CN112165252A - Narrow pulse control-based bootstrap drive circuit of BUCK converter - Google Patents
Narrow pulse control-based bootstrap drive circuit of BUCK converter Download PDFInfo
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- CN112165252A CN112165252A CN202011007864.8A CN202011007864A CN112165252A CN 112165252 A CN112165252 A CN 112165252A CN 202011007864 A CN202011007864 A CN 202011007864A CN 112165252 A CN112165252 A CN 112165252A
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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
- 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
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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
- H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
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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
- H02M1/36—Means for starting or stopping converters
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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
- H02M1/0003—Details of control, feedback or regulation circuits
- H02M1/0032—Control circuits allowing low power mode operation, e.g. in standby mode
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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
- H02M1/0054—Transistor switching losses
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
- Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
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- Dc-Dc Converters (AREA)
Abstract
The invention relates to a narrow pulse control-based bootstrap driving circuit of a BUCK converter, which at least comprises a BUCK circuit, wherein a bootstrap charging branch circuit and a driving chip for driving the bootstrap charging branch circuit are connected in the BUCK circuit, and under the condition that the BUCK circuit is in a light load/no-load state and the duty ratio of a main switching tube of the BUCK circuit is smaller than a first threshold value, the driving chip reduces the conduction time of a secondary switching tube in the bootstrap charging branch circuit on the basis of a narrow pulse driving mode so as to avoid negative currents generated by the BUCK circuit and the bootstrap charging branch circuit or reduce the negative currents in the BUCK circuit and the bootstrap charging branch circuit.
Description
Technical Field
The invention relates to the technical field of switching power supplies, in particular to a bootstrap drive circuit of a BUCK converter based on narrow pulse control.
Background
The BUCK circuit has a simple topology structure, and is widely used in various Step-down (Step-down) application scenarios. The BUCK circuit, also known as a BUCK converter, is basically characterized by a DC-DC conversion circuit, with an output voltage lower than the input voltage. BUCK converter is a non-isolated converterA DC converter. The input current of the BUCK converter is pulsating and the output current is continuous. Fig. 4 shows the most basic circuit of the BUCK converter, which may also be referred to as the basic topology of the BUCK converter. BUCK converter generally comprises a main switching tube Q1Freewheel diode D1Energy storage inductor L and output filter capacitor C2And an input filter capacitor C1. Input filter capacitor C1One side is connected with an input power supply. Output filter capacitor C2One side is connected with a load. The working principle of the BUCK converter is as follows:
main switch tube Q1Is controlled by the driving pulse output by the control circuit; when the control circuit pulse outputs high level, the main switch tube Q1Is turned on and freewheeling diode D1Is zero and the cathode voltage is the voltage of the input power supply, so that the freewheeling diode D1Reverse cut-off; the current of the input power supply flows through the energy storage inductor L and supplies power to the load, and the current of the energy storage inductor L gradually rises at the moment; self-inductance potential with a positive left end and a negative right end is generated at two ends of the energy storage inductor L to block the current from rising, and the energy storage inductor L converts the electric energy into magnetic energy to be stored. After the on-time, the control circuit pulse is low level, the main switch tube Q1The current in the energy storage inductor L can not suddenly change, and the self-inductance potential with the right end being positive and the left end being negative is generated at the two ends of the energy storage inductor L to block the current from dropping, so that the freewheeling diode D is enabled to be connected with the power supply1Forward biased conduction, so that the current in the energy storage inductor L flows to the freewheeling diode D1Forming a loop. At this time, the current value in the loop gradually decreases, and the magnetic energy stored in the energy storage inductor L is converted into electric energy and released to supply power to the load. After the turn-off time, the control circuit outputs high level by pulse, so that the main switching tube Q1Conducting and repeating the above process. The filter capacitor in the BUCK converter is used for reducing the fluctuation of the output voltage. Freewheeling diode D1Is an indispensable few element, if there is no such diode, the BUCK converter can not work normally, and the main switch tube Q1Under the condition of changing from on to off, the two ends of the energy storage inductor L generate high self-inductance potential so as toDamaged main switch tube Q1. The BUCK converter has two working modes, and the BUCK converter is divided into an inductive current continuous working mode and an inductive current discontinuous working mode according to whether the L current of the energy storage inductor is continuous or not, namely whether the L current of the energy storage inductor starts from zero or not at the beginning of each pulse period.
