SW7230 adaptive 100/120hz current ripple remover max input current 1 a parameters subject to change without notice www.semipower.com.cn 1 features ? adaptive 100/120hz current ripple remover ? input voltage range 5v~60v ? built - in 60v power mosfet ? led voltage low to 0.4v when led current is 1.3a ? programmable amplitude of led current ripple ? programmable maximum cathode voltage of led ? internal led current limitation ? short protection ? hot plug protection ? over temperature protection ? to252 - 5l package applications ? led lightning de s cription sw7 2 30 is used to drive a led string ( < 6 0v), and remove the 100/120hz current ripple on ac/dc power by a capacitor between vc and gnd. by sensing the led pin voltage via a resistor divider, SW7230 allow s user to setup the maximum cathode voltage of led string . SW7230 provides voltage limit thres hold and short threshold for protection. if the voltage on led pin exceeds limit threshold, the current ripple remov ing function is blocked , which could help limit the power dissipation on the chip. its considered that led is shorted when led voltage is h igher than short threshold and remains over 0.5 second. the internal mosfet shuts down when led is shorted. SW7230 also provides open and hot - plug protection.the maximum led current is internally limited at 1.3a. SW7230 provides over thermal protection . wh en otp is trigged, the current removing function is blocked, and then the temperature decreases. typical application
SW7230 adaptive 100/120hz current ripple remove r (max 1 a) www.semipower.com.cn 2 order ing information part marking package description top marking package form SW7230 to252 - 5l SW7230 absolute maximum rating 1 vin pin .... .. ..................... ......... 60 v led pin ............... .......... .... - 0.3~60 v vc, vlmt ..... ..... ............. .... - 0.3v to 6 v junction temperature 2) 3) ..... . ..... ... ....... 150oc lead temperature ........ . ... .. ........... 260 oc storage temperature ....... ... . . 65 oc to +150 oc recommend ed operating rang e vin .................................... 4.7 to 5 5 v led pin ........ ......... ... .. .... ... .... . <60 v maximum junction temperature (t j ) ........ ... 150oc thermal resistance ja j c to - 252 - 5l ..... ....... .. ....... ... 45 /w note 1) exceeding these ratings may damage the device. 2) the SW7230 guarantees robust performance from - 40c to 150c junction temperature. the junction temperature range s pecification is assured by design, characterization and correlation with statistical process controls. 3) t he SW7230 includes thermal protection that i s intended to protect the device in overload conditions. thermal protection is active when j unction temperature exceeds the maximum operating junction temperature. continuous operation over the specified absolute maximum operating junction temperature may damage the device. 4) measured on jesd51 - 7, 2 - layer pcb. pin configuration top view esop8
SW7230 adaptive 100/120hz current ripple remove r (max 1 a) www.semipower.com.cn 3 electrical charateristics vin = 12v, ta = 25oc, unless otherwise stated. item symbol condition min. typ. max. units v in start up voltage threshold v in_on 3.6 4.0 4.4 v v in operation current i in i led =1.0 a 0.12 0.20 0.34 ma led voltage limit threshold v th _ vlmt 0.9 1 1.1 v led short protection threshold v th _short 1.8 2 2.2 v led short protection delay tsp 0.35 0.5 0.65 s led open protection threshold i th_open 50 ma led open protection delay top 0.35 0.5 0.65 s regulated led pin voltage v ledr i led =1.0 a 0.2 5 0.4 0 0.65 v led current limit i clmt 1.0 1.3 1.6 a o ver thermal protection threshold otp 125 135 145 pin description to - 252 - 5l pin no . name description 1 vin power supply 2 led connect to cathode of led string 3 gnd power ground 4 vlmt led voltage limit programming 5 vc led current ripple programming
SW7230 adaptive 100/120hz current ripple remove r (max 1 a) www.semipower.com.cn 4 typical performance characteristics note the pre - driver is sw7 600 32 w t8 program whose output specification is 42 v/ 70 0ma and the output capacitance s choose electrolytic capacitor 960 uf. the v o noted in the figure below refers to the pre - driver output voltage, i led refers to the output current, v c refers to the SW7230 vc pin voltage and v led - refers to the SW7230 led pin voltage. pre - driver output current (vin=220v,io= 700 ma , vo= 42 v, electrolytic capacitor 960 uf/ 63 v ) current ripple: 448 ma, 64 % output current adding SW7230 (vin=220v,io= 70 0ma , vo= 42 v, electrolytic capacitor 960 uf/ 63 v ) current ripple: 18 ma, 4 % s ystem e fficiency comparison with or without SW7230 (vin=220v,io= 70 0ma , vo= 42 v, electrolytic capacitor 960 uf/ 63 v ) o utput open test o utput short test s tart up led hot plug test c ontinuous power on/off test 86 88 90 92 94 90 110 130 150 170 190 210 230 250 efficiency % vin(v) efficiency vs vin with/without SW7230
