Variable PC Power Supply Circuits


variable variable Power Supply Circuits

Many alternatives abound where a HeNe laser power supply must be constructed from scratch. Decisions must be made based on the size or range of sizes of the HeNe tube(s) to be powered, convenience, need for portability (well in a relative sort of way), availability of components, and so forth.

variable Power Supply Circuits

This chapter deals with the more practical aspects of HeNe laser power supply design including circuits for providing the HeNe tube operating voltage (AC line and inverter types), starters, regulators, and modulators. There are many options for each subsystem and it is often possible to mix and match as desired!
AC Line Operated Versus Inverter Based Power Supplies
A variety of techniques can be used to provide the starting and operating voltages for HeNe lasers. It is, after all, just a special type of gas discharge tube so almost any approach that can convince the HeNe tube to pass the proper current will be satisfactory.

* AC line operated approaches are generally larger and heavier due to the power transformer which must run at the line frequency – 50 or 60 Hz. The designs are very straightforward and aside from the power transformer, all parts are inexpensive and readily available.

* Inverter based approaches are generally small, light weight, and efficient, but may require more sophistication in design and hard-to-obtain, expensive, or custom parts.

These may run off of low voltage DC or the AC line but in the latter case convert the AC into DC first and then use a high frequency chopper and small transformer to generate their output.

Both types may include internal current regulation or have their voltage and current adjusted with a variable power input Variac or variable DC supply as appropriate.

Modulation inputs may also be provided to permit the transmission of audio or data over the HeNe beam to enable external closed loop control of beam power.

Some more sophisticated commercial power supply designs provide a variety of ‘soft start’ and other features to maximize HeNe tube life. Others enable ‘instant start’ for applications where the HeNe tube must be switched on and off frequently. These sorts of advanced forms of regulation are not really needed for general applications – which is just as well since the circuits tend to be proprietary and not available.

variable Power Supply Circuits