A power input voltage step-down circuit
By using a voltage divider resistor network in conjunction with MOSFETs and transistors, the step-down circuit solves the problems of complex structure, large size, or limited input voltage range in existing technologies, and achieves a simple step-down effect with a wide input voltage range.
Patent Information
- Application Number
- CN202522605358.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-09
- Publication Date
- 2026-11-06
- Estimated Expiration
- 2035-12-09
AI Technical Summary
Existing step-down circuits are complex in structure, large in size, or have a limited input voltage range, making them difficult to adapt to wide voltage input application scenarios.
A step-down circuit using a voltage divider resistor network in conjunction with MOSFETs and transistors achieves a wide voltage input step-down function by automatically switching the equivalent voltage divider ratio. The circuit structure is simple and compact.
It achieves a voltage reduction effect over a wide voltage range, simplifies the circuit structure, reduces costs and size, and adapts to automatic switching under different input voltage conditions.
Smart Images
Figure CN224947465U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of electronic circuit technology, specifically to a voltage conversion circuit, and more particularly to a step-down circuit that can adapt to a wide range of input voltages. Background Technology
[0002] In the field of power management technology, many electronic devices often receive a high-voltage signal with a wide range of variation at their power input terminals during actual operation. This signal needs to be stepped down before it can be used by subsequent low-voltage circuits. Currently, commonly used step-down solutions mainly include flyback converters and buck converters.
[0003] However, the existing solutions mentioned above all have certain limitations: flyback converters usually require components such as transformers and optocouplers, resulting in relatively complex circuit structures and large overall sizes, which is not conducive to miniaturization design; while traditional buck converters, although relatively simple in structure, usually have a narrow input voltage range (e.g., most are below 100V), making it difficult to directly adapt to wide voltage input application scenarios, often requiring additional pre-regulation or complex control circuits, which also increases system complexity and cost.
[0004] Therefore, there is still a lack of a buck circuit solution in the existing technology that can take into account the advantages of simple structure, compact size and wide input voltage adaptability. Summary of the Invention
[0005] This invention addresses the problems of complex structure, large size, or limited input range in existing wide input voltage buck circuits by providing a simple, compact wide input voltage buck circuit capable of multi-level voltage reduction.
[0006] To achieve the above objectives, the technical solution adopted by this utility model is as follows: This utility model provides a wide voltage input step-down circuit, connected between the power input terminal (Vin) and the power output terminal (Vout), comprising: A voltage divider resistor network is coupled between the power input terminal and the reference ground. The voltage divider resistor network includes a first resistor group, a second resistor group and a third resistor group. The first end of the first resistor group is connected to the power input terminal, and its second end is connected to the reference ground through the second resistor group and the third resistor group connected in parallel, forming a voltage divider node. The MOSFET has its drain connected to the power input terminal, its source connected to the power output terminal, and its gate connected to the voltage divider node. The first transient voltage suppression diode has its cathode connected to the power input terminal, and its anode connected to the reference ground via a fourth resistor and a fifth resistor connected in series. The transistor has its collector connected to at least one of the second and third resistor groups, its emitter connected to a reference ground, and its base connected to a common connection point between the fourth and fifth resistors.
[0007] As a further improvement of this utility model, the first resistor group is composed of a first resistor, the second resistor group is composed of a second resistor, and the third resistor group is composed of a third resistor.
[0008] As a further improvement of this utility model, an input protection circuit is connected in series between the power input terminal and the voltage divider resistor network.
[0009] As a further improvement of this utility model, the input protection circuit includes: a filter capacitor and a second transient voltage suppression diode connected in parallel between the power input terminal and the reference ground; and a reverse protection diode, the anode of which is connected to the power input terminal and the cathode of which is connected to the voltage divider resistor network.
[0010] Compared with the prior art, the present invention has the following beneficial effects: 1. By using a voltage divider resistor network in conjunction with MOSFETs and transistors, the voltage reduction function can be achieved using only a few conventional discrete components. The circuit structure is simple, which helps to reduce costs and overall size.
