CN110365206B - Spread spectrum circuit and DC-DC conversion circuit - Google Patents

Spread spectrum circuit and DC-DC conversion circuit Download PDF

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CN110365206B
CN110365206B CN201910661570.8A CN201910661570A CN110365206B CN 110365206 B CN110365206 B CN 110365206B CN 201910661570 A CN201910661570 A CN 201910661570A CN 110365206 B CN110365206 B CN 110365206B
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spread spectrum
circuit
resistor
voltage
modulation
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CN110365206A (en
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王建亭
苏俊宁
闫恒宇
侯小康
佟志钰
胡宗毅
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BOE Technology Group Co Ltd
Beijing BOE Display Technology Co Ltd
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BOE Technology Group Co Ltd
Beijing BOE Display Technology Co Ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/44—Circuits or arrangements for compensating for electromagnetic interference in converters or inverters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output

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  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Dc-Dc Converters (AREA)

Abstract

The invention provides a spread spectrum circuit and a DC-DC conversion circuit. The frequency spreading circuit comprises a modulation voltage circuit and a field effect transistor, wherein the modulation voltage circuit is connected with a grid electrode of the field effect transistor and is used for outputting periodic alternating modulation voltage signals to the grid electrode of the field effect transistor, a drain electrode of the field effect transistor is connected with a frequency setting pin or a compensation pin of a controller in the DC-DC conversion circuit, and resistance between a source electrode and a drain electrode of the field effect transistor is changed according to the periodic alternating modulation voltage signals. The invention uses the field effect transistor as the adjustable resistor for voltage control, is connected to the frequency setting pin or the compensation pin of the controller of the DC-DC conversion circuit, applies periodic alternating modulation voltage signals on the grid electrode of the field effect transistor, changes the resistance value of the resistor between the source electrode and the drain electrode of the field effect transistor, realizes the frequency spreading of the DC-DC conversion circuit, and effectively overcomes the defects of the existing solution, such as increased cost and process, unsatisfactory effect, and the like.

Description

Spread spectrum circuit and DC-DC conversion circuit
Technical Field
The invention relates to the technical field of display, in particular to a spread spectrum circuit and a DC-DC conversion circuit.
Background
In recent years, Liquid Crystal Display (LCD) devices and Organic Light Emitting Diode (OLED) devices have been widely used in electronic products such as televisions and mobile phones. In LCD and OLED designs, a DC-DC Converter (Direct current Converter) is often used to meet different power requirements in the design. For example, in the design of a logic (T-CON) panel of an LCD, it is generally necessary to generate an analog voltage AVDD of 17V from 12V or 5V by a Boost circuit (Boost Converter), a gate-on voltage VGH of 26V and a gate-off voltage VGL of-8V by a Charge Pump (Charge Pump), and a general purpose input/output (GPIO) voltage of about 1.1 to 1.2V, a chip core voltage Vcore, 1.8V, 2.5V, or 3.3V by a Buck circuit (Buck Converter). For another example, in a Light Emitting Diode (LED) backlight driving board of an LCD, a voltage boosting circuit is required to generate a power supply voltage for supplying power to an LED string.
At present, Electromagnetic compatibility (EMC) requirements of products applied to public environments or industrial environments are higher and higher, and EMC mandatory certification is required for new products to come into the market both abroad and domestically. The DC-DC conversion circuit has the characteristics of high frequency, wide frequency band, and high power density, and thus, it brings about a serious Electromagnetic Interference (EMI) problem. In order to reduce EMI and enable products to meet the requirements of EMC mandatory certification, the prior art generally adopts means of adding a metal shielding cover, adding a conductive adhesive tape, adding magnetic beads, adding a magnetic ring, pasting copper foil, pasting aluminum foil and the like, but the solutions not only increase the production cost and increase the production process, but also have unsatisfactory effect.
Disclosure of Invention
The technical problem to be solved by the embodiments of the present invention is to provide a spread spectrum circuit and a DC-DC conversion circuit, so as to overcome the defects of the existing solutions, such as increased cost and process, and unsatisfactory effect.
