CN204652222U - A kind of booster type dc-dc - Google Patents

Abstract

The utility model provides a kind of booster type dc-dc, is in series with inductance L, sustained diode, load resistance R1 ~ R4 and load resistance R0 between the both positive and negative polarity of described power supply Vin successively, the negative pole also ground connection of described power supply Vin; The Q end of described pulse width modulation type controller is connected with the grid of switching tube M, and detecte1 test side is connected with the rear end of load resistance R3, is connected after detecte2 test side is connected with the source class of switching tube M with the rear end of load resistance R4; The drain electrode of switching tube M is connected with the rear end of inductance L; Have transducer of the present utility model very high conversion efficiency, low-work voltage, undercurrent and overcurrent detect and the characteristic such as energy-saving mode control; There is provided biased by bandgap voltage reference to converter inside working point, greatly increase the stability of system, improve anti-mains fluctuations, the suppression of the interference that the change of temperature and noise cause.

Description

A kind of booster type dc-dc

Technical field

The utility model relates to electricity field, is specifically related to a kind of booster type dc-dc.

Background technology

D.C. regulated power supply is also dc-dc, Switching Power Supply or switch adjuster.D.C. regulated power supply, as a branch of power-supply system, is widely used in the fields such as communication, computer, household electrical appliance.Stabilized voltage power supply is divided into the large class of linear stable and switch voltage-stabilizing source two.The main feature of linear stable is that Correctional tube is operated in Linear Amplifer state, and have the advantages such as stability is high, good reliability, cost are lower, shortcoming is that conversion efficiency is low, and power consumption is large, volume is large, limits the application of linear stabilized power supply.Switching Power Supply is called as energy-efficient power supply, in recent years, along with the fast development of electronic device, electromagnetic material, voltage transformation technology, switch power technology obtains sizable breakthrough, can substitute linear stabilized power supply gradually, become the main product of stabilized voltage power supply.Switching Power Supply conversion efficiency is lower, and inner key components is operated in HF switch state, the poor stability of system, and anti-mains fluctuations ability is low, and does not possess undercurrent and overcurrent detects and control ability.

Utility model content

For solving the problems of the technologies described above, the utility model provides a kind of booster type dc-dc.

The utility model is achieved by the following technical programs.

A kind of booster type dc-dc that the utility model provides, comprises power supply Vin, inductance L, sustained diode, filter capacitor C, load resistance R0 ~ R4, pulse width modulation type controller and switching tube M; Inductance L, sustained diode, load resistance R1 ~ R4 and load resistance R0 is in series with successively, the negative pole also ground connection of described power supply Vin between the both positive and negative polarity of described power supply Vin; The Q end of described pulse width modulation type controller is connected with the grid of switching tube M, and detecte1 test side is connected with the rear end of load resistance R3, is connected after detecte2 test side is connected with the source class of switching tube M with the rear end of load resistance R4; The drain electrode of switching tube M is connected with the rear end of inductance L; Described filter capacitor C is in parallel with load resistance R1 ~ R4; Between described load resistance R1 and load resistance R2, between load resistance R2 and load resistance R3, be respectively arranged with voltage output end Vout1, Vout2.

Described pulse width modulation type controller comprise error amplifier A, main comparator C1, undercurrent comparator C2, overcurrent comparator C3, inverter inv1, saw-toothed wave generator U1, with or door XNOR1 ~ XNOR2, with door AND1 ~ AND3 or door OR1 ~ OR2, rest-set flip-flop U2, drive circuit drive and soft starting circuit soft-start, error amplifier A, main comparator C1, undercurrent comparator C2, overcurrent comparator C3 are all connected with enable signal end enable with the Enable Pin en of saw-toothed wave generator U1; The positive input terminal of error amplifier A and normal voltage V _ref1end connects, and negative input end is connected with detecte1 test side, and output is connected with the negative input end of main comparator C1; The positive input terminal of main comparator C1 is connected with the signal output part of saw-toothed wave generator U1, and output is connected with an input of door by inverter inv1; The output of main comparator C1 also with an input of door AND2 is connected; 1 pin of saw-toothed wave generator U1 and 2 pin respectively with V _in1end and V _in2end connects.

