DIY 12V battery car reading lights, door lights, tail lights, etc. are preferred. Constant current over the full voltage range.

 

Size: 28X18X6 mm

 

This board belongs to the buck type driver board. The input voltage should be higher than the LED VF value +3V to constant current. Some buyers mistakenly recognize the 6V drive three strings.

 

3 PT4115 based constant current drive technology

 

3. 1 Introduction to PT4115 chip

 

1) Very few external originals

 

2) Wide voltage input range: from 8 V to 30 V

 

3) Maximum output 1. 2 A current

 

4) Multiplex DIM pins for LED switching, analog dimming, PWM dimming

 

5) 5 % output current accuracy

 

6) LED open circuit protection

 

7) Up to 97% efficiency

 

8) Output adjustable constant current control method

 

9) Internally contains frequency-jittering characteristics to greatly improve EMI

 

3. 2 Typical Application Circuit
Turn left | turn right

 

Figure 4 PT4114 Typical Application Circuit

 

For PT4115 (see Figure 4) it can be applied to 12~18 V AC, or 8 V~30 V DC. Therefore, the scope of application is more extensive. Moreover, the driving circuit is simple, and the required components are all inexpensive. Suitable for batch and market.

 

3. 3 PT4115 constant current principle

 

Keep the sampling end (CSN) input voltage value constant current when the IC internal set value is constant with respect to the VIN voltage value. because:
Turn left | turn right

 

In the formula:

ILED --- current flowing through L ED ;

 

VCSN --- voltage detection terminal voltage;

 

RS --- current sampling resistor.

 

It can be seen from equation (1) that the current flowing through the LED can be made constant as long as the voltage at the sampling terminal is constant with respect to the voltage at the input terminal.

 

3. 4 PT4115 dimming measures

 

The PT4115 uses PWM dimming to turn off the LED current when the DIM pin voltage is lower than 0.3 V, and turn on the LED current when it is higher than 2.5 V.

 

The PWM dimming measure does not affect the LED efficacy compared to conventional linear dimming. The basic principle of PWM dimming is to keep the LED forward current constant, and by controlling the ratio of the time that the current is turned on and off, that is, the time during which the current is turned on every cycle. The advantage of PWM dimming is that the current of the LED forward conduction is always constant, and the chromaticity of the LED does not change like analog dimming. PWM dimming can precisely control the brightness of the LED while also ensuring the chromaticity of the LED illumination.

 

Linear dimming adjusts the light efficiency by changing the current flowing through the LED. The change in current flowing through the LED necessarily affects the chromaticity of the LED.

Therefore, PWM dimming has made great progress over traditional linear dimming.

 

3. 5 PT4115 frequency jitter to improve the principle of EMI

 

Frequency Jitter is a new way to solve EMI problems by dispersing harmonic interference energy. The frequency jitter technology refers to a method in which the operating frequency of the switching power supply is not fixed, but the EMI is reduced periodically by narrowband to broadband to reduce electromagnetic interference.

 

Frequency dithering techniques reduce narrowband EMI by extending the power supply noise spectrum. There are some limitations to the oscillator frequency (fs) that can be dithered. Some of these limitations are switching losses and magnetic circuit design. In order to keep the boost inductor as small as possible and keep the switching loss within the controllable range, the frequency jitter should not exceed 20% to 30% of the fundamental frequency.
3. 6 Dynamic temperature regulation and over temperature protection of PT4115

 

The PT4115 has dynamic temperature regulation and can be over-temperature protected based on this function.

 

1 x PT4115 6-30V input 0.6A LED constant current driver board