SSL4120 datasheet(31/48 Pages) NXP

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SSL4120

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Product data sheet

Rev. 2 — 1 November 2012

31 of 48

NXP Semiconductors

SSL4120

Resonant power supply controller IC with PFC for LED lighting

The protection timer is also started. The Restart state is activated when the OCR-HBC

condition is still present after the protection time has elapsed.

7.8.10.3

Overcurrent protection, OCP-HBC

Under normal operating conditions, OCR is able to ensure the current remains below the

specified maximum values. However, in the event of certain error conditions, it is not fast

enough to limit the current. OCP is implemented to protect against those error conditions.

The OCP level (Vocp(HBC) = 1 V and +1 V), is higher than the OCR level Vocr(HBC).

When the OCP level is reached, the frequency immediately jumps to the maximum value

using the soft-start reset, then a normal sweep down.

7.8.11 HBC capacitive mode regulation, CMR (HB pin)

The MOSFETs in the half-bridge drive the resonant circuit. Depending on the output load,

the output voltage and the switching frequency this resonant circuit can have an inductive

or a capacitive impedance. Inductive impedance is preferred because it facilitates efficient

zero-voltage switching.

Harmful switching in capacitive mode is avoided using the adaptive non-overlap time

function (see Section 7.8.4.2). An extra action is performed which results in Capacitive

Mode Regulation (CMR). CMR causes the half-bridge circuit to return to Inductive mode

from Capacitive mode.

Fig 18. Overcurrent regulation during start-up

Iocr

-Iocr

ICur(HBC)

Iss(hf)(SSHBC)

Iss(If)(SSHBC)

-Iss(If)(SSHBC)

-Iss(hf)(SSHBC)

ISSHBC/EN

VSSHBC/EN

Vfmin(SSHBC)

Vss(hf-lf)(SSHBC)

Vfmax(SSHBC)

Vreg

Fast soft start sweep (charge and discharge)

Slow soft start sweep (charge and discharge)

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