|TEA1751(L)T||HV start-up DCM/QR flyback controller with integrated DCM/QR PFC controller|
|TEA1751(L)T Datasheet PDF : 29 Pages |
GreenChip III SMPS control IC
Istartup(soft)PFC ≤ 60 μA
Fig 5. Soft start-up of PFC
7.2.6 Low power mode
When the output power of the flyback converter (see Section 7.3) is low, the flyback
converter switches over to frequency reduction mode. When frequency reduction mode is
entered by the flyback controller, the power factor correction circuit is switched off to
maintain high efficiency.
During low power mode operation the PFCCOMP pin is clamped to a minimal voltage of
2.7 V (typical) and a maximum voltage of 3.9 V (typical). The lower clamp voltage limits
the maximum power that is delivered when the PFC is switched on again. The upper
clamp voltage ensures that the PFC can return to its normal regulation point in a limited
amount of time when returning from low power mode.
As soon as the flyback converter leaves the frequency reduction mode, the power factor
correction circuit restores normal operation. To prevent continuous switching on and off of
the PFC circuit, a small hysteresis is build in, (60 mV (typical) on the FBCTRL pin).
7.2.7 Dual boost PFC
The PFC output voltage is modulated by the mains input voltage. The mains input voltage
is measured via the VINSENSE pin. The current is sourced from the VOSENSE pin if the
voltage on the VINSENSE pin drops below 2.2 V (typical). To ensure the stability of the
switch-over 200 mV is inserted around the 2.2 V, see Figure 6.
For low VINSENSE input voltages, the output current is 15 μA (typical). This output
current, in combination with the resistors on the VOSENSE pin, sets the lower PFC output
voltage level at low mains voltages. At high mains input voltages the current is switched to
zero. The PFC output voltage will then be at its maximum. As this current is zero in this
situation, it does not effect the accuracy of the PFC output voltage.
For proper switch-off behavior, the VOSENSE current is switched to its maximum value,
(15 μA (typical)), as soon as the voltage on pin VOSENSE drops below 2.1 V (typical).
Product data sheet
Rev. 02 — 23 December 2009
© NXP B.V. 2009. All rights reserved.
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