Power frequency rectification pulsating voltage driven group control dimming LED driver

Abstract

A high-frequency conversion step-down circuit is replaced, an LED load is directly driven by power frequency rectification output pulsating voltage, and the LED driver without high-frequency radiation is formed by adopting capacitor step-down, shunting, current limiting, follow current and composite load modes: 1, rectification output is smooth filtering without an electrolytic capacitor, and the service life of the driver depends on an LED lamp bead; 2, a correction circuit is not needed, the alternating current input current angle approaches 360 degrees, the power factor is high, and the harmonic wave is low; 3, the LED load current amplitude is constant, the adjusting process is low in power consumption, and a control circuit does not need to be additionally provided with a low-voltage power supply; 4, PWM cutting control is adopted to replace TRIAC phase control dimming of power frequency AC voltage; 5, a PWM pulse generator, a dimming controller and a PWM power frequency dimming power supply are arranged, and independent and remote group simulation and PWM dimming are achieved.

Description

Technical Field

[0001] This invention relates to LED lighting driver and dimming circuits: Background Technology

[0002] For LED driving and dimming methods, please refer to:

[0003] Optimized design of LED lighting driver power supply

[0004] The second edition, published by China Electric Power Press in April 2014, is awaited by Sha Zhanyou.

[0005] 1. High-frequency conversion LED driver circuit:

[0006] High-frequency radiation and withstand voltage;

[0007] High-frequency transformers, step-down inductors, and EMI electromagnetic devices are complex to manufacture;

[0008] To reduce the size of electromagnetic devices, the conversion frequency needs to be increased as much as possible, resulting in high-frequency radiation;

[0009] To meet the standard requirements for suppressing high-frequency radiation, the aluminum substrate must be grounded on the aluminum plate side, which would prevent it from passing the withstand voltage test.

[0010] Harmonics introduced by the rectifier filter capacitor;

[0011] High-frequency LED drivers in switching power supply mode require the mains voltage to be rectified and filtered into DC voltage first.

[0012] When using integrated circuit chips, the LED current control circuit requires an additional low-voltage DC power supply.

[0013] The initial charging inrush current of the rectifier filter capacitor is several times the rated current, causing the circuit breaker to malfunction.

[0014] The initial charging inrush current of a large number of driver filter capacitors causes a sudden drop in the power distribution system voltage, resulting in power supply voltage fluctuations; the nonlinear charging current of the rectifier filter capacitors will introduce harmonics into the power system, leading to a decrease in the power factor of the power supply system; the power frequency rectified pulsating voltage drive mode has no rectifier filter stage, which reduces the generation of harmonics from the source.

[0015] LED driver power factor correction:

[0016] Active power factor correction circuits are complex, increasing the cost of LED drivers;

[0017] The increased ripple current and frequency of the filter electrolytic capacitor in the high-frequency conversion correction mode lead to temperature rise and shortened lifespan.

[0018] The passive current-driven power factor correction circuit generates increased harmonic current and requires more electrolytic capacitors.

[0019] The lifespan of rectifier filter electrolytic capacitors is much shorter than that of LED chips, and the driver will fail before the LEDs reach their lifespan.

[0020] Faults caused by harmonic introduction:

[0021] The voltage waveform distortion of current power frequency power supplies is extremely severe. In addition to causing additional losses to the power system, high-order harmonics also lead to the following faults: These are examples from several organizations (including manufacturing companies, hotels, hospitals, securities companies, radio stations, and telecommunications operators) that I have observed and heard during electrical engineering certification and review training:

[0022] As the harmonic order of the power factor compensation capacitor in the power distribution system increases, the impedance decreases, the current increases, and the fuse blows.

[0023] The compensation capacitor bulges and deforms due to temperature rise, and ages rapidly.

[0024] The power frequency voltage and current waveforms are distorted, making it impossible to accurately determine the phase of the fundamental current, and the compensation function of the capacitor compensation equipment fails.

[0025] The neutral current in power distribution is the algebraic sum of the absolute values ​​of the higher harmonic currents of each phase, which increases losses and causes serious cable temperature rise.

[0026] Laying additional cables increases the cross-sectional area of ​​the neutral conductor for cooling, but wastes energy in cable manufacturing and a large amount of polymer materials and copper.

[0027] The distortion of the grid voltage waveform will further amplify the harmonic currents due to the power factor compensation capacitor and the rectifier filter electrolytic capacitor.

[0028] literature:

[0029] "Rectifier Filtering and DC-Link Capacitor Characteristics, Operating Status Analysis, and Selection" by Chen Yongzhen, published by Science Press in April 2013.

[0030] The first chapter of this document presents the voltage and current waveforms of the capacitor-filtered charging with different values ​​after the initial charging.

[0031] "Power Quality Control in Industrial Enterprises," edited by Chen Jianye et al., published by Machinery Industry Press in January 2008.

[0032] Chapter 3.4 Voltage Waveform Distortion 3.4.2 Harmonics (Page 116)

[0033] 2. High-frequency conversion driver dimming:

[0034] If the PWM dimming frequency is within the range of human hearing, the high-frequency transformer and inductor core will emit a buzzing noise.

[0035] Increasing the dimming frequency makes it difficult to transmit voltage for remote PWM dimming control.

[0036] Under the action of intermittent current in the winding, the parameters and frequency of the high-frequency magnetic core change, and magnetostriction leads to loosening of the magnetic core adhesive.

[0037] The dimming input of the remote dimming driver chip is subject to electromagnetic interference.

[0038] Three: High-frequency conversion driver TRIAC dimming:

[0039] As the TRIAC conduction angle decreases, the harmonic current of the power frequency power supply increases and the power factor decreases.

[0040] To overcome the ringing effect and the flickering phenomenon of the light source, an active damping circuit needs to be set up;

[0041] To resolve the abnormal shutdown phenomenon of TRIAC, a passive discharge circuit needs to be set up.

[0042] The LED driver circuit topology is too complex to accommodate the traditional TRIAC dimming mode of gas discharge lamps.

[0043] literature:

[0044] "Optimized Design of LED Lighting Driver Power Supply"

[0045] Chapter 8 LED Lighting Dimming Circuit Design:

[0046] Sections 5 through 9 dedicate significant space to introducing several TRIAC dimming driver circuits.

[0047] Section 3: Part 2: Introduction to the Technical Issues to be Solved in TRIAC Dimming

[0048] Section 7:2: Working Principle of TRIAC Flicker-Free Dimming Circuit

[0049] 4. Basic characteristics of a group-controlled dimming LED driver driven by a power frequency rectified pulsed voltage:

[0050] The dimming technology disclosed in the driver is an extension of the functionality of the invention patent "Practical LED Driver" (201910485298.2).

[0051] Driver circuit topology:

[0052] Capacitor-based step-down converters replace high-frequency step-down converters, greatly simplifying the circuit topology.

[0053] The constant current control circuit uses a portion of the LED load voltage as its power supply voltage, eliminating the need for an additional low-voltage DC power supply.

[0054] The LED load is directly driven by the mains frequency rectified voltage and has no high-frequency electromagnetic components.

[0055] There is no high-frequency electromagnetic radiation, the aluminum substrate does not need to be grounded, and the aluminum substrate is irrelevant to the withstand voltage test.

[0056] Power factor and harmonics:

[0057] It adopts direct drive with power frequency pulsating voltage, without rectifier filter electrolytic capacitors, which reduces driver harmonics and increases lifespan;

[0058] No power factor correction is required, the AC input current conduction angle approaches 360°, and the driver power factor is improved;

[0059] When a large number of drivers are powered on simultaneously, there is no inrush current, and the power supply system voltage remains stable.

[0060] Load current regulation:

[0061] No separate power supply is required; the regulating circuit uses the partial LED load voltage synchronized with the LED load current as the pulsating power supply.

[0062] In the shunt constant amplitude control mode, the incremental AC power supply voltage fluctuation is absorbed by the step-down capacitor, and the power consumption of the drive circuit is zero.

