CN112104203A - Switch current-limiting circuit and power chip - Google Patents

Switch current-limiting circuit and power chip Download PDF

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Publication number
CN112104203A
CN112104203A CN202011264504.6A CN202011264504A CN112104203A CN 112104203 A CN112104203 A CN 112104203A CN 202011264504 A CN202011264504 A CN 202011264504A CN 112104203 A CN112104203 A CN 112104203A
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output voltage
voltage
current
power supply
output
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CN112104203B (en
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李瑞平
许锦龙
刘彬
池伟
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Shanghai Xinlong Semiconductor Technology Co ltd Nanjing Branch
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Shanghai Xinlong Semiconductor Technology Co ltd Nanjing Branch
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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
    • 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
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0003—Details of control, feedback or regulation circuits
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0003—Details of control, feedback or regulation circuits
    • H02M1/0009—Devices or circuits for detecting current in a converter
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0003—Details of control, feedback or regulation circuits
    • H02M1/0038—Circuits or arrangements for suppressing, e.g. by masking incorrect turn-on or turn-off signals, e.g. due to current spikes in current mode control

Abstract

The invention provides a switch current-limiting circuit and a power chip, wherein the switch current-limiting circuit comprises: the device comprises a switch current detection module, an amplification module, a first comparison module, a charge and discharge module, a reset module and a second comparison module. When the power tube of the power chip is opened, the switch current-limiting circuit provided by the invention controls the turn-off of the power tube of the power chip by comparing the charging and discharging time of the first capacitor, thereby limiting the maximum output current. The invention can be used for generating the preset current for limiting the maximum output current of the power supply system by detecting the switch current of the on-resistance of the switch current-limiting circuit, wherein the preset current is not influenced by parameters such as inductance, input capacitance, output voltage and the like.

Description

Switch current-limiting circuit and power chip
Technical Field
The invention relates to the technical field of power supply chips, in particular to a switch current-limiting circuit and a power supply chip.
Background
Common control methods for BUCK conversion circuits (BUCK circuits) are Pulse Frequency Modulation (PFM) and Pulse Width Modulation (PWM). Which can be divided into a Continuous Conduction Mode (CCM), a critical conduction mode (BCM) and a Discontinuous Conduction Mode (DCM) according to the current state of the inductor during one switching period. In one working period of the power supply system, if the current in the inductor of the power supply system is always greater than zero, the power supply system operates in the CCM mode. In one working period, if the current on the inductor is zero before the power tube of the power supply chip is turned on, the power supply chip works in the BCM mode. In one working period, before the power tube of the power chip is conducted, the current on the inductor is already zero, and then the power chip works in a DCM mode.
In a conventional power supply system, the output current value of the power supply system is limited only by limiting the maximum switching current of a power tube, and when a power supply chip works according to a maximum current limit point, the output current of the corresponding power supply system is related to the voltage difference between input and output and inductance parameters; that is, when the input and output conditions change or the inductance changes, the maximum current output by the power supply system also changes, so that the problem that the function of accurately limiting the output current of the power supply system cannot be realized occurs. In addition, in the prior art, the current of the maximum power tube is generally limited, so that the power tube can be ensured to work relatively safely, but the maximum output current cannot be set accurately, and the maximum output current is greatly influenced by the inductor and the input and output voltages, so that the consistency of the product is poor in the final testing processes of short circuit, current limiting and the like. Once a constant current is output, an external setting is required, which increases the complexity of the design of peripheral circuits and also increases the cost.
Disclosure of Invention
The embodiment of the invention provides a switch current-limiting circuit, which controls the on-off of a power tube of a power supply chip according to the charging and discharging time of a first capacitor, so that the output current value of a power supply system can be accurately controlled.
