NCP1351PRINTGEVB NCP1351 16 V/32 V – 40 W Printer Power Supply Evaluation Board User'sManual http://onsemi.com EVAL BOARD USER’S MANUAL Description Natural Frequency Dithering: The quasi-fixed ton mode of operation improves the EMI signature since the switching frequency varies with the natural bulk ripple voltage. Extremely Low Start-up Current: Built on a proprietary circuitry, the NCP1351 startup section does not consume more than 10 mA during the startup sequence. The designer can thus easily combine startup time and standby consumption. Overload Protection Based on Fault Timer: Every designer knows the pain of building converters where a precise over current limit must be obtained. When the fault detection relies on the auxiliary VCC, the pain even increases. Here, the NCP1351 observes the lack of feedback current and starts a timer to countdown. At the end of its charge, the timer either triggers an auto-recovery sequence (auto-restart, B and D versions) or permanently latches-off (A and C). On C and D versions the fault timer is started at an output power corresponding to 60% of the maximum deliverable power; to allow transient peak power delivery. Latch Fault Input: A dedicated input lets the designer externally trigger the latch to build additional protections such as over-voltage (OVP) or over-temperature (OTP). The present document describes a printer power supply operated by the NCP1351, a fixed ton /variable off time controller. The board can deliver 10 W average on a 16 V output and 30 W average on a 32 V output with a transient peak power capability of 80 W. It however exhibits a low standby power: below 150 mW at no load whatever the input voltage. Let us first review the benefit of using the NCP1351: The NCP1351 at a Glance Fixed ton , Variable toff Current-mode Control: Implementing a fixed peak current mode control (hence the more appropriate term “quasi-fixed” ton), the NCP1351 modulates the off time duration according to the output power demand. In high power conditions, the switching frequency increases until a maximum is hit. This upper limit depends on an external capacitor selected by the designer. In light load conditions, the off time expands and the NCP1351 operates at a lower frequency. As the frequency reduces, the contribution of all frequency-dependent losses accordingly goes down (driver current, drain capacitive losses, switching losses), naturally improving the efficiency at various load levels. Peak Current Compression at Light Loads: Reducing the frequency will certainly force the converter to operate into the audible region. To prevent the transformer mechanical resonance, the NCP1351 gradually reduces – compresses – the peak current setpoint as the load becomes lighter. When the current reaches 30% of the nominal value, the compression stops and the off duration keeps expanding towards low frequencies. Low Standby-power: The frequency reduction technique offers an excellent solution for designers looking for low standby power converters. Also, compared to the skip-cycle method, the smooth off time expansion does not bring additional ripple in no-load conditions: the output voltage remains quiet. Semiconductor Components Industries, LLC, 2012 October, 2012 − Rev. 0 Figure 1. NCP1351 Evaluation Board 1 Publication Order Number: EVBUM2150/D NCP1351PRINTGEVB The Schematic detects a need for a frequency higher than 60 kHz, implying an overload condition, it will start to charge the timer capacitor: if the overload disappears, the timer capacitor goes back to zero. If the fault remains, the timer capacitor voltage reaches 5 V and latches off the controller. During the fault condition, the power supply will anyway deliver the output power while the switching frequency is below its maximum value of 100 kHz. The transformer has been derived using