Voltage reduction type conversion circuit with adjustable output voltage

Abstract

The utility model relates to the technical field of step-down conversion circuits, in particular to a step-down conversion circuit with adjustable output voltage, which comprises a step-down chip U1, a resistor R4, a resistor R5, a capacitor C3, an adjustable voltage pin ADJ and a voltage regulating transformer TR1, the voltage feedback end of the step-down chip U1 is electrically connected with one end of the resistor R4, one end of the adjustable voltage pin ADJ and one end of the resistor R5, and the other end of the resistor R5 is electrically connected with the capacitor C3. The other end of the resistor R5 is electrically connected with one end of the capacitor C3 and one end of a primary winding of the voltage regulating transformer TR1, the other end of the resistor R4 and the other end of the capacitor C3 are both grounded, the adjustable voltage pin ADJ is additionally arranged, under the condition that large cost is not increased, the output voltage of the product is adjustable, and the output voltage of the product can be adjusted according to different application voltage occasions. Only one or two resistors are needed to meet the requirements, so that the design cost is greatly saved, and the use amount of devices is reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of step-down conversion circuits, in particular to a step-down conversion circuit with adjustable output voltage. Background Art

[0002] The conventional Buck circuit (i.e., step-down conversion circuit) has a single output voltage, and a single model product has only one output voltage. In some applications that require different input voltages, different models of output voltage products are often required to meet the requirements for different voltage requirements. This is not only conducive to product model selection, but also not conducive to saving development costs. Utility Model Content

[0003] The technical problem to be solved by the utility model is: a step-down conversion circuit with adjustable output voltage, which can realize stable and adjustable output voltage.

[0004] In order to solve the above technical problems, the technical solution adopted by the utility model is:

[0005] A step-down conversion circuit with adjustable output voltage comprises a step-down chip U1, a resistor R4, a resistor R5, a capacitor C3, an adjustable voltage pin ADJ and a voltage regulating transformer TR1, wherein a voltage feedback end of the step-down chip U1 is electrically connected to one end of the resistor R4, the adjustable voltage pin ADJ and one end of the resistor R5 respectively, the other end of the resistor R5 is electrically connected to one end of the capacitor C3 and one end of the primary winding of the voltage regulating transformer TR1 respectively, and the other end of the resistor R4 and the other end of the capacitor C3 are both grounded.

[0006] Furthermore, it also includes a capacitor C5 and a capacitor C7, one end of the capacitor C5 is electrically connected to one end of the resistor R5, one end of the resistor R4, one end of the capacitor C7 and the voltage feedback end of the buck chip U1, the other end of the capacitor C5 is electrically connected to the other end of the resistor R5, one end of the capacitor C3 and one end of the primary winding of the voltage regulating transformer TR1, the other end of the capacitor C7 is electrically connected to the other end of the resistor R4 and the other end of the capacitor C7 is grounded.

[0007] Furthermore, it also includes a diode D2, the anode of which is electrically connected to the other end of the resistor R4 and the anode of the diode D2 is grounded, and the cathode of the diode D2 is electrically connected to one end of the resistor R5, one end of the resistor R4, the voltage feedback end of the buck chip U1 and the adjustable voltage pin ADJ.

[0008] Furthermore, it also includes a diode D1 and a capacitor C4, wherein the anode of the diode D1 is electrically connected to one end of the secondary winding of the voltage regulating transformer TR1, the cathode of the diode D1 is electrically connected to one end of the capacitor C4, and the other end of the capacitor C4 is electrically connected to the other end of the secondary winding of the voltage regulating transformer TR1.

[0009] Furthermore, a resistor R6 is included, one end of the resistor R6 is electrically connected to one end of the secondary winding of the voltage regulating transformer TR1, and the other end of the resistor R6 is electrically connected to the other end of the secondary winding of the voltage regulating transformer TR1.

[0010] The beneficial effects of the utility model are:

[0011] This solution sets a step-down chip U1, a resistor R4, a resistor R5, a capacitor C3, an adjustable voltage pin ADJ and a voltage regulating transformer TR1. After the power supply starts normally, the voltage feedback end of the step-down chip U1 is divided by the resistors R5 and R4 to form a stable first output voltage at the capacitor C3. Then, the voltage at the capacitor C3 passes through the voltage regulating transformer TR1. Without considering the voltage drop and the slight difference in the transformer winding, a stable second output voltage is obtained at both ends of the secondary winding of the voltage regulating transformer TR1. When it is necessary to obtain a stable third output voltage at both ends of the secondary winding of the voltage regulating transformer TR1, it is only necessary to weld a suitable resistor at the adjustable voltage pin ADJ, and the output voltage of the product can be changed from the second output voltage to the third output voltage, thereby achieving stable and adjustable output voltage. This solution makes the output voltage of the product adjustable without increasing the cost by adding the adjustable voltage pin ADJ. For different application voltage occasions, only one or two resistors are often needed to meet the requirements, which greatly saves the design cost and reduces the use of devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 The utility model is a circuit principle diagram of a step-down conversion circuit with adjustable output voltage. DETAILED DESCRIPTION

[0013] In order to explain the technical content, achieved objectives and effects of the present invention in detail, the following is an explanation in conjunction with the implementation modes and the accompanying drawings.

