The power supply is not a simple small box, it is equivalent to the heart of the active device, providing a constant supply of energy to the components. The quality of the power supply directly affects the performance of the components. Tests such as design, manufacturing, and quality management of power supplies require sophisticated electronic equipment to simulate the various characteristics of the power supply (ie, various specifications) and pass the verification before they can be put into use. one. Describe the input voltage affects the output voltage in several indicator forms . Absolute voltage regulation coefficient A. Absolute voltage regulation coefficient: indicates the ratio of the output DC variation ΔU0 of the regulated power supply to the input grid variation ΔUi when the load is constant. That is: K = ΔU0 / ΔUi. B. Relative voltage regulation coefficient: indicates the ratio of the relative change amount ΔUo of the regulator output DC voltage ΔUo to the relative change amount Ui of the output grid Ui when the load is constant. That is: S = ΔUo / Uo / △ Ui / Ui. 2. Grid adjustment rate It indicates the relative change in the output voltage of the regulated power supply when the input grid voltage changes by ±10% from the rated value, and is sometimes expressed in absolute value. 3. Voltage stability The load current is kept at any value within the rated range. The relative change of the output voltage caused by the change of the input voltage within the specified range is ΔUo/Uo percentage, which is called the voltage stability of the regulator. two. Several forms of indicators of the effect of load on output voltage 1. Load regulation rate (also called current regulation rate) Under the rated grid voltage, when the load current changes from zero to maximum, the maximum relative change of the output voltage is usually expressed as a percentage, and sometimes expressed as an absolute variation. 2. Output resistance (also called equivalent internal resistance or internal resistance) Under the rated grid voltage, the output resistance changes to ΔUo due to load current change ΔIL, then the output resistance is Ro=|△Uo/△IL| three. Several indicator forms of ripple voltage 　　 1. Maximum ripple voltage 　　 The absolute value of the ripple (including noise) of the output voltage at rated output voltage and load current, usually expressed as peak-to-peak or rms. 　　 2. Ripple coefficient Y (%) 　　 The ratio of the effective value of the output ripple voltage, Urms, to the output DC voltage, Uo, at rated load current, ie y=Umrs/Uo x100% 　　 3. Ripple voltage suppression ratio 　　 At a predetermined ripple frequency (for example, 50 Hz), the ratio of the ripple voltage Ui~ in the output voltage to the ripple voltage Uo~ in the output voltage, that is, the ripple voltage suppression ratio = Ui~/Uo~. 　 　 Here is a statement: noise is different from ripple. Ripple is a component that appears between the output terminals in synchronism with the input frequency and switching frequency. It is expressed as a peak to peak value, typically less than 0.5% of the output voltage; noise is present between the output terminals. A high-frequency component other than ripple is also expressed by a peak to peak value, which is generally about 1% of the output voltage. Ripple noise is a combination of the two, expressed as a peak to peak value, typically less than 2% of the output voltage. four. electric shock 　　 The inrush current is the maximum instantaneous current that the input current passes before it reaches a steady state when the input voltage is turned on or off at a predetermined time interval. Usually 20A - 30A. Fives. Overcurrent protection 　　 Overcurrent protection is a type of power load protection that prevents damage to the power supply and load from overloaded output currents, including short circuits on the output terminals. The set value of the overcurrent is generally 110% - 130% of the rated current. six. Overvoltage protection 　　 Overvoltage protection is a function of load protection for excessive voltage between terminals. Generally specified as 130% - 150% of the output voltage. Seven. Output undervoltage protection 　　 When the output voltage is below the standard value, it detects that the output voltage drops or stops the power supply and sends an alarm signal to protect the load and prevent misoperation. It is mostly about 80% - 30% of the output voltage. Eight. Overheating protection 　　 Stop the power supply and send an alarm signal when an abnormality occurs inside the power supply or when the power supply temperature rises excessively due to improper use. nine. Temperature drift and temperature coefficient 　　 Temperature drift: Changes in ambient temperature affect changes in the parameters of the component, causing a change in the output voltage of the regulator. The commonly used temperature coefficient indicates the magnitude of the temperature drift. 　　 Absolute temperature coefficient: A change in temperature of 1 degree Celsius causes a change in the output voltage value ΔUoT in V/°C or millivolts per degree Celsius. 　　 