CN113079609A - Constant current control chip, system and LED constant current drive circuit - Google Patents

Constant current control chip, system and LED constant current drive circuit Download PDF

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CN113079609A
CN113079609A CN202110624674.9A CN202110624674A CN113079609A CN 113079609 A CN113079609 A CN 113079609A CN 202110624674 A CN202110624674 A CN 202110624674A CN 113079609 A CN113079609 A CN 113079609A
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voltage
constant current
electrode
power supply
current control
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CN113079609B (en
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王建虎
李瑞平
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Shanghai Xinlong Semiconductor Technology Co ltd
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Shanghai Xinlong Semiconductor Technology Co ltd
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    • HELECTRICITY
    • H05ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05BELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/30Driver circuits
    • H05B45/345Current stabilisation; Maintaining constant current
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02HEMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H11/00Emergency protective circuit arrangements for preventing the switching-on in case an undesired electric working condition might result
    • H02H11/006Emergency protective circuit arrangements for preventing the switching-on in case an undesired electric working condition might result in case of too high or too low voltage
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02HEMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H3/00Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
    • H02H3/20Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess voltage
    • H02H3/207Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess voltage also responsive to under-voltage
    • HELECTRICITY
    • H05ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05BELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/10Controlling the intensity of the light
    • H05B45/14Controlling the intensity of the light using electrical feedback from LEDs or from LED modules
    • HELECTRICITY
    • H05ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05BELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/50Circuit arrangements for operating light-emitting diodes [LED] responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02BCLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B20/00Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
    • Y02B20/30Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

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  • Circuit Arrangement For Electric Light Sources In General (AREA)

Abstract

The invention provides a constant current control chip, a system and an LED constant current drive circuit, which relate to the technical field of integrated circuit chips, wherein the constant current control chip comprises: the device comprises a starting and dimming circuit module, a reference power supply module, a driving module and a constant current control module; setting a threshold value through two internal undervoltage protections, and closing a constant current control chip in due time under the condition that the voltage of a power supply voltage end VCC of the chip is reduced to a turn-off voltage due to the voltage reduction of an energy storage capacitor C2 in the work of a constant current control system; the chip is started when the voltage of the energy storage capacitor C2 rises to the internal starting voltage of the chip, so that the problem that the whole system is damaged due to the fact that the working point of an internal circuit of the chip deviates and the internal logic is disordered due to the fact that the voltage of a power supply voltage end VCC is too low is solved. The constant current control chip is simple in circuit structure, overvoltage protection, undervoltage protection and dimming functions are achieved through a small number of devices, and the cost of the LED constant current dimming system is reduced.

Description

Constant current control chip, system and LED constant current drive circuit
Technical Field
The invention relates to the technical field of integrated circuit chips, in particular to a constant current control chip, a constant current control system and an LED constant current driving circuit.
Background
An LED (Light Emitting Diode) is a solid semiconductor device capable of converting electric energy into visible Light, and has advantages of high Light Emitting efficiency, long life, and the like. LEDs have a diode characteristic and require constant current source drive to control the LED.
In the application of LED lighting in the market, a constant current control chip is usually adopted to design a constant current control system, and the common constant current control chip is divided into a common ground structure for taking electricity at an input end and a floating ground structure for taking electricity at an output end. Compared with a common ground structure, the floating structure has the advantages of simple structure, more convenient system design and obvious cost advantage. However, in the system adopting the floating structure constant current control chip, because the constant current control chip takes electricity from the output end when in work, the constant current control system can be charged very high at the output end under the condition that the LED is open-circuited. In the conventional constant current control system, the starting current charges the power supply capacitor through a large resistor, and the starting current is very small.
Therefore, the problem that the voltage of the power supply capacitor drops after the chip is started is that if the voltage of the power supply capacitor drops to a point that the internal working point of the chip circuit is affected, the internal part of the chip is in logic disorder when the rear-end output voltage still cannot charge the power supply capacitor, and the chip is damaged in serious conditions.
Disclosure of Invention
The invention provides a constant current control chip, a constant current control system and an LED constant current driving circuit in order to overcome the defects of the prior art.
In order to achieve the above object, an embodiment of the present invention provides a constant current control chip, including: the device comprises a starting and dimming circuit module, a reference power supply module, a driving module and a constant current control module; the starting and dimming circuit module, the reference power supply module, the driving module and the constant current control module use the voltage of a reference ground end VS as the internal reference voltage of the chip;
the starting and dimming circuit module detects the voltage of a power supply voltage end VCC, and when the voltage of the power supply voltage end VCC is increased from low to higher than a first undervoltage protection setting threshold UVLO _ H, a reference power supply module is started through a first undervoltage protection control signal so as to start a chip; when the voltage of a power supply voltage end VCC is reduced to be lower than a second undervoltage protection setting threshold UVLO _ L from high, a reference power supply module is closed through a second undervoltage protection control signal, and then a chip is closed; when the voltage of the power supply voltage end VCC is higher than the overvoltage protection set threshold value, the constant current control module is closed through the overvoltage protection control signal OVP, so that the voltage of the power supply voltage end VCC does not rise any more; the starting and dimming circuit module detects the sampling voltage of the sampling end CS, and controls GATEDRIVE the external NMOS power tube of the signal output end to be turned on or off according to the sampling voltage, thereby ensuring the average value of the output current of the sampling end CS to be constant; the reference power supply module receives the voltage of a power supply voltage end VCC, and turns on or off a chip internal voltage stabilization source voltage VDD and a chip internal reference voltage VREF according to a corresponding undervoltage protection control signal output by the starting and dimming circuit module; the constant current control module acquires a voltage VDD of a voltage stabilizing source inside a chip, a reference voltage VREF inside the chip and an overvoltage protection control signal OVP, and outputs a DRIVE control signal which is used as an input control signal of the driving module, and the overvoltage protection control signal OVP is used for closing the constant current control module; the output end of the driving module is an GATEDRIVE signal output end, and the output signal of the GATEDRIVE signal output end is controlled by obtaining the voltage VDD of the voltage stabilizing source inside the chip and the DRIVE control signal of the constant current control module, so that the on and off of an NMOS power tube externally connected with the GATEDRIVE signal output end are controlled.
Optionally, the starting and dimming circuit module includes a bias circuit, an overvoltage protection circuit, an undervoltage protection circuit, and a dimming circuit; the output end of the overvoltage protection circuit outputs the overvoltage protection control signal OVP; when the voltage of the first input end of the overvoltage protection circuit is higher than the overvoltage protection set threshold value, the overvoltage protection control signal OVP is changed from a high level to a low level; the input end of the under-voltage protection circuit is connected with a power supply voltage end VCC; when the voltage at the input end of the undervoltage protection circuit gradually rises and is lower than a second undervoltage protection setting threshold UVLO _ L, the output end of the undervoltage protection circuit outputs a high level; when the voltage at the input end of the undervoltage protection circuit continuously rises and is higher than a second undervoltage protection setting threshold value UVLO _ L and lower than a first undervoltage protection setting threshold value UVLO _ H, the output end of the undervoltage protection circuit keeps outputting a high level; when the voltage at the input end of the undervoltage protection circuit continues to rise to be higher than a first undervoltage protection setting threshold UVLO _ H, the output end of the undervoltage protection circuit is changed from a high level to a low level; when the voltage at the input end of the undervoltage protection circuit gradually drops and is higher than a second undervoltage protection setting threshold value UVLO _ L and lower than a first undervoltage protection setting threshold value UVLO _ H, the output end of the undervoltage protection circuit keeps a low level; when the voltage at the input end of the undervoltage protection circuit continuously drops to be lower than a second undervoltage protection setting threshold UVLO _ L, the output end of the undervoltage protection circuit is changed from a low level to a high level.
Optionally, the sampling terminal CS is used as both a feedback signal input terminal of the constant current control chip and a current output terminal of the dimming circuit;
sampling the sum of the voltage of the external dimming resistor and the voltage of the sampling resistor when the input end of the feedback signal is used;
the current output end of the dimming circuit outputs the current with constant average value.
