CN112345908B - Current detection circuit of power switch tube - Google Patents
Current detection circuit of power switch tube Download PDFInfo
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- CN112345908B CN112345908B CN202011177495.7A CN202011177495A CN112345908B CN 112345908 B CN112345908 B CN 112345908B CN 202011177495 A CN202011177495 A CN 202011177495A CN 112345908 B CN112345908 B CN 112345908B
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Abstract
The invention relates to a current detection circuit of a power switch tube, which at least comprises a first resistor, a first diode, a second diode, a third diode, a voltage stabilizing diode, a triode and the power switch tube, wherein the triode is connected with the drain electrode of the power switch tube to monitor the voltage drop of the drain electrode of the power switch tube so as to realize the current detection of the power switch tube, and the collector of the triode is connected through a branch circuit formed by a first resistor and a first diode in parallel, so that the first resistor and a first node connected with the collector of the triode in a parallel connection node of the first diode are used as feedback signals for feeding back whether the current of the power switch tube is too large or not, under the condition that the emitting electrode of the triode is directly connected with the drain electrode of the power switch tube, a third diode and a voltage stabilizing diode which are opposite in polarity are connected in parallel between the base electrode and the emitting electrode of the triode, and a second diode is connected in series between the collector electrode and the first node of the triode.
Description
Technical Field
The invention relates to the technical field of power electronics, in particular to a current detection circuit of a power switch tube.
Background
With the wider application of the power switch tube, how to ensure the reliability of the power switch tube in the conducting process is more and more important. Since the power switch tube usually has a large current passing through it during application, if the current exceeds the endurance limit of the power switch tube, the power switch tube may be damaged. Then the current of the power switch tube must be continuously detected and a feedback signal can be provided in order to ensure the reliability of the device. In the prior art, a resistor is generally added to a branch where a power switch tube is located, and the current on the branch is reflected by sampling the voltage drop on the resistor. But the sampling resistance increases the power loss of both. Another method is to use the variation of the drain-source voltage on the power switch tube to sample the current flowing through the power switch tube.
For example, chinese patent publication No. CN207117586U discloses an MOS transistor overcurrent protection circuit for MOS transistor connection, which includes a capacitor, a charging circuit, a discharging circuit, and an MOS transistor disconnecting circuit. The MOS tube disconnection circuit is connected in series between the capacitor and the G pole of the MOS tube and used for reducing the G pole voltage of the MOS tube when the charging voltage of the capacitor exceeds a preset voltage stabilization value, so that the MOS tube is cut off. The MOS tube disconnection circuit comprises a fourth triode, the C pole of the fourth triode is connected with the negative pole of a sixth diode, and the positive pole of the sixth diode is used for being connected with the G pole of the MOS tube. The technical solution disclosed in this patent document is to connect a diode in series between the power switch tube and the transistor to protect the fourth transistor and to realize the conversion of conduction voltage drop of the power tube to sample the current. However, the conduction voltage drop of a diode is related to the current flowing through and the temperature. With the increase of the voltage of the drain electrode of the power switch tube, namely the increase of the voltage at the cathode of the diode, the current flowing through the diode is reduced, so that the conduction voltage drop of the diode is reduced, and the actually detected current alarm point is higher than the designed current alarm point. Therefore, it is desirable to provide a current detection circuit for a power switch tube, which is used to solve the problem of inaccurate current detection caused by diode characteristics in an overcurrent detection circuit for a power switch tube.
Furthermore, on the one hand, due to the differences in understanding to the person skilled in the art; on the other hand, since the inventor has studied a lot of documents and patents when making the present invention, but the space is not limited to the details and contents listed in the above, however, the present invention is by no means free of the features of the prior art, but the present invention has been provided with all the features of the prior art, and the applicant reserves the right to increase the related prior art in the background.
