CN114421768A - Bootstrap capacitor under-voltage protection circuit, control chip and switching power supply - Google Patents
Bootstrap capacitor under-voltage protection circuit, control chip and switching power supply Download PDFInfo
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- CN114421768A CN114421768A CN202111669793.2A CN202111669793A CN114421768A CN 114421768 A CN114421768 A CN 114421768A CN 202111669793 A CN202111669793 A CN 202111669793A CN 114421768 A CN114421768 A CN 114421768A
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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
- 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
- H02M3/1582—Buck-boost converters
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/10—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers
- H02H7/12—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers
- H02H7/1213—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers for DC-DC 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
- H02M1/32—Means for protecting converters other than automatic disconnection
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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
- H02M3/06—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using resistors or capacitors, e.g. potential divider
- H02M3/07—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using resistors or capacitors, e.g. potential divider using capacitors charged and discharged alternately by semiconductor devices with control electrode, e.g. charge pumps
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Dc-Dc Converters (AREA)
Abstract
The utility model relates to a switching power supply field especially relates to bootstrap capacitor under-voltage protection circuit, control chip and switching power supply, and bootstrap capacitor under-voltage protection circuit is used for having power switch's switching power supply, and bootstrap capacitor under-voltage protection circuit includes: bootstrap capacitor, pull-down switch, detection circuitry and drive circuit detect bootstrap capacitor's capacitance voltage through setting up detection circuitry, do through setting up pull-down switch bootstrap capacitor charges, when detection circuitry detects bootstrap capacitor and appears the under-voltage condition, switches on and turn-off the alternative through drive circuit drive pull-down switch, charges bootstrap capacitor to bootstrap capacitor and reaches non-under-voltage state, has solved when charging for bootstrap capacitor, and pull-down switch switches on the problem of burning out the chip easily always, improves circuit's reliability.
Description
Technical Field
The application relates to the field of switching power supplies, in particular to a bootstrap capacitor under-voltage protection circuit, a control chip and a switching power supply.
Background
The switching power supply is a power supply which utilizes the modern power electronic technology to control the on-off time ratio of a switching transistor and maintain stable output, generally comprises a driving power supply (generally pulse width modulation driving) and a main circuit, and has the advantages of high efficiency and small volume, wherein a Boost circuit, a buck circuit and a Boost-buck circuit are common main circuit topologies.
Switching power supply chips such as direct current conversion chips are applied more and more widely in electronic products, a DC-DC conversion chip generally adopts an N-Metal-Oxide-Semiconductor (NMOS) device, the NMOS device needs a voltage higher than a source terminal thereof as a driving voltage of a gate thereof, the source terminal voltage of the NMOS device is approximately equal to a drain terminal voltage thereof after the NMOS device is turned on, and at this time, the driving voltage of the NMOS device needs to be raised by a bootstrap capacitor. Due to the existence of switching loss, the charge of the bootstrap capacitor is consumed, the capacitor voltage of the bootstrap capacitor is gradually reduced, and in order to ensure the stable operation of the direct current conversion chip and the correctness of the upper tube driving logic, it is required to ensure that the capacitor voltage of the bootstrap capacitor is higher than a certain threshold value.
When the dc conversion chip works in the idle state, the upper tube M1 is not turned on for a long time after entering the sleep state, the charge of the bootstrap capacitor Cboost is consumed and cannot be charged in time, the capacitor voltage of the bootstrap capacitor Cboost is continuously reduced, in order to protect the upper tube M1 logic correct, the capacitor voltage of the bootstrap capacitor Cboost needs to be detected in real time, the prior art keeps the lower tube in the on state when charging the bootstrap capacitor Cboost, the discharging time of the lower tube is uncontrollable, and the chip is easily burned.
Disclosure of Invention
The main purpose of this application is for providing bootstrap capacitor under-voltage protection circuit, control chip and switching power supply, aims at solving prior art when charging for bootstrap capacitor, burns out the problem of chip easily.
