CN108768183A - Broadband induction heating power based on resonant frequency tracking - Google Patents

Broadband induction heating power based on resonant frequency tracking Download PDF

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Publication number
CN108768183A
CN108768183A CN201810465731.1A CN201810465731A CN108768183A CN 108768183 A CN108768183 A CN 108768183A CN 201810465731 A CN201810465731 A CN 201810465731A CN 108768183 A CN108768183 A CN 108768183A
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digital
phase
signal
frequency
frequency word
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CN108768183B (en
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方旭
王同辉
叶树亮
唐波
侯德鑫
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China Jiliang University
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China Jiliang University
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M5/00—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases
    • H02M5/40—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc
    • H02M5/42—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters
    • H02M5/44—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac
    • H02M5/453—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M5/458—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
    • H02M1/088—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters for the simultaneous control of series or parallel connected semiconductor devices
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B6/00—Heating by electric, magnetic or electromagnetic fields
    • H05B6/02—Induction heating
    • H05B6/04—Sources of current
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0003—Details of control, feedback or regulation circuits
    • H02M1/0009—Devices or circuits for detecting current in a converter
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0003—Details of control, feedback or regulation circuits
    • H02M1/0012—Control circuits using digital or numerical techniques
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • General Induction Heating (AREA)
  • Inverter Devices (AREA)

Abstract

The invention discloses a kind of broadband induction heating powers based on resonant frequency tracking.Current rectifying and wave filtering circuit, full bridge inverter, impedance-matching transformer, resonance circuit, Zero-cross comparator circuit, digital frequency tracing control device and full bridge driving circuit of the present invention, wherein digital frequency tracing control device is made of digital phase discriminator, digital filter and digital oscillator；The digital phase discriminator is made of shaping filter and phase comparator, and the digital oscillator is made of phase difference frequency word controller, reference frequency word controller, phase angle threshold controller, frequency word controller and Direct Digital Synthesizer.The present invention has fast resonant frequency search, bandwidth and feature with high accuracy using digital frequency-tracking control utensil, the present invention carries out shaping using shaping filter to the signal for representing load voltage and current phase, reduce influence of the high dither noise to phase comparator, enhances the anti-interference ability of system.

Description

Broadband induction heating power based on resonant frequency tracking
Technical field
The invention belongs to power electronics field, be related to a kind of broadband induction applied to impulse eddy current thermal imaging plus Thermoelectric generator has high-precision, digital resonant frequency tracking technique.
Background technology
Impulse eddy current thermal imaging detection technique combines two kinds of non-destructive testing technologies of impulse eddy current and infrared thermal imaging, has Non-contact, the features such as area of detection is big, efficient and testing result is intuitive, aerospace, communications and transportation, core have been successfully applied to it The metal material non-destructive testing in the fields such as electricity reaction and Performance Evaluation.The technology includes mainly：Induction heating power, infrared acquisition Device and data processing algorithm, wherein induction heating power are the mostly important component parts of system, the startup time of power supply and are swashed Encourage flaw indication feature extraction, detection sensitivity and defect detection that the characteristics such as frequency range directly affect impulse eddy current thermal imaging Rate.
It is affected by temperature due to during sensing heating, being easy by the conductivity of heating sample and magnetic conductivity, it leads The resonant frequency of load is caused to shift.In order to ensure that system safety operation, conventional method use the frequency based on phase-locked loop chip Rate tracking technique, such as Chinese patent《Electromagnetic induction heater and electromagnetic oven》(notification number CN103607799B), this method are deposited The deficiencies of peripheral component is more, analog device is vulnerable to outside electromagnetic interference influence, tracking frequency band is narrow；In order to make up simulation The shortcomings that phaselocked loop, Chinese patent《A method of realizing phaselocked loop using resonance current maximum virtual value optimizing》(notification number CN103795407B), the resonant frequency of load is found using the method for tracking load current maximum value, but still has resonance The deficiencies such as the frequency search time is long, precision is low.
Invention content
In order to overcome, peripheral component existing for existing resonant frequency tracking technique is more, resonant frequency search is slow and precision is low The shortcomings that and deficiency, the present invention provides it is a kind of based on resonant frequency tracking broadband induction heating power.
