Related Manuals for Infineon XMC Series
Summary of Contents for Infineon XMC Series
- Page 1 XMC4000/1000 Microcontroller Series for Industrial Applications Intr oduct i on to D igi tal Po wer Con versio n Applic atio n Guid e V1.0 2015-01 Microcontrollers...
- Page 2 Infineon Technologies components may be used in life-support devices or systems only with the express written approval of Infineon Technologies, if a failure of such components can reasonably be expected to cause the failure of that life-support device or system or to affect the safety or effectiveness of that device or system. Life support devices or systems are intended to be implanted in the human body or to support and/or maintain and sustain and/or protect human life.
- Page 3 Introduction to Digital Power Conversion XMC4000/1000 Family Revision History Revision History Page or Item Subjects (major changes since previous revision) V1.0, 2015-01 Trademarks of Infineon Technologies AG AURIX™, C166™, CanPAK™, CIPOS™, CIPURSE™, CoolMOS™, CoolSET™, CORECONTROL™, CROSSAVE™, DAVE™, EasyPIM™, EconoBRIDGE™, EconoDUAL™, EconoPIM™, EiceDRIVER™, eupec™, FCOS™, HITFET™, HybridPACK™, I²RF™, ISOFACE™,...
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Page 4: Table Of Contents
2.3.2.2 Digital Switch Mode Controllers ....................11 2.3.2.3 ASIC controller versus MCU / DSP / DSC controllers ............12 Infineon XMC-families for Switch Mode Power Control ..............13 2.4.1 Power Conversion Oriented Peripheral Features ................ 14 2.4.1.1 Sensing ........................... 14 2.4.1.2... - Page 5 Introduction to Digital Power Conversion XMC4000/1000 Family Table of Contents Over Voltage and Over Current Protection (OVP / OCP) ..............50 Modulation ............................51 Voltage Control (VC) .......................... 52 6.1.1 Timing Scheme ..........................53 Current Control ........................... 55 6.2.1 Average Current Control (ACC) ....................55 6.2.2 Average Current Control, Edge-Aligned Scheme ................
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Page 6: About This Document
Introduction to Digital Power Conversion XMC4000/1000 Family About this document About this document Scope and Purpose This document aims to stimulate and challenge accepted solutions in the field of power applications with digital control, by revisiting the basics of electric energy transfer and creating a summarized picture of what can be achieved today with a weighted mix of embedded dedicated peripherals and computing power. -
Page 7: Comparison Of Power Conversion Methods
Introduction to Digital Power Conversion XMC4000/1000 Family Comparison of Power Conversion Methods Comparison of Power Conversion Methods What is Power Conversion Power conversion is the conversion of electric energy from one form to another. As long as it does not concern electro-mechanic equivalent energy that consumes energy (e.g. - Page 8 Introduction to Digital Power Conversion XMC4000/1000 Family Comparison of Power Conversion Methods Linear DC/DC Conversion Figure 1 Passive Linear Conversion Passive conversion means that there are no control components involved in the process that are capable of changing the conversion properties in any way; i.e. the steady state input-to-output transfer function is not adjustable in runtime.
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Page 9: Switch Mode Power Conversion
Introduction to Digital Power Conversion XMC4000/1000 Family Comparison of Power Conversion Methods 2.3.2 Switch Mode Power Conversion A Switch Mode DC/DC Converter output/input voltage ratio can be any value, including a negative value. That property is not covered by any Linear Voltage Converter, so most power conversion use- cases can be solved by Switch Mode, especially in the area of high power, where efficiency and form- factor are vital. - Page 10 Introduction to Digital Power Conversion XMC4000/1000 Family Comparison of Power Conversion Methods Switch Mode Power Conversion Principle – Compared to Linear Mode In switch mode voltage conversion, portions of energy, divided by switching in time lengths (T or T are transferred from a voltage source to an inductor (L) current as magnetic energy, cyclic in periods (T).
