CN115242054B - Power supply circuit for DC-DC converter - Google Patents

Power supply circuit for DC-DC converter Download PDF

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Publication number
CN115242054B
CN115242054B CN202210800583.0A CN202210800583A CN115242054B CN 115242054 B CN115242054 B CN 115242054B CN 202210800583 A CN202210800583 A CN 202210800583A CN 115242054 B CN115242054 B CN 115242054B
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circuit
coupled
transistor
output
driving circuit
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CN115242054A (en
Inventor
张宝全
李铎
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SG Micro Beijing Co Ltd
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SG Micro Beijing Co Ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0048—Circuits or arrangements for reducing losses
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0003—Details of control, feedback or regulation circuits
    • H02M1/0009—Devices or circuits for detecting current in a converter
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
    • H02M1/088—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters for the simultaneous control of series or parallel connected semiconductor devices
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
    • H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
    • H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
    • H02M3/158—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Dc-Dc Converters (AREA)

Abstract

The invention discloses a power supply circuit for a DC-DC converter, the power supply circuit is arranged in the DC-DC converter and comprises: a charging circuit, a current detection circuit, a signal generation circuit, a driving circuit, a switching circuit, a first transistor, a second transistor, an inductor, and an output circuit, wherein: the driving circuit drives the first transistor and the second transistor according to the current indication signal and the modulation signal; the first end of the switching circuit is coupled with the second end of the charging circuit, and the switching circuit controls the second end of the charging circuit to switch between a first switching state and a second switching state according to the current indication signal and the modulation signal; the control electrode of the first transistor is coupled with the first output end of the driving circuit, the first electrode is coupled with the input voltage end, and the second electrode is coupled with the first electrode of the second transistor and the first end of the inductor; the control electrode of the second transistor is coupled to the second output end of the driving circuit, and the second electrode is coupled to the ground end.

Description

Power supply circuit for DC-DC converter
Technical Field
The invention relates to the technical field of integrated circuits, in particular to a power supply circuit for a DC-DC converter.
Background
With the rapid development of the integrated circuit industry and the increasing market of integrated circuits, direct current-to-direct current (DC-DC) converters have received extensive attention and rapid development. The DC-DC converter is used as a high-efficiency switching power supply technology, has the advantages of quick dynamic response, simple control, direct control of output current and the like, and has wide application.
DC-DC converters often contain transistors and capacitors, wherein the capacitors are required to power the transistors to turn them on; however, since the power supply voltage generated by the capacitor in the conventional DC-DC converter is easily lost, the operation efficiency of the circuit is low.
Disclosure of Invention
The invention mainly aims to provide a power supply circuit for a DC-DC converter, which is used for solving the problem that the working efficiency of the circuit is lower because the power supply voltage generated by a capacitor in the traditional DC-DC converter is easy to lose.
In order to achieve the above object, a first aspect of the present invention provides a power supply circuit for a DC-DC converter, comprising:
The power supply circuit is provided in the DC-DC converter and includes: a charging circuit, a current detection circuit, a signal generation circuit, a driving circuit, a switching circuit, a first transistor, a second transistor, an inductor, and an output circuit, wherein:
the first end of the charging circuit is coupled with the input voltage end;
the current detection circuit is configured to generate a current indication signal according to an inductance current flowing through the inductor;
The signal generating circuit is configured to generate a modulation signal and provide the modulation signal to the driving circuit;
the driving circuit is configured to drive the first transistor and the second transistor according to the current indication signal and the modulation signal;
The first end of the switching circuit is coupled with the second end of the charging circuit, and the switching circuit is configured to control the second end of the charging circuit to switch between a first switching state and a second switching state according to the current indication signal and the modulation signal, wherein the first switching state is that the second end of the charging circuit is coupled with the ground terminal, and the second switching state is that the second end of the charging circuit is coupled with the second pole of the first transistor;
the control electrode of the first transistor is coupled with the first output end of the driving circuit, the first electrode is coupled with the input voltage end, and the second electrode is coupled with the first electrode of the second transistor and the first end of the inductor;
The control electrode of the second transistor is coupled with the second output end of the driving circuit, and the second electrode is coupled with the grounding end;
the second end of the inductor is coupled with the output voltage end; and
The output circuit is configured to generate an output voltage signal from the inductor current flowing through the inductor.
