A power supply system with a fast current limiting switch

Abstract

The present invention belongs to the technical field of output protection devices for power supply equipment, and discloses a power supply system with a fast current-limiting switch, including: a constant current source, a power conversion circuit, a post-stage circuit device, a current-limiting switch circuit, a single-chip microcomputer, a current-sensing resistor RS, a current detection circuit, an over-current comparison circuit, a drive circuit, a switching tube, a voltage detection circuit, capacitors C1, C2, C3, C4, C5, diodes D1, D2, D3, an inductor L1, and a switching tube Q1. When a short circuit or over-current occurs in the post-stage circuit device, the present invention can protect the power supply equipment while reducing the risk of damage to the circuit under test; when a short circuit occurs in the post-stage circuit device and there is a switching tube on the short-circuit loop, the present invention can protect the switching tube from damage and explosion, reduce the debugging risk, and also reduce the psychological pressure of the debugging personnel; the present invention can be used in the whole process of development and debugging of power electronic circuits, protect the post-stage circuit, and improve the work efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of output protection devices for power supply equipment, and particularly relates to a power supply system with a fast current-limiting switch. Background Art

[0002] When circuit devices are being debugged and operated, especially when power electronic circuits are being debugged, a separate power supply device is usually used to supply power to them.

[0003] Currently, for power supply devices on the market, the capacitance values of the output capacitors are usually relatively large. Especially when the power supply output is high voltage, the energy stored in the output capacitor will be very large. Although most power supply devices are of the constant current and constant voltage type, if a short circuit occurs in the subsequent circuit device, the power supply device will not limit the release of the energy on the output capacitor. When a short circuit problem occurs in the subsequent circuit device, this energy will be released instantaneously, which may cause damage to the components in the subsequent circuit device. If there is a switching transistor in the short-circuit loop, it may even cause the switching transistor to explode and catch fire.

[0004] Through the above analysis, the problems and defects existing in the prior art are as follows:

[0005] (1) When a short circuit problem occurs in the subsequent circuit device, this energy will be released instantaneously, which may cause damage to the components in the subsequent circuit device.

[0006] (2) If there is a switching transistor in the short-circuit loop, it may even cause the switching transistor to explode and catch fire. Summary of the Invention

[0007] To solve the above problems, the present invention improves the ordinary current-limiting protection circuit, places the current-limiting switch circuit at the rear end of the output capacitor, and simultaneously realizes fast detection and fast protection, obtaining a power supply system with a fast current-limiting switch, which can perform current-limiting protection on the subsequent circuit device and prevent damage to the components in the circuit.

[0008] The present invention is implemented as follows. A power supply system with a fast current-limiting switch, the power supply system with a fast current-limiting switch includes: a constant current source, a power conversion circuit, a subsequent circuit device, a current-limiting switch circuit, a single-chip microcomputer, a current-sensing resistor RS, a current detection circuit, an overcurrent comparison circuit, a drive circuit, a switching transistor, a voltage detection circuit, capacitors C1, C2, C3, C4, C5, diodes D1, D2, D3, an inductor L1, and a switching transistor Q1;

[0009] The constant current source is connected to both ends of the current-limiting switch circuit, the power conversion circuit is connected to the current-limiting switch circuit, the current-limiting switch circuit is connected to the subsequent circuit device, the current-sensing resistor RS is connected to the current detection circuit, the current detection circuit is connected to the single-chip microcomputer and the overcurrent comparison circuit, the drive circuit is connected to the single-chip microcomputer, the overcurrent comparison circuit, and the switching transistor, and the voltage detection circuit is connected to the single-chip microcomputer;

[0010] The output capacitors C1 to C3 of the power conversion circuit are connected to the switch tube Q1 and the π-type filter circuit (capacitor C4, inductor L1, capacitor C5) in sequence. The switch tube Q1 is turned on and off to control the output N3. The inductor L1 limits the rising slope of the output current. The π-type filter circuit appropriately filters the output voltage to reduce oscillation during the switching process of the switch tube Q1.

[0011] The current-sense resistor RS is sent to the microcontroller for sampling through the current detection circuit and is simultaneously transmitted to the overcurrent comparison circuit. The overcurrent comparison signal is read by the microcontroller and transmitted to the drive circuit to control the switch tube. If an overcurrent occurs, the overcurrent comparison signal becomes high and self-locked, and directly controls the switch tube to turn off. Otherwise, the overcurrent comparison signal is low, and Rs is placed at the positive output end, which can support the operation of parallel output of multiple power supply devices.

