A high-power, high-repetition-frequency short-pulse drive power supply system

Abstract

This invention belongs to the field of laser power supply technology and relates to a high-power, high-repetition-rate short-pulse driving power supply system. The system includes a DC-DC module, a pulse power generation module, an operating parameter detection module, and a control module. This invention employs frequency synthesis to generate high-repetition-rate pulse current, achieving a higher pulse current repetition rate compared to a single power transistor. It uses a GaN power transistor as the main power transistor, which has lower on-resistance, higher switching frequency, and faster turn-on time. In the system feedback, an FPGA chip and a high-speed ADC are used for current sampling, enabling feedback control of the high-repetition-rate pulse current.

Description

Technical Field

[0001] This invention belongs to the field of laser power supply technology and relates to a high-power, high-repetition-frequency short-pulse driving power supply system. Background Technology

[0002] With the development of modern technology, lidar is being applied in an increasing number of fields, such as autonomous driving, aerospace, and military. Lidar generates laser light by driving a laser and collects the time of laser echo. By calculating the laser's time of flight, it measures the distance between the laser's location and the target. The laser driver power supply is a crucial component of the lidar system. The laser's power and repetition rate are both controlled by the laser driver. A high-repetition-rate, high-power laser driver power supply enables lidar to achieve better dynamic response time and longer detection range. Therefore, laser driver power supplies have gradually become a research hotspot.

[0003] Currently, there are many methods for generating nanosecond-level pulse drives. The most widely used method is to generate short pulse drives using high-speed switching transistors. This method generates pulses by controlling the switching on and off of the transistor. However, as the repetition frequency increases, the switching losses of the transistor also increase, potentially leading to transistor damage. Furthermore, since the transistor can only control the circuit's on / off state, this method struggles to control the amplitude of the pulse current. Another application involves controlling the transistor's drive voltage to operate it in the linear region, effectively making it a variable resistor and controlling the pulse current output amplitude. However, this method significantly increases power consumption, easily damaging the transistor in high-power applications. Using high-power transistors like IGBTs, on the other hand, is impractical due to their slower switching speeds, hindering high repetition frequency applications.

[0004] Secondly, Marx generator circuits are also common circuit modules for generating short pulses. Marx generator circuits generate short-duration high-voltage pulses through the principle of parallel charging and series discharging of capacitors. However, Marx generator circuits are generally used to generate high-voltage pulses, and because they use capacitors as energy storage devices, it is difficult to achieve long-term pulse amplitude stability. In addition, gas switches are also used as pulse power devices. These gas switches are characterized by high current and high voltage, but they are easily damaged and difficult to maintain. Furthermore, most gas switches are limited in high-repetition-frequency pulse power applications.

[0005] Finally, most short-pulse power supplies employ open-loop control. Because short-pulse power supplies have narrow pulse widths, it is difficult to test their pulse amplitude, hence the prevalence of open-loop control. This can potentially affect the system's stability and accuracy. Summary of the Invention

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

[0007] The technical solution provided by this invention is: a high-power, high-repetition-frequency short-pulse drive power supply system, which includes a DC-DC module, a pulse power generation module, an operating parameter detection module, and a control module; wherein,

[0008] The DC-DC module is controlled by a synchronous buck-boost controller chip, whose current threshold pin and soft-start pin are connected to the output of a multi-channel DAC.

[0009] The pulse power generation module uses multiple parallel switching transistors as power devices; the switching of multiple parallel switching transistors is controlled by multiple signals with the same repetition frequency, and there is the same phase delay between each group of adjacent control signals;

[0010] 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 ground and the source stage of the parallel switching transistor; 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;

[0011] The control module is responsible for the hardware driving of all functional devices; the control module exchanges data with the host computer at a set frequency using the sampled slow multi-channel ADC data; the pulse power generation module controls the peak current through a feedback control algorithm; the control module uses the peak current data sampled by the high-speed single-channel ADC and the set value as input to the PI algorithm, and converts the result into the control parameters of the DAC to control the output of the DC-DC module.

[0012] 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.

[0013] Preferably, the parallel switching transistors are GaN switching transistors, and the number is eight.

[0014] Preferably, the system also includes a host computer that communicates with the FPGA control module and is responsible for system initialization, parameter setting, and operation monitoring; the parameter setting includes setting the pulse width, repetition frequency, and amplitude.

