BW6562A High PFC LED Driver Description The BW6562A is a cost effective high performance transition-mode (TM) power factor correction (PFC) controller IC optimized for high PFC LED driver, battery chargers and pre-regulator applications. The BW6562A integrates an internal start-up timer, a highly linear SOP-8 PACKAGE OUTLINE multiplier with Total Harmonics Distortion (THD) optimizer for near unity power factor, a Zero Current Detector (ZCD) to ensure transition-mode operation and a current sensing comparator with built-in leading edge blanking. With ZCD control, power MOSFET is always turned on with zero inductor current. Consequently, transition-mode control achieves lower switching loss and reduced noise. The BW6562A offers great protection coverage including system accurate adjustable over-voltage protection (OVP), input under-voltage lockout (UVLO), multiplier output clamp and GD output clamp for external power MOSFET protection. The totem pole output stage is capable of delivering sink/source Pin Configurations (Top View) drive current of +800mA/-600mA. The BW6562A is available in SOP-8 package. Features • Single stage fly-back controller with PFC • Transition-mode operation • Ultra-low start-up current • Internal start-up timer • Low operating supply current • Low quiescent current • Disable function on error amplifier (E/A) input Applications • Totem pole, push-pull output drive • Fly-back power converters • Adjustable output over-voltage protection • PFC pre-regulators to meet IEC61000-3-2 • Under-voltage lockout with hysteresis • Hi-end AC-DC adapter/charger • 1% Precision internal reference voltage • Electronic single stage LED driver Packing & Order Information • Electronic Ballast 3,000/Reel Publication Order Number: [BW6562A] © Bruckewell Technology Corporation Rev. A -2014 BW6562A High PFC LED Driver Typical Application Circuit PIN DESCRIPTIONS Pin Name Function Current sense input pin to the internal PWM comparator. The current flowing in the MOSFET is sensed through a resistor; the resulting voltage is CS applied to this pin and compared with an internal sinusoidal-shaped reference, generated by the multiplier, to switch on or off the external MOSFET. The pin is equipped with 200ns leading-edge blanking for improved noise immunity. GND Ground pin. Current return for both the signal part of the IC and the gate driver. Main input to the multiplier. MULT This pin is connected to the rectified mains voltage via a resistor divider and provides the sinusoidal reference to the current loop. Output pin of the error amplifier. COMP A compensation network is placed between this pin and INV to achieve stability of the voltage control loop and ensure high power factor and low THD. Inverting input pin of the error amplifier. INV The information on the output voltage of the PFC controller is fed into this pin through a resistor divider. The pin can also be used as chip enable/disable control pin. Zero current detection pin. ZCD Boost inductor’s demagnetization sensing input for transition-mode operation. A negativegoing edge triggers MOSFET’s turn-on. Publication Order Number: [BW6562A] © Bruckewell Technology Corporation Rev. A -2014 BW6562A High PFC LED Driver PIN DESCRIPTIONS Pin Name Function Gate driver output pin. GD The totem pole output stage is able to drive power MOSFET’s with a peak current of 600mA source and 800mA sink. The high-level voltage of this pin is clamped at about 12V to avoid excessive gate voltages in case the pin is supplied with a high VCC. System power input pin. VCC Supply voltage of both the signal part of the IC and the gate driver. Upper limit is extended to a maximum of 32V to provide a more headroom for supply voltage changes. This pin has an internal 34V (min.) Zener diode to protect the IC itself from over-voltage transients. ABSOLUTE MAXIMUM RATINGS (Note 1) Parameter Symbol Range Unit IC supply voltage VCC -0.3 ~ +40 V Output totem pole peak current IGD -600 (source) / +800 (sink) mA *(Note 2) -0.3 ~ +8.0 V IZCD ±10 mA 0.63 W TJ +150 °C TSTG -65 ~ +150 °C θJA 165 °C/W Analog inputs & outputs Zero current detector maximum current Continuous power dissipation (TA +25°C) 8 Pin SOP (de-rating 6.3mW/°C above +25°C) Junction temperature Storage temperature range Junction-to-ambient thermal resistance Note : 1. Exceeding these ratings could cause damage to the device. All voltages are with respect to ground. Currents are positive into, negative out of the specified terminal. 