CN212514765U - Valley bottom detection circuit, variable frequency power supply comprising valley bottom detection circuit and microwave equipment - Google Patents

Valley bottom detection circuit, variable frequency power supply comprising valley bottom detection circuit and microwave equipment Download PDF

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CN212514765U
CN212514765U CN202020572399.1U CN202020572399U CN212514765U CN 212514765 U CN212514765 U CN 212514765U CN 202020572399 U CN202020572399 U CN 202020572399U CN 212514765 U CN212514765 U CN 212514765U
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circuit
resistor
voltage signal
valley bottom
capacitor
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官继红
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Shenzhen Megmeet Electrical Co Ltd
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Shenzhen Megmeet Electrical Co Ltd
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    • 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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Abstract

The embodiment of the utility model provides a valley bottom detection circuitry reaches variable frequency power supply and microwave equipment including this valley bottom detection circuitry. The valley bottom detection circuit comprises a power conversion circuit, a differential circuit, an auxiliary circuit and a control circuit, wherein the power conversion circuit comprises a resonance circuit and a switch circuit and is used for receiving a first voltage signal and converting electric energy and outputting a second voltage signal, the differential circuit is connected with the power conversion circuit and is used for generating a third voltage signal according to the second voltage signal, the auxiliary circuit is used for applying a forward voltage signal to a first resistor of the differential circuit, the control circuit is connected with the differential circuit and is used for detecting a valley bottom signal according to the third voltage signal on the first resistor and the forward voltage signal and controlling the switch circuit to be conducted according to the valley bottom signal. Through the mode, the cost can be saved, the occupation of the area of the PCB can be reduced, accurate valley bottom signals can be obtained, and the switching loss of the switching tube is reduced.