the Excel spreadsheet available from the ON Semiconductor website which also gives transformer parameters. We came up to the following values: The design must fulfill the following specifications: Input Voltage: 88 – 265 Vac Output Voltage: 16 V @ 0.625 A and 32 V @ 1 A Nominal (40 W); with Transient 80 W Peak Power Capability during 40 ms, and 62 W Peak during 400 ms Over Power Protection below 100 W for the Whole Input Voltage Range (LPS) Latched Short-circuit Protection Latched Over-voltage Protection Latch Recovery Time below 3 s Brown-out Protection Start-up Time below 3 s Lp = 270 mH Np:Ns = 1:0.2 Np:Naux = 1:0.2 Ipk = 3 A In order to deliver the peak output power, the NCP1351 will increase its switching frequency up to the upper limit set by the CT capacitor. To not jeopardize the EMI test compliance, the switching frequency should be kept below 150 kHz. We will choose 100 kHz to have a good margin. As a result the switching frequency at nominal load will be around 50 kHz. Since we need to deliver 80 W of transient peak power while ensuring the power will never be above 100 W, we will use the C version of NCP1351, specially tailored for this kind of application. When the controller The transformer has been manufactured by Coilcraft (www.coilcraft.com). The leakage inductance is kept around 3% of the primary inductance, leading to a good efficiency and reduced losses in no-load conditions. The schematic appears on Figure 2. The converter operates in DCM at nominal power; and for peak power it goes CCM with close to 50% duty-cycle at low mains and stays CCM at high line. D5 D13 + C13 U1 C12 R5 R24 R6 R2 R23 C14 R14 C6 R8 C4 D9 8 7 6 5 L2 C15 + C16 C10 C8 X11 X4 R1 R11 + C7 R30 C23 X10 Figure 2. The Simplified 40 W Printer Board Featuring the NCP1351 Controller http://onsemi.com 2 + C17 32 V GND 16 V R31 R28 R18 D11 C1 Aux D10 + C3 C20 R20 L1 NCP1351C 1 2 3 4 R13 D7 + C19 D3 R10 X4x C18 R15 D4 X6 Fuse L3 + R19 R21 C21 R22 NCP1351PRINTGEVB controller is latched (a direct connection to the AC line would also work). Despite a small value for C3, the VCC still maintains in no-load conditions thanks to the split configuration: Two 330 kW resistors in series with a 60 V zener diode ensure a clean start-up sequence with the 4.7 mF capacitor (C3), not from the bulk capacitor as it is usually done; but from the fully rectified, unfiltered haversine. This configuration allows for a quick release time after the HV rail R5 330 k 1 8 2 7 3 6 4 5 + Cbulk R6 330 k D10 60 V VCC + C3 4.7 m NCP1351 + C7 22 m Aux Figure 3. The split VCC configuration helps to start-up in a small period of time (C3 to charge alone) but the addition of a second, larger capacitor (C7), ensures enough VCC in standby. NCP1351C transiently authorizes higher power, but safely latches off if the overpower lasts too long. To ensure a fault timer duration of at least 500 ms (to be able to deliver the 62 W power peak during 400 ms), the timer capacitor C10 must be 1.5 mF. This value will be adjusted depending on the specification, according to the maximum peak power duration the adapter must sustain. If anyway a constant overpower protection is needed over the whole input voltage range, a simple arrangement can be used: given the negative sensing technique, we can use a portion of the auxiliary signal during the on time, as it also swings negative. However, we don’t want this compensation for short TON durations since standby power can be affected. For this reason, we can insert a small integrator made of C9−R26 (see Figure 4). To avoid charging C9 during the flyback stroke, D14 clamps the positive excursion and offers a stronger negative voltage during the on time. The primary-side feedback current is fixed to roughly 300 mA via R8 and an additional bias is provided for the TL431. 