原厂授权代理商．深圳市诚信联科技有限公司，联系人：古小姐 ０７５５－８６０９１９６３／１３２４９８２７１７０ Ｑ：１１３９１９６８０６／１２６２３１４６７５ 2012/07/25 NU310 Lighting LED driver Data sheet Universal High Brightness LED Driver Feature Pin Assignment >90% Efficiency Universal rectified 85-265VAC input range Constant-Current LED driver Applications from a few mA to more than 1A output LED string from one to hundreds of diodes PWM Low-Frequency Dimming via Enable pin Input Voltage Surge ratings up to 500V Internal thermal overload protection SOP 8 Product Description The NU310 is a PWM high-efficiency LED driver Control IC. It allows efficient operation of High Brightness (HB) LEDs from voltage sources ranging from 85VAC up to 265VAC. The NU310 controls an external MOSFET at fixed switching frequency up to 300KHZ. The frequency can be programmed using a Single external resistor. The LED string is driven at constant current rather than constant voltage, thus providing constant light output and enhanced reliability. The output current can be programmed between a few milliamps and up to more than 1A. NU310 uses a rugged high voltage junction isolated process that can withstand an input voltage surge of up to 500V. Output current to an LED string can be programmed to any value between zero and its maximum value by applying an external control voltage at the linear dimming control input of the NU310. The NU310 provides a low-frequency PWM dimming input that can accept an external Control signal with a duty ratio of 0-100% and a frequency of up to a few kilohertz. Applications Terminal Description Pin name VIN Input voltage CS Senses LED string current GND Device ground CATE Drives the gate of the external MOSFET PWM_D VDD LD AC/DC LED Driver applications RGB Backlighting LED Driver ROSC Back Lighting of Flat Panel Displays Function General purpose constant current source Low Frequency PWM Dimming pin, also Enable input. Internal 100KΩ PULL-DOWN to GND Internally regulated supply voltage.7.5V nominal. Can supply up to 1 mA for external circuitry. A sufficient storage capacitor is used to provide storage when the rectified AC input is near the zero crossings. Linear Dimming by changing the current limit threshold at current sense comparator Oscillator control. A resistor connected between this pin and ground sets the PWM frequency Signage and Decorative LED Lighting Chargers Package Type SOP8 -1- Ver1.1 Please visit http://www.numen-tech.com for more patent information. th 3F., No. 96, Sec. 1, Jiafong 6 Road, Jhubei City, Hsinchu County 302, Taiwan. TEL: +886-3-658-9936 FAX: +886-3-550-2805 NumEn Tech. NU310 Absolute Maximum Ratings Parameter Value VIN to GND -0.5V to +520V CS -0.3V to (Vdd+0.3V) LD,PWM_D to GND -0.3V to (Vdd-0.3V) GATE to GND -0.3V to (Vdd+0.3V) VDDMAX 13.5V Continuous Power Dissipation(TA=25℃) (Note1) 630mW 8Pin SO(derate 6.3mW/℃ above =25℃) Operating Temperature Range -40℃ to +85℃ Junction Temperature +125℃ Storage Temperature Range -65℃ to +150℃ Note1: Exceeding these ratings could cause permanent damage to the device. All voltages are with respect to ground. Currents are positive into, negative Out of the specified terminal. -2- Ver1.1 Please visit http://www.numen-tech.com for more patent information. th 3F., No. 96, Sec. 1, Jiafong 6 Road, Jhubei City, Hsinchu County 302, Taiwan. TEL: +886-3-658-9936 FAX: +886-3-550-2805 NumEn Tech. NU310 Electrical Characteristics and Recommended Operating Conditions Characteristic Symbol Condition Min. Typ. Max. Unit Input Dc supply voltage range VINDC DC input voltage 15.0 - 500 V Shut-Down mode supply current IINSD Pin PWM_D to GND,VIN=15V - 0.5 1 mA Internally regulated voltage VDD 7.0 7.5 8.0 V Maximal pin VDD voltage VDDmax When an external voltage applied to pin VDD - - 13.5 V VDD Current available for external circuitry1 IDD(ext) VIN =15-100V - - 1.0 mA UVLO VIN rising 6.45 6.7 6.95 V △UVLO VIN falling - 500 - mV Pin PWM_D input low voltage VEN(IO) VIN=15-500V - - 1.0 V Pin PWN_D input high voltage VEN(hi) VIN=15-500V 2.4 - - V Pin PWN_D Pull- down resistance REN VEN=5V 50 100 150 KΩ Current sense pull-in Threshold voltage Vcs(hi) @TA=-40℃to+85℃ 225 250 275 mV VGATE(hi) lout=10mA VDD -0.3 - VDD V GATE low output Voltage VGATE(lo) lout= -10mA 0 - 0.3 V Rosc=1.00MΩ 20 25 30 Oscillator frequency fosc Rosc=226KΩ 80 100 120 - - 100 % VDD under voltage lockout threshold VDD under voltage lockout threshold GATE high putput Voltage VIN=15-500V,IDD(ext)=0,pin Gate open kHZ FPWMhf=25kHz,at Maximum Oscillator PWM Duty Cycle DMAXhf Linear Dimming pin Voltage range VLD @TA=<85℃,Vin=20V 0 - Vcs(hi) mV Current sense blanking interval TBLANK Vcs=0.55VLD, VLD=VDD - - 300 ns Delay from CS trip to Gate lo tDELAY - 300 ns GATE output rise time tRISE CGATE=500PF - 30 50 ns GATE output fall time tFALL CGATE=500PF - 30 50 ns Thermal shut down TSD - 150 GATE.CS to GND VIN =20V, VLD =0.15V,Vcs=0 - To 0.22V after T BLANK -3- ℃ Ver1.1 Please visit http://www.numen-tech.com for more patent information. th 