TWI499349B - Multi-stage LED driver circuit - Google Patents

Description

Multi-segment LED driver circuit

The invention belongs to the technical field of Light Emitting Diode (LED) power supply devices, in particular to a multi-segment LED driving circuit for adjusting the operation of each LED string according to the change of the voltage value of the AC input voltage. The state achieves high power conversion efficiency and high light utilization efficiency.

Since LEDs have been used in the lighting market due to their low power consumption and high efficiency, how to control the lighting brightness, work efficiency or service life of LED lamps has become the goal of various manufacturers. At present, LED lamps mostly use a constant current architecture control circuit, which is connected to an N-type Metal Oxide Semiconductor Field Effect Transistor (N-MOSFET) and a current resistor. The current resistance defines the drive current flowing through the LED. The current resistor receives the driving current and forms a feedback voltage at one of the two operational amplifiers, and the operational amplifier compares the voltage drop value with a reference voltage value, and then passes through the operational amplifier, the N-MOSFET, and The negative feedback circuit formed by the current resistors has a voltage drop across the current resistor fixed to be equal to the reference voltage value to maintain the driving current in a constant state, and at the same time, to limit THD (Total Harmonic Distortion, total) Harmonic distortion is conveniently limited to a limited range of products sold in various markets.

However, the AC voltage commonly used in countries around the world is not equivalent, and the driving current and THD change with the change of the input AC voltage. The larger the output power, the more difficult the THD is to control and cannot be stably maintained. Internally, the quality of the products is unstable and it is impossible to cut into some markets, limiting the economic value of the industry. At this time, if the safety components are added to stabilize the THD, the cost of the lamps is increased and the economic benefits are not favorable.

Therefore, how to drive a corresponding number of LED strings in response to changes in the voltage of the input AC in order to reduce the virtual power consumption while reducing the operating quality and THD under the condition that the LEDs are connected in series The operating temperature of the overall circuit is the subject of the invention.

In view of the problems of the prior art, the present invention aims to provide a multi-segment LED driving circuit with a simple structure, which serially connects and controls a plurality of LED strings through a single set of constant current control circuits, according to external AC power. The pressure value change state instantly adjusts the working state of each LED string to ensure that the overall circuit operates in the constant current mode, so that the stable circuit works and the service life is improved.

According to an object of the present invention, the multi-segment LED driving circuit is used in an alternating current mode for driving a plurality of light emitting diodes to ensure that a driving current flowing through the light emitting diodes has a constant current value, and the light is emitted. The diode is divided into a plurality of strings, and each of the strings is connected to each other to form a node, so that the string on one side of the node is an upper string and the other string on the opposite side of the node is a lower group. The string is characterized in that: the multi-segment LED driving circuit is provided with at least one detecting component, at least one comparing component and at least one adjusting component, the detecting component is telecommunicationly connected to the strings, and the comparing component is telecommunicationally connected to the detecting component And the adjusting component, wherein the adjusting component is electrically connected to each of the strings; the detecting component detects an input voltage of the string and an output voltage of the lower string to form a detection value to touch the The comparing component compares one of the operating pressure values fed back by the adjusting component with a reference value, and outputs a driving signal to adjust the adjusting component to control the flow of the driving current and drive the series of light to the second stage.

Wherein, the multi-segment LED driving circuit further comprises a current resistor, the detecting component is a gate, the comparing component is an operational amplifier, and the adjusting component is an N-channel metal oxide half field effect transistor (N Type Metal Oxide Semiconductor) Field-Effect Transistor (N-MOSFET), and one input end of the gate is coupled to the input end of the upper string, and the other input end is coupled to the output end of the lower string through an inverter, The output end of the NAND gate is coupled to the enable end of the comparison component. The gate of the adjusting component is coupled to the node between the upper string and the lower string, and the gate The pole is coupled to the output end of the comparing component, and the source is coupled to the negative input end of the comparing component and the current resistor, and the positive input end of the comparing component receives the reference value. In this way, the negative feedback circuit structure is configured such that the current resistor receives the driving current flowing through each of the strings and forms the operating voltage value at both ends thereof, and then feeds back to the operational amplifier, and based on the physical characteristics of the operational amplifier. The negative and positive input terminals of the operational amplifier should have the same voltage value: the reference value, that is, the voltage value of the current resistor is limited to be a constant reference value to ensure that the driving current is a fixed current value.