A first aspect of an embodiment of the present application provides a bootstrap capacitor under-voltage protection circuit, which is used for a switching power supply having a power switch, wherein the bootstrap capacitor under-voltage protection circuit includes: a bootstrap capacitor;
the power switch and the pull-down switch are connected between an input power supply and the ground in series, and the bootstrap capacitor is connected between an operating power supply and a series node of the power switch and the pull-down switch;
the detection circuit is connected with the bootstrap capacitor and is used for detecting the bootstrap voltage of the bootstrap capacitor, outputting a first level signal if the bootstrap capacitor is in an undervoltage state, and outputting a second level signal if the bootstrap capacitor is not in the undervoltage state; and
and the driving circuit is connected with the detection circuit and used for receiving the first level signal and generating a driving signal according to the first level signal so as to drive the pull-down switch to be switched on and off alternately, so that the bootstrap capacitor is charged by the working power supply until the bootstrap voltage reaches a non-undervoltage state.
In one embodiment, the pull-down switch is an NMOS transistor, a gate of the pull-down switch is connected to the driving circuit, a drain of the pull-down switch is connected to the power switch, and a source of the pull-down switch is grounded.
In one embodiment, the detection circuit comprises a comparator;
the first input end of the comparator is connected with the first end of the bootstrap capacitor and used for inputting the voltage value of the first end of the bootstrap capacitor, the second input end of the comparator is connected with the second end of the bootstrap capacitor and used for inputting the sum of a first preset voltage value and the voltage value of the second end of the bootstrap capacitor, the comparator is used for outputting a first level signal when the bootstrap voltage of the bootstrap capacitor is larger than the first preset voltage value, and outputting a second level signal when the bootstrap voltage of the bootstrap capacitor is smaller than the first preset voltage value.
In one embodiment, the driving circuit includes:
the level conversion circuit is connected with the detection circuit and is used for performing voltage conversion on the level signal output by the detection circuit, converting a high-side signal into a low-side signal and outputting the low-side signal to the clock circuit;
the clock circuit is connected with the level conversion circuit and is used for outputting a clock signal when the first level signal is received;
the control circuit is respectively connected with the detection circuit and the clock circuit and used for outputting a first control signal for controlling the power switch according to the output signal of the level conversion circuit and outputting a second control signal for controlling the pull-down switch according to the clock signal output by the clock circuit;
the first driving circuit is connected with the control circuit and used for driving the power switch according to the first control signal; and
and the second driving circuit is connected with the control circuit and used for driving the pull-down switch according to the second control signal.
In one embodiment, the pull-down switch is turned on and off alternately for a first preset time period and a second preset time period, wherein the first preset time period is shorter than the second preset time period.
In one embodiment, the first predetermined time period is 150 ns, and the second predetermined time period is 50 μ s.
In one embodiment, when the detection circuit detects that the bootstrap capacitor is in an under-voltage state, the driving circuit controls the power switch to be in an off state.
In one embodiment, when the detection circuit detects that the bootstrap capacitor is in a non-undervoltage state, the driving circuit controls the power switch to be in a normal working state.
A second aspect of the present application provides a control chip for a switching power supply, including the bootstrap capacitor under-voltage protection circuit in any of the above embodiments.
A third aspect of the present application provides a switching power supply, which includes a power switch, an energy storage element, and a bootstrap capacitor under-voltage protection circuit in the control chip for the switching power supply provided in the second aspect of the foregoing embodiment.
Compared with the prior art, the embodiment of the invention has the following beneficial effects: the bootstrap capacitor under-voltage protection circuit detects the capacitor voltage of the bootstrap capacitor by setting the detection circuit, and the bootstrap capacitor is charged by setting the pull-down switch, when the detection circuit detects that the bootstrap capacitor is under-voltage, the bootstrap capacitor is alternately switched on and off by pulling open under the drive of the drive circuit, the bootstrap capacitor is charged to the bootstrap capacitor to exit from the under-voltage state, and the problem that the chip is easily burnt down by always switching on the pull-down switch when the bootstrap capacitor is charged is solved, thereby improving the reliability of the circuit.
