SSL8516T datasheet(6/33 Pages) NXP

6 / 33 page

SSL8516T

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Product data sheet

Rev. 1 — 5 May 2014

6 of 33

NXP Semiconductors

SSL8516T

Greenchip PFC and flyback controller

The control logic activates the internal circuitry and switches off the HV charge current

when VCC passes the Vstartup level. First, the LATCH pin current source is activated and

the soft-start capacitors on the PFCSENSE and FBSENSE pins are charged. Also the

clamp circuit on the PFCCOMP pin is activated.

The PFC circuit is activated when the following conditions are met:

• the LATCH pin voltage exceeds the Ven(LATCH) voltage

• the PFCCOMP pin charging current drops below the absolute value of the

Ien(PFCCOMP) current

• the soft-start capacitor on the PFCSENSE pin is charged

If the soft-start capacitor on the FBSENSE pin is charged, the flyback converter is

activated. The flyback converter output voltage is then regulated to its nominal output

voltage. The auxiliary winding of the flyback converter takes over the IC supply

(see Figure 4).

If during start-up, the LATCH pin does not reach the Ven(LATCH) level before VCC reaches

Vth(UVLO), the LATCH pin output is deactivated. The charge current is switched on again.

When the flyback converter is started, VFBCTRL is monitored. If the output voltage does not

reach its intended regulation level within a specified time, VFBCTRL reaches the Vto(FBCTRL)

level. An error is then assumed and a safe restart is initiated.

When one of the safe restart or latched protection functions are triggered, both converters

stop switching and the VCC voltage drops to Vth(UVLO). A latched protection recharges

capacitor CVCC using Ich(low) from the HV pin, but does not restart the converters. To

provide safe restart protection, the capacitor is recharged using Ich(low) from the HV pin

and the device restarts (see Figure 1).

If OVP is triggered on the PFC circuit (VVOSENSE >VOVP(VOSENSE)), the PFC controller

stops switching until the VVOSENSE < VOVP(VOSENSE). If a mains UVP is detected,

VVINSENSE <Vstop(VINSENSE), the PFC controller stops switching until

VVINSENSE >Vstart(VINSENSE) again. OVP and UVP of the PFC circuit do not disable flyback

controller switching.

When the VCC pin voltage drops under the UVLO level, both controllers stop switching and

enter safe restart mode. In the safe restart mode, the VCC pin capacitor is recharged using

Ich(low) from the HV pin.

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