Filament current regulating circuit of microwave oven

Abstract

The utility model discloses a filament current regulating circuit of a microwave oven, which comprises a power supply module, a filtering frequency modulation module, a rectifier module, a transformer, a current control capacitor and a magnetron lamp, the power module is electrically connected with the filtering frequency modulation module; the filtering frequency modulation module is connected with the primary winding, and the rectification module is connected with the first secondary winding and used for rectifying voltage transmitted by the filtering frequency modulation module; one end of the current control capacitor is connected with the rectification module, the other end of the current control capacitor is connected with one end of the magnetron lamp, the other end of the magnetron lamp is connected with one end of the second secondary winding, the other end of the second secondary winding is connected with the rectification module, and the current control capacitor is used for adjusting filament current transmitted to the magnetron lamp. According to the scheme of the utility model, the capacitor and the magnetron lamp are connected in series, and the relation between the capacitive reactance of the capacitor and the variable current frequency is utilized, so that the current of the filament is accurately controlled, and the adjustment fineness of the current of the filament is improved.

Description

Technical Field

[0001] The utility model relates to the field of microwave ovens, in particular to a filament current regulating circuit of a microwave oven. Background Art

[0002] In the current market, inverter microwave ovens utilize a single-transistor step-up approach. The transformer's primary voltage is typically close to 1,000 volts, while the secondary winding powers the magnetron's filament. Because magnetrons draw approximately 10 amps and 3 volts, a voltage reduction is necessary, requiring the secondary winding to have fewer turns than the primary. In this case, the transformer's secondary winding typically has only two turns.

[0003] To adjust the filament current, traditional methods might involve changing the number of turns in the winding or adding an inductor in series with a Schottky rectifier. However, these methods can be challenging when adjusting the current range, as the adjustment can cause the current to be too large or too small, making it difficult to adjust to an appropriate current value. Therefore, to address the technical issues of the existing technology for controlling the filament current, which lacks precision and is difficult to adjust to an appropriate range, a new technology is needed to address this issue. Utility Model Content

[0004] The main purpose of the utility model is to provide a filament current regulating circuit for a microwave oven, aiming to solve the technical problem that the existing technology has insufficient adjustment precision for controlling the filament current and is difficult to adjust to an appropriate current range.

[0005] To achieve the above-mentioned object, the utility model proposes a filament current regulating circuit for a microwave oven, which comprises: a power supply module, a filter frequency modulation module, a rectifier module, a transformer, a current control capacitor, and a magnetron lamp, wherein the transformer is provided with a primary winding group, a first secondary winding coupled to the primary winding group, and a second secondary winding coupled to the primary winding group;

[0006] The power supply module is electrically connected to the filter frequency modulation module, and the filter frequency modulation module is used to filter the ripple of the output voltage of the power supply module;

[0007] The filtering and frequency modulation module is connected to the primary winding group, and the rectifying module is connected to the first secondary winding, and the rectifying module is used to rectify the voltage transmitted by the first secondary winding;

[0008] One end of the current-controlling capacitor is connected to the rectifier module, the other end of the current-controlling capacitor is connected to one end of the magnetron lamp, the other end of the magnetron lamp is connected to one end of the second secondary winding, and the other end of the second secondary winding is connected to the rectifier module. The current-controlling capacitor is used to adjust the filament current transmitted to the magnetron lamp.

[0009] Optionally, in a first implementation, the rectifier module includes: a first diode, a second diode, a third capacitor, and a fourth capacitor. The positive electrode of the first diode is connected to one end of the first secondary winding, the negative electrode of the first diode is connected to one end of the third capacitor, the other end of the third capacitor is simultaneously connected to one end of the fourth capacitor and the other end of the first secondary winding, the other end of the fourth capacitor is connected to the positive electrode of the second diode, and the negative electrode of the second diode is connected to one end of the first secondary winding.

[0010] Optionally, in a second implementation manner, one end of the current-control capacitor is connected to the anode of the second diode.

[0011] Optionally, in a third implementation, the other end of the second secondary winding is connected to the anode of the second diode.

[0012] Optionally, in a fourth implementation manner, the cathode of the first diode is connected to the chassis ground.

