阅读说明：本技术 具有过电流保护之电子装置 (Electronic device with over-current protection ) 是由 陈宛羚 于 2020-05-15 设计创作，主要内容包括：一种具有过电流保护之电子装置,包括过电流保护电路以及电源输出控制电路。电源输出控制电路根据切换开关决定是否将电源输入端提供的电源导通至电源输出端,过电流保护电路则用以在电源输入端产生过电流时,将切换开关之控制端设为接地,以控制电源输出控制电路将电源输入端与电源输出端电性断路以避免大电流通过电路而损坏电子组件。(An electronic device with over-current protection includes an over-current protection circuit and a power output control circuit. The power output control circuit determines whether to conduct the power provided by the power input end to the power output end according to the switch, and the over-current protection circuit is used for setting the control end of the switch to be grounded when the power input end generates over-current so as to control the power output control circuit to electrically disconnect the power input end and the power output end to prevent the large current from passing through the circuit to damage the electronic component.)

1. An electronic device with over-current protection, comprising an over-current protection circuit and a power output control circuit, wherein the power output control circuit is coupled to a power input terminal for providing a power source, the power input terminal is coupled to a reference input terminal through a reference resistor, and the power output control circuit determines whether to electrically connect the reference input terminal to a power output terminal according to a switch, when a control terminal of the switch is at a low voltage level or grounded, the reference input terminal and the power output terminal are electrically disconnected, the over-current protection circuit comprising:

a first resistor coupled between the reference input terminal and a first node;

a second resistor coupled between the first node and a ground terminal;

a third resistor;

a fourth resistor;

a fifth resistor coupled between a second node and the ground terminal;

a PNP type bipolar transistor, wherein the base of the PNP type bipolar transistor is coupled to the first node, the emitter of the PNP type bipolar transistor is coupled to the power input terminal, and the collector of the PNP type bipolar transistor is coupled to the second node via the fourth resistor;

a first NMOS transistor, wherein the drain of the first NMOS transistor is coupled to the first node through the third resistor, the gate of the first NMOS transistor is coupled to the second node, and the source of the first NMOS transistor is coupled to ground;

a first capacitor coupled between the second node and ground;

a first zener diode, an anode of the first zener diode being coupled to ground, and a cathode of the first zener diode being coupled to the second node;

a first diode, wherein the anode of the first diode is coupled to the control terminal of the switch, and the cathode of the first diode is coupled to the drain of the first NMOS transistor; and

a second diode, the anode of the second diode is coupled to the second node, the cathode of the first diode is coupled to the control terminal of the switch through a sixth resistor,

when the voltage difference between the power input terminal and the reference input terminal is greater than a first threshold value, the first PNP bipolar transistor and the first NMOS transistor are turned on to ground the control terminal of the switch, so as to control the power output control circuit to electrically disable the reference input terminal and the power output terminal.

2. The electronic device of claim 1, wherein the switch is an NMOS transistor, the control terminal is a gate of the switch, the gate of the switch is coupled to ground via a seventh resistor, and the source of the switch is coupled to ground.

3. The electronic device with over-current protection as claimed in claim 2, wherein when the gate of the switch is set to ground, the power output control circuit electrically disconnects the reference input terminal from the power output terminal; and

when the gate of the switch is set to a high voltage level, the power output control circuit electrically connects the reference input terminal and the power output terminal.

4. The electronic device with over-current protection as claimed in claim 2, wherein the power output control circuit further comprises:

a second capacitor;

a third diode, an anode of the third diode being coupled to the reference input terminal, a cathode of the third diode being coupled to the second capacitor;

an eighth resistor coupled between the anode and the cathode of the third diode;

a ninth resistor coupled between the second capacitor and a third node;

a first PMOS transistor, wherein the drain of the first PMOS transistor is coupled to the anode of the third diode, the gate of the first PMOS transistor is coupled to the third node, and the source of the first PMOS transistor is coupled to a fourth node;

a fourth diode, wherein the anode of the fourth diode is coupled to the third node;