Relative temperature coefficient: The temperature change of 1 °C causes the relative change of the output voltage △UoT/Uo, the unit is V/°C. ten. drift 　　 When the input voltage, load current and ambient temperature are kept constant, the stability of the component parameters will also cause the output voltage to change. The slow change is called drift, and the fast change is called noise. 　　 There are two ways to express drift: 　　 1. The output voltage value changes ΔUot within the specified time. 　　 2. The relative change in output voltage ΔUot/Uo within a specified time. 　　 The time to examine the drift can be set to 1 minute, 10 minutes, 1 hour, 8 hours or longer. Only in the higher precision regulator, there are two indicators of temperature coefficient and temperature drift. eleven. Response time 　　 The response time is the adjustment time when the output voltage of the regulator changes from the beginning to the new stable value when the load current changes suddenly. In a DC regulator, the output voltage waveform used in a rectangular wave load current is used to represent this characteristic, which is called over-special. twelve. distortion 　　 Distortion This is unique to AC voltage regulators. It means that the output waveform is not a positive waveform, and the waveform distortion is called, which is called distortion. thirteen. noise 　　 According to the audible frequency of 30Hz - 18kHZ, the switching frequency of the switching power supply is not a problem, but the power supply with the fan should be specified as needed. fourteen. Input noise 　　 In order to keep the switching power supply in a normal state, the input noise level is determined according to the rated input conditions and the pulse voltage (0 - peak) which is externally allowed and superimposed on the industrial frequency. Generally, the applied pulse width is 100-800us, and the applied voltage is 1000V. fifteen. surge 　　 This is to add a surge voltage to the input voltage at a predetermined number of times at intervals of 1 minute or more to avoid abnormal phenomena such as dielectric breakdown, flashover, and arc. The value specified for communication equipment, etc. is several thousand volts, typically 1200V. sixteen. Static noise 　　 Refers to a repetitive pulse-like static electricity that can maintain normal operation of the full output circuit when applied to any part of the power supply frame under rated input conditions. Generally guaranteed within 5 - 10KV. Seventeen. stability 　　 The maximum relative change in output voltage △Uo/Uo is allowed under the conditions of use. Eighteen. Electrical safety requirements (GB 4943-90) 　　 1. Power structure safety requirements 　　 1) Space requirements 　 　 The UL, CSA, and VDE safety regulations emphasize the surface and space requirements between live parts and between live and uncharged metal parts. UL, CSA requirements: between high-voltage conductors with inter-pole voltages greater than or equal to 250 VAC, and between high-voltage conductors and non-charged metal parts (not including conductors), should have a distance of 0.1 inches between surfaces and spaces. VDE requires a 3mm creep or 2mm clearance between the AC lines; IEC requirements: 3mm clearance between the AC lines and a 4mm clearance between the AC line and the ground conductor. In addition, VDE and IEC require a space of at least 8 mm between the output and input of the power supply. 　　 2) Dielectric experimental test method (high voltage: input and output, input and ground, input AC between two levels) 　　 3) Leakage current measurement 　 　 The leakage current is the current flowing through the ground of the input side. In the switching power supply, the current is mainly leaked through the bypass capacitor of the squelch filter. Both UL and CSA require that the exposed uncharged metal parts be connected to the earth. The leakage current is measured by connecting a 1.5K ohm resistor between these parts and the earth. The leakage current should be no more than 5 mA. VDE allows: a 1.5KΩ resistor to be connected to a 150nP capacitor. And apply 1.06 times the rated operating voltage. For data processing equipment, the leakage current should be no more than 3.5 mA. It is usually around 1 mA. 　　 4) Insulation resistance test 　　 VDE requirements: There should be a 7MΩ resistor between the input and the low voltage output circuit. Between the accessible metal part and the input, there should be a 2MΩ resistor or 500V DC for 1 minute. 　　 5) Printed circuit board requirements 　　 The requirement is a UL Listed 94V-2 material or a better material. 　　 2. Safety requirements for power transformer construction 　　 1) Transformer insulation 　　 The copper wire used for the winding of the transformer shall be an enameled wire, and other metal parts shall be coated with insulating materials such as porcelain and paint. 　　 2) Dielectric strength of the transformer 　　 Insulation rupture and arcing should not occur in the experiment. 　　 3) Insulation resistance of the transformer 　　 The insulation resistance between the windings of the transformer is at least 10M ohms. Apply 500 VDC to the core, the skeleton and the shield for 1 minute. There should be no breakdown or arcing. 　　 