WO2012022106A1 - 一种发光二极管恒流驱动电路的开路保护电路 - Google Patents

一种发光二极管恒流驱动电路的开路保护电路 Download PDF

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Publication number
WO2012022106A1
WO2012022106A1 PCT/CN2010/080618 CN2010080618W WO2012022106A1 WO 2012022106 A1 WO2012022106 A1 WO 2012022106A1 CN 2010080618 W CN2010080618 W CN 2010080618W WO 2012022106 A1 WO2012022106 A1 WO 2012022106A1
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WO
WIPO (PCT)
Prior art keywords
load branch
secondary winding
winding
current sharing
diode
Prior art date
Application number
PCT/CN2010/080618
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English (en)
French (fr)
Inventor
葛良安
姚晓莉
Original Assignee
英飞特电子（杭州）有限公司
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 英飞特电子（杭州）有限公司 filed Critical 英飞特电子（杭州）有限公司
Priority to US13/814,771 priority Critical patent/US9072126B2/en
Publication of WO2012022106A1 publication Critical patent/WO2012022106A1/zh

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Classifications

    • 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]
    • H05B45/385—Switched mode power supply [SMPS] using flyback topology
    • 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]
    • H05B45/50—Circuit arrangements for operating light-emitting diodes [LED] responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits
    • 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
    • H05B47/00—Circuit arrangements for operating light sources in general, i.e. where the type of light source is not relevant
    • H05B47/20—Responsive to malfunctions or to light source life; for protection
    • H05B47/24—Circuit arrangements for protecting against overvoltage
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B20/00—Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
    • Y02B20/30—Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Definitions

  • the present invention relates to a constant current driving circuit, and more particularly to an open circuit protection circuit for a constant current driving circuit of an LED.
  • each load consists of one or more LED lamps.
  • the two load voltages are different, it is necessary to balance the two load currents, that is, the total current outputted by the constant current drive circuit is distributed to each LED load according to the load.
  • the transformer TalO consists of the secondary winding WT10, which is connected to two rectifier circuits to supply power to the two loads A1 and A2.
  • This circuit achieves equalization across the two load branches Al, A2 via a current sharing transformer T10. If the load is more than two, such as N, then N-1 current sharing transformers are required.
  • This circuit has the following disadvantages: When one load connected to the current sharing transformer T10 is open, in order to make the other load connected to the current sharing transformer T10 work normally, the load branch corresponding to the open load will have an overvoltage, resulting in a circuit. damage.
  • FIG. 2 it is an open circuit protection circuit diagram of a prior art LED constant current driving circuit.
  • the circuit shown in Fig. 2 is connected to an open circuit protection circuit in parallel with each load output terminal of the LED constant current driving circuit on the basis of the circuit shown in Fig. 1.
  • the open circuit protection circuit is composed of a Zener diode ZD10, a first resistor R10, a second resistor R20, a first filter capacitor CplO and a thyristor SCR10.
  • the Zener diode ZD10 and the first resistor R10 and the second resistor R20 are connected in series at both ends of the load.
  • the first filter capacitor CplO is connected in parallel across the second resistor R20.
  • the thyristor SCR10 is connected in parallel at both ends of the load, and the gate of the thyristor SCR10 is connected to one end of the first resistor R10 and the second resistor R20.
  • the Zener diode ZD10 is reverse-conducted. After passing through the current limit of the first resistor R10 and the filtering of the first filter capacitor Cpl0 and the second resistor R20, the thyristor SCR10 will obtain a gate current.
  • the thyristor SCR10 leads Through, the load current flows through the thyristor SCR10 to lower the voltage, thus ensuring the normal operation of the LEDs of other load branches.
  • the open circuit protection circuit of the prior art has the following disadvantages: As shown in Fig. 2, when the thyristor SCR10 is turned on, the output capacitance ColO or Co20 is directly short-circuited. Due to the discharge of the output capacitor ColO or Co20, the device including the SCR10 is subjected to a large current stress, so that a device capable of withstanding a large current needs to be used, which increases the cost. Taking two loads as an example, when one load of the thyristor SCR10 is turned on, the current sharing winding of the current sharing transformer T10 is subjected to 1/2 of the output voltage. Since the current sharing transformer T10 is subjected to a relatively large voltage, it is necessary to use a relatively large current sharing transformer.
  • An open circuit protection circuit for a constant current driving circuit of a light emitting diode comprising: a transformer having at least one secondary winding connected to at least two load branches; The structure of each load branch is the same;
  • Each load branch and one secondary winding form a rectifying loop; the secondary winding has a tap end, and the secondary winding is divided into two secondary windings;
  • the circuit further includes: a current sharing transformer disposed in two adjacent load branches;
  • An open circuit protection module is respectively connected to each load branch, and the open circuit protection module includes a detection control unit and a processing unit:
  • the detecting control unit is configured to output a control signal to the processing unit when detecting that an output voltage of each load branch or a voltage proportional to the output voltage is not lower than a corresponding preset threshold; After receiving the control signal, short-circuiting a secondary winding of the corresponding load branch and a current sharing winding of the current sharing transformer connected in series.
  • the load branch comprises:
  • the same name of the secondary winding is terminated with the anode of the first diode, and the cathode of the first diode is connected to the different end of the secondary winding via the first output capacitor;
  • connection end of the first output capacitor and the cathode of the first diode is a positive output end of the load branch, and the other end of the first output capacitor is a negative output end of the load branch;
  • the processing unit includes a second diode, a first capacitor, and a switching device; wherein an anode of the second diode is connected to a tap end of the secondary winding, and the second diode is a cathode is connected to the first end of the switching device; a second end of the switching device is connected to a negative output end of the load branch, and a control end of the switching device is connected to a control signal output end of the detection control unit;
  • the first capacitor is coupled between the first end and the second end of the switching device.
  • the detection control unit comprises: a Zener diode, a first resistor, a second resistor, and a first filter capacitor;
  • the switching device is specifically a thyristor, an anode of the thyristor is a first end of the switching device, and a cathode of the thyristor is a second end of the switching device;
  • a cathode of the Zener diode is connected to a positive output end of the load branch, and an anode of the Zener diode is connected to a negative output end of the load branch via the first resistor and the second resistor, the first The filter capacitor is connected in parallel across the second resistor.
  • the load branch comprises:
  • a terminal of the same name of the secondary winding is connected to an anode of the first diode via a first output capacitor, and a cathode of the first diode is connected to a different end of the secondary winding;
  • connection end of the first output capacitor and the same end of the secondary winding is a positive output end of the load branch, and a connection end of the first output capacitor and an anode of the first diode is the load branch The negative output of the road;
  • a winding of the load branch and the current sharing transformer provided in the adjacent load branch is connected in series between the same-name end of the secondary winding and the positive output end of the load branch where the secondary winding is located.
  • the processing unit includes a second diode, a first capacitor, and a switching device; wherein a first end of the switching device is connected to a positive output end of the load branch, and a second end of the switching device Connected to the anode of the second diode, the cathode of the second diode is connected to the tap end of the secondary winding; the control terminal of the switching device is connected to the control signal output end of the detection control unit;
  • the first capacitor is coupled between the first end and the second end of the switching device.
  • the primary side of the transformer includes a primary winding and a switch; the transformer and the switch form a flyback topology circuit;
  • the same name end of the primary winding of the transformer is connected to one end of the switch, and the other end of the switch
  • the invention also provides an open circuit protection circuit of a constant current driving circuit of an LED, the circuit comprising: a transformer, the transformer having at least one secondary winding, connecting at least two load branches; each load branch structure is the same;
  • Each load branch and one secondary winding form a rectifying loop; the secondary winding has a tap end, and the secondary winding is divided into two secondary windings;
  • the circuit further includes: a current sharing transformer in each of the load branches connected in series; the primary current sharing windings of each current sharing transformer are respectively connected with a secondary side subwinding of the secondary winding corresponding to each load branch, and each current sharing transformer The secondary side current sharing windings are connected in series;
  • An open circuit protection module is respectively connected to each load branch, and the open circuit protection module includes a detection control unit and a processing unit:
  • the detecting control unit is configured to output a control signal to the processing unit when detecting that an output voltage of each load branch or a voltage proportional to the output voltage is not lower than a corresponding preset threshold; After receiving the control signal, the tap end of the secondary winding and the primary side of the current sharing transformer are short-circuited to one end of the secondary winding.
  • the load branch comprises:
  • the same name of the secondary winding is terminated with the anode of the first diode, and the cathode of the first diode is connected to the different end of the secondary winding via the first output capacitor;
  • a connecting end of the first output capacitor and a cathode of the first diode is a positive output end of the load branch, and another end of the first output capacitor is a negative output end of the load branch;
  • the primary current sharing winding of the current sharing transformer is connected in series between the different name end of the secondary winding and the negative output end of the load branch where the secondary winding is located.
  • the processing unit includes a second diode, a first capacitor, and a switching device; wherein an anode of the second diode is connected to a tap end of the secondary winding, and the second diode is a cathode is connected to the first end of the switching device; a second end of the switching device is connected to a negative output end of the load branch, and a control end of the switching device is connected to a control signal output end of the detection control unit;
  • the first capacitor is coupled between the first end and the second end of the switching device.
  • the detection control unit includes: a Zener diode, a first resistor, a second resistor, and a first filter capacitor;
  • the switching device is specifically a thyristor, an anode of the thyristor is a first end of the switching device, and a cathode of the thyristor is a second end of the switching device;
  • a cathode of the Zener diode is connected to a positive output end of the load branch, and an anode of the Zener diode is connected to a negative output end of the load branch via the first resistor and the second resistor, the first A filter capacitor is connected in parallel across the second resistor.
  • the load branch comprises:
  • a terminal of the same name of the secondary winding is connected to an anode of the first diode via a first output capacitor, and a cathode of the first diode is connected to a different end of the secondary winding;
  • connection end of the first output capacitor and the same end of the secondary winding is a positive output end of the load branch, and a connection end of the first output capacitor and an anode of the first diode is the load branch The negative output of the road;
  • the current sharing winding of the current sharing transformer is connected in series between the same-named end of the secondary winding and the positive output of the load branch where the secondary winding is located.
  • the processing unit includes a second diode, a first capacitor, and a switching device; wherein a first end of the switching device is connected to a positive output end of the load branch, and a second end of the switching device is An anode of the second diode, a cathode of the second diode is connected to a tap end of the secondary winding; a control terminal of the switching device is connected to a control signal output end of the detection control unit;
  • the first capacitor is coupled between the first end and the second end of the switching device.
  • the primary side of the transformer includes a primary winding and a switch; the transformer and the switch form a flyback topology circuit;
  • the same name end of the transformer primary winding is connected to one end of the switch, and the other end of the switch. According to a specific embodiment provided by the present invention, the present invention discloses the following technical effects:
  • the LED constant current driving circuit includes a secondary winding having a tap end, and the secondary winding is divided into two secondary windings; the series is connected in the adjacent two load branches.
  • the current sharing windings of the current sharing transformer are respectively connected to one secondary side subwinding of the secondary winding corresponding to each load branch.
  • An open circuit protection module is respectively connected to each load branch, the open circuit protection module includes a detection control unit and a processing unit, and the detection control unit is configured to detect an output voltage of each load branch or be proportional to the output voltage Outputting a control signal to the voltage when the voltage is not lower than the corresponding preset threshold
  • the processing unit is configured to: after receiving the control signal, short-circuit the tap end of the secondary winding and one end of the current sharing winding of the current sharing transformer not connected to the secondary winding.
  • the detection control unit detects that the output voltage or the voltage proportional to the output voltage is not lower than the corresponding preset threshold, and outputs a control signal to the processing unit, and the processing unit turns the tap end of the secondary winding and The current sharing winding of the current sharing transformer is short-circuited at one end of the secondary winding. Since there is no direct short-circuit to the output capacitor, the processing unit is subjected to less inrush current, thereby reducing the current stress of the relevant components in the processing unit. Therefore, in the embodiment, the processing unit can select related components with less current stress, thereby reducing the cost of the open circuit protection.
  • the open circuit protection module included in the load only shorts the tap end of the secondary winding and the current sharing winding of the current sharing transformer is not connected to one end of the secondary winding, and thus the processing of the open circuit protection module When the unit is short-circuited, the winding of the current sharing transformer is subjected to a small voltage, which can reduce the volume of the current sharing transformer.
  • FIG. 2 is an open circuit protection circuit diagram of a constant current driving circuit of the light emitting diode of the prior art
  • FIG. 3 is an open circuit protection circuit diagram of the constant current driving circuit of the light emitting diode according to the first embodiment of the present invention
  • FIG. 4 is a diagram of the light emitting diode of the second embodiment of the present invention.
  • FIG. 5 is an open circuit protection circuit diagram of the LED constant current driving circuit according to Embodiment 3 of the present invention
  • FIG. 6 is an open circuit protection circuit diagram of the LED constant current driving circuit according to Embodiment 4 of the present invention
  • FIG. 8 is an open circuit protection circuit diagram of a constant current driving circuit of a light emitting diode according to Embodiment 6 of the present invention;
  • FIG. 5 is an open circuit protection circuit diagram of the LED constant current driving circuit according to Embodiment 3 of the present invention
  • FIG. 6 is an open circuit protection circuit diagram of the LED constant current driving circuit according to Embodiment 4 of the present invention
  • FIG. 9 is a circuit diagram of an open circuit protection circuit of a light emitting diode constant current driving circuit according to Embodiment 6 of the present invention
  • FIG. 10 is an open circuit protection circuit diagram of a constant current driving circuit of an LED according to Embodiment 8 of the present invention
  • FIG. 11 is an open circuit protection circuit diagram of a constant current driving circuit of an LED according to Embodiment 9 of the present invention
  • FIG. 13 is an open circuit protection circuit diagram of a constant current driving circuit of an LED according to Embodiment 11 of the present invention
  • FIG. 14 is an open circuit protection circuit diagram of a constant current driving circuit of an LED according to Embodiment 12 of the present invention
  • FIG. 16 is an open circuit protection circuit diagram of a constant current driving circuit of the light emitting diode according to Embodiment 14 of the present invention
  • FIG. 17, is a constant current driving circuit of the light emitting diode according to Embodiment 15 of the present invention
  • FIG. 18 is an open circuit protection circuit diagram of the LED constant current driving circuit according to Embodiment 16 of the present invention
  • FIG. 19 is an open circuit protection circuit diagram of the LED constant current driving circuit according to Embodiment 17 of the present invention.
  • FIG. 3 it is an open circuit protection circuit diagram of a constant current driving circuit of an LED according to Embodiment 1 of the present invention.
  • the circuit includes: a transformer Tal.
  • the primary side of the transformer Tal includes a primary winding and a switch Si.
  • the same-name end of the primary winding of the transformer Tal is connected to one end of the switch Si, and the other end of the switch Si is connected to the negative pole of the power supply Vdc, and the opposite end of the primary winding of the transformer Tal is The positive pole of the power supply Vdc is connected.
  • the secondary side of the transformer Tal includes: a first secondary winding WT1 having two load branches connected to the load A1 and the load A2, respectively. Among them, each load branch structure is the same.
  • Each load branch forms a rectifying circuit with the first secondary winding WT1.
  • the rectifying circuit composed of the first load branch is: the first sub-side winding WT1 is terminated with the same name as the anode of the first diode D1, and the cathode of the first diode D1 is passed through the first output capacitor. Col is connected to the different end of the first secondary winding WT1.
  • the rectifying circuit composed of the second load branch is: the first sub-side winding WT1 is terminated with the same name as the anode of the first diode D2, and the cathode of the first diode D2 is connected to the first output capacitor Co2. A different name end of the side winding WT1.
  • the first output capacitors Col and Co2 respectively constitute an output end of the first load branch and the second load branch.
  • the connection end of the first output capacitor Col and the cathode of the first diode D1 is the positive output end of the first load branch, and the first output capacitor Col is another One end is the negative output of the first load branch.
  • the load A1 is coupled across the first output capacitor Col.
  • the secondary side of the transformer Tal further includes a first current sharing transformer T1.
  • the first current sharing transformer T1 includes a first current sharing winding W1 and a second current sharing winding W2, which are respectively connected in series in the first load branch and the second load branch.
  • the current sharing windings of the first current sharing transformer T1 are respectively connected in series at the different end of the first secondary winding WT1 and the negative output end of each load branch. between. specific:
  • the same name of the first current sharing winding W1 is terminated with the different end of the first secondary winding WT1, and the different name of the first current sharing winding W1 is terminated with the first load.
