CN100568329C - The power circuit that is used for vacuum fluorescent display - Google Patents

The power circuit that is used for vacuum fluorescent display Download PDF

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Publication number
CN100568329C
CN100568329C CNB2007101468409A CN200710146840A CN100568329C CN 100568329 C CN100568329 C CN 100568329C CN B2007101468409 A CNB2007101468409 A CN B2007101468409A CN 200710146840 A CN200710146840 A CN 200710146840A CN 100568329 C CN100568329 C CN 100568329C
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voltage
vin
switch
filament
capacitor
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CN101136162A (en
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龟田胜士
芝田和久
中西浩
寺上伸一
江口登志英
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Noritake Co Ltd
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Noritake Co Ltd
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Abstract

A kind of power circuit that is used for vacuum fluorescent display comprises step-up coil, input end, switching transistor, pwm control circuit, booster circuit, first glower end and second glower end.Step-up coil is arranged in the current path,, produces induced potential so that according to the variation of the electric current that is wherein flow through.Input end receives the dc voltage that will be applied to step-up coil one end.Switching transistor is arranged between the other end and ground wire of step-up coil.Pwm control circuit is the on/off switch transistor periodically.Booster circuit according to when switching transistor from conducting switch to by the time, the induced potential that produces in the other end place of step-up coil, the voltage after generation is boosted.First terminals with link to each other at the other end of step-up coil and the node between the switching transistor.The dc voltage that will be lower than the induced potential that produces at the other end place of step-up coil is applied on second terminals.

Description

The power circuit that is used for vacuum fluorescent display
The application is dividing an application of Chinese patent application " power circuit that is used for vacuum fluorescent display " (application number 200410064414.7) submitted on August 24th, 2004.
Technical field
The present invention relates to a kind of power circuit that invests on the vacuum fluorescent display.
Background technology
Vacuum fluorescent display be by make from have at least one side be the electron impact of coming out of the emission of cathode the transparent vacuum tube (shell) on the fluorophor that is coated on the anode, and make light-emitting phosphor, show the electron tube of required pattern.Usually, as this vacuum fluorescent display, the most frequent use is the display with triode structures, and described pliotron has the grid of the behavior that is used to control electronics.
Figure 15 shows traditional conventional vacuum fluorescence display and the circuit (referring to the open No.2002-260565 (list of references 1) of Japanese patent unexamined) that invests on the vacuum fluorescent display.With reference to Figure 15, reference number 1 expression vaccum fluorescent tube; 400 expressions invest the power circuit on the vaccum fluorescent tube 1.In vaccum fluorescent tube 1, find time to comprise in the shell 2: anode 5 comprises a plurality of anode electrodes 4 that are coated with fluorophor 3; Negative electrode 6 is oppositely arranged with the upper surface of anode 5; And grid 7, be arranged between anode 5 and the negative electrode 6, be used to control the electronics of launching from negative electrode 6.On anode substrate 8, form anode 5.
In this case, negative electrode 6 is the filaments that are coated with electronic emission material.Negative electrode 6 by centre-tapped transformer 9 with to exchange (AC) power supply 10 continuous, and the center tap ground connection of passing through transformer 9.Utilize this structure, AC filament voltage Ef is applied to the two ends (between terminal F1 and F2) of negative electrode 6.
Form grid 7 according to the trellis pattern, it receives direct current (DC) the voltage VDD2 from booster circuit 11.Each anode 4 all links to each other with driving circuit 12.Driving circuit 12 also receives the dc voltage VDD2 from booster circuit 11.Booster circuit 11 produces the dc voltage VDD2 that is used for anode/grid by input voltage vin (dc voltage) is boosted.Driving circuit 12 carries out ON/OFF control according to the input video data to the positive voltage that will be applied on each anode electrode 4.
[cut-off voltage]
In vacuum fluorescent display, when filament potential drops to the shutoff level of anode potential when following, the light transmit leakage may take place.That is, filament potential need be higher than the shutoff level of anode potential.This filament potential is called as cut-off voltage.
With reference to Figure 15, an end of negative electrode 6 and the average voltage between the GND (average voltage of glower end F1 side) equal the other end and the average voltage between the GND (average voltage of glower end F2 side) of negative electrode 6.This average voltage of negative electrode 6 is set to cut-off voltage.Can adjust this cut-off voltage by the value of the resistor R C1 between the center tap that is connected GND and transformer 9.
But, in above-mentioned conventional power source circuit 400,, exist following problem (1) to arrive (4) owing to use transformer 9 to obtain AC filament voltage Ef:
(1) produces bigger noise;
(2) need more cost and time designing power supply;
(3) when on vaccum fluorescent tube 1, showing required pattern, cause flicker; And
(4) need bigger power consumption.
Summary of the invention
An object of the present invention is to eliminate needs, and realize lower noise the filament drive transformer.
Another object of the present invention is to shorten the required time of designing power supply.
Another object of the present invention is when showing required pattern on vaccum fluorescent tube, prevents flicker.
Another object of the present invention is to realize lower power consumption.
