LDO circuit

Abstract

A voltage detection circuit for detecting a voltage supplied from a low dropout (LDO) voltage regulator, according to one embodiment proposed herein, may comprise: a voltage detector which senses a sensing voltage; a first switch which is provided between an LDO voltage regulator, providing a supply voltage through a first output terminal, and the voltage detector, and short-circuits or blocks the supply voltage and the sensing voltage sensed by the voltage detector; a second switch for controlling the ON / OFF of the first switch; and a comparator for controlling the ON / OFF of the second switch on the basis of the result of comparing the supply voltage and the sensing voltage.

Description

LDO circuit

[0001] The following examples relate to LDO circuits and to short-circuit prevention circuits for detecting output voltage in LDOs.

[0002]

[0003] LDO (low dropout) voltage regulators are widely used to provide stable power supply to chips or ICs used in electronic circuits.

[0004] LDO voltage regulators are primarily used in low-power power supplies because they have a small voltage difference between the input and output voltages. For example, an LDO voltage regulator can be used to convert a battery's 3.1 V power supply to the 2.5 V or 1.8 V power required by a chip.

[0005] LDO voltage regulators have the advantages of simple circuitry, fewer external components, and less noise.

[0006] The output voltage (Vref) of the LDO voltage regulator (10) can be supplied to the MCU (micro controller unit) (40) as illustrated in Fig. 1. In addition, the MCU (40) can sense the output voltage (Vref) of the LDO voltage regulator (10) using a voltage detector (30) to determine whether the voltage supplied to the MCU (40) is appropriate. At this time, a short-circuit prevention diode (20) can be provided between the output lead of the LDO voltage regulator (10) and the voltage detector (30) to prevent the supply voltage of the MCU (40) from being short-circuited.

[0007] In the structure illustrated in Fig. 1, the forward voltage drop of the short-circuit protection diode (20) is quite large, from 650 mV to 900 mV. For example, if the supply voltage of the MCU (40) is 1.8 V, the voltage measured by the voltage detector (30) may be quite low, from 1.15 V to 0.9 V.

[0008] If there is a large difference between the voltage (Vref) output from the original LDO voltage regulator (10) and supplied to the MCU and the voltage (Vd) detected by the voltage detector (30), there is a problem that a significant sensing error occurs in the MCU (40) that performs calculations and control using this, and there is a high possibility that the control logic will malfunction.

[0009]

[0010] The problem to be solved by the present invention is to provide a circuit that can provide a short circuit function while minimizing voltage sensing error in a voltage detector.

[0011] The tasks of the present invention are not limited to the technical tasks mentioned above, and other technical tasks not mentioned will be clearly understood by those skilled in the art from the description below.

[0012]

[0013] According to one embodiment of the present invention for solving the above problem, a voltage detection circuit for detecting a voltage supplied from an LDO (low dropout) voltage regulator may include a voltage detector for sensing a sensing voltage, an LDO voltage regulator for providing a supply voltage through a first output terminal, and a first switch provided between the voltage detector for short-circuiting or blocking the supply voltage and the sensing voltage sensed by the voltage detector, a second switch for controlling on / off of the first switch, and a comparator for controlling on / off of the second switch based on a result of comparing the supply voltage and the sensing voltage.

[0014] A voltage supply circuit for supplying voltage to a control device according to one embodiment for solving the above problem may include an LDO (low dropout) voltage regulator for providing a supply voltage to the control device through a first output terminal, a voltage detector for obtaining a voltage value sensed by a sensing voltage and providing the voltage value to the control device, a first switch provided between the LDO voltage regulator and the voltage detector for short-circuiting or blocking the supply voltage and the sensing voltage, a second switch for controlling on / off of the first switch, and a comparator for controlling on / off of the second switch based on a result of comparing the supply voltage and the sensing voltage.

[0015]

[0016] According to embodiments, the sensing error between the MCU supply voltage and the sensing voltage can be minimized.

[0017] According to embodiments, a short-circuit function for an MCU short-circuit power supply can be provided while minimizing the sensing error obtained by the MCU.

[0018] The effects according to the embodiments are not limited to those exemplified above, and more diverse effects are included in this specification.

