A switching device overcurrent protection circuit and a load driving circuit

Abstract

The embodiment of the present application discloses a switch device overcurrent protection circuit and a load driving circuit, relates to the technical field of switching power supply, and can realize overcurrent protection of a switch device at low cost.The switch device overcurrent protection circuit comprises a driving signal input end used for receiving a driving signal, a first resistor, an input end of the first resistor being connected to the driving signal input end, an output end of the first resistor being connected to a conduction control end of a switch device, a second resistor, an input end of the second resistor being connected to the driving signal input end, a clamping unit circuit, an input end of the clamping unit circuit being connected to an output end of the second resistor, an output end of the clamping unit circuit being connected to a signal output end of the switch device, a transistor control unit circuit, an input end of the transistor control unit circuit being connected to the output end of the second resistor, and an output end of the transistor control unit circuit being connected to at least the output end of the first resistor.The present application is applicable to various power conversion topologies.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of switching power supply, in particular to a switching device overcurrent protection circuit and a load driving circuit. BACKGROUND

[0002] At present, some semiconductor switching devices such as MOSFET (metallic oxide semiconductor field effect transistor, a commonly used power electronic semiconductor switching device) and the like are prone to damage due to the sharp increase of current flowing through the semiconductor device when turned on and subjected to instantaneous impact.

[0003] Some prior art uses sensor current detection and uses resistance to detect current to achieve overcurrent protection of the switching device, but the sensor cost is generally high, and the sensor scheme has low timeliness due to the bandwidth limitation of the sensor; the device occupies a large area, and when many devices are protected, it is not conducive to product design; and the use of resistance, although low in cost and small in size, the detection resistance in series will cause large loss, especially under high power conditions, the loss is considerable; the form of series resistance usually needs the help of an amplifier due to small voltage signal, which makes the response speed, occupied area and cost advantage of the circuit all decrease. SUMMARY

[0004] Therefore, the embodiments of the present application provide a switching device overcurrent protection circuit and a load driving circuit, which can realize overcurrent protection of the switching device at low cost.

[0005] To achieve the above-mentioned purposes,

[0006] In a first aspect, the embodiments of the present application provide a switching device overcurrent protection circuit, comprising:

[0007] a driving signal input end for receiving a driving signal;

[0008] a first resistor, an input end of the first resistor being connected to the driving signal input end, and an output end of the first resistor being used for connecting to a turn-on control end of the switching device;

[0009] a second resistor, an input end of the second resistor being connected to the driving signal input end;

[0010] a clamping unit circuit, an input end of the clamping unit circuit being connected to an output end of the second resistor, and an output end of the clamping unit circuit being used for connecting to a signal output end of the switching device;

[0011] a transistor control unit circuit, an input end of the transistor control unit circuit being connected to an output end of the second resistor, and an output end of the transistor control unit circuit being connected to at least an output end of the first resistor;

[0012] the transistor control unit circuit is configured to, when the current flowing through the switching device exceeds the safe current threshold during the conduction of the switching device, form a loop by turning on the output end of the first resistor and the output end of the transistor control unit circuit, and turn off the switching device.

[0013] Optionally, the clamping unit circuit comprises a first diode, an input end of the first diode being connected to an output end of the second resistor, and an output end of the first diode being connected to a signal output end of the switching device.

[0014] the transistor control unit circuit comprises a second diode, a transistor, and a delay charging and discharging circuit, an input end of the second diode being connected to an output end of the second resistor, an output end of the second diode being connected to a base of the transistor and an input end of the delay charging and discharging circuit respectively, a collector and an emitter of the transistor constituting an output end of the transistor control unit circuit, the collector of the transistor being connected to an output end of the first resistor, and the emitter of the transistor being grounded.

[0015] an output end of the delay charging and discharging circuit is grounded.

[0016] Optionally, the delay charging and discharging circuit comprises a third resistor and a first capacitor, input ends of the third resistor and the first capacitor being connected to an output end of the second diode, and output ends of the third resistor and the first capacitor being grounded.

