A、Why has the 24V system become an "invisible killer" for industrial equipment?

Among global industrial power supply failures, 24V systems account for as high as 68% (IEEE 2023 Industrial Power Reliability Report). A certain automobile manufacturing plant was shut down for 72 hours due to a breakdown of the 24V control board, resulting in direct losses of over 3 million yuan. This forms a sharp contrast with the perception of "safe voltage".

24V systems face three major threats in industrial scenarios:

• Input surge: Lightning strike/switching transient (typical energy over 500J)
• Short circuit at the output end: Differential mode surge caused by incorrect connection of the sensor/actuator
• Backflow voltage: The reverse current impact when multiple modules are supplied in parallel

B、Triple threats and Protection Logic of 24V Power Supply

Shanghai Leiditech Electronics has been deeply engaged in the field of electrostatic surge protection for over a decade, specializing in the design of electrostatic surge protection solutions for industrial power supplies. In response to the electrostatic surge protection requirements of complex industrial scenarios, it has built a reliable protection system for 24V electrical systems by leveraging its technical accumulation in solution design and component application.

• Overvoltage protection: The positive and negative terminals of the power input are connected in parallel with the Leiditech TVS diode SMBJ26CA. The clamping voltage is ≤42V (it should be lower than the maximum withstand voltage of the protected device DC-DC in the 24V power supply system. If 36V or 40V DC-DC is used, the Leiditech back-scan type TVS series can be selected. The low clamping voltage effectively protects the rear end) The current-carrying capacity is 14.3A (10/1000μs), and it can quickly discharge transient overvoltage.
• Overcurrent protection: Series Leiditech self-resetting fuse (PPTC) automatically disconnects in case of overcurrent (such as short circuit), and resumes after the fault is eliminated to prevent the power module from burning out.
• Anti-reverse connection: Polarity reverse connection protection is achieved by using PMOS (suitable for high-power scenarios above 20A, recommended is the LM5D28P10 type PMOS from Leiditech Electronics) or low-dropout Schottky diodes (suitable for low-power scenarios, such as Leiditech Electronics SK56C, 60V/5A).

C、Key protection points for the use of power supplies in industrial sites

Many engineers tend to focus on signal logic and communication protocols when designing, but neglect the fundamental guarantee role of the power supply system. During the service, the EMC delivery person from Shanghai Leiditech found that problems such as excessive voltage drop, improper common ground, surge impact, and unreasonable PCB layout are the main causes of module disconnection, reset or false triggering. Based on over a thousand service experiences, the EMC delivery guy from Shanghai Leiditech has summarized the following practical suggestions:

• • Independent power supply in zones: Strictly separate the power supply for the IO-Link master station, solenoid valves and power loads to eliminate crosstalk caused by common ground.
  • Select high-quality industrial power supplies with overvoltage/undervoltage protection: Ensure that the peak output ripple is less than 50mV, and reserve more than 20% of the capacity as a margin to avoid unstable power supply caused by load peaks.
  • Standardize grounding and shielding treatment: In communication-intensive areas, single-point grounding mode should be adopted, combined with metal-shielded cables to reduce common-mode interference paths. Shanghai Leiditech EMC service personnel particularly remind: PGND (protective ground) and GND (operating ground) should either be directly short circuit or completely isolated. It is strictly forbidden to form interference channels through indirect connection of devices.
  • Strictly control cable voltage drop: When the power supply cable exceeds 10m, reduce voltage loss by thickening the wire diameter or using double-wire parallelization. At the same time, avoid clustering high-power components to ensure heat dissipation and electromagnetic isolation effects.
  • Mandatory installation of surge absorption devices for inductive loads: Motors, coils and other equipment need to be connected in parallel with Leiditech electronic TVS diodes or RC absorption circuits, following the multi-level protection concept of "slow devices in front and fast devices behind" to block reverse current impacts.

• The EMC delivery man from Shanghai Leiditech provided on-site empowerment, and the production line was quickly restored within 60 minutes

The IO-Link substation module of a certain auto parts factory suddenly malfunctioned. There was no signal output at all in the four channels. The multimeter detected that there was no voltage at the power supply end of the module. The customer initially judged it to be a communication failure. After repeated debugging without success, they contacted the technical support of Leiditech.

Based on his experience in analyzing surge interference paths, the EMC guy from Shanghai Leiditech determined that it was not a communication issue but rather a trigger of the power protection mechanism. Through detection and circuit investigation, it was confirmed that a certain channel had a short circuit caused by cable damage, which triggered a differential mode surge impact. Thanks to the independent group power supply and short-circuit protection design of the power module, only the faulty channel was cut off from power supply, while the rest of the channels operated normally, without affecting the production capacity of the entire production line.

After the customer eliminated the short circuit and restored power, the module immediately resumed normal operation, with the entire downtime being less than 60 minutes. Reasonable power grouping and surge protection design not only prevent damage but also serve as the last line of defense for reliable on-site operation, avoiding the expansion of faults.

Conclusion: Precise protection leads to a stable system

The stable operation of industrial automation systems cannot do without standardized power supply architectures and compliant EMC protection designs. From the master station to the sub-station, from sensors to actuators, only by establishing a power protection system that complies with national standards can long-term trouble-free operation be achieved.

Shanghai Leiditech Electronics is committed to becoming a leading brand in electromagnetic compatibility solutions and component supply, offering products such as ESD, TVS, TSS, GDT, MOV, MOSFET, Zener, inductors, etc. Leiditech has an experienced R&D team that can provide personalized customization services based on customer needs and offer the most superior solutions to customers.