To regulate the rotation speed of low-power brush-type electric motors, a resistor is usually used, which is connected in series with the motor. But this connection method provides very low efficiency, and most importantly, does not allow for smooth adjustment of speed (finding a variable resistor of sufficient power for several tens of Ohms is not at all easy). And the main disadvantage of this method is that sometimes the rotor stops when the supply voltage decreases.
PWM regulators, which will be discussed in this article, allow for smooth adjustment of speed without the disadvantages listed above. In addition, PWM controllers can also be used to adjust the brightness of incandescent lamps.
Figure 1 shows a diagram of one of these PWM controllers. Field-effect transistor VT1 is a sawtooth voltage generator (with a repetition frequency of 150 Hz), and the operational amplifier on the DA1 chip works as a comparator that generates a PWM signal based on transistor VT2. The rotation speed is controlled by a variable resistor R5, which changes the width of the pulses. Due to the fact that their amplitude is equal to the supply voltage, the electric motor will not “slow down”, and in addition, it is possible to achieve a slower rotation than in normal mode.
The circuit of PWM regulators in Fig. 2 is similar to the previous one, but the master oscillator here is made using an operational amplifier (op-amp) DA1. This op-amp functions as a triangular voltage pulse generator with a repetition rate of 500 Hz. Variable resistor R7 allows for smooth rotation adjustment.
In Fig.3. A very interesting regulator circuit is presented. This PWM regulator made on integral timer NE555. The master oscillator has a repetition frequency of 500 Hz. The duration of the pulses, and therefore the rotor speed of the electric motor, can be adjusted in the range from 2 to 98% of the repetition period. Generator output PWM regulator on NE555 timer connected to a current amplifier made on transistor VT1 and actually controls the electric motor M1.
The main disadvantage of the schemes discussed above is the lack of elements for stabilizing the shaft speed when the load changes. But the following diagram, shown in Fig. 4, will help solve this problem.
This PWM regulator, like most similar devices, has a master voltage pulse generator of a triangular shape (repetition frequency 2 kHz), made on DA1.1.DA1.2, a comparator on DA1.3, an electronic switch on transistor VT1, as well as a pulse duty cycle regulator , and essentially the rotational speed of the electric motor is R6. A feature of the circuit is the presence of positive feedback through resistors R12, R11, diode VD1, capacitor C2, and DA1.4, which ensures a constant rotational speed of the electric motor shaft when the load changes. When connected PWM regulator to a specific electric motor, using resistor R12, the POS depth is adjusted, at which self-oscillations of the rotation speed do not occur when the load on the motor shaft increases or decreases.
Element base. In the circuits presented in the article, the following analogues of parts can be used: the KT117A transistor can be replaced with a KT117B-G or, as an option, with a 2N2646; KT817B - KT815, KT805; microcircuit K140UD7 to K140UD6, or KR544UD1, TL071, TL081; timer NE555 on S555, or KR1006VI1; chip TL074 to TL064, or TL084, LM324. If you need to connect a more powerful load to the PWM controller, the KT817 key transistor must be replaced with a more powerful field-effect transistor, alternatively, IRF3905 or similar. The specified transistor is capable of passing currents up to 50A.
Such a PWM controller can be used to control powerful loads, including low-voltage electric motors. Today I will try to make a small superficial review of this miracle module and show the main parts and principle of operation.
Naturally made in China, it’s a pity that many components on the board are worn out, although it’s clear what’s what.
The PWM regulator provides smooth power adjustment, the output voltage range is 10-50 Volts, which has been tested repeatedly. The maximum current is up to 60 Amps, and this makes it possible to use such a board to control (adjust) the speed of electric cars, scooters or bicycles. The module is specifically designed for such purposes due to the presence of quenching diodes, which are designed to protect field switches from motor self-induction. For those who want to purchase this product, here is the link
The board has 12 three-pin components in a TO220 package, each with its own heat sink, 4 of which are diodes, and the remaining 8 are field-effect transistors.
Chinese engineers have erased a lot on the board, including the field workers (or rather, they have no markings at all).
There is a master oscillator, at the output of which a divider is installed. Thus, two similar signals are received that are sent to the diver, and there are two of them.
Each driver controls a line of field switches (4 pieces); as a result, the power outputs of all field switches are connected in parallel.
The circuit is very well thought out, but the Chinese did not take into account one thing - there is no short circuit protection at the output.
In general, this is the second similar module I have, in the first version a low-resistance shunt was installed - a conversation with the seller confirmed that this is a current shunt from which readings are taken for the protection system, i.e. a drop is recorded on this particular shunt, but when the board arrived I I was shocked - there is a shunt, but the components of the protection circuit are simply not installed on the board, so the shunt plays the role of a banal jumper, as a result, this board burned out in an instant.
And the plateau we are talking about today is still alive and well, but again, it is very vulnerable due to the lack of protection.
In terms of the schematic part, everything is standard - a powerful PWM speed regulator for the engine, it is important not to exceed the maximum permissible input voltage (50 Volts max), otherwise the stabilizer circuit, which provides power to the PWM microcircuit and driver, will burn out.
You can also adjust the brightness of halogen lamps and other passive loads without any problems. I checked the regulator under a load of 30 Amps, the keys were barely warm, despite the small heat sinks, although this was to be expected, because PWM control is much more efficient than linear control.
You can adjust the supply voltage level using regulators with pulse width modulation. The advantage of this setting is that the output transistor operates in switch mode and can only be in two states - open or closed, which eliminates overheating, which means the use of a large radiator and, as a result, reduces energy costs.