Description

Valley bottom detection circuit, variable frequency power supply comprising valley bottom detection circuit and microwave equipment
Technical Field
The utility model relates to a variable frequency power supply technical field especially relates to a detection circuitry reaches variable frequency power supply and microwave equipment including this detection circuitry at the bottom of millet.
Background
In the existing circuit of the frequency conversion microwave power supply on the market at present, the current resonance power supply topology is a common technical means, as shown in fig. 1, an IGBT switching tube is used in the circuit to realize the on and off functions, and the resonance circuit topology is used, so that the loss caused by the IGBT switching tube in the switching process can be reduced by reducing the voltage at two ends of a resonance capacitor, particularly in the switching-on process, the voltage of the resonance capacitor has the lowest point, which is called as a valley value, and the valley detection circuit aims to detect the occurrence of the valley value signal and simultaneously turn on the IGBT switching tube, thereby further reducing the switching loss.
In the process of implementing the invention, the inventor finds that at least the following problems exist in the prior art: the voltage of a resonant capacitor of the transformer is sampled by using the resistor in the circuit structure, and because the voltage of the resonant capacitor is large, a large number of resistors are required, the cost is high, the area of the PCB is occupied, and the PCB cannot be further miniaturized; and the signal when the induced voltage of the transformer resets and the bottom signal are not completely corresponding, so that the detected bottom signal is inaccurate and generates extra switching loss.
SUMMERY OF THE UTILITY MODEL
The embodiment of the utility model provides a main technical problem who solves provides a detection circuitry and including this detection circuitry's at the bottom of the millet variable frequency power supply and microwave equipment, can practice thrift the cost and reduce to the occupation of PCB area and can obtain accurate at the bottom of the millet signal, reduce the switching loss of switch tube.
The embodiment of the utility model provides a following technical scheme: in a first aspect, a circuit for valley detection is provided, including:
the power conversion circuit comprises a resonance circuit and a switch circuit, and is used for receiving a first voltage signal, performing electric energy conversion on the first voltage signal and outputting a second voltage signal;
the differential circuit is connected with the power conversion circuit and comprises a second capacitor and a first resistor, and the differential circuit is used for generating a third voltage signal according to the second voltage signal;
an auxiliary circuit connected to the differentiating circuit for applying a forward voltage signal across the first resistor;
and the control circuit is connected with the differential circuit and used for detecting a valley signal according to the third voltage signal received by the first resistor and the forward voltage signal and controlling the switch circuit to be switched on according to the valley signal.
In an alternative form, the power conversion circuit includes: a first node and a second node, the first node being between the resonant circuit and the switching circuit, the second node being connected to ground; one end of the second capacitor is connected to the first node, the other end of the second capacitor is connected to one end of the first resistor, and the other end of the first resistor is connected to the second node.
In an alternative mode, the resonant circuit includes a first capacitor and a transformer, the first capacitor and the transformer are connected in parallel, one end of the first capacitor is connected to the positive electrode of the first voltage signal, and the other end of the first capacitor is connected to the first node. The switching circuit comprises an IGBT switching tube; the drain electrode of the IGBT switching tube is connected to the first node, the source electrode of the IGBT switching tube is connected to the second node, and the control circuit is connected with the grid electrode of the IGBT switching tube.
In an alternative form, the auxiliary circuit includes: the capacitor comprises an auxiliary power supply and a second resistor, wherein one end of the second resistor is connected with the positive electrode of the auxiliary power supply, and the other end of the second resistor is connected between the second capacitor and the first resistor.
In an alternative form, the control circuit includes: a reference voltage source, a comparator and a singlechip; the comparator comprises a first input end, a second input end and a comparator output end, wherein the first input end is connected with the reference voltage source, and the second input end is connected between the second capacitor and the first resistor;
the output end of the comparator is connected with the switch circuit through the singlechip.
In an optional manner, the auxiliary circuit further includes a third resistor, one end of the third resistor is connected between the second capacitor and the first resistor, and the other end of the third resistor is connected to the second resistor and the second input terminal, respectively.
In an alternative mode, the reference voltage source is a forward voltage, or the reference voltage source is grounded.
In a second aspect, the embodiment of the present invention further provides a variable frequency power supply, including a rectifier filter circuit and the valley bottom detection circuit as described above, the rectifier filter circuit is used for outputting a first voltage signal to the power conversion circuit of the valley bottom detection circuit.
In an optional manner, the variable frequency power supply includes a power supply chip, the power supply chip includes a reference voltage source, and when the control circuit of the valley detection circuit includes the reference voltage source, the reference voltage source is the reference voltage source.
In a third aspect, an embodiment of the present invention further provides a microwave device, including a magnetron and the variable frequency power supply as described above, where the variable frequency power supply is used to drive the magnetron.