a third capacitor coupled between the fourth node and the cathode of the fourth diode;

a tenth resistor coupled between the drain of the switch and the cathode of the fourth diode;

an eleventh resistor coupled between the third node and the fourth node;

an NPN bipolar transistor, wherein the base and emitter of the NPN bipolar transistor are coupled to the third node, and the collector of the NPN bipolar transistor is coupled to the fourth node;

a second zener diode, wherein an anode of the second zener diode is coupled to the third node, and a cathode of the second zener diode is coupled to the fourth node;

a fourth capacitor;

a fifth diode, an anode of which is coupled to the power output terminal through a fuse unit, and a cathode of which is coupled to the fourth capacitor;

a twelfth resistor coupled between the fourth capacitor and the third node;

a thirteenth resistor coupled between the anode and the cathode of the fifth diode;

a second PMOS transistor, wherein the drain of the second PMOS transistor is coupled to the anode of the fifth diode, the gate of the second PMOS transistor is coupled to the third node, and the source of the second PMOS transistor is coupled to the fourth node.

5. The electronic device with over-current protection as claimed in claim 2, further comprising:

a fifth capacitor; and

a current detection unit including a first detection terminal coupled to the power input terminal, a second detection terminal coupled to the reference input terminal, and an alarm signal terminal,

wherein the fifth capacitor and the reference resistor are coupled in parallel between the power input terminal and the reference input terminal,

wherein, when the current detecting unit detects that the voltage difference between the first detecting terminal and the second detecting terminal is not greater than a second threshold, the warning signal terminal of the current detecting unit outputs a high voltage level,

when the current detection unit detects that the voltage difference between the first detection end and the second detection end is greater than the second threshold value, the warning signal end of the current detection unit outputs a low voltage level.

6. The electronic device of claim 5, wherein the first threshold is greater than the second threshold.

7. The electronic device with over-current protection as claimed in claim 5, further comprising:

a control unit coupled between the warning signal terminal and the sixth resistor for determining whether to turn on the switch according to the voltage level of the warning signal terminal,

when the warning signal terminal is at a low voltage level or grounded, the control unit outputs a low voltage level to turn off the switch.

8. The electronic device with over-current protection as claimed in claim 7, further comprising:

a second NMOS transistor, wherein the drain of the second NMOS transistor is coupled to the warning signal terminal of the current detection unit, the gate of the second NMOS transistor is coupled to the second node, and the source of the first NMOS transistor is coupled to the ground terminal.

9. The electronic device of claim 8, wherein when the voltage difference between the power input terminal and the reference input terminal is greater than the first threshold, the first PNP bipolar transistor and the second NMOS transistor are turned on to ground the alarm signal terminal.

Technical Field

The present invention relates to an electronic device with over-current protection, and more particularly to an electronic device with an over-current protection circuit for preventing instantaneous large current from breaking down electronic components.

Background

Conventionally, in an electronic device, in order to avoid damage to components inside the electronic device due to excessive current input or output of a power supply, a current sensing component is generally provided to detect whether an excessive current is generated, and when the excessive current is generated, the current sensing component closes a corresponding switch to disconnect a current source from other components inside the electronic device, thereby preventing the components from being burned out by a continuous large current.

However, the current sensing device takes a long time from detecting an excessive current to turning off the corresponding switch, and if an excessive transient current is generated, sensitive devices in the circuit may be damaged before turning off the corresponding switch, for example, in the current electronic device, a Power output control circuit for a Universal Serial Bus (USB) often uses a metal oxide semiconductor field effect transistor (MOS transistor) as a switch for Power output, and the transient excessive current may damage the MOS transistor in a short time, so that the Power output control circuit cannot normally operate. Therefore, there is still a need for an improved over-current protection circuit for electronic devices to solve the above problems.

Disclosure of Invention

The present invention provides an electronic device having an over-current protection circuit for preventing a transient large current from breaking down an electronic component.

