CN101494417A

CN101494417A - Asynchronous voltage-boosting converter

Info

Publication number: CN101494417A
Application number: CNA2008100014634A
Authority: CN
Inventors: 黄宗伟; 林水木; 陈健生; 朱冠任
Original assignee: Richtek Technology Corp
Current assignee: Richtek Technology Corp
Priority date: 2008-01-21
Filing date: 2008-01-21
Publication date: 2009-07-29
Anticipated expiration: 2028-01-21
Also published as: CN101494417B

Abstract

The invention discloses an asynchronous boost converter, comprising a low voltage component connected between an input end and an output end of the converter. When the converter is closed, the connection between the input end and the output end of the converter is cut off by the low voltage component to realize the load shedding. As the converter employs the low voltage component to achieve load switching, the efficiency can be improved and the cost can be reduced.

Description

Asynchronous voltage-boosting converter

Technical field

The present invention relates to a kind of asynchronous voltage-boosting converter, specifically, is that a kind of low pressure assembly that uses is reached the asynchronous voltage-boosting converter that load is cut off.

Background technology

Fig. 1 is traditional asynchronous voltage-boosting converter 10, it obtains an electric current 2 chargings produces output voltage VO UT to capacitor C by inductance L 1 and Schottky (Schottky) diode D1 by switching power switch (not shown) in the chip 12, because Schottky diode D1 has less forward bias voltage drop VF, therefore can obtain usefulness preferably.Yet, when voltage-boosting converter 10 is closed by signal Enable, when supposing to still have 3.7V by the input voltage VIN that battery provides, diode D1 will be switched on, and then produce the output voltage of about 3.3V at output, thereby the generation leakage current flows to earth terminal GND through resistance R 1 and R2.For fear of the generation of leakage current, people such as McGinty reach load when No. 314 propositions utilize LDMOS or JFET to make Schottky diode close (shutdown) at transducer and cut off (load disconnection) at United States Patent (USP) the 7th, 126.In addition, also having a kind of known method is to connect a switch to cut off to reach load between Xiao Te phase diode D1 and output VOUT, yet, the output voltage VO UT of voltage-boosting converter 10 is the high pressure of 10～40V, so must use high potential assembly to be used as switch, high potential assembly is not only relatively more expensive, and the conducting resistance is also bigger, so efficient is relatively poor.

Therefore known asynchronous voltage-boosting converter exists above-mentioned all inconvenience and problem.

Summary of the invention

Purpose of the present invention is to propose a kind of low pressure assembly that uses and reaches the asynchronous voltage-boosting converter that load is cut off.

Another purpose of the present invention is to propose a kind of asynchronous voltage-boosting converter with short-circuit protection and load cut-out function.

A further object of the present invention, being to propose a kind ofly can provide the asynchronous voltage-boosting converter of stablizing pre-charge current and short circuit current protection.

For achieving the above object, technical solution of the present invention is:

A kind of asynchronous voltage-boosting converter comprises an electric capacity, an inductance, and a diode, a switch, a transistor and a pressure limiting circuit are cut off in a load, it is characterized in that:

Described electric capacity connects the output of described transducer;

Described inductance is connected between the input and a node of described transducer;

Described diode is connected between described node and the described output;

Described switch connects described node, by switch described switch produce an inductive current through the described electric capacity charging of described inductance and diode pair to produce an output voltage;

The described inductance of transistor AND gate is cut off in described load and diode is connected between described input and the output, when described transducer is closed, cuts off the binding between described input and the output, and it is the low pressure assembly that transistor is cut off in described load;

Described pressure limiting circuit limits the voltage between described load cut-out transistor gate and the source electrode.

The device of the feedback linearization degree of 1.5 ∑s of improvement of the present invention-Δ modulation D type amplifier can also be further achieved by the following technical measures.

Aforesaid transducer comprises more that wherein an impedance component is connected described load and cuts off between transistorized gate and the source electrode, cuts off transistor in order to close described load when described transducer is closed.

Aforesaid transducer comprises also that wherein a short-circuit protection circuit detects described output voltage, sends a short-circuit protection signal to close described switch when described output short circuit.

Aforesaid transducer, wherein said short-circuit protection circuit comprise a comparator when described output voltage is lower than a critical value, produce described short-circuit protection signal.

Aforesaid transducer comprises also that wherein a current providing circuit provides a short circuit current protection to described electric capacity when described output short circuit.

Aforesaid transducer, wherein said current providing circuit comprise that a current mirror mirror one reference current produces described short circuit current protection.

Aforesaid transducer, wherein said current mirror comprise that one connects described reference current and a mirror branch described reference current of mirror produces described short circuit current protection with reference to branch.

