CN104362853A - Reference voltage regulation circuit for suppressing chaos of DC-DC converter of switched capacitor - Google Patents
Reference voltage regulation circuit for suppressing chaos of DC-DC converter of switched capacitor Download PDFInfo
- Publication number
- CN104362853A CN104362853A CN201410583044.1A CN201410583044A CN104362853A CN 104362853 A CN104362853 A CN 104362853A CN 201410583044 A CN201410583044 A CN 201410583044A CN 104362853 A CN104362853 A CN 104362853A
- Authority
- CN
- China
- Prior art keywords
- resistance
- operational amplifier
- converter
- input
- output
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Landscapes
- Dc-Dc Converters (AREA)
Abstract
The invention discloses a reference voltage regulation circuit for suppressing chaos of a DC-DC converter of a switched capacitor and mainly solves the problem of instability in output voltage of the converter. The reference voltage regulation circuit is composed of two cascaded differential proportion operational amplifiers, wherein the two differential proportional operational amplifiers comprise two operational amplifiers U2 and U3, and peripheral resistors R5, R6, R7, R8, R9, R10, R11 and R12. Two input ends A and B of the differential proportional operational amplifiers are connected with output voltage VOUT and a reference voltage source VREF of the converter respectively, and an output end C is connected with a voltage feedback circuit of the converter. By reasonably setting the resistance of the peripheral resistors and adjusting the ratio of the feedback resistor R7 to the resistor R5 at the input ends, the regulated reference voltage VREF1 can be obtained at the output end C, so that variable resistance of the converter can be controlled and the output voltage of the converter is stable. The reference voltage regulation circuit is capable of effectively suppressing the chaos in the DC-DC converter and improving voltage conversion efficiency.
Description
Technical field
The invention belongs to electronic circuit technology field, relate to voltage-stabilized power supply circuit, can be used for the chaos phenomenon suppressing Switched-Capacitor DC-DC Converter.
Background technology
Along with people are to the continuous growth of the demand of the power-supply management system of miniaturization, high conversion efficiency, low cost, one as inductance type DC-DC converter substitutes, switching capacity type DC-DC converter obtains the motive force of development, is widely used in the portable set of single power supply.Switched-Capacitor DC-DC Converter some electric capacity and one group of switch carry out alternative solenoid, and this makes whole converter make to become possibility on a single chip.In switching capacity DC-DC, in order to obtain stable output voltage, converter needs reponse system to control it, there are two kinds of control modes: one is called linear model, namely by the size of the resistance of adjustable resistance in control circuit, control the size of charging and discharging currents, thus regulated output voltage; Another kind is called that skip cycle mode is also referred to as skip pattern, and the size namely by controlling duty ratio carrys out regulated output voltage.
Fig. 1 shows the circuit diagram of linear model Switched-Capacitor DC-DC Converter, and this circuit is primarily of adjustable resistance R
1, operational amplifier U
1, reference voltage source V
rEF, oscillator OSC, flying capcitor C
1, output capacitance C
2, the first low pressure NMOS tube M
1and the second low pressure NMOS tube M
2form.Linear model switching capacity DC-DC is by controlling adjustable resistance R
1size thus controls transfer to output capacitance C
2on electric current, with regulated output voltage V
oUT.
The work in linear model Switched-Capacitor DC-DC Converter circuit single cycle can be divided into charging and two stages of Energy Transfer: charging stage, the first low pressure NMOS tube M in DC-DC converter
1conducting second low pressure NMOS tube M
2cut-off, flying capcitor C
1by the input V of DC-DC converter
iNcharging; The Energy Transfer stage, the second low pressure NMOS tube M in DC-DC converter
2conducting first low pressure NMOS tube M
1cut-off, flying capcitor C
1to output capacitance C
2electric discharge.In the course of work of circuit, when supply voltage or load current change, regulate R by feedback loop control amplifier
1value, thus regulated output voltage.But, because Switched-Capacitor DC-DC Converter contains switch element, it is a kind of strongly non-linear system, under certain feedback condition, Switched-Capacitor DC-DC Converter can present abundant Nonlinear dynamic behaviors, makes system be in chaos state, easily causes the defect of three aspects: one is export unstable and be difficult to prediction, as shown in Figure 2, output voltage excursion is large and change irregular as seen from Figure 2; Two is that circuit performance worsens; Three is that voltage conversion efficiency reduces.