As can be seen from the basic topology of the BUCK converter shown in FIG. 4, the main switching tube Q of the BUCK converter1At high side, its source is not connected to the ground of the whole circuit, so that the main switch tube Q1The driving of (2) requires a power supply with reference to the source of Q1 and a high-side driving circuit. Common driving circuits are: the high-side isolation type driving circuit adopts a pulse transformer type, a driving circuit added with an isolation auxiliary power supply and a high-side driving chip, and a half-bridge bootstrap driving circuit. For adding an isolation auxiliary power supply, the design is complicated, the occupied space is large, and the design of a high-power density power supply is not facilitated. For the pulse transformer adopted as the drive, the pulse transformer is also large in size and is not suitable for application scenes with wide duty ratio change range. For the bootstrap circuit to provide energy for the high-side MOS switch tube driver, the bootstrap driving circuit is the simplest, but the bootstrap driving circuit also has its own limitations, generally, the bootstrap driving is more suitable for the synchronous rectification type BUCK converter whose lower tube is the MOS tube, when the lower tube is the conventional diode, the start-up of the bootstrap circuit has a certain problem, especially when the load is light load or no-load, the continuous switching may cause the bootstrap capacitor voltage to be unable to build up, thereby causing the BUCK converter to be unable to start up.
Based on this, chinese patent with publication number CN108448886B discloses a Buck converter bootstrap drive circuit, which includes a main circuit, an auxiliary power supply, a control circuit, a drive chip, a bootstrap circuit, and a bootstrap charging control circuit; the control circuit provides a signal square wave for the driving chip, and the driving chip outputs a corresponding driving signal to the main circuit and the bootstrap charging control circuit according to the signal square wave; the bootstrap circuit is connected with the driving chip and provides corresponding level conversion for the driving output, and the bootstrap charging control circuit provides a charging loop for the bootstrap circuit. As shown in FIG. 5, the MOS transistor M for the invention2Diode D2Resistance R1A charging loop is constructed for the bootstrap circuit, and normal and stable startup can be ensured even in no-load as long as the control is proper. Specifically, the bootstrap charging control circuit can provide a charging loop for a bootstrap capacitor in the bootstrap circuit in the starting process of the circuit, so that the self-starting function of the bootstrap circuit is realized, the self-starting function is not influenced by load conditions, and meanwhile, the bootstrap charging control circuit is only put into operation when the system is started, so that the unconditional operation of the self-starting circuit is avoided, the loss of the system is reduced, and the efficiency of the system is improved. However, in the scheme, light load is not considered, the duty ratio of the main switch tube is small, the output capacitor discharges through the added bootstrap charging branch circuit, negative current is generated on the inductor, the loss of the converter is increased, and meanwhile, the added diode and the MOS tube need to be of a type with larger capacity, so that the circuit cost is increased.
Furthermore, on the one hand, due to the differences in understanding to the person skilled in the art; on the other hand, since the inventor has studied a lot of documents and patents when making the present invention, but the space is not limited to the details and contents listed in the above, however, the present invention is by no means free of the features of the prior art, but the present invention has been provided with all the features of the prior art, and the applicant reserves the right to increase the related prior art in the background.
