TWI846437B - Fuse circuit - Google Patents

Abstract

A fuse circuit is provided. The fuse circuit includes a control switch, a fuse element, an electrostatic discharge protection circuit and an electrostatic discharge control circuit. A first terminal of the control switch is coupled to a first power terminal. A first terminal of the fuse element is coupled to a second terminal of the control switch. A second terminal of the fuse element is coupled to a third terminal of the control switch and a second power terminal. The electrostatic discharge protection circuit bypasses an electrostatic discharge energy from one of the first power terminal and the second power terminal to another of the first power terminal and the second power terminal. The electrostatic discharge control circuit turns off the control switch in response to the electrostatic discharge energy from one of the first power terminal and the second power terminal.

Description

Fuse circuit

The present invention relates to a fuse circuit, and in particular to a fuse circuit capable of reducing malfunction caused by electrostatic discharge.

Please refer to FIG. 1, which is a schematic diagram of a conventional fuse circuit. The fuse circuit 10 includes a fuse element FS, a control switch SW, and an electrostatic discharge protection circuit 11. The control switch SW performs a switching operation in response to a control signal SE. For example, when the control switch SW is disconnected in response to the control signal SE, the fuse element FS is not blown. Therefore, the back-end circuit corresponding to the fuse circuit 10 performs a first function or a first setting. When the control switch SW is turned on in response to the control signal SE, the fuse element FS is blown based on the power at the first power terminal TV1 and the second power terminal TV2. Therefore, the back-end circuit corresponding to the fuse circuit 10 performs a second function or a second setting.

The electrostatic discharge protection circuit 11 is coupled between the first power terminal TV1 and the second power terminal TV2. The electrostatic discharge protection circuit 11 can reduce the risk of the fuse element FS being directly subjected to electrostatic discharge (ESD) and being blown. However, the control switch SW has a parasitic capacitor CP. Part of the electrostatic discharge energy PESD from the power terminal TV1 will raise the voltage value at the control terminal of the control switch SW through the capacitive coupling of the parasitic capacitor CP. Therefore, the control switch SW is abnormally turned on. The fuse element FS is blown. In other words, although the electrostatic discharge protection circuit 11 can prevent the fuse element FS from being blown by electrostatic discharge ESD, it cannot prevent the control switch SW from being abnormally turned on by electrostatic discharge energy PESD.

The present invention provides a fuse circuit that can effectively reduce the risk of erroneous operation due to electrostatic discharge.

The fuse circuit of the present invention includes a control switch, a fuse element, an electrostatic discharge protection circuit and an electrostatic discharge control circuit. The first end of the control switch is coupled to the first power supply terminal. The first end of the fuse element is coupled to the second end of the control switch. The second end of the fuse element is coupled to the third end of the control switch and the second power supply terminal. The electrostatic discharge protection circuit is coupled between the first power supply terminal and the second power supply terminal. The electrostatic discharge protection circuit bypasses the electrostatic discharge energy from one of the first power supply terminal and the second power supply terminal to the other of the first power supply terminal and the second power supply terminal. The electrostatic discharge control circuit is coupled to the first power supply terminal, the second power supply terminal and the control end of the control switch. The electrostatic discharge control circuit responds to electrostatic discharge energy from one of the first power supply terminal and the second power supply terminal to disconnect the control switch.

Based on the above, the first end of the fuse element is coupled to the second end of the control switch. The second end of the fuse element is coupled to the third end of the control switch and the second power supply end. In this way, when electrostatic discharge energy from the second power supply end occurs, the electrostatic discharge energy is bypassed to the third end of the control switch through the second end of the fuse element. In addition, the electrostatic discharge control circuit responds to the electrostatic discharge energy from one of the first power supply end and the second power supply end to disconnect the control switch. In this way, when electrostatic discharge energy occurs, the control switch will not be abnormally turned on.

In order to make the above features and advantages of the present invention more clearly understood, the following is a detailed description of the embodiments with the accompanying drawings.

