Switching power supply air cooling heat dissipation circuit

Abstract

The utility model relates to an air-cooling heat dissipation circuit of a switching power supply. The air-cooling heat dissipation circuit comprises at least one fan with a PWM speed regulation function. At least one heat-sensitive sensor; the single chip microcomputer U1E is used for controlling the rotating speed of the fan according to the detected temperature; a divider resistor RE1; the working voltage of the single-chip microcomputer U1E is connected with one end of the heat-sensitive sensor, the other end of the RET is connected to one end of the divider resistor RE1 and then connected to the signal input end of the single-chip microcomputer U1E, and the other end of the divider resistor RE1 is grounded; the PWM signal access port of the fan is connected to the PWM signal output end of the single-chip microcomputer U1E, and the single-chip microcomputer controls the rotating speed of the fan through PWM signals. According to the invention, the switching power supply can be subjected to intelligent air-cooled heat dissipation by adopting a hardware and software hybrid control mode through the air-cooled heat dissipation circuit of the switching power supply in combination with the heat dissipation method. The rotating speed of the cooling fan is adjusted according to the change of the working heat of the power supply. The rotating speed noise is controlled, and the service life of the fan is prolonged. And the power supply works more reliably.

Description

Technical Field

[0001] The utility model relates to the technical field of electrical appliances, in particular to an air-cooling heat dissipation circuit for a switching power supply. Background Art

[0002] With the widespread application of switching power supplies in computers, communications, aerospace, instrumentation, and household appliances, demand for them is growing, and higher requirements are being placed on power supply efficiency, size, weight, and reliability. Switching power supplies, with their high efficiency, small size, and light weight, are gradually replacing inefficient and bulky linear power supplies in many areas.

[0003] The development of power electronics technology, especially the rapid development of high-power devices, has increased the power value of switching power supplies to a considerable level, making them highly stable and cost-effective. The market for their application is also becoming increasingly broad. Power equipment, laser engraving, communication base stations, and other applications all require high-power switching power supplies.

[0004] Traditional switching power supply cooling systems often use a fixed fan speed, that is, a forced fan cooling method, which cannot be dynamically adjusted according to the actual heat generation. That is, the switching power supply has a lot of changes in heat generation under different workloads. The fan cannot adjust the fan speed according to the heat generation, resulting in problems such as high energy consumption, high noise, and short life. Utility Model Content

[0005] In view of the shortcomings of the existing technology, the utility model provides a switching power supply air cooling heat dissipation circuit. The specific technical solution is as follows:

[0006] The air-cooling heat dissipation circuit of a switching power supply includes: at least one fan with a PWM speed regulation function, which is used to dissipate heat from the switching power supply; at least one thermistor, which can be a thermistor RET, which is used to detect the temperature of the main heating components inside the switching power supply; a single-chip microcomputer U1E, which is used to control the speed of the fan according to the detected temperature; a voltage divider resistor RE1; wherein, the operating voltage of the single-chip microcomputer U1E is VCC3.3V, and the VCC voltage 3.3V is connected to one end of the thermistor RET, the other end of the thermistor RET is connected to one end of the voltage divider resistor RE1, and then connected to the signal input end of the single-chip microcomputer U1E. The other end of the voltage divider resistor RE1 is grounded, so that the single-chip microcomputer U1E can collect the temperature signal; the PWM signal input port of the fan is connected to the PWM signal output end of the single-chip microcomputer U1E, and the single-chip microcomputer controls the speed of the fan through the PWM signal.

[0007] Preferably, a linear regulator U2E is also included to provide a stable 3.3V voltage. The operating voltage 3.3V of the microcontroller is connected to the output end of the linear regulator U2E through the VCC pin. The input end of the linear regulator U2E is connected to the 5V voltage, and the output end outputs a 3.3V voltage.

[0008] Preferably, more than one capacitor CE is included for filtering and stabilizing the voltage, and some of the capacitors CE are connected in parallel between the output end of the linear regulator U2E and the ground.

