Electronic fuse circuit

Abstract

The electronic fuse circuit is coupled to the load device at an output node, and comprises a fuse switch, a charge mercury circuit, a current-to-voltage circuit and a reset circuit. The fuse switch receives an input voltage to generate an output voltage at an output node, and generates an output current to the output node. The charge mercury circuit is coupled to the first node and controls the fuse switch according to a node voltage at the first node to control the output voltage. The current-to-voltage circuit is coupled to the fuse switch and the second node, and converts the output current to generate a current-dependent voltage at the second node. The reset circuit is coupled to the first node and the second node, and controls the node voltage to trigger the charge mercury circuit to turn off the fuse switch after a response time matched with a current threshold in response to the output current exceeding the current threshold. Through the reset circuit and the electronic fuse circuit, the problem that the abnormal large load current cannot be effectively responded during over-temperature protection can be avoided, and the problem that over-current protection is mistakenly touched can be avoided.

Description

Electronic fuse circuit Technical Field

[0001] This utility model relates to an electronic fuse circuit and a reset circuit, and more particularly to an electronic fuse circuit and a reset circuit that can operate according to a current threshold and a response time. Background Technology

[0002] In electronic fuse technology, the current that triggers the over-temperature protection of an electronic fuse is typically much higher than the current value used in normal applications (i.e., the current threshold for over-temperature protection is too high). This causes the electronic fuse to fail to shut off in response to abnormal current values ​​that are below the aforementioned current threshold but above the current value used in normal applications, thus failing to provide protection. This is especially true when electronic fuses are used in automotive systems, where the high safety requirements make the protection provided in response to abnormal current values ​​particularly important. Therefore, it is necessary to propose new approaches to address the aforementioned problems. Summary of the Invention

[0003] One embodiment of this utility model is an electronic fuse circuit. The electronic fuse circuit is coupled to a load device at an output node and includes a fuse switch, a mercury charge circuit, a current-to-voltage conversion circuit, and a first reset circuit. The fuse switch receives an input voltage to generate an output voltage at the output node and to generate an output current to the output node. The mercury charge circuit is coupled to the fuse switch and the first node and controls the fuse switch based on the node voltage at the first node to control the output voltage. The current-to-voltage conversion circuit is coupled to the fuse switch and a second node and converts the output current to generate a current-dependent voltage at the second node. The first reset circuit is coupled to the first node and the second node and determines whether the output current exceeds a first current threshold based on the current-dependent voltage. In response to an output current exceeding the first current threshold, after a first reaction time matching the first current threshold, the reset circuit controls the node voltage to trigger the mercury charge circuit to turn off the fuse switch.

[0004] In some embodiments, the first reset circuit includes an overcurrent response circuit, a reaction time generation circuit, and a disable circuit. The overcurrent response circuit is coupled to the second node and is used to generate a first indication signal based on the current-dependent voltage and a first reference voltage, wherein the first reference voltage corresponds to the first current threshold, and when the output current exceeds the first current threshold, the first indication signal switches to an enable voltage level. The reaction time generation circuit is coupled to the overcurrent response circuit and the third node and is used to selectively adjust the charging voltage at the third node based on the first indication signal to generate a second indication signal based on the charging voltage, wherein when the first indication signal switches to the enable voltage level, the voltage level of the charging voltage is adjusted to the second reference voltage based on the first reaction time, causing the second indication signal to switch to the enable voltage level. The disable circuit is coupled to the reaction time generation circuit and the first node and is used to switch the node voltage to a disable voltage level based on the second indication signal of the enable voltage level, causing the charge mercury circuit to turn off the fuse switch.

[0005] In some embodiments, the overcurrent response circuit includes a comparator. The positive input of the comparator is coupled to the second node and is used to receive the current-dependent voltage, the negative input of the comparator is used to receive the first reference voltage, and the output of the comparator is coupled to the reaction time generation circuit and is used to output the first indication signal.

[0006] In some embodiments, the reaction time generation circuit includes a current source, a switching circuit, a capacitor, and a comparator. The current source provides a charging current, wherein the current level of the charging current is fixed or proportional to the current level of the output current. The switching circuit is coupled to the overcurrent response circuit, the current source, and the third node, and is controlled by the first indication signal to turn on or off to selectively allow the charging current to pass. The capacitor is coupled to the third node and ground voltage, and is used to generate the charging voltage at the third node. The positive input of the comparator is coupled to the third node and is used to receive the charging voltage; the negative input of the comparator is used to receive the second reference voltage; and the output of the comparator is coupled to the disable circuit and is used to output the second indication signal.

[0007] In some embodiments, the disable circuit includes a level maintenance circuit and a switching circuit. The level maintenance circuit is coupled to the reaction time generation circuit and is used to generate a switching control signal that maintains the enable voltage level for a preset period based on the second indication signal of the enable voltage level. The switching circuit is coupled to the level maintenance circuit, the first node, and the ground voltage, and is used to turn on based on the switching control signal of the enable voltage level to switch the node voltage to the disable voltage level.

[0008] In some embodiments, the electronic fuse circuit further includes a second reset circuit. The second reset circuit is coupled to the first node and the second node, and is used to determine whether the output current exceeds a second current threshold based on the current-dependent voltage, and to trigger the charge mercury circuit to turn off the fuse switch after a second reaction time matching the second current threshold in response to the output current exceeding the second current threshold. The first current threshold and the first reaction time correspond to a first point on the first current-to-time curve, and the second current threshold and the second reaction time correspond to a second point on the first current-to-time curve.

[0009] In some embodiments, when the second current threshold is greater than the first current threshold, the second reaction time is shorter than the first reaction time, and when the second current threshold is less than the first current threshold, the second reaction time is longer than the first reaction time.

[0010] In some embodiments, the electronic fuse circuit further includes a control circuit. The control circuit is coupled to the first node and the second node to determine whether the output current exceeds a third current threshold based on the current-dependent voltage, and to trigger the charge mercury circuit to turn off the fuse switch after a third reaction time matching the third current threshold in response to the output current exceeding the third current threshold. The third current threshold and the third reaction time correspond to a first point on the second current-time curve.

