LM5020EVAL/NOPB

User's Guide SNVA082B – March 2004 – Revised May 2013 AN-1314 LM5020 Evaluation Board 1 Introduction The LM5020 evaluation board is designed to provide the design engineer with a fully functional nonisolated flyback power converter to evaluate the LM5020 controller. The performance of the evaluation board is as follows: • Input range: 30V to 75V (100V peak) • Output voltage: 3.3V • Output current: 0.2 to 4.5A • Measured efficiency: 85% at 1.5A, 83% at 4.5A • Board size: 1.25 × 2.5 × 0.5 inches • Load Regulation: 1.5% • Line Regulation: 0.1% • Line UVLO, Current Limit The printed circuit board consists of 2 layers of 2 ounce copper on FR4 material with a total thickness of 0.050 inches. Soldermask has been omitted from some areas to facilitate cooling. The unit is designed for continuous operation at rated load at < 40°C with normal convection cooling. 2 Theory of Operation The flyback converter is an inductive based converter in which inductive energy is stored by applying a voltage across an inductor in a similar manner to that of a boost converter. Here the similarity ends. A second coupled winding of the inductor transfers the energy to a secondary side rectifier after the voltage has been removed from the first winding. This allows the converter input and output grounds to be configured either isolated or non-isolated. There is also a voltage/current ratio change possible by altering the winding ratio between the first winding and the second winding. A semi-regulated auxiliary winding can also be provided. The flyback transformer is actually a coupled inductor with multiple windings wound on a single core. For simplification, we will refer to the first, driven winding, as the primary and the main output winding as the secondary winding of the flyback transformer. The transformer’s primary inductance is typically made as large as is practical. However, the airgap necessary to store the cycle energy lowers the obtainable inductance. The higher the primary inductance, the less input ripple current will be generated and the less input filtering will be required. As shown, the LM5020 directly drives a MOSFET switch to apply voltage across the primary. When the switch turns off, the secondary applies a forward current to the output rectifier and charges the output capacitor. In applications where the input voltage is considerably higher than the output voltage, the turns ratio between primary and secondary will reflect the input/output voltage ratio and the duty cycle. The LM5020 is a full-featured controller providing an internal start-up regulator, soft start, over-current and under-voltage lockout. All trademarks are the property of their respective owners. SNVA082B – March 2004 – Revised May 2013 Submit Documentation Feedback AN-1314 LM5020 Evaluation Board Copyright © 2004–2013, Texas Instruments Incorporated 1 Powering and Loading Considerations www.ti.com 30V - 75V V+ VOUT VCC VIN RT UVLO SS LM5020 OUT COMP CS FB COMPENSATION Simplified Flyback Converter Figure 1. Simplified Flyback Converter 3 Powering and Loading Considerations When applying power to the LM5020 evaluation board certain precautions should be followed. The LM5020 evaluation board is quite forgiving of load and input power variations. The possibility of shipping damage or infant failure is always a concern at first power-up. 4 Proper Connections Be sure to choose the correct wire size when attaching the source supply and the load. Monitor the current into and out of the UUT. Monitor the voltages in and out directly at the terminals of the UUT. The voltage drop across the connecting wires will yield inaccurate measurements. For accurate efficiency measurements, these precautions are especially important. 