1 mA at least must flow in the TL431 in worse case conditions (full load). Failure to respect this will degrade the power supply output impedance and regulation will suffer. A 2.7 kW value for R19 has proven to do just well, without degrading the standby power. The overvoltage protection uses a 17 V zener diode (D9) connected to the auxiliary VCC. When the voltage on this rail exceeds 17 V plus the NCP1351 5 V latch trip point (total is thus 22 V), the circuit latches-off and immediately pulls the VCC pin down to 6 V. The reset occurs when the injected current into the VCC pin falls below a few mA, that is to say when the power supply is disconnected from the mains outlet. To speed-up this reset phase, a connection to the fully rectified haversine resets the system faster (Figure 3). To satisfy the maximum power limit, we don’t need to add a true Over Power Protection (OPP) circuit since our http://onsemi.com 3 NCP1351PRINTGEVB Rcomp R26 470 k OPP Adjust 2.2 k C9 220 p D14 1N4148 Rcs Rsense 1 8 2 7 3 6 4 5 −N.Vin VCC + + Vaux NCP1351 Figure 4. A Simple Arrangement Provides an Adjustable Overpower Power Compensation Overpower Protection Level: A simple resistor connected between the auxiliary winding (that swings negative during the ON time) and the CT capacitor ensure a stable operation in CCM despite the duty cycle above 50% at very low line, due to the ripple on the bulk capacitor. The unique features of NCP1351C allow using a 100 mF bulk capacitor while delivering the transient peak power and ensuring the output is still regulated during line drop-outs. Finally, the clamping network maintains the drain voltage below 520 V at high-line (375 Vdc) which provides 85% derating for the 600 V BVdss device. The power supply is able to deliver a peak power of 85 W during 500 ms from 85 Vac to 270 Vac. It can deliver a constant output power of more than 40 W, but less than 80 W over the same input voltage range. Table 3. START-UP TIME Once assembled, the board has been operated during 15 min at full power to allow some warm-up time. We used a WT210A from Yokogawa to perform all power related measurements coupled to an electronic ac source. Table 1. EFFICIENCY 120 Vac 230 Vac 40 W 84.4% 85.4% 25 W 85.9% 85.9% 10 W 86.0% 85.1% 5W 85.5% 83.2% 2W 83.4% 79.5% 1W 77.7% 73.3% 0.5 W 70.0% 66.3% 85 Vac 230 Vac Start-up Duration 2.7 s 0.5 s In the above tables, we can see the excellent efficiency, especially at light load conditions thanks to the natural frequency foldback of the NCP1351. The no-load standby power stays below 150 mW at high line, a good performance for a dual output power supply able to deliver 80 W. Please note that the high-voltage probe observing the drain was removed and the load totally disconnected to avoid leakage. Despite operation in the audible range, we did not notice any noise problems coming from either the transformer or the RCD clamp capacitor. Measurements VIN (POUT) VIN (POUT = 40 W) 120 100 Vin(min) Vin(max) FSW 80 Table 2. NO-LOAD POWER VIN (POUT) 120 Vac 230 Vac No-load 75 mW 140 mW 60 CCM Transition 40 20 0 0 20 40 60 80 100 120 140 Pout Figure 5. Switching Freq. Variations vs. Output Load http://onsemi.com 4 NCP1351PRINTGEVB Scope Shots Below are some oscilloscope shots gathered on the evaluation board: 2.7 s 32 V VOUT VDRAIN Figure 6. Start-up Time, VIN = 85 Vac Figure 7. Maximum Output Power, VIN = 265 Vac Conclusion The limited number of surrounding components around the controller associated to useful features (timer-based protection, latch input) makes the NCP1351 an excellent choice for cost-sensitive printer adapter designs. The printer power supply built with the NCP1351 exhibits an excellent performance on several parameters like the efficiency and the low-load standby. The transient switching frequency increase allows to deliver peak power during a limited time; but if the overpower