CN103391000B - Controlled in Current Mode and Based for DC DC converters - Google Patents

Abstract

A kind of DC DC converters (100) include current control level (110), and the current control level is configured as the output voltage based on the DC DC converters (100), input voltage and reference voltage and provides threshold value.Turn-off time controller (130) can be configured as receiving the threshold value and control the turn-off time (TOFF) of the DC DC converters (100) based on the threshold value, so that the peak point current that the turn-off time produces with the DC DC converters (100) is inversely proportional.

Description

Controlled in Current Mode and Based for DC-DC converter

The cross reference of related application

This application claims entitled " the CURRENT MODE CONTROL WITH PEAK submitted on May 11st, 2012 The CURRENT DEPENDENT VARIABLE OFF-TIMEAND AUTOMATIC PULSE SKIPPING " U.S. is temporarily special The rights and interests of profit application 61/646,141, the provisional application is herein incorporated with it entirely through reference.

Technical field

This disclosure relates to a kind of system and method for the Controlled in Current Mode and Based for providing DC-DC converter.

Background technology

Voltage changer such as DC-DC converter has two kinds of forms.When input voltage will carry out voltage by converter When being incremented by, using boosting or incremental structure.When input voltage needs to be decremented to low voltage by converter, become using decompression Parallel operation.Therefore, buck converter is DC-DC converter of successively decreasing.It, which designs to be similar to, is incremented by booster converter, and as boosting becomes Like that, it is the switched-mode power supply using switch (such as transistor and diode), inductor and capacitor to parallel operation.Switch becomes Parallel operation can be relatively efficient (such as being 95% or higher for integrated circuit), and this causes them to be applied to for example By principal voltage (such as the 12-24V in 12V, laptop computer in desktop computer) the conversion reduction in computer everywhere The tasks such as the 0.8-1.8 volts needed for reason device.

The subject matter for the induction type DC-DC converter run with constant switching frequency is it under underloading with low electric power Efficiency is run, and this is due to height (constant) switching loss for depending primarily on switching frequency.In order to overcome the problem, designer The switch periods quantity under underloading is reduced using dancing mode or pulse string mode.The problem of these operator schemes is except it Produced in output outside high ripple voltage, they also need to extra detection and control circuit.

The content of the invention

In one example, current control level can be configured as the output voltage based on DC-DC converter, input voltage and Reference voltage provides threshold value.Turn-off time controller can be configured as receiving the threshold value and control the DC-DC based on the threshold value The turn-off time (TOFF) of converter so that the peak point current (IPEAK) that produces of the turn-off time and DC-DC converter into Inverse ratio.

In another example, a kind of method is included in the first input end offer threshold value of comparator to limit DC-DC conversion The turn-off time of device, so that the peak point current that the turn-off time produces with the DC-DC converter is inversely proportional.This method includes Ramp signal is produced in the second input of the comparator, the wherein ramp input is compared by the comparator with the threshold value Compared with so as to control the switching frequency of the DC-DC converter based on the turn-off time.

In another example, a kind of DC-DC converter includes current control level, and the current control level is configured as producing threshold Value is to set the turn-off time of DC-DC converter, so that the peak point current that the turn-off time produces with the DC-DC converter It is inversely proportional.The DC-DC converter may include TOFF controllers, and the TOFF controllers are configured as monitoring the threshold value and produce output To control the switching frequency of the DC-DC converter.Ramp generator can be configured to supply ramp signal to the TOFF controllers, Wherein the ramp signal is compared by the TOFF controllers with the threshold value, so that dynamic adjusts the switch of the DC-DC converter Frequency.

Brief description of the drawings

Fig. 1 shows the example of DC-DC converter, and it uses Controlled in Current Mode and Based dynamically to adjust the operation mould of the converter Formula.

Fig. 2 shows to provide the exemplary DC/DC converter circuits of the Controlled in Current Mode and Based of the converter.

Fig. 3 shows to describe the exemplary signal figure of the operator scheme of DC-DC converter.

Fig. 4 shows to provide the illustrative methods of the Controlled in Current Mode and Based of DC/DC converters.