To achieve these goals,, proposed a kind of power circuit that is used for vacuum fluorescent display, having comprised according to the present invention: inductance element, be arranged on the current path, so that according to the variation of the electric current that is wherein flow through, produce induced potential; Input end is at direct current (DC) voltage of an end that is applied to described inductance element; On-off element is arranged between the other end and ground wire of described inductance element; Control circuit, the periodically described on-off element of on/off; Booster circuit, according to described on-off element is being switched to when disconnecting from connection, the induced potential in that the described other end place of described inductance element produces produces the voltage after boosting; First terminals link to each other with the described other end of described inductance element and the node between the described on-off element; And second terminals, the dc voltage that will be lower than the described induced potential that produces at the described other end place of described inductance element is applied on it.
Description of drawings
Fig. 1 shows the circuit diagram according to the major part of the power circuit of the embodiment of the invention (first embodiment);
Fig. 2 shows the curve map of the voltage waveform (waveform at F1 place) at the glower end F1 place that appears among first embodiment;
Fig. 3 shows the glower end F1 that appears among first embodiment and the curve map of the waveform between the F2 (waveform between F1 and the F2);
Fig. 4 shows the circuit diagram according to the major part of the power circuit of another embodiment of the present invention (second embodiment);
Fig. 5 shows the curve map of the voltage waveform (waveform between F1 and the GND) at appearance glower end F1 place in a second embodiment;
Fig. 6 shows the curve map of the voltage waveform (waveform between F2 and the GND) at appearance glower end F2 place in a second embodiment;
Fig. 7 shows the appearance glower end F1 in a second embodiment and the curve map of the waveform between the F2 (waveform between F1 and the F2);
Fig. 8 shows the circuit diagram according to the major part of the power circuit of another embodiment of the present invention (the 3rd embodiment);
Fig. 9 shows the curve map of the voltage waveform (waveform between F1 and the GND) at the glower end F1 place that appears among the 3rd embodiment;
Figure 10 shows the curve map of the voltage waveform (waveform between F2 and the GND) at the glower end F2 place that appears among the 3rd embodiment;
Figure 11 shows the glower end F1 that appears among the 3rd embodiment and the curve map of the waveform between the F2 (waveform between F1 and the F2);
Figure 12 shows the circuit diagram according to the major part of the power circuit of another embodiment of the present invention (the 4th embodiment);
Figure 13 shows the curve map of the voltage waveform (waveform at F1 place) at the glower end F1 place that appears among the 4th embodiment;
Figure 14 shows the glower end F1 that appears among the 4th embodiment and the curve map of the waveform between the F2 (waveform between F1 and the F2);
Figure 15 shows traditional conventional vacuum fluorescent display tube and invests the block scheme of the circuit of vaccum fluorescent tube;
Figure 16 shows and produces the block scheme that is used for the dc voltage of anode/grid and filament is carried out the conventional power source circuit of pulsed drive; And
Figure 17 shows the oscillogram of the operation of this power circuit.
Embodiment
Below, with reference to the accompanying drawings, describe the present invention.
[first embodiment]
Fig. 1 shows the circuit diagram according to the major part of the power circuit of the embodiment of the invention (first embodiment).Power circuit 100 comprises capacitor (input smmothing capacitor) C0, step-up coil (inductance element) L, booster circuit 13, switching transistor (field effect transistor) TR, variohm (voltage regulator resistor device) 14, pwm control circuit 15 and resistor R 1 and R2.Power circuit has input end Pin, output terminal Pout, glower end F1 (first terminals) and glower end F2 (second terminals).
Vin is applied on the input end Pin with input voltage (dc voltage).The dc voltage VDD2 that is used for anode/grid from output terminal Pout output.The negative electrode of vaccum fluorescent tube 1 (filament) 6 is connected between glower end F1 and the F2.
In power circuit 100, step-up coil L is arranged on the current path Lin between input end Pin and the booster circuit 13, and, produces induced potential according to the variation of the electric current of the current path Lin that flows through.Input smmothing capacitor C0 is connected between the node and input end Pin between the end Pa of ground wire and step-up coil L.The other end Pb of step-up coil L links to each other with the drain electrode of switching transistor TR.The source ground of switching transistor TR (GND).Pwm control circuit 15 links to each other with the grid of switching transistor TR by resistor R 1.
Pwm control circuit 15 periodically produces the pulse signal with predetermined duty cycle, and [the ratio Vin/V0 that supposes Vin and V0 (describing after a while) is for ending dutycycle: Doff (Doff=Vin/V0), and (V0-Vin) with the ratio of V0 be conducting dutycycle: Don (Don=(V0-Vin)/V0], and, this pulse signal is offered the grid of switching transistor TR by resistor R 1.Notice that in pwm control circuit 15, cycle and dutycycle that can pulse signals be adjusted.
The other end Pb of step-up coil L links to each other with glower end F1 by voltage regulator resistor device 14 with node P1 between the drain electrode of switching transistor TR.That is, voltage regulator resistor device 14 links to each other with connecting line LR, and described connecting line LR is between glower end F1 and other end Pb and the node P1 between the switching transistor TR at step-up coil L.Pin is applied on the glower end F2 with input voltage (dc voltage).
