A low dropout linear regulator circuit that is mutually activated with a bandgap reference circuit

Abstract

The application discloses a low dropout linear regulator circuit which is mutually started with a bandgap reference circuit, and comprises a pre-starting circuit, an operational amplifier, a first NMOS transistor, and a bandgap reference circuit; the same-phase input end of the operational amplifier is connected with the output end of the pre-starting circuit; the gate of the first NMOS transistor is connected with the output end of the operational amplifier, and the source thereof is communicated with the input end of the bandgap reference circuit, so that an initial output voltage is generated to pre-start the bandgap reference circuit; the output end of the bandgap reference circuit is communicated with the pre-starting circuit, and after pre-starting, the LDO circuit is restarted to obtain a final output voltage, and the mutual starting of the LDO circuit and the bandgap reference circuit is realized. The application solves the problems that the traditional LDO circuit cannot provide stable bias current by itself, and the load capacity and transient response performance of the traditional bandgap reference type LDO circuit are poor, adopts a special mutual starting mechanism, simplifies the pre-starting and shutdown mechanism, improves the load capacity and transient response performance of the LDO circuit, guarantees the stable output voltage, and ensures the normal work of other modules of the system.

Description

Technical Field

[0001] This invention relates to the field of integrated circuit technology, and more specifically to a low-dropout linear regulator circuit that is inter-activated with a bandgap reference circuit. Background Technology

[0002] In integrated circuit power supply systems, low-voltage power systems utilize low-voltage transistors in their built-in circuits to ensure all circuits operate within a low voltage range. However, circuits in high-voltage power supply systems obviously cannot operate directly using a large number of high-voltage transistors, such as... Figure 1 As shown, for traditional high-voltage power supply systems, the LDO (Low Dropout Regulator) serves as the first-stage voltage output of the internal circuit, providing a low voltage range for subsequent circuits and ensuring that all subsequent circuits operate in a low voltage range.

[0003] However, the LDO circuit does not have a bandgap reference (bg) circuit to provide bias in the voltage domain, and it needs to provide its own bias current. At the same time, its internal self-starting circuit cannot provide a low temperature drift and stable bias current, which leads to a large deviation in the output voltage of the LDO circuit at different temperatures and between chips, which will eventually affect the operation of the entire high voltage system.

[0004] To provide a stable current bias, we generally use LDO circuits with a bandgap reference (bg) frame. Figure 2 A bandgap reference (bg) type LDO circuit (the circuit structure is existing technology and will not be described in detail here) that can operate in the high-voltage domain can provide a stable current bias for subsequent circuits in high-voltage power supply systems. However, the load-carrying capacity and transient response performance of the bandgap reference (bg) type LDO circuit are poor. Existing bg type LDO circuits can generally only drive lightly loaded modules and can only provide power to static circuits with low power consumption. Other circuit modules require additional LDO circuits to drive them, and they cannot drive large loads. Therefore, this type of bg type LDO circuit is difficult to provide a stable bias current for high-voltage systems.

[0005] Meanwhile, because the reference current generated by a bg-type LDO circuit is generated by a high-voltage transistor, this current cannot be replicated in a high-voltage power supply system, resulting in a significant waste of area. Therefore, this bg-type LDO circuit is not a very cost-effective choice. Thus, providing a stable current bias for the high-voltage chip system without affecting the LDO circuit's inherent good load-carrying capacity and transient response performance becomes particularly important. Summary of the Invention

[0006] The purpose of this invention is to provide a low-dropout linear regulator (LDO) circuit that can be inter-started with a bandgap reference circuit. This LDO circuit aims to solve the problems of traditional LDO circuits being unable to provide a stable bias current and the poor load-carrying capacity and transient response performance of traditional bg-type (bandgap reference) LDO circuits.

[0007] To achieve the above objectives, the present invention provides an LDO circuit that is inter-enabled with a bandgap reference circuit. The LDO circuit is connected to the bandgap reference circuit K, and the LDO circuit includes:

[0008] The pre-start circuit has its first input terminal connected to an external power module. It preprocesses the power supply voltage provided by the external power module to obtain the initial bias voltage.

[0009] An operational amplifier, with its non-inverting input connected to the output of a pre-startup circuit, is used to process the initial bias voltage to obtain the initial reference voltage.