[0014] Please refer to Figure 1 , the technical solution adopted by the utility model is:

[0015] A step-down conversion circuit with adjustable output voltage comprises a step-down chip U1, a resistor R4, a resistor R5, a capacitor C3, an adjustable voltage pin ADJ and a voltage regulating transformer TR1, wherein a voltage feedback end of the step-down chip U1 is electrically connected to one end of the resistor R4, the adjustable voltage pin ADJ and one end of the resistor R5 respectively, the other end of the resistor R5 is electrically connected to one end of the capacitor C3 and one end of the primary winding of the voltage regulating transformer TR1 respectively, and the other end of the resistor R4 and the other end of the capacitor C3 are both grounded.

[0016] From the above description, it can be seen that the beneficial effects of the utility model are:

[0017] This solution sets a step-down chip U1, a resistor R4, a resistor R5, a capacitor C3, an adjustable voltage pin ADJ and a voltage regulating transformer TR1. After the power supply starts normally, the voltage feedback end of the step-down chip U1 is divided by the resistors R5 and R4 to form a stable first output voltage at the capacitor C3. Then, the voltage at the capacitor C3 passes through the voltage regulating transformer TR1. Without considering the voltage drop and the slight difference in the transformer winding, a stable second output voltage is obtained at both ends of the secondary winding of the voltage regulating transformer TR1. When it is necessary to obtain a stable third output voltage at both ends of the secondary winding of the voltage regulating transformer TR1, it is only necessary to weld a suitable resistor at the adjustable voltage pin ADJ, and the output voltage of the product can be changed from the second output voltage to the third output voltage, thereby achieving stable and adjustable output voltage. This solution makes the output voltage of the product adjustable without increasing the cost by adding the adjustable voltage pin ADJ. For different application voltage occasions, only one or two resistors are often needed to meet the requirements, which greatly saves the design cost and reduces the use of devices.

[0018] Furthermore, it also includes a capacitor C5 and a capacitor C7, one end of the capacitor C5 is electrically connected to one end of the resistor R5, one end of the resistor R4, one end of the capacitor C7 and the voltage feedback end of the buck chip U1, the other end of the capacitor C5 is electrically connected to the other end of the resistor R5, one end of the capacitor C3 and one end of the primary winding of the voltage regulating transformer TR1, the other end of the capacitor C7 is electrically connected to the other end of the resistor R4 and the other end of the capacitor C7 is grounded.

[0019] From the above description, it can be seen that capacitor C5 and capacitor C7 are used to increase the zero point and pole of the product, which can prevent the output voltage of the product from oscillating.

[0020] Furthermore, it also includes a diode D2, the anode of which is electrically connected to the other end of the resistor R4 and the anode of the diode D2 is grounded, and the cathode of the diode D2 is electrically connected to one end of the resistor R5, one end of the resistor R4, the voltage feedback end of the buck chip U1 and the adjustable voltage pin ADJ.

[0021] From the above description, it can be known that the diode D2 can prevent static electricity from causing damage to the voltage feedback terminal (ie, the FB pin) of the buck chip U1.

[0022] Furthermore, it also includes a diode D1 and a capacitor C4, wherein the anode of the diode D1 is electrically connected to one end of the secondary winding of the voltage regulating transformer TR1, the cathode of the diode D1 is electrically connected to one end of the capacitor C4, and the other end of the capacitor C4 is electrically connected to the other end of the secondary winding of the voltage regulating transformer TR1.

[0023] From the above description, it can be seen that the diode D1 plays a rectifying role, and the capacitor C4 plays an energy storage filtering role.

[0024] Furthermore, a resistor R6 is included, one end of the resistor R6 is electrically connected to one end of the secondary winding of the voltage regulating transformer TR1, and the other end of the resistor R6 is electrically connected to the other end of the secondary winding of the voltage regulating transformer TR1.

[0025] From the above description, it can be seen that the resistor R6 acts as a dummy load to prevent the output voltage of the product from floating high when the product is unloaded.