According to an aspect of the present invention, a switching current limiting circuit is provided, which is suitable for a power chip, and includes: the switching current detection module is used for detecting the switching current of the power supply chip and outputting a first output voltage; the first comparison module is used for comparing the amplified first output voltage with a first preset voltage and outputting a second output voltage according to a comparison result; the charge and discharge module is used for performing charge and discharge operation on a first capacitor in the charge and discharge module according to the second output voltage and outputting a third output voltage; and the second comparison module is used for comparing the third output voltage with the second preset voltage and outputting a fourth output voltage and a first signal according to a comparison result, wherein the first signal is used for carrying out current-limiting protection on the power supply chip.
Optionally, the switching current limiting circuit further includes: and the amplifying module is connected with the output end of the switch current detection module and used for receiving the first output voltage and outputting a first amplified voltage after amplification, and the output end of the amplifying module is connected with the input end of the first comparison module.
Optionally, the switching current limiting circuit further includes: and the reset module is connected with the output end of the charge and discharge module and used for discharging the first capacitor.
Optionally, the switch current detection module includes: the first end of the on-resistor is connected with a power supply end, and the second end of the on-resistor is connected with the second output end of the switch current-limiting circuit; and the differential amplifier is used for amplifying and outputting the voltage of the on-resistance, and the amplified and output voltage of the on-resistance is a first output voltage.
Optionally, the charging and discharging module includes: the input end of the charging unit is connected with the output end of the first comparison module and used for charging the first capacitor according to the second output voltage; the charging timing unit is used for timing the charging of the first capacitor to obtain first time within the time when the power tube of the power supply chip is opened; the input end of the discharging unit is connected with the output end of the first comparing module, and the discharging unit is used for discharging the first capacitor according to the second output voltage within the time when the power tube of the power supply chip is opened; the discharge timing unit is used for timing the discharge of the first capacitor to obtain second time; and the comparison unit is used for comparing the first time with the second time and outputting the third output voltage according to a comparison result.
Optionally, when the power tube of the power chip is turned on and the second output voltage is at a high level, the charging unit starts to operate; and when the second output voltage is at a low level within the time when the power tube of the power supply chip is turned on, the discharge unit starts to work.
Optionally, in a time period when the power transistor of the power chip is turned on, when the first time is longer than the second time, the third output voltage is at a high level; and in the time when the power tube of the power supply chip is opened, the first time is less than or equal to the second time, and the third output voltage is at a low level.
Optionally, when the first amplified voltage is smaller than the first preset voltage, the second output voltage is at a high level; when the first amplified voltage is greater than the first preset voltage, the second output voltage is at a low level.
Optionally, when the third output voltage is less than the second preset voltage, the fourth output voltage is a low level; when the third output voltage is greater than a second preset voltage, the fourth output voltage is at a high level; when the fourth output voltage is inverted from a high level to a low level, the first signal is triggered, and a power tube of the power supply chip is in a cut-off state.
Another aspect of the present invention provides a power chip, which includes the aforementioned switch current-limiting circuit.
The invention provides a switch current-limiting circuit and a power supply chip. When the power tube of the power chip is opened, the switch current-limiting circuit provided by the invention controls the turn-off of the power tube of the power chip by comparing the charging and discharging time of the first capacitor, thereby limiting the maximum output current. The invention can be used for generating the preset current for limiting the maximum output current of the power supply system by detecting the switch current of the on-resistance of the switch current-limiting circuit, wherein the preset current is not influenced by inductance, input voltage, output voltage and the like. The invention can accurately limit the output current value of the power supply system by detecting the current of the on-resistance of the switch current-limiting circuit, thereby being applied to occasions with high requirement on the output current precision; a plurality of power supply systems can be connected in parallel, and the problem that the existing power supply systems cannot be used in parallel is solved.
Drawings
The technical solution and other advantages of the present invention will become apparent from the following detailed description of specific embodiments of the present invention, which is to be read in connection with the accompanying drawings.
Fig. 1 is a connection diagram of a switch current limiting circuit according to an embodiment of the invention.
