A non-isolated topology soft start circuit

Abstract

A non-isolated topology soft start circuit comprises an input end HV and an output end, specifically comprising a soft start circuit, wherein the soft start circuit comprises a diode D3 connected to the input end HV at one end, the other end of the diode D3 is connected to one end of a resistor R12, the other end of the resistor R12 is grounded through a capacitor C7, the other end of the resistor R12 is connected to one end of a resistor R15, the other end of the resistor R15 is grounded through a resistor R20 and a capacitor C11 respectively, the other end of the resistor R15 is connected to one end of a voltage regulator tube Z1, the other end of the voltage regulator tube Z1 is grounded through a resistor R21 and a capacitor C9 respectively, the other end of the voltage regulator tube Z1 is also connected to a reference end of a voltage regulator tube U2 through a resistor R18, a first conduction end of the voltage regulator tube U2 receives a voltage through a resistor R14, a second conduction end of the voltage regulator tube U2 is grounded, wherein the first conduction end is also connected to the base of a transistor Q2 through resistors R16 and R17 in sequence, the emitter of the transistor Q2 is grounded, and the collector is connected to an ADMI signal through a resistor R13.

Description

Technical Field

[0001] The invention relates to the field of LED power supplies, and in particular to a non-isolated topology soft start circuit. Background Art

[0002] In traditional LED driver power supplies, when the AC switch of the power supply is turned on, the output lamps will immediately output at full load. At that time, the current and voltage stress of the switch tube will be very large, because △I=C*DV / DT and ε=L*DI / DT. It can be seen from the above formula that as long as the voltage or current change rate is faster, the current and voltage spikes produced will be higher. Therefore, the semiconductor switch tube used will be subjected to considerable voltage or current stress, and the failure rate of the power supply will increase significantly. Summary of the invention

[0003] In order to solve the above problems, the present technical solution provides a non-isolated topology soft start circuit.

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

[0005] A non-isolated topology soft start circuit, comprising:

[0006] A main power circuit, wherein the main power is provided with an input terminal HV and an output terminal, and further comprises a transformer L1, wherein one end of a first coil of the transformer L1 is connected to the positive electrode of the output terminal through a diode D1, the other end of the first coil is connected to the negative electrode of the output terminal, one end of a second coil is connected to one end of a resistor R2, the other end of the resistor R2 is grounded through a capacitor C1 and a resistor R3 respectively, and the other end of the second coil is grounded;

[0007] A control IC circuit includes a main control unit U1, a voltage loop feedback end of the main control unit U1 is connected to the other end of a resistor R2, a signal receiving end of the main control unit U1 receives an ADMI signal through a resistor R10, a driving end of the main control unit U1 is connected to a gate of a MOS tube Q1 through a resistor R6, a source of the MOS tube Q1 is grounded through a sampling resistor RCS1, and a drain is connected to one end of a first coil;

[0008] It also includes a soft start circuit, which includes a diode D3 connected to the input terminal HV at one end, the other end of the diode D3 is connected to one end of a resistor R12, the other end of the resistor R12 is grounded through a capacitor C7, the other end of the resistor R12 is connected to one end of a resistor R15, the other end of the resistor R15 is grounded through a resistor R20 and a capacitor C11, the other end of the resistor R15 is connected to one end of a voltage regulator Z1, the other end of the voltage regulator Z1 is grounded through a resistor R21 and a capacitor C9, the other end of the voltage regulator Z1 is also connected to the reference end of the voltage regulator U2 through a resistor R18, the first conduction end of the voltage regulator U2 receives a voltage through a resistor R14, the second conduction end of the voltage regulator U2 is grounded, wherein the first conduction end is also connected to the base of the transistor Q2 through resistors R16 and R17 in sequence, the emitter of the transistor Q2 is grounded, and the collector is connected to the ADMI signal through a resistor R13.

[0009] In some embodiments, the enable terminal of the main control unit U1 receives a voltage through the resistor R4, and the resistor R4 is grounded through the resistor R11.

[0010] In some embodiments, the PWM dimming signal input terminal of the main control unit U1 receives a PWM signal.

