Direct current (DC) converters play an essential role in electronic circuits. Conventional high-efficiency DC voltage converters, especially step-up type, rely on switch-mode operation, where energy is periodically stored within and released from inductors and/or capacitors connected in a variety of circuit topologies. However, since these energy storage components, especially inductors, are difficult to scale down, miniaturization of switching converters for on-chip or in-package electronics faces fundamental challenges. Furthermore, the resulting switching currents produce electromagnetic noise, which can cause interference problems in nearby circuits, and even acoustic noise and mechanical vibrations that deteriorate the environment. In order to overcome the limitations of switch-mode converters, photonic transformers, where voltage conversion is achieved through the use of light emission and detection processes, have been demonstrated. However, the demonstrated efficiency is significantly below that of the switch-mode converter. Here we perform a theoretical analysis based on detailed balance, which shows that with a monolithically integrated design that enables efficient photon transport, the photonic transformer can operate with a near-unity conversion efficiency and high voltage conversion ratio. We validate the theoretical analysis with an experiment on a transformer constructed with off-the-shelf discrete components. Our experiment showcases near noiseless operation, as well as a voltage conversion ratio that is significantly higher than obtained in previous photonic transformer works. Our finding points to a high-performance optical solution to miniaturizing DC power converters for electronics and improving the electromagnetic compatibility and quality of electrical power.
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