CN114520502A

CN114520502A - Protection circuit system and electronic equipment

Info

Publication number: CN114520502A
Application number: CN202011304578.8A
Authority: CN
Inventors: 陈立国; 王静; J·德拉塞尔达卡塞多
Original assignee: Carrier Corp
Current assignee: Carrier Corp
Priority date: 2020-11-19
Filing date: 2020-11-19
Publication date: 2022-05-20

Abstract

The application relates to a protection circuit system and electronic equipment, protection circuit system includes current-limiting circuit, switch circuit and feedback circuit, wherein: the current limiting circuit is coupled to the input voltage, the switching circuit draws the output voltage, the current limiting circuit comprises a first transistor, the switching circuit comprises a second transistor, and the feedback circuit comprises a third transistor; the first transistor controls its state according to the output current flowing through the protection circuitry, thereby changing the control voltage of the second transistor; the switch circuit is coupled to the current limiting circuit and the second transistor forms electric power consumption according to output current flowing through; and the third transistor forms a feedback current according to the output voltage control, and the current limiting circuit controls the magnitude of the output current according to the feedback current based on the interpolar voltage drop of the first transistor. The protection circuit system can be used for preventing the circuit from overflowing, so that the safety of the circuit and electric equipment is guaranteed.

Description

Protection circuit system and electronic equipment

Technical Field

The present disclosure relates to the field of circuit security, and more particularly, to a protection circuit system and an electronic device including the same.

Background

For dc or pulsed dc type voltage output, existing overcurrent protection schemes are generally based on resettable fuse technology. The trip time of this technique is typically greater than a few milliseconds, and therefore there is a certain probability that other components in the power circuit may be damaged by heat build-up due to overcurrent. Furthermore, there are many prior art solutions that attempt to solve this problem either through expensive ASICs or through complex electronic circuit topologies.

Disclosure of Invention

The embodiment of the application provides a protection circuit system and electronic equipment comprising the same, and the protection circuit system can be used for preventing a circuit from overflowing, so that the safety of the circuit and electric equipment is guaranteed.

According to an aspect of the present application, there is provided a protection circuit system including a current limiting circuit, a switching circuit, and a feedback circuit, wherein: the current limiting circuit is coupled to an input voltage, the switching circuit draws an output voltage, the current limiting circuit comprises a first transistor, the switching circuit comprises a second transistor, and the feedback circuit comprises a third transistor; the first transistor controls the state thereof according to the output current flowing through the protection circuit system, thereby changing the control voltage of the second transistor; the switch circuit is coupled to the current limiting circuit and the second transistor forms an electrical power consumption according to the output current flowing through; and the third transistor forms a feedback current according to the output voltage control, and the current limiting circuit controls the magnitude of the output current according to the feedback current based on the interpolar voltage drop of the first transistor.

In some embodiments of the present application, optionally, the current limiting circuit further comprises a first resistor and a second resistor, the first resistor is connected in series to the first transistor, and the second resistor is connected in parallel to the series.

In some embodiments of the present application, optionally, the first transistor is a triode, and the first resistor is connected in series with a base of the first transistor.

In some embodiments of the present application, optionally, the switch circuit further includes a third resistor and a fourth resistor, the third resistor is connected in parallel to the second transistor, and the fourth resistor is connected in series to the parallel.

In some embodiments of the present application, optionally, the second transistor is a MOS transistor, and the third resistor is connected in parallel to a gate and a source of the second transistor.

In some embodiments of the present application, optionally, an emitter of the first transistor is coupled to a source of the second transistor via the second resistor, and a collector of the first transistor is coupled to a gate of the second transistor.

In some embodiments of the application, optionally, the feedback circuit further includes a fifth resistor, and the third transistor is coupled between the first transistor and the first resistor via the fifth resistor.

In some embodiments of the present application, optionally, the third transistor is a triode, and the output voltage is coupled to a base of the third transistor.

In some embodiments of the present application, optionally, the fifth resistor is coupled to an emitter of the third transistor.

According to another aspect of the present application, there is provided an electronic device comprising any one of the protection circuitry as described above.

Drawings

The above and other objects and advantages of the present application will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings, in which like or similar elements are designated by like reference numerals.

