CN103904871A - Control method of high-frequency heating power switch tube protection circuit - Google Patents
Control method of high-frequency heating power switch tube protection circuit Download PDFInfo
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- CN103904871A CN103904871A CN201410114897.0A CN201410114897A CN103904871A CN 103904871 A CN103904871 A CN 103904871A CN 201410114897 A CN201410114897 A CN 201410114897A CN 103904871 A CN103904871 A CN 103904871A
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Abstract
The invention discloses a control method of a high-frequency heating power switch tube protection circuit. Peak voltage of a resonance capacitor is calculated according to the cycle of voltage waveforms of the resonance capacitor and time of over-voltage in one cycle, and corresponding control measures are taken according to the peak voltage. According to the method, a peak value of the over-voltage is calculated by detecting duration of the over-voltage of the resonance capacitor, different control strategies are taken according to the peak value of the over-voltage, and accordingly a switch tube is protected. According to the method, the circuit is simple, the over-voltage value of the resonance capacitor can be quantized, the corresponding control strategies are taken, and protection measures are safe and reliable.
Description
[technical field]
The present invention relates to Switching Power Supply, relate in particular to a kind of control method of high-frequency heating power switching tube protection circuit.
[background technology]
Existing high-frequency heating power generally consists of the following components, and rectification filtering part part, by commercial power rectification the filtering high-frequency signal of input, offers the DC voltage that rear class is correct.Switch sections, generally forms single tube antiresonant circuit by an IGBT or two IGBT form half-bridge double-tube series resonant circuit.Resonance portion, is in series or in parallel to form by resonant capacitance and leakage transformer or stone or metal plate for standing a stove on as a precaution against fire coil.Output, forms to drive microwave oven magnetic or by magnetic induction heating load by voltage-multiplying circuit.Control section, by sampling input voltage, current signal, provides correct PWM, PFM signal, drives IGBT work.Protection part, by realizing the protection to power switch pipe to the detection of the signals such as input voltage, current signal, resonant capacitance voltage.
Fig. 1 is single tube parallel resonance high-frequency heating power power section schematic diagram.In Fig. 1, Vin+, Vin-are the filtered DC voltage of AC input rectifying, are the stone or metal plate for standing a stove on as a precaution against fire coil of electromagnetic oven when T1 is applied to electromagnetic oven, are the primary coil of leakage transformer of boosting while being applied to microwave oven.RL is load, while being applied to electromagnetic oven, for pot even load, is the magnetron load of secondary high pressure winding rectification rear drive while being applied to microwave oven.C1 is resonant capacitance, and Q1 is switching tube.Voltage after rectification is flowed through T1 and C1 by Q1 copped wave through Vin+, Vin-, forms HF switch voltage, passes to load by T1.
C1 and T1 form a shunt-resonant circuit, and in the time that Q1 turn-offs, C1 and T1 resonance, complete energy exchange, and its waveform is approximately sinusoidal wave half-wave, as shown in Figure 2.
Fig. 3 is two-tube half bridge series resonance high-frequency heating power power section schematic diagram.In Fig. 2, Q1, Q2 are switching tube, are the stone or metal plate for standing a stove on as a precaution against fire coil of electromagnetic oven when T1 is applied to electromagnetic oven, are the primary coil of leakage transformer of boosting while being applied to microwave oven.RL is load, while being applied to electromagnetic oven, for pot even load, is the magnetron load of secondary high pressure winding rectification rear drive while being applied to microwave oven.C1 is resonant capacitance, and C2 is capacitance, and R is resonant capacitance voltage sample resistance, ac input voltage after rectifying and wave-filtering, obtain DC input voltage vin+, Vin-, after the temporary ripple of switching tube Q1, Q2, the voltage after copped wave is under resonant component T1, C1 effect, form resonance, pass to load through T1.
C1 and T1 form series resonant tank, and the resonance potential on resonant capacitance is through capacitance, and as shown in Figure 4, its waveform is near sinusoidal ripple to the voltage waveform obtaining on sampling resistor R.
