CN102170222B - Suppression device for electromagnetic interferences in switching power supply - Google Patents
Suppression device for electromagnetic interferences in switching power supply Download PDFInfo
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- CN102170222B CN102170222B CN 201110105500 CN201110105500A CN102170222B CN 102170222 B CN102170222 B CN 102170222B CN 201110105500 CN201110105500 CN 201110105500 CN 201110105500 A CN201110105500 A CN 201110105500A CN 102170222 B CN102170222 B CN 102170222B
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Abstract
The invention discloses a suppression device for electromagnetic interferences to a switching power supply. The suppression device comprises a pulse width modulation signal control circuit (U1), a first resistor (Rt1), a first capacitor (Ct), a second resistor (Rt2), a third resistor (Rt3), an analog switch (U2) and a frequency division counter (U3), wherein the analog switch (U2) comprises a first output port and a second output port; the first output port is connected with a second end of the second resistor (Rt2); the second output port is connected with a second end of the third resistor (Rt3); the frequency division counter (U3) is used for generating a square wave with a preset frequency; and a frequency output port is connected with the analog switch (U2) and is used for controlling the on-off of the analog switch (U2). The suppression device disclosed by the invention has the advantage that the electromagnetic interferences to a plasma display switching power supply is reduced by using a frequency adjusting link in a peripheral circuit of a pulse width modulation control chip.
Description
Technical field
The invention belongs to the plasma TV field, be specifically related to a kind of restraining device of Switching Power Supply electromagnetic interference.
Background technology
Colour plasma display (PDP, Plasma Display Panel) is a kind of display device that developed rapidly in recent years.Colour plasma display becomes the first-selection of large scale display device with superior performance, the large-sized solor plasma display device has begun to come into the market at present, especially AC type AC-PDP has the advantages such as type of drive is simple and obtains to study widely and use, and can progressively be popularized in recent years.
The electromagnetic interference that Switching Power Supply produces is divided by the noise jamming source category, can be divided into spike and disturb two kinds of harmonious wave interference; If divide by coupling path, can be divided into two kinds of conducted interference and radiated interference.Illustrate respectively by disturbed sources of noise now:
(1) interference that causes the reverse recovery time of diode
There is larger forward current to flow through during rectifier diode forward conduction in the high-frequency rectification loop, be subjected to reversed bias voltage and turn to when cut-off at it, owing in the PN junction more carrier accumulation is arranged, thereby the following period of time before charge carrier disappears, electric current meeting reverse flow, the reverse recovery current that causes charge carrier to disappear sharply reduces and the very large curent change (di/dt) of generation.
The humorous wave interference that produces when (2) switching tube is worked
Power switch pipe flows through larger pulse current when conducting.For example the input current waveform of normal shock type, push-pull type and bridge converter is approximately square wave when resistive load, wherein contains abundant higher harmonic components.When adopting zero current, zero voltage switch, this humorous wave interference will be very little.In addition, power switch pipe is between the off period, and the current break that high frequency transformer winding leakage inductance causes also can produce spike and disturb.
(3) interference of ac input circuit generation
The Switching Power Supply input rectifying tube of no industrial frequency transformer can cause that between reverse recovery the high frequency attenuation vibration produces interference.The spike that Switching Power Supply produces disturbs harmonious wave interference energy, and the interference that forms that blazes abroad of the input-output line by Switching Power Supply is referred to as conducted interference; And the energy of harmonic wave and parasitic oscillation when propagating by input-output line, all can produce Electric and magnetic fields in the space.This interference that produces by electromagnetic radiation is called radiated interference.
(4) other reasons
The parasitic parameter of components and parts, the principle diagram design of Switching Power Supply is not perfect, printed substrate (PCB) cabling adopts manual layout usually, has very large randomness, the near-field interference of PCB is large, and the installation of device, placement on the printed panel, and the unreasonable EMI that can cause in orientation disturbs.
