X-capacitor control and startup multiplexing circuit, switch-mode power supply controller, and switch-mode power supply

Abstract

The present invention relates to an X-capacitor control and startup multiplexing circuit, a switching power supply controller, and a switching power supply, belonging to the field of switching power supplies. The X-capacitor control and startup multiplexing circuit includes: an ultra-high voltage switch J50, a high voltage switch M50, a voltage dividing unit, a voltage-controlled current source, a diode D50, a reference voltage source, a VAC overvoltage protection unit, a VAC undervoltage protection unit, and a VAC open-circuit control unit. By controlling the startup input port VACin, it realizes constant-current charging startup of the power supply port VDD and shuts off the startup current after startup, prohibits current backflow of the VDD port after the VDD port starts up, shuts off the switching power supply when the VACin port is undervoltage or overvoltage, and discharges the startup input port VACin to ground when the input of the switching power supply is disconnected, which not only ensures the safety of the user's electrical equipment but also improves the efficiency of the user's electrical equipment.

Description

Technical Field

[0001] The present invention relates to the field of switching power supplies, and particularly to an X-capacitor control and startup multiplexing circuit, a switching power supply controller, and a switching power supply. Background Art

[0002] As a power supply device for all electronic products, the power supply needs to meet more stringent safety standards and energy efficiency. Since traditional switching power supply systems use resistor startup and resistor discharge of X-capacitors, it is difficult to meet the current stringent standby power consumption requirements. The standby power consumption of traditional switching power supplies using resistor startup is difficult to meet the standard, and the system design becomes difficult as the power increases. In addition, when designing high-power power supplies, the X-capacitor is generally large. When the power supply is powered off, in order to avoid electric shock to the human body due to high voltage at the power input port, a discharge resistor is usually used to handle it, resulting in high power consumption and poor discharge effect, and it is still very easy to cause electric shock to the human body and lead to safety accidents.

[0003] Traditional switching power converters such as Figure 1 described Figure 1 depicts a traditional power conversion system 10, whose working waveform is as Figure 2 shown. By sampling the voltage in the secondary coil of the transformer TR to the FB port of the power converter 11 through a feedback device and sampling the current in the primary side coil of the transformer through the power transistor M1 and the current limiting resistor Rcs to the CS port of the traditional power converter 11 to generate a square wave signal (Vsw) with variable pulse width to control the on and off of the power transistor (M1) to complete the energy transfer of the transformer. Since the traditional switching power supply system 10 uses resistor startup, it is difficult to meet the energy efficiency standard of full-load standby power consumption. At the same time, it uses a resistor to discharge the X-capacitor when the input is disconnected, which not only increases the power consumption but also easily causes electric shock accidents to the human body. Therefore, it is necessary to adopt special technology to control the switching power supply system to avoid the above situations and meet the energy efficiency standard, so as to achieve the safety and high efficiency of protecting electrical equipment. Summary of the Invention

[0004] The purpose of the present invention is to provide an X-capacitor control and startup multiplexing circuit, a switching power supply controller, and a switching power supply, so as to improve the working efficiency and safety of the switching power supply system.

[0005] To achieve the above purpose, the present invention provides the following solutions:

[0006] An X-capacitor control and startup multiplexing circuit, the circuit comprising: an ultra-high voltage switch J50, a high voltage switch M50, a voltage dividing unit, a voltage-controlled current source, a diode D50, a reference voltage source, a VAC overvoltage protection unit, a VAC undervoltage protection unit, and a VAC open circuit control unit;

[0007] The first input terminal of the ultra-high voltage switch J50 and the input terminal of the voltage dividing unit are both connected to the start input port VACin of the circuit. The second input terminal of the ultra-high voltage switch J50 is grounded. The output terminal of the ultra-high voltage switch J50 is respectively connected to the drain of the high voltage switch M50 and the input terminal of the voltage-controlled current source. The source of the high voltage switch M50 is grounded;

[0008] The anode of the diode D50 is connected to the output terminal of the voltage-controlled current source. The cathode of the diode D50 is respectively connected to the input terminal of the reference voltage source and the power supply port VDD of the circuit;

[0009] The output terminal of the reference voltage source is respectively connected to the second input terminal and the voltage reference terminal of the VAC overvoltage protection unit, the first input terminal and the voltage reference terminal of the VAC undervoltage protection unit, and the second input terminal and the voltage reference terminal of the VAC open circuit control unit;

[0010] The output terminal of the voltage dividing unit is respectively connected to the first input terminal of the VAC overvoltage protection unit, the second input terminal of the VAC undervoltage protection unit, and the first input terminal of the VAC open circuit control unit;

[0011] The enable signal terminal EN of the circuit is respectively connected to the enable terminal of the voltage-controlled current source, the enable terminal of the VAC overvoltage protection unit, the enable terminal of the VAC undervoltage protection unit, and the enable terminal of the VAC open circuit control unit;

[0012] The output terminal of the VAC overvoltage protection unit serves as the VAC overvoltage protection signal terminal VACin_ovp of the circuit. The output terminal of the VAC undervoltage protection unit serves as the VAC undervoltage protection signal terminal VACin_uvp of the circuit. The VAC open circuit control logic signal output terminal of the VAC open circuit control unit is connected to the gate of the high voltage switch M50.

[0013] Optionally, the voltage dividing unit includes: a resistor R51 and a resistor R52;

[0014] One end of the resistor R51 is connected to the first input terminal of the ultra-high voltage switch J50 and the start input port VACin of the circuit. The other end of the resistor R51 is connected to one end of the resistor R52. The other end of the resistor R52 is grounded;

[0015] The common point connected between the other end of the resistor R51 and one end of the resistor R52 serves as the output terminal of the voltage dividing unit.

[0016] Optionally, the VAC overvoltage protection unit includes: a first comparator, a first timer, and a resistor R53;

[0017] The first input terminal of the first comparator is connected to the output terminal of the voltage dividing unit. The second input terminal of the first comparator is connected to one end of resistor R53, and the other end of resistor R53 is connected to the output terminal of the reference voltage source. The output terminal of the first comparator is connected to the input terminal of the first timer. The first voltage input terminal of the first comparator is connected to the output terminal of the reference voltage source, and the second voltage input terminal of the first comparator is connected to the enable signal terminal EN of the circuit.

