Wide-voltage constant-current output circuit

Abstract

The utility model discloses a wide-voltage constant-current output circuit, a low-voltage output power supply circuit, a low-voltage reference circuit and a negative feedback constant-current control circuit are arranged between a power supply end and a grounding end of the wide-voltage constant-current output circuit, the low-voltage output power supply circuit is arranged between the power supply end and the low-voltage reference circuit, and the negative feedback constant-current control circuit is arranged between the low-voltage reference circuit and the negative feedback constant-current control circuit. The negative feedback constant-current control circuit is arranged between the power supply end and the grounding end, and the low-voltage reference circuit is connected with the negative feedback constant-current control circuit and the grounding end. No matter how the high voltage input by the power supply end changes, the low-voltage output power supply circuit changes the input high voltage HV and then outputs stable low voltage LV, and outputs stable reference voltage Vref to the low-voltage reference circuit. And finally, stable constant current is output through the negative feedback constant current control circuit.

Description

Technical Field:

[0001] The utility model relates to the technical field of LED lamp circuits, and particularly refers to a wide-voltage constant-current output circuit applicable to LED lamp strings. Background Art:

[0002] LED lighting lamps have been widely used in various fields, such as products composed of several LED lamp cores like LED lamp strings and LED lamp panels. In order to ensure the normal and stable operation of such products, it is necessary to control the working current of the LED to achieve the constant-current output of the circuit. However, considering the voltage when the LED conducts and operates, the output circuit should have a wide-voltage input.

[0003] See the Chinese utility model patent with the patent number 202020686709.2, which discloses an LED lamp circuit with an ultra-wide input voltage, including: a wide-voltage control module, a rectification module, a power conversion module, a linear constant-current output module, and an LED load. The wide-voltage control module is used to play a role in stabilizing the output when the input voltage changes, including a pulse-width modulation component and a pulse-width modulation chip. The output end of the pulse-width modulation chip is connected to the control end of the pulse-width modulation component to control the duty cycle of the pulse-width modulation component; the rectification module is connected to the wide-voltage control module; the output end of the rectification module is connected to the input end of the power conversion module; the input end of the linear constant-current output module is connected to the output end of the power conversion module; the output end of the linear constant-current output module is connected to the LED load.

[0004] See the Chinese invention patent with the patent number 201610055173.2, which discloses an LED constant-current drive power supply with a wide input voltage range of 120 - 347VAC, including an AC input unit, a dual FLY-BUCK unit, a power factor adjustment unit, a wide-voltage startup unit, and an output constant-current source unit. The AC input unit includes an EMC filter processing circuit and a bridge full-wave rectifier connected in sequence. The input end of the EMC filter processing circuit is connected to the power supply grid, and the output end of the bridge full-wave rectifier is connected to the dual FLY-BUCK unit, the power factor adjustment unit, and the wide-voltage startup unit; the power factor adjustment unit and the wide-voltage startup unit are connected to the dual FLY-BUCK unit. The dual FLY-BUCK unit includes a single-stage PFC control circuit, a negative feedback sampling circuit, and a dual FLY-BUCK power conversion circuit. The output end of the dual FLY-BUCK power conversion circuit is connected to the output constant-current source unit, and the output end of the output constant-current source unit is connected to the LED product. This LED constant-current drive power supply achieves the indicators that the PF value is not less than 0.9 and the THD value is not greater than 20 when the input is in the full range and the output load is not less than 50%.

[0005] In the above two technical solutions, the circuit design is relatively complex and not applicable to LED string products. In order to overcome the deficiencies of existing products, the inventor of the present utility model has proposed the following technical solution through continuous research and development. Summary of the Utility Model:

[0006] The technical problem to be solved by the present utility model is to overcome the deficiencies of the prior art and provide a wide-voltage constant-current output circuit applicable to LED strings.

[0007] To solve the above technical problem, the present utility model adopts the following technical solution: A wide-voltage constant-current output circuit, between the power supply terminal and the ground terminal of the wide-voltage constant-current output circuit, there are included: a low-voltage output power supply circuit, a low-voltage reference circuit, and a negative-feedback constant-current control circuit. Among them, the low-voltage output power supply circuit is arranged between the power supply terminal and the low-voltage reference circuit, the negative-feedback constant-current control circuit is arranged between the power supply terminal and the ground terminal, and the low-voltage reference circuit is connected to the negative-feedback constant-current control circuit and the ground terminal.

[0008] Furthermore, in the above technical solution, the low-voltage output power supply circuit includes: a high-voltage input terminal HV, a first N-type MOS transistor N1 connected to the high-voltage input terminal HV, a second N-type MOS transistor N2, a third N-type MOS transistor N3 and a fourth N-type MOS transistor N4 connected to the first N-type MOS transistor N1, and the low voltage is output from the S pole of the second N-type MOS transistor N2.