Plasma display (PDP) power source special is according to its monopolizing characteristic, namely because plasma display voltage drive waveforms requires power supply that multiple different voltage is provided, need power supply to have multiple voltage output, power factor correction (PFC) part also will be arranged simultaneously, just so that the switching tube on the power panel and heavy-duty diode quantity are a lot, again because high-power wiring mostly is manual wiring, irrational part is arranged unavoidably, than the easier electromagnetic interference that causes of common power, add the plasma display driving circuits and be subject to causing easily misoperation after the electromagnetic interference, disturb display effect.So the inhibition of plasma display switch power special electromagnetic interference more should come into one's own.
The three elements that form electromagnetic interference are interference source, route of transmission and disturbed equipment.Thereby, suppress electromagnetic interference and also should set about from this three aspects:.At first should suppress interference source, directly eliminate cause of failures; Next is coupling and the radiation of eliminating between interference source and the disturbed equipment, the route of transmission that cuts off electromagnetic interference; The 3rd is the interference rejection ability that improves disturbed equipment, lowers it to the susceptibility of noise.Several measures that suppress at present to disturb all are that method commonly used is shielding, ground connection and filtering with the coupling channel that cuts off between electromagnetic interference source and the disturbed equipment basically.Above-mentioned all is effective ways, but seldom relates to direct control interference source, eliminates and disturbs, or improve the interference rejection ability of disturbed equipment.
In recent years, there is a kind of method that is called as the frequency jitter method to be suggested to reduce electromagnetic interference, the frequency jitter method is by the method for spread-spectrum switch tube grid pwm signal to be modulated, signal energy is expanded on the wider frequency range, thereby reduce electromagnetic interference on some characteristic frequency points.In fact, the method is a kind of controlled modulation to signal, and this method can obviously not increase the shake of pwm signal.Application attestation spread spectrum technique in the reality is effectively, and different modulation degree can reduce electromagnetic interference 7 to 20dB and not wait.But adopting said method needs the chip of some specific functions, bad control ease for use and cost.
In the prior art, the problem for the bad control ease for use of above-mentioned switching power supply of plasma display electromagnetic interference inhibition method and cost not yet proposes effective solution at present.
Summary of the invention
Order of the present invention is the restraining device that discloses a kind of Switching Power Supply electromagnetic interference, is used for solving the problem of the prior art ionic medium monitor switch power supply bad control ease for use of electromagnetic interference inhibition method and cost.
To achieve these goals, according to an aspect of the present invention, provide a kind of restraining device of Switching Power Supply electromagnetic interference, be achieved through the following technical solutions:
A kind of restraining device of Switching Power Supply electromagnetic interference comprises: the pulse-width signal control circuit, and having first frequency control end and second frequency provides end, is used for providing predetermined operating frequency; The first resistance, first end is connected with the first frequency control end, and the second end provides end to be connected with second frequency; The first electric capacity, first end is connected with the first frequency control end, the second end ground connection; This restraining device also comprises: the second resistance, first end are connected in the first frequency control end; The 3rd resistance, first end are connected in the first frequency control end; Analog switch comprises the first output port and the second output port, and the first output port is connected with the second end of the second resistance, and the second output port is connected in the second end of the 3rd resistance; And frequency counter, with at least one resistance and at least one Capacitance parallel connection, for generation of the square wave of predeterminated frequency; Frequency counter comprises the frequency output terminal mouth, and the frequency output terminal mouth is connected with analog switch, is used for the square wave by the output predeterminated frequency, the disconnection of control simulation switch and conducting.
Further, frequency counter also comprises: the counting port; Reseting port is connected with the counting port, is used for making the whole zero clearings of port of frequency counter after the default count cycle finishes, and restarts counting.
Further, the level of frequency output terminal mouth output changes according to default rule in predetermined period.
Further, when the counting port was finished a count cycle, frequency counter was to the defeated high level of reseting port.
Further, when reseting port is high level, the zero clearing of frequency output terminal mouth, the salty new counting that begins of counting end.
