A circuit for flexibly starting charging of a power supply port and a switching power supply system

Abstract

The present invention provides a circuit and a switching power supply system for flexibly starting the charging of a power supply port, which relates to the technical field of power supply starting circuits. The circuit is applied to a switching power supply system and includes a starting charging module, a constant current feedback temperature drift control module, an enabling determination module, and a ground short-circuit detection module. The constant current feedback temperature drift control module is respectively connected to the starting charging module, the enabling determination module, and the ground short-circuit detection module; the starting charging module is also respectively connected to the ground short-circuit detection module, the control starting port ST of the switching power supply system, and the power supply port VDD; the enabling determination module is connected to the enabling end EN of the switching power supply system. By setting the starting charging module and the constant current feedback temperature drift control module, the control starting port ST flexibly starts the charging of the power supply port VDD to avoid damaging the life of the switching power supply system when the power supply port VDD is short-circuited to the ground.

Description

Technical Field

[0001] The present invention relates to the technical field of power supply startup circuits, and particularly to a circuit and a switching power supply system for flexibly charging and starting a power supply port. 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. The traditional switching power supply system uses resistor startup, making it difficult to meet the current stringent standby power consumption requirements. Currently, popular switching power supply converters such as Figure 1 , and its working waveform is as Figure 2 . In the existing switching power supply system, the voltage in the secondary coil of the transformer TR is sampled to the FB port of the traditional switching power supply system 10 through the feedback device 12, and the current ICS in the primary coil of the transformer is sampled to the CS port of the switching power supply controller integrated circuit 11 through the power transistor M1 and the current limiting resistor Rcs to generate a square wave signal V with variable pulse width PWM , and the square wave signal V PWM generates a drive signal Vsw through the drive circuit DRIVER to control the on and off of the power transistor M1. It can be seen that in order to improve the standby efficiency, the traditional switching power supply system 10 directly sets an ultra-high voltage switch at the high-voltage input terminal ST to charge the power supply VDD port with a large current for startup, and closes the high-voltage switch after startup to save power consumption. This power supply system can easily meet the standby power consumption energy efficiency standard. However, currently, the ultra-high voltage startup switch startup technology directly pours a large current into the power supply port VDD for startup, and disconnects the startup path after the power supply startup process ends. When the power supply port VDD is short-circuited to the ground, the power supply is easily damaged or its life is severely reduced.

[0003] Therefore, there is an urgent need for a new type of switching power supply system that can reduce damage to the power supply while meeting the standby power consumption standard, and efficiently and safely protect the electrical equipment. Summary of the Invention

[0004] The purpose of the present invention is to provide a circuit and a switching power supply system for flexibly charging and starting a power supply port, which can avoid reducing the life of the switching power supply system when the power supply port VDD is short-circuited to the ground by controlling the flexible startup charging of the startup port ST to the power supply port VDD.

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

[0006] A circuit for flexibly charging and starting a power supply port, the circuit is applied to a switching power supply system, and the circuit includes:

[0007] A startup charging module, a constant current feedback temperature drift control module, an enable determination module, and a ground short circuit detection module;

[0008] The constant current feedback temperature drift control module is respectively connected to the start charging module, the enable determination module, and the ground short circuit detection module; the start charging module is also respectively connected to the ground short circuit detection module, the control start port ST of the switching power supply system, and the power supply port VDD; the enable determination module is connected to the enable end EN of the power-on and power-off enable circuit in the switching power supply system;

[0009] The enable determination module is used to receive an enable signal;

[0010] When the enable signal is 0, the start charging module generates a first signal V S1 or generates a second signal when the enable signal is 1;

[0011] When the enable signal is 0, the constant current feedback temperature drift control module generates a third signal V G1 ;

[0012] The first signal V S1 and the third signal V G1 are used to perform flexible charging on the power supply port VDD; the third signal is used to stop charging the power supply port VDD;

[0013] The ground short circuit detection module is used to detect whether there is a ground short circuit;

[0014] The constant current feedback temperature drift control module is also used to suppress the temperature drift of the charging current of the control start port ST to the power supply port VDD in case of a ground short circuit.

[0015] Optionally, the start charging module includes:

[0016] Switch tube J50, switch tube HN50, switch tube HP50, and diode D50;

[0017] The drain of the switch tube J50 is connected to the control start port ST;

[0018] The gate of the switch tube J50 is grounded;

[0019] The source of the switch tube J50 is respectively connected to the drain of the switch tube HN50 and the constant current feedback temperature drift control module;

[0020] The source of the switch tube HN50 is respectively connected to the source of the switch tube HP50 and the constant current feedback temperature drift control module;

[0021] The drain of the switch tube HP50 is respectively connected to the gate of the switch tube HP50, the constant current feedback temperature drift control module, the ground short circuit detection module, and the anode of the diode D50;

[0022] The cathode of the diode D50 is connected to the power supply port VDD.

