LDO (Low Dropout Regulator) power supply output regulating circuit and method and power supply device

Abstract

The invention discloses an LDO power supply output adjusting circuit and method and a power supply device in the technical field of power supply control, the adjusting circuit comprises an LDO power supply, a feedback circuit and a control circuit, the feedback circuit comprises a first divider resistor and a second divider resistor, the first divider resistor is connected between the feedback end and the output end of the LDO power supply, and the second divider resistor is connected between the feedback end and the output end of the LDO power supply. The first divider resistor is connected between the feedback end of the LDO power supply and the ground wire, the second divider resistor is connected between the feedback end of the LDO power supply and the ground wire, the connection point of the first divider resistor and the second divider resistor forms a divider node, the regulating circuit provides a simple and convenient circuit for regulating the output voltage of the program-controlled LDO power supply, the implementation process is free of a high-cost LDO chip and a redundant external microcontroller, and the regulating circuit is suitable for large-scale popularization and application. The LDO power supply can be realized through a micro-controlled DAC interface or a communication + DAC output chip in the control circuit, the control can realize the function of outputting different output voltages by one LDO power supply, and the use range of the LDO is fully expanded.

Description

Technical Field

[0001] This invention relates to the field of power control technology, specifically to an LDO power output regulation circuit, method, and power supply device. Background Technology

[0002] With the development of electronic technology, the types of circuit control are gradually increasing. Each control circuit cannot do without a power supply. However, considering cost and reliability factors, most control boards generally use low-cost LDO power supplies (low dropout linear regulators) to power the control board. The output ripple of LDO is smaller than that of switching power supplies, which can better meet the needs of the control board. However, due to the large variety of internal components in the control circuit, the power supply range of different component types is inconsistent, which leads to the need for multiple LDO power supplies to output different voltages to meet the normal operation of the control board.

[0003] Currently, adjustable LDO output voltage generally comes in two forms. One method involves acquiring the output voltage through the LDO chip's own FB feedback pin to achieve variable output voltage. However, this method usually requires a variable resistor in the LDO's FB feedback circuit. By changing different resistance values, the output voltage can be changed. This method is suitable for the product testing phase and can be manually adjusted. However, once the product is in mass production, if each product needs to be manually adjusted, it will increase labor costs and affect production efficiency, severely impacting production. The other method involves directly purchasing the power supply chip of the control chip integrated into the LDO. This allows communication with the microcontroller in the control circuit, enabling adjustable LDO output power through communication control. However, this type of LDO is usually more expensive, which contradicts the requirement of low-cost LDO power supply selection. Summary of the Invention

[0004] The purpose of this invention is to provide an LDO power output regulation circuit, method, and power supply device, which solves the problems of cost and output efficiency of the LDO power output regulation function in the prior art.

[0005] The present invention achieves the above objectives through the following technical solutions: An LDO power output regulation circuit, including An LDO power supply includes an input terminal, an output terminal, and a feedback terminal. The feedback circuit includes a first voltage divider resistor and a second voltage divider resistor. The first voltage divider resistor is connected between the feedback terminal and the output terminal of the LDO power supply, and the second voltage divider resistor is connected between the feedback terminal and the ground wire of the LDO power supply. The connection point of the first voltage divider resistor and the second voltage divider resistor forms a voltage divider node. A control circuit is used to output a program-controlled regulating voltage to the voltage divider node to regulate the current flowing through the first voltage divider resistor, thereby regulating the output voltage of the LDO power supply output terminal.

[0006] As a preferred embodiment of the present invention, the input terminal of the LDO power supply is connected to diode number one, the cathode of diode number one is connected to the input terminal, and diode number one is used for reverse protection at the input terminal.

[0007] In a preferred embodiment of the present invention, the control circuit includes a regulating voltage output unit and a current-limiting resistor. The regulating voltage output unit is used to output the required regulating voltage through program control. The current-limiting resistor is used to limit the current output by the regulating voltage output unit. It is controlled by a program, specifically a microcontroller with communication or DAC functions. The controller is programmed and controlled through the communication function, which allows for batch settings, improves efficiency, and ensures that each control circuit outputs a regulating voltage. The microcontroller is inexpensive, and the batch settings through the communication function effectively reduce labor costs. The selection of the current-limiting resistor R3 needs to consider the overall voltage division ratio to obtain a larger regulation range.