Drawings
FIG. 1 is a schematic circuit diagram of a portion of a prior art switching power supply;
FIG. 2 is a schematic diagram of a bootstrap capacitor under-voltage protection circuit in the prior art;
fig. 3 is a schematic diagram of a bootstrap capacitor under-voltage protection circuit according to an embodiment of the present application;
fig. 4 is a schematic diagram of a bootstrap capacitor under-voltage protection circuit according to an embodiment of the present application;
fig. 5 is a control timing diagram of an under-voltage protection circuit of a bootstrap capacitor according to an embodiment of the present application.
Detailed Description
In order to make the technical problems, technical solutions and advantageous effects to be solved by the present application clearer, the present application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application.
It will be understood that when an element is referred to as being "secured to" or "disposed on" another element, it can be directly on the other element or be indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or be indirectly connected to the other element.
It will be understood that the terms "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like, refer to an orientation or positional relationship illustrated in the drawings for convenience in describing the present application and to simplify description, and do not indicate or imply that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and thus should not be construed as limiting the present application.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present application, "a plurality" means two or more unless specifically limited otherwise.
As shown in fig. 1, for the BUCK circuit with the upper transistor being an NMOS transistor, in order to turn on the switching transistor M1, a bootstrap capacitor Cboost needs to be provided for the switching transistor M1 to provide a driving voltage required between the gate and the source of the switching transistor M1, when the switching transistor M1 is turned on, the voltage of the node SW is Vin, due to the existence of the bootstrap capacitor Cboost, the voltage at the node BS is the voltage at the node SW plus the voltage at the two ends of the bootstrap capacitor Cboost, i.e., the bootstrap voltage Vbs, the switching transistor M1 can be kept on, when the switching transistor M1 is turned off, the node SW is pulled low, and at this time, the power supply Vcc charges the bootstrap capacitor Cboost through the diode D1, so as to keep the voltage at the two ends of the bootstrap capacitor Cboost as the bootstrap voltage Vbs.
However, in the case of pre-biased start or no-load, the switch M1 is not turned on for a long time, and the charge on the bootstrap capacitor Cboost is consumed but cannot be charged in time, so that the voltage of the node SW cannot be pulled low, and the bootstrap capacitor Cboost cannot be charged. Therefore, a pull-down circuit is required to pull down the voltage of the node SW to charge the bootstrap capacitor Cboost, as shown in fig. 2, the lower tube M2 is controlled to be turned on by the driving circuit 2, and the voltage of the node SW is pulled down to charge the bootstrap capacitor Cboost. In the prior art, the lower tube M2 is always turned on when the bootstrap capacitor Cboost is applied, and the lower tube burns or even burns the chip due to the fact that the lower tube M2 has small on-resistance and uncontrollable discharge time.
As shown in fig. 3, to solve the above technical problem, a first aspect of the embodiments of the present application provides a bootstrap capacitor under-voltage protection circuit for a switching power supply having a power switch M1, where the bootstrap capacitor under-voltage protection circuit includes a bootstrap capacitor Cboost, a pull-down switch M2, a detection circuit 100 and a driving circuit 200, where the pull-down switch M2 and the power switch M1 are connected in series between an input power Vin and ground, the bootstrap capacitor Cboost is connected between an operating power Vcc and a node SW of a series connection node between the power switch M1 and the pull-down switch M2, the detection circuit 100 is connected to the bootstrap capacitor Cboost and is used for detecting a bootstrap voltage Vbs of the bootstrap capacitor Cboost, the detection circuit 100 is used for detecting whether the bootstrap voltage Vbs of the bootstrap capacitor Cboost is under-voltage, for example, when the voltage Vbs across the bootstrap capacitor Cboost is less than 2.5V, the bootstrap capacitor Cboost is considered to be in an under-voltage state, the detection circuit 100 outputs a first level signal when the capacitor Cboost is in an under-voltage state, when the bootstrap capacitor Cboost is in the non-undervoltage state, a second level signal is output, the driving circuit 200 is connected to the detection circuit 100, and is configured to receive the first level signal, when the first level signal is valid, the driving circuit 200 may release a clock signal, the clock signal is configured to control the pull-down switch M2 to turn on and off, the turn-on time is fixed and controllable, so that the bootstrap capacitor Cboost is charged by the operating power supply Vcc to its bootstrap voltage Vbs, and exits from the undervoltage state, for example, Vbs is greater than 2.8V, and it is considered that the bootstrap capacitor Cboost exits from the undervoltage state. In the process that the bootstrap capacitor Cboost is charged to the bootstrap voltage Vbs by the working power supply Vcc, that is, the bootstrap capacitor Cboost is considered to exit the undervoltage state, a state that the bootstrap voltage Vbs is greater than a first preset voltage value needs to be maintained for a certain time, so that it is avoided that the pull-down switch is turned off after the bootstrap capacitor Cboost is just charged to the bootstrap voltage Vbs thereof, which causes the bootstrap capacitor Cboost to be lower than the threshold value of the bootstrap voltage Vbs thereof again, the bootstrap capacitor Cboost is ensured to be reliably in the non-undervoltage state, an oscillation phenomenon is prevented, and the stability of the bootstrap circuit is further improved.