To solve the above-mentioned technical problems, the present invention provides an electronic device with over-current protection, comprising an over-current protection circuit and a power output control circuit, wherein the power output control circuit is coupled to a power input terminal for providing a power source, the power input terminal is coupled to a reference input terminal through a reference resistor, and the power output control circuit determines whether to electrically connect the reference input terminal to a power output terminal according to a switch, when a control terminal of the switch is at a low voltage level or grounded, the reference input terminal and the power output terminal are electrically disconnected, wherein the over-current protection circuit comprises: a first resistor coupled between the reference input terminal and a first node; a second resistor coupled between the first node and a ground terminal; a third resistor; a fourth resistor; a fifth resistor coupled between a second node and the ground terminal; a PNP type bipolar transistor (BJT), wherein a Base (Base) of the PNP type bipolar transistor is coupled to the first node, an Emitter (Emitter) of the PNP type bipolar transistor is coupled to the power input terminal, and a Collector (Collector) of the PNP type bipolar transistor is coupled to the second node via the fourth resistor; a first NMOS transistor, wherein a Drain (Drain) of the first NMOS transistor is coupled to the first node through the third resistor, a Gate (Gate) of the first NMOS transistor is coupled to the second node, and a Source (Source) of the first NMOS transistor is coupled to the second node; a first capacitor coupled between the second node and ground; a first Zener Diode (Zener Diode), an anode (anode) of the first Zener Diode being coupled to ground, and a cathode (cathode) of the first Zener Diode being coupled to the second node; a first Diode (Diode), an anode of the first Diode being coupled to the control terminal of the switch, a cathode of the first Diode being coupled to a drain of the first NMOS transistor; and a second diode, wherein an anode of the second diode is coupled to the second node, and a cathode of the first diode is coupled to the control terminal of the switch through a sixth resistor, wherein when a voltage difference between the power input terminal and the reference input terminal is greater than a first threshold value, the first PNP bipolar transistor and the first NMOS transistor are turned on to ground the control terminal of the switch, so as to control the power output control circuit to turn off the electrical connection between the reference input terminal and the power output terminal.

Preferably, the switch is an NMOS transistor, the control terminal is a gate of the switch, the gate of the switch is coupled to ground via a seventh resistor, and the source of the switch is coupled to ground.

Preferably, when the gate of the switch is grounded, the power output control circuit electrically disconnects the reference input terminal from the power output terminal; and when the gate of the switch is set to a high voltage level, the power output control circuit electrically connects the reference input terminal and the power output terminal.

Preferably, the power output control circuit further includes: a second capacitor; a third diode, an anode of the third diode being coupled to the reference input terminal, a cathode of the third diode being coupled to the second capacitor; an eighth resistor coupled between the anode and the cathode of the third diode; a ninth resistor coupled between the second capacitor and a third node; a first PMOS transistor, wherein the drain of the first PMOS transistor is coupled to the anode of the third diode, the gate of the first PMOS transistor is coupled to the third node, and the source of the first PMOS transistor is coupled to a fourth node; a fourth diode, wherein the anode of the fourth diode is coupled to the third node; a third capacitor coupled between the fourth node and the cathode of the fourth diode; a tenth resistor coupled between the drain of the switch and the cathode of the fourth diode; an eleventh resistor coupled between the third node and the fourth node; an NPN bipolar transistor, wherein the base and emitter of the NPN bipolar transistor are coupled to the third node, and the collector of the NPN bipolar transistor is coupled to the fourth node; a second zener diode, wherein an anode of the second zener diode is coupled to the third node, and a cathode of the second zener diode is coupled to the fourth node; a fourth capacitor; a fifth diode, an anode of which is coupled to the power output terminal through a fuse unit, and a cathode of which is coupled to the fourth capacitor; a twelfth resistor coupled between the fourth capacitor and the third node; a thirteenth resistor coupled between the anode and the cathode of the fifth diode; a second PMOS transistor, wherein the drain of the second PMOS transistor is coupled to the anode of the fifth diode, the gate of the second PMOS transistor is coupled to the third node, and the source of the second PMOS transistor is coupled to the fourth node.

