Synrad p250, User Manual, Page: 41 / 106

CONTROLLING LASER POWER PAGE | 41
Controlling laser power
This section includes the following subsections:
• Control signals
• Operating modes
Important Note: Because all OEM p250 lasers incorporate a built-in tickle generator (2- 6 μ s
pulses at 5kHz), there is no need to supply external tickle pulses. The application of external tickle
pulses may affect the p250’s pulsing performance.
Control signals
Much of the information provided in this section describes the application of PWM command signals to
the p250 laser. If using an alternate method of laser control, thoroughly review this section, controlling
laser power, as well as the following section, User I/O connections, for an understanding of the signal
requirements necessary to control p250 lasers.
Tickle pulse
Tickle pulses pre-ionize the laser gas to just below the lasing threshold so that a further increase in pulse
width adds enough energy to the plasma to cause laser emission. Tickle pulses cause the laser to
respond predictably and almost instantaneously to PWM Command signals, even when there is
considerable delay (laser off time) between applied Command signals. All p250 lasers incorporate a
built-in tickle generator, freeing customers from the need to supply external tickle pulses between lasing
commands.
Internal circuitry monitors the incoming PWM signal and determines the amount of time the laser was on
(lasing) during the last 200 microsecond (
μ
s) interval. If the lasers ‘on time’ was greater than the preset
tickle value, then no tickle pulse is generated because the PWM signal was sufficient to maintain a
plasma state. If no PWM signal was applied during the 200-
μ
s measurement period (or was shorter than
the preset tickle value), internal circuitry generates a tickle pulse such that the laser always receives a
pre-set amount of RF drive averaged over any 200-
μ
s interval.
Warning: Serious Personal Injury
Because of phase differences, external tickle pulses may combine with the internally generated tickle
signal causing the LASE LED to flicker during the transition from tickle to lasing.
Laser output may occur if the LASE LED flickers.