Implementation of 4-level intelligent dimmable electronic ballast circuit

This article introduces the working principle and implementation of a 4-level intelligent dimmable electronic ballast circuit　　　　using the Microchip microcontroller PIC12F629 and the IR company IRS2530D .

　　1 About IRS2530D and PIC12F629

　　1) Introduction to IRS2530D

　　IRS2530D adopts 8-pin DIP or 8-pin SOIC package. The pin diagram of IRS2530D is shown in Figure 1, the outer package diagram of IRS2130D is shown in Figure 2, the internal function block diagram of IRS2530D is shown in Figure 3, and the pin functions of IRS2530D are shown in Table 1.

Figure 1 IRS2530D pin diagram

Figure 2 IRS2130D package diagram

Figure 3 Internal functional block diagram of IRS2530D

　　Table 1 Pin functions of IRS2530D

　　2) Introduction to PIC12F629

　　The pin diagram of PIC12F629 is shown in Figure 4, and the pin function table of PIC12F629 is shown in Table 2.

Figure 4 PIC12F629 pin diagram

　　Table 2 PIC12F629 pin function table

　　The circuit working principle block diagram is shown in Figure 5, and the circuit working principle diagram is shown in Figure 6. The dimming control reference voltage is provided by the DIM pin of IC1 (IRS2530D), and the dimming control voltage is output by the GP2 pin of the microcontroller IC2 (PIC12F629). The GP pin of the microcontroller IC2 (PIC12F629) is a general I/O pin, and the function of the I/O pin can be set to high-impedance input or CMOS output through software. The dimming control square wave pulse voltage output by the GP2 pin of the microcontroller IC2 (PIC12F629) can obtain the DC dimming control voltage required by IRS2530D after RC filtering. In this circuit, the GP2 pin can output dimming control square wave pulse voltages of 4 pulse widths (pulse duty cycles). The larger the pulse duty cycle, the higher the DC dimming control level generated. [page]

Figure 5 Circuit working principle box

Figure 6 Circuit working principle diagram

　　In the electronic ballast circuit shown in Figure 6, the circuit load is a 25W CFL lamp load, which can achieve dimming control. The EMI filter in the circuit is used to filter out high-frequency interference signals from the AC mains power supply. The DC dimming control level is higher in the microcontroller PIC12F629.

　　In the electronic ballast circuit shown in Figure 6, the circuit load is a 25W CFL lamp load, which can achieve dimming control. The EMI filter in the circuit is used to filter out high-frequency interference signals from the AC mains power supply. The microcontroller PIC12F629 contains an EEPROM, which can be used to store the latest dimming setting level value before the power supply is cut off. This ensures that the electronic ballast can re-light the lamp load with the stored lamp brightness setting value after power is re-applied. The circuit flow chart is shown in Figure 7.

Figure 7 Circuit flow chart

　　The GP1 input pin of the microcontroller IC2 (PIC12F629) is connected to the 220V AC input mains power supply through a filter circuit with a very short delay time, which is used to quickly detect the connection or disconnection of the AC input mains power supply. When the 220V AC input mains power supply is disconnected, the 5V voltage stored on the capacitor C1 that powers IC2 is sufficient to power IC2 (PIC12F629) for 1s. When the 220V AC input mains power supply is disconnected, IC2 detects this rapid change and starts the timer. If the 220V AC input mains power supply is restored within 1s, the dimming level is reduced by 1 level. If the original dimming level is the lowest value, the dimming level becomes the maximum value. If the 220V AC input mains power supply is disconnected for more than 1s, the dimming level of the electronic ballast circuit remains unchanged. When the voltage on capacitor C1 is discharged to a value lower than the minimum operating voltage VDD of microcontroller IC2 (PIC12F629), microcontroller IC2 (PIC12F629) is in the shutdown state. [page]

　　The circuit board diagram and the actual diagram of the 4-level dimmable fluorescent lamp intelligent electronic ballast using IRS2530D are shown in FIG8 , FIG9 , and FIG10 , respectively.

Figure 8 Actual picture

Figure 9 Silkscreen layer diagram

Figure 10 Printed circuit board diagram