AC/DC power conversion for telecom infrastructure
The stable operation of telecommunications infrastructure (such as data centers, base stations, core routers, etc.) is highly dependent on reliable and efficient AC/DC power converters (hereafter referred to as "telecom power supplies"). They are responsible for converting alternating current (AC) from the grid into the stable direct current (DC) required by the internal electronic circuits of the equipment.
Working Principles (Based on Mainstream Switching Power Supply Technology)
Modern telecom power supplies widely employ high-frequency switching power supply technology. Its core principles are as follows:
Input Filtering and Rectification:
- AC input (e.g., 110/220V AC) first passes through an EMI filter to suppress high-frequency noise interference from the grid and prevent noise generated by the power supply itself from feeding back into the grid.
- A rectifier bridge converts the AC into unidirectional pulsating DC.
- Large input filter capacitors provide initial smoothing of the rectified pulsating DC.
Power Factor Correction (PFC):
- Traditional rectifier circuits draw peaky input current, resulting in low power factor (PF ~0.6-0.7) and high harmonic content, wasting grid capacity and interfering with other equipment.
- The PFC circuit (typically using a boost topology) forces the input current waveform to follow the input voltage waveform (approximating a sine wave), raising the power factor close to 1 (often required >0.99), and significantly reducing input current harmonic distortion to meet regulatory standards (e.g., IEC 61000-3-2).
DC/DC High-Frequency Inversion and Conversion:
- The relatively smooth high-voltage DC (~385V DC) after PFC correction.
- Core Conversion: An inverter circuit composed of high-frequency switching power devices (e.g., MOSFETs, IGBTs), under Pulse Width Modulation (PWM) control, converts this high-voltage DC into high-frequency (typically tens of kHz to hundreds of kHz or even MHz) square wave AC.
- A high-frequency transformer steps down and isolates this high-voltage, high-frequency AC to the required low voltage.
- Advantage: High-frequency transformers are significantly smaller and lighter compared to line-frequency transformers, which is key to the miniaturization of switching power supplies.
Secondary Rectification and Filtering:
- The low-voltage, high-frequency AC output from the transformer is rectified back to low-voltage DC using fast-recovery diodes or synchronous rectifier MOSFETs.
- An output filter circuit (LC filter) removes high-frequency ripple, yielding a smooth, low-ripple, stable DC output voltage (e.g., 12V, 48V).
Feedback Control Loop:
- The output voltage is sampled in real-time and compared with an internal precision reference voltage.
- An error amplifier generates an error signal.
- The PWM controller adjusts the conduction time (duty cycle) of the switching transistors based on the error signal, implementing closed-loop negative feedback control to ensure the output voltage remains highly stable under varying load and input voltage conditions.
Protection Circuits:
- Over-Voltage Protection (OVP): Prevents excessive output voltage from damaging the load.
- Over-Current/Short-Circuit Protection (OCP/SCP): Limits output current or cuts off output to protect the power supply and load.
- Over-Temperature Protection (OTP): Shuts down the power supply in case of abnormal heat dissipation.
- Input Under-Voltage/Over-Voltage Protection (UVP/OVP): Ensures the power supply operates within a safe input voltage range.
Main Architectures
Telecom power supply architectures vary depending on the application scenario, power level, redundancy requirements, and integration needs:
1.AC/DC Front-End Module + DC/DC Point-of-Load (PoL) Converters:
- AC/DC Front-End: Performs conversion from AC input to a DC bus (typically high-voltage DC, e.g., 380V), including PFC and isolated DC/DC conversion (outputting buses like 48V, 12V). Often uses brick modules.
- DC/DC PoL Converters: Mounted on the circuit board near the load (e.g., CPU, ASIC), converting the bus voltage (e.g., 48V, 12V) further into the precise low voltage required by the load chips (e.g., 3.3V, 1.8V, 1.0V). Uses isolated or non-isolated DC/DC converters.
- Advantages: High efficiency (reducing losses from long-distance, low-voltage, high-current transmission), modularity, distributed heat dissipation, flexible design.
Integrated AC/DC Power Module:
- Integrates all functions from AC input to the final required DC output (e.g., 12V) within a compact module (e.g., 1/4 brick, 1/2 brick, full brick).
