A control circuit for improving BUCK conversion efficiency and linear regulation rate

Abstract

A control circuit for improving BUCK conversion efficiency and linear regulation rate, comprising an input end, wherein the input end outputs a voltage HV+ after passing through a rectifier bridge BD1 and a transformer T1A, and the voltage HV- is grounded through resistors R10 and R11, and a common point of the resistors R10 and R11 is connected to a receiving end of a main control unit U3; and further comprising an operational amplifier unit U2, wherein a forward end of the operational amplifier unit U2 is connected to a voltage VC through resistors R5, R4, and a diode D3 in sequence, and a reverse end is connected to a voltage through resistor R6, an output end of the operational amplifier unit U2 is connected to a gate of a MOS tube Q3 through resistor R7, a source is grounded, and a drain is connected to the receiving end of the main control unit U3 through resistor R9.

Description

Technical Field

[0001] The invention relates to the field of LED power supplies, and in particular to a control circuit for improving BUCK conversion efficiency and linear regulation rate. Background Art

[0002] Currently, the BUCK topology LED power supply within a wide input voltage range has a lower conversion efficiency in the low input voltage range, which causes the LED power supply to have a high temperature at low input voltage and requires the power supply housing to be enlarged, thereby reducing the power density of the power supply and increasing the cost of the LED power supply. Summary of the invention

[0003] In order to solve the above problems, the present technical solution provides a control circuit for improving the BUCK conversion efficiency and linear regulation rate.

[0004] To achieve the above purpose, the technical solution is as follows:

[0005] A control circuit for improving BUCK conversion efficiency and linear regulation rate, comprising an input end, the input end outputs a voltage HV+ after passing through a rectifier bridge BD1 and a transformer T1A, the voltage HV- is grounded through a resistor R10 and a resistor R11, and the common point of the resistor R10 and the resistor R11 is connected to a receiving end of a main control unit U3;

[0006] It also includes an operational amplifier unit U2, the forward end of which is connected to the voltage VC through resistors R5, R4 and diode D3 in sequence, and the reverse end is connected to a voltage through resistor R6. The output end of the operational amplifier unit U2 is connected to the gate of the MOS tube Q3 through resistor R7, the source is grounded, and the drain is connected to the receiving end of the main control unit U3 through resistor R9.

[0007] In some embodiments, a MOS transistor Q4 is further included, wherein the gate of the MOS transistor Q4 is connected to the output end of the operational amplifier unit U2 through a resistor R8, the source is grounded, and the drain is connected to the reverse end of the operational amplifier unit U2 through a resistor R3.

[0008] In some embodiments, the positive terminal of the operational amplifier unit U2 is grounded through the capacitor C1 and the resistor R15, and the resistor R3 is grounded through the resistor R16.

[0009] In some embodiments, the resistor R8 is further connected to the voltage VCC through the resistor R19, the resistor R20 and the resistor R21 in sequence, the resistor R19 is connected to the gate of the MOS tube Q5, the source is grounded, and the drain is connected to the resistor R21;

[0010] It also includes a MOS tube Q6, the gate of the MOS tube Q6 is connected to the resistor R21, the source is grounded, and the drain is connected to the collection end of the main control unit U1 through the resistor R12 and the resistor R14 in sequence.

[0011] In some embodiments, the output end of the main control unit U1 is connected to the gate of the MOS tube Q2, the source is grounded through the resistor R13, and the drain is connected to the output end through the diode D2 and the transformer T1B.

[0012] The beneficial effects of this application are:

[0013] By adopting the circuit of the present application, the conversion efficiency of the BUCK topology LED power supply in the low input voltage range can be improved, and the change of its linear regulation rate can be controlled, so that the temperature of the LED power supply becomes lower at low input voltage, the required power supply housing becomes smaller, the power density of the power supply is improved, the power cost is reduced, and a high-performance energy-saving effect is achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for describing the embodiments are briefly introduced below.

[0015] Figure 1 It is a schematic structural diagram of an embodiment of the present invention. DETAILED DESCRIPTION

[0016] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0017] Please refer to Figure 1 As shown, a control circuit for improving BUCK conversion efficiency and linear regulation rate includes an input end, the input end outputs a voltage HV+ after passing through a rectifier bridge BD1 and a transformer T1A, the voltage HV- is grounded through a resistor R10 and a resistor R11, and the common point of the resistor R10 and the resistor R11 is connected to the receiving end of the main control unit U3;

[0018] It also includes an operational amplifier unit U2, the forward end of which is connected to the voltage VC through resistors R5, R4 and diode D3 in sequence, and the reverse end is connected to a voltage through resistor R6. The output end of the operational amplifier unit U2 is connected to the gate of the MOS tube Q3 through resistor R7, the source is grounded, and the drain is connected to the receiving end of the main control unit U3 through resistor R9.

[0019] In this embodiment, a MOS transistor Q4 is further included. The gate of the MOS transistor Q4 is connected to the output end of the operational amplifier unit U2 through a resistor R8, the source is grounded, and the drain is connected to the reverse end of the operational amplifier unit U2 through a resistor R3.

[0020] In this embodiment, the positive terminal of the operational amplifier unit U2 is grounded through the capacitor C1 and the resistor R15, and the resistor R3 is grounded through the resistor R16.

[0021] In this embodiment, the resistor R8 is also connected to the voltage VCC through the resistor R19, the resistor R20 and the resistor R21 in sequence. The resistor R19 is connected to the gate of the MOS tube Q5, the source is grounded, and the drain is connected to the resistor R21.

[0022] It also includes a MOS tube Q6, the gate of the MOS tube Q6 is connected to the resistor R21, the source is grounded, and the drain is connected to the collection end of the main control unit U1 through the resistor R12 and the resistor R14 in sequence.