4) Transformer humidity resistance 　 　 The transformer must be tested for insulation resistance and dielectric strength immediately after being placed in a humid environment and meet the requirements. The wet environment is generally: relative humidity of 92% (tolerance of 2%), temperature stability between 20 and 30 degrees Celsius, error of 1%, and the above experiment should be carried out immediately after being placed for at least 48 hours. At this point, the temperature of the transformer itself should not be 4 degrees Celsius higher than before entering the humid environment. 　　 5) VDE requirements for transformer temperature characteristics 　　 6) UL, CSA requirements for transformer temperature characteristics. 　　 Note: IEC - International ElectrotechnICal Commission 　　 VDE - Verbandes Deutcher ElectrotechnICer 　　 UL - Underwriters' Laboratories 　　 CSA - CANadian Standards Association 　　 FCC - Federal CommunICations Commission XIX. Radio disturbance (tested in accordance with GB 9254-1998) 　　 1. Power terminal disturbance voltage limit 　　 2. Radiated disturbance limit twenty. ElectromagnetIC test EMC (electromagnetIC compatiblity EMC) Electromagnetic compatibility is the ability of a device or system to function properly in a common electromagnetic environment without posing unacceptable electromagnetic interference to anything in the environment. Electromagnetic interference waves generally have two modes of transmission, which are evaluated in various ways. One is to transmit to the power line in a frequency band with a long wavelength, and to interfere with the transmitting area, generally below 30 MHz. The wavelength of this wavelength is less than one wavelength within the length of the power line attached to the electronic device, and the amount of radiation into the space is also small, so that the voltage generated on the power line can be grasped, and then fully evaluated. The amount of interference, this noise is called conducted noise. When the frequency reaches 30MHz or more, the wavelength will also become shorter. At this time, if only the noise source voltage generated on the power line is evaluated, it does not match the actual interference. Therefore, a method of evaluating the noise level by directly measuring the interference wave propagating into the space is used, and the noise is called radiation noise. The method for measuring radiation noise includes the above method of directly measuring the interference wave of the propagation space by the electric field intensity and the method of measuring the power leaked to the power line. Electromagnetic compatibility tests include the following tests: 1 Magnetic field sensitivity: (immunity) The degree of undesired response of equipment, subsystems or systems exposed to electromagnetic radiation. The smaller the sensitivity level, the higher the sensitivity and the worse the noise immunity. Fixed frequency, peak-to-peak magnetic field 2 Electrostatic discharge sensitivity: Charge transfer caused by objects with different electrostatic potentials being close to each other or in direct contact. The 300PF capacitor is charged to -15000V and discharged through a 500 ohm resistor. Can be overdone, but it should be normal after the release. Data transfer, storage, can not be lost 3 Power transient sensitivity: including spike signal sensitivity (0.5us 10us 2 times), voltage transient sensitivity (10%-30%, 30S recovery), frequency transient sensitivity (5 %-10%, 30S recovery). 4 Radiation sensitivity: A measure of the radiated interference field that causes the device to degrade. (14K-1GHz, electric field strength is 1V/M) 5 Conduction Sensitivity: A measure of the interference signal or voltage on a power supply, control or signal line when causing an undesired response or degrading performance of the device. (30Hz-50KHZ 3V, 50K-400M 1V) 6 Non-operating state magnetic field interference: 4.6m magnetic flux density in the package is less than 0.525uT, 0.9m 0.525Ut. 7 Working state Magnetic field interference: The AC flux density of the upper, lower, left and right AC is less than 0.5mT. 8 Conducted interference: Interference that propagates along the conductor. 10KHz-30MHz 60(48)dBuV. 9 Radiated interference: Electromagnetic interference propagating through electromagnetic waves in space. 10KHz-1000MHz 30 shielded room 60 (54) uV / m. twenty one. Environmental experiment 　 　 Environmental testing is the exposure of products or materials to natural or artificial environments to evaluate their performance under conditions of storage, transportation and use that may actually be encountered. Including low temperature, high temperature, constant damp heat, alternating damp heat, impact (impact and collision), vibration, constant acceleration, storage, mildew, corrosive atmosphere (such as salt spray), sand dust, air pressure (high pressure or low pressure), temperature change , flammability, sealing, water, radiation (sun or nuclear), soldering, joint strength, noise (micro-play 65DB). Hdmi Cables,Hdmi Cord,Micro Hdmi Cable,Extra Long Hdmi Cable UCOAX , https://www.ucoax.com