The bootstrap capacitor under-voltage protection circuit that this application embodiment first aspect provided detects bootstrap capacitor Cboost's capacitance voltage through setting up detection circuit 100, charge for bootstrap capacitor Cboost through setting up pull-down switch M2, when detection circuit 100 detects bootstrap capacitor Cboost and appear under-voltage condition, drive pull-down switch M2 through drive circuit 200 and switch on and turn off alternately, charge bootstrap capacitor Cboost to bootstrap capacitor Cboost and reach non-under-voltage state, when having solved for bootstrap capacitor Cboost to charge, pull-down switch M2 switches on the problem of burning out the chip easily always, improve the reliability of circuit.
In one embodiment, referring to fig. 3, the pull-down switch M2 is an NMOS transistor, the gate of the pull-down switch M2 is connected to the driving circuit 200, the drain of the pull-down switch M2 is connected to the power switch M1, and the source of the pull-down switch M2 is grounded.
In one embodiment, referring to fig. 4, the detection circuit 100 includes a comparator 110, the comparator 110 is, for example, a voltage comparator, a first input terminal of the comparator 110 is connected to a first terminal of the bootstrap capacitor Cboost, i.e., a node BS, for inputting a voltage value at the first terminal of the bootstrap capacitor Cboost, a second input terminal of the comparator 110 is connected to a second terminal of the bootstrap capacitor Cboost, i.e., a node SW, for inputting a sum of a first preset voltage value and a voltage value at a second terminal of the bootstrap capacitor Cboost, the comparator 110 compares two inputs thereof, outputs a first level signal when the bootstrap voltage Vbs of the bootstrap capacitor Cboost is greater than the first preset voltage value, and the comparator 110 flips and outputs a second level signal when the bootstrap voltage Vbs of the bootstrap capacitor Cboost is less than the second preset voltage value, where the first level signal is, e.g., a logic 1, the second level signal is, e.g., a logic 0, the first preset voltage value may be a bootstrap voltage Vbs of the bootstrap capacitor Cboost, such as 2.5V, and the second preset voltage value may be higher than the bootstrap voltage vboost of the bootstrap capacitor Cboost, such as 2.8V.
