Circuit for preventing overlarge voltage drop during empty and full load switching of switching power supply

Abstract

The utility model discloses a circuit for preventing overlarge voltage drop in the empty and full load switching of a switching power supply in the field of circuit design of the switching power supply, which comprises a voltage detection circuit, a control chip, a switching control circuit and a load resistor, and is characterized in that a first input end of the voltage detection circuit is connected with a voltage signal converted from an output current; the second input end of the voltage detection circuit is connected with preset reference voltage, the output end of the voltage detection circuit is connected with a detection pin of the control chip, a control pin of the control chip is connected with the input end of the switch control circuit, and the output end of the switch control circuit is connected with one end of the load resistor. The other end of the load resistor is connected with the positive electrode of the output voltage. The switching power supply solves the problems that the existing switching power supply is low in power supply reliability and is not beneficial to power supply miniaturization and cost reduction and efficiency improvement, can prevent the switching power supply from being overlarge in voltage drop during empty and full load switching, improves the reliability of the power supply, reduces the cost, and is beneficial to optimizing the size space of the power supply.

Description

TECHNICAL FIELD

[0001] The utility model relates to the switching power supply circuit design technical field, specifically, relate to a circuit that prevents switching power supply empty full load switching voltage drop too big. BACKGROUND

[0002] Switching power supply is widely used in modern electronic equipment, in order to meet various complex and changeable power demand, its performance is put forward more strict requirement. For example, in certain application scene, switching power supply needs to have the ability of flexible switching between no load and full load, not only can be stably operated when there is no any load connection, namely no load state, and when the load is suddenly connected, namely from no load to full load rapidly, the power supply can rapidly respond and stably output the required power. Similarly, when the load is removed, namely from full load to no load, the power supply should also be able to smoothly transition, and no large current impact or voltage fluctuation is generated. Secondly, switching power supply requires that its output voltage drop is small when facing load mutation, to avoid affecting the normal operation of equipment or causing data loss due to voltage drop too large.

[0003] In order to achieve the above requirements, the method of accelerating control loop and increasing output filter capacitor is generally used, however, the above two methods will cause the following defects:

[0004] 1, PCB wiring interference: when the control loop is accelerated, the requirement of PCB wiring is also improved accordingly, if the wiring is improper, high-frequency noise and interference may be introduced, which leads to unstable power supply loop and low power supply reliability.

[0005] 2, the weight and volume of power supply increase: the increase of capacitor usually means the increase of its physical size and weight, which is not conducive to the miniaturization and cost reduction of power supply.

[0006] The above defects need to be solved urgently. INVENTION CONTENTS

[0007] In order to solve the problems of low power supply reliability of existing switching power supply and not conducive to the miniaturization and cost reduction of power supply, the utility model provides a circuit that prevents switching power supply empty full load switching voltage drop too big.

[0008] The utility model technical scheme is as follows:

[0009] The utility model provides a circuit for preventing the voltage drop of switching power supply from being too large during empty load switching, which comprises a voltage detection circuit, a control chip, a switch control circuit and a load resistor, a first input end of the voltage detection circuit is connected with a voltage signal converted from an output current, a second input end of the voltage detection circuit is connected with a preset reference voltage, an output end of the voltage detection circuit is connected with a detection pin of the control chip, a control pin of the control chip is connected with an input end of the switch control circuit, an output end of the switch control circuit is connected with one end of the load resistor, and the other end of the load resistor is connected with a positive electrode of an output voltage.

[0010] According to the utility model, the voltage detection circuit comprises a detection circuit and a feedback circuit, a first input end of the detection circuit is connected with a voltage signal converted from an output current, a second input end of the detection circuit is connected with a preset reference voltage, an output end of the detection circuit is connected with an input end of the feedback circuit, and an output end of the feedback circuit is connected with a detection pin of the control chip.

