CA2063512A1 - Hearing aid with an end stage that operates in switching mode - Google Patents
Hearing aid with an end stage that operates in switching modeInfo
- Publication number
- CA2063512A1 CA2063512A1 CA002063512A CA2063512A CA2063512A1 CA 2063512 A1 CA2063512 A1 CA 2063512A1 CA 002063512 A CA002063512 A CA 002063512A CA 2063512 A CA2063512 A CA 2063512A CA 2063512 A1 CA2063512 A1 CA 2063512A1
- Authority
- CA
- Canada
- Prior art keywords
- hearing aid
- earpiece
- end stage
- decoupling means
- output circuit
- 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.)
- Abandoned
Links
Classifications
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
- H03F3/20—Power amplifiers, e.g. Class B amplifiers, Class C amplifiers
- H03F3/21—Power amplifiers, e.g. Class B amplifiers, Class C amplifiers with semiconductor devices only
- H03F3/217—Class D power amplifiers; Switching amplifiers
- H03F3/2171—Class D power amplifiers; Switching amplifiers with field-effect devices
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R25/00—Deaf-aid sets, i.e. electro-acoustic or electro-mechanical hearing aids; Electric tinnitus maskers providing an auditory perception
Abstract
Abstract In a hearing aid with an amplifier and with a push-pull end stage (6), which operates in switching mode and switches an earpiece (15) in an output circuit (19) with an ultrasonic frequency as a time function from an acoustic signal, it is intended to make it possible to influence the frequency response of the earpiece that is connected by a condensor that is connected in parallel to this.
To this end, the end stage incorporates at least one decoupling means (28, 29; 34; 38), through which an electrical signal that is dependent on the switched state of the earpiece (15) can be tapped off and acts through at least one feedback path (22 to 27; 35, 36, 26, 27) on the end stage (6) so as to increase the impedance of the output circuit (19).
Figure 1.
To this end, the end stage incorporates at least one decoupling means (28, 29; 34; 38), through which an electrical signal that is dependent on the switched state of the earpiece (15) can be tapped off and acts through at least one feedback path (22 to 27; 35, 36, 26, 27) on the end stage (6) so as to increase the impedance of the output circuit (19).
Figure 1.
Description
The pro~ont Inventlon rel-to~ to o hoorln~ ald ~Ith on ompllflor and ~Ith o pu8h pull end stage that operntes In s~itchlng mode end ~hich s~ltches an eerpiece In an output circuit as a time function of an acoustic signal ~ith en u~tresonicfrequency DE-PS 36 16 752 descrlbes a hearing aid of the type do~crlbed above In this knoun hearing aid the end stage ~hich operates in push-pull i3 configured as a Class D amplifier ~ith CHOS
tronsl~tor5; tho oarplece i8 rran~ed In the output clrcult of thls. A condensor is connocted In perallel ~ith this earpiece~n induct-nce is connacted in series ~Ith this kno~n par-llel clrcuit that comprlses the condensor and the earpiece The Inductance and the condensor act as a filter in the output circuit of tho push-pull stoge that acts as a bridge circuit and this is intended to suppress the s~itchlng Isampllngl frequency that lies In the ultrasonlc range The sultching frequency can be 40 or 100 kHz for example The output stage of the knoun s~itchlng amplifler ~push-pull end stoge) i8 l~-ys of a relatively lo~ Impedance ~mongst other thlngs because of the lo~ reslstance CMOS translstors ~CHOS
~ltch) If the frequency response of the earpiece ~tono frequencle~ of approxlmately 1 to 6 kHz) i~ to be influenced ~ith condensor th-t Is arr-nged electrlcally p-rallel to the earploce and/or motched to the ond stago because of the lo~ roslstance of the output st-go very largo cepecity conden~or ~ould have to bo used ~ condensor of such a klnd ~ould ho~ever areatlY dlmlnlsh the quollty of tho output 8taao of the s~ltching nmpllfler for thls reoson no resonance points tan occur in the frequency response of the kno~n s~ltchlng amplifier As a consequence In kno~n s~ltching amplifiers it is not possible to influence the frequency response of the earpiece (tonal frequency range voicefrequency ran9e) by a condensor that i8 connected in par~llel th reto No~ever a resonanco point of such a kind ~hlch can be dJustod by ~-y of n condensor Is deslrable for matchlng tho . ..... .. . -. . . .
. .
