Protection circuit system and electronic equipment

Abstract

The present application relates to a protection circuit system and electronic equipment, wherein the protection circuit system includes 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 leads to an output voltage, the current limiting circuit includes a first transistor, the switching circuit includes a second transistor, and the feedback circuit includes a third transistor; the first transistor controls its state according to the output current flowing through the protection circuit system, thereby changing the control voltage of the second transistor; the switching circuit is coupled to the current limiting circuit and the second transistor generates power consumption according to the output current flowing therethrough; and the third transistor controls the formation of a feedback current according to the output voltage, 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. The protection circuit system can be used to prevent circuit overcurrent, thereby ensuring the safety of the circuit and electrical equipment.

Description

Technical Field

[0001] The present application relates to the field of circuit safety, and in particular to a protection circuit system and an electronic device including the protection circuit system. Background Art

[0002] Existing overcurrent protection solutions for DC or pulsed DC voltage outputs typically rely on resettable fuses. This technology typically has a trip time exceeding several milliseconds, potentially damaging other components in the power supply circuit due to heat buildup caused by the overcurrent. Furthermore, many existing technologies attempt to address this issue using expensive ASICs or complex electronic circuit topologies. Summary of the Invention

[0003] Embodiments of the present application provide a protection circuit system and an electronic device including the same. The protection circuit system can be used to prevent circuit overcurrent, thereby ensuring the safety of the circuit and electrical equipment.

[0004] According to one aspect of the present application, a protection circuit system is provided, 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 out 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 its state according to the output current flowing through the protection circuit system, thereby changing the control voltage of the second transistor; the switching circuit is coupled to the current limiting circuit and the second transistor generates electrical power consumption according to the output current flowing therethrough; 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.

[0005] In some embodiments of the present application, optionally, the current limiting circuit further includes 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 connection.

[0006] In some embodiments of the present application, optionally, the first transistor is a triode, and the first resistor is connected in series to the base of the first transistor.

[0007] In some embodiments of the present application, optionally, the switching 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 connection.

[0008] In some embodiments of the present application, optionally, the second transistor is a MOS transistor, and the third resistor is connected in parallel to the gate and source of the second transistor.

[0009] In some embodiments of the present application, optionally, the emitter of the first transistor is coupled to the source of the second transistor via the second resistor, and the collector of the first transistor is coupled to the gate of the second transistor.

[0010] In some embodiments of the present 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.

[0011] In some embodiments of the present application, optionally, the third transistor is a triode, and the output voltage is coupled to the base of the third transistor.

[0012] In some embodiments of the present application, optionally, the fifth resistor is coupled to the emitter of the third transistor.

[0013] According to another aspect of the present application, an electronic device is provided, which includes any one of the protection circuit systems described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The above and other objects and advantages of the present application will become more fully apparent from the following detailed description taken in conjunction with the accompanying drawings, wherein the same or similar elements are denoted by the same reference numerals.

[0015] Figure 1 A schematic diagram of a protection circuit system according to an embodiment of the present application is shown.

[0016] Figure 2 A schematic diagram of a protection circuit system according to an embodiment of the present application is shown.

[0017] Figure 3 The figure shows an experimental situation of a protection circuit system according to an embodiment of the present application.

[0018] Figure 4 The figure shows an experimental situation of a protection circuit system according to an embodiment of the present application. DETAILED DESCRIPTION

[0019] For the purpose of brevity and illustration, the principles of the present application are described herein primarily with reference 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 circuit systems and electronic devices including the same, and that the same or similar principles may be implemented therein, without departing from the true spirit and scope of the present application.

[0020] According to one aspect of the present application, a protection circuit system is provided. Figure 1As shown, the protection circuit system 10 includes a current limiting circuit 102, a switching circuit 104, and a feedback circuit 106. The protection circuit system 10 is used to provide output voltage protection based on the input voltage. When the load is operating normally, the protection circuit system 10 does not experience significant voltage division, so the output voltage can be considered equal to the input voltage. The protection circuit system 10 is used to detect whether the output current is showing an overcurrent trend (e.g., caused by a short circuit in the load circuit). If an overcurrent trend is present, the protection circuit system 10 quickly reduces the output power to a sufficiently low level (e.g., at or below a preset overcurrent threshold), thereby preventing secondary hazards caused by heat accumulation.

