CN104901605A - Automobile air-conditioning system and blower speed regulation controller thereof - Google Patents
Automobile air-conditioning system and blower speed regulation controller thereof Download PDFInfo
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Abstract
In order to solve a problem that when a blower is driven in a PWM manner, frequent switching on/off of a heavy-current driving signal may cause electromagnetic radiation so as to cause electromagnetic interference on electronic devices in an automobile, the invention provides an automobile air-conditioning system and a blower speed regulation controller thereof. The blower speed regulation controller comprises a processing unit and a spread spectrum driving unit. The processing unit is used for receiving a shift signal transmitted from an air conditioner controller, generating a shift control signal according to the shift signal in order to transmit the shift control signal to the spread spectrum driving unit, and transmitting a frequency control signal to the spread spectrum driving unit. The spread spectrum driving unit is used for generating a PWM driving signal according to the shift control signal and the frequency control signal and transmitting the PWM driving signal to a driving switch of the blower. The duty ratio of the PWM driving signal is controlled by a shift control signal and the frequency of the PWM driving signal is controlled by the frequency control signal and fluctuates near the center frequency in a pseudo random signal modulation manner.
Description
Technical field
The present invention relates to automotive air-conditioning system, especially the speed setting controller of speeds control is carried out to air blast in its automotive air-conditioning system.
Background technology
Air conditioning for automobiles is the abbreviation that automobile indoor air regulates, in order to regulate the air parameters such as temperature, humidity, air velocity and air purity in car, for occupant provides the environment inside car of fresh and comfortable.Air-conditioning system is primarily of compositions such as compressor, air blast, condenser assembly, evaporator, heater, refrigerator pipes, warm wind water pipe, transducer, air-conditioner controller (i.e. air-conditioner ECU, ECU is writing a Chinese character in simplified form of Electronic Control Unit) and Air-Conditioning Control Panels.
Wherein air blast is a motor-driven fan, for sucking air and making it by evaporator or heater by force, makes air cooling or heats.Compared with the employing manual adjusting style of low side in ordinary passenger car, higher-end automobile adopts automatic control mode, and usual passenger vehicle air conditioner blower power is at 200-400W(watt) left and right.Current air blast generally adopts direct current machine, and type of drive mainly contains linear drive mode and the English full name of PWM(: Pulse Width Modulation, Chinese full name: pulse width modulation) type of drive two kinds.
Air blast speed governing in conventional air conditioning for automobiles, adopts linear drive mode, utilizes the size of resistance in loop to carry out regulation voltage, reaches and regulates rotation speed of fan object.Air-conditioner ECU generates Linear Control voltage, is in linear amplification region by power semiconductor switch, and regulate the drive current of direct current machine, circuit structure is simple.Shortcoming is that power switch is in linear amplification region, and conducting resistance is large, and a lot of power consumes in vain, needs large-area fin simultaneously.
The feature of PWM type of drive is that air-conditioner ECU exports a pwm signal, and as shown in Figure 1, one end of air blast 1 is connected to the anode B+ of vehicle-mounted low tension battery, and the other end is connected to the upper end of a power switch Q1, the lower end ground connection of described power switch Q1; The control end of its power switch Q1 receives the pwm signal that air-conditioner ECU sends, and by regulating the duty ratio of pwm signal to control the average current by air blast 1, power switch Q1 is operated in saturation region, and conducting resistance is very little, and overall power consumption is low.Current PWM type of drive has the trend replacing linear drive mode.But, PWM mode blower 1 still existing defects, usual passenger car air blast 1 maximum current is at 20A(ampere) left and right, the high-order frequency multiplication energy of drived control frequency is still larger, be in automotive electronics devices function interval, the frequent break-make of its PWM drive singal can cause electromagnetic radiation, and this electromagnetic radiation can impact other electronic devices in car.
Also although have some solutions existing, such as adopt the frequency reducing PWM drive singal, drive circuit end increases filter circuit simultaneously.But the equal existing defects of above-mentioned way, such as underfrequency can cause air blast air-out volume uneven, and the increase of filter circuit also can cause extra cost.
Summary of the invention
During for solving existing PWM mode blower, the frequent break-make of large driven current density signal can cause electromagnetic radiation, electromagnetic device in car is caused to the problem of electromagnetic interference, embodiments provides the speed setting controller of a kind of automotive air-conditioning system and air blast thereof.
The embodiment of the present invention provides a kind of speed setting controller of air blast on the one hand, comprises processing unit and spread spectrum driver element;
Described processing unit, for receiving the gear signal that air-conditioner controller sends, generating gear control signal according to described gear signal and sending to described spread spectrum driver element; And to described spread spectrum driver element transmission frequency control signal;
Described spread spectrum driver element, for generating PWM drive singal according to described gear control signal and described frequency control signal, and sends to the driving switch of air blast by described PWM drive singal;
Wherein, the duty ratio of described PWM drive singal controls by described gear control signal, and the frequency of described PWM drive singal controls by described frequency control signal, and swings near centre frequency in the mode of pseudo-random signal modulation.
