201220925 六、發明說明： 【發明所屬之技術領域】 本發明係有關led的驅動方法及驅動電路，尤其有關 適用於白光LED ( W LED )的三端可控矽調光器的驅動方 法及驅動電路。 【先前技術】 如今WLED照明技術的應用已經越來越廣泛，並且以 WLED取代傳統的燈泡照明已經成爲WLED照明技術發展的 一個主要趨勢。然而採用WLED取代傳統燈泡照明的一個 困難點在於WLED驅動電路必須與標準的三端可控矽調光 器相容以達成在照明過程中對WLED進行亮度調節，這不 僅是用戶的需求，而且可以延長WLED的使用壽命》 傳統的三端可控矽調光器都是爲純電阻性負載燈，諸 如白熾燈和碘鎢燈等設計的。由於WLED並不呈現電阻性 負載特性，因而採用傳統的三端可控矽調光器對WLED進 行調光並不能達到良好的效果。如圖1所示爲已知技術中 將傳統的三端可控矽調光電阻性燈照明驅動結構使用於驅 動WLED的驅動電路示意圖。該驅動電路100包括：三端可 控矽調光器101、電子變壓器103'整流器105和WLED驅動 器107，用以驅動WLED 109。三端可控矽調光器1〇1透過 調節其內部之三端雙向可控矽開關的導通時間以控制供電 交流電源（通常爲U0V-220V的交流電）向驅動電路100傳 輸的能量，以輸出一個導通角受控的高壓交流電。所述三 -5- 201220925 端雙向可控矽開關在一個供電週期內的導通時間用相應的 角度表示即爲導通角。通常所述三端雙向可控矽開關的開 通係由一個控制信號來予以控制，當三端雙向可控矽開關 中的電流減小到某一値時即自動關斷，因此控制信號到來 的時間決定了三端雙向可控矽開關的導通時間。電子變壓 器103接收所述高壓交流電並將其轉換爲低壓交流電。整 流器1 05將所述低壓交流電整流後輸出低壓直流電，用以 爲WLED驅動器107供電以驅動WLED 109操作。在調光過 程中，通常三端可控矽調光器101輸出的高壓交流電並非 均勻對稱的，那麼電子變壓器103輸出的低壓交流電也是 非對稱的，經過整流器1 05處理輸出的低壓直流信號中會 包含50 Hz的低頻交流電壓紋波，如果三端可控矽調光器 101輸出的高壓交流電在調光過程中發生某些導通角丟失 ，亦即，在某個供電週期內，如果控制三端雙向可控矽開 關開通的控制信號到來較晚，這樣三端雙向可控矽開關的 導通時間就較短，亦即，導通角較小，以至於三端雙向可 控矽開關未能及時完全導通，那麼這個較小的導通角就丟 失了，這樣整流器105輸出的低壓直流信號中還會包含低 於50 Hz的更低頻交流電壓紋波。這些50 Hz或者更低頻的 交流電壓紋波被輸入至WLED驅動器107會導致WLED 109 中有50 Hz或者更低頻的交流電流流過，從而引起WLED在 調光過程中閃燥，這是在實際應用中應當消除的。 因此，爲了避免調光過程中引起WLED閃爍，檢測三 端可控調光器的導通角並將其處理，以便調節WLED的亮 201220925 度是很重要的。 【發明內容】 本發明的目的在於解決現有三端可控矽調光器因存在 低頻交流電而造成調光過程閃爍的問題，提供一種適用於 三端可控矽調光器的WLED驅動方法及驅動電路，該驅動 方法及驅動電路可以檢測三端可控矽調光器的導通角並將 其應用於WLED的亮度調節，從而實現寬範圍、平滑無閃 爍的WLED調光。 本發明的另一目的在於提供應用於上述調光器中的電 子變壓器，以檢測其導通角並應用於WLED的亮度調節， 從而實現寬範圍、平滑無閃爍的WLED調光。 本發明採用的技術方案如下： —種適用於三端可控矽調光器的WLED驅動電路，包 括： 三端可控矽調光器，用以耦接高壓交流供電電源，以 輸出導通角受控的高壓交流電； 電子變壓器，用以接收所述高壓交流電，以輸出PWM 低壓直流電； WLED驅動器，用以接收所述PWM低壓直流電，以輸 出WLED驅動信號；以及 所述電子變壓器檢測所述高壓交流電的導通角，並且 基於該導通角而調節輸出的PW Μ低壓直流電的占空比。 在本發明的一個較佳實施例中，所述電子變壓器可以 201220925 包括：導通角檢測模組，導通角調變模組和變換器模組。 其中，所述導通角檢測模組，用以檢測所述高壓交流電的 導通角，基於所述導通角，以產生第一 PWM信號； 所述導通角調變模組，用以接收所述第一 PWM信號’ 將其濾波而產生反映第一 PWM信號之直流平均値的直流電 壓信號，並將所述直流電壓信號與一個三角波信號做比較 而輸出第二PWM信號；以及 所述變換器模組，受所述第二PWM信號所控制，將所 述高壓交流電轉換爲所述PWM低壓直流電。 最好，所述第一PWM信號的頻率和占空比與所述導通 角信號的頻率和占空比一致；及所述第二PWM信號的占空 比受所述導通角信號所調節，其頻率高於所述導通角信號 的頻率。 所述導通角檢測模組可以採用現有技術中的多種導通 角檢測電路結構來予以實現，例如根據本發明的一個實施 例，所述導通角檢測模組包括整流電路和類線性穩壓器電 路，其中， 所述整流電路，用以接收所述高壓交流電並將其整流 爲高壓直流電；以及 所述類線性穩壓器電路，包括至少一個穩壓二極體和 一個可控開關，所述穩壓二極體的陰極經由第一電阻器而 耦接所述高壓直流電，其陽極係耦接到地，所述可控開關 的閘極係耦接所述穩壓二極體的陰極，其汲極係耦接所述 高壓直流電，其源極經由第二電阻器而被耦接到地，所述 -8- 201220925 可控開關的源極用作爲所述導通角檢測模組的輸出端。 另外，在本發明的不同實施例中，還可以採用過零檢 測比較器電路來替換所述類線性穩壓器電路，所述過零檢 測比較器電路接收並處理所述高壓直流電，以輸出所述第 一 PWM信號，且當所述高壓直流電大於零時，所述第一 PWM信號爲高位準，而當所述高壓直流電降爲零，所述第 一 PWM信號爲低位準。 所述導通角調變模組可以包括：低通濾波器，用以將 所述第一 PWM信號濾波，以輸出所述直流電壓信號；以及 PWM比較器，用以將所述直流電壓信號與所述三角波 信號做比較而輸出所述第二PWM信號。 所述變換器模組可以是任何將高壓交流電轉換爲低壓 直流電的AC-DC變換器。 —種適用於三端可控矽調光器的WLED驅動方法，包 括： 接收高壓交流供電電源，以輸出導通角受控的高壓交 流電； 將所述高壓交流電轉變爲PWM低壓直流電；以及 將所述PWM低壓直流電輸入WLED驅動器以調節其驅 動 WLED， 其中，將所述高壓交流電轉變爲P W Μ低壓直流電還包 括檢測所述局壓父流電的導通角，並基於該導通角而調節 輸出的PWM低壓直流電的占空比。 根據本發明的一個較佳實施例，將所述高壓交流電轉 -9 - 201220925 變爲所述PWM低壓直流電的步驟包括： 檢測所述高壓交流電的導通角，並產生第一 PWM信號 將所述第一 PWM信號濾波，以產生反映第一 PWM信號 之直流平均値的直流電壓信號； 將所述直流電壓信號與一個三角波信號做比較，以產 生第二PWM信號；以及 基於所述第二PWM信號的控制，將所述高壓交流電轉 變爲所述PWM低壓直流電。 最好，所述第一 PWM信號的頻率和占空比與所述導通 角信號的頻率和占空比一致；及所述第二PWM信號的占空 比受所述導通角信號所調節，其頻率高於所述導通角信號 的頻率。 根據本發明的一個較佳實施例，透過導通角檢測模組 以檢測所述高壓交流電的導通角，所述導通角檢測模組包 括整流電路和類線性穩壓器電路，其中， 所述整流電路，用以接收所述高壓交流電並將其整流 爲高壓直流電；以及 所述類線性穩壓器電路，包括至少一個穩壓二極體和 一個可控開關，所述穩壓二極體的陰極經由第一電阻器而 耦接所述高壓直流電，其陽極係耦接到地，所述可控開關 的閘極係耦接所述穩壓二極體的陰極，其汲極係耦接所述 高壓直流電，其源極經由第二電阻器而被耦接到地，所述 可控開關的源極用作爲所述導通角檢測模組的輸出端。 -10- 201220925 另外，在本發明的不同實施例中，還可以採用過零檢 測比較器電路來替換所述類線性穩壓器電路’ # $ @胃# 測比較器電路接收並處理所述高壓直流電，以輸出所述第 一 PWM信號，且當所述高壓直流電大於零時’所述第一 PWM信號爲高位準，而當所述高壓直流電降爲零’所述第 一 PWM信號爲低位準。 根據本發明的一個較佳實施例，採用低通濾波器對所 述第一PWM信號濾波。 根據本發明的一個較佳實施例，透過PWM比較器以接 收所述直流電壓信號和所述三角波信號，以輸出所述第二 PWM信號。 根據本發明的一個較佳實施例，透過AC-DC變換器以 接收所述高壓交流電和所述第二PWM信號，將所述高壓交 流電轉變爲所述PWM低壓直流電。 本發明還提供一種電子變壓器，接收高壓交流電，且 輸出PWM低壓直流電，該電子變壓器包括： 導通角檢測模組，用以檢測所述高壓交流電的導通角 :以及 控制模組，基於檢測出的導通角信號，以調節輸出的 PWM低壓直流電的占空比。 本發明所提供的一種電子變壓器，所述控制模組包括 導通角調變模組和變換器模組，其中 所述導通角檢測模組，基於所述檢測出的導通角信號 ’以產生第一PWM信號； -11 - 201220925 所述導通角調變模組’用以接收所述第一PWM信號’ 將其濾波而產生反映第一 PWM信號之直流平均値的直流電 壓信號，並將所述直流電壓信號與三角波信號做比較而輸 出第二PWM信號；以及 所述變換器模組，受所述第二PWM信號所控制，將所 述高壓交流電轉換爲所述PWM低壓直流電。 本發明提供的一種電子變壓器’所述第一 PWM信號的 頻率和占空比與所述導通角信號的頻率和占空比一致；且 所述第二PWM信號的占空比受所述導通角信號所調節，其 頻率高於所述導通角信號的頻率。 本發明提供的一種電子變壓器，所述導通角檢測模組 包括整流電路和類線性穩壓器電路，其中， 所述整流電路，用以接收所述高壓交流電並將其整流 爲高壓直流電； 所述類線性穩壓器電路，包括至少一個穩壓二極體和 一個可控開關，所述穩壓二極體的陰極經由第一電阻器而 耦接所述高壓直流電，其陽極係耦接到地，所述可控開關 的閘極係耦接所述穏壓二極體的陰極，其汲極係耦接所述 高壓直流電，其源極經由第二電阻器而被耦接到地，所述 可控開關的源極用作爲所述導通角檢測模組的輸出端。201220925 VI. Description of the Invention: [Technical Field] The present invention relates to a driving method and a driving circuit for a LED, and more particularly to a driving method and a driving circuit for a three-terminal controllable dimming device suitable for a white LED (W LED ) . [Prior Art] Nowadays, the application of WLED lighting technology has become more and more extensive, and replacing traditional bulb lighting with WLED has become a major trend in the development of WLED lighting technology. However, one of the difficulties in replacing traditional bulb illumination with WLED is that the WLED driver circuit must be compatible with the standard three-terminal controllable dimmer to achieve brightness adjustment of the WLED during illumination, which is not only the user's needs, but also Extending the service life of WLEDs Traditional three-terminal controllable dimmers are designed for purely resistive load lamps such as incandescent lamps and