www.fairchildsemi.com KA7541 Simple Ballast Controller Features Descriptions • • • • • • • The KA7541 provides simple and high performance electronic ballast control functions. KA7541 is optimized for electronic ballast requiring a minimum board area, reduced component count and low power dissipation. Internal soft start circuitry eliminates the need for an external soft start PTC resistor. The initial soft start switching frequency and soft start time can be adjusted depending on the types of lamps. Protection circuitry has also been added to prevent burning out of switches in no lamp condition. output gate drive circuit clamps power MOSFET gate voltage irrespective of supply voltage Internal soft start Flexible soft start frequency No lamp protection Trimmed 1.5% internal bandgap reference Under voltage lock out with 1.8V of hysteresis Totem pole output with high state clamp Low start up and operating current 8-DIP 1 8-SOP 1 Rev. 1.0.3 ©2001 Fairchild Semiconductor Corporation KA7541 Internal Block Diagram UVLO 2V Ref − 1 CS 1.8V Internal bias + 0.22µF 2.5µA Vref UVLO Oscilator + + + 3V 8Ict 1V 30kΩ OUT 1 6 OUT 2 5 GND SQ Oscilator 3pF F.D R latch − 3 22kΩ 7 VCC 9.5V IC + 2 180pF RS VCC Ik = IS / 6 Ict Ct 8 − IH VZ + VCC Current mirror + Frequency divider IS Vref 2kΩ 40kΩ Ldet IH = Ik × (Vref − VSS) / Vref IS = Vref / RS − 4 5pF + Shut down signal 2V Absolute Maximum Ratings Parameter Symbol Value Unit VCC 30 V IOH, IOL ±300 mA Iclamp ±10 mA Soft start, and no lamp detection input voltage VIN −0.3 to 6 V Operating temperature range Topr -25 to 125 °C Storage temperature range Tstg −65 to 150 °C Supply voltage Peak drive output current Drive output clamping diodes VO>VCC, or VO<−0.3 8-DIP Power dissipation 8-SOP Thermal resistance (Junction-to-air) 8-DIP 8-SOP 0.8 Pd 0.5 100 θja 165 W °C/W Absolute Maximum Ratings (-25°°C≤ ≤Ta≤ ≤125°°C) 2 Parameter Symbol Value Unit Temperature stability for reference voltage (Vref) ∆Vref(Typ) 15 mV Temperature stability for operating frequency (fos) ∆fos(Typ) 5 kHz KA7541 Pin Assignments CS 1 8 VCC Ct 2 7 OUT1 RS 3 6 OUT2 Ldet 4 5 GND (Top View) Pin Definitions Pin Number Pin Name Pin Function Descrition 1 CS Soft start capacitor connection pin. The pin voltage determines the phase of soft start, normal mode. 2 CT Timing capacitor connection pin. The timing capacitor is charged and discharged to generate the sawtooth waveform that determines the oscillation frequency in the internal oscillator block. 3 RS Soft start resistor connection pin. The soft start resistor value determines the initial preheating switching frequency during soft start mode. 4 Ldet Input to the protection circuit. If the pin voltage is lower than 2V, the output of the gate driver is inhibited. 5 GND The ground potential of all the pins. 6 OUT 2 The output of a high-current power driver capable of driving the gate of a power MOSFET 7 OUT 1 The output of a high-current power driver capable of driving the gate of a power MOSFET. 8 VCC The logic and control power supply connection. 