WO2014154091A1 - 一种恒流驱动控制器及led恒流驱动电路 - Google Patents

一种恒流驱动控制器及led恒流驱动电路 Download PDF

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Publication number
WO2014154091A1
WO2014154091A1 PCT/CN2014/073243 CN2014073243W WO2014154091A1 WO 2014154091 A1 WO2014154091 A1 WO 2014154091A1 CN 2014073243 W CN2014073243 W CN 2014073243W WO 2014154091 A1 WO2014154091 A1 WO 2014154091A1
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circuit
constant current
switching
current driving
degaussing time
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PCT/CN2014/073243
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English (en)
French (fr)
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李照华
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深圳市明微电子股份有限公司
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Publication of WO2014154091A1 publication Critical patent/WO2014154091A1/zh

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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/30—Driver circuits
    • H05B45/37—Converter circuits
    • H05B45/3725—Switched mode power supply [SMPS]
    • H05B45/382—Switched mode power supply [SMPS] with galvanic isolation between input and output
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/30—Driver circuits
    • H05B45/37—Converter circuits
    • H05B45/3725—Switched mode power supply [SMPS]

Definitions

  • the invention belongs to the field of constant current driving circuit design, and particularly relates to a constant current driving controller and an LED constant current driving circuit.
  • the constant current control of the output current is realized by using the feedback signal of the primary coil of the transformer.
  • the prior art proposes an LED constant current driving circuit, which adjusts the switching current of the power tube through the degaussing time of the LED constant current driving circuit to eliminate the output current caused by the transformer inductance change. Deviation.
  • the LED constant current driving circuit adopts a primary feedback flyback structure.
  • the resistor R1 and the resistor R2 divide the voltage fed back via the auxiliary winding B1 of the primary winding T0;
  • the degaussing voltage sampling circuit in the constant current driving controller samples the divided signal of the resistor R1 and the resistor R2 through the feedback pin FB; degaussing time
  • the detecting module counts the duration of the voltage dividing signal to obtain a degaussing time;
  • the constant current logic control circuit generates a switching frequency control signal of the power tube NMOS through the degaussing time.
  • the degaussing time detection module obtains the degaussing time TDEM, the constant current logic control circuit can control the switching frequency f of the power tube NMOS through the switching frequency control signal to ensure the constant of the TDEM ⁇ f.
  • the auxiliary winding B1 of the transformer T0 and the voltage dividing resistor R1 and the voltage dividing resistor R2 are used to provide the degaussing detection signal for the feedback pin FB of the constant current driving controller.
  • the constant current driving controller has many peripheral circuit devices, high cost and large occupied area, and the constant current driving controller is easily exposed to external interference due to the exposure of the feedback pin FB, thereby reducing the LED constant current driving circuit. reliability.
  • the purpose of the embodiments of the present invention is to provide an LED constant current driving circuit, which aims to solve the problem that the primary side feedback flyback LED constant current driving circuit provided by the prior art uses the auxiliary winding of the transformer and the voltage dividing resistor to detect the degaussing signal, so that There are many peripheral circuit devices of the constant current drive controller, and the reliability of the circuit is low due to the exposure of the feedback pin FB.
  • the embodiment of the present invention is implemented as an LED constant current driving circuit, and the LED constant current driving circuit includes a transformer T1, a constant current driving controller, and a switch for controlling whether the primary coil of the transformer T1 is energized or not through a switch state.
  • a circuit, a rectifying and filtering circuit, the constant current driving controller comprising:
  • a control circuit configured to sample and time the degaussing time detection signal output by the capacitive circuit to obtain a degaussing time, and control a switching frequency of the switching circuit according to the degaussing time.
  • Another object of the embodiments of the present invention is to provide a constant current driving controller, where the constant current driving controller includes:
  • a control circuit for sampling and timing the degaussing time detection signal output by the capacitive circuit to obtain a degaussing time, and controlling a switching frequency of the external switching circuit according to the degaussing time.
