Light-load high-voltage power supply circuit

Abstract

A light-load high-voltage power supply circuit includes a controllable switch and an energy storage capacitor connected between an input power supply on the front-end side and a switching power supply on the output side, and a control circuit connected to the controllable switch and the energy storage capacitor respectively. The controllable switch is connected in series between the input power supply and the energy storage capacitor, and the energy storage capacitor is connected in parallel with the switching power supply. The control circuit collects the real-time voltage across the energy storage capacitor and compares it with the startup voltage of the switching power supply and a set threshold value. When the real-time voltage is less than or equal to the startup voltage, the controllable switch is controlled to conduct to supply power to the switching power supply and charge the energy storage capacitor. When the real-time voltage is greater than or equal to the threshold value, the controllable switch is controlled to disconnect, and the energy storage capacitor supplies power to the switching power supply, which can suppress the heat generation of the front-end circuit and reduce the temperature rise of the power supply circuit.

Description

Technical Field

[0001] The present invention belongs to the field of power supply, and particularly relates to a light-load high-voltage power supply circuit. Background Art

[0002] For comprehensive reasons such as improving safety, reliability, and expanding the applicable range, the structure of existing power supply circuits is becoming increasingly complex. When applied to some light-load occasions, the power consumption is large and the temperature rise is high. Summary of the Invention

[0003] The purpose of the present invention is to overcome the defects of the prior art and provide a light-load high-voltage power supply circuit with a low temperature rise.

[0004] To achieve the above purpose, the present invention adopts the following technical solutions:

[0005] A light-load high-voltage power supply circuit includes a controllable switch and an energy storage capacitor connected between an input power supply on the front-end side and a switching power supply on the output side, and a control circuit respectively connected to the controllable switch and the energy storage capacitor. The controllable switch is connected in series between the input power supply and the energy storage capacitor, and the energy storage capacitor is connected in parallel with the switching power supply;

[0006] The control circuit collects the real-time voltage across the energy storage capacitor and compares it with the startup voltage of the switching power supply and a set threshold. When the real-time voltage is less than or equal to the startup voltage, the control circuit controls the controllable switch to conduct, supplying power to the switching power supply and charging the energy storage capacitor. When the real-time voltage is greater than or equal to the threshold, the control circuit controls the controllable switch to disconnect, and the energy storage capacitor supplies power to the switching power supply.

[0007] Preferably, the control circuit includes a sampling module, a control module, and a power supply module. The power supply module supplies power to the control module. The sampling module is connected to the energy storage capacitor and the control module, collects the real-time voltage across the energy storage capacitor, and transmits it to the control module. The control module is connected to the controllable switch.

[0008] Preferably, the controllable switch is one of a MOS transistor, an IGBT, SiC, GaN, a relay, or a contactor.

[0009] Preferably, it further includes an instantaneous high-voltage control circuit connected between the input power supply and the controllable switch.

[0010] Preferably, the sampling module is an isolated sampling module with isolation protection.

[0011] Preferably, the controllable switch includes a MOS transistor, and the instantaneous high-voltage control circuit includes a limiting optocoupler U4; both ends of the series connection of resistor R17, resistor R18, diode D8, and diode D9 are connected in parallel with the energy storage capacitor. One side of the limiting optocoupler U4 is connected to the G pole and the S pole of the MOS transistor respectively, and the other side of the limiting optocoupler U4 is connected to both ends of resistor R18 respectively.

[0012] Preferably, the control module controls the on-off of the MOS transistor through a charging optocoupler U5. The control module includes a microcontroller chip U3. One side of the charging optocoupler U5 is connected to the G pole and the S pole of the MOS transistor respectively, and the other side of the charging optocoupler U5 is connected to the DRIVE port and the ground terminal of the microcontroller chip U3 respectively.

[0013] Preferably, the controllable switch includes a MOS transistor, the energy storage capacitor includes a capacitor C6, the control module includes a microcontroller chip U3, and the instantaneous high-voltage control circuit adopts a linear voltage stabilizing circuit with resistor voltage division. One end of the linear voltage stabilizing circuit is connected to the positive pole of the input power supply, the other end is connected to one end of the capacitor C6, the control end of the linear voltage stabilizing circuit is connected to the MOS transistor, the control end of the MOS transistor is connected to the DRIVE port of the microcontroller chip U3, the sampling module is connected to both ends of the capacitor C6, and the output end of the sampling module is connected to the AD_U port of the microcontroller chip U3.

[0014] Preferably, the linear voltage stabilizing circuit includes a resistor R1. One end of the resistor R1 is connected to the positive pole of the input power supply. The other end of the resistor R1, R3, R5, the collector of the triode Q1, the emitter of the triode Q1, resistor R7, R9, R11, the collector of the triode Q2, the emitter of the triode Q2, resistor R14, R17, R19, the collector of the triode Q3, the emitter of the triode Q3, resistor R20, R22, R24, the collector of the triode Q4, and the emitter of the triode Q4 are connected in sequence. The emitter of the triode Q4 is connected to one end of the capacitor C6; resistor R2, R4, R6, the base of the triode Q1, resistor R8, R10, R12, the base of the triode Q2, resistor R13, R16, R18, the base of the triode Q3, resistor R21, R23, R25, and the base of the triode Q4 are connected in sequence. The base of the triode Q4 is connected to the D pole of the MOS transistor. The S pole of the MOS transistor is connected to the negative pole of the input power supply, and the G pole of the MOS transistor is connected to the DRIVE port of the microcontroller chip U3.

