AND8262/D 8 W DVD Power Supply with NCP1027 Prepared by: Christophe Basso ON Semiconductor http://onsemi.com APPLICATION NOTE Overview Digital Video Disks players require a few different voltages to power the logic circuitry but also all servo−mechanisms linked to the tray and optical head actuators. The NCP1027 lends itself very well to this kind of applications where simple architectures lead to the lowest assembly cost. Despite the variety of low−end DVD players on the market, there is a common trend on the power supply requirements: • Universal input voltage: 85 to 265 Vac, 2 wire power cord • 5 different dc voltages, 1 non−filtered bias level: 1. 5 V / 1 A 2. 3.3 V / 1 A 3. – 12 V / 20 mA 4. + 12 V / 20 mA 5. – 23 V / 10 mA 6. Floating display bias • Low standby power in no−load and partial load conditions These specifications can fluctuate depending on a particular type of player but the basic power supply architecture remains the same. We will use a current−mode flyback regulator built around the integrated power switcher, the NCP1027. This DIP 8 package hosts a high performance controller together with a low RDS(on) 700 V BVdss MOSFET. On top of the standby needs, we have packed other interesting goodies in this circuit. They are summarized below: • Brown−out Detection: the controller will not allow operation in low mains conditions. You can adjust the level at which the circuit starts or stops operation. • Ramp Compensation: designing in Continuous Conduction Mode helps to reduce conduction losses. However, at low input voltage (85 Vac), the duty−cycle might exceed 50% and the risk exists to enter a subharmonic mode. A simple resistor to ground injects the right compensation level. • Over Power Protection: a resistive network to the bulk reduces the peak current capability and accordingly harnesses the maximum power at high line. As this is © Semiconductor Components Industries, LLC, 2006 August, 2006 − Rev. 0 • • done independently from the auxiliary VCC, the design gains in simplicity and execution speed. Latch−off Input: some manufacturers require a complete latch−off in presence of an external event, e.g. over temperature or a severe over−voltage protection. The controller offers this possibility via a dedicated input. Frequency Dithering: the switching frequency (here 65 kHz) is modulated during operation. This naturally spreads the harmonic content and reduces the peak value when analyzing the signature. Design Description Figure 2 shows the electrical schematic used for this application. The NCP1027 directly connects to the power transformer and a classical RCD clamping network prevents any BVdss runaways. A string of resistors (R14 , R15 and R9 ) set the minimum operating voltage to increase safety in case of a low input level: the circuit does not switch until enough voltage appears on the mains connector. During this time, VCC goes up and down via the activated high−voltage current source and self−supplies the controller. When the mains reaches the adequate level (70 Vac here), the power supply automatically resumes operation and performs its duty. Please note that bringing pin 3 above a certain level (3.5 V) permanently latches off the switcher. It can be useful in case safety specifications impose a complete shutdown in presence of a stringent event: Over Temperature Protection (OTP), latched OverVoltage Protection (OVP)… As this design enters the Continuous Conduction Mode (CCM) at low line, we have added some ramp compensation via a single resistor connected from pin 2 to ground: no sub−harmonic oscillations can be detected at low line input and full load. Thanks to the NCP1027, the power supply is inherently protected against short−circuits, whatever the VCC pin level is. An internal circuitry permanently monitors the feedback pin and starts a timer when pin 4 goes high (open−loop conditions in startup sequence or in a short−circuit condition). If the timer reaches completion before the fault has gone, the switcher stops all pulses and enters an auto−recovery protective mode. When the fault disappears, 1 Publication Order Number: AND8262/D AND8262/D the switcher resumes operation. However, the point at which the controller detects the fault can move in relationship to the input rail: the power delivered at