iodine-tungsten lamps. Since the WLED does not exhibit resistive load characteristics, the use of a conventional three-terminal controllable dimmer to dim the WLED does not achieve good results. FIG. 1 is a schematic diagram of a driving circuit for driving a WLED using a conventional three-terminal controllable dimming resistive lamp illumination driving structure in the prior art. The drive circuit 100 includes a three-terminal controllable dimmer 101, an electronic transformer 103' rectifier 105, and a WLED driver 107 for driving the WLED 109. The three-terminal controllable dimming device 1〇1 controls the conduction time of the internal three-terminal bidirectional controllable switch to control the energy transmitted to the driving circuit 100 by the AC power supply (usually U0V-220V AC) to output A high-voltage alternating current with a conduction angle controlled. The conduction time of the three-5-201220925 terminal bidirectional controllable switch in one power supply period is represented by a corresponding angle. Generally, the opening of the three-terminal bidirectional controllable switch is controlled by a control signal, and when the current in the three-terminal bidirectional controllable switch is reduced to a certain turn, it is automatically turned off, so the time when the control signal arrives The on-time of the three-terminal bidirectional controllable switch is determined. The electronic transformer 103 receives the high voltage alternating current and converts it into low voltage alternating current. The rectifier 105 rectifies the low voltage alternating current and outputs low voltage direct current for powering the WLED driver 107 to drive the WLED 109 to operate. In the dimming process, usually the high-voltage alternating current outputted by the three-terminal controllable dimmer 101 is not uniformly symmetrical, and the low-voltage alternating current outputted by the electronic transformer 103 is also asymmetric, and the low-voltage direct current signal processed by the rectifier 105 will be Contains 50 Hz low-frequency AC voltage ripple. If the high-voltage AC output from the three-terminal controllable dimmer 101 occurs during the dimming process, some conduction angle loss occurs, that is, within a certain power supply cycle, if the three-terminal control is performed. The control signal of the bidirectional controllable switch is late, so that the conduction time of the three-terminal bidirectional controllable switch is shorter, that is, the conduction angle is small, so that the three-terminal bidirectional controllable switch is not fully turned on in time. Then, the smaller conduction angle is lost, so that the low-voltage DC signal output by the rectifier 105 also contains a lower-frequency AC voltage ripple of less than 50 Hz. These 50 Hz or lower frequency AC voltage ripples are input to the WLED driver 107, which causes a 50 Hz or lower frequency AC current flowing through the WLED 109, causing the WLED to flash during the dimming process, which is practical. Should be eliminated. Therefore, in order to avoid the WLED flicker during the dimming process, it is important to detect the conduction angle of the three-terminal controllable dimmer and process it to adjust the brightness of the WLED 201220925. SUMMARY OF THE INVENTION The object of the present invention is to solve the problem that the existing three-terminal controllable dimmer is flickering due to the presence of low frequency alternating current, and provide a WLED driving method and driving suitable for the three-terminal controllable dimming device. The circuit, the driving method and the driving circuit can detect the conduction angle of the three-terminal controllable dimmer and apply it to the brightness adjustment of the WLED, thereby realizing a wide range, smooth and flicker-free WLED dimming. Another object of the present invention is to provide an electronic transformer applied to the above dimmer to detect its conduction angle and apply to the brightness adjustment of the WLED, thereby realizing a wide range, smooth flicker-free WLED dimming. The technical solution adopted by the invention is as follows: a WLED driving circuit suitable for a three-terminal controllable 矽 dimmer, comprising: a three-terminal controllable 矽 dimmer for coupling a high-voltage AC power supply to output a conduction angle a high voltage alternating current; an electronic transformer for receiving the high voltage alternating current to output PWM low voltage direct current; a WLED driver for receiving the PWM low voltage direct current to output a WLED driving signal; and the electronic transformer detecting the high voltage alternating current The conduction angle, and based on the conduction angle, adjusts the duty cycle of the output PW Μ low voltage direct current. In a preferred embodiment of the present invention, the electronic transformer may include: a conduction angle detecting module, a conduction angle modulation module, and a converter module. The conduction angle detecting module is configured to detect a conduction angle of the high-voltage alternating current, and generate a first PWM signal based on the conduction angle; and the conduction angle modulation module is configured to receive the first The PWM signal 'filters it to generate a DC voltage signal reflecting the DC average chirp of the first PWM signal, and compares the DC voltage signal with a triangular wave signal to output a second PWM signal; and the converter module, The high voltage alternating current is converted to the PWM low voltage direct current by the second PWM signal. Preferably, a frequency and a duty ratio of the first PWM signal are consistent with a frequency and a duty ratio of the conduction angle signal; and a duty ratio of the second PWM signal is adjusted by the conduction angle signal, The frequency is higher than the frequency of the conduction angle signal. The conduction angle detecting module can be implemented by using a plurality of conduction angle detecting circuit structures in the prior art. For example, according to an embodiment of the present invention, the conduction angle detecting module includes a rectifying circuit and a linear-like voltage regulator circuit. The rectifier circuit is configured to receive the high voltage alternating current and rectify it into high voltage direct current; and the linear regulator circuit includes at least one voltage stabilizing diode and a controllable switch, and the voltage regulator The cathode of the diode is coupled to the high voltage direct current via a first resistor, the anode of the diode is coupled to the ground, and the gate of the controllable switch is coupled to the cathode of the voltage stabilizing diode, and the drain thereof The high voltage direct current is coupled to the source, and the source thereof is coupled to the ground via a second resistor, and the source of the -8-201220925 controllable switch is used as an output end of the conduction angle detecting module. Additionally, in various embodiments of the present invention, a zero-crossing comparator circuit may be substituted for the linear-type regulator circuit, and the zero-crossing comparator circuit receives and processes the high-voltage direct current to output The first PWM signal is described, and when the high voltage direct current is greater than zero, the first PWM signal is at a high level, and when the high voltage direct current is zero, the first PWM signal is at a low level. The conduction angle modulation module may include: a low pass filter for filtering the first PWM signal to output the DC voltage signal; and a PWM comparator for combining the DC voltage signal with the The triangular wave signal is compared to output the second PWM signal. The converter module can be any AC-DC converter that converts high voltage alternating current to low voltage direct current. A WLED driving method suitable for a three-terminal controllable dimming device, comprising: receiving a high-voltage alternating current power supply to output a high-voltage alternating current with a conduction angle controlled; converting the high-voltage alternating current into a PWM low-voltage direct current; The PWM low voltage direct current input WLED driver adjusts the driving WLED thereof, wherein converting the high voltage alternating current into the PW Μ low voltage direct current further comprises detecting a conduction angle of the local pressure parent current, and adjusting the output PWM low voltage based on the conduction angle The duty cycle of the DC. According to a preferred embodiment of the present invention, the step of changing the high voltage alternating current to -9 - 201220925 to the PWM low voltage direct current comprises: detecting a conduction angle of the high voltage alternating current, and generating a first PWM signal to be the first a PWM signal filtering to generate a DC voltage signal reflecting a DC average chirp of the first PWM signal; comparing the DC voltage signal with a triangular wave signal to generate a second PWM signal; and based on the second PWM signal Controlling, converting the high voltage alternating current into the PWM low voltage direct current. Preferably, a frequency and a duty ratio of the first PWM signal are consistent with a frequency and a duty ratio of the conduction angle signal; and a duty ratio of the second PWM signal is adjusted by the conduction angle signal, The frequency is higher than the frequency of the conduction angle signal. According to a preferred embodiment of the present invention, the conduction angle detecting module is configured to detect a conduction angle of the high-voltage alternating current, and the conduction angle detecting module includes a rectifying circuit and a linear-like regulator circuit, wherein the rectifying circuit Receiving the high voltage alternating current and rectifying it into high voltage direct current; and the linear regulator circuit comprising at least one voltage stabilizing diode and a controllable switch, the cathode of the voltage stabilizing diode being via The first resistor is coupled to the high voltage direct current, the anode is coupled to the ground, the gate of the controllable switch is coupled to the cathode of the voltage stabilizing diode, and the drain is coupled to the high voltage The direct current is coupled to the ground via a second resistor, and the source of the controllable