Cheap LED lamps for indoor lighting need to have a good price/performance ratio, so optimizing product design is very important.
Based on the difference in power supply grid voltages around the world, LED lamps have two types of power supply voltage input: wide voltage input and constant voltage input; in order to be universally applicable to grid voltages in different regions, LED lamps with wide voltage input have become mainstream products, and wide voltage input The LED lamp power supply needs to use a switching constant current source power supply, which relies on the switching power supply to automatically buck-boost and output a constant DC current when the power supply network voltage changes from AC84-280V. LED lamp beads must work in a constant current environment to emit light normally and effectively without flicker.
LED switch constant current power supply
The switching constant current source power supply relies on the switching frequency of the machine and the transformer to automatically increase and decrease the voltage, respond to the fluctuation of the grid voltage, output a constant DC current, and provide it to the LED lamp beads to make it glow normally.
Grid current enters the LED drive power supply, firstly undergo EMC treatment, and convert AC to DC through the rectifier bridge stack; secondly, through the power control chip and transformer, the high-voltage DC voltage is reduced to the operating voltage required by the LED lamp beads with low loss, and the output is constant With a suitable working voltage that meets the VF voltage and IF constant current requirements of the LED lamp bead string, the LED lamp bead can emit light normally.
However, the grid voltage is 50Hz or 60Hz power frequency alternating current, and the voltage waveform is sine wave. Therefore, after rectification, the pulsating direct current rich in 50Hz power frequency and its double frequency ripple is obtained. The ripple is the residual AC component that must be passed through Only after the electrolytic capacitor is filtered, stored, charged and discharged, can a relatively smooth direct current be obtained.
The main chip control IC of the switching constant current source needs a clean power supply without ripple, and the ripple in its working circuit needs to be eliminated, so a bypass filter capacitor is required. The switching constant current power supply outputs the LED drive current through the transformer in the circuit, which is simply rectified into DC by the diode, so it will contain a lot of ripples. Low-frequency ripples will produce flicker that can be seen by the human eye. Electrolytic capacitors must be used to filter the ripples. net.