3 KA7541 Electrical Characteristics Unless otherwise specified, for typical values Vcc=14V, Ta=25oC, For Min/Max values Ta is the operating ambient temperature range with -25oC ≤ Ta ≤ 125oC and 11V ≤ VCC ≤ 30V Parameter Symbol Conditions Min. Typ. Max. Unit 8.5 9.5 10.5 V 1.3 1.8 2.3 V UNDER VOLTAGE LOCK OUT SECTION Start threshold voltage VTH(st) UVLO hysteresis HY(st) VCC increasing - SUPPLY CURRENT SECTION Start up supply current IST VCC<VTH(st) - 0.15 0.25 mA Operating supply current ICC Output not switching - 6 10 mA IDCC 50kHz, CI=1nF - 7 14 mA Vref Iref=0mA, Vcc=14V 1.95 2 2.05 V Dynamic operating supply current REFERENCE SECTION Reference voltage Line regulation ∆Vref 1 14V≤VCC≤25V - 0.1 10 mV Temperature stability of Vref ∆Vref 2 -25≤Ta≤125°C, Vcc=14V - 15 - mV OSCILLATOR SECTION Operating frequency fos VSS=3V, CT=470pF 44 50 56 KHz Operating dead time tod VSS=3V, Vcc=14V 2.4 2.9 3.4 µs Soft start frequency fss VSS=0V, CT=470pF 56 65 74 KHz Soft start dead time tsd VSS=0V, Vcc=14V 1.8 2.3 2.8 µs Rising time (note1) tr CI=1nF, Vcc=12V - 120 200 ns (note1) tf CI=1nF, Vcc=12V - 50 100 ns 12 15 18 V - - 1 V 1.9 2 2.1 V OUTPUT SECTION Falling time Maximum output voltage Vomax(o) VCC=20V Output voltage with UVLO activated Vomin(o) VCC=5V, IO=100µA NO LAMP PROTECTION SECTION No lamp detect voltage Vnd - Note: 1. These parameters, although guaranteed, are not 100% tested in production. 4 KA7541 Start-up Circuit Start up current is supplied to the IC through the start up resistor (Rst). In order to reduce the power dissipation in Rst, the Rst is connected to the full wave rectified output voltage. The following equation can be used to calculate the size of Rst Vin ( ac ) × 2 – Vth ( st ) ,max Rst < --------------------------------------------------------------------------Ist ,max 2 ( Vin ( ac_max ) ⋅ 2 – Vcc ) P RSt = ------------------------------------------------------------------------ ≤ 0.5W R St × 2 – 10.5- = 440kΩ = 85 ------------------------------------–3 0.25 × 10 R St ≥ 2 × ( Vin ( ac_max ) ⋅ 2 – Vcc ) 2 ∴260K ≤ R St ≤ 440K R St ≥ 260K The size of start up capacitor (Cst) is normally decided in terms of the start up time and operating current build up time with auxiliary operating current source. The turn off snubber capacitor (Cq2) and two diodes (D1, D2) constitute the auxiliary operating current source for the IC. The charging current through the Cq2 flows into the IC and also charges the start-up capacitor. If the size of Cq2 is increased, the VCC voltage of the Cst is also increased. Q1 Rectifier Output Q2 Cq2 Rst To VCC (Pin 8) D2 + − D1 Cst Figure 1. Start up circuit Oscillator The gate drive output frequency is as half as that of the triangular waveform in timing capacitor (Ct) at pin #2. In normal operating mode, the timing capacitor charging current is 50µA. The discharging current is seven times of the charging current (7× 50µA). The charging period of the timing capacitor is the on duty of the gate drive. The discharging period is the off duty of the gate drive. The rising slope and falling slope of the triangular waveform are as following. Rising slope: dv / dt = i / C = 50µA / Ct Falling slope: dv / dt = i / C = 7 × 50µA / Ct For example, when the timing capacitor is 180pF, ∆Tch = 6.69µ ∆Tdis = 0.956µ 5 KA7541 Vct (Pin #2) 2.86V 1.0V Voutput (Pin #6, 7) 14V 0V Charging Period(∆Tch) Discharging