20365-3159 91 P313~ E
froquency response of the particular earpiece thet i8 u6ed to the s~itching amptlfier and is elso usuat in end stnges that do not opernte in suitching mode It i8 the task of the present ~nvention to so configuro the ~itching amplifier in n hearina aid of tho type described in the introduction hereto such that it i8 possible to influence the frequency respon8e ot the earpiece that i8 connected to it by ~-y of condensor thet i~ connected in parellel thereto According to the present invention this ta~k has been solved by tho featuros ~et out in tho main clnlm. Pecause of thi~ enrplocos ~various type~ of oarpieces) l~ith various impedance curves (frequencv responGes) cnn elso be matchod to push-pull end stages thet operato ~n s~itching mode ~Ihich can be brought about for e~ompto by o condensor that i8 connectod in parallel to tho o-rpioce ~dditional dventago~ nd details of the pre~ent invention are ~et out in the subsequent description of embodiments ~hich is b-~od on th- drauings appendod hereto and in conJunction ~ith the claim~
The dre~llng- ~ho~ tho fo~lollng Figure 1: A ~ymbolic reprosentation of a hearing aid llith circuit~
t h - t a r o i n p r i n c i p I e e 8 8 e n t i a t t o t h e p r e 8 e n t invention;
Figure 2: A hearing ald as sho~n in figure 1 uith a variation ot tho faedback path;
Figuro 3: An impedance curve of an earpiece thnt i5 to be matched to tho ~uitching ~npl~fior;
Flgure4: A dra~ing sho~ing the effect of amplitudo of an input signal ~acoustic signal) by tho hearing aid sho~ln in figure 2;
Flgure 5: An earpiece ~i th a spocial decoupl ing means sho~n s~nbo~ ~cu~ ~y .
2063~12 ..... . .
Fioure 1 8ho~s s hearing llid 1 uith sn amplifier 2 to ~Ihich coustlc signals are fed from a mlcrophone 3 and ~/hlch is connected through an integrator 4 to an input 5 of a push-pull end stage 6 ts~itchlng amplifier) A gener-tor 7 produces an ultresonic frcquency that acts on a further input ô of the end stage 6 in the form a symmetrical delta voltllge In this embodiment the end stage 6 incorporates a comparator 9 at the input side This comparstor 9 forms a squere-uave signal ir the ultrasonic frequency renge from the t~o input signa~s (acoustic and ultrasonic)~ ~hlch corresponds to the ultrasonic frequency of the oener-tor 7 The square-l~ave signal exhibits (7) pulses of different durations In keeping lith the knoun manner in uhich comparetor operates the different duration of the individual pulses results on the one hand froR~ the transient value of the emp~itude of the acoustic slgnal at the input 5 and on the other hend from the veriable (delta) threshold voltage of the ultrasonic signal at theinput A of the comparator 9 As a cons quence of this there is a squnre-~lave signal present at an output 10 of the comparetor at ~Ihich the duration of the individusl pulses i8 dependont on tho ecoustlc signal in keeping ith knol~n pulse duretion modulation Semiconductors conf igured in this embodiment as complementary C110S
trensl~tors T1to T4 aro triggered by the squrre l~ave that i8 present et the output 10 of the comparator 9 To this end the output 10 oftho comparator 9 i8 connected through the uire 11 to the geto connoction G1 of the trsnsistor Tl and by ~ire 12 lith the oato connection G4 of the trsnsistor T4 In addition the output 10 of the comperetor9 i8 connocted through the l~ire 13 ~lith the inverter 14 in bhich the square-~ave signal is inverted so as 20 control ~sultch) thecomplementarytransistors T2 and T3 As o consequonce of this the transistors T2 and T3 are s~itched through thoir geto connections G2 and G3 ~ ith a complementsry square-~lave s~gnal Inthls embodiment the transistors T1 to T4 are arranged :: ., , .
in a ~heatfitone bridge circuit en earpiece 15 or the coil 16 thereof belng a component of a bridge brench betueen tho trensistors T1/T2 and T3/T4 7h brld3e circuit is connected to po~er source throu~h the positive operating voltage terminel 17 and tho negativo operating voltnge terminDtor 18 / e to hearing-aid battery (not shoun herein) The tran~i~tor~ Tl to T4 uhich are arranged in a brid~o circuit and the earplece 15 are ~l80 components of an output circuit 19 of the end 6tage 6 The end stage o operates in push-pull At th~9 time tho transistors T2 and T3 or the transistors Tl snd T4 re simultaneously conductive For purposes of simplifyin~ tho doscription ot the flou of current the effect of the earpioce impedance is not considered in the first instance Thus ~put simply) the current flous ~ithln the output circuit 19 durinyfir~t ~ultching stat- e 9 st-rting from the operatin~ voltagetorminol 17 throu~h e source terminel 53 and a drain terminat D3 of the conductivoly svitched transistor T3 then through the coil 16 o- tho earpiece 15 and throu3h the drain terminal D2 and the source terminal S2 of the conductively suitched transistor T2 to the operating voltage terminal 18. If in contrast to this in tho other case the transistors T2 and T4 are conductively suitched sterting from tho operatin~ voltaye terminal 17 the current flous through a ~ourco torminal 51 and droin torminel D1 of the transistor T1 in tho opposite diroction throu~h the eerpiece coil 16 to a drain terminal D4 and e sourcer terminel S4 of the translstor T4 to the negatlvo operating volta~e terminal 18 Ho~ovor the true current flou i8 much more complex becauso the e-rpiece 15 i8 not o purely ohmic resistance for the current that alternates uith an ultrasonic froquency; rather it is a frequency-dependent resistence (an impedance) For this reason the earpiece acts as a current accumuletor The accumulator effect is influenced by the duration of the individual pulses For this reason one can also ssy that the earpiece 15 in the output circuit .
. .
.