Speed setting controller disclosed in the embodiment of the present invention, receives the gear signal that air-conditioner controller exports, and regulates the duty ratio of PWM drive singal, to realize the driving to air blast according to default value.Because it is integrated with spread spectrum driver element in inside, in the mode of pseudo-random signal modulation, band spectrum modulation is carried out to control signal, the frequency of the PWM drive singal after band spectrum modulation is swung in certain limit near centre frequency, the electromagnetic noise of air blast entirety is also along with centre frequency swings, effectively can reduce average noise, reduce the electromagnetic interference to other electronic devices in car.The program is easy to implement, and cost is lower.
Preferably, described gear signal is PWM gear signal; Described speed setting controller also comprises an input capture device, described input capture device is connected between described processing unit and described air-conditioner controller, for receiving the PWM gear signal that described air-conditioner controller sends, gather rising edge and the trailing edge of described PWM gear signal, and described rising edge and trailing edge are sent to described processing unit.Adopt this input capture device, effectively can gather rising edge and the trailing edge of the PWM gear signal that air-conditioner controller sends, so, processing unit can obtain the duty ratio of the corresponding waveform of this PWM gear signal from this input capture device.
Preferably, described processing unit comprises: duty ratio computing module, for according to described rising edge and trailing edge, calculate the duty ratio obtaining described PWM gear signal, and according to described duty ratio, generate PWM gear control signal, send to described spread spectrum driver element;
Frequency control module, for obtaining the frequency control signal of storage, and sends it to described spread spectrum driver element.
Preferably, described speed setting controller also comprises a voltage feedback unit; Described voltage feedback unit is connected between the power supply end of described air blast and described processing unit, for detecting described blower end real-time voltage;
Described processing unit is also for gear control signal described in the real time end voltage-regulation of described air blast that detects according to described voltage feedback unit.
Adopt this voltage feedback unit, can the real time end voltage of Real-Time Monitoring air blast, the duty ratio of the real time end voltage-regulation PWM drive singal that processing unit feeds back according to air blast, ensures when the voltage fluctuation of the power supply of air blast, and blower air quantity exports still can keep stable.
Preferably, described spread spectrum driver element specifically comprises digital to analog converter, DDS circuit and drive circuit;
Described digital to analog converter, for receiving the gear control signal that described processing unit exports, and carries out digital-to-analogue conversion acquisition analog control signal to described gear control signal;
Described DDS circuit, for receiving the frequency control signal that described processing unit sends, being obtained by pseudo-random signal modulation and controlling and the frequency modulated signal swung near centre frequency by described frequency control signal;
Described drive circuit, for according to described analog control signal and described frequency modulated signal, by described analog control signal and described frequency modulated signal compound, obtain the PWM drive singal that duty ratio controls by described gear control signal, frequency swings near centre frequency, and described PWM drive singal is sent to described driving switch.
Adopt this kind of mode, can be built by simple circuit, namely obtain described duty ratio and control and the PWM drive singal swung near a certain centre frequency by described frequency control signal by described gear control signal control, frequency.
Preferably, described drive circuit is a comparator; The in-phase input end of described comparator is connected to described digital to analog converter, and described inverting input is connected to DDS circuit, and its output is connected to the control end of described power switch.Adopt this comparator, can effectively by analog control signal compound that the frequency modulated signal of the frequency-adjustable of DDS circuit evolving and described digital to analog converter generate; The PWM drive singal form described duty ratio to control by described gear control signal, frequency controls by described frequency control signal, swinging near a certain centre frequency.
Preferably, described DDS circuit comprises phase accumulator, sine looks into value table, digital to analog converter and low pass filter;
The output frequency fo of described DDS circuit is determined jointly by clock signal fc and frequency control signal K, the following formula of its relation: fo=fc × K/2N; Wherein, N is the word length of phase accumulator.
Embodiment of the present invention second aspect provides a kind of automotive air-conditioning system, comprises air-conditioner controller, speed setting controller, air blast and power switch;
Described air blast and power switch are connected in series on power supply; The input of described speed setting controller is connected to described air-conditioner controller, and its output is connected to the control end of described power switch;
Described speed setting controller comprises processing unit and spread spectrum driver element;
Described processing unit, for receiving the gear signal that described air-conditioner controller sends, generating gear control signal according to described gear signal and sending to described spread spectrum driver element; And to described spread spectrum driver element transmission frequency control signal;
Described spread spectrum driver element, for generating PWM drive singal according to described gear control signal and frequency control signal, and sends to the driving switch of described air blast by described PWM drive singal;
Wherein, the duty ratio of described PWM drive singal controls by described gear control signal, and the frequency of described PWM drive singal controls by described frequency control signal, and swings near centre frequency in the mode of pseudo-random signal modulation.
