A Unity Power Factor Bridgeless Isolated Cuk Converter Fed Brushless-DC Motor Drive


ABSTRACT: This work presents a power factor correction (PFC) based bridgeless isolated Cuk converter fed brushless DC (BLDC) motor drive. A variable DC link voltage of the voltage source inverter (VSI) feeding BLDC motor is used for its speed control. This allows the operation of VSI in fundamental frequency switching (FFS) to achieve an electronic commutation of BLDC motor for reduced switching losses. A bridgeless configuration of an isolated Cuk converter is derived for elimination of front end diode bridge rectifier (DBR) to reduce conduction losses in it. The proposed PFC based bridgeless isolated Cuk converter is designed to operate in discontinuous inductor current mode (DICM) to achieve an inherent PFC at AC mains. The proposed drive is controlled using a single voltage sensor to develop a cost effective solution. The proposed drive is implemented to achieve a unity power factor at AC mains for a wide range of speed control and supply voltages. An improved power quality is achieved at AC mains with power quality indices within limits of IEC 61000-3-2 standard.


  1. BLDC Motor
  2. Bridgeless Isolated Cuk Converter
  3. Discontinuous Inductor Current Mode
  4. Power Factor Correction
  5. Power Quality
  6. Voltage Source Inverter



Fig. 1. Proposed configuration of a bridgeless isolated Cuk converter feeding BLDC motor drive.

DC link voltage

Fig. 2. Test results of the proposed drive during its operation at rated loading condition with DC link voltage as (a) 130 V and (b) 50 V.

Fig. 3. Test results of the proposed drive during its operation at rated condition showing (a) input inductor currents (b) output inductors current and (c) HFT currents.

Fig. 4. Test results of the proposed drive during its operation at rated condition showing intermediate capacitors voltages (a) VC11 and VC12 and (b) VC21 and VC22.


Fig. 5. (a) Test results of the proposed drive during its operation at rated condition showing (a) voltage and current stress on PFC converter switches and (b) its enlarged waveforms.

Fig. 6. Test results of the proposed drive during (a) starting at DC link voltage of 50V, (b) speed control corresponding to change in DC link voltage fro 50V to 100V and (c) supply voltage fluctuation from 250V to 200V.



A new configuration of bridgeless isolated-Cuk converter fed BLDC motor drive has been proposed for low power household appliances. The speed control of BLDC motor has been achieved by controlling the DC link voltage of VSI feeding BLDC motor. This has facilitated the operation of VSI in low frequency switching mode for reducing the switching losses associated with it. This bridgeless isolated-Cuk converter has been designed for the elimination of diode bridge rectifier at the front-end for reducing the conduction losses in the front-end converter. This PFC converter has been operated in DICM for DC link voltage control and inherent power factor correction is achieved at the AC mains. A prototype of proposed drive has been implemented using a DSP. Satisfactory test results for proposed bridgeless isolated- Cuk-converter fed BLDC motor has been evaluated for its operation over complete speed range. Moreover, the performance of proposed drive is also evaluated for operation at wide range of supply voltages. The obtained power quality indices have been found within the limits of power quality standards such as IEC 61000-3-2.


[1] C. L. Xia, Permanent Magnet Brushless DC Motor Drives and Controls Wiley Press, Beijing, 2012.

[2] Y. Chen, C. Chiu, Y. Jhang, Z. Tang and R. Liang, “A Driver for the Single-Phase Brushless DC Fan Motor with Hybrid Winding Structure,” IEEE Trans. Ind. Electron., vol. 60, no. 10, pp. 4369

[3] X. Huang, A. Goodman, C. Gerada, Y. Fang and Q. L Matrix Converter Drive for a Brushless DC Motor in Aerospace Applications,” IEEE Trans. Ind. Elect., Sept. 2012.

[4] J. Moreno, M. E. Ortuzar and J. W. Dixon, “Energy for a hybrid electric vehicle, using ultra capacitors and neural networks,” IEEE Trans. Ind. Electron., vol.53, no.2, pp. 614

[5] P. Pillay and R. Krishnan, “Modeling of permanent magnet motor drives,” IEEE Trans. Ind. Elect.vol.35, no.4, pp. 537-541, Nov 1988.

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