lasts longer than the set fault timer, the controller safely latches off. http://onsemi.com 5 NCP1351PRINTGEVB PCB LAYOUT Figure 8. Top Side Components Figure 9. Copper Traces Figure 10. SMD Components http://onsemi.com 6 NCP1351PRINTGEVB U1 Fuse DF05M 220 n ELF−25F108A R14 0.33 3.4 k D14 NC NC R13 3.3 M R23 CS 3.3 M C9 C6 R2 4.7 M C5 OptoBase X4x FB 1.5 m 2.7 k R8 C4 0 R9 Ct D12 6V2 NC C101 4 3 2 1 5 6 7 8 Timer 1k R10 D9 10 n R11 1 k D2 17 V VCC D10 60 V 1N4148 NC 0 R12 R5 330 k 330 k + + NC D1 NC 10 n 1N4007 0 R1 15 R17 R6 D11 R7 4.7 m Q1 R26 0 NTC C10 C1 100 n C8 C7 47 m D4 BAS20 D3 10 m L1 Aux 0 C12 R15 150 k D7 R30 Vaux MBR20100 47 k C15 100 n X11 IRFIB6N60 C16 X4 1000 m D5 MBR20100 1000 m C19 + 2.2 n C18 100 n + C23 R24 NCP1351A 100 n C3 Jitter R25 OPP NC 180 p NC C13 100 m 1N4007 D13 + Rsense X6 C14 TL431 C17 SFH615A 2.7 k R19 C21 R22 100 n L3 4.7 m L2 C20 R28 3.24 k 105 k R20 R21 3.65 k 200 k R31 + 10 k 4.7 m + X10 1 k R18 100 m 100 m 32 V 16 V GND Figure 11. Schematic for the NCP1351 40 W Printer Evaluation Board http://onsemi.com 7 NCP1351PRINTGEVB Table 4. BILL OF MATERIAL FOR THE NCP1351 40 W PRINTER EVALUATION BOARD Designator Qty. Description Value Tolerance Footprint Manufacturer Manufacturer Part Number Substitution Allowed Lead Free C1, C4, C15, C18, C21 5 SMD Capacitor 100 nF/50 V 5% SOD−1206 Vishay VJ1206Y104KXAA Yes Yes C3 1 Electrolytic Capacitor 4.7 mF/50 V 20% Radial − OD 5 mm Panasonic ECEA1HN100U Yes Yes C6 1 SMD Capacitor 180 pF/50 V 5% SOD−1206 Vishay VJ1206A181KXAA Yes Yes C7 1 Electrolytic Capacitor 47 mF/50 V 20% Radial − OD 5 mm Panasonic ECA1HM470 Yes Yes C8 1 SMD Capacitor 10 nF/50 V 5% SOD−1206 Vishay VJ1206Y103KXAA Yes Yes C10 1 SMD Capacitor 1.5 mF 10% SOD−1206 Murata GRM31MR71C155K Yes Yes C12 1 Film Capacitor 10 nF/630 V 5% Radial Epcos B32521N8103J Yes Yes C13 1 Electrolytic Capacitor 100 mF/400 V 20% Radial − OD 20 mm United chemicon EKXG401ELL101MMN3S Yes Yes C14 1 X2 Capacitor 330 nF/250 Vac 20% Radial Epcos B32923A2334M Yes Yes C16 1 Electrolytic Capacitor 1,000 mF/50 V 20% Radial − OD 12.5 mm Panasonic ECA1HHG102 Yes Yes C17 1 Electrolytic Capacitor 100 mF/50 V 20% Radial − OD 10 mm Panasonic EEUEB1H101S Yes Yes C19 1 Electrolytic Capacitor 1,000 mF/25 V 20% Radial − OD 12.5 mm Panasonic ECA1EHG102 Yes Yes C20 1 Electrolytic Capacitor 100 mF/25 V 20% Radial − OD 10 mm Panasonic EEUEB1E101 Yes Yes C23 1 Y1 Capacitor 2.2 nF/250 Vac 20% Radial TDK CD12−E2GA222MYNS Yes Yes D1 1 SMD Resistor 0 W/0.25 W 5% SOD−1206 Vishay CRCW12060000Z0EA Yes Yes D3 1 High-voltage Switching Diode 200 mA/200 V − SOT−23 ON Semiconductor BAS20LT1G No Yes D4 1 Fast-recovery Rectifier 1 A/600 V − Axial ON Semiconductor 1N4937G No Yes D5, D7 2 Schottky Rectifier 20 A/100 V − TO−220 ON Semiconductor MBR20100CTG No Yes D9 1 Zener Diode 17 V/0.5 W 5% SOD−123 ON Semiconductor MMSZ5247BT1G No Yes D10 1 Zener Diode 60 V/0.5 W 5% SOD−123 ON Semiconductor MMSZ5264BT1G No Yes D11 1 Switching Diode 200 mA/75 V − SOD−123 ON Semiconductor MMSD4148T1G No Yes D12 1 Zener Diode 6.2 V/0.5 W 5% SOD−123 ON Semiconductor MMSZ5234BT1G No Yes D13 1 Standard Rectifier 1 A/1,000 V − Axial ON Semiconductor 1N4007G No Yes HS1 1 Heatsink 13.4C/W − Radial Aavid Thermalloy 531002B02500G Yes Yes HS2, HS3 2 TO-220 Heatsink 24C/W − − Aavid Thermalloy 577202B00000G Yes Yes U1 1 Rectifier Bridge 1 A/600 V − DIP−4 Micro Commercial Co. DB105-BP No Yes U2 1 CMOS IC − − SOIC−8 ON Semiconductor NCP1351CDR2G No Yes X4 1 Optocoupler − − DIP−4 CEL-NEC PS2501−1−H-A No Yes X6 1 Common-mode Choke 2 15 mH/1 A − Radial Panasonic ELF−25F108A No Yes X10 1 Shunt Regulator 2.5–36 V 5% TO−92 ON Semiconductor TL431CLPG No Yes X11 1 Power MOSFET N-Channel 3 A/600 V − TO−220 Rohm 2SK2792 No Yes T1 1 Transformer − − Radial Coilcraft GA0007−AL No Yes J1 1 Connector 230 Vac − Radial Qualtek 771W−X2/02 Yes Yes F1 1 