`
tronsl~tor5; tho oarplece i8 rran~ed In the output clrcult of thls. A condensor is connocted In perallel ~ith this earpiece~n induct-nce is connacted in series ~Ith this kno~n par-llel clrcuit that comprlses the condensor and the earpiece The Inductance and the condensor act as a filter in the output circuit of tho push-pull stoge that acts as a bridge circuit and this is intended to suppress the s~itchlng Isampllngl frequency that lies In the ultrasonlc range The sultching frequency can be 40 or 100 kHz for example The output stage of the knoun s~itchlng amplifler ~push-pull end stoge) i8 l~-ys of a relatively lo~ Impedance ~mongst other thlngs because of the lo~ reslstance CMOS translstors ~CHOS
~ltch) If the frequency response of the earpiece ~tono frequencle~ of approxlmately 1 to 6 kHz) i~ to be influenced ~ith condensor th-t Is arr-nged electrlcally p-rallel to the earploce and/or motched to the ond stago because of the lo~ roslstance of the output st-go very largo cepecity conden~or ~ould have to bo used ~ condensor of such a klnd ~ould ho~ever areatlY dlmlnlsh the quollty of tho output 8taao of the s~ltching nmpllfler for thls reoson no resonance points tan occur in the frequency response of the kno~n s~ltchlng amplifier As a consequence In kno~n s~ltching amplifiers it is not possible to influence the frequency response of the earpiece (tonal frequency range voicefrequency ran9e) by a condensor that i8 connected in par~llel th reto No~ever a resonanco point of such a kind ~hlch can be dJustod by ~-y of n condensor Is deslrable for matchlng tho . ..... .. . -. . . .
. .
20365-3159 91 P313~ E
froquency response of the particular earpiece thet i8 u6ed to the s~itching amptlfier and is elso usuat in end stnges that do not opernte in suitching mode It i8 the task of the present ~nvention to so configuro the ~itching amplifier in n hearina aid of tho type described in the introduction hereto such that it i8 possible to influence the frequency respon8e ot the earpiece that i8 connected to it by ~-y of condensor thet i~ connected in parellel thereto According to the present invention this ta~k has been solved by tho featuros ~et out in tho main clnlm. Pecause of thi~ enrplocos ~various type~ of oarpieces) l~ith various impedance curves (frequencv responGes) cnn elso be matchod to push-pull end stages thet operato ~n s~itching mode ~Ihich can be brought about for e~ompto by o condensor that i8 connectod in parallel to tho o-rpioce ~dditional dventago~ nd details of the pre~ent invention are ~et out in the subsequent description of embodiments ~hich is b-~od on th- drauings appendod hereto and in conJunction ~ith the claim~
The dre~llng- ~ho~ tho fo~lollng Figure 1: A ~ymbolic reprosentation of a hearing aid llith circuit~
t h - t a r o i n p r i n c i p I e e 8 8 e n t i a t t o t h e p r e 8 e n t invention;
Figure 2: A hearing ald as sho~n in figure 1 uith a variation ot tho faedback path;
Figuro 3: An impedance curve of an earpiece thnt i5 to be matched to tho ~uitching ~npl~fior;
Flgure4: A dra~ing sho~ing the effect of amplitudo of an input signal ~acoustic signal) by tho hearing aid sho~ln in figure 2;
Flgure 5: An earpiece ~i th a spocial decoupl ing means sho~n s~nbo~ ~cu~ ~y .
2063~12 ..... . .
Fioure 1 8ho~s s hearing llid 1 uith sn amplifier 2 to ~Ihich coustlc signals are fed from a mlcrophone 3 and ~/hlch is connected through an integrator 4 to an input 5 of a push-pull end stage 6 ts~itchlng amplifier) A gener-tor 7 produces an ultresonic frcquency that acts on a further input ô of the end stage 6 in the form a symmetrical delta voltllge In this embodiment the end stage 6 incorporates a comparator 9 at the input side This comparstor 9 forms a squere-uave signal ir the ultrasonic frequency renge from the t~o input signa~s (acoustic and ultrasonic)~ ~hlch corresponds to the ultrasonic frequency of the oener-tor 7 The square-l~ave signal exhibits (7) pulses of different durations In keeping lith the knoun manner in uhich comparetor operates the different duration of the individual pulses results on the one hand froR~ the transient value of the emp~itude of the acoustic slgnal at the input 5 and on the other hend from the veriable (delta) threshold voltage of the ultrasonic signal at theinput A of the comparator 9 As a cons quence of this there is a squnre-~lave signal present at an output 10 of the comparetor at ~Ihich the duration of the individusl pulses i8 dependont on tho ecoustlc signal in keeping ith knol~n pulse duretion modulation Semiconductors conf igured in this embodiment as complementary C110S
trensl~tors T1to T4 aro triggered by the squrre l~ave that i8 present et the output 10 of the comparator 9 To this end the output 10 oftho comparator 9 i8 connected through the uire 11 to the geto connoction G1 of the trsnsistor Tl and by ~ire 12 lith the oato connection G4 of the trsnsistor T4 In addition the output 10 of the comperetor9 i8 connocted through the l~ire 13 ~lith the inverter 14 in bhich the square-~ave signal is inverted so as 20 control ~sultch) thecomplementarytransistors T2 and T3 As o consequonce of this the transistors T2 and T3 are s~itched through thoir geto connections G2 and G3 ~ ith a complementsry square-~lave s~gnal Inthls embodiment the transistors T1 to T4 are arranged :: ., , .