[0011] In some embodiments, the VCC terminal of the main control unit U1 is connected to the input terminal HV through the resistor R5 and the resistor R1, and the VCC terminal is also grounded through the capacitor C2 and the capacitor C3 respectively.

[0012] In some embodiments, the current loop input end of the main control unit U1 is connected to one end of a resistor R9, the other end of the resistor R9 is connected to the gate of the MOS tube Q1 through a resistor R7, and the other end of the resistor R9 is also connected to the sampling resistor RCS1.

[0013] The beneficial effects of this application are:

[0014] This application adds a soft start circuit, which can effectively reduce the failure rate of the power supply, and it is very important to improve product quality. For some primary loads, the quality of the power supply is the core, because the power supply is the heart of the entire power system. Once the power supply fails, the entire system will be paralyzed. Therefore, improving the quality of the power supply has been the goal pursued by the entire power supply industry. At the same time, after adding the soft start circuit, when the output is an LED lamp, the light slowly changes from dark to bright, which is a gradual process. It also has a protective effect on the human eye, preventing the lamp from suddenly becoming brighter. The human eye has a temporary retention effect, which will make people feel uncomfortable and have no eye protection function. After adding the soft start, the light becomes soft and brighter, which has an eye protection effect.

[0015] This application improves the failure rate of the power supply, improves the quality of the power supply, and improves the customer experience and satisfaction. The circuit has high reliability, simple circuit, easy implementation, and lower cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] 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.

[0017] Figure 1 It is a schematic structural diagram of an embodiment of the present invention. DETAILED DESCRIPTION

[0018] 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.

[0019] Please refer to Figure 1 As shown, a non-isolated topology soft start circuit includes:

[0020] A main power circuit, wherein the main power is provided with an input terminal HV and an output terminal, and further comprises a transformer L1, wherein one end of a first coil of the transformer L1 is connected to the positive electrode of the output terminal through a diode D1, the other end of the first coil is connected to the negative electrode of the output terminal, one end of a second coil is connected to one end of a resistor R2, the other end of the resistor R2 is grounded through a capacitor C1 and a resistor R3 respectively, and the other end of the second coil is grounded;

[0021] A control IC circuit includes a main control unit U1, a voltage loop feedback end of the main control unit U1 is connected to the other end of a resistor R2, a signal receiving end of the main control unit U1 receives an ADMI signal through a resistor R10, a driving end of the main control unit U1 is connected to a gate of a MOS tube Q1 through a resistor R6, a source of the MOS tube Q1 is grounded through a sampling resistor RCS1, and a drain is connected to one end of a first coil;

[0022] It also includes a soft start circuit, which includes a diode D3 connected to the input terminal HV at one end, the other end of the diode D3 is connected to one end of a resistor R12, the other end of the resistor R12 is grounded through a capacitor C7, the other end of the resistor R12 is connected to one end of a resistor R15, the other end of the resistor R15 is grounded through a resistor R20 and a capacitor C11, the other end of the resistor R15 is connected to one end of a voltage regulator Z1, the other end of the voltage regulator Z1 is grounded through a resistor R21 and a capacitor C9, the other end of the voltage regulator Z1 is also connected to the reference end of the voltage regulator U2 through a resistor R18, the first conduction end of the voltage regulator U2 receives a voltage through a resistor R14, the second conduction end of the voltage regulator U2 is grounded, wherein the first conduction end is also connected to the base of the transistor Q2 through resistors R16 and R17 in sequence, the emitter of the transistor Q2 is grounded, and the collector is connected to the ADMI signal through a resistor R13.

[0023] In this embodiment, the enable terminal of the main control unit U1 receives a voltage through the resistor R4, and the resistor R4 is grounded through the resistor R11.

[0024] In this embodiment, the PWM dimming signal input terminal of the main control unit U1 receives a PWM signal.

[0025] In this embodiment, the VCC terminal of the main control unit U1 is connected to the input terminal HV through the resistor R5 and the resistor R1, and the VCC terminal is also grounded through the capacitor C2 and the capacitor C3.

[0026] In this embodiment, the current loop input end of the main control unit U1 is connected to one end of a resistor R9, the other end of the resistor R9 is connected to the gate of the MOS tube Q1 through a resistor R7, and the other end of the resistor R9 is also connected to the sampling resistor RCS1.

