VIPER31SP

VIPer31SP BATTERY CHARGER PRIMARY I.C. ADVANCE DATA T YPE VIPer31SP V DSS 600 V In 1A R DS(on) 6.5 Ω 10 FEATURE s RECTANGULAR CHARACTERISTIC, WITHOUT OPTOCOUPLER s INTERNALLY TRIMMED CURRENT REFERENCE s FIXED SWITCHING FREQUENCY, ADJUSTABLE UP TO 150 KHZ s AUXILIARY VOLTAGE REGULATOR s SOFT START AND SHUT DOWN CONTROL s AUTOMATIC BURST MODE OPERATION IN STAND-BY CONDITION ABLE TO MEET ”BLUE ANGEL” NORM ( where : VDDhyst IDD is the consumption current on the VDD pin when switching. Refer to specified IDD1 and IDD2 values. tSS is the start up time of the converter when the device begins to switch. Worst case is generally at full load. VDDhyst is the voltage hysteresis of the UVLO logic. Refer to the minimum specified value. CSTART = CVDD + CVCC is the sum of both capacitors on VDD and VCC pins. Once is defined, allot a standard 4.7 µF / 16 V on the VDD pin, and the rest on the VCC pin. The VDD capacitor insures a correct decoupling of the internal serial regulator between VCC and VDD. Soft start feature is implemented through the CREF capacitor which is also filtering the CREF voltage. The minimum value of this capacitor has to be set according to the switching frequency, in order to filter the charging and discharging current issued from the CREF pin (Refer to the current control description part). It can be increased from - 1. Define the maximum output voltage MAX for which the converter has still to OUT operate in constant current mode. V - 2. Check that the ratio between the minimum MIN MAX and V is OUT OUT lower than 2.5. This ratio is limited by the overvoltage protection value (Typically 29 V) and VDDreg (Typically 10 V) and their tolerances. operating output voltage V - 3. Compute the transformer turn ratio n from primary to secondary with the formula : np 100 n= = MAX ns V OUT - 4. Compute the sense resistance value with the formula : RS = n x 0.175 IOUT - 5. Compute the transformer turn ratio nAUX from auxiliary to secondary with the formula : na 25 nAUX = = MAX ns V OUT - 6. The current control function requires the converter to work in discontinuous mode. The primary inductance value LP of the transformer can be computed by respecting this constraint in all conditions, or by using the following MIN V x TSW n IN formula : LP = x where : 10 IOUT MIN V is the minimum input rectified DC voltage IN from the mains. 12/16 VIPer31SP Figure 13: Start Up Circuit and Sequence 2 mA VCC LDO Reg. AUXILIARY WINDING CVCC CVDD VDD ON/OFF UVLO LOGIC + Ref VIPer31 DRAIN (V) VCC VDDreg VDDon VDDoff tss VDD GND SOURCE t SC12150 this value to provide a soft start feature, of which the duration depends on some circuit parameters, like transformer ratio, sense resistor, output capacitors and load. The user will define the best appropriate value by experiments. SHORT CIRCUIT OPERATION In case of abnormal condition where the auxiliary winding is unable to provide the low voltage supply current to the VCC pin (i.e. short circuit on the output of the converter), the external capacitors discharge themselves down to the low threshold voltage VDDoff of the UVLO logic, and the device get back to the inactive state where the internal circuits are in standby mode and the start up current source is activated. The converter enters a endless start up cycle, with a start-up Figure 14 : Short circuit operation VDD VDDon VDDoff duty cycle defined by the ratio of charging current towards discharging when the VIPer31 tries to start. This ratio is fixed by design to 1.5 to 12, which gives a 11% start up duty cycle, while the power dissipation at start up is approximately 0.6 W, for a 230 Vrms input voltage. The average output short circuit current is the product of the start up duty cycle by the output current flowing during the active phase of the device (See figure 14). This output current is limited by either the CREF pin voltage, or the internal current limitation of 1.3 A. These values together with the low value of start-up duty cycle prevents the stress of the output rectifiers and of the transformer when in short circuit. t Iout Isc Average output current t SC12160 13/16 VIPer31SP OVERVOLTAGE PROTECTION If the output voltage accuracy is not a concern, but only a limitation is desired, the internal overvoltage protection can be used. In this case, five components can be taken out from the schematics of figure 10 (R3-R10-R6-C4-C5) and the input pin FB of the error amplifier is simply grounded. The internal overvoltage protection will act as soon as the VCC voltage reaches typically 29 V, by turning off the power mosfet switch. An hysteresis of about 3 V will enable again the switching of the device at a lower voltage level on the VCC pin. This results in an efficient voltage limitation, in a burst mode operation type, with some ripple on the output. Case by case experiments will define the correct value of output capacitor C3, according to the loading current in low output power condition. STANDBY MODE The standby mode is represented by a very low output current, corresponding to a full loaded battery in a battery charger application. The output voltage is limited by either the overvoltage protection or the error amplifier, according to the design. This results into different situations : - In case the overvoltage protection is used, the burst mode operation as described previously takes place, governed by the hysteresis of the overvoltage comparator. - If the error amplifier is used, many situation can occur, depending on the compensation network foreseen by the designer. These situations can range from a normal continuous operation, to burst mode. In any case, the output voltage will be regulated to the desired value. Note that the burst operation is providing a very low input power consumption, because it reduces the switching frequency, and thus commutation losses. Less than 1 W of input power can be observed in this operative mode, with a few hundreds of mW delivered to the secondary load. This is far compliant with standby standards, like the ”Blue Angel” one. 14/16 VIPer31SP Power SO-10 MECHANICAL DATA DIM. MIN. A A1 B c D D1 E E1 E2 E3 E4 e F H h L q α 0 o mm TYP. MAX. 3.65 0.10 0.60 0.55 9.60 7.60 9.50 7.40 7.60 6.35 6.10 1.27 1.25 13.80 0.50 1.20 1.70 8o 1.80 0.047 1.35 14.40 0.049 0.543 MIN. 0.132 0.000 0.016 0.013 0.370 0.291 0.366 0.283 0.283 0.240 0.232 3.35 0.00 0.40 0.35 9.40 7.40 9.30 7.20 7.20 6.10 5.90 inch TYP. MAX. 0.144 0.004 0.024 0.022 0.378 0.300 0.374 0.291 0.300 0.250 0.240 0.050 0.053 0.567 0.002 0.071 0.067 B 0.10 A B 10 = H = A F A1 = 6 = = = E = 1 5 e 0.25 M = E2 E3 E1 E4 = = A = SEATING PLANE DETAIL ”A” Q B C h D = D1 = = = SEATING PLANE = A1 L DETAIL ”A” α 0068039-C 15/16 VIPer31SP Information furnished is believed to be accurate and reliable. However, SGS-THOMSON Microelectronics assumes no responsability for the consequences of use of such information nor for any infringement of patents or other rights of third parties which may results from its use. No license is granted by implication or otherwise under any patent or patent rights of SGS-THOMSON Microelectronics. Specifications mentioned in this publication are subject to change without notice. This publication supersedes and replaces all information previously supplied. SGS-THOMSON Microelectronics products are not authorized for use as critical components in life support devices or systems without express written approval of SGS-THOMSON Microelectonics. © 1998 SGS-THOMSON Microelectronics - Printed in Italy - All Rights Reserved SGS-THOMSON Microelectronics GROUP OF COMPANIES Australia - Brazil - Canada - China - France - Germany - Italy - Japan - Korea - Malaysia - Malta - Morocco - The Netherlands Singapore - Spain - Sweden - Switzerland - Taiwan - Thailand - United Kingdom - U.S.A . .. 16/16