An automatic current-sharing buck constant-current drive circuit applicable to two LED strip lights

Abstract

The present invention relates to the technical field of LED strip control, and in particular to an automatic current-sharing step-down constant current driving circuit applicable to two LED strips, which includes a constant current driving module, a first power supply module, a second power supply module, a switching module, a power supply module, and a balance transformer. The constant current driving module is used to control the on / off of the switching module. When the switching module is turned on, the power supply module charges the energy storage inductor through the series connection of two windings of the energy storage inductor in the first power supply module and the second power supply module, and supplies power to the two LED strips at the same time. When the switching module is turned off, the two windings of the energy storage inductor in the first power supply module and the second power supply module discharge respectively to supply power to the two LED strips. Due to the effect of the balance transformer, the two windings of the energy storage inductor finish discharging at the same time, thus ensuring that the currents of the two LED strips are equal.

Description

Technical Field

[0001] The present invention relates to the technical field of LED strip control, and in particular to an automatic current-sharing step-down constant current drive circuit applicable to two LED strips. Background Art

[0002] At present, the step-down constant current drive circuit of LED strips has been widely applied in high-voltage and low-current applications, and has the advantages of high efficiency and good EMC. However, when LED strips are connected in parallel, the current of each LED strip cannot be equal. In addition, since LED strips have a negative temperature characteristic, the current deviation between the parallel-connected LED strips will become larger and larger, resulting in a risk of overcurrent burning of the LED strip with a large current. Therefore, the step-down constant current drive circuit can only drive one LED strip. For the case of controlling two LED strips, the current method is to connect the two LED strips in series and drive and use them as one LED strip.

[0003] However, the above method of connecting LED strips in series will cause the total voltage of the two LED strips to be too high, thus posing higher requirements for circuit insulation and safety, and making it unacceptable to some customers. Summary of the Invention

[0004] Based on the above problems, the present invention aims to provide an automatic current-sharing step-down constant current drive circuit applicable to two LED strips.

[0005] To solve the above technical problems, the present invention adopts the following technical solutions:

[0006] An automatic current-sharing step-down constant current drive circuit applicable to two LED strips provided by the present invention includes a constant current drive module, a first power supply module, a second power supply module, a switch module, a power supply module, a storage inductor, and a balance transformer. The first power supply module includes a first filter capacitor, a first storage winding, a first balance winding, and a first freewheeling diode. The second power supply module includes a second filter capacitor, a second storage winding, a second balance winding, and a second freewheeling diode. The constant current drive module is used to control the on-off of the switch module. The first storage winding and the second storage winding are both arranged on the storage inductor, and the first balance winding and the second balance winding are both arranged on the balance transformer. The first power supply module and the second power supply module are respectively externally connected to different LED strips;

[0007] When the switch module is turned on, the power supply module supplies power to the LED strips connected to the first power supply module and the second power supply module respectively, and the power supply module also charges the storage inductor through the first storage winding and the second storage winding, and the charging current flows into the same-named ends of the first storage winding and the second storage winding respectively;

[0008] When the switch module is turned off, the first energy storage winding discharges to an LED light bar through the first balancing winding and the first freewheeling diode, and the second energy storage winding discharges to another LED light bar through the second balancing winding and the second freewheeling diode. The balancing transformer is used to balance the voltage difference between the two LED light bars to ensure that the two windings of the energy storage inductor discharge simultaneously.

[0009] Further, the first balancing winding and the second balancing winding have the same name ends;

[0010] When the energy storage inductor discharges, the discharge current of the first energy storage winding flows into the first balancing winding through the same name end of the first balancing winding, and the discharge current of the second energy storage winding flows out of the second balancing winding through the same name end of the second balancing winding.

[0011] Further, the switch module includes a switching transistor and a sampling resistor. The switching transistor has a control terminal and two switching terminals. The constant current driving module is connected to the control terminal and controls the on-off between the two switching terminals through the control terminal. The two switching terminals are respectively connected to the first power supply module and the second power supply module. The sampling resistor is connected in series to the charging circuit, one end of the sampling resistor is grounded, and the constant current driving module is used to collect the voltage value of the sampling resistor and control the current flowing through the external LED light bar by controlling the voltage value of the sampling resistor.

[0012] The beneficial effects of the present invention: When the switch module is turned on, the power supply module charges the first power supply module and the second power supply module, and supplies power to the two LED light bars at the same time; when the switch module is turned off, the first power supply module and the second power supply module discharge respectively, and the balancing transformer is used to keep the discharge currents of the two the same, achieving a current sharing effect, thereby making the currents of the two LED light bars equal and ensuring the working life of the LED light bars.

[0013] Since one end of the sampling resistor is grounded, the voltage of one LED light bar with respect to the ground is the positive light bar voltage, and the voltage of the other LED light bar with respect to the ground is the negative light bar voltage. In this way, the absolute value of the voltage of the light bar with respect to the ground is not high, ensuring the insulation requirements of the system. Description of the Drawings

[0014] Figure 1 is a schematic diagram of the present invention.