The embodiment of the utility model provides a beneficial effect is: the valley bottom detection circuit comprises a power conversion circuit, a differential circuit, an auxiliary circuit and a control circuit, wherein the power conversion circuit comprises a resonance circuit and a switch circuit and is used for receiving a first voltage signal, converting electric energy and outputting a second voltage signal; the circuit adopts a simple differential circuit, uses few devices, occupies small PCB area, and has low cost, and a positive voltage is applied on the differential circuit to shift up a negative voltage section, so as to obtain an accurate comparison signal, thereby reducing the switching loss of the switching tube.
Drawings
One or more embodiments are illustrated by way of example in the accompanying drawings, which correspond to the figures in which like reference numerals refer to similar elements and which are not to scale unless otherwise specified.
FIG. 1 is a schematic diagram of a valley bottom detection circuit in the prior art;
fig. 2 is a block diagram of a valley bottom detection circuit provided in the embodiment of the present invention;
fig. 3 is a schematic circuit diagram of a valley bottom detection circuit according to an embodiment of the present invention;
fig. 4 is a schematic diagram of a timing diagram of a valley bottom detection circuit provided in an embodiment of the present invention;
fig. 5 is a schematic circuit diagram of a valley bottom detection circuit according to another embodiment of the present invention;
fig. 6 is a schematic circuit diagram of a valley bottom detection circuit according to another embodiment of the present invention.
Detailed Description
In order to facilitate understanding of the present invention, the present invention will be described in more detail with reference to the accompanying drawings and specific embodiments. It will be understood that when an element is referred to as being "secured to" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may be present. The terms "vertical," "horizontal," "left," "right," and the like as used herein are for descriptive purposes only.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.
Referring to fig. 2 and fig. 3, fig. 2 is a block diagram of a valley bottom detection circuit according to an embodiment of the present invention, and fig. 3 is a schematic circuit diagram of the valley bottom detection circuit according to an embodiment of the present invention, where the valley bottom detection circuit includes a power conversion circuit 10, a differential circuit 20, an auxiliary circuit 30, and a control circuit 40;
the power conversion circuit 10 is configured to receive the rectified and filtered first voltage signal, perform power conversion on the first voltage signal, and output a second voltage signal, and includes a resonant circuit 11, a switching circuit 12, a first node P1, and a second node P2; the first node P1 is located between the resonant circuit 11 and the switch circuit 12, and the second node P2 is grounded.
The resonant circuit 11 comprises a first capacitor C1 and a transformer T1, the first capacitor C1 is connected end to end with the transformer T1 to form a parallel connection, one end of the first capacitor C1 is connected with the positive electrode of the first voltage signal, and the other end of the first capacitor C1 is connected with a first node P1; the switching circuit 12 includes an IGBT Q1, a drain of the IGBT Q1 is connected to the first node, a source of the IGBT Q1 is connected to the second node, and a gate of the IGBT Q1 is connected to the control circuit 40. In other embodiments, the switching tube Q1 may be a switching tube such as a switching transistor.
A differentiating circuit 20 connected to the power converting circuit 10, including a second capacitor C2 and a first resistor R1, for generating a third voltage signal according to the second voltage signal;
an auxiliary circuit 30, connected to the differentiating circuit 20, for applying a positive voltage signal to the first resistor R1 to shift up a negative voltage segment of the first resistor R1 to obtain an accurate comparison signal, which includes an auxiliary power VCC and a second resistor R2; one end of the second resistor R2 is connected to the positive electrode of the auxiliary power VCC, and the other end of the second resistor R2 is connected between the second capacitor C2 and the first resistor R1 of the differential circuit 20;
the control circuit 40 is connected with the differential circuit 20, is used for detecting a valley signal according to the third voltage signal on the first resistor R1 and the forward voltage signal, and controls the switch circuit 12 to be conducted according to the valley signal, and comprises a reference voltage source REF, a comparator U1 and a singlechip U2; the comparator U1 includes a first input terminal connected to the reference voltage source REF, a second input terminal connected between the second capacitor C2 of the differentiating circuit 20 and the first resistor R1, and a comparator output terminal; the output end of the comparator is connected with the input end of the single chip microcomputer U2, and the output end of the single chip microcomputer U2 is connected with the grid electrode of the IGBT switching tube Q1.
In this embodiment, the voltage V of the first capacitor C1 in the resonant circuit 11 is differentiated by the differentiating circuit 20C1The period of time when the change is 0 is detected. In particular, the charging and discharging of the differentiating circuit 20 is caused during the charging and discharging of the resonant circuit 11, so that a follow-up voltage V1 is generated across the first resistor R1 of the differentiating circuit 20C1Varying voltage signal VR1When the first capacitor voltage V is appliedC1When the transformation slope is zero, the alternating current flowing through the first resistor R1 is 0, i.e. the voltage VR1To be 0, the auxiliary circuit 30 applies a forward voltage signal to the first resistor R1 of the differential circuit 20, so that the control circuit 40 can obtain an accurate valley signal, and the valley signal outputs a signal for controlling the switch circuit 12 to be turned on.
In the above manner, the reference voltage source REF may be ground, i.e., referenced to 0V; the reference voltage source REF may also be connected to a stable voltage.
