CN109787596B - Overcurrent protection circuit, switching tube driving circuit and electric equipment - Google Patents
Overcurrent protection circuit, switching tube driving circuit and electric equipment Download PDFInfo
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Abstract
The utility model provides an overcurrent protection circuit of switch tube circuit, includes the switch tube and is used for the drive signal source of switch tube break-make, overcurrent protection circuit is including first diode and judgement module, and overcurrent protection circuit is through adding judgement module and first diode, and the level of drive signal source output is greater than first threshold or switch tube's on-current is greater than the second threshold and turn off the switch tube, realizes the function of instant turn-off switch tube through hardware circuit, and then improves the corresponding speed to the protection of switch tube, has solved the protection mechanism singleness, the complex process and the slow problem of protection speed that exists among the traditional technical scheme.
Description
Technical Field
The invention belongs to the technical field of overcurrent protection, and particularly relates to an overcurrent protection circuit of a switching tube circuit, a switching tube driving circuit and electric equipment.
Background
At present, the traditional switching tube is generally controlled by software, for example, a circuit current is transmitted to an MCU through AD sampling, the MCU calculates, and then the PWM (Pulse Width Modulation, pulse modulation width) output is controlled according to the calculation result, so that the switching tube is controlled to be turned on or off, the protection mechanism is single, and the switching tube is turned off only after the switching tube is over-current in the control mode through AD sampling of the current, software calculation and PWM output adjustment, so that the process is complex and the protection speed is slow.
Therefore, the traditional technical scheme has the problems of single protection mechanism, complex process and low protection speed.
Disclosure of Invention
In view of the above, the embodiment of the invention provides an overcurrent protection circuit of a switching tube circuit, a switching tube driving circuit and electric equipment, which aim to solve the problems of single protection mechanism, complex process and low protection speed in the traditional technical scheme.
A first aspect of an embodiment of the present invention provides an electric apparatus, including a motor, and further including a switching tube driving circuit, where the switching tube is used to drive the motor.
The second aspect of the embodiment of the present invention provides the above-mentioned switching tube driving circuit, which includes an overcurrent protection circuit, a driving signal source, a switching tube, a load and a second power supply, wherein the driving signal source is connected with a control end of the switching tube, and the driving signal source includes:
the second power supply, the load and the switching tube are sequentially connected to the ground in series; or (b)
The second power supply, the switching tube and the load are sequentially connected to the ground in series.
A third aspect of the embodiments of the present invention provides an overcurrent protection circuit, configured to prevent an overcurrent of a switching tube circuit, where the switching tube circuit includes a switching tube and a driving signal source for driving the switching tube to be turned on or turned off, and the overcurrent protection circuit includes:
the negative electrode of the first diode is connected with the input end or the output end of the switch tube;
the first input end of the judging module is connected with a reference signal, the second end of the judging module is connected with the positive electrode of the first diode and the driving signal source, and the judging module is configured to output a control signal to turn off the driving signal received by the control end of the switching tube when the level of the driving signal output by the driving signal source is larger than a first threshold value or the on current of the switching tube is larger than a second threshold value.
In one embodiment, the judging module includes a first resistor, a first capacitor and a voltage comparator, wherein a first end of the first resistor is connected with the driving signal source, a second end of the first resistor, a first end of the first capacitor and a first input end of the voltage comparator are connected with an anode of the first diode, a second end of the first capacitor is grounded, and a second input end of the voltage comparator is connected with the reference signal.
In one embodiment, the judging module further includes a third resistor, a first end of the third resistor is connected to the positive electrode of the first diode, and a second end of the third resistor is connected to the second end of the first resistor, the first end of the first capacitor, and the first input end of the voltage comparator.
In one embodiment, the device further comprises a reference signal output module for generating the reference signal, wherein an input end of the reference signal output module is connected with a first power supply, and an output end of the reference signal output module is connected with a first input end of the judging module.
In one embodiment, the reference signal output module includes a fourth resistor and a fifth resistor, the first end of the fourth resistor is connected to the second power supply, the second end of the fourth resistor and the first end of the fifth resistor are connected to the second input end of the judging module, and the second end of the fifth resistor is grounded.