[0015] The high-power, high-repetition-frequency short-pulse drive power supply system provided by this invention uses frequency synthesis to generate high-repetition-frequency pulse current. Compared with a single power transistor, it can achieve a higher repetition-frequency pulse current. It uses a GaN power transistor as the main power transistor, which has lower on-resistance, higher switching frequency and faster turn-on time compared with MOSFET. In the system feedback, an FPGA and a high-speed ADC are used for current sampling, which can realize feedback control of high-repetition-frequency pulse current. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of a high-power, high-repetition-frequency short-pulse drive power supply system provided in an embodiment of the present invention.

[0017] Figure 2 This is a schematic diagram of the internal modules of the LT8390 chip;

[0018] Figure 3 This is a schematic diagram of frequency synthesis technology;

[0019] Figure 4 is a schematic diagram of the current sampling and processing circuit; 1 in the figure is a differential amplifier; 2 is an operational amplifier;

[0020] Figure 5 Schematic diagram of high repetition frequency pulse peak current sampling principle;

[0021] Figure 6 A schematic diagram showing the selection of actual sampling points. Detailed Implementation

[0022] To facilitate understanding of the present invention, it will be described in more detail below with reference to the accompanying 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. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the present invention.

[0023] The high-power, high-repetition-frequency short-pulse drive power supply system provided by this invention includes a DC-DC module, a pulse power generation module, an operating parameter detection module, and a control module. The control module uses an FPGA chip and performs voltage and current feedback control by acquiring the average output current of a buck-boost (synchronous buck-boost controller chip). Furthermore, it can control the pulse width, repetition frequency, and output current according to user requirements.

[0024] The synchronous buck-boost control chip for the DC-DC module is the commercially available LT8390 chip, a synchronous 4-switch buck-boost DC-DC controller. This chip has an input voltage range of 4-60 V and an output voltage capability of 0-60 V. It features a current output control pin (Ctrl), allowing control of the maximum DC output current by adjusting the voltage on this pin. In this invention, the conventional usage of the LT8390 is modified by connecting its Ctrl and SS pins to the output of a multi-channel DAC. This allows control of the DAC's output voltage to control both the output voltage and current of the DC-DC module.

[0025] The SS pin of the LT8390 chip is originally a soft-start pin. Initially, the SS pin is hardware-connected to ground. When the SS pin voltage is less than 0.2V, it enters the initialization state. In the initial state, SS is pulled low and waits for 10µs. Once SS is fully pulled low, it enters the PRE state and waits another 10µs. The SS pin is then connected to an internal 12.5µA current source to charge the external capacitor. When the SS pin voltage is greater than 1.75V, the chip enters the normal operating state. At this time, the internal error comparator is set to 1V, and the Vfb pin voltage is compared with 1V, thus controlling the output voltage. Figure 2 As shown, when the chip is in normal operating condition, the internal current source 3 of the LT8390 chip charges the external capacitor of the SS pin. When the capacitor voltage is equal to the reference voltage Vref, the chip reaches the preset voltage. In this invention, the SS pin is connected to the output of a 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, so the output voltage of the system can be controlled by controlling the voltage of the SS pin.

[0026] The output of the DC-DC module is connected to a filter capacitor array. The filter capacitor array serves two purposes: one is to filter the DC output, and the other is to reduce the impact of high-frequency loads on the DC circuit.

[0027] Finally, the output of the DC-DC module is connected to a MOSFET and a series resistor. After the DC-DC module completes power-on initialization, the output is greater than 0 V. In order to quickly reduce the DC output voltage, the MOSFET will be turned on, and the output voltage of the DC module will drop rapidly.

[0028] The design of the pulse power generation module employs a multi-transistor parallel circuit structure. For example... Figure 3 As shown, this invention generates multiple low-repetition-frequency signals, with each group of adjacent control signals having the same phase delay. Using these signals to control the on / off state of parallel switching transistors outputs a high-repetition-frequency signal. This method of generating a high-repetition-frequency signal effectively reduces the switching frequency of a single switching transistor, decreases switching losses, and avoids transistor damage caused by high repetition frequency.

[0029] For high-repetition-frequency power pulses, rise time is also a key factor affecting pulse output. In this invention, a GaN switch EPC2204 is selected as the parallel power switch. GaN switches have higher electron saturation velocity and lower resistance, meaning they offer faster switching speeds and higher efficiency.

[0030] Frequency synthesis technology is employed in the pulse power generation module. A multi-transistor parallel power supply topology is used. By controlling the control signals of multiple transistors, 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 transistors is the same. In addition, the parallel connection of multiple transistors increases the internal junction capacitance, which may reduce the conduction time of the switching transistors. Therefore, this invention uses 8 transistors in parallel, which can generate a repetition frequency up to 8 times that of a single control signal.