in a ~heatfitone bridge circuit en earpiece 15 or the coil 16 thereof belng a component of a bridge brench betueen tho trensistors T1/T2 and T3/T4 7h brld3e circuit is connected to po~er source throu~h the positive operating voltage terminel 17 and tho negativo operating voltnge terminDtor 18 / e to hearing-aid battery (not shoun herein) The tran~i~tor~ Tl to T4 uhich are arranged in a brid~o circuit and the earplece 15 are ~l80 components of an output circuit 19 of the end 6tage 6 The end stage o operates in push-pull At th~9 time tho transistors T2 and T3 or the transistors Tl snd T4 re simultaneously conductive For purposes of simplifyin~ tho doscription ot the flou of current the effect of the earpioce impedance is not considered in the first instance Thus ~put simply) the current flous ~ithln the output circuit 19 durinyfir~t ~ultching stat- e 9 st-rting from the operatin~ voltagetorminol 17 throu~h e source terminel 53 and a drain terminat D3 of the conductivoly svitched transistor T3 then through the coil 16 o- tho earpiece 15 and throu3h the drain terminal D2 and the source terminal S2 of the conductively suitched transistor T2 to the operating voltage terminal 18. If in contrast to this in tho other case the transistors T2 and T4 are conductively suitched sterting from tho operatin~ voltaye terminal 17 the current flous through a ~ourco torminal 51 and droin torminel D1 of the transistor T1 in tho opposite diroction throu~h the eerpiece coil 16 to a drain terminal D4 and e sourcer terminel S4 of the translstor T4 to the negatlvo operating volta~e terminal 18 Ho~ovor the true current flou i8 much more complex becauso the e-rpiece 15 i8 not o purely ohmic resistance for the current that alternates uith an ultrasonic froquency; rather it is a frequency-dependent resistence (an impedance) For this reason the earpiece acts as a current accumuletor The accumulator effect is influenced by the duration of the individual pulses For this reason one can also ssy that the earpiece 15 in the output circuit .
. .
.
`
2~6~12 19 of the ond fitllge 6 is ropolari~ed by the tranfiistors T1 to T4 thae are controlled uith nn ultrssonic frequency l~ith the frequency of the ultrasonic frequency that is emitted from the generDtor 7 ~nd A8 ~I time function of the amplitude of the acoustic SignDl at the input S of the comparator 9. As a con~equence the voltaoe at tho t~lo terminal~ 20 and 21 of the earplece lS that Is trlggered by the transistors T1 to T4 chanoes it~ polorlty ~ccording to the suitching frequency and according to the duratlon of the Indlvldual pulses. The disadvantRgos in tho output clrcuit 19 doscr~bed in tho introduction hereto result from this s~itchin3 mode.
According to the present invention o feedback pnth i8 provided in order to lncrease the impedance of the output circuit 19; in this embodiment this comprises the ~lires 22 to 24 en electronic s~litch 25 8 differential amplifier 20 a lo~-pass fileer 27 and the intel~rator 4. Uhen in the conductive state the transistors T1 to T4 that are conductively suitched each have so-cslled current-flo~
resistances (internDl). These current-flo~ resistances l~re shol n in Fl~ure 1 at the source terminals S1 and S2 by means of the re-istance symbols S1 and s2 that are dra~n l~ith dashed lines. The current-flou resistance 28 ~ppears ~Ihen T1 iS conductive nd current-flo~l resi8tance 29 sppe~rs ~hen T2 iS conductive.