[0017] Optionally, the transistor control unit circuit is specifically configured to, when the sum of the voltage loaded to the switching device and the voltage of the first diode reaches or exceeds the sum of the voltage between the base and the collector of the second diode and the transistor during the conduction of the switching device, trigger the transistor to turn on, the output end of the first resistor and the collector and the emitter of the transistor are turned on and grounded, and the switching device is turned off.

[0018] Optionally, the number of the first diode and the second diode is one or more.

[0019] Optionally, the transistor comprises at least one, or at least one Darlington tube composed of two transistors.

[0020] Optionally, the switching device comprises one or more of a power switch tube, a relay, and a contactor.

[0021] In a second aspect, an embodiment of the present application provides a load driving circuit, comprising: a driver configured to output a driving signal;

[0022] The switch device overcurrent protection circuit of any one of the first aspect is connected to the output end of the driver, and the signal output end of the switch device overcurrent protection circuit is configured to be connected to a load.

[0023] The switch device overcurrent protection circuit and the load driving circuit provided by the embodiments of the present application open the switch device through the conduction characteristics of PN junctions in diodes and transistors, combine the conduction characteristics of the switch device, and cooperate with the conduction characteristics of the switch device. When the current flowing through the switch device exceeds the safe current threshold during the conduction of the switch device, the switch device is turned off. Without passing through an expensive sensor, a mutual inductor and a sampling resistor with large loss, only the conduction characteristics of the switch device and the conduction characteristics of the PN junction are used to realize the overcurrent protection of the switch device at a low cost. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained without creative labor on the basis of these drawings.

[0025] Figure 1 The structure schematic diagram of the switch device overcurrent protection circuit of the embodiment of the present application is shown in the figure.

[0026] Figure 2 The application scenario schematic diagram of the switch device overcurrent protection circuit of the embodiment of the present application is shown in the figure.

[0027] Figure 3 The structure schematic diagram of the load driving circuit of the embodiment of the present application is shown in the figure. DETAILED DESCRIPTION

[0028] The embodiments of the present application will be described in detail below with reference to the drawings.

[0029] It should be clear that the described embodiments are only some embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0030] The switch device overcurrent protection circuit provided by the embodiment of the present application can solve the problem that the semiconductor switch device such as a MOSFET tube is damaged due to the sharp increase of current flowing through the semiconductor switch device caused by instantaneous impact when the semiconductor switch device is turned on, and is suitable for various power conversion topological circuits. The embodiment of the present application is described by taking a BOOST (voltage boosting circuit) as a topological circuit.

[0031] Embodiment one

[0032] Figure 1 The structure diagram of the switch device overcurrent protection circuit is shown in FIG. 1. Figure 1 As shown in FIG. 1, the switch device overcurrent protection circuit 1 comprises:

[0033] a driving signal input end 2 configured to receive a driving signal;

[0034] a first resistor R1, an input end of the first resistor R1 being connected to the driving signal input end 2, and an output end of the first resistor R1 being configured to be connected to a turn-on control end of the switch device M1;

[0035] a second resistor R2, an input end of the second resistor R2 being connected to the driving signal input end 2;

[0036] a clamping unit circuit 3, an input end of the clamping unit circuit 3 being connected to an output end of the second resistor R2, and an output end of the clamping unit circuit 3 being configured to be connected to a signal output end of the switch device M1;

[0037] a transistor control unit circuit 4, an input end of the transistor control unit circuit 4 being connected to the output end of the second resistor R2, and an output end of the transistor control unit circuit 4 being connected to at least the output end of the first resistor R1;

[0038] The transistor control unit circuit 4 is configured to form a loop by turning on the output end of the first resistor R1 and the output end of the transistor control unit circuit 4 when the current flowing through the switch device M1 exceeds a safe current threshold value during the conduction of the switch device M1, and turn off the switch device M1.

[0039] In some embodiments, the clamping unit circuit 3 comprises a first diode D1, an input end of the first diode D1 being connected to the output end of the second resistor R2, and an output end of the first diode D1 being configured to be connected to the signal output end of the switch device M1.