2. * : Pin 1 (INV), pin 2 (COMP), pin 3 (MULT), pin 4 (CS) RECOMMENDED OPERATING CONDITIONS (Note 4) Parameter Symbol Min. Max. Unit DC input supply voltage range, VCC to GND VCC 10.5 32 V INV input pin voltage range relative to GND VINV 2.455 2.545 V VMULT 0 3 V VCS 0 1.2 V TA -40 +85 °C MULT input pin voltage range relative to GND CS input pin voltage range relative to GND Ambient temperature range (Note 3) Note : 3. Maximum ambient temperature range is limited by allowable power dissipation. Publication Order Number: [BW6562A] © Bruckewell Technology Corporation Rev. A -2014 BW6562A High PFC LED Driver BLOCK DIAGRAM ELECTRICAL CHARACTERISTICS (Over recommended operating conditions unless otherwise specified. VCC 12V, TJ - 25°C ~ +125°C, CO 1nF) Supply voltage Parameter Symbol Conditions Min Operating range VCC After turn-on 10.5 Turn-on threshold VCC(ON) 11.7 Turn-off threshold V CC(OFF) 8.7 Hysteresis ΔVCC Zener voltage VZ ICC = 20mA Typ. Max. Units 32 V 12.5 13.3 V 9.0 9.3 V 3.0 4.0 V 34 38 V Typ. Max. Units 30 60 μA Supply current Parameter Symbol Conditions Start-up current ISTART Before turn-on, VCC=11V Quiescent current IQ After turn on 2.50 3.75 mA Operating supply current ICC 70kHz 3.5 5.0 mA Quiescent current IQ(OVP) During OVP, or VINV ≤ 150mV 1.7 2.2 mA Publication Order Number: [BW6562A] Min © Bruckewell Technology Corporation Rev. A -2014 BW6562A High PFC LED Driver Error amplifier Parameter Symbol Conditions Voltage feedback input threshold VINV 10.5V < VCC < 32V Line regulation ΔVLINE VCC=10.5V ~ 32V Input bias current IINV VINV=0V ~ 3V Voltage gain GV Open loop Gain-bandwidth product GB Source current ICOMP(SOURCE) VCOMP=4V, VINV=2.4V -2.0 -3.5 Sink current ICOMP(SINK) VCOMP=4V, VINV=2.6V 2.4 4.5 Upper clamp voltage VCOMP(UP) ISOURCE=0.5mA 5.3 5.7 6.0 V Lower clamp voltage VCOMP(LOW) ISINK=0.5mA 2.10 2.25 2.40 V Disable threshold VINV(DIS) 150 200 250 mV Re-start threshold VINV(EN) 380 450 520 mV Min Typ. Max. Units -1 μA Multiplier input Parameter Symbol Conditions Input bias current IMULT VMULT=0V ~ 4V Linear operation range VMULT Output max. slope ΔVCS /ΔVMULT (Note 4) Min Typ. Max. Units 2.455 2.500 2.545 V 2 5 mV -1 μA 60 80 Db 1 MHz -5.0 mA 0~3 VMULT=0V ~ 1V, VCOMP=Upper clamp mA V 1.0 1.1 V/V K VMULT=1V, VCOMP=4V 0.32 0.38 0.44 V Zero current detector Parameter Symbol Conditions Min Typ. Max. Units Upper clamp voltage VZCDH IZCD=2.5mA 5.0 5.7 6.5 V Lower clamp voltage VZCDL IZCD=-2.5mA -0.3 0 0.3 V VZCDA Positive-going edge 1.4 V Triggering voltage (Note 5) VZCDT Negative-going edge 0.7 V Input bias current IZCDB VZCD=1.0V ~ 4.5V 2 μA Source current capability IZCD(SOURCE) -2.5 mA Sink current capability IZCD(SINK) 2.5 mA Gain Arming voltage (Note 5) Output over-voltage Parameter Symbol Dynamic OVP triggering current IOVP 27 μA Hysteresis (Note 5) ΔIOVP 20 μA Static OVP threshold VOVP(TH) Publication Order Number: [BW6562A] Conditions Min 2.10 Typ. 2.25 Max. 2.40 Units V © Bruckewell Technology Corporation Rev. A -2014 BW6562A High PFC LED Driver Current sense comparator Parameter Symbol Conditions Input bias current ICS VCS=0V Leading edge blanking tLEB Delay to output tD(H-L) Current sense clamp VCS Min 100 Typ. 200 Max. Units -1 μA 300 ns 175 VCOMP=Upper clamp, VMULT=1.5V 1.00 1.08 ns 1.16 V VCS(OS_0V) VMULT=0V 25 mV VCS(OS_2.5V) VMULT=2.5V 5 mV Starter Parameter Symbol Conditions Start timer period tSTART Current sense offset Min Typ. Max. Units 75 190 300 μs Min Typ. Max. Units 0.6 1.2 V Zero current detector Parameter Symbol Conditions Output low voltage VOL ISINK=100mA Output high voltage VOH ISOURCE=5mA Peak source current ISOURCE(PK) -0.6 A Peak sink current ISINK(PK) 0.8 A Voltage fall time tFAL 30 70 ns Voltage rise time tRISE 60 110 ns Output clamp voltage VO(CLAMP) ISOURCE=5mA, VCC=20V 