WO2018028446A1

WO2018028446A1 - Integrated circuit, linear constant-current drive circuit, and control method therefor

Info

Publication number: WO2018028446A1
Application number: PCT/CN2017/094940
Authority: WO
Inventors: 邵蕴奇
Original assignee: 上海路傲电子科技有限公司
Priority date: 2016-08-12
Filing date: 2017-07-28
Publication date: 2018-02-15
Also published as: CN107454706A; CN107454706B

Abstract

An integrated circuit and a linear constant-current drive circuit. The linear constant-current drive circuit comprises a mains supply (VAC3), a rectifier bridge (DB3), an LED string (LED3), and an integrated circuit (U3). The integrated circuit is provided with three pins. The first pin (1) is a high-voltage end, the second end (2) is a ground, and the third pin (3) is a control end. An internal circuit comprises a controllable current source, an undervoltage detection circuit, and a power supply circuit. The power supply circuit obtains power from a high voltage end, and provides power and a signal reference to the integrated circuit. An input end of the rectifier bridge is connected to the mains supply, an output positive electrode is connected to an anode of an LED, an output negative electrode is grounded, and a cathode of the LED string is connected to the high voltage end. When a voltage of the mains supply is high, the increase of an input power is restricted; when the voltage of the mains supply is low, a current of the LED is decreased to restrict a current ripple of the LED; and when the voltage of the mains supply is normal, the current of the LED is kept constant.

Description

Integrated circuit and linear constant current driving circuit and control method thereof

Technical field

The present invention relates to an LED driving circuit and an implementation method of an integrated circuit, and more particularly to a linear constant current driving circuit and a control method thereof, and more particularly to a linear constant current driving scheme that can be implemented using a low cost dedicated integrated circuit.

Background technique

The current LED driving scheme is based on the traditional high-frequency switching power supply. This scheme uses high-frequency switching circuits, which are complicated in circuit and high in cost. Many manufacturers have begun to study simple, reliable and inexpensive linear constant current driving schemes.

1 is a linear constant current driving circuit currently used, comprising a mains VAC, a rectifier bridge DB, a storage capacitor C, an LED string, an integrated circuit U and a resistor Rs.

The input end of the rectifier bridge DB is connected to the mains VAC, the positive pole of the output terminal is connected to the anode of the LED string, the negative pole is grounded, and the storage capacitor C is connected in parallel at the output ends of the rectifier bridge to smooth the ripple of the rectified voltage; 3 feet: the first leg is the high voltage end, connected to the cathode of the LED string; the second leg is the current detecting end, grounded via the resistor Rs; the third leg is grounded.

The integrated circuit U1 internally includes a power supply circuit and a voltage controlled current source VCCS: the input end of the power supply circuit is connected to the high voltage end of the integrated circuit U, the output is the internal power supply of the integrated circuit and the voltage reference is provided; the voltage controlled current source VCCS includes two controls. And the two power terminals, the first control end is connected to the voltage reference Vref, the first power end is connected to the high voltage end of the integrated circuit U, and the second control end and the second power end are both connected to the current detecting end of the integrated circuit. The current setting value of the integrated circuit U is: I=Vref/Rs, and the current flowing through the LED string is also the same.

In this scheme, the highest voltage across the storage capacitor C is the peak of the commercial sine wave, the lowest The voltage is related to the current setting value of the integrated circuit U. That is to say, the highest voltage and the lowest voltage across the storage capacitor C change with the change of the mains, and the average voltage across the storage capacitor C also follows the mains. The change has changed, which brings two problems:

First, when the mains voltage rises, the average value of the voltage across the storage capacitor C rises, and the average value of the first pin of the integrated circuit U also rises, resulting in a decrease in the efficiency of the circuit and an increase in the power consumption of the integrated circuit U. Large, on the other hand, the decrease in efficiency when the mains voltage rises also causes the input power of the mains to increase as the mains voltage increases.

Secondly, when the mains voltage is lowered, the lowest voltage across the storage capacitor C and the voltage of the first leg of the integrated circuit U1 are also lowered. When the voltage of the first leg of the integrated circuit U drops sufficiently low, the integrated circuit U The current flowing up will no longer be constant. At this time, the current flowing through the LED string has a power frequency ripple, and the LED light will also flash at the power frequency.

