Flyback Converters. Before reading this section, please read the introduction. Sometimes an isolated voltage needs to be produced.
Flyback converters are very similar to boost converters in their architecture and performance, except with a flyback converter the inductor is replaced with the primary of a transformer and the output is taken from the secondary.
The following tutorial describes how to design a boundary mode flyback circuit where the circuit operates on the boundary between continuous and discontinuous conduction. A typical flyback converter is shown in FIG 1. FIG 1. This circuit converts 12V to a pseudo-isolated 5V and can support a load of 1A. This circuit is adequate to demonstrate the operation of a flyback converter, even though it does not offer full isolation — the feedback resistors R1 and R2 violate the isolation barrier.
Ignore components R4, D2, Q2 and C5. These just provide a linear regulator function to allow the LTC to be used with high input voltages. When the FET switches on, the current ramps up according to.
So in the case of FIG 1, the current ramps up at a rate of. When the MOSFET switches off, the voltage on both the primary and secondary windings increase in an effort to maintain the current flow. The winding that conducts first is the one in which the current flows and in the circuit in FIG 1, diode D1 conducts causing the energy to flow into the output capacitors C2, C6, C7.
In a boost converter, the inductor current ramps up linearly during charge and ramps down linearly during discharge. In a flyback converter, when the current ramps up in the primary, energy is built up in the transformer core. When the FET switches off this energy is dumped into the secondary allowing current to flow in the secondary, so the primary current collapses immediately to zero.
This causes an immediate rise in current in the secondary, after which the current in the secondary ramps down linearly as it discharges. For the sake of analysis, it is often better to treat the primary and secondary transformer windings as 2 separate inductors where energy is built up in the primary and dumped into the secondary.I would like to try using state space average models of corrent mode controllers like UC ucx family for transient and possibly ac analysis.
However I can't find documentation or schematic examples on how to connect and use such models, since they have extra-pins compared with same traditional switching model counterparts.
Thank you oldmouldy. The only match in Cadence help for "state average" I am able to find is the "dc transformer" in the pspice reference guide. The fractional ON time of the power supply switch is directly proportional to the DC output voltage of the state-average controller. Switching delay, rise and fall time specifications do not apply to these models.
Any suggestion? Last seen: 14 hours 24 min ago. Last seen: 1 month 1 day ago. Hope this helps. Download PSpice and try it for free! Download Free Trial. All rights reserved.The paper presents and discusses an algorithm for average modeling of the PWM modulator in switch-mode power systems by general purpose electronic circuit simulators such as PSPICE.How to control the duty cycle of the 555 timer
A comparison with previous theoretical models is conducted. To test the accuracy of the average PWM models comparison to cycle-by-cycle simulation was conducted. The proposed algorithm shows better accuracy than earlier counterparts. Today circuit simulation and computer-aided design are universally accepted engineering tools and have become industry standard method of product development.
Two approaches are possible for simulation of switched mode systems: cycle-by-cycle simulation and average behavior simulation. Cycle-by-cycle simulation is a quite straightforward approach. Cycle-by-cycle simulation can be performed programming the complete power electronic circuit to the simulator. Cycle-by-cycle simulation allows studding the power stage at the switching frequency scale and observing the instantaneous voltages and currents at any point in the circuit.
First disadvantage of cycle-by-cycle simulation is that simulating the detailed switching process is time consuming. This is particularly true for nontrivial practical cases. The second and by far more important limitation is that the cycle-by-cycle model of a switching circuit does not lend itself to frequency response analysis. This is because the switching stage has no stable operating point and, hence, does not allow the PSPICE simulator to perform linearization and calculate the small signal gains required for frequency response analysis.
Therefore, a different approach is needed to attain frequency domain simulation of the control loop. State Space Averaging is a classical theoretical analysis method of switch-mode power electronics systems [ 1 — 5 ]. Average modeling of the power stage can also be helpful in simulation as they can be readily implemented using PSPICE behavioral sources [ 6 — 8 ].
Average models are continuous and, hence, can be automatically linearized by the PSPICE simulator and prepared for the frequency domain analysis. The distinct characteristic of SMPS is that a switched-mode stage is employed as power processor, whereas the control circuits are mostly analog where Pulse Width Modulator PWM is used as an interface.
Here, as an example, an average current mode ACM system is shown. There are two major challenges in simulation of a switch-mode system. The first is modeling the switcher, whereas the second is modeling the PWM modulator.
The PWM modeling problem is that in practice the switching ripple propagates into the control loop and affects the switch on and off times. However, the average SIM model has no ripple components; therefore, in order to obtain accurate simulation results, software DCG should be programmed to predict the switching ripple effects using only the average signals of the SIM model.
