Power output restriction and the power-supply adapter that depends on the voltage modulation of load are providedTechnical field
The present invention is about a kind of power-supply adapter, and more particularly the present invention can provide power output restriction and the power-supply adapter that depends on the voltage modulation of load about a kind of.
Background technology
Fig. 1 is the system block diagrams of the power system of a kind of known portable computer (portable computer).As shown in Figure 1, power-supply adapter (power adapter) 100 is set at and converts AC-input voltage to output dc voltage, and this output dc voltage is used to provide the required power supply of work of portable computer 102.Portable computer 102 inside have battery pack (battery pack) 104 and DC-to-DC converter (DC-DC converter) 106, wherein DC-to-DC converter 106 is set at the needed voltage of internal structure that the direct voltage that power-supply adapter 100 is provided convertsportable computer 102 to, andbattery pack 104 is set at whenportable computer 102 is not powered by powersupply changeover device 100, provides power supply to operate portable computer 102.Generally speakingbattery pack 104 can be made up of a plurality of rechargeable batteries that are connected in series (rechargeable battery), it can be set at whenportable computer 102 is powered by power-supply adapter 100, by battery charger (battery charger) 108 with the output store energy of the power-supply adapter 100 of a part in wherein, and whenportable computer 102 is not powered by powersupply changeover device 100, wherein stored energy is sent to DC-to-DC converter 106 via voltage circuit (voltage rail) 109, makes DC-to-DC converter 106 that the needed voltage of internal structure ofportable computer 102 can be provided whereby.Battery charger 108 is set at the dc voltage drop that power-supply adapter 100 is provided and is pressed into the direct voltage that is suitable for being used for tobattery pack 104 chargings, so thatbattery pack 104 is charged.
Fig. 2 is the circuit block diagram of the power-supply adapter 100 of Fig. 1.As shown in Figure 2, power-supply adapter 100 comprisespower conversion unit 110, and it comprisesbridge rectifier 121,switch 122,Switch Control device 123,transformer 124, and current rectifying and wave filtering circuit 125.Bridge rectifier 121 receives input ac voltage Vin and input ac voltage Vin is converted to the direct voltage (full-waverectified DC voltage) of full-wave rectification.Transformer 124 has primary side winding (primary winding) Np and primary side winding (secondary winding) Ns, wherein primary side winding Np connects withswitch 122 and is set at and store the energy that is received from input ac voltage Vin when switch 122 conductings, and whenswitch 122 ends stored energy is transferred to primary side winding Ns two ends.Current rectifying andwave filtering circuit 125 is made up of rectifier diode Dr11 and filter capacitor Cf11, and it is set at the energy on the primary side winding Ns is carried out rectification and Filtering Processing to produce the output dc voltage Vo that is wanted.In addition, power-supply adapter also comprisesvoltage limiting circuit 126 and current limit circuit 127.Thisvoltage limiting circuit 126 comprises voltage divider (voltage divider), and it is formed and be couple to the output ofpower conversion unit 110 by resistance R 11 and R12, and it is set at generation a part of output voltage (fractional output voltage).Thisvoltage limiting circuit 126 also comprises voltage limit amplifier (voltage-limiting amplifier) 132, it is with voltage divider (R11, R12) the part output voltage that is provided and first reference voltage Vref 11 compare, and produce error controling signal according to result relatively.This error controling signal is sent toSwitch Control device 123 viaoptical coupler 128, so thatSwitch Control device 123 is adjusted the switching duty cycle (switching duty cycle) ofswitch 122 according to error controling signal, thereby the output voltage V o ofpower conversion unit 110 is limited on the predetermined value.Thiscurrent limit circuit 127 comprises current sensing resistor Rs11, it is arranged on the electric current return path (current returnpath) ofpower conversion unit 110, it is set at when the output current ofpower conversion unit 110 is flowed through current sensing resistor Rs11, produces the sensing voltage (sensedvoltage) that is directly proportional with output current at current sensing resistor Rs11 two ends.This sensing voltage is couple to the inverting input (inverting input terminal) of trsanscondutance amplifier (transconductance amplifier) 133, and the in-phase input end of trsanscondutance amplifier 133 (non-inverting input terminal) receives second reference voltage Vref 12, (R13 R14) produces and is directly proportional with maximum current (maximum current) this second reference voltage Vref 12 via the voltage divider that is couple to first reference voltage Vref 11.Trsanscondutance amplifier 133 compares the sensing voltage Vs and second reference voltage Vref 12, judges whereby whether the output current ofpower conversion unit 110 reaches maximum current.If the output current ofpower conversion unit 110 reaches maximum current,trsanscondutance amplifier 133 can produce over-current detection signal (overcurrent detection signal).This over-current detection signal is sent toSwitch Control device 123 viaoptical coupler 128, closes the situation generation of avoiding overcurrent at this maximum current so as to makingSwitch Control device 123 close with the output current of restrictionpower conversion unit 110.