12 15 V UVLO saturation VUVLO(SAT) VCC=0V ~ VCC(ON), ISINK=2mA 1.1 V 9.8 10 10.3 V Note : 4. The multiplier output is given by :VCS=K x VMULT x (VCOMP – 2.5) 5. Parameters guaranteed by design, functionality tested in production. Publication Order Number: [BW6562A] © Bruckewell Technology Corporation Rev. A -2014 BW6562A High PFC LED Driver Figure 4. Single-Stage PFC, Constant Voltage and Constant Current Figure 5. High Power Factor Battery Charger Publication Order Number: [BW6562A] © Bruckewell Technology Corporation Rev. A -2014 BW6562A High PFC LED Driver APPLICATION INFORMATION (PF) is defined by the ratio of average power and apparent Operation Overview power : The BW6562A is an excellent transition-mode power factor The major cause of this THD distortion is the inability of the correction controller for AC-DC switching mode power supply system to transfer energy effectively when the instantaneous line applications. It meets the IEC61000-3-2 requirement and is voltage is very low. This effect is magnified by the high-frequency intended for the use in those applications that demand low filter capacitor placed after the bridge rectifier, which retains power harmonics distortion. It integrates more functions to some residual voltage that causes the diodes of the bridge reduce the external components counts and the size. Its major rectifier to be reverse-biased and the input current flow to features are described as below. temporarily stop. Power Factor Correction and THD To overcome this issue, the circuit section designed in the The BW6562A features a one linear multiplier with THD BW6562A forces the PFC regulator to process more energy optimizer for near unity power factor. To explain PFC and THD near the line voltage zero-crossings, as compared to that relation. First, average power is defined by commanded by the control loop. This results in both, minimizing the time interval when energy transfer is lacking, and fully discharging the high-frequency filter capacitor after the bridge. where θ is phase shift between input voltage and current. Effective value of input voltage and current are defined by as The BW6562A is designed with a special circuit that reduces the follows : conduction dead-angle occurring to the AC where vs(t) is instantaneous value of input voltage,is(t) is To quantify degree of current waveform distortion, THD is written instantaneous value of input current,T is the cycle. by Therefore, PAV is written as : And apparent power is defined by If the current and voltage are in phase, then θ 0, which will lead where IRMS is the root mean square (RMS) value of iRMS. to cos(θ) 1, and the PF will be simplified as Therefore, based on the above equations, obtained power factor Publication Order Number: [BW6562A] © Bruckewell Technology Corporation Rev. A -2014 BW6562A High PFC LED Driver where R3 and R4 are top and bottom feedback resistor values (as shown in the Typical Application Circuit on page 1). Based on the equation 16, if THD is very small, then it will get If any abrupt change of output voltage, ΔVO > 0, occurs due to a near unity power factor. load drop, the voltage at pin INV will be kept at 2.5V by the local feedback of the EA, the network connected between INV and is shown in Typical Application Circuit on page 1. During the COMP would introduces a time constant to achieve high PF. start-up transient, the VCC is lower than the UVLO threshold The current through R4 will remain equal to 2.5/R4 but IR3 will voltage (VCC(ON)) thus there is no gate pulse produced from become : the BW6562A to drive power MOSFET. Therefore, the current through R6 will provide the startup current and to charge the capacitor C2. Whenever the VCC voltage is high enough to turn on the BW6562A and further to deliver the gate drive signal. type protection. The INV pin also provides additional function as Once the BW6562A is in normal operation, the supply current is a non-latched IC disable. A voltage below 0.2V shuts down the switched to and provided from the auxiliary winding of the PFC IC and reduces its consumption below 1.7mA. To re-start