Introduction to Push-Pull and Cascaded Power Converter Topologies

Transcription

1 Introduction to Push-Pull and Cascaded Power Converter Topologies Bob Bell Principal Applications Engineer July 10, Good Morning! Welcome to National Semiconductor s continuing series of ON-Line Seminars Today our topic is an introduction to a family of DC-DC power converters referred to as Cascaded 1

2 About the Presenter The author, Bob Bell, has been involved in the power conversion industry for 20 years, currently a Principal Applications Engineer for the National Semiconductor Phoenix Design Center. The Phoenix Design Center is developing next generation power conversion solutions for the telecommunications market. Education: BSEE Fairleigh Dickinson University, Teaneck, NJ 2 My name is Bob Bell. I have been employed with National Semiconductor for 2 years. I am an application engineer at the National Semiconductor Phoenix Arizona Design Center Here at the design center we have a team developing next generation power conversion solutions for the telecommunications industry. 2

3 Outline: Buck Regulator Family Lines Push-Pull Topology Introduction Push-Pull Controller Cascaded Push-Pull Topologies Cascaded Controller Cascaded Half-Bridge Topology Introduction 3 Today we will start off with a brief review of common DC to DC power converter topologies. Our main interest will be several topologies which apply to isolated DC to DC converters. The topologies which we will initially spend the most time with will be the Buck and the Push-Pull topology. Following the introduction we will introduce benefits and characteristics of Cascading two topologies together. 3

4 Common One-Switch Power Converter Topologies L Vin Vo Vin Vo Buck Converter Boost Converter Vin Np Ns L Vo Vi n Np Ns Vo Na ux Forward Converter Flyback Converter 4 Shown on this chart is the power stage arrangements for some of the most popular power converter topologies which use a single primary switching element. The Buck and Boost are the simplest and apply to non-isolated power converters. The Forwards and Flyback topology are used in isolated converters where it is desirable to electrically isolate the Primary and Secondary grounds. 4

5 Vin Np Np Common Two-Switch Power Converter Topologies Ns Ns L Vo Vin Np Ns Ns L Vo Push-Pull Converter Half Bridge Converter Vin L Np Ns Ns Vo Full Bridge Converter 5 Shown on this chart are several popular isolated power converters which use two or more primary switches. The Push-Pull and Half-Bridge require two switches while the Full-Bridge requires four switches. Generally the power capability increases from Push-Pull to Half-Bridge to Full-Bridge. 5

6 Buck Regulator Basics V IN I L D*T s I(Q1) T s Q1 I(D1) D1 L1 C1 V OUT V OUT = D * V IN 6 A more detailed look at the anatomy of a Buck regulator shows a switching section, comprised of Q1 and D1, and an output filter comprised of L1 and C1. The Buck regulator is used to efficiently step down voltages. The output voltage is given as Vin * D, where D is the duty cycle of the main switch Q. All of the transfer functions we will show assume the inductor current does not return to zero during the switching cycle, this is said to be Continuous operation. The Inductor current is made up of two parts; the switch current from Q1 and the rectifier current D1 6

7 Buck Converter Characteristics Non-Isolated Grounds Voltage Step-down Only Single Output Only Very High Efficiency Low Output Ripple Current High Input Ripple Current High Side (Isolated) Gate Drive Required Large Achievable Duty Cycle Range Wide Regulation Range (due to above) 7 {Read Chart} 7

8 Forward Converter D1 L1 + Vout Np Nr Ns D2 C1 + R Vin Q1 D3 I(L1) - Vout = Vin x D x Ns Np I(D1) = I(Q1) x Np/Ns I(D2) Same transfer function as a Buck converter with an added turns ratio term 8 The first isolated topology we will look at is the Forward. A Forward converter is a transformer isolated Buck regulator The output inductor current is still the composite of two different switch currents, in this case D1 and D2. D1 current is the secondary current from the transformer, which equals I(Q1) times the turns ratio (Np/Ns) The transfer function is the same as the Buck regulator with an additional transformer voltage gain term of Ns/Np 8

