Pros and cons of multiphase switching voltage regulators for processors. World of PC Peripherals

Microprocessors are the most powerful energy consumers in the world. modern computers. The current consumption of a modern microprocessor can reach several tens of amperes. At the same time, the quality of the supply voltage to the microprocessor is the most important factor determining the stability of the entire system. About how producers motherboards solve the problem of providing the microprocessor with powerful and high-quality power, as described in the article brought to your attention.

Preamble

The clock frequency of microprocessors is steadily increasing and now reaches several GHz. Promotion clock frequency microprocessor is accompanied by a significant increase in power consumption, and, accordingly, leads to an increase in the temperature of the processor crystal. In addition, the power consumption of microprocessors is also influenced by an increase in the number of transistors on its chip (than more modern processor, the higher the degree of integration it has). Although CMOS transistors, which form the basis of microprocessors, consume scanty currents when they are off, when we are talking about several million transistors located on the processor chip, this can no longer be neglected. The main energy consumption of CMOS transistors occurs at the moment of its switching on, and, naturally, the more often the transistors switch, the large quantity they consume energy. As a result, millions of transistors switching from high frequency, are capable of ensuring that the microprocessor consumes such a current, the value of which already reaches 50 amperes or more. Thus, the processor crystal begins to heat up greatly, which leads to a significant deterioration in the switching processes of transistors and can damage them. However, it is not possible to solve the problem solely by heat removal.

All this forces manufacturers to reduce the supply voltage of microprocessors, or more precisely, the supply voltage of its core. Reducing the supply voltage can solve the problem of power dissipated on the microprocessor chip and lower its temperature. If the very first microprocessors of the 80x86 family had a supply voltage of +5V (and the voltage reduction to +3.3V was first used in the I80486), then microprocessors of the latest generations can already operate with a supply voltage of +0.5V (see VR11 specification from Intel).

But the thing is that such low voltage are not generated by the system power supply. Let us remember that at its output only voltages of +3.3V, +5V and +12V are formed. Thus, the motherboard must have its own voltage regulator capable of lowering these “high-voltage” voltages to the level necessary to power the processor core, i.e. up to a value of 0.5 – 1.6 V (Fig.1).

Fig.1

Since this regulator provides conversion of DC voltage +12V to constant pressure, but of a lower value, the regulator is called DC-DC Converter (converter direct current to direct current). I would like to draw the attention of all specialists that the processor core voltage is now generated from a voltage of +12V, and not from +5V or +3.3V, as it might seem more logical. The fact is that the voltage of the +12V channel is the highest, and therefore it is possible to create significantly more power with a lower current value. Thus, in modern computing systems the most important voltage becomes +12V, and it is in this channel that the largest currents flow. This, by the way, is reflected in the standards describing the requirements for system units power supply, according to which the load capacity of the +12V channel is maximum. In addition, the power supply output must have two +12V voltage channels (+12V1 and +12V2), and the current in each of these channels must be controlled independently. One of these channels, namely +12V2, is designed specifically to power the processor core, and it is subject to the most stringent requirements for stability and the smallest tolerances for deviations from the nominal value.

It is also necessary to note the following point. Since the power consumed by processors is quite large (can reach almost 100 W), voltage conversion must be carried out using a pulse method. Linear conversion is not capable of providing a sufficiently high efficiency at such power, and will lead to significant losses, and therefore to heating of the converter elements. Today, only pulse conversion makes it possible to obtain an efficient and economical power source with small dimensions and an acceptable cost of implementation. Thus, on the motherboard there is a DC-DC Converter, which is a step-down pulse converter (Step Down or Trim).

DC-DC Converter Buck Type

A basic DC-DC buck converter circuit is shown in Fig.2. I would like to note that regulators of this type in modern imported literature are called Buck Converter or Buck Regulator. Transistor Q1 in this circuit is a switch that, when closed/opened, creates a pulse voltage from a direct voltage.

Fig.2

In this case, the amplitude of the generated pulses is 12V. To improve conversion efficiency, Q1 must switch at a high frequency (the higher the frequency, the more efficient the conversion). IN real circuits motherboard regulators, the switching frequency of the converter transistors can be in the range from 80 kHz to 2 MHz.

