SSL4120T datasheet(13/47 Pages) NXP

13 / 47 page

SSL4120T

All information provided in this document is subject to legal disclaimers.

Objective data sheet

Rev. 1 — 21 June 2012

13 of 47

NXP Semiconductors

SSL4120T

Resonant power supply control IC with PFC

Figure 6 shows the operation of the restart timer. Normally Cprot is discharged to 0 V.

When a restart is requested, Cprot is quickly charged to the upper switching level

Vu(RCPROT). Then the RCPROT pin becomes high ohmic and Cprot discharges through

Rprot. The restart time has elapsed when VRCPROT reaches the lower switching level

Vl(RCPROT) (typ. 0.5 V). The IC then restarts and Cprot is discharged.

7.5.3 Fast shut-down reset (pin SNSMAINS)

The latched Protection shut-down state will be reset when VSUPIC and VSUPHV drop below

their respective reset levels, Vrst(SUPIC) and Vrst(SUPHV). Typically, the PFC boost capacitor,

Cboost, will need to discharge before VSUPIC and VSUPHV drop below their reset levels,

which can take a long time.

Fast shut-down reset facilitates a faster reset. When the mains supply is interrupted, the

voltage on pin SNSMAINS will fall. As soon as VSNSMAINS falls below Vrst(SNSMAINS) and

subsequently rises again by a hysteresis value, the IC will leave the Protection shut-down

state. The boost capacitor Cboost does not need to be discharged to initiate a new start-up.

The Protection shut-down state can also be ended by pulling down the enable input (pin

SSHBC/EN).

7.5.4 Output overvoltage protection (pin SNSOUT)

The SSL4120T outputs are provided with overvoltage protection (OVP-output; see

Section 7.9). The output voltage can be measured via the auxiliary winding of the

resonant transformer. This voltage can be sensed at the SNSOUT pin via an external

rectifier and resistive divider. An overvoltage is detected when the SNSOUT voltage

exceeds Vovp(SNSOUT) (typ. 3.5 V). Once an overvoltage has been detected, the

SSL4120T will go to the Protection shut-down state.

Additional external protection circuits, such as an external overtemperature protection

circuit, can be connected to this pin. They should be connected to pin SNSOUT via a

diode so that the error condition will trigger an OVP event.

7.5.5 Output undervoltage protection (pin SNSOUT)

In applications where the SSL4120T is supplied from the auxiliary winding of the HBC

transformer, a SUPIC undervoltage protection event (UVP-SUPIC) will be triggered

automatically when an error condition results in a drop in the output voltage.

Fig 6.

Operation of the restart timer

passed

yes

Vu(RCPROT)

Vl(RCPROT)

Restart request

014aaa854

VRCPROT

Restart time

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