CN115248341A - Current detection circuit of switching device and switching power supply using same - Google Patents
Current detection circuit of switching device and switching power supply using same Download PDFInfo
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- CN115248341A CN115248341A CN202210366307.8A CN202210366307A CN115248341A CN 115248341 A CN115248341 A CN 115248341A CN 202210366307 A CN202210366307 A CN 202210366307A CN 115248341 A CN115248341 A CN 115248341A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/0092—Arrangements for measuring currents or voltages or for indicating presence or sign thereof measuring current only
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
- H02M1/088—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters for the simultaneous control of series or parallel connected semiconductor devices
Abstract
The application discloses switching power supply of switching device's current detection circuit and applied it, through the control of the first sampling pipe, voltage conversion circuit and the first electric current production circuit of being connected with power switch tube to make the electric current of the first power end place node of first sampling pipe with power switch tube's current information is direct proportional relation, thereby passes through the current information of the first power end place node of first sampling pipe can obtain power switch tube's current information. The current detection circuit of the invention can obtain the circuit information of the characterization power switch tube only by one sampling tube without sampling resistance, and has simple circuit and high efficiency.
Description
Technical Field
The invention relates to the technical field of power electronics, in particular to a current detection circuit of a switching device and a switching power supply using the same.
Background
In a conventional switching power supply circuit, a switching device is an indispensable component, and a triode, a field effect transistor, an insulated gate bipolar transistor, and the like can be used as the switching device in the switching power supply.
The switching device is a semiconductor device, and current flowing through the switching device needs to be monitored to ensure that the switching device can work more accurately and safely.
Disclosure of Invention
In view of the above, an object of the present invention is to provide a current detection circuit of a switching device and a switching power supply using the same, so as to solve the technical problem of the prior art that the current detection of the switching device affects the efficiency.
The technical scheme of the invention is to provide a current detection circuit of a switch device, which is used for detecting the current of a power switch tube and comprises a first sampling tube, a voltage conversion circuit, a first current generation circuit and a mirror image circuit, wherein a first power end of the first sampling tube is coupled with the mirror image circuit, a second power end of the first sampling tube is connected with a first power end of the power switch tube, and a common connection point of the first sampling tube and the power switch tube is marked as a first node; an input terminal of the voltage conversion circuit is coupled to the first node and receives a first power supply voltage to obtain a second voltage related to the voltage of the first node; the first input end of the first current generating circuit receives the second voltage, and the second input end of the first current generating circuit is coupled to the first power end of the first sampling tube so as to obtain a first current signal according to the second voltage and the node voltage of the first power end of the first sampling tube; the mirror image circuit receives the first current signal and the current of a node where a first power end of the first sampling tube is located, so that the first current signal and the current form a mirror image proportional relationship; and the current of the node where the first power end of the first sampling tube is located represents the current information of the power switch tube.
Preferably, the ratio of the current value of the node where the first power end of the first sampling tube is located to the current value of the power switch tube is in a direct proportion relation with the ratio of the on-resistance of the power switch tube to the on-resistance of the first sampling tube.
Preferably, the first sampling tube and the power switch tube have the same switch state.
Preferably, a second power terminal of the power switch tube is connected to a reference ground, when the voltage of the first node is greater than the voltage of the reference ground, the second voltage is K times the voltage of the first node, where K is a positive number greater than 1, and when the voltage of the first node is less than the voltage of the reference ground, the second voltage is zero.
Preferably, the voltage conversion circuit comprises a first operational amplifier circuit and a voltage divider circuit, a first input terminal of the first operational amplifier circuit is coupled to the first node, and a second input terminal of the first operational amplifier circuit is coupled to a first connection point in the voltage divider circuit; the voltage division circuit receives a first power supply voltage through a follower, the input end of the follower is coupled with the output end of the first operational amplifier circuit, the voltage of a second connection point in the voltage division circuit is used as a second voltage, and the voltage of the second connection point is K times of the voltage of the first connection point.
