Low dropout regulator with switchable reference voltage and control method

Abstract

The invention belongs to the technical field of voltage stabilizers, and discloses a low-dropout voltage stabilizer with a switchable reference voltage and a control method. The voltage stabilizer comprises an error amplifier, a band-gap reference source, a first transistor, a second transistor and a standby reference voltage circuit, when the signal output end of the band-gap reference source outputs a first signal, the first transistor is switched off, the second transistor is switched on, and the standby reference voltage circuit provides a second reference voltage for the negative input end of the error amplifier; and when the signal output end of the band-gap reference source outputs a second signal, the first transistor is switched on, the second transistor is switched off, and the band-gap reference source provides a first reference voltage for the error amplifier. According to the low dropout regulator, the reference voltage is allowed to be switched between the band-gap reference source and the standby reference voltage circuit so as to adapt to different input conditions and load conditions; the dependence on external high-voltage devices is reduced, the area and cost of the devices are reduced, and the power consumption of the circuit is reduced.

Description

Technical Field

[0001] The present application relates to the technical field of voltage regulators, and in particular to a low voltage dropout regulator with switchable reference voltage and a control method thereof. Background Art

[0002] Low dropout regulators (LDOs) are widely used in the field of power management due to their low noise and stability. However, in order for low dropout regulators to output accurate and stable output voltages, they rely on accurate reference voltages. The reference voltage is usually implemented by a bandgap reference circuit. In order for low dropout regulators to operate at higher input voltages, high-voltage resistant devices such as LDMOS (lateral double diffused metal oxide semiconductor) and EDMOS (enhanced double diffused metal oxide semiconductor) are required. These devices improve their voltage resistance by increasing the source-drain distance, but this also results in an increase in device area and higher costs. Summary of the invention

[0003] To this end, an embodiment of the present application provides a low-dropout regulator with switchable reference voltage and a control method, which allows the reference voltage to be switched between a bandgap reference source and a backup reference voltage circuit to adapt to different input conditions and load conditions; reduces dependence on external high-voltage devices, reduces device area and cost, and helps to reduce circuit power consumption.

[0004] In a first aspect, the present application provides a low-dropout regulator with a switchable reference voltage.

[0005] This application is achieved through the following technical solutions:

[0006] A low-dropout voltage regulator with switchable reference voltage, comprising:

[0007] Error amplifier;

[0008] A bandgap reference source, comprising an input terminal, a signal output terminal and a voltage output terminal, for providing a first reference voltage to the negative input terminal of the error amplifier, wherein the input terminal of the bandgap reference source is connected to the output terminal of the error amplifier;

[0009] a first transistor, wherein a gate of the first transistor is connected to a signal output terminal of the bandgap reference source, a drain of the first transistor is connected to a voltage output terminal of the bandgap reference source, and a source of the first transistor is connected to a negative input terminal of an error amplifier;

[0010] A reference voltage circuit is provided, for providing a second reference voltage to the negative input terminal of the error amplifier;

[0011] a second transistor, wherein a gate of the second transistor is connected to a signal output terminal of the bandgap reference source, a drain of the second transistor is connected to a reference voltage circuit, and a source of the second transistor is connected to a negative input terminal of an error amplifier;

[0012] When the signal output terminal of the bandgap reference source outputs the first signal, the first transistor is turned off, the second transistor is turned on, and the second reference voltage is provided to the negative input terminal of the error amplifier by the backup reference voltage circuit;

[0013] When the signal output terminal of the bandgap reference source outputs the second signal, the first transistor is turned on, the second transistor is turned off, and the bandgap reference source provides a first reference voltage to the error amplifier.

[0014] In a preferred example of the present application, it can be further configured that the reference voltage circuit includes a resistor R1 and a third transistor NMOS3, one end of the resistor R1 is connected to the source of the third transistor NMOS3, the other end of the resistor R1 is connected to the input power supply terminal, the drain of the third transistor NMOS3 is grounded, and the gate of the third transistor NMOS3 is connected to the drain of the second transistor.