[0012] Furthermore, the single-chip microcomputer directly outputs a control signal to the drive circuit to control the switching of the switch tube; the single-chip microcomputer detects the state of the reset button, outputs a reset operation signal to the overcurrent comparison circuit, releases the self-locking of the overcurrent comparison signal, and thus releases the protection state.

[0013] Furthermore, the logic of the reset operation signal and the overcurrent comparison signal is as follows: when a reset operation signal is generated, the overcurrent comparison signal is low regardless of whether there is an overcurrent; when no reset operation signal is generated, if an overcurrent occurs, the overcurrent comparison signal is high, and if no overcurrent occurs, the overcurrent comparison signal is low.

[0014] Furthermore, the logic of the overcurrent comparison signal, control signal to drive signal Drv is as follows: when the overcurrent comparison signal is low, the high and low of the control signal directly control the high and low of Drv; when the overcurrent comparison signal is high, Drv is low regardless of whether the control signal is high or low.

[0015] Furthermore, the function of the constant current source is that when the switch tube Q1 is turned off, the voltage at point N1 is first established, and the constant current source circuit begins to operate, generating a constant small current I to charge capacitors C4 and C5. If the downstream circuit equipment is in a short-circuit state, the voltage at N3 will not increase and will remain at 0. At this time, the software detects that the N3 voltage is less than the set threshold and prohibits the opening of the switch tube Q1. This situation is also applicable to the case where the short-circuit state of the downstream circuit equipment has not been resolved after a current limiting protection operation, and the operator still performs a reset operation. The voltage detection circuit combined with the software program prohibits the opening of the switch tube Q1, thereby improving the safety of the power supply.

[0016] Furthermore, the current detection circuit, overcurrent comparison circuit, and drive circuit are all implemented by hardware circuits, and the response speed can be very fast. When a short circuit occurs in the subsequent circuit device, the hardware circuit will immediately detect the overcurrent and quickly turn off the switching transistor. The capacitance value of the π-type filter circuit is very small, and the released energy is not enough to damage the devices of the subsequent circuit device.

[0017] Furthermore, the current limiting switch circuit part is composed of a single switching transistor and a π-type filter circuit.

[0018] Furthermore, the parameter selection principle of the π-type filter circuit is as follows: Determine the rated current of the inductor L1 according to the maximum current limiting value, determine the inductance value according to the limited current rising slope, overcurrent protection response time, and the maximum released energy during short circuit. Capacitors C4 and C5 provide a path for high-frequency ripple current at the output end, and their capacitances are much smaller than C1 - C3.

[0019] Furthermore, the diodes D1 and D2 are selected as ultra-fast recovery diodes.

[0020] Combined with the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solution to be protected by the present invention are as follows:

[0021] First, in view of the technical problems existing in the above prior art and the difficulty of solving this problem, closely combined with the technical solution to be protected by the present invention and the results and data during the R & D process, etc., analyze in detail and deeply how the technical solution of the present invention solves the technical problems and the creative technical effects brought after solving the problems. The specific description is as follows:

[0022] When a short circuit or overcurrent occurs in the subsequent circuit device of the present invention, it can protect the power supply device while reducing the risk of damage to the circuit under test.

[0023] When a short circuit occurs in the subsequent circuit device of the present invention and there is a switching transistor in the short circuit loop, it can protect the switching transistor from damage and explosion, reduce the debugging danger, and also reduce the psychological pressure of the debugging personnel.

[0024] The present invention can be used in the whole process of power electronics circuit development and debugging. While protecting the subsequent circuit, it improves the work efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is the circuit diagram of the power supply system with a fast current limiting switch provided by the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0026] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0027] In order to enable those skilled in the art to fully understand how to implement the present invention, this section provides an explanatory embodiment that expands on the technical solutions of the claims.

[0028] like Figure 1 As shown, a power supply system with a fast current limiting switch includes: a constant current source, a power conversion circuit, a subsequent circuit device, a current limiting switch circuit, a single-chip microcomputer, a current sensing resistor RS, a current detection circuit, an overcurrent comparison circuit, a drive circuit, a switch tube, a voltage detection circuit, capacitors C1, C2, C3, C4, and C5, diodes D1, D2, and D3, an inductor L1, and a switch tube Q1;