Embodiment

Fig. 1 shows an example of DC-DC converter 100, and it uses Controlled in Current Mode and Based dynamically to adjust the conversion The operator scheme of device.Including being configured as the output voltage based on the DC-DC converter, (VFB, it is base to DC-DC converter 100 In the feedback of output voltage), input voltage (VIN) and reference voltage (VREF) current control level 110 of threshold value is provided.As schemed Show, VREF and VFB are provided as input to the input stage 120 of driving current controlled stage 120.Turn-off time (TOFF) controller 130 can be configured as receiving the threshold value and control the turn-off time of the DC-DC converter 100 based on the threshold value, so that The peak point current (IPEAK) that the turn-off time produces with the DC-DC converter is inversely proportional.The threshold value can be based on the peak value detected Electric current and be dynamically adjusted.This, which is dynamically adjusted, enables the DC-DC converter 100 based on load current in different operations Operated under pattern (such as without switching mode, variable frequency switching mode, peak frequency switching mode).Ramp generator 140 is carried TOFF controllers are given for ramp signal, it can also be enabled or disabled according to the load state detected.Therefore, the threshold value And/or ramp signal can change according to the load current of the DC-DC converter 100 detected.

If for example, detecting very light load, ramp generator 140 (can for example pass through semiconductor device with disabled Part) so that the TOFF controllers 130 disable the electric current in the output end generation of DC-DC converter 100, and which increase the conversion The efficiency of device.For medium or intermediate loads, the ramp signal from ramp generator 140 causes the TOFF together with the threshold value Controller 130 enters variable frequency operator scheme, and wherein switching frequency changed based on the load current detected, this so that lead The threshold value is caused to change.For very heavy current loading, the threshold value variable is fixed, so that the DC-DC is converted Device 100 enters peak frequency and switched operating mode.As illustrated, the output from TOFF controllers 130 can be fed into TON Controller 150, it also helps to set the peak point current in DC-DC converter 100.TON controllers 150 control power switch circuit Power switch and inductor current in 160.Power switch circuit 160 by by current switching into inductor (such as FIG. 2 below It is shown) control the VOUT of DC-DC converter 100.Independent current control to TON controllers 150 is inputted by IPEAK controllers 170 are provided, and the IPEAK controllers 170 are operated based on ISETmin signals, and the ISETmin signals by input stage 120 with being driven I (contol) signal that dynamic current source 180 is produced is added.

In one example, current control level 110 may include that set the control electric current of DC-DC converter 100 first is brilliant Body pipe and the second transistor for setting threshold current for producing the threshold value, wherein these transistors described herein and other Circuit will be illustrated in following Fig. 2.Current source 180 can be configured to it is in parallel with control electric current, with set DC-DC conversion The minimum current ISETmin of device 100.Minimum current ISETmin can be according to below equation and minimum peak current value IPEAKmin is related：

IPEAKmin ≈ ISETmin*N,

The power switch that wherein N represents the electric current in the inductor of switching DC-DC converter 100 becomes with sensing the DC-DC Control electric current I (control) in parallel operation and the size of current relation between the sense switch of minimum current ISETmin sums.

As described above, ramp generator 140 provides ramp signal to TOFF controllers 130, to facilitate adjustment DC-DC conversion The switching frequency of device 100.TOFF controllers 130 may include comparator, and the comparator connects on the first input end of the comparator Receive the threshold value and receive the ramp signal from ramp generator 140 on the second input of the comparator to be TOFF Controller 130 provides comparator output, switch frequency of the comparator output control DC-DC converter under different loads situation Rate.It can be comprised in ramp generator 140 with electric current I (toff) semiconductor devices connected to enable pulse-skip pattern, In this mode, when the voltage at the semiconductor devices two ends is less than the threshold value, the output current is disabled.It can be semiconductor device Part provides various structures.For example, the semiconductor devices can be implemented as diode, such as semiconductor diode or diode connection Transistor npn npn.In other examples, the diode can be for example solid-state diode or can control electric current flow in or out The other devices of ramp generator.

Current source may be provided in ramp generator 140, and the current source is configured to connect to set with semiconductor devices TOFF electric currents I (toff) is determined, so that minimum turn-off time TOFF (min) of convenient adjustment DC-DC converter 100.Capacitor It can be used in series with semiconductor devices and the second current source, to facilitate the minimum turn-off time TOFF of adjustment DC-DC converter 100 (min).Controlled in Current Mode and Based and the dynamic mode switching of DC-DC converter 100 as described herein can be substantially applied to appoint The converter for type of anticipating.For example, DC-DC converter 100 can be configured as incremental structure or reduction structure.

