A ROVP circuit, a switching power supply controller, and a switching power supply

Abstract

The application discloses a ROVP circuit, a switching power supply controller and a switching power supply, and relates to the technical field of switching power supplies.The ROVP circuit comprises a nonlinear positive temperature drift current source circuit, a ROVP port circuit and a TOVP generator.The nonlinear positive temperature drift current source circuit outputs a nonlinear positive temperature drift current in response to a power supply signal.The ROVP port circuit converts the nonlinear positive temperature drift current into a charging current.The TOVP generator generates an overvoltage protection enable signal according to the charging current.The charging current increases in direct proportion to temperature.When the working temperature of the circuit is higher and higher, the charging current is larger and larger.The time of the overvoltage protection enable signal being a logic high pulse is shorter and shorter.Under the condition that the time of the overvoltage protection enable signal being a logic high pulse is short enough, the overvoltage protection is not triggered, and the high-temperature flash phenomenon of the lighting load driven by the switching power supply does not occur.

Description

Technical Field

[0001] This invention relates to the field of switching power supply technology, and in particular to a ROVP circuit, a switching power supply controller, and a switching power supply. Background Technology

[0002] As the power supply device for all electronic products, the power supply not only needs to meet user requirements but also needs to continuously meet users' ever-increasing demands for lower costs, especially in the highly competitive AC-to-DC lighting (ACDC LED driver) market. Traditional LED driver switching power supplies generally use a ROVP circuit for overvoltage protection (OVP). The OVP voltage is set by the resistance value between the external ROVP pin and ground, defining a fixed OVP voltage that does not change with temperature. This application works very well for traditional LED driver switching power supplies operating in non-saturated inductors, without any problems at high or low temperatures.

[0003] However, as competition in the lighting market intensifies, customers will try every means to reduce the overall cost of LEDs. Their first priority is to reduce the cost of external inductors. This leads to the inductor being in a state of critical saturation at room temperature and deep saturation at high temperatures during system operation. After deep saturation at high temperatures, the load-carrying capacity is severely reduced, causing the demagnetization time to touch the Tovp time that defines the OVP voltage, thus triggering the OVP to automatically restart and flash the lamp, making it impossible to operate normally across the entire temperature range.

[0004] Traditional AC-DC LED driver switching power supply systems, due to their use of zero-temperature-drift ROVP circuits, exhibit high-temperature flickering when using low-cost inductors, failing to meet the demands of new market users. Therefore, designing a ROVP circuit that can avoid high-temperature flickering is essential. Summary of the Invention

[0005] The purpose of this invention is to provide a ROVP circuit, a switching power supply controller, and a switching power supply to solve the problem of high-temperature flashing in the switching power supply system caused by the use of a zero-temperature drift ROVP circuit in the prior art when using a low-cost inductor.

[0006] To achieve the above objectives, the present invention provides the following solution:

[0007] A ROVP circuit, comprising:

[0008] A nonlinear positive temperature drift current source circuit is used to output a nonlinear positive temperature drift current in response to a power supply signal.

[0009] The ROVP port circuit is connected to the nonlinear positive temperature drift current source circuit and is used to convert the nonlinear positive temperature drift current into a charging current.

[0010] The TOVP generator is connected to the ROVP port circuit and is used to generate an overvoltage protection enable signal based on the charging current; the overvoltage protection enable signal is a logic high pulse with a duration inversely proportional to the charging current.

[0011] Optionally, the nonlinear positive temperature drift current source circuit includes: a zero temperature drift current source, a positive temperature drift current source, a first current mirror, a second current mirror, a third current mirror, and a fourth current mirror;

[0012] The first current mirror includes a first transistor and a second transistor, the second current mirror includes a third transistor and a fourth transistor, the third current mirror includes a fifth transistor and a sixth transistor, and the fourth current mirror includes a seventh transistor and an eighth transistor.

[0013] The input terminal of the positive temperature drift current source is connected to the input terminal of the zero temperature drift current source, the source of the third transistor, the source of the fourth transistor, the source of the seventh transistor, the source of the eighth transistor, the ROVP port circuit, and the VDD port of the ROVP circuit. The output terminal of the positive temperature drift current source is connected to the gate of the first transistor, the gate of the second transistor, and the drain of the first transistor. The sources of the first transistor and the second transistor are both grounded.

[0014] The first output terminal of the zero-temperature drift current source is connected to the drain of the second transistor; the second output terminal of the zero-temperature drift current source is connected to the drain of the fifth transistor, the gate of the fifth transistor, and the gate of the sixth transistor, respectively; the drain of the third transistor, the gate of the third transistor, and the gate of the fourth transistor are all connected to the drain of the second transistor; the drain of the fourth transistor is connected to the drain of the fifth transistor.

[0015] The drain, gate, and gate of the seventh transistor are all connected to the drain of the sixth transistor, and the source of the fifth transistor and the source of the sixth transistor are all grounded; the drain of the eighth transistor is connected to the ROVP port circuit.

[0016] Optionally, the ROVP port circuit includes: a first amplifier, a fifth current mirror, a ninth transistor, and a resistor; the fifth current mirror includes a tenth transistor and an eleventh transistor;

[0017] The inverting input terminal of the first amplifier is connected to the drain of the eighth transistor and the R of the ROVP circuit, respectively. OVPThe port is connected such that the non-inverting input of the first amplifier is connected to one end of the resistor, and the output of the first amplifier is connected to the gate of the tenth transistor and the gate of the eleventh transistor, respectively.

[0018] The drain of the tenth transistor and the drain of the eleventh transistor are both connected to the VDD port of the ROVP circuit; the source of the tenth transistor is connected to the drain of the ninth transistor, the gate of the ninth transistor and the source of the ninth transistor are both connected to one end of the resistor, and the other end of the resistor is grounded; the source of the eleventh transistor is connected to the TOVP generator.

