Understanding TPVC: The Converter That Doubles Power Processing

The Challenge with Traditional Converters

In modern energy systems—from electric vehicles to data centers—we increasingly rely on electrochemical sources like batteries, fuel cells, and electrolyzers. These devices share an important characteristic: their voltage varies within a relatively narrow range during operation.

For example, a lithium-ion battery cell operates between 2.7V and 3.6V across all states of charge. This means the voltage only needs to be controlled within a 50% to 100% range—not from zero to maximum.

Traditional DC-DC converters, however, are designed to switch the full voltage range. This means the semiconductors inside must handle voltages and currents that could be significantly higher than what's actually needed, leading to:

• Oversized, expensive components
• Lower efficiency due to switching losses
• Larger physical size and weight
• Wasted power processing capacity

Enter Partial Power Converters

Partial Power Converters (PPCs) emerged as a promising solution. The core idea is simple but powerful: only process a fraction of the total power flowing through the system, rather than the full amount.

Think of it like redirecting water in a river. Instead of pumping all the water through your system (full power processing), you only divert the amount needed to control the flow (partial power processing). This approach can dramatically improve efficiency and reduce costs.

However, most partial power converters have a critical flaw: they require a high-frequency transformer to redirect power. While these systems technically avoid galvanic isolation, the transformer itself adds significant:

• Cost
• Weight and volume
• Power losses

This largely defeats the purpose of partial power processing.

The YEMOY Solution: Transformerless Partial Voltage Converter (TPVC)

Our technology eliminates the transformer entirely while maintaining all the benefits of partial power conversion. The key innovation lies in switching only a fraction of the voltage instead of the full voltage.

How It Works

The TPVC uses a symmetrical architecture with two identical low-voltage sources (like battery cells) connected to a single high-voltage bus. The clever part is how we handle the midpoint voltage.

In most partial voltage designs, there's a fundamental problem: the capacitive midpoint sees a non-zero average current, making the voltage unstable. It simply doesn't work. However, by using two symmetrically-connected loads with identical characteristics, we can cancel the average current at the midpoint and achieve stable operation.

Key technical insight: The semiconductors only switch V_HV/2 (half the high voltage) instead of the full V_HV. This means we can use lower-rated components with better efficiency.

Measuring Success: Semiconductor Capacity Utilization Index (SCUI)

To quantify the advantage of our technology, researchers use the Semiconductor Capacity Utilization Index (SCUI). This metric measures how efficiently semiconductors are used:

SCUI = (Power Transferred) / (Peak Voltage × Peak Current of Semiconductors)

A higher SCUI means better semiconductor utilization, leading to higher efficiency, smaller components, or higher power capacity with the same components.

For traditional DC-DC converters (buck, boost, interleaved, etc.), the SCUI ranges from 0 to 1. The TPVC achieves an SCUI between 1 and 2—effectively doubling the power processing capacity compared to conventional topologies.

Natural Current Balancing: An Unexpected Benefit

One of the most surprising properties of the TPVC is its natural current balancing capability. By controlling just one current sensor and one control loop, we can regulate both load currents simultaneously, keeping them perfectly balanced.

This happens because both cells use identical duty cycles (the fraction of time switches are "on"). As long as the voltage difference between the two low-voltage sources remains small, the currents stay balanced automatically.

This property is particularly valuable when working with matched battery cells or fuel cell stacks, where maintaining balance is critical for longevity and safety.

Magnetic Coupling Enhancement (CTPVC)

The TPVC architecture also works exceptionally well with magnetic coupling using intercell transformers (ICT). This variant, called CTPVC (Coupled TPVC), offers additional benefits:

• Further reduced current ripple (up to 4× reduction)
• Smaller magnetic components
• Higher effective switching frequency without increasing losses

Unlike traditional interleaved converters where even slight duty cycle imbalances cause massive current imbalances and core saturation, the TPVC's natural balancing property makes it inherently compatible with magnetic coupling.

Real-World Performance

Experimental validation demonstrates impressive results:

• Efficiency: The TPVC maintains efficiency above 98.5% across a wide power range (700W to 3200W), reaching a peak of 99.5%
• CTPVC: Achieves 99.55% efficiency with even better ripple performance
• Balanced operation: Currents remain perfectly balanced even with up to 20% load voltage mismatch
• Wide operating range: Efficiency stays above 99% at powers exceeding 1500W for both TPVC and CTPVC

In comparison, standard dual-buck converters reach 99.25% efficiency but have a much narrower high-efficiency operating range.

Scalability to Higher Cell Counts

The TPVC architecture can be extended to 4, 6, or more cells. By using phase-shifted switching patterns (e.g., 180° between control signals), we can achieve interleaved operation benefits:

• Distributed losses across more devices
• Higher apparent switching frequency
• Minimal current ripple at 50% duty cycle

This makes the technology highly adaptable to different application requirements and power levels.

Why This Matters for Data Centers

Modern data centers, especially those powering AI infrastructure, face unprecedented power demands. They require:

• Extremely high efficiency to minimize energy waste and cooling costs
• High power density to maximize computing capability per square foot
• Reliable power conversion from high-voltage DC buses to rack-level voltages

The TPVC technology addresses all these needs by providing a converter architecture that processes twice the power of traditional designs with the same semiconductor ratings, while maintaining efficiency above 99% and eliminating bulky transformers.

Key Figures from the Research

The scientific paper includes several important diagrams that illustrate the technology:

• Figure 2: Basic principle showing why partial voltage conversion requires balanced loads
• Figure 4: Symmetric Partial Voltage Converter architecture showing the viable configuration
• Figure 5: SCUI comparison demonstrating the 2× advantage over conventional converters
• Figure 6: Midpoint voltage stability analysis across different duty cycles
• Figure 8: Current waveforms comparing uncoupled, phase-shifted, and magnetically coupled variants
• Table 2: Comprehensive experimental comparison between dual-buck, TPVC, and CTPVC topologies

Conclusion

The Transformerless Partial Voltage Converter represents a fundamental advancement in power electronics. By eliminating the transformer while maintaining partial power processing benefits, YEMOY's technology delivers:

• Double the power processing capacity (SCUI of 1-2 vs. 0-1)
• Efficiency exceeding 99% across wide operating ranges
• Natural current balancing with single-sensor control
• Excellent compatibility with magnetic coupling
• Scalability to multiple cell configurations

For applications involving electrochemical sources or any system where voltage varies in a limited range—including the massive power distribution challenges in modern data centers—the TPVC offers a compelling path toward higher efficiency, greater power density, and reduced costs.