  • the negative output of the branch is the same name of the first current sharing winding W1 is terminated with the different end of the first secondary winding WT1, and the different name of the first current sharing winding W1 is terminated with the first load.
  • the different name of the second current sharing winding W2 is terminated with the different name end of the first secondary winding WT1, and the same name of the second current sharing winding W2 is terminated with the second load The negative output of the branch.
  • the first secondary winding WT1 has a tap end. As shown in Fig. 3, the tap end divides the first secondary winding WT1 into a first secondary winding WT11 and a second secondary winding WT12. The different end of the first secondary winding WT11 is the same end of the second secondary winding WT12; the common side of the first secondary winding WT11 and the second secondary winding WT12 It is the tap end of the first secondary winding WT1.
  • an open circuit protection module 10 is added to each load branch, and the open circuit protection module 10 is respectively connected between the tap end of the first secondary winding WT1 and the negative output end of each load branch.
  • the first load branch is taken as an example for description.
  • An open circuit protection module 10 is connected in parallel between the negative outputs of the load branches.
  • the open circuit protection module 10 includes: a detection control unit 101 and a processing unit 102.
  • the detection control unit 101 is configured to detect an output voltage of the first load branch or a voltage proportional to the output voltage, when an output voltage of the first load branch is proportional to the output voltage When the voltage is not lower than the corresponding preset threshold, a control signal is output to the processing unit 102.
  • the processing unit 102 is coupled between the tap end of the first secondary winding WT1 and the negative output end of the first load branch (that is, the first current sharing winding W1 of the first current sharing transformer T1 is not connected As shown in FIG. 3, the processing unit 102 is coupled between the second secondary winding WT12 and the first current sharing winding W1. The processing unit 102 is configured to short-circuit the second secondary side sub-winding WT12 and the first current sharing winding W1 when receiving the control signal.
  • the open circuit protection module 10 is connected in parallel between the tapped end of the first secondary winding WT1 and the negative output of the second load branch.
  • the open circuit protection module 10 includes: a detection control unit 101 and a processing unit 102.
  • the detection control unit 101 is configured to detect an output voltage of the second load branch or a voltage proportional to the output voltage, when an output voltage of the second load branch is proportional to the output voltage When the voltage is not lower than the corresponding preset threshold, a control signal is output to the processing unit 102.
  • the processing unit 102 is coupled to the tap end of the first secondary winding WT1 and the negative output end of the second load branch (that is, the second current sharing winding W2 of the first current sharing transformer T1 is not connected to the first Between one end of the secondary winding WT1), as shown in FIG. 3, the processing unit 102 is coupled between the second secondary winding WT12 and the second equalizing winding W2.
  • the processing unit 102 is configured to short-circuit the second secondary winding WT12 and the second equalizing winding W2 when receiving the control signal.
  • the detection control unit 101 detects that the output voltage of the first load branch or the voltage proportional to the output voltage is not lower than the corresponding pre-
  • a control signal is output to the processing unit 102, so that the processing unit 102 shorts the second secondary winding WT12 and the current sharing winding W1 of the first current sharing transformer T1.
  • the circuit of the present embodiment does not directly short the first output capacitor Col, so that the inrush current to be received by the processing unit 102 is small, thereby reducing the current stress of the relevant components in the processing unit 102. Therefore, the processing unit 102 in the embodiment can select related components with less current stress, thereby reducing the cost of the open circuit protection.
  • the parallel open circuit protection module in the load branch only shorts a secondary side sub-winding of the secondary winding and the current sharing transformer connected in series therewith
  • the current sharing winding when the processing unit of the open circuit protection module is short-circuited, the current sharing winding of the current sharing transformer connected in series in the load branch is less than 1/2 of the output voltage of the load branch, so it can be reduced The volume of a small current transformer.
  • FIG. 4 it is an open circuit protection circuit diagram of a constant current driving circuit of a light emitting diode according to a second embodiment of the present invention.
  • 4 is a diagram showing a specific implementation of a processing unit in the circuit shown in FIG.
  • the processing unit may also be implemented in other implementation manners.
  • the processing unit 102 may include: a second diode D11, a first capacitor Cl, and a switching device Sl.
  • the anode of the second diode D11 is connected to the tap end of the first secondary winding WT1, and the cathode of the second diode D11 is connected to the first end of the switching device S1;
  • a second terminal of the first load branch is connected to the negative output end of the first load branch, and a control terminal of the switch device S1 is connected to the control signal output end of the detection control unit 101;
  • the first capacitor C1 is coupled to the Between the first end and the second end of the switching device S1.
  • the first capacitor C1 functions as a filter.
  • the switching device S1 in the control processing unit 102 When the detection control unit 101 detects that the load of the load branch is working normally, the switching device S1 in the control processing unit 102 is in an open circuit or high impedance state; when the detection control unit 101 detects an open load or an overvoltage ( Specifically, when the output voltage of the load branch or the voltage proportional to the output voltage is not lower than a corresponding preset threshold, the switching device S1 in the processing unit 102 is controlled to be turned on or in a low impedance state, thereby The branch of the first secondary side winding WT11 of the transformer Tal and the current sharing winding of the current sharing transformer T1 are at a low impedance.
  • the detection control unit 101 can be used to detect the output voltage of each load branch, and can also be used to detect a voltage proportional to the output voltage of each load branch. The following is explained separately.
  • FIG. 5 it is an open circuit protection circuit diagram of a constant current driving circuit of a light emitting diode according to a third embodiment of the present invention.
  • FIG. 5 is a specific implementation diagram of the detection control unit of the open circuit protection circuit shown in FIG. 4.
  • the detection control unit 101 detects the output voltage of each load branch.
  • the detection control unit may also be implemented in other implementation manners.
  • the detection control unit 101 includes: a Zener diode ZD1, a first resistor R11, a second resistor R12, and a first filter capacitor Cpl.
  • the processing unit 102 differs from that shown in FIG. 3 in that:
  • the switching device S1 is specifically a thyristor S11.
  • the detection control circuit 101 is configured to detect whether the output voltage of each load branch exceeds a preset threshold. Therefore, correspondingly, the detection control circuit 101 is connected between the positive output terminal and the negative output terminal of each load branch.
  • the cathode of the Zener diode ZD1 is connected to the positive output end of the first load branch, and the anode thereof is connected to the negative output end of the first load branch via the first resistor R11 and the second resistor R12.
  • the first filter capacitor Cpl is connected in parallel across the second resistor R12.
  • the gate of the thyristor S11 is substantially the control end of the processing unit 102, connected to the common end of the first resistor R11 and the second resistor R12, and the anode of the thyristor S11 is connected to the cathode of the second diode D11,
  • the anode of the second diode D11 is connected to the tap end of the first secondary winding WT1
  • the cathode of the thyristor S11 is connected to the negative output end of the first load branch
  • the first capacitor C1 is coupled to
  • the switching device ie, the thyristor S11
  • the switching device ie, the thyristor S11
  • the Zener diode ZD1 is turned on. After the Zener diode ZD1 is turned on, after the current limiting of the first resistor R11 and the filtering of the second resistor R12 and the first filter capacitor Cpl, the control current is output to the gate of the thyristor S11. When the control current is not lower than the threshold value of the thyristor S11, the thyristor S11 is turned on, thereby short-circuiting the branch of the second secondary winding WT12 and the first equalizing winding W1.
  • the circuit does not directly short-circuit the first output capacitor Col, so the processing unit 102 receives a small inrush current and reduces the current stress of the thyristor S11. Therefore, in the embodiment, the processing unit 102 can select a thyristor with a small current stress to reduce The cost of open circuit protection.
  • the open circuit protection module included in the load branch only shorts a secondary side sub-winding of the secondary winding and a current sharing winding of the current sharing transformer connected thereto, Therefore, when the processing unit of the open circuit protection module is short-circuited, the current-sharing winding of the current-sharing transformer is subjected to a voltage less than 1/2 of the output voltage of the entire load branch, so that the volume of the current-sharing transformer can be reduced.
  • the voltage detected by the detection control unit is the output voltage of the load branch, thereby directly determining whether the output voltage of the load branch is normal.
  • the detection The control unit can also indirectly determine whether the output voltage is normal by detecting any voltage in the load branch that is proportional to the output voltage to determine if the load branch needs to be open protected.
  • the secondary side of the transformer Tal includes only one secondary winding.
  • the secondary side of the transformer Tal may further include a plurality of secondary windings.
  • the open circuit protection module still applies. Referring to Fig. 6, there is shown an open circuit protection circuit diagram of a constant current driving circuit of a light emitting diode according to a fourth embodiment of the present invention.
  • the transformer Tal has two secondary windings as an example for description.
  • the open circuit protection circuit of the constant current driving circuit of the fourth embodiment shown in FIG. 6 is different from the circuit of the first embodiment shown in FIG. 3 in that: the transformer Tal includes two secondary windings: a first secondary winding WT1 and a second secondary winding The winding WT2; the circuit comprises two load branches, wherein the first load branch is connected to the first secondary winding WT1 and the second load branch is connected to the second secondary winding WT2.
  • the connection manner of each of the load branches and the secondary windings is the same as that of the first embodiment.
  • the current sharing windings of the first current sharing transformer T1 are respectively connected in series between the different ends of the secondary windings and the negative output ends of the respective load branches.
  • the different end of the WT1, the different name of the first current sharing winding W1 is terminated with the negative output end of the first load branch.
  • the different name of the second current sharing winding W2 is terminated with the different name end of the second secondary winding WT2, and the same name of the second current sharing winding W2 is terminated with the second load The negative output of the branch.
  • the first secondary winding WT1 and the second secondary winding WT2 each have a tap end.
  • the tap end of the first secondary winding WT1 divides the first secondary winding WT1 into a first secondary winding WT11 and a second secondary winding WT12; the second secondary winding WT2
  • the tap end divides the second secondary winding WT2 into a first secondary winding WT21 and a second secondary winding WT22.
  • an open circuit protection module 20 is added to each load branch, and the open circuit protection module 20 is respectively connected to the tap end of each secondary winding and the negative output end of the load branch where the secondary winding is located. between.
  • the open circuit protection module 20 includes a detection control unit 201 and a processing unit 202.
  • the detection control unit 201 is configured to detect an output voltage of each load branch or the input When the voltage proportional to the output voltage is not lower than the corresponding preset threshold, a control signal is output to the processing unit 202.
  • the processing unit 202 is configured to short-circuit a secondary winding of the secondary winding and a current sharing winding of the current sharing transformer connected in series with the control signal.
  • the secondary side of the transformer Tal includes a plurality of secondary windings
  • the current sharing winding of the current sharing transformer is connected in series to the opposite end of each secondary winding and the load corresponding to the secondary winding
  • the open circuit protection module described in the previous embodiments is equally applicable to the negative output of the branch.
  • FIG. 7 there is shown an open circuit protection circuit diagram of a constant current driving circuit of a light emitting diode according to a fifth embodiment of the present invention.
  • the open circuit protection circuit of the constant current driving circuit of the fifth embodiment is different from the circuit of the fourth embodiment shown in FIG. 6 in that: the circuit includes three secondary windings WT1 to WT3, and each secondary winding is respectively connected to one load branch. .
  • the circuit requires two current sharing transformers T1 and T2 for sequentially connecting the load branches of the adjacent two secondary windings.
  • the first current sharing transformer T1 is connected to the first load branch of the first secondary winding WT1 and the second load branch of the second secondary winding WT2; the second current sharing transformer T2 is connected to the second secondary side. a second load branch of the winding WT2 and a third load branch of the third secondary winding WT3; and so on.
  • a representative second load branch will now be described as an example.
  • a first current sharing transformer is sequentially connected in series between the different end of the second secondary winding WT2 and the negative output end of the second load branch The second current sharing winding W2 of T1 and the first current sharing winding W3 of the second current sharing transformer T2.
  • the second sub-winding WT2 is terminated by a different name of the second current sharing winding W2 of the first current sharing transformer T1; the second current sharing winding of the first current sharing transformer T1 is terminated by the same name The same name end of the first current sharing winding W3 of the second current sharing transformer T2, and the different name of the first current sharing winding W3 is terminated to the negative output end of the second load branch.
  • the open circuit protection module 30 is connected.
  • the connection mode and working principle are the same as those described in the foregoing embodiments, and details are not described herein again.
  • two different current-sharing transformer windings may be connected in series in one load branch, and two current-sharing transformer windings connected in series with the secondary-side sub-winding in the corresponding load branch have two Then, after the corresponding processing unit receives the control signal, the one secondary side winding and The two current sharing windings in series are shorted.
  • N-1 current sharing transformers are required for sequentially connecting the load branches of the adjacent two secondary windings.
  • the open circuit protection circuit of the embodiment of the present invention is also applicable to the case of N secondary windings, and will not be described herein.
  • N-1 current sharing transformers are also needed for sequentially connecting the adjacent two loads of the secondary winding. Branch road.
  • FIG. 8 there is shown an open circuit protection circuit diagram of a constant current driving circuit of a light emitting diode according to a sixth embodiment of the present invention.
  • the first secondary winding WT1 is connected to the three-way load branch as an example for description.
  • the circuit requires two current sharing transformers T1 and T2 for sequentially connecting the adjacent two load branches of the first secondary winding WT1.
  • the first current sharing transformer T1 is connected to the first load branch and the second load branch; the second current sharing transformer T2 is connected to the second load branch and the third load branch.
  • a representative second load branch will now be described as an example.
  • a second current sharing winding W2 of the first current sharing transformer T1 is sequentially connected in series between the different-name end of the first secondary winding WT1 and the negative output end of the second load branch The first current sharing winding W3 of the two current sharing transformer T2.
  • the different name of the first secondary winding WT1 is terminated to the different end of the second current sharing winding W2 of the first current sharing transformer T1; the same name termination of the second current sharing winding W2 of the first current sharing transformer T1
  • the same name end of the first current sharing winding W3 of the second current sharing transformer T2 and the different name of the first current sharing winding W3 is terminated to the negative output end of the second load branch.
  • the open circuit protection module 40 is connected.
  • the connection mode and working principle are the same as those described in the foregoing embodiments, and details are not described herein again.
  • the current sharing windings of the current sharing transformer are connected in series between the different end of the secondary winding and the negative output of each load branch.
  • the current sharing winding of the current sharing transformer may also be connected between the same-name end of the secondary winding and the positive output end of each load branch.
  • FIG. 9 is an open circuit protection circuit of a constant current driving circuit of an LED according to Embodiment 7 of the present invention; Figure.
  • the difference between the open circuit protection circuit of the constant current driving circuit shown in FIG. 9 and the second embodiment shown in FIG. 4 is that: the first current sharing winding W1 and the second current sharing winding W2 of the first current sharing transformer T1 are respectively connected in series.
  • the first end winding WT1 has the same name end and the positive output end of each load branch.
  • the secondary side of the transformer Tal includes: a first secondary winding WT1 having two load branches connected to the load A1 and the load A2, respectively. Among them, each load branch structure is the same.
  • the first load branch includes: the same end of the first secondary winding WT1 is connected to the anode of the first diode D1 via the first output capacitor Col, and the cathode of the first diode D1 is connected to the first secondary winding The different name of WT1.
  • the second load branch includes: an anode of the same name of the first secondary winding WT1 connected to the anode of the first diode D2 via the first output capacitor Co2, and a cathode of the first diode D2 connected to the first secondary winding The different name of WT1.
  • the first output capacitors Col and Co2 respectively constitute an output end of the first load branch and the second load branch.
  • the connection end of the first output capacitor Col and the same end of the first secondary winding WT1 is the positive output end of the first load branch
  • the first output The connection end of the capacitor Col and the anode of the first diode D1 is the negative output end of the first load branch.
  • the load A1 is coupled across the first output capacitor Col.
  • the secondary side of the transformer Tal further includes a first current sharing transformer T1.
  • the first current sharing transformer T1 includes a first current sharing winding W1 and a second current sharing winding W2, which are respectively connected in series in the first load branch and the second load branch.
  • the current sharing windings of the first current sharing transformer T1 are respectively connected in series between the same name end of the first secondary winding WT1 and the positive output end of each load branch .
  • the same name of the first current sharing winding W1 is terminated with the same name end of the first secondary winding WT1, and the different name of the first current sharing winding W1 is terminated with the first load branch The positive output of the road.