FIG. 1 shows a schematic diagram of protection circuitry according to one embodiment of the present application.

FIG. 2 shows a schematic diagram of protection circuitry according to one embodiment of the present application.

Fig. 3 shows an experimental situation of a protection circuit system according to an embodiment of the present application.

Fig. 4 shows an experimental situation of a protection circuit system according to an embodiment of the present application.

Detailed Description

For the purposes of brevity and explanation, the principles of the present application are described herein with reference primarily to exemplary embodiments thereof. However, those skilled in the art will readily recognize that the same principles are equally applicable to all types of protection circuitry and electronic devices that include the same, and that these same or similar principles may be implemented therein, with any such variations not departing from the true spirit and scope of the present application.

According to an aspect of the present application, a protection circuitry is provided. As shown in fig. 1, the protection circuitry 10 includes a current limiting circuit 102, a switching circuit 104, and a feedback circuit 106. The protection circuitry 10 is configured to provide protection for the output voltage based on the input voltage, and the protection circuitry 10 does not have a large voltage division during normal operation of the load, and thus the output voltage can be considered equal to the input voltage. The protection circuit system 10 is configured to detect whether the output current has an overcurrent trend (e.g., caused by a short circuit of a load circuit), and if the output current has the overcurrent trend, rapidly decrease the output power to the outside to decrease the output current to a small enough value (e.g., a preset overcurrent threshold or below), so as to avoid a secondary disaster caused by heat accumulation.

The current limiting circuit 102 of the protection circuitry 10 is coupled to an input voltage, e.g., a constant voltage source. It should be noted that the protection circuit system of the present invention is applied to a dc voltage, and thus the input voltage and the output voltage described in the context of the present invention are both referred to as a dc voltage. Specifically, in some examples, a positive polarity of the input voltage may be introduced directly to the current limit circuit, for example, and a negative polarity of the input voltage may be introduced to the current limit circuit 102 through the structure of other circuits. The switching circuit 104 draws the output voltage, and in particular, in some examples, the positive polarity of the output voltage may be drawn directly from the switching circuit 104, while the negative polarity of the output voltage may be drawn directly from the negative polarity of the input voltage.

The operation is described above in terms of positive polarity of the input voltage and the output voltage, and in some examples of the present application, "coupled to the input voltage" and "coupled out of the output voltage" and so on are used to illustrate the operation principle of the protection circuit system 10 for positive polarity, while negative polarity is connected into the circuit in a conventional manner in the art. In other examples, depending on the type of components or circuit design requirements in the protection circuit system 10 (specifically, the current limiting circuit 102, the switching circuit 104, and the feedback circuit 106), it is also possible to operate with respect to the negative polarity of the input voltage and the output voltage, and the scope of protection of the present invention extends to such variations.

The current limiting circuit 102 of the protection circuitry 10 includes a first transistor, the switching circuit 104 includes a second transistor, and the feedback circuit 106 includes a third transistor (not shown in fig. 1), which in a specific example of the invention are not necessarily of the same type or style. In addition, the first, second, third, and the like in the present invention are merely distinguished by formal names, and accompanying words are not limited technically, and in other examples, some or all of the first transistor, the second transistor, and the third transistor may have the same model or type. The invention is not limited herein to a particular type and model of transistor in order to be able to carry out the functions described in the context of the invention.

As will be understood from the context of the present invention, a transistor in the present invention refers to a transistor (excluding diodes, etc.) that can be controlled to operate, and typically includes three pins. In some examples, the transistor may be a P-MOS transistor, an N-MOS transistor, a PNP transistor, an NPN transistor, or the like. Depending on the type of the transistor, the current limiting circuit 102, the switching circuit 104, and the feedback circuit 106 may be controlled in accordance with the positive polarity of the input voltage and the output voltage, or may be controlled in accordance with the negative polarity of the input voltage and the output voltage.

The first transistor of the current limiting circuit 102 may control its state according to the output current flowing through the protection circuitry 10 and finally flowing to the load, and specifically may control whether the first transistor is turned on or not. For example, if the load circuit is abnormal, the output current may be larger than a certain set value or reach a set value boundary and have a further increasing trend, and at this time, the first transistor will be controlled to be turned on, so as to further realize the control of the second transistor of the switch circuit 104; in case the output to the load is normal, the output current is not sufficient to turn on the first transistor, which will maintain the off-state of the first transistor.