[0018] The voltage reference terminal of the first timer is connected to the output terminal of the reference voltage source. The enable terminal of the first timer is connected to the enable signal terminal EN of the circuit. The output terminal of the first timer serves as the VAC overvoltage protection signal terminal VACin_ovp of the circuit.

[0019] Optionally, the VAC undervoltage protection unit includes: a second comparator, a second timer, and resistor R54.

[0020] The first input terminal of the second comparator is connected to one end of resistor R54, and the other end of resistor R54 is connected to one end of resistor R53. The second input terminal of the second comparator is connected to the output terminal of the voltage dividing unit. The output terminal of the second comparator is connected to the input terminal of the second timer. The first voltage input terminal of the second comparator is connected to the output terminal of the reference voltage source, and the second voltage input terminal of the second comparator is connected to the enable signal terminal EN of the circuit.

[0021] The voltage reference terminal of the second timer is connected to the output terminal of the reference voltage source. The enable terminal of the second timer is connected to the enable signal terminal EN of the circuit. The output terminal of the second timer serves as the VAC undervoltage protection signal terminal VACin_uvp of the circuit.

[0022] Optionally, the VAC open - circuit control unit includes: a third comparator, a third timer, resistor R55, and resistor R56.

[0023] The first input terminal of the third comparator is connected to the output terminal of the voltage dividing unit. The second input terminal of the third comparator is respectively connected to one end of resistor R55 and one end of resistor R56. The other end of resistor R55 is connected to one end of resistor R54, and the other end of resistor R56 is grounded. The output terminal of the third comparator is connected to the input terminal of the third timer. The first voltage input terminal of the third comparator is connected to the output terminal of the reference voltage source, and the second voltage input terminal of the third comparator is connected to the enable signal terminal EN of the circuit.

[0024] The voltage reference terminal of the third timer is connected to the output terminal of the reference voltage source. The enable terminal of the third timer is connected to the enable signal terminal EN of the circuit. The output terminal of the third timer is connected to the gate of the high - voltage switch M50.

[0025] Optionally, the circuit further includes: resistor R50;

[0026] One end of resistor R50 is respectively connected to the output end of ultra-high voltage switch J50 and the input end of the voltage-controlled current source, and the other end of resistor R50 is connected to the drain of high voltage switch M50.

[0027] A switching power supply controller, the controller includes: a power-on and power-off enable circuit UVLO, a pulse width modulator PWM, a driver circuit DRIVER, and the aforementioned X-capacitor control and startup multiplexing circuit;

[0028] The input end of driver circuit DRIVER is respectively connected to the power supply ports VDD and VAC of the X-capacitor control and startup multiplexing circuit, the VAC overvoltage protection signal terminal VACin_ovp and the VAC undervoltage protection signal terminal VACin_uvp, the input end of the power-on and power-off enable circuit UVLO, and the output end of the pulse width modulator PWM; the output end of driver circuit DRIVER serves as the switching signal output end of the controller;

[0029] The output end of the power-on and power-off enable circuit UVLO is connected to the enable signal terminal EN of the X-capacitor control and startup multiplexing circuit;

[0030] The input end of the power-on and power-off enable circuit UVLO serves as the power supply port of the controller; the startup input port VACin of the X-capacitor control and startup multiplexing circuit serves as the startup input port VACin of the controller, the first input end of the pulse width modulator PWM serves as the feedback port of the controller, the second input end of the pulse width modulator PWM serves as the current monitoring port of the controller, and the ground port of the controller is grounded.

[0031] A switching power supply, the switching power supply includes: a transformer TR, a power switch M1, a feedback device, and the aforementioned switching power supply controller;

[0032] One end of the primary coil of transformer TR is connected to the drain of power transistor M1, and the other end of the primary coil of transformer TR serves as the voltage input end of the switching power supply; one end of the secondary coil of transformer TR is connected to one end of the feedback device; both ends of the secondary coil of transformer TR serve as the DC voltage output end of the switching power supply;

[0033] The gate of power transistor M1 is connected to the switching signal output end of the switching power supply controller, and the source of power transistor M1 is connected to the current monitoring port of the switching power supply controller;

[0034] The other end of the feedback device is connected to the feedback port of the switching power supply controller.

[0035] Optionally, the switching power supply further includes: capacitor Cx, full-wave rectifier diode Dx1, full-wave rectifier diode Dx2, full-wave rectifier diode D1, and capacitor C1;

[0036] Both ends of capacitor Cx are respectively connected to both ends of the input line voltage; the anode of full-wave rectifier diode Dx1 is respectively connected to one end of capacitor Cx and the first end of full-wave rectifier diode D1; the cathode of full-wave rectifier diode Dx1 is respectively connected to the cathode of full-wave rectifier diode Dx2 and the start input port VACin of the switching power supply controller; the anode of full-wave rectifier diode Dx2 is respectively connected to the other end of capacitor Cx and the second end of full-wave rectifier diode D1;

[0037] The third end of full-wave rectifier diode D1 is connected to one end of capacitor C1 and then grounded, and the fourth end of full-wave rectifier diode D1 is respectively connected to the other end of capacitor C1 and the other end of the primary coil of transformer TR.

[0038] Optionally, the switching power supply further includes: resistor R1, diode D2, capacitor C VDD and auxiliary coil La;

[0039] One end of resistor R1 is respectively connected to one end of capacitor C VDD and the power supply port of the switching power supply controller, and the other end of resistor R1 is connected to the cathode of diode D2; the other end of capacitor C VDD is grounded;

[0040] One end of auxiliary coil La is connected to the anode of diode D2, and the other end of auxiliary coil La is grounded.