[0023] Optionally, the constant current feedback temperature drift control module includes:

[0024] A constant current feedback circuit and a temperature drift control circuit;

[0025] The constant current feedback circuit is respectively connected to the start charging module, the enable determination module, the ground short circuit detection module and the temperature drift control circuit;

[0026] The temperature drift control circuit is also connected to the enable determination module and the ground short circuit detection module.

[0027] Optionally, the constant current feedback circuit includes:

[0028] Resistor R57, clamping diode Z50, switching transistor HP51, switching transistor HN52 and resistor R55;

[0029] The first end of the resistor R57 is respectively connected to the source of the switching transistor J50 and the drain of the switching transistor HN50;

[0030] The second end of the resistor R57 is respectively connected to the gate of the switching transistor HN50, the cathode of the clamping diode Z50, the enable determination module and the drain of the switching transistor HN52;

[0031] The anode of the clamping diode Z50 is respectively connected to the source of the switching transistor HP51, the source of the switching transistor HN50 and the source of the switching transistor HP50;

[0032] The source of the switching transistor HN52 is connected to the temperature drift control circuit;

[0033] The gate of the switching transistor HN52 is respectively connected to the first end of the resistor R55 and the temperature drift control circuit;

[0034] The second end of the resistor R55 is respectively connected to the drain of the switching transistor HP51 and the temperature drift control circuit;

[0035] The gate of the switching transistor HP51 is respectively connected to the gate of the switching transistor HP50, the drain of the switching transistor HP50, the ground short circuit detection module and the anode of the diode D50.

[0036] Optionally, the temperature drift control circuit includes:

[0037] Clamping diode Z51, resistor R53 and resistor R54;

[0038] The cathode of the clamping tube Z51 is respectively connected to the gate of the switching tube HN52 and the first end of the resistor R55;

[0039] The anode of the clamping tube Z51, the source of the switching tube HN52, and the first end of the resistor R54 are all grounded;

[0040] The second end of the resistor R54 is respectively connected to the ground short - circuit detection module and the first end of the resistor R53;

[0041] The second end of the resistor R53 is respectively connected to the second end of the resistor R55 and the drain of the switching tube HP51.

[0042] Optionally, the enable determination module includes:

[0043] Resistor R56 and switching tube HN53;

[0044] The first end of the resistor R56 is respectively connected to the gate of the switching tube HN53 and the enable terminal EN of the power - on / off enable circuit in the switching power supply system;

[0045] The second end of the resistor R56 and the source of the switching tube HN53 are both grounded;

[0046] The drain of the switching tube HN53 is respectively connected to the second end of the resistor R57, the gate of the switching tube HN50, the cathode of the clamping tube Z50, and the drain of the switching tube HN52.

[0047] Optionally, the ground short - circuit detection module includes:

[0048] Resistor R51, resistor R52, clamping tube Z52, and switching tube HN51;

[0049] The first end of the resistor R51 is respectively connected to the gate of the switching tube HP51, the gate of the switching tube HP50, the drain of the switching tube HP50, and the anode of the diode D50;

[0050] The second end of the resistor R51 is respectively connected to the first end of the resistor R52, the cathode of the clamping tube Z52, and the gate of the switching tube HN51;

[0051] The second end of the resistor R52, the anode of the clamping tube Z52, and the source of the switching tube HN51 are all grounded;

[0052] The drain of the switching tube HN51 is respectively connected to the second end of the resistor R54 and the first end of the resistor R53.

[0053] Optionally, the switching tube J50 is an ultra - high - voltage switching tube;

[0054] The switching transistors HN50, the switching transistor HN51, the switching transistor HN52, and the switching transistor HN53 are all high-voltage N-type switches;

[0055] The switching transistors HP50 and the switching transistor HP51 are both high-voltage P-type switches.

[0056] A switching power supply system applies the circuit for flexibly charging and starting a power supply port described above.

[0057] According to the specific embodiments provided by the present invention, the following technical effects are disclosed by the present invention:

[0058] The present invention provides a circuit and a switching power supply system for flexibly charging and starting a power supply port. The circuit is applied to a switching power supply system and includes a starting charging module, a constant current feedback temperature drift control module, an enabling determination module, and a ground short circuit detection module. The constant current feedback temperature drift control module is respectively connected to the starting charging module, the enabling determination module, and the ground short circuit detection module; the starting charging module is also respectively connected to the ground short circuit detection module, the control starting port ST of the switching power supply system, and the power supply port VDD; the enabling determination module is connected to the enabling end EN of the switching power supply system. By setting the starting charging module and the constant current feedback temperature drift control module, the control starting port ST flexibly starts charging the power supply port VDD to avoid damaging the lifespan of the switching power supply system when the power supply port VDD is short-circuited to the ground. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] 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.

