AU01 DC/DC CONVERTER

1. Product description

This unit steps up the voltage from low voltage power sources, such as fuel cells, to a more useful voltage. The output voltage is regulated to about 5 volts, and this value will be maintained even if the input voltage drops to about 1 volt. The unit will continue to work for input voltages down to 0.7 volts, but the output will fall to around 2.5 or 3 volts. However, this voltage is still enough to run small radios and other electronic devices.

With one of our FC01 Mini Fuel Cells, running on sodium borohydride fuel, the unit will run a range of electronic devices, such as small radios. It can also be used with small PEM fuel cells.

This unit does NOT generate power, so while the voltage from the fuel cell is increased, the current is reduced. For example, the output from the fuel cell might be a 100mA current at 0.8 volts, and the DC/DC converter will give out 21 mA at 3 volts.

The unit has leads with 4mm plugs fitted. It is supplied as an 8x6 cm circuit board, as shown below.

The unit below is powered from the input voltage, and needs no batteries or other power supply.

2. Instructions

The unit could hardly be simpler to use:-

• Connect the negative (black) input lead to the negative terminal of the power source, e.g. the fuel cell.
• Similarly, connect the positive (red) input lead to the positive terminal of the fuel cell.
• Optionally, you could check the unit is working by connecting a voltmeter to the output sockets. The voltage should be around 5 volts, but might be as low as 2.5 or 3 V if using just a single cell as the power source. (If it is not, then probably the fuel cell is set up incorrectly. Check that the input voltage is about 0.8 volts or more.)
• Now connect the load to the screw terminals, as in the picture above. If the unit does not work, use a voltmeter to check the voltages. If the input voltage has fallen to below 0.7 volts, then the load is drawing too much current, and cannot be powered by the system. This could be because the load is not suitable, or because the fuel cell is not set up properly.
• Once connected, the switch allows the DC/DC convertor to be "switched out", with the output terminals connected directly to the fuel cell. This is very useful for testing.

Input voltage: 0.7 to 5.0 volts

Output voltage: 5.0 volts normally, but falling to about 3.0 volts if the input voltage is less than 1.0 volts.

Efficiency up to 90%, depending on the input voltage. (See graphs below)

Maximum power: 2 W @ 3 volts input, 500 mW @ 1.4 volts input, 60 mW @ 0.7 volts input

Connectors: Leads supplied for the input. Screw terminals for the output.

Size:8 x 6 cm

4. Performance

The efficiency and output power of the circuit depend strongly on the conditions in which it is used, particularly the input voltage.

The first graph below shows the output that can be expected from the unit when the input is one (lower line) or two (upper line) of our FC01 Mini Fuel Cells, running on NaBH₄ fuel, at room temperature. (The cells will need swirling from time to time to mix the fuel to maintain the higher currents.) Note that the single cell power output is enough to run most small radios that normally use a 3 V (i.e. 2 AA batteries) supply, such as the Sony ICF-303.

5. Application

The two pictures below show the unit in use with one of our mini fuel cells, and the second shows it being used with a demonstration PEM fuel cell made by H-TEC. The reason the unit is so useful is that it allows low voltage (high current) devices such as fuel cells to power a much wider range of devices.

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