Adopt the automotive air-conditioning system that the embodiment of the present invention provides, because it is integrated with a spread spectrum driver element in speed setting controller, in the mode of pseudo-random signal modulation, band spectrum modulation is carried out to control signal, the frequency of the PWM drive singal after band spectrum modulation is swung in certain limit near centre frequency, the electromagnetic noise of air blast entirety is also along with centre frequency swings, effectively can reduce average noise, reduce the electromagnetic interference to other electronic devices in car.Meanwhile, ensure that the air-out volume of air blast, the program is easy to implement, and cost is lower.
Accompanying drawing explanation
Fig. 1 is the schematic diagram of the PWM drive pattern that in prior art, air blast drives by power switch;
Fig. 2 is a kind of speed setting controller blower module diagram provided in the specific embodiment of the invention;
Fig. 3 is the speed setting controller blower module diagram of the enterprising one-step optimization in Fig. 2 basis;
Fig. 4 is the speed setting controller blower module diagram of the enterprising one-step optimization in Fig. 3 basis;
Fig. 5 is the speed setting controller blower module diagram of the enterprising one-step optimization in Fig. 4 basis;
Fig. 6 be noise after band spectrum modulation with raw noise compare schematic diagram;
Fig. 7 is DDS schematic block circuit diagram;
Fig. 8 is the drive signal waveform figure generating duty ratio and changeable frequency in spread spectrum driver element.
Wherein, 1, air blast; 2, speed setting controller; 3, air-conditioner controller; 21, processing unit; 22, spread spectrum driver element; 23, input capture device; 24, voltage feedback unit; 25, crystal oscillator; 26, external memory unit; 27, power adapter; 28, reset circuit; 29, watchdog circuit; 211, duty ratio computing module; 212, frequency control module; 241, analog to digital converter; 242, bleeder circuit; 221, DDS circuit; 222, digital to analog converter; 223, comparator; 261, Flash; 262, RAM; Q1, power switch.
Embodiment
In order to make technical problem solved by the invention, technical scheme and beneficial effect clearly understand, below in conjunction with drawings and Examples, the present invention is further elaborated.Should be appreciated that specific embodiment described herein only in order to explain the present invention, be not intended to limit the present invention.
Embodiment 1
This example carries out specific explanations explanation by the speed setting controller of air blast provided by the invention.As shown in Figure 2, the speed setting controller 2 of the air blast 1 that this example provides, comprises as lower unit: processing unit 21 and spread spectrum driver element 22;
Described processing unit 21, for receiving the gear signal that air-conditioner controller 3 sends, generating gear control signal according to described gear signal and sending to described spread spectrum driver element 22; And to described spread spectrum driver element 22 transmission frequency control signal;
Described spread spectrum driver element 22, for generating PWM drive singal according to described gear control signal and described frequency control signal, and sends to the driving switch Q1 of air blast 1 by described PWM drive singal;
Wherein, the duty ratio of described PWM drive singal controls by described gear control signal, and the frequency of described PWM drive singal controls by described frequency control signal, and swings near centre frequency in the mode of pseudo-random signal modulation.
The power supply generally vehicle-mounted low tension battery of direct employing of air blast 1, namely directly vehicle-mounted low tension battery is adopted in this example, as shown in Figure 2, the anode B+ of vehicle-mounted low tension battery is connected to the upper end of air blast 1, the lower end ground connection of lower termination power switch Q1, the power switch Q1 of air blast 1, is namely equivalent to the negative terminal receiving vehicle-mounted low tension battery, form current circuit, realize the power supply of power supply to air blast 1.Certainly, also DC power supply can be set separately.
Carried in the introduction, existing air-conditioner controller 3 exports a pwm signal, controls the average current by air blast 1 by regulating pwm signal duty ratio.In this example air-conditioner controller 3 will send gear signal (or claim air volume signal, because it finally determines the size of discharge quantity of fan), its gear signal characterizes the height of gear (or claiming air quantity) by the size of the duty ratio of signal, the gear signal of corresponding for air blast 1 air quantity according to the input such as driver's setting, automobile interior exterior temperature, quantity of illumination COMPREHENSIVE CALCULATING air blast 1 air quantity, and is sent to speed setting controller 2(or claims speed adjusting module by air-conditioner controller 3).The PWM drive singal gear signal that air-conditioner controller 3 sends being converted to actual air blast 1 is responsible for by speed setting controller 2.As known in Fig. 2, the drive singal in this example by controlling the break-make of power switch Q1, to realize the control to air blast 1 air quantity.
