The high efficiency DC-DC conversion equipment of underloading
Technical field
The invention belongs to the electronic circuit technology field, relate to analog integrated circuit, particularly a kind ofly can when underload, realize high efficiency DC-DC transducer, can be used in all kinds of portable type electronic products.
Background technology
The DC-DC transducer is widely used in all kinds of portable products such as mobile phone, panel computer and digital camera as important power management class circuit.Than linear voltage regulator, the switching type power supply managing chip, like the DC-DC transducer, maximum advantage is exactly the efficient height.And in portable use, the height of DC-DC efficient under underload has determined the stand-by time of portable product system to a great extent.Therefore, in recent years, low-power consumption, high efficiency one of the research focus that is designed to for numerous portable use.
The power consumption of DC-DC transducer is generally by conduction loss, and quiescent dissipation three parts of switching loss and chip internal analog circuit are formed.Wherein conduction loss mainly is the energy that conducting resistance consumed that electric current flows through power tube; Increase with the chip load current increases; Switching loss is in each work period; Owing to driving power pipe gate capacitance discharges and recharges the dynamic loss that produces, quiescent dissipation is the consumption of chip internal analog circuit when work, and switching loss and quiescent dissipation are all irrelevant with chip load current size.So chip is when heavy duty, conduction loss is main loss, and when underloading, switching loss and quiescent dissipation have constituted the main loss of transducer.Because the efficient during the portable set standby depends primarily on the power consumption of DC-DC under the underload situation, improve the efficient of DC-DC when underload, just can effectively prolong the battery service time of portable set.
Shown the structured flowchart of the DC/DC buck converter of traditional pulse-width-modulated mode PWM control like Fig. 1, this transducer is made up of error amplification, modulation and power output and feedback and three modules of filtering.Fig. 2 has shown the electrical schematic diagram of this type of DC-DC transducer, and is as shown in Figure 2, and this transducer produces the grid end control signal of power MOS pipe through the PWM comparator; Operating frequency is constant, though can, medium load realize high efficiency when arriving heavy load, under light load condition; Because the operating frequency of pwm pattern immobilizes; Along with reducing of load with the switching loss of frequency dependence, and each analog circuit of chip internal works always, quiescent dissipation does not reduce yet; Therefore cause the light-load efficiency of whole DC-DC transducer extremely low, when using, shortened the battery service time of portable electric appts.
Summary of the invention
The objective of the invention is to deficiency to above-mentioned existing PWM control DC/DC transducer; Provide a kind of underloading high efficiency DC-DC conversion equipment,, reduced the operating frequency of DC-DC transducer with when the underload; Close analog circuit unnecessary in the chip, improve the efficient of DC-DC transducer.
For realizing above-mentioned purpose, comprise error amplifier 4, modulation and power take off 5 and filtering and ultramagnifier 6; This modulation and power take off 5 respectively with the input SW of the output VC of error amplifier 4 and filtering and ultramagnifier 6 in succession, the output FB of this filtering and ultramagnifier 6 is connected to the inverting input N of error amplifier 4, with closed control loop; It is characterized in that:
Said modulation and power take off 5; Have additional upper and lower two power tube detection port; And last pipe detection port HS is connected with pipe underloading detector 1; Under manage detection port LS and be connected with down pipe underloading detector 2, to guarantee that DC-DC all can accurately detect the load current size under various work duty ratios, realize steadily switching;
Said error amplifier 4; Have additional control input end SK; It is connected with underloading high efficiency controller 3, and this underloading high efficiency controller is provided with three inputs and two output ports, and first input end A is connected to the output of pipe underloading detector 1; The second input B is connected to down the output of pipe underloading detector 2; Result with to two underloading detectors judges that comprehensively the 3rd input C is connected to the edge detection port PD of modulation and power take off 5, to extract the switching signal of power tube on off state; The first output D is connected to the dormancy control end ST of modulation and power take off 5; To export the sleep signal SLEEP of whole conversion equipment; The control transformation device quits work when sleep signal SLEEP is effective, and the second output E is connected to the benchmark switching controls end SK of error amplifier 4; With the control dormancy time, improve light-load efficiency.
The high efficiency DC-DC conversion equipment of above-mentioned underloading is characterized in that: said modulation and power take off 5 are made up of PWM comparing unit, driving control unit, last power tube MP1 and following power tube MN1; This driving control unit is provided with three inputs; Be connected respectively to the output of PWM comparing unit, first output of underloading high efficiency controller 3 and the work clock signal OSC of DC-DC; Two outputs are connected respectively to the grid end of power tube MP1 and MN1, with the conducting of power controlling pipe with end.