Next, the resulting pulse voltage is smoothed by inductor L1 and electrolytic capacitor C1. As a result, a constant voltage is created at C1, but of a smaller magnitude. In this case, the magnitude of the created DC voltage will be proportional to the width of the pulses received at output Q1. If Q1 is turned on for a longer time, then the energy stored in L1 will also be greater, which ultimately causes the voltage across C1 to increase. Accordingly, and vice versa - with a shorter duration of the open state of transistor Q1, the voltage on C1 decreases. This method of direct voltage regulation is called pulse width modulation - PWM (Pulse Width Modulation).

A very important element of the circuit is diode D1. This diode maintains the load current generated by inductor L1 during those periods of time when transistor Q1 is closed. In other words, when Q1 is open, the inductor current and load current are provided by the power source, and energy is stored in the inductor. After transistor Q1 turns off, the load current is maintained by the energy stored in the inductor. This current flows through D1, i.e. the inductor energy is spent to maintain the load current ( see fig.3).

Fig.3

However, practical buck regulator circuits that generate high currents present some problems. The fact is that most diodes do not operate sufficiently fast, and also have a relatively high open resistance p-n junction. All this is not decisive at low load currents. But at high currents, all this leads to significant losses, strong heating of diode D1, voltage surges and the occurrence of reverse currents through the diode when switching transistor Q1. That is why this scheme was modified to increase performance and reduce losses, as a result of which another transistor was used instead of diode D1 - Q2 (Fig.4).

Fig.4

Transistor Q2, being a MOSFET, has a very low on-resistance and high operating speed. Since Q2 performs the function of a diode, it operates synchronously with Q1, but strictly in antiphase, i.e. at the moment Q1 is closed, transistor Q2 opens, and, conversely, when Q1 is open, transistor Q2 is closed (see Fig. 5).

Fig.5

This is the only possible solution for organizing voltage converters on modern motherboards, where, as we have already said, very high currents are required to power the processor.

Having completed the review of the basic technologies for organizing switching voltage regulators, we move on to considering practical schemes for their implementation.

Fundamentals of organizing processor core voltage regulators

It’s worth mentioning right away that quite a long time ago, component manufacturers began producing specialized microcircuits designed for building switching voltage regulators on motherboards personal computers. The use of such specialized microcircuits makes it possible to improve the characteristics of regulators, ensure their high compactness and reduce the cost of both the regulators themselves and the cost of their development. Today, there are three types of microcircuits used in voltage regulators on motherboards designed to power the processor core:

- the main controller (Main Controller), which is also called a PWM controller (PWM-Controller) or a voltage regulator (Voltage Regulator);

- driver for controlling MOS transistors (Synchronous-Rectifier MOSFET Driver);

- a combined controller that combines the functions of both a PWM controller and a MOS transistor driver.

Taking into account the variety of microcircuits used, in modern motherboards we can find two main options for constructing switching voltage regulators to power the processor core.

I option. This option is typical for use in motherboards entry level, characterized by low productivity, i.e. it is most often used on motherboards that do not provide for the use of high-performance and powerful processors. In this embodiment, the power transistors of the converter are controlled by a combined controller microcircuit. This chip provides the following functions:

- reading the state of the processor supply voltage identification signals (VIDn);

- generation of PWM signals for synchronous control of power MOS transistors;

- control of the value of the generated supply voltage;

- implementation of current protection of power MOS transistors;

- generation of a signal confirming correct work regulator and the presence at its output of the correct voltage to power the processor core (PGOOD signal).

An example of such a voltage regulator option is presented in Fig.6. In this case, as we see, the power transistors are directly connected to the outputs of the combined controller chip. The HIP6004 chip was often used as such a controller.

Fig.6

Option II. This option is typical for motherboards designed to work with high-performance processors. Since a high-performance processor requires the consumption of high currents, the voltage regulator is made multi-channel (Fig. 7).