[0011] In some embodiments, when the first current threshold and the third current threshold are the same, the third reaction time is shorter than the first reaction time, and when the first reaction time and the third reaction time are the same, the first current threshold is greater than the third current threshold.

[0012] Another embodiment of this invention is a reset circuit. This reset circuit, in response to the output current of a fuse switch exceeding a current threshold, triggers a charge mercury circuit to turn off the fuse switch after a reaction time matching the current threshold. It includes an overcurrent response circuit, a reaction time generation circuit, and a disable circuit. The overcurrent response circuit is coupled to a current-to-voltage conversion circuit at a first node and generates a first indication signal based on a first reference voltage and a current-dependent voltage at the first node. The first reference voltage corresponds to the current threshold. When the output current exceeds the current threshold, the first indication signal switches to an enable voltage level. The reaction time generation circuit is coupled to the overcurrent response circuit and a second node and selectively adjusts the charging voltage at the second node based on the first indication signal to generate a second indication signal based on the charging voltage. When the first indication signal switches to the enable voltage level, the charging voltage level is adjusted to the second reference voltage based on the reaction time, causing the second indication signal to switch to the enable voltage level. The disable circuit is coupled to the reaction time generating circuit and coupled to the mercury charge circuit at the third node. It is used to switch the node voltage at the third node to the disable voltage level according to the second indication signal of the enable voltage level, so that the mercury charge circuit turns off the fuse switch.

[0013] In summary, by resetting the circuit to react to a specific current threshold, the electronic fuse circuit can implement overcurrent protection and avoid the problem of failing to effectively respond to abnormally high load currents due to an excessively high current threshold applied to over-temperature protection. Furthermore, by delaying the fuse switch off only after a reaction time matched to the current threshold, the electronic fuse circuit also avoids the problem of accidental overcurrent protection activation due to surge currents. Therefore, the electronic fuse circuit of this invention has the advantage of high reliability. Attached Figure Description

[0014] Figure 1 is a circuit block diagram of an electronic fuse circuit according to some embodiments of the present invention.

[0015] Figure 2 is a timing diagram of some signals associated with an electronic fuse circuit according to some embodiments of the present invention.

[0016] Figure 3 is a circuit diagram of an electronic fuse circuit according to some embodiments of the present invention.

[0017] Figure 4 is a circuit diagram of an electronic fuse circuit according to some embodiments of the present invention.

[0018] Figure 5 is a circuit diagram of an electronic fuse circuit according to some embodiments of the present invention.

[0019] Figure 6 is a graph showing the relationship between output current and response time according to some embodiments of the present invention.

[0020] Figure 7 is a circuit diagram of an electronic fuse circuit according to some embodiments of the present invention.

[0021] Figure 8 is a graph showing the relationship between output current and response time according to some embodiments of the present invention.

[0022] Figure 9 is a circuit diagram of an electronic fuse circuit according to some embodiments of the present invention.

[0023] Figure 10 is a timing diagram of some signals associated with an electronic fuse circuit according to some embodiments of the present invention. Detailed Implementation

[0024] The following is a detailed description of the embodiments in conjunction with the accompanying drawings. However, the specific embodiments described are only for explaining this case and are not intended to limit this case. The description of the structural operations is not intended to limit the order of their execution. Any structure that is recombined with elements and produces a device with equivalent functions is within the scope of this utility model.

[0025] Unless otherwise specified, the terms used throughout the specification and claims generally have their ordinary meaning in the context of the art, the content disclosed herein, and the specific content.

[0026] The terms "coupled" or "connected" as used in this article can refer to two or more components making direct physical or electrical contact with each other, or making indirect physical or electrical contact with each other, or to two or more components operating or moving together.

[0027] For clarity and ease of explanation, in some of the accompanying drawings, the number indexes [1] to [N] are used to refer to individual components or signals, but this is not intended to limit the number of components or signals to a specific number. In addition, if only the component or signal symbol is used without specifying the number index of the component or signal symbol, it means that the component or signal symbol refers to any unspecified one in the component or signal group to which it belongs.

[0028] Please refer to Figure 1, which is a circuit block diagram of an electronic fuse circuit 100 according to some embodiments of the present invention. In some embodiments, the electronic fuse circuit 100 is coupled to a power supply (not shown) at the input node NIN and to a load device 10 at the output node NOUT, so as to provide at least one of a variety of protections, such as overcurrent protection, overvoltage protection, overtemperature protection, and short circuit protection, to the load device 10 when the power supply supplies power to the load device 10.

[0029] In some embodiments, the electronic fuse circuit 100 includes a fuse switch 101, a charge-to-voltage circuit 102, a current-to-voltage circuit 103, and a reset circuit 104. As shown in FIG1, the fuse switch 101 is coupled to the input node NIN to receive the input voltage VIN provided by the power supply, and coupled to the output node NOUT to generate an output voltage VOUT at the output node NOUT. In addition, the fuse switch 101 also generates an output current IL to the output node NOUT. That is, by receiving the input voltage VIN provided by the power supply through the fuse switch 101, the electronic fuse circuit 100 generates an output current IL and an output voltage VOUT to supply power to the load device 10.

[0030] A charge-to-voltage circuit 102 is coupled to fuse switch 101 and node NC, and is used to control fuse switch 101 based on the node voltage VC at node NC, thereby controlling the state of output voltage VOUT. Specifically, the level of output voltage VOUT can be controlled to be the level of input voltage VIN or can be controlled to be in a floating state. A current-to-voltage circuit 103 is coupled to fuse switch 101 and node NA, and is used to convert output current IL to generate current-dependent voltage VA at node NA.

