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DG_1711_PL21_1712_143020
XDPL8221 digital PFC + flyback controller IC
XDP™ digital power
Ordering code: REF-XDPL8221-U100W
About this document
Scope and purpose
This document is a step-by-step guide to designing a high-performance dual-stage digital PFC + flyback AC-DC
converter using the XDPL8221 controller for LED lighting applications. The document also describes parameter
handling for typical Infineon use cases using the Infineon .dp Vision tool for the Infineon XDPL8221.
Intended audience
This document is intended for anyone wishing to design a high-performance dual-stage digital PFC + flyback
AC/DC-DC converter for LED lighting based on the XDPL8221 digital controller.
Table of contents
About this document ....................................................................................................................... 1
Table of contents ............................................................................................................................ 1
1
Introduction .......................................................................................................................... 3
1.1
Product highlights ................................................................................................................................... 3
1.2
Design features ........................................................................................................................................ 3
1.3
Target applications ................................................................................................................................. 3
1.4
Pin configuration and description .......................................................................................................... 4
2
Hardware design .................................................................................................................... 6
2.1
System specification of a 100 W driver for LED lighting applications ................................................... 6
2.2
Schematic ................................................................................................................................................ 7
2.3
Bridge rectifier ......................................................................................................................................... 8
2.4
Design PFC boost converter .................................................................................................................... 8
2.4.1
Main PFC boost inductor .................................................................................................................... 8
2.4.2
PFC boost diode ............................................................................................................................... 11
2.4.3
PFC power MOSFET .......................................................................................................................... 13
2.4.4
PFC MOSFET gate driver .................................................................................................................. 13
2.4.5
PFC CS and ZCD ................................................................................................................................ 14
2.4.6
PFC output voltage sense ................................................................................................................ 16
2.4.7
PFC output capacitor ....................................................................................................................... 18
2.4.8
PFC multi-mode control................................................................................................................... 18
2.4.9
PFC start-up and steady-state control ............................................................................................ 20
2.4.10
Input voltage sensing ....................................................................................................................... 21
2.4.11
PFC protection features ................................................................................................................... 22
2.4.11.1
Bus voltage protection................................................................................................................ 23
2.4.11.2
Input voltage protection ............................................................................................................. 25
2.4.11.3
Over-current protection.............................................................................................................. 25
2.4.11.4
Soft-start failure .......................................................................................................................... 26
Design Guide
www.infineon.com/XDP
Please read the Important Notice and Warnings at the end of this document
page 1 of 61
V 1.0
2019-1-23
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Summary of Contents for Infineon XDPL8221
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Page 1: Table Of Contents
This document is a step-by-step guide to designing a high-performance dual-stage digital PFC + flyback AC-DC converter using the XDPL8221 controller for LED lighting applications. The document also describes parameter handling for typical Infineon use cases using the Infineon .dp Vision tool for the Infineon XDPL8221. Intended audience This document is intended for anyone wishing to design a high-performance dual-stage digital PFC + flyback AC/DC-DC converter for LED lighting based on the XDPL8221 digital controller. - Page 2 Flyback CCM protection ......................47 2.5.13.7 Soft-start failure .......................... 48 2.5.13.8 Other flyback protections ......................48 Design the power supply for XDPL8221 ....................48 Design the bleeder ..........................50 Design the adaptive temperature protection ..................52 Design the dimming interface ....................... 53 2.10 UART interface ............................
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Page 3: Introduction
XDP™ digital power Introduction Introduction The XDPL8221 digital controller IC belongs to the Infineon XDP digital power family. It provides an independent PFC boost and flyback dual-stage control to achieve an output that combines Constant Voltage (CV), Constant Current (CC) and Limited Power (LP) for LED luminaires. The IC is available in a PG-DSO-16 package and supports many features with only a minimal requirement of external components. -
Page 4: Pin Configuration And Description
XDPL8221 digital PFC + flyback controller IC XDP™ digital power Introduction Figure 1 XDPL8221 typical application schematic Pin configuration and description Pin assignments and basic pin description information are shown below. Figure 2 Pin configuration of XDPL8221 Table 1 Pin definitions and functions... - Page 5 XDPL8221 digital PFC + flyback controller IC XDP™ digital power Introduction IC power supply Ground IC ground Flyback Zero-Crossing Detection (ZCD) Connected to the flyback auxiliary winding via a resistive divider for ZCD as well as primary-side output voltage sensing for output regulation and back-up bus voltage...
