Gm6182

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GM6182 Off-line LED Lighting Driver with EZ DimmingTM FEATURES • • • • • • • • • • • • • • DESCRIPTION The GM6182 is a high power-factor, constant current driver IC for offline LED lamps. It can accept input voltage range of 90V to 270VAC. It is based on a sinusoidal buck/forward topology and achieves very high power factor, typically 0.97 or better. Energy Star SSL compliant 90V to 270VAC input range High power factor: better than 0.97 High efficiency: up to 92% sinusoidal buck, 88% sinusoidal forward No need for any electrolytic capacitor 450mV current-limit voltage Improved line regulation Natural current-limited soft start (no inrush current) EZ Dimming TM Over-temperature protection No-load protection, open feedback loop protection Natural spread spectrum (~10dB EMI reduction) 80uA start up current Available in MSOP-10 package The GM6182 supports both non-isolated (buck) and isolated (forward) designs. It has a built-in EZ Dimming feature. It counts the number of wall switch toggling and changes the light output accordingly. To retrofit an existing lighting fixture with a dimming feature, all it takes is to replace a conventional light bulb with a GM6182 LED light bulb. There is no need for rewiring, or installing a triac dimmer. The EZ Dimming provides 3 dimming levels below full power, 60%, 40%, and 20%. It maintains high power factor, and high efficiency at any dimming level. APPLICATIONS • • • Rev. 1.0 – March 26, 2011 The GM6182 provides an on-chip over-temperature protection. It shuts down the switching when its o junction temperature exceeds 150 C. General LED lighting Stairway, hallway, or warehouse lighting Lighting for public buildings including airports, train stations, subway stations, schools, factories Note: GreenMark patents:.US 7,295,452 and US 7,750,616. Other patents pending TYPICAL APPLICATION Cy2 0.5A fuse 1nF, 3kV HD06 (600V, 0.8A) AC V+ Cx C1 0.1u C2 0.1u AC V- 90V ~ 130VAC R1 1M R3 680k 1mH R2 20k C4 1n D3 C8 4.7u R4 330k D5 VCC D2 200V VDD 1W LED x 8 D4,D5: ES1D VDD 47 0.2u Q1 GATE 330 GM6182 VCC2 ISEN 1u GND CT 680p 1mH C3 6.8u VSINE 1M EFD15 D4 96T/96T/12T CAL FBK 1n Rsen 0.72 Q1: FDD3N40 400V, 3.4Ω or AOD3N50 500V, 3.0Ω GT6182 app forward 20k 1 GM6182 ABSOLUTE MAXIMUM RATINGS Operating Junction Temperature…….–40oC to 125oC Storage Temperature Range.………….–65oC to 150oC Lead Temperature (Soldering, 10 sec.).…………300oC Supply Voltage VDD, GATE to GND….………….……..…-0.3V to 22V Power Outputs and Control VCC, ISEN, VCC2 to GND…………….. -0.3V to 6.0V CT, VSINE, FBK, CAL to GND ...............-0.3V to 6.0V Package Thermal Resistance TJA …….. 150oC/W 10 9 8 7 6 1 2 3 4 5 PACKAGE / ORDER INFORMATION PIN DESCRIPTION PIN 1 2 NAME VCC CT 3 4 5 FBK GND CAL 2 FUNCTION 5V LDO output Sets the Toff length and the nominal switching frequency Feedback input (from an opto-coupler) Ground Calibration for high line input power PIN 10 9 NAME VDD GATE 8 7 6 ISEN VSINE VCC2 FUNCTION Chip supply voltage Gate drive output for external MOSFET Current sense voltage input Scaled sinusoidal ac input waveform Supply for 2-bit counter GM6182 ELECTRICAL CHARACTERISTICS (VDD = 12.0V. Typical values are at TA = +25oC) Parameter Supply Power Section VDD supply voltage range Operating current Start-up current OVP trip point Conditions Min 7.0 Typ Max Units 17.5 12.0 2.3 60 18.5 3.0 80 19.0 V mA uA V Turn-on threshold voltage 10.0 12.0 16.0 V Turn-off threshold voltage 5.8 6.0 6.2 V 4.9 5.5 6.0 V Fsw =100kHz, Ciss = 1nF VDD = 9.0V UVLO Section LDO Section VCC output voltage Vin from 7V to 16V Protection Section Internal OTP shutdown threshold Internal OTP shutdown reset Switching is turned off. †Note 1. Switching is resumed †Note 1. 