10, 100, 200, 300, 400, 500: Fuse circuit

11. 110: Electrostatic discharge protection circuit

120, 220, 320, 420, 520: Electrostatic discharge control circuit

221, 321, 421, 521: Sensing circuit

222, 422: Inverter

CF: Capacitor

CP: parasitic capacitance

CV1: Electrostatic discharge energy waveform

CV2, CV3: voltage waveform

FS: Fuse element

M1: P-type MOSFET

M2: N-type MOSFET

PESD, PESD1, PESD2: electrostatic discharge energy

RE, RF: Resistors

SE: Control signal

SF: Sensing signal

SFB: reverse sensing signal

SW, SWC: control switch

SWP: protection switch

TV1: First power supply terminal

TV2: Second power supply terminal

VH: Reference high voltage

VL: Reference low voltage

Figure 1 is a schematic diagram of the current fuse circuit.

FIG2 is a schematic diagram of a fuse circuit according to the first embodiment of the present invention.

FIG3 is a schematic diagram of a fuse circuit according to the second embodiment of the present invention.

FIG4 is a voltage waveform diagram of the control end of the control switch according to an embodiment of the present invention.

FIG5 is a schematic diagram of a fuse circuit according to the third embodiment of the present invention.

FIG6 is a schematic diagram of a fuse circuit according to the fourth embodiment of the present invention.

FIG7 is a schematic diagram of a fuse circuit according to the fifth embodiment of the present invention.

Some embodiments of the present invention will be described in detail with reference to the accompanying drawings. The component symbols cited in the following description will be regarded as the same or similar components when the same component symbols appear in different drawings. These embodiments are only part of the present invention and do not disclose all possible implementation methods of the present invention. More precisely, these embodiments are only examples within the scope of the patent application of the present invention.

Please refer to FIG. 2, which is a schematic diagram of a fuse circuit according to the first embodiment of the present invention. In this embodiment, the fuse circuit 100 includes a control switch SWC, a fuse element FS, an electrostatic discharge protection circuit 110, and an electrostatic discharge control circuit 120. The first end of the control switch SWC is coupled to the first power supply terminal TV1. The first end of the fuse element FS is coupled to the second end of the control switch SWC. The second end of the fuse element FS is coupled to the third end of the control switch SWC and the second power supply terminal TV2. In this embodiment, the first power supply terminal TV1 and the second power supply terminal TV2 are pads, pins, or connection nodes that receive different reference voltages.

In normal operation, when the control switch SWC is disconnected in response to the control signal SE, the fuse element FS will not be blown. Therefore, the back-end circuit corresponding to the fuse circuit 100 will perform the first function or the first setting based on the fuse element FS that has not been blown. When the control switch SWC is turned on in response to the control signal SE, an electrical connection path is formed between the first end of the control switch SWC and the second end of the control switch SWC. The fuse element FS will be blown based on the different reference voltages at the power terminals TV1 and TV2. Therefore, the back-end circuit corresponding to the fuse circuit 100 will perform the second function or the second setting based on the blown fuse element FS. The control signal SE can be provided by an external circuit (not shown). In this embodiment, the third end of the control switch SWC is different from the first end, the second end and the control end of the control switch SWC. The third end of the control switch SWC is, for example, an additional electrode of the control switch SWC.

In this embodiment, the electrostatic discharge protection circuit 110 is coupled between the first power terminal TV1 and the second power terminal TV2. The electrostatic discharge protection circuit 110 bypasses the electrostatic discharge energy from one of the first power terminal TV1 and the second power terminal TV2 to the other of the first power terminal and the second power terminal. For example, the electrostatic discharge protection circuit 110 bypasses the electrostatic discharge energy PESD1 from the first power terminal TV1 to the second power terminal TV2. For example, the electrostatic discharge protection circuit 110 bypasses the electrostatic discharge energy PESD2 from the second power terminal TV2 to the first power terminal TV1.

