CN212183432U - PWM speed regulation circuit with overload protection and speed regulation device - Google Patents
PWM speed regulation circuit with overload protection and speed regulation device Download PDFInfo
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- CN212183432U CN212183432U CN201921794806.7U CN201921794806U CN212183432U CN 212183432 U CN212183432 U CN 212183432U CN 201921794806 U CN201921794806 U CN 201921794806U CN 212183432 U CN212183432 U CN 212183432U
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Abstract
The patent relates to the technical field of cooling fan control, and particularly discloses a PWM speed regulating circuit with overload protection, which is used for being connected between a PWM control signal and a fan and comprises a driving unit, a filtering unit, an output unit and an overload protection unit; the driving unit is used for intermittently outputting direct current amplified by current to the outside according to the duty ratio of the accessed PWM control signal so as to drive the fan; an output unit for inputting the direct current into the fan; the filtering unit is used for outputting and filtering the direct current; and the overload protection unit is connected between the negative electrode of the output unit and the driving unit and is used for monitoring the current intensity on the fan and controlling the driving unit to stop driving the fan if the current intensity is higher than the rated current intensity of the fan. The patent also discloses a PWM speed adjusting device, has the reduction consumption, improves the work efficiency of fan, guarantees the long-term reliable work's of equipment technical effect.
Description
Technical Field
The utility model relates to a consolidate quick-witted case technical field, specifically disclose a take overload protection's PWM speed governing circuit and speed adjusting device.
Background
With the development of electronic technology, the size of electronic devices is gradually reduced, but the efficiency is continuously increased, so that the heat dissipation problem of electronic devices is more and more serious. Therefore, the design technology of the heat dissipation fan installed in the electronic device, which mainly provides the heat dissipation function, becomes the most important point for the designer to study, and the design of the heat dissipation fan needs to be energy-saving and environment-friendly besides the heat dissipation problem, and the conversion efficiency of the circuit for controlling the heat dissipation fan is also the important point to be considered in the design. At present, the common heat dissipation modes such as air cooling, heat pipe and water cooling are adopted, and the heat dissipation effect is gradually reduced according to the water cooling, the heat pipe and the air cooling. Because of the complex heat pipe and water cooling process, high cost, etc., the air cooling mode is generally adopted in small and medium-sized equipment.
Air cooling is mainly to transfer heat to the surrounding environment (finally, to dissipate heat through air) through a fan, a heat sink and the like, so as to achieve the purpose of heat dissipation. The air cooling has the advantages of simple structure, lower cost compared with other heat dissipation methods, safety, reliability and mature technology; the disadvantages are noise, limited fan life, etc. In the prior art, an electronic device adopting air cooling heat dissipation generally starts a heat dissipation fan at the same time of starting the electronic device, and the heat dissipation fan is in a high-speed running state in the whole starting process; in fact, most of devices have the characteristic of intermittent work or load change, when the load is not connected or the load is light, the fan does not need to work or work at full speed, and the heat dissipation requirement can be met only by the low-speed operation of the radiating fins or the fan, so that a fan rotating speed control circuit is required to be additionally arranged on the fan to control the fan to accelerate the rotating speed when needed, the heat dissipation efficiency is improved, the rotating speed is reduced when not needed, the energy is saved, and the service life of the fan can be prolonged.
In the prior art, a linear series voltage-reducing circuit is mostly adopted in a fan rotating speed control circuit, and the circuit is characterized in that a voltage-adjustable element is connected in series between a fan and a power supply loop, when the voltage borne by the series element is high, the voltage distributed to the fan by the circuit is low, and the rotating speed of the fan is low; if the voltage to which the series element is subjected is low, the voltage that the circuit distributes to the fan is high and the fan speed is high. The current in the series circuit is equal, when the voltage on the fan is low, the voltage on the series element is high, the power consumed by the series element is equal to voltage multiplied by current, because the voltage is higher, the power consumed by the series element is also quite large, the working efficiency of the circuit is only less than 40%, the consumed power is mostly changed into thermal power, the reliability of the circuit is poor, the output load is also very small, so that the number of controllable fans is small, and generally the number of controllable fans cannot exceed 2.
