An Analysis Of The MEAN WELL DRS Series DIN-Rail Power Supply Functions

Explanation of the Wake-Up Mechanism

The figures below illustrate the output voltage waveforms during the Wake-Up sequence, both with and without a battery connected to the BAT terminal. The yellow waveform represents the main output voltage, while the blue waveform represents the voltage at the BAT terminal.

When no battery is connected to the BAT terminal, the Wake-Up sequence repeats every 5 minutes. For applications where no battery is deployed and the system is sensitive to output voltage fluctuations, this periodic wake-up function can be disabled via communication commands (setting `Wake_UP_EN = 0` within `UPS_CONFIG`), ensuring that the wake-up process occurs only once upon initial startup.

Explanation of the TIME_BUFFERING Function

In practical applications, simple hardware logic-where a power outage immediately triggers battery discharge-is no longer sufficient to meet the complex requirements of modern power grids and unattended intelligent systems.

To address this, the DRS series incorporates three configurable parameters: `TIME_BUFFERING` (backup duration), `UPS_Delay_Time` (delay before entering backup shutdown mode), and `UPS_Shutdown_Time` (timing for backup-mode restart). The logical relationship between these parameters and the AC power grid is illustrated in the figure below.

BAT_TEST (Battery Test) Function Description

The DRS series is typically used in conjunction with a battery. To ensure the reliability of the backup power system, it features a built-in "BAT_Test" (Battery Test) function, which periodically checks whether the battery is over-discharged or in an abnormal state.

The image below illustrates the output voltage waveforms during the battery test procedure: the yellow waveform represents the main output voltage, while the blue waveform represents the output voltage at the BAT (battery) terminal.

Additional Notes

The DRS series also supports "AC Priority" and "Load Priority" modes; a brief explanation of these is provided below.

When AC mains power is available, the unit prioritizes AC supply to conserve battery energy; in this state, it is not possible to switch to battery power via the "force start" function. In the absence of AC power, the "force start" function can be used to switch to battery power, allowing the DRS to operate-a feature particularly useful for scenarios such as on-site installation and commissioning.

Furthermore, MEAN WELL is actively developing the DRS-960-a 960W model for the security power supply family-with an official launch expected in the first half of 2027. Stay tuned!