In order to solve the above technical problem, an embodiment of the present invention provides a spread spectrum circuit, including a modulation voltage circuit and a field effect transistor, where the modulation voltage circuit is connected to a gate of the field effect transistor and is configured to output a periodic alternating modulation voltage signal to the gate of the field effect transistor, a drain of the field effect transistor is connected to a frequency setting pin or a compensation pin of a controller in a DC-DC conversion circuit, and a resistance between a source and a drain of the field effect transistor is changed according to the periodic alternating modulation voltage signal.
Optionally, the field effect transistor includes a metal oxide semiconductor field effect transistor MOSFET, a gate of the MOSFET is connected to the modulation node, a source of the MOSFET is connected to the ground terminal, and a drain of the MOSFET is connected to a frequency setting pin of the controller in the DC-DC conversion circuit through a fourth spreading resistor.
Optionally, the frequency setting pin comprises a FREQ pin, an RT/SYNC pin, or an RT pin.
Optionally, the field effect transistor includes a metal oxide semiconductor field effect transistor MOSFET, a gate of the MOSFET is connected to the modulation node, a source of the MOSFET is connected to the ground terminal, and a drain of the MOSFET is connected to the compensation pin of the controller in the DC-DC conversion circuit through a fourth spreading resistor and a third spreading capacitor.
Optionally, the compensation leg comprises a COMP leg.
Optionally, the modulation voltage circuit includes a signal input terminal, a modulation node, a voltage terminal, a ground terminal, a first spreading resistor, a second spreading resistor, a third spreading resistor, and a first spreading capacitor; wherein the content of the first and second substances,
one end of the first spread spectrum resistor is connected with the signal input end, and the other end of the first spread spectrum resistor is connected with the modulation node;
one end of the second spread spectrum resistor is connected with the voltage end, and the other end of the second spread spectrum resistor is connected with the modulation node;
one end of the third spread spectrum resistor is connected with the modulation node, and the other end of the third spread spectrum resistor is connected with the grounding end;
and the first end of the first spread spectrum capacitor is connected with the modulation node, and the second end of the first spread spectrum capacitor is connected with the grounding end.
Optionally, the signal input terminal outputs an output enable signal, a polarity control signal or a data strobe signal of the liquid crystal module.
Optionally, the modulation voltage circuit includes a signal input terminal, a modulation node, a voltage terminal, a ground terminal, a first spreading resistor, a second spreading resistor, a third spreading resistor, a fifth spreading resistor, a first spreading capacitor, a second spreading capacitor, and a first spreading transistor; wherein the content of the first and second substances,
the grid electrode of the first spread spectrum transistor is connected with the signal input end, the source electrode of the first spread spectrum transistor is connected with the voltage end, and the drain electrode of the first spread spectrum transistor is connected with the grounding end through a fifth spread spectrum resistor;
one end of the first spread spectrum resistor is connected with the drain electrode of the first spread spectrum transistor, and the other end of the first spread spectrum resistor is connected with the modulation node;
one end of the second spread spectrum resistor is connected with the voltage end, and the other end of the second spread spectrum resistor is connected with the modulation node;
one end of the third spread spectrum resistor is connected with the modulation node, and the other end of the third spread spectrum resistor is connected with the grounding end;
the first end of the first spread spectrum capacitor is connected with the modulation node, and the second end of the first spread spectrum capacitor is connected with the grounding end;
and the first end of the second spread spectrum capacitor is connected with the drain electrode of the first spread spectrum transistor, and the second end of the second spread spectrum capacitor is connected with the grounding end.
Optionally, the signal input end outputs a touch scanning data locking signal of the liquid crystal module.
The embodiment of the invention also provides a DC-DC conversion circuit which comprises the spread spectrum circuit.