In one embodiment, an output end of the judging module is connected with the driving signal source, and the driving signal source receives the control signal.
In one embodiment, the device further comprises a switch module, wherein a control end of the switch module is connected with an output end of the judging module and is connected between the driving signal source and the control end of the switch tube, and the switch module is configured to control on-off of the driving signal according to a control signal output by the judging module.
In one embodiment, the switch module includes a second resistor and a power switch tube, a control end of the power switch tube is connected to a control end of the switch module through the second resistor, an input end of the power switch tube is connected between the driving signal source and the control end of the switch tube, and an output end of the power switch tube is grounded.
According to the overcurrent protection circuit of the switching tube circuit, the judging module and the first diode are added, when the level of a driving signal output by the driving signal source is larger than the first threshold value or the on current of the switching tube is larger than the second threshold value, the switching tube is turned off, the function of immediately turning off the switching tube is realized through the hardware circuit, the corresponding speed of protection of the switching tube is further improved, and the problems of single protection mechanism, complex process and low protection speed in the traditional technical scheme are solved.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments or the description of the prior art will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic circuit diagram of a switching tube driving circuit according to an embodiment of the present invention;
fig. 2 is a schematic circuit diagram of a switching tube driving circuit according to another embodiment of the present invention;
fig. 3 is a schematic circuit diagram of a switching tube driving circuit according to another embodiment of the present invention;
fig. 4 is a schematic circuit diagram of an overcurrent protection circuit of a switching tube circuit according to an embodiment of the present invention;
fig. 5 is a schematic circuit diagram of an overcurrent protection circuit of a switching tube circuit according to another embodiment of the present invention;
fig. 6 is a schematic circuit diagram of an overcurrent protection circuit of a switching tube circuit according to another embodiment of the present invention;
fig. 7 is a schematic circuit diagram of an overcurrent protection circuit of a switching tube circuit according to another embodiment of the present invention;
FIG. 8 is a schematic diagram of an exemplary circuit of a determination module in the over-current protection circuit of the switching tube circuit shown in FIG. 4;
FIG. 9 is a schematic diagram of another example circuit of the determination module in the over-current protection circuit of the switching tube circuit shown in FIG. 4;
fig. 10 is a schematic circuit diagram of an overcurrent protection circuit of a switching tube circuit according to another embodiment of the present invention;
FIG. 11 is a schematic circuit diagram of an example reference signal output module in the over-current protection circuit of the switching tube circuit shown in FIG. 10;
fig. 12 is a schematic circuit diagram of an overcurrent protection circuit of a switching tube circuit according to another embodiment of the present invention;
fig. 13 is a schematic circuit diagram of an overcurrent protection circuit of a switching tube circuit according to another embodiment of the present invention;
FIG. 14 is an exemplary circuit schematic of a switch module in the over-current protection circuit of the switching tube circuit shown in FIG. 13;
fig. 15 is a schematic circuit diagram of an overcurrent protection circuit of a switching tube circuit according to another embodiment of the present invention;
fig. 16 is a schematic circuit diagram of an overcurrent protection circuit of a switching tube circuit according to another embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
The first embodiment of the invention provides electric equipment, which comprises a motor and further comprises a switching tube driving circuit, wherein the switching tube is used for driving the motor.
Referring to fig. 1 and 2, a switching tube driving circuit according to a second embodiment of the present invention includes an over-current protection circuit 200, a driving signal source 101, a switching tube 102, a load 103, and a power source 104, where the over-current protection circuit 200 is configured to turn off the switching tube 102 when a level of a driving signal output by the driving signal source 101 is greater than a first threshold value or an on current of the switching tube 102 is greater than a second threshold value, and it is understood that the load may be a non-power generating device or equipment such as a resistor, a brake module, etc., where:
in one embodiment, referring to fig. 1, the power source 104, the load 103, and the switching tube 102 are sequentially connected in series to ground.
In one embodiment, referring to fig. 2, the power source 104, the switching tube 102, and the load 103 are sequentially connected in series to ground.