[0008] As a preferred embodiment of the present invention, the control circuit further includes a second diode, the cathode of which is connected to the voltage divider node. The second diode is used to prevent the reference voltage VF of the LDO from flowing back to the control voltage output unit when the control voltage output unit is not working or is not enabled, thus preventing the control voltage output unit from malfunctioning. However, the second diode D2 itself has a voltage drop, which will affect the actual function of the control voltage output by the control circuit at the voltage divider node. Therefore, when selecting the second diode D2, a diode with a smaller voltage drop should be selected as much as possible, as this voltage drop affects the adjustment range of the analog quantity of the control voltage output unit.

[0009] As a preferred embodiment of the present invention, the adjustable voltage output unit is a DAC chip or an MCU controller with DAC pins. The DAC chip / MCU controller is used to control the output of an adjustable voltage through a set program. The DAC chip or MCU controller should preferably be a chip with strong load-carrying capacity.

[0010] As a preferred embodiment of the present invention, the output voltage of the LDO power supply is obtained based on the following formula: ; in, This refers to the output voltage of the LDO power supply. This is the reference voltage at the feedback terminal of the LDO power supply; It is the regulating voltage output by the regulating voltage output unit; This is the voltage drop across diode number two; It is the resistance value of the first voltage divider resistor; This is the resistance value of the second voltage divider resistor; It is the resistance value of the current-limiting resistor.

[0011] On the one hand, the present invention also proposes an adjustment method based on the above-mentioned LDO power output adjustment circuit, comprising the following steps: Obtain the target output voltage at the LDO power supply output terminal, and determine the control voltage of the control circuit based on the target output voltage and the resistance values ​​of the current limiting resistor, the first voltage divider resistor, and the second voltage divider resistor. The control circuit executes the program and outputs the regulated voltage between the two voltage divider resistors, causing the feedback voltage of the LDO power supply to deviate from the reference voltage. The LDO power supply adjusts the output voltage to bring the feedback voltage closer to the reference voltage. When the feedback voltage equals the reference voltage, the LDO power supply output voltage no longer needs adjustment, and the target output voltage is obtained for output.

[0012] As a preferred embodiment of the present invention, determining the regulating voltage of the control circuit based on the target output voltage and the resistance values ​​of the current-limiting resistor, the first voltage-dividing resistor, and the second voltage-dividing resistor includes: The current value flowing through the first voltage divider resistor is obtained based on the target output voltage and the reference voltage, and the current value flowing through the second voltage divider resistor is obtained based on the reference voltage; The current value flowing through the current-limiting resistor is obtained based on the current value flowing through the second voltage divider resistor and the current value flowing through the first voltage divider resistor. The voltage difference across the current-limiting resistor is obtained based on the current value flowing through the current-limiting resistor and the resistance value of the current-limiting resistor. The required input control voltage is determined based on the voltage difference across the current-limiting resistor and the reference voltage. This adjustment method constructs the relationship between voltage and current through circuit characteristics, and calculates the control voltage required for the MCU controller output based on this relationship, thereby achieving the adjustment method of the LDO power supply output voltage.

[0013] On the other hand, the present invention also proposes a power supply device, including the above-mentioned LDO power output regulation circuit, which can be a power supply module of the central control device of a new energy vehicle, used to supply power to the central control device.

[0014] The beneficial effects of this invention are as follows: This invention provides a simple circuit for adjustable output voltage of a programmable LDO power supply. The process does not require a high-cost LDO chip or an unnecessary external microcontroller. It can be achieved through the internal microcontroller's DAC interface or communication + DAC output chip. This control can realize the function of different output voltages of an LDO power supply, which greatly improves the application range of LDO. The circuit is simple, uses fewer types and quantities of components, and has a high degree of integration.

