CN113422505B - Voltage overshoot protection circuit, switching power supply chip and switching power supply system - Google Patents
Voltage overshoot protection circuit, switching power supply chip and switching power supply system Download PDFInfo
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- CN113422505B CN113422505B CN202110770075.8A CN202110770075A CN113422505B CN 113422505 B CN113422505 B CN 113422505B CN 202110770075 A CN202110770075 A CN 202110770075A CN 113422505 B CN113422505 B CN 113422505B
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Abstract
The invention provides a voltage overshoot protection circuit, a switching power supply chip and a switching power supply system, which are applied to the technical field of switching power supplies. The invention provides a voltage overshoot protection circuit for solving voltage overshoot of an output end voltage of a switching power supply chip. Specifically, the output end voltage of the switching power supply chip is collected through the voltage overshoot control module, and under the condition that the output end voltage is higher than a first voltage threshold value (output end voltage overshoot), the constant current discharge control module is started, so that redundant energy generated by the overshoot voltage is dissipated (discharged) in a thermal mode through a discharge loop in the constant current discharge control module, the output end voltage is reduced, voltage overshoot of the output end of the switching power supply chip is restrained, further, damage to a rear-stage unit is avoided, and the performance and the reliability of the switching power supply chip are improved.
Description
Technical Field
The invention relates to the technical field of switch circuits, in particular to a voltage overshoot protection circuit, a switch power supply chip and a switch power supply system.
Background
At present, in a DC-DC (direct current to direct current) power supply system, a load connected to an output end of a switching power supply chip sometimes has a switching application from a heavy load to a light load, such as a moment when WIFI signal transmission ends, a moment when a solenoid valve drive is stopped, and the like. In the process of switching the load from a heavy load to a light load, when the load at the output end of the switching power supply is the heavy load, a large amount of energy is stored in an inductor externally connected with the output end of the switching power supply chip, and the energy is finally stored in an output capacitor, so that the voltage of the output capacitor is increased (namely the voltage of the output end is increased), namely the voltage of the output end of the switching power supply chip is overshot. Moreover, the voltage overshoot of the output end of the switching power supply chip is a challenge to withstand the voltage of a rear-stage component, so that when the design is not correct, the overshoot voltage of the output end of the switching power supply chip easily causes the damage of a rear-stage unit.
Although, according to the principle of the switching power supply chip itself, in the switching process from the heavy load to the light load of the load connected with the switching power supply chip, the switching power supply chip can relieve the problem of voltage overshoot at the output end through internal adjustment. However, since the adjustment of the switching power supply chip requires a certain time, when the switching power supply chip detects that there is overshoot at the output terminal, the chip also needs several cycles to completely turn off the power transistor, so that in the internal adjustment process of the switching power supply chip, the power transistor controlling whether the switching power supply chip is turned off or not is always in the on-off state, and thus the voltage at the output terminal of the switching power supply chip further rises, and the overshoot increases.
Disclosure of Invention
The invention aims to provide a voltage overshoot protection circuit, a switching power supply chip and a switching power supply system, so that when the load of the switching power supply chip suddenly changes from a heavy load to a light load, the voltage overshoot at the output end of the switching power supply chip is inhibited, and the performance and the reliability of the switching power supply chip are improved.
In a first aspect, in order to solve the above technical problem, the present invention provides a voltage overshoot protection circuit, which is applied to output voltage overshoot control of a switching power supply chip, where the switching power supply chip has a switch control terminal SW for controlling whether an input voltage is output, a first output voltage feedback pin FB and a second output voltage feedback pin FB1 for feeding back a change of the output voltage, and a power tube for adjusting the output voltage.
The voltage overshoot protection circuit may include: and the power tube current acquisition module is connected with the output end of the power tube and used for detecting the output current of the power tube before the output voltage of the switching power supply chip is overshot and outputting a second voltage obtained by converting the output current into the voltage.
And the voltage overshoot control module is connected with the second output voltage feedback pin FB1 and the constant current discharge control module, and is used for controlling the constant current discharge control module to start a discharge working mode when the voltage of the second output voltage feedback pin FB1 is higher than a first voltage threshold value, and controlling the constant current discharge control module to stop the discharge working mode when the voltage of the second output voltage feedback pin FB1 is lower than a second voltage threshold value.
And the constant current discharge control module is connected with the power tube current acquisition module and the voltage overshoot control module and is used for starting a discharge working mode by taking the second voltage as a reference voltage and under the control of the voltage overshoot control module, and discharging redundant energy generated by the overshoot voltage when the output voltage of the switching power supply chip overshoots so as to reduce the output voltage.
Further, the power tube current collection module may include first to fourth resistors, a first operational amplifier, a second operational amplifier, and a first diode, where the first operational amplifier and the second operational amplifier may each include a non-inverting input terminal, an inverting input terminal, and an output terminal.
One end of the first resistor is connected with the source electrode of the power tube and the input voltage, the other end of the first resistor is connected with one end of the third resistor and the inverting input end of the first operational amplifier, the drain electrode of the power tube is connected with one end of the second resistor, the other end of the second resistor is connected with one end of the fourth resistor and the non-inverting input end of the first operational amplifier, and the other end of the fourth resistor is connected with a reference ground end; the other end of the third resistor is connected with the output end of the first operational amplifier and the non-inverting input end of the second operational amplifier, the output end of the second operational amplifier is connected with the anode of the first diode, and the cathode of the first diode is connected with the inverting input end of the second operational amplifier and serves as the output end of the power tube current collection module to be connected with the constant current discharge control module.
Further, the voltage overshoot control module may include an input terminal, an output terminal, eighth to eleventh resistors, a fourth operational amplifier, and a not gate, wherein the fourth operational amplifier includes a non-inverting input terminal, an inverting input terminal, and an output terminal.
One end of the eighth resistor is connected to the second output voltage feedback pin FB1 and serves as an input end of the voltage overshoot control module to acquire the output voltage of the switching power supply chip, the other end of the eighth resistor is connected to the ninth resistor and an inverting input end of the fourth operational amplifier, and the other end of the ninth resistor is connected to the reference ground; the non-inverting input end of the fourth operational amplifier is connected with one end of the tenth resistor and one end of the eleventh resistor, the other end of the tenth resistor is connected with a preset reference voltage, the other end of the eleventh resistor is connected with the output end of the fourth operational amplifier and the input end of the not gate, the output end of the not gate is used as the output end of the voltage overshoot control module and is connected with the constant current discharge control module, and therefore whether the discharge working mode is started or not is controlled by the constant current discharge control module according to a comparison result of the voltage of the second output voltage feedback pin FB1, obtained by dividing the acquired output voltage, and the first voltage threshold and/or the second voltage threshold.
