CN204376704U - Control circuit for voltage converter - Google Patents
Control circuit for voltage converter Download PDFInfo
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- CN204376704U CN204376704U CN201420384826.8U CN201420384826U CN204376704U CN 204376704 U CN204376704 U CN 204376704U CN 201420384826 U CN201420384826 U CN 201420384826U CN 204376704 U CN204376704 U CN 204376704U
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Abstract
A control circuit for a voltage converter is disclosed, including a chopper amplifier, a sample-and-hold circuit, a first comparator, and a logic circuit. A chopper amplifier having a first input, a second input, and an output, the error amplified signal being provided at the output based on a reference signal and a feedback signal. A sample and hold circuit to sample the error amplified signal and provide a hold signal at an output. A first comparator having a first input coupled to the output of the sample and hold circuit, a second input receiving the current feedback signal, and an output providing a first logic signal. A logic circuit having a first input, a second input and an output, the switching signal being provided at the output based on the first and second logic signals. The control circuit can reduce the influence of noise or offset voltage of the input transistor of the error amplifier on the output voltage VOUT or the load current IOUT.
Description
Technical field
Embodiment of the present utility model relates to electronic circuit, but more specifically not exclusively relates to a kind of control circuit for electric pressure converter especially DC-DC electric pressure converter.
Background technology
DC-DC electric pressure converter is a kind of conventional electric pressure converter, and it is a kind of DC of acceptance input voltage and provides the electronic device of DC output voltage to load.Dc-dc is generally configured to provide adjusted DC output voltage or electric current (" load voltage " or " load current ") based at some unadjusted DC source voltages to load.Such as in the application of many automobiles (wherein battery provides the DC power source with approximate 12 volts of unadjusted voltages), dc-dc can be used for receiving unadjusted 12 volts of DC as source voltage provides adjusted DC output voltage or electric current to drive the various electronic circuits in vehicle (instrument, annex, engine control, lighting apparatus, radio/stereo etc.).DC output voltage can be lower, higher or identical than the source voltage from battery.Again such as in some illumination application, dc-dc can be used for receiving unadjusted 12 volts of DC as source voltage provides adjusted DC output current with driving LED.
Fig. 1 illustrates the circuit diagram of a existing dc-dc 10.Dc-dc 10 comprises control circuit 100 and switching circuit 110.Switching circuit 110 comprises at least one power switch M1, and power switch M1 has control end, first end and the second end.Under the effect of control signal CTRL, input voltage VIN is converted to output voltage VO UT by switching circuit 110.Switching circuit 110 can have various topological structures, such as Buck type buck configuration, Boost type boost configuration and the topological structure such as normal shock or flyback.
Control circuit 100 comprises error amplifier 101, comparator 102 and logical circuit 103.Error amplifier 101 has first input end, the second input and output, provides error amplification signal VEAO based on reference signal VREF and output voltage VO UT at output.In another embodiment, error amplifier 101 can also provide error amplification signal VEAO based on the comparative result of reference signal VREF and the voltage signal characterizing load current IOUT at output.Comparator 102, has first input end, the second input and output, and the comparative result based on error amplification signal VEA and current feedback signal RFLTI provides the first logical signal VL1 at output.Current feedback signal RFLTI can the electric current of reaction power switch M1, the electric current of inductance L, such as, by the electric current of current sensing circuit 104 detection power switch M1 or inductance, or the superposing of the signal of reaction power switch M1 electric current and slope compensation signal.Logical circuit 103, has first input end, the second input and output, provides switching signal CTRL based on the first logical signal VL1 and the second logical signal VL2 at output.Second logical signal VL2 can be the clock signal produced by oscillator 105.
Output voltage VO UT clamper near reference signal VREF, thus makes switch converters 10 can provide stable output voltage VO UT or load current IOUT for load by the error amplifier 101 of dc-dc 10.In some applications, the magnitude of voltage of reference signal VREF may be lower, such as 200mV.And the offset voltage of error amplifier (OFFSET) can be tall and big tens millivolts, such as 50mV.Now, output voltage VO UT or load current IOUT will be made to produce the error of 25%.In addition, the noise of error amplifier input transistors also can by loop reaction on output voltage VO UT or load current IOUT.How reducing the noise of error amplifier input transistors and the impact of offset voltage, is the difficult problem that those skilled in the art face.
Utility model content
For solving the problem, the utility model provides a kind of control circuit for electric pressure converter, described electric pressure converter has at least one power switch, described control circuit comprises: chopper amplifier, there is first input end, the second input and output, there is provided error amplification signal based on reference signal and feedback signal at output, wherein said feedback signal reflects load current or the output voltage of described electric pressure converter; Sampling hold circuit, has control end, input and output, under adopting and protecting control signal effect, and the described error amplification signal provide inhibit signal at output of sampling; First comparator, comprise first input end, the second input and output, its first input end is coupled to the output of described sampling hold circuit, its second input received current feedback signal, and its output provides the first logical signal; And logical circuit, there is first input end, the second input and output, provide switching signal based on described first logical signal and the second logical signal at output.