[0013] Optionally, in a fifth implementation, the filtering and frequency modulation module includes: a first capacitor, a second capacitor, an IGBT transistor, and a PWM control signal source, the collector of the IGBT transistor is connected to one end of the first capacitor, the emitter of the IGBT transistor is connected to one end of the second capacitor, and the gate of the IGBT transistor is connected to the PWM control signal source, so that the PWM control signal source controls the opening and closing of the IGBT transistor.

[0014] Optionally, in a sixth implementation manner, the first capacitor is connected in parallel with the power module, and the first capacitor is used to filter the ripple of the output voltage of the power module.

[0015] Optionally, in a seventh implementation manner, the second capacitor is connected in parallel with the primary winding group, and the other end of the second capacitor is connected to the other end of the first capacitor.

[0016] Optionally, in an eighth implementation, the power module includes a circuit breaker, the first leg and the second leg of the circuit breaker are electrically connected to the live wire and the neutral wire of the mains respectively, the third leg of the circuit breaker is connected to the other end of the second capacitor, and the fourth leg of the circuit breaker is connected to one end of the emitter of the IGBT transistor.

[0017] Optionally, in a ninth implementation, the first leg is connected in series to a fuse, the fuse is connected to a live wire of the mains power, and the fourth leg is grounded.

[0018] In an embodiment of the present invention, a circuit scheme is proposed for connecting a magnetron lamp and a capacitor in series for use in a variable-frequency microwave oven to adjust the filament current. Utilizing the characteristic that the capacitive reactance of the capacitor decreases as the frequency increases, the current passing through the magnetron lamp can be more accurately controlled by changing the capacitance value of the capacitor and the operating frequency of the microwave oven. Different current values ​​can be adapted to different operating states of the magnetron lamp, thereby solving the technical problem of the prior art in that the adjustment precision of the filament current is insufficient and it is difficult to adjust to a suitable current range. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0020] Figure 1 This is a first structural diagram of the filament current regulating circuit of the microwave oven of the present invention;

[0021] Figure 2 This is a second structural diagram of the filament current regulating circuit of the microwave oven of the present invention;

[0022] Description of Figure Numbers:

[0023] 10-power module, 20-filter frequency modulation module, 30-rectifier module, T1-primary winding group, T1A-first secondary winding, T1B-second secondary winding, L1-magnetron lamp, C3-current control capacitor, F1-fuse, C1-first capacitor, C2-second capacitor, C4-third capacitor, C5-fourth capacitor, D1-first diode, D2-second diode, BR1-circuit breaker, IGBT-IGBT transistor.

[0024] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0026] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement status, etc. between the various components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indications will also change accordingly.

[0027] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of such features. In addition, if the meaning of "and / or" appearing in the full text is to include three parallel schemes, taking "A and / or B" as an example, it includes scheme A, or scheme B, or a scheme in which A and B are satisfied at the same time. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0028] The utility model provides a filament current regulating circuit for a microwave oven.

[0029] In the embodiment of the present utility model, Figure 1 As shown, the filament current regulation circuit of the microwave oven includes: a power module 10, a filter frequency modulation module 20, a rectifier module 30, a transformer, a current control capacitor C3, and a magnetron lamp L1. The transformer is provided with a primary winding T1, a first secondary winding T1A coupled to the primary winding T1, and a second secondary winding T1B coupled to the primary winding T1. In actual use, the transformer is a step-down transformer. The number of turns of the primary winding T1 of the transformer is greater than the number of turns of the first secondary winding T1A, and the number of turns of the primary winding T1 of the transformer is greater than the number of turns of the second secondary winding T1B, so that the second secondary winding T1B can provide a reduced voltage power supply to the series-connected magnetron lamp L1 and the current control capacitor C3.

[0030] However, the present invention does not limit the type of transformer. In some application scenarios, the transformer can be implemented as a step-up transformer. For example, a portable microwave oven is powered by a lead-acid battery, and a step-up circuit is provided inside the microwave oven for cooking. If the external voltage of the magnetron lamp L1 is insufficient, a step-up transformer can be used. In this case, the number of windings of the primary winding group T1 can be smaller than the number of windings of the second secondary winding T1B, so that the second secondary winding group T1B can provide a stepped-up power supply to the series-connected magnetron lamp L1 and the current-control capacitor C3.

[0031] like Figure 1 As shown, the power module 10 is electrically connected to the filter frequency modulation module 20, so that the power module 10 outputs a voltage to the filter frequency modulation module 20, and the filter frequency modulation module 20 filters the ripple in the output voltage of the power module 10. The power module 10 can be an AC voltage provided by an external power grid, or it can be a DC voltage provided by a battery that is converted and boosted into an AC voltage.