Further, the constant current discharge control module may include fifth to seventh resistors, a capacitor, a first MOS transistor, a second MOS transistor, a third operational amplifier, and a sampling resistor, where the third operational amplifier includes a non-inverting input terminal, an inverting input terminal, and an output terminal.
One end of the fifth resistor is connected with the output end of the power tube current acquisition module, the other end of the fifth resistor is connected with the upper pole plate of the capacitor and the drain electrode of the first MOS tube, the source electrode of the first MOS tube is connected with one end of the sixth resistor and the non-inverting input end of the third operational amplifier, the grid electrode of the first MOS tube is connected with the output end of the voltage overshoot control module, the output end of the third operational amplifier is connected with the seventh resistor and the grid electrode of the second MOS tube, the drain electrode of the second MOS tube is connected with the output voltage of the switching power supply chip, and the source electrode of the second MOS tube is connected with the output voltage of the switching power supply chip
The inverting input end of the third operational amplifier and one end of the sampling resistor are connected, and the other end of the sampling resistor, the other end of the seventh resistor, the other end of the sixth resistor and the lower pole plate of the capacitor are all connected with the reference ground end.
Further, the first to fourth operational amplifiers may further include a power supply terminal and a ground terminal; the power supply end of the first operational amplifier is connected with the input voltage so that the first operational amplifier can obtain electric energy through the input voltage, and the power supply ends of the second to fourth operational amplifiers are connected to the power supply voltage inside the chip so that the second to fourth operational amplifiers can obtain electric energy through the power supply voltage inside the chip; the first to fourth operational amplifiers are connected to the reference ground terminal through the ground terminal.
In a second aspect, based on the voltage overshoot protection circuit, the invention further provides a switching power supply chip. Specifically, the switching power supply chip may include all other components included in the voltage overshoot protection circuit except the capacitor, the second MOS transistor, the sampling resistor, the eighth resistor, and the ninth resistor.
Furthermore, the capacitor, the second MOS transistor, the sampling resistor, the eighth resistor, and the ninth resistor included in the voltage overshoot protection circuit may be all disposed outside the switching power supply chip, so that a user may configure the components disposed outside the switching power supply chip by himself, thereby improving flexibility of the switching power supply chip.
Furthermore, a transconductance amplifier, a voltage stabilizing module, a sawtooth wave generating module, a pulse modulation signal generating module, a power tube driving module and a frequency compensating module can be further arranged inside the switching power supply chip.
The transconductance amplifier is used for carrying out error amplification on the difference between the reference voltage and the voltage of the output voltage feedback pin.
The voltage stabilizing module is used for providing working voltage for each functional module contained in the switching power supply chip.
The sawtooth wave generating module is used for forming sawtooth wave signals.
The pulse modulation signal generation module is used for comparing the sawtooth wave signal with the output signal of the transconductance amplifier to form a pulse modulation signal.
The power tube driving module is used for converting the pulse modulation signal into a power tube driving signal and driving the power tube through the power tube driving signal so as to enable the voltage of the output voltage feedback pin to be equal to the reference voltage.
The frequency compensation module is used for performing frequency compensation on the output signal of the transconductance amplifier so as to stabilize the output voltage of the switching power supply chip.
Further, the voltage regulation module may further include a reference voltage unit for providing a required reference voltage for each functional module included in the switching power supply chip.
In a third aspect, based on the switching power supply chip, the invention further provides a switching power supply system, which may specifically include: the switching power supply chip comprises the switching power supply chip, and an input filter capacitor, an inductor, a second diode, an upper divider resistor, a lower divider resistor, a feed-forward capacitor and an output filter capacitor which are arranged outside the switching power supply chip.
The positive electrode of the input filter capacitor is connected with the input voltage of the switching power supply chip, and the negative electrode of the input filter capacitor and the grounding end of the switching power supply chip are both connected with the reference grounding end.
The one end of inductance with switching power supply chip's on-off control end and the negative pole of second diode is connected, the other end with go up divider resistance's one end and feedforward capacitance's last polar plate is connected, go up divider resistance's the other end with lower divider resistance's one end, feedforward capacitance's bottom plate and first output voltage feedback pin FB is connected, just lower divider resistance's the other end and the positive pole of second diode all with the reference ground end is connected.
And the anode of the output filter capacitor is connected with the switch control end, and the cathode of the output filter capacitor is connected with the reference ground end.
Furthermore, the switching power supply chip is also provided with a filter capacitor access pin for externally connecting the capacitor, a second output end for externally connecting the second MOS tube and a third output end for externally connecting the sampling resistor.
The upper pole plate of the capacitor in the constant current discharge control module is connected with a filter capacitor access pin of the switching power supply chip, and the lower pole plate of the capacitor is connected with the reference ground end.
The grid of second MOS pipe with switching power supply chip's second output is connected, the source electrode of second MOS pipe with sampling resistor's one end all with switching power supply chip's third output is connected, the drain electrode of second MOS pipe with the inductance go up divider resistor's one end and output filter capacitor's positive pole is connected, sampling resistor's the other end with reference ground end is connected.
One end of the eighth resistor is connected to the anode of the output filter capacitor, one end of the upper divider resistor and the other end of the inductor, the other end of the eighth resistor is connected to one end of the ninth resistor and the second output voltage feedback pin FB1 of the switching power supply chip, and the other end of the ninth resistor is connected to the reference ground.
Compared with the prior art, the invention has the following beneficial effects:
the invention provides a voltage overshoot protection circuit for solving voltage overshoot of an output end voltage of a switching power supply chip. Specifically, the output end voltage of the switching power supply chip is collected through the voltage overshoot control module, and under the condition that the output end voltage is higher than a first voltage threshold value (output end voltage overshoot), the constant current discharge control module is started, so that redundant energy generated by the overshoot voltage is dissipated (discharged) in a thermal mode through a discharge loop in the constant current discharge control module, the output end voltage is reduced, the voltage overshoot of the output end of the switching power supply chip is restrained, further, the damage to a rear-stage unit is avoided, and the performance and the reliability of the switching power supply chip are improved.
In addition, as part of components in the voltage overshoot protection circuit provided by the invention can be arranged outside the switch power supply chip, a user can configure the components arranged outside the switch power supply chip according to actual requirements, and the design flexibility and stability of the switch power supply chip are further improved.
Drawings
Fig. 1 is a circuit diagram of a voltage overshoot protection circuit according to an embodiment of the present invention.
Fig. 2 is a circuit diagram of a switching power supply chip according to an embodiment of the invention.
