CN103906314A - LED drive circuit and method based on voltage memory and segmented current limiting - Google Patents

Abstract

The invention discloses an LED drive circuit and method based on voltage memory and segmented current limiting. The circuit comprises a rectifying circuit, a voltage division circuit, a voltage increasing and reducing detection module, a voltage memory module, a comparator set, a control logic module, a high-voltage switch circuit, a detection resistor, a current detection comparator and an LED lamp string. According to the drive method of the circuit, according to the increasing and reducing characteristics of the directly-rectified direct-current ripple voltages, the segmented type lightening control mode is adopted in the load of the LED lamp string. The drive circuit solves the problem of the influence of the difference of voltage current characteristics of an LED chip adopted by the lamp string in the actual application on drive currents, the work current of the LED lamp string in the whole work period is limited within the designed largest current value Imax, the problems of lower brightness caused by undercurrents and damage, caused by overcurrents, to the LED chip are solved, the light-emitting efficiency of the LED lamp is improved, and meanwhile overcurrent protection can be carried out on an LED device well.

Description

LED driving circuit and method based on voltage memory and segmental current limiting

technical field

The present invention relates to an LED drive circuit and method, in particular to an LED drive circuit and method that utilizes DC pulsating voltage directly rectified by AC mains for power supply, uses voltage memory and section current limiting, and belongs to the technical field of LED drive .

Background technique

The LED lighting drive circuit is the power supply circuit required to enable the lighting equipment using LEDs as light-emitting devices to work normally, and can provide the required voltage and current for the normal operation of the LED device. The structural frame of the LED lighting drive circuit is shown in Figure 1, which is mainly composed of a rectifier circuit, an auxiliary power supply circuit, a power conversion circuit and a feedback loop. The input AC power is transformed into DC high voltage by the rectifier circuit, and the DC high voltage is generated by the auxiliary power supply circuit to generate a stable DC low voltage for power conversion circuit. The power conversion circuit converts the DC high voltage into the voltage and current required for the LED device to work, and the feedback loop The working state of the LED is detected, and the working voltage and current of the LED device are stabilized at the design point through feedback control.

At present, because LEDs have higher energy-saving efficiency than traditional light sources, their applications are becoming more and more extensive, and the driving power structures used in various LED lighting products are also becoming more and more abundant. The existing LED segmented power supply is shown in Figure 2, and its working process is as follows: When the output voltage of the rectifier circuit is lower than U1, the NMOS tubes Q1, Q2, Q3, and Q4 are turned on, and the L1 segment LED works; the output of the rectifier circuit When the voltage is higher than U1 and lower than U2, the NMOS transistor Q1 is turned off, Q2, Q3, and Q4 are turned on, and the L1 and L2 segment LEDs work; when the output voltage of the rectifier circuit is higher than U2 and lower than U3, the NMOS transistor Q1 and Q2 are turned off. Q3 and Q4 are turned on, L1, L2, and L3 segment LEDs work; when the rectifier circuit output voltage is higher than U3 and lower than U4, NMOS tubes Q1, Q2, Q3 are turned off, Q4 is turned on, L1, L2, L3, L4 segment LEDs Work; when the output voltage of the rectifier circuit is higher than U4, the NMOS transistors Q1, Q2, Q3, and Q4 are turned off, and the LEDs of L1, L2, L3, and L4 do not work.

The segmented LED drive circuit described above does not require electrolytic capacitors for voltage energy storage, the power factor is high, and the life of the entire lamp will not be limited by capacitors. However, this driving method also has shortcomings, which can be seen from the volt-ampere characteristics of LED devices. Under its normal working voltage condition, small differences in voltage will lead to obvious fluctuations in current, and the light intensity of LED is mainly related to the current flowing through LED; in practical applications, even if the LED chips produced by the same manufacturer in the same batch, There will also be differences in the volt-ampere characteristic curve, so the segmented driving method based on the fixed voltage division ratio, due to the reference voltage accuracy used for comparison and the difference in the volt-ampere characteristic of the LED chip, the working current of the LED in the light string cannot be determined. Accurate prediction and design, under-current or over-current driving status. Undercurrent will cause the brightness of the light string to be dim, while overcurrent will cause damage to the LED chip.

Contents of the invention

The object of the present invention is to solve the above-mentioned defects of the prior art, and provide an LED drive circuit based on voltage memory and segmental current limiting, which is simple in structure and easy to use, and does not require inductive devices or electrolytic capacitors.

Another object of the present invention is to provide a driving method for an LED driving circuit based on voltage memory and segmental current limiting.