9 Forward Diode Currents Forward Diode D1 Current Freewheel Diode D2 Current Vin =48V Vout =3.3V Iout = 5A 9 This slide shows each of the rectifier diode currents which sum together to form the inductor current. 9

10 Forward Converter Characteristics A Forward Converter is a Buck type converter with an added isolation transformer Grounds are isolated Voltage Step-down or Step-up Multiple Outputs Possible Low Output Ripple Current High Input Ripple Current Simple Gate Drive Limited Achievable Duty Cycle Range 10 {Read Chart} 10

11 Push-Pull Topology n p n s D1 L C + + R Vout - n p n s Vin V g D2 PUSH Q2 PULL Q1 Q1 Q2 D Vout = Vin x D x Ns x 2 Np 11 The Push-Pull topology is basically a Forward converter with two primaries. The primary switches alternately power their respective windings. When Q1 is active current flows through D1. When Q2 is active current flows through D2. The secondary is arranged in a center tapped configuration as shown. The output filter sees twice the switching frequency of either Q1 or Q2. The transfer function is similar to the Forward converter, where D is the duty cycle of a given primary, that accounts for the 2X term. When neither Q1 nor Q2 are active the output inductor current splits between the two output diodes. A transformer reset winding shown on the Forward topology is not necessary. 11

12 Push-Pull Switching Waveforms Output Inductor Current I (L1) Vin = 48V Vout =3.3V Iout = 5A Push Primary Switch V DS(Q1) Pull Primary Switch V DS(Q2) 12 Shown here are oscilloscope waveforms for the Drain voltages of the two primary switches and the output inductor current. When a given primary is active the Drain voltage is zero and the alternate switches Drain is 2X the input voltage. This is due to the transformer voltage bring reflected from the active primary to in-active primary. When neither switch is active then both Drain voltages are at the input voltage. 12

13 Push-Pull Diode Currents Output Diode Current I (D1) Vin = 48V Vout =3.3V Iout = 5A Output Diode Current I (D2) 13 Shown here is the current for each of the two output diodes. These two current sum to form the output inductor current shown on the previous slide. Note that as discussed previously when neither of the primary switches are active, the output inductor current has a negative slope and flows half in each of the two secondary diodes. 13

14 Core Utilization: Forward & Push-Pull Converters FLUX DENSITY B (GAUSS) FLUX DENSITY B (GAUSS) Operation in Quadrant 1 only B SAT Operation in Quadrants 1 & 3 B SAT B R MAGNETIC FIELD INTENSITY H (OERSTED) MAGNETIC FIELD INTENSITY H (OERSTED) Forward Converter B-H Operating Area Push-Pull Converter B-H Operating Area 14 Shown here are the transformer BH curves for the Forward and the Push-Pull topology. The X axis represents Magnetic Field Intensity which is proportional to the Ampere*Turns. The Y axis represents Flux Density which is proportional to the Core area and the Volt * Seconds for the winding that is active. The slope is proportional to the primary magnetizing inductance. The Forward converter operates in a single quadrant of the BH curve, moving up the curve when the switch is active and resetting during the OFF time. The Push-Pull converter operates in two quadrants of the BH curve, see-sawing back and forth as the each primary is activated. This important fact allows the maximum power capability of a Push-Pull transformer to be twice that of a Forward transformer. 14

15 Push-Pull Characteristics A Push-Pull Converter is a Buck type converter with a dual drive winding isolation transformer Push-Pull transformers and filters are much smaller than standard Forward converter filters Voltage Stress of the Primary Switches is: Vin *2 Voltage Step-down or Step-up Multiple Outputs Possible Low Output Ripple Current Lower Input Ripple Current Simple Gate Drive (dual) Large Achievable Duty Cycle Range 15 {Read Chart} 15

