Rosewill Computer Case 422 Informacje Techniczne Pobierz pdf (Strona 77)

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Chapter 4 • Disassembly and Power

Standby Power Supply (SPS)

A device similar to a UPS is an SPS (standby power supply). An SPS contains a battery like

the UPS, but the battery provides power to the computer only when it loses AC power. It does

not provide constant power, like the UPS. An SPS is not as effective as a UPS because the SPS

must detect a power-out condition first and then switch over to the battery to supply power to

the computer. As a result, SPS switching time is important. Any time under 5 milliseconds is

fine for most systems. Figures 4.35 and 4.36 show the differences between how SPSs and UPSs

work.

SPS/Line interactive UPS normal operation

(solid line)

1. AC power is brought through the UPS.

2. The battery is charged simultaneously.

3. With some units, small over or

undervoltages are evened out

before sending through the UPS.

SPS/Line interactive UPS abnormal power

operation (dashed line)

1. When high voltage or large undervoltage

for some units and with loss of power is

present in all units, DC power from the

battery is sent to the inverter for as long

as the battery lasts.

2. The DC power is converted to AC and

provided to the attached devices.

InverterBattery

Battery

charger

Switch

Figure 4.35 SPS/line interactive UPS operation

Filter/Rectifier

Online UPS normal operation (solid line)

1. AC power is brought into the UPS

and cleaned up by the filter and

converted to DC by the rectifier.

2. The battery is charged and outputs

DC to the inverter.

3. The DC is converted to AC and

provided to the attached devices.

Online UPS abnormal

power operation (dashed line)

1. When the battery has died,

the attached devices still

receive power through

the bypass circuit.

Inverter

Battery

Bypass

Figure 4.36 Online UPS operation

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