The electronic devices used in LED switching power supplies are mainly: LED diodes, IGBTs and MOSFETs. SCR has a small number of applications in switching power supply input rectifier circuits and soft-start circuits. GTR is difficult to drive and has low switching frequency, and is gradually replaced by IGBT and MOSFET.

Three conditions for LED switching power supply

1. The switch is: the power electronic device works in the switching state instead of the linear state

2. High frequency: Power electronic devices work at high frequency instead of low frequency close to the power frequency

3. DC: The output of the switching power supply is DC instead of AC

Common sense description of basic parameters of LED switching power supply:

①Ripple and noise measurement method: use a 12" twisted pair cable, and the terminals should be connected in parallel with 0.1uF and 47uF capacitors, and measure at 20MHz bandwidth

②The efficiency is tested under the input voltage of 230VAC, the rated load, and the ambient temperature of 25℃.

Accuracy: including setting error, linear adjustment rate and load adjustment rate.

Linear Regulation Test Method: Test from Low Voltage to High Voltage at Rated Load

Load regulation test method: from 0%-100% rated load.

Start-up time is measured at a cold start, fast and frequent power on and off may increase the start-up time

The difference between LED switching power supply and ordinary switching power supply

What is the difference between the LED switching power supply and the ordinary switch? The biggest difference is that the LED power supply is a constant current source, and the general switching power supply is a constant voltage source. The design difficulty of LED switching power supply is volume and price.

LED switching power supply:

A constant current is required.

Low temperature, low heat and long life

Small size 

Waterproof, anti-corrosion and anti-static

High frequency pollution, high frequency pollution of ordinary switching power supply is serious, even if the output DC is filtered by inductance and large capacitor, the waveform is very complex. Poor power supply, the power supply itself may not be bad, but the LED life and light decay are greatly reduced.

The LED switching power supply circuit is actually mostly composed of a switching power supply circuit + a feedback circuit.