Fig. 2 is a schematic diagram of a power chip according to an embodiment of the invention.
Fig. 3 is a schematic diagram of a power supply system according to an embodiment of the invention.
FIG. 4 shows the peak current I of the first inductor L1 in the embodiment of the present inventionPEAK、ISET/Io、IvallyA diagram of the correspondence of the current to the voltage of the first capacitor C1 over time.
Fig. 5 is a waveform diagram of current and voltage waveforms of each node when the power supply system operates when the first signal is triggered according to the embodiment of the present invention.
Fig. 6 is a waveform diagram of current and voltage waveforms of nodes when the power supply system operates without triggering the first signal in the embodiment of the present invention.
Detailed Description
The technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Specifically, referring to fig. 1, the present invention provides a switching current limiting circuit 100 suitable for a power chip.
The switching current limiting circuit includes: the circuit comprises a switching current detection module 110, an amplification module 120, a first comparison module 130, a charge and discharge module 140, a reset module 150 and a second comparison module 160.
The switching current detection module 110 is configured to detect a switching current of the power chip and output a first output voltage Va.
The amplifying module 120 is connected to the output end of the switching current detecting module 110, and is configured to receive the first output voltage Va and output a first amplified voltage Vb after amplification, and the output end of the amplifying module 120 is connected to the input end of the first comparing module 130.
The first comparing module 130 is configured to compare the first amplified voltage Vb (i.e., the amplified voltage of the first output voltage Va) with a first preset voltage, and output a second output voltage Vc according to the comparison result.
When the first amplified voltage Vb is smaller than the first preset voltage, the second output voltage Vc is at a high level. When the first amplified voltage Vb is greater than the first preset voltage, the second output voltage Vc is at a low level.
The charge and discharge module 140 is configured to charge and discharge the first capacitor C1 in the charge and discharge module 140 according to the second output voltage Vc, and output a third output voltage Vd.
The reset module 150 is connected to the output end of the charge and discharge module 140, and is configured to discharge the first capacitor C1.
The second comparing module 160 is configured to compare the third output voltage Vd with a second preset voltage, and output a fourth output voltage Vo to the first output terminal of the switching current-limiting circuit 100 according to the comparison result, and the second comparing module 160 further outputs a first signal, where the first signal is used to perform current-limiting protection on the power chip.
And when the third output voltage Vd is less than a second preset voltage, the fourth output voltage Vo is at a low level. And when the third output voltage Vd is greater than the second preset voltage, the fourth output voltage Vo is at a high level.
When the fourth output voltage Vo is inverted from a high level to a low level, the power tube of the power chip is in a cut-off state.
The structure and function of each module will be specifically described below.
The switching current detection module 110 includes: an on-resistance Rdson and a differential amplifier.
The first end of the on-resistance Rdson is connected with a power supply end VCC, the second end of the on-resistance Rdson is connected with the second output end SW of the switch current-limiting circuit, and the on-resistance Rdson is the on-resistance of a power tube of the power supply chip.
The differential amplifier is used for amplifying and outputting the voltage of the on-resistance Rdson, and the amplified and output voltage of the on-resistance Rdson is a first output voltage Va.
Specifically, the differential amplifier includes a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, and a first operational amplifier OP 1.
A first end of the first resistor R1 is connected to the power supply terminal VCC and a first end of the on-resistance Rdson, respectively.
The first end of the second resistor R2 is connected to the second end of the first resistor R1. A second end of the second resistor R2 is connected to ground.
A first end of the third resistor R3 is connected to a second end of the on-resistance Rdson and a second output end SW of the switching current limiting circuit, respectively.
A first end of the fourth resistor R4 is connected to a second end of the third resistor R3, a second end of the fourth resistor R4 is connected to an output end of the switch current detection module, and the output end of the switch current detection module outputs a first output voltage Va.
