Automatic backflow prevention circuit
Through the automatic anti-reflow circuit composed of P-channel MOS tube and PNP transistor, the problems of high loss and high cost in the prior art are solved, and the low loss and low cost anti-reflow effect is achieved.
Patent Information
- Application Number
- CN202421681082.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-07-16
- Publication Date
- 2025-07-25
- Estimated Expiration
- 2034-07-16
AI Technical Summary
The prior art has high loss or high cost problems when preventing return flow, especially in large current applications, diode heating loss is large, and back-to-back dual MOS tube solution requires adding logic control circuits, which are complex in structure and high cost.
The automatic anti-reflow circuit consisting of P-channel MOS tube, PNP transistor and resistor unit is automatically controlled by voltage difference to avoid reflow, with a simple structure and low cost.
It realizes automatic anti-reflow with low loss. The voltage drop is smaller than that of the diode when the MOS tube is turned on, and no logic control is required, which reduces the energy consumption and cost of the circuit.
Smart Images
Figure CN223156708U_ABST
Abstract
Description
Technical Field
[0001] The utility model belongs to the technical field of circuit protection, and specifically relates to an automatic anti-backflow circuit. Background Art
[0002] In portable devices for docking and circuits containing motors, etc., there will be a situation where the input voltage is less than the output voltage. If no protection measures are taken, it will cause the circuit to malfunction at best and burn out components at worst. Currently, there are two mainstream anti-backflow solutions. The first is to set a diode in the main circuit. However, the diode has a voltage drop, and in applications with large currents, the diode will have a large heat loss, reducing the circuit efficiency. The second is to use a back-to-back dual MOS transistor to prevent backflow. This form must be controlled by high and low levels, and a logic control circuit needs to be added, resulting in high cost, complex structure, and large volume. Summary of the Invention
[0003] Aiming at the above deficiencies, the utility model provides an automatic anti-backflow circuit, which can automatically prevent backflow, has low loss, simple structure, and low cost.
[0004] To solve the above technical problems, the embodiments of the utility model adopt the following technical solutions:
[0005] The embodiments of the utility model provide an automatic anti-backflow circuit, which includes a MOS transistor, a first triode, and a second triode. The drain of the MOS transistor is connected to the input end, and the source of the MOS transistor is connected to the output end; the emitter of the first triode is connected to the input end, the collector is connected to the first end of the first resistor unit, and the collector is connected to the base; the second end of the first resistor unit is grounded; the emitter of the second triode is connected to the output end, the collector is connected to the first end of the second resistor unit, and the second end of the second resistor unit is grounded; the base of the second triode is connected to the base of the first triode; the collector of the second triode is connected to the gate of the MOS transistor; both the first resistor unit and the second resistor unit include at least one resistor.
[0006] As a further improvement of the embodiments of the utility model, the MOS transistor is a P-channel MOS transistor.
[0007] As a further improvement of the embodiments of the utility model, the first triode is a PNP triode.
[0008] As a further improvement of the embodiments of the utility model, the second triode is a PNP triode.
[0009] As a further improvement of the embodiments of the utility model, the first resistor unit includes a first resistor.
[0010] As a further improvement of the embodiments of the utility model, the second resistor unit includes a second resistor.
[0011] Compared with the prior art, the technical solution of the present utility model has the following beneficial effects: An automatic anti-backflow circuit provided by the present utility model. If the input terminal voltage is less than the output terminal voltage, the first triode is cut off, the second triode is turned on, the gate voltage of the MOS tube is pulled high, the MOS tube is cut off, and the input terminal and the output terminal are disconnected to prevent backflow. If the input terminal voltage is greater than the output terminal voltage, the first triode is turned on, the second triode is cut off, the gate voltage of the MOS tube is pulled low, the MOS tube is turned on, and the input terminal and the output terminal are connected, and the output terminal outputs voltage. For the automatic anti-backflow circuit provided by the present utility model, the voltage drop when the MOS is turned on is much smaller than that of an ordinary diode, and the loss is also much smaller than that of an ordinary diode, effectively reducing the voltage drop loss. For the automatic anti-backflow circuit provided by the present utility model, the circuit is automatically turned on when the input terminal voltage is greater than the output terminal voltage, and the circuit is automatically turned off when the output terminal voltage is greater than the input terminal voltage. There is no need to use level control, the structure is simple, and the cost is low. Description of the Drawings
[0012] Figure 1 It is a schematic structural diagram of the automatic anti-backflow circuit according to an embodiment of the present utility model.