In practical applications, during the operation of the circuit, the single loss caused by the hard switch being turned on at the valley bottom can be calculated according to the following formula: q is 1/2CV 2; q is capacitor energy storage; c: a capacitance capacity; v: when the IGBT switching tube is switched on, the capacitor voltage is applied; from the above formula, it is known that reducing the voltage of the resonant capacitor when the IGBT switching tube is turned on can effectively reduce the turn-on loss.
This embodiment also provides a timing chart of the voltage across the first capacitor C1 and the voltage across the first resistor R1 during the operation of the circuit shown in FIG. 3, to further illustrate how the voltage across the first capacitor V isC1The valley is detected when it is minimized to further reduce the switching losses.
As shown in fig. 4, the voltage V is present across the first capacitor C1C1During the variation period, a current is generated in the first resistor R1, and a voltage V applied to the first resistor R1R1Will not be zero; when the voltage V of the first capacitor C1C1When the voltage reaches the peak value and the valley value, the voltage transformation slope is zero, the current applied to the first resistor R1 is zero, and the voltage V isR1Is zero, so that the voltage V across the first resistor R1R1The zero-crossing period reflects the voltage V of the first capacitor C1C1Time to peak or trough; and because of the existence of the reference voltage source REF and the auxiliary circuit 30, the voltage at the non-reference voltage source input terminal (i.e. the second input terminal) of the comparator U1 may exceed the stable voltage input at the reference voltage source REF input terminal of the comparator U1 in a static state, and at this time, the comparator U1 will flip, so that the falling edge of the comparator switching from high level to low level or the rising edge of the comparator switching from low level to high level can be used as a valley signal for triggering the turn-on of the IGBT switching tube Q1, and the turn-on loss at this time can be further reduced.
As another implementation manner of the present embodiment, as shown in fig. 5, the difference from the above embodiment is that the auxiliary circuit 30 further includes a third resistor R3, and the second resistor R2 and the second input terminal of the comparator U1 are connected between the second resistor C2 and the first resistor R1 through the third resistor R3.
Specifically, the anode of the auxiliary power source VCC is connected to one end of a second resistor R2, the other end of the second resistor R2 is connected to one end of a third resistor R3, the other end of the third resistor R3 is connected between a second capacitor C2 and a first resistor R1 in the differentiating circuit 20, a second input terminal of a comparator U1 in the control circuit 40 is connected between the first resistor R2 and the resistor R3, and a first input terminal of a comparator U1 is connected to a reference voltage source REF; wherein, the auxiliary power source VCC applies a forward voltage to the first resistor R1 through a voltage division process, when the voltage V is applied across the first capacitor C1 in the resonant circuit 11C1When the valley is reached, the forward voltage can cause the comparator U1 to be connected between the resistor R2 and the resistor R3Exceeds the voltage of the comparator U1 input at one end of the reference voltage source REF, thereby obtaining a valley signal.
It will be appreciated that the functional blocks described above are merely illustrative, in that blocks illustrated as separate components may or may not be physically separate.
For example, in some other embodiments, as shown in fig. 6, the control circuit 40 employs a single-chip microcomputer U3 with a comparator function directly. One input end of the singlechip U3 is connected with a reference voltage source REF, the other input end of the singlechip U3 is connected between the second capacitor C2 and the first resistor R1, and the output end of the singlechip U1 is connected with the grid of an IGBT switching tube Q1 in the switching circuit 12.
In the embodiment of the present invention, the valley bottom detection circuit includes a power conversion circuit, a differential circuit, an auxiliary circuit and a control circuit, the power conversion circuit includes a resonant circuit and a switch circuit, and is configured to receive a first voltage signal and perform power conversion, output a second voltage signal, the differential circuit is connected to the power conversion circuit, and is configured to generate a third voltage signal according to the second voltage signal, the auxiliary circuit is connected to the differential circuit, and is configured to apply a forward voltage signal to a first resistor of the differential circuit, the control circuit is connected to the differential circuit, and is configured to detect the valley bottom signal according to the third voltage signal on the first resistor and the forward voltage signal, and control the switch circuit to be turned on according to the valley bottom signal; the circuit adopts a simple differential circuit, uses few devices, occupies small PCB area, and has low cost, and a positive voltage is applied on the differential circuit to shift up a negative voltage section, so as to obtain an accurate comparison signal, thereby reducing the switching loss of the switching tube.
The utility model discloses the implementation still provides a variable frequency power supply, including rectification filter circuit and as above the bottom of the valley detection circuitry, rectification filter circuit is used for exporting bottom of the valley detection circuitry's power conversion circuit first voltage signal.
Optionally, the variable frequency power supply includes a power supply chip, the power supply chip includes a reference voltage source, and when the control circuit of the valley bottom detection circuit includes the reference voltage source, the reference voltage source may be directly the reference voltage source to further reduce devices.
The utility model discloses the implementation still provides a microwave equipment, including magnetron and as above variable frequency power supply, variable frequency power supply is used for the drive magnetron.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit it; within the idea of the invention, also technical features in the above embodiments or in different embodiments can be combined, steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity; although the present invention has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present application.