The purpose of the present invention can be achieved by taking the following technical solutions:

LED drive circuit based on voltage memory and segmental current limiting, including a rectifier circuit, a voltage divider circuit, a comparator group, a high-voltage switch circuit and an LED light string, the rectifier circuit is connected to the voltage divider circuit, and the high-voltage switch circuit is connected to the LED The lamp string is connected, the LED lamp string is connected with the rectifier circuit, and it is characterized in that: it also includes a voltage rise and fall detection module, a voltage memory module, a control logic module, a current detection resistor and a current detection comparator, the voltage memory module, the comparator The device group, the control logic module, the high-voltage switch circuit and the LED light string are connected in sequence; the voltage divider circuit is respectively connected with the voltage rise and fall detection module and the voltage memory module, and the voltage rise and fall detection module is respectively connected with the voltage memory module and the control logic The module is connected, the control logic module is connected with the voltage memory module; the high-voltage switch circuit is connected to the common ground terminal of the power supply through the current-sensing resistor, and one input terminal of the current-sensing comparator is connected to the common terminal of the current-sensing resistor and the high-voltage switch circuit connection point, the other input terminal is connected to the reference voltage, and the output terminal of the current detection comparator is connected to the control logic module.

Preferably, the voltage memory module is composed of a plurality of voltage holders, and the output terminal of each voltage holder is respectively connected to a comparator group.

Preferably, each voltage holder is composed of a capacitor and an operational amplifier.

Preferably, the comparator group is composed of a plurality of voltage comparators, one input terminal of each voltage comparator is connected to the output terminal of each voltage holder in one-to-one correspondence, and the other input terminals are connected together. It is connected with the voltage dividing circuit, and the output terminal of each voltage comparator is respectively connected with the control logic module.

Preferably, the control logic module is composed of multiple D flip-flops and combined digital logic required to complete the function, and the control logic module uses the output of each voltage comparator in the comparator group and the output of the voltage rise and fall detection module and the output of the current-sense comparator as the input signal.

Preferably, the voltage rise and fall detection module is composed of a differential unit circuit and a voltage comparator, and outputs a square wave signal indicating the rise and fall state of the DC pulsating voltage.

Preferably, the high-voltage switch circuit is composed of a plurality of high-voltage NMOS transistors, and the storage state of each D flip-flop corresponds to the switching state of each high-voltage NMOS transistor; the source phase of each high-voltage NMOS transistor After being connected together, it is connected to the common ground terminal of the power supply through the current detection resistor. One input terminal of the current detection comparator is connected to the common connection point between the current detection resistor and the source of each high-voltage NMOS transistor, and the other input terminal is connected to the reference voltage. ; The drain of each high-voltage NMOS tube is connected to the LED light string.

Preferably, the LED lamp string is composed of a plurality of LED lamp segments connected in series, and the number of the LED lamp segments is consistent with the number of high-voltage NMOS tubes.

Another object of the present invention can be achieved by taking the following technical solutions:

The driving method of the LED driving circuit based on voltage memory and subsection current limiting is characterized in that it comprises the following steps:

1) After the AC mains is rectified by the rectifier circuit, it outputs high-voltage DC pulsating voltage;

2) The voltage dividing circuit divides the high-voltage DC pulsating voltage rectified by the rectifying circuit according to a certain ratio, and outputs the low-voltage DC pulsating voltage;

3) The voltage rise and fall detection module converts the divided low-voltage DC pulsating voltage into a square wave signal used to indicate the rising process and falling process of the low-voltage DC pulsating voltage;

4) During the rising process of the low-voltage DC pulsating voltage, when the voltage is at the valley value, each high-voltage NMOS tube is in the conduction state. At this time, only the LED lamp segment directly connected to the high-voltage DC pulsating voltage is connected to the effective drive output port , when the voltage rises to make the driving current of the LED lamp section reach the current limit value, the voltage drop on the current detection resistor is higher than the reference voltage, the output voltage of the current detection comparator is over-current reversed, and the control logic module detects the signal reverse , so that the high-voltage NMOS tube connected to the negative pole of the LED lamp segment is turned off, and the next LED lamp segment connected to the LED lamp segment is connected to the effective drive output port together, and the current on the LED lamp string returns below the current limit value , the output voltage of the current detection comparator returns to before the overcurrent reversal occurs; according to this rule, every time the current limit value is reached, the high-voltage NMOS tube connected to the negative pole of the part of the LED light string that has been connected is turned off, so that the The number of LED lamp segments connected to the effective drive output port gradually increases; when all LED lamp segments are connected, the rise of the high-voltage DC pulsating voltage makes the current reach the current limit again, and all high-voltage NMOS in the high-voltage switch circuit are turned off tube, disconnect all the LED lamp segments in the LED light string from the power supply, the control process during the rising process of the DC pulsating voltage is called the forward control process; in the forward control process, the voltage memory module sequentially records the LED The voltage instantaneous value of the low-voltage DC pulsating voltage every time the working current of the light string reaches the current limit value;

