KR20130031719A - System control unit, led driver including the unit and static current regulation method for the driver - Google Patents

Abstract

PURPOSE: A system control unit, an LED driver including the system control unit, and a constant current controlling method of the LED driver are provided to effectively control a secondary constant current even if an input current is an interchange type, thereby improve the power factor. CONSTITUTION: A diode current peak value predictor(341) detects a first peak value which is the biggest among the current flowing in a power transistor, and predicts a second peak value by using the first peak value. A diode turn-off point detector(342) detects a point of time when the diode connected to a secondary side coil is turned off. A power transistor turn-off point detector(343) detects a point of time when the power transistor is turned off by using a gate controlling signal. An average value calculation(344) produces an average value by averaging the output current of a pulse shape corresponding to the current supplied to an LED diode array for a constant time section. A pulse controller(345) renews the gate control signal by using the average value. [Reference numerals] (AA) Primary side; (BB) Secondary side

Description

System control unit, LED driver including the system control unit and the constant current control method of the LED driver {System control unit, LED driver including the unit and static current regulation method for the driver}

The present invention relates to a LED driver and a constant current control method for the LED driver, in particular, the time when the power transistor connected to the primary coil is turned off, the time when the diode connected to the secondary coil is turned off and the power transistor on the primary side Using the peak value of the current flowing and the time that the current flows through the secondary diode, the current flowing through the LED connected to the secondary side is predicted and the average value is used to control the gate control signal for controlling the operation of the power transistor. The present invention relates to an LED driver for controlling a constant current generated and finally supplied to an LED array and a method of controlling the constant current of the LED driver.

LED lighting refers to a lighting device that can maintain a constant brightness by configuring a constant current to flow through the LED. The brightness of the LED can be controlled by controlling the magnitude of the constant current flowing through the LED, which is said to be constant current control when the average current flowing through the LED is constant.

1 is a circuit diagram of a conventional LED driver.

Referring to FIG. 1, the LED driver 100 includes a power conversion unit 110, a transformer 120, a switching unit 130, a system control unit 140, and a primary side zero current detection unit 150.

The power conversion unit 110 rectifies the AC voltage V _ac supplied to the primary side in the full-wave rectifier 111 and generates the DC input voltage V _IN using the first capacitor C1. The switching unit 130 includes a power transistor Q1 and a switching resistor Rs connected in series, and the power transistor Q1 operates in response to the gate control signal V _G. The transformer 120 uses the primary winding of the coil constituting the transformer 120 to convert the DC input voltage V _IN generated from the power converter 110 according to the switching operation of the power transistor Q1 connected to the primary coil. It transfers to the secondary side according to the winding ratio of T1) and the secondary winding T2. The primary zero current detecting unit 150 is dropped on the diode D1 connected to the secondary coil in a section in which the power transistor is turned off during a process in which energy stored in the primary side of the transformer 120 is transferred to the secondary side. The resonance voltage reflected as the sum of the voltage (V _F ) and the voltage (V _O ) dropping on the LED array connected to the secondary side and the ratio of the number of secondary windings (N _s ) and the auxiliary winding (N _a ) V _W ).

The system controller 140 includes an output current (I _O ) predictor 141, a diode turn-on interval predictor 142, a voltage predictor 143 that drops on the LED array, and a gate control signal generator 144. The output current I _O predictor 141 predicts the current I _O flowing through the LED array 160 using the voltage CS corresponding to the current I _ds flowing in the power transistor Q1. The diode turn-on period predictor 142 uses the divided voltage V _{S obtained} by dividing the resonance voltage V _W by a constant ratio to determine a time period T _D at which the diode D1 connected to the secondary coil is turned on. Predict. The voltage predictor 143 falling on the LED array divides the divided voltage V _{S obtained} by dividing the feedback voltage V _W and the time interval T _D at which the diode D1 connected to the secondary coil turns on. The voltage V _O dropping to the LED array 160 is used to predict the voltage. The gate control signal generator 144 generates a gate control signal V _G that determines the amount of constant current provided to the LED array 160 by using the voltage V _O falling on the LED array 160.