[0041] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0042] The present invention discloses an X-capacitor control and startup multiplexing circuit, a switch-mode power supply controller, and a switch-mode power supply. The X-capacitor control and startup multiplexing circuit responds to the startup input port VACin and the enable signal terminal EN to generate an overvoltage protection enable signal at the VAC overvoltage protection signal terminal VACin_ovp and an undervoltage protection enable signal at the VAC undervoltage protection signal terminal VACin_uvp, and responds to the enable signal terminal EN and the power supply port VDD to generate protection enable signals at the VAC overvoltage protection signal terminal VACin_ovp and the VAC undervoltage protection signal terminal VACin_uvp. When the system input VAC voltage is too high or too low, the switch-mode power supply controller is turned off to avoid damaging the switch-mode power supply, and the diode D50 can prevent the current from flowing back at the power supply port VDD, improving the safety of the switch-mode power supply system. Further, when the input at the VAC port is disconnected, the startup input port VACin is quickly discharged to zero to ensure the safety of the X-capacitor for the human body. That is, the present invention realizes the constant-current charging startup of the power supply port VDD and turns off the startup current after startup by controlling the startup input port VACin, prohibits the current from flowing back at the VDD port after the startup of the port VDD, turns off the switch-mode power supply when the port VACin is undervoltage or overvoltage, and discharges the startup input port VACin to the ground when the input of the switch-mode power supply is disconnected, which not only ensures the safety of the user's electrical equipment but also improves the efficiency of the user's electrical equipment. Brief Description of the Drawings

[0043] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0044] Figure 1 is a structural schematic diagram of a traditional switch-mode power supply converter;

[0045] Figure 2 is a working waveform diagram of a traditional switch-mode power supply converter;

[0046] Figure 3 is a structural diagram of the X-capacitor control and startup multiplexing circuit provided by the present invention;

[0047] Figure 4 is a structural diagram of the switch-mode power supply provided by the present invention;

[0048] Figure 5 is a comparison diagram of the startup timing waveforms of the system after the input line voltage VAC of the switch-mode power supply provided by the present invention and the traditional switch-mode power supply;

[0049] Figure 6It is a comparison diagram of the timing waveforms of the voltage of the X capacitor when the AC input line voltage VAC of the switching power supply provided by the present invention is disconnected from that of the traditional switching power supply;

[0050] Figure 7 It is a waveform comparison diagram of the switching power supply of the present invention and the traditional switching power supply when the AC input line voltage VAC is overvoltage or undervoltage.

[0051] Symbol description: 10 - traditional switching power supply, 11 - traditional power converter, 12 - feedback device, 20 - power-on / off enabling circuit, 30 - pulse width modulator, 40 - drive circuit, 50 - X capacitor control and start multiplexing circuit, 51 - voltage-controlled current source, 52 - reference voltage source, 53 - first timer, 54 - third timer, 55 - second timer, 56 - third comparator, 57 - second comparator, 58 - first comparator, 10A - switching power supply, 11A - switching power supply controller. Specific embodiments

[0052] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0053] The purpose of the present invention is to provide an X capacitor control and start multiplexing circuit, a switching power supply controller and a switching power supply, so as to improve the working efficiency and safety of the switching power supply system.

[0054] In order to make the above objects, features and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0055] Embodiment 1

[0056] The embodiment of the present invention provides an X capacitor control and start multiplexing circuit 50, as Figure 3 shown, including: ultra-high voltage switch J50, high voltage switch M50, voltage dividing unit, voltage-controlled current source 51, diode D50, reference voltage source 52, VAC overvoltage protection unit, VAC undervoltage protection unit and VAC open circuit control unit.

[0057] The first input terminal of the ultra-high voltage switch J50 and the input terminal of the voltage dividing unit are both connected to the start input port VACin of the circuit. The second input terminal of the ultra-high voltage switch J50 is grounded. The output terminal of the ultra-high voltage switch J50 is respectively connected to the drain of the high voltage switch M50 and the input terminal of the voltage-controlled current source 51. The source of the high voltage switch M50 is grounded. The anode of the diode D50 is connected to the output terminal of the voltage-controlled current source 51, and the cathode of the diode D50 is respectively connected to the input terminal of the reference voltage source 52 and the power supply port VDD of the circuit. The output terminal of the reference voltage source 52 is respectively connected to the second input terminal and the voltage reference terminal of the VAC overvoltage protection unit, the first input terminal and the voltage reference terminal of the VAC undervoltage protection unit, and the second input terminal and the voltage reference terminal of the VAC open circuit control unit. The output terminal of the voltage dividing unit is respectively connected to the first input terminal of the VAC overvoltage protection unit, the second input terminal of the VAC undervoltage protection unit, and the first input terminal of the VAC open circuit control unit. The enable signal terminal EN of the circuit is respectively connected to the enable terminal of the voltage-controlled current source 51, the enable terminal of the VAC overvoltage protection unit, the enable terminal of the VAC undervoltage protection unit, and the enable terminal of the VAC open circuit control unit. The output terminal of the VAC overvoltage protection unit serves as the VAC overvoltage protection signal terminal VACin_ovp of the circuit. The output terminal of the VAC undervoltage protection unit serves as the VAC undervoltage protection signal terminal VACin_uvp of the circuit. The VAC open circuit control logic signal output terminal of the VAC open circuit control unit is connected to the gate of the high voltage switch M50.

[0058] The input VACin of the ultra-high voltage switch J50 is 90 - 264 VAC, and its output terminal is a voltage slightly higher than V DD When the input EN voltage signal of the voltage-controlled current source 51 is logic "0", the maximum output is I CH0 of I CH_VDD current. When its input EN voltage signal is logic "1", the output current is 0, and the voltage-controlled current source 51 is turned off.