Aforesaid transducer, wherein said mirror branch comprises that described load cuts off transistor.

Aforesaid transducer comprises further that wherein a current providing circuit provides pre-charge current that described electric capacity is charged when described transducer starts.

Aforesaid transducer, wherein said current providing circuit comprise that a current mirror mirror one reference current produces described pre-charge current.

Aforesaid transducer, wherein said current mirror comprise that one connects described reference current and a mirror branch described reference current of mirror produces described pre-charge current with reference to branch.

After adopting technique scheme, asynchronous voltage-boosting converter of the present invention uses the low pressure assembly to reach the load switching, thereby obtains the advantage of raising the efficiency and reducing cost.

Description of drawings

Fig. 1 is traditional asynchronous voltage-boosting converter;

Fig. 2 is embodiments of the invention;

The restriction of voltage VGS in Fig. 3 key diagram 2 transducers;

The short-circuit protection of Fig. 4 key diagram 2 transducers;

The pre-charge current of Fig. 5 displayed map 2 transducers;

Fig. 6 illustrates the load cut-out of transducer 20 in the embodiments of the invention.

Embodiment

See also Fig. 2; Fig. 2 is embodiments of the invention; in asynchronous voltage-boosting converter 20; inductance L is connected between input voltage VIN and the node V24LX; switch N1 is connected between node V24LX and the earth terminal GND; switch N1 should be from the control signal PWM of PWM logical circuit 24 and is switched; and then produce inductive current Iout through inductance L; charging produces output voltage V 24OUT to load RL to capacitor C o to embed (embedded) diode D1 and transistor P1; inverter 22 anti-phase enable signal EN produce signal ENB; transistor P1 is the load cutting assembly; because transistor P1 is the low pressure assembly; therefore in order to prevent that transistor P1 from damaging because of high pressure; use the voltage VGS between pressure limiting circuit 26 limit transistor P1 gates and the source electrode; make it be not more than a critical value; for example be not more than 5V; current providing circuit 28 charges to capacitor C o in order to stable pre-charge current and short circuit current to be provided; short-circuit protection circuit 30 detects output voltage V 24OUT to produce short-circuit protection signal Sc to PWM logical circuit 24 at the output short-circuit of transducer 20 during to earth terminal GND, makes its off switch N1.

Fig. 3 illustrates the restriction of voltage VGS in the transducer 20, wherein waveform 40 is for providing to the enable signal of transducer 20 external pins, waveform 42 is the transducer 20 enable signal EN after inner delayed, waveform 44 is the voltage VDS1 between transistor P1 drain and the source electrode, waveform 46 is the voltage VDS2 between transistor P0 drain and the source electrode, and waveform 48 is the voltage VGS between transistor P1 gate and the source electrode.Fig. 4 illustrates the short-circuit protection of transducer 20, and wherein waveform 50 is the voltage on the node V24LX, and waveform 52 is output voltage V 24OUT, and waveform 54 is electric current I out.The pre-charge current of Fig. 5 display converter 20, wherein waveform 56 is electric current I out, and waveform 58 is output voltage V 24OUT, and waveform 60 is the voltage on the node V24LX, and waveform 62 is signal EN.Fig. 6 illustrates the load cut-out of transducer 20 in the embodiments of the invention, and wherein, waveform 64 is electric current I out, and waveform 66 is output voltage V 24OUT, and waveform 68 is the voltage on the node V24LX, and waveform 70 is signal EN.

See also Fig. 2, Fig. 3 and Fig. 5, when signal EN transfers high levle to, shown in time t0, transducer 20 starts, suppose that input voltage VIN is 3.7V, because PWM logical circuit 24 does not also provide control signal PWM with diverter switch N1, so the voltage on the node V24DD approximates input voltage VIN, suppose that pressure limiting circuit 26 comprises five diodes that are connected into by the transistor of low pressure, and the forward bias voltage drop of each diode is 1V, so the maximum of the voltage VGS between transistor P1 gate and the source electrode will be limited in about 5V, voltage on node V24DD this moment approximately has only 3.7V again, so the voltage on the node A will equal 0, so transistor P0 and P1 and transistor N2 in the current providing circuit 28, N3 and N4 open (turn on), transistor P0 and P1 form current mirror, wherein transistor P0 connects electric current I 3 as reference branch, transistor P1 produces stable pre-charge current Iout as mirror branch mirror electric current I 3 capacitor C o is charged, make output voltage V 24OUT rise to 3.7V, shown in the waveform 56 of Fig. 5, electric current I 3=I1+I2 again is so can get pre-charge current