  • the constant current driving controller realizes the degaussing time of the primary coil of the transformer through the characteristics of the direct current crossing of the capacitive circuit itself, and then the control circuit in the constant current driving controller realizes the degaussing time according to the obtained degaussing time. Control of the switching frequency of the switching circuit.
  • the use of the auxiliary winding and the voltage dividing resistor of the transformer is avoided, the peripheral circuit structure of the constant current driving controller is simplified, the circuit integration degree is improved, the cost is reduced, and the area of the system board is reduced. The problem of low reliability caused by the exposure of the feedback pin FB is avoided.
  • FIG. 1 is a circuit diagram of a primary side feedback flyback LED constant current driving circuit provided by the prior art
  • FIG. 2 is a circuit diagram of an LED constant current driving circuit according to Embodiment 1 of the present invention.
  • FIG. 3 is a circuit diagram of an LED constant current driving circuit according to Embodiment 2 of the present invention.
  • FIG. 4 is a circuit diagram of an LED constant current driving circuit according to Embodiment 3 of the present invention.
  • FIG. 5 is a circuit diagram of an LED constant current driving circuit according to Embodiment 4 of the present invention.
  • the LED constant current driving circuit provided by the present invention utilizes the characteristics of the blocking and passing of the capacitive circuit itself in the constant current driving controller to realize the degaussing time detection of the primary coil of the transformer, and then The control circuit in the constant current drive controller realizes the control of the switching frequency of the switching circuit according to the obtained degaussing time.
  • Embodiment 1 of the present invention proposes an LED constant current driving circuit, as shown in FIG. 2, for the convenience of description, only parts related to Embodiment 1 of the present invention are shown.
  • the LED constant current driving circuit includes a transformer T1, and further includes: a switching circuit 2, the voltage input end of the switching circuit 2 is connected to the positive pole Vin+ of the power supply, and the voltage output end of the switching circuit 2 is connected to the first end of the primary coil of the transformer T1.
  • the second end of the primary winding of the transformer T1 is connected to the negative pole of the power supply Vin-, the switching circuit 2 is used to control the energization of the primary coil of the transformer T1 through the switching state; the constant current driving controller 1 connected to the switching circuit 2; the rectifying and filtering circuit 3.
  • the input end of the rectifying and filtering circuit 3 is connected to the secondary coil of the transformer T1, the output end of the rectifying and filtering circuit 3 is connected to the load, and the rectifying and filtering circuit 3 is used for rectifying and filtering the output voltage of the secondary coil of the transformer T1.
  • the constant current driving controller 1 further includes: a capacitive circuit 11 and a capacitive circuit 11 The input terminal is connected to the voltage input end of the switch circuit 2, the capacitive circuit 11 is used for outputting the degaussing time detection signal; the control circuit 12, the input end of the control circuit 12 is connected to the output end of the capacitive circuit 11, and the output end of the control circuit 12 is connected to the switch.
  • the control input circuit of the circuit 2 is used for sampling and timing the degaussing time detection signal outputted by the capacitive circuit 11, obtaining degaussing time, and controlling the switching frequency of the switching circuit 2 according to the degaussing time to realize the switching circuit 2
  • the switching frequency is controlled such that the product of the switching frequency of the switching circuit 2 and the degaussing time is a constant value.
  • the constant current driving controller realizes the degaussing time detection of the primary coil of the transformer through the characteristics of the direct current crossing of the capacitive circuit itself, and then is driven by the constant current driving controller.
  • the control circuit realizes the control of the switching frequency of the switching circuit according to the obtained degaussing time.
  • a second embodiment of the present invention proposes an LED constant current driving circuit. As shown in FIG. 3, for the convenience of description, only parts related to the second embodiment of the present invention are shown. Different from the first embodiment, the circuit structure of the capacitive circuit 11, the control circuit 12, the switching circuit 2, and the rectifying and filtering circuit 3 is refined in the second embodiment.
  • the capacitive circuit 11 may include a switching transistor Q1.
