A DC low-side drive switch circuit with short-circuit and overload protection functions

Abstract

The invention discloses a DC low-side drive switch circuit with short-circuit and overload protection functions, and relates to the technical field of DC low-side drive. A short-circuit protection detection circuit feeds back an output state to a control circuit to realize opening of the control circuit, and then fully opens the drive circuit. When a switch signal input is at a low level, the control circuit realizes no-signal driving, and a drive circuit of the drive circuit is disconnected to realize a switch closing function. After a short circuit occurs in an external load circuit, the short-circuit protection detection circuit turns off the control circuit, and then turns off the drive circuit to achieve the purpose of protection. When an external load circuit is overloaded, an overload protection detection threshold feedback circuit transmits overload information to the control circuit to realize turning off the drive circuit, and achieves the purpose of protection. Short-circuit protection of an output terminal and a power supply terminal, and overload protection when a drive current is overloaded are realized. After the circuit output short circuit or overload failure is eliminated, the switch function can be restored.

Description

Technical Field

[0001] The invention relates to the technical field of direct current low-side drive, and in particular to a direct current low-side drive switch circuit with short circuit and overload protection functions. Background Art

[0002] At present, many applications in modern automotive electronic circuits use high-side and low-side switches as drive outputs. These output drivers are very likely to cause output overload or short circuit when operating in complex automotive electronic and electrical systems, causing irreversible operational failure of the automotive electronic and electrical systems. Although some semiconductor companies have launched driver ICs with short-circuit protection, these driver ICs are extremely expensive in applications, causing great cost overhead in cost-constrained applications.

[0003] Therefore, how to solve the above problems is what we urgently need. Summary of the invention

[0004] In view of this, the purpose of the present invention is to overcome the shortcomings and deficiencies of the above-mentioned prior art, and to provide a DC low-side drive switch circuit with short-circuit and overload protection functions, which can realize short-circuit protection between the output end and the power supply end, and can realize overload protection when the driving current is overloaded. After the circuit output short circuit or overload failure is eliminated, the switch function can be restored. After the circuit parameters are determined, the circuit operation does not require debugging, and compared with the short-circuit protection driver IC, the circuit has low cost.

[0005] The present invention is achieved through the following technical solutions:

[0006] A DC low-side drive switch circuit with short-circuit and overload protection functions, comprising a start-up circuit, a control circuit, an overload protection detection threshold feedback circuit, a protection circuit, a short-circuit protection detection circuit, a drive circuit and a load circuit;

[0007] The startup circuit is connected to the control circuit, the startup circuit is connected to the drive circuit, and the load circuit is connected to the drive circuit;

[0008] The overload protection detection threshold feedback circuit is connected to the drive circuit, and the short circuit protection detection circuit is connected to the drive circuit, the control circuit and the overload protection detection threshold feedback circuit;

[0009] The protection circuit is connected to the overload protection detection threshold feedback circuit, the short-circuit protection detection circuit and the drive circuit; the start-up circuit receives a switch signal input to start the drive output, the short-circuit protection detection circuit positively feeds back the drive output state to the control circuit, the control circuit is started, and the drive circuit is started accordingly;

[0010] When the switch signal input is at a low level, the control circuit has no signal drive and the drive circuit is disconnected;

[0011] When the driving circuit is driven, when a short circuit occurs in the load circuit, the driving output increases;

[0012] When the voltage drops to the short-circuit protection threshold, the short-circuit protection detection circuit turns off the control circuit and the drive circuit;

[0013] When the load circuit is overloaded, the overload protection detection threshold feedback circuit transmits the overload information to the control circuit to cut off the control circuit and disconnect the drive circuit.

[0014] In this scheme, after the start-up circuit receives the switch signal input, the start-up circuit starts the drive output, and the output state is positively fed back to the control circuit through the short-circuit protection detection circuit to realize the opening of the control circuit, and then the drive circuit is fully opened; when the switch signal input is a low level (ground level), the control circuit is driven without a signal, and the drive circuit of the drive circuit is disconnected to realize the switch closing function; when the drive circuit is driven, after a short circuit occurs in the external load circuit, the drive output rises sharply. When the voltage drops to the short-circuit protection threshold, the short-circuit protection detection circuit turns off the control circuit, and then turns off the drive circuit to achieve the purpose of protection. When the external load circuit is overloaded, the overload protection detection threshold feedback circuit transmits the overload information to the control circuit, turns off the control circuit, thereby realizing the shutdown of the drive circuit and achieving the purpose of protection.