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Page 11: Analog Switch Mode Controllers
Introduction to Digital Power Conversion XMC4000/1000 Family Comparison of Power Conversion Methods 2.3.2.1 Analog Switch Mode Controllers Traditional Analog Controllers have a significant BOM (Bill of Materials) list of OpAmps, comparators, filters, and so on. They cover just a limited range of topologies and do not adapt autonomously to condition changes in run-time. -
Page 12: Asic Controller Versus Mcu / Dsp / Dsc Controllers
Introduction to Digital Power Conversion XMC4000/1000 Family Comparison of Power Conversion Methods 2.3.2.3 ASIC controller versus MCU / DSP / DSC controllers Here we outline some of the guiding properties to be considered, for the type of controller to choose when selecting for High-end versus Low-end. -
Page 13: Infineon Xmc-Families For Switch Mode Power Control
The Power Conversion Oriented XMC Devices 3-Level Architecture Control Loop Figure 4 The XMC series for power control meets the performance challenges and demands of today’s embedded control applications. The high performance, real-time capability is achieved with an ARM- Cortex architecture, with or without DSP, and a Floating Point Unit (FPU). -
Page 14: Power Conversion Oriented Peripheral Features
Introduction to Digital Power Conversion XMC4000/1000 Family Comparison of Power Conversion Methods 2.4.1 Power Conversion Oriented Peripheral Features Here we highlight features of the XMC-family embedded peripherals that are essential for the significant tasks required in power conversion control loops. 2.4.1.1 Sensing Analog values are monitored, or detected upon crossing level limits, via Versatile Analog-to-Digital... -
Page 15: Pwm Generation
Introduction to Digital Power Conversion XMC4000/1000 Family Comparison of Power Conversion Methods 2.4.1.4 PWM Generation The XMC CAPCOM Units (CCU4 or CCU8) timer slices can be regarded as “timer-cells” that can cooperate and fit together like “puzzle pieces” to form matrices of sophisticated and compound timing functions. -
Page 16: Converter Topologies
Introduction to Digital Power Conversion XMC4000/1000 Family Converter Topologies Converter Topologies The fundamental power converter topologies that we focus on in this document are: Buck (“Step-Down”) (Section 3.1) − Conventional − Interleaved − Synchronous − Inverted Boost (“Step-Up”) (Section 3.2) −... -
Page 17: Buck
Introduction to Digital Power Conversion XMC4000/1000 Family Converter Topologies Buck A Buck converter can only generate lower output average voltage (V ) than the input voltage (V and is therefore also referred to as a “Step-Down” converter. The DC/DC conversion is non-isolating, in the sense that there is a common ground between input and output. -
Page 18: Boost
Introduction to Digital Power Conversion XMC4000/1000 Family Converter Topologies Boost A Boost converter is non-isolating and can only generate a higher output average voltage than the input supply voltage. It is therefore called a “Step-Up” converter. There is one exception to note however. The Inverted Buck-Boost converter theoretically generates an output voltage from 0 to minus infinity. -
Page 19: Pfc
Introduction to Digital Power Conversion XMC4000/1000 Family Converter Topologies Abstract The Power Factor (PF) is defined as the transfer ratio of real power [Watt] to apparent power [VA]: PF = Real Power / Apparent Power [Watt / VA] The Power-Factor-Correction (PFC) purpose is (according to the environmental context) to achieve: Real Power = Apparent Power i.e.: PF = 1... - Page 20 Introduction to Digital Power Conversion XMC4000/1000 Family Converter Topologies PFC Variants There are different types of PFC circuits, which mix a balance of complexity versus performance. Here we show just some of the basic topologies. These can be mixed into more sophisticated, multi- phased, interleaved, full-bridgeless PFCs by Synchronous rectification.
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Page 21: Phase-Shift Full-Bridge (Psfb)
Introduction to Digital Power Conversion XMC4000/1000 Family Converter Topologies Phase-Shift Full-Bridge (PSFB) The PSFB is a Phase-Shift-Full-Bridge DC/DC converter. Power is transferred in a Phase-Shift (PS) via a Full-Bridge (FB), a transformer, a rectifier and filter. The PSFB is an isolating converter. PSFB Principle Figure 9 PSFB power conversion stages... -
Page 22: Llc (Inductor-Inductor-Capacitor)
Introduction to Digital Power Conversion XMC4000/1000 Family Converter Topologies LLC (Inductor-Inductor-Capacitor) The LLC converter is a series resonant converter. Power is transferred in a sinusoidal manner, so the switching devices are softly commutated by ZVS (Zero-Voltage-Switching) and without capacitive loss. A transformer takes part in the process, making the LLC an isolating converter. LLC Principle –... -
Page 23: Generic Digital Power Converter
Introduction to Digital Power Conversion XMC4000/1000 Family Converter Topologies Generic Digital Power Converter There is a mutual property of all DC/DC power converters: Energy from an input power source is periodically stored as magnetic energy in the air-gap of inductors (L), and converted into certain output power voltage-current pairs via some rectifier-and-capacitor (C) filter configuration. -
Page 24: Pwm Generation
Introduction to Digital Power Conversion XMC4000/1000 Family PWM Generation PWM Generation Single Channel The PWM duty cycle range is 0 – 100% for all available combinations of alignments, count and in/output modes. Status bit ST can be set to 1 or 0 by timer compare or period events, or by external events (even if stopped timer). -
Page 25: Dual Channel With Complementary Outputs With Dead-Time, Using Ccu8
Introduction to Digital Power Conversion XMC4000/1000 Family PWM Generation Dual Channel with Complementary Outputs with Dead-Time, using CCU8 By using both channels (Ch1 and Ch2) in a CC8y timer slice, it is possible to output a dual pair of complementary PWM signals to target 1 or 2 full-bridges. Dead-Time insertion of individual rise-/fall times can be provided independently, as well as accurate output active level settings and trap care. - Page 26 Introduction to Digital Power Conversion XMC4000/1000 Family PWM Generation PWM Duty-Cycle Control by Period Register PWM modulation (with fixed cycle period target option) is achieved by adding a ∆PR-value and respectively substracting the same ∆PR-value to the period registers of the PWM channel single-shot timer pair.