Disclosure of Invention
In view of the deficiencies of the prior art, the present invention provides a current detection circuit for a power switch tube, which at least includes a first resistor R1, a first diode D1, a second diode D2, a third diode D3, a zener diode D4, a transistor Q1, and a power switch tube Q2. The triode Q1 is connected to the drain of the power switch Q2 to monitor the voltage drop at the drain of the power switch Q2, so as to detect the current of the power switch Q2. The collector of the transistor Q1 is connected through a branch constructed by the first resistor R1 connected in parallel with the first diode D1 so that the first node of the parallel node of the first resistor R1 and the first diode D1 connected with the collector of the transistor Q1 serves as a feedback signal for feeding back whether the current of the power switch Q2 is excessive. In the case that the emitter of the transistor Q1 is directly connected to the drain of the power switch Q2, a third diode D3 and the zener diode D4, which have opposite polarities to each other, are connected in parallel between the base and the emitter of the transistor Q1. The second diode D2 is connected in series between the collector of the transistor Q1 and the first node. Aiming at the problem that the conducting voltage drop of a diode connected in series between a power switch tube and a triode is influenced by current, so that the actually detected current alarm point is higher than the designed current alarm point, the invention removes the diode connected in series between the drain electrode of the power switch tube Q2 and the emitter electrode of the triode Q1, and realizes the protection of the triode Q1 by respectively arranging diodes at the collector electrode and the emitter electrode of the triode Q1. The problem that the actually detected current alarm point is far higher than the designed current alarm point due to the fact that the conduction voltage drop of the diode is related to the current flowing through the diode is solved, and the reliability of the current detection circuit is improved. In addition, the current flowing through the power switch tube Q2 is collected through the change of the drain voltage of the power switch tube Q2, mainly the voltage drop change of the on and off of the triode Q1 and the current value flowing through the power switch tube Q2 are correspondingly converted, but the on of the triode Q1 is also related to the temperature, the influence caused by the diode can be overcome by connecting the triode Q1 with the drain of the power switch tube Q2, however, the interference caused by the temperature factor of the triode Q1 is also introduced, and the on voltage drop of the third diode D3 and the voltage stabilizing diode D4 is also related to the flowing current and temperature, so the influence of the temperature on the voltage is reduced through the simultaneous change of the triode Q1, the power switch tube Q2 and the voltage stabilizing diode D4, and the current detection accuracy is improved. Specifically, the lower the required forward bias voltage, the higher the temperature of transistor Q1. The larger the on-resistance of the power switch Q2 with increasing temperature. Under the same current flowing condition, the voltage of the second voltage V2 is higher, and the second voltage V2 change simultaneously, so that the influence of temperature on the voltage is reduced, and the accuracy of current detection is improved. Similarly, the reverse voltage of the transistor Q1, the conduction voltage drop of the third diode D3, and the regulated voltage value of the zener diode D4 may be changed simultaneously by providing the zener diode D4 and the third diode D3 having the same temperature characteristics as the transistor Q1, so as to counteract the influence, thereby protecting the transistor Q1.
According to a preferred embodiment, the current detection circuit further comprises a second resistor R2, a third resistor R3 and a capacitor C1. The driving signal is connected to the gate of the power switch Q2, and enters into the second resistor R2 and the second node opposite to the first node among the nodes where the first resistor R1 and the first diode D1 are connected in parallel, respectively. The first node is grounded through the capacitor C1 for filtering and RC delay.
According to a preferred embodiment, the second resistor R2 is connected to the transistor Q1 and the third resistor R3, respectively. The base of the transistor Q1 is connected to the second resistor R2, and the transistor Q1 is connected in parallel to the third resistor R3. The third resistor R3 is grounded relative to one end of the second resistor R2.
According to a preferred embodiment, the anodes of the first diode D1 and the second diode D2 are connected to the capacitor C1, respectively. Without issuing the driving signal, the current of the capacitor C1 flows through the first node into the first and second diodes D1 and D2, respectively. The first diode D1 and the second diode D2 are in a conducting state. And then the current of the capacitor C1 is discharged through the first diode D1, the second diode D2 and the first resistor R1 so that the feedback signal becomes a low state.
According to a preferred embodiment, without sending out the driving signal, the power switch Q2 is in a cut-off state so that the second voltage V2 at the drain of the power transistor Q2 is at a high level. When the driving signal is sent out, the driving signal drives the power switch tube Q2 to be in a conducting state. The driving signal enters the second resistor R2 and the first resistor R1 respectively to make the transistor Q1 in a conducting state, so as to pull the second voltage V2 to a low potential.