Booster circuit 13 comprises that n charge pump CHP1 is to CHPn.Charge pump CHP1 comprises diode (commutation diode) D1 1And D1 2And capacitor (output smoothing/charge pump capacitor) C1a and C1b.Diode D1 1Anode link to each other diode D1 with the end of step-up coil L 1Negative electrode and diode D1 2Anode link to each other.The end of capacitor C1a and diode D1 1Negative electrode and diode D1 2Anode link to each other.The other end ground connection of capacitor C1a.The end of capacitor C1b and diode D1 2Negative electrode link to each other, and the other end Pb of the other end and step-up coil L, promptly the node P1 between step-up coil L, booster circuit 13 and the switching transistor TR is continuous.
Charge pump CHP2 is to CHPn -1Have the structure identical with charge pump CHP1.Last charge pump CHPn comprises diode Dn and capacitor Cn.The anode of diode Dn be right after charge pump CHPn the preceding -1Diode D (n-1) 2Negative electrode link to each other, and the negative electrode of diode Dn links to each other with output terminal Pout.Capacitor Cn is connected between the negative electrode and ground wire of diode Dn.
[boost operations]
Pwm control circuit 15 periodically produces the pulse signal with predetermined duty cycle, and offers the grid of switching transistor TR by resistor R 1.Switching transistor TR repeats the conduction and cut-off operation according to this pulse signal.In this case, when switching transistor TR from conducting switch to by the time, node P1 place between step-up coil L and switching transistor TR produces voltage (induced potential) V0 that is higher than input voltage vin.
Voltage V0 is applied on the booster circuit 13.In booster circuit 13, by diode D1 1, with the voltage V0 that produces at node P1 place the capacitor C1a of charge pump CHP1 being charged, the V1 of charging potential of charge pump becomes V0 (V1=V0).When switching transistor TR switches to conducting from ending, by diode D1 2, with the V1 of charging potential of capacitor C1a capacitor V1b is charged, and the charging potential of capacitor becomes V0.When switching transistor TR once more from conducting switch to by the time, with the V0 of charging potential of the induced potential V0 rising capacitor C1b that produces at node P1 place, and the V2 of charging potential of the capacitor C2a among the charge pump CHP2 becomes 2V0 (V2=2V0).
Subsequently, along with the repetition of this operation, raise at the voltage V0 of stage P1 place generation to the CHPn order by charge pump CHP1.As a result, obtain voltage nV0 from output terminal Pout, as the dc voltage VDD2 (VDD2=nV0) that is used for anode/cathode.That is,, can obtain dc voltage VDD2 doubly, that be used for anode/grid than the high n of voltage V0 by making the voltage V0 that produces at node P1 place by booster circuit 13.The quantity of charge pump is adjusted the numerical value of the dc voltage VDD2 that is used for anode/grid in conducting dutycycle Don that can be by switching transistor TR and the booster circuit 13.
[filament voltage]
[waveform] at the F1 place
Fig. 2 shows the voltage waveform (waveform at F1 place) that appears at glower end F1 place by above-mentioned boost operations.With reference to Fig. 2, reference symbol ton represents the ON time of switching transistor TR, and toff represents the closing time of switching transistor TR.In the following description, ignore the voltage drop of locating at switching transistor TR, diode D and capacitor C etc.
When switching transistor TR conducting, because glower end F1 by voltage regulator resistor device 14 ground connection, the voltage of the voltage drop VR at resistor 14 places therefore occurred adjusting than voltage V0 high voltage.In this case, suppose that Rf is the resistance of negative electrode 6, R is the resistance of voltage regulator resistor device 14, then with VR=Vin{R/ (Rf+R) } be illustrated in the voltage drop VR at voltage regulator resistor device 14 places, because the current potential of glower end F2 is Vin.Therefore, by VR=Vin{R/ (Rf+R) } provide the current potential of glower end F1.
When switching transistor TR ends, because the voltage V0 that will produce at node P1 place by voltage regulator resistor device 14 is applied on the glower end F1, therefore the voltage of the voltage drop VR at resistor 14 places appearred adjusting than voltage V0 low-voltage.In this case, be illustrated in the voltage drop VR at voltage regulator resistor device 14 places with VR=(V0-Vin) { R/ (Rf+R) }, because this moment, the current potential at node P1 place is V0.Therefore, provide the current potential of glower end F1 by V0-(V0-Vin) { R/ (Rf+R) }.
[waveform between F1 and the F2]
Voltage waveform between glower end F1 and the F2 (waveform between F1 and the F2) becomes and is similar to shown in Figure 3ly, wherein input voltage vin is applied on the glower end F2 as benchmark, and glower end F1 side is "+" side.That is, be applied to the voltage at filament 6 two ends,, become voltage (AC filament voltage) with square waveform because the periodicity conduction and cut-off of switching transistor TR is switched.