About the gear signal that air-conditioner controller 3 sends, if its be processing unit 21 can the signal of Direct Recognition, then can be connected directly to the input pin of processing unit 21.When its be processing unit 21 can not the signal of Direct Recognition time, generally also arranging an input capture device 23, realize the input of its gear signal, is example than gear signal is PWM gear signal as described above; As shown in Figure 3, described speed setting controller 2 can also comprise an input capture device 23, described input capture device 23 is connected between described processing unit 21 and described air-conditioner controller 3, for receiving the PWM gear signal that described air-conditioner controller 3 sends, gather rising edge and the trailing edge of described PWM gear signal, and described rising edge and trailing edge are sent to described processing unit 21.Adopt this input capture device 23, effectively can gather rising edge and the trailing edge of the PWM gear signal that air-conditioner controller 3 sends, so, processing unit 21 obtains the duty ratio of the corresponding waveform of this PWM gear signal from this input capture device 23.
Processing unit 21 in this example is after receiving the PWM gear signal sent of above-mentioned air-conditioner controller 3, on the one hand, carry out inter-process, obtain the duty ratio of PWM gear signal, to export PWM gear control signal to follow-up spread spectrum driver element 22, meanwhile, on the other hand, its processing unit 21 sends frequency control signal.This PWM gear control signal is the signal that treated unit 21 processes the output of backward spread spectrum driver element 22.This PWM gear control signal exports being converted into PWM drive singal with frequency control signal in follow-up spread spectrum driver element 22, to control the break-make of subsequent drive switch Q1.For this reason, for realizing above-mentioned functions, as shown in Figure 3, Figure 4, this processing unit 21 at least needs to comprise with lower module: duty ratio computing module 211 and frequency control module 212;
Duty ratio computing module 211, for according to described rising edge and trailing edge, calculates the duty ratio obtaining described PWM gear signal, and according to described duty ratio, generates PWM gear control signal, send to described spread spectrum driver element 22;
Frequency control module 212, for obtaining the frequency control signal of storage, and sends it to described spread spectrum driver element 22.
Concrete, the input of this duty ratio computing module 211 is connected to the output of described input capture device 23; The output of duty ratio computing module 211 is connected to spread spectrum driver element 22.The output of this frequency control module 212 is also connected to this spread spectrum driver element 22.
Processing unit 21 can for having output, exporting the processor that also can carry out certain logical operation.Also internal storage unit is integrated with in general processor, the English full name of such as RAM(: Random Access Memory, Chinese full name: random asccess memory), the English full name of ROM(: ReadOnly Memory, Chinese full name: read-only memory) etc., it can adopt processor conventional in electricity field, its structure and software etc. are not transformed in this example, and only utilize common processor to realize the processing capacity needed in this example.
As shown in Figure 5, when processing unit 21 is without storage inside module, described speed setting controller 2 also comprises external memory unit 26, and described external memory unit 26 is connected with described processing unit 21.By external external memory unit 26, realize the storage of configuration data and fault message.Said frequencies control signal also can be stored in this external memory unit.Certainly, this frequency control signal also can be stored in the storage inside module of speed setting controller.
Preferably, described external memory unit 26 can comprise the English full name of a Flash(: Flash Memory, and Chinese is called for short: flash memory) 261 and RAM262.Generally the data such as configuration data and fault message are stored in Flash, when needs call, call related data by RAM.
So, this spread spectrum driver element 22 1 aspect can according to gear control signal, control the duty ratio of the PWM drive singal exported by gear control signal, simultaneously, also carry out band spectrum modulation according to frequency control signal, control signal by original single-frequency is modulated to the control signal changed in certain spectral range, the frequency of this PWM drive singal is controlled by frequency control signal, swings near centre frequency.The PWM drive singal exporting (needing if desired through amplifying) can Direct driver power switch Q1 action.As shown in Figure 6, without the drive singal of band spectrum modulation, the intensity of its raw noise is higher, after band spectrum modulation is carried out to control signal, the frequency of its PWM drive singal swings in certain limit near centre frequency, the electromagnetic noise of air blast 1 entirety, also along with centre frequency swings, effectively can reduce average noise.The i.e. frequency of the PWM drive singal of dynamic adjustments air blast 1, makes its power spectral density disperse, in certain frequency range, to reduce the noise effect to electronic device in automobile.