[0060] Figure 1 It is the circuit diagram of the switching power supply system in the prior art;

[0061] Figure 2 It is the working waveform diagram of the switching power supply system in the prior art;

[0062] Figure 3 It is the circuit diagram for flexibly charging and starting the power supply port in Embodiment 1 of the present invention;

[0063] Figure 4 It is the circuit diagram of the switching power supply system in Embodiment 3 of the present invention;

[0064] Figure 5 It is the working timing diagram of the switching power supply system when the external connection mode A is adopted in Embodiment 3 of the present invention;

[0065] Figure 6 It is the working timing diagram of the switching power supply system in external connection mode B in Embodiment 3 of the present invention. Specific Embodiments

[0066] 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.

[0067] The purpose of the present invention is to provide a circuit and a switching power supply system for flexibly starting charging of a power supply port. By controlling the start-up port ST to flexibly start charging the power supply port VDD, the life of the switching power supply system can be prevented from being damaged when the power supply port VDD is short-circuited to the ground.

[0068] 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 in conjunction with the accompanying drawings and specific embodiments.

[0069] Figures 1-6 Among them, 10 represents a commercially popular switching power supply system without the present invention; 10A represents the switching power supply system of the present invention; 11 represents a commercially popular switching power supply controller integrated circuit without the present invention; 11A represents the switching power supply controller integrated circuit of the present invention; 12 represents a feedback device (FEEDBACK); 20 represents an under-voltage lockout circuit (UVLO); 30 represents a pulse width modulator (PWM); 40 represents a driver circuit (DRIVER); 50 represents the start-up circuit function block of the switching power supply controller 10; 50A represents the circuit for flexibly starting charging of the power supply port (StartUp) of the present invention; Option (A) represents the external connection mode A of the ST port of the present invention 11A; Option (B) represents the external connection mode B of the ST port of the present invention 11A; 60A represents the working timing diagram of the switching power supply system in external connection mode A; 60B represents the working timing diagram of the switching power supply system in external connection mode B; 70 represents the working timing diagram of the switching power supply system in the prior art.

[0070] M1 represents an external power switch tube; TR represents a transformer; Lp represents the primary coil of TR; Ls represents the secondary coil of TR; La represents the auxiliary coil of TR, which is responsible for supplying power to the capacitor C of the VDD port VDD Power supply; D1 represents a full-wave rectifier diode for AC input; D2, D3, D4, D5, and D50 all represent diodes; R1, Rx, Rcs, R50, R51, R52, R53, R54, R55, R56, and R57 all represent resistors; C1, Cx, CVDD Both C1 and C2 represent capacitors; J50 represents an ultra-high voltage switch; HN50, HN51, HN52, HN53, and HN54 all represent high-voltage N-type switches, that is, high-voltage N-type transistors; HP50 and HP51 represent high-voltage P-type current mirror transistors; Z50, Z51, and Z52 all represent clamping diodes; VDD represents the power supply port; ST represents the start port; FB represents the feedback port; CS represents the primary coil current monitoring port of the transformer; DRV represents the drive output port; GND represents the ground port.

[0071] VAC represents the input AC voltage; VACN represents one end of the input AC voltage; Vo represents the DC output voltage of the switching power supply system 10; Ics represents the primary coil current of the transformer TR; Vsw represents the switching signal of the drive output; V FB represents the feedback voltage; V DD represents the supply port voltage; V PWM represents the output signal of the pulse width comparator; EN represents the enable signal output by the UVLO functional block.

[0072] I J represents the conduction current of J50; I CH_VDD represents the conduction current of HP50; I50 represents the mirror feedback current of the charging current I CH_VDD , that is, the conduction current of HP51; V JS represents the voltage of the third terminal of J50; V S1 represents the voltage of the third terminal of HN50, that is, the source voltage of HN50; V GS1 represents the voltage difference between the second and third terminals of HN50, that is, the gate-source voltage difference of HN50; V G1 represents the voltage of the second terminal of HN50, that is, the gate voltage of HN50; V G2 represents the voltage of the second terminal of HN52, that is, the gate voltage of HN52; V G3 represents the voltage of the second terminal of HN51, that is, the gate voltage of HN51; V D3 represents the voltage of the first terminal of HN51, that is, the drain voltage of HN51; V DD1 represents the voltage of the first terminal of HP50, that is, the drain voltage of HP50; I51 represents the current of R51; I52 represents the conduction current of HN52; V ST represents the signal of the ST port; V THN represents the turn-on threshold voltage of all N-type switch transistors; V DD_SCP_TH represents the voltage determination threshold for a short circuit between the VDD port and the ground. When V DD is lower than V DD_SCP_TH it is determined that there is a short circuit between the VDD port and the ground, and the charging current of the VDD port is compressed several times to avoid damage to the control circuit.

