© Koninklijke Philips Electronics N.V. 2005. All rights reserved.

Objective data sheet

Rev. 01 — 18 May 2005

6 of 22

Philips Semiconductors

TEA1530AT

GreenChip

™II SMPS control IC

7.5 Cycle skipping

At very low power levels, a cycle skipping mode activates. An internal control voltage

this voltage increases to a higher value; see Figure 5.

7.6 Continuous Conduction Mode (CCM)

The IC operates in the so-called Fixed Frequency Continuous Conduction Mode (FF

7.7 OverCurrent Protection (OCP)

The primary peak-current in the transformer is measured accurately cycle-by-cycle using

internal level equal to 1.5V - Vctrl (also see section 7.3). The OCP detection is

caused by the switch-on spikes.

7.8 Control pin protection

If pin CTRL becomes open-circuit or is disconnected, a fault condition is assumed and the

converter will stop switching immediately. Operation recommences when the fault

condition is removed.

7.9 Adjustable slope compensation

A slope compensation function has been added at pin CTRL; see Figure 6. The slope

compensation function prevents sub-harmonic oscillation in CCM at duty cycles over

50 %. The CTRL voltage is modulated by sourcing a (non-constant) current out of

voltage proportionally with the on-time, which therefore limits the OCP level. A longer

on-time results in a higher CTRL voltage, this increase in CTRL voltage will decrease the

compensation prevents modulation of the on-time (duty cycle) while operating in FF CCM.

A possible drawback of sub-harmonic oscillation can be output voltage ripple.