2005. 12. 6 1/5 semiconductor technical data KIA3802F bipolar linear integrated circuit revision no : 0 lcd backlight inverter controller features input voltage range of 7v to 20v low cost, push-pull inverter topology internal open lamp protection and over voltage detecting built-in stand-by function integrated with burst mode control, wide dimming range soft-start timer function reduces the number of componerts supports multiple ccfls application lcd monitor notebook computer block diagram flp-16 l 1 8 9 16 b1 p d h a g t b2 0.20+0.1/-0.05 p t 1.27 millimeters 0.4 0.1 0.15+0.1/-0.05 9.88 0.2 b2 g h l d a b1 dim 6.00 0.3 1.63 0.2 0.65 0.2 3.94 0.2 + _ + _ + _ + _ + _ + _ out1 out2 ct rt gnd in - time r ovp en sst cmp vcc v ref pwm comparator KIA3802F burst mode osc ct rt lct lct v dim v dim lpwm lpwm 1 2 3 5 6 7 8 9 10 11 12 13 14 15 16 4 out out out open reference over voltage v ref v cc v cc v cc 2v 3v 2.5v - q + q clk timer out push pull controller err amp
2005.12.6 2/5 KIA3802F revision no : 0 pin description maximum rating (ta = 25 , unless otherwise noted.) rating symbol limits unit power supply voltage v cc 20 v power dissipation(ta=25 ) p d 400 mw output current i o(max) 50 ma operating temp. t opr -20 ~ 85 storage temp. t stg -55 ~ 150 recommended operating conditions rating symbol limits unit power supply voltage v cc 7 ~ 20 v oscillation frequency f osc 30 ~ 200 khz timing resister rt 3 ~ 30 no. symbol i/o description 1 enable i enable input. 2 cmp i compensation output of the error amplifier. 3 sst i soft-start capacitor. 4 ct i timing capacitor. 5 rt i timing resistor set operating frequency. 6 lct i triangular wave for burst-mode dimming; frequency. 7 v dim i input analog signal for burst-mode dimming control. 8 lpwm o low-frequency pwm signal for burst-mode dimming control. 9 out1 o output 1. 10 gnd i ground. 11 out2 o output 2. 12 v cc i voltage source for the ic. 13 ovp i output voltage sense; vth=2v. 14 v ref o reference voltage output ; 5v typical. 15 timer i capacitor for ccfl ignition duration. 16 in- i inverting input.
2005.12.6 3/5 KIA3802F revision no : 0 electrical characteristics ( v cc =12v; v en =2.0v, ta=25 , unless oterwise noted.) parameter symbol test conditions min typ max unit reference voltage nominal voltage v ref i ref = 1 4.75 5.0 5.25 v line regulation v cc =7v to 20v - 2.0 25 load regulation i ref = 1.0 ~ 5 - 3.0 15 high frequency oscillator (1) initial accuracy f hosc ct=1.2 , rt=10 106 116 126 ramp peak - 2.5 - v ramp vally - 0 - v low frequency oscillator initial accuracy f losc lct = 470 - 210 - ramp peak - 2.5 - v ramp vally - 0.7 - v low frequency pwm duty cycle range v diml - 0.6 - v v dimh - 2.5 - v error amplifier (2) input voltage range 0 - 4.0 v open loop voltage gain - 80 - unity gain bandwidth r cmp =2 - 1 - power supply rejection - 60 - threshold enable output off v en(off) 0 - 0.5 v output on v en(on) 2.0 - 5 open lamp protection v cmp output on -> off - 3 - v over voltage protection v ovp output on -> off - 2 - v supply supply current i cc(off) v en =0v - - 100 supply current i cc(on) v dim =0v - 8 10 output low state output voltage v ol i o(sink) =1 - 0.5 1.6 v i o(sink) =50 - 0.5 1.6 high state output voltage v oh i o(source) =1 10 10.5 - v i o(source) =50 10 10.5 - rise time t r c out =2 - 50 200 fall time t f c out =2 - 50 200 note 1 : the lamp oscillotor frequency is the half of the ramp wave frequency. note 2 : only verified by simulation. not 100% tested.
