一种新型过流保护电路设计

与多数以"中断"模式实现保护不同,文章提出了一种用于低压差线性稳压器(LDO)的过流保护电路设计新方案,通过"屏蔽电路"屏蔽过流信号,使LDO不因过流信号干扰而中断运行。为了防止屏蔽时间内的过大电流烧毁功率管,提供过大电流关断电路,当屏蔽时间内负载电流太大可能瞬间烧毁功率管时能及时关断功率管,保证功率管的安全。该电路的屏蔽时间可以根据需要设定。CSMC0.5μmBiCMOS工艺Cadence spectre仿真结果表明,改进后的过流保护电路能有效屏蔽设定时间内的过流信号,扩大了正常工作区的范围,保证了LDO更高效安全地运行。

Design of A New Over-current Protection

Different with many other over-current protection circuit using ＂interrupt＂ mode,a new circuit for LDO（Low-Dropout voltage regulator） with adding ＂shielding＂ mode has been presented in this paper.By shielding the over-current signals,the LDO keeps working rather than interrupts when the over-current happens.In order to prevent the large current distroying the the power transistor in the shielding time,a large current shut-down circuit is also supplied,which can shut down the transistor immedietly.The screen time,which is determined by the power transistor,can be designed.The simulated results,by the tools of Cadence spectre with CSMC 0.5μ m BiCMOS technology,show that the improved over-current protection circuit can effectively shield the overcurrent signals and keep the LDO working safely.