Current Mode Feedback Control in buck controllers.

[srijan]

Could anyone be kind enough to elaborate on what exactly is current mode control in buck controllers and what is an emulated current ramp?. Are there buck controllers which can drive 10 A at a 30 V Output.

I was going through some buck converters listed on the website of national semiconductor and many of them operate on the current mode of control.

Can such converters be used as stable current sources?

 

[grieblm]

Here's a **broken link removed** of how current-mode control works. Basically, the current through the load is being controlled in order to regulate the output voltage to a constant setpoint. Both the Linear Technology LTC3703 or LT3724 can output 10A at 30V. Keep in mind that these are constant Voltage outputs and not constant current.

What you may be asking about is a constant current source. It really doesn't make sense to talk about an output voltage when discussing a current source since the output voltage will vary although the current is kept constant. When the load impedance increases, the output voltage increases to keep the current constant. The LT3755-2 is capable of operating in a constant current configuration to drive loads like high-current LEDs.

 

[srijan]

Thank you for your response.
What I need to design is a charger for a 7 cell lithium ion battery pack.
First I need to supply 10 A (CC Phase) constantly for about an hour till the battery voltage exceeds 29.4 V and then I need to stop when the current decays (CV Phase) to less than 0.1 A. How do I go about designing the above?