The embodiment of the invention provides a frequency spreading circuit and a DC-DC conversion circuit, wherein a field effect transistor is used as an adjustable resistor for voltage control, the adjustable resistor is connected to a frequency setting pin or a compensation pin of a controller of the DC-DC conversion circuit, a periodic alternating modulation voltage signal is applied to a grid electrode of the field effect transistor used as the adjustable resistor, the resistance value of a resistor between a source electrode and a drain electrode of the field effect transistor is changed, the frequency spreading of the DC-DC conversion circuit is realized, the defects of cost increase, process increase, unsatisfactory effect and the like of the existing solution are effectively overcome, and the DC-DC conversion circuit can meet EMC mandatory certification requirements.
Of course, not all of the advantages described above need to be achieved at the same time in the practice of any one product or method of the invention. Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the embodiments of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
Drawings
The accompanying drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the example serve to explain the principles of the invention and not to limit the invention. The shapes and sizes of the various elements in the drawings are not to scale and are merely intended to illustrate the invention.
FIG. 1 is a schematic diagram of a conventional boost circuit;
FIG. 2 is a schematic diagram of a conventional voltage-reducing circuit;
FIG. 3 is a schematic diagram of a conventional LED driving circuit;
FIG. 4 is a schematic diagram of a spread spectrum circuit according to an embodiment of the present invention;
FIG. 5 is a schematic diagram of a first embodiment of a spread spectrum circuit of the present invention;
FIG. 6 is a schematic diagram of a voltage step-down circuit according to a first embodiment of the present invention;
FIG. 7 shows a MOSFET V according to the first embodiment of the present inventionGS-IDSA graph;
FIG. 8 is a schematic diagram of a boost circuit according to a first embodiment of the present invention;
FIG. 9 is a schematic diagram of a second embodiment of a spread spectrum circuit of the present invention;
fig. 10 is a schematic structural diagram of a spreading circuit according to a third embodiment of the present invention.
Detailed Description
The following detailed description of embodiments of the invention is provided in connection with the accompanying drawings and examples. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention. It should be noted that the embodiments and features of the embodiments in the present application may be arbitrarily combined with each other without conflict.
Unless defined otherwise, technical or scientific terms used in the disclosure of the embodiments of the present invention should have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. The use of "first," "second," and similar language in the embodiments of the present invention does not denote any order, quantity, or importance, but rather the terms "first," "second," and similar language are used to distinguish one element from another. The word "comprising" or "comprises", and the like, means that the element or item listed before the word covers the element or item listed after the word and its equivalents, but does not exclude other elements or items. The terms "connected" or "coupled" and the like are not restricted to physical or mechanical connections, but may include electrical connections, whether direct or indirect.
It will be appreciated by those skilled in the art that the transistors employed in all embodiments of the present application may be thin film transistors or field effect transistors or other devices having the same characteristics. Preferably, the thin film transistor used in the embodiment of the present invention may be an oxide semiconductor transistor. Since the source and the drain of the transistor used herein are symmetrical, the source and the drain may be interchanged, so in the embodiment of the present invention, in order to distinguish two poles of the transistor except the gate, one of the electrodes is referred to as a first pole, the other electrode is referred to as a second pole, the first pole may be the source or the drain, and the second pole may be the drain or the source. Meanwhile, the thin film transistor or the field effect transistor may be an n-type transistor or a p-type transistor.
Fig. 1 is a schematic structural diagram of a conventional boost circuit, fig. 2 is a schematic structural diagram of a conventional buck circuit, and fig. 3 is a schematic structural diagram of a conventional LED driving circuit. As shown in fig. 1 to 3, these DC-DC conversion circuits all use a tank oscillator circuit composed of a controller IC and peripheral circuits, and have fixed and set oscillation frequencies. Whether fixed or set, once the parameters of the resistance and capacitance arranged on the periphery are determined, the oscillation frequency is fixed at a frequency. Wherein, the FREQ pin in fig. 1, the RT/SYNC pin in fig. 2, and the RT pin in fig. 3 are setting pins of oscillation frequency, and the resistance R is set by the frequencyTThe oscillation frequency is set according to the resistance value of the resistor R, and once the frequency is set to be the resistor RTThe oscillation frequency is fixed. The inventor of the present application has found that the oscillation frequency of the DC-DC conversion circuits is fixed at a frequency, which results in failure of radiation emission (radiated emissions) generated by oscillation frequency, overshoot self-excited frequency and frequency multiplication in EMC test, but by extending the frequency range of radiationThe concentration of the radiation energy can be reduced. Therefore, the embodiment of the invention provides a spread spectrum circuit for a DC-DC conversion circuit, so that the DC-DC conversion circuit can meet the EMC mandatory certification requirement.