[0015] Preferably, the control module includes a microcontroller chip U3, and the sampling module includes a resistor R9, a resistor R12, a resistor R10, and a capacitor C13. One end of the series connection of the resistor R9 and the resistor R12 is connected to one end of the energy storage capacitor, and the other end is grounded. The node between the resistor R9 and the resistor R12 is connected to the AD_U port of the microcontroller chip U3 through the resistor R10, and the capacitor C13 is connected between the AD_U port of the microcontroller chip U3 and the ground terminal.

[0016] Preferably, the switching power supply is a buck-type switching power supply, which includes a buck switching power supply chip U1. A capacitor C4 is connected in parallel between the BP terminal and the S terminal of the buck switching power supply chip U1. A resistor R6, a capacitor C5, and a diode D4 are respectively connected in parallel between the FB terminal and the S terminal of the buck switching power supply chip U1. A resistor R4 is connected between the ends of the resistor R6 and the capacitor C5 connected to the FB terminal of the buck switching power supply chip U1. An inductor L3 is connected between the ends of the capacitor C5 and the diode D4 connected to the S terminal of the buck switching power supply chip U1. A diode D6 is connected between the S terminal of the buck switching power supply chip U1 and the negative pole of the input power supply and is connected to one end of the capacitor C4. A capacitor C8 is connected between the S terminal of the buck switching power supply chip U1 and the negative pole of the input power supply and is connected to one end of the diode D4. A resistor R8 is connected in parallel with the capacitor C8, and the power supply is output from the end connected to the diode D4; the buck-type switching power supply further includes a DC-DC module power supply chip U2. The Vi terminal of the DC-DC module power supply chip U2 is connected to the node of the resistor R8 and the diode D4. A capacitor C9 is connected in parallel between the Vi and G terminals of the DC-DC module power supply chip U2, and the G terminal of the DC-DC module power supply chip U2 is grounded. Capacitors C6 and C7 are respectively connected in parallel between the +Vo section and the -Vo terminal of the DC-DC module power supply chip U2.

[0017] Preferably, the control module includes a microcontroller chip U3, and the sampling module includes a first isolation optocoupler U4, a second isolation optocoupler U5, a first voltage dividing circuit, and a second voltage dividing circuit. The first voltage dividing circuit is connected in parallel with the energy storage capacitor, and the second voltage dividing circuit is connected in parallel with the energy storage capacitor. The first voltage dividing circuit includes a resistor R20, a resistor R22, a resistor R27, a diode D8, and a diode D9 connected in series in sequence. Two ends of one side of the first isolation optocoupler U4, one end of which is connected to the PC6 terminal of the microcontroller chip U3 and is also connected to one end of the resistor R24, the other end is grounded, and the other end of the resistor R24 is connected to the signal power supply. Two ends of the other side of the first isolation optocoupler U4 are connected in parallel with the resistor R27; the second voltage dividing circuit includes a resistor R21, a resistor R26, and a resistor R33 connected in series in sequence. Two ends of one side of the second isolation optocoupler U5, one end of which is connected to the PC5 terminal of the microcontroller chip U3 and is also connected to one end of the resistor R25, the other end is grounded, and the other end of the resistor R25 is connected to the signal power supply. One end of the two ends of the other side of the second isolation optocoupler U5 is connected to the 12V power supply through a resistor R31, and the other end is connected to the first end of a voltage regulator U6, and the second end and the third end of the voltage regulator U6 are connected in parallel with the resistor R33.

[0018] In the light-load high-voltage power supply circuit of the present invention, a controllable switch and an energy storage capacitor are provided between the input power supply on the front-end side and the switching power supply on the output side. When the real-time voltage across the energy storage capacitor is less than or equal to the startup voltage of the switching power supply, the controllable switch is controlled to conduct, supplying power to the switching power supply and charging the energy storage capacitor. When the real-time voltage is greater than or equal to the preset threshold, the controllable switch is controlled to disconnect, and the energy storage capacitor supplies power to the switching power supply. During the period when the controllable switch is disconnected, the circuits on the front-end side of the energy storage capacitor do not work due to the disconnection of the controllable switch, and the energy storage capacitor supplies power, which can significantly suppress the heat generation of the front-end circuit, reduce the temperature rise of the power supply circuit, and prevent overheating.

