Universal Step-Down PWM Control For High Brightness LED Lighting Control HT7L4091 Revision: v1.10 Date: ����������������� November 01, 2011 HT7L4091 Universal Step-Down PWM Control For High Brightness LED Lighting Control Table of Contents Features.......................................................................................................................... 4 Applications.................................................................................................................... 4 General Description....................................................................................................... 4 Ordering Information..................................................................................................... 4 Pin Assignment.............................................................................................................. 5 Pin Description............................................................................................................... 5 Absolute Maximum Ratings.......................................................................................... 5 Recommended Operating Ranges................................................................................ 6 Block Diagram................................................................................................................ 6 Electrical Characteristics.............................................................................................. 7 Functional Description.................................................................................................. 8 LED Current Control.................................................................................................................. 8 Programmable Off Time............................................................................................................ 8 Current Sense........................................................................................................................... 9 Leading-Edge Blanking............................................................................................................. 9 Frequency Jitter Function.......................................................................................................... 9 Input Supply Current................................................................................................................. 9 Start-up Current and Auxiliary Power Source......................................................................... 10 Linear Dimming....................................................................................................................... 10 PWM Dimming........................................................................................................................ 10 LED Open and Short Circuit Protection.................................................................................. 10 Enhanced Short Circuit Protection.......................................................................................... 11 Application Description............................................................................................... 12 Input Bulk Capacitor – C1....................................................................................................... 12 Switching Frequency and Duty Cycle..................................................................................... 13 Turn-off Time........................................................................................................................... 13 Off-time Resistor – RT ............................................................................................................ 14 Inductor Design....................................................................................................................... 14 Current Sense Resistor – RCS ................................................................................................ 14 Input Supply Current .............................................................................................................. 15 Input Limit Resistor (RIN)......................................................................................................... 15 Output Capacitor – CO ............................................................................................................ 15 Typical Performance Characteristics......................................................................... 16 Efficiency vs. Power Supply Circuit – Working Frequency..................................................... 16 Efficiency for Resistor Only Power and Single Input Voltage.................................................. 17 Efficiency Using Resistor Only Power and 85~265 VAC Input.................................................. 18 Typical Application Circuit.......................................................................................... 