switch is used as an output of the conduction angle detecting module. -10- 201220925 Additionally, in various embodiments of the present invention, a zero-crossing comparator circuit may be employed to replace the linear-like regulator circuit ' # $ @胃# 测 comparator circuit receives and processes the high voltage Direct current to output the first PWM signal, and when the high voltage direct current is greater than zero, the first PWM signal is at a high level, and when the high voltage direct current is zero, the first PWM signal is at a low level . In accordance with a preferred embodiment of the present invention, the first PWM signal is filtered using a low pass filter. In accordance with a preferred embodiment of the present invention, the DC voltage signal and the triangular wave signal are received by a PWM comparator to output the second PWM signal. In accordance with a preferred embodiment of the present invention, the high voltage AC power is converted to the PWM low voltage DC power by an AC-DC converter to receive the high voltage alternating current and the second PWM signal. The invention also provides an electronic transformer for receiving high voltage alternating current and outputting PWM low voltage direct current, the electronic transformer comprising: a conduction angle detecting module for detecting a conduction angle of the high voltage alternating current: and a control module, based on the detected conduction The angular signal is used to adjust the duty cycle of the output PWM low voltage DC. An electronic transformer provided by the present invention, the control module includes a conduction angle modulation module and a converter module, wherein the conduction angle detection module is based on the detected conduction angle signal 'to generate a first PWM signal; -11 - 201220925 The conduction angle modulation module 'is configured to receive the first PWM signal' to filter it to generate a DC voltage signal reflecting the DC average 値 of the first PWM signal, and to generate the DC The voltage signal is compared with the triangular wave signal to output a second PWM signal; and the converter module is controlled by the second PWM signal to convert the high voltage alternating current into the PWM low voltage direct current. The frequency and duty ratio of the first PWM signal of the electronic transformer of the present invention are consistent with the frequency and duty ratio of the conduction angle signal; and the duty ratio of the second PWM signal is affected by the conduction angle The signal is adjusted with a frequency higher than the frequency of the conduction angle signal. An electronic transformer provided by the present invention, the conduction angle detecting module includes a rectifying circuit and a linear regulator circuit, wherein the rectifying circuit is configured to receive the high voltage alternating current and rectify it into high voltage direct current; a linear regulator circuit comprising at least one voltage stabilizing diode and a controllable switch, the cathode of the voltage stabilizing diode being coupled to the high voltage direct current via a first resistor, the anode of which is coupled to the ground The gate of the controllable switch is coupled to the cathode of the rolling diode, the drain of the diode is coupled to the high voltage direct current, and the source thereof is coupled to the ground via a second resistor. The source of the controllable switch is used as the output of the conduction angle detecting module.
本發明提供的一種電子變壓器，所述類線性穩壓器電 路還可以採用過零檢測比較器電路來替換，所述過零檢測 比較器電路接收並處理所述高壓直流電，以輸出所述第一 PWM信號，且當所述高壓直流電大於零時，所述第一 PWM -12- 201220925 信號爲高位準’而當所述高壓直流電降爲零’所述第一 PWM信號爲低位準。 本發明提供的一種電子變壓器’所述導通角調變模組 包括低通濾波器和PWM比較器，其中， 所述低通濾波器’用以接收所述第一 p WM信號，並將 其轉變爲所述直流電壓信號；以及 所述PWM比較器，用以將所述直流電壓信號與所述三 角波信號做比較而輸出所述第二PWM信號。 本發明提供的一種電子變壓器’所述變換器模組是將 高壓交流電轉換爲低壓直流電的AC-DC變換器。 本發明之適用於三端可控矽調光器的WLED驅動方法 及驅動電路的有益效果是：本發明所提供之適用於三端可 控矽調光器的WLED驅動方法及驅動電路提供一種新穎的 電子變壓器，可以檢測三端可控矽調光器所輸出的高壓交 流電的導通角，並將所述高壓交流電轉變爲占空比受所述 導通角所調節的PWM低壓直流電。該PWM低壓直流電爲 WLED驅動器供電以驅動WLED操作，調節三端可控矽調光 器即可以改變所述PWM低壓直流電壓信號的占空比，從而 調節流過WLED燈管的平均電流，以改變WLED的亮度，所 述PWM低壓直流電中不包含頻率爲50 Hz及50 HZ以下的交 流電壓紋波，因此，本發明之適用於三端可控矽調光器的 WLED驅動方法、驅動電路及其中所應用的電子變壓器可 以實現對WLED的平滑無閃爍調光。 -13- 201220925 【實施方式】 下面詳細說明本發明實施例的三端可控矽調光WLED 驅動方法及驅動電路。在接下來的說明中，一些具體的細 節，例如實施例中的具體電路結構和這些電路元件的具體 參數，都用來對本發明的實施例提供更好的理解。本技術 他現 其實 者被 或以 節可 細也 多明 很發 少本 缺’ 在下 使況 即情 ’ 的 解合 理結 以等 可料 員 材 人、 術件 技元 的、 域法 領方 。 圖2爲本發明一個實施例的三端可控矽調光W LED驅動 電路示意圖。該驅動電路200主要包括三端可控矽調光器 202、電子變壓器204和WLED驅動器206用以驅動WLED燈 管208。其中： 所述三端可控矽調光器202，用以接收高壓交流供電 電壓U1，並產生導通角受控的高壓交流電U2; 所述電子變壓器204，檢測所述高壓交流電U2的導通 角，並將所述高壓交流電U2轉換爲一個占空比受所述導通 角所調節的PWM (脈衝寬度調變）低壓直流電U3 ; 所述WLED驅動器206，接收所述PWM低壓直流電U3 ，並輸出WLED驅動電流ILED，以驅動所述WLED 2 08操作 〇 如圖3所示，根據本發明一個實施例的三端可控矽調 光WLED驅動電路200，所述電子變壓器204包括三個主要 部分：導通角檢測模組、導通角調變模組和變換器模組。 其中： -14- 201220925 所述導通角檢測模組，係耦接所述三端可控矽調光器 202的輸出端，用以接收所述高壓交流電U2，並輸出表徵 所述高壓交流電U2的導通角的第一PWM信號Ua ; 所述導通角調變模組，係耦接所述導通角檢測模組的 輸出端，用以接收所述第一 PWM信號Ua，將其進行低通濾 波而產生一個直流電壓信號Ude，並將所述直流電壓信號 Udc與一個三角波信號做比較，以輸出第二PWM信號Um ; 所述變換器模組，係耦接所述三端可控矽調光器202 的輸出端和所述導通角調變模組的輸出端，以分別接收所 述高壓交流電U2和所述第二PWM信號Um，並受所述第二 PWM信號Um的控制而將所述高壓交流電U2轉換爲所述 PWM低壓直流電U3。 如圖4所示爲根據本發明一個實施例的三端可控矽調 光WLED驅動電路在正常操作情況下的主要信號波形圖。 下面將結合圖4所示的波形圖對本發明所提出的三端可控 矽調光WLED驅動電路200的操作原理作進一步闡述。 