Fan drive circuit

Abstract

The present disclosure relates to a fan driving circuit. The fan driving circuit comprises a voltage regulating module for regulating the high level voltage of an input PWM signal to a predetermined reference voltage; a shaping module connected with the voltage regulating module for shaping the voltage output by the voltage regulating module into direct current; a voltage stabilizing module connected with the shaping module for stabilizing the voltage output by the shaping module; and a filtering module connected with the voltage stabilizing module for filtering the voltage output by the voltage stabilizing module and providing the filtered voltage to a fan. For the fan driving circuit of the present disclosure, different duty cycle PWM signals are input, and after voltage stabilizing control, corresponding constant supply voltage is output to the fan, thereby realizing constant voltage multi-stage control of the fan. Through input of the PWM signal, the present disclosure can quickly and accurately adjust the speed of the fan while providing constant voltage to the fan.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of electronic circuits, in particular to a fan driving circuit. BACKGROUND

[0002] With the increasing integration of vehicle infotainment system functions, the heat dissipation problem is becoming more and more important, and in some vehicles, a cooling fan is introduced to provide air cooling to solve the heat dissipation problem. For high-speed DC motors of the fan, a constant voltage drive of a small voltage (for example, less than 5V) is required, and it is best to be able to multi-stage control the speed of the fan.

[0003] In the related art, a Low Dropout Regulator (LDO) integrated circuit chip is used to realize the constant voltage drive of the fan, but the design cost is expensive, and there is currently no good solution for the multi-stage speed control function of the fan. SUMMARY

[0004] The purpose of the present disclosure is to provide a fan driving circuit with a multi-stage speed control function and capable of constant voltage drive.

[0005] In order to achieve the above-mentioned purpose, the present disclosure provides a fan driving circuit, which comprises:

[0006] a voltage regulating module, configured to adjust the high level voltage of an input pulse width modulation (PWM) signal to a predetermined reference voltage;

[0007] a shaping module, connected with the voltage regulating module, configured to shape the voltage output by the voltage regulating module into direct current (DC);

[0008] a voltage stabilizing module, connected with the shaping module, configured to stabilize the voltage output by the shaping module;

[0009] a filtering module, connected with the voltage stabilizing module, configured to filter the voltage output by the voltage stabilizing module and provide the filtered voltage to a fan.

[0010] Optionally, the voltage regulating module comprises a first triode, a second triode, a third triode, a first resistor, a second resistor, a third resistor and a fourth resistor, wherein the emitter of the first triode is connected to a power supply, the base of the first triode is connected to the collector of the second triode, the collector of the first triode is connected to the collector of the third triode through the fourth resistor, connected to the ground line through the third resistor, and connected to the base of the third triode through the first resistor, the base of the second triode is connected to an enable signal end of the voltage regulating module, the emitter of the second triode is connected to the ground line, the base of the third triode is connected to a PWM signal input end of the voltage regulating module through the second resistor, and the emitter of the third triode is connected to the ground line.

[0011] Optionally, the shaping module comprises a fifth resistor and a first capacitor, one end of the fifth resistor is connected to the output end of the voltage regulating module, the other end of the fifth resistor is connected to the ground line through the first capacitor, and the other end of the fifth resistor serves as the output end of the shaping module.

[0012] Optionally, the voltage stabilizing module comprises:

[0013] a voltage feedback submodule configured to generate a feedback signal according to an output voltage of the voltage stabilizing module;

[0014] a signal amplification submodule connected to the voltage feedback submodule and configured to amplify the feedback signal to generate an amplified signal, wherein the signal amplification submodule comprises two transistors of the same type;

[0015] a voltage stabilizing adjustment submodule connected to the signal amplification submodule and configured to stabilize voltage according to the amplified signal, and an output voltage of the voltage stabilizing adjustment submodule serves as the output voltage of the voltage stabilizing module.

[0016] The input voltage and the output voltage of the voltage stabilizing module have a fixed corresponding relationship due to the circuit structures in the signal amplification submodule and the voltage feedback submodule.