[0029] The constant current source is connected to both ends of the current limiting switch circuit, the power conversion circuit is connected to the current limiting switch circuit, the current limiting switch circuit is connected to the subsequent circuit equipment, the current sensing resistor RS is connected to the current detection circuit, the current detection circuit is connected to the single-chip microcomputer and the overcurrent comparison circuit, the drive circuit is connected to the single-chip microcomputer, the overcurrent comparison circuit, and the switch tube, and the voltage detection circuit is connected to the single-chip microcomputer;

[0030] The output capacitors C1 to C3 of the power conversion circuit are connected to the switch tube Q1 and the π-type filter circuit (capacitor C4, inductor L1, capacitor C5) in sequence. The switch tube Q1 is turned on and off to control the output N3. The inductor L1 limits the rising slope of the output current. The π-type filter circuit appropriately filters the output voltage to reduce oscillation during the switching process of the switch tube Q1.

[0031] The current-sense resistor RS is sent to the microcontroller for sampling through the current detection circuit and is simultaneously transmitted to the overcurrent comparison circuit. The overcurrent comparison signal is read by the microcontroller and transmitted to the drive circuit to control the switch tube. If an overcurrent occurs, the overcurrent comparison signal becomes high and self-locked, and directly controls the switch tube to turn off. Otherwise, the overcurrent comparison signal is low, and Rs is placed at the positive output end, which can support the operation of parallel output of multiple power supply devices.

[0032] The single chip microcomputer directly outputs a control signal to the drive circuit to control the switch of the switch tube; the single chip microcomputer detects the state of the reset button and outputs a reset operation signal to the overcurrent comparison circuit to release the self-locking of the overcurrent comparison signal, thereby releasing the protection state.

[0033] The logic of the reset operation signal and the overcurrent comparison signal is as follows: when the reset operation signal is generated, the overcurrent comparison signal is low regardless of whether there is an overcurrent; when no reset operation signal is generated, if overcurrent occurs, the overcurrent comparison signal is high, and if no overcurrent occurs, the overcurrent comparison signal is low.

[0034] The logic of the overcurrent comparison signal, control signal to drive signal Drv is as follows: when the overcurrent comparison signal is low, the high and low of the control signal directly control the high and low of Drv; when the overcurrent comparison signal is high, Drv is low regardless of whether the control signal is high or low.

[0035] The function of the constant current source is that when the switch Q1 is turned off, the voltage at point N1 is established, and the constant current source circuit begins to operate, generating a constant small current I to charge capacitors C4 and C5. If the downstream circuit equipment is in a short-circuit state, the voltage at N3 will not increase and will remain at 0. At this time, the software detects that the voltage at N3 is less than the set threshold and prohibits the opening of the switch Q1. This situation also applies to the case where the short-circuit state of the downstream circuit equipment has not been resolved after a current limiting protection operation, and the operator still performs a reset operation. The voltage detection circuit combined with the software program prohibits the opening of the switch Q1, thereby improving the safety of the power supply.

[0036] The current detection circuit, overcurrent comparison circuit, and drive circuit are all implemented by hardware circuits, and the response speed can be very fast. When a short circuit occurs in the subsequent circuit equipment, the hardware circuit will immediately detect the overcurrent and quickly turn off the switch tube. The capacitance value of the π-type filter circuit is very small, and the energy released is not enough to damage the components of the subsequent circuit equipment.

[0037] The current limiting switch circuit part is composed of a single switch tube and a π-type filter circuit.

[0038] The parameters of the π-type filter circuit are selected according to the following principles: the rated current of the inductor L1 is determined according to the maximum current limit value, and the inductor value is determined according to the limited current rise slope, the current limit protection response time, and the maximum released energy during a short circuit. Capacitors C4 and C5 provide a high-frequency ripple current path for the output end, and their capacitance is much smaller than that of C1-C3.

[0039] The diodes D1 and D2 are ultrafast recovery diodes.

[0040] In order to prove the creativity and technical value of the technical solution of the present invention, this section is an application example of applying the claimed technical solution to specific products or related technologies.

[0041] Working principle of the present invention:

[0042] At the output end of the conventional power supply (i.e., after the output capacitors C1 to C3 of the power conversion circuit), the switch tube Q1 and the π-type filter circuit (capacitor C4, inductor L1, capacitor C5) are connected in sequence. The switch tube Q1 is turned on and off to control the presence or absence of the output N3. The inductor L1 limits the rising slope of the output current. The π-type filter circuit appropriately filters the output voltage to reduce oscillation during the switching process of the switch tube Q1.

