Low-cost voltage-adjustable power supply circuit

Abstract

The utility model discloses a low-cost voltage-adjustable power supply circuit, which is characterized in that a power supply input end VIN of the circuit is respectively connected with one end of a first resistor R1 and a collector electrode of an NPN triode Q1, and the other end of the first resistor R1 is respectively connected with one end of a second resistor R2 and a base electrode of the NPN triode Q1; the other end of the second resistor R2, one end of the third resistor R3 and one end of the first capacitor C1 are grounded; the emitter electrode of the NPN triode Q1, the other end of the third resistor R3 and the other end electrode of the first capacitor C1 are all connected with a power supply output end VOUT. According to the utility model, the voltage of the power supply output end VOUT can be flexibly changed only by simply adjusting the resistance values of the first resistor R1 and the second resistor R2; different requirements of various devices or chips in an electronic product on the voltage of a power supply are well met, the low-cost triode is adopted to replace a high-price power supply chip, and the material cost of the electronic product can be greatly reduced.

Description

Technical Field

[0001] The utility model belongs to the technical field of power supply circuits, and particularly relates to a low-cost adjustable voltage power supply circuit. Background Art

[0002] With the development of science and technology and the continuous increase in the complexity of electronic products, the voltages of the power supplies for most internal devices or chips of electronic products are also different, and there are more and more, such as 5V, 3.3V, 2.5V, 1.8V, 1.5V, 1.2V, 1.0V, etc. As a hardware developer, when selecting a power supply chip, it is necessary to consider both meeting the performance design requirements and reducing the material cost. The balance between the two is a topic that hardware developers cannot avoid. The price of power supply chips is not cheap. If we blindly choose the existing power supply chip solutions on the market, it will be impossible to better reduce the material cost of electronic products. Content of the Utility Model

[0003] To achieve the above object, the technical solution of the utility model is as follows: A low-cost adjustable voltage power supply circuit, the power input terminal VIN of the circuit is respectively connected to one end of the first resistor R1 and the collector of the NPN transistor Q1, and the other end of the first resistor R1 is respectively connected to one end of the second resistor R2 and the base of the NPN transistor Q1; the other end of the second resistor R2, one end of the third resistor R3 and one end of the first capacitor C1 are all grounded; the emitter of the NPN transistor Q1, the other end of the third resistor R3 and the other end of the first capacitor C1 are all connected to the power output terminal VOUT.

[0004] As an improvement of the utility model, after the voltage of the power input terminal VIN is divided by the resistors of the first resistor R1 and the second resistor R2, it is sent to the base of the NPN transistor Q1, and the base voltage VB = VIN * R2 / (R1 + R2).

[0005] As an improvement of the utility model, the conduction voltage between the base and the emitter of the NPN transistor Q1 is VBE. When the emitter voltage of the NPN transistor Q1, the voltage of the power output terminal VOUT is less than VIN * R2 / (R1 + R2) - VBE, the NPN transistor Q1 conducts, and the VOUT voltage rises rapidly.

[0006] As an improvement of the utility model, when the voltage of the power output terminal VOUT is greater than VIN * R2 / (R1 + R2) - VBE, the NPN transistor Q1 turns off, and the VOUT voltage drops rapidly again. This cycle repeats, and the voltage of the power output terminal VOUT stabilizes at VIN * R2 / (R1 + R2) - VBE.

[0007] As an improvement of the present utility model, the NPN transistor Q1 adopts the model MMBT3904 or BCX56.

[0008] As an improvement of the present utility model, the output current of the power output terminal VOUT corresponding to MMBT3904 is at most 200 mA, and the output current of the power output terminal VOUT corresponding to BCX56 is at most 1000 mA.

[0009] Compared with the prior art, the beneficial effects of the present utility model are as follows: The present utility model can flexibly change the voltage of the power output terminal VOUT only by simply adjusting the resistance values of the first resistor R1 and the second resistor R2, which well meets the different requirements of various different devices or chips inside electronic products for the voltage of the power supply. At the same time, the present utility model uses low-cost triodes to replace high-price power chips, which can greatly reduce the material cost of electronic products. Description of the Drawings

[0010] Figure 1 It is a schematic diagram of the power circuit structure in the present utility model;

[0011] Figure 2 It is a schematic diagram of the power circuit structure in this embodiment;

[0012] Figure 3 It is a circuit simulation diagram in this embodiment. Specific Embodiments

[0013] The following further clarifies the present utility model in conjunction with the drawings and specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present utility model and not to limit the scope of the present utility model.

[0014] Embodiment: As Figures 1-3 shown, the embodiment discloses a low-cost adjustable voltage power circuit, wherein the power input terminal VIN is respectively connected to one end of the first resistor R1 and the collector of the NPN transistor Q1, and the other end of the first resistor R1 is respectively connected to one end of the second resistor R2 and the base of the NPN transistor Q1; the other end of the second resistor R2, one end of the third resistor R3, and one end of the first capacitor C1 are all grounded; the emitter of the NPN transistor Q1, the other end of the third resistor R3, and the other end of the first capacitor C1 are all connected to the power output terminal VOUT.