在調光過程中，所述三端可控矽調光器202接收高壓 交流供電電壓U1，透過調節其內部三端雙向可控矽開關的 導通時間，使得所述高壓交流供電電壓U 1在一個週期內僅 在所述三端雙向可控矽開關的導通時間內向驅動電路200 傳輸能量。通常所述三端雙向可控矽開關的開通係由一個 控制信號來予以控制，當三端雙向可控矽開關中電流減小 到某一値時即自動關斷，因此控制信號到來的時間決定了 三端雙向可控矽開關的導通時間。所述三端雙向可控矽開 -15- 201220925 關在一個供電週期內的導通時間用相對應的角度表示即爲 導通角。因此，所述三端可控矽調光器2 02處理所述高壓 交流供電電壓U1，以輸出導通角受控的高壓交流電U2。 所述電子變壓器204透過所述導通角檢測模組來檢測所述 導通角，並產生第一 PWM信號Ua，使得所述第一 PWM信 號Ua的頻率和占空比與所述導通角信號的頻率和占空比相 同。所述第一PWM信號Ua輸入所述導通角調變模組，經過 低通濾波而產生一個直流電壓信號Ud。，該直流電壓信號 Udc反映了所述第一 PWM信號Ua的直流平均値，將所述直 流電壓信號Ude與一個三角波信號做比較而產生第二PWM 信號Um，則所述第二PWM信號Um的占空比受所述導通角 所調節，且其頻率將大大高於所述導通角信號的頻率。所 述第二PWM信號Um被輸入所述變換器模組，以控制其將 所述高壓交流電壓信號U2轉換爲所述PWM低壓直流電U3 。所述PWM低壓直流電U3的頻率和占空比與所述第二 PWM信號Um的頻率和占空比一致，因而，其占空比反映 了所述高壓交流電U2的導通角，其幅値被調節在一個預先 設定的穏定値，例如12 V，以爲WLED驅動器206供電。當 所述PWM低壓直流電U3爲高位準時，WLED驅動器206向 WLED 208提供恒定的操作電流；當所述PWM低壓直流電 U3爲低位準時，WLED驅動器206不向WLED 208供電， WLED 2 08中無電流流過。因此，調節所述三端可控矽調 光器202 ’以改變其輸出高壓交流電U2的導通角，即可以 調節所述電子變壓器204輸出的所述PWM低壓直流電U3的 -16- 201220925 占空比，從而控制所述WLED驅動器206爲所述WLED 208 提供的平均電流大小’實現對W L E D 2 0 8亮度的調節。由 於本發明所提出的實施例中所述電子變壓器204輸出的所 述PWM低壓直流電U3的頻率和占空比與所述第二PWM信 號Um的頻率和占空比一致，因而其頻率大大高於所述導 通角信號的頻率，從而所述pWM低壓直流電U3中不包含頻 率爲50 Hz及5〇 Hz以下的交流電壓紋波，則在調光過程中 ，所述WLED燈管208不會發生閃爍現象。 在本發明的不同實施例中，所述導通角檢測模組可以 採用現有技術中的多種導通角檢測電路結構來實現。如圖 5所示爲根據本發明一個實施例之導通角檢測模組的電路 結構圖。該電路500包括：整流電路501和類線性穩壓器電 路5 02。其中，所述整流電路501係由四個耐高壓二極體D1 、D 2、D 3和D 4所組成，D 1和D 2的串聯組合以及D 3和D 4的 串聯組合係並聯耦接於供電線L 1與地之間，並且D 1和D3 的陰極係耦接供電線L 1，D2和D4的陽極係耦接到地，所 述高壓交流電U2的一端係耦接D1的陽極和D2的陰極，其 另一端係耦接D3的陽極和D4的陰極；所述類線性穩壓器 電路5 02包括第一電阻器R1、第一穩壓二極體D5、第二穩 壓二極體D6、電晶體Q1，第二電阻器R2和電容器C1，所 述第一電阻器R 1的一端係耦接供電線L 1，其另一端係耦接 所述第一穩壓二極體D5的陰極，所述第一穩壓二極體D5 的陽極係耦接所述第二穩壓二極體D 6的陰極和所述電晶體 Q 1的閘極，所述第二穩壓二極體D6的陽極係耦接到地’ -17- 201220925 所述電晶體Q 1的汲極係耦接供電線L 1，其源極透過所述第 二電阻器R2而被耦接到地，所述電容器C 1係並聯耦接於第 二電阻器R2的兩端，所述電晶體Q 1的源極和所述第二電阻 器R2的非接地端一起用作爲該電路500的輸出端。該電路 5 00的操作原理如下：所述高壓交流電U2經由所述整流電 路501而被整流後，其正半波保持原樣，且其負半波被翻 轉爲正半波，則載入於供電線L 1上的線電壓UL 1，如圖6 所示；所述類線性穩壓器電路502係由該線電壓UL1所供電 ，當所述第一穩壓二極體D5上的電壓到達其反向擊穿電壓 時，所述第二穩壓二極體D6上的電壓開始上升，導通角檢 測電路5 00的輸出電壓Ua等於穩壓二極體D6上的電壓減去 電晶體Q 1的閘極-源極電壓，由於此時電晶體Q 1係操作於 線性區，其閘極-源極電壓很小，因此Ua接近於穩壓二極 體D6上的電壓；當穩壓二極體D6上的電壓也到達其反向 擊穿電壓之後，D6上的電壓被鉗位在其反向擊穿電壓上， 同時，Ua也被鉗位在一個接近於D6的反向擊穿電壓的電位 上（D6的反向擊穿電壓減去Q1的閘極-源極電壓）。穩壓 二極體D5和D6的反向擊穿電壓一般不大，則Ua的上升邊 緣與三端可控矽調光器2 02中的三端雙向可控矽開關的導 通時刻基本一致，同理，U a的下降邊緣與三端雙向可控矽 開關的關斷時刻也基本一致，當三端雙向可控矽開關被關 斷，則線電壓UL1變爲零，那麼Ua也將跳變爲零，因此Ua 是一個脈衝信號，其脈寬與三端雙向可控矽開關的導通時 間一致，因而實現了對高壓交流電U2的導通角之檢測。本 -18 - 201220925 領域的技術人員應該理解，該電路500還可以有多種等效 變化’例如去掉所述第一穩壓二極體D 5，仍可以實現相同 的導通角檢測功能，所述電晶體Q 1還可以是其他可控開關 裝置’諸如BJT。另外，本領域的技術人員應該理解，在 本發明的不同實施例中，還可以採用過零檢測比較器電路 來替換所述電路5 00中的類線性穩壓器電路502，將所述線 電壓UL1經過零檢測比較器電路處理，而輸出所述第一 PWM信號Ua ’ 一旦所述線電壓ul 1大於零，則過零檢測比 較器電路輸出的Ua信號跳變爲高位準，一旦所述線電壓 UL 1降到零，則過零檢測比較器電路輸出的Ua信號跳變爲 低位準’因此，所述第一 PWM信號的脈寬反映了所述高壓 交流信號U2的導通角。 在本發明的不同實施例中，所述導通角調變模組包括 低通濾波器和PWM比較器，其中，所述低通濾波器用以接 收所述第一 PWM信號Ua並將其轉變爲所述直流電壓信號 Udc，所述PWM比較器接收所述直流電壓信號並將其與一 個三角波信號做比較，而輸出所述第二PWM信號Um。 在本發明的不同實施例中，所述變換器模組可以是任 何將高壓交流電轉換爲低壓直流電的AC-DC變換器。 本發明實施例的三端可控矽調光W LED驅動方法及驅 動電路成功地實現了採用三端可控矽調光器對WLED進行 平滑無閃爍調光的目的，可以達到良好的WLED照明亮度 調節效果。 本發明的各個實施例的三端可控矽調光WLED驅動電 -19- 201220925 路控制電路可以在積體電路層級上用低成本和低複雜性的 方式來予以實現。 上述本發明的說明書和實施方式僅僅是示例性的適用 於三端可控矽調光器的WLED驅動方法及驅動電路，並不 用於限定本發明的範圍。對於揭示的實施例進行變化和修 改都是可能的，其他可行的選擇性實施例和對實施例中元 件的等同變化可以被本技術領域的普通技術人員所瞭解。 本發明所揭示的實施例的其他變化和修改並不超出本發明 的精神和保護範圍。 【圖式簡單說明】 下面的圖形例示本發明的實施方式。這些圖形和實施 方式以非限制性、非窮舉性的方式提供了本發明的一些實 施例* 圖1示出了現有技術中的一種採用三端可控矽調光器 的WLED驅動電路示意圖。 圖2爲根據本發明一個實施例之適用於三端可控矽調 光器的WLED驅動電路示意圖。 圖3爲根據本發明一個實施例之適用於三端可控矽調 光器的WLED驅動電路中電子變壓器電路示意圖。 圖4爲根據本發明一個實施例之適用於三端可控矽調 光器的WLED驅動電路主要信號波形示意圖。 圖5爲根據本發明一個實施例之適用於三端可控矽調 光器的WLED驅動電路中導通角檢測模組的電路結構圖。 -20- 201220925 圖6爲圖5所示的導通角檢測電路的主要信號波形示意 圖0 【主要元件符號說明】 200 :驅動電路 202 :三端可控矽調光器 204 :電子變壓器 206 : WLED驅動器 208 ： WLED 燈管 1 0 0 :驅動電路 1 0 1 :三端可控矽調光器 103 :電子變壓器 105 :整流器 107 : WLED驅動器 109：白光 LED ( WLED ) 5 〇 〇 :電路 5 0 1 :整流電路 5 02 :類線性穩壓器電路 -21 -The invention provides an electronic transformer, the linear regulator circuit can also be replaced by a zero-crossing detection comparator circuit, which receives and processes the high-voltage direct current to output the first a PWM signal, and when the high voltage direct current is greater than zero, the first PWM -12-201220925 signal is at a high level 'and when the high voltage direct current is zero', the first PWM signal is at a low level. An electronic transformer of the invention provides the conduction angle modulation module comprising a low pass filter and a PWM comparator, wherein the low pass filter is configured to receive the first p WM signal and transform it And the PWM comparator is configured to compare the DC voltage signal with the triangular wave signal to output the second PWM signal. An electronic transformer provided by the present invention is an AC-DC converter that converts high voltage alternating current into low voltage direct current. The invention has the beneficial effects of the WLED driving method and the driving circuit applicable to the three-terminal controllable 矽 dimmer: the WLED driving method and the driving circuit for the three-terminal controllable 矽 dimmer provided by the invention provide a novel The electronic transformer can detect the conduction angle of the high-voltage alternating current output by the three-terminal controllable dimmer and convert the high-voltage alternating current into a PWM low-voltage direct current whose duty ratio is regulated by the conduction angle. The PWM low-voltage direct current powers the WLED driver to drive the