The present invention includes：Current rectifying and wave filtering circuit, full bridge inverter, impedance-matching transformer, resonance circuit, Zero-cross comparator Circuit, digital frequency tracing control device and full bridge driving circuit.
Current rectifying and wave filtering circuit is by four power diode Ds1、Ds2、Ds3、Ds4With electrolytic capacitor CdComposition, input terminal and city It is electrically connected, output end is connected with the input terminal of full bridge inverter.
Full bridge inverter includes four power tubes, four Ultrafast recovery diodes, in the hourglass source electrode of power tube S1~S4 Respectively one Ultrafast recovery diode of inverse parallel, and the source electrode of S1 be connected with the drain electrode of S3 composition on the left of bridge arm midpoint G2, S2 source electrodes are connected the midpoint G1, G1 and the G2 that constitute right side bridge arm with S4 drain electrodes as signal output end and impedance-matching transformer phase Even.
The input terminal of impedance-matching transformer is connected with the output end of full bridge inverter, output end and resonance circuit Input terminal is connected.
Resonance circuit is popped one's head in by yoke, detection sample and resonant capacitance C form, wherein between yoke probe and detection sample Electromagnetic Coupling Characteristic can be equivalent to lumped parameter R and L, input terminal is connected with the output end of impedance-matching transformer.
Zero-cross comparator circuit is made of current transformer, sampling resistor, low-pass filter, high speed zero-crossing comparator, will be born The current bus bar for carrying resonance circuit passes through the centre bore of current transformer, the current signal for obtaining resonance circuit, through zero passage Obtain representing the signal S of load current phase after comparator processingI, and input to digital frequency tracing control device.
Digital frequency tracing control device is made of digital phase discriminator, digital filter and digital oscillator, after processing The pwm signal for exporting two-way complementation, outputs it to full bridge driving circuit.
Tetra- road signal of SW1, SW2, SW3 and SW4 is exported after full bridge driving circuit processing, is respectively used to driving power switching tube S1, S2, S3 and S4.
Further, the digital oscillator of digital frequency tracing control device includes mainly：Reference frequency word controller, phase angle Threshold controller, phase difference frequency word controller, frequency word controller and DDS, by reference frequency word controller and phase angle threshold value Controller determines reference frequency word M0With the signal N for representing phase angle threshold values, the specific implementation of digital frequency tracing control device Cheng Wei：
(1) the representative load current phase signal S for exporting zero-crossing comparatorIAnd Direct Digital Synthesizer (Direct Digital Synthesizer, DDS) output wherein represents load voltage phase signal S all the wayUIt is input to whole Mode filter pre-defines the state of variable to detect S under the action of system clock by judgementIAnd SUThe rising edge of signal And failing edge, the high dither noise of two paths of signals is filtered out by delay, and the signal S after shaping is exportedI' and SU' input to Phase comparator, wherein SI' and SU' it is respectively SIAnd SUSignal after shaping filter.
(2) phase comparator is by comparing two-way input signal SI' and SU' rising edge arrive time obtain its phase pass System, and obtain two-way output signal up and dn and input to digital filter, wherein up/dn is phase signal all the way, then separately Dn/up is comparison signal all the way.
(3) digital filter under the action of system clock by the high level modulation of two-way input signal up and dn at a system The pulse of row, and N is calculated by counter1And N2, wherein N1And N2The duty ratio size of up and dn is respectively represented, finally By count value N1And N2Input to the phase difference frequency word controller of digital oscillator.
(4) phase difference frequency word controller is to count value N1And N2It obtains representing phase difference size after carrying out difference operation N, and phase difference frequency word Δ M is determined according to the size of N valuesi(i=0,1 ..., k), finally by N and Δ MiInput to frequency word control Device processed.
(5) frequency word controller is by phase difference frequency word Δ MiWith the reference frequency word M of reference frequency word controller output0 Algebraic operation is carried out, frequency word M is obtainedi+1(i=0,1 ..., k), and by frequency word Mi+1Input to DDS, successively recycle (1)~ (4) until N values are more than or equal to zero and represent the signal N of phase angle threshold value less than or equal to the output of phase angle threshold controllers, then frequency word Mi+1It remains unchanged.