In this embodiment, the electrostatic discharge control circuit 120 is coupled to the first power terminal TV1, the second power terminal TV2 and the control terminal of the control switch SWC. The electrostatic discharge control circuit 120 responds to the electrostatic discharge energy (one of the electrostatic discharge energies PESD1 and PESD2) from one of the first power terminal TV1 and the second power terminal TV2 to disconnect the control switch SWC. When an electrostatic discharge (ESD) event occurs, the electrostatic discharge control circuit 120 uses one of the electrostatic discharge energy PESD1 and the electrostatic discharge energy PESD2 to disconnect the control switch SWC. In other words, when an ESD event occurs, the electrostatic discharge control circuit 120 does not allow the control switch SWC to be turned on.

It is worth mentioning here that the second end of the fuse element FS is coupled to the third end of the control switch SWC and the second power supply terminal TV2. In this way, when an ESD event occurs at the second power supply terminal TV2, the electrostatic discharge energy PESD2 will be bypassed to the third end of the control switch SWC through the second end of the fuse element FS, and will not flow through the fuse element FS to melt the fuse element FS. In addition, the electrostatic discharge control circuit 120 responds to one of the electrostatic discharge energies PESD1 and PESD2 to disconnect the control switch SWC. In this way, when electrostatic discharge energy occurs, the control switch will not be abnormally turned on. When an ESD event occurs, the control switch SWC will not be abnormally turned on due to the electrostatic discharge energies PESD1 and PESD2.

In this embodiment, when an ESD event occurs, the electrostatic discharge protection circuit 110 can discharge most of the electrostatic discharge energy PESD1, PESD2 without allowing the electrostatic discharge energy PESD1, PESD2 to flow directly through the control switch SWC. However, a small amount of the electrostatic discharge energy PESD1, PESD2 will still change the voltage level at the control end of the control switch SWC through the capacitive coupling of the parasitic capacitance of the control switch SWC. Therefore, the electrostatic discharge control circuit 120 can prevent the voltage level at the control end of the control switch SWC from changing abnormally due to the electrostatic discharge energy PESD1, PESD2.

Please refer to FIG. 3, which is a schematic diagram of a fuse circuit according to a second embodiment of the present invention. In this embodiment, the fuse circuit 200 includes a control switch SWC, a fuse element FS, an electrostatic discharge protection circuit 110, and an electrostatic discharge control circuit 220. The first end of the control switch SWC is coupled to the first power supply terminal TV1. The first end of the fuse element FS is coupled to the second end of the control switch SWC. The second end of the fuse element FS is coupled to the third end of the control switch SWC and the second power supply terminal TV2. In this embodiment, the control switch SWC can be an N-type transistor in any form. The control switch SWC of this embodiment is implemented, for example, with an N-type metal oxide semiconductor field effect transistor (Metal-Oxide-Semiconductor Field-Effect Transistor, MOSFET). Therefore, the first end of the control switch SWC is the drain electrode. The second end of the control switch SWC is the source electrode. The third end of the control switch SWC is the base electrode. The control end of the control switch SWC is the gate electrode.

It should be noted that the first end of the fuse element FS is connected to the source electrode of the control switch SWC. The second end of the fuse element FS is connected to the base electrode of the control switch SWC and the second power terminal TV2. Therefore, based on the above connection method, the fuse circuit 200 prevents the electrostatic discharge energy PESD1 and PESD2 from flowing through the fuse element FS through the parasitic diode (i.e., body diode) of the control switch SWC, thereby preventing the fuse element FS from being unexpectedly burned.

In some embodiments, the control switch SWC can be implemented by an NPN bipolar transistor (BJT) or an N-type thin film transistor (TFT).

The electrostatic discharge protection circuit 110 is coupled between the first power terminal TV1 and the second power terminal TV2. The implementation of the electrostatic discharge protection circuit 110 has been clearly described in the embodiment of FIG. 2 , so it will not be repeated here.

In this embodiment, the electrostatic discharge control circuit 220 includes a sensing circuit 221, an inverter 222, and a protection switch SWP. The sensing circuit 221 is coupled between the first power terminal TV1 and the second power terminal TV2. The sensing circuit 221 provides a sensing signal SF according to one of the electrostatic discharge energy PESD1 from the first power terminal TV1 and the electrostatic discharge energy PESD2 from the second power terminal TV2.

