本論文首先實現了具自我調校無感式電流估測器之數位多模降壓型轉換器。本架構電流資訊之取得只需要迴路所使用之電壓ADC，大大降低了硬體成本與ADC所消耗的能量。電流估測器的係數與系統實際電感值、電感DCR值之匹配會大大的影響估測的準確度，所以本論文提出一套自我校正的方法，使得電流估測器得以估測準確的電感電流資訊。再者，本論文提出了以電流估測器估測電流的方式，實現系統在PWM與PFM兩種模式的操作，能有效提升輕載效率。本論文以FPGA為實驗平台，進行量測並驗證所提出之概念，證明確實能準確校正電感電流估測器之係數與估測電感電流，且準確切換PWM與PFM兩種模式，提升輕載效率。

A digitally controlled multi-mode DC-DC buck converter with a self-tuning inductor current estimator has been implemented in this thesis. To minimize hardware costs and power consumption, only one ADC is used in the proposed current estimator which is able to estimate both average value and ripple value of inductor current. Prior knowledge of the inductance, inductor DC resistance (DCR) and series resistance values, which depend on temperature, operating conditions and components process variation have huge impact on the accuracy of current estimator.
Therefore a tuning method is proposed to identify system parameter such as output capacitor and equivalent resistances helping current estimator estimate the inductor current more accurately. Furthermore, this work realizes a sensorless multi-mode digital dc-dc controller. Estimate load current by proposed current estimator. The controller can change modes between PWM and PFM without zero current detector and current sensor. Multi-mode can boost the light load efficient and maintain good regulation in wide load range. The system was implemented on the FPGA platform with the power stage on PCB. Results show that they can really improve efficiency and regulation. After FPGA prototype, we use TSMC90GUTM process for chip fabrication.

[1] "Overload Protection in Digitally Controlled DC-DC Converters," 2006 37th IEEE Power Electronics Specialists Conference, Jeju, 2006, pp. 1-6.
[2] Z. Lukić, S. M. Ahsanuzzaman, Z. Zhao and A. Prodić, "Sensorless Self-Tuning Digital CPM Controller With Multiple Parameter Estimation and Thermal Stress Equalization," in IEEE Transactions on Power Electronics, vol. 26, no. 12, pp. 3948-3963, Dec. 2011.
[3] 郭致賢,"使用漣波電流合成技術之遲滯升壓穩壓器研究," 國立成功大學電機工程學系碩士論文, 2013.
[4] T. G. Wang, Xunwei Zhou and F. C. Lee, "A low voltage high efficiency and high power density DC/DC converter," PESC97. Record 28th Annual IEEE Power Electronics Specialists Conference. Formerly Power Conditioning Specialists Conference 1970-71. Power Processing and Electronic Specialists Conference 1972, St. Louis, MO, 1997, pp. 240-245 vol.1.
[5] A. Prodic and D. Maksimovic, "Digital PWM controller and current estimator for a low-power switching converter," COMPEL 2000. 7th Workshop on Computers in Power Electronics. Proceedings (Cat. No.00TH8535), Blacksburg, VA, 2000, pp. 123-128.
[6] A. Radić, D. Baik, A. Straka, A. Prodić and R. de Nie, "Noninvasive self-tuning output capacitor time constant estimator for low power digitally controlled DC-DC converters," 2013 Twenty-Eighth Annual IEEE Applied Power Electronics Conference and Exposition (APEC), Long Beach, CA, 2013, pp. 559-562.
[7] Y. Yan, P. H. Liu, F. Lee, Q. Li and S. Tian, "V2 control with capacitor current ramp compensation using lossless capacitor current sensing," 2013 IEEE Energy Conversion Congress and Exposition, Denver, CO, 2013, pp. 117-124.
[8] W. Schults, Lossless current sensing with SENSEFET enhance the motor drive, Motorola technical report, 1988.
[9] K. Y. Cheng, F. Yu, F. C. Lee and P. Mattavelli, "Digital Enhanced V2-Type Constant On-Time Control Using Inductor Current Ramp Estimation for a Buck Converter With Low-ESR Capacitors," in IEEE Transactions on Power Electronics, vol. 28, no. 3, pp. 1241-1252, March 2013.
[10] P. H. Liu, Y. Yan, F. C. Lee and Q. Li, "Auto-tuning and self-calibration techniques for V2 control with capacitor current ramp compensation using lossless capacitor current sensing," 2014 IEEE Energy Conversion Congress and Exposition (ECCE), Pittsburgh, PA, 2014, pp. 1105-1112.