[0059] The X-capacitor control and start-up multiplexing circuit 50 performs constant-current start-up on the power supply port VDD after drawing current at the start-up input port VACin in response to its enable signal terminal EN. The X-capacitor control and start-up multiplexing circuit 50 generates a protection enable signal at the VAC overvoltage protection signal terminal VACin_ovp in response to the start-up input port VACin and the enable signal terminal EN. The X-capacitor control and start-up multiplexing circuit 50 generates a protection enable signal at the VAC undervoltage protection signal terminal VACin_uvp in response to the start-up input port VACin and the enable signal terminal EN. The X-capacitor control and start-up multiplexing circuit 50 generates an overvoltage protection enable signal at the VAC overvoltage protection signal terminal VACin_ovp and an undervoltage protection enable signal at the VAC undervoltage protection signal terminal VACin_uvp in response to the enable signal terminal EN and the power supply port VDD. When the input VAC voltage of the system is too high or too low, the switch-mode power supply controller 11A is turned off to avoid damaging the switch-mode power supply system, thus achieving a better safety effect. After the start-up of the power supply port VDD is completed in response to the enable signal terminal EN, the X-capacitor control and start-up multiplexing circuit 50 turns off the charging current of the start-up input port VACin to the power supply port VDD, which can achieve the effect of saving system power consumption. The internal device D50 of the X-capacitor control and start-up multiplexing circuit 50 can prevent the current reverse injection action of the power supply port VDD of the X-capacitor control and start-up multiplexing circuit 50. The temperature drift of the charging current of the X-capacitor control and start-up multiplexing circuit 50 to the power supply port VDD is close to zero. The X-capacitor control and start-up multiplexing circuit 50 responds to the start-up input port VACin. When the input at the VAC port is disconnected, the start-up input port VACin is quickly discharged to zero to ensure the safety of the X-capacitor to the human body.

[0060] Voltage levels of 110 kV to 220 kV are referred to as high voltage. Voltage levels of 330 kV to 500 kV are referred to as extra-high voltage.

[0061] Exemplarily, the voltage dividing unit includes: resistor R51 and resistor R52. One end of resistor R51 is connected to the first input terminal of the extra-high voltage switch J50 and the start-up input port VACin of the circuit. The other end of resistor R51 is connected to one end of resistor R52, and the other end of resistor R52 is grounded. The common point connected between the other end of resistor R51 and one end of resistor R52 serves as the output terminal of the voltage dividing unit.

[0062] Exemplarily, the VAC overvoltage protection unit includes: a first comparator 58, a first timer 53, and a resistor R53. The first input terminal of the first comparator 58 is connected to the output terminal of the voltage dividing unit. The second input terminal of the first comparator 58 is connected to one end of the resistor R53, and the other end of the resistor R53 is connected to the output terminal of the reference voltage unit 52. The output terminal of the first comparator 58 is connected to the input terminal of the first timer 53. The first voltage input terminal of the first comparator 58 is connected to the output terminal of the reference voltage unit 52, and the second voltage input terminal of the first comparator 58 is connected to the enable signal terminal EN of the circuit. The voltage reference terminal of the first timer 53 is connected to the output terminal of the reference voltage unit 52, the enable terminal of the first timer 53 is connected to the enable signal terminal EN of the circuit, and the output terminal of the first timer 53 serves as the VAC overvoltage protection signal terminal VACin_ovp of the circuit.

[0063] Exemplarily, the VAC undervoltage protection unit includes: a second comparator 57, a second timer 55, and a resistor R54. The first input terminal of the second comparator 57 is connected to one end of the resistor R54, and the other end of the resistor R54 is connected to one end of the resistor R53. The second input terminal of the second comparator 57 is connected to the output terminal of the voltage dividing unit. The output terminal of the second comparator 57 is connected to the input terminal of the second timer 55. The first voltage input terminal of the second comparator 57 is connected to the output terminal of the reference voltage unit 52, and the second voltage input terminal of the second comparator 57 is connected to the enable signal terminal EN of the circuit. The voltage reference terminal of the second timer 55 is connected to the output terminal of the reference voltage unit 52, the enable terminal of the second timer 55 is connected to the enable signal terminal EN of the circuit, and the output terminal of the second timer 55 serves as the VAC undervoltage protection signal terminal VACin_uvp of the circuit.

[0064] Exemplarily, the VAC open - circuit control unit includes: a third comparator 56, a third timer 54, a resistor R55, and a resistor R56. The first input terminal of the third comparator 56 is connected to the output terminal of the voltage dividing unit. The second input terminal of the third comparator 56 is respectively connected to one end of the resistor R55 and one end of the resistor R56. The other end of the resistor R55 is connected to one end of the resistor R54, and the other end of the resistor R56 is grounded. The output terminal of the third comparator 56 is connected to the input terminal of the third timer 54. The first voltage input terminal of the third comparator 56 is connected to the output terminal of the reference voltage unit 52, and the second voltage input terminal of the third comparator 56 is connected to the enable signal terminal EN of the circuit. The voltage reference terminal of the third timer 54 is connected to the output terminal of the reference voltage unit 52, the enable terminal of the third timer 54 is connected to the enable signal terminal EN of the circuit, and the output terminal of the third timer 54 is connected to the gate of the high - voltage switch M50.

[0065] When the inputs of the first timer 53, the second timer 55, and the third timer 54 are logic low, their outputs are logic low. When their inputs are logic high and the timing reaches the timing times T1, T2, and T3, their outputs flip to logic high. The outputs of the first comparator 58, the second comparator 57, and the third comparator 56 are in phase with the positive terminals. That is, when the voltage of the positive terminal is higher than the voltage of the negative terminal, the output is logic high; otherwise, the output is logic low.

[0066] Exemplarily, the circuit further includes: a resistor R50. One end of the resistor R50 is respectively connected to the output terminal of the ultra-high voltage switch J50 and the input terminal of the voltage-controlled current source 51, and the other end of the resistor R50 is connected to the drain of the high-voltage switch M50.

[0067] Figure 3 In, V ACin : Starting input voltage, VACin1: Divided voltage of VACin, I J : Conducting current of J50, I discharge : Discharge current, V JS : Output terminal voltage of J50, VACin_open: Control logic signal for VAC open circuit, I CH_VDD : Charging current of the switching power supply 10A, V DD : Power supply port voltage, VREF: Reference voltage source 52, TIMER1: First timer 53, TIMER2: Second timer 55, TIMER3: Third timer 54, C1: First comparator 58, C2: Second comparator 57, C3: Third comparator 56, vref: Output terminal voltage of the reference voltage source 52 (VREF), vref1: Reference voltage 1, vref2: Reference voltage 2, vref3: Reference voltage 3, ovp_en: Overvoltage protection enable signal, uvp_en: Undervoltage protection enable signal, open_en: Open circuit enable signal.