Disclosure of Invention
In view of the deficiencies of the prior art, the invention provides a BUCK converter bootstrap driving circuit based on narrow pulse control, which at least comprises a BUCK circuit. And the BUCK circuit is connected with a bootstrap charging branch circuit and a driving chip for driving the bootstrap charging branch circuit. The driving chip controls a switching tube in the bootstrap charging branch circuit based on a narrow pulse driving mode, so that the bootstrap charging time is ensured, and large negative current is prevented from appearing in the branch circuit when the load is light or no load. Preferably, the BUCK circuit is in a light load/no-load state, and a main switching tube Q of the BUCK circuit1Under the condition that the duty ratio is smaller than a first threshold value, the driving chip reduces the auxiliary switching tube Q in the bootstrap charging branch circuit based on a narrow pulse driving mode2OfAnd the turn-on time is set to prevent the BUCK circuit and the bootstrap charging branch circuit from generating negative current or reduce the negative current in the BUCK circuit and the bootstrap charging branch circuit. When the load is heavy or the inductive current is continuous, the problem of starting the bootstrap circuit is solved through the bootstrap charging branch circuit. The problems that when the load is light and the duty ratio of the main switching tube is small, the conduction time of the switching tube is long, negative current is easy to appear in inductive current, loss is increased, and meanwhile when the negative current is large, devices capable of conducting large current need to be selected for the switching tube and the diode, and the cost of the whole circuit is increased are solved. Aiming at the problem, the invention adopts a narrow pulse driving mode to control the auxiliary switching tube Q in the bootstrap charging branch2Since the pulse width of the narrow pulse driving signal is very narrow, the auxiliary switch tube Q2The conduction time of the inductor is very short, so that the inductor current cannot generate a negative current path, and the negative inductor current during light load or no load is greatly reduced.
According to a preferred embodiment, the BUCK circuit comprises at least a main switching transistor Q1Freewheel diode D1Energy storage inductor L and input filter capacitor C1And an output filter capacitor C2. The freewheeling diode D1Are connected in parallel with the bootstrap charging branch. The bootstrap charging branch comprises at least a first diode D2Auxiliary switch tube Q2Auxiliary power supply VCCBootstrap capacitor C3And a narrow pulse drive circuit. The freewheeling diode D1And the first diode D2And auxiliary switch tube Q2In parallel, the first diode D2And a secondary switch tube Q2Are connected in series. The auxiliary power supply VCCAnd is connected with the driving chip. The driving chip is connected with the auxiliary switching tube Q through a narrow pulse driving circuit2Is connected to the gate of (1).
According to a preferred embodiment, the auxiliary power supply V is connected to the power supplyCCAnd the bootstrap capacitor C3A second diode D is arranged between3. The auxiliary power supply VCCA second diode D3Bootstrap capacitor C3A first diode D2And a secondary switching tube Q2Are connected in sequence to form a bootstrapAnd a charging loop.
According to a preferred embodiment, the driving chip is configured to generate two paths of the first complementary driving signal Ho and the second complementary driving signal Lo with the dead zone. The first complementary driving signal Ho is used for driving the main switching tube Q1. The second complementary driving signal Lo passes through the narrow pulse driving circuit and the auxiliary switch tube Q2。
According to a preferred embodiment, the driving chip is further connected to the main switching tube Q1Is connected to the source. The main switch tube Q1Through said first diode D2And auxiliary switch tube Q2And (4) grounding.
According to a preferred embodiment, the narrow pulse driving circuit comprises at least a first resistor R1Adjusting the capacitance C4A third diode D4A first triode Q3A fourth diode D5A second resistor R2And a second triode Q4. The port of the second complementary driving signal Lo and the first resistor R1A third diode D4And a first triode Q3Is connected. The auxiliary switch tube Q2Respectively with a fourth diode D5And a second triode Q4Is connected.
According to a preferred embodiment, the first resistor R of the narrow pulse driving circuit1A third diode D4A first triode Q3Forming a first parallel loop. The adjusting capacitor C4Is connected with the first parallel loop, and the other end is grounded.
According to a preferred embodiment, the first transistor Q is a transistor of the second type3Respectively with the fourth diode D5And a second resistor R2And (4) connecting. The fourth diode D5And the second triode Q4The second resistor R of2And the second triode Q4Are connected. The second triode Q4Respectively with the adjusting capacitor C4A second resistor R2And the auxiliary switch tube Q2Is connected to the source. Or the second triode Q4The collector of (a) is grounded.
