A kind of open loop charge pump circuit reducing output voltage ripple
Technical field
The present invention relates to electronic circuit technology field, espespecially a kind of open loop charge pump circuit.
Background technology
Charge-pump type step-up circuit is the modal DC-DC of portable electric appts (Direct Current, direct current) boost power supply circuits, compare inductive type Boost circuit, EMI (the Electro Magnetic Interference of charge-pump type step-up circuit, electromagnetic interference) performance is better, it adopts pump electric capacity of boosting to carry out storage power, and the charge/discharge that controls booster electric capacity by control circuit reaches boosting and exported by energy trasfer.
In general, charge-pump type step-up circuit is divided into closed loop charge pump circuit and open loop charge pump circuit, wherein, closed loop charge pump circuit is controlled by loop, export one than the lower slightly constant output voltage of boosting multiple, and the conducting resistance of constant output voltage to be grid voltage when controlling the switching tube conducting of boost module inside by the loop of closed loop adjust switching tube realizes.The switching tube of such closed loop charge pump circuit operationally boost module inside can not conducting completely, so the most obvious shortcoming of closed loop charge pump circuit is that conversion efficiency and driving force are all lower, and the control circuit of closed loop charge pump also more complicated, the power consumption of whole circuit and the chip area of integrated circuit are also all larger.
Typical open loop charge pump circuit as shown in Figure 1, is made up of work clock generation module 200, overvoltage protection signal generation module 100, voltage up control signal generation module 300 and boost module 400.Wherein, work clock generation module 200 produces the switch clock signal V required for boost module 400
oSC, V
oSCsignal produces voltage up control signal V through voltage up control signal generation module 300
c, boost module 400 is according to voltage up control signal V
ccontrol complete conducting and the cut-off of the switching tube of boost module 400 inside, to the charge pump capacitor C of boosting
fLYING1and C
fLYING2carry out discharge and recharge, final generation output voltage V
oUT.
Grid voltage during the internal switch pipe conducting of closed loop of comparing charge pump circuit controls by loop, when open loop charge pump circuit controls the switching tube conducting of inner boosting, grid voltage is directly ceiling voltage (NMOS tube)/minimum voltage (PMOS), and switching tube is abundant conducting.The switching tube conducting resistance of abundant conducting is minimum, so the driving force of open loop charge pump circuit can perform to ultimate attainment, Simultaneous Switching pipe conducting resistance is minimum, and also minimum at the power of boost module 400 internal consumption, efficiency is also the highest.So compare closed loop charge pump circuit, driving force and the efficiency of open loop charge pump circuit improve all greatly.
It can also be seen that from Fig. 1, in order to limit the ceiling voltage that open loop charge pump exports, general open loop charge pump circuit has over-voltage protecting function.Overvoltage protection signal generation module 100 detects the first output voltage signal V
oUT, as the first output voltage signal V
oUTexceed protection threshold voltage V
oVP1time, produce effective overvoltage protection signal V
oV, overvoltage protection signal V
oVafter voltage up control signal generation module 300, pass through V
ccontrol boost module 400 internal switch pipe and stop boosting work, to limit the first output voltage signal V
oUTcontinuation raises and reaches the object of overvoltage protection, after stopping boosting work, and the first output voltage signal V
oUTdue to load R
lOADcan reduce gradually, but work as V
oUTbe reduced to and cancel overvoltage protection threshold voltage V
oVP2time, overvoltage protection signal V
oVit is invalid to become, voltage up control signal V
ccontrol boost module 400 internal switch pipe to rework, output voltage raises.If the first output voltage signal V
oUTat V
oVP1and V
oVP2between repeatedly change, then overvoltage protection can be triggered repeatedly, output voltage V when overvoltage protection triggers repeatedly
oUTwith overvoltage protection signal V
oVwaveform as shown in Figure 2.
Because the switching tube of open loop charge pump circuit operationally boost module 400 inside is all abundant conducting; but in order to consider the driving force of open loop charge pump; thus in the design process of open loop charge pump circuit, generally current-limiting circuit is not set or the cut-off current value of current-limiting circuit is arranged larger, like this as overvoltage protection signal V
oVafter neutralizing, recover internal switch pipe in the process of boosting work at boost module 400 and can flow through very large transient current, thus the first output voltage signal V
oUTtriggering overvoltage protection of leaping high within very short time makes overvoltage protection signal V
oVbecome effectively and restart to carry out overvoltage protection.But be elevated to the effective overvoltage protection signal V of generation from the first output voltage signal
oVagain to stopping all occurring certain time delay in the process of boosting; again owing to giving the charging and discharging currents of the charge pump current of boosting very large when open loop charge pump circuit is resumed work; when causing overvoltage protection, output voltage ripple is very large, the first output voltage signal V after such overvoltage protection
oUTjust need the time more grown just can be reduced to and cancel overvoltage protection threshold voltage V
oVP2, reduce the first output voltage signal V
oUTripple frequency.