In one embodiment of the present invention the current-flo~
reslst-nces 28 ond 29 are used as decoupllng me~ns throu~h ~hlch an electricsl slllnal that is dependent on the s~litched state of the earpieco 15 can be tapped off. The current-flou resistances 28 and 29 are not physically present as distinct components but aluays a p p e a r u i t h i n t h e t r a n s i s t o r s T 1 o r T 2 ~ r e s p e c t i v e l y i n alternntion vhen the semiconductors T1 or T2 respectively ~re 8ui tched conduct i ve I y i n counterphase wi th the ul t rasoni c frequency. Thus the electrical signal l~hich is dependent on the ~itched 8tato ot the earpiece can be tapped off throu~h the transistor T1 by means of the llires 23 and 24 end through the r , 2~63512 translstor T2 by means of tho ulres 22 end 23 The eloctronlc sultch 25 Incorporates en Input pole 39 that Is connected ulth the ulre 22 of the one feedback path Another Input pole 40 of the s~litch 25 Is connected~lth the ~Ire 24 of the other feedbock peth In output pole 30 on the suitch 25 Is connected ulth an Input 31 o~ the ditferentlal amplifler 26 Another Input 32 at the dl~tor-ntlol amplltlor 26 Is connected 11th the other ~common) ulre 23 of tha above mentloned feedback pathsIn this embodlmont the electronlc sultch 25 Is connected through sultch control 33 ulth the output 10 of the comparator 9 Thus the sultch 25 1-controll-d by sultchlng slgnal that Is dependent on th-ultraaonlc tr-qu-ncy Thls mean~ thet the electrlcol slgnals d-rlv-d from both d-coupllng meens 28 and 29 and ~hlch re dep-nd-nt on the sultched st-te o- the e-rpiece 15 can ct phased correctly on the end stage 6 In order to Increese the Inpedance of the output clrcult 19 Important advanteges of this apeci-l embodiment of the present Inv-ntlon ar- that component- ~trenslstors) that er- nec-ssery for anoth-r purpose ar- us-d as docoupling means In the end stage 6 For thls r-a-on no eddltlonal compon-nt Is r-qulr-d ~ a decoupllng m-ansSince the curr-nt-flo~ reslstors 28 and 29 r-ohmic and oth-rui-e forl~ D serles clrcuit ~lththe earploc- 15 a volt-g- that Is proportlonal to the earplece current can be r-adlly tapp-d off through thefie decoupllng means 28 nd 29 as a f-edback signal In thls respect It Is also very Important thatb-ceu-- o~ th- llmln-tlon of addltion-l ~reparete~ d-coupllng m-ans in the output clrcult 19 of the end stage 6 no edditlonel voltag- drop ~hlch uould degrade th- efflci-ncy or th- output pou-r of th- nd stag- 6 can occur In arpleces of thls kind th- sl~all-st voltage drops heve a v-ry dlsruptlve ffect for the h--rlng aids ar- gen-rally operated uith on operating volteg- o-only 1 3 V
::
'' ~', ~ :':~ , ,: `
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: . . ~: : :
Another speciol embodiment is sho~ln in Figure Z In this embodiment it i8 essentially only the feedback psth and the decoupling mesns th~t sre configured differently to those in the elrbodiment shoun in Figure 1 According to Figure 2 a resistance34 i8 used as the decoupling means The resistsnce 34 is connected in sories ~ith the earpiece ~lithin ono brid~e branch bet~een the transi~tor- T1~T2 ond T3/T4 ~' ~ consequenco st the ono roslstsnco~4, In ev-ry ~ltch-d stato ot th oarpIoco thoro ~lill bo a voltogo drop uhich ~ill be passed through the uires 35 and 36 to the inputs 32 and 31 of tho ditferentiul emplifior 26 ~s an electric~l slgnsl thet is dopendent on the suitchod ststo of tho e~rpiece Beceuso of the special arrangement of the decoupling resistance 34 in the bridge brsnch of the output circuit 19 the sllitching device thlt comprlso- the sl~itch 26 and the suitch control 33 i5 eliminatod ~hich is advantogeous. The lo~-pass fllter 27 can have a limitin9 froquoncy of 10 kH2 80 thet the tone frequencies (scoustlc) be passed and the ultrssonic frequency thot s~itches the end ste~le 6 ~ill be blocked If tho end rtage 6 or the output circuit 19 aro approprietoly deslgned ~ ith o filtor thet blocks the ultrssonic troquency nd ~ith epproprlsto coupling ot the feedbeck psth tho lo~l-pass filtor 27 in tho foedback psth can also be oliminated llith tho t~lo vorients of s honring aid according to the presont invontion whlch are sho~m in Figures 1 and 2 the impedance of the output circuit 19 can bo raised so much thet differont el~rpIeces 15 cen be matched uith the help of a condensor 37 to the push-pull ond stogo o of the hesrinq eid 1 ~hich oporlltes in sl~itchinu modo end the froqu-ncy rosponse of the psrtlcular esrpieco 15 thst i8 used cen be chongod by o condensor 37 that is in parallel to this In particular becauso of the confi~luretion of the hesrin~ sid eccordign to the present invention the qu~lity of the output circuit is higher becouse of ~thich there is a peak ~resonsnco) in tho froquoncy respon~o of tho output circuit ~hich is ~d~ustoblo by moens of tho condensor 37 ,:~
:: , ., ` `' 2063~12 The manner in ~Ihich the feedback lorks in a hearin~ aid according to the present invention Is shoun in Figure 2 and explained briofly and inslmplified form in conjunction uith Figures 3 and 4 Figure 3 shows the impedence curve of an earpiece 15 uhich can vary according to the type of earpiece In the present example on the basis of Flgure 3 the impodance of the earpiece amounts to approximately 1 kOhm et 1 kHz and to approximately 10 koh~ at 10 kNz In Flgure 4 the continuous curve U5 represonts the acoustic signal that i8 present at the output of the flmplifier 2 and at un Input of the Integrator 4 in Flgure 2 ~hich is connected to thls The curve U~n indicated by thedashed line in Figure 4 represents a volt-ge that In Fi~ure 2 i- pre6ent at the input 5 of the comparator clrcuit 9 as voltage U~n The difference bet~een the t~o voltages Us end U~n results from the signal UR or IUR; compare the t~lo correspondlng orro~s In Figure 4 In Figure 2 the voltage UR
i~ al90 passed to an input of the Integrator 4 and uas generated through the differential amplifier 26 from a voltage drop IR at the rosl-tance 34 The current iR i9 proportional to the earpiece current 'H The earpiece current iH decreases as the impedance of the earpiece 15 increases Thus the voltago UR Is smal lor As a consequence less of the voltago U5 is subtr~cted In the integratlng element 4 so that as a rosult tho voltage U~n i8 gr-at-r t th- Input 5 of the comparator 9 Thls rosult~ in longor pul-o duratlon at tho output 10 of the comp~rlltor 9 This leads once again to a longor through s\litching duration of the transistors lsl~itches e 9 Tl and T4 Thus there is a longer integration time of the earpiece current iH and of the current i~
in tho bridgo branch of tho output circuit 19 ~hich i8 tho samo as an increaso in curront Tho original drop of iR iS thus balanced out to a largo oxtont In the t~o embodlments as in Figuros 1 and 2 that have been descr~bed the push-putl end stage 6 is operated es a bridge circult in an output circuit 19 Ho~over in o ho-ring ald accordlng to the present Invention It 18 also posslble not to r ~' , ' ~.