According to a preferred embodiment, the narrow pulse driving circuit is configured to be able to at least adjust the first resistance R1And/or adjusting the capacitance C4The pulse width of the narrow pulse is adjusted.
According to a preferred embodiment, the driving chip is configured to control the secondary switching tube Q by the narrow pulse generated by the narrow pulse driving circuit2The on-time of (c). The bootstrap capacitor C3Through the auxiliary switch tube Q2To the bootstrap capacitor C3And (6) charging. The driving chip is configured to turn on the secondary switching tube Q at least once through at least once generated narrow pulse2Thereby accumulating the bootstrap capacitance C3The charging time of (c).
Drawings
FIG. 1 is a schematic circuit diagram of a preferred embodiment of the present invention;
FIG. 2 is a schematic diagram of a narrow pulse driving circuit according to the present invention;
FIG. 3 is a schematic diagram of a narrow pulse drive signal of the present invention;
FIG. 4 is a schematic diagram of a prior art BUCK circuit configuration;
FIG. 5 is a prior art BUCK converter bootstrap drive circuit.
List of reference numerals
Q1: main switch tube Q2: auxiliary switch tube Q3: a first triode
Q4: second triode D1: freewheeling diode D2: first diode
D3: second diode D4: third diode D5: fourth diode
C1: input filter capacitor C2: output filter capacitor C3: bootstrap capacitor
C4: adjusting the capacitance R1: a first resistor R2: second resistance
L: energy storage inductance VCC: an auxiliary power supply Ho: first complementary drive signal
Lo: second complementary drive signal
Detailed Description
The following detailed description is made with reference to the accompanying drawings.
It is preferable to explain the technical problem of the present invention in detail. For the bootstrap drive circuit of the BUCK converter of the synchronous rectification type, when the BUCK circuit is in a light load/no load state, the energy storage inductor L enters a current discontinuous working mode. At the moment, the output filter capacitor C2The energy storage inductor L and the added bootstrap charging loop are discharged to generate a large negative current, which causes extra loss. Meanwhile, if the negative current is overloaded, the added MOS tube (such as the auxiliary switch tube Q)2) And the diode needs to select a high-current MOS tube and a high-current diode, so that the cost of the device is increased. Specifically, as shown in fig. 1, 4 and 5, in the state where the BUCK circuit is in the light load/no load state, a situation where the current crosses zero may occur. And the switching tube Q is switched in the synchronous rectification2Is a MOSFET tube. The current of the MOSFET can be from drain to source and from source to drain, so that when the current of the BUCK circuit is freewheeling (such as the output filter capacitor C in FIG. 4)2Energy storage inductor L and freewheeling diode D1Forming a loop, or an output filter capacitor C2Energy storage inductor L and freewheeling diode D1And bootstrap charging circuit), the output voltage is higher than the node voltage of the switching tube, so that the current flows back, and the inductor current is reversed. Preferably, as shown in FIG. 1, an output filter capacitor C2Energy storage inductor and first diode D2Auxiliary switch tube Q2Forming a loop. At the auxiliary switch tube Q2On the condition of conduction, a negative current flows through the first diode D2And auxiliary switch tube Q2Thus causing extra loss, and also requiring the first diode D2And auxiliary switch tube Q2Of the type using large capacityNumber, increasing costs. Therefore, in order to solve the above problems, there are two solutions, one is to adopt a device with a large capacity model, and the other is to optimize the main switch tube Q1The duty cycle of (c). However, the main switch tube Q1The duty cycle may not always remain high, which increases switching losses.