19 Rev. 1.10 2 November 01, 2011 HT7L4091 Universal Step-Down PWM Control For High Brightness LED Lighting Control Other Application Circuit............................................................................................. 20 No Input Bulk Capacitor Circuit .............................................................................................. 20 High Efficiency Circuit............................................................................................................. 20 BJT Power Supply Application Circuit..................................................................................... 21 Package Information.................................................................................................... 23 8-pin SOP (150mil) Outline Dimensions................................................................................. 23 Reel Dimensions..................................................................................................................... 24 Carrier Tape Dimensions......................................................................................................... 25 Rev. 1.10 3 November 01, 2011 HT7L4091 Universal Step-Down PWM Control For High Brightness LED Lighting Control Features ●● Input supply AC voltage range: 100V~240V ●● Ultra Low Power-on Start-up current < 30μA ●● Integrated 25V Zener diode internally connected to VIN pin ●● 5V LDO output voltage with 6mA driving current for external components ●● Frequency jitter function for enhanced EMI performance ●● Efficiency > 85% ●● Under Voltage Lockout Function - UVLO ●● Current mode operation with cycle-by-cycle current limiting ●● Over Temperature Protection Function ●● High-current FET Drive Output ●● Linear and PWM Dimming Function ●● Enhanced Short Circuit Protection Function Applications ●● AC/DC and DC/DC Power control For High Power LED Lighting ●● RGB back lighting LED driver ●● Flat Panel Displays Back Lighting ●● General Purpose Constant Current Source ●● Signage and Decorative LED lighting ●● Battery Chargers General Description The HT7L4091 device provides a low-cost solution for active current mode PWM controls of High Intensity LED drive systems supplied by either AC or DC line power lines. The device operates in constant off-time mode which is suitable for buck LED drivers. The low start-up and operating currents provides flexible power requirements for high efficiency or low cost applications. The switch frequency off-time can be programmed using an external resistor. The peak current mode control achieves good output current regulation without requiring loop compensations for a wide range of input voltages. Included in the device is a PWM dimming input which can accept an external control signal with a duty ratio from 0 to 100%. The output current can be programmed from 0 to 250mA by applying an external control voltage on the linear dimming control input. The device includes a frequency jitter function which helps to reduce EMI power supply emissions. from damage should the LEDs be short circuited. . The device requires a minimum number of external standard components and is available in an 8-pin NSOP package for small area PCB applications. Ordering Information Part Number. Rev. 1.10 Function Description HT7L4091 Frequency Jitter Function Enabled HT7L4091-1 Frequency Jitter Function Disabled 4 November 01, 2011 HT7L4091 Universal Step-Down PWM Control For High Brightness LED Lighting Control Pin Assignment VIN 1 8 RT CS 2 7 LD GND 3 6 VDD GDR 4 5 PDM HT7L4091 8 SOP-A Pin Description Pin Name I/O Description VIN I Input voltage pin CS I LED string current sense input GND — Power ground GDR O Gate driver for the external MOSFET PDM I PWM dimming pin Also functions as enable input pin. VDD O Positive Power supply Used for the internal circuits except the gate driver circuit. A 0.1μF capacitor must be connected between the VDD and the GND pins. LD I Linear dimming pin Set the current sense threshold as long as the voltage on this pin is less than 250mV (typ.). RT I Oscillator control pin A resistor is connected between the RT and the GND pins to set the off-time. Absolute Maximum Ratings Output Current Peak ....................................................................................................................... 1A Storage Temperature Range.......................................................................................-65°C ~ +150°C Junction Temperature Range......................................................................................-40°C ~ +150°C CS, PDM, LD ,RT, to GND..................................................................................-0.3V to (VDD +0.3V) Power Dissipation at Ta<25 °C................................................................................................... 0.6W Thermal Resistance, SOP-8 θJA..........................................................................................150°C/W ESD Voltage Protection, Human Body Model............................................................................. 