high line is slightly greater than at low line. The guilty is the total propagation delay from the current sense comparator to the output latch. Fortunately, it can easily be compensated via current injection in pin 7, as shown in AND8241/D. Again, if your design specifications impose a precise output over current protection, implementing this solution can represent a viable option. The output feedback implements a so−called weighted control where two outputs are observed. Depending on the required precision, a weight is imposed on each control loop, let us select 30% for the 5 V and 70% for the 3.3 V. Calculation is as follows: 1. select a bridge current. We will use 250 mA with our TL431. 2. evaluate the lower side resistor given the considered output voltage: Rupper * 5 V + 10 k + 33.3 kW 0.3 Rupper * 3.3 V + 3.2 k + 4570 W 0.7 These two resistors are respectively made of R4 – R6 and R3 – R7 on the final schematic. A simple 100 nF introduces a pole−zero combination together with C16 . Finally, various inductors are placed on the outputs to reduce the switching ripple down to an acceptable level. Transformer The transformer is made by Pulse Engineering and has the reference 2472.0003A (please BOM details). The device exhibits the following turn ratios and inductance, its pinout appears on Figure 1: Lp = 2.2 mH Lleak < 40 mH @ 100 kHz W1:W2 (aux. winding) = 74:14 W1:W4 (5 V) = 74:1 W1:W3 (3.3 V) = 74:2 W1:W5 (12 V) = 74:4 W1:W6 (– 22 V) = 74:12 W1:W7 (FL1 and FL2) = 74:3 Rupper * 5 V + 5 * 2.5 + 10 kW 250 m Rupper * 3.3 V + 3.3 * 2.5 + 3.2 kW 250 m 3. now apply the selected weighting factor to each resistor: 7 +12 V 11 +Vin W5 +5 V 10 W1 W4 8 +3.3 V W3 Drain 3 9 W6 +VCC 1 12 −22 V 13 +F W7 W2 2 14 −F Figure 1. The Transformer Pinout Showing an AC Stacked Winding Configuration Given the selected core, the transformer can deliver an output power up to 12 W. Thanks to pin 7, you can precisely alter the peak current limit and thus, the maximum output to the level of your choice: a wide range of DVD players applications can then be covered. http://onsemi.com 2 AND8262/D D3 1N4934 1 C1 10 mF 63 V + 233 m 2 7 R14 2.2 M F1 LCM 1 3 TR1 R8 47 R15 2.7 M PT1 DF08 R27 47 k C7 10 n + IN − C55 47 mF Type = 400 V + R13 5.6 k D1 1N4007 C18 220 nF _X2 7 6 5 IC1 NCP1027 1 C4 10 nF C8 22 mF 10 V 2 3 C16 1n + IC3 R16 R9 75 k 27 k Figure 2. The Complete Application Schematic, Primary Side http://onsemi.com 3 4 AND8262/D C20 470 p R2 150 13 D12 1N4148 14 R12 1k GND R5 820 D8 1N4934 L8 10 mH FL2 12 FL1 + 200 m D4 1N963 C9 47 mF _35 V 9 C2 100 n + C19 47 mF _16 V −22 V −12 V L2 10 m D14 1N5822 3.3 V 8 5.0 V + 36 m C5 100 m C14 470 mF _10 V 9 12 V L3 10 m D13 1N5822 10 + 56 m C6 100 mF 10 V C15 470 mF _10 V 9 D15 1N4934 11 C21 470 mF _16 V 142 m + 9 R4 330 R3 270 R6 33 k R7 4.3 k C13 2.2 nF Type = Y1 IC3 R11 1.0 k R10 1.0 k C12 100 nF IC2 TL431 R1 10 k Figure 3. The Complete Application Schematic, Secondary Side http://onsemi.com 4 AND8262/D Operating Waveforms and Test Results To perform some tests, we have loaded the prototype converter with a DVD player and artificially loaded some of its outputs, mainly the +3.3 V and the +5 V. The static board load is the following: 3.3 V = 700 mA 5 V = 500 mA 12 V = 20 mA –12 V = 25 mA – 23 V = 2 mA A 520 mA peak current was then added on top of the 5 V or the 3.3 V output. Results are displayed below: 520 mA 3.3 V 5V Figure 4. Both Input Levels Give the Same Performance when the 5 V is Loaded by 520 mA Peaks. 520 mA 3.3 V 5V Figure 5. Here, the 3 V is Loaded by 520 mA Peaks on Top of its Current Consumption http://onsemi.com 5 AND8262/D I(5V5) I(5V) 5V5 5V Figure 6. Opening the Tray Gives Birth to a Current Train of Pulses As these plots reveal, the voltage variations stay well within 5% of the nominal output. When left operated at 230 Vac in no−load conditions, the input standby power is 0.5 W. Figure 7. EMI plot of a DVD player powered by the power supply – the dark blue curve corresponds to the Quasi−Peak sweep whereas the light blue describes the Average sweep. The efficiency lies around 75% from 90 Vac up to 265 Vac. The NCP1027 case temperature moves between 60°C (low line) and 54°C (high line). In both cases, the ambient was 25°C. The Brown−Out protection imposes an operating window above 82 Vac (start−up) and