LED two-wire dimming power supply circuit

Abstract

The utility model discloses an LED two-line dimming power supply circuit. The VDD end of the main control unit U1 receives voltage, the PWM output end of the main control unit U1 is connected with one end of the resistor R2, the other end of the resistor R2 is connected with the grid electrode of the MOS tube Q1, the source electrode of the resistor R2 is grounded, and the drain electrode of the resistor R2 is connected with the output end; according to the invention, a modulation and demodulation mode can be realized between a constant-voltage power supply and a constant-current power supply, the constant-voltage dimming power supply emits a modulated voltage signal through two output positive and negative wires, and after the DC-to-DC power supply receives the signal, the DC-to-DC power supply outputs the modulated voltage signal to the sampling unit U2, and the sampling end of the sampling unit U2 is connected with the PWM output end of the main control unit U1, and the voltage sampling end of the sampling unit U2 is connected with the output end of the main control unit U1. The dimming signal is extracted through the demodulation circuit, and then the DC-to-DC power supply is controlled to realize dimming, so that the problems that the dimming depth is too small and the dimming frequency is not high are solved.

Description

Technical Field

[0001] The utility model relates to the field of LED power supplies, in particular to an LED two-wire dimming power supply circuit. Background Art

[0002] In some LED lighting applications, such as magnetic track lights, underground lights and other occasions that require constant current dimming, direct input of AC power will bring higher risks or the size of the power supply space is relatively small. At this time, a constant voltage dimming power supply plus multiple DC-to-DC constant current power supplies are needed to achieve dimming applications. The front-stage constant voltage dimming power supply has only two positive and negative wires connected to the rear-stage DC-to-DC constant current power supply. While the front-stage realizes dimming, the rear-stage realizes dimming of the LED lamp according to the signals on the positive and negative output lines.

[0003] There are existing solutions on the market. The front stage uses ordinary constant voltage light strip dimming power supply, and the back stage uses ordinary DC to DC constant current power supply to achieve dimming. The above solution can also achieve dimming, but there are also some problems.

[0004] 1. The minimum brightness of dimming is not low enough, that is, the dimming depth is too shallow;

[0005] 2. The dimming frequency cannot be too high, otherwise there will be noise in some applications;

[0006] 3. If the dimming frequency is too high, it will result in the inability to dim or almost no dimming effect. Utility Model Content

[0007] In order to solve the above problems, the present technical solution provides an LED two-wire dimming power supply circuit.

[0008] To achieve the above purpose, the technical solution is as follows:

[0009] LED two-wire dimming power supply circuit, including;

[0010] A main control unit U1, wherein the VDD terminal of the main control unit U1 receives a voltage, the PWM output terminal thereof is connected to one end of a resistor R2, the other end of the resistor R2 is connected to the gate of the MOS tube Q1, the source thereof is grounded, and the drain thereof is connected to the output terminal;

[0011] The sampling unit U2 has a collection end connected to the PWM output end of the main control unit U1, and a voltage collection end connected to the output end.

[0012] In some embodiments, a capacitor C1 is connected between the positive and negative electrodes of the output terminal.

[0013] In some embodiments, a resistor R1 is disposed between the source and the gate of the MOS transistor Q1.

[0014] In some embodiments, a signal demodulation circuit is further included, which includes a demodulation unit U1, wherein the positive electrode of the light-emitting end of the demodulation unit U1 is connected to a voltage through a resistor, the negative electrode of the light-emitting end is grounded, the VCC end of the demodulation unit U1 is connected to the emitter of the transistor Q1, the base of the transistor Q1 is connected to the voltage VDD through a resistor R2, and the collector thereof is also connected to the voltage VDD;

[0015] The output end of the demodulation unit U1 is connected to the base of the transistor Q2 through the resistor R4, the collector of the transistor Q2 receives the PWM signal, and the emitter of the transistor Q2 is grounded.

[0016] In some embodiments, the VCC terminal of the demodulation unit U1 is also connected to the PWM signal through a resistor R5;

[0017] The output end of the demodulation unit U1 is also grounded via a resistor R3.

[0018] The beneficial effects of this application are:

[0019] The present application can modulate and demodulate between a constant voltage power supply and a constant current power supply. The constant voltage dimming power supply sends a modulated voltage signal through two positive and negative output lines. After the DC-to-DC power supply receives the signal, it extracts the dimming signal through the demodulation circuit, and then controls the DC-to-DC power supply to achieve dimming, thereby solving the problem of too shallow dimming depth and low dimming frequency. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present utility model, the following briefly introduces the drawings required for describing the embodiments.

[0021] Figure 1 It is a schematic diagram of the modulation circuit structure of an embodiment of the utility model;

[0022] Figure 2 It is a schematic diagram of the structure of a signal demodulation circuit according to an embodiment of the utility model;

[0023] Figure 3 It is a schematic diagram of the sampling circuit structure of the second embodiment of the utility model. DETAILED DESCRIPTION

[0024] In order to make the technical problems, technical solutions and beneficial effects solved by the utility model more clear, the utility model is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the utility model and are not used to limit the utility model.

[0025] Please refer to Figure 1 As shown, the LED two-wire dimming power supply circuit includes:

[0026] A main control unit U1, wherein the VDD terminal of the main control unit U1 receives a voltage, the PWM output terminal thereof is connected to one end of a resistor R2, the other end of the resistor R2 is connected to the gate of the MOS tube Q1, the source thereof is grounded, and the drain thereof is connected to the output terminal;

[0027] The sampling unit U2 has a collection end connected to the PWM output end of the main control unit U1, and a voltage collection end connected to the output end.