Fig. 3 is a circuit diagram of a switching power supply system according to an embodiment of the invention.
Fig. 4a to 4d are graphs comparing waveforms of each key node of a switching power supply system using the voltage overshoot protection circuit of the present invention and an output voltage of a switching power supply system not using the voltage overshoot protection circuit of the present invention in an embodiment of the present invention.
Wherein, in the attached drawings,
10-a power tube current acquisition module; 20-constant current discharge control module;
30-a voltage overshoot control module; 40-a voltage stabilizing module;
50-a sawtooth wave generation module; 60-a pulse modulation signal generation module;
70-power tube driving module; 80-a frequency compensation module;
VIN-input voltage; v1 — first voltage;
v2 — output terminal voltage of second voltage/power tube current collection module 10;
m1-first MOS tube; m2-second MOS tube;
a-a power tube; OP 1-first operational amplifier;
OP 2-second operational amplifier; OP 3-first operational amplifier;
COMP 1-fourth operational amplifier; NOT 1-NOT gate;
VREF/VREF 1-reference voltage; GND-reference ground;
100-switching power supply chip; R1-R11-first to eleventh resistors;
VO-output voltage; VH-first voltage threshold/upper threshold voltage;
VL-second voltage threshold/lower threshold voltage; VDD-supply voltage inside the chip;
c1-capacitance; RCS-sampling resistance;
FB-first output Voltage feedback Pin; SW-switch control terminal;
a CT-filter capacitor is connected into a pin; MGATE-a second output;
MCS-third output; CIN/C2-input filter capacitance;
COUT-output filter capacitance; d1 — first diode;
d2 — second diode; l1-inductance;
OTA 1-transconductance amplifier; RT-upper divider resistance;
RB-lower divider resistance; CFF-feedforward capacitance;
FB1 — second output voltage feedback pin FB 1; RD-sampling resistance of the power tube A;
Detailed Description
To further clarify the objects, advantages and features of the present invention, a more particular description of the invention will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. It is to be noted that the drawings are in greatly simplified form and are not to scale, but are merely intended to facilitate and clarify the explanation of the embodiments of the present invention. Further, the structures illustrated in the drawings are often part of actual structures. In particular, the drawings may have different emphasis points and may sometimes be scaled differently.
As used in this application, the singular forms "a", "an" and "the" include plural referents, the term "or" is generally employed in a sense including "and/or," the terms "a" and "an" are generally employed in a sense including "at least one," the terms "at least two" are generally employed in a sense including "two or more," and the terms "first", "second" and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicit to the number of technical features indicated. Thus, features defined as "first", "second" and "third" may explicitly or implicitly include one or at least two of the features, "one end" and "the other end" and "proximal end" and "distal end" generally refer to the corresponding two parts, which include not only the end points, but also the terms "mounted", "connected" and "connected" should be understood broadly, e.g., as a fixed connection, as a detachable connection, or as an integral part; can be mechanically or electrically connected; either directly or indirectly through intervening media, either internally or in any other relationship. Furthermore, as used in the present invention, the disposition of an element with another element generally only means that there is a connection, coupling, fit or driving relationship between the two elements, and the connection, coupling, fit or driving relationship between the two elements may be direct or indirect through intermediate elements, and cannot be understood as indicating or implying any spatial positional relationship between the two elements, i.e., an element may be in any orientation inside, outside, above, below or to one side of another element, unless the content clearly indicates otherwise. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
As described in the background art, although the switching power supply chip can be internally adjusted to alleviate the overshoot of the output terminal voltage in the switching process from the heavy load to the light load of the connected load according to the principle of the switching power supply chip. However, since the adjustment of the switching power supply chip requires a certain time, when the switching power supply chip detects that there is overshoot at the output terminal, the chip also needs several cycles to completely turn off the power transistor, so that in the internal adjustment process of the switching power supply chip, the power transistor controlling whether the switching power supply chip is turned off or not is always in the on-off state, and thus the voltage at the output terminal of the switching power supply chip further rises, and the overshoot increases.
Therefore, in order to solve the above problems, a core idea of the present invention is to provide a voltage overshoot protection circuit, a switching power supply chip, and a switching power supply system, so as to suppress voltage overshoot at an output terminal of the switching power supply chip when a load of the switching power supply chip suddenly changes from a heavy load to a light load, thereby improving performance and reliability of the switching power supply chip.
The voltage overshoot protection circuit, the switching power supply chip and the switching power supply system of the present invention will be described in further detail below. The present invention will now be described in more detail with reference to the accompanying drawings, 1 through 4 a-4 d, wherein preferred embodiments of the invention are shown, it being understood that one skilled in the art could modify the invention herein described while still achieving the advantageous results of the invention. Accordingly, the following description should be construed as broadly as possible to those skilled in the art and not as limiting the invention.
Referring to fig. 1 in combination with fig. 2, fig. 1 is a circuit diagram of a voltage overshoot protection circuit according to an embodiment of the invention, and fig. 2 is a circuit diagram of a switching power supply chip including the voltage overshoot protection circuit shown in fig. 1. Specifically, the voltage overshoot protection circuit provided in the embodiment of the present invention can be specifically applied to the output voltage overshoot control of a switching power supply chip (as shown in fig. 2). The switching power supply chip is provided with an input end VIN connected with an input voltage, a switching control end SW used for controlling whether the input voltage is output or not, an output voltage feedback pin FB used for feeding back the output voltage change, a second output voltage feedback pin FB1 used for being equivalent to the voltage FB of the output voltage feedback pin, and a power tube A used for regulating the output voltage. Specifically, the voltage overshoot protection circuit provided by the present invention may include: a power tube current collection module 10, a constant current discharge control module 20 and a voltage overshoot control module 30, wherein,
the power tube current collection module 10 is connected to the output end of the power tube a, and is used for detecting the output current of the power tube a before the output voltage of the switching power supply chip overshoots
And outputting the output current
Converted into a second voltage V2.
In the voltage overshoot protection circuit shown in fig. 1, for convenience of understanding, the power transistor a may be equivalent to the corresponding sampling resistor RD (on-resistance of the power transistor a), and in other embodiments, the power transistor may be equivalent to a resistor connected in series with the power transistor.
Specifically, the power tube current collection module 10 may include first to fourth resistors R1-R4, a first operational amplifier OP1, a second operational amplifier OP2, and a first diode D1, wherein each of the first operational amplifier OP1 and the second operational amplifier OP2 may include a non-inverting input (+), an inverting input (-) and an output.