[0073] I CH0 represents the constant current value of the charging current at the VDD port when the VDD port voltage exceeds V DD_SCP_TH ; I CH1 represents the constant current value of the charging current at the VDD port when the VDD port is short - circuited to the ground; k HN52 represents the electrical constant of HN52; k HN50 represents the electrical constant of HN50; V THJ represents the pinch - off threshold of J50. Embodiment

[0074] As Figure 3 , this embodiment provides a circuit for flexibly starting the charging of a power supply port. This circuit is applied to a switching power supply system. The circuit includes: a start - up charging module, a constant - current feedback temperature - drift control module, an enable determination module, and a ground - short - circuit detection module.

[0075] The constant - current feedback temperature - drift control module is respectively connected to the start - up charging module, the enable determination module, and the ground - short - circuit detection module; the start - up charging module is also respectively connected to the ground - short - circuit detection module, the control start - up port ST of the switching power supply system, and the power supply port VDD; the enable determination module is connected to the enable terminal EN of the switching power supply system; wherein the enable determination module is used to receive an enable signal; the start - up charging module generates a first signal V S1 when the enable signal is 0 or generates a second signal when the enable signal is 1; the constant - current feedback temperature - drift control module generates a third signal V G1 when the enable signal is 0; the first signal V S1 and the third signal V G1 are used to flexibly charge the power supply port VDD; the third signal is used to stop charging the power supply port VDD; the ground - short - circuit detection module is used to detect whether there is a ground - short - circuit; the constant - current feedback temperature - drift control module is also used to suppress the temperature - drift of the charging current at the control start - up port ST to the power supply port VDD when there is a ground - short - circuit.

[0076] Specifically, the start - up charging module includes: a switching transistor J50, a switching transistor HN50, a switching transistor HP50, and a diode D50; the drain of the switching transistor J50 is connected to the control start - up port ST; the gate of the switching transistor J50 is grounded; the source of the switching transistor J50 is respectively connected to the drain of the switching transistor HN50 and the constant - current feedback temperature - drift control module; the source of the switching transistor HN50 is respectively connected to the source of the switching transistor HP50 and the constant - current feedback temperature - drift control module; the drain of the switching transistor HP50 is respectively connected to the gate of the switching transistor HP50, the constant - current feedback temperature - drift control module, the ground - short - circuit detection module, and the anode of the diode D50; the cathode of the diode D50 is connected to the power supply port VDD.

[0077] In addition, the constant current feedback temperature drift control module includes a constant current feedback circuit and a temperature drift control circuit; the constant current feedback circuit is respectively connected to the start charging module, the enable determination module, the ground short circuit detection module and the temperature drift control circuit; the temperature drift control circuit is also connected to the enable determination module and the ground short circuit detection module.

[0078] Specifically, the constant current feedback circuit includes: resistor R57, clamping diode Z50, switching transistor HP51, switching transistor HN52 and resistor R55; the first end of resistor R57 is respectively connected to the source of switching transistor J50 and the drain of switching transistor HN50; the second end of resistor R57 is respectively connected to the gate of switching transistor HN50, the cathode of clamping diode Z50, the enable determination module and the drain of switching transistor HN52; the anode of clamping diode Z50 is respectively connected to the source of switching transistor HP51, the source of switching transistor HN50 and the source of switching transistor HP50; the source of switching transistor HN52 is connected to the temperature drift control circuit; the gate of switching transistor HN52 is respectively connected to the first end of resistor R55 and the constant current feedback circuit; the second end of resistor R55 is respectively connected to the drain of switching transistor HP51 and the temperature drift control circuit; the gate of switching transistor HP51 is respectively connected to the gate of switching transistor HP50, the drain of switching transistor HP50, the ground short circuit detection module and the anode of diode D50.

[0079] In addition, the temperature drift control circuit includes clamping diode Z51, resistor R53 and resistor R54; the cathode of clamping diode Z51 is respectively connected to the gate of switching transistor HN52 and the first end of resistor R55; the anode of clamping diode Z51, the source of switching transistor HN52 and the first end of resistor R54 are all grounded; the second end of resistor R54 is respectively connected to the ground short circuit detection module and the first end of resistor R53; the second end of resistor R53 is respectively connected to the second end of resistor R55 and the drain of switching transistor HP51.

[0080] The enable determination module includes: resistor R56 and switching transistor HN53; the first end of resistor R56 is respectively connected to the gate of switching transistor HN53 and the enable terminal EN of the switching power supply system; the second end of resistor R56 and the source of switching transistor HN53 are both grounded; the drain of switching transistor HN53 is respectively connected to the second end of resistor R57, the gate of switching transistor HN50, the cathode of clamping diode Z50 and the drain of switching transistor HN52.

[0081] In addition, the ground short - circuit detection module includes: resistor R51, resistor R52, clamping diode Z52, and switching transistor HN51; the first end of resistor R51 is respectively connected to the gate of switching transistor HP51, the gate of switching transistor HP50, the drain of switching transistor HP50, and the anode of diode D50; the second end of resistor R51 is respectively connected to the first end of resistor R52, the cathode of clamping diode Z52, and the gate of switching transistor HN51; the second end of resistor R52, the anode of clamping diode Z52, and the source of switching transistor HN51 are all grounded; the drain of switching transistor HN51 is respectively connected to the second end of resistor R54 and the first end of resistor R53.