[0015] Figure 2 is a simplified circuit diagram of the present invention when the switch module is turned on.

[0016] Figure 3 is a simplified circuit diagram of the present invention when the switch module is turned off.

[0017] Reference numerals: 1 - constant current driving module, 2 - first power supply module, 3 - second power supply module, 4 - switching module, 5 - power supply module, C1 - first filter capacitor, C2 - second filter capacitor, D1 - first freewheeling diode, D2 - second freewheeling diode, L - energy storage inductor, M1 - first balancing winding, M2 - second balancing winding, N1 - first energy storage winding, N2 - second energy storage winding, Q - switching transistor, R - sampling resistor, T - balancing transformer. Detailed implementation manners

[0018] For the convenience of those skilled in the art to understand, the present invention will be further described below in conjunction with embodiments and drawings. The content mentioned in the implementation manners is not a limitation to the present invention. The present invention will be described in detail below with reference to the drawings.

[0019] As Figure 1 shown, an automatic current-sharing step-down constant current driving circuit applicable to two LED light strips provided by the present invention includes a constant current driving module 1, a first power supply module 2, a second power supply module 3, a switching module 4, a power supply module 5, an energy storage inductor L, and a balancing transformer T. The first power supply module 2 includes a first filter capacitor C1, a first energy storage winding N1, a first balancing winding M1, and a first freewheeling diode D1. The second power supply module 3 includes a second filter capacitor C2, a second energy storage winding N2, a second balancing winding M2, and a second freewheeling diode D2. The constant current driving module 1 is used to control the on-off of the switching module 4. The first energy storage winding N1 and the second energy storage winding N2 are both arranged on the energy storage inductor L. The first balancing winding M1 and the second balancing winding M2 are both arranged on the balancing transformer T. The first power supply module 2 and the second power supply module 3 are respectively externally connected to different LED light strips.

[0020] The first power supply module 2 and the second power supply module 3 of the present invention are respectively connected to different LED light strips. Specifically, the first balancing winding M1, the first energy storage winding N1, the first freewheeling diode D1, and the first filter capacitor C1 are connected in series, and the first filter capacitor C1 is connected in parallel with the external LED light strip. The second balancing winding M2, the second energy storage winding N2, the second freewheeling diode D2, and the second filter capacitor C2 are connected in series, and the second filter capacitor C2 is connected in parallel with another external LED light strip. In this connection manner, the first filter capacitor C1 and the second filter capacitor C2 are used to filter the ripples in the current flowing through the LED light strip, so as to ensure the stable operation of the LED light strip.

[0021] The working principle of the present invention is as follows: As Figure 2 shown, when the switching module 4 is turned on, the power supply module 5 supplies power to the LED light strips connected by the first power supply module 2 and the second power supply module 3 respectively. At the same time, the power supply module 5 also charges the energy storage inductor L through the first energy storage winding N1 and the second energy storage winding N2, and the charging currents flow into the same-name ends of the first energy storage winding N1 and the second energy storage winding N2 respectively.

[0022] As Figure 3 shown, when the switch module 4 is turned off, the first energy storage winding N1 discharges to the first LED light bar through the first balancing winding M1 and the first freewheeling diode D1, and the second energy storage winding N2 discharges to the second LED light bar through the second balancing winding M2 and the second freewheeling diode D2. The balancing transformer T is used to balance the voltage difference between the two LED light bars to ensure that the two windings of the energy storage inductor L discharge completely at the same time.

[0023] The effect of the balancing transformer T is as follows: Due to reasons such as manufacturing processes and materials, the voltages of the two LED light bars are necessarily different. Therefore, when the energy storage inductor L discharges, the winding voltage is clamped by the lower LED voltage, resulting in all the energy flowing to the low-voltage LED light bar and causing overcurrent. At this time, because the present invention has the balancing transformer T, the voltage difference between the LED light bars is borne by the balancing windings of the balancing transformer T. At this time, the winding voltage of the balancing transformer T is half of the voltage difference between the two LED light bars. Since the voltages of the two windings of the energy storage inductor L are equal, which is the voltage of the lowest LED light bar plus half of the voltage difference between the two LED light bars, that is, the balancing transformer T transfers the energy that the low-voltage LED light bar does not need to the high-voltage LED light bar, ensuring that the discharge voltages of the two windings of the energy storage inductor are equal, thus achieving the effect of synchronous discharge.

[0024] In this embodiment, the first balancing winding M1 and the second balancing winding M2 have the same name ends. The current output by the first energy storage winding N1 flows in the direction of flowing into the first balancing winding M1 through the same name end of the first balancing winding M1, and the current of the second energy storage winding N2 flows in the direction of flowing out of the second balancing winding M2 through the same name end of the second balancing winding M2. Through the connection of the above same name ends, the balancing transformer T can ensure the effect of balancing the equal discharge of the two power supply modules.

