Step-down switching power supply circuit

Abstract

The utility model relates to a step-down switching power supply circuit, which comprises a feedback acquisition circuit, a feedback control circuit and a BUCK step-down circuit for step-down, the feedback acquisition circuit is arranged at the output end of the BUCK step-down circuit so as to acquire and monitor the output voltage; the input end of the feedback control circuit is connected with the output end of the feedback acquisition circuit; and the output end of the feedback control circuit is connected with the controlled end of the switching tube of the BUCK step-down circuit so as to adjust the output voltage of the BUCK step-down circuit according to the output of the feedback acquisition circuit. According to the technical scheme and the circuit scheme of the utility model, a special power supply chip is not needed, so that the cost is very low, and the circuit is not limited by the capacity and supply of chip manufacturers, and has very strong practicability; according to the circuit scheme, the on-off of the switching tube can be automatically adjusted along with the load current, and the efficiency is high; the scheme can realize common-ground output and can be suitable for various occasions.

Description

Technical Field

[0001] The utility model relates to the technical field of power supply circuits, in particular to a step-down switching power supply circuit. Background Art

[0002] A switching power supply is a high-frequency power conversion device, which converts a standard voltage into the voltage or current required by the user through different forms of architecture. Switching power supplies have been widely used in various industries due to their high efficiency, small size and light weight, among which BUCK step-down switching power supplies are the most widely used. Among them, there are many step-down power supply chip products with a voltage below 100V, and the competition is fierce.

[0003] The existing BUCK switching power supply chips on the market are restricted by semiconductor process technology. The input voltage of this type of chip is mainly concentrated below 100V. For step-down power supplies with input voltages greater than 100V or even above 300V, the industry can only use low-voltage switching power supply chips to control high-voltage power tubes, and then use transformers to convert voltage and then rectify to generate low-voltage power. However, this method has increased losses in high-voltage power tubes, transformers, and secondary rectifier diodes, so the overall efficiency is low and the circuit cost is high. In addition, since its input and output are not grounded, it is inconvenient when grounding is required. Utility Model Content

[0004] Based on this, it is necessary to provide a buck switching power supply circuit to address the problem of low efficiency of the existing BUCK buck circuit.

[0005] A step-down switching power supply circuit comprises a feedback collection circuit, a feedback control circuit and a BUCK step-down circuit for stepping down the voltage; the feedback collection circuit is arranged at the output end of the BUCK step-down circuit to collect and monitor the output voltage; the input end of the feedback control circuit is connected to the output end of the feedback collection circuit; the output end of the feedback control circuit is connected to the controlled end of the switch tube of the BUCK step-down circuit to adjust the output voltage of the BUCK step-down circuit according to the output of the feedback collection circuit.

[0006] Furthermore, the BUCK step-down circuit includes a first switch tube, a first inductor, a third diode, a first capacitor, a first resistor and a fourth resistor; the input end of the first switch tube is connected to the input positive electrode, the output end of the first switch tube is connected to the first end of the first inductor, and the second end of the first inductor is connected to the output positive electrode; the first capacitor is connected in parallel to the output positive electrode and the output negative electrode; the positive electrode of the third diode is connected to the output negative electrode, and the negative electrode of the third diode is connected to the first end of the first inductor; the first end of the first resistor is connected to the input positive electrode, the second end of the first resistor is connected to the first end of the fourth resistor, the second end of the first resistor is also connected to the controlled end of the first switch tube, and the second end of the fourth resistor is connected to the input negative electrode and the output negative electrode.

[0007] Furthermore, the feedback acquisition circuit includes a fifth resistor, a seventh resistor, and a third switch tube, the first end of the fifth resistor is connected to the output positive electrode, the second end of the fifth resistor is connected to the first end of the seventh resistor, and the second end of the seventh resistor is connected to the output negative electrode; the input end of the third switch tube is connected to the input end of the feedback control circuit, and the output end of the third switch tube is connected to the input negative electrode; the second end of the fifth resistor is also connected to the controlled end of the third switch tube to control the switching of the third switch tube.

[0008] Furthermore, the feedback control circuit includes a second switch tube, a second resistor, a third resistor and a first diode; the input end of the second switch tube is connected to the input positive electrode, the output end of the second switch tube is connected to the positive electrode of the first diode; the cathode of the first diode is connected to the controlled end of the first switch tube; the first end of the second resistor is connected to the input positive electrode, the second end of the second resistor is connected to the first end of the third resistor, the second end of the third resistor is connected to the input end of the third switch tube, and the second end of the second resistor is connected to the controlled end of the second switch tube.

