Low-dropout linear voltage stabilizing circuit and electronic equipment

Abstract

The utility model relates to the technical field of power supplies, and provides a low-dropout linear voltage stabilizing circuit and electronic equipment. Comprising a control module and a current adjusting tube. The control module comprises a sampling circuit, a comparison amplifying circuit and a driving circuit; a first end of the sampling circuit is connected with an output voltage end, and a second end is connected with a reference end of the comparison amplification circuit; the output end of the comparison amplifying circuit is connected with the base of the driving circuit, the collector of the driving circuit is connected with the base of the current adjusting tube, and the collector of the current adjusting tube serves as an output voltage end; the control module carries out voltage division sampling on the output voltage through the sampling circuit, a feedback signal is generated after the output voltage is compared with the internal reference voltage through the comparison amplification circuit, and the driving circuit adjusts the conduction state of the current adjusting tube so as to adjust the input and output voltage difference. The voltage stabilizing function is achieved, meanwhile, the voltage difference is remarkably reduced, the voltage difference limitation of a traditional linear voltage stabilizer is broken through, the energy efficiency requirement of a low-power-consumption scene is met, and the reliable and perfect overcurrent and short-circuit protection function is achieved.

Description

Technical Field

[0001] This application relates to the field of power supply technology, specifically to a low dropout linear voltage regulator circuit and electronic equipment. Background Technology

[0002] Traditional linear voltage regulators (such as the 78XX series, LM1117, LT108X, etc.) are generally based on an emitter follower architecture. Their regulator transistors need to maintain a base-emitter voltage (VBE≥0.7V), resulting in an input-output voltage difference that must be higher than 1.5V to maintain linear regulation. For example, while the ME6206's voltage difference drops to 0.38V under a 200mA load, its maximum output current is only 300mA, and the voltage difference increases exponentially with increasing load (voltage difference >1.2V at 500mA). This inherent characteristic of the architecture makes the device unable to operate stably in low-voltage input scenarios (such as lithium battery power supply) due to insufficient voltage difference. Simultaneously, the excessively high on-resistance of the regulator transistor leads to a surge in power consumption (efficiency <45%), severely limiting power supply efficiency.

[0003] In addition, traditional devices lack an active short-circuit current suppression mechanism. When a short circuit occurs at the output, the current of the regulating tube instantly exceeds 2A (such as the typical value of LM1117), which causes the device to fail thermally. An additional overcurrent protection circuit is required, which further increases the system complexity and cost.

[0004] In summary, existing linear voltage regulation technologies suffer from drawbacks such as large input-output voltage difference, low energy efficiency, and lack of safety protection. Summary of the Invention

[0005] In view of this, the embodiments of this application provide a low dropout linear regulator circuit and electronic device, which significantly reduces the dropout while achieving the voltage regulation function, breaks through the dropout limitation of traditional linear regulators, meets the energy efficiency requirements of low power consumption scenarios, and has reliable and complete overcurrent and short circuit protection functions.

[0006] A first aspect of this application provides a low dropout linear voltage regulator circuit, including a control module and a current regulating transistor;

[0007] The control module includes a sampling circuit, a comparison amplification circuit, and a driving circuit;

[0008] The first terminal of the sampling circuit is connected to the output voltage terminal, and the second terminal is connected to the reference terminal of the comparator amplifier circuit.

[0009] The output terminal of the comparator amplifier circuit is connected to the base of the driver circuit, the collector of the driver circuit is connected to the base of the current regulating transistor, and the collector of the current regulating transistor serves as the output voltage terminal.

[0010] The control module performs voltage division sampling on the output voltage through a sampling circuit, and after comparison with the internal reference voltage through a comparison amplification circuit, a feedback signal is generated. The driving circuit adjusts the conduction state of the current regulating tube to regulate the input-output voltage difference.