According to an embodiment of the present utility model, described power switch has first end, the second end and control end, wherein first end receives input voltage, control end receives described switching signal, described dc-dc converter also comprises: secondary switching tube, has first end, the second end and control end, and wherein first end is coupled to the second end of described power switch, second end ground connection, control end is coupled to described logical circuit; And inductor, have first end and the second end, wherein first end is electrically coupled to the second end of described power switch and the first end of time switching tube, and its second end provides described output voltage.
According to an embodiment of the present utility model, described current feedback signal reacts the electric current of described power switch or reflects signal and the slope compensation signal sum of described power switch electric current; Described first logical signal is in order to logical circuit described in set, and described second logical signal resets the clock signal of described logical circuit.
According to an embodiment of the present utility model, described chopper amplifier comprises the first chopping modulation device, input stage, the second chopping modulation device and output stage, described control circuit also comprises frequency dividing circuit, described frequency dividing circuit, by described second logical signal or described switching signal frequency division, provides chopping modulation signal to control described first chopping modulation device and described second chopping modulation device at output.
According to an embodiment of the present utility model, described in adopt protect cycle of control signal be chopping cycle integral multiple.
The utility model also provides a kind of control circuit for electric pressure converter, described electric pressure converter has at least one power switch, described control circuit comprises: chopper amplifier, there is first input end, the second input and output, there is provided error amplification signal based on reference signal and feedback signal at output, wherein said feedback signal reflects load current or the output voltage of described dc-dc converter; Sampling hold circuit, has control end, input and output, under adopting and protecting control signal effect, and the described error amplification signal provide inhibit signal at output of sampling; First comparator, comprise first input end, the second input and output, its first input end is coupled to the output of described sampling hold circuit, and its second input receives described feedback signal, and its output provides Continuity signal; Cut-off signals produces circuit, provides cut-off signals at its output; And logical circuit, there is first input end, the second input and output, provide switching signal based on described Continuity signal and described cut-off signals at output.
According to an embodiment of the present utility model, described switching signal is for controlling the turn-on and turn-off of described power switch, and described power switch is the main switch of Buck type reduction voltage circuit or Boost type booster circuit or forward converter or anti exciting converter.
According to an embodiment of the present utility model, described power switch has first end, the second end and control end, wherein first end receives input voltage, control end receives described switching signal, described dc-dc converter also comprises: secondary switching tube, has first end, the second end and control end, and wherein first end is coupled to the second end of described power switch, second end ground connection, control end is coupled to described logical circuit; And inductor, have first end and the second end, wherein first end is electrically coupled to the second end of described power switch and the first end of time switching tube, and its second end provides described output voltage.
According to an embodiment of the present utility model, described chopper amplifier comprises the first chopping modulation device, input stage, the second chopping modulation device and output stage, described control circuit also comprises frequency dividing circuit, described frequency dividing circuit, by described cut-off signals or described switching signal frequency division, provides chopping modulation signal to control described first chopping modulation device and described second chopping modulation device at output.
According to an embodiment of the present utility model, described in adopt protect cycle of control signal be chopping cycle integral multiple.
According to an embodiment of the present utility model, described control circuit also comprises: current sensing circuit, has input and output, and the electric current based on described power switch produces described current sensing signal; Turn off threshold generation circuits, there is input and output, adjust described shutoff threshold value based on the frequency of described switching signal and setpoint frequency, make the frequency of described switching signal be equal to, or greater than in fact described setpoint frequency; And described cut-off signals produces circuit, provide described cut-off signals based on the comparative result turning off threshold signal and current sensing signal at output.
According to an embodiment of the present utility model, described current sensing circuit comprises current detection circuit, and described current detection circuit detects the electric current that described power switch flows through, and powers on to miscarry give birth to described shutoff threshold signal based on described power switch.
According to an embodiment of the present utility model, described current sensing circuit comprises current analog circuit, described current analog circuit detects the voltage of described power switch one end or the difference of described power switch first end and the second terminal voltage, simulates electric current that described power switch flows through to produce described shutoff threshold signal.
According to an embodiment of the present utility model, phase-locked loop is comprised at described shutoff threshold generation circuits, described phase-locked loop receives reference frequency signal and described switching signal, produces described shutoff threshold signal based on the difference in cycle of described reference clock signal and described switching signal or the difference of frequency.
According to an embodiment of the present utility model, comprise: the first electric capacity at described shutoff threshold generation circuits, have first end and the second end, its second end is coupled to ground; First switch, have first end, the second end and control end, its first end is coupled to the first voltage by the first current source, and its second end couples the first end of described first electric capacity; Second switch, has first end, the second end and control end, and its first end couples the first end of described first electric capacity, and its second end is coupled to described earth potential; Second electric capacity, has first end and the second end, and its second end is coupled to ground; 3rd switch, have first end, the second end and control end, its first end is coupled to the second voltage by the second current source, and its second end is coupled to the first end of described second electric capacity; 4th switch, has first end, the second end and control end, and its first end couples the first end of described first electric capacity, and its second end is coupled to described earth potential by the 3rd current source; Second comparator, has first input end, the second input and output, and its first input end is coupled to the first end of described first electric capacity, and its second input receives the second reference signal; And second logical circuit, there is first input end, the second input, the first output and the second output, its first input end is coupled to the output of described second comparator, its second input receives described switching signal, and its output provides multiple control signal to control the turn-on and turn-off of described first to fourth switch.