Fig.7

The presence of several channels allows you to reduce the current value of each channel, i.e. reduce the currents switched by MOS transistors. This, in turn, increases the reliability of the entire circuit and allows the use of less powerful transistors, which has a positive effect on the cost of both the regulator itself and the motherboard as a whole.

This version of the regulator is characterized by the use of two types of microcircuits: the main PWM controller and MOS transistor drivers. Synchronous control of MOS transistors is carried out by drivers, each of which can control either one or two pairs of transistors. The driver ensures antiphase switching of transistors in accordance with the input signal (most often denoted PWM), which determines the switching frequency and the open time of the transistors. The number of driver chips corresponds to the number of switching regulator channels.

All drivers are controlled by the Main Controller, the main functions of which include:

-generating pulses to control MOS transistor drivers;

- changing the width of these control pulses in order to stabilize the output voltage of the regulator;

- control of the output voltage of the regulator;

- ensuring current protection of MOS transistors;

- reading the state of the processor supply voltage identification signals (VIDn).

In addition to these functions, other auxiliary functions can be performed, the presence of which will be determined by the type of main controller used.

The general diagram of such a voltage regulator is presented in Fig.8. Most modern main controllers are 4-channel, i.e. have 4 PWM output signals to control transistor drivers.

Fig.8

So, at the current time, voltage regulators for the processor core can be 2-channel, 3-channel and 4-channel.

An example of the implementation of a 2-channel regulator is presented at Fig.9. This regulator is built using a Main Controller chip of the HIP6301 type, which, in principle, is four-channel, but two channels remain unused.

Fig.9

HIP6601B chips are used as key drivers in this circuit.

An example of the implementation of a 4-channel regulator using the same Main Controller is presented at Fig.10.

Fig.10

The HIP6301 controller decodes the processor core voltage taking into account the 5-bit identification code (VID0 - VID4) and generates output PWM pulses with a frequency of up to 1.5 MHz. In addition, it generates the PGOOD (good power) signal if the processor core voltage generated by the voltage regulator matches the value set using the VIDn signals.

Features of multi-channel regulators

When using multi-channel voltage regulators, there are several problems that motherboard developers have to solve. The fact is that each channel is a pulse regulator, which, switching at a high frequency, creates current pulses at its output. These pulses, naturally, must be smoothed out, and electrolytic capacitors and chokes are used for this. But the fact is that due to the high current load, the capacitance of the capacitors and the inductance of the chokes are still not enough to create a truly constant voltage, as a result of which ripples are observed on the processor power bus (Fig. 11). Moreover, neither an increase in the number of capacitors, nor an increase in the capacitor capacity and inductance of the chokes, nor an increase in the conversion frequency (unless we are talking about increasing the frequency several times) can save you from these ripples. Naturally, these ripples can lead to unstable operation of the processor.

Fig.11

A way out of the problem was found in the use of a multichannel voltage regulator architecture. But it will still not be possible to solve the problem just by using several parallel channels. It is necessary to make sure that the keys of different channels switch with a phase shift, i.e. they should open one after the other. This will make it possible for each channel to maintain the output current of the regulator for a strictly designated period of time. In other words, the smoothing capacitors will be recharged constantly, but from different channels at different times. So, for example, when using a 4-channel regulator, the output capacitors are recharged four times during one clock period of the controller, i.e. pulse currents of individual channels are shifted in phase relative to each other by 90° (see Fig. 12). This corresponds to an increase in the conversion frequency by 4 times, and if the switching frequency of the transistors of each channel is 0.5 MHz, then the pulse frequency on the smoothing capacitor will already be 2 MHz.

Fig.12

Thus, PWM pulses that are generated at the output of the main controller microcircuit (PWM output signals) must follow a certain phase shift and this phase shift is determined by the internal architecture of the microcircuit and is set, as a rule, already at the design stage of the microcircuit. But some controllers allow you to configure them for different operating modes: 2-phase, 3-phase or 4-phase control (how this is done can be found in the descriptions of the controllers themselves).