the IC, choke (transformer). Lower start-up current requirement on the the voltage on this pin must exceed 0.45V. The main usage of PFC controller will help to increase the value of R6 and then this function is a remote ON/OFF control input that can be driven reduce the power consumption on R6. By using CMOS process by a PWM controller for power management purposes. and the special circuit design, the maximum start-up current of However, it also offers a certain degree of additional safety since the BW6562A is only 60μA. If a higher resistance value of R6 is it will cause the IC to shutdown in case lower resistor of the chosen, it usually takes more time to start-up. To carefully select output divider is shorted to ground or if the upper resistor is the value of R6 and C2 will optimize the power consumption and missing or fails open. start-up time. Zero Current Detection Output Voltage Setting The zero current detection block switches on the external The BW6562A monitors the output voltage signal at INV pin MOSFET as the current through the boost inductor has gone to through a resistor divider pair R3 and R4. A transconductance zero using an auxiliary winding coupled with the inductor. This amplifier is used instead of the conventional voltage amplifier. feature allows transitionmode operation. If the voltage of the This trans-conductance amplifier (voltage controlled current ZCD pin goes higher than 1.4V, the ZCD comparator waits until source) also provides the additional OVP function. Neglecting the voltage goes below 0.7V. If the voltage goes below OVP is ripple current, current flowing through R3, IR3, will equal to calculate by current through R4, IR4, As the non-inverting input of the error amplifier is biased inside the BW6562A at 2.5V, and output voltage is determined by the following relationship. An important advantage of this technique is that the over voltage level can be set independently from the regulated output voltage; the latter depends on the ratio of R3 to R4, the former on the individual value of R3. Another advantage is the precision because the tolerance of the detection current is about 12%, i.e. Publication Order Number: [BW6562A] © Bruckewell Technology Corporation Rev. A -2014 BW6562A High PFC LED Driver 12% tolerance on ΔVO. Since ΔVO << VO, the tolerance on the However, the total pulse width of the turn-on spike is decided by absolute value will be proportionally reduced. the output power, circuit design and layout. It is strongly When the loading of PFC pre-regulator becomes very low, the recommended to adopt a smaller RC filter for higher power output voltage tends to stay steadily above the nominal value, application to avoid the CS pin being damaged by the negative which is not the case that OVP is triggered by abrupt voltage turn-on spike. increase. If this situation happens, the error amplifier output will saturate low, hence, when this is detected, the external power Multiplier transistor is switched OFF, and the IC is put in an idle state The internal multiplier takes two inputs, one from a portion of the (Static OVP). Normal operation is resumed as the error amplifier instantaneous rectified line voltage (via pin 3 MULT) and the goes back into its linear region. As a result, the device will work in other from the output of the E/A (via pin 2 COMP), to feed the burstmode, with a repetition rate that can be very low. When PWM comparator to determine the exact instant when the either OVP is activated, the quiescent consumption of the IC is MOSFET is to be switched off. The output of multiplier would be reduced to minimum by the discharge of the VCC capacitor and rectified sinusoid as similar as instantaneous rectified line voltage increase the hold-up capability of the IC supply. different only with scaling factor determined by output of E/A. The output is then fed into PWM comparator to compare with The OVP function in the BW6562A is an auto-recovery 0.7V, the current sense clamp voltage VCS (at 1.08V), to switch MOSFET zero current detection turns on the MOSFET. The ZCD pin is off. protected internally by two clamps, 5.7V