Optionally, the first end of the driving circuit is coupled to the third end of the charging circuit, and the second end of the driving circuit is coupled to the second end of the switching circuit;
the driving circuit comprises a first driving circuit and a second driving circuit;
The signal generating circuit is configured to generate a modulation signal and provide the modulation signal to the first driving circuit and the second driving circuit;
the first driving circuit is configured to drive a first transistor according to the modulation signal, and a control electrode of the first transistor is coupled with an output end of the first driving circuit;
The second driving circuit is configured to drive the second transistor according to the current indication signal and the modulation signal, and a control electrode of the second transistor is coupled to an output end of the second driving circuit.
Further, an input end of the first driving circuit is coupled with an output end of the signal generating circuit, and a second end of the first driving circuit is coupled with a first end of the switching circuit;
The first input end of the second driving circuit is coupled with the output end of the current detection circuit, and the second input end of the second driving circuit is coupled with the output end of the signal generation circuit.
Optionally, the switching circuit comprises a trigger and a single pole double throw switch, wherein:
The first input end of the trigger is coupled with the output end of the signal generating circuit, the second input end of the trigger is coupled with the output end of the current detecting circuit, the output end of the trigger is coupled with the control end of the single-pole double-throw switch, and the trigger is configured to control the single-pole double-throw switch according to the current indication signal output by the current detecting circuit and the modulation signal output by the signal generating circuit;
the first end of the single pole double throw switch is coupled to the second end of the charging circuit, the second end of the single pole double throw switch is coupled to the second pole of the first transistor, the third end of the single pole double throw switch is coupled to the ground, and the single pole double throw switch is configured to control the second end of the charging circuit to switch between the second end of the single pole double throw switch and the third end of the single pole double throw switch.
Further, the switching circuit also comprises a delay device,
The delay device is configured to be positioned between the current detection circuit and the trigger, a first end of the delay device is coupled with the output end of the current detection circuit, and a second end of the delay device is coupled with the second input end of the trigger.
Optionally, the charging circuit includes: a diode, and a first capacitor, wherein:
The first end of the diode is coupled with the input voltage end, and the second end of the diode is coupled with the first end of the first capacitor and the first end of the first driving circuit;
The second end of the first capacitor is coupled to the first end of the switching circuit.
Optionally, the current detection circuit comprises a zero crossing detector configured to generate the current indicative signal when the inductance current flowing through the inductor is 0.
Optionally, the modulated signal generated by the signal generating circuit comprises a pulse width modulated signal.
Optionally, the output circuit includes: a first resistor, a second resistor, a third resistor, a fourth resistor, and a second capacitor;
wherein a first end of the first resistor is coupled to the second end of the inductor and the output voltage end, and a second end of the first resistor is coupled to a first end of the second resistor;
the second end of the second resistor is coupled with the second pole of the second transistor and the ground terminal;
The first end of the third resistor is coupled with the second end of the inductor and the output voltage end, and the second end of the third resistor is coupled with the second pole of the second transistor and the ground end;
the first end of the fourth resistor is coupled with the second end of the inductor and the output voltage end, and the second end of the fourth resistor is coupled with the first end of the second capacitor;
The second terminal of the second capacitor is coupled to the second pole of the second transistor and the ground terminal.
A second aspect of the invention provides a DC-DC converter comprising the power supply circuit provided in any one of the first aspects.
