Cixi Xinke Electronic Technology Co., Ltd. , https://www.cxxinke.com
Switching power supplies generate a significant amount of noise, primarily from the power conversion and output rectification and filtering stages. Components such as switching transistors, rectifiers, transformers, and output inductors all contribute to this noise. Without proper mitigation, the peak voltage on the output can be several times higher than the fundamental output voltage. These peaks typically appear on the rising and falling edges of the switching pulses—especially when the switch is turned on or off. The peak is often larger during turn-on.
Here are 10 effective methods to suppress the voltage spikes on the secondary side rectifier diodes:
1. Choose a Schottky diode with soft recovery characteristics, or add series inductance before the rectifier. Magnetic beads made from ferrite materials that exhibit high impedance at high frequencies can also help reduce high-frequency oscillations.
2. Implement an RC snubber circuit on the secondary side to further reduce the amplitude of leading edge spikes and minimize oscillation during the diode's reverse recovery phase.
3. Connect multiple rectifier diodes in parallel. Increasing the current rating of the rectifier can reduce the reverse recovery time, limit the reverse short-circuit current, and thus suppress current spikes while reducing conduction losses.
4. Optimize component layout by minimizing the area of the large current loop. This helps reduce electromagnetic interference (EMI) and improves overall performance.
For trailing edge spike suppression:
5. Select a fast-switching rectifier diode to reduce the time it takes for the diode to transition from conducting to blocking mode, thereby minimizing the spike.
6. Use a transformer core with high magnetic permeability to keep the excitation current as low as possible during operation.
7. Choose materials with high magnetic flux density to prevent transformer saturation under harsh conditions. It’s recommended to operate at around half or one-third of the saturation flux density.
8. Opt for a closed magnetic circuit core, such as a PQ core, to reduce leakage inductance and improve efficiency.
9. Minimize leakage inductance in high-frequency transformer windings by using a sandwich winding technique or a multi-layer winding method. Distribute the windings evenly across the core and consider the skin effect when using enameled wire.
10. Add an RC snubber circuit across the drain and source (DS) terminals of the switching transistor to dampen voltage spikes caused by parasitic inductances.
By implementing these strategies, you can significantly reduce voltage spikes and improve the reliability and efficiency of your power supply design.
September 13, 2025