[0021] The current limiting circuit 102 of the protection circuit system 10 is coupled to an input voltage, for example, a constant voltage source. It should be noted that the protection circuit system of the present invention is used under a DC voltage, and therefore the input voltage and output voltage recorded in the context of the present invention all refer to DC voltage. Specifically, in some examples, for example, the positive polarity of the input voltage can be directly introduced into the current limiting circuit, and the negative polarity of the input voltage can be introduced into the current limiting circuit 102 through the structure of other circuits. The switching circuit 104 draws out the output voltage. Specifically, in some examples, the positive polarity of the output voltage can be directly drawn from the switching circuit 104, and the negative polarity of the output voltage can be directly drawn from the negative polarity of the input voltage.

[0022] The above examples illustrate how the protection circuit system 10 can operate with positive polarity input and output voltages. In some examples of this application, terms such as "coupled to the input voltage" and "derived from the output voltage" describe the operating principle of the protection circuit system 10 with respect to positive polarity, while negative polarity is connected to the circuit according to conventional connection methods in the art. In other examples, depending on the types of components in the protection circuit system 10 (specifically, the current limiting circuit 102, the switch circuit 104, and the feedback circuit 106) or circuit design requirements, it is also possible to operate with negative polarity input and output voltages. The scope of protection of the present invention extends to such variations.

[0023] The current limiting circuit 102 of the protection circuit system 10 includes a first transistor, the switch circuit 104 includes a second transistor, and the feedback circuit 106 includes a third transistor ( Figure 1 (not shown) In a specific example of the present invention, the first transistor, the second transistor, and the third transistor do not necessarily have the same model or type. In addition, the first, second, and third in the present invention are only used to distinguish the names in a formal way, and the words following them do not impose technical restrictions. 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 present invention does not limit the specific type and model of the transistor, as long as it can achieve the functions described in the context of the present invention.

[0024] As described in the context of the present invention, a transistor in the present invention refers to a transistor capable of controlled operation (excluding diodes, etc.), typically comprising three pins. In some examples, the transistor may be a P-MOS transistor, an N-MOS transistor, a PNP transistor, or an NPN transistor. Depending on the type of transistor, the current limiting circuit 102, the switch circuit 104, and the feedback circuit 106 may be controlled based on the positive polarity of the input voltage or the output voltage, or based on the negative polarity of the input voltage or the output voltage.

[0025] The first transistor of the current limiting circuit 102 can control its state based on the output current flowing through the protection circuit system 10 and ultimately to the load. Specifically, it can control whether the first transistor is turned on or off. For example, if the load circuit is abnormal, the output current may exceed a certain set value or reach the set value limit and show a trend of further increase. In this case, the first transistor will be controlled to turn on, thereby further implementing control of the second transistor of the switch circuit 104. When the output to the load is normal, the output current is insufficient to turn on the first transistor, and the first transistor will remain in the off state.

[0026] The on / off state of the first transistor of current limiting circuit 102 is used to change the control voltage of the second transistor of switch circuit 104. This control voltage controls the state of the second transistor (specifically, its on / off state), thereby achieving current control of protection circuit system 10. The polarity controlled by the control voltage is referred to as the controlled (two) poles in this application, and the PN junction between them is referred to as the PN junction between the (two) controlled poles. The third pole of the transistor may be connected to a constant or nearly constant voltage point and is therefore described in this application as being unaffected by the control voltage.

[0027] For example, when the output current reaches a preset overcurrent threshold, the first transistor will instantly turn on. At this point, the control voltage of the second transistor will satisfy the conditions for turning it off (e.g., the control voltage is equal between the two controlled electrodes) due to the conduction of the first transistor. If the second transistor turns off, the output current will approach zero, and the first transistor will also turn off. At this point, the control voltage of the second transistor will again satisfy the conditions for turning it on. In theory, the above process will repeat itself, ultimately leading to a balanced circuit state, where the first transistor will be exactly on, and the output current flowing through the protection circuit system 10 will be equal to or approximately equal to the preset overcurrent threshold.

