LiDAR’s power and size problem

Overcoming the known power and size limitations in LiDAR design is critical to enabling scalable, cost-effective adoption across markets. The post LiDAR’s power and size problem appeared first on EDN.

Electronics Jan 8, 2026 0 1 Add to Reading List

Awareness of LiDAR and advanced laser technologies has grown significantly in recent years. This is in no small part due to their use in autonomous vehicles such as those from Waymo, Nuro, and Cruise, plus those from traditional brands such as Volvo, Mercedes, and Toyota. It’s also making its way into consumer applications; for example, the iPhone Pro (12 and up) includes a LiDAR scanner for time-of-flight (ToF) distance calculations.

The potential of LiDAR technologies extends beyond cars, including applications such as range-finding in golf and hunting sights. However, the nature of the technology used to power all these systems means that solutions currently on the market tend to be bulkier and more power-intensive than is ideal. Even within automotive, the cost, power consumption, and size of LiDAR modules continue to limit adoption.

Tesla, for example, has chosen to leave out LiDAR completely and rely primarily on vision cameras. Waymo does use LiDAR, but has reduced the number of sensors in its sixth-generation vehicles: from five to four.

Overcoming the known power and size limitations in LiDAR design is critical to enabling scalable, cost-effective adoption across markets. Doing so also creates the potential to develop new application sectors, such as bicycle traffic or blind-spot alerts.

In this article, we’ll examine the core technical challenges facing laser drivers that have tended to restrict wider use. We’ll also explore a new class of laser driver that is both smaller and significantly more power efficient, helping to address these issues.

Powering ToF laser drivers

The main power demand within a LiDAR module comes from the combination of the laser diode and its associated driver that together generate pulsed emissions in the visible or near-infrared spectrum. Depending on the application, the LiDAR may need to measure distances up to several hundred meters, which can require optical power of 100-200 W. Since the efficiency of the laser diodes is typically 20-30%, the peak driving power delivered to the laser must be around 1 kW.

On the other hand, the pulse duration must be short to ensure accuracy and adequate resolution, particularly for objects at close distances. In addition, since the peak optical power is high, limiting the pulse duration is critical to ensure the total energy conforms to health guidelines for eye safety. Fulfilling all these requirements typically calls for pulses of 5 ns or less.

Operating the laser thus requires the driver to switch a high current at extremely high speed. Standing in the designer’s way, the inductance associated with circuit connections, board parasitics, and bondwires of IC packages is enough to prevent the current from changing instantaneously.

These small parasitic inductances are intrinsic to the circuit and cannot be eliminated. However, by introducing a parallel capacitance, it is possible to create a resonant circuit that takes advantage of this inductance to achieve a short pulse duration. If the overall parasitic inductance is about 1 nH and the pulse duration is to be a few nanoseconds, the capacitance can be only a few nano Farads or less. With such a low value of capacitance, the applied voltage must be on the order of 100 V to achieve the desired peak power in the laser. This must be provided by boosting the available supply voltage.

Discrete laser driver

Figure 1 shows the circuit diagram for a resonant laser-diode driver, including the resonant capacitor (C_supply) and effective circuit inductance (L_bond). A boost regulator provides the high voltage needed to operate the resonant circuit.

Figure 1 Resonant gate driver and boost regulator, including the resonant capacitor (C_supply) and effective circuit inductance (L_bond). (Source: Silanna Semiconductor)

The circuit requires a boost voltage regulator, depicted as Boost voltage regulator (VR) in the diagram, to provide the high voltage needed at C_supply to deliver the required energy. The circuit as shown contains a discrete gate driver for the main switching transistor (FET), which must be controlled separately to generate the desired switching signals.

In addition, isolation resistance is needed between C_filter and C_supply, shown in the diagram, to ensure the resonant circuit can operate properly. This is relatively inefficient, as no more than 50% of the energy is transferred from the filter side to C_supply.

Handheld equipment limitations

In smaller equipment types, such as handheld ranging devices and action cameras, the high voltage must be derived from a small battery of low nominal voltage—typically a 3-V CR2 or a 3.7-V (nominal voltage, up to 4.2 V) lithium battery—which is usually the main power source.

Figure 2 shows a comparable schematic for a laser-diode driver powered from a 3.7-V rechargeable lithium battery. Achieving the required voltage using a discrete boost VR and laser-diode driver is complex, and designers need to be very careful about efficiency.

Multiple step-up converters are often used, but efficiency drops rapidly. If two stages are used, each with an efficiency of 90%, the combined efficiency across the two stages is only 81%.

Figure 2 A laser driver operated from a rechargeable lithium battery, two stages are used for a combined efficiency of 80%. (Source: Silanna Semiconductor)

In addition, there are stringent constraints on enclosure size, and the devices are often sealed to prevent dust or water ingress. On the other hand, sealing also prevents cooling airflow, thereby making thermal management more difficult. In addition, high overall efficiency is essential to maximize battery life while ensuring the high optical power needed for long range and high accuracy.