Fig. 5 is the testing circuit of the high-frequency heating power shown in Fig. 1; with two comparators detect the voltage of resonant capacitance C1; the output of two comparators accesses respectively PWM control system; to realize overvoltage or the overcurrent protection to power switch pipe, PWM control system at least comprises voltage and electric current sample, Digital PWM loop and the communication module after PWM generator, AC input rectifying.Communication module is for receiving the power instruction that control panel sends, and power instruction is sent to digitlization loop, and digitlization loop, by the error between the power instruction that calculates actual input power and control panel and send, is controlled the service time Ton of PWM.Two comparators are set respectively different voltage comparison values, a comparator reference magnitude of voltage is established relatively lowly, after this comparator is triggered by overvoltage, PWM control system reduces the service time Ton of switching tube, the reference voltage value of another comparator is established to such an extent that relatively want high, after this comparator is triggered, the pwm signal of on-off switching tube.This control method circuit complexity, cannot realize the quantification of resonant capacitance voltage, and the effect of control is also difficult for assessment.
[summary of the invention]
The technical problem to be solved in the present invention is to provide a kind of control method of high-frequency heating power switching tube protection circuit, and testing circuit is simple, the overvoltage value of resonant capacitance can be quantized, to take corresponding control measure to realize protection to power switch pipe.
In order to solve the problems of the technologies described above; the technical solution used in the present invention is; a kind of control method of high-frequency heating power switching tube protection circuit; according to the superpotential time in the cycle of resonant capacitance voltage waveform and one-period; calculate the crest voltage of resonant capacitance, take corresponding control measure according to the size of crest voltage.
Above-described control method, the crest voltage Vpeak of resonant capacitance obtains by following formula:
Vpeak=Vref/cos(dt/T×90°)；
Wherein, Vref is reference voltage, and dt is the superpotential time in voltage waveform of resonant capacitance, and T is the positive half period of resonant capacitance voltage waveform.
Above-described control method, high-frequency heating power is single tube parallel resonance high-frequency heating power, in the time that the crest voltage of resonant capacitance exceedes the first set point, reduces the service time of switching tube; In the time that the crest voltage of resonant capacitance exceedes the second set point, the pwm control signal of on-off switching tube.
Above-described control method, the turn-off time that the value of the cycle T of resonant capacitance voltage waveform is switching tube.
Above-described control method, the voltage of resonant capacitance obtains from the two ends of switching tube by sample circuit, the voltage signal output end of sample circuit connects the first input end of comparator, and second of comparator is inputted the reference voltage described in termination, the output termination PWM control system of comparator; The superpotential time draws by comparator.
Above-described control method, high-frequency heating power is two-tube half bridge series resonance high-frequency heating power, in the time that the crest voltage of resonant capacitance exceedes the first set point, reduces the cycle of switching tube pwm control signal; In the time that the crest voltage of resonant capacitance exceedes the second set point, the pwm control signal of on-off switching tube.
Above-described control method, the value of the cycle T of resonant capacitance voltage waveform is the half period of switching tube pwm control signal.
Above-described control method, the voltage of resonant capacitance obtains from the two ends of resonant capacitance by sample circuit, the voltage signal output end of sample circuit connects the first input end of comparator, and second of comparator is inputted the reference voltage described in termination, the output termination PWM control system of comparator; The superpotential time draws by comparator.
The present invention, by detecting the superpotential duration of resonant capacitance, calculates overvoltage peak value, adopts different control strategies according to the size of overvoltage peak value, and rate switching tube is realized to protection.Circuit of the present invention is simple, resonance potential overvoltage value can be quantized, and take corresponding control strategy, and safeguard measure is safe and reliable.
[accompanying drawing explanation]
Below in conjunction with the drawings and specific embodiments, the present invention is further detailed explanation.
Fig. 1 is the schematic diagram of prior art single tube parallel resonance high-frequency heating power power section circuit.
Fig. 2 is the pipe collector of contactor shown in Fig. 1 voltage oscillogram.
Fig. 3 is the schematic diagram of the two-tube half bridge series resonance high-frequency heating power of prior art power section circuit.
Fig. 4 is the ohmically voltage oscillogram of circuit sampling shown in Fig. 3.
Fig. 5 is the schematic diagram of prior art high-frequency heating power testing circuit.
Fig. 6 is the schematic diagram of the embodiment of the present invention.
Fig. 7 is the schematic diagram of the embodiment of the present invention 1 single tube parallel resonance high-frequency heating power switching tube protection circuit.
Fig. 8 is the schematic diagram of the two-tube half bridge series resonance high-frequency heating power of the embodiment of the present invention 1 switching tube protection circuit.
