LED constant current control device in PWM dimming mode

The invention discloses an LED constant current control device in a PWM dimming mode, comprising AC mains supply, a steady voltage source module with adjustable output voltage, a PWM dimming module, an LED light resource, a current sampling module, a current sampling time determining module, an MCU module, a constant current control module and a photosensitive device, wherein the AC mains supply is connected with the steady voltage source module with adjustable output voltage, the steady voltage source module with adjustable output voltage is connected with the PWM dimming module which is connected with the LED light resource, and the LED light resource is connected with the current sampling module; and the current sampling module, the current sampling time determining module and the photosensitive device are connected with the MCU module, PWM output by the MCU module is connected with the PWM dimming module and the current sampling time determining module, the other path of the MCU module is connected with the constant current control module, and the constant current control module is connected with the steady voltage source module with adjustable output voltage. The invention can prolong the service life of an LED and improves the efficiency of the LED power supply.