WO2016086897A1 - 电流过零点检测电路及方法，负载电压检测电路及方法 - Google Patents

电流过零点检测电路及方法，负载电压检测电路及方法 Download PDF

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WO2016086897A1
WO2016086897A1 PCT/CN2015/096469 CN2015096469W WO2016086897A1 WO 2016086897 A1 WO2016086897 A1 WO 2016086897A1 CN 2015096469 W CN2015096469 W CN 2015096469W WO 2016086897 A1 WO2016086897 A1 WO 2016086897A1
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Prior art keywords
voltage
load
diode
detecting circuit
voltage dividing
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PCT/CN2015/096469
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English (en)
French (fr)
Inventor
周逊伟
黄必亮
陆阳
季悦
任远程
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杰华特微电子（杭州）有限公司
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Priority to US15/612,998 priority Critical patent/US10411685B2/en
Publication of WO2016086897A1 publication Critical patent/WO2016086897A1/zh

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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K5/00—Manipulating of pulses not covered by one of the other main groups of this subclass
    • H03K5/153—Arrangements in which a pulse is delivered at the instant when a predetermined characteristic of an input signal is present or at a fixed time interval after this instant
    • H03K5/1536—Zero-crossing detectors
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G01R19/175—Indicating the instants of passage of current or voltage through a given value, e.g. passage through zero
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G01R19/25—Arrangements for measuring currents or voltages or for indicating presence or sign thereof using digital measurement techniques
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
    • H03K17/13—Modifications for switching at zero crossing
    • H03K17/133—Modifications for switching at zero crossing in field-effect transistor switches
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
    • H03K17/51—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used
    • H03K17/56—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used by the use, as active elements, of semiconductor devices
    • H03K17/60—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used by the use, as active elements, of semiconductor devices the devices being bipolar transistors
    • H03K17/68—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used by the use, as active elements, of semiconductor devices the devices being bipolar transistors specially adapted for switching ac currents or voltages
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K5/00—Manipulating of pulses not covered by one of the other main groups of this subclass
    • H03K5/22—Circuits having more than one input and one output for comparing pulses or pulse trains with each other according to input signal characteristics, e.g. slope, integral
    • H03K5/24—Circuits having more than one input and one output for comparing pulses or pulse trains with each other according to input signal characteristics, e.g. slope, integral the characteristic being amplitude
    • H03K5/2436—Circuits having more than one input and one output for comparing pulses or pulse trains with each other according to input signal characteristics, e.g. slope, integral the characteristic being amplitude using a combination of bipolar and field-effect transistors
    • H03K5/2454—Circuits having more than one input and one output for comparing pulses or pulse trains with each other according to input signal characteristics, e.g. slope, integral the characteristic being amplitude using a combination of bipolar and field-effect transistors using clock signals
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K5/00—Manipulating of pulses not covered by one of the other main groups of this subclass
    • H03K5/22—Circuits having more than one input and one output for comparing pulses or pulse trains with each other according to input signal characteristics, e.g. slope, integral
    • H03K5/24—Circuits having more than one input and one output for comparing pulses or pulse trains with each other according to input signal characteristics, e.g. slope, integral the characteristic being amplitude
    • H03K5/2463—Circuits having more than one input and one output for comparing pulses or pulse trains with each other according to input signal characteristics, e.g. slope, integral the characteristic being amplitude using diodes
    • 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
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G01R19/0084—Arrangements for measuring currents or voltages or for indicating presence or sign thereof measuring voltage only

Definitions

  • the invention relates to the technical field of circuit detection, in particular to a current zero-crossing detecting circuit and a corresponding current zero-crossing detecting method, a load voltage detecting circuit and a corresponding load voltage detecting method.
  • LED driver circuits With the rapid development of LEDs, the design of LED driver circuits is endless. However, the existing LED driver circuits are more complicated in designing functions such as output overload and overvoltage protection.
  • the common LED load detection circuit uses transformer windings, which leads to the overall complexity of the circuit, large volume and high cost.
  • the problem to be solved by the present invention is to provide a current zero-crossing detecting circuit and method, a load voltage detecting circuit and a method, which can quickly obtain a load voltage and can quickly determine a diode current zero-crossing point, and have a small circuit volume and low cost.
  • an embodiment of the present invention provides a current zero-crossing detecting circuit, including: a load power circuit, a voltage dividing resistor, a switching tube, and a zero-crossing detecting circuit, wherein the load power circuit includes a load, a diode, and an inductor, and The load, the diode and the inductor are connected in series to form a ring circuit, one end of the load power circuit is connected to the working voltage input end, and the other end of the load power circuit is opposite to the first end of the switch tube and the first end of the voltage dividing resistor Connected, the second end of the voltage dividing resistor is grounded together with the second end of the switching tube, and the switching voltage is used to control the load voltage, and the voltage dividing end of the voltage dividing resistor and the signal of the zero crossing detecting circuit The input terminals are connected, and the zero-crossing detection circuit is used to determine whether the diode current crosses zero.
  • the zero-crossing detection circuit includes a signal input terminal, a sample-and-hold module, a second reference voltage module, and a second comparator, and the sample-and-hold module is connected to the second reference voltage module, and the sample-and-hold module One end is connected to the signal input end, one end of the second reference voltage module serves as a first input end of the second comparator, and the signal input end serves as a second input end of the second comparator.
  • one end of the load in the load power circuit, the negative pole of the diode is connected to the working voltage input end, the other end of the load is connected to one end of the inductor, and the other end of the inductor is connected to the positive pole of the diode. And connected to the first end of the switch tube and the first end of the voltage dividing resistor.
  • the load power supply circuit comprises: a transformer winding, a diode and a load, wherein one end of the load is connected to a negative pole of the diode, and the other end of the load is connected to one end of a secondary side of the transformer winding, the secondary side of the transformer winding The other end of the transformer is connected to the positive pole of the diode, and one end of the primary side of the transformer winding is connected to the working voltage input end, and the other end of the primary side of the transformer winding and the first end of the switch tube and the first end of the voltage dividing resistor Connected.
  • one end of the load in the load power circuit, one end of the inductor is connected to the working voltage input end, and the other end of the load is connected to the negative end of the diode, and the positive end of the diode and the other end of the inductor Connected to and connected to the first end of the switch tube and the first end of the voltage dividing resistor.
  • the load is an LED.
  • the load has a second capacitor connected in parallel.