[0019]

[0020] FIG. 1 is a diagram illustrating a circuit for sensing an MCU supply voltage according to one embodiment.

[0021] FIG. 2 is a diagram illustrating an improved circuit for sensing an MCU supply voltage according to an embodiment of the present document.

[0022] Figure 3 is a diagram showing the characteristics of a typical transistor.

[0023]

[0024] Specific structural or functional descriptions of embodiments according to the concept of the present invention disclosed in this specification are merely illustrative for the purpose of explaining embodiments according to the concept of the present invention, and embodiments according to the concept of the present invention may be implemented in various forms and are not limited to the embodiments described in this specification.

[0025] Embodiments according to the concept of the present invention may have various modifications and take various forms, and thus, embodiments are illustrated in the drawings and described in detail in this specification. However, this is not intended to limit embodiments according to the concept of the present invention to specific disclosed forms, but rather includes all modifications, equivalents, or alternatives falling within the spirit and technical scope of the present invention.

[0026] While terms such as "first" or "second" may be used to describe various components, these components should not be limited by these terms. These terms are intended solely to distinguish one component from another. For example, a first component may be referred to as a second component, and similarly, a second component may also be referred to as a first component, without departing from the scope of the invention.

[0027] When a component is referred to as being "connected" or "connected" to another component, it should be understood that it may be directly connected or connected to that other component, but that there may be other components in between. Conversely, when a component is referred to as being "directly connected" or "directly connected" to another component, it should be understood that there are no other components in between. Other expressions that describe the relationship between components, such as "between" and "directly between" or "adjacent to" and "directly adjacent to", should be interpreted similarly.

[0028] The terminology used herein is for the purpose of describing specific embodiments only and is not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise.

[0029] In this specification, it should be understood that terms such as “comprise” or “have” are intended to specify the presence of a described feature, number, step, operation, component, part, or combination thereof, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0030] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs.

[0031] Terms defined in commonly used dictionaries should be interpreted to have a meaning consistent with their meaning in the context of the relevant technology, and will not be interpreted in an idealized or overly formal sense unless expressly defined herein.

[0032] In the following description, identical identifiers indicate identical configurations, and unnecessary redundant descriptions and explanations of known technologies are omitted.

[0033] Hereinafter, the present invention will be described in detail by describing a preferred embodiment of the present invention with reference to the attached drawings.

[0034] FIG. 2 is a diagram illustrating an improved supply voltage sensing circuit according to an embodiment of the present document.

[0035] Referring to Fig. 2, in order to reduce the difference between the supply voltage (Vref) provided to the MCU (40) and the sensing voltage (Vd) sensed by the voltage detector (30), a circuit including a comparator (210), a first switch (220), and a second switch (230) instead of the diode illustrated in Fig. 1 is proposed. Here, the first switch (220) may be a PNP transistor, and the second switch may be an NPN transistor.

[0036] Referring to FIG. 2, the supply voltage sensing circuit may further include a plurality of capacitors (C1, C2, C3, C4) and resistors (R1 to R9). Here, the plurality of capacitors (C1, C2, C3, C4) are for stabilizing the voltage, and even if only some of them are present, they may be sufficient to perform the corresponding function.

[0037] Referring to FIG. 2, the supply voltage (Vref) can be provided by an LDO (low dropout) regulator.

[0038] A saturated transistor can be used to minimize the difference between the supply voltage (Vref) provided to the MCU (40) and the sensing voltage (Vd) sensed by the voltage detector (30). A saturated transistor has a low emitter-collector voltage (V CE ) so that if the transistor (220) in the circuit of Fig. 2 is in a saturated state, the difference between the MCU (40) supply voltage (Vref) and the sensing voltage (Vd) sensed by the voltage detector (30) can be minimized.

[0039] Figure 3 is a diagram showing the characteristics of a typical transistor.

[0040] A transistor has three terminals: a base, an emitter, and a collector. It can be an amplifying device in which, when voltage or current is applied to the base, an amplified current flows between the emitter and the collector.

[0041] Referring to FIG. 3, the transistor can have an operating region of an active region (310), a cur-off region (320), and a saturation region (330) depending on the magnitude of the voltage applied to the base and the magnitude of the current resulting therefrom.