[0015] It should be noted that: the switching signal is the control (excitation) signal of the driving circuit switch, which can be a general switching quantity or a continuous pulse signal; the protection circuit is mainly used to absorb parasitic energy in the circuit, such as overvoltage or negative pulse signals generated in the circuit. In addition, the overload protection detection threshold feedback circuit is composed of two circuits, specifically, an overload detection circuit for detecting the switch load current condition and a feedback circuit for transmitting the detected overload information to the control circuit, which work together to control the overload protection of the switch driving circuit in real time.

[0016] Further, the startup circuit includes a first resistor, a second resistor and a first capacitor; the control circuit includes a first transistor, which is a PNP transistor; the short-circuit protection detection circuit includes a first voltage regulator diode and a third resistor; the drive circuit includes a second diode, which is an NPN transistor;

[0017] Two ends of the first resistor and two ends of the first capacitor are connected to the emitter and collector of the first transistor respectively, and the second resistor is connected in series between the collector of the first transistor and the base of the second diode;

[0018] The base of the first transistor is connected to the collector of the third resistor, the first voltage stabilizing diode and the second diode in sequence;

[0019] The emitter of the first transistor inputs a switching signal, and the collector of the second transistor outputs a switching signal.

[0020] Preferably, the overload protection detection threshold feedback circuit includes a fifth resistor, a sixth resistor, a third transistor, a ninth resistor, a tenth resistor and a fourth transistor;

[0021] Wherein, the third transistor is an NPN transistor, and the fourth transistor is a PNP transistor;

[0022] A fifth resistor and a sixth resistor are connected in series between the emitter of the second diode and the base of the third transistor;

[0023] The ninth resistor is arranged between the collector of the third triode and the base of the fourth triode, and the two ends of the tenth resistor are respectively connected to the emitter and the base of the fourth triode;

[0024] A unidirectional conductive device is also connected in series between the collector of the fourth transistor and the base of the first transistor.

[0025] Preferably, the unidirectionally conductive device is a diode, the anode of the diode is connected to the collector of the fourth transistor, and the cathode of the diode is connected to the third resistor and the base of the first transistor.

[0026] Preferably, the emitter of the second transistor is also connected to one end of the fourth resistor, and the other end of the fourth resistor is grounded to form an overload detection circuit.

[0027] Furthermore, the anode of the first voltage stabilizing diode is connected to a second diode, the collector of the second transistor is connected to the anode of the second diode and the anode of the first voltage stabilizing diode, the cathode of the second diode is connected to a switching load, one end of the switching load is respectively connected to the emitter of the fourth transistor and the cathode of the second diode, and the other end is connected to the second voltage stabilizing diode.

[0028] Preferably, the emitter of the third transistor is grounded.

[0029] Preferably, the anode of the second voltage stabilizing diode is grounded, the cathode of the second voltage stabilizing diode is connected to the switch input output, and the anode of the second diode inputs a high level.

[0030] Optionally, the second voltage regulator diode may be replaced by a transient voltage suppressor diode.

[0031] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0032] The present invention discloses a DC low-side drive switch circuit with short-circuit and overload protection functions. The circuit has overload protection capability, overcomes the strategy that the output terminal must be short-circuited to ground for protection, can be applied to various types of loads, and has an adjustable protection threshold voltage to achieve different overload protection requirements. By using a two-stage control circuit, the switch can be quickly started, which can effectively solve the problem of an electronic switch drive circuit having no output protection function, avoid accidents caused by a load circuit short circuit, thereby improving the safety of the use of the electrical system, and the circuit has a practical effect on applications with low integration and cost requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, constitute a part of this application, and do not constitute a limitation of the embodiments of the present invention. In the drawings:

[0034] Figure 1 A circuit structure block diagram of an embodiment of the present invention;

[0035] Figure 2 Schematic diagram of the circuit in the embodiment of the present invention. DETAILED DESCRIPTION

[0036] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0037] In the following description, a large number of specific details are set forth in order to provide a thorough understanding of the present invention. However, it is apparent to one of ordinary skill in the art that these specific details are not necessarily employed to practice the present invention. In other instances, well-known structures, circuits, materials, or methods are not specifically described in order to avoid obscuring the present invention.