According to an embodiment of the present utility model, described shutoff threshold generation circuits also comprises clamp circuit, in order to set the maximum of described shutoff threshold value.
According to an embodiment of the present utility model, when described shutoff threshold signal is less than clamp voltage, the frequency of described switching signal equals described setpoint frequency; Described shutoff threshold signal is by after described clamp circuit clamper, and the frequency of described switching signal is greater than described setpoint frequency.
The utility model also provides a kind of control circuit for electric pressure converter, described electric pressure converter has at least one power switch, described control circuit comprises: chopper amplifier, there is first input end, the second input and output, there is provided error amplification signal based on reference signal and feedback signal at output, wherein said feedback signal reflects load current or the output voltage of described electric pressure converter; First comparator, comprise first input end, the second input and output, its first input end is coupled to the output of described sampling hold circuit, its second input received current feedback signal, and its output provides the first logical signal; And logical circuit, there is first input end, the second input and output, provide switching signal based on described first logical signal and the second logical signal at output; It is characterized in that, the chopping frequency of described chopper amplifier is the integral multiple of described switching signal.
According to an embodiment of the present utility model, described current feedback signal reacts the electric current of described power switch or reflects signal and the slope compensation signal sum of described power switch electric current; Described first logical signal is in order to logical circuit described in set, and described second logical signal resets the clock signal of described logical circuit.
The control circuit for dc-dc that the utility model provides reduces the noise of error amplifier input transistors or the impact of offset voltage, improves the precision of output voltage VO UT or load current IOUT.
Accompanying drawing explanation
The utility model illustrates by example and with reference to the mode of accompanying drawing, wherein:
Fig. 1 illustrates the circuit diagram of a existing dc-dc 10;
Fig. 2 illustrates the circuit diagram of a dc-dc 20 according to the utility model one enforcement;
Fig. 3 illustrates the circuit diagram of a chopper amplifier 300 according to the utility model one enforcement;
Fig. 4 illustrates the oscillogram in chopper amplifier 300 course of work;
Fig. 5 illustrates the oscillogram in dc-dc 20 course of work;
Fig. 6 illustrates the circuit diagram of a dc-dc 60 according to the utility model one enforcement;
Fig. 7 illustrates the oscillogram in dc-dc 60 course of work;
Fig. 8 illustrates the circuit diagram of a dc-dc 80 according to the utility model one enforcement;
Fig. 9 illustrates the oscillogram in dc-dc 80 course of work; And
Figure 10 illustrates that a shutoff threshold implemented according to the utility model one produces the circuit diagram of circuit 805.
Embodiment
Specific embodiment hereinafter described represents exemplary embodiment of the present utility model, and be only in essence example illustrate and unrestricted.In the description, mention that " embodiment " or " embodiment " mean to be included at least one embodiment of the present utility model in conjunction with the special characteristic described by this embodiment, structure or characteristic.Term " in one embodiment " in the description each position occurs all not relating to identical embodiment, neither mutually get rid of other embodiments or various embodiments.All features disclosed in this specification, or the step in disclosed all methods or process, except mutually exclusive feature and/or step, all can combine by any way.
Describe embodiment of the present utility model below with reference to the accompanying drawings in detail.The Reference numeral running through institute's drawings attached identical represents identical parts or feature.
Fig. 2 illustrates the circuit diagram of a dc-dc 20 according to the utility model one enforcement.Dc-dc 20 comprises control circuit 200 and switching circuit 110.Control circuit 200 comprises chopper amplifier 201, comparator 102 and logical circuit 103.
Chopper amplifier 201 has first input end, the second input and output, provides error amplification signal VEAO based on reference signal VREF and output voltage VO UT at output.Chopper amplifier 201 have employed copped wave structure (Chopper), comprise the first chopping modulation device 2011, input stage 2012, second chopping modulation device 2013 and output stage 2014, wherein the first chopping modulation device 2011 is for receiving reference signal VREF and output voltage VO UT, input stage 2012 is coupled between the first chopping modulation device 2011 and the second chopping modulation device 2013, and output stage 2014 receives the output signal of the second chopping modulation device 2013 and provides error amplification signal VEAO.Chopping modulation signal FCHP is in order to control the first chopping modulation device 2011 and the second chopping modulation device 2013.
Fig. 3 illustrates the circuit diagram of a chopper amplifier 300 according to the utility model one enforcement.Chopper amplifier 300 comprises the first chopping modulation device 301, input stage 302, second chopping modulation device 303 and output stage 304.In Fig. 3, differential signal VDIF represents the difference of reference signal VREF and output voltage VO UT, VOS is the offset voltage of input stage 302, and VO1 is the output voltage of input stage 302, and VO2 is the output signal (i.e. the input signal of output stage 304) of the second chopping modulation device 303.Output stage 304 in order to filtering high-frequency signal, suppose that its gain is 1 at this, can be similar to and think a low pass filter LPF.The output signal of output stage 304 is configured to the output signal (i.e. error amplification signal VEAO) of chopper amplifier 300.