Adopt such scheme, the duty ratio of the PWM drive singal that its spread spectrum driver element 22 exports depends on gear signal, processing unit 21 will regulate the PWM drive singal duty ratio of air blast 1 according to default value, when gear signal is constant, will export the PWM drive singal of constant duty ratio.At this moment, there is less defect, automobile is in actual moving process, the power supply of powering for air blast 1 is generally vehicle-mounted low tension battery, namely air blast 1 upper end in such as Fig. 1-Fig. 5 is connected to the anode B+ of vehicle-mounted low tension battery, the output electricity of vehicle-mounted low tension battery is generally 12 volts or 24 volts, its output voltage is subject to the impact of various low pressure consuming parts, namely air blast real time end voltage be equivalent to the real-time output voltage of power supply, or can regard the voltage of positive pole relative to ground of power supply as.Therefore the real time end voltage of air blast easily fluctuates along with the change of car load electrical load, so, will affect the discharge quantity of fan of air blast 1.
For preventing this kind of situation from occurring, in this example, further improvement is done to speed setting controller 2.As shown in Figure 4, described speed setting controller 2 also comprises a voltage feedback unit 24; Between the power supply end that described voltage feedback unit 24 is connected to described air blast 1 and described processing unit 21, for detecting the real time end voltage of described air blast 1;
Described processing unit 21 also for the real time end voltage of the described air blast according to described voltage feedback unit 24 detection, regulates described gear control signal in real time.
Adopt this voltage feedback unit 24, can the real time end voltage of Real-Time Monitoring air blast, the duty ratio of the real time end voltage-regulation PWM drive singal that processing unit 21 feeds back according to air blast 1, ensures when the voltage fluctuation of air blast 1 power supply, and air blast 1 air quantity still can keep stable.Such as, when air blast real time end voltage (for real-time voltage) reduces, its duty ratio is done and is raised by a small margin, keeps stable to realize its final effective output voltage.
Carry out concrete principle below to explain, air blast 1 discharge quantity of fan size can be described as being determined by drive singal equivalent voltage Veff.And the equivalent voltage Veff=VB*duty of this drive singal.Wherein, VB is air blast 1 terminal voltage, and duty is the duty ratio of PWM drive singal.The equivalent voltage Veff of the corresponding PWM drive singal of different gear signal can be obtained by priori data, is stored in Flash.Due in actual condition, engine start whether, the reason of changes of electrical load, equivalent voltage VB can fluctuate in certain limit.Adopt this voltage feedback unit 24 to detect the real time end voltage of air blast, and adjust according to the duty ratio duty of above-mentioned formula to PWM drive singal.Namely such as, when the real time end voltage of its air blast reduces, constant for ensureing output equivalent voltage Veff, its duty ratio need be improved.When the real time end voltage of air blast raises, constant for ensureing output equivalent voltage Veff, its duty ratio need be reduced.
As a kind of mode of concrete enforcement, as shown in Figure 5, described voltage feedback unit 24 comprises bleeder circuit 242 and the English full name of analog to digital converter 241(: Analog-to-Digital Converter, English abbreviation: ADC);
Between the positive terminal that described bleeder circuit 242 is connected on the power supply of described air blast 1 and ground, the input of described analog to digital converter 241 is connected on described bleeder circuit 242, and output is connected to described processing unit 21.Concrete, as shown in Figure 5, an end of its bleeder circuit 242 is connected on the anode B+ of vehicle-mounted low tension battery.The supply voltage of general processing unit 21 is 5 volts, if directly with vehicle-mounted low tension battery for power supply, will the carrying scope of processing unit 21 be exceeded.The topmost object of this bleeder circuit 242 is the voltage that the voltage of the anode preventing its vehicle-mounted low tension battery can receive far above processing unit 21, causes the carrying scope of the input pin exceeding processing unit 21.In this example, as shown in Figure 5, described bleeder circuit 242 comprises the resistance of two series connection; The input of described analog to digital converter 241 is connected between the resistance of described two series connection.Namely comprise the first resistance R1 and the second resistance R2 shown in Fig. 5, this analog to digital converter 241 is connected between described first resistance R1 and the second resistance R2.In this example, adopt analog to digital converter 241 couples of blower end voltage VB to detect in real time, according to the duty ratio duty of VB change modulates drive singal, keep described equivalent voltage Veff certain, ensure that the certain of air blast 1 air quantity.
As a kind of mode of concrete enforcement, mention above, general processing unit 21 can not directly adopt vehicle-mounted low tension battery as power supply, therefore, as shown in Figure 5, the described speed setting controller 2 that this example provides also comprises a power adapter 27, and the input of described power adapter 27 is connected to described vehicle-mounted low tension battery, and output is connected to described processing unit 21.Physical circuit connects as shown in Figure 5, and its power adapter 27 is connected between the anode B+ of vehicle-mounted low tension battery and ground, exports suitable voltage to processing unit 21 after conversion.Adopt this kind of mode, for processing unit 21 provides suitable power supply.
