Switching power supply test specification - Solutions - Huaqiang Electronic Network

Filter 18.432M

1 Describes several forms of input voltage affecting the output voltage (1) Voltage regulation coefficient 1 Absolute voltage regulation coefficient K
When the load is constant, the ratio of the DC voltage variation ΔUo of the regulated power supply to the input grid voltage variation ΔUi is K=ΔUo/△Ui.
2 relative voltage regulation coefficient S
When the load is constant, the ratio of the relative change amount ΔUo/Uo of the regulator output DC voltage Uo to the relative change amount ΔUi/Ui of the input grid voltage Ui, that is, S=ΔUo/Uo / ΔUi/Ui.
(2) The grid regulation rate 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.
2 Several types of indicators that affect the output voltage (1) Load regulation rate (also called current regulation rate)
At rated grid voltage, the maximum relative change in output voltage, when the load current changes from zero to a maximum, is expressed as a percentage, often expressed as an absolute change.
(2) Output resistance (also known as equivalent internal resistance or internal resistance)
Under the rated grid voltage, the output resistance changes to ΔUo due to the load current change ΔIL, and the output resistance is Ro=|ΔUo/ΔIL|Ω.
3 Several forms of ripple voltage (1) Maximum ripple voltage The absolute value of the output voltage ripple (including noise) at rated output voltage and load current, usually expressed as peak or rms value.
(2) Ripple coefficient Y (%)
At rated load current, the ratio of the effective value of the output ripple voltage, Urms, to the output DC voltage, Uo, is Y = Umrs / Uo x 100%.
(3) The ripple voltage rejection ratio is the ratio of the ripple voltage Ui~ in the input voltage to the ripple voltage Uo~ in the output voltage at a specified ripple frequency (for example, 50 Hz), that is, the ripple voltage suppression ratio = Ui~ /Uo~ .
4 Electrical safety requirements (1) Safety requirements for power supply structures 1 Space requirements The UL, CSA, and VDE safety regulations emphasize the surface and space distance requirements between live parts and between live and non-charged metal parts. UL, CSA requirements: between high-voltage conductors with inter-electrode voltages greater than or equal to 250 VAC, and between high-voltage conductors and non-charged metal parts (excluding wires), between surfaces and spaces, should have a distance of 0.1 吋VDE requires 3mm creep or 2mm clearance between AC lines; IEC requirements: 3mm clearance between AC lines and 4mm clearance between AC line and 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 for high voltage: input and output, input and ground, input AC between two levels.
3 Leakage current measurement Leakage current is the current flowing through the input side ground. In the switching power supply, the leakage current is mainly passed through the bypass capacitor of the squelch filter. Both UL and CSA require that the exposed uncharged metal parts should be connected to the earth. The leakage current is measured by connecting a 1.5kΩ resistor between these parts and the ground, and the leakage current should be no more than 5mA. VDE allows a 1.5kΩ resistor to be connected to a 150nPF capacitor and applies 1.06 times the rated voltage. For data processing equipment, the leakage current should be no more than 3.5mA, typically around 1mA.
4 Insulation resistance test VDE requirements: There should be a 7MΩ resistor between the input and low voltage output circuits. Between the accessible metal part and the input, there should be 2MΩ resistance or 500V DC voltage for 1min.
5 Printed circuit boards require UL approved 94V-2 materials or better materials.
(2) Safety requirements for the structure of the power transformer 1 The copper wire used for the winding of the transformer 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 In the experiment, there should be no cracking and arcing of the insulation layer.
3 Insulation resistance of the transformer The insulation resistance between the transformer windings is at least 10MΩ. Apply 500V DC voltage between the winding and the core, the skeleton and the shielding layer for 1min. 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: the relative humidity is 92% (tolerance is 2%), the temperature is stable between 20 ° C and 30 ° C, the error is allowed to 1%, and the above experiment is carried out immediately after being placed at least 48 hours. At this point, the temperature of the transformer itself should not be 4 °C higher than before entering the humid environment.
5 VDE requirements for transformer temperature characteristics.
6 UL, CSA requirements for transformer temperature characteristics.
5 Electromagnetic Compatibility Test Electromagnetic compatibility refers to 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, and they must be priced according to each route. One is to transmit to the power line in a frequency band with a longer wavelength, and to interfere with the transmission area, generally below 30 MHz. Such a longer wavelength has less than one wavelength in 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 thus the frequency can be sufficient. * Estimate the size of the interference, which 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 supply line is *price, it does not match the actual interference. Therefore, a method of directly measuring the magnitude of the interference wave* valence noise propagating into the space is adopted, and the noise is called radiation noise. The method of measuring radiation noise includes a method of directly measuring an interference wave of a propagation space by electric field strength and a method of measuring power leaked to a power line.
The electromagnetic compatibility test includes the following test contents:
1 Magnetic field sensitivity (immunity) The degree of undesired response of equipment, subsystems or systems to exposure to electromagnetic radiation. The smaller the sensitivity level, the higher the sensitivity and the worse the noise immunity. Includes magnetic field testing of fixed frequency, peak-to-peak value.
2 Electrostatic discharge sensitivity Charge transfer caused by objects with different electrostatic potentials approaching or directly contacting each other. The 300PF capacitor is charged to -15000V and discharged through a 500Ω resistor. Can be overdone, but it should be normal after the release. After the test, data transfer and storage cannot be lost.
3 Power supply transient sensitivity includes spike signal sensitivity (0.5μs, 10μs 2x), voltage transient sensitivity (10%-30%, 30S recovery), frequency transient sensitivity (5%-10%, 30S recovery) ).
4 Radiation sensitivity is a measure of the radiated interference field that causes the device to degrade. (14kHz-1GHz, electric field strength is 1V/M).
5 Conductivity Sensitivity A measure of an interfering signal or voltage on a power supply, control, or signal line when it causes an undesired response from the device or causes its performance to degrade. (30Hz-50kHz/3V, 50kHz -400MHz/1V).
6 Non-operating state magnetic field interference box 4.6m, magnetic flux density is less than 0.525μT; 0.9m, 0.525μT.
7 Working state magnetic field interference upper, lower, left and right AC flux density is less than 0.5mT.
8 Conducted interference interferes with the propagation of the conductor. 10kHz-30MHz, 60(48)dBμV.
9 Radiated interference Electromagnetic interference propagating through electromagnetic waves in space. 10kHz-1000MHz, 30 shielded room 60 (54) μV / m.