[0010] The first NMOS transistor (N-Metal-Oxide-Semiconductor) has its gate connected to the output of the operational amplifier and its source connected to the input of the bandgap reference circuit. It is used to process the initial reference voltage, obtain the initial output voltage, and transmit it to the bandgap reference circuit to pre-start the bandgap reference circuit.

[0011] The output terminal of the bandgap reference circuit is connected to the second input terminal of the pre-start circuit. After the bandgap reference circuit pre-starts, it generates a bias current signal and transmits it back to the pre-start circuit and the operational amplifier. The pre-start circuit and the operational amplifier combine the bias current signal to adjust and output the restart reference voltage, which is transmitted to the first NMOS transistor to obtain the final output voltage, thereby realizing the mutual start-up of the LDO circuit and the bandgap reference circuit.

[0012] In one embodiment of this solution, the LDO circuit further includes:

[0013] The first resistor has its first end connected to the source of the first NMOS transistor and its second end connected to the inverting input of the operational amplifier.

[0014] The second resistor has its first end connected to the second end of the first resistor, and its second end is grounded.

[0015] The first and second resistors are used to divide the voltage between the operational amplifier and the first NMOS transistor.

[0016] In one embodiment of this solution, the pre-start circuit further includes: a diode, a third resistor, and a fourth resistor; the positive terminal of the diode is grounded, and the negative terminal is connected to the first end of the third resistor; the second end of the third resistor is connected to the operational amplifier; the first end of the fourth resistor is connected to the second end of the third resistor, and the second end of the fourth resistor is grounded.

[0017] As the external power supply voltage increases, the diode generates a diode voltage, which, after being divided by the third and fourth resistors, generates the initial bias voltage V. gate Wherein, the initial bias voltage V gate satisfy:

[0018]

[0019] Among them, V d R is the diode voltage, and R3 and R4 are the resistance values ​​of the third and fourth resistors, respectively.

[0020] In one embodiment of this solution, the operational amplifier further includes: a second NMOS transistor and a fifth resistor; the gate of the second NMOS transistor is connected to the second terminal of the third resistor and the first terminal of the fourth resistor, respectively; the drain of the second NMOS transistor is connected to the first terminal of the third resistor; the source of the second NMOS transistor is connected to the first terminal of the fifth resistor; and the second terminal of the fifth resistor is grounded.

[0021] After receiving the initial bias voltage from the pre-startup circuit, the second NMOS transistor performs voltage division with the fifth resistor and outputs an initial reference voltage, where the initial reference voltage is V. pre And satisfy:

[0022] V pre =I pre R5

[0023] Where R5 is the resistance value of the fifth resistor; I pre The initial reference current is given, and it satisfies...

[0024]

[0025] Among them, V th This is the threshold voltage of the second NMOS transistor.

[0026] In one embodiment of this solution, the LDO circuit obtains the initial output voltage V. out_pre And satisfy:

[0027]

[0028] Wherein, R1 and R2 are the resistance values ​​of the first resistor and the second resistor, respectively.

[0029] In one embodiment of this scheme, the restart reference voltage generated by the operational amplifier in conjunction with the bias current signal provided by the bandgap reference circuit is V. ref And satisfy:

[0030] V ref =I ref R5

[0031] Among them, I ref This is the bias current signal provided after the bandgap reference circuit K is started.

[0032] In one implementation of this scheme, the restart reference voltage is greater than the initial reference voltage.

[0033] In one embodiment of this solution, the operational amplifier, in conjunction with the bias current signal generated by the bandgap reference circuit, adjusts the LDO circuit to automatically shut down during the restart phase.

[0034] In one embodiment of this solution, when the difference between the threshold voltage of the second NMOS transistor and the restart reference voltage is less than the threshold voltage of the second NMOS transistor, the second NMOS transistor automatically shuts down the pre-startup circuit during the restart phase. In another embodiment of this solution, the LDO circuit is connected to an external power supply module to supply power to its internal modules.

[0035] Compared with the prior art, the present invention has at least one of the following beneficial effects:

[0036] 1. The LDO circuit provided by this invention abandons the traditional bandgap reference type LDO architecture mode and nests the LDO circuit with the bandgap reference circuit. First, the bandgap reference circuit is started by the LDO pre-start circuit, and then the bandgap reference circuit drives the LDO circuit to start again and shuts down the pre-start circuit, so as to realize the mutual start-up of the LDO circuit and the bandgap reference circuit.