Another disadvantage of this scheme is that the third leg of the integrated circuit directly flows through the LED current, so the microprocessor, potentiometer, etc. cannot directly control or adjust the current of the LED string, that is, it is inconvenient to use an external control signal pair. LED dimming.

In summary, there is a need for a linear constant current driving scheme that stabilizes input power when the mains voltage is high and suppresses LED current ripple when the mains voltage is low, and the linear constant current driving scheme facilitates control of external signals.

Summary of the invention

In view of the technical defects existing in the prior art, the present invention provides an integrated circuit, a linear constant current driving circuit and a control method thereof, and the specific technical solutions are as follows:

The present invention provides an integrated circuit for use in a linear constant current driving circuit having three legs. The first leg is a high voltage end, the second leg is a ground, and the third leg is a control end. The integrated circuit includes a controllable current source, an undervoltage detection circuit, and a power supply circuit. The power supply circuit takes power from the high voltage terminal to supply power to the integrated circuit. Provide a signal reference.

Preferably, the controllable current source has two power terminals and a current setting terminal, the first power terminal of the two power terminals is grounded, the second power terminal is connected to the high voltage terminal, and the current setting terminal is connected to the control terminal.

Preferably, the current at the second power terminal increases as the current at the current set terminal increases.

Preferably, the current at the second power terminal decreases as the voltage at the control terminal increases.

Preferably, the controllable current source comprises a signal reference and a voltage control current source, the voltage control current source comprises two signal terminals and two current terminals, wherein one signal terminal is connected to the signal reference and the other signal terminal is connected to the current device. Fixed, the two current terminals are respectively connected to the two power terminals of the controllable current source.

Preferably, the controllable current source comprises a signal reference and a current control current source, the current control current source comprises two signal terminals and two current terminals, wherein one signal terminal is connected to the signal reference and the other signal terminal is connected to the current device. Fixed, the two current terminals are respectively connected to the two power terminals of the controllable current source.

Preferably, the undervoltage detection circuit comprises an input end and an output end, the output end is connected to the control end, and further comprises a preset threshold for setting the undervoltage threshold of the mains, when the input signal is lower than the preset threshold The undervoltage detection circuit is in an action state, and the output terminal outputs a compensation current; when the input terminal signal is higher than the preset threshold, the undervoltage detection circuit is in a non-operating state, and the output terminal is in a high impedance state.

Preferably, the input end of the undervoltage detecting circuit detects the voltage of the high voltage terminal and flows through the high voltage end Any one or more of the current and the output voltage of the power supply circuit.

In addition, the present invention further provides a linear constant current driving circuit, including a mains, a rectifier bridge, an LED string and the above integrated circuit; the input end of the rectifier bridge is connected to the mains, the output positive pole is connected to the LED anode, and the output negative pole is grounded; The cathode of the LED string is connected to the high voltage end.

Preferably, the linear constant current driving circuit further comprises a setting resistor for setting the current of the LED string, and the two ends of the setting resistor are respectively connected to the control end and the ground.

Preferably, the linear constant current driving circuit further comprises a signal source for controlling the current of the LED string, and two ends of the signal source are respectively connected to the control terminal and the ground.

Preferably, the linear constant current driving circuit further comprises a filter capacitor connected in parallel at both ends of the set resistor.

Preferably, the linear constant current driving circuit further comprises a storage capacitor, one end of the storage capacitor is connected to the output positive pole of the rectifier bridge, and the other end is grounded.

Preferably, the linear constant current driving circuit further comprises an overvoltage detecting circuit; the input end of the overvoltage detecting circuit detects the voltage of one end of any one of the LED strings, and the output end of the overvoltage detecting circuit is connected to the control end.

Preferably, the current at the output of the overvoltage detection circuit increases as the mains increases.

Preferably, the overvoltage detection circuit further comprises a bias threshold for setting an overvoltage threshold of the mains. When the mains voltage is lower than the overvoltage threshold, the bias threshold is cut off, and the output of the overvoltage detection circuit has no current. Output; when the mains voltage exceeds the overvoltage threshold, the bias threshold is turned on, and the current at the output of the overvoltage detection circuit increases as the mains voltage increases.

Preferably, the bias threshold is a diode.