[0042] The active region (310) may be a region where the current between the emitter and the collector increases in proportion to the current applied to the base. In the example of Fig. 3, if the current flowing in the base is 40 uA, the current flowing in the collector may be 40 mA, a current amplified 1000 times.

[0043] The cutoff region (320) is a region where the voltage or current applied to the base is too small to allow current to flow between the emitter and the collector, and the saturation region (330) is a region where the voltage or current applied to the base is large to cause the voltage between the emitter and the collector to be almost 0 V.

[0044] Referring to Figure 3, the emitter-collector voltage (V) in the saturation region (330) CE ) can be seen to drop to almost 0 V. In one embodiment, when the base current is applied to 20 uA, it can be seen that the voltage between the emitter and collector gradually drops along the line (340) in the active region (310) and then drops to almost 0 V when it reaches the saturation state (330).

[0045] Therefore, if the transistor (220) in the circuit of Fig. 2 is saturated, the difference between the MCU (40) supply voltage (Vref) and the sensing voltage (Vd) sensed by the voltage detector (30) can be minimized.

[0046] Referring to FIG. 2, a comparator (210) compares the voltages of a first input terminal (IN+) and a second input terminal (IN-), and if the voltage of the first input terminal (IN+) is greater than the voltage of the second input terminal (IN-), a first control voltage that turns on a transistor (230) can be output to an output terminal (OUT), and if the voltage of the first input terminal (IN+) is less than the voltage of the second input terminal (IN-), a second control voltage that turns off a transistor (230) can be output. Here, the first control voltage may be the MCU (40) supply voltage (Vref), and the second control voltage may be a 0 V (GND) voltage, but is not limited thereto. Referring to FIG. 2, the voltage input to the first input terminal (IN+) is a voltage obtained by dividing the MCU (40) supply voltage (Vref) by the resistor (R1) and the resistor (R2), and the voltage input to the second input terminal (IN-) is a voltage obtained by dividing the sensing voltage (Vd) by the resistor (R3) and the resistor (R4). Therefore, in order to compare the MCU (40) supply voltage (Vref) and the sensing voltage (Vd), the ratio of the resistor (R1) and the resistor (R2) and the ratio of the resistor (R3) and the resistor (R4) must be the same. According to one embodiment, the resistor (R1) and the resistor (R3) may have the same resistance value, and the resistor (R2) and the resistor (R4) may have the same resistance value.

[0047] At this time, an additional capacitor (C4) can be connected in parallel with a resistor (R2), which can be used to reduce and stabilize the noise of the voltage input to the first input terminal (IN+).

[0048] Similarly, a capacitor can be connected in parallel with the resistor (R4) to stabilize the voltage input to the second input terminal (IN+). However, when the capacitor is connected in parallel with the resistor (R4), it may not be easy to prevent short circuits because it is impossible to respond to minute voltage changes. To prevent this, the ratios of the resistors (R1) and (R2) and the ratios of the resistors (R3) and (R4) can be made different so that short circuit prevention can start at a voltage where the sensing voltage (Vd) is slightly lower than the supply voltage (Vref).

[0049] Referring to Fig. 2, when a first control voltage is output from the output terminal (OUT) of the comparator (210), the corresponding voltage is applied to the base of the transistor (230), and accordingly, current flows between the emitter and collector of the transistor (230). At this time, the size of the current applied to the base of the transistor (230) can be determined by the ratio of the resistance (R8) and the resistance (R9).

[0050] When a current flows between the emitter and collector of the transistor (230), the current is applied to the base of the transistor (220). Accordingly, the transistor (220) turns on and a current flows between the emitter and the collector. At this time, the size of the current applied to the base of the transistor (220) is determined by the ratio of the resistance (R7) and the resistance (R6). Since the current applied to the base of the transistor (220) is a current amplified by the transistor (230), it can be quite large, and accordingly, the transistor (220) can immediately enter a saturation state. When the transistor (220) enters a saturation state, as shown in FIG. 3, the voltage (V) between the emitter and the collector CE ) can be lowered to almost 0V, thereby minimizing the difference between the MCU (40) supply voltage (Vref) and the sensing voltage (Vd).