Iout=(I1+I2) * K formula 1

Wherein, K is a transistor P0 peace P1 electric current mirror ratio.When output voltage V 24OUT is charged to 3.7V by pre-charge current, transistor N2, N3 and N4 close, the drain of transistor P1 and the voltage VDS1 between the source electrode will drop to 0, shown in the waveform 44 of Fig. 3, voltage VDS2 between transistor P0 drain and the source electrode is about 1.2V in addition, so the voltage VGS between transistor P1 gate and the source electrode also is pulled to about 1.2V, shown in the waveform 46 and 48 of Fig. 3, when time t1, PWM logical circuit 24 provides control signal PWM with diverter switch N1, so output voltage V 24OUT rises, and voltage VGS also and then rises, and is limited in about 5V by pressure limiting circuit 26 at last.

With reference to Fig. 2 and Fig. 4; when the output short-circuit of transducer 20 during to earth terminal GND; shown in time t2; electric current I out increases and voltage and output voltage V 24OUT on the node V24LX descends; when output voltage V 24OUT is lower than a critical value; switch N8 opens; comparator 32 in the short-circuit protection circuit 30 is a reference voltage Vr and the voltage Vs relevant with output voltage V 24OUT relatively; when voltage Vs is lower than reference voltage Vr; comparator 32 output short circuit protection signal Sc make PWM logical circuit 24 off switch N1; after switch N1 closes; voltage on the node V24DD equals input voltage VIN once more; therefore, the switch N2 in the current providing circuit 28; N3 and N4 open once more to form current mirror mirror electric current I 3 and produce stable short circuit current protection Iout=(I1+I2) * K, shown in the waveform 54 of Fig. 4.

With reference to Fig. 2 and Fig. 6, when signal EN transfers low level to when closing transducer 20, shown in time t3, transistor N0 opens and makes output voltage V 24OUT drop to 0 at leisure, at this moment, resistance R 1 is moved to the current potential of transistor P1 gate with node V24DD idiostatic at leisure, so the voltage VGS between transistor P1 gate and the source electrode also will slowly reduce to 0, shown in the waveform 48 of Fig. 3, at last, transistor P1 is closed to cut off the binding between input voltage VIN and the output V24OUT, avoids producing electric current I out and flows to output V24OUT by input VIN.Waveform 64 by Fig. 6 can find out when transducer 20 is closed, do not have electric current I out to produce really.

Above embodiment is only for the usefulness that the present invention is described, but not limitation of the present invention, person skilled in the relevant technique under the situation that does not break away from the spirit and scope of the present invention, can also be made various conversion or variation.Therefore, all technical schemes that are equal to also should belong to category of the present invention, should be limited by each claim.

Claims

1. an asynchronous voltage-boosting converter comprises an electric capacity, an inductance, and a diode, a switch, a transistor and a pressure limiting circuit are cut off in a load, it is characterized in that:

Described electric capacity connects the output of described transducer;

Described diode is connected between described node and the described output;

2. transducer as claimed in claim 1 is characterized in that: comprise that more an impedance component is connected described load and cuts off between transistorized gate and the source electrode, cut off transistor in order to close described load when described transducer is closed.

3. transducer as claimed in claim 1 is characterized in that: comprise that also a short-circuit protection circuit detects described output voltage, send a short-circuit protection signal to close described switch when described output short circuit.

4. transducer as claimed in claim 3 is characterized in that: described short-circuit protection circuit comprises a comparator when described output voltage is lower than a critical value, produces described short-circuit protection signal.

5. transducer as claimed in claim 3 is characterized in that: comprise that also a current providing circuit provides a short circuit current protection to described electric capacity when described output short circuit.

6. transducer as claimed in claim 5 is characterized in that: described current providing circuit comprises that a current mirror mirror one reference current produces described short circuit current protection.

7. transducer as claimed in claim 6 is characterized in that: described current mirror comprises that one connects described reference current and a mirror branch described reference current of mirror produces described short circuit current protection with reference to branch.

8. transducer as claimed in claim 7 is characterized in that: described mirror branch comprises that described load cuts off transistor.

9. transducer as claimed in claim 1 is characterized in that: comprise that further a current providing circuit provides pre-charge current that described electric capacity is charged when described transducer starts.

10. transducer as claimed in claim 9 is characterized in that: described current providing circuit comprises that a current mirror mirror one reference current produces described pre-charge current.

11. transducer as claimed in claim 10 is characterized in that: described current mirror comprises that one connects described reference current and a mirror branch described reference current of mirror produces described pre-charge current with reference to branch.

12. transducer as claimed in claim 11 is characterized in that: described mirror branch comprises that described load cuts off transistor.