FIG. 2 shows waveforms at certain nodes of the LED driver shown in FIG. 1.

Referring to FIG. 2, the current I _ds flowing in the power transistor Q1 increases in a section T _{ON in} which the power transistor Q1 is turned on and turns off in one unit section T _S. At (T _S -T _ON ), no current flows.

The current I _D flowing in the diode D1 connected to the secondary coil is turned on at the moment when the power transistor Q1 is turned off, and the peak value I _pk of the current I _ds flowing in the power transistor Q1 and The peak value I _{D_p} of the diode current multiplied by the winding ratio N _P / N _S of the primary winding N _P and the secondary winding N _S of the coil constituting the transformer 120 flows. . The current I _D flowing through the diode D1 connected to the secondary coil gradually decreases from the peak value I _{D_p} of the diode current at the beginning of turn-on, and when the diode D1 connected to the secondary coil is turned off, The current goes to zero.

The resonance voltage V _W indicates a negative voltage level when the power transistor Q1 is turned on, but the voltage V dropped on the diode D1 connected to the secondary coil when the power transistor Q1 is turned off. _F ) and the voltage level multiplied by the ratio of the voltage (V _O ) dropped to the LED array 160 connected to the secondary side and the ratio of the number of secondary windings (N _s ) and the auxiliary winding (N _a ) It exhibits a constant resonance characteristic when the diode D1 connected to the coil is turned off. Here, the resonance characteristic refers to LC resonance between a parasitic capacitor (not shown) formed between the drain and the source terminal of the turned off power transistor Q1 and the inductor forming the transformer 120.

In the case of the LED driver illustrated in FIG. 1, in order to generate the gate control signal V _G , the peak value I _pk of the current I _ds flowing through the power transistor Q1 and the coil of the transformer 120 are generated. Winding ratio (N _P / N _S ) of primary winding (N _P ) and secondary winding (N _S ), one period (T _S ) of gate control signal (V _G ), and turn-on of secondary side diode (D1) It is necessary to know all the periods T _D , and using them to generate a new gate control signal V _G has a disadvantage in that a large amount of calculation is required and a circuit becomes complicated.

An object of the present invention is to provide a system control unit that calculates a pulsed output current using a small number of parameters and generates a gate control signal using an average value of the pulsed output current. .

Another technical problem to be solved by the present invention is an LED driver including a system control unit for calculating a pulse type output current using a small number of parameters and generating a gate control signal using the average value of the pulse type output current. Is to provide.

Another technical problem to be solved by the present invention, a constant current control method of the LED driver to calculate the output current in the pulse form using a small number of parameters and to generate a gate control signal using the average value of the output current in the pulse form. Is to provide.

According to an aspect of the present disclosure, a system control unit includes: a power transistor operating in response to a gate control signal; a switching unit having a switching resistor installed between the power transistor and a ground voltage; a primary coil In response to the switching operation of the switching unit connected to the transformer for transmitting the input voltage to the secondary side at a constant rate and the voltage dropped on the LED diode array connected to the secondary coil and the diode connected to the secondary coil of the transformer And a LED driver including a primary zero current sensing unit configured to generate a resonance voltage reflecting a voltage, wherein a second largest current among the current flowing through the power transistor and the diode connected to the secondary coil using the resonance voltage is used. Predict the peak value, the power transistor The average value of the current supplied to the LED diode array for a certain period of time using the time when the power is turned off, the time when the diode connected to the secondary coil is turned off, and the second peak value, and the average value is used. Update the gate control signal.