[0038] Throughout the specification, references to "one embodiment," "an embodiment," "an example," or "an example" mean that a particular feature, structure, or characteristic described in conjunction with the embodiment or example is included in at least one embodiment of the present invention. Therefore, the phrases "one embodiment," "an embodiment," "an example," or "an example" appearing in various places throughout the specification do not necessarily all refer to the same embodiment or example. In addition, particular features, structures, or characteristics may be combined in one or more embodiments or examples in any suitable combination and / or sub-combination. In addition, it will be appreciated by those of ordinary skill in the art that the figures provided herein are for illustrative purposes and that the figures are not necessarily drawn to scale. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0039] In the description of the present invention, it should be understood that the terms "front", "rear", "left", "right", "up", "down", "vertical", "horizontal", "high", "low", "inside", "outside", etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as limiting the scope of protection of the present invention.

[0040] Example

[0041] like Figure 1As shown, the present invention provides a DC low-side drive switch circuit with short-circuit and overload protection functions, including a start-up circuit, a control circuit, an overload protection detection threshold feedback circuit, a protection circuit, a short-circuit protection detection circuit, a drive circuit and a load circuit. The control circuit is mainly used to drive the opening, holding and closing of the drive circuit. The load circuit is mainly an energy consumption circuit or device that mainly realizes specific actions. The start-up circuit is connected to the control circuit, the start-up circuit is connected to the drive circuit, and the load circuit is connected to the drive circuit; the overload protection detection threshold feedback circuit is connected to the drive circuit, and the short-circuit protection detection circuit is connected to the drive circuit, the control circuit and the overload protection detection threshold feedback circuit; the protection circuit is connected to the overload protection detection threshold feedback circuit, the short-circuit protection detection circuit and the drive circuit, and monitors the output terminal voltage in real time to realize the output terminal short-circuit protection of the output terminal or the output protection when the output terminal voltage rises sharply due to other reasons. When the start-up circuit receives the switch signal input to start the drive output, the short-circuit protection detection circuit positively feeds back the drive output state to the control circuit, the control circuit is started, and the drive circuit is started; when the switch signal input is low level, the control circuit has no signal drive , the drive circuit is disconnected; when the drive circuit is driving, when a short circuit occurs in the load circuit, the drive output rises; when the voltage drops to the short-circuit protection threshold, the short-circuit protection detection circuit turns off the control circuit and the drive circuit is turned off; when the load circuit is overloaded, the overload protection detection threshold feedback circuit transmits the overload information to the control circuit to turn off the control circuit and disconnect the drive circuit. After the start-up circuit receives the switch signal input, the start-up circuit starts the drive output, and the output state is positively fed back to the control circuit through the short-circuit protection detection circuit to realize the opening of the control circuit, thereby making the drive circuit fully open; When the switch signal input is at a low level (ground level), the control circuit is driven without a signal, the drive circuit of the drive circuit is disconnected, and the switch closing function is realized; when the drive circuit is driven, after a short circuit occurs in the external load circuit, the drive output rises sharply. When the voltage drops to the short circuit protection threshold, the short circuit protection detection circuit turns off the control circuit, and then turns off the drive circuit to achieve the purpose of protection. When the external load circuit is overloaded, the overload protection detection threshold feedback circuit transmits the overload information to the control circuit, turns off the control circuit, and thus turns off the drive circuit to achieve the purpose of protection.