5) During the falling process of the low-voltage DC pulsating voltage, the voltage value memorized by the voltage memory module remains unchanged, and is input to the comparator group for comparison processing. The square wave sequence output by the comparator group reversely reproduces the LED during the voltage rising process. Every time the light string reaches the current limit value, each control node; at each control node, the output state of the comparator group will change, and the control logic module will detect this state change, and then reverse and gradually restore each closed state in the high-voltage switch circuit. In the process of reverse symmetric control, if all the high-voltage NMOS tubes in the high-voltage switch circuit are turned off at the peak point of the high-voltage DC pulsating voltage In the off state, when the high-voltage DC pulsating voltage drops through the first control node, the control logic module restores the high-voltage NMOS tube that was turned off in the forward control process to the conduction state, and all LED lamp segments in the LED light string are connected Effectively drive the output port; when the high-voltage DC pulsating voltage drops and passes through the second control node, the control logic module restores the conduction state of the penultimate high-voltage NMOS tube that was turned off during the forward control process, so that the LED lights in the string are turned off The number of LED lamp segments connected to the effective drive output port is reduced by one segment; according to this rule, when the high-voltage DC pulsating voltage drops and passes through one control node, the conduction state of one high-voltage NMOS tube that is turned off will be restored, so that the LED The number of LED lamp segments connected to the effective drive output port in the light string is gradually reduced until all high-voltage NMOS tubes are restored to the conduction state, and the number of LED lamp segments connected to the effective drive output port in the LED lamp string is 1 segment .

Preferably, the voltage rise and fall detection module in step 3) converts the divided low-voltage DC pulsating voltage into a square wave signal for indicating the rising process and falling process of the low-voltage DC pulsating voltage, specifically:

The voltage rise and fall detection module converts the divided low-voltage DC pulsating voltage into a square wave signal with only two levels, high and low. The two different levels of the square wave signal indicate the rising process and falling process of the low-voltage DC pulsating voltage respectively. Among them, the high level indicates the rising process, and the low level indicates the falling process, and the opposite direction of the original signal can be obtained by inverting the square wave signal.

Compared with the prior art, the present invention has the following beneficial effects:

The LED drive circuit based on voltage memory and segmental current limiting of the present invention adopts a segmented lighting control method for the LED lamp string load according to the rise and fall characteristics of the direct-current pulsating voltage after direct rectification, and solves the problem of the lamp string in practical applications. The difference in volt-ampere characteristics of the used LED chips affects the driving current, so that the working current of the LED light string in the entire working cycle is limited to the maximum current value Imax designed to avoid dimming and over-brightness caused by undercurrent. The problem of LED chip damage caused by current flow, while improving the luminous efficiency of LED lamps, it can better protect LED devices from overcurrent.

Description of drawings

Figure 1 is a structural diagram of the LED drive circuit.

Fig. 2 is a structural principle block diagram of an existing linear segmented LED driving circuit.

FIG. 3 is a block diagram of the structure and principle of the LED drive circuit based on voltage memory and segmental current limiting in the present invention.

FIG. 4 is a working waveform diagram of the driving method of the LED driving circuit based on voltage memory and segmental current limiting in the present invention.

Detailed ways

Example 1:

The present invention will be described in further detail below in conjunction with the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

As shown in Figure 3, the LED drive circuit based on voltage memory and segmental current limiting in this embodiment includes a rectifier circuit 1, a voltage divider circuit 2, a voltage rise and fall detection module 3, a voltage memory module 4, a comparator group 5, and a control logic Module 6, high-voltage switching circuit 7, current-sensing resistor 8 (Ris), current-sensing comparator 9 (Icomp) and LED light string 10; the voltage rise and fall detection module 3 is composed of a differential unit circuit and a voltage comparator; the The voltage memory module 4 is composed of 4 voltage holders, numbered from top to bottom as H1, H2, H3 and H4, and each voltage holder is composed of a capacitor and an operational amplifier; the comparator group 5 is composed of 4 Composed of voltage comparators, numbers are respectively Comp1, Comp2, Comp3 and Comp4 from top to bottom; the control logic module 6 is composed of 4 D flip-flops and combined digital logic required to complete the function; the high-voltage switch circuit 7 is composed of Composed of 4 high-voltage NMOS tubes, numbered from top to bottom are Q1, Q2, Q3 and Q4; the LED light string 10 is composed of 4 LED lamp segments, numbered from top to bottom are L1, L2, L3 and L4 ,in:

After the AC mains is rectified by the rectifier circuit 1, it outputs a periodic high-voltage DC pulsating voltage (referred to as HVDCP). The process of changing from the peak value to the valley value is a descending process;

The voltage divider circuit 2 linearly divides the HVDCP rectified by the rectifier circuit 1 according to a certain ratio to obtain a low-voltage DC pulsating voltage (referred to as LVDCP), which is used as a voltage rise and fall detection module 3, a voltage memory module 4 and a comparator group. 5 input signal, compared with the rectified HVDCP, the phase and period of the LVDCP are the same as it, and the voltage value is proportional to it;

The voltage rise and fall detection module 3 converts the LVDCP divided by the voltage divider circuit 2 into a square wave signal RFC with only two levels of high and low, and the two different levels of the square wave signal RFC indicate the rise and fall of the LVDCP respectively. Process, such as a high level indicates the rising process, and a low level indicates the falling process. After inverting the signal, the indication mode opposite to the original signal can be obtained; the circuit module that needs to use the RFC signal during work has a voltage memory module 4 and control logic module 6;

The voltage memory module 4 sequentially records the instantaneous value of the LVDCP when the driving current of the LED lamp string 10 reaches the current limit value each time during the rising process of the DC pulsating voltage (HVDCP or LVDCP), due to the linear ratio of the voltage divider circuit 2 The relationship between the recorded instantaneous voltage value of LVDCP and the instantaneous voltage value of HVDCP at the moment is also in a one-to-one linear proportional relationship. It adopts an analog method for voltage memory, and the number of voltage holders used is in DC pulsation The number of instantaneous voltage values that need to be memorized during a voltage rise of the voltage (HVDCP or LVDCP), that is, the number of segments of the LED light string 10 (both are 4); the voltage memory module 4 is in the DC pulse voltage ( During the descending process of HVDCP or LVDCP), the voltage value of its memory remains unchanged, and is input to the comparator group 5 for comparison processing;

In the comparator group 5, one input terminal of the voltage comparators Comp1, Comp2, Comp3 and Comp4 is respectively connected to the output terminals of the voltage holders H1, H2, H3 and H4 in one-to-one correspondence, and the other input terminal is connected to After being together, it is connected with the voltage divider circuit 2, that is, LVDCP is used as the input signal of the input terminal; the comparator group 5 compares the output of the voltage memory module 4 with the LVDCP during the decline process of the DC pulsating voltage (HVDCP or LVDCP) , output the square wave sequence corresponding to the voltage comparators Comp1, Comp2, Comp3 and Comp4, each output square wave, the change of its high and low level indicates whether the LVDCP has dropped to the memory voltage value input by the corresponding voltage comparator, The square wave sequence reversely reproduces each control node when the LED lamp string 10 reaches the current limit value during the voltage rising process, and is input to the control logic module 6 for processing;

In the control logic module 6, the storage state of each D flip-flop corresponds to the switch state of the high-voltage NMOS transistor in the high-voltage switch circuit 7, that is, the control logic module 6 can output a switch signal to the high-voltage switch circuit 7. High-voltage NMOS tubes Q1, Q2, Q3 and Q4 are switched on and off; the positive pole of the LED lamp segment L1 is connected to the HVDCP output by the rectifier circuit 1, and the connection point is N0; the negative pole of the LED lamp segment L1 is connected to the output of the LED lamp segment L2 Positive connection, the connection point is N1, the connection point N1 is connected to the drain of the high-voltage NMOS tube Q1; the negative pole of the LED lamp segment L2 is connected to the positive pole of the LED lamp segment L3, the connection point is N2, and the connection point N2 is connected to the high-voltage NMOS tube The drain of Q2 is connected; the negative pole of the LED lamp segment L3 is connected to the positive pole of the LED lamp segment L4, the connection point is N3, and the connection point N3 is connected to the drain of the high-voltage NMOS tube Q3; the negative pole of the LED lamp segment L4 is connected to the drain of the LED lamp segment L4. The drain of the high-voltage NMOS transistor Q4 is connected, and the connection point is N4; the sources of the high-voltage NMOS transistors Q1, Q2, Q3, and Q4 are connected together and then connected to one end of the current-sensing resistor Ris, and the connection point is N5. The other terminal of the resistor Ris is connected to the common ground of the power supply; one input terminal of the current-sensing comparator Icomp is connected to the common connection point N5 of the current-sensing resistor Ris and the sources of the high-voltage NMOS transistors Q1, Q2, Q3 and Q4, and the other The input terminal is connected to the reference voltage Vref;