In the power supply circuit for a DC-DC converter provided by the embodiment of the invention, the power supply circuit is provided in the DC-DC converter and includes: the charging circuit comprises a charging circuit, a current detection circuit, a signal generation circuit, a driving circuit, a switching circuit, a first transistor, a second transistor, an inductor and an output circuit, wherein a first end of the switching circuit is coupled with a second end of the charging circuit, the switching circuit is configured to control the second end of the charging circuit to switch between a first switching state and a second switching state according to a current indication signal and a modulation signal, the first switching state is that the second end of the charging circuit is coupled with a grounding end, and the second switching state is that the second end of the charging circuit is coupled with a second pole of the first transistor; the second end of the charging circuit is controlled to be switched between the ground and the second electrode of the first transistor, so that the charging circuit is charged and supplemented when the charging circuit is grounded, and the power supply is realized when the charging circuit is coupled with the second electrode of the first transistor, so that the loss is not easy to cause, the efficiency of the light load circuit is improved, and the problem that the working efficiency of the circuit is lower due to the fact that the power supply voltage generated by the capacitor in the existing DC-DC converter is easy to be lost is solved.
Drawings
In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the drawings which are required in the description of the embodiments or the prior art will be briefly described, it being obvious that the drawings in the description below are only some embodiments of the invention and that other drawings can be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a circuit diagram of a conventional power supply circuit for a DC-DC converter;
Fig. 2 is an exemplary block diagram of a power supply circuit for a DC-DC converter provided by an embodiment of the present invention;
fig. 3 is an exemplary circuit diagram of a power supply circuit for a DC-DC converter provided by an embodiment of the present invention;
fig. 4 is a diagram of exemplary simulation results of a power supply circuit for a DC-DC converter according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. It will be apparent that the described embodiments are some, but not all, embodiments of the invention. All other embodiments, which can be obtained by a person skilled in the art without creative efforts, based on the described embodiments of the present invention also fall within the protection scope of the present invention.
Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the inventive subject matter belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the specification and relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. As used herein, a statement that two or more parts are "connected" or "coupled" together shall mean that the parts are joined together either directly or joined through one or more intermediate parts.
In all embodiments of the present invention, since the source and drain (emitter and collector) of the transistor are symmetrical and the on-current direction between the source and drain (emitter and collector) of the N-type transistor and the P-type transistor is opposite, in embodiments of the present invention the controlled middle terminal of the transistor is referred to as the control pole and the remaining two terminals of the transistor are referred to as the first pole and the second pole, respectively. The transistors employed in the embodiments of the present invention are mainly switching transistors. In addition, terms such as "first" and "second" are used merely to distinguish one component (or portion of a component) from another component (or another portion of a component).
Fig. 1 shows an exemplary circuit diagram of a supply circuit for a DC-DC converter. The DC-DC converter can convert one direct current voltage into other direct current voltages, wherein PWM is a power tube starting signal adopting a pulse width modulation mode, the frequency of switching pulse is certain, and the output voltage is stable by changing the pulse output width; ZCD is zero-crossing detection circuit or zero-crossing detector, used for zero-crossing detection or zero current detection, ZCD signal is regarded as closing down tube signal, break down tube; SBD is a Schottky diode; BST and SW represent two nodes in the circuit and corresponding voltage values respectively; vin is the input voltage, vout is the output voltage, cout is the output capacitance, and Resr is the equivalent series resistance.
In BUCK type DC-DC applications, when an NMOS fet is selected as the power transistor, a BST capacitor is required to power the high side driver_ Hside of its driving portion.
When the zero crossing detection circuit ZCD detects that the current flowing through the inductor L decreases to 0 at the time of light load, the voltage at the SW node is changed from 0 to the output voltage Vout, and at this time, the voltage across the capacitor Cbst remains unchanged, and the voltage at the BST node is bst=vin+sw. As the off-time Toff of the power transistor is prolonged, the charge on the capacitor Cbst gradually decreases along with the leakage, so that the voltage difference between bst=vin, BST and SW becomes: vin-sw=vin-Vout. When the power tube needs to be started, if Vin-Vout is smaller than a power tube starting threshold Vgs (th), the power tube cannot be started, and even if the power tube can be started, the power tube cannot be started, and the on resistance is bad because the Vgs pressure difference of the power tube is lower, so that the system efficiency is affected.