In this case, represent to be applied to the effective value Ef of the filament voltage at filament 6 two ends by following formula:
Ef={Vin·(V0-Vin)} 1/2·{Rf/(Rf+R)} …(1)
It is evident that from equation (1) resistance and voltage V0 by voltage regulator resistor device 14 can adjust filament voltage Ef.Should be noted in the discussion above that therefore, V0 is determined by the quantity of the charge pump in the booster circuit 13 owing to VDD2=nV0 and V0=VDD2/n.That is, can change the numerical value of V0 by the quantity that changes charge pump.
Should be noted that if there is not voltage regulator resistor device 14 (R=0), then by the effective value Ef of following equation indication lamp filament voltage:
Ef={Vin·(V0-Vin)} 1/2 …(2)
[cut-off voltage]
In power circuit 100, represent the average voltage VF1 and the VF2 at glower end F1 and F2 place with VF1=VF2=Vin.For example, if there is not voltage regulator resistor device 14 (R=0 Ω), then
VF1=V0·Doff=V0·(Vin/V0)=Vin
Because VF2=Vin (linking to each other) with Vin,
VF1=VF2=Vin
If have voltage regulator resistor device 14, then
VF1={V0-(V0-Vin)·(R/(Rf+R))}·Doff+Vin·(R/(Rf+R))·Don
={V0-(V0-Vin)·(R/(Rf+R))}·(Vin/V0)+Vin·(R/(Rf+R))·((V0-Vin)/V0)
={1-(R/(Rf+R))}·Vin+Vin·(R/(Rf+R))
=Vin·{(Rf/(Rf+R)+R/(Rf+R))}=Vin
Because VF2=Vin (linking to each other) with Vin,
VF1=VF2=Vin。
The cut-off voltage (when anode disconnects, making the filament potential of zero luminance) at glower end F1 place is equated with glower end F2 place.In addition, can be by adjusting the resistance R of voltage regulator resistor device 14, the minimum value of filament potential and the potential difference (PD) VR between the earth potential (VR=Vin{R/ (Rf+R) }) are set arbitrarily.
[when Vin changes, the variation of Ef ratio]
The variation ratio of Ef when obtaining the Vin variation by physical device.Even this scope that makes it can confirm Vi n is bigger, filament voltage Ef remains stable.
(1) when V0=10V,
Vin=4.5V:Ef={4.5·(10-4.5)} 1/2=4.97Vrms
Vin=5.0V:Ef={5·(10-5)} 1/2=5.00Vrms
Vin=5.5V:Ef={5.5·(10-5.5)} 1/2=4.97Vrms
When changing in the scope of Vin ± 10%, Ef changes in ± 0.6% scope.
(2) when V0=10V,
Vin=4.0V:Ef={4.0·(10-4.0)} 1/2=4.90Vrms
Vin=5.0V:Ef={5·(10-5)} 1/2=5.00Vrms
Vin=6.0V:Ef={6.0·(10-6.0)} 1/2=4.90Vrms
When changing in the scope of Vin ± 20%, Ef changes in ± 2% scope.
(3) when V0=15V,
Vin=4.5V:Ef={4.5·(15-4.5)} 1/2=6.87Vrms
Vin=5.0V:Ef={5·(15-5)} 1/2=7.07Vrms
Vin=5.5V:Ef={5.5·(15-5.5)} 1/2=7.23Vrms
When changing in the scope of Vin ± 10%, Ef changes in-2.8% to+2.3% scope.
In power circuit 100, the dc voltage that will be applied on the input end Pin is set to identical voltage Vin with dc voltage on will being applied to glower end F2.But, as long as the dc voltage that will be applied on the glower end F2 is lower than at the induced potential V0 of node P1 place generation just enough.That is, this voltage needn't always equal to be applied to the dc voltage Vin on the input end Pin.
As mentioned above, according to power circuit 100, during owing to anode 5 that will be applied to vaccum fluorescent tube 1 in generation and the booster voltage VDD2 on the grid 7, use the periodicity conduction and cut-off operation of switching transistor TR, produce AC filament voltage Ef, therefore do not need the filament drive transformer.This can realize low-noise structure.
In addition, this circuit can be made of commercial component, and without any need for the design of transformer cost.In addition, can shorten the required time of designing power supply.In addition, by adjusting cycle, can make the drive cycle of filament 6 and display connect cycle synchronisation from the pulse signal of pwm control circuit 15.This can prevent the shake when showing required pattern on vaccum fluorescent tube 1.Owing to do not use transformer, can realize low power consumption.
In addition, because the induced potential V0 that uses the end at step-up coil L to produce obtains filament voltage Ef, voltage loss is less, and the having good stability of filament voltage Ef.Even work as in the battery-operated operation, when input voltage change or instability, the stability of filament voltage Ef is still better.
[second embodiment]
Fig. 4 shows the major part according to the power circuit of another embodiment of the present invention (second embodiment).Power circuit 200 comprises control circuit 16A, booster circuit 17 and cut-off circuit 18A, and has input end Pin, output terminal Pout and glower end F1 and F2.Vin is applied on the input end Pin with dc voltage (input voltage).The dc voltage VDD2 that is used for anode/grid from output terminal Pout output.The negative electrode of vaccum fluorescent tube 1 (filament) 6 is connected between glower end F1 and the F2.