SUMMERY OF THE UTILITY MODEL
The utility model provides a take overload protection's PWM speed governing circuit to PWM speed governing circuit loss power among the solution prior art is great, and the reliability of circuit is poor, the little technical problem of load of output.
The PWM speed regulating circuit with the overload protection is used for being connected between a PWM control signal and a fan and comprises a driving unit, a filtering unit, an output unit and an overload protection unit;
the driving unit is used for intermittently outputting direct current amplified by current to the outside according to the duty ratio of the accessed PWM control signal so as to drive the fan;
the positive end of the output unit is connected with the positive electrode of the fan, and the negative end of the output unit is connected with the negative electrode of the fan and used for inputting the direct current into the fan;
the filtering unit is connected between the driving unit and the anode of the output unit and is used for outputting and filtering the direct current;
and the overload protection unit is connected between the negative electrode of the output unit and the driving unit and is used for monitoring the current intensity on the fan and controlling the driving unit to stop driving the fan if the current intensity is higher than the rated current intensity of the fan.
Further, the driving unit comprises a PWM signal processing module and a power switch module;
the PWM signal processing module mainly comprises a first voltage comparator and a first N-channel field effect transistor, wherein the PWM signal is connected to the positive input end of the first voltage comparator through a protection resistor, the output of the first voltage comparator is connected to the grid electrode of the first N-channel field effect transistor through a divider resistor, and the grid electrode is also connected to a control signal sent by the overload protection unit;
the source electrode of the first N-channel field effect transistor is grounded, and the drain electrode of the first N-channel field effect transistor is used for outputting a switching signal outwards;
the negative input end of the first voltage comparator is used for being connected with feedback from the output end of the power switch module through a resistor R8;
the power switch module mainly comprises a P-channel field effect transistor, wherein the grid electrode of the P-channel field effect transistor is used for accessing the switch signal, the source electrode of the P-channel field effect transistor is used for connecting an external direct-current power supply, and the drain electrode of the P-channel field effect transistor is used for outputting current outwards; the source electrode and the grid electrode part are also connected with a protective resistor.
Further, the filtering unit comprises an inductor and two capacitors, the inductor is connected between the output end of the driving unit and the positive end of the output unit, and two ends of the inductor are grounded through one capacitor respectively.
Further, the output unit comprises a diode and an isolation capacitor which are connected in parallel between the positive terminal and the negative terminal, and the diode limits the current direction to only flow from the negative terminal to the positive terminal through the diode.
Further, the overload protection unit comprises a resistor R6 and a calculation module, wherein one end of the resistor R6 is connected with the negative electrode end of the output unit, and the other end of the resistor R6 is grounded;
the computing module is provided with a positive input end, a negative input end and an output end, the positive input end is connected to one end, connected with the output unit, of the resistor R6, and the negative input end is connected to one end, connected with the ground, of the resistor R6;
the computing module mainly comprises a second voltage comparator and a second N-channel field effect transistor;
the positive input end of the second voltage comparator is connected to one end of the resistor R6 output unit through a resistor R5, the negative input end of the second voltage comparator is connected to one end of the resistor R6 which is grounded through a resistor R7, and the negative input end is connected to a direct current power supply for calculation through a resistor R3;
the resistor R3 and the resistor R7 are used together to make the voltage on the negative input end be a constant voltage;
the magnitude of the constant voltage is the magnitude of the voltage across the resistor R6 plus the minimum identified voltage difference of the second voltage comparator when the current level across the fan is equal to the rated current;
the grid electrode of the second N-channel field effect transistor is connected to the output of the second voltage comparator through another divider resistor, the source electrode is grounded, and the drain electrode outputs a control signal outwards.