[0009] Furthermore, in the above technical solution, the second N-type MOS transistor N2 is a high-voltage-resistant depletion-type N-type MOS transistor.

[0010] Furthermore, in the above technical solution, the low-voltage reference circuit includes: a fifth N-type MOS transistor N5, a sixth N-type MOS transistor N6, and the reference voltage Vref is output to the negative-feedback constant-current control circuit 3

[0011] Furthermore, in the above technical solution, the fifth N-type MOS transistor N5 is a depletion-type N-type MOS transistor; the sixth N-type MOS transistor N6 is an enhancement-type N-type MOS transistor.

[0012] Furthermore, in the above technical solution, the negative-feedback constant-current control circuit includes: a low-voltage operational amplifier circuit and a seventh N-type MOS transistor N7. Among them, the reference voltage Vref output by the low-voltage reference circuit 2 and the feedback voltage Vfb output from the S pole of the seventh N-type MOS transistor N7 are input from the input terminal of the low-voltage operational amplifier circuit. The output terminal of the low-voltage operational amplifier circuit is connected to the G pole of the seventh N-type MOS transistor N7, and a stable current is output from the S pole of the seventh N-type MOS transistor N7 through a current-setting resistor R.

[0013] Furthermore, in the above technical solution, the seventh N-type MOS transistor N7 is a high-voltage-resistant depletion-type N-type MOS transistor.

[0014] Furthermore, in the above technical solution, the low-voltage reference circuit is connected to a temperature protection circuit.

[0015] The working principle of the present utility model is as follows: Regardless of how the high voltage input at the power supply terminal changes, the input high voltage HV is changed by the low-voltage output power supply circuit and then a stable low voltage LV is output, and a stable reference voltage Vref is output to the low-voltage reference circuit. Finally, a stable constant current is output through the negative feedback constant current control circuit. After adopting the above technical solution, the advantages of the present utility model compared with existing products are as follows: The circuit of the present utility model is simple. Even when the input voltage range at the power supply terminal of the circuit fluctuates within a relatively wide range of 0.6V to 24V, the finally output constant current is still stable enough. Description of the Drawings:

[0016] Figure 1 is the circuit schematic diagram of the present utility model;

[0017] Figure 2 is the circuit diagram of the low-voltage output power supply in the present utility model;

[0018] Figure 3 is the circuit diagram of the low-voltage reference circuit in the present utility model;

[0019] Figure 4 is the circuit diagram of the negative feedback constant current control circuit in the present utility model;

[0020] Figure 5 is the circuit diagram of the low-voltage operational amplifier circuit in the negative feedback constant current control circuit of the present utility model. Detailed Embodiments:

[0021] The present utility model will be further described below in conjunction with specific embodiments and the drawings.

[0022] The present utility model is a wide-voltage constant current output circuit. As shown in Figure 1 the wide-voltage constant current output circuit includes: a low-voltage output power supply circuit 1, a low-voltage reference circuit 2, and a negative feedback constant current control circuit 3.

[0023] The utility model can be made into a current control chip for LED lamp strings and the like. During actual production, the chip has only two ports, namely a power supply terminal and a connection circuit terminal. Among them, the power supply terminal serves both as the input pin of the chip power supply terminal and as the output pin of the load constant current output terminal. That is, the power supply terminal should be able to withstand high-voltage input, such as the power supply withstand voltage requirements of 12V or 24V. At the same time, as the constant current output terminal of the load, when there are too many LEDs connected in series in the load and the constant current output terminal may be lower than 0.7V, the working state of the entire circuit is stable and the function of the constant current output is stable.

[0024] Specifically, the low-voltage output power supply circuit 1 is arranged between the power supply terminal and the low-voltage reference circuit 2, and the negative feedback constant current control circuit 3 is arranged between the power supply terminal and the ground terminal. The low-voltage reference circuit 2 is connected to the negative feedback constant current control circuit 3 and the ground terminal. The working principle of the utility model is as follows: No matter how the high voltage input at the power supply terminal changes, the input high voltage HV is changed by the low-voltage output power supply circuit 1 and then a stable low voltage LV is output, and a stable reference voltage Vref is output to the low-voltage reference circuit 2. Finally, a stable constant current is output through the negative feedback constant current control circuit 3.

[0025] In addition, the low-voltage reference circuit 2 can also be connected to a temperature protection circuit 4, and the circuit is protected against temperature through the temperature protection circuit 4. When the operating temperature is too high, the circuit stops working.

