A synchronous starting circuit and constant current deep dimming power supply

Abstract

The present invention discloses a synchronous starting circuit and a constant current deep dimming power supply. When the output voltage of a constant current source does not reach the starting voltage of an LED lamp, an enabling switch circuit and a starting switch circuit are both disconnected. When the output voltage of the constant current source reaches the starting voltage of the LED lamp, the enabling switch circuit is turned on to output a power-off signal. The power-off signal is used to control the constant current source to stop outputting current so as to wait for the output voltage of other constant current sources to reach the starting voltage of the corresponding LED lamp. Taking the moment when the constant current source starts to output voltage as the starting point, after a preset time, each starting switch circuit receives a synchronous starting signal, each starting switch circuit is turned on, and each constant current source discharges to power the LED lamp, thereby realizing simultaneous starting of multiple LED lamps and timely starting of a single LED lamp.

Description

Technical Field

[0001] The invention relates to the technical field of LED power supplies, and in particular to a synchronous starting circuit and a constant current deep dimming power supply. Background Art

[0002] LED power supplies on the market are now divided into two categories: constant voltage power supplies and constant current power supplies. In the constant current circuit solution, in order to improve output stability, it is necessary to add a larger electrolytic capacitor in the output circuit to reduce the current ripple. For multiple LED power supplies, each LED power supply has a different dimming depth. Among them, for a power supply with a higher dimming depth, when it is started at a lower brightness (smaller current), it is known from C=Q / U and Q=I*T that for a capacitor with a fixed capacitance, the voltage across its two ends is proportional to the charging current, so the required charging time is longer. On the contrary, for a power supply with a lower dimming depth, the required charging time is shorter. Based on this, it is difficult to start each LED power supply synchronously, resulting in an unfriendly user experience. Summary of the invention

[0003] Therefore, the technical problem to be solved by the present invention is to solve the response delay problem caused by the charging process when single or multi-channel LED lamps are started with a smaller current in the prior art, thereby providing a synchronous starting circuit and a constant current deep dimming power supply.

[0004] In order to achieve the above object, the present invention provides the following technical solutions:

[0005] In the first aspect, an embodiment of the present invention provides a synchronous start circuit, wherein the front stage of the synchronous start circuit is connected to a constant current source of an LED lamp, and the rear stage of the synchronous start circuit is connected to the LED lamp. The synchronous start circuit includes: an enable switch circuit and a start switch circuit, wherein the constant current source, a first end of which is connected to the first end of the LED lamp; the enable switch circuit, a control end of which is connected to the second end of the constant current source, a first end of which is connected to the second end of the LED lamp, and a second end of which is connected to the enable end of the constant current source; the start switch circuit, a control end of which receives a synchronous start signal, a first end of which is connected to an external power supply voltage, a second end of which is connected to the second end of the constant current source, and a third end of which is connected to the The second end is connected; the synchronous start signal is used to turn on the start switch circuit of the synchronous start circuit of each LED lamp to control the constant current source of each LED lamp to discharge simultaneously; when the output voltage of the constant current source does not reach the start voltage of the LED lamp, the enable switch circuit and the start switch circuit are both disconnected; when the output voltage of the constant current source reaches the start voltage of the LED lamp, the enable switch circuit is turned on to output a power-off signal, and the power-off signal is used to control the constant current source to stop outputting current; taking the moment when the constant current source starts to output voltage as the starting point, after a preset time, the start switch circuit receives the synchronous start signal, the start switch circuit is turned on, and the constant current source discharges to power the LED lamp.

[0006] In one embodiment, the enabling switch circuit includes: a first enabling switch circuit and a second enabling switch circuit, wherein the first enabling switch circuit has a control end connected to the second end of a constant current source, a first end connected to the second end of an LED lamp, and a second end connected to the control end of the second enabling switch circuit; the second enabling switch circuit has a first end connected to the enabling end of the constant current source and a second end connected to ground; when the output voltage of the constant current source does not reach the starting voltage of the LED lamp, the first enabling switch circuit and the second enabling switch circuit are both disconnected; when the output voltage of the constant current source reaches the starting voltage of the LED lamp, the first enabling switch circuit and the second enabling switch circuit are both turned on, and the first end of the second enabling switch circuit outputs a power-off signal.

[0007] In one embodiment, the first enabling switch circuit includes: a first resistor and a first switch, wherein the control end of the first switch is connected to the second end of the constant current source through the first resistor, the first end is connected to the second end of the LED lamp, and the second end is connected to the control end of the second enabling switch circuit.

[0008] In one embodiment, the second enabling switch circuit includes: a second resistor and a second switch, wherein the second switch has a control end connected to the second end of the first enabling switch circuit through the second resistor, a first end connected to the enabling end of the constant current source, and a second end grounded.

[0009] In one embodiment, the second enabling switch circuit further includes: a third resistor; and the control end of the second switch is also grounded through the third resistor.

[0010] In one embodiment, the starting switch circuit includes: a first starting switch circuit and a second starting switch circuit, wherein the first starting switch circuit has a control end receiving a synchronous starting signal, a first end connected to an external power supply voltage, and a second end connected to a first end of the second starting switch circuit; the second starting switch circuit has a second end connected to a second end of the LED lamp, and a third end connected to a second end of a constant current source; when the output voltage of the constant current source does not reach the starting voltage of the LED lamp, the first starting switch circuit and the second starting switch circuit are both disconnected; when the output voltage of the constant current source reaches the starting voltage of the LED lamp, after a preset time, the first starting switch circuit receives the synchronous starting signal and is turned on, the second starting switch circuit is turned on, and the constant current source discharges to power the LED lamp.

[0011] In one embodiment, the first startup switch circuit includes: a third switch, a fourth switch, a fourth resistor, and a fifth resistor, wherein the third switch has a control end that receives a synchronous startup signal through the fourth resistor, a first end that is connected to the control end of the fourth switch through the fifth resistor, and a second end that is grounded; and the fourth switch has a first end that is connected to an external power supply voltage, and a second end that is connected to the first end of the second startup switch circuit (122).

[0012] In one embodiment, the second startup switch circuit includes: a fifth switch, a sixth resistor and a seventh resistor, wherein the fifth switch has a control end connected to the second end of the first startup switch circuit through the sixth resistor, and its control end is also connected to the second end of the constant current source through the seventh resistor, its first end is connected to the second end of the LED lamp, and its second end is connected to the second end of the constant current source.

[0013] In one embodiment, the second startup switch circuit further includes: a first diode, a cathode of which is connected to the first end of the sixth resistor, and an anode of which is connected to the second end of the sixth resistor.

[0014] In one embodiment, the second startup switch circuit further includes: a filter capacitor, which is used to connect the control end of the fifth switch and the second end of the fifth switch.

[0015] In a second aspect, an embodiment of the present invention provides a constant current deep dimming power supply, comprising: a synchronous start circuit and a constant current source of the first aspect, wherein the constant current source, a first end of which is connected to the first end of the LED lamp, and a second end of which is connected to the first end of the synchronous start circuit; a synchronous start circuit, a second end of which is connected to the second end of the LED lamp, a third end of which is connected to the enable end of the constant current source, a fourth end of which inputs a synchronous start signal, and a fifth end of which is connected to an external power supply voltage; when the output voltage of the constant current source does not reach the starting voltage of the LED lamp, the synchronous start circuit is disconnected; when the output voltage of the constant current source reaches the starting voltage of the LED lamp, the synchronous start circuit outputs a power-off signal, and the constant current source no longer outputs current; starting from the moment when the constant current source starts to output voltage, after a preset time, the synchronous start circuit receives the synchronous start signal, and the constant current source discharges to power the LED lamp.

[0016] In one embodiment, the constant current source includes: a voltage conversion circuit and an electrolytic capacitor, wherein the voltage conversion circuit has a first end connected to the first end of the electrolytic capacitor and the first end of the LED lamp, a second end connected to the second end of the electrolytic capacitor and the first end of the synchronous start circuit, and an enable end connected to the third end of the synchronous start circuit; when the voltage conversion circuit receives a charging signal, the voltage conversion circuit charges the electrolytic capacitor; when the voltage of the electrolytic capacitor does not reach the starting voltage of the LED lamp, the synchronous start circuit is disconnected; when the voltage of the electrolytic capacitor reaches the starting voltage of the LED lamp, the synchronous start circuit outputs a power-off signal, and the voltage conversion circuit no longer charges the electrolytic capacitor; after a preset time from the time the voltage conversion circuit receives the charging signal, the synchronous start circuit receives the synchronous start signal, and the electrolytic capacitor discharges to power the LED lamp.

[0017] The technical solution of the present invention has the following advantages:

[0018] The synchronous starting circuit and constant current deep dimming power supply provided by the present invention are such that when the output voltage of the constant current source does not reach the starting voltage of the LED lamp, the enabling switch circuit and the starting switch circuit are both disconnected; when the output voltage of the constant current source reaches the starting voltage of the LED lamp, the enabling switch circuit is turned on to output a power-off signal, and the power-off signal is used to control the constant current source to stop outputting current, so as to wait for the output voltage of other constant current sources to reach the starting voltage of the corresponding LED lamp; taking the moment when the constant current source starts to output voltage as the starting point, after a preset time, each starting switch circuit receives the synchronous starting signal, each starting switch circuit is turned on, and each constant current source discharges to power the LED lamp, thereby realizing simultaneous starting of multiple LED lamps and timely starting of a single LED lamp. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 A composition diagram of a specific example of a synchronous starting circuit provided by an embodiment of the present invention;

[0021] Figure 2 A composition diagram of another specific example of a synchronous starting circuit provided by an embodiment of the present invention;

[0022] Figure 3 A topological diagram of a synchronous start-up circuit provided in an embodiment of the present invention;

[0023] Figure 4 A composition diagram of another specific example of a synchronous starting circuit provided by an embodiment of the present invention;

[0024] Figure 5 A composition diagram of a specific example of a constant current deep dimming power supply provided by an embodiment of the present invention;

[0025] Figure 6 A composition diagram of a specific example of a constant current deep dimming power supply provided by an embodiment of the present invention;

[0026] Figure 7 A topological diagram of a constant current deep dimming power supply provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0027] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0029] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, it can also be the internal connection of two components, it can be a wireless connection, or it can be a wired connection. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0030] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0031] Example 1

[0032] The embodiment of the present invention provides a synchronous starting circuit, such as Figure 1 As shown, the front stage of the synchronous starting circuit is connected to the constant current source 2 of one LED lamp, and the rear stage of the synchronous starting circuit is connected to the LED lamp, wherein the electrolytic capacitor inside the constant current source 2 of each LED lamp can be the same or different, and the starting voltage of each LED lamp can be the same or different, such as Figure 1 As shown, the synchronous start-up circuit includes: an enabling switch circuit 11 and a start-up switch circuit 12 .

[0033] like Figure 1 As shown, a constant current source 2 has a first end connected to a first end of the LED lamp; the constant current source 2 may be a common constant current source 2 in the field of LED technology, and is not limited here.

[0034] like Figure 1As shown, the enabling switch circuit 11 has a control end connected to the second end of the constant current source 2 , a first end connected to the second end of the LED lamp, and a second end connected to the enabling end of the constant current source 2 .

[0035] like Figure 1 As shown, the start switch circuit 12 has a control end receiving a synchronous start signal, a first end connected to an external power supply voltage, a second end connected to a second end of the constant current source 2, and a third end connected to a second end of the LED lamp. The synchronous start signal is sent by an external controller, which may be a single-chip microcomputer, but this is only an example and is not intended to be limiting.

[0036] Specifically, the embodiment of the present invention limits the time for the controller to send the synchronous start signal, as follows:

[0037] (1) When there is only one LED lamp, the controller uses the moment when the constant current source starts to output current as the starting point for delay. The delay time needs to be slightly longer than the time when the constant current source voltage reaches the LED lamp start voltage. Only then can the controller send a synchronous start signal to the start switch circuit.

[0038] (2) When there are multiple LED lamps, one constant current source powers one lamp and each constant current source starts working at the same time. The controller uses the moment when each constant current source starts to output current as the starting point for delay. When the voltage of each constant current source reaches the starting voltage of the corresponding LED lamp, the controller sends a synchronous start signal to each start switch circuit.

[0039] In order to be able to start each LED lamp at the same time, the time when the output voltage of the constant current source 2 of each LED lamp reaches the starting voltage of the corresponding LED lamp can be based on the time when each constant current source 2 starts to output voltage as the starting point. After a preset time (the preset time needs to ensure that the output voltage of each constant current source 2 reaches the starting voltage of the corresponding LED lamp), a synchronous start signal is sent to the starting switch circuit 12 of each synchronous start circuit, so as to control each starting switch circuit 12 to conduct, so as to control the constant current source 2 of each LED lamp to discharge simultaneously, thereby powering the LED lamp.

[0040] Specifically, when the output voltage of the constant current source 2 does not reach the starting voltage of the LED lamp, the enabling switch circuit 11 is disconnected; when the output voltage of the constant current source 2 reaches the starting voltage of the LED lamp, the enabling switch circuit 11 is turned on to output a power-off signal, and the power-off signal is used to control the constant current source 2 to no longer output current.

[0041] Exemplarily, the constant current source 2 may include a voltage conversion circuit and an electrolytic capacitor, wherein the discharge voltage of the electrolytic capacitor is used to power the LED lamp, wherein the voltage conversion circuit may be a BUCK circuit. After the constant current source 2 is started, the BUCK circuit charges the electrolytic capacitor. Since the voltage of the electrolytic capacitor will not immediately reach the starting voltage of the LED lamp, the LED lamp is powered off. At the same time, the voltage of the electrolytic capacitor will not immediately reach the starting voltage of the enable switch circuit 11, so the enable switch circuit 11 is disconnected. When the voltage of the electrolytic capacitor reaches the starting voltage of the enable switch circuit 11, the enable switch circuit 11 is turned on, and the enable switch circuit 11 sends a power-off signal to the enable end of the constant current source 2 (BUCK circuit), and the BUCK circuit no longer charges the electrolytic capacitor.

[0042] Specifically, the conduction of the start switch circuit 12 requires two conditions, namely: one is that the external power supply voltage reaches its start voltage, and the other is that the synchronous start signal is received. Before receiving the synchronous start signal, the start switch circuit 12 is always connected to the external power supply voltage. Once the synchronous start signal is received, the start switch circuit 12 is immediately turned on. However, in order to ensure that all LED lamps are started at the same time, all the start switch circuits 12 will receive the synchronous start signal only after the output voltage of all the constant current sources 2 reaches the start voltage of the LED lamps. Therefore, when the output voltage of the constant current source 2 does not reach the start voltage of the LED lamp, the start switch circuit 12 is disconnected.

[0043] Based on the above analysis, taking the constant current source 2 including the BUCK circuit and the electrolytic capacitor as an example, the working process of the synchronous start-up circuit of the embodiment of the present invention is as follows:

[0044] Step 1: The BUCK circuit is started, and the BUCK circuit charges the electrolytic capacitor. When the voltage of the electrolytic capacitor does not reach the starting voltage of the LED lamp, the enabling switch circuit 11 and the starting switch circuit 12 are in the disconnected state;

[0045] Step 2: When the voltage of the electrolytic capacitor reaches the starting voltage of the LED lamp, the voltage of the electrolytic capacitor is sufficient to turn on the enabling switch circuit 11, but the starting switch circuit 12 is turned off, and the enabling switch circuit 11 sends a power-off signal to the enabling end of the BUCK circuit, and the BUCK circuit stops charging the electrolytic capacitor;

[0046] Step 3: Starting from the start of the BUCK circuit, after a preset time, the start switch circuit 12 receives a synchronous start signal, the start switch circuit 12 is turned on, and the electrolytic capacitor discharges to power the LED lamp.

[0047] In a specific embodiment, if Figure 2 As shown, the enabling switch circuit 11 includes: a first enabling switch circuit 111 and a second enabling switch circuit 112 .

[0048] like Figure 2 As shown, the first enabling switch circuit 111 has a control end connected to the second end of the constant current source 2, a first end connected to the second end of the LED lamp, and a second end connected to the control end of the second enabling switch circuit 112; the first enabling switch circuit 111 can be a circuit including a switching function element.

[0049] like Figure 2 As shown, the second enabling switch circuit 112 has a first end connected to the enabling end of the constant current source 2 and a second end grounded; the second enabling switch circuit 112 may be a circuit including a switching function element.

[0050] Specifically, when the output voltage of the constant current source 2 does not reach the starting voltage of the LED lamp, the first enabling switch circuit 111 and the second enabling switch circuit 112 are both disconnected; when the output voltage of the constant current source 2 reaches the starting voltage of the LED lamp, the first enabling switch circuit 111 and the second enabling switch circuit 112 are both turned on, and the first end of the second enabling switch circuit 112 outputs a power-off signal, which controls the constant current source 2 to no longer output current, that is, the BUCK circuit no longer charges the electrolytic capacitor.

[0051] In a specific embodiment, if Figure 3 As shown, the first enabling switch circuit 111 includes: a first resistor R1 and a first switch Q1, wherein the control end of the first switch Q1 is connected to the second end of the constant current source 2 through the first resistor R1, the first end of the first switch Q1 is connected to the second end of the LED lamp, and the second end of the first switch Q1 is connected to the control end of the second enabling switch circuit 112 (i.e., the control end of the fifth switch Q5). Figure 3 Pin 1 of the interface CN1 is connected to the first end of the LED lamp, and pin 2 of the interface CN1 is connected to the second end of the LED lamp.

[0052] Specifically, by setting the threshold voltage of the first switch Q1 to be equal to the starting voltage of the LED lamp, when the output voltage of the constant current source 2 does not reach the starting voltage of the LED lamp, the output voltage of the constant current source 2 must not reach the threshold voltage of the first switch Q1, and the first switch Q1 is disconnected; when the output voltage of the constant current source 2 reaches the starting voltage of the LED lamp, the output voltage of the constant current source 2 must also reach the threshold voltage of the first switch Q1, and the first switch Q1 is turned on.

[0053] In a specific embodiment, if Figure 3 As shown, the second enabling switch circuit 112 includes: a second resistor R2 and a second switch Q2, wherein the second switch Q2 has a control end connected to the second end of the first enabling switch circuit 111 through the second resistor R2, a first end connected to the enabling end of the constant current source 2, and a second end grounded.

[0054] Specifically, when the first switch Q1 is turned off, the control end of the second switch Q2 is subjected to low voltage, and the second switch Q2 is turned off; when the first switch Q1 is turned on, the control end of the second switch Q2 is subjected to high voltage, and the second switch Q2 is turned on. The first end of the second switch Q2 outputs a power-off signal to the enable end (EN end) of the constant current source 2. Since the second end of the second switch Q2 is grounded, the enable end is pulled low, and the constant current source 2 no longer outputs current. In other words, when the output voltage of the constant current source 2 reaches the starting voltage of the LED lamp, the first switch Q1 and the second switch Q2 are both turned on, the enable end of the constant current source 2 is pulled low, and the constant current source 2 no longer outputs current.

[0055] It should be noted that Figure 3 The first switch Q1 and the second switch Q2 in the embodiment are taken as power devices IGBT, but this is only an example and is not intended to be limiting.

[0056] In a specific embodiment, if Figure 3 As shown, the second enabling switch circuit 112 further includes: a third resistor R3; and the control end of the second switch Q2 is also grounded through the third resistor R3.

[0057] Specifically, a third resistor R3 is disposed between the control terminal and the second terminal of the second switch Q2 to prevent the voltage of the second switch Q2 from overshooting.

[0058] In a specific embodiment, if Figure 4 As shown, the startup switch circuit 12 includes: a first startup switch circuit 121 and a second startup switch circuit 122 .

[0059] like Figure 4 As shown, the first startup switch circuit 121 has a control end that receives a synchronous startup signal, a first end that is connected to an external power supply voltage, and a second end that is connected to a first end of a second startup switch circuit; the first startup switch circuit 121 may be a circuit that includes a switching function element.

[0060] like Figure 4 As shown, the second start switch circuit 122 has a second end connected to the second end of the LED lamp, and a third end connected to the second end of the constant current source 2; the second start switch circuit 122 can be a circuit including a switch function element.

[0061] In order to ensure that each LED lamp starts at the same time, it is necessary to ensure that the output voltage of the constant current source 2 of each LED lamp reaches the starting voltage value of each LED lamp before the first starting switch circuit 121 receives the synchronous starting signal. As can be seen from the above, the function of the enabling switch circuit 11 is actually to ensure that before the starting switch circuit 12 receives the signal, when the output voltage of the constant current source 2 reaches the starting voltage of the LED lamp, the constant current source 2 is controlled to stop outputting current to wait for synchronous starting. Therefore, when the output voltage of the constant current source 2 does not reach the starting voltage of the LED lamp, the first starting switch circuit 121 and the second starting switch circuit 122 are both disconnected, and the LED lamp will not light up at this time. Once the output voltage of the constant current source 2 reaches the starting voltage of the LED lamp, and after a preset time, the first starting switch circuit 121 receives the synchronous starting signal and turns on, the second starting switch circuit 122 turns on, the constant current source 2 discharges to power the LED lamp, and the LED lamp lights up.

[0062] In a specific embodiment, if Figure 3 As shown, the first startup switch circuit 121 includes: a third switch Q3, a fourth switch Q4, a fourth resistor R4, and a fifth resistor R5, wherein the control end of the third switch Q3 receives a synchronous startup signal ( Figure 3 The CTL end is connected to the controller, and the controller sends the synchronous start signal to the third switch Q3 through the CTL end, and its first end is connected to the control end of the fourth switch Q4 through the fifth resistor R5, and its second end is grounded; the fourth switch Q4, its first end is connected to the external power supply voltage (VCC), and its second end is connected to the first end of the second start switch circuit (one end of the sixth resistor R6).

[0063] It should be noted that Figure 3 The third switch Q3 and the fourth switch Q4 in the embodiment are both power devices IGBT, but this is only an example and is not intended to be limiting.

[0064] Specifically, taking the third switch Q3 and the fourth switch Q4 as an example, both of which are power devices IGBT, the synchronous start signal must be a high-level signal. When the third switch Q3 does not receive the synchronous start signal, the control end of the third switch Q3 is pulled low, and the third switch Q3 is disconnected. Since the fourth switch Q4 is an NPN-type IGBT, the fourth switch Q4 is disconnected, and the second end of the sixth resistor R6 outputs a low level to the second start switch; when the third switch Q3 receives the synchronous start signal, the third switch Q3 is turned on, and the control end of the fourth switch Q4 is pulled low. Since the fourth switch Q4 is an NPN-type IGBT, the fourth switch Q4 is turned on, and the second end of the sixth resistor R6 outputs a high level to the second start switch circuit 122.

[0065] In a specific embodiment, if Figure 3As shown, the second startup switch circuit 122 includes: a fifth switch Q5, a sixth resistor R6 and a seventh resistor R7. The fifth switch Q5 has a control end connected to the second end of the first startup switch circuit 121 through the sixth resistor R6, and a control end connected to the second end of the constant current source 2 through the seventh resistor R7, a first end connected to the second end of the LED lamp, and a second end connected to the second end of the constant current source 2.

[0066] It should be noted that Figure 3 The fifth switch Q5 in the embodiment is a power device MOSFET, but this is only an example and is not intended to be limiting.

[0067] Specifically, when the first startup switch circuit 121 is turned off, that is, the third switch Q3 and the fourth switch Q4 are both turned off, the control end of the fifth switch Q5 inputs a low level, that is, the divided voltage of the sixth resistor R6 and the seventh resistor R7 is less than the threshold voltage of the fifth switch Q5, the fifth switch Q5 is still in a disconnected state, the 2nd foot of the interface CN1 is disconnected from the second end of the constant current source 2, and the LED lamp cannot be lit; when the first startup switch circuit 121 is turned on, that is, the third switch Q3 and the fourth switch Q4 are both turned on, the control end of the fifth switch Q5 inputs a high level, that is, the divided voltage of the sixth resistor R6 and the seventh resistor R7 is greater than the threshold voltage of the fifth switch Q5, the fifth switch Q5 is turned on, the 2nd foot of the interface CN1 is connected to the second end of the constant current source 2, forming a discharge circuit of the constant current source 2, and the LED lamp is lit.

[0068] In a specific embodiment, if Figure 3 As shown, the second startup switch circuit 122 further includes: a first diode D1 , a cathode of which is connected to the first end of the sixth resistor R6 , and an anode of which is connected to the second end of the sixth resistor R6 .

[0069] Specifically, the first diode D1 is connected in parallel with the seventh resistor R7 to protect the second startup switch circuit 122, which is actually to protect the fifth switch Q5. Figure 3 As shown, the second startup switch circuit 122 further includes: a filter capacitor C1, which is used to connect the control end of the fifth switch Q5 and the second end of the fifth switch Q5.

[0070] Specifically, the filter capacitor C1 is set to eliminate the effect of MOSFET turning on caused by voltage changes. Therefore, the gate-drain capacitor Cgd and the gate-source capacitor Cgs exist. Cgd is more sensitive to voltage changes and needs to be connected in parallel to eliminate the effect. If a MOSFET with a small enough Cgd is selected, this capacitor can be omitted.

[0071] Example 2

[0072] The embodiment of the present invention provides a constant current deep dimming power supply, such as Figure 5As shown, it includes: the synchronous starting circuit 1 and the constant current source 2 of embodiment 1.

[0073] like Figure 5 As shown, the constant current source 2 has a first end connected to the first end of the LED lamp, and a second end connected to the first end of the synchronous starting circuit 1; the output voltage of the constant current source 2 will not immediately reach the starting voltage of the LED lamp, and its voltage rise time is determined by the characteristics of its internal components.

[0074] like Figure 5 As shown, the synchronous start circuit 1 has a second end connected to the second end of the LED lamp, a third end connected to the enable end of the constant current source 2, a fourth end inputting a synchronous start signal, and a fifth end connected to an external power supply voltage.

[0075] Specifically, when the output voltage of the constant current source 2 does not reach the starting voltage of the LED lamp, the synchronous starting circuit 1 is disconnected; when the output voltage of the constant current source 2 reaches the starting voltage of the LED lamp, the synchronous starting circuit 1 outputs a power-off signal, and the constant current source 2 no longer outputs current; from the moment the constant current source 2 starts to output voltage, after a preset time, the synchronous starting circuit 1 receives the synchronous starting signal, and the constant current source 2 discharges to power the LED lamp.

[0076] It should be noted that the constant current source 2 in Embodiment 2 is actually the constant current source in Embodiment 1, so the two constant current sources have the same function and structure.

[0077] Specifically, the synchronous start circuit 1 realizes two functions: 1. When the output voltage of the constant current source 2 reaches the start voltage of the LED lamp, the constant current source 2 is controlled to stop outputting current. 2. When the synchronous start signal is received again, a discharge circuit of the constant current source 2 is formed to supply power to the LED lamp. The above functions have been described in detail in Embodiment 1 and will not be repeated here.

[0078] In a specific embodiment, if Figure 6 As shown, the constant current source 2 includes: a voltage conversion circuit 21 and an electrolytic capacitor C2, wherein the voltage conversion circuit 21, a first end thereof is connected to the first end of the electrolytic capacitor C2 and the first end of the LED lamp, a second end thereof is connected to the second end of the electrolytic capacitor C2 and the first end of the synchronous start circuit 1, and an enable end thereof is connected to the third end of the synchronous start circuit 1; when the voltage conversion circuit 21 receives a charging signal, the voltage conversion circuit 21 charges the electrolytic capacitor C2;

[0079] Specifically, the voltage conversion circuit 21 can be a BUCK circuit. When the voltage of the electrolytic capacitor C2 does not reach the starting voltage of the LED lamp, the synchronous starting circuit 1 is disconnected; when the voltage of the electrolytic capacitor C2 reaches the starting voltage of the LED lamp, the synchronous starting circuit 1 outputs a power-off signal, and the voltage conversion circuit 21 no longer charges the electrolytic capacitor C2; after a preset time from the time the voltage conversion circuit 21 receives the charging signal, the synchronous starting circuit 1 receives the synchronous starting signal, and the electrolytic capacitor C2 discharges to power the LED lamp.

[0080] The working principle of the voltage conversion circuit 21 and the electrolytic capacitor C2 is actually the same as the working principle of the BUCK circuit and the electrolytic capacitor C2 in the first embodiment, and will not be described in detail here.

[0081] For example, when the voltage conversion circuit 21 is a BUCK circuit, its topology is as follows: Figure 7 shown. Figure 7 In the embodiment, the DC-DC chip N1, the eighth resistor R8, the second diode D2, the inductor L1, and the sixth switch Q6 form a BUCK circuit to output a constant current to charge the electrolytic capacitor C2.

[0082] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the scope of protection of the invention.

Claims

1. A synchronous starting circuit, characterized in that: The synchronous starting circuit (1) is connected to a constant current source (2) of an LED lamp at the front stage, and is connected to the LED lamp at the rear stage. The synchronous starting circuit (1) comprises: an enabling switch circuit (11) and a starting switch circuit (12), wherein: A constant current source (2), a first end of which is connected to a first end of the LED lamp; An enabling switch circuit (11), wherein a control end thereof is connected to the second end of the constant current source (2), a first end thereof is connected to the second end of the LED lamp, and a second end thereof is connected to the enabling end of the constant current source (2); A starting switch circuit (12), whose control end receives a synchronous starting signal, whose first end is connected to an external power supply voltage, whose second end is connected to the second end of the constant current source (2), and whose third end is connected to the second end of the LED lamp; the synchronous starting signal is used to turn on the starting switch circuit (12) of the synchronous starting circuit (1) of each LED lamp, so as to control the constant current source (2) of each LED lamp to discharge simultaneously; When the output voltage of the constant current source (2) does not reach the starting voltage of the LED lamp, the enabling switch circuit (11) and the starting switch circuit (12) are both disconnected; When the output voltage of the constant current source (2) reaches the starting voltage of the LED lamp, the enabling switch circuit (11) is turned on to output a power-off signal, and the power-off signal is used to control the constant current source (2) to stop outputting current; Taking the moment when the constant current source (2) starts to output voltage as the starting point, after a preset time, the start switch circuit (12) receives a synchronous start signal, the start switch circuit (12) is turned on, and the constant current source (2) discharges to supply power to the LED lamp.

2. The synchronous starting circuit according to claim 1, characterized in that: The enabling switch circuit (11) comprises: a first enabling switch circuit (111) and a second enabling switch circuit (112), wherein: A first enabling switch circuit (111), whose control end is connected to the second end of the constant current source (2), whose first end is connected to the second end of the LED lamp, and whose second end is connected to the control end of the second enabling switch circuit (112); A second enabling switch circuit (112), a first end of which is connected to the enabling end of the constant current source (2), and a second end of which is grounded; When the output voltage of the constant current source (2) does not reach the starting voltage of the LED lamp, the first enabling switch circuit (111) and the second enabling switch circuit (112) are both disconnected; When the output voltage of the constant current source (2) reaches the starting voltage of the LED lamp, the first enabling switch circuit (111) and the second enabling switch circuit (112) are both turned on, and the first end of the second enabling switch circuit (112) outputs a power-off signal.

3. The synchronous starting circuit according to claim 2, characterized in that: The first enabling switch circuit (111) comprises: a first resistor (R1) and a first switch (Q1), wherein: A first switch (Q1), whose control end is connected to the second end of the constant current source (2) through the first resistor (R1), whose first end is connected to the second end of the LED lamp, and whose second end is connected to the control end of the second enabling switch circuit (112).

4. The synchronous starting circuit according to claim 2, characterized in that: The second enabling switch circuit (112) comprises: a second resistor (R2) and a second switch (Q2), wherein: A second switch (Q2), whose control end is connected to the second end of the first enabling switch circuit (111) through the second resistor (R2), whose first end is connected to the enabling end of the constant current source (2), and whose second end is grounded.

5. The synchronous starting circuit according to claim 4, characterized in that: The second enabling switch circuit (112) further includes: A third resistor (R3); The control end of the second switch (Q2) is also grounded through the third resistor (R3).

6. The synchronous starting circuit according to claim 1, characterized in that: The startup switch circuit (12) comprises: a first startup switch circuit (121) and a second startup switch circuit (122), wherein: A first start switch circuit (121), whose control end receives a synchronous start signal, whose first end is connected to an external power supply voltage, and whose second end is connected to a first end of the second start switch circuit (122); A second starting switch circuit (122), a second end of which is connected to the second end of the LED lamp, and a third end of which is connected to the second end of the constant current source (2); When the output voltage of the constant current source (2) does not reach the starting voltage of the LED lamp, the first starting switch circuit (121) and the second starting switch circuit (122) are both disconnected; When the output voltage of the constant current source (2) reaches the starting voltage of the LED lamp, after a preset time, the first starting switch circuit (121) receives a synchronous starting signal and turns on, the second starting switch circuit (122) turns on, and the constant current source (2) discharges to supply power to the LED lamp.

7. The synchronous starting circuit according to claim 6, characterized in that: The first startup switch circuit (121) comprises: a third switch (Q3), a fourth switch (Q4), a fourth resistor (R4), and a fifth resistor (R5), wherein: a third switch (Q3), whose control end receives the synchronous start signal through the fourth resistor (R4), whose first end is connected to the control end of the fourth switch (Q4) through the fifth resistor (R5), and whose second end is grounded; A fourth switch (Q4) has a first end connected to an external power supply voltage and a second end connected to a first end of the second start switch circuit (122).

8. The synchronous starting circuit according to claim 6, characterized in that: The second startup switch circuit (122) comprises: a fifth switch (Q5), a sixth resistor (R6) and a seventh resistor (R7), wherein: A fifth switch (Q5), whose control end is connected to the second end of the first starting switch circuit (121) through the sixth resistor (R6), whose control end is also connected to the second end of the constant current source (2) through the seventh resistor (R7), whose first end is connected to the second end of the LED lamp, and whose second end is connected to the second end of the constant current source (2).

9. The synchronous starting circuit according to claim 8, characterized in that: The second startup switch circuit (122) further includes: A first diode (D1) has a cathode connected to the first end of the sixth resistor (R6) and an anode connected to the second end of the sixth resistor (R6).

10. The synchronous starting circuit according to claim 9, characterized in that: The second startup switch circuit (122) further includes: A filter capacitor (C1) is used to connect the control end of the fifth switch (Q5) and the second end of the fifth switch (Q5).

11. A constant current deep dimming power supply, characterized in that: include: The synchronous starting circuit (1) and the constant current source (2) according to any one of claims 1 to 10, wherein: A constant current source (2), a first end of which is connected to a first end of the LED lamp, and a second end of which is connected to a first end of the synchronous starting circuit (1); A synchronous start circuit (1), the second end of which is connected to the second end of the LED lamp, the third end of which is connected to the enable end of the constant current source (2), the fourth end of which inputs a synchronous start signal, and the fifth end of which is connected to an external power supply voltage; When the output voltage of the constant current source (2) does not reach the starting voltage of the LED lamp, the synchronous starting circuit (1) is disconnected; When the output voltage of the constant current source (2) reaches the starting voltage of the LED lamp, the synchronous starting circuit (1) outputs a power-off signal, and the constant current source (2) no longer outputs current; From the moment when the constant current source (2) starts to output voltage, after a preset time, the synchronous start circuit (1) receives a synchronous start signal, and the constant current source (2) discharges to supply power to the LED lamp.

12. The constant current deep dimming power supply according to claim 11, characterized in that: The constant current source (2) comprises: a voltage conversion circuit (21) and an electrolytic capacitor (C2), wherein: A voltage conversion circuit (21), wherein a first end of the voltage conversion circuit (21) is connected to a first end of the electrolytic capacitor (C2) and a first end of the LED lamp, a second end of the voltage conversion circuit (21) is connected to a second end of the electrolytic capacitor (C2) and a first end of the synchronous starting circuit (1), and an enabling end of the voltage conversion circuit (21) is connected to a third end of the synchronous starting circuit (1); When the voltage conversion circuit (21) receives a charging signal, the voltage conversion circuit (21) charges the electrolytic capacitor (C2); When the voltage of the electrolytic capacitor (C2) does not reach the starting voltage of the LED lamp, the synchronous starting circuit (1) is disconnected; When the voltage of the electrolytic capacitor (C2) reaches the starting voltage of the LED lamp, the synchronous starting circuit (1) outputs a power-off signal, and the voltage conversion circuit (21) no longer charges the electrolytic capacitor (C2); After a preset time has passed since the voltage conversion circuit (21) received the charging signal, the synchronous start circuit (1) receives the synchronous start signal, and the electrolytic capacitor (C2) discharges to supply power to the LED lamp.

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