AND8142/D A 6.0 W/12 W Universal Mains Adapter with the NCP101X Prepared by: Christophe Basso ON Semiconductor http://onsemi.com APPLICATION NOTE controller. The resistor in series with the auxiliary winding limits the current in the active VCC clamp, in case the auxiliary winding is connected. Please note that this option enables the optocoupler fail−safe protection: if the loop gets accidentally opened, the VCC grows−up and imposes an abnormal current into the VCC pin. The internal circuitry detects it and the controller is fully latched−off. The user must unplug the converter from the mains until VCC collapses below 4.0 V to reset all internal logic blocks. The present report depicts a demonstration board built around the NCP1013P06, a new monolithic high−voltage switcher. Delivering 6.0 W from 90 VAC to 250 VAC, the board complies with EMI testing CISPR0022 and offers the ability to either use the Dynamic Self−Supply or an auxiliary winding. With this latter, the converter passes less than 100 mW in a no−load situation at 230 VAC. Schematic Description Figure 1 portrays the board application schematic whose heart is powered by the NCP1013 operating at 65 kHz. This frequency is selected for a) passing the CISPR0022 EMI specification (that starts at 150 kHz) more easily b) reducing the switching losses. As one can see from Figure 1, a jumper exists and offers the ability to disconnect the Dynamic Self−Supply (DSS): when left open, the DSS powers the controller and introduces frequency jittering thanks to the VCC ripple injected inside the circuit. It also offers a precise short−circuit trip point since the decision is taken independently of any loosely coupled auxiliary winding. The input power consumption is directly the current needed to power the controller multiplied by the rectified bulk voltage. If we assume an average controller current of 1.0 mA and a bulk level of 330 VDC, the input power will be around 330 mW in a no−load situation. If the jumper is now put in place, the DSS disconnects itself and the standby power reduces below 100 mW. Precise numbers are given in a summary table at the end of this document. An RCD network safely clamps the maximum drain excursion below 700 V at the highest mains conditions, e.g. Vbulk = 370 V. A small 1.0 nF capacitor decouples the FB to ground and prevents any noise from coupling inside the Semiconductor Components Industries, LLC, 2004 January, 2004 − Rev. 0 Practical Measurements Some typical measurements are detailed below and highlight the impact between the DSS or the auxiliary winding implementation. All measurements were carried in a 25°C operating temperature. Standby Power When the load is removed, it becomes possible to measure the power absorbed by the demoboard in both operating modes, DSS or auxiliary winding. It is required to let the converter warm up for 15 minutes before recording the numbers: DSS: Vin = 120 VDC, Iout = 0, Pin = 130 mW Vin = 330 VDC, Iout = 0, Pin = 320 mW Aux.: Vin = 120 VDC, Iout = 0, Pin = 69 mW Vin = 330 VDC, Iout = 0, Pin = 66 mW The slight difference in the low/high numbers with the auxiliary winding is due to the startup leakage current (35 A), although very low, this number decreases as the junction heats up (the internal controller consumption too). With 330 VDC, the die temperature is slightly higher than with 120 VDC and it explains the minor difference. 1 Publication Order Number: AND8142/D 1N4148 D4 JP1 2 J3 1 C8 2.2 nF 400 V T1 Aux + C10 47 F/35 V R7 150 k/ 1W + T1 A9619−C 2x15 mH CM L1 Schaffner RN112−06/2 Universal Input 220 nF C1 X2 C6a C6b 470 F/16 V R3 1k NCP1013P06 + C2 47 F/ 400 V + 12 V @ 0.85 + 47 F/16 V C7 GND D3 MUR160 R2 3.3 k B1 SMD L2 10 H D2 MBRS360T3 R5 39 k 1 VCC GND 8 2 NC NC 7 3 NC NC 6 4 FB D 5 IC3 + 47 F/16 V C3 C4 C9 1 nF IC1 SFH615A−2 100 nF IC2 TLV431 C5 2.2 nF Y1 Type R6 4.3 k AND8142/D 2 http://onsemi.com Figure 1. The Electrical Schematic of the 6.0 W Power Supply Supply Jumper Off: DSS Activated On: Aux. Winding R_L322 AND8142/D Efficiency Output Voltage Versus Output Current As the DSS is directly drawing current from the rectified rail via the drain pin, the average consumption permanently present (though lowered when skip is activated) slightly degrades the efficiency at light loads and low output power. Nevertheless, efficiency is still above 50% at 730 mW output power. Figures 2 and 3 portray the efficiency evolution at both input voltages with either DSS or auxiliary winding. Using the DSS or an auxiliary winding makes a big difference in the ability to let the power supply detect an over current condition. Both versions will be protected against real short−circuits (Rload = 0), but the DSS will naturally offer an improved performance when a precision trip point is needed. This is mainly due to the poor coupling between the auxiliary winding and the power winding which prevents proper collapsing when Vout goes low. Also, the built−in OVP forces us to grow the auxiliary voltage, which does not play in our favor either. 