(6) DDS is under the action of system clock, to frequency word Mi+1It adds up, the value after adding up is deposited with frequency word The threshold value of device is compared, and exports the PWM1 and PWM2 of two-way complementation.
The automatic search work process of resonant frequency of digital frequency tracing control device is：
(1) after induction heating power system starts, by count value N1And N2It carries out difference operation and obtains N, determined according to N Phase difference frequency word Δ Mi(i=0,1 ..., k), expression formula is：
In formula：kdFor matching factor；fiFor working frequency；fclkFor system clock frequency.
(2) frequency word controller is by phase difference frequency word Δ Mi(i=0,1 ..., k) and frequency word Mi(i=0,1 ..., k) Algebraic operation is carried out, updated frequency word M is calculatedi+1(i=0,1 ..., k).Wherein, work as N<0 or N>NsWhen, Mi+1= Mi-ΔMi；As 0≤N≤NsWhen, Mi+1=Mi.Finally by frequency word Mi+1(i=0,1 ..., k) input to DDS.
(3) DDS is under the action of system clock, to the frequency word M of inputi+1(i=0,1 ..., k) adds up, and will tire out Value after adding is compared with the threshold value of n bit frequency word registers, exports PWM1 the and PWM2 square-wave signals of two-way complementation, and its Frequency is fi+1(i=0,1 ..., k).
(4) it repeats step (1) and arrives step (3), until induction heating power system stalls.
The beneficial effects of the present invention are：
1, the present invention has fast resonant frequency search, bandwidth and spy with high accuracy using digital frequency-tracking control utensil Point.
2, the present invention carries out shaping using shaping filter to the signal for representing load voltage and current phase, reduces height Influence of the frequency jittering noise to phase comparator, enhances the anti-interference ability of system.
3, the present invention generates PWM wave using DDS principles, enhances the frequency discrimination precision of frequency-tracking system, makes broadband sense Answer heating power supply more stable.
Description of the drawings
Fig. 1 is broadband induction heating power system block diagram；
Fig. 2 is digital frequency tracing control device structure diagram；
Fig. 3 is shaping filter sequence diagram；
Fig. 4 is phase comparator sequence diagram；
Fig. 5 is digital filter sequence diagram；
Fig. 6 is frequency word controller flow chart；
Fig. 7 is that DDS generates PWM sequence diagrams.
Specific implementation mode
In order to keep the objectives, technical solutions, and advantages of the present invention clear, the present invention is done into one below in conjunction with attached drawing Walk explanation：
As shown in Figure 1, a kind of resonant frequency tracking technique of broadband induction heating power includes：Current rectifying and wave filtering circuit, Full bridge inverter, impedance-matching transformer, resonance circuit, Zero-cross comparator circuit, digital frequency tracing control device and full-bridge Driving circuit.
Current rectifying and wave filtering circuit includes four rectifier diode Ds1、Ds2、Ds3、Ds4With electrolytic capacitor Cd, wherein Ds1And Ds2P Pole is separately connected Ds3And Ds4The poles N constitute A, B point, Ds1And Ds2The poles N be connected to C points, Ds3And Ds4The poles P be connected to D points, filter Wave capacitance CdAnode and cathode be connected respectively to C points and D points, the exchange of input terminal A, B point connection 220V/50Hz of the module Alternating current, output end C points connect the drain electrode of full bridge inverter metal-oxide-semiconductor S1 and S2, and output end D points connect the source of metal-oxide-semiconductor S3 and S4 Pole.
Hourglass source electrode difference inverse parallel Ultrafast recovery diode D1, D2 of metal-oxide-semiconductor S1, S2, S3, S4 in full bridge inverter, D3, D4, the source electrode of metal-oxide-semiconductor S1 and the drain electrode of metal-oxide-semiconductor S3, which are connected, constitutes the midpoint G2 of left side bridge arm, metal-oxide-semiconductor S2 source electrodes and metal-oxide-semiconductor S4 drain electrodes, which are connected, constitutes the midpoint G1 of right side bridge arm.
The G1 and G2 of the input terminal connection full-bridge inverter of impedance-matching transformer, output end connect resonance circuit.
Resonance circuit is popped one's head in by yoke, detection sample and resonant capacitance C form, wherein between yoke probe and detection sample Electromagnetic Coupling Characteristic can be equivalent to lumped parameter R and L, input terminal is connected with the output end of impedance-matching transformer；Zero passage Comparison circuit is by current transformer TA, sampling resistor Rs、R1And C1Low-pass filter, the high speed zero-crossing comparator U1 compositions of composition, The current bus bar of load resonant circuit is passed through to the centre bore of current transformer, the current signal for obtaining resonance circuit, warp Obtain representing the signal S of current phase after zero-crossing comparator processingIInput to digital frequency tracing control device.
Digital frequency tracing control device is made of digital phase discriminator, digital filter and digital oscillator, after processing PWM1 the and PWM2 signals for exporting two-way complementation, are inputted to full bridge driving circuit；It is exported after full bridge driving circuit is handled Tetra- road signal of SW1, SW2, SW3 and SW4 is respectively used to driving metal-oxide-semiconductor S1, S2, S3 and S4.
Further, as Fig. 2 digital frequency tracing control devices designed include mainly：Shaping filter, phase comparator, Digital filter, phase difference frequency word controller, reference frequency word controller, phase angle threshold controller, frequency word controller and Direct Digital Synthesizer (Direct Digital Synthesizer, DDS).
Shaping filter as described in Figure 3 mainly filters out input signal SUAnd SIHigh dither noise.L2H_U is main Detect input signal SURising edge, H2L_U predominantly detects input signal SUFailing edge；In order to judge the rising of input signal Edge and failing edge introduce variable F1_U, F2_U, F1_U=1, F2_U=1 under original state, when module is started to work, F1_U =SU, F2_U=1, H2L_U=((F2_U==1)s && (F1_U==0)), L2H_U=((F2_U==0) && (F1_U== 1)), in input signal SURising edge L2H_U generate the pulse signal of a clock cycle and held when detecting L2H_U=1 Line delay operates, and after delay time delay, isL_U will produce the pulse signal of a clock cycle；Then believe in input Number SUFailing edge H2L_U generate the pulse signal of a clock cycle and execute delay operation when detecting H2L_U=1, Delay time delay terminates, and isH_U will produce the pulse signal of a clock cycle；It is defeated in the rising edge for detecting isH_U Go out signal SU' height is set, output signal S when detecting the rising edge of isL_UU' set low.Similarly, L2H_I predominantly detects input signal SIRising edge, H2L_I predominantly detects input signal SIFailing edge；In order to judge the rising edge and failing edge of input signal, draw Enter variable F1_I, F2_I, F1_I=1, F2_I=1 under original state, when module is started to work, F1_I=SI, F2_I=1, ((F2_I==1)s && (F1_I==0)), ((F2_I==0)s && (F1_I==1)) believes L2H_I=H2L_I=in input Number SIRising edge L2H_I generate the pulse signal of a clock cycle and execute delay operation when detecting L2H_I=1, After delay time delay, isL_I will produce the pulse signal of a clock cycle；Then in input signal SIDecline The pulse signal that a clock cycle is generated along H2L_I executes delay operation, delay time when detecting H2L_I=1 Delay terminates, and isH_I will produce the pulse signal of a clock cycle；The output signal in the rising edge for detecting isH_I SI' height is set, output signal S when detecting the rising edge of isL_II' set low.
Phase comparator as described in Figure 4 is made of double D trigger-types phase discriminators, SU' be phase discriminator all the way input signal, Represent load voltage phase signal；SI' be another way phase discriminator input signal, represent load current phase signal.SU' connection D type flip flop output termination up, SI' the d type flip flop output termination dn, up and dn of connection be connected to couple D by a NAND gate The reset terminal of trigger-type phase discriminator.Work as SU' advanced SI' when, up output phase difference signals, dn is comparison signal；Work as SU' lag SI’ When, dn output phase difference signals, up is comparison signal.
Digital filter block as described in Figure 5 is made of counter and latch.Three are generated according to input signal up/dn Kind signal：Count enable signal cnt_en, reset signal cnt_clr and latch data signal cnt_latch, specific work are counted It is as process：(1) rising edge of up/dn signals is waited for, while judging the state of reset signal；(2) when reset signal is low electricity Usually counter starts to start, and level conversion occurs for rising edges of the cnt_ensig in up/dn, divides similar to by up/dn signals two Frequently, when cnt_en is high level, counter cnt is started counting up；When cnt_en is low level, counter cnt values are kept not Become；(3) when cnt_latch is high level, the value of counter cnt is latched, when cnt_clr is low level, The value of counter cnt is reset；(4) count value for obtaining up is N1, the count value of dn is N2, by count value N1、N2Input to phase Potential difference frequency word controller.
The structure of the digital oscillator of digital frequency tracing control device is as shown in Figure 2.First, it is controlled by reference frequency word Device and phase angle threshold controller determine reference frequency word M0With the signal N for representing phase angle threshold values.Its resonant frequency searches for work automatically It is as process：
(1) after induction heating power system starts, the waiting of phase difference frequency controller represents phase signal and compares The count value N of signal dutyfactor size1And N2Arrival, and by count value N1And N2Difference operation is carried out to obtain representing phase difference The N of size determines phase difference frequency word Δ M according to Ni(i=0,1 ..., k), wherein Δ MiIt is determined by following formula：
In formula：kdFor matching factor；fiFor working frequency；fclkFor system clock.
(2) as shown in fig. 6, frequency word controller is by phase difference frequency word Δ Mi(i=0,1 ..., k) and frequency word Mi(i= 0,1 ..., k) algebraic operation is carried out, updated frequency word M is calculatedi+1(i=0,1 ..., k).Wherein, work as N<0 or N>Ns When, Mi+1=Mi-ΔMi；As 0≤N≤NsWhen, Mi+1=Mi.Finally by frequency word Mi+1(i=0,1 ..., k) input to DDS.
(3) DDS as described in Figure 7 generates pwm signal.Using 32 frequency word registers, in each clock cycle Rising edge adds up to accumulator cnt1, cnt2, original state cnt1=0, cnt2=0.When rising edge clock arrives, Accumulator executes cnt1=cnt1+Mi+1If the value of accumulator cnt1 is more than or equal to zero and is less than or equal to (32 ' H80000000- tdead) when, then PWM1=1；If the value of accumulator cnt1 is more than (32 ' H80000000-tdead) when, then PWM1=0；Work as accumulator Value when being more than 32 ' HFFFFFFFF, can automatic clear.At the same time, when rising edge clock arrives, accumulator executes cnt2 =cnt2+Mi+1If the value of accumulator cnt2 is more than or equal to 32 ' H80000000 and is less than or equal to (32 ' HFFFFFFFF-tdead), Then PWM2=1；If the value of accumulator cnt2 is more than or equal to zero and is less than 32 ' H80000000, PWM2=0.By this principle, Two-way complementation can be generated and with dead time tdeadPWM1 and PWM2 signals.
(4) step (1)-step (3) is repeated, until induction heating power system stalls.
Content described in this specification embodiment is only enumerating to the way of realization of inventive concept, protection of the invention Range is not construed as being only limitted to the concrete form that embodiment is stated, protection scope of the present invention is also and in art technology Personnel according to present inventive concept it is conceivable that equivalent technologies mean.