In one embodiment, referring to fig. 4, the driving circuit 200 includes a level shifter 210, a clock circuit 220, a control circuit 230, a first driving circuit 240 and a second driving circuit 250, wherein the level shifter 210 is connected to the detection circuit 100 for performing voltage conversion on a level signal output by the detection circuit 100 and converting a high-side signal of the power switch M1 into a low-side signal of the pull-down switch M2. The clock circuit 220 is connected to the level shift circuit 210, and is configured to output a clock signal CLK when receiving the first level signal from the detection circuit 100, where the clock signal CLK is a pulse signal. The control circuit 230 is connected to the detection circuit 100 and the clock circuit 220, respectively, and the control circuit 230 is configured to output a first control signal for controlling the power switch M1 according to the output signal of the level shift circuit 210, and output a second control signal for controlling the pull-down switch M2 according to the clock signal CLK output by the clock circuit 220. The first driving circuit 240 is connected to the control circuit 230, the first driving circuit 240 is configured to drive the power switch M1 to turn on or off according to a first control signal output by the control circuit 230, the second driving circuit 250 is connected to the control circuit 230, and the second driving circuit 250 is configured to drive the pull-down switch M2 to turn on or off according to a second control signal output by the control circuit 230. The control circuit 230 may be an integrated logic circuit or a control chip, and the first driving circuit 240 and the second driving circuit 250 may be common MOS transistor drivers. The clock circuit 220 is configured to alternately control the on and off of the pull-down switch M2, wherein the clock signal CLK output by the clock circuit 220 is masked when the pull-down switch M2 is turned off, i.e., the clock signal CLK is masked by the control circuit 230 when the pull-down switch M2 is not required to be alternately turned on or off by the clock signal CLK. The alternation of on and off specifically means that the pull-down switch M2 is turned on for a period of time and then turned off for a period of time, and then the pull-down switch M2 is turned on, so that the periodic on and off are realized, and the pull-down switch M2 is prevented from being turned on all the time to burn the chip.
In one embodiment, the pull-down switch M2 is turned on and off alternately for a first preset time and a second preset time, where the first preset time is shorter than the second preset time, because the on-resistance of the pull-down switch M2 is small, it is avoided that the pull-down switch M2 is kept in its on state all the time and is burned, the pull-down switch M2 is turned on within the first preset time, the bootstrap capacitor Cboost starts to charge, and the pull-down switch M2 is turned off within the second preset time, because the on-time and the off-time are short relative to the charge consumption time of the bootstrap capacitor Cboost, the bootstrap voltage Vbs of the bootstrap capacitor Cboost will rise all the time until the bootstrap voltage Vbs of the bootstrap capacitor Cboost is greater than 2.8V, and it is avoided that the pull-down switch M2 is turned on all the time and burns the chip.
In one embodiment, the first predetermined time period is 150 ns and the second predetermined time period is 50 ns.
In one embodiment, when the detection circuit 100 detects that the bootstrap capacitor Cboost is in an under-voltage state, the driving circuit 200 controls the power switch M1 to be in an off state, and when the detection circuit 100 detects that the charge on the bootstrap capacitor Cboost is consumed and cannot be charged in time to generate an under-voltage state, in order to protect the logic correctness of the power switch M1, the driving circuit 200 controls to turn off the power switch M1, so as to maintain the logic correctness of the power switch M1, and improve the circuit stability.
In one embodiment, when the detection circuit 100 detects that the bootstrap capacitor Cboost is in the non-undervoltage state, the detection circuit 100 exits the detection state, and the driving circuit 200 controls the power switch M1 to be in the normal operating state, that is, when the voltage of the bootstrap capacitor Cboost is not undervoltage, or after charging, the bootstrap voltage Vbs is greater than a first preset voltage value, the detection circuit 100 exits the detection state, where the exiting the detection state specifically means that the detection circuit 100 is in the standby detection state, and waits for the next time when the voltage of the bootstrap capacitor Cboost changes into the undervoltage state, so that the loss of the bootstrap capacitor undervoltage detection circuit is further reduced, and the reliability of the circuit is improved.
The bootstrap capacitor under-voltage protection circuit that this application embodiment first aspect provided detects bootstrap capacitor Cboost's capacitance voltage through setting up detection circuitry 100, do through setting up pull-down switch M2 the bootstrap capacitor charges, when detection circuitry 100 detects bootstrap capacitor Cboost and appears the under-voltage condition, drive pull-down switch M2 through drive circuit 200 and switch on and turn off alternately, charge bootstrap capacitor Cboost to bootstrap capacitor Cboost and reach non-under-voltage state, when having solved for bootstrap capacitor Cboost to charge, pull-down switch M2 switches on the problem of burning out the chip easily always, the reliability of improvement circuit.