[0015] This invention outputs a programmable adjustable voltage through the DAC pin of the MCU controller. This voltage acts on the voltage divider node, allowing control over the current values ​​of the first and second voltage divider resistors. Within the adjustable range, the output voltage of the LDO can be infinitely adjusted with high precision and low cost. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the control logic of the present invention; Figure 2 This is a circuit diagram of the present invention; Figure 3 This is a schematic diagram of a specific control circuit of the present invention; In the diagram: D1: Diode 1; D2: Diode 2; R1: First voltage divider resistor; R2: Second voltage divider resistor; R3: Current limiting resistor. Detailed Implementation

[0017] The present application will now be described in further detail with reference to the accompanying drawings. It should be noted that the following specific embodiments are only used to further illustrate the present application and should not be construed as limiting the scope of protection of the present application. Those skilled in the art can make some non-essential improvements and adjustments to the present application based on the above application content.

[0018] Example 1 like Figure 1-2 As shown, an LDO power supply output regulation circuit includes an LDO power supply, a feedback circuit, and a control circuit. An LDO power supply includes an input terminal, an output terminal, and a feedback terminal; The feedback circuit includes a first voltage divider resistor R1 and a second voltage divider resistor R2. The first voltage divider resistor R1 is connected between the feedback terminal FB and the output terminal OUT of the LDO power supply, and the second voltage divider resistor R2 is connected between the feedback terminal FB and the ground wire of the LDO power supply. The connection point of the first voltage divider resistor R1 and the second voltage divider resistor R2 forms a voltage divider node. The control circuit outputs a program-controlled regulating voltage to the voltage divider node between the first voltage divider resistor R1 and the second voltage divider resistor R2, so as to regulate the current flowing through the first voltage divider resistor R1, and thus regulate the output voltage of the LDO power supply output terminal.

[0019] An LDO power supply is a low-voltage linear DC regulator. Its core function is to convert the input voltage (such as 5V) into a lower and more stable output voltage (such as 3.3V). Its key advantages are extremely small voltage drop, with the input / output voltage difference as low as tens of millivolts. At the same time, it has low output ripple noise, making it suitable for scenarios with high requirements for power purity.

[0020] This solution provides a simple circuit for adjustable output voltage of a programmable LDO power supply. The implementation process does not require the use of high-cost LDO chips and redundant external microcontrollers. It can be achieved through the internal micro-controller DAC interface or communication + DAC output chip of the control circuit. This control method can realize the function of different output voltages of an LDO power supply, which greatly improves the application range of LDO power supply. At the same time, the circuit is simple, uses fewer types and numbers of components, has a high degree of integration, and is easy to implement.

[0021] In one implementation, the input terminal of the LDO power supply in this embodiment is used to connect to an external power supply, and a diode D1 is also provided between the input terminal and the external power supply. The cathode of the diode D1 is connected to the input terminal. The diode D1 is used to prevent reverse polarity at the input terminal of the LDO power supply. The external power supply also has a ground terminal.

[0022] For further information, see Figure 3 This embodiment proposes a control circuit, which includes a regulating voltage output unit and a current-limiting resistor R3. The regulating voltage output unit is used to output a regulating voltage and is controlled by a program, specifically a microcontroller with communication or DAC functions. The current-limiting resistor R3 is used to limit the output current of the regulating voltage output unit and also serves as another voltage divider resistor, which is optional. The selection of the current-limiting resistor R3 needs to consider the overall voltage division ratio to obtain a larger regulation range. In the specific implementation process, the controller is programmed and controlled through the communication function. The communication function allows for batch settings, improving efficiency and ensuring that each control circuit outputs a regulating voltage. This microcontroller is inexpensive, and the batch setting through the communication function effectively reduces labor costs, significantly reducing the overall cost of LDO power supply output voltage regulation.

