Adaptive soft-start charging circuit for AC dimming LED driver

Abstract

The invention discloses an adaptive soft-start charging circuit for an AC dimming type LED drive power supply, comprising a power supply circuit and a start-up circuit, an adaptive soft-start circuit is added to the start-up circuit, and the adaptive soft-start circuit Including two comparators, a logic AND gate and a timer, the adaptive soft-start circuit detects Vdd, and the highest and lowest values ​​of the detected Vdd operating voltage are sent to the input terminals of the two comparators respectively, and the two comparators A square wave pulse signal is generated by the input of the logic AND gate, and the square wave pulse signal is sent to the timer to generate a time parameter, and the time parameter increases the duty cycle of the PWM signal and controls the width of the single pulse. The invention solves the problem that the LED lamp cannot be started normally under the input of the dimmer, completely preserves the over-current and short-circuit protection function of the system, and can accurately judge the short-circuit situation; ensures the safety and stability of the circuit work, especially in high-brightness dimming and without 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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