Generally speaking the known power-supply adapter 100 that is used for portable computer is a kind of power-supply adapter of deciding voltage (constant voltage).Because the output voltage of power-supply adapter 100 is fixed, the output current of power-supply adapter 100 just can determine its power output.According to the constant voltage characteristic of power-supply adapter 100, the output voltage of power-supply adapter 100 for fixing situation under, the output current of power-supply adapter 100 can continue to rise.The power output increase that the output current of power-supply adapter 100 rises and represented power-supply adapter 100.If the output current of power-supply adapter 100 has surpassed maximum current, then can cause the situation of overpower (overpower) to take place.In this case, overheated problem takes place in power-supply adapter 100 easily, and then reduces the useful life of power-supply adapter 100.
In addition, when power-supply adapter 100 via DC-to-DC converter 106 during toportable computer 102 power supply, power-supply adapter 100 also can charge tobattery pack 104 viabattery charger 108 simultaneously.Whenbattery pack 104 inside during the electric energy of storage compartment, 104 smaller charging currents of needs of battery pack are come its charging.The load current (load current) that the charging current ofbattery pack 104 has reduced to represent power-supply adapter 100 to be sent tobattery pack 104 reduces, that is the output voltage ofbattery pack 104 must rise.Yet the output voltage of known as previously mentioned power-supply adapter 100 all is fixed usually.In this case, can produce sizable power loss (power loss) onbattery charger 108 and DC-to-DC converter 106, and reduce the conversion efficiency (conversion efficiency) ofbattery charger 108 and DC-to-DC converter 106.
Comprehensive the above, if the output voltage of power-supply adapter 100 can be come modulation according to load for the demand of load current adjustment, and make that power-supply adapter 100 can be in the power output of restriction power-supply adapter 100 when output current reaches threshold current, just can solve the conversion efficiency that power-supply adapter 100 overheated problem takes place easily and promotesbattery charger 108 and DC-to-DC converter 106, reduce the power loss thatbattery charger 108 and DC-to-DC converter 106 inside are produced simultaneously.
Therefore need to propose a kind of power-supply adapter, the power output that its function that power output restriction is provided reaches threshold time limit system power-supply adapter with the output current when power-supply adapter is in a predetermined value, and can come its output voltage of modulation according to the current controling signal from load end.
Summary of the invention
The object of the present invention is to provide a kind of power-supply adapter, when it can reach threshold value at the output current when power-supply adapter power output is limited on the predetermined value.
Another object of the present invention is to provide a kind of power-supply adapter, it can be accepted the current controling signal that transmitted by load end and come its output voltage of modulation according to current controling signal.
According to a preferred embodiment of the invention, it provides a kind of power-supply adapter, and it comprises power conversion unit, have ON-OFF control circuit, power conversion unit is set will import power supply, for example AC power, convert out-put supply to, DC power supply for example is to provide power supply to load; Voltage limiting circuit is couple to the output of this power conversion unit, and it is set at by this ON-OFF control circuit the output voltage of this power conversion unit is limited in one first predetermined value; And Power Limitation circuit, be couple to the output of this power conversion unit, it is set at when the output current of this power conversion unit reaches threshold current, by this ON-OFF control circuit with the product limit of the output voltage of this power conversion unit and output current in one second predetermined value.
According to described power-supply adapter, wherein this voltage limiting circuit is couple to the voltage output end of this power conversion unit.
According to described power-supply adapter, wherein this voltage limiting circuit comprises the voltage limit amplifier, it is set at the output voltage of this power conversion unit and first reference voltage is compared, and send error controling signal to this ON-OFF control circuit according to result relatively, thereby the output voltage of this power conversion unit is limited in this first predetermined value by this ON-OFF control circuit.