In summary, the present invention adjusts the load level by instantaneously detecting the change of the voltage value of the external alternating current through a simple circuit structure, so that the light-emitting diode strings are illuminated by the upper and lower segments to maintain the driving current. A constant current value improves the lifetime and efficiency of the overall circuit. Furthermore, those skilled in the relevant art should readily know that the detecting component, the comparing component and the adjusting component can be directly used in the form of electronic components in the circuit, or can be directly formed into a control unit. When the detecting component, the comparing component, and the adjusting component are in a plurality of usage modes, the detecting components are sequentially electrically connected to the input end of the upper string and the lower string The output end, and the adjusting components are electrically connected to the output terminals of the corresponding string in sequence. Alternatively, the detecting component, the comparing component, and the adjusting component may be formed into a single chip unit and then integrated in a control chip, and the control chips may be connected to each other through a corresponding pair of extended pins. The number of uses of the control wafer is augmented or reduced according to the number of uses of the strings. In this way, the practical needs of the circuit of the LED lamp are improved, and the industrial utilization and economic value thereof are effectively improved.

1‧‧‧Multi-section LED driver circuit

10‧‧‧Rectifier Module

11‧‧‧Control module

110‧‧‧Detecting parts

1100‧‧‧ reverser

111‧‧‧Comparative parts

112‧‧‧Adjustment parts

113‧‧‧current resistance

12‧‧‧Lighting diode

120‧‧‧Upper string

121‧‧‧After the string

13‧‧‧Control unit

14‧‧‧Control chip

2‧‧‧External power supply

3‧‧‧THD improvement circuit

30‧‧‧Compensation resistance

Figure 1 is a block diagram of a preferred embodiment of the present invention.

Figure 2 is a circuit diagram of an embodiment of the preferred embodiment of the present invention.

Figure 3 is a circuit diagram of a second embodiment of the preferred embodiment of the present invention.

Figure 4 is a circuit diagram of a third embodiment of the preferred embodiment of the present invention.

Figure 5 is a circuit diagram of a fourth embodiment of the preferred embodiment of the present invention.

Figure 6 is a waveform diagram of a fourth embodiment of the preferred embodiment of the present invention.

Figure 7 is a circuit diagram of a fifth embodiment of the preferred embodiment of the present invention.

In order for your review board to have a clear understanding of the contents of the present invention, please refer to the following description for matching drawings.

Please refer to FIG. 1 and FIG. 2, which are block diagrams of a preferred embodiment of the present invention, and a circuit diagram of an embodiment. As shown in the figure, the multi-segment LED driving circuit 1 is provided with a rectifying module 10, a control module 11 and a plurality of LEDs 12 for sequentially driving the LEDs 12 in an AC mode. In order to ensure that the driving current flowing through the light-emitting diodes 12 has a constant current value. The LEDs 12 are formed into a plurality of strings, and each of the strings is connected to each other to form a node, so that the string on the node side is an upper string 120 and the opposite side of the node. The string is the next string 121. For example, the light-emitting diodes 12 are divided into the upper string 120 and the lower string 121 from the top to the bottom, and then the intersection is formed to form the node (V ₁ ). The rectifier circuit 10 can be coupled to an external power source 2 for the bridge rectifier to rectify the AC voltage to form a variable DC voltage for the control module 11 and the LEDs 12. The control module 11 is provided with a detecting component 110, a comparing component 111, an adjusting component 112 and a current resistance (R _cs ) 113, and the detecting component 110 can be a gate and the comparing component 111 is an operation. The amplifier, and the regulating component 112, is an N-MOSFET. One input end of the sluice gate is coupled to the output end of the rectifying circuit 10 and the input end of the upper string 120, and the other input end is coupled to the output end of the lower string 121 through an inverter 1100. The detecting component 110 detects an input voltage of one of the upper strings 120 and an output voltage of one of the lower strings 121 to form a detection value. The drain of the N-MOSFET is coupled to the node (V ₁ ) between the upper string 120 and the lower string 121, the gate is coupled to the output of the operational amplifier, and the source is coupled to the negative of the operational amplifier The input terminal and the current resistor 113 are configured to form a negative feedback circuit structure such that the current resistor 113 receives the driving current flowing through each of the strings to form an operational voltage value at both ends thereof. The positive input terminal of the comparison component 111 receives a reference value (V _ref ), and the enable terminal is coupled to the output terminal of the gate to compare the current resistance 113 by using the reference value when receiving the detection value. After the feedback of the operating voltage value, a driving signal is output to adjust the adjusting component 112 to control the flow of the driving current to drive the series of light to be driven in the second stage.