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Page 6: Hardware Design
XDPL8221 digital PFC + flyback controller IC XDP™ digital power Hardware design Hardware design The hardware design part provides detailed calculations of power component values as well as the setting of parameters of general functions and protection features for both PFC boost and flyback converters. Useful tips on PCB layout are included to help customers optimize their PCB design. -
Page 7: Schematic
XDPL8221 digital PFC + flyback controller IC XDP™ digital power Hardware design Schematic Figure 3 XDPL8221 100 W driver schematic Design Guide 7 of 61 V 1.0 2019-1-23... -
Page 8: Bridge Rectifier
DC voltage as input, which ensures flicker-free light output. This chapter describes the methodology for designing the QRM PFC boost converter based on the XDPL8221, including PFC boost inductor design, equations for power loss estimation, and a selection guide for power semiconductor devices and passive components. - Page 9 For the maximum output power, higher PFC inductance has longer on-time and lower switching frequency. It • must be guaranteed that these two parameters are still within the limits of the XDPL8221. Higher PFC inductance leads to a larger choke size and more winding turns, which causes more winding loss.
- Page 10 XDPL8221 digital PFC + flyback controller IC XDP™ digital power Hardware design = √2 ∗ = 2.12 Maximum input peak current: = 2 ∗ = 4.24 Maximum inductor peak current: Figure 4 Boost inductor current waveform in a switching cycle...
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Page 11: Pfc Boost Diode
B is recommended not to exceed 0.3. In the Infineon 100 W driver reference design, the PFC boost inductor is constructed by Würth Elektronik using part no. 750343236 as a design example. - Page 12 • As the PFC boost converter is controlled by the XDPL8221 in the QRM + DCM mode, the PFC boost diode current goes back to zero while the PFC MOSFET turns on. So there is no current commutation between the PFC diode and MOSFET and thus no switching loss by reverse recovery.
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Page 13: Pfc Power Mosfet
The gate-driver power is typically dissipated in the external gate resistor and gate-driver itself and thus does not need to be considered in the thermal calculation of the MOSFET. In the 100 W driver reference design, the 600 V Infineon MOSFET IPA60R190C6 from the C6 family is used. With = 1.5 ∗... -
Page 14: Pfc Cs And Zcd
PFC CS and ZCD The pin CSPFC of the XDPL8221 is used for two different purposes in one switching cycle. During the on-time of the PFC MOSFET, it is used as a CS pin. The CS of the PFC boost converter is used to limit the turn-on time of the PFC MOSFET by sensing the peak current flowing through the MOSFET in order to protect it and also the boost inductor from an over-power situation. - Page 15 XDPL8221 digital PFC + flyback controller IC XDP™ digital power Hardware design Figure 6 Schematic of shared CS and ZCD functions at the CSPFC pin The ratio of the resistor divider R and R decides the amplitude of the oscillation at the CSPFC pin. So...
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Page 16: Pfc Output Voltage Sense
Bus voltage measurement Inside the XDPL8221, the VS pin is connected to an 8-bit ADC, which utilizes two voltage ranges for the bus voltage measurement results. This gives the advantage on the one hand that the whole voltage range started from 0 V is monitored. - Page 17 VS1_PFC VS1_PFC Note: As indicated in the XDPL8221 datasheet, the V pin voltage must be higher than 3.4 V before the voltage of VS exceeds 1.2 V. So it is recommended to select the divider with the highest impedance. This also helps to reduce the power consumption in standby mode.
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Page 18: Pfc Output Capacitor
XDPL8221 digital PFC + flyback controller IC XDP™ digital power Hardware design Parameter Symbol Value Unit Nominal PFC boost converter output voltage XDPL8221 internal ADC reference voltage 2.428 Bus voltage sensing divider upper resistor 3.32 x 3 MΩ VS1_PFC Bus voltage sensing divider lower resistor 52.3... - Page 19 Therefore multi-mode control is implemented. The XDPL8221 uses QRM + DCM operation for PFC load regulation. At full load and heavy load, the PFC is running with QRM1 for the best power efficiency. When the load decreases, the XDPL8221 reduces the on-time and switching frequency at the same time by adding an additional delay into each switching cycle through selecting further inductor current valleys to achieve QR2M and up to maximum QRM5 (configurable) operation.