[embodiment]
As shown in Figure 6, t1 to t4 interval is the half-wave voltage of a sine wave, and referred to as A waveform, t5 to t8 interval is another sinusoidal wave half-wave voltage, referred to as B waveform.The identical T that is of cycle of A waveform and B waveform, the amplitude of B waveform is greater than A waveform.
Vref is for setting reference voltage.The voltage magnitude of A waveform is little, and its part that exceedes reference voltage is also less, and the time of overage is that t2 is to t3 interval, herein referred to as dtA.The voltage magnitude of B waveform is large, and its part that exceedes reference voltage is also larger, and the time of overage is that t6 is to t7 interval, herein referred to as dtB.From figure, can obviously find out, because the amplitude of B waveform is higher than A waveform, dtB is also obviously greater than dtA.
Be T sinusoidal wave period, and reference voltage is Vref, and the overvoltage time is dtA and dtB, can be calculated by following formula for crest voltage Peak_A and the Peak_B of sinusoidal wave A waveform and B waveform:
Peak_A=Vref/cos (dtA/T × 90 °) formula 1
Or PeaK_A=Vref/cos{[(t3-t2)/2]/[t3-t1-(t3-t2)/2] } formula 2
Peak_B=Vref/cos (dtB/T × 90 °) formula 3
Or PeaK_B=Vref/cos{[(t7-t6)/2]/[t7-t5-(t7-t6)/2] } formula 4
For the single tube parallel resonance high-frequency heating power circuit shown in Fig. 1, the turn-off time Toff that sinusoidal wave half wave cycles is switching tube, overvoltage time (t3-t2) or (t7-t6) can draw by comparator, therefore can through type 1 or formula 2 calculate superpotential peak value Peak_A and Peak_B.
For two-tube half bridge series resonance high-frequency heating power circuit shown in Fig. 2, sinusoidal wave cycle T is the cycle of the pwm control signal of switching tube, overvoltage time (t3-t2) or (t7-t6) can draw by comparator, thus can through type 1 or formula 2 calculate superpotential peak value.
Obtain peak overvoltage quantized value, can adopt different relative strategies, such as the single tube parallel resonance high-frequency heating power circuit for shown in Fig. 1, when crest voltage be less than switching tube maximum working voltage 85% time, reduce the service time Ton of switching tube, and be evaluated in the response time of loop, regulate and whether achieve the goal, if crest voltage does not decline, continue to reduce service time Ton, if crest voltage exceed switching tube maximum working voltage 95% time, can directly turn-off pwm control signal.
For the two-tube half bridge series resonance high-frequency heating power circuit shown in Fig. 3, equally, when overvoltage can system can tolerance range in, for example, when overvoltage be less than switching tube maximum working voltage 85% time, reduce the cycle of the pwm control signal of switching tube, and be evaluated in the response time of loop, whether overvoltage declines, if crest voltage does not decline, continue the cycle of the pwm control signal that reduces switching tube, if crest voltage exceedes the certain value of default, the pwm control signal of direct on-off switching tube.
Fig. 7 shows the application of the embodiment of the present invention on single tube parallel resonance high-frequency heating power circuit, the voltage (being equal to the C1 voltage of resonant capacitance) of switching tube Q1 is by divider resistance R1, after R2 dividing potential drop, deliver to an input of comparator U1, reference voltage Vref is connected to another input of comparator, in the time that overvoltage occurs, the overvoltage time of PWM control system metering PWM turn-off time Toff and comparator, calculate overvoltage value, produce regulating error signal according to the size of crest voltage, error signal size determines the value that PWM service time reduces, when crest voltage be greater than switching tube maximum working voltage 85% time, employing reduces the strategy of PWM service time Ton, in the time that crest voltage is greater than switching tube maximum working voltage 95%, the pwm control signal of direct on-off switching tube.Because above-mentioned PWM control system is generally made up of single-chip microcomputer, computing capability a little less than, can be write the value of 1/cos θ as tabular value, the value of 1/cos θ draws by look-up method.
Fig. 8 shows the application of the present invention at two-tube half bridge series resonance high-frequency heating power circuit, the voltage of resonant capacitance C1 is delivered to an input of comparator U1 after by divider resistance R1, R2 dividing potential drop, reference voltage Vref is connected to another input of comparator, in the time that overvoltage occurs, the cycle of pwm control signal of PWM control system metering switch pipe and the overvoltage time of comparator, calculate crest voltage value, as mentioned above, can take to reduce the cycle of pwm control signal or turn-off pwm control signal according to the size of crest voltage equally.