3F., No. 96, Sec. 1, Jiafong 6 Road, Jhubei City, Hsinchu County 302, Taiwan. TEL: +886-3-658-9936 FAX: +886-3-550-2805 NumEn Tech. NU310 Block diagram VIN VIN VDD LDO OSC 7.5V ROSC VDD S Q 250mV GATE R LD CS PWM_D NU310 Rsense GND Typical Application Circuit -4- Ver1.1 Please visit http://www.numen-tech.com for more patent information. th 3F., No. 96, Sec. 1, Jiafong 6 Road, Jhubei City, Hsinchu County 302, Taiwan. TEL: +886-3-658-9936 FAX: +886-3-550-2805 NumEn Tech. NU310 Application Information AC/DC Off-Line Applications Optionally, a simple passive power factor correction circuit, consisting of 3 diodes and 2 capacitors, can be added as shown in the typical application circuit diagram of Figure 1. The NU310 is a low-cost off-line buck or boost converter control IC specifically designed for driving multi-LED stings or arrays. It can be operated from either universal AC line or any DC voltage between 8-450V. Optionally, a passive power factor correction circuit can be used in order to pass the AC harmonic limits set by EN 61000-3-2 Class C for lighting equipment having input power less than 25W. The NU310 can drive up to hundreds of High-Brightness (HB) LEDs or multiple strings of HB LEDs. The LED arrays can be configured as a series or series/parallel connection. The NU310 regulates constant current that ensures controlled brightness and spectrum of the LEDs, and extends their lifetime. The NU310 features an enable pin (PWM_D) that allows PWM control of brightness. The NU310 can also control brightness of LEDs by programming continuous output current of the LED driver (so-called linear dimming) when a control voltage is applied to the LD pin. The NU310 includes an internal high-voltage linear regulator that powers all internal circuits and can also serve as a bias supply for low voltage external circuitry. Supply Current A current of 1mA is needed to start the NU310. As shown in block diagram, this current is internally generated in NU310without using bulky startup resistors typically required in the offline applications. Moreover, in many applications the NU310can be continuously powered using its internal linear regulator that provides a regulated voltage of 7.5V for all internal circuits. Setting Light Output When the buck converter topology of Figure 1 is selected, the peak CS voltage is a good representation of the average current in the LED. However, there is a certain error associated with this current sensing method that needs to be accounted for. This error is introduced by the difference between the peak and the average current in the inductor. For example if the peak-to-peak ripple current in the inductor is 150mA, to get a 500mA LED current, the sense resistor should be 250mV/(500mA+ 0.5*150mA) = 0.43Ω. LED Driver Operation The NU310 can control all basic types of converters, isolated or non-isolated, operating in continuous or discontinuous conduction mode. When the gate signal enhances the external power MOSFET, the LED driver stores the input energy in an inductor or in the primary inductance of a transformer and, depending on the converter type, may partially deliver the energy directly to LEDs The energy stored in the magnetic component is further delivered to the output during the off cycle of the power MOSFET producing current through the string of LEDs (Flyback mode of operation). When the voltage at the VDD pin exceeds the UVLO threshold the gate drive is enabled. The output current is controlled by means of limiting peak current in the external power MOSFET. A current sense resistor is connected in series with the source terminal of the MOSFET. The voltage from the sense resistor is applied to the CS pin of the NU310. When the voltage at CS pin exceeds a peak current sense voltage threshold, the gate drive signal terminates, and the power MOSFET turns off. The threshold is internally set to 250mV, or it can be programmed externally by applying voltage to the LD pin. When soft start is required, a capacitor can be connected to the LD pin to allow this voltage to ramp at a desired rate, therefore, assuring that output current of the LED ramps gradually. Dimming Dimming can be accomplished in two ways, separately or combined, depending on the application. Light output of the LED can be controlled either by linear change of its current, or by switching the current on and off while maintaining it constant. The second dimming method (so-called PWM dimming) controls the LED brightness by varying the duty ratio of the output current. The linear dimming can be implemented by applying a control voltage from 0 to 250mV to the LD pin. This control voltage overrides the internally set 250mV threshold level of the CS pin and programs the output current accordingly. For example, a potentiometer connected between VDD and ground can program the control voltage at the CS pin. Applying a control voltage higher than 250mV will not change the output current