[0028] The present application adds a set of signal modulation circuits at the output end of the constant voltage power supply, so that a complete PWM dimming signal is generated on the positive and negative lines of the constant voltage power supply output. The main control unit U1 is connected to the MOS tube Q1 through R2, and the modulation signal is generated on the output positive and negative lines Vo+ and Vo- by controlling the opening and closing of Q1. The sampling unit U2 further enhances the integrity of the signal by sampling the PWM signal sent by U1 and the voltage signal on Vo+ and Vo-, and eliminates the interference on the Vo+ and Vo- lines caused by parasitic inductance and capacitance on the line.

[0029] In this embodiment, a capacitor C1 is connected between the positive and negative electrodes of the output end.

[0030] In this embodiment, a resistor R1 is provided between the source and the gate of the MOS transistor Q1.

[0031] refer to Figure 2 A signal demodulation circuit is added to the second-level DCDC circuit, and also includes a signal demodulation circuit, which includes a demodulation unit U1, the positive electrode of the light-emitting end of the demodulation unit U1 is connected to a voltage through a resistor, the negative electrode of the light-emitting end is grounded, the VCC end of the demodulation unit U1 is connected to the emitter of the transistor Q1, the base of the transistor Q1 is connected to the voltage VDD through a resistor R2, and its collector is also connected to the voltage VDD;

[0032] The output end of the demodulation unit U1 is connected to the base of the transistor Q2 through the resistor R4, the collector of the transistor Q2 receives the PWM signal, and the emitter of the transistor Q2 is grounded.

[0033] In this embodiment, the VCC terminal of the demodulation unit U1 is also connected to the PWM signal through the resistor R5;

[0034] The output end of the demodulation unit U1 is also grounded via a resistor R3.

[0035] When Vo+ and Vo- are high levels, the primary side of the optocoupler U1 is turned on, pin 5 of U1 outputs a low level, Q2 is turned off, and the PWM signal is high level, realizing the sampling and conversion of the high levels of Vo+ and Vo-; when Vo+ and Vo- are low levels, the primary side of the optocoupler U1 is turned off, pin 5 of U1 outputs a high level, Q2 is turned on, and the PWM signal is low level, realizing the sampling and conversion of the low levels of Vo+ and Vo-.

[0036] This circuit realizes the signal sampling and conversion of Vo+ and Vo- through the optocoupler U1 and the transistor Q2. The optocoupler U1 isolates the interference of the bad signals on Vo+ and Vo- on the output PWM signal, and realizes the stability of the PWM sampling signal.

[0037] As an example of a sampling circuit, please refer to Figure 3 , C1 is the output capacitor of AC to DC converter. When PWM is a high-level signal, Q1 is turned on, Vo+ and Vo- are connected to the output of AC to DC converter, and the output voltage is normal. At this time, the PWM signal passes through U1, causing Q2 to be turned off; when PWM is a low-level signal, Q1 is turned off, Vo+ and Vo- are disconnected from the output of AC to DC converter, and the PWM signal passes through U1 to turn on Q2. The residual voltage on Vo+ and Vo- is quickly released through R3 and Q2. The voltage drop of Vo+ and Vo- can quickly follow the drop speed of the PWM signal and there is no residual voltage, which provides good conditions for the second-level DC to DC circuit to sample the Vo+ and Vo- voltage signals.

[0038] The above description is only a preferred embodiment of the present application and is not intended to limit the scope of implementation of the present application. Other principles and basic structures that are the same or similar to those of the present application are within the protection scope of the present application.

Claims

1. LED two-wire dimming power supply circuit, characterized in that: include; A main control unit U1, wherein the VDD terminal of the main control unit U1 receives a voltage, the PWM output terminal thereof is connected to one end of a resistor R2, the other end of the resistor R2 is connected to the gate of the MOS tube Q1, the source thereof is grounded, and the drain thereof is connected to the output terminal; The sampling unit U2 has a collection end connected to the PWM output end of the main control unit U1, and a voltage collection end connected to the output end.

2. The LED two-wire dimming power supply circuit according to claim 1, characterized in that: A capacitor C1 is connected between the positive and negative electrodes of the output end.

3. The LED two-wire dimming power supply circuit according to claim 2, characterized in that: A resistor R1 is provided between the source and the gate of the MOS transistor Q1.

4. The LED two-wire dimming power supply circuit according to claim 1, characterized in that: It also includes a signal demodulation circuit, which includes a demodulation unit U1, the positive electrode of the light-emitting end of the demodulation unit U1 is connected to a voltage through a resistor, the negative electrode of the light-emitting end is grounded, the VCC end of the demodulation unit U1 is connected to the emitter of the transistor Q1, the base of the transistor Q1 is connected to the voltage VDD through a resistor R2, and the collector is also connected to the voltage VDD; The output end of the demodulation unit U1 is connected to the base of the transistor Q2 through the resistor R4, the collector of the transistor Q2 receives the PWM signal, and the emitter of the transistor Q2 is grounded.

5. The LED two-wire dimming power supply circuit according to claim 4, characterized in that: The VCC terminal of the demodulation unit U1 is also connected to the PWM signal through the resistor R5; The output end of the demodulation unit U1 is also grounded via a resistor R3.

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