[0015] In a preferred example of the present application, it can be further configured that the first transistor is an NMOS transistor and the second transistor is a PMOS transistor.

[0016] In a preferred example of the present application, it can be further configured that the first signal is a low-level signal for indicating that the bandgap reference source is in a normal power-on state.

[0017] In a preferred example of the present application, it can be further configured that the second signal is a high-level signal for indicating that the bandgap reference source is in a non-operating state.

[0018] In a preferred example of the present application, it can be further configured that the signal output end of the bandgap reference source also includes:

[0019] An output signal control circuit, comprising a transistor PMOS3, a transistor PMOS4, a transistor PMOS5, a resistor R3, a resistor R4, a resistor R5, a transistor Q1 and a transistor Q2;

[0020] The signal output end of the error amplifier is connected to the source of transistor PMOS3, the source of transistor PMOS4, and the source of transistor PMOS5, the gate of transistor PMOS3 is connected to the drain of transistor PMOS4, the gate of transistor PMOS5 is connected to the drain of transistor PMOS4, one end of resistor R3 is connected to the drain of transistor PMOS3, the other end of resistor R3 is grounded, the collector of transistor Q1 is connected to the drain of transistor PMOS4, the emitter of transistor Q1 is connected to one end of resistor R4, resistor R4 is connected in series with resistor R5, the gate of transistor Q1 is connected to the gate of transistor Q2, the collector of transistor Q2 is connected to the drain of transistor PMOS5, and the emitter of transistor Q2 is connected between resistor R4 and resistor R5.

[0021] In a preferred example of the present application, it can be further configured that when the output voltage VDD at the output end of the error amplifier is less than the preset operating voltage of the bandgap reference source, transistor PMOS3 is turned off, transistor PMOS4 is turned off, transistor PMOS5 is turned off, and the voltage value of the signal output end of the bandgap reference source is 0.

[0022] In a preferred example of the present application, it can be further configured that when the output voltage VDD at the output end of the error amplifier is greater than or equal to the preset operating voltage of the bandgap reference source, the transistor PMOS3 is turned on and the voltage value at the signal output end of the bandgap reference source increases to the output voltage VDD.

[0023] In a preferred example of the present application, it can be further configured that the second reference voltage provided by the reference voltage circuit is adjustable to 1.2V.

[0024] In a second aspect, the present application provides a control method for a low-dropout regulator with switchable reference voltage.

[0025] This application is achieved through the following technical solutions:

[0026] A control method for a low-dropout voltage regulator with switchable reference voltage, the method comprising:

[0027] In addition to the bandgap reference source, a standby reference voltage circuit is added, wherein the bandgap reference source is used to provide a first reference voltage to the error amplifier, and the standby reference voltage circuit is used to provide a second reference voltage to the error amplifier;

[0028] When the bandgap reference source is in a state where it cannot be powered on normally, the backup reference voltage circuit provides a second reference voltage for the negative input terminal of the error amplifier;

[0029] When the bandgap reference source is in a normal power-on state, the bandgap reference source provides a first reference voltage for the negative input terminal of the error amplifier.

[0030] In summary, compared with the prior art, the technical solution provided in the embodiment of the present application has at least the following beneficial effects:

[0031] The low voltage difference regulator of the present application includes: an error amplifier; a bandgap reference source, which is used to provide a first reference voltage to the negative input terminal of the error amplifier, wherein the input terminal of the bandgap reference source is connected to the output terminal of the error amplifier; a first transistor, wherein the gate of the first transistor is connected to the signal output terminal of the bandgap reference source, the drain is connected to the voltage output terminal of the bandgap reference source, and the source is connected to the negative input terminal of the error amplifier; a standby reference voltage circuit, which is used to provide a second reference voltage to the negative input terminal of the error amplifier; a second transistor, wherein the gate of the second transistor is connected to the signal output terminal of the bandgap reference source, the drain is connected to the standby reference voltage circuit, and the source is connected to the negative input terminal of the error amplifier; when the signal output terminal of the bandgap reference source outputs a first signal, the first transistor is turned off, the second transistor is turned on, and the standby reference voltage circuit provides the second reference voltage to the negative input terminal of the error amplifier; when the signal output terminal of the bandgap reference source outputs a second signal, the first transistor is turned on, the second transistor is turned off, and the bandgap reference source provides the first reference voltage to the error amplifier. The low voltage dropout regulator of the present application allows the reference voltage to be switched between a bandgap reference source and a backup reference voltage circuit to adapt to different input conditions and load conditions; reduces the dependence on external high-voltage devices, reduces device area and cost, and helps to reduce circuit power consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 A schematic diagram of the structure of a low-dropout voltage regulator with switchable reference voltage provided in an embodiment of the present application;