If the first output voltage signal V
oUTripple excessive, such open loop charge pump circuit just can not be powered to the equipment of the little output ripple of ask for something, and output voltage ripple is excessive, also can reduce driving force and the efficiency of open loop charge pump; In addition, the output voltage ripple frequency reduction caused because output voltage ripple is excessive also can impact some application, the words that such as open loop charge pump circuit is powered to audio parts, the output voltage ripple frequency of open loop charge pump circuit is reduced to lower than 20kHz, then can cause interference to audio signal, the noise that generation can be heard, reduce tonequality, thus a kind of open loop charge pump circuit that can reduce output voltage ripple has been called a kind of demand.
Summary of the invention
For the problems referred to above, the present invention aims to provide a kind of open loop charge pump circuit reducing output voltage ripple, it adds output voltage ripple control module on the basis of original open loop charge pump circuit, with the problem that the ripple solving the first output voltage signal is excessive.
Technical scheme provided by the invention is as follows:
A kind of open loop charge pump circuit reducing output voltage ripple, described open loop charge pump circuit comprises: for generating the overvoltage protection signal generation module of overvoltage protection signal according to the first output voltage signal of described open loop charge pump circuit, for generation of the work clock generation module of switch clock signal, for generating the voltage up control signal generation module of voltage up control signal according to described switch clock signal and described overvoltage protection signal, for realizing to the boost module of described first output voltage signal control and for carrying out to described first output voltage signal the output voltage ripple control module that ripple control exports the second output voltage signal according to described voltage up control signal, wherein, the input of described overvoltage protection signal generation module is connected with the output of described boost module, output is connected with the input of described voltage up control signal generation module, the output of described work clock generation module is connected with the input of described voltage up control signal generation module, the output of described voltage up control signal generation module is connected with the input of described boost module, the input of described output voltage ripple control module is connected with the output of described boost module.
In the technical program, the ripple of the first output voltage signal is controlled by output voltage ripple control module, certainly, in invention, namely the ripple of control first output voltage signal that mention here refers to the ripple of reduction first output voltage signal, so only needs to add output voltage ripple control module on the basis of original charge pump and can realize open loop charge pump and require to apply in less application at some ripples.
Preferably, in described open loop charge pump circuit, also comprise at least one output capacitance, one end of described output capacitance be connected with the output of described output voltage ripple control module, other end ground connection, for stablizing the ripple of described second output voltage signal.
In the technical program, the voltage that make use of the voltage at output capacitance two ends can not suddenly change to realize the object that open loop charge pump circuit reduces the first output voltage signal ripple.
Preferably; described overvoltage protection signal generation module, described voltage up control signal generation module, described work clock generation module, described boost module and described voltage ripple control module are integrated into the first circuit chip, realize the control to the first output voltage signal ripple.
In the technical program, above-mentioned module integration is realized object in the first circuit chip, realize simplifying of open loop charge pump circuit.
Preferably, described output voltage ripple control module comprises a ripple control resistance, and one end of described ripple control resistance is connected with the output of described boost module, the other end is connected with described output capacitance.
In the technical program, output voltage ripple control module is a ripple control resistance, realizes the reduction to the first output voltage signal ripple by this ripple control resistance and the common effect of output capacitance.
Preferably; described overvoltage protection signal generation module, described voltage up control signal generation module, described work clock generation module and described boost module are integrated into second circuit chip, and the described input of voltage ripple control module is connected with the output of integrated circuit, output is connected with one end of described output capacitance.
Preferably, described output voltage ripple control module comprises a ripple control resistance, and one end of described ripple control resistance is connected with the output of described boost module, the other end is connected with described output capacitance.
In the technical program, output voltage ripple control module is a ripple control resistance, realizes the reduction to the first output voltage signal ripple by this ripple control resistance and the common effect of output capacitance.