According to a preferred embodiment, when the second voltage V2 is pulled to a low level, the feedback signal is pulled to a low level through the second diode D2, the transistor Q1 and the power switch Q2 which are in a conducting state. The second voltage V2 increases with increasing current through the power switch Q2. In the case where the second voltage V2 rises above the forward biased on voltage of the transistor Q1, the transistor Q1 is in an off state such that the voltage of the feedback signal is pulled high.
According to a preferred embodiment, in the case that the driving signal is not sent out, so that the transistor Q1 and the power switch Q2 are turned off, and the second voltage V2 is at a high level, the reverse voltage between the emitter and the base of the transistor Q1 is the conducting voltage drop of the third diode D2 and the regulated voltage value of the regulated diode D4, so as to avoid the breakdown of the transistor Q1. In the off state of the transistor Q1, the cathode of the second diode D2 is connected to the collector of the transistor Q1 to prevent the feedback signal from being pulled high.
According to a preferred embodiment, the cut-off voltage of the transistor Q1 is reduced as the ratio of the second resistor R2 to the third resistor R3 is increased, thereby modifying the current alarm value of the power switch Q2.
The invention also discloses another current detection circuit of a power switch tube, which at least comprises a first resistor R1, a second resistor R2, a third resistor R3, a first diode D1, a capacitor C1, a triode Q1 and a power switch tube Q2, wherein the triode Q1 is indirectly connected with the drain electrode of the power switch tube Q2 through direct connection/connection to monitor the current of the power switch Q2, wherein,
the collector of the transistor Q1 is connected through a branch constructed by the first resistor R1 in parallel with a first diode D1 and in series with the capacitor C1 such that the first node of the parallel node of the first resistor R1 and the first diode D1, which is connected with the collector of the transistor Q1 and the capacitor C1, serves as a feedback signal for feeding back whether the current of the power switch tube Q2 is excessive,
the first node feeds back the transistor Q1 to output a high level or a low level according to the second voltage V2 at the drain of the power tube Q2 through the second resistor R2 and the third resistor R3.
According to a preferred embodiment, a driving signal is connected to the gate of the power switch Q2 and enters the second resistor R2 and a second node opposite to the first node among the nodes where the first resistor R1 is connected in parallel with the first diode D1,
the driving signal is respectively connected to the base of the transistor Q1 and the third resistor R3 in a parallel mode through the second resistor R2.
Drawings
FIG. 1 is a schematic circuit diagram of a preferred embodiment of the present invention;
fig. 2 is a circuit schematic diagram of another preferred embodiment of the present invention.
List of reference numerals
R1: first resistance R2: second resistance R3: third resistance
D1: first diode D2: second diode D3: third diode
D4: zener diode Q1: a transistor Q2: power switch tube
C1: capacitance V1: first voltage V2: second voltage
Detailed Description
The present invention will be described in detail with reference to the accompanying drawings.
Example 1
The embodiment discloses a current detection circuit of a power switch tube, which at least comprises a first resistor R1, a second resistor R2, a third resistor R3, a first diode D1, a capacitor C1, a triode Q1 and a power switch tube Q2. The transistor Q1 monitors the current of the power switch Q2 by being directly/indirectly connected to the drain of the power switch Q2. The collector of the transistor Q1 is connected through a branch constructed by a first resistor R1 in parallel with a first diode D1 and in series with a capacitor C1. The first node of the parallel node of the first resistor R1 and the first diode D1, which is connected with the collector of the transistor Q1 and the capacitor connection C1, is used as a feedback signal for feeding back whether the current of the power switch Q2 is excessive or not. The first node feeds back the transistor Q1 to output a high level or a low level in a manner that the second voltage V2 at the drain of the power transistor Q2 varies through the second resistor R2 and the third resistor R3.