According to described power-supply adapter, wherein this voltage limiting circuit is set at reception by current controling signal that load transmitted, and send load current according to current controling signal and adjust signal, thereby come the output voltage of this power conversion unit of modulation by this ON-OFF control circuit to this ON-OFF control circuit.
According to described power-supply adapter, wherein this Power Limitation circuit comprises current sensing device, in order to detect the output current of this power conversion unit, and Power Limitation amplifier, it is set at the voltage of the output current that will represent this current sensing device to detect and represents second reference voltage of this threshold current to compare, and when the output current of this power conversion unit reaches this threshold current, send power limit signal to this ON-OFF control circuit, thereby the power output of this power conversion unit is limited in this second predetermined value by this ON-OFF control circuit.
According to described power-supply adapter, wherein this current sensing device is made up of resistance.
According to described power-supply adapter, also comprise current limit circuit, it comprises trsanscondutance amplifier, in order to the voltage that will represent the output current that this current sensing device detects with represent the 3rd reference voltage of maximum current to compare, and when the output current of this power conversion unit reaches this maximum current, send over-current detection signal to this ON-OFF control circuit, thereby the output current of this power conversion unit is limited in this maximum current by this ON-OFF control circuit.
The present invention also provides a kind of power-supply adapter, and it comprises: power conversion unit, have ON-OFF control circuit, and power conversion unit is set at and becomes out-put supply to offer load the input power source conversion; Voltage limiting circuit is couple to the output of this power conversion unit, and it is set at by this ON-OFF control circuit the output voltage of this power conversion unit is limited in one first predetermined value; And Power Limitation circuit, be couple to the output of this power conversion unit, it is set at when the output current of this power conversion unit reaches threshold current, by this ON-OFF control circuit with the product limit of the output voltage of this power conversion unit and output current in one second predetermined value; Wherein, this voltage limiting circuit is set at reception by current controling signal that load transmitted, and send load current according to current controling signal and adjust signal, thereby come the output voltage of this power conversion unit of modulation by this ON-OFF control circuit to this ON-OFF control circuit.
According to described power-supply adapter, wherein this voltage limiting circuit comprises the voltage limit amplifier, it is set at the output voltage of this power conversion unit and first reference voltage is compared, and send error controling signal to this ON-OFF control circuit according to result relatively, thereby the output voltage of this power conversion unit is limited in this first predetermined value by this ON-OFF control circuit.
According to described power-supply adapter, wherein this Power Limitation circuit comprises current sensing device, in order to detect the output current of this power conversion unit, and Power Limitation amplifier, it is set at the voltage of representing the output current that this current sensing device detects and represents second reference voltage of this threshold current to compare, and when the output current of this power conversion unit reaches this threshold current, send power limit signal to this ON-OFF control circuit, thereby the power output of this power conversion unit is limited in this second predetermined value by this ON-OFF control circuit.
According to described power-supply adapter, also comprise current limit circuit, it comprises trsanscondutance amplifier, in order to the voltage that will represent the output current that this current sensing device detects with represent the 3rd reference voltage of maximum current to compare, and when the output current of this power conversion unit reaches this maximum current, send over-current detection signal to this ON-OFF control circuit, thereby the output current of this power conversion unit is limited in this maximum current by this ON-OFF control circuit.
The present invention also provides a kind of power-supply adapter, and it comprises: power conversion unit, have ON-OFF control circuit, and power conversion unit is set at and becomes out-put supply to offer load the input power source conversion; Voltage limiting circuit is received the output of this power conversion unit, and it is set at by this ON-OFF control circuit the output voltage of this power conversion unit is limited in one first predetermined value; The Power Limitation circuit, be couple to the output of this power conversion unit, it is set at when the output current of this power conversion unit reaches threshold current, limits the product limit of the output voltage of this power conversion unit and output current in one second predetermined value by this ON-OFF control circuit; And current limit circuit, being couple to the output of this power conversion unit, it is set at when the output current of this power conversion unit reaches maximum current, and the output current that limits this power conversion unit by this ON-OFF control circuit is at this maximum current; Wherein, this voltage limiting circuit is set at reception by current controling signal that load transmitted, and send load current according to current controling signal and adjust signal, thereby come the output voltage of this power conversion unit of modulation by this ON-OFF control circuit to this ON-OFF control circuit.
