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Part Number: DRV2700EVM-HV500
I want to use the DRV2700EVM-HV500 to provide the power to the load which described below:
1、the load is a constant current source with max current 100mA，4k impedance.
2、the current pulse width is 0.2ms，the frequency is 100Hz，and 500 times repeat.
like the pic below
when I set the DRV2700EVM-HV500 to output 500V and connect the load like above pic，the DRV2700EVM-HV500 can't provide enough power to my load.And the output voltage drop from 500V to 380V.
So I want to know how can I increase the output power of DRV2700EVM-HV500，make it can meet my load and the output voltage do not drop below 430V.
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Our team is taking a look at this. I will provide an answer in few moments.
Best regards,Luis Fernando Rodríguez S.
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In reply to Luis Fernando Rodriguez S.:
I can only suggest to modify the switch states SW3 and SW4 in order to achieve the highest voltage value (please try with both switches down to see the maximum level).
However, the DRV2700 is designed to handle piezo actuator loads. The voltage level depends of the capacitance value that the piezo load has. Unfortunately, it seems that you are using another kind of load. So, we cannot guarantee that it will work.
Please let me know if you have additional questions or comments on this. We will be glad to help you.
I know the DRV2700 is designed to handle piezo actuator loads.But I think if the power is enough,it can also drive my load as described above.I have set the switch states SW3 and SW4 both down,so make sure it can output 500 voltage.It can make sure that the EVM board can not meet the power,so I need to know how to change the DRV2700EVM-HV500's circuit in order to improve the output power,e.g.change another transformer？
In reply to Zoyee:
As you mentioned, there should be something in the circuit that cannot reach the power due to the kind of load. Just to verify if this load can be supported, could you try with a higher load to reduce the output power? If you can find a load that doesn't drop down the output voltage, it would be easier to find a transformer with better capabilities to handle the actual load. Does this make sense?
Again, we cannot guarantee that it will work since it is a different usage of our circuit. However, this would give us an idea if it is capable to work or not.
I have known the output power is not enough to my load.So I need to know how to increase the output power of the DRV2700EVM-HV500.Please give some advice to me.If the output power increase 50% than now,it can meet my requirement.
I would recommend to start reducing the Rext resistor from 10k to 6k. This modification will increase the boost converter limit current to around a 50%.
In addition, could you provide details about the output voltage that you get when no load is connected?
I set the SW3 and SW4 both down,and using the multimeter to measure the voltage and get 493V when no load is connected.
I have tried Rext resistor from 10k to 8k，when I connected my load，I heard the sounds come from transformer.I checked the datasheet of the transformer，the rated current is 0.6A RMS.I guessd the transformer was saturated.So we may need a another better transformer which has higher saturation current performance.I need TI’s assistance to tell me how to design the transformer.
For your design, it is important to remember that the primary must support a saturation current of 1A to reach 100mA at the secondary. Based on the values that you provided, the primary and secondary must support 50W each as minimum (1A, 50V for the primary and 100mA, 500V for the secondary). Also, remember that the power factor of the transformer is below 1. Usually, it is around 0.75. So, you would need a transformer with the capability to handle 67W on the primary and secondary.
If you can get a transformer with these characteristics, you may get the output that you expect without risk of voltage dropping.
I do not think we need a so large power transformer.Because the current 100mA just the pulse with 0.2ms width in 100Hz.So we can not calculate the power using "P=U*i=500V*100mA=50w".Maybe we should consider about the average power？
In addition,I have tested the DRV2700EVM-HV500 to connect my load and set the current as 70mA,the load is show below figure.It can support the load.We do not need to keep the output 500V stable，just do not drop below 450V which can be accept to us.
If this is the case, then you would need to get a transformer with 50% more capabilities than the one used in the EVM. As you mentioned, the datasheet indicates that the transformer has a rated current of 0.6Arms. I would recommend to find a transformer with around 1.1Arms (taking into account the power loss due to the power factor). This should be enough to handle your load.
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