Further, analog switch also comprises input port, and when the input port input high level, the high level switch that analog switch is corresponding is switched on.
Prior art is compared, the invention has the beneficial effects as follows: the electromagnetic interference that reduces Switching Power Supply by frequency of utilization adjustment link in the peripheral circuit of chip pwm chip, the method can be applicable to most of common used PWM control chip simultaneously, greatly increased convenience and flexibility, the cost that increases simultaneously circuit part also is far smaller than the price of special chip.
Description of drawings
Accompanying drawing described herein is used to provide a further understanding of the present invention, consists of the application's a part, and illustrative examples of the present invention and explanation thereof are used for explaining the present invention, do not consist of improper restriction of the present invention.In the accompanying drawings:
Fig. 1 is the restraining device internal structure schematic diagram of embodiment of the invention Switching Power Supply electromagnetic interference;
Fig. 2 is the pin definitions figure of embodiment of the invention frequency counter; And
Fig. 3 is pin definitions and the internal structure schematic diagram of embodiment of the invention analog switch.
Embodiment
Need to prove that in the situation of not conflicting, embodiment and the feature among the embodiment among the application can make up mutually.Describe below with reference to the accompanying drawings and in conjunction with the embodiments the present invention in detail.
Fig. 1 is a kind of restraining device internal structure schematic diagram of Switching Power Supply electromagnetic interference.
As shown in Figure 1, a kind of restraining device of Switching Power Supply electromagnetic interference comprises, pulse-width signal control circuit U1, and having first frequency control end and second frequency provides end, is used for providing predetermined operating frequency; The first resistance R t1, first end is connected with the first frequency control end, and the second end provides end to be connected with second frequency; The first capacitor C t, first end is connected with the first frequency control end, the second end ground connection; The second resistance R t2, first end is connected in the first frequency control end; The 3rd resistance R t3, first end is connected in the first frequency control end; Analog switch U2 comprises the first output port and the second output port, and the first output port is connected with the second end of the second resistance R t2, and the second output port is connected in the second end of the 3rd resistance R t3; And frequency counter U3, in parallel with at least one resistance R S and at least one capacitor C T, for generation of the square wave of predeterminated frequency; Frequency counter U3 comprises the frequency output terminal mouth, and the frequency output terminal mouth is connected with analog switch U2, is used for the square wave by the output predeterminated frequency, disconnection and the conducting of control simulation switch U2.
Fig. 2 is the pin definitions figure of embodiment of the invention frequency counter.
Preferably, core of the present invention frequency counter, commonly used have a CD4060 etc., and its pin definitions and internal structure are as shown in Figure 2.The 4060th, the frequency counter that a kind of band resets, by at the access resistance of 10,11 pin 9, and electric capacity, can produce the square wave of certain frequency, the computing formula of square wave frequency is: f ≈ 1/2.2RTCT when RS=10RT, and the frequency of each output pin output square wave is fi=f/2i, wherein i is the label of corresponding pin, is 8 such as i value corresponding to the 14th pin Q8.4060 the 12nd pin is the reset end, in case 12 pin level are high, the whole zero clearings of all output pins restart counting.
Fig. 3 is pin definitions and the internal structure schematic diagram of embodiment of the invention analog switch.
Preferably, analog switch adopts CD4066 and resistance capacitance that some are essential etc., and 4066 pin definitions and internal structure are as shown in Figure 3.The 4066th, a kind of four analog switches, when the level on a certain control pin is high, corresponding switch conduction, otherwise the power supply of open circuit is produced by power circuit.
