WIWO DC-DC CONVERTER

INTRODUCTION

BASIC DC-DC CONVERTERS:

• BUCK CONVERTER

• BOOST CONVERTER

• CUK CONVERTER

• BUCK-BOOST CONVERTER

NEED FOR A NEW SWITCHING CONVERTER ?

MOTIVATION IN THE SEARCH FOR NEW SWITCHING CONVERTER

• The basic buck and boost converters can be

transformed into a number of new topologies by bringing in the tapped inductor.

• The proposed tapped-inductor buck-derived & boost derived converters are shown with their corresponding voltage conversion ratios.

Fig.1 Buck-derived converters with tapped inductors

Fig.2 Voltage conversion ratio of buck-derived converters with tapped inductors. (a) 0 < n < ∞ (b) 0 < n < ∞ (c) n > 1 (d) n > 1.

Fig.3 Boost derived inductors with tapped inductors

Fig.4.Voltage conversion ratio of boost-derived converters with tapped inductors (a) 0 < n < ∞ (b) 0 < n < ∞ (c) 0 < n <1 (d) 0 < n < 1.

• From the conversion ratio plot, the converters of Fig.1(a) & 3(a) has wider step-down & step-up responses.

• These two topologies may be combined to form a new two-switch topology, with an extended conversion range.

WIWO DC-DC CONVERTER

Fig.5.Proposed Wide-Input-Wide-Output DC-DC converter

• Wide-Input-Wide-Output (WIWO) DC-DC converter is an integration of buck and boost converters via a tapped inductor.

• It can operate in both buck mode & boost mode.

• Buck Mode:

Switch S1 is assigned a high-frequency switching signal & whereas S2 is switched complementarily to S1. The diode D is kept ON by the inductor L2 current.

• Boost Mode:

Switch S2 made continuously ON and it issues the required duty cycle signal for the S1 switch & diode D is forced to switch on and off complementarily to S1.

• Transition between step-down and step-up modes is achieved by a proper control scheme.

CONTROL SCHEME

• For proper operation of WIWO, PWM control circuitry is used.

• Vm is the magnitude of sawtooth wave.

• Control voltage Vc=mVm.

• Buck Mode: 0 ≤ m < 1• Boost Mode: 1 ≤ m ≤ 2

Fig.6 WIWO control circuitry

OPERATING PRINCIPLE

Fig.7 Four states of the WIWO converter. (a) Buck-mode charging state. (b) Buck-mode discharging state (c) Boost-mode charging state

(d) Boost-mode discharging state.

Fig.8 Waveforms of the WIWO dc–dc converter. (a) Buck mode. (b) Boost mode.

VOLTAGE TRANSFER CHARACTERISTICS

• For n = 1, the voltage transfer ratio is smooth , where as for other values of n, the curves exhibit a slope change.

• The buck to boost switch over point is at m = 1.Fig.9 Voltage transfer characteristics

APPLICATIONS

• WIWO DC–DC CONVERTER WITH THE SYNCHRONOUS RECTIFIER

Fig.10 WIWO DC–DC converter with the synchronous rectifier

• BIDIRECTIONAL WIWO DC–DC CONVERTER

Fig.11 Bidirectional WIWO DC–DC converter

• WIWO PFC AC–DC CONVERTER

Fig.12 Waveforms passing through WIWO DC-DC converter PFC circuit

CONCLUSION

• WIWO is an integration of buck and boost converters.

• It retains the features of both the buck and the boost converters.

• It achieves wider step-up and wider step-down DC-DC conversion range.

• It has a simple structure and moderate component count.

• The transition between the operating modes is inherently smooth, and causes no transient disturbance.

BIBLIOGRAPHY

• Hao Cheng, Keyue Ma Smedley, “A Wide –Input-Wide-Output(WIWO)DC-DCConverter”,vol.25,no.2, February 2010.

• H. Cheng and K. Smedley, “Wide input wide output (WIWO) dc–dc converter,”in Proc. IEEE Appl. Power Electron. Conf. Expo., 2008.

• J.-H. Park and B.-H. Cho, “Non isolation soft-switching buck converter with tapped-inductor for wide-input extreme step-down applications,”IEEE Trans. Circuits Syst. I, Reg. Papers, vol. 54, no. Aug. 2007.

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