Optionally, the bias circuit includes a PMOS transistor M1, an NMOS transistor M2, a PMOS transistor M3, an NMOS transistor M4, a PMOS transistor M5, a PMOS transistor M6, an NPN transistor Q1, an NPN transistor Q2, a resistor R4, a resistor R5, a resistor R6, a capacitor C4, a capacitor C5, a diode D3, a diode D4, and a diode D5; the source electrode of the M1 is connected with a power supply voltage terminal VCC, the grid electrode of the M1 is connected with the source electrode of the M1, and the drain electrode of the M1 is connected with the grid electrode of the M2; the drain electrode of M2 is respectively connected with the drain electrode of M3 and the drain electrode of M4, and the source electrode of M2 is connected with the source electrode of M4; the source electrode of the M3 is connected with a power supply voltage terminal VCC, the grid electrode of the M3 is connected with the drain electrode of the M3, and the drain electrode of the M3 is connected with the grid electrode of the M5; the grid electrode of the M4 is respectively connected with the drain electrode of the M5 and the collector electrode of the Q1; the source electrode of the M5 is connected with a power supply voltage terminal VCC, and the grid electrode of the M5 is connected with the grid electrode of the M6; the source electrode of the M6 is connected with a power supply voltage terminal VCC; the base of Q1 is connected with the base of Q2, and the emitter of Q1 is respectively connected with the second ends of a reference ground terminal VS and R6; a collector of Q2 is connected with a drain of M6, and an emitter of Q2 is connected with a first end of R6; a first end of the C4 is connected with the grid of the M2, and a second end of the C4 is connected with a reference ground end VS; a first end of the C5 is connected with the grid of the M4, and a second end of the C5 is connected with a reference ground end VS; a first end of R4 is connected with the grid of M2, and a second end of R4 is connected with a reference ground end VS; a first end of R5 is connected with the source of M2, and a second end of R5 is connected with a reference ground end VS; the anode of D3 is connected with the drain of M1, and the cathode of D3 is connected with the anode of D4; the negative electrode of the D4 is connected with the positive electrode of the D5; the negative electrode of D5 is connected to the reference ground terminal VS.
Optionally, the overvoltage protection circuit includes a PMOS transistor M7, a PMOS transistor M8, an NPN triode Q3, a resistor R7, and a zener diode DZ 1; the source electrode of the M7 is connected with a power supply voltage end VCC, the grid electrode of the M7 is connected with the grid electrode of the M6, and the drain electrode of the M7 is connected with the cathode of the DZ 1; the source electrode of the M8 is connected with a power supply voltage terminal VCC, the grid electrode of the M8 is connected with the grid electrode of the M7, and the drain electrode of the M8 is connected with the collector electrode of the Q3; a collector of Q3 is used as an output end of an overvoltage protection control signal OVP, a base of Q3 is connected with the anode of DZ1, and an emitter is connected with a reference ground end VS; the first end of R7 is connected with the positive pole of DZ1, and the second end of R7 is connected with the reference ground end VS.
Optionally, the under-voltage protection circuit includes PMOS transistors M9, M10, M11, M12, M14, M15, M17, M18, M19, M20, M21, M23, NMOS transistors M13, M16, M22, M24, PNP triodes Q4, Q5, resistors R8, R9, zener diodes DZ2, DZ3, M9 source, M10 source, M14 source, M18 source, M19 source, M21 source, and M23 source are respectively connected to the power supply voltage terminal VCC, 387m 9 gate is connected to the output terminal of the bias circuit, and M9 drain is connected to the negative electrode of DZ 2; the grid electrode of M10 is connected with the grid electrode of M9, the grid electrode of M14, the grid electrode of M18, the grid electrode of M19, the grid electrode of M21 and the grid electrode of M23, and the drain electrode of M10 is connected with the cathode of DZ 3; the positive electrode of DZ2 is connected with the positive electrode of D6; the positive electrode of DZ3 is connected with the first end of R8; the second end of R8, the second end of R9, the collector of Q4, the collector of Q5, the source of M13, the source of M16, the source of M22 and the source of M24 are respectively connected with a reference ground end VS; the negative electrode of the D6 is connected with the positive electrode of the D7; the negative electrode of the D7 is connected with the first end of the R8; the base of Q4 is connected with the positive electrode of DZ3, and the emitter of Q4 is connected with the drain of M11; the drain electrode of the M14 is respectively connected with the source electrode of M11, the source electrode of M12, the source electrode of M15 and the source electrode of M17; the grid electrode of the M11 is connected with the drain electrode of the M11; the M12 gate is connected with the M11 gate; the drain electrode of the M12 is connected with the drain electrode of the M13; the grid electrode of M13 is respectively connected with the grid electrode of M16 and the drain electrode of M16; the grid electrode of M15 is respectively connected with the grid electrode of M17 and the drain electrode of M17, and the drain electrode of M15 is connected with the drain electrode of M16; the drain electrode of the M17 is connected with the emitter electrode of the Q5; the base of Q5 is connected with the drain of M18; a first end of R9 is connected with a base of Q5; the drain electrode of the M19 is connected with the source electrode of the M20; the grid electrode of M20 is connected with the drain electrode of M21, and the drain electrode of M20 is connected with the base electrode of Q5; the drain electrode of the M21 is connected with the drain electrode of the M22; the grid electrode of the M22 is connected with the drain electrode of the M13; the drain electrode of the M23 is connected with the drain electrode of the M24; the grid electrode of M24 is connected with the drain electrode of M22, and the drain electrode of M24 is used as the output end of the undervoltage protection circuit.
Optionally, the dimming circuit includes a PNP transistor Q6, an NPN transistor Q7, a PNP transistor Q8, a PNP transistor Q9, and a resistor R10; an emitter of Q6 is connected with a power supply voltage end VCC, a base of Q6 is respectively connected with an emitter of Q8 and a base of Q9, and a collector of Q6 is respectively connected with a collector of Q7 and a base of Q8; the base of the Q7 is used as a second input end of the dimming circuit and is connected with the reference power supply module to receive the chip internal reference voltage VREF, and the emitter of the Q7 is connected with the first end of the R10; a second end of the R10 is connected with a reference ground end VS; the collector of Q8 is connected with a reference ground terminal VS; the emitter of the Q9 is connected with a power supply voltage terminal VCC, and the collector of the Q9 is connected with the sampling terminal CS as the output end of the dimming circuit.
Optionally, when the voltage value of the sampling voltage is the first dimming voltage threshold, controlling an NMOS power tube externally connected to the signal output end of GATEDRIVE to be turned on; when the voltage value of the sampling voltage is the second dimming voltage threshold, controlling an external NMOS power tube of the GATEDRIVE signal output end to be turned off; the first dimming voltage threshold is a difference between a preset average voltage value of the sampling terminal CS and a preset voltage VX, and the second dimming voltage threshold is a sum of the sampling terminal CS and the preset voltage VX.
The embodiment of the invention provides a constant current control system, which comprises a resistor R1, a dimming resistor R2, a sampling resistor R3, an NMOS power tube NM1, a filter capacitor C1, a power supply capacitor C2, a filter capacitor C3, an energy storage inductor L1, a Schottky diode D2 and the constant current control chip; the first end of the R1 is used as a system input end, and the second end of the R1 is connected with a power supply voltage end VCC of the constant current control chip; a first end of R2 is connected with a sampling end CS of the constant current control chip, and a second end of R2 is connected with a first end of R3; the second end of the R3 is connected with a reference ground end VS of the constant current control chip; the drain of the NM1 is connected with the first end of the R1, the grid of the NM1 is connected with the GATEDRIVE signal output end of the constant current control chip, and the source of the NM1 is connected with the second end of the R2; the first end of the C1 is connected with the positive pole of a DC power supply V1, and the second end of the C1 is connected with the GND end; a first end of the C2 is connected with a second end of the R1, and a second end of the C2 is connected with a reference ground end VS of the constant current control chip; a first end of C3 is connected with a second end of L1, and a second end of C3 is connected with a GND end; a first end of L1 is connected with a second end of R3, and a second end of L1 is connected with the anode of D2 as a system output end; the negative electrode of D2 is connected with the first end of C2; the anode of D1 is connected to GND terminal, and the cathode of D1 is connected to the source of NM 1.
The embodiment of the invention also provides an LED constant current driving circuit, which comprises a power supply circuit, an LED circuit and the constant current control system; and the system input end of the constant current control system is connected with the power circuit, and the system output end of the constant current control system is connected with the LED circuit.
In conclusion, the beneficial effects of the invention are as follows:
the constant current control chip and the constant current control system have the functions of overvoltage protection, undervoltage protection and dimming, and the chip is closed timely under the condition that the voltage of a power supply voltage end VCC (VCC) of the constant current control chip is reduced due to the voltage reduction of an energy storage capacitor C2 in the working process of the constant current control system by setting the threshold through two undervoltage protections inside; the chip is started when the voltage of the energy storage capacitor C2 rises to the internal starting voltage of the chip, so that the problems that the working point of an internal circuit of the chip is deviated due to the fact that the VCC voltage of a power supply voltage end is too low, internal logic is disordered, and the whole system is damaged are solved; meanwhile, a threshold value is set through internal overvoltage protection, and under the condition that the voltage of the energy storage capacitor C2 rises to cause the voltage of a power supply voltage end VCC of the constant current control chip to be too large in the working process of the constant current control system, the charging of the energy storage inductor L1 is stopped, so that the voltage of the power supply voltage end VCC does not rise any more. The stability of the constant current control chip and the reliability of the constant current control system are improved.
