Drive circuit for buzzer with low startup voltage to prevent burnout caused by reverse connection of power supply and ground

Abstract

The present invention provides a drive circuit for preventing the power supply and ground from being connected reversely and burning out in a buzzer with a low startup voltage, which includes a substrate current-limiting resistor R2, a driving NMOS transistor, a current-limiting resistor R1, and an internal circuit. The source of the driving NMOS transistor is connected to the ground wire and the drain is connected to the output terminal. The substrate of the driving NMOS transistor is connected to the source of the driving NMOS transistor through the substrate current-limiting resistor R2, and the internal circuit is connected to the power supply through the current-limiting resistor R1. In the present invention, the substrate of the MOS transistor is connected to the source terminal through a substrate current-limiting resistor, and the internal circuit is powered through the current-limiting resistor R1, so that when the power line and the ground wire are connected reversely, the power consumption can be greatly reduced, thereby preventing the circuit from being burned out. During normal use, the substrate current-limiting resistor R2 between the substrate and the source terminal of the driving NMOS transistor will not excessively increase the resistance between the source terminal and the drain terminal of the driving NMOS transistor, and by appropriately selecting the current-limiting resistor, the drive circuit of the present invention can be started and operated at a very low voltage.

Description

Technical Field

[0001] The present invention relates to the field of buzzer circuits, and particularly to a drive circuit for preventing the power supply and ground from being reversely connected and burning out in a buzzer with a low startup voltage. Background Art

[0002] Traditional circuits for preventing the power supply line and the ground line from being reversely connected and causing chip burnout are as Figure 1 shown. A diode D is connected in series between the internal circuit and the driving NMOS transistor. When the power supply line and the ground line are reversely connected, that is, the power supply line of the chip is mistakenly connected to the ground line and the ground line of the chip is mistakenly connected to the power supply line, the diode D is reverse-biased and in the cut-off state, so as to achieve the purpose of preventing the power supply line and the ground line from being reversely connected and causing chip burnout. The disadvantage of this circuit is that during normal operation, the startup voltage of the chip is higher than that without the diode D by a diode forward conduction voltage. Summary of the Invention

[0003] The present invention provides a drive circuit for preventing the power supply and ground from being reversely connected and burning out in a buzzer with a low startup voltage, so as to solve the problem of raising the startup voltage of the drive circuit when the prior art prevents the power supply line and the ground line from being reversely connected and causing chip burnout.

[0004] To solve the above technical problems, as Figure 2 shown, the present invention provides a drive circuit for preventing the power supply and ground from being reversely connected and burning out in a buzzer with a low startup voltage, including a substrate current-limiting resistor R2, a current-limiting resistor R1, a driving NMOS transistor, and an internal circuit. The source of the driving NMOS transistor is connected to the ground line and the drain is connected to the output terminal. The output terminal is externally connected to the electromagnetic coil of the buzzer. The substrate of the driving NMOS transistor is connected to the source of the driving NMOS transistor through the substrate current-limiting resistor R2. The internal circuit is connected to the power supply through the current-limiting resistor R1, that is, the internal circuit is powered through the current-limiting resistor R1. The internal circuit is other circuit modules on the same chip as the frequency correction module, oscillator, frequency divider, etc. described in the present invention.

[0005] Preferably, the substrate current-limiting resistor R2 is a parasitic substrate resistor, and the distance between the contact between the driving NMOS transistor and the substrate and the drain end of the driving NMOS transistor is increased, generally more than twice the minimum value of the design rule, so as to increase the resistance value of the substrate parasitic current-limiting resistor.

[0006] Preferably, the substrate current-limiting resistor R2 is replaced by a diode, and the replaced diode is connected between the substrate and the source of the driving NMOS transistor, or between the substrate of the driving NMOS transistor and the ground line.

[0007] Preferably, the substrate current-limiting resistor R2 is connected in series with a parasitic substrate resistor and other integrated circuit resistors.

[0008] Preferably, there is at least one current-limiting resistor R1 between the internal circuit and the power supply.

[0009] Preferably, when there are multiple current-limiting resistors R1, each current-limiting resistor R1 corresponds to a different internal circuit respectively.

[0010] Beneficial effects brought by the present invention: In the present invention, the substrate of the driving NMOS transistor is connected to the source terminal through a substrate current-limiting resistor, or by increasing the resistance value of the parasitic substrate resistor of the driving NMOS transistor, and the internal circuit is powered through a current-limiting resistor, so that when the power supply line and the ground line are connected reversely, the power consumption can be greatly reduced, thereby preventing the circuit from being burned out. The distance between the contact between the driving NMOS transistor and the substrate and the drain terminal of the driving NMOS transistor is increased to increase the resistance value of the parasitic substrate current-limiting resistor, and this substrate current-limiting resistor can be a parasitic resistor or a combination of other integrated circuit resistors and parasitic resistors. During normal use, the substrate current-limiting resistor between the substrate and the source terminal of the driving NMOS transistor will not excessively increase the resistance value between the source terminal and the drain terminal of the driving NMOS transistor, and by appropriately selecting the current-limiting resistor connected between the power supply and the internal circuit, the driving circuit of the present invention can be started to work at a very low voltage. Description of the Drawings

[0011] Figure 1 Schematic circuit diagram of the buzzer in the background art.

