CN211018790U - Low-side electronic switch circuit - Google Patents
Low-side electronic switch circuit Download PDFInfo
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- CN211018790U CN211018790U CN202020432729.7U CN202020432729U CN211018790U CN 211018790 U CN211018790 U CN 211018790U CN 202020432729 U CN202020432729 U CN 202020432729U CN 211018790 U CN211018790 U CN 211018790U
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Abstract
The utility model provides a low-side electronic switch circuit, which comprises a field effect transistor, a triode, a first resistor, a second resistor, a third resistor and a fourth resistor; the grid electrode of the field effect transistor is respectively connected with one end of the first resistor and the collector electrode of the triode, the drain electrode of the field effect transistor is respectively connected with one end of an external load and one end of the fourth resistor, and the source electrode of the field effect transistor is respectively connected with one end of the second resistor and one end of the third resistor; the other end of the first resistor is connected with the output end of the microprocessor; the base electrode of the triode is connected with one end of the second resistor; the other end of the third resistor is respectively connected with the other end of the fourth resistor and an analog converter of the microprocessor; the utility model can conveniently set the protection current by adjusting the resistance value of the second resistor; the hard protection is provided, so that the low-side electronic switch can be effectively prevented from being damaged before being turned off; it is possible to diagnose whether the external load is normal or open/short to ground, and the external load voltage before turning on.
Description
Technical Field
The utility model relates to an overcurrent detection and protection circuit especially indicates a diagnosable load is opened a way, the load overflows to can provide a low limit electronic switch circuit of quick protection.
Background
With the development of electronic technology, customers put higher demands on the diagnosis and protection functions of circuits; when the external load is short-circuited to the power supply, the internal driving circuit is not damaged, and can be diagnosed in time for further processing such as load shutdown and warning message sending.
The low-side electronic switch circuits commonly used at present include the following:
the first is various special electronic switch driving chips with temperature protection and current detection, when an external load is short-circuited, the temperature of the chip begins to rise, the chip is automatically disconnected from the driving when the temperature is high to a certain degree, and the chip is automatically started when the chip is cooled down, so that the operation is repeated repeatedly, and the chip fails until the operation is circulated for a certain number of times; if the chip has a fault output or a diagnostic circuit is added outside, the output can be switched off after the fault occurs so as to protect the chip; the chip has higher cost, and the chip can not realize higher current detection precision in places needing higher current detection, such as soft short circuit and the like; the second one is to connect a resistor with smaller resistance value in series with the electronic switch, and the microprocessor detects the voltage on the resistor to judge the state of the load; when the load is short-circuited to cause overcurrent, the microprocessor can turn off the electronic switch to protect the switch, but when the load is short-circuited, the delay from the microprocessor detecting the current to the turning off of the switch can cause damage or direct damage of the electronic switch.
SUMMERY OF THE UTILITY MODEL
In view of the above shortcoming of the prior art, an object of the utility model is to provide a low limit electronic switch circuit for it is with high costs, low to detect the precision to overflow to detect among the solution prior art, causes the problem of electronic switch damage easily.
In order to achieve the above object, the present invention provides a low-side electronic switch circuit, which comprises a field effect transistor, a triode, a first resistor, a second resistor, a third resistor and a fourth resistor; a grid electrode of the field effect transistor is respectively connected with one end of the first resistor and a collector electrode of the triode, a drain electrode of the field effect transistor is respectively connected with one end of an external load and one end of the fourth resistor, and a source electrode of the field effect transistor is respectively connected with a first end of the second resistor and one end of the third resistor; the other end of the first resistor is connected with the output end of the microprocessor; the emitting electrode of the triode is grounded, and the base electrode of the triode is connected with the first end of the second resistor; the other end of the external load is connected with a load power supply; the other end of the third resistor is respectively connected with the other end of the fourth resistor and an analog converter of the microprocessor; and the second end of the second resistor is grounded.
In an embodiment of the present invention, the field effect transistor is a metal-oxide semiconductor field effect transistor; the triode is an NPN triode.
As described above, the low-side electronic switch circuit of the present invention has the following beneficial effects:
(1) the protection current can be conveniently set by adjusting the resistance value of the second resistor;
(2) the low-side electronic switch circuit provides hard protection, and can effectively prevent the low-side electronic switch from being damaged before being turned off;
(3) before the low-side electronic switch circuit is started, whether the external load is normal or open/short-circuited to the ground or not and the voltage of the external load can be diagnosed;
(4) with only one analog input port, the microprocessor can diagnose the load current and the voltage sustained on the electronic switch in an abnormal state.