setting. When higher current is desired, select a smaller sense resistor. The PWM dimming scheme can be implemented by applying an external PWM signal to the PWM_D pin. The PWM signal can be generated by a microcontroller or a pulse generator with a duty cycle proportional to the amount of desired light output. This signal enables and disables the converter modulating the LED current in the PWM fashion. In this mode, LED current can be in one of the two states: zero or the nominal current set by the current sense resistor. It is -5- Ver1.1 Please visit http://www.numen-tech.com for more patent information. th 3F., No. 96, Sec. 1, Jiafong 6 Road, Jhubei City, Hsinchu County 302, Taiwan. TEL: +886-3-658-9936 FAX: +886-3-550-2805 NumEn Tech. NU310 not possible to use this method to achieve average brightness levels higher than the one set by the current sense threshold level of the NU310. By using the PWM control method of the NU310, the light output can be adjusted between zero and 100%. The accuracy of the PWM dimming method is limited only by the minimum gate pulse width, which is a fraction of a percent of the low frequency duty cycle. Some of the typical waveforms illustrating the PWM dimming method used with the application circuit of Figure 1 are given below. Programming Operating Frequency The required value of the inductor is given by: L = (VIN - VLEDs) * TON / (0.3 * ILED) = 4.6mH Input Bulk Capacitor An input filter capacitor should be designed to hold the rectified AC voltage above twice the LED string voltage throughout the AC line cycle. Assuming 15% relative voltage ripple across the capacitor, a simplified formula for the minimum value of the bulk input capacitor is given by: CMIN = ILED*VLEDs*0.06/VIN^2 CMIN = 22 μF, a value 22μF/250V can be used. The operating frequency of the oscillator is programmed between 25 and 300kHz using an external resistor connected to the Rosc pin: FOSC = 25000/ (Rosc [kΩ] + 22) [kHz] A passive PFC circuit at the input requires using two series connected capacitors at the place of calculated CMIN. Each of these identical capacitors should be rated for 1/2 of the input voltage and have twice as much capacitance. Enable Power Factor Correction When the input power to the LED driver does not exceed 25W, a simple passive power factor correction circuit can be added to the NU310 typical application circuit of Figure 1 in order to pass the AC line harmonic limits of the EN610003-2 standard for Class C equipment. The typical application circuit diagram shows how this can be done without affecting the rest of the circuit significantly. A simple circuit consisting of 3 diodes and 2 capacitors is added across the rectified AC line input to improve the line current harmonic distortion and to achieve a power factor greater than 0.85. The NU310 can be turned off by pulling the PWM_D pin to ground. When disabled, the NU310 draws quiescent current of less than 1mA. Output Open Circuit Protection When the buck topology is used, and the LED is connected in series with the inductor, there is no need for any protection against an open circuit condition in the LED string. Open LED connection means no switching and can be continuous. DC/DC Low Voltage Applications Inductor Design Buck Converter Operation Referring to the typical application circuit below the value can be calculated from the desired peak-to-peak LED ripple current in the inductor. Typically, such ripple current is selected to be 30% of the nominal LED current. In the example given here, the nominal current ILED is 350mA. The next step is determining the total voltage drop across the LED string. For example, when the string consists of 10 High-Brightness LEDs and each diode has a forward voltage drop of 3.0V at its nominal current; the total LED voltage VLEDS is 30V. Knowing the nominal rectified input voltage VIN = 120V*1.41 = 169V, the switching duty ratio can be determined, as: The buck power conversion topology can be used when the LED string voltage is needed to be lower than the input supply voltage. The design procedure for a buck LED driver outlined in the previous chapters can be applied to the low voltage LED drivers as well. However, the designer must keep in mind that the input voltage must be maintained higher than 2 times the forward voltage drop across the LEDs. This limitation is related to the output current instability that may develop when the NU310 buck converter operates at a duty cycle greater than 0.5. This instability reveals itself as an oscillation of the output current at a sub-harmonic of the switching frequency. Flyback Operation D = VLEDs /VIN = 30/169 = 0.177 Then, given the switching frequency, in this example: fOSC = 50KHz, the required on-time of the MOSFET transistor can be calculated: TON = D/fOSC = 3.5 microsecond This power conversion topology can be used when the forward voltage drop of the LED string is higher, equal or lower than the input