Capacitor Charging Power Supply Distributed Energy Storage Topology

High-power pulsed systems, such as solid-state lasers for manufacturing, pulsed radar transmitters, electromagnetic launchers, and medical X-ray generators, require the rapid delivery of immense energy in a short burst. This energy is typically stored in high-voltage capacitor banks prior to discharge. The capacitor charging power supply (CCPS) is responsible for replenishing this bank from the mains supply in the brief inter-pulse period. As pulse repetition frequencies (PRF) and energy per pulse increase, the peak power demand on the CCPS becomes staggering, posing challenges for efficiency, component stress, and facility power infrastructure. The distributed energy storage topology is an architectural solution that fundamentally reconfigures the power conversion chain to address these challenges by interposing intermediate, distributed energy buffers between the AC input and the final capacitor bank.

The conventional approach is a direct, single-stage conversion from AC line to the high-voltage DC required by the capacitor bank (e.g., 1kV to 10kV). This requires power components (switches, transformers, diodes) rated for the full output voltage and must handle the entire peak charging power. During the charge cycle, the supply draws a high, distorted current from the AC line, causing poor power factor and harmonic pollution. The distributed topology breaks this monolithic process into multiple, cascaded power conversion stages, each with its own localized energy storage element, such as a DC-link capacitor or a small battery module.

A canonical example is a two-stage system. The first stage is an active power factor correction (PFC) front-end that draws smooth, sinusoidal current from the AC line and charges a moderate-voltage DC bus capacitor (e.g., 800V DC) with high efficiency and near-unity power factor. This stage operates continuously, slowly and steadily transferring energy from the grid into this intermediate storage capacitor. The second stage is a bank of modular, isolated DC-DC converter modules connected in series to achieve the final high voltage. These modules draw energy from the common 800V DC bus, not directly from the AC line. When a charge cycle is initiated, these modules pull energy from the intermediate DC bus capacitor to charge the main pulse-forming capacitor bank. The key advantage is that the high peak power for charging is supplied primarily by the intermediate storage capacitor, not instantaneously from the AC grid. The front-end PFC stage only needs to be sized to replenish the intermediate bus's energy on average between pulses, which is a much lower power level than the peak charge power. This dramatically reduces the stress on the input AC components, minimizes input current harmonics, and can significantly reduce the required capacity of the facility electrical service.

The distributed concept can be extended further. Instead of a single intermediate bus, a cascaded multi-level architecture can be employed. For instance, the final series-connected DC-DC modules might each have their own input capacitor. Energy is then sequentially "pushed" from the front-end through a chain of these buffers. This creates a natural impedance matching and allows for the use of lower-voltage, higher-reliability, and more cost-effective semiconductor switches (like 600V IGBTs or MOSFETs) throughout the system, as no single component sees the full output voltage. Reliability is enhanced through inherent modularity; if one DC-DC module fails, the system can often continue at a reduced output voltage or with redundancy.

Control strategies become central to optimizing performance. An energy management controller oversees the entire system. It calculates the energy required for the next pulse based on the capacitor bank voltage and desired final voltage. It then schedules the charging sequence, commanding the modular converters to transfer energy from the distributed buffers to the main bank in a controlled manner, potentially interleaving their operation to minimize ripple on the intermediate buses. Advanced versions incorporate wide-bandgap semiconductors (SiC or GaN) in the modular DC-DC stages, enabling higher switching frequencies, which reduces the size of magnetic components and allows for faster charge rates and higher PRFs. Furthermore, this topology readily interfaces with alternative energy sources, such as regenerative energy recovered from the pulsed load itself (e.g., from a magnetic pulse compressor) or from local renewable sources, which can be fed directly into the intermediate DC bus.

In essence, the distributed energy storage topology transforms the capacitor charging power supply from a high-peak-power line-frequency device into a sophisticated energy router. It buffers and shapes power demand from the grid, enables the use of modular, high-frequency conversion techniques, and improves overall system efficiency, power quality, and reliability. This architecture is essential for the next generation of high-average-power pulsed systems used in industrial laser ablation, scientific plasma research, and particle accelerator injectors, where the demands on the electrical infrastructure must be tamed without compromising pulse performance.