In order to reduce the on-resistance, the related art turns on the down tube LS (or part of the down tube) before the high-side power tube HS is turned on during light load, and then the capacitor Cbst is recharged to a predetermined value, and then the power tube is turned on. However, this approach results in a loss of efficiency and an increase in output voltage ripple. For example, when the circuit is operated in this condition, the lower tube is turned on before the power tube is turned on, and the peak inductor current is about: 100ns 3v/0.24 u=1.25a, this decrease in inductor current will cause additional losses to the system.
Fig. 2 shows an exemplary block diagram of a power supply circuit for a DC-DC converter according to an embodiment of the present invention. Wherein the power supply circuit is provided in the DC-DC converter and the power supply circuit includes: a charging circuit, a current detection circuit, a signal generation circuit, a driving circuit, a switching circuit, a first transistor M1, a second transistor M2, an inductor, and an output circuit, wherein:
The first end of the charging circuit is coupled with the input voltage end Vin;
the current detection circuit is configured to generate a current indication signal according to an inductance current flowing through the inductor L; the current detection circuit includes a zero-crossing detector configured to generate a current indication signal when the inductance current flowing through the inductor L is 0. The power supply circuit provided by the embodiment of the invention is applied to a discontinuous conduction mode (DCM mode), the DCM mode always returns to 0 in a switching period, namely the inductor is reset, and when the inductor current is detected to be zero, a ZCD signal is generated to disconnect the down tube.
The signal generating circuit is configured to generate a modulation signal and provide the modulation signal to the driving circuit; the modulation signal generated by the signal generating circuit comprises a pulse width modulation signal PWM;
The driving circuit is configured to drive the first transistor M1 and the second transistor M2 according to the current indication signal and the modulation signal, the first transistor M1 may be a high-side power transistor HS as an upper transistor, and the second transistor M2 may be a low-side power transistor LS as a lower transistor;
The first end of the switching circuit is coupled with the second end of the charging circuit, and the switching circuit is configured to control the second end of the charging circuit to switch between a first switching state and a second switching state according to the current indication signal and the modulation signal, wherein the first switching state is that the second end of the charging circuit is coupled with the ground end GND, and the second switching state is that the second end of the charging circuit is coupled with the second pole of the first transistor M1; in the first switching state, the second end of the charging circuit is grounded, and in the second switching state, the second end of the charging circuit is connected with the second pole of the first transistor M1;
the control electrode of the first transistor M1 is coupled to the first output end of the driving circuit, the first electrode is coupled to the input voltage end Vin, and the second electrode is coupled to the first electrode of the second transistor M2 and the first end of the inductor L;
The control electrode of the second transistor M2 is coupled to the second output end of the driving circuit, and the second electrode is coupled to the ground end GND;
The second end of the inductor L is coupled with the output voltage end Vout;
The output circuit is configured to generate an output voltage signal according to an inductance current flowing through the inductor L, a first terminal of the output circuit is coupled to the output voltage terminal Vout, and a second terminal of the output circuit is coupled to the ground terminal GND.
Fig. 3 shows an exemplary circuit diagram of a power supply circuit for a DC-DC converter according to an embodiment of the present invention. In fig. 3, the charging circuit includes: the first capacitor may be a bootstrap capacitor Cbst, a first end of the diode is coupled to the input voltage terminal Vin, and a second end of the diode is coupled to a first end of the first capacitor and a first end of the first driving circuit; the second end of the first capacitor is coupled to the first end of the switching circuit.