6KV ESD Voltage Protection, Machine Model................................................................................... 400V Note: These are stress ratings only. Stresses exceeding the range specified under “Absolute Maximum Ratings” may cause substantial damage to the device. Functional operation of this device at other conditions beyond those listed in the specification is not implied and prolonged exposure to extreme conditions may affect device reliability. Rev. 1.10 5 November 01, 2011 HT7L4091 Universal Step-Down PWM Control For High Brightness LED Lighting Control Recommended Operating Ranges Input Supply Voltage....................................................................................UVLO(H)+0.1V ~ VClamp Operating Temperature Range....................................................................................-40°C ~ +105°C Note 1: Absolute maximum ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is intended to be functional, but do not guarantee specific performance limits. The guaranteed specifications apply only for the test conditions listed. Note 2: The power supply pin should not be driven by a DC, low impedance power source greater than the VCLAMP voltage specified in the Electrical Characteristics section. Block Diagram VIN PDM ON UVLO 25V VDD LDO PWMD 100k GDR OTP Power On Reset 0.5V Q CS R QB S Blank 0.25V Q RT OSC (jitter) R QB S LD GND Rev. 1.10 6 November 01, 2011 HT7L4091 Universal Step-Down PWM Control For High Brightness LED Lighting Control Electrical Characteristics Symbol Description (VIN=17V, Ta=25°C, unless otherwise specified) Test Condition Min. Typ. Max. Unit — Input VINDC Input DC supply voltage 8.5 — VClamp V — 0.6 1 mA — 15 30 μA 25 27.6 V IIN Input Operation Current VINDC ≥ 17V, RT = 410kΩ GDR pin floating IINST Startup Input current VINDC < 15V, RT = 410kΩ VClamp VIN Clamp Voltage IIN=10mA 22.4 Internal Regulator VDD Internally regulated voltage VINDC=12V~26V 4.5 5 5.5 V ΔVDD, line Line regulation of VDD VINDC=12V~26V, IDD = 0mA 0 — 100 mV ΔVDD, load Load regulation of VDD VINDC=17V, IDD = 0mA ~ 3mA 0 — 100 mV VUVLO(H) VINDC under voltage lockout high VINDC rising threshold 7.5 8 8.5 V VUVLO(L) VINDC under voltage lockout low threshold VINDC falling 6.7 7.2 7.7 V VEN(L) Input low voltage for PDM pin VINDC=12V~26V — — 0.8 V VEN(H) Input high voltage for PDM pin VINDC=12V~26V 2.0 — — V REN PDM pin Pull-low resistor — 50 100 150 KΩ VCS(TH) Current sense trip threshold voltage — 0.24 0.248 0.255 V Tdelay Delay from CS trip to GDR — 110 — ns VLD Linear Dimming pin voltage range 0 — VCS_TH V Tblank Blanking interval Toff Off time RT=410kΩ VOL GATE Output Low Level VOH GATE Output High Level Trise Tfall TOTP Thermal shutdown temperature ∆TOTP Thermal shutdown temperature hysteresis ∆fJitter Switch frequency jitter ratio TJP Jitter Period VCS-short Short circuit protection Voltage VCS =VCS_TH + 50mV — — 200 300 400 ns 14.7 16.4 18.1 μs VINDC = 17V, Io = -20mA — — 0.3 V VINDC = 17V, Io = 20mA 12 — — V Gate output rise time CGATE = 500pF — 120 — ns Gate output fall time CGATE = 500pF — 50 — ns — — 140 — — — — 25 — — — — ±4 — % — 4 — ms 0.45 0.5 0.55 V fsw = 60kHz — Note 3: Specifications are production tested at TA=room temperature. Specifications over the -40°C to 85°C operating temperature range are assured by design, characterization and correlation with Statistical Quality Controls (SQC). Rev. 1.10 7 November 01, 2011 HT7L4091 Universal Step-Down PWM Control For High Brightness LED Lighting Control Functional Description The HT7L4091 is a universal AC/DC constant current LED driver designed for peak current mode control. The device provides both LED Linear and PWM dimming current functions. The high input voltage from a rectified 85V to 260V AC power is clamped to under 25V by an external circuit and an internal Zener diode. The device also contains an input Under-Voltage-Lockout (UVLO) circuit. When the voltage supplied on the VIN pin exceeds the UVLO high threshold, the gate driver is enabled. If the input voltage falls below the UVLO low threshold, the gate driver is turned off. LED Current Control The HT7L4091 device is a constant off-time peak current mode controller. With reference to the Application Circuit, the LED peak current is programmed by an external current sense resistor (RCS) connected between the CS and the ground pins. The CS pin is connected to a non-inverting terminal of an internal comparator of which an internal 250mV reference is tied to the inverting terminal. The LED peak current through the RCS resistor will generate a voltage which is applied on the comparator non-inverting terminal and compare with the internal 250mV reference voltage. If the voltage on the CS pin is less than the internal reference voltage 250mV, the LED gate driving circuitry will be turned on. While the voltage on the CS pin is larger than the internal reference voltage, the LED gate driving circuitry will be turned off for a constant Toff time. After the Toff time, the gate driving circuitry will be turn on if the voltage on the CS pin is less than the internal reference voltage. Good line regulation is a feature of constant off-time operation and the LED current is independent of the input voltage. Since the inductor current ripple is dependent on the LED string voltage, the LED string voltage variation will result in LED current variation. This is typically not a problem since the LED voltage variation for a given load is fairly small. RCS can be calculated using the following equation: = R CS 0.