To better explain the working flow of the bootstrap capacitor under-voltage protection circuit provided in the first aspect of the embodiment of the present application, the following description is made with reference to a timing chart of various signals when the circuit specifically works, as shown in fig. 5, which is a control timing chart, HG is a control signal for driving the power switch M1, LG is a control signal for driving the pull-down switch M2, BS-SW is a voltage difference between the node BS and the node SW, VBSUV is a level signal output by the detection circuit 100 through the level shift circuit 210, VBSUV signal is inverted to indicate that the bootstrap capacitor Cboost is in an under-voltage state, CLK is a clock signal, when the bootstrap capacitor Cboost is in the under-voltage state, the clock signal CLK is a periodic pulse signal, and controls the pull-down switch M2 to be turned on and off periodically corresponding to the timing sequence of the LG signal, and during the period on and off of the pull-down switch M2 is alternated, the bootstrap capacitor Cboost is charged until the under-voltage state is reached, the BS-SW can be turned off after a period of time when the BS-SW exceeds the second preset voltage value by 2.5V, namely, hysteresis exists, so that the BS-SW is prevented from being turned off after being charged to the threshold value, and the BS-SW is prevented from being turned off after being turned off, so that the BS-SW is lower than the threshold value after being turned off, and then starts to be raised, and then is reduced after being turned off, namely, oscillation occurs, thereby solving the problem that when a bootstrap capacitor Cboost is charged, a pull-down switch M2 is always turned on, so that a chip is easily burnt, and improving the reliability of the circuit.
A second aspect of the embodiments of the present application provides a control chip for a switching power supply, including the bootstrap capacitor under-voltage protection circuit in any of the above embodiments, where the control chip is, for example, a DC-DC conversion chip.
A third aspect of the embodiments of the present application provides a switching power supply, which includes a power switch, an energy storage element, and a bootstrap capacitor under-voltage protection circuit provided in the first aspect of the embodiments of the present application.
The above-mentioned embodiments are only used for illustrating the technical solutions of the present application, and not for limiting the same; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; such modifications and substitutions do not substantially depart from the spirit and scope of the embodiments of the present application and are intended to be included within the scope of the present application.
Claims (10)
1. A bootstrap capacitor under-voltage protection circuit for a switching power supply having a power switch, the bootstrap capacitor under-voltage protection circuit comprising:
a bootstrap capacitor;
the power switch and the pull-down switch are connected between an input power supply and the ground in series, and the bootstrap capacitor is connected between an operating power supply and a series node of the power switch and the pull-down switch;
the detection circuit is connected with the bootstrap capacitor and is used for detecting the voltage at two ends of the bootstrap capacitor, outputting a first level signal if the bootstrap capacitor is in an undervoltage state, and outputting a second level signal if the bootstrap capacitor is not in the undervoltage state; and
and the driving circuit is connected with the detection circuit and used for receiving the first level signal and generating a driving signal according to the first level signal so as to drive the pull-down switch to be switched on and off alternately, so that the bootstrap capacitor is charged by the working power supply until the bootstrap voltage reaches a non-undervoltage state.
2. The bootstrap capacitor under-voltage protection circuit of claim 1, wherein the pull-down switch is an NMOS transistor, a gate of the pull-down switch is connected to the driving circuit, a drain of the pull-down switch is connected to the power switch, and a source of the pull-down switch is grounded.
3. The bootstrap capacitor under-voltage protection circuit of claim 1, wherein the detection circuit includes a comparator;
the first input end of the comparator is connected with the first end of the bootstrap capacitor and used for inputting the voltage value of the first end of the bootstrap capacitor, the second input end of the comparator is connected with the second end of the bootstrap capacitor and used for inputting the sum of a first preset voltage value and the voltage value of the second end of the bootstrap capacitor, the comparator is used for outputting a first level signal when the bootstrap voltage of the bootstrap capacitor is larger than the first preset voltage value, and outputting a second level signal when the bootstrap voltage of the bootstrap capacitor is smaller than the first preset voltage value.