Drawings
Fig. 1 is a schematic structural diagram of a low-side electronic switching circuit according to the present invention.
Detailed Description
The following description is provided for illustrative embodiments of the present invention, and other advantages and effects of the present invention will be readily apparent to those skilled in the art from the disclosure herein. The present invention can also be implemented or applied through other different specific embodiments, and various details in the present specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It is to be noted that the features in the following embodiments and examples may be combined with each other without conflict.
It should be noted that the drawings provided in the following embodiments are only for illustrating the basic idea of the present invention, and the drawings only show the components related to the present invention rather than being drawn according to the number, shape and size of the components in actual implementation, and the form, amount and ratio of the components in actual implementation can be changed at will, and the layout of the components may be more complicated.
The utility model provides a can the short-circuit protection of quick response, save microprocessor port resource, can provide the low limit electronic switch circuit that the soft short circuit of load open circuit detected.
The low-side electronic switch circuit of the present invention will be explained in detail with reference to the drawings.
As shown in fig. 1, in an embodiment, the low-side electronic switch circuit of the present invention includes a field effect transistor Q1, a transistor Q2, a first resistor R1, a second resistor R2, a third resistor R3, and a fourth resistor R4.
A gate of the field effect transistor Q1 is connected to one end of the first resistor R1 and a collector of the triode Q2, a drain of the field effect transistor Q1 is connected to one end of an external load Rload and one end of the fourth resistor R4, and a source of the field effect transistor Q1 is connected to a first end of the second resistor R2 and one end of the third resistor R3; the other end of the first resistor R1 is connected with an output end MCU _ output of the microprocessor; the emitter of the triode Q2 is grounded, and the base of the triode Q2 is connected with the first end of the second resistor R2; the other end of the external load Rload is connected with a load power supply Vload; the other end of the third resistor R3 is respectively connected with the other end of the fourth resistor R4 and an analog converter MCU _ ADC of the microprocessor; the second end of the second resistor R2 is grounded.
It should be noted that the output terminal of the fet is connected to the high-side switch of the load, and the output terminal of the fet is connected to the low-side switch of the ground.
The working principle of the low-side electronic switching circuit is as follows:
in the low-side electronic switch circuit, the field effect transistor Q1 is a low-side electronic switch for driving an external load Rload, and when the output of the microprocessor is high level, that is, the MCU _ output end outputs high level, the field effect transistor Q1 is turned on, and the external load Rload operates; the second resistor R2 is a current detection resistor, generally ranging from several ohms to several tens of ohms, which should be much larger than the on-resistance Rdson of the field effect transistor Q1; the combination of the transistor Q2 and the first resistor R1 and the second resistor R2 is used to set the drain of the fet Q1 to provide a fast-responding current limit when the external load Rload is shorted to the load power Vload, and to prevent the fet Q1 from being damaged by excessive current in a short time, and the set hard current limit value is Vbe/R2 (Vbe is the voltage difference between the base and the emitter of the transistor Q2), because the voltage of Vbe has a large range of variation, and the resistance value of R2 is selected to make the Vbemin/R2 slightly larger than the maximum current value of the external load Rload during normal operation; the third resistor R3 and the fourth resistor R4 are typically in the range of tens of kiloohms.
When the load current Iload is in a normal range, the field effect transistor Q1 is completely conducted, the voltage detected by an analog converter MCU _ ADC of the microprocessor is Iload × [ R2+ Rdson × R3/(R3 + R4) ], the detected voltage is approximately equal to Iload × R2 when the on-resistance Rdson of the fet Q1 is far smaller than the second resistor R2, when the external load Rload is in a soft short circuit and the load current Iload does not cause the action of the triode Q2, the microprocessor can easily diagnose the state of the external load Rload through the voltage on the second resistor R2, when the external load Rload is in an abnormal state and the load current is larger, the triode Q2 starts to be conducted, the collector of the triode Q2 limits the grid voltage of the field effect transistor Q1 so that the vdf Q1 is in a state, the voltage difference between the drain and the source of the field effect transistor Q1 is linearly reduced along with the voltage of the external load Rload, the resistance value is linearly reduced, and the microprocessor can detect whether the microprocessor can drive the Vtap V63R 94R 53 and the microprocessor can output a fourth resistor R8428 or the microprocessor can be output according to a short circuit with the voltage when the voltage detected by a short circuit, and the third resistor R3.
The field effect transistor Q1 is used as a switch, and the meaning of on corresponds to the switch being closed; the on and off of the field effect transistor is controlled by the gate-source voltage.
In one embodiment, the fet Q1 is a metal-oxide semiconductor fet; the transistor Q2 is an NPN transistor.