16 LM5030 Push-Pull Controller Features Internal V start-up regulator CM control, internal slope comp. Set frequency with single resistor 100k 600kHz Synchronizable Oscillator Error amp Precision 1.25V reference Programmable soft-start Dual mode over-current protection Direct opto-coupler interface Integrated 1.5A gate drivers Fixed output driver deadtime Thermal shutdown Vin Rt / SYNC COMP 1.25V VFB SS CS OSC 45uA 0 5V 5K 100K 1.4V 50K 2K 0.5V 0.625V CLK SLOPECOMP RAMP GENERATOR PWM ENABLE CLK LOGIC J K S 7.7V REG R Vcc Vcc Vcc OUT1 OUT2 RTN Packages: MSOP10, LLP10 (4mm x 4mm) SS / SD SS 10uA 0.45V SHUTDOWN COMPARATOR 16 National Semiconductor has developed a controller designed specifically for the Push-Pull topology. The LM5030 controller has many innovative features. Although designed for the Push-Pull topology this versatile controller can be used for most common power converters <Read Features> 16

17 LM5030 Push-Pull Demo Board Performance: Input Range: 36 to 75V Output Voltage: 3.3V Output Current: 0 to 10A Board Size: 2.3 x 2.3 x 0.45 Load Regulation: 1% Line Regulation: 0.1% Current Limit Measured Efficiency: 5A 17 Shown here is a demo board utilizing the LM5030 controller in a Push- Pull topology. The power level is on the low side for a Push-Pull implementation. The purpose is to demonstrate the operation of the controller. The waveform shown earlier were taken from this board. <Read Performance> 17

18 LM5030 Push-Pull Demo Board 36V-75Vin to 10A Input: 36 75V Output: 10A 18 Shown here is the schematic for the 33W demo board. Note the controller connects directly to the input voltage to provide the initial bias power on Vcc. Once operational, then the winding on the output inductor provides the bias power. 18

19 LM5030 3G Base Station RF Power Supply Performance: Input Range: 36 to 75V Output Voltage: 27V Output Current: 0 to 30A Board Size: 6 x 4 x 2 Load Regulation: 1% Line Regulation: 0.1% Line UVLO, Current Limit Output OV Protection Measured Efficiency: 30A (810W) 19 Shown on this slide is an actual application at the higher end of the Push-Pull power capability. This unit is designed to power a telcom Base Station RF Power Amplifier. <Read Performance> 19

20 LM5030 3G Base Station RF Supply -48Vin to 30A 20 Shown here is the schematic for the 810W design. The schematic although more complicated then the 33W design, all of the same basic blocks exist. 20

21 Vin Buck Stage Cascaded Buck & Push-Pull Power Converter (Voltage Fed) Push-Pull Stage N : N : 1 : 1 Vpp Vout BUCK CONTROL CONTROLLER PUSH OSCILLATOR FEEDBACK PULL Buck Control Output is pulse-width modulated to regulate Vout Push-Pull Outputs operate continuously, alternating at 50% duty cycle Buck Stage: Vpp = Vin * D Push-Pull Stage: Vout = Vpp / N Overall: Vout = Vin x D/N 21 Now let s combine a Buck Regulator stage and a Push-Pull stage. The first thing to note here is that,each switch of the Push-Pull Stage is set to operate alternating at 50% duty cycle. This essentially configures the PP stage as an ideal DC transformer. A voltage presented to the Vpp node will be transferred to the output divided by the transformer turns ratio. It is the Buck stage that is actually used to regulate the output. If we combine the Buck Stage transfer function and the Push-Pull stage transfer function we get the overall transfer function as shown. The Push-Pull stage is said to be Voltage Fed since the Vpp node contains the output capacitor from the Buck Stage. The Push-Pull switches actually operate slightly less than 50% duty cycle such that there is no overlap during the switching transitions. 21