`; - 20635~2 operate the push-pull end stage in the bridge clrcuit. The end ~ta~o can incorporate only t~lO tran~istors for examp~e these belng supplied through an earpiece ~ith a centre tap.
Figure 5 sholls another esrpiece 15 llith a coil 16 and the terminals 20 and 21 that according to Figures 1 or 2 can be arranged in the bridge brnnch of the output circuit 19. According to another variant of the present invention in Figure 5 a sampling device can be coupled inductively -ith the coil 16 of the earpiece 15 as a decoupling moens. The sampling device 38 can be accommodated ~Ithin the e~ociated housing ~not sho~n herein) of tho eerpiec 15. In this connection the sampling device 38 can be formed as a secondary ~inding of tho coil 10. Tho feedback voltage Up can be passedto the differentialamplifier 26 single pole ~ns sho~n) or double pole.
: .
According to the present invention o feedback pnth i8 provided in order to lncrease the impedance of the output circuit 19; in this embodiment this comprises the ~lires 22 to 24 en electronic s~litch 25 8 differential amplifier 20 a lo~-pass fileer 27 and the intel~rator 4. Uhen in the conductive state the transistors T1 to T4 that are conductively suitched each have so-cslled current-flo~
resistances (internDl). These current-flo~ resistances l~re shol n in Fl~ure 1 at the source terminals S1 and S2 by means of the re-istance symbols S1 and s2 that are dra~n l~ith dashed lines. The current-flou resistance 28 ~ppears ~Ihen T1 iS conductive nd current-flo~l resi8tance 29 sppe~rs ~hen T2 iS conductive.
In one embodiment of the present invention the current-flo~
reslst-nces 28 ond 29 are used as decoupllng me~ns throu~h ~hlch an electricsl slllnal that is dependent on the s~litched state of the earpieco 15 can be tapped off. The current-flou resistances 28 and 29 are not physically present as distinct components but aluays a p p e a r u i t h i n t h e t r a n s i s t o r s T 1 o r T 2 ~ r e s p e c t i v e l y i n alternntion vhen the semiconductors T1 or T2 respectively ~re 8ui tched conduct i ve I y i n counterphase wi th the ul t rasoni c frequency. Thus the electrical signal l~hich is dependent on the ~itched 8tato ot the earpiece can be tapped off throu~h the transistor T1 by means of the llires 23 and 24 end through the r , 2~63512 translstor T2 by means of tho ulres 22 end 23 The eloctronlc sultch 25 Incorporates en Input pole 39 that Is connected ulth the ulre 22 of the one feedback path Another Input pole 40 of the s~litch 25 Is connected~lth the ~Ire 24 of the other feedbock peth In output pole 30 on the suitch 25 Is connected ulth an Input 31 o~ the ditferentlal amplifler 26 Another Input 32 at the dl~tor-ntlol amplltlor 26 Is connected 11th the other ~common) ulre 23 of tha above mentloned feedback pathsIn this embodlmont the electronlc sultch 25 Is connected through sultch control 33 ulth the output 10 of the comparator 9 Thus the sultch 25 1-controll-d by sultchlng slgnal that Is dependent on th-ultraaonlc tr-qu-ncy Thls mean~ thet the electrlcol slgnals d-rlv-d from both d-coupllng meens 28 and 29 and ~hlch re dep-nd-nt on the sultched st-te o- the e-rpiece 15 can ct phased correctly on the end stage 6 In order to Increese the Inpedance of the output clrcult 19 Important advanteges of this apeci-l embodiment of the present Inv-ntlon ar- that component- ~trenslstors) that er- nec-ssery for anoth-r purpose ar- us-d as docoupling means In the end stage 6 For thls r-a-on no eddltlonal compon-nt Is r-qulr-d ~ a decoupllng m-ansSince the curr-nt-flo~ reslstors 28 and 29 r-ohmic and oth-rui-e forl~ D serles clrcuit ~lththe earploc- 15 a volt-g- that Is proportlonal to the earplece current can be r-adlly tapp-d off through thefie decoupllng means 28 nd 29 as a f-edback signal In thls respect It Is also very Important thatb-ceu-- o~ th- llmln-tlon of addltion-l ~reparete~ d-coupllng m-ans in the output clrcult 19 of the end stage 6 no edditlonel voltag- drop ~hlch uould degrade th- efflci-ncy or th- output pou-r of th- nd stag- 6 can occur In arpleces of thls kind th- sl~all-st voltage drops heve a v-ry dlsruptlve ffect for the h--rlng aids ar- gen-rally operated uith on operating volteg- o-only 1 3 V
::
'' ~', ~ :':~ , ,: `
,' . , :
: . . ~: : :