�5 = Ipeak 0.�5 1 + 1 × Ripple ⋅ ILED � ( ) Where Ipeak is the Maximum LED Current, Ripple is the Peak to Peak LED Current, and ILED is the Average LED Current. Ripple can be controlled by the inductor. Toff × Vout I LED × Ripple=I Ripple = L Refer to “Inductor Design” for the inductor calculation. Refer to “Programmable Off Time” for Toff calculation. Programmable Off Time The device operates in a constant off-time mode. A resistor connected between the RT pin and the ground pin generates a constant current source which is used to charge an internal capacitor and determine the off-time. Increasing the resistance reduces the amplitude of the current source and increases the off-time. The relationship between the resistor RT and the off-time is given by the following formula: Toff = CT × RT CT=36pF~44pF, CT_typ=40pF. For a given Toff and duty cycle, the switching frequency (fs) can be decided. The duty cycle is determined by the input and output voltages. Rev. 1.10 8 November 01, 2011 HT7L4091 Universal Step-Down PWM Control For High Brightness LED Lighting Control Current Sense The current sense input is connected to the non-inverting inputs of two comparators. The inverting terminal of one comparator is tied to an internal 250mV reference whereas the other comparator inverting terminal is connected to the LD pin. The outputs of both these comparators are fed into an OR gate and the output of the OR gate is fed into the reset pin of a flip-flop. If a flip-flop reset event is triggered by the OR gate output a signal occurs where the external MOSFET gate driving circuitry will be turned off. Therefore, the comparator which has the lower voltage at the inverting terminal determines when the gate driving output is turned off. Leading-Edge Blanking Each time the power MOSFET is switched on, a turn-on transient spike will occur on the CS pin. To avoid premature termination of the switching pulse, a TBlank leading-edge blank time is generated during the MOSFET switch turn-on to prevent false triggering of the current sense comparator. During this blanking period, the current-limit comparator is disabled and the gate driving circuitry will not be switched off. In certain rare situations, the internal blanking time might not be long enough to filter out the turnon spike. In such situations, it will be necessary to add an external RC filter between the external sense resistor (RCS) and the CS pin. Frequency Jitter Function The device also includes a frequency jitter function. The frequency has a variation range of +4% to -4% within four milliseconds. The frequency jitter function helps reduce power supply line EMI emissions with minimum line filters. Input Supply Current The input supply current is determined by the input operating current and the current drawn by the external MOSFET gate driver. This means that the input supply current depends upon the switching frequency and the external MOSFET gate charge. IINSP = IIN + Qgate × fS , where IINSP is the input supply current taken from the VIN pin, fS is the switching frequency Qgate is the gate charge of the external MOSFET and IIN is the input operation current. The application circuit should provide enough IINSP to ensure the application can work properly Rev. 1.10 9 November 01, 2011 HT7L4091 Universal Step-Down PWM Control For High Brightness LED Lighting Control Start-up Current and Auxiliary Power Source The power consumption of the HT7L4091 is one of the major efficiency losses if IINSP drops from the rectified AC source whose voltage is much higher than the voltage used by the device. For efficiency improvements, a small start-up current from the rectified AC source is used to start up the HT7L4091 and IINSP can be provided from the auxiliary power source, for example: auxiliary winding. The start-up current should take into consideration the Cin (Vin Capacitor) charge current and the current consumption of the HT7L4091 during start-up (Iinst). The Cin charge current shall consider how fast (tstart-up) the application is required to start operation. The start-up current can be calculated using the follow equation: Istart −= I inst + up Cin × VUVLO( H ) t start − up The current from auxiliary power source should be: = I aux I INSP − Istart −up The start-up current allows a start-up resistor with a high resistance and a low-power rating. The start-up resistor (RINST) is used to supply the start-up power for the device from the rectified AC source. RINST