According to described power-supply adapter, wherein this voltage limiting circuit comprises the voltage limit amplifier, it is set at the output voltage of this power conversion unit and first reference voltage is compared, and send error controling signal to this ON-OFF control circuit according to comparative result, thereby the output voltage of this power conversion unit is limited in this first predetermined value by this ON-OFF control circuit.
According to described power-supply adapter, wherein this Power Limitation circuit comprises current sensing device, in order to detect the output current of this power conversion unit, and Power Limitation amplifier, it is set at the voltage of the output current that will represent this current sensing device to detect and represents second reference voltage of this threshold current to compare, and when the output current of this power conversion unit reaches this threshold current, send power limit signal to this ON-OFF control circuit, thereby the power output of this power conversion unit is limited in this second predetermined value by this ON-OFF control circuit.
According to described power-supply adapter, wherein this current limit circuit comprises trsanscondutance amplifier, in order to the voltage that will represent the output current that this current sensing device detects with represent the 3rd reference voltage of maximum current to compare, and when the output current of this power conversion unit reaches this maximum current, send over-current detection signal to this ON-OFF control circuit, thereby the output current of this power conversion unit is limited in this maximum current by this ON-OFF control circuit.
The power-supply adapter that power output restriction and the voltage modulation that depends on load be provided of the present invention is the effective power output of managing electrical power adapter of its restricting circuits compared with prior art, avoiding producing overpowering situation because output current is excessive takes place, and the control that can be depending on load end comes the output voltage of modulation power-supply adapter, is provided to the load current of load end with adjustment.Because power-supply adapter of the present invention can come elasticity modulation output voltage and load current according to the demand of load end, make the loss of power of load end significantly reduce and power-efficient significantly promotes, and the line design complexity and the manufacturing cost of load end are reduced.
Advantage of the present invention and feature by following embodiment and in conjunction with the detailed description of following accompanying drawing, can access more deep understanding.
Description of drawings
Fig. 1 shows a kind of system block diagrams of power system of known portable computer;
Fig. 2 is the circuit block diagram of the power-supply adapter of Fig. 1;
Fig. 3 shows the system block diagrams of power system of the portable computer of the preferred embodiments of the present invention; And
Fig. 4 is the circuit block diagram of the power-supply adapter of Fig. 3.
Wherein, description of reference numerals is as follows:
Fig. 1:
100: power-supply adapter
102: portable computer
104: battery pack
106: DC-to-DC converter
108: battery charger
109: voltage circuit
Fig. 2:
110: power conversion unit
121: bridge rectifier
122: switch
123: the Switch Control device
124: transformer
125: current rectifying and wave filtering circuit
126: voltage limiting circuit
127: current limit circuit
128: optical coupler
132: the voltage limit amplifier
133: trsanscondutance amplifier
Rs11: current sensing resistor
Fig. 3:
300: power-supply adapter
302: portable computer
304: battery pack
306: DC-to-DC converter
308: battery manager
309: voltage circuit
Fig. 4:
310: power conversion unit
321: bridge rectifier
322: switch
323: the Switch Control device
324: transformer
325: current rectifying and wave filtering circuit
326: voltage limiting circuit
327: the Power Limitation circuit
328: optical coupler
329: current limit circuit
332: the voltage limit amplifier
333: the Power Limitation amplifier
334: trsanscondutance amplifier
Rs31: current sensing resistor
Embodiment
The preferred embodiment that embodies feature of the present invention and advantage will be described in detail in the explanation of back.Be understood that the present invention can have various variations on different embodiment, it does not depart from the scope of the present invention, and explanation wherein and accompanying drawing be when explaining usefulness in itself, but not in order to restriction the present invention.