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Page 27: On/Off Control
Introduction to Digital Power Conversion XMC4000/1000 Family PWM Generation ON/OFF Control Since all the individual ‘timer-cells’ of a CCU can be mapped to act upon virtually any external event and function request, then theoretically any on-chip module can be considered to control a PWM. For example, an ADC or comparators can join in the PWM control loops in this way, acting on analog events. -
Page 28: Fixed On-Time With Frequency Limit Control
Introduction to Digital Power Conversion XMC4000/1000 Family PWM Generation Fixed ON-Time with Frequency Limit Control In power switch control with FOT PWM, it is mandatory to have pulse rate limiting add-ons in the loop, ensuring a minimum of off-time to be fed back by the conversion process in each FOT start request. Another extreme is maximum off-time. - Page 29 Introduction to Digital Power Conversion XMC4000/1000 Family PWM Generation The ZCD Event Window (Slice3) There is a memory function required to keep track of a ZCD event that might happen before a FOT pulse is allowed to start, due to the f -period restriction.
- Page 30 Introduction to Digital Power Conversion XMC4000/1000 Family PWM Generation Monitoring the FOT pulse rate The FOT pulse rate is monitored by the free running f timer (Slice2). This timer is flushed on max–min each FOT timer start. If the next ZCD event occurs before the f -period compare event, then the next FOT start must wait because of f -period.
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Page 31: Fixed Off-Time (Fofft)
Introduction to Digital Power Conversion XMC4000/1000 Family PWM Generation Fixed Off-Time (FOFFT) In Fixed Off-Time switch mode, each PWM On-Time pulse is variable and terminated when the inductor current slope hits the peak-current detection level. On each of these events the current slope will fall, with a fixed Off-time, before next pulse, controlled by a timer. -
Page 32: Phase Shift Control
Introduction to Digital Power Conversion XMC4000/1000 Family PWM Generation Phase Shift Control There are two types: Fixed Phase Shift (180 , 120 , 90 , and so on) Variable Phase Shift Fixed Phase Shift This is used for interleave applications with multi-phase converters. The interleave function has the benefit of overlapping discontinuities in the current path, reducing ripple and therefore allowing for higher frequency and smaller components. -
Page 33: Edge Aligned Mode
Introduction to Digital Power Conversion XMC4000/1000 Family PWM Generation 4.10.2 Edge Aligned Mode Dual PWM channels with fixed phase-shift can be provided by two CCU4 slices in edge-aligned compare mode, representing each PWM channel by the associated output of each status bit. There should be a Global Start and Synchronization sequence, before the system is prepared for run- time. -
Page 34: Interleave
Introduction to Digital Power Conversion XMC4000/1000 Family PWM Generation 4.10.3 Interleave The Interleave approach offers reduced current ripple and a continuous current flow into the rectifier and filter output stage of the converter. A higher frequency and smaller components can be used. This concept is often used in high power, high voltage (e.g. -
Page 35: Variable Phase-Shift
Introduction to Digital Power Conversion XMC4000/1000 Family PWM Generation 4.11 Variable Phase-Shift A Phase-Shift Full-Bridge (PSFB) offers the benefits of using a transformer in the DC/DC conversion path, for level adaption or isolation. The phase-shift of two PWM signals to the bridge control inputs converts the bridge DC rail voltage proportionally to a transformable AC-voltage, with a defined ratio (See also Figure The target DC output voltage is rectified and LC-filtered after the secondary coils of the transformer. - Page 36 Introduction to Digital Power Conversion XMC4000/1000 Family PWM Generation PWM Phase-Shift Master-Slave Principle A CC8-slice (e.g. CC80) and its two compare channels can be used as a master for the PSFB control as follows: Channel1 − The CC80CR1 compare events control the phase-shift of the PWM pulse stream (S) from a slave timer (e.g.