Further, the rated current is 1A, the direct current power supply for calculation is a voltage source of 5V, the resistance values of the resistor R5 and the resistor R7 are 1K Ω, the resistance value of the resistor R6 is 0.22 Ω, and the resistance value of the resistor R3 is 22K Ω.
Further, the capacitor is a surface-mounted polar capacitor, the capacitance value is 100 muH, and the rated voltage is 25V;
the inductance value of the inductor is 2.2 muH, and the rated current is 3A.
The utility model discloses under the condition of establishing the adjustable component of series connection voltage on power supply loop, utilize output "duty cycle" ingeniously to realize the rotational speed control to radiator fan, avoided the fan unnecessary rotation when low temperature, reduced unnecessary running noise effectively to the effectual life who prolongs the fan. The utility model discloses just, faced the voltage adjustable element of series connection on power supply circuit, reduced power loss greatly, in addition, the overload protection unit is added to this embodiment, and the heavy current that produces in the twinkling of an eye when can effectively stopping the stifled commentaries on classics of fan or short circuit burns out drive unit, can directly reduce the fault rate, reduces equipment cost of maintenance, and this circuit is with low costs, simple structure, very be suitable for the practicality.
The utility model also provides a PWM speed regulating device, which comprises the PWM speed regulating circuit with overload protection, a MCU and a temperature sensor;
the input end of the PWM speed regulating circuit is connected to the PWM signal output end of the MCU processor, and the output end of the PWM speed regulating circuit is connected with the fan;
and the temperature sensor is connected to the temperature signal input end of the MCU.
Will the utility model provides an among the PWM speed adjusting device, PWM speed adjusting circuit is connected to the PWM signal output part of MCU treater, and cooperation temperature sensor uses and can reach more accurate rotational speed control data. When the MCU processor detects that the working temperature of the equipment reaches a higher temperature through the temperature sensor, the MCU adjusts and increases the duty ratio of PWM output to increase the rotating speed of the fan, so that the equipment is cooled rapidly; when the MCU processor detects that the working temperature of the equipment is reduced, the MCU adjusts the duty ratio for reducing the PWM output to reduce the rotating speed of the fan, reduce the noise of the fan, reduce the power consumption, improve the working efficiency of the fan, ensure the long-term reliable work of the equipment and improve the stability of the equipment.
Drawings
Fig. 1 is an exemplary diagram of a PWM control signal in the present invention;
fig. 2 is a circuit diagram of a PWM speed regulation circuit with overload protection according to an embodiment of the present invention.
Fig. 3 is a logic block diagram of the PWM speed adjusting device connected to the fan according to the embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the following embodiments:
in order to effectively solve the heat dissipation problem and reduce unnecessary operation of the heat dissipation fan as much as possible, the embodiment designs a PWM speed regulation circuit with overload protection based on the PWM speed regulation principle.
According to the principle of PWM control, in a PWM drive control regulation system, power is turned on and off at a fixed frequency, and a typical PWM signal is as shown in fig. 3, with the "on" time (T) in one cycle being varied as needed1) And "off time (T)2) By varying the "duty cycle" (T) of the voltage across the armature of the fan's dc motor1/(T2+T1) To control the speed of the motor, PWM is also referred to as "switch drive", the PWM signal in this embodiment being implemented by the MCU processor via a rotary element.