LED driver according to an embodiment of the present invention for achieving the above another technical problem, a power conversion unit, a switching unit, a transformer, a primary side zero current detection unit and a system control unit. The power conversion unit rectifies the supply voltage of the AC type to generate an input voltage. The switching unit includes a power transistor that operates in response to a gate control signal and a switching resistor disposed between the power transistor and a ground voltage. The transformer transmits the input voltage or the supply voltage in the form of direct current to the secondary side in response to the switching operation of the switching unit connected to the primary side coil. The primary current zero sensing unit generates a resonance voltage reflecting the voltage dropped in the LED diode array and the voltage dropped in the diode connected to the secondary coil of the transformer. The system controller predicts the largest second peak value among the currents flowing through the diode connected to the secondary coil by using the current flowing through the power transistor and the resonance voltage, and when the power transistor is turned off, the secondary side The average value of the current supplied to the LED diode array for a predetermined time period is obtained using the time point when the diode connected to the coil is turned off and the second peak value, and the gate control signal is generated using the average value.

LED driver constant current control method according to an embodiment of the present invention for achieving the another technical problem, is applied to the LED driver of claim 1, the parameter extraction step, output current generation step, average value generation step and gate control And a signal generation step. The parameter extracting step may include a largest first peak value among currents flowing through the power transistor, a second largest peak value among currents flowing through a diode connected to the secondary side of the transformer, a time point at which the power transistor is turned off, and The time point at which the current flowing in the diode connected to the secondary side becomes zero is detected. The output current generating step generates the pulsed output current using the second peak value, the time when the power transistor is turned off, and the time when the diode current connected to the secondary side of the transformer becomes zero. The average value generating step generates an average value obtained by averaging the output currents of the pulse type included within a predetermined time interval. The gate control signal generating step generates the gate control signal in response to the average value.

Since the LED driver and the constant current control method of the LED driver according to the present invention are controlled using the average value of the output current obtained by using a small number of parameters for the constant current control, the hardware required for the calculation is simple because the operation is not complicated. .

In addition, even when the input current is not a direct current form, the secondary constant current can be effectively controlled. In this case, the power factor is improved compared to the case where the input current is a direct current form.

1 is a circuit diagram of a conventional LED driver.
FIG. 2 shows waveforms at certain nodes of the LED driver shown in FIG. 1.
3 is a circuit diagram of an LED driver according to an embodiment of the present invention.
4 is a flowchart illustrating a method of controlling a constant current of an LED driver according to an exemplary embodiment of the present invention.
5 illustrates an electrical waveform at a predetermined node of the LED driver according to an embodiment of the present invention.
6 illustrates a current flowing through a power transistor when the input voltage is a DC voltage having a large ripple.

In order to fully understand the present invention and the operational advantages of the present invention and the objects achieved by the practice of the present invention, reference should be made to the accompanying drawings, which are provided for explaining exemplary embodiments of the present invention, and the contents of the accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Like reference symbols in the drawings denote like elements.

The core idea of the present invention is to convert the current supplied to the LED array connected to the secondary side using a small number of parameters into a pulse type current, and using an average value of a plurality of converted output currents belonging to a predetermined time interval. The gate control signal for controlling the operation of the vehicle side switching element is generated.

3 is a circuit diagram of an LED driver according to an embodiment of the present invention.

Referring to FIG. 3, the LED driver 300 performs a function of transferring the input voltage V _IN supplied to the primary coil to the diode array 360 connected to the secondary circuit, and the power converter 310. A transformer 320, a switching unit 330, a system control unit 340, and a primary side zero current detection unit 350 are included.

In the present embodiment, the supply voltage supplied to the LED driver 300 is described as an example of the AC voltage (V _ac ), but the supply voltage is not limited thereto. For example, the supply voltage may be a DC voltage. When the supply voltage is a DC voltage, the LED driver 300 of the present exemplary embodiment may not include the power converter 310.

The power converter 310 includes a rectifier 311 and a first capacitor C1 connected between the output terminal of the rectifier 311 and the ground GND. The power converter 310 rectifies the AC voltage V _ac into the rectifier 311 and converts the voltage rectified by the first capacitor C1 into the input voltage V _IN . The input voltage (V _IN ) is a direct current voltage having little ripple or very small ripple when the capacitance of the first capacitor C1 is large, but a large ripple exists when the capacitance is small. Can be voltage. DC voltage with large ripple includes a voltage having a waveform substantially similar to the waveform of the rectified voltage. As will be described in detail below, in the present embodiment, the input voltage V _IN may be effectively operated even when the DC voltage is large as well as when the input voltage V _IN has no ripple or a small ripple.

