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The LT1173 consumes just 110µA supply current at standby, making it ideal for applications where low quiescent current is important. The device can deliver 5V at 80mA from a 3V input in step-up mode or 5V at 200mA from a 12V input in step-down mode. It has built-in overload protection, defends against short-circuits, and even protects against over-temperature. Best of all, you simply plug it in and start using it. It can handle input between 9V and 36V and put out between 5 and 5.3V depending on the power you put into the module. The power supply for the test was providing 12V, but due to the voltage drop in the ammeter, the input voltage of the modules is a bit lower. Results
However, in the real world, this is not always the case. Instead of knowing the supplier and manufacturer, you need to discuss them with your family and friends. They may have personal experience that can be beneficial to you. I calculated the efficiency of each module per each type of load as: eff = Pin/Pout = (Vin*Iin)/(Vout*Iout) All the circuits have different performance. The voltage divider circuit is not recommended for use in the high current application as it has a low output current and lower efficiency. LM7805 12v to 5v converter: The above schematic diagram shows the electrical symbol for a Schottky diode. 12V – 5V Circuit DiagramListed chip efficiency is within 5-10% of the measured module efficiency. The delta could be due to inefficiencies in the module itself or due to differences in the overall conditions (temperature, etc). The box itself is sealed and has four USB connections on the other side. It is possible to connect four 5V devices at the same time! The converter handles input current between 8-35V and provides a steady 5V/3A supply. It’s also waterproof and can be screwed into position. The properly connected heat-ink is a must otherwise it can destroy the IC317. The input voltage must be 1.5V or more than the required output voltage.
Few points worth mentioning: first, the “Cigar”, with its fixed USB output connector is providing voltage that is too high by proper USB standards. It could be due to old age or just bad quality. The difference is about 10% and I would consider it not usable. Second, most modules are capable of input voltages up to about 25 volts, but few can do 40 volts and higher. Kudos for that. Switching circuit properties Module Peak current refers to ability to provide high current for a limited length of time. Max current refers to maximum current the module can provide consistently. Mind that some modules mention that operating at max current might require an additional heat-sink or cooling solution. Datasheets of some of the chips used in the modules contained an efficiency graph. The efficiency is a function of voltage and current. When available, I added the listed chip efficiency for the relevant Vin and Iout in the last column. Some modules have efficiency charts that don’t cover low current ranges, which might be an indication for the type of load the chips were (not) designed for. Output current of 25mA Module The LT1173 is a versatile micropower DC-DC converter. The device requires only three external components to deliver a fixed output of 5V or 12V. Supply voltage ranges from 2.0V to 12V in step-up mode and to 30V in step-down mode. The LT1173 functions equally well in step-up, step-down or inverting applications. One 12v battery, 100-ohm resistor ( higher value is recommended), 5.1V zener diode ( greater than 1W), some connecting wire, and soldering iron for permanent joints.
E.g., in an LM2596-based adjustable DC-DC converter, it was “forgotten” to install a capacitor between the output and sense-input (thereby multiplying the output ripple with a factor related to the difference between output voltage and sense-voltage of 1.23V(Cff in LM2596 datasheet: https://www.onsemi.com/pub/Collateral/LM2596-D.PDF). However, adding a 15nF capacitor did not solve all of the ripple (I would consider a ripple up to 100mV acceptable). The above circuit diagram shows the circuit along with all the calculated values for our required operation. Working of 12V to 5V Circuit This module has the same connections as “Fine” but it is a bit larger. It was sold as “3A DC-DC 9V/12V/24V to 5V USB Step Down Power Module 2A Precise Vehicle Charger”. Voltage and current It works, BUT it only works at one value of load current and it wastes most of the power supplied. If the load value changes, the voltage will change, since there is no regulation. However, it will survive a short circuit at the output and protect the 12V source from shorting out.
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