Fig. 4 is a schematic structural diagram of a spread spectrum circuit according to an embodiment of the present invention. As shown in fig. 4, the main structure of the frequency spreading circuit according to the embodiment of the present invention includes a modulation voltage circuit 10 and a field effect transistor 20, wherein the modulation voltage circuit 10 is connected to a gate of the field effect transistor 20 and is configured to output a periodic alternating modulation voltage signal to the gate of the field effect transistor 20, and a drain of the field effect transistor 20 is connected to a frequency setting pin or a compensation pin of a controller IC in the DC-DC converter circuit 100 and is configured to change a resistance value of a resistor between source and drain of the field effect transistor 20 according to the periodic alternating modulation voltage signal, so as to change an oscillation frequency of the DC-DC converter circuit 100 and implement frequency spreading of the DC-DC converter circuit.
The embodiment of the invention provides a spread spectrum circuit, which utilizes a field effect transistor as an adjustable resistor for voltage control and is connected to a frequency setting pin or a compensation pin of a controller IC, a periodic alternating modulation voltage signal is applied to a grid electrode of the field effect transistor as the adjustable resistor, the resistance value of a resistor between a source electrode and a drain electrode of the field effect transistor is changed, the resistance value of the frequency setting resistor of the controller IC is further changed, the oscillation frequency of a DC-DC conversion circuit is changed, the spread spectrum of the DC-DC conversion circuit is realized, and the DC-DC conversion circuit can meet the EMC mandatory authentication requirement.
The technical solution of the present invention will be described in detail by the following specific examples.
First embodiment
Fig. 5 is a schematic structural diagram of a first embodiment of a spread spectrum circuit of the present invention. As shown in fig. 5, in the present embodiment, the modulation voltage circuit includes a signal INPUT terminal INPUT, a modulation node Vb, a voltage terminal V1, a ground terminal V2, and a first spreading resistor R1*A second spreading resistor R2*A third spreading resistor R3*And a first spreading capacitor C1*. Wherein, the first spread spectrum resistor R1*Is connected to the signal INPUT terminal INPUT, a first spreading resistor R1*And the other end thereof is connected to the modulation node Vb. Second spreading resistor R2*One terminal of and voltageA terminal V1 and a second spread-spectrum resistor R2*And the other end thereof is connected to the modulation node Vb. Third spreading resistor R3*Is connected to the modulation node Vb, and a third spreading resistor R3*And the other end thereof is connected to a ground terminal V2. First spread spectrum capacitor C1*Is connected to the modulation node Vb, a first spreading capacitor C1*And a second terminal thereof is connected to a ground terminal V2.
In this embodiment, the Field Effect Transistor is a Metal Oxide Semiconductor Field Effect Transistor (MOSFET), a gate of the MOSFET is connected to the modulation node Vb, a source of the MOSFET is connected to the ground terminal V2, and a drain of the MOSFET passes through the fourth spreading resistor R4*Is connected to the frequency setting pin of the controller IC in the DC-DC conversion circuit 100.
In this embodiment, the signal INPUT terminal INPUT uses the existing line frequency signals of the liquid crystal module, including the output enable signal OE, the polarity control signal POL, or the data strobe signal DE, and these line frequency signals are all square wave signals. The voltage end V1 adopts the general input and output voltage VGPIO output by the prior T-CON of the liquid crystal module.
