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| Q factor of LC filter for TEC driver |
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| Gibson486:
I am making a filter for a TEC (only needs to go one direction). The values I intend to use are an inductance of 33uH and a capacitance of around 270uF. I did this to minimize ripple at my frequency (~40khz PWM), so these values attenuate close to 60db at my frequency. I plotted the frequency analysis, but it showed that I have a high Q value and it peaks at around 1.5kHz. Since I am not really interested in the band of the peaked value, could it be ignored? I could dampen it and put a resistor in front of the filter, but the TEC is over 5 amps, so that would be a huge resistor. Thanks! |
| Benta:
??? https://en.wikipedia.org/wiki/TEC |
| Gibson486:
Thermal Electric Cooler (aka peltier) |
| duak:
I worked on a few projects that used PWM TEC drivers. I don't remember the details as I didn't design that section but I don't recall any particular problems with using a simple LC filter. I do remember that the designer used powdered metal inductors instead of ferrite inductors. We'd have to know more about the circuit, especially if there's some sort of feedback from the filter output. If the circuit is open loop, I wouldn't think there would be a problem because there should be anything to excite the LC resonance. The load impedance has to be considered - have you determined what the TEC's dynamic resistance is over the range of drive currents? If you need more damping, you might be able to add a parallel RC network across the filter cap, but it depends on the dynamic resistance of the TEC. A small consideration is that TECs generate a bit of power when there is a temperature difference across them. In one case, this sneak power source kept one of the power bus indicators on for a few minutes and caused a few minutes of head scratching. |
| Gibson486:
It's just open loop. There is feedback, but for temperature, not the circuit itself. I am not sure what a powered metal inductor is. I had to use this big one from coilcraft though because it needed to be able to handle the 5 amps. |
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