AC/DC Power Supply Test Solutions

Power Supply Development Overview

The power supply industry is the energy-based industry for the entire electronics industry. With the diversification of power electronic equipment and the enhancement of people's awareness of energy conservation and environmental protection, the power supply market has become prosperous and active, and competition has intensified.

Power supplies are particularly complex and diverse, and can be roughly divided into several categories, such as AC/DC power supplies, DC/AC power supplies, DC/DC power supplies, and AC/AC power supplies; and can be divided into adapters, UPS, PC power supplies, communication power supplies, security power supplies, medical power supplies, aviation power supplies, etc. Looking at these types of power supplies, their future development trends are just as pointed out by industry experts: 1. Smaller form factor, that is, increased power density, 2. Higher efficiency, that is, to reach 80% or even more than 90%, 3. Lower cost per watt.

All these put forward more stringent requirements for power supply testing to ensure that the power supply that meets high requirements can adapt to more demanding use environments. This article mainly introduces the AC/DC power supply testing solution provided by Beijing RIGOL Technology Co., Ltd. (RIGOL).

Main test parameters of AC/DC power supply

Among the many types of power products, AC/DC power supply is one of the most widely used power supplies. For example, common notebook adapters, mobile phone adapters, PC power supplies, etc. are typical AC/DC switching power supplies, and AC/DC switching power supply modules in the electronics market also belong to this category.

In order to ensure the excellent quality of the products shipped out of the factory and further improve the performance indicators of AC/DC power supplies, power supply manufacturers usually need to go through a rigorous testing process, which includes a wide variety of test items such as output test, input test, protection test, safety test, environmental test and EMC test. Among these test items, more attention should be paid to the AC/DC power supply characteristics of the AC input range, power regulation rate, load regulation rate, ripple and noise, start-up and hold time, rise time, overload protection, overvoltage protection, withstand voltage insulation, leakage current, electromagnetic compatibility, power efficiency and other performance characteristic parameters.

In order to meet complex testing requirements and help power supply manufacturers improve the quality of power supply products, RIGOL's application engineers conducted in-depth research on the power supply industry and provided users with an efficient and fast AC/DC power supply testing system.

AC/DC Power Supply Test Solution

A typical AC/DC power supply test system includes a programmable AC power supply, a programmable electronic load, a high-precision digital multimeter, a digital oscilloscope, a multi-channel programmable switch, an industrial computer and test software.

In the test system, the performance and quality of the selected instruments and equipment are directly related to the stability and efficiency of the test system. As a leading supplier of measuring instruments and solutions in China, RIGOL provides digital oscilloscopes DS1302CA and digital multimeters DM3058, which have extremely high technical indicators and stable product performance among the same-end products.

The dual-channel digital oscilloscope DS1302CA has a bandwidth of 300MHz and a real-time sampling rate of 2GS/s, which can accurately complete power ripple tests and other basic tests; the standard USB interface and RS-232 interface provide users with a variety of optional system integration solutions; in addition, the optional USB-GPIB module can connect the DS1302CA to the test system of the GPIB bus. As shown in Figure 1.

Figure 1 RIGOL DS1302CA digital oscilloscope

DM3058 is a 5.5-digit high-precision digital multimeter with 240,000 readings. It is equipped with USB, RS-232, GPIB and Ethernet interfaces that comply with the LXI-C standard. It can be easily connected to various types of bus network systems. In terms of program control instructions, it not only has instructions that comply with the SCPI standard, but is also compatible with the instructions of similar mainstream products on the market, and can be directly replaced.

Figure 2 RIGOL DM3058 digital multimeter

At the same time, the measurement accuracy has reached the advanced level of similar products. The basic DC voltage accuracy reaches 0.015%+0.003%, the basic DC current accuracy reaches 0.02%+0.005%, and the basic resistance accuracy reaches 0.02%+0.003%, which provides a guarantee for the accuracy of the test data. In addition, its AC test frequency range reaches 1MHz, which ensures the test of high-frequency switching power supplies. The measurement of 10A large current does not require the replacement of jacks and test leads, which greatly improves the test efficiency and ensures the safe use of the instrument.