In this embodiment, the inverter 222 is coupled to the sensing circuit 221. The inverter 222 generates an inverted sensing signal SFB according to the sensing signal SF. The protection switch SWP is coupled to the inverter 222, the second power terminal TV2, and the control terminal of the control switch SWC. The protection switch SWP connects the control terminal of the control switch to the second power terminal TV2 according to the inverted sensing signal SFB, thereby disconnecting the control switch SWC.

In this embodiment, the sensing circuit 221 includes a resistor RF and a capacitor CF. The resistor RF is coupled between the first power terminal TV1 and the input terminal of the inverter 222. The capacitor CF is coupled between the input terminal of the inverter 222 and the second power terminal TV2. The first end of the protection switch SWP is coupled to the control end of the control switch SWC. The second end of the protection switch SWP is coupled to the second power terminal TV2. The control end of the protection switch SWP is coupled to the output end of the inverter 222. The protection switch SWP is implemented, for example, with an N-type MOSFET. The first power terminal TV1 receives a reference high voltage VH. The second power terminal TV2 receives a reference low voltage VL (for example, grounded, but the present invention is not limited thereto).

Electrostatic discharge energy PESD1, PESD2 is a high-frequency transient signal. Therefore, when an ESD event occurs at one of the first power terminal TV1 and the second power terminal TV2, the impedance of the capacitor CF is reduced. This causes the sensing signal SF to have a low voltage level. The inverted sensing signal SFB output by the inverter 222 has a high voltage level. Therefore, the protection switch SWP is turned on in response to the high voltage level of the inverted sensing signal SFB. The turned-on protection switch SWP uses the reference low voltage VL to pull down the voltage value at the control end of the control switch SWC. Therefore, when an ESD event occurs at one of the first power terminal TV1 and the second power terminal TV2, the electrostatic discharge control circuit 220 disconnects the control switch SWC.

On the other hand, when no ESD event occurs, the capacitor CF forms a short circuit. Therefore, the sensing signal SF has a high voltage level. The reverse sensing signal SFB has a low voltage level. Therefore, the protection switch SWP is disconnected in response to the low voltage level of the reverse sensing signal SFB. The control switch SWC operates in response to the control signal SE.

In this embodiment, in order to reduce the layout area of the sensing circuit 221, at least one of the resistor RF and the capacitor CF can be implemented by a transistor (the present invention is not limited to this).

In this embodiment, the inverter 222 can be implemented by a complementary metal-oxide-semiconductor (CMOS) element (the present invention is not limited thereto). The inverter 222 includes a P-type MOSFET M1 and an N-type MOSFET M2. The first end of the P-type MOSFET M1 is coupled to the first power terminal TV1. The second end of the P-type MOSFET M1 is coupled to the control end of the protection switch SWP. The control end of the P-type MOSFET M1 is coupled to the sensing circuit 221. The first end of the N-type MOSFET M2 is coupled to the second end of the P-type MOSFET M1. The second end of the N-type MOSFET M2 is coupled to the second power terminal TV2. The control end of the N-type MOSFET M2 is coupled to the sensing circuit 221.

In this embodiment, the electrostatic discharge control circuit 220 further includes a resistor RE. The resistor RE is coupled between the control terminal of the control switch SWC and the second power terminal TV2. The resistor RE is used to stabilize the voltage level of the control signal SE. In addition, when the control signal SE is not provided, the control terminal of the control switch SWC receives the reference low voltage VL through the resistor RE. Therefore, the control switch SWC is disconnected. In some embodiments, the resistor RE may be omitted. In some embodiments, the resistor RE may be set in an external circuit for providing the control signal SE.