22 Cascaded Voltage-Fed Converter Benefits A Voltage-Fed Push-Pull Converter is a Buck type converter consisting of a Buck Regulation stage followed by (cascaded by) a Push-Pull Isolation Stage The Push-Pull Stage FET voltage stresses are reduced to Vout x N x 2 over all line conditions The output rectification can be easily optimized due to reduced and fixed voltage stresses The output rectification is further optimized since the power is equally shared between the rectifiers over all load and line conditions Favorable topology for wide input ranges 22 22

23 Current Fed Push-Pull Concept Buck Stage Push-Pull Stage OUTPUT INDUCTOR REMOVED 33-76V Vout Vcc Vcc HB Vin HD LD HI LI HO HS LO BUCK OUT CAP REMOVED LM5041 LM5101 Vss PUSH FB PULL FEEDBACK Push and Pull outputs operate continuously, alternating with a s light overlap. Output voltage is controlled by the Buck stage which operates at 2X the Push-Pull frequency. Continuous output current from the Push-Pull stage requires minimal filtering. High Efficiency achieved with low Push-Pull switching losses and matched Sync rectifier loading 23 The cascaded Voltage Fed Buck and Push-Pull is a viable design approach, however there are several large components which can be removed, while still maintaining all of the performance benefits of the cascaded approach. On the previous Voltage-fed slide, note we had 2 complete L-C filters. The Buck Stage capacitor and the PP stage inductor can be removed and actually provide several benefits. Shown here is a Current-fed cascaded Buck and Push-Pull Stage. The Push-Pull stage is said to be current fed since only the Buck inductor, which acts a current source feeds the Push-Pull. In this case the Push-Pull switches need to have a very small overlap at the switching transitions to maintain the inductor current path. In the Voltage-fed a small dead time is required. An example which we will look at next is a 2.5 Volt output, which has been designed with an 8 to 1 transformer turns ratio. Working from the output back yields a voltage at the Vpp node of 20 Volts. 23

24 Cascaded Current-Fed Converter Benefits A Current-Fed Push-Pull Converter is a Buck type converter consisting of a Buck Regulation stage followed by (cascaded by) a Push-Pull Isolation Stage There is no high current output inductor! Reduced switching loss in Push-Pull stage Favorable topology for multiple outputs since all outputs are tightly coupled Favorable topology for wide input ranges, since the Buck stage pre-regulates while the Push-Pull and Secondary operate independently of the input voltage level 24 24

25 Current-Fed Switching Voltages Trace 1: Push_Pull SWPUSHV DS Trace 2: Push_Pull SWPULL V DS Vin = 60V Vout =2.5V Iout = 20A Trace 3: Buck Stage Switching Node Note: There is an overlap time where both the Push and the Pull switches are ON. This is required to maintain the inductor current path. 25 Shown here are scope plots of the Push-Pull stage drain voltages and the voltage at the common junction of the Buck stage switches. Note that the Buck stage operates at twice the frequency of either the Push or Pull switch. Also note the overlap of the of the Push-Pull stage. 25

26 Current-Fed Push-Pull Switches Ch 1,2 Push-Pull V DS Ch 3,4 Push-Pull I DS Vin = 48V Vout =2.5V Iout = 20A 26 Shown here are scope plots of the Push-Pull Drain voltages and Push- Pull switch currents. On the next slide we will take a more detailed look at the switching transitions of these waveforms 26

27 Current-Fed Switch Waveforms Expanded Scale Ch 1,2 Push-Pull V DS Ch 3,4 Push-Pull I DS Note: Each switch carries ½ the current, during the overlap time Vin = 48V Vout =2.5V Iout = 20A 27 One of the many advantages of the cascaded approach is a reduction in switching losses in the Push Pull stage switches. You can note during the overlap time when both switches are ON the Buck inductor current divides equally between the two switches. At the conclusion of the overlap time the drain voltage is already at zero and therefore the switching losses are cut in half. 27

