SSL4120T All information provided in this document is subject to legal disclaimers. © NXP B.V. 2012. All rights reserved.
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 C
SUPIC
. 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, V
SUPHV
>V
det(SUPHV)
.
This is the case with a stand-alone application where C
SUPIC
is initially charged from
the HV start-up source. The start level is V
start(hvd)(SUPIC)
(typ. 22 V). The wide
difference between the start and stop (V
uvp(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, V
SUPHV
<V
det(SUPHV)
.
This is the case when the SSL4120T is supplied from an external DC source. The
start level is V
start(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, V
uvp(SUPIC)
(typ. 15 V).
The IC will stop operating when V
SUPIC
drops below V
uvp(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
(I
dism(SUPIC)
).
• SUPIC charge, SUPREG charge, Thermal hold, Restart and Protection shut-down
states
Only a small section of the IC is active while C
SUPIC
and C
SUPREG
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 I
protm(SUPIC)
.