In Fig. 1, participate in shown in Figure 1ly the element application of Fig. 2-3, power supply pwm chip U1 is the UC3845 that commonly uses, and 4 pin meet capacitor C t to ground, and connecting resistance Rt1 connects 2,4 pin of U2 simultaneously to 8 pin; The 5 pin ground connection of U1; 6 footnotes note black patch, the G end of driven MOS FET; 7 pin of U1 connect power Vcc; The 8 pin connecting resistance Rt2 of U1 are to 1 pin of U2, and resistance R t3 is to 3 pin of U2.The 5 pin connecting resistance R1 of analog switch U2 are to 5 pin of U3, the 7 pin ground connection of U2, and 14 pin of U2 connect power Vcc, and the 13 pin connecting resistance R2 of U2 are to 7 pin of U3.The 8 pin ground connection of frequency counter U3,16 pin connect power Vcc, and 4 pin connect 12 pin, and 9 pin meet capacitor C T to ground, and 10 pin connecting resistance RT are to ground, and 11 pin connecting resistance RS are to ground.Hypothesis Rt1=10K, Ct=2.2nF during normal operation, output PWM wave frequency f=1.72/RC ≈ 78.2KHz.
Suppose Rs=470K, RT=47K, CT=4.7nF.The frequency of 4060 chip RC concussion calculates f ≈ 2KHz according to formula.Q4 output square wave frequency f=125Hz, Q5 output square wave frequency f=65.5Hz.Q6 connects the reset end, i.e. CD4060 zero clearing when T=2/65.5 ≈ 30ms restarts counting.Q4Q5 output changes by 00 → 10 → 01 → 11 → 00 rule, and the cycle is 30ms.Because of its change frequency much smaller than the PWM wave frequency, so can the output of UC3845 not impacted.
When Q4Q5 was output as 00, two switches that CD4066 is corresponding disconnected, and 4 pin and the resistance between 8 pin of access UC3845 are 10K.Output PWM wave frequency f=1.72/RC ≈ 78.2KHz.
When Q4Q5 was output as 10, two switches one logical that CD4066 is corresponding were disconnected, and 4 pin of access UC3845 and the resistance between 8 pin are that 10K and 40K are in parallel.Output PWM wave frequency f=1.72/RC=1.72/8K2.2nF ≈ 97.7KHz.
When Q4Q5 was output as 01, two switches one disconnected that CD4066 is corresponding were logical, and 4 pin of access UC3845 and the resistance between 8 pin still are that 10K and 40K are in parallel.Output PWM wave frequency f=1.72/RC=1.72/8K2.2nF ≈ 97.7KHz.
When Q4Q5 was output as 11, two switches that CD4066 is corresponding were all connected, and 4 pin and the resistance between 8 pin of access UC3845 are 10K and two 40K parallel connections.Output PWM wave frequency f=1.72/RC=1.72/6.67K2.2nF ≈ 117.3KHz.
By above-mentioned a kind of circuit structure, the PWM wave frequency of UC3845 is changed in a scope, thereby the electromagnetic interference on a certain fixed frequency point, has been got to the purpose that electromagnetism suppresses because reducing in frequency fluctuation.Because of the frequency of its variation frequency much smaller than PWM ripple itself, so can not impact the output of UC3845 and the output of power supply.Simultaneously frequency counter and analog switch are very common, and cost is not high yet, and circuit simple in structure has very high practicality.
By technique scheme, the frequency of utilization adjustment link reduces the electromagnetic interference of Switching Power Supply in the peripheral circuit of chip pwm chip, provides new thinking for suppressing the Switching Power Supply electromagnetic interference.The method can be applicable to most of common used PWM control chip simultaneously, has greatly increased convenience and flexibility, and the cost that increases simultaneously circuit part also is far smaller than the price of special chip.
The above is the preferred embodiments of the present invention only, is not limited to the present invention, and for a person skilled in the art, the present invention can have various modifications and variations.Within the spirit and principles in the present invention all, any modification of doing, be equal to replacement, improvement etc., all should be included within protection scope of the present invention.