Preferably, the first current generating circuit includes a second operational amplifier circuit and a first voltage-controlled current source, a first input terminal of the second operational amplifier circuit receives the second voltage, a second input terminal of the second operational amplifier circuit is coupled to the first power terminal of the first sampling tube, and the first voltage-controlled current source receives an output signal of an output terminal of the second operational amplifier circuit to obtain the first current signal.
Preferably, the mirror circuit includes two symmetrically mirrored switching tubes, first ends of the two switching tubes both receive the second power supply voltage, a second end of one of the two switching tubes is coupled to the output end of the first current generating circuit, and a second end of the other switching tube is coupled to the first power end of the first sampling tube.
In a second aspect, a switching power supply is provided, which includes a power switch tube, and the switching power supply includes a control circuit, the above current detection circuit of the control circuit is used to detect the working current of the power switch tube.
Preferably, the first sampling tube and the power switch tube are integrated into one chip.
Preferably, the control circuit further comprises a current direction judging circuit, the current direction judging circuit judges the direction of the current flowing through the power switch tube according to the voltage of the first node and the voltage of the second power end of the power switch tube,
when the voltage of the first node is greater than the voltage of the second power end of the power switch tube, the current direction of the power switch tube is from the first power end to the second power end,
when the voltage of the first node is smaller than the voltage of the second power end of the power switch tube, the current direction of the power switch tube is from the second power end to the first power end.
By adopting the circuit structure, the current of the node where the first power end of the first sampling tube is located is related to the current information of the power switch tube through the control of the first sampling tube, the voltage conversion circuit and the first current generation circuit which are connected with the power switch tube, so that the current information of the power switch tube can be obtained through the current information of the node where the first power end of the first sampling tube is located.
Drawings
Fig. 1 is a circuit block diagram of a current detection circuit of a switching device according to the present invention;
FIG. 2 is a circuit implementation of a current sensing circuit of a switching device according to the present invention;
FIG. 3 is a circuit block diagram of a switching power supply according to the present invention;
Detailed Description
Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, but the present invention is not limited to only these embodiments. The invention is intended to cover alternatives, modifications, equivalents and alternatives which may be included within the spirit and scope of the invention.
In the following description of the preferred embodiments of the present invention, specific details are set forth in order to provide a thorough understanding of the present invention, and it will be apparent to those skilled in the art that the present invention may be practiced without these specific details.
The invention is described in more detail in the following paragraphs by way of example with reference to the accompanying drawings. It should be noted that the drawings are in simplified form and are not to precise scale, which is only used for convenience and clarity to assist in describing the embodiments of the present invention.
Referring to fig. 1, a circuit block diagram of a current detection circuit of a switching device according to the present invention and fig. 2 is a circuit implementation diagram of a current detection circuit of a switching device according to the present invention, the switching device may be a power switch transistor M0, and the current detection circuit of this embodiment includes a first sampling transistor M1, a voltage conversion circuit, a first current generation circuit, and a mirror circuit. As shown in fig. 1, a first power terminal (e.g., a source) of the first sampling tube M1 is coupled to the mirror circuit, a second power terminal (e.g., a drain) is connected to a first power terminal (e.g., a drain) of the power switch tube, and a common connection point of the first sampling tube and the power switch tube is denoted as a first node and denoted as SW. In this embodiment, the current I1 of the node where the first power end of the first sampling tube is located represents the current information I0 of the power switch tube. In this embodiment, the first sampling tube and the power switch tube are in the same switch state, that is, when the power switch tube is turned on, the first sampling tube is also turned on to obtain information representing the current of the power switch tube. The switching action of the first sampling tube and the power switch tube can be controlled by a control circuit of a switching power supply where the current detection circuit is located.