Cut-off circuit 18A comprises first switch SW 1, second switch SW2, resistor R, diode D1 and D2, capacitor C1 and C2.Switch SW 1 and SW2 are connected between the incoming line Lin and ground wire (GND) that is used for dc voltage Vin.In this was connected in series, switch SW 1 was positioned at the incoming line Lin side of dc voltage Vin, and switch SW 2 is positioned at the ground wire side.Resistor R 4 is in parallel with switch SW 1 with the series circuit 18-1 of diode D2 and D1.
In cut-off circuit 18A, diode D1 is used as constant voltage elements, prevents element and diode D2 is used as adverse current.Diode D2 is than the more close incoming line Lin side that is used for dc voltage Vin of diode D1.That is, the anode of diode D2 links to each other with the incoming line Lin that is used for supply voltage Vin by resistor R 4, and the negative electrode of diode D2 links to each other with the anode of diode D1.The negative electrode of diode D1 links to each other with node between switch SW 1 and the SW2.Resistor R 4 is used as the resistor that is used for being provided with the forward current that flows into diode D1 and D2.
Capacitor C1 is in parallel with diode D1.That is, the end of capacitor C1 links to each other with the anode of diode D1 (input end of constant voltage elements), and the other end of capacitor C1 links to each other with the negative electrode (output terminal of constant voltage elements) of diode D1.Glower end F1 links to each other with the anode of diode D1 and the node PA between the capacitor C1.Capacitor C2 is connected between glower end F2 and the ground wire.
Control circuit 16A with dc voltage as working power, and along opposite direction periodically switch SW 1 and the SW2 of on/off cut-off circuit 18A.That is, control circuit 16A periodically repeats the operation of " cut-off switch SW2 when connecting switch SW 1, and connect switch SW 2 in cut-off switch SW1 ".17 couples of dc voltage Vin of booster circuit boost, so that produce the dc voltage VDD2 that is used for anode/grid.
Should be noted in the discussion above that in control circuit 16A along opposite direction and periodically when on/off switch SW1 and SW2, can adjust switch periods T and the dutycycle (connect dutycycle and disconnect dutycycle) of switch SW 1 and SW2.Suppose that ton is switch SW 1 time of connecting (=wherein time of disconnecting of switch SW 2) wherein, and toff is time of disconnecting of switch SW 1 (=wherein switch SW 2 time of connecting) wherein, switch periods T is provided by T=ton+toff.In addition, the connection dutycycle Don with switch SW 1 is expressed as Don=ton/T.The disconnection dutycycle of switch SW 1 is expressed as Doff=toff/T=(T-ton)/T=1-Don.
[filament voltage]
[waveform between F1 and the GND]
Fig. 5 shows when control circuit 16A carries out on to switch SW1 and SW2, appears at the voltage waveform (waveform between F1 and the GND) at glower end F1 place.
When connecting switch SW 2 as cut-off switch SW1, electric current flows through the path that is made of resistor R 4, diode D2, diode D1 and switch SW 2, and the Vc1 of charging voltage of the capacitor C1 forward voltage VF that becomes and equal diode D1.As a result, in the interval of toff, the voltage between F1 and the GND becomes Vc1=VF.
During cut-off switch SW2, by switch SW 1, with the Vc1 of the charging voltage addition of dc voltage Vin and capacitor C1, the current potential at node PA place becomes Vin+Vc1 when connecting switch SW 1.Therefore, in the interval of ton, the voltage between F1 and the GND becomes Vin+Vc1.In this case, although the current potential at node PA place is higher than Vin,, there is not electric current to flow into incoming line Lin because the adverse current of diode D2 prevents effect.
[waveform between F2 and the GND]
Fig. 6 shows when control circuit 16A carries out on to switch SW1 and SW2, appears at the voltage waveform (waveform between F2 and the GND) at glower end F2 place.
During cut-off switch SW2, by switch SW 1, with the Vc1 of the charging voltage addition of dc voltage Vin and capacitor C1, the current potential at node PA place becomes Vin+Vc1 when connecting switch SW 1.As a result, electric current I f1 flows into filament 6, and by electric current (charging current) If1 capacitor C2 is charged.
When connecting switch SW 2 as cut-off switch SW1, the current potential at node PA place returns Vc1.As a result, the discharge current If2 from capacitor C2 flows into filament 6.
The electric current I f1Don that when connecting switch SW 1 capacitor C2 is charged equals when connecting switch SW 2 the electric current I f2Doff from capacitor C2 discharge.If If1Don>If2Doff, although Vc2 increases, If2 also increases.As a result, Vc2 descends.If If1Don<If2Doff, although Vc2 descends, If1 increases.As a result, Vc2 increases.At last and since Vc2 trend towards constant, If1Don=If2Doff.
