Buck controllers (external switch) are not a specific brand but a category of voltage regulator modules used in power electronics. These controllers are produced by various companies worldwide, including Texas Instruments (USA), Analog Devices (USA), and Infineon Technologies (Germany). They serve industries such as automotive, industrial automation, and consumer electronics, providing efficient DC-DC voltage conversion. Key products include synchronous buck controllers, step-down regulators, and power management ICs, designed to optimize energy efficiency and performance in applications like servers, telecom equipment, and renewable energy systems.