In one example, the input terminal of the voltage converting circuit is coupled to the first node SW and receives a first power voltage, such as Vcc, to obtain a second voltage associated with the voltage of the first node, and specifically, the voltage converting circuit here includes a first operational amplifier circuit and a voltage dividing circuit, the voltage dividing circuit receives the first power voltage Vcc through a follower, where the follower can be implemented by a MOS switch M2, and the source voltage following function can be implemented by controlling the control terminal of the MOS switch M2 to operate in a saturation region. The voltage division circuit comprises resistors R3 and R4 which are sequentially connected in series between a switch tube M2 and a reference ground end, the resistance values of the resistors R3 and R4 are set to be equal and can also be set to be in a certain multiple relation, a first input end of the first operational amplifier circuit is coupled to the first node SW, and a second input end of the first operational amplifier circuit is coupled to a first connecting point in the voltage division circuit, such as a middle connecting point of the resistors R3 and R4; the control terminal of the first switch is coupled to the output terminal of the first operational amplifier circuit, and the voltage of a second connection point in the voltage divider circuit is taken as a second voltage, such as VA, where the second connection point is a node different from the first connection point, and the voltage of the second connection point is K times the voltage of the first connection point, and the node of the switch tube M2 and the resistor R3 in fig. 1 is taken as the second connection point. In this embodiment, a second power terminal of the power switch tube is connected to a reference ground, when the voltage of the first node is greater than the voltage of the reference ground, the second voltage VA is K times the voltage of the first node, K is a positive number greater than 1, K depends on the magnitude proportional relationship between the resistors R3 and R4, when the voltage of the first node is less than the voltage of the reference ground, the second voltage is zero, and the output voltage is at least zero voltage of the reference ground according to the principle of the first operational amplifier circuit.
In this embodiment, the first current generating circuit includes a second operational amplifier circuit and a first voltage-controlled current source, the first voltage-controlled current source may be implemented by an MOS switch M3, for example, the MOS switch M3 is controlled to operate in a saturation region to obtain a corresponding current according to an output of the second operational amplifier circuit, a first input end of the second operational amplifier circuit receives the second voltage VA, a second input end of the second operational amplifier circuit is coupled to the first power end of the first sampling tube to obtain a voltage VB, and the first voltage-controlled current source receives an output signal of an output end of the second operational amplifier circuit to obtain the first current signal I2.
In this embodiment, the mirror circuit includes two switching tubes, such as a switching tube M4 and a switching tube M5, which are mirror-imaged symmetrically, first ends of the two switching tubes both receive a second power voltage, such as Vcc, and the first power voltage and the second power voltage may be equal or unequal, a second end of one of the two switching tubes is coupled to an output end of the first current generating circuit to obtain a first current signal I2, and a second end of the other switching tube is coupled to a first power end of the first sampling tube to obtain a current of the first power end of the first sampling tube, where the current of the first power end of the first sampling tube is denoted as I1. According to the working principle of the current mirror, the mirror image circuit receives the first current signal and the current of the node where the first power end of the first sampling tube is located, and the first current signal and the current of the node where the first power end of the first sampling tube is located are in a mirror image proportional relationship, which can be an equal proportional mirror image relationship or a proportional mirror image relationship.
According to the circuit diagram shown in fig. 3, when the power switch M0 is turned on,the flowing current direction can be from the first power end to the second power end, such as from the drain to the source, which is denoted as direction (1), or from the second power end to the first power end, such as from the source to the drain, which is denoted as direction (2). When the current direction is the direction (1), the voltage of the first power end is greater than the voltage of the second power end, that is, the voltage of the first node is greater than the voltage of the reference ground end, according to the operational amplifier principle, the voltage of the first connection point is the voltage of SW, which is marked as V SW If the resistors R3 and R4 are equal, the voltage at the second connection point is 2 VSW For the second operational amplifier circuit, according to the operational amplifier principle, the voltage of the first power end of the first sampling tube is 2V SW Then, the current I1 through the first sampling tube is:
I1＝(2V SW -V SW )/R M1 ＝V SW /R M1 (1)
wherein R is M1 The conduction internal resistance of the first sampling tube.