90 80 Aux 14 DSS 60 12 50 OUTPUT VOLTAGE (V) EFFICIENCY (%) 70 40 30 20 10 0 0 1 2 3 4 5 OUTPUT POWER (W) 6 7 6 4 DSS 0 Aux 0 0.5 1 1.5 2 2.5 OUTPUT CURRENT (A) 3 3.5 DSS 70 Operating Curves It is important to check that critical parameters are well within control before releasing the board to production. Following are some curves captured on the demonstration board with their individual comments. 60 50 40 30 20 10 0 Aux Figure 4. Vout vs Iout (330 Vdc) The DSS Offers a Better Performance to Detect an Overcurrent Condition 90 EFFICIENCY (%) 8 2 Figure 2. Efficiency vs Power, Vin = 330 Vdc Efficiency at High Input Line 80 10 0 1 2 3 4 5 OUTPUT POWER (W) 6 7 Figure 3. Efficiency vs Power, Vin = 120 Vdc Efficiency at Low Input Line http://onsemi.com 3 AND8142/D Drain−Source Waveform 585 V Vds(t) Figure 5. Drain−Source Voltage Captured at Vin = 370 VDC with Maximum Output Power the loop is closed (e.g. Vout reaches its target). The displayed level of 585 V gives sufficient room when compared to the internal MOSFET BVdss of 700 V. This shot has been taken just before the maximum current trip point is reached. It corresponds to the highest peak power and the largest reflected voltage on the drain. This event also occurs during the start−up sequence, just before Feedback Loop Closure Loop is closed here . . . Vfb Error is checked here Vcc Figure 6. It is Important to Check for a Safe Start−Up Sequence At power−on, the controller delivers the maximum peak current. During this time, an error flag is internally raised, signalling that the power supply has reached the maximum peak limit. The fault management circuitry consists in checking the presence of this flag every time the ripple on the VCC pin comes down to 7.5 V. If the error flag is activated at this time, the controller considers the presence of a fault and it triggers the protective burst mode. As a result, since the VCC capacitor must be sized to give enough room to let Vout reach the target before the VCC ripple touches the 7.5 V setpoint. Worse case corresponds to 120 VDC and maximum output power, e.g. 6.0 W in our case. http://onsemi.com 4 AND8142/D Short−Circuit Protection Vds Vcc Figure 7. A Short−Circuit has Occurred, the Controller Enters Burst−Mode start−up source is re−activated and a new start−up attempt is made. This is an auto−recovery system: if the fault fades away, the power supply resumes its operation. As we explained above, when the 7.5 V internal check reveals that the error flag is raised, the controller stops pulsing and reduces its consumption. VCC thus falls down until another lower level is reached (VCClatch) where the Optocoupler Fail−Safe Protection 22 V Unloaded Vout Loaded Figure 8. Fail−Safe Optocoupler Protection Triggered by a Short on the Secondary LED fully latches off and all activity is stopped. The DSS keeps going up and down, but the power supply is permanently stopped. The user needs to reset the controller by unplugging the converter to have VCC falling down below 4.0 V where the latch is reset. When the feedback loop is broken, the auxiliary and output voltages run away. When the VCC pin is supplied by the auxiliary winding (jumper is on), an internal circuitry clamps to 8.7 V typical (a kind of active zener diode). When the auxiliary level runs away, it pushes more current into the active zener. If this current exceeds a given level, the circuit http://onsemi.com 5 AND8142/D Fault Margin Normal Startup Vaux Figure 9. It’s also important that start−up overshoots do not have the bad luck to trigger the fail−safe circuitry. supply gets latched at start−up. Figure 9 confirms the adequate margin with the demo. Playing on R2 will offer a reduction of the overvoltage level, but can affect the margin as well as the standby consumption (e.g. if the active zener is turned on in standby, it is more difficult to go below 100 mW). A 100 nF capacitor connected over the TL431 offers a pure integral compensation. Despite its simplicity, this kind of capacitive network can engender start−up overshoots. If the overshoot is low, as on this board, there is no problem. However, it is important to check that, again, a sufficient margin exists between a normal start−up and a real fault detection. If this margin is too small, there are risks that the Conducted EMI Sweeps QP QP AV AV Figure 10. When the DSS is on, EMI Jittering is Active Figure 11. The Aux Winding Deactivates the Jittering winding is put in place, it disconnects the frequency sweep. Nevertheless, the