Let's see a show of hands how many of you have used cel phone charger even like the iphone charger or any of the newer smart phone chargers. Well how may hands are up in the air Guess what there constant current supply that do to things one there output is fixed at 5 volts till you over load them then it drops off to a point that they shut down.
Cel phone charger are a constant current supply fixed at 5 volts. That's the newer one's like the iphone use's and most smart phones use What part don't you understand I'm talking about the charger that plugs in the wallnot how it disconnects the battery from it.
TND3295 W Cellular Phone CCCV(Constant Current ConstantVoltage) AC-DC Adapter
This reference document describes a built-and-tested,GreenPoint solution for a cellular phone Constant CurrentConstant Voltage (CCCV) AC-DC adapter. This design isintended for isolated, low power, universal input off-lineapplications where a constant current/constant voltageoutput (CCCV) is required for charging NiCd, NiMH,Lithium-ion or similar batteries. Typical applications wouldinclude cell phone chargers or cordless phone chargers.
I not giving them any thing there I just tested about 100 of them as to there rating and did a lot of digging on the net QuoteTND3295 W Cellular Phone CCCV(Constant Current ConstantVoltage) AC-DC Adapterbetter charger like the smart phones and iphone use these in them and thereNot this same chip but one like it.
(section 5: "Circuit operation")For output currents less than 1 A the circuit performs as a constant voltage source. ... Although very simple, this current sense circuit will provide a constant current output of approximately 1 A all the way down to an output voltage of 1 V.
I'm pretty sure that a constant current switchmode power supply (LED Driver) and a constant voltage switchmode power supply (cell phones) are awfully similar. One would take feedback from the load voltage, and the other would take feedback from current sense resistor om series with the load. Any switchmode chip ought to be able to implement either type of supply with minor changes in wiring.In "Lab" power supplies, "CCCV" generally means "constant voltage with a current LIMIT", and defines the way the supply behaves when the current limit is exceeded. This is supported by the TND329 datasheet:Quote(section 5: "Circuit operation")For output currents less than 1 A the circuit performs as a constant voltage source. ... Although very simple, this current sense circuit will provide a constant current output of approximately 1 A all the way down to an output voltage of 1 V. In other words, a "CCCV supply" provides a constant voltage up to the current limit, and then decreases the voltage as needed not to exceed the desired current. (as opposed to simpler regulators, that might just shut down in over-current situations.) Some Li-ion battery charging chips assume that the power supply has a current limit built-in to it, but a cell phone supply will normally operate in a constant voltage mode.In general, that's not quite the behavior you'd want from an LED driver style of CC supply. In that case, you want the voltage to go to any value needed to force the target current through the load. This permits you to use varying numbers of LEDs in series in your light, for instance. I haven't studied the current flood of "LED driver" chips to see how they're different from other switchmode chips; there may be other simplifying factors that permit a cheaper design and justify having a separate chip (oh, like not needing to provide clean DC, for instance.)
Let's see a show of hands how many of you have used cel phone charger even like the iphone charger......
Cel phone charger are a constant current supply fixed at 5 volts
300mA+/-5%. Now, why on earth would I want to power my Arduino board using something like this? Can anyone explain why my board would want to have a device trying to drive a fixed 300mA current into it? Makes no sense, unless maybe the p/s were jiggered after the fact.