When the constant current control chip is in a working state, the sampling voltage is subjected to signal processing, and the peak current and the valley current of the energy storage inductor L1 are controlled by switching the power tube NM1 to realize constant current output, so that the LED circuit is dimmed. And the sampling end CS of the constant current control chip is used as a sampling end of the sampling voltage and a current output end of the dimming circuit. Compared with a floating ground constant current control chip adopting independent sampling pins and dimming pins, the system application design and the packaging design are greatly simplified.
The embodiment of the invention provides an LED constant current driving circuit adopting a constant current control chip manufactured by using a transistor analog circuit integrated circuit, which has a simple circuit structure, realizes overvoltage protection, undervoltage protection and dimming functions by a small number of devices, and reduces the cost of an LED constant current dimming system.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
Fig. 1 is a schematic circuit diagram of an LED constant current driving circuit according to an embodiment of the present invention;
fig. 2 is a schematic block diagram of an internal functional module of a constant current control chip according to an embodiment of the present invention;
fig. 3 is a schematic circuit diagram of a starting and dimming circuit module according to an embodiment of the present invention;
FIG. 4 is a schematic circuit diagram of a bias circuit according to an embodiment of the present invention;
FIG. 5 is a schematic circuit diagram of an over-voltage protection circuit according to an embodiment of the present invention;
fig. 6 is a schematic circuit diagram of an under-voltage protection circuit according to an embodiment of the present invention;
fig. 7 is a schematic circuit diagram of a dimming circuit according to an embodiment of the present invention;
fig. 8 is a simulation diagram of the overvoltage protection function of the overvoltage protection circuit according to the embodiment of the invention;
fig. 9 is a simulation diagram of the under-voltage protection function of the under-voltage protection circuit according to the embodiment of the present invention;
fig. 10 is a simulation diagram of a dimming function of the dimming circuit according to the embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to examples, which are illustrative of the present invention and are not to be construed as being limited thereto.
The embodiment of the invention firstly provides an LED constant current driving circuit, please refer to fig. 1, which includes a power circuit 20, an LED circuit 30, and a constant current control system 10; the system input end of the constant current control system 10 is connected with the power circuit 20, and the system output end of the constant current control system is connected with the LED circuit 30. In the present embodiment, the power supply circuit 20 includes a dc power supply V1.
The LED circuit 30 includes a light emitting diode LED1, a light emitting diode LED2, a light emitting diode LED 3; the anode of the LED1 is connected to the output end of the constant current control system 10, the cathode of the LED1 is connected to the anode of the LED2, the cathode of the LED2 is connected to the anode of the LED3, and the cathode of the LED3 is connected to the GND terminal.
The constant current control system 10 includes: the LED driving circuit comprises a resistor R1, a dimming resistor R2, a sampling resistor R3, an NMOS power tube NM1, a filter capacitor C1, a power supply capacitor C2, a filter capacitor C3, an energy storage inductor L1, a Schottky diode D2 and a constant current control chip 100; a first end of the R1 is used as a system input end, and a second end of the R1 is connected with a power supply voltage end VCC of the constant current control chip 100; a first end of R2 is connected with a sampling end CS of the constant current control chip 100, and a second end of R2 is connected with a first end of R3; a second end of the R3 is connected to a reference ground end VS of the constant current control chip 100; the drain of the NM1 is connected with the first end of the R1, the grid of the NM1 is connected with the GATEDRIVE signal output end of the constant current control chip 100, and the source of the NM1 is connected with the second end of the R2; the first end of the C1 is connected with the positive pole of a DC power supply V1, and the second end of the C1 is connected with the GND end; a first end of the C2 is connected with a second end of the R1, and a second end of the C2 is connected with a reference ground end VS of the constant current control chip 100; a first end of C3 is connected with a second end of L1, and a second end of C3 is connected with a GND end; a first end of the L1 is connected with a second end of the R3, and a second end of the L1 is connected with the anode of the D2 as a system output end of the constant current control system 10; the negative electrode of D2 is connected with the first end of C2; the anode of D1 is connected to GND terminal, and the cathode of D1 is connected to the source of NM 1.
In the embodiment of the present invention, the power circuit 20 and the LED circuit 30 are only an implementation manner of an LED constant current driving circuit, and a person skilled in the art may select different power circuits and LED circuits as needed, which is not described herein again.
The working process of the LED constant current driving circuit provided by the embodiment of the invention is as follows: the system input end of the constant current control system 10 is connected to the positive electrode of a direct current power supply V1 in the power circuit 20, the direct current power supply V1 starts to charge a power supply capacitor C2 through a resistor R1, and at this time, no voltage difference exists between two ends of the power supply capacitor C2, and the constant current control chip 100 is in an unopened state. The dc power supply V1 continuously charges the power supply capacitor C2, and the voltage across the capacitor of the power supply capacitor C2 continuously rises, because the first terminal of the power supply capacitor C2 is connected to the power supply voltage terminal VCC of the constant current control chip 100, the voltage at the first terminal of C2 is equal to the voltage at the power supply voltage terminal VCC. When the voltage of the power supply capacitor C2 rises to the first undervoltage protection setting threshold UVLO _ H inside the constant current control chip 100, the constant current control chip 100 starts to work, the constant current control system 10 is turned on, and after the constant current control system 10 is stabilized, the system output end of the constant current control system 10 starts to output a current with a constant average value to the LED circuit 30 to supply power to the LED circuit 30.
After the constant current control chip 100 starts operating, the internal power consumption of the constant current control chip 100 increases. The resistance value of the resistor R1 is generally large, the charging current of the dc power supply V1 for charging the power supply capacitor C2 through the resistor R1 is very small, and at this time, the constant current control system 10 is just started, if the LED circuit 30 is an LED lamp (with a voltage of about 3.0V), since the chip starting voltage is about 6V, the voltage at the two ends of the power supply capacitor C2 is about 6V, and since the voltage VOUT at the system output end of the constant current control system 10 is smaller than the voltage at the two ends of the power supply capacitor C2, the voltage VOUT at the system output end of the constant current control system 10 cannot charge the power supply capacitor C2 through the schottky diode D2, and the voltage of the power supply capacitor C2 continuously drops. The voltage of the power supply capacitor C2 is too low, which may cause the operating point of the internal circuit of the constant current control chip 100 to shift, and the internal logic of the constant current control chip 100 to be disordered, thereby causing the damage to the constant current control system 10. Therefore, when the voltage of the C2 drops to the second undervoltage protection setting threshold UVLO _ L inside the constant current control chip 100, and the voltage VOUT at the system output terminal of the constant current control system 10 still cannot charge the C2, the constant current control chip 100 stops working, the NMOS power tube NM1 is turned off, the constant current control system 10 is turned off, and the system output terminal of the constant current control system no longer outputs a current with a constant average value to the LED circuit 30, and no power is supplied to the LED circuit 30.
After the constant current control chip 100 is turned off, the power consumption of the constant current control chip 100 is reduced, the direct current power supply V1 continuously charges C2 through R1, and after an NMOS power tube NM1 is turned off, the direct current power supply V1 continuously charges C2 through R1, when the voltage of the power supply capacitor C2 rises again to a first undervoltage protection setting threshold UVLO _ H inside the constant current control chip 100, the constant current control chip 100 restarts, if the LED circuit 30 is formed by connecting 2 LED lamp beads in series (the voltage of the LED lamp bead is about 3.0V), the voltage VOUT of the system output end of the constant current control system 10 is about 6V, the power supply capacitor C2 can be charged through D2, the voltage at two ends of the power supply capacitor C2 is maintained at about 6V, the power supply capacitor C2 can continuously supply power to the constant current control chip 100, and the system output end of the constant current control system can output a constant average value current to supply power the LED circuit 30; if the LED circuit 30 is formed by connecting 3 LED bulbs in series (the voltage of the LED bulbs is about 3.0V), the voltage VOUT of the output end of the constant current control system 10 is about 9V, and the power supply capacitor C2 can be charged through D2, the voltage at two ends of the power supply capacitor C2 is maintained at about 9V, the power supply capacitor C2 can continuously supply power to the constant current control chip 100, and the system output end of the constant current control system can output a current with a constant average value to supply power to the LED circuit 30; based on this, in principle, no matter how many LED lamps the LED circuit 30 is connected in series, the voltage VOUT at the system output end of the constant current control system 10 is equal to the voltages at the two ends of the LED circuit 30, and the voltage difference between the two ends of the power supply capacitor C2 is equal to the voltages at the two ends of the LED circuit 30, but because the overvoltage protection setting threshold value inside the constant current control chip 100 is set, when the number of LED lamps the LED circuit 30 is connected in series exceeds a certain number, the VCC voltage value at the power supply voltage end is higher than the overvoltage protection setting threshold value inside the constant current control chip 100, and at this time, the constant current control chip 100 controls the NMOS power tube NM1 to be turned off, the voltages at the two ends of the LED circuit 30 are no longer increased, the voltage at the power supply voltage end VCC is.