[0040] The transistor control unit circuit 4 comprises a second diode D2, a triode N1 and a delay charging and discharging circuit, the input end of the second diode D2 is connected to the output end of the second resistor R2, the output end of the second diode D2 is connected to the base of the triode N1 and the input end of the delay charging and discharging circuit respectively, the collector and the emitter of the triode N1 constitute the output end of the transistor control unit circuit, the collector of the triode N1 is connected to the output end of the first resistor R1, and the emitter of the triode N1 is grounded.

[0041] The output end of the delay charging and discharging circuit is grounded.

[0042] Specifically, the diode is packaged by a PN junction, corresponding electrode leads and a tube shell, therefore, the diode has the one-way conductivity of the PN junction, the diode is turned on when a forward voltage is added, and the diode is cut off when a reverse voltage is added; the triode is equivalent to two diodes, so as long as the PN junction voltage difference is greater than 0.7V, the triode can be turned on with current, and the triode used in the embodiment of the present application is NPN type, which can be turned on as long as the base voltage is greater than the emitter voltage by 0.7V.

[0043] In some embodiments, the delay charging and discharging circuit comprises a third resistor R3 and a first capacitor C1, the input end of the third resistor R3 and the first capacitor C1 is connected to the output end of the second diode R2, and the output end of the third resistor R3 and the first capacitor C1 is grounded.

[0044] In some embodiments, the transistor control unit circuit 4 is specifically configured to be used for triggering the triode to be turned on when the sum of the voltage loaded to the switching device and the voltage of the first diode reaches or exceeds the sum of the voltage between the base and the emitter of the second diode and the triode in the process that the switching device is turned on, the output end of the first resistor and the collector and the emitter of the triode are turned on and grounded, and the switching device is turned off.

[0045] Figure 2 An application scenario schematic diagram of the switching device overcurrent protection circuit in the embodiment of the present application is a direct current relay switching device principle diagram, and the switching device overcurrent protection circuit provided by the embodiment of the present application can realize the period-by-period overcurrent protection of the MOSFET tube.

[0046] Specifically, referring to Figure 2As shown, the input end of the first resistor R1 is connected to the driving signal input end of the driver, and the output end is connected to the gate of the MOSFET M1; the input end of the second resistor R2 is also connected to the driving signal input end of the driver, and the output end is connected to the input end of the clamping unit circuit and the transistor control unit circuit, wherein the clamping unit circuit comprises a first diode D1, the input end of the first diode D1 is connected to the output end of the second resistor R2, and the output end of the first diode D1 is connected to the drain of the MOSFET M1; the transistor control circuit comprises a second diode D2, a transistor N1 and a delay charging and discharging circuit, the delay charging and discharging circuit comprises a third resistor R3 and a first capacitor C1, the input end of the second diode D2 is connected to the output end of the second resistor R2, the output end of the second diode D2 is connected to the base of the transistor N1 and the input end of the delay charging and discharging circuit, the collector and the emitter of the transistor N1 constitute the output end of the transistor control unit circuit, the collector of the transistor N1 is connected to the output end of the first resistor R1, and the emitter of the transistor N1 is grounded; and the output end of the delay charging and discharging circuit is grounded.

[0047] In the embodiment of the present application, the transistor N1 is NPN type, and the general conduction voltage is 0.7V.

[0048] Figure 2 As shown in the application scenario diagram of the switch device overcurrent protection circuit in the embodiment of the present application, when the circuit is normally working, the driver outputs a driving signal, and the voltage at point A starts to rise, part of the voltage at this point acts on the gate of M1 through the first resistor R1, and the other part forms a loop through the second resistor R2, the second diode D2, the third resistor R3 and the first capacitor C1, at this time, due to the action of the first capacitor C1, the voltage of the transistor N1 does not reach the conduction voltage, and the transistor N1 cannot be turned on, and M1 is driven away under the action of the first resistor R1, and is normally turned on.

[0049] When M1 is turned on, the voltage at point A has two paths after passing through the second resistor R2, one path is from point A, the second resistor R2, the first diode D1, M1 to the ground, and the other path is from point A, the second resistor R2, the second diode D2, the third resistor (or the PN junction between the base and the emitter of the transistor N1) to the ground. When M1 is turned on, there is a voltage drop due to the conduction resistance of M1, and when the current flowing through M1 is small, VD1+Vds<VD2+Vbe; wherein: VD1 and VD2 are the conduction voltage drops of the first diode D1 and the second diode D2, and Vbe is the conduction voltage drop between the base and the emitter of the transistor N1.

