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The output voltage of Boost circuit is very high

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letan

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Hi everyone,
I design a Boost circuit with specification:
Input: 3.3v
Output: 5v, 50mA
After soft-start, the output voltage increases very high: around 18v. Then it decreases to 10v, but very slowly.
How can I control the output voltage?
Best Regard!
Thanks
 

try to check your feedback resistor values
 

The boost converter have duty cycle to be controlled. PWM is usually used for this, and the formula is Vo/Vs = 1 / (1-D) where D is the duty cycle ratio. In the transient response it is normally that the voltage increase that high (it's because of inductor stuff), can you tell me what controller is used in that circuit?
 

so what topology you used for your boost circuit?
 

Hi everyone,
I think that problem: the current supply for MOSFET is very high. I'm going to design a current sense amplifier for Boost circuit. Can anyone help me?
Thanks!
 

The transistor current can be measured ground referenced at the source, very easy I think.
 

Hi everyone,
I've used DSP to increase or decrease Ton which supplies for gate of MOSFET.
How can I control the output voltage when it's higher than value I want?
 

letan said:
Hi everyone,
I've used DSP to increase or decrease Ton which supplies for gate of MOSFET.
How can I control the output voltage when it's higher than value I want?
Click to expand...

try to use feedback control, for example direct duty ratio control, using PID or hysteresis...
 

As a humorous comment: Seems like using a DSP instead of a well-tried boost controller turns out as reinventing the square wheel?

Actually, digital SMPS controllers are possible and also used by major manufacturers, e. g. TI with upward tendency. Clearly the control loop gain must have the correct sign, I think it should reduce ton for Vout>Vset. As said, most analog PWM controllers are realizing a PI or PID charateristics. With integrator, properties as wind-up stop may be important, it is achieved in analog circuits by appropriate design of amplifier voltage ranges.
 

Thanks a lot!
This is thing I need!
 

did you get it, other wise i can help you....
 

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