In one embodiment, referring to fig. 3, the power source 104, the load 103, the switching tube 102, and the voltage dividing module 105 are sequentially connected in series to the ground, and may be formed of a device having a voltage dividing function, such as a resistor or a potentiometer.
It should be understood that the switching tube driving circuit of the present embodiment includes at least one switching tube, and when N switching tubes are included, the switching tube driving circuit correspondingly includes N overcurrent protection circuits.
In the embodiment, by adding the overcurrent protection circuit, the overcurrent protection of the switching tube can be realized without software and only through hardware feedback, so that the corresponding speed of the protection of the switching tube is improved, and the problems of complex process and low protection speed in the traditional technical scheme are solved.
Referring to fig. 4, a circuit schematic of an overcurrent protection circuit of a switching tube circuit is provided in a third embodiment of the present invention, and for convenience of explanation, only the portions related to the present embodiment are shown in detail as follows:
in one embodiment, the overcurrent protection circuit of the switching tube circuit includes a switching tube 102 and a driving signal source 101 for driving the switching tube 102 to be turned on or off, where a control end of the switching tube 102 is connected to the driving signal source 101, and the switching tube 102 may be formed of a three-terminal switching tube or a switching tube chip, such as a MOS tube, an IGBT thyristor or a triode, which has a function of controlling the on or off of the circuit, for convenience of understanding, for example: when the switching tube 102 is an NMOS tube, the grid electrode of the NMOS tube is the control end of the switching tube 102, the drain electrode of the NMOS tube is the input end of the switching tube 102, and the source electrode of the NMOS tube is the output end of the switching tube 102; when the switch tube 102 is a PMOS tube, the gate of the PMOS tube is the control end of the switch tube 102, the source of the PMOS tube is the input end of the switch tube 102, the drain of the PMOS tube is the output end of the switch tube 102, and the like when other devices are selected.
The overcurrent protection circuit includes a diode D1 and a determination module 210, where the cathode of the diode D1 is connected to the input end or the output end of the switching tube 102, the first input end of the determination module 210 is connected to a reference signal, the second end of the determination module 210 is connected to the anode of the diode D1 and the driving signal source 101, the overcurrent protection circuit uses unidirectional conductivity of the diode D1 to avoid that the current of the switching tube circuit flows to the second end of the determination module 210 of the overcurrent protection circuit, so as to affect the determination of the determination module 210, the determination module 210 is configured to output a control signal to turn off the driving signal received by the control end of the switching tube 102 when the level of the driving signal outputted by the driving signal source 101 is greater than a first threshold value or the on current of the switching tube 102 is greater than a second threshold value, and the determination module 210 may be composed of a device capable of comparing the voltage of the two input ends and outputting different level signals according to the comparison result, for example, a voltage comparator or a microprocessor, a resistor or a capacitor, etc., it should be understood that the driving signal and the reference signal may be the level signal according to the preset maximum value and the driving signal.
According to the overcurrent protection circuit in the embodiment of the invention, whether the voltage value between the input end and the output end of the switching tube 102 exceeds the design threshold value or not is monitored in real time when the switching tube 102 is in the on operation, so that whether the current value flowing through the switching tube 102 exceeds the maximum current value specified by the design or not is judged, and the switching tube 102 which is opened is kept to be opened or closed through hardware feedback. When the switching tube 102 is not opened, the feedback signal does not influence the on-off control of the driving system on the switching tube 102; when the system works normally, the switching tube 102 is in an on state, and the feedback signal does not influence the on-off control of the driving system on the switching tube 102; when the system is in an abnormal working state, for example, the upper bridge arm and the lower bridge arm of the driving system are simultaneously conducted, the braking resistor is short-circuited, and the like, so that the voltage value between the input end and the output end of the switching tube 102 exceeds a design threshold value, and when the input end and the output end of the switching tube 102 are normally opened and working, the internal resistance value can be known from a specification, and according to the formula i=u/R, the current value flowing through the switching tube 102 can be judged to exceed the maximum threshold value of the design current accordingly, so that the switching tube 102 can be turned off in time without software control by a hardware feedback signal, and the circuit safety is timely protected.
