SSL4120T datasheet(10/47 Pages) NXP

10 / 47 page

SSL4120T

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Objective data sheet

Rev. 1 — 21 June 2012

10 of 47

NXP Semiconductors

SSL4120T

Resonant power supply control IC with PFC

7.4 Enable input (pin SSHBC/EN)

The power supply application can be completely disabled by pulling pin SSHBC/EN LOW.

Figure 4 illustrates the internal functionality. When a voltage is present on pin SUPHV or

on pin SUPIC, a current Ipu(EN) (typ. 42

μA) flows out of SSHBC/EN. If the pin is not

pulled-down, this current will lift the voltage up to Vpu(EN) (typ. 3 V). Since this voltage is

above both Ven(PFC)(EN) (typ. 1.2 V) and Ven(IC)(EN) (typ. 2.2 V), the IC will be completely

enabled.

The IC can be completely disabled by pulling the voltage on SSHBC/EN down below both

Ven(PFC)(EN) and Ven(IC)(EN) via an opto-coupler driven from the secondary side of the HBC

transformer (see Figure 4). The PFC controller will stop switching immediately, but the

HBC controller will continue switching until the low-side stroke is active. It is also possible

to control the voltage on SSHBC/EN from another circuit on the secondary side via a

diode. The external pull-down current must be larger than the internal soft start charge

current Iss(hf)(SSHBC).

If the voltage on SSHBC/EN is pulled down below Ven(IC)(EN), but not below Ven(PFC)(EN),

only the HBC will be disabled. This feature can be useful when another power converter is

connected to the boost voltage of the PFC.

The low-side power switch of the HBC will be on when the HBC is disabled via the

SSHBC/EN pin.

Boost charge

Boost voltage is built up by operational PFC.

Operational supply

Output voltage is generated. Both PFC and HBC controllers are fully operational.

Restart

Activated when a protection function is triggered. Restart timer is activated. During this time,

PFC and HBC controllers are disabled and CSUPREG is not charged. CSUPIC is charged.

Protection shut-down

Activated when a protection function is triggered. IC is not operational. PFC and HBC controllers

are disabled and CSUPIC and CSUPREG are not charged.

Table 3.

Operating states …continued

State

Description

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