Analog Modules Inc. (AMI) outlines how switch-mode laser diode driver architectures offer a high-efficiency alternative to linear driver designs, enabling smaller size, lower losses, and improved performance for high-current pulsed laser applications. Read more >>
Early work, including a resonant buck converter disclosed in 1994, showed that the power losses in the transistor switch do not depend directly on storage capacitor voltage. This allows the capacitor voltage to droop more than in a linear design and reduces the number of capacitors required, resulting in a smaller unit.
AMI extended this concept by operating multiple buck converter switches in parallel with offset timing to minimize output current ripple. AMI patents describe a multiphase, current-controlled switching design that provides current-regulated pulses to laser diode loads. A polyphase diode driver architecture is also disclosed in which multiple switching stages sum together to produce a current pulse output.
Key advantages of this technique include the use of small surface-mount components without heatsinks, typical efficiencies of approximately 90%, low conduction and switching losses, and digital signal processing to correct for capacitor droop and load variation. These designs tolerate wide variations in storage capacitor voltage, ESR, capacitance, and laser diode voltage, and require no output choke or filter.
Model 774A.
AMI’s Model 774A implements the polyphase approach, delivering up to 200 A at 44 V (8 kW peak), and integrates a power converter stage and sealed storage capacitor. Additional patented circuits allow control of capacitor recharge rate to minimize peak input current and use pre-charged inductors to achieve fast risetimes and high currents.
For lower repetition-rate laser rangefinders, AMI miniaturized a dual-phase switching design to a very small form factor, later adding digital control and burst-mode capability. While slightly less efficient than the polyphase architecture, the dual-phase design maintains high efficiency relative to linear drivers, supports peak currents around 100 A, and dynamically adjusts timing and duty cycle to maintain low ripple as the capacitor discharges. Extensions using multiple phases and a common intelligent controller generate pulsed currents up to 200 A for battery-critical designator applications.
AMI’s latest switch-mode laser diode driver designs use patented polyphase switching into multiple inductors with virtually zero turn-on losses, low ripple, and high switching frequency. Efficiencies exceeding 90% are achieved while accommodating a wide range of laser diode load voltages and input supply levels.
To find out more information, read ‘Switch Mode Laser Diode Driver Design’ here >>
