APPLICATION NOTE Consumption Shutdown Capability: NCP1653 particu

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AND8184/D Four Steps Design Continuous Conduction Mode Stage Using NCP1653
APPLICATION NOTE Consumption Shutdown Capability:
NCP1653 particularly, minimizes consumptions during startup phase shutdown mode. Hence, stage losses extremely when circuit off. This feature helps meet more stringent standby power specifications. Grounding Feedback (pin1) forces NCP1653 shutdown mode. Safety Protections: NCP1653 permanently monitors input output voltages, coil current temperature protect system from possible over-stresses. More specifically, following protections make stage extremely robust reliable: Maximum Current Limit: circuit immediately turns MOSFET coil current exceeds maximum permissible level. NCP1653 also prevents turn power switch long coil current below this limit. This feature protects stage during startup phase when large in-rush currents charge output capacitor. Undervoltage Protection/Shutdown: circuit keeps shutdown mode long feedback current indicates that output voltage lower than regulation level. this case, NCP1653 consumption very (<50 mA). This feature protects stage from starting operation case line conditions failure feedback network (e.g., connection). Overvoltage Protection: Given bandwidth regulation block, stages exhibit dangerous output voltage overshoots because abrupt load input voltage variations (e.g. startup). Overvoltage Protection (OVP) turns Power Switch soon Vout exceeds threshold (107% regulation level).
This paper proposes steps rapidly design Continuous Conduction Mode (CCM) stage driven NCP1653. process illustrated following practical application: Maximum output power: Input voltage range: from Vrms Vrms Regulation output voltage: Switching frequency: INTRODUCTION NCP1653 controller Continuous Conduction Mode (CCM) Power Factor Correction step-up pre-converters. controls power switch conduction time (PWM) fixed frequency mode dependence instantaneous coil current. Housed DIP8 package, circuit minimizes number external components drastically simplifies implementation. also integrates high safety protection features that make NCP1653 driver robust compact stages like effective input power runaway clamping circuitry. Generally, NCP1653 ideal candidate systems where cost-effectiveness, reliability high power factor parameters. incorporates necessary features build compact rugged stage: Compactness Flexibility: Easy implement, NCP1653 yields near-unity power factor simple robust manner. Despite external components count requires, circuit sacrifices neither performance flexibility. Instead, simply adjusting external resistor, even choose have circuit operated traditional follower boost mode (1).
(1)The
"Follower Boost" mode makes pre-converter output voltage stabilize level that varies linearly versus line amplitude. This technique aims reducing difference between output input voltages optimize boost efficiency minimize cost stage (refer MC33260 NCP1653 data sheet www.onsemi.com).
Semiconductor Components Industries, LLC, 2004
November, 2004 Rev.
Publication Order Number: AND8184/D
AND8184/D
Over-Power Limitation: NCP1653 senses coil current input voltage based this information, circuit able detect excessive power levels. this case, grounds regulation block (nonfiltered) output long calculated power keeps high.
Thermal Shutdown: internal thermal circuitry forces power switch when junction temperature exceeds 150°C typically. circuit resumes operation once temperature drops below about 120°C (30°C hysteresis).
STAGE DIMENSIONING
Diode Bridge Rin1 Filter
Vout
Rfb3
Rfb2
Rfb1
NCP1653
CVcc Cbulk
Rin2 Cin2
Cfb1
Cin1
Earth
Rcs1
Rcs2
Ccs2
Rsense
Figure Generic Schematic
Step Power Components Selection Basically, coil, bulk capacitor power silicon devices dimensioned usually", that done with other PFC. This section does detail this process, simply states some points.
Coil Selection
Typically, targets peak-to-peak ripple between line current maximum amplitude ((Iin)max). Therefore target ripple line, coil inductance given following equation:
(Pout)max VacLL VacLL Vout VacLL 2*L*f
generally selects coil limit current ripple below certain pre-determined level, instance "15% when input current maximum. input current amplitude, (Iin), maximum line high power. Hence, (Iin)max
(Pout)max (eq. VacLL
(eq.
Hence, coil inductance
VacLL2 VacLL (eq. Vout (Pout)max
where (Pout)max maximum output power, efficiency VacLL line lowest level. Consequently, assume efficiency, application leads following maximum line peak current: (0.92 that other hand, could show that sinusoid top, peak-to-peak ripple coil current, given following equation: Vac). (eq.
Vout
combination output voltage (Vout) switching frequency, leads coil inductance range practice, have chosen that more specifically, leads about ripple. Finally, neglects switching ripple coil current, value equates line current. other words: (Icoil)rms Pout
(eq.
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AND8184/D
maximum current coil then:
(Pout)max (eq. ((Icoil)rms)max VacLL Output Bulk Capacitor
coil specification then: (Icoil)max (maximum amplitude line current ripple) (Icoil)rms
Power Silicon Devices
Unless another constraint specified (the hold-up time instance), main criterion when choosing bulk capacitance maximum voltage ripple (100 ripple exhibited bulk voltage(2)). voltage ripple constraint requires that:
Cbulk Pout (dVpk Vout
(eq.