The on/off state of the first transistor of the current limiting circuit 102 will be used to vary the control voltage of the second transistor of the switching circuit 104, which will control the state of the second transistor (which may specifically be its on/off state), thereby enabling current control of the protection circuitry 10. The polarity controlled by the control voltage is referred to as the controlled (bi-) pole in this application, and the PN junction therebetween is referred to as the PN junction between the controlled (bi-) poles. While the third pole of the transistor may be switched in to a constant or nearly constant voltage point and is thus described in this application as not being affected by the control voltage.

For example, when the output current reaches a preset overcurrent threshold, the first transistor will be turned on instantly, and the control voltage of the second transistor will satisfy the condition for turning off the first transistor due to the turning on of the first transistor (e.g., the control voltage is between two controlled poles, etc.). If the second transistor is turned off, the output current will approach zero, and the first transistor will be turned off accordingly, and the control voltage of the second transistor will satisfy the condition … … for turning on. Ideally, the above process cycles back and forth such that the circuit is finally in an equilibrium state, i.e. the first transistor will just turn on, and the output current flowing through the protection circuitry 10 will be equal to or close to the preset overcurrent threshold.

In this manner, the entire circuit (including protection circuitry 10 and other connected circuitry) may be protected from load circuit overcurrent in the event of an overcurrent trend. In addition, when the output current is below the set value, the circuit works normally, at this time, the first transistor will be in an off state, and the second transistor will be in an on state. It should be noted that the above process does not introduce the function of the feedback circuit 106 in order to illustrate the principle of the present invention in steps. The reader will be more aware of how the protection circuitry 10 of the present invention operates in conjunction with the action of the feedback circuit 106, which will be described in detail below.

The switch circuit 104 is coupled to the current limiting circuit 102 and the second transistor forms an electrical power consumption from the output current flowing through the second transistor, which may also be referred to as a power consumption transistor. When the load circuit is normal, the voltage drop across the switching circuit 104 is small and the output current flowing through the protection circuitry 10 (the switching circuit 104) and ultimately to the load is also at a design level, then the power consumption of the switching circuit 104 (specifically, the second transistor) is negligible. When the load circuit is subject to an overcurrent trend due to too small a load impedance, the switching circuit 104 will take a large portion of the voltage drop of the input voltage if the feedback circuit 106 is not considered, and will take a large power on the second transistor even if the current through the second transistor is small. Thus, the power consumption endurance of the power consumption transistor is high, and the requirement is further increased in consideration of design redundancy, which is not reimburseable for low-cost design.

It should be noted that, although the above description only describes the operation principle of the current limiting circuit 102 and the switching circuit 104, the above described principle should be regarded as the basic description when the feedback circuit 106 is introduced to describe the basic principle of the present invention.

In the present invention, the third transistor of the feedback circuit 106 may form a feedback current according to the output voltage control, and the current limiting circuit 102 controls the magnitude of the further output current according to the feedback current based on the inter-electrode voltage drop of the first transistor.

In some examples, one of the controlled two poles of the third transistor may be introduced (or introduced through other means) to the positive polarity of the input voltage, and the other pole may be introduced to the positive polarity of the output voltage. Since the input voltage is constant, the control voltage of one polarity is constant or approximately constant, and thus the output voltage will be the control voltage of the third transistor. In some examples, when the output voltage is smaller, the feedback current caused by the third transistor may be larger, and the current limiting circuit 102 may control the output current to be smaller, so as to successfully realize the adjustment of the magnitude of the output current according to the monitoring of the output voltage. The inter-electrode voltage drop of the first transistor in this application at least includes the voltage drop when the PN junction between the two electrodes controlled by the output current in the first transistor is in saturation conduction, and is, for example, 0.65V.