[0063] In the current-limiting constant amplitude control mode, the power consumption of the LED load series limiting transistor is zero when operating at rated power frequency voltage.

[0064] The voltage drop of the AC voltage fluctuation limiting transistor is only the increment of the sinusoidal voltage amplitude, and the loss is extremely low as the current decreases.

[0065] Composite LED load with capacitor step-down freewheeling constant voltage limiting control mode: LED load current is continuous and flicker-free.

[0066] The circuit topology of rectifier output without capacitor filtering is the best and simplest way to reduce harmonic generation and improve power factor.

[0067] 5. Dimming Mode:

[0068] As a fundamental requirement for intelligent lighting control, the dimming circuit topology is extremely simple, and the dimming voltage transmission line does not require shielding.

[0069] Multiple control modes enable independent and tiered group dimming:

[0070] The pulse voltage from the PWM pulse generator controls the dimming of the LED driver via an optocoupler.

[0071] The PWM dimming controller controls the dimming of the LED driver;

[0072] PWM power frequency dimming power supply controls the dimming of LED drivers using AC power.

[0073] Drawing catalog:

[0074] 1. PWM pulse generator: Figure (1)

[0075] 2. PWM dimming controller: Figure (2)

[0076] 3. PWM power supply for dimming at mains frequency: Figure (3)

[0077] 4. AC capacitor step-down and shunt control PWM dimming LED driver: Figure (4-1, 2)

[0078] Independent PWM dimming: Figure (4-1)

[0079] Group-controlled PWM dimming: Figure (4-2)

[0080] 5. AC capacitor step-down limiting control PWM dimming LED driver: Figure (5)

[0081] 6. Capacitor-driven step-down freewheeling constant voltage limiting control dimming LED driver: Figure (6)

[0082] 7: PWM Modulated AC Voltage Dimming LED Driver: Figure (7)

[0083] 8: Composite load NPN transistor limited PWM dimming LED driver: Figure (8)

[0084] 9: Composite load PNP tube limited PWM dimming LED driver: Figure (9)

[0085] 10: Heat dissipation structure of the lamp: Figure (10)

[0086] Technical solution and beneficial effects:

[0087] 1. PWM pulse generator: Figure (1)

[0088] A constant-frequency duty-cycle adjustable oscillator controlled by a light-controlled bistable trigger generates PWM pulses.

[0089] The PWM pulse voltage is the base drive voltage of the emitter-output transistor, and its emitter outputs extended PWM pulse current.

[0090] When the emitter output transistor is in the off state, a low-resistance resistor is connected between the emitter and ground.

[0091] Beneficial effects:

[0092] The dimming frequency can be selected arbitrarily; if the frequency is reduced, unshielded wires can be used to transmit PWM pulse voltage.

[0093] PWM pulse voltage control of multiple LED drivers enables group dimming;

[0094] The zero-state output resistance to ground of PWM reduces electromagnetic interference in the dimming circuit.

[0095] 2. PWM dimming controller: Figure (2)

[0096] The PWM dimming controller is a variable relaxation oscillation circuit that controls the LED driver by switching the oscillating transistor on and off.

[0097] The relaxation oscillation frequency and duty cycle are regulated by DC voltage, and the LED load is dimmed in PWM mode.

[0098] Beneficial effects:

[0099] The relaxation oscillation circuit is extremely simple, and the timing capacitor also serves as a filter for electromagnetic interference from the control cable.

[0100] DC voltage control of multiple LED drivers enables group dimming.

[0101] 3. PWM power supply for dimming at mains frequency: Figure (3)

[0102] A PWM pulse-controlled AC solid-state switch forms an AC dimming power supply, which outputs a PWM-chopped modulated power frequency AC voltage.

[0103] When there is no PWM voltage input, the AC dimming power supply outputs a normal, continuous AC voltage.

[0104] Beneficial effects:

[0105] It replaces TRIAC dimming with thyristor, eliminating the need for active damping and passive discharge circuits;

[0106] PWM chopping AC voltage cutting mode has a simpler circuit, improved power factor, and reduced harmonics compared to phase-controlled voltage regulation mode.

[0107] A distributed group control dimming system is formed by controlling multiple LED drivers with a PWM power supply.

[0108] 4. AC capacitor step-down and shunt control PWM dimming LED driver diagram (4-1, 2)

[0109] Basic characteristics of the circuit:

[0110] The series capacitor in the AC power supply is the input voltage of the step-down rectifier bridge;

[0111] The pulsating voltage output by the buck rectifier bridge is the driving voltage for the LED load;

[0112] The amount of harmonics generated by the driver, the pulse width of the LED and AC power supply current, and the voltage of the LED load network all depend on the voltage of the LED load network.

[0113] Beneficial effects:

[0114] Capacitor-based step-down converters replace high-frequency buck converters, greatly simplifying the circuit topology.

[0115] The rectified output has no harmonics generated by the charging of the filter electrolytic capacitor, and the driver lifespan depends on the LED.

[0116] The driver has no electromagnetic components and no high-frequency electromagnetic radiation. The aluminum substrate does not need to be grounded, which improves the lightning protection withstand voltage stress.

[0117] When the LED load network voltage is much smaller than the step-down capacitor voltage, the conduction angle of the LED load pulsating current during the power frequency half-cycle approaches 180°.

[0118] The circuit is simple and can be assembled into high-power lamps by connecting multiple sets of drive circuits in parallel.

[0119] Shunt-type constant amplitude circuit:

[0120] The shunt circuit and the LED load are connected in parallel to form a shunt constant amplitude regulation circuit;

[0121] The shunt circuit turns on when the LED load current amplitude exceeds the set value, shunting the LED load current amplitude that exceeds the limit;

[0122] When the rectifier bridge output is short-circuited by the shunt circuit, the AC input current is continuous.

[0123] No power factor correction is required, and the AC input current conduction angle approaches 360°.

[0124] Beneficial effects:

[0125] When the shunt regulation circuit operates in the switching state, the power fluctuation increment is absorbed by the step-down capacitor at the input of the rectifier bridge.

[0126] The control circuit does not require a separate low-voltage power supply, the driver has extremely low power consumption and almost no loss.

[0127] Hysteresis-free elimination of excessive current introduced by transient overvoltage pulses in power frequency power supplies;

[0128] The driver is capacitively reactant, which helps improve the power factor of the power system.

[0129] Dimming mode:

[0130] The dimming modes are diverse, and the driver can achieve independent and group control PWM dimming in the intermittent short-circuit LED load mode;

[0131] The cascade control dimming system is greatly simplified, and the AC input current of the driver is continuous during the dimming process.

[0132] 5: AC capacitor step-down limiting control PWM dimming LED driver (Figure 5)

[0133] Basic characteristics of limiting circuits:

[0134] A limiting transistor is connected in series in the LED load network to form a limiting load current constant amplitude circuit;

[0135] The transistor voltage drop is adjusted to limit the voltage fluctuation of the LED based on the fluctuation of the AC voltage and the temperature rise of the LED, thereby maintaining a constant LED load current amplitude.

[0136] Beneficial effects:

[0137] When operating at rated power frequency voltage, the power consumption of the LED load series-connected limiting transistor is zero.

[0138] During the adjustment process, the voltage drop of the limiting transistor is only the fluctuation increment of the sinusoidal voltage amplitude, and the current decreases with extremely low loss.

[0139] Dimming mode:

[0140] Independent analog dimming is achieved by continuously adjusting the internal resistance of the limiting transistor;

[0141] PWM group control dimming is achieved by controlling the on / off state of the limiting transistor.

[0142] Beneficial effects:

[0143] Analog dimming drivers have extremely low dimming losses;

[0144] The on / off limiting transistor mode PWM dimming driver has no dimming loss.