The current I0 of the power switch tube is as follows:
I0＝V SW /R M0 (2)
wherein R is M0 The conduction internal resistance of the power switch tube.
From equations (1) and (2) we can derive:
I0＝I1*R M1 /R M0 (3)
according to the formula (3), the current of the power switch tube is in a direct proportion relation with the current of the first sampling tube, and the proportionality coefficient is related with the on-resistance of the power switch tube and the on-resistance of the first sampling tube.
When the current direction is direction (2), then the voltage of first power end is less than the voltage of second power end, promptly when the voltage of first node is less than reference ground end voltage, according to the fortune principle of putting, the voltage of first tie point is zero, then the voltage of second tie point is also zero, to second fortune circuit of putting, according to the fortune principle of putting, the voltage of first power end of first sampling pipe is also zero, then current I1 through first sampling pipe is:
I1＝(0-V SW )/R M1 ＝-V SW /R M1 (4)
the current I0 of the power switch tube is as follows:
I0＝V SW /R M0 (5)
from equations (4) and (5) we can derive:
I0＝|I1|*R M1 /R M0 (6)
according to the formula (6), the current of the power switch tube and the current value of the first sampling tube are in a direct proportional relation, and the proportionality coefficient is related to the on-resistances of the two.
According to the formula (3) and the formula (6), the ratio of the current value of the node where the first power end of the first sampling tube is located to the current value of the power switch tube is in direct proportion to the ratio of the on-resistance of the power switch tube to the on-resistance of the first sampling tube.
In this embodiment, by the current detection circuit, current detection of the power switch tube can be achieved only by the first sampling tube and the operational amplifier circuit, current information representing the power switch tube can be obtained by current detection of the first power end of the first sampling tube or current sampling of the first power tube in a mirror relationship with the current of the first power tube of the first sampling tube, sampling is convenient, and circuit implementation is simple. The obtained current information can be used as information of subsequent control, such as current limiting, overcurrent protection and the like, and can further detect the direction of the current as information of switch control.
Referring to fig. 3, a circuit block diagram of a switching power supply according to the present invention is shown, where the switching power supply takes a Buck circuit as an example, and a power switch tube is a switch tube M0, and the switching power supply includes a control circuit, where the control circuit includes the above-mentioned current detection circuit, and the current detection circuit is used to detect a working current of the power switch tube.
In one embodiment, the first sampling tube and the power switch tube are integrated in one chip. In addition, the first sampling tube and the power switch tube are switch tubes with the same parameters, so that the first sampling tube and the power switch tube have the same degradation characteristics, and the current detection is more accurate.
In one embodiment, the control circuit further includes a current direction determining circuit, the current direction determining circuit determines a current direction flowing through the power switch tube according to a voltage of the first node and a voltage of the second power terminal of the power switch tube, when the voltage of the first node is greater than the voltage of the second power terminal of the power switch tube, the current direction of the power switch tube is from the first power terminal to the second power terminal, and when the voltage of the first node is less than the voltage of the second power terminal of the power switch tube, the current direction of the power switch tube is from the second power terminal to the first power terminal. Therefore, by combining the absolute value information of the current detected by the current detection circuit, the comprehensive current information of the power switch tube can be obtained and can be used by a subsequent switch control circuit.
The above-described embodiments do not limit the scope of the present invention. Any modification, equivalent replacement, and improvement made within the spirit and principle of the above-described embodiments should be included in the protection scope of the technical solution.
Claims (10)
1. A current detection circuit of a switching device is used for detecting the current of a power switching tube and is characterized by comprising a first sampling tube, a voltage conversion circuit, a first current generation circuit and a mirror image circuit,
a first power end of the first sampling tube is coupled with the mirror circuit, a second power end of the first sampling tube is connected with a first power end of the power switch tube, and a common connection point of the first sampling tube and the power switch tube is marked as a first node;
an input terminal of the voltage conversion circuit is coupled to the first node and receives a first power supply voltage to obtain a second voltage related to the voltage of the first node;
the first input end of the first current generating circuit receives the second voltage, and the second input end of the first current generating circuit is coupled to the first power end of the first sampling tube so as to obtain a first current signal according to the second voltage and the node voltage of the first power end of the first sampling tube;
the mirror image circuit receives the first current signal and the current of a node where a first power end of the first sampling tube is located, so that the first current signal and the current form a mirror image proportional relationship;
and the current of the node where the first power end of the first sampling tube is located represents the current information of the power switch tube.