[0033] Figure 2 A circuit diagram of a low-dropout regulator with switchable reference voltage provided by an embodiment of the present application;

[0034] Figure 3 A schematic diagram of an output signal control circuit provided in one embodiment of the present application;

[0035] Description of reference numerals:

[0036] Error amplifier 1, bandgap reference source 2, reference voltage circuit 3, first transistor 4, second transistor 5. DETAILED DESCRIPTION

[0037] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

[0038] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0039] In addition, the term "and / or" in this application is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this application, unless otherwise specified, generally indicates that the associated objects before and after are in an "or" relationship.

[0040] In this application, the terms "first", "second", etc. are used to distinguish identical or similar items with basically the same effects and functions. It should be understood that there is no logical or temporal dependency between "first", "second", and "nth", nor is there any limitation on quantity and execution order.

[0041] In the embodiments of the present application, words such as "exemplary" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a specific way.

[0042] The structure of the existing low-dropout voltage regulator means that the bandgap reference source may need to work at a higher voltage when the dropout voltage (Dropout Voltage) is high, so it is necessary to use a high-voltage device that can withstand a higher voltage. The error amplifier is responsible for comparing the reference voltage and the output voltage, and adjusting the gate voltage of the power tube to keep the output voltage stable. Similarly, under high dropout voltage, the voltage difference between the input end (reference voltage) and the output end (output voltage) of the error amplifier is large, so it is necessary to use a high-voltage error amplifier that can handle a higher voltage difference. In order to prevent the Bandgap (bandgap reference source) from working at a high voltage, a voltage regulator module can also be used to power the Bandgap. For example, the voltage regulator module uses a voltage regulator tube to provide a 5V voltage, so that the Bandgap only needs to work at a 5V power supply and does not require a high-voltage device. However, the voltage regulator module needs to use a high-voltage device. In addition, the voltage regulator module itself will consume a certain current and increase the power consumption of the overall circuit.

[0043] In order to solve the above problems, the present application proposes a low voltage dropout regulator with switchable reference voltage and a control method. The embodiments of the present application are further described in detail below in conjunction with the drawings in the specification.

[0044] like Figure 1 As shown, a low voltage dropout regulator with switchable reference voltage is provided by a first exemplary embodiment of the present application, which includes:

[0045] Error amplifier 1;

[0046] A bandgap reference source 2, comprising an input terminal, a signal output terminal and a voltage output terminal, wherein the voltage output terminal is used to provide a first reference voltage to the negative input terminal of the error amplifier 1, the input terminal of the bandgap reference source 2 is connected to the output terminal of the error amplifier 1, and the signal output terminal is used to output a signal indicating the working state of the bandgap reference source 2;

[0047] a first transistor 4, wherein the gate of the first transistor 4 is connected to the signal output terminal of the bandgap reference source 2, the drain of the first transistor 4 is connected to the voltage output terminal of the bandgap reference source 2, and the source of the first transistor 4 is connected to the negative input terminal of the error amplifier 1;

[0048] A reference voltage circuit 3 is provided, for providing a second reference voltage to the negative input terminal of the error amplifier 1;

[0049] a second transistor 5, wherein the gate of the second transistor 5 is connected to the signal output terminal of the bandgap reference source 2, the drain of the second transistor 5 is connected to the reference voltage circuit 3, and the source of the second transistor 5 is connected to the negative input terminal of the error amplifier 1;

[0050] When the signal output terminal of the bandgap reference source 2 outputs the first signal, the first transistor 4 is turned off, the second transistor 5 is turned on, and the backup reference voltage circuit 3 provides a second reference voltage to the negative input terminal of the error amplifier 1;

[0051] When the signal output terminal of the bandgap reference source 2 outputs the second signal, the first transistor 4 is turned on, the second transistor 5 is turned off, and the bandgap reference source 2 provides the first reference voltage to the error amplifier 1. The second signal and the first signal are different signals.