[0068] The X-capacitor control and startup multiplexing circuit of the present invention can be applied to switching power supplies, etc. By controlling the input port VACin in the circuit, the switching power supply system containing the present invention can work more safely and efficiently.

[0069] Embodiment 2

[0070] A switching power supply controller 11A, as Figure 4 shown, includes: a power-on and power-off enable circuit UVLO20, a pulse width modulator PWM30, a drive circuit DRIVER40, and the aforementioned X-capacitor control and startup multiplexing circuit 50.

[0071] The input terminals of the driver circuit DRIVER40 are respectively connected to the power supply port VDD of the X-capacitor control and startup multiplexing circuit 50, the overvoltage protection signal terminal VACin_ovp and undervoltage protection signal terminal VACin_uvp of VAC, the input terminal of the power-on and power-off enabling circuit UVLO20, and the output terminal of the pulse width modulator PWM30; the output terminal of the driver circuit DRIVER40 serves as the switch signal output terminal of the controller. The output terminal of the power-on and power-off enabling circuit UVLO20 is connected to the enable signal terminal EN of the X-capacitor control and startup multiplexing circuit 50. The input terminal of the power-on and power-off enabling circuit UVLO20 serves as the power supply port of the controller; the startup input port VACin of the X-capacitor control and startup multiplexing circuit 50 serves as the startup input port VACin of the controller, the first input terminal of the pulse width modulator PWM30 serves as the feedback port of the controller, the second input terminal of the pulse width modulator PWM30 serves as the current monitoring port of the controller, and the ground port of the controller is grounded.

[0072] The switching power supply controller 11A can be applied to transformer secondary-side feedback isolated and transformer primary-side feedback isolated switching power supply systems. The driver circuit switching power supply controller 11A consists of an X-capacitor control and startup multiplexing circuit, a power-on and power-off enabling circuit 20, a pulse width modulator 30, and a driver circuit 40 embedded in an integrated circuit to save external components.

[0073] Figure 4 In, V PWM : Pulse width comparator output signal, Vsw: Switching signal, VDD: Power supply port, VACin: Startup input port, FB: Feedback port, CS: Current monitoring port, DRV: Drive output port, GND: Ground port.

[0074] Embodiment 3

[0075] A switching power supply 10A, as Figure 4 shown, the switching power supply 10A includes: a transformer TR, a power switch tube M1, a feedback device 12, and the aforementioned driver circuit switching power supply controller 11A.

[0076] One end of the primary coil of the transformer TR is connected to the drain of the power tube M1, and the other end of the primary coil of the transformer TR serves as the voltage input terminal of the switching power supply 10A; one end of the secondary coil of the transformer TR is connected to one end of the feedback device 12; both ends of the secondary coil of the transformer TR serve as the DC voltage output terminals of the switching power supply 10A. The gate of the power tube M1 is connected to the switching signal output terminal of the driver circuit switching power supply controller 11A, and the source of the power tube M1 is connected to the current monitoring port of the driver circuit switching power supply controller 11A. The other end of the feedback device 12 is connected to the feedback port of the driver circuit switching power supply controller 11A.

[0077] The X-capacitor control and startup multiplexing circuit 50 is embedded in an integrated circuit of a driving circuit switch-mode power supply controller 11A.

[0078] The driving circuit switch-mode power supply controller 11A is coupled to a feedback device 12 provided at the output end of a transformer TR to generate a switching signal V SW , and the switching signal V SW regulates the pulse width of the transformer TR through a power switch, thereby controlling the energy transmission of the switch-mode power supply 10A incorporating the circuit of the present invention; the driving circuit switch-mode power supply controller 11A is composed of an X-capacitor control and startup multiplexing circuit 50, a power-on / off enabling circuit 20, a pulse width modulator 30, and a driving circuit 40 coupled together.

[0079] A user can perform constant-current startup on the switch-mode power supply 10A incorporating the present invention through a startup input port VACin. After the power supply system completes startup, the startup path can be automatically cut off to save energy consumption, maximizing the safety and efficiency of the user's electrical equipment; the X-capacitor control and startup multiplexing circuit 50 responds to the startup input port VACin. When the voltage at this port is too high or too low, a protection action is triggered to turn off the switch-mode power supply 10A incorporating the present invention, thereby ensuring the safety of the switch-mode power supply 10A adopting the present invention; the X-capacitor control and startup multiplexing circuit 50 responds to the startup input port VACin. When the input VAC of the switch-mode power supply 10A incorporating the present invention is disconnected, the startup input port VACin is quickly discharged to ground, thereby ensuring the electrical safety of the switch-mode power supply 10A adopting the present invention to the human body.

[0080] Exemplarily, the switch-mode power supply 10A further includes: a capacitor Cx, a full-wave rectifier diode Dx1, a full-wave rectifier diode Dx2, a full-wave rectifier diode D1, and a capacitor C1. Two ends of the capacitor Cx are respectively connected to two ends of the input line voltage; the anode of the full-wave rectifier diode Dx1 is respectively connected to one end of the capacitor Cx and the first end of the full-wave rectifier diode D1; the cathode of the full-wave rectifier diode Dx1 is respectively connected to the cathode of the full-wave rectifier diode Dx2 and the startup input port VACin of the driving circuit switch-mode power supply controller 11A; the anode of the full-wave rectifier diode Dx2 is respectively connected to the other end of the capacitor Cx and the second end of the full-wave rectifier diode D1. The third end of the full-wave rectifier diode D1 is connected to one end of the capacitor C1 and then grounded, and the fourth end of the full-wave rectifier diode D1 is respectively connected to the other end of the capacitor C1 and the other end of the primary coil of the transformer TR.