The invention also provides a linear constant current driving circuit, comprising a mains, a rectifier bridge, an LED string and an integrated circuit, an overvoltage detection circuit, a set resistor, a filter capacitor and a storage capacitor; the input end of the rectifier bridge is connected to the mains The output positive pole is connected to the LED anode, the output negative pole is grounded; the cathode of the LED string is connected to the high voltage end; the storage capacitor is connected in parallel at the output positive and negative ends of the rectifier bridge; one end of the set resistor is connected to the control end, and the other end is grounded; One end of the filter capacitor is connected to the control end, and the other end is grounded; the input end of the overvoltage detection circuit detects the voltage of one end of any one of the LED strings, and the output end of the overvoltage detection circuit is connected to the control end; the overvoltage detection circuit includes a The bias threshold is used to set the overvoltage threshold of the mains. When the mains voltage is lower than the overvoltage threshold, the bias threshold is cut off, and the output of the overvoltage detection circuit has no current output; when the mains voltage exceeds the overvoltage gate In a limited time, the bias threshold is turned on, and the current at the output of the overvoltage detection circuit increases as the mains voltage increases.

Preferably, when the mains voltage is lower than the undervoltage threshold, the linear constant current driving circuit controls the current of the LED to decrease as the mains voltage decreases; conversely, the linear constant current driving circuit controls the current of the LED to be constant.

Preferably, when the mains voltage is higher than the undervoltage threshold, the linear constant current driving circuit controls the current of the LED to decrease as the mains voltage increases.

Preferably, when the mains voltage is higher than the overvoltage threshold, the linear constant current driving circuit controls the current of the LED to decrease as the mains voltage increases; when the mains voltage is between the overvoltage threshold and the undervoltage threshold, the linearity The constant current drive circuit controls the current of the LED to be constant.

The present invention provides an integrated circuit and a linear constant current driving circuit having the following advantages:

1) When the mains voltage changes, the change in input power is small.

2) When the mains voltage changes, the current ripple of the LED is small.

3) When the mains voltage is high, the input power is inhibited from increasing; when the mains voltage is low, the LED current is reduced to suppress the current ripple of the LED; and the LED current is kept constant when the mains voltage is normal.

4) The external signal can be used to adjust the current of the LED to achieve dimming of the LED.

5) The above functions can be implemented using an integrated circuit in a 3-pin package outline.

DRAWINGS

Figure 1 shows a linear constant current drive circuit currently in use.

2 is a circuit diagram of a linear constant current driving circuit of the first embodiment.

3 is a circuit diagram of a linear constant current driving circuit of the second embodiment.

4 is a circuit diagram of a linear constant current driving circuit of the third embodiment.

Fig. 5 is a circuit diagram of a linear constant current driving circuit of the fourth embodiment.

detailed description

The present invention will be further described below in conjunction with the drawings and specific embodiments.

Embodiment 1

As shown in FIG. 2, the linear constant current driving circuit includes: a mains VAC1, a rectifier bridge DB1, a storage capacitor CE1, an LED string LED1, a set resistor RS1, a filter capacitor CF1, and an integrated circuit U1.

The input end of the rectifier bridge DB1 is connected to the mains VAC1, the output positive pole is connected to the anode of the LED string LED1, and the output negative pole is grounded.

The storage capacitor CE1 is connected in parallel across the output of the rectifier bridge to smooth the output voltage of the rectifier bridge DB1.

The integrated circuit U1 has three legs, the first leg 1 is a high voltage end and is connected to the cathode of the LED string; the second leg 2 is a ground end and is connected to the ground; the third leg 3 is a control end, and is grounded via a set resistor RS1. The filter capacitor CF1 is connected in parallel at both ends of the RS1.

The integrated circuit internal circuit includes a controllable current source, an undervoltage detection circuit, and a power supply circuit.

The power supply circuit draws power from the high voltage terminal 1 to supply power to the integrated circuit and provide a signal reference.

The controllable current source comprises two power terminals and a current setting terminal, the first power terminal of the two power terminals is grounded, the second power terminal is connected to the high voltage terminal 1, the current setting terminal is connected to the control terminal 3, and the second The current at the power terminal increases as the current at the current set terminal increases, or the current at the second power terminal decreases as the voltage at the control terminal increases.

The undervoltage detection circuit has an input end and an output end, and the output end is connected to the control end, and the undervoltage detection circuit further includes a preset threshold for setting the undervoltage threshold of the mains, when the input signal is lower than the pre- When the threshold is set, the undervoltage detection circuit is in an operating state, and outputs a compensation current to the control terminal 3. When the input signal is higher than the preset threshold, the undervoltage detection circuit is in a non-operating state, and the output terminal is in a high impedance state.