It should be noted that example described herein can be provided by different circuit implementations, it includes being discrete Or integrated numeral or simulation embodiment.For example, resistance/capacitance wave filter can be used in one example, or at it SCF can be used in its example.Similarly, in some instances, trsanscondutance amplifier can be used, and is shown other Voltage-controlled operational amplifier can be used in example.Field-effect transistor can be used in some cases, and in other cases Junction transistor or diode can be used.Some control units are used as discrete embodiment, such as by reference signal and control The comparator that signal processed is compared, and in other examples, can use and be operated and passed through by processor instruction The controller that DA and AD converters exchange data carrys out monitoring criteria voltage and produces control signal in DC-DC converter 100.

Fig. 2 shows a kind of exemplary DC-DC converter circuit 200 that Controlled in Current Mode and Based is provided for converter.Circuit 200 include input stage 210, the input stage include monitoring input V-REF and V-FEEDBACK (identical with the VFB in Fig. 1) and The trsanscondutance amplifier 212 that its output end is filtered by resistor Rcomp and capacitor Ccomp respectively.Input stage 210 drives Current control level 214, the current control level includes the first transistor M1 and resistor R1 to set the control electricity of DC-DC converter Stream, and including second transistor M2 and resistor R2 to set the threshold current of the converter, threshold current setting resistance The threshold voltage at device R3 two ends.The threshold voltage at R3 two ends is applied to the input of TOFF comparators 216, and wherein TOFF compares The threshold voltage that device refers to the TOFF controllers 130 in Fig. 1 and R3 two ends refers to threshold voltage in Fig. 1.Ramp generator 220 provide other inputs to TOFF comparators 216.Ramp generator 220 may include I (toff) current source, under underloading Diode D, the capacitor Ctoff of the slope of control ramp signal and the transistor 222 for resetting ramp generator of operation.

As further example, reference marker 250 represent the diode D in ramp generator 220 some are replaceable Structure.In this illustration, interchangeable example arrangement includes being configured and operated brilliant for the diode connecting-type of diode Body pipe.

Output feeding TON controllers (TON-FF) 224 (such as bistable state multi-harmonic-oscillations from TOFF comparators 216 Device), itself and then driving power on-off circuit 230.Another input to TON controllers 224 is (such as right from IPEAK comparators 234 IPEAK controllers 170 that should be in Fig. 1) receive.IPEAK comparators 234 are received and inductor electricity from power switch circuit 230 The relevant input of stream and it is designated I (control) control electric current with representative and is designated ISETmin fixed current source Current related other inputs of (with reference to the current source 180 in Fig. 1) sum.Power switch circuit 230 may include to be driven by grid Inductor L, power switch and rectifier that dynamic device 240 drives.Power switch circuit 230 may also comprise input capacitor Cin, bear Carry capacitor Cload and zero (ZERO) comparator 244.

As illustrated, power switch circuit 230 receives VIN and switches by inductor L electric current to produce VOUT.Input Voltage VIN also may be provided to ramp generator and threshold resistance device R3 one end.VIN is inputted also by offer current source The sense switch of ISETmin and M1 and R1 current control paths and be sensed.

In one aspect, circuit 200 can control the turn-off time of DC-DC converter, so that being identified by increase By transistor M2 and resistor R2, the extra current controlled stage that is controlled by the output of amplifier 212 cause TOFF~1/ IPEAK.The drain current of the extra level limits the threshold voltage of the TOFF comparators 216 at R3 two ends.Current source ISET (min) with In parallel by M1/R1 control electric current, peak point current is defined to IPEAK=[I (control)+ISET (MIN)] * N by it, its Power limitation switchs the current ratio between sense switch.Diode D can be with TOFF ramp generators 220 current source I (toff) it is arranged in series.Under full load conditions, minimum TOFF may be expressed as：TOFF (min)=(C (toff)/I (toff)) * (VIN*R2/(R2+R3)).For underloading situation, M2 drain current is because R3 two ends have less voltage drop and reduce.Cause This, the voltage on the inverting input of TOFF comparators 216 rises, and this causes TOFF to raise, and hence in so that DC-DC is converted The switching frequency of device reduces.

In the case where underloading or zero are carried, when the voltage drop at R3 two ends is less than diode D forward voltage, TOFF comparators 216 Non-inverting input no longer can reach reference voltage on inverting input, this causes TOFF to approach infinity.Whole system Therefore wait in this condition or " pulse-skip ", until the output voltage of amplifier 212 is high enough to so that R3 two ends Voltage and the forward voltage at diode D two ends match.As described above, diode D can have numerous embodiments, it can To be the MOS transistor of real junction diode or PCH/NCH diode operations, such as shown in 250.