A first power end of the first operational amplifier OP1 is connected to the power supply end VCC, a second power end of the first operational amplifier OP1 is connected to a ground end, a positive input end of the first operational amplifier OP1 is connected to the second end of the first resistor R1 and the first end of the second resistor R2, a negative input end of the first operational amplifier OP1 is connected to the second end of the third resistor R3 and the first end of the fourth resistor R4, and an output end of the first operational amplifier OP1 is connected to the output end of the switching current detection module and the second end of the fourth resistor R4.
During the conduction period of the switch current-limiting circuit, the current ISW of the power supply chip power tube rises with a fixed slope, the voltage across the on-resistance Rdson is VRdson, and if R1= R3 and R2= R4 are set, the first output voltage Va can be obtained:
Va=（R2/R1）*VRdosn。
the amplification module 120 includes: a second operational amplifier OP2, a fifth resistor R5 and a sixth resistor R6.
A first power supply end of the second operational amplifier OP2 is connected with a power supply voltage end VDD inside the power chip; the second power terminal of the second operational amplifier OP2 is connected to the ground terminal. A positive input end of the second operational amplifier OP2 is connected to an output end of the switch current detection module, and is configured to receive the first output voltage Va; a negative input terminal of the second operational amplifier OP2 is connected to a first terminal of the fifth resistor R5 and a first terminal of the sixth resistor R6, respectively. The output end of the second operational amplifier OP2 is connected to the output end of the amplifying module, and the output end of the second operational amplifier OP2 outputs the amplified first amplified voltage Vb.
A first end of the fifth resistor R5 is connected to a first end of the sixth resistor R6, and a second end of the fifth resistor R5 is connected to an output end of the second operational amplifier OP2 and an output end of the amplifying module 120, respectively.
In the amplifying module, the second operational amplifier OP2, the fifth resistor R5 and the sixth resistor R6 form a non-inverting amplifier, wherein the relationship between the first output voltage Va and the first amplified voltage Vb is as follows:
Vb=（1+R5/R6）*Va
since the voltage VRdson of the on-resistance is generally small, and cannot reach the amplitude suitable for the post-processing through the first differential amplification of the operational amplifier OP1, the second operational amplifier OP2 is additionally added to amplify in phase, so that the first amplified voltage Vb can reach a higher value, and the subsequent circuit can conveniently process the signal.
The first comparing module 130 includes: a first comparator COMP1 and a first reference voltage source VT 1.
A first power supply end of the first comparator COMP1 is connected with a power supply voltage end VDD inside the power supply chip; the second power supply terminal of the first comparator COMP1 is connected to the ground terminal. A positive input end of the first comparator COMP1 is connected to a first end of the first standard voltage source VT 1; an inverting input terminal of the first comparator COMP1 is connected to the output terminal of the amplifying module 120, and is configured to receive the amplified first amplified voltage Vb; the output end of the first comparator COMP1 is connected to the input end of the first comparing module 130; the output terminal of the first comparing module 130 outputs a second output voltage Vc.
The second terminal of the first standard voltage source VT1 is connected to ground, and the first standard voltage source VT1 is configured to generate a first predetermined voltage.
The charge and discharge module 140 includes: the device comprises a charging unit, a charging timing unit, a discharging timing unit and a comparing unit.
The input terminal of the charging unit is connected to the output terminal of the first comparing module 130, and is used for charging the first capacitor C1 according to the second output voltage Vc. And in the time when the power tube of the power chip is turned on, the charging timing unit is used for charging the first capacitor C1 to obtain a first time.
The input terminal of the discharging unit is connected to the output terminal of the first comparing module 130, and is configured to discharge the first capacitor C1 according to the second output voltage Vc. And in the time when the power tube of the power chip is opened, the discharge timing unit is used for discharging and timing the first capacitor C1 to obtain a second time.