Fig. 6 is a schematic diagram of the voltage step-down circuit according to the first embodiment of the invention. As shown in FIG. 6, the drain of the MOSFET passes through a fourth spreading resistor R4*The RT/SYNC pin of the controller IC in the DC-DC conversion circuit 100 is connected to a frequency setting resistor R, and the RT/SYNC pin of the controller IC in the DC-DC conversion circuit 100 is connected to a frequency setting resistor RTTherefore, in this embodiment, after the RT/SYNC pin is connected to the spectrum spreading circuit, it is equivalent to setting the resistor R at the original frequencyTA variable resistor is connected in parallel, and the oscillation frequency of the DC-DC conversion circuit 100 is changed, so that the DC-DC conversion circuit 100 oscillates in a frequency range. Since the spread spectrum circuit of this embodiment controls the resistance change between the source and the drain of the field effect transistor by the periodically alternating modulation voltage signal, the resistance value of the spread spectrum circuit of this embodiment is periodically changed, i.e. it is equal to the original frequency setting resistor RTThe resistance value of the parallel resistor changes periodically, so that the oscillation frequency of the DC-DC conversion circuit 100 changes periodically, and the spread spectrum of the oscillation frequency of the DC-DC conversion circuit 100 is realized.
In this embodiment, the setting manner of the related parameters of the spreading resistor and the spreading capacitor in the modulation voltage circuit is as follows:
(1) first, the oscillation frequency F and the frequency setting resistance R of the DC-DC conversion circuit are obtainedT. Due to the oscillation frequency F and the frequency setting resistor RTIs determined by the specification of the controller IC, so that the oscillation frequency F and the frequency setting resistance R can be obtained from the design data of the designed DC-DC conversion circuitT. For example, for the boost circuit shown in FIG. 1, when R isTWhen the frequency is 176K omega, the oscillation frequency is 600 KHz; for the buck circuit shown in FIG. 2, when R isTWhen the frequency is 49.9K omega, the oscillation frequency is 500 KHz; for the LED driving circuit shown in FIG. 3, when R isTWhen 51K Ω, the oscillation frequency is 1 MHz.
(2) Subsequently, the spreading deviation K is set. According to the circuit characteristics, the spread spectrum deviation K may be set to 1% to 20% so that the oscillation frequency after spreading is F-K × F to F + K × F. In order to obtain a good EMC effect, the spread spectrum deviation K is preferably set to 5% to 15%. In this embodiment, the spread spectrum deviation K is set to 10%, the original oscillation frequency F is 500KHz, and the oscillation frequency after spreading is 450KHz to 500 KHz. According to a frequency setting formula in the specification of the controller IC, the frequency setting resistor R after frequency spreading can be calculatedTIs between 44.7K omega and 55.7K omega.
(3) Subsequently, the parameters of the MOSFET and the parameter of the modulation node Vb are selected. In this embodiment, the periodically alternating modulated voltage signal operates in the amplification region of the MOSFET. FIG. 7 shows a MOSFET V according to the first embodiment of the present inventionGS-IDSGraph is shown. As shown in FIG. 7, for the Drain to Source voltage V DS5V, when Gate to Source (Gate to Source) voltage VGSBetween 2V and 3V, the Drain-to-Source current IDSThe current is about 0-100 mA, so that the variable resistance between the source and the drain of the MOSFET is between 50 omega and infinity, and the requirement of the embodiment can be met.
(4) Subsequently, the INPUT signal of the signal INPUT terminal INPUT is selected. In this embodiment, the selection of the existing line frequency signals of the liquid crystal module includes the output enable signal OE, the polarity control signal POL, or the data strobe signal DE, and these line frequency signals are all square wave signals.
(5) Subsequently, circuit parameters are selected. In this embodiment, the resistance R is set according to the spreading deviation K set in the above, the oscillation frequency after spreading is 450KHz to 500KHz, and the frequency after spreadingTThe values are 44.7K omega-55.7K omega, and the related parameters of the spread spectrum circuit of the embodiment can be obtained through calculation. Wherein the resistance R is set according to the frequency before spreadingTAnd a fourth spreading resistor R4*Are equal to 44.7K omega and 55.7K omega, respectively, a fourth spreading resistor R4 can be obtained*The resistance value of (c).