[0023] The expandable control circuit also includes diode D2. The cathode of diode D2 is connected to the voltage divider node. Diode D2 is used to prevent the LDO's reference voltage VF from flowing back into the voltage divider unit when the voltage output unit is not working or not in use, which could cause the voltage output unit to malfunction. However, diode D2 itself has a voltage drop, which will affect the actual function of the control circuit's output voltage at the voltage divider node. Therefore, when selecting diode D2, a diode with a smaller voltage drop should be selected as much as possible. This voltage drop affects the adjustment range of the analog quantity of the voltage output unit. The diode clamping information is available in the product manual and can be obtained directly or through testing.

[0024] Specifically, the voltage regulation output unit in this embodiment can be set as a DAC chip or an MCU controller with DAC pins. This embodiment takes an MCU controller with DAC pins as an example. According to the output voltage required by the LDO power supply, the regulation voltage that needs to be input to the voltage divider node is calculated by the program. Then, the MCU controller is controlled by the program to output the required regulation voltage. The DAC chip or MCU controller should be selected as a chip with strong load capacity as much as possible so that it can load the second diode D2, the current limiting resistor R3 and the second voltage divider resistor R2. It should be noted that although the MCU controller can directly output an adjustable voltage, it is unstable due to load changes. If it is used for output, the output voltage of the MCU controller will also change when the load of the external circuit changes. Furthermore, the output current of the MCU controller is in the milliampere range. Therefore, it cannot be directly used in circuits with unstable loads and large currents. This solution uses it to regulate the feedback terminal of the LDO power supply in a stable load environment. Under this load, there are only diode D2, current-limiting resistor R3, and second voltage divider resistor R2. Their resistance and voltage drop are all fixed values, and they will not cause fluctuations in the regulated voltage output of the MCU controller during stable operation.

[0025] The control logic in this embodiment is as follows: The normal output voltage of the LDO power supply is mainly determined by the voltage division ratio of the first voltage divider resistor R1 and the second voltage divider resistor R2. When the MCU controller DAC does not output the control voltage, the LDO output voltage formula is as shown in equation (1): (1) However, this method can only output a fixed voltage, which is also a commonly used voltage divider method in the prior art. This voltage divider method relies on the resistance adjustment of the first voltage divider resistor R1 and the second voltage divider resistor R2. In actual production, the efficiency of adjusting each product is low and it is not suitable for mass production. The method of adjustment in this implementation is the same as the prior art scheme of adjusting voltage only through the first voltage divider resistor R1 and the second voltage divider resistor R2 when the MCU controller DAC does not output the control voltage. At this time, the LDO power supply output voltage is at the upper limit of the adjustment range.

[0026] When an adjustable output voltage is required: The MCU controller controls the output of an adjustable analog signal via the DAC output pin. This voltage, after passing through current-limiting resistor R3 and diode D2, is connected to the voltage divider node of the first voltage divider resistor R1 and the second voltage divider resistor R2. Since the reference voltage VF inside the LDO power supply remains constant, when the sampling pin of the feedback terminal FB detects a voltage deviation from the reference voltage VF, the output voltage is adjusted. This ensures that the voltage collected at the feedback terminal FB equals the reference voltage VF. Therefore, it can be analyzed that when the circuit tends to stabilize: The current flowing through the second voltage divider resistor R2 = the current flowing through the first voltage divider resistor R1 + the current flowing through the current limiting resistor R3 and the second diode D2. The voltage drop of the second diode D2 is VD, therefore we can derive equation (2): (2) Further, we can derive equation (3): (3) in, The output voltage of the LDO power supply is regulated by the voltage sampled at the feedback terminal. When the voltage sampled at the feedback terminal deviates from the reference voltage, the LDO power supply directionally regulates the output voltage to maintain the voltage at the feedback terminal. Return to reference voltage; The reference voltage for the feedback terminal of the LDO power supply is provided in the LDO power supply manufacturer's manual and remains unchanged. It is the regulating voltage output by the regulating voltage output unit, which can be controlled and adjusted by the MCU controller to obtain the required voltage according to the needs of the circuit board. Then, the result can be obtained by calculation using equation (3). By adjusting the voltage output by the programmable controller of the voltage output unit, the output of the LDO power supply can be controlled to output the required voltage. ; The voltage drop across diode D2 is provided in the diode manual and remains constant. It is the resistance value of the first voltage divider resistor R1; It is the resistance value of the second voltage divider resistor R2; This is the resistance value of the current-limiting resistor R3. All of them are fixed resistors.

