The utility model relates to the technical field of lamp power supplies, aims to solve the technical problem that the existing
LED lamp is poor in time
delay effect, and discloses an LED gradually-bright and gradually-dark
control circuit which comprises an LED
assembly, a switch SW, a PNP type
triode Q5 and a constant-
current driver U11, a collector
electrode of the
triode Q5 is grounded in series through a first
voltage division circuit, and the collector
electrode of the
triode Q5 is grounded through a second
voltage division circuit. An emitter of the triode Q5 is connected to a direct-current power supply V +, an intermediate node of the first series
voltage division circuit is connected with an enable end of the constant-
current driver U11, the enable end is grounded through a
capacitor C21, a power switch end of the constant-
current driver U11 is connected with a current sampling end of the constant-current driver U11 sequentially through an
inductor L3 and an LED
assembly, the current sampling end is connected to the direct-current power supply V + through a current detection
resistor, and the direct-current power supply V + is connected with the LED
assembly. The power input end of the constant-current driver U11 is connected to the direct-current power supply V +, and the ground end of the constant-current driver U11 is grounded. Compared with an existing circuit, the constant-current driver U11 participates, so that the control precision is high, the dimming ratio is high, and the
delay effect is better.