  • the voltage input terminal of the switching transistor Q1 is connected to the voltage input terminal of the switching circuit 2 as an input terminal of the capacitive circuit 11, and the voltage output terminal of the switching transistor Q1 is used as a capacitive circuit.
  • the output of 11 is connected to the input of control circuit 12, and the capacitance in capacitive circuit 11 is formed by the source-drain parasitic capacitance of switching transistor Q1.
  • the switching transistor Q1 is an N-channel MOS transistor, the drain of the MOS transistor Q1 serves as a voltage input terminal of the switching transistor Q1, the source of the MOS transistor Q1 is connected to the gate of the MOS transistor Q1, and the gate of the MOS transistor Q1. As the voltage output terminal of the switching transistor Q1.
  • the parasitic capacitance of the source and the drain of the MOS transistor Q1 is utilized to realize the characteristics of the through-current crossing of the capacitive circuit 11.
  • control circuit 12 may include: a degaussing voltage sampling circuit 121.
  • the input end of the degaussing voltage sampling circuit 121 is connected to the output end of the capacitive circuit 11 as an input end of the control circuit 12, and the degaussing voltage sampling circuit 121 is used for capacitive compatibility.
  • the degaussing time detection signal outputted by the circuit 11 is sampled to obtain a sampling signal; the degaussing time detecting circuit 122, the input end of the degaussing time detecting circuit 122 is connected to the output end of the degaussing voltage sampling circuit 121, and the degaussing time detecting circuit 122 is configured to perform sampling signal Timing, the degaussing time is obtained; the constant current logic control circuit 123, the input end of the constant current logic control circuit 123 is connected to the output end of the degaussing time detecting circuit 122, and the output end of the constant current logic controlling circuit 123 is connected as the output end of the control circuit 12.
  • the control input terminal of the switching circuit 2, the constant current logic control circuit 123 is for controlling the switching frequency of the switching circuit 2 based on the degaussing time obtained by the degaussing time detecting circuit 122.
  • the degaussing voltage sampling circuit 121 can be implemented by using a voltage comparator.
  • the voltage comparator compares the degaussing time detection signal with a reference voltage to obtain a sampling signal. For example, if the reference voltage is 1V, when the degaussing time detection signal is higher than 1V, the voltage comparator outputs a high level as a sampling signal; when the degaussing time detection signal is less than or equal to 1V, the voltage comparator output is low as a sampling signal. Level.
  • the degaussing time detecting circuit 122 counts the high level or the low level of the voltage comparator output to obtain the degaussing time.
  • the switching circuit 2 may include a switching transistor Q2 and a resistor R4.
  • the voltage input end of the switch tube Q2 is connected as the voltage input end of the switch circuit 2 to the positive pole Vin+ of the power supply
  • the voltage output end of the switch tube Q2 is connected to one end of the resistor R4, the other end of the resistor R4 is grounded, and the other end of the resistor R4 is simultaneously
  • the voltage output of the switching circuit 2 is connected to the first end of the primary winding of the transformer T1.
  • the control terminal of the switching transistor Q2 is connected to the output of the control circuit 12 as a control input of the switching circuit 2.
  • the switching transistor Q2 is an N-channel MOS transistor, the drain of the MOS transistor Q2 serves as a voltage input terminal of the switching transistor Q2, the source of the MOS transistor Q2 serves as a voltage output terminal of the switching transistor Q2, and the gate of the MOS transistor Q2 The pole serves as the control end of the switching transistor Q2.
  • the rectifying and filtering circuit 3 may include a diode D2 and a capacitor C2.
  • the anode of the diode D2 is connected as the input end of the rectifying and filtering circuit 3 to the first end of the secondary winding of the transformer T1, the other end of the diode D2 is connected to one end of the capacitor C2, and the other end of the capacitor C2 is connected to the secondary coil of the transformer T1.
  • both ends of the capacitor C2 are connected to the load as the output of the rectifying and filtering circuit 3.