[0019] In addition, through the instantaneous high-voltage control circuit, especially by adopting a linear voltage stabilization circuit, the applicable range of the power supply circuit is extended, and it can be applicable not only to voltages below DC 600V but also to voltages as high as DC 1500V. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a schematic diagram of the principle of the light-load high-voltage power supply circuit described in the embodiment of the present invention;

[0021] Figures 2A - 2E is a circuit diagram of the first embodiment of the light-load high-voltage power supply circuit of the present invention;

[0022] Figures 3A - 3D is a circuit diagram of the second embodiment of the light-load high-voltage power supply circuit of the present invention;

[0023] Figures 4A - 4CIt is the circuit diagram of the third embodiment of the light-load high-voltage power supply circuit of the present invention. Detailed implementation manners

[0024] The following combines the Figures 1 to 4C given embodiments to further illustrate the detailed implementation manners of the light-load high-voltage power supply circuit of the present invention. The light-load high-voltage power supply circuit of the present invention is not limited to the descriptions of the following embodiments.

[0025] As Figure 1 shown, the light-load high-voltage power supply circuit of the present invention includes a controllable switch and an energy storage capacitor connected between the input power supply on the front-end side and the switched-mode power supply on the output side, and a control circuit respectively connected to the controllable switch and the energy storage capacitor. The controllable switch is connected in series between the input power supply and the energy storage capacitor, and the energy storage capacitor is connected in parallel with the switched-mode power supply; the control circuit collects the real-time voltage across the energy storage capacitor and compares it with the start-up voltage of the switched-mode power supply and a set threshold value; when the real-time voltage is less than or equal to the start-up voltage, the controllable switch is controlled to conduct to supply power to the switched-mode power supply and charge the energy storage capacitor, and when the real-time voltage is greater than or equal to the threshold value, the controllable switch is controlled to disconnect, and the energy storage capacitor supplies power to the switched-mode power supply. The high-voltage input power supply supplies power to the load through the light-load high-voltage power supply circuit of the present invention. During the period when the controllable switch is disconnected, the circuits on the front-end side of the energy storage capacitor, such as the input power supply providing the high-voltage power supply, do not work due to the disconnection of the controllable switch, and the energy storage capacitor supplies power, which can significantly suppress the heat generation of the front-end circuit, reduce the temperature rise of the power supply circuit, prevent overheating, and is suitable for power supply of light loads.

[0026] The switched-mode power supply can be a buck-type switched-mode power supply. The buck-type switched-mode power supply steps down and / or stabilizes the input high voltage and then outputs it to supply power to the load. The energy storage capacitor is connected to the front end of the buck-type switched-mode power supply and is connected in parallel with the buck-type switched-mode power supply. The controllable switch is connected in series to the front end of the energy storage capacitor, either in series with the positive or negative pole of the circuit. The controllable switch can be a transistor such as a MOS transistor, an IGBT, a SiC or a GaN, or a mechanical switch such as a relay or a contactor. The switched-mode power supply can also be a boost-type switched-mode power supply, or other power supply sources, which all fall within the protection scope of the present invention.

[0027] The control circuit is connected to the energy storage capacitor and collects the real-time voltage across the energy storage capacitor; the control circuit is connected to the control terminal of the controllable switch and is used to control the opening and closing of the controllable switch; the control circuit compares the real-time voltage across the energy storage capacitor collected with the startup voltage of the buck-type switching power supply and a set threshold value; when the real-time voltage is less than or equal to the startup voltage, it controls the controllable switch to conduct, supplying power to the buck-type switching power supply and charging the energy storage capacitor, and when the real-time voltage is greater than or equal to the threshold value, it controls the controllable switch to disconnect, and the energy storage capacitor supplies power to the buck-type switching power supply, which is suitable for power supply under light load. The input power supply and the energy storage capacitor alternately supply power to the load through the buck-type switching power supply. When the input power supply supplies power to the load, it also supplies power to the energy storage capacitor. When the real-time voltage across the energy storage capacitor is greater than or equal to the threshold value, the energy storage capacitor supplies power. At this time, the circuit on the front-end side of the energy storage capacitor does not work during the disconnection of the controllable switch, which can significantly suppress the heating of the front-end circuit and reduce the temperature rise. The startup voltage is a known value and can be adjusted and set as needed.

[0028] Preferably, as Figure 1 shown, the control circuit includes a sampling module, a control module, and a power supply module. The power supply module supplies power to the control module. The power supply module is connected to the positive and negative poles of the input end of the high-voltage power supply circuit for light load, that is, connected to the positive and negative poles of the high-voltage input power supply, obtains the power supply, performs step-down, filtering and other processes, and is used to supply power to the control module, or the power supply module is connected to the switching power supply, obtains the power supply, processes it, and is used to supply power to the control module.

[0029] The sampling module is connected to the energy storage capacitor and the control module, collects the real-time voltage across the energy storage capacitor, and transmits it to the control module. The sampling module is an isolated sampling module with isolation protection. For example, sampling isolation is performed through an electric couple. The sampling module can perform sampling by means of resistor voltage division; the control module is connected to the controllable switch. The control module compares the real-time voltage collected by the sampling module with a preset threshold value and the startup voltage of the buck-type switching power supply, and performs the on-off operation of the corresponding controllable switch according to the comparison result; the control module can be implemented by a hardware circuit including a comparator or in a programmable manner including a microcontroller or a single-chip microcomputer.