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Page 37: Power Conversion Control Example
Introduction to Digital Power Conversion XMC4000/1000 Family PWM Generation 4.11.1 Power Conversion Control Example The PSFB controller performs DC/DC power conversion in stages: 1. Split the DC input voltage (V ) in to two phase-shifted pulse streams (Ph and Ph ), controlled by a PWM Phase-Shift-Master-Slave configuration with the CCU8 slice pair CC80/-81 (See also Figure... -
Page 38: Zero-Voltage Switching (Zvs) Control
Introduction to Digital Power Conversion XMC4000/1000 Family PWM Generation 4.11.2 Zero-Voltage Switching (ZVS) Control ZVS implies nearly lossless transitions. In combination with smooth zero crossing by resonance components, an almost ideal switching process is achievable. This effect can be made by controlling the free-wheeling currents and using the parasitic stray reactive elements (See also Figure 27). -
Page 39: Adding High Resolution Channel (Hrc) - Hrpwm
Introduction to Digital Power Conversion XMC4000/1000 Family PWM Generation Adding High Resolution Channel (HRC) – HRPWM 4.12 There are devices in the XMC family series offering High Resolution Channel (HRC) Generation. The High Resolution PWM (HRPWM) can be used with the CC8 slices and the CSG (Comparator and Slope Generator). -
Page 40: Pwm Dead-Time Compensation
Introduction to Digital Power Conversion XMC4000/1000 Family PWM Generation Output The HRPWM path offers dynamic Dead-Time Insertion and Active Output Level Selection. 4.12.1 PWM Dead-Time Compensation The Dead-Time parameters for rise or fall-time can be independently changed, at any time, in any mode, from one switch cycle to another. -
Page 41: Half-Bridge Llc Control Using ½ Ccu4
Introduction to Digital Power Conversion XMC4000/1000 Family PWM Generation 4.13 Half-Bridge LLC Control using ½ CCU4 LLC Converter Power Transfer by Pulse Frequency Modulation Control (PFM) The power transfer through an LLC converter can be controlled by frequency and/or PWM. The operating point should focus on the inductive property slope of the gain-vs-frequency characteristic curve, where the current phase is delayed and the gain will be reduced by increasing the frequency. -
Page 42: Half-Bridge Llc Control - Synchronous Rectification Using Ccu4
Introduction to Digital Power Conversion XMC4000/1000 Family PWM Generation 4.14 Half-Bridge LLC Control - Synchronous Rectification using CCU4 A single CCU4 CAPCOM unit is capable of driving an entire LLC converter with synchronous rectifier. Dead-time insertions are implemented in all switch commutations. The MOSFETs in the rectifier stage offer lower voltage drop than diodes do for high currents. -
Page 43: Full-Bridge Llc Control Using Hrc - Synchronous Rectification
Introduction to Digital Power Conversion XMC4000/1000 Family PWM Generation Full-Bridge LLC Control Using HRC – Synchronous Rectification 4.15 Here slices from different CAPCOM units (CCUs) interact on event control. A CCU8 slice timer (CC80) creates Pulse-Frequency Modulation (PFM), optionally with PWM for Full- Bridge control. -
Page 44: Full-Bridge Llc Control - Synchronous Rectification Using Hrc
Introduction to Digital Power Conversion XMC4000/1000 Family PWM Generation Full-Bridge LLC Control – Synchronous Rectification Using HRC 4.16 The Full-Bridge LLC control by Pulse-Frequency-Modulated (PFM) and complementary PWM signal- pairs, with individual Dead-Time Insertions, offer a tailor-made matrix of variables for an LLC converter, including a phase adjustable synchronous rectification for alignment to the sinusoidal current phase. - Page 45 Introduction to Digital Power Conversion XMC4000/1000 Family PWM Generation Synchronous Rectification Phase-Shift by Using the Timer-Load Input Function This alternative, to phase-shift a PWM, is useful here. The CC81 timer-load input function needs to be mapped in the interconnection matrix to be requested on every CC80 One-Match event. The CC81CR2 register is chosen as a timer load source, acting as a type of “mailbox”...