There are some researches show and state variable Time-delayed feedback control mode or application self-adapting slope compensation control strategy etc. can have been adopted to suppress its chaos phenomenon for inductive type DC-DC converter, but do not provided the specific embodiments how suppressing Switched-Capacitor DC-DC Converter chaos phenomenon.
Summary of the invention
The object of the invention is to the problem occurring chaos phenomenon for existing linear switch electric capacity DC-DC converter, a kind of reference voltage regulating circuit suppressing linear switch electric capacity DC-DC converter chaos phenomenon is proposed, to control the converter being in chaos state, improve voltage conversion efficiency.
For achieving the above object, the present invention includes the difference proportion operational amplifier of two cascades; First difference proportion operational amplifier is by the first operational amplifier U
2and the first forward end resistance R of periphery
5, the first negative end resistance R
6, the first feedback resistance R
7, the first divider resistance R
8composition; Second difference proportion operational amplifier is by the second operation amplifier U
3and the second forward end resistance R of periphery
9second negative end resistance R
10, the second feedback resistance R
11, the second divider resistance R
12composition, is characterized in that:
First forward end resistance R
5with the first negative end resistance R
6resistance identical, the first feedback resistance R
7with the first divider resistance R
8resistance identical, the first forward end resistance R
7with the R of the first feedback resistance
5the ratio of resistance adjusts between 0 ~ 1; Second forward end resistance R
9, the second negative end resistance R
10, the second feedback resistance R
11with the second divider resistance R
12resistance is identical;
By regulating the first feedback resistance R
7with first forward end resistance R
5the ratio of resistance, makes the voltage of Switched-Capacitor DC-DC Converter stable output.
Said reference voltage alignment circuit, is characterized in that:
First forward end resistance R
5, its one end connects the output V of DC-DC converter
oUT, the other end connects the first operational amplifier U
2positive input, for controlling the first operational amplifier U
2input and output ratio, the size of its value is a kilohm level;
First negative end resistance R
6, its one end connects reference voltage source V
rEF, the other end connects the first operational amplifier U
2negative input, for controlling the first operational amplifier U
2input and output ratio, this negative end resistance R
6value and the first forward end resistance R
5value identical;
First feedback resistance R
7, its one end connects the first operational amplifier U
2positive input, other end concatenation operation amplifier U
2output V
1, for controlling the first operational amplifier U
2input and output ratio, the first feedback resistance R
7with the first forward end resistance R
5ratio range be 0 ~ 1;
First divider resistance R
8, its one end connects the negative input end of the first operational amplifier, other end ground connection, for controlling the first operational amplifier U
2input and output ratio, this divider resistance R
8value and the first feedback resistance R
7value identical.
Said reference voltage alignment circuit, is characterized in that:
Second forward end resistance R
9, its one end connects the first operational amplifier U
2output V
1, the other end connects the second operational amplifier U
3positive input terminal, for controlling the second operational amplifier U
3input and output ratio, the size of its value is a kilohm level;
Second negative end resistance R
10, its one end connects reference voltage source V
rEF, the other end connects the second operational amplifier U
3negative input, for controlling the second operational amplifier U
3input and output ratio, this negative end resistance R
10value and the second forward end resistance R
9value identical;
Second feedback resistance R
11, its one end connects the second operational amplifier U
3positive input, the other end connects the second operational amplifier U
3output V
rEF1, for controlling the second operational amplifier U
3input and output ratio, this feedback resistance R
11value and the second forward end resistance R
9value identical;
Second divider resistance R
12, its one end connects the second operational amplifier U
3negative input, other end ground connection, for controlling the second operational amplifier U
3input and output ratio, this divider resistance R
12value and the second forward end resistance R
9value identical;
Second operational amplifier U
3, its output is connected to the comparator U of DC-DC converter
1negative input, for controlling its variable resistor R
1resistance.