28 Why is it important to reduce secondary rectification losses? Transformer 20% Control 10% Secondary Rectifiers 40% Filter Inductor 15% Primary Switching 15% Estimate for typical 3.3V Output, 35 80V Input 28 Why is it important to pick a topology which offers the best opportunities to reduce losses in the secondary synchronous rectifiers? A look at a typical power loss budget of a 3.3V power converter shows approximately 40% of the overall power conversion losses occur in the secondary rectification. 28

29 Comparison of Rectifier Stresses Rectifier Voltage Stresses Voltage Stresses for Example Conditions Topology Example: Assumptions Forward Vin x (Ns/Np) 20V High Line with XFR Ratio 4:1 Push-Pull Vin x (Ns/Np) x V High Line with XFR Ratio 6:1 Cascaded PP Vout x 2 6.6V All Line conditions XFR Ratio 6:1 Topology Rectifier Current Ratios Example: 3.3V output, 35-80V input Current Ratios for Example Conditions Example: Assumptions Forward Iout x D and Iout x (1-D) 16 / 84% Ratio at High Line Push-Pull 50% x Iout 50% All line conditions Cascaded PP 50% x Iout 50% All line conditions 29 This chart compares secondary rectifier stresses for three of the topologies we have talked about so far. The comparison example is a 3.3 Volt output with a 35 to 80 Volt input. On the top chart voltage stresses are compared. As you can see for the Forward and the Push-Pull the voltage stresses are proportional to the input voltage. At high line the calculated stresses are mush higher then the Cascaded topology whose rectifier stresses are only proportional to Vout. All of the compared topologies have two secondary rectifiers. The lower chart compares the ratio of ON times for each topology. The Push-Pull and the Cascade have balanced loading on the two secondary rectifiers. The loading ratio on the rectifiers for a Forward topology vary in proportion to the input voltage. Optimized and reliable designs are more readily accomplished with balanced loading. 29

30 Sync Rectifier Waveforms Ch 1 Sync1 V DS Ch 2 Sync2 V DS Vin = 48V Vout =2.5V Iout = 20A 30 This scope plot shows the drain voltage waveforms the two synchronous rectifiers in a 2.5 Volt output. Excluding the switching spike, the voltage stress is as expected 5 volts. 30

31 LM5041 Cascaded PWM Controller Features: Internal 100V Capable Start-up Bias Regulator Programmable Line Under Voltage Lockout with Adjustable Hysteresis Current Mode Control Internal Error Amplifier with Reference Dual Mode Over-Current Protection Internal Push-Pull Gate Drivers with Programmable Overlap or Deadtime Programmable Soft-Start Programmable Oscillator with Sync Capability Precision Reference Thermal Shutdown (165 C) Packages: TSSOP16 and LLP16 (5 x 5 mm) 31 National Semiconductor has developed a controller designed specifically for Cascaded topologies. The LM5041 controller has many innovative features. <Read Features> 31

32 LM5041 Block Diagram Vin ENABLE 9V REG Vcc UVLO COMP 0.75V FB 45uA 0 SS 5V 2.5V SLOPECOMP RAMP GENERATOR 5K 1.4V 100K 50K UVLO HYSTERESIS (20uA) PWM LOGIC LOGIC Vcc UVLO CLK S 5V REF OFF TIME GENERATOR LM ONLY Q Vref HD LD CS 2K 0.5V R Q Vcc CLK + LEB 0.6V OSC DRIVER PUSH SS SS 10uA OSCILLATOR CLK DIVIDE BY 2 DEADTIME OR OVERLAP CONTROL Vcc ENABLE 0.45V SHUTDOWN COMPARATOR Rt / SYNC PULL DRIVER TIME 32 Shown here is the block diagram for the LM5041 cascaded controller. Note on the right are the 4 switch control outputs. Gate drivers are included within the device for the Push and Pull outputs. A resistor connected to the TIME pin is used to set either overlap or deadtime of the Push-Pull outputs. Connecting the resistor to ground sets overlap time. Connecting the resistor to REF sets deadtime. The Buck stage outputs are logic level controls which work with National s new LM5100 family of Buck Stage Gate drivers. The bias, control and protection circuits used in this controller are very similar to the LM5030 controller, which is current mode control. A unique LM5041 feature is a line under voltage lockout (UVLO) with adjustable hysteresis. 32