A multivibrator with an adjustable duty cycle is built on VT1 and VT2. The repetition frequency of which is about 7 kHz. From the collector of the second transistor, pulses go to a powerful switching transistor MOSFET N302AP, which controls the connected load. The duty cycle is changed by trimming resistance R4. At the extreme left position of this resistance, see the top figure, the output pulses are narrow, which indicates a minimum output power. In the extreme right position, the device operates at maximum power.
As a load, you can connect incandescent lamps (including 12 volt ones), DC electric motors to the regulator, and even regulate the current in the charger.
The design is very simple, and if installed correctly, they begin to work immediately. As a control key, as in the previous case, a powerful field-effect n-channel transistor is used.
If you suddenly need to regulate the voltage on a load, one of the contacts of which is connected to ground (this happens in a car), then a circuit is used in which the drain of an n-channel field-effect transistor is connected to the plus of the power supply, and the load is connected to the source.
It is convenient to regulate the supply voltage of powerful consumers using regulators with pulse-width modulation. The advantage of such regulators is that the output transistor operates in switch mode, which means it has two states - open or closed. It is known that the greatest heating of the transistor occurs in a half-open state, which leads to the need to install it on a large area radiator and save it from overheating.
I propose a simple PWM regulator circuit. The device is powered from a 12V constant voltage source. With the specified instance of the transistor, it can withstand current up to 10A.
Let's consider the operation of the device: A multivibrator with an adjustable duty cycle is assembled on transistors VT1 and VT2. The pulse repetition rate is about 7 kHz. From the collector of transistor VT2, pulses are sent to key transistor VT3, which controls the load. The duty cycle is regulated by variable resistor R4. When the slider of this resistor is in the extreme left position, see the top diagram, the pulses at the output of the device are narrow, which indicates the minimum output power of the regulator. In the extreme right position, see the bottom diagram, the pulses are wide, the regulator operates at full power.
Diagram of PWM operation in KT1
Using this regulator, you can control 12 V household incandescent lamps, a DC motor with an insulated housing. If the regulator is used in a car, where the minus is connected to the body, the connection should be made through a pnp transistor, as shown in the figure.
Details: Almost any low-frequency transistors can operate in the generator, for example KT315, KT3102. Key transistor IRF3205, IRF9530. We can replace the pnp transistor P210 with KT825, and the load can be connected to a current of up to 20A!
And in conclusion, it should be said that this regulator has been working in my car with an interior heating engine for more than two years.
List of radioelements
| Designation | Type | Denomination | Quantity | Note | Shop | My notepad |
|---|---|---|---|---|---|---|
| VT1, VT2 | Bipolar transistor | KTC3198 | 2 | To notepad | ||
| VT3 | Field-effect transistor | N302AP | 1 | To notepad | ||
| C1 | Electrolytic capacitor | 220uF 16V | 1 | To notepad | ||
| C2, C3 | Capacitor | 4700 pF | 2 | To notepad | ||
| R1, R6 | Resistor | 4.7 kOhm | 2 | To notepad | ||
| R2 | Resistor | 2.2 kOhm | 1 | To notepad | ||
| R3 | Resistor | 27 kOhm | 1 | To notepad | ||
| R4 | Variable resistor | 150 kOhm | 1 | To notepad | ||
| R5 | Resistor |
Another electronic device with wide application.
It is a powerful PWM (PWM) controller with smooth manual control. It operates at a constant voltage of 10-50V (it is better not to go beyond the range of 12-40V) and is suitable for regulating the power of various consumers (lamps, LEDs, motors, heaters) with a maximum current consumption of 40A.
Sent in a standard padded envelope 
The case is held together with latches that break easily, so open it carefully. 
Inside the circuit board and the removed regulator knob 
The printed circuit board is double-sided fiberglass, soldering and installation are neat. Connection via a powerful terminal block. 
Ventilation slots in the case are ineffective, because... almost completely covered by the printed circuit board. 
When assembled it looks something like this 
The actual dimensions are slightly larger than stated: 123x55x40mm
Schematic diagram of the device 
The declared PWM frequency is 12kHz. The actual frequency varies in the range of 12-13kHz when adjusting the output power.
If necessary, the PWM operating frequency can be reduced by soldering the desired capacitor in parallel with C5 (initial capacitance 1nF). It is not advisable to increase the frequency, because switching losses will increase.
The variable resistor has a built-in switch in the leftmost position that allows you to turn off the device. There is also a red LED on the board that lights up when the regulator is operating.
For some reason, the markings on the PWM controller chip have been carefully erased, although it’s easy to guess that it’s an analogue of NE555 :)
The regulation range is close to the stated 5-100%
Element CW1 looks like a current stabilizer in the diode body, but I’m not sure exactly...
As with most power regulators, regulation is carried out via the negative conductor. There is no short circuit protection.
There are initially no markings on the mosfets and diode assembly; they are located on individual radiators with thermal paste.
The regulator can operate on an inductive load, because At the output there is an assembly of protective Schottky diodes, which suppresses the self-induction EMF.
A test with a current of 20A showed that the radiators heat up slightly and can draw more, presumably up to 30A. The measured total resistance of the open channels of field workers is only 0.002 Ohm (drops 0.04V at a current of 20A).
If you reduce the PWM frequency, you will pull out all the declared 40A. Sorry I can't check...
You can draw your own conclusions, I liked the device :)
I'm planning to buy +56 Add to favorites I liked the review +38 +85
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