can be calculated using the following equation: R INST = 2 ⋅ Vmin,AC − VUVLO(H) Istart-up Linear Dimming The Linear Dimming pin is used to control the LED current. The VDD pin voltage can be connected to the LD pin to obtain a voltage corresponding to the desired voltage across RCS. The LD pin can adjust the current level to reduce the illumination intensity of the LEDs. To adjust the external LD pin voltage from 0mV to 250mV can adjust the LED current during operation. To use the internal 250mV as the reference voltage, the LD pin can be connected to VDD. PWM Dimming An external enable input named PDM is provided and can be utilized for PWM dimming of the LED string. When the external PWM signal is zero, the gate driving circuitry is turned off while the gate driving circuits are turned on when the PWM signal is high. LED Open and Short Circuit Protection There will be no abnormal behavior if the LEDs are open circuit. While some LEDs are shorted, the output voltage will be adjusted automatically for the condition. Rev. 1.10 10 November 01, 2011 HT7L4091 Universal Step-Down PWM Control For High Brightness LED Lighting Control Enhanced Short Circuit Protection When most LEDs are shorted in the application circuit, the current regulation may lose control resulting in the current increasing to an extremely high level. When the current is more than twice of the set Ipeak, resulting from externally shorted LEDs, the device will shut down gate driving operations. The operation state is shown in the accompanying figure. When the circuit is operating normally, VCS can be limited to VCS-TH, while some LEDs are shorted, the LED current is still limited and the output voltage is adjusted to meet the current requirement. If the circuit encounters a serious short, the voltage increase of (current) in TBlank would be larger than the decrease in TOFF, VCS will exceed VCS-TH and reach VCS-Short. The HT7L4091 will then shut down the gate driver until UVLO resets the HT7L4091. Slight Short Normal Serious Short Shut Down VCS-Sho�t VCS-TH VCS TBlank TOff Cin Rlim D1 L1 CVDD VDD Vin LD GDR CS PDM RT RCS GND Clim Rev. 1.10 11 November 01, 2011 HT7L4091 Universal Step-Down PWM Control For High Brightness LED Lighting Control Application Description This section shows how to design a buck circuit LED application using a simple example. For other application conditions, such as high efficiency solutions, refer to the HT7L4091 application notes for more details. For example: AC Input voltage: VAC_typ =110Vrms; VAC_min =95Vrms; VAC_max =125Vrms; FAC=60Hz Target working condition: FPWM > 40kHz Output Voltage: LED string ×LED Voltage =8×(3~3.3)=24V~26.4V, typical 25.2 Average Output LED Current: ILED= 400mA Expected efficiency: η=90% Refer to the typical application circuit. Input Bulk Capacitor – C1 The input Bulk Capacitor determines the ripple amplitude of input voltage after rectification. A large capacitance generates a smaller input voltage ripple amplitude. The first design criterion to meet is that the maximum LED string voltage should be less than 80% of the minimum AC input voltage (Vmin,AC). Note that 80% is a rough estimate here. Here the large ripple amplitude has a wide frequency variation which leads to increase in circuit power losses. Assume that the input voltage DC ripple (ΔVDCripple%) is equal to 30% and then calculate the C1 value. � ×VAC_min ×(1-ΔVDCripple%)×0.8= � ×95×(1-30%)×0.8=75.2V>26.4V(Maximum Output Voltage) Above formula means 30% input voltage ripple is approved that exceed output voltage. Finally, a useful rule can find the valley voltage of the input voltage. Using the figure below, it is necessary to calculate the charge time and discharge time of the input bulk capacitor. VIN 8.333ms = 1 120Hz ΔV Tcharge Tdischarge t The waveform of input voltage in the C1 = TCP Charge period: Tcha�ge = Rev. 1.10 1 = 8.333ms 2 × FAC ∆V sin−1(1 − ) TCP VI� × 1 − , where � 90 12 ∆V VI� = ΔVDCripple% November 01, 2011 HT7L4091 Universal Step-Down PWM Control For High Brightness LED Lighting Control Tdischarge=TCP– Tcharge TDischarge =8.333ms – 8.333�s sin−1(1 − 30%) × 1 − = 6.2232ms � 90 Then, the minimum capacitor value can be calculated as: C1 ≥ (2 × n × VLED�ax × ILED ) × TDischa�ge η× ( 2 × VAC�in ) � − ( VDC�in ) � = (2 × 16 × 3.3V × 200mA) × 6.2232ms = 14.3uF � � 0.9 × � × 85 − � × 85 × 0.7 ( ) ( ) Choose C1=22uF Considering ±20% capacitance variation, the worst case lower value of the capacitance is 17.6uF, which is much larger than 14.3uF. It can be calculated that the input DC ripple is 24.5% when the input Buck capacitor is 17.6uF. Therefore, if the real capacitor value is less than the calculated value, the voltage ripple will exceed the maximum range of 30% which is the specified assumption in the calculation. Switching Frequency and Duty Cycle Frequency interference should be taken into account to minimise interference with other electrical appliances. Here set the minimum switching frequency to a value of 40kHz for safety. If EMI suppression is good, the switching frequency can be decreased to 30kHz to obtain better efficiency. Since the HT7L4091 operates in constant off time, the switching frequency would be changed by the input and output voltage. The slowest switching frequency occurs when the duty cycle is at a maximum value. The maximum duty cycle can be calculated as, = D�ax Vo_ �ax = VDC_ �in n ⋅ VLED_ �ax + VF�D1 2 ⋅ VAC_ �in × (1 − V�ipple ) = 3.3 × 8 + 1.3 =0.2731 � × 95 × (1-�4.5%) Turn-off Time Toff = Rev. 1.10 1 − D�ax FPWM_ �in = 1 − 0.