My goal is to use two parallel TECs (massive 50x50mm 226W jobs) to transfer heat from one thermal resevoir to another. Depending on various system factors, I will want to change the rate at which heat is moved. The heat will always be travelling in one direction. The peak current draw by the TECs should be around 10A each. At 10A, the TEC voltage should be roughly 10V. The load line is somewhat non-linear, but it's close, so we'll call them 1 ohm passive loads. So I have a total of a 0.5ohm passive load. I need to adjust from 2A to 20A (or 1-10V) to set my thermal transfer rate. Because the TECs are essentially passive, my load doesn't change, which means the important response time is response to a changing setpoint. Because the thermal resevoirs are quite large, response time is pretty much not important. Even a 1s response time is adequate. The important considerations are cost of materials and efficiency. Since the heat moved through a TEC is dependant on the current through the TEC, I've decided that I should attempt to control the current rather than the voltage applied to the TECs. I intend to sense the load current, and use it (through an opamp) as the feedback voltage. (unless there's something I can do with current mode PWM?) I'll compare this feedback voltage to a setpoint that I generate with a DAC, then use the resulting error voltage to set the operating point of the PWM. AFAIK TECs require the smoothest current they can get, which is why I started looking into multi-phase designs. If I'm mistaken about the preference of TECs to have flat current, then I can certainly use a single-phase PWM, however, my concern is then that the ripple current from my 12V supply will be quite large, which I want to avoid. So I still like the idea of a multi-phase controller. What I want to avoid is using two PWMs with a sync controller and a load-share controller. I'd much rather use a converter that is designed to use multiple phases. Thanks again, Brendan Xiaofan Chen wrote: >On 9/6/06, Brendan Moran wrote: > > >>I want to make a multiphase SMPS with a variable output voltage from 2V >>to 10V. The current through this supply would be 4A-20A. (it's attached >>to a passive load). The load, however, doesn't like ripple current, so >>I thought that a two-phase SMPS would be a good idea. Even some of the >>4-phase SMPSes look nice until I see that they only go up to 3.3V >> >> >> > >What is the requirement for the ripple current? I think there is no reason >why you can not use a single phase Synchronous Buck converter >for your application. You can always use higher value output capacitors >(more capacitors in parallel, but check if the ESR and stability) and higher >\value to reduce the ripple current if you do not need very fast response >time. What is your load? > >Those multi-phase PWM controller are often designed for motherboard >VRM application. In those cases, response time is quite fast. > >Regards, >Xiaofan > > -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist