CN108832838B - Constant-power driving power supply and driving method based on ARM and multiplier - Google Patents
Constant-power driving power supply and driving method based on ARM and multiplier Download PDFInfo
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- CN108832838B CN108832838B CN201810660932.7A CN201810660932A CN108832838B CN 108832838 B CN108832838 B CN 108832838B CN 201810660932 A CN201810660932 A CN 201810660932A CN 108832838 B CN108832838 B CN 108832838B
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Abstract
The invention relates to an ultrasonic power supply technology, in order to provide a constant power supply with high power factor and quick response, reduce the complexity of a system and improve the detection precision, the constant power driving power supply and the driving method based on an ARM and a multiplier have the following structures: the first part is a driving circuit which comprises a DDS chip, an integrated PWM wave control chip and an inversion amplifying circuit; the second part is a sampling matching circuit; the third part is a signal conditioning circuit; and the fourth part is a micro-control module which consists of an ARM microprocessor and realizes constant power control by adjusting the frequency and the duty ratio of the PWM wave. The invention is mainly applied to the design and manufacture occasions of the ultrasonic power supply.
Description
Technical Field
The invention relates to the technical field of power supplies, in particular to the technical field of ultrasonic drive power supplies, and discloses a constant-power ultrasonic drive power supply based on an ARM (advanced RISC machine) and a multiplier.
Background
The ultrasonic technology is based on electronic technology and computer technology, is widely applied to the fields of machinery, aviation, electronics, materials, medicine and the like, and is an internationally recognized high and new technical field. An ultrasonic driving power supply, referred to as an ultrasonic power supply for short, converts commercial power with the frequency of 50Hz, the voltage of 220V or 380V into alternating current with the frequency of more than 20kHz and the voltage of hundreds to thousands of volts, provides high-frequency energy for an ultrasonic transducer, is a core component of an ultrasonic system, and the performance of the ultrasonic power supply directly determines the performance of the ultrasonic system. The key technology of the ultrasonic power supply is frequency tracking and constant power control of the transducer.
The frequency tracking of the transducer is always the focus and hot spot of the ultrasonic power research, and is mostly realized by adopting a phase locking mode at present. In contrast, constant power ultrasound power systems are less developed, and in fact, the constant power of ultrasound systems is of great significance, especially in the fields of ultrasound cleaning, ultrasound extraction, ultrasound processing, and the like. Firstly, whether the power is constant or not directly influences the experience of a user, and a stable ultrasonic instrument brings better experience to the user; secondly, the quality of ultrasonic processing and ultrasonic cleaning is directly influenced by the constancy of the power, and the stable output power can bring better processing and cleaning effects; finally, the safety of the ultrasonic system is determined by the constant power control, the service lives of the transducer, the amplitude transformer, the welding head and the like are greatly shortened by the severe power change, and the system is burnt even if the instantaneous power is too high, so that potential safety hazards are caused.
The output power of an ultrasound system is affected by many factors, which make constant power control difficult, including: 1) a change in load; 2) changes in the environment such as temperature, humidity, etc.; 3) transducer status, such as differences between transducers, transducer aging, mounting, etc.; 4) the drive frequency is selected to have different power outputs, and the series resonance frequency (i.e. mechanical resonance frequency) of the transducer is mostly adopted as the drive frequency at present. Of the above factors, the variation in load and the driving frequency are the main influencing factors.
For a long time, scholars at home and abroad carry out extensive research in the field of ultrasonic power supplies, the performance of the ultrasonic power supplies is greatly improved, but still, the scholars have some defects which are mainly as follows: 1) the accurate tracking of the resonant frequency is pursued, so that the power difference after frequency tracking is huge under different conditions; 2) due to the error of the tuning matching circuit, after frequency tracking, the power factor of the system is low, the related national regulations are not met, and the heating value of the driving circuit is increased; 3) the existing constant power control ultrasonic power supply mostly adopts a stepping mode to adjust power, has low adjustment speed and is not suitable for occasions with severe load change.
In order to solve the defects, the invention designs a constant power driving power supply with high power factor and quick response.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention aims to provide a constant power supply with high power factor and quick response, which comprises the following components:
(1) an active power detection circuit based on a multiplier is designed, and replaces a traditional peak value or effective value detection circuit, so that the active power of a system can be directly detected, the complexity of the system is reduced, and the detection precision is improved.
(2) A voltage and current sampling and phase detection circuit and a corresponding signal processing circuit are designed, and a phase correction circuit is added for error compensation, so that the accuracy of phase detection is ensured.
(3) A constant power control algorithm based on an ARM (advanced RISC machines) microcontroller is designed, the power factor and the active power of the system are monitored in real time, and the system can quickly and stably work near the set rated power on the premise of maintaining the high power factor of the system.
Therefore, the invention adopts the technical scheme that the constant power driving power supply based on the ARM and the multiplier has the following structure:
the first part is a driving circuit which comprises a DDS (Direct Digital Synthesizer) chip, an integrated PWM (pulse Width modulation) wave control chip and an inversion amplifying circuit, wherein an ARM microprocessor outputs two DA (Digital to Analog converter) signals to control the oscillation frequency and the duty ratio of an oscillator of the integrated PWM wave control chip, controls the DDS chip to output square waves with any frequency to the synchronizing end of the integrated PWM wave control chip, controls the frequency of the output PWM waves, drives the PWM square waves to be output to the inversion amplifying circuit, and then is coupled to a transducer through a transformer to be output;
the second part is a sampling matching circuit, an LC network is adopted to match the transducer, an inductor in the LC network is connected with the transducer in series, a capacitor in the LC network is connected with the transducer in parallel to realize the tuning and impedance matching of the transducer, a current sensor collects the current flowing through the transducer, and a precision resistor is connected with two ends of a transformer in parallel to collect voltage signals;
the third part is a signal conditioning circuit, voltage and current sampling signals are firstly subjected to signal amplification through a signal amplification circuit, then are filtered by a switched capacitor filter circuit to remove noise and harmonic components, and are subjected to phase correction through a phase shift circuit; one path of the corrected signal is connected with a multiplier, the other path of the corrected signal is connected with a phase discrimination circuit, the multiplier multiplies voltage and current signals to obtain a signal containing active power information, then a direct current signal is obtained through a low-pass filter and is transmitted to an AD (analog to digital converter) port of an ARM microprocessor for detection, the phase discrimination circuit converts the voltage and current signals into square wave pulses containing phase angle information and transmits the square wave pulses to an I/O (input/output) port of the microprocessor for phase angle detection; the switched capacitor filter circuit is two identical path band-pass filter circuits composed of switched capacitor filters, the center frequency of the switched capacitor filter circuit is controlled by an ARM microprocessor to output frequency square waves, the center frequency of the switched capacitor filter circuit is completely consistent with the PWM wave frequency of the driving transducer, and the filtered signal gains are guaranteed to be consistent;
the fourth part is a micro control module which consists of an ARM microprocessor, wherein the ARM microprocessor is used for controlling the DDS chip to output pulse square wave signals to control the central frequency of the switched capacitor filter besides finishing the control and integration of the PWM wave control chip and the DDS chip which are described in the first part so as to realize the tracking filtering of the sampling signals; and constant power control is realized by adjusting the frequency and the duty ratio of the PWM wave.
The specific steps for realizing the constant power control are as follows:
a) setting the initial sweep frequency range as (f)d,fu) Let fu＝F1，fd＝F2Setting the driving duty ratio as C, and making C equal to C1In which F is1、F2、C1Setting k as 1 for a set constant, wherein k is the frequency of frequency sweeping iteration;
b) controlling the drive circuit at a frequency
Duty cycle c drives the transducer;
c) sampling, detecting the phase angle theta of voltage and current, if- △<θ<△ is the allowable phase error, and the driving frequency f is the allowable phase errorkIs the working frequency;
if theta>△, then let fu＝fkK is k +1, go to step b);
otherwise, let fd＝fkK is k +1, go to step b);
d) at a frequency fkThe duty ratio c drives the transducer to detect the active power P of the system;
e) to judge P, if 0.99P0<P<1.05P0，P0To set the power level, the frequency f is setkDuty cycle c drives the transducer;
otherwise, it orders
Jumping to the step d);
f) detecting the phase angles theta of the voltage and the current, if- △ < theta < △, jumping to the step d), and circularly executing, otherwise, re-sweeping the frequency, and jumping to the step a).
The constant power driving power supply driving method based on the ARM and the multiplier is realized by means of the driving power supply device, and specifically comprises the following steps:
a) setting the initial sweep frequency range as (f)d,fu) Let fu＝F1，fd＝F2Setting the driving duty ratio as C, and making C equal to C1In which F is1、F2、C1Setting k as 1 for a set constant, wherein k is the frequency of frequency sweeping iteration;
b) controlling the drive circuit at a frequency
Duty cycle c drives the transducer;
c) sampling, detecting the phase angle theta of voltage and current, if- △<θ<△ is the allowable phase error, and the driving frequency f is the allowable phase errorkIs the working frequency;
if theta>△, then let fu＝fkK is k +1, go to step b);
otherwise, let fd＝fkK is k +1, go to step b);
d) at a frequency fkThe duty ratio c drives the transducer to detect the active power P of the system;
e) to judge P, if 0.99P0<P<1.05P0，P0To set the power level, the frequency f is setkDuty cycle c drives the transducer;
otherwise, it ordersJumping to the step d);
f) detecting the phase angles theta of the voltage and the current, if- △ < theta < △, jumping to the step d), and circularly executing, otherwise, re-sweeping the frequency, and jumping to the step a).
Further, the steps d), e) and f) are carried out, the power is constant, the transducer is driven by the PWM wave, the output power of the transducer is in direct proportion to the duty ratio c of the PWM wave, and the Pulse Width Modulation (PWM) wave is enabled to be in direct proportionDirectly adjust P to P0And directly tracking to the duty ratio corresponding to the required power in one step of iteration.
Further, if the load, environment, etc. do not change greatly, the system will cycle between steps d), e), f) to stabilize the active power of the transducer at P0And on the left and right, if the load is greatly changed and the frequency of the transducer is shifted, the loop is jumped out, the step a) is operated again, the frequency tracking is carried out again, and then the constant rate control is carried out.
The invention has the characteristics and beneficial effects that:
(1) the ARM microprocessor is used for controlling the DDS chip to output frequency square waves to a synchronous end of the PWM integrated control chip, the frequency of the driving PWM waves is accurately controlled, frequency drift of the oscillation type frequency generator is effectively avoided, digital frequency control is achieved, and the operation is stable and reliable;
(2) the central frequency of the switched capacitor filter is controlled in real time by using the ARM microprocessor to control the DDS chip to output frequency square waves, so that a constant-bandwidth tracking filter is realized, the amplitude change after filtering of signals with different frequencies is avoided when the frequency of a sampling signal fluctuates, and the power detection precision is improved;
(3) the multiplier is used for directly detecting the active power, namely the actual output power of the transducer, so that the influence of errors in the detection of effective values of voltage and current on a detection result is avoided, the detection precision is improved, and the system complexity is reduced. In addition, the conditioning circuit of the voltage and current signals adopts the same amplifying and filtering circuit and is added with a phase-shifting circuit, and phase correction is carried out before operation, so that the phase discrimination precision is improved;
(4) the system is always maintained at a high power factor, the energy utilization rate and the EMC performance of the system are improved, and the high power factor can reduce the heat productivity of the MOS tube and the transformer and prolong the service life of the system;
(5) the ultrasonic power supply is quickly stabilized near the preset power by taking the stable power output as a control key point through closed-loop control, and the constant of the output power is controlled by continuously detecting the phase and power information of the system;
(6) the adaptive capacity is strong, the system has wide applicability, the precision requirement on the matching network is low, and the constant power output can be fast under the conditions of slight mismatching and load change.
In summary, compared with other ultrasonic power supplies, the ultrasonic power supply has the advantages of simple structure, high response speed, constant power, high power factor and the like.
Description of the drawings:
fig. 1 is a block diagram of a system of a constant power driving power supply based on an ARM and a multiplier.
Fig. 2 is a flow chart of a constant power control algorithm.
Fig. 3 is a graph of the effect of the constant rate control algorithm.
In fig. 1, 1 is a driving circuit, 2 is a sampling matching circuit, 3 is a signal conditioning circuit, 4 is a microprocessor module, 5 is an inverter amplifying circuit, 6 is an integrated PWM generator circuit, 7 is a sampling precision resistor, 8 is a current sensor, 9 is a piezoelectric ultrasonic transducer, 10 is a signal amplifying circuit, 11 is a switched capacitor filter, 12 is a phase shifting circuit, 13 is a zero-crossing comparator circuit, 14 is a multiplier circuit, 15 is a phase discrimination circuit, 16 is a low pass filter circuit, 17 is an ARM microprocessor, and 18 is a DDS chip.
Detailed Description
The invention adopts the technical scheme that a constant power driving power supply based on an ARM and a multiplier comprises the following four parts:
the first part is a driving circuit, as shown in fig. 1, which comprises a DDS (Direct Digital Synthesizer) chip 18, an integrated PWM (pulse Width modulation) wave control chip 6 (such as SG3525A) and an inverting amplifier circuit 5, wherein an ARM microprocessor outputs two da (Digital to Analog converter) signals to control the oscillation frequency and duty ratio of an integrated PWM wave control chip oscillator, and the ARM microprocessor controls the DDS chip to output square waves with any frequency to a synchronizing terminal of the integrated PWM wave control chip to accurately control the output PWM wave frequency, thereby realizing the synchronization and accurate control of the driving PWM square waves, and outputs the driving PWM square waves to the inverting amplifier circuit 5 to amplify the signals into power signals required by a transducer.
The second part is a sampling matching circuit, as shown in fig. 1, an LC network is used to match the transducer to achieve tuning and impedance matching of the transducer, so that the series resonant frequency of the transducer is consistent with the matched resonant frequency, and the equivalent resistance of the system is reduced. The current sensor 8 is used for collecting the current flowing through the transducer, the precision resistor 7 is connected in parallel with the two ends of the transformer for collecting voltage signals, and the voltage signals at the two ends of the traditional collecting transducer are replaced, so that the fluctuation of the sampling signals is smaller.
The third part is a signal conditioning circuit, as shown in fig. 1, a voltage and current sampling signal is firstly subjected to signal amplification through a signal amplification circuit 10, then is subjected to noise and harmonic component filtering through a switched capacitor filter circuit 11, and is subjected to phase correction through a phase shift circuit 12; the corrected signal is connected to a multiplier 14 in one path, and connected to a phase detection circuit 15 in one path, the multiplier multiplies the voltage signal and the current signal to obtain a signal containing active power information, then the signal is passed through a low-pass filter 16 to obtain a direct current signal, and the direct current signal is transmitted to an AD (analog to Digital converter) port of the ARM microprocessor for detection, and the phase detection circuit converts the voltage signal and the current signal into a square wave pulse containing phase angle information and transmits the square wave pulse to an I/O (input/output) port of the microprocessor for phase angle detection. The switched capacitor filter circuit 11 is two identical bandpass filter circuits composed of switched capacitor filters (such as LTC1068 and LTC1064), the center frequency of the switched capacitor filter circuit is controlled by an ARM to control the output frequency square wave of a DDS chip in real time, and the center frequency of the switched capacitor filter circuit is completely consistent with the frequency of a PWM wave driving a transducer, so that the filtered signal gains are ensured to be consistent.
The fourth part is a micro control module, as shown in fig. 1, which is composed of an ARM microprocessor 17 and an external circuit, the microprocessor outputs two paths of DA signals to control the oscillation frequency and duty ratio of the integrated PWM wave control chip oscillator, and the microprocessor controls the DDS chip to output any frequency square waves to the integrated PWM wave control chip synchronization end through spi (serial Peripheral interface) communication to control the output PWM wave frequency thereof, thereby realizing the synchronization and accurate control of the driving PWM square wave frequency; the microprocessor controls the DDS chip to output pulse square wave signals to control the center frequency of the switched capacitor filter so as to realize the tracking filtering of the sampling signals; the microprocessor detects active power information output by the multiplier by using an internal AD interface, and interacts with a display screen and a user key through an SPI protocol; the microprocessor is programmed to realize the automatic acquisition, operation and processing of the signals and realize a constant power control algorithm.
The specific implementation process is as follows:
the DA port of the ARM microprocessor 17 outputs direct current voltage to the PWM wave control integrated chip 6, so that the frequency of the oscillator is f1And simultaneously controlling the DDS chip 18 to output a pulse square wave with the frequency f to the synchronous end of the PWM wave control integrated chip 6, so that the pulse square wave with the frequency f is output by the DDS chip and the PWM driving square wave with the frequency f slightly larger than f1Taking f as 1.02f1。
Furthermore, the driving square wave passes through the half-bridge inverting and amplifying circuit 5, then is transformed by the transformer and then is applied to the matching circuit and two ends of the energy converter 17, and the energy converter 17 is driven to work. The sampling resistor 7 and the current sensor 8 respectively sample to obtain voltage and current signals, the voltage and current signals are amplified by the signal amplifying circuit 10 and transmitted to the switched capacitor filter 11, and the ARM microprocessor controls the central frequency of the switched capacitor filter to be consistent with the signal frequency and filters harmonic waves and noise. The filtered current signal is passed through a phase modulation circuit 12, and before the system is started, phase correction is performed to compensate for the phase delay of voltage and current samplesDifference to obtain a voltage of a single frequency
Current signal
Is provided with
Is 0, then.
Further, the phase-modulated voltage and current signals are divided into two paths, one path of the phase-modulated voltage and current signals is transmitted to the comparator 13 to be converted into square waves, and then transmitted to the phase discrimination circuit 15 to obtain pulse square waves containing phase angle information, and the pulse square waves are transmitted to an I/O port of the ARM microprocessor to be subjected to pulse capture, and a voltage and current phase angle theta is calculated; the other path is transmitted to the multiplier 14 to output the voltage
And current signal
Multiplication, let:
u, I are voltage and current amplitudes, w is signal frequency, the multiplier outputs the result U0Comprises the following steps:
where E is a fixed value, a constant determined by the multiplier chip. It can be seen that U0The medium-frequency component contains high-frequency components, and the direct-current voltage U is obtained after low-pass filtering1Comprises the following steps:
as can be seen, 2EU1The total active power of the output end is obtained, and the matching inductor, the matching capacitor and the static capacitor of the transducer only contain reactive power components, so that the 2EU1I.e. the active power of the transducer. U shape1The active power P is obtained by the ARM microprocessor through AD sampling, so that the active power P is monitored in real time.
Correspondingly, a flow chart of a constant power control algorithm of the constant power driving power supply based on the ARM and the multiplier is shown in fig. 2, and the specific steps are as follows:
a) setting the initial sweep frequency range as (f)d,fu) Let fu＝F1，fd＝F2Setting the driving duty ratio as C, and making C equal to C1In which F is1、F2、C1Setting k as 1 for a set constant, wherein k is the frequency of frequency sweeping iteration;
b) controlling the drive circuit at a frequency
Duty cycle c drives the transducer;
c) sampling, detecting the phase angle theta of voltage and current, if- △<θ<△ (△ is allowable phase error), the driving frequency f is set at the timekIs the working frequency;
if theta>△, then let fu＝fkK is k +1, go to step b);
otherwise, let fd＝fkK is k +1, go to step b);
d) at a frequency fkThe duty ratio c drives the transducer to detect the active power P of the system;
e) to judge P, if 0.99P0<P<1.05P0(P0To set the power level), at the frequency f at that timekDuty cycle c drives the transducer;
otherwise, it orders
Jump to stepStep d);
f) detecting the phase angles theta of the voltage and the current, if- △ < theta < △, jumping to the step d), and circularly executing, otherwise, re-sweeping the frequency, and jumping to the step a).
The system is executed according to the steps, and the phase angle theta of the voltage and the current is controlled to be close to 0 DEG through the steps a), b) and c) based on bisection frequency tracking, so that the transducer is driven at the frequency close to the series resonance frequency of the transducer, and a higher power factor is obtained, wherein the power factor of the transducer loop is cos theta, when △ is set to be 8 DEG, the power factor of the transducer loop is above 0.99, when △ is set to be 15 DEG, the power factor of the transducer loop is above 0.966, when △ is set to be 20 DEG, the power factor of the transducer loop is above 0.94, and when △ is set to be 25 DEG, the power factor of the transducer loop is above 0.906.
Further, the steps d), e) and f) are carried out, the power is constant, the transducer is driven by the PWM wave, the output power of the transducer is in direct proportion to the duty ratio c of the PWM wave, and the Pulse Width Modulation (PWM) wave is enabled to be in direct proportion
Then P can be directly adjusted to P0And left and right, directly tracking to the duty ratio corresponding to the required power in one step of iteration.
Further, if the load, environment, etc. do not change greatly, the system will cycle between steps d), e), f) to stabilize the active power of the transducer at P0And on the left and right, if the load is greatly changed and the frequency of the transducer is shifted, the loop is jumped out, the step a) is operated again, the frequency tracking is carried out again, and then the constant rate control is carried out. Through the process, the ultrasonic transducer can have constant power output under the condition of load change, and the high power factor of the system is kept.
The invention is described in detail below with reference to the drawings and the detailed description.
In fig. 1, the driving circuit 1 is composed of a PWM wave control ic 6 and a half-bridge inverting amplifier circuit 5, and the DA port of the ARM microprocessor 17 outputs a dc voltage to the PWM wave control ic 6 to make the oscillator frequency f1And simultaneously controlling the DDS chip 18 to output a pulse square wave with the frequency f to the synchronous end of the PWM wave control integrated chip 6, so that the pulse square wave with the frequency f is output by the DDS chip and the PWM driving square wave with the frequency f slightly larger than f1Taking f as 1.02f1. The driving square wave passes through the half-bridge inverting and amplifying circuit 5, then is transformed by the transformer and then is added to the two ends of the matching circuit and the energy converter 17, and the energy converter 17 is driven to work. The sampling resistor 7 and the current sensor 8 respectively sample to obtain voltage and current signals, the voltage and current signals are amplified by the signal amplifying circuit 10 and transmitted to the switched capacitor filter 11, and the ARM microprocessor controls the central frequency of the switched capacitor filter to be consistent with the signal frequency and filters harmonic waves and noise. The filtered current signal passes through a phase modulation circuit 12, before the system is started, phase correction is firstly carried out to compensate the phase delay difference of voltage and current sampling, and a sinusoidal voltage signal with single frequency is obtainedCurrent signal
Is provided with
Is 0.
Further, the phase-modulated voltage and current signals are divided into two paths, one path of the phase-modulated voltage and current signals is transmitted to the comparator 13 to be converted into square waves, and then transmitted to the phase discrimination circuit 15 to obtain pulse square waves containing phase angle information, and the pulse square waves are transmitted to an I/O port of the ARM microprocessor to be subjected to pulse capture, and a voltage and current phase angle theta is calculated; the other path is transmitted to the multiplier 14 to output the voltage
And current signal
Multiplication, let:
u, I are the voltage and current amplitudes, w is the signal frequency, the multiplier outputs the result U0Comprises the following steps:
where E is a constant fixed voltage determined by the multiplier chip. It can be seen that U0The medium-frequency component contains high-frequency components, and the direct-current voltage U is obtained after low-pass filtering1Comprises the following steps:
as can be seen, 2EU1The total active power of the output end is obtained, and the matching inductor, the matching capacitor and the static capacitor of the transducer only contain reactive power components, so that the 2EU1I.e. the active power of the transducer. U shape1The active power P is obtained by the ARM microprocessor through AD sampling, so that the active power P is monitored in real time.
Correspondingly, a flow chart of a constant power control algorithm of the constant power driving power supply based on the ARM and the multiplier is shown in fig. 2, and the specific steps are as follows:
a) setting the initial sweep frequency range as (f)d,fu) Let fu＝F1，fd＝F2Setting the driving duty ratio as C, and making C equal to C1In which F is1、F2、C1Setting k as 1 for a set constant, wherein k is the frequency of frequency sweeping iteration;
b) controlling the drive circuit at a frequency
Duty cycle c drives the transducer;
c) sampling, detecting the phase angle theta of voltage and current, if- △<θ<△ (△ is allowable phase error), the driving frequency f is set at the timekIs the working frequency;
if theta>△, then let fu＝fkK is k +1, go to step b);
otherwise, let fd＝fkK is k +1, go to step b);
d) at a frequency fkThe duty ratio c drives the transducer to detect the active power P of the system;
e) to judge P, if 0.99P0<P<1.05P0(P0To set the power level), at the frequency f at that timekDuty cycle c drives the transducer;
otherwise, it orders
Jumping to the step d);
f) detecting the phase angles theta of the voltage and the current, if- △ < theta < △, jumping to the step d), and circularly executing, otherwise, re-sweeping the frequency, and jumping to the step a).
The system is executed according to the steps, and the phase angle theta of the voltage and the current is controlled to be close to 0 DEG through the steps a), b) and c) based on bisection frequency tracking, so that the transducer is driven at the frequency close to the series resonance frequency of the transducer, and a higher power factor is obtained, wherein the power factor of the transducer loop is cos theta, when △ is set to be 8 DEG, the power factor of the transducer loop is above 0.99, when △ is set to be 15 DEG, the power factor of the transducer loop is above 0.966, when △ is set to be 20 DEG, the power factor of the transducer loop is above 0.94, and when △ is set to be 25 DEG, the power factor of the transducer loop is above 0.906.
Further, the steps d), e) and f) are carried out, the power is constant, the transducer is driven by the PWM wave, the output power of the transducer is in direct proportion to the duty ratio c of the PWM wave, and the Pulse Width Modulation (PWM) wave is enabled to be in direct proportion
Then P can be directly adjusted to P0And left and right, directly tracking to the duty ratio corresponding to the required power in one step of iteration.
Further, if the load, environment, etc. do not change much, the system will be in stepCirculating between the steps d), e) and f) to stabilize the active power of the transducer at P0And on the left and right, if the load is greatly changed and the frequency of the transducer is shifted, the loop is jumped out, the step a) is operated again, the frequency tracking is carried out again, and then the constant rate control is carried out. Through the process, the ultrasonic transducer can have constant power output under the condition of load change, and the high power factor of the system is kept.
In a verification experiment, after the ultrasonic transducer is loaded, the series resonance frequency is 37486hz, the load resistance is equivalent to 210.3 omega, the Q value of the transducer is about 50, the driving voltage is 200V, the algorithm is started to run in a wider initial sweep frequency range, and F is set1＝35000hz、F2＝45000hz，C1＝0.2，△＝4°，P0The operation results are shown in fig. 3, where the phase angle satisfies the requirement when k is 10, i.e., the 10 th adjustment, the power factor is 0.998, the power is then constant, and when k is 11, the power is stabilized at about 50W, where c is 0.702. Therefore, the system can rapidly realize the constant power output of the ultrasonic transducer in a wider frequency range and keep a higher power factor of the system.
