TWI851659B - Voltage detector - Google Patents

Abstract

The present invention discloses a voltage detector for comparing an input voltage with a reference voltage to generate an output voltage at an output end. The voltage detector includes: a first transistor for converting the voltage difference between the input voltage and the reference voltage into a first current; and a second transistor connected in series with the first transistor, the second transistor having a gate and a source coupled to each other to output a fixed second current. When the current value of the first current is greater than the current value of the second current, the output voltage is a first level voltage, and when the current value of the first current is less than the current value of the second current, the output voltage is a second level voltage. The voltage detector provided by the present invention has a low power consumption characteristic and can realize a system with reduced power consumption.

Description

Voltage detector

The present disclosure relates to a voltage detector, and more particularly to a voltage detector operating in a sub-critical region.

In recent years, the Internet of Things (IoT) and IoT devices have developed rapidly. One of the most important considerations in IoT applications is low power consumption to achieve longer battery life. For some basic blocks (such as bandgap reference and under voltage lock out (UVLO) circuits), they should always remain awake to maintain the most basic functions. In fact, the energy required to keep the device in the startup and detection state may far exceed the energy for normal operation. In these cases, it is particularly important to reduce or even eliminate the detection power consumption, so as to extend the battery life and realize a system with reduced power consumption.

Taking UVLO as an example, existing solutions include the following two types: (1) comparator-based UVLO and (2) delay-based UVLO. However, the above two types of UVLO have the following disadvantages: (1) For comparator-based UVLO, although the UVLO threshold voltage can be accurately determined, it will consume more current to achieve the purpose; (2) For delay-based UVLO, although zero static current is consumed, it cannot guarantee the absolute value of the UVLO threshold voltage. Therefore, the known technology really needs to be improved.

In view of this, how to provide a voltage detector suitable for operating in the subcritical region and having low power consumption characteristics is a problem to be solved.

The present invention discloses a voltage detector for comparing an input voltage with a reference voltage to generate an output voltage at an output end. The voltage detector includes: a first transistor for converting the voltage difference between the input voltage and the reference voltage into a first current; and a second transistor connected in series with the first transistor, the second transistor having a gate and a source coupled to each other to output a fixed second current. When the current value of the first current is greater than the current value of the second current, the output voltage is a first level voltage, and when the current value of the first current is less than the current value of the second current, the output voltage is a second level voltage.

In one embodiment of the present invention, the first transistor has a gate receiving the reference voltage, a source receiving the input voltage, and a drain coupled to the output terminal; and wherein the second transistor has a gate, a source coupled to the output terminal, and a drain coupled to a ground terminal. In one embodiment of the present invention, the first level voltage is the input voltage, and the second level voltage is a ground voltage.

In one embodiment of the present invention, the first transistor and the second transistor are P-type metal oxide semiconductor field effect transistors (PMOSFET).

In one embodiment of the present invention, the first transistor has a gate receiving the reference voltage, a source receiving the input voltage, and a drain coupled to the output terminal; and wherein the second transistor has a gate, a source coupled to a ground terminal, and a drain coupled to the output terminal.

In one embodiment of the present invention, the first level voltage is the input voltage, and the second level voltage is the ground voltage.

In one embodiment of the present invention, the first transistor is a P-type metal oxide semiconductor field effect transistor, and the second transistor is an N-type metal oxide semiconductor field effect transistor (NMOSFET).

In one embodiment of the present invention, the first transistor has a gate receiving the input voltage, a drain coupled to the output terminal, and a source receiving the reference voltage, wherein the second transistor has a gate, a source coupled to the output terminal, and a drain coupled to the power voltage.

In one embodiment of the present invention, the first level voltage is the reference voltage, and the second level voltage is the power supply voltage.

In one embodiment of the present invention, the first transistor and the second transistor are N-type metal oxide semiconductor field effect transistors.

In one embodiment of the present invention, the first transistor has a gate receiving the input voltage, a drain coupled to the output terminal, and a source receiving the reference voltage, wherein the second transistor has a gate, a source coupled to the power voltage, and a drain coupled to the output terminal.

In one embodiment of the present invention, the first level voltage is the reference voltage, and the second level voltage is the power supply voltage.

In one embodiment of the present invention, the first transistor is an N-type metal oxide semiconductor field effect transistor, and the second transistor is a P-type metal oxide semiconductor field effect transistor.

The voltage detector of the present invention utilizes a comparator-based structure, and uses a MOS transistor that operates in a sub-threshold region and is coupled to the gate and source as a tiny ideal current source, so that the entire comparator has an extremely low quiescent current, thereby achieving the purpose of significantly reducing power consumption.