Wherein one end of the first resistor R1 is connected to the source of the power transistor a (or one end of the sampling resistor RD corresponding thereto) and the input voltage VIN, the other end is connected to one end of the third resistor R3 and the inverting input (-) of the first operational amplifier OP1, the drain of the power transistor a is connected to one end of the second resistor R2, the other end of the second resistor R2 is connected to one end of the fourth resistor R4 and the non-inverting input (+) of the first operational amplifier OP1, and the other end of the fourth resistor R4 is connected to the ground GND; the other end of the third resistor R3 is connected to the output end of the first operational amplifier OP1 and the non-inverting input end (+) of the second operational amplifier OP2, the output end of the second operational amplifier OP2 is connected to the anode of the first diode D1, the cathode of the first diode D1 is connected to the inverting input end (-) of the second operational amplifier OP2, and is used as the output end of the power tube current collection module 10 to connect to the constant current discharge control module 20.
In this embodiment, the power tube current collecting module 10 is specifically configured to detect the output current of the power tube a before the voltage of the output terminal of the switching power supply chip overshoots
To output the output current
The voltage corresponding to the peak current of the power tube a is used as the reference voltage of the leakage current of the constant current discharge control module 20, so that the leakage current of the constant current discharge control module 20 is at a reasonable value, and the leakage current is converted into the second voltage V2, so that the output current of the power tube a is obtained through the second operational amplifier OP2 provided by the power tube current collection module 10
To the constant current discharge control module 20. The first to fourth resistors R1 to R4 and the first operational amplifier OP1 form a differential amplifier, and since the input voltage of the inverting input (-) of the first operational amplifier OP1 is high, in order to ensure the normal operation of the first operational amplifier OP1, the power supply of the first operational amplifier OP1 needs to be connected to the input voltage VIN, and the ground terminal thereof needs to be connected to the ground reference GND.
For example, if the resistances of the first to fourth resistors R1 to R4 are all equal, that is, R1= R2= R3= R4, the output voltage V1 of the first operational amplifier OP1 may be represented by the following formula:
wherein the content of the first and second substances,
the current is the output current of the power tube A connected in the switching power supply chip, and RD is the sampling resistor corresponding to the power tube A.
In addition, the second operational amplifier OP2 and the first diode D1 form a voltage follower, and the fifth resistor R5 and the capacitor C1 in the constant current discharge control module 20 form a filter. Therefore, no matter whether the constant current discharge control module 20 is in the discharge operation mode or in the off-discharge operation mode, the capacitor C1 having the function of storing energy cannot be discharged through the second operational amplifier OP2 due to the presence of the first diode D1, so that the voltage of the second voltage V2 is the peak voltage of the first voltage V1; when the constant current discharge control module 20 is ignored, the voltage value of the second voltage V2 of the output end voltage of the power tube current collection module 10 is equal to the voltage value of the first voltage V1 (voltage following characteristic), i.e., V2= V1, so that the output current of the power tube a is adjusted to be equal to the output current of the power tube a (voltage following characteristic)
To the constant current discharge control module 20.
It can be understood that, since the power transistor generally operates at a certain duty cycle when operating, the output current of the power transistor a
Generally, the first voltage V1 and the second voltage V2 are pulse signals. Moreover, since the output end of the power tube current collection module 10 in the embodiment of the present invention is connected to the first diode D1, when the constant current discharge control module 20 is in the discharge operation mode, it collects the current of the power tube aThe maximum current.
Further, the constant current discharge control module 20 is connected to the power tube current collection module 10 and the voltage overshoot control module 30, and configured to start a discharge operation mode with the second voltage V2 as a reference voltage and under the control of the voltage overshoot control module 30, and discharge excess energy generated by an overshoot voltage when the output voltage of the switching power supply chip overshoots, so as to reduce the output voltage VO.
Specifically, the constant current discharge control module 20 may include fifth to seventh resistors R5 to R7, a capacitor C1, a first MOS transistor M1, a second MOS transistor M2, a third operational amplifier OP3, and a sampling resistor RCS, wherein the third operational amplifier OP3 may include a non-inverting input (+), an inverting input (-) and an output.
One end of the fifth resistor R5 is connected to the output terminal of the power tube current collection module 10, the other end is connected to the upper plate of the capacitor C1 and the drain of the first MOS transistor M1, the source of the first MOS transistor M1 is connected to one end of the sixth resistor R6 and the non-inverting input terminal (+) of the third operational amplifier OP3, the gate of the first MOS transistor M1 is connected to the output terminal of the voltage overshoot control module 30, the output terminal of the third operational amplifier OP3 is connected to the seventh resistor R7 and the gate of the second MOS transistor M2, the drain of the second MOS transistor M2 is connected to the input terminal of the voltage overshoot control module 30 (or understood as being connected to the output voltage of the switching power chip), and the source of the second MOS transistor M2 is connected to the inverting input terminal (-) of the third operational amplifier 3 and one end of the sampling resistor RCS, the other end of the sampling resistor RCS, the other end of the seventh resistor R7, the other end of the sixth resistor R6 and the lower plate of the capacitor C1 are all connected with the reference ground terminal GND.
In this embodiment, the fifth resistor R5 and the capacitor C1 in the constant current discharge control module 10 form a filter circuit, so when M1 is turned off, since the first diode D1 is connected in series to the output terminal of the second operational amplifier OP2 in the power tube current collection module 10, the capacitor C1 can only be charged through the resistor R5, and there is no discharge loop. Thus, although the voltage V2 is a pulse signal, the voltage V3 will slightly rush to the maximum value of the voltage V2. In addition, since the capacitor C1 has no discharge loop, even if the voltage V2 drops to 0V, the voltage across the capacitor C1 can be maintained for a long time. The second MOS transistor M2 and the sampling resistor RCS form a bleeder circuit, so that the voltage V7 at the output end of the voltage overshoot control module 30 controls the first MOS transistor M1 to turn on and off, and the voltage M1 controls the MOS transistor M2 to turn on and off, so that when the voltage V7 is a high voltage, the voltage M1 is controlled to turn on, and since the resistance of the sixth resistor R6 is set to be very large, it can be considered that the voltage V4 at the non-inverting input end (+) of the third operational amplifier OP3 is the same as the voltage V3 at the two ends of the capacitor C1, and therefore when the output voltage of the switching power supply chip overshoots, redundant energy generated by the overshoot voltage is dissipated at the M2 in a thermal manner, thereby achieving the purpose of reducing the output end voltage VO.
