LED is a solid state light source that relies on electr […]
LED is a solid state light source that relies on electronic transitions to convert electrical energy into light energy. Currently, white LEDs have made great strides in the field of backlighting, especially in handheld mobile devices. The power supply voltage of handheld mobile devices is often powered by a single lithium battery. For series-connected LED backlights, the voltage of the lithium battery is far from Meet the requirements, require additional step-up drive circuit.
In accordance with the connection, LED driver chip can be divided into two series and parallel type:
The tandem driver chip needs to connect the LEDs in series with each other in series. The main advantage of the boost DC-DC converter is that the current flowing through the LED under any operating conditions is equal, which ensures that the LED's brightness is the same In addition, smaller PCB resource requirements, higher design flexibility and higher efficiency are also outstanding advantages. However, the drive circuit architecture is more complex, the external inductance must be used, the higher the cost, while larger EMI radiation, and the need for high-pressure process support.
Parallel drive chips need to be driven in parallel with the LED, the main charge pump DCDC converter, the external circuit does not require inductance, the lower the cost, the circuit can be produced using low-voltage process, but the main disadvantage is that different LED Current deviation, the efficiency is not high.