[0025] In this embodiment, the switch module 4 includes a switching transistor Q and a sampling resistor R. The switching transistor Q has a control end and two switching ends. The constant current driving module 1 is connected to the control end and controls the on-off between the two switching ends through the control end. The two switching ends are respectively connected to the first power supply module 2 and the second power supply module 3. The sampling resistor R is connected in series to the charging circuit, and one end of the sampling resistor is grounded. The constant current driving module 1 is used to collect the voltage value of the sampling resistor R, and the constant current driving module 1 can control the LED current only by changing the voltage value of the sampling resistor R.

[0026] Since one end of the sampling resistor is grounded, the voltage of one LED strip with respect to ground is a positive strip voltage, and the voltage of the other LED strip with respect to ground is a negative strip voltage. Therefore, the absolute value of the voltage of the LED strip with respect to ground is not high, ensuring the insulation requirements of the system. In the prior art, since the two strips are directly connected in series and driven as one strip, the voltage of the LED strip with respect to ground in the prior art is the sum of the voltages of the two positive strips, which is one strip voltage higher than that of the present invention.

[0027] Obviously, compared with the prior art, the present invention has lower requirements for insulation and thus has more advantages.

[0028] In actual use, the switching transistor Q is preferably a MOS transistor. Whether the constant current driving module 1 applies a voltage to the gate (i.e., the control terminal) to determine whether to control the source and drain (i.e., the two switching terminals) to conduct; the sampling resistor R has a sampling effect. The constant current driving module detects the voltage across the sampling resistor. When this voltage reaches the preset control voltage, the voltage applied to the gate is removed, and the source and drain of the MOS transistor are turned off, and the energy storage inductor starts to discharge. When the energy storage inductor finishes discharging, the constant current driving module applies a voltage to the gate of the MOS transistor again to turn on the source and drain of the MOS transistor and start the next charging cycle. In this way, the average value of the current in the energy storage inductor winding is the working current of the LED strip. By controlling the voltage across the sampling resistor, the magnitude of the current in the LED strip can be controlled. Since the charging current and the discharging current in the two windings of the energy storage inductor are exactly equal, the currents in the two LED strips are also equal.

[0029] Specifically, the power supply module 5 and the constant current driving module 1 described in this embodiment are both conventional circuits and will not be elaborated here.

[0030] The above is only a preferred embodiment of the present invention and does not impose any form of limitation on the present invention. Although the present invention is disclosed above in a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art, without departing from the scope of the technical solution of the present invention, when making some changes or modifications using the above-disclosed technical content as equivalent change equivalent embodiments, but as long as it does not depart from the content of the technical solution of the present invention, any simple modification, equivalent change and modification made to the above embodiments according to the technical means of the present invention all fall within the scope of the technical solution of the present invention.

Claims

1. An automatic current-sharing step-down constant-current drive circuit applicable to two LED light bars, characterized in that: It includes a constant current driving module, a first power supply module, a second power supply module, a switching module, a power supply module, a storage inductor, and a balance transformer. The first power supply module includes a first filter capacitor, a first energy storage winding, a first balance winding, and a first freewheeling diode. The second power supply module includes a second filter capacitor, a second energy storage winding, a second balance winding, and a second freewheeling diode. The constant current driving module is used to control the on / off of the switching module. The first energy storage winding and the second energy storage winding are both arranged on the storage inductor, and the first balance winding and the second balance winding are both arranged on the balance transformer. The first power supply module and the second power supply module are respectively externally connected to different LED light strips. When the switching module is turned on, the power supply module supplies power to the LED light strips respectively connected to the first power supply module and the second power supply module, and the power supply module also charges the storage inductor through the first energy storage winding and the second energy storage winding, and the charging current flows into the same-name ends of the first energy storage winding and the second energy storage winding respectively. When the switching module is turned off, the first energy storage winding discharges to one LED light strip through the first balance winding and the first freewheeling diode, and the second energy storage winding discharges to the other LED light strip through the second balance winding and the second freewheeling diode. The first balance winding and the second balance winding have the same-name ends. When the storage inductor discharges, the discharge current of the first energy storage winding flows into the first balance winding through the same-name end of the first balance winding, and the discharge current of the second energy storage winding flows out of the second balance winding through the same-name end of the second balance winding. The switching module includes a switching tube and a sampling resistor. The switching tube has a control end and two switching ends. The constant current driving module is connected to the control end and controls the on / off between the two switching ends through the control end. The two switching ends are respectively connected to the first power supply module and the second power supply module. The sampling resistor is connected in series to the charging circuit, one end of the sampling resistor is grounded, and the constant current driving module is used to collect the voltage value of the sampling resistor and control the current flowing through the external LED light strip by controlling the voltage value of the sampling resistor.

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