Preferably, the electronic device with overcurrent protection further comprises: a fifth capacitor; and a current detection unit including a first detection terminal coupled to the power input terminal, a second detection terminal coupled to the reference input terminal, and an alarm signal terminal, wherein the fifth capacitor and the reference resistor are coupled in parallel between the power input terminal and the reference input terminal. In addition, when the current detection unit detects that the voltage difference between the first detection end and the second detection end is not greater than a second threshold value, the warning signal end of the current detection unit outputs a high voltage level. In addition, when the current detecting unit detects that the voltage difference between the first detecting terminal and the second detecting terminal is greater than the second threshold, the warning signal terminal of the current detecting unit outputs a low voltage level.

Preferably, the first threshold is larger than the second threshold.

Preferably, the electronic device with overcurrent protection further comprises: and a control unit coupled between the warning signal terminal and the sixth resistor for determining whether to turn on the switch according to a voltage level of the warning signal terminal, wherein when the warning signal terminal is at a low voltage level or grounded, the control unit outputs the low voltage level to turn off the switch.

Preferably, the electronic device with overcurrent protection further comprises: a second NMOS transistor, wherein the drain of the second NMOS transistor is coupled to the warning signal terminal of the current detection unit, the gate of the second NMOS transistor is coupled to the second node, and the source of the first NMOS transistor is coupled to the ground terminal.

Preferably, when the voltage difference between the power input terminal and the reference input terminal is greater than the first threshold, the first PNP bipolar transistor and the second NMOS transistor are turned on to ground the warning signal terminal.

Compared with the prior art, the present invention can rapidly turn off the switch SW by the arrangement of the overcurrent protection circuit 110, so as to prevent the large current from passing through the electronic components in the power output control circuit 120 and being damaged. On the other hand, since the overcurrent protection circuit 110 is formed by commonly used and low-cost electronic components, the arrangement is more flexible by adjusting the resistance value of the resistor, and the arrangement cost is also reduced.

[ description of the drawings ]

Other features and advantages of the present invention will become apparent from the following detailed description of the preferred embodiments with reference to the accompanying drawings, in which:

FIG. 1 is a schematic diagram of an electronic device with over-current protection.

[ detailed description ] embodiments

The embodiments or examples shown in the figures are expressed in a particular manner as set forth below. It is to be understood that the embodiment or examples are not to be construed as limiting. Any alterations and modifications in the described embodiments, and any further applications of the principles of the invention as described herein are contemplated as would normally occur to one skilled in the art to which the invention relates.

FIG. 1 is a schematic diagram of an electronic device 100 with over-current protection. In some embodiments of the invention, the electronic device 100 includes an overcurrent protection circuit 110, a power output control circuit 120, a control unit 130, and a current detection unit 140. The electronic device 100 further has a power input terminal VIN for providing power, the power input terminal VIN is coupled to the power output control circuit 120 through a resistor Rf, and a terminal of the resistor Rf coupled to the power output control circuit 120 is a reference input terminal Vref. The power output control circuit 120 is used to determine whether to electrically connect the reference input terminal Vref and the power output terminal VOUT, so as to correspondingly control whether to provide power output to the power output terminal VOUT.

In some embodiments, the power output control circuit 120 determines whether to provide power to the power output terminal VOUT according to the switch SW, and when the control terminal of the switch SW is at a low voltage level or grounded, the power output control circuit 120 will be electrically disconnected between the reference input terminal Vref and the power output terminal VOUT. On the contrary, when the control terminal of the switch SW is at a high voltage level, the power output control circuit 120 electrically connects the reference input terminal Vref and the power output terminal VOUT. In some embodiments of the present invention, the switch SW is an NMOS transistor, and the control terminal is the gate of the NMOS transistor. It should be understood that the control terminal of the switch SW is coupled to the overcurrent protection circuit 110 and the control unit 130, so that the overcurrent protection circuit 110 and the control unit 130 can control the power output control circuit 120 to control whether the reference input terminal Vref is electrically connected to the power output terminal VOUT.

