 |
Electronic Components Datasheet Search |
|
|
Electronic Components Datasheet Search |
|
LT1509ISW Datasheet(PDF) 9 Page - Linear Technology |
|
||||||||||||||||||||||||||||||
LT1509ISW Datasheet(HTML) 9 Page - Linear Technology |
|
|
9 / 16 page  9 LT1509 (PIN)(RS)(25)(RIAC + 25k) (VIN2)(RREF) VAOUT = 2 + See Figure 2 for RREF. VAOUT is squared in the multiplier, resulting in excellent performance over a wide range of output power and input voltage without the addition of feedforward line frequency ripple. Care must be taken to avoid feeding switching frequency noise into the multiplier from the IAC pin. An internal 25k is provided in series with the low impedance multiplier input so that only a capacitor from the IAC pin to GND1 is required to filter noise. The maximum multiplier output current, which ultimately limits the input line cur- rent, is set by a resistor from the RSET pin to GND1 according to the formula: IM(MAX) = 3.75V/RSET. Figure 5 shows IM versus IAC for various values of VAOUT. Note that Figure 5 data was taken with RSET = 15k. APPLICATIONS INFORMATION The multiplier output acts as the command signal to the current loop error amplifier. During steady-state operation the voltage across RREF = (IM)(RREF) = (IIN)(RS). Based on this the value for RS is determined by: (IM(MAX))(RREF)(VIN)(eff) POUT 2 RS ≤ √ with RSET = 15k, IM(MAX) = 3.75/15k = 250µA. For a 300W converter with an efficiency (eff) of 0.8 at low line (90VRMS) and RREF set to 4k, RS should be less than: (250 µA)(4k)(90VAC)(0.8) 300W 2 = 0.169 Ω √ A 0.15 Ω resistor will yield a maximum peak input current of (IM(MAX))(RREF/RS) = (250µA)(4k)/0.15Ω = 6.67A. For a 100kHz switching frequency with RSET = 15k, CSET = 1.5/ (100kHz)(15k) = 1nF. For added protection the LT1509 provides a second independent current limit comparator. When the input voltage to the comparator (PKLIM pin) dips below 0V, GTDR1 pin quickly goes low turning off the PFC power switch. A resistor divider from VREF to RS (Figure 6) senses the voltage across the line current sense resistor (RS) and limits the peak input line current to [(7.5V/R1) + 50 µA] (R2/RS). The 50µA represents the PKLIM input current which flows out of the PKLIM pin. With R1 = 10k and R2 = 1.8k, IIN = 9.6A peak above the 6.67A peak average plus the input inductor peak ripple current. Always use RSET to set the primary line current limit. The PKLIM comparator is only for secondary protection. When the line current reaches the primary limit, VOUT can no longer be supported with the given input current and begins to fall. System stability is maintained by the current loop which is controlled by the current amplifier. When the Oscillator Frequency and Maximum Line Current Setting The oscillator frequency is set by RSET and CSET. RSET is the resistor from the RSET pin to GND1 and CSET is the capacitor from the CSET pin to GND1. RSET should be determined first. The oscillator frequency, which is equal to the switching frequency for both the PFC and PWM section, is determined by: 1.5 (RSET)(CSET) fOSC = IAC (µA) 0 300 150 0 LT1509 • F05 250 500 VAOUT = 7V VAOUT = 6.5V VAOUT = 6V VAOUT = 5.5V VAOUT = 5V VAOUT = 4.5V VAOUT = 4V VAOUT = 3.5V VAOUT = 3V VAOUT = 2.5V Figure 5. Multiplier Current IM vs IAC and VAOUT + – ILINE RS 0.15 Ω IPKLIM C1 1nF 7.5V VREF PKLIM C1 IS TO REJECT NOISE, CURRENT LIMIT DELAY IS ABOUT 2 µs R2 1.8k R1 10k – + LT1509 • F06 LT1509 Figure 6 |
Similar Part No. - LT1509ISW |
|
Similar Description - LT1509ISW |
|
|
|
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 |
English ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
