Working principle of pulse laser power control circuit
The control part of pulsed laser power supply mainly consists of signal source, signal processing and delay regulation, pulse power amplification, energy storage voltage control and other circuits. The main circuit structure of the pulsed laser power supply we developed adopts resonant switching technology, which can be closed when the current passes zero, effectively reducing the switching loss and improving the conversion efficiency. According to the composition of the main circuit, the control circuit mainly completes the charge control, discharge control, time chain between charge and discharge, Q delay control and other functions. Add isolation measures between the main circuit and the control circuit interface to prevent the main circuit from interfering with the control circuit.
Pulse laser power charging control
The charging circuit of the main circuit is composed of two circuits. IGBT is a half-bridge circuit composed of inverter switch components. The phase difference of the two switches reaches 180 degrees, so the phase difference of the two control signals also needs to be guaranteed at 180 degrees. In the inverter cycle, each IGBT inverter switch should be completed to divert and close the intermittent current respectively. In order to prevent the half-bridge circuit from going through, the time is set between the adjacent pulse cycles of the two control signals so that the two inverter switches are closed at the same time.
When the circuit is working, the two pulse widths can be adjusted, the phase difference is 180 degrees, and the synthesis frequency of the two oscillation signals is 22KHz. When charging, the charge and discharge chain and stop charging control terminal are high, allowing the charging control signal to pass through the gate circuit, and then control the inverter switch of the main circuit through the pulse amplifying and isolating circuit. When the energy storage capacitor of the main circuit is charged to the predetermined voltage, Change the charging control terminal to low level, block the charging control signal, and stop the charging process. In addition, when discharging, the control end of the charge-discharge chain will generate 1-2ms wide low level blocking charging control signal to prevent timely stopping charging in case of sudden discharge.
Discharge control of pulsed laser power supply
The discharge circuit of the main circuit is controlled by the SCR switch discharge control signal, which closes when the discharge current reaches zero. We set several fixed discharge frequencies as 1Hz, 5Hz, 10Hz, 20Hz and 40Hz. In addition, it also has the function of manual single discharge and external clock coding control. It has the characteristics of diverse discharge frequency, convenient adjustment and flexibility.
When the circuit is working, the oscillator generates a 2MHz clock pulse for the counter to count. When the end count of the counter is equal to the preset number of the numerical comparator, the Q end of the numerical comparator outputs a pulse signal equal to the width of the clock pulse. At the same time, the pulse signal resets the counter and makes the counter start counting again. When the second count of the counter is equal to the preset number of the numerical comparator, two pulse signals are output at the Q end of the numerical comparator. In this way, a series of pulses are obtained at the output of the numerical comparator with a width of the clock pulse width (i.e. 250ns) and a frequency of F=2MHz* and the reciprocal preset number.
The frequency division error obtained by this method is ±250ns high precision. Since the subsequent circuits are in edge-triggered mode, there is no special requirement for pulse width change, so the whole discharge accuracy is ±250ns. After further frequency division, shaping, pulse amplification and isolation of the pulse signal, the discharge switch SCR is triggered, and the charge-discharge chain control signal and Q-delay adjustment synchronization signal are obtained.