The positive input terminal of undercurrent comparator C2, the negative input end of overcurrent comparator C3 are all connected with detecte2 test side, the negative input end of undercurrent comparator C2 and normal voltage V _ref2end connects, and the positive input terminal of overcurrent comparator C3 is unsettled; The output of undercurrent comparator C2 respectively with or the B of door XNOR1 hold, with or the B of door XNOR2 hold and or the input of door OR2 be connected, the output of overcurrent comparator C3 respectively with together or the A of door XNOR1 holds, with or the A of door XNOR2 holds and or the input of door OR1 be connected.

Output that is same or door XNOR1 is connected with another input of door AND1, and output that is same or door XNOR2 is connected with another input of door AND2; With the output of door AND1 with or another input of door OR1 be connected, with the output of door AND2 with or another input of door OR2 be connected, door OR1 with or the output of door OR2 is held with the S of rest-set flip-flop U2 respectively and R holds and is connected, the output of rest-set flip-flop U2 is connected with an input of door AND3; To be held with enable signal enable by soft starting circuit soft-start with another input of door AND3 and be connected, output passes through drive circuit drive and is connected with the output Q of pulse width modulation type controller.

Described main comparator A comprises switching tube M1 ~ M13 and inverter inv2, and switching tube M5, M6, M8 all hold with power supply Vdd with the source class of M10 and be connected, and the grid of switching tube M5 with M6 is all held with bias current Bias and is connected; The drain electrode of switching tube M5 is connected with the source class of switching tube M1 and M2 respectively; The grid of M1 with M2 of opening the light is connected with power supply Vin+ and Vin-respectively, and the drain electrode of switching tube M1 is connected with the drain electrode of switching tube M12, the drain and gate of switching tube M3 respectively, and the grid of switching tube M3 is also connected with the grid of switching tube M4.

The drain electrode of switching tube M4 is connected with the drain electrode of switching tube M2, the grid of switching tube M7 respectively; The grid of the drain electrode of switching tube M7, the drain electrode of switching tube M6, switching tube M8 is connected with the grid of switching tube M9; The grid of the drain electrode of switching tube M9, the drain electrode of switching tube M8, switching tube M10 is connected with the grid of switching tube M11; The drain electrode of switching tube M10 is connected with the drain electrode of switching tube M11 and M13 respectively and is connected with voltage output end Vout3 afterwards; Enable signal enable is connected with the signal input part of inverter inv2, and the signal output part of inverter inv2 is connected with the grid of switching tube M12 and M13 respectively; The equal ground connection of source class of switching tube M12, M3, M4, M7, M9, M11 and M13.

Described undercurrent comparator C2 comprises switching tube M14 ~ M17 and operational amplifier B, the source class of switching tube M16 with M17 is all held with power supply Vdd and is connected, grid is all held with bias current Bias and is connected, the drain electrode of switching tube M16 is connected with the source class of switching tube M14 and the positive input terminal of operational amplifier B respectively, and the drain electrode of switching tube M17 is connected with the source class of switching tube M15 and the negative input end of operational amplifier B respectively; The output of operational amplifier B is connected with the output end vo ut4 of undercurrent comparator C2; The grid of switching tube M14 is held with power supply Vin+ and is connected, and drain electrode is connected with the drain electrode of switching tube M15, the grounded-grid of switching tube M15.

The beneficial effects of the utility model are: the booster type dc-dc providing a kind of high conversion efficiency, output ripple and low, and this transducer has very high conversion efficiency, low-work voltage, undercurrent and overcurrent and detects and the characteristic such as energy-saving mode control; There is provided biased by bandgap voltage reference to converter inside working point, greatly increase the stability of system, improve anti-mains fluctuations, the suppression of the interference that the change of temperature and noise cause; And adopting the CMOS technology of 0.25 μm, its conversion efficiency can reach more than 90%, and be under the condition of 2.5V at input voltage, output voltage is 3.3V and 5V of standard.