[0082] Among them, switching transistor J50 is an ultra - high - voltage switch; switching transistors HN50, HN51, HN52, and HN53 are all high - voltage N - type switches; switching transistors HP50 and HP51 are all high - voltage P - type switches.

[0083] A circuit for flexibly starting the charging of a power supply port provided in this embodiment is composed of an ultra - high - voltage switch J50, high - voltage switches HN50, HN51, HN52, and HN53, resistors R51, R52, R53, R54, R55, R56, and R57, diodes D50, clamping diodes Z50, Z51, and Z52, and current sources HP50 and HP51 connected according to electrical properties; according to the logic control signal EN and the input voltage signal V ST generates and outputs a control signal V G1 , V G1 and the voltage difference V S1 between V GS1 controls the switching transistor HN50 to charge the VDD port through the ultra - high - voltage switch J50, switching transistor HN50, switching transistor HP50, and diode D50. V DD1 =V DD +Vbe (Vbe is the forward junction voltage drop of D50) controls the charging current value I CH_VDD of the VDD port. When the voltage of V DD is close to 0, the charging current of the VDD port is very small; when the voltage of V DD is relatively high, the charging current of the VDD port is very large. Therefore, by judging the voltage of the VDD port, the entire charging start - up process can be flexibly completed, avoiding damage to the circuit due to excessive charging current when the VDD port is short - circuited to the ground. In addition, R53, R54, and HN52 also ensure that the charging current of the VDD port is close to zero temperature drift, ensuring the consistency within the high - and low - temperature range during the start - up process and protecting the safety of the electrical appliance. In addition, D50 is a diode with the unidirectional conduction characteristic of conducting in the forward direction and blocking in the reverse direction. The VDD port is connected to the cathode of D50, which can prevent the current from flowing back from the VDD port to the ST port when the ST port is connected to a low - voltage signal, resulting in system failure.

[0084] The flexible charging startup circuit for the power supply port starts up its power supply port VDD by drawing current at its control startup port ST in response to its enable terminal EN; the flexible charging startup circuit for the power supply port starts up its power supply port VDD flexibly by drawing current at its control startup port ST in response to its enable terminal EN and the power supply port VDD, which can avoid the life loss of the ultra-high voltage switch J50 when VDD is short-circuited to the ground, thus achieving a better safety effect; the flexible charging startup circuit for the power supply port generates a shutdown of the external charging to its power supply port VDD at its control startup port ST in response to its enable terminal EN, which can achieve the effect of saving system power consumption;

[0085] Among them, the internal device clamping diodes (Z50, Z51, and Z52) can protect the gate oxide layers of the high-voltage switches (HN50, HN51, and HN52) safely; the internal device diode D50 can avoid the current backflow action of the power supply port VDD to the control startup port ST. The current sources (HP50 and HP51), the high-voltage switches (HN51 and HN52), and the resistors (R51, R52, R53, and R54) can define the maximum value of the charging current of the control startup port ST to the power supply port VDD. The high-voltage switch HN52 and the resistors (R53 and R54) can suppress the temperature drift of the charging current of the control startup port ST of the flexible charging startup circuit for the power supply port to the power supply port VDD.

[0086] This embodiment can be applied to both the secondary-side feedback switching power supply and the primary-side feedback switching power supply of the transformer.

[0087] The working principle of this embodiment is as follows:

[0088] During the charging process of VDD starting from 0, when V DD <VDD ON (where VDD ON is the power-on threshold), EN is at logic "0", controlling HN53 to disconnect. At this time:

[0089] V DD1 =V DD +Vbe (1)

[0090] V G3 =V DD1 (R52 / (R52 + R51)) (2)

[0091] V G3 = (V DD +Vbe) (R52 / (R52 + R51)) (3)

[0092] V THNis the conduction threshold of the N-type switch. Resistors R52 and R51 are ultra-large resistors with a matching ratio coefficient of β (β > 1). Resistors R53 and R54 are precise resistors with a matching ratio coefficient of θ (θ >> 1). R56 and R57 are ultra-large resistors to save power consumption.

[0093] R51 = βR52 (4)

[0094] R54 = θR53 (5)

[0095] If V G3 < V THN , then V G3 is logic "0", controlling HN51 to disconnect. The gate voltage of HN52 is V G2 , then there is:

[0096] V G2 = I50(R53 + R54) > V THN (6)

[0097] I52 = k HN52 (V G2 - V THN ) 2 (7)

[0098] V G1 = V JS - I52×R57 (8)

[0099] V GS1 = V G1 - V S1 = V JS - I52×R57 - V S1 (9)

[0100] Among them, V G1 , V S1 are the gate and source voltages of HN50 respectively, and V GS1 is the voltage difference between the gate and source of HN50. V JS is the source voltage of the third terminal of J50, and also the drain voltage of HN50. k HN52 is the electrical constant of HN52.