Claims (1)
1. A constant power driving power supply based on an ARM and a multiplier is characterized by comprising the following structures:
the first part is a driving circuit which comprises a DDS (direct Digital synthesizer) chip, an integrated PWM (pulse width modulation) wave control chip and an inversion amplifying circuit; the ARM microprocessor outputs two DA (digital analog converter) signals to control the oscillation frequency and the duty ratio of an oscillator of the integrated PWM wave control chip, the ARM microprocessor controls the DDS chip to output square waves with any frequency to the synchronous end of the integrated PWM wave control chip, the frequency of the output PWM waves is controlled, the PWM square waves are driven to be output to an inversion amplifying circuit, and then the PWM square waves are coupled to the energy converter through a transformer to be output;
the second part is a sampling matching circuit, an LC network is adopted to match the transducer, an inductor in the LC network is connected with the transducer in series, a capacitor in the LC network is connected with the transducer in parallel to realize the tuning and impedance matching of the transducer, a current sensor collects the current flowing through the transducer, and a precision resistor is connected with two ends of a transformer in parallel to collect voltage signals;
the third part is a signal conditioning circuit, voltage and current sampling signals are firstly subjected to signal amplification through a signal amplification circuit, then are filtered by a switched capacitor filter circuit to remove noise and harmonic components, and are subjected to phase correction through a phase shift circuit; one path of the corrected signal is connected with a multiplier, the other path of the corrected signal is connected with a phase discrimination circuit, the multiplier multiplies voltage and current signals to obtain a signal containing active power information, then a direct current signal is obtained through a low-pass filter and is transmitted to an AD (analog to digital converter) port of an ARM microprocessor for detection, the phase discrimination circuit converts the voltage and current signals into square wave pulses containing phase angle information and transmits the square wave pulses to an I/O (input/output) port of the microprocessor for phase angle detection; the switched capacitor filter circuit is two identical path band-pass filter circuits composed of switched capacitor filters, the center frequency of the switched capacitor filter circuit is controlled by an ARM microprocessor to output frequency square waves, the center frequency of the switched capacitor filter circuit is completely consistent with the PWM wave frequency of the driving transducer, and the filtered signal gains are guaranteed to be consistent;
the fourth part is a micro control module which consists of an ARM microprocessor, wherein the ARM microprocessor is used for controlling the DDS chip to output pulse square wave signals to control the central frequency of the switched capacitor filter besides finishing the control and integration of the PWM wave control chip and the DDS chip which are described in the first part so as to realize the tracking filtering of the sampling signals; constant power control is realized by adjusting the frequency and the duty ratio of the PWM wave;
when in work:
a) setting the initial sweep frequency range as (f)d,fu) Let fu＝F1，fd＝F2Setting the driving duty ratio as C, and making C equal to C1In which F is1、F2、C1Setting k as 1 for a set constant, wherein k is the frequency of frequency sweeping iteration;
b) controlling the drive circuit at a frequency
Duty cycle c drive transductionA machine;
c) sampling, detecting the phase angle theta of voltage and current, if-delta<θ<Δ, Δ is an allowable phase error, and the driving frequency f is set to the allowable phase errorkIs the working frequency;
if theta>Δ, then let fu＝fkK is k +1, go to step b);
otherwise, let fd＝fkK is k +1, go to step b);
d) at a frequency fkThe duty ratio c drives the transducer to detect the active power P of the system;
e) to judge P, if 0.99P0<P<1.05P0，P0To set the power level, the frequency f is setkDuty cycle c drives the transducer;
otherwise, it orders
Jumping to the step d);
f) detecting a phase angle theta of the voltage and the current, and if-delta is less than theta and less than delta, jumping to the step d) and circularly executing; otherwise, re-sweeping, and jumping to the step a).
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| CN110702971B (en) * | 2019-09-10 | 2021-11-26 | 天津大学 | Ultrasonic driving power supply capable of automatically tracking series resonant frequency of transducer |
| CN112752378B (en) * | 2019-10-29 | 2023-01-20 | 华润微集成电路(无锡)有限公司 | Silicon controlled rectifier dimming circuit |
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