[0023] In this embodiment, the output end of the main control unit U1 is connected to the gate of the MOS tube Q2, the source is grounded through the resistor R13, and the drain is connected to the output end through the diode D2 and the transformer T1B.

[0024] If the AC input voltage range of L, N is 200-480VAC rated input, and the power output voltage of LED+, LED- is 210-360VDC, the output voltage RMS value at the HV+ potential is generally controlled at about 755V through the U3 PFC control chip. This results in the conversion efficiency of the BUCK at the rated input of 200-277VAC being lower than that at the rated input of 380VAC-480VAC, especially at the rated input of 200VAC, the conversion efficiency is lower and the temperature is higher. With the circuit of the present invention, when the positive electrode VC potential after rectification of the BD1 bridge stack passes through the D3 anti-backflow diode, and the energy storage of the C2 and C1 capacitors and the R4, R5, R15 resistors divide the voltage to the positive end of the first pin of the U2 operational amplifier is less than the voltage divided by the 5V reference through the R6, R3, R16 resistors to the negative end of the third pin of the U2 operational amplifier, the output end of the fourth pin of the U2 operational amplifier is at a low potential. At this time, the Q3 N-channel MOS tube is not turned on through the voltage division of the R7 and R18 resistors, and the R9 pull-down resistor is disconnected from the GND, so that the HV+ potential increases through the voltage division of the R10 and R11 resistors to the U3 PFC control chip second pin VSENSE, which is greater than the control voltage of VSENSE, so that the U3 PFC control chip controls the HV+ potential to be reduced to 600VDC, that is, the U1 BUCK control chip, the Q2 N-channel MOS, the D2 diode, and the T1 The input voltage HV+ potential of the BUCK topology composed of BUCK transformer, EC2 electrolytic capacitor, etc. is reduced from 755VDC to 600VDC, thereby reducing the eddy current loss of the BUCK topology core and the switching loss of the MOS tube, and the overall efficiency is improved by about 0.5%. This improves the power density of the power supply, reduces the power cost, and plays a good energy-saving role.

[0025] In addition, when the output terminal of the 4th pin of the U2 operational amplifier becomes a low potential to reduce the BUCK input voltage, if the output current of the BUCK topology increases, the Q6 MOS tube can be turned off through the voltage division of the resistors R19, R20, and R22 (the R21 resistor and the Q5 MOS are canceled at this time), and the pull-down path of the R12 resistor is disconnected, thereby correcting the reduction of the BUCK output current; if the output current of the BUCK topology decreases, the Q5 MOS tube can be turned off through the R19 resistor (the R20 resistor is canceled at this time), so that the VCC potential can turn on the Q6 MOS tube through the voltage division of the R21 and R22 resistors, and the R12 resistor is pulled down to the GND ground, thereby correcting the increase of the BUCK output current, and well controlling the problem of the product linear regulation rate, ensuring that the circuit for improving efficiency can be reliably applied in the product.

[0026] In a BUCK power supply within a wide input voltage range, the power efficiency in a low input voltage range is about 1.5% lower than the conversion efficiency in a high input voltage range. By adopting the circuit of the present invention, the conversion efficiency of the LED power supply of the BUCK topology in a low input voltage range can be improved by 0.5%, and its linear regulation rate can be controlled, so that the temperature of the LED power supply in a low input voltage range becomes lower, the required power supply housing becomes smaller, the power density of the power supply is improved, the power cost is reduced, and a good high-performance energy-saving effect is achieved.

[0027] 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. A control circuit for improving BUCK conversion efficiency and linear regulation rate, characterized in that: It includes an input end, the voltage HV+ and the voltage HV- outputted from the input end after passing through the rectifier bridge BD1 and the transformer T1A are grounded through the resistor R10 and the resistor R11, and the common point of the resistor R10 and the resistor R11 is connected to the vsense receiving end of the main control unit U3; It also includes an operational amplifier unit U2, the forward end of which is connected to a voltage VC through a resistor R5, a resistor R4 and a diode D3 in sequence, and the reverse end is connected to a voltage through a resistor R6. The output end of the operational amplifier unit U2 is connected to a gate of a MOS tube Q3 through a resistor R7, the source of the MOS tube Q3 is grounded, and the drain of the MOS tube Q3 is connected to a vsense receiving end of the main control unit U3 through a resistor R9.

2. A control circuit for improving BUCK conversion efficiency and linear regulation rate according to claim 1, characterized in that: It also includes a MOS transistor Q4, a gate of which is connected to the output end of the operational amplifier unit U2 through a resistor R8, a source of which is grounded, and a drain of which is connected to the reverse end of the operational amplifier unit U2 through a resistor R3.

3. A control circuit for improving BUCK conversion efficiency and linear regulation rate according to claim 2, characterized in that: The positive end of the operational amplifier unit U2 is grounded through the capacitor C1 and the resistor R15, and the resistor R3 is grounded through the resistor R16.

4. The control circuit for improving BUCK conversion efficiency and linear regulation rate according to claim 2, characterized in that: The resistor R8 is also connected to the voltage VCC via the resistor R19, the resistor R20 and the resistor R21 in sequence. The resistor R19 is connected to the gate of the MOS tube Q5, the source is grounded, and the drain is connected to the resistor R21. It also includes a MOS tube Q6, the gate of the MOS tube Q6 is connected to the resistor R21, the source is grounded, and the drain is connected to the collection end of the main control unit U1 through the resistor R12 and the resistor R14 in sequence.

5. A control circuit for improving BUCK conversion efficiency and linear regulation rate according to claim 4, characterized in that: The output end of the main control unit U1 is connected to the gate of the MOS tube Q2, the source is grounded through a resistor R13, and the drain is connected to the output end through a diode D2 and a transformer T1B.

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