Distinctive features:

  • Smallest Dual Boost Converter: 16-pin QSOP
  • Efficiency 90%
  • Start with 1.5V power supply
  • Maximum total current consumption 85 µA
  • Current consumption in shutdown mode 1 µA
  • Separate shutdown inputs
  • Drives two N-channel surface mount MOSFETs
  • Low battery detection comparator input and output
  • Can be used as a boost or buck converter

Areas of use:

  • Portable equipment with 2- and 3-cell power supply
  • Organizers
  • Electronic translators
  • Portable, portable instrumentation
  • Laptop computers
  • Personal digital assistants (PDAs)
  • Dual power supplies (logic and LCD power supply)

Typical connection diagram:

Pin locations:

Description of pins:

SENSE1 Entrance feedback converter 1 in fixed output voltage mode
VDD Supply voltage input
BOOT Boost generator enable input for starting at 1.5 V supply
FB1, FB2 Feedback and preset voltage selection inputs
EXT1, EXT2 Driver outputs
PGND High current general
GND General
CS1, CS2 Current control comparator inputs
SHDN1, SHDN2 Shutdown inputs
LBI Battery discharge control comparator input (threshold 1.25V)
REF Reference voltage output
LBO Battery discharge control comparator output

Description:

The MAX863 is a dual-output DC-DC converter that contains two independent boost controllers in one compact package. The IC is made using Bi-CMOS technology and consumes only 85 μA when both controllers are operating. The minimum input supply voltage is 1.5V, which allows this IC to be used in organizers, translators and other low-power portable equipment. MAX863 provides efficiency conversion 90% at load current from 20 mA to 1A. This small-sized IC is available in 16-pin. QSOP package, which occupies the same dimensions as the 8-pin. SOIC package.

The IC uses a current-limiting pulse-frequency modulation architecture, which is characterized by low startup current surges and low current consumption, thereby providing high efficiency. conversion to wide range loading. Each controller controls a low-cost, external, N-channel MOSFET that is sized optimized for any output current and voltage.

In higher-power systems, two MAX863s can be used to generate 5V, 3.3V, 12V, and 28V voltages using only two or three batteries as a power source. To speed up design timelines, the MAX863EVKIT evaluation kit is available. If a single output controller is required, see the MAX608 and MAX1771 documentation.

The device has a menu. Entering the menu, moving in it and exiting is carried out by simultaneously pressing the “H” and “B” buttons. During this process, the corresponding mnemonic appears on the indicator, “H-U”, “B-U” (lower and upper voltage limits), “H-I”, “B-I” (lower and upper current limits), “P-0”, “P-1” - manual or automatic mode, turning on the relay after the voltage or current returns to the specified limits. “-З-” signals that the set parameters are being written to non-volatile memory and exiting the menu mode. In menu mode, the “H” and “B” buttons allow you to change parameters in one direction or another, and holding the button for about 3 seconds speeds up the parameter change. The change occurs in a circle, 99.8-99.9-0.0-0.01, etc. When the set limits are exceeded, the relay is switched off and the indicator begins to flash, signaling an accident. That. The device allows you to both charge and discharge the battery to a certain voltage. Moreover, auto mode allows you to keep the battery constantly charged, and manually control the battery capacity, in A/hours.

A few notes. Don't forget to power 74HC595, 16N - +5V, 8N - ground. It is better to use a pair of resistors 3K3 and 10K on the buttons. The polarity of the indicator does not matter; it is selected by a resistor on the 11th leg of the controller (as in the diagram).

Application example for charge/discharge battery:

Hex file for the PIC16F676 microcontroller, with control functions.
You do not have access to download files from our server- firmware file for a voltmeter with parameters Umax=99.9V; Imax=9.99A; Pmax=99.9/999 W; Cmax=9.99 A/h.
You do not have access to download files from our server- hex_file of a voltammeter with truncated functions, only Umax=99.9V and Imax=9.99A

With this lesson I begin a series of articles devoted to switching stabilizers, digital regulators, and output power control devices.

The goal I set is to develop a controller for a refrigerator based on a Peltier element.

We will make an analogue of my development, only implemented on the basis of an Arduino board.