[0027] Specifically, a non-isolated topology soft start circuit works as follows:

[0028] 001 is the main power circuit, which is a step-down BUCK circuit. HV is the high-voltage DC signal sent after the PFC circuit. After being filtered by E1, it passes through the output LED lamp, then passes through the energy storage transformer L1, then passes through the switch tube Q1, and then flows back to E1. Among them, D1 is the freewheeling diode of the energy storage transformer L1. In the second half cycle, it sends energy to the output end.

[0029] 002 is the control IC circuit. The first pin of IC is the PWM dimming signal input port. The dimming signal is sent to IC through the R8 current limiting resistor for PWM dimming. The second pin of IC is the IC enable terminal. The VCC voltage is divided by R4 and R11, and the voltage signal is sent to pin 2. When the voltage of pin 2 is greater than 0.6, the seventh driving pin of the control IC will output a driving signal to drive the switch tube Q1 to work. When the voltage of pin 2 is lower than 0.6, the IC will lock the output driving signal and the power supply will stop working. The third pin of IC is the voltage loop feedback pin. The output voltage signal of the output end of the power supply is divided by R2 and R3, filtered and decoupled by C1, and sent to pin 3 for comparison with the internal reference voltage to adjust the output voltage. The fourth pin of IC is the analog dimming pin. The analog signal ADIM is connected to pin 4 through R10 and dimmed by the internal comparator. The 6th pin of IC is the input pin of the current loop. The current of the main circuit of the power supply obtains the voltage signal through the sampling resistor RCS1, and then is filtered through R9 and C6, and then sent to the 6th pin to be compared with the internal comparator reference signal to adjust the output current value. The 7th pin of IC is the driving pin of the switch tube Q1. The driving signal is sent to the base of the switch tube Q1 through R6 and R7. The base voltage signal is used to adjust the chopping action of the power tube Q1. The 8th pin of IC is the VCC power supply pin of the chip, which provides energy input for IC.

[0030] 003 is the circuit of this application (soft start circuit), in which D3 has the detection function of the power input voltage, HV is the voltage on the large electrolytic after PFC rectification. At the moment when AC is just powered on, the PFC circuit has not yet worked normally, and the HV voltage is in the process of slowly climbing, because the input large electrolytic needs to be charged, and the charging time is about 1000mS. When the VCC voltage of the PFC circuit is established, the PFC circuit works normally, and then the HV voltage is fully established to reach the designed voltage value (such as 220VAC input, the HV voltage needs to rise to about 430VDC.)

[0031] Now D3 takes the voltage from HV, and then passes through R12 and C7 for filtering, and then passes through R15, R20 for voltage division, and C11 performs second-order filtering. At this time, the voltage of C11 is very clean and has less noise. Before the HV voltage value has fully reached the preset value of 430VDC, after voltage division, the voltage value of C11 has not reached the voltage value of the voltage regulator Z1, and the voltage value of R21, C9, and R18 is 0 at this time, so U2 is TL431 (three-terminal voltage regulator) and is not turned on. If you want U2 to be turned on, you must let the first pin of U2: TL431 reach 2.5V or more before it will open. Since U2 is not conducting, the voltage at pin 2 of U2 is still the voltage value of VCC. Then the VCC voltage is divided by R16 and R19, filtered by R17 and C10, and sent to the base of transistor Q2. Since the base of the transistor must be greater than 0.7V, the transistor will be turned on. At this time, the base voltage sent is greater than 0.7V, so the transistor is turned on. Therefore, the ADIM signal of the main control IC passes through R13, and the CE of the transistor is connected to the ground. Since the ADIM signal is grounded and pulled low, the main control IC will turn off the output and will not drive the main switch tube Q1. Therefore, there is no output at the output end in this state (the lamp is not lit). When HV reaches the preset voltage value, the voltage divider value of R15 and R20 exceeds the voltage regulator value of the voltage regulator Z1, Z1 is excited, and the voltage after Z1 reaches more than 2.5V, so U2 (TL431) starts to conduct, and the potential between R14 and R16 is pulled down to the ground, so the base of the Q2 transistor has no driving voltage and is forced to cut off and conduct. At this time, the ADIM signal changes from low level to high level, and the output of the main control IC is no longer locked, and starts to send a driving signal to the power tube Q1, so the entire power supply starts to output energy, and the lamp is lit. The whole process realizes the soft start process of the output, and perfectly solves the problem of overshoot at startup.