The preferred embodiments of the present invention are presented among Fig. 3.As shown in Figure 3, power-supply adapter (poweradapter) 300 is set at and converts AC-input voltage to output dc voltage, and this output dc voltage is used to provide the required power supply of work of portable computer 302.Portable computer 302 inside have battery pack (battery pack) 304 and DC-to-DC converter (DC-DC converter) 306, wherein DC-to-DC converter 306 is set at the needed voltage of internal structure that the direct voltage that power-supply adapter 300 is provided converts portable computer 302 to, and battery pack 304 is to be set at when portable computer 302 is not powered by power supply changeover device 300, provides power supply to move portable computer 302.Generally speaking battery pack 304 can be made up of a plurality of rechargeable batteries that are connected in series (rechargeable battery), it can be set at when portable computer is powered by power-supply adapter, with the output store energy of the power-supply adapter 300 of a part therein, and when portable computer 302 is not powered by power supply changeover device 300, wherein stored energy is sent to DC-to-DC converter 306 via voltage circuit (voltage rail) 309, makes DC-to-DC converter 306 that the needed voltage of internal structure of portable computer 302 can be provided whereby.Battery manager (battery management controller) 308 is set at the relevant informations such as battery temperature, cell voltage, residual capacity, charging interval, charging voltage and charging current of monitoring battery group 304; and provide overcurrent protection (overcurrent protection), overvoltage protection (overvoltage protection) to give battery pack 304, with the charging operations and the protection battery pack 304 of control battery pack 304 with not enough voltage protection protective effects such as (under-voltage protection).
Fig. 4 is the circuit block diagram of the power-supply adapter 300 of Fig. 3.As shown in Figure 4, power-supply adapter 300 comprises power conversion unit 310, and it comprises bridge rectifier 321, switch 322, Switch Control device 323, transformer 324, and current rectifying and wave filtering circuit 325.Bridge rectifier 321 receives input ac voltage Vin and this input ac voltage is converted to the direct voltage (full-waverectified DC voltage) of full-wave rectification.Transformer 324 has primary side winding (primary winding) Np and primary side winding (secondary winding) Ns, wherein primary side winding Np connects with switch 322 and is set at and store the energy that is received from input ac voltage Vin when switch 322 conductings, and when switch 322 ends stored energy is transferred to primary side winding Ns two ends.Current rectifying and wave filtering circuit 325 is made up of rectifier diode Dr31 and filter capacitor Cf31, and it is set at the energy on the primary side winding Ns is carried out rectification and Filtering Processing to produce the output dc voltage Vo that is wanted.It is noted that power-supply adapter shown in Figure 4 300 is that configuration and setting is flyback topological structure (flyback topology), yet power-supply adapter of the present invention can adopt the power supply changeover device topology of other kind to finish, for example forward topological structure (forward topology), asymmetrical half-bridge topological structure (asymmetrical half-bridgetopology) or the like.In addition, power-supply adapter also comprises voltage limiting circuit 326 and Power Limitation circuit 327.This voltage limiting circuit 326 is couple to the output of power conversion unit 310 and comprises voltage divider, and it is formed with R36 and be set at by resistance R 35 produces a part output voltage (fractional output voltage).This voltage limiting circuit 326 also comprises voltage divider, and it is made up of with R42 resistance R 41 and is couple to first reference voltage Vref 31.(R41 R42) is set at and is used for producing a part of first reference voltage V voltage dividerIDVoltage limiting circuit 326 also comprises voltage limit amplifier (voltage-limiting amplifier) 332, and it is with voltage divider (R35, part output voltage that R36) is provided and voltage divider (R41, the part first reference voltage V that R42) is providedIDCompare, and produce error controling signal according to result relatively.This error controling signal is sent to Switch Control device 323 via optical coupler 328, so that Switch Control device 323 is adjusted the switching duty cycle (switching duty cycle) of switch 322 according to error controling signal, thereby the output voltage V o of power conversion unit 310 is limited on the predetermined value.
Power Limitation circuit 327 is couple to the output of power conversion unit 310, and it comprises current sensing resistor Rs31, resistance R 31, R32, R33, R34, and Power Limitation amplifier (power-limitingamplifier) 333.Resistance R 31 is couple between circuit node N31 and the N32, and resistance R 32 is couple between positive voltage output end and the node N32.Because circuit node N31 and the circuit node N33 that is positioned on the electric current return path of power conversion unit 310 are connected to same ground connection reference edge (groundreference), it is identical with voltage on the node N33 that voltage on the node N31 can be considered, on circuit node N32, produce a current signal whereby, its voltage by current sense resistor Rs31 two ends adds that a small positive bias is formed, and represents the output current of power conversion unit 310.This current signal is couple to the reverse input end of Power Limitation amplifier.In addition, second reference voltage Vref 32 is couple to the in-phase input end of Power Limitation amplifier 333, and (R33 R34) produces and is directly proportional with threshold current (threshold current) via the voltage divider that is couple to first reference voltage Vref 31 for it.Therefore can produce the signal of representing electric current on node N35, it is made up of second reference voltage Vref 32.Power Limitation amplifier 333 is relatively represented the signal of output current of power conversion unit 310 and the signal of representing threshold current, judges whereby whether the output current of power conversion unit 310 reaches threshold current.If the output current of power conversion unit 310 reaches threshold current, Power Limitation amplifier 333 can send power limit signal and be sent to Switch Control device 323 via optical coupler 328, so that Switch Control device 323 is limited in a predetermined value with the output voltage of power conversion unit 310 and the product of output current (product).Therefore, when Power Limitation circuit 327 just can reach threshold current at the output current when power conversion unit 310, driving switch switch controller 323 was limited in a predetermined value with the power output of power conversion unit 310, took place to avoid overpowering situation.