[0017] Optionally, the signal amplification submodule comprises a fourth transistor, a fifth transistor and a sixth resistor, wherein the fourth transistor and the fifth transistor are two NPN transistors of the same type, the emitter of the fourth transistor and the emitter of the fifth transistor are connected and connected to the ground line through the sixth resistor, the base of the fourth transistor is connected to the output end of the shaping module, the collector of the fourth transistor serves as the output end of the signal amplification submodule, the base of the fifth transistor is connected to the output end of the voltage feedback submodule, and the collector of the fifth transistor is connected to the output end of the voltage stabilizing adjustment submodule.

[0018] Optionally, the voltage feedback submodule comprises a seventh resistor and an eighth resistor, the output end of the voltage stabilizing adjustment submodule is connected to the ground line through the eighth resistor and the seventh resistor in sequence, and a node between the eighth resistor and the seventh resistor serves as the output end of the voltage feedback submodule.

[0019] Optionally, the voltage stabilizing and regulating sub-module comprises a sixth transistor, a ninth resistor and a second capacitor, the power input end of the voltage stabilizing and regulating sub-module is connected to the output end of the shaping module in sequence through the ninth resistor and the second capacitor, the node between the ninth resistor and the second capacitor is connected to the output end of the signal amplifying sub-module, the sixth transistor is a PNP type transistor, the emitter of the sixth transistor is connected to the power input end of the voltage stabilizing module, the base of the sixth transistor is connected to the output end of the signal amplifying sub-module, and the collector of the sixth transistor serves as the output end of the voltage stabilizing module.

[0020] Optionally, the filtering module comprises a voltage stabilizing diode and a third capacitor, one end of the third capacitor is connected to the cathode of the voltage stabilizing diode, the other end of the third capacitor is connected to the anode of the voltage stabilizing diode and the ground wire, the cathode of the voltage stabilizing diode is connected to the output end of the voltage stabilizing module and serves as the output end of the filtering module.

[0021] Optionally, the fourth transistor and the fifth transistor are both BC847.

[0022] Optionally, the power of the sixth transistor is greater than or equal to 250mW.

[0023] Through the above technical solution, different PWM signals with different duty cycles are input, different direct current voltages are generated after the voltage regulating module and the shaping module, and then the corresponding constant power supply voltage is output to the fan after voltage stabilizing control, so that the constant voltage multi-stage control of the fan is realized, and if the speed of the fan needs to be changed, only the duty cycle of the input PWM signal needs to be controlled and changed. The disclosure can quickly and accurately adjust the speed of the fan while providing constant voltage to the fan by inputting the PWM signal.

[0024] Other features and advantages of the disclosure will be described in detail in the following specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0025] The accompanying drawings are included to provide a further understanding of the disclosure and constitute a part of the specification, and are used together with the following specific embodiments to explain the disclosure, but do not constitute a limitation on the disclosure. In the drawings:

[0026] Figure 1 is a structural block diagram of a fan driving circuit provided by an exemplary embodiment;

[0027] Figure 2 is a circuit schematic diagram of a fan driving circuit provided by an exemplary embodiment. DETAILED DESCRIPTION

[0028] The specific embodiments of the present disclosure are described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present disclosure, and are not intended to limit the present disclosure.

[0029] Figure 1 is a structural block diagram of a fan driving circuit provided by an exemplary embodiment. As shown in Figure 1 , the fan driving circuit can include a voltage regulating module 10, a shaping module 20, a voltage stabilizing module 30, and a filtering module 40.

[0030] The voltage regulating module 10 is used to adjust the high-level voltage of the input pulse width modulation (PWM) signal to a predetermined reference voltage.

[0031] The shaping module 20 is connected with the voltage regulating module 10, and is used to shape the voltage output by the voltage regulating module 10 into direct current.

[0032] The voltage stabilizing module 30 is connected with the shaping module 20, and is used to stabilize the voltage output by the shaping module 20.