Please refer to FIG. 3, which is a circuit diagram of a second embodiment of the preferred embodiment of the present invention. As shown in the figure, the light-emitting diodes 12 are divided into S ₁ ~S _n strings from top to bottom and S ₁ and S ₂ , S ₂ and S ₃ , S ₃ and S ₄ ...S. _The nodes V ₁ , V ₂ , V ₃ ... V _n-1 are formed between the _n-1 and S _n strings, respectively, and the upper string 120 and the lower string 121 are described above, and the string is S ₂ for example, the study compared the node V ₁ and the terms of the set of rope 120 for node V ₂ for the string 121, i.e., in addition to the string S ₁ to the string S _n, the remaining group The string can be said to be the upper string or the lower string. The detecting component 110, the comparing component 111 and the adjusting component 112 can be configured to form a control unit, for example, an IC provided with five positions of VH, VD ₁ , VD ₂ , CS and GND is used in the circuit, so that The control module 11 is in the form of the control unit 13 having the IC ₁ ~ IC _n and the current resistor 113, so that one of the input terminals of the gate of the IC ₁ is coupled to the output end of the rectifier circuit 10 through the VH pin. and said first set of input strings S _1, and the other input terminal through a reverse VD ₂ pin coupled to an output terminal of the second string S _2, namely node V _2; the N-MOSFET through the drain The VD ₁ pin is coupled to the node V ₁ , the gate is coupled to the output of the operational amplifier, and the source is coupled to the negative input of the operational amplifier and coupled to the current resistor 113 through the CS pin. The gate and one input of the IC ₂ 'VH pin is coupled through the input terminal of the second string S _2, namely V ₁ and the IC VD node of the pin _11, and the other input pin through VD ₂ The output terminal of the third string S _{3 is} coupled to the node V ₃ ; the drain of the N-MOSFET is coupled to the node V ₂ through the VD ₁ pin, and the gate is coupled to the output of the operational amplifier. The source is coupled to the negative input terminal of the operational amplifier and coupled to the current resistor 113 through the CS pin, and so on, the detecting components 110 of the IC ₁ ~ IC _n are sequentially electrically connected. The input end of the upper string 120 and the output end of the lower string 121, and the adjusting components 112 are electrically connected to the output ends of the corresponding string.

When the external power supply 2 inputs 110V _AC , its voltage level is increased by 0V with time (t) sine wave. At this time, IC ₁ obtains appropriate power from the VH pin to activate the IC function, and the gate is high. Level voltage (1). When the voltage input by the external power source 2 does not exceed the total operating threshold voltage of the two LED strings of S ₁ and S ₂ , the VD ₂ pin receives a low level voltage (0), and the reverse after 1100 reverse, i.e. the output of the aND gate of the detection value of the high voltage level, so as to enable the operational amplifier outputs the drive signal of the high level voltage of the turned adjustment member 112, such that the driving of the light emitting S ₁ The polar body 12 emits light, and the current resistance is controlled by the current resistor 113 to be a constant current value. Then, when the voltage input by the external power source 2 continues to rise beyond the total operating threshold voltage of the two LED strings of S ₁ and S ₂ , the LEDs 12 of S ₂ will be turned on, and the IC The VH pin of ₂ will obtain the appropriate power to start the IC function. At this time, the driving current flowing through S ₁ is maintained as V _ref /R _cs , but then the current value flowing into S ₂ will increase and the current flowing into IC ₁ will be increased. The current value of the N-MOSFET is reduced. After the driving current flowing through S ₂ is gradually increased and the VD ₂ pin of IC ₁ receives a high level voltage (1), IC ₁ turns off the regulating component 112 to cause the driving current to flow through S ₁ and S _{2 .} And the current is still fixed at V _ref /R _cs . When the external power source with the input of the second voltage rising driving IC _n and operation of IC _n-1 VD pin system ₂ receives a high-level voltage (1), the driving current flowing through the S ₁ + S ₂ + The constant current V _ref /R _{cs of} S ₃ +...+S _n . It can be seen that the voltage value of the external power source 2 rises from 0V to 110. V, and the total operating threshold voltage of the light-emitting diodes 12 is less than 110 At V, the strings will be sequentially illuminated by S ₁ , S ₁ + S ₂ , ..., S ₁ + S ₂ + S ₃ + ... + S _n .