The high efficiency DC-DC conversion equipment of above-mentioned underloading is characterized in that: the said pipe underloading detector 1 of going up is made up of an average current sampling unit and a comparing unit; The normal phase input end of this comparing unit is connected to going up of modulation and power take off 5 through the average current sampling unit and manages detection port HS; Flow through the electric current of power tube MP1 with detection; Inverting input connects a fixing reference voltage Ref1, is used to set that power tube is light, heavy duty judgement thresholding.
The high efficiency DC-DC conversion equipment of above-mentioned underloading is characterized in that: the said underloading of pipe down detector 2 is made up of an average current sampling unit and a comparing unit; The normal phase input end of this comparing unit is connected to the following pipe detection port LS of modulation and power take off 5 through the average current sampling unit; Flow through the electric current of power tube MN1 with detection; Inverting input connects a fixing reference voltage Ref2, is used to set down that power tube is light, heavy duty judgement thresholding.
The high efficiency DC-DC conversion equipment of above-mentioned underloading is characterized in that: said underloading high efficiency controller 3 is made up of rising edge detecting unit, logic control element and pulse frequency modulated PFM comparing unit; Logic control element is provided with five inputs; Be connected respectively to pipe underloading detector 1, manage the output of underloading detector 2, PFM comparing unit, rising edge detecting unit and the work clock signal OSC of DC-DC down, its two outputs are connected respectively to the benchmark switching controls end SK of error amplification module and the dormancy control end ST of modulation and power take off 5.
The high efficiency DC-DC conversion equipment of above-mentioned underloading is characterized in that: said Logic control module is made up of a counting unit and a dormancy control unit, and Light is to the dormancy control unit for this counting unit output underloading control signal.
The high efficiency DC-DC conversion equipment of above-mentioned underloading is characterized in that: said PFM comparison module is provided with two inputs, and its inverting input is connected to the inverting input of error amplifier 7, and normal phase input end connects a fixing reference voltage Ref5.
The present invention compared with prior art has the following advantages:
(1) the present invention makes DC-DC under various work duty ratios, all can accurately detect the load current size owing to added upper and lower pipe underloading detector, steadily to switch to the underloading pattern, has improved the reliability of chip operation.
(2) the present invention is owing to added underloading high efficiency controller; Make DC-DC when the underloading pattern is worked; Automatic intermittent entering resting state; Off switch pipe and most of analog circuit to be reducing switching loss and quiescent dissipation, and can improve the efficient of DC-DC when underload is worked according to load current size adjustment dormancy time length.
Description of drawings
Fig. 1 is the structured flowchart of the DC/DC conversion equipment of conventional P WM control;
Fig. 2 is the circuit theory diagrams of the DC/DC conversion equipment of conventional P WM control;
Fig. 3 is the structured flowchart of the high efficiency DC-DC conversion equipment of underloading of the present invention;
Fig. 4 is the circuit theory diagrams of the high efficiency DC-DC conversion equipment of underloading of the present invention;
Fig. 5 is the circuit theory diagrams of logic control element in the underloading high efficiency controller among the present invention.
Embodiment
Below in conjunction with accompanying drawing and embodiment the present invention is further described.
With reference to Fig. 3, the high efficiency DC-DC conversion equipment of underloading of the present invention comprises: on manage underloading detector 1, manage underloading detector 2, underloading high efficiency controller 3, error amplifier 4, modulation and power take off 5 and filtering and ultramagnifier 6 down.Wherein, Modulation and power take off 5 are provided with an input, an output, dormancy control end ST, last power tube test side HS, following power tube test side LS and an edge test side PD; This input is connected to the second output E of underloading high efficiency controller 3 through error amplifier 4; Output is connected to the inverting input of error amplifier 4 through filtering and ultramagnifier 6; Last power tube test side HS is connected to the first input end A of underloading high efficiency controller 3 through last pipe underloading detector 1; Following power tube test side LS is connected to the second input B of underloading high efficiency controller 3 through managing underloading detector 2 down, and test side, edge PD is connected to the 3rd input C of underloading high efficiency controller 3, and dormancy control end ST is connected to the first output D of underloading high efficiency controller 3.