Preferably, the current detection circuit shown in fig. 2 is suitable for application scenarios where the current detection accuracy is not high but fast detection is required. A second diode D2 is connected in series between an emitter of a triode Q1 of the current detection circuit and a drain of a power switch tube Q2 and is used for detecting the voltage of the drain of the power switch Q2. As shown in fig. 2, the driving signal is connected to the gate of the power switch Q2. The driving signals enter the second resistor R2 and a second node opposite to the first node among the nodes connected in parallel with the first diode D1 by the first resistor R1, respectively. The driving signal is respectively connected to the base of the transistor Q1 and the third resistor R3 in parallel through the second resistor R2. When the driving signal (Driver) drives the power switch Q2 to conduct, the transistor Q1 is simultaneously conducted. The Feedback signal (Feedback) at the first node is pulled to a low level due to the discharge of the capacitor C1. As the current flowing through the power switch Q2 increases, the second voltage V2 at the drain of the power switch Q2 gradually increases. When the second voltage V2 rises to the cut-off voltage of the second diode D2, the second diode D2 is cut off, and the transistor Q1 is simultaneously cut off. The Feedback signal (Feedback) of the first node is pulled to a high potential. Preferably, the cut-off voltage of the second diode D2, i.e., the current alarm value of the power switch Q2, can be adjusted by modifying the ratio of the second resistor R2 to the third resistor R3.
Example 2
This embodiment is a further improvement of embodiment 1, and repeated contents are not described again.
As shown in fig. 1, the present embodiment provides a current detection circuit for a power switch tube, which at least includes a first resistor R1, a first diode D1, a second diode D2, a third diode D3, a zener diode D4, a transistor Q1, and a power switch tube Q2. The transistor Q1 is connected to the drain of the power switch Q2 to monitor the voltage drop at the drain of the power switch Q2, so as to detect the current of the power switch Q2. The collector of the transistor Q1 is connected through a branch formed by a first resistor R1 connected in parallel with a first diode D1 such that the first node of the parallel connection node of the first resistor R1 and the first diode D1 connected to the collector of the transistor Q1 serves as a feedback signal for whether the current of the feedback power switch Q2 is excessive. Preferably, the source of the power switch Q2 is grounded. In the case where the emitter of the transistor Q1 is directly connected to the drain of the power switch Q2, a third diode D3 and a zener diode D4, which have opposite polarities to each other, are connected in parallel between the base and the emitter of the transistor Q1. A second diode D2 is connected in series between the collector of transistor Q1 and the first node. Aiming at the problem that the conducting voltage drop of a diode connected in series between a power switch tube and a triode is influenced by current, so that the actually detected current alarm point is higher than the designed current alarm point, the invention removes the diode connected in series between the drain electrode of the power switch tube Q2 and the emitter electrode of the triode Q1, and realizes the protection of the triode Q1 by respectively arranging diodes at the collector electrode and the emitter electrode of the triode Q1. The problem that the actually detected current alarm point is far higher than the designed current alarm point due to the fact that the conduction voltage drop of the diode is related to the current flowing through the diode is solved. The reliability of the current detection circuit is improved. In addition, the current flowing through the power switch tube Q2 is collected through the change of the drain voltage of the power switch tube Q2, mainly the voltage drop change of the on and off of the triode Q1 and the current value flowing through the power switch tube Q2 are correspondingly converted, but the on of the triode Q1 is also related to the temperature, the influence caused by the diode can be overcome by connecting the triode Q1 with the drain of the power switch tube Q2, however, the interference caused by the temperature factor of the triode Q1 is also introduced, and the on voltage drop of the third diode D3 and the voltage stabilizing diode D4 is also related to the flowing current and temperature, so the influence of the temperature on the voltage is reduced through the simultaneous change of the triode Q1, the power switch tube Q2 and the voltage stabilizing diode D4, and the current detection accuracy is improved. Specifically, the lower the required forward bias voltage, the higher the temperature of transistor Q1. The larger the on-resistance of the power switch Q2 with increasing temperature. Under the same current flowing condition, the voltage of the second voltage V2 is higher, and the second voltage V2 change simultaneously, so that the influence of temperature on the voltage is reduced, and the accuracy of current detection is improved. Similarly, the reverse voltage of the transistor Q1, the conduction voltage drop of the third diode D3, and the regulated voltage value of the zener diode D4 may be changed simultaneously by providing the zener diode D4 and the third diode D3 having the same temperature characteristics as the transistor Q1, so as to counteract the influence, thereby protecting the transistor Q1.