SW7230 adaptive 100/120hz current ripple remove r (max 1 a) www.semipower.com.cn 5 functional description SW7230 is designed for driving one led string ( 50v ) and removing the 100/120hz led current ripple. t heory of o peration the led string and SW7230 are both supplied by an ac/dc current source. the led pin is connected to the cathode of led string. SW7230 transfers the led current ripple to voltage ripple on chip, and ensures the constant voltage across led string and the current flow through led string. the scalable adaptive function of SW7230 can regulate the cathode voltage of led string to minimum to improve the efficiency of the system. current ripple removing t he capacitor c c between vc and gnd is a integration capacitor. SW7230 transform the voltage on c c to a reference voltage. the current regulator regulates led current via negative feedback control . the relationship between the voltage on c c and led current is shown as following: i led = v vc * 800 (ma) c c should be large enough in order to remove the current ripple of the led string. however, too large capacitor may slow down the dynamic response. adaptive regulation SW7230 control the voltage on c c by monitoring the operation state of built - in nmosfet. the efficiency of system is relatively low when nmosfet is working in the saturation region. SW7230 detects it and charges c c to raise the v vc and i led , then the output volta ge of power supply is reduced, and the voltage drop on nmosfet decreases. conversely, when nmosfet is working in the linear region, led current regulation loop is open. SW7230 detects it and discharges c c to reduce the v vc and i led , then the output voltage of power supply is raised, and the led current regulation loop is close. led pin voltage limit the voltage ripple on led pin is very large when the current ripple is removed, which would bring large power dissipation on chip. the resistor divider connected between led and gnd can setup the limit value of led pin voltage . the limit threshold is calculated as below: v limit = 1v * (r lmt1 +r lmt2 )/r lmt2 led current limit the current of led is limited at 1.3a internally . the current limitation can protect the chip when led is short connected or hot - plug. s a t u r a t i o n r e g i o n r e g u l a t o r c l o s e l o o p c h a r g e c c l i n e a r r e g i o n r e g u l a t o r o p e n l o o p d i s c h a r g e c c i l e d v l e d r e g u l a t e d l e d p i n v o l t a g e
SW7230 adaptive 100/120hz current ripple remove r (max 1 a) www.semipower.com.cn 6 the function of current limit is higher priority than led pin voltage limit. it means that the voltage on led pin is limited when led current exceed 1.3a. led short protection when t he voltage input to vlmt pin is exceed 2v and the state holds for more than 0.5 second, SW7230 considers the led string is short connected, and shut down the internal mosfet. the shut down state is latched until system restart. open and hot - plug protecti on when SW7230 detects that led current is lower than 50ma, and the state holds for more than 0.5 second, SW7230 considers the led string is open connected, and shuts down the internal mosfet. if the led string is connected suddenly during the open state, the voltage on led pin is raised rapidly and exceeds the led pin voltage limit threshold. then the open state is reset, internal mosfet is turned on and the led current is limited at 1.3a. over thermal protection SW7230 monitors operation temperature. when the temperature is higher than 140 , the current ripple removing function is blocked, which could help chip cooling. over thermal protection will not be reset until the system restart. pcb design guideline 1. the bypass capacitor of vin should be placed as close as possible to the vin pin and gnd pin of ic. 2. SW7230 should be placed far away from the power devices such as mosfet and sbd. 3. the area of led current loop should be as small as possible. 4. t he area of the copper on the pcb will directly affect the temperature rise of ic.