For example, it has been described above that the current limiting circuit 102 includes a first transistor, and in some examples, if the first transistor is a PNP transistor, the voltage drop across the PN junction between the emitter and the base of the first transistor is fixed when the first transistor is in the on state. The voltage drop across the PN junction may be made up of two parts, one caused by the output current and the other caused by the feedback current. As the feedback current is larger, its contribution to the voltage drop over the PN junction will be larger, and correspondingly, the contribution to the voltage drop caused by the output current will be smaller. In some examples, if the voltage drop is formed by a resistive element, the output current will also decrease according to ohm's law. In other examples, the first transistor may be another type of transistor, and the voltage drop across the PN junction between the transistors may also be used to control the output current. The present application also does not limit how the voltage drop across the inter-electrode PN junction of the first transistor is configured, so that it can simultaneously take in the contributions of the output current and the feedback current.

Due to the introduction of the feedback circuit 106, when the output has an overcurrent tendency, such as due to a short circuit, the output current of the circuit 10 will be significantly less than if the feedback circuit 106 was not introduced. Therefore, the power consumption resistance index of the second transistor can be remarkably reduced, and the circuit cost can be further reduced.

In some embodiments of the present application, as shown in fig. 2, based on the corresponding example of fig. 1, the protection circuitry 20 supplies power to the load 210 according to a power supply 201, the protection circuitry 20 including the current limiting circuit 102, the switching circuit 104, and the feedback circuit 106. In the protection circuit system 20, the current limiting circuit 102 further specifically includes a first resistor 203 and a second resistor 204, the first resistor 203 is connected in series to the first transistor 202, and the second resistor 204 is connected in parallel to a series circuit formed by the first resistor 203 and the first transistor 202. Thus, a voltage drop in a resistive circuit including the first resistor 203 and the second resistor 204 can be used as a control voltage between the two electrodes of the first transistor 202.

When no current flows (or almost negligible) across the first resistor 203 in series with the first transistor 202, the voltage drop across the second resistor 204 will allow independent control of the on/off state of the first transistor 202; in other words, the flowing current (output current) across the second resistor 204 will control the on/off state of the first transistor 202. When a current flows through the first resistor 203 in series with the first transistor 202, the sum of the voltage drops across the first resistor 203 and the second resistor 204 constitutes the control voltage for the first transistor 202.

After the first transistor 202 is turned on, the voltage drop across the PN junction between the first resistor 203 and the second resistor 204 can be kept constant, and the sum of the voltage drops across the first resistor 203 and the second resistor 204 is equal to the voltage drop across the PN junction (e.g., about 0.65V). If the voltage drop across the first resistor 203 increases, the voltage drop across the second resistor 204 will adaptively decrease, with the result that the current across the second resistor 204 will decrease.

In some embodiments of the present application, the first transistor is a transistor, and the first resistor is connected in series with a base of the first transistor. Referring further to fig. 2, if the first transistor 202 is a PNP transistor, the first resistor 203 is connected to its base, and the second resistor 204 is connected to its emitter. After the first transistor 202 is turned on, the voltage drop across the PN junction between the base and the emitter can be kept constant (e.g., 0.65V), and the sum of the voltage drops across the first resistor 203 and the second resistor 204 is equal to the voltage drop across the PN junction (also 0.65V). If the voltage drop across the first resistor 203 increases (e.g., increases by 0.2V), the voltage drop across the second resistor 204 decreases (e.g., decreases by 0.2V), and as a result, the current across the second resistor 204 decreases (0.2V divided by the resistance of the second resistor 204), and thus the current (output current) flowing through the second resistor 204 decreases. In addition, after reading the present application, the skilled person may also configure the first transistor 202 as a NPN-type transistor according to the above description, and this also should be considered as falling within the scope of the present invention.

In some embodiments of the present application, as shown in fig. 2, the switch circuit 104 further includes a third resistor 206 and a fourth resistor 207, the third resistor 206 is connected in parallel to the second transistor 205, and the fourth resistor 207 is connected in series to a parallel circuit formed by the third resistor 206 and the second transistor 205. In the normal load condition, the third resistor 206 and the fourth resistor 207 form a voltage dividing circuit to provide the operating voltage for the second transistor 205.