5 Source Power At low input line voltage (30V) the input current will be approximately 0.63A, while at high input line voltage the input current will be approximately 0.23. Therefore to fully test the LM5020 evaluation board a DC power supply capable of at least 75V and 1A is required. The power supply must have adjustments for both voltage and current. An accurate readout of output current is desirable since the current is not subject to loss in the cables as voltage is. The power supply and cabling must present a low impedance to the UUT. Insufficient cabling or a high impedance power supply will cause droop during power supply application with the UUT inrush current. If large enough, this droop will cause a chattering condition upon power up. This chattering condition is an interaction with the UUT undervoltage lockout, the cabling impedance and the inrush current. 6 Loading An appropriate electronic load specified for operation down to 2.0V is desirable. The maximum load current is specified as 4.5A. Minimum load is specified at 5% or 0.23A. The resistance of a maximum load is 0.73Ω (including cables). The resistance of a minimum load is 14.4Ω. 2 AN-1314 LM5020 Evaluation Board SNVA082B – March 2004 – Revised May 2013 Submit Documentation Feedback Copyright © 2004–2013, Texas Instruments Incorporated Powering Up www.ti.com 7 Powering Up Using the shutdown feature provided on the UUT will allow powering up the source supply initially with a low current level. It is suggested that the load be kept reasonably low during the first power up. Set the current limit of the source supply to provide about 1½ times the wattage of the load. As you remove the connection from the shutdown pin to ground, immediately check for 3.3 volts at the output. If more than a couple of seconds pass without seeing an output voltage, remove input power. A quick efficiency check is the best way to confirm that the UUT is operating properly. If something is amiss you can be reasonably sure that it will affect the efficiency adversely. Few parameters can be incorrect in a switching power supply without creating additional losses and potentially damaging heat. An efficiency above 80% is expected. After the unit is verified operationally, it can be powered up without use of the shutdown pin. 8 Typical Evaluation Setup Scope Volt-meter + 75 Volt, 1 Amp Power Supply Evaluation Board + IN Volt-meter ON/OFF (SHUTDOWN) Current-meter + OUT Electronic Load - Current Meter Jumper or single-pole switch Figure 2. Typical Evaluation Setup 9 Performance Characteristics 9.1 Turn-on Waveforms When applying power to the LM5020 evaluation board a certain sequence of events must occur. The softstart feature allows for a minimal output voltage for a short time until the feedback loop can stabilize without overshoot. Figure 3, Figure 4, and Figure 5 show typical turn-on waveforms at no load, 5% load, and at full load. Input voltage, output voltage and output current are shown. Figure 6 shows the initial ramp-up of the Vcc pin to 7.7 volts through the internal regulator. The auxiliary winding starts to supply a higher voltage as the output voltage rises. The resulting second ramp is shown following the soft-start delay. This sequence is nearly identical for all loads and input voltages. Trace 1: Input Voltage, at 30VDC. Volts/div = 20.0V Trace 2: Output Voltage, no load. Volts/div = 2.0V Trace 3: Output Current, no load. Amps/div = 100mA Horizontal Resolution = 1.0ms/div Figure 3. Typical Turn-on Waveforms at No Load Trace 1: Input Voltage, at 30VDC. Volts/div = 20.0V Trace 2: Output Voltage, at 5% load. Volts/div = 2.0V Trace 3: Output Current, at 5% load. Amps/div = 100mA Horizontal Resolution = 1.0ms/div Figure 4. Typical Turn-on Waveforms at 5% Load SNVA082B – March 2004 – Revised May 2013 Submit Documentation Feedback