WLED operation, and the three-terminal controllable dimmer can adjust the duty cycle of the PWM low-voltage DC voltage signal, thereby adjusting the average current flowing through the WLED tube to change The brightness of the WLED, the PWM low-voltage direct current does not include the AC voltage ripple with a frequency of 50 Hz or less; therefore, the WLED driving method and the driving circuit of the present invention applicable to the three-terminal controllable 矽 dimmer The applied electronic transformer can achieve smooth flicker-free dimming of the WLED. -13-201220925 [Embodiment] Hereinafter, a three-terminal controllable dimming WLED driving method and a driving circuit of an embodiment of the present invention will be described in detail. In the following description, some specific details, such as specific circuit configurations in the embodiments and specific parameters of these circuit elements, are used to provide a better understanding of the embodiments of the invention. In this technology, he is actually being able to be succinct and succinct, and he is very succinct, and he lacks the deficiencies of the affair, and the tactics of the syllabus. 2 is a schematic diagram of a three-terminal controllable dimming W LED driving circuit according to an embodiment of the present invention. The drive circuit 200 mainly includes a three-terminal controllable dimmer 202, an electronic transformer 204, and a WLED driver 206 for driving the WLED lamp 208. The three-terminal controllable dimming device 202 is configured to receive the high-voltage alternating current supply voltage U1 and generate a high-voltage alternating current U2 with a conduction angle controlled; the electronic transformer 204 detects a conduction angle of the high-voltage alternating current U2, And converting the high voltage alternating current U2 into a PWM (pulse width modulation) low voltage direct current U3 whose duty ratio is adjusted by the conduction angle; the WLED driver 206 receives the PWM low voltage direct current U3 and outputs a WLED drive A current ILED for driving the WLED 208 operation, as shown in FIG. 3, a three-terminal steerable dimming WLED driving circuit 200 according to an embodiment of the present invention, the electronic transformer 204 comprising three main portions: a conduction angle The detection module, the conduction angle modulation module and the converter module. The conduction angle detecting module is coupled to the output end of the three-terminal controllable dimming device 202 for receiving the high-voltage alternating current U2 and outputting the high-voltage alternating current U2. a first PWM signal Ua of the conduction angle; the conduction angle modulation module is coupled to the output end of the conduction angle detection module for receiving the first PWM signal Ua and performing low-pass filtering thereof Generating a DC voltage signal Ude, and comparing the DC voltage signal Udc with a triangular wave signal to output a second PWM signal Um; the converter module is coupled to the three-terminal controllable dimmer An output of the 202 and an output of the conduction angle modulation module to receive the high voltage alternating current U2 and the second PWM signal Um, respectively, and controlled by the second PWM signal Um The alternating current U2 is converted to the PWM low voltage direct current U3. FIG. 4 is a diagram showing main signal waveforms of a three-terminal controllable dimming WLED driving circuit in a normal operation according to an embodiment of the present invention. The operation principle of the three-terminal controllable dimming WLED driving circuit 200 proposed by the present invention will be further described below in conjunction with the waveform diagram shown in FIG. In the dimming process, the three-terminal controllable dimmer 202 receives the high-voltage AC supply voltage U1, and adjusts the on-time of the internal three-terminal bidirectional controllable switch so that the high-voltage AC supply voltage U 1 is in one Energy is transferred to the drive circuit 200 only during the on-time of the triac. Generally, the opening of the three-terminal bidirectional controllable switch is controlled by a control signal. When the current in the three-terminal bidirectional controllable switch is reduced to a certain turn, the switch is automatically turned off, so the timing of the arrival of the control signal is determined. The on-time of the three-terminal bidirectional controllable switch. The three-terminal bidirectional controllable split -15-201220925 The on-time in a power supply cycle is represented by a corresponding angle. Therefore, the three-terminal controllable dimmer 222 processes the high-voltage AC supply voltage U1 to output a high-voltage alternating current U2 whose conduction angle is controlled. The electronic transformer 204 detects the conduction angle through the conduction angle detecting module, and generates a first PWM signal Ua such that a frequency and a duty ratio of the first PWM signal Ua and a frequency of the conduction angle signal Same as duty cycle. The first PWM signal Ua is input to the conduction angle modulation module, and is subjected to low-pass filtering to