After adopting copped wave structure, differential signal VDIF is modulated to chopping frequency (generally having hundreds of KHz) by first chopping modulation device 301, after input stage 302 is amplified, be again modulated to the frequency of input signal own by second chopping modulation device 303.Offset voltage VOS and noise are only modulated once by second chopping modulation device 303 and are appeared at chopping frequency and odd harmonic place, are then low-pass filtered device LPF (output stage 304) filtering.Fig. 4 illustrates the oscillogram in chopper amplifier 300 course of work.As shown in Figure 4, the chopping modulation signal FCHP of 50% duty ratio is used to control the first chopping modulation device 301 and the second chopping modulation device 303 of chopper amplifier 300.Half period before chopping cycle, K switch 1 and K3 conducting, K2 and K4 ends, and output signal VO1 and VO2 is respectively
VO1＝A×(VDIF+VOS)；
VO2＝A×(VDIF+VOS)
Wherein A is the multiplication factor of input stage 301.In the rear half period of chopping cycle, K switch 2 and K4 conducting, K1 and K3 ends, then output signal VO1 and VO2 and be respectively
VO1＝A×(VOS-VDIF)；
VO2＝A×(VDIF-VOS)
After the low pass filter of output stage 304, the mean value of VO2 and VEAO be,
VEAO＝0.5×A×(VOS+VDIF)+0.5×A×(VDIF-VOS)＝A×VDIF
Copped wave structure eliminates the impact of offset voltage VOS on differential signal VDIF, avoids the precision of offset voltage VOS or noise effect output voltage VO UT or load current IOUT.
In certain embodiments, due to the restriction in integrated circuit technology, such as, cannot provide excessive resistance or electric capacity, output stage 2014 generally cannot provide very low cut-off frequency.In other embodiment, due to the requirement of dc-dc converter loop stability or error amplifier stability, error amplifier cannot provide very low cut-off frequency.These restrictions can make error amplification signal VEAO be a triangular signal or fluctuation signal and non-constant signal changed.In certain embodiments, VEAO numerical value determines power switch M1 conducting or turns off the moment, and the fluctuation of VEAO may cause turn-on instant or turn off the moment inconsistent, and then little time large when causing duty ratio.In constant on-time (COT) or constant off-time type electric pressure converter, little time large when the error amplification signal VEAO of change also can cause switch periods.
One of solution to the problems described above is integral multiple chopping frequency being set to switching signal CTRL frequency.When Fig. 5 illustrates that chopping modulation signal FCHP frequency is the second logical signal VL2 frequency (i.e. switching frequency) 1 times, electric pressure converter 200 runs oscillogram.When error amplification signal VEAO and current feedback signal RFLTI is periodicity collaborative variation, current feedback signal RFLTI and error amplification signal VEAO " meets " at same magnitude of voltage, thus switching signal CTRL duty ratio is consistent.But the selection due to chopping modulation signal optimum is the square-wave signal of 50% duty ratio, this is that the clock signal of the second logical signal frequency 2 times carries out frequency division with regard to needing to provide frequency.In portion voltage transducer, oscillator needs to provide the triangular wave identical with switching frequency, thus cannot provide the clock signal of 2 times of switching frequencies simultaneously.Also have some electric pressure converters itself not need oscillator, this just needs for chopping modulation device arranges separately oscillator to arrange chopping frequency.
For solving the problem, sampling hold circuit can be increased in the rear class of chopper amplifier 201.Fig. 6 illustrates the circuit diagram of a dc-dc 60 according to the utility model one enforcement.Dc-dc 60 comprises control circuit 600 and switching circuit 110.Control circuit 600 comprises chopper amplifier 201, comparator 102, logical circuit 103 and sampling hold circuit 601.Sampling hold circuit 601 comprise control end, input output and, control end receive adopts protect control signal VSH, input receive and sampling error amplifying signal VEAO, output provides inhibit signal VHOD.When adopt protect control signal VHS enable time, sampling hold circuit 601 sampling error amplifying signal VEAO and export output to until adopt protect control signal VHS next time enable.In one embodiment, chopping modulation signal FCHP can be used to protect control signal VHS as adopting.
Fig. 7 illustrates the oscillogram in dc-dc 40 course of work.As shown in the figure, in a certain moment of each chopping cycle, sampling hold circuit 601 sampling error amplifying signal VEAO, by sampling, the magnitude of voltage obtained exports and keeps until next cycle.Because the output signal VHOD of sampling hold circuit remains unchanged, avoid the change of power converter switches frequency or duty ratio.