Specifically, when the voltage overshoot control module 30 detects that the voltage of V8 is greater than VH, it indicates that the voltage VO at the output terminal overshoots, and since the voltage of V8 is greater than VH, V7 outputs high level, the high level of V7 controls the conduction of the first MOS transistor M1 and the conduction of M1 of the constant current discharge control module 20, and controls the conduction of M2, that is, the constant current discharge control module 20 operates in the discharge operation mode (the output voltage VO is discharged through the second MOS transistor M2 in the constant current discharge control module 20 to decrease to a normal value); when the voltage overshoot control module 30 detects that the voltage of V8 is less than VL, it indicates that the voltage VO at the output terminal is normal, and since the voltage of V8 is less than VL, V7 outputs low level, the low level of V7 controls the first MOS transistor M1 of the constant current discharge control module 20 to turn off, M1 to turn off, and M2 to turn off, that is, M2 of the constant current discharge control module 20 does not discharge any more.
And when the voltage of V8 is less than VL, V7 outputs low level, and V7 controls the first MOS transistor M1 of the constant current discharge control module 20 to turn off, the sixth resistor R6 connects the non-inverting input terminal (+) of the third operational amplifier OP3 to ground, so as to prevent the non-inverting input terminal (+) of the third operational amplifier OP3 from floating and causing an abnormality. When M1 is turned on, the voltage V3 of the capacitor C1 will gradually decrease due to the presence of the sixth resistor R6, but actually we only need to keep the voltage V3 of the capacitor C1 for a short time when M1 is turned on, so the requirement for the capacity of the capacitor C1 is not very high.
Further, since in the constant current discharge control module 20, the third operational amplifier OP3, the second MOS transistor M2, the sampling resistor RCS and the sixth resistor R6 form a linear constant current discharge loop, the current flowing through the M2 can be expressed as:
from the above formula, if the resistance value of the sampling resistor RCS is set to be equal to the resistance value of the equivalent resistor RD of the power tube a, when M1 is turned off, the voltage of V4 is 0V, and the current flowing through M2 is 0V
Is 0A; when M1 is turned on, a current flows through M2
About the output current of the power tube at the previous moment
Peak value of (a). Therefore, the invention can consume the redundant electric energy generated by the overshoot of the output voltage VO on the second MOS transistor M2 through this part of circuit, thereby ensuring that the output capacitance in the switching power supply system is not overshot basically, or the overshoot degree is within an acceptable range, further ensuring the stability of the subsequent stage operation, and, by externally arranging M2, it can set a proper heat dissipation condition through reasonable calculation, ensure the stability of the system operation, and specifically how to externally arrange M2, the invention will be explained in detail in the corresponding part of the switching power supply system shown in fig. 3 as follows.
Since the second MOS transistor M2 needs to be externally connected, the resistor R7 is used to prevent the second MOS transistor M2 from being damaged due to excessive charge accumulation between the gate and the source GS thereof.
Further, the voltage overshoot control module 30 is connected to the second output voltage feedback pin FB1 and the constant current discharge control module 20, and is configured to control the constant current discharge control module 20 to turn on the discharge operation mode when the voltage of the second output voltage feedback pin FB1 is higher than a first voltage threshold VH, and control the constant current discharge control module 20 to turn off the discharge operation mode when the voltage of the second output voltage feedback pin FB1 is lower than a second voltage threshold VL.
Specifically, the voltage overshoot control module 30 may include an input terminal, an output terminal, an eighth R8 to an eleventh resistor R11, a fourth operational amplifier COMP1, and a NOT gate NOT1, wherein the fourth operational amplifier COMP1 includes a non-inverting input terminal (+), an inverting input terminal (-) and an output terminal.
One end of the eighth resistor R8 is connected to the second output voltage feedback pin FB1 and serves as an input end of the voltage overshoot control module 30 to acquire the output voltage VO of the switching power supply chip, the other end of the eighth resistor R8 is connected to the ninth resistor R9 and an inverting input end (-) of the fourth operational amplifier COMP1, and the other end of the ninth resistor R9 is connected to the ground reference terminal GND; a non-inverting input terminal (+) of the fourth operational amplifier COMP1 is connected to one end of the tenth resistor R10 and one end of the eleventh resistor R11, the other end of the tenth resistor R10 is connected to a preset reference voltage VREF1, the other end of the eleventh resistor R11 is connected to an output terminal of the fourth operational amplifier COMP1 and an input terminal of the NOT gate NOT1, an output terminal of the NOT gate NOT1 is used as an output terminal of the voltage overshoot control module 30, and is connected to the constant current discharge control module 20, so as to control whether the constant current discharge control module 20 starts a discharge operation mode according to a comparison result between the voltage of the second output voltage feedback pin FB1 obtained by dividing the collected output voltage VO and the first voltage threshold and/or the second voltage threshold VL.
The fourth operational amplifier COMP1 further includes a power supply end and a ground end, the power supply end of the fourth operational amplifier COMP1 is connected to a power supply voltage VDD inside the chip, so that the fourth operational amplifier COMP1 obtains electric energy through the power supply voltage VDD inside the chip, and the fourth operational amplifier COMP1 is connected to the ground reference end GND through the ground end.
In the embodiment of the present invention, the eighth resistor R8 and the ninth resistor R9 divide voltage through resistors, and acquire the output voltage VO of the switching power supply chip, so as to obtain a divided voltage V8, specifically, the V8 may be represented by the following formula:
where VO is the output voltage of the switching power supply system, and R8 and R9 are the resistances of the resistors. As can be seen from the above formula, it can be known whether the output voltage VO of the switching power supply system overshoots by detecting the voltage value of the voltage V8, that is, if V8 is too high, it indicates that VO is too high.
As can be seen from fig. 1, the tenth resistor R10, the eleventh resistor R11, the fourth operational amplifier COMP1, and the NOT gate NOT1 constitute a hysteretic comparator, wherein the fourth operational amplifier COMP1 is a comparator capable of outputting from a rail to a rail, so that the highest output voltage is VDD, and the lowest output voltage is 0V, and the upper threshold voltage VH (first voltage threshold) and the lower threshold voltage VL (second voltage threshold) of the hysteretic comparator can be respectively expressed as:
when the voltage V8 is greater than the upper threshold voltage VH (first voltage threshold) of the hysteresis comparator, it indicates that the output voltage VO is too high, and at this time, the output terminal voltage V7 of the NOT gate 1 outputs a high level; when the voltage V8 is smaller than the lower threshold voltage VL (the second voltage threshold) of the hysteretic comparator, which indicates that the output voltage VO is normal, the output terminal voltage V7 of the NOT gate NOT1 outputs a low level; when the voltage V8 is between VL and VH, the voltage V7 at the output terminal of the NOT gate NOT1 remains unchanged from the previous operation state. The reason why the hysteresis comparator is used here is to prevent the control circuit of the M2 from oscillating when the second MOS transistor M2 discharges, which affects the performance of the circuit.