[0081] Exemplarily, the switch-mode power supply 10A further includes: a resistor R1, a diode D2, a capacitor C VDD and an auxiliary coil La. One end of the resistor R1 is respectively connected to the capacitor C VDDOne end is connected to the power supply port of the driving circuit switching power supply controller 11A, and the other end of the resistor R1 is connected to the cathode of the diode D2; the other end of the capacitor C VDD The other end is grounded. One end of the auxiliary coil La is connected to the anode of the diode D2, and the other end of the auxiliary coil La is grounded.

[0082] Figure 4 Among them, VAC: input line voltage, Vo: DC output voltage of the switching power supply, Lp: primary coil of the transformer TR, Ls: secondary coil of the transformer TR, La: auxiliary coil of the transformer TR, and the auxiliary coil La is responsible for charging the capacitor C at the VDD port VDD Power supply, D3: diode, C2: capacitor, Ics: primary coil current of the transformer TR, V FB : feedback voltage, Vcs: monitoring current.

[0083] Refer to Figure 4 , one end of the secondary coil of the transformer TR is connected to the anode of the diode D3, one end of the capacitor C2 is connected to the cathode of the diode D3, and the other end of the capacitor C2 is connected to the other end of the secondary coil of the transformer TR.

[0084] Exemplarily, the switching power supply 10A further includes: a resistor Rcs. One end of the resistor Rcs is connected to the source electrode of the power transistor M1, and the other end of the resistor Rcs is grounded.

[0085] The present invention can realize the constant current charging start of the power supply port VDD by controlling the port VACin, turn off the start current after the start is completed, prevent the current from flowing back into the VDD port after the VDD port starts successfully, turn off the switching power supply 10A including the present invention when the port VACin is under-voltage or over-voltage, and discharge the port VACin to the ground when the input of the switching power supply 10A including the present invention is disconnected, which not only ensures the safety of the user's electrical equipment but also improves the efficiency of the user's electrical equipment, and has a high market application prospect.

[0086] The working waveform of an X-capacitor control and startup multiplexing circuit 50 of the present invention is as shown in Figure 5 , Figure 6 , Figure 7 shown, and its working principle is as follows:

[0087] During the charging process of VDD starting from 0, when VDD < VDD ON (VDD ON is the power-on threshold), EN is logic "0", which controls the voltage-controlled current source 51, and its output current is I CH_VDD , and charges the VDD port to start. The I CH_VDDIt is ultra-low temperature drift. EN is logic "0", setting the outputs of all comparators and timers to "0". VACin_open is logic "0", thus controlling M50 to disconnect.

[0088] During the process of VDD charging and powering on starting from 0, when VDD > VDD ON , EN is logic "1", turning off the voltage-controlled current source 51, and the starting charging current I at the VDD port CH_VDD is 0, saving the current power consumption of starting charging. At this time, the start of the VDD port ends, and the entire circuit enters normal operation. After startup, VDD is higher than VDD ON and much higher than the anode voltage of D50. D50 reversely isolates the VDD port, avoiding phenomena such as reverse current injection from the VDD port to the circuit 50 causing power loss and startup failure.

[0089] VTHN is the conduction threshold of the high-voltage switch. R51 and R52 are ultra-large resistors with a matching ratio coefficient of β (0 < β < 1). R53, R54, R55, and R56 are precise resistors with matching ratio coefficients of θ1, θ2, θ3 (0 < θ3 < θ2 < θ1 < 1).

[0090] R52 = β(R51 + R52) (1)

[0091] R56 = θ3(R53 + R54 + R55 + R56) (2)

[0092] R55 + R56 = θ2(R53 + R54 + R55 + R56) (3)

[0093] R54 + R55 + R56 = θ1(R53 + R54 + R55 + R56) (4)

[0094] The reference voltage generator 52 responds to the port VDD to generate a reference voltage source vref. The reference voltages vref1, vref2, and vref3 are obtained by voltage division through the resistors R53 to R56.

[0095] vref1 = θ1 × vref (5)

[0096] vref2 = θ2 × vref (6)

[0097] vref3 = θ3 × vref (7)

[0098] VACin1 = β × VACin (8)

[0099] Therefore, when the input VAC of the switching power supply system of the present invention is overvoltage,

[0100] VACin1 = β × VACin > vref1 = θ1 × vref (9)

[0101] After the first comparator 58 outputs ovp_en as logic "1", the first timer 53 starts counting. If the duration reaches time T1, the first timer 53 outputs VACin_ovp as logic "1", turning off the switching power supply controller 11A of the drive circuit of the present invention to avoid damage caused by overvoltage at the input of system 10A.

[0102] If the input VAC of the switching power supply system of the present invention is undervoltage,

[0103] VACin1 = β × VACin < vref2 = θ2 × vref (10)

[0104] After the second comparator 57 outputs uvp_en as logic "1", the second timer 55 starts counting. If the duration reaches time T2, the output of the second timer 55 is logic "1", turning off the switching power supply controller 11A of the drive circuit of the present invention to avoid damage caused by undervoltage at the input of system 10A.

[0105] When the input VAC of the switching power supply system of the present invention is disconnected, if:

[0106] VACin1 = β × VACin > vref3 = θ3 × vref (11)

[0107] That is, VACin > Vxcap_disch_th = θ3 × vref / β (12)

[0108] Here, Vxcap_disch_th < 36V is the VACin voltage threshold for X-capacitor discharge. After the third comparator 56 outputs open_en as logic "1", the third timer 54 starts counting. If the duration reaches time T3, the third timer 54 outputs VACin_open as logic "1", controlling M50 to conduct. Therefore, the VACin port will discharge to the ground through M50, R50, and J50. As a result, when the input of the switching power supply 10A of the present invention is powered off, the X-capacitor can be discharged to the ground within time T4 (T4 << 0.3s), avoiding the human electric shock accident caused by the power-off of system 10A.

[0109] The switching power supply 10A incorporating the present invention not only realizes safety and wide-temperature operation consistency but also minimizes standby power consumption.