[0145] 6: Capacitor-driven step-down freewheeling constant voltage limiting control dimming LED driver (Figure 6)

[0146] Basic characteristics of the circuit:

[0147] A limiting transistor connected in series in the LED load network forms a limiting constant amplitude circuit;

[0148] A capacitor is connected in series at both input terminals of the step-down rectifier bridge, and the output pulsating voltage drives the LED load;

[0149] The LED load current driven by the buck rectifier bridge leads the power frequency voltage and decays to zero within the phase angle related to the voltage peak.

[0150] A voltage divider circuit with a step-down capacitor connected in parallel and an energy storage capacitor connected in series at the output terminal of a direct-drive rectifier bridge with power frequency voltage.

[0151] The sinusoidal pulsating voltage of the energy storage capacitor provides freewheeling current for the LED load during the period when the load current decays to zero.

[0152] The pulse width of the sinusoidal pulsating voltage of the energy storage capacitor, which is slightly greater than the load voltage, should be the pulse width at which the LED load current decays to zero.

[0153] The energy storage capacitor can be used directly as a freewheeling current for the LED load (Figure 6-1), or as a freewheeling current through a voltage regulator circuit (Figure 6-2).

[0154] Beneficial effects:

[0155] Instead of the BUCK high-frequency converter circuit, the LED load current is a constant amplitude, continuous, and smooth DC current.

[0156] The driver has a continuous LED load current, and the AC input current vector and phase angle of the two rectifier bridges are 360°.

[0157] The output voltage of the direct-drive rectifier bridge at power frequency does not require smoothing filtering to reduce harmonics.

[0158] Dimming mode:

[0159] PWM dimming control circuit diagram (2) controls the driver to intermittently turn the limiting transistor on and off to achieve independent and group dimming.

[0160] literature:

[0161] "Characteristics, operating status analysis, and selection of rectifier filters and DC-Link capacitors" Figure 1-9

[0162] 7: PWM Modulated AC Voltage Dimming LED Driver (Figure 7)

[0163] Multiple sets of limiting LED driver rectifier bridges are connected in parallel at their AC input terminals to form a dimming bus;

[0164] The PWM power frequency dimming power supply diagram (3) controls the AC input voltage of the LED driver to achieve group dimming.

[0165] Beneficial effects:

[0166] It replaces TRIAC dimming with thyristor, eliminating the need for active damping and passive discharge circuits;

[0167] Compared to phase-controlled voltage regulation, PWM-based AC voltage cutting mode has a simpler circuit, improved power factor, and reduced harmonics.

[0168] A distributed group control dimming system can be formed by controlling multiple groups of limiting LED driver circuits with PWM dimming power supply.

[0169] 8: Composite load NPN transistor limited PWM dimming LED driver (Figure 8)

[0170] Basic characteristics of the circuit:

[0171] The driver is configured with two sets of rectifier bridges to output pulsating voltage to drive two sets of LED loads;

[0172] A set of independent LED loads is driven by a direct-controlled rectifier bridge directly driven by the mains frequency power supply;

[0173] A direct-controlled rectifier bridge and a step-down rectifier bridge connected in series with a step-down capacitor at the input end jointly drive a set of shared LED loads;

[0174] The driver adjusts the internal resistance of the limiting transistor connected in series with the two sets of LED loads to maintain the constant LED load current amplitude.

[0175] Beneficial effects:

[0176] The LED load driven by the two sets of rectifier bridges can be set to near DC drive, and the driver will not flicker.

[0177] The superposition of AC input currents from the two rectifier bridges widens the conduction angle to nearly 360°, reducing harmonics and improving the power factor.

[0178] LED load current average value control:

[0179] As the voltage fluctuation of the power frequency AC power supply increases, the amplitude of the LED load current remains constant, and the pulse width and average value increase.

[0180] The driver follows the increment of the power frequency voltage to maintain a constant average value of the LED load current in a double-limiting mode.

[0181] Dimming mode:

[0182] Group dimming is achieved by controlling the on / off state of the limiting transistor Qi through the pulse voltage output by the PWM pulse generator.

[0183] 9: Composite load PNP tube limited PWM dimming LED driver (Figure 9)

[0184] The driver circuit topology and control mode are similar to those in Figure (8), and its circuit characteristics are as follows:

[0185] The limiting transistor is a PNP transistor;

[0186] LED load current constant amplitude control adopts a standard operational amplifier;

[0187] The operating power supply voltage of the operational amplifier is based on the pulsating voltage of a portion of the LED load.

[0188] 10: Heat dissipation structure diagram of the lamp (10)

[0189] The current market trend of increasing the number of LEDs in bulb lamps to distribute heat dissipation increases the driver failure rate.

[0190] Air between the aluminum substrate of bulb lamps and the heat sink of street lamps and the lamp housing increases thermal resistance and makes heat dissipation difficult.

[0191] Bulb heat dissipation:

[0192] High-power LED beads are used to replace dozens of low-power LED beads, simplifying the manufacturing process of bulb lamp boards and reducing the failure rate.

[0193] Increase the thickness of the bulb's screw thread material, and use the screw thread metal as the LED heat sink.

[0194] Streetlight heat dissipation:

[0195] Additional insulation is added to the aluminum substrate direct-connected heat sink and the exposed metal components of the lamp;

[0196] Additional insulation is achieved by filling the space between the metal casing of the lamp and the aluminum substrate heat sink with insulating and thermally conductive black glue to enhance heat dissipation.

[0197] Beneficial effects:

[0198] By using the metal of the lamp housing or the screw base of the bulb as a heat sink, the thermal resistance of the aluminum substrate is reduced.

[0199] As the number of LEDs decreases, the energy efficiency of bulb lamps improves and the failure rate decreases. Attached Figure Description

[0200] Figure 1 The PWM pulse voltage is generated to control the LED driver circuit, enabling independent and group dimming. Figure 2 Independent and group dimming is achieved by controlling the LED driver circuit with the switching of a variable relaxation oscillator transistor. Figure 3 The power frequency voltage is chopped into a power frequency dimming power supply for LED drivers to achieve cascade group control dimming; Figure 4 shows a capacitor-driven step-down circuit that uses either shunt or intermittent short-circuit LED load current mode to maintain constant LED load amplitude and dimming. Figure 5 A capacitor-driven step-down circuit adjusts the LED load network using an additional series resistor to maintain constant LED load amplitude and dimming. Figure 6 shows the capacitor buck driver circuit where the LED load current is filled by the voltage of the additional energy storage capacitor during the intermittent period of the LED load current. Figure 7 The power frequency voltage chopper voltage is the AC input power supply for the capacitor-step-down LED driver; Figure 8 and Figure 9 The power factor of the driver is improved by using AC voltage direct drive and capacitor step-down drive to improve the phase difference of two sets of LED loads; Figure 10 Measures to improve the heat dissipation of LED beads are proposed. Specific implementation circuit:

[0201] Symbol rules:

[0202] Direct-controlled rectifier bridge DZV: Input terminal directly connected to power frequency power supply JZL, JZE;

[0203] DZC step-down rectifier bridge: A step-down capacitor is connected in series between the input terminal and the AC power supply;

[0204] LED loads: PHC, JHC and PHV, JHV.

[0205] 1. PWM pulse generator: Figure (1)

[0206] The 555A is used to construct a constant frequency, variable duty cycle oscillator;

[0207] When the 555A outputs a high level, it charges the timing capacitor CT via the diode DC. As the voltage at pin 6 rises, the output turns to a low level.

[0208] The diode DF is the timer capacitor CT, which discharges through pin 7 of the 555A circuit. As the voltage at pin 2 decreases, the output turns high.

[0209] The oscillation frequency is determined by changing the values ​​of resistors RC, RT, and RF.

[0210] Adjusting the resistor RT changes the charging and discharging time constant, thus regulating the oscillation duty cycle.

[0211] Remote control circuit:

[0212] The 555B is used to form a bistable trigger, with trigger terminal 2 and reset terminal 6 controlled by a button and photoresistors RG and RD, respectively.