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Page 46: Sensing
Introduction to Digital Power Conversion XMC4000/1000 Family Sensing Sensing The XMC analog input signal sensing front-end, with dedicated features for switch-mode power control applications, covers: VADC channels Analog Voltage / Current measurements Fast Compare mode features, using result compare registers and sticky Fast Compare Result (FCR) Flags ... -
Page 47: Pwm With Fast Compare Mode Hysteretic Switching
Introduction to Digital Power Conversion XMC4000/1000 Family Sensing VADC Channel in Fast Compare Mode Figure 34 Fast Compare Result The outcome from a Fast Compare event is an affected Fast Compare Result flag (FCR) associated to the VADC channel. The FCR flag is sticky; i.e. it keeps its status until the result reference level has been crossed again, and untill te Outside-Band has been detected on the opposite side of the hysteresis range. -
Page 48: Peak Control Using Fast Compare Mode
Introduction to Digital Power Conversion XMC4000/1000 Family Sensing Peak & Zero-Crossing Detection (PCC & ZCD) in Fast Compare Mode Figure 35 5.1.3 Peak Control Using Fast Compare mode This type of sensing is called Peak-Detection; i.e. the detection event occurs when the analog signal has ramped-up to and crosses a defined level. -
Page 49: Zcd Control Using Fast Compare Mode
Introduction to Digital Power Conversion XMC4000/1000 Family Sensing 5.1.4 ZCD Control Using Fast Compare mode This type of sensing is called Valley-Detection (the opposite of Peak-Detection). In this example, the selected Valley-Detection level is Zero. To utilize the hysteresis effectively, map: ... -
Page 50: Over Voltage And Over Current Protection (Ovp / Ocp)
Introduction to Digital Power Conversion XMC4000/1000 Family Sensing Over Voltage and Over Current Protection (OVP / OCP) Limit Checking Input Signals The Valid Band for Limit-Checking an analog input signal, has a freely programmable position and size within the entire result range. The settings should be mapped in two boundary registers(0/1). Out-of-Range will set a BFL, if the corresponding activation / enable flags (BFLA / BFLE) are set. -
Page 51: Modulation
Introduction to Digital Power Conversion XMC4000/1000 Family Modulation Modulation The modulation task is to maintain the steady state duty-cycle-to-output-voltage transfer function of a sense-modulate-drive control loop in a switch-mode power converter. Each modulation mode (course of action) meets certain required properties and frequency response of the converter transfer function. -
Page 52: Voltage Control (Vc)
Introduction to Digital Power Conversion XMC4000/1000 Family Modulation Voltage Control (VC) Reference Topology Buck converter. Steady State Transfer Function The steady state duty-cycle-to-output transfer function here is based on V =D*V , maintained by the variable duty-cycle D (%) of a fixed frequency PWM from a CCU, driving the switch (Q). The feed-back function of the VC loop modulates D, so that the target output voltage is maintained. -
Page 53: Timing Scheme
Introduction to Digital Power Conversion XMC4000/1000 Family Modulation 6.1.1 Timing Scheme The PWM is generated by a CCU4/8 timer in compare mode. A Compare Register (CR) controls the duty-cycle (D). The “sense-loop-drive” process (marked by a yellow background in the following figure) is repeated with a time constant of n loop cycles, while the sensing and averaging of V is processed each cycle. - Page 54 Introduction to Digital Power Conversion XMC4000/1000 Family Modulation Steady State Frequency Response in Voltage Control The transfer function frequency response will be stabilized by the H(z) transfer compensating software; using DSP operations on discrete time variables, maintained by the Interrupt Service Request (ISR) provider, stimulated by the VADC result stream, due to the conversion trigger from the PWM cycles.
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Page 55: Current Control
Introduction to Digital Power Conversion XMC4000/1000 Family Modulation Current Control 6.2.1 Average Current Control (ACC) Reference Topology Inversed Buck Converter. A current generator, based on Average Current Control (ACC) of the inductor current, offers a voltage drop between the supply rail and the load output that is nearly without any power loss, but might cause some CPU load. -
Page 56: Average Current Control, Edge-Aligned Scheme
Introduction to Digital Power Conversion XMC4000/1000 Family Modulation Steady State DC Average Current Mode Control Loop A long term average output voltage, based on n accumulated samples by the ISR, represents a proportional value of the average current I ), and has a fixed target value relative to a voltage Avrg reference. - Page 57 Introduction to Digital Power Conversion XMC4000/1000 Family Modulation PWM and ACC Sampling Points, Controlled by Dual-Channel Compare Events The Compare Register CR1 value defines the Duty-Cycle. CR2 defines the ACC sampling points and is a ‘follower’ to CR1 by its value = CR1 value.