In view of the above technical problems, the present invention provides a BUCK converter bootstrap driving circuit based on narrow pulse control. Preferably, as shown in fig. 1, the BUCK converter bootstrap driving circuit based on narrow pulse control of the present invention includes at least a BUCK circuit. The BUCK circuit is connected with a bootstrap charging branch circuit and a driving chip for driving the bootstrap charging branch circuit. The driving chip controls a switching tube in the bootstrap charging branch circuit based on a narrow pulse driving mode, so that large negative current in the branch circuit during light load or no load is avoided while the bootstrap charging duration is ensured. Preferably, the BUCK circuit is in a light load/no load state and the main switch tube Q of the BUCK circuit1Under the condition that the duty ratio is smaller than the first threshold value, the driving chip reduces the auxiliary switching tube Q in the bootstrap charging branch circuit based on a narrow pulse driving mode2To prevent the BUCK circuit and the bootstrap charging branch from generating negative current or reduce the negative current in the BUCK circuit and the bootstrap charging branch. Preferably, the first threshold may be between 50% and 5%. When the load is heavy or the inductive current is continuous, the problem of starting the bootstrap circuit is solved through the bootstrap charging branch circuit. The problems that when the load is light and the duty ratio of the main switching tube is small, the conduction time of the switching tube is long, negative current is easy to appear in inductive current, loss is increased, and meanwhile when the negative current is large, devices capable of conducting large current need to be selected for the switching tube and the diode, and the cost of the whole circuit is increased are solved. Aiming at the problem, the invention adopts a narrow pulse driving mode to control the auxiliary switching tube Q in the bootstrap charging branch2Since the pulse width of the narrow pulse driving signal is very narrow, the auxiliary switch tube Q2The conduction time of the inductor is very short, so that the inductor current cannot generate a negative current path, and the negative inductor current during light load or no load is greatly reduced.
Preferably, the BUCK circuit is as shown in FIGS. 1 and 4Less main switch tube Q1Freewheel diode D1Energy storage inductor L and input filter capacitor C1And an output filter capacitor C2. Preferably, as shown in fig. 1, a freewheeling diode D1The two ends of the bootstrap charging branch circuit are connected in parallel. The bootstrap charging branch comprises at least a first diode D2Auxiliary switch tube Q2Auxiliary power supply VCCBootstrap capacitor C3And a narrow pulse drive circuit. Freewheeling diode D1Are respectively connected with the first diode D2And auxiliary switch tube Q2And (4) connecting in parallel. First diode D2And a secondary switch tube Q2Are connected in series. Auxiliary power supply VCCAnd is connected with the driving chip. I.e. auxiliary power supply VCCAnd supplying power to the driving chip. The driving chip drives the circuit and the auxiliary switch tube Q through the narrow pulse2Is connected to the gate of (1). Preferably, one path of the driving chip is connected to ground. One-way interface of driving chip and main switch tube Q1Is connected to the gate of (a). One-way interface of driving chip and main switch tube Q1Is connected to the source of (a). Preferably, the secondary switching tube Q2The source of (a) is grounded. Main switch tube Q1Source electrode of and first diode D2Is connected to the cathode. Therefore, the main switch tube Q1Through a first diode D2And auxiliary switch tube Q2And (4) grounding.