As shown in Figure 4, it is the working waveform diagram of the LED drive circuit based on voltage memory and segmental current limiting in this embodiment. The dotted line in the upper part is the waveform of the low-voltage DC pulsating voltage signal LVDCP, and the thick solid line is the voltage rise and fall detection circuit. The square wave waveform of the output signal RFC, Umax is the peak value of LCDCP; the dotted line in the lower part is the waveform of the low-voltage DC pulsating voltage signal LVDCP, Umax is the peak value of LCDCP, and the thick solid line is the waveform diagram of the current I LED flowing through the _LED light string , Imax is the peak value of I _LED (that is, the current limit value), which is determined by the reference voltage Vref input to the current detection comparator Icomp and the current detection resistor Ris, I _LED =Vref/Ris.

As shown in Fig. 3 and Fig. 4, the driving method of the LED driving circuit based on voltage memory and segmental current limiting in this embodiment includes the following steps:

1) After the AC mains is rectified by the rectifier circuit 1, it outputs HVDCP;

2) The voltage divider circuit 2 divides the HVDCP rectified by the rectifier circuit 1 according to a certain ratio, and outputs the LVDCP;

3) The voltage rise and fall detection module 3 converts the divided low-voltage DC pulsating voltage into a square wave signal RFC with only two levels of high and low. The output signal RFC is high level, the output signal RFC of the voltage rise and fall detection module 3 is low level during the falling process, and the control logic module 6 determines its control mode according to the high and low level states of RFC. The control flow of the descent process is described:

4) During the rising process of LVDCP, when the voltage is at the valley value, each high-voltage NMOS transistor Q1, Q2, Q3, and Q4 is in the conduction state, corresponding to the time point t0 in Figure 4; in the process from time period t0 to t1 In the middle, the high-voltage NMOS transistors Q1, Q2, Q3 and Q4 are in the conduction state, and the connection points N1, N2, N3 and N4 are all shorted to the connection point N5 by the conduction state of Q1, Q2, Q3 and Q4, and the LED lamp segment L2 , L3 and L4 are invalid, and the LED lamp section L1 is connected between the HVDCP and the connection point N5 to be effectively driven; at time point t1, the driving current I _LED flowing through the connected LED lamp section in the LED lamp string 10 reaches The current limit value Imax, the output state of the current detection comparator Icomp has an overcurrent reversal, the control logic module 6 detects the overcurrent reversal, and the output signal controls the voltage memory module 4. The voltage holder H1 remembers the instantaneous voltage value Ua of the LVDCP at this time , so that the high-voltage NMOS transistor Q1 is in the off state, and the high-voltage NMOS transistors Q2, Q3 and Q4 are kept in the on-state; during the period from t1 to t2, the high-voltage NMOS transistor Q1 is in the off Q4 remains on, the connection points N2, N3 and N4 are shorted to the connection point N5 by the conduction state of the high-voltage NMOS transistors Q2, Q3 and Q4, the LED lamp segments L3 and L4 are invalid, and the LED lamp segments L1 and L2 are connected in series Connected between HVDCP and connection point N5 to be effectively driven; after Q1 is turned off, I _LED drops below Imax again, and the output of the current detection comparator Icomp returns to the state before the overcurrent reversal occurs. At time point t2, the drive current I LED flowing through the connected _LED lamp segment in the LED light string 10 reaches the current limit value Imax, the output state of the current detection comparator Icomp is over-current reversed, and the control logic module 6 detects that When the overcurrent is reversed, the output signal controls the voltage memory module 4, and the voltage holder H2 remembers the instantaneous voltage value Ub of the LVDCP at this time, so that the high-voltage NMOS transistors Q1 and Q2 are in the off state, and the high-voltage NMOS transistors Q3 and Q4 are kept in the on-state; During the period from t2 to t3, the high-voltage NMOS transistors Q1 and Q2 are in the off state, Q3 and Q4 are in the on state, and the connection points N3 and N4 are shorted to N5 by the on state of Q3 and Q4, and the LED lights Section L4 is invalid, and LED lamp sections L1, L2 and L3 are connected in series between HVDCP and connection point N5 to be effectively driven; after Q1 and Q2 are turned off, I _LED drops below Imax again, and the current detection comparator Icomp The output returns to the state before the overcurrent reversal occurs; at the time point t3, the driving current I _LED flowing through the connected LED lamp segment in the LED light string 10 reaches the current limit value Imax, and the output state of the current detection comparator Icomp When an overcurrent reversal occurs, the control logic module 6 detects the overcurrent reversal, and the output signal controls the voltage memory module 4. The voltage holder H3 remembers the instantaneous voltage value Uc of the LVDCP at this time, so that the high-voltage NMOS transistors Q1, Q2 and Q3 are turned off. state, the high-voltage NMOS transistor Q4 remains on; during the period from t3 to t4, the high-voltage NMOS transistors Q1, Q2, and Q3 are in the off state, the high-voltage NMOS transistor Q4 remains on, and the connection point N4 is blocked by the high-voltage NMOS The conduction state of the tube Q4 is shorted to the connection point N5, and the LED lamp segments L1, L2, L3 and L4 are connected in series between the HVDCP and the connection point N5 to be effectively driven; after Q1, Q2 and Q3 are turned off, I _{The LED} drops below Imax again, and the output of the current _detection comparator Icomp recovers to the state before the overcurrent reversal occurs; The current limit value Imax, the output state of the current detection comparator Icomp has overcurrent reversal, the control logic module 6 detects the overcurrent reversal, the output signal controls the voltage memory module 4, and the voltage holder H4 remembers the instantaneous voltage value Ud of the LVDCP at this time , so that the high-voltage NMOS transistors Q1, Q2, Q3, and Q4 are in the off state; during the period from the time period t4 to the peak value of LCDCP, the high-voltage NMOS transistors Q1, Q2, Q3, and Q4 are in the off state, and the LED lamp segments L1, L2 , L3 and L4 are disconnected from the effective output ports, and the value of I _LED is 0, so as to avoid the LED light string 10 from being damaged due to overcurrent caused by the continuous rise of the voltage; after Q1, Q2, Q3 and Q4 are turned off, I _LED restarts Falling below Imax, the output of the current detection comparator Icomp returns to the state before the overcurrent reversal occurs;

