System block diagram, open-loop, closed-loop, stability, system calibration, etc
This part mainly divides the functions of switching power supply from the perspective of control system, introduces open-loop, closed-loop, stability and so on. On this basis, it introduces the correction of switching power supply system, and tries to explain the causes of linear adjustment rate, load adjustment rate, output steady-state error and so on in theory. Bode diagram is the most commonly used analysis tool in the field of engineering technology. How to apply it to the design of switching power supply loop?
1.1 switching power supply system
1.2 open loop and closed loop system
1.3 dynamic and steady state of switching power supply
1.4 compensation correction
2. Common PFC, DC-DC power stage transmission characteristics, and the corresponding loop control strategy
This part mainly introduces the control mode and transmission characteristics of common PFC in DCM, CRM and CCM, and the transmission characteristics of common DC-DC in voltage control mode and peak current control mode, so as to talk about the corresponding loop compensation strategy.
3. I, II, III compensation circuit based on 431 and optocoupler and I, II, III compensation circuit based on operational amplifier and optocoupler
This part mainly summarizes the classic I, II and III compensation circuits composed of 431, optocoupler and operational amplifier, and gives the transfer function.
4. Loop control design practice
This part mainly involves the dynamic load characteristics of switching power supply, the selection of ride through frequency, the placement of poles and zeros, etc.
Through the summary of the first three parts, a design example of flyback quasi resonant converter is given, and the calculation sheet is written by using Mathcad.
5. The influence of optocoupler and output LC filter on the loop
In practical design, the influence of optocoupler and output LC on the loop is often ignored, and rarely mentioned in many IC application notes. This part attempts to analyze the parasitic parameters of the optocoupler, the influence of the output LC filter on the stability of the system and how to avoid it.