[0051] When the sensing voltage (Vd) increases, it is necessary to separate the emitter and collector by turning the transistor (220) in the cut-off region, i.e., turning it off.

[0052] Referring to FIGS. 2 and 3, when the sensing voltage (Vd) increases and the voltage of the first input terminal (IN+) becomes lower than the voltage of the second input terminal (IN-), a second control voltage is output from the output terminal (OUT) of the comparator (210). Then, a voltage of 0 V is applied to the base of the transistor (230), and accordingly, current does not flow, and the transistor (230) is in the cutoff region, i.e., turned off. When the transistor (230) is in the cutoff region, current does not flow between the emitter and collector of the transistor (230).

[0053] When current stops flowing in the emitter and collector of the transistor (230), current also stops flowing in the base of the transistor (220) connected thereto. Then, the transistor (220) also turns off and operates in the cutoff region, entering a cutoff state where current cannot flow between the emitter and collector. In other words, a short circuit occurs between the emitter and collector of the transistor (230).

[0054] As shown in Fig. 2, by using a switch using a comparator and two transistors, the MCU supply voltage (Vref) and the sensing voltage (Vd) can be made to be almost the same level in the normal state, and when the sensing voltage (Vd) becomes greater than the MCU supply voltage (Vref) and a short circuit is required, the switches can be turned off, that is, the operating area of ​​the transistors can be made a cut-off area, thereby short-circuiting the MCU supply voltage (Vref) and the sensing voltage (Vd).

[0055] Accordingly, this paper presents a solution to the problem of high forward voltage drop of conventional diodes.

[0056] The voltage supply circuit and voltage detection circuit based on the LDO voltage regulator proposed in this paper can be summarized as follows.

[0057] A voltage supply circuit for supplying voltage to a control device according to one embodiment proposed in this document may include an LDO (low dropout) voltage regulator for providing a supply voltage to the control device through a first output terminal, a voltage detector for obtaining a voltage value sensed by a sensing voltage and providing the voltage value to the control device, a first switch provided between the LDO voltage regulator and the voltage detector for short-circuiting or blocking the supply voltage and the sensing voltage, a second switch for controlling on / off of the first switch, and a comparator for controlling on / off of the second switch based on a result of comparing the supply voltage and the sensing voltage.

[0058] A voltage detection circuit for detecting a voltage supplied from an LDO (low dropout) voltage regulator according to one embodiment proposed in this document may include a voltage detector for sensing a sensing voltage, an LDO voltage regulator for providing a supply voltage through a first output terminal, and a first switch provided between the voltage detector for short-circuiting or blocking the supply voltage and the sensing voltage sensed by the voltage detector, a second switch for controlling on / off of the first switch, and a comparator for controlling on / off of the second switch based on a result of comparing the supply voltage and the sensing voltage.

[0059] Additionally, the comparator can output a first control voltage that turns on the second switch when the supply voltage is greater than the sensing voltage, and can output a second control voltage that turns off the second switch when the sensing voltage is greater than the supply voltage.

[0060] Additionally, when the second switch is turned on, current can flow to turn on the first switch, and when the second switch is turned off, current can be cut off to turn off the first switch.

[0061] Additionally, the first switch may be a PNP transistor including a first emitter terminal, a first base terminal, and a first collector terminal, and the second switch may be an NPN transistor including a second emitter terminal, a second base terminal, and a second collector terminal.

[0062] In addition, the first output terminal may be connected to the first emitter terminal, the first collector terminal may be connected to the voltage detector to provide the sensing voltage, the first base terminal may be connected to the second collector terminal, the second emitter terminal may be connected to a ground voltage, the second base terminal may be connected to the second output terminal of the comparator, and the second collector terminal may be connected to the first base terminal.

[0063] In addition, the comparator may be configured to include a first input terminal, a second input terminal, and the second output terminal, and a first voltage obtained by dividing the supply voltage through a first divider circuit is applied to the first input terminal, and a second voltage obtained by dividing the sensing voltage through a second divider circuit is applied to the second input terminal.

[0064] In addition, the first divider circuit may be configured by connecting a first resistor and a second resistor in series, and the second divider circuit may be configured by connecting a third resistor and a fourth resistor in series.