[0030] As Figures 2A - 4C shown, the high-voltage power supply circuit for light load of the present invention further includes an instantaneous high-voltage control circuit, which is connected between the input power supply and the controllable switch and processes the instantaneous high voltage during circuit startup.

[0031] Embodiment 1

[0032] As Figures 2A - 2EAs shown in the figure, the light-load high-voltage power supply circuit of this embodiment provides a DC power supply circuit applicable to ordinary circuits. The controllable switch includes MOS transistor Q1. In this embodiment, MOS transistor Q1 is connected to the negative pole of the input power supply. The energy storage capacitor includes capacitor C1. The control circuit includes microcontroller chip U3, and the model of this embodiment is STM8S103F3P6. The switching power supply is a buck-type switching power supply, including buck switching power supply chip U1 with the model of LNK306D. The instantaneous high-voltage control circuit includes limiting optocoupler U4. The sampling module includes resistors R9, R12, R10 and capacitor C13.

[0033] As Figure 2D shown in the figure, in the light-load high-voltage power supply circuit of this embodiment, MOS transistor Q1 is connected in series in the power supply circuit, and the voltage across capacitor C1 is sampled. The corresponding comparison and control process is realized through the control circuit. Among them, the control circuit exists in the form of microcontroller chip U3 in the power supply circuit. In the actual operation process of this embodiment, the sampling data of the real-time voltage collected by the sampling module is transmitted to chip U3 through the AD_U port (number 14) of microcontroller chip U3. The specific voltage acquisition value can be set according to the specific usage environment, such as 1 / 500 or 1 / 300 of the actual voltage, etc. The DRIVE port (number 13) of the microcontroller chip is connected to the control end of MOS transistor Q1 to transmit the on / off control signal. In the actual operation process of this embodiment, the instantaneous high voltage at the start of the circuit acts through limiting optocoupler U4 independent of the control circuit. When the voltage in the circuit is higher than 300V, the limiting optocoupler U4 will control to pull down the potential of MOS transistor Q1 to protect the subsequent circuit.

[0034] As Figure 2A shown in the figure, the instantaneous high-voltage control circuit includes limiting optocoupler U4; the two ends after resistors R17, R18, diode D8, and diode D9 are connected in series are connected in parallel with energy storage capacitor C1. One side of limiting optocoupler U4 is respectively connected to the G pole and S pole of MOS transistor Q1, and the other side of limiting optocoupler U4 is respectively connected to both ends of resistor R18. When the voltage in the circuit is higher than 300V, the limiting optocoupler U4 will control to pull down the potential of MOS transistor Q1 to protect the subsequent circuit. The control module controls the on / off of MOS transistor Q1 through charging optocoupler U5. One side of charging optocoupler U5 is respectively connected to the G pole and S pole of MOS transistor Q1, and the other side of charging optocoupler U5 is respectively connected to the DRIVE port of microcontroller chip U3 and the ground terminal. After the circuit operates normally, the control circuit controls the on / off of switch transistor Q1 through charging optocoupler U5 to realize the reciprocating charge and discharge of the stored energy.

[0035] Specifically, both ends of the S pole and D pole of the MOS transistor Q1 are connected in series to the negative pole of the input power supply. The G pole and S pole of the MOS transistor Q1 are respectively connected to both ends of one side of the limiting optocoupler U4, and are also connected to both ends of one side of the charging optocoupler U5. The other side of the limiting optocoupler U4 is connected in parallel with the resistor R18. One end of the resistor R18 is grounded through the diodes D8 and D9, and the other end is connected to one end of the capacitor C1 through the resistors R17 and R14. The other end of the capacitor C1 is connected to the negative pole of the input power supply. One end of the other side of the charging optocoupler U5 is grounded, and the other end is connected to the DRIVE port of the microcontroller chip U3 through the resistor R19; the G pole of the MOS transistor Q1 is connected to the positive pole of the input power supply through a resistor R13 and at least one other voltage-dividing resistor. Capacitors C16, diode D7, and bidirectional transient voltage suppressor TVS1 are respectively connected in parallel to both ends of the series connection of the G pole of the MOS transistor Q1 and the resistor R13. Resistor R15 is also connected in parallel to both ends of the G pole and S pole of the MOS transistor Q1;

[0036] As Figure 2B shown, a first filter circuit is connected between the capacitor C1 and the buck switching power supply, and a second filter circuit is connected between the capacitor C1 and the input power supply. The first filter circuit includes an inductor L2 and a capacitor C2. The capacitor C2 is connected in parallel with the capacitor C1. The inductor L2 is connected between one end of the capacitor C2 and one end of the capacitor C1. The node between the inductor L2 and the capacitor C2 of the first filter circuit is connected to the D port of the buck switching power supply chip U1. The second filter circuit includes an inductor L1 and a capacitor C3. The capacitor C3 is connected in parallel with the capacitor C1. One end of the inductor L1 is connected to the node between the capacitor C3 and the capacitor C1, and the other end (P+ node) is connected to one end of the at least one voltage-dividing resistor. A diode D5 is also connected to the other end of the inductor L1. One end of the diode D5 and one end of the capacitor C3 are both connected to the negative pole of the input power supply (grounded). The other end (P+ node) of the diode D5 and the other end of the inductor L1 are both connected to one end of the at least one voltage-dividing resistor. In this embodiment, the at least one voltage-dividing resistor includes resistors R1, R2, R3, R5, and R7 connected in series, which can be adjusted as needed.