According to a preferred embodiment, the current detection circuit further comprises a second resistor R2, a third resistor R3 and a capacitor C1. The driving signal is connected to the gate of the power switch Q2, and enters into the second resistor R2 and the second node opposite to the first node among the nodes where the first resistor R1 and the first diode D1 are connected in parallel, respectively. The first node is grounded through capacitor C1 for filtering and RC delay. Through the setting mode, the condition that the feedback signal is triggered by mistake can be avoided.
According to a preferred embodiment, the second resistor R2 is connected to the transistor Q1 and the third resistor R3, respectively. The base of the transistor Q1 is connected to a second resistor R2. A transistor Q1 is connected in parallel with the third resistor R3. The third resistor R3 is grounded at one end opposite to the second resistor R2. With this arrangement, the capacitor C1 can be grounded through the second resistor R2 and the third resistor R3 and then discharged.
According to a preferred embodiment, the anodes of the first diode D1 and the second diode D2 are connected to a capacitor C1, respectively. In the case where the driving signal is not issued, the current of the capacitor C1 flows through the first node into the first diode D1 and the second diode D2, respectively. The first diode D1 and the second diode D2 are in a conducting state. With this arrangement, the current of the capacitor C1 is discharged through the first diode D1, the second diode D2, and the first resistor R1 so that the feedback signal becomes a low state. Through the setting mode, the feedback signal of the first node can be rapidly changed into a low level state under the condition that the driving signal is not sent out or the driving signal is at a low level, and further the condition of false triggering is avoided.
According to a preferred embodiment, the power switch Q2 is turned off when no driving signal is asserted, so that the second voltage V2 at the drain of the power transistor Q2 is at a high level. Preferably, the second voltage V2 is at an external level (normally high level), so the second voltage V2 is always at a high level when the power switch Q2 is not turned on. In the case of a drive signal, the drive signal drives the power switch Q2 to a conducting state. The driving signal enters the second resistor R2 and the first resistor R1 respectively to make the transistor Q1 in a conducting state, so as to pull the second voltage V2 to a low potential.
According to a preferred embodiment, when the second voltage V2 is pulled to a low level, the feedback signal is pulled to a low level through the second diode D2, the transistor Q1 and the power switch Q2 which are in a conducting state. The second voltage V2 increases with an increase in current flowing through the power switch Q2. In the case where the second voltage V2 rises above the forward biased on voltage of transistor Q1, transistor Q1 is in an off state such that the voltage of the feedback signal is pulled high.
According to a preferred embodiment, in the case that the transistor Q1 and the power switch Q2 are turned off and the second voltage V2 is at a high level without sending a driving signal, the reverse voltage between the emitter and the base of the transistor Q1 is the conduction voltage drop of the third diode D2 and the regulated voltage value of the regulated diode D4, so as to prevent the transistor Q1 from being broken down. In the off state of the transistor Q1, the cathode of the second diode D2 is connected to the collector of the transistor Q1 to prevent the feedback signal from being pulled high. Through the arrangement, the triode Q1 can be protected by the second diode D2, the third diode D3 and the voltage stabilizing diode D4. Specifically, the second diode D2 prevents the feedback signal from being pulled high when the transistor Q1 is turned off, regardless of whether the driving signal (Driver) is asserted. Furthermore, in the case that the driving signal (Driver) is not sent out or is low, the transistor Q1 and the power switch Q2 are in the off state, the second low voltage V2 is high, and if the third diode D3 and the zener diode D4 are not provided, a high reverse voltage exists between the emitter and the base of the transistor Q1, which may cause the transistor Q1 to break down. After the third diode D3 and the zener diode D4 are added, the voltage found by the transistor Q1 is the conduction voltage drop of the third diode D2 and the regulated voltage value of the zener diode D4, so as to prevent the transistor Q1 from being broken down.