[0031] The operating parameter detection module includes a sampling resistor, a differential amplifier, an operational amplifier, a slow ADC, and a high-speed ADC.

[0032] The sampling resistor is placed between ground and the source of the parallel-connected switching transistor. The current sampling processing circuit is as follows: Figure 4 As shown. The two ends of the sampling resistor are connected to the terminals of resistors R2 and R3. Differential amplifier 1 is selected as LMH5401, and the gain-bandwidth product of operational amplifier 2 is 8GHz, which meets the requirements of this invention. The resistance value of the sampling resistor is selected as 6 mΩ, and 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 signal is input into the high-speed ADC and the operational amplifier respectively. The signal input to the high-speed ADC is used for pulse current feedback control. Another set of signals passes through resistors into 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 status detection and output current display.

[0033] The peak current signal is sampled using an ADC3564, a 14-bit single-channel ADC with a sampling rate of up to 125 MSPS, which fully meets the requirements of this invention.

[0034] To monitor the system output in real time, this invention samples the average current, output voltage, and peak current of the power supply system. A slow dual-channel ADC is used to sample the output voltage and current of the DC-DC circuit, with the ISMON pin of the LT8390 chip outputting the sampled output current. One ADC channel samples the ISMON pin voltage to obtain the average output current, while the other ADC channel samples the output voltage after voltage division.

[0035] During the current rise phase, the average output current of the current pulse can be obtained by sampling and measuring the midpoint of a single pulse. For example... Figure 5 As shown, feedback control of the output current can be achieved by monitoring the change in the output current with each pulse. Once the system reaches a stable state, the output current remains stable, and sampling at this point allows for monitoring of the system's operating status.

[0036] In actual testing, because the actual waveform may exhibit switching oscillations, sampling at the midpoint during short pulse widths might result in sampling at points of waveform oscillation. Therefore, this invention sets the sampling position to a position further after the midpoint to avoid sampling oscillating waveforms. Figure 6 As shown.

[0037] The repetition frequency and duty cycle of the switching signal are fixed values. This 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 pulse power supply with controllable peak current. The control algorithm adopts a PI control algorithm. The sampled peak current endpoint is used as the real-time value of the PI, and the peak current setpoint 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, ultimately achieving the goal of controllable peak current. Since the output voltage rise of the DC-DC module can be achieved by adjusting the duty cycle, but the voltage drop may be slow due to load influence, the rise time of the peak current is extended to prevent it from exceeding the set value in order to control the normal operation of the algorithm.

[0038] The control system consists of an FPGA chip and a host computer. The FPGA chip communicates with the host computer via an RS-485 serial port. The host computer is responsible for the initialization, parameter setting, and operation monitoring of the power supply system. Pulse width, repetition frequency, and amplitude can be set in the host computer. Furthermore, the host computer receives real-time power supply operating parameters to prevent operational failures.

[0039] The entire power system operates under the control of the FPGA chip. The FPGA chip is responsible for communication with the host computer and driving the various functional devices. Upon receiving an initialization command, the DC-DC module performs power-on initialization and begins generating switching transistor drive signals. These drive signals can be generated internally by the FPGA chip or synchronized with external signals. When internal generation is selected, the user-defined pulse time and width parameters are transmitted to the FPGA chip, and the required pulse signals are generated by the FPGA's internal PLL. The signals are then separated according to the number of parallel switches, driving each switch individually. If external signal input is selected, the external signal is input to the FPGA chip through a reserved I / O port, processed internally, and then used to generate drive signals.

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 operating parameter detection module, and a control module; among which, The DC-DC module is controlled by a synchronous buck-boost controller chip, whose current threshold pin and soft-start pin are connected to the output of a multi-channel DAC. The pulse power generation module uses multiple parallel switching transistors as power devices; the switching of multiple parallel switching transistors 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 ground and the source stage of the parallel switching transistor; 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 driving of all functional devices; the control module exchanges data with the host computer at a set frequency using the sampled slow multi-channel ADC data; the pulse power generation module controls the peak current through a feedback control algorithm; the control module uses the peak current data sampled by the high-speed single-channel ADC and the set value as input to the PI algorithm, and converts the result into the control parameters of the DAC to control the output of the DC-DC module.

2. The high-power, high-repetition-frequency short-pulse drive 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 transistor and a series resistor; the MOS field-effect transistor is used to quickly reduce the output voltage of the DC-DC module.

3. The high-power, high-repetition-frequency short-pulse drive power supply system according to claim 1, characterized in that: The parallel switching transistors are selected from GaN transistors, and there are eight of them.

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

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

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