main description

S4225M is a switch color temperature control chip with state memory, that is, it can memorize the state before turning off the light. When the light is turned on next time, the lamp directly enters the state before the last time the light is turned off, which increases the convenience of use. The chip has a built-in 400V switch tube, which simplifies the peripheral circuit structure. This series of chips adopts the patented technology of Xinfeiling, which can not only simplify the number of peripheral components to the greatest extent, but also ensure the logic consistency when multiple power supplies are applied at the same time.

In order to expand the application field, the S4225M series can be used in the isolated flyback structure and the Buck structure, which provides convenience for the design of the power supply.

Features

With state memory function, it is more convenient to use

Built-in 400V switch tube, no need for external switch tube

Quick reset function to solve the problem of asynchronous

There is no problem of logical disorder when multiple power supplies are used at the same time

Built-in voltage limiting circuit to ensure a wider operating range compatible with isolated and non-isolated applications

Patented technology, stable performance

Scope of application

LED power supply for switching color temperature

logical order

The logical sequence of the S4225M is D1->D2->D1+D2, where D1 and D2 represent the first and second LED light strings respectively.

Function Description

1. Power supply

The S4225M is powered by the VCC pin. In the application, the VCC pin is connected to the positive pole of the power output through a current limiting resistor R2. Since the working current of the IC is about 0.8mA, there must be a margin in the design considering the factors affecting the working current such as temperature changes.

2. Detection

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

The over-sense resistor R1 is connected to one end of the constant current power supply inductor and the positive electrode of the freewheeling diode, as shown in the typical application diagram. The chip judges whether the input switch is closed or disconnected through the CLK pin. When the input switch is closed, the CLK pin detects the waveform of the square wave, and when the input switch is open, the square wave detected by the CLK pin disappears. In order to filter out noise and avoid false triggering, the S4225M is designed with a judgment

The delay time Td(on) for disconnecting the closed state and the delay time Td(off) for judging the open state of the switch. The selection of the detection resistor R1 must ensure that the current flowing through R1 must be less than 2mA when the other end of the detection resistor has a negative voltage.

3. Drive

S4225M has built-in two 400V switch tubes, the peripheral application circuit has been greatly simplified, the saturation voltage of the switch tubes is 1.2V (IDx=300mA). The S4225M is suitable for applications where the output current is less than 300mA.

4. Status control

The S4225M has a built-in power-down storage unit, which can still save data for up to ten years without power. When the light is turned off, the S4225M will store the state before the light is turned off into the internal storage unit. When the light is turned on next time, the S4225M will directly retrieve the state in the storage unit as the output state, and 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 switch the color of the lamp to the color temperature you like, after turning off the light, the S4225M will remember the color temperature that the user likes, and directly enter the color temperature that the user likes the next time you turn on the light. Although the S4225M can remember the state of the last time the light was turned off, and directly enter the state of the last time the light was turned off the next time the light is turned on, the S4225M can still switch the color temperature through the input switch. If the user needs to switch the color temperature of the light, just turn the light back on within a few seconds after turning off the light, and the light will switch to the next state. When the light is turned on again, the color temperature of the light will be switched to the next state. In this cycle, the S4225M has a total of three states. As mentioned above, S4225M has a color temperature switching window for a few seconds after turning off the light, that is, if the light is turned on again within this window, the color temperature of the lamp will switch to the next state. The size of this color temperature switching window is determined by the size of the VDD capacitor. In general, the color temperature switching window corresponding to a 1uF VDD capacitor

is about 4S. When the light-off time exceeds the color temperature switching window and then it is turned on again, the state of the lamp is the color temperature state of the last time the light was turned off. Since the S4225M will remember the state before the last time the light was turned off, it is not like a general color temperature control chip. After a period of time after the light is turned off, the internal state of the chip will return to the initial state, so when the state is inconsistent, you can turn off the light and If you turn on the lights for a long enough time, all the lights will return to the initial state, and the chip with memory cannot recover from power failure. After returning to the same state, the S4225M has a built-in quick reset function, that is, if the light is turned on again within 200ms after turning off the light, the S4225M will return to the initial state.

@To sum up, the state change of S4225M is based on the duration of the light off. When the light off time is within 200ms, the state returns to the initial state, and when the light off time is within 200ms to 4S (VDD capacitor is 1uF), Then the state switches to the next state, and when the light-off time exceeds 4S, the state of the S4225M remains the state of the last time the light was turned off.

5. S4225M design skills

When designing the S4225M PCB board, following the following principles will have

Better performance:

1. The VDD capacitor should be placed as close as possible to the chip VDD and gnd pins.

2. The heat dissipation of S4225M should be considered as much as possible in the PCB layout.