  • the embodiment of the invention further provides a current zero-crossing point detection method using the current zero-crossing point detecting circuit, comprising:
  • the switch When the switch is turned off and the diode is turned on, the voltage of the voltage divider terminal of the voltage divider resistor is sampled and held, and the result of subtracting the reference voltage from the voltage is compared with the voltage of the voltage divider terminal of the voltage divider resistor obtained in real time, and the score obtained in real time is obtained.
  • the instantaneous voltage of the terminal voltage is lower than the voltage of the voltage dividing terminal minus the reference voltage, it can be judged as the diode current zero crossing point.
  • the reference voltage is a voltage of the second reference voltage module.
  • the embodiment of the invention further provides a load voltage detecting circuit, comprising: a load power circuit, a voltage dividing resistor, a switch tube, a voltage detecting circuit and a zero-crossing detecting circuit, wherein the load power circuit comprises a load, a diode and an inductor, and the The load, the diode and the inductor are connected in series to form a ring circuit, one end of the load power circuit is connected to the working voltage input end, and the other end of the load power circuit is opposite to the first end of the switch tube and the first end of the voltage dividing resistor Connecting, the second end of the voltage dividing resistor is grounded together with the second end of the switch tube, and the load voltage is controlled by the switch tube, and the voltage dividing end of the voltage dividing resistor and the signal input end of the voltage detecting circuit are connected The signal input end of the zero-crossing detection circuit is connected, and the zero-crossing detection circuit is used to determine the diode current zero-crossing point to obtain the diode con
  • the selection end of the voltage selection module is connected to one end of the averaging module, and the averaging module averages the input signals during the switching tube conduction and the diode conduction period, The average value of the output is the load voltage.
  • the zero-crossing detection circuit includes a signal input terminal, a sample-and-hold module, a second reference voltage module, and a second comparator, and the sample-and-hold module is connected to the second reference voltage module, and the sample-and-hold module One end is connected to the signal input end, one end of the second reference voltage module serves as a first input end of the second comparator, and the signal input end serves as a second input end of the second comparator.
  • the load voltage detecting circuit and the zero-crossing detecting circuit share a sample-and-hold module.
  • the voltage detecting circuit and the zero-crossing detecting circuit are located in the load control circuit.
  • the load control circuit controls the control end of the switch tube to turn off the switch tube.
  • the first end of the switch tube is connected to the other end of the load power circuit, the second end of the switch tube is grounded, and the control end of the switch tube is connected to the load control circuit.
  • one end of the load in the load power circuit, the negative pole of the diode is connected to the working voltage input end, the other end of the load is connected to one end of the inductor, and the other end of the inductor is connected to the positive pole of the diode. And connected to the first end of the switch tube and the first end of the voltage dividing resistor.
  • the load power circuit comprises: a transformer winding, a diode and a load, one end of the load is connected to a negative pole of the diode, and the other end of the load is connected to one end of a secondary side of the transformer winding, the transformer winding The other end of the secondary side is connected to the positive pole of the diode, and one end of the primary side of the transformer winding is connected to the working voltage input end, and the other end of the primary side of the transformer winding and the first end of the switch tube and the voltage dividing resistor are One end is connected.
  • one end of the load in the load power circuit, one end of the inductor is connected to the working voltage input end, and the other end of the load is connected to the negative end of the diode, and the positive end of the diode and the other end of the inductor Connected to and connected to the first end of the switch tube and the first end of the voltage dividing resistor.
  • the load is an LED.
  • the load has a second capacitor connected in parallel.
  • the embodiment of the invention further provides a load voltage detecting method using the load voltage detecting circuit, which comprises:
  • the switch When the switch is turned off and the diode is turned on, the voltage of the voltage dividing end of the voltage dividing resistor is sampled and held, and the result of subtracting the reference voltage from the voltage is compared with the voltage of the voltage dividing terminal of the voltage dividing resistor obtained in real time, and the partial voltage obtained in real time is obtained.
  • the instantaneous voltage of the terminal voltage is lower than the voltage of the voltage dividing terminal minus the reference voltage, it can be determined that the diode current crosses the zero point, thereby obtaining the diode conduction time;
  • the voltage of the voltage dividing terminal of the sample and hold, the on-time of the switch tube and the on-time of the diode are calculated, and the load voltage is calculated.
  • the average value is the load voltage.
  • the zero-crossing detection circuit After the voltage division resistor is divided by the voltage dividing resistor, the zero-crossing detection circuit can easily detect the diode current zero-crossing point, and the diode conduction time is obtained, and the detection efficiency is high and the cost is low.
  • the technical solution first uses the zero-crossing detection circuit to detect the diode current zero-crossing point, obtains the diode conduction time, and then uses the load voltage detection circuit to utilize the voltage of the sample-holding voltage-dividing terminal, and the switching tube conduction time and the diode conduction time.
  • the calculation obtains the load voltage, the structure is simple, the detection efficiency is high, and the cost is low.
  • FIG. 1 is a schematic structural view of a load voltage detecting circuit according to a first embodiment of the present invention
  • FIG. 2 is a schematic structural diagram of a zero-crossing detecting circuit according to an embodiment of the present invention.
  • FIG. 3 is a schematic structural diagram of a voltage detecting circuit according to an embodiment of the present invention.
  • 4 and 5 are waveform diagrams of voltage and current according to an embodiment of the present invention.
  • FIG. 6 is a schematic structural diagram of a load voltage detecting circuit according to a second embodiment of the present invention.
  • Fig. 7 is a view showing the configuration of a load voltage detecting circuit of a third embodiment of the present invention.
  • a load voltage detecting circuit including: a load power circuit 14, a voltage dividing resistor 16, a switch tube 15, a voltage detecting circuit 18, and a zero-crossing detecting circuit 19,
  • the load power circuit 14 includes a load 11, a diode 13 and an inductor 12, and the load 11, the diode 13 and the inductor 12 are connected in series to form a loop circuit, and one end of the load power supply circuit 14 is connected to an operating voltage input terminal Vin, the load power supply circuit 14 The other end is connected to the first end of the switch tube 15 and the first end of the voltage dividing resistor 16 , and the second end of the voltage dividing resistor 16 is grounded together with the second end of the switch tube 15 , and the switch tube is used 15 is controlled by the load voltage, and the voltage dividing end of the voltage dividing resistor 16 is connected to the signal input end of the voltage detecting circuit 18 and the signal input end of the zero-crossing detecting circuit 19, and the zero-crossing detecting circuit 19 determines whether
  • the diode conduction time is obtained, and the voltage detecting circuit 18 obtains the voltage-dividing terminal feedback voltage of the voltage dividing resistor 16 by sampling and holding, and uses the switching tube conduction time and the diode to conduct. Between, the load voltage acquired by calculation.