[0011] In one embodiment, the reference terminal of the comparator amplifier circuit is connected to the second terminal of the sampling circuit, the second terminal of the sampling circuit is the voltage divider node of the sampling circuit, the cathode of the comparator amplifier circuit is connected to the first terminal of the sampling circuit through a third resistor, and is connected to the base of the driving circuit and one end of a first resistor through a second resistor, and the other end of the first resistor is connected to the collector of the driving circuit.

[0012] In one embodiment, the driving circuit is an NPN transistor, with the emitter of the driving circuit grounded through a sixth resistor, the base connected to the cathode of the comparator amplifier circuit, and the collector connected to the base of the current regulating transistor.

[0013] In one embodiment, the current regulating transistor is a PNP transistor, with its emitter connected to the input voltage terminal, its collector connected to the output voltage terminal, and its base connected to the collector of the driving circuit.

[0014] In one embodiment, a Zener diode is further included, the anode of which is connected to the emitter of the driving circuit, and the cathode of which is connected to the first terminal of the sampling circuit.

[0015] In one embodiment, the system further includes a filter capacitor bank, comprising a first capacitor and a second capacitor connected in parallel between the input voltage terminal and ground, and a third capacitor and a fourth capacitor connected in parallel between the output voltage terminal and ground.

[0016] A second aspect of this application provides an electronic device including a low-dropout linear regulator circuit as provided in the first aspect of this application.

[0017] The low-dropout linear voltage regulator circuit provided in the first aspect of this application includes a control module and a current regulating transistor. The control module includes a sampling circuit, a comparison amplification circuit, and a driving circuit. A first terminal of the sampling circuit is connected to the output voltage terminal, and a second terminal is connected to the reference terminal of the comparison amplification circuit. The output terminal of the comparison amplification circuit is connected to the base of the driving circuit, and the collector of the driving circuit is connected to the base of the current regulating transistor. The collector of the current regulating transistor serves as the output voltage terminal. The control module performs voltage division sampling on the output voltage through the sampling circuit, compares it with an internal reference voltage through the comparison amplification circuit to generate a feedback signal, and the driving circuit adjusts the conduction state of the current regulating transistor to regulate the input-output voltage difference. Through the two-stage closed-loop architecture of "control module-regulating transistor", the voltage drop is significantly reduced while achieving voltage regulation. The sampling circuit monitors the output voltage in real time and generates a feedback signal by amplifying the error, dynamically adjusting the conduction state of the regulating transistor. The direct connection of the regulating transistor's collector to the load eliminates the additional voltage drop of traditional emitter follower structures and optimizes the conduction path impedance. The adaptive mechanism of closed-loop control ensures that the input voltage always approaches the minimum critical value of the output voltage, maintaining a stable voltage difference over a wide load range. This architecture, through the synergistic optimization of control loop response characteristics and conduction path, overcomes the voltage difference limitations of traditional linear regulators, meeting the energy efficiency requirements of low-power scenarios. Simultaneously, the control module monitors the output voltage status in real time. When a short circuit is detected at the output, the drive circuit rapidly reduces the base drive level of the regulating transistor, forcing it out of the saturation region and into a low-current amplification state. This dynamic adjustment mechanism limits the short-circuit current to the nonlinear decay range of the regulating transistor's β value. Compared to traditional regulators that rely on fixed threshold triggering for protection, this solution utilizes the bandwidth advantage of the control loop to achieve a μs-level response, completely eliminating the dangerous condition of the regulating transistor continuously conducting during a short circuit, reducing the peak short-circuit current, and eliminating the need for external protection circuits, thus balancing safety and cost-effectiveness.

[0018] It is understandable that the beneficial effects of the second aspect mentioned above can be found in the relevant descriptions in the first aspect mentioned above, and will not be repeated here. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the control section connection of a low dropout linear voltage regulator circuit provided in an embodiment of this application;

[0021] Figure 2This is a schematic diagram of a typical application circuit of the low dropout linear regulator circuit provided in an embodiment of this application. Detailed Implementation

[0022] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of this application with unnecessary detail.