When the LED in the LED circuit 30 is open-circuited, the voltage VOUT at the system output terminal of the constant current control system 10 is not clamped by the LED lamp, and the voltages at the two ends of the LED circuit 30 will rise rapidly and be uncontrolled, so that the VCC voltage value at the power supply voltage terminal will rise rapidly, and when the VCC voltage value at the power supply voltage terminal is higher than the overvoltage protection setting threshold value inside the constant current control chip 100, the constant current control chip 100 controls the NMOS power tube NM1 to be turned off, the voltages at the two ends of the LED circuit 30 will not rise any more, the VCC voltage at the power supply voltage terminal will not rise any more, and the constant current control chip 100 will not be damaged by high voltage.
In addition, the constant current control system 10 supplies power to the LED circuit 30 through the system output terminal when the constant current control chip 100 is in a working state. The reference ground end VS is a reference ground of the constant current control chip, the resistor R2 is a dimming resistor, the resistor R3 is a sampling resistor, the sampling end CS is used as a sampling end of a sampling voltage and a constant current output end, and the sampling voltage is composed of a voltage drop of the resistor R2 and the resistor R3. When the power transistor NM1 is turned on, the source of the NM1 is raised to the voltage VIN of the dc power supply V1 (the transistor drop of the NM1 is ignored here), the sampling voltage VCS of the sampling terminal CS is IOUT × R3+ I11 × R2, and the sampling voltage of the sampling terminal CS is referenced to the voltage of the ground terminal VS. The constant current control chip 100 processes the sampling voltage and controls the peak current and the valley current of the energy storage inductor L1 by switching the power transistor NM1 to realize constant current. In this embodiment, when the sampling voltage is the preset average voltage of the sampling terminal CS minus the preset voltage VX, the power tube NM1 is turned on; when the sampling voltage is the sum of the preset average voltage of the sampling end CS and the preset voltage VX, the power tube is closed, wherein the preset voltage is a voltage value which is set at will, the average voltage of the sampling end CS is the preset average voltage, at the moment, the average current IOUT = (VCS-R2) I11)/R3 of the energy storage inductor L1 is obtained, the average value of the IOUT can be adjusted by adjusting the resistance value of the dimming resistor R2, and therefore dimming is achieved. According to the constant current control chip, through two internal undervoltage protection setting thresholds, when the voltage of an energy storage capacitor C2 drops to cause the voltage of a power supply voltage end VCC of the constant current control chip to drop to a second undervoltage protection setting threshold UVLO _ L in the working process of a constant current control system, the chip is closed; the chip is started when the voltage of the energy storage capacitor C2 rises to the internal starting voltage of the chip, so that the problems that the working point of an internal circuit of the chip is deviated due to the fact that the VCC voltage of a power supply voltage end is too low, the internal logic of the chip is disordered, and the whole system is damaged are solved; meanwhile, a threshold value is set through internal overvoltage protection, under the condition that the voltage of the energy storage capacitor C2 rises to cause the voltage of the power supply voltage end VCC of the constant current control chip to be too large in the working process of the constant current control system, the energy storage of the energy storage inductor L1 is stopped, and the voltage of the power supply voltage end VCC is further prevented from rising, so that the stability of the constant current control chip and the reliability of the constant current control system are improved.
The constant current control chip of the embodiment of the invention is an integrated circuit which is realized by adopting a transistor analog circuit integrated circuit manufacturing process. Referring to fig. 2, a schematic block diagram of internal functional modules of the constant current control chip 100 according to the embodiment of the present invention includes: a starting and dimming circuit module 1001, a reference power supply module 1002, a driving module 1003 and a constant current control module 1004; the starting and dimming circuit module 1001, the reference power supply module 1002, the driving module 1003 and the constant current control module 1004 adopt a transistor analog circuit integrated circuit manufacturing process and use the voltage of a reference ground end VS as the internal reference voltage of the chip.
The input of the start and dimming circuit module 1001 is the voltage of the power supply voltage terminal VCC, which is used to provide an IBIAS signal and an under-voltage protection control signal for the reference power supply module 1002, and is also responsible for providing an over-voltage protection control signal OVP for the constant current control module 1004. After the constant current control system is powered on, the voltage VIN of a direct current power supply V1 charges a power supply capacitor C2 through R1, at this time, the chip internal start and dimming circuit module 1001 starts to detect the voltage of a power supply voltage end VCC, when the voltage of the power supply voltage end VCC is increased from low to higher than a first undervoltage protection setting threshold UVLO _ H, the reference power supply module 1002 is turned on through a first undervoltage protection control signal, the chip internal voltage stabilization source voltage VDD and the chip internal reference voltage VREF are established, the constant current control chip 100 starts to work, the voltage VOUT of the system output end of the constant current control system rises, and the voltage of C2 drops; when the voltage of the power supply voltage end VCC is reduced from high to be lower than the second undervoltage protection setting threshold UVLO _ L and the voltage of the voltage VOUT of the system output end still cannot charge the capacitor C2 through D2, the reference power module 1002 is turned off through the second undervoltage protection control signal to turn off the chip, the switching power tube NM1 is turned off, the power consumption of the chip is reduced, the voltage VIN of the dc power supply V1 continuously charges the capacitor C2 through R1, the voltage of the power supply voltage end VCC rises under the charging effect of the external power supply capacitor, and when the voltage of the power supply voltage end VCC reaches the first undervoltage protection setting threshold UVLO _ H again, the chip is restarted. The start-up and dimming circuit module 1001 detects the voltage VOUT of the system output terminal, and when the voltage of the power supply voltage terminal VCC is higher than the overvoltage protection setting threshold, the constant current control module is turned off by the overvoltage protection control signal OVP so that the voltage VOUT of the system output terminal is not increased any more, and thus the voltage of the power supply voltage terminal VCC is not increased any more.
The reference power supply module 1002 receives a voltage of a power supply voltage terminal VCC, and turns on or off a chip internal voltage regulator voltage VDD and a chip internal reference voltage VREF according to a corresponding under-voltage protection control signal output by the start and dimming circuit module 1001.
The constant current control module 1004 performs inverse calculation on the current magnitude of the energy storage inductor L1 at the corresponding moment by judging the voltage of the CS port, obtains the voltage VDD of the voltage regulator inside the chip, the reference voltage VREF inside the chip and the overvoltage protection control signal OVP, and controls the average current of the inductor by adjusting the average voltage of the CS end when the power tube is turned on, thereby realizing the constant current function. In the present embodiment, the CS port voltage is generally set to 0.2V, and dimming can be achieved by adjusting the resistance of the dimming resistor R2.
The output end of the driving module 1003 is an GATEDRIVE signal output end, and the output signal of the GATEDRIVE signal output end is controlled by obtaining the voltage VDD of the voltage regulator inside the chip and the DRIVE control signal of the constant current control module 1004, so that the on and off of an NMOS power tube externally connected to the GATEDRIVE signal output end are controlled.
Fig. 3 is a schematic circuit diagram of a start-up and dimming circuit module according to an embodiment of the present invention, where the start-up and dimming circuit module includes a bias circuit 10001, an over-voltage protection circuit 10002, an under-voltage protection circuit 10003, and a dimming circuit 10004.
In this embodiment, a first input end of the bias circuit 10001 is connected to a power voltage terminal VCC, a second input end of the bias circuit 10001 is connected to a ground reference terminal VS, and an output end of the bias circuit 10001 is respectively connected to the overvoltage protection circuit 10002 and the undervoltage protection circuit 10003 and provides a reference current for the overvoltage protection circuit 10002 and the undervoltage protection circuit 10003. A first input end of the overvoltage protection circuit is connected to the power voltage VCC, a second input end of the overvoltage protection circuit 10002 is connected to an output end of the bias circuit 10001, and an output end of the overvoltage protection circuit 10002 outputs the overvoltage protection control signal OVP. A first input end of the undervoltage protection circuit 10003 is connected to the power supply voltage VCC, and a second input end of the undervoltage protection circuit 10003 is connected to an output end of the dimming circuit 10004. The first input end of the dimming circuit 10004 is connected to the power supply voltage terminal VCC, the second input end of the dimming circuit 10004 is connected to the reference power supply module to receive the chip internal reference voltage VREF, and the output end of the dimming circuit is connected to the sampling terminal CS.