The operation of the proposed average PWM model is demonstrated by time domain and frequency domain simulations. The paper also conducts a comparison with previously reported results. Particularly, in the discontinuous current mode the proposed algorithm shows better accuracy than earlier counterparts.
The principle of ACM is to implement a multiloop control system in which the inner loop see Figure 1controls the average current and makes it tightly follow the outer loop command. These features are very desirable and provide good tracking performance. Consequently, the current programming signal at the output of CA,has an average component,with a superimposed attenuated inductor current ripple, as shown in Figure 3.
The ripple is scaled by the gain of the current sensing network,and the CA amplifier gain at the switching frequency.Getting Start Introduction Input File 2.
Another quirk of PSpice is the designation for Comparison of Sources. The VPULSE is often used for a transient simulation of a circuit where we want to make it act like a square wave source.
SPICE model The SPICE model of a bipolar transistor includes a variety of parasitic circuit elements and some process related parameters in addition to the elements previously discussed in this chapter. The original circuit had a sinusoidal input 9 cos 2t.
You can also select a group of parts and CTRLdrag to - copy those parts. DC the DC component of the wave. Logarithmic is customary. Model Sub-Kind. Use PSpice to analyze time response of first order filters Compute the response times of your filters.
I have provided the image of the desired waveforms from the book and my Pspice circuit. PSpice Create Netlist. Note the use of the VSIN source for this input. OrCAD R Please also follow the guide below in order to correctly import our models into Cadence. For now just leave it at the default choice and click OK.
You can find it on my Angel homepage for this course. This is so that the original PSpice model does not get modified. Discover features you didn't know existed and get the most out of those you already know about.
Pspice Presentation - Free download as Powerpoint Presentation. I used the circuit shown below to experiment with this but never had success in figuring it out.
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How do you place such a part? There are examples of all four types of standard simulation and a selection of different plots. To wire parts together, click the Place Wire icon. For an old master, they are much easier to set up, and are a lot less confusing.
If we need a graphical output, PSpice can transfer its data to the Probe program for graphing purposes. My question is how to properly set-up this circuit in Pspice because my waveforms look incorrect.
My OPA model files both. Dave showed me how to use them.Skip to Main Content. A not-for-profit organization, IEEE is the world's largest technical professional organization dedicated to advancing technology for the benefit of humanity. Use of this web site signifies your agreement to the terms and conditions.
First, a duty cycle generator is mathematically derived, considering the transient-state of the current-loop. This technique plays an important role when the operating modes are changed under a considerable amount of step load change. Second, taking advantage of the analog behavioral modeling of PSpice, duty cycle generators for both the time and frequency domain analyses are built into a PSpice file. The accuracy of these models is verified through the computer simulations, which is compared to the actual circuit for the time domain analysis and the small signal model for the frequency analysis.
Article :. Date of Publication: Nov. DOI: Need Help?This course covers advanced converter control techniques, including averaged-switch modeling and Spice simulations, modeling and design of peak current mode and average current mode controlled converters, as well as an introduction to control of single-phase ac grid tied rectifiers and inverters.
Design and simulation examples include wide bandwidth point-of-load voltage regulators, low-harmonic power-factor-correction rectifiers, and grid-tied inverters for solar photovoltaic power systems.
Upon completion of the course, you will be able to model, design control loops, and simulate state-of-the-art pulse-width modulated PWM dc-dc converters, dc-ac inverters, ac-dc rectifiers, and other power electronics systems. Excellent course. I cannot recommend this course as well as the whole specialization enough.
Absolute value for the money spent. Loupe Copy. Advanced Converter Control Techniques. Course 4 of 6 in the Power Electronics Specialization. Enroll for Free. From the lesson. Introduction to Advanced Converter Control Techniques course, and the Week 1 Module on averaged switch modeling and simulations.
It only takes a minute to sign up. I need to do a transient analysis of my BJT cascode amplifier. Well, your pulse width is not quite right for a square wave, but it is close. Sign up to join this community. The best answers are voted up and rise to the top. Home Questions Tags Users Unanswered. Asked 1 year, 6 months ago. Active 1 year, 6 months ago. Viewed 3k times. My simulation result shown above.
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I converted my comment into an answer BTW. That plot is not the output of the vpulse source so not relevant here.
Also, the error you made is very small, you cannot see that 10ns error you made in such a plot. Your duty cycle is Active Oldest Votes. Bimpelrekkie Bimpelrekkie Elliot Alderson Elliot Alderson Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name.
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