[0013] Description of the Main Component Symbols
[0014] Input terminal Vin
[0015] Output terminal Vout
[0016] MOS tube Q1
[0017] First triode Q2
[0018] Second triode Q3
[0019] First resistor R1
[0020] Second resistor R2
[0021] Ground terminal GND Detailed Embodiment
[0022] Next, in conjunction with the drawings, the technical solution of the present utility model will be described in detail.
[0023] An embodiment of the present utility model provides an automatic anti-backflow circuit, as Figure 1As shown, it includes MOS transistor Q1, first triode Q2 and second triode Q3. The drain of MOS transistor Q1 is connected to the input terminal Vin, and the source of MOS transistor Q1 is connected to the output terminal Vout. The emitter of the first triode Q2 is connected to the input terminal Vin, the collector is connected to the first end of the first resistor unit, and the collector is connected to the base. The second end of the first resistor unit is grounded. The emitter of the second triode Q3 is connected to the output terminal, the collector is connected to the first end of the second resistor unit, and the second end of the second resistor unit is grounded. The base of the second triode Q3 is connected to the base of the first triode Q2. The collector of the second triode Q3 is connected to the gate of the MOS transistor Q1. Both the first resistor unit and the second resistor unit include at least one resistor.
[0024] Among them, the MOS transistor Q1 is a P-channel MOS transistor. The first triode Q2 is a PNP triode. The second triode Q3 is a PNP triode. The first resistor unit is the first resistor R1. The second resistor unit is the second resistor R2.
[0025] For the automatic anti-backflow circuit of the above embodiment, during operation, if the input terminal voltage is less than the output terminal voltage, the first triode is cut off, the second triode is turned on, the gate voltage of the MOS transistor is pulled up, the MOS transistor is cut off, and the input terminal is disconnected from the output terminal to prevent backflow. If the input terminal voltage is greater than the output terminal voltage, the first triode is turned on, the second triode is cut off, the gate voltage of the MOS transistor is pulled down, the MOS transistor is turned on, the input terminal and the output terminal are connected, and the output terminal outputs voltage.
[0026] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above specific embodiments. The above specific embodiments and the descriptions in the specification are only for further explaining the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed.
Claims
1. An automatic anti-backflow circuit, characterized in that, It includes a MOS transistor, a first triode, and a second triode. The drain of the MOS transistor is connected to the input terminal, and the source of the MOS transistor is connected to the output terminal; the emitter of the first triode is connected to the input terminal, the collector is connected to the first end of the first resistor unit, and the collector is connected to the base; the second end of the first resistor unit is grounded; the emitter of the second triode is connected to the output terminal, the collector is connected to the first end of the second resistor unit, and the second end of the second resistor unit is grounded; the base of the second triode is connected to the base of the first triode; the collector of the second triode is connected to the gate of the MOS transistor; both the first resistor unit and the second resistor unit include at least one resistor.
2. The automatic anti-backflow circuit according to claim 1, characterized in that, The MOS transistor is a P-channel MOS transistor.
3. The automatic anti-backflow circuit according to claim 1, characterized in that, The first triode is a PNP triode.
4. The automatic anti-backflow circuit according to claim 1, wherein The second triode is a PNP triode.
5. The automatic anti-backflow circuit according to claim 1, wherein The first resistor unit includes a first resistor.
6. The automatic anti-backflow circuit according to claim 1, characterized in that, The second resistor unit includes a second resistor.