[0050] At this time, the conduction voltage drop between the second diode D2 and the base and emitter of the triode N1 is clamped by the conduction voltage drop of the first diode D1 and M1, the triode N1 does not act, and M1 is normally turned on; as the current of M1 increases, the conduction voltage drop of M1 increases, when the current flowing through the switching device M1 exceeds the safe current threshold, VD1+Vds≥VD2+Vbe, that is, when the sum of the voltage of the switching device M1 and the voltage of the first diode D1 reaches or exceeds the sum of the voltage between the second diode D2 and the base and emitter of the triode N1, the triode N1 is triggered to be turned on, the output end of the first resistor R1 and the collector and emitter of the triode N1 are turned on and grounded, and the switching device M1 is turned off.

[0051] At this time, as shown in Figure 2 , due to the rise of the drain voltage of M1, Vds increases sharply, according to the reverse bias characteristics of the PN junction in the diode, the diode D1 cannot be turned on again, and a stable state is formed until the driver is turned off to reset the circuit, thereby effectively protecting M1 from being damaged due to excessive current. When a new switching period starts, since the circuit has been reset when the driver is turned off, protection can be provided again, so that period-by-period overcurrent protection can be formed.

[0052] In some embodiments, the number of the first diode and the second diode is one or more.

[0053] In some embodiments, the triode includes at least one, or includes at least one Darlington tube composed of two triodes.

[0054] In some embodiments, the switching device includes one or more of a power switch tube, a relay, and a contactor.

[0055] Specifically, in the overcurrent protection circuit of the switching device, the first resistor R1 can be changed to a combination of multiple resistors, and is not limited to one resistor. In addition, in order to change the switching speed of the switching device, the first resistor R1 can also be changed to a combination of a diode and a resistor, or a combination of a triode and a resistor, or other forms that change the switching speed. The triode in the transistor control unit circuit can also use a Darlington tube, and the switching device is not limited to a MOSFET tube, but can also be replaced by other semiconductor devices, such as an IGBT (Insulated-Gate Bipolar Transistor, a commonly used power electronic semiconductor switching device), or even a relay, a contactor, etc. The modified circuit is also considered as an extension of the present application and belongs to the scope of the present application.

[0056] Further, as shown in Figure 3 , the embodiment of the present application provides a load driving circuit, comprising: a driver, configured to output a driving signal;

[0057] The switch device overcurrent protection circuit of any of the above, the drive signal input end of the switch device overcurrent protection circuit is connected to the output end of the driver, and the signal output end of the switch device overcurrent protection circuit is used for connecting the load.

[0058] The drive circuit is used for amplifying the signal of the control circuit and outputting a drive signal; the function of the drive circuit is to amplify the PWN pulse output by the control circuit to a sufficient level to drive the power transistor; only the turn-on control signal needs to be provided for the half-controlled device, and both the turn-on control signal and the turn-off control signal need to be provided for the fully-controlled device, so as to ensure that the device is reliably turned on or turned off according to the requirement. The control circuit can be added before the drive circuit.

[0059] In summary, the switch device overcurrent protection circuit and the load drive circuit provided by the embodiment of the present application comprise: a drive signal input end used for receiving a drive signal; a first resistor, an input end of the first resistor being connected to the drive signal input end, and an output end of the first resistor being used for being connected to a turn-on control end of the switch device; a second resistor, an input end of the second resistor being connected to the drive signal input end; a clamping unit circuit, an input end of the clamping unit circuit being connected to an output end of the second resistor, and an output end of the clamping unit circuit being used for being connected to a signal output end of the switch device; a transistor control unit circuit, an input end of the transistor control unit circuit being connected to the output end of the second resistor, and an output end of the transistor control unit circuit being connected to at least the output end of the first resistor; the transistor control unit circuit is configured to, in a conduction process of the switch device, when a current flowing through the switch device exceeds a safe current threshold, the output end of the first resistor and the output end of the transistor control unit circuit are turned on to form a loop, and the switch device is turned off. By the turn-on characteristics of PN junctions in diodes and transistors and the turn-on characteristics of the switch device, the switch device is turned on, and in combination with the turn-on characteristics of the switch device, the switch device is turned off in time when the current flowing through the switch device exceeds the safe current threshold in the conduction process of the switch device.