150 o 100 o C C Gate Drive Section Source current Sink current Fsw =100kHz, Ciss = 1nF Fsw =100kHz, Ciss = 1nF 15 15 30 30 nsec nsec 400 450 500 mV 1.45 1.50 1.55 V Current Sense Section Current limit reference voltage Current sense level-shift reference Leading edge blanking time Propagation delay † Note 2 From OCP to Vgate drops to 0.9*VDD †Note 1 350 nsec 100 nsec PFC and Line Regulation Section Line regulation reference CAL pin on-state voltage FBK pin output resistance 2.50 1.7 V V kΩ Ct = 680pF. †Note 3 8.3 usec No counting 0.1 4 Sink current = 0.1mA 0.3 Oscillator Section Toff length Counter Section Operating current Number of dimming steps 0.2 uA steps †Note 1: The parameter is guaranteed by design. It is not tested in production. †Note 2: The current sense level-shift reference is correlated to a 1.20V internal reference voltage through a voltage follower buffer. †Note 3: The CT capacitance required for a target Toff is, CT = Toff / 12.2k 3 GM6182 FUNCTIONAL BLOCK DIAGRAM AC V+ Cin R1 R3 C4 AC V- 100V ~ 270VAC R2 C6 1u VSINE Auto Range Waveform Modulator C5 0.2u R5 1M VCC2 VCC 6.8u VDD OVP 2-bit Counter & Dim Control LDO 1.7k FBK CAL R Q30 turns on at high line Q Gate Drive GATE S Qb Level Shift ISEN LEB Q30 Toff GM6182 0.45V GND CT Fig. 1 Functional Block Diagram 4 GM6182 APPLICATION INFORMATION The GM6182 is essentially an extension of the GM6108A, a high power-factor, constant current driver IC for offline LED lighting. The major new feature is the EZ Dimming. The GM6182 can accept input voltage range of 90V to 270VAC. It is based on a proprietary sinusoidal buck/forward topology to achieve very high power factor, typically 0.97 or better. 100kHz, the duty cycle D basically obeys the following equation: Vin*D = Vo = Vf where Vf is the combined forward voltage of the series-connected LEDs. Toff = (1-D) *Tsw = (1-D)/Fsw That is, Fsw = (1-D) / Toff = (1 – Vf/Vin) / Toff So if we keep Toff constant, the switching frequency Fsw will be higher when Vin is high. The GM6182 supports both non-isolated (buck topology) and isolated (forward topology) designs. It has a start-up current of less than 80uA. A bias winding on the buck converter’s inductor or the forward converter’s transformer provides the VDD power to sustain circuit operation after start up. For 110VAC input, most of input power happens when Vin is above 60V. If Vf = 25V, and Toff = 8.5us, Fsw will be 68.6kHz at Vin = 60V. Fsw increases to 98kHz at Vin = 150V. Setting the Switching Frequency Setting up Sinusoidal LED Current Waveform The GM6182 is basically a constant-Toff switching regulator. Its nominal switching frequency, Fsw, can be adjusted via connecting a capacitor on the CT pin, according to the following equation: The LED current waveform follows the rectified sinusoidal waveform of the AC input voltage. Use a voltage divider R1-R2 to provide a proper amplitude at the VSINE pin. The required VSINE amplitude is 2.5V. RT*CT = Toff = (1-D) / Fsw, High Power Factor where RT is a 12.5kΩ equivalent timing resistance. For an 8W LED lighting with 110Vac input such as shown in Fig. 2, Fsw is selected to be 100kHz. At Vpeak = 152V, D is about 17%, and Toff is about 8.4u Because of the in-phase sinusoidal LED current waveform, a GM6182 application circuit achieves excellent power factor, typically better than 0.95. To set Toff = 8.4 usec, we need CT to be 672pF. Using a 680pF capacitor will yield a Toff of about 8.5 usec. An important advantage of the GM6182 LED lighting driver is there is no need for a large electrolytic or tantalum filter capacitor after the input bridge rectifier. Most conventional LED driver designs require an input filter capacitor in the order of 1uF per watt. Natural Frequency Jittering The switching frequency of a GM6182 converter is naturally modulated as Vin varies and follows the AC line’s sinusoidal waveform. This natural frequency jittering helps the LED lighting fixture to meet EMI compliance test. For 110VAC input, Vin varies from 0V to 150V peak. Since the switching frequency is typically near In contrast, GM6182 requires only two small EMI filter capacitors, C1 and C2, of about 0.22uF to filter out highfrequency switching noise from feeding back to the AC lines. Universal Input Range GM6182 can achieve higher efficiency when its input range is either 90V to 130Vac (i.e low line), or 180V to 270Vac (i.e. high line). The low line AC voltage is used in 5 GM6182 USA, Canada, Japan, and Taiwan. Most of other countries use high line AC voltage of 200V to 