[0042] As a preferred embodiment of the above, Figure 1 and Figure 2As shown, the start-up circuit includes a first resistor R1, a second resistor R2 and a first capacitor C1; the control circuit includes a first transistor Q1, which is a PNP transistor; the short-circuit protection detection circuit includes a first voltage-stabilizing diode DZ1 and a third resistor R3; the drive circuit includes a second transistor Q2, which is an NPN transistor; both ends of the first resistor R1 and both ends of the first capacitor C1 are respectively connected to the emitter and collector of the first transistor Q1, and the collector of the first transistor Q1 and the base of the second transistor Q2 are connected in series with the second resistor R2; the base of the first transistor Q1 is connected to the third resistor R3, the first voltage-stabilizing diode DZ1 and the collector of the second transistor Q2 in sequence; the emitter of the first transistor Q1 inputs a switching signal, and the collector of the second transistor Q2 outputs a switch output.

[0043] As a preferred embodiment of the above, Figure 1 and Figure 2 As shown, the overload protection detection threshold feedback circuit includes a fifth resistor R5, a sixth resistor R6, a third triode Q3, a ninth resistor R9, a tenth resistor R10 and a fourth triode Q4; wherein the third triode Q3 is an NPN triode, and the fourth triode Q4 is a PNP triode; the fifth resistor R5 and the sixth resistor R6 are connected in series between the emitter of the second triode Q2 and the base of the third triode Q3; a ninth resistor R9 is arranged between the collector of the third triode Q3 and the base of the fourth triode Q4, and both ends of the tenth resistor R10 are respectively connected to the emitter and the base of the fourth triode Q4, and a unidirectional conductive device is also connected in series between the collector of the fourth triode Q4 and the base of the first triode Q1.

[0044] As a preferred embodiment of the above, Figure 2 As shown, the unidirectionally conducting device is a first diode D1 , the anode of the first diode D1 is connected to the collector of the fourth transistor Q4 , and the cathode of the first diode D1 is connected to the third resistor R3 and the base of the first transistor Q1 .

[0045] As a preferred embodiment of the above, as shown in the figure, the emitter of the second transistor Q2 is also connected to one end of the fourth resistor R4, and the other end of the fourth resistor R4 is grounded to form an overload detection circuit.

[0046] As a preferred embodiment of the above, Figure 2 As shown, the anode of the first zener diode DZ1 is connected to the second diode D2, the collector of the second transistor Q2 is connected to the anode of the second diode D2 and the anode DZ1 of the first zener diode, the cathode of the second diode D2 is connected to the switching load RL, one end of the switching load RL is respectively connected to the emitter of the fourth transistor Q4 and the cathode of the second diode D2, and the other end is connected to the second zener diode DZ2.

[0047] As a preferred embodiment of the above, Figure 2 As shown, the emitter of the third transistor Q3 is grounded.

[0048] In addition, if Figure 2 As shown, the anode of the second voltage stabilizing diode DZ2 is grounded, the cathode of the second voltage stabilizing diode DZ2 is connected to the switch input output, and the anode of the second diode DZ2 inputs a high level.

[0049] In addition, if Figure 2 As shown, the second Zener diode can be replaced by a transient voltage suppressor diode TVS.

[0050] Working process:

[0051] like Figure 2 As shown:

[0052] During normal operation: when the Input output is at a high level (VCC), the input high level passes through the first capacitor C1, the second resistor R2, the second transistor Q2, and the fourth resistor R4 to the ground, causing the base of the second transistor Q2 to generate current, causing the collector and emitter of the second transistor Q2 to be pre-conducted; in the pre-conduction stage of the second transistor Q2, the collector voltage of the second transistor Q2 is pulled down, which will cause the Input input high level to pass through the first transistor Q1, the third resistor R3, the first voltage zener diode DZ1, the second transistor Q2, and the fourth resistor R4 to the ground, causing the first transistor Q1 to generate base current, causing the emitter and collector of the first transistor Q1 to be turned on. After the above process, the second transistor Q2 will be continuously loaded and driven by the Input input high level, so that the second transistor Q2 is in the on state. When the Input input high level is cancelled, the base current of the second transistor Q2 is de-energized, the second transistor Q2 is cut off, and the drive is turned off.