[0101] I J = I52 + I CH_VDD + I50 = k J50 (V THJ ) 2 ×(1 - V JS / V THJ ) 2 (10)

[0102] Among them, I Jis the conduction current of J50, V THJ is the pinch-off threshold voltage of J50, k J50 is the electrical constant of J50. V S1 are the gate and source voltages of HN50, respectively, V GS1 is the voltage difference between the gate and source of HN50. Equation (10) can determine V JS .

[0103] Therefore, according to Equation (6), it can be known that V G2 is logic "1", controlling HN52 to conduct, V G1 decreases, then V GS1 = V G1 - V S1 becomes lower, the conduction of HN50 becomes weaker, and the conduction current of HN50 is I50 + I CH_VDD then becomes smaller. Because HP50 and HP51 are a pair of current mirrors, therefore:

[0104] I50 + I CH_VDD = k HN50 (V GS1 - V THN ) 2 (11)

[0105] I50 = ⍺I CH_VDD (12)

[0106] (⍺ + 1)I CH_VDD = k HN50 (V GS1 - V THN ) 2 (13)

[0107] I CH_VDD = k HN50 (V GS1 - V THN ) 2 / (⍺ + 1) (14)

[0108] Substituting Equation (14) into Equation (12) gives:

[0109] I50 = ⍺k HN50 (V GS1 - V THN ) 2 / (⍺ + 1) (15)

[0110] Here, k HN50 is the electrical constant of HN50, ⍺ is the mirror ratio coefficient of the HP50 and HP51 current mirrors, and ⍺ << 1.

[0111] In the constant current feedback loop composed of switching transistor HN50, switching transistor HP50, switching transistor HP51, resistor R53, resistor R54, switching transistor HN52 and resistor R57, if I50 + I CH_VDD = (⍺ + 1)I50 / ⍺ = (⍺ + 1)I CH_VDD increases, causing I CH_VDD and I50 to increase. Therefore, V G2 = I50(R53 + R54) becomes higher, causing HN52 to conduct more strongly. I52 = k HN52 (V G2 - V THN ) 2 increases, then V G1 = V JS - I52×R57 decreases.

[0112] Because the increase in I CH_VDD causes the gate-source voltage difference V GS（HP50） = V S1 - V DD1 of HP50 to increase, resulting in an increase in V S1 . As a result, the gate-source voltage difference V GS1 = V G1 - V S1 of HN50 becomes lower, causing I50 + I CH_VDD = k HN50 (V GS1 - V THN ) 2 to decrease. Therefore, the constant current feedback loop (equivalent to a constant current source) in this embodiment forms a negative feedback effect, and finally the value of I50 + I CH_VDD is limited to the value defined by formula (11). The flow path of the charging current of the VDD port is from ST à J50 à HN50 à HP50 à D5 à VDD.

[0113] When V G3 = (V DD + Vbe)(R52 / (R52 + R51)) = (V DD + Vbe) / (β + 1) < V THN , HN51 is turned off. At this time:

[0114] I CH_VDD = I CH1 = I50 / ⍺ = V G2 / (⍺(R53 + R54)) (16)

[0115] I51 = VDD1 / (R51 + R52) = (V DD + Vbe) / (R51 + R52) << I CH_VDD (17)

[0116] The charging current for the VDD port is (I CH_VDD + I51). According to Equation (17), it can be seen that I51 is much smaller than I CH_VDD . At this time, the charging current for the VDD port is approximately equal to I CH_VDD = I CH1 .

[0117] V DD_SCP_TH = (β + 1)V THN – Vbe (18)

[0118] Among them, DD_SCP_TH = (β + 1)V THN – Vbe is the short - circuit threshold of the VDD port to the ground. When V DD is lower than V DD_SCP_TH , it is recognized that the VDD port is short - circuited to the ground. The charging current I CH_VDD of the VDD port is compressed several times and becomes a low - current value I CH1 to avoid damage to the control circuit.

[0119] When V G3 = (V DD + Vbe)(R52 / (R52 + R51)) = (V DD + Vbe) / (β + 1) ≥ V THN , that is, when V DD ≥ V DD_SCP_TH = (β + 1)V THN – Vbe, HN51 conducts, and V D3 is equal to 0.

[0120] I CH_VDD = I CH0 = I50 / ⍺ = V G2 / (⍺R54) (19)

[0121] I51 << I CH_VDD (20)

[0122] The charging current for the VDD port is (I CH_VDD + I51). According to Equation (17), it can be seen that I51 is much smaller than I CH_VDD . Therefore, according to Equations (19) and (20), it can be known that the charging current for the VDD port is approximately equal to I CH_VDD = I CH0 .