The above embodiment circuit of the present invention is simple, resonance potential overvoltage value can be quantized, and take corresponding control strategy, safe and reliable.
Claims (8)
1. the control method of a high-frequency heating power switching tube protection circuit; it is characterized in that; according to the superpotential time in the cycle of resonant capacitance voltage waveform and one-period, calculate the crest voltage of resonant capacitance, take corresponding control measure according to the size of crest voltage.
2. control method according to claim 1, is characterized in that, the crest voltage Vpeak of resonant capacitance obtains by following formula:
Vpeak=Vref/cos(dt/T×90°)；
Wherein, Vref is reference voltage, and dt is the superpotential time in voltage waveform of resonant capacitance, and T is the positive half period of resonant capacitance voltage waveform.
3. control method according to claim 2, is characterized in that, high-frequency heating power is single tube parallel resonance high-frequency heating power, in the time that the crest voltage of resonant capacitance exceedes the first set point, reduces the service time of switching tube; In the time that the crest voltage of resonant capacitance exceedes the second set point, the pwm control signal of on-off switching tube.
4. control method according to claim 3, is characterized in that, the turn-off time that the value of the cycle T of resonant capacitance voltage waveform is switching tube.
5. control method according to claim 3, it is characterized in that, the voltage of resonant capacitance obtains from the two ends of switching tube by sample circuit, the voltage signal output end of sample circuit connects the first input end of comparator, reference voltage described in the second input termination of comparator, the output termination PWM control system of comparator; The superpotential time draws by comparator.
6. control method according to claim 2, is characterized in that, high-frequency heating power is two-tube half bridge series resonance high-frequency heating power, in the time that the crest voltage of resonant capacitance exceedes the first set point, reduces the cycle of switching tube pwm control signal; In the time that the crest voltage of resonant capacitance exceedes the second set point, the pwm control signal of on-off switching tube.
7. control method according to claim 6, is characterized in that, the value of the cycle T of resonant capacitance voltage waveform is the half period of switching tube pwm control signal.
8. control method according to claim 6, it is characterized in that, the voltage of resonant capacitance obtains from the two ends of resonant capacitance by sample circuit, the voltage signal output end of sample circuit connects the first input end of comparator, reference voltage described in the second input termination of comparator, the output termination PWM control system of comparator; The superpotential time draws by comparator.
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| CN201410114897.0A CN103904871B (en) | 2014-03-25 | 2014-03-25 | The control method of high-frequency heating power switching tube protection circuit |
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| CN201410114897.0A CN103904871B (en) | 2014-03-25 | 2014-03-25 | The control method of high-frequency heating power switching tube protection circuit |
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| CN103904871B CN103904871B (en) | 2016-09-07 |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN106572552A (en) * | 2015-10-13 | 2017-04-19 | 佛山市顺德区美的电热电器制造有限公司 | Control method and apparatus for turning-on time of power switch tube in electromagnetic heating system |
| CN107920398A (en) * | 2016-10-08 | 2018-04-17 | 佛山市顺德区美的电热电器制造有限公司 | A kind of control method and device of electromagnetic equipment, electromagnetic equipment |
| CN109818328A (en) * | 2019-03-19 | 2019-05-28 | 浪潮商用机器有限公司 | A kind of switch power over-voltage protection circuit |
| CN111193383A (en) * | 2020-01-22 | 2020-05-22 | 维沃移动通信有限公司 | Power control circuit and electronic device |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN106572552A (en) * | 2015-10-13 | 2017-04-19 | 佛山市顺德区美的电热电器制造有限公司 | Control method and apparatus for turning-on time of power switch tube in electromagnetic heating system |
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| CN107920398A (en) * | 2016-10-08 | 2018-04-17 | 佛山市顺德区美的电热电器制造有限公司 | A kind of control method and device of electromagnetic equipment, electromagnetic equipment |
| CN109818328A (en) * | 2019-03-19 | 2019-05-28 | 浪潮商用机器有限公司 | A kind of switch power over-voltage protection circuit |
| CN111193383A (en) * | 2020-01-22 | 2020-05-22 | 维沃移动通信有限公司 | Power control circuit and electronic device |
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