Accompanying drawing explanation

Fig. 1 is circuit diagram of the present utility model;

Fig. 2 is the circuit diagram of pulse width modulation type controller in Fig. 1;

Fig. 3 is the circuit diagram of main comparator in Fig. 2;

Fig. 4 is the circuit diagram of undercurrent comparator in Fig. 2;

Fig. 5 is the sensitivity analysis analogous diagram of main comparator in Fig. 3;

Fig. 6 is the sensitivity analysis analogous diagram of undercurrent comparator in Fig. 4;

Fig. 7 is the simulation result figure of Fig. 1.

Embodiment

Further describe the technical solution of the utility model below, but described in claimed scope is not limited to.

A kind of booster type dc-dc as shown in Fig. 1 ~ Fig. 7, comprises power supply Vin, inductance L, sustained diode, filter capacitor C, load resistance R0 ~ R4, pulse width modulation type controller and switching tube M; Inductance L, sustained diode, load resistance R1 ~ R4 and load resistance R0 is in series with successively, the negative pole also ground connection of described power supply Vin between the both positive and negative polarity of described power supply Vin; The Q end of described pulse width modulation type controller is connected with the grid of switching tube M, and detecte1 test side is connected with the rear end of load resistance R3, is connected after detecte2 test side is connected with the source class of switching tube M with the rear end of load resistance R4; The drain electrode of switching tube M is connected with the rear end of inductance L; Described filter capacitor C is in parallel with load resistance R1 ~ R4; Between described load resistance R1 and load resistance R2, between load resistance R2 and load resistance R3, be respectively arranged with voltage output end Vout1, Vout2.The control impuls of switching tube M is provided by pulse width modulation type controller (PWM).Switching tube M4 controls conducting or cut-off by input pulse.When switching tube M conducting, power supply is to inductance L energy storage, and inductive current increases, and its induced electromotive force is left positive right negative.Because switching tube M conducting resistance is close to zero, the voltage on filter capacitor C is upper just lower negative, then sustained diode is in reverse blocking state, and the voltage on filter capacitor C is discharged by load resistance; When switching tube M ends, inductive current reduces, and the induced electromotive force in inductance L is that the right side is just being born in a left side, and now diode is in forward conduction, and supply voltage and inductance L voltage are added and charge to filter capacitor C.Therefore, a pulse period, will higher than input voltage through the filtered output voltage average value of filter capacitor C.

Under the condition of inductance L current continuity, the control impuls cycle of configuration switch pipe M is T, and switching tube M ON time is 0 ~ T1; Switching tube M deadline is T1 ~ T, and the curent change in inductance L is at switching tube M conducting equal with deadline (Δ I), then circuit working is divided into two kinds of situations by the M conducting of Fig. 1 breaker in middle pipe and cut-off:

(1) switching tube M conduction period, now sustained diode cut-off, the electric current in inductance L rises, and the expression formula of its circuit is:

$\begin{array}{ccc}{V}_{\mathrm{in}}& L\·\frac{\begin{array}{cc}{I}_2& I_1\end{array}}{T_1}& L\·\frac{I}{T_1}\end{array}---\left(1\right)$

(2) between the switching tube M off period, because the electric current in inductance L can not suddenly change, then sustained diode conducting, the expression formula of its circuit is:

$\begin{array}{ccc}{V}_{\mathrm{out}}& V_{\mathrm{in}}& L\·\frac{I}{T_2}\end{array}---\left(2\right)$

Then: $\begin{array}{ccc}I& \frac{V_{\mathrm{in}}\·T_1}{L}& \frac{\left(\begin{array}{cc}{V}_{\mathrm{out}}& V_{\mathrm{in}}\end{array}\right)T_2}{L}\end{array}---\left(3\right)$

When setting the duty ratio of control impuls as k, switching tube M ON time is T ₁kT; Metal-oxide-semiconductor deadline is T ₂(1 k) T.By T ₁, T ₂(3) formula of bringing into obtains:

$\begin{array}{cc}{V}_{\mathrm{out}}& \frac{V_{\mathrm{in}}}{\begin{array}{cc}1& k\end{array}}\end{array}---\left(4\right)$

As can be seen from the above equation, because k is less than 1, then this dc-dc is boosting type converter, and the output voltage of transducer is greater than input voltage.