Circuit layout and size

The high speeds and slew rates involved in making the LiDAR transmitter work call for proper consideration of circuit layout and component selection. A gallium nitride (GaN) transistor is typically preferred for its ability to support fast switching at high voltage compared to an ordinary silicon MOSFET. Careful attention to ground connections is also required to prevent voltage overshoots and ground bounce from disrupting proper transistor switching and potentially damaging the transistor.

Also, a compact module design is difficult to achieve due to efficiency limitations and thermal management challenges. The inefficiencies in the discrete circuit implementation mean operating at high power produces high losses and increased self-heating that can cause the operating temperature to rise. However, while short pulses can reduce the average thermal load, current slew rates must be extremely high. If this cannot be maintained consistently, extra losses, more heat, and degraded performance can result.

A heatsink is the preferred thermal management solution, although a large heatsink can be needed, leading to a larger overall module size and increased bill of materials cost. In addition, ensuring eye safety calls for a fast shutdown in the event of a circuit fault.

Bringing the boost stage, isolation, GaN FET driver, and control logic into a single compact IC (see Figure 3) achieves greater functional integration and offers a route to higher efficiency, smaller form factors, and enhanced safety through nanosecond-level fault response.

Figure 3 An integrated driver designed for resonant capacitor charging combines short pulse width with high power and efficiency. This circuit was implemented with Silanna SL2001 dual-output driver. (Source: Silanna Semiconductor)

While leveraging resonant-capacitor charging to achieve short, tightly controlled pulse duration, this integration avoids the energy losses incurred in the capacitor-to-capacitor transfer circuitry. The fault sensing and reporting can be brought on-chip, alongside these timing and control features.

This approach is seen in LiDAR driver ICs like the Silanna FirePower family, which integrate all the functions needed for charging and firing edge-emitting laser (EEL) or vertical-cavity surface-emitting laser (VCSEL) resonant-mode laser diodes at sub-3-ns pulse width. Figure 4 shows how an experimental setup produced a 400-W pulse of 2.94 ns, operating with a capacitor voltage boosted to 120 V with a resonant capacitor value of 2.48 nF.

Figure 4 Test pulse produced using integrated driver and circuit configuration as in Figure 3. (Source: Silanna Semiconductor)

The driver maintains control of the resonant capacitor energy and eliminates any effects of input voltage fluctuations, while on-chip logic sets the output power and performs fault monitoring to ensure eye safety. The combined effects of advanced integration and accurate logic-based control can save 90% of charging power losses compared to a discrete implementation and realize an overall charging efficiency of 85%. The control logic and fault monitoring are configured through an I²C connection.

Of the two devices in this family, the SL2001 works with a supply voltage from 3 V to 24 V and provides a dual GaN/MOS drive that enables peak laser power greater than 1000 W with a pulse-repetition frequency up to several MHz. The second device, the SL2002, is a single-channel driver targeted for lower power applications and is optimized for low input voltage (3 V-6 V) operation. Working off a low supply voltage, this driver’s 80-V laser diode voltage and 1 MHz repetition rate are suited to handheld applications such as rangefinders and 3D mapping devices. Figure 5 shows how the SL2002 can simplify the driving circuit for a battery-operated ranging device powered from a 3.7 V lithium battery.

Figure 5 Simplified circuit diagram for low-voltage battery-operated ranging. (Source: Silanna Semiconductor)

Shrinking LiDAR modules

LiDAR has been a key component in the success of automated driving, working in conjunction with other sensors, including radar, cameras, and ultrasonic detectors, to complete the vehicle’s perception system. However, LiDAR modules must become smaller and more energy-efficient to earn their place in future vehicle generations and fulfil opportunities beyond the automotive sphere.

Focusing innovation on the laser-driving circuitry unlocks the path to next-generation LiDAR that is smaller, faster, and more energy-efficient than before. New, single-chip drivers that deliver high optical output power with tightly controlled, nanosecond pulse width enable LiDAR to address tomorrow’s cars as well as handheld devices such as rangefinders.

Ahsan Zaman is Director of Marketing at Silanna Semiconductor, Inc. for the FirePowerTM Laser Drivers line of products. He joined the company in 2018 through the acquisition of Appulse Power, a Toronto, Canada-based Startup company for AC-DC power supplies, where he was a co-founder and VP of Engineering. Prior to that, Ahsan received his B.A.Sc., M.A.Sc., and Ph.D. degrees in Electrical Engineering from the University of Toronto, Canada, in 2009, 2012, and 2015, respectively. He has more than a decade of experience in power converter architectures, mixed-signal IC design, low-volume and high-efficiency power management solutions for portable electronic devices, and advanced control methods for high-frequency switch-mode power supplies. Ahsan has previously collaborated with industry-leading semiconductor companies such as Qualcomm, TI, NXP, EXAR etc., and co-authored more than 20 IEEE conference and journal publications, and holds several patents in this field