�731 =18.173us 40k 13 November 01, 2011 HT7L4091 Universal Step-Down PWM Control For High Brightness LED Lighting Control Off-time Resistor – RT A resistor connected to the RT pin determines the off-time which has a variation range from -10% to +10%. Since the working frequency has a minimum target, the CT is considered to calculated the RT: Toff = CT×RT → RT ≤ 18.173us = 413.03kΩ 44pF Choose 390KΩ and 13KΩ for RT are used The off time is: Toff_typ= CT_typ×RT = 40p x 403K = 16.1us Toff_max= CT_max×RT = 44p x 403K = 17.7us Toff_min= CT_max×RT = 36p x 403K = 14.5us The actual minimum frequency can be calculated as: F = PWM_ �in 1 − D�ax 1 − 0.�731 = = 41.17K Toff_ �ax 17.7u FPWM_TYP@Vac_min= 44.3KHz, FPWM_MAX@Vac_min =50.1 KHz Inductor Design The ripple current is selected to be 30% of the nominal LED current. If the LED average current ILED is 400mA, the LED string Voltage = n × VLED, max = 8 × 3.3V where VLED, max is the LED maximum forward voltage, then the inductor can be calculated by the following formula. L= Toff × n × VLED��ax 17.7us 8 3.15 = = 3.717mH ILED × Ripple 400mA 0.3 Choose L=3.8 mH Current Sense Resistor – RCS This current flows through the external sense resistor RCS and produces a ramp voltage on the CS pin. The comparators are constantly comparing the CS pin voltage with both the voltage on the LD pin and the internal 250mV reference voltage. Once the blanking time has elapsed, the output of these comparators can then reset the flip flop. When one output of these two comparators switches high, the flip flop is reset and the gate drive output switches low. The gate drive output stays low until the SR flip flop is set by the oscillator. In assuming a 30% ripple in the inductor, the current sense resistor RCS can be obtained using the following formula: = RCS 0.�5 = Ipeak 0.�5 0.�5 = = 0.543Ω (1 + 0.5 × 0.3) × 400�A 1 1+ × Ripple ⋅ ILEDavg � ( ) Choose RCS = 0.54Ω Rev. 1.10 14 November 01, 2011 HT7L4091 Universal Step-Down PWM Control For High Brightness LED Lighting Control Input Supply Current Assume that the input current drawn by the internal circuit from the VIN pin is the sum of the current with a value of 1.0mA and the current drawn by the gate driver of the external MOSFET (which in turn depends upon the switching frequency and the gate charge of the external FET). Assume that the gate charge Qgate is equal to 12nC. II�SP = II� + Qgate ⋅ FPWM = 1mA + 12nC × 50kHz = 1.6mA , where IINSP is the input current taken from the VIN pin, FPWM is the switching frequency, Qgate is the gate charge of the external FET and IIN is the current taken by the internal circuit. FPWM is considered about the minimum input voltage and CT has a minimum value. Input Limit Resistor (RIN) In this design, VAC_min = 95Vrms, VUVLO(H)_max = 17V Rin = 2 ⋅ VAC_ min × (1 − ∆VDCripple% ) − VUVLO(H)_max = II�SP � × 95 × (1 − 30%) − 17 =62.4kΩ 1.6�A Choose Rin=60kΩ The input limit resistor consider the high input voltage from the rectified clamp voltage of the internal Zener diode and operating current. Two 30KΩ / 1W resistors are used for Rin. Output Capacitor – CO The capacitor, CO, filters the current through the LEDs thus limiting the peak current of the LED string. Increasing the inductor ripple current corresponds to decreasing the inductor value and inductor size. In order to reduce the inductor value and size and obtain a smaller LED current ripple, the addition of a capacitor CO is a good way to do this. Usually, a several μF output capacitor is added in practical application circuits. Adding CO connected across the LED strings can reduce the LED current ripple and while increasing the inductor current ripple variation can decrease the inductor value and size. To assume inductor current ripple is 80%, a smaller inductor value could be calculated. L= Toff × n × VLED _ �ax 17.7us × 8 × 3.15 = =1.393mH ILED × Ripple 400�A × 0.8 Choose L=1.4mH and CO=1uF The actual values of CO and RCS may need to be adjusted to reduce the current ripple and obtain the target average LED current. A 1uF capacitor and an RCS as shown in the above calculation are a good start point to obtain an acceptable result. Since it takes some effort, it can reduce the inductor size/cost significantly. Rev. 1.10 15 November 01, 2011 HT7L4091 Universal Step-Down PWM Control For High Brightness LED Lighting Control Typical Performance Characteristics There are many different factors to influence efficiency of the application, such as