[0033] The filtering module 40 is connected with the voltage stabilizing module 30, and is used to filter the voltage output by the voltage stabilizing module 30 and then provide the voltage to the fan.

[0034] Through the above technical solution, the PWM signal with different duty cycles is input, different direct current voltages are generated after the voltage regulating module and the shaping module, and then the corresponding constant power supply voltage is output to the fan after the voltage stabilizing control, so that the constant voltage multi-stage control of the fan is realized. If the speed of the fan needs to be changed, only the duty cycle of the input PWM signal needs to be controlled and changed. The present disclosure can quickly and accurately adjust the speed of the fan while providing constant voltage to the fan by inputting the PWM signal.

[0035] Figure 2 is a circuit schematic diagram of a fan driving circuit provided by an exemplary embodiment. This embodiment can be used as a fan constant voltage multi-stage speed regulation circuit in a vehicle infotainment system. The input power VBATT of the fan driving circuit can be the voltage of the vehicle battery, and a stable 5V voltage can be output to the external fan.

[0036] In Figure 2In the embodiment of the application, the voltage regulating module 10 can include a first transistor Q1, a second transistor Q2, a third transistor Q3, a first resistor R1, a second resistor R2, a third resistor R3 and a fourth resistor R4. The emitter of the first transistor Q1 is connected to a power supply (VG3V3), the base of the first transistor Q1 is connected to the collector of the second transistor Q2, the collector (node P2) of the first transistor Q1 is connected to the collector (node P3) of the third transistor Q3 through the fourth resistor R4, connected to the ground line through the third resistor R3, and connected to the base (node P1) of the third transistor Q3 through the first resistor R1. The base of the second transistor Q2 is connected to the enable signal end (FAN_EN) of the voltage regulating module 10, and the emitter of the second transistor Q2 is connected to the ground line (GND). The base of the third transistor Q3 is connected to the PWM signal input end (FAN_Speed) of the voltage regulating module 10 through the second resistor R2, and the emitter of the third transistor Q3 is connected to the ground line.

[0037] The enable control signal of the fan driving circuit can be a signal FAN_EN from a motor control unit (MCU) of the vehicle. When the FAN_EN is high, the second transistor Q2 is saturated and turned on to the ground, and the first transistor Q1 is saturated and turned on, so that the 3.3V voltage of VG3V3 is turned on to provide a pull-up power supply for the first resistor R1, the third resistor R3 and the fourth resistor R4. The FAN_Speed signal is a PWM signal generated by the MCU, that is, a fan speed control signal. The voltage of VG3V3 is a predetermined reference voltage. The output (node P3) end of the voltage regulating module 10 also outputs a PWM signal, and the high level is the voltage of VG3V3. After being filtered by a fifth resistor R5 and a first capacitor C1, the node P4 is shaped into a direct current voltage VP4. By controlling the different duty cycles of the PWM signal, the output voltage value (FAN+) of the rear-end voltage stabilizing module is adjusted, and fan constant voltage multi-stage control is realized.

[0038] The shaping module 20 can include a fifth resistor R5 and a first capacitor C1. One end of the fifth resistor R5 is connected to the output end (node P3) of the voltage regulating module 10, the other end of the fifth resistor R5 is connected to the ground line (GND) through the first capacitor C1, and the other end of the fifth resistor R5 serves as the output end (node P4) of the shaping module 20.

[0039] The voltage stabilizing module 30 can include a voltage feedback sub-module, a signal amplification sub-module and a voltage stabilizing adjustment sub-module.

[0040] The voltage feedback sub-module is configured to generate a feedback signal according to the output voltage of the voltage stabilizing module 30.

[0041] The signal amplification sub-module is connected with the voltage feedback sub-module and configured to amplify the feedback signal to generate an amplified signal. The signal amplification module includes two transistors of the same type.

[0042] The voltage stabilizing and regulating sub-module is connected with the signal amplifying sub-module, and is configured to stabilize voltage according to the amplified signal, and an output voltage of the voltage stabilizing and regulating sub-module is taken as an output voltage of the voltage stabilizing module 30.