[0026] Please refer to Figure 1 , Embodiment 1 of the present utility model is:

[0027] A step-down conversion circuit with adjustable output voltage comprises a step-down chip U1 (model: TPP362082), a resistor R4 (resistance value: 4.12 kΩ), a resistor R5 (resistance value: 13.3 kΩ), a capacitor C3 (capacitance value: 10 μF), an adjustable voltage pin ADJ and a voltage regulating transformer TR1 (in this embodiment, the turns ratio of the voltage regulating transformer TR1 is 1:2), wherein a voltage feedback end (i.e., an FB pin) of the step-down chip U1 is electrically connected to one end of the resistor R4, the adjustable voltage pin ADJ and one end of the resistor R5 respectively, the other end of the resistor R5 is electrically connected to one end of the capacitor C3 and one end of the primary winding of the voltage regulating transformer TR1 respectively, and the other end of the resistor R4 and the other end of the capacitor C3 are both grounded.

[0028] The preset voltage at the capacitor C3 is reflected to the output terminal through the turns ratio of the voltage regulating transformer TR1 to achieve the desired output voltage.

[0029] The adjustable voltage pin ADJ is used to connect an adjustable resistor. In this embodiment, the connected adjustable resistor is represented by resistor R7.

[0030] The above-mentioned step-down conversion circuit with adjustable output voltage also includes a capacitor C5 (capacitance value is 68nF) and a capacitor C7 (capacitance value is 2.2nF), one end of the capacitor C5 is electrically connected to one end of the resistor R5, one end of the resistor R4, one end of the capacitor C7 and the voltage feedback end of the step-down chip U1, the other end of the capacitor C5 is electrically connected to the other end of the resistor R5, one end of the capacitor C3 and one end of the primary winding of the voltage regulating transformer TR1, the other end of the capacitor C7 is electrically connected to the other end of the resistor R4 and the other end of the capacitor C7 is grounded.

[0031] The above-mentioned step-down conversion circuit with adjustable output voltage also includes a diode D2 (model CESD5V0D5), the anode of the diode D2 is electrically connected to the other end of the resistor R4 and the anode of the diode D2 is grounded, and the cathode of the diode D2 is electrically connected to one end of the resistor R5, one end of the resistor R4, the voltage feedback end of the step-down chip U1 and the adjustable voltage pin ADJ.

[0032] The above-mentioned step-down conversion circuit with adjustable output voltage also includes a diode D1 (model SL110-F1-0000HF) and a capacitor C4 (capacitance value is 4.7μF), the anode of the diode D1 is electrically connected to one end of the secondary winding of the voltage regulating transformer TR1, the cathode of the diode D1 is electrically connected to one end of the capacitor C4, and the other end of the capacitor C4 is electrically connected to the other end of the secondary winding of the voltage regulating transformer TR1.

[0033] The above-mentioned step-down conversion circuit with adjustable output voltage also includes a resistor R6 (resistance value is 6.2kΩ), one end of the resistor R6 is electrically connected to one end of the secondary winding of the voltage regulating transformer TR1, and the other end of the resistor R6 is electrically connected to the other end of the secondary winding of the voltage regulating transformer TR1.

[0034] The above-mentioned step-down converter circuit with adjustable output voltage further includes a resistor R1 (resistance value is 95.3kΩ), a resistor R2 (resistance value is 41.5kΩ), a resistor R3, a capacitor C1 (capacitance value is 4.7μF) and a capacitor C2 (capacitance value is 100nF). For the specific connection relationship between the components, please refer to Figure 1 Resistors R2 and R3 are connected in parallel and in series with resistor R1 to form an undervoltage circuit. Resistor R3 is used as a fine-tuning resistor and is not used in this circuit. Capacitor C1 is an input filter capacitor, and capacitor C2 is a bypass capacitor to power the built-in MOS tube of chip U1.

[0035] The working principle of the above-mentioned step-down conversion circuit with adjustable output voltage is as follows:

[0036] After the power supply starts normally, the voltage feedback end (i.e., the FB pin) of the buck chip U1 is divided by resistors R5 and R4 to form a stable first-level voltage of about 2.5V at capacitor C3.

[0037] The voltage at capacitor C3 then passes through the voltage regulating transformer TR1, rectified by diode D1, and filtered by capacitor C4. Without considering the voltage drop and slight difference in transformer windings, a stable 5V output voltage is obtained across capacitor C4.

[0038] When a stable voltage of 12V is required at the output end, the voltage at the capacitor C3 needs to be increased. Since the turns ratio of the voltage regulating transformer TR1 in this embodiment is 1:2, the voltage at the capacitor C3 must be at least 6V.

[0039] From the original data, we can see that R5 = 13.3kΩ, R4 = 4.12kΩ;

[0040] According to the formula V C3 =(R5 / R 并 +1)*0.6, we can see that when V C3 =6V, we can get R 并 =1.47kΩ;

[0041] By R 并 =R4*R7 / (R4+R7), we can get R7=2.28kΩ;

[0042] It can be concluded that when a 2.28kΩ resistor is soldered to the adjustable voltage pin ADJ, the output voltage of the product can be changed from 5V to 12V.