Because If1Don=If2Doff, (Vin+Vc1-Vc2) Don=(Vc2-Vc1) (1-Don), the bracket in removing this equation when simplifying this equation, VinDon+Vc1Don-Vc2Don=Vc2-Vc2Don-Vc1+Vc1Don.That is, obtain VinDon=Vc2-Vc1.Therefore, Vc2=VinDon+Vc1, and the voltage between F2 and the GND toff at interval and ton interim all become Vc2=VinDon+Vc1.
[waveform between F1 and the F2]
With reference to being applied to voltage Vc2=VinDon+Vc1 on the glower end F2, the voltage waveform between glower end F1 and the F2 (waveform between F1 and the F2) become be similar to shown in Figure 7.That is, the voltage that is applied to filament 6 two ends becomes the voltage (AC filament voltage) with square waveform, and owing to the on of control circuit 16A to switch SW1 and SW2, its voltage width is represented with Vin.
[effective value of filament voltage]
Suppose that ef1 connects switch SW 1 and the effective voltage that is applied to filament 6 two ends during cut-off switch SW2, then ef1=(Vin+Vc1-Vc2) Don 1/2With this equation of Vc2=VinDon+Vc1 substitution, obtain:
ef1=(Vin+Vc1-Vin·Don-Vc1)·Don 1/2
=Vin·(1-Don)·Don 1/2 …(3)
Suppose that ef2 is cut-off switch SW1 and be applied to the effective voltage at filament 6 two ends when connecting switch SW 2, then ef2=(Vc2-Vc1) Doff 1/2=(Vc2-Vc1) (1-Don) 1/2With this equation of Vc2=VinDon+Vc1 substitution, obtain:
ef2=(Vin·Don+Vc1-Vc1)·(1-Don) 1/2
=Vin·Don·(1-Don) 1/2 …(4)
By ef=(ef1 2+ ef2 2) 1/2Provide the effective value of the filament voltage that is applied to filament 6 two ends.With this equation two ends square, obtain ef 2=[Vin (1-Don) Don 1/2] 2+ [VinDon (1-Don) 1/2] 2=Vin 2(1-Don) 2Don+Vin 2Don 2(1-Don)=Vin 2(1-Don) Don[(1-Don)+Don]=Vin 2(1-Don) Don.According to this equation, provide the effective value of the filament voltage that is applied to filament 6 two ends by following formula:
ef=Vin·[(1-Don)·Don] 1/2 …(5)
According to equation (5), making the maximized condition of effective value of filament voltage is Don=0.5, and when this condition satisfies, is provided the effective value of filament voltage by ef=0.5Vin.It is evident that thus, in the present embodiment,, can in the scope of ef≤0.5Vin, the effective value of filament voltage be set arbitrarily by adjusting the connection dutycycle Don of switch SW 1.
[cut-off voltage]
In power circuit 200, provide average voltage (average voltage of the glower end F1 side) VF1 at glower end F1 place by following formula:
VF1=(Vin+Vc1)·Don+Vc1·(1-Don)
=Vin·Don+Vc1 …(6)
Provide average voltage (average voltage of the glower end F2 side) VF2 at glower end F2 place by following formula:
VF2=Vc2
=Vin·Don+Vc1 …(7)
Therefore, the cut-off voltage at glower end F1 place becomes and equals the cut-off voltage at glower end F2 place.As institute from equation (6) and (7) is conspicuous, can be by adjusting the charging voltage Vc1 of capacitor C1, promptly the connection dutycycle of the forward voltage VF of diode D1 and switch SW 1 is provided with this cut-off voltage arbitrarily.
In power circuit 200, because as mentioned above, provide cut-off voltage with VinDon+Vc1, can be provided with cut-off voltage lower, increased the degree of freedom of cut-off voltage.In conventional power source circuit 400 as shown in figure 15, can use resistor R C1 to adjust cut-off voltage.But, cut-off voltage can not be reduced to the average voltage between the center tap that is lower than terminals F1 and F2 and transformer 9.That is, the degree of freedom of design cut-off voltage is lower.In contrast, in the power circuit 200 of present embodiment,, cut-off voltage can be set arbitrarily by the forward voltage VF of diode D1 and the connection dutycycle Don of switch SW 1.This has increased the degree of freedom of cut-off voltage.
Should be noted that the applicant had before once proposed in list of references 2 (the open No.2003-29711 of Japanese patent unexamined) disclosed " driving the method and the driving circuit of vaccum fluorescent tube ".Figure 16 shows disclosed power circuit 500 in list of references 2.Figure 17 shows the operation of power circuit 500.In power circuit 500, reference number 20 expressions produce the logic power of DC power supply VCC according to input voltage (dc voltage) Vin; 21 expressions produce the reference oscillator of reference clock signal PC1; And 22 expression be 1/2 to produce 1/2 frequency dividing circuit of external timing signal PC2 by frequency division of the frequency to reference clock signal PC1.
Reference number 23 expression exports from output terminal OUT1 and OUT2 the filament drive device of complementary differential pulse voltage PLin and P by switching input voltage vin.To be applied on the filament 6 from the differential pulse voltage PLin and the P of filament drive device 23.By this operation, AC filament voltage Ef is applied to filament 6 two ends (between terminals F1 and F2).Reference number 24 expression is to from the differential pulse voltage PLin of filament drive device 23 outputs with P boosts and rectification and export the booster circuit of resulting voltage as the dc voltage VDD2 that is used for anode/grid.