  • the load power circuit 14 includes a diode 13, an inductor 12 and a load 11. One end of the load 11 and the negative pole of the diode 13 are connected to the operating voltage input terminal Vin. The other end of the load 11 is One end of the inductor 12 is connected, and the other end of the inductor 12 is connected to the anode of the diode 13 and is connected to the first end of the switch tube 15 and the first end of the voltage dividing resistor 16.
  • the load 11 is an LED.
  • the diode 13 is in line with the direction of the LED.
  • the load may also be other electrical devices with which the voltage of the load is detected.
  • the first end of the switch tube 15 is connected to the other end of the load power circuit 14, the second end of the switch tube 15 is grounded, and the control end of the switch tube 15 is connected to the load control circuit 17.
  • the switching transistor is a MOS transistor.
  • the switch tube can also be a triode or the like.
  • the voltage dividing resistor 16 includes a first voltage dividing resistor R1 and a second voltage dividing resistor R2, and the first end of the switching tube 15 is used by the first voltage dividing resistor R1 and the second voltage dividing resistor R2.
  • the voltage is divided, and the voltage dividing end between the first voltage dividing resistor R1 and the second voltage dividing resistor R2 is connected to the signal input end of the zero-crossing detecting circuit 19 and the first signal input terminal of the voltage detecting circuit 18.
  • the voltage dividing resistor may also be a resistor, and the voltage dividing end of the voltage dividing resistor is connected to the signal input end of the zero-crossing detecting circuit and the first signal input end of the voltage detecting circuit.
  • the sample-and-hold module 93 samples and holds the voltage-divided terminal feedback voltage V FB obtained by the signal input terminal 91, obtains the sample-and-hold voltage V FBS , and passes the second reference voltage module.
  • the voltage V1 of 94 is such that the voltage at the first input of the second comparator 95 is V FBS -V1.
  • the comparison is performed by the real-time voltage of the second comparator 95 and the voltage dividing terminal feedback voltage V FB .
  • the second comparator 95 is turned over to determine the diode current zero crossing.
  • the diode current zero crossing can be easily obtained by the zero-crossing detecting circuit 19, thereby obtaining the diode conduction time.
  • the zero-crossing detection circuit 19 can form a current zero-crossing detection circuit with the load power supply circuit 14, the voltage dividing resistor 16, and the switching tube 15 for detecting the diode current zero-crossing point.
  • the load voltage detecting circuit 18 can easily obtain the load voltage by using the diode conduction time and the switching tube conduction time.
  • the voltage detecting circuit 18 includes a first signal input terminal 81, a second signal input terminal 82, a sample and hold module 83, a voltage selection module 84, and an averaging module 85.
  • the signal input terminal 81 is connected to one end of the sample and hold module 83, and the voltage of the voltage dividing end of the voltage dividing resistor is sampled and held.
  • the other end of the sample and hold module 83 is connected to the first end of the voltage selecting module 84.
  • the second terminal of the selection module 84 is grounded, that is, 0V, and the second signal input terminal 82 is connected to the voltage selection module 84 for inputting the diode conduction time and the switch tube conduction time, and the voltage selection module 84 is selected.
  • the terminal is connected to one end of the averaging module 85, and the averaging module 85 averages the input signal during the turn-on of the switch and the conduction of the diode.
  • the select terminal of the voltage selection module 84 and the voltage The first end of the selection module 84 is connected to average the voltage of the voltage divider terminal of the sample and hold.
  • the selection terminal of the voltage selection module 84 and the voltage selection module 84 The second end of the connection is connected, and the voltage of 0V is averaged, and the average value of the output is the load voltage.
  • the continuous current mode means that during the freewheeling of the diode, the inductor current drop has not yet reached zero, that is, the next switching cycle is performed, and the inductor current is always maintained at a positive value.
  • the critical continuous current mode refers to the current switching cycle immediately when the inductor current drops to zero during the freewheeling of the diode.
  • the inductor current has a point of zero at each cycle, and the waveform of the voltage-divider end feedback voltage V FB is as follows.
  • the interrupted current mode refers to the inductor current has dropped to zero during the diode freewheeling, and after a period of time, the next switching cycle is performed, and the inductor current is in each cycle.
  • the diode When the inductor current drops to 0, the diode is automatically turned off, the voltage at the first end of the switch begins to drop, and the voltage divider V FB and the switch are first. The voltage at the terminal decreases proportionally.
  • the voltage at the voltage dividing end V FB When the voltage at the voltage dividing end V FB is detected to be lower than the voltage at which the diode is turned on, it can be judged as the zero crossing point of the inductor current.
  • the sample and hold 83 samples and holds the voltage of the voltage dividing end when the diode is turned on in the previous period, and the selected end of the voltage selecting module 84 and the voltage selecting module 84 are in the on-time of the switching tube.
  • the first end is connected to average the voltage of the voltage dividing end of the sample and hold.
  • the selected end of the voltage selecting module 84 is connected to the second end of the voltage selecting module 84 to average the 0V voltage. It is equivalent to reconstructing a dotted waveform of V FBS according to the voltage dividing end feedback voltage V FB of FIG. 5 (see FIG. 5 ).
  • the dotted waveform voltage is the voltage dividing end when the diode is turned on in the previous period.
  • the feedback voltage V FB ie K*Vin.
  • the dotted waveform voltage is grounded and is 0.
  • D' (1-D)
  • D' ⁇ (1-D) the average time between the switch and the diode is not on average, and the average module is not averaged.
  • the zero-crossing detection circuit 19 and the voltage detection circuit 18 are located in the same load control circuit 17 or the control chip, and the load control circuit 17 or the control chip is used to obtain the diode conduction time and the switch-on time. At the same time, when the load voltage overvoltage is detected, the switch tube 15 is closed by the control terminal Vc of the switch tube.
  • the voltage detecting circuit 18 and the zero-crossing detecting circuit 19 share the same sample-and-hold module or use different sample-and-hold modules.
  • the zero-crossing detection circuit 19, the voltage detecting circuit 18, and the control terminal of the switching transistor 15 may also be located in different control chips or load control circuits.