[11] M. K. Song, L. Chen, J. Sankman, S. Terry and D. Ma, "A 20V 8.4W 20MHz four-phase GaN DC-DC converter with fully on-chip dual-SR bootstrapped GaN FET driver achieving 4ns constant propagation delay and 1ns switching rise time," 2015 IEEE International Solid-State Circuits Conference - (ISSCC) Digest of Technical Papers, San Francisco, CA, 2015, pp. 1-3.
[12] S. Y. Huang, K. Y. Fang, Y. W. Huang, S. H. Chien and T. H. Kuo, "Capacitor-current-sensor calibration technique and application in a 4-phase buck converter with load-transient optimization," 2016 IEEE International Solid-State Circuits Conference (ISSCC), San Francisco, CA, 2016, pp. 228-229.
[13] Man Pun Chan; Mok, P.K.T., "A Monolithic Digital Ripple-Based Adaptive-Off-Time DC-DC Converter With a Digital Inductor Current Sensor," in Solid-State Circuits, IEEE Journal of , vol.49, no.8, pp.1837-1847, Aug. 2014
[14] E. Meyer, Z. Zhang and Y. F. Liu, "Digital Charge Balance Controller to Improve the Loading/Unloading Transient Response of Buck Converters," in IEEE Transactions on Power Electronics, vol. 27, no. 3, pp. 1314-1326, March 2012.
[15] E. Meyer and Y. F. Liu, "Digital Charge Balance Controller With an Auxiliary Circuit for Improved Unloading Transient Performance of Buck Converters," in IEEE Transactions on Power Electronics, vol. 28, no. 1, pp. 357-370, Jan. 2013.
[16] Lei Hua and Shiguo Luo, "Design considerations of time constant mismatch problem for inductor DCR current sensing method," Twenty-First Annual IEEE Applied Power Electronics Conference and Exposition, 2006. APEC '06., Dallas, TX, 2006, pp. 7
[17] E. Dallago, M. Passoni and G. Sassone, "Lossless current sensing in low-voltage high-current DC/DC modular supplies," in IEEE Transactions on Industrial Electronics, vol. 47, no. 6, pp. 1249-1252, Dec 2000.
[18] P. Midya, P. T. Krein and M. F. Greuel, "Sensorless current mode control-an observer-based technique for DC-DC converters," in IEEE Transactions on Power Electronics, vol. 16, no. 4, pp. 522-526, Jul 2001.
[19] Cheung Fai Lee and P. K. T. Mok, "A monolithic current-mode CMOS DC-DC converter with on-chip current-sensing technique," in IEEE Journal of Solid-State Circuits, vol. 39, no. 1, pp. 3-14, Jan. 2004.
[20] R. W. Erickson and D. Maksimovic, Fundamentals of Power Electronics, 2ed ed.: Springer, 2001.
[21] C.H. Tsai, C. H. Yang, J. H. Shiau and B. T. Yeh, "Digitally Controlled Switching Converter with Automatic Multi-Mode Switching," in IEEE Transactions on Power Electronics, vol. 29, no. 4, pp. 1830-1839, April 2014.
[22] A. Prodic, et al., "Design and implementation of a digital PWM controller for a high-frequency switching DC-DC power converter," in Industrial Electronics Society, 2001. IECON '01. The 27th Annual Conference of the IEEE, 2001, pp. 893-898 vol.2.
[23] A. Prodic and D. Maksimovic, "Design of a digital PID regulator based on look-up tables for control of high-frequency DC-DC converters," in Computers in Power Electronics, 2002. Proceedings. 2002 IEEE Workshop on, 2002, pp. 18-22.
[24] A. V. Peterchev and S. R. Sanders, "Quantization resolution and limit cycling in digitally controlled PWM converters," in Power Electronics Specialists Conference, 2001. PESC. 2001 IEEE 32nd Annual, 2001, pp. 465-471 vol.2.
[25] A. Syed, et al., "Digital pulse width modulator architectures," in Power Electronics Specialists Conference, 2004. PESC 04. 2004 IEEE 35th Annual, 2004, pp. 4689-4695 Vol.6.