[0028] In this way, when an overcurrent trend occurs, the entire circuit (including the protection circuit system 10 and other connected circuits) can be protected from the effects of overcurrent in the load circuit. Furthermore, when the output current is below the set value, the circuit operates normally, with the first transistor being off and the second transistor being on. It should be noted that, in order to illustrate the principles of the present invention in a step-by-step manner, the above process does not include the function of feedback circuit 106. The reader will have a clearer understanding of the operation of the protection circuit system 10 of the present invention when combined with the detailed description of the function of feedback circuit 106 below.

[0029] Switching circuit 104 is coupled to current limiting circuit 102, and the second transistor consumes power based on the output current flowing through the second transistor. The second transistor can also be referred to as a power transistor. When the load circuit is operating normally, the voltage drop across switching circuit 104 is low, and the output current flowing through protection circuit system 10 (switching circuit 104) and ultimately to the load is within the design level. Therefore, the power consumption of switching circuit 104 (specifically, the second transistor) is negligible. When the load circuit exhibits an overcurrent tendency due to low load impedance, without considering the effect of feedback circuit 106, switching circuit 104 will bear most of the voltage drop across the input voltage. Even with a low current flowing through the second transistor, the second transistor will still bear a significant amount of power. This results in a higher power consumption tolerance for the power transistor, which can be further increased when design redundancy is considered, which is not worth the cost for a low-cost design.

[0030] It should be noted that although the above content only describes the working principles of the current limiting circuit 102 and the switching circuit 104, when the feedback circuit 106 is introduced to describe the basic principles of the present invention, the principles described above should be regarded as a basic explanation thereof.

[0031] In the present invention, the third transistor of the feedback circuit 106 can form a feedback current according to the output voltage control, and the current limiting circuit 102 further controls the magnitude of the output current according to the feedback current based on the inter-electrode voltage drop of the first transistor.

[0032] In some examples, one of the two controlled electrodes of the third transistor can be introduced (or introduced through other components) to the positive polarity of the input voltage, and the other electrode can 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 serve as the control voltage of the third transistor. In some examples, the smaller the output voltage, the larger the feedback current caused by the third transistor can be, and the current limiting circuit 102 can control the output current to be smaller, thereby successfully achieving the adjustment of the output current based on the monitoring of the output voltage. In this application, the inter-electrode voltage drop of the first transistor includes at least the voltage drop of the PN junction between the two electrodes controlled by the output current in the first transistor when it is in saturation conduction, for example, 0.65V.

[0033] For example, the current limiting circuit 102 has been described above as including a first transistor. In some examples, if the first transistor is a PNP-type transistor, the voltage drop across the PN junction between its emitter and base is fixed when it is in the on state. The voltage drop across the PN junction can be composed of two parts: one part caused by the output current and the other part caused by the feedback current. The larger the feedback current, the greater its contribution to the voltage drop across the PN junction. Correspondingly, the contribution of the voltage drop caused by the output current will be smaller. In some examples, if the voltage drop is formed by a resistive element, according to Ohm's law, the output current will also decrease. In other examples, the first transistor may also be another type of transistor, and the voltage drop across the PN junction between its electrodes can also be used to achieve output current control. This application does not limit how the voltage drop across the PN junction between the electrodes of the first transistor is constructed, as long as it can simultaneously incorporate the contributions of the output current and the feedback current.

[0034] Due to the introduction of feedback circuit 106, when an overcurrent trend occurs at the output, such as caused by a short circuit, the output current of circuit 10 will be significantly lower than when feedback circuit 106 is not introduced. Therefore, the power consumption indicator of the second transistor can be significantly reduced, thereby further reducing circuit cost.

[0035] In some embodiments of the present application, Figure 2 As shown, based on Figure 1 In a corresponding example, the protection circuit system 20 supplies power to the load 210 based on the power supply 201. The protection circuit system 20 includes a current limiting circuit 102, a switching circuit 104, and a 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 the series circuit formed by the first resistor 203 and the first transistor 202. Therefore, the voltage drop across the resistive circuit formed by the first resistor 203 and the second resistor 204 can be used as the control voltage between the two electrodes of the first transistor 202.

[0036] When no current flows through the first resistor 203 connected in series with the first transistor 202 (or when current is almost negligible), the voltage drop across the second resistor 204 can independently control the on / off state of the first transistor 202. In other words, the current (output current) flowing through the second resistor 204 can control the on / off state of the first transistor 202. When current flows through the first resistor 203 connected 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 of the first transistor 202.