In one embodiment, can by the second logical signal VL2 frequency division to obtain the signal of 50% duty ratio as chopping modulation signal FCHP, now chopping cycle T is 2 times of switch periods.As shown in Figure 6, the second logical signal VL2 obtains through frequency dividing circuit 602 the chopping modulation signal FCHP that duty ratio is 50%.After frequency division, the cycle of chopping modulation signal FCHP is generally the even-multiple of the second logical signal VL2 (i.e. switching frequency), such as 2 times, 4 times or 6 times.Chopping modulation signal FCHP produces a spike and protects control signal VSH as adopting after pulse unit 603.Adopt the integral multiple that the cycle of protecting control signal VSH is generally chopping cycle T, such as 1,2,3 times.Adopt protect control signal VSH can at the not enable sampling hold circuit 601 in the same time of a chopping cycle T.The introducing of sampling hold circuit 601, eliminates the dependence of chopping frequency to switching frequency.
In one embodiment, especially do not use in the application of oscillator, can by switching signal CTRL frequency division to obtain the chopping modulation signal FCHP of 50% duty ratio.
Fig. 8 illustrates the circuit diagram of a dc-dc 80 according to the utility model one enforcement.Dc-dc 80 comprises control circuit 800 and switching circuit 810.Switching circuit 810 have employed synchronous buck transformation topology, comprises main switch M1, secondary switching tube M2, inductor L and output capacitor C.Switching circuit 810 passes through conducting and the shutoff of switching tube M1 and M2, and input voltage VIN is converted to output voltage VO UT.One end of main switch M1 receives input voltage VIN, and the other end is electrically coupled to one end of time switching tube M2.The other end ground connection of secondary switching tube M2.One end of inductor L is electrically coupled to the link of switching tube M1 and M2, and output capacitor COUT electric coupling is between the other end and ground of inductor L.The voltage at output capacitor COUT two ends is output voltage VO UT.
Control circuit 800 comprises chopper amplifier 201, sampling hold circuit 601, Continuity signal produces circuit 801, cut-off signals produces circuit 802 and logical circuit 803.
Chopper amplifier 201 comprises first input end, the second input and output, and its first input end receives reference signal VREF, and its second input receiving feedback signals VFB, its output provides error amplification signal VEAO.Sampling hold circuit 601 sampling error amplifying signal VEAO, provides inhibit signal VHOD at output.Switching signal VCTRL produces chopping modulation signal FCHP to control chopper amplifier 201 through frequency dividing circuit 602, and chopping modulation signal FCHP produces to adopt through pulse unit 603 and protects control signal VSH to control sample frequency and the sampling instant of sampling hold circuit 601.In one embodiment, cut-off signals OFFSET can be produced chopping modulation signal FCHP to control chopper amplifier 201 through frequency dividing circuit 602.In one embodiment, chopping modulation signal FCHP can be directly used to protect control signal VHS to control sample frequency and the sampling instant of sampling hold circuit 601 as adopting.In other embodiments, other signal controlling can also be used to control chopper amplifier 201 and sampling hold circuit 601.
Continuity signal produces circuit 801 and comprises the first comparator COM1, and its first input end is coupled to the output of sampling hold circuit 601, and tool second input receiving feedback signals VFB, tool output provides Continuity signal ONSET.In the embodiment shown in fig. 8, resistance RF1 and RF2 forms sample circuit provides feedback signal VFB with sampling and outputting voltage VOUT.In other embodiments, feedback signal VFB can also reflect the load current IOUT of dc-dc 80.
Cut-off signals produces circuit 802, provides cut-off signals OFFSET at its output.Cut-off signals produces circuit 802 can produce various cut-off signals OFFSET based on multi-signal, the pulse signal of a constant pulse width (such as corresponding constant on-time or constant off-time) is such as directly provided, more such as provides a pulse signal based on the comparative result of the signal of reference voltage and reaction power switch M1 electric current.In constant on-time or constant off-time control, cut-off signals produces circuit 802 can produce cut-off signals OFFSET based on the comparative result of reference signal and triangular signal, can also produce cut-off signals OFFSET based on the comparative result of input voltage VIN or output voltage VO UT and triangular signal.In one particular embodiment, cut-off signals produces circuit 802 and comprises comparator COM2, comparator COM2 has first input end, the second input and output, provides cut-off signals OFFSET based on the comparative result turning off threshold value OFFTH and current sensing signal RFLTI at output.Wherein, current sensing signal RFLTI is provided by current sensing circuit 804, and turning off threshold value OFFTH provides by turning off threshold generation circuits 805.
Current sensing circuit 804, has input and output, and its input is coupled to one end of main switch M1, based on the electric current I M1 generation current sensing signal RFLTI of main switch M1.In one embodiment, current sensing circuit 804 detects the electric current I M1 of main switch M1, is zoomed in or out by electric current I M1, then optionally the current signal after amplifying is converted to voltage signal using as current sensing signal RFLTI.In another embodiment, turn off that threshold generation circuits 804 can also be simulated based on the voltage of switching tube M1 (difference of first end voltage, the second terminal voltage or both end voltage), the change of the electric current I M1 of virtual or fitting power switch M1, to produce the voltage signal or current signal that are directly proportional to electric current I M1 as current sensing signal RFLTI.When main switch M1 conducting, the electric current I M1 in inductance L equals inductive current IL.For this reason, the electric current I M1 of main switch M1 can be obtained by detecting inductive current IL, and this equivalent way is no more than protection range of the present utility model.