[0052] Preferably, if Figure 2 As shown, the reference voltage circuit includes a resistor R1 and a third transistor NMOS3, one end of the resistor R1 is connected to the source of the third transistor NMOS3, the other end of the resistor R1 is connected to the input power supply terminal, the drain of the third transistor NMOS3 is grounded, and the gate of the third transistor NMOS3 is connected to the drain of the second transistor.

[0053] Specifically, the low voltage dropout regulator of the present application generates a second reference voltage Vgs by using the resistor R1 and the third transistor NMOS3 of the reference voltage circuit in addition to the bandgap reference source. The generated Vgs can be modulated to about 1.2V, which is close to the reference voltage (also called the first reference voltage) provided by the Bandgap. In this way, the LDO output voltage fluctuation caused by the switching between the first reference voltage and the second reference voltage can be reduced.

[0054] Preferably, considering that NMOS transistors perform better at low voltages and PMOS transistors perform better at high voltages, the first transistor is an NMOS transistor and the second transistor is a PMOS transistor, so that the circuit can operate in a wider voltage range.

[0055] Preferably, the first signal is a low level signal, used to indicate that the bandgap reference source is in a normal power-on state.

[0056] Specifically, the signal output end of Bandgap (bandgap reference source) outputs a signal Vbg_OK for indicating whether the bandgap reference source is powered on and working normally. When the input end of Bandgap is not powered or the output is abnormal, Vbg_OK at the signal output end of Bandgap (bandgap reference source) is a low-level signal. At this time, transistor MOS2 is turned off, transistor MOS1 is turned on, and the second reference voltage Vgs generated by the reference voltage circuit 3 is used as the reference voltage of the error amplifier. It should be noted that the abnormal Bandgap output means that the bandgap reference source (Bandgap) fails to provide the expected stable reference voltage.

[0057] Preferably, the second signal is a high level signal, used to indicate that the bandgap reference source is in an inoperable state.

[0058] Specifically, when the input end of Bandgap can output a normal voltage, Vbg_OK at the signal output end of Bandgap (bandgap reference source) is a high level signal. At this time, transistor MOS2 is turned on, transistor MOS1 is turned off, and Vbg outputted from the voltage output end of Bandgap (bandgap reference source) is used as the reference voltage of the error amplifier.

[0059] At the beginning of power-on, because the VB voltage is low, the output voltage of the error amplifier is 0 or very low, which is not enough to make the Bandgap work normally. The Vbg_OK at the signal output end of the Bandgap (bandgap reference source) is 0. At this time, the reference voltage circuit normally generates the Vgs voltage and provides the reference voltage to the error amplifier, which can make the LDO work normally.

[0060] As the LDO output voltage VOUT increases, Bandgap starts to work, and the Vbg_OK output of the signal output terminal of Bandgap (bandgap reference source) becomes high, at which time transistor MOS2 turns on and transistor MOS1 turns off. The reference voltage of the error amplifier switches to an accurate and stable bandgap reference voltage (i.e., the first reference voltage).

[0061] By switching between the bandgap reference source and the backup reference voltage, the stability and reliability of the circuit are improved, ensuring that a stable reference voltage can be provided under various circumstances.

