Get best of the week

Power Stage Designer Utility - Power Electronics Developer Tool

Greetings! I want to talk about a very interesting utility for an electronics developer, which I have been using in my professional activity for a long time. The Stage Designer tool the Power TM from Texas Instruments - instrument from the "mast hev" set power supply designers, converters, power electronics. As the name implies, the utility is designed to calculate the parameters of the power part (power stage), and also includes some additional features that help in solving related problems.


Key features of the utility:


  • Calculation of the main parameters of the converter;
  • Parameter calculator feedback loop «Loop Calculator» ;
  • Calculation of losses of the MOSFET transistor "FET Losses" ;
  • Calculation of capacitors "Capacitor Calculator" ;
  • Calculation of damping chains "Snubber Calculator" ;
  • Calculation of the parameters of the regulation / stabilization circuits of the output voltage “Output Voltage Scaling” ;
  • Converter units «Unit Converter» .

Calculation of the main parameters of the converter


We start the program and see this set of topologies:



We select the topology for the calculation. For example, I will choose an active clamp forward converter. As the calculated values, I introduced the parameters of one of my developments - a DC / DC converter on a DIN rail. The calculation window looks like this:



Here you can set the input parameters for the calculation and see the results. In the "Design Values" area, the parameters to be set, in the "Recommended Values" area , parameters recommended by the program, the values ​​of which can be selected and entered in the "Choose Values" area . In the "Calculated Values" area, the values ​​calculated by the program.

In addition, all circuit elements highlighted in yellow are clickable. You can see the shape of the current and voltage on the element, as well as the main parameters at various values ​​of the input voltage and load current:


Some notes on the calculation:

  • If you enter values ​​that are different from the recommended ones, the calculated values ​​may not correspond to the required ones, while the discrepancy is highlighted in red;
  • . , «Inductance»;
  • , , , ;
  • . , : , — , , /, .

«Loop Calculator»


A utility for analyzing the stability / dynamics of a converter, building amplitude-frequency (AFC) and phase-frequency (PFC) characteristics.


In the General Information section , the initial parameters of the converter for calculation are entered.

In the "Control Sheme" section , the type and control mode of the power unit are selected. For example, “VMC Buck” is a buck converter, voltage mode control. "CMC Forward" - linear converter, current control (current mode control).

In the Compensation Network section , the type of correction circuit is selected, the circuit itself can be seen by clicking on the COMP Networks button .


In the "Gain Information" section , parameters are defined that determine the loop gain, in particular:

  • V ramp - PWM ramp voltage, amplitude of the PWM saw;
  • G m - Error amplifier transconductance, slope of the characteristic / active conductivity of the OS amplifier, this parameter is given when using an amplifier with current feedback in the compensation circuit (transimpedance amplifier);
  • R s - Current sense resistor, resistance of the current sensor resistor;
  • A s - Current sense amplifier gain, current gain;
  • A OL - Error Amplifier open loop gain, gain of the error amplifier when the OS is open;
  • GBWP — Gain-bandwidth product — ( , );
  • RP/RD — Optocoupler transfer ratio, ;
  • Vslope — Slope compensation voltage/slope compensation multiplier (SLM), / . .

In the "Component Values" section, the parameters of the correcting circuits are set. In the "Suggested Compensation Values" section , the values ​​of the parameters of the correcting circuits proposed by the program are set. In the Poles & Zeros section, calculated zeros and poles of the transfer function. In the "Graphs" section , you can choose which characteristics to build:

  • Power section of the converter ( “Gain Power Stage”, “Phase Power Stage” );
  • Error Amplifier ( “Gain Error Amplifier”, “Phase Error Amplifier” );
  • Full characteristics of the system ( “Total Gain”, “Total Phase” );
  • Error amplifier with open OS ( “Gain Error Amplifier (Open Loop)” )

It should be noted that the task of constructing and analyzing transfer functions is not in itself trivial, even using this utility. If I have time, I’ll write a separate article with a brief manual and practical example of use.

Calculation of losses of the MOSFET transistor "FET Losses"


This utility allows you to evaluate the static and dynamic losses in the MOSFET transistor of the converter. When you run the utility from the main calculation window of the converter, the initial data (currents and voltages on the key) are transferred to the General Circuit Information section . The areas “FET1” and “FET2” are completely identical, this allows you to compare two different transistors in terms of losses. Let's look at an example of calculation.

In my development, I used the IRFI4227 transistor as a power switch. I will not say that even five years ago (when the IP was developed, given as an example in the initial calculation) it was the best choice, however, it was dictated by the fact that this transistor was already in the enterprise database, used in mass-produced products, had in stock. In addition, for this IP, there were rather tough price targets, so a decision was made to heat the transistor to fit the transistor on the aluminum module case, and since I wanted to provide a simple and technological assembly, I needed a transistor in an insulated case.

So, for example, let's compare the losses in IRFI4227 with the losses that can be achieved by applying modern MOSFET. As can be seen from the calculation, in this circuit, the maximum voltage on the key is 45V, so I picked up a 60V transistor type IPA060N06NM5S from Infineon, as one of the industry leaders. The transistor chose more or less balanced by the “lightness” of the shutter and the channel resistance.

Now you need to fill in the required parameters. Consider the example of the IRFI4227 transistor. Open the datasheet - I highlighted the parameters that are used in the calculation:


It should be noted that the value of the channel resistance is recorded taking into account the dependence on the crystal temperature, the temperature is selected 80 ° C.

