PCX-7421 CW/QCW Laser Diode Driver

PCX-7421 CW/QCW Laser Diode Driver Overview：

PCX-7421Datasheet

The PCX-7421 is an air-cooled, high-powered CW/QCW current source designed to drive diode lasers, bars, and arrays. The pulsed output current is adjustable from 50 mA to 21.5 A, the pulse width is adjustable from 50 ns to 500 ms, and the rise time is under 25 ns. The pulse repetition rate is selectable from 40 Hz to 100 kHz with the internal source, and from single-shot to 1 MHz with an external source.

The instrument provides both QCW (pulsed) and CW (DC) outputs. It serves as a CW driver at currents from 3.0 A to 5.8 A, and as a pulsed/QCW driver at currents from 50 mA to 21.5 A. The output may be biased to any CW current from 0.050 A to 5.8 A, then pulsed above that bias up to 15.7 A maximum. A bias-pulsing feature allows the bias current to be pulsed and triggered independently from the main current.

Directed Energy, Inc. is now a division of Berkeley Nucleonics. The PCX-7421 is the same design, built in California, with one support path. Operation runs from intuitive front-panel controls, and the OLED display confirms bias and pulsed current setpoints, internal trigger pulse width and frequency, and any error or fault messages.

How It Works:

A laser diode driver is a current source. The compliance voltage, 24 V on the PCX-7421, is the maximum voltage available to maintain the programmed current through the diode and the interconnect. Holding the current flat through the pulse is what preserves optical pulse shape, so every specification is measured with a low-inductance twisted-pair interconnect to the load.

The PCX-7421 separates the operating point from the pulse. A CW bias holds the diode anywhere from 0.050 A to 5.8 A, and the main current pulses above that floor up to 15.7 A in biased operation, or up to the full 21.5 A as a standalone pulsed/QCW source. Because the bias channel can be pulsed and triggered independently, the diode can be pre-conditioned and the main pulse fired with separate timing, which is useful for QCW thermal management and for shaping the leading edge of optical output.

CW, QCW, and pulsed. Run continuous current from 3.0 A to 5.8 A for CW operation, or pulse from 50 mA to 21.5 A for QCW and pulsed work. QCW lets a diode bar deliver high peak power while keeping average power, and junction temperature, within limits.

Safe operating area:

The safe operating area sets the boundary for combined current and voltage at the load. Maximum output power rises with output voltage across the 24 V compliance window, reaching roughly 380 W near full compliance. Where the diode operating point lands inside this envelope depends on the diode forward voltage and the drop across the interconnect, which is why every measurement uses the supplied low-inductance cable.

Pulse & Bias Amplitude:

All specifications are measured with a low-inductance twisted-pair interconnect cable to a load. The PCX-7421 meets or exceeds these specifications.

Note 1. Laser diode drivers are current sources. The compliance voltage is the maximum voltage available to maintain the programmed current.

Output waveforms：

The two captures show biased operation, where a CW bias holds the diode and the main current pulses above it. Each is taken at a 100 kHz internal trigger rate. In the first, a 6 A bias and a 16 A main pulse stack to a flat-topped output with a measured rise time of 22.6 ns, inside the under 25 ns specification.

The second capture uses a lighter 1 A bias and a 3 A main pulse with equal 3.5 microsecond bias and main widths. The flat top through each pulse is what preserves optical pulse shape, and it depends on driving the load through the supplied low-inductance twisted-pair interconnect.

Trigger Specifications：

General Specifications：

Output Protection & Safety：

The PCX-7421 uses advanced circuitry to protect both the diode and the driver. At turn-on, and at any time the output is not enabled, the output is electronically shorted to ground so that no current flows through the diode. This short-on-disable behavior is the primary defense against accidental diode damage during connection and setup.

A front-panel interlock key gates the output. When the key is off, the output is disabled. To enable the output, the key must be on and the system enable must be made, either manually or through the computer interface. A remote interlock is also provided, so the driver can be tied into a larger safety chain.

Stay within compliance and use the supplied cable. Keep the combined diode forward voltage and interconnect drop inside the 24 V compliance window. Always drive the load through the supplied low-impedance twisted-pair cables so the specified rise time and pulse fidelity hold.

Control & Interfaces：

The PCX-7421 is operated through intuitive front-panel controls, with an OLED display that gives immediate visual confirmation of every operating parameter, including bias and pulsed current setpoints, internal trigger pulse width and frequency, and error or fault messages.

For automated applications, complete control of the driver is provided through RS-232 and USB computer interfaces. Up to five system configurations can be stored in internal non-volatile memory, providing instant recall of frequently used setups. USB driver support covers Windows 7 through 10, Windows XP, Linux, and Mac OS X.

Applications：

The PCX-7421 fits applications that need high pulsed current with independent bias control, across CW, QCW, and pulsed modes.

Ordering Information：

Each PCX-7421 is delivered with two output twisted-pair cables, one laser output PCBA, and a BNC shorting connector.