Logical circuit, has first input end, the second input and output, provides switching signal CTRL based on Continuity signal ONSET and cut-off signals OFFSET at output.In one embodiment, logical circuit 803 comprises rest-set flip-flop RS1, there is first input end S to receive Continuity signal ONSET, the second input R to receive cut-off signals OFFSET and output Q, provide switching signal CTRL based on Continuity signal ONSET and cut-off signals OFFSET at output Q.
Fig. 9 illustrates according to the oscillogram in dc-dc 80 running of the utility model embodiment.At a time, when VFB in feedback shop is lower than when adopting guarantor voltage VHOD, the Continuity signal ONSET that Continuity signal produces the output of circuit 101 is high level by low transition, and the switching signal CTRL that logical circuit 803 exports is that high level is to open power switch M1 by low transition.After power switch M1 opens, the electric current I M1 of power switch continues to increase, and current sensing signal RFLTI also increases thereupon, and when current sensing signal RFLTI increases to shutoff threshold signal OFFSET, power switch M1 closes.Turn off threshold generation circuits 805 and compare the frequency of switching signal CTRL and the difference of (clock signal clk) setpoint frequency FQREF, turn off threshold value OFFTH by adjustment and make the frequency of switching signal CTRL equal in fact setpoint frequency FQREF.In Fig. 9, power switch M1 turn off phase, current sensing signal RFLTI can slowly reduce, and as in Fig. 9, dotted line represents, also can reduce rapidly.
In one embodiment, turn off threshold generation circuits 805, there is input and output, based on frequency and the setpoint frequency FQREF adjustment shutoff threshold value OFFTH of switching signal CTRL, make the frequency of switching signal CTRL equal in fact setpoint frequency FQREF.Turn off threshold generation circuits 805 and comprise a phase-locked loop pll, this PLL has first input end with reception control signal CTRL, first input end, to receive reference clock signal CLK, based on the difference of control signal CTRL and reference clock signal CLK frequency, provides at output and turns off threshold value OFFTH.
Figure 10 illustrates the circuit diagram of the shutoff threshold generation circuits 805 according to the utility model embodiment.Turn off threshold generation circuits 805 and comprise first to fourth current source I1 ~ I4, the first electric capacity C1, the first switch S 1, second switch S2, the second electric capacity C2, the 3rd switch S 3, the 4th switch S 4, comparator COM3 and logical circuit 8051.First electric capacity C1, has first end and the second end, and its second end is coupled to earth potential GND.First switch S 1, has first end, the second end and control end, and its first end is coupled to the first voltage V1 by the first current source I1, and its second end is coupled to the first end of the first electric capacity C1.Second switch S2, has first end, the second end and control end, and its first end couples the first end of the first electric capacity C1, and its second end is coupled to earth potential GND.Second electric capacity C2, has first end and the second end, and its second end is coupled to earth potential GND.3rd switch S 3, has first end, the second end and control end, and its first end is coupled to the second voltage V2 by the second current source I2, and its second end couples the first end of the second electric capacity C2, and wherein the second voltage V2 can equal the first voltage V1.4th switch S 4, has first end, the second end and control end, and tool first end couples the first end of the first electric capacity C1, and its second end is coupled to earth potential GND by the 3rd current source I3.Comparator COM3, has first input end, the second input and output, and its first input end is coupled to the first end of the first electric capacity C1, and its second termination receives the second reference signal VREF2.Logical circuit 8051, there is first input end, the second input, the first output and the second output, its first input end is coupled to the output of comparator COM3, its second input couples receiving key signal CTRL, and its output provides multiple control signal to control the turn-on and turn-off of first to fourth switch S 1 ~ S4.
In one embodiment, the second logical circuit 8051 comprises rest-set flip-flop, has first input end S with receiving key signal CTRL, the second input R to receive output signal and the output Q of comparator COM3.Logical circuit 8051 can also optionally comprise pulse-triggered unit 8052, there is input and output, input receiving key signal CTRL, there is provided pulse signal PULSE based on the rising edge of switching signal or trailing edge at output, its output is coupled to the first input end S of rest-set flip-flop.
In some embodiments, turn off threshold generation circuits 805 and can also comprise clamp circuit CLAMP, the maximum voltage of VC2 can be limited in a clamped voltage value VCLAP by clamp circuit.After adopting clamp circuit CLAMP, under underload, during load current change, turn off threshold generation circuits 405 and adjust based on the frequency of switching signal CTRL and setpoint frequency FQREF and turn off threshold value OFFTH, make the frequency of switching signal CTRL equal in fact setpoint frequency FQREF.Under heavy duty, turn off threshold value OFFTH by clamper, system will improve the frequency of switching signal CTRL to provide enough load currents.
Although the utility model is described in conjunction with its concrete illustrative embodiments, it is apparent that multiple alternative, amendment and distortion be apparent for those skilled in the art.Thus, the illustrative embodiments of the present utility model illustrated at this is schematic and and non-limiting.Can modify when not departing from spirit and scope of the present utility model.