[0065] And the first terminal of the first resistor is applied with the supply voltage, the second terminal of the first resistor (R1) and the first terminal of the second resistor are connected, the second terminal of the second resistor is connected to the ground voltage, the first input terminal is connected with the second terminal of the first resistor and the first terminal of the first resistor to receive the first voltage, the first terminal of the third resistor is applied with the sensing voltage, the second terminal of the third resistor and the first terminal of the fourth resistor are connected, the second terminal of the fourth resistor is connected to the ground voltage, and the second input terminal is connected with the second terminal of the third resistor and the first terminal of the fourth resistor to receive the second voltage.

[0066] Additionally, the resistance value ratio between the first resistor and the second resistor may be the same as the resistance value ratio between the third resistor and the fourth resistor.

[0067] Additionally, the first divider circuit may further include a capacitor connected in parallel with the second resistor.

[0068] In addition, the comparator can output the first control voltage to the second output terminal when the first voltage applied to the first input terminal is greater than the second voltage applied to the second input terminal, and can output the second control voltage to the second output terminal when the first voltage applied to the first input terminal is less than the second voltage applied to the second input terminal.

[0069] In addition, when the supply voltage is output to the second output terminal, the first transistor may operate in a saturation state, and when the ground voltage is output to the second output terminal, the second transistor may operate in a cut-off state.

[0070] Additionally, the first output terminal and the second output terminal may be connected with a resistor therebetween.

[0071] Meanwhile, in the embodiment of FIG. 2, only the MCU (micro controller unit) is illustrated, but it will be understood that any IC, chip, control device, CPU, or processor that performs the same or similar functions as the MCU can replace the MCU.

Claims

1. In a voltage detection circuit that detects the voltage supplied from an LDO (low dropout) voltage regulator, A voltage detector for sensing the sensing voltage; A first switch provided between an LDO voltage regulator providing a supply voltage through a first output terminal and the voltage detector, and short-circuiting or blocking the supply voltage and the sensing voltage sensed by the voltage detector; A second switch controlling the ON / OFF of the first switch; and Including a comparator that controls on / off of the second switch based on the result of comparing the supply voltage and the sensing voltage. Voltage detection circuit.

2. In paragraph 1, The above comparator, If the above supply voltage is greater than the above sensing voltage, a first control voltage is output to turn on the second switch, If the sensing voltage is greater than the supply voltage, a second control voltage is output to turn off the second switch. Voltage detection circuit.

3. In paragraph 2, When the second switch is turned on, current flows to turn on the first switch, When the second switch is turned off, the current is cut off, thereby turning off the first switch. Voltage detection circuit.

4. In paragraph 3, The above first switch is a PNP transistor including a first emitter terminal, a first base terminal, and a first collector terminal, The above second switch is an NPN transistor including a second emitter terminal, a second base terminal, and a second collector terminal, The above first output terminal is connected to the above first emitter terminal, The above first collector terminal is connected to the voltage detector to provide the sensing voltage, The above first base terminal is connected to the above second collector terminal, The above second emitter terminal is connected to ground voltage, The second base terminal is connected to the second output terminal of the comparator, The above second collector terminal is connected to the above first base terminal, Voltage detection circuit.

5. In paragraph 4, The above comparator includes a first input terminal, a second input terminal, and the second output terminal, A first voltage obtained by dividing the supply voltage is applied to the first input terminal through the first division circuit, The second input terminal is configured to receive a second voltage obtained by dividing the sensing voltage through a second divider circuit. Voltage detection circuit.

6. In paragraph 5, The above first divider circuit is configured by connecting the first resistor and the second resistor in series, The above second divider circuit is configured by connecting the third resistor and the fourth resistor in series, The first terminal of the above first resistor is applied with the above supply voltage, The second terminal of the first resistor and the first terminal of the second resistor (R2) are connected, The second terminal of the second resistor is connected to the ground voltage, The first input terminal is connected to the second terminal of the first resistor and the first terminal of the second resistor to receive the first voltage, The first terminal of the third resistor is applied with the sensing voltage, The second terminal of the third resistor and the first terminal of the fourth resistor are connected, The second terminal of the above fourth resistor is connected to the ground voltage, The second input terminal is connected to the second terminal of the third resistor and the first terminal of the fourth resistor to receive the second voltage. Voltage detection circuit.