[0043] The function of the constant current source: When the switch tube Q1 is turned off, the voltage at point N1 is established first, and the constant current source circuit starts to operate, generating a constant small current I to charge capacitors C4 and C5. If the downstream circuit equipment is in a short-circuit state, the voltage at N3 will not increase and will always be 0. At this time, the software detects that the N3 voltage is less than the set threshold and prohibits the opening of the switch tube Q1. This situation also applies to the situation where, after a current limiting protection operation, if the short-circuit state of the downstream circuit equipment has not been released and the operator still performs a reset operation, the voltage detection circuit combined with the software program prohibits the opening of the switch tube Q1, thereby improving the safety of the power supply.

[0044] Voltage detection is performed at points N1 and N3 respectively, and the voltage signals are sent to the microcontroller for sampling.

[0045] Function of D2: When the switch tube Q1 is turned off, the resonance of capacitor C4 and inductor L1 may cause the voltage at point N2 to be lower than 0V. D2 clamps the voltage at point N2 to prevent the switch tube Q1 from being broken down.

[0046] Function of D1: When the subsequent circuit equipment is turned off, the resonance of inductor L1 and capacitor C5 will cause the voltage at point N3 to be higher than the voltage at point N1. D1 clamps the voltage at point N3 to prevent the input voltage of the subsequent circuit equipment from being too high and damaging the circuit.

[0047] Function of D3: After the switch tube Q1 is turned off, when the inductor current of inductor L1 drops to 0, the capacitor C5 resonates with the inductor in the subsequent circuit, which may cause the voltage at point N3 to be lower than 0V. D2 clamps the voltage at point N3 to prevent the input voltage of the subsequent circuit equipment from being negative and damaging the circuit.

[0048] Rs acts as a current-sense resistor. The current is sampled by the microcontroller through the current detection circuit and transmitted to the overcurrent comparator circuit. The microcontroller reads the overcurrent comparison signal and transmits it to the driver circuit to control the switching transistor. If an overcurrent condition occurs, the overcurrent comparison signal goes high and self-latches, directly shutting off the switching transistor. Otherwise, the overcurrent comparison signal remains low. Placing Rs at the positive output terminal supports parallel operation of multiple power supply outputs.

[0049] The single-chip microcomputer directly outputs a control signal to the drive circuit to control the on / off of the switching tube. The single-chip microcomputer detects the status of the reset button and outputs a reset operation signal to the overcurrent comparison circuit to release the self-locking of the overcurrent comparison signal, thereby releasing the protection state.

[0050] The logic of the reset operation signal and the overcurrent comparison signal is as follows: when a reset operation signal is generated, regardless of whether there is an overcurrent situation, the overcurrent comparison signal is low; when no reset operation signal is generated, if an overcurrent occurs, the overcurrent comparison signal is high, and if no overcurrent occurs, the overcurrent comparison signal is low.

[0051] The logic of the overcurrent comparison signal and the control signal to the drive signal Drv is as follows: when the overcurrent comparison signal is low, the high and low levels of the control signal directly control the high and low levels of Drv; when the overcurrent comparison signal is high, regardless of whether the control signal is high or low, Drv is low.

[0052] The principle of protecting the circuit under test from damage in case of a short circuit: The current detection circuit, the overcurrent comparison circuit, and the drive circuit are all implemented by hardware circuits, and the response speed can be very fast. When a short circuit occurs in the subsequent circuit device, the hardware circuit will immediately detect the overcurrent and quickly turn off the switching tube. Moreover, the capacitance value of the π-type filter circuit is very small, and the released energy is not enough to damage the devices of the subsequent circuit device.

[0053] In the description of the present invention, unless otherwise specified, the meaning of "a plurality of" is two or more; the orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", "inner", "outer", "front end", "rear end", "head", "tail", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention. In addition, the terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0054] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention shall be covered by the protection scope of the present invention.