240V. Since LED lighting products are installed permanently, single-range driver is in general acceptable. However, to simplify inventory and sales management, some LED lighting makers prefer to use universal input range designs. Please keep in mind there is always some tradeoff between universal input range and power efficiency. Typically, we shall expect the efficiency will drop by about 2% for the universal range design. Line Regulation and Calibration For low-line input range of 90Vac to 130Vac, GM6182 provides good line regulation of +/-3%. For high-line input range of 180Vac to 270Vac, GM6182 also provides a good line regulation of +/- 3%. However, for universal input range of 90Vac to 270Vac, we need to place a resistor, Rcal, between CAL (Pin 5) and FBK (Pin 3) to achieve tight line regulation. This calibration resistance is related to the lamp power rating and VF value. We recommend to start with a 20K value for Rcal. After actual measurement of high-line output power, increase Rcal if high-line power is lower than low-line power; reduce Rcal if high-line power is higher than low-line power. Fig. 2 110VAC 8W Isolated LED Light Bulb with EZ Dimming 6 GM6182 A. Ideal sinusoidal current waveform B. 115VAC, full phase current waveform C. 115VAC, 75o phase current waveform D. 115VAC, 20o phase current waveform Fig. 3 Triac dimmer waveform distortion at different dimming level 7 GM6182 E-Cap Free A large electrolytic capacitor not only takes up significant PC board space, its limited life, usually less than several thousand hours, may seriously downgrade the usable life of an LED lighting fixture. The operating life of an electrolytic capacitor can be expressed as Lop = Mv*Lb* 2 [(Tm-Ta)/10] where Lop is the expected operating life in hours. Mv is a voltage multiplier for voltage de-rating. Lb is the expected operating life in hours at full rated voltage and temperature. Tm is the maximum permitted capacitor internal temperature in oC. Ta is the actual capacitor internal temperature in oC. In other words, an electrolytic capacitor’s life will be cut in half for every 10oC of temperature rise. In fact, a major challenge in designing an LED lighting fixture confirming to the conventional incandescent light bulb form factor such as MR16, A19, PAR30, or PAR38 is the thermal management. The LED driver circuit is enclosed inside of a completely sealed chamber with elevated temperature. It is common to measure internal chamber temperature of 100oC or higher. This harsh operating condition often takes a toll on electrolytic capacitors. Therefore, a top priority in designing a long-life LED lighting is, eliminating the need for any electrolytic capacitors. EZ Dimming Concept Most lighting today, including residential, office, and commercial lighting, is not dimmable. Although the lighting industry has long recognized the need for dimmable lighting for power saving, a practical and cost-effective dimming solution is yet to be found. Triac dimmer The triac dimmers were developed many decades ago for control the light output of incandescent lamps. Basically, a triac dimmer uses an RC timing circuit to control the firing angle of the AC voltage supplied to 8 the lamp. That is, a triac dimmer chops off some leading portion of the AC voltage waveform, thus reducing the effective conduction time of the lamp current. Fig. 3 shows the current waveform at different firing angles. The triac dimmer works well for the incandescent lamp which is a pure resistive load. Unfortunately, the triac dimmer has many drawbacks: (1) The voltage chopping and triggering of triac at line frequency will generate inrush current, electromagnetic interference, and audible noise; (2) The chopped-off current waveform is severely distorted and results in poor power factor. Further, most fluorescent lamps and compact fluorescent lamps (CFLs) are not compatible with triac dimmers. In fact, most electronic ballasts for fluorescent lamps will mal-function or could be damaged when applied to a triac dimmer. Similarly, the triac dimmer is not friendly with LED lighting either. While there are several LED driver