- Widely used in embedded telecom equipment, small cell base stations, access devices, and other space-constrained scenarios.
Rack-Mounted/System-Level Power Supply:
- Installed within telecom equipment racks or as standalone units.
- Provides higher output power (hundreds of watts to kilowatts or more).
- Typically contains multiple paralleled power modules, supporting N+1 or N+N redundancy configurations to ensure uninterrupted system power if a single module fails.
- Output is commonly 48V (traditional telecom standard) or 12V (common in modern data center servers).
- Features comprehensive monitoring and management functions (via interfaces like PMBus, I2C).
Distributed Power Architecture (DPA):
- Predominantly used in large telecom equipment (e.g., core routers, high-end switches).
- Central AC/DC Conversion Unit: Generates an intermediate high-voltage DC (HVDC) bus (e.g., 380V HVDC).
- Distributed DC/DC Converters: Located on individual circuit boards, converting the HVDC bus voltage to the low DC voltages needed by chips on that board.
- Advantages: Highest efficiency (minimizes multi-stage conversion losses), high power density, low distribution losses (HVDC transmission requires lower current), flexible system design.
Outdoor Power System:
- Specifically designed for harsh outdoor environments like base stations and remote access points.
- Includes AC/DC rectifier modules, DC/DC converter modules (e.g., 48V to board voltage).
- Features wide input voltage range, wide operating temperature range, lightning protection, dust/water resistance, and other high-reliability designs.
- Typically integrates a battery management system (BMS) to support -48V DC batteries as backup power.
Market Trends
The telecom power supply market is strongly driven by demands from cloud computing, 5G/6G, artificial intelligence (AI), and the Internet of Things (IoT), exhibiting the following major trends:
Ultra-High Efficiency:
- Data centers consume massive energy; power supply efficiency gains directly reduce Power Usage Effectiveness (PUE). Titanium efficiency level (e.g., 96%+) is now standard for high-end data centers, pushing towards even higher levels.
- Regulations (e.g., 80 PLUS, CoC Tier, ENERGY STAR) continuously raise minimum efficiency requirements.
Ultra-High Power Density:
- Equipment size continuously shrinks, demanding more power per unit volume. Achieved by increasing switching frequency, improving topologies (e.g., LLC resonant), optimizing thermal design (e.g., liquid cooling), and adopting new devices.
- Watts per cubic inch becomes a key metric.
Intelligence and Digital Control:
- Digital power management chips are increasingly prevalent, enabling finer control, higher conversion efficiency, and better dynamic response.
- Built-in monitoring (voltage, current, temperature, power, efficiency, fault diagnostics) reported via standard interfaces.
- Supports remote configuration, firmware updates, and predictive maintenance.
Wide Input Voltage Range:
- Adaptation to different global grid environments and fluctuations (e.g., 90-264VAC or wider), especially in regions with unstable grids.
Rise of High-Voltage DC (HVDC) Power Distribution:
- Increased adoption of HVDC (e.g., 240V/336V/380V) in large data centers.
- Advantages: Eliminates the AC/DC conversion stage within servers, improving overall system efficiency; lower distribution losses; simplifies UPS architecture; enhances reliability. Requires server power supplies compatible with HVDC input.
Evolution and Resurgence of 48V Power Architecture:
Green and Eco-Friendly:
- Compliance with environmental regulations like RoHS, REACH.
- Low standby power consumption.
- Use of environmentally friendly materials, reducing carbon footprint.
- Design for recyclability.
Adoption of Wide-Bandgap (WBG) Semiconductor Materials:
- Silicon Carbide (SiC): High voltage/temperature tolerance, good high-frequency characteristics, low losses; particularly suitable for high-power PFC and high-voltage DC/DC conversion stages (e.g., data center front-end power, solar inverters).
- Both significantly enhance efficiency and power density.
Modularity and Standardization:
- Standardized form factors (brick modules) facilitate system integration and supply chain management.
- Modular design enables flexible capacity expansion and redundancy, improving availability and serviceability.
Enhanced Reliability and Safety :
- The requirement for "five nines" (99.999%) or higher availability in telecom infrastructure drives power supply design towards higher Mean Time Between Failures (MTBF).
- More comprehensive multi-level protection mechanisms.
- Compliance with stricter safety certification standards.
The advantages of SMC
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