[0023] It should also be understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0024] Furthermore, in the description of this application and the appended claims, the terms "first," "second," "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0025] References to "one embodiment" or "some embodiments" as described in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0026] like Figure 1 As shown, this application embodiment provides a low dropout linear regulator circuit, including a control module IC1 and a current adjustment transistor TR2;

[0027] The control module IC1 includes a sampling circuit, namely a sampling circuit composed of resistors R4 and R5, a comparison amplifier circuit TL431, and a driver circuit TR1;

[0028] The first terminal of sampling circuit R4 and R5 is connected to the output voltage terminal Vout, and the second terminal is connected to the reference terminal REF of the comparator amplifier circuit TL431.

[0029] The cathode of the output terminal of the comparator amplifier circuit TL431 is connected to the base of the driver circuit TR1, the collector of the driver circuit TR1 is connected to the base of the current regulating transistor TR2, and the collector of the current regulating transistor TR2 serves as the output voltage terminal.

[0030] The control module IC1 samples the output voltage through sampling circuits R4 and R5, and after comparison with the internal reference voltage of 2.5V by the comparison amplifier circuit TL431, a feedback signal is generated. The driving circuit TR1 adjusts the conduction state of the current regulating transistor TR2 to regulate the input-output voltage difference.

[0031] In the application, the output voltage is sampled by the sampling circuit composed of R4 and R5. Under normal circumstances, the sampling signal voltage sent to the reference pin of IC1 is 2.5V. The Zener diode Z1 is usually selected to be about 2 / 3 of the output voltage to control the minimum emitter voltage of TR1.

[0032] R1 provides the initial base current for the operation of TR1. Subsequently, R2, R3, and IC1 work together to provide the base bias current for the base of TR1 during the voltage regulation process.

[0033] A typical application circuit diagram of a low dropout linear regulator is shown below. Figure 2 As shown, the regulating transistor TR2 here is a PNP transistor. Pin 1 of the module controls the base of the regulating transistor, pin 2 samples the output voltage, and pin 3 is grounded.

[0034] This application embodiment includes a control module and a current regulating transistor. The control module includes a sampling circuit, a comparison amplification circuit, and a driving circuit. The first terminal of the sampling circuit is connected to the output voltage terminal, and the second terminal is connected to the reference terminal of the comparison amplification circuit. The output terminal of the comparison amplification circuit is connected to the base of the driving circuit, and the collector of the driving circuit is connected to the base of the current regulating transistor. The collector of the current regulating transistor serves as the output voltage terminal. The control module performs voltage division sampling on the output voltage through the sampling circuit, compares it with the internal reference voltage through the comparison amplification circuit to generate a feedback signal, and the driving circuit adjusts the conduction state of the current regulating transistor to regulate the input-output voltage difference. Through the two-stage closed-loop architecture of "control module-regulating transistor", the voltage difference is significantly reduced while achieving voltage regulation. The sampling circuit monitors the output voltage in real time, and combines it with error amplification to generate a feedback signal to dynamically adjust the conduction state of the regulating transistor. The design of the regulating transistor's collector being directly connected to the load eliminates the additional voltage drop of the traditional emitter follower structure and optimizes the conduction path impedance. The adaptive mechanism of the closed-loop control ensures that the input voltage always approaches the minimum critical value of the output voltage, maintaining a stable voltage difference over a wide load range. This architecture overcomes the voltage drop limitation of traditional linear regulators by co-optimizing the control loop response characteristics and conduction path, thus meeting the energy efficiency requirements of low-power scenarios.

[0035] In one embodiment, the reference terminal REF of the comparator amplifier circuit TL431 is connected to the second terminal of the sampling circuit, which is the midpoint of the voltage divider nodes R4 and R5 of the sampling circuit. The cathode of the comparator amplifier circuit TL431 is connected to the first terminal of the sampling circuit through the third resistor R3, and to the base of the driving circuit TR1 and one end of the first resistor R1 through the second resistor R2. The other end of the first resistor R1 is connected to the collector of the driving circuit TR1.

