J. Semicond. > 2013, Volume 34 > Issue 10 > 105002
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SEMICONDUCTOR INTEGRATED CIRCUITS

A novel buck/LDO dual-mode DC-DC converter for efficiency improvement

Shiquan Fan, Zhongming Xue, Hao Lu, Hui Zhao and Li Geng

+ Author Affiliations

 Corresponding author: Geng Li, gengli@mail.xjtu.edu.cn

DOI: 10.1088/1674-4926/34/10/105002

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Abstract: A novel buck/LDO dual-mode (BLDM) converter using a multiplexing power MOS transistor is proposed, which adaptively switches between buck mode and LDO mode to improve conversion efficiency. The chip was fabricated in a standard 0.35 μm CMOS process. Measurement results show that the peak efficiency is 97%. For the light load operation, the efficiency is improved by 14%. The efficiency keeps higher than 82.5% for the load current of 50 mA without any complex control or extra EMI due to the normal method of pulse frequency modulation (PFM) control used for improving the light load efficiency. It does not cost much extra chip area because no additional regulator PMOS is needed. It is more suitable for noise-restricted systems and battery-powered electronic devices for when battery voltage drops because of long hours of work.

Key words: high efficiency, buck converter, LDO regulator, dual-mode converter, multiplexing transistor



[1]
Wu P Y, Tsui S Y S, Mok P K T. Area-and power-efficient monolithic buck converters with pseudo-type Ⅲ compensation. IEEE J Solid-State Circuits, 2010, 45(8):1446 doi: 10.1109/JSSC.2010.2047451
[2]
Bandyopadhyay S, Ramadass Y K, Chandrakasan A P. 20μ A to 100 mA DC-DC converter with 2.8-4.2 V battery supply for portable applications in 45 nm CMOS. IEEE J Solid-State Circuits, 2011, 46(12):2807 doi: 10.1109/JSSC.2011.2162914
[3]
Huang H W, Chen K H, Kuo S Y. Dithering skip modulation, width and dead time controllers in highly efficient DC-DC converters for system-on-chip applications. IEEE J Solid-State Circuits, 2007, 42(11):2451 doi: 10.1109/JSSC.2007.907175
[4]
Lee Y T, Wei C L, Chen C H. An integrated step-down DC-DC converter with low output voltage ripple. IEEE Conference on Industrial Electronics and Applications (ICIEA), 2010:1373 http://ieeexplore.ieee.org/document/5514889/?arnumber=5514889&filter%3DAND(p_IS_Number:5514667)
[5]
Shen Z H, Min H. Combination method of DC-DC converter and LDO to improve efficiency and load regulation. Electron Lett, 2011:615 http://ieeexplore.ieee.org/document/5767256/authors
[6]
Gong X H, Ni J H, Hong Z L, et al. An 80% peak efficiency, 0.84 mW sleep power consumption, fully-integrated DC-DC converter with buck/LDO mode control. IEEE Custom Integrated Circuit Conference (CICC), 2011:1
Fig. 1.  Block diagram of the proposed BLDM converter.

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Fig. 2.  Structure of the BLDM converter.

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Fig. 3.  Efficiency of Buck mode and LDO mode with (a) Vout = 0.8 V and (b) Vout = 3.3 V

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Fig. 4.  Schematic of the mode switch circuit.

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Fig. 5.  AC response of the buck mode.

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Fig. 6.  (a) Circuit structure of the LDO regulator. (b) AC response of the LDO mode.

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Fig. 7.  Chip micrograph.

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Fig. 8.  Measured waveforms of (a) buck mode with 0.8 V output, (b) buck mode with 3.3 V output, (c) LDO mode with input voltage step-change of 0.2 V, (d) transient response from Buck to LDO when the input voltage steps down from 4 to 3.6 V and (e) transient response from LDO to buck mode when the input voltage steps up from 3.6 to 4 V when the output voltage is 3.3 V.

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Fig. 9.  Measured power conversion efficiency changed with input voltage and the load current.

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Table 1.   Performance summary.
[1]
Wu P Y, Tsui S Y S, Mok P K T. Area-and power-efficient monolithic buck converters with pseudo-type Ⅲ compensation. IEEE J Solid-State Circuits, 2010, 45(8):1446 doi: 10.1109/JSSC.2010.2047451
[2]
Bandyopadhyay S, Ramadass Y K, Chandrakasan A P. 20μ A to 100 mA DC-DC converter with 2.8-4.2 V battery supply for portable applications in 45 nm CMOS. IEEE J Solid-State Circuits, 2011, 46(12):2807 doi: 10.1109/JSSC.2011.2162914
[3]
Huang H W, Chen K H, Kuo S Y. Dithering skip modulation, width and dead time controllers in highly efficient DC-DC converters for system-on-chip applications. IEEE J Solid-State Circuits, 2007, 42(11):2451 doi: 10.1109/JSSC.2007.907175
[4]
Lee Y T, Wei C L, Chen C H. An integrated step-down DC-DC converter with low output voltage ripple. IEEE Conference on Industrial Electronics and Applications (ICIEA), 2010:1373 http://ieeexplore.ieee.org/document/5514889/?arnumber=5514889&filter%3DAND(p_IS_Number:5514667)
[5]
Shen Z H, Min H. Combination method of DC-DC converter and LDO to improve efficiency and load regulation. Electron Lett, 2011:615 http://ieeexplore.ieee.org/document/5767256/authors
[6]
Gong X H, Ni J H, Hong Z L, et al. An 80% peak efficiency, 0.84 mW sleep power consumption, fully-integrated DC-DC converter with buck/LDO mode control. IEEE Custom Integrated Circuit Conference (CICC), 2011:1

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    Received: 07 March 2013 Revised: 02 April 2013 Online: Published: 01 October 2013

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      Article Navigation >  Journal of Semiconductors  > 2013  >  34(10): 105002
      Shiquan Fan, Zhongming Xue, Hao Lu, Hui Zhao, Li Geng. A novel buck/LDO dual-mode DC-DC converter for efficiency improvement[J]. Journal of Semiconductors, 2013, 34(10): 105002. doi: 10.1088/1674-4926/34/10/105002 ****S Q Fan, Z M Xue, H Lu, H Zhao, L Geng. A novel buck/LDO dual-mode DC-DC converter for efficiency improvement[J]. J. Semicond., 2013, 34(10): 105002. doi: 10.1088/1674-4926/34/10/105002.
      Citation:
      Shiquan Fan, Zhongming Xue, Hao Lu, Hui Zhao, Li Geng. A novel buck/LDO dual-mode DC-DC converter for efficiency improvement[J]. Journal of Semiconductors, 2013, 34(10): 105002. doi: 10.1088/1674-4926/34/10/105002 ****
      S Q Fan, Z M Xue, H Lu, H Zhao, L Geng. A novel buck/LDO dual-mode DC-DC converter for efficiency improvement[J]. J. Semicond., 2013, 34(10): 105002. doi: 10.1088/1674-4926/34/10/105002.
      shu

      A novel buck/LDO dual-mode DC-DC converter for efficiency improvement

      DOI: 10.1088/1674-4926/34/10/105002

      • School of Electronic and Information Engineering, Xi'an Jiaotong University, Xi'an 710049, China

      Funds:

      the National Natural Science Foundation of China 61271089

      Project supported by the National Natural Science Foundation of China (Nos. 60971049, 61271089)

      the National Natural Science Foundation of China 60971049

      More Information
      • Corresponding author: Geng Li, gengli@mail.xjtu.edu.cn
      • Received Date: 2013-03-07
      • Revised Date: 2013-04-02
      • Published Date: 2013-10-01

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