2. The current detection circuit according to claim 1, wherein a ratio of a current value of a node where the first power terminal of the first sampling tube is located to a current value of the power switch tube is in direct proportion to a ratio of an on-resistance of the power switch tube to an on-resistance of the first sampling tube.
3. The current detection circuit of claim 1, wherein the first sampling tube and the power switch tube have the same switching state.
4. The current sensing circuit of claim 1, wherein the second power terminal of the power switch tube is coupled to a ground reference terminal,
when the voltage of the first node is greater than the voltage of the reference ground, the second voltage is K times of the voltage of the first node, and K is a positive number greater than 1,
when the voltage of the first node is less than the reference ground voltage, the second voltage is zero.
5. The current detection circuit of claim 4, wherein the voltage conversion circuit comprises a first operational amplifier circuit and a voltage divider circuit,
a first input end of the first operational amplifier circuit is coupled to the first node, and a second input end of the first operational amplifier circuit is coupled to a first connecting point in the voltage division circuit;
the voltage dividing circuit receives a first power supply voltage through a follower, the input end of the follower is coupled with the output end of the first operational amplifier circuit, the voltage of a second connecting point in the voltage dividing circuit is used as a second voltage, and the voltage of the second connecting point is K times of the voltage of the first connecting point.
6. The current detection circuit of claim 1, wherein the first current generation circuit comprises a second operational amplifier circuit and a first voltage controlled current source,
a first input terminal of the second operational amplifier circuit receives the second voltage, a second input terminal is coupled to a first power terminal of the first sampling tube,
the first voltage-controlled current source receives an output signal of the output end of the second operational amplifier circuit to obtain the first current signal.
7. The current sensing circuit of claim 1, wherein the mirror circuit comprises two switching transistors that are symmetrically mirrored,
the first ends of the two switch tubes receive a second power supply voltage, the second end of one of the two switch tubes is coupled to the output end of the first current generation circuit, and the second end of the other switch tube is coupled to the first power end of the first sampling tube.
8. A switching power supply comprising a power switching transistor, characterized in that the switching power supply comprises a control circuit comprising a current sensing circuit according to any one of claims 1-7,
the current detection circuit is used for detecting the working current of the power switch tube.
9. The switching power supply of claim 8, wherein the first sampling tube and the power switch tube are integrated in one chip.
10. The switching power supply according to claim 8, wherein the control circuit further comprises a current direction judging circuit,
the current direction judging circuit judges the current direction flowing through the power switch tube according to the voltage of the first node and the voltage of the second power end of the power switch tube,
when the voltage of the first node is greater than the voltage of the second power end of the power switch tube, the current direction of the power switch tube is from the first power end to the second power end,
when the voltage of the first node is smaller than the voltage of the second power end of the power switch tube, the current direction of the power switch tube is from the second power end to the first power end.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210366307.8A CN115248341A (en) | 2022-04-08 | 2022-04-08 | Current detection circuit of switching device and switching power supply using same |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202210366307.8A CN115248341A (en) | 2022-04-08 | 2022-04-08 | Current detection circuit of switching device and switching power supply using same |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116047147A (en) * | 2023-01-28 | 2023-05-02 | 苏州贝克微电子股份有限公司 | High-precision current detecting circuit |
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2022
- 2022-04-08 CN CN202210366307.8A patent/CN115248341A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116047147A (en) * | 2023-01-28 | 2023-05-02 | 苏州贝克微电子股份有限公司 | High-precision current detecting circuit |
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