[0011] According to the utility model, the detection circuit comprises a resistor R1, one end of the resistor R1 is connected with the preset reference voltage, the other end of the resistor R1 is respectively connected with one end of a resistor R2, one end of a capacitor C1, a positive electrode input end of an operational amplifier U2 and an input end of the feedback circuit, the other end of the resistor R2, the other end of the capacitor C1 and one end of a capacitor C5 are all connected with a negative electrode of a power supply voltage, the other end of the capacitor C5 and the positive electrode end of the operational amplifier U2 are all connected with a positive electrode of the power supply voltage, a negative electrode input end of the operational amplifier U2 is respectively connected with one end of a capacitor C2 and one end of a resistor R3, the negative electrode end of the operational amplifier U2 and the other end of the capacitor C2 are all connected with the negative electrode of the power supply voltage, the other end of the resistor R3 is connected with the voltage signal converted from the output current, and an output end of the operational amplifier U2 is connected with the detection pin of the control chip.

[0012] According to the utility model, the feedback circuit comprises a resistor R8, one end of the resistor R8 is connected with an output end of the detection circuit, the other end of the resistor R8 is connected with one end of a diode group D1, the other end of the diode group D1 and one end of a resistor R4 are all connected with the detection pin of the control chip, and the other end of the resistor R4 is connected with the positive electrode of the power supply voltage.

[0013] According to the utility model, the diode group D1 comprises two diodes, and the two diodes are connected in parallel.

[0014] According to the utility model, the second pin of the control chip is connected with the output end of the voltage detection circuit, the first pin of the control chip is connected with the positive pole of the power supply voltage and one end of the capacitor C3 respectively, the other end of the capacitor C3 is connected with the negative pole of the power supply voltage, the third pin of the control chip and the fourth pin of the control chip are both connected with the negative pole of the power supply voltage, the fifth pin of the control chip and one end of the capacitor C4 are both connected with the positive pole of the power supply voltage, the eighth pin of the control chip and the other end of the capacitor C4 are both connected with the negative pole of the output voltage, the sixth pin of the control chip and the seventh pin of the control chip are both connected with the input end of the switch control circuit.

[0015] According to the utility model, the switch control circuit comprises a MOS tube Q1, the G pole of the MOS tube Q1 is connected with the control pin of the control chip, the S pole of the MOS tube Q1 is connected with the negative pole of the output voltage, and the D pole of the MOS tube Q1 is connected with the load resistance.

[0016] According to the utility model, the switch control circuit further comprises resistors R5 and R6, one end of the resistor R5 is connected with the control pin of the control chip, the other end of the resistor R5 and one end of the resistor R6 are both connected with the G pole of the MOS tube Q1, and the other end of the resistor R6 is connected with the negative pole of the output voltage.

[0017] According to the utility model, the MOS tube Q1 is an N channel enhancement type.

[0018] According to the utility model, the beneficial effects are as follows:

[0019] In the above circuit for preventing the voltage drop of the switching power supply from being too large during the switching between the no-load and full-load, the output current is converted into a voltage signal by the conversion device, the voltage detection circuit can capture the change of the output voltage in real time and transmit the signal to the control chip, the control chip controls the current passing through the load resistance through the switch control circuit, when the output is in the no-load or light-load operation, the load resistance is in the working state (equivalent to the switching power supply with a certain load), so that the voltage drop of the output can be improved when the output is switched between the no-load and full-load, when the output is in the heavy-load operation, the load resistance does not work, unnecessary energy consumption is avoided, and the efficiency of the power supply during the heavy-load operation can be improved. The utility model only needs to add a small number of components, so that the voltage drop of the switching power supply during the switching between the no-load and full-load is small without changing other design parameters, thereby preventing the voltage drop of the switching power supply from being too large during the switching between the no-load and full-load, improving the reliability of the power supply, reducing the cost, and being beneficial to optimizing the size of the power supply. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1A circuit diagram of the voltage detection circuit;

[0021] Figure 2 A circuit diagram of the voltage detection circuit;

[0022] Figure 3 A circuit diagram of the detection circuit;

[0023] Figure 4 A circuit diagram of the feedback circuit;

[0024] Figure 5 A circuit diagram of the control chip;

[0025] Figure 6 A circuit diagram of the switch control circuit;

[0026] Figure 7 A circuit diagram of the load resistor. DETAILED DESCRIPTION

[0027] In order to make the technical problems, technical solutions and beneficial effects to be solved by the utility model more clearly understood, the utility model will be further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the utility model and not to limit the utility model.