In some embodiments of the present invention, the overcurrent protection circuit 110 includes resistors R1, R2, R3, R4, R5, PNP bipolar transistor BJT1, NMOS1, capacitor C1, zener diode Z1, diodes D1, and D2. As shown in FIG. 1, the resistor R1 has one end coupled to the reference input Vref and the other end coupled to the node N1. The resistor R2 has one end coupled to the node N1 and the other end coupled to the ground GND. The resistor R3 has one end coupled to the node N1 and the other end coupled to the cathode of the diode D1 and the Drain (Drain) of the NMOS transistor NMOS 1. The Base (Base) of the PNP bipolar transistor BJT1 is coupled to the node N1, the Emitter (Emitter) is coupled to the power input VIN, and the Collector (Collector) is coupled to the resistor R4. The resistor R4 has one end coupled to the PNP bipolar transistor BJT1 and the other end coupled to the node N2. The drain of the NMOS transistor NMOS1 is coupled to the diode D1 and the resistor R3, the Gate (Gate) is coupled to the node N2, and the Source (Source) is coupled to the ground GND. The resistor R5 has one end coupled to the node N2 and the other end coupled to the ground GND. The capacitor C1 has one end coupled to the node N2 and the other end coupled to the ground GND. The cathode (cathode) of the diode D1 is coupled to the NMOS transistor 1, and the anode (anode) is coupled to the control terminal of the switch SW of the power output control circuit 120. The Zener Diode (Zener Diode) Z1 has an anode coupled to ground GND and a cathode coupled to node N2. The diode D2 has an anode coupled to the node N2 and a cathode coupled to the resistor R6 of the power output control circuit 120.

In some embodiments, when the voltage difference between the power input terminal VIN and the reference input terminal Vref is greater than the first threshold, i.e. a large current is generated between the power input terminal VIN and the reference input terminal Vref, the PNP bipolar transistor BJT1 and the NMOS transistor NMOS1 are turned on accordingly, so that the gate (control terminal) of the switch SW is set to be grounded through the conduction of the diode D2 and the NMOS transistor NMOS1, and the power output control circuit 120 will not turn on the reference input terminal Vref and the power output terminal VOUT electrically, thereby preventing the large current from passing through the electronic components in the power output control circuit 120 and damaging the electronic components. It should be appreciated that if the user wants to avoid the over current of more than 110A, when the resistor Rf is 0.005 ohm, the first threshold is set to 0.55V, and the resistances of the resistor R1 and the resistor R2 are respectively 1K ohm and 75K ohm, so that when the voltage difference between the reference input terminal Vref and the power output terminal VOUT is more than 0.55V, the voltage division at the node N1 can turn on the PNP bipolar transistor BJT 1. The protection threshold for any over-current can be achieved by adjusting the resistances of the resistor R1 and the resistor R2, but the invention is not limited to the above examples.

In some preferred embodiments, the resistor R1 is 1K ohm, the resistor R2 is 75K ohm, the resistor R3 is 10K ohm, the resistor R4 is 10K ohm, the resistor R5 is 10K ohm, the BJT1 of the PNP bipolar transistor is PMBT3906, the NMOS1 is 2N7002, the capacitor C1 is 100pF, the zener diode Z1 is BZT52-C3V6X, the diode D1 is BAT54C, and the diode D2 is BAT 54C. It should be appreciated that the above examples are merely preferred examples and that any suitably replaceable electronic components are still within the scope of the present invention.