[0019] Optionally, the TOVP generator includes a capacitor, a switching transistor, a Schmitt inverter, a first inverter, a NAND gate, and a second inverter;

[0020] One end of the capacitor is connected to the source of the eleventh transistor, the drain of the switching transistor, and the input of the Schmitt inverter, respectively; the other end of the capacitor is connected to the source of the switching transistor and ground, respectively; the gate of the switching transistor is connected to the input of the first inverter and the TON port of the ROVP circuit, respectively.

[0021] The output of the Schmitt trigger inverter is connected to the first input of the NAND gate, the output of the first inverter is connected to the second input of the NAND gate, the output of the NAND gate is connected to the input of the second inverter, and the output of the second inverter is connected to the TOVP port of the ROVP circuit.

[0022] Optionally, the first current mirror and the third current mirror are n-type current mirrors; the second current mirror, the fourth current mirror, and the fifth current mirror are p-type current mirrors.

[0023] Optionally, when the power supply signal is logic high, the switching transistor is turned on, the level of the capacitor is cleared to zero, the output signal of the Schmitt inverter is logic high, the output signal of the first inverter is logic low, and the overvoltage protection enable signal output by the second inverter is logic low.

[0024] When the power supply signal is logic low, the switching transistor is turned off, the capacitor starts charging, the potential at one end of the capacitor rises, the output signal of the Schmitt inverter is logic high, the output signal of the first inverter is logic high, and the overvoltage protection enable signal output by the second inverter is logic high.

[0025] When the potential at one end of the capacitor exceeds the external input voltage threshold of the Schmitt inverter, the output signal of the Schmitt inverter is logic low, and the overvoltage protection enable signal output by the second inverter is logic low.

[0026] A switching power supply controller, the switching power supply controller including the aforementioned ROVP circuit, the switching power supply controller further including a power supply circuit, a control circuit, a drive circuit, a demagnetization detection circuit, a leading-edge blanking circuit, a second amplifier and a power transistor;

[0027] The input terminal of the power supply circuit is connected to the HV port of the switching power supply controller. The first output terminal of the power supply circuit is connected to the VDD port of the ROVP circuit, the first input terminal of the control circuit, the first input terminal of the drive circuit, the first input terminal of the demagnetization detection circuit, the first input terminal of the leading edge blanking circuit, and the first input terminal of the second amplifier. The second output terminal of the power supply circuit is connected to the second input terminal of the second amplifier.

[0028] The TOVP port of the ROVP circuit is connected to the second input terminal of the control circuit. The output terminal of the control circuit is connected to the TON port of the ROVP circuit and the second input terminal of the drive circuit. The output terminal of the drive circuit is connected to the gate of the power transistor, the second input terminal of the demagnetization detection circuit, and the second input terminal of the leading-edge blanking circuit. The drain of the power transistor is connected to the Drain port of the switching power supply controller. The source of the power transistor is connected to the third input terminal of the second amplifier and the CS port of the switching power supply controller.

[0029] The output of the demagnetization detection circuit is connected to the third input of the control circuit; the output of the leading edge blanking circuit is connected to the fourth input of the control circuit; the output of the second amplifier is connected to the fifth input of the control circuit; and the GND port of the switching power supply controller is grounded.

[0030] A switching power supply, the switching power supply including the switching power supply controller, the switching power supply further including a full-wave rectifier diode, a first capacitor, an inductor, a freewheeling diode, a second capacitor, a dummy load resistor, an LED string, a first resistor and a second resistor.

[0031] The first and second ends of the full-wave rectifier diode are connected across the VAC input terminal of the switching power supply. The third end of the full-wave rectifier diode is connected to the lower plate of the first capacitor and ground, respectively. The fourth end of the full-wave rectifier diode is connected to the upper plate of the first capacitor, the HV port of the switching power supply controller, the negative terminal of the freewheeling diode, the upper plate of the second capacitor, one end of the dummy load resistor, and the input terminal of the LED string.

[0032] The positive terminal of the freewheeling diode is connected to the Drain port of the switching power supply controller and one end of the inductor, respectively. The other end of the inductor is connected to the lower plate of the second capacitor, the other end of the dummy load resistor, and the output terminal of the LED string.

[0033] One end of the first resistor is connected to R of the switching power supply controller. OVP The first resistor is connected to the CS port of the power supply controller, and the other end of the second resistor is grounded.

[0034] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0035] The ROVP circuit, switching power supply controller, and switching power supply provided by this invention can prevent high-temperature flashing of lights. The ROVP circuit includes a nonlinear positive temperature drift current source circuit, a ROVP port circuit, and a TOVP generator. The nonlinear positive temperature drift current source circuit outputs a nonlinear positive temperature drift current in response to the power supply signal. The ROVP port circuit converts the nonlinear positive temperature drift current into a charging current. The TOVP generator generates an overvoltage protection enable signal based on the charging current. The pulse duration of the overvoltage protection enable signal (logic high) is inversely proportional to the charging current. The charging current increases proportionally with temperature. As the circuit operating temperature increases, the charging current increases, and the pulse duration of the overvoltage protection enable signal (logic high) becomes shorter. If the pulse duration of the overvoltage protection enable signal (logic high) is sufficiently short, overvoltage protection will not be triggered, and the lighting load driven by the switching power supply will not experience high-temperature flashing. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a circuit diagram of a traditional switching power supply;

[0038] Figure 2 This is a schematic diagram of the normal temperature operating waveform 90 of a traditional switching power supply;

[0039] Figure 3 This is a schematic diagram of the high-temperature operating waveform 100 of a traditional switching power supply;

[0040] Figure 4 A circuit diagram of the ROVP circuit provided by the present invention;

[0041] Figure 5 A circuit diagram of the switching power supply provided by the present invention;

[0042] Figure 6 The graph showing the relationship between the pulse duration of the logic high overvoltage protection enable signal generated by the TOVP generator provided by this invention and the circuit operating temperature.