[26] National Semiconductor. LM3676 [Online]. Available: http://www.national.com/pf/LM/LM3676.html#Overview
[27] Texas Instruments. TPS62040 [Online]. Available: http://focus.ti.com/docs/prod/folders/print/tps62040.html
[28] Intersil. ISL9105 [Online]. Available: http://www.intersil.com/products/deviceinfo.asp?pn=ISL9105
[29] Fairchird. FAN5355 [Online]. Available: http://www.fairchildsemi.com/ds/FA%2FFAN5355.pdf
[30] X. Zhang and D. Maksimovic, "Multi-Mode Digital Controller for Synchronous Buck Converters Operating Over Wide Ranges of Input Voltages and Load Currents," IEEE Trans. Power Electronics, vol. 25, pp. 1958-1965, 2010.
[31] K. Yamada, et al., "High efficiency DC-DC converter for wide-ranging loads with gradual reverse current stopping technique," IEEJ Trans. Electrical and Electronic Engineering, vol. 3, pp. 715-720, 2008.
[32] R. Erickson and D. Maksimovic, "High Efficiency DC-DC Converters for Battery-Operated Systems with Energy Management," in Worldwide Wireless Communications, Annual Reviews on Telecommunications, 1995, pp. 103-109.
[33] National Semiconductor. Magnetic Buck Converters for Portable Applications [Online]. Available: www.national.com/appinfo/power/files/buck_converters.pdf
[34] J. Xiao, et al., "A 4-ua quiescent-current dual-mode digitally controlled buck converter IC for cellular phone applications," IEEE J. Solid-State Circuits, vol. 39, pp. 2342-2348, 2004.
[35] Upal Sengupta, "PWM and PFM Operation of DC/DC Converters for Portable Applications," in Portable Power Design Seminar, 2007.
[36] R. Redl and S. Jian, "Ripple-Based Control of Switching Regulators - An Overview," IEEE Trans. Power Electronics, vol. 24, pp. 2669-2680, 2009.
[37] Power Electronics Technology. Determine Buck Converter Efficiency in PFM Mode [Online]. Available: http://powerelectronics.com/mag/709PET22.pdf
[38] F.-F. Ma, et al., "A Monolithic Current-Mode Buck Converter With Advanced Control and Protection Circuits," IEEE Trans. Power Electronics, vol. 22, pp. 1836-1846, 2007.
[39] H.-W. Huang, et al., "Dithering Skip Modulation, Width and Dead Time Controllers in Highly Efficient DC-DC Converters for System-On-Chip Applications," IEEE J. Solid-State Circuits, vol. 42, pp. 2451-2465, 2007.
[40] W.-R. Liou, et al., "A High Efficiency Dual-Mode Buck Converter IC For Portable Applications," IEEE Trans. Power Electronics., vol. 23, pp. 667-677, 2008.
[41] S. Seungchul, et al., "High efficiency DC-DC converter with auto-mode transition for mobile SOC applications," in Proc. IEEE SoC Design Conf, 2010, pp. 345-348.
[42] A. Prodic and D. Maksimovic, "Digital PWM controller and current estimator for a low-power switching converter," in Proc. IEEE Computers in Power Electronics Conf., 2000, pp. 123-128.
[43] Texas Instruments. DC-DC Power Conversions and System Design Considerations for Battery Operated System [Online]. Available: http://focus.ti.com/download/trng/docs/seminar/Topic 6 - DC-DC Power Conversion and System Design Considerations for Battery Operated System.pdf
[44] H. Peng, A. Prodic, E. Alarcon and D. Maksimovic, "Modeling of Quantization Effects in Digitally Controlled DC–DC Converters," in IEEE Transactions on Power Electronics, vol. 22, no. 1, pp. 208-215, Jan. 2007.
[45] W.-H. Chang and L.-P. Tai, "Design of a digital power IC," in Proc. IEEE Int. Symp. VLSI Design, Automation and Test, 2010, pp. 41-44.
[46] J. A. Abu Qahouq, "Control Scheme for Sensorless Operation and Detection of CCM and DCM Operation Modes in Synchronous Switching Power Converters," in IEEE Transactions on Power Electronics, vol. 25, no. 10, pp. 2489-2495, Oct. 2010.
[47] 蕭峻竑,"具動態電壓調節功能之無電流感測多模式數位直流-直流控制器," 國立成功大學電機工程學系碩士論文, 2011.
[48] S. Kapat, "Configurable Multimode Digital Control for Light Load DC–DC Converters With Improved Spectrum and Smooth Transition," in IEEE Transactions on Power Electronics, vol. 31, no. 3, pp. 2680-2688, March 2016.
