Low loss LED driver by increasing efficiency, extending lithium battery life accelerating the green process of the system

　　Author ：Iflowpower – پورٽيبل پاور اسٽيشن فراهم ڪندڙ

Low-power illumination drives typically use simple linear regulators to configure them into constant current mode (Figure 1A). Linear regulator has the advantages of simple design. However, its important disadvantage is that the power consumption is large, because the excess voltage is scattered by the heat dissipation resistance and adjustment tube itself.

Such thermal loss also sees the green process of the system. The higher the heat loss, the higher the requirements of the cooling device (fan or large metal radiator), the more energy consumed, and the more space and weight will also be taken, but also add new in material costs and manufacturing time. An alternative solution is to adopt a switch mode adjustment architecture, such as a Buck or Boost regulator (Figure 1B).

Such regulators typically have a feedback voltage of 0.8V to 1.3V for adjusting current flowing through the LED.

The current measuring circuit used to establish the voltage is usually a small resistance in series with the LED. The voltage across the resistor acts as a feedback voltage, which can maintain constant current power supply for LEDs. This architecture reduces the loss of the regulator itself, but the power consumption of the current resistance makes the system loss still exists.

In order to reduce the power consumption of the current resistance, a low loss current detection circuit should be used, for example, the feedback voltage required for the switching converter is supplied in a manner using resistor / op amp. A dedicated precision detection amplifier, such as MAX9938H, a detection gain of 100V / V at both ends of the current resistor. This method can reduce the loss of the feedback circuit to several milliwatts, and even a small crucible lead on the board is used as a small insulation resistance, the cost is almost zero, which can be seen that this method has great attraction.

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