SSL4120T datasheet(6/47 Pages) NXP

6 / 47 page

SSL4120T

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Objective data sheet

Rev. 1 — 21 June 2012

6 of 47

NXP Semiconductors

SSL4120T

Resonant power supply control IC with PFC

7.2 Power supply

The SSL4120T contains several supply related pins.

7.2.1 Low-voltage supply input (pin SUPIC)

The SUPIC pin is the main low-voltage supply input to the IC. All internal circuits (other

than the high voltage circuit) are directly or indirectly (via SUPREG) supplied from this pin.

SUPIC is connected externally to a buffer capacitor CSUPIC. This buffer capacitor can be

charged in several ways:

• from the internal high voltage start-up source

• from the auxiliary winding of the HBC transformer

• from the capacitive supply of the switching half-bridge node

• from an external DC supply, e.g. a standby supply

The IC starts operating when voltage on SUPIC reaches the start level, provided that the

voltage on SUPREG has also reached the start level. The start level depends on the

condition of the SUPHV pin:

• High voltage present on SUPHV, VSUPHV >Vdet(SUPHV).

This is the case with a stand-alone application where CSUPIC is initially charged from

the HV start-up source. The start level is Vstart(hvd)(SUPIC) (typ. 22 V). The wide

difference between the start and stop (Vuvp(SUPIC)) levels allows energy to be stored in

the SUPIC buffer capacitor which is used to supply the IC until the output voltage has

stabilized.

• Not connected or no voltage present at SUPHV, VSUPHV <Vdet(SUPHV).

This is the case when the SSL4120T is supplied from an external DC source. The

start level is Vstart(nohvd)(SUPIC) (typ. 17 V). The IC is supplied from the DC supply

during start-up. To minimize power dissipation, the DC supply to pin SUPIC should be

above, but close to, Vuvp(SUPIC) (typ. 15 V).

The IC will stop operating when VSUPIC drops below Vuvp(SUPIC). This is the SUPIC

UnderVoltage Protection (UVP) voltage (UVP-SUPIC; see Section 7.9). The PFC

controller will stop switching immediately, but the HBC controller will continue operating

until the low-side MOSFET becomes active.

The current consumption depends on the state of the IC. The SSL4120T operating states

are described in Section 7.3.

• Disabled IC state

When the IC is disabled via the SSHBC/EN pin, the current consumption is very low

(Idism(SUPIC)).

• SUPIC charge, SUPREG charge, Thermal hold, Restart and Protection shut-down

states

Only a small section of the IC is active while CSUPIC and CSUPREG are charging during

a restart sequence prior to start-up or during shut-down after a protection function has

been activated. The PFC and HBC controllers are disabled. Current consumption is

limited to Iprotm(SUPIC).

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