It should be noted that the low-side electronic switch circuit can be applied to electronic modules such as multimedia systems, vehicle body control modules, air conditioner control heads, combination meters and the like, which need to drive external current loads; when the microprocessor outputs a high level, the external load starts to work, and the analog converter of the microprocessor can diagnose the state of the external load; when the load is abnormal, the microprocessor turns off the output of the electronic switch, and the triode provides instantaneous protection in the process of diagnosing the microprocessor.
In summary, the low-side electronic switch circuit of the present invention can conveniently set the protection current by adjusting the resistance of the second resistor; the low-side electronic switch circuit provides hard protection, and can effectively prevent the low-side electronic switch from being damaged before being turned off; before the low-side electronic switch circuit is started, whether the external load is normal or open/short-circuited to the ground or not and the voltage of the external load can be diagnosed; only one analog input port is used, the microprocessor can diagnose the load current and the voltage born by the electronic switch in an abnormal state; therefore, the utility model effectively overcomes various defects in the prior art and has high industrial utilization value.
The above embodiments are merely illustrative of the principles and effects of the present invention, and are not to be construed as limiting the invention. Modifications and variations can be made to the above-described embodiments by those skilled in the art without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which may be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.
Claims (2)
1. A low-side electronic switching circuit, comprising: the circuit comprises a field effect transistor, a triode, a first resistor, a second resistor, a third resistor and a fourth resistor;
a grid electrode of the field effect transistor is respectively connected with one end of the first resistor and a collector electrode of the triode, a drain electrode of the field effect transistor is respectively connected with one end of an external load and one end of the fourth resistor, and a source electrode of the field effect transistor is respectively connected with a first end of the second resistor and one end of the third resistor; the other end of the first resistor is connected with the output end of the microprocessor; the emitting electrode of the triode is grounded, and the base electrode of the triode is connected with the first end of the second resistor; the other end of the external load is connected with a load power supply; the other end of the third resistor is respectively connected with the other end of the fourth resistor and an analog converter of the microprocessor; and the second end of the second resistor is grounded.
2. The low-side electronic switch circuit according to claim 1, wherein the field effect transistor is a metal-oxide semiconductor field effect transistor; the triode is an NPN triode.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202020432729.7U CN211018790U (en) | 2020-03-30 | 2020-03-30 | Low-side electronic switch circuit |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202020432729.7U CN211018790U (en) | 2020-03-30 | 2020-03-30 | Low-side electronic switch circuit |
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| CN211018790U true CN211018790U (en) | 2020-07-14 |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112255937A (en) * | 2020-09-18 | 2021-01-22 | 惠州市德赛西威汽车电子股份有限公司 | Automobile combination instrument control circuit capable of detecting low-side load open circuit |
| CN112737287A (en) * | 2021-01-08 | 2021-04-30 | 雅安小航电器有限责任公司 | Direct-current low-side driving switch circuit with short circuit and overload protection functions |
| CN112736859A (en) * | 2020-12-29 | 2021-04-30 | 联合汽车电子有限公司 | Overcurrent diagnosis processing circuit and low-side drive circuit |
| CN113659814A (en) * | 2021-08-18 | 2021-11-16 | 睿驰电装(大连)电动系统有限公司 | High-low side driving circuit, high-low side driving system and automobile control system |
-
2020
- 2020-03-30 CN CN202020432729.7U patent/CN211018790U/en active Active
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112255937A (en) * | 2020-09-18 | 2021-01-22 | 惠州市德赛西威汽车电子股份有限公司 | Automobile combination instrument control circuit capable of detecting low-side load open circuit |
| CN112255937B (en) * | 2020-09-18 | 2024-03-19 | 惠州市德赛西威汽车电子股份有限公司 | Automobile combination instrument control circuit capable of detecting low-side load open circuit |
| CN112736859A (en) * | 2020-12-29 | 2021-04-30 | 联合汽车电子有限公司 | Overcurrent diagnosis processing circuit and low-side drive circuit |
| CN112736859B (en) * | 2020-12-29 | 2024-04-26 | 联合汽车电子有限公司 | Overcurrent diagnosis processing circuit and low-side driving circuit |
| CN112737287A (en) * | 2021-01-08 | 2021-04-30 | 雅安小航电器有限责任公司 | Direct-current low-side driving switch circuit with short circuit and overload protection functions |
| CN113659814A (en) * | 2021-08-18 | 2021-11-16 | 睿驰电装(大连)电动系统有限公司 | High-low side driving circuit, high-low side driving system and automobile control system |
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