电流模开关电源高精度电感电流采样方法研究

Research on High Precision Inductance Current Sensing Method of Current Mode Switching Power Supply

针对高精度峰值电流模控制的Buck-Boost型DC/DC开关电源,提出了一种利用功率管导通电阻对电感电流信息采样的高精度采样电路,解决了传统结构中受PVT影响使得采样增益漂移不稳定的问题,为避免浪涌电流对芯片造成的冲击而损坏芯片,在采样电路的基础上集成了限流保护电路,进而提高了芯片寿命与可靠性。基于0.18μm高压BCD工艺对提出的方法进行了具体电路设计与物理实现验证,测试结果表明:在输入电压2.9~4.5 V,温度-40~85℃条件下采样电流精度最高可达99.7%,误差最大仅相差2.5%,所设计的结构相较于传统方法受PVT的影响大幅降低。设计限流保护值为2.15 A,测试结果表明限流保护电路能够在电感电流为2.14 A时关断主开关管,误差仅为0.005%,避免了电感电流过大对芯片造成的冲击。该结构已在一款BuckBoost型开关电源中得到成功的应用。

Aiming at Buck-Boost DC/DC power supply with high precision peak current mode control,a high precision sensing circuit using power tube conduction resistance to sense inductance current information is proposed,which solves the problem that the sampling gain drift of in traditional structure is unstable due to the influence of PVT.In order to avoid damage caused by inrush current,a current limiting protection circuit is integrated on the basis of sensing circuit,which improves the life and reliability of the chip.Based on 0.18 μm high voltage BCD process,the circuit design and physical implementation of the proposed method are verified.The test results show that:when the input voltage is 2.9~4.5 V and the temperature is-40~85℃,the sensing current accuracy is up to 99.7%,and the maximum error difference is only 2.5%.Compared with the traditional method,the design structure is significantly less affected by PVT.The design value of current limiting protection is 2.15 A,and the test results show that the current limiting protection circuit can turn off the main switch tube when the inductance current is 2.14 A,and the error is only 0.005%,avoiding the impact of excessive inductance current on the chip.This structure has been successfully applied in a Buck-Boost power supply.