  • the second embodiment of the present invention further provides another load voltage detecting circuit.
  • the load power circuit 20 includes: a transformer winding 22, a diode 23, and a Two capacitors 24 and a load 21, the second capacitor 24 and the load 21 are connected in parallel, one end is connected to the negative pole of the diode 23, the second capacitor 24 is connected in parallel with the load 21, and the other end is connected to one end of the secondary side of the transformer winding 22 The other end of the secondary side of the transformer winding 22 is connected to the positive pole of the diode 23.
  • One end of the primary side of the transformer winding 22 is connected to the working voltage input terminal Vin, and the other end of the primary side of the transformer winding 22 is connected to the switch tube.
  • the first end of 15 is connected to the first end of the voltage dividing resistor 16.
  • the waveform of the first end of the reconstructed switch tube is the voltage at the first end of the switch tube (Vin+n*Vo) when the diode is turned on during the D period, and the voltage during the D' period is 0; this voltage is at (D+D'
  • the second capacitor may not be connected in parallel on both sides of the load.
  • the third embodiment of the present invention further provides another load voltage detecting circuit.
  • the load power circuit 30 includes a diode 33, an inductor 32, and a second. Capacitor 34 and load 31, one end of the parallel connection of the load 31 and the second capacitor 34, one end of the inductor 32 and the working voltage input terminal Vin Connected, the other end of the parallel connection of the load 31 and the second capacitor 34 is connected to the negative end of the diode 33.
  • the positive end of the diode 33 is connected to the other end of the inductor 32 and to the first end of the switch tube 15.
  • the first ends of the voltage dividing resistors 16 are connected.
  • the second capacitor may not be connected in parallel on both sides of the load.
  • the embodiment of the present invention first provides a current zero-crossing detection method, including:
  • the switch When the switch is turned off and the diode is turned on, the voltage of the voltage divider terminal of the voltage divider resistor is sampled and held, and the result of subtracting the reference voltage from the voltage is compared with the voltage of the voltage divider terminal of the voltage divider resistor obtained in real time.
  • the instantaneous voltage of the terminal voltage is lower than the voltage of the voltage dividing terminal minus the reference voltage, it can be judged as the diode current zero crossing point.
  • the embodiment of the present invention further provides a load voltage detecting method, including:
  • the switch When the switch is turned off and the diode is turned on, the voltage of the voltage dividing end of the voltage dividing resistor is sampled and held, and the result of subtracting the reference voltage from the voltage is compared with the voltage of the voltage dividing terminal of the voltage dividing resistor obtained in real time, and the partial voltage obtained in real time is obtained.