[0037] 2. The LDO circuit provided by this invention provides a bias current during the restart phase that is provided by a bandgap reference circuit. This gives the LDO circuit a stable bias current with low temperature drift, which ensures that the output of the LDO circuit has good robustness and temperature characteristics, thus ensuring the operation of other modules in the system.

[0038] 3. The LDO circuit provided by this invention does not rely on a bandgap reference architecture to provide stable bias. Compared with traditional bandgap reference type LDO circuits, it has stronger load-carrying capacity and better transient response. The overshoot voltage and undershoot voltage are only 1 / 10 or even less of those of bandgap reference type LDO. Therefore, this inter-start LDO circuit can drive larger loads and can save on additional LDOs.

[0039] 4. This invention only requires two resistors and one MOSFET to realize the pre-start-up and shutdown of the LDO circuit. The special startup mechanism and the simple design of the startup and shutdown circuits make it easy to implement. Attached Figure Description

[0040] Figure 1 A circuit diagram of a traditional high-voltage power supply system;

[0041] Figure 2 This is a schematic diagram of a traditional bg-type LDO circuit;

[0042] Figure 3 This is a schematic diagram of the inter-start structure of the LDO circuit and the bandgap reference circuit K provided by the present invention;

[0043] Figure 4 The voltage and current change trend diagrams of the pre-startup and restart status table of the LDO circuit provided by the present invention;

[0044] Figure 5 This is a detailed schematic diagram of the internal structure of the LDO circuit in this embodiment of the present invention. Detailed Implementation

[0045] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. These embodiments are only used to illustrate the present invention and are not intended to limit the scope of protection of the present invention.

[0046] This invention relates to a low-dropout linear regulator (LDO) circuit that interoperates with a bandgap reference circuit, such as... Figure 3 As shown, the LDO circuit includes: a pre-startup circuit 1, an operational amplifier 2, a first NMOS transistor M1, a first resistor R1, and a second resistor R2. The LDO circuit is connected to an external power supply module VDD to power its internal modules. Simultaneously, the LDO circuit is connected to a bandgap reference circuit K to perform mutual startup with the bandgap reference circuit K.

[0047] Specifically, such as Figure 3 and Figure 4 As shown, the first input terminal of the pre-start circuit 1 is connected to the external power module VDD, and the power supply voltage provided by the external power module VDD is preprocessed to obtain the initial bias voltage V. gate The non-inverting input of operational amplifier 2 is connected to the output of pre-startup circuit 1 to adjust the initial bias voltage V. gate Perform calculations to obtain the initial reference voltage V. pre The gate of the first NMOS transistor M1 is connected to the output of operational amplifier 2, and its source is connected to the input of the bandgap reference circuit K, used to input the initial reference voltage V. pre Processing is performed to obtain the initial output voltage V. out_preThe signal is transmitted to the bandgap reference circuit K for pre-startup. The output of the bandgap reference circuit K is connected to the second input of the pre-startup circuit 1. After pre-startup, the bandgap reference circuit K generates a bias current signal I. ref And transmit it back to pre-start circuit 1 and operational amplifier 2, which in turn combine the bias current signal I. ref Continuously adjust and output restart reference voltage V ref The voltage is transmitted to the first NMOS transistor M1 to obtain the final output voltage V. out .

[0048] Among them, the initial output voltage V output during the pre-start-up phase of the LDO circuit out_pre The voltage is sufficient to meet the normal startup requirements of the bandgap reference circuit K, and the initial output voltage V out_pre The value is not very high, therefore, the bandgap reference circuit K pre-starts up to generate a bias current signal I. ref Subsequently, as the restart voltage signal gradually increases until it reaches the set voltage of operational amplifier 2, operational amplifier 2 shuts off the pre-start circuit, thus allowing the LDO circuit to obtain the final output voltage V. out This enabled the LDO circuit to mutually start with the bandgap reference circuit K.

[0049] At the same time, such as Figure 3 As shown, in this LDO circuit, the first terminal of the first resistor R1 is connected to the source of the first NMOS transistor M1, and the second terminal is connected to the inverting input of the operational amplifier 2; the first terminal of the second resistor R2 is connected to the second terminal of the first resistor R1, and the second terminal is grounded. The first resistor R1 and the second resistor R2 are used to divide the voltage between the operational amplifier 2 and the first NMOS transistor M1.