[0060] Further, the switch device overcurrent protection circuit provided by the embodiment of the present application does not pass through an expensive sensor, a mutual inductor and a sampling resistor with large loss, and only uses the turn-on characteristics of the switch device and the turn-on characteristics of PN junctions, so that the overcurrent protection of the switch device can be realized at low cost.

[0061] Further, the switch device overcurrent protection circuit provided by the embodiment of the present application not only has few devices, low price, small occupied area, but also has almost no loss, and can be applied to almost all power conversion topologies such as single-tube and multi-tube, and has important significance for overcurrent protection of semiconductor devices.

[0062] It is to be noted that, in the present document, relational terms such as first and second and the like can be used solely to distinguish one entity or action from another entity or action without necessarily implying any actual relationship or order between such entities or actions. Also, the terms "comprises", "comprising", or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by "comprises... a" does not, without more constraints, exclude the presence of additional identical elements in the process, method, article, or apparatus that comprises the element.

[0063] Each of the embodiments in the present specification is described in a related manner, and the same or similar parts between the embodiments can be mutually referred to, and each of the embodiments focuses on the difference from other embodiments.

[0064] For the convenience of description, the above relay control system is described in various functional units / circuits / modules respectively according to functions. Of course, the functions of each unit / module can be implemented in the same or multiple software and / or hardware when implementing the present application.

[0065] The above description is merely specific embodiments of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A circuit for overcurrent protection of a switching device, characterized in that include: The drive signal input terminal is used to receive drive signals; A first resistor, the input terminal of which is connected to the drive signal input terminal, and the output terminal of which is connected to the conduction control terminal of the switching device; The second resistor, the input terminal of which is connected to the drive signal input terminal; The clamping unit circuit includes a first diode, the input terminal of which is connected to the output terminal of the second resistor, and the output terminal of the first diode is used to connect to the signal output terminal of the switching device. A transistor control unit circuit, wherein the input terminal of the transistor control unit circuit is connected to the output terminal of the second resistor, and the output terminal of the transistor control unit circuit is at least connected to the output terminal of the first resistor; The transistor control unit circuit includes: a second diode, a transistor, and a time-delayed charge / discharge circuit. The input terminal of the second diode is connected to the output terminal of the second resistor. The output terminal of the second diode is connected to the base of the transistor and the input terminal of the time-delayed charge / discharge circuit. The collector and emitter of the transistor constitute the output terminal of the transistor control unit circuit. The collector of the transistor is connected to the output terminal of the first resistor. The emitter of the transistor is grounded. The output terminal of the delayed charging and discharging circuit is grounded. The transistor control unit circuit is specifically configured to, during the conduction process of the switching device, when the sum of the voltage applied to the switching device and the voltage of the first diode reaches or exceeds the sum of the voltages between the second diode and the base and collector of the transistor, trigger the transistor to conduct, the output terminal of the first resistor is connected to the collector and emitter of the transistor and grounded, and the switching device is turned off.

2. The overcurrent protection circuit of claim 1, wherein, The delayed charging and discharging circuit includes a third resistor and a first capacitor. The input terminals of the third resistor and the first capacitor are connected to the output terminal of the second diode, and the output terminals of the third resistor and the first capacitor are grounded.

3. The overcurrent protection circuit of claim 1, wherein, The number of the first diode and the second diode is one or more.

4. The overcurrent protection circuit of claim 1, wherein, The transistor includes at least one, or at least one Darlington transistor composed of two transistors.

5. The overcurrent protection circuit of claim 1, wherein, The switching device includes one or more of the following: power switching transistors, relays, and contactors.

6. A load driving circuit characterized by comprising: include: A driver, used to output drive signals; The switching device overcurrent protection circuit according to any one of claims 1 to 5, wherein the drive signal input terminal of the switching device overcurrent protection circuit is connected to the output terminal of the driver, and the signal output terminal of the switching device overcurrent protection circuit is used to connect to the load.

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