Described pulse width modulation type controller comprise error amplifier A, main comparator C1, undercurrent comparator C2, overcurrent comparator C3, inverter inv1, saw-toothed wave generator U1, with or door XNOR1 ~ XNOR2, with door AND1 ~ AND3 or door OR1 ~ OR2, rest-set flip-flop U2, drive circuit drive and soft starting circuit soft-start, error amplifier A, main comparator C1, undercurrent comparator C2, overcurrent comparator C3 are all connected with enable signal end enable with the Enable Pin en of saw-toothed wave generator U1; The positive input terminal of error amplifier A and normal voltage V _ref1end connects, and negative input end is connected with detecte1 test side, and output is connected with the negative input end of main comparator C1; The positive input terminal of main comparator C1 is connected with the signal output part of saw-toothed wave generator U1, and output is connected with an input of door by inverter inv1; The output of main comparator C1 also with an input of door AND2 is connected; 1 pin of saw-toothed wave generator U1 and 2 pin respectively with V _in1end and V _in2end connects.Detecte1 test side and detecte2 test side are the test side of PWM-Controller pulse width modulation type controller respectively.V _in1end and V _in2end is all voltage signal end, is the voltage signal that in Fig. 1, voltage output end Vout1 and Vout2 passes through respectively.

The positive input terminal of undercurrent comparator C2, the negative input end of overcurrent comparator C3 are all connected with detecte2 test side, the negative input end of undercurrent comparator C2 and normal voltage V _ref2end connects, and the positive input terminal of overcurrent comparator C3 is unsettled; The output of undercurrent comparator C2 respectively with or the B of door XNOR1 hold, with or the B of door XNOR2 hold and or the input of door OR2 be connected, the output of overcurrent comparator C3 respectively with together or the A of door XNOR1 holds, with or the A of door XNOR2 holds and or the input of door OR1 be connected.

Output that is same or door XNOR1 is connected with another input of door AND1, and output that is same or door XNOR2 is connected with another input of door AND2; With the output of door AND1 with or another input of door OR1 be connected, with the output of door AND2 with or another input of door OR2 be connected, door OR1 with or the output of door OR2 is held with the S of rest-set flip-flop U2 respectively and R holds and is connected, the output of rest-set flip-flop U2 is connected with an input of door AND3; To be held with enable signal enable by soft starting circuit soft-start with another input of door AND3 and be connected, output passes through drive circuit drive and is connected with the output Q of pulse width modulation type controller.