In an alternative embodiment of the present invention, a first end of the driving circuit is coupled to the third end of the charging circuit, and a second end of the driving circuit is coupled to the second end of the switching circuit;
the driving circuit comprises a first driving circuit and a second driving circuit; the first driving circuit may be a high-side driving circuit driver_ Hside, and the second driving circuit may be a low-side driving circuit driver_ Lside;
The signal generating circuit is configured to generate a modulation signal and provide the modulation signal to the first driving circuit and the second driving circuit;
The first driving circuit is configured to drive the first transistor M1 according to the modulation signal, and the control electrode of the first transistor M1 is coupled with the output end of the first driving circuit;
The second driving circuit is configured to drive the second transistor M2 according to the current indication signal and the modulation signal, and a control electrode of the second transistor M2 is coupled to an output terminal of the second driving circuit.
The input end of the first driving circuit is coupled with the output end of the signal generating circuit, and the second end of the first driving circuit is coupled with the first end of the switching circuit;
The first input end of the second driving circuit is coupled with the output end of the current detection circuit, and the second input end of the second driving circuit is coupled with the output end of the signal generation circuit.
In a preferred embodiment provided by the present invention, the switching circuit comprises a trigger and a single pole double throw switch K, wherein: the trigger can be an RS trigger, and the RS trigger comprises an input end R, an input end S and an output end Q;
The first input end of the trigger is coupled with the output end of the signal generating circuit, the second input end of the trigger is coupled with the output end of the current detecting circuit, the output end of the trigger is coupled with the control end of the single-pole double-throw switch K, and the trigger is configured to control the single-pole double-throw switch K according to the current indication signal output by the current detecting circuit and the modulation signal output by the signal generating circuit; the first input end can be an input end R of the RS trigger, and a modulation signal generated by an output end of the signal generating circuit is input to the input end R; the second input end can be an input end S of the RS trigger, and a current indication signal generated by an output end of the current detection circuit is input to the input end S; the output end Q can control the single-pole double-throw switch K according to the input modulation signal and the current indication signal;
The first end of the single pole double throw switch K is coupled to the second end of the charging circuit, the second end of the single pole double throw switch K is coupled to the second pole of the first transistor M1, the third end of the single pole double throw switch K is coupled to the ground GND, and the single pole double throw switch K is configured to control the second end of the charging circuit to switch between the second end of the single pole double throw switch K and the third end of the single pole double throw switch K. The single-pole double-throw switch K can control the second end of the charging circuit to be grounded or connected with the second pole of the upper tube, and control the second end of the charging circuit to be switched between two states of being grounded and connected with the second pole of the upper tube.
The single-pole double-throw switch K switches the connection end of the lower polar plate of the BST capacitor Cbst to GND only when the inductance current is reduced to 0 under light load, and the lower polar plate of the capacitor Cbst is communicated with the SW node under other states. When the zero-crossing detection circuit ZCD detects that the inductance current is 0, a current indication signal is sent out, the lower tube is disconnected, the switch is switched from the original SW position to the GND position, and at the moment, vin charges and supplements electricity for the BST capacitor Cbst; when the modulation signal PWM arrives, the power tube is started, and then the switch is switched back to the original SW.
Through the trigger and the single-pole double-throw switch included in the switch circuit, no extra power tube switch action is caused, the voltage of the lower polar plate of the BST capacitor is switched by only a small switch, the structure is simple, the problem that the charge loss of the BST capacitor is not complemented because the upper polar plate voltage is raised is solved on the premise that the complex charge pump or the operational amplifier is not increased to supplement electricity to the BST capacitor and the static current is not increased, the extra loss is almost avoided, and the efficiency is improved under light load.