[0027] As can be seen from equation (3), the output voltage of the LDO power supply Mainly affected It changes with the changes. The larger, The smaller, Output accuracy is affected The adjustment accuracy and the accuracy of the LDO power supply itself are affected.

[0028] It should be noted that the first voltage divider resistor R1 and the second voltage divider resistor R2 should be selected to maximize the voltage division range of the LDO power supply output voltage; the selection of the current limiting resistor R3 needs to take into account the overall voltage division ratio.

[0029] By using the above method, the LDO output can be adjusted by utilizing the DAC output of the MCU controller in the control circuit itself, thus realizing the adjustable function of the programmable LDO power output.

[0030] On the one hand, the present invention also proposes an adjustment method based on the above-mentioned LDO power output adjustment circuit, comprising the following steps: The target output voltage at the LDO power supply output terminal is obtained. Based on the target output voltage and the resistance values ​​of the current-limiting resistor R3, the first voltage divider resistor R1, and the second voltage divider resistor R2, the regulation voltage of the control circuit is determined. Specifically, when this LDO power supply output regulation circuit is applied to a circuit board, the target output voltage at the LDO power supply output terminal is determined according to the required output voltage on the circuit board. ; Furthermore, by setting a program, the control circuit outputs the aforementioned regulating voltage. The control circuit executes this program, outputting the regulating voltage between the two voltage divider resistors, causing the feedback voltage of the LDO power supply to deviate from the reference voltage. LDO power supplies adjust the output voltage. Make the feedback voltage tend towards the reference voltage. Specifically, the MCU controller outputs according to the regulated voltage via program control. The output flows through the current-limiting resistor R3 and diode D2, then acts on the voltage divider node between the first and second voltage divider resistors R1 and R2. The LDO power supply's feedback terminal FB samples the voltage at the voltage divider node; when this voltage equals the reference voltage... LDO power supply output voltage No further adjustments are needed; the target output voltage is obtained and then output.

[0031] In this embodiment, based on the target output voltage The process of determining the control circuit's regulating voltage, based on the resistance values ​​of current-limiting resistor R3, first voltage-dividing resistor R1, and second voltage-dividing resistor R2, specifically includes: [The text abruptly ends here, likely due to an incomplete sentence or missing information.] and reference voltage Obtain the current value flowing through the first voltage divider resistor R1, and the target output voltage. and reference voltage The voltage across the first voltage divider resistor R1 is the current value, and the ratio of this voltage difference to the resistance of the first voltage divider resistor R1 is the current value, based on a reference voltage. Obtain the current value flowing through the second voltage divider resistor R2, and the reference voltage. The current value is the ratio of the voltage difference at the ground terminal of the second voltage divider resistor R2 to the resistance value of the second voltage divider resistor R2. The current value flowing through the current-limiting resistor R3 is obtained based on the current value flowing through the second voltage divider resistor R2 and the current value flowing through the first voltage divider resistor R1, where the current flowing through the second voltage divider resistor R2 = the current flowing through the first voltage divider resistor R1 + the current flowing through the current-limiting resistor R3 and the second diode D2. The voltage difference across the current-limiting resistor R3 is obtained based on the current value flowing through the current-limiting resistor R3 and the resistance value of the current-limiting resistor R3. Finally, the current value is determined based on the voltage difference across the current-limiting resistor R3, the voltage drop across the second diode D2, and the reference voltage. Determine the required input control voltage.

[0032] In this regulation method, the relationship between voltage and current is established through circuit characteristics, and the required control voltage of the MCU controller is calculated and determined based on this relationship, thereby achieving the regulation method of the LDO power supply output voltage.

