I know this would probably never take wind, but its an Idea I like to share.
It would be Board that integrates bench top DP projects, like bus pirate, bus blaster, OSLS, the DSO, the upcoming PS...
the board would have a usb hub, and powersupply distribution.
for this to work there would have to be some changes/or not to existing DP PCB. the idea is to have all the DP projects have an extension to their PCB for a PCI type board to board interface. and for them all to be able to plug into the integration board, like pci cards plug into a motherboard.
the point is that all the diferent PCB would still retain their mobility in the sence that they could alwasy be unpluged from the integration board and be standalone products, with their own power supply and usb conectivity.
ofcourse this could be done even today with a usb hub and a powersuply board that would have all the conections made trough wires, but that would look like a Big mess of wires,
sorry, but i am unable to acess that part of the forum, i just asumed when i saw dp.com post right after my post on the forum that they were corelated.
anyway I developed an idea for a digitaly controled PS, that i am gonna build just as soon as my exams are over, in about a month.
the idea is relativly simple, it uses one 555, 3 comparators and 2 curent sense amplifiers. its a clasic buck topology. the 555 controles the switch. the 555 is setup in such a whay that when a low pulse comes on its triger it gives out a low pulse witch is >= to fixed RC time. it goes low as soon as the trigger goes low, and stays low either for a fixed time or if the triger is still low it stays low untill the triger goes high.
the low output turns the switch on, high turns it off.
conected to the triger are 3 comparators. one that compares output Voltage to dac set referance. the second compares the inductor current trough high side curent aplifier, to a pre set maximum inductor current reference. and the third inductor compares the ouput current to a second dac set refference. (here the max9611-12 could be used) when either of them goes low, the triger goes low and the switch is off.
I simulated it and it works rather well. the frequency is variable and depends on many things but two things can be controled: the charge rate of the inductor, and the 555 minimum off time, witch is used to stop any comparator oscilations contoling the switch.
Inductor charge rate is calculated trough its maximum current and inductance. and the 555 minimum off time trough the rc network. for this cicuit to work on higher Frequancies and thus give more stability and fewer cost of the inductor, it needs comparators with low propagation delay and a 555 with a low propagation delay, because what is the point if you register that the current has crossed a pre set 4 amps when it takes the circuit a further time to respond and thus your current jumps to 5A, witch fries your inductor.
Plz coment and critique the design if you find any faults with it, thanks. [attachment=2] [attachment=1] [attachment=0]
the output current comparator is mising but its a simply the max 9612 added to the triger.
the reason for doing this is that is easy to understand, simple to work with, and gives full control of the circuit to the designer. by seting up different reference voltages you could control maximum Inductor current, maximum output current, output voltage. by lets say making the maximum inductor current reference a function of the output current you could have an addapting maximum current for incresed stability, and higher freq operation. and this is done by driving the maximum current comparator with the output of the output current amplifier.
I just found some excelent IC-s from maxim, those guys seriosly know what they are doing.
MAX9611, MAX9612 they are high side current sensing amplifiers with integraded 12bit ADC, I2C interface, and opAMP/comparator.
by adding only a resistor and a Pmos to it you get current limiting, and 12bit A/D over the i2c for output voltage, current, temp, even set reference. by driving the reference via a DAC you get full digital control over current limiting. and you dont have to use any MC A/D chanels since the IC does it all for you. a
nd by using a lm78s40 or lm723 by driving its reference with a DAC you get full voltage regulation, and if you implement the i2c DAC you get full control over only 2pins over the whole power supply.
Maxim MAX5137 are 2 chanel 12 bit high precision low power DAC with SPI interface and ready out for easy ddaisy chaning. the 12bit version is around 3$ and the 16 bit is around 6$ witch is not much, with the benefit that maxim is briliant at giving out samples world wide.
what about using a spi 16bit DAC to control the reference voltage for the error comparator in lm78s40. it would lower the noise from the PWM/filter design.
similar design could be used with a lm723 liner precision regulator, and the current limit could be controled via a RSense in parralel with a 1k digital pot. from witch the wipper could be conected to the Rsence lead of the 723 IC