Preferably, also comprise the first charge pump capacitor being connected in parallel on described boost module two ends respectively and the second charge pump capacitor in described open loop charge pump circuit, described boost module is by the output of the first output voltage signal described in the charge and discharge control of described first charge pump capacitor and described second charge pump capacitor.
In open loop charge pump circuit provided by the invention, control by adding the ripple of output voltage ripple control module to the first output voltage signal in original open loop charge pump circuit, improve the ripple frequency of the first output voltage signal while reducing the ripple of the first output voltage signal, improve driving force and the efficiency of circuit relative to existing open loop charge pump circuit; Efficiently solve due to the excessive problem caused of the first output voltage signal ripple simultaneously, extend the application of open loop charge pump circuit, namely open loop charge pump circuit provided by the invention can be applied in the less application of ask for something first output voltage signal ripple; In addition, due to the raising of the first output voltage signal ripple frequency, efficiently solve the too low problem such as tonequality reduction, noise occurred of the first output voltage signal ripple frequency caused because load power consumption is lower.
Accompanying drawing explanation
Below by clearly understandable mode, accompanying drawings preferred implementation, is further described above-mentioned characteristic, technical characteristic, advantage and implementation thereof.
Fig. 1 is existing open loop charge pump circuit structural representation;
Fig. 2 is output voltage and the overvoltage protection signal oscillogram that existing open loop charge pump circuit triggers overvoltage protection repeatedly;
Fig. 3 is output voltage and the overvoltage protection signal waveform enlarged drawing that existing open loop charge pump circuit triggers overvoltage protection repeatedly;
Fig. 4 is two-stage comparator circuit figure in existing open loop charge pump circuit;
Fig. 5 is the structural representation of open loop charge pump circuit first embodiment reducing voltage ripple in the present invention;
Fig. 6 is the structural representation of open loop charge pump circuit second embodiment reducing voltage ripple in the present invention;
Fig. 7 is existing open loop charge pump circuit and open loop charge pump circuit overvoltage protection comparison of wave shape figure of the present invention.
Reference numeral:
C
fLYING1-the first charge pump capacitor, C
fLYING2-the second charge pump capacitor,
V
sP-the first output voltage signal, V
oUT-the second output voltage signal, V
oSC-switch clock signal,
V
oV-overvoltage protection signal, V
oVP1-the first output voltage threshold value, V
oVP2-the second output voltage threshold value,
V
c-voltage up control signal, R
lOAD-output loading, C
oUT-output capacitance,
The parasitic capacitance that in CL1-two stage comparator, the first order exports and load capacitance sum;
The parasitic capacitance that in CL2-two stage comparator, the second level exports and load capacitance sum;
100-overvoltage protection signal generation module, 200-work clock generation module,
300-voltage up control signal generation module, 400-boost module, 500-output voltage ripple control module.
Embodiment
In order to be illustrated more clearly in the embodiment of the present invention or technical scheme of the prior art, contrast accompanying drawing is illustrated the specific embodiment of the present invention below.Apparently, accompanying drawing in the following describes is only some embodiments of the present invention, for those of ordinary skill in the art, under the prerequisite not paying creative work, other accompanying drawing can also be obtained according to these accompanying drawings, and obtain other execution mode.
Be illustrated in figure 3 output voltage and overvoltage protection signal waveform enlarged drawing that existing open loop charge pump circuit triggers overvoltage protection repeatedly, as can be seen from the figure, in existing open loop charge pump circuit (as shown in Figure 1), as output voltage signal V
oUTrise to the first output voltage threshold value V
oVP1afterwards, overvoltage protection signal V
oVdo not become effectively immediately, but will after Δ T time delay after a while overvoltage protection signal V
oVjust can become effectively; Similarly, as output voltage signal V
oUTbe reduced to the second output voltage threshold value V
oVP2(namely aforesaidly cancel overvoltage protection threshold voltage V
oVP2) after also want time delay a period of time Δ T after overvoltage protection signal V
oVjust can become effectively, which increase the output voltage signal V in this open loop charge circuit
oUTripple.
The reason of above-mentioned time delay is caused to be to include in overvoltage protection signal generation module 100 two stage comparator as shown in Figure 4; CL1 wherein in diagram is parasitic capacitance and the load capacitance sum of first order output, and CL2 is parasitic capacitance and the load capacitance sum of second level output.Total time delay of this two stage comparator is that two-stage delayed addition obtains, and wherein first order time delay is that the first order exports V
oDvoltage jump to from quiescent point and the second level exported jump to the quiescent potential time used, concrete as formula (1):
Wherein, wherein Δ V
oDfor first order output voltage V
oDthe difference jumping to the voltage of working point is exported, I to making the second level from quiescent point voltage jump
m5it is the bias current of NMOS tube M5 in diagram.