The switching unit 330 is a power transistor Q1 that operates in response to the gate control signal V _G generated by the system control unit 340, and a switching resistor Rs installed between the power transistor Q1 and the ground GND. ).

The transformer 320 transmits the input voltage V _IN to the secondary coil at a constant rate in response to a switching operation of the switching unit 330 connected to the primary coil. Assuming that the number of turns of the primary coil included in the transformer 320 is N _P and the number of turns of the secondary coil is N _S , the constant ratio is the number of turns of the primary side coil N _P and the number of turns of the secondary side coil ( N _S ) means the winding ratio.

The zero current detector 350 generates a divided voltage V _{DIV obtained} by dividing the resonance voltage V _W using two resistors R ₁ and R ₂ . Resonance voltage (V _W ) is the voltage (V _O ) that is dropped on the LED diode array 360 and the voltage (V _di ) that is dropped on the diode (D1) connected to the secondary coil of the transformer 320, the secondary winding number ( It is the voltage reflected by the ratio of N _S ) and the auxiliary winding number N _a . The divided voltage V _DIV is a voltage obtained by dividing the resonance voltage V _W by the ratio between the resistors R ₁ and R ₂ . In the following description, even if there is no special mention, the relationship between the resonance voltage V _W and the divided voltage V _DIV is maintained.

The system controller 340 includes a diode current peak value predictor 341, a diode turn off time detector 342, a power transistor turn off time detector 343, an average value calculator 344, and a pulse controller 345.

The diode current peak value predictor 341 detects the largest first peak value I _{ds_p} among the currents I _ds flowing through the power transistor Q1, and _uses the first peak value I _{ds_p} to determine the second peak. _{Predict the} value I _{D_p} . The second peak value I _{D_p} is the largest current among the currents flowing in the secondary side diode D1 and is the winding of the primary coil winding number N _P and the secondary coil winding number N _S of the transformer 320. It can be predicted by multiplying the ratio by the first peak value I _{ds_p} .

The diode turn-off time detector 342 detects a time point t ₂ at which the diode D1 connected to the secondary coil is turned off using the split voltage V _DIV . The divided voltage V _DIV is a voltage V _di which drops on the diode D1 connected to the secondary coil at the moment when the power transistor Q1 is turned off and a voltage V drops on the LED array 160 connected to the secondary side. At the point in time t ₂ at which the diode D1 connected to the secondary coil is turned off, having a voltage level multiplied by the sum of _O ) and the winding ratio of the secondary winding number N _S and the secondary winding number N _a . It shows a constant resonance characteristic.

Referring to FIG. 2, it can be seen that the voltage level of the resonance voltage V _W decreases rapidly at the time t ₂ when the diode D1 connected to the secondary coil is turned off. This part is equally applicable to the present embodiment. Accordingly, the diode turn-off time detector 342 may detect a time point t ₂ at which the diode D1 is turned off by detecting a time point when the voltage level of the resonance voltage V _W decreases rapidly through a differentiator.

The power transistor turn off time detector 343 detects a time t ₁ at which the power transistor Q1 is turned off using the gate control signal V _G.

The average value calculator 344 LED diode using the power transistor (Q1) is turned to be off-time (t _1), two side diode when the (D1) is turned off (t ₂₎ and the second peak value (I _{D_p)} The output current I _{O_PWM in the} form of a pulse corresponding to the current I ₀ supplied to the array 360 is accumulated, and the output current included in a predetermined time interval among the accumulated output currents I _{O_PWM} I _{O_PWM} ) is averaged to generate their average value I _{O_avg} .

Output current (I _{O_PWM),} the pulse width (width) is a power transistor (Q1) is to the turn which is turned off is connected to the secondary coil from the time (t ₁₎ a diode (D1) is turned off the time (t _2), The pulse amplitude preferably has a value 1/2 times the second peak value I _{D_p} . However, the pulse size of the output current I _{O_PWM} is not limited to 1/2 of the second peak value I _{D_p} , and may have various multiples such as 1/4 and 2 times. The form of the output current I _{O_PWM} will be described later.