  • the second name of the second current sharing winding W2 is terminated with the same name end of the first secondary winding WT1, and the same name of the second current sharing winding W2 is terminated with the second load branch
  • the first secondary winding WT1 has a tap end. As shown in FIG. 9, the tap end divides the first secondary winding WT1 into a first secondary winding WT11 and a second secondary winding WT12. The different end of the first secondary winding WT11 is the same end of the second secondary winding WT12; the common side of the first secondary winding WT11 and the second secondary winding WT12 It is the tap end of the first secondary winding WT1.
  • an open circuit protection module 50 is added to each load branch, and the open circuit protection module 50 is respectively connected between the tap end of the first secondary winding WT1 and the positive output end of each load branch.
  • the first load branch is taken as an example for description.
  • An open circuit protection module 50 is connected in parallel between the tapped end of the first secondary winding WT1 and the positive output of the first secondary branch.
  • the open circuit protection module 50 includes: a detection control unit 501 and a processing unit 502.
  • the detection control unit 501 is configured to detect an output voltage of the first load branch or a voltage proportional to the output voltage, when an output voltage of the first load branch is proportional to the output voltage When the voltage is not lower than the corresponding preset threshold, a control signal is output to the processing unit 502.
  • the processing unit 502 is coupled between the tap end of the first secondary winding WT1 and the positive output end of the first load branch. As shown in FIG. 9, the processing unit 502 is coupled to the first pair. Between the edge winding WT11 and the first current sharing winding W1. The processing unit 502 is configured to short-circuit the first secondary side sub-winding WT11 and the first current sharing winding W1 when receiving the control signal.
  • the open circuit protection module 50 is connected in parallel between the tapped end of the first secondary winding WT1 and the positive output of the second load branch.
  • the open circuit protection module 50 includes: a detection control unit 501 and a processing unit 502.
  • the detection control unit 501 is configured to detect an output voltage of the second load branch or a voltage proportional to the output voltage, when an output voltage of the second load branch is proportional to the output voltage When the voltage is not lower than the corresponding preset threshold, a control signal is output to the processing unit 502.
  • the processing unit 502 is coupled between the tap end of the first secondary winding WT1 and the positive output end of the second load branch. As shown in FIG. 9, the processing unit 502 is coupled to the first pair. Between the edge winding WT11 and the second current sharing winding W2. The processing unit 502 is configured to short-circuit the first secondary side sub-winding WT11 and the second current sharing winding W2 when receiving the control signal.
  • the detection control unit 501 detects that the output voltage of the first load branch or the voltage proportional to the output voltage is not lower than the corresponding At the preset threshold, a control signal is output to the processing unit 502 such that the processing unit 502 shorts the first secondary winding WT11 and the second current winding W2.
  • the circuit of this embodiment does not directly short the first output capacitor Col, so that the inrush current that the processing unit 502 is subjected to is small, thereby reducing the current stress of the relevant components in the processing unit 502. Therefore, the processing unit 502 in this embodiment can select related components with less current stress, which reduces the cost of open circuit protection.
  • the open circuit protection module connected in parallel in the load branch only short-circuits the secondary winding connected to the current sharing winding, so when the open circuit protection module is processed
  • the current sharing winding of the current sharing transformer connected in series in the load branch is less than 1/2 of the output voltage of the load branch, so the volume of the current sharing transformer can be reduced.
  • processing unit may also be implemented in other implementation manners.
  • the processing unit 502 can include: a second diode D11, a first capacitor Cl, and a switching device Sl.
  • the first end of the switching device S1 is connected to the positive output end of the first load branch, the second end of the switching device S1 is connected to the anode of the second diode D11, and the second second a cathode of the pole tube D11 is connected to a tap end of the first secondary winding WT1; a control terminal of the switching device S1 is connected to a control signal output end of the detection control unit 501; the first capacitor C1 is coupled to the Between the first end and the second end of the switching device S1.
  • the first capacitor C1 functions as a filter.
  • the switching device S1 in the control processing unit 502 When the detection control unit 501 detects that the load of the load branch is working normally, the switching device S1 in the control processing unit 502 is in an open circuit or high impedance state; when the detection control unit 501 detects an open load or an overvoltage ( Specifically, when the output voltage of the load branch or the voltage proportional to the output voltage is not lower than a corresponding preset threshold, the switching device S1 in the processing unit 502 is controlled to be turned on or in a low impedance state, thereby The branch of the first secondary side winding WT11 of the transformer Tal and the current sharing winding of the current sharing transformer T1 are at a low impedance.
  • the detection control unit 501 can be used to detect the output voltage of each load branch, and can also be used to detect a voltage proportional to the output voltage of each load branch, which is the same as the previous embodiment, and is no longer Narration.
  • the current sharing winding of the current sharing transformer may also be connected in series between the same-name end of each secondary winding and the positive output end of the corresponding load branch.
  • the open circuit protection circuit of the embodiment of the invention is also applicable. Referring to FIG. 10, it is an open circuit protection circuit diagram of a constant current driving circuit of an LED according to Embodiment 8 of the present invention.
  • the transformer Tal has two secondary windings as an example for description.
  • the transformer Tal includes two secondary windings: a first secondary winding WT1 and a second secondary winding WT2; the circuit includes two load branches, wherein the first load branch is connected to the first secondary winding WT1, The second load branch is connected to the second secondary winding WT2.
  • the current sharing windings of the first current sharing transformer T1 are respectively connected in series between the same-name end of each secondary winding and the positive output end of each load branch.
  • the connection manner of each load branch and the secondary winding is the same as that of the seventh embodiment.
  • an open circuit protection module 60 is added to each load branch.
  • the connection relationship and working principle of the open circuit protection module 60 are the same as those in the seventh embodiment shown in FIG.
  • FIG. 11 there is shown an open circuit protection circuit diagram of a constant current driving circuit for a light emitting diode according to a ninth embodiment of the present invention.
  • the open circuit protection circuit of the constant current driving circuit of the ninth embodiment is different from the circuit of the eighth embodiment shown in FIG. 10 in that: the circuit includes three secondary windings WT1 to WT3, and each secondary winding is respectively connected to one load branch. .
  • the circuit requires two current sharing transformers T1 and T2 for sequentially connecting the load branches of the adjacent two secondary windings, as shown in FIG.
  • the open circuit protection module 70 is connected to each of the load branches.
  • the connection mode and working principle are the same as those described in the foregoing embodiments, and details are not described herein again.
  • N-1 current sharing transformers are required for sequentially connecting the load branches of the adjacent two secondary windings.
  • the open circuit protection circuit of the embodiment of the present invention is also applicable to the case of N secondary windings, and will not be described herein.
  • N-1 current sharing transformers are also needed for sequentially connecting the adjacent two load branches of the secondary winding.
  • FIG. 12 there is shown an open circuit protection circuit diagram of a constant current driving circuit of a light emitting diode according to a tenth embodiment of the present invention.
  • the first secondary winding WT1 is connected to the three-way load branch as an example for description.
  • the circuit requires two current sharing transformers T1 and T2 for sequentially connecting the adjacent two load branches of the first secondary winding WT1.
  • the first current sharing transformer T1 is connected to the first load.
  • the branch and the second load branch; the second current sharing transformer T2 connects the second load branch and the third load branch.
  • the open circuit protection module 80 is connected to each load branch.
  • the connection mode and working principle are the same as those described in the foregoing embodiments, and details are not described herein again.
  • the current equalization of each load is realized by separately connecting the primary and secondary windings of the current sharing transformer.
  • 13 is an open circuit protection circuit diagram of a constant current driving circuit of an LED according to Embodiment 11 of the present invention.
  • the circuit includes: a transformer Tal.
  • the primary side of the transformer Tal includes a primary winding and a switch Si.
  • the secondary side of the transformer Tal includes: a first secondary winding WT1 having two load branches connected to the load A1 and the load A2, respectively.
  • the structure of each load branch is the same, and the circuit structure of each load branch is the same as that of the embodiment shown in FIG. 3, and details are not described herein again.
  • the secondary side of the transformer Tal further includes a first current sharing transformer T10 and a second current sharing transformer T20.
  • the first current sharing transformer T10 includes a primary side current sharing winding W11 and a secondary side current sharing winding W12.
  • the second current sharing transformer ⁇ 20 includes a primary side current sharing winding W21 and a secondary side current sharing winding W22. Specifically, the same name of the primary current sharing winding W11 of the first current sharing transformer T10 is terminated with the different end of the first secondary winding WT1, and the primary current sharing winding of the first current sharing transformer T10 is W11.
  • the same name of the primary current sharing winding W21 of the second current sharing transformer T20 is terminated with the different name end of the first secondary winding WT1, the first name
  • the differential current terminal of the primary current sharing winding W21 of the two current sharing transformer T20 is terminated with the negative output end of the second load branch; the first current sharing transformer
  • the same name of the secondary side current sharing winding W12 of T10 is terminated with the different name end of the secondary side current sharing winding W22 of the second current sharing transformer T20, and the different name of the secondary current sharing winding W12 of the first current sharing transformer T10 The terminal of the same name of the secondary side current sharing winding W22 of the second current sharing transformer T20 is terminated.
  • the first secondary winding WT1 has a tap end. As shown in FIG. 13, the tap end divides the first secondary winding WT1 into a first secondary winding WT11 and a second secondary winding. As shown in FIG. 13, an open circuit protection module 100 is respectively added to each load branch, and the open circuit protection module 100 is respectively connected between the tap end of the first secondary winding WT1 and the negative output end of each load branch.
  • the first load branch is taken as an example for description.
  • An open circuit protection module 100 is connected in parallel between the tapped end of the first secondary winding WT1 and the negative output of the first secondary branch.
  • the open circuit protection module 100 includes: a detection control unit 1001 and a processing unit 1002.
  • the detection control unit 1001 is configured to detect an output voltage of the first load branch or a voltage proportional to the output voltage, when an output voltage of the first load branch is proportional to the output voltage When the voltage is not lower than the corresponding preset threshold, a control signal is output to the processing unit 1002.
  • the processing unit 1002 is coupled between the tap end of the first secondary winding WT1 and the negative output end of the first load branch. As shown in FIG. 13, the processing unit 1002 is coupled to the second pair.
  • the edge winding WT12 is connected between the primary current sharing winding W11 of the first current sharing transformer T10.
  • the processing unit 1002 is configured to short-circuit the second secondary winding WT12 and the primary current sharing winding W11 of the first current sharing transformer T10 when receiving the control signal.
  • the open circuit protection module 100 is connected in parallel between the tapped end of the first secondary winding WT1 and the negative output of the second load branch.
  • the open circuit protection module 100 includes: a detection control unit 1001 and a processing unit 1002.
  • the detection control unit 1001 is configured to detect an output voltage of the second load branch or a voltage proportional to the output voltage, when an output voltage of the second load branch is proportional to the output voltage When the voltage is not lower than the corresponding preset threshold, a control signal is output to the processing unit 1002.
  • the processing unit 1002 is coupled between the tap end of the first secondary winding WT1 and the negative output end of the second load branch. As shown in FIG. 13, the processing unit 1002 is coupled to the second pair.
  • the edge winding WT12 is between the primary winding W1 of the second current sharing transformer T20.
  • the processing unit 1002 is configured to short-circuit the primary winding W1 of the second secondary winding WT12 and the second equalizing transformer T20 when receiving the control signal.
  • the detection control unit 1001 detects that the output voltage of the first load branch or the voltage proportional to the output voltage is not lower than the corresponding pre-
  • a control signal is output to the processing unit 1002, so that the processing unit 1002 short-circuits the second secondary winding WT12 and the primary current sharing winding W11 of the first current sharing transformer T10.
  • the circuit of this embodiment does not directly short the first output capacitor Col, so that the inrush current tolerated by the processing unit 1002 is small, thereby reducing the current stress of the relevant components in the processing unit 1002. Therefore, the processing unit 1002 in the embodiment can select related components with less current stress, thereby reducing the cost of the open circuit protection.
  • the open circuit protection module in the load branch of the road only shorts the secondary winding connected to the primary current sharing winding of the current sharing transformer, thus
  • the processing unit of the open circuit protection module is short-circuited, the primary side current sharing winding of the current sharing transformer connected in series in the load branch is less than 1/2 of the output voltage of the load branch, so the volume of the current sharing transformer can be reduced.
  • processing unit may also be implemented in other implementation manners.
  • the processing unit 1002 may include: a second diode D11, a first capacitor Cl, and a switching device Sl.
  • the anode of the second diode D11 is connected to the tap end of the first secondary winding WT1, and the cathode of the second diode D11 is connected to the first end of the switching device S1;
  • a second terminal of S1 is connected to a negative output end of the first load branch, and a control terminal of the switching device S1 is connected to a control signal output end of the detection control unit 1001;
  • the first capacitor C1 is coupled to the Between the first end and the second end of the switching device S1.
  • the first capacitor C1 functions as a filter.
  • the switching device S1 in the control processing unit 1002 When the detection control unit 1001 detects that the load of the load branch is working normally, the switching device S1 in the control processing unit 1002 is in an open circuit or high impedance state; when the detection control unit 1001 detects an open load or an overvoltage ( Specifically, when the output voltage of the load branch or the voltage proportional to the output voltage is not lower than a corresponding preset threshold, the switching device S1 in the processing unit 1002 is controlled to be turned on or in a low impedance state, thereby The second secondary side winding WT12 of the transformer Tal and the branch of the primary current sharing winding W11 of the first equalizing transformer T10 are at a low impedance.
  • the detection control unit 1001 can be used to detect the output voltage of each load branch, and can also be used to detect a voltage proportional to the output voltage of each load branch.
  • the following is only an example of the first case.
  • FIG. 14 is a circuit diagram of an open circuit protection circuit of a constant current driving circuit of a light emitting diode according to Embodiment 12 of the present invention.
  • FIG. 14 is a specific implementation manner of the detection control unit of the open circuit protection circuit shown in FIG. Figure.
  • the detection control unit detects an output voltage of each load branch.
  • the detection control unit may also be implemented by other implementation manners.
  • the detection control unit 1001 includes: a Zener diode ZD1, a first resistor R11, a second resistor R12, and a first filter capacitor Cpl.
  • the processing unit 1002 is different from that shown in FIG.
  • the switching device S1 is specifically a thyristor S11.
  • the detection control circuit 1001 is configured to detect whether the output voltage of each load branch exceeds a preset threshold. Therefore, correspondingly, the detection control circuit 1001 is connected between the positive output terminal and the negative output terminal of each load branch.
  • the cathode of the Zener diode ZD1 is connected to the positive output end of the first load branch, and the anode thereof is connected to the negative output end of the first load branch via the first resistor R11 and the second resistor R12.
  • the first filter capacitor Cpl is connected in parallel across the second resistor R12.
  • the gate of the thyristor S11 is substantially the control end of the processing unit 1002, connected to the common end of the first resistor R11 and the second resistor R12, and the anode of the thyristor S11 is connected to the cathode of the second diode D11,
  • the anode of the second diode D11 is connected to the tap end of the first secondary winding WT1
  • the cathode of the thyristor S11 is connected to the negative output end of the first load branch
  • the first capacitor C1 is coupled to Between the first end and the second end of the switching device.
  • the detection control unit can also indirectly determine whether the output voltage is normal by detecting any voltage in the load branch that is proportional to the output voltage to determine whether open circuit protection is required for the load branch.
  • the secondary side of the transformer Tal includes only one secondary winding.
  • the secondary side of the transformer Tal may further include a plurality of secondary windings.
  • the present invention The open circuit protection module provided by the embodiment still applies. Referring to Fig. 15, there is shown an open circuit protection circuit diagram of a constant current driving circuit of a light emitting diode according to a thirteenth embodiment of the present invention.
  • the transformer Tal has two secondary windings as an example for description.
  • the open circuit protection circuit of the constant current driving circuit of the thirteenth embodiment shown in FIG. 15 is different from the circuit of the eleventh embodiment shown in FIG. 13 in that the transformer Tal includes two secondary windings: a first secondary winding WT1 and a second The secondary winding WT2; the circuit includes two load branches, wherein the first load branch is connected to the first secondary winding WT1, and the second load branch is connected to the second secondary winding WT2. Negative The connection manner of the load branch and the secondary winding is the same as that of the eleventh embodiment.
  • the primary current sharing windings of the current sharing transformer are respectively connected in series between the different name ends of the secondary windings and the negative output ends of the respective load branches.
  • the same name of the primary current sharing winding W11 of the first current sharing transformer T10 is terminated with the different end of the first secondary winding WT1, and the primary side of the first current sharing transformer T10
  • the different name of the current sharing winding W11 is terminated to the negative output end of the first load branch.