[0032] This application collects the input voltage signal and determines whether the subsequent stage needs to work at full power through conditional selection. If the input voltage is not enough, the subsequent stage will suspend the output. When the input voltage is fully established, the control IC will open the duty cycle and the drive signal will be turned on so that the subsequent stage can work at full load. When the output is an LED lamp, the light slowly changes from dark to bright, which is a gradual process. It also protects the human eye and prevents the lamp from suddenly becoming bright. The human eye will have a temporary retention effect, which will make people feel uncomfortable and have no eye protection function. After adding soft start, the light becomes soft and bright, which has an eye protection effect.

[0033] This application is mainly used in non-isolated LED lamps. Based on the traditional LED driver power supply, the power supply startup timing is optimized and upgraded to change the PWM drive of the control IC. At the moment of power on, the duty cycle is minimized, and then the duty cycle is slowly increased, and finally the full load output is completed to complete the soft start process. The circuit has high reliability, can improve the electrical performance of the LED driver power supply, optimize the design parameters, improve the user experience, and make customers more satisfied.

[0034] 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 non-isolated topology soft start circuit, characterized in that: include; A main power circuit, wherein the main power is provided with an input terminal HV and an output terminal, and further comprises a transformer L1, wherein one end of a first coil of the transformer L1 is connected to the positive electrode of the output terminal through a diode D1, the other end of the first coil is connected to the negative electrode of the output terminal, one end of a second coil is connected to one end of a resistor R2, the other end of the resistor R2 is grounded through a capacitor C1 and a resistor R3 respectively, and the other end of the second coil is grounded; A control IC circuit includes a main control unit U1, a voltage loop feedback end of the main control unit U1 is connected to the other end of a resistor R2, a signal receiving end of the main control unit U1 receives an ADMI signal through a resistor R10, a driving end of the main control unit U1 is connected to a gate of a MOS tube Q1 through a resistor R6, a source of the MOS tube Q1 is grounded through a sampling resistor RCS1, and a drain is connected to one end of a first coil; It also includes a soft start circuit, which includes a diode D3 connected to the input terminal HV at one end, the other end of the diode D3 is connected to one end of a resistor R12, the other end of the resistor R12 is grounded through a capacitor C7, the other end of the resistor R12 is connected to one end of a resistor R15, the other end of the resistor R15 is grounded through a resistor R20 and a capacitor C11, the other end of the resistor R15 is connected to one end of a voltage regulator Z1, the other end of the voltage regulator Z1 is grounded through a resistor R21 and a capacitor C9, the other end of the voltage regulator Z1 is also connected to the reference end of the voltage regulator U2 through a resistor R18, the first conduction end of the voltage regulator U2 receives a voltage through a resistor R14, the second conduction end of the voltage regulator U2 is grounded, wherein the first conduction end is also connected to the base of the transistor Q2 through resistors R16 and R17 in sequence, the emitter of the transistor Q2 is grounded, and the collector is connected to the ADMI signal through a resistor R13.

2. A non-isolated topology soft start circuit according to claim 1, characterized in that: The enable terminal of the main control unit U1 receives a voltage through the resistor R4, and the resistor R4 is grounded through the resistor R11.

3. A non-isolated topology soft start circuit according to claim 2, characterized in that: The PWM dimming signal input terminal of the main control unit U1 receives a PWM signal.

4. The non-isolated topology soft start circuit according to claim 3, characterized in that: The VCC terminal of the main control unit U1 is connected to the input terminal HV through the resistor R5 and the resistor R1, and the VCC terminal is also grounded through the capacitor C2 and the capacitor C3 respectively.

5. The non-isolated topology soft start circuit according to claim 4, characterized in that: The current loop input end of the main control unit U1 is connected to one end of the resistor R9, the other end of the resistor R9 is connected to the gate of the MOS tube Q1 through the resistor R7, and the other end of the resistor R9 is also connected to the sampling resistor RCS1.

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