stops operations below 56 Vac. These numbers can of course be altered by playing on R14 , R15 and R9 (for calculation details, please the NCP1027 data−sheet). The front−end filter includes a simple 2 x 6.8 mH common mode inductor whose leakage inductance forms a differential mode filter together with C18. The EMI plot in both Quasi−Peak (QP) and Average modes looks good as testified by Figure 7. Both sweeps were obtained with the DVD chassis operating and connected to the earth via a wire. Figure 8 and 9 show the pcb silkscreen and the copper traces. http://onsemi.com 6 AND8262/D Figure 8. The Demoboard Silkscreen Figure 9. PCB Copper Layout As we stated, the transformer is available from Pulse Engineering at the following address: Pulse Italy s.r.l con s.u. Via Ticino, 2C I−22070 Senna Comasco (CO) − ITALY Tel: +39031463071 Fax:+390314630790 e−mail: [email protected] website: www.pulseeng.com http://onsemi.com 7 AND8262/D Bill of Materials − NCP1027 Designator C1 Qty 1 20% Footprint radial Manufacturer Panasonic Manufacturer Part Number ECA1JM100 100nF/50V 10nF/100V 10nF/630V 100uF/16V 10% 10% 10% 20% radial radial radial radial Murata Murata Vishay Panasonic 22uF/16V 20% radial 47uF/35V 20% 2.2nF/250V 470uF/16V yes rper71h104k2m1a05u rper72a103k2m1b05a mkt1822310635 eca1cm101 yes yes yes yes no no no no Panasonic ECA1CM220 yes no radial Panasonic ECA1VM470 yes no 20% 20% radial radial Ceramite BC Comp. 440ld22 2222−13555471 yes yes no no 1nF/100V 220nF/630V 47uF/16V 10% 20% 20% radial radial radial Murata Evox Rifa Panasonic rper72a102k phe840md6220m ECA1CM470 yes yes yes no no no 470pF/100V 100nF/630V 47uF/400V 5% 20% 20% radial radial radial AVX Evox Rifa Panasonic sr211a471jtr phe840mx6100m ECA2GM470 yes yes yes yes no yes 1A/1000V 1A/100V 0% 0% axial axial ON Semiconductor ON Semiconductor 1n4007g 1n4934g yes yes yes yes 12V/0.5W 0.2A/75V 0% 0% axial axial 1n963b 1n4148 yes yes yes no 3A/40V 500mA/temp NCP1027 0% 0% 2.5−36V/1−100mA sfh6156/ 2p/250V 2/ 2% 0% 0% 0% Fairchild Philips Semiconductor ON Semiconductor Schurter ON Semiconductor ON Semiconductor Vishay Multicomp Weidmuller 1n5822g 0034.6612 NCP1027 tl431ilpg sfh6156−2t jr−201s pm5.08/2/90 yes yes yes yes yes yes yes yes no yes yes yes no no Schaffner Wurth Elektronik Schaffner General Semiconductor Neohm Neohm Neohm Neohm Neohm Neohm Phoenix Passive Components Neohm Neohm Neohm rn112−1.2/02 744772100 rn114−0.8/02 DB106G yes yes yes yes no yes no no cfr25j10k cfr25j150R cfr25j270R cfr25j330R cfr25j820R cfr25j33k mrs25−4k3−1% yes yes yes yes yes yes yes no no no no no no yes cfr25j47R cfr25j27k cfr25j1k0 yes yes yes no no no cfr25j15k cfr25j2M2 sfr25−2m7−5% yes yes yes no no yes mrs25−75k−1% yes yes cfr200j47k yes no Value 10uF/63V C2,C12 C4 C7 C5,C6 2 1 1 2 C8 1 C9 1 C13 C14,C15, C21 C16 C18 C19 1 3 C20 C22 C55 1 1 1 D1 D3,D8, D15 D4 D12 1 3 D13,D14 F1 IC1 IC2 IC3 J1 J2,J3,J4, J5 LCM L2,L3,L8 L9 PT1 2 1 1 1 1 1 4 zener diode hight−speed diode schottky diode fuse CMOS IC shunt regulator optocoupler connector connector 1 3 1 1 inductor inductor inductor diode bridge 2*6.8mH/1.2A 10uH/2.6A 2*27mH/0.8A 800V/1A 0% 20% 0% 0% axial radial dip8 to92 SMD radial rad5.0 8mm radial radial radial dil R1 R2 R3 R4 R5 R6 R7 1 1 1 1 1 1 1 resistor resistor resistor resistor resistor resistor resistor 10kR/0.33W 150R/0.33W 270R/0.33W 330R/0.33W 820R/0.33W 33kR/0.33W 4.3kR/0.6W 5% 5% 5% 5% 5% 5% 1% axial axial axial axial axial axial axial R8 R9 R10,R11, R12 R13 R14 R15 1 1 3 resistor resistor resistor 47R/0.33W 27kR/0.33W 1kR/0.33W 5% 5% 5% axial axial axial 1 1 1 resistor resistor resistor 5.6kR/0.33W 2.2MR/0.33W 2.7MR/0.4W 5% 5% 5% axial axial axial R16 1 R27 TR1 1 1 1 1 1 1 1 Substitution Allowed Lead Free no Description electrolytic capacitor capacitor capacitor capacitor electrolytic capacitor electrolytic capacitor electrolytic capacitor y1 capacitor electrolytic capacitor capacitor x2 capacitor electrolytic capacitor capacitor x2 capacitor electrolytic capacitor rectifier diode rectifier diode Tolerance Neohm Neohm Phoenix Passive Components resistor 75kR/0.6W 1% axial Phoenix Passive Components resistor 47kR/2W 5% axial Neohm 2472.0003A − multi−output transformer from Pulse Engineering http://onsemi.com 8 AND8262/D Figure 10. 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