7. In paragraph 6, The resistance value ratio between the first and second resistors is characterized by being the same as the resistance value ratio between the third and fourth resistors. Voltage detection circuit.

8. In paragraph 6, The above first division circuit Further comprising a capacitor connected in parallel with the second resistor, Voltage detection circuit.

9. In paragraph 5, The above comparator, When the first voltage applied to the first input terminal is greater than the second voltage applied to the second input terminal, the first control voltage is output to the second output terminal, When the first voltage applied to the first input terminal is less than the second voltage applied to the second input terminal, the second control voltage is output to the second output terminal. Voltage detection circuit.

10. In paragraph 5, The first output terminal and the second output terminal are characterized in that they are connected with a resistor therebetween. Voltage detection circuit.

11. In a voltage supply circuit that supplies voltage to a control device, An LDO (low dropout) voltage regulator providing a supply voltage to the control device through a first output terminal; A voltage detector which senses a voltage and obtains a voltage value and provides it to the control device; A first switch provided between the LDO voltage regulator and the voltage detector to short-circuit or cut off the supply voltage and the sensing voltage; A second switch controlling the on / off of the first switch; Including a comparator that controls on / off of the second switch based on the result of comparing the supply voltage and the sensing voltage. Voltage supply circuit.

12. In paragraph 11, The above comparator, If the above supply voltage is greater than the above sensing voltage, a first control voltage is output to turn on the second switch, If the sensing voltage is greater than the supply voltage, a second control voltage is output to turn off the second switch. Voltage supply circuit.

13. In paragraph 12, When the second switch is turned on, current flows to turn on the first switch, and when it is turned off, current is cut off to turn off the first switch. Voltage supply circuit.

14. In paragraph 13, The above first switch is a PNP transistor including a first emitter terminal, a first base terminal, and a first collector terminal, The above second switch is an NPN transistor including a second emitter terminal, a second base terminal, and a second collector terminal, The above first output terminal is connected to the above first emitter terminal, The above first collector terminal is connected to the voltage detector to provide the sensing voltage, The above first base terminal is connected to the above second collector terminal, The above second emitter terminal is connected to ground voltage, The second base terminal is connected to the second output terminal of the comparator, The above second collector terminal is connected to the above first base terminal, Voltage supply circuit.

15. In paragraph 14, The above comparator includes a first input terminal, a second input terminal, and the second output terminal, A first voltage obtained by dividing the supply voltage is applied to the first input terminal through the first division circuit, The second input terminal is configured to receive a second voltage obtained by dividing the sensing voltage through a second divider circuit. Voltage supply circuit.

16. In paragraph 15, The above first divider circuit is configured by connecting the first resistor and the second resistor in series, The above second divider circuit is configured by connecting the third resistor and the fourth resistor in series, The first terminal of the above first resistor is applied with the above supply voltage, The second terminal of the first resistor and the first terminal of the second resistor (R2) are connected, The second terminal of the second resistor is connected to the ground voltage, The first input terminal is connected to the second terminal of the first resistor and the first terminal of the second resistor to receive the first voltage, The first terminal of the third resistor is applied with the sensing voltage, The second terminal of the third resistor and the first terminal of the fourth resistor are connected, The second terminal of the above fourth resistor is connected to the ground voltage, The second input terminal is connected to the second terminal of the third resistor and the first terminal of the fourth resistor to receive the second voltage. Voltage supply circuit.

17. In paragraph 16, The resistance value ratio between the first and second resistors is characterized by being the same as the resistance value ratio between the third and fourth resistors. Voltage supply circuit.

18. In paragraph 16, The above first division circuit Further comprising a capacitor connected in parallel with the second resistor, Voltage supply circuit.

19. In Article 15, The above comparator, When the first voltage applied to the first input terminal is greater than the second voltage applied to the second input terminal, the first control voltage is output to the second output terminal, When the first voltage applied to the first input terminal is less than the second voltage applied to the second input terminal, the second control voltage is output to the second output terminal. Voltage supply circuit.

20. In paragraph 15, The first output terminal and the second output terminal are characterized in that they are connected with a resistor therebetween. Voltage supply circuit.

Images