the output power, working frequency, power supply circuit of the HT7L4091 and so on. The following are some measured results. Efficiency vs. Power Supply Circuit – Working Frequency There are several different power supply circuits for the device. Reference to the “Application circuit” for some examples. The different circuits provide different advantages, such as high efficiency or low cost. Follow are some efficiency compare for different power supply circuits. The condition i s VA C = 8 5 VA C ~ 2 6 0 VA C , F P W M > = 5 0 K H z ( H T 7 L 4 0 9 1 w o r k i n g f r e q u e n c y ) , output=52Vx0.2A=10.4W. Decreasing FPWM or increasing the output power can enhance the efficiency. efficiency compare in different application circuits (freq,min=50kHz) 92 efficiency (%) 90 88 86 auxiliary circuit 84 82 BJT circuit 80 typical circuit 78 80 130 180 230 280 Vac (V) The following is an example to enhance the efficiency by reducing the FPWM (HT7L4091 working frequency) to >=30 KHz. 93 efficiency compare with different frequency in two application circuits efficiency (%) 91 89 auxiliary circuit 30kHz 87 BJT circuit 30kHz auxiliary circuit 50kHz 85 83 BJT circuit 50kHz 81 80 130 180 230 280 Vac (V) Rev. 1.10 16 November 01, 2011 HT7L4091 Universal Step-Down PWM Control For High Brightness LED Lighting Control Efficiency for Resistor Only Power and Single Input Voltage The results of these curves are that each voltage corresponds to each input limit resistor. Theseresults show how good the application is designed for a narrow voltage range using a resistor to power the device. The “LED string” means how many LEDs are in one string. 16S means there are 16 LEDs in one string. The output (LED) power is kept at 10W. Input Voltage vs. Efficiency 95 Efficiency(%) 90 16S LED 14S LED 12S LED 85 80 10S LED 75 8S LED 70 65 80 130 180 230 280 Vac(V) LED String vs. Efficiency 95 85Vac 110Vac 170Vac 220Vac 260Vac Efficiency(%) 90 85 80 75 70 65 6 8 10 12 14 16 18 LED String Input voltage vs. LED Current LED Current(mA) 450 8S LED 400 350 10S LED 300 12S LED 250 14S LED 16S LED 200 150 80 130 180 230 280 Vac(V) Rev. 1.10 17 November 01, 2011 HT7L4091 Universal Step-Down PWM Control For High Brightness LED Lighting Control LED String vs. LED current LED current(mA) 450 85Vac 110Vac 170Vac 220Vac 400 350 300 260Vac 250 200 150 6 8 10 12 14 16 18 LED String Efficiency Using Resistor Only Power and 85~265 VAC Input These result curves use the same input limit resistor with different voltages. These results show the performance only using a resistor to power up the device for a full range voltage input. For improved efficiency with a full range voltage input, refer to the following application circuit. Input Voltage vs. Efficiency 95 Efficiency(%) 90 85 16S LED 14S LED 12S LED 10S LED 8S LED 80 75 70 65 60 80 130 180 230 280 Vac(V) LED String vs. Efficiency 95 85Vac 110Vac 170Vac 220Vac 260Vac Efficiency(%) 90 85 80 75 70 65 60 6 8 10 12 14 16 18 LED String Rev. 1.10 18 November 01, 2011 HT7L4091 Universal Step-Down PWM Control For High Brightness LED Lighting Control Input voltage vs. LED Current LED Current(mA) 460 8S LED 410 360 10S LED 310 12S LED 260 14S LED 16S LED 210 160 80 130 180 230 280 Vac(V) LED String vs. LED current LED current(mA) 460 410 360 310 260Vac 220Vac 170Vac 110Va 85Vac 260 210 160 6 8 10 12 14 16 18 LED String Typical Application Circuit EMI Lc RIN AC Ca1 Ca2 C1 Cfilter 22uF 400V 0.1uF 400V Zin PDM RT CT 5pF MOSFET GDR VDD C7 CIN 1uF/50V VIN LD 0.1uF VLED L Lc Essential components Used optional components Unused optional components Co D1 CS GND Rc CC Rcs RT This typical application circuit uses a fundamental buck converter circuit. Adding a CO capacitor can reduce the LED current ripple or reduce the inductor size while adding the RC and CC components can reduce spikes on the CS pin. If frequency jittering is considered to reduce EMI an optional 5pF CT may be used to stabilise the effect. Rev. 1.10 19 November 01, 2011 HT7L4091 Universal Step-Down PWM Control For High Brightness LED Lighting Control Other Application Circuit No Input Bulk Capacitor Circuit EMI Lc RIN Ra AC Ca1 Ca2 Co D1 Cfilter VLED L 0.1uF 400V Rb CIN Lc 1uF/50V VIN LD Essential components Used optional components Unused optional components 0.1uF C7 MOSFET GDR VDD CS PDM RT CT 5pF Rc GND Rcs CC RT The application circuit is a low cost implementation which can improve the PF used within the signal input voltage range. The auxiliary winding application circuit can be chosen when used for a universal input voltage. If frequency jittering is considered to reduce EMI effects, an optional 5pF capacitor may be added for stabilisation purposes. Refer to the application notes for more details. For more details refer to the application note. High Efficiency Circuit EMI Lc RIN AC Ca1 Ca2 C1 Cfilter 22uF 400V 0.1uF 400V D1 Zin VLED Tr CIN 1uF/50V Lc Ra LD GDR VDD C7 Essential components Used optional components Unused optional components PDM RT CT 5pF Rsb VIN Dg Rg MOSFET