[0009] Furthermore, the step-down switching power supply circuit also includes a second diode and a sixth resistor, the anode of the second diode is connected to the output end of the second switch tube, the cathode of the second diode is connected to the first end of the sixth resistor, and the second end of the sixth resistor is connected to the controlled end of the third switch tube.

[0010] Furthermore, the first switch tube and the third switch tube are both MOS tubes, and the second switch tube is a triode.

[0011] Furthermore, the VDS withstand voltage of the first switch tube is at least 300V.

[0012] The technical solution of the utility model does not require the use of a dedicated power chip, which is not only low-cost, but also not subject to the production capacity and supply restrictions of chip manufacturers, and has strong practicality. The circuit solution automatically adjusts the on-off of the switch tube according to the load current, and has high efficiency; the solution can achieve common ground output and can be applied to a variety of occasions. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 The utility model is a circuit diagram of a step-down switching power supply circuit according to an embodiment of the present invention. DETAILED DESCRIPTION

[0014] In order to make the above-mentioned purposes, features and advantages of the utility model more obvious and easy to understand, the specific implementation methods of the utility model are described clearly and completely below in conjunction with the accompanying drawings. Obviously, the specific details described below are only part of the embodiments of the utility model, and the utility model can also be implemented in many other embodiments different from those described here. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the protection scope of the utility model.

[0015] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only and do not represent the only implementation method.

[0016] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0017] In one embodiment, see Figure 1 As shown, a buck switching power supply circuit includes a feedback collection circuit, a feedback control circuit and a BUCK buck circuit for bucking; the feedback collection circuit is arranged at the output end of the BUCK buck circuit to collect and monitor the output voltage; the input end of the feedback control circuit is connected to the output end of the feedback collection circuit; the output end of the feedback control circuit is connected to the controlled end of the switch tube of the BUCK buck circuit to adjust the output voltage of the BUCK buck circuit according to the output of the feedback collection circuit.

[0018] This circuit solution does not require the use of a dedicated power chip, which is not only low-cost, but also not subject to the production capacity and supply restrictions of chip manufacturers, and has strong practicality; this circuit solution will automatically adjust the on and off of the switch tube according to the load current, and has high efficiency; this solution can achieve common ground output and can be applied to a variety of occasions.

[0019] On the basis of the present embodiment, the BUCK buck circuit includes a first switch tube, a first inductor, a third diode, a first capacitor, a first resistor and a fourth resistor; the input end of the first switch tube is connected to the input positive electrode, the output end of the first switch tube is connected to the first end of the first inductor, and the second end of the first inductor is connected to the output positive electrode; the first capacitor is connected in parallel to the output positive electrode and the output negative electrode; the positive electrode of the third diode is connected to the output negative electrode, and the negative electrode of the third diode is connected to the first end of the first inductor; the first end of the first resistor is connected to the input positive electrode, the second end of the first resistor is connected to the first end of the fourth resistor, the second end of the first resistor is also connected to the controlled end of the first switch tube, and the second end of the fourth resistor is connected to the input negative electrode and the output negative electrode. Of course, the circuit structure of the BUCK buck circuit can also be other, as long as it can achieve the required function, and is not limited to the description in the present embodiment.

[0020] The feedback collection circuit includes a fifth resistor, a seventh resistor, and a third switch tube. The first end of the fifth resistor is connected to the output positive electrode, the second end of the fifth resistor is connected to the first end of the seventh resistor, and the second end of the seventh resistor is connected to the output negative electrode; the input end of the third switch tube is connected to the input end of the feedback control circuit, and the output end of the third switch tube is connected to the input negative electrode; the second end of the fifth resistor is also connected to the controlled end of the third switch tube to control the switch of the third switch tube. Of course, the circuit structure of the feedback collection circuit can also be other, as long as it can achieve the required function, and is not limited to the description in this embodiment.