Referring to fig. 1 and 5, in one embodiment, when the power source 104, the load 103, and the switching tube 102 are sequentially connected in series to the ground, that is, when the output end of the switching tube 102 is directly grounded, the cathode of the diode D1 is connected to the input end of the switching tube 102, the first input end of the judging module 210 is connected to the reference signal, and the second end of the judging module 210 is connected to the anode of the diode D1 and the driving signal source 101, which operates as follows: when the switching tube circuit does not work, that is, when the driving signal source 101 outputs a low level, the switching tube 102 is in an off state, the second end level of the judging module 210 is 0, the first end level of the judging module 210 is a preset reference level Uref, the preset reference level Uref is debugged into the normal working voltage of the switching tube circuit, and at the moment, the first end level of the judging module 210 is greater than the second end level, so that the driving signal received by the control end capable of closing the switching tube 102 is not output; when the switching tube circuit works normally, the driving signal source 101 outputs a high level, the switching tube 102 is conducted, and at the moment, the voltage sum of the switching tube 102 and the voltage of the diode D1 is smaller than or equal to a reference level Uref by debugging; when the switching tube circuit is not operating normally, for example, the driving signal output by the driving signal source 101 is greater than the level that should be output in advance or the voltage of the switching tube 102+the voltage of the diode D1 is greater than the reference level Uref, the judging module 210 outputs a control signal to turn off the driving signal received by the control terminal of the switching tube 102.
Referring to fig. 2 and 6, in one embodiment, when the power supply 104, the switching tube 102, and the load 103 are sequentially connected in series to the ground, that is, when the output terminal of the switching tube 102 is grounded via the load 103, the cathode of the diode D1 is connected to the output terminal of the switching tube 102, the first input terminal of the judging module 210 is connected to the reference signal, and the second terminal of the judging module 210 is connected to the anode of the diode D1 and the driving signal source 101, which operates as follows: when the switching tube circuit does not work, that is, when the driving signal source 101 outputs a low level, the switching tube 102 is in an off state, the second end level of the judging module 210 is 0, the first end level of the judging module 210 is a preset reference level Uref, the preset reference level Uref is debugged into the normal working voltage of the switching tube circuit, and at the moment, the first end level of the judging module 210 is greater than the second end level, so that the driving signal received by the control end capable of closing the switching tube 102 is not output; when the switching tube circuit works normally, the driving signal source 101 outputs a high level, the switching tube 102 is conducted, and the voltage of the diode D1 and the voltage of the load 103 are debugged at the moment so that the added value of the voltage is smaller than or equal to a reference level Uref; when the switching tube circuit is not operating normally, for example, the driving signal output by the driving signal source 101 is greater than the level that should be output originally preset or the value of the sum of the voltage of the diode D1 and the voltage of the load 103 is greater than the reference level Uref when the switching tube circuit is over-current due to other problems, the judging module 210 outputs the driving signal that the control signal turns off the control end of the switching tube 102.
Referring to fig. 3 and fig. 7, in one embodiment, when the power source 104, the load 103 and the switching tube 102 are sequentially connected in series, and the output end of the switching tube 102 is grounded through the voltage dividing module 105, the cathode of the diode D1 is connected to the output end of the switching tube 102, the first input end of the judging module 210 is connected to the reference signal, and the second end of the judging module 210 is connected to the anode of the diode D1 and the driving signal source 101, and the working principle thereof can refer to the previous embodiment.
Referring to fig. 8, in one embodiment, the determining module 210 includes a first resistor R1, a first capacitor C1, and a voltage comparator U1, where a first end of the first resistor R1 is connected to the driving signal source 101, a second end of the first resistor R1, a first end of the first capacitor C1, and a first input end of the voltage comparator U1 are connected to the positive electrode of the diode D1, a second end of the first capacitor C1 is grounded, and a second input end of the voltage comparator U1 is connected to the reference signal, and it is understood that in this embodiment, the values of the first resistor R1 and the first capacitor C1 may be adjusted or the first resistor R1 and the first capacitor C1 may be selected as appropriate according to the actual need, so that the first input end level of the voltage comparator U1 is not higher than the reference signal during normal operation of the switching tube 102 (from cut-off to full conduction period), and the charging characteristic of the first input end of the voltage comparator U1 is avoided.