[0050] Specifically, such as Figure 5 As shown in this embodiment, to analyze in detail the signal transmission relationship between the pre-startup stage and the restart stage, a schematic diagram of the internal circuit structure of a common pre-startup circuit 1 and operational amplifier 2 is provided. Among them, as... Figure 5As shown, the pre-startup circuit 1 includes at least: a power supply module VDD, a diode D1, a third resistor R3, a fourth resistor R4, and a second NMOS transistor M2; the positive terminal of diode D1 is grounded, and its negative terminal is connected to the first end of the third resistor R3; the second end of the third resistor R3 is connected to the operational amplifier 2; the first end of the fourth resistor R4 is connected to the second end of the third resistor R3, and the second end of the fourth resistor R4 is grounded; the gate of the second NMOS transistor M2 is connected to the second end of the third resistor R3 and the first end of the fourth resistor R4, respectively, and the drain of the second NMOS transistor M2 is connected to the first end of the third resistor R3. The operational amplifier 2 also includes at least: a fifth resistor R5; the source of the second NMOS transistor M2 in the pre-startup circuit 1 is connected to the first end of the fifth resistor R5, and the second end of the fifth resistor R5 is grounded.

[0051] During the pre-startup phase, diode D1 in pre-startup circuit 1 generates a diode voltage V as the power supply voltage VDD of the power module rises. d After being divided by the third resistor R3 and the fourth resistor R4, the voltage is transmitted to the second NMOS transistor M2, providing the second NMOS transistor M2 with an initial bias voltage V. gate Specifically, the initial bias voltage V gate satisfy:

[0052]

[0053] The fifth resistor R5 in operational amplifier 2 divides the voltage of the second NMOS transistor M2, thereby enabling operational amplifier 2 to output the initial reference voltage V. pre and initial reference current I pre And respectively satisfy:

[0054] V pre =I pre R5

[0055]

[0056] Among them, V th The threshold voltage of the second NMOS transistor M2;

[0057] Therefore, the LDO circuit obtains the initial output voltage V. out_pre And the initial output voltage V out_pre satisfy:

[0058]

[0059] The initial output voltage V at this time out_pre This voltage is sufficient to meet the normal startup requirements of the bandgap reference circuit K. After the bandgap reference circuit K has started up, operational amplifier 2 combines with the bias current signal I provided by the bandgap reference circuit K. refThe generated restart reference voltage V ref At this point, the reference voltage V is restarted. ref satisfy:

[0060] V ref =I ref R5

[0061] Among them, the restart reference voltage V ref Greater than the initial reference voltage V pre .

[0062] At the same time, the threshold voltage V of the second NMOS transistor M2 th With restart reference voltage V ref The difference is less than the threshold voltage V of the second NMOS transistor M2. th During the restart phase, the second NMOS transistor M2 shuts down the pre-startup circuit of the LDO.

[0063] Working principle of the invention:

[0064] The pre-start circuit preprocesses the power supply voltage provided by the external power module to obtain the initial bias voltage; the operational amplifier performs calculations on the initial bias voltage to obtain the initial reference voltage; the first NMOS transistor processes the initial reference voltage to obtain the initial output voltage and transmits it to the bandgap reference circuit for pre-starting the bandgap reference circuit; after the bandgap reference circuit pre-starts, it generates a bias current signal and transmits it back to the pre-start circuit and the operational amplifier. The pre-start circuit and the operational amplifier combine the bias current signal to adjust and output the restart reference voltage, which is transmitted to the first NMOS transistor to obtain the final output voltage, thereby realizing the mutual start-up of the LDO circuit and the bandgap reference circuit.

[0065] In summary, the present invention provides an LDO circuit that can be mutually started with a bandgap reference circuit. This invention solves the problems of traditional LDO circuits being unable to provide a stable bias current on their own, and the poor load-carrying capacity and transient response performance of traditional bandgap reference LDO circuits. It adopts a special mutual-start mechanism, simplifies the pre-start and shutdown mechanisms, improves the load-carrying capacity and transient response performance of the LDO circuit, ensures a stable output voltage, and also ensures the normal operation of other modules in the system.

