Other applications of AC power when testing power supplies
Inrush current
From the results, when the power supply is turned on at any point of the AC input sine wave, the inrush current must not damage the power supply or cause the fuse to blow. The power supply should allow AC switches, bridge rectifier circuits, fuses, and EMI filter components to withstand the surge level. In the past, the random switching method of confirming the maximum inrush current was very time-consuming. The maximum inrush current usually occurs when the maximum voltage is turned on. Now this test and measurement task can be quickly completed using the designated phase switching function of the AC power supply.
Figure 4：The left picture sets the AC power output to start at 90 degrees, and the right picture sets the output to start at 270 degrees
AC power Ipeak measurement function
The measurement of inrush current requires an oscilloscope and a current probe. The upper left of Figure 5 is an enlarged screenshot of the measurement results of the current probe. The maximum current measured is 34A. The lower left of Figure 5 shows the measurement result of the AC power supply through the Ipeak measurement function, which is 33.39A. Although there is still a slight difference with the current probe, AC power supply with this measurement function can still be used as a simple judgment when there is no current probe at hand.
Figure 5 : Comparison of AC power Ipeak measurement function and oscilloscope current probe to catch inrush current
DC Mode Applications for AC Power: Testing LVDC, HVDC Power Supplies
The power supplies used in the telecommunications room or the server power supplies of the data center, in addition to the conventional AC power supply as the input, the renewable energy or the DC power supply of the uninterruptible power system can also be used as the input. These types of power supplies are divided into LVDC or HVDC, LVDC is used in the telecommunications room, the voltage is 48V required by the computer room, and the voltage of HVDC is 180V~400V or 336V. GW Instek ASR-2000/3000 series AC/DC dual-purpose power supply can meet the applications of these voltages and for the rated power in the specifications, the rated power of DC is equal to the rated power of AC.
For similar designs on the market, most of the DC rated power are only between 0.5 and 0.8 of the AC rated power. At this time, in order to meet the power demand, for 3kVA DC rated power requirement, if it is a 0.5 design, an AC 6kVA model is required to have 3kVA DC capability, so the cost of procurement will increase, while the design of full power will not have this problem. In addition, when converting AC to DC, most designs are to stop the AC output first and then switch to the DC output mode. Such conversion may cause the DUT to be shut down and then restarted. GW Instek ASR-2000/3000 series adopts seamless transition design and there will be no such issue. Figure 6 is a schematic diagram of the two conversion designs.
Figure 6：The left picture is the transition mode that may cause downtime; the right picture is the seamless transition mode
DC mode application of AC power supply: Make up for applications where the response speed of DC power supply is not fast enough
Take GW Instek ASR-2000/3000 series specifications as an example：
Time Mode: The rise time is less than or equal to 100us (Figure 7)
Figure 7：Time mode response speed
Slope Mode: Rising with a fixed slope, 1.5V every 1us (Figure 8)
Figure 8：Response speed of slope mode
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| Figure 9：ASR-2000 measured rise time of time mode (-550V to 500V) | Figure 10：ASR-2000 measured rise time of slope mode |
For automated tests that require fast response, the DC mode of the AC power supply can compensate insufficient DC power supply. Such capability can verify the feedforward control mechanism or verify the power-on response.
However, the ripple and noise of the DC mode of the AC power supply are larger than those of the DC power supply, and there is no constant current mode of the DC power supply.
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| Figure 11：ASR-2000 measured fall time of time mode (-550V to 500V) | Figure 12：ASR-2000 measured fall time of slope mode |