Claims (7)

1. the broadband induction heating power based on resonant frequency tracking, it is characterised in that：It is inverse including current rectifying and wave filtering circuit, full-bridge Become circuit, impedance-matching transformer, resonance circuit, Zero-cross comparator circuit, digital frequency tracing control device and full-bridge driving electricity Road；
The digital frequency tracing control device is made of digital phase discriminator, digital filter and digital oscillator；The number Digit phase discriminator is made of shaping filter and phase comparator, and the digital oscillator is by phase difference frequency word controller, base Quasi- frequency word controller, phase angle threshold controller, frequency word controller and Direct Digital Synthesizer composition；
The specific implementation process of the digital frequency tracing control device is：
(1) the representative load current phase signal S for exporting zero-crossing comparatorIWith Direct Digital Synthesizer output its In represent load voltage phase signal S all the wayUIt is input to shaping filter, it is advance by judging under the action of system clock The state of defined variable detects SIAnd SUThe rising edge and failing edge of signal, the high dither of two paths of signals is filtered out by delay Noise, and the signal S after shaping is exportedI' and SU' input to phase comparator, wherein SI' and SU' it is respectively SIAnd SUShaping Filtered signal；
(2) phase comparator is by comparing two-way input signal SI' and SU' rising edge arrive time obtain its phase relation, obtain To two-way output signal up and dn and digital filter is inputed to, wherein being phase signal all the way, then another way is to compare letter Number；
(3) digital filter under the action of system clock by the high level modulation of two-way input signal up and dn at a series of Pulse, and N is calculated by counter1And N2, wherein N1And N2The duty ratio size of up and dn is respectively represented, it finally will meter Numerical value of N1And N2Input to the phase difference frequency word controller of digital oscillator；
(4) phase difference frequency word controller is to count value N1And N2Obtain representing the N of phase difference size after progress difference operation, and Phase difference frequency word Δ M is determined according to the size of N valuesi, i=0,1 ..., k, finally by N and Δ MiInput to frequency word controller；
(5) frequency word controller is by phase difference frequency word Δ MiWith the reference frequency word M of reference frequency word controller output0It carries out Algebraic operation obtains frequency word Mi+1, and by frequency word Mi+1Input to Direct Digital Synthesizer, successively recycle (1)~ (4) until N values are more than or equal to zero and represent the signal N of phase angle threshold value less than or equal to the output of phase angle threshold controllers, then frequency word Mi+1It remains unchanged；
(6) Direct Digital Synthesizer is under the action of system clock, to frequency word Mi+1It adds up, after cumulative Value is compared with the threshold value of frequency word register, exports the PWM1 and PWM2 of two-way complementation to full bridge driving circuit.
2. the broadband induction heating power according to claim 1 based on resonant frequency tracking, it is characterised in that：It is described Current rectifying and wave filtering circuit by four power diode Ds1、Ds2、Ds3、Ds4With electrolytic capacitor CdComposition, input terminal and alternating current phase Even, output end is connected with the input terminal of full bridge inverter.
3. the broadband induction heating power according to claim 1 based on resonant frequency tracking, it is characterised in that：It is described Full bridge inverter include four power tubes S1, S2, S3, S4 and four Ultrafast recovery diodes D1, D2, D3, D4, each The hourglass source electrode of power tube distinguishes one Ultrafast recovery diode of inverse parallel, and the drain electrode of the source electrode of power tube S1 and power tube S3 It is connected and constitutes the midpoint G2 of left side bridge arm, power tube S2 source electrodes are connected with power tube S4 drain electrodes constitutes the midpoint G1 of right side bridge arm, Midpoint G1, G2 are connected as the signal output end of full bridge inverter with impedance-matching transformer.
4. the broadband induction heating power according to claim 1 based on resonant frequency tracking, it is characterised in that：It is described The input terminal of impedance-matching transformer be connected with the output end of full bridge inverter, the input terminal of output end and resonance circuit It is connected.
5. the broadband induction heating power according to claim 1 based on resonant frequency tracking, it is characterised in that：It is described Resonance circuit by yoke probe, detection sample and resonant capacitance C form, wherein yoke probe and detection sample between electromagnetism Coupled characteristic can be equivalent to lumped parameter R and L.
6. the broadband induction heating power according to claim 1 based on resonant frequency tracking, it is characterised in that：It is described Zero-cross comparator circuit be made of current transformer, sampling resistor, low-pass filter, zero-crossing comparator, the resonance circuit Current bus bar passes through the centre bore of current transformer, the current signal for obtaining resonance circuit, after zero-crossing comparator is handled Obtain representing the signal S of load current phaseI, and input to digital frequency tracing control device.
7. the broadband induction heating power according to claim 1 based on resonant frequency tracking, it is characterised in that：It is described Full bridge driving circuit processing after export tetra- road signal of SW1, SW2, SW3 and SW4, be respectively used to driving power switching tube S1, S2, S3 and S4.
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CN109379795A (en) * 2018-11-29 2019-02-22 洛阳升华感应加热股份有限公司 The reverse frequency of induction heating power tracks locking phase control system
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