The average calculator 344 may be implemented as a low pass filter that receives the output current I _{O_PWM} for a predetermined time period and generates an average value I _{O_avg} . The predetermined time period may be determined by the frequency of the AC voltage V _ac when the first capacitor C1 is converted into the input voltage V _IN .

The pulse controller 345 generates the gate control signal V _G using the average value I _{O_avg} . The current I _ds flowing in the power transistor Q1 is a resistance value of the node voltage V _CS and the switching resistor Rs to which the power transistor Q1 and the switching resistor Rs are connected, even without using a current meter. Can be easily predicted.

4 is a flowchart illustrating a method of controlling a constant current of an LED driver according to an exemplary embodiment of the present invention.

4, the constant current control method 400 of the LED driver is applied to the LED driver shown in Figure 3, the power supply step 410, parameter extraction step 420, pulse type output current generation step ( 430, a predetermined time interval determination step 440, an average value generation step 450, and a gate control signal generation step 460.

The power supply step 410 supplies power required for the operation of the LED driver 300. The parameter extraction step 420 may include the largest first peak value I _{ds_p} of the currents flowing through the power transistor Q1 and the largest second peak value of the currents flowing through the diode D1 connected to the secondary side of the transformer 320. (I _{D_p),} the power transistor (Q1) is detected, the turn which is turned off the time (t ₁₎ and the current flowing through the diode (D1) connected to the secondary side of the transformer 320 is 0 (zero) point in time (t ₂₎ Here, the second peak value I _{D_p} is a ratio of the windings of the primary winding N1 and the secondary winding N2 of the coil constituting the transformer 320 and the first peak value I. _{ds_p} ).

The pulsed output current generation step 430 may include a second peak value I _{D_p} , a time point t ₁ at which the power transistor is turned off, and a current of the diode D1 connected to the secondary side of the transformer 320 is zero. The output time I _{O_PWM in the} form of a pulse is generated using the time point t ₂ . Pulse shape of the output current (I _{O_PWM)} is, the pulse width (width) is a power transistor (Q1) is turned on is turned off is connected to the secondary coil from the time (t ₁₎ a diode (D1) is turned to be off-time (t ₂ ), And the amplitude is half of the second peak value I _{D_p} .

The predetermined time interval determination step 440 includes the parameter extraction step 420 and the pulsed output current generation step 430 when the pulsed output current I _{O_PWM} is included within a predetermined time interval (Yes). If the output current I _{O_PWM in the} form of a pulse is not included within a predetermined time interval (No), the average value generating step 450 is performed.

The average value generating step 450 generates an average value I _{O_avg obtained} by averaging the output currents I _{O_PWM} in a pulse form included within a predetermined time interval. The gate control signal generation step 460 generates a gate control signal V _G in response to the average value I _{O_avg} .

The parameter extraction step 420, the pulsed output current generation step 430, the predetermined time interval determination step 440, the average value generation step 450, and the gate control signal generation step 460 are performed by the LED driver 300. The operation is repeated while supplying a constant current to the array 360.

In the present embodiment, the output current I _{O_PWM} has been exemplified in the case where the pulse amplitude has a value 1/2 times the second peak value I _{D_p} , but the pulse size of the output current I _{O_PWM} is When it does not correspond to 1/2 times the second peak value I _{D_p} , for example, when it has a multiple value such as 1/4 times, 1/6 times, or 2 times the second peak value I _{D_p} The average value generating step 450 may further include a correction step of multiplying the average value I _{O_avg} by 2, 3, and 1/4, respectively.

5 illustrates an electrical waveform at a predetermined node of the LED driver according to an embodiment of the present invention.