According to a preferred embodiment, the cut-off voltage of the transistor Q1 is reduced as the ratio of the second resistor R2 to the third resistor R3 is increased, thereby modifying the current alarm value of the power switch Q2. The adjustment of the current alarm value can be realized through the setting mode. Specifically, when the driving signal (Driver) is asserted or is at a high level, the power switch Q2 is turned on, and the second low voltage V2 is determined by the current Id flowing through the power switch Q2. In normal operation, the second voltage V2-the first voltage V1 is smaller than the forward bias voltage of the transistor Q1, and the transistor Q1 is turned on. The Feedback signal (Feedback) of the first node is pulled to a low level through the second diode D2, the transistor Q1 and the power switch Q2. When the second voltage V2-the voltage value of the first voltage V1 is greater than the forward bias voltage of the transistor Q1, the transistor Q1 is turned off, and the Feedback signal (Feedback) at the first node is pulled to a high level through the first resistor R1.
The detection principle of the invention is as follows: the current flowing through the power switch tube Q2 is sampled through the voltage change at the drain electrode of the power switch tube Q2, namely the conduction voltage drop is detected through the characteristic that the conduction voltage drop of the power switch tube Q2 changes along with the current, and the change of the conduction voltage drop is correspondingly converted with the current value flowing through the power switch tube Q2, so that the current detection is realized. However, in the prior art, a diode is connected in series between the emitter of the transistor Q1 and the drain of the power switch Q2 for protection of the transistor Q1 and conversion of the conduction voltage drop. However, the voltage drop of the diode conduction is also related to the current flowing through, and when the second voltage V2 increases, the current flowing through the diode decreases, and the voltage drop of the diode conduction decreases accordingly, so that the current alarm point obtained by actual inspection is far higher than the designed current alarm point. The invention realizes the protection of the triode Q1 by removing the diode connected between the drain electrode of the power switch tube Q2 and the emitter electrode of the triode Q1 and respectively arranging the diodes at the collector electrode and the emitter electrode of the triode Q1. The problem that the actually detected current alarm point is far higher than the designed current alarm point due to the fact that the conduction voltage drop of the diode is related to the current flowing through the diode is solved, and the reliability of the current detection circuit is improved.
Preferably, when the power switch Q2 is turned on and operated in the linear region, the power switch Q2 is used as a switch, which is considered to be an equivalent resistor, assuming that the drain and source voltages are small. For a known equivalent resistance, the switching current depends on the voltage drop between the drain and the source of the power switch Q2. However, the temperature change can cause the mobility and the threshold voltage to change, so that the equivalent resistance of the power switch tube Q2 changes nonlinearly, and the error range can reach-40% to 80%. The power switch Q2 generally has a positive temperature coefficient, and its resistance increases with increasing temperature, and its current decreases with increasing temperature of the power switch Q2. When the transistor Q1 is saturated, the collector-junction saturation voltage drop decreases with an increase in temperature, and the collector-emitter voltage of the transistor also decreases with an increase in temperature, so that the current flowing through the transistor Q1 increases with an increase in temperature when the load resistance is fixed. In order to overcome the influence of the change of the transistor Q1 along with the temperature on the current detection of the power switch tube Q2, the invention utilizes the change characteristics of the transistor Q1 and the power switch Q2 on the basis of the arrangement, namely, when the temperature changes, the forward bias voltage required by the transistor Q1 along with the temperature rise is lower, and the on-resistance of the power switch tube Q2 along with the temperature rise is higher, and the second voltage V2 is higher under the condition of the same flowing current. Therefore, the forward bias voltage of the triode Q1 and the second voltage V2 at the drain of the power switch Q2 are changed simultaneously, and the influence on the voltage is counteracted, so that the current detection precision is higher.
The present specification encompasses multiple inventive concepts and the applicant reserves the right to submit divisional applications according to each inventive concept. The present description contains several inventive concepts, such as "preferably", "according to a preferred embodiment" or "optionally", each indicating that the respective paragraph discloses a separate concept, the applicant reserves the right to submit divisional applications according to each inventive concept.