As shown in fig. 2, the PWM speed-adjusting circuit in this embodiment includes a driving unit, a filtering unit, an output unit, and an overload protection unit;
the core components of the voltage output unit are a voltage comparator U1A, a P-channel field effect transistor Q1 and an N-channel field effect transistor Q2;
the filtering power supply is an LC filtering circuit, and comprises an inductor L1(2.2 muH 3A), a capacitor C1(100 muH 25V) and a capacitor C2(100 muH 25V), wherein the capacitors C1 and C2 are surface-mounted polarized capacitors (CAPPOL 3)
The output unit is a diode D1 and a capacitor C3(0.1 muH) which are connected in parallel, and the model of the diode D1 is 1N 4148W;
the main components of the overload protection unit are an N-channel field effect transistor Q3, a voltage comparator U1B, a resistor R6(0.22 omega), an R3(22K omega), an R5(1K) and an R7 (1K);
the models of the voltage comparators U1A and U1B in the embodiment are LM 358; the model of the P-channel field effect transistor Q1 is PMOS-2, and the model of the N-channel field effect transistors Q2 and Q3 are both 2N 7002.
The principle of operation of the circuit is as follows:
the PWM signal is accessed from the positive pole input of the voltage comparator U1A, the voltage comparator U1A provides 5V working voltage by a direct current power supply VCC5, the output of the voltage comparator U1A is connected to the grid electrode of the N-channel field effect transistor Q2, the N-channel field effect transistor Q2 is used for PWM signal processing and provides driving voltage for the grid electrode of the P-channel field effect transistor Q1 to control the on-off of the Q1, therefore, the source electrode of the N-channel field effect transistor Q2 is grounded, and the drain electrode is connected to the grid electrode of the P-channel field effect transistor Q1;
the P-channel fet Q1 is used as a power switch (current amplifier) to drive the fan load, so its source is connected to the dc power source VCC12(12V), and its drain is connected as an output to the filter unit, which is responsible for filtering the output current, and a part of the current output from the drain of the P-channel fet Q1 is fed back to the negative input of the voltage comparator U1A after passing through R8(27K Ω) connected between the drain and the negative input of the voltage comparator U1A, and is compared as a feedback with the PWM signal at the positive input of U1A, so if the PWM signal at the positive input of the voltage comparator U1A is high, the output of the voltage comparator U1A is also high.
The diode D1 and the capacitor C3 in the output unit are connected in parallel with the load fan F1 in the present embodiment to prevent the back electromotive force of the motor from damaging the pfet Q1, so that the flow direction of the diode D1 is set to be limited to flow from the negative pole of the load to the positive pole of the load.
The maximum current output by the load is 1A, if the maximum current output by the load exceeds 1A, the fan and the control circuit may be damaged, and in order to ensure that the circuit works normally, an overload protection unit is added in the embodiment, and the working principle is as follows:
if the positive input voltage of the voltage comparator U1B is greater than the negative input voltage by 3mV, the output is high level, otherwise, the output is low level, and the voltage at the two ends of the resistor R6(0.220 omega) is monitored by the voltage comparator U1B to control the on-off of the N-channel field effect transistor Q3, so that the mode switching of controlling the normal work and the stop work of the load is achieved. For this purpose, the resistor R6 is connected to the negative pole of the fan F1, and this terminal is also connected to the positive input of the voltage comparator U1B; the other end of the resistor R6 is grounded, and the other end is also connected to the negative input of the voltage comparator U1B;
a resistor R5(1K) and a resistor R7(1K) are respectively connected between the positive input and the negative input of the voltage comparator U1B and the two ends of the resistor R6; a resistor R3(22K) is connected between a direct current power supply VCC5(5V) and the negative electrode input of the voltage comparator U1B; the voltage comparator U1B is supplied with an operating voltage of 5V from a dc power supply VCC 5.
When the load current is 1A, the positive input voltage of the voltage comparator U1B is:
V5＝VR6＝R6×1A＝0.220Ω×1A＝0.220V；
the negative input voltage of the voltage comparator U1B is constant, and the voltage is:
V4＝VR7＝5V×R3/(R3+R7)＝5V×1/(1+22)＝0.217V；
when the load current is greater than 1A, V5-V4If the voltage is higher than 3mV, the output of the voltage comparator U1B is at a high level, that is, the gate of the N-channel fet Q3 is at a high level, so that the N-channel fet Q3 is turned on, the gate of the N-channel fet Q2 is at a low level, the N-channel fet Q2 is turned off, the gate of the P-channel fet Q1 is at a high level, and the P-channel fet Q1 is turned off, that is, the load stops working, thereby achieving the effect of protecting the circuit and the load motor.