The comparison unit is used for comparing the first time with the second time and outputting the final state of the third output voltage Vd according to the comparison result. When the first time is longer than the second time within the time when the power tube of the power chip is opened, the final state of the third output voltage Vd is at a high level; and in the time when the power tube of the power chip is opened, when the first time is less than or equal to the second time, the final state of the third output voltage Vd is a low level.
When the second output voltage Vc is at a high level within the time that the power tube of the power supply chip is turned on, the charging unit starts to work; and in the time when the power tube of the power supply chip is turned on, when the second output voltage Vc is at a low level, the discharge unit starts to work.
Specifically, the charge and discharge module 140 includes: a first transistor Q1, a second transistor Q2, a second transistor Q3, a third transistor Q3, a fourth transistor Q4, a fifth transistor Q5, a sixth transistor Q6, a seventh transistor Q7, an eighth transistor Q8, a ninth transistor Q9, and a first capacitor C1.
The gate of the first transistor Q1 is connected to the output terminal of the first comparing module 130; the source of the first transistor Q1 is connected to the power chip internal supply voltage terminal VDD.
The gate of the second transistor Q2 is connected to the output terminal of the first comparison module 130; the source of the second transistor Q2 is connected to the ground terminal; the drain of the second transistor Q2 is connected to the drain of the first transistor Q1.
The source of the third transistor Q3 is connected to the internal supply voltage terminal VDD.
The source of the fourth transistor Q4 is connected to the drain of the third transistor Q3; the gate of the fourth transistor Q4 is connected to the drain of the first transistor Q1 and the drain of the second transistor Q2, respectively.
The gate of the fifth transistor Q5 is respectively connected with the drain of the first transistor Q1, the drain of the second transistor Q2 and the gate of the fourth transistor Q4; the drain of the fifth transistor Q5 is connected to the drain of the fourth transistor Q4.
The drain of the sixth transistor Q6 is connected to the source of the fifth transistor Q5, and the source of the sixth transistor Q6 is connected to the ground.
The gate of the seventh transistor Q7 is connected to the gate of the third transistor Q3; the source electrode of the seventh transistor Q7 is connected with the internal power supply voltage end VDD of the power supply chip; the drain of the seventh transistor Q7 is connected to the gate of the sixth transistor Q6.
The gate of the eighth transistor Q8 is connected to the drain of the eighth transistor Q8, the drain of the seventh transistor Q7 and the gate of the sixth transistor Q6, respectively; the drain of the eighth transistor Q8 is connected to the drain of the seventh transistor Q7; the source of the eighth transistor Q8 is connected to the ground terminal.
A gate of the ninth transistor Q9 is connected to the gate of the seventh transistor Q7, the drain of the ninth transistor Q9, and the gate of the third transistor Q3, respectively; the source of the ninth transistor Q9 is connected to the power supply chip internal supply voltage terminal VDD; the drain of the ninth transistor Q9 is connected to the gate of the seventh transistor Q7 and the gate of the third transistor Q3, respectively.
A first side of the first capacitor C1 is connected to the drain of the fifth transistor Q5, the drain of the fourth transistor Q4, and the output terminal of the charge and discharge module 140, respectively; the second side of the first capacitor C1 is connected to the ground terminal.
The output end of the charge-discharge module 140 outputs a third output voltage Vd.
When the second output voltage Vc is at a high level, the fourth transistor Q4 is turned on, the fifth transistor Q5 is turned off, and the first capacitor C1 is charged. When the second output voltage Vc is at a low level, the fifth transistor Q5 is turned on, the fourth transistor Q4 is turned off, and the first capacitor C1 is discharged.
Because the transistors (Q3, Q6-Q9) form a current mirror, the current charged by the fourth transistor Q4 and the current discharged by the fifth transistor Q5 of the first capacitor C1 are the same, the current IS1, and the voltage difference between the two ends of the capacitor IS Vd.
The second comparing module 160 includes: a second comparator COMP2 and a second reference voltage source VT 2.
