SSL8516T datasheet(8/33 Pages) NXP

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SSL8516T

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Product data sheet

Rev. 1 — 5 May 2014

8 of 33

NXP Semiconductors

SSL8516T

Greenchip PFC and flyback controller

7.1.3 Supply management

All internal reference voltages are derived from a temperature compensated and trimmed

on-chip band gap circuit. Internal reference currents are derived from a temperature

compensated and trimmed on-chip current reference circuit.

7.1.4 Latch input

The LATCH pin is a general-purpose input pin which is used to switch off both converters.

The pin sources a current IO(LATCH) of 30.5 A. Switching of both converters is stopped

when VLATCH is < 494 mV. A latched protection is triggered. It can be reset by removing

the voltage from both the VCC and HV pins or by the fast latch reset function

(see Section 7.1.5).

At initial start-up, switching is prevented until the capacitor on the LATCH pin is charged

above 582 mV. No internal filtering is performed on this pin. An internal 1.75 V clamp

protects the pin from excessive voltages.

7.1.5 Fast latch reset

In a typical application, the mains can be interrupted briefly to reset the latched protection.

The bulk capacitor Cbulk does not have to discharge for this latched protection to reset.

When the VINSENSE voltage drops below 750 mV and is then raised to 860 mV, the

latched protection is reset.

The latched protection is also reset by removing both the voltage on the VCC and HV pins.

7.1.6 Overtemperature protection

An accurate internal temperature protection is provided in the IC. When the junction

temperature exceeds the thermal shut-down temperature, the IC stops switching. While

OTP is active, the capacitor CVCC is not recharged from the HV mains. If the VCC supply

voltage is not sufficient, the OTP circuit is supplied from the HV pin.

OTP is a safe restart protection.

7.2 Power factor correction circuit

The Power Factor Correction (PFC) circuit operates in Quasi-Resonant (QR) or

Discontinuous Conduction Mode (DCM) with valley switching. The next primary stroke is

only started when the previous secondary stroke has ended and the voltage across the

PFC MOSFET has reached the minimum value.

VPFCAUX is used to detect transformer demagnetization and the minimum voltage across

the external PFC MOSFET switch.

7.2.1 ton control (PFCCOMP pin)

The power factor correction circuit is operated in ton control. The resulting mains harmonic

reduction is well within the class-C lighting requirements.

VPFCCOMP determines the on-time of the PFC. The VVOSENSE is the transconductance

amplifier input which outputs current to the PFCCOMP pin. The regulation

VVOSENSE = 2.5 V. The network connected to the PFCCOMP pin and the

transconductance amplifier determine the dynamic behavior of the PFC control.

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