Based on the above embodiments, in an alternative embodiment of the present invention, the switch circuit further includes a Delay device Delay configured to be located between the current detection circuit and the trigger, a first end of the Delay device is coupled to the output terminal of the current detection circuit, and a second end of the Delay device is coupled to the second input terminal of the trigger. The Delay device Delay can Delay and display a switching signal for switching the switch from the connected SW node to the ground during simulation, so that the switching signal is prevented from being displayed at the high-frequency fuzzy position of SW ringing, and the switching point can be clearly displayed in the simulation result.
In an alternative embodiment provided by the present invention, an output circuit includes: a first resistor R1, a second resistor R2, a third resistor R L, a fourth resistor Resr, and a second capacitor Cout;
wherein a first end of the first resistor R1 is coupled to the second end of the inductor L and the output voltage terminal Vout, and a second end of the first resistor R1 is coupled to a first end of the second resistor R2;
the second end of the second resistor R2 is coupled to the second pole of the second transistor M2 and the ground GND;
The first end of the third resistor R L is coupled to the second end of the inductor L and the output voltage end Vout, and the second end of the third resistor R L is coupled to the second pole of the second transistor M2 and the ground end GND;
A first terminal of the fourth resistor Resr is coupled to the second terminal of the inductor L and the output voltage terminal Vout, and a second terminal of the fourth resistor Resr is coupled to the first terminal of the second capacitor Cout;
The second terminal of the second capacitor Cout is coupled to the second pole of the second transistor M2 and the ground GND.
The invention also provides a DC-DC converter, comprising the power supply circuit of any one of the above embodiments.
The operation of the power supply circuit for a DC-DC converter according to an embodiment of the present invention is described below with reference to the example of fig. 3.
After the voltage at the light load SW node is turned from 0 to Vout, the lower plate of the BST capacitor Cbst is changed to GND so as to maintain the charge quantity of the BST capacitor; when the upper tube power tube is started, the potential of the lower polar plate of the BST capacitor is switched back to SW, and the normal switching action of the upper tube power tube is completed.
When the zero-crossing detection circuit ZCD detects that the inductance current is 0, a ZCD signal is sent out, the lower tube is disconnected, and the switch is switched from the original SW position to the GND position; when the modulation signal PWM arrives, the upper tube is opened, and the switch is switched back to the original SW. Under light load, the switch switches the connection end of the lower polar plate of the capacitor Cbst to GND only after the inductance current is reduced to 0, and under other states, the lower polar plate of the BST capacitor Cbst is communicated with the SW node.
The RS trigger and the single-pole double-throw switch in the embodiment of the invention can not cause extra power tube switch action, only a small switch is used for switching the voltage of the lower polar plate of the BST capacitor, the structure is simple, a complex charge pump or an operational amplifier is not required to be added, the problem that the charge loss of the BST capacitor is not complemented because the upper polar plate voltage is raised on the premise of not increasing the quiescent current is solved, the extra loss is almost avoided, and the efficiency is improved under light load.
Fig. 4 shows an exemplary simulation result diagram of a power supply circuit for a DC-DC converter according to an embodiment of the present invention.
In the embodiment of the invention, vin= V, vout =3v is taken as an example for simulation, the BST leakage condition is more intuitively displayed at a high temperature, under a light load of 125 DEG high temperature, when the switching point is defined at about 4uS after the inductance current is 0, the switching point is selected, in order to avoid displaying the switching signal at the SW ringing high-frequency fuzzy part, the switching point is clearly displayed in the simulation result, and before the ZCD signal is input to the input end S of the RS trigger, the switching signal for switching the switch from the connected SW node to the ground is displayed through a delay device when the simulation is delayed.
According to simulation results, before the connection end of the lower polar plate of the capacitor is switched from the SW node to the grounding end at the switching point, the BST capacitor is leaked by 10uA current, the voltage of the BST capacitor is reduced by 100mV only by 4uS (the Toff time can be as long as tens of mS under light load), and the voltage difference of the BST capacitor is replenished back to Vin value after switching, namely, the voltage of the BST capacitor is charged and replenished back to 5V without delaying the second starting.