power supply still passes the limit. Figures 12 and 13 show the same plots but when the converter is powered from a 230 VAC input source. EMI effects are also visible on Figure 12. Figures 10 and 11 portray the conducted EMI sweeps captured at Vin = 100 VAC. One can see the nice spreading effect of the frequency sweep on Figure 10 where the high−frequency noise is artificially reduced: it naturally offers more margin to pass the limit. When the auxiliary http://onsemi.com 6 AND8142/D Conducted EMI Sweeps QP QP AV AV Figure 12. When the DSS is on, the Frequency Jitters Figure 13. The Aux Winding Stops the Jittering Stability Check By pulsing the converter output, it becomes possible to detect any oscillations in the way the converter reacts. Figure 14 shows stable results at low and high line, for a 10% to 100% current excursion. High Line Low Line Figure 14. Pulsing the Output Current Confirms the Stability at Both High and Low Line Conditions Increasing the Output Power The current demonstration board is supplied with a Coilcraft A9619−C transformer featuring a primary inductance of 3.0 mH. This device allows an output power of 6.0 W continuous on a 70°C ambient temperature. However, with the same board, it is possible to raise the output power up to 12 W on a 230 VAC 15% application. 1. Plug another transformer, the Coilcraft B0570−B that features a 3.4 mH primary inductor but whose turn ratio is higher. The pinout is compatible with the PCB, it is thus easy to wire it. 2. Replace the NCP1013P06 by an NCP1013P10, the 100 kHz version. 3. Replace the 150 k RCD resistor (R7) by a 100 k/2.0 W value. The rest is kept unchanged. Please note that the board is now able to deliver up to 12 W output power. Experiments have shown that if the NCP1013P10 layout is improved (more copper area), the new board can experimentally deliver up to 19 W of continuous power in a 60°C ambient temperature. http://onsemi.com 7 AND8142/D Conclusion This board shows how to build, and test for reliability, a power supply made around the new NCP101X device. Despite a DIP8 package, the converter can be used in a variety of applications ranging from auxiliary power supplies up to a few watts converters. Once the chip specification is understood, it becomes a child’s play to make it work! 6.0 W − Universal Mains NCP101X Demonstration Board Part List Reference Value Part Number Manufacturer Comment R2 3.3 k − Any 1/4 W Thru Holes R3 1.0 k − Any 1206 SMD R4 − − − Not Wired R5 39 k − Any 1/4 W Thru Holes R6 4.3 k − Any 1206 SMD R7 150 k 2322 194 13154 BC Comp. PRO1 Thru Holes R_L3 22 − Any 1/4 W Thru Holes Replaces L3 L1 2 x 15 mH RN112−0.6/02 Schaffner CM Mode L2 10 H 744 772 100 Wurth Elect. LC Filter L3 − − − Not Wired B1 800 V/1.0 A DF08M General Semiconductor DIP8 D2 MBRS360T3 − ON Semiconductor SMD Type D3 MUR160 − ON Semiconductor Axial D4 1N4148 − Any Axial C1 220 nF/X2 2222 335 5224 BC Comp. X2 Type C2 47 F/400 V ECA2GM470 Panasonic Radial C3 47 F/16 V ECA1CM470 Panasonic − C4 100 nF/25 V − Any 1206 SMD C5 2.2 nF WKP222MCMBFOK Vishay Y1 C6b 470 F/16 V ECA1CM471 Panasonic Radial C6a 470 F/16 V ECA1CM471 Panasonic Radial C7 47 F/16 V ECA1CM470 Panasonic Radial C8 2.2 nF/400 V R82MC1220DQ02J Arcotronics − C9 1.0 nF/10 V − Any 1206 SMD C10 47 F/35 V ECA1VM470 Panasonic Radial C11 − − − Not Wired IC1 SFH615A−2 − Siemens SMD IC2 TLV431ALP − ON Semiconductor TO92 IC3 NCP1013P06 − ON Semiconductor DIP8 T1 A9619−C − Coilcraft − J1 Connector PX0786/PC Bulgin Mains Inlet J2 Connector L145202010002 LMI 12 V Output J3 Connector 4710334140400 Kontek − JP1 Jumper Shunts − Any − Feet Board Feet LCBS−TF−M4−6−01 Richco 9.5 mm Height Coilcraft 1102 Silver Lake Road Cary IL 60013 Tel. US: 800−322−2645 Tel. (WW) : 847−639−6400 Fax: 847−639−1469 www.coilcraft.com www.coilcraft.com.cn email: [email protected] http://onsemi.com 8 AND8142/D Figure 15. PCB Layout and Component Views http://onsemi.com 9 AND8142/D ON Semiconductor and are registered trademarks of Semiconductor Components Industries, LLC (SCILLC). SCILLC reserves the right to make changes without further notice to any products herein. SCILLC makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does SCILLC assume any liability arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation special, consequential or incidental damages. “Typical” parameters which may be provided in SCILLC data sheets and/or specifications can and do vary in different applications and actual performance may vary over time. All operating parameters, including “Typicals” must be validated for each customer application by customer’s technical experts. SCILLC does not convey any license under its patent rights nor the rights of others. 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