Referring to FIG. 5, the current I _ds flowing in the power transistor Q1 increases in a section in which the power transistor Q1 is turned on, and the current does not flow in a section in which the current transistor is turned off. Same as the case. Here, t ₁ denotes a time point at which the power transistor Q1 is turned off, and this time point can be easily detected from the gate control signal V _G applied to the power transistor Q1.

The current I _D flowing in the diode D1 connected to the secondary coil is turned on at the moment when the power transistor Q1 is turned off, and the peak value I _pk of the current I _ds flowing in the power transistor Q1 and The peak value I _{D_p} of the diode current having a magnitude multiplied by the winding ratio N _P / N _S of the primary winding N1 and the secondary winding N2 of the coil constituting the transformer 120 flows. The current I _D flowing through the diode D1 connected to the secondary coil gradually decreases from the peak value I _{D_p} of the diode current, and at the time t ₂ when the diode D1 connected to the secondary coil is turned off. Becomes zero. The time t ₂ at which the diode D1 connected to the secondary coil is turned off may be detected by various methods. However, in the present invention, as described above, the resonance voltage V _W may be determined by using two resistors R ₁ and R _2. It is proposed to simply detect using the divided voltage (V _DIV ) divided by.

The current I _D flowing through the diode D1 connected to the secondary side coil will be supplied to the LED array 360 connected to the secondary side circuit as it is. However, as shown in FIG. 5, the current is not continuously supplied but is discontinuously supplied. The total energy supplied also varies from moment to moment.

According to an embodiment of the present invention, the current I _D flowing through the diode D1 connected to the secondary coil during a predetermined time period is averaged, and the average value is applied to the LED array 360. It is to control the constant current supplied.

To implement this, first, the current supplied to the LED array 360 is defined as an output current I _{O_PWM in the} form of a pulse. In order to indicate the output current I _{O_PWM in} pulse form, the width and magnitude of the pulse must be determined.

The width of the pulse is a time interval (| t ₂ -t ₁ |) at which the current I _D flowing through the diode D1 connected to the secondary coil is activated.

Referring to FIG. 5, the current I _D flowing through the diode D1 gradually decreases as time passes with the diode peak value I _{D_p} at the start point t _{1 of} the section, thereby ending the t point. ₂ ) has a value of zero. The actual waveform will have a different shape from the triangular waveform shown in FIG. 5, but will have a shape close to the triangular waveform in the actual case. Therefore, the magnitude of the pulse is half of the diode peak value I _{D_p} .

As described above, an average value I _{O_avg} may be obtained by averaging a plurality of pulses of the output current I _{O_PWM} included in a predetermined time interval.

As it described above, to generate a gate control signal (V _G) in the case of the present invention, prior to a period of the gate control signal (V _G) (T _S) and a second turn-on period of the primary diode (D1) (T _D ) is not required, the power transistor (Q1) is turned on, which is turned off the time (t ₁₎ and the diode (D1) connected to the secondary coil is turned off the time (t ₂₎ can be simply obtained, the power transistor (Q1 Since the peak value I _pk of the current I _ds flowing through) can be obtained in the same manner as in the conventional case, the hardware is simpler than that of the conventional LED driver. In addition, the constant current control method of operating the LED driver is also simplified, and the operation is not complicated and the gate control signal V _G can be generated in a short time.

According to an exemplary embodiment of the present invention, the input voltage V _IN may be effectively operated as well as a DC voltage having a large value as well as a DC voltage having a large ripple.

6 illustrates a current flowing through a power transistor when the input voltage is a DC voltage having a large ripple.

Referring to FIG. 6, the current I _ds flowing in the power transistor Q1 has a sawtooth shape, and when the highest point thereof is connected, the input voltage V _IN having the waveform of the rectified voltage form is connected.

When the input voltage V _IN is a DC voltage having a large ripple, a voltage having a waveform in the form of a rectified voltage is applied to the transformer 320. In general, the frequency of the AC current V _ac supplied to the LED driver is applied. (50 ~ 60Hz). Since the frequency of the gate control signal V _G controlling the operation of the power transistor Q1 has a frequency of several tens of KHz, the current I _ds flowing through the power transistor has a shape as shown in FIG. 6.