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Page 58: Discontinuous To Continuous Current Recovery By Timer-Load
Introduction to Digital Power Conversion XMC4000/1000 Family Modulation 6.2.3 Discontinuous to Continuous Current Recovery by Timer-Load If the inductor current reaches 0 (i.e. if the stored magnetic energy in the inductor is entirely consumed by the load, before the successive PWM starts loading it again), then the switch mode has entered Discontinuous Conduction Mode (DCM), where the steady state duty-cycle-to-output I not due. -
Page 59: Acc Center Aligned Scheme
Introduction to Digital Power Conversion XMC4000/1000 Family Modulation 6.2.4 ACC Center Aligned Scheme In this diagram the CCU4/8 slice timer works in center aligned mode. The average current is sensed via the VADC connection to the current sensor each time the timer hits ... -
Page 60: Peak Current Control (Pcc)
Introduction to Digital Power Conversion XMC4000/1000 Family Modulation Peak Current Control (PCC) The steady state duty-cycle-to-output transfer function in current control is maintained by two essential control loops: A fast inherent loop, reacting on limit current detections on a cycle-by-cycle basis ... - Page 61 Introduction to Digital Power Conversion XMC4000/1000 Family Modulation PCC Modulation Terms PCC modulation is noise sensitive. The On-Time is unpredictable and has to be overall controlled: D > 50% causes sub-oscillations that must be damped by peak current reference Slope Compensation ...
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Page 62: Pcc Timing Scheme
Introduction to Digital Power Conversion XMC4000/1000 Family Modulation 6.3.1 PCC Timing Scheme The inherent PCC reflection is simplified here by a Status Bit (ST) Override operation in hardware on a peak-detection by which the On-Time will be terminated in the PWM cycle. The Sense-Loop-Drive process (marked by the blue background in the following diagram) is the peak reference control loop. -
Page 63: Blanking, Filtering And Clamping
Introduction to Digital Power Conversion XMC4000/1000 Family Modulation Blanking, Filtering and Clamping Blanking Blanking compare mode is essential to avoid prematurely switching off the MOSFET because of noise that is induced when it is turned on. A dedicated blanking timer, in single-shot mode, is one way to create a time window to disable the comparator output and get a peak-detection accept window. -
Page 64: Slope Compensation
Introduction to Digital Power Conversion XMC4000/1000 Family Modulation Slope Compensation A Negative Characteristic with Positive Properties Slope compensation should not be seen just as a design burden to remove sub-oscillations. There are also advantages in using Slope Compensation. For example, inherent average current mode control without using the CPU, or a custom closed loop response by a damping factor that is adjustable via Slope Compensation. -
Page 65: Fast Average Current Mode Pcc
Introduction to Digital Power Conversion XMC4000/1000 Family Modulation 6.5.2 Fast Average Current Mode PCC The steady state duty-cycle-to-output CCM Average Current through the inductor (L) is a DC current on half the ∆I ripple height. ∆I = DTV / L where: or = -V toggling across the inductor D = duty-cycle. -
Page 66: Vin Independent Average Current Mode
Introduction to Digital Power Conversion XMC4000/1000 Family Modulation 6.5.3 independent Average Current mode The PCC average current can be maintained in a fast inherent loop, created by a Slope Compensation of the Peak Current. This loop will react to input voltage variations on a cycle-by-cycle basis and force the average current towards the target level, before any reaction from the long-term software control. -
Page 67: Slope Compensation Conditions - Pcc
Introduction to Digital Power Conversion XMC4000/1000 Family Modulation Slope Compensation Conditions – PCC 6.5.4 The slope compensation of the Peak Current has to comply with some boundary conditions. This brings stability into the control loop, and there are parameters that improve properties such as a damping effect or system variation endurance, supported in runtime by software in the long-term loop. - Page 68 Introduction to Digital Power Conversion XMC4000/1000 Family Modulation The two expressions for the stability condition shown here are just two different outcomes from the same calculation. > 0,5(s ) is good as a quick check point. If “s “ is replaced by s D/(1-D), then the other one appears as;...
- Page 69 Introduction to Digital Power Conversion XMC4000/1000 Family Modulation Slope Compensation: Stability Condition (2) A consequence of the stability criteria for Slope Compensation in a fixed frequency CCM converter, is the duty-cycle limited range, up to a certain D level. The area below the Slope Compensation ramp and the D will limit the range of the duty-cycle-to- output voltage transfer function operating points.