33 LM5041 Current Fed Push-Pull Demo Board Performance: Input Range: 36 to 75V Output Voltage: 2.5V Output Current: 0 to 50A Board Size: 2.3 x 3.0 x 0.5 Load Regulation: 1% Line Regulation: 0.1% Line UVLO, Current Limit Measured Efficiency: 50A 33 Cascaded Converter Evaluation Board. 125W, 90% Efficient, 40 mv pp Ripple Noise Input range -36 to -75 V Output 50 A 4-layer Board 2.3" x 3" x 0.5". Components mounted on a single side of the board. Planar magnetic (Coilcraft standard product). 100V Chipset LM5041 Cascaded Controller & LM5101 Synchronous Buck Driver 33

34 LM5041 / LM5100 Demo Board 50A Cascaded DC-DC Converter 34 Shown here is the schematic for the LM5041 demo board. 34

35 Cascaded Half-Bridge Concept Half-Bridge Stage Vout Vin 33-76V Vin Vcc HD Buck Stage VDD L1 T1 T1 VDD LD LM5041 LM5102 LM5100 PUSH PULL FB FEED BACK 35 The Cascaded approach can be extended to many other configurations. Here a Buck stage is cascaded with a half bridge stage. In this case the Half-Bridge is said to be voltage fed, since the splitter capacitors are necessary for proper operation. This approach offers the benefit of further reduced voltage stresses on the primary side switches, of (Vout X N) where N is the turns ratio and a single primary winding. 35

36 Cascaded Half-Bridge Characteristics A Cascaded Half-Bridge Converter is a Buck type converter consisting of a Buck Regulation stage followed by (cascaded by) a Half-Bridge Isolation Stage. The isolation stage is Voltage-Fed. Voltage splitter capacitors and a small output stage inductor are required. Dead time is required for Half-Bridge switches The Half-Bridge Stage FET stresses are reduced, to Vout x N. (2x less than the Push-Pull) 36 36

37 Cascaded Full-Bridge Concept Full-Bridge Stage Vout Vin 33-76V Buck Stage L1 T1 Vcc Vin HD VDD VDD T1 VDD LD LM5041 LM5102 LM5100 LM5100 PUSH PULL COMP FEED BACK 37 Another cascaded approach is a Buck Stage cascaded with a Full- Bridge Stage. The benefit here is: Reduced primary FET voltage stress of (Vout X N) Reduced switch current relative to the half-bridge and a single primary winding. 37

38 Cascaded Full-Bridge Characteristics A Cascaded Full-Bridge Converter is a Buck type converter consisting of a Buck Regulation stage followed by (cascaded by) a Full-Bridge Isolation Stage The isolation stage is Current-Fed No voltage splitter capacitors or output stage inductor are required as in the Cascaded Half-Bridge Overlap time is required for Isolation Stage switches The Full-Bridge Stage voltage stresses are Vout x N, similar to the half-bridge Full-Bridge Stage current levels are half that of a Half-Bridge

39 High Side Gate Driver Operation VIN VIN Vcc HI LEVEL SHIFT Q2 Vcc HI LEVEL SHIFT Q2 Vcc Vcc Q1 Q1 LI LI Initially Q1 is activated by Low Side control Cboot is charged from Vcc through D1, Q1 Cboot is charged to (Vcc-Vdiode) Floating Vcc, referenced to Q2 source, is available for upper gate driver Q2 Gate drive voltage is provided by Cboot 39 High side gate drivers are necessary to drive the Gate of the Buck Switch. An effective way to do this is with a Bootstrapping technique. On the left illustration, when a low side switch is ON, charge flows from Vcc to charge up a high side bootstrap capacitor. The charge on this capacitor is now available to drive the high side gate as shown on the right illustration. National Semiconductor has developed a family of dual gate drivers with level shifter designed specifically for Buck and Bridge configurations. 39

