Understanding Isolation Voltage of Power Modules: What is 3000VDC Isolation Voltage and Its Applications?

The rapid development of the microelectronics industry has made the electromagnetic environment of product usage scenarios increasingly complex, greatly affecting product stability. Manufacturers of embedded products add various isolation devices or isolation circuits to reduce interference in the working environment and enhance equipment stability.

As the energy supply part of embedded devices, the power supply is the prerequisite for stable product operation. Power isolation is particularly important, and the application of isolated power supply modules has become an essential part of embedded device design.

In industrial equipment, power isolation between two devices is required. A DC converter with a transformer is used to separate the two power supplies, making them independent from each other, thus reducing external interference!

Figure 1: Internal Block Diagram of Isolation Power Supply

As shown in Figure 1, the internal block diagram of the isolation DC-DC power supply module.

Isolation voltage refers to the maximum insulation voltage that two systems without direct electrical connection can withstand.

Different applications of power isolation require different parameter selections. For example, AD-DC power isolation generally requires an isolation voltage of 3000VAC to 4000VAC for typical industrial applications; DC-DC power isolation generally requires 1000VDC to 2000VDC, with special industries possibly requiring higher levels, such as the medical industry requiring 6000VDC.

First, let’s differentiate the units of various voltage indicators, commonly ADC, VAC, and RMS, as shown below.

VAC/VDC refers to AC voltage and DC voltage respectively, but isolation voltage cannot simply be converted between AC and DC. For instance, while 3000VAC has a peak voltage of 4242V, in practical applications, an isolation voltage of 3000VAC is not equivalent to 4242VDC.

The specific reasons include two points:

1. For isolation modules, there is an isolation capacitor between input and output. For DC signals, the impedance of the capacitor is infinite, so the size of the isolation capacitor does not significantly affect DC signals. However, for AC signals, it has a significant impact, resulting in increased leakage current or direct exceeding of standards, causing system alarms.

2. Another difference between AC and DC is that frequency affects the dielectric constant of insulating materials. Frequency can lead to a decrease in the dielectric constant of insulating materials; the higher the dielectric constant, the stronger the insulation capability.

RMS refers to the root mean square value, simply representing the amount of work done by AC voltage equivalent to DC voltage over a unit time. In other words, an AC voltage with an RMS value of 10V does the same work as a 10V DC voltage under the same load over the same time. This unit is generally not used as a measurement unit for isolation voltage.

To ensure the stability and safety of isolation voltage and to prevent breakdown of isolation power supply modules, we need to calculate the creepage distance. The shortest space distance measured along the surface of insulating materials between two conductive parts or between a conductive part and equipment or easily accessible surfaces is called creepage distance. Creepage distance = surface distance/system maximum voltage, depending on the degree of pollution.

Figure 2: Schematic Diagram of Creepage Distance

In the IEC60950 and GB4943-2011 standards, the minimum safety distances required for different voltage levels are specified, which include both electrical distance and creepage distance. For switch-mode power supplies, the minimum safety distances that need to be ensured include the following two aspects:

1. Safety distance from the primary circuit to the shell (protective ground);

2. Safety distance between the primary circuit and the secondary circuit.

The advantages and disadvantages of isolation power supplies compared to non-isolation power supplies are shown in Figure 3.

Figure 3: Comparison between Isolation and Non-Isolation Power Supplies

Various interferences in application scenarios of embedded products can threaten product stability. During the product design phase, selecting a good isolation power supply module and isolation communication module can effectively shield against interferences from the environment, ensuring stable operation of the product.

We often see news reports of mobile phones exploding during charging or electric shocks while charging. Isolation power supply modules can ensure stable operation of products and, more importantly, protect the life and property safety of users.

Currently, isolation power supplies are used in two ways: discrete devices and DC-DC power modules, as shown in the comparison below.

Once the performance requirements of the product are somewhat clear, the next step is to begin the design and development process, starting with the selection of the circuit scheme. Below are some common “negative examples” listed for everyone.

For instance, when designing a circuit that converts AC input to DC output, many people immediately think of using a power frequency conversion circuit scheme because it is relatively simple, requiring just a power frequency transformer plus rectification and filtering, as shown in Figure 4. The efficiency of products using this scheme is very low, and their size is very large, often accompanied by annoying power frequency eddy current noise. In contrast, the module scheme selects suitable transformers and ensures product consistency through multiple processes, guaranteeing the final performance of the product.

Figure 4: Transformer Scheme Comparison

Once the circuit scheme is confirmed, the next step is to design the performance parameters of the product, which involves designing, calculating, and selecting structural materials for the electronic components in the circuit scheme. This stage must consider various factors.

1. Material Selection.Professional module power supply manufacturers can achieve this by selecting optimal material specifications based on different product specifications and application conditions, discarding unnecessary material specifications.

2. PCB Design for Power Modules.Due to the PCB design specifications required for module power supply products, considerations must include thermal design, EMC design, interference design, and production process design, among others. Therefore, PCB design is treated as one of the most important steps in the development process of module power supply products, as shown in Figure 5.

Figure 5: PCB Design Requirements

ZLG Zhiyuan Electronics’ isolation DC-DC power supply can provide stable and reliable driving voltage for user systems and effectively solve problems caused by static electricity and surges that lead to unstable power supply, making it an ideal solution for powering subsystems such as data acquisition and communication on the board. The isolation voltage level covers 1000VDC to 6000VDC, meeting all operating conditions.

Compared to traditional designs, ZLG Zhiyuan Electronics’ constant voltage series isolation power supply modules adopt the industry’s best solutions from topology structure, chip schemes to components, achieving higher integration and reliability, providing standard and reliable solutions for user I/O and communication isolation applications.

If you have any questions, please feel free to add ZLG’s official customer service WeChat account for consultation: zlgmcu-888.