However, the parameters Q gs , Q g (th) , V miller in LH are absent, so what to do? Fortunately, TI specialists took care of the users of their tools and by clicking on the Info button I found such a hint:


Let us turn to the corresponding schedule in LH:


And also here is such an explanatory diagram:


And we get the missing parameters: Q gs = 24nC; Q g (th) = 15 nC; V miller = 6.5V.

The final comparative calculation is shown in the screenshot below. It can be seen that the more modern IPA060N06NM5S transistor (and also selected for the given voltage) has several times smaller both static and dynamic losses than IRFI4227.


However, if we talk about dynamic losses, in my opinion, this calculation should still be considered approximate, estimated. There are several reasons for this, for example, it is not known exactly which stray inductances are present in the circuit, and accordingly, the switching conditions may not be taken into account. The second is the high variability of the loss model. Say, the parameter V GS (th) of the IRFI4227 transistor in the datasheet is not exactly normalized, but the range is 3.0-5.0V. Accordingly, for the calculation, I chose a value of 4.0V, for the same value I determined the parameter Q g (th) according to the Typical Gate Charge characteristic . If we use the boundary values ​​of 3V and 5V, then the dynamic losses change almost one and a half times.

Accordingly, my recommendation is that you can and should consider the dynamics, especially despite the fact that the Power Stage Designer Tool allows you to do this quite quickly. However, the data obtained must be used as estimates and confirmed by tests.

Capacitor Calculator


There are two tabs in this calculation. The first is Capacitor Current Sharing . Here you can calculate the effective currents of capacitors when they are connected in parallel. It is useful when several capacitors of different capacities and with different ESRs are installed at the converter output and it is necessary to determine what proportion of current ripples each of them will take upon itself.


The second is Bulk Capacitor for AC / DC Power Supplies . In it, you can calculate the required capacity at the input of the converter. It is assumed that there is no active KKM, that is, at the input after the rectifier, a storage capacitor is immediately installed.


Calculation of damping chains "Snubber Calculator"


There are also two independent tabs in this calculation. The first is “RC-Snubber for Rectifiers” , which allows you to calculate the values ​​of the elements of the damper RC-circuit of the rectifier.

I will demonstrate in practice how this works. At my fingertips was the board of one of my developments - a power supply for a PLC, IP power 25 W, topology - a return path. As rectifier diodes, MURD620 used two pieces in parallel. So, we completely remove the damper circuit from the output rectifier diodes and see this form of voltage:


As can be seen from the waveform, there is no surge at the maximum reverse voltage, but there are fluctuations after the end of the current output by the secondary winding (the converter operates in intermittent current mode). Let's see if it is possible to suppress these fluctuations using the technique of this utility.

Stretched to measure the oscillation frequency:


It can be seen that the period is 575 ns, which corresponds to a frequency of 1.74 MHz. Now we add a 470pF capacitor parallel to the output diodes. Where does this meaning come from? The description of the technique says that you need to take a capacitance several times higher than the capacitance of the diode transition. In this case, the oscillations occur at almost zero voltage, respectively, according to the dependence of the capacitance on the voltage (from the datasheet to the diode) we get the value 50pF, I have two diodes, the total capacitance is 100pF, we multiply this value by five. I took a 470pF capacitor from what was at hand. By the way, it is imperative that the class of dielectric of the capacitor be NP0, or, in extreme cases, X7R.

We look at the shape of the voltage:


The oscillation period has changed, similarly by stretching the waveform, we measure a period of 875 ns, which corresponds to a frequency of 1.14 MHz.


Enter the obtained values:


In accordance with the recommendations of the utility, I installed a damping RC circuit with ratings of 1000pF, 250Ω. The following form of voltage was obtained:


It can be seen that the oscillations were suppressed. Of course, you still need to check how much power is dissipated in the resistor, but that's another story.

The second tab is “RCD-Snubber for Flyback Converters” . In it, you can count the clamper RCD circuit for a flyback converter.


Calculation of parameters of output voltage stabilization circuits “Output Voltage Scaling”


On the “Output Voltage Resistor Divider” tab , you can calculate the parameters of the resistor divider of the output voltage stabilization circuit. Moreover, it is possible to indicate from which row the resistors E24, E48 or E96 should be selected. It is also possible to set the permissible deviation of the reference voltage source.


On the “Dynamic Analog Output Voltage Scaling” tab, a similar circuit is calculated, but for the case of regulating the output voltage by an analog signal.


And the third tab in this section is “Dynamic Digital Output Voltage Scaling” . Allows you to calculate a set of resistors to control the output voltage of discrete signals.


Unit Converter



Well, I think there are no comments here.

Conclusion


Utility Power Stage Designer, like any other tool is designed to solve a certain range of tasks. Do not think that it will make anyone a professional developer of power electronics in no time. Without an understanding of the processes occurring in the circuit, this is hardly possible. Nevertheless, the capabilities of the program can significantly simplify the life of the developer. For example, I use this tool for preliminary calculation and selection of the converter topology. You can spend just a few minutes to calculate the currents and voltages on the elements, estimate losses, evaluate the applicability of the topology. This does not negate the fact that the next step is to make a full, more detailed calculation.

I hope you find this short review useful. The utility is available on the Texas Instruments website.
Interesting developments!

Power is cool. Deal with it.

More articles:


All Articles