SSL4120T datasheet(8/47 Pages) NXP

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SSL4120T

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Objective data sheet

Rev. 1 — 21 June 2012

8 of 47

NXP Semiconductors

SSL4120T

Resonant power supply control IC with PFC

external diode DSUPHS. The voltage drop between SUPREG and SUPHS can be

minimized by carefully selecting the appropriate diode, especially when using large

MOSFETs and high switching frequencies.

7.2.4 High voltage supply input (pin SUPHV)

In a stand-alone power supply application, this pin is connected to the boost voltage.

CSUPIC and CSUPREG will be charged by the HV start-up source (which delivers a constant

current from SUPHV to SUPIC) via this pin.

Short-circuit protection on pin SUPIC (SCP-SUPIC; see Section 7.9) limits the dissipation

in the HV start-up source when SUPIC is shorted to ground and limits the current on

SUPHV (to Ired(SUPHV)) as long as the voltage on SUPIC is below Vscp(SUPIC).

Under normal operating conditions, the voltage on pin SUPIC will exceed Vscp(SUPIC) very

quickly after start-up and the HV start-up source will switch to the nominal current

Inom(SUPHV).

During start-up and restart, the HV start-up source will charge CSUPIC and regulate the

voltage on SUPIC by hysteretic control. So the start level has a small degree of hysteresis

Vstart(hys)(SUPIC). The HV start-up source switches-off when VSUPIC exceeds the start level

Vstart(hvd)(SUPIC). Current consumption through pin SUPHV will be low (Itko(SUPHV)).

Once start-up is complete and the HBC controller is operating, SUPIC can be supplied

from the auxiliary winding of the HBC transformer. In this operational state, the HV

start-up source is disabled.

7.3 Flow diagram

The operation of the SSL4120T can be divided into a number of states - see Figure 3. The

abbreviations used in Figure 3 are explained In Table 8.

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