Figure 3 Test system block diagram

In the display unit, DM3058 uses a 256×64 LCD display, which is rare in multimeters. Various function parameter settings use menu-based operations, which enhances ease of use outside the system.

Figure 3 shows a test system built using RIGOL DS1302CA and DM3058. This test system can complete the test of important power supply performance characteristics that AC/DC power supply manufacturers are concerned about. The following takes the test of AC/DC power supply efficiency, power supply ripple, and input voltage regulation as an example to specifically introduce the test process of the test system.

Energy conservation and environmental protection are hot topics in all industries today, and the power supply industry is a pioneer in advocating energy conservation and environmental protection. Currently, many Asian power supply manufacturers have set their sights on developing new energy-saving products with energy efficiency of more than 88% or even more than 90% at half load. So, in order to accurately obtain power supply efficiency data during the test process, four measurements are generally required, namely, measuring the efficiency at 25%, 50%, 75% and 100% load respectively, and then taking the average value as the efficiency of the power supply.

Ripple noise is also an important performance indicator for measuring the quality of AC/DC power supply products. Ripple refers to the peak-to-peak value of the AC component superimposed on the output DC voltage. Generally, the ripple should not exceed 1% of the output voltage.

When testing the output voltage ripple, the industrial computer first controls the output of the programmable power supply, and its output can make the power supply enter the normal working state. Then the programmable electronic load is controlled to make the power supply reach the 100% load state. Then the DS1302CA oscilloscope is connected to the output end of the power supply by the multi-channel switch. The digital oscilloscope is set to DC coupling through the industrial computer, and a 1:1 probe input is used. In addition, in order to better observe the stable ripple signal, the "bandwidth limit" of the oscilloscope can be turned on. Finally, the peak-to-peak value of the ripple signal measured by the digital oscilloscope is uploaded to the computer for storage, and the ripple voltage of the power supply is obtained, as shown in Figure 4.

Figure 4 Power supply ripple voltage value measured by RIGOL DS1302CA

Input voltage regulation is an important indicator used to measure the adaptability of an AC/DC power supply under load and harsh power grid environment. Input voltage regulation refers to the rate of change of output voltage when the input voltage changes within the rated range.

The measurement of input voltage regulation is completed by controlling the programmable power supply, multi-channel switch, and electronic load through an industrial computer, and working in conjunction with a digital multimeter. Assuming that the input voltage range of an AC/DC power supply with a rated output of 12V is between 115 and 264VAC, during the test, the load is set to full load, the programmable power supply output is adjusted from 115VAC to 264VAC, and then the DM3058 digital multimeter is used to test the output DC voltage of each stage, and the data is recorded in the industrial computer. Then, the input voltage regulation of the AC/DC power supply can be calculated according to the formula.

Figure 5 RIGOL DM3058 digital multimeter measurement interface

Fast measurement and communication speeds are also important features of DM3058. In program-controlled testing, taking the measurement of DC 24V voltage as an example, medium-speed measurement is used on the enterprise test platform. The fastest time required by similar multimeters is 360ms, while RIGOL DM3058 only needs 250ms. If 177 items such as DC voltage, AC voltage, frequency, and resistance are continuously measured on the test platform, DM3058 only needs 88s to complete the whole set of measurements, which is 10s shorter than similar multimeters. The efficiency improvement brought to the entire production test process cannot be underestimated.

The above are several typical parameters of AC/DC power supply measured by this test system. This measurement system can not only help users complete the test function efficiently and quickly, but also provide a strong guarantee for users to improve product quality. As a rising test and measurement manufacturer in China, RIGOL will always focus on measurement, adhere to independent innovation, provide users with more innovative industry solutions, and truly reflect customer value.