[0031] Reset circuit 104 is coupled to nodes NA and NC to determine whether the output current IL exceeds a current threshold based on the current-dependent voltage VA. In response to an output current IL exceeding the current threshold, after a reaction time matched to the current threshold, it triggers charge mercury circuit 102 to turn off fuse switch 101. In some embodiments, the current threshold and reaction time correspond to a point on the current-to-time curve, as will be explained in detail in Figure 6 later.

[0032] As explained above, by responding to a specific current threshold through the reset circuit 104, the electronic fuse circuit 100 can implement overcurrent protection and avoid the problem of failing to effectively respond to abnormally large load currents due to an excessively high current threshold applied to over-temperature protection. Furthermore, by ensuring that the reset circuit 104 turns off the fuse switch 101 only after a reaction time matched to the current threshold, the electronic fuse circuit 100 can also avoid the problem of accidental overcurrent protection activation due to surge current. Therefore, the electronic fuse circuit 100 of this invention has the advantage of high reliability.

[0033] The reset circuit 104 will be further described next with reference to Figures 1 and 2. Figure 2 is a timing diagram of some signals associated with the electronic fuse circuit according to some embodiments of the present invention. In the embodiment of Figure 1, the reset circuit 104 includes an overcurrent response circuit 141, a response time generation circuit 142, and a disable circuit 143.

[0034] Overcurrent response circuit 141 is coupled to node NA and generates an indication signal S1 based on the current-dependent voltage VA and the reference voltage VREF1 shown in Figure 2. Reaction time generation circuit 142 is coupled to overcurrent response circuit 141 and selectively adjusts the charging voltage VB shown in Figure 2 based on indication signal S1 to generate indication signal S2 based on the charging voltage VB. Disable circuit 143 is coupled to reaction time generation circuit 142 and node NC and switches the node voltage VC to the disable voltage level (during the period between the two time points T2 and T3 in Figure 2) based on the enable voltage level indication signal S2, causing fuse switch 101 to turn off. Overcurrent response circuit 141, reaction time generation circuit 142, and disable circuit 143 will be further explained in later paragraphs with reference to Figures 2 and 3.

[0035] Figure 3 is a circuit diagram of an electronic fuse circuit 300 according to some embodiments of the present invention. The main difference between the electronic fuse circuit 300 of Figure 3 and the electronic fuse circuit 100 of Figure 1 is the number of reset circuits 104. For example, the electronic fuse circuit 100 includes a single reset circuit 104, while the electronic fuse circuit 300 includes N reset circuits 104[1] to 104[N].

[0036] In the embodiment of FIG3, the fuse switch 101 includes a transistor M1. The transistor M1 can be implemented using an N-type metal-oxide-semiconductor transistor, but this invention is not limited thereto. As shown in FIG3, a first terminal (e.g., the drain terminal) of the transistor M1 can be coupled to the input node NIN and receive the input voltage VIN. A second terminal (e.g., the source terminal) of the transistor M1 can be coupled to the output node NOUT with a load resistor RL (i.e., the equivalent resistance of the load device 10 of FIG1), outputting an output current IL to the output node NOUT and generating an output voltage VOUT at the output node NOUT. The control terminal (e.g., the gate terminal) of the transistor M1 is coupled to a mercury charge circuit 102, such that the fuse switch 101 can be controlled by the mercury charge circuit 102 to be turned on or off.

[0037] The mercury charge circuit 102 can be coupled to node NC via a pull-up circuit PH. The pull-up circuit PH can be biased by the power supply voltage VS to control the node voltage VC at node NC at an enable voltage level. At the enable voltage level of node voltage VC, the mercury charge circuit 102 controls the fuse switch 101 to turn on. Specifically, the power supply voltage VS can be the same as the input voltage VIN, but this invention is not limited thereto.

[0038] The current-to-voltage circuit 103 includes a resistor RSH, an amplifier A1, a resistor RF, and a capacitor CF. The two ends of the resistor RSH are coupled to the second terminal of transistor M1 and the load resistor RL, respectively. The two input terminals of amplifier A1 (i.e., the positive input terminal and the negative input terminal) are coupled to the two ends of the resistor RSH, respectively. The two ends of the resistor RF are coupled to the output terminal of amplifier A1 and node NA, respectively. The two ends of the capacitor CF are coupled to node NA and ground voltage GND, respectively. With this configuration, the output current IL can flow through the resistor RSH to the load resistor RL, causing a voltage difference (not shown in the figure) to be generated across the resistor RSH. The voltage difference is amplified by amplifier A1 and filtered by the filter circuit composed of resistor RF and capacitor CF to generate a current-dependent voltage VA at node NA. It should be understood that the voltage level of the current-dependent voltage VA will be proportional to the current level of the output current IL.

[0039] N reset circuits 104[1] to 104[N] may have the same or similar structure and operation. Therefore, the structure and operation of each reset circuit 104 will be described next using reset circuit 104[1] as an example.

[0040] The overcurrent response circuit 141 in the reset circuit 104[1] includes a comparator CP1. The positive input terminal of the comparator CP1 (indicated by "+" in the figures) is coupled to node NA and receives the current-dependent voltage VA. The negative input terminal of the comparator CP1 (indicated by "-" in the figures) receives the reference voltage VREF1. The output terminal of the comparator CP1 is coupled to the response time generation circuit 142 and outputs an indication signal S1. With this configuration, the comparator CP1 can switch or adjust the voltage level of the indication signal S1 based on the comparison result between the current-dependent voltage VA and the reference voltage VREF1. In addition, the comparator CP1 can be biased by the power supply voltage VS and the ground voltage GND.

[0041] It should be understood that the current-dependent voltage VA and the reference voltage VREF1 correspond to the output current IL and the current threshold, respectively. That is, the overcurrent response circuit 141 can determine whether the output current IL exceeds the current threshold by comparing the current-dependent voltage VA with the reference voltage VREF1.