As indicated by the broken line in Fig. 2, the input terminal of the undervoltage detecting circuit detects any one or more of the output voltage of the power supply circuit, the voltage of the high voltage terminal, and the current flowing through the high voltage terminal.

The working principle of the linear constant current driving circuit shown in Fig. 2 will be described below:

When the mains VAC1 is in the normal voltage range, the lowest voltage across the storage capacitor CE1 can still provide sufficient voltage for the integrated circuit U1 after overcoming the voltage drop of the LED string LED1, thus flowing through the LED string LED1 and the integrated circuit U1. The current is constant. Under this condition, the undervoltage detection circuit is in a non-operating state, and its output does not affect the signal of the control terminal of the integrated circuit U1. No. The signal of the U1 control terminal is determined by the setting resistor RS1. Therefore, the resistance of the setting resistor RS1 sets the current of the LED string LED1.

If the VAC1 voltage of the mains gradually decreases, the lowest voltage across the storage capacitor CE1 will gradually decrease. After overcoming the voltage drop of the LED string LED1, the voltage at the high voltage end of the integrated circuit U1 also gradually decreases, when the output voltage of the power supply circuit and the high voltage end When one or more of the voltage and the current flowing through the high voltage terminal are lower than the preset threshold, the utility power is lower than the undervoltage threshold, the undervoltage detection circuit is in an operating state, and a compensation current is output to the control terminal, and filtered by the filter capacitor CF1. The voltage at the control terminal rises, and the current flowing through the current setting terminal decreases. Therefore, the current flowing through the LED string LED1 and the integrated circuit U1 also begins to decrease. This process causes the output voltage of the power supply circuit in the integrated circuit U1, the voltage at the high voltage terminal, and The lower limit of one or more parameters of the current flowing through the high voltage terminal is controlled. As a result, when the commercial power is lower than the undervoltage threshold, the current flowing through the LED string LED1 also follows with the gradual decrease of the commercial VAC1 voltage. In addition, due to the filtering effect of the filter capacitor CF1, the voltage ripple of the control terminal is small, so that the current ripple flowing through the LED string LED1 is also small.

In this embodiment, when the mains voltage is lower than the undervoltage threshold, the current of the linear constant current driving circuit controlling the LED decreases as the mains voltage decreases, and the current ripple of the LED is suppressed; otherwise, the linear constant current driving The circuit controls the LED current to be constant.

Embodiment 2

As shown in FIG. 3, in the second embodiment, based on all the functions of the linear constant current driving circuit in the first embodiment, the signal source S2 is added.

In this embodiment, the linear constant current driving circuit includes: a mains VAC2, a rectifier bridge DB2, a storage capacitor CE2, an LED string LED2, a set resistor RS2, a filter capacitor CF2, an integrated circuit U2, and a signal source S2. The signal source S2 is connected in parallel at both ends of the set resistor RS2. The connection mode and working principle of other components are the same as those in the first embodiment, and will not be described again.

When the output signal amplitude of the signal source S2 is changed, the control terminal voltage of the integrated circuit U2 and the current signal flowing through the current setting terminal are changed accordingly, and the current flowing through the LED string LED2 and the integrated circuit U2 also changes.

In this embodiment, the dimming control of the LED can be realized by controlling the output signal of the signal source S2.

Embodiment 3

As shown in FIG. 4, on the basis of all the functions of the linear constant current driving circuit in the first embodiment, the overvoltage detecting circuit OVD3 is added to detect the voltage of one end of any one of the LED strings LED3.

In this embodiment, the linear constant current driving circuit includes: a mains VAC3, a rectifier bridge DB3, a storage capacitor CE3, an LED string LED3, a set resistor RS3, a filter capacitor CF3, an integrated circuit U3, and an overvoltage detection circuit OVD3. The output end of the overvoltage detection circuit is connected to the control terminal 3 of the integrated circuit U3. The connection mode and working principle of the other components are the same as those in the first embodiment, and will not be described again.

The inside of the overvoltage detecting circuit OVD3 includes at least one resistor, and the current at the output of the overvoltage detecting circuit OVD3 increases as the voltage of the commercial VAC3 increases. When the overvoltage detection circuit OVD3 When the current at the output of the output increases, the voltage at the control terminal of the integrated circuit U3 rises, the current signal flowing through the current setting terminal decreases, and the current flowing through the LED string LED3 and the integrated circuit U3 also decreases; vice versa.