Claims (10)

1. A valley bottom detection circuit, comprising:
the power conversion circuit comprises a resonance circuit and a switch circuit, and is used for receiving a first voltage signal, performing electric energy conversion on the first voltage signal and outputting a second voltage signal;
the differential circuit is connected with the power conversion circuit and comprises a second capacitor and a first resistor, and the differential circuit is used for generating a third voltage signal according to the second voltage signal;
an auxiliary circuit connected to the differentiating circuit for applying a forward voltage signal across the first resistor;
and the control circuit is connected with the differential circuit and used for detecting a valley signal according to the third voltage signal on the first resistor and the forward voltage signal and controlling the switch circuit to be switched on according to the valley signal.
2. The valley bottom detection circuit according to claim 1,
the power conversion circuit comprises a first node and a second node, wherein the first node is positioned between the resonance circuit and the switch circuit, and the second node is grounded;
one end of the second capacitor is connected to the first node, the other end of the second capacitor is connected to one end of the first resistor, and the other end of the first resistor is connected to the second node.
3. The valley bottom detection circuit according to claim 2,
the resonant circuit comprises a first capacitor and a transformer, the first capacitor and the transformer are connected in parallel, one end of the first capacitor is connected with the anode of the first voltage signal, and the other end of the first capacitor is connected to the first node;
the switching circuit comprises an IGBT switching tube, the drain electrode of the IGBT switching tube is connected to the first node, the source electrode of the IGBT switching tube is connected to the second node, and the control circuit is connected with the grid electrode of the IGBT switching tube.
4. The valley bottom detection circuit according to any of claims 1 to 3,
the auxiliary circuit comprises an auxiliary power supply and a second resistor, one end of the second resistor is connected with the positive electrode of the auxiliary power supply, and the other end of the second resistor is connected between the second capacitor and the first resistor.
5. The valley bottom detection circuit according to claim 4,
the control circuit comprises a reference voltage source, a comparator and a singlechip;
the comparator comprises a first input end, a second input end and a comparator output end, wherein the first input end is connected with the reference voltage source, and the second input end is connected between the second capacitor and the first resistor;
the output end of the comparator is connected with the switch circuit through the singlechip.
6. The valley bottom detection circuit according to claim 5,
the auxiliary circuit further comprises a third resistor, one end of the third resistor is connected between the second capacitor and the first resistor, and the other end of the third resistor is connected with the second resistor and the second input end respectively.
7. The valley bottom detection circuit according to claim 5,
the reference voltage source is a forward voltage, or the reference voltage source is grounded.
8. A variable frequency power supply comprising a rectifying filter circuit for outputting the first voltage signal to a power conversion circuit of the valley detection circuit and the valley detection circuit of any of claims 1 to 7.
9. The variable frequency power supply of claim 8,
the variable frequency power supply comprises a power supply chip, the power supply chip comprises a reference voltage source,
when the control circuit of the valley bottom detection circuit includes a reference voltage source, the reference voltage source is the reference voltage source.
10. A microwave device comprising a magnetron and a variable frequency power supply as claimed in claim 8 or 9 for driving the magnetron.
CN202020572399.1U 2020-04-16 2020-04-16 Valley bottom detection circuit, variable frequency power supply comprising valley bottom detection circuit and microwave equipment Active CN212514765U (en)

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CN202020572399.1U CN212514765U (en) 2020-04-16 2020-04-16 Valley bottom detection circuit, variable frequency power supply comprising valley bottom detection circuit and microwave equipment

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202020572399.1U CN212514765U (en) 2020-04-16 2020-04-16 Valley bottom detection circuit, variable frequency power supply comprising valley bottom detection circuit and microwave equipment

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CN212514765U true CN212514765U (en) 2021-02-09

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