[0123] During the charging process of VDD starting from 0, when V DD > VDD ON , EN is logic "1", controlling HN53 to conduct, V G1 becomes a low level, HN50 disconnects, and the starting charging current I of the VDD portCH_VDD =0, VDD port startup is completed. Since R57 resistance is too large, the current I flowing through R57 and J50 is J The minimum is approximately equal to 0, so at this time, the power consumption of circuit 50A is approximately equal to 0.

[0124] After startup CH_VDD is 0, then V DD1 is 0, and V DD Higher than VDD ON >>0, so D50 is needed to reversely isolate the VDD port to prevent the VDD port from feeding back the circuit 50A current, causing power loss and startup failure.

[0125] In addition, due to the startup process I CH_VDD =I CH0 =V G2 / (⍺R54)or I CH_VDD =I CH1 =V G2 / (⍺(R53+R54)), R53, R54 and V G2 Have the same temperature coefficient, so no matter high or low temperature I CH_VDD They all remain almost unchanged, achieving ultra-low temperature drift.

[0126] The clamping tubes Z51, Z52, and Z53 in the circuit 50A are Zener tubes, which can protect the gate oxide layer of the switch tubes HN50, HN51, and HN52 from being broken down, thereby increasing the stability and safety of the circuit 50A. DD When the voltage is ultra-low, the logic signal EN must be equal to "0" to ensure the working stability of the charging action of the circuit 50A. Example

[0127] This embodiment provides a switching power supply system, and the switching power supply system uses a circuit for starting flexible charging of a power port as described in any one of the above items. Example

[0128] like Figure 4, this embodiment provides a switching power supply system including a transformer, a switching power supply controller integrated circuit, a power switch transistor, and a feedback device. The feedback device is disposed at the output end of the transformer, and the switching power supply controller integrated circuit is coupled to the feedback device to generate a switching signal to adjust the pulse width of the transformer through the power switch transistor. The switching power supply controller integrated circuit is composed of a flexible charging startup circuit for the power supply port, a power-on and power-off enabling circuit, a pulse width modulator, and a driving circuit coupled together. Flexible startup is performed through the ST port: during initial startup, small-current flexible startup is carried out, and then large-current rapid startup is performed, which can avoid damage and life loss when the power supply port VDD is shorted to ground. Moreover, after the power supply system is started, the startup path can be automatically cut off to save energy consumption, maximizing the safety and efficiency of the user's electrical equipment. It can complete the control of ultra-low temperature drift for its startup charging current, thus ensuring the consistency of the charging startup process within a wide temperature range.

[0129] Among them, the switching power supply controller integrated circuit can be applied to transformer secondary-side feedback isolated and transformer primary-side feedback isolated switching power supply systems. The switching power supply controller integrated circuit consists of a startup circuit, a power-on and power-off enabling circuit, a pulse width modulator, and a driving circuit embedded in the same integrated circuit to save external components; such as Figure 4 , there are two external connection methods for the ST port, which is convenient for users to design the programmability of the maximum standby efficiency of the switching power supply system. The system of the switching power supply controller integrated circuit can be a secondary-side feedback type switching power supply system; or a primary-side feedback type switching power supply system.

[0130] The switching power supply system of this embodiment not only realizes safety but also realizes the consistency of wide-temperature operation, and at the same time has minimized standby power consumption. The startup timing waveform is as Figure 5 and Figure 6 shown. The switching power supply system provided in this embodiment has a process of flexible increase in the charging current after inputting VAC, while Figure 2 in the traditional switching power supply system, the charging current directly reaches the maximum value instantaneously after inputting VAC for charging I CH_VDD , with a large power consumption, and damage or life loss accidents will occur when the VDD port is shorted to ground. After a special situation where the VDD port is shorted to ground occurs, the startup charging current of the switching power supply system of the present invention is extremely small, the power consumption is close to 0, and no damage or life loss accidents will occur.

[0131] Each embodiment in this specification is described in a progressive manner. The key point of each embodiment is to illustrate the differences from other embodiments. The same or similar parts among the embodiments can be referred to each other. 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 manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A circuit for flexibly starting charging of a power supply port, characterized in that, The circuit is applied to a switching power supply system, and the circuit includes: a start-up charging module, a constant-current feedback temperature drift control module, an enable determination module, and a ground short-circuit detection module; The constant-current feedback temperature drift control module is respectively connected to the start-up charging module, the enable determination module, and the ground short-circuit detection module; the start-up charging module is also respectively connected to the ground short-circuit detection module, the control start port ST of the switching power supply system, and the power supply port VDD; the enable determination module is connected to the enable end EN of the power-on and power-off enable circuit in the switching power supply system; The constant-current feedback temperature drift control module includes: a constant-current feedback circuit and a temperature drift control circuit; The constant-current feedback circuit is respectively connected to the start-up charging module, the enable determination module, the ground short-circuit detection module, and the temperature drift control circuit; The temperature drift control circuit is also connected to the enable determination module and the ground short-circuit detection module; The enable determination module is used to receive an enable signal; The startup charging module generates a first signal V when the enable signal is 0 S1 or generates a second signal when the enable signal is 1; The constant current feedback temperature drift control module generates a third signal V when the enable signal is 0 G1 ; The first signal V S1 and the third signal V G1 are used for flexibly charging the power supply port VDD; the third signal is used for stopping the charging of the power supply port VDD; The ground short-circuit detection module is used to detect whether there is a ground short-circuit; The constant-current feedback temperature drift control module is also used to suppress the temperature drift of the charging current of the control start port ST to the power supply port VDD during a ground short-circuit.