In this embodiment, the detecting component 110, the comparing component 111, and the adjusting component 112 can also be formed into a single chip unit and then integrated in a control chip 14. For example, the inner chip is provided with two chip units as shown in FIG. The control chip 14 is such that the drain of the N-MOSFET of one chip unit is coupled to the input terminal of the other chip unit and the VD ₁ pin, and one of the input terminals of the chip unit is coupled to the VH. a pin, and the other input is coupled to the drain of the N-MOSFET of the other chip unit, and then connected to the VD ₂ pin, and amplifying a VD ₃ pin for connecting the other chip unit to the gate An input. Alternatively, the control chip 14 is provided with a three-chip unit and VD ₁ to VD ₄ pins are provided for use in a THD (Total Harmonic Distortion) improvement circuit 3 of an LED lamp as shown in FIG. The four LEDs of the LEDs 12 are controlled to reduce the THD of the linear driving circuit of the LED lamp and increase the power factor (PF) by increasing or decreasing the AC voltage waveform of the external power source 2 ). The THD improving circuit 30 is provided with a compensating resistor 30, such as the actual measuring signal waveform shown in FIG. 6, the driving current (I _{LED_1} ) is the LEDs 12 having a single-segment string and the THD is not provided. An output current waveform of the LED lamp of the circuit 3 and the compensation resistor 30 is improved; the driving current (I _{LED_2} ) is the LED diode 12 having a four- _segment string and the THD improving circuit 3 is not provided and the compensation is a current waveform of the resistor 30; the driving current (I _{LED_3} ) is a light-emitting diode 12 having a four- _segment string, and a current waveform of the THD improving circuit 3 without the compensation resistor 30; the driving current ( I _{LED_4} is a four- _segment string of the LEDs 12 and is provided with the current waveform of the THD improving circuit 3 and the compensation resistor 30. It can be seen that the conduction period of the I _{LED_1} is short and the current waveform does not change with the voltage waveform. It has poor THD and PF values. The conduction period of I _{LED_2} increases, but the current waveform does not change with the voltage waveform, which makes the THD and PF values improve, but it is still not ideal. The conduction period of I _{LED_3} increases and the current waveform changes with the voltage waveform, which greatly improves the THD and PF values. The conduction period of I _{LED_4} increases and the current waveform changes with the voltage waveform. When the voltage of the external power source is higher, the current drop in the conduction period is larger, so that the input power of the LED lamp is not increased due to the input voltage. And the function that produces dramatic changes. In this manner, the multi-segment LED driving circuit 1 expands the time during which the driving current varies with the change of the external power source 2, and the THD value of the linear driving circuit can be surely kept constant within a limited range.

Incidentally, when the number of the light-emitting diodes 12 is increased and divided into eight strings as shown in FIG. 7, the control module 11 can add another control chip 14 for coupling the newly added four. The strings are serially connected to each other through the VCONNECT_O and VCONNECT pins, which greatly simplifies the assembly structure and facilitates manufacturing.

The above description is only illustrative of preferred embodiments and not limiting. Any equivalent modifications or alterations to the spirit and scope of the invention are intended to be included in the scope of the appended claims.