Rc CS GND Da Cc Rs RT The application circuit uses the auxiliary inductor to supply the device power to obtain better efficiency. If frequency jittering is used to reduce EMI interference effects, an optional 5pF capacitor may be used for stabilisation purposes. For more details, refer to the application note for auxiliary inductor applications. For more details refert to the application note. Rev. 1.10 20 November 01, 2011 HT7L4091 Universal Step-Down PWM Control For High Brightness LED Lighting Control BJT Power Supply Application Circuit The application circuit uses a BJT to supply the device power to obtain better efficiency. EMI Lc RIN BJT AC Ca1 Ca2 C1 Cfilter CIN 22uF 400V 0.1uF 400V Co D1 Zin 1uF 50V VLED L Lc VIN LD 0.1uF C7 PDM RT CT 5pF MOSFET GDR VDD CS GND Rc CC Rcs RT If frequency jittering is considered to reduce EMI an optional 5pF CT may be used to stabilise the effect. For more details refer to the application note. Rev. 1.10 21 November 01, 2011 HT7L4091 Universal Step-Down PWM Control For High Brightness LED Lighting Control Bill of Materials AC Input voltage: VAC_typ =110Vrms; VAC_min =95Vrms; VAC_max =115Vrms, FPWM ≥ 40kHz Output Voltage: LED string Voltage =24~26.4V Average Output LED Current: ILED= 400mA R+L+EMI circuit (8S20P) Components Value Package Part Number RT 1 390kΩ+ 13kΩ SMD 0805 — RCS 1 R300(0.3Ω)+R240(0.24Ω) SMD 1206 — C1 1 22uF/ 200V CapXon Radial Cfilter 1 0.1uF/ 200V Radial — RIN 1 30kΩ/1W x 2 AXIAL-0.6 — CIN 1 1uF / 50V SMD 0805 — 3~3.3V/30mA Everlight P-LCC-2 L2���������� C��������� -B4556��� AC2CB2 P0260AD LED Rev. 1.10 Quantity 160 FK series MOSFET 1 2A/600V NIKO-SEM DPAK C7 1 0.1uF SMD 0805 DBridge 1 1A/400V DF-S DF04S-T D1 1 2A/600V SMB STTH2R06U U1 1 HT7L4091 NSOP8 HOLTEK L 1 3.8mH Coilcraft 335D CM6676-AL 22 — November 01, 2011 HT7L4091 Universal Step-Down PWM Control For High Brightness LED Lighting Control Package Information 8-pin SOP (150mil) Outline Dimensions ●● MS-012 Symbol Nom. Max. A 0.228 ― 0.244 B 0.150 ― 0.157 C 0.012 ― 0.020 C’ 0.188 ― 0.197 D ― ― 0.069 E ― 0.050 ― F 0.004 ― 0.010 G 0.016 ― 0.050 H 0.007 ― 0.010 α 0° ― 8° Symbol Rev. 1.10 Dimensions in inch Min. Dimensions in mm Min. Nom. Max. A 5.79 ― 6.20 B 3.81 ― 3.99 C 0.30 ― 0.51 C’ 4.78 ― 5.00 D ― ― 1.75 E ― 1.27 ― F 0.10 ― 0.25 G 0.41 ― 1.27 H 0.18 ― 0.25 α 0° ― 8° 23 November 01, 2011 HT7L4091 Universal Step-Down PWM Control For High Brightness LED Lighting Control Reel Dimensions ●● SOP 8N Symbol Rev. 1.10 Description Dimensions in mm A Reel Outer Diameter 330.0±1.0 B Reel Inner Diameter 100.0±1.5 C Spindle Hole Diameter 13.0+0.5/-0.2 D Key Slit Width T1 Space Between Flange 12.8+0.3/-0.2 T2 Reel Thickness 18.2±0.2 2.0±0.5 24 November 01, 2011 HT7L4091 Universal Step-Down PWM Control For High Brightness LED Lighting Control Carrier Tape Dimensions ●● SOP 8N Symbol Rev. 1.10 Description Dimensions in mm W Carrier Tape Width P Cavity Pitch 8.0±0.1 E Perforation Position 1.75±0.1 F Cavity to Perforation (Width Direction) 5.5±0.1 D Perforation Diameter 1.55±0.1 D1 Cavity Hole Diameter 1.50+0.25/-0.00 P0 Perforation Pitch 4.0±0.1 P1 Cavity to Perforation (Length Direction) 2.0±0.1 A0 Cavity Length 6.4±0.1 B0 Cavity Width 5.2±0.1 K0 Cavity Depth 2.1±0.1 t Carrier Tape Thickness C Cover Tape Width 12.0+0.3/-0.1 0.30±0.05 9.3±0.1 25 November 01, 2011 HT7L4091 Universal Step-Down PWM Control For High Brightness LED Lighting Control Holtek Semiconductor Inc. (Headquarters) No.3, Creation Rd. II, Science Park, Hsinchu, Taiwan Tel: 886-3-563-1999 Fax: 886-3-563-1189 http://www.holtek.com.tw Holtek Semiconductor Inc. (Taipei Sales Office) 4F-2, No. 3-2, YuanQu St., Nankang Software Park, Taipei 115, Taiwan Tel: 886-2-2655-7070 Fax: 886-2-2655-7373 Fax: 886-2-2655-7383 (International sales hotline) Holtek Semiconductor Inc. (Shenzhen Sales Office) 5F, Unit A, Productivity Building, No.5 Gaoxin M 2nd Road, Nanshan District, Shenzhen, China 518057 Tel: 86-755-8616-9908, 86-755-8616-9308 Fax: 86-755-8616-9722 Holtek Semiconductor (USA), Inc. (North America Sales Office) 46729 Fremont Blvd., Fremont, CA 94538, USA Tel: 1-510-252-9880 Fax: 1-510-252-9885 http://www.holtek.com Copyright© 2011 by HOLTEK SEMICONDUCTOR INC. The information appearing in this Data Sheet is believed to be accurate at the time of publication. However, Holtek assumes no responsibility arising from the use of the specifications described. The applications mentioned herein are used solely for the purpose of illustration and Holtek makes no warranty or representation that such applications will be suitable without further modification, nor recommends the use of its products for application that may present a risk to human life due to malfunction or otherwise. Holtek's products are not authorized for use as critical components in life support devices or systems. Holtek reserves the right to alter its products without prior notification. For the most up-to-date information, please visit our web site at http://www.holtek.com.tw. Rev. 1.10 26 November 01, 2011