[0043] When a stable voltage of 24V is required across capacitor C4, the voltage at capacitor C3 needs to be increased. Since the turns ratio of the voltage regulating transformer TR1 in this embodiment is 1:2, the voltage at capacitor C3 must be at least 12V.

[0044] From the original data, we can see that R5 = 13.3kΩ, R4 = 4.12kΩ;

[0045] According to the formula V C3 =(R5 / R 并 +1)*0.6, we can see that when V C3 =12V, we can get R 并 =0.7kΩ;

[0046] By R 并 =R4*R7 / (R4+R7), we can get R7=0.84kΩ;

[0047] It can be concluded that when a 0.84KΩ resistor is soldered to the adjustable voltage pin ADJ, the output voltage of the product can be changed from 5V to 24V.

[0048] In summary, the utility model provides a step-down conversion circuit with adjustable output voltage. By setting a step-down chip U1, a resistor R4, a resistor R5, a capacitor C3, an adjustable voltage pin ADJ and a voltage regulating transformer TR1, after the power supply is normally started, the voltage feedback end of the step-down chip U1 is divided by the resistors R5 and R4 to form a stable first output voltage at the capacitor C3. Then, the voltage at the capacitor C3 passes through the voltage regulating transformer TR1. Without considering the voltage drop and the slight difference in the transformer winding, a stable second output voltage is obtained at both ends of the secondary winding of the voltage regulating transformer TR1. When a stable third output voltage is required at both ends of the secondary winding of the voltage regulating transformer TR1, only a suitable resistor needs to be welded at the adjustable voltage pin ADJ, and the output voltage of the product can be changed from the second output voltage to the third output voltage, thereby realizing stable and adjustable output voltage. By adding the adjustable voltage pin ADJ, the scheme makes the output voltage of the product adjustable without increasing the cost. For different application voltage occasions, only one or two resistors are often needed to meet the requirements, which greatly saves the design cost and reduces the use of devices.

[0049] The above description is only an embodiment of the present invention, and does not limit the patent scope of the present invention. Any equivalent transformations made using the contents of the specification and drawings of the present invention, or directly or indirectly applied in the relevant technical field, are also included in the patent protection scope of the present invention.

Claims

1. A step-down converter circuit with adjustable output voltage, characterized in that: It includes a step-down chip U1, a resistor R4, a resistor R5, a capacitor C3, an adjustable voltage pin ADJ and a voltage regulating transformer TR1. The voltage feedback end of the step-down chip U1 is electrically connected to one end of the resistor R4, the adjustable voltage pin ADJ and one end of the resistor R5 respectively. The other end of the resistor R5 is electrically connected to one end of the capacitor C3 and one end of the primary winding of the voltage regulating transformer TR1 respectively. The other end of the resistor R4 and the other end of the capacitor C3 are both grounded.

2. The step-down converter circuit with adjustable output voltage according to claim 1, characterized in that: It also includes a capacitor C5 and a capacitor C7, one end of the capacitor C5 is electrically connected to one end of the resistor R5, one end of the resistor R4, one end of the capacitor C7 and the voltage feedback end of the buck chip U1, the other end of the capacitor C5 is electrically connected to the other end of the resistor R5, one end of the capacitor C3 and one end of the primary winding of the voltage regulating transformer TR1, the other end of the capacitor C7 is electrically connected to the other end of the resistor R4 and the other end of the capacitor C7 is grounded.

3. The step-down converter circuit with adjustable output voltage according to claim 1, characterized in that: It also includes a diode D2, the anode of which is electrically connected to the other end of the resistor R4 and the anode of the diode D2 is grounded, and the cathode of the diode D2 is electrically connected to one end of the resistor R5, one end of the resistor R4, the voltage feedback end of the buck chip U1 and the adjustable voltage pin ADJ.

4. The step-down converter circuit with adjustable output voltage according to claim 1, characterized in that: It also includes a diode D1 and a capacitor C4, wherein the anode of the diode D1 is electrically connected to one end of the secondary winding of the voltage regulating transformer TR1, the cathode of the diode D1 is electrically connected to one end of the capacitor C4, and the other end of the capacitor C4 is electrically connected to the other end of the secondary winding of the voltage regulating transformer TR1.

5. The step-down converter circuit with adjustable output voltage according to claim 1, characterized in that: A resistor R6 is also included, one end of the resistor R6 is electrically connected to one end of the secondary winding of the voltage regulating transformer TR1, and the other end of the resistor R6 is electrically connected to the other end of the secondary winding of the voltage regulating transformer TR1.

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