When the signal that enable signal enable holds is " 0 ", chip is in electricity-saving state; When the signal that enable signal enable holds is " 1 ", chip is in normal operating conditions.The voltage signal that detect1 test side detects, through error amplifier A and 2.5V normal voltage V _ref1after produce error signal, this error signal receives the negative input end of main comparator C1, and the output of the positive input termination saw-toothed wave generator U1 of main comparator C1 connects.Main comparator C1 produces the pulse that an output duty cycle changes with error voltage signal under the acting in conjunction of sawtooth signal and error signal.When the voltage signal detected when detect 2 test side is between 10mV to 500mV, the output of undercurrent comparator C2 and overcurrent comparator C3 is " 0 ", through with or door XNOR1 and XNOR2 after export and be " 1 ", this signal respectively as the input signal with door AND1 and AND2, is then only decided by the output signal of main comparator C1 with the output of door AND1 and AND2; Simultaneously the low level signal of undercurrent comparator C2 and overcurrent comparator C3 export as or the input of door, or the output signal of main comparator C1 is also only depended in the output of door OR1 and OR2. the voltage signal detected when detect 1 test side is lower than 2.5V, the R input of rest-set flip-flop U2 is delivered on pulse signal one tunnel that main comparator C1 output duty cycle is larger, another road signal delivers to the S input of rest-set flip-flop U2 after inverter is anti-phase, so the output of rest-set flip-flop U2 makes the electric current of main circuit rise after current drives.Otherwise the voltage signal detected when detect1 test side is higher than 2.5V, and the electric current of main circuit declines.Change the electric current that control wave duty ratio can regulate main circuit, the voltage signal detected as main circuit test side detect 2 is lower than 10mV, undercurrent comparator C2 and overcurrent comparator C3 exports and is respectively " 1 " and " 0 ", same or door exports as " 0 ", two shield with door by this low level output, the S end of rest-set flip-flop U2 is all by set, R end is by reset, so exporting Q is " 1 ", make main circuit current increase rapidly, thus guarantee that circuit working is at continuous duty (CCM).Equally, the voltage signal that main circuit test side detect 2 detects is higher than 500mV, overcurrent comparator C3 exports as " 1 ", undercurrent comparator C2 exports as " 0 ", main comparator C1 conductively-closed, and the S end of rest-set flip-flop U2 is all set to " 0 ", R end is set to " 1 " simultaneously, export Q to be set to " 0 ", main circuit current is declined rapidly, thus effectively prevent power switch pipe overcurrent and damage.

Described main comparator A comprises switching tube M1 ~ M13 and inverter inv2, and switching tube M5, M6, M8 all hold with power supply Vdd with the source class of M10 and be connected, and the grid of switching tube M5 with M6 is all held with bias current Bias and is connected; The drain electrode of switching tube M5 is connected with the source class of switching tube M1 and M2 respectively; The grid of M1 with M2 of opening the light is connected with power supply Vin+ and Vin-respectively, and the drain electrode of switching tube M1 is connected with the drain electrode of switching tube M12, the drain and gate of switching tube M3 respectively, and the grid of switching tube M3 is also connected with the grid of switching tube M4.The drain electrode of switching tube M4 is connected with the drain electrode of switching tube M2, the grid of switching tube M7 respectively; The grid of the drain electrode of switching tube M7, the drain electrode of switching tube M6, switching tube M8 is connected with the grid of switching tube M9; The grid of the drain electrode of switching tube M9, the drain electrode of switching tube M8, switching tube M10 is connected with the grid of switching tube M11; The drain electrode of switching tube M10 is connected with the drain electrode of switching tube M11 and M13 respectively and is connected with voltage output end Vout3 afterwards; Enable signal enable is connected with the signal input part of inverter inv2, and the signal output part of inverter inv2 is connected with the grid of switching tube M12 and M13 respectively; The equal ground connection of source class of switching tube M12, M3, M4, M7, M9, M11 and M13.

The key modules of control unit is main comparator C1, and main comparator C1 is divided into simulation part and numerical portion.Simulation part is divided into two-stage differential amplifying circuit: first order amplifier is differential amplifier, and the second level is common-source amplifier.The output signal of saw-toothed wave generator and the output signal of error amplifier compare by first order amplifier, and the output signal of generation is through the input signal of common-source amplifier amplification as A/D conversion circuit.Numerical portion is two-stage standard CMOS inverter, and its function is that the analog signal of comparative result is converted to digital signal, and improves its current driving ability.As can be seen from analogous diagram, input direct voltage is from 2.495V to 2.505V, and two breakover points of its curve of output from low level to high level are respectively 2.499V and 2.501V, so the sensitivity of main comparator is similar to 1mV, meet the requirement of controller.

