DsPIC30F on the pulse xenon lamp drive system design
With the computers, machinery, electronics technology, road vehicle testing makes large-scale, rapid and accurate access to the road use of information possible. Detection of the vehicle speed video camera system in accordance with the ordinary into the camera, high-speed video cameras and digital cameras, high-speed camera which is mainly used for road surface cracks, pits and other damage to the state of image acquisition. However, in the use of high-speed cameras, most cars used in testing is an ongoing source of exposure. As a result of low intensity light source, when used in practice are often necessary to increase the exposure time to achieve high-quality image data. Therefore, the light irradiation intensity can improve the quality of image data. Pulsed xenon lamp and the brightness will be able to resolve the contradiction with the accompanying heat. Discharge when it is sending a strong light, but a very short flash duration, so the heat was less affected. Because of the instantaneous optical power, and to restore the good image of the levels .
Pulsed xenon lamp in order to extend the life span and improve the efficiency of photoelectric conversion, must be developed pulsed xenon lamp for the drive system. This article is designed to meet the pulse xenon lamp from the work of the Hui, pre-combustion and high-voltage discharge of the drive system in three stages. Pulsed xenon lamp drive system to control the use of Microchip dsPIC30F chip. The chip is a single-chip microcomputer and dsp technology will be a combination of high-performance 16-bit digital signal controller, a combination of single-chip microcomputer (MCU) to control functions and integrates the advantages of a wide range of peripherals, as well as digital signal processors (DSP) of computing power and data-processing capacity . In addition, it has to deal with unusual events, such as software development environment has also shown a strong performance . DsPIC30F chips due to internal resource-rich, based on the dsPIC30F platform for the development of pulsed xenon lamp drive system requires very little of the peripherals, not only the anti-jamming system, and reliability to meet the pulse xenon lamp in a variety of environments to run the request, and can improve system flexibility, reduce development time, lower development costs.
Drive system hardware design
Drive system from the pulsed xenon lamp-hui can provide sufficient input voltage (about 5kV) glow discharge to occur, in the pre-combustion and high-voltage discharge can provide a stable simmer current (about 100mA) and high-voltage discharge voltage (1 ~ 3kV). Four groups of the system-driven pulse xenon lamp parallel to dsPIC30F4011 chip as the core, the hardware structure as shown in Figure 1, the main control circuit by the dsPIC30F, high charge-discharge circuit, pre-ignition circuit, high voltage circuit from Hui, panel display and output computer communication interfaces.
Figure 1 Pulsed xenon lamp drive system hardware structure
dsPIC30F control circuit
dsPIC30F to control circuitry for the control dsPIC30F4011 chip, the main pulse xenon lamp from the work of Hui, pre-combustion and high-voltage discharge at the time of the three stages of the work of the corresponding conditioning circuit, as well as the protection of signal detection and processing and display panels. Control circuit to the main electrical power control, the input voltage 220V/AC drive system access to the main loop, including the high-voltage charge-discharge circuit, pre-combustion and high-voltage circuits from circuit-hui. And then through the power of transformation, the output pulse xenon lamp can work in three phases of the voltage needed.
From Hui, the control circuit so that the relay contact normally closed disconnect, high pressure from the work of Hui circuit, the occurrence of glow discharge; from FAI, the relay closed, high pressure from the circuit to stop working-hui, the beginning of the work of pre-ignition circuit, the output pulse xenon lamp simmer current maintenance work; Since then, the pulse xenon lamp gradually reached the equivalent resistance and maintain a constant steady-state, by the glow discharge to arc discharge transition.
Pulsed xenon lamp was after the success of pre-combustion, high-pressure work circuit charge and discharge control circuit falling edge trigger signal synchronous high-voltage charge and discharge control circuit of IGBT power switching devices to charge capacitor charging and discharging. After the completion of capacitor charging control circuit to trigger thyristor conduction so that the charge-discharge capacitor discharge, pulsed xenon arc lamps have a stroboscopic phenomenon. Trigger signal is divided into inside and outside the trigger trigger, trigger signals within the pulse xenon lamp is mainly used in front of the normal work of debugging, in general the lower frequencies, the internal timer by dsPIC30F4011 output 10Hz, and a negative pulse to trigger signals within the 0.2ms; outside trigger signals from the normal working hours of high-speed camera synchronized signal, the frequency of arrival of 30kHz, the input capture by the dsPIC30F4011 sync functions to control the high-voltage charge-discharge circuit. High-voltage charge-discharge output circuit through the high-pressure high-voltage input to regulate the size, the dsPIC30F4011 within 10 A / D conversion module acquisition the size of a given high-voltage analog input, and then collect the data output in accordance with the size of a given high voltage value, thereby adjustable high-voltage charge-discharge circuit output 1 ~ 3kV high voltage. At the same time, dsPIC30F4011 in accordance with the signal detected in the panel to show a variety of state and deal with failure, so that the system is stable and reliable.
The system through the computer communication interface for remote control, from the dsPIC30F4011 serial communication interface to start to stop, both within and outside the trigger, high-pressure release and various signal conditioning charging instructions, which can be completely divorced from manual operation of the device.