S101: Step

S102: Step

S103: Step

200: Voltage detector

201: Transistor

203: Transistor

205: Transistor

207: Transistor

210: Voltage detector

300: Voltage detector

301: Transistor

303: Transistor

305: Transistor

307: Transistor

310: Voltage detector

400: Internet of Things components

401: Voltage regulator circuit

403: Voltage detector

405: Internal main circuit

500: Internet of Things components

501:Battery

503: Voltage detector

505: Internal main circuit

VIN: Input voltage

VREF: reference voltage

VDD: power supply voltage

VOUT: output voltage

In the figures: [Figure 1] is a flow chart of a voltage detection method provided by an embodiment of the present invention; [Figure 2A] and [Figure 2B] are circuit diagrams of a voltage detector provided by an embodiment of the present invention; [Figure 3A] and [Figure 3B] are circuit diagrams of a voltage detector provided by an embodiment of the present invention; [Figure 4] is a block diagram of an Internet of Things component of a voltage detector using one embodiment of the present invention; [Figure 5] is a block diagram of an Internet of Things component of a voltage detector using another embodiment of the present invention.

The following is a detailed description of the implementation method with reference to the drawings. Note that the present invention is not limited to the following description, and a person with ordinary knowledge in the relevant technical field can easily understand the fact that its method and detailed content can be transformed into various forms without departing from the spirit and scope of the present invention. Therefore, the present invention should not be interpreted as being limited to the content recorded in the implementation method shown below.

The ordinal numbers such as "first" and "second" used in this manual are added to avoid confusion between components, not to limit the number.

A transistor is a type of semiconductor element that can amplify current or voltage, control conduction or non-conduction switching, etc. The transistors in this manual include metal oxide semiconductor field effect transistors (MOSFET).

First, please refer to Figure 1, which shows a flow chart of a voltage detection method of an embodiment of the present invention, including the following steps:

Step S101: Convert the voltage difference between the input voltage and the reference voltage into a current signal A.

Step S102: Compare the current signal A with another fixed current signal B.

Among them, the current signal A is generated according to the voltage difference between the input voltage received by a transistor and the reference voltage, and the current signal B is generated by another transistor with a gate and a source coupled to each other. The comparison between the current signal A and the current signal B can be performed by, for example, an ammeter.

Step S103: Determine whether A is greater than B.

If A is greater than B, the output voltage signal VOUT is equal to 1 (indicating that the input voltage is greater than the reference voltage); if A is less than B, the output voltage signal VOUT is equal to 0 (indicating that the input voltage is less than the reference voltage).

Thus, the present invention can compare the input voltage with the reference voltage through the above voltage detection method to determine which of the input voltage and the reference voltage has a higher potential.

Implementation method 1

In this embodiment, a voltage detector of an embodiment of the present invention is described with reference to the drawings.

FIG. 2A and FIG. 2B show an example of the structure of a voltage detector of an embodiment of the present invention. Referring to FIG. 2A , the voltage detector 200 includes a transistor 201 and a transistor 203 for comparing an input voltage VIN with a reference voltage VREF, and generating an output voltage VOUT corresponding to the comparison result at the output end. The input voltage VIN can be, for example, a battery voltage.

The transistor 201 has a gate receiving the reference voltage VREF, a source receiving the input voltage VIN, and a drain coupled to the output terminal. The transistor 201 is used to convert the voltage difference between the input voltage VIN and the reference voltage VREF into a current _IA .

Transistor 203 is connected in series with transistor 201, and has a gate, a source coupled to the output terminal, and a drain coupled to the ground terminal. It is worth noting that the gate and source of transistor 203 are coupled to each other, so that transistor 203 operates in a sub-threshold region, thereby outputting a fixed current I _B and can serve as a constant current source.

When the current value of current _IA is greater than the current value of current _IB , the output terminal outputs the input voltage (high-level voltage). When the current value of current _IA is less than the current value of current _IB , the output terminal outputs the ground voltage (low-level voltage).

That is, when the output voltage VOUT is high, it means that the input voltage VIN is greater than the reference voltage VREF. Conversely, when the output voltage VOUT is low, it means that the input voltage VIN is less than the reference voltage VREF. In this way, the high-low relationship between the input voltage VIN and the reference voltage VREF can be determined through the output voltage corresponding to the comparison result of the input voltage VIN and the reference voltage VREF.