Please refer to Figure 3 and Figure 4 at the same time. Figure 4 is a voltage waveform diagram at the control end of the control switch according to an embodiment of the present invention. Figure 4 shows the waveform CV1 of electrostatic discharge energy, the voltage waveform CV2 at the control end of the control switch (such as the control switch SW shown in Figure 1) of the prior art, and the voltage waveform CV3 at the control end of the control switch SWC of the present embodiment. The waveform CV1 of electrostatic discharge energy can be a voltage waveform or a current waveform.

In this embodiment, when an ESD event occurs, voltage waveforms CV2 and CV3 will follow the waveform CV1 of the electrostatic discharge energy. It should be noted that in this embodiment, at the time point of the peak value of the waveform CV1 of the electrostatic discharge energy, the voltage peak value of the voltage waveform CV3 is significantly lower than the voltage peak value of the voltage waveform CV2. This is because the turned-on protection switch SWP will pull down the voltage value at the control end of the control switch SWC. The voltage peak value of the voltage waveform CV3 is not enough to turn on the control switch SWC.

Please refer to FIG. 5, which is a schematic diagram of a fuse circuit according to the third embodiment of the present invention. In this embodiment, the fuse circuit 300 includes a control switch SWC, a fuse element FS, an electrostatic discharge protection circuit 110, an electrostatic discharge control circuit 320, and a resistor RE. The first end of the control switch SWC is coupled to the first power supply terminal TV1. The first end of the fuse element FS is coupled to the second end of the control switch SWC. The second end of the fuse element FS is coupled to the third end of the control switch SWC and the second power supply terminal TV2. In this embodiment, the control switch SWC can be an N-type transistor in any form. Similar to the embodiment of FIG. 3, the control switch SWC of this embodiment is implemented, for example, with an N-type MOSFET.

The electrostatic discharge protection circuit 110 is coupled between the first power terminal TV1 and the second power terminal TV2. The resistor RE is coupled between the control terminal of the control switch SWC and the second power terminal TV2. The implementation of the electrostatic discharge protection circuit 110 has been clearly described in the embodiment of FIG. 2, so it will not be repeated here. The implementation of the resistor RE has been clearly described in the embodiment of FIG. 3, so it will not be repeated here.

In this embodiment, the electrostatic discharge control circuit 320 includes a sensing circuit 321 and a protection switch SWP. The sensing circuit 321 is coupled between the first power terminal TV1 and the second power terminal TV2. The sensing circuit 321 provides a sensing signal SF according to one of the electrostatic discharge energy PESD1 from the first power terminal TV1 and the electrostatic discharge energy PESD2 from the second power terminal TV2.

In this embodiment, the protection switch SWP is coupled to the sensing circuit 321, the second power terminal TV2 and the control terminal of the control switch SWC. The protection switch SWP connects the control terminal of the control switch SWC to the second power terminal TV2 according to the sensing signal SF, thereby disconnecting the control switch SWC.

In this embodiment, the sensing circuit 321 includes a resistor RF and a capacitor CF. The capacitor CF is coupled between the first power terminal TV1 and the control terminal of the protection switch SWP. The resistor RF is coupled between the control terminal of the protection switch SWP and the second power terminal TV2. The first end of the protection switch SWP is coupled to the control terminal of the control switch SWC. The second end of the protection switch SWP is coupled to the second power terminal TV2. The control terminal of the protection switch SWP is coupled to the sensing circuit 321. The protection switch SWP is implemented, for example, with an N-type MOSFET. The first power terminal TV1 receives a reference high voltage VH. The second power terminal TV2 receives a reference low voltage VL.

When an ESD event occurs, the impedance of the capacitor CF is reduced. This causes the sensing signal SF to have a high voltage level. Therefore, the protection switch SWP is turned on in response to the high voltage level of the sensing signal SF. The turned-on protection switch SWP pulls down the voltage value of the control terminal of the control switch SWC. Therefore, when an ESD event occurs at one of the first power terminal TV1 and the second power terminal TV2, the electrostatic discharge control circuit 320 disconnects the control switch SWC.

On the other hand, when no ESD event occurs, the capacitor CF forms a short circuit. Therefore, the sensing signal SF has a low voltage level. Therefore, the protection switch SWP responds to the low voltage level of the sensing signal SF and is disconnected. The control switch SWC responds to the control signal SE to operate.