Generally, diode bridge, power MOSFET output diode will placed same heatsink. rule thumb, estimate that heatsink will have dissipate around: output power wide mains applications (92% being generally targeted minimum efficiency) output power European mains applications Among sources losses that contribute this heating, list: diodes bridge conduction losses that estimated following equation:
Pbridge Pout Pout VacLL VacLL
(eq.
where (dVpk-pk)max maximum permissible peak-to-peak voltage ripple line angular frequency. application, let's allow voltage ripple "3.5% ((dVpk-pk)max Vout). This requirement leads following bulk capacitance:
Cbulk 89.7 3902
(eq.
closest higher normalized value.
Hold-up Time Requirement:
some hold-time requirement specified, this would lead following additional constraint:
Cbulk Pout tHOLD where Vout1 nominal (Vout12 Vout22)
where forward voltage bridge diodes. MOSFET conduction losses, that neglects current ripple, given
(pon)max RDSON VacLL VacLL Vout
(eq.
output voltage (390 Vout2 minimum acceptable level Vout tHOLD hold-up time. tHOLD Vout2 lead Cbulk 96.6 With this specification, still valid choice. However, calculation based average Vout1 value instead minimum level resulting from ripple. Hence, would more robust option.
Bulk Capacitor Heating:
output diode conduction losses: (Iout Vf), where Iout load current diode forward voltage. maximum output current being nearly 0.75 (300 W/390 diode conduction losses range 0.75 (assuming case, have: Pbridge assuming that (pon)max RDSon. application, RDSon MOSFET (0.19 implemented avoid excessive MOSFET losses. Assuming that RDSon doubles high temperatures, maximum conduction losses about Pdiode 0.75 diode MOSFET switching losses highly dependent diode choice, MOSFET drive speed possible presence some snubbering circuitry. Hence, their prediction tough inaccurate exercise that will made this paper. Instead, they just assumed part power budget initially specified heatsink Pout case). Experimental tests will ensure that estimation correct.
must also checked that enough prevent current that flows through from overheating bulk capacitor. This current depending input impedance downstream converter, computed here. simple solution consists experimentally measuring worst case: line, high power. first approach, rapidly estimate magnitude making simulation (refer www.onsemi.com download IsSpice PSpice NCP1653 model).
(2)The
input current voltage being sinusoidal, stages deliver squared sinusoidal power that matches load power demand average only. When power load lower than load demand, output capacitor discharges while charges when supplied power exceeds load consumption. consequence, output voltage exhibits ripple (e.g., ripple Europe USA) that inherent function.
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AND8184/D
Step Feedback Arrangement shown Figure feedback arrangement consists filtering capacitor avoid that some switching noise injected into pin1. capacitor traditionally implemented. resistor connected between output voltage rail pin1 provide circuit with feedback current proportional Vout. practice, generally implements three resistors safety considerations (see Figure given that Vout high voltage, accidental shortage feedback resistor would destroy controller. That better have several series resistors instead only one). capacitor (applied pin2) sets regulation bandwidth together with internal resistor. Choose range effective filtering ripple. (Rfb Rfb1 Rfb2 Rfb3), regulation output voltage given
Vout Vpin1 (RFB Iref)
(eq.
other words, input voltage sensing circuitry must designed that (Ipin3 when (Vac VacLL) where VacLL line lowest level. Hence, portrayed Figure sensing arrangement consists (optional) filtering capacitor Cin1 that placed between pin3 ground protect from possible surrounding noise. should range resistors Rin1 Rin2 dimensioned adjust pin3 current. capacitor Cin2 that forms pass filter together with Rin2, able effectively filter line ripple (Vin rectified sinusoid). time constant range should targeted make pin3 current substantially constant proportional mean input voltage:
Ipin3 Vpin3 Rin1 Rin2
(eq.
where <Vin> average input voltage Vpin3 pin3 voltage (Vpin3 being rectified sinusoid,
Ipin3 2*Vac Vpin3 Rin1 Rin2
where: Vpin1 pin1 voltage (about total feedback resistor placed between Vout pin1 Iref internal current reference (200 regulate output voltage equate must then select following resistance:
1.94
(eq.
sensing network must designed that: (Ipin3 when (Vac VacLL), hence:
Rin1 Rin2 VacLL)
(eq.
approximately obtain 1.94 resistance implementing: (Rfb1 Rfb2 (Rfb3 kW). These normalized values precisely give: (Rfb 1.92 that regulation level, which acceptable. Finally:
Rfb1 Rfb2 Rfb3 Cfb1
(60021 VacLL) 266667
case, VacLL Hence: Rin1 Rin2 5.13 Let's choose: Rin1 Rin2 aforementioned, time constant (Rin2 Cin2) should range then:
Cin2 Let's select: Cin2
Step Input Voltage Sensing NCP1653 monitors input voltage (Vin rectified line sinusoid). Practically, pin3 designed sink current that proportional average value. This current information mainly used over-power limitation block. proper tuning this protection, input sensing network must force constant current into when line lowest level.
