the system will not enter the OK state. The input of the internal error amplifier is connected to SS. At this time, the voltage of Vfb will be compared with the voltage of the SS pin. Therefore, the output voltage of the system can be controlled by controlling the voltage of the SS pin.

[0017] The output of the DC-DC module is connected to a filter capacitor array. The filter capacitor array has two functions. One is to filter the DC output, and the other is to reduce the impact of the high-frequency load at the back end on the DC circuit.

[0018] Finally, the output of the DC-DC module is also connected to a MOSFET and a series resistor. When the DC-DC module completes power-on initialization and the output is greater than 0 V at this time, in order to quickly reduce the DC output voltage, the MOSFET will be turned on, and the output voltage of the DC module can drop rapidly.

[0019] In the design of the pulse power generation module, a circuit structure with multiple tubes in parallel is adopted. AsFigure 3 As shown, in the present invention, multiple signals with low repetition frequencies are generated, and there is the same phase delay between each group of adjacent control signals. By using these signals to control the on / off of the parallel switching tubes, a signal with a high repetition frequency can be output. This method of generating a high repetition frequency signal can effectively reduce the switching frequency on a single switching tube, reduce the switching loss, and avoid damage to the switching tube caused by the high repetition frequency.

[0020] For high repetition frequency power pulses, the rise time is also crucial for pulse output. In the present invention, the GaN switching tube EPC2204 is selected as the parallel power switching tube. The GaN switching tube has a higher electron saturation velocity and lower resistance, which means it has a faster switching speed and higher efficiency.

[0021] In the pulse power generation module, a frequency synthesis technology is adopted. A power supply topology with multiple tubes in parallel is used. By controlling the control signals of multiple tubes, multiple low-frequency control signals can be synthesized into a high-frequency output signal. These control signals have the same repetition frequency, and the delay between the control signals of adjacent tubes is the same. In addition, the parallel connection of multiple tubes will increase the internal junction capacitance, which may reduce the conduction time of the switching tube. Therefore, in the present invention, 8 tubes are connected in parallel, and the highest repetition frequency that can be generated is 8 times the frequency of a single control signal.

[0022] The operating parameter detection module includes a sampling resistor, a differential amplifier, an operational amplifier, a slow ADC, and a high-speed ADC.

[0023] The sampling resistor is placed between the ground and the source of the parallel switching tubes. The processing circuit for current sampling is as Figure 4 shown. The two ends of the sampling resistor are connected to the ends of resistors R2 and R3. The differential amplifier 1 selects LMH5401, and the gain-bandwidth product of the operational amplifier 2 is 8 GHz, meeting the requirements of the present invention. The resistance value of the sampling resistor is selected as 6 mΩ, the amplification factor of the operational amplifier is 10 times. At this time, R2 = R3 = 49.9, R4 = R5 = 500. The amplification factor of the differential amplifier is 10 times, and the output differential signals are respectively input into the high-speed ADC and the operational amplifier. The signal input into the high-speed ADC is used for the feedback control of the pulse current. Another group of signals passes through resistors and enters the operational amplifier to convert the differential output into a single-ended output. R6 = R7 = 40, R8 = R9 = 160, and the amplification factor of the single-ended operational amplifier is 4 times. At this time, the total amplification factor is 40 times. This signal is output externally and can be used for system operation state detection and display of the output current magnitude.

[0024] The ADC3564 is used to sample the peak current signal. The ADC3564 is a 14-bit single-channel ADC with a sampling rate as high as 125 MSPS, fully meeting the needs of the present invention.

[0025] In order to monitor the output of the system in real time, the present invention samples the average current, output voltage, and peak current of the power supply system in real time. Among them, a slow two-channel ADC is used to sample the output voltage and output current of the DC-DC circuit, and the sampled output current is output from the ISMON pin of the LT8390 chip. One ADC channel samples the voltage of the ISMON pin to obtain the average output current, and the other ADC channel samples the output voltage after voltage division.

[0026] During the current rising stage, by sampling and measuring the midpoint of a single pulse, the average output current of the current pulse can be obtained. As Figure 5 shown, the feedback control of the output current can be realized by the change of each pulse current output. When the system reaches a stable state, the output current is stable, and sampling at this time can monitor the system operation state.

