Scope of application

LED power supply for switching color temperature

S4120M is a switch color temperature control core with state memory

It can remember the state when the light is turned off, and it will be displayed directly when the light is turned on next time.

Now, the convenience of use has been increased. S4120M can not only drive

Thyristor, and can drive MOS tube. This series of chips uses

With the core technology of Feiling, it is possible to simplify the

The number of peripheral components can ensure that when multiple power supplies are applied at the same time

logical consistency.

In order to expand the field of application, the S4120M series can be used

In the isolated flyback structure and the Buck structure, the design of the power supply is improved.

for convenience.

Function Description

1. Power supply

S4120M is powered through the VCC pin, in the application

Connect the VCC pin to the power output through a current limiting resistor R2

the positive pole. Since the operating current of the IC is about 0.8mA, consider

To temperature changes and other factors that affect the working current, it must be in the design

Leave a margin.

2. Detection

The detection pin of the chip is CLK. In the application, the CLK pin is connected to

The over-sensing resistor R1 is connected to the constant current power supply inductor and the freewheeling diode

One end of the positive connection, as shown in the typical application diagram. chip pass

The CLK pin judges whether the input switch is closed or disconnected. When the input is on

When the input is closed, the CLK pin detects the waveform of the square wave, when the input is open

When the switch is turned off, the square wave detected by the CLK pin disappears. in order to filter

To eliminate noise and avoid false triggering, the S4120M is internally designed with a judgment

The delay time Td(on) of disconnecting and closing state and judging that the switch is off

Delay time Td(off) for ON state.

The selection of the detection resistor R1 must ensure that when the other

When negative pressure occurs at the outer end, the current flowing through R1 must be less than

2mA. 3. Drive

The S4120M series is compatible with both thyristor and MOS

FET, without any external changes, the IC automatically recognizes the connected

type of switch tube. When driving a thyristor, the drive current is approximately

250uA. When driving MOS FET, the large output of the driving pin

The voltage is about 6V. Since the driving pin voltage of S4120M is 6V

The following, so when used to drive a MOSFET, the threshold must be selected

lower voltage MOSFET. 4. Status control

S4120M built-in power-down storage unit, in the case of no power

, the data can still be stored for up to ten years. S4120M is off

When the light is on, the state before turning off the light will be stored in the internal storage unit.

When the light is turned on next time, the S4120M will directly recall the

The data is the state of the output, the user does not need to switch every time the light is turned on

to the color temperature you like, because the user only needs to change the color temperature of the lamp

Change to your favorite state, S4120M will remember it after turning off the light

The user's favorite color temperature will be displayed directly when the light is turned on next time.

S4120M can remember the last time the light was turned off, and

Enter directly when the lights are turned on. But the S4120M can still pass the input

Enter the switch to switch the color temperature again. If the user needs to toggle the light

color temperature, just turn the light back on within a few seconds of turning it off, and the light

The tool will switch to the next state, if you need to switch the color again

temperature, just turn off the light and turn it back on in seconds, the color temperature of the light

will switch to the next state. In this cycle, the S4120M has a total of

three states. As mentioned above, the S4120M has a few seconds after turning off the lights

The color temperature switching window, that is, if the light is turned on again within this window,

The color temperature of the lamp switches to the next state, this color temperature switching window

The size is determined by the size of the VDD capacitor, generally 47uF

The color temperature switching window corresponding to the VDD capacitor is about 5S.

The switching window of the S4120M is also affected by the output voltage and output voltage.

Shenzhen Xinfeiling Semiconductor Co., Ltd.

S4120M switch color temperature control chip with state memory

S4120M-DS-2p1

The effect of the output capacitor (C3) if the output voltage and the output capacitor

Larger will make the switching window larger, and the size of the final switching window can be

Adjust the VDD capacitance according to the actual test results to get the required time

between. When the light-off time exceeds the color temperature switching window, and the light is turned on again, the

The state is the color temperature state when the light was last turned off.

In applications where multiple lights are controlled from the same wall switch,

It is very likely that the color temperature of the lamps will be different when installing lamps, changing lamps, etc.

caused problems. Different from conventional chips without memory, using

The S4120M's lamps cannot be turned off long enough to

There are fixtures initialized. S4120M has built-in reset function for easy operation.

Yes, you can quickly restore all lights to the same state. that is

Turn on the light again within 200ms after turning off the light, and the S4120M will recover.

to the initial state.

In summary, the state changes of the S4120M are all based on turning off the lights.

duration, when the turn-off time is within 200ms, the state

restore to the initial state, and when the turn-off time is within the switching window,

then the state switches to the next state, and when the off time exceeds the switching

window, the state of the S4120M remains the same as when the light was turned off last time.

5. S4120M design skills

When designing the S4120M PCB board, following the following principles will have

Better performance:

1. The VDD capacitor should be as close as possible to the VDD and GND pins of the chip.

foot;

2. The power supply distance of the VCC pin should be as short as possible;

3. Consider the heat dissipation of the S4120M as much as possible in the PCB layout.

question.