With reference to Figure 16, the average voltage between an end of filament 6 and the output terminal OUT1 of filament drive device 23 (average voltage of glower end F1 side) equals the average voltage (average voltage of glower end F2 side) between the output terminal OUT2 of the other end of filament 6 and filament drive device 23.This average voltage of filament 6 is set to cut-off voltage.Can by adjustment be connected the numerical value of the resistor R C2 between F1 and the OUT1 and be connected F2 and OUT2 between the numerical value of resistor R C3 adjust this cut-off voltage.
In power circuit 500, connect with filament 6 owing to be used to adjust the resistor R C2 and the RC3 of cut-off voltage, because the voltage drop of resistor R C2 and RC3, input voltage vin can not be used as the voltage that will be applied on the filament 6 fully.In addition, the power that resistor R C2 and RC3 consumed is bigger, and filament 6 also consumes bigger power.That is, the general power that is consumed is very big.In addition,, must use to have the rated power that can bear this power and the driver of size, cause the increase of cost as filament drive device 23.When filament voltage Ef is stablized, bigger loss takes place, caused relatively poor efficient.
In contrast, in the power circuit 200 of second embodiment, be applied on the filament 6, whole input voltage vin be used as the voltage that will be applied on the filament 6 owing to will have the voltage of voltage width Vin and square waveform.In addition,, there is not the power consumption that causes owing to resistance, obtained lower power consumption owing to the supply path of filament 6, do not have resistance in input voltage vin.This makes its rated power that can reduce circuit unit, rated current and power consumption, and realizes the reduction on assembly cost and the size.
Similar with the power circuit 100 of first embodiment, the power circuit 200 of second embodiment does not use the filament drive transformer, can realize lower noise.In addition, the design transformer does not need higher cost, therefore, can shorten the required time of designing power supply.In addition, by adjusting, can make the drive cycle of filament 6 and display connect cycle synchronisation from the switch SW 1 of control circuit 16A and the on/off cycle of SW2.This can prevent the shake when showing required pattern on vaccum fluorescent tube 1.
[the 3rd embodiment]
Fig. 8 shows the application of power circuit shown in Figure 4 200.In power circuit 300, third and fourth switch SW 3 and SW4 are connected between the incoming line Lin and ground wire that is used for dc voltage Vin.In this series circuit, switch SW 3 is positioned at the incoming line Lin side of dc voltage Vin, and switch SW 4 is positioned at the ground wire side.Capacitor C2 is connected glower end F2 and between the node PB between switch SW 3 and the SW4.
It is right that switch SW 1 and switch SW 4 constitute first switch, and switch SW 2 and switch SW 3 formation second switches are right.Control circuit 16B is according to reverse direction, periodically and alternately on/off first switch to (SW1 and SW4) and second switch to (SW2 and SW3).
Promptly, control circuit 16B periodically repeats the operation of " when connecting first switch to (SW1 and SW4) at the same time; disconnect second switch simultaneously to (SW2 and SW3), and when disconnecting first switch to (SW1 and SW4) at the same time, connecting second switch simultaneously to (SW2 and SW3) ".
Fig. 9,10 and 11 shows respectively and corresponds respectively to Fig. 5,6 and 7 F1 and waveform between the waveform between the GND, F2 and the GND and the waveform between F1 and the F2.As from institute these waveforms is conspicuous, in power circuit 300, with the same in the power circuit 200, the voltage (AC filament voltage) that will have square waveform is applied on the filament 6.But in this case, the voltage width that will be applied to the voltage with square waveform on the filament 6 is set to 2Vin.
In power circuit 300, if first switch equals second switch to (SW2 and SW3), then Vc1=Vc2 to the on/off dutycycle of (SW1 and SW4).In addition, the average voltage VF1 and the VF2 that represent glower end F1 and F2 place with VF1=VF2=VinDon+Vc1.By ef=Vin (2Don) 1/2Provide the effective value ef of filament voltage.
In above-mentioned power circuit 200 and 300, will be as on-off elements such as transistor and FET as switch SW 1 to SW4.In the series circuit 18-1 of the resistor R 4 that links to each other with first switch SW 1 and diode D2 and D1, resistor R 4 can be arranged between diode D1 and the D2, perhaps be arranged on diode D1 and between the node between switch SW 1 and the SW2.In addition, diode D1 is used as constant voltage elements, prevents element and diode D2 is used as adverse current.But these elements are not limited to diode.
In addition, the situation of power circuit 201 as shown in figure 12 (the 4th embodiment) can be applied to the technology of the cut-off circuit 18A in the power circuit 200 of second embodiment power circuit 100 of first embodiment.Figure 13 shows the waveform at the F1 place in the power circuit 200 of second embodiment.Figure 14 shows F1 in the power circuit 201 and the waveform between the F2.In power circuit 201, because If1Doff=If2Don, [(V0+Vc1-Vc2)/Rf] (1-Don)=[(Vc2-Vc1)/and Rf] Don, V0+Vc1-Vc2=V0[(V0-Vin)/V0], and Vc2=Vin+Vc1, then VF1=Vin+Vc1, and VF2=Vc2=Vin+Vc1=VF1.Can calculate filament voltage Ef according to the mode identical with second embodiment.
