Electronic Components Datasheet Search |
|
AN441 Datasheet(PDF) 9 Page - STMicroelectronics |
|
AN441 Datasheet(HTML) 9 Page - STMicroelectronics |
9 / 16 page AN441 Typical examples of inrush current reduction Doc ID 3579 Rev 3 9/16 Triac turn on at peak mains voltage allows the reduction of the peak inrush current by 75% compared to a zero voltage switch on as shown in Figure 8. The reduction of first peak current allows: – Use of a lower Triac range (lower IT(RMS) range), – Safer margin for the Triac (ITSM). 3.2 Transformer for lighting A Triac could be used to dim SELV (safety extra low voltage) halogen lamps. In this case the lamps are connected at the secondary winding of a 220 V to 12 V step-down transformer. The Triac is then connected on this transformer in series with the primary winding (Figure 9). The power applied to the lamp is controlled by the variation of the conducting angle of the Triac and allows dimming the brightness of the lamp. Figure 9. Typical schematic of a light dimmer for SELV halogen lamps Like microwave oven transformers, transformers for lighting application present an overcurrent if they are switched on at zero voltage due to magnetizing current. This inrush current is increased if the lamp filament is cold. Filament resistance decreases when the temperature decreases. The high current due to the cold filament effect could cause transformer magnetic core saturation, which then drastically increases the primary winding inrush current. To reduce the inrush current, an appropriate triggering needs to be used. Table 1 shows different halogen lamp test results used with a transformer. The table shows that the maximum peak current is lower when the load is triggered at zero current. Indeed the ratio between peak current at zero voltage and at peak voltage triggering is in the range of 2 to 4. It should also be noted that, in case of triggering at peak voltage, some transformers (transformer 1 and 2) have a peak inrush current close to 13 times the steady state peak current whereas others feature a ratio lower than 7 (transformer 3). This is linked to the low-saturation level of some low-quality transformers. V MAINS |
Similar Part No. - AN441 |
|
Similar Description - AN441 |
|
|
Link URL |
Privacy Policy |
ALLDATASHEET.COM |
Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Datasheet Upload | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
Family Site : ic2ic.com |
icmetro.com |