[0036] This embodiment creatively constructs a dual current path by setting up a dual-resistor network (R2 / R3) in the TL431 feedback loop. The voltage divider node is directly connected to the reference source terminal, enabling millivolt-level error detection of the output voltage. R3 serves as an error signal transmission channel, forming a sudden impedance change path when the output voltage fluctuates, causing a step change in the base voltage of the driver transistor, resulting in higher sensitivity than the traditional single-resistor feedback scheme. The base bias function of R2 ensures that the driver transistor maintains its linear operating region under extreme conditions, avoiding false triggering of the protection mechanism.

[0037] In one embodiment, the driving circuit TR1 is an NPN transistor. The emitter of the driving circuit TR1 is grounded to GND through the sixth resistor R6, the base is connected to the cathode of the comparator amplifier circuit TL431, and the collector is connected to the base of the current regulating transistor TR2.

[0038] This embodiment of the application forms a precision current mirror structure by combining an NPN type driver transistor with an emitter resistor R6. R6 limits the maximum emitter current of the driver transistor through negative feedback, controlling the base drive current of the regulating transistor within a safe threshold, effectively solving the thermal runaway problem that traditional LDOs are prone to during load surges. This design reduces the short-circuit protection response time to the microsecond level, and through the direct coupling of the collector potential of TR1 and the base potential of TR2, achieves synchronous state control of the two transistor stages, significantly enhancing system stability.

[0039] In one embodiment, the current regulating transistor TR2 is a PNP transistor. The emitter of the current regulating transistor TR2 is connected to the input voltage terminal Vin, the collector is connected to the output voltage terminal Vout, and the base is connected to the collector of the driving circuit TR1.

[0040] The regulating transistor in this embodiment adopts an emitter-in, collector-output PNP transistor topology, fully utilizing the low input impedance characteristics of the common-base circuit. This configuration enables the regulating transistor to exhibit switch-like characteristics when saturated, greatly reducing conduction losses. Simultaneously, the base drive signal directly originates from the high-swing voltage of the preceding collector, overcoming the low β value of the PNP transistor and ensuring that the voltage difference remains within a low range even under a 2A high-current output.

[0041] In one embodiment, a Zener diode Z1 is also included, with the anode of the Zener diode Z1 connected to the emitter of the driving circuit TR1 and the cathode connected to the first terminal of the sampling circuit.

[0042] In this embodiment, the Zener diode Z1 establishes a dynamic voltage clamp at the emitter of the driver diode, forming a dual protection mechanism: on the one hand, it locks the minimum emitter voltage of TR1 at 2 / 3 of the output voltage to prevent recovery delay caused by deep saturation; on the other hand, when the output is short-circuited, it forms a voltage divider network with R6, forcing the driver diode out of the saturation region. This design enables the circuit to maintain effective control even when the input voltage drops to a critical value, thus extending the operating voltage range.

[0043] In one embodiment, the system further includes a filter capacitor group C1, C2, C3, and C4, comprising a first capacitor C1 and a second capacitor C2 connected in parallel between the input voltage terminal Vin and ground GND, and a third capacitor C3 and a fourth capacitor C4 connected in parallel between the output voltage terminal Vout and ground GND.

[0044] The four-capacitor combined filtering scheme in this application achieves full-band noise suppression through differentiated parameter design: C1 / C2 can handle kHz-level switching noise, while C3 / C4 can filter out MHz-level high-frequency interference. The π-type filter structure at the input / output terminals generates a ripple rejection ratio of over 60dB, making it particularly suitable for powering noise-sensitive circuits such as ADCs and RF modules.