generate a DC voltage signal Ud. The DC voltage signal Udc reflects the DC average 値 of the first PWM signal Ua, and compares the DC voltage signal Ude with a triangular wave signal to generate a second PWM signal Um, where the second PWM signal Um The duty cycle is regulated by the conduction angle and its frequency will be much higher than the frequency of the conduction angle signal. The second PWM signal Um is input to the converter module to control it to convert the high voltage AC voltage signal U2 into the PWM low voltage DC U3. The frequency and duty ratio of the PWM low-voltage direct current U3 are consistent with the frequency and duty ratio of the second PWM signal Um, and thus, the duty ratio thereof reflects the conduction angle of the high-voltage alternating current U2, and the amplitude thereof is adjusted. At a predetermined setting, such as 12 V, the WLED driver 206 is powered. When the PWM low voltage direct current U3 is at a high level, the WLED driver 206 provides a constant operating current to the WLED 208; when the PWM low voltage direct current U3 is at a low level, the WLED driver 206 does not supply power to the WLED 208, and no current flows in the WLED 2 08. Over. Therefore, the three-terminal controllable dimmer 202' is adjusted to change the conduction angle of the output high-voltage alternating current U2, that is, the -16-201220925 duty ratio of the PWM low-voltage direct current U3 output by the electronic transformer 204 can be adjusted. , thereby controlling the average current magnitude provided by the WLED driver 206 for the WLED 208 to achieve adjustment of the brightness of the WLED 206. Since the frequency and duty ratio of the PWM low-voltage direct current U3 output by the electronic transformer 204 in the embodiment of the present invention are consistent with the frequency and duty ratio of the second PWM signal Um, the frequency thereof is much higher than The frequency of the conduction angle signal, so that the pWM low-voltage direct current U3 does not include an alternating current voltage ripple with a frequency of 50 Hz or less, and the WLED tube 208 does not flicker during the dimming process. phenomenon. In various embodiments of the present invention, the conduction angle detecting module can be implemented by using a plurality of conduction angle detecting circuit structures in the prior art. FIG. 5 is a circuit diagram showing a conduction angle detecting module according to an embodiment of the present invention. The circuit 500 includes a rectifier circuit 501 and a linear-like regulator circuit 502. Wherein, the rectifier circuit 501 is composed of four high voltage resistant diodes D1, D2, D3 and D4, the series combination of D1 and D2 and the series combination of D3 and D4 are coupled in parallel. Between the power supply line L1 and the ground, and the cathodes of the D1 and D3 are coupled to the anodes of the power supply lines L1, D2 and D4, and the anode of the high-voltage alternating current U2 is coupled to the anode of the D1 and The cathode of D2 is coupled to the anode of D3 and the cathode of D4; the linear regulator circuit 502 includes a first resistor R1, a first voltage regulator diode D5, and a second voltage regulator diode The body D6, the transistor Q1, the second resistor R2 and the capacitor C1, one end of the first resistor R1 is coupled to the power supply line L1, and the other end is coupled to the first voltage regulator diode D5 a cathode of the first voltage stabilizing diode D5 coupled to a cathode of the second voltage stabilizing diode D 6 and a gate of the transistor Q 1 , the second voltage stabilizing diode The anode of the body D6 is coupled to the ground electrode of the transistor Q 1 and coupled to the power supply line L1, and the source thereof is coupled to the ground through the second resistor R2. Capacitor C 1 The two ends of the second resistor R2 are coupled in parallel, and the source of the transistor Q1 and the non-ground terminal of the second resistor R2 are used together as an output terminal of the circuit 500. The operation principle of the circuit 500 is as follows: after the high-voltage alternating current U2 is rectified via the rectifying circuit 501, the positive half-wave remains as it is, and the negative half-wave is inverted to a positive half-wave, and is loaded on the power supply line. The line voltage UL1 on L 1 is as shown in FIG. 6; the linear regulator circuit 502 is powered by the line voltage UL1, when the voltage on the first voltage stabilizing diode D5 reaches its opposite When the breakdown voltage is applied, the voltage on the second voltage stabilizing diode D6 starts to rise, and the output voltage Ua of the conduction angle detecting circuit 500 is equal to the voltage on the voltage stabilizing diode D6 minus the gate of the transistor Q1. The pole-source voltage, since the transistor Q 1 is operating in the linear region, the gate-source voltage is small, so Ua is close to the voltage on the voltage regulator diode D6; when the voltage regulator diode D6 After the upper voltage also reaches its reverse breakdown voltage, the voltage on D6 is clamped to its reverse breakdown voltage, while Ua is also clamped at a potential close