It should be noted that the above-mentioned embodiments are exemplary, and that those skilled in the art, having benefit of the present disclosure, may devise various arrangements that are within the scope of the present disclosure and that fall within the scope of the invention. It should be understood by those skilled in the art that the present specification and figures are illustrative only and are not limiting upon the claims. The scope of the invention is defined by the claims and their equivalents.
Claims (9)
1. A current detection circuit of a power switch tube is characterized by at least comprising a first resistor (R1), a first diode (D1), a second diode (D2), a third diode (D3), a voltage stabilizing diode (D4), a triode (Q1) and a power switch tube (Q2), wherein the triode (Q1) is connected with the drain electrode of the power switch tube (Q2) to monitor the voltage drop of the drain electrode of the power switch tube (Q2) so as to realize the detection of the current of the power switch tube (Q2), and the collector electrode of the triode (Q1) is connected with a branch circuit formed by the first resistor (R1) and a first diode (D1) in parallel connection to enable a first node connected with the collector electrode of the triode (Q1) in the parallel connection node of the first resistor (R1) and the first diode (D1) to be used as a feedback signal for feeding back whether the current of the power switch tube (Q2) is too large or not, wherein, in case that the emitter of the transistor (Q1) is directly connected with the drain of the power switch tube (Q2), a third diode (D3) and the zener diode (D4) with opposite polarities to each other are connected in parallel between the base and the emitter of the transistor (Q1), and the second diode (D2) is connected in series between the collector of the transistor (Q1) and the first node.
2. The current sensing circuit of claim 1, further comprising a second resistor (R2), a third resistor (R3), and a capacitor (C1), wherein a driving signal is connected to the gate of the power switch (Q2) and enters the second resistor (R2) and a second node opposite the first node of a first resistor (R1) and a first diode (D1) parallel node, respectively, wherein the first node is grounded via the capacitor (C1) for filtering and RC delay.
3. The current detection circuit according to claim 2, wherein the second resistor (R2) is connected to the transistor (Q1) and the third resistor (R3), respectively, wherein the base of the transistor (Q1) is connected to the second resistor (R2), and the transistor (Q1) is connected in parallel to a third resistor (R3), and one end of the third resistor (R3) opposite to the second resistor (R2) is grounded.
4. The current detection circuit according to claim 3, wherein the anodes of the first diode (D1) and the second diode (D2) are respectively connected to the capacitor (C1), wherein, in the case where the driving signal is not issued, the current of the capacitor (C1) flows through the first node and enters the first diode (D1) and the second diode (D2), respectively, wherein the first diode (D1) and the second diode (D2) are in a conducting state, and the current of the capacitor (C1) flows through the first diode (D1), the second diode (D2) and the first resistor (R1) to discharge so that the feedback signal becomes a low state.
5. The current detection circuit according to claim 4, wherein in a case where the driving signal is not asserted, the power switch (Q2) is in a cut-off state such that the second voltage (V2) at the drain of the power switch (Q2) is at a high level, wherein in a case where the driving signal is asserted, the driving signal drives the power switch (Q2) in a conducting state, and the driving signal enters the second resistor (R2) and the first resistor (R1) such that the transistor (Q1) is in a conducting state, thereby pulling the second voltage (V2) to a low level.
6. The current detection circuit according to claim 5, wherein when the second voltage (V2) is pulled to a low level, the feedback signal is pulled to a low level through the second diode (D2), the transistor (Q1), and the power switch (Q2) in a conducting state, and
the second voltage (V2) increases with increasing current through the power switch (Q2), wherein, in the event that the second voltage (V2) rises above a forward bias on voltage of the transistor (Q1), the transistor (Q1) is in an off state such that the voltage of the feedback signal is pulled high.
7. The current detection circuit according to claim 6, wherein, in a case where the driving signal is not sent out such that the transistor (Q1) and the power switch (Q2) are turned off and the second voltage (V2) is at a high level, a reverse voltage between an emitter and a base of the transistor (Q1) is an on-state voltage drop of the third diode (D2) and a regulated voltage value of the regulated diode (D4) so as to prevent the transistor (Q1) from being broken down, and in a case where the transistor (Q1) is in a turned-off state, a cathode of the second diode (D2) is connected to a collector of the transistor (Q1) so as to prevent the feedback signal from being pulled to a high potential.