[0037] 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 remain constant. At this point, 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., approximately 0.65V). If the voltage drop across the first resistor 203 increases, the voltage drop across the second resistor 204 will decrease accordingly, resulting in a decrease in the current flowing through the second resistor 204.

[0038] In some embodiments of the present application, the first transistor is a triode, and the first resistor is connected in series with the base of the first transistor. Figure 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 remain constant (e.g., 0.65V). At this time, 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., by 0.2V), the voltage drop across the second resistor 204 will decrease (e.g., by 0.2V). As a result, the current through the second resistor 204 will decrease (0.2V divided by the resistance value of the second resistor 204), and thus the current flowing through the second resistor 204 (the output current) will also decrease. In addition, after reading this application, those skilled in the art may also configure the circuit according to the above disclosure to configure the first transistor 202 as an NPN transistor, and this should also be considered to fall within the scope of protection of the present invention.

[0039] In some embodiments of the present application, Figure 2 As shown, 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 the parallel circuit formed by the third resistor 206 and the second transistor 205. When the load is normal, the third resistor 206 and the fourth resistor 207 form a voltage divider circuit to provide an operating voltage for the second transistor 205.

[0040] 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 source of the second transistor 205. A power MOS transistor can have a better power consumption tolerance index and thus can be used as a power transistor in the switch circuit 104. Figure 2 As shown in FIG, the second transistor 205 is a P-MOS tube, and the third resistor 206 and the fourth resistor 207 provide an initial bias voltage for the second transistor 205. Therefore, when the output current is normal, the second transistor 205 will be in the on state.

[0041] Continue to see Figure 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 in the on state, the voltage between the gate and source of the second transistor 205 (the control voltage) will be limited to a lower voltage, thereby reducing the output current of the second transistor 205 and ultimately stabilizing the output current (reaching a preset overcurrent threshold) as described above. The above connection and coupling method is applicable to the P-MOS transistor shown in the figure. In addition, after reading this application, those skilled in the art can also configure a circuit in which the second transistor 205 is an N-MOS according to the above basic principles, which should also be considered to fall within the scope of protection of the present invention.

[0042] See also Figure 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, so the feedback current (the current flowing through the fifth resistor 209) can be reflected by the current on the first resistor 203.

[0043] Furthermore, when the output current of the protection circuit system 20 is at a reasonable level, the voltage across the PN junction between the two controlled electrodes of the third transistor 208 (approximately equal) is insufficient to turn on the third transistor 208. When the output current of the protection circuit system 20 tends to exceed the reasonable level, the current limiting circuit 102 and the switch circuit 104 will operate, and at this point, the voltage across the PN junction between the two controlled electrodes may meet the conditions for turning on the third transistor 208.

[0044] As described above, after first transistor 202 is turned on, the voltage drop across the PN junction between the two electrodes connected to the circuit can remain constant. At this time, the sum of the voltage drops across first resistor 203 and second resistor 204 is equal to the voltage drop across the PN junction. If the feedback current increases, the voltage drop across first resistor 203 increases; further, the voltage drop across second resistor 204 decreases accordingly, resulting in a decrease in the current flowing through second resistor 204 and, consequently, a decrease in the output current.

[0045] Continue to see Figure 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 can be, for example, a transistor of the same model or 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. The emitter of the third transistor 208 can be coupled to the positive polarity of the input voltage via other circuit components as shown in the figure.

[0046] Continue to see Figure 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 a circuit in which the third transistor 208 is an NPN transistor according to the above content, and this should also be considered to fall within the scope of protection of the present invention.

[0047] It should be noted that although Figure 2 The basic principles of the present invention are illustrated by taking the first transistor 202, the second transistor 205, and the third transistor 208 as a PNP transistor, a P-MOS transistor, and a PNP transistor as examples, respectively. However, those skilled in the art can apply the principles of the present invention to other types of transistors after reading this application, and the scope of protection of the present invention is not limited to the listed transistor types.

[0048] The specific specifications of each transistor, resistor, etc. in the present invention can be selected according to actual needs and experience. For example, if the preset overcurrent threshold is I th The voltage drop across the PN junction between the controlled electrodes of the first transistor 202 is U PN , then the resistance of the second resistor 204 can be selected to be approximately U PN / I th For another example, the third resistor 206 and the fourth resistor 207 can be selected to be a resistor in the range of 100 kΩ to 500 kΩ.