[0032] The filter-frequency modulation module 20 is electrically connected to the primary winding T1. Both ends of the primary winding T1 are connected to the filter-frequency modulation module 20. The primary winding T1 is coupled to the first secondary winding T1A, while the primary winding T1 is coupled to the second secondary winding T1B. The filter-frequency modulation module 20 filters the AC voltage output by the power module 10 and transmits it to the primary winding T1. The primary winding T1 then transforms the voltage and transmits it to the first and second secondary windings T1A and T1B.

[0033] The rectifier module 30 is connected to both ends of the first secondary winding T1A so that the first secondary winding T1A transmits the boosted voltage received by electromagnetic induction to the rectifier module 30 , and the rectifier module 30 rectifies the boosted voltage transmitted by the first secondary winding T1A.

[0034] One end of the current-controlling capacitor C3 is connected to the rectifier module 30, and the other end of the current-controlling capacitor C3 is connected to one end of the magnetron lamp L1. The current-controlling capacitor C3 and the magnetron lamp L1 are connected in series. The current-controlling capacitor C3 generates different impedances based on different AC voltage frequencies. The impedance of the capacitor decreases as the AC voltage frequency increases. The current flowing through the magnetron lamp L1 is controlled by changing the AC voltage frequency and the capacitance value.

[0035] The other end of the magnetron lamp L1 is connected to one end of the second secondary winding T1B, and the other end of the second secondary winding T1B is connected to the rectifier module 30. The current source adjusted by the current control capacitor C1 can be the second secondary winding T1B directly supplying power to the current control capacitor C1 and the magnetron lamp L1, or the first secondary winding T1A is transmitted to the rectifier module 30, and the rectifier module 30 outputs the rectified AC voltage to the current control capacitor C1 and the magnetron lamp L1. The specific voltage input direction needs to be determined by the number of windings of the first secondary winding T1A and the second secondary winding T1B and the positive and negative magnitude of the voltage.

[0036] The working principle of the present invention is as follows: the power supply module 10 outputs AC or DC power and enters the filter frequency modulation module 20, and the filter frequency modulation module 20 performs parallel resonance processing on the voltage to generate a ripple-filtered AC voltage which is transmitted to the primary winding group T1 of the transformer, and the primary winding group T1 transmits the voltage to the coupled first secondary winding T1A and the second secondary winding T1B through electromagnetic induction, and then the rectifier module 30 rectifies the transmission voltage of the first secondary winding T1A, and the voltage transmitted by the rectifier module 30 and the second secondary winding T1B is integrated into a low-voltage high-frequency AC voltage. Signal Vac, the capacitance value of the current-control capacitor C3 is c, the frequency of the Vac signal is f, and the voltage of the Vac signal is V. At this time, the impedance of the current-control capacitor C3 with the magnetron lamp L1 is Z = 1 / (2πfc), and the internal resistance of the magnetron lamp L1 is r. Then the actual current passing through the magnetron lamp L1 is I = V / (r+1 / (2πfc)). In this way, we can obtain the appropriate filament current by changing the capacitance value of the capacitor and the operating frequency, so as to adapt to different magnetrons or different working states of the magnetron and meet the voltage and current requirements of the magnetron lamp L1 of about 3V10A.

[0037] like Figure 2 As shown, there are multiple specific implementations in the specific embodiments of the present invention.

[0038] First specific embodiment

[0039] In a first specific embodiment, the rectifier module 30 includes: a first diode D1, a second diode D2, a third capacitor C4, and a fourth capacitor C5. The positive electrode of the first diode D1 is connected to one end of the first secondary winding T1A, the negative electrode of the first diode D1 is connected to one end of the third capacitor C4, the other end of the third capacitor C4 is simultaneously connected to one end of the fourth capacitor C5 and the other end of the first secondary winding T1A, the other end of the fourth capacitor C5 is connected to the positive electrode of the second diode D2, and the negative electrode of the second diode D2 is connected to one end of the first secondary winding T1A.

[0040] Furthermore, one end of the current control capacitor C3 is connected to the anode of the second diode D2, and the other end of the second secondary winding T1B is connected to the anode of the second diode D2.

[0041] Optionally, the cathode of the first diode D1 is connected to the chassis ground. The cathode of the first diode D1 may also be directly grounded to conduct away excess charge during the rectification process.