5) During the falling process of LVDCP, the control logic module 6 determines the switching states of the high-voltage NMOS transistors Q1, Q2, Q3 and Q4 according to the output signal of the comparator group 5; during the process from the peak point of LVDCP to t5, the LVDCP The voltage value U _LV >Ud>Uc>Ub>Ua, the output states of the voltage comparators Comp1, Comp2, Comp3 and Comp4 in the comparator group 5 remain unchanged, and the high-voltage NMOS transistors Q1, Q2, Q3 and Q4 remain off state, the LED lamp segments L1, L2, L3 and L4 are disconnected from the effective output ports, and the value of I _LED is 0; during the time point t5 to t6, Ud>U _LV >Uc>Ub>Ua, the voltage comparator The output state of Comp1 changes, and the output states of the voltage comparators Comp2, Comp3, and Comp4 remain unchanged. At this time, the control logic module 6 turns on the high-voltage NMOS transistor Q4 according to the output states of Comp1, Comp2, Comp3, and Comp4, and the high-voltage NMOS transistor Q4 is turned on. Q1, Q2, and Q3 remain in the off state, and the LED lamp segments L1, L2, L3, and L4 are connected in series between the HVDCP and the connection point N5 to be effectively driven; The voltage values are equal, and the connected LED lamp segments are the same, so the values of I _LED at time points t5 and t4 are equal, and are equal to Imax. During the process from time point t5 to t6, the current I _LED decreases as the voltage drops; During the time point t6 to t7, Ud>Uc>U _LV >Ub>Ua, the output state of the voltage comparator Comp2 changes, and the output states of the voltage comparators Comp1, Comp3 and Comp4 remain unchanged. At this time, the control logic Module 6 turns on the high-voltage NMOS transistors Q3 and Q4 according to the output states of the voltage comparators Comp1, Comp2, Comp3 and Comp4, keeps the high-voltage NMOS transistors Q1 and Q2 off, and connects the LED lamp segments L1, L2 and L3 to the HVDCP in series The connection point N5 is effectively driven, and the LED lamp segment L4 is invalid; at the time point t6, since the voltage of the LVDCP is equal to the voltage value of the LVDCP at the time point t3, and the connected LED lamp segments are the same, the time t6 and t3 The value of the point _ILED is equal and equal to Imax, and during the period from time point t6 to t7, the current ILED decreases as the voltage drops. During the time point t7 to t8, Ud>Uc>Ub>U _LV >Ua, the output state of the voltage comparator Comp3 changes, and the output states of the voltage comparators Comp1, Comp2 and Comp4 remain unchanged. At this time, the control logic Module 6 turns on the high-voltage NMOS transistors Q2, Q3, and Q4 according to the output states of the voltage comparators Comp1, Comp2, Comp3, and Comp4, keeps the high-voltage NMOS transistor Q1 off, and connects the LED lamp segments L1 and L2 in series to the HVDCP and connects The point N5 is effectively driven, and the LED lamp segments L3 and L4 are invalid; at the time point t7, since the voltage of the LVDCP is equal to the voltage value of the LVDCP at the time point of t2, and the connected LED lamp segment is the same, so t7 and t2 time The value of the point _ILED is equal and equal to Imax, and during the period from time point t7 to t8, the current ILED decreases as the voltage drops. During the time point t8 to t9, Ud>Uc>Ub>Ua>ULV, the output state of the voltage comparator Comp4 changes, and the output states of the voltage comparators Comp1, Comp2 and Comp3 remain unchanged. At this time, the control logic module 6 According to the output state of the voltage comparators Comp1, Comp2, Comp3 and Comp4, the high-voltage NMOS transistors Q1, Q2, Q3 and Q4 are turned on, and the LED lamp segment L1 is connected in series between the HVDCP and the connection point N5 to be effectively driven, and the LED lamp Segments L2, L3, and L4 are invalid; at time point t8, since the voltage of LVDCP is equal to the voltage value of LVDCP at time point t1, and the connected LED lamp segment is the same, the value of t8 is equal to the value of I _LED at time point t1, and It is equal to Imax, and during the process from time point t8 to t9, the current ILED decreases as the voltage drops, and the LED drive control process within one LCDCP cycle is completed.