[0012] Figure 2 It is a schematic circuit structure diagram according to the present invention.

[0013] Figure 3 It is a schematic structure diagram of a driving circuit for a buzzer with a low start-up voltage to prevent the power supply and ground from being connected reversely and burned out according to the first embodiment of the present invention.

[0014] Figure 4 It is a schematic structure diagram of a driving circuit for a buzzer with a low start-up voltage to prevent the power supply and ground from being connected reversely and burned out according to the second embodiment of the present invention.

[0015] Figure 5 It is a schematic diagram of increasing the substrate current-limiting resistor according to the third embodiment of the present invention. Detailed Description of the Invention

[0016] To make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0017] As Figure 2As shown in the figure, the present invention provides a drive circuit for preventing the power supply and ground from being connected reversely and burning out in a buzzer with a low startup voltage, including a substrate current-limiting resistor R2, a current-limiting resistor R1, a driving NMOS transistor, and an internal circuit. The source of the driving NMOS transistor is connected to the ground wire and the drain is connected to the output terminal. The output terminal is externally connected to the electromagnetic coil of the buzzer. The substrate of the driving NMOS transistor is connected to the source of the driving NMOS transistor through the substrate current-limiting resistor R2. The internal circuit is connected to the power supply through the current-limiting resistor R1, that is, the internal circuit is powered through the current-limiting resistor R1.

[0018] Preferably, the substrate current-limiting resistor R2 is a parasitic substrate resistor. Increasing the distance between the contact of the driving NMOS transistor and the substrate and the drain end of the driving NMOS transistor will increase the resistance value of the substrate parasitic resistor, thereby increasing the substrate current-limiting resistor, generally greater than twice the minimum value of the design rule. The greater the distance, the greater the resistance value.

[0019] Preferably, the substrate current-limiting resistor R2 is replaced by a diode. The replaced diode is connected between the substrate and the source of the driving NMOS transistor, or between the substrate of the driving NMOS transistor and the ground wire.

[0020] Preferably, the substrate current-limiting resistor R2 is connected in series with a parasitic substrate resistor and other integrated circuit resistors.

[0021] Preferably, there is at least one current-limiting resistor R1 between the internal circuit and the power supply.

[0022] Preferably, when there are multiple current-limiting resistors R1, each current-limiting resistor corresponds to a different internal circuit.

[0023] The internal circuit is other circuit modules on the same chip as the frequency correction module, oscillator, frequency divider, etc. described in the present invention. Generally, except for the port circuit and the ESD protection circuit, the internal circuit is powered by the power supply through the current-limiting resistor R1. Because the current during the operation of the internal circuit is not large and the resistance value of the current-limiting resistor R1 is not too large, the voltage on the current-limiting resistor R1 is not large either, so it will not reduce the startup voltage for the normal operation of the entire circuit. Assuming that the current-limiting resistor R1 is 1000 ohms and the current is 0.1 mA, the voltage drop across the current-limiting resistor R1 is 0.1 V. This voltage is much smaller than the typical value of the forward conduction voltage drop of the diode, which is 0.7 V. When the power supply voltage is 5 V, if the power line and the ground wire are connected reversely, the power consumption flowing through the current-limiting resistor R1 and the internal circuit is 25 mW, which will not cause the chip circuit to burn out. At the same time, if the power line and the ground wire are connected reversely, the path from the substrate to the drain of the driving NMOS transistor is current-limited through the substrate current-limiting resistor, which also reduces the power consumption and will not cause the chip circuit to burn out.

[0024] First Embodiment:

[0025] As Figure 3 shown, a drive circuit for preventing a buzzer from having a low startup voltage and burning out due to reverse connection of power supply and ground provided by the present invention includes a current-limiting resistor R1, a current-limiting resistor R2, a current-limiting resistor R3, an internal circuit 1, an internal circuit 2, an internal circuit 3, a substrate current-limiting resistor R4, and a driving NMOS transistor. Among them, the source of the driving NMOS transistor is connected to the ground wire and the drain is connected to the output terminal. The output terminal is externally connected to the electromagnetic coil of the buzzer. The substrate of the driving NMOS transistor is connected to the source of the MOS transistor through the substrate current-limiting resistor R4. The internal circuit 1 is connected to the power supply through the current-limiting resistor R1. The internal circuit 2 is connected to the power supply through the current-limiting resistor R2. The internal circuit 3 is connected to the power supply through the current-limiting resistor R3, that is, the internal circuit is powered through the current-limiting resistor.

[0026] When the power supply line and the ground wire are reversely connected, the internal circuits respectively limit the current through the current-limiting resistor R1, the current-limiting resistor R2, and the current-limiting resistor R3 to reduce power consumption, thereby preventing the chip from burning out. The path from the substrate to the drain of the driving NMOS transistor is current-limited through the substrate current-limiting resistor R4, which also reduces power consumption, so that the chip circuit will not be burned out.