The said pipe underloading detector 1 of going up; Constitute by a last average current sampling unit and a last comparing unit HCOMP; As shown in Figure 4; The normal phase input end that should go up comparing unit HCOMP is gone up pipe detection port HS through what the average current sampling unit was connected to modulation and power take off 5, flows through the electric current of power tube MP1, generation sampled voltage signal PS with detection; Inverting input connects a fixing reference voltage Ref1, is used for judging signal PLLD with sampled voltage signal PS to produce the pipe underloading.
The said underloading of pipe down detector 2 is made up of a following average current sampling unit and a following comparing unit LCOMP.The normal phase input end of this time comparing unit LCOMP is connected to the following pipe detection port LS of modulation and power take off 5 through the average current sampling unit; Flow through the electric current of power tube MN1 down with detection; Produce sampled voltage signal NS; Inverting input connects a fixing reference voltage Ref2, is used for judging signal NLLD with sampled voltage signal NS to produce the pipe underloading.
Said underloading high efficiency controller 3; Form by rising edge detecting unit, logic control element and pulse frequency modulated PFM comparing unit; Logic control element is provided with two outputs of five inputs; Five inputs are connected respectively to pipe underloading detector 1, manage the output and the clock signal OSC of underloading detector 2, PFM comparing unit, rising edge detecting unit down; Two outputs are connected respectively to the benchmark switching controls end SK of error amplification module and the dormancy control end ST of modulation and power take off 5; This logic control element comprises a counting unit and a dormancy control unit, connects through underloading control signal light between counting unit and the dormancy control unit; The PFM comparing unit is provided with two inputs, and its inverting input is connected to the inverting input of error amplifier 4, and normal phase input end connects a fixing reference voltage Ref5; With reference to Fig. 5, said Logic control module.
Said error amplifier 4 is provided with two normal phase input ends; First normal phase input end connects fixing reference voltage Ref3, and second normal phase input end connects fixing reference voltage Ref4.
Said modulation and power take off 5 are made up of PWM comparing unit, driving control unit, last power tube MP1 and following power tube MN1; This driving control unit is provided with three inputs; Be connected respectively to the output of PWM comparing unit, the first output D and the clock signal OSC of underloading high efficiency controller 3; Two outputs are connected respectively to the grid end of power tube MP1 and following power tube MN1, with the conducting of power controlling pipe and end; The drain terminal of power tube MP and MN1 links to each other, and is connected to the input SW of filtering and ultramagnifier 6 as the output of modulation and power take off 5; The PWM comparing unit is provided with two inputs, and its normal phase input end is connected to the output of error amplifier 4 as the modulation and the input of power take off 5, and inverting input connects a fixing ramp voltage Ramp.
Said filtering and ultramagnifier 6, by inductance L, capacitor C and two resistance R 1, R2 form; This inductance L is connected with capacitor C and is constituted the LC filter; Be connected in parallel between the output and zero-potential point of modulation and power take off 5; Resistance R 1 be connected between the common port and zero-potential point of inductance L and capacitor C after R2 connects, the common port of resistance R 1 and R2 is connected to the inverting input of error amplifier 4 as the output of said filtering and ultramagnifier 6.
Concrete operation principle of the present invention is:
With reference to Fig. 4, on manage underloading detector 1 and sample through the average current of last average current sampling unit convection current overpower metal-oxide-semiconductor MP1, the current signal that again sampling is obtained is converted into sampled voltage signal PS; Through last comparing unit HCOMP this sampled voltage PS and fixed reference voltage Ref1 are compared then; Owing to this sampled voltage signal PS all along with the increase of load current reduces; So when load current is reduced to certain value; Sampled voltage PS will be higher than reference voltage Ref1, on manage underloading and judge that signal PLLD becomes logic high by logic low, promptly go up the pipe underloading and judge that signal PLLD is effective.The operation principle of managing underloading detector 2 down is identical with the operation principle of last pipe underloading detector 1; Its output lower tube underloading judges that signal NLLD is also through relatively sampled voltage signal NS and fixed reference voltage Ref2 obtain; Promptly when sampled voltage NS is higher than reference voltage Ref2; Under manage underloading and judge that signal NLLD becomes logic high by logic low, this manages underloading at present and judges that signal NLLD is effective.