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Page 70: Slope Compensation Conditions: Pcc 'Stable Area' Examples
Introduction to Digital Power Conversion XMC4000/1000 Family Modulation Slope Compensation Conditions: PCC ‘Stable Area’ examples 6.5.5 Assumption Fixed Frequency (FF) PCC PCC Stability: Considering ‘Outside Stable Area’ or ‘Faulty Compensation Slope’ The diagram shows four different test scenarios of an inductor current (I ), in a fixed frequency PCC CCM Buck converter reference model. -
Page 71: Without Slope Compensation, Fixed-On-Time (Fot) Zcd Control
Introduction to Digital Power Conversion XMC4000/1000 Family Modulation PCC Stable Area – Considering Slope Response upon Input Voltage +V Variation Figure 54 6.5.6 Without Slope Compensation, Fixed-ON-Time (FOT) ZCD Control There are current mode control loops that do not suffer from parasitic sub-oscillations, such as Fixed- On-Time (FOT) ZCD (Zero-Crossing-Detection) Mode Control, where the current reflections are forced in to stability by the Fixed On-Time term. -
Page 72: Ccm, Crm (Crcm) And Dcm
Introduction to Digital Power Conversion XMC4000/1000 Family Modulation CCM, CRM (CrCM) and DCM In a switch mode DC/DC converter, there are two DC voltages with different polarities toggling across the inductor. Depending on polarity, the current will rise or fall linearly, due to the self-inductance. The inductor energy will grow during one voltage polarity and be consumed by the load during the other. - Page 73 Introduction to Digital Power Conversion XMC4000/1000 Family Modulation Magnetic Voltage x Time (Vs) Balance Criteria The stored magnetic energy in a homogeneous inductor volume V is: ½*B*H*V B is the magnetic field density, flux [Voltage*Seconds/m ] and H is the magnetizing field [Amperes/m]. The loading and unloading of the inductor magnetic energy within two current levels is balanced if the product of voltage (V ) and time during energy loading is equal to the product of voltage (V...
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Page 74: Crm: Pfc Using Fixed-On-Time (Fot)
Introduction to Digital Power Conversion XMC4000/1000 Family Modulation CRM: PFC using Fixed-On-Time (FOT) A PFC in CRM mode commutates the MOSFET by fixed length, on-time pulses that are separated by the time it takes until the inductor current hits the ZCD point again after each pulse. This kind of control satisfies CRM. -
Page 75: Ccm / (Dcm): Pfc Using Fixed-Off-Time (Fofft)
Introduction to Digital Power Conversion XMC4000/1000 Family Modulation CCM / (DCM): PFC using Fixed-Off-Time (FOFFT) A PFC in FOFFT mode, commutates the MOSFET by an equidistant, on-time pulse stream, where each pulse length is the time it takes till the inductor current hits the Peak Current (PCC) level. With this kind of control the inductor current ripples along the average current envelope, satisfying CCM, except the DCM close to zero. -
Page 76: Ccm: Pfc Example Using Average Current Mode Control
Introduction to Digital Power Conversion XMC4000/1000 Family Modulation CCM: PFC example using Average Current Mode Control For high power PFC rectifiers, Average Current Control (ACC) is preferable. These do not suffer the same degree of noise sensitivity as a PCC and do not cause as much EMI. The ACC PFC rectifiers show better EMC conditions for high power converters. -
Page 77: Control Loops
Introduction to Digital Power Conversion XMC4000/1000 Family Control Loops Control Loops This section summarizes the basics in SMPS control with the XMC series feature set. XMC4000 series with focus on High-end systems. XMC1000 series with focus on Mid/Low-end solutions. -
Page 78: Using Embedded Acmp And External Slope Compensation Ramp
Introduction to Digital Power Conversion XMC4000/1000 Family Control Loops Comparator and Slope Generation unit (CSG) A CSG combines all the essential interaction factors for a system adaptive inductor current control, in any modulation mode, with a CMP-DAC-pair unit. The flexible input selectors map the external signals into internal functions. - Page 79 Introduction to Digital Power Conversion XMC4000/1000 Family Control Loops Inductor Current Measurement with Add-On Slope Compensation Ramp (plus Blanking) A linear ramp (V ) can be created by a capacitor that is charged with a time-constant exceeding the switch period (T). The ramp (V ) and the input signal (I ]) are added onto the input ACMP/P, for the slope...
- Page 80 Introduction to Digital Power Conversion XMC4000/1000 Family Control Loops CCU 4 Slope Compensation respective CCU 4 Blanking Control The CCU 4 Slope Compensation MOSFET is OFF during each PWM pulse; i.e. the capacitor voltage via a resistor. This ‘SC-Ramp’ voltage and the Current Measurement can ramp up by current from V voltage are added via a respective resistor to the ACMP/P input and so invoke Slope Compensation.