A first power supply end of the second comparator COMP2 is connected with a power supply voltage end VDD inside the power supply chip; a second power supply terminal of the second comparator COMP2 is connected to the ground terminal. An inverting input terminal of the second comparator COMP2 is connected to the first terminal of the second reference voltage source VT2, and the second reference voltage source VT2 generates a second preset voltage. A positive input end of the second comparator COMP2 is connected to an output end of the charge and discharge module 140, and is configured to receive the third output voltage Vd; an output end of the second comparator COMP2 is connected to a first output end of the switching current limiting circuit 100, and the first output end outputs a fourth output voltage V0.
The second terminal of the second reference voltage source VT2 is connected to the ground terminal.
When the third output voltage Vd is higher than the second preset voltage, the first output terminal of the switching current limiting circuit 100 outputs a high level, otherwise, outputs a low level. The second preset voltage may be set to be very low, that is, the voltage charged by the charge-discharge module 140 to the first capacitor C1 may reach a voltage higher than the second preset voltage immediately, so that an error generated by the charging time may be ignored. When the fourth output voltage Vo is inverted from the high level to the low level, the power tube of the power chip is turned off, after the period of the switch current-limiting current is over, and when the next period starts, the modulation and demodulation signal PWM is at the high level, the power tube of the power chip is turned on again, and the fourth output voltage Vo is inverted from the low level to the high level again (the modulation and demodulation signal PWM and the fourth output voltage Vo are two independent signals and cannot affect each other).
The reset module 150 includes: a tenth transistor Q10, an eleventh transistor Q11, and a seventh resistor R7.
The gate of the tenth transistor Q10 is connected to the modulation and demodulation signal PWM of the power chip; the source of the tenth transistor Q10 is connected to the ground terminal; the drain of the tenth transistor Q10 is connected to the second terminal of the seventh resistor R7.
The gate of the eleventh transistor Q11 is connected to the drain of the tenth transistor Q10 and the second end of the seventh resistor R7, respectively; the source of the eleventh transistor Q11 is connected to the ground terminal; the drain of the eleventh transistor Q11 is connected to the output terminal of the charge and discharge module 140 and the input terminal of the second comparison module 160, respectively.
A first end of the seventh resistor R7 is connected with the internal power supply voltage end VDD of the power supply chip; a second terminal of the seventh resistor R7 is connected to the gate of the eleventh transistor Q11.
As shown in fig. 2, the present invention provides a power chip 200, where the power chip 200 includes the switching current limiting circuit 100.
As shown in fig. 3, the present invention further provides a power supply system, which includes the power supply chip 200, a first inductor L1, a diode D1, a second capacitor C2, a third capacitor C3, an output capacitor COUT, and an input capacitor CIN.
The power chip 200 includes a power supply pin VIN, an output pin SW, an enable pin EN, a ground pin GND, and a feedback pin FB.
Specifically, the power supply pin VIN is respectively connected to a first side of the input capacitor CIN and a first side of the second capacitor C2; the output pin SW is respectively connected to the first end of the first inductor L1 and the cathode of the diode D1; the grounding pin GND is connected with a grounding end; the feedback pin FB is connected to the second end of the first inductor L1, the first side of the third capacitor C3, and the first side of the output capacitor COUT, respectively.
The second side of the third capacitor C3 is connected to the ground terminal; the second side of the output capacitor COUT is connected with a grounding end; the anode of the diode D1 is connected with the ground terminal; the second side of the second capacitor C2 is connected with the ground terminal; and the second side of the input capacitor CIN is connected with the grounding end.
Referring to fig. 4, 5 and 6, for the power supply system, when the power supply system operates in the BCM or CCM mode (when the power supply system operates in the DCM mode, it is described that the output current value of the power supply chip is much smaller than the set value, and there is no need to consider the current limiting problem. As shown in fig. 2, the output current Io of the power supply system is equal to the peak current (I) of the first inductorPEAK) With valley current (I)VALLEY) Half of the sum, when the power transistor is turned on, the current of the first inductor L1 is the same as the current ISW in the switched current limiting circuit, i.e.:
Io=( IPEAK + IVALLEY )/2。
when the power tube of the power chip is turned on, the current flowing through the power tube is also equal to the current of the first inductor L1.