[0042] The reaction time generation circuit 142 in the reset circuit 104[1] includes a current source CS1, a switching circuit SW, a capacitor CD1, and a comparator CP2. The current source CS1 can be biased by the power supply voltage VS to provide a charging current IS1. The switching circuit SW is coupled to the overcurrent response circuit 141, the current source CS1, and the node NB, and can be turned on or off by the indication signal S1 to selectively allow the charging current IS1 to pass. The capacitor CD1 is coupled to the node NB and the ground voltage GND, and can generate a charging voltage VB at the node NB. The positive input terminal of the comparator CP2 is coupled to the node NB and receives the charging voltage VB. The negative input terminal of the comparator CP2 receives the reference voltage VREF0. The output terminal of the comparator CP2 is coupled to the disable circuit 143 and outputs an indication signal S2. With this configuration, the comparator CP2 can switch or adjust the voltage level of the indication signal S2 according to the comparison result between the charging voltage VB and the reference voltage VREF0. In addition, the comparator CP2 can be biased by the power supply voltage VS and the ground voltage GND.

[0043] The disable circuit 143 in the reset circuit 104[1] includes a level maintenance circuit KL and a switching circuit. The level maintenance circuit KL can be implemented by a latching circuit or other suitable circuit, but this invention is not limited thereto. The switching circuit can be implemented by a transistor M2 (e.g., an N-type metal-oxide-semiconductor transistor), but this invention is not limited thereto. The level maintenance circuit KL is coupled to the control terminal of the reaction time generation circuit 142 and the transistor M2. The first terminal of the transistor M2 can be coupled to node NC. The second terminal of the transistor M2 can be coupled to ground voltage GND.

[0044] Please refer to Figure 2 again. During period PD1, the load device 10 operates normally, and therefore the output current IL remains at the steady-state voltage level for most of the time. During period PD2, which follows PD1, the load device 10 fails to operate normally due to some non-ideal factors, and therefore the output current IL begins to increase from the steady-state voltage level. Furthermore, the current-dependent voltage VA increases accordingly based on the change in output current IL.

[0045] At a certain time point T1 in PD2, the current-dependent voltage VA exceeds the reference voltage VREF1. Therefore, the comparator CP1 of the overcurrent response circuit 141 switches the indication signal S1 from the disabled voltage level to the enabled voltage level. It should be understood that the disabled voltage level indication signal S1 is used to indicate that the output current IL has not exceeded the current threshold, while the enabled voltage level indication signal S1 is used to indicate that the output current IL has exceeded the current threshold.

[0046] The switching circuit SW of the reaction time generation circuit 142 is controlled by the enable voltage level indication signal S1 to switch from the off state to the on state, causing the charging current IS1 to start charging the capacitor CD1. As shown in Figure 2, the charging voltage VB at node NB begins to increase at time point T1. At time point T2, the charging voltage VB exceeds the reference voltage VREF0, therefore the comparator CP2 of the reaction time generation circuit 142 switches the indication signal S2 from the disable voltage level to the enable voltage level. In the embodiment of Figure 3, the current level of the charging current IS1 is fixed and is not related to the current level of the output current IL.

[0047] The level maintenance circuit KL generates a switching control signal S3 based on the enable voltage level indication signal S2, which maintains the enable voltage level for a preset period (e.g., between the two time points T2 and T3 in Figure 2). The transistor M2 (i.e., the switching circuit) in the disable circuit 143 is turned on according to the enable voltage level switching control signal S3 to switch the node voltage VC from the enable voltage level to the ground voltage GND (which can be regarded as the disable voltage level). Through the node voltage VC of the disable voltage level, the charge mercury circuit 102 controls the fuse switch 101 to turn off, causing the output current IL to drop significantly to the zero current level.

[0048] As shown in Figure 2, in response to the significant decrease in output current IL, the current-dependent voltage VA and the charging voltage VB also decrease significantly. It is worth noting that between the two time points T2 and T3, transistor M2 remains on due to the control of the level maintenance circuit KL, and will not turn off despite the significant decrease in charging voltage VB. In this way, the electronic fuse circuit of this invention avoids the situation where the fuse switch 101 only turns off for a short time and fails to effectively reduce the output current IL.

[0049] As explained above, even if the reset circuit 104 detects that the output current IL exceeds the current threshold at time T1, the reset circuit 104 only triggers the charge mercury circuit 102 to control the fuse switch 101 to turn off at time T2 by switching the node voltage VC to the disable voltage level. In other words, the reset circuit 104 does not trigger the charge mercury circuit 102 to control the fuse switch 101 to turn off between the two time points T1 and T2. It should be understood that the time difference between these two time points T1 and T2 is the aforementioned reaction time matching the current threshold (corresponding to the reference voltage VREF1). Therefore, the voltage level of the charging voltage VB is adjusted to the reference voltage VREF0 based on the reaction time, causing the indicator signal S2 to switch to the enable voltage level.

[0050] Furthermore, in some embodiments, the reset circuit 104[1] is disposed on a wafer 301[1], and the current-to-voltage circuit 103 is coupled to the reset circuit 104[1] through the wafer 301[1]. In other embodiments, some components of the reset circuit 104[1] are disposed on the wafer 301[1]. For example, in the embodiment of FIG3, the components in the overcurrent response circuit 141 and the disable circuit 143 are disposed on the wafer 301[1], and the current source CS1, the switch circuit SW, and the comparator CP2 of the reaction time generation circuit 142 are disposed on the wafer 301[1], while the capacitor CD1 of the reaction time generation circuit 142 is disposed outside the wafer 301[1]. The mercury charge circuit 102 is disposed on another wafer 302, and the fuse switch 101 is coupled to the mercury charge circuit 102 through the wafer 302.

