|TEA1552||GreenChip™II SMPS control IC|
|TEA1552 Datasheet PDF : 24 Pages |
GreenChip™II SMPS control IC
VCOadj 1 VCO adjustment input
2 programmable current sense input
3 standby indication or control output
DRIVER 4 gate driver output
5 high voltage safety spacer, not
6 high voltage safety spacer, not
7 drain of external MOS switch, input for
start-up current and valley sensing
8 supply voltage
9 not connected
11 5 V output
12 lock input
13 control input
14 input from auxiliary winding for
demagnetization timing, OVP and OPP
The TEA1552 is the controller of a compact flyback
converter, with the IC situated at the primary side.
An auxiliary winding of the transformer provides
demagnetization detection and powers the IC after
The TEA1552 operates in multi modes (see Fig.4).
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 reached over almost the complete
universal mains range.
To prevent very high frequency operation at lower loads,
the quasi-resonant operation changes smoothly in fixed
frequency PWM control.
At very low power (standby) levels, the frequency is
controlled down, via the VCO, to a minimum frequency of
approximately 25 kHz.
DRIVER 4 TEA1552T 11 VCC(5V)
Start-up, mains enabling operation level and
undervoltage lock-out (see Figs 11 and 12)
Initially, the IC is self supplying from the rectified mains
voltage via pin DRAIN. Supply capacitor CVCC is charged
by the internal start-up current source to a level of
approximately 4 V or higher, depending on the drain
voltage. Once the drain voltage exceeds the M-level
(mains-dependent operation-enabling level), the start-up
current source will continue charging capacitor CVCC
(switch S1 will be opened); see Fig.2. The IC will activate
the power converter as soon as the voltage on pin VCC
passes the level VCC(start). The IC supply 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).
The moment the voltage on pin VCC drops below the
undervoltage lock-out level VUVLO, 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
Fig.3 Pin configuration.
All (internal) reference voltages are derived from a
temperature compensated, on-chip band gap circuit.
2002 Aug 27
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