[49] S. Kapat, B. C. Mandi and A. Patra, "Voltage-Mode Digital Pulse Skipping Control of a DC–DC Converter With Stable Periodic Behavior and Improved Light-Load Efficiency," in IEEE Transactions on Power Electronics, vol. 31, no. 4, pp. 3372-3379, April 2016.
[50] R. Poley and A. Shirsavar, “Digital Peak Current Mode Control With Slope Compensation Using the TMS320F2803x,” Application Report, 2012. [Online]. Available: http://www.ti.com/lit/an/sprabe7a/sprabe7a.pdf
[51] B. Lee, M. K. Song, A. Maity and D. B. Ma, "A 25MHz 4-phase SAW hysteretic DC-DC converter with 1-cycle APC achieving 190ns tsettle to 4A load transient and above 80% efficiency in 96.7% of the power range," 2017 IEEE International Solid-State Circuits Conference (ISSCC), San Francisco, CA, 2017, pp. 190-191.
[52] J. Sankman, M. K. Song and D. Ma, "A 40-MHz current-mode hysteretic controlled switching converter with digital push-pull current pumping technique for high performance microprocessors," Technical Papers of 2014 International Symposium on VLSI Design, Automation and Test, Hsinchu, 2014, pp. 1-4.
[53] Tom Ribarich. “Enhancing switch-mode power performance with RDS(on) current sensing” Internet: http://www.infineon.com/dgdl/1099psd1404.pdf?fileId=5546d462533600a401535695b6142b78 [January 04 2014]
[54] J. A. Abu Qahouq, L. Huang, and D. Huard, "Efficiency-based auto-tuning of current sensing and sharing loops in multiphase converters," IEEE Trans. Power Electron., vol. 23, no. 2, pp. 1009–1013, Mar. 2008.
[55] Texas Instruments, “TPS65916 3.1-V to 5.2-V, 5 Buck Converter and 5 LDO Power Management IC (PMIC)”, Available at http://www.ti.com/lit/ds/symlink/tps65916.pdf.
[56] ALTERA, "DE1-SoC_User_manual_reve,” ALTERA Datasheet.
[57] "AD7822: 3 V/5 V, 2 MSPS, 8-Bit, 1-/4-/8-Channel Sampling ADCs," Analog Device Datasheet, 2006. [Online]. Available: http://www.analog.com/media/en/technical-documentation/data-sheets/AD7822_7825_7829.pdf
[58] Intersil Corp., ZL8801 Data Sheet, June 2015 [Online]. Available: www.intersil.com
[59] Texas Instruments Inc., TPS40428 Data Sheet, June 2015. [Online]. Available: www.ti.com
[60] D. Stack, A. Kelly and T. Conway, "A high accuracy and high bandwidth current sense circuit for digitally controlled DC-DC buck converters," 2016 IEEE Applied Power Electronics Conference and Exposition (APEC), Long Beach, CA, 2016, pp. 1670-1674.
[61] R. K. Singh and R. Goel, "A novel lossless digital inductor current sensing technique based control implementation for switching DC/DC converter," 2015 IEEE International Conference on Industrial Technology (ICIT), Seville, 2015, pp. 2030-2035.
[62] F. Su and W. H. Ki, "Digitally assisted quasi-V2 hysteretic buck converter with fixed frequency and without using large-ESR capacitor," 2009 IEEE International Solid-State Circuits Conference - Digest of Technical Papers, San Francisco, CA, 2009, pp. 446-447,447a.
[63] H. Peng, D. I. Anderson and M. M. Hella, "A 100 MHz Two-Phase Four-Segment DC-DC Converter With Light Load Efficiency Enhancement in 0.18/spl mu/m CMOS," in IEEE Transactions on Circuits and Systems I: Regular Papers, vol. 60, no. 8, pp. 2213-2224, Aug. 2013.
[64] Z. Zhao and A. Prodic, "Continuous-Time Digital Controller for High-Frequency DC-DC Converters," in IEEE Transactions on Power Electronics, vol. 23, no. 2, pp. 564-573, March 2008.
[65] Henry J ZHang, "PCB-layout considerations for nonisolated switching power supplies," Linear Tech, Sept. 2012.
[66] Chris Richardson, "PCB Layout Considerations for Switchers," National Semiconductor, May. 2008.
