This video provides a detailed comparative analysis of two 50W open-frame power supplies: one based on traditional silicon (Si) technology and a modern counterpart utilizing Gallium Nitride (GaN) transistors. The GaN power supply is significantly smaller and lighter, primarily due to its higher switching frequency which allows for smaller passive components and contributes to higher efficiency. Through comprehensive efficiency testing and a component-by-component teardown, the video demonstrates the GaN supply's superior performance, including higher overall efficiency (92% vs. 85% peak), drastically lower no-load power consumption (110mW vs. 1.2W), and better output voltage regulation. Key GaN advantages highlighted include lower switching losses, reduced gate charge, and the absence of a body diode in the GaN FET, leading to improved switching performance. The analysis meticulously examines differences in mains rectifiers, input/output capacitors (showcasing the use of polymer and MLCCs in the GaN PSU), the transformer (a planar design in the GaN PSU), output rectification (synchronous rectification in the GaN PSU), and EMI filtering, clearly explaining how GaN technology combined with modern design practices results in a more compact and efficient power supply.
Gallium Nitride vs. Silicon: A Deep Dive into Modern Power Supply Miniaturization and Efficiency
00:00:02 Introduction to GaN: Gallium Nitride (GaN) is a semiconductor material offering significant advantages over silicon in power electronics, enabling smaller, lighter, and more efficient power supplies primarily through higher switching frequencies.
00:00:46 Size and Efficiency Preview: A 50W GaN power supply is roughly one-third the volume and weight of a comparable silicon-based unit. The silicon PSU has large heatsinks, while the GaN PSU's lack of substantial heatsinking (only an EMI shield) points to its higher efficiency.
00:02:13 Efficiency Testing Methodology: The video employs a Zimmer power analyzer and a Kikasui electronic load, utilizing Kelvin sense connections for precise measurement of input/output power and efficiency across various load conditions.
00:04:56 GaN Superior Efficiency: The GaN power supply demonstrates consistently higher efficiency, reaching a peak of 92% compared to the silicon supply's 85%. This ~7% absolute difference translates to nearly halving the power losses.
00:05:54 Drastically Lower No-Load Consumption: A key advantage of the GaN PSU is its minimal no-load power consumption of 110mW, significantly lower than the silicon PSU's 1.2W, greatly improving light-load efficiency.
00:06:59 Improved Output Load Regulation: The GaN power supply shows much better output voltage stability under load, dropping only 10mV at full load compared to the silicon supply's 90mV drop, attributed to superior design practices like precise voltage feedback.
00:08:38 Mains Rectifier Comparison: The GaN PSU features a tiny surface-mount rectifier, over 10 times smaller than the silicon PSU's, mainly due to the older unit's oversized component. While losses are similar, the smaller GaN part runs hotter by design.
00:11:10 Input Capacitor Reduction: The GaN PSU's main input capacitor is smaller (56µF vs. 100µF). This is possible because GaN's higher switching frequency enables faster control loops that can compensate for the increased voltage ripple on a smaller capacitor. The GaN PSU also uses a higher quality Rubicon capacitor.
00:13:20 Advanced Input Stage in GaN PSU: The GaN supply uses Multi-Layer Ceramic Capacitors (MLCCs) near the GaN FET for high-frequency decoupling and an additional inductor to isolate the main input capacitor from high-frequency currents, enhancing efficiency and component lifespan.
00:14:56 GaN Transistor Advantages: The GaN FET is much smaller and offers lower on-resistance and significantly reduced switching losses due to properties like low gate charge, no body diode (eliminating reverse recovery issues), and lower Miller capacitance. Its "figure of merit" (R_DS(on) * Q_g) is almost 100 times better than the silicon MOSFET.
00:16:37 Planar Transformer Technology: The GaN power supply utilizes a planar transformer, where windings are integrated into a PCB. This allows for greater consistency, lower cost, and optimized designs that minimize losses by carefully managing magnetic fields (e.g., fringing flux near air gaps) and enabling effective interleaving for reduced leakage inductance.
00:20:49 Synchronous Rectification for Output: Instead of a traditional diode, the GaN PSU employs active (or synchronous) rectification using a MOSFET on the output. This drastically reduces conduction losses, contributing over 4% to the overall efficiency gain.
00:22:31 Optimized Output Filtering: The GaN PSU uses MLCCs for high-frequency output ripple and a main polymer output capacitor (superior to electrolytic types in ESR and lifespan), with an inductor to separate filtering tasks. The total output capacitance is about a third (due to higher frequency) and the volume a tenth (due to lower voltage rating) of the silicon PSU's.
00:26:30 Smaller EMI Filter: Higher switching frequencies and techniques like frequency jitter allow the GaN PSU to use a smaller and simpler input EMI filter (common mode choke, X-capacitors) while still meeting regulatory requirements.
00:28:24 Overall Design Excellence: The video praises the Cosel GaN power supply for its meticulous engineering, incorporating modern components (e.g., surface-mount Y-capacitor) and thoughtful layout choices (e.g., direct voltage sense traces to the output connector for better regulation).
00:28:54 Key Reasons for Component Miniaturization: The significant size reduction in the GaN power supply is attributed to a combination of GaN's inherent advantages (enabling higher frequency operation), the use of advanced component technologies (planar magnetics, synchronous rectification, polymer capacitors, MLCCs), and overall optimized circuit design.