In the voltage overshoot protection circuit for solving the voltage overshoot of the output end voltage of the switching power supply chip, the voltage overshoot control module is used for collecting the output end voltage of the switching power supply chip, and the constant current discharge control module is started under the condition that the output end voltage is higher than a first voltage threshold value (output end voltage overshoot), so that redundant energy generated by the overshoot voltage is dissipated (discharged) in a thermal mode through a discharge loop in the constant current discharge control module, the output end voltage is reduced, the voltage overshoot of the output end of the switching power supply chip is inhibited, further the damage to a rear-stage unit is avoided, and the performance and the reliability of the switching power supply chip are improved.
With continuing reference to fig. 2 and with reference to fig. 3, based on the same inventive concept, the invention further provides a switching power supply chip 100, which includes all other components included in the voltage overshoot protection circuit (as shown in fig. 1) except for the capacitor C1, the second MOS transistor M2, the sampling resistor RCS, the eighth resistor R8, and the ninth resistor R9.
In addition, the capacitor C1, the second MOS transistor M2, the sampling resistor RCS, the eighth resistor R8, and the ninth resistor R9 included in the voltage overshoot protection circuit are all disposed outside the switching power chip 100, so that a user can configure the components disposed outside the switching power chip 100 by himself, thereby improving the flexibility of the switching power chip.
In this embodiment, in order to improve the flexibility and stability of the switching power supply chip 100, and based on the situation that some components need to be manually operated, the inventor of the present invention proposes that some components in the voltage overshoot protection circuit designed by the inventor are disposed outside the switching power supply chip by adding an external pin of the switching power supply chip 100, and specifically, the invention provides that the capacitor C1, the second MOS transistor M2, the sampling resistor RCS, the eighth resistor R8, and the ninth resistor R9 are disposed outside the switching power supply chip 100. Therefore, the switching power supply chip 100 may further have a filter capacitor access pin CT for externally connecting the capacitor C1, a second output terminal MGATE for externally connecting the second MOS transistor M2, and a third output terminal MCS for externally connecting the sampling resistor RCS.
Since the second MOS transistor M2 needs to be externally connected, the resistor R7 is used to prevent the MOS transistor M2 from being damaged due to excessive charge accumulation between the gate and the source GS.
Further, as shown in fig. 2, the switching power supply chip 100 may further include a transconductance amplifier OTA1, a voltage regulator module 40, a sawtooth wave generating module 50, a pulse modulation signal generating module 60, a power tube driving module 70, and a frequency compensation module 80.
The transconductance amplifier OTA1 is used for performing error amplification on the difference between the reference voltage and the voltage of the output voltage feedback pin FB.
The voltage stabilizing module 40 is configured to provide a working voltage for each functional module included in the switching power supply chip.
The sawtooth wave generation module 50 is used for forming a sawtooth wave signal.
The pulse modulation signal generation module 60 is configured to compare the sawtooth signal with the output signal of the transconductance amplifier OTA1 to form a pulse modulation signal.
The power tube driving module 70 is configured to convert the pulse modulation signal into a power tube driving signal, and drive the power tube a by the power tube driving signal, so that the voltage of the output voltage feedback pin FB is equal to the reference voltage VREF.
The frequency compensation module 80 is configured to perform frequency compensation on the output signal of the transconductance amplifier to stabilize the output voltage of the switching power supply chip, so as to obtain a purpose of stabilizing the output voltage.
Further, the voltage stabilizing module 40 further includes a reference voltage unit (not shown) for providing a required reference voltage for each functional module included in the switching power supply chip.
Because part of the components in the voltage overshoot protection circuit provided by the invention can be arranged outside the switching power supply chip 100, a user can configure the components arranged outside the switching power supply chip according to actual requirements, and the design flexibility and stability of the switching power supply chip 100 are further improved.
In addition, referring to fig. 3, based on the same inventive concept, the present invention further provides a switching power supply system, and fig. 3 is a circuit schematic diagram of the switching power supply system provided in an embodiment of the present invention. As shown in fig. 3, the switching power supply system provided by the present invention may include: the switching power supply chip 100 shown in fig. 2, and an input filter capacitor CIN, an inductor L1, a second diode D2, an upper voltage-dividing resistor RT, a lower voltage-dividing resistor RB, a feed-forward capacitor CFF, and an output filter capacitor COUT disposed outside the switching power supply chip 100.
The positive electrode of the input filter capacitor CIN is connected to the input voltage VIN of the switching power supply chip 100, and the negative electrode of the input filter capacitor CIN and the ground terminal GND of the switching power supply chip 100 are both connected to the ground reference terminal GND.
Inductor L1's one end with switching power supply chip 100's on-off control end SW and second diode D2's negative pole is connected, the other end with go up divider resistance RT's one end the last polar plate of feedforward electric capacity CFF is connected, go up divider resistance RT's the other end with the one end of divider resistance RB down the lower polar plate of feedforward electric capacity CFF and first output voltage feedback pin FB is connected, just the other end of divider resistance RB down and second diode D2's positive pole all with reference ground end GND connects.
The positive electrode of the output filter capacitor COUT is connected with the switch control end SW, and the negative electrode of the output filter capacitor COUT is connected with the reference ground end GND.
In addition, the connection between the partial components arranged outside the switching power supply chip 100 in the voltage overshoot protection circuit provided by the present invention and the switching power supply chip 100 may specifically be: an upper electrode plate of the capacitor C1 in the constant current discharge control module 10 is connected to a filter capacitor access pin CT of the switching power supply chip 100, and a lower electrode plate of the capacitor C1 is connected to the reference ground GND.
The gate of the second MOS transistor M2 is connected to the second output terminal MGATE of the switching power supply chip 100, the source of the second MOS transistor M2 and one end of the sampling resistor RCS are both connected to the third output terminal MCS of the switching power supply chip 100, the drain of the second MOS transistor M2 is connected to the inductor L1, one end of the equivalent resistor RT of the potentiometer and the anode of the output filter capacitor COUT, and the other end of the sampling resistor RCS is connected to the ground reference terminal GND.
One end of the eighth resistor R8 is connected to the anode of the output filter capacitor COUT, one end of the equivalent resistor RT of the potentiometer and the other end of the inductor L1, the other end of the eighth resistor R8 is connected to one end of the ninth resistor R9 and the second output voltage feedback pin FB1 of the switching power supply chip 100, and the other end of the ninth resistor R9 is connected to the ground reference terminal GND.