Described undercurrent comparator C2 comprises switching tube M14 ~ M17 and operational amplifier B, the source class of switching tube M16 with M17 is all held with power supply Vdd and is connected, grid is all held with bias current Bias and is connected, the drain electrode of switching tube M16 is connected with the source class of switching tube M14 and the positive input terminal of operational amplifier B respectively, and the drain electrode of switching tube M17 is connected with the source class of switching tube M15 and the negative input end of operational amplifier B respectively; The output of operational amplifier B is connected with the output end vo ut4 of undercurrent comparator C2; The grid of switching tube M14 is held with power supply Vin+ and is connected, and drain electrode is connected with the drain electrode of switching tube M15, the grounded-grid of switching tube M15.

Undercurrent comparator C2 will detect the voltage lower than 10mV, then the input voltage sensitivity of undercurrent comparator C2 is less than 1mV.In order to increase the sensitivity of comparator, the utility model adds voltage lifting circuit in the input stage of main comparator C1 circuit.Described voltage lifting circuit is made up of M14 ~ M17 tetra-switching tubes.The comparator threshold voltage of the A point shown in Fig. 4 is transferred to 10mV, then V _in+the very faint detection voltage obtained at major loop test point detect 2 place after M1 amplifies with 10mV voltage compare, therefore improve the sensitivity of undercurrent comparator C2.

As shown in Figure 6, be the sensitivity analogous diagram of undercurrent comparator.As can be seen from the figure, power supply V _in+input voltage from 9.5mV to 10.5mV, two breakover points of its curve of output from low level to high level are respectively 9.95mV and 10.05mV, so the sensitivity of main comparator C1 is similar to 0.05mV, meet the needs of system.

As shown in Figure 7, the simulation result figure of dc-dc.Described simulated conditions is: supply voltage 5V; The input voltage of 2.5V adds when time 1ms, and circuit working is in continuous mode.Can obtain from simulation result: output voltage is respectively 3.3V and 5V; Overshoot voltage is 0.5V ~ 0.8V; Ripple voltage is less than 30mV; The stable output time is approximately 1.2ms.Have this transducer very high conversion efficiency, low-work voltage, undercurrent and overcurrent detect and the characteristic such as energy-saving mode control; There is provided biased by bandgap voltage reference to converter inside working point, greatly increase the stability of system, improve anti-mains fluctuations, the suppression of the interference that the change of temperature and noise cause; And adopting the CMOS technology of 0.25 μm, its conversion efficiency can reach more than 90%.

Claims (4)

1. a booster type dc-dc, comprise power supply Vin, inductance L, sustained diode, filter capacitor C, load resistance R0 ~ R4, pulse width modulation type controller and switching tube M, it is characterized in that: between the both positive and negative polarity of described power supply Vin, be in series with inductance L, sustained diode, load resistance R1 ~ R4 and load resistance R0 successively, the negative pole also ground connection of described power supply Vin; The Q end of described pulse width modulation type controller is connected with the grid of switching tube M, and detecte1 test side is connected with the rear end of load resistance R3, is connected after detecte2 test side is connected with the source class of switching tube M with the rear end of load resistance R4;

The drain electrode of switching tube M is connected with the rear end of inductance L; Described filter capacitor C is in parallel with load resistance R1 ~ R4; Between described load resistance R1 and load resistance R2, between load resistance R2 and load resistance R3, be respectively arranged with voltage output end Vout1, Vout2.

2. booster type dc-dc as claimed in claim 1, it is characterized in that: described pulse width modulation type controller comprises error amplifier A, main comparator C1, undercurrent comparator C2, overcurrent comparator C3, inverter inv1, saw-toothed wave generator U1, with or door XNOR1 ~ XNOR2, with door AND1 ~ AND3, or door OR1 ~ OR2, rest-set flip-flop U2, drive circuit drive and soft starting circuit soft-start, error amplifier A, main comparator C1, undercurrent comparator C2, overcurrent comparator C3 is all connected with enable signal end enable with the Enable Pin en of saw-toothed wave generator U1, the positive input terminal of error amplifier A and normal voltage V _ref1end connects, and negative input end is connected with detecte1 test side, and output is connected with the negative input end of main comparator C1, the positive input terminal of main comparator C1 is connected with the signal output part of saw-toothed wave generator U1, and output is connected with an input of door by inverter inv1, the output of main comparator C1 also with an input of door AND2 is connected,