In fig. 2, R1, R2, R4, R9, and R11 are protection resistors, and have a resistance value of 10K Ω, and R10 and R12 are divider resistors, and have a resistance value of 2K Ω, which is a conventional technical means for those skilled in the art and will not be described herein.
The present embodiment further provides a PWM speed adjusting device, as shown in fig. 3, the device includes the PWM speed adjusting circuit with overload protection in the present embodiment, and further includes an MCU and a temperature sensor; the input end of the PWM speed regulating circuit is connected to the PWM signal output end of the MCU processor, and the output end of the PWM speed regulating circuit is connected with the fan; and the temperature sensor is connected to the temperature signal input end of the MCU.
The PWM speed regulating circuit in the embodiment is connected to the PWM signal output end of the MCU processor, and more accurate rotating speed control data can be achieved by matching with the temperature sensor. When the MCU processor detects that the working temperature of the equipment reaches a higher temperature through the temperature sensor, the MCU adjusts and increases the duty ratio of PWM output to increase the rotating speed of the fan, so that the equipment is cooled rapidly; when the MCU processor detects that the working temperature of the equipment is reduced, the MCU adjusts the duty ratio for reducing the PWM output to reduce the rotating speed of the fan, reduce the noise of the fan, reduce the power consumption and improve the working efficiency of the fan. The long-term reliable work of equipment is guaranteed, and the stability of the equipment is improved.
The embodiment skillfully realizes the rotation speed control of the cooling fan, avoids unnecessary rotation of the fan at low temperature, effectively reduces unnecessary operation noise and effectively prolongs the service life of the fan. The overload protection unit is added to the embodiment, so that the driving unit can be burnt by a large current generated in the moment when the fan is blocked or short-circuited, the failure rate can be directly reduced, the equipment maintenance cost is reduced, the circuit is low in cost, and the circuit is simple in structure and very suitable for practicality.
The above description is only an example of the present invention, and the common general knowledge of the known specific structures and characteristics of the embodiments is not described herein. It should be noted that, for those skilled in the art, without departing from the structure of the present invention, several modifications and improvements can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicability of the patent. The scope of the claims of the present application shall be determined by the contents of the claims, and the description of the embodiments and the like in the specification shall be used to explain the contents of the claims.
Claims (8)
1. A PWM speed regulation circuit with overload protection is used for being connected between a PWM control signal and a fan and is characterized by comprising a driving unit, a filtering unit, an output unit and an overload protection unit;
the driving unit is used for intermittently outputting direct current amplified by current to the outside according to the duty ratio of the accessed PWM control signal so as to drive the fan;
the positive end of the output unit is connected with the positive electrode of the fan, and the negative end of the output unit is connected with the negative electrode of the fan and used for inputting the direct current into the fan;
the filtering unit is connected between the driving unit and the anode of the output unit and is used for outputting and filtering the direct current;
and the overload protection unit is connected between the negative electrode of the output unit and the driving unit and is used for monitoring the current intensity on the fan and controlling the driving unit to stop driving the fan if the current intensity is higher than the rated current intensity of the fan.
2. The PWM speed regulation circuit with overload protection according to claim 1, wherein: the driving unit comprises a PWM signal processing module and a power switch module;
the PWM signal processing module mainly comprises a first voltage comparator and a first N-channel field effect transistor, wherein the PWM signal is connected to the positive input end of the first voltage comparator through a protection resistor, the output of the first voltage comparator is connected to the grid electrode of the first N-channel field effect transistor through a divider resistor, and the grid electrode is also connected to a control signal sent by the overload protection unit;
the source electrode of the first N-channel field effect transistor is grounded, and the drain electrode of the first N-channel field effect transistor is used for outputting a switching signal outwards;
the negative input end of the first voltage comparator is used for being connected with feedback from the output end of the power switch module through a resistor R8;
the power switch module mainly comprises a P-channel field effect transistor, wherein the grid electrode of the P-channel field effect transistor is used for accessing the switch signal, the source electrode of the P-channel field effect transistor is used for connecting an external direct-current power supply, and the drain electrode of the P-channel field effect transistor is used for outputting current outwards; the source electrode and the grid electrode part are also connected with a protective resistor.