Period(∆Tdis) Figure 2. Oscillator sawtooth & Output gate drive waveform As a result, the switching frequency is as following Ts = 2 × (∆Tch + ∆Tdis) = 15.29µ fsw = 1 / TS = 65KHz The explicit equation calculating the size of the timing capacitor for a certain switching frequency is written below. –6 11.76 × 10 C t = --------------------------------f sw Soft Start The switching frequency is linearly decreasing from the pre-heating frequency to the normal switching frequency. In KA7541, the initial pre-heating frequency can be adjusted depending on the types of the lamps used. During the pre-heating mode, a sixth of the soft start current (IS) which flows through the soft start resistor (RS) at pin #3 is added to the normal timing capacitor charging current (50µA). The rising and falling slope of the triangular waveform are increased due to this added current. Soft start current (IS) = 2V / RS Rising slope: dv / dt = i / C = (50µA + IS / 6) / Ct Falling slope: dv / dt = i / C = 7 × (50µA + IS / 6) / Ct So, once the value of RS and Ct are known, the pre-heating frequency can be calculated straightforward by using the following equation. – 6 0.33 50 × 10 + ----------Rs fsw ( pre ) = ------------------------------------------Ct × 4.25 The dead time ratio during pre-heating mode is maintained to be constant as well as in normal mode. (on duty: dead time = 7:1 ) The voltage of the soft start capacitor (CS) determines the soft start time (tss). When VCC voltage exceeds the start-up voltage (Vth(st)), the soft start capacitor start to be charged by the current source (313nA). The switching frequency decreases linearly to fsw(nor) from fsw(pre) until the soft start capacitor voltage (VCS) touches 2V. Therefore the soft start duration time (tss) can be acquired by the following formula. 6 KA7541 × V----------------tss = Cs i –6 0.2 × 10 × 2= ----------------------------------= 1.28s –9 313 × 10 For example, the soft start capacitor of 0.2µF makes the soft start time (tss) to be 1.28sec. fsw, VCS fsw (pre) fsw (nor) 2V tss Figure 3. Frequency & Soft start capacitor voltage variation during soft start No Lamp Protection When the voltage at pin #4 is lower than 2V, the gate drive output is off state, so the external power MOSFET stops switching. In no lamp protection circuit the dc link voltage is divided by a couple of resistors including both lamp filaments, and The divided voltage is applied to the pin #4 before the MOSFETs start switching. R4 V R4 = Vdd × --------------------------------------------------------------------R2 + R 3 + 2 × Rf R 1 + ------------------------------------------ + R 4 2 15KΩ ≅ 400 × --------------------------------------------------------------------------------------------+ 680KΩ- + 15KΩ 180KΩ + 330KΩ -------------------------------------------2 R3 V 3 = V 2 × -------------------- ≅ 200V R2 + R3 When in normal mode the average voltage of the V3 is the half of the dc link voltage (Vdd). So, in order to make stable start condition, the resistors are designed to make the voltage of V3 to be the half of the dc link voltage. 