4. The bootstrap capacitor under-voltage protection circuit of claim 1, wherein the drive circuit comprises:
the level conversion circuit is connected with the detection circuit and is used for performing voltage conversion on the level signal output by the detection circuit, converting a high-side signal into a low-side signal and outputting the low-side signal to the clock circuit;
the clock circuit is connected with the level conversion circuit and is used for outputting a clock signal when the first level signal is received;
the control circuit is respectively connected with the detection circuit and the clock circuit and used for outputting a first control signal for controlling the power switch according to the output signal of the level conversion circuit and outputting a second control signal for controlling the pull-down switch according to the clock signal output by the clock circuit;
the first driving circuit is connected with the control circuit and used for driving the power switch according to the first control signal; and
and the second driving circuit is connected with the control circuit and used for driving the pull-down switch according to the second control signal.
5. The bootstrap capacitor under-voltage protection circuit of claim 1, wherein the pull-down switch is turned on and off alternately for a first preset duration and for a second preset duration, wherein the first preset duration is less than the second preset duration.
6. The bootstrap capacitor under-voltage protection circuit of claim 5, wherein the first predetermined duration is 150 nanoseconds and the second predetermined duration is 50 microseconds.
7. The bootstrap capacitor under-voltage protection circuit of claim 1, wherein the drive circuit controls the power switch to be in an off state when the detection circuit detects that the bootstrap capacitor is in an under-voltage state.
8. The bootstrap capacitor under-voltage protection circuit of claim 1, wherein the driving circuit controls the power switch to be in a normal operation state when the detection circuit detects that the bootstrap capacitor is in a non-under-voltage state.
9. A control chip for a switching power supply, comprising the bootstrap capacitor under-voltage protection circuit of any one of claims 1 to 8.
10. A switching power supply comprising a power switch and an energy storage element, and further comprising the bootstrap capacitor under-voltage protection circuit of claim 9.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111669793.2A CN114421768A (en) | 2021-12-30 | 2021-12-30 | Bootstrap capacitor under-voltage protection circuit, control chip and switching power supply |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111669793.2A CN114421768A (en) | 2021-12-30 | 2021-12-30 | Bootstrap capacitor under-voltage protection circuit, control chip and switching power supply |
Publications (1)
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115684985A (en) * | 2023-01-05 | 2023-02-03 | 深圳市思远半导体有限公司 | Detection circuit and method for switching power supply, chip and electronic equipment |
| CN116707278A (en) * | 2023-08-08 | 2023-09-05 | 上海英联电子科技有限公司 | Bootstrap capacitor charging control circuit and DC-DC conversion circuit |
| CN117155126A (en) * | 2023-03-14 | 2023-12-01 | 荣耀终端有限公司 | Terminal device and control method |
| CN117410939A (en) * | 2023-12-15 | 2024-01-16 | 东莞市长工微电子有限公司 | Under-voltage processing method of bootstrap capacitor and related device |
-
2021
- 2021-12-30 CN CN202111669793.2A patent/CN114421768A/en active Pending
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115684985A (en) * | 2023-01-05 | 2023-02-03 | 深圳市思远半导体有限公司 | Detection circuit and method for switching power supply, chip and electronic equipment |
| CN117155126A (en) * | 2023-03-14 | 2023-12-01 | 荣耀终端有限公司 | Terminal device and control method |
| CN116707278A (en) * | 2023-08-08 | 2023-09-05 | 上海英联电子科技有限公司 | Bootstrap capacitor charging control circuit and DC-DC conversion circuit |
| CN116707278B (en) * | 2023-08-08 | 2023-10-20 | 上海英联电子科技有限公司 | Bootstrap capacitor charging control circuit and DC-DC conversion circuit |
| CN117410939A (en) * | 2023-12-15 | 2024-01-16 | 东莞市长工微电子有限公司 | Under-voltage processing method of bootstrap capacitor and related device |
| CN117410939B (en) * | 2023-12-15 | 2024-04-19 | 东莞市长工微电子有限公司 | Under-voltage processing method of bootstrap capacitor and related device |
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