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Page 81: Using Fadc Compare Mode; Slope Compensation Add-On
Introduction to Digital Power Conversion XMC4000/1000 Family Control Loops Using FADC Compare Mode; Slope Compensation Add-On The Low-end XMC devices that do not offer an embedded analog comparator are still able to meet the functionality of current mode control to a greater or lesser extent, by using the Fast Compare Mode of a VADC: The inductor signal (I ]) is slope compensated by an add-on circuit and compared to a fixed digital... - Page 82 Introduction to Digital Power Conversion XMC4000/1000 Family Control Loops FADC PCC Slope Compensation Circuit; Clarification Example This circuit is a downsized version of the corresponding ACMP example in Figure 64. The RC- network accomplishes external linear control of a slope compensation voltage ramp. ACMP PCC Slope Compensation Clarification Figure 66 CCU 4 Blanking Control...
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Page 83: Open Loop Gain Stabilization (Frequency Compensation)
Introduction to Digital Power Conversion XMC4000/1000 Family Control Loops Open Loop Gain Stabilization (Frequency Compensation) Here we look at how power converter frequency properties and stability is affected by the control modes; i.e. voltage mode versus current mode control. Voltage Mode Control, Open Loop Gain (See 7.4.1). -
Page 84: Open Loop Gain Voltage Mode
Introduction to Digital Power Conversion XMC4000/1000 Family Control Loops 7.4.1 Open Loop Gain Voltage Mode The voltage mode control is a relatively slow loop, due to the 2 order low pass filter (H ), the inductor (L), capacitor (C) and output load (R). Other transfer functions in the loop are: ... -
Page 85: Open Loop Gain Bode Plot, Voltage Mode Stabilization
Introduction to Digital Power Conversion XMC4000/1000 Family Control Loops The frequency compensation needs 3 poles and a double-zero to accomplish a nearly 20-dB/decade slope at the 0-dB level crossing point, for stability, by an appropriate phase margin and damping factor. 7.4.2 Open Loop Gain Bode Plot, Voltage Mode Stabilization The voltage mode control open loop gain is a product of the following transfer functions:... -
Page 86: Open Loop Gain Current Mode W/ Slope Compensation
Introduction to Digital Power Conversion XMC4000/1000 Family Control Loops 7.4.3 Open Loop Gain Current Mode w/ Slope Compensation A representative principle of current mode control is chosen here: The Peak Current Control (PCC). Slope Compensation is included, which has a prominent role in the dynamics of the open loop gain ‘played’... -
Page 87: Open Loop Gain Bode Plot, Current Mode Stabilization
Introduction to Digital Power Conversion XMC4000/1000 Family Control Loops 7.4.4 Open Loop Gain Bode Plot, Current Mode Stabilization The voltage mode control open loop gain is a product of the following transfer functions: (s) * H (s) * H (s) * H (s) * H (Assume H (s) = 1) -
Page 88: Application Software
Introduction to Digital Power Conversion XMC4000/1000 Family Application Software Application Software Application software that focuses on for example the following topic areas, for the essential final system properties, can be easily added to the main control tasks of the power transfer: ... -
Page 89: Safety
Introduction to Digital Power Conversion XMC4000/1000 Family Application Software Safety Protections -> Over-Voltage (OV) / Over Current OC) protections, reaction to OV/OC: e.g. TRAP request with shut-down support by hardware and software service providers. Feed-Forward Control option, by including monitoring of input variations for early prediction of protection reaction. -
Page 90: Digital Switch Mode Control By New Feed-Forward Techniques
Introduction to Digital Power Conversion XMC4000/1000 Family Application Software Digital Switch Mode Control by New Feed-Forward Techniques With computer technology the feed-forward terms can anticipate system changes before they impact the output state of the power converter; i.e. the control loop does not have to be simply reactive in a traditional way, but may add commands for the desired output state upon given calculation models. - Page 91 Introduction to Digital Power Conversion XMC4000/1000 Family Application Software Abbreviations Abbreviations used in this document Table 3 Alternating Current Average Current Mode Control ACMP Analog Comparator (embedded) Analog-to-Digital Converter App / Apps Application / Applications Bill-Of-Material CAPCOM Capture/Compare (unit) CC4y CAPCOM Unit 4 Timer Slice instance y CC8y CAPCOM Unit 8 Timer Slice instance y...
- Page 92 Introduction to Digital Power Conversion XMC4000/1000 Family Application Software Abbreviations table (continued) Table 4 Peak Current Mode Control Power Factor Correction (filter) Pulse Frequency Modulation PSFB Phase Shift Full Bridge Pulse Width Modulation Slope Generator Synchronous Rectification Software Total Harmonic Distortion VADC Versatile Analog-to-Digital Converter Zero Crossing Detection...
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