Specifically, please refer to fig. 4 for a schematic circuit diagram of the bias circuit, where the bias circuit 10001 includes a PMOS transistor M1, an NMOS transistor M2, a PMOS transistor M3, an NMOS transistor M4, a PMOS transistor M5, a PMOS transistor M6, an NPN triode Q1, an NPN triode Q2, a resistor R4, a resistor R5, a resistor R6, a capacitor C4, a capacitor C5, a diode D3, a diode D4, and a diode D5; the source of the M1 is connected with a power supply voltage terminal VCC, the grid of the M1 is connected with the source of the M1, and the drain of the M1 is connected with the grid of the M2; the drain electrode of M2 is respectively connected with the drain electrode of M3 and the drain electrode of M4, and the source electrode of M2 is connected with the source electrode of M4; the source electrode of the M3 is connected with a power supply voltage terminal VCC, the grid electrode of the M3 is connected with the drain electrode of the M3, and the drain electrode of the M3 is connected with the grid electrode of the M5; the grid electrode of the M4 is respectively connected with the drain electrode of the M5 and the collector electrode of the Q1; the source electrode of the M5 is connected with a power supply voltage terminal VCC, and the grid electrode of the M5 is connected with the grid electrode of the M6; the source electrode of the M6 is connected with a power supply voltage terminal VCC; the base of Q1 is connected with the base of Q2, and the emitter of Q1 is respectively connected with the second ends of a reference ground terminal VS and R6; a collector of Q2 is connected with a drain of M6, and an emitter of Q2 is connected with a first end of R6; a first end of the C4 is connected with the grid of the M2, and a second end of the C4 is connected with a reference ground end VS; a first end of the C5 is connected with the grid of the M4, and a second end of the C5 is connected with a reference ground end VS; a first end of R4 is connected with the grid of M2, and a second end of R4 is connected with a reference ground end VS; a first end of R5 is connected with the source of M2, and a second end of R5 is connected with a reference ground end VS; the anode of D3 is connected with the drain of M1, and the cathode of D3 is connected with the anode of D4; the negative electrode of the D4 is connected with the positive electrode of the D5; the negative electrode of D5 is connected to the reference ground terminal VS.
The specific working principle of the bias circuit 10001 is as follows: the bias circuit 10001 generates a bias voltage to provide the bias voltage for the other PMOS transistors used as the current mirror. When the system is powered on, VGS =0 of M1, and M1 is not conducted. In practice, although M1 has no on condition, it has reverse leakage current, which is small and can charge capacitor C4, where M1 can be regarded as a current source with small current. The size of the current I1 can be adjusted by adjusting the width and the length of the M1, and the voltage of the upper plate of the C4 is finally stabilized by setting the resistance value of R4. After power-on, I1 starts to charge C4, the voltage of C4 rises, VGS of M2 gradually rises, current flows between the source and the drain of M2, current flows from M3 to a reference ground end VS through M2 and R5, and a current mirror composed of M3, M5 and M6 starts to work. Because the circuit composed of M3, M4 and R5 and the circuit composed of M5, M6, Q1, Q2 and R6 provide bias mutually, the magnitude of the three currents of M3, M5 and M6 is related to the width-to-length ratio of each MOS transistor. In the embodiment of the invention, the width-length ratios of M3, M5 and M6 are consistent, so that I2= I3= I4. The ratio of the emitter areas of the Q1 and the Q2 is 1:2, the I4 size can be solved through a triode current formula, and the current size of each branch circuit can be further solved according to the proportion. The function of M1, M2, C4 and R4 is to provide a small starting current to help the starting of the reference current source composed of M3, M4, M5, M6, Q1, Q2, R5 and R6. The gate voltage of M2 after the system is stabilized can be determined by reasonably setting the value of R4, and in the bias circuit 10001 according to the embodiment of the present invention, VGS of M4 after the system is stabilized is greater than VGS of M2, so that most of I2 current flows into the GND terminal through M4 and R5. Thus, the devices M1, M2, C4 and R4 have no influence on subsequent circuits after the system is stabilized. Because the capacitors in the integrated circuit process are generally low-voltage devices, the functions of the D3, the D4 and the D5 are to filter burrs and prevent the C4 from being broken down due to overhigh voltage under extreme conditions to damage the chip.
Please refer to fig. 5 as a schematic circuit diagram of an overvoltage protection circuit 10002, in fig. 5, an overvoltage protection circuit 10002 is arranged inside a dashed-line frame, and an external component having a connection relationship with an internal component of the overvoltage protection circuit 10002 is arranged outside the dashed-line frame, where the external component is only a part of components in the starting and dimming circuit module, and the connection relationship is also only a connection relationship between the internal component of the overvoltage protection circuit 10002 and an external directly connected component, and connection relationships between other external components are omitted, so as to make fig. 5 simpler, and specific connection relationships between other parts can refer to fig. 3.
Specifically, the overvoltage protection circuit 10002 includes a PMOS transistor M7, a PMOS transistor M8, an NPN transistor Q3, a resistor R7, and a zener diode DZ 1; the source electrode of the M7 is connected with a power supply voltage terminal VCC, the grid electrode of the M7 is connected with the grid electrode of the M6, and the drain electrode of the M7 is connected with the cathode of the DZ 1; the source electrode of the M8 is connected with a power supply voltage terminal VCC, the grid electrode of the M8 is connected with the grid electrode of the M7, and the drain electrode of the M8 is connected with the collector electrode of the Q3; a collector of Q3 is used as an output end of an overvoltage protection control signal OVP, a base of Q3 is connected with the anode of DZ1, and an emitter is connected with a reference ground end VS; the first end of R7 is connected with the positive pole of DZ1, and the second end of R7 is connected with the reference ground end VS.
The working principle of the overvoltage protection circuit 10002 is as follows: the over-voltage protection circuit 10002 detects the voltage of the power supply terminal VCC, and when the voltage of the power supply terminal VCC is greater than VDZ1 (ignoring the voltage drop of M7), VDZ1 breaks down. If the voltage of the power supply voltage end VCC continues to rise by 0.7V, the voltage at the two ends of the voltage regulator tube VDZ1 is unchanged. At this time, the BE terminal voltage of Q3 is 0.7V, Q3 is turned on, and the over-voltage protection control signal OVP changes from high level to low level. The R7 resistance is typically large and acts as a pull-down resistor, shunting a small portion of the I5 current. The over-voltage protection control signal OVP turns off the power transistor NM1 by controlling the constant current control module 1004, so that the voltage VOUT at the output end of the system does not rise any more, and thus the voltage at the power supply voltage end VCC does not rise any more, thereby realizing the over-voltage protection function.
Referring to fig. 8, a simulation diagram of the overvoltage protection function of the overvoltage protection circuit 10002 according to the embodiment of the present invention is shown, in which fig. 8 sequentially shows a voltage waveform of a power voltage terminal VCC, a voltage waveform of an a point, and a waveform of an overvoltage protection control signal OVP at an output terminal of the overvoltage protection circuit 10002 from top to bottom. When the voltage of a power supply voltage end VCC is larger than a set value, the voltage of the point A is changed from low to high, the overvoltage protection control signal OVP is changed from high to low, and the overvoltage protection circuit has an overvoltage protection function. When the voltage at point a is low level, the waveform of the OVP front segment of the overvoltage protection control signal at this time changes more synchronously with the VCC voltage at the power supply voltage terminal, and also rises along a fixed slope.
Please refer to fig. 6 as a schematic circuit diagram of the undervoltage protection circuit, in fig. 6, an undervoltage protection circuit 10003 is arranged inside a dashed-line frame, and an external component having a connection relationship with an internal component of the undervoltage protection circuit 10003 is arranged outside the dashed-line frame, where the external component is only a part of components in the start and dimming circuit module, and the connection relationship is also only a connection relationship between the internal component of the undervoltage protection circuit 10003 and an external directly connected component, and a connection relationship between other external components is omitted, so as to make fig. 6 simpler, and a specific connection relationship between other parts can refer to fig. 3.