[0043] Figure 7 A schematic diagram of the 90A operating waveform at room temperature of the switching power supply provided by the present invention;

[0044] Figure 8 This is a schematic diagram of the high-temperature operating waveform of the switching power supply provided by the present invention, which is 100A.

[0045] Symbol Explanation: Nonlinear positive temperature drift current source circuit - I308, ROVP port circuit - I309, TOVP generator - I307, Zero temperature drift current source - I302, Positive temperature drift current source - I302a, First transistor - mn2, Second transistor - mn2a, Third transistor - mp304, Fourth transistor - mp304a, Fifth transistor - mn3, Sixth transistor - mn3a, Seventh transistor - mp305, Eighth transistor - mp305a, First amplifier - I301, Ninth transistor - mp303, Resistor - R 301 Tenth transistor - mp301, eleventh transistor - mp302, capacitor - C 301 Switching transistor - mn1, Schmitt inverter - I305, first inverter - I306, NAND gate - I304, second inverter - I303. Detailed Implementation

[0046] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0047] like Figure 1As shown, a conventional ACDC LED Driver switching power supply 10 samples the peak current in the inductor L1 coil through the power transistor M1 to the CS port of the power converter 11, and compares it with the reference voltage V. REF After comparison, the amplifier EA controls the processor CTRL to generate T. ON Signal, then T ON The signal is used by the DRIVER function block to generate a square wave signal with varying pulse width (T). SW The signal controls the power transistor M1 to turn on and off to complete the energy transfer of inductor L1.

[0048] like Figure 2 and Figure 3 As shown, since traditional switching power supplies use a zero-temperature-drift ROVP circuit 30, when users use low-cost inductors in the switching power supply, the inductor saturation deepens when the LED switching power supply system operates in a sealed high-temperature environment. Based on the normal-temperature operating waveform 90 and the high-temperature operating waveform 100 of the traditional switching power supply, the demagnetization time t of the traditional switching power supply is... DEM1 As inductor L1 saturates, the voltage decreases, but the pulse time t of the overvoltage signal generated by the zero-temperature drift ROVP circuit 30 remains constant. OVP It will not change, so when the demagnetization time t DEM1 Pulse time t when encountering an overvoltage signal OVP At that time, i.e., t DEM1 <t OVP This triggers the OVP overvoltage protection, causing an automatic restart and resulting in the flashing light. An automatic restart time greater than 10 milliseconds is required. auto-recovery V CS The voltage at the CS port of a traditional switching power supply, V CSTH The turn-off threshold voltage at the CS port of a traditional switching power supply, αV CSTH α is the CS port voltage corresponding to the inflection point of the CS voltage slope when the inductor L1 is in deep saturation, 0 < α < 1.

[0049] The purpose of this invention is to provide a ROVP circuit, a switching power supply controller, and a switching power supply. The ROVP circuit of this invention can resist high-temperature magnetic saturation, and can achieve the application of low-cost inductors in the switching power supply without causing high-temperature flashing in the switching power supply system.

[0050] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0051] Example 1

[0052] like Figure 4As shown, Embodiment 1 of the present invention provides a ROVP circuit, including: a nonlinear positive temperature drift current source circuit I308, a ROVP port circuit I309, and a TOVP generator I307.

[0053] The nonlinear positive temperature drift current source circuit I308 is used to output a nonlinear positive temperature drift current in response to the power supply signal; the ROVP port circuit I309 is connected to the nonlinear positive temperature drift current source circuit I308 and is used to convert the nonlinear positive temperature drift current into a charging current; the TOVP generator I307 is connected to the ROVP port circuit I309 and is used to generate an overvoltage protection enable signal based on the charging current; the overvoltage protection enable signal is a logic high pulse with a duration inversely proportional to the charging current.

[0054] Furthermore, the nonlinear positive temperature drift current source circuit I308 includes: a zero temperature drift current source I302, a positive temperature drift current source I302a, a first current mirror, a second current mirror, a third current mirror, and a fourth current mirror. The first and third current mirrors are n-type current mirrors; the second and fourth current mirrors are p-type current mirrors.

[0055] The first current mirror includes a first transistor MN2 and a second transistor MN2A. The second current mirror includes a third transistor MP304 and a fourth transistor MP304A. The third current mirror also includes a fifth transistor MN3 and a sixth transistor MN3A. The fourth current mirror includes a seventh transistor MP305 and an eighth transistor MP305A. The scaling factor between the second transistor MN2A and the first transistor MN2 is K1; the scaling factor between the fourth transistor MP304A and the third transistor MP304 is K2; the scaling factor between the sixth transistor MN3A and the fifth transistor MN3 is K3; and the scaling factor between the eighth transistor MP305A and the seventh transistor MP305 is K4. Each transistor has a gate at its first terminal, a source at its second terminal, and a drain at its third terminal.

[0056] The input terminal of the positive temperature drift current source I302a is connected to the input terminal of the zero temperature drift current source I302, the source of the third transistor mp304, the source of the fourth transistor mp304a, the source of the seventh transistor mp305, the source of the eighth transistor mp305a, the ROVP port circuit I309, and the VDD port of the ROVP circuit. The output terminal of the positive temperature drift current source I302a is connected to the gate of the first transistor mn2, the gate of the second transistor mn2a, and the drain of the first transistor mn2. The source of the first transistor mn2 and the source of the second transistor mn2a are both grounded.