In some embodiments of the present invention, the power output control circuit 120 includes resistors R6, R7, R8, R9, R10, R11, R12, R13, capacitors C2, C3, C4, diodes D3, D4, D5, PMOS transistors PMOS1, PMOS2, a switch SW, zener diode Z2, NPN bipolar transistor BJT2, and a fuse unit F. As shown in fig. 1, one end of the resistor R6 is coupled to the anode of the diode D1 and the gate of the switch SW, and the other end is coupled to the cathode of the diode D2 and the control unit 130. One end of the resistor R7 is coupled to the gate of the switch SW, and the other end is coupled to the source of the switch SW and the ground GND. The resistor R8 is connected in parallel with the diode D3, the anode of the diode D3 is coupled to the reference input terminal Vref, and the cathode is coupled to the capacitor C2. One end of the capacitor C2 is coupled to the cathode of the diode D3, and the other end is coupled to the resistor R9. One end of the resistor R9 is coupled to the capacitor C2, and the other end is coupled to the node N3. The drain of the PMOS transistor PMOS1 is coupled to the reference input Vref, the gate is coupled to the node N3, and the source is coupled to the node N4. One end of the capacitor C3 is coupled to the node N4, and the other end is coupled to the cathode of the diode D4. The diode D4 has an anode coupled to the node N3, and a cathode coupled to the capacitor C3 and the resistor R10. One end of the resistor R10 is coupled to the capacitor C3 and the cathode of the diode D4, and the other end is coupled to the drain of the switch SW. One terminal of the resistor R11 is coupled to the node N3, and the other terminal is coupled to the node N4. The base and emitter of NPN bipolar transistor BJT2 are coupled to node N3, and the collector is coupled to node N4. The anode of the zener diode Z2 is coupled to the node N3, and the cathode is coupled to the node N4. The resistor R13 is connected in parallel with the diode D5, the anode of the diode D5 is coupled to the power output terminal VOUT through the fuse unit F, and the cathode is coupled to the capacitor C4. One end of the capacitor C2 is coupled to the cathode of the diode D5, and the other end is coupled to the resistor R12. One end of the resistor R12 is coupled to the capacitor C4, and the other end is coupled to the node N3. The drain of the PMOS transistor PMOS2 is coupled to the anode of the diode D5 and the fuse unit F, the gate is coupled to the node N3, and the source is coupled to the node N4.

In some embodiments, when the gate of the switch SW is set to ground, at least one of the PMOS transistors PMOS1 and PMOS2 in the power output control circuit 120 will be turned off, so that the reference input terminal Vref and the power output terminal VOUT are electrically turned off. On the other hand, when the gate of the switch SW is set to the high voltage level, the PMOS transistors PMOS1 and PMOS2 in the power output control circuit 120 are turned on, so that the reference input terminal Vref and the power output terminal VOUT are electrically connected.

In some preferred embodiments, the power output control circuit 120 includes a resistor R6 of 1K ohm, a resistor R7 of 4.99K ohm, a resistor R8 of 49.9K ohm, a resistor R9 of 100 ohm, a resistor R10 of 20K ohm, a resistor R11 of 49.9K ohm, a resistor R12 of 100 ohm, a resistor R13 of 49.9K ohm, a capacitor C2 of 1 μ F, a capacitor C3 of 1000pF, a capacitor C4 of 1 μ F, diodes D3, D4, D5 of MMSD4148T1G, PMOS transistors 1, PMOS2 of Si 7101-Ti-GE 3, a switch SW of NMOS transistor and of 2N7002, a zener diode Z2 of BZT 69552-C6V 2, and a BJT 3908653 of NPN diode. It should be appreciated that the above examples are merely preferred examples and that any suitably replaceable electronic components are still within the scope of the present invention.

In some embodiments of the present invention, the electronic device 100 further has a current detection unit 140. The current detecting unit 140 has an alarm signal terminal ALR, detecting terminals IN1 and IN2, respectively coupled to the power input terminal VIN and the reference input terminal Vref. In addition, the capacitor C5 and the resistor Rf are coupled in parallel between the power input terminal VIN and the reference input terminal Vref. IN some embodiments, the alert signal terminal ALR of the current detection unit 140 continuously outputs the high voltage level when the current detection unit 140 detects that the voltage difference between the detection terminals IN1 and IN2 is not greater than the second threshold, whereas the alert signal terminal ALR of the current detection unit 140 outputs the low voltage level when the current detection unit 140 detects that the voltage difference between the detection terminals IN1 and IN2 is greater than the second threshold. In other words, when a large current is generated in the resistor Rf, the warning signal terminal ALR of the current detection unit 140 outputs a low voltage level. In some preferred embodiments, capacitor C5 is 22pF, resistor Rf is 0.005 ohm, and current detecting unit 140 may be a current detecting chip of type INA300aid sosor.