Preferably, at the auxiliary power supply VCCAnd a bootstrap capacitor C3A second diode D is arranged between3. Auxiliary power supply VCCA second diode D3Bootstrap capacitor C3A first diode D2And a secondary switching tube Q2And the two are connected in sequence to form a bootstrap charging loop. Preferably, in the secondary switching tube Q2Under the condition of conduction, the bootstrap charging loop can supply bootstrap capacitor C3And (6) charging. Preferably, the driving chip is configured to generate two paths of the first complementary driving signal Ho and the second complementary driving signal Lo with the dead zone. The first complementary driving signal Ho is used for driving the main switch tube Q1. The second complementary driving signal Lo passes through the narrow pulse driving circuit and the auxiliary switch tube Q2. Preferably, the Vs port of the driving chip is connected with the main switch tube Q1Is connected to the source of (a). Through the arrangement mode, theIt is seen that a negative current is generated and applied to the bootstrap capacitor C3Charging requires auxiliary switch tube Q2Is turned on. It should be noted that the negative current is generated by the output filter capacitor C2An energy storage inductor L and a first diode D2Auxiliary switch tube Q2The circuit formed is switched on, i.e. the auxiliary switching tube Q is required2And conducting. Even if the auxiliary switch tube Q2When the capacitor is conducted, the capacitor discharges to enable the energy storage inductor L to generate negative inductor current, and time is needed, namely, the whole loop passes through the output filter capacitor C2The negative inductive current generated by discharging also needs a certain time, so that only the auxiliary switch tube Q is used2A large negative inductor current is generated only when the capacitor is turned on for a long time. Based on the control, the auxiliary switch tube Q is controlled by narrow pulse2I.e. the secondary switching tube Q2The on-time of the auxiliary switch tube Q is the duration of the narrow pulse2The conduction time of the inductor is short, so that negative inductive current cannot be generated in a conducted loop, or the generated negative inductive current is extremely small. In addition, the switch tube Q2The conduction of the capacitor can make the bootstrap charging loop be the bootstrap capacitor C3And (6) charging. Thus the switch tube Q2The turn-on time of the capacitor also needs to be ensured3Can be charged with sufficient electric quantity, i.e. the bootstrap capacitor C needs to be ensured3The charging time of (c). Aiming at the problem, on one hand, the pulse width of the narrow pulse can be adjusted to meet the requirement of a bootstrap capacitor C3While ensuring that the pulse width is small enough not to generate a large negative inductor current. Preferably, a bootstrap capacitance C is taken into account3The charging time of (C) can be accumulated, while the time of generating negative inductive current can not be accumulated, i.e. bootstrap capacitor C3Can be charged for a plurality of times in a short time, and the negative current can not be accumulated and increased by a plurality of times of short-time conduction, so that the period of the narrow pulse can be reduced at the same time, and the auxiliary switching tube Q is enabled to be connected with the output end of the voltage regulator2Multiple short-time conduction to ensure bootstrap capacitor C3The charging time is simultaneously avoided, and the generation of negative inductive current is avoided.
Preferably, the driving chip is configured to control the secondary switching tube Q by a narrow pulse generated by the narrow pulse driving circuit2OfAnd (7) passing time. Bootstrap capacitor C3Through the auxiliary switch tube Q2To bootstrap the capacitor C3And (6) charging. The driving chip is configured to turn on the secondary switching tube Q at least once through the narrow pulse generated at least once2Thereby accumulating a bootstrap capacitance C3The charging time of (c).
Through the above setting mode, the beneficial effect who reaches is:
on one hand, the large negative current in the inductor can be avoided, and the efficiency of the circuit is improved;
on the other hand, no large current flows in the added bootstrap charging branch circuit, and the components can be selected from components with smaller current capacity, so that the circuit cost is reduced.
Preferably, the narrow pulse driving circuit includes at least a first resistor R1Adjusting the capacitance C4A third diode D4A first triode Q3A fourth diode D5A second resistor R2And a second triode Q4. The port of the second complementary driving signal Lo and the first resistor R1A third diode D4And a first triode Q3Is connected. Auxiliary switch tube Q2Respectively with a fourth diode D5And a second triode Q4Is connected.
According to a preferred embodiment, the first resistor R of the narrow pulse drive circuit1A third diode D4A first triode Q3Forming a first parallel loop. Adjusting capacitance C4Is connected with the first parallel loop, and the other end is grounded.
According to a preferred embodiment, the first transistor Q3Respectively with a fourth diode D5And a second resistor R2And (4) connecting. Fourth diode D5And a second triode Q4A second resistor R2And a second triode Q4Are connected. Second triode Q4Respectively with the adjusting capacitor C4A second resistor R2And a secondary switching tube Q2Is connected to the source. Or a second triode Q4The collector of (a) is grounded.