Claims

1. A power supply system with a fast current limiting switch, characterized in that, include: Constant current source, power conversion circuit, post-stage circuit equipment, current limiting switch circuit, single-chip microcomputer, current sensing resistor RS, current detection circuit, overcurrent comparison circuit, drive circuit, switch tube, voltage detection circuit; The constant current source is connected to both ends of the current limiting switch circuit, the power conversion circuit is connected to the input end of the current limiting switch circuit, the output end of the current limiting switch circuit is connected to the input end of the subsequent circuit device, the current detection resistor RS is connected to the current detection circuit, the current detection circuit is connected to the single-chip microcomputer and the overcurrent comparison circuit, the drive circuit is connected to the single-chip microcomputer, the overcurrent comparison circuit, and the switch tube, and the voltage detection circuit is connected to the single-chip microcomputer; The rear ends of the output capacitors C1 to C3 of the power conversion circuit are connected in sequence to a π-type filter circuit consisting of a switch tube Q1, a capacitor C4, an inductor L1, and a capacitor C5. The switching of the switch tube Q1 is used to control the presence or absence of the output N3. The inductor L1 is used to limit the rising slope of the output current. The π-type filter circuit is used to appropriately filter the output voltage to reduce oscillation during the switching process of the switch tube Q1. The current-sense resistor RS is sent to the microcontroller for sampling through the current detection circuit and is simultaneously transmitted to the overcurrent comparison circuit. The overcurrent comparison signal is read by the microcontroller and transmitted to the drive circuit to control the switch tube. If an overcurrent occurs, the overcurrent comparison signal becomes high and self-locked, and directly controls the switch tube to turn off. Otherwise, the overcurrent comparison signal is low. Rs is placed at the positive output terminal, which can support the operation of multiple power supply devices outputting in parallel. The single-chip microcomputer directly outputs a control signal to the drive circuit to control the switching of the switch tube; the single-chip microcomputer detects the state of the reset button and outputs a reset operation signal to the overcurrent comparison circuit to release the self-locking of the overcurrent comparison signal, thereby releasing the protection state; The logic of the reset operation signal and the overcurrent comparison signal is as follows: when the reset operation signal is generated, the overcurrent comparison signal is low regardless of whether there is an overcurrent; when the reset operation signal is not generated, if there is an overcurrent, the overcurrent comparison signal is high, and if there is no overcurrent, the overcurrent comparison signal is low; The logic of the overcurrent comparison signal, control signal to drive signal Drv is as follows: when the overcurrent comparison signal is low, the high and low of the control signal directly control the high and low of Drv; when the overcurrent comparison signal is high, Drv is low regardless of whether the control signal is high or low; The function of the constant current source is that when the switch tube Q1 is turned off, the voltage at point N1 is first established, and the constant current source circuit starts to work, generating a constant small current I to charge capacitors C4 and C5. If the subsequent circuit equipment is in a short-circuit state, the voltage at N3 will not increase and will always be 0. At this time, the software detects that the voltage at N3 is less than the set threshold and prohibits the opening of the switch tube Q1. This situation is also applicable to the case where, after a current limiting protection operation, if the short-circuit state of the subsequent circuit equipment has not been released and the operator still performs a reset operation, the voltage detection circuit combined with the software program prohibits the opening of the switch tube Q1, thereby improving the safety of the power supply. The positive electrode of diode D1 is connected to the common terminal of C5, L1, D3, and the RS resistor, and the negative electrode is connected to the common terminal of Q1, C1, C2, and C3. D1 has two functions. The first is to bypass the body diode of Q1 to enhance the surge resistance. The second is to provide a freewheeling path for L1 when L1 stores too much energy, so that the stored energy is released into the input capacitor, so that the output voltage does not exceed the input voltage. The negative electrode of diode D2 is connected to the ground of the entire circuit, and the positive electrode is connected to the common terminal of Q1, C4, and L1. The function of D2 is to provide a freewheeling circuit path for the L1 inductor. When L1 stores too much energy, it provides a freewheeling path for L1, so that the stored energy is released into the input capacitor, so that the output voltage does not exceed the input voltage.

2. The power supply system with a fast current limiting switch according to claim 1, wherein The current detection circuit, overcurrent comparison circuit, and drive circuit are all implemented by hardware circuits, and the response speed can be very fast. When a short circuit occurs in the subsequent circuit device, the hardware circuit will immediately detect the overcurrent and quickly turn off the switch tube. The capacitance value of the π-type filter circuit is very small, and the released energy is not enough to damage the devices of the subsequent circuit device.

3. The power supply system with a fast current limiting switch according to claim 1, wherein The current limiting switch circuit part consists of a single switch tube and a π-type filter circuit.

4. The power supply system with a fast current limiting switch according to claim 3, characterized in that, The parameter selection principle of the π-type filter circuit is as follows: Determine the rated current of inductor L1 according to the maximum current limiting value, determine the inductance value according to the limited current rising slope, overcurrent protection response time, and the maximum released energy during short circuit. Capacitors C4 and C5 provide a high-frequency ripple current path for the output terminal, and their capacitance is much smaller than that of C1 - C3.

5. The power supply system with a fast current limiting switch as claimed in claim 1, wherein Diodes D1 and D2 are selected as ultra-fast recovery diodes.

Images