Self-adaptive soft start charging circuit for AC dimming LED drive power supply

Abstract

The invention discloses a self-adaptive soft start charging circuit for an AC dimming LED drive power supply. The self-adaptive soft start charging circuit comprises a power supply circuit and a start circuit, wherein an adaptive soft start circuit is added to the start circuit and comprises two comparators, a logic AND gate and a timer; the adaptive soft start circuit detects Vdd, transmits the detected highest value and lowest value of a Vdd working voltage to input ends of the two comparators respectively; input of the two comparators generates a square wave pulse signal through the relationship of the logic AND gate; the square wave pulse signal is transmitted to the timer to generate a time parameter; and the time parameter increases the duty ratio of a PWM signal and controls the width of a single pulse. The self-adaptive soft start charging circuit solves the problem that an LED lamp cannot be normally started under the input of a dimmer, completely preserves over-current and short-circuit protection functions of a system, can accurately judge the short-circuit condition, and ensures the working safety and stability of the circuit, especially under the condition of high-brightness dimming and in the absence of the dimmer.

Description

technical field [0001] The invention discloses an adaptive soft-start charging circuit for an AC dimming type LED drive power supply, and relates to the technical field. Background technique [0002] In recent years, LED lighting has been widely accepted for engineering and household applications. Due to the existence of a large number of AC thyristor dimmers, the driving power of LED lamps must be compatible with the thyristor phase-cutting input voltage (AC), otherwise there will be stroboscopic, light jumping or failure to start. Among them, system start-up is a serious problem and urgent need in practicality, especially the knob of the AC dimmer is placed at a lower luminous flux position in most cases when the light is turned on. In this case, it will cause , The phenomenon that the lamps flicker back and forth or cannot be lit at all. [0003] Common circuits in the prior art such as figure 1 As shown, under the condition of AC dimming input, the most commonly used ...

AI Technical Summary

Problems solved by technology

When the dimmer is connected, because the voltage of the output capacitor increases very slowly, even if there is no short circuit at the output, because PSVR cannot reach a fixed voltage for a long time, the circuit will misjudgment and turn off the system by mistake, which will worsen the difficulty of starting

Its actual phenomenon can refer to image 3 , although Vdd has not dropped to the minimum value of the normal operating voltage, but due to a short-circuit misjudgment, the system is shut down (PWM signal is 0), and cannot be started

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