[0213] The output terminal of the 555B is connected to the forced reset terminal 4 of the 555A oscillator to remotely control the oscillator to start and stop oscillation.

[0214] PWM pulse output circuit:

[0215] The output voltage of the 555A transistor drives the emitter follower transistor QV via resistor RB.

[0216] The emitter of QV is connected to pin 7 of the 555A via resistor RE to reduce the zero-state output resistance of the PWM pulse;

[0217] The emitter output voltage of transistor QV is the dimming pulse voltage of the PWM pulse generator.

[0218] literature:

[0219] "A Collection of Principles and Practical Circuits of the 555 Timer" edited by Yang Zhaoxuan and Ding Runtao

[0220] Tianjin University Press published Chapters 2 and 30 in December 1989.

[0221] 2. PWM dimming controller: Figure (2)

[0222] The PWM dimming controller is a DC voltage controlled relaxation oscillator, and the oscillating transistor QT outputs control pulses when it is turned on and off.

[0223] Oscillating transistor off state:

[0224] The emitter of the oscillator transistor QT is connected in series with the Zener diode DWT and grounded; the thyristor SCR is connected in parallel with DWT.

[0225] The DC control voltage is connected in series with the dimming resistor RC, which is used as the timing capacitor CT during charging via the diode DC. During this period, the transistor QT is turned off.

[0226] The timing capacitor CT also serves as an electromagnetic interference filter for the control terminal.

[0227] Oscillating transistor conduction state:

[0228] Transistor QT turns on when the charging voltage of timing capacitor CT is greater than the Zener voltage of QT base-emitter junction and Zener diode DWT.

[0229] The SCR thyristor is triggered to conduct via resistor RSK, and the short-circuit Zener diode DWT grounds the emitter of transistor QT.

[0230] The base drive current of transistor QT is the discharge current of timing capacitor CT through resistor RF.

[0231] The connection point between resistor RC and diode DC anode is grounded via diode DF and transistor QT, and the CT charging voltage disappears.

[0232] When the timing capacitor CT discharges to a low level, the transistors QT and SCR turn off, and the capacitor CT is recharged.

[0233] Oscillation frequency and duty cycle adjustment:

[0234] The conduction pulse width of transistor QT is constant and positively correlated with the time constant RF×CT and the Zener voltage of Zener diode DWT.

[0235] The turn-off pulse width of the transistor QT is positively correlated with the time constant RC×CT and negatively correlated with the DC control voltage of the oscillator.

[0236] As the control voltage increases, the CT charging speed increases, the oscillation frequency increases, and the transistor turn-off pulse width and its duty cycle decrease.

[0237] LED brightness is inversely proportional to the external DC dimming voltage.

[0238] 3. PWM power supply for dimming at mains frequency: Figure (3)

[0239] The AC solid-state switch is controlled by PWM voltage, and the control period is 1 / n of the power frequency period. Starting from the zero point of the sine wave, it is divided into several segments along the X-axis. The AC solid-state switch alternately turns on and off in sequence, cutting the sine wave into a comb shape, which is the PWM voltage regulation mode of the power frequency AC power supply.

[0240] literature:

[0241] "Power Converter Circuits" published by Machinery Industry Press in October 2008.

[0242] (US): Translated by William Shepherd, Li Zhang, Shen Jing, Zhang Zhengnan, et al.

[0243] Voltage regulation mode: Page 189, Section 8.2.4 Figure 8 -4

[0244] Specific circuit:

[0245] The rectifier bridge DT and the transistor QT controlled by the optocoupler UTG form an AC solid-state switch;

[0246] The output voltage of the rectifier bridge DK drives the transistor QT of the AC solid-state switch via resistor RB;

[0247] The pulse output from the PWM pulse generator is switched on and off via the optocoupler UTG to control the base drive current of the transistor QT.

[0248] A distributed group control dimming system is formed by controlling multiple LED drivers with intermittent output of AC solid-state switch power frequency AC voltage.

[0249] When there is no PWM voltage input, the AC dimming power supply outputs a normal, continuous AC voltage.

[0250] 4. AC capacitor step-down and shunt control PWM dimming LED driver: Figure (4-1, 2)

[0251] Current detection circuit DI:

[0252] The driver current sensing circuit DI uses a precision voltage reference device TL431;

[0253] The TL431 is equivalent to an operational amplifier, with the control electrode considered as the non-inverting input and the anode as the inverting input.

[0254] Anode grounding: TL431 is equivalent to a non-inverting amplifier;

[0255] The equivalent inverting input voltage is a fixed value, equal to the TL431 reference voltage of 2.5V;

[0256] That is, when the external voltage of the TL431 controller is greater than 2.5V, the internal resistance of the current detection circuit DI decreases;

[0257] Anode not grounded: TL431 is equivalent to an inverting amplifier;

[0258] The equivalent non-inverting input voltage is a fixed value, set at the sum of the LED rated current sampling voltage and the TL431 reference voltage;

[0259] That is, the external voltage connected to the anode of TL431 is greater than the set voltage of the control electrode, and the internal resistance of the current detection circuit DI increases;

[0260] literature:

[0261] "Motorola Linear and Interface Circuits Handbook" compiled by Liu Renpu et al.

[0262] First edition published by Machinery Industry Press, September 1994.

[0263] 5-16 Equivalent circuit block diagram of TL431A, B series

[0264] LED load circuit:

[0265] AC power supply JZL is connected in series with capacitor CZL, which is the input voltage of step-down rectifier bridge DZC;

[0266] LED diodes PHC, JHC, DH2, and DH1 are connected in series with a grounded current sampling resistor RI to form an LED load;

[0267] The output pulsating voltage of the step-down rectifier bridge DZC is the driving voltage for the LED load.

[0268] LED load current setting and detection:

[0269] The TL431 reference voltage is the LED load current setting value;

[0270] The voltage across resistor RI is the LED load current detection value.

[0271] Current sensing circuit DI control electrode voltage:

[0272] The voltage of the series circuit between the current-limiting resistor RW and the Zener diode DW with its anode grounded is derived from the anode of the LED load DH2.

[0273] Resistors RK, RKT, and LED load current sampling resistor RI are connected in series and in parallel with Zener diode DW;

[0274] The voltage at the moving contact of resistor RKT, i.e., the voltage at the control electrode DI, is controlled by the voltage sampled from the load current of resistor RI.

[0275] LED load current shunt adjustment:

[0276] The TL431 current sensing circuit DI with the anode grounded is connected in parallel with the LED load. When the LED load is at its rated current, DI is turned off.

[0277] As the LED load current increases, the voltage across the current sensing resistor RI rises, causing DI to conduct and shunt the LED load current.

[0278] The DI can only shunt excessive load current, and it turns off when the LED load current decreases to the set value.

[0279] The conduction of DI is controlled by the voltage of the current sensing resistor RI, which keeps the load current amplitude constant at the set value.

[0280] Independent PWM dimming: Figure (4-1)

[0281] The principle of setting up a relaxation oscillator with the LED load voltage as the power supply is similar to that of the aforementioned Figure (1-2);

[0282] An external dimming circuit is formed by connecting a switch SW and a dimming resistor RC in series.

[0283] The collector of the oscillator transistor QT and the DC anode of the charging diode are connected to the output terminal of the rectifier bridge DZC.

[0284] The diode's DC cathode is connected to the switch SW to provide dimming control power to the oscillator;

[0285] Adjusting the resistor RC changes the charging speed of the timing capacitor CT, and controls the on / off frequency and duty cycle of the oscillator transistor QT.

[0286] The transistor QT is connected in parallel with the LED load, and the driver dims the LED load by intermittently turning QT on and off to short-circuit it.

[0287] PWM pulse generator controls group dimming: Figure (4-2)

[0288] The diode DL is connected in series with the resistor RL to charge the capacitor CL. The charging voltage is derived from the series voltage of the LED loads DH2 and DH1.

[0289] The collector of the optocoupler UTG transistor is connected to capacitor CL, and the emitter is connected to the series connection point of RK and RKT via resistor RTG.