The simulation result diagram shown in fig. 4 is a diagram of the switching position of one cycle in the periodic action, and when the next cycle is entered and the second time is started, the simulation result is repeated from the reset point.
From the above description, it can be seen that the following technical effects are achieved:
the second end of the charging circuit is controlled to be switched between the ground and the second electrode of the first transistor, so that the charging circuit realizes charging and supplementing electricity when the charging circuit is grounded, and the charging circuit is powered when the charging circuit is coupled with the second electrode of the first transistor, so that loss is not easy to cause, the efficiency of a light load circuit is improved, and the problem that the working efficiency of the circuit is lower due to the fact that the power supply voltage generated by a capacitor in the existing DC-DC converter is easy to be lost is solved;
The switching circuit in the invention can not cause extra power tube switching action, only uses a small switch to switch the voltage of the lower polar plate of the BST capacitor, has simple structure, does not need to add a complex charge pump or operational amplifier, and can solve the problem that the charge loss of the BST capacitor is not complemented because the voltage of the upper polar plate is raised on the premise of not increasing static current, almost has no extra loss, and improves the efficiency under light load.
The flowcharts and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of apparatus and methods according to various embodiments of the present disclosure. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of instructions, which comprises one or more executable instructions for implementing the specified logical function(s). In some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems which perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.
As used herein and in the appended claims, the singular forms of words include the plural and vice versa, unless the context clearly dictates otherwise. Thus, when referring to the singular, the plural of the corresponding term is generally included. Similarly, the terms "comprising" and "including" are to be construed as being inclusive rather than exclusive. Likewise, the terms "comprising" and "or" should be interpreted as inclusive, unless such an interpretation is expressly prohibited herein. Where the term "example" is used herein, particularly when it follows a set of terms, the "example" is merely exemplary and illustrative and should not be considered exclusive or broad.
Further aspects and scope will become apparent from the description provided herein. It is to be understood that various aspects of the application may be implemented alone or in combination with one or more other aspects. It should also be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
Although embodiments of the present invention have been described in connection with the accompanying drawings, various modifications and variations may be made by those skilled in the art without departing from the spirit and scope of the invention, and such modifications and variations fall within the scope of the invention as defined by the appended claims.

Claims (10)

1. A power supply circuit for a DC-DC converter, characterized in that the power supply circuit is provided in the DC-DC converter and the power supply circuit comprises: a charging circuit, a current detection circuit, a signal generation circuit, a driving circuit, a switching circuit, a first transistor, a second transistor, an inductor, and an output circuit, wherein:
the first end of the charging circuit is coupled with the input voltage end;
the current detection circuit is configured to generate a current indication signal according to an inductance current flowing through the inductor;
The signal generating circuit is configured to generate a modulation signal and provide the modulation signal to the driving circuit;
The driving circuit is configured to drive the first transistor and the second transistor according to the current indication signal and the modulation signal;
the first end of the switching circuit is coupled with the second end of the charging circuit, and the switching circuit is configured to control the second end of the charging circuit to switch between a first switching state and a second switching state according to the current indication signal and the modulation signal, wherein the first switching state is that the second end of the charging circuit is coupled with the ground end, and the second switching state is that the second end of the charging circuit is coupled with the second pole of the first transistor;
The control electrode of the first transistor is coupled with the first output end of the driving circuit, the first electrode is coupled with the input voltage end, and the second electrode is coupled with the first electrode of the second transistor and the first end of the inductor;
the control electrode of the second transistor is coupled with the second output end of the driving circuit, and the second electrode is coupled with the grounding end;
the second end of the inductor is coupled with the output voltage end; and
The output circuit is configured to generate an output voltage signal from an inductor current flowing through the inductor.