[0037] As Figure 2A shown, a varistor RV1 is also connected between the positive and negative poles of the input power supply. The positive pole of the input power supply is connected to one end of the at least one voltage-dividing resistor connected in series through the diodes D1, D2, and D3. The other end of the at least one voltage-dividing resistor is connected to the diode D7.

[0038] The switching power supply is a buck-type switching power supply, including a buck switching power supply chip U1, which has a buck and voltage regulation function. In this embodiment, the model of the buck switching power supply chip U1 is LNK306D. A capacitor C4 is connected in parallel between the BP terminal and the S terminal of the buck switching power supply chip U1. A resistor R6, a capacitor C5, and a diode D4 are respectively connected in parallel between the FB terminal and the S terminal of the buck switching power supply chip U1. A resistor R4 is connected between the ends of the resistor R6 and the capacitor C5 connected to the FB terminal of the buck switching power supply chip U1. An inductor L3 is connected between the ends of the capacitor C5 and the diode D4 connected to the S terminal of the buck switching power supply chip U1. A diode D6 is connected between the S terminal of the buck switching power supply chip U1 and the negative pole of the input power supply, and is connected to one end of the capacitor C4. A capacitor C8 is connected between the S terminal of the buck switching power supply chip U1 and the negative pole of the input power supply and is connected to one end of the diode D4. A resistor R8 is connected in parallel with the capacitor C8, and a 12V power supply is output from the end connected to the diode D4. The buck-type switching power supply further includes a DC-DC module power supply chip U2, which provides isolation for the load. The Vi terminal of the DC-DC module power supply chip U2 is connected to the node of the resistor R8 and the diode D4. A capacitor C9 is connected in parallel between the Vi and G terminals of the DC-DC module power supply chip U2, and the G terminal of the DC-DC module power supply chip U2 is grounded. Capacitors C6 and C7 are respectively connected in parallel between the +Vo section and the -Vo terminal of the DC-DC module power supply chip U2. In this embodiment, the model of the chip U2 is F1212S-2WR2.

[0039] As Figure 2C shown, the sampling module includes a resistor R9, a resistor R12, a resistor R10, and a capacitor C13. One end of the series connection of the resistor R9 and the resistor R12 is connected to one end of the energy storage capacitor, and the other end is grounded. The node between the resistor R9 and the resistor R12 is connected to the AD_U port of the microcontroller chip U3 through the resistor R10. The capacitor C13 is connected between the AD_U port of the microcontroller chip U3 and the ground terminal. As Figure 2E shown, the power supply module includes a power supply chip VOT1, which is connected to the switching power supply, converts the input 12V power supply into a 5V power supply, and supplies power to the microcontroller chip U3 of the control circuit. In this embodiment, the model of the power supply chip VOT1 is HT7550 / SO-89.

[0040] Embodiment 2

[0041] As Figures 3A - 3D shown, the light-load high-voltage power supply circuit of this embodiment can be applied to a power supply circuit of 500 - 1500VDC. The controllable switch includes an MOS transistor Q5. The energy storage capacitor includes a capacitor C6. The switching power supply is a buck-type switching power supply, including a buck switching power supply chip U1, with a model of LNK306D. The control circuit includes a microcontroller chip U3.

[0042] The main difference between this embodiment and the first embodiment lies in the instantaneous high-voltage control circuit at the front end. The instantaneous high-voltage control circuit adopts a linear voltage regulator circuit with resistor voltage division and a MOS transistor Q5 is connected in series. Specifically, as Figure 3A shown, one end of the linear voltage regulator circuit is connected to the positive pole of the input power supply, and the other end is connected to one end of the capacitor C6. The control end of the linear voltage regulator circuit is connected to the MOS transistor Q5, the control end of the MOS transistor Q5 is connected to the DRIVE port of the microcontroller chip U3, the sampling module is connected across the capacitor C6, and the output end of the sampling module is connected to the AD_U port of the microcontroller chip U3.