The present invention compared with prior art has the following advantages:
The present invention, owing to rationally arranging resistance parameter at reference voltage regulating circuit, namely arranges the first forward end resistance R
5resistance and the R of the first negative end
6resistance identical, the first feedback resistance R
7resistance and the first divider resistance R
8resistance identical, the second forward end resistance R
9resistance, the second negative end resistance R
10resistance, the second feedback resistance R
11resistance and the second divider resistance R
12resistance equal, therefore by setting the first feedback resistance R
7with the first forward end resistance R
5the ratio of resistance, make to work as V
oUTvalue be greater than V
rEFtime, V
rEF1value increase, therefore R
1value increase, C
2on voltage reduce, thus make V
oUTvalue reduce; Work as V
oUTvalue be less than V
rEFtime, make V
rEF1value reduce, R
1value reduce, C
2on voltage increase, thus make V
oUTvalue increase, carry out regulated output voltage V accordingly
oUT.
Accompanying drawing explanation
Fig. 1 is the circuit diagram of traditional linear model Switched-Capacitor DC-DC Converter;
Fig. 2 is the oscillogram of the output of traditional linear model Switched-Capacitor DC-DC Converter;
Fig. 3 is circuit theory diagrams of the present invention;
Fig. 4 is the instance graph that the present invention is applied in Switched-Capacitor DC-DC Converter;
Fig. 5 is the oscillogram of the output applying linear model Switched-Capacitor DC-DC Converter of the present invention.
Embodiment
Below in conjunction with accompanying drawing and embodiment, the invention will be further described.
With reference to Fig. 3, the present invention is made up of the difference proportion operational amplifier of two cascades, and it is provided with two inputs A, B, an output C.Wherein: the first difference proportion operational amplifier is by the first operational amplifier U
2and the first forward end resistance R of periphery
5, the first negative end resistance R
6, the first feedback resistance R
7, the first divider resistance R
8composition; Second difference proportion operational amplifier is by the second operation amplifier U
3and the second forward end resistance R of periphery
9, the second negative end resistance R
10, the second feedback resistance R
11, the second divider resistance R
12composition, the output of the second operational amplifier is the output C of circuit of the present invention.
Described first forward end resistance R
5with the first negative end resistance R
6resistance identical, the first feedback resistance R
7with the first divider resistance R
8resistance identical, the first forward end resistance R
7with the R of the first feedback resistance
5the ratio of resistance adjusts between 0 ~ 1; This first forward end resistance R
5one end as positive input terminal A of the present invention, the other end connects the first operational amplifier U
2positive input, for controlling the first operational amplifier U
2input and output ratio, the size of its value is a kilohm level, and this example value is 10K Ω but does not limit to 10K Ω;
Described first negative end resistance R
6, its one end connects reference voltage source V
rEF, and as the negative input end B of circuit of the present invention, the other end connects the first operational amplifier U
2negative input, for controlling the first operational amplifier U
2input and output ratio, this negative end resistance R
6value and the first forward end resistance R
5value identical;
Described first feedback resistance R
7, its one end connects the first operational amplifier U
2positive input, other end concatenation operation amplifier U
2output V
1, for controlling the first operational amplifier U
2input and output ratio, the first feedback resistance R
7with the first forward end resistance R
5ratio range be 0 ~ 1, this example is got 0.665 but is not limited to 0.665;
Described first divider resistance R
8, its one end connects the negative input end of the first operational amplifier, other end ground connection, for controlling the first operational amplifier U
2input and output ratio, this divider resistance R
8value and the first feedback resistance R
7value identical.
Described second forward end resistance R
9, the second negative end resistance R
10, the second feedback resistance R
11with the second divider resistance R
12resistance is identical;
This second forward end resistance R
9, its one end connects the first operational amplifier U
2output V
1, the other end connects the second operational amplifier U
3positive input terminal, for controlling the second operational amplifier U
3input and output ratio, the second forward end resistance R
9size be a kilohm level, this example is got 1K Ω but is not limited to 1K Ω;
Described second negative end resistance R
10, its one end connects reference voltage source V
rEF, the other end connects the second operational amplifier U
3negative input, for controlling the second operational amplifier U
3input and output ratio, this negative end resistance R
10value and the second forward end resistance R
9value identical;
Described second feedback resistance R
11, its one end connects the second operational amplifier U
3positive input, the other end connects the second operational amplifier U
3output V
rEF1, for controlling the input and output ratio of the second operational amplifier, this feedback resistance R
11value and the second forward end resistance R
9value identical;
Described second divider resistance R
12, its one end connects the second operational amplifier U
3negative input, other end ground connection, for controlling the second operational amplifier U
3input and output ratio, this divider resistance R
12value and the second forward end resistance R
9value identical.