[0057] The first output terminal of the zero-temperature drift current source I302 is connected to the drain of the second transistor mn2a; the second output terminal of the zero-temperature drift current source I302 is connected to the drain of the fifth transistor mn3, the gate of the fifth transistor mn3, and the gate of the sixth transistor mn3a, respectively; the drain of the third transistor mp304, the gate of the third transistor mp304, and the gate of the fourth transistor mp304a are all connected to the drain of the second transistor mn2a; the drain of the fourth transistor mp304a is connected to the drain of the fifth transistor mn3.

[0058] The drain of the seventh transistor mp305, the gate of the seventh transistor mp305, and the gate of the eighth transistor mp305a are all connected to the drain of the sixth transistor mn3a. The source of the fifth transistor mn3 and the source of the sixth transistor mn3a are both grounded. The drain of the eighth transistor mp305a is connected to the ROVP port circuit I309.

[0059] Furthermore, the ROVP port circuit I309 includes: a first amplifier I301, a fifth current mirror, a ninth transistor mp303, and a resistor R. 301 The fifth current mirror includes the tenth transistor mp301 and the eleventh transistor mp302. The fifth current mirror is a p-type current mirror. Resistor R 301 This is a zero-temperature-drift resistor. The scaling factor between the tenth transistor mp301 and the eleventh transistor mp302 is K5.

[0060] The inverting input of the first amplifier I301 is connected to the drain of the eighth transistor mp305a and the R of the ROVP circuit, respectively. OVP The port is connected as follows: the non-inverting input of the first amplifier I301 is connected to one end of the resistor, and the output of the first amplifier I301 is connected to the gate of the tenth transistor mp301 and the gate of the eleventh transistor mp302, respectively.

[0061] The drain of the tenth transistor mp301 and the drain of the eleventh transistor mp302 are both connected to the VDD port of the ROVP circuit; the source of the tenth transistor mp301 is connected to the drain of the ninth transistor mp303, and the gate and source of the ninth transistor mp303 are both connected to one end of a resistor, with the other end of the resistor grounded; the source of the eleventh transistor mp302 is connected to the ROVP generator I307.

[0062] Furthermore, the TOVP generator I307 includes capacitor C 301 Switching transistor mn1, Schmitt inverter I305, first inverter I306, NAND gate I304, and second inverter I303.

[0063] Capacitor C 301One end of the capacitor is connected to the source of the eleventh transistor mp302, the drain of the switching transistor mn1, and the input of the Schmitt inverter, respectively. The other end of the capacitor is connected to the source of the switching transistor mn1 and ground, respectively. The gate of the switching transistor mn1 is connected to the input of the first inverter I306 and the TON port of the ROVP circuit, respectively.

[0064] The output of Schmitt inverter I305 is connected to the first input of NAND gate I304, the output of first inverter I306 is connected to the second input of NAND gate I304, the output of NAND gate I304 is connected to the input of second inverter I303, and the output of second inverter I303 is connected to the TOVP port of ROVP circuit.

[0065] V of the ROVP circuit DD The signal is a low-voltage DC power supply. The nonlinear positive temperature drift current source circuit I308 responds to the low-voltage DC power supply by outputting a nonlinear positive temperature drift current I. OVP1 I OVP1 A DC voltage V is generated across the externally connected resistor R2. ROVP The ROVP port circuit I309 responds to V ROVP Generate charging current I OVP The TOVP generator I307 responds to the charging current I OVP and the T of the ROVP circuit ON The signal generates the control signal T for the open-circuit output (OVP). OVP That is, the ROVP circuit responds to V DD R OVP and T ON Generate control signal T OVP Control signal T OVP It can shut down the chip output when the system output is open.

[0066] Furthermore, when the ROVP circuit is operating, the zero-temperature drift current source I302 in the nonlinear positive temperature drift current source circuit I308 outputs two zero-temperature drift currents I... OVP3 and I OVP3a The positive temperature drift current source I302a outputs a positive temperature drift current I. OVP4 I OVP4 After passing through the first current mirror, it is proportionally changed to I. OVP4a =K1×I OVP4 Its relationship with I OVP3a Subtraction yields I OVP5a =I OVP4a -I OVP3a =K1×I OVP4 -I OVP3a I OVP5a After passing through the second current mirror, it is proportionally transformed to I.OVP5 =K2×I OVP5a , that is I OVP5 =K2×(K1×I OVP4 -I OVP3a ). I OVP5 with I OVP3 Adding them together gives I OVP6 =K2×(K1×I OVP4 -I OVP3a )+I OVP3 I OVP6 I is obtained after transformation by the third current mirror. OVP6a =K3×I OVP6 =K3×(K2×(K1×I) OVP4 -I OVP3a )+I OVP3 ). I OVP6a After being proportionally transformed by the fourth current mirror, it becomes I. OVP1 =K4×I OVP6a =K4×(K3×(K2×(K1×I) OVP4 -I OVP3a )+I OVP3 The current is output to the ROVP port circuit I309 as a reference current.

[0067] Furthermore, the current I generated by the nonlinear positive temperature drift current source circuit I308 OVP1 A voltage V is generated as the current flows through the external resistor R2 to ground. ROVP =I OVP1 ×R2, in the ROVP port circuit I309, the first amplifier I301, the fifth current mirror, and the resistor form a voltage follower, also called a buffer, with voltage V. ROVP After passing through the voltage follower and landing on the resistor, the voltage V6 at the non-inverting input of the first amplifier I301 is V. ROVP This results in the generation of current I. OVP2 =V ROVP / R 301 , that is I OVP2 =(I OVP1 ×R2) / R 301 I OVP2 After transformation by the fifth current mirror, I is obtained. OVP =(I OVP1 ×R2) / (K5×R 301 ), I OVP The input current is used as the charging current for the charging capacitor in the TOVP generator I307.