2. The circuit for flexibly starting charging of a power supply port according to claim 1, characterized in that The start-up charging module includes: a switching transistor J50, a switching transistor HN50, a switching transistor HP50, and a diode D50; The drain of the switching transistor J50 is connected to the control start port ST; The gate of the switching transistor J50 is grounded; The source of the switching transistor J50 is respectively connected to the drain of the switching transistor HN50 and the constant-current feedback temperature drift control module; The source of the switching transistor HN50 is respectively connected to the source of the switching transistor HP50 and the constant-current feedback temperature drift control module; The drain of the switching transistor HP50 is respectively connected to the gate of the switching transistor HP50, the constant-current feedback temperature drift control module, the ground short-circuit detection module, and the anode of the diode D50; The cathode of the diode D50 is connected to the power supply port VDD.

3. The circuit for flexibly starting charging of a power supply port according to claim 2, wherein The constant-current feedback circuit includes: a resistor R57, a clamping diode Z50, a switching transistor HP51, a switching transistor HN52, and a resistor R55; The first end of the resistor R57 is respectively connected to the source of the switching transistor J50 and the drain of the switching transistor HN50; The second end of the resistor R57 is respectively connected to the gate of the switching transistor HN50, the cathode of the clamping diode Z50, the enable determination module, and the drain of the switching transistor HN52; The anode of the clamping diode Z50 is respectively connected to the source of the switching transistor HP51, the source of the switching transistor HN50, and the source of the switching transistor HP50; The source of the switching transistor HN52 is connected to the temperature drift control circuit; The gate of the switching transistor HN52 is respectively connected to the first end of the resistor R55 and the temperature drift control circuit; The second end of the resistor R55 is respectively connected to the drain of the switching transistor HP51 and the temperature drift control circuit; The gate of the switching transistor HP51 is connected to the gate of the switching transistor HP50, the drain of the switching transistor HP50, the ground short-circuit detection module, and the anode of the diode D50, respectively.

4. A circuit for flexibly starting charging of a power supply port according to claim 3, characterized in that, The temperature drift control circuit includes: A clamping transistor Z51, a resistor R53, and a resistor R54; The cathode of the clamping transistor Z51 is connected to the gate of the switching transistor HN52 and the first end of the resistor R55, respectively; The anode of the clamping transistor Z51, the source of the switching transistor HN52, and the first end of the resistor R54 are all grounded; The second end of the resistor R54 is connected to the ground short-circuit detection module and the first end of the resistor R53, respectively; The second end of the resistor R53 is connected to the second end of the resistor R55 and the drain of the switching transistor HP51, respectively.

5. A circuit for flexibly starting charging of a power supply port according to claim 4, characterized in that, The enable determination module includes: A resistor R56 and a switching transistor HN53; The first end of the resistor R56 is connected to the gate of the switching transistor HN53 and the enable terminal EN of the power-on / off enable circuit in the switching power supply system, respectively; The second end of the resistor R56 and the source of the switching transistor HN53 are both grounded; The drain of the switching transistor HN53 is connected to the second end of the resistor R57, which is connected to the gate of the switching transistor HN50, the cathode of the clamping transistor Z50, and the drain of the switching transistor HN52, respectively.

6. The circuit for flexibly starting charging of a power supply port according to claim 5, wherein The ground short-circuit detection module includes: A resistor R51, a resistor R52, a clamping transistor Z52, and a switching transistor HN51; The first end of the resistor R51 is connected to the gate of the switching transistor HP51, the gate of the switching transistor HP50, the drain of the switching transistor HP50, and the anode of the diode D50, respectively; The second end of the resistor R51 is connected to the first end of the resistor R52, the cathode of the clamping transistor Z52, and the gate of the switching transistor HN51, respectively; The second end of the resistor R52, the anode of the clamping transistor Z52, and the source of the switching transistor HN51 are all grounded; The drain of the switching transistor HN51 is connected to the second end of the resistor R54 and the first end of the resistor R53, respectively.

7. According to the circuit for flexibly charging and starting a power supply port as described in claim 6, characterized in that The switching transistor J50 is an ultra-high voltage switch; The switching transistors HN50, HN51, HN52, and HN53 are all high-voltage N-type switches; The switching transistors HP50 and HP51 are both high-voltage P-type switches.

8. A switching power supply system, characterized in that, The switching power supply system applies the circuit for flexibly charging and starting a power supply port as described in any one of claims 1-7.

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