Specifically, the undervoltage protection circuit 10003 includes a PMOS transistor M9, a PMOS transistor M10, a PMOS transistor M11, a PMOS transistor M12, an NMOS transistor M13, a PMOS transistor M14, a PMOS transistor M15, an NMOS transistor M16, a PMOS transistor M17, a PMOS transistor M18, a PMOS transistor M19, a PMOS transistor M20, a PMOS transistor M21, an NMOS transistor M22, a PMOS transistor M23, an NMOS transistor M24, a PNP triode Q4, a PNP triode Q5, a resistor R8, a resistor R9, a zener diode DZ2, and a zener diode DZ 3; m9, M10, DZ2, DZ3, D6, D7 and R8 form an under-voltage detection circuit; m11, M12, M13, M14, M15, M16, M17, Q4 and Q5 form a comparator circuit; m18, M19, M20, M21, M22, M23, M24 and R9 form a rear-end output circuit; the source electrode of the M9 is connected with a power supply voltage terminal VCC, the grid electrode of the M9 is connected with the output end of the bias circuit, and the drain electrode of the M9 is connected with the cathode of the DZ 2; the source electrode of the M10 is connected with a power supply voltage end VCC, the grid electrode of the M10 is connected with the grid electrode of the M9, and the drain electrode of the M10 is connected with the cathode of the DZ 3; the positive electrode of DZ2 is connected with the positive electrode of D6; the positive electrode of DZ3 is connected with the first end of R8; a second end of the R8 is connected with a reference ground end VS; the negative electrode of the D6 is connected with the positive electrode of the D7; the negative electrode of the D7 is connected with the first end of the R8; the base electrode of Q4 is used as the positive phase input end of the comparator circuit and is connected with the positive electrode of DZ3, the emitter electrode of Q4 is connected with the drain electrode of M11, and the collector electrode of Q4 is connected with a reference ground end VS; the source electrode of M14 is connected with a power supply voltage end VCC, the grid electrode of M14 is connected with the grid electrode of M10, and the drain electrode of M14 is respectively connected with the source electrode of M11, the source electrode of M12, the source electrode of M15 and the source electrode of M17; the grid electrode of the M11 is connected with the drain electrode of the M11; the M12 gate is connected with the M11 gate; the drain electrode of the M12 is connected with the drain electrode of the M13; the grid electrode of M13 is respectively connected with the grid electrode of M16 and the drain electrode of M16, and the source electrode of M13 is connected with a reference ground terminal VS; the grid electrode of M15 is respectively connected with the grid electrode of M17 and the drain electrode of M17, and the drain electrode of M15 is connected with the drain electrode of M16; the source of the M16 is connected with a reference ground terminal VS; the drain electrode of the M17 is connected with the emitter electrode of the Q5; the base electrode of Q5 is used as the inverting input end of the comparator circuit and is connected with the drain electrode of M18, and the collector electrode of Q5 is connected with a reference ground end VS; the source electrode of the M18 is connected with a power supply voltage terminal VCC, and the grid electrode of the M18 is connected with the grid electrode of the M14; wherein a first terminal of R9 is connected with a base of Q5, and a second terminal of R9 is connected with a reference ground terminal VS; the source electrode of the M19 is connected with a power supply voltage terminal VCC, the grid electrode of the M19 is connected with the grid electrode of the M18, and the drain electrode of the M19 is connected with the source electrode of the M20; the grid electrode of M20 is connected with the drain electrode of M21, and the drain electrode of M20 is connected with the base electrode of Q5; the source electrode of the M21 is connected with a power supply voltage terminal VCC, the grid electrode of the M21 is connected with the grid electrode of the M19, and the drain electrode of the M21 is connected with the drain electrode of the M22; the grid electrode of M22 is connected with the drain electrode of M13, and the source electrode of M22 is connected with a reference ground terminal VS; the source electrode of the M23 is connected with a power supply voltage terminal VCC, the grid electrode of the M23 is connected with the grid electrode of the M21, and the drain electrode of the M23 is connected with the drain electrode of the M24; the drain of the M24 is used as the output end of the undervoltage protection circuit to output a first undervoltage protection control signal or a second undervoltage protection control signal, the grid of the M24 is connected with the drain of the M22, and the source of the M24 is connected with the reference ground end VS.
The operating principle of the undervoltage protection circuit 10003 is as follows: after power-on, the voltage of the power supply voltage terminal VCC gradually rises, at this time, the voltage of the power supply voltage terminal VCC is lower, the DZ2 and the DZ3 are not broken down, at this time, no current flows on the R8, the voltage at the point B is at a low level, that is, the input terminal of the Q4 is at a low level. At this time, I8 flows through R9 to generate a voltage drop, i.e., the level at point C is higher than the level at point B, and the output terminal D of the comparator circuit composed of M11, M12, M13, M14, M15, M16, M17, M18, Q4 and Q5 outputs a high level, so point E is low, M20 is turned on, and I9 flows into R9 through M20 to generate a voltage drop. The voltage at point C is (I8 + I9) × R9, R9 < R8 < 2R9 in the present invention, I6= I7= I8= I9. When the voltage of the chip power supply voltage terminal VCC continuously rises to VDZ3+ I7R 8 (ignoring M10 tube voltage drop), a voltage regulator tube VDZ3 is broken down, a current I7 flows through R8 to generate voltage drop, the voltage at the point B is I7R 8, the voltage at the point C is (I8 + I9) R9 because R9 is greater than R8 and less than 2R9, the voltage at the point B is still lower than the point C, the D level of the output end of the comparator circuit is unchanged, and the level at the point E is also unchanged. When the voltage of the power supply voltage terminal VCC continues to rise and reaches VDZ2+ VD6+ VD7+ (I7+ I6) × R8, VDZ2 breaks down, the current I6 flows to the resistor R8 to generate voltage drop, the voltage at the point B is (I6 + I7) × R8, the voltage at the point B is greater than the voltage at the point C, the output terminal D of the comparator circuit changes from high level to low level, the voltage at the point E changes from low level to high level, the M20 is turned off, only the voltage at the point I8 flows to the reference ground terminal VS through R9, and the voltage at the point C is I8 × R9. The first undervoltage protection setting threshold UVLO _ H in the embodiment of the present invention is VDZ2+ VD6+ VD7+ (I7+ I6) × R8. The second undervoltage protection setting threshold UVLO _ L is VDZ3+ I7 × R8. When the voltage of the power supply voltage end VCC is reduced to be smaller than the first undervoltage protection setting threshold UVLO _ H, DZ2 is recovered at the moment, only I7 flows through the resistor R8, the voltage at the point B is I7 × R8, the voltage at the point C is I8 × R9, because R9 is greater than R8 and less than 2R9, the voltage at the point B is higher than the voltage at the point C, the output of the comparator circuit is still low level, E keeps high level, and the output end of the undervoltage protection circuit keeps low level. When the voltage of the power supply voltage end VCC is reduced to be smaller than the second undervoltage protection setting threshold UVLO _ L, DZ3 is recovered, no current flows through the resistor R8, the voltage at the point B is zero, the voltage at the point C is I8 × R9, the voltage at the point B is lower than the voltage at the point C, the output end D of the comparator is changed from low level to high level, the voltage at the point E is changed from high level to low level, M20 is turned on again, the voltage at the point C is changed into (I8 + I9) R9, and the output end of the undervoltage protection circuit is changed from low level to high level. Thus, the undervoltage protection module circuit 10003 can realize that when the voltage VCC of the power supply terminal is greater than the first undervoltage protection setting threshold UVLO _ H, the output end of the undervoltage protection circuit outputs a low level to turn on the chip, when the voltage VCC of the power supply terminal is less than the second undervoltage protection setting threshold UVLO _ L, the output end of the undervoltage protection circuit outputs a high level to turn off the chip, and when the voltage VCC of the power supply terminal is between the first undervoltage protection setting threshold UVLO _ H and the second undervoltage protection setting threshold UVLO _ L, the last state is maintained.
Referring to fig. 9, which is a simulation diagram of the undervoltage protection function of the undervoltage protection circuit according to the embodiment of the present invention, fig. 9 sequentially shows a VCC voltage signal waveform of the power voltage terminal, a C-point voltage signal waveform, an E-point voltage signal waveform, and a signal waveform of the output terminal of the undervoltage protection circuit from top to bottom. When the voltage of a power supply voltage end VCC is larger than a first undervoltage protection setting threshold value UVLO _ H, a voltage signal at an E point changes from low to high, a signal at an output end of an undervoltage protection circuit changes from high to low, and a voltage signal at a C point drops to half of the maximum value. When the voltage of a power supply voltage end VCC is smaller than a first undervoltage protection setting threshold value UVLO _ H, a voltage signal of an E point and a signal of an output end of an undervoltage protection circuit are not changed; when the voltage of a power supply voltage end VCC is smaller than a second undervoltage protection setting threshold value UVLO _ L, the waveform of a voltage signal at the point E is changed from high to low, a signal at the output end of the undervoltage protection circuit is changed from low to high, and a voltage signal at the point C is restored to the maximum value; when the voltage of the power supply voltage end VCC is larger than the second undervoltage protection setting threshold value UVLO _ L again, the voltage signal of the point E and the signal of the output end of the undervoltage protection circuit are not changed.