[0028] As Figure 1 shown, the utility model provides a circuit that prevents switch power supply empty full load switching voltage drop too big, including voltage detection circuit, control chip U1, switch control circuit, load resistance R7, voltage detection circuit's first input end is connected with the voltage signal that output current converts, voltage detection circuit's second input end is connected with preset reference voltage REF, voltage detection circuit's output end is connected with control chip U1's detection pin, control chip U1's control pin is connected with switch control circuit's input end, switch control circuit's output end is connected with load resistance R7 one end, load resistance R7's other end is connected with output voltage's anode. Output current is converted into voltage signal through conversion device, voltage detection circuit can capture the change situation of output voltage in real time, and signal is passed to control chip, and control chip controls the current through load resistance through switch control circuit.

[0029] As Figure 1 , Figure 2 shown, in the embodiment, voltage detection circuit includes detection circuit, feedback circuit, detection circuit's first input end is connected with the voltage signal that output current converts, detection circuit's second input end is connected with preset reference voltage REF, detection circuit's output end is connected with feedback circuit's input end, feedback circuit's output end is connected with control chip U1's detection pin.

[0030] As Figure 2 ,Figure 3 As shown, specifically, the detection circuit includes resistor R1, one end of resistor R1 is connected with preset reference voltage REF, the other end of resistor R1 is connected with one end of resistor R2, one end of capacitor C1, positive supply input end of operational amplifier U2, input end of feedback circuit respectively, the other end of resistor R2, the other end of capacitor C1, one end of capacitor C5 are all connected with negative pole GND of supply voltage, the other end of capacitor C5, positive supply end of operational amplifier U2 are all connected with positive pole VCC of supply voltage, negative supply input end of operational amplifier U2 is connected with one end of capacitor C2, one end of resistor R3 respectively, negative supply end of operational amplifier U2, the other end of capacitor C2 are all connected with negative pole GND of supply voltage, the other end of resistor R3 is connected with voltage signal converted from output current, the output end of operational amplifier U2 is connected with detection pin of control chip U1.

[0031] As shown in the figure, Figure 2 , Figure 4 In the embodiment, the feedback circuit includes resistor R8, one end of resistor R8 is connected with output end of the detection circuit, the other end of resistor R8 is connected with one end of diode group D1, the other end of diode group D1, one end of resistor R4 are all connected with detection pin of control chip U1, the other end of resistor R4 is connected with positive pole VCC of supply voltage.

[0032] As shown in the figure, Figures 1 to 4 In the voltage detection circuit, resistor R1 and resistor R2 are voltage dividing resistors, resistor R3 is an anti-interference resistor, capacitor C1, capacitor C2, capacitor C5 are filter capacitors, output current is converted into voltage signal N1 through conversion device (current transformer or Hall current sensor), is divided by resistor R1 and resistor R2 and filtered by capacitor C1, and then sent to the positive supply input end of operational amplifier U2, preset reference voltage REF is filtered by resistor R3 and capacitor C2, and then sent to the negative supply input end of operational amplifier U1, the output end of operational amplifier U2 and its positive supply input end realize positive feedback through resistor R4, resistor R8 and diode group D1, due to the existence of positive feedback of operational amplifier U2, the output current needs to have a suitable current back difference for signal flip of operational amplifier U2, so under the condition of static load, the circuit will not repeatedly act. In addition, diode group D1 includes two diodes, and the two diodes are connected in parallel.