7 KA7541 DC Link Voltage (Vdd) R1 V2 Rfilament Rfilament Rfilament Rfilament R2 V3 R3 To pin #4 R4 C4 Figure 4. Lamp detection resistor network 8 KA7541 Application Circuit <85 ~ 265VAC Input, 400VDC, 32W×2 Lamps Ballast> Full-wave Rectified Output PFC Output L2 D5 D3 D4 D1 C5 R3 R6 R4 R8 D2 R5 D6 NTC Q1 C2 C9 5 6 Idet OUT C6 GND 8 C4 Vcc C3 7 R1 4 CS MULT 3 1 C1 2 INV EA_OUT FAN7527 L1 TNR F1 R2 C8 R9 R7 C7 AC INPUT To PFC Output R15 Q2 T1 Q3 R11 C14 C18 C20 L3 L4 C21 D7 To full-wave rectified voltage R12 C19 C15 R14 R10 C17 C16 R16 Z1 5 6 C11 C12 GND Ldet R17 4 Rs 3 2 Ct CS KA7541 1 C10 OUT2 7 OUT1 Vcc 8 D8 R13 C13 R18 R19 9 KA7541 Component Listing 10 Part number Value Note Manufacturer R1 2.7MΩ 1/4W - R2 18kΩ 1/4W - R3, 12 R4, 13 150kΩ 22kΩ 1W 1/4W - R5, 10, 11 47Ω 1/4W - R6 3.3Ω 1/4W - R7 R8 0.2Ω 1.2MΩ 1W 1/4W - R9 103 Variable resistor - R14 180kΩ 1/4W - R15, 16 R17, 18 330kΩ 680kΩ 1/4W 1/4W - R19 15kΩ 1/4W - C1, 2 150nF, 275vac Box-Cap - C3, 4 2200pF, 3000V Y-Cap - C5 C6, 10 0.22µF, 630V 47µF, 35V Miller-Cap Electrolytic - C7 0.33µF MLCC - C8 1nF, 25V Ceramic - C9 C11, 21 47µF, 450V 0.22µF, 25V Electrolytic Ceramic - C12 180pF, 25V Ceramic - C13 0.1µF, 25V Ceramic - C14 C15, 16 1nF, 630V 4700pF, 1000V Miller-Cap Miller-Cap - C17, 18, 19, 20 6800pF, 630V Miller-Cap - Q1, 2, 3 500V, 3.6A FQPF6N50 FairChild D1, 2, 3, 4 D5 1000V, 1A 1000V, 1A 1N4007 UF4007 - D6 75V, 150mA 1N4148 - D7, 8 600V, 1A 1N4937 - ZD1 L1 15V, 1W 45mH 1N4744 Line Filter - L2 590µH (62T:5T) EI3026 L3, 4 3.1mH (120T) EI2820 - T1 F1 1.2mH(30T:60T) 250V, 3A EE1614 Fuse - TNR 470V 471 - NTC 10Ω 10D09 - KA7541 Mechanical Dimensions Package Dimensions in millimeters 8-SOP MIN #5 6.00 ±0.30 0.236 ±0.012 8° 0~ +0.10 0.15 -0.05 +0.004 0.006 -0.002 MAX0.10 MAX0.004 1.80 MAX 0.071 3.95 ±0.20 0.156 ±0.008 5.72 0.225 0.41 ±0.10 0.016 ±0.004 #4 1.27 0.050 #8 5.13 MAX 0.202 #1 4.92 ±0.20 0.194 ±0.008 ( 0.56 ) 0.022 1.55 ±0.20 0.061 ±0.008 0.1~0.25 0.004~0.001 0.50 ±0.20 0.020 ±0.008 11 KA7541 Mechanical Dimensions (Continued) Package Dimensions in millimeters 1.524 ±0.10 #5 2.54 0.100 5.08 MAX 0.200 7.62 0.300 3.40 ±0.20 0.134 ±0.008 +0.10 0.25 –0.05 +0.004 0~15° 12 0.010 –0.002 3.30 ±0.30 0.130 ±0.012 0.33 MIN 0.013 0.060 ±0.004 #4 0.018 ±0.004 #8 9.60 MAX 0.378 #1 9.20 ±0.20 0.362 ±0.008 ( 6.40 ±0.20 0.252 ±0.008 0.46 ±0.10 0.79 ) 0.031 8-DIP KA7541 Ordering Information Product Number Package KA7541 8-DIP KA7541D 8-SOP Operating Temperature -25°C ~ +125°C 13 KA7541 DISCLAIMER FAIRCHILD SEMICONDUCTOR RESERVES THE RIGHT TO MAKE CHANGES WITHOUT FURTHER NOTICE TO ANY PRODUCTS HEREIN TO IMPROVE RELIABILITY, FUNCTION OR DESIGN. FAIRCHILD DOES NOT ASSUME ANY LIABILITY ARISING OUT OF THE APPLICATION OR USE OF ANY PRODUCT OR CIRCUIT DESCRIBED HEREIN; NEITHER DOES IT CONVEY ANY LICENSE UNDER ITS PATENT RIGHTS, NOR THE RIGHTS OF OTHERS. LIFE SUPPORT POLICY FAIRCHILD’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF FAIRCHILD SEMICONDUCTOR CORPORATION. As used herein: 1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and (c) whose failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury of the user. 2. A critical component in any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness. www.fairchildsemi.com 9/27/01 0.0m 001 Stock#DSxxxxxxxx 2001 Fairchild Semiconductor Corporation