Line Regulation
Load Regulation
Conmine Regulation
Output Ripple & Noise
Input Power, Efficiency
Dynamic or Transient Response (Dynamic or Transient Response)
Set-Up and Hold-Up times
General Function Test
Power regulation
The power regulation ratio is defined as the power supply's ability to provide a stable output voltage when the input voltage changes. The test procedure is as follows: After the power supply to be tested is stabilized under the normal input voltage and load conditions, it is measured and recorded at a low input voltage (Min), a normal input voltage (Normal), and a high input voltage (Max). Output voltage value. The power regulation ratio is usually a percentage of the output voltage deviation due to a change in input voltage at a nominal load (Nominal Load), as shown in the following formula:
[Vo(max)-Vo(min)] / Vo(normal)
2. Load regulation
The load regulation ratio is defined as the ability of the switching power supply to provide a stable output voltage when the output load current changes. The test procedure is as follows: After the power supply under test is stabilized under normal input voltage and load conditions, the output voltage under normal load is measured, and then measured under light load (Min) and heavy load (Max) respectively. Record the output voltage value (Vo (max) and Vo (min)), and the load regulation rate is usually the percentage of the output voltage deviation rate caused by the change of the load current under the normal fixed input voltage, as shown in the following formula :
[Vo(max)-Vo(min)] / Vo(normal)
3. Comprehensive adjustment rate
The overall adjustment rate is defined as the power supply's ability to provide a stable output voltage when the input voltage and output load current change. This is a combination of power regulation and load regulation. This test is a combination of the power regulation and load regulation described above. It provides a more accurate verification of the power supply's performance under changing input voltage and load conditions. The overall adjustment rate is expressed in the following manner: The deviation of the output voltage of the input voltage and the change of the output load current must be within the specified upper and lower limit voltage limits (that is, within the absolute values ​​of the upper and lower limits of the output voltage) or within a certain percentage limit. .
4. Output noise
The output noise (PARD) refers to the voltage value of the periodic and random deviation of the average DC output voltage under the condition that the input voltage and output load current do not change. The output noise is all the unwanted AC and noise components on the regulated and filtered DC output voltage (including the low frequency 50/60Hz power multiplication signal, the high frequency switching signal higher than 20 KHz and its harmonics The wave, together with other random signals, is usually expressed in units of mVp-p peak-to-peak voltage.
The specifications of the general switching power supply are within 1% of the output DC output voltage as the specifications of the output noise, and its frequency bandwidth is 20Hz to 20MHz. The worst case of the power supply when it is actually working (such as the maximum output load current, the minimum input supply voltage, etc.). If the power supply is under harsh environmental conditions, the output DC voltage plus the noise output instantaneous voltage can still maintain stability. The output voltage does not exceed the output high and low voltage limits, otherwise it may cause the power supply voltage to exceed or fall below the withstand voltage of the logic circuit (such as a TTL circuit) and cause malfunction and further cause a crash.
At the same time, the measurement circuit must have good isolation and impedance matching. In order to avoid unnecessary interference, ringing and standing waves on the wire, double coax cables are generally used and 50Ω are used at the end points thereof, and a differential type is used. Measure the method (can avoid the noise current of the ground loop), in order to obtain the correct measurement result.
5. Input power and efficiency
The power supply's input power is defined by the following formula:
True Power = Pav(watt) = Vrms x Arms x Power Factor is the integrated value of the product of its input voltage and current for a period. It should be noted that Watt≠VrmsArms but Watt = VrmsArmsxP.F., where PF is the power Power factor, usually no power factor correction The power factor of the circuit power supply is around 0.6 to 0.7, and its power factor is between 1 and 0.
The efficiency of the power supply is defined as the ratio of the sum of the output DC power to the input power. Efficiency provides verification of correct operation of the power supply. If the efficiency exceeds the specified range, there is a problem with the design or the material of the part. If the efficiency is too low, the heat dissipation will increase and the service life will be affected.
6. Dynamic load or transient load
A fixed voltage output power supply has a feedback control loop in the design, which can continuously maintain its output voltage with a stable output voltage. Due to the fact that the feedback control loop has a certain bandwidth, it limits the response of the power supply to changes in the load current. If the phase shift between the input and output of the control loop is 1 when the gain (Unity Gain) is greater than 180 degrees, the output of the power supply will be unstable, out of control or oscillate. In fact, the load current when the power supply is working is also dynamic and not always maintained (such as the hard disk, floppy drive, CPU or RAM operation, etc.), so dynamic load testing is extremely important for the power supply. The programmable electronic load can be used to simulate the worst case load conditions of the power supply during actual operation, such as rapid rise and fall of the load current, cycle, etc. If the power supply is under severe load conditions, it can maintain a stable output voltage. Do not generate overshoot or undershoot. Otherwise, the output voltage of the power supply will exceed the load component (such as the TTL circuit, the instantaneous output voltage should be between 4.75V and 5.25V, which will not cause TTL logic. The malfunction of the circuit withstands the power supply voltage and malfunctions, further causing a crash.
7. Start-up time and hold time
The start-up time is the time from when the power supply is connected from the input to the power supply until the output voltage rises within the regulation range. Take a power supply with an output of 5V as an example. The start-up time is from the power-on until the output voltage reaches 4.75. V's time.
The hold time is the time from when the power supply is turned off from the input to when the output voltage falls outside the regulation range. Take a power supply with an output of 5V as an example. The hold time is from shutdown to output voltage lower than 4.75V. The time until the time is usually 17ms or more, in order to prevent the power company from being affected by less than half a week or one week.
8. Others
Under the premise that the power supply has some specific protection functions, it also needs to carry out protection function tests, such as over-voltage protection (OVP) test, short-circuit protection test, over-voltage protection, etc.