[0043] The instantaneous high-voltage control circuit includes a plurality of linearly regulated groups connected in sequence, and each linearly regulated group includes a number of resistors and a triode. This embodiment includes four linearly regulated groups. Specifically, the resistors R1 - R6 and the triode Q1 form a linearly regulated group, the resistors R7 - R12 and the triode Q2 form a linearly regulated group, the resistors R13 - R14, R16 - R19 and the triode Q3 form a linearly regulated group, and the resistors R20 - R25 and the triode Q4 form a linearly regulated group. Specifically, the linear voltage regulator circuit includes the resistor R1. One end of the resistor R1 is connected to the positive pole of the input power supply, and the other end of the resistor R1, R3, R5, the collector of the triode Q1, the emitter of the triode Q1, the resistor R7, R9, R11, the collector of the triode Q2, the emitter of the triode Q2, the resistor R14, R17, R19, the collector of the triode Q3, the emitter of the triode Q3, the resistor R20, R22, R24, the collector of the triode Q4, and the emitter of the triode Q4 are connected in sequence. The emitter of the triode Q4 is connected to one end of the capacitor C6; the resistors R2, R4, R6, the base of the triode Q1, the resistor R8, R10, R12, the base of the triode Q2, the resistor R13, R16, R18, the base of the triode Q3, the resistor R21, R23, R25, and the base of the triode Q4 are connected in sequence. The base of the triode Q4 is connected to the D pole of the MOS transistor Q5, the S pole of the MOS transistor Q5 is connected to the negative pole of the input power supply, and the G pole of the MOS transistor Q5 is connected to the DRIVE port of the microcontroller chip U3.

[0044] The sampling module includes the resistors R27, R29, R30 and R33, and detects the real-time voltage across the energy storage capacitor C6 by means of resistor voltage division. The series-connected resistors R27, R29, R30 and R33 are connected in parallel across the capacitor C6, and the node between R30 and R33 is connected to the control circuit through the resistor R31, that is, connected to the AD_U port of the microcontroller chip U3.

[0045] The control module includes the microcontroller chip U3, which is basically the same as that in the first embodiment and will not be elaborated here.

[0046] The switching power supply includes a buck switching power supply chip U1, which is basically the same as the embodiment and will not be elaborated here.

[0047] In this embodiment, the collected value of the specific voltage of the sampling module can be 1 / 300 of the actual voltage, and the corresponding comparison and control processes are implemented through the control circuit. Among them, the control circuit exists in the power supply circuit with the control chip. The sampled data of the real-time voltage is transmitted to the chip through the AD_U port (number 14), and the control signal is implemented through the DRIVE port (number 13). During the actual operation of this embodiment, the instantaneous high voltage at the start of the circuit is stepped down through the linear voltage stabilizing circuit of the front-end resistor voltage division, so that the voltage is stabilized at about DC 300V.

[0048] Embodiment III

[0049] As Figures 4A - 4C shown, the light-load high-voltage power supply circuit of this embodiment is applicable to the high-voltage DC power supply circuit. The controllable switch includes the MOS transistor Q5, the energy storage capacitor includes the capacitor C1, the switching power supply is a buck-type switching power supply, including a buck switching power supply chip U1, with the model number LNK306D, and the control circuit includes a microcontroller chip U3.

[0050] The instantaneous high-voltage control circuit of this embodiment adopts a linear voltage stabilizing circuit of resistor voltage division. At the front end of the circuit, a linear voltage stabilizing circuit of resistor voltage division is used as the instantaneous high-voltage control circuit, and the switching transistor Q5 is connected in series. Similar to Embodiment II, Figure 3A it will not be elaborated here. The switching power supply is similar to that of Embodiment I Figure 2B and Embodiment II Figure 3B and will not be elaborated here. The sampling module is an isolation sampling module, which detects the real-time voltage across the energy storage capacitor C1 by means of resistor voltage division, and a first isolation optocoupler U4 and a second isolation optocoupler U5 are provided between the control circuit and the sampling circuit for isolation. The voltage is collected in an isolated manner to prevent overvoltage from damaging the circuit board. When the voltage is higher than the isolation preset value, it is conducted through the first isolation optocoupler U4; when the voltage is lower than or equal to the isolation preset value, the second isolation optocoupler U5 is turned off to provide an isolation signal for the microcontroller chip U3 to process. In this embodiment, the collected value of the specific voltage of the sampling module can be 1 / 100 of the actual voltage. Of course, the isolation sampling module of this embodiment can be applied to any one of the three embodiments of the present invention.

[0051] Preferably, as Figure 4BAs shown, the sampling module includes a first isolation optocoupler U4, a second isolation optocoupler U5, a first voltage dividing circuit and a second voltage dividing circuit. The first voltage dividing circuit is connected in parallel with the energy storage capacitor, and the second voltage dividing circuit is connected in parallel with the energy storage capacitor. The first voltage dividing circuit includes a resistor R20, a resistor R22, a resistor R27, a diode D8 and a diode D9 connected in series in sequence. Two ends of one side of the first isolation optocoupler U4, one end of which is connected to the PC6 terminal (number 16) of the microcontroller chip U3 and is connected to one end of the resistor R24, and the other end is grounded. The other end of the resistor R24 is connected to a 5V signal power supply. Two ends of the other side of the first isolation optocoupler U4 are connected in parallel with the resistor R27. The second voltage dividing circuit includes a resistor R21, a resistor R26 and a resistor R33 connected in series in sequence. Two ends of one side of the second isolation optocoupler U5, one end of which is connected to the PC5 terminal (number 15) of the microcontroller chip U3 and is connected to one end of the resistor R25, and the other end is grounded. The other end of the resistor R25 is connected to a 5V signal power supply. One end of the two ends of the other side of the second isolation optocoupler U5 is connected to the 12V power supply through the resistor R31, and the other end is connected to the first end of the voltage regulator U6. The second end and the third end of the voltage regulator U6 are connected in parallel with the resistor R33. When the voltage is higher than the isolation preset value, it is conducted through the first isolation optocoupler U4. When the voltage is lower than or equal to the isolation preset value, the second isolation optocoupler U5 is turned off, and the microcontroller chip U3 receives a low level, providing an isolation signal for the microcontroller chip U3 to process.