[0068] Furthermore, in the TOVP generator I307, when the input signals of the first inverter I306, the second inverter I303, and the Schmitt inverter I305 are all logic low, the output overvoltage protection enable signal is logic high; when the input signals of the first inverter I306, the second inverter I303, and the Schmitt inverter are all logic high, the output overvoltage protection enable signal flips to logic low. Similarly, when either input signal of the NAND gate I304 is logic low, the output overvoltage protection enable signal is logic high; when both input signals of the NAND gate I304 are logic high, the output overvoltage protection enable signal flips to logic low. When the gate signal of the switching transistor mn1 is logic low, its drain has no effect; when the gate signal of the switching transistor mn1 is logic high, its drain signal is logic low. The first terminal of the switching transistor mn1 is the gate, the second terminal is the source, and the third terminal is the drain.

[0069] When the power supply signal is logic high, switching transistor MN1 is turned on, the capacitor's level is cleared, the Schmitt trigger output signal is logic high, the first inverter I306 output signal is logic low, and the overvoltage protection enable signal output by the second inverter I303 is logic low. When the power supply signal is logic low, switching transistor MN1 is turned off, the capacitor begins to charge, the potential at one end of the capacitor rises, and the Schmitt trigger output signal is logic high, the first inverter I306 output signal is logic high, and the overvoltage protection enable signal output by the second inverter I303 is logic high. When the potential at one end of the capacitor exceeds the external input voltage threshold of the Schmitt trigger, the Schmitt trigger output signal is logic low, and the overvoltage protection enable signal output by the second inverter I303 is logic low.

[0070] The ROVP circuit provided in Embodiment 1 of this invention can be applied in a switching power supply controller. Through the R... OVP The port control makes the LED lamp driver switching power supply system containing this invention more cost-effective and competitive in the market. The overvoltage protection enable signal generated by the ROVP circuit has an increasingly shorter pulse duration (logic high). If the pulse duration of the overvoltage protection enable signal is sufficiently short, overvoltage protection will not be triggered, and the lighting load driven by the switching power supply will not experience high-temperature flashing.

[0071] Example 2

[0072] Regarding the ROVP circuit provided in Embodiment 1, Embodiment 2 of the present invention provides a switching power supply controller, such as... Figure 5 As shown, the switching power supply controller 11A includes an ROVP circuit 30A (i.e., Smart OVP) and a power supply circuit 20 (i.e., Power&V). REFThe switching power supply controller 11A comprises a control circuit 40 (CTRL), a drive circuit 50 (DRIVER), a demagnetization detection circuit 60 (OZS), a leading-edge blanking circuit 70 (LEB), a second amplifier 80 (EA), and a power transistor M1. All components of the switching power supply controller 11A are embedded in an integrated circuit to save on external components, thereby reducing the cost of the control circuit and enabling portable applications.

[0073] The input terminal of the power supply circuit 20 is connected to the HV port of the switching power supply controller. The first output terminal of the power supply circuit 20 is connected to the VDD port of the ROVP circuit 30A, the first input terminal of the control circuit 40, the first input terminal of the drive circuit 50, the first input terminal of the demagnetization detection circuit 60, the first input terminal of the leading edge blanking circuit 70, and the first input terminal of the second amplifier 80. The second output terminal of the power supply circuit 20 is connected to the second input terminal of the second amplifier 80.

[0074] The TOVP port of the ROVP circuit 30A is connected to the second input terminal of the control circuit 40. The output terminal of the control circuit 40 is connected to the TON port of the ROVP circuit 30A and the second input terminal of the drive circuit 50. The output terminal of the drive circuit 50 is connected to the gate of the power transistor M1, the second input terminal of the demagnetization detection circuit 60, and the second input terminal of the leading-edge blanking circuit 70. The drain of the power transistor M1 is connected to the Drain port of the switching power supply controller. The source of the power transistor M1 is connected to the third input terminal of the second amplifier 80 and the CS port of the switching power supply controller. OVP The port is the R of the ROVP circuit 30A. OVP port.

[0075] The output of the demagnetization detection circuit 60 is connected to the third input of the control circuit 40; the output of the leading edge blanking circuit 70 is connected to the fourth input of the control circuit 40; the output of the second amplifier 80 is connected to the fifth input of the control circuit 40; and the GND port of the switching power supply controller is grounded.

[0076] The switching power supply controller provided in Embodiment 2 of the present invention can be applied to switching power supplies for LED lamp drivers. The switching power supply can be a single-inductor non-isolated LED lamp switching power supply system. The present invention meets the user's demand for reducing inductor costs and has high market application prospects.

[0077] Example 3

[0078] Regarding the switching power supply controller provided in Embodiment 2, Embodiment 3 of the present invention provides a switching power supply, such as... Figure 5As shown, the switching power supply 10A includes a switching power supply controller 11A, a full-wave rectifier diode D1, a first capacitor C1, an inductor L1, a freewheeling diode D3, a second capacitor C2, a dummy load resistor R1, an LED string, a first resistor R2, and a second resistor R CS Inductor L1 is a non-isolated inductor. ON -Control circuit output signal, T SW - Power drive signal, VDD - Power supply port, VAC - AC input port, R OVP - External resistor R2 sets the output open-circuit overvoltage protection; CS - current monitoring port; external Rcs sets the peak current of inductor L1; DRV - drive output port; GND - ground port; HV - high voltage power supply port; Drain - drain drive port of power transistor M1; I CS -Inductor current, V CS- Port CS voltage.