In addition; see also Fig. 3;battery manager 308 couples withbattery pack 304, so that relevant informations such as the battery temperature of monitoringbattery group 304, cell voltage, residual capacity, charging interval, charging voltage and charging current, and provide protective effect to battery pack 304.Battery manager 308 can be set at according to the cell voltage that is measured in addition, sends control signal Icontrol and gives power-supply adapter 300.This current controling signal Icontrol is current signal and the reverse input end that is coupled to thevoltage limit amplifier 332 in thevoltage limiting circuit 326, as shown in Figure 4, make the output ofvoltage limit amplifier 332 to react to control signal Icontrol, and then send load current and adjust the output voltage that signal (load currentregulation signal) comes driving switch switch controller modulationpower conversion unit 310, adjust the charging current that offersbattery pack 304 whereby.In addition, the part first reference voltage V shown in Figure 4IDAlso can be sent tobattery manager 308, makebattery manager 308 can understand the output power value of powersupply changeover device 300 whereby, as shown in Figure 3 via this input/output interface.
In addition, power-supply adapter 300 optionally comprises current limit circuit 329, and it is made up of current sensing resistor Rs31 and trsanscondutance amplifier 334.Current sensing resistor Rs31 is arranged on the electric current return path of power conversion unit 310, it is set at when the output current of power conversion unit 310 is flowed through current sensing resistor Rs31, produces the sensing voltage (sensed voltage) that is directly proportional with output current at current sensing resistor Rs31 two ends.This sensing voltage is couple to the inverting input of trsanscondutance amplifier 334, and the in-phase input end of trsanscondutance amplifier 334 receives the 3rd reference voltage Vref 33, (R37 R38) produces and is directly proportional with maximum current (maximumcurrent) via the voltage divider that is couple to first reference voltage Vref 31 for it.Trsanscondutance amplifier 334 compares sensing voltage and the 3rd reference voltage Vref 33, judges whereby whether the output current of power conversion unit 310 reaches maximum current.If the output current of power conversion unit 310 reaches maximum current, trsanscondutance amplifier 334 can produce over-current detection signal (overcurrent detection signal).This over-current detection signal is sent to Switch Control device 323 via optical coupler 328, so that the output current of Switch Control device 323 restriction power conversion units 310 takes place with the situation of avoiding overcurrent at this maximum current.
Comprehensive the above, the present invention proposes a kind of power-supply adapter, its configuration and setting is for when output current reaches threshold current, the power output of restriction power-supply adapter is in a predetermined value, and the Switch Control device that the current controling signal that controller sent that can receive load end (battery pack) comes the driving power adapter to be finishing the modulation of output voltage, and then adjusts the load current (offering the charging current of battery pack) that is provided to load end.Power-supply adapter of the present invention is compared as can be known with the known power-supply adapter of Fig. 1, the Power Limitation circuit of institute of the present invention specific implementation is the power output of managing electrical power adapter effectively, avoiding producing overpowering situation because output current is excessive takes place, and the control that can be depending on load end comes the output voltage of modulation power-supply adapter, is provided to the load current of load end with adjustment.Clearly, because power-supply adapter of the present invention can come elasticity modulation output voltage and load current according to the demand of load end, make the loss of power of load end significantly reduce and power-efficient significantly promotes, and the line design complexity and the manufacturing cost of load end are reduced.
The present invention can carry out various variations and modification by those skilled in the art, yet does not break away from the scope of claims institute desire protection.