An accurately controlled, compact and cost reduced power source for OEM laser diode applications

October 16, 2010
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A Vicor customer based in Northern Italy designs, develops and manufactures diode based laser sources and systems for the industrial, medical and scientific markets. They can provide system, kit or component level solutions and develop products from initial concept through to full commercial production. Uses include laser markers for industrial and civil applications, and laser sources for health therapy.

Laser diodes used in such applications require high current, accurately controlled electrical power. Delivering such current to the laser can be problematic, as typically the power source is at some distance from the diode. Passing a heavy current over such a distance, either across PCB tracking or through cabling can incur I²R heating losses as well as causing difficulties in control.

A Vicor product based solution was developed through co-operation between Vicor Italy, their Italian distributor, and the customer. Vicor’s solution is based on the V.I Chip VTM V048T020T080 current multiplier, which provides 80 A output and can be placed extremely close to the laser diode, eliminating I²R losses. The VTM’s large current output is controlled by the output voltage of a remote regulator designed by the customer.

This pre-regulator is a high speed solution based on a standard power operational amplifier with a regulated and trimmable 48 VDC pulsed output that is transformed into a 2 V output by the VTM. The linear regulator can shape the pulsed output with high waveform fidelity that is unaffected by the VTM. Forced convection cooling is used because of the high power dissipation of the linear PRM and of the laser diode. Feedback to the PRM comes from a Hall Effect sensor reading the output current in the secondary of the VTM; this allows galvanic isolation to be preserved.

This has now become a production solution for the customer, with an annual demand of 200 units. In addition to offering the performance essential for the laser diode’s operation, this power system design offers other advantages, including an easily understood power circuit, the use of standard components, a reduced component count, space saving on the pcb and reduced costs.

This solution could be adapted for a wider range of applications as well. Standard diodes exhibit the same characteristics as laser diodes, and, with the same control accuracy difficulties as they approach the knee of their current-voltage curve, they could similarly benefit from this tightly controlled power design.

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