[0290] Multiple sets of optocouplers with UTG diodes are connected in series with matching resistors RP and then connected in parallel to form a dimming bus.

[0291] The PWM pulse generator dimming pulse voltage controls the dimming bus, forcibly increasing the DI control electrode voltage;

[0292] By disconnecting the current sensing resistor RI from voltage control, and intermittently short-circuiting the LED load via DI, remote PWM group control dimming is achieved.

[0293] Group control of PWM dimming by PWM dimming controller: Figure (4-2)

[0294] Multiple sets of driver isolation diodes (DG) have their anodes connected to the output terminals of the rectifier bridge (DZC), and their cathodes are connected in parallel to form a dimming bus.

[0295] The collector of the transistor in the PWM dimming controller is connected to the dimming bus, and the LED load is intermittently short-circuited to achieve group control dimming.

[0296] 5: AC capacitor step-down limiting control PWM dimming LED driver (Figure 5)

[0297] LED load circuit:

[0298] AC power supply JZL is connected in series with capacitor CZL, which is the input voltage of step-down rectifier bridge DZC;

[0299] LED diodes PHC, JHC, DHL, DH2, and DH1 are connected in series with current sensing resistor RI and grounded to form an LED load;

[0300] The output pulsating voltage of the step-down rectifier bridge DZC is the driving voltage for the LED load.

[0301] Base current of limiting transistor Qi:

[0302] An NPN limiting transistor Qi is connected in series with the LED load;

[0303] The LED load DHL, resistor RHL, and transistor QHL form a constant current source to provide base drive current for limiting transistor Qi;

[0304] The TL431 current detection circuit uses DI as the anode grounded and RI as the cathode series resistor to shunt and limit the base current of transistor QI.

[0305] LED load current setting and detection:

[0306] The TL431 reference voltage is the LED load current setting value;

[0307] The voltage across resistor RI is the LED load current detection value.

[0308] Current detection circuit DI control electrode voltage;

[0309] The voltage of the series circuit between the current-limiting resistor RW and the Zener diode DW with its anode grounded is derived from the anode of the LED load DH2.

[0310] Resistors RK, RKT, and LED load current sampling resistor RI are connected in series and in parallel with Zener diode DW;

[0311] The voltage at the moving contact of resistor RKT, i.e., the voltage at the control electrode DI, is controlled by the voltage sampled from the load current of resistor RI.

[0312] LED load current limiting adjustment:

[0313] The LED load current is at the rated value, and the limiting transistor Qi is in a saturated conduction state.

[0314] As the LED load current increases, the DI control electrode voltage rises and the internal resistance decreases, causing the base current of the limiting transistor Qi to decrease.

[0315] The driver maintains a constant LED load current amplitude by adjusting the internal resistance of the limiting transistor Qi.

[0316] Independent analog dimming;

[0317] An external analog dimming circuit consisting of a battery BT, a switch SW, and a resistor RTG connected in series is connected in parallel with an optocoupler UTG diode.

[0318] The collector of the optocoupler UTG transistor is connected in series with a pull-up resistor RL, and the anode voltage of the LED load DHL is used as the power supply voltage.

[0319] The emitter connection point of the UTG transistor is the series connection point of resistors RK and RKT, which controls the voltage of the control electrode in the current detection circuit DI.

[0320] Adjusting the external dimming circuit resistor RTG causes the DI cathode voltage to follow the changes in UTG diode current and transistor internal resistance.

[0321] Adjusting the internal resistance of DI changes the base current of transistor Qi; independent analog dimming is achieved by adjusting the internal resistance of Qi.

[0322] Group-controlled PWM dimming:

[0323] Multiple sets of driver optocouplers and UTG diodes are connected in series with matching resistors and then in parallel to form a dimming bus.

[0324] PWM pulse generator diagram (1) The dimming pulse voltage controls the dimming bus, causing the optocoupler UTG to turn on and off;

[0325] The DI is forced to intermittently enter the on / off state, and the PWM group control dimming is realized by the intermittent on / off mode of the limiting transistor Qi.

[0326] 6: Capacitor-driven step-down freewheeling constant voltage limiting control dimming LED driver (Figure 6)

[0327] LED load circuit:

[0328] LED diodes PHC, JHC, DH2, and DH1 are connected in series with current sensing resistor RI and grounded to form an LED load;

[0329] A step-down capacitor CZL and CZE are connected in series between the two input terminals of the step-down rectifier bridge DZC and the AC power supply.

[0330] The pulsating voltage output from the step-down rectifier bridge DZC drives the LED load;

[0331] LED load current:

[0332] The LED load current driven by the DZC output voltage leads the power frequency voltage and decays to zero within the voltage peak-related phase angle.

[0333] The DZV input terminal of the rectifier bridge is directly connected to the AC power supply.

[0334] A voltage divider circuit with a step-down capacitor CJ connected in parallel and an energy storage capacitor CV connected in series at the output terminal of DZV.

[0335] The sinusoidal pulsating voltage of the energy storage capacitor CV provides freewheeling current for the LED load during the period when the load current decays to zero.

[0336] The pulse width of the sinusoidal pulsating voltage CV, which is slightly greater than the load voltage, should be the pulse width at which the LED load current decays to zero.

[0337] The CV voltage can be directly used as a freewheeling current for the LED load via the isolation diode DH; Figure (6-1)

[0338] The CV voltage is the input voltage of the voltage regulator circuit VR, and the output of VR is used as the freewheeling current for the LED load via DH; Figure (6-2)

[0339] The driver LED load current is continuous, and the AC input current vector and phase angle of the two rectifier bridges are 360°.

[0340] Base current of limiting transistor Qi:

[0341] A PNP limiting transistor Qi is connected in series with the LED load;

[0342] TL431 current sensing circuit: DI anode series current sampling resistor RI grounded;

[0343] The cathode series resistor RDI provides base current for the PNP transistor Qi.

[0344] LED load current setting and detection:

[0345] The voltage across resistor RI, which is the anode voltage of current sensing stage DI, is the LED load current sensing value.

[0346] The voltage of the current sensing stage DI controller electrode is the set value of the LED load current.

[0347] The current setting voltage is equal to the sum of the voltage across the rated load current sampling resistor RI and the TL431 reference voltage;

[0348] That is, when the voltage of the current sensing stage DI controller electrode is equal to the set value, the LED load current is the rated value.

[0349] LED load current limiting adjustment:

[0350] The voltage in the series circuit of resistor RV and temperature-compensated LED diode DHV with cathode ground is taken from the anode of LED load DH3.

[0351] The DHV diode is embedded in the LED load heat sink or soldered to the same aluminum substrate as the LED load.

[0352] The resistor RK is connected in series with RKT and in parallel with the LED diode DHV. The voltage at the moving contact of RKT is the control electrode voltage of DI.

[0353] Adjust resistor RKT to make the DI control electrode voltage equal to the LED load current setting value;

[0354] As the LED load temperature rises, the voltage of the DI control electrode in the current detection circuit decreases and its internal resistance increases.

[0355] The LED load current exceeds the limit, causing the anode voltage of the current detection circuit DI to rise and the internal resistance to increase.

[0356] The driver adjusts the base drive current of the limiting transistor Qi to control the LED load current amplitude while keeping the internal resistance of Qi constant.

[0357] PWM group control dimming circuit:

[0358] The current detection circuit DI's control electrode is connected to the anode of the isolation diode DG, and the cathode of DG is the dimming bus;

[0359] The PWM dimming controller (2) intermittently grounds the dimming bus to dim in the intermittent shutdown mode of DI and transistor QI.

[0360] 7: PWM Modulated AC Voltage Dimming LED Driver (Figure 7)

[0361] PWM pulse generator ( Figure 1 )Control PWM power frequency dimming power supply ( Figure 3 Output chopper-controlled AC voltage;

[0362] The chopper-controlled AC voltage is an AC capacitor-based step-down and limiting control PWM dimming LED driver. Figure 5 (Power supply);

[0363] Dimming is achieved by adjusting the duty cycle of the output pulse of the PWM pulse generator oscillator.