Described first operational amplifier U
2with the second operational amplifier U
3adopt LM301 but be not not limited to LM301 model.
Below in conjunction with Fig. 4, operation principle of the present invention is described in detail:
Fig. 4 is the Switched-Capacitor DC-DC Converter adding circuit of the present invention, and this DC-DC converter is by adjustable resistance R
1, operational amplifier U
1, reference voltage source V
rEF, oscillator OSC, flying capcitor C
1, output capacitance C
2, the first low pressure NMOS tube M
1, the second low pressure NMOS tube M
2and circuit of the present invention is formed.
The work in linear model Switched-Capacitor DC-DC Converter circuit single cycle can be divided into charging and two stages of Energy Transfer.Wherein, in the charging stage, the first low pressure NMOS tube M in DC-DC converter
1conducting second low pressure NMOS tube M
2cut-off, flying capcitor C
1by the input V of Switched-Capacitor DC-DC Converter
iNcharging; In the Energy Transfer stage, the second low pressure NMOS tube M in DC-DC converter
2conducting first low pressure NMOS tube M
1cut-off, flying capcitor C
1to output capacitance C
2electric discharge.The output V of positive input terminal A of the present invention and dc-dc
oUTbe connected, negative input end B and reference voltage source V
rEFbe connected, output C exports the reference voltage V after adjustment
rEF1be used for controlling the adjustable resistance R of DC-DC converter
1value.
In the course of work of circuit, when supply voltage or load current change, by comparing its output voltage V
oUTwith reference voltage source V
rEFsize regulate variable resistance R
1value, thus regulated output voltage.But, because Switched-Capacitor DC-DC Converter contains switch element, be a kind of strongly non-linear system, under certain feedback condition, Switched-Capacitor DC-DC Converter can present abundant Nonlinear dynamic behaviors, makes system be in chaos state, export unstable, circuit performance declines.After accessing circuit of the present invention, output C exports the reference voltage V after adjustment
rEF1, this voltage and fixing reference voltage source V
rEFdifference, its value can with the output voltage V of DC-DC converter
oUTvalue change, by rationally arranging reference voltage regulating circuit resistance parameter, namely the first forward end resistance R is set
5resistance and the R of the first negative end
6resistance identical, the first feedback resistance R
7resistance and the first divider resistance R
8resistance identical, the second forward end resistance R
9resistance, the second negative end resistance R
10resistance, the second feedback resistance R
11resistance and the second divider resistance R
12resistance equal, make:
The input voltage of the first difference scaling circuit is V
oUTand V
rEFtime, output voltage V
1value be:
The input voltage of the second difference scaling circuit is V
1and V
rEFtime, output voltage V
rEF1value be:
I.e. output voltage V
oUTduring increase, the reference voltage V after adjustment
rEF1increase, output voltage V
oUTduring reduction, the reference voltage V after adjustment
rEF1reduce, thus inhibit the chaos phenomenon in Switched-Capacitor DC-DC Converter, make the output voltage V of system
oUTstable.
Fig. 5 show add the oscillogram of output of the Switched-Capacitor DC-DC Converter after invention circuit.
As seen from Figure 5, the output voltage stabilization of the DC-DC converter after circuit of the present invention is added.
By the output voltage contrast not adding the DC-DC converter of circuit of the present invention shown in Fig. 5 and Fig. 2, the chaos phenomenon that present invention inhibits DC-DC converter can be found out, make stable system performance.
Below be only a preferred example of the present invention, do not form any limitation of the invention, obviously under design of the present invention, different changes and improvement can be carried out to its circuit, but these are all at the row of protection of the present invention.
