Supplement: Power


of the voltage drop – typically via the DC-OK signal at the output of the power supply. After detecting the outage, the buffer module takes over the load supply until it is completely discharged. This time span can be used to transfer the system to a defined, safe state and ensure a fault-free restart.


Note:


Image 1: Temporal progression of a bridging phase during a power outage using a buffer module.


If the actual load is below the maximum permissible output current of the buffer module, the available buffer time is extended accordingly. Therefore, careful choice of the power supply considering the actual power consumption is crucial for the effectiveness of the shutdown strategy.


Securing sub-branches


By using an additional redundancy module, the output side of the power supply can be divided into a buffered and an unbuffered sub-branch. Power-intensive consumers such as actuators are operated directly at the power supply and are not included in the buffering. The buffer energy is thus exclusively available for more sensitive components such as sensors, PLCs, industrial PCs or logic.


Image 2: During extended power outages, buffer modules extend the buffer time to transfer the system to a safe state.


on increasing the voltage during the development process.


The period after the power outage must also be considered, as the upstream power supply must seamlessly take over after the interruption. Therefore, when designing the buffering, the selection of a suitable power supply unit with appropriate startup behaviour is crucial.


The following graphic shows the temporal progression of a complete bridging phase during a power outage. The upper graph shows the mains voltage (AC), which is converted into a regulated DC voltage at the output in the power supply. The lower curve shows the DC output voltage at the load connected to the buffer module. Green indicates normal operation with applied mains voltage; red indicates the state during a power outage. As soon as the output voltage of the power supply falls below the threshold


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of 22.5 V, the buffer module seamlessly takes over the supply of the connected consumers with stable DC voltage. After the mains voltage returns, the power supply ensures the supply again without interruption.


PULS offers the option to configure the minimum buffer voltage specifically to 1 V below the set output voltage in the buffer modules of the UF series. For example, if an output voltage of 28 V is set at the power supply, the buffer module can be parameterised to buffer up to a lower limit of 27 V – instead of the standard threshold of 22.5 V.


In practice, this means that a user supplies their loads with 28 V via the power supply. In standard operation, the buffer module would only become active at a voltage drop to 22.5 V. However, with the optional voltage adjustment, buffering can already occur from 27 V, which is


particularly advantageous for voltage- sensitive loads or tighter tolerance requirements.


Controlled shutdown during extended power outages Capacitor-based buffer modules are also suitable for applications where only a limited bridging time is required after a power outage before the system can be safely shut down and de-energised. The requirement for this is the early detection


This targeted protection of individual branches significantly increases the available buffer time – depending on the system structure, it can range into the seconds and thus enables reliable data storage and controlled shutdown sequences. For particularly compact implementation, buffer modules with integrated decoupling function are also available, such as devices of the UC10 series.


Increasing buffer time and peak current capability


Buffer modules of the UF series with electrolytic capacitors functionally behave like electronic capacitors and can be easily operated in parallel with the power supply output or directly at the load. By cascading multiple modules, the user can specifically extend the buffer time and simultaneously increase the peak current capability of the power supply – without having to oversize the power supply.


Continues on page 26


Image 3: By skillfully dividing into load branches, control functions can be buffered for a longer period. Components in Electronics July/August 2025 25


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