  • the instantaneous voltage of the terminal voltage is lower than the voltage of the voltage dividing terminal minus the reference voltage, it can be determined that the diode current crosses the zero point, thereby obtaining the diode conduction time;
  • the voltage of the voltage dividing terminal of the sample and hold, the on-time of the switch tube and the on-time of the diode are calculated, and the load voltage is calculated.
  • the waveform of the dotted line waveform sampled and held is the voltage-divided end feedback voltage V FB when the diode is turned on in the previous period, that is, K*Vin.
  • V FB voltage-divided end feedback voltage
  • the output voltage is grounded by the voltage selection module, the output voltage is adjusted to 0V, and the dotted waveform is averaged between D and D' (D is the ratio of the time when the switch is turned on, and D' is the diode conducting.

Abstract

一种电流过零点检测电路及方法，负载电压检测电路及方法，所述电流过零点检测电路，包括：负载电源电路（14）、分压电阻（16）、开关管（15）、过零点检测电路（19），所述负载电源电路（14）包括负载（11）、二极管（13）和电感（12），所述负载电源电路（14）的一端与工作电压输入端相连接，所述负载电源电路（14）的另一端与开关管（15）的第一端、分压电阻（16）的第一端连接，所述分压电阻（16）的第二端连同所述开关管（15）的第二端接地，利用所述开关管（15）对于负载电压进行控制，所述分压电阻（16）的分压端与过零点检测电路（19）的信号输入端相连接，利用过零点检测电路（19）判断二极管（13）电流是否过零点，从而获得二极管（13）导通时间。且所述负载电压检测电路利用二极管（13）导通时间和开关管（15）导通时间，可以获得负载电压。所述电路结构简单，检测效率高，成本低。

Description

电流过零点检测电路及方法，负载电压检测电路及方法 技术领域
本发明涉及电路检测技术领域，特别涉及一种电流过零点检测电路及对应的电流过零点检测方法，负载电压检测电路及对应的负载电压检测方法。
背景技术
随着LED的快速发展，LED驱动电路的设计层出不穷。但是现有的LED驱动电路在输出过载、过压保护等功能方面的设计都比较复杂。常见的LED负载检测电路采用变压器绕组，导致电路整体比较复杂，体积大，成本高。
发明内容
本发明解决的问题是提供一种电流过零点检测电路及方法，负载电压检测电路及方法，能快速获得负载电压并能快速判断二极管电流过零点，电路体积小，成本低。
为解决上述问题，本发明实施例提供了一种电流过零点检测电路，包括：负载电源电路、分压电阻、开关管、过零点检测电路，所述负载电源电路包括负载、二极管和电感，且所述负载、二极管和电感串联形成环形电路，所述负载电源电路的一端与工作电压输入端相连接，所述负载电源电路的另一端与开关管的第一端、分压电阻的第一端相连接，所述分压电阻的第二端连同所述开关管的第二端接地，利用所述开关管对于负载电压进行控制，所述分压电阻的分压端与过零点检测电路的信号输入端相连接，利用过零点检测电路判断二极管电流是否过零点。
可选的，所述过零点检测电路包括信号输入端、采样保持模块、第二基准电压模块和第二比较器，所述采样保持模块和第二基准电压模块相连，且所述采样保持模块的一端与信号输入端相连，所述第二基准电压模块的一端作为第二比较器的第一输入端，所述信号输入端作为第二比较器的第二输入端。
可选的，所述负载电源电路中负载的一端、二极管的负极与工作电压输入端相连接，所述负载的另一端与电感的一端相连接，所述电感的另一端与二极管的正极相连接且与开关管的第一端、分压电阻的第一端相连接。
可选的，所述负载电源电路包括：变压器绕组、二极管和负载，所述负载一端与二极管的负极相连接，所述负载另一端与变压器绕组副边的一端相连接，所述变压器绕组副边的另一端与二极管的正极相连接，所述变压器绕组原边的一端与工作电压输入端相连接，所述变压器绕组原边的另一端与开关管的第一端、分压电阻的第一端相连接。
可选的，所述负载电源电路中负载的一端、电感的一端与工作电压输入端相连接，所述负载的另一端与二极管的负极一端相连接，所述二极管的正极一端与电感的另一端相连接且与开关管的第一端、分压电阻的第一端相连接。
可选的，所述负载为LED。
可选的，所述负载并联有第二电容。
本发明实施例还提供了一种利用所述的电流过零点检测电路的电流过零点检测方法，包括：
利用分压电阻采集分压电阻的分压端的电压波形；
当开关管关闭、二极管导通时，采样保持分压电阻的分压端电压，将该电压减去基准电压的结果与实时获得的分压电阻的分压端电压进行比较，当实时获得的分压端电压的瞬时电压低于分压端电压减去基准电压的结果时，即可判断为二极管电流过零点。
可选的，所述基准电压为第二基准电压模块的电压。
本发明实施例还提供了一种负载电压检测电路，包括：负载电源电路、分压电阻、开关管、电压检测电路和过零点检测电路，所述负载电源电路包括负载、二极管和电感，且所述负载、二极管和电感串联形成环形电路，所述负载电源电路的一端与工作电压输入端相连接，所述负载电源电路的另一端与开关管的第一端、分压电阻的第一端相连接，所述分压电阻的第二端连同所述开关管的第二端接地，利用所述开关管对于负载电压进行控制，所述分压电阻的分压端与电压检测电路的信号输入端、过零点检测电路的信号输入端相连接，利用过零点检测电路判断二极管电流过零点，获得二极管导通时间，所述电压检测电路利用分压端采样保持的电压，及开关管导通时间和二极管导通时间，获取负载电压。
可选的，所述电压检测电路包括第一信号输入端、第二信号输入端、采样保持模块、电压选择模块和平均模块，所述第一信号输入端与采样保持模块的一端相连接，对分压端的电压进行采样保持，所述采样保持模块的另一端与电压选择模块的第一端相连，所述电压选择模块的第二端接地，所述第二信号输入端与电压选择模块相连，用于输入二极管导通时间和开关管导通时间，所述电压选择模块的选择端与平均模块的一端相连，平均模块在开关管导通和二极管导通期间对所输入的信号进行平均，其输出的平均值即为负载电压。