[0027] However, in actual tests, due to possible switching oscillations in the actual waveform, when the pulse width is short, sampling the midpoint value may sample the waveform oscillation. Therefore, the present invention sets the sampling position to a position behind the midpoint to avoid sampling the oscillating waveform, as Figure 6 shown.

[0028] Among them, both the repetition frequency and duty cycle of the switching signal are fixed values. The present invention adjusts the output voltage of the DC-DC module by sampling the midpoint value of the peak current output to achieve a high-repetition-frequency pulsed power supply with controllable peak current. The control algorithm uses a PI control algorithm. The sampled peak current end point is used as the real-time value of the PI, and the peak current set value is used as the input of the PI algorithm. The output value of the PI is used to control the output voltage of the front-end DC-DC module, and finally the purpose of controllable peak current is achieved. Since the output voltage of the DC-DC module can be increased by adjusting the duty cycle, but when the voltage drops, it may drop slowly due to the influence of the load. Therefore, in order to ensure the normal operation of the control algorithm, the rising time of the peak current is extended to avoid exceeding the set value.

[0029] The control system consists of an FPGA chip and a host computer. The FPGA chip communicates with the host computer through an RS 485 serial port. The host computer is responsible for functions such as the initialization, parameter setting, and operation monitoring of the power supply system. The pulse width, repetition frequency, amplitude, etc. can be set in the host computer. And the host computer will receive the operation parameters of the power supply in real time to avoid operation failures.

[0030] The entire power supply system operates under the control of the FPGA chip. The FPGA chip is responsible for communicating with the host computer and driving each functional device. When the FPGA chip receives the initialization command, the DC-DC module powers on and initializes, and starts generating the switching tube drive signal. The switching tube drive signal can be generated internally by the FPGA chip or synchronized with an external signal. When choosing to generate the drive signal internally by the FPGA chip, the pulse time and width parameters set by the user are transmitted into the FPGA chip, and the required pulse signal is generated through the PLL inside the FPGA chip, and the signal is separated according to the number of parallel switching tubes to drive each switching tube respectively. If an external signal input is selected, the external signal is input into the FPGA chip through the reserved IO port, and after being processed by the internal program, the drive signal is generated.

Claims

1. A high-power, high-repetition-frequency short-pulse drive power supply system, characterized in that: The system includes a DC-DC module, a pulse power generation module, an operation parameter detection module and a control module; wherein, The DC-DC module is controlled by a synchronous buck-boost controller chip, and a current threshold pin and a soft start pin of the synchronous buck-boost controller chip are connected to the output end of the multi-channel DAC; The pulse power generation module uses multiple parallel switch tubes as power devices; the on and off of the multiple parallel switch tubes are controlled by multiple signals with the same repetition frequency, and there is the same phase delay between each group of adjacent control signals; The operating parameter detection module includes a slow multi-channel ADC, a high-speed single-channel ADC, a sampling resistor and a differential amplifier; the sampling resistor is connected between the ground and the source of the parallel switch tube; the two ends of the sampling resistor are connected to the differential amplifier; the slow multi-channel ADC is connected to two functional pins of the synchronous buck-boost controller chip to measure the output voltage and average current of the DC-DC module respectively; The control module is responsible for the hardware drive of all functional devices; the control module exchanges data with the host computer according to the set frequency based on the sampled slow multi-channel ADC data; the pulse power generation module controls the peak current through the feedback control algorithm; the control module uses the peak current data and the set value sampled by the high-speed single-channel ADC as the input of the PI algorithm, and converts the result into the control parameter of the DAC to control the output of the DC-DC module.

2. The high-power, high-repetition-frequency short-pulse driving power supply system according to claim 1, characterized in that: The output of the DC-DC module is also connected to a MOS field effect tube and a series resistor; the MOS field effect tube is used to quickly reduce the output voltage of the DC-DC module.

3. The high-power, high-repetition-frequency short-pulse driving power supply system according to claim 1, characterized in that: The parallel switch tubes are GaN switch tubes, and the number is eight.

4. The high-power, high-repetition-frequency short-pulse driving power supply system according to any one of claims 1 to 3, characterized in that: The control module adopts FPGA chip.

5. The high-power, high-repetition-frequency short-pulse driving power supply system according to any one of claims 1 to 3, characterized in that: The host computer is responsible for system initialization, parameter setting and operation monitoring; the parameter setting includes the setting of pulse width, repetition frequency and amplitude.

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