Power

Use a low-quiescent-current switcher for high-voltage conversion

14th December 2018
Alex Lynn
0

Texas Instruments explains that, in battery-operated environments, it’s important to pay attention to quiescent current when designing your power system block diagram. Some applications, such as cordless handheld garden tools, lighting controls and cordless lawnmowers, have low-quiescent-current specifications. These tools operate with a battery pack that has an operating voltage range from 12 to 48V or higher.

Using a low-dropout regulator (LDO) to convert this higher battery voltage to a lower voltage would increase power dissipation in the pass device transistor and drain the battery faster when the standby load current is large. For example, if you have a 48V battery pack and try to convert it down to a 5V or 3.3V rail, then the conversion efficiency is roughly VOUT/VIN, which in a 5V output case will be 10.4%. The input current drained from the battery will be the same as the output current.

If your standby current for all monitoring peripherals is 5-10mA; this current would drain out of the battery directly if you just used an LDO. A DC/DC converter reduces the input current consumption because of the switching action of the internal field-effect transistors (FETs).

To learn more, click here.

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