Claims (3)
1. suppress a reference voltage regulating circuit for Switched-Capacitor DC-DC Converter chaos phenomenon, the present invention includes the difference proportion operational amplifier of two cascades; First difference proportion operational amplifier is by the first operational amplifier U
2and the first forward end resistance R of periphery
5, the first negative end resistance R
6, the first feedback resistance R
7, the first divider resistance R
8composition; Second difference proportion operational amplifier is by the second operation amplifier U
3and the second forward end resistance R of periphery
9second negative end resistance R
10, the second feedback resistance R
11, the second divider resistance R
12composition, is characterized in that:
First forward end resistance R5 is identical with the resistance of the first negative end resistance R6, and the first feedback resistance R7 is identical with the resistance of the first divider resistance R8, and the ratio of the R5 resistance of the first forward end resistance R7 and the first feedback resistance adjusts between 0 ~ 1; Second forward end resistance R9, the second negative end resistance R10, the second feedback resistance R11 are identical with the second divider resistance R12 resistance;
By regulating the ratio of the forward end resistance R5 resistance of the first feedback resistance R7 and first, make the voltage of Switched-Capacitor DC-DC Converter stable output.
2. reference voltage alignment circuit according to claim 1, is characterized in that:
First forward end resistance R
5, its one end connects the output V of DC-DC converter
oUT, the other end connects the first operational amplifier U
2positive input, for controlling the first operational amplifier U
2input and output ratio, the size of its value is a kilohm level;
First negative end resistance R
6, its one end connects reference voltage source V
rEF, the other end connects the first operational amplifier U
2negative input, for controlling the first operational amplifier U
2input and output ratio, this negative end resistance R
6value and the first forward end resistance R
5value identical;
First feedback resistance R
7, its one end connects the first operational amplifier U
2positive input, other end concatenation operation amplifier U
2output V
1, for controlling the first operational amplifier U
2input and output ratio, the first feedback resistance R
7with the first forward end resistance R
5ratio range be 0 ~ 1;
First divider resistance R
8, its one end connects the negative input end of the first operational amplifier, other end ground connection, for controlling the first operational amplifier U
2input and output ratio, this divider resistance R
8value and the first feedback resistance R
7value identical.
3. reference voltage alignment circuit according to claim 1, is characterized in that:
Second forward end resistance R
9, its one end connects the first operational amplifier U
2output V
1, the other end connects the second operational amplifier U
3positive input terminal, for controlling the second operational amplifier U
3input and output ratio, the size of its value is a kilohm level;
Second negative end resistance R
10, its one end connects reference voltage source V
rEF, the other end connects the second operational amplifier U
3negative input, for controlling the second operational amplifier U
3input and output ratio, this negative end resistance R
10value and the second forward end resistance R
9value identical;
Second feedback resistance R
11, its one end connects the second operational amplifier U
3positive input, the other end connects the second operational amplifier U
3output V
rEF1, for controlling the second operational amplifier U
3input and output ratio, this feedback resistance R
11value and the second forward end resistance R
9value identical;
Second divider resistance R12, its one end connects the negative input of the second operational amplifier U3, other end ground connection, and for controlling the input and output ratio of the second operational amplifier U3, the value of this divider resistance R12 is identical with the value of the second forward end resistance R9;
Second operational amplifier U3, its output is connected to the negative input of the comparator U1 of DC-DC converter, for controlling the resistance of its variable resistor R1.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
CN201410583044.1A CN104362853A (en) | 2014-10-27 | 2014-10-27 | Reference voltage regulation circuit for suppressing chaos of DC-DC converter of switched capacitor |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