circuits developed to be compatible with triac dimmers, many technical issues remain un-solvable: (a) Poor power factor – by nature, a triac dimmer has low power factor; (b) Poor line regulation -- another nature of the triac dimmer; (c) Distorted current waveform; (d) Inrush current and EMI noise. Further, a common issue with triac dimmable LED lamp is the flickering at low dimming level. This is due to at deep dimming level, the load current may be lower than the hold current level of the triac, causing the triac to return to blocking state prematurely. Eventually, the unstable on/off operation of the triac and its interaction with the dimmable LED drive circuit often results in an intermittent operation or flickering. In order to resolve this flickering issue, nearly all triac-dimmable LED driver circuits add a bleeder resistor (i. e. dummy load). A typical bleeder resistor dissipates about 1W to 2W. However, in doing so, most of the power saving benefit of a dimmable lighting is lost again. EZ dimmer The EZ Dimming of the GM6182 provides a simple and reliable solution to LED lighting applications. Essentially, the EZ Dimming simply counts the number of wall switch toggling and steps down the lamp power to 60%, 40%, and 20% accordingly. GM6182 As shown in Fig. 4, when the user turns on the wall switch initially, a GM6182 LED lamp starts at full power. Each subsequent wall switch toggling instructs the GM6182 to step down power to 60%, 40%, 20%, respectively. Another toggling will return it to full power again. In essence, an EZ dimming LED light works exactly the same way as a non-dimmable light. It is fully on when the wall switch is turned to the ON position (UP position). It is fully off when the wall switch is turned to the OFF position (DOWN position). However, during night hours, people want to dim the lights in hallways, restrooms, office lobbies, parking garages, or in public buildings like hospitals, airports, schools, train, subway, and bus stations, etc. A first toggle (a quick OFF-ON motion of the wall switch) dims the light to 60% power. Another toggle dims the light to 40% power. A third toggle dims the light to 20% power. One more toggle will resume the light to full power. To jump directly from any dimming level to full on, one simply turns the wall switch to OFF position for more than 1.5 seconds, and turn it to the ON position again. To jump directly from any power level to fully off, one simply turns the wall switch to the OFF position. Power line quality and energy efficiency Fig. 5 shows the input current waveform of Fig. 2 circuit operating at 110Vac and different dimming levels. Fig. 6 shows a 220Vac input, 8W isolated LED lamp. Fig. 7 shows the input current waveform at different dimming level. GM6182 maintains excellent power factor and efficiency at all dimming levels. Notice, using 1uF for C6 will keep VCC2 high for more than 1 second when the wall switch is turned off. VCC2 is a local supply to keep the counter register content alive when the wall switch toggles off briefly. Also, a toggle action should be completed in less than 1.5 seconds. It is observed most people would toggle the wall switch in about 0.2 to 0.8 second. Table 1 compares the EZ Dimming with the Triac dimming methods and their pros and cons. Fig. 4 EZ Dimming Operation Confidential 9 GM6182 Top Trace: input voltage Bottom trace: input current Fig. 5A Full level, Fig. 5B 60% level Fig. 5C 40% level, Fig. 5D 20% level Fig. 5 EZ dimming current waveform at different dimming level 10 Confidential GM6182 Fig. 6 220VAC 8W Isolated LED Light Bulb with EZ Dimming Fig. 7 EZ dimming current waveform at different dimming level (Fig. 6 circuit at 220Vac input) Confidential 11 GM6182 TABLE 1 Triac Dimming EZ Dimming Power factor As low as < 0.10 Efficiency Cost to installing a wall dimmer True power saving Inrush current spike, waveform distortion EMI interference As low as < 10% Parts and labor (>$20 per unit) No (1~2W dummy load) Severe Maintain >90% power factor at any dimming level Maintain >80% efficiency None Yes Clean and smooth Severe None PACKAGE DIMENSIONS 12 Confidential