User manual INFINEON TDA 16847-2 DATA SHEET VERSION1.3

[. . . ] 3 , J u l y 2 0 0 3 TDA 16846 TDA 16846-2 TDA 16847 TDA 16847-2 Controller for Switch Mode Power Supplies Supporting Low Power Standby and Power Factor Power Management & Supply Never stop thinking. TDA 16846/TDA 16846-2 Revision History: Current Version: 2003-07-31 Previous Version Data Sheet TDA 16846: 2000-01-14 Previous Version Data Sheet TDA 16846-2: 2002-07-30 Page (in previous Version) 20 Page (in current Version) 20 Subjects (major changes since last revision) The data sheets for TDA 16846 and TDA 16846-2 have been combined in this version. Some measuring values are updated: Pin 1 basic value 1 V1B1 and V1B2 slightly changed. Pin 2 discharge current I2DC min changed from 0. 5 mA to 0. 6 mA. Pin 14 overvoltage V14OVmax threshold changed from 17. 0 V to 17. 1 V. [. . . ] A second function of this pin is the primary voltage dependent fold back point correction (only active in free running mode). This pin has to be connected via a series resistor to the gate of the power transistor. Connection for supply voltage and startup capacitor. After startup, the supply voltage is produced by the control winding of the transformer and rectified by an external diode. 5 2003-07-31 3 4 5 6 7 8 9 10 11 12 13 14 Data Sheet TDA 16846 TDA 16846-2 1. 5 Block Diagrams Figure 2 Data Sheet TDA 16846-2 6 2003-07-31 TDA 16846 TDA 16846-2 Figure 3 Data Sheet TDA 16847-2 7 2003-07-31 TDA 16846 TDA 16846-2 2 Functional Description Start Up Behaviour (Pin 14) When power is applied to the chip and the voltage V14 at Pin 14 (VCC) is less than the upper threshold (VON) of the Supply Voltage Comparator (SVC), then the input current I14 will be less than 100 µA. The chip is not active (off state) and driver output (Pin 13) and control output (Pin 4) will be actively held low. When V14 exceeds the upper SVC threshold (VON) the chip starts working and I14 increases. When V14 falls below the lower SVC threshold (VOFF) the chip starts again from its initial condition. Figure 4 shows the start-up circuit and Figure 5 shows the voltage V14 during start up. Charging of C14 is done by resistor R2 of the "Primary Current Simulation" (see later) and the internal diode D1, so no additional start up resistor is needed. The capacitor C14 delivers the supply current until the auxiliary winding of the transformer supplies the chip with current through the external diode D14. It is recommended to apply a small RF snubber capacitor of e. g. 100 nF parallel to the electrolytic capacitor at pin 14 as shown in the application circuits in Figures 15, 16 , and 17. To avoid multiple pulses during start up in fixed frequency mode (danger of transformer saturation), the IC works in freerunning mode until the pulses at pin 3 (RZI) exceed the 2. 5 V threshold (only TDA 16846-2, TDA 16847-2). Figure 4 Startup Circuit Data Sheet 8 2003-07-31 TDA 16846 TDA 16846-2 Figure 5 Startup Voltage Diagram Primary Current Simulation PCS (Pin 2) / Current Limiting A voltage proportional to the current of the power transistor is generated at Pin 2 by the RC-combination R2, C2 (Figure 4). The voltage at Pin 2 is forced to 1. 5 V when the power transistor is switched off and during its switch on time C2 is charged by R2 from the rectified mains. The equation of V2 and the current in the power transistor (Iprimary) is : V 2 = 1, 5 V + L primary × I primary ------------------------------R2 × C2 Lprimary: Primary inductance of the transformer The voltage V2 is applied to one input of the On Time Comparator ONTC (see Figure 2). If V2 exceeds the control voltage, the driver switches off (current limiting). The maximum value of the control voltage is the internal reference voltage 5 V, so the maximum current in the power transistor (IMprimary) is : 3, 5 V × R 2 × C 2 I Mprimary = -------------------------------------L primary The control voltage can be reduced by either the Error Amplifier EA (current mode regulation), or by an opto coupler at Pin 5 (regulation with opto coupler isolation) or by the voltage V11 at Pin 11 (Fold Back Point Correction). Data Sheet 9 2003-07-31 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. 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 : (4 V ­ V 11 / 3 ) × R 2 × C 2 I Mprimary = -----------------------------------------------------------L primary 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. [. . . ] Thus the average of the sawtooth voltage V8 at Pin 8 is proportional to the converter´s output power (at constant output voltages). The charge current I8 for C8 is set by the resistor R9 at Pin 9: I8 = 5 V/R9 Data Sheet 17 2003-07-31 TDA 16846 TDA 16846-2 Secondly, a High Power Shutdown Comparator (FC2) is implemented: When the voltage V6 at Pin 6 exceeds 1. 2 V the Error Flip Flop (ERR) is set. The output voltage of the power measurement circuit (Pin 8) is smoothed by R8/C6 and applied to the "high power shutdown" input at Pin 6. The relation between this voltage V6 and the output power of the converter P is approximately: V6 (P × LSecondary × 5 V)/(VOUT2 × C8 × R9) LSecondary: The transformers secondary inductance VOUT: The converters output voltage So the time constant of R9/C8 for a certain high power shutdown level PSD is: R9 × C8 (PSD × LSecondary × 4. 2)/VOUT2 The converters high power shutdown level can be adjusted lower (by R9, C8) than the current limit level (see "current limiting"). [. . . ]