Safety regulations are safety regulations, which refer to the specifications that products must maintain and comply with during design. That is to say, the safety standards currently used by various products are formulated according to the different characteristics and needs of the products, as well as the safety requirements of the products. Since safety requirements and understandings are constantly changing, the standards are constantly updated.
Different from the performance requirements in product design, safety regulations emphasize the protection of users and maintenance personnel, so that users can use the product conveniently without being harmed by certain defects in electronic products. This is allowed in the safety test standards Part or all of the functions of the equipment are lost, but it is required that the equipment will not cause danger to users when part or all of the functions are lost. This is also the biggest difference between safety standards and product design: product design mainly considers how to achieve functions and maintain them. Functional integrity and product adaptability to the environment. Safety regulations use safety specifications to consider the design of electronic products and strive to make products safer. As long as the device can meet certain conditions without causing danger to the user or the outside world, then the safety design is qualified - although the device may no longer be usable or become a pile of waste.The basic requirements of safety regulations are: the design and structure of the product must be able to ensure that under normal use and possible malfunction conditions, it will not cause electric shock or other dangers to the user, and will not cause harm to the surrounding environment. In particular, the product must not cause any harm to the surrounding environment. During design and production, double protection measures should be provided against possible dangers.
The purpose of safety testing is to ensure that the equipment will not cause harm to users or other objects under any circumstances. Therefore, the test mainly includes the following aspects of testing:
1. Input test
The purpose of the safety input test is to examine whether the input circuit of the product design can withstand the product's operating current when the input meets the normal working requirements of the product. The regulations in the product standards are: the maximum power consumption input current cannot be greater than 110% of the product's nominal current value. This nominal value also tells the user the minimum current required for the product to work safely, so that the user must prepare for such an electrical environment before using this device.
2. Stability test of safety signs
Safety warning signs used to warn or prompt users must be stable and reliable. They cannot become blurred after being used for a period of time, resulting in the loss of warning prompts, which may ultimately lead to user misuse. Danger, or directly lead to accidents. Therefore, the stability of the security logo needs to be tested. The safety standard stipulates: test with water for 15 seconds, and then test with gasoline for 15 seconds. The mark must not be blurred.
3. Capacitor discharge test
For devices with pluggable power supplies, the power cord is often pulled out of the socket, and the power plug pulled out of the socket is often placed arbitrarily by someone or can be touched by the human body at any time. This leads to a problem. When the power of the device is unplugged, because the device contains capacitive components, the power socket of the device is actually charged at the moment of unplugging. As the capacitor discharges, the residual voltage on the device socket will disappear. However, if the capacitor is discharged for too long, it may cause an electric shock if the user inadvertently touches the metal part of the plug, or damage other devices or the device itself if it is left carelessly. Therefore, each complete machine safety standard has strict regulations on the capacitor discharge time of the equipment. When designing products, the time for capacitor discharge should be considered, and when necessary, a special discharge circuit should be used to ensure that the device can reliably discharge after the device is unplugged.
4. SELV circuit stability test
SELV circuit is a safe low-voltage circuit. This circuit is safe for users. For example, the DC output terminal of a mobile phone charger and the mobile phone are safe and can be touched without risk. Note: SELV circuits have different interpretations in different standards. For example, the interpretation in IEC60364 is different from IEC60950-1. Therefore, you need to pay attention to which standard SELV falls under, and the dangers are also different.
A SELV circuit needs to meet special requirements to be a SELV circuit. These requirements are that, in the event of a single fault, it still meets the SELV circuit requirements. Therefore, each SELV circuit needs to be tested under a single fault to prove that the SELV circuit is stable. During the test, single faults are introduced one by one and the SELV circuit is monitored.
5. Power limiting source circuit
Since the output power of power-limited source circuits is very small, it is known from experience that they will not cause a fire hazard. Therefore, in the safety standards, special lowering requirements are made for the enclosures of such circuits. Their flame retardant rating is UL94V. -2. Therefore, equipment nominally equipped with such circuits needs to be tested to prove that the equipment meets the requirements of power-limited source circuits.
6. Current limiting source circuit
The current limiting source current requires that when the circuit is normal and under a single fault, the outgoing current is below the safe limit and will not cause danger to people. Resistors for isolating primary and secondary circuits require shock-resistant resistors that meet special standards. The specific requirements for the current limiting source circuit are as follows:
When the frequency does not exceed 1KHz, a 2000R10% non-inductive resistor is connected between any two components in the current-limiting circuit or between any such component and ground. The steady-state current flowing through the resistor should not exceed 0.7 When the mA peak value or 2mA DC value frequency is higher than 1KHz, the 0.7mA limit should be multiplied by the frequency value in KHz, but should not exceed 70mA AC peak voltage U for components that do not exceed 450V AC peak over DC value, The capacitance of its circuit should not exceed 0.1uF. For components whose voltage exceeds 0.45KV AC peak value or DC value, but does not exceed 15KV AC peak value or DC value, the capacitance of the circuit should not exceed 45/UnF, where U is in KV, and the voltage U exceeds 15KV AC peak value or DC value. The capacitance of the circuit should not exceed 700/U2nF, where the unit of U is KV
7. Grounding continuous test
For some equipment, the casing must be grounded, otherwise charges will accumulate on the touchable surface and dangerous voltages will be generated. Protective grounding is to discharge these charges through the ground. Safety testing stipulates the size of the ground conductor used in the ground continuity test and the requirements for the resistance of the ground conductor. It also specifies the conditions and test time of the ground test for different currents.
8. Moisture test
Moisture testing is to simulate the safety performance of equipment in extreme environments. After the equipment is manufactured, it is required to be able to operate safely under any humidity conditions and not to fail to operate normally due to excessive humidity in the rainy season. Therefore, when designing, it must be considered that the equipment meets safety requirements under foreseeable humidity, so humidity testing is necessary. Testing requirements vary slightly depending on the standards.
9. Torque test
The external wires of the equipment are often bent and deformed by external forces during use. This test is to test the number of bends that the wire can withstand, to ensure that the wire and other wires will not break due to external force during the product life cycle, and to avoid dangers such as exposure of dangerous wires.
10. Stability test
During normal use of equipment, there are often different external forces acting on it. For example, for equipment that is as tall as the human body or higher than the human body, someone may rely on it or climb the equipment when performing equipment maintenance; for equipment that is shorter, Equipment with a flat top that may be used by people as a platform to stand on or place items on. Since the equipment needs to be subjected to external forces in various directions, the equipment needs to be designed to consider the collapse and overturning of the equipment under various circumstances. And the stability of the equipment needs to be tested after the design is completed. Ensure the stability of the equipment meets safety requirements.
11. Shell stress test
During the use of the equipment, it will be subject to various external forces. These external forces may deform the equipment shell. These deformations may cause the components inside the equipment to be in an abnormal state and cause danger, or the indicators may not meet the requirements. Therefore, these effects must be considered when designing equipment, and these indicators must be tested during safety certification.
12. Drop test
Small devices or desktop equipment may fall from hands or work surfaces to the ground during normal use. These drops may affect the safety indicators inside the device. Therefore, the impact of this situation must be considered when designing equipment, and these indicators need to be tested during safety certification. The requirement is that after the equipment falls, its functions can be lost, but it cannot cause danger to the user.
13. Stress release test
If there is a dangerous circuit inside the equipment, during normal use of the equipment, it is not allowed to cause the dangerous circuit part to deform due to the shell of the equipment. These effects must be considered when designing equipment, and these indicators must be tested during safety certification.
14. Battery charge and discharge test
If there is a rechargeable battery inside the device, charge and discharge tests, charging tests under single fault, and overcharge tests need to be performed. This is because the device needs to charge and discharge the battery during normal use, and when the device fails but the main functions have not been lost, the user may not discover the device failure at this time and will still charge the device in the normal hype manner. The battery is charged and discharged. In this case, the charging and discharging of the equipment battery is required to be safe, and no danger such as explosion may occur due to equipment failure.
15. Equipment temperature rise test
Among the safety tests, the temperature rise test is the most important. Although the equipment and instruments used in the test are the same as those in the artificial climate environment test, the trial inspection items and test devices and purposes are very different. The artificial climate environment mainly examines the adaptability and reliability of the equipment. Safety regulations examine whether the equipment can work safely. Here is an example to illustrate their differences: Safety testing mainly tests the temperature of safety devices, such as the operating temperature of insulating materials under normal circumstances. This temperature is lower than the maximum allowable temperature of insulating materials at the highest allowed operating temperature of the equipment. For example, the temperature of the insulating material tested in an environment of 25°C is 100°C, and the insulating material can only operate safely below 130°C. This is critical to defining the maximum operating temperature allowed by the equipment. If the equipment has an ambient temperature of 50°C, then the insulating material The test temperature converted to an ambient temperature of 50°C should be 125°C. If it meets the requirement of less than 130°C, the test passes. If the equipment has an ambient temperature of 60°C, then the test temperature converted to the ambient temperature of 60°C should be 135°C. If it is greater than the 130°C requirement, the test will fail. Similarly, other safety devices also need to be tested for operating temperature. to determine whether the requirements are met.
As insulating materials or plastic parts that support hazardous voltages, ball pressure testing is required to ensure that the plastic parts have sufficient support strength when hazardous voltage components operate at high temperatures. The test temperature is 40K higher than the highest temperature measured in the temperature rise test, and not lower than 125℃. The ball pressure time is maintained at the required temperature for 1H.
17. Contact current test
Contact current is often referred to as leakage current. This current needs to be strictly controlled, and various safety standards have strict regulations. Therefore, this current must be strictly controlled during design and tested during product certification.
18. Withstand voltage test
Withstand voltage test is also called withstand voltage test or high voltage test. It is mainly used to examine the endurance capability of equipment insulation and whether the designed insulation meets the design requirements. Various types of insulation have different test voltages. The pressure test is performed after moisture treatment to examine the equipment's ability to withstand moisture.
19. Abnormal testing
Abnormality testing is divided into single fault testing, incorrect usage testing, and common abnormal usage testing. Single fault test means that the equipment is in a fault state and the equipment is required to be safe. Misuse refers to equipment that adjusts the device. Testing the device when the position or status of the device is abnormal requires that the device be safe. The test allows for functional loss of the device in this situation. Common abnormal usage test: Abnormal usage refers to certain changes in the usage environment of the device due to people's certain usage habits, resulting in an extremely unfavorable situation for the heat dissipation of the device. The purpose of this test is to determine whether the device is in compliance with the design environment. Environmental adaptability when working under different conditions. Common abnormal uses include: not taking off the dust cover covering the TV when using the TV, putting the mobile phone in the mobile phone bag, etc.