  • an LED constant current driving circuit is proposed. As shown in FIG. 4, only parts related to the third embodiment of the present invention are shown for convenience of description.
  • the circuit configuration of the control circuit 12, the switch circuit 2, and the rectification filter circuit 3 is the same as that of the second embodiment, and will not be described herein.
  • the capacitive circuit 11 can include a capacitor C3.
  • One end of the capacitor C3 is connected to the voltage input terminal of the switch circuit 2 as the input end of the capacitive circuit 11, and the other end of the capacitor C3 is used as the capacitor.
  • the output of the control circuit 12 is connected to the output of the circuit 11.
  • Embodiment 4 of the present invention proposes an LED constant current driving circuit, as shown in FIG. 5.
  • the circuit configuration of the control circuit 12, the switch circuit 2, and the rectification filter circuit 3 is the same as that of the second embodiment, and will not be described herein.
  • the capacitive circuit 11 can include: a switch tube Q1, the capacitance in the capacitive circuit 11 is formed by the source-drain parasitic capacitance of the switch tube Q1, and the voltage input end of the switch tube Q1 is used as a capacitive
  • the input terminal of the circuit 11 is connected to the voltage input terminal of the switching circuit 2, and the voltage output terminal of the switching transistor Q1 is connected to the input terminal of the control circuit 12 as the output terminal of the capacitive circuit 11.
  • the switching transistor Q1 is preferably an N-channel MOS transistor, the drain of the MOS transistor Q1 is used as the voltage input terminal of the switching transistor Q1, the source of the MOS transistor Q1 is suspended, and the gate of the MOS transistor Q1 is used as the switching transistor Q1. Voltage output.