可选的，所述过零点检测电路包括信号输入端、采样保持模块、第二基准电压模块和第二比较器，所述采样保持模块和第二基准电压模块相连，且所述采样保持模块的一端与信号输入端相连，所述第二基准电压模块的一端作为第二比较器的第一输入端，所述信号输入端作为第二比较器的第二输入端。
可选的，所述负载电压检测电路和过零点检测电路共用采样保持模块。
可选的，所述电压检测电路、过零点检测电路位于负载控制电路中，当检测到负载电压过压，负载控制电路控制开关管的控制端关断开关管。
可选的，所述开关管的第一端与负载电源电路的另一端相连接，所述开关管的第二端接地，所述开关管的控制端与负载控制电路相连接。
可选的，所述负载电源电路中负载的一端、二极管的负极与工作电压输入端相连接，所述负载的另一端与电感的一端相连接，所述电感的另一端与二极管的正极相连接且与开关管的第一端、分压电阻的第一端相连接。
可选的，所述负载电源电路包括：变压器绕组、二极管和负载，所述负载的一端与二极管的负极相连接，所述负载的另一端与变压器绕组副边的一端相连接，所述变压器绕组副边的另一端与二极管的正极相连接，所述变压器绕组原边的一端与工作电压输入端相连接，所述变压器绕组原边的另一端与开关管的第一端、分压电阻的第一端相连接。
可选的，所述负载电源电路中负载的一端、电感的一端与工作电压输入端相连接，所述负载的另一端与二极管的负极一端相连接，所述二极管的正极一端与电感的另一端相连接且与开关管的第一端、分压电阻的第一端相连接。
可选的，所述负载为LED。
可选的，所述负载并联有第二电容。
本发明实施例还提供了一种利用所述的负载电压检测电路的负载电压检测方法，包括：
利用分压电阻采集分压电阻分压端的电压；
当开关管关闭、二极管导通时，采样保持分压电阻分压端的电压，将该电压减去基准电压的结果与实时获得的分压电阻的分压端电压进行比较，当实时获得的分压端电压的瞬时电压低于分压端电压减去基准电压的结果时，即可判断为二极管电流过零点，从而获得二极管导通时间；
获得二极管导通时间后，利用采样保持的分压端的电压，及开关管导通时间和二极管导通时间，计算获得负载电压。
可选的，在开关管导通时间，采样前一个周期二极管导通时所采样保持的分压端电压，在二极管导通时间，采样0V电压，将两个时间段内的采样电压进行平均，其平均值就是负载电压。
与现有技术相比，本技术方案具有以下优点：
本发明技术方案通过分压电阻进行分压后，通过过零点检测电路能很容易检测出二极管电流过零点，获得二极管的导通时间，检测效率高，成本低。
同时本技术方案先利用过零点检测电路检测二极管电流过零点，获得二极管导通时间，再利用负载电压检测电路，利用所采样保持的分压端的电压，及开关管导通时间和二极管导通时间，计算获得负载电压，结构简单，检测效率高，成本低。
附图说明
图1是本发明第一实施例的负载电压检测电路的结构示意图；
图2是本发明实施例的过零点检测电路的结构示意图；
图3是本发明实施例的电压检测电路的结构示意图；
图4和图5是本发明实施例的电压电流波形图；
图6是本发明第二实施例的负载电压检测电路的结构示意图；
图7是本发明第三实施例的负载电压检测电路的结构示意图。
具体实施方式
下面结合附图，通过具体实施例，对本发明的技术方案进行清楚、完整的描述。
请参考图1，为本发明实施例的一种负载电压检测电路，包括：负载电源电路14、分压电阻16、开关管15、电压检测电路18和过零点检测电路19，所述负载电源电路14包括负载11、二极管13和电感12，且所述负载11、二极管13和电感12串联形成环形电路，所述负载电源电路14的一端与工作电压输入端Vin相连接，所述负载电源电路14的另一端与开关管15的第一端、分压电阻16的第一端相连接，所述分压电阻16的第二端连同所述开关管15的第二端接地，利用所述开关管15对于负载电压进行控制，所述分压电阻16的分压端与电压检测电路18的信号输入端、过零点检测电路19的信号输入端相连接，利用过零点检测电路19判断二极管电流是否过零点，获得二极管导通时间，所述电压检测电路18通过采样保持获得分压电阻16的分压端反馈电压，并利用开关管导通时间和二极管导通时间，通过运算获取负载电压。
在本实施例中，所述负载电源电路14包括二极管13、电感12和负载11，所述负载11的一端、二极管13的负极与工作电压输入端Vin相连接，所述负载11的另一端与电感12的一端相连接，所述电感12的另一端与二极管13的正极相连接且与开关管15的第一端、分压电阻16的第一端相连接。
在本实施例中，所述负载11为LED。且所述二极管13与LED的方向相一致。
在其他实施例中，所述负载还可以为其他电学器件，利用所述电压检测电路对负载的电压进行检测。
所述工作电压输入端Vin和接地端之间还连接有第一电容C1，所述第一电容是为了维持工作电压的稳定。在其他实施例中，所述LED两端还连接有第二电容，所述第二电容用于对负载电流进行滤波。
所述开关管15的第一端与负载电源电路14的另一端相连接，所述开关管15的第二端接地，所述开关管15的控制端与负载控制电路17相连接。
在本实施例中，所述开关管为MOS晶体管。在其他实施例中，所述开关管还可以为三极管等。
在本实施例中，所述分压电阻16包括第一分压电阻R1和第二分压电阻R2，利用所述第一分压电阻R1和第二分压电阻R2将开关管15第一端的电压进行分压，第一分压电阻R1和第二分压电阻R2之间的分压端与过零点检测电路19的信号输入端、电压检测电路18的第一信号输入端相连接。
在其他实施例中，所述分压电阻也可以为一个电阻，且分压电阻的分压端与过零点检测电路的信号输入端、电压检测电路的第一信号输入端相连接。
在本实施例中，请参考图2，所述过零点检测电路19包括信号输入端91、采样保持模块93、第二基准电压模块94和第二比较器95，所述采样保持模块93和第二基准电压模块94相连，且所述采样保持模块93的一端与信号输入端91相连，所述第二基准电压模块94的一端作为第二比较器95的第一输入端，所述信号输入端91作为第二比较器95的第二输入端。
在开关管关断之后，二极管导通时，所述采样保持模块93对信号输入端91获得的分压端反馈电压VFB进行采样保持，获得采样保持电压VFBS，并通过第二基准电压模块94的电压V1，使得第二比较器95的第一输入端的电压为VFBS-V1。通过第二比较器95和分压端反馈电压VFB的实时电压进行比较。当VFB瞬时电压低于VFBS-V1时，第二比较器95翻转，即可判断为二极管电流过零点。
利用所述过零点检测电路19可以很容易获得二极管电流过零点，从而获得二极管导通时间。所述过零点检测电路19可以单独与负载电源电路14、分压电阻16、开关管15形成一个电流过零点检测电路，用于检测二极管电流过零点。而在本实施例中，所述过零点检测电路19获得二极管导通时间后，利用对二极管导通时间和开关管导通时间，负载电压检测电路18可以很容易获得负载电压。
在本实施例中，请参考图3，所述电压检测电路18包括第一信号输入端81、第二信号输入端82、采样保持模块83、电压选择模块84和平均模块85，所述第一信号输入端81与采样保持模块83的一端相连接，对分压电阻的分压端的电压进行采样保持，所述采样保持模块83的另一端与电压选择模块84的第一端相连，所述电压选择模块84的第二端接地，即为0V，所述第二信号输入端82与电压选择模块84相连，用于输入二极管导通时间和开关管导通时间，所述电压选择模块84的选择端与平均模块85的一端相连，平均模块85在开关管导通和二极管导通期间对所输入的信号进行平均，在开关管导通时间，所述电压选择模块84的选择端与所述电压选择模块84的第一端相连，将采样保持的分压端的电压进行平均，在二极管导通时间，所述电压选择模块84的选择端与所述电压选择模块84的第二端相连，将0V电压进行平均，其输出的平均值就是负载电压。