When the initial voltage of the first capacitor C1 is V1 and the power transistor of the power chip is turned on, the current of the first inductor L1 is at the valley value IVALLEY(this time is t 0), and the value is I at this timeCHARGETo constant-current charge the first capacitor C1. At time t1, the current of the first inductor L1 reaches the predetermined current ISETThe first capacitor C1 is charged to V2, which begins at IDISCHARGEIs constant current, discharges the first capacitor C1 to the initial voltage V1, at the time t2, when I isCHARGE=IDISCHARGE= I, the capacitance charge-discharge formula is as follows:
I=C*dv/dt
substituting the above values, the charging time tc from t0 to t1 has:
I*dt=C1*dv
Figure 157467DEST_PATH_IMAGE001
tc=t1-t0= C1*(V2-V1)/I
similarly, the discharge time td can be obtained by:
td=t2-t1= C1*(V2-V1)/I
as can be seen from the above, the charging and discharging times of the first capacitor C1 are equal.
When the first capacitor C1 reaches the initial voltage V1 again, the power tube of the power chip is turned off, and since the current of the power tube is equal to the current of the first inductor L1 during the conduction period of the power tube of the power chip, all rising with a fixed slope K, it can be obtained:
IVALLEY+K*tc=ISET
ISET+K*td=IPEAK
since normal current limiting, tc = td, the two equations are subtracted:
IPEAK - ISET = ISET - IVALLEY
finishing to obtain:
ISET =( IPEAK + IVALLEY )/2=Io
thereby realizing the preset current I of the set power supply systemSETIn line with the maximum output current of the power supply system.
The power supply system provided by the invention can detect the current ISW at the on-resistance Rdson of the switch current-limiting circuit and pass through the preset current ISETAnd generating the maximum output current of the power supply system. A predetermined current ISETNamely, the maximum output current of the power supply system, the maximum output current is hardly affected by the inductance of the first inductor L1, the input voltage, the output voltage, and the like.
The invention can accurately limit the output current value of the power supply system by detecting the current ISW of the on-resistance Rdson of the switch current-limiting circuit, thereby being applied to occasions with high requirements on the output current precision, such as LED constant current drive and the field of battery charging.
In addition, a plurality of power supply systems can be mutually combined and connected in parallel, so that the problem that the conventional power supply systems cannot be directly connected in parallel for use is solved.
The above detailed description is made on the switch current-limiting circuit and the power chip provided by the embodiment of the present invention, and a specific example is applied in the present document to explain the principle and the implementation manner of the present invention, and the description of the above embodiment is only used to help understanding the technical scheme and the core idea of the present invention; those of ordinary skill in the art will understand that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.

Claims (9)

1. A switch current-limiting circuit is suitable for a power chip and is characterized in that,
the switching current limiting circuit includes:
the switching current detection module is used for detecting the switching current of the power supply chip and outputting a first output voltage;
the first comparison module is used for comparing the amplified first output voltage with a first preset voltage and outputting a second output voltage according to a comparison result;
the charge and discharge module is used for performing charge and discharge operation on a first capacitor in the charge and discharge module according to the second output voltage and outputting a third output voltage; and
the second comparison module is used for comparing the third output voltage with a second preset voltage and outputting a fourth output voltage and a first signal from a first output end of the switch current-limiting circuit according to a comparison result, wherein the first signal is used for carrying out current-limiting protection on the power supply chip;
wherein, the charge-discharge module includes:
the input end of the charging unit is connected with the output end of the first comparison module and used for charging the first capacitor according to the second output voltage;
the charging timing unit is used for timing the charging of the first capacitor to obtain first time within the time when the power tube of the power supply chip is opened;
the input end of the discharging unit is connected with the output end of the first comparing module and used for discharging the first capacitor according to the second output voltage; and
the discharge timing unit is used for timing the discharge of the first capacitor to obtain second time within the time when the power tube of the power supply chip is opened; and
and the comparison unit is used for comparing the first time with the second time and outputting the third output voltage according to a comparison result.
