Current sampling switching circuit and LED constant-current power supply

The invention discloses a current sampling switching circuit and an LED constant-current power supply. The current sampling switching circuit comprises a constant-current chip control circuit, a current sampling unit, a first resistor and a second resistor, one end of the first resistor is connected with a sampling current port and one end of the second resistor, the other end of the first resistor is grounded, and the other end of the second resistor is connected with the constant-current chip control circuit and the current sampling unit. The constant-current chip control circuit controls the output of the sampling current by using an opening switch of the current sampling unit; the constant-current power supply comprises a current sampling circuit, an EMI filter circuit, a half-bridge harmonic circuit, a rectifying filter output circuit and a power factor correction circuit. In the current sampling switching circuit and the LED constant-current power supply, all the circuits cooperatively work, so that the