TEA1532BT_TEA1532CT_1

© NXP B.V. 2007. All rights reserved.

Product data sheet

Rev. 01 — 18 January 2007

6 of 23

NXP Semiconductors

TEA1532BT; TEA1532CT

GreenChip II SMPS control IC

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

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

In fixed frequency continuous conduction mode, which can be activated by grounding

pin DEM, the internal oscillator determines the start of the next converter stroke.

In both operating modes, a cycle skipping mode is activated at very low power (standby)

levels.

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

Refer to Figure 9 and Figure 10. Initially, the IC is self supplying from the rectified mains

current source to a level of about 4 V or higher, depending on the drain voltage. Once the

(green function). The IC supply is taken over by the auxiliary winding of the flyback

converter.

stops switching and performs a safe restart from the rectified mains voltage. In the safe

7.2 Supply management

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

band gap circuit.

7.3 Oscillator

The fixed frequency of the oscillator is set by an internal current source and capacitor.

7.4 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.

7.5 Current control mode

Current control mode is used for its good line regulation behavior.

The primary current is sensed across an external resistor and compared with the internal

control voltage. The driver output is latched in the logic, preventing multiple switch-on.

The internal control voltage is inversely proportional to the external pin CTRL voltage, with

an offset of 1.5 V. This means that a voltage range from 1 V to approximately 1.5 V on

pin CTRL will result in an internal control voltage range from 0.5 V to 0 V (a high external

control voltage results in a low duty cycle).