[0042] The working principle of the first specific embodiment is as follows: the first secondary winding T1A receives a voltage of about 2 kilovolts transmitted from the primary winding group T1 by electromagnetic induction. After being rectified by the first diode D1 and the second diode D2, and filtered by the third capacitor C4 and the fourth capacitor C5, the voltage is superimposed together to generate a high voltage of about 4 kilovolts, which is transmitted to the magnetron lamp L1. The current passing through the magnetron lamp L1 is limited by the current control capacitor C3.

[0043] Beneficial effects of the first specific embodiment: This specific embodiment provides a connection method between a rectifier module, a magnetron lamp L1, and a current-control capacitor C3, which increases the voltage transmitted to the magnetron lamp L1 during the rectification process. This solution can cooperate with a booster to more accurately control the voltage input to the magnetron lamp L1, thereby improving the control accuracy of this circuit for the current of the magnetron lamp L1.

[0044] Second specific embodiment

[0045] In a second embodiment, the filter frequency modulation module 20 includes: a first capacitor C1, a second capacitor C2, an IGBT transistor (IGBT), and a PWM control signal source. The collector of the IGBT transistor (IGBT) is connected to one end of the first capacitor C1, the emitter of the IGBT transistor (IGBT) is connected to one end of the second capacitor C2, and the gate of the IGBT transistor (IGBT) is connected to the PWM control signal source, which controls the switching of the IGBT transistor. The first capacitor C1 is connected in parallel with the power module 10 to filter the ripple of the output voltage of the power module 10. The second capacitor C2 is connected in parallel with the primary winding T1, and the other end of the second capacitor C2 is connected to the other end of the first capacitor C1.

[0046] The working principle of the second specific embodiment is as follows: the AC power output by the power module 10 is filtered by the first parallel capacitor C1 to generate a DC voltage. The DC voltage on the first capacitor C1 is periodically closed and opened under the control of the PWM control signal source of the IGBT transistor (IGBT) through the second capacitor C2. The second capacitor C2 is connected in parallel with the primary winding group T1 to generate parallel resonance, generating an AC voltage with a frequency of tens of K. The primary winding group T1 transmits the AC voltage to the coupled first secondary winding T1A and the second secondary winding T1B.

[0047] Beneficial effects of the second specific embodiment: This specific embodiment realizes the conversion of AC voltage into DC voltage and generates AC signal through parallel resonance, effectively filtering the voltage noise in the power module 10, and uses the IGBT transistor (IGBT) and PWM control signal source to accurately control the voltage frequency output from the primary winding group T1, thereby realizing frequency control of the voltage signal input to the magnetron lamp L1 and the current control capacitor C3, and improving the control of the current flowing through the magnetron lamp L1.

[0048] Third specific embodiment

[0049] In a third embodiment, the power module 10 includes a circuit breaker BR1. A first leg 1 and a second leg 2 of the circuit breaker BR1 are electrically connected to the live line ACL and the neutral line ACN of a mains power supply, respectively. Specifically, the mains power supply can be a 220V, 110V, or 100V AC power grid. The first leg 1 is connected to the live line ACL, and the second leg 2 is connected to the neutral line ACN. A third leg 3 of the circuit breaker BR1 is connected to the other end of a second capacitor C1. A fourth leg 4 of the circuit breaker BR1 is connected to one end of the emitter of an IGBT transistor (IGBT).

[0050] Furthermore, a fuse F1 is connected in series with the first leg 1, which is connected to the AC power supply, and the fourth leg 4 is connected to the ground. This configuration improves the safety of the circuit breaker BR1. When the current is too high, the fuse F1 can be blown to protect the circuit and the accumulated charge can be discharged to the ground, ensuring safe use of the circuit.

[0051] The third embodiment operates as follows: Connecting an external AC power source to circuit breaker BR1, the AC power from the external AC power source is filtered and converted into DC power by connecting the terminals of the second capacitor C1. Connecting the fourth leg to the emitter of the IGBT effectively removes excess charge passing through the IGBT, preventing charge accumulation and circuit damage.

[0052] Beneficial effects of the third specific embodiment: When an external AC voltage is connected, a safe voltage output of the circuit is achieved through the connection mode of the circuit breaker BR1, and the circuit is safely used during the AC filtering process through the parallel connection of the circuit breaker BR1 and the first capacitor C1.

