A communication power supply during full-load testing exhibited MOSFET switching losses 30% higher than expected due to reverse recovery spikes from the output rectifier. Engineers checked the gate resistors and RC snubber circuits before finally tracing the problem to the rectifier's reverse recovery. This is not uncommon in continuous-mode converters – when the input voltage is high, switching losses caused by reverse recovery can even exceed the conduction losses of the power switch.
SHINHOM's EMI Amorphous Beads are built around the Z-shaped B-H loop of cobalt-based amorphous alloy. Through three core technical characteristics – high inductance at the zero-crossing point, extremely low saturated inductance, and low-loss amorphous alloy – they provide a simplified and effective solution for spike noise suppression in switching power supplies. The following analysis examines their engineering value from these three core technologies.
Core Technology 1: High Inductance at Zero-Crossing – Effectively Suppressing Reverse Recovery Spikes
Technical Description
- High inductance at zero-crossing current
- Suppress reverse-recovery spike noise
- Softening diode reverse-recovery phenomenon
Engineering Value
- In continuous-mode converters, the output rectifier has forward current flowing before the voltage reverses, and reverse recovery generates large current spikes. NB/NK Series Amorphous Beads present high inductance at current zero-crossing, effectively suppressing this spike and reducing switching losses
- The positioning as a Semiconductor Noise Suppression Core makes it an ideal series element for output rectifiers and freewheeling diodes
- Diode reverse-recovery protection: Reduces the impact of reverse recovery current on the diode, extending device life
SHINHOM Corresponding Capability: The NB/NK series presents high inductance at the zero-crossing point, specifically designed for reverse recovery suppression in output rectifiers and freewheeling diodes.
Core Technology 2: Extremely Low Saturated Inductance – Maintaining Linear Behaviour After Saturation
Technical Description
- Very low saturated inductance: The bead enters saturation quickly, but after saturation the inductance is extremely low, so it does not become a new noise source
- Z-shape B-H Loop Amorphous Core: Cobalt-based amorphous alloy has a rectangular/Z-shaped hysteresis loop, with high permeability and fast saturation, but retains a segment of linear inductance behaviour
- Saturable Amorphous Choke Core: Utilises the saturable characteristic to respond quickly when needed, and does not affect normal circuit operation after saturation
Engineering Value
- Conventional ferrite beads experience a sharp drop in inductance after saturation and may lose noise suppression capability. The Cobalt-based Amorphous Noise-suppression Beads with their Z-shaped B-H loop design retain linear behaviour after saturation, preventing the bead itself from becoming a noise source
- Suppress MOSFET ringing & voltage spike: During MOSFET switching, the bead's extremely low saturated inductance helps suppress ringing without affecting switching speed
- Ringing noise suppression: Suitable for ringing suppression in switching power supplies
SHINHOM Corresponding Capability: Cobalt-based amorphous Z-shaped B-H loop design, retaining linear behaviour after saturation, suitable for MOSFET ringing suppression and bridge circuit protection.
Core Technology 3: Low-Loss Amorphous Alloy – Improving Efficiency and Simplifying Design
Technical Description
- Low-loss amorphous alloy: Compared with conventional ferrite, amorphous alloy has lower loss at high frequencies
- Simplify noise-suppression circuit design: A single bead can replace a complex RC snubber network, reducing component count
- Square / Z-shaped hysteresis B-H loop: The material characteristics determine that the bead responds quickly when needed and has low loss when not needed
Engineering Value
- Low loss means low self-heating of the bead, adding no extra thermal burden to the switching power supply and helping improve overall efficiency
- Simplified design: Engineers do not need complex RC parameter tuning – simply connect the Spike Killer Amorphous Bead in series with the rectifier or MOSFET gate to achieve spike suppression and ringing protection
- Suitable for cost- and efficiency-sensitive applications such as battery charger power supplies and AC-DC adapters
SHINHOM Corresponding Capability: Low-loss amorphous alloy reduces bead self-heating; a single bead replaces the RC snubber network, simplifying design and improving efficiency.
Traditional Ferrite Beads vs SHINHOM Amorphous Beads
| Comparison Dimension | Traditional Ferrite Beads | SHINHOM Amorphous Beads |
|---|---|---|
| Reverse recovery suppression | Limited | High inductance at zero-crossing, effectively suppresses |
| Behaviour after saturation | Inductance drops sharply, may fail | Extremely low saturated inductance, retains linear behaviour |
| High-frequency loss | Relatively high | Low-loss amorphous alloy |
| Circuit complexity | Requires RC snubber network | A single bead simplifies design |
| Applicable scenarios | General noise suppression | Reverse recovery, MOSFET ringing, bridge circuits |
Application Matching
| Application Scenario | Core Requirements | How NB/NK Series Amorphous Beads Meet Them |
|---|---|---|
| Switching power supplies (SMPS) | Suppress reverse recovery spikes, improve efficiency | High inductance at zero-crossing + low-loss amorphous alloy |
| Continuous-mode converters | Soften diode reverse recovery, protect rectifier | Connected in series with the output rectifier to suppress spikes |
| UPS power supplies | Reliably suppress spike noise | Z-shaped B-H loop for fast response |
| Communication network power supplies | High-frequency ringing suppression | Extremely low saturated inductance + ringing noise suppression |
| Battery chargers / AC-DC adapters | Simplify design, low cost | A single bead replaces the RC snubber network |
| MOSFET/BJT motor control | Suppress MOSFET ringing and voltage spikes | Extremely low saturated inductance + ringing protection |
| Semiconductor bridge circuits | Bridge circuit spike noise suppression | Fast saturation + retained linear behaviour |
Why Choose SHINHOM's EMI Amorphous Beads?
SHINHOM's NB/NK series amorphous beads have been mass-deployed in communication power supplies, UPS, and motor control projects. The Z-shaped B-H loop characteristics of cobalt-based amorphous alloy have been verified through long-term field experience, helping engineers replace complex RC snubber networks with a single bead and simplifying noise suppression circuit design.
Provide your circuit topology, reverse recovery current magnitude, and switching frequency, and we will respond with selection recommendations and a sample support plan within 1 working day.
Conclusion: Providing a Simplified Spike Noise Suppression Solution for Switching Power Supplies
SHINHOM's EMI Amorphous Beads suppress reverse recovery spikes with high inductance at zero-crossing, prevent the bead itself from becoming a noise source with extremely low saturated inductance, and improve efficiency and simplify noise suppression circuit design with low-loss amorphous alloy. Combined with the Z-shaped B-H loop characteristics of cobalt-based amorphous material, they provide a reliable spike noise suppression solution for switching power supplies, continuous-mode converters, UPS, communication network power supplies, battery chargers, and motor control circuits.
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