Fig. 3 shows to describe exemplary signal Figure 30 0 of the operator scheme of DC-DC converter.Figure 30 0 shows at chart 310 Go out the inductor current of DC-DC converter and the positive input of Fig. 2 TOFF comparators 216 is shown at chart 320 and born defeated Enter.Under the conditions of underloading, because positive input no longer reaches the negative input of TOFF comparators, the system is automatically stopped switching (jump Pattern).Under intermediate load condition, TOFF comparator thresholds voltage (negative input of TOFF comparators) follows inductor current, It ends at variable frequency (such as voltage-controlled oscillator (VCO)) operation.Under fully loaded transportation condition, negative input stops movement, So that TOFF comparators are run with fixed threshold voltage now, it ends to fix maximum frequency operation.

In view of aforementioned structure and function described above feature, a kind of illustrative methods are better understood with reference to Fig. 4.Though So for the simplicity of explanation, this method is shown and described as being sequentially performed, it shall be understood that and understanding, the party Method be not limited to shown here order because some parts of this method can according to different order illustrated and described herein To occur and/or while occur.This method can be performed by a variety of parts configured in such as IC or controller.

Fig. 4 shows to provide the illustrative methods 400 of the Controlled in Current Mode and Based of DC-DC converter.At 410, method 400 is wrapped The first input end included in comparator provides threshold value (for example, by current control level 110 in Fig. 1) to convert for DC-DC Device sets the turn-off time so that the peak point current that the turn-off time produces with DC-DC converter is inversely proportional.At 420, method 400 the second inputs for being included in the comparator produce ramp signal, and the wherein ramp input passes through the comparator and the threshold value Compare, so as to control the switching frequency of DC-DC converter based on the turn-off time.At 430, method 400 is included when half When the voltage at conductor device two ends is less than the threshold value, the DC- is disabled using the semiconductor devices connected with the ramp signal The switching frequency of DC converters.

Although not shown, method 400 may also comprise when semiconductor devices conducting and the threshold value is in the DC-DC converter Maximum current load under when being dynamically adjusted, enable the variable frequency operation of the DC-DC converter.This may include to work as the threshold When value is changed into the maximum current load for being fixed on the DC-DC converter, the maximum frequency operation of DC-DC converter is enabled.Method 400 when may also comprise using minimum turn-off of the first current source connected with the semiconductor devices to limit the DC-DC converter Between electric current Itoff.This method sets this using the second current source in parallel with the control electric current of the DC-DC converter The minimum current ISETmin of DC-DC converter.Minimum current ISETmin can according to equation IPEAKmin ≈ ISETmin*N with Minimum peak electric current IPEAKmin is related, and wherein N represents the power switch of the electric current in the inductor for switching the DC-DC converter The size of current relation between sense switch with sensing the minimum current ISETmin in the DC-DC converter.

Described above is example.Certainly, these parts can not possibly be described here or the every kind of of method thinks The combination arrived, still, it will be appreciated by those of ordinary skill in the art that can also have multiple combinations and deformation.Therefore, the disclosure is anticipated It is intended to all such changes, the modification and variation for including falling within the scope of the present application, including appended claims.Such as this paper institutes With, term " comprising " mean including but not limited to this, term "comprising" means including but not limited to this.Term "based" is anticipated Taste, which, to be at least partially based on.In addition, when the disclosure or claims quote " one ", " one ", " first " or " another " element or During its equivalent, it should be interpreted as including one or more than one this class component, it is not required that or exclude two or more This multiple class component.

Claims (16)

1. a kind of DC-DC converter, it includes：

Current control level, it is configured as the output voltage based on the DC-DC converter, input voltage and reference voltage and provided Threshold value, wherein the current control level further comprise for the DC-DC converter set control electric current the first transistor and Setting is used to produce the second transistor of the threshold current of the threshold value；And

Turn-off time controller, it is configured as receiving the threshold value and controls the DC-DC converter based on the threshold value Turn-off time TOFF so that the peak point current IPEAK that produces of the turn-off time and the DC-DC converter is into anti- Than wherein the first current source is in parallel with the control electric current to be DC-DC converter setting minimum current ISETmin.

