The voltage on the COMP pin is proportional to the amount of peak current the switch will be turned off at. Pulse by Pulse Current Limiting" shows the current sense resistor's connection to the built in current sense amplifier and gives the equation which determines the current setting vs. The current sense amplifier in the chip receives a voltage from across a current sense resistor which therefore is proportional to the output current. It sends a switching pulse of current into the output circuit, measures the output circuit's ramping current, and it terminates the output current of the switching pulse by opening the pass switch when the output current has reached the determined current value. EDIT: Ok so it is a current mode IC, so the pulse by pulse current limiting is fundamental to its control design. TI has lots of good SMPS ICs, so you can hardly go wrong by picking one that is stated to be appropriate for your SMPS topology and desired control mode, power level, and having the particular extra features you want. Some designs sense the voltage across the switched inductor and can estimate the current from it.
Current mode pwm series#
Some designs sense the voltage across small resistance a series connected current sense resistor which is in the circuit of the pass FET. Some designs sense drain to source voltage across the resistance of the pass FET itself. In general cycle by cycle current limiting involves starting a switching pulse by turning the power supply pass FET on and during all or part of the time the pass transistor is on the IC senses some voltage that is proportional to the current flowing through the pass FET. The data sheet should go into details about the control mode (current mode control vs.
0 kommentar(er)