Referring to fig. 7, a schematic circuit diagram of a light-adjusting circuit is shown, in which the light-adjusting circuit 10004 includes a PNP transistor Q6, an NPN transistor Q7, a PNP transistor Q8, a PNP transistor Q9, and a resistor R10; the emitter of Q6 is connected with a power supply voltage end VCC, the base of Q6 is respectively connected with the emitter of Q8 and the base of Q9, and the collector of Q6 is respectively connected with the collector of Q7 and the base of Q8; the base of the Q7 is used as a second input end of the dimming circuit and is connected with the reference power supply module to receive the chip internal reference voltage VREF, and the emitter of the Q7 is connected with the first end of the R10; a second end of the R10 is connected with a reference ground end VS; the collector of Q8 is connected with a reference ground terminal VS; the emitter of the Q9 is connected with a power supply voltage terminal VCC, and the collector of the Q9 is connected with the sampling terminal CS as the output end of the dimming circuit.
The specific working principle of the dimming circuit 10004 is as follows: after the chip internal reference voltage VREF is established, I10 and I11 are established. The I10, I11 size is related to the emitter area ratio of Q6, Q9, I10= I11 in the present embodiment. Wherein I10= (VREF-VBEQ 7)/R10. After the chip internal reference voltage VREF is established, I11 flows to the energy storage inductor L1 through R2 and R3, at this time, the sampling terminal CS samples voltage = I11 × R2+ (I11+ IOUT) × R3 ≈ I11 × R2+ IOUT ≈ R3 (I11 is far smaller than IOUT in practical application), I11 is a current with a constant average value output when the sampling terminal CS is used as a current output terminal of the dimming circuit, so in practical application, when the voltage value of the sampling voltage is a first dimming voltage threshold, the NMOS power tube externally connected to the signal output terminal of GATEDRIVE is controlled to be turned on; when the voltage value of the sampling voltage is the second dimming voltage threshold, controlling an external NMOS power tube of the GATEDRIVE signal output end to be turned off; the first dimming voltage threshold is a difference between a preset average voltage value of the sampling terminal CS and a preset voltage VX, and the second dimming voltage threshold is a sum of the sampling terminal CS and the preset voltage VX, so that the average current IOUT = (VCS-R2 × I11)/R3 of the system is obtained.
Fig. 10 is a simulation diagram of a dimming function of the dimming circuit according to the present invention, according to the formula IOUT = (CS-R2 × I11)/R3. In this embodiment, the sampling resistors R3=250m Ω, I11=100ua, the center value of the CS sampling voltage at the sampling end is set to be 0.2V, and the CS sampling voltage is respectively substituted into IOUT =600ma, IOUT =400ma, and IOUT =200ma to calculate corresponding R2 values to be 500 Ω, 1000 Ω, and 1500 Ω, and the calculated values are used to construct a simulation circuit to simulate three times to obtain the image in fig. 10, so that it can be seen that the average current of the LED can be stabilized at the set value.
In addition, it should be noted that the specific embodiments described in the present specification may differ in the shape of the components, the names of the components, and the like. All equivalent or simple changes of the structure, the characteristics and the principle of the invention which are described in the patent conception of the invention are included in the protection scope of the patent of the invention. Various modifications, additions and substitutions for the specific embodiments described may be made by those skilled in the art without departing from the scope of the invention as defined in the accompanying claims.

Claims (10)

1. A constant current control chip, comprising: the device comprises a starting and dimming circuit module, a reference power supply module, a driving module and a constant current control module; the starting and dimming circuit module, the reference power supply module, the driving module and the constant current control module use the voltage of a reference ground end VS as the internal reference voltage of the chip;
the starting and dimming circuit module detects the voltage of a power supply voltage end VCC, and when the voltage of the power supply voltage end VCC is increased from low to higher than a first undervoltage protection setting threshold UVLO _ H, a reference power supply module is started through a first undervoltage protection control signal so as to start a chip; when the voltage of a power supply voltage end VCC is reduced to be lower than a second undervoltage protection setting threshold UVLO _ L from high, a reference power supply module is closed through a second undervoltage protection control signal, and then a chip is closed; when the voltage of the power supply voltage end VCC is higher than the overvoltage protection set threshold value, the constant current control module is closed through the overvoltage protection control signal OVP, so that the voltage of the power supply voltage end VCC does not rise any more; the starting and dimming circuit module detects the sampling voltage of the sampling end CS, and controls GATEDRIVE the external NMOS power tube of the signal output end to be turned on or off according to the sampling voltage, thereby ensuring the average value of the output current of the sampling end CS to be constant;
the reference power supply module receives the voltage of a power supply voltage end VCC, and turns on or off a chip internal voltage stabilization source voltage VDD and a chip internal reference voltage VREF according to a corresponding undervoltage protection control signal output by the starting and dimming circuit module;
the constant current control module acquires a voltage VDD of a voltage stabilizing source inside a chip, a reference voltage VREF inside the chip and an overvoltage protection control signal OVP, and outputs a DRIVE control signal which is used as an input control signal of the driving module, and the overvoltage protection control signal OVP is used for closing the constant current control module;
the output end of the driving module is an GATEDRIVE signal output end, and the output signal of the GATEDRIVE signal output end is controlled by obtaining the voltage VDD of the voltage stabilizing source inside the chip and the DRIVE control signal of the constant current control module, so that the on and off of an NMOS power tube externally connected with the GATEDRIVE signal output end are controlled.
2. The constant current control chip according to claim 1, wherein the start-up and dimming circuit module comprises a bias circuit, an overvoltage protection circuit, an undervoltage protection circuit and a dimming circuit;
the output end of the overvoltage protection circuit outputs the overvoltage protection control signal OVP; when the voltage of the first input end of the overvoltage protection circuit is higher than the overvoltage protection set threshold value, the overvoltage protection control signal OVP is changed from a high level to a low level;
the input end of the under-voltage protection circuit is connected with a power supply voltage end VCC; when the voltage at the input end of the undervoltage protection circuit gradually rises and is lower than a second undervoltage protection setting threshold UVLO _ L, the output end of the undervoltage protection circuit outputs a high level; when the voltage at the input end of the undervoltage protection circuit continuously rises and is higher than a second undervoltage protection setting threshold value UVLO _ L and lower than a first undervoltage protection setting threshold value UVLO _ H, the output end of the undervoltage protection circuit keeps outputting a high level; when the voltage at the input end of the undervoltage protection circuit continues to rise to be higher than a first undervoltage protection setting threshold UVLO _ H, the output end of the undervoltage protection circuit is changed from a high level to a low level; when the voltage at the input end of the undervoltage protection circuit gradually drops and is higher than a second undervoltage protection setting threshold value UVLO _ L and lower than a first undervoltage protection setting threshold value UVLO _ H, the output end of the undervoltage protection circuit keeps a low level; when the voltage at the input end of the undervoltage protection circuit continuously drops to be lower than a second undervoltage protection setting threshold UVLO _ L, the output end of the undervoltage protection circuit is changed from a low level to a high level.
3. The constant current control chip according to claim 1 or 2, wherein the sampling terminal CS serves as both a feedback signal input terminal of the constant current control chip and a current output terminal of the dimming circuit;
sampling the sum of the voltage of the external dimming resistor and the voltage of the sampling resistor when the input end of the feedback signal is used;
the current output end of the dimming circuit outputs the current with constant average value.
4. The constant current control chip according to claim 2, wherein the bias circuit comprises a PMOS transistor M1, an NMOS transistor M2, a PMOS transistor M3, an NMOS transistor M4, a PMOS transistor M5, a PMOS transistor M6, an NPN transistor Q1, an NPN transistor Q2, a resistor R4, a resistor R5, a resistor R6, a capacitor C4, a capacitor C5, a diode D3, a diode D4, and a diode D5, a source of M1 is connected to a power supply voltage terminal VCC, a gate of M1 is connected to a source of M1, and a drain of M1 is connected to a gate of M2; the drain electrode of M2 is respectively connected with the drain electrode of M3 and the drain electrode of M4, and the source electrode of M2 is connected with the source electrode of M4; the source electrode of the M3 is connected with a power supply voltage terminal VCC, the grid electrode of the M3 is connected with the drain electrode of the M3, and the drain electrode of the M3 is connected with the grid electrode of the M5; the grid electrode of the M4 is respectively connected with the drain electrode of the M5 and the collector electrode of the Q1; the source electrode of the M5 is connected with a power supply voltage terminal VCC, and the grid electrode of the M5 is connected with the grid electrode of the M6; the source electrode of the M6 is connected with a power supply voltage terminal VCC; the base of Q1 is connected with the base of Q2, and the emitter of Q1 is respectively connected with the second ends of a reference ground terminal VS and R6; a collector of Q2 is connected with a drain of M6, and an emitter of Q2 is connected with a first end of R6; a first end of the C4 is connected with the grid of the M2, and a second end of the C4 is connected with a reference ground end VS; a first end of the C5 is connected with the grid of the M4, and a second end of the C5 is connected with a reference ground end VS; a first end of R4 is connected with the grid of M2, and a second end of R4 is connected with a reference ground end VS; a first end of R5 is connected with the source of M2, and a second end of R5 is connected with a reference ground end VS; the anode of D3 is connected with the drain of M1, and the cathode of D3 is connected with the anode of D4; the negative electrode of the D4 is connected with the positive electrode of the D5; the negative electrode of D5 is connected to the reference ground terminal VS.
