SPH4692 View Datasheet(PDF) - Siemens AG
Part Name
Description
Manufacturer
SPH4692 Datasheet PDF : 22 Pages
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SPH 4692
Regulation, Overload and No-Load Behaviour
When the IC has started up, it is operating in the regulation range. The potential at pin 1 typically is
400 mV. If the output is loaded, the regulation amplifier allows broader impulses (V15 = H). The peak
voltage value at pin 2 increases up to V2S max. If the secondary load is further increased, the
overload amplifier begins to regulate the pulse width downward. This point is referred to as the
overload point of the power supply. As the IC supply voltage V16 is directly proportional to the
secondary voltage, it goes down in accordance with the overload regulation behaviour. If V16 falls
below the value V16 min, the IC goes into burst operation. As the time constant of the half-wave
charge-up is relatively large, the short-circuit power remains small. The overload amplifier cuts back
to the pulse width tpk. This pulse width must remain possible, in order to permit the IC to start-up
without problems from the virtual short-circuit, which every switching on with V1 = 0 represents. If
the secondary side is unloaded, the loading impulses (V15 = H) become shorter. The frequency
increases up to the resonance frequency of the system. If the load is further reduced, the secondary
voltages and V16 increase. When V16 = V16 max, the logic is blocked. The IC converts to burst
operation. This renders the circuit absolutely safe under no-load conditions.
Behaviour when Temperature Exceeds Limit
An integrated temperature protection disables the logic when the chip temperature becomes too
high. The IC automatically interrogates the temperature and starts as soon as the temperature
decreases to permissible values.
Semiconductor Group
8
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