LC5200 series LE...

  • 2022-09-15 14:32:14

LC5200 series LED driver

Features and advantages

Power voltage, VBB, maximum 450 V, recommended 25 to 400 V; Note: The minimum voltage may be different depends on the LED load

output current IO ( Maximum option:

0.5, LC5205D

1.0, LC5210D

Hengliu control circuit:

fixed turning off time PWM constant current control, constant current control, constant current control, constant current control, The disconnection time can be adjusted by external components

External adjustable input voltage output current

to reference pins

output current through external PWM signals; low send to TOFF quotation The signal of the foot cutting output current and the signal input of the pins of the pwm pins can be dimmed

IOl Second Lock Protection (UVLO)

Over -current protection (OCP); atresia to respond to a short circuit to respond to a response to responding to a short circuit.

Heating protection (TSD); Protecting IC

The temperature is too high, and automatically restarts

The temperature drops below the threshold

Instructions

[ 123] The LC5200 series is an offline LED driver integrated circuit, including the main controller integrated circuit (MIC) and power MOSFET. Its high -voltage capacity allows direct connection to a wide range of power voltage range from 25 to 400 V (recommended). LC5200 uses the current mode of constant LED. Packaging is a standard 8 -needle DIP, removed for sale 7 to get a greater climbing distance from the power supply.

All the performance characteristics given are only designed by the circuit or system baseline, and at the nominal value operating voltage and the ambient temperature of 25 ° C. Essence

Unless otherwise explained, the electrical characteristics are valid at TA u003d 25 ° C and VBB u003d 140 V

The regulator

The LC5200 series provides an output voltage of 12 V from the internal circuit and external components from the power supply voltage on the VBB pin for power supply. When the grid capacitance is charged in the MOSFET, it generates a current, causing ripple voltage. This may affect the operation, so connecting a 0.1 μF ceramic capacitor to stable operations at the REG pin.

current control

The current control adopts a PWM topology structure with a fixed turnover time. This output current level can be set by the input voltage setting of the input voltage on the REF, and the voltage of the voltage resistance on the current. In addition, the fixed shutdown time can be adjusted to the external capacitors and resistors at the TOFF pin.

Impurd voltage lock

This can prevent the output circuit from the ULVO threshold voltage when the internal power supply voltage of the internal power supply is reduced by the shutdown of the device can be prevented by shutting down. VUVLO. In addition, the UVLO circuit is used for over -current power -on function protection (OCP).

TSD (heat shutdown)

When the temperature of the main control chip (MIC) exceeds TSD, the threshold temperature, TTSD, the device shuts down the output (the system logic continues to run) to avoid abnormal temperature rise. When the temperature decreases due to lag, TTSDHYS or if the power supply voltage is recycled, the device will return to normal operation. Note: The main thermal source is MOSFET, when the heat spreads to microphone and induction. Therefore, the rapid increase of MOSFET may damage the device.

OCP (Overcurrent Protection)

When the input voltage of the induction pin reaches the OCP threshold, VOCP, it turns out the output and switch to the locking mode. Related from the lock mode neatly, please turn off the power supply. Note: OCP is used to protect the device from being affected by current. OCP may not work in the short circuit of LED because the coil may inhibit the increase in current.

Internal switching logic

This device can open or close the status of the MOSFET gate -drive circuit current control sensing circuit and protection circuit.

The driver operation

This includes the MOSFET gate drive circuit. The two device versions in the LC5200 series are different from each other's MOSFET current rated values. Select the rated value that currently matches the current application circuit.

Typical application instance

FIG. 1 shows a typical circuit application. See the table below for external components of values.

Component value settings

LED LED current should not exceed the LC5200 device current rating. Set the total voltage drop on the LED series to less than VBB; otherwise, the LED string is extinguished. As a general design principle, the PWM offsetting time should be longer. If there is a small voltage of the LED string, it should be shorter if the voltage on the LED series drops high. For LC5205D, it is recommended that the voltage on the LED series drops to 9 to 30 V to ensure that the normal operation

The higher the inductance of the component, the smaller the width of the ripple the output current, the more output currents have the output current. Essence Under normal circumstances, it is recommended to be 0.5 to 20 mh. It is also necessary to ensure that the coil will not be saturated at the peak of the ripple. Saturation will cause damage to the high wave current LED or device. The diode provides a channel for re -cycle current. If the diode uses the slow recovery characteristics, it will cause the current when the MOSFET is turned on, as well as increased noise and may cause equipment failure. In addition, it can improve efficiency. So Sanken RL3A super fast recovery diode, or it is recommended to use diode with better or equivalent recovery characteristics (50ns). This is the main power supply rectifier capacitor. The larger the capacitor, the smaller the ripple voltage generated. In addition, because higher output power will increase the ripple voltage, the appropriate capacitance should be selected for the output power. Even if the capacitance is low (such as 1000 PF) and the ripple voltage increases, the device works. This also allows a non -electrolytic capacitor design that can extend the life of the unit and reduce the size and cost of the unit. However, if the ripple voltage is lower than the LC5200 UVLO threshold, or the voltage lower than the LED string is dropped, the LED will rotate during that time. C1 The capacitor is used to stabilize the internal regulator circuit operation. A 0.1 μF capacitor may be as close to the device as possible to correctly operate MOSFET. Use the capacitor value to cause the switching speed and failure, but the capacitance value starts slowly.

The following formulas: ipak u003d vreg × r2/([R1+R2] × RS)

For example, if the target is an IPEAK of 0.35 A, the formula becomes: iPeak≈12 (V v ) × 20 (kΩ)/([20 (kΩ) +680 (kΩ)] × 1Ω) u003d 0.35 ampere

According to this, R1 u003d 20kΩ, R2 u003d 680kΩ, RS u003d 1Ω

] Please note that R1 and R2 can cause internal regulators. Therefore, in order to minimize power consumption, please follow the following formulas: (R1+R2) GT; 500,000 Euros In the actual design, due to the delay in internal circuits, the current peak is often higher than the estimated value. This is obviously under high DI/DT conditions, which may be an inductance by high VBB or low coil. For the resistance RS, because the output current runs through it, using a power consumption. These determine the PWM shutdown time, TPOFF. Figure 2 shows the PWM cut off time curve based on different COFF and ROFF values. At the recommendation value, the PWM shutdown time is about 20 μs: ROFF u003d 560 KΩ, COFF u003d 220 PF.

current control

PWM current control work is shown in Figure 3. PWM open cycle. During the MOSFET drive, the current runs through the ion path (as shown in the red panel A in Figure 3). MOSFET is closed. During the connection, the current with the red waveform in the panel B, when it reaches VSENSE, the threshold voltage is closed.

PWM cycle is closed. During the MOSFET shutdown, the energy on the coil and coils occurred by the inverter of the hostess during the connection time, and the current IOFF runs power off through the blue channel of the group A.

MOSFET opens. After the fixed shutdown time, from the external capacitor and resistance in the TOFF pin, the MOSFET rotates againOpen and repeat the above operation. Figure 4 shows the current control circuit, Figure 5 shows the timing diagram of the circuit. When the MOSFET opens, the two load current and VSEN of the two sensor RS are across the sensor RS. The output of vsen and vsen is the opposite gt; VREF (see point A in Figure 5). This will be reset a RS 后 lock and it will cause several logical circuits of MOSFET after the signal is passed. At the same time, the COFF on the TOFF pin is charged by the internal MOS switch. When the compensation inverter input (connected to the TOFF pin) voltage is lower than 2 V, the Comp1 output is reverse, and it sets the RS memory. This offses the MOS switch and starts the COFF charging process through ROFF. The COFF voltage (TOFF PIN) increases as it increases. When its voltage reaches 3 volts and the comp1 output becomes higher, it opens MOSFET (point B in Figure 5). The cycle of the blank pulse circuit is covered with the sound or noise, and the EDGE is opened from the closing edge to the end to ensure the correct PWM operation.

LED current settings and dimming

The output current can be set up with two optional methods: Internal PWM control. The LC5200 series provides a fixed off -cutting time PWM current control operation, allowing the number of external components of an LED constant current control circuit. The output current is calculated according to the following formula: IO u003d VREF/RS

According to this formula, there are two methods to calculate the available control of LED current: simulation control, change the reference pin voltage, as shown in the middle, panels, panels, panels, panels, panels A)

PWM integrated control, input the external PWM signal through the low -pass filter (LPF) and connect the output to the reference sales (Figure 6, panel B). Among these two methods, the TOFF PIN voltage is used for use. To rotate the MOSFET opening or level, so the circuit is shown in Figure 6, the panel C can also adjust the output current through external signals. In this application, when the external small signal MOSFET is turned on, the LC5200 stops the output pulse.

External PWM control. In this control method, the LC5200 allows direct switching to MOSFET for PWM synchronization operations or other reasons for the LED array. Using this method, a pull -up distributioner is connected from the Ref as shown in Figure 7. Capacitors and resistors are removed from the TOFF pin instead of the PWM signal input to the TOFF pin. Please note that the internal peak current control of this method is disabled; therefore, it needs to be used for an external current control circuit for constant current operation. However, over -current protection is still in a state of activation to protect the current of LC5200 and LEDs. The Tiff needle threshold has lagging characteristics: from lt; 2V to MOSFET, from gt; 3V to MOSFET. Therefore, use 5VCompatible input of CMOS control.

About TRIAC Lighting Control (Phase Control)

The commonly used bidirectional gates tubing tube tube is mainly used for resistance load. They need two -way crystal gates pipes to maintain current phase phase phase phase phase phase phase phase phase phase phase phase phase phase phase phase phase phase phase phase phase phase phase phase phase phase phase phase control. The LC5200 series does not respond to this type of lighting device because it does not create the current during the maintenance of the maintenance period.

Increased power factor

The proportion of LED current and AC input voltage increased the power factor, and the LC5200 can be used to achieve a series of reference pins. Figure 8 shows the application circuit. Without AC rectifier capacitors, R2 and R3 generate a low voltage of AC voltage as the AC voltage for reference sales. In this way, LED current follows the AC voltage and increases the power factor. If the reference voltage fluctuation range is large, the clamping diode is connected in parallel to protect the REF pin. In this case, the reference voltage will cause distortion (low waveform in Figure 8) and may lead to a reduction in power factor. Figure 9 shows the actual operation waveform. The display board A shows the operation under the fixed reference pin voltage, and the panel B display the operation of the exchange ratio reference pins voltage. For these two operations, there is no use of an exchange capacitor. The yellow waveform is the AC input current, and the black waveform is 2 KHz low -pass filter waveform. In panel B, the current forms a sine waveform, which means that the power factor is improved.

Figure 9. Power factor improvement work waveform: 100VAC, 5 white LED series, LED average current 0.5A; black trajectory: AC input current IAC2 KHz low -pass filter u003d 500 mA/div; red trace line: 2 kHz low -pass filter after low -pass filter IAC u003d 200 MA/DIV.