According to a preferred embodiment, the narrow pulse driving circuit is configured to be able to at least adjust the first resistance R1And/or adjusting the capacitance C4The pulse width of the narrow pulse is adjusted. By this arrangement, the period of the narrow pulse can be adjusted.
According to a preferred embodiment, the secondary switching tube Q2And the circuit is configured to turn on or off a path of an inductive current generating a negative current based on the charging time of the bootstrap capacitor under the driving of the narrow pulse generated by the narrow pulse driving circuit. Preferably, the narrow pulse driving circuit generates a narrow pulse driving signal as shown in fig. 3, and the sub-switch Q is turned on or off due to the very narrow pulse width of the narrow pulse driving signal2The on-time of the capacitor is very short, a negative current path is not generated for the inductive current under the condition of ensuring the charging time of the bootstrap capacitor, and the negative inductive current during light load or no load is greatly reduced.
The present specification encompasses multiple inventive concepts and the applicant reserves the right to submit divisional applications according to each inventive concept. The present description contains several inventive concepts, such as "preferably", "according to a preferred embodiment" or "optionally", each indicating that the respective paragraph discloses a separate concept, the applicant reserves the right to submit divisional applications according to each inventive concept.
It should be noted that the above-mentioned embodiments are exemplary, and that those skilled in the art, having benefit of the present disclosure, may devise various arrangements that are within the scope of the present disclosure and that fall within the scope of the invention. It should be understood by those skilled in the art that the present specification and figures are illustrative only and are not limiting upon the claims. The scope of the invention is defined by the claims and their equivalents.
Claims (10)
1. A bootstrap driving circuit of BUCK converter based on narrow pulse control at least comprises a BUCK circuit, and is characterized in that a bootstrap charging branch circuit and a driving chip for driving the bootstrap charging branch circuit are connected in the BUCK circuit, wherein,
when the BUCK circuit is in a light load/no-load state and a main switching tube (Q) of the BUCK circuit1) When the duty ratio is smaller than the first threshold value, the driving chip reduces the secondary switching tube (Q) in the bootstrap charging branch circuit based on a narrow pulse driving mode2) To prevent the BUCK circuit and the bootstrap charging branch from generating negative current or reduce the negative current in the BUCK circuit and the bootstrap charging branch.
2. BUCK converter bootstrap drive circuit in accordance with claim 1, characterized in that the BUCK circuit comprises at least a main switching tube (Q)1) Freewheel diode (D)1) Energy storage inductor (L), input filter capacitor (C)1) And an output filter capacitor (C)2) Wherein, in the step (A),
the freewheeling diode (D)1) Is connected in parallel with the bootstrap charging branch, wherein,
the bootstrap-charging branch comprises at least a first diode (D)2) And a secondary switch tube (Q)2) Auxiliary power supply (V)CC) Bootstrap capacitor (C)3) And a narrow pulse drive circuit, wherein,
the freewheeling diode (D)1) Respectively connected with the first diode (D)2) And a secondary switching tube (Q)2) In parallel, the first diode (D)2) And auxiliary switch tube (Q)2) Are connected in series;
the auxiliary power supply (V)CC) Is connected with the driving chip, and the driving chip is connected with the auxiliary switching tube (Q) through a narrow pulse driving circuit2) Is connected to the gate of (1).
3. BUCK converter bootstrap drive circuit in accordance with claim 2, characterized in that at the auxiliary power supply (V)CC) And the bootstrap capacitor (C)3) A second diode (D) is arranged between the two3) Wherein, in the step (A),
the auxiliary power supply (V)CC) A second diode (D)3) Bootstrap capacitor (C)3) A first diode (D)2) And a secondary switchPipe closing (Q)2) And the two are connected in sequence to form a bootstrap charging loop.