[0027] Second Embodiment:

[0028] As Figure 4 shown, a drive circuit for preventing a buzzer from having a low startup voltage and burning out due to reverse connection of power supply and ground provided by the present invention includes a current-limiting resistor R1, an internal circuit, a diode, and a driving NMOS transistor. The source of the driving NMOS transistor is connected to the ground wire and the drain is connected to the output terminal. The output terminal is externally connected to the electromagnetic coil of the buzzer. The substrate of the driving NMOS transistor is connected to the source of the driving NMOS transistor through the diode, or the substrate of the driving NMOS transistor is connected to the ground wire through the diode. The internal circuit is connected to the power supply through the current-limiting resistor R1, that is, the internal circuit is powered through the current-limiting resistor R1.

[0029] When the power supply line and the ground wire are reversely connected, the internal circuit limits the current through the current-limiting resistor R1 to reduce power consumption, thereby preventing the chip from burning out. The path from the substrate to the drain of the driving NMOS transistor is current-limited through the diode D, that is, the path is in the cut-off state, so that the chip circuit will not be burned out.

[0030] Third Embodiment:

[0031] As Figure 1As shown in the figure, a driving circuit for preventing the power supply and ground from being connected reversely and burning out due to low starting voltage of a buzzer provided by the present invention includes a substrate current-limiting resistor R2, a current-limiting resistor R1, a driving NMOS transistor, and an internal circuit. Among them, the source of the driving NMOS transistor is connected to the ground wire and the drain is connected to the output terminal. The output terminal is externally connected to the electromagnetic coil of the buzzer. The substrate of the driving NMOS transistor is connected to the source of the driving NMOS transistor through the substrate current-limiting resistor R2. The internal circuit is connected to the power supply through the current-limiting resistor R1, that is, the internal circuit is powered through the current-limiting resistor R1.

[0032] As Figure 1 shown, the substrate current-limiting resistor R2 is a parasitic substrate resistor. As Figure 5 shown, increasing the distance between the contact of the driving NMOS transistor with the substrate and the drain end of the driving NMOS transistor will increase the resistance value of the substrate parasitic resistor, thereby increasing Figure 1 the substrate current-limiting resistor R2 mentioned above, which is generally more than twice the minimum value of the design rule. The greater the distance, the greater the resistance value.

[0033] In summary, in the present invention, the substrate of the driving NMOS transistor is connected to the source end through a substrate current-limiting resistor, and the internal circuit is powered through a current-limiting resistor, so that when the power supply line and the ground wire are connected reversely, the power consumption can be greatly reduced, thereby preventing the circuit from being burned out. During normal use, the substrate current-limiting resistor between the substrate and the source end of the driving NMOS transistor will not excessively increase the resistance between the source end and the drain end of the driving NMOS transistor, and by appropriately selecting the current-limiting resistor connected between the power supply and the internal circuit, the driving circuit of the present invention can start to work at a very low voltage.

[0034] The above are only embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the scope of the claims of the present invention.

Claims

1. A driving circuit for preventing the buzzer from being burned out due to reverse connection of power supply and ground at low startup voltage, characterized in that, It includes a substrate current-limiting resistor R2, a current-limiting resistor R1, a driving NMOS transistor, and an internal circuit. The source of the driving NMOS transistor is connected to the ground wire and the drain is connected to the output terminal. The output terminal is externally connected to the electromagnetic coil of a buzzer. The substrate of the driving NMOS transistor is connected to the source of the driving NMOS transistor through the substrate current-limiting resistor R2. The internal circuit is connected to the power supply through the current-limiting resistor R1, that is, the internal circuit is powered by the current-limiting resistor R1. The internal circuit includes a frequency correction module, an oscillator, and a frequency divider.

2. The driving circuit for preventing the buzzer from being burned out due to reverse connection of power supply and ground at low startup voltage according to claim 1, characterized in that, The substrate current-limiting resistor R2 is a parasitic substrate resistor, and the substrate current-limiting resistor R2 increases as the distance between the substrate contact and the drain end of the driving NMOS transistor increases; the substrate current-limiting resistor R2 is more than twice the minimum value of the design rule.

3. The driving circuit for preventing the buzzer from being burned out due to reverse connection of power supply and ground at low startup voltage according to claim 2, characterized in that, The substrate current-limiting resistor R2 is a parasitic substrate resistor connected in series with other integrated circuit resistors.

4. The driving circuit for preventing the buzzer from being burned out due to reverse connection of power supply and ground at low startup voltage according to claim 3, characterized in that, There is at least one current-limiting resistor R1 between the internal circuit and the power supply.

5. The driving circuit for preventing the buzzer from being burned out due to reverse connection of power supply and ground at low startup voltage according to claim 4, characterized in that, When there are multiple current-limiting resistors R1, each current-limiting resistor corresponds to a different internal circuit.

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