As an example, assume a general input-output voltage V of a T-CON outputGPIOThe maximum voltage Vbmax of the spread-spectrum node Vb is 3V, the minimum voltage Vbmin is 2V, the voltage of the spread-spectrum node Vb is approximately changed by a sine wave, and then the first spread-spectrum resistor R1 is formed by the square wave with the voltage of 3.3V and the voltage of OE/POL/DE of 0-3.3V*A second spreading resistor R2*And a third spreading resistor R3*Is determined by the following formula:
Figure BDA0002138723890000081
where "/" denotes the resistance value in the parallel relationship.
First spread spectrum capacitor C1*Is determined by 2 τ ═ FH, where τ is a time constant and FH is the horizontal frequency of the liquid crystal module, i.e., FH
Figure BDA0002138723890000082
The technical solution of the embodiment of the present invention is further explained by the working process of the spread spectrum circuit.
It can be seen from the above working process of the spread spectrum circuit in this embodiment that this embodiment ingeniously utilizes the controller IC resource of the existing DC-DC conversion circuit and the signal resource of the liquid crystal module, and by setting the modulation voltage circuit and the MOSFET, the MOSFET is used as the adjustable resistor for voltage control and is connected to the RT/SYNC pin of the controller IC, and the modulation voltage circuit applies a periodic alternating modulation voltage signal to the gate of the MOSFET used as the adjustable resistor, and changes the resistance between the source and the drain of the MOSFET, thereby changing the frequency setting resistance of the controller IC in the DC-DC conversion circuit, further changing the oscillation frequency of the DC-DC conversion circuit, and finally realizing the expansion of the oscillation frequency of the DC-DC conversion circuit. The spread spectrum of the DC-DC conversion circuit expands the radiation frequency range of the DC-DC conversion circuit, eliminates radiation energy concentration, reduces electromagnetic emission, and enables the DC-DC conversion circuit to meet the EMC mandatory certification requirement. The present embodiment utilizes the existing line frequency signal of the liquid crystal module, such as OE/POL/DE, to adjust the voltage of the modulation node Vb through the modulation voltage circuit, i.e. to adjust the periodic alternating modulation voltage signal applied to the gate of the MOSFET. The spread spectrum circuit has the characteristics of simple circuit structure, ideal spread spectrum effect, strong practicability, easiness in implementation and the like, and effectively solves the problem of EMC (electro magnetic compatibility) difficulty in electronic product design. Compared with the existing solutions of increasing a metal shielding cover, increasing a conductive adhesive tape, increasing a magnetic bead, increasing a magnetic ring, pasting a copper foil, pasting an aluminum foil and the like, the embodiment not only effectively reduces the production cost and the production process, but also reduces the EMC rectification time, improves the working efficiency and has good application prospect.
Fig. 8 is a schematic diagram of a boost circuit according to a first embodiment of the present invention. As shown in FIG. 8, the difference from the structure shown in FIG. 6 is that the drain of the MOSFET passes through a fourth spreading resistor R4*Is connected to the FREQ pin of the controller IC in the DC-DC conversion circuit 100. Similarly, the spread spectrum circuit of the present embodiment can also be applied to the DC-DC converter circuit shown in fig. 3, and the drain of the MOSFET passes through the fourth spread spectrum resistor R4*And is connected with an RT pin of a controller IC in the DC-DC conversion circuit.