[0021] Furthermore, the feedback control circuit includes a second switch tube, a second resistor, a third resistor and a first diode; the input end of the second switch tube is connected to the input positive electrode, the output end of the second switch tube is connected to the positive electrode of the first diode; the negative electrode of the first diode is connected to the controlled end of the first switch tube; the first end of the second resistor is connected to the input positive electrode, the second end of the second resistor is connected to the first end of the third resistor, the second end of the third resistor is connected to the input end of the third switch tube, and the second end of the second resistor is connected to the controlled end of the second switch tube. Of course, the circuit structure of the feedback control circuit can also be other, as long as it can achieve the required function, and is not limited to the description in this embodiment.

[0022] Specifically, the step-down switching power supply circuit also includes a second diode and a sixth resistor, the anode of the second diode is connected to the output end of the second switch tube, the cathode of the second diode is connected to the first end of the sixth resistor, and the second end of the sixth resistor is connected to the controlled end of the third switch tube.

[0023] Furthermore, the first switch tube and the third switch tube are both MOS tubes, and the second switch tube is a triode. Specifically, the VDS withstand voltage of the first switch tube is at least 300V.

[0024] The specific working process of the circuit of the embodiment of the utility model is as follows:

[0025] Output voltage increasing process: when the input power supply is just connected to the power supply, the voltage of the first capacitor C1 is relatively low, the voltage divided by the fifth resistor R5 and the seventh resistor R7 is lower than the VGS turn-on voltage of the third switch tube Q3, the third switch tube Q3 is in the off state, there is no current on the third resistor R3, the second resistor R2 turns the second switch tube Q2 off, and the first diode D1 and the second diode D2 are therefore also in a reverse voltage state. After the first resistor R1 and the fourth resistor R4 divide the voltage, the first switch tube Q1 is driven to be fully turned on, and the input power charges the first capacitor C1 through the first switch tube Q1 and the first inductor L1, so that the voltage of the first capacitor C1 gradually increases.

[0026] The shutdown control process after the output voltage reaches the set value: when the voltage across the first capacitor C1 (i.e., the output voltage) rises to the required voltage setting value (e.g., 15V), the voltage value of the output voltage after being divided by the fifth resistor R5 and the seventh resistor R7 is greater than the VGS turn-on voltage of the third switch tube Q3 (e.g., the fifth resistor R5 is 6.5k, the seventh resistor R7 is 1k, and the VGS turn-on voltage is 2V), so that the third switch tube Q3 is turned on, and the third resistor R3 is equivalent to being grounded, so that the second switch tube Q2 is turned on. At this time, the input voltage is connected to the positive electrode of the first diode D1 through the second switch tube Q2, so that the GS pole of the first switch tube Q1 The voltage is less than 1V, so that the first switch tube Q1 is turned off; after the first switch tube Q1 is turned off, the current on the first inductor L1 cannot change suddenly, and the current is continued through the third diode D3, so that the voltage of the first capacitor C1 continues to increase briefly; at this time, the input voltage is also connected to the positive electrode of the second diode D2 through the second switch tube Q2, and after passing through the sixth resistor R6, the voltage division value of the fifth resistor R5 and the seventh resistor R7 is further increased (for example, the input voltage is 300V, and the resistance of the sixth resistor R6 is 3M. ​​At this time, the voltage division value of the fifth resistor R5 and the seventh resistor R7 will add 0.1V, increasing from 2V to 2.1V), thereby accelerating the shutdown process of the third switch tube Q3.

[0027] Output voltage drop process: Since the first switch tube Q1 has been turned off, the energy on the first inductor L1 is quickly released after the third diode D3 continues to flow, and the voltage on the first capacitor C1 no longer rises. At this time, when the output end is connected to a load, the voltage of the first capacitor C1 will begin to gradually drop. The speed of the drop is related to the capacity of the first capacitor C1 and the load current.

[0028] Output voltage recovery and rising process: when the voltage of the first capacitor C1 drops to the voltage at the node of the fifth resistor R5 and the seventh resistor R7, which is less than the VGS turn-on voltage of the third switch tube Q3 (for example, the output voltage drops to 14.3V, and the G pole of the third switch tube Q3 drops to 2V at this time), the third switch tube Q3 is turned off, there is no current on the third resistor R3, and the voltage across the second resistor R2 becomes high, so that the second switch tube Q2 is turned off. At this time, the first diode D1 and the second diode D2 are restored to the reverse voltage state, and there is no current on the sixth resistor R6. The G pole voltage of the third switch tube Q3 is further accelerated to decrease to below 2V, so that the third switch tube Q3 is accelerated to turn off; at this time, the G pole voltage of the first switch tube Q1 drops, so that the first switch tube Q1 is restored to conduction, and the input voltage charges the first capacitor C1 through the first switch tube Q1 and the first inductor L1, and the voltage of the first capacitor C1 is restored to rise.