[0015] The voltage of the power input terminal VIN is divided by the resistors of the first resistor R1 and the second resistor R2 and then sent to the base of the NPN transistor Q1. The base voltage VB = VIN * R2 / (R1 + R2). The conduction voltage between the base and the emitter of the NPN transistor Q1 is VBE. When the emitter voltage of the NPN transistor Q1, that is, the voltage of the power output terminal VOUT, is less than VIN * R2 / (R1 + R2) - VBE, the NPN transistor Q1 conducts and the VOUT voltage rises rapidly; when the voltage of the power output terminal VOUT is greater than VIN * R2 / (R1 + R2) - VBE, the NPN transistor Q1 turns off and the VOUT voltage drops rapidly again; this cycle repeats, and the voltage of the power output terminal VOUT stabilizes at VIN * R2 / (R1 + R2) - VBE. Usually, the conduction voltage of the NPN transistor VBE = 0.6V, so VOUT = VIN * R2 / (R1 + R2) - 0.6.

[0016] Among them, the power input terminal VIN is connected to a 5V power supply, that is, VIN = 5V.

[0017] Among them, the first resistor R1 is 680Ω, the second resistor R2 is 2.2kΩ, the third resistor R3 is 33kΩ, and the first capacitor C1 is 10uF.

[0018] Among them, the NPN transistor Q1 can be of models such as MMBT3904 and BCX56. The maximum output current of the power output terminal VOUT corresponding to MMBT3904 is 200mA, and the maximum output current of the power output terminal VOUT corresponding to BCX56 is 1000mA.

[0019] It can be calculated that VOUT = VIN * R2 / (R1 + R2) - 0.6 = 5 * 2200 / (680 + 2200) - 0.6 = 3.219445V.

[0020] As shown in the circuit simulation result of the embodiment, VOUT = 3.306712V.

[0021] The calculation result and the simulation result of the voltage of the power output terminal VOUT are basically the same.

[0022] In the above embodiment, by simply adjusting the resistance values of the first resistor R1 and the second resistor R2, the voltage of the power output terminal VOUT can be flexibly changed. Using the low-cost adjustable voltage power supply circuit provided in the above embodiment, the power output terminal VOUT supplies power to the internal devices or chips of electronic products, and can well meet the different requirements of various internal devices or chips of electronic products for the supply voltage.

[0023] Working principle: In this utility model, the voltage of the power input terminal VIN is divided by the resistances of the first resistor R1 and the second resistor R2 and then sent to the base of the NPN transistor Q1. The base voltage VB = VIN * R2 / (R1 + R2). The conduction voltage between the base and the emitter of the NPN transistor Q1 is VBE. When the emitter voltage of the NPN transistor Q1, that is, the voltage of the power output terminal VOUT, is less than VIN * R2 / (R1 + R2) - VBE, the NPN transistor Q1 conducts and the VOUT voltage rises rapidly; while when the voltage of the power output terminal VOUT is greater than VIN * R2 / (R1 + R2) - VBE, the NPN transistor Q1 turns off and the VOUT voltage drops rapidly again; this cycle repeats, and the voltage of the power output terminal VOUT stabilizes at VIN * R2 / (R1 + R2) - VBE. Usually, the conduction voltage VBE of the NPN transistor is 0.6V, so VOUT = VIN * R2 / (R1 + R2) - 0.6.

[0024] It should be noted that the above content only illustrates the technical idea of this utility model and cannot be used to limit the protection scope of this utility model. For those of ordinary skill in the art, without departing from the principle of this utility model, several improvements and refinements can still be made, and these improvements and refinements all fall within the protection scope of the claims of this utility model.

Claims

1. A low-cost adjustable voltage power supply circuit, characterized in that: The power input terminal VIN of the circuit is respectively connected to one end of the first resistor R1 and the collector of the NPN transistor Q1, and the other end of the first resistor R1 is respectively connected to one end of the second resistor R2 and the base of the NPN transistor Q1; the other end of the second resistor R2, one end of the third resistor R3 and one end of the first capacitor C1 are all grounded; the emitter of the NPN transistor Q1, the other end of the third resistor R3 and the other end of the first capacitor C1 are all connected to the power output terminal VOUT.

2. A low-cost adjustable voltage power supply circuit according to claim 1, characterized in that: The voltage at the power input terminal VIN is divided by the first resistor R1 and the second resistor R2 and then sent to the base of the NPN transistor Q1. The base voltage VB=VIN*R2 / (R1+R2).

3. A low-cost adjustable voltage power supply circuit according to claim 2, characterized in that: The conduction voltage between the base and emitter of the NPN transistor Q1 is VBE. When the emitter voltage of the NPN transistor Q1 and the voltage at the power output terminal VOUT are less than VIN*R2 / (R1+R2)-VBE, the NPN transistor Q1 is turned on and the VOUT voltage rises rapidly.

4. A low-cost adjustable voltage power supply circuit according to claim 3, characterized in that: When the voltage at the power output terminal VOUT is greater than VIN*R2 / (R1+R2)-VBE, the NPN transistor Q1 is turned off, and the VOUT voltage drops rapidly again, and the cycle repeats until the voltage at the power output terminal VOUT stabilizes at VIN*R2 / (R1+R2)-VBE.

5. A low-cost adjustable voltage power supply circuit according to claim 4, characterized in that: The NPN transistor Q1 adopts MMBT3904 or BCX56 model.

6. A low-cost adjustable voltage power supply circuit according to claim 5, characterized in that: The maximum output current of the power output terminal VOUT corresponding to MMBT3904 is 200mA, and the maximum output current of the power output terminal VOUT corresponding to BCX56 is 1000mA.

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