AN-1314 LM5020 Evaluation Board Copyright © 2004–2013, Texas Instruments Incorporated 3 Performance Characteristics www.ti.com Trace 1: Input Voltage, at 30VDC. Volts/div = 20.0V Trace 2: Output Voltage, at full load. Volts/div = 2.0V Trace 3: Output Current, at full load. Amps/div = 2.0A Horizontal Resolution = 1.0ms/div Figure 5. Typical Turn-on Waveforms at Full Load 9.2 Trace 1: VCC pin with VIN = 30VDC, Load = 4.5A Volts/div = 5.0V Trace 2: VIN approaching 30VDC Volts/div = 20.0V Horizontal Resolution = 2.0ms/div Figure 6. Initial Ramp-up of the Vcc Pin to 7.7V Through the Internal Regulator Load Step Response Figure 7 shows the load step response at Vin = 30VDC for an instantaneous load change from 5% to full load. The input voltage, output voltage and output current are shown. 9.3 Ripple Voltage and Ripple Current Figure 8 shows the output ripple voltage, the output ripple current and the input ripple current relative to the LM5020 gate drive. Trace 1: Input Voltage, at 30VDC Volts/div = 20.0V Trace 2: Output Voltage, at 3.3VDC Volts/div = 2.0V Trace 3: Load changing from 0.23A to 4.5A instantaneously Amps/div = 2.0A Horizontal Resolution = 1.0ms/div Figure 7. Load Step Response at Vin = 30VDC for an Instantaneous Load Change from 5% to Full Load 4 Trace 1: Q1 gate drive at Vin = 48VDC Volts/div = 20.0V Trace 2: Output ripple voltage Volts/div = 100mV Trace 3: Output ripple current Amps/div = 20.0mA Trace 4: Input ripple current Amps/div = 100mA Horizontal Resolution = 2.0µs/div Figure 8. Output Ripple Voltage, Output Ripple Current, and Input Ripple Current AN-1314 LM5020 Evaluation Board SNVA082B – March 2004 – Revised May 2013 Submit Documentation Feedback Copyright © 2004–2013, Texas Instruments Incorporated Performance Characteristics www.ti.com 9.4 Transformer Waveforms Figure 9, Figure 10, and Figure 11 show typical waveforms at the junction of Q1 MOSFET and the transformer primary winding. Also shown are typical waveforms at the junction of the transformer secondary and the output rectifier, D3. Figure 9 reflects an input voltage of 30VDC and a load of 4.5A. Figure 10 reflects an input voltage of 50VDC with the same load. Figure 11 reflects an input voltage of 75VDC, also at full load. Trace 1: Drain of Q1 at Vin = 30VDC; Volts/div = 50.0V Trace 2: Anode of D3; Volts/div = 10.0V Horizontal Resolution = 0.5µs/div Figure 9. Typical Waveforms Trace 1: Drain of Q1 at Vin = 50VDC; Volts/div = 50.0V Trace 2: Anode of D3; Volts/div = 10.0V Horizontal Resolution = 0.5µs/div Figure 10. Typical Waveforms Trace 1: Drain of Q1 at Vin = 75VDC; Volts/div = 50.0V Trace 2: Anode of D3; Volts/div = 10.0V Horizontal Resolution = 0.5µs/div Figure 11. Typical Waveforms SNVA082B – March 2004 – Revised May 2013 Submit Documentation Feedback AN-1314 LM5020 Evaluation Board Copyright © 2004–2013, Texas Instruments Incorporated 5 Bill of Materials 10 www.ti.com Bill of Materials The Bill of Materials is listed in Table 1 and includes the manufacturer and part number. Table 1. Bill of Materials Designator 6 Description Manufacturer Part Number C1 2.2µF, 100V, CER, X7R, 1812 TDK C4532X7R2A225M C2 2.2µF, 100V, CER, X7R, 1812 TDK C4532X7R2A225M C3 0.01µF, 50V, CER, X7R, 0805 TDK C2012X7R1H103K C4 0.1µF, 100V, CER, X7R, 1206 TDK C3216X7R2A104K C5 0.01µF, 50V, CER, X7R, 0805 TDK C2012X7R1H103K C6 220pF, 50V, CER, COG, 0805 TDK C2012COG1H221J C7 3300pF, 50V, CER, COG, 0805 TDK C2012COG1H332K C8 100pF, 50V, CER, COG, 0805 TDK C2012COG1H101J C9 0.1µF, 50V, CER, X7R, 0805 TDK C2012X7R1H104K C10 4.7µF, 16V, CER, X7R, 1206 TDK C3216X7R1C475K C11 1000pF, 50V, CER, COG, 0805 TDK C2012COG1H102J C12 470pF, 50V, CER, COG, 0805 TDK C2012COG1H471J C13 100µF, 4V, CER, X7S, 1812 TDK C4532X7S0G107M C14 100µF, 4V, CER, X7S, 1812 TDK C4532X7S0G107M C15 270µF, 4V, ALUM