2. The power supply circuit of claim 1, wherein a first terminal of the driving circuit is coupled to a third terminal of the charging circuit, and a second terminal of the driving circuit is coupled to a second terminal of the switching circuit;
The driving circuit comprises a first driving circuit and a second driving circuit;
The signal generating circuit is configured to generate a modulation signal and supply the modulation signal to the first driving circuit and the second driving circuit;
the first driving circuit is configured to drive the first transistor according to the modulation signal, and a control electrode of the first transistor is coupled with an output end of the first driving circuit;
The second driving circuit is configured to drive the second transistor according to the current indication signal and the modulation signal, and a control electrode of the second transistor is coupled to an output end of the second driving circuit.
3. The power supply circuit of claim 2, wherein an input of the first drive circuit is coupled to an output of the signal generating circuit, and a second of the first drive circuit is coupled to a first of the switching circuits;
The first input end of the second driving circuit is coupled with the output end of the current detection circuit, and the second input end of the second driving circuit is coupled with the output end of the signal generation circuit.
4. The power supply circuit of claim 1, wherein the switching circuit comprises a flip-flop and a single pole double throw switch, wherein:
The first input end of the trigger is coupled with the output end of the signal generating circuit, the second input end of the trigger is coupled with the output end of the current detecting circuit, the output end of the trigger is coupled with the control end of the single-pole double-throw switch, and the trigger is configured to control the single-pole double-throw switch according to the current indication signal output by the current detecting circuit and the modulation signal output by the signal generating circuit;
The first end of the single pole double throw switch is coupled to the second end of the charging circuit, the second end of the single pole double throw switch is coupled to the second pole of the first transistor, the third end of the single pole double throw switch is coupled to the ground, and the single pole double throw switch is configured to control the second end of the charging circuit to switch between being coupled to the second end of the single pole double throw switch and being coupled to the third end of the single pole double throw switch.
5. The power supply circuit of claim 4, wherein the switching circuit further comprises a delay,
The delay device is configured to be positioned between the current detection circuit and the trigger, a first end of the delay device is coupled with an output end of the current detection circuit, and a second end of the delay device is coupled with a second input end of the trigger.
6. The power supply circuit of claim 1, wherein the charging circuit comprises: a diode, and a first capacitor, wherein:
the first end of the diode is coupled with the input voltage end, and the second end of the diode is coupled with the first end of the first capacitor and the first end of the first driving circuit;
the second terminal of the first capacitor is coupled to the first terminal of the switching circuit.
7. The power supply circuit of claim 1, wherein the current detection circuit comprises a zero crossing detector configured to generate a current indication signal when an inductance current flowing through the inductor is 0.
8. The power supply circuit of claim 1, wherein the modulated signal generated by the signal generation circuit comprises a pulse width modulated signal.
9. The power supply circuit of claim 1, wherein the output circuit comprises: a first resistor, a second resistor, a third resistor, a fourth resistor, and a second capacitor;
Wherein a first end of the first resistor is coupled to a second end of the inductor and the output voltage end, and a second end of the first resistor is coupled to a first end of the second resistor;
A second terminal of the second resistor is coupled to a second terminal of the second transistor and to ground;
a first end of the third resistor is coupled with a second end of the inductor and the output voltage end, and a second end of the third resistor is coupled with a second pole of the second transistor and a ground end;
A first end of the fourth resistor is coupled to the second end of the inductor and the output voltage end, and a second end of the fourth resistor is coupled to the first end of the second capacitor;
The second terminal of the second capacitor is coupled to the second pole of the second transistor and to ground.
10. A DC-DC converter, characterized in that the DC-DC converter comprises the supply circuit of any one of claims 1-9.
CN202210800583.0A 2022-07-06 2022-07-06 Power supply circuit for DC-DC converter Active CN115242054B (en)

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TWI837937B (en) * 2022-11-10 2024-04-01 茂達電子股份有限公司 Power converter having high-side driving mechanism consuming low power
CN116317483B (en) * 2023-05-15 2023-08-22 成都市易冲半导体有限公司 Charge pump driving circuit and driving control system

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