The amount of accumulated energy cannot be determined on the basis of the voltage on capacitor terminals only. Unfortunately, the well known relationship for typical capacitors that allows to determine the information, that is (1/2) C U 2, cannot be used. In all these applications, the key parameter is the information on the amount of accumulated energy in the supercapacitor. Additionally, high charge/discharge rates make them effective for applications in energy recovery systems used for example in transportation or renewable energy sources. The ability to accumulate charge without any chemical reactions makes such elements to have hundreds of times higher number of charge/discharge cycles in comparison to typical batteries. Users can customize GreenPAK to implement all of these modes as shown in Figure 4.As of today, supercapacitors are the main components of many devices and systems, e.g., backup power and electricity recovery systems as well as automotive applications, hybrid vehicles and many others. It's common to have a bypass mode which powers the load directly from the main power supply, a charging mode to charge the supercapacitor, and a discharging mode when the supercapacitor must power the load.In order to allow an external host controller to determine when to begin charging the supercapacitor, the GreenPAK can be easily configured to receive a Charge_EN signal on one of its GPIO pins.Every GreenPAK includes several GPIOs, Look Up Tables, ACMPs, and counters which can be configured to do this. A supercapacitor power management circuit should charge a supercapacitor up to a pre-determined voltage and then discharge it when the main voltage supply drops below a set voltage.The ESD diode is optional, but is recommended for applications where the supercapacitor is removable by the user.Ī GreenPAK with integrated power switches can be configured to charge and discharge a 1-cell supercapacitor as shown in the Figure 3 circuit and corresponding Figure 4 GreenPAK design implementation.Each cell balancing module can be stacked on top of each other to create a system that can charge several stacked supercapacitors in series.GreenPAK’s fully programmable CNT/DLY blocks provide flexibility to work with a wide range of timing configurations.
To signal overcharging, a FLAG output can be configured to go HIGH if the voltage across the supercapacitor remains too high for more than a set time period.GreenPAK has analog comparators with voltage references that can configured for specific application requirements. When the voltage across the supercapacitor reaches its charging threshold, an active cell balancing circuit allows current to flow through a balancing resistor.A simple modular supercapacitor active cell balancing solution using GreenPAK is shown in Figure 1 and the corresponding GreenPAK design implementation is shown in Figure 2. Cell balancing is required to ensure that each cell stays within its rated voltage because inevitable cell mismatches will cause overvoltage fault conditions during operation. rated for 48V or more) have even more stacked cells to achieve their rated voltages. Similarly, higher voltage supercapacitor modules (e.g. Supercapacitors that are rated for 5.5V are often a stack of two cells with a rated voltage of 2.7V each.
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