Please refer to FIG. 6, which is a schematic diagram of a fuse circuit according to the fourth embodiment of the present invention. In this embodiment, in this embodiment, the fuse circuit 400 includes a control switch SWC, a fuse element FS, an electrostatic discharge protection circuit 110, an electrostatic discharge control circuit 420 and a resistor RE. The first end of the control switch SWC is coupled to the first power supply terminal TV1. The first end of the fuse element FS is coupled to the second end of the control switch SWC. The second end of the fuse element FS is coupled to the third end of the control switch SWC and the second power supply terminal TV2. In this embodiment, the control switch SWC can be a P-type transistor in any form. The control switch SWC of this embodiment is implemented, for example, with a P-type MOSFET. Therefore, the first end of the control switch SWC is a drain electrode. The second end of the control switch SWC is a source electrode. The third terminal of the control switch SWC is the base electrode. The control terminal of the control switch SWC is the gate electrode. The first power terminal TV1 receives the reference low voltage VL. The second power terminal TV2 receives the reference high voltage VH.

It should be noted that the first end of the fuse element FS is connected to the source electrode of the control switch SWC. The second end of the fuse element FS is connected to the base electrode of the control switch SWC and the second power supply terminal TV2. Therefore, based on the above connection method, the fuse circuit 400 prevents the electrostatic discharge energy PESD1 and PESD2 from flowing through the fuse element FS through the parasitic diode (i.e., body diode) of the control switch SWC, thereby preventing the fuse element FS from being unexpectedly burned. In some embodiments, the control switch SWC can be implemented by a PNP type BJT or a P type TFT.

The electrostatic discharge protection circuit 110 is coupled between the first power supply terminal TV1 and the second power supply terminal TV2. The resistor RE is coupled between the control terminal of the control switch SWC and the second power supply terminal TV2. The implementation of the electrostatic discharge protection circuit 110 has been clearly described in the embodiment of FIG. 2, so it will not be repeated here. The implementation of the resistor RE has been clearly described in the embodiment of FIG. 3, so it will not be repeated here.

In this embodiment, the electrostatic discharge control circuit 420 includes a sensing circuit 421, an inverter 422, and a protection switch SWP. The sensing circuit 421 is coupled between the first power terminal TV1 and the second power terminal TV2. The sensing circuit 421 provides a sensing signal SF according to one of the electrostatic discharge energy PESD1 from the first power terminal TV1 and the electrostatic discharge energy PESD2 from the second power terminal TV2.

In this embodiment, the inverter 422 is coupled to the sensing circuit 421. The inverter 422 generates an inverted sensing signal SFB according to the sensing signal SF. The protection switch SWP is coupled to the inverter 422, the second power terminal TV2, and the control terminal of the control switch SWC. The protection switch SWP connects the control terminal of the control switch to the second power terminal TV2 according to the inverted sensing signal SFB, thereby disconnecting the control switch SWC.

In this embodiment, the sensing circuit 421 includes a resistor RF and a capacitor CF. The resistor RF is coupled between the first power terminal TV1 and the input terminal of the inverter 422. The capacitor CF is coupled between the input terminal of the inverter 422 and the second power terminal TV2. The first terminal of the protection switch SWP is coupled to the control terminal of the control switch SWC. The second terminal of the protection switch SWP is coupled to the second power terminal TV2. The control terminal of the protection switch SWP is coupled to the output terminal of the inverter 422.

When an ESD event occurs at one of the first power terminal TV1 and the second power terminal TV2, the impedance of the capacitor CF is reduced. This causes the sensing signal SF to have a high voltage level. The inverted sensing signal SFB has a low voltage level. Therefore, the protection switch SWP is turned on in response to the low voltage level of the inverted sensing signal SFB. The turned-on protection switch SWP uses the reference high voltage VH to raise the voltage value at the control end of the control switch SWC. Therefore, when an ESD event occurs at one of the first power terminal TV1 and the second power terminal TV2, the electrostatic discharge control circuit 420 disconnects the control switch SWC.