  • the fifth embodiment of the present invention provides a constant current driving controller, and the structure thereof is as described in any one of the first embodiment to the fourth embodiment, and details are not described herein.
  • the constant current driving controller realizes the degaussing time of the primary coil of the transformer through the characteristics of the direct current crossing of the capacitive circuit itself, and then the control circuit in the constant current driving controller realizes the degaussing time according to the obtained degaussing time. Control of the switching frequency of the switching circuit.
  • the use of the auxiliary winding and the voltage dividing resistor of the transformer is avoided, the peripheral circuit structure of the constant current driving controller is simplified, the circuit integration degree is improved, the cost is reduced, and the area of the system board is reduced. The problem of low reliability caused by the exposure of the feedback pin FB is avoided.

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Abstract

一种恒流驱动控制器及LED恒流驱动电路。恒流驱动控制器包括：容性电路，用于输出消磁时间检测信号；控制电路，用于对容性电路输出的消磁时间检测信号进行采样和计时，得到消磁时间，并根据消磁时间控制外部的开关电路的开关频率。LED恒流驱动电路包括变压器、上述恒流驱动控制器、开关电路、整流滤波电路。所述恒流驱动控制器不使用变压器的辅助绕组和分压电阻，简化了外围电路结构，提高了电路集成度，降低了成本，缩小了系统板的面积，并避免了反馈引脚外露引起的可靠性低的问题。

Description

一种恒流驱动控制器及LED恒流驱动电路 技术领域
本发明属于恒流驱动电路设计领域，尤其涉及一种恒流驱动控制器及LED恒流驱动电路。
 背景技术
在原边反馈反激式LED恒流驱动电路中，利用变压器初级线圈的反馈信号，实现对输出电流的恒流控制。其控制原理是：假设该原边反馈反激式LED恒流驱动电路的输出电压为Vout，输出电流为Iout，变压器初级线圈的电感量为Lp，变压器初级线圈的峰值电流为Ip，电路工作频率（即电路中功率管的开关频率）为f，变压器次级侧整流二极管的导通压降是Vd，则有Iout=（Lp×Ip2×f）/[2×（Vout+Vd）]；若控制f/（Vout+Vd）为一固定值，并控制Ip恒定，则输出电流Iout恒定；若控制Ip2/（Vout+Vd）为一固定值，且控制f为一固定值，也可使得输出电流Iout恒定。但由于在实际量产中，由于变压器Lp不一致，因此有可能导致输出电流存在偏差。为此，如图1所示，现有技术提出了一种LED恒流驱动电路，其通过消磁时间调整功率管的开关频率的LED恒流驱动电路，以消除变压器感量变化导致的输出电流存在的偏差。
