Objective. As evidence of the effectiveness of acupuncture for low back pain (LBP) is inconsistent, we aimed to critically appraise the evidence from relevant systematic reviews.Methods. Systematic reviews of randomized controlled trials (RCTs) concerning acupuncture and LBP were searched in seven databases. Internal validity and external validity of systematic reviews were assessed. Systematic reviews were categorized and high quality reviews assigned greater weightings. Conclusions were generated from a narrative synthesis of the outcomes of subgroup comparisons.Results. Sixteen systematic reviews were appraised. Overall, the methodological quality was low and external validity weak. For acute LBP, evidence that acupuncture has a more favorable effect than sham acupuncture in relieving pain was inconsistent; it had a similar effect on improving function. For chronic LBP, evidence consistently demonstrated that acupuncture provides short-term clinically relevant benefits for pain relief and functional improvement compared with no treatment or acupuncture plus another conventional intervention.Conclusion. Systematic reviews of variable quality showed that acupuncture, either used in isolation or as an adjunct to conventional therapy, provides short-term improvements in pain and function for chronic LBP. More efforts are needed to improve both internal and external validity of systematic reviews and RCTs in this area.

The traditional balance circuit is employed to balance the retired battery string. It will occupy some space for the extra switches, inductors, or/and capacitors of the energy storage system. This letter is trying to share the inductor of the DC/DC converter with the balance system by utilizing the current ripple on the inductor of the multi-winding transformer. And the balance circuit does not require additional switches and control logic. The results of dynamic charging conditions show that the circuit is appropriate for balancing the battery string, and the system efficiency with the proposed approach reaches 94.1% at rated 28W input power. The balance system only increases one diode and one inductor for each cell, which reduces the cost by 60% and 66% separately compared with the traditional resistance equalizer and transformer-based equalizer.

Wireless power transfer (WPT)-based voltage equalizers (VEs) are desired for flexible and secure balanced charging of unmanned aerial vehicles (UAVs). However, the existing WPT-based VEs fail to balance the cells once the onboard receiver (Rx) is away from the transmitter (Tx), and the efficiency and capacity are limited. This article proposes a reconfigurable WPT-based multiport hybrid charging approach to achieve UAV’s cell string balancing under multiple states. By converging one Tx port, one Rx bidirectional port, and two voltage-balance (Vx) driving ports, the approach enables the source-to-cell (STC) and pack-to-cell (PTC) charging/balancing, which achieves cell balancing during charging, discharging, and standing conditions. Circuit analyses of the corresponding topology validate its operating principles and basic performance. Efficiency and capacity in the STC balance mode are improved with the combined Rx and Vx output ports. The cell’s voltage equivalation can still be realized without Tx in the PTC balance mode. Asymmetric Tx and Rx coils and orthogonal Vx coils integrated into Rx are designed with specific coupling or decoupling as the multiport WPT coupler to enable the charging and balancing with a robust misalignment tolerance. An experimental prototype for eight cells is established, and the test results demonstrate the effectiveness of this scheme.

In the hybrid energy storage system (HESS), the voltages between the battery cell and the supercapacitor cell are different, increasing the circuit and control complexity of the balance system. Therefore, a bidirectional integrated equalizer based on the Sepic–Zeta converter is proposed for the HESS, which realizes both battery string and supercapacitor string balance during the energy exchange. The inductors in the Sepic–Zeta converter are used as the primary side of the balanced multiwinding transformer. The Sepic–Zeta converter generates the current ripples to drive the multiwinding transformer. The secondary side generates currents to balance the HESS, and hence, the equalizer itself is essentially switchless. Therefore, the proposed circuit can reduce the complexity of the HESS. Experimental and comparative results show that the proposed equalizer achieves the balance of the HESS.

In a high-voltage energy storage system (HV-ESS), the voltage equalizer faces two challenges: 1) improving the extensibility and 2) reducing the number of switches. Therefore, an integrated voltage equalizer based on parallel transformers is proposed, which uses one mosfet to balance the HV-ESS. All the bottom-layer transformers (BLT) are paralleled, and the input voltages of BLTs are identical. Moreover, the top-layer transformer (TLT) drives parallel-BLTs, directly transforming balanced energy to each battery cell. Whatever the number of the BLT, the TLT uses one secondary winding to drive. Thus, the proposed voltage equalizer is highly scalable. The experimental results show that the proposed circuit effectively balances nine series-connected battery cells. It provides a highly scalable integrated voltage equalizer for the HV-ESS.

Wireless power transfer (WPT)-based voltage equalizer (VE) shows unique advantages due to its physical isolation. Meanwhile, the markets of high-power fast charging have imposed significant needs for high-voltage wireless charging systems. However, a WPT-based charging equalizer cannot support a large-scale cell-string. This article proposes a wireless charging VE with modularity to balance cascaded cell-strings automatically using multiple coils. The WPT system's intrinsic high-frequency power is used to power the voltage multiplier (VM). Only two diodes and one capacitor are required for an extra cell, which enables fewer components and a simple structure. Circuit analysis and a one-transmitter–two-receiver charging equalization experiment validate the system's operating principles. The voltage gaps among eight ultracapacitor (UC) cells are equalized from 1.1 to 0.01 V, with an overall efficiency of 76.5% under a 35.2-V output. Nonideal conditions with coupling mismatch and frequency shifts are also analyzed to reveal the system's characteristics. It contributes several ways to providing general modular wireless charging equalization solutions for large-scale cell-string with lower cost and higher scalability.