[0053] When the output terminal is short-circuited to the power supply or the output terminal voltage is abnormally high, the low-side switch is turned on during normal operation, and the second transistor Q2 is turned on. When the output terminal is short-circuited to the power supply VCC, due to the action of the second transistor Q2 and the fourth resistor R4, the output terminal voltage of the second transistor Q2 reaches VCC sharply in a short time or the voltage difference between the two ends of the first voltage zener diode DZ1 is less than the voltage stabilization voltage of the first voltage zener diode DZ1, the base current of the first transistor Q1 is de-energized, and the first transistor Q1 is cut off, thereby de-energizing the base loop current of the second transistor Q2, and cutting off the output of the second transistor Q2.

[0054] The principle of abnormal increase of output voltage is the same as above, which is mainly to make the output voltage rise to the point where the voltage across the first voltage zener diode DZ1 is less than the zener voltage of the first voltage zener diode DZ1, so that the base current of the first transistor Q1 is cut off.

[0055] When the output of the second transistor Q2 is stopped, the first capacitor C1 is discharged through the first resistor R1 to release the stored energy of the first capacitor C1 so that the first capacitor C1 can function as a starting capacitor again during the next switch.

[0056] In addition, the first voltage stabilizing diode DZ1 plays a role in controlling the threshold value of the short-circuit protection threshold voltage, and different voltage stabilizing values ​​can be used to adjust the response speed of the short-circuit protection.

[0057] When the output circuit current is overloaded, the low-side switch is turned on according to the above normal working process, and the second transistor Q2 is turned on. When the output end is overloaded, when the voltage on the fourth resistor R4 is greater than 0.6V, the third transistor Q3 is turned on, thereby turning on the fourth transistor Q4, increasing the base voltage of the first transistor Q1, and the base current of the first transistor Q1 is de-energized, and the first transistor Q1 is turned off, thereby de-energizing the base loop current of the second transistor Q2, and turning off the second transistor Q2.

[0058] When the output of the second transistor Q2 is stopped, the first capacitor C1 is discharged through the first resistor R1 to release the stored energy of the first capacitor C1 so that the first capacitor C1 can function as a starting capacitor again during the next switch.

[0059] By adjusting the resistance value of the fourth resistor R4, the size of the overload protection current can be adjusted, that is, the load capacity of the switch can be adjusted. The fifth resistor R5, the second capacitor C2, and the sixth resistor R6 form the base drive of the third transistor Q3. The second capacitor C2 mainly filters out the impact of the impact current when the second transistor Q2 is turned on. The impact is mainly the impact of the bulb load. For other purely resistive or inductive loads, this capacitor can be used without connection. When the second capacitor C2 is connected, the protection circuit action will be delayed. The overload capacity time of the second transistor Q2 should be greater than the delay time when the second capacitor C2 is added.

[0060] In addition, the second diode D2 in the circuit functions to discharge and freewheel the inductive load RL.

[0061] The first diode D1 in the circuit performs unidirectional control on the first transistor Q1 to prevent the first transistor Q1 from being in reverse current and causing circuit failure.

[0062] The second voltage stabilizing diode DZ2 is mainly used to provide overvoltage protection or negative pulse protection for the second triode Q2 if there is a momentary high pulse or negative pulse at the output end. It clamps the high pulse in the positive direction and performs freewheeling in the negative direction. This device can be selected as a transient voltage suppression diode TVS device.

[0063] In a DC low-side drive switch circuit with short-circuit and overload protection functions of the present invention, relevant parameters are not clearly given, and the circuit parameters can be adjusted according to requirements so that the circuit matches the protection of the corresponding power output.

