The output section of the POWIM-PD is the pulsed driver. It is a diametric mixture of power and finesse and is easily understood as an analog to a dam. To see this recall that a dam holds back a huge body of water and will let some of the water pass through when the dam controller desires it to. The pulse driver works in the same way. The voltage that is gated from the Power Integrating Module (POWIM) is like the water and the pulsing circuitry is like the dam. The pulsing circuitry only allows current to flow for a short period of time, and then shuts the flow off. The voltage stays active at the output continuously like water backed up in a reservoir, but the current will flow only when the Pulsed Driver (PD) allows it.
The time for which the current flows is 28.8 nanoseconds. Then the current is shut down. During the on time the current can become very high in magnitude. But because it is on for such a short period of time the power delivered to the load works like a very gentle but effective stroke to the load. Thus, the device at the output is rapidly energized and then rapidly cut off from the source of energy and allowed to relax to its natural de-energized state, ideally. That is the finesse of the output. Light emitting devices can be safely attached at the output and is protected from destruction by the pulse limitation. Two characteristics of the pulse provide this protection.
The duration of the pulses is called the pulse width and the time from the beginning of one pulse to the beginning of the next pulse is called the period. The period of the PD is 288 microseconds. Together the pulse width and the period define a property called the duty cycle. This is the amount of time that the current flows compared to the period of the pulse. It is usually expressed in percent. The PD has a duty cycle of 0.01% on average.
The pulses occur about 3500 times per second and this is the frequency of the PD. The cumulative effect of all these pulses appears to be continuous operation of light emitting devices, but you now know that the device is off most of the time (99.99% of the time in fact!). That is why even your most delicate LEDs can be safely connected to the POWIM-PD and operate with voltages as high as 15 volts connected at the input of the POWIM-. You can operated LEDs with unmodified power from solar panels or battery banks without worry.
The PD has a dual means of connecting loads to the circuit board. There is a two terminal pad and a two terminal screw terminal. These connection points are parallel and so more than one load can be placed in parallel across the pulsed driver output. For example, a modulating device or circuit can be connected in parallel to a light emitting device to create a communication circuit. This is an example of how the POWIM-PD can be used for telecommunications applications. Or if you feel that your light emitting device is to delicate to be connected to the PD without further protection, you can use the second port to add a protection diode or resistor to the circuit. This will divert some of the current around the light emitting device like a river or channel does with water currents.
When driving a common LED, the PD is very stable and will not over drive the load. Instead it errs on the side of caution and may under pulse the load every now and then. The pulses always occur on time, but on occasion they may come up short in magnitude or appear negative in a measurement with a low cost oscilloscope. The reason for this is that the pulse current is occasionally stopped with a negative going pulse, in the same manner that one normally does with a SCR. The design intention is to simply stop the positive current and allow it to collapse to zero, but that is beyond the capability of the circuit components and sometimes the current may reverse due to device switch-off time limitations. This enables fast switching of the load current both on and off and is the reason why the pulse width in the load is precise. The trade-off is statistical jitter in the pulse magnitude which, in terms of protection and longevity of light emitting devices, is a benefit. Be aware of this stochastic behavior and make note of it if your application requires consistent exactness in the pulse magnitude. Some units may have magnitude consistency and some may not and it may depend on the load connected. This is not an exact science. Rely, in this case, on your measurement skills. On average one out of six pulses may be lower than the others by about 30% maximum. If you have purchased a POWIM-PD that has no magnitude jitter then you have a premium unit and your device is worth much more than you paid for it. Put it up for auction!
On the other hand, the magnitude jitter could be caused by some property of the load (an LED) and all of the units are premium. We will only know this when we create forums and knowledge sharing sites on the Internet for this device.
Exercise: Test the the output of the PD on an oscilloscope. Is the height (magnitude) of the pulses the same every time? (Hint: Set the time base at 100 microseconds per division and be sure you have a load connected. An LED at the output with 15V at the input makes a good test setup.)