[0045] The working principle of this application embodiment is as follows:

[0046] Scenario 1

[0047] When the output voltage decreases, and the sampling signal voltage (REF terminal of TR1) is less than 2.5V, there is only 1mA of current between the anode and cathode of IC1, with no pull-down effect. The current flows through pin 2, R3, R2, the emitter junction of TR1, and R6 to ground, keeping TR1 in the ON state. This causes the control signal voltage at pin 1 to decrease. Figure 2 When the regulating transistor TR2 is turned on, the output voltage increases.

[0048] In the application, when the output voltage is at the preset value, the voltage sampled by the voltage divider network (R4 / R5) is lower than the 2.5V reference of TL431 (IC1). At this time, IC1 maintains a high impedance state between the cathode and anode (only 1mA level leakage current), the voltage drop of R3 is extremely small, and the base of TR1 obtains sufficient drive current (about 5mA) through R2, making it in a deep saturation conduction state. The collector voltage Vc1 is pulled down to below 0.3V. This low-level signal acts on the base of the PNP type regulating transistor TR2, making its emitter junction forward bias voltage Veb reach above 0.7V. TR2 enters the full conduction mode (saturation voltage drop ≤0.3V), and the input voltage Vin is stably output to the load through the low impedance path of TR2. At this time, the system is in a closed-loop voltage regulation balance state.

[0049] Scenario 2

[0050] When the output voltage increases, and the sampling signal voltage (REF terminal of TR1) reaches or exceeds 2.5V, with a small change in the REF terminal voltage, the current flowing between the anode and cathode of TR1 will change from 1mA to 100mA. IC1 is in a pull-down state, and the current to ground through pin 2, R3, and IC1 increases. The base voltage supplied to TR1 through R2 decreases, and the collector voltage increases, meaning the control signal voltage at pin 1 increases. Figure 2 When the base voltage of the regulating transistor TR2 rises, its conduction state changes, and the output voltage drops.

[0051] In applications, when the output voltage Vout increases due to load changes or input fluctuations, the sampling voltage of the voltage divider network (R4 / R5) exceeds the 2.5V reference inside TL431 (IC1), triggering a sudden drop in the cathode-anode impedance of IC1 (from megaohms to hundreds of ohms), forming a low-impedance path Vout→R3→IC1→GND. The current flowing through R3 surges from 1mA to 100mA; the voltage drop across R3 ΔV_R3 (=I_cathode×R3) increases significantly, causing the base voltage Vb1 of TR1 to drop from 0... When the voltage drops from 0.7V to below 0.4V, TR1 is forced to exit the saturation region and enter the amplification state. Its collector voltage Vc1 jumps from 0.3V to near Vin (e.g., 11.5V in a 12V system). This high-level signal is applied to the base of the PNP regulating transistor TR2, causing the forward bias voltage Veb of the TR2 emitter junction to drop from 0.7V to below 0.5V. The conduction level weakens, and the collector-emitter equivalent resistance Rce increases. Finally, through negative feedback regulation of ΔVout=Vin-Iout×Rce, the output voltage drops back to the preset value.

[0052] Scenario 3

[0053] When the output terminal is short-circuited, i.e., pins 2 and 3 are short-circuited, the base voltage of TR1 provided by R2 decreases rapidly after voltage division by R3 and IC1. The base of TR1 can only obtain a small current from pin 1 through R1, resulting in a higher output voltage at pin 1. The regulating transistor TR2 enters the small current amplification state from the saturation state.

[0054] Regarding overload protection: The maximum output current of this circuit is the product of the current when TR1 is on and the current amplification factor β2 of the regulating transistor TR2. The maximum current when TR1 is on is determined by the output voltage, the current amplification factor β1 of TR1, and resistor R6. Therefore, the maximum output current of this voltage regulator circuit is controllable, typically reaching 2A. When the overload is severe and the required output current exceeds the circuit's maximum output current, the output voltage will inevitably decrease, thus achieving overload protection.