  • the same name of the primary current sharing winding W21 of the second current sharing winding transformer T20 is terminated with the different name end of the second secondary winding WT2, and the second current sharing winding transformer T20
  • the different name of the primary current sharing winding W21 is terminated with the negative output end of the second load branch.
  • the first secondary winding WT1 and the second secondary winding WT2 each have a tap end.
  • an open circuit protection module 200 is added to each load branch, and the open circuit protection module 200 is respectively connected to the tap end of each secondary winding and the negative output end of the load branch where the secondary winding is located. between.
  • the open circuit protection module 200 includes: a detection control unit 2001 and a processing unit 2002.
  • the detection control unit 2001 is configured to output a control signal to the processing unit 2002 when detecting that an output voltage of each load branch or a voltage proportional to the output voltage is not lower than a corresponding preset threshold.
  • the processing unit 2002 is configured to short-circuit the branch where the secondary side winding connected to the primary current sharing winding of the current sharing transformer is located after receiving the control signal.
  • the secondary side of the transformer Tal includes a plurality of secondary windings
  • the primary current sharing windings of the current sharing transformers are connected in series at the opposite end of each secondary winding and the secondary winding
  • the open circuit protection module described in the previous embodiments is also applicable when the negative output of the load branch is used.
  • FIG. 16 there is shown an open circuit protection circuit diagram of a constant current driving circuit for a light emitting diode according to a fourteenth embodiment of the present invention.
  • the open circuit protection circuit of the constant current driving circuit of the fourteenth embodiment is different from the circuit of the thirteenth embodiment shown in FIG. 15 in that: the circuit includes three secondary windings WT1 to WT3, and each secondary winding is respectively connected to one load. Branch road.
  • the circuit requires three current sharing transformers T10, ⁇ 20 and ⁇ 30 for sequentially connecting the load branches of the adjacent two secondary windings.
  • the first current sharing transformer T10 and the second current sharing The transformer T20 is connected to the first load branch of the first secondary winding WT1 and the second load branch of the second secondary winding WT2; the second current sharing transformer T2 and the third current sharing transformer T30 are connected to the second secondary winding WT2 A third load branch of the second load branch and the third secondary winding WT3.
  • the same name of the primary current sharing winding W11 of the first current sharing transformer T10 is terminated with the different end of the first secondary winding WT1, and the primary side of the first current sharing transformer T10 is The different name of the current winding W11 is terminated with the negative output end of the first load branch; the same name of the primary current sharing winding W21 of the second current sharing transformer T20 is terminated with the different name end of the second secondary winding WT2, The first-side current sharing winding T20 of the second current sharing transformer T20 is terminated by a negative-term output of the second load branch; the same-side termination of the primary current-averaging winding W31 of the third current-sharing transformer T30 The different end of the third secondary winding WT3, the different name of the primary current sharing winding W31 of the third current sharing transformer T30 is terminated with the negative output of the second load branch.
  • the same name of the secondary current sharing winding W12 of the first current sharing transformer T10 is terminated with the different end of the secondary current sharing winding W22 of the second current sharing transformer T20, and the secondary side of the second current sharing transformer T20
  • the same name of the current sharing winding W22 is terminated with the different name end of the secondary current sharing winding W32 of the third current sharing transformer T30, and the same name of the secondary current sharing winding W32 of the third current sharing transformer T30 is terminated.
  • the secondary side of the current sharing transformer T10 is a different name of the secondary winding W12.
  • the open circuit protection module 300 is connected.
  • the connection mode and working principle are the same as those described in the foregoing embodiments, and details are not described herein again.
  • the secondary side of the transformer Tal when the secondary side of the transformer Tal includes N secondary windings, then N equalizing transformers are required for sequentially connecting the load branches of the adjacent two secondary windings.
  • the open circuit protection circuit of the embodiment of the present invention is also applicable to the case of N secondary windings, and will not be described herein.
  • N equalizing transformers are also needed for sequentially connecting the adjacent two load branches of the secondary winding.
  • FIG. 17 there is shown an open circuit protection circuit diagram of a constant current driving circuit for a light emitting diode according to a fifteenth embodiment of the present invention.
  • the first secondary winding WT1 is connected to the three-way load branch as an example for description.
  • the circuit requires three current sharing transformers T10, ⁇ 20 and ⁇ 30 for sequentially connecting the first Adjacent two load branches of the secondary winding WT1.
  • the open circuit protection module 400 is connected.
  • the connection mode and working principle are the same as those described in the foregoing embodiments, and details are not described herein again.
  • the primary side current sharing windings of the current sharing transformers are connected in series between the different name ends of the secondary windings and the negative output ends of the respective load branches.
  • the primary current sharing winding of the current sharing transformer may also be connected between the same-named end of the secondary winding and the positive output of each load branch.
  • FIG. 18 there is shown an open circuit protection circuit diagram of a constant current driving circuit of a light emitting diode according to a sixteenth embodiment of the present invention.
  • the open circuit protection circuit of the constant current driving circuit shown in FIG. 18 is different from the eleventh embodiment shown in FIG. 13 in that the primary side current sharing windings of the current sharing transformers are respectively connected in series at the same name end of the first secondary winding and each load. Between the positive outputs of the branches.
  • the secondary side of the transformer Tal includes: a first secondary winding WT1 having two load branches connected to the load A1 and the load A2, respectively. Among them, each load branch structure is the same.
  • the first load branch includes: the same end of the first secondary winding WT1 is connected to the anode of the first diode D1 via the first output capacitor Col, and the cathode of the first diode D1 is connected to the first secondary winding The different name of WT1.
  • the second load branch includes: an anode of the same name of the first secondary winding WT1 connected to the anode of the first diode D2 via the first output capacitor Co2, and a cathode of the first diode D2 connected to the first secondary winding The different name of WT1.
  • the first output capacitors Col and Co2 respectively constitute an output end of the first load branch and the second load branch.
  • the connection end of the first output capacitor Col and the same end of the first secondary winding WT1 is the positive output end of the first load branch
  • the first output The connection end of the capacitor Col and the anode of the first diode D1 is the negative output end of the first load branch.
  • the load A1 is coupled across the first output capacitor Col.
  • the secondary side of the transformer Tal further includes a first current sharing transformer T10 and a second current sharing transformer T20.
  • the same name of the primary current sharing winding W11 of the first current sharing transformer T10 is terminated with the same name end of the first secondary winding WT1, and the opposite end of the primary current sharing winding W11 of the first current sharing transformer T10 Connected to the positive output end of the first load branch; the primary current sharing winding W21 of the second current sharing transformer ⁇ 20 Terminating the same name end of the first secondary winding WT1, the first side of the first current sharing transformer T20 is terminated by a different name of the second load branch; the first The same name of the secondary current sharing winding W12 of the current sharing transformer T10 is terminated with the different name end of the secondary current sharing winding W22 of the second current sharing transformer T20, and the difference of the secondary current sharing winding W12 of the first current sharing transformer T10 The name is terminated with the same name end of the secondary side current sharing winding W22 of the second current sharing transformer T20.
  • the first secondary winding WT1 has a tap end, and the first secondary winding WT1 is divided into a first secondary winding WT11 and a second secondary winding WT12.
  • an open circuit protection module 500 is added to each load branch, and the open circuit protection module 500 is respectively connected between the tap end of the first secondary winding WT1 and the positive output end of each load branch.
  • the first load branch is taken as an example for description.
  • An open circuit protection module 500 is connected in parallel between the tap end of the first secondary winding WT1 and the positive output of the first load branch.
  • the open circuit protection module 500 includes: a detection control unit 5001 and a processing unit 5002.
  • the detection control unit 5001 is configured to detect an output voltage of the first load branch or a voltage proportional to the output voltage, when an output voltage of the first load branch is proportional to the output voltage When the voltage is not lower than the corresponding preset threshold, a control signal is output to the processing unit 5002.
  • the processing unit 5002 is coupled between the tap end of the first secondary winding WT1 and the positive output end of the first load branch. As shown in FIG. 18, the processing unit 5002 is coupled to the first pair.
  • the edge winding WT11 is between the primary winding W11 of the first current sharing transformer.
  • the processing unit 5002 is configured to short-circuit the first secondary winding WT11 and the primary winding W11 of the first current sharing transformer when receiving the control signal.
  • the open circuit protection module 500 is connected in parallel between the tapped end of the first secondary winding WT1 and the positive output of the second load branch.
  • the open circuit protection module 500 includes: a detection control unit 5001 and a processing unit 5002.
  • the detection control unit 5001 is configured to detect an output voltage of the second load branch or a voltage proportional to the output voltage, when an output voltage of the second load branch is proportional to the output voltage When the voltage is not lower than the corresponding preset threshold, a control signal is output to the processing unit 5002.
  • the processing unit 5002 is coupled between the tap end of the first secondary winding WT1 and the positive output end of the second load branch. As shown in FIG. 18, the processing unit 5002 is coupled to the first pair.
  • the edge winding WT11 is between the primary winding W21 of the second current sharing transformer.
  • the processing unit 5002 is configured to short-circuit the first secondary winding WT11 and the primary winding W21 of the second current sharing transformer when receiving the control signal.
  • processing unit may also be implemented in other implementation manners.
  • the processing unit 5002 may include: a second diode D11, a first capacitor Cl, and a switching device Sl.
  • the first end of the switching device S1 is connected to the positive output end of the first load branch, the second end of the switching device S1 is connected to the anode of the second diode D11, and the second second a cathode of the pole D11 is connected to a tap end of the first secondary winding WT1; a control terminal of the switching device S1 is connected to a control signal output end of the detection control unit 5001; the first capacitor C1 is coupled to the Between the first end and the second end of the switching device S1.
  • the first capacitor C1 functions as a filter.
  • the detection control unit 5001 may be configured to detect an output voltage of each load branch, and may also be used to detect a voltage proportional to the output voltage of each load branch, which is the same as the foregoing embodiment, and is not Let me repeat.
  • the current sharing winding of the current sharing transformer may also be connected in series between the different end of each secondary winding and the negative output of each load branch.
  • the open circuit protection circuit of the embodiment of the invention is also applicable. Referring to Figure 19, there is shown an open circuit protection circuit diagram of a constant current driving circuit for a light emitting diode according to a seventeenth embodiment of the present invention.
  • the transformer Tal has two secondary windings as an example for description.
  • the transformer Tal includes two secondary windings: a first secondary winding WT1 and a second secondary winding WT2; the circuit includes two load branches, wherein the first load branch is connected to the first secondary winding WT1, The second load branch is connected to the second secondary winding WT2.
  • the current sharing windings of the first current sharing transformer T1 are respectively connected in series between the same-name end of each secondary winding and the positive output end of each load branch.
  • the connection manner of each load branch and the secondary winding is the same as that of the sixteenth embodiment.
  • an open circuit protection module 600 is added to each load branch.
  • the connection relationship and working principle of the open circuit protection module 600 are the same as those of the embodiment 16 shown in FIG. 18, and details are not described herein.
  • the secondary side of the transformer Tal when the secondary side of the transformer Tal includes N secondary windings or a secondary winding connected to the N load branches, the primary winding of the current sharing transformer is connected in series with the secondary winding.
  • the open circuit protection circuit provided by the embodiment of the present invention is also applicable to the case of the same name end and the positive output end of each load branch.
  • the circuit structure and working principle are the same as those of the foregoing embodiment, and details are not described herein again.

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Description

一种发光二极管恒流驱动电路的开路保护电路
本申请要求于 2010 年 8 月 16 日提交中国专利局、 申请号为 201010257482.0、 发明名称为"一种发光二极管恒流驱动电路的开路保护电路" 的中国专利申请的优先权， 其全部内容通过引用结合在本申请中。
技术领域
本发明涉及恒流驱动电路，特别是涉及一种发光二极管恒流驱动电路的开 路保护电路。
背景技术
多路输出的发光二极管 （LED, Light Emitting Diode ) 恒流驱动电路中， 每路负载由一个或多个 LED灯组成。 当两路负载电压不相同时， 需要平衡两 路负载电流， 即实现恒流驱动电路输出的总电流按负载需要分配给每路 LED 负载。
参照图 1 , 为典型的发光二极管恒流驱动电路图。 变压器 TalO包括副边 绕组 WT10, 接两路整流回路， 为两路负载 A1和 A2供电。 此电路通过一均 流变压器 T10实现两负载支路 Al、 A2上的均衡。 若负载为两路以上， 如 N 路， 则需要 N-1个均流变压器。 此电路存在如下缺点： 当均流变压器 T10连 接的某一路负载开路时， 为了使均流变压器 T10连接的另一路负载正常工作， 会导致开路的负载所对应的负载支路出现过电压， 导致电路损坏。
参照图 2, 为现有技术的发光二极管恒流驱动电路的开路保护电路图。 图 2所示电路在图 1所示电路的基础上分别在发光二极管恒流驱动电路的每个负 载输出端并联一个开路保护电路。 此开路保护电路由稳压二极管 ZD10、 第一 电阻 R10、 第二电阻 R20、 第一滤波电容 CplO和晶闸管 SCR10组成。 所述稳 压二极管 ZD10和第一电阻 R10、第二电阻 R20串联在一起连接在负载的两端。 第一滤波电容 CplO并联在第二电阻 R20的两端。 晶闸管 SCR10并联在负载 的两端， 所述晶闸管 SCR10的门极连接在第一电阻 R10与第二电阻 R20相连 的一端。 当某负载开路或出现过电压时，如果该负载支路的输出电压不低于稳 压二极管 ZD10的稳压值，则稳压二极管 ZD10反向导通。在经过第一电阻 R10 的限流和第一滤波电容 Cpl0、 第二电阻 R20的滤波之后， 晶闸管 SCR10将获 得一个门极电流。 如果此电流不低于晶闸管 SCR10的门值， 晶闸管 SCR10导 通， 负载电流流过晶闸管 SCR10,使电压降低，从而保证其他负载支路的 LED 正常工作。
但是， 现有技术所述开路保护电路存在以下缺点： 结合图 2所示， 当晶闸 管 SCR10导通时， 输出电容 ColO或 Co20直接被短路。 由于输出电容 ColO 或 Co20的放电，使包括 SCR10在内的器件承受较大的电流应力，所以需要使 用能承受较大电流的器件， 增加了成本。 以两路负载为例， 当一路负载的晶闸 管 SCR10导通时， 均流变压器 T10的均流绕组承受 1/2的输出电压。 由于均 流变压器 T10承受电压比较大， 所以需要使用体积较大的均流变压器。
发明内容
本发明的目的是提供一种发光二极管恒流驱动电路的开路保护电路，能够 降低成本、 减小均流变压器体积。
为实现上述目的， 本发明提供了如下方案： 一种发光二极管恒流驱动电路 的开路保护电路，所述电路包括： 变压器，所述变压器具有至少一个副边绕组， 连接至少两路负载支路； 各负载支路结构相同；
每个负载支路与一个副边绕组组成一个整流回路；所述副边绕组具有抽头 端， 将所述副边绕组划分为两个副边子绕组；
所述电路还包括： 设置在相邻的两路负载支路内的均流变压器；
为各负载支路分别连接一开路保护模块，所述开路保护模块包括检测控制 单元和处理单元：
所述检测控制单元用于当检测到各负载支路的输出电压或与所述输出电 压成比例的电压不低于相应的预设阈值时， 输出控制信号至所述处理单元； 所述处理单元用于接收到所述控制信号后，将对应负载支路中一个副边子 绕组和与其串联的均流变压器的均流绕组短路。
优选地， 所述负载支路包括：
副边绕组的同名端接第一二极管的阳极，所述第一二极管的阴极经第一输 出电容接所述副边绕组的异名端；
所述第一输出电容与所述第一二极管的阴极的连接端为所述负载支路的 正输出端， 所述第一输出电容的另一端为所述负载支路的负输出端；
在所述副边绕组的异名端和所述副边绕组所在负载支路的负输出端之间 串联有本负载支路与相邻负载支路中设置的均流变压器的一个绕组。 优选地， 所述处理单元包括第二二极管、 第一电容、 开关器件； 其中， 所述第二二极管的阳极接所述副边绕组的抽头端 ,所述第二二极管的阴极 接所述开关器件的第一端； 所述开关器件的第二端接所述负载支路的负输出 端， 所述开关器件的控制端接所述检测控制单元的控制信号输出端；
所述第一电容并联接在所述开关器件的第一端和第二端之间。
优选地， 所述检测控制单元包括： 稳压二极管、 第一电阻、 第二电阻、 第 一滤波电容；
所述开关器件具体为晶闸管， 所述晶闸管的阳极为所述开关器件的第一 端， 所述晶闸管的阴极为所述开关器件的第二端；
所述稳压二极管的阴极接所述负载支路的正输出端，所述稳压二极管的阳 极经所述第一电阻和第二电阻接所述负载支路的负输出端，所述第一滤波电容 并联在第二电阻两端。
优选地， 所述负载支路包括：
副边绕组的同名端经第一输出电容接第一二极管的阳极，所述第一二极管 的阴极接所述副边绕组的异名端；
所述第一输出电容与所述副边绕组的同名端的连接端为所述负载支路的 正输出端，所述第一输出电容与第一二极管的阳极的连接端为所述负载支路的 负输出端；
在所述副边绕组的同名端和所述副边绕组所在负载支路的正输出端之间 串联有本负载支路与相邻负载支路中设置的均流变压器的一个绕组。
优选地， 所述处理单元包括第二二极管、 第一电容、 开关器件； 其中， 所述开关器件的第一端接所述负载支路的正输出端，所述开关器件的第二 端接所述第二二极管的阳极， 所述第二二极管的阴极接所述副边绕组的抽头 端； 所述开关器件的控制端接所述检测控制单元的控制信号输出端；
所述第一电容并联接在所述开关器件的第一端和第二端之间。
优选地， 所述变压器的原边包括原边绕组和开关； 所述变压器与所述开关 组成反激拓朴电路；
所述变压器原边绕组的同名端与所述开关的一端相连，所述开关的另一端 本发明还提供一种发光二极管恒流驱动电路的开路保护电路，所述电路包 括： 变压器， 所述变压器具有至少一个副边绕组， 连接至少两路负载支路； 各 负载支路结构相同；
每个负载支路与一个副边绕组组成一个整流回路；所述副边绕组具有抽头 端， 将所述副边绕组划分为两个副边子绕组；
所述电路还包括： 串联各负载支路内的均流变压器； 各均流变压器的原边 均流绕组分别与各负载支路对应的副边绕组的一个副边子绕组相连，各均流变 压器的副边均流绕组依次串联；
为各负载支路分别连接一开路保护模块，所述开路保护模块包括检测控制 单元和处理单元：
所述检测控制单元用于当检测到各负载支路的输出电压或与所述输出电 压成比例的电压不低于相应的预设阈值时， 输出控制信号至所述处理单元； 所述处理单元用于接收到所述控制信号后，将所述副边绕组的抽头端和所 述均流变压器的原边均流绕组未连接副边绕组的一端短路。
优选地， 所述负载支路包括：
副边绕组的同名端接第一二极管的阳极，所述第一二极管的阴极经第一输 出电容接所述副边绕组的异名端；
所述第一输出电容与第一二极管的阴极的连接端为所述负载支路的正输 出端， 所述第一输出电容的另一端为所述负载支路的负输出端；
所述均流变压器的原边均流绕组串联接在所述副边绕组的异名端和所述 副边绕组所在负载支路的负输出端之间。
优选地， 所述处理单元包括第二二极管、 第一电容、 开关器件； 其中， 所述第二二极管的阳极接所述副边绕组的抽头端 ,所述第二二极管的阴极 接所述开关器件的第一端； 所述开关器件的第二端接所述负载支路的负输出 端， 所述开关器件的控制端接所述检测控制单元的控制信号输出端；
所述第一电容并联接在所述开关器件的第一端和第二端之间。
优选地， 所述检测控制单元包括： 稳压二极管、 第一电阻、 第二电阻、 第 一滤波电容； 所述开关器件具体为晶闸管， 所述晶闸管的阳极为所述开关器件的第一 端， 所述晶闸管的阴极为所述开关器件的第二端；
所述稳压二极管的阴极接所述负载支路的正输出端，所述稳压二极管的阳 极经所述第一电阻和第二电阻接所述负载支路的负输出端，所述第一滤波电容 并联在所述第二电阻两端。
优选地， 所述负载支路包括：
副边绕组的同名端经第一输出电容接第一二极管的阳极，所述第一二极管 的阴极接所述副边绕组的异名端；
所述第一输出电容与所述副边绕组的同名端的连接端为所述负载支路的 正输出端，所述第一输出电容与第一二极管的阳极的连接端为所述负载支路的 负输出端；
所述均流变压器的均流绕组串联接在所述副边绕组的同名端和所述副边 绕组所在负载支路的正输出端之间。
优选地， 所述处理单元包括第二二极管、 第一电容、 开关器件； 其中， 所述开关器件的第一端接负载支路的正输出端，所述开关器件的第二端接 所述第二二极管的阳极， 所述第二二极管的阴极接所述副边绕组的抽头端； 所 述开关器件的控制端接所述检测控制单元的控制信号输出端；
所述第一电容并联接在所述开关器件的第一端和第二端之间。
优选地， 所述变压器的原边包括原边绕组和开关； 所述变压器与所述开关 组成反激拓朴电路；
所述变压器原边绕组的同名端与所述开关的一端相连，所述开关的另一端 根据本发明提供的具体实施例， 本发明公开了以下技术效果：
本发明实施例中，所述发光二极管恒流驱动电路包括的副边绕组具有抽头 端，将所述副边绕组划分为两个副边子绕组； 串联在相邻的两路负载支路内的 均流变压器的均流绕组分别与各负载支路对应的副边绕组的一个副边子绕组 相连。 为各负载支路分别连接一开路保护模块， 所述开路保护模块包括检测控 制单元和处理单元，所述检测控制单元用于当检测到各负载支路的输出电压或 与所述输出电压成比例的电压不低于相应的预设阈值时，输出控制信号至所述 处理单元； 所述处理单元用于接收到所述控制信号后，将所述副边绕组的抽头 端和所述均流变压器的均流绕组未接副边绕组的一端短路。
当负载开路时，检测控制单元检测到输出电压或与所述输出电压成比例的 电压不低于相应的预设阈值时，输出一控制信号到处理单元， 处理单元将副边 绕组的抽头端和所述均流变压器的均流绕组未接副边绕组的一端短路。由于没 有直接短路输出电容，使得处理单元承受的沖击电流较小， 由此降低了处理单 元中相关元件的电流应力。 因此， 本实施例中处理单元可以选取电流应力较小 的相关元件， 降低了开路保护的成本。
同时， 当某路负载开路时， 该路负载包括的开路保护模块仅仅短路副边绕 组的抽头端和所述均流变压器的均流绕组未接副边绕组的一端，因而当开路保 护模块的处理单元短路时， 均流变压器的绕组承受的电压较小， 可以减小均流 变压器的体积。
附图说明
为了更清楚地说明本发明实施例或现有技术中的技术方案，下面将对实施 例中所需要使用的附图作筒单地介绍， 显而易见地， 下面描述中的附图仅仅是 本发明的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动性 的前提下， 还可以根据这些附图获得其他的附图。
图 1 , 典型的发光二极管恒流驱动电路图；
图 2, 现有技术的发光二极管恒流驱动电路的开路保护电路图； 图 3 , 本发明实施例一的发光二极管恒流驱动电路的开路保护电路图； 图 4, 本发明实施例二的发光二极管恒流驱动电路的开路保护电路图； 图 5 , 本发明实施例三的发光二极管恒流驱动电路的开路保护电路图； 图 6, 本发明实施例四的发光二极管恒流驱动电路的开路保护电路图； 图 7, 本发明实施例五的发光二极管恒流驱动电路的开路保护电路图； 图 8, 本发明实施例六的发光二极管恒流驱动电路的开路保护电路图； 图 9, 本发明实施例七的发光二极管恒流驱动电路的开路保护电路图； 图 10, 本发明实施例八的发光二极管恒流驱动电路的开路保护电路图； 图 11 , 本发明实施例九的发光二极管恒流驱动电路的开路保护电路图； 图 12, 本发明实施例十的发光二极管恒流驱动电路的开路保护电路图； 图 13, 本发明实施例十一的发光二极管恒流驱动电路的开路保护电路图； 图 14, 本发明实施例十二的发光二极管恒流驱动电路的开路保护电路图； 图 15, 本发明实施例十三的发光二极管恒流驱动电路的开路保护电路图； 图 16, 本发明实施例十四的发光二极管恒流驱动电路的开路保护电路图； 图 17, 本发明实施例十五的发光二极管恒流驱动电路的开路保护电路图； 图 18, 本发明实施例十六的发光二极管恒流驱动电路的开路保护电路图； 图 19, 本发明实施例十七的发光二极管恒流驱动电路的开路保护电路图。 具体实施方式
下面将结合本发明实施例中的附图，对本发明实施例中的技术方案进行清 楚、 完整地描述， 显然， 所描述的实施例仅仅是本发明一部分实施例， 而不是 全部的实施例。基于本发明中的实施例， 本领域普通技术人员在没有做出创造 性劳动前提下所获得的所有其他实施例， 都属于本发明保护的范围。
本发明的目的是提供一种发光二极管恒流驱动电路的开路保护电路，能够 降低成本、 减小均流变压器体积。
为使本发明的上述目的、特征和优点能够更加明显易懂， 下面结合附图和 具体实施方式对本发明作进一步详细的说明。
参照图 3, 为本发明实施例一的发光二极管恒流驱动电路的开路保护电路 图。
如图 3所示， 所述电路包括： 变压器 Tal。
所述变压器 Tal 的原边包括原边绕组和开关 Si。 所述变压器与所述开关
Si组成反激拓朴电路。具体的，所述变压器 Tal的原边绕组的同名端与所述开 关 Si的一端相连， 所述开关 Si的另一端与电源 Vdc的负极相连接， 所述变压 器 Tal原边绕组的异名端与电源 Vdc的正极相连接。
所述变压器 Tal的副边包括： 第一副边绕组 WT1 , 具有两路负载支路， 分别连接负载 A1和负载 A2。 其中， 每路负载支路结构相同。
各负载支路均与第一副边绕组 WT1组成一个整流回路。 具体的： 所述第一负载支路组成的整流回路为： 第一副边绕组 WT1的同名端接第 一二极管 D1的阳极， 所述第一二极管 D1的阴极经第一输出电容 Col接第一 副边绕组 WT1的异名端。 所述第二负载支路组成的整流回路为： 第一副边绕组 WT1的同名端接第 一二极管 D2的阳极， 所述第一二极管 D2的阴极经第一输出电容 Co2接第一 副边绕组 WT1的异名端。
其中， 所述第一输出电容 Col和 Co2分别构成所述第一负载支路和第二 负载支路的输出端。 以第一负载支路为例进行说明， 所述第一输出电容 Col 与第一二极管 D1的阴极的连接端为第一负载支路的正输出端， 所述第一输出 电容 Col的另一端为所述第一负载支路的负输出端。所述负载 A1并联接在所 述第一输出电容 Col两端。
如图 3所示， 为了实现该恒流驱动电路的多路负载均流， 所述变压器 Tal 的副边还包括第一均流变压器 Tl。所述第一均流变压器 T1包括第一均流绕组 W1和第二均流绕组 W2, 分别串联在所述第一负载支路和所述第二负载支路 中。
本发明实施例一中， 对于各负载支路， 所述第一均流变压器 T1的均流绕 组分别串联在所述第一副边绕组 WT1 的异名端与各负载支路的负输出端之 间。 具体的：
对于第一负载支路，所述第一均流绕组 W1的同名端接所述第一副边绕组 WT1 的异名端， 所述第一均流绕组 W1 的异名端接所述第一负载支路的负输 出端。
对于第二负载支路，所述第二均流绕组 W2的异名端接所述第一副边绕组 WT1 的异名端， 所述第二均流绕组 W2的同名端接所述第二负载支路的负输 出端。
本发明实施例中， 所述第一副边绕组 WT1具有抽头端。 如图 3所示， 所 述抽头端将第一副边绕组 WT1划分为第一副边子绕组 WT11和第二副边子绕 组 WT12。 所述第一副边子绕组 WT11 的异名端即为所述第二副边子绕组 WT12的同名端；所述第一副边子绕组 WT11与所述第二副边子绕组 WT12公 共端即为第一副边绕组 WT1的抽头端。
如图 3所示， 为各负载支路分别增加一开路保护模块 10, 所述开路保护 模块 10分别接在第一副边绕组 WT1的抽头端与各负载支路的负输出端之间。
以第一负载支路为例进行说明。 在第一副边绕组 WT1的抽头端与第一负 载支路的负输出端之间并联开路保护模块 10。 所述开路保护模块 10包括： 检 测控制单元 101和处理单元 102。
所述检测控制单元 101 用于检测所述第一负载支路的输出电压或与所述 输出电压成比例的电压，当所述第一负载支路的输出电压或与所述输出电压成 比例的电压不低于相应的预设阈值时， 输出控制信号至所述处理单元 102。
所述处理单元 102并联接在所述第一副边绕组 WT1的抽头端与第一负载 支路的负输出端之间 （也即为第一均流变压器 T1的第一均流绕组 W1未连接 第一副边绕组 WT1的一端 ),如图 3可知，所述处理单元 102即为并联接在第 二副边子绕组 WT12和第一均流绕组 W1之间。所述处理单元 102用于当接收 到所述控制信号时， 将第二副边子绕组 WT12和第一均流绕组 W1短路。
同样， 对于第二负载支路， 在第一副边绕组 WT1的抽头端与第二负载支 路的负输出端之间并联开路保护模块 10。 所述开路保护模块 10包括： 检测控 制单元 101和处理单元 102。
所述检测控制单元 101 用于检测所述第二负载支路的输出电压或与所述 输出电压成比例的电压，当所述第二负载支路的输出电压或与所述输出电压成 比例的电压不低于相应的预设阈值时， 输出控制信号至所述处理单元 102。
所述处理单元 102并联接在所述第一副边绕组 WT1的抽头端与第二负载 支路的负输出端 （也即为第一均流变压器 T1的第二均流绕组 W2未连接第一 副边绕组 WT1的一端）之间， 如图 3可知， 所述处理单元 102即为并联接在 第二副边子绕组 WT12和第二均流绕组 W2之间。所述处理单元 102用于当接 收到所述控制信号时， 将第二副边子绕组 WT12和第二均流绕组 W2短路。
本实施例中，以第一负载支路为例， 当负载 A1开路时，检测控制单元 101 检测到第一负载支路的输出电压或与所述输出电压成比例的电压不低于相应 的预设阈值时， 输出一控制信号至处理单元 102, 使得所述处理单元 102将所 述第二副边子绕组 WT12和所述第一均流变压器 T1的均流绕组 W1短路。 本 实施例所述电路没有直接短路第一输出电容 Col ,使得所以处理单元 102承受 的沖击电流较小， 由此降 了处理单元 102中相关元件的电流应力。 因此， 本 实施例中所述处理单元 102可以选取电流应力较小的相关元件，降低了开路保 护的成本。 同时， 由于本实施例中， 当某路负载支路开路时， 该路负载支路中并联的 开路保护模块仅仅短路所述副边绕组的一个副边子绕组和与其串联的所述均 流变压器的均流绕组， 因而当所述开路保护模块的处理单元短路时， 该负载支 路中串联的均流变压器的均流绕组承受的电压小于该负载支路输出电压的 1/2, 所以可以减小均流变压器的体积。
参照图 4, 为本发明实施例二的发光二极管恒流驱动电路的开路保护电路 图。 图 4为图 3所示电路中处理单元的一种具体实现方式图。 当然， 在本发明 其他实施例中， 所述处理单元还可以采用其他的实施方式实现。
具体的， 以第一负载支路为例进行说明。 如图 4所示， 所述处理单元 102 可以包括： 第二二极管 Dll、 第一电容 Cl、 开关器件 Sl。 其中， 所述第二二 极管 D11的阳极接所述第一副边绕组 WT1的抽头端，所述第二二极管 D11的 阴极接所述开关器件 S1的第一端；所述开关器件 S1的第二端接所述第一负载 支路的负输出端， 所述开关器件 S1的控制端接所述检测控制单元 101的控制 信号输出端； 所述第一电容 C1并联接在所述开关器件 S1的第一端和第二端 之间。 其中， 所述第一电容 C1起滤波作用。
当所述检测控制单元 101检测到负载支路的负载正常工作时，控制处理单 元 102中的开关器件 S1为开路或高阻抗状态； 当所述检测控制单元 101检测 到负载开路或过压时（具体为负载支路的输出电压或与所述输出电压成比例的 电压不低于相应的预设阈值） 时， 控制所述处理单元 102中的开关器件 S1导 通或为低阻抗状态，从而使得变压器 Tal的第一副边子绕组 WT11和均流变压 器 T1的均流绕组所在支路处于低阻抗。
本发明实施例中，所述检测控制单元 101可以用于检测各负载支路的输出 电压，也可以用于检测与各负载支路输出电压成比例的电压。 下面分别进行阐 述。
参照图 5, 为本发明实施例三的发光二极管恒流驱动电路的开路保护电路 图。 图 5为图 4所示开路保护电路的检测控制单元的一种具体实现方式图。 图 5中， 所述检测控制单元 101检测各负载支路的输出电压。 当然， 在本发明其 他实施例中， 所述检测控制单元还可以采用其他的实施方式实现。
图 5所示的开路保护电路中， 仍以第一负载支路为例进行说明。对于所述 开路保护模块 10, 所述检测控制单元 101 包括： 稳压二极管 ZD1、 第一电阻 Rll、 第二电阻 R12、 第一滤波电容 Cpl; 所述处理单元 102与图 3所示的区 别在于： 所述开关器件 S1具体为晶闸管 Sll。
需要说明的是， 本发明实施例三中， 所述检测控制电路 101用于检测各负 载支路的输出电压是否超过预设的阈值。 因此， 对应的， 所述检测控制电路 101接在各负载支路的正输出端和负输出端之间。
具体的， 所述稳压二极管 ZD1 的阴极接所述第一负载支路的正输出端， 其阳极经第一电阻 R11和第二电阻 R12接所述第一负载支路的负输出端， 所 述第一滤波电容 Cpl并联在第二电阻 R12两端。
所述晶闸管 S11 的门极为所述处理单元 102的控制端， 接第一电阻 R11 和第二电阻 R12的公共端， 所述晶闸管 S11的阳极接所述第二二极管 D11的 阴极， 所述第二二极管 D11的阳极接所述第一副边绕组 WT1的抽头端， 所述 晶闸管 S 11的阴极接所述第一负载支路的负输出端， 所述第一电容 C1并联接 在所述开关器件（即为晶闸管 S11 ) 的第一端和第二端之间。
本实施例中， 以第一负载支路为例， 当负载 A1开路， 所述第一负载支路 的输出电压不低于稳压二极管 ZD1的稳压值时， 稳压二极管 ZD1导通。 稳压 二极管 ZD1导通后， 经过第一电阻 R11的限流和第二电阻 R12、 第一滤波电 容 Cpl的滤波后， 输出控制电流给晶闸管 S11的门极。 当所述控制电流不低 于晶闸管 S11 的门槛值时， 晶闸管 S11导通， 进而将第二副边子绕组 WT12 和第一均流绕组 W1 所在的支路短路。 所述电路没有直接短路第一输出电容 Col ,所以处理单元 102承受的沖击电流较小，降低了晶闸管 S11的电流应力， 故本实施例中处理单元 102可以选取电流应力较小的晶闸管，降低了开路保护 的成本。
同时， 由于本实施例中， 当某路负载支路开路时， 该路负载支路包括的开 路保护模块仅仅短路副边绕组的一个副边子绕组和与其串联的均流变压器的 均流绕组， 因而当开路保护模块的处理单元短路时， 均流变压器的均流绕组承 受的电压小于整个负载支路输出电压的 1/2,故而可以减小均流变压器的体积。
在本发明实施例三中，所述检测控制单元检测的电压为负载支路的输出电 压， 以此直接判断该负载支路的输出电压是否正常。 在实际应用中， 所述检测 控制单元也可以通过检测负载支路中任何与输出电压成比例的电压来间接判 断输出电压是否正常， 以确定是否需要对该负载支路进行开路保护。
本发明实施例一至三中， 变压器 Tal的副边均只包括一个副边绕组， 在实 际应用中， 所述变压器 Tal的副边还可以包括多个副边绕组， 此时， 本发明实 施例提供的开路保护模块仍然适用。参照图 6所示， 为本发明实施例四的发光 二极管恒流驱动电路的开路保护电路图。 本发明实施例四中， 以变压器 Tal具 有两个副边绕组为例进行说明。
图 6所示实施例四的恒流驱动电路的开路保护电路与图 3所示实施例一的 电路的区别在于： 变压器 Tal包括两个副边绕组： 第一副边绕组 WT1和第二 副边绕组 WT2; 所述电路包括两路负载支路， 其中， 第一负载支路连接在第 一副边绕组 WT1上，第二负载支路连接在第二副边绕组 WT2上。各负载支路 与副边绕组的连接方式与实施例一相同。
如图 6所示， 第一均流变压器 T1的均流绕组分别串联在各副边绕组的异 名端与各负载支路的负输出端之间。 具体的，
对于第一负载支路，所述第一均流绕组 W1的同名端接所述第一副边绕组
WT1 的异名端， 所述第一均流绕组 W1 的异名端接所述第一负载支路的负输 出端。
对于第二负载支路，所述第二均流绕组 W2的异名端接所述第二副边绕组 WT2的异名端， 所述第二均流绕组 W2的同名端接所述第二负载支路的负输 出端。
本发明实施例中，所述第一副边绕组 WT1和第二副边绕组 WT2均具有抽 头端。 如图 6所示， 所述第一副边绕组 WT1 的抽头端将第一副边绕组 WT1 划分为第一副边子绕组 WT11 和第二副边子绕组 WT12; 所述第二副边绕组 WT2的抽头端将第二副边绕组 WT2划分为第一副边子绕组 WT21和第二副边 子绕组 WT22。
如图 6所示， 为各负载支路分别增加一开路保护模块 20, 所述开路保护 模块 20分别接在各副边绕组的抽头端与该副边绕组所在的负载支路的负输出 端之间。其中，所述开路保护模块 20包括：检测控制单元 201和处理单元 202。
所述检测控制单元 201 用于当检测到各负载支路的输出电压或与所述输 出电压成比例的电压不低于相应的预设阈值时，输出控制信号至所述处理单元 202。
所述处理单元 202用于接收到所述控制信号后，将与所述副边绕组的一个 副边子绕组和与其串联的均流变压器的均流绕组短路。
在实际应用中， 对于所述变压器 Tal的副边包括多个副边绕组的情况， 当 所述均流变压器的均流绕组串联在各副边绕组的异名端和该副边绕组对应的 负载支路的负输出端时， 前述实施例所述的开路保护模块同样适用。
参照图 7所示，为本发明实施例五的发光二极管恒流驱动电路的开路保护 电路图。本实施例五的恒流驱动电路的开路保护电路与图 6所示实施例四的电 路的区别在于： 所述电路包括三个副边绕组 WT1至 WT3, 各副边绕组分别连 接一路负载支路。
此时， 该电路需要两个均流变压器 T1和 T2, 用于依次连接相邻的两个副 边绕组的负载支路。 如图 7所示， 第一均流变压器 T1连接第一副边绕组 WT1 的第一负载支路和第二副边绕组 WT2 的第二负载支路； 第二均流变压器 T2 连接第二副边绕组 WT2的第二负载支路和第三副边绕组 WT3的第三负载支 路； 依次类推。
现以具有代表性的第二负载支路为例进行说明。
其中， 对于第二副边绕组 WT2 的第二负载支路， 在第二副边绕组 WT2 的异名端和其所在的第二负载支路的负输出端之间依次串联有第一均流变压 器 T1的第二均流绕组 W2、 第二均流变压器 T2的第一均流绕组 W3。
其中， 所述第二副边绕组 WT2的异名端接第一均流变压器 T1的第二均 流绕组 W2的异名端； 第一均流变压器 T1的第二均流绕组 W2的同名端接第 二均流变压器 T2的第一均流绕组 W3的同名端， 所述第一均流绕组 W3的异 名端接第二负载支路的负输出端。
此时， 对于各负载支路， 分别连接开路保护模块 30。 其连接方式和工作 原理与前面各实施例所述相同， 在此不再赘述。
需要说明的是， 当负载支路为多路时， 在一个负载支路中可能串联两个不 同均流变压器的绕组，对应负载支路中的与副边子绕组串联的均流变压器绕组 有两个， 则对应的处理单元接收到所述控制信号后，将该一个副边子绕组和与 其串联的两个均流绕组短路。
在本发明其他实施例中， 当变压器 Tal的副边包括 N个副边绕组时， 则 需要 N-1个均流变压器，用于依次连接相邻的两个副边绕组的负载支路。本发 明实施例所述开路保护电路对于 N个副边绕组的情况同样适用， 在此不再赘 述。
当然， 在实际应用中， 还存在一个副边绕组， 连接 N路负载支路的情况， 此时也需要 N-1个均流变压器，用于依次连接该副边绕组的相邻的两个负载支 路。
参照图 8所示，为本发明实施例六的发光二极管恒流驱动电路的开路保护 电路图。 本发明实施例六中， 以第一副边绕组 WT1连接三路负载支路为例进 行说明。
此时， 该电路需要两个均流变压器 T1和 T2, 用于依次连接第一副边绕组 WT1的相邻两个负载支路。 如图 8所示， 第一均流变压器 T1连接第一负载支 路和第二负载支路； 第二均流变压器 T2连接第二负载支路和第三负载支路。
现以具有代表性的第二负载支路为例进行说明。
其中， 对于第二负载支路， 在第一副边绕组 WT1的异名端和第二负载支 路的负输出端之间依次串联有第一均流变压器 T1的第二均流绕组 W2、 第二 均流变压器 T2的第一均流绕组 W3。
其中， 所述第一副边绕组 WT1 的异名端接第一均流变压器 T1的第二均 流绕组 W2的异名端； 第一均流变压器 T1的第二均流绕组 W2的同名端接第 二均流变压器 T2的第一均流绕组 W3的同名端， 所述第一均流绕组 W3的异 名端接第二负载支路的负输出端。
此时， 对于各负载支路， 分别连接开路保护模块 40。 其连接方式和工作 原理与前面各实施例所述相同， 在此不再赘述。
在本发明实施例一至六所述的开路保护电路中，均流变压器的均流绕组均 串联在副边绕组的异名端和各负载支路的负输出端之间。在实际应用中， 所述 均流变压器的均流绕组还可以接在副边绕组的同名端和各负载支路的正输出 端之间。
参照图 9, 为本发明实施例七的发光二极管恒流驱动电路的开路保护电路 图。图 9所示的恒流驱动电路的开路保护电路与图 4所示实施例二的区别在于： 所述第一均流变压器 T1的第一均流绕组 W1和第二均流绕组 W2分别串联在 第一副边绕组 WT1的同名端和各负载支路的正输出端之间。
如图 9所示， 所述变压器 Tal的副边包括： 第一副边绕组 WT1 , 具有两 路负载支路， 分别连接负载 A1和负载 A2。 其中， 每路负载支路结构相同。
所述第一负载支路包括：第一副边绕组 WT1的同名端经第一输出电容 Col 接第一二极管 D1 的阳极， 所述第一二极管 D1 的阴极接第一副边绕组 WT1 的异名端。
所述第二负载支路包括：第一副边绕组 WT1的同名端经第一输出电容 Co2 接第一二极管 D2的阳极， 所述第一二极管 D2的阴极接第一副边绕组 WT1 的异名端。
其中， 所述第一输出电容 Col和 Co2分别构成所述第一负载支路和第二 负载支路的输出端。 以第一负载支路为例进行说明， 所述第一输出电容 Col 与所述第一副边绕组 WT1 的同名端的连接端为所述第一负载支路的正输出 端，所述第一输出电容 Col与第一二极管 D1的阳极的连接端为第一负载支路 的负输出端。 所述负载 A1并联接在所述第一输出电容 Col两端。
如图 9所示， 为了实现该恒流驱动电路的多路负载均流， 所述变压器 Tal 的副边还包括第一均流变压器 Tl。所述第一均流变压器 T1包括第一均流绕组 W1和第二均流绕组 W2, 分别串联在所述第一负载支路和所述第二负载支路 中。
本发明实施例七中， 对于各负载支路， 所述第一均流变压器 T1的均流绕 组分别串联在所述第一副边绕组 WT1 的同名端与各负载支路的正输出端之 间。 具体的：
对于第一负载支路，所述第一均流绕组 W1的同名端接所述第一副边绕组 WT1 的同名端， 所述第一均流绕组 W1 的异名端接所述第一负载支路的正输 出端。
对于第二负载支路，所述第二均流绕组 W2的异名端接所述第一副边绕组 WT1 的同名端， 所述第二均流绕组 W2的同名端接所述第二负载支路的正输 出端。 本发明实施例中， 所述第一副边绕组 WT1具有抽头端。 如图 9所示， 所 述抽头端将第一副边绕组 WT1划分为第一副边子绕组 WT11和第二副边子绕 组 WT12。 所述第一副边子绕组 WT11 的异名端即为所述第二副边子绕组 WT12的同名端；所述第一副边子绕组 WT11与所述第二副边子绕组 WT12公 共端即为第一副边绕组 WT1的抽头端。
如图 9所示， 为各负载支路分别增加一开路保护模块 50, 所述开路保护 模块 50分别接在第一副边绕组 WT1的抽头端与各负载支路的正输出端之间。
以第一负载支路为例进行说明。 在第一副边绕组 WT1的抽头端与第一负 载支路的正输出端之间并联开路保护模块 50。 所述开路保护模块 50包括： 检 测控制单元 501和处理单元 502。
所述检测控制单元 501 用于检测所述第一负载支路的输出电压或与所述 输出电压成比例的电压，当所述第一负载支路的输出电压或与所述输出电压成 比例的电压不低于相应的预设阈值时， 输出控制信号至所述处理单元 502。
所述处理单元 502并联接在所述第一副边绕组 WT1的抽头端与第一负载 支路的正输出端之间，如图 9可知， 所述处理单元 502即为并联接在第一副边 子绕组 WT11和第一均流绕组 W1之间。所述处理单元 502用于当接收到所述 控制信号时， 将第一副边子绕组 WT11和第一均流绕组 W1短路。
同样， 对于第二负载支路， 在第一副边绕组 WT1的抽头端与第二负载支 路的正输出端之间并联开路保护模块 50。 所述开路保护模块 50包括： 检测控 制单元 501和处理单元 502。
所述检测控制单元 501 用于检测所述第二负载支路的输出电压或与所述 输出电压成比例的电压，当所述第二负载支路的输出电压或与所述输出电压成 比例的电压不低于相应的预设阈值时， 输出控制信号至所述处理单元 502。
所述处理单元 502并联接在所述第一副边绕组 WT1的抽头端与第二负载 支路的正输出端之间，如图 9可知， 所述处理单元 502即为并联接在第一副边 子绕组 WT11和第二均流绕组 W2之间。所述处理单元 502用于当接收到所述 控制信号时， 将第一副边子绕组 WT11和第二均流绕组 W2短路。
本实施例中，以第一负载支路为例， 当负载 A1开路时，检测控制单元 501 检测到第一负载支路的输出电压或与所述输出电压成比例的电压不低于相应 的预设阈值时， 输出一控制信号至处理单元 502, 使得所述处理单元 502将第 一副边子绕组 WT11和第二均流绕组 W2短路。本实施例所述电路没有直接短 路第一输出电容 Col , 使得所以处理单元 502承受的沖击电流较小， 由此降低 了处理单元 502中相关元件的电流应力。 因此， 本实施例中所述处理单元 502 可以选取电流应力较小的相关元件， 降低了开路保护的成本。
同时， 由于本实施例中， 当某路负载支路开路时， 该路负载支路中并联的 开路保护模块仅仅短路与均流绕组相连的副边子绕组，因而当所述开路保护模 块的处理单元短路时，该负载支路中串联的均流变压器的均流绕组承受的电压 小于该负载支路输出电压的 1/2, 所以可以减小均流变压器的体积。
需要说明的是， 图 9所示中，给出了处理单元的一种具体实现方式。 当然， 在本发明其他实施例中， 所述处理单元还可以采用其他的实施方式实现。
具体的， 以第一负载支路为例进行说明。 如图 9所示， 所述处理单元 502 可以包括： 第二二极管 Dll、 第一电容 Cl、 开关器件 Sl。 其中， 所述开关器 件 S1的第一端接所述第一负载支路的正输出端，所述开关器件 S1的第二端接 所述第二二极管 D11的阳极， 所述第二二极管 D11的阴极接所述第一副边绕 组 WT1的抽头端；所述开关器件 S1的控制端接所述检测控制单元 501的控制 信号输出端； 所述第一电容 C1并联接在所述开关器件 S1的第一端和第二端 之间。 其中， 所述第一电容 C1起滤波作用。
当所述检测控制单元 501检测到负载支路的负载正常工作时，控制处理单 元 502中的开关器件 S1为开路或高阻抗状态； 当所述检测控制单元 501检测 到负载开路或过压时（具体为负载支路的输出电压或与所述输出电压成比例的 电压不低于相应的预设阈值） 时， 控制所述处理单元 502中的开关器件 S1导 通或为低阻抗状态，从而使得变压器 Tal的第一副边子绕组 WT11和均流变压 器 T1的均流绕组所在支路处于低阻抗。
本发明实施例中，所述检测控制单元 501可以用于检测各负载支路的输出 电压，也可以用于检测与各负载支路输出电压成比例的电压， 与前述实施例相 同， 再次不再赘述。
同样， 当变压器 Tal的副边包括多个副边绕组时， 所述均流变压器的均流 绕组也可以串联在各副边绕组的同名端和对应负载支路的正输出端之间， 此 时， 本发明实施例所述开路保护电路同样适用。 具体参照图 10, 为本发明实 施例八的发光二极管恒流驱动电路的开路保护电路图。本发明实施例八中， 以 变压器 Tal具有两个副边绕组为例进行说明。
变压器 Tal包括两个副边绕组：第一副边绕组 WT1和第二副边绕组 WT2; 所述电路包括两路负载支路， 其中， 第一负载支路连接在第一副边绕组 WT1 上， 第二负载支路连接在第二副边绕组 WT2上。 第一均流变压器 T1的均流 绕组分别串联在各副边绕组的同名端与各负载支路的正输出端之间。各负载支 路与副边绕组的连接方式与实施例七相同。
如图 10所示， 为各负载支路分别增加一开路保护模块 60, 所述开路保护 模块 60的连接关系和工作原理与图 9所示实施例七相同， 不再赘述。
参照图 11所示， 为本发明实施例九的发光二极管恒流驱动电路的开路保 护电路图。 本实施例九的恒流驱动电路的开路保护电路与图 10所示实施例八 的电路的区别在于： 所述电路包括三个副边绕组 WT1至 WT3, 各副边绕组分 别连接一路负载支路。
此时， 该电路需要两个均流变压器 T1和 T2, 用于依次连接相邻的两个副 边绕组的负载支路， 如图 11所示。
此时， 对于各负载支路， 分别连接开路保护模块 70。 其连接方式和工作 原理与前面各实施例所述相同， 在此不再赘述。
在本发明其他实施例中， 当变压器 Tal的副边包括 N个副边绕组时， 则 需要 N-1个均流变压器，用于依次连接相邻的两个副边绕组的负载支路。本发 明实施例所述开路保护电路对于 N个副边绕组的情况同样适用， 在此不再赘 述。
当然， 在实际应用中， 当一个副边绕组连接 N路负载支路的情况， 也需 要 N-1个均流变压器， 用于依次连接该副边绕组的相邻的两个负载支路。
参照图 12所示， 为本发明实施例十的发光二极管恒流驱动电路的开路保 护电路图。 本发明实施例十中， 以第一副边绕组 WT1连接三路负载支路为例 进行说明。
此时， 该电路需要两个均流变压器 T1和 T2, 用于依次连接第一副边绕组 WT1的相邻两个负载支路。 如图 12所示， 第一均流变压器 T1连接第一负载 支路和第二负载支路;第二均流变压器 T2连接第二负载支路和第三负载支路。 此时， 对于各负载支路， 分别连接开路保护模块 80。 其连接方式和工作 原理与前面各实施例所述相同， 在此不再赘述。 以上各实施例中，对带多路负载的恒流驱动电路而言， 各路负载的电流均 衡是通过分别串联均流变压器的原副边绕组来实现的。在实际应用中，还可以 通过将两个均流变压器的副边串联（具体为，各均流变压器的副边绕组首尾相 连） 来实现。 参照图 13 , 为本发明实施例十一的发光二极管恒流驱动电路的 开路保护电路图。
如图 13所示， 所述电路包括： 变压器 Tal。 所述变压器 Tal的原边包括 原边绕组和开关 Si。
所述变压器 Tal的副边包括： 第一副边绕组 WT1 , 具有两路负载支路， 分别连接负载 A1和负载 A2。 其中， 每路负载支路结构相同， 且各负载支路 的电路结构与图 3所示实施例一相同， 在此不再赘述。
如图 13所示，为了实现该恒流驱动电路的多路负载均流，所述变压器 Tal 的副边还包括第一均流变压器 T10和第二均流变压器 T20。
所述第一均流变压器 T10包括原边均流绕组 W11和副边均流绕组 W12; 所述第二均流变压器 Τ20包括原边均流绕组 W21和副边均流绕组 W22。 具体 的， 所述第一均流变压器 T10的原边均流绕组 W11的同名端接所述第一副边 绕组 WT1的异名端，所述第一均流变压器 T10的原边均流绕组 W11的异名端 接第一负载支路的负输出端； 所述第二均流变压器 T20的原边均流绕组 W21 的同名端接所述第一副边绕组 WT1的异名端， 所述第二均流变压器 T20的原 边均流绕组 W21的异名端接第二负载支路的负输出端； 所述第一均流变压器
T10的副边均流绕组 W12的同名端接所述第二均流变压器 T20的副边均流绕 组 W22的异名端，所述第一均流变压器 T10的副边均流绕组 W12的异名端接 所述第二均流变压器 T20的副边均流绕组 W22的同名端。
本发明实施例中， 所述第一副边绕组 WT1具有抽头端。 如图 13所示， 所 述抽头端将第一副边绕组 WT1划分为第一副边子绕组 WT11和第二副边子绕 如图 13所示， 为各负载支路分别增加一开路保护模块 100, 所述开路保 护模块 100分别接在第一副边绕组 WT1的抽头端与各负载支路的负输出端之 间。
以第一负载支路为例进行说明。 在第一副边绕组 WT1的抽头端与第一负 载支路的负输出端之间并联开路保护模块 100。 所述开路保护模块 100包括： 检测控制单元 1001和处理单元 1002。
所述检测控制单元 1001用于检测所述第一负载支路的输出电压或与所述 输出电压成比例的电压，当所述第一负载支路的输出电压或与所述输出电压成 比例的电压不低于相应的预设阈值时， 输出控制信号至所述处理单元 1002。
所述处理单元 1002并联接在所述第一副边绕组 WT1的抽头端与第一负载 支路的负输出端之间，如图 13可知， 所述处理单元 1002即为并联接在第二副 边子绕组 WT12和第一均流变压器 T10的原边均流绕组 W11之间。 所述处理 单元 1002用于当接收到所述控制信号时， 将第二副边子绕组 WT12和第一均 流变压器 T10的原边均流绕组 W11短路。
同样， 对于第二负载支路， 在第一副边绕组 WT1的抽头端与第二负载支 路的负输出端之间并联开路保护模块 100。 所述开路保护模块 100包括： 检测 控制单元 1001和处理单元 1002。
所述检测控制单元 1001用于检测所述第二负载支路的输出电压或与所述 输出电压成比例的电压，当所述第二负载支路的输出电压或与所述输出电压成 比例的电压不低于相应的预设阈值时， 输出控制信号至所述处理单元 1002。
所述处理单元 1002并联接在所述第一副边绕组 WT1的抽头端与第二负载 支路的负输出端之间，如图 13可知， 所述处理单元 1002即为并联接在第二副 边子绕组 WT12和第二均流变压器 T20的原边绕组 W21之间。 所述处理单元 1002用于当接收到所述控制信号时， 将第二副边子绕组 WT12和第二均流变 压器 T20的原边绕组 W21短路。
本实施例中，以第一负载支路为例，当负载 A1开路时，检测控制单元 1001 检测到第一负载支路的输出电压或与所述输出电压成比例的电压不低于相应 的预设阈值时， 输出一控制信号至处理单元 1002, 使得所述处理单元 1002将 将第二副边子绕组 WT12和第一均流变压器 T10的原边均流绕组 W11短路。 本实施例所述电路没有直接短路第一输出电容 Col , 使得所述处理单元 1002 承受的沖击电流较小， 由此降低了处理单元 1002中相关元件的电流应力。 因 此， 本实施例中所述处理单元 1002可以选取电流应力较小的相关元件， 降低 了开路保护的成本。
同时， 由于本实施例中， 当某路负载支路开路时， 该路负载支路中并联的 开路保护模块仅仅短路与均流变压器的原边均流绕组相连的副边子绕组，因而 当所述开路保护模块的处理单元短路时，该负载支路中串联的均流变压器的原 边均流绕组承受的电压小于该负载支路输出电压的 1/2, 所以可以减小均流变 压器的体积。
需要说明的是， 图 13所示电路中给出了处理单元的一种具体实现方式。 当然，在本发明其他实施例中，所述处理单元还可以采用其他的实施方式实现。
具体的，以第一负载支路为例进行说明。如图 13所示，所述处理单元 1002 可以包括： 第二二极管 Dll、 第一电容 Cl、 开关器件 Sl。 其中， 所述第二二 极管 D11的阳极接所述第一副边绕组 WT1的抽头端，所述第二二极管 D11的 阴极接所述开关器件 S1的第一端；所述开关器件 S1的第二端接所述第一负载 支路的负输出端，所述开关器件 S1的控制端接所述检测控制单元 1001的控制 信号输出端； 所述第一电容 C1并联接在所述开关器件 S1的第一端和第二端 之间。 其中， 所述第一电容 C1起滤波作用。
当所述检测控制单元 1001检测到负载支路的负载正常工作时， 控制处理 单元 1002中的开关器件 S1为开路或高阻抗状态； 当所述检测控制单元 1001 检测到负载开路或过压时（具体为负载支路的输出电压或与所述输出电压成比 例的电压不低于相应的预设阈值） 时， 控制所述处理单元 1002中的开关器件 S1导通或为低阻抗状态， 从而使得变压器 Tal的第二副边子绕组 WT12和第 一均流变压器 T10的原边均流绕组 W11所在支路处于低阻抗。
本发明实施例中， 所述检测控制单元 1001可以用于检测各负载支路的输 出电压，也可以用于检测与各负载支路输出电压成比例的电压。 下面仅以第一 种情况为例进行阐述。
参照图 14, 为本发明实施例十二的发光二极管恒流驱动电路的开路保护 电路图。图 14为图 13所示开路保护电路的检测控制单元的一种具体实现方式 图。 图 14中， 所述检测控制单元检测各负载支路的输出电压。 当然， 在本发 明其他实施例中， 所述检测控制单元还可以采用其他的实施方式实现。
图 14所示的开路保护电路中， 仍以第一负载支路为例进行说明。 对于所 述开路保护模块 100, 所述检测控制单元 1001 包括： 稳压二极管 ZD1、 第一 电阻 Rll、 第二电阻 R12、 第一滤波电容 Cpl; 所述处理单元 1002与图 14所 示的区别在于： 所述开关器件 S1具体为晶闸管 Sll。
需要说明的是， 本发明实施例十二中， 所述检测控制电路 1001用于检测 各负载支路的输出电压是否超过预设的阈值。 因此， 对应的， 所述检测控制电 路 1001接在各负载支路的正输出端和负输出端之间。
具体的， 所述稳压二极管 ZD1 的阴极接所述第一负载支路的正输出端， 其阳极经第一电阻 R11和第二电阻 R12接所述第一负载支路的负输出端， 所 述第一滤波电容 Cpl并联在第二电阻 R12两端。
所述晶闸管 S11的门极为所述处理单元 1002的控制端， 接第一电阻 R11 和第二电阻 R12的公共端， 所述晶闸管 S11的阳极接所述第二二极管 D11的 阴极， 所述第二二极管 D11的阳极接所述第一副边绕组 WT1的抽头端， 所述 晶闸管 S 11的阴极接所述第一负载支路的负输出端， 所述第一电容 C1并联接 在所述开关器件的第一端和第二端之间。
在实际应用中，所述检测控制单元也可以通过检测负载支路中任何与输出 电压成比例的电压来间接判断输出电压是否正常，以确定是否需要对该负载支 路进行开路保护。 其具体实现方式较多， 在此不再赘述。
本发明实施例十一至十二中， 变压器 Tal的副边均只包括一个副边绕组， 在实际应用中， 所述变压器 Tal的副边还可以包括多个副边绕组， 此时， 本发 明实施例提供的开路保护模块仍然适用。 参照图 15所示， 为本发明实施例十 三的发光二极管恒流驱动电路的开路保护电路图。本发明实施例十三中， 以变 压器 Tal具有两个副边绕组为例进行说明。
图 15所示实施例十三的恒流驱动电路的开路保护电路与图 13所示实施例 十一的电路的区别在于： 变压器 Tal 包括两个副边绕组： 第一副边绕组 WT1 和第二副边绕组 WT2; 所述电路包括两路负载支路， 其中， 第一负载支路连 接在第一副边绕组 WT1上，第二负载支路连接在第二副边绕组 WT2上。各负 载支路与副边绕组的连接方式与实施例十一相同。
如图 15所示， 均流变压器的原边均流绕组分别串联在各副边绕组的异名 端与各负载支路的负输出端之间。 具体的，
对于第一负载支路， 所述第一均流变压器 T10的原边均流绕组 W11的同 名端接所述第一副边绕组 WT1的异名端， 所述第一均流变压器 T10的原边均 流绕组 W11的异名端接所述第一负载支路的负输出端。
对于第二负载支路， 所述第二均流绕组变压器 T20的原边均流绕组 W21 的同名端接所述第二副边绕组 WT2的异名端， 所述第二均流绕组变压器 T20 的原边均流绕组 W21的异名端接所述第二负载支路的负输出端。
本发明实施例中，所述第一副边绕组 WT1和第二副边绕组 WT2均具有抽 头端。
如图 15所示， 为各负载支路分别增加一开路保护模块 200, 所述开路保 护模块 200 分别接在各副边绕组的抽头端与该副边绕组所在的负载支路的负 输出端之间。 其中， 所述开路保护模块 200包括： 检测控制单元 2001和处理 单元 2002。
所述检测控制单元 2001用于当检测到各负载支路的输出电压或与所述输 出电压成比例的电压不低于相应的预设阈值时，输出控制信号至所述处理单元 2002。
所述处理单元 2002用于接收到所述控制信号后， 将与均流变压器的原边 均流绕组相连的副边子绕组所在的支路短路。
在实际应用中， 对于所述变压器 Tal的副边包括多个副边绕组的情况， 当 各均流变压器的原边均流绕组串联在各副边绕组的异名端和该副边绕组对应 的负载支路的负输出端时， 前述实施例所述的开路保护模块同样适用。
参照图 16所示， 为本发明实施例十四的发光二极管恒流驱动电路的开路 保护电路图。 本实施例十四的恒流驱动电路的开路保护电路与图 15所示实施 例十三的电路的区别在于： 所述电路包括三个副边绕组 WT1至 WT3, 各副边 绕组分别连接一路负载支路。
此时， 该电路需要三个均流变压器 T10、 Τ20和 Τ30, 用于依次连接相邻 的两个副边绕组的负载支路。 如图 16所示， 第一均流变压器 T10和第二均流 变压器 T20连接第一副边绕组 WT1的第一负载支路和第二副边绕组 WT2的 第二负载支路； 第二均流变压器 T2和第三均流变压器 T30连接第二副边绕组 WT2的第二负载支路和第三副边绕组 WT3的第三负载支路。
如图 16所示，所述第一均流变压器 T10的原边均流绕组 W11的同名端接 所述第一副边绕组 WT1的异名端， 所述第一均流变压器 T10的原边均流绕组 W11的异名端接第一负载支路的负输出端； 所述第二均流变压器 T20的原边 均流绕组 W21的同名端接所述第二副边绕组 WT2的异名端，所述第二均流变 压器 T20的原边均流绕组 W21的异名端接第二负载支路的负输出端； 所述第 三均流变压器 T30的原边均流绕组 W31 的同名端接所述第三副边绕组 WT3 的异名端， 所述第三均流变压器 T30的原边均流绕组 W31的异名端接第二负 载支路的负输出端。
所述第一均流变压器 T10的副边均流绕组 W12的同名端接所述第二均流 变压器 T20的副边均流绕组 W22的异名端， 所述第二均流变压器 T20的副边 均流绕组 W22的同名端接所述第三均流变压器 T30的副边均流绕组 W32的异 名端， 所述第三均流变压器 T30的副边均流绕组 W32的同名端接所述第一均 流变压器 T10的副边均流绕组 W12的异名端。
此时， 对于各负载支路， 分别连接开路保护模块 300。 其连接方式和工作 原理与前面各实施例所述相同， 在此不再赘述。
在本发明其他实施例中， 当变压器 Tal的副边包括 N个副边绕组时， 则 需要 N个均流变压器， 用于依次连接相邻的两个副边绕组的负载支路。 本发 明实施例所述开路保护电路对于 N个副边绕组的情况同样适用， 在此不再赘 述。
当然， 在实际应用中， 还存在一个副边绕组， 连接 N路负载支路的情况， 此时也需要 N个均流变压器， 用于依次连接该副边绕组的相邻的两个负载支 路。
参照图 17所示， 为本发明实施例十五的发光二极管恒流驱动电路的开路 保护电路图。 本发明实施例十五中， 以第一副边绕组 WT1连接三路负载支路 为例进行说明。
此时， 该电路需要三个均流变压器 T10、 Τ20和 Τ30, 用于依次连接第一 副边绕组 WT1的相邻两个负载支路。
此时， 对于各负载支路， 分别连接开路保护模块 400。 其连接方式和工作 原理与前面各实施例所述相同， 在此不再赘述。
在本发明实施例十一至十五所述的开路保护电路中，各均流变压器的原边 均流绕组均串联在副边绕组的异名端和各负载支路的负输出端之间。在实际应 用中，所述均流变压器的原边均流绕组还可以接在副边绕组的同名端和各负载 支路的正输出端之间。
参照图 18, 为本发明实施例十六的发光二极管恒流驱动电路的开路保护 电路图。图 18所示的恒流驱动电路的开路保护电路与图 13所示实施例十一的 区别在于：各均流变压器的原边均流绕组分别串联在第一副边绕组的同名端和 各负载支路的正输出端之间。
如图 18所示， 所述变压器 Tal的副边包括： 第一副边绕组 WT1 , 具有两 路负载支路， 分别连接负载 A1和负载 A2。 其中， 每路负载支路结构相同。
所述第一负载支路包括：第一副边绕组 WT1的同名端经第一输出电容 Col 接第一二极管 D1 的阳极， 所述第一二极管 D1 的阴极接第一副边绕组 WT1 的异名端。
所述第二负载支路包括：第一副边绕组 WT1的同名端经第一输出电容 Co2 接第一二极管 D2的阳极， 所述第一二极管 D2 的阴极接第一副边绕组 WT1 的异名端。
其中， 所述第一输出电容 Col和 Co2分别构成所述第一负载支路和第二 负载支路的输出端。 以第一负载支路为例进行说明， 所述第一输出电容 Col 与所述第一副边绕组 WT1 的同名端的连接端为所述第一负载支路的正输出 端，所述第一输出电容 Col与第一二极管 D1的阳极的连接端为第一负载支路 的负输出端。 所述负载 A1并联接在所述第一输出电容 Col两端。
如图 18所示，为了实现该恒流驱动电路的多路负载均流，所述变压器 Tal 的副边还包括第一均流变压器 T10和第二均流变压器 T20。
所述第一均流变压器 T10的原边均流绕组 W11的同名端接所述第一副边 绕组 WT1的同名端，所述第一均流变压器 T10的原边均流绕组 W11的异名端 接第一负载支路的正输出端； 所述第二均流变压器 Τ20的原边均流绕组 W21 的同名端接所述第一副边绕组 WT1的同名端， 所述第一均流变压器 T20的原 边均流绕组 W21的异名端接第二负载支路的正输出端； 所述第一均流变压器 T10 的副边均流绕组 W12 的同名端接第二均流变压器 T20 的副边均流绕组 W22的异名端， 所述第一均流变压器 T10的副边均流绕组 W12的异名端接第 二均流变压器 T20的副边均流绕组 W22的同名端。
本发明实施例中， 所述第一副边绕组 WT1具有抽头端， 将所述第一副边 绕组 WT1划分为第一副边子绕组 WT11和第二副边子绕组 WT12。
如图 18所示， 为各负载支路分别增加一开路保护模块 500, 所述开路保 护模块 500分别接在第一副边绕组 WT1的抽头端与各负载支路的正输出端之 间。
以第一负载支路为例进行说明。 在第一副边绕组 WT1的抽头端与第一负 载支路的正输出端之间并联开路保护模块 500。 所述开路保护模块 500包括： 检测控制单元 5001和处理单元 5002。
所述检测控制单元 5001用于检测所述第一负载支路的输出电压或与所述 输出电压成比例的电压，当所述第一负载支路的输出电压或与所述输出电压成 比例的电压不低于相应的预设阈值时， 输出控制信号至所述处理单元 5002。
所述处理单元 5002并联接在所述第一副边绕组 WT1的抽头端与第一负载 支路的正输出端之间，如图 18可知， 所述处理单元 5002即为并联接在第一副 边子绕组 WT11和第一均流变压器的原边绕组 W11之间。 所述处理单元 5002 用于当接收到所述控制信号时，将第一副边子绕组 WT11和第一均流变压器的 原边绕组 W11短路。
同样， 对于第二负载支路， 在第一副边绕组 WT1的抽头端与第二负载支 路的正输出端之间并联开路保护模块 500。 所述开路保护模块 500包括： 检测 控制单元 5001和处理单元 5002。
所述检测控制单元 5001用于检测所述第二负载支路的输出电压或与所述 输出电压成比例的电压，当所述第二负载支路的输出电压或与所述输出电压成 比例的电压不低于相应的预设阈值时， 输出控制信号至所述处理单元 5002。
所述处理单元 5002并联接在所述第一副边绕组 WT1的抽头端与第二负载 支路的正输出端之间，如图 18可知， 所述处理单元 5002即为并联接在第一副 边子绕组 WT11和第二均流变压器的原边绕组 W21之间。 所述处理单元 5002 用于当接收到所述控制信号时，将第一副边子绕组 WT11和第二均流变压器的 原边绕组 W21短路。
需要说明的是， 图 18所示中， 给出了处理单元的一种具体实现方式。 当 然， 在本发明其他实施例中， 所述处理单元还可以采用其他的实施方式实现。
具体的，以第一负载支路为例进行说明。如图 18所示，所述处理单元 5002 可以包括： 第二二极管 Dll、 第一电容 Cl、 开关器件 Sl。 其中， 所述开关器 件 S1的第一端接所述第一负载支路的正输出端，所述开关器件 S1的第二端接 所述第二二极管 D11的阳极， 所述第二二极管 D11的阴极接所述第一副边绕 组 WT1的抽头端； 所述开关器件 S1的控制端接所述检测控制单元 5001的控 制信号输出端； 所述第一电容 C1并联接在所述开关器件 S1的第一端和第二 端之间。 其中， 所述第一电容 C1起滤波作用。
本发明实施例中， 所述检测控制单元 5001可以用于检测各负载支路的输 出电压，也可以用于检测与各负载支路输出电压成比例的电压， 与前述实施例 相同， 在此不再赘述。
同样， 当变压器 Tal的副边包括多个副边绕组时， 所述均流变压器的均流 绕组也可以串联在各副边绕组的异名端和各负载支路的负输出端之间， 此时， 本发明实施例所述开路保护电路同样适用。 具体参照图 19, 为本发明实施例 十七的发光二极管恒流驱动电路的开路保护电路图。本发明实施例十七中， 以 变压器 Tal具有两个副边绕组为例进行说明。
变压器 Tal包括两个副边绕组：第一副边绕组 WT1和第二副边绕组 WT2; 所述电路包括两路负载支路， 其中， 第一负载支路连接在第一副边绕组 WT1 上， 第二负载支路连接在第二副边绕组 WT2上。 第一均流变压器 T1的均流 绕组分别串联在各副边绕组的同名端与各负载支路的正输出端之间。各负载支 路与副边绕组的连接方式与实施例十六相同。
如图 19所示， 为各负载支路分别增加一开路保护模块 600, 所述开路保 护模块 600的连接关系和工作原理与图 18所示实施例十六相同， 不再赘述。
在本发明其他实施例中， 当变压器 Tal的副边包括 N个副边绕组或一个 副边绕组连接 N条负载支路时， 对于均流变压器的原边绕组串联在副边绕组 的同名端和各负载支路的正输出端之间的情况，本发明实施例提供的开路保护 电路同样适用， 其电路结构和工作原理与前述实施例相同， 在此不再赘述。
以上对本发明所提供的一种发光二极管恒流驱动电路的开路保护电路，进 述， 以上实施例的说明只是用于帮助理解本发明的方法及其核心思想； 同时， 对于本领域的一般技术人员，依据本发明的思想，在具体实施方式及应用范围 上均会有改变之处。 综上所述， 本说明书内容不应理解为对本发明的限制。

Claims

权 利 要 求
1、 一种发光二极管恒流驱动电路的开路保护电路， 其特征在于， 所述电 路包括： 变压器，所述变压器具有至少一个副边绕组，连接至少两路负载支路； 各负载支路结构相同；
每个负载支路与一个副边绕组组成一个整流回路；所述副边绕组具有抽头 端， 将所述副边绕组划分为两个副边子绕组；
所述电路还包括： 设置在相邻的两路负载支路内的均流变压器；
为各负载支路分别连接一开路保护模块，所述开路保护模块包括检测控制 单元和处理单元：
所述检测控制单元用于当检测到各负载支路的输出电压或与所述输出电 压成比例的电压不低于相应的预设阈值时， 输出控制信号至所述处理单元； 所述处理单元用于接收到所述控制信号后，将对应负载支路中的一个副边 子绕组和与其串联的均流变压器的均流绕组短路。
2、 根据权利要求 1所述的发光二极管恒流驱动电路的开路保护电路， 其 特征在于， 所述负载支路包括：
副边绕组的同名端接第一二极管的阳极，所述第一二极管的阴极经第一输 出电容接所述副边绕组的异名端；
所述第一输出电容与所述第一二极管的阴极的连接端为所述负载支路的 正输出端， 所述第一输出电容的另一端为所述负载支路的负输出端；
在所述副边绕组的异名端和所述副边绕组所在负载支路的负输出端之间 串联有本负载支路与相邻负载支路中设置的均流变压器的一个绕组。
3、 根据权利要求 2所述的发光二极管恒流驱动电路的开路保护电路， 其 特征在于， 所述处理单元包括第二二极管、 第一电容、 开关器件； 其中，
所述第二二极管的阳极接所述副边绕组的抽头端 ,所述第二二极管的阴极 接所述开关器件的第一端； 所述开关器件的第二端接所述负载支路的负输出 端， 所述开关器件的控制端接所述检测控制单元的控制信号输出端；
所述第一电容并联接在所述开关器件的第一端和第二端之间。
4、 根据权利要求 3所述的发光二极管恒流驱动电路的开路保护电路， 其 特征在于， 所述检测控制单元包括： 稳压二极管、 第一电阻、 第二电阻、 第一 滤波电容；
所述开关器件具体为晶闸管， 所述晶闸管的阳极为所述开关器件的第一 端， 所述晶闸管的阴极为所述开关器件的第二端；
所述稳压二极管的阴极接所述负载支路的正输出端，所述稳压二极管的阳 极经所述第一电阻和第二电阻接所述负载支路的负输出端，所述第一滤波电容 并联在第二电阻两端。
5、 根据权利要求 1所述的发光二极管恒流驱动电路的开路保护电路， 其 特征在于， 所述负载支路包括：
副边绕组的同名端经第一输出电容接第一二极管的阳极，所述第一二极管 的阴极接所述副边绕组的异名端；
所述第一输出电容与所述副边绕组的同名端的连接端为所述负载支路的 正输出端，所述第一输出电容与第一二极管的阳极的连接端为所述负载支路的 负输出端；
在所述副边绕组的同名端和所述副边绕组所在负载支路的正输出端之间 串联有本负载支路与相邻负载支路中设置的均流变压器的一个绕组。
6、 根据权利要求 5所述的发光二极管恒流驱动电路的开路保护电路， 其 特征在于， 所述处理单元包括第二二极管、 第一电容、 开关器件； 其中，
所述开关器件的第一端接所述负载支路的正输出端，所述开关器件的第二 端接所述第二二极管的阳极， 所述第二二极管的阴极接所述副边绕组的抽头 端； 所述开关器件的控制端接所述检测控制单元的控制信号输出端；
所述第一电容并联接在所述开关器件的第一端和第二端之间。
7、 根据权利要求 1至 6任一项所述的发光二极管恒流驱动电路的开路保 护电路， 其特征在于， 所述变压器的原边包括原边绕组和开关； 所述变压器与 所述开关组成反激拓朴电路；
所述变压器原边绕组的同名端与所述开关的一端相连，所述开关的另一端
8、 一种发光二极管恒流驱动电路的开路保护电路， 其特征在于， 所述电 路包括： 变压器，所述变压器具有至少一个副边绕组，连接至少两路负载支路； 各负载支路结构相同； 每个负载支路与一个副边绕组组成一个整流回路；所述副边绕组具有抽头 端， 将所述副边绕组划分为两个副边子绕组；
所述电路还包括： 串联各负载支路内的均流变压器； 各均流变压器的原边 均流绕组分别与各负载支路对应的副边绕组的一个副边子绕组相连，各均流变 压器的副边均流绕组依次串联；
为各负载支路分别连接一开路保护模块，所述开路保护模块包括检测控制 单元和处理单元：
所述检测控制单元用于当检测到各负载支路的输出电压或与所述输出电 压成比例的电压不低于相应的预设阈值时， 输出控制信号至所述处理单元； 所述处理单元用于接收到所述控制信号后，将所述副边绕组的抽头端和所 述均流变压器的原边均流绕组未连接副边绕组的一端短路。
9、 根据权利要求 8所述的发光二极管恒流驱动电路的开路保护电路， 其 特征在于， 所述负载支路包括：
副边绕组的同名端接第一二极管的阳极，所述第一二极管的阴极经第一输 出电容接所述副边绕组的异名端；
所述第一输出电容与第一二极管的阴极的连接端为所述负载支路的正输 出端， 所述第一输出电容的另一端为所述负载支路的负输出端；
所述均流变压器的原边均流绕组串联接在所述副边绕组的异名端和所述 副边绕组所在负载支路的负输出端之间。
10、根据权利要求 9所述的发光二极管恒流驱动电路的开路保护电路， 其 特征在于， 所述处理单元包括第二二极管、 第一电容、 开关器件； 其中， 所述第二二极管的阳极接所述副边绕组的抽头端 ,所述第二二极管的阴极 接所述开关器件的第一端； 所述开关器件的第二端接所述负载支路的负输出 端， 所述开关器件的控制端接所述检测控制单元的控制信号输出端；
所述第一电容并联接在所述开关器件的第一端和第二端之间。
11、 根据权利要求 10所述的发光二极管恒流驱动电路的开路保护电路， 其特征在于， 所述检测控制单元包括： 稳压二极管、 第一电阻、 第二电阻、 第 一滤波电容；
所述开关器件具体为晶闸管， 所述晶闸管的阳极为所述开关器件的第一 端， 所述晶闸管的阴极为所述开关器件的第二端；
所述稳压二极管的阴极接所述负载支路的正输出端，所述稳压二极管的阳 极经所述第一电阻和第二电阻接所述负载支路的负输出端，所述第一滤波电容 并联在所述第二电阻两端。
12、根据权利要求 8所述的发光二极管恒流驱动电路的开路保护电路， 其 特征在于， 所述负载支路包括：
副边绕组的同名端经第一输出电容接第一二极管的阳极，所述第一二极管 的阴极接所述副边绕组的异名端；
所述第一输出电容与所述副边绕组的同名端的连接端为所述负载支路的 正输出端，所述第一输出电容与第一二极管的阳极的连接端为所述负载支路的 负输出端；
所述均流变压器的均流绕组串联接在所述副边绕组的同名端和所述副边 绕组所在负载支路的正输出端之间。
13、 根据权利要求 12所述的发光二极管恒流驱动电路的开路保护电路， 其特征在于， 所述处理单元包括第二二极管、 第一电容、 开关器件； 其中， 所述开关器件的第一端接负载支路的正输出端，所述开关器件的第二端接 所述第二二极管的阳极， 所述第二二极管的阴极接所述副边绕组的抽头端； 所 述开关器件的控制端接所述检测控制单元的控制信号输出端；
所述第一电容并联接在所述开关器件的第一端和第二端之间。
14、 根据权利要求 8至 13任一项所述的发光二极管恒流驱动电路的开路 保护电路， 其特征在于， 所述变压器的原边包括原边绕组和开关； 所述变压器 与所述开关组成反激拓朴电路；
所述变压器原边绕组的同名端与所述开关的一端相连，所述开关的另一端
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