8. The current detection circuit according to claim 7, wherein the cut-off voltage of the transistor (Q1) becomes smaller as the ratio of the second resistor (R2) to the third resistor (R3) becomes larger, thereby modifying the current alarm value of the power switch (Q2).
9. A current detection circuit of a power switch tube is characterized by at least comprising a first resistor (R1), a second resistor (R2), a third resistor (R3), a first diode (D1), a capacitor (C1), a triode (Q1) and a power switch tube (Q2), the triode (Q1) is directly/indirectly connected with the drain electrode of the power switch tube (Q2) to monitor the current of the power switch tube (Q2), wherein the collector of the transistor (Q1) is connected through a branch constructed by the first resistor (R1) in parallel with a first diode (D1) and in series with the capacitor (C1) such that a first node of the first resistor (R1) and first diode (D1) parallel node connected to the collector of the transistor (Q1) and the capacitor connection (C1) serves as a feedback signal to feedback whether the current of the power switch tube (Q2) is excessive; a driving signal is connected with a grid electrode of the power switch tube (Q2), the driving signal is respectively connected to a base electrode of the triode (Q1) and the third resistor (R3) in a parallel mode through the second resistor (R2), and the driving signal respectively enters a second node opposite to the first node in a parallel connection node of the second resistor (R2) and the first resistor (R1) and the first diode (D1); wherein the first node feeds back the transistor (Q1) to output a high level or a low level as a function of the second voltage (V2) at the drain of the power switch (Q2) through the second resistor (R2) and a third resistor (R3).
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| CN202011177495.7A CN112345908B (en) | 2020-10-27 | 2020-10-27 | Current detection circuit of power switch tube |
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| CN202011177495.7A CN112345908B (en) | 2020-10-27 | 2020-10-27 | Current detection circuit of power switch tube |
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| CN112345908B true CN112345908B (en) | 2021-07-27 |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN202384752U (en) * | 2011-12-15 | 2012-08-15 | 安徽华东光电技术研究所 | Switching power supply overcurrent protection circuit |
| US8890579B2 (en) * | 2012-07-20 | 2014-11-18 | Texas Instruments Incorporated | Circuit for current sensing in high-voltage transistor |
| CN104363011A (en) * | 2014-10-11 | 2015-02-18 | 浙江大学 | Over-current detection and protection circuit for IGBT (insulated gate bipolar transistor) |
| CN206348384U (en) * | 2016-01-27 | 2017-07-21 | 深圳市瑞之辰科技有限公司 | The over-current detection circuit of power switch |
| CN105954570B (en) * | 2016-06-13 | 2018-09-11 | 王良坤 | A kind of high side power pipe over-current detection circuit of simplification |
| CN205921376U (en) * | 2016-07-01 | 2017-02-01 | 上海芯导电子科技有限公司 | Overvoltage protection circuit |
| CN207398813U (en) * | 2017-10-26 | 2018-05-22 | 广州视源电子科技股份有限公司 | Current foldback circuit and electronic equipment |
| CN108896899B (en) * | 2018-07-23 | 2021-07-23 | 广东志高暖通设备股份有限公司 | Integrated switch tube overcurrent detection circuit |
| CN109787596B (en) * | 2018-12-25 | 2023-08-04 | 深圳市优必选科技有限公司 | Overcurrent protection circuit, switching tube driving circuit and electric equipment |
| CN210982594U (en) * | 2019-09-26 | 2020-07-10 | 上海稊米汽车科技有限公司 | Control circuit for monitoring current threshold |
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Address after: No.99, Jingbei 6th Road, Zhengzhou area (Jingkai), Henan pilot Free Trade Zone, Zhengzhou, Henan Province, 450000 Patentee after: Henan Jiachen Intelligent Control Co.,Ltd. Address before: No.99, Jingbei 6th Road, Zhengzhou area (Jingkai), Henan pilot Free Trade Zone, Zhengzhou, Henan Province, 450000 Patentee before: ZHENGZHOU JIACHEN ELECTRIC Co.,Ltd. |