TEA1553T_1

© NXP B.V. 2007. All rights reserved.

Product data sheet

Rev. 01 — 3 July 2007

6 of 27

NXP Semiconductors

TEA1553T

GreenChip II SMPS control IC

The next converter stroke is started only after demagnetization of the transformer current

(zero current switching), while the drain voltage has reached the lowest voltage to prevent

switching losses (green function). The primary resonant circuit of primary inductance and

drain capacitor ensures this quasi-resonant operation. The design can be optimized in

such a way that zero voltage switching can be achieved over almost the whole of the

universal mains range.

To prevent very high frequency operation at lower loads, the quasi-resonant operation

changes smoothly in fixed frequency Pulse Width Modulation (PWM) control.

At low power levels, the frequency is controlled via the Voltage Controlled Oscillator

(VCO), down to a minimum of about 25 kHz.

At very low power levels (standby), a cycle skipping mode will be activated.

7.1 Start-up, mains enabling operation level and undervoltage lock-out

Initially, the IC is self-supplying from the rectified mains voltage via pin DRAIN. Supply

(mains-dependent operation-enabling voltage), the start-up current source will continue

is taken over by the auxiliary winding as soon as the output voltage reaches its intended

level and the IC supply from the mains voltage is subsequently stopped for high efficiency

operation (green function).

level, the IC stops switching and enters a safe restart from the rectified mains voltage.

Inhibiting the auxiliary supply by external means causes the converter to operate in a

stable, well defined burst mode. (See Figure 14 and Figure 15).

7.2 Supply management

All (internal) reference voltages are derived from a temperature compensated, on-chip

band gap circuit.

Fig 4.

Multi mode operation

FIXED

014aaa002

quasi-resonant

125 kHz

f

VCO

25 kHz

POWER