A kind of concrete example is given below to spread spectrum driver element 22, as shown in Figure 5, described spread spectrum driver element 22 specifically comprises the English full name of digital to analog converter 222(: Digital-to-Analog Converter, English abbreviation: DAC), the English full name of DDS(: Direct Digital Frequency Synthesis, Chinese full name: direct digital frequency synthesis technology; I.e. DDFS, is generally called for short DDS) circuit and drive circuit;
Described digital to analog converter 222, for receiving the gear control signal that described processing unit 21 exports, and carries out digital-to-analogue conversion acquisition analog control signal to described gear control signal;
Described DDS circuit 221, for receiving the frequency control signal that described processing unit 21 sends, being obtained by pseudo-random signal modulation and controlling and the frequency modulated signal swung near centre frequency by described frequency control signal;
Described drive circuit, for according to described analog control signal and described frequency modulated signal, by described analog control signal and described frequency modulated signal compound, obtain the PWM drive singal that duty ratio controls by described gear control signal, frequency swings near centre frequency; And described PWM drive singal is sent to described driving switch.
Adopt this kind of mode, can be built by simple circuit, namely obtain described duty ratio and control and the PWM drive singal swung near a certain centre frequency by described frequency control signal by described gear control signal control, frequency.
Wherein, as shown in Figure 5, described drive circuit is a comparator 223; The in-phase input end of described comparator 223 is connected to described digital to analog converter 222, and described inverting input is connected to DDS circuit 221, and its output is connected to the power switch Q1 of blower 1.Adopt this comparator 223, the analog control signal compound that the frequency modulated signal of the frequency-adjustable that can effectively be generated by DDS circuit 221 and described digital to analog converter generate, form described duty ratio to control by described gear control signal, frequency controls and the PWM drive singal swung near a certain centre frequency by described frequency control signal.
Crystal oscillator is integrated with in general processing unit 21, if without crystal oscillator, also can an external crystal oscillator, as shown in Figure 5, described speed setting controller 2 also comprises a crystal oscillator 25, described crystal oscillator 25 is connected to described DDS circuit 221 and described processing unit 21 respectively, for described DDS circuit 221 and described processing unit 21 provide unified clock.
So-called DDS refers to direct digital frequency synthesis technology, is a kind of new frequency synthesis technique of directly synthesizing required waveform from phase place concept.Namely DDS circuit 221 utilizes a kind of circuit of direct digital frequency synthesis technology.It is conventionally known to one of skill in the art, in recent years, technology and the horizontal development of device, this makes DDS synthetic technology have also been obtained development at full speed, it considerably beyond the level that traditional frequency synthesis technique can reach, is use frequency synthesis technique the most widely at present in relative bandwidth, frequency switching time, phase continuity, orthogonal output, high resolution and a series of performance index such as integrated.As shown in Figure 7, its structure looks into value table, DAC(digital to analog converter by phase accumulator, sine to its principle) and low pass filter form.Wherein fc is clock frequency, K is frequency control signal, N is the word length of phase accumulator, m is ROM address figure place, n is the data-line width (being also generally the figure place of DAC) of ROM, fo is output frequency, and output frequency fo is determined jointly by fc and K, the following formula of its relation: fo=fc × K/2N.In this programme, frequency control signal K is exported by processing unit 21, and the clock frequency fc as benchmark is then provided by crystal oscillator 25.Namely as above-mentioned said, be stored in advance in memory cell by setting one frequency control signal K(in processing unit 21), this frequency control signal K determines the frequency range that DDS circuit 221 exports.
Adopt above-mentioned spread-spectrum modulation technique, namely air blast 1 drives pwm signal frequency not fix, and pseudo-random signal can be adopted to modulate.Spread spectrum amplitude can be expressed as Δ f=(fmax-fmin)/f0.Wherein fmax characterizes the peak frequency of band spectrum modulation, and fmin characterizes the minimum frequency of band spectrum modulation.Adopt this kind of spread-spectrum modulation technique, the energy dissipation being equivalent to drive singal, in a frequency band range, effectively reduces peak electricity levels of electromagnetic radiation.Pseudo-random signal is nbit(position by a length) linear feedback shift register generate.Pseudo-random signal repetition rate is the n power times of 2 of CPU operation frequency, and n is larger, and randomness is better, and signal spectrum distribution is more even.