[0009] Preferably, the capacitor CE is provided with three groups, namely capacitor CE1, capacitor CE2 and capacitor CE3. The first pin of the linear regulator U2E is grounded, the first pin of the linear regulator U2E is grounded, the capacitor CE3 is connected in parallel between the second and third pins of the linear regulator U2E, the third pin of the linear regulator U2E outputs a 3.3V voltage, and the capacitor CE1 and capacitor CE2 are connected in parallel between the third and first pins of the linear regulator U2E.

[0010] Preferably, the fans are provided with two groups, namely fan FAN1 and fan FAN2, and one pin of the PWM signal input port of the fans FAN1 and FAN2 is connected to the second pin of the single chip microcomputer U1E.

[0011] Preferably, the program burning port of the single-chip microcomputer U1E is connected to the VCC power supply port and ground of the single-chip microcomputer for burning the control program;

[0012] Preferably, the fourth pin of the microcontroller U1E is the first port of the program burning port CN1, the resistor RE2 is connected to the VCC power supply port of the fourteenth pin of the microcontroller U1E, the second end of the burning port CN1 is connected to VCC, the third end of the burning port CN1 is grounded, the fifth pin of the microcontroller U1E is grounded, and the fifth end of the burning port CN1 is connected to the twelfth pin of the microcontroller U1E.

[0013] The beneficial effects of the utility model are:

[0014] In this application, a switching power supply air-cooling heat dissipation circuit is combined with a heat dissipation method that collects thermistor ADC values, calculates the average temperature, calculates the fan duty cycle based on the average temperature, and sets the calculated duty cycle. This allows for intelligent air cooling of 2400W and other series switching power supplies using a hybrid hardware-software control method. The cooling fan speed is adjusted based on changes in the power supply's operating heat output, controlling speed noise and extending the fan's service life, making the power supply more reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is the principle diagram of the air-cooling heat dissipation circuit of the switching power supply in this utility model;

[0016] Figure 2 This is a flow chart of the method for controlling air cooling and heat dissipation of a switching power supply in the present invention;

[0017] Figure 3 This is a schematic diagram of the control signal waveform of the blower in the utility model. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0019] Example 1

[0020] The market for this technology is expanding rapidly. Applications such as power equipment, laser engraving, and communication base stations all require high-power switching power supplies, such as the 2400W series. These power supplies require forced fan cooling. Heat generation varies significantly under varying loads, and the fan intelligently adjusts speed based on this heat generation to control speed and noise, thereby extending its lifespan. This is particularly important for high-power switching power supplies. Precise fan speed control requires the coordinated collaboration of hardware and software.

[0021] This embodiment provides an air-cooled heat dissipation circuit for a switching power supply, comprising: at least one fan with a PWM speed regulation function, for dissipating heat from the switching power supply; at least one thermistor, for detecting the temperature of a major heating component within the switching power supply; a single-chip microcomputer U1E, for controlling the speed of the fan according to the detected temperature; and a voltage-dividing resistor RE1; wherein the operating voltage of the single-chip microcomputer U1E is VCC 3.3V, and the VCC voltage 3.3V is connected to one end of the thermistor, the other end of RET is connected to one end of the voltage-dividing resistor RE1, and then to the signal input end of the single-chip microcomputer U1E, and the other end of the voltage-dividing resistor RE1 is grounded, so that the single-chip microcomputer U1E can collect a temperature signal, that is, the connection point between the thermistor and the voltage-dividing resistor is connected to the signal input end of the single-chip microcomputer;

[0022] The PWM signal input port of the fan is connected to the PWM signal output port of the single chip microcomputer U1E, and the single chip microcomputer controls the speed of the fan through the PWM signal.

[0023] It also includes a linear regulator U2E, which is used to provide a stable 3.3V voltage to the microcontroller for power supply. The operating voltage 3.3V of the microcontroller is connected to the output end of the linear regulator U2E through the VCC pin. The input end of the linear regulator U2E is connected to the 5V voltage, and the output end outputs a 3.3V voltage.