如图1所示，该LED恒流驱动电路采用原边反馈反激式结构。电阻R1和电阻R2对经由初级线圈T0的辅助绕组B1反馈的电压进行分压；恒流驱动控制器中的消磁电压采样电路通过反馈引脚FB采样电阻R1和电阻R2的分压信号；消磁时间检测模块对该分压信号持续时间进行计时，得到消磁时间；恒流逻辑控制电路通过消磁时间生成功率管NMOS的开关频率控制信号。假设消磁时间为TDEM，功率管NMOS的开关频率为f，变压器初级绕组与次级绕组的匝数比为N，结合伏秒特性，Nx(Vout+Vd)xTDEM= Lp×Ip，则有：Iout=（N×Ip×TDEM×f）/2，由于初级线圈的峰值电流Ip恒定，通过调整TDEM×f为一恒定值，即可实现Iout的恒定输出，因此，消磁时间检测模块在得到消磁时间TDEM后，恒流逻辑控制电路可通过开关频率控制信号，控制功率管NMOS的开关频率f，以保证TDEM×f的恒定。
但现有技术提供的上述LED恒流驱动电路中，由于需利用变压器T0的辅助绕组B1、以及分压电阻R1和分压电阻R2来为恒流驱动控制器的反馈引脚FB提供消磁检测信号，使得恒流驱动控制器的外围电路器件较多，成本较高且占用面积较大，同时由于反馈引脚FB外露，使得恒流驱动控制器易于受到外部干扰，降低了LED恒流驱动电路的可靠性。
 技术问题
本发明实施例的目的在于提供LED恒流驱动电路，旨在解决现有技术提供的原边反馈反激式LED恒流驱动电路采用变压器的辅助绕组和分压电阻实现消磁信号的检测，使得其恒流驱动控制器的外围电路器件较多，且由于反馈引脚FB外露而使得该电路可靠性低的问题。
 技术解决方案
本发明实施例是这样实现的，一种LED恒流驱动电路，所述LED恒流驱动电路包括变压器T1、恒流驱动控制器、通过开关状态控制所述变压器T1的初级线圈通电与否的开关电路，整流滤波电路，所述恒流驱动控制器包括：
容性电路，用于输出消磁时间检测信号；
控制电路，用于对所述容性电路输出的所述消磁时间检测信号进行采样和计时，得到消磁时间，并根据所述消磁时间控制所述开关电路的开关频率。
本发明实施例的另一目的在于提供一种恒流驱动控制器，所述恒流驱动控制器包括：
容性电路，用于输出消磁时间检测信号；
控制电路，用于对所述容性电路输出的所述消磁时间检测信号进行采样和计时，得到消磁时间，并根据所述消磁时间控制外部的开关电路的开关频率。
 有益效果
本发明中，恒流驱动控制器通过容性电路自身的隔直通交的特性，来实现变压器初级线圈的消磁时间的检测，之后由恒流驱动控制器中的控制电路根据得到的消磁时间，实现对开关电路的开关频率的控制。相对于现有技术，避免了变压器的辅助绕组和分压电阻的使用，简化了恒流驱动控制器的外围电路结构，提高了电路集成度，降低了成本且缩小了系统板的面积，同时，避免了反馈引脚FB外露而引起的可靠性低的问题。
附图说明
图1是现有技术提供的原边反馈反激式LED恒流驱动电路的电路图；
图2是本发明实施例一提供的LED恒流驱动电路的电路图；
图3是本发明实施例二提供的LED恒流驱动电路的电路图；
图4是本发明实施例三提供的LED恒流驱动电路的电路图；
图5是本发明实施例四提供的LED恒流驱动电路的电路图。
 本发明的实施方式
为了使本发明的目的、技术方案及优点更加清楚明白，以下结合附图及实施例，对本发明进行进一步详细说明。应当理解，此处所描述的具体实施例仅仅用以解释本发明，并不用于限定本发明。
针对现有技术存在的问题，本发明提供的LED恒流驱动电路是利用恒流驱动控制器中的容性电路自身的隔直通交的特性，来实现变压器初级线圈的消磁时间的检测，之后由恒流驱动控制器中的控制电路根据得到的消磁时间，实现对开关电路的开关频率的控制。以下将结合实施例详细说明本发明的实现方式：
实施例一
本发明实施例一提出了一种LED恒流驱动电路，如图2所示，为了便于说明，仅示出了与本发明实施例一相关的部分。
详细而言，该LED恒流驱动电路包括变压器T1，还包括：开关电路2，开关电路2的电压输入端连接电源正极Vin+，开关电路2的电压输出端连接变压器T1的初级线圈的第一端，变压器T1的初级线圈的第二端连接电源负极Vin-，开关电路2用于通过开关状态控制变压器T1的初级线圈的通电与否；连接开关电路2的恒流驱动控制器1；整流滤波电路3，整流滤波电路3的输入端连接变压器T1的次级线圈，整流滤波电路3的输出端连接负载，整流滤波电路3用于对变压器T1的次级线圈的输出电压进行整流及滤波处理。其中，恒流驱动控制器1又包括：容性电路11，容性电路11的 输入端连接开关电路2的电压输入端，容性电路11用于输出消磁时间检测信号；控制电路12，控制电路12的输入端连接容性电路11的输出端，控制电路12的输出端连接开关电路2的控制输入端，控制电路12用于对容性电路11输出的消磁时间检测信号进行采样和计时，得到消磁时间，并根据消磁时间控制开关电路2的开关频率，以实现对开关电路2的开关频率的控制，使得开关电路2的开关频率与消磁时间的乘积为一恒定值。