In the comparator architecture of FIG. 2A , transistor 201 and transistor 203 are both P-type metal oxide semiconductor field effect transistors (PMOSFET). It is worth noting that transistor 203 with a gate and a source coupled to each other can be regarded as a current source, and the current I _B generated is extremely small, for example, in the range of 100pA to 10nA. Since the quiescent current of the entire comparator is determined by this current source (approximately in the range of 100pA to 10nA), the power consumption can be reduced.

In addition, the structure of the voltage detector 210 shown in FIG. 2B is similar to that of the voltage detector 200 shown in FIG. 2A . The voltage detector 210 includes a transistor 205 and a transistor 207 . The difference between FIG. 2B and FIG. 2A is that the transistor 207 in FIG. 2B uses an N-type metal oxide semiconductor field effect transistor (NMOSFET). The rest of the concepts and principles are similar to those in FIG. 2A , so they will not be described here in detail.

Implementation method 2

In this embodiment, a voltage detector of another embodiment of the present invention is described with reference to Figures 3A and 3B.

FIG. 3A and FIG. 3B show a structural example of a voltage detector of another embodiment of the present invention. Referring to FIG. 3A , the voltage detector 300 includes a transistor 301 and a transistor 303 for comparing an input voltage VIN with a reference voltage VREF to generate an output voltage VOUT corresponding to the comparison result at an output terminal.

The transistor 301 has a gate, a drain receiving a power voltage VDD, and a source coupled to the output terminal. It is worth noting that the gate and source of the transistor 301 are coupled to each other, which enables the transistor 301 to operate in the sub-threshold region and act as a constant current source to output a fixed current I _C .

The transistor 303 is connected in series with the transistor 301 and has a gate receiving the input voltage VIN, a drain coupled to the output terminal, and a source receiving the reference voltage VREF. The transistor 303 is used to convert the voltage difference between the input voltage VIN and the reference voltage VREF into a current _ID .

When the current value of current _IC is greater than the current value of current _ID , the output voltage VOUT is equal to the power supply voltage VDD. When the current value of current _IC is less than the current value of current _ID , the output voltage VOUT is equal to the reference voltage VREF.

In FIG. 3A , transistor 301 and transistor 303 are both NMOS transistors. The current _IC output by transistor 301 with its gate and source coupled to each other is very small (e.g., in the range of 100pA to 10nA). Since the quiescent current of the entire comparator is determined by a current source in the range of approximately 100pA to 10nA, the purpose of reducing power consumption can be achieved.

In addition, the structure of the voltage detector 310 shown in FIG. 3B is similar to the voltage detector 300 shown in FIG. 3A . The voltage detector 310 includes a transistor 305 and a transistor 307 . The difference from FIG. 3A is that the transistor 305 uses a PMOS transistor. The rest of the operating principle is similar to that of FIG. 3A , so it will not be described here.

FIG4 is a block diagram of an IoT component using a voltage detector according to an embodiment of the present invention. Referring to FIG4 , the IoT component 400 includes a voltage regulator 401 , a voltage detector 403 , and an internal main circuit 405 . The voltage regulator circuit 401 receives the voltage of the power source (or battery) and outputs a voltage to the voltage detector 403. The output voltage gradually increases from low. When the voltage detector 403 detects that the output voltage of the voltage regulator circuit 401 exceeds a specific value, it means that the output voltage has reached the range where the internal circuit can operate normally. At this time, the voltage detector 403 transmits a start control signal to the internal main circuit 405 to start working.

FIG5 is a block diagram of an IoT device using a voltage detector according to another embodiment of the present invention. As shown in FIG5 , the IoT device 500 includes a battery 501 , a voltage detector 503 , and an internal main circuit 505 . The voltage detector 503 is used to detect the voltage of the battery 501 (such as a solar cell, a thermoelectric cell or other type of power source). When the voltage value of the battery is detected to be lower than a predetermined value (the voltage is too low), a low voltage warning signal is transmitted to the internal main circuit 505. At the same time, a warning can be issued to the remote control system through a communication method such as the network, warning that the battery power is insufficient and the battery needs to be replaced, or warning that the IoT component 500 is about to go offline, etc.; if the voltage detector 503 detects that the voltage value of the battery is higher than a predetermined value (the voltage is too high), an overvoltage warning signal is transmitted to the internal main circuit 505, and a warning can be issued to remind the system of abnormality.

Since the voltage detector of the present invention can maintain very low detection power consumption at ordinary times, even when it is applied to an IoT device that needs to remain activated for a long time (such as a burglar alarm or activity monitor that needs to be in standby mode for a long time), the power consumption accumulated over a long period of time is still very low. For the IoT device itself, it can also reduce the overall power consumption, so as to achieve an IoT device with low power consumption and realize a low power consumption system.