[0026] See Figure 2 As shown, the low-voltage output power supply circuit 1 includes: a high-voltage input terminal HV, a first N-type MOS transistor N1 connected to the high-voltage input terminal HV, a second N-type MOS transistor N2, a third N-type MOS transistor N3 and a fourth N-type MOS transistor N4 connected to the first N-type MOS transistor N1. The low voltage LV is output from the S pole of the second N-type MOS transistor N2. Since the low voltage LV output by the second N-type MOS transistor N2 needs to provide a stable built-in low-voltage power supply for various internal functional modules and needs to withstand high-voltage input, N2 uses a high-voltage depletion-type N-type MOS transistor device.

[0027] The working principle of the low-voltage output power supply circuit 1 is as follows: The voltage at the G terminal of the second N-type MOS transistor N2 = Vgs(N1) + Vgs(N3). Also, since the second N-type MOS transistor N2 is a depletion-type N-type MOS transistor, Vgs(N2) is approximately 0V. Therefore, the voltage at the S terminal of the second N-type MOS transistor N2 is approximately the same as its G terminal, that is, the output LV of this low-voltage output power supply circuit (LDO) 1 is approximately the voltage at the G terminal. The fourth N-type MOS transistor N4 also uses a depletion-type N-type MOS transistor. Since Vgs(N4) = 0, the current flowing through the fourth N-type MOS transistor N4 is constant, and thus the current flowing through the first N-type MOS transistor N1 is also constant, that is, Vgs(N1) is constant. As a result, as the voltage at the HV terminal increases, most of the current flows away from the S terminal of the third N-type MOS transistor N3, and Vgs(N3) is in the saturation region state, and the range of the current flowing through it is several tens to 200 μA. For the third N-type MOS transistor N3, W / L = 200u / 0.6u, then it can be ensured that: when the high-voltage output terminal HV changes over the full range (for example, a change in voltage difference of 20V), the change in Vgs(N3) is very small, usually only several tens of mV, and the value is approximately constant, thereby achieving the stability of the output LV of this low-voltage output power supply circuit (LDO) 1.

[0028] The low voltage LV output by the low-voltage output power supply circuit 1 is approximately equal to the threshold voltage Vth01 of the first N-type MOS transistor N1 plus the threshold voltage Vth02 of the second N-type MOS transistor N2, that is, LV is approximately equal to Vth01 + Vth02. The key design point of the low-voltage output power supply circuit (LDO) 1 is that the second N-type MOS transistor N2 is a high-voltage-resistant enhancement-type N-type MOS transistor. In this way, its Vgs(N2) can be as low as 0V at the lowest, and the range of Vds(N2) can be 0 to 25V, keeping the voltage at the S terminal of the second N-type MOS transistor N2 stable at Vth01 + Vth02.

[0029] See Figure 3 As shown, the low-voltage reference circuit 2 includes: a fifth N-type MOS transistor N5 and a sixth N-type MOS transistor N6. The fifth N-type MOS transistor N5 is a depletion-type N-type MOS transistor, which acts as a current mirror. Since Vgs(N5) = 0, the current is approximately constant. The sixth N-type MOS transistor N6 is an enhancement-type N-type MOS transistor. Since the current is approximately constant, Vgs(N6) is also constant.

[0030] This low-voltage reference circuit 2 can be adjusted to have a minimum operating voltage in the range of 0.6V ± 50mV by connecting different numbers of N-type MOS transistors in parallel. At the same time, since the LV output from the low-voltage output power supply circuit 1 has good consistency over the full voltage range and the voltage fluctuation amplitude is not large, the reference voltage Vref output by this low-voltage reference circuit 2 is also stable over the full range.

[0031] See Figure 4 As shown, this is the circuit diagram of the negative feedback constant current control circuit 3, where the reference voltage Vref is output to the negative feedback constant current control circuit 3. The negative feedback constant current control circuit 3 includes: a low-voltage operational amplifier circuit 30 and a seventh N-type MOS transistor N7. Among them, the reference voltage Vref output by the low-voltage reference circuit 2 and the feedback voltage Vfb output from the S pole of the seventh N-type MOS transistor N7 are input from the input terminal of the low-voltage operational amplifier circuit 30. The output terminal of the low-voltage operational amplifier circuit 30 is connected to the G pole of the seventh N-type MOS transistor N7, and a stable current is output from the S pole of the seventh N-type MOS transistor N7 through a current setting resistor R.

[0032] In the negative feedback constant current control circuit 3, a low-voltage operational amplifier circuit 30 is used to maintain the stability of negative feedback. When operating under wide voltage conditions, the seventh N-type MOS transistor N7 has a risk of instability. Therefore, the low-voltage reference circuit 2 is used to provide a stable reference potential Vref. As long as the low-voltage operational amplifier circuit 30 can operate normally, a stable feedback voltage Vfb can be obtained finally, and Vfb = Vref.