[67] S. Saggini, D. Zambotti, E. Bertelli and M. Ghioni, "Digital Autotuning System for Inductor Current Sensing in Voltage Regulation Module Applications," in IEEE Transactions on Power Electronics, vol. 23, no. 5, pp. 2500-2506, Sept. 2008.
[68] S. Kapat, B. C. Mandi and A. Patra, "Voltage-Mode Digital Pulse Skipping Control of a DC–DC Converter With Stable Periodic Behavior and Improved Light-Load Efficiency," in IEEE Transactions on Power Electronics, vol. 31, no. 4, pp. 3372-3379, April 2016.
[69] P. H. Chen, C. S. Wu and K. C. Lin, "A 50 nW-to-10 mW Output Power Tri-Mode Digital Buck Converter With Self-Tracking Zero Current Detection for Photovoltaic Energy Harvesting," in IEEE Journal of Solid-State Circuits, vol. 51, no. 2, pp. 523-532, Feb. 2016.
[70] M. Yamada, N. B. Tran, T. Miyazaki, Y. Yoshihara and R. Fujimoto, "All-digital single-inductor multiple-output DC-DC converter with over 65.3% efficiency in 1 uW to 50 mW load range and 86.3% peak efficiency,"in 2016 IEEE Asian Solid-State Circuits Conference (A-SSCC), Toyama, 2016, pp. 213-216.
[71] H. H. Lee and P. H. Chen, "A single-inductor dual-input dual-output (SIDIDO) power management with sequential pulse-skip modulation for battery/PV hybrid systems," 2016 IEEE Asian Solid-State Circuits Conference (A-SSCC), Toyama, 2016, pp. 293-296.
[72] J. Gordillo and C. Aguilar, "A Simple Sensorless Current Sharing Technique for Multiphase DC–DC Buck Converters," in IEEE Transactions on Power Electronics, vol. 32, no. 5, pp. 3480-3489, May 2017.
[73] W. Huang and J. A. Abu Qahouq, "Input Voltage Ripple-Based Sensorless Current Sharing Autotuning Controller for Multiphase DC–DC Converters," in IEEE Transactions on Industry Applications, vol. 52, no. 5, pp. 4117-4125, Sept.-Oct. 2016.
[74] Texas Instruments Inc., LM25141 Data Sheet, March 2017. [Online]. Available: http://www.ti.com/lit/ds/symlink/lm25141.pdf
[75] J.-J. Chen, “An Active Current-Sensing Constant-Frequency HCC Buck Converter Using Phase-Frequency-Locked Techniques,”in IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, vol. 55, no. 4, pp. 761-769, Apr. 2008.
[76] J.-J. Chen, F.-C. Yang and, C.-C. Chen”A New Monolithic Fast-Response Buck Converter Using Spike-Reduction Current-Sensing Circuits” IEEE Trans. Industrial Electron., vol. 55, pp. 1101–1111, Mar. 2008.
[77] Texas Instruments., Benefits of a multiphase buck converter. [Online]Available: http://www.ti.com/lit/an/slyt449/slyt449.pdf
[78] Texas Instruments., Merits of multiphase buck DC/DC converters in small form factor applications. [Online]Available: http://www.ti.com/lit/wp/slyy072/slyy072.pdf
[79] M.-T. Tsai, D. Y. Chen, C.-J. J. Chen, C.-H. Chiu, W.-H. Chang, “Modeling and design of current balancing control in voltage-mode multiphase interleaved voltage regulators”, in Proc. of International Power Electronics Conf. (IPEC), 2010.
[80] Patent US6674274, "Multiple phase switching regulators with stage shedding" nline]Available: https://www.google.com.tw/patents/US6674274.
[81] J. Wei and F. C. Lee, "Two-stage voltage regulator for laptop computer cpus and the corresponding advanced control schemes to improve lightload performance," in Proc. IEEE APEC, 2004, pp. 1294–1300 vol.2.