Another speciol embodiment is sho~ln in Figure Z In this embodiment it i8 essentially only the feedback psth and the decoupling mesns th~t sre configured differently to those in the elrbodiment shoun in Figure 1 According to Figure 2 a resistance34 i8 used as the decoupling means The resistsnce 34 is connected in sories ~ith the earpiece ~lithin ono brid~e branch bet~een the transi~tor- T1~T2 ond T3/T4 ~' ~ consequenco st the ono roslstsnco~4, In ev-ry ~ltch-d stato ot th oarpIoco thoro ~lill bo a voltogo drop uhich ~ill be passed through the uires 35 and 36 to the inputs 32 and 31 of tho ditferentiul emplifior 26 ~s an electric~l slgnsl thet is dopendent on the suitchod ststo of tho e~rpiece Beceuso of the special arrangement of the decoupling resistance 34 in the bridge brsnch of the output circuit 19 the sllitching device thlt comprlso- the sl~itch 26 and the suitch control 33 i5 eliminatod ~hich is advantogeous. The lo~-pass fllter 27 can have a limitin9 froquoncy of 10 kH2 80 thet the tone frequencies (scoustlc) be passed and the ultrssonic frequency thot s~itches the end ste~le 6 ~ill be blocked If tho end rtage 6 or the output circuit 19 aro approprietoly deslgned ~ ith o filtor thet blocks the ultrssonic troquency nd ~ith epproprlsto coupling ot the feedbeck psth tho lo~l-pass filtor 27 in tho foedback psth can also be oliminated llith tho t~lo vorients of s honring aid according to the presont invontion whlch are sho~m in Figures 1 and 2 the impedance of the output circuit 19 can bo raised so much thet differont el~rpIeces 15 cen be matched uith the help of a condensor 37 to the push-pull ond stogo o of the hesrinq eid 1 ~hich oporlltes in sl~itchinu modo end the froqu-ncy rosponse of the psrtlcular esrpieco 15 thst i8 used cen be chongod by o condensor 37 that is in parallel to this In particular becauso of the confi~luretion of the hesrin~ sid eccordign to the present invention the qu~lity of the output circuit is higher becouse of ~thich there is a peak ~resonsnco) in tho froquoncy respon~o of tho output circuit ~hich is ~d~ustoblo by moens of tho condensor 37 ,:~
:: , ., ` `' 2063~12 The manner in ~Ihich the feedback lorks in a hearin~ aid according to the present invention Is shoun in Figure 2 and explained briofly and inslmplified form in conjunction uith Figures 3 and 4 Figure 3 shows the impedence curve of an earpiece 15 uhich can vary according to the type of earpiece In the present example on the basis of Flgure 3 the impodance of the earpiece amounts to approximately 1 kOhm et 1 kHz and to approximately 10 koh~ at 10 kNz In Flgure 4 the continuous curve U5 represonts the acoustic signal that i8 present at the output of the flmplifier 2 and at un Input of the Integrator 4 in Flgure 2 ~hich is connected to thls The curve U~n indicated by thedashed line in Figure 4 represents a volt-ge that In Fi~ure 2 i- pre6ent at the input 5 of the comparator clrcuit 9 as voltage U~n The difference bet~een the t~o voltages Us end U~n results from the signal UR or IUR; compare the t~lo correspondlng orro~s In Figure 4 In Figure 2 the voltage UR
i~ al90 passed to an input of the Integrator 4 and uas generated through the differential amplifier 26 from a voltage drop IR at the rosl-tance 34 The current iR i9 proportional to the earpiece current 'H The earpiece current iH decreases as the impedance of the earpiece 15 increases Thus the voltago UR Is smal lor As a consequence less of the voltago U5 is subtr~cted In the integratlng element 4 so that as a rosult tho voltage U~n i8 gr-at-r t th- Input 5 of the comparator 9 Thls rosult~ in longor pul-o duratlon at tho output 10 of the comp~rlltor 9 This leads once again to a longor through s\litching duration of the transistors lsl~itches e 9 Tl and T4 Thus there is a longer integration time of the earpiece current iH and of the current i~
in tho bridgo branch of tho output circuit 19 ~hich i8 tho samo as an increaso in curront Tho original drop of iR iS thus balanced out to a largo oxtont In the t~o embodlments as in Figuros 1 and 2 that have been descr~bed the push-putl end stage 6 is operated es a bridge circult in an output circuit 19 Ho~over in o ho-ring ald accordlng to the present Invention It 18 also posslble not to r ~' , ' ~.
`; - 20635~2 operate the push-pull end stage in the bridge clrcuit. The end ~ta~o can incorporate only t~lO tran~istors for examp~e these belng supplied through an earpiece ~ith a centre tap.