当电路工作于连续电流模式或临界连续电流模式时，所述连续电流模式是指在二极管续流期间，电感电流下降尚未达到零，即进行下一个开关周期，电感电流一直保持为正值，所述临界连续电流模式是指二极管续流期间，电感电流下降到零之时，立即进行下一个开关周 期，电感电流在每个周期都有一个点为零，分压端反馈电压VFB的波形如图4所示，其中K＝R2/(R1+R2)。在开关管开通时，VFB＝0；在开关管关断时，且电感电流为正值时，二极管导通，忽略二极管的导通压降，VFB＝K*Vin。开关管导通的时间比例为D，二极管导通的时间比例为D’＝(1-D)。
当电路工作于断续电流模式时，所述断续电流模式是指二极管续流期间，电感电流已经下降到零，且过一段时间后，才进行下一个开关周期，电感电流在每个周期都有一段时间为零，分压端反馈电压VFB的波形如图5所示：在开关管关断，且电感电流为正值时，二极管导通，忽略二极管的导通压降，VFB＝K*Vin；在二极管导通期间，电感电流逐渐下降，当电感电流下降到0时，二极管自动关断，开关管第一端的电压开始下降，分压端反馈电压VFB和开关管第一端的电压成比例下降。当检测到分压端反馈电压VFB低于二极管导通时的电压，即可判断为电感电流过零点。
在本实施例中，所述采样保持83对前一个周期二极管导通时分压端的电压进行采样保持，在开关管导通时间，所述电压选择模块84的选择端与所述电压选择模块84的第一端相连，将采样保持的分压端的电压进行平均，在二极管导通时间，所述电压选择模块84的选择端与所述电压选择模块84的第二端相连，将0V电压进行平均，相当于根据图5的分压端反馈电压VFB重构一个VFBS的虚线波形(见图5)，在开关管15开通时，虚线波形电压为前一个周期二极管导通时的分压端反馈电压VFB，即K*Vin。在其他时刻，虚线波形电压接地，均为0。对虚线波形在D和D’之间进行平均(D为开关管导通的时间比例，D’为二极管导通的时间比例)，即可获得LED电压K*VLED＝K*Vin*D/(D+D’)。对于连续电流模式或临界电流模式，D’＝(1-D)；对于断续电流模式D’<(1-D)，开关管和二极管均不导通的时间，平均模块不进行平均。
在本实施例中，过零点检测电路19、电压检测电路18位于同一个负载控制电路17或控制芯片中，所述负载控制电路17或控制芯片用于获得二极管导通时间和开关管导通时间，同时当检测到负载电压过压，利用开关管的控制端Vc关闭开关管15。
所述电压检测电路18和过零点检测电路19共用同一个采样保持模块或采用不同的采样保持模块。
在本实施例中，所述过零点检测电路19、电压检测电路18和开关管15的控制端也可以位于不同的控制芯片或负载控制电路中。
本发明第二实施例还提供了另一种负载电压检测电路，请参考图6，其余部分都相同，只有负载电源电路不相同，所述负载电源电路20包括：变压器绕组22、二极管23、第二电容24和负载21，所述第二电容24和负载21并联后一端与二极管23的负极相连接，所述第二电容24和负载21并联后另一端与变压器绕组22副边的一端相连接，所述变压器绕组22副边的另一端与二极管23的正极相连接，所述变压器绕组22原边的一端与工作电压输入端Vin相连接，所述变压器绕组22原边的另一端与开关管15的第一端、分压电阻16的第一端相连接。
由于开关管15导通的时间为D，二极管22导通时间为D’，两者关系满足D*Vin＝D’*n*Vo，Vo就是输出电压，即LED电压，n是变压器22的变比；重构开关管第一端的波形在D时段为二极管导通时开关管第一端的电压(Vin+n*Vo)，D’时段电压为0；将此电压在(D+D’)时间内进行平均得到D*(Vin+n*Vo)/(D+D’)＝n*Vo，即输出负载电压。
在其它实施例中，所述负载的两侧也可以不并联有第二电容。
本发明第三实施例还提供了另一种负载电压检测电路，请参考图7，其余部分都相同，只有负载电源电路不相同，所述负载电源电路30包括：二极管33、电感32、第二电容34和负载31，所述负载31和第二电容34并联结构的一端、电感32的一端与工作电压输入端Vin 相连接，所述负载31和第二电容34并联结构的另一端与二极管33的负极一端相连接，所述二极管33的正极一端与电感32的另一端相连接且与开关管15的第一端、分压电阻16的第一端相连接。
由于开关管15导通的时间为D，二极管22导通时间为D’，两者关系满足D*Vin＝D’*Vo，重构开关管15第一端的波形在D时段为二极管导通时开关管第一端的电压(Vin+Vo)，D’时段电压为0；将此电压在(D+D’)时间内进行平均得到D*(Vin+Vo)/(D+D’)＝Vo，即输出负载电压。
在其它实施例中，所述负载的两侧也可以不并联有第二电容。
基于上述电路，本发明实施例首先提供了一种电流过零点检测方法，包括：
利用分压电阻采集分压电阻的分压端的电压波形；
当开关管关闭，二极管导通时，采样保持分压电阻的分压端电压，将该电压减去基准电压的结果与实时获得的分压电阻的分压端电压进行比较，当实时获得的分压端电压的瞬时电压低于分压端电压减去基准电压的结果时，即可判断为二极管电流过零点。
此外，基于上述负载电压检测电路，本发明实施例还提供了一种负载电压检测方法，包括：
利用分压电阻采集分压电阻分压端的电压；
当开关管关闭，二极管导通时，采样保持分压电阻分压端的电压，将该电压减去基准电压的结果与实时获得的分压电阻的分压端电压进行比较，当实时获得的分压端电压的瞬时电压低于分压端电压减去基准电压的结果时，即可判断为二极管电流过零点，从而获得二极管导通时间；
获得二极管导通时间后，利用采样保持的分压端的电压，及开关管导通时间和二极管导通时间，计算获得负载电压。
在本发明第一实施例中，在开关管15开通时，采样保持的虚线波形电压为前一个周期二极管导通时的分压端反馈电压VFB，即K*Vin。在二极管导通时，利用电压选择模块将输出电压接地，输出电压调为0V，对虚线波形在D和D’之间进行平均(D为开关管导通的时间比例，D’为二极管导通的时间比例)，即可获得LED电压K*VLED＝K*Vin*D/(D+D’)。
在本发明第二实施例中，由于开关管15导通的时间为D，二极管22导通时间为D’，两者关系满足D*Vin＝D’*n*Vo，重构开关管第一端的波形在D时段为二极管导通时开关管第一端的电压(Vin+n*Vo)，D’时段电压为0；将此电压在(D+D’)时间内进行平均得到D*(Vin+n*Vo)/(D+D’)＝n*Vo，即输出负载电压。
在本发明第三实施例中，由于开关管15导通的时间为D，二极管22导通时间为D’，两者关系满足D*Vin＝D’*Vo，重构开关管第一端的波形在D时段为二极管导通时开关管第一端的电压(Vin+Vo)，D’时段电压为0；将此电压在(D+D’)时间内进行平均得到D*(Vin+Vo)/(D+D’)＝Vo，即输出负载电压。
本发明虽然已以较佳实施例公开如上，但其并不是用来限定本发明，任何本领域技术人员在不脱离本发明的精神和范围内，都可以利用上述揭示的方法和技术内容对本发明技术方案做出可能的变动和修改，因此，凡是未脱离本发明技术方案的内容，依据本发明的技术实质对以上实施例所作的任何简单修改、等同变化及修饰，均属于本发明技术方案的保护范围。

