CCS/TMDSSOLARUINVKIT: C2000 micro inverter questions

Hm.. well there are some aspects of soft switching because of the clamped flyback. However there is still conduction loss. I think you may be able to change heatsink etc. or use a different FET.

Well. Refer to test results on page 52 of "tidu405bUG", the "Pin" reaches 316.87W so I suppose that the clamped flyback on TMDSSOLARUINVKIT is capable to handle 270W; otherwise, the efficiency would never be up to 90%. Is soft-switching implemented with of clamped flyback in TMDSSOLARUINVKIT?

From what i know and understand it,

1. Energy stored in T1 mag inductance (Lm) transferred to C2, fly-back action.
2. T1 leakage inductance (Lp, Ls) energy transferred to Cac during fly-back operation
3. Np:Ns = 5:27, Vin = 30V, Duty = 61.5%, Vout = 416V
4. Lowest switch volt stress compared to other fly-back topologies.
5. Resonance between leakage ind and diode (D1, D2) parasitic caps causes reduced
circulating current in primary clamp circuit. Reduces conduction losses in clamp circuit .
6. Resonance between leakage ind and diode parasitic caps causes additional boost action.
7. Primary switch (both FETs) ZVS turn on

Are you able to read the FET part number of the device used on Flyback?

Hi Manish,
I am using the development kit "TMDSSOLARUINVKIT" with 110Vrms output, and Vin=30V, Duty=46.3%, Vbus=275V; however, I can't see ZVS when I checked Vgs and Vds of Q9. The part number of FET is "IRFB4227" which are implemented on the development kit by the way.

Hm , I have asked my manager to look at this as he designed the HW, but he is  out of office for a couple of weeks.

In the meanwhile can you provide some waveforms for the Vgs and Vds ? I am attaching our experimental result above done good 5 + years ago... 

you also may want to check in open loop first.. 

As per the spec the max load with 120Vac input is about 140W. So you must be overloading it with 270W.

2.4 Solar Micro Inverter Electrical Specifications
Following lists the key highlights of the micro inverter.
 Panel Voltage: 28V (Min) to 45V (Max)
 DC bus voltage: 400V (max)
 Output Power: 280W @ 220Vac, 140W @ 110Vac
 DC-DC & DC-AC combined efficiency ~92% at 50% rated load, THD~5%

Shamim

It looks like with the 319W test at 220 Vrms we may have been streching the coverter spec , I will recommend you to test with the spec provided above only.

Hi Shamin,
It is my understanding that "TMDSSOLARUINVKIT" has two stages; they are, an active clamp flyback converter with a secondary voltage multiplier and a DC-AC inverter, and they are separated. Whatever the DC-AC inverter output (280W or 140W), the active clamp flyback converter should be capable convert 280W output power. The only difference is that higher output voltage will introduce lower output current on inverter side. Am I right?

Hi Manish,
Well. Even though I tested output power at 280W, there is still thermal issue at Q9.

Hi Manish,

  The yellow and blue colors are Vgs and Vds of Q9, respectively.I also tested it in open loop (build 1).

Hi Shamim,
Actually I have replaced Q9 several times since it burned out frequently. Let me check the Vgs voltage under open loop again and see if there is something wrong with my measurement. Thanks.