[0364] Multiple sets of AC capacitor step-down limiting control PWM dimming LED drivers are connected in parallel at their AC input terminals to form a dimming bus;

[0365] The dimming bus is controlled by a PWM AC dimming power supply to form a tiered group control dimming system.

[0366] 8: Composite load NPN transistor limited PWM dimming LED driver (Figure 8)

[0367] LED load circuit;

[0368] The input terminal of the direct-controlled rectifier bridge DZV is directly connected to the AC power supply, and the output voltage drives the independent LED loads PHV and JHV.

[0369] LED loads PHC, JHC, DHL, DH3, DH2, and DH1 are connected in series with a current sampling resistor RI grounded to form a common load.

[0370] A step-down capacitor CZL and CZE are connected in series between the two input terminals of the step-down rectifier bridge DZC and the AC power supply.

[0371] The pulsating voltages output from the rectifier bridges DZV and DZC jointly drive a shared load.

[0372] An independent load, an NPN limiting transistor Qi, and a shared load are connected in series to form an LED composite load.

[0373] LED load current waveform, amplitude, and phase angle under DZV drive state of direct-controlled rectifier bridge:

[0374] When the LED load current is not in the limiting state, it is a sinusoidal pulsating wave synchronized with the power frequency.

[0375] The voltage amplitude of a single LED is 1 / N of the pulsating voltage amplitude output by the rectifier bridge DZV, where N is the number of LEDs connected in series.

[0376] The AC power input current and the pulse current of a single LED have a contact angle of 180° / N;

[0377] In the limiting and regulating state, the LED load current is a flat-top sinusoidal pulsating wave synchronized with the power frequency;

[0378] In the limiting regulation state, the sinusoidal pulsating voltage drop of transistor QI is only the amplitude of the power frequency voltage fluctuation increment and its pulse width.

[0379] The waveform, amplitude, and phase angle of the LED common load current in the DZC driving state of the buck rectifier bridge:

[0380] The common load current of LEDs driven by the buck rectifier bridge is approximately a square wave;

[0381] The common load current leads the power frequency voltage by ≤90° and begins to decay when the rate of change of the power frequency sinusoidal voltage slows down as it approaches its peak.

[0382] As the number of LEDs connected in series decreases, the phase of the shared load current advances and the on-angle increases;

[0383] The common load current is filled and superimposed by the sinusoidal pulsating current driven by the direct-controlled rectifier bridge DZV during the decay to zero;

[0384] The phase angle between the AC input current of the driver and the shared load current of the LED approaches 360°.

[0385] Limiting transistor Qi base current;

[0386] The LED load DHL, resistor RHL, and transistor QHL form a constant current source to provide base drive current for limiting transistor Qi;

[0387] The current detection circuit DI anode is connected in series with resistor RI and grounded, and DI cathode controls the base voltage of QB through Zener diode DW;

[0388] The emitter of transistor QB is grounded, and the collector is connected in series with resistor RQI to shunt and limit the base drive current of transistor QI.

[0389] LED load current setting and detection:

[0390] The sum of the voltage across the rated load current sampling resistor RI and the TL431 reference voltage is the LED load current setting value;

[0391] That is, when the voltage of the current sensing stage DI controller electrode is equal to the set value, the LED load current is the rated value.

[0392] The voltage in the series circuit of resistor RV and temperature-compensated LED diode DHV with cathode ground is taken from the anode of LED load DH3.

[0393] The DHV diode is embedded in the LED load heat sink or soldered to the same aluminum substrate as the LED load.

[0394] Resistor RK is connected in series with RKT and parallel with DHV. Adjusting the moving contact of RKT makes the voltage of the DI control electrode equal to the set value.

[0395] The voltage across the load current sampling resistor RI, which is the voltage between the anode and ground of the current sensing stage DI, is the LED load current detection value.

[0396] LED load current limiting adjustment:

[0397] As the LED load temperature rises, the DHV tube voltage and the DI control electrode voltage decrease, while the DI cathode voltage rises.

[0398] The LED load current increases as the power supply voltage rises, and the increase in the anode voltage of the current detection circuit DI causes the cathode voltage to rise.

[0399] The DI cathode is connected in series with a pull-up resistor RDI, which controls the base voltage of QB via a Zener diode DW.

[0400] As the base voltage of transistor QB increases, the base current of limiting transistor QI decreases and its internal resistance increases.

[0401] The driver controls the LED load current amplitude in the mode of adjusting the internal resistance of the limiting transistor Qi.

[0402] Additional limiting adjustment for power frequency voltage fluctuations:

[0403] As the mains frequency power supply voltage increases, the average LED load current also increases.

[0404] As the AC voltage increases, the driver enters the limiting regulation state, the internal resistance of QI increases, and the anode voltage of the constant current source DHL rises.

[0405] The resistor RF is connected in series with the DHL anode and RFT to ground the voltage divider to detect the increase in power supply voltage.

[0406] Resistor RWF limits the current of Zener diode DWF, and auxiliary limiting transistor QFL is connected in series with Zener diode DWF to ground;

[0407] When the sliding point voltage of resistor RFT is greater than the base-to-ground voltage of transistor QFL, QFL enters the conducting state.

[0408] The collector series resistor RFL of transistor QFL shunts the base drive current of transistor QI;

[0409] The driver increases the internal resistance of the transistor Qi and decreases the LED load current amplitude in a secondary limiting mode to keep its average value constant.

[0410] Dimming circuit:

[0411] The optocoupler UTG1 intermittently controls the base voltage of transistor QB and switches on and off to shunt and limit the base current of transistor Qi.

[0412] The optocoupler UTG2 intermittently controls the constant current source, and the switching on and off controls the base current of the limiting transistor Qi.

[0413] Multiple sets of optocouplers, UTG1 and UTG2, have their diode input terminals connected in series with matching resistors and then connected in parallel to form a dimming bus.

[0414] The dimming bus is controlled by the dimming pulse voltage output by the PWM dimming driver;

[0415] The driver implements PWM group control dimming using the intermittent switching mode of the limiting transistor Qi.

[0416] 9: Composite load PNP tube limited PWM dimming LED driver (Figure 9)

[0417] The driver circuit topology and control mode are similar to those in Figure (8), and its circuit characteristics are as follows:

[0418] The limiting transistor is a PNP transistor, and the LED load current constant amplitude control adopts a standard operational amplifier;

[0419] The operating power supply voltage of the operational amplifier is based on the pulsating voltage of a portion of the LED load.

[0420] LED load circuit;

[0421] The input terminal of the direct-controlled rectifier bridge DZV is directly connected to the AC power supply, and the output voltage drives the independent LED loads PHV and JHV.

[0422] LED loads PHC, JHC, DH3, DH2, and DH1 are connected in series with LED current sampling resistor RI and grounded to form a common load;

[0423] A step-down capacitor CZL and CZE are connected in series between the two input terminals of the step-down rectifier bridge DZC and the AC power supply.

[0424] The pulsating voltages output from the rectifier bridges DZV and DZC jointly drive a shared load.

[0425] An independent load, a PNP limiting transistor Qi, and a shared load are connected in series to form an LED composite load.

[0426] Limiting transistor Qi;

[0427] The emitter resistor RQI of transistor QB is grounded, and the collector current is the drive current of the limiting transistor QI.

[0428] The output voltage of the operational amplifier ARI, through the pull-up resistor RB, is the base drive voltage of the transistor QB, which controls its collector current.

[0429] The driver adjusts the internal resistance of the PNP limiting transistor Qi to maintain the constant LED load current amplitude.

[0430] LED load current setting and detection:

[0431] The voltage in the series circuit of resistor RV and temperature-compensated LED diode DHV with cathode ground is taken from the anode of LED load DH3.