Claims (6)
1. the restraining device of a Switching Power Supply electromagnetic interference comprises:
Pulse-width signal control circuit (U1), having first frequency control end and second frequency provides end, is used for providing predetermined operating frequency;
The first resistance (Rt1), first end is connected with described first frequency control end, and the second end provides end to be connected with described second frequency;
The first electric capacity (Ct), first end is connected with described first frequency control end, the second end ground connection;
It is characterized in that, also comprise:
The second resistance (Rt2), first end is connected in described second frequency end is provided;
The 3rd resistance (Rt3), first end is connected in described second frequency end is provided;
Analog switch (U2) comprises the first output port and the second output port, and described the first output port is connected with the second end of described the second resistance (Rt2), and described the second output port is connected in the second end of described the 3rd resistance (Rt3); And
Frequency counter (U3), in parallel with at least one resistance (RS) and at least one electric capacity (CT), for generation of the square wave of predeterminated frequency; Described frequency counter (U3) comprises the frequency output terminal mouth, and described frequency output terminal mouth is connected with described analog switch (U2), is used for the square wave by the described predeterminated frequency of output, controls disconnection and the conducting of described analog switch (U2).
2. restraining device according to claim 1 is characterized in that, described frequency counter (U3) also comprises:
The counting port;
Reseting port is connected with described counting port, is used for making the whole zero clearings of port of described frequency counter (U3) after the default count cycle finishes, and restarts counting.
3. restraining device according to claim 2 is characterized in that,
The level of described frequency output terminal mouth output changes according to default rule in predetermined period.
4. restraining device according to claim 2 is characterized in that,
When described counting port was finished a count cycle, described frequency counter (U3) gave described reseting port defeated high level.
5. restraining device according to claim 4 is characterized in that,
When described reseting port is high level, the zero clearing of described frequency output terminal mouth, the salty new counting that begins of described counting end.
6. restraining device according to claim 1 is characterized in that, described analog switch (U2) also comprises input port, and when described input port input high level, the high level switch that described analog switch (U2) is corresponding is switched on.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 201110105500 CN102170222B (en) | 2010-09-30 | 2011-04-26 | Suppression device for electromagnetic interferences in switching power supply |
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| Application Number | Priority Date | Filing Date | Title |
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| CN201010507898 | 2010-09-30 | ||
| CN201010507898.3 | 2010-09-30 | ||
| CN 201110105500 CN102170222B (en) | 2010-09-30 | 2011-04-26 | Suppression device for electromagnetic interferences in switching power supply |
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| CN102170222A CN102170222A (en) | 2011-08-31 |
| CN102170222B true CN102170222B (en) | 2013-03-20 |
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| CN 201110105500 Expired - Fee Related CN102170222B (en) | 2010-09-30 | 2011-04-26 | Suppression device for electromagnetic interferences in switching power supply |
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Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN105610316A (en) * | 2015-08-14 | 2016-05-25 | 许继电源有限公司 | Frequency jittering circuit |
| CN110325025B (en) * | 2019-06-18 | 2021-03-26 | 中国船舶工业系统工程研究院 | System and method for reducing electromagnetic interference of equipment based on pulse modulation circuit |
| CN112084714B (en) * | 2020-09-14 | 2023-03-07 | 重庆长安新能源汽车科技有限公司 | Whole vehicle electromagnetic interference suppression method based on data driving |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7177166B1 (en) * | 2005-08-30 | 2007-02-13 | Microchip Technology Incorporated | Pulse width modulation frequency dithering in a switch mode power supply |
| CN101262170A (en) * | 2008-04-18 | 2008-09-10 | 苏州博创集成电路设计有限公司 | Frequency jitter implementation method and frequency jitter circuit |
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Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7177166B1 (en) * | 2005-08-30 | 2007-02-13 | Microchip Technology Incorporated | Pulse width modulation frequency dithering in a switch mode power supply |
| CN101262170A (en) * | 2008-04-18 | 2008-09-10 | 苏州博创集成电路设计有限公司 | Frequency jitter implementation method and frequency jitter circuit |
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Granted publication date: 20130320 Termination date: 20160426 |