In some embodiments of the present invention, the control unit 130 is coupled to the gate (control terminal) of the switch SW through a resistor R6, and is used for determining whether to turn on the switch SW according to the voltage level of the warning signal terminal ALR. When the warning signal terminal ALR is at a low voltage level or grounded, the control unit 130 outputs the low voltage level to turn off the switch SW. IN detail, when the current detection unit 140 detects that the voltage difference between the detection terminals IN1 and IN2 is greater than the second threshold, the warning signal terminal ALR of the current detection unit 140 outputs a low voltage level, and the control unit 130 outputs the low voltage level to turn off the switch SW, so that the reference input terminal Vref and the power output terminal VOUT are electrically turned off to prevent the electronic device from being damaged by a large current. It should be understood that although the current detecting unit 140 can prevent the electronic components from being damaged by the large current by turning off the switch SW through the control unit 130 when the current detecting unit 140 detects the relatively large current, the current detecting unit 140 has a slower response speed than the overcurrent protection circuit 110, so that the electronic components cannot be cut off in time when the current is too large to damage the internal circuit in a short time. Therefore, in some embodiments, the control unit 130 and the current detection unit 140 are mainly used for overcurrent protection with low current, and the overcurrent protection circuit 110 is mainly used for overcurrent protection with high current, in other words, the first threshold is larger than the second threshold.

In addition, in order to avoid that the control unit 130 erroneously generates a high voltage level to turn on the switch SW when the current detection unit 140 does not timely switch the warning signal terminal ALR to a low voltage level, in some embodiments, an NMOS transistor NMOS2 is further disposed between the overcurrent protection circuit 110 and the control unit 130, and a gate of an NMOS transistor NMOS2 is coupled to the node N2, a source is coupled to the ground terminal GND, and a drain is coupled to the warning signal terminal ALR. Therefore, when the voltage difference between the power input terminal VIN and the reference input terminal Vref is greater than the first threshold, the PNP bipolar transistor BJT and the NMOS transistor NMOS2 are turned on to set the warning signal terminal ALR to be grounded, so that the control unit 130 outputs a low voltage level or is grounded, thereby preventing the switching switch SW from being turned on erroneously due to a high voltage level. In some preferred embodiments, the NMOS transistor NMOS2 has a model number of 2N 7002.

In summary, the present invention can rapidly turn off the switch SW by the arrangement of the overcurrent protection circuit 110, so as to prevent the large current from passing through the electronic components in the power output control circuit 120 and being damaged. On the other hand, since the overcurrent protection circuit 110 is formed by commonly used and low-cost electronic components, the arrangement is more flexible by adjusting the resistance value of the resistor, and the arrangement cost is also reduced.

The methods of the present invention, or certain aspects or portions thereof, may take the form of program code. The program code may be embodied in tangible media, such as floppy diskettes, cd-roms, hard drives, or any other machine-readable storage medium, wherein, when the program code is loaded into and executed by a machine, such as a computer, the machine thereby becomes an apparatus for practicing the invention. The program code may also be transmitted over some transmission medium, such as over electrical wiring or cabling, through fiber optics, or via any other form of transmission, wherein, when the program code is received and loaded into and executed by a machine, such as a computer, the machine becomes an apparatus for practicing the invention. When implemented in a general-purpose processing unit, the program code combines with the processing unit to provide a unique apparatus that operates analogously to specific logic circuits.

While the present invention has been described with reference to preferred embodiments, it is to be understood that the above disclosure is not intended to limit the embodiments of the invention. On the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Furthermore, the appended claims are to be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.