[0051] The difference between any of the multiple reset circuits 104[2] to 104[N] and reset circuit 104[1] lies in the voltage signal used for comparison with the current-dependent voltage VA and the capacitor element used to generate the charging voltage VB. For example, if reset circuit 104[1] uses a reference voltage VREF1 and a capacitor CD1, then reset circuit 104[2] may use a reference voltage VREF2 greater than the reference voltage VREF1 and a capacitor CD2 with a capacitance value less than that of capacitor CD1. Further, reset circuit 104[N] may use another reference voltage VREFN greater than the reference voltage VREF2 and another capacitor CDN with a capacitance value less than that of capacitor CD2. It should be understood that the larger the voltage signal used for comparison with the current-dependent voltage VA, the larger the set current threshold. Also, the smaller the capacitance value of the capacitor element used to generate the charging voltage VB, the shorter the set response time. With this configuration, the N reset circuits 104[1] to 104[N] in Figure 3 can define the current-time curve C1 as shown in Figure 6 below.

[0052] Compared to the electronic fuse circuit 100 in Figure 1, the electronic fuse circuit 300 can implement overcurrent protection for multiple different current abnormalities of the load device 10 by using N reset circuits 104[1]~104[N] to react according to the current-time curve C1. Therefore, it has higher reliability.

[0053] Please refer to Figure 4, which is a circuit diagram of an electronic fuse circuit 400 according to some embodiments of the present invention. Compared to the electronic fuse circuit 300 in Figure 3, the electronic fuse circuit 400 in Figure 4, in addition to providing overcurrent protection for multiple different current abnormalities of the load device 10 with multiple different response times, also includes an over-temperature protection circuit 105. The electronic fuse circuit 400 can implement over-temperature protection through the over-temperature protection circuit 105. For example, the over-temperature protection circuit 105 can detect the junction temperature of transistor M1 and can trigger the charge mercury circuit 102 to turn off the fuse switch 101 when the junction temperature of transistor M1 exceeds a temperature threshold.

[0054] Furthermore, please refer to Figures 3 and 4 together. The implementation of the current-to-voltage circuit 103 in Figure 4 differs from that in Figure 3. In the embodiment of Figure 4, the current-to-voltage circuit 103 includes a current sensing circuit CSC and a resistor RS. The current sensing circuit CSC is coupled to the second terminal of transistor M1 and node NA. The resistor RS is coupled to node NA and ground voltage GND. During operation, the current sensing circuit CSC detects the output current IL to generate a sense current IRP that is proportional to the output current IL. In one embodiment, the current sensing circuit CSC can be implemented using a current-controlled current source (CCCS). For example, the sense current IRP can be 1 / K1 times the output current IL, where K1 can be a value greater than 1. The sense current IRP passes through the resistor RS to generate a current-dependent voltage VA at node NA. Furthermore, as shown in Figure 4, the over-temperature protection circuit 105 is coupled to the mercury charge circuit 102, and together with the fuse switch 101, the mercury charge circuit 102, and the current detection circuit CSC of the current-to-voltage converter 103, it is located on a wafer 401, which is different from the wafer 301. It can be seen that in Figure 4, the current detection circuit CSC of the current-to-voltage converter 103 is located inside the wafer 401, while the resistor RS of the current-to-voltage converter 103 is located outside the wafer 401. That is, some components of the current-to-voltage converter 103 are located on the wafer 401.

[0055] Please refer to Figure 5, which is a circuit diagram of an electronic fuse circuit 500 according to some embodiments of the present invention. Compared to the electronic fuse circuit 400 of Figure 4, the electronic fuse circuit 500 of Figure 5 uses only a single reset circuit 104 to implement overcurrent protection for multiple different current abnormalities of the load device 10 with multiple different response times. In some embodiments, the fuse switch 101, the charge mercury circuit 102, the current-to-voltage circuit 103, the reset circuit 104, and the over-temperature protection circuit 105 are all disposed on the chip 501. In other embodiments, some components of the reset circuit 104 and some components of the current-to-voltage circuit 103 are disposed on the chip 501. For example, as in the embodiment of Figure 5, the components in the overcurrent response circuit 141 and the disable circuit 143 are disposed on the chip 501, the current source CS2, the switch circuit SW, and the comparator CP2 of the response time generation circuit 142 are disposed on the chip 501, while the capacitor CD1 of the response time generation circuit 142 is disposed outside the chip 501. In addition, the current detection circuit CSC of the current-to-voltage circuit 103 is located inside the chip 501, while the resistor RS of the current-to-voltage circuit 103 is located outside the chip 501.

[0056] In the embodiment of FIG5, the reaction time generation circuit 142 in the reset circuit 104 uses a current source CS2 instead of the current source CS1 used in the embodiments of FIG3 or FIG4. It is worth noting that the charging current IS2 provided by the current source CS2 is in a preset ratio to the output current IL. For example, the charging current IS2 can be K2 / K1 times the output current IL, where K2 can be a fixed constant. Specifically, the larger the output current IL, the larger the charging current IS2. Furthermore, the larger the charging current IS2 used to generate the charging voltage VB, the shorter the set reaction time. With this configuration, the single reset circuit 104 of FIG5 can also define a current-time curve C1 as shown in FIG6 below.

[0057] As illustrated in Figures 3, 4, and 5, the electronic fuse circuits 300, 400, and 500 can all implement overcurrent protection for multiple different current abnormalities of the load device 10 by using the current-to-time curve C1 and matching multiple different response times. Please refer to Figure 6, which is a schematic diagram of the current-to-time curve C1 according to some embodiments of this utility model.

[0058] In Figure 6, point P1 on the current-time curve C1 is defined by the current threshold of current value I1 and the response time of duration TR1. Current value I1 and duration TR1 can correspond to the reference voltage VREF1 and the capacitance value of capacitor CD1 in the embodiments of Figure 3 or Figure 4, respectively. Point P2 on the current-time curve C1 is defined by the current threshold of current value I2 and the response time of duration TR2. Current value I2 and duration TR2 can correspond to the reference voltage VREF2 and the capacitance value of capacitor CD2 in the embodiments of Figure 3 or Figure 4, respectively. Furthermore, point PN on the current-time curve C1 is defined by the current threshold of current value IN and the response time of duration TRN. Current value IN and duration TRN can correspond to the reference voltage VREFN and the capacitance value of capacitor CDN in the embodiments of Figure 3 or Figure 4, respectively.