[0079] The first and second ends of the full-wave rectifier diode D1 are connected across the VAC input terminal of the switching power supply. The third end of the full-wave rectifier diode D1 is connected to the lower plate of the first capacitor C1 and ground, respectively. The fourth end of the full-wave rectifier diode D1 is connected to the upper plate of the first capacitor C1, the HV port of the switching power supply controller 11A, the negative terminal of the freewheeling diode D3, the upper plate of the second capacitor C2, one end of the dummy load resistor R1, and the input terminal of the LED string.

[0080] The positive terminal of the freewheeling diode D3 is connected to the Drain port of the switching power supply controller 11A and one end of the inductor L1. The other end of the inductor L1 is connected to the lower plate of the second capacitor C2, the other end of the dummy load resistor R1, and the output terminal of the LED string.

[0081] One end of the first resistor is connected to the R of the switching power supply controller 11A. OVP The first resistor is connected to the CS port of the switching power supply controller 11A, and the other end of the second resistor is grounded. The first resistor is used to set the output open-circuit overvoltage protection, and the second resistor connected to the current monitoring port is used to set the peak current of inductor L1.

[0082] Users via R OVP The port performs nonlinear positive temperature drift on the 10A switching power supply included in this embodiment. OVP The timing operation completes the nonlinear positive temperature drift operation of the voltage threshold for output open-circuit overvoltage protection, which enables the LED string to not flicker at high temperatures when the switching power supply is operating in the saturation state of inductor L1, thus meeting the user's demand for reducing inductor costs.

[0083] When the output of a switching power supply is open-circuited, the open-circuit voltage will continuously increase, easily damaging external components. Therefore, most switching power supplies include output open-circuit protection, i.e., ROVP protection. The protection voltage is supplied through port R. OVP The first resistor is used to set the value.

[0084] When the first resistor is connected to port R OVP After the land, by Figure 4 It can be known that:

[0085] V ROVP =I OVP1 ×R2;

[0086] I OVP2 =V ROVP / R 301 =(I OVP1 ×R2) / R 301 ;

[0087] I OVP =I OVP2 / K5=I OVP1 R2 / (K5R 301 );

[0088] Here, we assume the scaling factor between the second and first transistors is K1, the scaling factor between the fourth and third transistors is K2, the scaling factor between the sixth and fifth transistors is K3, the scaling factor between the eighth and seventh transistors is K4, and the scaling factor between the tenth and eleventh transistors is K5; K1, K2, K3, K4, and K5 are all natural numbers greater than 1, and I OVP3 >I OVP5 Therefore, we can deduce that:

[0089] I OVP1 =K4×K3×I OVP6 ;

[0090] I OVP4a =K1×I OVP4 ;

[0091] I OVP4a =I OVP5a +I OVP3a ;

[0092] I OVP5 =K2×I OVP5a ;

[0093] I OVP6 =I OVP5 +I OVP3 ;

[0094] Therefore, when I OVP4a <IOVP3a At that time, I OVP5a =0; when I OVP4a >I OVP3a At that time, I OVP5a =I OVP4a -I OVP3a .

[0095] So when I OVP4a OVP3a At that time, I OVP1 =I OVP3 ×K4×K3; when I OVP4a >I OVP3a At that time, I OVP =((K1I OVP4 -I OVP3a )×K2+I OVP3 ()×K4×K3×R2) / (K5×R 301 ); due to I OVP3 and I OVP3a All of these are from the output of the zero-temperature drift current mirror I302, therefore I OVP3 and I OVP3a Both are zero-temperature drift currents. And I OVP4 The output from the positive temperature drift current mirror I302a, therefore I OVP4 This is the positive temperature drift current.

[0096] I OVP4 =I0+θ×t TEMP ;

[0097] Among them, t TEMP I0 is the circuit operating temperature, where I0 is the temperature at 0°C OVP4 The value of θ, where θ is the temperature coefficient.

[0098] I OVP =((K1(I0+θ×t) TEMP )-I OVP3a K2+I OVP3 ()×K4×K3×R2) / (K5×R 301 );

[0099] Let the constant coefficients be K4×K3 / (K5×R). 301 If ) = β, then we have,

[0100] I OVP =((K1(I0+θ×t) TEMP )-I OVP3a K2+I OVP3 )×β×R2;

[0101] Therefore, when t TEMP ≤(I OVP3a When -I0) / θ, ​

[0102] I OVP =β×I OVP3 ×R2;

[0103] When t TEMP >(I OVP3a When -I0) / θ,

[0104] I OVP =β×I OVP3 ×R2+(K1(I0+θ×t TEMP )-I OVP3a )β×K2×R2;

[0105] It can be seen that when t TEMP >(I OVP3a When -I0) / θ, as the circuit operating temperature t TEMP As it continues to rise, I OVP The increase is proportional, where t TEMP =(I OVP3a -I0) / θ is the nonlinear positive temperature drift current I OVP Temperature threshold.

[0106] I OVP As capacitor C 301 The charging current source, for signal T ON After a delay, the signal is processed by a digital logic gate circuit consisting of a Schmitt inverter I305, a first inverter I306, a NAND gate I304, and a second inverter I303 to obtain a control signal T. OVP Control signal T OVP This is the overvoltage protection enable signal. Positive pulse signal T OVP The time width is proportional to the capacitor C 301 Inversely proportional to the charging current I OVP .

[0107] The input voltage threshold of the sham Schmitt inverter I305 is V. TH So there is.

[0108] t OVP =V TH ×C 301 / I OVP ;

[0109] The pulse time t can be seen from the formula. OVP with I OVP They are inversely proportional, therefore t OVP It exhibits nonlinear negative temperature drift characteristics.

[0110] like Figure 6 As shown, the pulse time t OVP The curve showing the relationship between the circuit operating temperature and the operating temperature.