[0024] That is, the linear regulator U2E powers the microcontroller, the VOUT output voltage is 3.3V, and 5V is used as the input voltage of this linear regulator, so that the linear regulator converts 5V to 3.3V to power the microcontroller.

[0025] The device further includes one or more capacitors CE for filtering and stabilizing the voltage. Some of the capacitors CE are connected in parallel between the output terminal of the linear regulator U2E and the ground.

[0026] Among them, the capacitor CE is provided with three groups, namely capacitor CE1, capacitor CE2 and capacitor CE3. The first pin of the linear voltage regulator U2E is grounded, the first pin of the linear voltage regulator U2E is grounded, the capacitor CE3 is connected in parallel between the second and third pins of the linear voltage regulator U2E, the third pin of the linear voltage regulator U2E outputs a 3.3V voltage, and the capacitor CE1 and capacitor CE2 are connected in parallel between the third and first pins of the linear voltage regulator U2E.

[0027] There are two groups of fans, namely fan FAN1 and fan FAN2. One pin of the PWM signal input port of the fans FAN1 and FAN2 is connected to the second pin of the microcontroller U1E. Specifically, the second pin corresponds to the output end of the PWM signal.

[0028] Specifically, the microcontroller model may be the PIC16F1827, a high-performance RISC CPU with a C compiler architecture and 256 bytes of data EEPROM. The operating voltage is 1.8V-5.5V (PIC16F1826 / 27), and the operating current is typically 75μA at 1MHz and 1.8V. The programmable period ranges from 1ms to 268s, and it includes two capture / compare / PWM modules and two Enhanced CCP (ECCP) modules for PWM control.

[0029] Specifically, because the fan speed must be controlled, the fan speed must vary according to the power supply's heat generation stage, and the temperature of the main heat-generating components within the power supply must be controlled within a reasonable range. Accuracy is crucial, so a precision thermistor is used to detect heat changes. A microcontroller program is used to control the fan's duty cycle PWM signal, adjusting the fan speed with a precise duty cycle to achieve optimal temperature control. Therefore, a fan with PWM speed control is suitable for cooling the power supply.

[0030] Taking a 2400W power supply as an example, considering the heating conditions of the 2400W power supply components, a 12V0.6A DC fan with a maximum speed of 7500 rpm and PWM speed regulation function can be selected for heat dissipation. The specific model is Xinruilian's RDH6025B. The principle of its speed control can be found in the following content.

[0031] Specifically, the maximum input voltage V INH :2.8~20VDC, minimum input voltage V INL : 0.6V (maximum) Input impedance: 10kΩ (minimum), PWM frequency: 25kHz, PWM frequency range of control signal: 30Hz~300kHz.

[0032] exist Figure 3 The input signal waveform is shown in Figure 1. It is a square wave with a certain periodicity. The rising and falling edges of the square wave are very sharp, indicating that the signal changes rapidly. This waveform is often used in PWM technology, where the high-level time of the square wave (duty cycle) determines the average voltage and current at the load.

[0033] Combine Figure 3 , Table 1 shows the corresponding relationship between duty cycle and speed (RPM):

[0034] When the duty cycle is 0%, the speed is 0 RPM and the fan stops rotating.

[0035] When the duty cycle is 50%, the speed is 5600RPM.

[0036] When the duty cycle is 100%, the speed is 7500RPM.

[0037] Duty Cycle (%) 0％ 50％ 100％ RPM(Ref.) 0 5600 7500

[0038] Table 1

[0039] Specifically, the EC2F103 thermal sensor is recommended. Its resistance is 10K at 25°C. B is defined as the material constant, equivalent to the slope, reflecting how quickly the resistance changes with temperature. Its value is 3435K, and the operating temperature range is -40°C to 110°C. Changes in resistance cause changes in voltage, which in turn alters the duty cycle.