supply voltage. For example, the buck-boost topology can be appropriate when input voltage is supplied by an automotive battery (12V) and output string -6- Ver1.1 Please visit http://www.numen-tech.com for more patent information. th 3F., No. 96, Sec. 1, Jiafong 6 Road, Jhubei City, Hsinchu County 302, Taiwan. TEL: +886-3-658-9936 FAX: +886-3-550-2805 NumEn Tech. NU310 consists of three to six HB LEDs, as the case may be for tail and break signal lights. In the buck-boost converter, the energy from the input source is first stored in the inductor or a Flyback transformer when the switching transistor is ON. The energy is then delivered to the output during the OFF time of the transistor. When the energy stored in the Flyback inductor is not fully depleted by the next switching cycle (continuous conduction mode) the DC conversion between input and output voltage is given by: VOUT = - VIN *D/ (1-D) The output voltage can be either higher or lower than the input voltage, depending on duty ratio. Let us discuss the above example of an automotive LED driver that needs to drive three HB LEDs at 350mA. Knowing the nominal input voltage VIN=12V, the nominal duty ratio can be determined, as D= VLEDs / (VIN + VLEDs) =9/ (12+9) =0.43 Then, given the switching frequency, in this example fOSC=50KHz, the required on-time of the MOSFET transistor can be calculated: TON =D/fOSC=8.6 microsecond The required value of the inductor is given by: L = VIN * TON / (0.3 * ILED) = 0.98mH, use 1mH Output Capacitor Unlike the buck topology, the buck-boost converter requires an output filter capacitor to deliver power to the LED string during the ON time of switching the transistor, when the Flyback inductor current is diverted from the output of the converter. In order to average the current in the LED, this capacitor must present impedance to the switching output AC ripple current that is much lower than the dynamic impedance ROUT of the LED string. If we assume ROUT =3 Ohm in our example, in order to attenuate the switching ripple by a factor of 10, a capacitor with equivalent series resistance (ESR) of 0.3 Ohm is needed. A chip SMT tantalum capacitor can be selected for this purpose. Figure 1: Typical Application Circuit -7- Ver1.1 Please visit http://www.numen-tech.com for more patent information. th 3F., No. 96, Sec. 1, Jiafong 6 Road, Jhubei City, Hsinchu County 302, Taiwan. TEL: +886-3-658-9936 FAX: +886-3-550-2805 NumEn Tech. NU310 Figure 2: Isolated Circuit Figure 3: NU310 75V_220mA Application Circuit Figure 4: NU310 25V_350mA Application Circuit -8- Ver1.1 Please visit http://www.numen-tech.com for more patent information. th 3F., No. 96, Sec. 1, Jiafong 6 Road, Jhubei City, Hsinchu County 302, Taiwan. TEL: +886-3-658-9936 FAX: +886-3-550-2805 NumEn Tech. NU310 Package Dimensions SOP-8 -9- Ver1.1 Please visit http://www.numen-tech.com for more patent information. th 3F., No. 96, Sec. 1, Jiafong 6 Road, Jhubei City, Hsinchu County 302, Taiwan. TEL: +886-3-658-9936 FAX: +886-3-550-2805 NumEn Tech. NU310 Restrictions on product use NUMEN Tech. reserves the right to update these specifications in the future. The information contained herein is subject to change without notice. NUMEN Technology will continually working to improve the quality and reliability of its products. Nevertheless, semiconductor device in general can malfunction or fail due to their inherent electrical sensitivity and vulnerability to physical stress. It is the responsibility of the buyer, when utilizing NUMEN products, to comply with the standards of safety in making a safe design for the entire system, and to avoid situations in which a malfunction or failure of such NUMEN products could cause loss of human life, bodily injury or damage to property. In developing your designs, please ensure that NUMEN products are used within specified operating ranges as set forth in the most recent NUMEN products specifications. The NUMEN products listed in this document are intended for usage in general electronics applications (lighting system, personal equipment, office equipment, measuring equipment, industrial robotics, domestic appliances, etc.). These NUMEN products are neither intended nor warranted for usage in equipment that requires extraordinarily high quality and/or reliability or a malfunction or failure of which may cause loss of human life or bodily injury (“Unintended Usage”). Unintended Usage include atomic energy control instruments, airplane or spaceship instruments, transportation instruments, traffic signal instruments, combustion control instruments, medical instruments, all types of safety devices, etc.. Unintended Usage of NUMEN products listed in this document shall be made at the customer’s own risk. - 10 - Ver1.1 Please visit http://www.numen-tech.com for more patent information. th 3F., No. 96, Sec. 1, Jiafong 6 Road, Jhubei City, Hsinchu County 302, Taiwan. TEL: +886-3-658-9936 FAX: +886-3-550-2805