[0111] When t TEMP ≤(I OVP3a When -I0) / θ, t OVP It is a constant value that does not change with temperature, that is,

[0112] t OVP =V TH ×C 301 / (β×I OVP3 ×R2);

[0113] When t TEMP >(I OVP3a When -I0) / θ, t OVP It decreases as temperature increases, that is,

[0114] t OVP =V TH C 301 / (β×I OVP3 ×R2+(K1(I0+θ×t TEMP )-I OVP3a )β×K2×R2.

[0115] The switching power supply 10A of this invention operates in the inductor current critical mode. When the power transistor M1 is turned on, the current flowing through the energy storage inductor L1 rises from zero, and the on-time is t. ON =I PK ×L1 / (V IN -V LED ), where I PK V is the peak current in inductor L1. IN V is the voltage between the upper and lower plates of capacitor C1. LED The voltage difference of the LED string is V O .

[0116] When power transistor M1 is turned off, the current flowing through energy storage inductor L1 decreases from its peak value. When the current in inductor L1 drops to zero, the internal logic of the switching power supply controller 11A turns power transistor M1 back on. Therefore, the demagnetization time of power transistor M1 is t. DEM1 =I PK ×L1 / V LED .

[0117] When the LED string is open-circuited, the output voltage gradually increases, and the demagnetization time shortens. Therefore, the demagnetization time t can be calculated as needed. DEM1 To set the open-circuit protection voltage V of the LED string OVP , t OVP =I PK ×L1 / V OVP =(V CSTH ×L1) / (RCS ×V OVP ), where V CSTH For CS port signal V CS The turn-off threshold voltage, V OVP This is the open-circuit protection voltage for the LED. Therefore, V OVP =(V CSTH ×L1) / (R CS ×t OVP ), that is, LED open-circuit protection voltage V OVP With t OVP They are inversely proportional.

[0118] When the LED is open-circuited, the load becomes a dummy load R1. Because the resistance of R1 is very large, the output voltage V... O Very high, demagnetization signal T DEM Demagnetization time t DEM1 It becomes smaller, less than the signal T. OVP Time t OVP This triggers the OVP overvoltage protection mechanism, causing the power system 10A to enter the automatic restart sequence, thus realizing the open-circuit OVP protection function.

[0119] like Figure 7 and Figure 8 As shown, the switching power supply 10A using the ROVP circuit of the present invention, according to the normal temperature operating waveform 90A and the high temperature operating waveform 100A of the switching power supply according to the present invention, shows that due to the control signal T OVP Pulse time t OVP-SMART The temperature will drop rapidly as the temperature rises, thus avoiding the deep saturation of the inductor at high temperatures. OVP-SMART Less than demagnetization time t DEM1 , i.e. t DEM1 >t OVP-SMART Therefore, even with more severe inductance saturation at high temperatures, LEDs will not flicker. The 10A switching power supply containing the circuit of this invention enables LEDs to operate stably even when they are deeply magnetically saturated at high temperatures.

[0120] This invention can achieve this by controlling port R OVP This operation enables LED switching power supply systems operating in L1 inductor saturation state to prevent flickering at high temperatures, meeting users' demands for reducing inductor costs and possessing high market application prospects.

[0121] This invention provides a ROVP circuit, a switching power supply controller, and a switching power supply. The ROVP circuit is a high-temperature magnetic saturation resistant ROVP circuit. Through control and processing of the ROVP circuit, the LED string driver switching power supply can operate in a high-temperature inductor saturation state without falsely triggering overvoltage protection (i.e., OVP). The ROVP circuit responds to R... OVPThe signals at the port and TON port trigger overvoltage protection and shut down the LED string's switching power supply controller 11A when the 10A output of the LED string's switching power supply is open-circuited, preventing damage to the LED string's switching power supply system 10A and thus achieving better safety. The ROVP circuit responds to R... OVP When the LED string's 10A switching power supply is not open, the signals at the port and TON port will not trigger overvoltage protection when the inductor L1 is in a state of slight saturation at room temperature or deep saturation at high temperature. This prevents the LED string from flickering and thus meets the customer's demand for using lower-cost inductors.

[0122] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0123] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the circuit and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. An ROVP circuit, characterized by, include: A nonlinear positive temperature drift current source circuit is used to output a nonlinear positive temperature drift current in response to a power supply signal. The ROVP port circuit is connected to the nonlinear positive temperature drift current source circuit and is used to convert the nonlinear positive temperature drift current into a charging current. The TOVP generator is connected to the ROVP port circuit and is used to generate an overvoltage protection enable signal based on the charging current. The overvoltage protection enable signal is a logic high pulse duration that is inversely proportional to the charging current. The nonlinear positive temperature drift current source circuit includes: a zero temperature drift current source, a positive temperature drift current source, a first current mirror, a second current mirror, a third current mirror, and a fourth current mirror; The first current mirror includes a first transistor and a second transistor, the second current mirror includes a third transistor and a fourth transistor, the third current mirror includes a fifth transistor and a sixth transistor, and the fourth current mirror includes a seventh transistor and an eighth transistor. The input terminal of the positive temperature drift current source is connected to the input terminal of the zero temperature drift current source, the source of the third transistor, the source of the fourth transistor, the source of the seventh transistor, the source of the eighth transistor, the ROVP port circuit, and the VDD port of the ROVP circuit. The output terminal of the positive temperature drift current source is connected to the gate of the first transistor, the gate of the second transistor, and the drain of the first transistor. The sources of the first transistor and the second transistor are both grounded. The first output terminal of the zero-temperature drift current source is connected to the drain of the second transistor; the second output terminal of the zero-temperature drift current source is connected to the drain of the fifth transistor, the gate of the fifth transistor, and the gate of the sixth transistor, respectively; the drain of the third transistor, the gate of the third transistor, and the gate of the fourth transistor are all connected to the drain of the second transistor; the drain of the fourth transistor is connected to the drain of the fifth transistor. The drain, gate, and gate of the seventh transistor are all connected to the drain of the sixth transistor, and the source of the fifth transistor and the source of the sixth transistor are all grounded; the drain of the eighth transistor is connected to the ROVP port circuit.

