Test of DC-DC 7A 9-60V to 3-32V

DSC_5851

Official specifications: I got this module from ebay dealer: best-for-sell

DSC_5850

The module arrived in a anti static bag.

DSC_5852 DSC_5853

DSC_5854 DSC_5855

DSC_5856 DSC_5857

DSC_5858




Testing
Voltage Current

Current and voltage readouts looks precise, it is possible to adjust them.

For all my test curves see here.

Load%20sweep%209V%20Out%3D5V

With 5V out and 9V in the converter can deliver about 6A with a loss of 4W. Output drops a bit when load increases.

Load%20sweep%2050V%20Out%3D5V

With higher input voltage the output current increases slightly (My test is limited to 7A), but the power loss increases greatly. During one of these tests I saw a discolored LCD due to heat.

Load%20sweep%2050V%20Out%3D12V

Increasing the output voltage limits the delivered power, here the current is down to about 4.8A and the power loss is very high.

Load%20sweep%2050V%20Out%3D32V

Increasing the output voltage to maximum, reduces the maximum current to about 3.7A, with less voltage to drop the power loss is lower.

Voltage%20sweep%203.0A%20Out%3D5V%20input%20current
Voltage%20sweep%203.0A%20Out%3D5V

With 5V 3A out it works nicely with any input voltage from about 8V and up. The efficiency is best with low voltage difference.

Voltage%20sweep%203.0A%20Out%3D24V%20input%20current
Voltage%20sweep%203.0A%20Out%3D24V

With 24V out the efficiency is high, but it need about 27V to deliver 24V

No%20load%20voltage%20sweep%20Out%3D5V

With low output voltage the idle current is fairly low when the input voltage is high.

No%20load%20voltage%20sweep%20Out%3D32V

But with higher output voltage the idle current will increase.

5ohm5Vin12V

The noise on the output is fairly high, even at moderate loads or unloaded. This is the 200kHz switcher that is a bit low on output filtering.

LoadOn5Vin12V

Turning a load on do not change the voltage much.

LoadOff5Vin12V

But turning it off makes the voltage jump a bit, with higher input voltage the output jumps more.

Load%20test%205.5A%20Out%3D5V

A load test with 12V input and 5V output at 5.5A, this means about 4 watt power loss in the converter.

Temp6728

M1: 53.0C, HS1: 98.7C
About 100C, this is rather warm.

Temp6729

M1: 60.3C, M2: 73.8C, HS1: 90.2C
The aluminium heatsink looks cool, but they are not, they are just bad at radiating heat.

Load%20test%203.0A%20Out%3D24V

A load test with 50V input and 24V output at 3A, this means about 6 watt power loss in the converter. The display did change color with this heat.

Temp6731

M1: 87.5C, HS1: 157.2C
At 160C something is way to hot and it looks like it is the inductor.

Temp6733

M1: 97.7C, M2: 103.4C, HS1: 151.3C



A closer look at the circuit

DSC_6485

It was easy to remove the two covering sheets.

DSC_6486

This side has the input and output terminals, the capacitors, the large and very hot inductor. There is also a small switcher (XL7005A 0.4A) withs own small inductor and diode for local power supply.
For measuring current a 0.02ohm resistor is used, this resistor is on the other side and a OpAmp (LM358) to amplify the signal. The 0.02ohm resistor on this side is for the switcher on the other side.

DSC_6494

The microprocessor (STC8A4K64S2A12: 64K flash, 4K ram 8051 based) is hidden below the display. This version do not have EEPROM, this means is probably uses the flash to remember voltage setting. The controlling DAC must be with PWM and some filters, this may explain the slow setting rate when releasing the buttons.

DSC_6487

DSC_6488 DSC_6490


DSC_6489

DSC_6491

On the bottom are two heatsinks and a 3.3V regulator (7133). This regulator can only handle up to 24V input, this means a preregulator is needed, this is the small switcher on the other side of the circuit board.

DSC_6492

Removing the heatsink shows 3 transistors and one switcher controller (LT3800: 60V input, 36V output). Two of the transistors are used by the switcher, the last is input polarity protection (Nice detail).

DSC_6493



Conclusion

This DC-DC converter works fairly well, but be a bit vary about the specifications and do not use it directly with low voltage chips, it can be used as preregulator, but place a LDO regulator after this switcher to get rid of the noise and spikes.
For stuff running at 12V or higher the noise and spikes is not very significant and it works fine, but check my curves for current output and power loss. A 4 watt loss heats it significantly.



Notes

The converter was supplied by a reader for review.

Index to other tests