40 LM5100, LM5101 High Voltage Buck Stage Gate Driver Features 2-Amp Driver for High and Low Side N-Channel MOSFETs Independent inputs (TTL-LM5101, CMOS-LM5100) Bootstraps supply voltage to 116VDC Short Propagation Delay (45ns) Fast Rise, Fall times (10ns into 1nF) Unaffected by supply glitching, HS ringing VDD Supply under-voltage lock-out (6.7V) Low power consumption 0.5MHz) Pin for pin compatible with HIP2100 / 2101 Package: SOIC-8, LLP-10 (4x4mm) HI Vcc LI Vss Typical Applications Cascaded Power Converters Half Bridge Power Converters Full Bridge Power Converters Two Switch Forward Power Converters Active Clamp Forward Power Converters UVLO UVLO LEVEL SHIFT HB HO HS LO 40 The first two devices I would like to introduce are the LM5100 and the LM5101. The devices independently control both a high side and a low side gate. The LM5100 has CMOS level inputs, while the LM5101 has TTL level input thresholds. 40

41 LM5102 Driver with Adjustable Leading Edge Delay Features 2-Amp Driver for High and Low Side MOSFETs Independently Adjustable Leading Edge Delays Bootstraps drive high side gate to 116VDC Short Propagation Delay (45ns) Fast Rise and Fall times (10ns into 1nF) VDD Supply under-voltage lock-out (6.7V) Low power consumption 0.5MHz) Packages: MSOP-10, LLP-10 (4 x 4mm) Typical Applications Cascaded Power Converters Half and Full Bridge Power Converters Two Switch Forward Power Converters Active Clamp Forward Power Converters HI LI DLY Logic DLY Logic VDD HB HO HS LO RT1 RT2 41 The next device is similar to the LM5101 with the addition of independently adjustable delays for each output. We will see on the next chart the effect of the added delays. 41

42 LM5102 Timing Diagram LM5102 Adjustable Leading Edge Delay HI K x RT1 HO LI LO K x RT2 42 For the LM5102 each output has independently adjustable leading edge delays set by resistors R1 and R2. The delays have the effect on the outputs to create dead-time. This feature is very useful to prevent excessive shoot-through currents on switching transitions. 42

43 LM5104 Driver with Adaptive Deadtime, Programmable Delay Features 2Amp Driver for Complementary High and Low Side FETs Adaptive Deadtime with programmable additional delay Single TTL-Level logic input Bootstraps drive high side gate to 116VDC Short propagation delay (45ns) Fast rise and fall times (10ns into 1nF) V DD supply under-voltage lock-out (6.7V) Low power consumption 0.5MHz) Packages: SOIC-8, LLP-10 IN K x RT HO T PROP LO T PROP K x RT Typical Applications Cascaded Power Converters High Voltage Buck Regulators Active Clamp Forward Power Converters IN LM5104 Adapt Logic Adapt Logic VDD DLY Logic DLY Logic RT HB HO HS LO 43 The last device in the LM5100 family is the LM5104. This device has a single input to control both the high and low gates. This device features an adaptive deadtime feature, whereby a gate is not enabled until the opposite gate has been turned off. Additional turn-on delay can be added at each transition set by RT. This device allows minimal deadtimes while maintaining a robust gate drive scheme for Buck Stage drive applications with a single input. 43

44 Summary: New 100V controllers and drivers enable higher performance power converters with a minimum of external components: LM5030 Push Pull Controller LM5041 Cascade Controller LM510X Gate Drivers Questions or Comments? This concludes my presentation. All of the devices described today are available for immediate sampling. At this time we have time for a couple of questions. 44