2. The ROVP circuit of claim 1, wherein, The ROVP port circuit includes: a first amplifier, a fifth current mirror, a ninth transistor, and a resistor; the fifth current mirror includes a tenth transistor and an eleventh transistor; The inverting input terminal of the first amplifier is connected to the drain of the eighth transistor and the ROVP port of the ROVP circuit, respectively; the non-inverting input terminal of the first amplifier is connected to one end of the resistor; and the output terminal of the first amplifier is connected to the gate of the tenth transistor and the gate of the eleventh transistor, respectively. The drain of the tenth transistor and the drain of the eleventh transistor are connected with the VDD port of the ROVP circuit; the source of the tenth transistor is connected with the drain of the ninth transistor, the gate of the ninth transistor and the source of the ninth transistor are connected with one end of the resistor, and the other end of the resistor is grounded; the source of the eleventh transistor is connected with the TOVP generator.

3. The ROVP circuit of claim 2, wherein, The TOVP generator comprises a capacitor, a switch transistor, a Schmitt inverter, a first inverter, a NAND gate and a second inverter; One end of the capacitor is connected with the source of the eleventh transistor, the drain of the switch transistor and the input of the Schmitt inverter respectively, and the other end of the capacitor is connected with the source of the switch transistor and the ground respectively; the gate of the switch transistor is connected with the input of the first inverter and the TON port of the ROVP circuit respectively; The output of the Schmitt inverter is connected with the first input of the NAND gate, the output of the first inverter is connected with the second input of the NAND gate, the output of the NAND gate is connected with the input of the second inverter, and the output of the second inverter is connected with the TOVP port of the ROVP circuit.

4. The ROVP circuit of claim 2, wherein, The first current mirror and the third current mirror are n-type current mirrors; the second current mirror, the fourth current mirror and the fifth current mirror are p-type current mirrors.

5. The ROVP circuit of claim 3, wherein, When the power signal is logic high, the switch transistor is turned on, the level of the capacitor is cleared, the output signal of the Schmitt inverter is logic high, the output signal of the first inverter is logic low, and the over-voltage protection enable signal output by the second inverter is logic low; When the power signal is logic low, the switch transistor is turned off, the capacitor starts to charge, the potential of one end of the capacitor rises, the output signal of the Schmitt inverter is logic high, the output signal of the first inverter is logic high, and the over-voltage protection enable signal output by the second inverter is logic high; When the potential of one end of the capacitor exceeds the external input voltage threshold of the Schmitt inverter, the output signal of the Schmitt inverter is logic low, and the over-voltage protection enable signal output by the second inverter is logic low.

6. A switching power supply controller characterized by comprising: The switching power supply controller comprises the ROVP circuit of any one of claims 1-5, and further comprises a power supply circuit, a control circuit, a driving circuit, a demagnetization detection circuit, a front porch blanking circuit, a second amplifier and a power tube; The input of the power supply circuit is connected with the HV port of the switching power supply controller, the first output of the power supply circuit is connected with the VDD port of the ROVP circuit, the first input of the control circuit, the first input of the driving circuit, the first input of the demagnetization detection circuit, the first input of the front porch blanking circuit and the first input of the second amplifier respectively, and the second output of the power supply circuit is connected with the second input of the second amplifier; The TOVP port of the ROVP circuit is connected with the second input end of the control circuit, the output end of the control circuit is connected with the TON port of the ROVP circuit and the second input end of the driving circuit respectively, the output end of the driving circuit is connected with the gate of the power tube, the second input end of the demagnetization detection circuit and the second input end of the front porch blanking circuit respectively; the drain of the power tube is connected with the Drain port of the switching power supply controller, the source of the power tube is connected with the third input end of the second amplifier and the CS port of the switching power supply controller respectively; The output end of the demagnetization detection circuit is connected with the third input end of the control circuit; the output end of the front porch blanking circuit is connected with the fourth input end of the control circuit; the output end of the second amplifier is connected with the fifth input end of the control circuit, and the GND port of the switching power supply controller is grounded.

7. A switching power supply, characterized by comprising: The switching power supply comprises the switching power supply controller of claim 6, and further comprises a full-wave rectifier diode, a first capacitor, an inductor, a freewheeling diode, a second capacitor, a dummy load resistor, an LED lamp string, a first resistor and a second resistor. The first end of the full-wave rectifier diode and the second end of the full-wave rectifier diode are connected across the VAC input end of the switching power supply, the third end of the full-wave rectifier diode is connected with the lower plate of the first capacitor and the ground respectively, and the fourth end of the full-wave rectifier diode is connected with the upper plate of the first capacitor, the HV port of the switching power supply controller, the negative electrode of the freewheeling diode, the upper plate of the second capacitor, one end of the dummy load resistor and the input end of the LED lamp string respectively; The positive electrode of the freewheeling diode is connected with the Drain port of the switching power supply controller and one end of the inductor respectively, and the other end of the inductor is connected with the lower plate of the second capacitor, the other end of the dummy load resistor and the output end of the LED lamp string respectively; One end of the first resistor is connected with the ROVP port of the switching power supply controller, and the other end of the first resistor is grounded; one end of the second resistor is connected with the CS port of the switching power supply controller, and the other end of the second resistor is grounded.

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