[0033] As shown in the figure, Figure 1 , Figure 5As shown in the figure, in the embodiment, the second pin of the control chip U1 is connected with the resistor R4, the output terminal of the operational amplifier U2 and the diode group D1 respectively, the first pin of the control chip U1 is connected with the positive pole VCC of the power supply voltage and one end of the capacitor C3 respectively, the other end of the capacitor C3 is connected with the negative pole GND of the power supply voltage, the third pin of the control chip U1 and the fourth pin of the control chip U1 are both connected with the negative pole GND of the power supply voltage, the fifth pin of the control chip U1 and one end of the capacitor C4 are both connected with the positive pole of the power supply voltage VDD, the eighth pin of the control chip U1 and the other end of the capacitor C4 are both connected with the negative pole VOUT- of the output voltage, the sixth pin of the control chip U1 and the seventh pin of the control chip U1 are both connected with the input terminal of the switch control circuit. The capacitor C3 and the capacitor C4 are filter capacitors, the control chip U1 is an isolation IC chip, and the signal amplified by the operational amplifier U2 passes through the control chip U1 to control the current flowing through the load resistor R7 through the switch control circuit.

[0034] As shown in the figure, Figure 1 , Figure 6 , Figure 7 As shown in the figure, in the embodiment, the switch control circuit comprises a MOS tube Q1, a resistor R5 and a resistor R6, one end of the resistor R5 is connected with the fifth pin and the sixth pin of the control chip U1, the other end of the resistor R5 and one end of the resistor R6 are both connected with the G pole of the MOS tube Q1, the S pole of the MOS tube Q1 and the other end of the resistor R6 are both connected with the negative pole VOUT- of the output voltage, the D pole of the MOS tube Q1 is connected with one end of the load resistor R7, and the other end of the load resistor R7 is connected with the positive pole VOUT+ of the output voltage. In addition, the MOS tube Q1 is an N-channel enhancement type, and in actual use, the model of the MOS tube Q1 can be designed according to actual needs.

[0035] In the embodiment, the resistor R5 and the resistor R6 are voltage dividing resistors, the signal amplified by the operational amplifier U2 passes through the control chip U1, and then passes through the voltage dividing resistors R5 and R6 to control the turn-on and turn-off of the MOS tube Q1, so as to control the current flowing through the load resistor R7, when the output is in an idle state or a light load state, the load resistor R7 is in a working state (equivalent to the power supply carrying a certain load), so that when the output switches between the idle state and the full load state, the voltage drop of the output voltage can be improved; when the output is in a heavy load state, the load resistor R7 does not work, unnecessary energy consumption is avoided, and the efficiency of the power supply in the heavy load state can be improved. The utility model only needs to add a small number of components, so that the output voltage drop of the switching power supply is small when switching between the idle state and the full load state without changing other design parameters, thereby preventing the output voltage drop of the switching power supply from being too large when switching between the idle state and the full load state, improving the reliability of the power supply, reducing the cost, and being conducive to optimizing the size of the power supply space.

[0036] It should be understood that, for those skilled in the art, improvements or changes can be made according to the above description, and all these improvements and changes shall belong to the protection scope of the appended claims of the utility model.

[0037] The utility model patent is exemplarily described above in combination with the drawings, and obviously the implementation of the utility model patent is not limited by the above-mentioned mode. As long as various improvements are made by adopting the method concept and technical scheme of the utility model patent, or the concept and technical scheme of the utility model patent is directly applied to other occasions without improvement, it is within the protection scope of the utility model.

Claims

1. A circuit for preventing excessive voltage drop during no-load and full-load switching of a switching power supply, characterized in that, The voltage detection circuit comprises a detection circuit and a feedback circuit, the first input end of the detection circuit is connected with the voltage signal converted by the output current, the second input end of the detection circuit is connected with the preset reference voltage, the output end of the detection circuit is connected with the input end of the feedback circuit, and the output end of the feedback circuit is connected with the detection pin of the control chip.

