DC/DC boost converter voltage drop when connected to load

boostdc/dc converterswitch-mode-power-supply

For my senior design project, I am trying to generate two voltage levels or rails from a battery powered circuit (12 V and 3.3 V.)

I am using an adjustable boost converter for the 12V rail and a fixed one for the 3.3 V.

The battery is a Li-ion 3.7 V_nom, 2200 mAh from Tenergy.

The boost converter is the ADP1613 and I also have a backup, the LM2735.

The 3.3 V is the LD3985M33R (buck.)

The loads I will be powering with the 12 V rail are:

  1. An electromagnet that draws a max of 450 mA according to the manufacturer (but in testing measured 150 mA)

  2. 4 strings of of 4 LEDs, running at 20 mA each, which puts each string at around 80 mA (the forward voltage is around 2 V for each LED)

  3. The bias voltage of an audio amplifier, the LM386N.

The 3.3 V is powering:

  1. An MSP430,

  2. A CC3200

  3. An LED driver.

The issue:

When I connect any load to my boost converter, the voltage output drops significantly.

For the electromagnet, it drops to around 4 to 5 V.

With the LEDs, it drops to around 7 to 8 V.

For the audio amplifier, it drops to around 6 to 7 V.

Unloaded, the boost converter provides around 12 V.

Best Answer

It sounds like that one or more of your components are not rated for the input current your stepup requires. You need to look closer at your battery and your inductor. You are roughly triple your output voltage of 12V, that means your input current will be about 3 times the output current: 800mA@12V = 2.5A@4V. Will your battery supply this current? Will it also supply the double amount if the switcher is drawing the current in pulse mode? Same for your inductor, is it rated for at least 5 Amps?

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