1 pin of saw-toothed wave generator U1 and 2 pin respectively with V _in1end and V _in2end connects;

The positive input terminal of undercurrent comparator C2, the negative input end of overcurrent comparator C3 are all connected with detecte2 test side, the negative input end of undercurrent comparator C2 and normal voltage V _ref2end connects, and the positive input terminal of overcurrent comparator C3 is unsettled; The output of undercurrent comparator C2 respectively with or the B of door XNOR1 hold, with or the B of door XNOR2 hold and or the input of door OR2 be connected, the output of overcurrent comparator C3 respectively with together or the A of door XNOR1 holds, with or the A of door XNOR2 holds and or the input of door OR1 be connected;

Output that is same or door XNOR1 is connected with another input of door AND1, and output that is same or door XNOR2 is connected with another input of door AND2; With the output of door AND1 with or another input of door OR1 be connected, with the output of door AND2 with or another input of door OR2 be connected, door OR1 with or the output of door OR2 is held with the S of rest-set flip-flop U2 respectively and R holds and is connected, the output of rest-set flip-flop U2 is connected with an input of door AND3;

To be held with enable signal enable by soft starting circuit soft-start with another input of door AND3 and be connected, output passes through drive circuit drive and is connected with the output Q of pulse width modulation type controller.

3. booster type dc-dc as claimed in claim 2, it is characterized in that: described main comparator A comprises switching tube M1 ~ M13 and inverter inv2, switching tube M5, M6, M8 all hold with power supply Vdd with the source class of M10 and are connected, and the grid of switching tube M5 with M6 is all held with bias current Bias and is connected; The drain electrode of switching tube M5 is connected with the source class of switching tube M1 and M2 respectively; The grid of M1 with M2 of opening the light is connected with power supply Vin+ and Vin-respectively, and the drain electrode of switching tube M1 is connected with the drain electrode of switching tube M12, the drain and gate of switching tube M3 respectively, and the grid of switching tube M3 is also connected with the grid of switching tube M4;

The drain electrode of switching tube M4 is connected with the drain electrode of switching tube M2, the grid of switching tube M7 respectively; The grid of the drain electrode of switching tube M7, the drain electrode of switching tube M6, switching tube M8 is connected with the grid of switching tube M9; The grid of the drain electrode of switching tube M9, the drain electrode of switching tube M8, switching tube M10 is connected with the grid of switching tube M11; The drain electrode of switching tube M10 is connected with the drain electrode of switching tube M11 and M13 respectively and is connected with voltage output end Vout3 afterwards;

Enable signal enable is connected with the signal input part of inverter inv2, and the signal output part of inverter inv2 is connected with the grid of switching tube M12 and M13 respectively;

The equal ground connection of source class of switching tube M12, M3, M4, M7, M9, M11 and M13.

4. booster type dc-dc as claimed in claim 2, it is characterized in that: described undercurrent comparator C2 comprises switching tube M14 ~ M17 and operational amplifier B, the source class of switching tube M16 with M17 is all held with power supply Vdd and is connected, grid is all held with bias current Bias and is connected, the drain electrode of switching tube M16 is connected with the source class of switching tube M14 and the positive input terminal of operational amplifier B respectively, and the drain electrode of switching tube M17 is connected with the source class of switching tube M15 and the negative input end of operational amplifier B respectively; The output of operational amplifier B is connected with the output end vo ut4 of undercurrent comparator C2;

The grid of switching tube M14 is held with power supply Vin+ and is connected, and drain electrode is connected with the drain electrode of switching tube M15, the grounded-grid of switching tube M15.