Due to the filtering effect of the filter capacitor CF3, the voltage ripple of the control terminal is small, so that the current ripple flowing through the LED string LED3 is not affected by the storage capacitor voltage ripple.

The overvoltage detection circuit realizes that when the mains voltage is higher than the undervoltage threshold, the current of the LED decreases as the mains voltage increases.

The overvoltage detection circuit 0VD3 may also include an offset threshold for setting the overvoltage threshold of the mains VAC3. When the mains VAC3 voltage is lower than the overvoltage threshold, the bias threshold is cut off, and the output of the overvoltage detection circuit 0VD3 There is no current output at the terminal, the overvoltage detection circuit 0VD3 does not work; when the commercial VAC3 voltage exceeds the overvoltage threshold, the bias threshold is turned on, and the current at the output of the overvoltage detection circuit 0VD3 increases with the increase of the commercial VAC3 voltage. . When the current at the output of the overvoltage detecting circuit 0VD3 increases, the voltage of the control terminal of the integrated circuit U3 rises, the current signal flowing through the current setting terminal decreases, and the current flowing through the LED string LED3 and the integrated circuit U3 also decreases. ;vice versa.

The overvoltage detection circuit realizes that when the mains voltage is higher than the overvoltage threshold, the current of the LED decreases as the mains voltage increases; when the mains voltage does not exceed the overvoltage threshold, the current of the LED is not detected by the overvoltage. Circuit influence.

This embodiment can achieve two different positive effects:

1. When the mains voltage is higher than the undervoltage threshold, the current of the LED decreases with the increase of the mains voltage, which compensates for the change of the input power; conversely, the current of the LED decreases with the decrease of the mains voltage, and the suppression The current ripple of the LED.

2. When the mains voltage is higher than the overvoltage threshold, the current of the LED decreases with the increase of the mains voltage, which compensates for the change of the input power; when the mains voltage is lower than the undervoltage threshold, the current of the LED follows The mains voltage is lowered and lowered, and the current ripple of the LED is suppressed; when the mains voltage is between the overvoltage threshold and the undervoltage threshold, the current of the LED is constant.

Embodiment 4

As shown in FIG. 5, the linear constant current driving circuit includes: mains VAC4, rectifier bridge DB4, storage capacitor CE4, LED string LED4, setting resistor RS4, filter capacitor CF4, integrated circuit U4, and overvoltage detection circuit OVD4.

The input end of the rectifier bridge DB4 is connected to the mains VAC4, the output positive pole is connected to the anode of the LED string LED4, and the output negative pole is grounded.

The storage capacitor CE4 is connected in parallel across the output of the rectifier bridge DB4 to smooth the output voltage of the rectifier bridge DB4.

The LED string LED4 is a combination of several LEDs in parallel.

The integrated circuit U4 has three legs, the first leg is a high voltage terminal 1 and is connected to the cathode of the LED string LED3; the second leg is a ground terminal 2, which is connected to the ground; the third leg 3 is a control terminal, which is grounded via a set resistor RS4. The filter capacitor CF4 is connected in parallel at both ends of the RS4.

The integrated circuit internal circuit includes a controllable current source CCS4, an undervoltage detection circuit UVD4, and a power supply circuit.

The controllable current source CCS4 has two power terminals and one current setting terminal. The first power terminal of the two power terminals is grounded, the second power terminal is connected to the high voltage terminal 1, and the current setting terminal is connected to the control terminal 3.

The controllable current source CCS4 internally includes a signal reference V2 and a current control current source. The current control current source includes two signal terminals and two control terminals, and the two control terminals are respectively connected to the signal reference V2 and the current setting terminal, and two The power terminals are respectively connected to two power terminals of the controllable current source CCS4.

The undervoltage detection circuit UVD4 internally includes a preset threshold V1, a first resistor R1, a second resistor R2, and a transistor Q1. The collector of the transistor Q1 serves as an output of the undervoltage detection circuit UVD4, and is connected to the control terminal 3 of the integrated circuit U3. The pole is connected to the preset threshold V1, and the base is connected to the input end of the undervoltage detecting circuit UVD4 via the first resistor R1. The input terminal detects the output voltage of the power supply circuit, and the second resistor R2 is connected to the base of the transistor Q1 at one end and grounded at the other end. .