In the embodiment, RT/RB = R8/R9 of the potentiometer should be satisfied in practical use, so that it can be ensured that the FB voltage is consistent with the FB1 voltage during normal operation (the reason why the FB voltage is not combined with the FB1 voltage is that a voltage dividing resistor often adds a feedforward capacitor CFF to the FB voltage, and the FB voltage is different from the FB1 voltage during drastic change of the output voltage VO).
In the switching power supply system provided by the present invention, the input filter capacitor CIN and the output filter capacitor COUT may be one capacitor device or a plurality of capacitor devices connected in parallel. Illustratively, as shown in fig. 3, the capacitor C2 is also an input filter capacitor.
Referring to fig. 4a to 4d, fig. 4a to 4d are graphs comparing waveforms of each key node of a switching power supply system using the voltage overshoot protection circuit of the present invention and an output voltage of a switching power supply system not using the voltage overshoot protection circuit of the present invention according to an embodiment of the present invention. Fig. 4a, 4b and 4c are waveform diagrams of each key node when the output load fluctuation of the switching power supply system using the voltage overshoot protection circuit of the present invention is large, and fig. 4d is a waveform diagram of the output voltage of the switching power supply system not using the voltage overshoot protection circuit of the present invention.
As can be seen from fig. 4a, the output voltage VO of the switching power supply system using the voltage overshoot protection circuit of the present invention does not overshoot by more than 5.5V, and such overshoot is very safe for the subsequent system. As can be seen from fig. 4b, the maximum value of the output end current IO of the switching power supply system using the voltage overshoot protection circuit of the present invention is about 3A, and the minimum value is about 0A, and it can be seen from fig. 4b that, in the process from 3A to 0A, the falling speed of the output end current IO is very fast, and generally speaking, the faster the speed, the greater the test on the power supply. Fig. 4c is a waveform diagram of the current flowing through the MOS transistor M2, and it can be seen from fig. 4c that, when the system load current changes from heavy to light, the MOS transistor M2 rapidly flows a large current to provide a release loop for the extra energy, thereby reducing the overshoot problem of the output voltage. As can be seen from fig. 4d, in the case of sudden change of the system load (under the same load condition), the voltage VO at the output terminal of the system has a very significant overshoot, and the overshoot voltage is close to 7V, which is very challenging for the following load. Obviously, when the switching power supply system adopting the voltage overshoot protection circuit of the invention suddenly changes from heavy load to light load, the overshoot of the voltage at the output end of the switching power supply system is well inhibited.
In summary, the present invention provides a voltage overshoot protection circuit for solving voltage overshoot at the output terminal of a switching power supply chip. Specifically, the output end voltage of the switching power supply chip is collected through the voltage overshoot control module, and under the condition that the output end voltage is higher than a first voltage threshold value (output end voltage overshoot), the constant current discharge control module is started, so that redundant energy generated by the overshoot voltage is dissipated (discharged) in a thermal mode through a discharge loop in the constant current discharge control module, the output end voltage is reduced, the voltage overshoot of the output end of the switching power supply chip is restrained, further, the damage to a rear-stage unit is avoided, and the performance and the reliability of the switching power supply chip are improved.
In addition, as part of components in the voltage overshoot protection circuit provided by the invention can be arranged outside the switch power supply chip, a user can configure the components arranged outside the switch power supply chip according to actual requirements, and the design flexibility and stability of the switch power supply chip are further improved.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example" or "a specific example" or the like are intended to mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. And the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments. Furthermore, various embodiments or examples described in this specification can be combined and combined by those skilled in the art.
The above description is only a preferred embodiment of the present invention, and does not limit the present invention in any way. It will be understood by those skilled in the art that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (9)
1. A voltage overshoot protection circuit applied to output voltage overshoot control of a switching power supply chip, the switching power supply chip having a switch control terminal SW for controlling whether an input voltage is output, a first output voltage feedback pin FB and a second output voltage feedback pin FB1 for feeding back a change of the output voltage, and a power tube for regulating the output voltage, the voltage overshoot protection circuit comprising:
the power tube current acquisition module is connected with the output end of the power tube and used for detecting the output current of the power tube before the output voltage of the switching power supply chip is overshot and outputting a second voltage after the output current is converted into the voltage;
the voltage overshoot control module is connected with the second output voltage feedback pin FB1 and the constant current discharge control module, and is used for controlling the constant current discharge control module to start a discharge working mode when the voltage of the second output voltage feedback pin FB1 is higher than a first voltage threshold value, and controlling the constant current discharge control module to stop the discharge working mode when the voltage of the second output voltage feedback pin FB1 is lower than a second voltage threshold value, wherein the first voltage threshold value is larger than a second voltage threshold value;
and the constant current discharge control module is connected with the power tube current acquisition module and the voltage overshoot control module and is used for starting a discharge working mode by taking the second voltage as a reference voltage and under the control of the voltage overshoot control module, and discharging redundant energy generated by the overshoot voltage when the output voltage of the switching power supply chip overshoots so as to reduce the output voltage.
2. The voltage overshoot protection circuit of claim 1, wherein the power transistor current collection module comprises a first resistor, a second resistor, a third resistor, a fourth resistor, a first operational amplifier, a second operational amplifier, and a first diode, wherein the first operational amplifier and the second operational amplifier each comprise a non-inverting input terminal, an inverting input terminal, and an output terminal;
one end of the first resistor is connected with the source electrode of the power tube and the input voltage, the other end of the first resistor is connected with one end of the third resistor and the inverting input end of the first operational amplifier, the drain electrode of the power tube is connected with one end of the second resistor, the other end of the second resistor is connected with one end of the fourth resistor and the non-inverting input end of the first operational amplifier, and the other end of the fourth resistor is connected with a reference ground end; the other end of the third resistor is connected with the output end of the first operational amplifier and the non-inverting input end of the second operational amplifier, the output end of the second operational amplifier is connected with the anode of the first diode, and the cathode of the first diode is connected with the inverting input end of the second operational amplifier and serves as the output end of the power tube current collection module to be connected with the constant current discharge control module.
3. The voltage overshoot protection circuit of claim 2, wherein the voltage overshoot control module comprises an input, an output, an eighth resistor, a ninth resistor, a tenth resistor, an eleventh resistor, a fourth operational amplifier, and a not gate, wherein the fourth operational amplifier comprises a non-inverting input, an inverting input, and an output;
one end of the eighth resistor is connected with the output voltage of the switching power supply chip and serves as the input end of the voltage overshoot control module to collect the output voltage of the switching power supply chip, the other end of the eighth resistor is connected with the ninth resistor and the inverted input end of the fourth operational amplifier, and the other end of the ninth resistor is connected with the reference ground end; the non-inverting input end of the fourth operational amplifier is connected with one end of the tenth resistor and one end of the eleventh resistor, the other end of the tenth resistor is connected with a preset reference voltage, the other end of the eleventh resistor is connected with the output end of the fourth operational amplifier and the input end of the not gate, the output end of the not gate is used as the output end of the voltage overshoot control module and is connected with the constant current discharge control module, and therefore whether the discharge working mode is started or not is controlled by the constant current discharge control module according to a comparison result of the voltage of the second output voltage feedback pin FB1, obtained by dividing the acquired output voltage, and the first voltage threshold and/or the second voltage threshold.