upper clamp and 0V lower clamp. The 190μs timer generates a MOSFET turn on signal if the driver output has been low for more than 190μs from the falling edge of the driver output. Current Sensing and Leading Edge Blanking The typical current mode of PFC controller feedbacks the current signals to close the control loop and achieve regulation. The BW6562A detects the primary MOSFET current from the CS pin; this is for the pulse-by-pulse current limit. The maximum voltage threshold of the current sensing pin is set at 1.08V. From above, the MOSFET peak current can be obtained from below. The formula governing all parameters is given by multiplier output : A 200ns leading edge blanking (LEB) time is included in the input of CS pin to prevent the false-trigger from the current spike. In the low power application, if the total pulse width of the turn-on where K is the multiplier gain. System designer needs to spikes is less than 200ns and the negative spike on the CS pin calculate R1 and R2, for different input mains circumstances. doesn’t exceed -0.3V, it could eliminated the RC filter. Figure 1 and 2 explain multiplier characteristics and VCS clamps vs. TJ respectively. Publication Order Number: [BW6562A] © Bruckewell Technology Corporation Rev. A -2014 BW6562A High PFC LED Driver Output Drive Stage ●The input capacitance can be reduced to replace bulky and An output stage of a push-pull buffer, with typical expensive high voltage electrolytic capacitor (as required by +800mA/-600mA driving capability is incorporated to drive a regular offline SMPS) by a small size, cheaper film capacitor power MOSFET directly. The output voltage is clamped at 12V ●Transition-mode ensures low turn-on losses in MOSFET and to protect the MOSFET gate even when the VCC voltage is higher efficiency can be achieved. higher than 12V. ●Lower parts count means lower material cost as well as lower assembly cost for limited space. Few details information about this, please refer separate Application Note for details. High PF Battery Charger The single stage PFC can also be adopted as battery charger. Figure 5 presents an off-line universal mains battery charger that can drive up to 30W. This solution also uses an isolated feedback with an optocoupler and the BW7103. To use the BW6562A IC in a lead-acid battery charger circuit with high PFC, the DC output voltage and the maximum permissible DC output charging current needs to be Example Applications decided on the basis of the specific battery to be charged. For Single Stage LED Driver with PFC the lead-acid batteries of different nominal voltages, the fixed One of major applications of the BW6562A is to provide a single constant-voltage, current limited, charging mode, the typical stage power module with high PF for LED lighting. The following voltage level suggested by most lead-acid battery manufactures circuit, Figure 4, shows a simplified fly-back AC-DC converter are as follows : with both constant current (CC) and constant voltage (CV) feedback from output side, to prevent overload and also provide an over-voltage protection facility. This solution uses an isolated feedback with an optocoupler and the SQ7103 (+2.5V voltage reference and dual Op-Amps), each one for voltage and current regulation respectively. As LED The maximum lead-acid battery charging current is decided by lighting application, the BW6562A offers the following the battery amp-hour capacity, represented as 'C'. The lead-acid advantages that make this solution an appropriate method battery manufacturers in general prefer a low battery charging against the traditionally PWM controller, where a good PF value current set at “C/20” Amp for slow-charging, for improved life of is required : the battery. However, in case of ‘fast-charging’ and if permitted by the battery manufacturer, the maximum battery charging current can be set at “C/10” Amp. A charge-depleted battery will Publication Order Number: [BW6562A] © Bruckewell Technology Corporation Rev. A -2014 BW6562A High PFC LED Driver initially draw the maximum charging current. As the battery amplifier is set to be narrow