Second embodiment
Fig. 9 is a schematic structural diagram of a second embodiment of the spread spectrum circuit of the present invention. As shown in fig. 9, in the present embodiment, the modulation voltage circuit includes a signal INPUT terminal INPUT, a modulation node Vb, a voltage terminal V1, a ground terminal V2, and a first spreading resistor R1*A second spreading resistor R2*A third spreading resistor R3*A fifth spreading resistor R5*A first spread-spectrum capacitor C1*Second spread spectrum power supplyC2*And a first spreading transistor T1. The first spread spectrum transistor T1 has a gate connected to the signal INPUT terminal INPUT, a source connected to the voltage terminal V1, and a drain connected to the fifth spread spectrum resistor R5*And is connected to ground terminal V2. First spreading resistor R1*Is connected to the drain of a first spreading transistor T1, a first spreading resistor R1*And the other end thereof is connected to the modulation node Vb. Second spreading resistor R2*Is connected with a voltage terminal V1, a second spread spectrum resistor R2*And the other end thereof is connected to the modulation node Vb. Third spreading resistor R3*Is connected to the modulation node Vb, and a third spreading resistor R3*And the other end thereof is connected to a ground terminal V2. First spread spectrum capacitor C1*Is connected to modulation node Vb and a second terminal is connected to ground terminal V2. Second spreading capacitor C2*Is connected to the drain of the first spread spectrum transistor T1, and is connected to the ground terminal V2. In this embodiment, the gate of the MOSFET is connected to the modulation node Vb, the source is connected to the ground terminal V2, and the drain is connected to the fourth spreading resistor R4*Is connected to the frequency setting pin of the controller IC in the DC-DC conversion circuit 100.
In this embodiment, the signal INPUT terminal INPUT is touch scan data lock signal TP of liquid crystal module T-CON, and the voltage terminal V1 is universal INPUT/output voltage V output by the existing T-CON of the liquid crystal moduleGPIO，VGPIO＝3.3V。
The spreading principle of this embodiment is the same as that of the first embodiment, except that the signal INPUT terminal INPUT is changed from the line frequency signal OE/POL/DE of the first embodiment to the touch scan data lock signal TP, the modulation node Vb generation circuit is adjusted accordingly, and a fifth spreading resistor R5 is provided*A second spreading capacitor C2*And a first spreading transistor T1 for making the voltage of the spreading node Vb approximate a sine wave change. The spread spectrum circuit of the present embodiment can be applied to a DC-DC conversion circuit such as a boost circuit, a buck circuit, and an LED driving circuit, and the technical effects of the foregoing first embodiment can be obtained as well.
Third embodiment
Fig. 10 is a schematic structural diagram of a spreading circuit according to a third embodiment of the present invention. Front sideThe spread spectrum circuit of the first and second embodiments is applied to a controller IC having a frequency setting pin, such as an RT/SYNC pin, a FREQ pin or an RT pin. As shown in fig. 10, the DC-DC conversion circuit controller IC has no frequency setting pin, but has a compensation pin COMP. The main structure of the spread spectrum circuit of this embodiment is the same as that of the spread spectrum circuit of the first embodiment, except that the drain of the MOSFET passes through a fourth spreading resistor R4*And a third spreading capacitor C3*Is connected to the compensation pin COMP of the controller IC in the DC-DC conversion circuit 100.
The compensation pin COMP of the spread spectrum circuit connection controller IC of this embodiment is equivalent to a resistor connected in series with the original frequency setting resistor R3, thereby changing the oscillation frequency of the DC-DC converter circuit 100. The working principle of the spread spectrum circuit of this embodiment is the same as that of the first embodiment, and the spread spectrum circuit can be applied to a DC-DC conversion circuit such as a boost circuit, a buck circuit, and an LED driving circuit with a compensation pin COMP, and the technical effects of the first embodiment can be obtained as well. And will not be described in detail herein.
Fourth embodiment
Based on the inventive concept of the foregoing embodiments, the present invention further provides a DC-DC conversion circuit, which includes the foregoing spread spectrum circuit, and the DC-DC conversion circuit is used in display devices such as LCD and OLED.
In the description of the embodiments of the present invention, it should be understood that the terms "middle", "upper", "lower", "front", "rear", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed in a particular orientation, and be operated, and thus, should not be construed as limiting the present invention.