Second level time delay exports from supply voltage V
dD(or GND) changes to the time making next stage saltus step required voltage (this voltage is the half of supply voltage) here, concrete as formula (2) and (3):
(output voltage V
oby high step-down) (2)
Or
(output voltage V
ouprised by low) (3)
Can obtain total comparison time delay is:
ΔT=ΔT1+ΔT2
In existing open loop charge pump circuit, above-mentioned comparison time delay is always greatly about 100 ~ 300ns (nanosecond) left and right, if the comparator time delay of pressing 200ns calculates, and open loop charge pump output capacitance C
oUTfor 1uF (microfarad), overvoltage protection signal V
oVcancelling rear switching tube On current is that 1A calculates, then output voltage ripple is:
In order to solve the problem, be respectively open loop charge pump circuit first embodiment of reduction output voltage ripple provided by the invention and the structural representation of the second embodiment as shown in Figure 5 and Figure 6, as can be seen from the figure, reduce all to include overvoltage protection signal generation module 100 in the open loop charge pump circuit of output voltage ripple in first embodiment and the second real-time example, work clock generation module 200, voltage up control signal generation module 300, boost module 400 and output voltage ripple control module 500, wherein, the input of overvoltage protection signal generation module 100 is connected with the output of boost module 400, output is connected with the input of voltage up control signal generation module 300, the output of work clock generation module 200 is connected with the input of voltage up control signal generation module 300, the output of voltage up control signal generation module 300 is connected with the input of boost module 400, the input of output voltage ripple control module 500 is connected with the output of boost module 400.In first embodiment and the second embodiment difference yes; in a first embodiment; overvoltage protection signal generation module 100, voltage up control signal generation module 300, work clock generation module 200, boost module 400 and voltage ripple control module are integrated into the first circuit chip, realize the first output voltage signal V
sPthe control of ripple; And in a second embodiment; overvoltage protection signal generation module 100, voltage up control signal generation module 300, work clock generation module 200 and boost module 400 are integrated into second circuit chip; voltage ripple control module is not integrated in second circuit chip, but is arranged between output capacitance and boost module 400.Can find out, the difference in two embodiments is only whether be integrated in integrated circuit (IC) chip by output voltage ripple control module 500, and it is two kinds of real-time modes of open loop charge pump circuit of the present invention, and its function realized is the same.
In simple terms in the course of the work, first the open loop charge pump circuit in above-mentioned two embodiments passes through the first output voltage signal V that overvoltage protection signal generation module 100 divided ring charge pump circuit (boost module 400) exports
sPdetect, and by this first output voltage signal V
sPwith the first output voltage threshold value V
oVP1with the second output voltage threshold value V
oVP2(the first output voltage threshold value V
oVP1be greater than the second output voltage threshold value V
oVP2) compare, as the first output voltage signal V
sPbe greater than the first output voltage threshold value V
oVP1time, then overvoltage protection signal generation module 100 produces effective overvoltage protection signal V
oVand by this overvoltage protection signal V
oVbe sent to voltage up control signal generation module 300; Meanwhile, work clock generation module 200 generates switch clock signal V
oSCand this signal is sent to voltage up control signal generation module 300; Subsequently, voltage up control signal generation module 300 is according to the overvoltage protection signal V received
oVwith switch clock signal V
oSCgenerate corresponding voltage up control signal V
cand by this signal input boost module 400; And then by using this voltage up control signal V in boost module 400
ccontrol boost module 400 internal switch pipe and stop boosting work, prevent the first output voltage signal V
sPcontinue to rise, thus reach the object of overvoltage protection.As the first output voltage signal V
sPafter stopping rising, at output loading R
lOADeffect under this first output voltage signal V
sPcan reduce until be reduced to the second output voltage threshold value V gradually
oVP2time, then overvoltage protection signal V
oVit is invalid to become, afterwards voltage up control signal V
ccontrol boost module 400 internal switch pipe to rework, the first output voltage signal V
sPrise.Such first output voltage signal V
sPat the first output voltage threshold value V
oVP1with the second output voltage threshold value V
oVP2between repeatedly change, then overvoltage protection signal generation module 100 can be triggered repeatedly, this first output voltage signal V
sPwith overvoltage protection signal V
oVwaveform as illustrated in fig 2 and fig.Again in order to reduce the first output voltage signal V
sPripple, output voltage ripple is controlled 500 outputs being arranged on boost module 400 by us, reaches reduction first output voltage signal V by this output voltage ripple control module 500
sPripple and the second output voltage signal V
oUTthe object of ripple, improves the first output voltage signal V simultaneously
sPripple frequency and the second output voltage V
oUTripple frequency.
