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Hi , I have softstart issue of UCC256404(for 1500W 24V/62.5A). The high/low side gate signal sometimes stop after softstart stage. It has any possible reason cause this issue?
CH1 low side gate ; CH2:FB pin
CH3:high side gatte ; Ch4: Lr current
Hi Manikanta P:
If remove the upper resistor at the LL/ss pin ,it will affect softsoft function? I have many times adjust softstart then damage the LLC MOS ,so I need to sure this way is safe . Then I try two ways can improve this issue (1. increase softstart time 2.derease feedback capacitor)
Now I have another issue . The resonant current will increase suddenly. But the softstart switching frequency decrease smoothly.
Have any suggesttion to improve this issue? I try to increase softstart time, but if softstart time longer than output voltage rise time.It will casue output voltgae overshoot.
CH1: low side gate
CH2:FB pin
CH3:high side gate
CH4: resonant current
Fig.1 (LL/SS= 220nF , 309K/140K)
CH1: low side gate
CH2:FB pin
CH3:the output voltage
CH4: resonant current
Fig.2 (Fig.1 (LL/SS= 330nF , 232K/100K)
Hi Manikanta P:
If remove the upper resistor at the LL/ss pin ,it will affect softsoft function? I have many times adjust softstart then damage the LLC MOS ,so I need to sure this way is safe . Then I try two ways can improve this issue (1. increase softstart time 2.derease feedback capacitor)
Now I have another issue . The resonant current will increase suddenly. But the softstart switching frequency decrease smoothly.
Have any suggesttion to improve this issue? I try to increase softstart time, but if softstart time longer than output voltage rise time.It will casue output voltgae overshoot.
CH1: low side gate
CH2:FB pin
CH3:high side gate
CH4: resonant current
Fig.1 (LL/SS= 220nF , 309K/140K)
CH1: low side gate
CH2:FB pin
CH3:the output voltage
CH4: resonant current
Fig.2 (Fig.1 (LL/SS= 330nF , 232K/100K)
Hi,
First of all, you can not use LLC half bridge topology for more than 1kW. If you are still in evaluation phase, you can try to use phase shift full bridge topology (UCC28950 data sheet, product information and support | TI.com) for this application.
CH1 low side gate ; CH2:FB pin
CH3:high side gatte ; Ch4: Lr current
Here controller is going into the burst mode. So removing upper resistor at the LL/SS pin will make the BMTL as 0.2 which is the lowest value.
Also, you can reduce the lower VCR capacitor value to avoid the burst mode.
Regards
Manikanta P