2. The switched current limit circuit of claim 1, further comprising:
and the amplifying module is connected with the output end of the switch current detection module and used for receiving the first amplified voltage output after the first output voltage is amplified, and the output end of the amplifying module is connected with the input end of the first comparison module.
3. The switched current limit circuit of claim 1, further comprising:
and the reset module is connected with the output end of the charge and discharge module and used for discharging the first capacitor.
4. The switched current-limiting circuit of claim 1,
the switching current detection module includes:
the first end of the on-resistor is connected with a power supply end, and the second end of the on-resistor is connected with the second output end of the switch current-limiting circuit; and
and the differential amplifier is used for amplifying and outputting the voltage of the on-resistance, and the amplified and output voltage of the on-resistance is a first output voltage.
5. The switched current-limiting circuit of claim 1,
within the time that a power tube of the power supply chip is turned on, if the second output voltage is at a high level, the charging unit starts to work;
and in the time when the power tube of the power supply chip is opened, if the second output voltage is at a low level, the discharge unit starts to work.
6. The switched current-limiting circuit of claim 1,
within the time that a power tube of the power supply chip is opened, if the first time is greater than the second time, the third output voltage is at a high level;
and in the time when the power tube of the power supply chip is opened, if the first time is less than or equal to the second time, the third output voltage is at a low level.
7. The switched current-limiting circuit of claim 2,
when the first amplification voltage is smaller than the first preset voltage, the second output voltage is at a high level; when the first amplified voltage is greater than the first preset voltage, the second output voltage is at a low level.
8. The switched current-limiting circuit of claim 1,
when the third output voltage is less than the second preset voltage, the fourth output voltage is at a low level; when the third output voltage is greater than the second preset voltage, the fourth output voltage is at a high level;
when the fourth output voltage is inverted from a high level to a low level, the first signal is triggered, and the power tube of the power supply chip is turned from on to off.
9. A power supply chip comprising the switching current limiting circuit of any one of claims 1 to 8.
CN202011264504.6A 2020-11-13 2020-11-13 Switch current-limiting circuit and power chip Active CN112104203B (en)

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CN112260229A (en) * 2020-12-23 2021-01-22 上海芯龙半导体技术股份有限公司南京分公司 Power chip circuit
CN112255451A (en) * 2020-12-21 2021-01-22 上海芯龙半导体技术股份有限公司南京分公司 Overcurrent detection circuit, overcurrent protection circuit and switching power supply
CN113258771A (en) * 2021-07-15 2021-08-13 上海芯龙半导体技术股份有限公司南京分公司 Control circuit and power supply chip

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CN106877846A (en) * 2017-03-28 2017-06-20 杰华特微电子（张家港）有限公司 A kind of pulse-generating circuit, switching power circuit and average current computational methods
CN208581162U (en) * 2017-09-30 2019-03-05 杰华特微电子（杭州）有限公司 A kind of current-limiting protection circuit and switching power circuit

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CN106877846A (en) * 2017-03-28 2017-06-20 杰华特微电子（张家港）有限公司 A kind of pulse-generating circuit, switching power circuit and average current computational methods
CN208581162U (en) * 2017-09-30 2019-03-05 杰华特微电子（杭州）有限公司 A kind of current-limiting protection circuit and switching power circuit

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CN112255451A (en) * 2020-12-21 2021-01-22 上海芯龙半导体技术股份有限公司南京分公司 Overcurrent detection circuit, overcurrent protection circuit and switching power supply
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