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Page 20: Pfc Start-Up And Steady-State Control
PFC soft-start failure will be triggered. This is shown in Figure The XDPL8221 PFC stage uses the PIT1 (Proportional-Integral-T1) controller to control the bus voltage in start- up and steady-state operation: Term P is proportional to the bus voltage error (difference between current bus voltage value and the •... -
Page 21: Input Voltage Sensing
This eliminates the possible flicker in the deep dimming condition. For all PIT1 controller gain parameters in the XDPL8221: the higher the gain value, the lower the gain. The important design parameters for PFC boost converter start-up control are summarized in the table below:... -
Page 22: Pfc Protection Features
20 x 3 = 60 kΩ 2.4.11 PFC protection features The XDPL8221 digital controller provides all-round protections for both power components and input/output of the PFC boost converter. As illustrated below in the control state machine (Figure 15), the protections are active after the system enters the start-up checks state (when V voltage reaches the on-threshold). -
Page 23: Bus Voltage Protection
XDPL8221 digital PFC + flyback controller IC XDP™ digital power Hardware design start-up checks, the input/output are monitored before PFC starts to protect against possible under-/over- voltage. After the system is in the soft-start state, more protections such as over-current, over-power and CCM protection are also activated. - Page 24 XDPL8221 will enter latch mode. The OVP2 threshold is defined as a VS pin voltage of 2.8 V, which together with the bus voltage sense divider results in the corresponding voltage at the bus.
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Page 25: Input Voltage Protection
Input voltage protection Input voltage protection is realized by monitoring the voltage at the HV pin. After the XDPL8221 has become active and before the PFC boost converter is started, the input voltage is first checked. Once the input RMS... -
Page 26: Soft-Start Failure
The flyback converter takes the boosted DC voltage as input and converts it to a configurable wide-range DC output with the programmable constant current on the secondary side. The XDPL8221 controller provides a primary-side output voltage and current control without the external regulator on the secondary side. This... -
Page 27: Designing The Flyback Transformer
XDPL8221 digital PFC + flyback controller IC XDP™ digital power Hardware design Nominal DC input voltage Maximum DC input voltage bus_max Maximum flyback converter output power O_max Minimum switching frequency sw_FB_min Estimated flyback converter power efficiency η Less than 93... -
Page 28: Primary Magnetizing Inductance
XDPL8221 digital PFC + flyback controller IC XDP™ digital power Hardware design During turn-off of the primary-side MOSFET, energy stored in leakage inductance will charge up the C of the primary MOSFET, causing an over-voltage spike to occur on top of the steady-state stress voltage. Depending on... - Page 29 XDPL8221 digital PFC + flyback controller IC XDP™ digital power Hardware design But as the voltage and current could change at the full output power, the more critical working point happens at the maximum output current under full load. So the possible minimum duty cycle at full power in QRM operation ∗...
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Page 30: Flyback Transformer Winding Turns
The primary auxiliary winding is separated into two parts. One is the forward winding, which provides the power for the XDPL8221 controller. This ensures the precision of the primary-side regulation. As this winding operates in the forward mode, so the winding voltage is proportional to the bus voltage when the flyback MOSFET turns on and is independent from the output voltage. - Page 31 In order to avoid core saturation and achieve an optimized core loss, the flux density B is recommended not to exceed 0.3. In the Infineon 100 W driver reference design, the flyback transformer is constructed by Würth Elektronik using part no. 750317672-Rev00 as a design example.
- Page 32 XDPL8221 digital PFC + flyback controller IC XDP™ digital power Hardware design ∗ = 0.55 W The maximum primary-side DC conduction loss can be calculated as: ∗ = 1.24 W The maximum secondary-side DC conduction loss can be calculated as:...
