Abstract: A dimmable LED drive circuit and a control method is provided in the present disclosure. The dimmable LED drive circuit may include a thyristor dimmer, a bleeder current circuit, and an LED circuit. The bleeder current circuit may provide a current required by the thyristor dimmer when an input voltage does not reach a forward voltage of the LED circuit. The dimmable LED drive circuit may further include a thyristor chopping angle detection circuit and a bleeder current control circuit. The thyristor chopping angle detection circuit may obtain a first electrical parameter signal characterizing a thyristor chopping angle when the thyristor dimmer is in a conducting state. The bleeder current control circuit may compare the first electrical parameter signal with a first threshold, and control the bleeder current circuit according to a comparison result.

Abstract: The present disclosure provides a current adjustment circuit. The current adjustment circuit may include a dimming switch coupled to an inductor disposed in a lighting sub-circuit, a zero-crossing detector, and a time control sub-circuit. The dimming switch may be configured to control power supply states of the inductor. The zero-crossing detector may be configured to detect an ending time of a current of the inductor, and to generate a zero-crossing signal. The time control sub-circuit may include a first capacitor and a second capacitor and configured to receive the zero-crossing signal, and generate a control signal that is configured to control the dimming switch to initiate a switching cycle for the inductor. The switching cycle may start after a delay time and the delay time is controlled by a first charging time of the first capacitor and a second charging time of the second capacitor.

Abstract: The present disclosure provides a current adjustment circuit. The current adjustment circuit includes a lighting sub-circuit, a dimming switch disposed in the lighting sub-circuit, a switch control sub-circuit connected to the dimming switch and the lighting sub-circuit, and a time control sub-circuit connected to the switch control sub-circuit. Time of switch-off period in a switching cycle of the current adjustment circuit is adjusted under control of the time control sub-circuit and the switch control sub-circuit. Brightness of the current adjustment circuit is adjusted based on the output current of the current adjustment circuit. The present disclosure may reduce or even eliminate influence of factors such as circuit parasitic parameters on an LED light source, ensure consistency of each light source, and optimize display effect of the LED light source.

Abstract: A dimmable LED drive circuit and a control method is provided in the present disclosure. The dimmable LED drive circuit may include a thyristor dimmer, a bleeder current circuit, and an LED circuit. The bleeder current circuit may provide a current required by the thyristor dimmer when an input voltage does not reach a forward voltage of the LED circuit. The dimmable LED drive circuit may further include a thyristor chopping angle detection circuit and a bleeder current control circuit. The thyristor chopping angle detection circuit may obtain a first electrical parameter signal characterizing a thyristor chopping angle when the thyristor dimmer is in a conducting state. The bleeder current control circuit may compare the first electrical parameter signal with a first threshold, and control the bleeder current circuit according to a comparison result.