TDA16847 查看數據表（PDF） - Infineon Technologies

零件编号

产品描述 (功能)

生产厂家

TDA16847

Controller for Switch Mode Power Supplies Supporting Low Power Standby and Power Factor Correction

Infineon Technologies 

TDA 16846

TDA 16846-2

Fold Back Point Correction PVC (Pin 11)

V11 is derived from a voltage divider connected to the rectified mains and reduces the

limit of the possible current maximum in the power transistor if the mains voltage

increases. I.e. this limit is independent of the mains (only active in free running mode).

The maximum current (IMprimary) depending on the voltage V11 at Pin 11 is

:

IMprimary

=

-(-4-----V-----–-----V----1--1----⁄--3----)----×----R-----2----×----C-----2-

Lprimary

Off-Time Circuit OTC (Pin 1)

Figure 6 shows the Off-Time Circuit which determines the load dependent frequency

curve. When the driver switches off (Figure 7) the capacitor C1 is charged first by current

I1L (approx. 0.5 mA, for extended ringing suppression time). As soon as the voltage at

pin 3 reaches the level V3L (2.5 V), the charging current is switched to the higher value

I1H (approx. 1 mA, for normal ringing suppression time). This current flows until the

capacitor’s voltage reaches 3.5 V. The charge time TC1 is

:

TC1

≈

C-----1----×-----1---,--5-----V-

1mA

For proper operation of the special internal anti- jitter circuit, TC1 (rising time for I1H only)

should have the same value as the resonance time “tR” of the power circuit (Figure 7).

After charging C1 up to 3.5 V the current source is disconnected and C1 is discharged by

resistor R1. The voltage V1 at Pin 1 is applied to the Off-Time Comparator (OFTC). The

other input of OFTC is the control voltage. The value of the control voltage at the input

of OFTC is limited to a minimum of 2 V (for stable frequency at very light load). The On-

Time Flip Flop (ONTF) is set, if the output of OFTC is high 1) and the voltage V3 at Pin 3

falls below 25 mV (zero crossing signal is high). This ensures switching on of the power

transistor at minimum voltage. If no zero crossing signal is coming into pin 3, the power

transistor is switched on after an additional delay until V1 falls below 1.5 V (see Figure 6,

OFTCD). As long as V1 is higher than the limited control voltage, ONTF is disabled to

suppress wrong zero crossings of V3, due to parasitic oscillations from the transformer

after switch-off. The discharge time of C1 is a function of the control voltage.

1) i.e. V1 is less than the limited control voltage.

.

Control Voltage Output Power Off-time TD1

1.5 - 2 V

2 - 3.5 V

Low

Medium

Constant (TD1MAX.), const. frequency stand by

Decreasing

3.5 - 5 V

High

Free running, switch-on at first minimum

Data Sheet

10

2003-07-31

Share Link: