CN201708990U - Open circuit protection circuit - Google Patents
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- CN201708990U CN201708990U CN2010201941796U CN201020194179U CN201708990U CN 201708990 U CN201708990 U CN 201708990U CN 2010201941796 U CN2010201941796 U CN 2010201941796U CN 201020194179 U CN201020194179 U CN 201020194179U CN 201708990 U CN201708990 U CN 201708990U
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Abstract
The utility model discloses an open circuit protection circuit, which comprises two load branch circuits of a constant current drive circuit, a voltage regulating unit, an open circuit detection unit and a short circuit unit, wherein two connecting terminals of the voltage regulating unit are connected with two same-polarity terminals of the two load branch circuits, and the other same-polarity terminals of the two load branch circuits are equipotential; and the two same-polarity terminals of the two load branch circuits are respectively connected with two input terminals of the open circuit detection unit, and an output terminal of the open circuit detection unit is connected with a control terminal of the short circuit unit. The open circuit protection circuit has low realization cost and wider scope of application.
Description
Technical Field
The utility model relates to a constant current drive technique especially relates to an open circuit protection circuit.
Background
The Light Emitting Diode (LED) constant current driving circuit with multi-path output generally comprises a constant current driving main circuit and at least two load branches, wherein each load branch is connected with at least one LED load in series. Because the load is a plurality of branches, in the constant current driving circuit, load current balance on the plurality of load branches needs to be realized, that is, the total current output by the constant current driving main circuit is distributed to each path of LED load according to the load requirement.
In practical application, to realize load current balancing on load branches of an LED constant current driving circuit, an LED constant current driving circuit structure shown in fig. 1 may be used, and in the driving circuit, load current balancing on every two load branches is correspondingly realized by using a current sharing transformer.
However, in the above LED constant current driving circuit, once an LED load on a certain load branch is opened, an abnormal overvoltage phenomenon occurs in the load branch. If it is ensured that the LED load on a certain load branch is open-circuited, the LED loads on other load branches can still work normally, and an open-circuit protection circuit needs to be additionally added to the load branch.
A conventional open circuit protection circuit in the prior art is shown in fig. 2, and is respectively disposed on each load branch of the LED constant current driving circuit, and each open circuit protection circuit respectively includes a thyristor (a thyristor SCR is shown in the figure) and two resistors (a first resistor R1 and a second resistor R2 are shown in the figure). When overvoltage occurs to a certain load branch, the thyristor corresponding to the load branch is triggered to be conducted, and the load branch is short-circuited, so that normal work of the LED load on other load branches is guaranteed.
However, in the open-circuit protection circuit implemented by the way that the load branch is short-circuited by the thyristor, once an overvoltage phenomenon occurs, the impact current flowing through the thyristor is very large, so that a large-current thyristor needs to be selected in practical application, and the implementation cost of the open-circuit protection circuit is too high; moreover, if the main circuit of the LED constant current driving circuit adopts a BOOST topology structure, since the BOOST type circuits cannot directly perform load branch short circuit connection, the open circuit protection circuit cannot be applied to the LED constant current driving circuit, and the application range is small.
SUMMERY OF THE UTILITY MODEL
In view of this, the present invention provides an open circuit protection circuit, which has a low cost and a wide application range.
Therefore, the embodiment of the utility model provides an adopt following technical scheme:
an embodiment of the utility model provides an open circuit protection circuit, include: two load branches of the constant current driving circuit, a voltage stabilizing unit, an open circuit detection unit and a short circuit unit, wherein,
two connecting ends of the voltage stabilizing unit are connected with two ends of the two load branches with the same polarity, and the other two ends of the two load branches with the same polarity are equipotential; the two ends of the two load branches with the same polarity are also respectively connected with two input ends of the open circuit detection unit; the output end of the open circuit detection unit is connected with the control end of the short circuit unit;
the voltage stabilizing unit is used for: when the voltage difference value between two ends with the same polarity of the two load branches is larger than a preset first difference threshold value, clamping the voltage at the end with the larger voltage value in the two ends with the same polarity of the two load branches at the voltage at the end with the smaller voltage value;
the open circuit detection unit is used for: respectively detecting the voltages of the two input ends, respectively comparing each detected voltage with a preset first reference voltage, and controlling the short-circuit unit to short-circuit the current-sharing transformers corresponding to the two load branches when any detected voltage is greater than the first reference voltage;
and the short-circuit unit is used for short-circuiting the current-sharing transformers corresponding to the two load branches under the control of the open-circuit detection unit.
Wherein the voltage stabilization unit includes: a first voltage regulator tube and a second voltage regulator tube; wherein,
the anode of the first voltage-stabilizing tube and the anode of the second voltage-stabilizing tube are used as two connecting ends of the voltage-stabilizing units; and the cathode of the first voltage-stabilizing tube is connected with the cathode of the second voltage-stabilizing tube.
The open circuit detection unit includes: the circuit comprises a first diode, a second diode, a third resistor, a fourth resistor and a first comparator; wherein,
the anode of the first diode and the anode of the second diode are used as two input ends of the open circuit detection unit; the cathode of the first diode and the cathode of the second diode are grounded through the third resistor and the fourth resistor respectively in sequence; the connection point of the third resistor and the fourth resistor is connected with the anode of the first comparator; the cathode of the first comparator is connected with the preset first reference voltage; the output end of the first comparator is used as the output end of the open circuit detection unit.
The short circuit unit includes: a first short-circuit switch; the control end of the first short-circuit switch is used as the control end of the short-circuit unit; and the first end and the second end of the first short-circuit switch are connected with the two ends of any winding of the current-sharing transformer corresponding to the two load branches.
The short circuit unit includes: the third auxiliary winding and the second short-circuit switch of the current-sharing transformer correspond to the two load branches;
the first end of the third auxiliary winding is connected with the first end of the second short-circuit switch, and the second end of the second short-circuit switch is connected with the second end of the third auxiliary winding; and the control end of the second short-circuit switch is used as the control end of the short-circuit unit.
The embodiment of the utility model provides a still provide another kind of open circuit protection circuit, include: at least three load branches of the constant current driving circuit, a voltage stabilizing unit, an open circuit detection unit and a short circuit unit, wherein,
a pair of load branches of the at least three load branches corresponds to a voltage stabilizing unit, and two connecting ends of the voltage stabilizing unit are connected with two ends of the corresponding pair of load branches with the same polarity; one end of each of the at least three load branches, which is not connected with the voltage stabilizing unit, is equipotential; the open circuit detection unit comprises at least three input ends, and each input end is connected with one end of a load branch circuit connected with the voltage stabilizing unit; the output end of the open circuit detection unit is connected with the control end of the short circuit unit;
the voltage stabilizing unit is used for: when the voltage difference value between two ends with the same polarity of a pair of load branches corresponding to the voltage stabilizing unit is larger than a preset second difference threshold value, clamping the voltage of one end with the larger voltage value in the two ends with the same polarity of the corresponding pair of load branches at the voltage of one end with the smaller voltage value;
the open circuit detection unit is used for respectively detecting the voltages of the at least three input ends, comparing each detected voltage with a preset second reference voltage, and controlling the short circuit unit to short circuit each current-sharing transformer corresponding to the at least three load branches when any detected voltage is greater than the second reference voltage;
and the short-circuit unit is used for short-circuiting each current-sharing transformer corresponding to the at least three load branches under the control of the open-circuit detection unit.
Wherein the voltage stabilization unit includes: a third and a fourth stabilivolt; wherein,
the anode of the third voltage-stabilizing tube and the anode of the fourth voltage-stabilizing tube are used as two connecting ends of the voltage-stabilizing units; and the cathode of the third voltage-stabilizing tube is connected with the cathode of the fourth voltage-stabilizing tube.
The open circuit detection unit includes: at least two diodes, a third resistor, a fourth resistor and a second comparator; wherein,
anodes of the at least two diodes are used as input ends of the open circuit detection units; cathodes of the at least two diodes are grounded through a third resistor and a fourth resistor respectively in sequence; the connection point of the third resistor and the fourth resistor is connected with the anode of the second comparator; the cathode of the second comparator is connected with the preset second reference voltage; and the output end of the second comparator is used as the output end of the open circuit detection unit.
The short circuit unit includes: at least two short-circuit switches; the control end of each short-circuit switch is used as the control end of the short-circuit unit; any winding of each current sharing transformer corresponding to the at least three load branches is connected with one short-circuit switch in parallel.
The short circuit unit includes: the third auxiliary winding of each current-sharing transformer corresponding to the at least three load branches, the diode corresponding to each auxiliary winding and the third short-circuit switch; wherein,
the first end of each third auxiliary winding is connected with the first end of a third short-circuit switch through a diode corresponding to the third auxiliary winding, and the second end of the third short-circuit switch and the second end of each third auxiliary winding are grounded; and the control end of the third short-circuit switch is used as the control end of the short-circuit unit.
The technical effect analysis of the technical scheme is as follows:
the two ends with the same polarity of the two load branches are connected with the two connecting ends of the voltage stabilizing unit, and the other two ends with the same polarity are equipotential, so that when the voltage is increased due to the fact that one load branch is opened, the output voltage of the opened load branch is clamped to the normal output voltage of the other load branch through the voltage stabilizing unit, and the overvoltage problem of the opened load branch is prevented under the condition that the other load branch works normally; when the voltage of the load branch circuits with the open circuit is increased, the increased voltage is detected by the open circuit detection unit, so that the short circuit unit is controlled to short circuit the current equalizing transformers corresponding to the two load branch circuits, overlarge current cannot flow in the voltage stabilizing unit, the voltage stabilizing unit can be realized by selecting devices with smaller current, the realization cost of the voltage stabilizing unit is reduced, and the realization cost of the open circuit protection circuit is further reduced; in addition, the open circuit protection circuit does not perform direct short circuit processing on the load branch, so that the open circuit protection circuit can be also suitable for a constant current driving circuit based on a BOOST topological structure, and has a wider application range compared with the open circuit protection circuit in the prior art.
Drawings
FIG. 1 is a schematic diagram of an implementation structure of a prior art LED constant current driving circuit;
FIG. 2 is a schematic diagram of an open-circuit protection circuit of a prior art LED constant current driving circuit;
fig. 3 is an exemplary diagram of an implementation structure of a first open circuit protection circuit according to an embodiment of the present invention;
fig. 4 is a diagram illustrating another implementation structure of a first open-circuit protection circuit according to an embodiment of the present invention;
fig. 5 is a diagram illustrating a structure of a first open-circuit protection circuit according to an embodiment of the present invention;
fig. 6 is an exemplary diagram of an implementation structure of a second open circuit protection circuit according to the embodiment of the present invention.
Detailed Description
Hereinafter, the implementation of the open circuit protection circuit according to the embodiment of the present invention will be described in detail with reference to the accompanying drawings.
The embodiment of the present invention provides an open-circuit protection circuit, which can be applied not only to the LED constant current driving circuit shown in fig. 1, but also to other LED constant current driving circuits, such as an LED constant current driving circuit based on a BOOST topology structure, as long as the open-circuit protection circuit realizes current balance between two load branches through a constant current driver; furthermore, although the open circuit protection circuit of the present invention is described in the following embodiments with respect to an LED constant current driving circuit, the open circuit protection circuit may be applied to a constant current driving circuit that drives other loads, includes at least two load branches, and achieves current balance between the load branches through a current sharing transformer.
In an embodiment of the open circuit protection circuit of the present invention, the open circuit protection is performed by using two load branches of at least two load branches included in the constant current driving circuit as processing objects. In this embodiment, the utility model discloses an open circuit protection circuit includes: two load branches of the constant current driving circuit, a voltage stabilizing unit, an open circuit detection unit and a short circuit unit, wherein,
two connecting ends of the voltage stabilizing unit are respectively connected with two ends of the two load branches with the same polarity, and the other two ends of the two load branches with the same polarity are equipotential; the two ends of the two load branches with the same polarity are also respectively connected with two input ends of the open circuit detection unit; the output end of the open circuit detection unit is connected with the control end of the short circuit unit;
the voltage stabilizing unit is used for: when the voltage difference value between two ends with the same polarity of the two load branches is larger than a preset first difference threshold value, clamping the voltage at the end with the larger voltage value in the two ends with the same polarity of the two load branches at the voltage at the end with the smaller voltage value;
the open circuit detection unit is used for: respectively detecting the voltages of the two input ends, respectively comparing each detected voltage with a preset first reference voltage, and controlling the short-circuit unit to short-circuit the current-sharing transformers corresponding to the two load branches when any detected voltage is greater than the first reference voltage;
and the short-circuit unit is used for short-circuiting the current-sharing transformers corresponding to the two load branches under the control of the open-circuit detection unit.
Above the embodiment of the utility model provides an open circuit protection circuit realizes that open circuit protection principle does:
because a voltage stabilizing unit is connected between two ends with the same polarity of the two load branches, the other two ends with the same polarity are equipotential, when the voltage difference value between the two ends with the same polarity is not smaller than a preset first difference threshold value, the phenomenon of open circuit and overvoltage of one load branch is indicated, so that the voltage stabilizing circuit clamps the output of the load branch which is open circuit and is in overvoltage to the normal output of the other load branch, and the load branch which is in normal output continues to keep a normal working state; and, the open circuit detection unit detects that one load branch has opened a way simultaneously, at this moment, through controlling the short circuit unit short circuit current sharing transformer, thereby make current sharing transformer no longer balance the electric current of two load branches, thereby not only realized opening a way the protection to the load branch that takes place to open a way the overvoltage phenomenon, kept the normal work of other load branches, still guaranteed that the electric current that flows through in the voltage stabilizing unit is less, reduced the consumption of voltage stabilizing unit, thereby voltage stabilizing unit can select the device that the electric current is less to realize, reduce the realization cost of voltage stabilizing unit, and then reduce the realization cost of open a way protection circuit.
The two connection ends of the voltage stabilizing unit are connected to positive ends of the two load branches and negative ends of the two load branches, which is not limited herein.
In addition, for a specific application scenario of the above embodiment, the constant current driving circuit may be a constant current driving circuit including only two load branches, or may be a constant current driving circuit including more than two load branches, and is not limited here. When the constant current driving circuit including more than two load branches is subjected to open circuit protection of the load branches, the open circuit protection circuit can be arranged only on a certain two load branches designated on the constant current driving circuit, so that the certain two designated load branches are subjected to open circuit protection; or, if need carry out the protection of opening a way to all load branch roads of constant current drive circuit, then can regard two adjacent load branch roads as in the embodiment of the utility model provides an in two load branch roads, perhaps, also can regard every pair of load branch road in the load branch road more than two as in the embodiment of the utility model provides an in two load branch roads to set up the protection circuit of opening a way respectively. For example: assuming that the constant current driving circuit M includes 3 load branches including a load branch 1, a load branch 2, and a load branch 3, the load branch 1 and the load branch 2, and the load branch 2 and the load branch 3 may be respectively used as the two load branches in the embodiment of the present invention, and the open circuit protection circuit is respectively constructed; or, also can regard as load branch road 1 and load branch road 2, load branch road 2 and load branch road 3 and load branch road 1 and load branch road 3 respectively the embodiment of the utility model provides an in two load branch roads, establish respectively open circuit protection circuit to the realization is to the open circuit protection of each load branch road of constant current driver M.
By way of example, assuming that the LED constant current driving circuit shown in fig. 1 includes only two load branches, as shown in fig. 3, wherein,
the voltage stabilization unit may include: a first and a second voltage regulator ZD1 and ZD 2; the anode of the first voltage-regulator tube ZD1 and the anode of the second voltage-regulator tube ZD2 are used as two connecting ends of the voltage-regulator units and are respectively connected with the positive ends of the first load branch A1 and the second load branch A2; the cathode of the first voltage-stabilizing tube ZD1 is connected with the cathode of the second voltage-stabilizing tube ZD 2;
the open circuit detection unit may include: a first diode D1, a second diode D2, a third resistor R3, a fourth resistor R4, and a first comparator IC 1; wherein,
the anode of the first diode D1 and the anode of the second diode D2 are used as two input ends of the open circuit detection unit, and are respectively connected to the positive end of the first load branch a1 and the positive end of the second load branch a2, so as to detect the voltages of the positive ends of the first load branch a1 and the second load branch a 2; the cathode of the first diode D1 and the cathode of the second diode D2 are grounded through a third resistor R3 and a fourth resistor R4 in sequence respectively; the connection point of the third resistor R3 and the fourth resistor R4 is connected with the anode of the first comparator IC 1; the cathode of the first comparator IC1 is connected to the preset first reference voltage Vref 1; the output end of the first comparator IC1 is used as the output end of the open circuit detection unit and is connected with the control end of the short circuit unit;
as shown in fig. 3, the short-circuit unit may be implemented by a short-circuit switch, and specifically, the short-circuit unit includes: a first short switch S1; the control end of the first short-circuit switch S1 is used as the control end of the short-circuit unit and is connected to the output end of the open-circuit detection unit; the first short-circuit switch S1 is connected in parallel to a winding of the current sharing transformer T1 corresponding to the load branches a1 and a2 (in fig. 3, the second winding W2 of the current sharing transformer is connected, and in practical applications, the first short-circuit switch S1 may also be connected in parallel to the first winding W1 of the current sharing transformer), that is: the first end and the second end of the first short-circuit switch S1 are connected with the two ends of any winding of the current-sharing transformer T1 corresponding to the two load branches.
In the short-circuit unit shown in fig. 3, the short-circuit to the current sharing transformer is implemented by short-circuiting one winding of the current sharing transformer, or in practical application, the short-circuit unit may also be implemented by the following structure:
the short-circuiting unit includes: the third auxiliary windings and the second short-circuit switches of the current-sharing transformers corresponding to the two load branches; wherein,
the first end of the third auxiliary winding is connected with the first end of the second short-circuit switch, and the second end of the second short-circuit switch is connected with the second end of the third auxiliary winding; and the control end of the second short-circuit switch is used as the control end of the short-circuit unit. That is, the current sharing transformer includes three windings, two of which are connected in the main power circuit (same as described in fig. 3), and a third auxiliary winding magnetically coupled to the two windings is used for an open circuit protection circuit, and the purpose of short-circuiting the current sharing transformer is achieved by short-circuiting the third auxiliary winding.
In the exemplary diagram shown in fig. 3, the negative terminals of the first load branch a1 and the second load branch a2 are equipotential through grounding, and in practical applications, the equipotential at one end with the same polarity of the load branches can also be achieved through common connection with a common voltage or through short-circuit connection between endpoints, which is not described herein.
As shown in fig. 4, a main circuit structure of the constant current driver based on the BOOST topology result is given, which includes two load branches, and the above open circuit protection circuit of the embodiment of the present invention can be applied equally, wherein, the voltage stabilizing unit, the open circuit detection unit and the short circuit unit can refer to the structure of the corresponding unit in fig. 3, which is not repeated here.
If fig. 5, then has given one the utility model discloses realization scheme when open circuit protection circuit is applied to the constant current driver including more than two load branch roads, as shown in fig. 5, will two adjacent load branch roads constitute a set of in the constant current driver, as in the embodiment of the utility model discloses in the embodiment two load branch roads, each load branch road of group correspond a voltage stabilizing unit, an open circuit detecting element and a short circuit unit to the open circuit protection of each load branch road of the constant current driver including more than three load branch roads has been realized. As shown in fig. 5, the implementation of each unit in the example shown in fig. 5 may also refer to fig. 3, which is not described herein again.
For the open circuit protection circuit in the above embodiment, two ends of two load branches with the same polarity are connected to two connection ends of the voltage stabilization unit, and the other two ends with the same polarity are equipotential, so that when one of the load branches is open circuit to cause voltage rise, the output voltage of the open load branch is clamped to the normal output voltage of the other load branch through the voltage stabilization unit, thereby preventing the open load branch from overvoltage under the condition of ensuring the normal operation of the other load branch; when the voltage of the load branch circuit with the open circuit is increased, the increased voltage is detected by the open circuit detection unit, so that the short circuit unit is controlled to short circuit the current equalizing transformers corresponding to the two load branch circuits, overlarge current cannot flow in the voltage stabilizing unit, the voltage stabilizing unit can be realized by selecting a device with smaller current, the realization cost of the voltage stabilizing unit is reduced, and the realization cost of the open circuit protection circuit is further reduced; in addition, the open circuit protection circuit does not perform direct short circuit processing on the load branch, so that the open circuit protection circuit can be also suitable for a constant current driving circuit based on a BOOST topological structure, and has a wider application range compared with the open circuit protection circuit in the prior art.
In another embodiment of the present invention, at least three load branches in the constant current driver are used as processing objects to jointly perform open circuit protection. The at least three load branches may be at least three load branches arbitrarily selected from the constant current driver, wherein the number m of the load branches protected by the constant current driver is greater than or equal to 3. At this time, the process of the present invention,
the utility model discloses open circuit protection circuit includes: at least three load branches of the constant current driving circuit, a voltage stabilizing unit, an open circuit detection unit and a short circuit unit, wherein,
a pair of load branches of the at least three load branches corresponds to a voltage stabilizing unit, and two connecting ends of the voltage stabilizing unit are connected with two ends of the corresponding pair of load branches with the same polarity; one end of the at least three load branches which is not connected with the voltage stabilizing unit is equipotential; the open circuit detection unit comprises at least three input ends, and each input end is connected with one end of a load branch circuit connected with the voltage stabilizing unit; the output end of the open circuit detection unit is connected with the control end of the short circuit unit;
in the at least three load branches, it is required to ensure that each load branch corresponds to at least one voltage stabilizing unit, so as to ensure that when a certain load branch is open-circuited, the output voltage of the load branch which is open-circuited can be clamped by another normal load branch which is commonly connected with the load branch which is open-circuited and the voltage stabilizing unit. Therefore, when the number of the load branches is m (m is greater than or equal to 3), the number of the voltage stabilizing units is at least m-1.
The voltage stabilizing unit is used for: when the voltage difference value between two ends with the same polarity of a pair of load branches corresponding to the voltage stabilizing unit is larger than a preset second difference threshold value, clamping the voltage of one end with the larger voltage value in the two ends with the same polarity of the corresponding pair of load branches at the voltage of one end with the smaller voltage value;
the open circuit detection unit is used for respectively detecting the voltages of the at least three input ends, comparing each detected voltage with a preset second reference voltage, and controlling the short circuit unit to short circuit each current-sharing transformer corresponding to the at least three load branches when any detected voltage is greater than the second reference voltage;
and the short-circuit unit is used for short-circuiting each current-sharing transformer corresponding to the at least three load branches under the control of the open-circuit detection unit.
Above the embodiment of the utility model provides an open circuit protection circuit realizes that open circuit protection principle does:
because a voltage stabilizing unit is connected between two ends with the same polarity of the two load branches, the other two ends with the same polarity are equipotential, when the voltage difference value between the two ends with the same polarity is not less than a preset first difference threshold value, the phenomenon of open circuit and overvoltage of one load branch is indicated, so that the output of the load branch with the open circuit and overvoltage of the voltage stabilizing circuit is clamped at the normal output of the other load branch, and the load branch with the normal output continuously keeps the normal working state; and the open circuit detection unit detects that one load branch circuit is open circuit, at the moment, the short circuit unit is controlled to short circuit each current sharing transformer corresponding to at least three load branch circuits, so that the current sharing transformers corresponding to at least three load branch circuits do not balance the current of the load branch circuits any more, open circuit protection is realized for the load branch circuits with open circuit overvoltage, normal work of other load branch circuits is kept, the current flowing through the voltage stabilizing unit is ensured to be small, the power consumption of the voltage stabilizing unit is reduced, the voltage stabilizing unit can be realized by selecting devices with small current, the realization cost of the voltage stabilizing unit is reduced, and the realization cost of the open circuit protection circuit is reduced.
The two connection ends of the voltage stabilizing unit are connected to positive ends of the two load branches and negative ends of the two load branches, which is not limited herein.
In addition, for a specific application scenario of the above embodiment, the constant current driving circuit may include any two or more load branches, and performs open circuit protection on all the load branches, or performs open circuit protection on some two or more load branches specified in the constant current driving circuit, which is not limited herein.
The structure of the voltage stabilizing unit may be similar to that in fig. 3 to 5, and is implemented by two voltage stabilizing tubes connected in series in the direction, specifically, the voltage stabilizing unit includes: a third and a fourth stabilivolt; wherein,
the anode of the third voltage-stabilizing tube and the anode of the fourth voltage-stabilizing tube are used as two connecting ends of the voltage-stabilizing units; and the cathode of the third voltage-stabilizing tube is connected with the cathode of the fourth voltage-stabilizing tube.
The open circuit detection unit may include: at least three diodes, a third resistor, a fourth resistor and a second comparator; wherein,
anodes of the at least three diodes are used as input ends of the open circuit detection units, each input end corresponds to one load branch in the at least three load branches, and the input end is connected with one end of the load branch connected with the corresponding voltage stabilizing circuit; the cathodes of the at least three diodes are grounded through a third resistor and a fourth resistor respectively in sequence; the connection point of the third resistor and the fourth resistor is connected with the anode of the second comparator; the cathode of the second comparator is connected with the preset second reference voltage; the output end of the second comparator is used as the output end of the open circuit detection unit and is connected with the control end of the short circuit unit.
In addition, the short-circuit unit can be implemented in at least two ways, and one structure of the short-circuit unit includes: at least two short-circuit switches; the control ends of the short-circuit switches are connected and are used as the control ends of the short-circuit units together; any winding of each current sharing transformer corresponding to the at least three load branches is connected with one short-circuit switch in parallel. Namely: each current sharing transformer corresponds to a short-circuit switch, and the short-circuit switch is connected with a winding of the corresponding current sharing transformer in parallel to control whether the corresponding current sharing transformer is short-circuited or not.
In another implementation, the short circuit unit includes: the third auxiliary winding of each current-sharing transformer corresponding to the at least three load branches, the diode corresponding to each auxiliary winding and the third short-circuit switch; wherein,
the first end of each third auxiliary winding is connected with the first end of a third short-circuit switch through a diode corresponding to the third auxiliary winding, and the second end of the third short-circuit switch and the second end of each third auxiliary winding are grounded; and the control end of the third short-circuit switch is used as the control end of the short-circuit unit.
That is, each third auxiliary winding corresponds to a diode, so that through the above connection relationship, each third auxiliary winding, the diode corresponding to the third auxiliary winding, and the third short-circuit switch form a loop, when the third short-circuit switch is short-circuited, all the third auxiliary windings are short-circuited, and further all the current-sharing transformers corresponding to the at least three load branches are short-circuited.
For example, as shown in fig. 6, a schematic diagram of an implementation of an open-circuit protection circuit of a constant current driver is provided, where the constant current driver includes N (N is greater than or equal to 3) load branches; wherein,
two adjacent load branches are used as a pair of load branches and correspond to a voltage stabilizing unit, the voltage stabilizing unit is respectively formed by two voltage stabilizing tubes which are reversely connected in series, for example, the voltage stabilizing units corresponding to the load branches A1 and A2 comprise voltage stabilizing tubes ZD11 and ZD12, the voltage stabilizing units corresponding to the load branches A2 and A3 comprise voltage stabilizing tubes ZD21 and ZD22 which are reversely connected in series, and the like, and the description is omitted;
the open circuit detection unit comprises N input ends which are respectively and correspondingly connected with the positive ends of the load branch circuits A1-AN, the voltage value of the positive end of the corresponding load branch circuit is detected, and the negative end of each load branch circuit is grounded. Each input end of the open circuit detection unit is grounded through the corresponding diode (D12, D22.. DN2), the third resistor R3 and the fourth resistor R4 in sequence; a connection point of the third resistor R3 and the fourth resistor R4 is connected with an anode of the second comparator IC2, and a cathode of the second comparator IC2 is connected with a second reference voltage Vref 2; the input terminal of the second comparator IC2 is connected to the control terminal of the short-circuit unit (i.e., the control terminal of the third short-circuit switch S3 in fig. 6);
in the open circuit protection circuit shown in fig. 6, the short circuit unit includes: third auxiliary windings of N-1 current sharing transformers T1-TN-1 corresponding to the N load branches are respectively W13 and W23.. W (N-1)3 shown in FIG. 6; each third auxiliary winding corresponds to a diode which is respectively D13 and D23.. D (N-1) 3; the first end of each third auxiliary winding is connected with the first end of a third short-circuit switch S3 through a corresponding diode; a second terminal of each of the third auxiliary windings and a second terminal of the third short switch S3 are grounded.
Under the constant current driver and the open circuit protection circuit structure thereof shown in fig. 6, when any load branch of the constant current driver is open, the voltage stabilizing circuit corresponding to the load branch will automatically clamp the positive terminal voltage of the open load branch to the positive terminal voltage of another normal load branch connected with the voltage stabilizing circuit, so as to prevent the open load branch from generating overvoltage; and the open circuit detection unit detects that the voltage at the positive end of the open load branch is higher than the second reference voltage, and outputs a control signal through the second comparator to control the short circuit of the third short-circuit switch S3 in the short circuit unit, so that the purpose of short-circuiting each current-sharing transformer corresponding to the N load branches is achieved through the third auxiliary winding of the current-sharing transformer short-circuiting the N load branches, and the current flowing through the voltage stabilizing circuit corresponding to the open load branch is ensured to be smaller.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, a plurality of modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (10)
1. An open circuit protection circuit, comprising: two load branches of the constant current driving circuit, a voltage stabilizing unit, an open circuit detection unit and a short circuit unit, wherein,
two connecting ends of the voltage stabilizing unit are connected with two ends of the two load branches with the same polarity, and the other two ends of the two load branches with the same polarity are equipotential; the two ends of the two load branches with the same polarity are also respectively connected with two input ends of the open circuit detection unit; the output end of the open circuit detection unit is connected with the control end of the short circuit unit;
the voltage stabilizing unit is used for: when the voltage difference value between two ends with the same polarity of the two load branches is larger than a preset first difference threshold value, clamping the voltage at the end with the larger voltage value in the two ends with the same polarity of the two load branches at the voltage at the end with the smaller voltage value;
the open circuit detection unit is used for: respectively detecting the voltages of the two input ends, respectively comparing each detected voltage with a preset first reference voltage, and controlling the short-circuit unit to short-circuit the current-sharing transformers corresponding to the two load branches when any detected voltage is greater than the first reference voltage;
and the short-circuit unit is used for short-circuiting the current-sharing transformers corresponding to the two load branches under the control of the open-circuit detection unit.
2. The circuit of claim 1, wherein the voltage stabilization unit comprises: a first voltage regulator tube and a second voltage regulator tube; wherein,
the anode of the first voltage-stabilizing tube and the anode of the second voltage-stabilizing tube are used as two connecting ends of the voltage-stabilizing units; and the cathode of the first voltage-stabilizing tube is connected with the cathode of the second voltage-stabilizing tube.
3. The circuit according to claim 1 or 2, wherein the open circuit detection unit comprises: the circuit comprises a first diode, a second diode, a third resistor, a fourth resistor and a first comparator; wherein,
the anode of the first diode and the anode of the second diode are used as two input ends of the open circuit detection unit; the cathode of the first diode and the cathode of the second diode are grounded through the third resistor and the fourth resistor respectively in sequence; the connection point of the third resistor and the fourth resistor is connected with the anode of the first comparator; the cathode of the first comparator is connected with the preset first reference voltage; the output end of the first comparator is used as the output end of the open circuit detection unit.
4. The circuit according to claim 1 or 2, wherein the short-circuiting unit comprises: a first short-circuit switch; the control end of the first short-circuit switch is used as the control end of the short-circuit unit; and the first end and the second end of the first short-circuit switch are connected with the two ends of any winding of the current-sharing transformer corresponding to the two load branches.
5. The circuit according to claim 1 or 2, wherein the short-circuiting unit comprises: the third auxiliary winding and the second short-circuit switch of the current-sharing transformer correspond to the two load branches;
the first end of the third auxiliary winding is connected with the first end of the second short-circuit switch, and the second end of the second short-circuit switch is connected with the second end of the third auxiliary winding; and the control end of the second short-circuit switch is used as the control end of the short-circuit unit.
6. An open circuit protection circuit, comprising: at least three load branches of the constant current driving circuit, a voltage stabilizing unit, an open circuit detection unit and a short circuit unit, wherein,
a pair of load branches of the at least three load branches corresponds to a voltage stabilizing unit, and two connecting ends of the voltage stabilizing unit are connected with two ends of the corresponding pair of load branches with the same polarity; one end of each of the at least three load branches, which is not connected with the voltage stabilizing unit, is equipotential; the open circuit detection unit comprises at least three input ends, and each input end is connected with one end of a load branch circuit connected with the voltage stabilizing unit; the output end of the open circuit detection unit is connected with the control end of the short circuit unit;
the voltage stabilizing unit is used for: when the voltage difference value between two ends with the same polarity of a pair of load branches corresponding to the voltage stabilizing unit is larger than a preset second difference threshold value, clamping the voltage of one end with the larger voltage value in the two ends with the same polarity of the corresponding pair of load branches at the voltage of one end with the smaller voltage value;
the open circuit detection unit is used for respectively detecting the voltages of the at least three input ends, comparing each detected voltage with a preset second reference voltage, and controlling the short circuit unit to short circuit each current-sharing transformer corresponding to the at least three load branches when any detected voltage is greater than the second reference voltage;
and the short-circuit unit is used for short-circuiting each current-sharing transformer corresponding to the at least three load branches under the control of the open-circuit detection unit.
7. The circuit of claim 6, wherein the voltage stabilization unit comprises: a third and a fourth stabilivolt; wherein,
the anode of the third voltage-stabilizing tube and the anode of the fourth voltage-stabilizing tube are used as two connecting ends of the voltage-stabilizing units; and the cathode of the third voltage-stabilizing tube is connected with the cathode of the fourth voltage-stabilizing tube.
8. The circuit according to claim 6 or 7, wherein the open circuit detection unit comprises: at least two diodes, a third resistor, a fourth resistor and a second comparator; wherein,
anodes of the at least two diodes are used as input ends of the open circuit detection units; cathodes of the at least two diodes are grounded through a third resistor and a fourth resistor respectively in sequence; the connection point of the third resistor and the fourth resistor is connected with the anode of the second comparator; the cathode of the second comparator is connected with the preset second reference voltage; and the output end of the second comparator is used as the output end of the open circuit detection unit.
9. The circuit according to claim 6 or 7, wherein the short-circuiting unit comprises: at least two short-circuit switches; the control end of each short-circuit switch is used as the control end of the short-circuit unit; any winding of each current sharing transformer corresponding to the at least three load branches is connected with one short-circuit switch in parallel.
10. The circuit according to claim 6 or 7, wherein the short-circuiting unit comprises: the third auxiliary winding of each current-sharing transformer corresponding to the at least three load branches, the diode corresponding to each auxiliary winding and the third short-circuit switch; wherein,
the first end of each third auxiliary winding is connected with the first end of a third short-circuit switch through a diode corresponding to the third auxiliary winding, and the second end of the third short-circuit switch and the second end of each third auxiliary winding are grounded; and the control end of the third short-circuit switch is used as the control end of the short-circuit unit.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2010201941796U CN201708990U (en) | 2010-05-12 | 2010-05-12 | Open circuit protection circuit |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2010201941796U CN201708990U (en) | 2010-05-12 | 2010-05-12 | Open circuit protection circuit |
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| CN201708990U true CN201708990U (en) | 2011-01-12 |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110167227A (en) * | 2018-02-14 | 2019-08-23 | 松下知识产权经营株式会社 | Open loop protection circuit, power supply circuit, open-circuit-protection method and lighting device |
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2010
- 2010-05-12 CN CN2010201941796U patent/CN201708990U/en not_active Expired - Lifetime
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110167227A (en) * | 2018-02-14 | 2019-08-23 | 松下知识产权经营株式会社 | Open loop protection circuit, power supply circuit, open-circuit-protection method and lighting device |
| CN110167227B (en) * | 2018-02-14 | 2022-09-09 | 松下知识产权经营株式会社 | Open-circuit protection circuit, power supply circuit, open-circuit protection method and lighting device |
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