Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

current mode vs. voltage mode PWM control

Status
Not open for further replies.
T

tdy

Member level 3
Joined
Mar 19, 2008
Messages
57
Helped
4
Reputation
8
Reaction score
2
Trophy points
1,288
Location
Navy
Activity points
1,534
current mode vs voltage mode

I am wandering why for the current control method there is a RS flip-flop be connected after the comparator before sending the driving signal to the swithing gate. But for voltage controller there is not such a block. Can anybody explain?
 

voltage mode vs current mode

A flip-flop is also used in many voltage mode controllers, e. g. classical 3524. It assures that only one output pulse is generated for each clock periode.
 

    T

    tdy

    Points: 2
    Helpful Answer Positive Rating
voltage mode pwm

can u give some abnormal operation examples for the unintended driving signal?
 

flip flop pwm

If you don't use a flip-flop or some memory element, then you will suffer noise issues when you turn on the big power switches.

For example, if VM is only using a ramp and capacitor, then when the ramp exceeds the error voltage and you try to turn on the mosfet, switching noise can cause the comparator to flip back from 1->0.

If you have a flip-flop, we only care about the first comparator edge and we toggle the switch on/off cleanly. If you don't have a flip-flop, your converter can give several ON-OFF glitches at the start and end of each switching cycle.

A flip flop is cheap. You need to use one.
 
  • Like
Reactions: bajanbruce

    T

    tdy

    Points: 2
    Helpful Answer Positive Rating
    B

    bajanbruce

    Points: 2
    Helpful Answer Positive Rating
current mode pwm controller

Your explanation is very helpful. Thank you verymuch.
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top