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Page 33: Flyback Primary Power Mosfet
(total gate charge). The gate driver power is typically dissipated in the external gate resistor and gate driver itself and thus does not need to be considered in the thermal calculation of the MOSFET. In the 100 W driver reference design, the 800 V Infineon MOSFET IPA80R450P7 in the P7 family is used. With the = 2 ∗... -
Page 34: Flyback Mosfet Gate Driver
2.5.3 Flyback MOSFET gate driver The XDPL8221 flyback gate driver offers the following advanced features: Configurable charge current from 100 to 150 mA for turn-on slope optimization with .dp Vision tool • Configurable gate voltage from 4.5 to 15 V •... - Page 35 XDPL8221 digital PFC + flyback controller IC XDP™ digital power Hardware design Figure 20 MOSFET drain-source voltage and snubber capacitor voltage The RCD snubber network limits the high voltage spike, turning on the snubber diode once the MOSFET drain voltage exceeds a certain voltage limit and absorbing the current in the leakage inductance. The voltage over- shoot V limited by the RCD snubber is related to the power dissipation in the clamping network.
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Page 36: Flyback Secondary Rectifier Diode
XDPL8221 digital PFC + flyback controller IC XDP™ digital power Hardware design ∗ ∗ ∗ ∗ Then the clamping circuit resistor is calculated as: In order to reduce the power stress of the snubber resistor, it is recommended to separate the resistor to two parallel connected resistors. -
Page 37: Flyback Secondary Snubber
XDPL8221 digital PFC + flyback controller IC XDP™ digital power Hardware design 2.5.6 Flyback secondary snubber When the primary-side MOSFET is turned on, severe voltage oscillation occurs across the secondary-side diode, as shown in Figure 21. This is caused by the oscillation between the diode parasitic capacitance C... -
Page 38: Flyback Zcd Divider
The XDPL8221 digital controller provides primary-side flyback converter control of output current and output voltage. No external feedback components are necessary for the current control, as the primary-side regulation control loop is fully integrated. This primary-side control feature is realized through the ZCD pin of the XDPL8221, which has three functions:... -
Page 39: Flyback Cs Resistor
• out_OV = 0.2 V (refer to the XDPL8221 datasheet) • ZCD_clamp = 2.66 V is the upper measurement range (refer to the XDPL8221 datasheet) • ZCD_max = 3.2 mA (refer to the XDPL8221 datasheet) • ZCD_clamp_max In the 100 W driver reference design, R = 68 kΩ... -
Page 40: Flyback Operating Window
LED string has to be below a configurable maximum value V out_set In the case of LED loads including a power stage (e.g. Infineon BCR linear regulators or Infineon DC-DC buck • ILD2111, ILD6150, ILD1151), the XDPL8221 operates in CV, ensuring a constant voltage V to the load. - Page 41 XDPL8221 digital PFC + flyback controller IC XDP™ digital power Hardware design For CC schemes, the internal reference current I is weighted according to thermal management and a • out_full dimming curve to yield I . The calculated output current I...
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Page 42: Flyback Multi-Mode Control
2.5.11 Flyback multi-mode control The control loop of the XDPL8221 uses three different switching modes as shown in Figure 24. QRM1 is optimized for high efficiency at heavy loads while DCM and ABM are used in light-load and dim-to-off conditions. -
Page 43: Flyback Start-Up Control
2.5.12 Flyback start-up control After the bus voltage reaches the threshold V for the flyback converter to start up, the XDPL8221 bus_start_FB controller initiates a soft-start for the flyback converter to minimize the switching stress for the flyback power MOSFET and secondary rectifier diode. - Page 44 Figure 25 Flyback start-up control For CC schemes with LED strings at output: after the soft-start is finished, the XDPL8221 control loop should • take over with ABM and a very lower power transfer. The parameter ABM should be set in CC and this init prevents an incorrect output current before the PWM dimming level is detected.