The above is only a preferred embodiment of the patent of the present invention, but the protection scope of the patent of the present invention is not limited thereto. For example, the number of voltage holders, voltage comparators, high-voltage NMOS tubes, etc. can be changed. Within the scope disclosed by the patent of the present invention, those skilled in the art make equivalent replacements or changes according to the technical solution of the patent of the present invention and its inventive concepts, all of which belong to the scope of protection of the patent of the present invention.

Claims (10)

1. the LED drive circuit with segmentation current limliting based on voltage memory, comprise rectification circuit, bleeder circuit, comparator bank, high voltage switch circuit and LED lamp string, described rectification circuit is connected with bleeder circuit, described high voltage switch circuit and LED lamp series winding connect, described LED lamp string is connected with rectification circuit, it is characterized in that: also comprise voltage rise and fall detection module, voltage memory module, control logic module, inspection leakage resistance and inspection stream comparator, described voltage memory module, comparator bank, control logic module, high voltage switch circuit and LED lamp string are connected successively; Described bleeder circuit is connected with voltage rise and fall detection module and voltage memory module respectively, and described voltage rise and fall detection module is connected with voltage memory module and control logic module respectively, and described control logic module is connected with voltage memory module; Described high voltage switch circuit is held and is connected altogether with power supply by inspection leakage resistance, an input termination of described inspection stream comparator is examined the points of common connection of leakage resistance and high voltage switch circuit, another input termination reference voltage, the output of described inspection stream comparator is connected with control logic module.

2. the LED drive circuit based on voltage memory and segmentation current limliting according to claim 1, is characterized in that: described voltage memory module is made up of multiple voltage retainers, and the output of described each voltage retainer is connected with comparator bank respectively.

3. the LED drive circuit based on voltage memory and segmentation current limliting according to claim 2, is characterized in that: described each voltage retainer is made up of electric capacity and operational amplifier.

4. the LED drive circuit based on voltage memory and segmentation current limliting according to claim 2, it is characterized in that: described comparator bank is made up of multiple voltage comparators, an input of described each voltage comparator and the output of each voltage retainer connect one to one, after another input is connected together, be connected with bleeder circuit, the output of described each voltage comparator is connected with control logic module respectively.

5. the LED drive circuit based on voltage memory and segmentation current limliting according to claim 4, it is characterized in that: described control logic module is by multiple d type flip flops and complete the required combined digital logical constitution of function, described control logic module is using output, the output of voltage rise and fall detection module and the output of inspection stream comparator of each voltage comparator in comparator bank as input signal.

6. the LED drive circuit based on voltage memory and segmentation current limliting according to claim 5, it is characterized in that: described voltage rise and fall detection module is made up of differentiation element circuit and voltage comparator the square-wave signal of output instruction DC pulse moving voltage rise and fall state.

7. the LED drive circuit based on voltage memory and segmentation current limliting according to claim 5, it is characterized in that: described high voltage switch circuit is made up of multiple high pressure NMOS pipes, the on off state of the store status of described each d type flip flop and each high pressure NMOS pipe is corresponding one by one; After the source electrode of described each high pressure NMOS pipe is connected together, holds and be connected altogether with power supply through inspection leakage resistance, the points of common connection of an input termination inspection leakage resistance of described inspection stream comparator and the source electrode of each high pressure NMOS pipe, another input termination reference voltage; The drain electrode of described each high pressure NMOS pipe and LED lamp series winding connect.