[0059] It should be understood that the charging current IS2 provided by the current source CS2 in Figure 5 will also have multiple different current levels depending on the changes in the output current IL (e.g., current value I1, current value I2, current value IN, etc.) to correspond to multiple different response times (e.g., duration TR1, duration TR2, duration TRN, etc.).

[0060] Therefore, when the current threshold corresponding to the reference voltage VREFN (i.e., the current value IN) is greater than the current threshold corresponding to the reference voltage VREF1 (i.e., the current value I1), the response time (i.e., the duration TRN) corresponding to the capacitor CDN is shorter than the response time (i.e., the duration TR1) corresponding to the capacitor CD1. From another perspective, when the current threshold corresponding to the reference voltage VREF1 (i.e., the current value I1) is less than the current threshold corresponding to the reference voltage VREFN (i.e., the current value IN), the response time (i.e., the duration TR1) corresponding to the capacitor CD1 is longer than the response time (i.e., the duration TRN) corresponding to the capacitor CDN.

[0061] Please refer to Figure 7, which is a circuit diagram of an electronic fuse circuit 700 according to some embodiments of the present invention. Compared to the electronic fuse circuit 500 of Figure 5, the electronic fuse circuit 700 of Figure 7 further includes a control circuit 701. The control circuit 701 is coupled to nodes NA and NC, and includes an analog-to-digital converter 711, a computing circuit 712, and a switching circuit 713. The analog-to-digital converter 711 is coupled to node NA, the computing circuit 712 is coupled to the analog-to-digital converter 711, and the switching circuit 713 is coupled to node NC. The control circuit 701 can be implemented using a microcontroller (MCU). The analog-to-digital converter 711 can be implemented using an analog-to-digital converter (ADC). The computing circuit 712 can be implemented using a central processing unit (CPU). The switching circuit 713 can be implemented using a transistor M3 (e.g., an N-type metal-oxide-semiconductor transistor). The implementation of the control circuit 701 of the present invention is not limited to the above. The control terminal of the transistor M3 can be coupled to the computing circuit 712. The first terminal of transistor M3 can be coupled to node NC. The second terminal of transistor M3 can be coupled to ground voltage GND.

[0062] The operation of the control circuit 701 will then be explained with reference to Figures 7 and 8. Figure 8 is a schematic diagram illustrating the relationship between current versus time curves C1, C2, and CB according to some embodiments of the present invention.

[0063] In some embodiments, the analog-to-digital converter 711 receives the current-dependent voltage VA from node NA and performs an analog-to-digital conversion on the current-dependent voltage VA to generate a digital voltage DA. The calculation circuit 712 receives the digital voltage DA and determines, based on the digital voltage DA, whether the output current IL exceeds one of a plurality of current thresholds defined by the current-to-time curve C2 (e.g., the current value IM in Figure 8). When it is determined that the output current IL exceeds one of the plurality of current thresholds defined by the current-to-time curve C2, the calculation circuit 712 starts timing and determines whether one of a plurality of reaction times matching one of the plurality of current thresholds has elapsed (e.g., duration TRM2 in Figure 8). When it is determined that one of the plurality of reaction times matching one of the plurality of current thresholds has elapsed, the calculation circuit 712 turns on the switching circuit 713 by controlling the voltage at the control terminal of transistor M3 to the enable voltage level. Accordingly, the node voltage VC of node NC will switch to the disable voltage level (i.e., ground voltage GND), causing the charge mercury circuit 102 to control the fuse switch 101 to turn off.

[0064] Therefore, the control circuit 701 can determine whether the output current IL exceeds any current threshold defined by the current-time curve C2 based on the current-dependent voltage VA, and can trigger the charge mercury circuit 102 to turn off the fuse switch 101 after a reaction time matching any current threshold defined by the current-time curve C2 in response to the output current IL exceeding any current threshold defined by the current-time curve C2.

[0065] As shown in Figure 8, when the current threshold used by the reset circuit 104 (e.g., the current value IM corresponding to point PM1) is the same as the current threshold used by the control circuit 701 (e.g., the current value IM corresponding to point PM2), the response time used by the control circuit 701 (i.e., the duration TRM2 corresponding to point PM2) is shorter than the response time used by the reset circuit 104 (i.e., the duration TRM1 corresponding to point PM1). From another perspective, when the response time used by the control circuit 701 (e.g., the duration TRO corresponding to point PO2) is the same as the response time used by the reset circuit 104 (e.g., the duration TRO corresponding to point PO1), the current threshold used by the reset circuit 104 (i.e., the current value IO1 corresponding to point PO1) is greater than the current threshold used by the control circuit 701 (i.e., the current value IO2 corresponding to point PO2).

[0066] Furthermore, in Figure 8, the current-to-time curve CB represents the ignition boundary of the wiring harness connected to the power distribution module used in the electronic fuse circuit 700. For example, if the output current IL exceeds any current threshold defined by the current-to-time curve CB, and the output current IL is not reduced to zero current level within the corresponding reaction time, the wiring harness in the circuit may begin to burn, resulting in circuit damage. Therefore, in Figure 8, current-to-time curves C1 and C2 are set to the left of the current-to-time curve CB.

[0067] As further explained above, in Figure 8, the current-to-time curve C2 is set to the left of the current-to-time curve C1. Therefore, even if the control circuit 701 fails, the electronic fuse circuit 700 can still provide overcurrent protection through the reset circuit 104.

[0068] Please refer to Figure 9, which is a circuit diagram of an electronic fuse circuit 900 according to some embodiments of the present invention. Compared to the electronic fuse circuit 300 of Figure 3, the electronic fuse circuit 900 of Figure 9 further includes a short-circuit protection circuit 106 to implement short-circuit protection. The short-circuit protection circuit 106 can be coupled to the output node NOUT and node NC of Figure 1.

