The input section of the Power Integrating Module with Pulsed Driver is the section of the circuit that accomplishes the power integration. It is designed to take two DC voltages and integrate them to the output of the section. The product is designed to work with dynamic sources like the kinds found in renewable energy systems, for example. The integration involves one of the following operations.

Gate the highest of the two voltages to the output.

Share current from both sources at the output.

Gate one of the voltages to the output and disable the other based on hysteresis.

The function that the input executes is determined by the design and the module that you purchase will do one or more of these functions. This circuit inherits it capabilities from the PowerPath technology of Linear Technology Corporation [1]. The unique features that you will acquire are designed into the product and its function is decided before manufacture. If you have purchased a module that can be configured dynamically, then your circuit may perform more than one of the possible power integrations at the input.

No matter which configuration you have purchased, you will find that the POWIM- is a very robust section of the product in that it will tolerate deviations from the configuration that it was designed for and provide output under some abnormal conditions. You should watch out for this if this robust behavior is not desired.

Exercise: Test the POWIM- section of your module with some safe conditions that are different from those for which it was designed. What do you find? Make a note of the conditions used and the results obtained for your reference.

Configuration One will gate the primary voltage, Pwr1, to the output and is designed to have the voltage that is on Pwr1 higher than the voltage on Pwr2. You have this configuration if your model number is POWIM-PD13.5-12V The input is set to work in this mode by a hysteresis network of resistors. This network sets two trip points for the POWIM-. When the voltage on Pwr1 fall below trip point one the source at Pwr2 is gated to the output and Pwr1 is cut off from it. Pwr2 stays on the output until the voltage at Pwr1 rises to trip point two at which point Pwr1 is once again at the output and Pwr2 is cut off. In this configuration all of the control is based on the voltage at Pwr1 and Pwr2 is a back-up source that is lower in voltage than Pwr1. The table below gives the  model numbers and the trip points that they are designed to work on.

Notice that the source does not switch at the same voltage both times. Pwr1 switches off at 12V when its voltage is going down and it switches back on at 13.5 volts when its voltage is rising. This is the hysteresis effect provided by the resistor network. The voltage on Pwr1 must get 1.5 volts above its trip point to return back onto the output. This hysteresis, in effect, sets how long Pwr1 operates before it is relieved by its back-up source, Pwr2 and how long Pwr1 can recharge before taking the load again. In the model 13.5-12V POWIM- the source at Pwr1 must be a new battery bank or some source that can rise above 13.5 repeatedly after dropping off.

Exercise: Find out what will happen if the voltage of your source connected to Pwr2 has a magnitude that is situated in the middle of the hysteresis interval. Does the switching happen in the same way as it does when Pwr2 is below the bottom of the hysteresis interval? Refer to Application Note 005

The model 13.5-12V POWIM uses the top 1.5 volts of a 12V battery bank. It is best suited for sources like solar panels and automotive alternators that normally operate at 13.5 volts and above. If the solar panels are connected to Pwr1 and the back-up batteries are connected to Pwr2 then the drop-off of solar power that will inevitably occur will cause the battery bank to replace the panels as the power source. If the battery bank runs down before the solar power rises above 13.5 volts they will still be connected to the load and your load will not have an adequate power source. Because of this possibility you must make sure that Pwr1 will get back to 13.5V before the back-up batteries run down. For solar applications this means that Pwr2 must be a robust power source like a big battery bank with many ampere-hours or perhaps the power grid stepped down to 12V DC

Test Your Knowledge

Take the Input Quiz .

References

[1] www.linear.com