Referring to fig. 9, in an embodiment, the determining module 210 further includes a third resistor R3, a first end of the third resistor R3 is connected to the anode of the diode D1, and a second end of the third resistor R3 is connected to the second end of the first resistor R1, the first end of the first capacitor C1, and the first input end of the voltage comparator U1.
Referring to fig. 10, in one embodiment, the over-current protection circuit further includes a reference signal output module 230 for generating a reference signal, an input terminal of the reference signal output module 230 is connected to the first power supply, and an output terminal of the reference signal output module 230 is connected to the first terminal of the determination module 210.
Referring to fig. 11, in an embodiment, the reference signal output module 230 includes a fourth resistor R4 and a fifth resistor R5, the first end of the fourth resistor R4 is connected to the power source 104, the second end of the fourth resistor R4 and the first end of the fifth resistor R5 are commonly connected to the second input end of the determination module 210, and the second end of the fifth resistor R5 is grounded.
Referring to fig. 12, in one embodiment, the output end of the determining module 210 is connected to the driving signal source 101, it should be understood that the driving signal source 101 may be formed by a driving chip, and the control signal output by the determining module 210 is directly sent to the driving signal source 101, so that the driving signal source 101 stops outputting the driving signal or outputs a low level, and then turns off the switching tube 102.
Referring to fig. 13, in an embodiment, the overcurrent protection circuit further includes a switch module 220, where the switch module 220 is configured to be turned on or off according to a control signal output by the judging module 210, so that the switch tube 102 is turned off or on, the switch module 220 may be formed by a device having a function of being turned on or off according to a control signal, such as the switch tube 102 or a switch chip, a control end of the switch module 220 is connected to an output end of the judging module 210, an input end of the switch module 220 is connected to a control end of the switch tube 102, and an output end of the switch module 220 is grounded.
Referring to fig. 14, in one embodiment, the switch module 220 includes a second resistor R2 and a power switch Q2, the control end of the power switch Q2 is connected to the control end of the switch module 220 through the second resistor R2, the input end of the power switch Q2 is connected between the driving signal source 101 and the control end of the switch Q1, the output end of the power switch Q2 is grounded, and the power switch Q2 can select different power switch devices according to the type of the switch Q1 and the type of the voltage comparator.
For easy understanding, taking the switch tube Q1 as an NMOS tube, the power switch tube Q2 as a triode, the selection of the power switch tube Q2 is illustrated as follows:
when the first input end of the voltage comparator U1 is a negative phase input end and the second input end of the voltage comparator U1 is a positive phase input end, the power switch Q2 should select a PNP triode, and at this time, the working principle is as follows: when the negative phase input end voltage of the voltage comparator U1 is smaller than the input end voltage of Yu Zhengxiang, namely when the current does not exceed the threshold value, the voltage comparator U1 outputs a high level, and at the moment, the power switch tube Q2 is not conducted, and the original switch tube circuit operates normally; when the voltage of the negative phase input end of the voltage comparator U1 is larger than that of the positive phase input end, namely when the current exceeds a threshold value, the voltage comparator U1 outputs a low level, and at the moment, the power switching tube Q2 is turned on, so that the switching tube Q1 is turned off timely;
when the first input end of the voltage comparator U1 is a positive phase input end and the second input end of the voltage comparator U1 is a negative phase input end, the power switch Q2 should select NPN triode, and at this time, the working principle is as follows: when the voltage of the positive phase input end of the voltage comparator U1 is smaller than that of the negative phase input end, namely when the current does not exceed a threshold value, the voltage comparator U1 outputs a low level, at the moment, the power switch tube Q2 is not conducted, and the original switch tube circuit operates normally; when the voltage of the positive phase input end of the voltage comparator U1 is larger than that of the negative phase input end, namely when the current exceeds a threshold value, the voltage comparator U1 outputs a high level, and the power switch tube Q2 is turned on at the moment, so that the switch tube Q1 is turned off timely.