3. The PWM speed regulation circuit with overload protection according to claim 1, wherein: the filter unit comprises an inductor and two capacitors, the inductor is connected between the output end of the drive unit and the positive end of the output unit, and the two ends of the inductor are grounded through the capacitors respectively.
4. The PWM speed regulation circuit with overload protection according to claim 1, wherein: the output unit comprises a diode and an isolation capacitor which are connected between the positive terminal and the negative terminal in parallel, and the current direction limited by the diode is that the current can only flow from the negative terminal to the positive terminal through the diode.
5. The PWM speed regulation circuit with overload protection according to claim 1, wherein: the overload protection unit comprises a resistor R6 and a calculation module, wherein one end of the resistor R6 is connected with the negative electrode end of the output unit, and the other end of the resistor R6 is grounded;
the computing module is provided with a positive input end, a negative input end and an output end, the positive input end is connected to one end, connected with the output unit, of the resistor R6, and the negative input end is connected to one end, connected with the ground, of the resistor R6;
the computing module mainly comprises a second voltage comparator and a second N-channel field effect transistor;
the positive input end of the second voltage comparator is connected to one end of the resistor R6 output unit through a resistor R5, the negative input end of the second voltage comparator is connected to one end of the resistor R6 which is grounded through a resistor R7, and the negative input end is connected to a direct current power supply for calculation through a resistor R3;
the resistor R3 and the resistor R7 are used together to make the voltage on the negative input end be a constant voltage;
the magnitude of the constant voltage is the magnitude of the voltage across the resistor R6 plus the minimum identified voltage difference of the second voltage comparator when the current level across the fan is equal to the rated current;
the grid electrode of the second N-channel field effect transistor is connected to the output of the second voltage comparator through another divider resistor, the source electrode is grounded, and the drain electrode outputs a control signal outwards.
6. The PWM speed regulation circuit with overload protection according to claim 5, wherein: the rated current is 1A, the direct current power supply for calculation is a voltage source of 5V, the resistance values of the resistor R5 and the resistor R7 are 1K Ω, the resistance value of the resistor R6 is 0.22 Ω, and the resistance value of the resistor R3 is 22K Ω.
7. The PWM speed regulation circuit with overload protection according to claim 3, wherein: the capacitor is a surface-mounted polar capacitor, the capacitance value is 100 mu H, and the rated voltage is 25V;
the inductance value of the inductor is 2.2 muH, and the rated current is 3A.
8. A PWM speed control apparatus, comprising the PWM speed control circuit with overload protection according to any one of claims 1 to 7, further comprising an MCU and a temperature sensor;
the input end of the PWM speed regulating circuit is connected to the PWM signal output end of the MCU processor, and the output end of the PWM speed regulating circuit is connected with the fan;
and the temperature sensor is connected to the temperature signal input end of the MCU.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201921794806.7U CN212183432U (en) | 2019-10-23 | 2019-10-23 | PWM speed regulation circuit with overload protection and speed regulation device |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201921794806.7U CN212183432U (en) | 2019-10-23 | 2019-10-23 | PWM speed regulation circuit with overload protection and speed regulation device |
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| CN212183432U true CN212183432U (en) | 2020-12-18 |
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| CN201921794806.7U Active CN212183432U (en) | 2019-10-23 | 2019-10-23 | PWM speed regulation circuit with overload protection and speed regulation device |
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