Used in this disclosure measure word " ", " one " etc. do not get rid of plural number." first ", " second " in literary composition etc. only represent the sequencing occurred in describing the embodiments of the present, so that distinguish like." first ", " second " go out to be now only and make in the fast understanding to claim instead of in order to be limited in detail in the claims.Any Reference numeral in claims all should not be construed as the restriction to scope.
Claims (19)
1. for a control circuit for electric pressure converter, described electric pressure converter has at least one power switch, and described control circuit comprises:
Chopper amplifier, has first input end, the second input and output, provides error amplification signal based on reference signal and feedback signal at output, and wherein said feedback signal reflects load current or the output voltage of described electric pressure converter;
Sampling hold circuit, has control end, input and output, under adopting and protecting control signal effect, and the described error amplification signal provide inhibit signal at output of sampling;
First comparator, comprise first input end, the second input and output, its first input end is coupled to the output of described sampling hold circuit, its second input received current feedback signal, and its output provides the first logical signal; And
Logical circuit, has first input end, the second input and output, provides switching signal based on described first logical signal and the second logical signal at output.
2. control circuit according to claim 1, is characterized in that, described power switch has first end, the second end and control end, and wherein first end receives input voltage, and control end receives described switching signal, and described dc-dc converter also comprises:
Secondary switching tube, has first end, the second end and control end, and wherein first end is coupled to the second end of described power switch, the second end ground connection, and control end is coupled to described logical circuit; And
Inductor, has first end and the second end, and wherein first end is electrically coupled to the second end of described power switch and the first end of time switching tube, and its second end provides described output voltage.
3. control circuit according to claim 1, is characterized in that, described current feedback signal reacts the electric current of described power switch or reflects signal and the slope compensation signal sum of described power switch electric current; Described first logical signal is in order to logical circuit described in set, and described second logical signal resets the clock signal of described logical circuit.
4. control circuit according to claim 1, it is characterized in that, described chopper amplifier comprises the first chopping modulation device, input stage, the second chopping modulation device and output stage, described control circuit also comprises frequency dividing circuit, described frequency dividing circuit, by described second logical signal or described switching signal frequency division, provides chopping modulation signal to control described first chopping modulation device and described second chopping modulation device at output.
5. control circuit according to claim 1, is characterized in that, described in adopt protect cycle of control signal be chopping cycle integral multiple.
6. for a control circuit for electric pressure converter, described electric pressure converter has at least one power switch, and described control circuit comprises:
Chopper amplifier, has first input end, the second input and output, provides error amplification signal based on reference signal and feedback signal at output, and wherein said feedback signal reflects load current or the output voltage of described dc-dc converter;
Sampling hold circuit, has control end, input and output, under adopting and protecting control signal effect, and the described error amplification signal provide inhibit signal at output of sampling;
First comparator, comprise first input end, the second input and output, its first input end is coupled to the output of described sampling hold circuit, and its second input receives described feedback signal, and its output provides Continuity signal;
Cut-off signals produces circuit, provides cut-off signals at its output; And
Logical circuit, has first input end, the second input and output, provides switching signal based on described Continuity signal and described cut-off signals at output.
7. control circuit according to claim 6, it is characterized in that, described switching signal is for controlling the turn-on and turn-off of described power switch, and described power switch is the main switch of Buck type reduction voltage circuit or Boost type booster circuit or forward converter or anti exciting converter.
8. control circuit according to claim 6, is characterized in that, described power switch has first end, the second end and control end, and wherein first end receives input voltage, and control end receives described switching signal, and described dc-dc converter also comprises:
Secondary switching tube, has first end, the second end and control end, and wherein first end is coupled to the second end of described power switch, the second end ground connection, and control end is coupled to described logical circuit; And
Inductor, has first end and the second end, and wherein first end is electrically coupled to the second end of described power switch and the first end of time switching tube, and its second end provides described output voltage.
9. control circuit according to claim 6, it is characterized in that, described chopper amplifier comprises the first chopping modulation device, input stage, the second chopping modulation device and output stage, described control circuit also comprises frequency dividing circuit, described frequency dividing circuit, by described cut-off signals or described switching signal frequency division, provides chopping modulation signal to control described first chopping modulation device and described second chopping modulation device at output.
10. control circuit according to claim 6, is characterized in that, described in adopt protect cycle of control signal be chopping cycle integral multiple.
11. control circuits according to claim 6, is characterized in that, described control circuit also comprises:
Current sensing circuit, has input and output, and the electric current based on described power switch produces described current sensing signal;
Turn off threshold generation circuits, there is input and output, adjust described shutoff threshold value based on the frequency of described switching signal and setpoint frequency, make the frequency of described switching signal be equal to, or greater than in fact described setpoint frequency; And
Described cut-off signals produces circuit, provides described cut-off signals based on the comparative result turning off threshold signal and current sensing signal at output.
12. control circuits according to claim 11, it is characterized in that, described current sensing circuit comprises current detection circuit, and described current detection circuit detects the electric current that described power switch flows through, and powers on to miscarry give birth to described shutoff threshold signal based on described power switch.