Note: Rin2 should selected small compared Rin1 that small portion input voltage applies across Cin1. case, ratio (Rin1/Rin2 allows ceramic capacitor Cin1. Finally:
Rin1 Rin2 Cin1 Cin2
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AND8184/D
Step Current Sense Network current sense circuitry consists current sensing resistor Rsense. resistor Rcs1 that sets current limit threshold. resistor Rcs2 that adjusts stage power capability. capacitor Ccs2. Pin3 sources current that proportional coil current. Ccs2 must filter coil current ripple that Ipin3 actually proportional input current.
Rsense Rcs1 Ccs2
Rcs2 adjusts maximum power stage supply given chosen output voltage level. choosing Rcs2 high enough, force "Follower Boost" operation(3). following equation select Rcs2:
Rcs2 Rcs1 Iref Vref Rsense (Pout)max VoutLL VacLL
(eq.
free implement current sense resistor (Rsense) your choice. Practically, losses considerations dictate value. neglects ripple current, maximum Rsense losses estimated following equation:
(pRsense)max Rsense (Pout)max VacLL
(eq.
rule thumb, choose Rsense that dissipation does exceed 0.5% (Pout)max. This criterion leads
Rsense 0.005 VacLL)2 (Pout)max
(eq.
where: input voltage sensing global resistance (Rin Rin1 Rin2) Iref internal current reference (200 Vref internal voltage reference (2.5 VacLL lowest level line voltage (Pout)max maximum output power efficiency VacLL (Pout)max VoutLL output voltage corresponding VacLL full load conditions. traditional mode, VoutLL targeted regulation level (390 general). Follower Boost, choose lower value. application traditional (constant output voltage). Hence, VoutLL equates Rcs2
0.92 2.85 5.17 2.5V
application, solving precedent equation gives: Rsense Hence, Rsense that would spend about acceptable choice.
Rcs1
(eq.
Simply select Rcs1 order desired overcurrent limit:
Rcs1 Rsense (Icoil)max Iref
(eq.
Let's take normalized resistor. correct filtering pin3 voltage switching ripple, time constant (Rcs2 Ccs2) should taken range This time constant large enough filter switching ripple enough distort frequency component (that rectified sinusoid). Hence: Ccs2
Rcs2
where: (Icoil)max maximum coil current Iref internal current source (200 step1 indicates that maximum coil current Rsense selected, Rcs1 that
application this leads following Ccs2 value: Ccs2 Let's take Ccs2 Finally:
Rsense Rcs1 2.85 Rcs2 Ccs2
(3)The
"Follower Boost" mode makes pre-converter output voltage stabilize level that varies linearly versus line amplitude. This technique aims reducing difference between output input voltages optimize boost efficiency minimize cost stage (refer MC33260 NCP1653 data sheet www.onsemi.com).
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AND8184/D
Summary
Steps Components Select maximum switching peak-to-peak ripple coil current Coil Inductance Step Coil Inductance, Bulk Capacitor Power Silicon Formula Choose value between 50%. (DIcoil)pk-pk (Icoil)max VacLL Vout Application
VacLL2 (Pout)max
Maximum coil current
(Icoil)max
(Pout)max VacLL (Pout)max VacLL
(Icoil)max
coil current
((Icoil)rms)max Cbulk
((Icoil)rms)max
Bulk Capacitor Value
89.7 3902
(hold-up time current considerations being taken into account) Rfb1 Rfb2 Rfb3 Cfb1 Rfb1 Rfb2 Rfb3 Vout Cfb1 2*VacLL Rin1 Rin2 Rfb1 Rfb2 Rfb3 Cfb1
Step Feedback Arrangement
Rin1 Rin2 Step Input Voltage Sensing Cin1 Cin2
(Rin Rin1 Rin2) Choose: Rin1 Rin2 Cin1 Cin2 Rin2 Choose Rsense that dissipation keeps reasonable (e.g., select Rsense that pRsense less than 0/5% (Pout)max). VacLL)2 Rsense 0.5% (Pout)max Cin1 Cin2
Rsense
Rsense
Step Current rrent Sense Network
Rcs1
Rcs1 Rcs2
Rsense (Icoil)max
Rcs1 2.85
Rcs1 (Rin1 Rin2) VacLL Rsense (Pout)max VoutLL Rcs2
Rcs2 where (mW) Ccs2 Ccs2 Rcs2
Ccs2
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KBU6K Type Rfb3 NCP1653
Rfb2 Rfb1
CSD04060
Type 2.85
AND8184/D
Figure Application Schematic
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Type snap-in SPP20N60S
Type
Type
Earth
AND8184/D
CONCLUSION
shown this paper, NCP1653 represents major leap towards compactness ease implementation. desired, circuitry Figure yields high power factor ratios good efficiency. more information this application, please refer Application Note AND8185/D www.onsemi.com that gives more details
practical implementation (BOM, plots.) circuit performance (THD, efficiency.). Excel Spreadsheet available RKSHEET.XLS automatically computes calculations present this application note.
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AND8184/D

APPLICATION NOTE Consumption Shutdown Capability: NCP1653 particu

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