[0040] Table 2 is a reference table of some temperature resistance values ​​of thermistor EC2F103. As thermistor resistance changes at different temperatures, the sampling signal voltage value will also change accordingly.

[0041] Temperature (deg.C) Resistance value (kOhms) Temperature (deg.C) Resistance value (kOhms) 0 27.4936 60 3.02234 10 18.0151 70 2.2322 25 10 80 1.6725 30 8.3096 90 1.2704 40 5.825 100 0.9774

[0042] Table 2

[0043] The program burning port of the single-chip microcomputer U1E is connected to the VCC power supply port and ground of the single-chip microcomputer for burning the control program.

[0044] Specifically, the fourth pin of the microcontroller U1E is the first port of the program burning port CN1, and the resistor RE2 is connected to the VCC power supply port of the fourteenth pin of the microcontroller U1E. Specifically, the MCLR pin of the first port of the current burning port CN1 is externally connected to the resistor RE2 and connected to VCC, and the internal reset mode is selected. This is the mode selection resistor, the second end of the burning port CN1 is connected to VCC, the third end of the burning port CN1 is grounded, the fifth pin of the microcontroller U1E is grounded, and the fifth end of the burning port CN1 is connected to the twelfth pin of the microcontroller U1E.

[0045] Example 2

[0046] This embodiment provides a method for controlling air cooling and heat dissipation of a switching power supply, using the above-mentioned switching power supply air cooling and heat dissipation circuit. The method includes the following steps:

[0047] Initialize the system and PWM module;

[0048] The voltage signal value of the thermistor is collected and then converted into an ADC value through an ADC (analog-to-digital converter). That is, the ADC value is collected and the duty cycle of the fan is calculated according to the average temperature. Specifically, the average temperature can be calculated by a program in conjunction with a single-chip microcomputer. After the analog signal (such as a voltage signal) is converted into a digital signal through the ADC, the ADC value is obtained for processing and analysis by a digital system.

[0049] Calculate the fan duty cycle based on the average temperature;

[0050] Set the calculated duty cycle to control the fan speed.

[0051] The step of calculating the average temperature includes:

[0052] Initialize the system and PWM module;

[0053] Collect 20-100 ADC values, specifically 50 ADC values, and calculate the average value;

[0054] Convert the average ADC value to an average temperature value.

[0055] Specifically, when converting to temperature values, please refer to:

[0056] First, the voltage value across the thermistor is read through the ADC, and this value is the ADC value.

[0057] Calculate the resistance value: Use the formula Rt = ADC * R0 / (ADC_max - ADC) to calculate the actual resistance value (Rt) of the thermistor at the measured temperature, where ADC_max is the maximum value of ADC.

[0058] Calculate the temperature value: Use the relationship between the thermistor resistance and temperature formula Rt = R0*exp(B*(1 / T-1 / T0)) to calculate the temperature value (T), where T0 is the reference temperature (such as 25°C) and B is the material constant of the thermistor.

[0059] Specifically, Rt: the resistance of the thermistor at temperature T.

[0060] R0: The nominal resistance of the thermistor at the reference temperature T0 (usually 25°C).

[0061] B: The B value of a thermistor, also known as the thermal coefficient, is a key parameter that describes the sensitivity of the resistance value to changes in temperature.

[0062] EXP is the abbreviation of exponential function, which means the exponential function with e (the base of natural logarithms, approximately equal to 2.71828) as the base.

[0063] The step of calculating the duty cycle of the fan includes:

[0064] The initial duty cycle is set to 15%;

[0065] If the temperature is below 25°C, the duty cycle remains at 15%;

[0066] If the temperature is higher than 80°C, the duty cycle is set to 60%;

[0067] If the temperature is between 25°C and 80°C, the duty cycle is calculated using a linear formula: "duty = 0.818*(temp-25)+15", where temp is the temperature value.