[0049] The protection circuit system described above can be used in circuits or devices with an output current below 1.5A, Figure 3 and Figure 4 FIG. 2 shows the experimental results of a protection circuit system according to an embodiment of the present application. Figure 3 As shown in the figure, under normal load conditions, the output voltage will remain essentially equal to the input voltage, and the output current can vary within a preset range based on the load conditions (e.g., the total resistance of a purely linear load). If the load becomes abnormal, the output current will tend to exceed the preset overcurrent value, triggering the components in the circuit to operate. Figure 3 As shown in the middle slashed area, the circuit characteristics will fold back from the upper right to the lower left of the figure. At this time, the output current and output voltage will also drop significantly. Figure 4 If the output current is normal, it indicates that the external load is normal, or that the external load resistance is at a reasonable level. At this time, the power consumption of the second transistor can be ignored. As the external load resistance decreases, if the output current tends to exceed the reasonable level, the second transistor will act as a power consumption component. Until the external load resistance reaches a specific value, the power consumption of the second transistor reaches the highest level. At this time, if the external load resistance continues to decrease, the current on the second transistor (output current) will decrease. Therefore, if the voltage drop across the second transistor is considered to be basically unchanged (approximately equal to the input voltage), the power consumption of the second transistor will also decrease.

[0050] According to another aspect of the present application, an electronic device is provided, which includes any one of the protection circuit systems described above. Electronic devices such as sound and light alarms can include any one of the protection circuit systems described in this application, thereby avoiding the risks caused by faults such as short circuits in the load part of the electronic device. The protection circuit system can be integrated into the transformer of the electronic device, with the constant low voltage output by the transformer as the input voltage of the protection circuit system, and the output voltage of the protection circuit system is introduced into the electronic device. The protection circuit system can also be directly integrated into the electronic device, with the constant low voltage input from the outside as the input voltage of the protection circuit system, and the output voltage of the protection circuit system is introduced as the working energy of the electronic device.

[0051] The above are only specific embodiments of the present application, but the scope of protection of the present application is not limited thereto. Those skilled in the art can think of other feasible changes or replacements based on the technical scope disclosed in this application, and such changes or replacements are all included in the scope of protection of the present application. In the absence of conflict, the embodiments of the present application and the features in the embodiments can also be combined with each other. The scope of protection of the present application shall be based on the description of the claims.

Claims

1. A protection circuit system, comprising a current limiting circuit, a switching circuit, and a feedback circuit, wherein: The current limiting circuit is coupled to an input voltage, the switch circuit leads to an output voltage, the current limiting circuit includes a first transistor, the switch circuit includes a second transistor, and the feedback circuit includes a third transistor; The first transistor controls its state 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 therethrough; 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, wherein the inter-electrode voltage drop is composed of a first voltage drop component caused by the feedback current and a second voltage drop component caused by the output current. 2 . The circuit system of claim 1 , wherein the current limiting circuit further comprises a first resistor and a second resistor, the first resistor being connected in series to the first transistor, and the second resistor being connected in parallel to the series connection. 3 . The circuit system according to claim 2 , wherein the first transistor is a triode, and the first resistor is connected in series with the base of the first transistor. 4 . The circuit system according to claim 3 , wherein the switch circuit further comprises 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 connection. 5 . The circuit system according to claim 4 , wherein the second transistor is a MOS transistor, and the third resistor is connected in parallel to the gate and source of the second transistor. 6 . The circuit system of claim 5 , the emitter of the first transistor being coupled to the source of the second transistor via the second resistor, and the collector of the first transistor being coupled to the gate of the second transistor. 7 . The circuit system according to claim 2 , wherein the feedback circuit further comprises a fifth resistor, and the third transistor is coupled between the first transistor and the first resistor via the fifth resistor. 8 . The circuit system of claim 7 , wherein the third transistor is a triode, and the output voltage is coupled to a base of the third transistor. 9 . The circuit system of claim 8 , wherein the fifth resistor is coupled to an emitter of the third transistor.

10. An electronic device comprising the protection circuit system according to any one of claims 1 to 9.

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