Efficient Buck Converters for Automotive Point-of-Load Applications
By Macgyver Lee, DCDC Marketing Manager
It’s become cliché to describe today’s cars as “computers on wheels”, but how about “power systems you can drive”? Any modern vehicle needs multiple power converters and system components to provide the right voltage and current to the huge number of onboard devices.
For electric vehicles (EVs), the addition of a powertrain and large lithium-ion battery brings another layer of complexity. Being able to charge the battery rapidly, and safely, is a vital part of the car’s electrical systems.
In any car today, there will be many electronic control units (ECUs) that run various functions, from infotainment to engine control. Newer ECUs in recent vehicles may have faster processors for handling large amounts of data, such as video from onboard cameras, and may also use high-speed network links such as Ethernet—all adding to their demands for power.
Requirements for Power Systems
What demands does this create for power designers? They need to build efficient systems to minimize heat dissipation and wasted energy. These systems must also be compact and able to cope with the harsh automotive environment with excellent reliability.
The best approach is typically a distributed power architecture, with point of load (PoL) converters near each ECU and electrically powered device. These converters meet the voltage and current demands of the components they supply in an efficient, compact form factor.
Efficient PoL Converters
Two recent synchronous buck converters that meet all these requirements are the AP64203Q and AP64303Q from Diodes Incorporated (Diodes). They deliver high efficiency in automotive PoL applications, with a wide input voltage range of 3.8V to 40V, and working across the full range for internal combustion engine (ICE) vehicles. The devices’ continuous output currents are rated at 2A (AP64203Q) and 3A (AP64303Q).
The AP64203Q and AP64303Q have an adjustable switching frequency of up to 2.5MHz. This enables them to minimize the overall power system footprint by requiring fewer and smaller external components. The converters’ high level of integration also reduces the need for external components, further saving board space.
The converters include integrated power MOSFET switches (120mΩ high-side and 55mΩ low-side), which provide high-efficiency step-down conversion. To further improve efficiency, their BIAS feature helps reduce internal power consumption.
Their efficiency is excellent: the AP64303Q enables a continuous load current of up to 3A with efficiency as high as 95%, while the AP64203Q achieves a similar efficiency figure at its continuous load current of 2A.
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