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Page 45: Flyback Protection Features
The flyback gate driver will be disabled at once by hardware and the PFC stage is disabled too by the firmware. After that, the XDPL8221 will enter auto-restart mode. The important design parameters for primary over-current protection are summarized in Table 33. -
Page 46: Flyback Output Under-Voltage Protection
Auto-restart – In addition to the output over-voltage provided by the XDPL8221 from the primary side, there are two other analog hardware protection features necessary against the output over-voltage: To protect the secondary output capacitors, a zener diode with a current limitation resistor will clamp the •... -
Page 47: Flyback Output Over-Current Protection
In the soft-start phase, CCM operation is allowed for a limited time, but in other conditions, the XDPL8221 must enter the protection mode. CCM operation is monitored at the flyback ZCD pin. When the ZCD signal does not come until the maximum switching period time-out happens, it will be treated as a CCM cycle. -
Page 48: Soft-Start Failure
The start-up cell is connected through the HV pin to the rectified AC or DC input. After the the XDPL8221 is active, the start-up cell is switched off. The charging current is dependent on the RMS value of the input voltage. Using AC input as an example, the maximum charge current through the start-up cell happens at maximum AC input: √... - Page 49 PFC auxiliary winding • When the XDPL8221 is active, the start-up cell will be switched off. After the input AC/DC detection, the XDPL8221 will start the PFC boost converter. The V capacitors can then be charged by the PFC auxiliary winding. Due to the slowly increased voltage difference across the PFC boost inductor in the start-up phase, the charging current is very limited at the beginning.
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Page 50: Design The Bleeder
With a start-up time 50 ms of PFC and 30 ms start-up time for flyback, the time-to-light can be controlled within = 197 250 ms as follows: The important parameters for designing the power supply for the XDPL8221 are summarized in Table 41. Table 41 Power supply for XDPL8221 design parameters... - Page 51 A weak bleeder discharges constantly in the operation. It will generate a small load even in the very light-load condition, which can be very important for the XDPL8221 and the dimming circuit power supply. This bleeder can also be used if customers wish to have a constant output voltage when the output is open. In this case, a stronger passive bleeder is required and higher power consumption is expected.
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Page 52: Design The Adaptive Temperature Protection
Please note that the internal temperature sensor can only protect external components which have sufficient thermal coupling to the XDPL8221. The external temperature sensor can be used to protect the temperature of external components (e.g. power MOSFETs or LED engine). -
Page 53: Design The Dimming Interface
For PWM dimming, the PWM pin is used to sense the duty cycle of the applied PWM signal to determine the output current level. The XDPL8221 can be configured to use either a linear or a quadratic dimming curve. Either normal or inverted dimming curves can be selected. - Page 54 LED strings’ output voltage, the minimum output power must be designed according to the lowest output voltage. The important parameters for designing the dimming interface of the XDPL8221 are summarized in Table 43. Design Guide 54 of 61 V 1.0...
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Page 55: Uart Interface
Star connection of grounding A good grounding of the XDPL8221 is proven to minimize the risk of mutual interference among signals: The electrolytic PFC bulk cap ground is taken as the system ground reference at the primary side. The other •... -
Page 56: Filtering Capacitors Of Xdpl8221
IC controller, and will trigger some unwanted protections. These capacitors are usually made from ceramic and must be placed very close to the XDPL8221 and the ground of them must be connected to the IC ground as closely as possible. - Page 57 XDPL8221 digital PFC + flyback controller IC XDP™ digital power Hardware design Any PCB track with high current should be designed to be as short and wide as possible to reduce the parasitic • inductance, such as traces through the MOSFET drain-source and shunt resistors.
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Page 58: Configuration Set-Up And Procedures
Configuration set-up and procedures Configuration set-up and procedures As the XDPL8221 is by default burned with parameters for a 50 W Infineon reference board, users must configure the XDPL8221 with calculated 100 W driver hardware components and other parameter values. This is achieved by entering the hardware configuration and the application’s requirements into the .dp Vision tool. -
Page 59: References
XDPL8221 digital PFC + flyback controller IC XDP™ digital power References References XDPL8221 Datasheet .dp Vision Basic Mode User Manual XDPL8221 100 W CSV file description XDPL8221 UART Interface First Steps with XDPL8221 Power Management Selection Guide: http://www.infineon.com/powermanagement-selectionguide Design Guide 59 of 61 V 1.0... -
Page 60: Revision History
XDPL8221 digital PFC + flyback controller IC XDP™ digital power Table of contents Revision history Document Date of release Description of changes version 2018-10-23 First release Design Guide 60 of 61 V 1.0 2019-1-23... - Page 61 Infineon Technologies hereby disclaims dangerous substances. For information on the types © 2019 Infineon Technologies AG. any and all warranties and liabilities of any kind in question please contact your nearest Infineon All Rights Reserved. (including without limitation warranties of non- Technologies office.