4. The BUCK converter bootstrap drive circuit of claim 3, characterized in that the drive chip is configured to generate two paths of a first complementary drive signal (Ho) and a second complementary drive signal (Lo) with dead zone, wherein,
the first complementary driving signal (Ho) is used for driving the main switching tube (Q)1) The second complementary driving signal (Lo) passes through the narrow pulse driving circuit and the secondary switch tube (Q)2)。
5. BUCK converter bootstrap drive circuit as claimed in claim 4, characterized in that said driver chip is also connected to said main switching tube (Q)1) And the main switching tube (Q)1) Through said first diode (D)2) And a secondary switching tube (Q)2) And (4) grounding.
6. BUCK converter bootstrap drive circuit in accordance with claim 5, characterized in that said narrow pulse drive circuit comprises at least a first resistance (R)1) Adjusting the capacitance (C)4) A third diode (D)4) A first triode (Q)3) A fourth diode (D)5) A second resistor (R)2) And a second triode (Q)4) Wherein, in the step (A),
the port of the second complementary drive signal (Lo) and the first resistor (R)1) A third diode (D)4) And a first triode (Q)3) The transmitting stage of (a);
the auxiliary switch tube (Q)2) Respectively with a fourth diode (D)5) And a second triode (Q)4) Is connected.
7. BUCK converter bootstrap drive circuit in accordance with claim 6, characterized in that the first resistance (R) of the narrow pulse drive circuit1) A third diode (D)4) A first triode (Q)3) A first parallel loop is formed, wherein,
the adjusting capacitor (C)4) Is connected with the first parallel loop, and the other end is grounded.
8. BUCK converter bootstrap drive circuit in accordance with claim 7, characterized in that the first transistor (Q)3) Respectively with the fourth diode (D)5) And a second resistance (R)2) Connecting;
the fourth diode (D)5) And said second triode (Q)4) The second resistor (R) of2) And said second triode (Q)4) The base level of (a) is connected, wherein,
the second triode (Q)4) Respectively with the adjusting capacitance (C)4) A second resistor (R)2) And the auxiliary switching tube (Q)2) Is connected to the source of the first transistor,
or the second triode (Q)4) The collector of (a) is grounded.
9. BUCK converter bootstrap drive circuit in accordance with claim 8, characterized in that the narrow pulse drive circuit is configured at least capable of being adjusted by the first resistance (R) at least1) And/or adjusting the capacitance (C)4) The pulse width of the narrow pulse is adjusted.
10. BUCK converter bootstrap drive circuit as claimed in claim 9, characterized in that said drive chip is configured to control said secondary switching tube (Q) by means of a narrow pulse generated by said narrow pulse drive circuit2) The on-time of (a), wherein,
the bootstrap capacitor (C)3) Through the auxiliary switch tube (Q)2) To the bootstrap capacitor (C)3) Charging, wherein the charging is carried out by charging,
the driving chip is configured to turn on the secondary switching tube (Q) at least once by at least once generated narrow pulse2) Thereby accumulating the bootstrap capacitance (C)3) The charging time of (c).
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| CN113193732A (en) * | 2021-04-27 | 2021-07-30 | 成都稳海半导体有限公司 | Self-adaptive charging bootstrap power supply |
| US11205958B2 (en) | 2019-09-18 | 2021-12-21 | Delta Electronics, Inc. | Power conversion system |
| US11205963B2 (en) * | 2019-09-18 | 2021-12-21 | Delta Electronics, Inc. | Multiphase buck converter with extended duty cycle range using multiple bootstrap capacitors |
| US11309878B2 (en) | 2019-09-18 | 2022-04-19 | Delta Electronics, Inc. | Power conversion system |
| US11532428B2 (en) | 2019-09-18 | 2022-12-20 | Delta Electronics, Inc. | Power conversion system and magnetic component thereof |
| TWI829015B (en) * | 2021-07-12 | 2024-01-11 | 大陸商昂寶電子（上海）有限公司 | Charge Sharing Bootstrap Charging Control System for Buck-Boost Converters |
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| US11205963B2 (en) * | 2019-09-18 | 2021-12-21 | Delta Electronics, Inc. | Multiphase buck converter with extended duty cycle range using multiple bootstrap capacitors |
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