In this case, the current flowing in the secondary side is a value obtained by multiplying the peak value I _pk by the ratio of the number of turns of the primary and secondary coils of the transformer 320. Therefore, since the secondary side current has the same shape as the primary side, power factor correction should be performed. Since the turn-on and turn-off periods of the power transistor Q1 are variable, in the conventional case, a complicated operation for power factor correction is performed every switching period. Should be performed.

In one embodiment of the present invention, since the average value of the current supplied to the LED array 360 is calculated and used, power factor correction is not necessary separately.

While the present invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments. It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope of the present invention.

100: conventional LED driver
110: power conversion unit 120: transformer
130: switching unit 140: system control unit
150: primary zero current sensing unit 160: LED array
300: LED driver according to an embodiment of the present invention
310: power conversion unit 320: transformer
330: switching unit 340: system control unit
350: primary zero current detection unit 360: LED array
400: LED driver constant current control method according to an embodiment of the present invention
410: power supply step 420: parameter extraction step
430: output current generation step 440: determination of a predetermined time interval
450: gate control signal generation step

Claims (20)

A switching unit having a power transistor operating in response to a gate control signal and a switching resistor provided between the power transistor and a ground voltage; and a secondary side of the input voltage at a constant rate in response to a switching operation of the switching unit connected to a primary coil. An LED driver comprising a transformer for transmitting a coil and a primary side zero current sensing unit for generating a resonance voltage reflecting a voltage dropped on an LED diode array connected to the secondary coil and a voltage dropped on a diode connected to the secondary coil of the transformer. In the system control unit that configures,
The second peak value of the current flowing through the diode connected to the secondary coil is predicted using the current flowing through the power transistor and the resonance voltage, and at the time when the power transistor is turned off, the diode connected to the secondary coil The average value of the current supplied to the LED diode array for a predetermined time interval by using the time point is turned off and the second peak value, and the system control unit for updating the gate control signal using the average value . The method of claim 1, wherein the system control unit,
A diode current peak value predictor for detecting the largest first peak value among the currents flowing through the power transistor and predicting the second peak value using the first peak value;
A diode turn off time detector for detecting a time when the diode connected to the secondary coil is turned off using the resonance voltage;
A power transistor turn-off time detector for detecting a time when the power transistor is turned off using the gate control signal;
The output current in the form of a pulse corresponding to the current supplied to the LED diode array using the time when the power transistor is turned off, the time when the diode connected to the secondary coil is turned off, and the second peak value is a predetermined time interval. An average value calculator for generating the average value by averaging for a while; And
And a pulse controller for updating the gate control signal using the average value. The method of claim 2, wherein the diode current peak value predictor,
Predicting the second peak value by multiplying the ratio of the primary winding number and the secondary winding number of the coil constituting the transformer by the first peak value,
The constant ratio is a system control unit, characterized in that the ratio of the number of primary and secondary windings of the coil constituting the transformer. The method of claim 2, wherein the pulsed output current,
The width of the pulse is from the time when the power transistor is turned off to the time when the diode connected to the secondary coil is turned off, the magnitude of the pulse is a half of the second peak value. The method of claim 2, wherein the average calculator,
And a low pass filter configured to receive the pulsed output current for a predetermined time period and generate the average value. The method of claim 1, wherein the current flowing through the power transistor,
And a voltage falling between the power transistor and the switching resistor connected in series and configuring the switching unit, and using the resistance value of the switching resistor.
Power conversion unit to generate an input voltage by rectifying the AC supply voltage
A switching unit having a power transistor operating in response to a gate control signal and a switching resistor disposed between the power transistor and a ground voltage;
A transformer configured to transmit the input voltage or the DC supply voltage to the secondary side at a constant rate in response to a switching operation of the switching unit connected to the primary side coil;
A primary zero current detector configured to generate a resonance voltage reflecting the voltage dropped on the LED diode array and the voltage dropped on the diode connected to the secondary coil of the transformer; And