[0052] Through the above buck switching power supply circuit, the following technical effects can be achieved:

[0053] 1. In the case of low load, since the controllable switch is turned off during the discharge process of the energy storage capacitor, while reducing its own conduction loss, the circuit in front of the energy storage capacitor is also cut off, which can effectively reduce the temperature rise of itself and the front-end circuit, suppress heat generation, and prevent overheating.

[0054] 2. The applicable range of the power supply circuit is expanded, and it can be applied not only to voltages below DC 600V, but also to voltages as high as DC 1500V.

[0055] The above content is a further detailed description of the present invention in combination with specific preferred embodiments. It cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention belongs, without departing from the concept of the present invention, several simple deductions or substitutions can still be made, which should all be regarded as belonging to the protection scope of the present invention.

Claims

1. A light-load high-voltage power supply circuit, characterized in that: It includes a controllable switch and an energy storage capacitor connected between an input power supply on the front-end side and a switching power supply on the output side, and a control circuit respectively connected to the controllable switch and the energy storage capacitor. The controllable switch is connected in series between the input power supply and the energy storage capacitor, and the energy storage capacitor is connected in parallel with the switching power supply; The control circuit collects the real-time voltage across the energy storage capacitor and compares it with the startup voltage of the switching power supply and a set threshold; when the real-time voltage is less than or equal to the startup voltage, it controls the controllable switch to conduct, supply power to the switching power supply, and charge the energy storage capacitor. When the real-time voltage is greater than or equal to the threshold, it controls the controllable switch to disconnect, and the energy storage capacitor supplies power to the switching power supply; The control circuit includes a sampling module, a control module, and a power supply module. The power supply module supplies power to the control module. The sampling module is connected to the energy storage capacitor and the control module, collects the real-time voltage across the energy storage capacitor, and transmits it to the control module. The control module is connected to the controllable switch; It further includes an instantaneous high-voltage control circuit connected between the input power supply and the controllable switch; the controllable switch includes a MOS transistor, and the instantaneous high-voltage control circuit includes a limiting optocoupler U4; both ends of the series connection of resistor R17, resistor R18, diode D8, and diode D9 are connected in parallel with the energy storage capacitor. One side of the limiting optocoupler U4 is respectively connected to the G pole and the S pole of the MOS transistor, and the other side of the limiting optocoupler U4 is respectively connected to both ends of resistor R18.

2. A light-load high-voltage power supply circuit, characterized in that: It includes a controllable switch and an energy storage capacitor connected between an input power supply on the front-end side and a switching power supply on the output side, and a control circuit respectively connected to the controllable switch and the energy storage capacitor. The controllable switch is connected in series between the input power supply and the energy storage capacitor, and the energy storage capacitor is connected in parallel with the switching power supply; The control circuit collects the real-time voltage across the energy storage capacitor and compares it with the startup voltage of the switching power supply and a set threshold; when the real-time voltage is less than or equal to the startup voltage, it controls the controllable switch to conduct, supply power to the switching power supply, and charge the energy storage capacitor. When the real-time voltage is greater than or equal to the threshold, it controls the controllable switch to disconnect, and the energy storage capacitor supplies power to the switching power supply; The control circuit includes a sampling module, a control module, and a power supply module. The power supply module supplies power to the control module. The sampling module is connected to the energy storage capacitor and the control module, collects the real-time voltage across the energy storage capacitor, and transmits it to the control module. The control module is connected to the controllable switch; It also includes an instantaneous high-voltage control circuit connected between the input power supply and the controllable switch; the controllable switch includes a MOS transistor, the energy storage capacitor includes capacitor C6, the control module includes a microcontroller chip U3, the instantaneous high-voltage control circuit adopts a linear voltage-stabilizing circuit with resistor voltage division, one end of the linear voltage-stabilizing circuit is connected to the positive pole of the input power supply, the other end is connected to one end of capacitor C6, the control end of the linear voltage-stabilizing circuit is connected to the MOS transistor, and the control end of the MOS transistor is connected to the DRIVE port of the microcontroller chip U3. The sampling module is connected across capacitor C6, and the output end of the sampling module is connected to the AD_U port of the microcontroller chip U3.

3. The light-load high-voltage power supply circuit according to claim 1 or 2, characterized in that: The sampling module is an isolated sampling module with isolation protection.