From pre-ignition circuit-hui
Hui from the principle of pre-ignition circuit shown in Figure 2, the main circuit from the high-frequency push-pull converters, high frequency transformers, high voltage starter circuit, UC3825 control circuit, dsPIC30F control circuit, as well as pre-ignition detection circuit, input and output rectifier filter circuit. 220V AC input voltage through the transformer isolation, rectifier filter as a push-pull converter after the input, push-pull converter input voltage will be converted into high frequency AC voltage pulse through the completion of high-frequency transformer isolation voltage and high frequency matching function ; After following the link in the output rectifier filter, dsPIC30F4011 in accordance with pre-ignition detection circuit detects the current signal control relay output voltage and high-pressure pre-combustion from voltage-hui. UC3825 control circuit UC3825 by high-speed PWM controller and the external circuit, in accordance with the main push-pull circuit transform the current feedback signal, in order to provide the PWM drive switching device.
Figure 2-hui simmer circuit diagram
High-voltage charge-discharge circuit
High-voltage charge-discharge circuit principle shown in Figure 3, the main circuit composed by IGBT full-bridge converters, capacitor charge-discharge circuit, UCC3895 control circuit, dsPIC30F control circuit, overcurrent protection, discharge detection and input and output rectifier filter circuit . Input 220V AC full-bridge diode rectifier through after the high-voltage capacitor filter, full-bridge converter input voltage will be converted into high frequency AC voltage pulse through the completion of high-frequency transformer isolation voltage and high frequency matching function, and then after the output rectifier to charge and discharge capacitors charge. After the completion of capacitor charging, dsPIC30F4011 triggered thyristor VT1 control capacitor discharge through the pulse xenon lamp to produce stroboscopic arc. DsPIC30F control circuit at the same time over-current protection and discharge in accordance with signal detection and treatment of IGBT fault blockade.
Driving System Software Design
Drive system by the main program of the software modules and subroutines. The main program flow chart shown in Figure 4, the main program to complete the main long-distance communication control and manual control of the man-machine interface services, panel display and failure to deal with. Long-distance communication control and manual control procedures at the time of the basic processes, as shown in Figure 5, only when long-range communication to control the serial communication by the single-chip computer to complete single-chip transmission of commands. Subroutine modules, including input capture interrupt, Timer1 timer interrupt, A / D conversion and processing subroutine, given the output of high pressure and serial communication subroutine subprogram.
The main program flow chart of Figure 4
dsPIC30F4011 devices have many to allow the exchange of information with the outside world of peripherals, including timers, input capture module, 10-bit A / D converter and the UART serial communication module 6 by way of the PWM duty cycle output at any time to update [ 5].
Figure 5 Manual / remote communication control program flow chart
Input Capture interrupt subroutine is detected on the Input Capture pin for each input and generate an interrupt falling edge, the output trigger signal and synchronous signal blocking IGBT, while the hardware interrupt flag to be a home, each to enter the Input Capture interrupt After the required software interrupt flag cleared. In addition, after the completion of the first interruption of the input capture control register zero reset, and then re-configured parameters, to initialize input capture function.
Timer1 timer interrupt subroutine is Timer1 by setting the delay timer for each produced an interruption of 0.1s, while the hardware interrupt flag to be a home, the resulting negative 10Hz and 0.2ms pulse width for the trigger signal and the synchronization signal blocking IGBT . Every time after entering the interrupt timer Timer1 interrupt flag to be on the software cleared.
A / D conversion using timer Timer3 time, each model automatically converted 10ms, that is, ADCON1 = 0x0044; scanning input method 16 sampling points each after the interruption, that is, ADCON2 = 0x043C. The system uses 2-way channel scanning input, a conversion, each channel signal path are collected eight sampling points, and then for the average processing, reduction of external interference on the data, and enhance the reliability of the data.
High-voltage output of a given subroutine is the use of internal PWM generator dsPIC30F4011 given in accordance with the analog input corresponding load duty cycle, which corresponds to a different high-voltage output of a given value. PWM signal to configure the output mode as an independent PWMCON1 = 0x0101, run in free mode PTCON = 0x8040, and set the base value of cycle time PTPER = 0x7FFF.
Serial port is set to interrupt the highest priority interrupt to interrupt reception, the prohibition of sending interruption. The value of baud rate generator by the formula U2BRG = FCY / (16 × baud rate) calculated by -1, which for the instruction cycle clock FCY frequency, baud rate select 9600bps, through the receiver and transmitter for data transmission.
In this paper, high-performance-based dsPIC30F4011 digital signal controller pulse xenon lamp drive system makes full use of high-performance dsPIC30F4011 digital signal controller's internal resources, improve the speed drive system, and simplifies circuit design, shortened development time, reduce development costs and improve the reliability of the drive and anti-jamming. Developed this program in accordance with the high-speed flash photography and debug instrument has been successfully installed on vehicles running on road detection. Debugging and running the actual show that the reliable operation of this drive system stability, anti-interference ability, small size, low cost, to drive a variety of models of pulsed xenon lamp.
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