Please advise, the voltage of the 5V circuit drops after adding load

Knight97538

Please advise, the voltage of the 5V circuit drops after adding load [Copy link]

 

The board is made according to the circuit diagram below. The input 12V battery is powered. The no-load output voltage is normal. When a load is added, the voltage drops below 3V.

Is there something wrong?

maychang

"When a load is added, the voltage drops below 3V. Is there something wrong?"

There seems to be nothing wrong with the electrical schematic.

maychang

maychang posted on 2022-4-28 17:45 "When the load is added, the voltage drops below 3V. Is there a problem?" There seems to be no problem with the electrical schematic.

"When a load is added, the voltage drops below 3V"

How big is your "load"? You can say the resistance value or the current size.

winner0945

1. How much resistance is added to the load?

2. What is the actual voltage of the 12V power supply battery and how is the heat dissipation of the chip?

Fred_1977

First of all, when your output is 15W, can your input provide more than 15W of power? If it can't, it will fall.

qwqwqw2088

There is no problem with the circuit. Maybe the parameters of some device are wrong or the power is not enough.

chunyang

Pay attention to several parameters: load power, front-stage input power power, and energy storage inductor parameters.

luck_gfb

The original poster didn't say how big the load is. How do others analyze it? It's best to upload the PCB board diagram as well. A bad layout will also affect normal operation.

Knight97538

luck_gfb posted on 2022-4-29 09:26 The OP didn't say how big the load is. How do others analyze it? It's best to upload the PCB board diagram as well. A bad layout will also affect normal operation.

Thanks for your advice

The PCB diagram is like this

Knight97538

maychang posted on 2022-4-28 17:46 "When a load is added, the voltage drops below 3V." How big is your "load"? You can say the resistance value or the current size...

The load current is about 2A, and the full load is 2.5A

Knight97538

winner0945 posted on 2022-4-28 17:49 1. How much resistance is added to the load? 2. What is the actual voltage of the 12V power supply battery, and how is the heat dissipation of the chip?

Prepare to use a regulated power supply',

The current test is using a 12V battery

Knight97538

chunyang posted on 2022-4-28 19:19 Pay attention to several parameters: load power, front-stage input power power, and energy storage inductor parameters.

The diode is not currently used, it is HER304

This tube has a maximum of 3A

What other component parameters need to be considered?

maychang

Knight97538 posted on 2022-4-29 09:33 The load current is about 2A, full load 2.5A

A current of 2.5A should be no problem.

Then we need to check whether the input voltage drops when loaded, whether the DC resistance of the inductor is too large, and whether the inductor is magnetically saturated when outputting maximum current.

chunyang

Knight97538 posted on 2022-4-29 09:49 The diode is not currently used. The HER304 is the maximum current of this tube. What other component parameters need to be considered?

First test the input voltage of the front stage. If the voltage of the front stage drops sharply below the tolerance of the power chip when loaded, it is obviously impossible to output normally. In terms of inductance, it is necessary to pay attention to the current carrying capacity. Parameters that need to be concerned about: inductance, rated current carrying capacity, DC internal resistance, and operating frequency.

不亦心

LZ replace the output solid state with ordinary aluminum electrolytic and try it

qwqwqw2088

There is no problem with the PCB wiring diagram

Improper use of the device is likely to

Inductors and capacitors are suspect.

Chad4133

Looks like the circuit is correct, but can you make sure use the right components and circuit trace correctly.

se7ens

The load current is a little smaller than the design value.

You can try adjusting the inductor or the freewheeling diode.

Knight97538

se7ens posted on 2022-4-30 10:18 If the load current is a little smaller than the design value, you can try adjusting the inductor or the freewheeling diode

Thanks

Already solved, made a common sense mistake

The inductor was not enough during the actual welding and the test result was only 20uH.