In the description of the embodiments of the present invention, it should be noted that, unless explicitly stated or limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
Although the embodiments of the present invention have been described above, the above description is only for the convenience of understanding the present invention, and is not intended to limit the present invention. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (2)

1. A spread spectrum circuit is applied to a liquid crystal display device and is characterized in that the spread spectrum circuit utilizes a controller IC resource of a DC-DC conversion circuit and a signal resource of the liquid crystal display device; the spread spectrum circuit comprises a modulation voltage circuit and a field effect transistor, wherein the modulation voltage circuit is connected with a grid electrode of the field effect transistor and is used for outputting a periodic alternating modulation voltage signal to the grid electrode of the field effect transistor, a drain electrode of the field effect transistor is connected with a compensation pin of a controller in the DC-DC conversion circuit, and resistance between a source electrode and a drain electrode of the field effect transistor is changed according to the periodic alternating modulation voltage signal; the field effect transistor comprises a metal oxide semiconductor field effect transistor MOSFET, the grid electrode of the MOSFET is connected with the modulation node, the source electrode of the MOSFET is connected with the grounding end, the drain electrode of the MOSFET is connected with a compensation pin of the controller in the DC-DC conversion circuit through a fourth spread spectrum resistor and a third spread spectrum capacitor, and the compensation pin comprises a COMP pin; the input signal of the modulation voltage circuit comprises an output enable signal, a polarity control signal or a data strobe signal of the display device; the voltage end of the modulation voltage circuit adopts a universal input and output voltage V output by a liquid crystal module T-CONGPIOThe output enable signal, the polarity control signal or the data strobe signal are 0-3.3V square wave signals, and the universal inputOutput voltage VGPIOThe maximum voltage of the modulation node is 3V, the minimum voltage of the modulation node is 2V, the voltage of the modulation node is approximately changed by sine wave, and the voltage of the modulation node is adjusted through the modulation voltage circuit, namely, a periodic alternating modulation voltage signal applied to the grid electrode of the metal oxide semiconductor field effect transistor MOSFET is adjusted;
the modulation voltage circuit comprises a signal input end, a modulation node, a voltage end, a grounding end, a first spread spectrum resistor, a second spread spectrum resistor, a third spread spectrum resistor and a first spread spectrum capacitor; wherein the content of the first and second substances,
one end of the first spread spectrum resistor is connected with the signal input end, and the other end of the first spread spectrum resistor is connected with the modulation node;
one end of the second spread spectrum resistor is connected with the voltage end, and the other end of the second spread spectrum resistor is connected with the modulation node;
one end of the third spread spectrum resistor is connected with the modulation node, and the other end of the third spread spectrum resistor is connected with the grounding end;
and the first end of the first spread spectrum capacitor is connected with the modulation node, and the second end of the first spread spectrum capacitor is connected with the grounding end.
2. A DC-DC conversion circuit characterized by comprising the spread spectrum circuit according to claim 1.
CN201910661570.8A 2019-07-22 2019-07-22 Spread spectrum circuit and DC-DC conversion circuit Active CN110365206B (en)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103384117A (en) * 2012-05-03 2013-11-06 台达电子企业管理（上海）有限公司 Frequency conversion mode converter and regulation and control method thereof
CN104038046A (en) * 2014-05-15 2014-09-10 青岛海信宽带多媒体技术有限公司 Frequency jittering circuit and switching power supply
CN104242613A (en) * 2014-08-26 2014-12-24 中国电子科技集团公司第四十一研究所 Synchronous spread spectrum circuit and method applied to program control direct-current power supply

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103384117A (en) * 2012-05-03 2013-11-06 台达电子企业管理（上海）有限公司 Frequency conversion mode converter and regulation and control method thereof
CN104038046A (en) * 2014-05-15 2014-09-10 青岛海信宽带多媒体技术有限公司 Frequency jittering circuit and switching power supply
CN104242613A (en) * 2014-08-26 2014-12-24 中国电子科技集团公司第四十一研究所 Synchronous spread spectrum circuit and method applied to program control direct-current power supply

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