[0110] The comparison of the startup timing waveforms of the switching power supply 10A with the present invention and the traditional switching power supply 10 after the input line voltage VAC is as Figure 5 shown. From Figure 5As can be seen from the waveform, in the switching power supply 10A of the present invention, after the input VAC, VDD rapidly rises to VDD ON and then shuts off the startup current. The startup current I CH_VDD is 0, saving power loss. In the traditional switching power supply 10 system, after the input VAC, VDD rises to VDD ON and then it is unable to shut off the startup current, resulting in a fixed power consumption on the startup resistor.

[0111] Figure 6 Figure shows the comparison of the timing waveforms of the voltage of the X capacitor when the AC input line voltage VAC of the switching power supply 10A with the present invention and the traditional switching power supply 10 is disconnected. From Figure 6 the waveform, it can be seen that after the system input VAC of the switching power supply 10A of the present invention is disconnected, after detecting that the third timer 54 times to reach the time T3, the voltage VACin of the X capacitor is discharged to ground within a very short time T4. However, the traditional switching power supply 10 keeps a high voltage (far exceeding the human body voltage of 36V) after the system input VAC is disconnected, which will electrocute the human body when the human body touches the input port of the system, causing an accident.

[0112] Figure 7 Figure shows the comparison of the waveforms when the AC input line voltage VAC of the switching power supply 10A with the present invention and the traditional switching power supply 10 is overvoltage or undervoltage. From Figure 7 the waveform, it can be seen that when the input VAC of the switching power supply 10A of the present invention is undervoltage and continuously occurs to reach the timing time T2 of the second timer 55, the signal VACin_uvp is logic "1" to shut off the drive output Vsw of the system and enter the automatic restart protection mode of the VDD terminal, protecting the switching power supply 10A; when the input VAC of the switching power supply 10A of the present invention is overvoltage and continuously occurs to reach the timing time T1 of the timer 53, the signal VACin_ovp is logic "1" to shut off the drive output Vsw of the system and enter the automatic restart protection mode of the VDD, protecting the switching power supply 10A. After the above protection is released, the system will resume normal operation after the next automatic restart of VDD. For the traditional switching power supply system 10, from the waveform, we can see that regardless of whether the input VAC of the system is overvoltage or undervoltage, the drive signal Vsw of the system works normally. In this way, if the VAC voltage is too high, when the power transistor M1 shuts off during the switching operation, the drain voltage of the power transistor M1 will be too high due to flyback, causing damage. If the VAC is too low, transformer saturation will occur, resulting in a blast accident.

[0113] Figure 1 In, Rst: startup resistor of the switching power supply system, I ST : charging current of the switching power supply system. Figure 2 In, V FB : feedback voltage.

[0114] In this specification, the various embodiments are described in a progressive manner. Each embodiment focuses on the differences from other embodiments, and the same or similar parts among the various embodiments can be referred to each other.

[0115] Specific examples are used in this article to elaborate on the principles and implementation manners of the present invention. The descriptions of the above embodiments are only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation on the present invention.

Claims

1. An X-capacitor control and startup multiplexing circuit, characterized in that, The circuit includes: an ultra-high voltage switch J50, a high voltage switch M50, a voltage dividing unit, a voltage-controlled current source, a diode D50, a reference voltage source, a VAC overvoltage protection unit, a VAC undervoltage protection unit, and a VAC open-circuit control unit; The first input terminal of the ultra-high voltage switch J50 and the input terminal of the voltage dividing unit are both connected to the start input port VACin of the circuit. The second input terminal of the ultra-high voltage switch J50 is grounded. The output terminal of the ultra-high voltage switch J50 is respectively connected to the drain of the high voltage switch M50 and the input terminal of the voltage-controlled current source. The source of the high voltage switch M50 is grounded; The anode of the diode D50 is connected to the output terminal of the voltage-controlled current source. The cathode of the diode D50 is respectively connected to the input terminal of the reference voltage source and the power supply port VDD of the circuit; The output terminal of the reference voltage source is respectively connected to the second input terminal and the voltage reference terminal of the VAC overvoltage protection unit, the first input terminal and the voltage reference terminal of the VAC undervoltage protection unit, and the second input terminal and the voltage reference terminal of the VAC open-circuit control unit. The output terminal of the reference voltage source is series-divided by resistors R53, R54, R55, and R56 to obtain reference voltages vref1, vref2, and vref3, which are respectively input to the other input terminals of the VAC overvoltage protection unit, the VAC undervoltage protection unit, and the VAC open-circuit control unit; The output terminal of the voltage dividing unit is respectively connected to the first input terminal of the VAC overvoltage protection unit, the second input terminal of the VAC undervoltage protection unit, and the first input terminal of the VAC open-circuit control unit; The enable signal terminal EN of the circuit is respectively connected to the enable terminal of the voltage-controlled current source, the enable terminal of the VAC overvoltage protection unit, the enable terminal of the VAC undervoltage protection unit, and the enable terminal of the VAC open-circuit control unit; The output terminal of the VAC overvoltage protection unit serves as the VAC overvoltage protection signal terminal VACin_ovp of the circuit. The output terminal of the VAC undervoltage protection unit serves as the VAC undervoltage protection signal terminal VACin_uvp of the circuit. The VAC open-circuit control logic signal output terminal of the VAC open-circuit control unit is connected to the gate of the high voltage switch M50.

2. The X-capacitor control and startup multiplexing circuit according to claim 1, wherein The voltage dividing unit includes: resistors R51 and R52; One end of the resistor R51 is connected to the first input terminal of the ultra-high voltage switch J50 and the start input port VACin of the circuit. The other end of the resistor R51 is connected to one end of the resistor R52. The other end of the resistor R52 is grounded; The common point connected between the other end of the resistor R51 and one end of the resistor R52 serves as the output terminal of the voltage dividing unit.