  • This development interested many people, and I received letters asking me to implement it on Arduino.
  • Development is ideal for learning hardware and software digital regulators. In addition, it combines many tasks studied in previous lessons:
    • measurement of analog signals;
    • working with buttons;
    • connection of display systems;
    • temperature measurement;
    • work with EEPROM;
    • connection with a computer;
    • parallel processes;
    • and much more.

I will carry out the development sequentially, step by step, explaining my actions. I don’t know what the result will be. I hope for a full working project of a refrigerator controller.

I don't have a finished project. I will write lessons based on the current state, so during testing it may turn out that at some stage I made a mistake. I will fix it. This is better than me debugging the development and producing ready-made solutions.

Differences between development and prototype.

The only thing functional difference from the development prototype on a PIC controller is the lack of a fast voltage stabilizer that compensates for supply voltage ripples.

Those. this option The device must be powered from a stabilized power source with a low ripple level (no more than 5%). All modern impulse blocks nutrition.

And the option of power supply from an unstabilized power supply (transformer, rectifier, capacitive filter) is excluded. The speed of the Arduino system does not allow implementing a fast voltage regulator. I recommend reading about the power requirements of the Peltier element.

Development of the general structure of the device.

At this stage you need to understand in general terms:

  • what elements the system consists of;
  • on which controller to perform it;
  • are there enough conclusions and functionality controller.

I imagine the controller as a “black box” or “garbage pit” and connect everything I need to it. Then I see if, for example, the Arduino UNO R3 board is suitable for these purposes.

In my interpretation it looks like this.

I drew a rectangle - the controller and all the signals necessary to connect the system elements.

I decided that I needed to connect to the board:

  • LCD indicator (to display results and modes);
  • 3 buttons (for control);
  • error LED;
  • fan control key (to turn on the hot side radiator fan);
  • pulse stabilizer key (to adjust the power of the Peltier element);
  • analogue load current measurement input;
  • analogue load voltage measurement input;
  • temperature sensor in the chamber (precise 1-wire sensor DS18B20);
  • radiator temperature sensor (haven’t decided which sensor yet, most likely also DS18B20);
  • computer communication signals.

There were 18 signals in total. The Arduino UNO R3 or Arduino NANO board has 20 pins. There are still 2 conclusions left in reserve. You might want to connect another button, or an LED, or a humidity sensor, or a cold side fan... We need 2 or 3 analog inputs, the board has 6. That is. everything suits us.

You can assign pin numbers immediately or during development. I made an appointment right away. The connection is made through connectors, you can always change them. Please note that pin assignments are not final.

Pulse stabilizers.

To accurately stabilize the temperature and operate the Peltier element in optimal mode, it is necessary to regulate the power on it. Regulators can be analog (linear) and pulse (key).

Analog regulators are a regulating element and a load connected in series to a power source. By changing the resistance of the regulating element, the voltage or current on the load is adjusted. As a rule, a bipolar transistor is used as a regulating element.

The control element operates in linear mode. It produces “extra” power. At high currents, stabilizers of this type get very hot and have low efficiency. Typical linear stabilizer voltage is the 7805 chip.

This option does not suit us. We will make a pulse (key) stabilizer.

Switching stabilizers are different. We need a buck switching regulator. The load voltage in such devices is always lower than the supply voltage. The circuit of a step-down switching regulator looks like this.

And this is a diagram of the regulator operation.

Transistor VT operates in key mode, i.e. it can only have two states: open or closed. The control device, in our case a microcontroller, switches the transistor with a certain frequency and duty cycle.

  • When the transistor is open, current flows through the circuit: power supply, transistor switch VT, inductor L, load.
  • When the key is open, the energy accumulated in the inductor is supplied to the load. Current flows through the circuit: inductor, VD diode, load.

Thus, the constant voltage at the output of the regulator depends on the ratio of the time of the open (topen) and closed switch (tclose), i.e. on the duty cycle of control pulses. By changing the duty cycle, the microcontroller can change the voltage across the load. Capacitor C smoothes out ripple in the output voltage.