[0033] On the other hand, the present invention also proposes a power supply device, including the above-mentioned LDO power output regulation circuit. As one embodiment, the power supply device can be a power supply module for the central control device of a new energy vehicle, which is used to supply power to the central control device, or a power supply module for the power control circuit board of a power battery. In another implementation field, the power supply device can also be a power supply module for the controller of an automated production line.

[0034] The above embodiments merely illustrate several implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention.

Claims

1. An LDO power output regulation circuit, characterized in that, include An LDO power supply includes an input terminal, an output terminal, and a feedback terminal. The feedback circuit includes a first voltage divider resistor and a second voltage divider resistor. The first voltage divider resistor is connected between the feedback terminal and the output terminal of the LDO power supply, and the second voltage divider resistor is connected between the feedback terminal and the ground wire of the LDO power supply. The connection point of the first voltage divider resistor and the second voltage divider resistor forms a voltage divider node. A control circuit is used to output a program-controlled regulating voltage to the voltage divider node to regulate the current flowing through the first voltage divider resistor, thereby regulating the output voltage of the LDO power supply output terminal.

2. The LDO power output regulation circuit according to claim 1, characterized in that, The input terminal of the LDO power supply is connected to diode number one, and the cathode of diode number one is connected to the input terminal.

3. The LDO power output regulation circuit according to claim 1, characterized in that, The control circuit includes a regulating voltage output unit and a current-limiting resistor. The regulating voltage output unit is used to output the required regulating voltage through program control, and the current-limiting resistor is used to limit the current output by the regulating voltage output unit.

4. The LDO power output regulation circuit according to claim 3, characterized in that, The control circuit also includes a second diode, the cathode of which is connected to the voltage divider node to prevent voltage backflow from the voltage divider node and regulate the voltage output unit.

5. The LDO power output regulation circuit according to claim 3, characterized in that, The adjustable voltage output unit is a DAC chip or an MCU controller with DAC pins. The DAC chip / MCU controller is used to control the output of an adjustable voltage through a programmed setting.

6. The LDO power output regulation circuit according to claim 4, characterized in that, The output voltage of the LDO power supply is obtained based on the following formula: ； in, This refers to the output voltage of the LDO power supply. This is the reference voltage at the feedback terminal of the LDO power supply; It is the regulating voltage output by the regulating voltage output unit; This is the voltage drop across diode number two; It is the resistance value of the first voltage divider resistor; It is the resistance value of the second voltage divider resistor; It is the resistance value of the current-limiting resistor.

7. An LDO power output regulation method, implemented based on the LDO power output regulation circuit according to any one of claims 1-6, characterized in that, The method includes the following steps: Obtain the target output voltage at the LDO power supply output terminal, and determine the control voltage of the control circuit based on the target output voltage and the resistance values ​​of the current limiting resistor, the first voltage divider resistor, and the second voltage divider resistor. The control circuit executes the program and outputs the regulated voltage between the two voltage divider resistors, causing the feedback voltage of the LDO power supply to deviate from the reference voltage. The LDO power supply adjusts the output voltage to bring the feedback voltage closer to the reference voltage. When the feedback voltage equals the reference voltage, the LDO power supply output voltage no longer needs adjustment, and the target output voltage is obtained for output.

8. The LDO power output regulation method according to claim 7, characterized in that, The step of determining the control circuit's regulating voltage based on the target output voltage and the resistance values ​​of the current-limiting resistor, the first voltage-dividing resistor, and the second voltage-dividing resistor includes: The current value flowing through the first voltage divider resistor is obtained based on the target output voltage and the reference voltage, and the current value flowing through the second voltage divider resistor is obtained based on the reference voltage; The current value flowing through the current-limiting resistor is obtained based on the current value flowing through the second voltage divider resistor and the current value flowing through the first voltage divider resistor. The voltage difference across the current-limiting resistor is obtained based on the current value flowing through the current-limiting resistor and the resistance value of the current-limiting resistor. The required input control voltage is determined based on the voltage difference across the current-limiting resistor and the reference voltage.

9. A power supply device, characterized in that, Includes the LDO power output regulation circuit as described in any one of claims 1-6.

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