Furthermore, the two stage comparator input in the overvoltage protection signal generation module 100 in open loop charge pump circuit provided by the invention inputs the first output voltage signal V respectively
sP, the first output voltage threshold value V
oVP1with the second output voltage threshold value V
oVP2, output is connected with the input of voltage up control signal generation module 300.The positive input terminal Vp of two stage comparator meets the first output voltage signal V
sPvoltage division signal (V
sPsignal amplitude is too large, is generally divided to about 1V with divider resistance), the negative input end Vn of two stage comparator meets a reference voltage signal Vref, this reference voltage signal be the reference voltage V ref1 that compares of selection two and Vref2 one of them.As the output voltage V of comparator
oin order to select Vref1 during low level, (corresponding OVP threshold voltage is V
oPV1), as the output voltage V of comparator
oin order to select Vref2 during high level, (corresponding OVP threshold voltage is V
oVP2).V after starting
sPrise from 0V, work as V
sPvoltage is elevated to higher than V
oVP1time, comparator output voltage V
obecome high level, after OVP protection, work as V
sPvoltage is reduced to lower than V
oVP2time, comparator output voltage V
obecome low level.Output rusults Vo in diagram is the overvoltage protection signal V exported in overvoltage protection signal generation module 100
oV.Further, the first charge pump capacitor C being connected in parallel on boost module 400 two ends respectively is also comprised in open loop charge pump circuit
fLYING1with the second charge pump capacitor C
fLYING2, boost module 400 is by the first charge pump capacitor C
fLYING1with the second charge pump capacitor C
fLYING2charge and discharge control first output voltage signal V
sPoutput.
In addition, in order to realize object of the present invention, in open loop charge pump circuit, at least one output capacitance C is also comprised
oUT, and this output capacitance C
oUTone end be connected with the output of output voltage ripple control module 500, other end ground connection, for stablizing the second output voltage signal V
oUTripple.In a particular embodiment, output voltage ripple control module 500 is a ripple control resistance, and one end of ripple control resistance is connected with the output of boost module 400, the other end and output capacitance C
oUTconnect.Fig. 7 is existing open loop charge pump circuit and open loop charge pump circuit overvoltage protection comparison of wave shape figure of the present invention, and as can be seen from the figure, the open loop charge pump circuit in the present invention is at overvoltage protection signal V
oVtime effective, boost module 400 stops boosting, does not now have electric current through ripple control resistance, thus the first output voltage signal V at now ripple control resistance two ends
sPwith the second output voltage signal V
oUTequal, and as overvoltage protection signal V
oVwhen the boost module 400 that neutralizes starts to boost work, the first charge pump capacitor C
fLYING1with the second charge pump capacitor C
fLYING2charging and discharging currents through ripple control resistance, the second output voltage signal V
oUTat output capacitance C
oUTeffect can not suddenly change, thus the first output voltage signal V
sPat the second output voltage signal V
oUTbasis on add the voltage at ripple control resistance two ends, and then there is voltage jump (sudden change value is the voltage at ripple control resistance two ends) at this point, and then the second output voltage signal V
oUTwith the first output voltage signal V
sPvoltage synchronous raises, due at the first output voltage signal V
sPadd said mutation voltage, so when all parameters of existing open loop charge pump circuit are all constant, output voltage ripple reduces the magnitude of voltage at ripple control resistance two ends, and as can be seen from Figure 7 output voltage ripple frequency also improves simultaneously, and then reaches object of the present invention.Be noted that in the present invention, we do not limit the occurrence of ripple control resistance, can adjust according to actual conditions.
It should be noted that above-described embodiment all can independent assortment as required.The above is only the preferred embodiment of the present invention; it should be pointed out that for those skilled in the art, under the premise without departing from the principles of the invention; can also make some improvements and modifications, these improvements and modifications also should be considered as protection scope of the present invention.