CN201410583044.1A CN104362853A (en) | 2014-10-27 | 2014-10-27 | Reference voltage regulation circuit for suppressing chaos of DC-DC converter of switched capacitor |
Publications (1)
Publication Number | Publication Date |
---|---|
CN104362853A true CN104362853A (en) | 2015-02-18 |
Family
ID=52530089
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
CN201410583044.1A Pending CN104362853A (en) | 2014-10-27 | 2014-10-27 | Reference voltage regulation circuit for suppressing chaos of DC-DC converter of switched capacitor |
Country Status (1)
Country | Link |
---|---|
CN (1) | CN104362853A (en) |
Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
KR20000066709A (en) * | 1999-04-20 | 2000-11-15 | 최규용 | Central process unit having multiple value by suppressing chaos |
CN201616763U (en) * | 2010-02-11 | 2010-10-27 | 华南理工大学 | Circuit using PWM chip chaos for inhibiting switch converter EMI |
CN102290989A (en) * | 2010-06-21 | 2011-12-21 | 纬创资通股份有限公司 | Voltage adjusting module and power supply device |
CN103956884A (en) * | 2013-03-15 | 2014-07-30 | 成都芯源系统有限公司 | Reference compensation unit and switching type voltage adjustment circuit |
-
2014
- 2014-10-27 CN CN201410583044.1A patent/CN104362853A/en active Pending
Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
KR20000066709A (en) * | 1999-04-20 | 2000-11-15 | 최규용 | Central process unit having multiple value by suppressing chaos |
CN201616763U (en) * | 2010-02-11 | 2010-10-27 | 华南理工大学 | Circuit using PWM chip chaos for inhibiting switch converter EMI |
CN102290989A (en) * | 2010-06-21 | 2011-12-21 | 纬创资通股份有限公司 | Voltage adjusting module and power supply device |
CN103956884A (en) * | 2013-03-15 | 2014-07-30 | 成都芯源系统有限公司 | Reference compensation unit and switching type voltage adjustment circuit |
Non-Patent Citations (2)
Title |
---|
尹奕光: "PWM型DC/DC变换器混沌机理的研究", 《中国博士学位论文电子期刊网》 * |
李先锐: "高性能白光LED驱动电荷泵DC-DC设计技术研究", 《中国博士学位论文电子期刊网》 * |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
CN101015112B (en) | DC-DC converter with adaptive switching parameter adjustment | |
CN101515756B (en) | Multimode method and system for high-efficiency power control | |
Jung et al. | Control design for robust tracking and smooth transition in power systems with battery/supercapacitor hybrid energy storage devices | |
CN103441658B (en) | A kind of Boost controller and Boost converter | |
CN201985759U (en) | DCDC (direct current direct current) output circuit | |
CN103887972B (en) | Mixed control circuit of DVS system switch DC-DC converter and control method of mixed control circuit of DVS system switch DC-DC converter | |
CN102255504B (en) | Switch control circuit and method thereof | |
US20140292288A1 (en) | I+hu 2 +l Average Current Mode (ACM) Control for Switching Power Converters | |
CN103532347B (en) | A kind of PWM-type switching power circuit | |
CN104038048A (en) | Boost converter | |
CN105207480B (en) | The synchronous buck type DC DC converters of output ripple and low during a kind of underloading | |
CN107147292A (en) | A kind of controlled buck converter of ON time | |
KR102549239B1 (en) | Buck-boost converter using delta-sigma mudulator | |
CN101951135B (en) | Flyback switching power supply and over-current protection method thereof | |
CN102403901A (en) | Controllers for power converters and control method | |
CN102832814A (en) | Method for controlling hysteresis with voltage feedforward quickly | |
CN103346663A (en) | Hysteresis control method of Boost convertor | |
CN110311562A (en) | A kind of DC-DC converter | |
Gu et al. | Voltage regulator buck converter with a tapped inductor for fast transient response application | |
Chakraborty et al. | Combination of buck and boost modes to minimize transients in the output of a positive buck-boost converter | |
CN103036432A (en) | Pulse width modulation (PWM) hysteresis control method based on ripple | |
CN103546034B (en) | A kind of compounding feedforward control type Hysteresis control system | |
CN105553255A (en) | Constant on-time variable-frequency control method for switched-capacitor converter | |
CN104300779B (en) | Output voltage meets the DC/DC converters of y=kx+b relations with regulation voltage | |
CN104362853A (en) | Reference voltage regulation circuit for suppressing chaos of DC-DC converter of switched capacitor |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
C06 | Publication | ||
PB01 | Publication | ||
C10 | Entry into substantive examination | ||
SE01 | Entry into force of request for substantive examination | ||
WD01 | Invention patent application deemed withdrawn after publication |
Application publication date: 20150218 |
|
WD01 | Invention patent application deemed withdrawn after publication |