[0043] The input voltage and the output voltage of the voltage stabilizing module 30 have a fixed corresponding relationship due to the circuit structure of the signal amplifying sub-module and the voltage feedback sub-module.

[0044] The signal amplifying sub-module can include a fourth transistor Q4, a fifth transistor Q5 and a sixth resistor R6. The fourth transistor Q4 and the fifth transistor Q5 are two NPN transistors of the same type. For example, the fourth transistor Q4 and the fifth transistor Q5 are both BC847.

[0045] The emitter of the fourth transistor Q4 and the emitter of the fifth transistor Q5 are connected (node P7) and grounded through the sixth resistor R6, the base of the fourth transistor Q4 is connected to the output end (node P4) of the shaping module 20, the collector (node P5) of the fourth transistor Q4 is taken as the output end of the signal amplifying sub-module, the base (node P8) of the fifth transistor Q5 is connected to the output end of the voltage feedback sub-module, and the collector (node P6) of the fifth transistor Q5 is connected to the output end of the voltage stabilizing and regulating sub-module.

[0046] The voltage feedback sub-module can include a seventh resistor R7 and an eighth resistor R8. The output end (node P6) of the voltage stabilizing and regulating sub-module is sequentially grounded through the eighth resistor R8 and the seventh resistor R7, and the node between the eighth resistor R8 and the seventh resistor R7 is taken as the output end (node P8) of the voltage feedback sub-module.

[0047] The seventh resistor R7 and the eighth resistor R8 should follow the formula Vout=VP8 / (r7 / (r7+r8)). For example, when VP8 is 2V and the target Vout is 5V, 5=2 / (r7 / (r7+r8)), when the resistance value r8 of the eighth resistor R8 is 15Kohm, the resistance value r7 of the seventh resistor R7 must be 10Kohm.

[0048] Since the emitter of the fourth transistor Q4 and the emitter of the fifth transistor Q5 are both connected to node P7, the emitter voltage of the fourth transistor Q4 and the emitter voltage of the fifth transistor Q5 are equal, i.e. Ve_Q5 = Ve_Q4. Since the base-to-emitter PN junction voltage of the same type of transistor is approximately equal, Vbe_Q5 = Vbe_Q4, when the fourth transistor Q4 and the fifth transistor Q5 are of the same type, the base voltage of the fourth transistor Q4 and the base voltage of the fifth transistor Q5 are equal, i.e. Vb_Q5 = Vb_Q4. The duty cycle of the FAN_Speed signal can be adjusted to adjust the DC voltage VP4 at node P4 after filtering by the fifth resistor R5 and the first capacitor C1. According to VP4 = VP8, Vout = VP8 / (R7 / (R7+R8)), the Vout value is obtained, i.e. the constant voltage value of the FAN+ output.

[0049] Moreover, the use of the double-transistor architecture of the fourth transistor Q4 and the fifth transistor Q5 of the same type can achieve the suppression of the temperature drift of the transistor parameters.

[0050] The voltage stabilizing and adjusting sub-module can include a sixth transistor Q6, a ninth resistor R9, and a second capacitor C2. The power input end (VBATT) of the voltage stabilizing and adjusting sub-module is connected to the output end (node P4) of the shaping module 20 in sequence through the ninth resistor R9 and the second capacitor C2, and the node between the ninth resistor R9 and the second capacitor C2 is connected to the output end (node P5) of the signal amplifying sub-module. The sixth transistor Q6 is a PNP type transistor. The emitter of the sixth transistor Q6 is connected to the power input end (VBATT) of the voltage stabilizing module 30, the base of the sixth transistor Q6 is connected to the output end (node P5) of the signal amplifying sub-module, and the collector of the sixth transistor Q6 serves as the output end (node P6) of the voltage stabilizing module 30.