As mentioned above, according to the present invention,, do not need to use any filament drive transformer, and can realize low noise owing to produce the AC filament voltage by the periodicity on/off operation that utilizes on-off element.In addition, do not need to design the expensive of transformer, and can shorten the required time of designing power supply.In addition, this can prevent the shake when showing required pattern on vaccum fluorescent tube 1, and realizes low power consumption.

Claims (2)

1. power circuit that is used for vacuum fluorescent display is characterized in that comprising:
First and second on-off elements (SW1, SW2) of series connection, be arranged between the incoming line (Lin) and ground wire (GND) that is used to import dc voltage (Vin), described first on-off element (SW1) is than the more close incoming line that is used to import dc voltage of described second switch element (SW2);
The series circuit (18-1) in parallel with described first on-off element (SW1), comprise that the resistor (R4), the adverse current that are one another in series prevent element (D2) and constant voltage elements (D1), described adverse current prevents that element (D2) is than the more close incoming line that is used to import dc voltage of described constant voltage elements (D1);
First capacitor (C1) is connected between the input end and output terminal of described constant voltage elements (D1);
First terminals (F1) link to each other with the input end of described constant voltage elements (D1) and the node (PA) between described first capacitor (C1);
Second capacitor (C2) is connected between second terminals (F2) and the ground wire (GND); And
Control device (16A), be used for periodically repeating following operation: when connecting described first on-off element (SW1), disconnect described second switch element (SW2), and when disconnecting described first on-off element (SW1), connect described second switch element (SW2).
2. power circuit that is used for vacuum fluorescent display is characterized in that comprising:
First and second on-off elements (SW1, SW2) of series connection, be arranged between the incoming line (Lin) and ground wire (GND) that is used to import dc voltage (Vin), described first on-off element (SW1) is than the more close incoming line that is used to import dc voltage of described second switch element (SW2);
Third and fourth on-off element (SW3, SW4) of series connection, be arranged between the incoming line (Lin) and ground wire (GND) that is used to import dc voltage (Vin), described the 3rd on-off element (SW3) is than the more close incoming line that is used to import dc voltage of described the 4th on-off element (SW4);
The series circuit (18-1) in parallel with described first on-off element (SW1), comprise that the resistor (R4), the adverse current that are one another in series prevent element (D2) and constant voltage elements (D1), described adverse current prevents that element (D2) is than the more close incoming line that is used to import dc voltage of described constant voltage elements (D1);
First capacitor (C1) is connected between the input end and output terminal of described constant voltage elements (D1);
First terminals (F1) link to each other with the input end of described constant voltage elements (D1) and the node (PA) between described first capacitor (C1);
Second capacitor (C2), be connected second terminals (F2) and be positioned at described the 3rd on-off element (SW3) and described the 4th on-off element (SW4) between node (PB) between; And
Control device (16B), be used for periodically repeating following operation: it is right to disconnect the second switch element when connection first on-off element is right, and it is right to connect the second switch element when disconnection first on-off element is right, described first on-off element is to comprising described first on-off element (SW1) and described the 4th on-off element (SW4), and described second switch element is to comprising described second switch element (SW2) and described the 3rd on-off element (SW3).
CNB2007101468409A 2003-08-27 2004-08-24 The power circuit that is used for vacuum fluorescent display Expired - Fee Related CN100568329C (en)

Applications Claiming Priority (3)

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JP2003302538 2003-08-27
JP2003302538A JP4181463B2 (en) 2003-08-27 2003-08-27 Fluorescent display power supply circuit
JP2003418233 2003-12-16

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JP4533445B2 (en) * 2008-04-15 2010-09-01 ノリタケ伊勢電子株式会社 Power supply circuit for filament of fluorescent display tube
JP5297116B2 (en) * 2008-08-18 2013-09-25 ローム株式会社 Booster circuit and power supply device using the same
CN108932924B (en) * 2017-05-25 2023-05-23 上海璞丰光电科技有限公司 Novel topological structure vacuum fluorescent screen power supply
JP6667937B2 (en) * 2017-08-23 2020-03-18 双葉電子工業株式会社 Display device, fluorescent display tube
CN107742970A (en) * 2017-10-11 2018-02-27 湖北久之洋红外系统股份有限公司 A kind of Si APD bias circuits
CN107911024B (en) * 2017-12-11 2019-12-03 三峡大学 A kind of high efficiency series hybrid multiport DC/DC converter
CN107947572B (en) * 2017-12-11 2019-12-03 三峡大学 A kind of series hybrid multiport DC/DC converter suitable for energy-storage units access
JPWO2019203355A1 (en) 2018-04-20 2021-05-13 国立大学法人静岡大学 Impedance adjustment circuit, power conversion element and power supply element

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