[0011] 2. By setting up a second and third resistor group in parallel and using a transistor to control its on / off state, the equivalent voltage division ratio can be automatically switched under different input voltage conditions, thereby realizing two voltage reduction ratios and effectively expanding the wide voltage input adaptability range of the circuit. Attached Figure Description
[0012] Figure 1 This is the circuit of an embodiment of the present utility model; Explanation of main component symbols First transient voltage suppression diode D1 Second transient voltage suppressor diode TVS1 MOSFET Q1 Diode D2 Transistor Q2 Capacitor C1 First resistor R1 Second resistor R2 Third resistor R3 Fourth resistor R4 Fifth resistor R5 Detailed Implementation
[0013] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only for explaining the present utility model and are not intended to limit the scope of protection of the present utility model.
[0014] This utility model embodiment provides a wide-voltage input step-down circuit for converting a wide-range high-voltage input into a lower voltage suitable for subsequent circuit operation. Please refer to... Figure 1 The circuit mainly consists of two parts: an input protection circuit and a step-down circuit. The input protection circuit is used to absorb static electricity, suppress surges, and prevent reverse power connection to improve system reliability; the step-down circuit is used to reduce the input voltage to within the maximum input voltage allowed by the downstream load (e.g., a specific function chip U1).
[0015] Specifically, in a preferred embodiment, the input protection circuit includes a capacitor C1, a second transient voltage suppressor diode TVS1, and a reverse connection protection diode D2. The capacitor C1 and the second transient voltage suppressor diode TVS1 are connected in parallel between the power input terminal Vin and the reference ground. The capacitor C1 is primarily used to absorb high-frequency interference and static electricity, while the second transient voltage suppressor diode TVS1 is used to suppress voltage surges at the input terminal. The anode of the reverse connection protection diode D2 is connected to the power input terminal Vin, and the cathode is connected to the input terminal of the subsequent step-down circuit (i.e., the voltage divider resistor network).
[0016] The step-down circuit mainly includes a voltage divider resistor network, a MOSFET Q1, a transistor Q2, a first transient voltage suppressor diode D1, and a fourth resistor R4 and a fifth resistor R5. The voltage divider resistor network consists of a first resistor R1, a second resistor R2, and a third resistor R3. One end of the first resistor R1 is connected to the output terminal of the input protection circuit (i.e., the cathode of the second transient voltage suppressor diode D2), and the other end is connected to the reference ground through the parallel connection of the second resistor R2 and the third resistor R3, forming a voltage divider node F at this connection point. The drain of the MOSFET Q1 is connected to the output terminal of the input protection circuit, the source is connected to the output terminal Vout of the step-down circuit, and the gate is connected to the voltage divider node F. The cathode of the first transient voltage suppressor diode D1 is connected to the power input terminal Vin, and the anode is connected to the reference ground through the series connection of the fourth resistor R4 and the fifth resistor R5. The collector of the transistor Q2 is connected to the second resistor R2, the emitter is connected to the reference ground, and the base is connected to the common connection point between the fourth resistor R4 and the fifth resistor R5.
[0017] In one application scenario of this embodiment, the power output terminal Vout is connected to the power supply pin V_Desc of the subsequent functional unit U1 to provide it with a stepped-down operating voltage. U1 can be any integrated circuit chip requiring wide voltage input adaptation, such as a specific power management chip, microcontroller, or driver chip.
[0018] The circuit works as follows: When the input voltage Vin is lower than the first threshold voltage V1, the first transient voltage suppression diode D1 is in the off state, and the transistor Q2 is turned off due to insufficient base voltage. At this time, the voltage at the voltage divider node F is determined by the series voltage divider of the first resistor R1 and the third resistor R3, and the gate voltage of the MOSFET Q1 is approximately (Vin - 0.7V) * R3 / (R1 + R3), and its source output voltage is stabilized at the corresponding level.