[0062] Preferably, if Figure 3 As shown, it is a method to realize Vbg_OK of the signal output terminal of the Bandgap (bandgap reference source). The signal output terminal of the bandgap reference source also includes:

[0063] An output signal control circuit, comprising a transistor PMOS3, a transistor PMOS4, a transistor PMOS5, a resistor R3, a resistor R4, a resistor R5, a transistor Q1 and a transistor Q2;

[0064] The signal output end of the error amplifier is connected to the source of transistor PMOS3, the source of transistor PMOS4, and the source of transistor PMOS5, the gate of transistor PMOS3 is connected to the drain of transistor PMOS4, the gate of transistor PMOS5 is connected to the drain of transistor PMOS4, one end of resistor R3 is connected to the drain of transistor PMOS3, the other end of resistor R3 is grounded, the collector of transistor Q1 is connected to the drain of transistor PMOS4, the emitter of transistor Q1 is connected to one end of resistor R4, resistor R4 is connected in series with resistor R5, the gate of transistor Q1 is connected to the gate of transistor Q2, the collector of transistor Q2 is connected to the drain of transistor PMOS5, and the emitter of transistor Q2 is connected between resistor R4 and resistor R5.

[0065] Preferably, when the output voltage VDD of the output end of the error amplifier is less than the preset operating voltage of the bandgap reference source, the transistor PMOS3 is turned off, the transistor PMOS4 is turned off, the transistor PMOS5 is turned off, and the voltage value of the signal output end of the bandgap reference source is 0.

[0066] Specifically, when the output voltage VDD of the output end of the error amplifier is too low and the bandgap reference source cannot work, transistor PMOS3 is turned off, transistor PMOS4 is turned off, and transistor PMOS5 is turned off. No current flows through transistor PMOS3, transistor PMOS4 and transistor PMOS5. At this time, the Vbg_OK voltage of the signal output end of the bandgap reference source is 0.

[0067] Preferably, when the output voltage VDD of the output terminal of the error amplifier is greater than or equal to the preset operating voltage of the bandgap reference source, the bandgap reference source works normally, the transistor PMOS3 is turned on, and the voltage value of the signal output terminal of the bandgap reference source increases to the output voltage VDD.

[0068] Preferably, the second reference voltage provided by the reference voltage circuit is adjustable to 1.2V.

[0069] A second exemplary embodiment of the present application provides a control method for a low-voltage dropout regulator with switchable reference voltage. The method is based on the low-voltage dropout regulator of the first exemplary embodiment of the present application and specifically includes the following steps:

[0070] In addition to the bandgap reference source, a standby reference voltage circuit is added, wherein the bandgap reference source is used to provide a first reference voltage to the error amplifier, and the standby reference voltage circuit is used to provide a second reference voltage to the error amplifier;

[0071] When the bandgap reference source is in a state where it cannot be powered on normally, the backup reference voltage circuit provides a second reference voltage for the negative input terminal of the error amplifier;

[0072] When the bandgap reference source is in a normal power-on state, the bandgap reference source provides a first reference voltage for the negative input terminal of the error amplifier.

[0073] The specific limitations of the control method of the low-dropout regulator with switchable reference voltage provided in this embodiment can be found in the above embodiments of the low-dropout regulator with switchable reference voltage, which will not be described in detail here.

[0074] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0075] Those skilled in the art can clearly understand that for the convenience and simplicity of description, only the division of the above-mentioned functional units and modules is used as an example. In actual applications, the above-mentioned functions can be distributed and completed by different functional units and modules as needed, that is, the internal structure of the system described in the present application is divided into different functional units or modules to complete all or part of the functions described above.

Claims

1. A low dropout regulator with switchable reference voltage, characterized in that: include: Error amplifier; A bandgap reference source, comprising an input terminal, a signal output terminal and a voltage output terminal, for providing a first reference voltage to the negative input terminal of the error amplifier, wherein the input terminal of the bandgap reference source is connected to the output terminal of the error amplifier; a first transistor, wherein a gate of the first transistor is connected to a signal output terminal of the bandgap reference source, a drain of the first transistor is connected to a voltage output terminal of the bandgap reference source, and a source of the first transistor is connected to a negative input terminal of an error amplifier; A reference voltage circuit is provided, for providing a second reference voltage to the negative input terminal of the error amplifier; a second transistor, wherein a gate of the second transistor is connected to a signal output terminal of the bandgap reference source, a drain of the second transistor is connected to a reference voltage circuit, and a source of the second transistor is connected to a negative input terminal of an error amplifier; When the signal output terminal of the bandgap reference source outputs the first signal, the first transistor is turned off, the second transistor is turned on, and the second reference voltage is provided to the negative input terminal of the error amplifier by the backup reference voltage circuit; When the signal output terminal of the bandgap reference source outputs the second signal, the first transistor is turned on, the second transistor is turned off, and the bandgap reference source provides a first reference voltage to the error amplifier.

