800V HVDC Bleeder Resistor Application Solution
The Safety Guardian of High-Voltage AI Server Architectures
As the demand for high power density and energy efficiency in AI Servers rapidly escalates, the 800V HVDC architecture has emerged as the mainstream design for next-generation data centers and high-end server power systems.
In high-voltage DC architectures, bus capacitors store a large amount of energy. To ensure personnel safety after system shutdown and to protect downstream circuit components, the bleeder resistor plays a critical role, safely discharging residual high voltage within a specified time and preventing risks associated with remaining capacitor voltage.
800V HVDC Design Requirements & Technical Considerations
When designing bleeder resistors for 800V HVDC systems, several key factors must be evaluated:
• Bus capacitance (µF)
• Target discharge time (seconds)
• Maximum instantaneous pulse energy (Joules)
• Resistor voltage withstand capability
• Long-term stability and reliability
Case Study: (800V Bleeder Conditions)
Design Tip:
Capacitance and discharge time are the core parameters for selecting resistance values and determining series/parallel configurations. The design must simultaneously satisfy safety discharge windows and the energy-handling capacity of individual resistors.
Discharge Energy Calculation and Selection Criteria
Capacitor Stored Energy Calculation Formula：
For a typical system using 800V / 60µF as an example: To ensure optimal energy distribution and reliability, Firstohm recommends a series configuration of 4 units of SRM301 (3W).
• Energy Distribution: Each resistor bears approximately 5J of pulse energy.
• Safety Margin: This configuration effectively disperses voltage and instantaneous thermal stress, significantly improving the system’s safety margin
Recommended Product: SRM301 Surge Resistant MELF Resistor
• Model: SRM301 (3W)
• Dimensions: 4.0 × 10.5 mm
• Resistance: 1.5KΩ ±5% (Typical for 4-pcs series configuration)
Key Advantages of the SRM series:
• High Pulse Endurance: Specifically designed for instantaneous discharge applications.
• Safety Certified: Passed the German VDE safety certification.
• MELF Structure: The cylindrical MELF design provides superior heat dissipation and higher reliability compared to standard flat chips.
• Compact Design: Ideal for modular designs and high-density PCB layouts
Empirical Validation & Test Results
To verify reliability, the SRM301 underwent rigorous high-voltage pulse testing：
• Test Setup: 4 units in series, placed at the capacitor backend
• Charge/Discharge Voltage: 800VDC.
• Capacitance: 60µF.
• Cycle: 5s Charge / 1s Discharge for 100 cycles.
• Result: Resistance change ΔR = 0.035% (PASS)
The results demonstrate that the SRM301 maintains exceptional stability and reliability even under extreme high-voltage pulse discharge conditions。
Typical Application Scenarios
• AI Server Power Modules (800V HVDC Architecture)
• Data Center: Bus Capacitor Discharge Modules
• High-Voltage AC/DC Power Supplies
• Energy Storage Systems (ESS) and Battery Backup Units (BBU)
Firstohm – Surge Resistant MELF Resistors Specifications
Why Choose Firstohm?
In 800V HVDC high-voltage applications, component reliability and safety are far more critical than cost. Firstohm’s SRM series provides a trustworthy solution for AI and data center power systems through superior pulse-handling capabilities and long-term stability.