[0053] Beneficial effects of the present invention: The present invention proposes a circuit solution for connecting a magnetron lamp and a capacitor in series and applying the solution to a variable-frequency microwave oven to adjust the filament current. By utilizing the characteristic that the capacitive reactance of the capacitor decreases as the frequency increases, the current passing through the magnetron lamp can be more accurately controlled by changing the capacitance value of the capacitor and the operating frequency of the microwave oven. The current can be adapted to different operating states of the magnetron lamp, thus solving the technical problem in the prior art of insufficient adjustment precision for controlling the filament current and making it difficult to adjust to a suitable current range.

[0054] The above description is merely an optional embodiment of the present invention and does not limit the patent scope of the present invention. All equivalent structural transformations made by utilizing the contents of the present invention specification and drawings under the inventive concept of the present invention, or direct / indirect application in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A filament current regulating circuit for a microwave oven, characterized in that: The filament current regulating circuit of the microwave oven includes: a power supply module, a filter frequency modulation module, a rectifier module, a transformer, a current control capacitor, and a magnetron lamp, wherein the transformer is provided with a primary winding group, a first secondary winding coupled to the primary winding group, and a second secondary winding coupled to the primary winding group; The power supply module is electrically connected to the filter frequency modulation module, and the filter frequency modulation module is used to filter the ripple of the output voltage of the power supply module; The filtering and frequency modulation module is connected to the primary winding group, and the rectifying module is connected to the first secondary winding, and the rectifying module is used to rectify the voltage transmitted by the first secondary winding; One end of the current-controlling capacitor is connected to the rectifier module, the other end of the current-controlling capacitor is connected to one end of the magnetron lamp, the other end of the magnetron lamp is connected to one end of the second secondary winding, and the other end of the second secondary winding is connected to the rectifier module. The current-controlling capacitor is used to adjust the filament current transmitted to the magnetron lamp.

2. The filament current regulating circuit of a microwave oven according to claim 1, characterized in that: The rectifier module includes: a first diode, a second diode, a third capacitor, and a fourth capacitor. The positive electrode of the first diode is connected to one end of the first secondary winding, the negative electrode of the first diode is connected to one end of the third capacitor, the other end of the third capacitor is simultaneously connected to one end of the fourth capacitor and the other end of the first secondary winding, the other end of the fourth capacitor is connected to the positive electrode of the second diode, and the negative electrode of the second diode is connected to one end of the first secondary winding.

3. The filament current regulating circuit of the microwave oven according to claim 2, characterized in that: One end of the current-control capacitor is connected to the anode of the second diode.

4. The filament current regulating circuit of a microwave oven according to claim 3, characterized in that: The other end of the second secondary winding is connected to the anode of the second diode.

5. The filament current regulating circuit of a microwave oven according to any one of claims 2 to 4, characterized in that: The cathode of the first diode is connected to the chassis ground.

6. The filament current regulating circuit of a microwave oven according to claim 1, wherein: The filtering and frequency modulation module includes: a first capacitor, a second capacitor, an IGBT transistor, and a PWM control signal source. The collector of the IGBT transistor is connected to one end of the first capacitor, the emitter of the IGBT transistor is connected to one end of the second capacitor, and the gate of the IGBT transistor is connected to the PWM control signal source so that the PWM control signal source controls the opening and closing of the IGBT transistor.

7. The filament current regulating circuit of a microwave oven according to claim 6, characterized in that: The first capacitor is connected in parallel with the power module, and is used to filter the ripple of the output voltage of the power module.

8. The filament current regulating circuit of a microwave oven according to claim 6, wherein: The second capacitor is connected in parallel with the primary winding group, and the other end of the second capacitor is connected to the other end of the first capacitor.

9. The filament current regulating circuit of a microwave oven according to any one of claims 6 to 8, characterized in that: The power module includes a circuit breaker, wherein the first leg and the second leg of the circuit breaker are electrically connected to the live wire and the neutral wire of the mains respectively, the third leg of the circuit breaker is connected to the other end of the second capacitor, and the fourth leg of the circuit breaker is connected to one end of the emitter of the IGBT transistor.

10. The filament current regulating circuit of the microwave oven according to claim 9, characterized in that: The first leg is connected in series to a fuse, the fuse is connected to a live wire of the mains, and the fourth leg is grounded.

Images