Claims (22)

  1. 一种电流过零点检测电路，其特征在于，包括：负载电源电路、分压电阻、开关管、过零点检测电路，所述负载电源电路包括负载、二极管和电感，且所述负载、二极管和电感串联形成环形电路，所述负载电源电路的一端与工作电压输入端相连接，所述负载电源电路的另一端与开关管的第一端、分压电阻的第一端相连接，所述分压电阻的第二端连同所述开关管的第二端接地，利用所述开关管对于负载电压进行控制，所述分压电阻的分压端与过零点检测电路的信号输入端相连接，利用过零点检测电路获得二极管的电流过零点。
  2. 如权利要求1所述的电流过零点检测电路，其特征在于，所述过零点检测电路包括信号输入端、采样保持模块、第二基准电压模块和第二比较器，所述采样保持模块和第二基准电压模块相连，且所述采样保持模块的一端与信号输入端相连，所述第二基准电压模块的一端作为第二比较器的第一输入端，所述信号输入端作为第二比较器的第二输入端。
  3. 如权利要求1所述的电流过零点检测电路，其特征在于，所述负载电源电路中负载的一端、二极管的负极与工作电压输入端相连接，所述负载的另一端与电感的一端相连接，所述电感的另一端与二极管的正极相连接且与开关管的第一端、分压电阻的第一端相连接。
  4. 如权利要求1所述的电流过零点检测电路，其特征在于，所述负载电源电路包括：变压器绕组、二极管和负载，所述负载的一端与二极管的负极相连接，所述负载的另一端与变压器绕组副边的一端相连接，所述变压器绕组副边的另一端与二极管的正极相连接，所述变压器绕组原边的一端与工作电压输入端相连接，所述变压器绕组原边的另一端与开关管的第一端、分压电阻的第一端相连接。
  5. 如权利要求1所述的电流过零点检测电路，其特征在于，所述负载电源电路中负载的一端、电感的一端与工作电压输入端相连接，所述负载的另一端与二极管的负极一端相连接，所述二极管的正极一端与电感的另一端相连接且与开关管的第一端、分压电阻的第一端相连接。
  6. 如权利要求1所述的电流过零点检测电路，其特征在于，所述负载为LED。
  7. 如权利要求1所述的电流过零点检测电路，其特征在于，所述负载并联有第二电容。
  8. 一种利用权利要求1～7任意一项所述的电流过零点检测电路的电流过零点检测方法，其特征在于，包括：
    利用分压电阻采集分压电阻的分压端的电压波形；
    当开关管关闭、二极管导通时，采样保持分压电阻的分压端电压，将该电压减去基准电 压的结果与实时获得的分压电阻的分压端电压进行比较，当实时获得的分压端电压的瞬时电压低于分压端电压减去基准电压的结果时，即可判断为二极管电流过零点。
  9. 如权利要求8所述的电流过零点检测方法，其特征在于，所述基准电压为第二基准电压模块的电压。
  10. 一种负载电压检测电路，其特征在于，包括：负载电源电路、分压电阻、开关管、电压检测电路和过零点检测电路，所述负载电源电路包括负载、负载、二极管和电感，且所述负载、二极管和电感串联形成环形电路，所述负载电源电路的一端与工作电压输入端相连接，所述负载电源电路的另一端与开关管的第一端、分压电阻的第一端相连接，所述分压电阻的第二端连同所述开关管的第二端接地，利用所述开关管对于负载电压进行控制，所述分压电阻的分压端与电压检测电路的信号输入端、过零点检测电路的信号输入端相连接，利用过零点检测电路判断二极管电流是否过零点，获得二极管导通时间；所述电压检测电路利用分压端采样保持的电压，及开关管导通时间和二极管导通时间，获取负载电压。
  11. 如权利要求10所述的负载电压检测电路，其特征在于，所述电压检测电路包括第一信号输入端、第二信号输入端、采样保持模块、电压选择模块和平均模块，所述第一信号输入端与采样保持模块的一端相连接，对分压端的电压进行采样保持，所述采样保持模块的另一端与电压选择模块的第一端相连，所述电压选择模块的第二端接地，所述第二信号输入端与电压选择模块相连，用于输入二极管导通时间和开关管导通时间，所述电压选择模块的选择端与平均模块的一端相连，平均模块在开关管导通和二极管导通期间对所输入的信号进行平均，其输出的平均值即为负载电压。
  12. 如权利要求10所述的负载电压检测电路，其特征在于，所述过零点检测电路包括信号输入端、采样保持模块、第二基准电压模块和第二比较器，所述采样保持模块和第二基准电压模块相连，且所述采样保持模块的一端与信号输入端相连，所述第二基准电压模块的一端作为第二比较器的第一输入端，所述信号输入端作为第二比较器的第二输入端。
  13. 如权利要求10所述的负载电压检测电路，其特征在于，所述负载电压检测电路和过零点检测电路共用采样保持模块。
  14. 如权利要求10所述的负载电压检测电路，其特征在于，所述电压检测电路、过零点检测电路位于负载控制电路中，当检测到负载电压过压，负载控制电路控制开关管的控制端关断开关管。
  15. 如权利要求14所述的负载电压检测电路，其特征在于，所述开关管的第一端与负载电 源电路的另一端相连接，所述开关管的第二端接地，所述开关管的控制端与负载控制电路相连接。
  16. 如权利要求10所述的负载电压检测电路，其特征在于，所述负载电源电路中负载的一端、二极管的负极与工作电压输入端相连接，所述负载的另一端与电感的一端相连接，所述电感的另一端与二极管的正极相连接且与开关管的第一端、分压电阻的第一端相连接。
  17. 如权利要求10所述的负载电压检测电路，其特征在于，所述负载电源电路包括：变压器绕组、二极管和负载，所述负载的一端与二极管的负极相连接，所述负载的另一端与变压器绕组副边的一端相连接，所述变压器绕组副边的另一端与二极管的正极相连接，所述变压器绕组原边的一端与工作电压输入端相连接，所述变压器绕组原边的另一端与开关管的第一端、分压电阻的第一端相连接。
  18. 如权利要求10所述的负载电压检测电路，其特征在于，所述负载电源电路中负载的一端、电感的一端与工作电压输入端相连接，所述负载的另一端与二极管的负极一端相连接，所述二极管的正极一端与电感的另一端相连接且与开关管的第一端、分压电阻的第一端相连接。
  19. 如权利要求10所述的负载电压检测电路，其特征在于，所述负载为LED。
  20. 如权利要求10所述的负载电压检测电路，其特征在于，所述负载并联有第二电容。
  21. 一种利用权利要求10～20任意一项所述的负载电压检测电路的负载电压检测方法，其特征在于，包括：
    利用分压电阻采集分压电阻分压端的电压；
    当开关管关闭，二极管导通时，采样保持分压电阻分压端的电压，将该电压减去基准电压的结果与实时获得的分压电阻的分压端电压进行比较，当实时获得的分压端电压的瞬时电压低于分压端电压减去基准电压的结果时，即可判断为二极管电流过零点，从而获得二极管导通时间；
    获得二极管导通时间后，利用采样保持的分压端的电压，及开关管导通时间和二极管导通时间，计算获得负载电压。
  22. 如权利要求21所述的负载电压检测方法，其特征在于，在开关管导通时间，采样前一个周期二极管导通时所采样保持的分压端电压，在二极管导通时间，采样0V电压，将两个时间段内的采样电压进行平均，其平均值就是负载电压。
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