4. The voltage overshoot protection circuit according to claim 3, wherein the constant current discharge control module comprises a fifth resistor, a sixth resistor, a seventh resistor, a capacitor, a first MOS transistor, a second MOS transistor, a third operational amplifier and a sampling resistor, wherein the third operational amplifier comprises a non-inverting input terminal, an inverting input terminal and an output terminal;
one end of the fifth resistor is connected with the output end of the power tube current acquisition module, the other end of the fifth resistor is connected with the upper polar plate of the capacitor and the drain electrode of the first MOS tube, the source electrode of the first MOS tube is connected with one end of the sixth resistor and the non-inverting input end of the third operational amplifier, the grid electrode of the first MOS tube is connected with the output end of the voltage overshoot control module, the output end of the third operational amplifier is connected with one end of the seventh resistor and the grid electrode of the second MOS tube, the drain electrode of the second MOS tube is connected with the output voltage of the switching power supply chip, and the source electrode of the second MOS tube is connected with the inverting input end of the third operational amplifier and one end of the sampling resistor, the other end of the sampling resistor, the other end of the seventh resistor, the other end of the sixth resistor and the lower pole plate of the capacitor are all connected with the reference ground end.
5. The voltage overshoot protection circuit of claim 4, wherein the second stage
The operational amplifier, the second operational amplifier, the third operational amplifier and the fourth operational amplifier respectively comprise a power supply end and a grounding end; the power supply end of the first operational amplifier is connected with the input voltage so that the first operational amplifier can obtain electric energy through the input voltage, and the power supply ends of the second operational amplifier, the third operational amplifier and the fourth operational amplifier are all connected into the power supply voltage inside a chip so that the second operational amplifier, the third operational amplifier and the fourth operational amplifier can obtain electric energy through the power supply voltage inside the chip; the first operational amplifier, the second operational amplifier, the third operational amplifier and the fourth operational amplifier are connected with the reference ground end through the grounding end.
6. A switching power supply chip comprising the voltage overshoot protection circuit according to any one of claims 1 to 5, wherein the capacitor, the second MOS transistor, the sampling resistor, the eighth resistor, and the ninth resistor included in the voltage overshoot protection circuit are all disposed outside the switching power supply chip, so that a user can configure the components disposed outside the switching power supply chip by himself/herself, thereby improving the flexibility of the switching power supply chip.
7. The switching power supply chip according to claim 6, wherein a transconductance amplifier, a voltage regulator module, a sawtooth wave generating module, a pulse modulation signal generating module, a power tube driving module and a frequency compensation module are further disposed inside the switching power supply chip,
the transconductance amplifier is used for carrying out error amplification on the difference between the reference voltage and the voltage of the output voltage feedback pin FB;
the voltage stabilizing module is used for providing working voltage for each functional module contained in the switching power supply chip; the sawtooth wave generating module is used for forming a sawtooth wave signal;
the pulse modulation signal generation module is used for comparing the sawtooth wave signal with an output signal of the transconductance amplifier to form a pulse modulation signal;
the power tube driving module is used for converting the pulse modulation signal into a power tube driving signal and driving the power tube through the power tube driving signal so as to enable the voltage of the output voltage feedback pin FB to be equal to the reference voltage;
the frequency compensation module is used for performing frequency compensation on the output signal of the transconductance amplifier so as to stabilize the output voltage of the switching power supply chip.
8. A switching power supply system, comprising: the switching power supply chip according to any one of claims 6 to 7, and an input filter capacitor, an inductor, a second diode, an upper voltage-dividing resistor, a lower voltage-dividing resistor, a feed-forward capacitor, and an output filter capacitor, which are provided outside the switching power supply chip,
the anode of the input filter capacitor is connected with the input voltage of the switch power supply chip, and the cathode of the input filter capacitor and the grounding end of the switch power supply chip are both connected with the reference ground end;
one end of the inductor is connected with a switch control end of the switch power supply chip and a cathode of the second diode, the other end of the inductor is connected with one end of the upper divider resistor and an upper polar plate of the feedforward capacitor, the other end of the upper divider resistor is connected with one end of the lower divider resistor, a lower polar plate of the feedforward capacitor and the first output voltage feedback pin FB, and the other end of the lower divider resistor and an anode of the second diode are both connected with the reference ground end;
and the anode of the output filter capacitor is connected with the switch control end, and the cathode of the output filter capacitor is connected with the reference ground end.
9. The switching power supply system according to claim 8, wherein the switching power supply chip further has a filter capacitor access pin for externally connecting the capacitor, a second output terminal for externally connecting the second MOS transistor, and a third output terminal for externally connecting the sampling resistor, wherein,
the upper polar plate of the capacitor in the constant current discharge control module is connected with a filter capacitor access pin of the switching power supply chip, and the lower polar plate of the capacitor is connected with the reference ground end;
the grid electrode of the second MOS tube is connected with the second output end of the switching power supply chip, the source electrode of the second MOS tube and one end of the sampling resistor are both connected with the third output end of the switching power supply chip, the drain electrode of the second MOS tube is connected with the inductor, one end of the upper divider resistor and the anode of the output filter capacitor, and the other end of the sampling resistor is connected with the reference ground end;
one end of the eighth resistor is connected to the anode of the output filter capacitor, one end of the upper divider resistor and the other end of the inductor, the other end of the eighth resistor is connected to one end of the ninth resistor and the second output voltage feedback pin FB1 of the switching power supply chip, and the other end of the ninth resistor is connected to the reference ground.
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| CN114860017B (en) * | 2022-04-15 | 2023-09-26 | 芯海科技（深圳）股份有限公司 | LDO circuit, control method, chip and electronic equipment |
| CN115623466B (en) * | 2022-12-19 | 2023-02-28 | 北京紫光青藤微系统有限公司 | Method and device for controlling power tube, electronic equipment and storage medium |
| CN115955085B (en) * | 2023-03-10 | 2023-06-02 | 晶艺半导体有限公司 | Driving circuit, driving method thereof, control circuit and power supply chip |
| CN117255445B (en) * | 2023-11-16 | 2024-02-09 | 佛山联创华联电子有限公司 | LED drive control circuit |
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