本发明实施例一提供的LED恒流驱动电路中，恒流驱动控制器通过容性电路自身的隔直通交的特性，来实现变压器初级线圈的消磁时间的检测，之后由恒流驱动控制器中的控制电路根据得到的消磁时间，实现对开关电路的开关频率的控制。相对于现有技术，避免了变压器的辅助绕组和分压电阻的使用，简化了恒流驱动控制器的外围电路结构，提高了电路集成度，降低了成本且缩小了系统板的面积，同时，避免了反馈引脚FB外露而引起的可靠性低的问题。
实施例二
本发明实施例二提出了一种LED恒流驱动电路，如图3所示，为了便于说明，仅示出了与本发明实施例二相关的部分。与实施例一不同，实施例二对其中的容性电路11、控制电路12、开关电路2以及整流滤波电路3的电路结构进行了细化。
具体地，容性电路11可以包括：开关管Q1，开关管Q1的电压输入端作为容性电路11的输入端而连接开关电路2的电压输入端，开关管Q1的电压输出端作为容性电路11的输出端而连接控制电路12的输入端，容性电路11中的电容由开关管Q1的源漏寄生电容形成。优选地，开关管Q1为一N沟道的MOS管，MOS管Q1的漏极作为开关管Q1的电压输入端，MOS管Q1的源极连接MOS管Q1的栅极，MOS管Q1的栅极作为开关管Q1的电压输出端。
本发明实施例二中，利用MOS管Q1的源漏极的寄生电容，实现容性电路11所具备的隔直通交的特性。
具体地，控制电路12可以包括：消磁电压采样电路121，消磁电压采样电路121的输入端作为控制电路12的输入端而连接容性电路11的输出端，消磁电压采样电路121用于对容性电路11输出的消磁时间检测信号进行采样，得到采样信号；消磁时间检测电路122，消磁时间检测电路122的输入端连接消磁电压采样电路121的输出端，消磁时间检测电路122用于对采样信号进行计时，得到消磁时间；恒流逻辑控制电路123，恒流逻辑控制电路123的输入端连接消磁时间检测电路122的输出端，恒流逻辑控制电路123的输出端作为控制电路12的输出端而连接开关电路2的控制输入端，恒流逻辑控制电路123用于根据消磁时间检测电路122得到的消磁时间控制开关电路2的开关频率。
本发明实施例二中，消磁电压采样电路121可利用一电压比较器实现。该电压比较器将消磁时间检测信号与一基准电压进行比较，进而得到采样信号。例如，若基准电压为1V，则当消磁时间检测信号高于1V时，电压比较器输出作为采样信号的高电平；当消磁时间检测信号小于或等于1V，电压比较器输出作为采样信号的低电平。此时，消磁时间检测电路122对电压比较器输出的高电平或低电平进行计时，即可得到消磁时间。
具体地，开关电路2可以包括：开关管Q2和电阻R4。其中，开关管Q2的电压输入端作为开关电路2的电压输入端而连接电源正极Vin+，开关管Q2的电压输出端连接电阻R4的一端，电阻R4的另一端接地，电阻R4的另一端同时作为开关电路2的电压输出端而连接变压器T1的初级线圈的第一端。开关管Q2的控制端作为开关电路2的控制输入端而连接控制电路12的输出端。优选地，开关管Q2为一N沟道的MOS管，MOS管Q2的漏极作为开关管Q2的电压输入端，MOS管Q2的源极作为开关管Q2的电压输出端，MOS管Q2的栅极作为开关管Q2的控制端。
具体地，整流滤波电路3可以包括：二极管D2和电容C2。其中，二极管D2的正极作为整流滤波电路3的输入端而连接变压器T1的次级线圈的第一端，二极管D2的另一端连接电容C2的一端，电容C2的另一端连接变压器T1的次级线圈的第二端，电容C2的两端作为整流滤波电路3的输出端而连接负载。
实施例三
本发明实施例三提出了一种LED恒流驱动电路，如图4所示，为了便于说明，仅示出了与本发明实施例三相关的部分。其中，控制电路12、开关电路2以及整流滤波电路3的电路结构与实施例二相同，在此不赘述。
与实施例二不同，实施例三中，容性电路11可以包括：电容C3，电容C3的一端作为容性电路11的输入端而连接开关电路2的电压输入端，电容C3的另一端作为容性电路11的输出端而连接控制电路12的输入端。
实施例四
本发明实施例四提出了一种LED恒流驱动电路，如图5所示，为了便于说明，仅示出了与本发明实施例四相关的部分。其中，控制电路12、开关电路2以及整流滤波电路3的电路结构与实施例二相同，在此不赘述。
与实施例二不同，实施例四中，容性电路11可以包括：开关管Q1，容性电路11中的电容由开关管Q1的源漏寄生电容形成，开关管Q1的电压输入端作为容性电路11的输入端而连接开关电路2的电压输入端，开关管Q1的电压输出端作为容性电路11的输出端而连接控制电路12的输入端。同样地，开关管Q1优选为一N沟道的MOS管，MOS管Q1的漏极作为开关管Q1的电压输入端，MOS管Q1的源极悬空，MOS管Q1的栅极作为开关管Q1的电压输出端。