[82] Texas Instruments., TPS65311-Q1 BUCK1 Controller DCR Current Sensing. [Online]Available: http://www.ti.com/lit/an/slva791/slva791.pdf
[83] "Dual Phase PMBus™ ChargeMode™ Control DC/DC Digital Controller," Intersil Datasheet, 2015. [Online]. Available: http://www.intersil.com/content/dam/Intersil/documents/zl88/zl8801.pdf
[84] H. P. Forghani-zadeh and G. A. Rincon-Mora, "A lossless, accurate, self-calibrating current-sensing technique for DC-DC converters," 31st Annual Conference of IEEE Industrial Electronics Society, 2005. IECON 2005., 2005, pp. 6
[85] Analog Devices., Peak Current Mode and Continuous Current Mode DC-to-DC converter Modeling and Loop Compensation Design Considerations. [Online]Available: http://www.analog.com/media/en/technical-documentation/technical-articles/Peak-Current-Mode-and-Continuous-Current-Mode-DC-to-DC-Converter-Modeling.pdf
[86] " LTC3878 - Fast, Wide Operating Range No RSENSE Step-Down DC/DC Controller," Linear Technology Datasheet, 2009. [Online]. Available: http://cds.linear.com/docs/en/datasheet/3878fa.pdf
[87] RICHTEK. RT8802A, "2/3/4/5-Phase PWM Controller for High-Density Power Supply" [Online]. Available: http://www.richtek.com/assets/product_file/RT8802A/DS8802A-09.pdf
[88] Intersil. ISL6307, "6-Phase PWM Controller with 8 Bit VID Code Capable of Precision RDS(ON) or DCR Differential Current" [Online]. Available: https://www.intersil.com/content/dam/Intersil/documents/isl6/isl6307.pdf
[89] RICHTEK, RT8884B, "Multi-Phase PWM Controller for CPU Core Power Supply" [Online]. Available: http://www.richtek.com/assets/product_file/RT8884B/DS8884B-01.pdf
[90] RICHTEK, RT8894A, "Dual-Channel, Multi-Phase PWM Controller with I2C Interface for AMD SVI2 CPU Power Supply" [Online]. Available: http://www.richtek.com/assets/product_file/RT8894A/DS8894A-05.pdf
[91] A. Devices. ADP3180, "6-Bit Programmable 2-, 3-, 4-Phase Synchronous Buck Controller" [Online]. Available: http://datasheet.octopart.com/ADP3180JRUZ-REEL-Analog-Devices-datasheet-9161.pdf
[92] ASUS, P8P67 DELUXE, "T6306_P8P67_Deluxe" [Online]. Available: https://www.asus.com/tw/Motherboards/P8P67_DELUXE/helpdesk_manual/
[93] Maxim, "MAX8640Y/MAX8640Z Data Sheet: Tiny 500mA, 4MHz/2MHz Synchronous Step-Down DC-DC Converters, " Rev. 3, June 2008, Accessed on Dec. 3, 2008 .
[94] C. H. Tsai, S. M. Lin, and C. S. Huang, "A Fast-Transient Quasi-V2 Switching Buck Regulator Using AOT Control With a Load Current Correction (LCC) Technique," IEEE Trans. Power Electron., vol. 28, no. 8, pp. 3949-3957, Aug. 2013.
[95] K. Y. Hu, S. M. Lin and C. H. Tsai, "A Fixed-Frequency Quasi- V2 Hysteretic Buck Converter With PLL-Based Two-Stage Adaptive Window Control," in IEEE Transactions on Circuits and Systems I: Regular Papers, vol. 62, no. 10, pp. 2565-2573, Oct. 2015.
[96] K. Y. Cheng, F. Yu, Y. Yan, F. C. Lee, P. Mattavelli and W. Wu, "Analysis of multi-phase hybrid ripple-based adaptive on-time control for voltage regulator modules," 2012 Twenty-Seventh Annual IEEE Applied Power Electronics Conference and Exposition (APEC), Orlando, FL, 2012, pp. 1088-1095.
[97] 鄧君曉,"數位適應性導通時間控制降壓型轉換器研究與實作," 國立成功大學電機工程學系碩士論文, 2015.
[98] Y.Y. Mai and P.K.T. Mok, "A Constant Frequency Output-Ripple-Voltage-Based Buck Converter Without Using Large ESR Capacitor, " IEEE Trans. Circuits and Systems-II, vol. 55, no. 8, pp. 748-752, Aug., 2008.
[99] W. Huang, "A new control for multi-phase buck converter with fast transient response," in Proc. IEEE APEC’01 Conf., 2001, pp. 273-279
[100] A. Prodic and D. Maksimovic, "Mixed-signal simulation of digitally controlled switching converters," in 2002 IEEE Workshop on Computers in Power Electronics, 2002. Proceedings., 2002, pp. 100-105.