The overvoltage detection circuit OVD4 includes an overvoltage detection resistor RC4 and a Zener diode VB4. One end of the overvoltage detection resistor RC4 is connected to the anode of the rectifier bridge DB4, the other end is connected to the cathode of the Zener diode VB4, and the anode of the Zener diode VB4 is connected. Go to the control terminal 3 of the integrated circuit U4.

When the mains VAC4 is in the normal voltage range, the output of the overvoltage detection circuit OVD4 and the undervoltage detection circuit UVD4 are in a high-impedance state, which has no influence on the control terminal of the integrated circuit U4, and the current of the controllable current source CCS4 is only set. The resistance of the resistor RS4 determines that the current of the LED string LED4 is a constant value, and the linear constant current driving circuit operates in a constant current mode; when the commercial VAC4 voltage is higher than When the overvoltage threshold set by the Zener diode VB4 is set, the Zener diode VB4 is turned on, and the commercial VAC4 injects current to the control terminal of the integrated circuit U4 via the overvoltage detecting resistor RC4 and the Zener diode VB4, and the linear constant current driving circuit operates. Overvoltage protection mode, the current of the LED string LED4 decreases with the increase of the commercial VAC4 voltage; when the commercial VAC4 voltage decreases, the lowest voltage across the storage capacitor CE4, the lowest voltage of the high-voltage terminal of the integrated circuit U4, and the power supply circuit The minimum output voltage is also reduced. When the output voltage of the power supply circuit is divided by the first resistor R1 and the second resistor R2 and is lower than the preset threshold V1, the transistor Q1 is turned on, and a compensation current is output to the control terminal, and the linear constant The flow drive circuit operates in an undervoltage protection mode, and the current of the LED string LED4 decreases as the mains VAC4 voltage decreases. Whether operating in the overvoltage protection mode or operating in the undervoltage protection mode, the filter capacitor CF4 ensures that the control terminal signal of the integrated circuit U4 has a lower ripple, which makes the linear constant current drive circuit of the present embodiment In any mode, the current on the LED string LED4 can be made to have a lower ripple.

The positive effects that this embodiment can achieve are:

When the mains voltage is higher than the overvoltage threshold, the current of the LED decreases as the mains voltage increases, compensating for the change of the input power; when the mains voltage is lower than the undervoltage threshold, the current of the LED follows the mains The voltage is lowered and lowered, and the current ripple of the LED is suppressed; when the commercial voltage is between the overvoltage threshold and the undervoltage threshold, the current of the LED is constant.

The above embodiments are intended to be illustrative and not to limit the scope of the invention, and various changes and modifications may be made without departing from the scope of the appended claims. . The word "comprising" or "comprises" or "a" or "an" In the claims, these circuits Several of them can be represented by one, and the electronic device items are the same, just because some methods are described in mutually different dependent claims, and it is not stated that the combination of these methods cannot be used for profit.

Claims

An integrated circuit for use in a linear constant current driving circuit, characterized in that: having three legs, a first leg is a high voltage terminal, a second leg is a ground, and a third leg is a control terminal, and the integrated circuit includes a controllable A current source, an undervoltage detection circuit, and a power supply circuit, the power supply circuit takes power from the high voltage terminal to supply power to the integrated circuit and provide a signal reference.
The integrated circuit of claim 1 wherein said controllable current source has two power terminals and a current setting terminal, wherein said first power terminal of said two power terminals is grounded, said second power terminal Connected to the high voltage terminal, the current setting terminal is connected to the control terminal.
The integrated circuit of claim 2 wherein the current at said second power terminal increases as the current at said current set terminal increases.
The integrated circuit of claim 2 wherein the current at said second power terminal decreases as the voltage at said control terminal increases.
The integrated circuit of claim 2 wherein said controllable current source comprises a signal reference and a voltage controlled current source, said voltage controlled current source comprising two signal terminals and two current terminals, one of The signal terminal is coupled to the signal reference and the other signal terminal is coupled to a current setting terminal, the two current terminals being coupled to two power terminals of the controllable current source, respectively.
The integrated circuit of claim 2 wherein said controllable current source comprises a signal reference and a current control current source, said current control current source comprising two signal terminals and two current terminals, one of The signal terminal is coupled to the signal reference and the other signal terminal is coupled to a current setting terminal, the two current terminals being coupled to two power terminals of the controllable current source, respectively.
The integrated circuit according to claim 1, wherein the undervoltage detecting circuit comprises an input end and an output end, the output end is connected to the control end, and further comprises a preset threshold for setting the mains The undervoltage threshold, when the input signal is lower than the preset threshold, the undervoltage detection circuit is in an action state, and the output terminal outputs a compensation current; when the input signal is higher than the preset threshold, the The undervoltage detection circuit is in a non-operating state, and the output terminal is in a high impedance state.
The integrated circuit according to claim 7, wherein said input terminal of said undervoltage detecting circuit detects any one of a voltage of said high voltage terminal, a current flowing through said high voltage terminal, and an output voltage of said power supply circuit or Multiple.
A linear constant current driving circuit, comprising: a mains, a rectifier bridge, an LED string, and an integrated circuit according to any one of claims 1 to 8;

