Overcurrent protection circuit with boost and push-pull cascade circuit

Abstract

The invention discloses an overcurrent protection circuit in which BOOST cooperates with a PUSH-PULL cascaded circuit, including a front-stage BOOST circuit, a rear-stage PUSH-PULL circuit, a protection locking circuit and a protection reset circuit. The BOOST circuit works in a PWM state, and the PUSH-PULL The PULL circuit works in the full pulse width complementary state. The invention directly samples the output current on a pair of push-pull switch tubes of PUSH-PULL, and directly pulls down the push-pull drive circuit after confirming the overcurrent state by a high-speed comparator to realize fast protection, and at the same time, in order to avoid continuous protection of a single drive cycle Action, increased protection locking circuit. The invention has simple principle, fewer components and fast action speed, can ensure the reliability of the long-term short circuit of the whole machine, and solves the overload and short circuit protection difficulties of the BOOST circuit when it is used at a high power level.

Description

technical field [0001] The invention relates to the field of protection circuits, in particular to an overcurrent protection circuit in which BOOST cooperates with a PUSH-PULL cascade circuit. Background technique [0002] In BOOST with PUSH-PULL cascade circuit or single-stage BOOST circuit, it is more difficult to deal with or solve the short circuit protection function. Therefore, single-stage BOOST circuits are generally used in low-power integrated IC applications, or cascaded with a single-stage circuit with protection functions, such as PWM or LLC circuits. The most common application of this method is AC / DC power supply with PFC function. However, in the application of DC / DC, the latter stage of the above-mentioned cascaded circuit works in a full duty cycle state to meet the needs of soft switching. In principle, it is impossible to achieve a steady-state current-limited (power-limited) state by adjusting the duty cycle. However, the pre-stage BOOST circuit can o...

AI Technical Summary

Problems solved by technology

[0003] Compared with the technical scheme of BUCK and PUSH-PULL, the combination of BOOST and PUSH-PULL has obvious advantages in the efficiency of the whole machine at low voltage input, but if it cannot solve the problem of short-circuit protection, its use is risky.

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