In some embodiments of the present application, the second transistor 205 is a MOS transistor, and the third resistor 206 is connected in parallel to the gate and the source of the second transistor 205. The power MOS transistor may have a better power consumption tolerance, and thus may be used as a power transistor in the switch circuit 104. In fig. 2, it is shown that the second transistor 205 is a P-MOS transistor, and the third resistor 206 and the fourth resistor 207 provide an initial bias voltage for the second transistor 205, so that the second transistor 205 will be in a conducting state under the condition that the output current is normal.

With continued reference to fig. 2, in some embodiments of the present application, the emitter of the first transistor 202 is coupled to the source of the second transistor 205 via the second resistor 204, and the collector of the first transistor 202 is coupled to the gate of the second transistor 205. Thus, if the first transistor 202 is turned on, the voltage (control voltage) between the gate and the source of the second transistor 205 will be limited to a lower voltage, so that the output current of the second transistor 205 will decrease and eventually smooth (reach the predetermined over-current threshold) as described above. The above connection coupling method is suitable for the illustrated P-MOS transistor, and after reading this application, those skilled in the art may also set the second transistor 205 as an N-MOS circuit according to the above basic principle, which should also be considered as falling within the scope of the present invention.

Referring to fig. 2, in some embodiments of the present application, the feedback circuit 106 further includes a fifth resistor 209, and the third transistor 208 is coupled between the first transistor 202 and the first resistor 203 via the fifth resistor 209. With this design, the current flowing through the fifth resistor 209 will mainly come from the current flowing through the first resistor 203, and thus the feedback current (the current flowing through the fifth resistor 209) can be represented by the current on the first resistor 203.

Furthermore, when the output current in the protection circuitry 20 is at a reasonable level, the voltage across the controlled interpolar PN junction of the third transistor 208 (approximately equipotential) is insufficient to open the third transistor 208. When the output current in the protection circuit system 20 tends to exceed a reasonable level, the current limiting circuit 102 and the switching circuit 104 will act, and the voltage across the PN junction between the two controlled terminals will probably satisfy the condition of turning on the third transistor 208.

According to the above description, after the first transistor 202 is turned on, the voltage drop across the PN junction connected between the two poles of the circuit can be kept constant, and the sum of the voltage drops across the first resistor 203 and the second resistor 204 is equal to the voltage drop across the PN junction. If the feedback current increases, the voltage drop across the first resistor 203 increases; further, the voltage drop across the second resistor 204 will be reduced, with the result that the current across the second resistor 204, and thus the output current, will be reduced.

With continued reference to fig. 2, in some embodiments of the present application, the third transistor 208 is a triode and the output voltage is coupled to the base of the third transistor 208. Specifically, the third transistor 208 may be, for example, a transistor of the same type or the same specification as the first transistor 202. In some examples, the positive polarity of the output voltage is coupled to the base of the third transistor 208 and the negative polarity of the output voltage (input voltage) is coupled to the collector of the third transistor 208. While the emitter of the third transistor 208 may be coupled to the positive polarity of the input voltage via other circuit portions as shown.

With continued reference to fig. 2, in some embodiments of the present application, if the third transistor 208 is a PNP transistor, the fifth resistor 209 is coupled to the emitter of the third transistor 208. After reading this application, those skilled in the art may also configure the third transistor 208 as a NPN-type transistor according to the above description, and this should also be considered as falling within the scope of the present invention.

It should be noted that although the basic principles of the present invention are illustrated in fig. 2 by using the first transistor 202, the second transistor 205, and the third transistor 208 as PNP type triodes, P-MOS transistors, and PNP type triodes, respectively, after reading this application, those skilled in the art can apply the principles of the present invention to other types of transistors, and the protection scope of the present invention is not limited by the types of transistors listed.

The specific specifications of each transistor, resistor and the like in the invention can be selected according to actual needs and experience. For example, if the predetermined over-current threshold is I_thThe voltage drop across the controlled interpolar PN junction of the first transistor 202 is U_PNThen the value of the second resistor 204 may be selected to be approximately U_PN/I_thThe size of (2). As another example, the third resistor 206 and the fourth resistor 207 may be selected to have a resistance on the order of 100 kQ to 500 kQ.