3. The X-capacitor control and startup multiplexing circuit according to claim 1, characterized in that, The VAC overvoltage protection unit includes: a first comparator, a first timer, and a resistor R53; The first input terminal of the first comparator is connected to the output terminal of the voltage dividing unit. The second input terminal of the first comparator is connected to one end of the resistor R53. The other end of the resistor R53 is connected to the output terminal of the reference voltage source. The output terminal of the first comparator is connected to the input terminal of the first timer. The first voltage input terminal of the first comparator is connected to the output terminal of the reference voltage source. The second voltage input terminal of the first comparator is connected to the enable signal terminal EN of the circuit; The voltage reference terminal of the first timer is connected to the output terminal of the reference voltage device. The enable terminal of the first timer is connected to the enable signal terminal EN of the circuit. The output terminal of the first timer serves as the VAC overvoltage protection signal terminal VACin_ovp of the circuit.

4. The X-capacitor control and startup multiplexing circuit according to claim 3, wherein, The VAC undervoltage protection unit includes: a second comparator, a second timer, and a resistor R54; One end of the first input terminal of the second comparator is connected to one end of the resistor R54. The other end of the resistor R54 is connected to one end of the resistor R53. The second input terminal of the second comparator is connected to the output terminal of the voltage dividing unit. The output terminal of the second comparator is connected to the input terminal of the second timer. The first voltage input terminal of the second comparator is connected to the output terminal of the reference voltage device. The second voltage input terminal of the second comparator is connected to the enable signal terminal EN of the circuit; The voltage reference terminal of the second timer is connected to the output terminal of the reference voltage device. The enable terminal of the second timer is connected to the enable signal terminal EN of the circuit. The output terminal of the second timer serves as the VAC undervoltage protection signal terminal VACin_uvp of the circuit.

5. The X-capacitor control and startup multiplexing circuit according to claim 4, wherein The VAC open circuit control unit includes: a third comparator, a third timer, a resistor R55, and a resistor R56; One end of the first input terminal of the third comparator is connected to the output terminal of the voltage dividing unit. The second input terminal of the third comparator is respectively connected to one end of the resistor R55 and one end of the resistor R56. The other end of the resistor R55 is connected to one end of the resistor R54. The other end of the resistor R56 is grounded. The output terminal of the third comparator is connected to the input terminal of the third timer. The first voltage input terminal of the third comparator is connected to the output terminal of the reference voltage device. The second voltage input terminal of the third comparator is connected to the enable signal terminal EN of the circuit; The voltage reference terminal of the third timer is connected to the output terminal of the reference voltage device. The enable terminal of the third timer is connected to the enable signal terminal EN of the circuit. The output terminal of the third timer is connected to the gate of the high-voltage switch M50.

6. The X-capacitor control and startup multiplexing circuit according to claim 1, wherein The circuit further includes: a resistor R50; One end of the resistor R50 is respectively connected to the output terminal of the ultra-high-voltage switch J50 and the input terminal of the voltage-controlled current device. The other end of the resistor R50 is connected to the drain of the high-voltage switch M50.

7. A switching power supply controller, characterized in that, The controller includes: a power-on / off enable circuit UVLO, a pulse width modulator PWM, a drive circuit DRIVER, and the X-capacitor control and startup multiplexing circuit according to any one of claims 1-6; The input terminals of the drive circuit DRIVER are respectively connected to the power supply ports VDD of the X-capacitor control and startup multiplexing circuit, the VAC overvoltage protection signal terminal VACin_ovp and the VAC undervoltage protection signal terminal VACin_uvp, the input terminal of the power-on / off enable circuit UVLO, and the output terminal of the pulse width modulator PWM. The output terminal of the drive circuit DRIVER serves as the switch signal output terminal of the controller; The output terminal of the power-on / off enable circuit UVLO is connected to the enable signal terminal EN of the X-capacitor control and startup multiplexing circuit; The input terminal of the power-on and power-off enabling circuit UVLO serves as the power supply port of the controller; the start input port VACin of the X-capacitor control and start multiplexing circuit serves as the start input port VACin of the controller, the first input terminal of the pulse width modulator PWM serves as the feedback port of the controller, the second input terminal of the pulse width modulator PWM serves as the current monitoring port of the controller, and the ground port of the controller is grounded.

8. A switching power supply, characterized in that, The switching power supply includes: a transformer TR, a power switch tube M1, a feedback device, and the switching power supply controller according to claim 7; One end of the primary coil of the transformer TR is connected to the drain of the power tube M1, and the other end of the primary coil of the transformer TR serves as the voltage input terminal of the switching power supply; one end of the secondary coil of the transformer TR is connected to one end of the feedback device; both ends of the secondary coil of the transformer TR serve as the DC voltage output terminals of the switching power supply; The gate of the power tube M1 is connected to the switching signal output terminal of the switching power supply controller, and the source of the power tube M1 is connected to the current monitoring port of the switching power supply controller; The other end of the feedback device is connected to the feedback port of the switching power supply controller.

9. The switching power supply according to claim 8, characterized in that, The switching power supply further includes: a capacitor Cx, a full-wave rectifier diode Dx1, a full-wave rectifier diode Dx2, a full-wave rectifier diode D1, and a capacitor C1; Both ends of the capacitor Cx are respectively connected to both ends of the input line voltage; the anode of the full-wave rectifier diode Dx1 is respectively connected to one end of the capacitor Cx and the first end of the full-wave rectifier diode D1; the cathode of the full-wave rectifier diode Dx1 is respectively connected to the cathode of the full-wave rectifier diode Dx2 and the start input port VACin of the switching power supply controller; the anode of the full-wave rectifier diode Dx2 is respectively connected to the other end of the capacitor Cx and the second end of the full-wave rectifier diode D1; The third end of the full-wave rectifier diode D1 is connected to one end of the capacitor C1 and then grounded, and the fourth end of the full-wave rectifier diode D1 is respectively connected to the other end of the capacitor C1 and the other end of the primary coil of the transformer TR.

10. The switching power supply according to claim 8, wherein, The switching power supply further includes: resistor R1, diode D2, capacitor C VDD and auxiliary coil La; One end of resistor R1 is respectively connected to one end of capacitor C VDD and the power supply port of the switching power supply controller. The other end of resistor R1 is connected to the cathode of diode D2; the other end of capacitor C VDD is grounded; One end of the auxiliary coil La is connected to the anode of the diode D2, and the other end of the auxiliary coil La is grounded.

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