8. the LED drive circuit based on voltage memory and segmentation current limliting according to claim 7, is characterized in that: described LED lamp string is composed in series by multiple LED lamp sections, and the quantity of described LED lamp section is consistent with the quantity of high pressure NMOS pipe.

9. the driving method with the LED drive circuit of segmentation current limliting based on voltage memory, is characterized in that comprising the following steps:

1) electric main, after rectification circuit rectification, is exported high voltage direct current pulsating voltage;

2) the high voltage direct current pulsating voltage of bleeder circuit after to rectification circuit rectification carries out dividing potential drop according to a certain percentage, output low-voltage direct pulsating voltage;

3) voltage rise and fall detection module converts the low-voltage direct pulsating voltage after dividing potential drop to be used to indicate the uphill process of low-voltage direct pulsating voltage and the square-wave signal of decline process to;

4) in the uphill process of low-voltage direct pulsating voltage, voltage is in the time of valley, each high pressure NMOS pipe is in conducting state, now only have the LED lamp section being directly connected with high voltage direct current pulsating voltage to be access in effective driver output port, when rising, voltage make the drive current of this LED lamp section reach cut-off current, pressure drop on inspection leakage resistance is higher than reference voltage, the output voltage generation overcurrent upset of inspection stream comparator, control logic module detects the upset of this signal, the high pressure NMOS pipe being connected with this LED lamp section negative pole is turned off, together with next the LED lamp section being connected with this LED lamp section, be access in effective driver output port, electric current on LED lamp string is got back to below cut-off current, before the output voltage of inspection stream comparator returns to overcurrent upset occurs, according to this rule, often reach primary current cut-off current and just turn-off the high pressure NMOS pipe being connected with the part negative pole being access in LED lamp string, the LED lamp hop count amount that is access in effective driver output port is progressively increased, when all LED lamp Duan Jun are access in, the rising of high voltage direct current pulsating voltage makes electric current reach cut-off current again, turn-off all high pressure NMOS pipes in high voltage switch circuit, the disconnection that is connected by all LED lamp sections in LED lamp string with power supply, the control procedure in the uphill process of this DC pulse moving voltage is called forward control procedure, in forward control procedure, the instantaneous voltage of low-voltage direct pulsating voltage when the operating current that voltage memory module is write down LED lamp string successively reaches cut-off current at every turn,

5) in the decline process of low-voltage direct pulsating voltage, the magnitude of voltage of voltage memory module memory remains unchanged, be input to comparator bank and compare processing, the square wave sequence of comparator bank output has oppositely reappeared in voltage uphill process when LED lamp string reaches Current Limits flow valuve at every turn that each controls node; Control node at each, the output state of comparator bank can change, control logic module detects this state variation, oppositely progressively recovers that in high voltage switch circuit, each is turned off the conducting state of high pressure NMOS pipe, realizes the reverse symmetry control to LED lamp string; In the process of reverse symmetry control, if all high pressure NMOS pipes in the peak point place of high voltage direct current pulsating voltage high voltage switch circuit are in off state, in the time that high voltage direct current pulsating voltage declines through the 1st control node, control logic module makes the high pressure NMOS pipe being finally turned off in forward control procedure recover conducting state, and in LED lamp string, all LED lamp sections are access in effective driver output port; In the time that high voltage direct current pulsating voltage declines through the 2nd control node, control logic module makes the high pressure NMOS pipe that in forward control procedure, second-to-last is turned off recover conducting state, makes the LED lamp section that is access in effective driver output port in LED lamp string reduce 1 section; According to this rule, after this high voltage direct current pulsating voltage declines and often controls when node through 1, just recover the conducting state of 1 high pressure NMOS pipe being turned off, the LED lamp section that is access in effective driver output port in LED lamp string is gradually reduced, until all high pressure NMOS pipes all recover conducting state, till the quantity that is access in the LED lamp section of effective driver output port in LED lamp string is 1 section.

According to claim 9 based on voltage memory the driving method with the LED drive circuit of segmentation current limliting, it is characterized in that: step 3) described voltage rise and fall detection module converts the low-voltage direct pulsating voltage after dividing potential drop to be used to indicate the uphill process of low-voltage direct pulsating voltage and the square-wave signal of decline process is specially to:

Voltage rise and fall detection module converts the low-voltage direct pulsating voltage after dividing potential drop to the square-wave signal that only has two kinds of level of height, two kinds of varying levels of this square-wave signal uphill process and decline process of indication low-voltage DC pulse moving voltage respectively, wherein high level instruction uphill process, low level instruction decline process, can obtain the indicating mode contrary with original signal by this square wave signal inversion.

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