Agilent Technologies AN 372-1 manual

Agilent AN 372-1 Power Supply T esting Application Note An electronic load offers a broad range of operating modes, providing versatile loading configurations needed for characterizing and verifying DC power supply design specifications.[...]

2 As regulated-pow er supply technology ev olves, testing methods for design verification and product function require more sophisticated electronic equip- ment. The different po wer suppl y architectures and output combinations also dictat e the need for versatile test instruments that can accommodat e a broad range of specifications. As a result,[...]

3 P ow er supplies are used in a wide variety of prod- ucts and test systems. As a result, t he tests per- formed to deter mine operating specifications can differ from manufacturer to manufacturer , or from end user to end user . For instance, t he tests per- formed in an R&D environment are primaril y for po wer supply design v erification. T[...]

4 Load T ransient Recovery Time A constant voltage DC pow er supply is designed with a feedback loop which continuously acts to maintain t he output voltage at a steady-st ate level. The feedback loop has a finite bandwidth, which limits the ability of t he po wer supply to respond to a change in the load cur rent. If the time delay between the po [...]

5 F or a step change in load cur rent, a marginally stable CV pow er supply will hav e a ringing voltage output. This defeats the purpose of the po wer sup- ply’s regulation circuitry and can be damaging to voltage-sensitive loads. An exam ple of a voltage- sensitive load is the logic circuitry in a computer . In this case, a computer manufacture[...]

6 Load Effect (Load Regulation) Load Effect or Load Regulation is a static per form- ance measurement which defines t he ability of a po wer supply under test to remain within specif ied output limits for a predetermined load change (see Figure 3). In a CV pow er supply , the inf luenced quantity of interest is the st eady-st ate output cur- rent. [...]

7 Current Limit Characterization Cur rent limit measurements demonstrat e the deg ree t o which a constant voltage pow er supply limits its maximum output current to a preset value. This preset value can be fixed or variable throughout a specified range. There are basically three types of current limiting design implementations: 1. Conventional cur[...]

8 P ARD (Periodic and Random Deviation) P ARD (f ormerly known as ripple and noise) is the periodic and random deviation of the DC output voltage from its a verage value, o ver a specified bandwidth, and wit h all other parameters con- stant. It is represent ative of all undesirable A C and noise components that remain in the DC output voltage aft [...]

9 T est Overview/Procedures T o make P ARD measurements, t he electronic load used should operate in CR mode for constant volt- age and constant cur rent po wer supplies. The load should also hav e lo wer P ARD than the pow er sup- ply being tested. This is especially important when measuring the P ARD of linear po wer supplies, since t hey typical[...]

10 Efficiency The eff iciency of a pow er supply is simply the ratio of its tot al output po wer to its tot al input po wer . T o obt ain the tr ue input po wer (rms voltage x in-phase rms cur rent) of a typical A C-to-DC converting po wer supply , commerciall y available wattmeters or A C sources can be used to measure the necessar y paramet ers. [...]

11 T o fully characterize the st ar t-up sequence of the po wer supply under test, measurements must be made of the output voltage response to t he instan- t aneous application of the AC in put (see Figure 1 1). A digital oscilloscope should be used so t hat stor- age of the output values can be accomplished f or the measured st ar t-up time period[...]

12 An observation of any DC po wer supply data sheet fr om a po wer suppl y manufacturer reveals a number of design specifications t hat must be verified and tested. These t ests oft en differ in technique and in the test equipment t hat is used to measure t he var- ious parameters. The common aspect of all of these tests is that a met hod of contr[...]

13 The Agilent Electronic Load Family offers the po wer suppl y test er t he solution f or man y of the tests t hat must be performed. For bench or system applica- tions in large or small scale testing environments, Agilent Electronic Loads pro vide high quality and reliability with superior per formance, features, and documentation. This will make[...]

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