to the reverse breakdown voltage of D6. (D6 reverse breakdown voltage minus Q1 gate-source voltage). The reverse breakdown voltage of the voltage regulator diodes D5 and D6 is generally small, and the rising edge of the Ua is substantially the same as the conduction time of the three-terminal bidirectional controllable switch in the three-terminal controllable dimmer 222. The falling edge of U a is basically the same as the turn-off timing of the three-terminal bidirectional controllable switch. When the three-terminal bidirectional controllable switch is turned off, the line voltage UL1 becomes zero, then Ua will also jump. Zero, so Ua is a pulse signal whose pulse width is consistent with the on-time of the three-terminal bidirectional controllable switch, thus realizing the detection of the conduction angle of the high-voltage alternating current U2. It should be understood by those skilled in the art of -18 - 201220925 that the circuit 500 can also have various equivalent changes, for example, removing the first voltage stabilizing diode D 5, and still achieving the same conduction angle detecting function, the electric Crystal Q 1 can also be other controllable switching devices such as BJT. In addition, those skilled in the art should understand that in various embodiments of the present invention, a zero-crossing comparator circuit can also be used to replace the linear-like regulator circuit 502 in the circuit 500, and the line voltage is UL1 is processed by a zero-detection comparator circuit, and the first PWM signal Ua' is output. Once the line voltage ul 1 is greater than zero, the Ua signal output by the zero-crossing detection comparator circuit jumps to a high level once the line When the voltage UL 1 falls to zero, the Ua signal outputted by the zero-crossing detection comparator circuit jumps to a low level. Therefore, the pulse width of the first PWM signal reflects the conduction angle of the high-voltage AC signal U2. In a different embodiment of the present invention, the conduction angle modulation module includes a low pass filter and a PWM comparator, wherein the low pass filter is configured to receive the first PWM signal Ua and convert it into a The DC voltage signal Udc is received by the PWM comparator and compared with a triangular wave signal to output the second PWM signal Um. In various embodiments of the invention, the converter module can be any AC-DC converter that converts high voltage alternating current to low voltage direct current. The three-terminal controllable dimming W LED driving method and the driving circuit of the embodiment of the invention successfully realize the purpose of smoothing flicker-free dimming of the WLED by using the three-terminal controllable dimming device, and can achieve good WLED illumination brightness. Adjust the effect. The three-terminal controllable dimming WLED driver of various embodiments of the present invention can be implemented at a low level and low complexity at the integrated circuit level. The above description and embodiments of the present invention are merely exemplary WLED driving methods and driving circuits for a three-terminal controllable dimmer, and are not intended to limit the scope of the present invention. Variations and modifications of the disclosed embodiments are possible, and other possible alternative embodiments and equivalent variations to the elements of the embodiments will be apparent to those of ordinary skill in the art. Other variations and modifications of the disclosed embodiments of the invention are beyond the spirit and scope of the invention. BRIEF DESCRIPTION OF THE DRAWINGS The following drawings illustrate embodiments of the present invention. These figures and embodiments provide some embodiments of the present invention in a non-limiting, non-exhaustive manner. Figure 1 shows a schematic diagram of a prior art WLED driver circuit employing a three-terminal controllable dimmer. 2 is a schematic diagram of a WLED driving circuit suitable for a three-terminal controllable 矽 dimmer in accordance with one embodiment of the present invention. 3 is a circuit diagram of an electronic transformer circuit in a WLED driving circuit suitable for a three-terminal controllable xenon dimmer according to an embodiment of the present invention. 4 is a schematic diagram showing main signal waveforms of a WLED driving circuit suitable for a three-terminal controllable xenon dimmer according to an embodiment of the present invention. 5 is a circuit configuration diagram of a conduction angle detecting module in a WLED driving circuit suitable for a three-terminal controllable xenon dimmer according to an embodiment of the present invention. -20- 201220925 Figure 6 is a schematic diagram of the main signal waveforms of the conduction angle detecting circuit shown in Figure 5. [Main component symbol description] 200: Driving circuit 202: Three-terminal controllable dimming device 204: Electronic transformer 206: WLED driver 208 : WLED tube 1 0 0 : drive circuit 1 0 1 : three-terminal controllable dimmer 103 : electronic transformer 105 : rectifier 107 : WLED driver 109 : white LED ( WLED ) 5 〇〇 : circuit 5 0 1 : Rectifier circuit 5 02 : linear regulator circuit - 21 -