It should be understood that the same shall apply when other types of switching tubes Q2 are selected.
Referring to fig. 15, taking one embodiment as an example, the working principle of the over-current protection circuit is described in detail, where the switching tube circuit includes a driving signal source 101, a switching tube Q1, a resistor R6, a load 103 and a power VCC1, the over-current protection circuit includes a diode D1, a judging module 210 and a switching module 220, the first power VCC1 is assumed to be 24V, the second power VCC2 is assumed to be 15V, the on level of the driving signal source 101 driving the switching tube Q1 is drive_g=15v, the specification of the switching tube Q1 can accurately know that the on internal resistance of D-S is R (Q1), the on time of the switching tube is t seconds by combining the condition of a gate resistor R6, the reference level Uref of the second input end of the voltage comparator U1 is 15v×r5/(r4+r5), and the resistance value of R3 is assumed to be 0 ohm (in practical application, the designer can accurately know that the on voltage drop of the diode D1 is the specification of the diode D1 according to design threshold requirement).
When the driving signal source 101 outputs a low level, the switching tube Q1 is in an off state, and at this time, the level of the first input end of the voltage comparator U1 is 0V, the level of the second input end of the voltage comparator U1 is 15v×r5/(r4+r5), the level of the second input end of the voltage comparator U1 is greater than the level of the first input end of the voltage comparator U1, and then the output end of the voltage comparator U1 outputs a high level 15V, the switching tube Q2 is not turned on, and the switching tube Q1 is kept in the off state.
When the driving signal source 101 outputs a 15V level, assuming that the moment when the driving signal source 101 starts outputting a high level is t0, the values of the resistor R1, the capacitor C1, the resistor R4, and the resistor R5 suitable for verification are selected respectively, so that the switching tube Q1 completes the switching-on process completely within the time t0 to t0+t (the time period is the time period from the off to the on of the switching tube Q1, the drain C of the switching tube Q1 is kept at a high level), the charging voltage Ut < [15v×r5/(r4+r5) ] at the first input terminal of the voltage comparator U1, the value of the first input terminal Ut of the voltage comparator U1 can be calculated by the RC charging and discharging formula (ut=0v+ (15V-0v) [1-exp (-t/(r1×c1)) ]), and after the time t0+t, the maximum current value through the switching tube Q1 is assumed to be I (Q1), the current value is designed by a designer according to different I (Q1), the value is usually selected by a designer, the switching tube Q1 is required to be a suitable for verification according to the different I (Q1) and Q1, and the value is required to be selected according to the different values (I1): [ I (Q1) ×R (Q1) +U (D1) ]. Ltoreq.15V×R5/(R4+R5) ], and when the value I of the current flowing through the switching tube Q1 is greater than I (Q1), the following voltage relationship exists in the whole circuit: when the driving signal source is driven normally, the current value flowing through the switching tube Q1 is smaller than or equal to I (Q1), at the moment, the second input end of the voltage comparator U1 is larger than the first input end level of the voltage comparator U1, the output end of the voltage comparator U1 outputs high level 15V, the switching tube Q2 is not conducted, and the switching tube Q1 is kept in an on state.
When the driving signal source 101 generates a driving signal and the value I of the current flowing through the switching tube Q1 is greater than the design threshold I (Q1) of the designer, for abnormal driving of the driving signal source, there is a relationship in the above analysis: and the second input end of the voltage comparator U1 is smaller than the first input end level of the voltage comparator U1, the output end of the voltage comparator U1 outputs low level, Q4 is conducted to be in a saturated on state, the grid electrode of the switching tube Q1 is pulled to be in low level, and therefore the switching tube Q1 is turned off, further increase of the current value of the switching tube Q1 is avoided, the timely protection switching tube Q1 is burnt out, and reliability and safety of a switching tube circuit are greatly improved.