实施例五
本发明实施例五提出了一种恒流驱动控制器，其结构如上实施例一至实施例四中任一实施例所述，在此不赘述。
本发明中，恒流驱动控制器通过容性电路自身的隔直通交的特性，来实现变压器初级线圈的消磁时间的检测，之后由恒流驱动控制器中的控制电路根据得到的消磁时间，实现对开关电路的开关频率的控制。相对于现有技术，避免了变压器的辅助绕组和分压电阻的使用，简化了恒流驱动控制器的外围电路结构，提高了电路集成度，降低了成本且缩小了系统板的面积，同时，避免了反馈引脚FB外露而引起的可靠性低的问题。
本领域普通技术人员可以理解实现上述实施例方法中的全部或部分步骤是可以通过程序来控制相关的硬件完成，所述的程序可以在存储于一计算机可读取存储介质中，所述的存储介质，如ROM/RAM、磁盘、光盘等。
以上所述仅为本发明的较佳实施例而已，并不用以限制本发明，凡在本发明的精神和原则之内所作的任何修改、等同替换和改进等，均应包含在本发明的保护范围之内。

Claims (10)

  1. 一种LED恒流驱动电路，其特征在于，所述LED恒流驱动电路包括变压器T1、恒流驱动控制器、通过开关状态控制所述变压器T1的初级线圈通电与否的开关电路、整流滤波电路，所述恒流驱动控制器包括：
    容性电路，用于输出消磁时间检测信号；
    控制电路，用于对所述容性电路输出的所述消磁时间检测信号进行采样和计时，得到消磁时间，并根据所述消磁时间控制所述开关电路的开关频率。
  2. 如权利要求1所述的LED恒流驱动电路，其特征在于，所述容性电路包括：
    开关管Q1，所述开关管Q1的电压输入端连接所述开关电路的电压输入端，所述开关管Q1的电压输出端连接所述控制电路的输入端。
  3. 如权利要求2所述的LED恒流驱动电路，其特征在于，所述开关管Q1为一N沟道的MOS管，所述MOS管的漏极作为所述开关管Q1的电压输入端，所述MOS管的源极悬空或连接所述MOS管的栅极，所述MOS管的栅极作为所述开关管Q1的电压输出端。
  4. 如权利要求1所述的LED恒流驱动电路，其特征在于，所述容性电路包括：
    电容C3，所述电容C3的一端连接所述开关电路的电压输入端，所述电容C3的另一端连接所述控制电路的输入端。
  5. 如权利要求1至4任一项所述的LED恒流驱动电路，其特征在于，所述控制电路包括：
    消磁电压采样电路，用于对所述容性电路输出的所述消磁时间检测信号进行采样，得到采样信号；
    消磁时间检测电路，用于对所述消磁电压采样电路得到的所述采样信号进行计时，得到消磁时间；
    恒流逻辑控制电路，用于根据所述消磁时间检测电路得到的所述消磁时间控制所述开关电路的开关频率。
  6. 如权利要求1至4任一项所述的LED恒流驱动电路，其特征在于，所述开关电路包括：开关管Q2和电阻R4；
    所述开关管Q2的电压输入端连接电源正极，所述开关管Q2的电压输出端连接所述电阻R4的一端，所述电阻R4的另一端接地，所述电阻R4的另一端同时连接所述变压器T1的初级线圈的第一端；所述开关管Q2的控制端连接所述控制电路的输出端。
  7. 如权利要求1至4任一项所述的LED恒流驱动电路，其特征在于，所述LED恒流驱动电路还包括整流滤波电路，所述整流滤波电路包括：二极管D2和电容C2；
    所述二极管D2的正极连接所述变压器T1的次级线圈的第一端，所述二极管D2的另一端连接所述电容C2的一端，所述电容C2的另一端连接所述变压器T1的次级线圈的第二端，所述电容C2的两端连接负载。
  8. 一种恒流驱动控制器，其特征在于，所述恒流驱动控制器包括：
    容性电路，用于输出消磁时间检测信号；
    控制电路，用于对所述容性电路输出的所述消磁时间检测信号进行采样和计时，得到消磁时间，并根据所述消磁时间控制外部的开关电路的开关频率。
  9. 如权利要求9所述的恒流驱动控制器，其特征在于，所述容性电路包括：
    开关管Q1，所述开关管Q1的电压输入端连接所述开关电路的电压输入端，所述开关管Q1的电压输出端连接所述控制电路的输入端。
  10. 如权利要求9所述的恒流驱动控制器，其特征在于，所述容性电路包括：
    电容C3，所述电容C3的一端连接所述开关电路的电压输入端，所述电容C3的另一端连接所述控制电路的输入端。
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