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Motore di ricerca datesheet componenti elettronici |
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Motore di ricerca datesheet componenti elettronici |
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L6560AD Scheda tecnica(PDF) 4 Page - STMicroelectronics |
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L6560AD Scheda tecnica(HTML) 4 Page - STMicroelectronics |
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4 / 11 page  OVER VOLTAGE PROTECTION OVP The output voltage is expected to be kept by the operation of the PFC circuits close to its reference value that is set by the ratio of the two external re- sistors R1 and R2 (see fig. 2), taking into consid- eration that the non inverting input of the error amplifier is biased inside the L6560 at 2.5V. In steady state conditions, the current through R1 and R2 is: ISC = ∆Voutsc − 2.5 R1 or ISC = 2.5 R2 and, if the external compensation network is made only with a capacitor C, the current through C is equal zero. When the output voltage increases abruptly the current through R1 becomes: IR1 = Vout − 2.5 R1 IR1 = Voutsc +∆VOUT − 2.5 R1 = Isc +∆I. Since the current through R2 doesn’t change, the ∆I current must flow through the capacitor C and enter in the error amplifier. This current is mirrored inside the L6560, and compared with a precise internal reference of 40 µA. Whenever such 40µA limit is exceed, the OVP protection is triggered (Dynamic OVP), and the external power transistor is switched off, until the overvoltage situation disappears. However if the overvoltage persists, before that the transient condition of dynamic circuit exhausts, an internal comparator (Static OVP) latches the OVP condi- tion keeping the external power switch turned off (see fig. 1). The OVP value is threfore set by the equation OVP = ∆Vout = R1 ⋅ 40µA. Typical values for R1,R2 and C are reported in the application circuit. The overvoltage can be set independently from the average output voltage. The precision in setting the overvoltage threshold is 7% of the overvoltage value (for instance ∆V= 60V ± 4.2V). ELECTRICAL CHARACTERISTICS (continued) ZERO CURRENT DETECTOR Symbol Pin Parameter Test Condition Min. Typ. Max. Unit VZCD 5 Input Threshold Voltage Rising Edge 1.8 2.3 V Hysteresis 0.3 0.5 0.7 V VZCD 5 Clamp Voltage IZCD = 3mA 5 5.7 6.4 V VZCD 5 Clamp Voltage IZCD = –3mA 0.4 0.7 1 V OUTPUT SECTION Symbol Pin Parameter Test Condition Min. Typ. Max. Unit VGD 7 Dropout Voltage IGDsource = 200mA 1.2 2 V IGDsource = 20mA 0.7 1 V IGDsink = 200mA 1.5 V IGDsink = 20mA 0.3 V tr 7 Output Voltage Rise Time CL = 1nF 50 120 ns tf 7 Output Voltage Fall Time CL = 1nF 40 100 ns OUTPUT OVERVOLTAGE SECTION Symbol Pin Parameter Test Condition Min. Typ. Max. Unit IOVP 2 OVP Triggering Current 36 40 44 µA RESTART TIMER Symbol Pin Parameter Test Condition Min. Typ. Max. Unit tSTART Start Timer 45 60 µs L6560 - L6560A 4/11 |
Codice articolo simile - L6560AD |
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Descrizione simile - L6560AD |
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