SW7230 adaptive 100/120hz current ripple remove r (max 1 a) www.semipower.com.cn 7 application note SW7230 design guide: 1. design considerations: a) the withstand voltage of led pin is 60v, so the overvoltage of the pre - driver must be less than 60v in order to protect the chip in short circuit condition. b) the output should be connected to the leds when testing the characteristics of SW7230 including open and short circuit test. 2. the recommended operating current of sw72 30 is 0.8 a (max 1 a). the power loss and temperature ris e of the chip depend on the amplitude of the output current ripple and the final amplitude required. 3. based on the power factor correction of the pre - driver, the law of conservation of energy and the reasonable tempera ture rise of the SW7230 , the output capacitance of the pre - driver can be approximately calculated as follows: p in : i nput power p out : o utpu t power p d : p ower loss of SW7230 i led : led current u: o utput voltage v min : the minimum led pin voltage u: peak to peak output voltage ripple v led - : led - pin voltage t: line cycle : efficiency of the system a) the power factor correction of the pre - driver and the law of conservation of energy: b) the energy formula of capacitance: c) the reasonable temperature ris e of the SW7230 d) the smaller output power, the larger capacitance is needed as it can be see n in the equation above. e) for example : i. given p d = 1 w (equivalent to 4 5 temperature rise); =0.85; f=1/t=50hz then, the result shows in the following figure: t e p i n p t / 8
SW7230 adaptive 100/120hz current ripple remove r (max 1 a) www.semipower.com.cn 8 ii. given p d = 2 w (equivalent to 90 temperature rise); =0.85; f=1/t=50hz t hen the result show s in the below: 4. by sensing the led pin voltage via a resistor divider, SW7230 allows user to setup the maximum cathode voltage of led string. because of the voltage limit threshold 1v and the short threshold 2v, t he value of the resistance between led and vlmit pin should choose 400k and the other should choose 100k under normal circumstances. 5. the value of the capacitor between vc and gnd can de termine the final amplitude of the current ripple. it should be large enough in order to remove the current ripple of the led string. however, too large capacitor may slow down the dynamic response. in normal condition, 1uf or 2.2uf is reasonable. 500 1000 1500 2000 2500 3000 3500 4000 0.5 0.6 0.7 0.8 0.9 1 output capacitance(uf) led current (a) output capacitance vs led current @pd=1w pout=5w pout=10w pout=15w pout=20w 200 500 800 1100 1400 1700 0.5 0.6 0.7 0.8 0.9 1 output capacitance(uf) led current (a) output capacitance vs led current @pd=2w pout=5w pout=10w pout=15w pout=20w
SW7230 adaptive 100/120hz current ripple remove r (max 1 a) www.semipower.com.cn 9 application reference reference 1
SW7230 adaptive 100/120hz current ripple remove r (max 1 a) www.semipower.com.cn 10 package outline to - 252 - 5l unit: mm 5 . 5 0 0 . 2 5 2 . 3 0 0 . 2 0 0 . 5 1 0 . 1 0 1 . 5 9 0 . 2 0 0 0 . 2 5 0 . 5 1 0 . 1 0 6 . 5 0 0 . 2 5 5 . 3 0 0 . 2 0 1 . 4 0 0 . 2 0 0 . 5 0 0 . 1 0 1 . 2 7 t y p 9 . 5 1 0 . 2 4 . 9 0 0 . 2 5 3 . 5 0 0 . 2 5 5 . 3 0 0 . 2 5
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