[0064] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A DC low-side drive switch circuit with short circuit and overload protection functions, characterized in that: It includes a start-up circuit, a control circuit, an overload protection detection threshold feedback circuit, a protection circuit, a short-circuit protection detection circuit, a drive circuit and a load circuit; The startup circuit is connected to the control circuit, the startup circuit is connected to the drive circuit, and the load circuit is connected to the drive circuit; The overload protection detection threshold feedback circuit is connected to the drive circuit, and the short circuit protection detection circuit is connected to the drive circuit, the control circuit and the overload protection detection threshold feedback circuit; The protection circuit is connected to the overload protection detection threshold feedback circuit, the short circuit protection detection circuit and the drive circuit; When the start-up circuit receives a switch signal input to start the drive output, the short-circuit protection detection circuit feeds back the drive output state to the control circuit, the control circuit starts, and the drive circuit starts accordingly; When the switch signal input is at a low level, the control circuit has no signal drive, and the drive circuit of the drive circuit is disconnected; When the driving circuit is driven, when a short circuit occurs in the load circuit, the driving output increases; When the voltage drops to the short-circuit protection threshold, the short-circuit protection detection circuit turns off the control circuit and the drive circuit; When the load circuit is overloaded, the overload protection detection threshold feedback circuit transmits the overload information to the control circuit to cut off the control circuit and disconnect the drive circuit; Wherein, the startup circuit includes a first resistor, a second resistor and a first capacitor; the control circuit includes a first transistor, and the first transistor is a PNP transistor; the short-circuit protection detection circuit includes a first voltage-stabilizing diode and a third resistor; the drive circuit includes a second transistor, and the second transistor is an NPN transistor; Two ends of the first resistor and two ends of the first capacitor are connected to the emitter and collector of the first triode respectively, and the second resistor is connected in series between the collector of the first triode and the base of the second triode; The base of the first transistor is connected to the third resistor, the first voltage stabilizing diode and the collector of the second transistor in sequence; The emitter of the first transistor inputs a switch signal, and the collector of the second transistor outputs a switch drive output; Wherein, the overload protection detection threshold feedback circuit includes a fifth resistor, a sixth resistor, a third transistor, a ninth resistor, a tenth resistor and a fourth transistor; Wherein, the third transistor is an NPN transistor, and the fourth transistor is a PNP transistor; A fifth resistor and a sixth resistor are connected in series between the emitter of the second triode and the base of the third triode; The ninth resistor is arranged between the collector of the third triode and the base of the fourth triode, and the two ends of the tenth resistor are respectively connected to the emitter and the base of the fourth triode; A unidirectional conductive device is also connected in series between the collector of the fourth transistor and the base of the first transistor; The unidirectional conductive device is a first diode, the anode of the first diode is connected to the collector of the fourth transistor, and the cathode of the first diode is connected to the third resistor and the base of the first transistor.

2. A DC low-side drive switch circuit with short-circuit and overload protection functions according to claim 1, characterized in that: The emitter of the second transistor is also connected to one end of a fourth resistor, and the other end of the fourth resistor is grounded to form an overload detection circuit.

3. A DC low-side drive switch circuit with short-circuit and overload protection functions according to claim 1, characterized in that: One end of the second resistor is also connected to the first resistor and the first capacitor respectively, a second capacitor is also connected between the fifth resistor and the sixth resistor, one end of the second capacitor is respectively connected to the fifth resistor and the sixth resistor, and the other end of the second capacitor is grounded.

4. A DC low-side drive switch circuit with short-circuit and overload protection functions according to claim 1, characterized in that: The anode of the first voltage-stabilizing diode is connected to the second diode, the collector of the second transistor is connected to the anode of the second diode and the anode of the first voltage-stabilizing diode, the cathode of the second diode is connected to a switching load, one end of the switching load is respectively connected to the emitter of the fourth transistor and the cathode of the second diode, and the other end is connected to the second voltage-stabilizing diode.

5. A DC low-side drive switch circuit with short-circuit and overload protection functions according to claim 1, characterized in that: The emitter of the third transistor is grounded.

6. A DC low-side drive switch circuit with short-circuit and overload protection functions according to claim 4, characterized in that: The anode of the second voltage stabilizing diode is grounded, the cathode of the second voltage stabilizing diode is connected to the switch drive output, and the anode of the second diode inputs a high level.

7. A DC low-side drive switch circuit with short-circuit and overload protection functions according to claim 4, characterized in that: The second voltage stabilizing diode may be replaced by a transient voltage suppressor diode.

Images