2. The low-dropout regulator with switchable reference voltage according to claim 1, characterized in that: The reference voltage circuit includes a resistor R1 and a third transistor NMOS3, one end of the resistor R1 is connected to the source of the third transistor NMOS3, the other end of the resistor R1 is connected to the input power supply terminal, the drain of the third transistor NMOS3 is grounded, and the gate of the third transistor NMOS3 is connected to the drain of the second transistor.

3. The low-dropout regulator with switchable reference voltage according to claim 1, characterized in that: The first transistor is an NMOS transistor, and the second transistor is a PMOS transistor.

4. The low-dropout regulator with switchable reference voltage according to claim 1, characterized in that: The first signal is a low level signal, which is used to indicate that the bandgap reference source is in a normal power-on state.

5. The low-dropout regulator with switchable reference voltage according to claim 4, characterized in that: The second signal is a high level signal, which is used to indicate that the bandgap reference source is in an inoperable state.

6. The low-dropout regulator with switchable reference voltage according to claim 1, characterized in that: The signal output terminal of the bandgap reference source also includes: An output signal control circuit, comprising a transistor PMOS3, a transistor PMOS4, a transistor PMOS5, a resistor R3, a resistor R4, a resistor R5, a transistor Q1 and a transistor Q2; The signal output end of the error amplifier is connected to the source of transistor PMOS3, the source of transistor PMOS4, and the source of transistor PMOS5, the gate of transistor PMOS3 is connected to the drain of transistor PMOS4, the gate of transistor PMOS5 is connected to the drain of transistor PMOS4, one end of resistor R3 is connected to the drain of transistor PMOS3, the other end of resistor R3 is grounded, the collector of transistor Q1 is connected to the drain of transistor PMOS4, the emitter of transistor Q1 is connected to one end of resistor R4, resistor R4 is connected in series with resistor R5, the gate of transistor Q1 is connected to the gate of transistor Q2, the collector of transistor Q2 is connected to the drain of transistor PMOS5, and the emitter of transistor Q2 is connected between resistor R4 and resistor R5.

7. The low-dropout regulator with switchable reference voltage according to claim 6, characterized in that: When the output voltage VDD of the output end of the error amplifier is less than the preset operating voltage of the bandgap reference source, the transistor PMOS3 is turned off, the transistor PMOS4 is turned off, the transistor PMOS5 is turned off, and the voltage value of the signal output end of the bandgap reference source is 0.

8. The low-dropout regulator with switchable reference voltage according to claim 6, characterized in that: When the output voltage VDD of the output terminal of the error amplifier is greater than or equal to the preset operating voltage of the bandgap reference source, the transistor PMOS3 is turned on, and the voltage value of the signal output terminal of the bandgap reference source increases to the output voltage VDD.

9. The low-dropout regulator with switchable reference voltage according to claim 6, characterized in that: The second reference voltage provided by the reference voltage circuit is adjustable to 1.2V.

10. A control method for a low voltage dropout regulator with switchable reference voltage, characterized in that: include: In addition to the bandgap reference source, a standby reference voltage circuit is added, wherein the bandgap reference source is used to provide a first reference voltage to the error amplifier, and the standby reference voltage circuit is used to provide a second reference voltage to the error amplifier; When the bandgap reference source is in a state where it cannot be powered on normally, the backup reference voltage circuit provides a second reference voltage for the negative input terminal of the error amplifier; When the bandgap reference source is in a normal power-on state, the bandgap reference source provides a first reference voltage for the negative input terminal of the error amplifier.

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