[0066] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A low-dropout linear regulator (LDO) circuit that interoperates with a bandgap reference circuit, characterized in that, include: The pre-start circuit has its first input terminal connected to an external power module. It preprocesses the power supply voltage provided by the external power module to obtain the initial bias voltage. An operational amplifier, with its non-inverting input connected to the output of the pre-start-up circuit, is used to process the initial bias voltage to obtain an initial reference voltage. The first NMOS transistor, with its gate connected to the output of the operational amplifier and its source connected to the input of the bandgap reference circuit, processes the initial reference voltage to obtain an initial output voltage, which is then transmitted to the bandgap reference circuit for pre-startup. The initial output voltage is sufficient to meet the voltage required for normal startup of the bandgap reference circuit. The output of the bandgap reference circuit is connected to the second input of the pre-startup circuit. After pre-startup, the bandgap reference circuit generates a bias current signal, which is transmitted back to the pre-startup circuit and the operational amplifier. The pre-startup circuit and the operational amplifier, in conjunction with the bias current signal, adjust and output a restart reference voltage, which is transmitted to the first NMOS transistor to obtain the final output voltage. This achieves mutual startup between the LDO circuit and the bandgap reference circuit. After the bandgap reference circuit generates the bias current signal during pre-startup, as the restart reference voltage gradually increases until it reaches the set voltage of the operational amplifier, the operational amplifier turns off the pre-startup circuit. The restart reference voltage is greater than the initial reference voltage. The LDO circuit also includes: The first resistor has its first end connected to the source of the first NMOS transistor and its second end connected to the inverting input of the operational amplifier. The second resistor has its first end connected to the second end of the first resistor, and its second end is grounded. The first resistor and the second resistor are used to divide the voltage between the operational amplifier and the first NMOS transistor; The operational amplifier further includes a second NMOS transistor and a fifth resistor; the gate of the second NMOS transistor is connected to the second terminal of the third resistor and the first terminal of the fourth resistor respectively to obtain an initial bias voltage; the drain of the second NMOS transistor is connected to the first terminal of the third resistor; the source of the second NMOS transistor is connected to the first terminal of the fifth resistor; the second terminal of the fifth resistor is grounded to cooperate with the second NMOS transistor to generate an initial reference current and an initial reference voltage, and to provide a reference load for the restart reference voltage; When the difference between the gate voltage of the second NMOS transistor and the restart reference voltage is less than the threshold voltage of the second NMOS transistor, the second NMOS transistor automatically shuts down the pre-startup circuit during the restart phase.

2. The low-dropout linear regulator (LDO) circuit with inter-start capability with a bandgap reference circuit as described in claim 1, characterized in that, The pre-start circuit further includes: a diode, a third resistor, and a fourth resistor; the positive terminal of the diode is grounded, and the negative terminal is connected to the first end of the third resistor; the second end of the third resistor is connected to the operational amplifier; the first end of the fourth resistor is connected to the second end of the third resistor, and the second end of the fourth resistor is grounded; The diode generates a diode voltage as the external power voltage rises, and generates the initial bias voltage V gate , and satisfies: Among them, V d R3 represents the diode voltage, and R4 represents the resistance values ​​of the third resistor and the fourth resistor, respectively.

3. The low-dropout linear regulator (LDO) circuit with inter-start capability with a bandgap reference circuit as described in claim 2, characterized in that, After receiving the initial bias voltage transmitted by the pre-start-up circuit, the second NMOS transistor performs voltage division with the fifth resistor and outputs the initial reference voltage, which is V. pre And satisfy: Wherein, R5 is the resistance value of the fifth resistor; I pre The initial reference current generated by the operational amplifier, and satisfying... Among them, V th The threshold voltage of the second NMOS transistor is denoted as .

4. The low-dropout linear regulator (LDO) circuit with inter-start capability with a bandgap reference circuit as described in claim 3, characterized in that, The LDO circuit obtains the initial output voltage as V. out_pre And satisfy: Wherein, R1 and R2 are the resistance values ​​of the first resistor and the second resistor, respectively.

5. The low-dropout linear regulator (LDO) circuit with inter-start capability with a bandgap reference circuit as described in claim 4, characterized in that, The restart reference voltage generated by the operational amplifier in conjunction with the bias current signal provided by the bandgap reference circuit is V. ref And satisfy: Among them, I ref The bias current signal provided after the bandgap reference circuit is started.

6. The low-dropout linear regulator (LDO) circuit with inter-start capability with a bandgap reference circuit as described in claim 1, characterized in that, The LDO circuit is connected to an external power supply module to power its internal modules.

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