[0055] In applications, when a short circuit occurs at the output (pins 2 and 3 short circuit), the circuit achieves protection through the following closed-loop regulation process:

[0056] The output voltage Vout drops sharply to near zero potential, causing the sampling voltage at the REF terminal of the error amplifier IC1 (such as TL431) to fall below the reference value. Its cathode-anode impedance rises sharply, and the current flowing through R3 drops sharply from the mA level in normal conditions to the μA level, causing the voltage drop across R3 to disappear. At this time, the base voltage of TR1 can only obtain a weak current through R1 due to the failure of the main power supply path (Vout→R2). The base potential Vb1 drops below 0.2V, causing the NPN type TR1 to leave the saturation region and enter the critical cutoff state. The electrode voltage Vc1 rapidly rises to near the power supply voltage. This voltage signal is transmitted to the base of the PNP regulating transistor TR2, causing the emitter junction bias voltage Veb to approach the conduction threshold (0.7V). This forces TR2 to exit the saturation conduction state and enter the low current amplification region. The collector current is limited by the small base drive current provided by TR1, ultimately suppressing the short-circuit current to below 100mA. Simultaneously, the cutoff state of IC1 and the current limiting effect of TR2 form a positive feedback lockout mechanism, ensuring that the protection state continues until manual reset after the short-circuit fault is cleared. This process is completed within microseconds, achieving lossless current limiting through the linkage of three transistors, combining fast response and thermal stability.

[0057] This application also provides an electronic device, including a low-dropout linear regulator circuit as provided in the first aspect of this application.

[0058] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0059] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A low dropout linear voltage regulator circuit, characterized by comprising: The low-voltage-difference linear voltage stabilizing circuit comprises a control module and a current adjusting tube. The control module comprises a sampling circuit, a comparison amplification circuit and a driving circuit. The first end of the sampling circuit is connected to an output voltage terminal, and the second end is connected to the reference terminal of the comparison amplification circuit. The output terminal of the comparison amplification circuit is connected to the base of the driving circuit, the collector of the driving circuit is connected to the base of the current adjusting tube, and the collector of the current adjusting tube serves as the output voltage terminal. The control module samples the output voltage through the sampling circuit, compares the voltage with an internal reference voltage through the comparison amplification circuit to generate a feedback signal, and adjusts the on-off state of the current adjusting tube through the driving circuit to adjust the input-output voltage difference.

2. The low dropout linear regulator circuit of claim 1, wherein, The reference terminal of the comparison amplification circuit is connected to the second end of the sampling circuit, the second end of the sampling circuit is a voltage dividing node of the sampling circuit, the cathode of the comparison amplification circuit is connected to the first end of the sampling circuit through a third resistor and to the base of the driving circuit and one end of a first resistor through a second resistor, and the other end of the first resistor is connected to the collector of the driving circuit.

3. The low dropout linear regulator circuit of claim 1, wherein, The driving circuit is an NPN transistor, the emitter of the driving circuit is connected to ground through a sixth resistor, the base is connected to the cathode of the comparison amplification circuit, and the collector is connected to the base of the current adjusting tube.

4. The low dropout linear regulator of claim 1, wherein, The current adjusting tube is a PNP transistor, the emitter of the current adjusting tube is connected to an input voltage terminal, the collector is connected to an output voltage terminal, and the base is connected to the collector of the driving circuit.

5. The low dropout linear regulator of claim 1, wherein, The low-voltage-difference linear voltage stabilizing circuit further comprises a voltage stabilizing tube, the anode of the voltage stabilizing tube is connected to the emitter of the driving circuit, and the cathode is connected to the first end of the sampling circuit.

6. The low dropout linear regulator of claim 1, wherein, The low-voltage-difference linear voltage stabilizing circuit further comprises a filter capacitor group, which comprises a first capacitor and a second capacitor connected in parallel between the input voltage terminal and ground, and a third capacitor and a fourth capacitor connected in parallel between the output voltage terminal and ground.

7. An electronic device, comprising: The low-voltage-difference linear voltage stabilizing circuit comprises the low-voltage-difference linear voltage stabilizing circuit according to any one of claims 1 to 6.

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