The protection circuitry described above may be employed in, for example, a circuit or device having an output current below 1.5A, and fig. 3 and 4 show experimental results of the protection circuitry according to one embodiment of the present application. As shown in fig. 3, in the case where the load is normal, the output voltage will remain substantially equal to the input voltage, and the output current may vary within a preset range according to the load condition (e.g., the total resistance of a purely linear load). If the load is abnormal, the output current tends to exceed the preset overcurrent value, and devices in the circuit are triggered by the output current and act. As shown by the hatched portion in fig. 3, the circuit characteristic will be folded back (fold back) from the upper right to the lower left in the figure, and the output current and the output voltage will also be significantly reduced. With continued reference to fig. 4, if the output current is normal, it indicates that the external load is normal, or the resistance of the external load is at a reasonable level, and the power consumption of the second transistor is negligible. As the external load resistance decreases, the second transistor will now act as a power consuming component if the output current tends to exceed a reasonable level. And when the resistance value of the external load reaches a specific value, the power consumption of the second transistor reaches the highest level. At this time, if the external load resistance value continues to decrease, the current (output current) on the second transistor will decrease, and thus if the voltage drop across the second transistor is regarded as substantially constant (approximately equal to the input voltage), the power consumption on the second transistor will also decrease accordingly.

According to another aspect of the present application, there is provided an electronic device comprising any one of the protection circuitry as described above. An electronic device such as an audible and visual alarm may include any of the protection circuitry described in this application so that the risk of a malfunction such as a short circuit occurring in a load portion of the electronic device can be avoided. The protection circuitry may be integrated into a transformer of the electronic device with a constant low voltage output by the transformer as an input voltage to the protection circuitry and an output voltage of the protection circuitry being introduced to the electronic device. The protection circuit system can also be directly integrated in the electronic equipment, and the constant low voltage input from the outside is used as the input voltage of the protection circuit system, and the output voltage of the protection circuit system is introduced to be used as the working energy of the electronic equipment.

The above are merely specific embodiments of the present application, but the scope of the present application is not limited thereto. Other possible variations or alternatives may occur to those skilled in the art based on the technical scope disclosed in the present application, and are all covered by the scope of the present application. In the present invention, the embodiments and features of the embodiments may be combined with each other without conflict. The scope of protection of the present application is subject to the description of the claims.

Claims

1. A protection circuitry comprising a current limiting circuit, a switching circuit, and a feedback circuit, wherein:

the current limiting circuit is coupled to an input voltage, the switching circuit draws an output voltage, the current limiting circuit comprises a first transistor, the switching circuit comprises a second transistor, and the feedback circuit comprises a third transistor;

the first transistor controls the state thereof according to the output current flowing through the protection circuit system, thereby changing the control voltage of the second transistor;

the switch circuit is coupled to the current limiting circuit and the second transistor forms an electrical power consumption according to the output current flowing through; and

the third transistor forms a feedback current according to the output voltage control, and the current limiting circuit controls the magnitude of the output current according to the feedback current based on the inter-electrode voltage drop of the first transistor.

2. The circuit of claim 1, the current limiting circuit further comprising a first resistor and a second resistor, the first resistor connected in series to the first transistor and the second resistor connected in parallel to the series.

3. The circuit of claim 2, the first transistor being a transistor and the first resistor being in series with a base of the first transistor.

4. The circuit of claim 3, the switching circuit further comprising a third resistor and a fourth resistor, the third resistor being connected in parallel to the second transistor and the fourth resistor being connected in series to the parallel.

5. The circuit of claim 4, the second transistor being a MOS transistor and the third resistor being connected in parallel to the gate and source of the second transistor.

6. The circuit of claim 5, an emitter of the first transistor coupled to a source of the second transistor via the second resistor, and a collector of the first transistor coupled to a gate of the second transistor.

7. The circuit of claim 2, the feedback circuit further comprising a fifth resistor, the third transistor coupled between the first transistor and the first resistor via the fifth resistor.

8. The circuit of claim 7, the third transistor being a triode, and the output voltage being coupled to a base of the third transistor.

9. The circuit of claim 8, the fifth resistance coupled to an emitter of the third transistor.

10. An electronic device comprising the protection circuitry of any one of claims 1-9.