[0432] The DHV diode is embedded in the LED load heat sink or soldered to the same aluminum substrate as the LED load.

[0433] Resistor RK is connected in series with RKT and in parallel with LED diode DHV;

[0434] The voltage at the non-inverting input of the operational amplifier ARI, which is the voltage at the sliding contact of the resistor RKT, is the set value of the LED load current.

[0435] The voltage at the inverting input of the op-amp ARI is the voltage across the current sensing resistor RI, which is the LED load current sensing value.

[0436] LED load current limiting adjustment:

[0437] The power supply voltage for op-amp ARI is taken from the series voltage of DH3, DH2, and DH1;

[0438] The voltage at the non-inverting input of the operational amplifier ARI varies with the DHV voltage of the temperature-compensated LED diode.

[0439] The voltage at the inverting input of op-amp ARI changes with the voltage detected by the current in resistor RI.

[0440] As the LED load temperature rises, the DHV tube voltage drops, or the LED load current increases, causing the op-amp ARI output voltage to decrease.

[0441] When the base drive voltage of transistor QB decreases, the base drive current of limiting transistor QI decreases and its internal resistance increases.

[0442] The driver maintains a constant LED load current amplitude by adjusting the internal resistance of the limiting transistor Qi.

[0443] Additional limiting adjustment for power frequency voltage fluctuations:

[0444] The power supply voltage for the operational amplifier ARF is taken from the series voltage of DH3, DH2, and DH1.

[0445] The voltage at the non-inverting input of the additional limiting circuit operational amplifier ARF, and the voltage at the Zener diode DW, is the reference value for the secondary limiting adjustment voltage.

[0446] A resistor RF is connected in series with RFT grounded and then in parallel to the output of the rectifier bridge DZC to detect the power frequency voltage fluctuation.

[0447] The voltage at the inverting input terminal of the operational amplifier ARF, i.e., the sliding contact voltage of the RFT, is the detected value of the power frequency voltage fluctuation.

[0448] When the detected value is greater than the reference value: the ARF output voltage drops, the diode DF turns on, and the transistor QB drive voltage decreases;

[0449] The limiting transistor Qi's drive current decreases, causing its internal resistance to increase again; the driver's secondary limiting remains constant, maintaining its average value.

[0450] Dimming circuit:

[0451] Optocoupler UK dims in a mode that controls the ARI setpoint of the detection level;

[0452] The optocoupler UB dims in mode by controlling the base drive voltage of the emitter output transistor QB.

[0453] Multiple sets of optocouplers with UK and UB diodes are connected in series with matching resistors and then connected in parallel to form a dimming bus.

[0454] The dimming bus is controlled by the dimming pulse voltage output by the PWM dimming driver;

[0455] The driver implements PWM group control dimming using the intermittent switching mode of the limiting transistor Qi.

[0456] 10: Heat dissipation and insulation of the driver: Figure (10)

[0457] Insulating and thermally conductive resin is filled between the aluminum substrate heat sink and the metal casing of the lamp.

[0458] Increase the thickness of the screw thread material in high-power bulbs to utilize the metal of the screw thread for heat dissipation.

Claims

1. One: PWM pulse generator: It includes: 555A oscillator; 555B Optically Controlled Bistable Trigger; Transistor QV; Its features are: A 555A constant-frequency duty-cycle adjustable oscillator is controlled by a 555B optically controlled bistable trigger to generate PWM pulses. The PWM pulse voltage is the base drive voltage of the emitter-output transistor QV, and the emitter of QV extends the PWM pulse output current. The QV transistor outputs a PWM dimming pulse voltage from its emitter.

2. PWM dimming controller: It includes: Oscillating transistor QT: Zener diode DWT: SCR (Syroscope Retrieval System): Timed Capacitive CT: Charging resistor RC: Discharge resistor RF: DC charging diode; Discharge diode DF; Its features are: The PWM dimming controller is a relaxation oscillator, and its oscillation frequency and duty cycle are adjusted by DC voltage. The oscillating transistor QT outputs PWM dimming control pulses when it is turned on and off. Oscillating transistor QT off state: The emitter of the oscillator transistor QT is connected in series with the Zener diode DWT and grounded; the thyristor SCR is connected in parallel with DWT. The DC dimming voltage is such that the charging voltage of the timing capacitor CT is lower than the Zener voltage of the Zener diode DWT, and the transistor QT is turned off. The conduction state of the oscillating transistor QT: When the charging voltage of the timing capacitor CT is greater than the Zener voltage of the Zener diode DWT, the transistor QT and the thyristor SCR are turned on. When the emitter of transistor QT is grounded, the charging voltage of timing capacitor CT is short-circuited, and timing capacitor CT discharges. The discharge current of capacitor CT keeps transistor QT on until CT discharges to a low level and transistor QT turns off again. Three: PWM mains frequency dimming power supply: It includes: Rectifier bridges DT and DK: Transistor QT: Optocoupler UTG: Its features are: The rectifier bridge DT and the transistor QT form an AC solid-state switch; The output voltage of rectifier bridge DK drives transistor QT through a resistor; The on / off state of the UTG transistor in the optocoupler controls the base current of the QT transistor in the AC solid-state switch; The PWM pulse generator outputs a pulse voltage to drive the optocoupler UTG; The rectifier bridges DT and DK form a PWM power frequency dimming power supply, which outputs a chopper-controlled power frequency AC voltage. When there is no PWM voltage input, the PWM power frequency dimming power supply outputs a normal continuous AC voltage.

4. AC capacitor step-down and shunt control PWM dimming LED driver: It includes: Step-down capacitor CZL; Rectifier bridge DZC; LED load; Relaxation oscillator; External dimming circuit; Current detection circuit DI; PWM pulse generator: PWM dimming controller: Optocoupler UTG; External dimming circuit; Its features are: LED load driving voltage: The series step-down capacitor CZL of the power frequency AC voltage is the input voltage of the rectifier bridge DZC; The pulsating voltage output by the DZC rectifier bridge is the driving voltage for the LED load; LED load current shunt adjustment: The current detection circuit DI is connected in parallel with the LED load to form a shunt constant amplitude regulation circuit; The driver maintains a constant amplitude when the LED load current exceeds the limit by conducting the current sensing circuit DI; Independent PWM dimming: A relaxation oscillator is controlled by a resistor, using the LED load voltage as the power supply. An external dimming circuit is formed by connecting a switch SW and a dimming resistor RC in series. Adjusting the dimming resistor RC changes the pulse width and duty cycle of the oscillator transistor; The oscillator transistor is connected in parallel with the LED load, and the LED load is intermittently short-circuited to achieve independent PWM dimming. Group-controlled PWM dimming: Dimming is controlled by the PWM pulse generator: Multiple sets of driver optocoupler input diodes are connected in series with matching resistors and then connected in parallel to form a dimming bus; The dimming pulse voltage of the PWM pulse generator controls the dimming bus; The optocoupler transistor causes the voltage at the control electrode of the current detection circuit DI to rise intermittently. The current detection circuit DI is intermittently conducting, short-circuiting the LED load to achieve remote PWM group control dimming; The dimming is controlled by the PWM dimming controller in a group: The output terminals of each step-down rectifier bridge of multiple drivers are connected to the anodes of isolation diodes, and the cathodes of the diodes are connected in parallel to form a dimming bus. The transistor QT of the PWM dimming controller is connected to the dimming bus and is connected in parallel with all LED loads through each isolation diode; The driver achieves PWM group control dimming by intermittently shorting the LED load with the transistor of the PWM dimming controller.