[0069] As shown in Figure 9, the short-circuit protection circuit 106 includes a diode D1, a resistor R1, and a transistor M4. The control terminal of transistor M4 can be coupled to the output node NOUT via the load resistor RL. The first terminal of transistor M4 can be coupled to the anode of diode D1. The second terminal of transistor M4 can be coupled to node NC. The two ends of resistor R1 are respectively coupled to the second terminal and the control terminal of transistor M4. The cathode of diode D1 can be coupled to the output node NOUT via the load resistor RL. Transistor M4 can be implemented using a P-type metal-oxide-semiconductor transistor, and diode D1 can be implemented using a Schottky diode, but this invention is not limited thereto. As shown in Figure 9, the electronic fuse circuit 900 also includes a switch 901, and switch 901 is coupled to the output node NOUT and the ground voltage GND.

[0070] The operation of the short-circuit protection circuit 106 will then be explained with reference to Figures 9 and 10. Figure 10 is a timing diagram of some signals associated with the electronic fuse circuit 900 according to some embodiments of the present invention.

[0071] As shown in Figure 10, during period PD3, the load device 10 operates normally, and thus the output voltage VOUT remains at a steady-state voltage level. During period PD4 following period PD3, the electronic fuse circuit 900 is in a safety test mode regarding output-to-ground short-circuit protection (SCP). In the safety test mode, switch 901 is turned on, causing a short-circuit event to occur at output node NOUT. Therefore, at a time point T4, the output voltage VOUT switches to, for example, ground voltage GND. In the embodiment of Figure 9, when the output voltage VOUT has just switched to ground voltage GND, the node voltage VC of node NC is still at the enable voltage level. Accordingly, a voltage difference (not shown) is generated across resistor R1, causing transistor M4 to turn on. After transistor M4 turns on, the node voltage VC of node NC switches to ground voltage GND or a voltage level close to ground voltage GND (as shown in Figure 10) by the limitation of the conducting diode D1, further causing the charge mercury circuit 102 to turn off fuse switch 101. It should be understood that after the fuse switch 101 is turned off, the output current IL, the current-dependent voltage VA, and the charging voltage VB will also change accordingly. In short, the short-circuit protection circuit 106 is used to switch the node voltage VC to the disabled voltage level in the safety test mode (i.e., when the output voltage VOUT switches to the ground voltage GND), thereby turning off the fuse switch 101 and providing output-to-ground protection.

[0072] At a time point T5, switch 901 is turned off, eliminating the short circuit event on output node NOUT. The output voltage VOUT returns to the steady-state voltage level, causing short-circuit protection circuit 106 to turn off transistor M4 and diode D1. Next, the node voltage VC of node NC is switched to the enable voltage level via pull-up circuit PH, causing charge mercury circuit 102 to conduct fuse switch 101. Therefore, the output current IL and current-dependent voltage VA will also change accordingly. In the embodiment of FIG10, the charging voltage VB is maintained at, for example, ground voltage GND because the current-dependent voltage VA does not exceed the reference voltage VREF1.

[0073] In another embodiment, the short-circuit protection circuit 106 may not include resistor R1 and transistor M4. In this case, the anode of diode D1 is directly connected to node NC, and the cathode of diode D1 is directly connected to output node NOUT. When the electronic fuse circuit 900 is in safety test mode, switch 901 is turned on, causing a short-circuit event to occur at output node NOUT. Therefore, the output voltage VOUT switches to ground voltage GND. When the output voltage VOUT just switches to ground voltage GND, the node voltage VC of node NC is still at the enable voltage level. At this time, diode D1 is turned on based on the voltage difference between node voltage VC and output voltage VOUT. The node voltage VC is switched to ground voltage GND or a voltage level close to ground voltage GND by the limitation of the turned-on diode D1, further causing the charge mercury circuit 102 to turn off fuse switch 101. In short, the short-circuit protection circuit 106 is used to switch the node voltage VC to the disable voltage level in safety test mode, causing fuse switch 101 to turn off, thereby providing output-to-ground protection. When switch 901 is turned off, the short circuit event on output node NOUT disappears. The output voltage VOUT returns to the steady-state voltage level, turning off diode D1. Then, the node voltage VC of node NC is switched to the enable voltage level through pull-up circuit PH, causing the mercury charge circuit 102 to turn on fuse switch 101. According to this embodiment, when the electronic fuse circuit 900 enters the safety test mode, the mercury charge circuit 102 can quickly turn off fuse switch 101.

[0074] Based on the above, the electronic fuse circuit proposed in this invention can not only implement overcurrent protection but also output-to-ground short-circuit protection, thereby improving the safety and reliability of the electronic fuse circuit. In particular, when the electronic fuse circuit proposed in this invention is applied to an automotive power distribution module, the electronic fuse circuit can shut off the fuse switch by implementing overcurrent protection or output-to-ground short-circuit protection when an abnormality occurs (e.g., excessive load current) or when entering a specific mode (e.g., safety test mode), thereby preventing the wiring harness connected to the power distribution module from burning.

[0075] Although the present invention has been disclosed above with reference to embodiments, it is not intended to limit the present invention. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

[0076] [Symbol Explanation]