2. The circuit for preventing a switching power supply from switching over-voltage at no-load and full-load according to claim 1, characterized in that, The voltage detection circuit comprises a detection circuit and a feedback circuit, the first input end of the detection circuit is connected with the voltage signal converted by the output current, the second input end of the detection circuit is connected with the preset reference voltage, the output end of the detection circuit is connected with the input end of the feedback circuit, and the output end of the feedback circuit is connected with the detection pin of the control chip.

3. The circuit for preventing the output voltage from being excessively reduced due to the switching between the light load and the no load of the switching power supply according to claim 2, wherein The detection circuit comprises a resistor R1, one end of the resistor R1 is connected with the preset reference voltage, the other end of the resistor R1 is respectively connected with one end of a resistor R2, one end of a capacitor C1, the positive power supply input end of an operational amplifier U2 and the input end of the feedback circuit, the other end of the resistor R2, the other end of the capacitor C1 and one end of a capacitor C5 are all connected with the negative pole of the power supply voltage, the other end of the capacitor C5 and the positive power supply end of the operational amplifier U2 are all connected with the positive pole of the power supply voltage, the negative power supply input end of the operational amplifier U2 is respectively connected with one end of a capacitor C2 and one end of a resistor R3, the negative power supply end of the operational amplifier U2 and the other end of the capacitor C2 are all connected with the negative pole of the power supply voltage, the other end of the resistor R3 is connected with the voltage signal converted by the output current, and the output end of the operational amplifier U2 is connected with the detection pin of the control chip.

4. The circuit for preventing a switching power supply from switching over-voltage at no-load and full-load according to claim 2, characterized in that, The feedback circuit comprises a resistor R8, one end of the resistor R8 is connected with the output end of the detection circuit, the other end of the resistor R8 is connected with one end of a diode group D1, the other end of the diode group D1 and one end of a resistor R4 are all connected with the detection pin of the control chip, and the other end of the resistor R4 is connected with the positive pole of the power supply voltage.

5. The circuit for preventing a switching power supply from switching over-voltage at no-load and full-load according to claim 4, wherein The diode group D1 comprises two diodes which are connected in parallel.

6. The circuit for preventing a switching power supply from switching over-voltage at no-load and full-load according to claim 1, characterized in that, The second pin of the control chip is connected with the output end of the voltage detection circuit, the first pin of the control chip is respectively connected with the positive pole of the power supply voltage and one end of a capacitor C3, the other end of the capacitor C3 is connected with the negative pole of the power supply voltage, the third pin of the control chip and the fourth pin of the control chip are all connected with the negative pole of the power supply voltage, the fifth pin of the control chip and one end of a capacitor C4 are all connected with the positive pole of the power supply voltage, the eighth pin of the control chip and the other end of the capacitor C4 are all connected with the negative pole of the output voltage, and the sixth pin of the control chip and the seventh pin of the control chip are all connected with the input end of the switch control circuit.

7. The circuit for preventing a switching power supply from switching over-voltage at no-load and full-load according to claim 1, characterized in that, The switch control circuit comprises a MOS tube Q1, a G pole of the MOS tube Q1 is connected with a control pin of the control chip, an S pole of the MOS tube Q1 is connected with a negative pole of an output voltage, and a D pole of the MOS tube Q1 is connected with the load resistor.

8. The circuit for preventing a switching power supply from switching over-voltage at no-load and full-load according to claim 7, characterized in that, The switch control circuit further comprises a resistor R5 and a resistor R6, one end of the resistor R5 is connected with the control pin of the control chip, the other end of the resistor R5 and one end of the resistor R6 are both connected with the G pole of the MOS tube Q1, and the other end of the resistor R6 is connected with the negative pole of the output voltage.

9. The circuit for preventing a switching power supply from switching over-voltage at no-load and full-load according to claim 7, characterized in that, The MOS tube Q1 is an N channel enhancement type.

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