Instruction/ maintenance manual of the product AN 372-1 Agilent Technologies
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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.
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.
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.
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 .
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.
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.
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.
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).
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.
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.
By internet, phone, or fax, get assist ance with all your test and measurement needs. Online Assistance www .agilent.com/find/assist Phone or Fax United States: (tel) 1 800 452 4844 Canada: (tel) 1 87.
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