Often on a 5 volt supply there can be difficulty designing it so that the overvoltage crowbar fires below 7 volts where damage may be caused to circuits being protected. The SF6 series drivers provide protection features which are simple to set-up and more than adequate to protect your LD. The laser protection circuits are energized by VBB, which is why this power comes up first. This is especially useful in a device using TTL components as these are very sensitive to overvoltage. The purpose of the protection circuit, according to the present invention, is to provide a means to protect the laser diode 1 from over laser beam power conditions, over and under temperature conditions, and transient voltage or current spikes on power up and power down conditions. The laser output efficiency is reduced at elevated temperatures, and the added current will further elevate that temperature reducing the efficiency further of both the laser diode 1 and photodiode 2.

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The output device 1, is a semiconductor laser diode.

This enables the threshold clock, which clocks counters to crosbar from an initial value of hex. Thyristor overvoltage protection circuit The SCR over voltage crowbar or protection circuit is connected between the output of the power supply and ground.

Laser Diode Driver, OEM Small Form Factor Industrial Driver

The lower the voltage the greater the margins needed. Patents disclose various laser diode control techniques which do not sufficiently solve the problems of automatic power control and protection of a laser diode: Output Current Range I: This drops enough voltage across resistor 99 to turn on transistor Once the permissible emitted light power is reached, excessive excitation current is diverted to the shunt circuit.

Their is a pin on the control connector which shows the crowbar protection circuit status. United States Patent Crpwbar high power drivers offer a highly reliable crowbar clamp to short the current and disable power to your laser diode. This can reduce the efficiency of the back facet photodiode ceowbar and cause the laser power servo-loop to overdrive the laser diode 1. A below temperature condition can indicate a broken connection to the thermistor which, with a negative temperature coefficient, can cause heating of the laser and lead to thermal run away and destruction of the laser diode.


LDY High Power Diode Laser Drivers | Lumina Power

In the example described, the gate of FET 34 must be about 2 volts lower than the source 4 which is at ground potential for the transistor 34 to be on, or the crowbar switch 14 to be closed. The thyristor crowbar circuit shown is very simple, only using a few components.

The driver sources current and begins to operate when the 5V input enable pin is high. Operation of the circuit begins by autothresholding, which is a means to crowbsr bring the laser power to a threshold level. A power-on reset circuit asserts the digital signal. Policies and guidelines Contact us.

The protective circuit includes a transducer whose output is controlled by the laser light, a limit circuit cooperating with the transducer and a current shunt circuit energized by the limit circuit and switched in parallel with the semi-conductor crowbxr. The modules are initially enabled by applying an active high 3.

Semiconductor laser diode controller cfowbar laser diode biasing control method. The laser imaging apparatus of the present invention includes a laser diode for producing a laser light output, an electrical power supply for supplying electrical power to said laser diode, a shunt circuit for shunting power around said laser diode, a laser power monitor for monitoring the laser light output of said laser diode, a thermal monitor for monitoring the temperature of said laser diode, a power supply monitor for monitoring the voltage power supply driving drowbar laser diode and control means for controlling said shunt means to shunt power around said laser diode in response to one or more of the following signals:.

This cycle of thermal runaway can result in damage and failure of the laser diode 1. Also, a crowbar is more likely than a clamp to deactivate a device by blowing a fuse or tripping a breakerbringing attention to the faulty equipment.


Practical Electronics/Crowbar circuit

Shunting the current in such a manner is referred to as placing a crowbar across the laser diode 1. The circuit must have a fuse or circuit-breaker, as without it the power supply or the crowbar circuit will be damaged. The firing voltage of the tthyristor crowbar circuit is set by the Zener diode. In the crowbar drive circuit 45 shown in FIG.

The crowbar will short the output while the module is in an over-current shutdown or an over-temperature shutdown mode. By looking at the voltages involved it is very easy to see why the inclusion of overvoltage protection is so crowbbar. The digital image can be crwbar in a magnetic or optical disk drive provided in processor It is simple even if a little crude, but can protect crowbxr expensive item of equipment from the possible failure of the series regulator element.

SCR Thyristor Crowbar: overvoltage protection circuit

The advantage of a crowbar over a clamp is that the low holding voltage of the crowbar lets it carry higher fault current without dissipating much power which could otherwise cause overheating. This places the crowbar switch 14 across the laser diode 1 and insures that the laser diode 1 is protected from power-on transients.

Supplier Directory For everything from distribution to test equipment, components and more, our directory covers it. As will be described later, the threshold level is not the same as that defined by laser diode manufacturers, but is a level at which the laser power output functional dependence upon laser crowvar is linear.