According to the scheme, the maximum current value flowing through the switching tube can be designed according to actual application requirements, different switching tubes, diodes and resistor configurations are selected and verified through a data manual of the device, and therefore when the current flowing through the switching tube is larger than a design threshold value, the switching tube is turned off through a hardware feedback signal, and the reliability and the safety of a switching tube circuit are improved.
Referring to fig. 16, taking another embodiment as an example, the working principle of the overcurrent protection circuit is described in detail, where the switching tube circuit includes a driving signal source 101, a switching tube Q1, a resistor R6, a load 103, a resistor R7 and a power supply VCC1, for convenience in calculation and understanding, where the resistor R7 may be used as a voltage dividing module 105 or another load, an output end of the switching tube Q1 is grounded via the resistor R7, the overcurrent protection circuit includes a diode D1, a judging module 210 and a switching module 220, assuming that the first power supply VCC1 is 24V, the second power supply VCC2 is 15V, an on level of the driving signal source 101 driving the switching tube Q1 is drive_g=15v, and under a condition of 15V driving level, a conduction internal resistance of D-S is R (Q1), and a condition of a gate resistor R6 is combined, and a turn-on time is t seconds, and a reference level U of a second input end of the voltage ref is 15×r5/(R4+r5), and a value of the resistor is designed as a practical value, and the resistor is designed according to the practical requirement; the specification of the diode D1 can accurately know that the conduction tube voltage drop of the diode D1 is U (D1).
When the driving signal source 101 outputs a low level, the switching tube Q1 is in an off state, and at this time, the level of the first input end of the voltage comparator U1 is 0V, the level of the second input end of the voltage comparator U1 is 15v×r5/(r4+r5), the level of the second input end of the voltage comparator U1 is greater than the level of the first input end of the voltage comparator U1, and then the output end of the voltage comparator U1 outputs a high level 15V, the switching tube Q2 is not turned on, and the switching tube Q1 is kept in the off state.
When the driving signal source 101 outputs a level of 15V, assuming that the moment when the driving signal source 101 starts outputting a high level is t0, the values of the resistor R1, the capacitor C1, the resistor R4, and the resistor R5 are selected to be suitable for verification, respectively, so that the switching tube Q1 completes the switching-on process completely within the time t0 to t0+t (the time period is the time period from the off to the on of the switching tube Q1, the drain C of the switching tube Q1 is kept at a high level), the charging voltage Ut < [15v×r5/(r4+r5) ] of the first input terminal of the voltage comparator U1, the value of the first input terminal voltage Ut of the voltage comparator U1 can be calculated by the RC charging and discharging formula (ut=0v+ (15V-0V) [1-exp (-t/(R1×c1)) ], and thereafter, assuming that the maximum current value through the switching tube Q1 is equal to the maximum current value through the resistor R7 is I (R7), the value of the first input terminal voltage Ut of the voltage comparator U1 can be selected to be suitable for verification according to the different values of the resistor R7, and the current value of the resistor R1 can be selected according to the different values of the current values (R7, the current value of the resistor R1 and the resistor R1 is selected to be suitable for verification): [ I (R7) R (R7) +U (D1) ]. Ltoreq.15V.R5/(R4+R5) ], and when the value of the current I flowing through the resistor R7 is greater than I (Q1), the relationship exists: [ R7+U (D1) ] > 15V R5/(R4+R5) ]; when the driving signal source 101 drives normally, the current value flowing through the switching tube Q1 is less than or equal to I (R7), and at this time, the second input end of the voltage comparator U1 is greater than the first input end level of the voltage comparator U1, and then the output end of the voltage comparator U1 outputs a high level 15V, the switching tube Q2 is not turned on, and the switching tube Q1 maintains an on state.
When the driving signal source 101 generates the driving signal and the current value I flowing through the switching tube Q1 is greater than the design threshold value I (R7) of the designer, for abnormal braking (such as the driving signal source outputs an abnormal driving signal or the braking system is short-circuited to cause the damage to the system caused by the current of the braking system), there is a relationship in the analysis: and the second input end of the voltage comparator U1 is smaller than the first input end level of the voltage comparator U1, the output end of the voltage comparator U1 outputs low level, Q4 is conducted to be in a saturated on state, the grid electrode of the switching tube Q1 is pulled to be in low level, the switching tube Q1 is turned off, further increase of the current value of the switching tube Q1 is avoided, the timely protection switching tube Q1 is burnt out, and reliability and safety of a switching tube circuit are greatly improved.