The main advantage of this control method is high efficiency. The transistor is always in the open or closed state. Therefore, little power is dissipated on it - always either the voltage on the transistor is close to zero, or the current is 0.

This is a classic switching buck regulator circuit. In it, the key transistor is disconnected from the common wire. The transistor is difficult to control and requires special bias circuits to the supply voltage bus.

So I changed the scheme. In it, the load is separated from the common wire, but a key is attached to the common wire. This solution allows you to control a transistor switch from a microcontroller signal using a simple current driver-amplifier.

  • When the switch is closed, current flows into the load through the circuit: power supply, inductor L, switch VT (the current path is shown in red).
  • When the switch is open, the energy accumulated in the inductor is returned to the load through the regenerative diode VD (the current path is shown in blue).

Practical implementation of a key regulator.

We need to implement a pulse regulator node with the following functions:

  • the actual key regulator (key, choke, regenerative diode, smoothing capacitor);
  • load voltage measurement circuit;
  • regulator current measurement circuit;
  • hardware overcurrent protection.

I took the regulator circuit from .

Pulse regulator circuit for working with Arduino board.

I used IRF7313 MOSFET transistors as a power switch. In the article about increasing the power of the Peltier element controller, I wrote in detail about these transistors, about possible replacements and about the requirements for key transistors for this circuit. Here is the link to technical documentation.

A key MOSFET transistor driver is assembled on transistors VT1 and VT2. This is just a current amplifier; in terms of voltage, it even attenuates the signal to about 4.3 V. Therefore, the key transistor must be low-threshold. There are different options for implementing MOSFET transistor drivers. Including using integrated drivers. This option is the simplest and cheapest.

To measure the voltage across the load, a divider R1, R2 is used. With these values ​​of resistor resistance and a reference voltage source of 1.1 V, the measurement range is 0 ... 17.2 V. The circuit allows you to measure the voltage at the second load terminal relative to the common wire. We calculate the voltage at the load, knowing the voltage of the power source:

Uload = Usupply – Umeasured.

It is clear that the accuracy of the measurement will depend on the stability of the power supply voltage. But we do not need high accuracy in measuring voltage, current, or load power. We only need to accurately measure and maintain temperature. We will measure it with high accuracy. And if the system shows that the power is set at 10 W on the Peltier element, but in fact it is 10.5 W, this will not affect the operation of the device in any way. This applies to all other energy parameters.

The current is measured using a current sensor resistor R8. Components R6 and C2 form a simple low-pass filter.

The elements R7 and VT3 contain the simplest hardware protection. If the current in the circuit exceeds 12 A, then the voltage across resistor R8 will reach the transistor opening threshold of 0.6 V. The transistor will open and close the RES (reset) pin of the microcontroller to ground. Everything should turn off. Unfortunately, the threshold for operation of such protection is determined by the base-emitter voltage of the bipolar transistor (0.6 V). Because of this, the protection is triggered only at significant currents. You can use an analog comparator, but this will complicate the circuit.

The current will be measured more accurately as the resistance of the current sensor R8 increases. But this will lead to the release of significant power on it. Even with a resistance of 0.05 Ohm and a current of 5 A, resistor R8 dissipates 5 * 5 * 0.05 = 1.25 W. Note that resistor R8 has a power of 2 W.

Now what current are we measuring. We measure the current consumption of the switching regulator from the power supply. The circuit for measuring this parameter is much simpler than the circuit for measuring load current. Our load is “untied” from the common wire. For the system to operate, it is necessary to measure electrical power at the Peltier element. We will calculate the power consumed by the regulator by multiplying the power supply voltage by the current consumed. Let's assume that our regulator has an efficiency of 100% and decide that this is the power on the Peltier element. In fact, the efficiency of the regulator will be 90-95%, but this error will not affect the operation of the system in any way.

Components L2, L3, C5 – a simple radio interference filter. It may not be necessary.

Calculation of the choke of the key stabilizer.

The throttle has two parameters that are important to us:

  • inductance;
  • saturation current.

The required inductance of the inductor is determined by the PWM frequency and the permissible ripple of the inductor current. There is a lot of information on this topic. I will give the most simplified calculation.