Since when the DC-DC conversion equipment when working less than 20% little duty ratio; The ON time of last power tube MP1 is very short; The average current that the average current sampling unit can't convection current overpower pipe MP1 is correctly sampled; Cause the pipe underloading that goes up of pipe underloading detector 1 output to judge that signal PLLD can not in time switch to effective status, promptly go up pipe underloading detector 1 and detect error; Otherwise; When the DC-DC conversion equipment when surpassing 80% big space rate work; The ON time of following power tube MN1 is very short, and the average current sampling unit can't correctly be sampled to the average current of power tube MN1 under flowing through, causes the following pipe underloading of pipe underloading detector 2 outputs down to judge that signal NLLD can not in time switch to effective status; Promptly pipe underloading detector 2 detects error down; So design is worked upper and lower two underloading detectors simultaneously among the present invention,, think that then the load current of DC-DC conversion equipment belongs to light load currents as long as the output signal of upper and lower two underloading detectors has one for effective status; Guaranteed that the underloading detector when the DC-DC conversion equipment works in various work duty ratio, all can accurately judge light load currents.
For improving the light load efficiency of DC-DC conversion equipment, the present invention has designed the underloading mode of operation.With reference to Fig. 5, on manage underloading and judge signal PLLD, manage underloading down and judge that signal NLLD, the output signal PDE of rising edge detecting unit and the output signal PFMO of PFM comparator are linked into the logic control element in the underloading high efficiency controller 3 simultaneously; When last pipe underloading is judged signal PLLD or when the pipe underloading judges that signal NLLD is effective down, the counting module of logic control element through wherein is to the output signal PDE counting of rising edge detecting unit; When continuous counter was expired 2N, counting module output Light signal was a logic high, and the DC-DC conversion equipment gets into the underloading mode of operation; Otherwise judge signal PLLD and following pipe underloading when last pipe underloading and judge that signal NLLD is simultaneously invalid; And when counting module is expired N to signal PDE continuous counter number; Counting module output Light signal is a logic low, and the DC-DC conversion equipment withdraws from the underloading mode of operation, and N is any positive integer.
When the DC-DC conversion equipment works in light load mode, logic control element through dormancy control module output reference switching signal HFCTL to error amplifier 4, at this moment; Benchmark switching signal HFCTL is a logic high, and effective normal phase input end of departure amplifier 4 switches to second normal phase input end from its first normal phase input end, simultaneously through the output signal PDE counting of counting module to the rising edge detecting unit; After count value reaches 10, detect upper and lower pipe underloading and judge signal PLLD and NLLD, if one of them of these two underloadings judgement signals becomes effectively; The sleep signal SLEEP of then dormancy control module output transfers logic high to; Be that sleep signal is effective, control whole DC-DC conversion equipment and get into resting state, at this moment; Most operating circuit is closed; When the quiescent current of whole conversion equipment drops to operate as normal thereupon 1/10th, upper and lower two power tubes all end, so the quiescent dissipation of transducer declines to a great extent; Switching loss is zero; Make the overall losses of DC-DC conversion equipment under resting state very little, benchmark switching signal HFCTL switches to logic low simultaneously, and effective normal phase input end of departure amplifier 4 resets to first normal phase input end.
Because when the DC-DC conversion equipment worked in resting state, upper and lower two power tubes all ended, cause the output voltage VO UT of DC-DC conversion equipment to descend, fall is designated as Vf, and the output signal FB of filtering and ultramagnifier 6 also descends thereupon.When the value of FB was lower than the normal phase input end voltage Ref5 of PFM comparing unit, the output signal PFMO of PFM comparing unit switched to logic high by logic low, and control sleep signal SLEEP switches to logic low; Be that sleep signal is invalid, the DC-DC conversion equipment withdraws from resting state, and this moment, all circuit were resumed work; Upper and lower power tube MP1, MN1 alternate conduction; And effective normal phase input end of error amplifier 4 switches to second normal phase input end again, because the reference voltage Ref4 that second normal phase input end is connect is higher than the reference voltage Ref3 that its first normal phase input end is connect; The output voltage VO UT of DC-DC conversion equipment after the DC-DC conversion equipment withdraws from park mode with the rising certain amplitude; Be designated as Vr,, can make this ascensional range Vr through regulating the difference of reference voltage Ref4 and Ref3; Just in time offset output voltage VO UT decline scope Vf when resting state, thereby the mean value of output voltage VO UT is kept when making underload constant.
It is thus clear that the underloading mode of operation that the present invention designed makes the alternation under work and dormancy two states of DC-DC conversion equipment, utilizes the power loss that conversion equipment is extremely low under the resting state to improve the efficient of whole conversion equipment when the underloading mode of operation greatly.
Below only be a preferred example of the present invention, do not constitute, obviously under design of the present invention, can carry out different changes and improvement, but these are all at the row of protection of the present invention its circuit to any restriction of the present invention.