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, and alternatives falling within the spirit and principles of the invention.
Claims (9)
1. An overcurrent protection circuit of a switching tube circuit, the switching tube circuit includes a switching tube and a driving signal source for driving the switching tube to be turned on and off, the overcurrent protection circuit includes:
the negative electrode of the first diode is connected with the input end or the output end of the switch tube;
the first input end of the judging module is connected with a reference signal, the second end of the judging module is connected with the positive electrode of the first diode and the driving signal source, and the judging module is configured to output a control signal to turn off the driving signal received by the control end of the switching tube when the level of the driving signal output by the driving signal source is greater than a first threshold value;
the judging module comprises a first resistor, a first capacitor, a third resistor and a voltage comparator, wherein the first end of the first resistor is connected with the driving signal source, the second end of the first resistor, the first end of the first capacitor and the first input end of the voltage comparator are connected with the positive electrode of the first diode, the second end of the first capacitor is grounded, the second input end of the voltage comparator is connected with the reference signal, the first end of the third resistor is connected with the positive electrode of the first diode, and the second end of the third resistor is connected with the second end of the first resistor, the first end of the first capacitor and the first input end of the voltage comparator.
2. The overcurrent protection circuit of claim 1, wherein the determination module is further configured to output a control signal to turn off the drive signal received by the control terminal of the switching tube when the on-current of the switching tube is greater than a second threshold.
3. The overcurrent protection circuit according to claim 1 or 2, further comprising a reference signal output module for generating the reference signal, wherein an input terminal of the reference signal output module is connected to the first power supply, and an output terminal of the reference signal output module is connected to the first input terminal of the determination module.
4. The overcurrent protection circuit of claim 3, wherein the reference signal output module comprises a fourth resistor and a fifth resistor, the first end of the fourth resistor is connected to the second power supply, the second end of the fourth resistor and the first end of the fifth resistor are commonly connected to the second input end of the judging module, and the second end of the fifth resistor is grounded.
5. The overcurrent protection circuit according to claim 1 or 2, wherein an output terminal of the judging module is connected to the driving signal source, and the driving signal source receives the control signal.
6. The overcurrent protection circuit according to claim 1 or 2, further comprising a switching module, wherein a control end of the switching module is connected to an output end of the judging module and is connected between the driving signal source and the control end of the switching tube, and the switching module is configured to control on-off of the driving signal according to a control signal output by the judging module.
7. The overcurrent protection circuit of claim 6, wherein the switching module comprises a second resistor and a power switching tube, a control end of the power switching tube is connected to a control end of the switching module through the second resistor, an input end of the power switching tube is connected between the driving signal source and the control end of the power switching tube, and an output end of the power switching tube is grounded.
8. A switching tube driving circuit, comprising the overcurrent protection circuit of any one of claims 1-7, a driving signal source, a switching tube, a load and a second power supply, wherein the driving signal source is connected with a control end of the switching tube, and the switching tube driving circuit comprises:
the second power supply, the load and the switching tube are sequentially connected to the ground in series; or (b)
The second power supply, the switching tube and the load are sequentially connected to the ground in series.
9. An electrically powered device comprising an electric motor, further comprising the switching tube drive circuit of claim 8, the switching tube being configured to drive the electric motor.
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| CN110368176B (en) * | 2019-07-24 | 2021-08-20 | 郑州大学第一附属医院 | Thermotherapy device for rheumatism and immunity department |
| CN112448702A (en) * | 2020-10-22 | 2021-03-05 | 珠海格力电器股份有限公司 | Drive protection circuit and method and electrical equipment |
| CN112345908B (en) * | 2020-10-27 | 2021-07-27 | 郑州嘉晨电器有限公司 | Current detection circuit of power switch tube |
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