[0019] When the input voltage Vin rises to between the first threshold voltage V1 and the second threshold voltage V2 (i.e., V2≥Vin≥V1), the first transient voltage suppression diode D1 conducts in reverse, causing current to flow through the fifth resistor R5, thereby raising the base voltage of transistor Q2 and turning it on. After transistor Q2 is turned on, its collector and emitter are approximately short-circuited. At this time, the voltage at the voltage divider node F is determined by the first resistor R1, the second resistor R2, and the third resistor R3, specifically approximately (Vin - 0.7) * ((R1 * R3) / (R2 + R3)) / (R1 + (R1 * R3) / (R2 + R3)). Therefore, the relationship between the gate voltage and the source output voltage of MOSFET Q1 changes with the input voltage, realizing automatic switching of the buck ratio.
[0020] In a specific embodiment of this utility model, the maximum input voltage of the back-end chip U1 is set to 60V, and the maximum value of the power supply input voltage Vin is 180V. The resistance values of the first resistor R1, the second resistor R2, and the third resistor R3 are all 100kΩ, the resistance value of the fourth resistor R4 is 93kΩ, and the resistance value of the fifth resistor R5 is 7kΩ. A transient voltage suppression diode with a reverse breakdown voltage of 110V is selected as the first transient voltage suppression diode D1.
[0021] When the input voltage Vin < 120V, the first transient voltage suppressor diode D1 does not break down, and transistor Q2 is cut off. At this time, the source output voltage Vout of MOSFET Q1 ≈ (Vin - 0.7V) * 100kΩ / (100kΩ + 100kΩ) ≈ 0.5 * (Vin - 0.7V). When Vin is close to 120V, Vout is calculated to be approximately 59.6V, which is lower than the upper limit of U1 of 60V.
[0022] When the input voltage is 120V≤Vin≤180V, the first transient voltage suppression diode D1 is reverse-biased and the transistor Q2 is saturated and conducting. Current flows through the second resistor R2, changing the voltage division ratio. The source output voltage Vout of the MOSFET Q1 is approximately (Vin - 0.7V) * 50kΩ / (100kΩ + 50kΩ) = 0.333 * (Vin - 0.7V). Calculations show that when Vin is 120V and 180V, Vout is approximately 39.8V and 59.8V respectively, both within the safe input voltage range of U1.
[0023] Through the above mechanism, the circuit in this embodiment automatically achieves adaptive voltage reduction for two different input voltage ranges, ensuring that the output voltage is limited to the range allowed by the back-end chip U1 throughout the entire wide input voltage range.
[0024] The above embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Although this utility model 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; and these modifications or substitutions do not cause the corresponding technical solutions to depart from the protection scope of this utility model.
Claims
1. A power input voltage step-down circuit, connected between the power input terminal and the power output terminal, characterized in that, include: A voltage divider resistor network is coupled between the power input terminal and the reference ground. The voltage divider resistor network includes a first resistor group, a second resistor group and a third resistor group. The first end of the first resistor group is connected to the power input terminal, and its second end is connected to the reference ground through the second resistor group and the third resistor group connected in parallel, forming a voltage divider node. The MOSFET has its drain connected to the power input terminal, its source connected to the power output terminal, and its gate connected to the voltage divider node. The first transient voltage suppression diode has its cathode connected to the power input terminal, and its anode connected to the reference ground via a fourth resistor and a fifth resistor connected in series. The transistor has its collector connected to at least one of the second and third resistor groups, its emitter connected to a reference ground, and its base connected to a common connection point between the fourth and fifth resistors.
2. The power input voltage step-down circuit according to claim 1, characterized by, The first resistor group is composed of a first resistor, the second resistor group is composed of a second resistor, and the third resistor group is composed of a third resistor.
3. A power supply input voltage step-down circuit according to claim 1 or 2, characterized in that, An input protection circuit is also connected in series between the power input terminal and the voltage divider resistor network.
4. The power input voltage reduction circuit according to claim 3, characterized in that, The input protection circuit includes: a filter capacitor and a second transient voltage suppression diode connected in parallel between the power input terminal and the reference ground; and a reverse protection diode, whose anode is connected to the power input terminal and whose cathode is connected to the voltage divider resistor network.