13. control circuits according to claim 11, it is characterized in that, described current sensing circuit comprises current analog circuit, described current analog circuit detects the voltage of described power switch one end or the difference of described power switch first end and the second terminal voltage, simulates electric current that described power switch flows through to produce described shutoff threshold signal.
14. control circuits according to claim 11, it is characterized in that, phase-locked loop is comprised at described shutoff threshold generation circuits, described phase-locked loop receives reference frequency signal and described switching signal, produces described shutoff threshold signal based on the difference in cycle of described reference clock signal and described switching signal or the difference of frequency.
15. control circuits according to claim 11, is characterized in that, comprise at described shutoff threshold generation circuits:
First electric capacity, has first end and the second end, and its second end is coupled to earth potential;
First switch, have first end, the second end and control end, its first end is coupled to the first voltage by the first current source, and its second end couples the first end of described first electric capacity;
Second switch, has first end, the second end and control end, and its first end couples the first end of described first electric capacity, and its second end is coupled to described earth potential;
Second electric capacity, has first end and the second end, and its second end is coupled to described earth potential;
3rd switch, have first end, the second end and control end, its first end is coupled to the second voltage by the second current source, and its second end is coupled to the first end of described second electric capacity;
4th switch, has first end, the second end and control end, and its first end couples the first end of described first electric capacity, and its second end is coupled to described earth potential by the 3rd current source;
Second comparator, has first input end, the second input and output, and its first input end is coupled to the first end of described first electric capacity, and its second input receives the second reference signal; And
Second logical circuit, there is first input end, the second input, the first output and the second output, its first input end is coupled to the output of described second comparator, its second input receives described switching signal, and its output provides multiple control signal to control the turn-on and turn-off of described first to fourth switch.
16. control circuits according to claims 14 or 15, it is characterized in that, described shutoff threshold generation circuits also comprises clamp circuit, in order to set the maximum of described shutoff threshold value.
17. control circuits according to claim 16, is characterized in that, when described shutoff threshold signal is less than clamp voltage, the frequency of described switching signal equals described setpoint frequency; Described shutoff threshold signal is by after described clamp circuit clamper, and the frequency of described switching signal is greater than described setpoint frequency.
18. 1 kinds of control circuits for electric pressure converter, described electric pressure converter has at least one power switch, and described control circuit comprises:
Chopper amplifier, has first input end, the second input and output, provides error amplification signal based on reference signal and feedback signal at output, and wherein said feedback signal reflects load current or the output voltage of described electric pressure converter;
First comparator, comprise first input end, the second input and output, its first input end is coupled to the output of described chopper amplifier, its second input received current feedback signal, and its output provides the first logical signal; And
Logical circuit, has first input end, the second input and output, provides switching signal based on described first logical signal and the second logical signal at output;
It is characterized in that, the chopping frequency of described chopper amplifier is the integral multiple of described switching signal.
19. control circuits according to claim 18, is characterized in that, described current feedback signal reacts the electric current of described power switch or reflects signal and the slope compensation signal sum of described power switch electric current; Described first logical signal is in order to logical circuit described in set, and described second logical signal resets the clock signal of described logical circuit.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201420384826.8U CN204376704U (en) | 2014-07-11 | 2014-07-11 | Control circuit for voltage converter |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201420384826.8U CN204376704U (en) | 2014-07-11 | 2014-07-11 | Control circuit for voltage converter |
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| CN204376704U true CN204376704U (en) | 2015-06-03 |
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| CN201420384826.8U Withdrawn - After Issue CN204376704U (en) | 2014-07-11 | 2014-07-11 | Control circuit for voltage converter |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104065266A (en) * | 2014-07-11 | 2014-09-24 | 成都芯源系统有限公司 | Control circuit for voltage converter |
| CN112787482A (en) * | 2019-11-05 | 2021-05-11 | 晶豪科技股份有限公司 | Transient enhancement circuit and constant on-time converter using the same |
| CN114157139A (en) * | 2021-11-29 | 2022-03-08 | 英麦科（厦门）微电子科技有限公司 | Fixed-frequency hysteresis current control circuit based on phase-locked loop |
-
2014
- 2014-07-11 CN CN201420384826.8U patent/CN204376704U/en not_active Withdrawn - After Issue
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104065266A (en) * | 2014-07-11 | 2014-09-24 | 成都芯源系统有限公司 | Control circuit for voltage converter |
| CN112787482A (en) * | 2019-11-05 | 2021-05-11 | 晶豪科技股份有限公司 | Transient enhancement circuit and constant on-time converter using the same |
| CN114157139A (en) * | 2021-11-29 | 2022-03-08 | 英麦科（厦门）微电子科技有限公司 | Fixed-frequency hysteresis current control circuit based on phase-locked loop |
| CN114157139B (en) * | 2021-11-29 | 2024-05-24 | 拓尔微电子股份有限公司 | Fixed-frequency hysteresis current control circuit based on phase-locked loop |
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Granted publication date: 20150603 Effective date of abandoning: 20171215 |