2. DC-DC converter as claimed in claim 1, wherein the minimum current ISETmin according to below equation with it is described The minimum value IPEAKmin of the peak point current of DC-DC converter is related：

IPEAKmin≈ISETmin*N

Wherein N represents the power switch for being configured as switching the electric current in the inductor of the DC-DC converter with being configured as Magnitude relationship between the sense switch for the minimum current ISETmin for sensing the DC-DC converter.

3. DC-DC converter as claimed in claim 1, it further comprises ramp generator, the ramp generator by with Offer ramp signal is set to TOFF controllers with the adjustment for the switching frequency for facilitating the DC-DC converter.

4. DC-DC converter as claimed in claim 3, wherein the TOFF controllers further comprise comparator, the ratio It is configured as receiving the threshold value on the first input end of the comparator and in the second input of the comparator compared with device The ramp signal is received on end, so as to control the DC-DC converter in different loads bar for TOFF controllers generation The comparator output of the switching frequency under part.

5. DC-DC converter as claimed in claim 3, it further comprises connecting with starting impulse with the ramp generator The semiconductor devices of dancing mode, under the pulse-skip pattern, when the voltage at slope capacitor C (toff) two ends is less than institute Output current is disabled when stating threshold value.

6. DC-DC converter as claimed in claim 5, wherein the semiconductor devices includes diode or is configured as two The transistor of pole pipe.

7. DC-DC converter as claimed in claim 6, it further comprises connecting with the semiconductor devices setting TOFF Electric current Itoff the second current source, to facilitate minimum turn-off time TOFF (min) for adjusting the DC-DC converter.

8. DC-DC converter as claimed in claim 7, it further comprises and the semiconductor devices and second electric current Source-series capacitor, to facilitate minimum turn-off time TOFF (min) for adjusting the DC-DC converter.

9. DC-DC converter as claimed in claim 1, wherein the DC-DC converter is configured as incremental structure or successively decreased Structure.

10. a kind of method for being used to provide the Controlled in Current Mode and Based of DC-DC converter, it includes：

There is provided threshold value to set the turn-off time of DC-DC converter in the first input end of comparator so that the turn-off time The peak point current produced with the DC-DC converter is inversely proportional；And

Ramp signal is produced in the circuit of the second input of the comparator is coupled to, wherein the ramp input passes through institute State comparator to be compared with the threshold value, so as to control the switch frequency of the DC-DC converter based on the turn-off time Rate, further comprises, when the voltage at the semiconductor devices two ends connected with the ramp signal is less than the threshold value, utilizing institute Semiconductor devices is stated to disable the switching frequency of the DC-DC converter.

11. method as claimed in claim 10, it further comprises when semiconductor devices conducting and the threshold value exists When being dynamically adjusted under the maximum current load of the DC-DC converter, the variable frequency behaviour of the DC-DC converter is enabled Make.

12. method as claimed in claim 11, it further comprises when the threshold value is changed into being fixed on the DC-DC converter Maximum current load when, enable the maximum frequency operation of the DC-DC converter.

13. method as claimed in claim 10, it further comprises utilizing the first electric current connected with the semiconductor devices Source limits the minimum turn-off time current Itoff of the DC-DC converter.

14. method as claimed in claim 10, it further comprises using in parallel with the control electric current of the DC-DC converter The second current source set the minimum current ISETmin of the DC-DC converter.

15. method as claimed in claim 14, wherein the minimum current ISETmin is according to below equation and minimum peak electricity Flow valuve IPEAKmin is related：

IPEAKmin ≈ ISETmin*N,

The power switch that wherein N represents the electric current in the inductor of the switching DC-DC converter is converted with sensing the DC-DC Control electric current I (control) in device and the size of current between the sense switch of the minimum current ISETmin sums are closed System.

16. a kind of DC-DC converter, it includes：

Current control level, it is configured as producing threshold value to limit the turn-off time of DC-DC converter, so that the shut-off The peak point current that time produces with the DC-DC converter is inversely proportional；

TOFF controllers, it is configured as monitoring the threshold value and produces output to control the switch frequency of the DC-DC converter Rate；And

Ramp generator, it is configured to supply ramp signal to the TOFF controllers, wherein the TOFF controllers are by institute Ramp signal is stated compared with the threshold value with the switching frequency of the dynamic adjustment DC-DC converter, is further comprised and institute The semiconductor devices of ramp signal series connection is stated, when the voltage at slope capacitor C (toff) two ends is less than the threshold value, institute State the switching frequency that semiconductor devices disables the DC-DC converter.