[0077] 10: Loading device

[0078] 100, 300, 400, 500, 700, 900: Electronic fuse circuit

[0079] 101: Fuse Switch

[0080] 102: Charged Mercury Circuit

[0081] 103: Current to Voltage Converter Circuit

[0082] 104: Reset Circuit

[0083] 105: Over-temperature protection circuit

[0084] 106: Short circuit protection circuit

[0085] 141: Overcurrent Response Circuit

[0086] 142: Reaction Time Generation Circuit

[0087] 143: Disabled Circuits

[0088] 301, 302, 401, 501: Chips

[0089] 701: Control Circuit

[0090] 711: Analog-to-Digital Converter Circuit

[0091] 712: Calculation Circuit

[0092] 713: Switching Circuit

[0093] 901: Switch

[0094] A1: Amplifier

[0095] CD1, CD2, CDN, CF: Capacitors

[0096] CP1, CP2: Comparators

[0097] CS1, CS2: Current sources

[0098] CSC: Current Detection Circuit

[0099] D1: Diode

[0100] DA: Digital Voltage

[0101] GND: Grounding voltage

[0102] C1, C2, CB: Current versus time curves

[0103] IL: Output current

[0104] IRP: Sensing Current

[0105] IS1, IS2: Charging current

[0106] I1, I2, IN, IM, IO1, IO2: Current values

[0107] KL: Level Maintenance Circuit

[0108] M1, M2, M3, M4: Transistors

[0109] NA, NB, NC: Nodes

[0110] NIN: Input node

[0111] NOUT: Output node

[0112] P1, P2, PN, PM1, PM2, PO1, PO2: Points

[0113] PD1, PD2, PD3, PD4: Period

[0114] PH: Pull-up circuit

[0115] R1, RF, RS, RSH: Resistors

[0116] RL: Load resistance

[0117] S1, S2: Indicator signals

[0118] S3: Switch control signal

[0119] SW: Switching circuit

[0120] T1, T2, T3, T4, T5: Time points

[0121] TR1, TR2, TRN, TRM1, TRM2, TRO: Duration

[0122] VA: Current-dependent voltage

[0123] VB: Charging voltage

[0124] VC: Node voltage

[0125] VIN: Input voltage

[0126] VOUT: Output voltage

[0127] VREF0, VREF1, VREF2, VREFN: Reference voltage

[0128] VS: Power supply voltage.

Claims

1. An electronic fuse circuit, characterized in that, Coupled to a load device at an output node, and comprising: a fuse switch for receiving an input voltage to generate an output voltage at the output node and for generating an output current to the output node; A charge mercury circuit is coupled to the fuse switch and the first node, and is used to control the fuse switch based on the node voltage at the first node, so as to control the output voltage. A current-to-voltage circuit is coupled to the fuse switch and the second node, and is used to convert the output current to generate a current-dependent voltage at the second node; And a first reset circuit, coupled to the first node and the second node, is used to determine whether the output current exceeds a first current threshold based on the current-dependent voltage, and to control the node voltage to trigger the charge mercury circuit to turn off the fuse switch after a first reaction time matching the first current threshold in response to the output current exceeding the first current threshold.

2. The electronic fuse circuit according to claim 1, characterized in that, The first reset circuit includes: an overcurrent response circuit coupled to the second node, used to generate a first indication signal based on the current-dependent voltage and a first reference voltage, wherein the first reference voltage corresponds to the first current threshold, and when the output current exceeds the first current threshold, the first indication signal switches to an enable voltage level; and a reaction time generation circuit coupled to the overcurrent response circuit and the third node, used to selectively adjust the charging voltage at the third node based on the first indication signal to generate a second indication signal based on the charging voltage, wherein when the first indication signal switches to the enable voltage level, the voltage level of the charging voltage is adjusted to the second reference voltage based on the first reaction time, so that the second indication signal switches to the enable voltage level. And a disable circuit, coupled to the reaction time generation circuit and the first node, and used to switch the node voltage to the disable voltage level according to the second indication signal of the enable voltage level, so that the charge mercury circuit turns off the fuse switch.

3. The electronic fuse circuit according to claim 2, characterized in that, The overcurrent response circuit includes: a comparator, wherein the positive input of the comparator is coupled to the second node and is used to receive the current-dependent voltage, the negative input of the comparator is used to receive the first reference voltage, and the output of the comparator is coupled to the reaction time generation circuit and is used to output the first indication signal.

4. The electronic fuse circuit according to claim 2, characterized in that, The reaction time generation circuit includes: a current source for providing a charging current, wherein the current level of the charging current is fixed or proportional to the current level of the output current; and a switching circuit coupled to the overcurrent response circuit, the current source and the third node, and for being controlled by the first indication signal to be turned on or off to selectively allow the charging current to pass through. A capacitor is coupled to the third node and the ground voltage, and is used to generate the charging voltage at the third node; The comparator has a positive input terminal coupled to the third node for receiving the charging voltage, a negative input terminal for receiving the second reference voltage, and an output terminal coupled to the disable circuit for outputting the second indication signal.

5. The electronic fuse circuit according to claim 2, characterized in that, The disable circuit includes: a level maintenance circuit coupled to the reaction time generation circuit, and used to generate a switching control signal that is maintained at the enable voltage level for a preset period based on the second indication signal of the enable voltage level; And a switching circuit, coupled to the level maintenance circuit, the first node and the ground voltage, and used to turn on the switching control signal according to the enable voltage level, so as to switch the node voltage to the disable voltage level.

6. The electronic fuse circuit according to claim 1, characterized in that, It also includes: a second reset circuit, coupled to the first node and the second node, for determining whether the output current exceeds a second current threshold based on the current-dependent voltage, and for triggering the charge mercury circuit to turn off the fuse switch after a second reaction time matching the second current threshold in response to the output current exceeding the second current threshold, wherein the first current threshold and the first reaction time correspond to a first point of the first current-to-time curve, and the second current threshold and the second reaction time correspond to a second point of the first current-to-time curve.

7. The electronic fuse circuit according to claim 6, characterized in that, When the second current threshold is greater than the first current threshold, the second reaction time is shorter than the first reaction time; and when the second current threshold is less than the first current threshold, the second reaction time is longer than the first reaction time.

8. The electronic fuse circuit according to claim 1, characterized in that, It also includes: a control circuit coupled to the first node and the second node, used to determine whether the output current exceeds a third current threshold based on the current-dependent voltage, and used to trigger the charge mercury circuit to turn off the fuse switch after a third reaction time matching the third current threshold in response to the output current exceeding the third current threshold, wherein the third current threshold and the third reaction time correspond to the first point of the second current-time curve.

9. The electronic fuse circuit according to claim 8, characterized in that, When the first current threshold and the third current threshold are the same, the third reaction time is shorter than the first reaction time; when the first reaction time and the third reaction time are the same, the first current threshold is greater than the third current threshold.

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