4. The light-load high-voltage power supply circuit according to claim 1, characterized in that: The control module controls the on-off of the MOS transistor through a charging optocoupler U5. The control module includes a microcontroller chip U3. Two ends of one side of the charging optocoupler U5 are respectively connected to the G pole and the S pole of the MOS transistor, and two ends of the other side of the charging optocoupler U5 are respectively connected to the DRIVE port of the microcontroller chip U3 and the ground terminal.

5. The light-load high-voltage power supply circuit according to claim 2, wherein: The linear voltage-stabilizing circuit includes resistor R1. One end of resistor R1 is connected to the positive pole of the input power supply. The other end of resistor R1, R3, R5, the collector of triode Q1, the emitter of triode Q1, resistor R7, R9, R11, the collector of triode Q2, the emitter of triode Q2, resistor R14, R17, R19, the collector of triode Q3, the emitter of triode Q3, resistor R20, R22, R24, the collector of triode Q4, and the emitter of triode Q4 are connected in sequence. The emitter of triode Q4 is connected to one end of capacitor C6. Resistors R2, R4, R6, the base of triode Q1, resistor R8, R10, R12, the base of triode Q2, resistor R13, R16, R18, the base of triode Q3, resistor R21, R23, R25, and the base of triode Q4 are connected in sequence. The base of triode Q4 is connected to the D pole of the MOS transistor. The S pole of the MOS transistor is connected to the negative pole of the input power supply, and the G pole of the MOS transistor is connected to the DRIVE port of the microcontroller chip U3.

6. The light-load high-voltage power supply circuit according to claim 1 or 2, characterized in that: The control module includes a microcontroller chip U3. The sampling module includes resistors R9, R12, R10, and capacitor C13. One end of the series connection of resistors R9 and R12 is connected to one end of the energy storage capacitor, and the other end is grounded. The node between resistors R9 and R12 is connected to the AD_U port of the microcontroller chip U3 through resistor R10. Capacitor C13 is connected between the AD_U port of the microcontroller chip U3 and the ground terminal.

7. The light-load high-voltage power supply circuit according to claim 1 or 2, characterized in that: The switching power supply is a buck-type switching power supply, which includes a buck switching power supply chip U1. A capacitor C4 is connected in parallel between the BP terminal and the S terminal of the buck switching power supply chip U1. A resistor R6, a capacitor C5, and a diode D4 are respectively connected in parallel between the FB terminal and the S terminal of the buck switching power supply chip U1. A resistor R4 is connected between the ends of the resistor R6 and the capacitor C5 connected to the FB terminal of the buck switching power supply chip U1. An inductor L3 is connected between the ends of the capacitor C5 and the diode D4 connected to the S terminal of the buck switching power supply chip U1. A diode D6 is connected between the S terminal of the buck switching power supply chip U1 and the negative pole of the input power supply, and is connected to one end of the capacitor C4. A capacitor C8 is connected between the S terminal of the buck switching power supply chip U1 and the negative pole of the input power supply and is connected to one end of the diode D4. A resistor R8 is connected in parallel with the capacitor C8, and the power supply is output from the end connected to the diode D4; the buck-type switching power supply further includes a DC-DC module power supply chip U2. The Vi terminal of the DC-DC module power supply chip U2 is connected to the node of the resistor R8 and the diode D4. A capacitor C9 is connected in parallel between the Vi and G terminals of the DC-DC module power supply chip U2, and the G terminal of the DC-DC module power supply chip U2 is grounded. Capacitors C6 and C7 are respectively connected in parallel between the +Vo section and the -Vo terminal of the DC-DC module power supply chip U2.

8. The light-load high-voltage power supply circuit according to claim 1 or 2, characterized in that: The control module includes a microcontroller chip U3. The sampling module includes a first isolation optocoupler U4, a second isolation optocoupler U5, a first voltage dividing circuit, and a second voltage dividing circuit. The first voltage dividing circuit is connected in parallel with the energy storage capacitor, and the second voltage dividing circuit is connected in parallel with the energy storage capacitor. The first voltage dividing circuit includes a resistor R20, a resistor R22, a resistor R27, a diode D8, and a diode D9 connected in series in sequence. One of the two ends on one side of the first isolation optocoupler U4 is connected to the PC6 terminal of the microcontroller chip U3 and is connected to one end of the resistor R24, and the other end is grounded. The other end of the resistor R24 is connected to the signal power supply. The two ends on the other side of the first isolation optocoupler U4 are connected in parallel with the resistor R27; the second voltage dividing circuit includes a resistor R21, a resistor R26, and a resistor R33 connected in series in sequence. One of the two ends on one side of the second isolation optocoupler U5 is connected to the PC5 terminal of the microcontroller chip U3 and is connected to one end of the resistor R25, and the other end is grounded. The other end of the resistor R25 is connected to the signal power supply. One of the two ends on the other side of the second isolation optocoupler U5 is connected to the 12V power supply through a resistor R31, and the other end is connected to the first end of a voltage regulator U6, and the second end and the third end of the voltage regulator U6 are connected in parallel with the resistor R33.

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