Fuse 2 A/250 Vac T Radial Wickmann 37212000411 Yes Yes L1 1 SMD Inductor 10 mH − SMD Coilcraft DO1605T−ML No Yes L2, L3 2 Inductor 4.7 mH/4.3 A 20% Radial API Delevan Inc. 4554−4R7M Yes Yes R1 1 SMD Resistor 15 W/0.25 W 5% SOD−1206 Vishay CRCW120615R0JNEA Yes Yes http://onsemi.com 8 NCP1351PRINTGEVB Table 4. BILL OF MATERIAL FOR THE NCP1351 40 W PRINTER EVALUATION BOARD (continued) Designator Qty. Description Value Tolerance Footprint Manufacturer Manufacturer Part Number Substitution Allowed Lead Free R2 1 Resistor 4.7 MW/0.33 W 5% Axial − − Yes Yes R5, R6 2 SMD Resistor 330kW/0.25 W 1% SOD−1206 Vishay CRCW1206330RFKEA Yes Yes R7 1 SMD Resistor 0 W/0.25 W 5% SOD−1206 Vishay CRCW12060000Z0EA Yes Yes R8, R19 2 SMD Resistor 2.7 kW/0.25 W 5% SOD−1206 Vishay CRCW12062R70JNEA Yes Yes R9, R12 2 SMD Resistor 0 W/0.25 W 5% SOD−1206 Vishay CRCW12060000Z0EA Yes Yes R10, R11, R18 3 SMD Resistor 1 kW/0.25 W 5% SOD−1206 Vishay CRCW12061K00JNEA Yes Yes R13 1 SMD Resistor 3.4 kW/0.25 W 1% SOD−1206 Vishay CRCW12063K40FKEA Yes Yes R14 1 SMD Resistor 0.33 W/0.5 W 1% SOD−1206 − − Yes Yes R15 1 Resistor 150 kW/2 W 5% Axial − − Yes Yes R20 1 SMD Resistor 100 kW/0.25 W 1% SOD−1206 Vishay CRCW1206100KFKEA Yes Yes R21 1 SMD Resistor 56 kW/0.25 W 1% SOD−1206 Vishay CRCW120656K0FKEA Yes Yes R22 1 SMD Resistor 10 kW/0.25 W 1% SOD−1206 Vishay CRCW120610K0FKEA Yes Yes R23, R24 2 SMD Resistor 3.3 MW/0.25 W 5% SOD−1206 Vishay CRCW12063M30JNEA Yes Yes R26 1 SMD Resistor 0 W/0.25 W 1% SOD−1206 Vishay CRCW12060000FKEA Yes Yes R28 1 SMD Resistor 8.2 kW/0.25 W 1% SOD−1206 Vishay CRCW12068K20FKEA Yes Yes R30 1 SMD Resistor 47 kW/0.25 W 1% SOD−1206 Vishay CRCW120647K0FKEA Yes Yes R31 1 SMD Resistor 180 kW/0.25 W 1% SOD−1206 Vishay CRCW1206180KFKEA Yes Yes TEST PROCEDURE AC Input (85−265 Vac) 16 V Output 0V Figure 12. Test Procedure Schematic WARNING: 32 V Output Be careful when manipulating the boards in operation, lethal voltages up to 600 V are present on the primary side. An isolation transformer is also recommended for safer manipulations. Necessary Equipment Test Procedure 1. Apply 110 Vac on the Vin pins. Output pins are left floating. 2. Measure the output voltage between pins +16 V et GND and between +32 V and GND with a volt-meter on the 50 V range. The measurements should be respectively 16 and 32 volts (10%). 1 current limited 230 Vrms AC source (current limited to avoid board destruction in case of a defective part) 1 DC volt-meter able to measure up to 50 V DC 2 programmable electronic loads http://onsemi.com 9 NCP1351PRINTGEVB The power supply should go to short-circuit protection. Measure the output voltages that should be 0 V. 6. Change the current setpoint for the electronic load connected between pins +32 V and GND back to 1 A. Turn off the AC voltage source. Wait 5 seconds. Apply it again, the outputs should rise again. Measure the output voltages that should again be respectively 16 and 32 volts (10%). 7. If every step has gone well, the board is considered to be ok. 3. Connect an electronic load between pins +32 V and GND, and set up a current of 1 A. Connect another electronic load between pins +16 V and GND, and set up a current of 0.625 A. Measure the output voltages that should be respectively 16 and 32 volts (10%). 4. Change the voltage applied on the Vin pins to 230 Vac. Measure the output voltages that should again be respectively 16 and 32 volts (10%). 5. Change the current setpoint for the electronic load connected between pins +32 V and GND to 2.8 A. Microsoft Excel is a registered trademark of Microsoft Corporation. ON Semiconductor and are registered trademarks of Semiconductor Components Industries, LLC (SCILLC). SCILLC owns the rights to a number of patents, trademarks, copyrights, trade secrets, and other intellectual property. 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