The input end of the rectifier bridge is connected to the mains, the output positive pole is connected to the LED anode, and the output negative pole is grounded; the cathode of the LED string is connected to the high voltage end.
The linear constant current driving circuit according to claim 9, further comprising: a setting resistor for setting a current of the LED string, wherein two ends of the setting resistor are respectively connected to the control terminal and Ground.
The linear constant current driving circuit according to claim 9, further comprising a signal source for controlling current of said LED string, wherein two ends of said signal source are respectively connected to said control terminal and ground.
The linear constant current driving circuit according to claim 9, further comprising a filter capacitor connected in parallel at both ends of said set resistor.
The linear constant current driving circuit according to claim 9, further comprising a storage capacitor, one end of the storage capacitor is connected to the output positive pole of the rectifier bridge, and the other end is grounded.
The linear constant current driving circuit according to claim 9, further comprising: an overvoltage detecting circuit; wherein an input end of said overvoltage detecting circuit detects a voltage of one end of any one of said LED strings, said An output of the overvoltage detecting circuit is connected to the control terminal.
The linear constant current driving circuit according to claim 14, wherein the current at the output terminal of said overvoltage detecting circuit increases as the commercial power increases.
The linear constant current driving circuit according to claim 14, wherein said overvoltage detecting circuit further comprises a bias threshold for setting an overvoltage threshold of the mains, when the mains voltage is lower than said When the threshold is limited, the bias threshold is cut off, and the output of the overvoltage detection circuit has no current output; when the mains voltage exceeds the overvoltage threshold, the bias threshold is turned on, and the current of the output of the overvoltage detection circuit It increases as the mains voltage increases.
The linear constant current driving circuit according to claim 16, wherein the bias threshold is a diode.
A linear constant current driving circuit, comprising: a mains, a rectifier bridge, an LED string and the integrated circuit according to claim 7, an overvoltage detecting circuit, a setting resistor, a filter capacitor and a storage capacitor;

The input end of the rectifier bridge is connected to the mains, the output positive pole is connected to the LED anode, and the output negative pole is grounded; the cathode of the LED string is connected to the high voltage end;

The energy storage capacitor is connected in parallel at the output positive and negative ends of the rectifier bridge;

One end of the set resistor is connected to the control end, and the other end is grounded;

One end of the filter capacitor is connected to the control end, and the other end is grounded;

The input end of the overvoltage detecting circuit detects the voltage of one end of any one of the LED strings, and the output end of the overvoltage detecting circuit is connected to the control end;

The overvoltage detection circuit includes a bias threshold for setting an overvoltage threshold of the mains. When the mains voltage is lower than the overvoltage threshold, the bias threshold is cut off, and the overvoltage detection circuit The output has no current output; when the mains voltage exceeds the overvoltage threshold, the bias threshold is turned on, and the current at the output of the overvoltage detection circuit increases as the mains voltage increases.
A control method using the linear constant current driving circuit of claim 18, wherein when the mains voltage is lower than the undervoltage threshold, the linear constant current driving circuit controls the current of the LED along with the city The electric constant voltage is lowered to decrease; conversely, the linear constant current driving circuit controls the current of the LED to be constant.
The control method of the linear constant current driving circuit according to claim 18, wherein when the mains voltage is higher than the undervoltage threshold, the linear constant current driving circuit controls the current of the LED along with the mains voltage. The increase is lowered.
The control method of the linear constant current driving circuit according to claim 18, wherein when the mains voltage is higher than the overvoltage threshold, the linear constant current driving circuit controls the current of the LED along with the mains voltage Increasing and decreasing; when the mains voltage is between the overvoltage threshold and the undervoltage threshold, the linear constant current driving circuit controls the current of the LED to be constant.