ORG, 3018 PKG KEMET A700X277M0004AT D1 DUAL, SIGNAL, COM CATH, SOT-23 CENTRAL SEMICONDUCTOR CMPD2838E-NSA D2 DUAL, SIGNAL, COM CATH, SOT-23 CENTRAL SEMICONDUCTOR CMPD2838E-NSA D3 SCHOTTKY RECT, 8A, 35V, D2PAK ON SEMICONDUCTOR J1 TERMINAL BLOCK, SCREW, 2 POS PHOENIX CONTACT MKDS ½-3.81 J2 TERMINAL BLOCK, SCREW, 2 POS PHOENIX CONTACT MKDS ½-3.81 Q1 MOSFET, N-CH, 150V, 85mΩ, PWR SO8 R1 10.0Ω, 1%, THICK FILM, 1206 VISHAY CRCW120610R0J R2 61.9K, 1%, THICK FILM, 1206 VISHAY CRCW12066192F R3 2.87K, 1%, THICK FILM, 0805 VISHAY CRCW08052871F R4 1.00K, 1%, THICK FILM, 0805 VISHAY CRCW08051001F R5 15.0K, 1%, THICK FILM, 0805 VISHAY CRCW08051502F R6 12.4K, 1%, THICK FILM, 0805 VISHAY CRCW08051242F R7 100Ω, 1%, THICK FILM, 0805 VISHAY CRCW08051000F R8 0.47Ω, 1%, THICK FILM, 1206 VISHAY CRCW12060R47F R9 0.47Ω, 1%, THICK FILM, 1206 VISHAY CRCW12060R47F R10 10.0Ω, 1%, 1W, THICK FILM, 2512 VISHAY CRCW251210R0J R11 2.43K, 1%, THICK FILM, 0805 VISHAY CRCW08052431F R12 1.47K, 1%, THICK FILM, 0805 VISHAY CRCW08051471F R13 20.0Ω, 1%, THICK FILM, 0805 VISHAY CRCW080520R0F SD TERMINAL, SMALL TEST POINT KEYSTONE 5002 SYNC TERMINAL, SMALL TEST POINT KEYSTONE 5002 T1 TRANSFORMER, FLYBACK, EFD20 COILCRAFT B0695-A OR T1 TRANSFORMER, FLYBACK, EFD20 PULSE PA0751 VISHAY/SILICONIX MBRD835L Si7898DP U1 CONTROLLER, SINGLE OUT, PWM, VSSOP-10 TEXAS INSTRUMENTS LM5020 Z1 ZENER, 30V, SMB PKG. ON SEMICONDUCTOR 1SMB5936B AN-1314 LM5020 Evaluation Board SNVA082B – March 2004 – Revised May 2013 Submit Documentation Feedback Copyright © 2004–2013, Texas Instruments Incorporated PCB Layouts www.ti.com 11 PCB Layouts The layers of the printed circuit board are shown in top down order. View is from the top down. Scale is approximately X2.0. The printed circuit board consists of 2 layers of 2 ounce copper on FR4 material with a total thickness of 0.050 inches. SNVA082B – March 2004 – Revised May 2013 Submit Documentation Feedback AN-1314 LM5020 Evaluation Board Copyright © 2004–2013, Texas Instruments Incorporated 7 PCB Layouts 8 www.ti.com AN-1314 LM5020 Evaluation Board SNVA082B – March 2004 – Revised May 2013 Submit Documentation Feedback Copyright © 2004–2013, Texas Instruments Incorporated PCB Layouts www.ti.com SNVA082B – March 2004 – Revised May 2013 Submit Documentation Feedback AN-1314 LM5020 Evaluation Board Copyright © 2004–2013, Texas Instruments Incorporated 9 Application Circuit 12 www.ti.com Application Circuit C9 R10 R13 T1 V+ J1 30-75V IN 1 J2 +3.3V 2 C12 470 pF D2 CMPD2838E 20 0.1 PF 10, 1W 1 C13 100 PF GND D3 MBRD835L 2 GND R2 61.9k R1 10 C4 0.1 PF SD R3 2.87k GND C10 4.7 PF 1 7 GND VIN VCC UVLO 3 9 C6 220 pF R5 15.0k 10 C8 100 pF R6 12.4k COMP RT CS VFB SS GND GND Q1 Si7898DP R11 2.43k 4 5 R12 1.47k R7 8 2 100 6 R8 0.47 R9 0.47 GND C11 1000 pF LM5020 C5 0.01 PF C7 3300 pF D1 CMPD2838E GND GND U1 R4 1.00k OUT SYNC GND GND GND C3 0.01 PF GND Z1 GND 1SMB5936B 5 6 7 8 GND C2 2.2 PF OUT RTN 4 3 2 1 C1 2.2 PF C15 270 PF GND GND GND C14 100 PF GND GND GND GND Figure 12. Application Circuit: Input 36V to 78V, Output 3.3V, 4.5A 10 AN-1314 LM5020 Evaluation Board SNVA082B – March 2004 – Revised May 2013 Submit Documentation Feedback Copyright © 2004–2013, Texas Instruments Incorporated IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, enhancements, improvements and other changes to its semiconductor products and services per JESD46, latest issue, and to discontinue any product or service per JESD48, latest issue. Buyers should obtain the latest relevant information before placing orders and should verify that such information is current and complete. All semiconductor products (also referred to herein as “components”) are sold subject to TI’s terms and conditions of sale supplied at the time of order acknowledgment. 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