Figure 5 sholls another esrpiece 15 llith a coil 16 and the terminals 20 and 21 that according to Figures 1 or 2 can be arranged in the bridge brnnch of the output circuit 19. According to another variant of the present invention in Figure 5 a sampling device can be coupled inductively -ith the coil 16 of the earpiece 15 as a decoupling moens. The sampling device 38 can be accommodated ~Ithin the e~ociated housing ~not sho~n herein) of tho eerpiec 15. In this connection the sampling device 38 can be formed as a secondary ~inding of tho coil 10. Tho feedback voltage Up can be passedto the differentialamplifier 26 single pole ~ns sho~n) or double pole.
: .
Claims (10)
1. A hearing aid with an amplifier (2) and with a push-pull end stage (6), which operates in switching mode, and an earpiece (15) in an output circuit (19) that switches an earpiece (15) in an output circuit as a time function from an acoustic signal with an ultrasonic frequency, the end stage incorporating at least one decoupling means (28, 29; 24; 28), through which an electrical signal (UR), which is dependent on the switched state of the earpiece (15), can be tapped, and acts through at least one feedback path (22 to 27; 35, 36, 26, 27) on the end stage (6) in order to increase the impedance of the output circuit (19).
2. A hearing aid as defined in claim 1, the decoupling means (34) forming a series circuit with the earpiece (15).
3. A hearing aid as defined in claim 1 or claim 2, the signal (UR) that is decoupled from the decoupling means (28, 29; 34;
38) being a voltage that is proportional to the earpiece voltage.
38) being a voltage that is proportional to the earpiece voltage.
4. A hearing aid as defined in one of the claims 1 to 3, the decoupling means being a resistance (28, 29; 34) that is arranged in the output circuit (19).
5. A hearing aid as defined in one of the claims 1 to 4, a component (T1, T2) that is present in the output circuit being used as decoupling means.
6. A hearing aid as defined in one of the claims 1 to 5, the particular current-flow resistor that appears in alternation at two semiconductor components (T1, T2) of the end stage (6) that are conductively switched in push-pull with the ultrasonic frequency being used as the decoupling means.
7. A hearing aid as defined in claim 6, at least one wire (22, 23, 24) of the particular decoupling path (22 to 27) being led from each of the two semiconductor components (T1, T2) to, in each instance, one input pole (39, 40) of an electronic switch (25), the switch (25) being controlled by a switching signal that is dependent on the ultrasonic frequency and connected through an output pole (30) with an input (31) of a differential amplifier (26) in the feedback path.
8. A hearing aid as defined in claim 1 to 7, the signal that is tapped off through the decoupling means (28, 29; 34; 38) being passed to an integrator (4) that is connected with the input (5) of the end stage that operates in switching mode.
9. A hearing aid as defined in one of the claims 1 to 3, the decoupling means being configured as an inductively acting means (38).
10. A hearing aid as defined in one of the claims 1 to 3, the decoupling means being configured as a sampling device (38) that is connected with the coil (16) of the earpiece (15).
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| EP91104449A EP0504460B1 (en) | 1991-03-21 | 1991-03-21 | Hearing aid with a switching amplifier output stage |
| EP91104449.3 | 1991-03-21 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2063512A1 true CA2063512A1 (en) | 1992-09-22 |
Family
ID=8206553
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002063512A Abandoned CA2063512A1 (en) | 1991-03-21 | 1992-03-19 | Hearing aid with an end stage that operates in switching mode |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0504460B1 (en) |
| AT (1) | ATE118132T1 (en) |
| CA (1) | CA2063512A1 (en) |
| DE (1) | DE59104497D1 (en) |
| DK (1) | DK0504460T3 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5815581A (en) * | 1995-10-19 | 1998-09-29 | Mitel Semiconductor, Inc. | Class D hearing aid amplifier with feedback |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5672998A (en) * | 1995-08-09 | 1997-09-30 | Harris Corporation | Class D amplifier and method |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5014016A (en) * | 1989-04-13 | 1991-05-07 | Beltone Electronics Corporation | Switching amplifier |
-
1991
- 1991-03-21 EP EP91104449A patent/EP0504460B1/en not_active Expired - Lifetime
- 1991-03-21 DE DE59104497T patent/DE59104497D1/en not_active Expired - Fee Related
- 1991-03-21 AT AT91104449T patent/ATE118132T1/en not_active IP Right Cessation
- 1991-03-21 DK DK91104449.3T patent/DK0504460T3/en active
-
1992
- 1992-03-19 CA CA002063512A patent/CA2063512A1/en not_active Abandoned
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5815581A (en) * | 1995-10-19 | 1998-09-29 | Mitel Semiconductor, Inc. | Class D hearing aid amplifier with feedback |
Also Published As
| Publication number | Publication date |
|---|---|
| DK0504460T3 (en) | 1995-07-10 |
| EP0504460B1 (en) | 1995-02-01 |
| DE59104497D1 (en) | 1995-03-16 |
| ATE118132T1 (en) | 1995-02-15 |
| EP0504460A1 (en) | 1992-09-23 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Discontinued |