As shown in Figure 8, DDS circuit 221 exports triangular wave (also can be other waveforms, as square wave etc.), and its signal amplitude is fixed as the output voltage VCC of the inner power adapter 27 of speed setting controller 2, and the cycle is controlled by processing unit 21.Processing unit 21 calculates the output voltage Vcomp of above-mentioned digital to analog converter 222 according to Veff simultaneously, i.e. Vcomp=VCC*duty.As shown in Figure 8, wherein, waveform a is the waveform of the analog control signal that digital to analog converter 222 exports, the i.e. waveform of its output voltage Vcomp, it is when duty ratio is certain, and output is the analog control signal of a voltage constant, is shown as straight line in figure.Waveform b is the frequency modulated signal that DDS circuit 221 exports, and the waveform shown in its figure is triangular wave.The frequency modulated signal that analog control signal after digital to analog converter 222 and DDS circuit 221 export is after above-mentioned comparator 223, export a PWM drive singal, the waveform of its PWM drive singal is the square wave shown in waveform c, this square wave as PWM drive singal by Direct driver power switch Q1 action.
For preventing speed setting controller 2 from occurring exception better, in this example, described speed setting controller 2 also comprises reset circuit 28 and watchdog circuit 29.When powering on or circuit occurs abnormal, circuit is returned back to initial condition.When the program of processing unit 21 enters endless loop, jump out endless loop by watchdog circuit 29.
To sum up, the disclosed speed setting controller 2 of this example, receives the gear signal that air-conditioner controller 3 exports, regulates the PWM drive singal duty ratio of air blast 1, to realize the driving to air blast 1 according to default value.Because it is integrated with spread spectrum driver element 22 in inside, band spectrum modulation is carried out to control signal, the frequency of the PWM drive singal after band spectrum modulation is swung in certain limit near centre frequency, the electromagnetic noise of air blast 1 entirety is also along with centre frequency swings, effectively can reduce average noise, reduce the electromagnetic interference to other electronic devices in car.Meanwhile, ensure that the air-out volume of air blast 1, the program is easy to implement, and cost is lower.
Embodiment 2
This example will carry out specific explanations explanation to automotive air-conditioning system provided by the invention.
As shown in Figure 5, this example gives a kind of concrete automotive air-conditioning system, comprises air-conditioner controller 3, speed setting controller 2, air blast 1 and power switch Q1;
Described air blast 1 is connected in series on power supply with power switch Q1; The input of described speed setting controller 2 is connected to described air-conditioner controller 3, and its output is connected to the control end of described power switch Q1; Wherein, the described speed setting controller 2 mentioned for above-described embodiment 1 of described speed setting controller 2.
Certainly, automotive air-conditioning system can also comprise compressor, condenser assembly, evaporator, heater, refrigerator pipes, warm wind water pipe, transducer, Air-Conditioning Control Panel etc., it is technology known in those skilled in the art, and it is little with the inventive point degree of association of the present invention, therefore, repeat no more.Concrete introduction done in embodiment 1 by speed setting controller 2, so also no longer carry out repeat specification.
Adopt the automotive air-conditioning system that example provides, because it is integrated with a spread spectrum driver element 22 in speed setting controller 2, band spectrum modulation is carried out to control signal, the frequency of the PWM drive singal after band spectrum modulation is swung in certain limit near centre frequency, the electromagnetic noise of air blast 1 entirety is also along with centre frequency swings, effectively can reduce average noise, reduce the electromagnetic interference to other electronic devices in car.Meanwhile, ensure that the air-out volume of air blast 1, the program is easy to implement, and cost is lower.
The foregoing is only preferred embodiment of the present invention, not in order to limit the present invention, all any amendments done within the spirit and principles in the present invention, equivalent replacement and improvement etc., all should be included within protection scope of the present invention.
Claims (12)
1. a speed setting controller for air blast, is characterized in that, comprises processing unit and spread spectrum driver element;
Described processing unit, for receiving the gear signal that air-conditioner controller sends, generating gear control signal according to described gear signal and sending to described spread spectrum driver element; And to described spread spectrum driver element transmission frequency control signal;
Described spread spectrum driver element, for generating PWM drive singal according to described gear control signal and described frequency control signal, and sends to the driving switch of air blast by described PWM drive singal;
Wherein, the duty ratio of described PWM drive singal controls by described gear control signal, and the frequency of described PWM drive singal controls by described frequency control signal, and swings near centre frequency in the mode of pseudo-random signal modulation.
2. speed setting controller according to claim 1, is characterized in that, described gear signal is PWM gear signal; Described speed setting controller also comprises an input capture device, described input capture device is connected between described processing unit and described air-conditioner controller, for receiving the PWM gear signal that described air-conditioner controller sends, gather rising edge and the trailing edge of described PWM gear signal, and described rising edge and trailing edge are sent to described processing unit.
3. speed setting controller according to claim 2, is characterized in that, described processing unit comprises:
Duty ratio computing module, for according to described rising edge and trailing edge, calculates the duty ratio obtaining described PWM gear signal, and according to described duty ratio, generates PWM gear control signal, send to described spread spectrum driver element;
Frequency control module, for obtaining the frequency control signal of storage, and sends to described spread spectrum driver element by described frequency control signal.
