UCC25660: Ho and LO have not output signals

meng John

Part Number: UCC25660

Hi Experts,

  I am using the ucc256601 to do a half bridege boosted circuits with input 390Vdc and output 1kV, 
  250W and found some strange signals as following :

1. The HV (pin1) signal is a 0.5Hz square wave with 120Hz sine carrier waves.

2. The Test (pin7) signal is a 0.5Hz square wave.

3. The Lo(pin 11) signal is 0v~ and Ho(pin15) is 10.4vdc~

Conditions:

Input voltage is 390Vdc which is apply for half bridge circuit.

Vccp(pin12) is 12Vdc; LL voltage (pin6) is 0.99V; V5p (pin8) is 5Vdc; BLK(pin3) is 1.22Vdc.

Questions:

Are the HV and Test' signal normal waves ? if not, what are the reasons of generating abnormal waves?
How could I make the Ho and Lo output a normal wave ?

Thanks,

John

1 month ago

0 SIRIPURAM YAMINI 1 month ago

TI__Expert 3125 points

Hi John,

Can you please share your schematic and design calculator with us.

regards,

Yamini.

0 meng John 1 month ago in reply to SIRIPURAM YAMINI

Prodigy 195 points

Hi Yamini:

please see the materials as following:

1. Schematic

2. Calculator:

Thanks,

John

0 SIRIPURAM YAMINI 1 month ago in reply to meng John

TI__Expert 3125 points

Hi John,

TSET (pin7) should not be like that. Are you getting any LO pulse ( even for small span of time ).

Can you please send your Pin Vs Vfb replica graph and TSET settings ( missing from the shared design calculator).

Regards,

Yamini.

0 meng John 1 month ago in reply to SIRIPURAM YAMINI

Prodigy 195 points

Hi Yamini,

There are not any output signals both LO (pin11) and FB(pin5) whose outputs are 0v~ . Anyway , could the chip output signals on Lo (pin11) in the absence of the half bridge circuit ?

Thanks,

John

0 SIRIPURAM YAMINI 1 month ago in reply to meng John

TI__Expert 3125 points

Hi John,

To check whether LO is coming from the IC, you need to supply VCC=15V and BLK around 1.5V externally.

Reagrds,

Yamini.

0 meng John 1 month ago in reply to SIRIPURAM YAMINI

Prodigy 195 points

Hi Yamini:

About the BLK voltage , please taking a look at the parameters from the specification sheet below:

In my opinion, if the BLK is higher the 1.02v , then the LLC operate and the output of Lo / Ho will be stopped ,right or no ?

Thanks,

John

0 SIRIPURAM YAMINI 1 month ago in reply to meng John

TI__Expert 3125 points

Hi John,

If the BLK voltage is less than the BLK stop ,then the controller will stop.

Regards,

Yamini.

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UCC25660: Ho and LO have not output signals