Two-Switch Voltage Equalizer Using a Series-Resonant Voltage Multiplier Operating in Frequency-Multiplied Discontinuous Conduction Mode for Series-Connected Supercapacitors

Abstract

SUMMARYCell voltage equalizers are necessary to ensure years of operation and maximize the chargeable/dischargeable energy of seriesconnected supercapacitors (SCs). A two-switch voltage equalizer using a series-resonant voltage multiplier operating in frequency-multiplied discontinuous conduction mode (DCM) is proposed for series-connected SCs in this paper. The frequency-multiplied mode virtually increases the operation frequency and hence mitigates the negative impact of the impedance mismatch of capacitors on equalization performance, allowing multi-layer ceramic capacitors (MLCCs) to be used instead of bulky and costly tantalum capacitors, the conventional approach when using voltage multipliers in equalizers. Furthermore, the DCM operation inherently provides the constant current characteristic, realizing the excessive current protection that is desirable for SCs, which experience 0 V and equivalently become an equivalent short-circuit load. Experimental equalization tests were performed for eight SCs connected in series under two frequency conditions to verify the improved equalization performance at the increased virtual operation frequencies. The standard deviation of cell voltages under the higher-frequency condition was lower than that under the lower-frequency condition, demonstrating superior equalization performance at higher frequencies.

Interleaved PFC balance charger with passive lossless snubber for series-connected batteries

“…The multi-output charger with voltage multiplier is composed of diodes and capacitors. The output voltages can be more uniform because less parameter variations among diodes and capacitors [15][16][17].…”

A low cost battery equalizing scheme with buck-boost and series LC converter using synchronous phase-shift controller

“…Many non-dissipative schemes for higher efficiency were proposed in literature [1,2,3,4,5,6,8,9,10,11,12,13,14]. However, in most of the schemes, the costs are relatively high because each battery cell needs two or more electrical switches [2,5,7,9,10,11,13].…”

“…However, in most of the schemes, the costs are relatively high because each battery cell needs two or more electrical switches [2,5,7,9,10,11,13]. Or the voltage tolerance of each switch is high when the switch is connected to series battery cells [3,5,14,15], or much more diodes and capacitors are used [4,12], and are not able to do modularization either.…”