We applied voltage to the inductor and the current through it began to increase. Increase, but did not appear, because some current was already flowing through the inductor at the moment I was turned on).


The transistor opened. The voltage is connected to the inductor:

Uchoke = Usupply – Uload.

The current through the inductor began to increase according to the law:

Ithrottle = Uthrottle * topen / L

  • topen – pulse duration public key;
  • L - inductance.

Those. the value of the inductor current ripple or how much the current has increased during the open key is determined by the expression:

Ioff – Ion = Uthrottle * topen / L

The load voltage may vary. And it determines the voltage at the throttle. There are formulas that take this into account. But in our case, I would take the following values:

  • supply voltage 12 V;
  • minimum voltage on the Peltier element 5 V;
  • This means the maximum voltage at the inductor is 12 – 5 = 7 V.

The duration of the public key pulse topen is determined by the frequency of the PWM period. The higher it is, the less inductance the inductor is needed. The maximum PWM frequency of the Arduino board is 62.5 kHz. I will tell you how to get this frequency in the next lesson. We will use it.

Let's take the worst case scenario - the PWM switches exactly in the middle of the period.

  • Period duration 1 / 62500 Hz = 0.000016 sec = 16 µs;
  • Public key duration = 8 µs.

Current ripple in such circuits is usually set to 20% of the average current. This should not be confused with output voltage ripple. They are smoothed out by capacitors at the output of the circuit.

If we allow a current of 5 A, then we will take a current ripple of 10% or 0.5 A.

L = Uchoke * topen / Ipulsation = 7 * 8 / 0.5 = 112 µH.

Inductor saturation current.

Everything in the world has a limit. And the throttle too. At some current it ceases to be an inductance. This is the saturation current of the inductor.

In our case, the maximum inductor current is defined as the average current plus ripple, i.e. 5.5 A. But it is better to choose the saturation current with a margin. If we want hardware protection to work in this version of the circuit, then it must be at least 12 A.

The saturation current is determined by the air gap in the inductor magnetic circuit. In articles about Peltier element controllers, I talked about the design of the inductor. If I start to expand on this topic in detail, we will leave Arduino, programming, and I don’t know when we will return.

My throttle looks like this.


Naturally, the inductor winding wire must be of sufficient cross-section. The calculation is simple - determining heat losses due to the active resistance of the winding.

Active winding resistance:

Ra = ρ * l / S,

  • Ra – active resistance of the winding;
  • Ρ – resistivity of the material, for copper 0.0175 Ohm mm2 / m;
  • l – winding length;
  • S – winding wire cross-section.

Heat losses at the active resistance of the inductor:

The key regulator consumes a fair amount of current from the power supply and this current should not be allowed to pass through the Arduino board. The diagram shows that the wires from the power supply are connected directly to the blocking capacitors C6 and C7.

The main pulse currents of the circuit pass through circuit C6, load, L1, D2, R8. This chain must be closed by bonds with a minimum length.

The common wire and power bus of the Arduino board are connected to blocking capacitor C6.

The signal wires between the Arduino board and the key stabilizer module must be of a minimum length. It is better to place capacitors C1 and C2 on the connectors for connecting to the board.

I assembled the circuit on a board. I soldered only the necessary components. My assembled circuit looks like this.

I set the PWM to 50% and checked the operation of the circuit.

  • When powered by a computer, the board generated a specified PWM.
  • When autonomously powered from an external power supply, everything worked great. Pulses with good edges were formed at the inductor, and there was a constant voltage at the output.
  • When I turned on the power from both the computer and the external power supply at the same time, my Arduino board burned out.

My stupid mistake. I’ll tell you so that no one repeats it. In general, connecting external unit You need to be careful when it comes to food, call all connections.

The following happened to me. There was no diode VD2 on the diagram. I added it after this trouble. I figured that the board could be powered from an external source via the Vin pin. He himself wrote in Lesson 2 that the board can receive power from an external source through the connector (RWRIN signal). But I thought it was the same signal, just on different connectors.

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