[0029] It can be seen from the above working process that when the output voltage is less than the set value, the first switch tube Q1 will be turned on to increase the output voltage. When the output voltage reaches the set value, the first switch tube Q1 will automatically turn off to reduce the output voltage. The entire circuit will work in a switching state, and the ratio of the on-time to the off-time will automatically change with the load current, so that the output voltage is stabilized within a certain range.

[0030] The technical solution of the utility model does not require the use of a dedicated power chip, and the circuit solution is not only low in cost, but also not subject to the production capacity and supply restrictions of chip manufacturers, and has strong practicality; the circuit solution automatically adjusts the on and off of the switch tube according to the load current, and has high efficiency; the solution can achieve common ground output, and can be suitable for a variety of occasions.

[0031] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0032] The above-mentioned embodiments only express several implementation methods of the utility model, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the utility model patent. It should be pointed out that for ordinary technicians in this field, several deformations, substitutions and improvements can be made without departing from the concept of the utility model, which should be included in the protection scope of the utility model. Therefore, the protection scope of the utility model patent should be based on the claims.

Claims

1. A step-down switching power supply circuit, characterized in that: include: Feedback collection circuit, feedback control circuit and BUCK step-down circuit for stepping down voltage; The feedback collection circuit is arranged at the output end of the BUCK buck circuit to collect and monitor the output voltage; the input end of the feedback control circuit is connected to the output end of the feedback collection circuit; the output end of the feedback control circuit is connected to the controlled end of the switch tube of the BUCK buck circuit to adjust the output voltage of the BUCK buck circuit according to the output of the feedback collection circuit.

2. The step-down switching power supply circuit according to claim 1, characterized in that: The BUCK step-down circuit includes a first switch tube, a first inductor, a third diode, a first capacitor, a first resistor and a fourth resistor; the input end of the first switch tube is connected to the input positive electrode, the output end of the first switch tube is connected to the first end of the first inductor, and the second end of the first inductor is connected to the output positive electrode; the first capacitor is connected in parallel to the output positive electrode and the output negative electrode; the positive electrode of the third diode is connected to the output negative electrode, and the negative electrode of the third diode is connected to the first end of the first inductor; the first end of the first resistor is connected to the input positive electrode, the second end of the first resistor is connected to the first end of the fourth resistor, the second end of the first resistor is also connected to the controlled end of the first switch tube, and the second end of the fourth resistor is connected to the input negative electrode and the output negative electrode.

3. The step-down switching power supply circuit according to claim 2, characterized in that: The feedback acquisition circuit includes a fifth resistor, a seventh resistor, and a third switch tube. The first end of the fifth resistor is connected to the output positive electrode, the second end of the fifth resistor is connected to the first end of the seventh resistor, and the second end of the seventh resistor is connected to the output negative electrode; the input end of the third switch tube is connected to the input end of the feedback control circuit, and the output end of the third switch tube is connected to the input negative electrode; the second end of the fifth resistor is also connected to the controlled end of the third switch tube to control the switch of the third switch tube.

4. The step-down switching power supply circuit according to claim 3, characterized in that: The feedback control circuit includes a second switch tube, a second resistor, a third resistor and a first diode; the input end of the second switch tube is connected to the input positive electrode, the output end of the second switch tube is connected to the positive electrode of the first diode; the cathode of the first diode is connected to the controlled end of the first switch tube; the first end of the second resistor is connected to the input positive electrode, the second end of the second resistor is connected to the first end of the third resistor, the second end of the third resistor is connected to the input end of the third switch tube, and the second end of the second resistor is connected to the controlled end of the second switch tube.

5. The step-down switching power supply circuit according to claim 4, characterized in that: It also includes a second diode and a sixth resistor, wherein the anode of the second diode is connected to the output end of the second switch tube, the cathode of the second diode is connected to the first end of the sixth resistor, and the second end of the sixth resistor is connected to the controlled end of the third switch tube.

6. The step-down switching power supply circuit according to claim 5, characterized in that: The first switch tube and the third switch tube are both MOS tubes, and the second switch tube is a triode.

7. The step-down switching power supply circuit according to claim 6, characterized in that: The VDS withstand voltage of the first switch tube is at least 300V.

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