On the other hand, when no ESD event occurs, the capacitor CF forms a short circuit. Therefore, the sensing signal SF has a low voltage level. The inverted sensing signal SFB has a high voltage level. Therefore, the protection switch SWP is disconnected in response to the high voltage level of the sensing signal SF. The control switch SWC operates in response to the control signal SE.

In this embodiment, the inverter 422 can be implemented by a CMOS element (the present invention is not limited thereto). The inverter 422 includes a P-type MOSFET M1 and an N-type MOSFET M2. The first end of the P-type MOSFET M1 is coupled to the second power supply terminal TV2. The second end of the P-type MOSFET M1 is coupled to the control end of the protection switch SWP. The control end of the P-type MOSFET M1 is coupled to the sensing circuit 421. The first end of the N-type MOSFET M2 is coupled to the second end of the P-type MOSFET M1. The second end of the N-type MOSFET M2 is coupled to the first power supply terminal TV1. The control end of the N-type MOSFET M2 is coupled to the sensing circuit 421.

Please refer to FIG. 7, which is a schematic diagram of a fuse circuit according to the fifth embodiment of the present invention. In this embodiment, the fuse circuit 500 includes a control switch SWC, a fuse element FS, an electrostatic discharge protection circuit 110, an electrostatic discharge control circuit 520, and a resistor RE. The first end of the control switch SWC is coupled to the first power supply terminal TV1. The first end of the fuse element FS is coupled to the second end of the control switch SWC. The second end of the fuse element FS is coupled to the third end of the control switch SWC and the second power supply terminal TV2. In this embodiment, the control switch SWC can be an N-type transistor of any form. Similar to the embodiment of FIG. 6, the control switch SWC of this embodiment is implemented, for example, with a P-type MOSFET. The first power supply terminal TV1 receives a reference high voltage VH. The second power supply terminal TV2 receives a reference low voltage VL.

The electrostatic discharge protection circuit 110 is coupled between the first power supply terminal TV1 and the second power supply terminal TV2. The resistor RE is coupled between the control terminal of the control switch SWC and the second power supply terminal TV2. The implementation of the electrostatic discharge protection circuit 110 has been clearly described in the embodiment of FIG. 2, so it will not be repeated here. The implementation of the resistor RE has been clearly described in the embodiment of FIG. 3, so it will not be repeated here.

In this embodiment, the electrostatic discharge control circuit 520 includes a sensing circuit 521 and a protection switch SWP. The sensing circuit 521 is coupled between the first power terminal TV1 and the second power terminal TV2. The sensing circuit 521 provides a sensing signal SF according to one of the electrostatic discharge energy PESD1 from the first power terminal TV1 and the electrostatic discharge energy PESD2 from the second power terminal TV2.

In this embodiment, the protection switch SWP is coupled to the sensing circuit 521, the second power terminal TV2 and the control terminal of the control switch SWC. The protection switch SWP connects the control terminal of the control switch SWC to the second power terminal TV2 according to the sensing signal SF, thereby disconnecting the control switch SWC.

In this embodiment, the sensing circuit 521 includes a resistor RF and a capacitor CF. The capacitor CF is coupled between the first power terminal TV1 and the control terminal of the protection switch SWP. The resistor RF is coupled between the control terminal of the protection switch SWP and the second power terminal TV2. The first terminal of the protection switch SWP is coupled to the control terminal of the control switch SWC. The second terminal of the protection switch SWP is coupled to the second power terminal TV2. The control terminal of the protection switch SWP is coupled to the sensing circuit 521. The protection switch SWP is implemented, for example, with an N-type MOSFET.

When an ESD event occurs, the impedance of the capacitor CF is reduced. This causes the sensing signal SF to have a low voltage level. Therefore, the protection switch SWP is turned on in response to the low voltage level of the sensing signal SF. The turned-on protection switch SWP uses the reference high voltage VH to raise the voltage value at the control end of the control switch SWC. Therefore, when an ESD event occurs at one of the first power terminal TV1 and the second power terminal TV2, the electrostatic discharge control circuit 520 disconnects the control switch SWC.