[0051] Figure 2 In the embodiment, the working range of the VBATT input voltage is 9V-16V, and the target output VOUT voltage is constant. By using the instantaneous polarity method analysis, it is assumed that the current VBATT input voltage is V1. When the input voltage suddenly increases and is greater than V1, the voltage VP8 fed back to node P8 by the voltage division of the seventh resistor R7 and the eighth resistor R8 in the voltage feedback sub-module will increase.

[0052] Since the base-to-emitter voltage Vbe_Q5 of the fifth transistor Q5 is fixed, the voltage VP7 at node P7 increases. Since the fourth transistor Q4 and the fifth transistor Q5 share the emitter, the emitter voltage Ve_Q4 of the fourth transistor Q4 increases. Since the voltage VP8 at node P8 (i.e. the base voltage of the fifth transistor Q5) is constant, the base-to-emitter voltage Vbe_Q4 of the fourth transistor Q4 = VP4-Ve_Q4, so Vbe_Q4 decreases.

[0053] According to the transistor's input transfer characteristics, a decrease in Vbe_Q4 leads to a decrease in the base current Ib_Q4 of the fourth transistor Q4. According to the transistor's output characteristics, a decrease in Ib_Q4 leads to an increase in the collector-emitter voltage Vce_Q4 of the fourth transistor Q4. The increase in Vce_Q4 leads to a decrease in the current IR6 in the sixth resistor R6, which in turn leads to a decrease in the base current Ib_Q6 of the sixth transistor Q6.

[0054] Regarding transistor Q6, based on its output characteristics, the decrease in base current Ib_Q6 leads to an increase in the emitter-collector voltage Vec_Q6. Since Vout = VBATT - Vec_Q6, the increase in Vec_Q6, through negative feedback, reduces Vout. The ultimate goal is to regulate the voltage Vec_Q6, thereby stabilizing Vout. In this process, transistor Q6, operating in the amplification region, achieves negative feedback regulation by dynamically adjusting the emitter-collector voltage Vec_Q6.

[0055] Since transistor Q6 needs to handle a relatively large power, it is safer to choose a transistor with a power rating greater than or equal to 250mW. A 250mW transistor, with an output voltage of 5V, can tolerate a maximum current of 500mA, which is greater than the maximum operating current of all fans currently on the market.

[0056] The filter module 40 may include a Zener diode D1 and a third capacitor C3. One end of the third capacitor C3 is connected to the cathode of the Zener diode D1, and the other end of the third capacitor C3 is connected to the anode of the Zener diode D1 and grounded. The cathode of the Zener diode D1 is connected to the output terminal of the voltage regulator module 30 and serves as the output terminal of the filter module 40.

[0057] like Figure 2 As shown, the fan can output a speed feedback signal (FAN_Speed_FB) to the MCU (not shown). The MCU can pre-store the fan speed control strategy. Based on the real-time acquired fan speed and the strategy, the MCU outputs the PWM signal (FAN_Speed) required for the next step to the fan drive circuit.

[0058] The preferred embodiments of the present disclosure have been described in detail above with reference to the accompanying drawings. However, the present disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present disclosure, various simple modifications can be made to the technical solutions of the present disclosure, and these simple modifications all fall within the protection scope of the present disclosure.

[0059] It should also be noted that various technical features described in the above detailed description are capable of being combined in any suitable manner unless otherwise explicitly stated. To avoid unnecessary repetition, various possible combinations of features are not all explicitly described in the present disclosure.

[0060] Furthermore, various embodiments of the present disclosure can be combined in any suitable manner, as long as it does not contradict the idea of the present disclosure, and it should be considered as disclosed in the present disclosure.

