应用于 DC-DC 的一种高精度过流保护电路

文章基于电流模同步降压DC-DC转换器，提出一种高精度可编程阈值的过流保护电路。基于SENSEFET电流采样技术设计一种全周期电流采样电路，克服了传统方案只能采样1/2周期的局限；通过外接电阻编程与修调电路，不仅扩展了电流保护范围，还降低了温度等因素对电流阈值的影响；采用三级运放构建的比较器进一步提升了电路的比较速度。该过流保护电路采用$0.18\mu \mathrm{m}$ BCD工艺设计实现，仿真结果表明，其能够在 $10~\mathrm{ns}$ 内快速响应，实现精度达 $96\%$ 的电流保护，并适用于多种DC-DC芯片类型。

In this paper, an overcurrent protection circuit with high-precision programmable threshold is proposed based on the current-mode synchronous step-down DC-DC converter. A full-cycle sampling circuit based on SENSEFET current sampling is designed, which solves the disadvantage that only half a cycle can be sampled. The current threshold is programmed and the circuit is trimmed by the external resistor, which increases the current protection range and reduces the current threshold, which is affected by temperature and other factors. A comparator consisting of a three-stage op-amp is used to improve the comparison speed of the circuit. The circuit is designed using a$0.18\mu \mathrm{m}$ BCD process, and the simulation results show that the circuit can perform fast(10 ns) and accurate(96% accuracy) current protection, and can be applied to many types of DC-DC chips.