2005.12.6 4/5 KIA3802F revision no : 0 application circuit r10 30k c9 470n c9 470n c3 47u c7 2.2u c8 1.2n c6 2.2u c11 100n c2 100n c21 39n KIA3802F trans 1 d1 kds226 c20 22p/3kv short c4 100n c5 2.7n c17 r11 r8 39 39 c1 220u r3 10k r5 47k r23 1k r22 2.0k r12 10k r9 10k r6 100k r4 20k timer ovp ovp vin fb ic soft cmp v dim v dim v cc gnd gnd v ref out1 out2 ct rt lct in- en lpwm ccfl1 v in v in v en q1 krx103u
2005.12.6 5/5 KIA3802F revision no : 0 functional description 1) main frequency (lamp operation frequency) a resistor rt and a capacitor ct determine the main frequency of ic. the main frequency can be calculated as below equation: 2) open lamp protection open lamp protection in the ignition time is provided through both ovp and timer pin to ensure a rated voltage is achieved and a required timing is satisfied. if time that timer capacitor charges to 3v is long than the ccfl ignition time, it can prevent over-operating by protection circuit. 3) error amplifier the ccfl current is regulated through the error amplifier. error amplifier output (cmp) voltage and ramp wave (ct) make the pwm pulses. the non-inverting reference is at 2.5v nominal. 4) ovp when the output voltage reaches the threshold, it commands the pwm controller to maintain the current driving level. this ensures that output gets sufficient striking voltage while operating the power transformer safely. the ovp threshold is set at 2v nominal. 5) on/off function the enable pin provides the function to turn on and off the output without shut down the supply voltage. the threshold of the enable is set at 2.0v. 6) soft-start the soft-start function is provided with a capacitor connected to sst pin. it provides a rate of rise for the pulse width where switches are turned on. a 2.2 capacitor connected on the sst pin can set a 0.4 second period for striking the lamp. 7) burst-mode dimming the burst-mode frequency is determined by a capacitor connected to lct pin. the frequency can be calculated by: to compare the input of v dim pin with the ramp wave(lct) makes the pwm pulses for burst-mode dimming. the lpwm pin is pulled to v ref to make the dark portion of the ccfl output burst and the floating state to make the bright portion. a less than 0.6v input on v dim pin will obtain 100% brightness. transformer design 1. transformer turns ratio calculation of the required turns ratio involves the estimation of two critical factors. 1). estimating minimum primary voltage. the minimum primary voltage is obtained from the value of the low supply voltage. 2). estimating maximum secondary voltage. the secondary is composed of a ballast capacitor, a voltage divide capacitor and the lamp parasitic capacitor. the voltage across the ballast capacitor can be calculated as below equation: v ballast c = x ballast i lamp the maximum secondary voltage can be calculated as below equation: transformer turns ratio is: 2. required number of secondary turns from the core constant provided by the core manufacturer, you will need the effective core cross sectional area(ae). from the faraday's law, the required number of secondary turns would be: 3. required number of primary turns from the turns ratio and number of secondary turns 4. determination of wire gauge wire gauge can be done by an acceptable current density. from the assumed current density (500cmil) and the current that flows through wires, the required circular mils is: cmils = c dlim i rms from the awg table, pick a wire-gauge that would fit limit. using the selected wire diameter and bobbin information, determine if this wire gauge will fit in the space allotted. (when the space factor[sf] is accounted for) main [khz] = ct[nf] rt[k ] 6.8 10 2 ? f f [hz] = lct[nf] rt[k ] 1 10 6 ? vsecondary = v lamp 2 v ballast c 2 + n = v primary v secondary n secondary = v secondary t max b 10 8 a e n primary = n secondary n
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