4. speed setting controller according to any one of claim 1 to 3, is characterized in that, described speed setting controller also comprises a voltage feedback unit; Described voltage feedback unit is connected between the power supply end of described air blast and described processing unit, for detecting the real time end voltage of described air blast;
Described processing unit is also for gear control signal described in the real time end Voltage Cortrol of described air blast that detects according to described voltage feedback unit.
5. speed setting controller according to claim 4, is characterized in that, described spread spectrum driver element specifically comprises digital to analog converter, DDS circuit and drive circuit;
Described digital to analog converter, for receiving the gear control signal that described processing unit exports, and carries out digital-to-analogue conversion acquisition analog control signal to described gear control signal;
Described DDS circuit, for receiving the frequency control signal that described processing unit sends, being obtained by pseudo-random signal modulation and controlling and the frequency modulated signal swung near centre frequency by described frequency control signal;
Described drive circuit, for according to described analog control signal and described frequency modulated signal, by described analog control signal and described frequency modulated signal compound, obtain the PWM drive singal that duty ratio controls by described gear control signal, frequency swings near centre frequency, and described PWM drive singal is sent to described driving switch.
6. speed setting controller according to claim 5, is characterized in that, described drive circuit is a comparator;
The in-phase input end of described comparator is connected to described digital to analog converter, and described inverting input is connected to DDS circuit, and its output is connected to the control end of described power switch.
7. speed setting controller according to claim 6, is characterized in that, described DDS circuit comprises phase accumulator, sine looks into value table, digital to analog converter and low pass filter;
The output frequency fo of described DDS circuit is determined jointly by clock signal fc and frequency control signal K, the following formula of its relation: fo=fc × K/2N; Wherein, N is the word length of phase accumulator.
8. an automotive air-conditioning system, comprises air-conditioner controller, speed setting controller, air blast and power switch;
Described air blast and described power switch are connected in series on power supply; The input of described speed setting controller is connected to described air-conditioner controller, and its output is connected to the control end of described power switch;
It is characterized in that, described speed setting controller comprises processing unit and spread spectrum driver element;
Described processing unit, for receiving the gear signal that described air-conditioner controller sends, generating gear control signal according to described gear signal and sending to described spread spectrum driver element; And to described spread spectrum driver element transmission frequency control signal;
Described spread spectrum driver element, for generating PWM drive singal according to described gear control signal and frequency control signal, and sends to the driving switch of described air blast by described PWM drive singal;
Wherein, the duty ratio of described PWM drive singal controls by described gear control signal, and the frequency of described PWM drive singal controls by described frequency control signal, and swings near centre frequency in the mode of pseudo-random signal modulation.
9. automotive air-conditioning system according to claim 8, is characterized in that, described gear signal is PWM gear signal;
Described speed setting controller also comprises an input capture device, described input capture device is connected between described processing unit and described air-conditioner controller, for receiving the PWM gear signal that described air-conditioner controller sends, gather rising edge and the trailing edge of described PWM gear signal, and described rising edge and trailing edge are sent to described processing unit.
10. automotive air-conditioning system according to claim 9, is characterized in that, described processing unit comprises:
Duty ratio computing module, for according to described rising edge and trailing edge, calculates the duty ratio obtaining described PWM gear signal, and according to described duty ratio, generates PWM gear control signal, send to described spread spectrum driver element;
Frequency control module, for obtaining the frequency control signal of storage, and sends it to described spread spectrum driver element.
11. automotive air-conditioning systems according to Claim 8 in-10 described in any one, it is characterized in that, described speed setting controller also comprises a voltage feedback unit; Described voltage feedback unit is connected between the power supply end of described air blast and described processing unit, for detecting the real time end voltage of described air blast;
Described processing unit is also for gear control signal described in the real time end Voltage Cortrol of described air blast that detects according to described voltage feedback unit.
12. automotive air-conditioning systems according to claim 11, is characterized in that, described spread spectrum driver element specifically comprises digital to analog converter, DDS circuit and drive circuit;
Described digital to analog converter, for receiving the gear control signal that described processing unit exports, and carries out digital-to-analogue conversion acquisition analog control signal to described gear control signal;
Described DDS circuit, for receiving the frequency control signal that described processing unit sends, being obtained by pseudo-random signal modulation and controlling and the frequency modulated signal swung near centre frequency by described frequency control signal;
Described drive circuit, for according to described analog control signal and described frequency modulated signal, by described analog control signal and described frequency modulated signal compound, obtain the PWM drive singal that duty ratio controls by described gear control signal, frequency swings near centre frequency, and described PWM drive singal is sent to described driving switch.
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