5. AC capacitor step-down limiting control PWM dimming LED driver: It includes: Step-down capacitor CZL; Rectifier bridge DZC; Constant current source; NPN limiting transistor QI; Current detection circuit DI; Optocoupler UTG; External dimming circuitry; Its features are: LED load driving voltage: The power frequency AC voltage is connected in series with the step-down capacitor CZL, which is the input voltage of the step-down rectifier bridge DZC. The pulsating voltage output by the rectifier bridge DZC is the driving voltage for the LED load. LED load current regulation: An NPN limiting transistor Qi is connected in series with the LED load; The constant current source provides the base drive current for the NPN limiting transistor Qi; The current detection circuit DI shunts and limits the base drive current of the transistor Qi; The driver adjusts the internal resistance of the limiting transistor Qi to keep the LED load current amplitude constant in current-limiting mode; Independent dimming: An external dimming circuit consisting of a battery BT, a switch SW, and a dimming resistor connected in series is connected in parallel with the input terminal of the optocoupler. Adjust the dimming resistor of the dimming circuit to change the internal resistance of the optocoupler transistor and the control electrode voltage of the current detection circuit DI; Independent analog dimming is achieved by continuously adjusting the base current of the limiting transistor Qi and changing its internal resistance. Group control dimming: The input terminals of the UTG diodes of each optocoupler in multiple drivers are connected in series with matching resistors and then connected in parallel to form a dimming bus. The PWM pulse generator dimming pulse voltage controls the dimming bus, causing the adjustment circuit DI to intermittently enter the saturation conduction state. Intermittently control the base current of the limiting transistor Qi to achieve PWM group control dimming in the intermittent on / off mode of the limiting transistor Qi.

6. Capacitor-driven step-down, freewheeling, constant voltage, limiting control, dimming LED driver: It includes: DZC step-down rectifier bridge; Direct-controlled rectifier bridge DZV; DC step-down capacitor CJ and energy storage capacitor CV; LED load network; PNP limiting transistor; Voltage regulator circuit VR; Freewheeling diode DH; Current detection circuit DI; Optocoupler UTG; PWM dimming pulse generator; Its features LED load current: A capacitor is connected in series at both input terminals of the DZC step-down rectifier bridge to output a pulsating voltage to drive the LED load; The LED load current driven by the DZC output leads the power frequency voltage and intermittently decays to zero within the phase angle related to the peak power frequency voltage. A voltage divider circuit with a step-down capacitor CJ connected in parallel and an energy storage capacitor CV connected in series at the output terminal of the power frequency voltage direct-drive rectifier bridge DZV. The sinusoidal pulsating voltage CV of the energy storage capacitor provides freewheeling current for the LED load during periods of load current interruption. The pulse width of the sinusoidal pulsating voltage CV of the energy storage capacitor, which is slightly greater than the load voltage, should be the pulse width at which the LED load current decays to zero. CV voltage can be directly used for LED load freewheeling; CV voltage is the input voltage of the voltage regulator circuit VR, and VR output voltage is the freewheeling current of the LED load; LED load current control: A PNP limiting transistor is connected in series in the LED load to form a limiting constant amplitude circuit; The cathode of the current detection circuit DI provides the base drive current for the limiting transistor Qi; The driver maintains a constant LED load current amplitude by adjusting the internal resistance of the PNP limiting transistor. Dimming mode: Multiple sets of driver optocouplers and UTG diodes are connected in series with matching resistors and then connected in parallel to form a dimming bus. The PWM pulse generator controls the optocoupler via a dimming bus; The UTG transistor controls the current detection circuit DI, which turns the PNP limiting transistor Qi on and off to achieve PWM group control dimming.

7. PWM Modulated AC Voltage Dimming LED Driver: It includes: PWM pulse generator; PWM power frequency dimming power supply: AC capacitor step-down limiting control PWM dimming LED driver; Its features are: The PWM pulse generator controls the PWM power frequency dimming power supply to output a chopper-controlled AC voltage; The chopper-controlled AC voltage is the power supply for the AC capacitor step-down limiting control PWM dimming LED driver; Dimming mode is achieved by adjusting the duty cycle of the output pulse of the PWM pulse generator oscillator; Multiple sets of AC capacitor step-down limiting control PWM dimming LED drivers are connected in parallel at their AC input terminals to form a dimming bus; The dimming bus is controlled by the PWM AC dimming power supply to form a tiered group control dimming system.

8. Composite load NPN transistor limited PWM dimming LED driver: It includes: Direct-controlled rectifier bridge DZV; Independent LED load; DZC step-down rectifier bridge; Shared LED load; Constant current source; NPN limiting transistor QI; Transistor QB; Auxiliary limiting transistor QFL; Current detection circuit DI; Optocouplers UTG1 and UTG2; Its features are: LED load circuit: The input terminal of the direct-controlled rectifier bridge DZV is directly connected to the AC power supply, and the output voltage drives the independent LED load. A step-down capacitor is connected in series between the two input terminals of the DZC step-down rectifier bridge and the AC power supply. The output voltages of the direct-controlled rectifier bridge and the buck rectifier bridge jointly drive the LED shared load; LED load current control: An NPN limiting transistor Qi is inserted into the series circuit of an independent LED load and a shared LED load. The constant current source provides the base drive current for the limiting transistor Qi; Transistor QB shunts and limits the base drive current of transistor QI; The current sensing stage DI controls the base voltage of the shunt transistor QB to regulate the drive current of the limiting transistor QI; The driver controls the LED load current amplitude by changing the Qi internal resistance mode; Additional limiting adjustment for power frequency voltage fluctuations: The base drive current of the limiting transistor QI rises according to the fluctuation of the AC power supply voltage; The driver performs secondary limiting of the LED load current in the mode of readjusting the internal resistance of the limiting transistor Qi; Dimming circuit: The optocoupler UTG1 intermittently controls the base voltage of transistor QB and switches on and off to shunt and limit the base current of transistor Qi. The optocoupler UTG2 intermittently controls the constant current source, and the switching on and off controls the base current of the limiting transistor Qi. Multiple sets of optocouplers, UTG1 and UTG2, have their diode input terminals connected in series with matching resistors and then connected in parallel to form a dimming bus. The dimming bus is controlled by the dimming pulse voltage of the PWM pulse generator; The driver implements PWM group control dimming using the intermittent switching mode of the limiting transistor Qi.

9. Composite load PNP transistor limited PWM dimming LED driver: It includes: Direct-controlled rectifier bridge DZV; Independent LED load; DZC step-down rectifier bridge; Shared LED load; PNP limiting transistor QI; Drive transistor QB; Operational amplifiers ARI and ARF; Optocouplers UK and UB; Its features are: LED load circuit: The input terminal DZV of the direct-controlled rectifier bridge is directly connected to the AC power supply, and the output voltage drives the independent LED load. A step-down capacitor is connected in series between the two input terminals of the DZC step-down rectifier bridge and the AC power supply. The output voltages of the direct-controlled rectifier bridge and the buck rectifier bridge work together to drive a group of LEDs sharing a load. LED load current control: A PNP limiting transistor Qi is inserted into the series circuit of an independent LED load and a shared LED load. The driving transistor QB provides the base drive current for the limiting transistor Qi; The operational amplifier ARI controls the base voltage of transistor QB to regulate the base drive current of limiting transistor QI; The driver controls the LED load current amplitude in Qi internal resistance adjustment mode; Additional limiting adjustment for power frequency voltage fluctuations: The operational amplifier ARF follows the rise of the AC voltage and shunts the base drive current of the limiting transistor QI; The driver performs secondary limiting of the LED load current in the mode of readjusting the internal resistance of the limiting transistor Qi; Dimming circuit: The optocoupler UK controls the current setting of the operational amplifier ARI; The optocoupler UB controls the base drive voltage of the transistor QB; Multiple sets of optocouplers with UK and UB diodes are connected in series with matching resistors and then connected in parallel to form a dimming bus. The dimming bus is controlled by the dimming pulse voltage of the PWM pulse generator; The driver implements PWM group control dimming using the intermittent switching mode of the limiting transistor Qi.

10. Driver heat dissipation and insulation: Insulating and thermally conductive resin is filled between the aluminum substrate heat sink and the metal casing of the lamp. Increase the thickness of the screw thread material in high-power bulbs to utilize the metal of the screw thread for heat dissipation.

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