within 20kHz, the output would be a gradually gets charged, the charging current will gradually DC value over a given half-cycle. Output of E/A fed into reduce. multiplier, multiplied by portion of the rectified mains voltage, will generate a scaled rectified sinusoid whose peak amplitude PFC Pre-Regulator depends on the rectified mains peak voltage as well as the value Major application of the BW6562A is to implement a wide-range of error signal. mains input PFC pre-regulator, which will be acting the input stage for the cascaded isolation DC-DC converter, and can The output of the multiplier is fed into the non-inverting pin of the deliver above 350W in general. Typical application circuit internal PWM comparator. As the output from multiplier, a diagram is showed on page 1. There are two methods; in sinusoidal reference for PWM, equals to the voltage on the general, to design preregulator stage, one is with fixed frequency current sense CS pin (#4), the MOSFET will be turned off. As a while the other is with fixed on time. consequence, the peak inductor current will be enveloped by a rectified sinusoid. After the MOSFET is turned off, the boost The BW6562A can be implemented by fixed on time due to its inductor discharges its stored energy to the load until zero simplicity and less expensive, while the fixed frequency current is detected and turns on MOSFET again. technique is more complicated and beyond the scope of this application note. In fixed on time mode, the BW6562A is also In case there is no auxiliary winding on the boost inductor, a working in transition mode where the inductor current will be turn solution can be implemented by simply connecting the ZCD pin on when zero crossing is detected. By using boost switching to the drain of the power MOSFET through an RC network as techniques, a PFC is shape the input current by drawing a shown in Figure 3. In this way the high-frequency edges quasi-sinusoidal current to be in-phase with the line voltage. A experienced by the drain will be transferred to the ZCD pin, simplified circuit, shown in Figure 3, can explain the operation as hence arming and triggering the ZCD comparator. follows : Also in this case the resistance value must be properly chosen to limit the current sourced/sunk by the ZCD pin. In typical applications with output voltages around 400V, recommended values for these components as 22pF (or 33pF) for CZCD and 330kΩ for RZCD. With these values proper operation is ensured even with few volts difference between the regulated output voltage and the peak input voltage. The AC mains voltage is rectified by a diode bridge and delivered to the boost converter which boosts the rectified input voltage to a higher regulated DC bus VO. The error amplifier compares a portion of the output voltage with an internal reference and generates a signal error proportional to the difference between them. The bandwidth of the internal error Publication Order Number: [BW6562A] © Bruckewell Technology Corporation Rev. A -2014 BW6562A High PFC LED Driver Disclaimer ALL PRODUCT, PRODUCT SPECIFICATIONS AND DATA ARE SUBJECT TO CHANGE WITHOUT NOTICE TO IMPROVE RELIABILITY, FUNCTION OR DESIGN OR OTHERWISE. Bruckewell Technology Inc., its affiliates, agents, and employees, and all persons acting on its or their behalf (collectively, “Bruckewell”), disclaim any and all liability for any errors, inaccuracies or incompleteness contained in any datasheet or in any other disclosure relating to any product. Bruckewell makes no warranty, representation or guarantee regarding the suitability of the products for any particular purpose or the continuing production of any product. To the maximum extent permitted by applicable law, Bruckewell disclaims (i) Any and all liability arising out of the application or use of any product. 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Product specifications do not expand or otherwise modify Bruckewell’s terms and conditions of purchase, including but not limited to the warranty expressed therei Publication Order Number: [BW6562A] © Bruckewell Technology Corporation Rev. A -2014