The second peak value of the current flowing through the diode connected to the secondary coil is predicted using the current flowing through the power transistor and the resonance voltage, and at the time when the power transistor is turned off, the diode connected to the secondary coil A system controller which obtains an average value of the current supplied to the LED diode array for a predetermined time period using the time point at which the power is turned off and the second peak value, and updates the gate control signal using the average value. LED driver, characterized in that. The method of claim 7, wherein the system control unit,
A diode current peak value predictor for detecting the largest first peak value among the currents flowing through the power transistor and predicting the second peak value using the first peak value;
A diode turn off time detector for detecting a time when the diode connected to the secondary coil is turned off using the resonance voltage;
A power transistor turn-off time detector for detecting a time when the power transistor is turned off using the gate control signal;
The output current in the form of a pulse corresponding to the current supplied to the LED diode array using the time when the power transistor is turned off, the time when the diode connected to the secondary coil is turned off, and the second peak value is a predetermined time interval. An average value calculator for generating the average value by averaging for a while; And
And a pulse controller for updating the gate control signal using the average value. The method of claim 8, wherein the diode current peak value predictor,
Predicting the second peak value by multiplying the ratio of the primary winding number and the secondary winding number of the coil constituting the transformer by the first peak value,
The constant ratio is an LED driver, characterized in that the ratio of the number of primary and secondary windings of the coil constituting the transformer. The method of claim 8, wherein the pulsed output current,
Wherein the width of the pulse is from the time when the power transistor is turned off to the time when the diode connected to the secondary coil is turned off, and the magnitude of the pulse is half of the second peak value. The method of claim 8, wherein the average value calculator,
An LED driver, characterized in that the low-pass filter for generating the average value by receiving the output current of the pulse form for a predetermined time period. The method of claim 7, wherein
The predetermined time period is determined by the frequency of the AC voltage LED driver. The method of claim 7, wherein the current flowing through the power transistor,
The LED driver, characterized in that for predicting by using the resistance value of the switching resistor and the voltage dropped between the power transistor and the switching resistor connected in series.
In the constant current control method of the LED driver according to claim 7,
The largest first peak value of the current flowing through the power transistor, the second largest peak value of the current flowing through the diode connected to the secondary side of the transformer, the time when the power transistor is turned off and the diode connected to the secondary side of the transformer A parameter extraction step of detecting a time point at which the current flowing in the current becomes zero;
Generating an output current in the form of a pulse by using the second peak value, a time when the power transistor is turned off, and a time when the diode current connected to the secondary side of the transformer becomes zero;
Generating an average value of averaging the output currents of the pulse type included within a predetermined time interval; And
And a gate control signal generating step of generating the gate control signal in response to the average value. 15. The method of claim 14,
The second largest peak value of the current flowing through the diode connected to the secondary side of the transformer,
And a ratio of the number of primary and secondary windings of the coil constituting the transformer and the first peak value. The method of claim 15, wherein the pulsed output current,
The width of the pulse is from the time when the power transistor is turned off to the time when the diode connected to the secondary coil is turned off, the magnitude of the pulse is half the second peak value, the constant current control method of the LED driver . 16. The method of claim 15,
The constant time interval is a constant current control method of the LED driver, characterized in that determined by the frequency of the AC voltage. 15. The method of claim 14,
When the pulsed output current is included within a predetermined time interval, the parameter extraction step and the pulsed output current generation step are performed, and the pulsed output current is not included within a predetermined time interval. If not, the constant current control method of the LED driver, characterized in that further comprising a predetermined time interval determination step to perform the average value generating step. 19. The method of claim 18,
The parameter extraction step, the output current generation step of the pulse form, the predetermined time interval determination step, the average value generation step and the gate control signal generation step is repeatedly performed while the LED driver supplies a constant current to the LED array. The constant current control method of the LED driver characterized by the above-mentioned. The method of claim 14, wherein the current flowing through the power transistor,
And a voltage falling between the power transistor and the switching resistor connected in series and configured by the switching unit, and using the resistance value of the switching resistor to predict the constant current of the LED driver.

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