In summary, the present invention provides a voltage detector based on a comparator, which is used to compare an input voltage with a reference voltage and determine which one has a higher potential. Since a transistor operating in a sub-critical region and coupled to a gate and a source as a constant current source is used in the comparator structure, the static current of the comparator as a whole is extremely low, thereby achieving the purpose of low static current loss and low power consumption.

The above is only the preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope of the present invention.

200: Voltage detector

201: Transistor

203: Transistor

I _A : Current

I _B : Current

VIN: Input voltage

VREF: Reference voltage

VOUT: output voltage

Claims (12)

A voltage detector is used to compare an input voltage with a reference voltage to generate an output voltage at an output terminal. The voltage detector comprises: a first transistor, used to convert the voltage difference between the input voltage and the reference voltage into a first current; and a second transistor connected in series with the first transistor, the second transistor having a gate and a source coupled to each other to output a fixed second current, wherein when the current value of the first current is greater than the current value of the second current, the output voltage is output. When the current value of the first current is less than the current value of the second current, the output voltage is the second level voltage, wherein the first transistor has a gate receiving the reference voltage, a source receiving the input voltage, and a drain coupled to the output terminal; and wherein the second transistor has a gate, a source coupled to the output terminal, and a drain coupled to the ground terminal. For example, in the voltage detector of item 1 of the patent application scope, the first level voltage is the input voltage, and the second level voltage is the ground voltage. For example, in the voltage detector of item 1 of the patent application, the first transistor and the second transistor are P-type metal oxide semiconductor field effect transistors (PMOSFET). A voltage detector is used to compare an input voltage with a reference voltage to generate an output voltage at an output terminal. The voltage detector comprises: a first transistor, used to convert the voltage difference between the input voltage and the reference voltage into a first current; and a second transistor connected in series with the first transistor, the second transistor having a gate and a source coupled to each other to output a fixed second current, wherein when the current value of the first current is greater than the current value of the second current, the output voltage is output. When the current value of the first current is less than the current value of the second current, the output voltage is the second level voltage, wherein the first transistor has a gate receiving the reference voltage, a source receiving the input voltage, and a drain coupled to the output terminal; and wherein the second transistor has a gate, a source coupled to the ground terminal, and a drain coupled to the output terminal. For example, in the voltage detector of item 4 of the patent application scope, the first level voltage is the input voltage, and the second level voltage is the ground voltage. For example, in the voltage detector of item 4 of the patent application, the first transistor is a PMOSFET, and the second transistor is an N-type metal oxide semiconductor field effect transistor (NMOSFET). A voltage detector is used to compare an input voltage with a reference voltage to generate an output voltage at an output terminal. The voltage detector comprises: a first transistor for converting the voltage difference between the input voltage and the reference voltage into a first current; and a second transistor connected in series with the first transistor, the second transistor having a gate and a source coupled to each other to output a fixed second current, wherein when the current value of the first current is greater than the second current When the current value of the first current is less than the current value of the second current, the output voltage is the second level voltage, wherein the first transistor has a gate receiving the input voltage, a drain coupled to the output terminal, and a source receiving the reference voltage, and wherein the second transistor has a gate, a source coupled to the output terminal, and a drain coupled to the power voltage. For example, the voltage detector of item 7 of the patent application scope, wherein the first level voltage is the reference voltage, and the second level voltage is the power supply voltage. For example, in the voltage detector of item 7 of the patent application, the first transistor and the second transistor are NMOSFETs. A voltage detector is used to compare an input voltage with a reference voltage to generate an output voltage at an output terminal. The voltage detector comprises: a first transistor for converting the voltage difference between the input voltage and the reference voltage into a first current; and a second transistor connected in series with the first transistor, the second transistor having a gate and a source coupled to each other to output a fixed second current, wherein when the current value of the first current is greater than the second current When the current value of the first current is less than the current value of the second current, the output voltage is the second level voltage, wherein the first transistor has a gate receiving the input voltage, a drain coupled to the output terminal, and a source receiving the reference voltage, and wherein the second transistor has a gate, a source coupled to the power voltage, and a drain coupled to the output terminal. For example, the voltage detector of item 10 of the patent application scope, wherein the first level voltage is the reference voltage, and the second level voltage is the power supply voltage. For example, in the voltage detector of item 10 of the patent application, the first transistor is an NMOSFET and the second transistor is a PMOSFET.

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