[0068] The calculated duty cycle is converted into a 16-bit PWM value; the fan speed is set via the PWM signal output terminal.

[0069] Table 3 shows the test data and description using a 2400W (52V46A) power supply as an example.

[0070] Thermistor temperature ℃ Thermistor value (K) Calculate temp voltage (V) DUTY% 25 10 1.65 15 30 8.3096 1.9856 19 40 5.825 2.0851 27 50 4.1605 2.3302 35 60 3.0234 2.5337 44 70 2.2322 2.7001 52 80 1.6725 2.8227 60

[0071] Table 3

[0072] Specifically, the temp voltage divider (V) value is calculated using the formula: V = 3.3V*(RE1 / thermistor). For example, when the thermistor temperature is 25°C, the temp voltage divider (V) value is V = 3.3*10 / 20 = 1.65V.

[0073] Specifically, the thermistor is installed on the radiator HS2, and the specific model is HFB86 radiator.

[0074] The PWM duty cycle is determined by the formula 0.818*(temp-25)+15, with a minimum duty cycle of 15% at 25°C and a maximum duty cycle of 60% at 80°C (fan speed 6400 rpm). The duty cycle coefficient formula and the thermistor's mounting position on the heat sink can be adjusted in the program to reduce the maximum fan speed to below 6500 rpm, thereby reducing power supply noise and extending fan life (the power supply temperature rise also meets the requirements).

[0075] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. The air-cooling heat dissipation circuit of the switching power supply is characterized by: include: At least one fan with PWM speed regulation function, used to dissipate heat from the switching power supply; At least one thermal sensor for detecting the temperature of the main heating components inside the switching power supply; The single chip microcomputer U1E is used to control the speed of the fan according to the detected temperature; A voltage divider resistor RE1; The working voltage of the single-chip microcomputer U1E is connected to one end of the thermistor, the other end of the thermistor is connected to one end of the voltage divider resistor RE1, and then connected to the signal input end of the single-chip microcomputer U1E. The other end of the voltage divider resistor RE1 is grounded, so that the single-chip microcomputer U1E can collect the temperature signal; The PWM signal input port of the fan is connected to the PWM signal output port of the single chip microcomputer U1E, and the single chip microcomputer controls the speed of the fan through the PWM signal.

2. The switching power supply air-cooling heat dissipation circuit according to claim 1, characterized in that: It also includes a linear regulator U2E. The working voltage of the microcontroller is connected to the output end of the linear regulator U2E through the VCC pin. The input end of the linear regulator U2E is connected to a 5V voltage, and the output end outputs a 3.3V voltage.

3. The switching power supply air-cooling heat dissipation circuit according to claim 2, characterized in that: It also includes one or more capacitors CE for filtering and stabilizing the voltage. Some of the capacitors CE are connected in parallel between the output terminal of the linear regulator U2E and the ground.

4. The switching power supply air-cooling heat dissipation circuit according to claim 3, characterized in that: The capacitor CE is provided with three groups, namely capacitor CE1, capacitor CE2 and capacitor CE3. The first pin of the linear voltage regulator U2E is grounded, the first pin of the linear voltage regulator U2E is grounded, the capacitor CE3 is connected in parallel between the second and third pins of the linear voltage regulator U2E, the third pin of the linear voltage regulator U2E outputs a 3.3V voltage, and the capacitor CE1 and capacitor CE2 are connected in parallel between the third and first pins of the linear voltage regulator U2E.

5. The switching power supply air-cooling heat dissipation circuit according to claim 1, characterized in that: The fans are provided with two groups, namely fan FAN1 and fan FAN2. One pin of the PWM signal input port of the fans FAN1 and FAN2 is connected to the second pin of the single chip microcomputer U1E.

6. The switching power supply air-cooling heat dissipation circuit according to claim 1, characterized in that: The program burning port of the single-chip microcomputer U1E is connected to the VCC power supply port and ground of the single-chip microcomputer U1E for burning the control program.

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