[0033] Thus, it can be seen that even when the voltage range of the power supply terminal of this circuit fluctuates between 0.6V and 24V, as long as the reference voltage Vref is kept stable enough and the low-voltage operational amplifier circuit 30 is stable enough. Then the final output constant current I = Vfb / R will be stable enough. The stability of the reference voltage Vref over the full range can ensure the stability of the current output over the full range.

[0034] The seventh N-type MOS transistor N7 described above uses a high-voltage-resistant depletion-type Nmos device, and the characteristic is that Vgs(N7) can be as low as 0V at the lowest. In this way, the output voltage of the low-voltage operational amplifier circuit 30 does not need to be very high, and only 0 to 0.5V can meet the application requirements. The change range of Vds(N7) can be 0 to 25V. At the same time, the low-voltage operational amplifier circuit 30 can also ensure that the entire module can have a complete output function even at a minimum voltage of 0.6V.

[0035] See Figure 5 As shown, this is an embodiment of the low-voltage operational amplifier circuit 30 in the present invention, where Figure 5 P1 in it is a bias current mirror Ibias, which can be as low as 0.5uA at the lowest. P2 and P3 are a pair of low-threshold P-type MOS transistors. P2 and P3 can adopt a large-size tube structure design, which can further reduce the overall operating voltage of the low-voltage operational amplifier circuit 30. In order to ensure that the output Vout of the low-voltage operational amplifier circuit 30 can meet the wide swing output (RailtoRail) at low voltages, a second-order operational amplifier can be used in this embodiment. The N-type MOS transistor N8 is designed into a large-size tube structure, which is also to meet the low-voltage requirements.

[0036] Certainly, the above are only specific embodiments of the present utility model and are not intended to limit the scope of implementation of the present utility model. Any equivalent changes or modifications made according to the structure, features, and principles described in the scope of the patent application of the present utility model shall be included within the scope of the patent application of the present utility model.

Claims

1. A wide voltage constant current output circuit, characterized in that: The wide voltage constant current output circuit comprises, between the power supply end and the ground end: a low voltage output power supply circuit (1), a low voltage reference circuit (2), and a negative feedback constant current control circuit (3), wherein the low voltage output power supply circuit (1) is arranged between the power supply end and the low voltage reference circuit (2), the negative feedback constant current control circuit (3) is arranged between the power supply end and the ground end, and the low voltage reference circuit (2) is connected to the negative feedback constant current control circuit (3) and the ground end.

2. A wide voltage constant current output circuit according to claim 1, characterized in that: The low-voltage output power supply circuit (1) comprises: a high-voltage input terminal HV, a first N-type MOS transistor (N1) connected to the high-voltage input terminal HV, a second N-type MOS transistor (N2), a third N-type MOS transistor (N3) and a fourth N-type MOS transistor (N4) connected to the first N-type MOS transistor (N1); a low voltage LV is output from the S pole of the second N-type MOS transistor (N2) to a low-voltage reference circuit (2).

3. A wide voltage constant current output circuit according to claim 2, characterized in that: The second N-type MOS tube (N2) is a high-voltage-resistant depletion-type N-type MOS tube.

4. A wide voltage constant current output circuit according to claim 1, characterized in that: The low voltage reference circuit (2) comprises: a fifth N-type MOS transistor (N5) and a sixth N-type MOS transistor (N6); the reference voltage Vref is output to a negative feedback constant current control circuit (3).

5. A wide voltage constant current output circuit according to claim 4, characterized in that: The fifth N-type MOS transistor (N5) is a depletion-type N-type MOS transistor; and the sixth N-type MOS transistor (N6) is an enhancement-type N-type MOS transistor.

6. A wide voltage constant current output circuit according to claim 4, characterized in that: The negative feedback constant current control circuit (3) comprises: a low voltage operational amplifier circuit (30) and a seventh N-type MOS transistor (N7), wherein a reference voltage Vref output by a low voltage reference circuit (2) and a feedback voltage Vfb output by an S-pole of the seventh N-type MOS transistor (N7) are input from an input end of the low voltage operational amplifier circuit (30), an output end of the low voltage operational amplifier circuit (30) is connected to a G-pole of the seventh N-type MOS transistor (N7), and an S-pole of the seventh N-type MOS transistor (N7) outputs a stable current after passing through a current setting resistor R.

7. A wide voltage constant current output circuit according to claim 6, characterized in that: The seventh N-type MOS tube (N7) is a high-voltage-resistant depletion-type N-type MOS tube.

8. A wide voltage constant current output circuit according to any one of claims 1 to 7, characterized in that: The low voltage reference circuit (2) is connected to a temperature protection circuit (4).

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