1‧‧‧Multi-section LED driver circuit

10‧‧‧Rectifier Module

11‧‧‧Control module

110‧‧‧Detecting parts

111‧‧‧Comparative parts

112‧‧‧Adjustment parts

12‧‧‧Lighting diode

2‧‧‧External power supply

Claims (9)

A multi-segment LED driving circuit for driving a plurality of light emitting diodes in an alternating current mode to ensure that a driving current flowing through the light emitting diodes has a constant current value, and the light emitting diodes are distinguished For a plurality of strings, each of the strings is connected to each other to form a node such that the string on one side of the node is an upper string and the other string on the opposite side of the node is a lower string. The multi-segment LED driving circuit is provided with at least one detecting component, at least one comparing component and at least one adjusting component, wherein the detecting component is telecommunicationly connected to the strings, and the comparing component electrically connects the detecting component and the adjusting component And the adjusting component is electrically connected to each of the strings; the detecting component respectively detects one input voltage of the upper string and one output voltage of the lower string to form a detection value, so as to touch the comparison component to utilize A reference value compares one of the operational pressure values fed back by the regulating component to output a driving signal to adjust the regulating component to control the flow of the driving current and to drive the string illumination in a sub-segment. The multi-segment LED driving circuit of claim 1, wherein the detecting component is a gate, one input end is coupled to the input end of the upper string, and the other input end is coupled to an inverter The output end of the lower string is coupled, and the output end of the gate is connected to the trigger end of the comparison component. The multi-segment LED driving circuit of claim 2, wherein the comparing component is an operational amplifier, the positive input terminal thereof receives the reference value, the negative input terminal is electrically connected to the output end of the regulating component, and the operational amplifier The output end is electrically connected to the trigger end of the adjusting component, and the enable terminal of the operational amplifier is coupled to the output end of the AND gate. The multi-segment LED driving circuit of claim 3, wherein the adjusting component is an N-type metal Oxide Semiconductor Field-Effect Transistor (N-MOSFET), and the drain is coupled to the anode The node between the upper string and the lower string, the gate is coupled to the output end of the operational amplifier, and the source is coupled to the negative input terminal of the operational amplifier to form a negative feedback circuit structure to provide stable current control effect . For example, the multi-segment LED driving circuit described in claim 4 is further provided with a current resistor. The system is coupled to the source of the N-channel MOSFET to cause the driving current flowing through each of the strings to form the operating pressure at both ends thereof. The multi-segment LED driving circuit of claim 1, wherein when the detecting component, the comparing component and the adjusting component are in a plurality of use modes, the detecting components are electrically connected to the corresponding string in sequence. And the input end and the output end of the two sets of the two strings of the string, and the adjusting components are electrically connected to the output ends of the corresponding string. A multi-segment LED driving circuit for driving a plurality of light emitting diodes in an alternating current mode to ensure that a driving current flowing through the light emitting diodes has a constant current value, and the light emitting diodes are distinguished For a plurality of strings, each of the strings is connected to each other to form a node such that the string on one side of the node is an upper string and the other string on the opposite side of the node is a lower string. The multi-segment LED driving circuit has a plurality of control units, and each of the control units is provided with a detecting component, a comparing component and an adjusting component, and the detecting component electrically connects the upper string and the lower string, Comparing the component to the detecting component and the adjusting component, and the adjusting component is electrically connected to each of the strings; the detecting component detects an input voltage of the upper string and an output voltage of the lower string to form a Detecting a value for the comparing component to output a driving signal by comparing a reference value to turn the adjusting component on or off to control the number of strings through which the driving current flows. A multi-segment LED driving circuit for driving a plurality of light emitting diodes in an alternating current mode to ensure that a driving current flowing through the light emitting diodes has a constant current value, and the light emitting diodes are distinguished For a plurality of strings, each of the strings is connected to each other to form a node such that the string on one side of the node is an upper string and the other string on the opposite side of the node is a lower string. The multi-segment LED driving circuit has at least one control chip, the control chip is provided with a plurality of control units, and each of the control units is provided with a detecting component, a comparing component and an adjusting component, and the detecting component is electrically connected to the control component. The upper string and the lower string, the comparison component is telecommunicationally connected to the detecting component and the adjusting component, and the adjusting component is electrically connected to each of the strings; the detecting component detects an input voltage of the upper string and the One of the lower strings outputs a voltage to form And a detection value for the comparison component to output a driving signal by comparing a reference value to turn on or off the adjusting component to control the number of strings through which the driving current flows. The multi-segment LED driving circuit of claim 8, wherein when the control chip is in a plurality of use modes, the control chips are connected to each other through a corresponding one of the pair of extension pins, according to the group of strings. The number of uses is used to amplify or reduce the number of uses of the control chip.