Ripple Suppression Technology in High-Voltage Power Supplies for Electron Beam Applications

In industrial applications such as electron beam welding, precision melting, and vacuum coating, the ripple coefficient of high-voltage power supplies directly determines process quality. Ripple (AC pulsation in the output voltage) causes electron beam trajectory drift, uneven welds, or material structural defects. Traditional filtering techniques struggle to meet requirements due to the size and voltage limitations of high-voltage capacitors, necessitating efficient ripple suppression through optimized main circuit topologies, closed-loop control, and advanced compensation technologies. 
1. Main Circuit Topology Optimization
• Coupled Inductor Design: In Zeta or Cuk converters, winding input and output inductors on the same magnetic core and optimizing mutual inductance (typically  M \approx 0.75L , where  L  is the inductance value) cancels ripple components in input/output currents. When the coupling coefficient  k  satisfies  k = n  ( n  is the turns ratio), output current ripple approaches zero. 
• Multiphase Rectification and Voltage Multiplier Circuits: A 12-phase rectification technique (two star/delta winding sets in series) reduces harmonic pollution. Combined with Cockcroft-Walton full-wave voltage multiplier circuits (e.g., 10-stage), symmetric full-wave rectification minimizes filter capacitance and suppresses high-frequency ripple. 
2. Closed-Loop Control Strategies
• Compound Control Mechanism: Integrates feedforward control with PI/PID regulators. The feedforward channel detects input voltage fluctuations and adjusts the duty cycle in advance to mitigate 20% grid fluctuations. A voltage-current dual-loop structure (outer voltage PID + inner current PID) enhances dynamic response accuracy, achieving output voltage stability of ±0.5%. 
• Adaptive Regulation: Digital controllers dynamically adjust loop parameters based on load changes (e.g., electron gun equivalent resistance of 300 kΩ), preventing increased ripple from narrow pulse widths under light loads in traditional single-loop systems. 
3. Advanced Ripple Compensation Techniques
• Active Compensation Circuits: Inject inverse ripple current into the output. Hall sensors detect ripple components, and operational amplifiers generate compensation signals, achieving over 40 dB of ripple attenuation (i.e., amplitude reduction to 1%). 
• Digital Harmonic Injection: DSP analyzes ripple spectra and injects reverse harmonics at resonant peaks (e.g., 20 kHz switching frequency), canceling specific noise frequencies. Suitable for isolated topologies. 
4. Common-Mode Noise and Parasitic Parameter Suppression
• Low-Parasitic Layout: Shortening distances between power devices and heat sinks reduces parasitic capacitance. Adding common-mode chokes and Y-capacitors at the output suppresses common-mode ripple. 
• Electromagnetic Shielding: High-voltage divider resistors are enclosed in shielded boxes, and feedback signals are transmitted via opto-isolation to block discharge spike interference in control circuits. 
Technology Trends
Future ripple suppression will focus on wide-bandgap semiconductors (SiC/GaN) to increase switching frequencies to hundreds of kHz, combined with AI algorithms for self-tuning parameters. For example, neural networks predict ripple characteristics during load transients and dynamically adjust compensation phases, further reducing the ripple coefficient below 0.1% to support high-precision electron beam processing equipment.