On the other hand, when no ESD event occurs, the capacitor CF forms a short circuit. Therefore, the sensing signal SF has a high voltage level. Therefore, the protection switch SWP is disconnected in response to the high voltage level of the sensing signal SF. The control switch SWC operates in response to the control signal SE.

In summary, the first end of the fuse element is coupled to the second end of the control switch. The second end of the fuse element is coupled to the third end of the control switch and the second power supply end. In this way, when electrostatic discharge energy from the second power supply end occurs, the electrostatic discharge energy is bypassed to the third end of the control switch through the second end of the fuse element. In addition, the electrostatic discharge control circuit responds to the electrostatic discharge energy from one of the first power supply end and the second power supply end to disconnect the control switch. In this way, when electrostatic discharge energy occurs, the control switch will not be abnormally turned on.

Although the present invention has been disclosed as above by the embodiments, it is not intended to limit the present invention. Anyone with ordinary knowledge in the relevant technical field can make some changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the scope defined by the attached patent application.

100: Fuse circuit

110: Electrostatic discharge protection circuit

120: Electrostatic discharge control circuit

FS: Fuse element

PESD1, PESD2: electrostatic discharge energy

SE: Control signal

SWC: Control switch

TV1: First power supply terminal

TV2: Second power supply terminal

Claims (10)

A fuse circuit comprises: a control switch, a first end of the control switch coupled to a first power supply terminal; a fuse element, a first end of the fuse element coupled to a second end of the control switch, and a second end of the fuse element coupled to a third end of the control switch and a second power supply terminal; an electrostatic discharge protection circuit coupled between the first power supply terminal and the second power supply terminal, configured to bypass electrostatic discharge energy from one of the first power supply terminal and the second power supply terminal to the other of the first power supply terminal and the second power supply terminal; and an electrostatic discharge control circuit coupled to the first power supply terminal, the second power supply terminal and a control end of the control switch, configured to disconnect the control switch in response to electrostatic discharge energy from one of the first power supply terminal and the second power supply terminal. A fuse circuit as described in claim 1, wherein: the control switch is a transistor, the first end of the control switch is a drain electrode, the second end of the control switch is a source electrode, the third end of the control switch is a base electrode, and the control end of the control switch is a gate electrode. A fuse circuit as described in claim 1, wherein when electrostatic discharge energy occurs from the second power supply terminal, the electrostatic discharge energy is bypassed to the third terminal of the control switch via the second terminal of the fuse element. A fuse circuit as described in claim 1, wherein the electrostatic discharge control circuit comprises: a sensing circuit coupled between the first power terminal and the second power terminal, configured to provide a sensing signal based on electrostatic discharge energy from one of the first power terminal and the second power terminal; and a protection switch coupled to the sensing circuit, the second power terminal and the control terminal of the control switch, configured to connect the control terminal of the control switch to the second power terminal based on the sensing signal, thereby disconnecting the control switch. The fuse circuit as described in claim 4, wherein the electrostatic discharge control circuit further comprises: An inverter coupled between the sensing circuit and the protection switch, configured to invert the sensing signal. A fuse circuit as described in claim 5, wherein the sensing circuit comprises: a resistor coupled between the first power supply terminal and the input terminal of the inverter; and a capacitor coupled between the input terminal of the inverter and the second power supply terminal. A fuse circuit as described in claim 4, wherein: the control switch is an N-type transistor, the first power supply terminal receives a reference high voltage, and the second power supply terminal receives a reference low voltage. A fuse circuit as described in claim 7, wherein: the protection switch is an N-type transistor, and the sensing signal has a low voltage level. A fuse circuit as described in claim 4, wherein: the control switch is a P-type transistor, the first power supply terminal receives a reference low voltage, and the second power supply terminal receives a reference high voltage. A fuse circuit as described in claim 9, wherein: the protection switch is a P-type transistor, and the sensing signal has a high voltage level.

Images