Claims

1. A fan drive circuit, characterized in that, The fan drive circuit is used to output a stable 5V voltage to the external fan. The fan drive circuit includes: The voltage regulation module is used to adjust the high-level voltage of the input pulse width modulation (PWM) signal to a predetermined reference voltage. A shaping module, connected to the voltage regulating module, is used to shape the voltage output by the voltage regulating module into direct current. A voltage regulator module, connected to the shaping module, is used to regulate the voltage output by the shaping module; A filtering module, connected to the voltage regulator module, is used to filter the voltage output by the voltage regulator module and then supply it to the fan. The voltage regulation module includes a first transistor, a second transistor, a third transistor, a first resistor, a second resistor, a third resistor, and a fourth resistor. The emitter of the first transistor is connected to the power supply. The base of the first transistor is connected to the collector of the second transistor. The collector of the first transistor is connected to the collector of the third transistor through the fourth resistor, and grounded through the third resistor. It is also connected to the base of the third transistor through the first resistor. The base of the second transistor is connected to the enable signal terminal of the voltage regulation module. The emitter of the second transistor is grounded. The base of the third transistor is connected to the PWM signal input terminal of the voltage regulation module through the second resistor. The emitter of the third transistor is grounded.

2. The fan drive circuit according to claim 1, characterized in that, The shaping module includes a fifth resistor and a first capacitor. One end of the fifth resistor is connected to the output terminal of the voltage regulation module, and the other end of the fifth resistor is grounded through the first capacitor. The other end of the fifth resistor serves as the output terminal of the shaping module.

3. The fan drive circuit according to claim 1, characterized in that, The voltage regulator module includes: A voltage feedback submodule is used to generate a feedback signal based on the output voltage of the voltage regulator module; A signal amplification submodule, connected to the voltage feedback submodule, is used to amplify the feedback signal to generate an amplified signal. The signal amplification module includes two transistors of the same type. A voltage regulation submodule, connected to the signal amplification submodule, is used to regulate voltage according to the amplified signal, and the output voltage of the voltage regulation submodule is used as the output voltage of the voltage regulation module. The input voltage and output voltage of the voltage regulator module have a fixed correspondence due to the circuit structure in the signal amplification submodule and the voltage feedback submodule.

4. The fan drive circuit according to claim 3, characterized in that, The signal amplification submodule includes a fourth transistor, a fifth transistor, and a sixth resistor. The fourth and fifth transistors are two identical NPN transistors. The emitters of the fourth and fifth transistors are connected and grounded through the sixth resistor. The base of the fourth transistor is connected to the output of the shaping module, and the collector of the fourth transistor serves as the output of the signal amplification submodule. The base of the fifth transistor is connected to the output of the voltage feedback submodule, and the collector of the fifth transistor is connected to the output of the voltage regulation submodule.

5. The fan drive circuit according to claim 3, characterized in that, The voltage feedback submodule includes a seventh resistor and an eighth resistor. The output terminal of the voltage regulation submodule is grounded through the eighth resistor and the seventh resistor in sequence. The node between the eighth resistor and the seventh resistor serves as the output terminal of the voltage feedback submodule.

6. The fan drive circuit according to claim 3, characterized in that, The voltage regulation submodule includes a sixth transistor, a ninth resistor, and a second capacitor. The power input terminal of the voltage regulation submodule is connected to the output terminal of the shaping module through the ninth resistor and the second capacitor in sequence. The node between the ninth resistor and the second capacitor is connected to the output terminal of the signal amplification submodule. The sixth transistor is a PNP transistor. The emitter of the sixth transistor is connected to the power input terminal of the voltage regulation module, the base of the sixth transistor is connected to the output terminal of the signal amplification submodule, and the collector of the sixth transistor serves as the output terminal of the voltage regulation module.

7. The fan drive circuit according to claim 1, characterized in that, The filtering module includes a Zener diode and a third capacitor. One end of the third capacitor is connected to the cathode of the Zener diode, and the other end of the third capacitor is connected to the anode of the Zener diode and grounded. The cathode of the Zener diode is connected to the output terminal of the voltage regulation module and serves as the output terminal of the filtering module.

8. The fan drive circuit according to claim 4, characterized in that, The fourth and fifth transistors are both BC847.

9. The fan drive circuit according to claim 6, characterized in that, The power of the sixth transistor is greater than or equal to 250mW.

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