5. The constant current control chip of claim 2, wherein the overvoltage protection circuit comprises a PMOS transistor M7, a PMOS transistor M8, an NPN transistor Q3, a resistor R7, and a zener diode DZ1, wherein a source of M7 is connected to a power supply voltage terminal VCC, a gate of M7 is connected to a gate of M6, and a drain of M7 is connected to a negative electrode of DZ 1; the source electrode of the M8 is connected with a power supply voltage terminal VCC, the grid electrode of the M8 is connected with the grid electrode of the M7, and the drain electrode of the M8 is connected with the collector electrode of the Q3; a collector of Q3 is used as an output end of an overvoltage protection control signal OVP, a base of Q3 is connected with the anode of DZ1, and an emitter is connected with a reference ground end VS; the first end of R7 is connected with the positive pole of DZ1, and the second end of R7 is connected with the reference ground end VS.
6. The constant current control chip of claim 2, wherein the under-voltage protection circuit comprises PMOS transistors M9, M10, M11, M12, M14, M15, M17, M18, M19, M20, M21, M23, NMOS transistors M13, M16, M22, M24, PNP triodes Q4, Q5, resistors R8, R9, zener diodes DZ2, DZ3, M9 sources, M10 sources, M14 sources, M18 sources, M19 sources, M21 sources, M23 sources are respectively connected to the power supply voltage terminal VCC, M9 gates are connected to the output terminal of the bias circuit, and M9 drains are connected to the negative terminal of DZ 2; the grid electrode of M10 is connected with the grid electrode of M9, the grid electrode of M14, the grid electrode of M18, the grid electrode of M19, the grid electrode of M21 and the grid electrode of M23, and the drain electrode of M10 is connected with the cathode of DZ 3; the positive electrode of DZ2 is connected with the positive electrode of D6; the positive electrode of DZ3 is connected with the first end of R8; the second end of R8, the second end of R9, the collector of Q4, the collector of Q5, the source of M13, the source of M16, the source of M22 and the source of M24 are respectively connected with a reference ground end VS; the negative electrode of the D6 is connected with the positive electrode of the D7; the negative electrode of the D7 is connected with the first end of the R8; the base of Q4 is connected with the positive electrode of DZ3, and the emitter of Q4 is connected with the drain of M11; the drain electrode of the M14 is respectively connected with the source electrode of M11, the source electrode of M12, the source electrode of M15 and the source electrode of M17; the grid electrode of the M11 is connected with the drain electrode of the M11; the M12 gate is connected with the M11 gate; the drain electrode of the M12 is connected with the drain electrode of the M13; the grid electrode of M13 is respectively connected with the grid electrode of M16 and the drain electrode of M16; the grid electrode of M15 is respectively connected with the grid electrode of M17 and the drain electrode of M17, and the drain electrode of M15 is connected with the drain electrode of M16; the drain electrode of the M17 is connected with the emitter electrode of the Q5; the base of Q5 is connected with the drain of M18; a first end of R9 is connected with a base of Q5; the drain electrode of the M19 is connected with the source electrode of the M20; the grid electrode of M20 is connected with the drain electrode of M21, and the drain electrode of M20 is connected with the base electrode of Q5; the drain electrode of the M21 is connected with the drain electrode of the M22; the grid electrode of the M22 is connected with the drain electrode of the M13; the drain electrode of the M23 is connected with the drain electrode of the M24; the grid electrode of M24 is connected with the drain electrode of M22, and the drain electrode of M24 is used as the output end of the undervoltage protection circuit.
7. The constant current control chip of claim 2, wherein the dimming circuit comprises a PNP transistor Q6, an NPN transistor Q7, a PNP transistor Q8, a PNP transistor Q9, a resistor R10; the emitter of Q6 is connected with a power supply voltage end VCC, the base of Q6 is respectively connected with the emitter of Q8 and the base of Q9, and the collector of Q6 is respectively connected with the collector of Q7 and the base of Q8; the base of the Q7 is used as a second input end of the dimming circuit and is connected with the reference power supply module to receive the chip internal reference voltage VREF, and the emitter of the Q7 is connected with the first end of the R10; a second end of the R10 is connected with a reference ground end VS; the collector of Q8 is connected with a reference ground terminal VS; the emitter of the Q9 is connected with a power supply voltage terminal VCC, and the collector of the Q9 is connected with the sampling terminal CS as the output end of the dimming circuit.
8. The constant current control chip according to claim 1, wherein when the voltage value of the sampling voltage is a first dimming voltage threshold, an NMOS power transistor externally connected to the signal output terminal of the control GATEDRIVE is turned on; when the voltage value of the sampling voltage is the second dimming voltage threshold, controlling an external NMOS power tube of the GATEDRIVE signal output end to be turned off; the first dimming voltage threshold is a difference between a preset average voltage value of the sampling terminal CS and a preset voltage VX, and the second dimming voltage threshold is a sum of the sampling terminal CS and the preset voltage VX.
9. A constant current control system is characterized by comprising a resistor R1, a dimming resistor R2, a sampling resistor R3, an NMOS power tube NM1, a filter capacitor C1, a power supply capacitor C2, a filter capacitor C3, an energy storage inductor L1, a Schottky diode D1, a Schottky diode D2 and a constant current control chip as claimed in any one of claims 1 to 8; the first end of the R1 is used as a system input end, and the second end of the R1 is connected with a power supply voltage end VCC of the constant current control chip; a first end of R2 is connected with a sampling end CS of the constant current control chip, and a second end of R2 is connected with a first end of R3; the second end of the R3 is connected with a reference ground end VS of the constant current control chip; the drain of the NM1 is connected with the first end of the R1, the grid of the NM1 is connected with the GATEDRIVE signal output end of the constant current control chip, and the source of the NM1 is connected with the second end of the R2; the first end of the C1 is connected with the positive pole of a DC power supply V1, and the second end of the C1 is connected with the GND end; a first end of the C2 is connected with a second end of the R1, and a second end of the C2 is connected with a reference ground end VS of the constant current control chip; a first end of C3 is connected with a second end of L1, and a second end of C3 is connected with a GND end; a first end of L1 is connected with a second end of R3, and a second end of L1 is connected with the anode of D2 as a system output end; the negative electrode of D2 is connected with the first end of C2; the anode of D1 is connected to GND terminal, and the cathode of D1 is connected to the source of NM 1.
10. An LED constant current drive circuit, which is characterized by comprising a power supply circuit, an LED circuit and the constant current control system as claimed in claim 9; and the system input end of the constant current control system is connected with the power circuit, and the system output end of the constant current control system is connected with the LED circuit.
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CN111954342A (en) * 2020-08-11 2020-11-17 深圳市必易微电子股份有限公司 Dimming control circuit, dimming control method and LED drive circuit
CN112512163A (en) * 2020-12-08 2021-03-16 四川力士达智慧照明科技有限公司 Output overvoltage protection control circuit and drive circuit

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CN113363941A (en) * 2021-07-16 2021-09-07 绍兴光大芯业微电子有限公司 Circuit structure for realizing overvoltage protection in hot plugging process of motor driving chip
CN113572355A (en) * 2021-09-26 2021-10-29 苏州贝克微电子有限公司 Power supply circuit with stable output voltage
CN113572355B (en) * 2021-09-26 2021-12-14 苏州贝克微电子有限公司 Power supply circuit with stable output voltage
CN114678830A (en) * 2022-04-20 2022-06-28 天长市富安电子有限公司 A low-power dimming circuit and its power supply method
CN114678830B (en) * 2022-04-20 2024-12-13 天长市富安电子有限公司 A low power consumption dimming circuit and power supply method thereof
CN116456537A (en) * 2023-04-28 2023-07-18 上海晶丰明源半导体股份有限公司 Interface control circuit, control method and interface control device
CN116456537B (en) * 2023-04-28 2024-02-02 上海晶丰明源半导体股份有限公司 Interface control circuit, control method and interface control device

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