EZ-0011: 8-bit MCU LED lighting control scheme

Renesas’ 78K0/Ix2 8-bit monolithic microcontroller series includes 78K0/IY2, 78K0/IA2 and 78K0/IB2, using 78K0 CPU core, high-speed clock up to 10MHz, supply voltage VDD from 2.7V to 5.5V, VDD is The working mode current at 5V is 350μA, and the STOP mode current is 0.58μA, which is mainly used for LED lighting control. This article describes the main features, block diagram of the 78K0/Ix2 8-bit monolithic microcontroller, as well as the main features of the 78K0/IB2 PFC LED Lighting Evaluation Board, LED lighting system block diagram, circuit diagram, and corresponding bill of materials.

Key Features of 78K0/Ix2 8-Bit Monolithic Microcontrollers

78K0 CPU cores

• Low power consumption (VDD = 5.0V)

• Internal high-speed oscillation operating mode: 350μA (typ.) (operating at fCPU = 1MHz)

EZ-0011: 8-bit MCU LED lighting control scheme
Figure 1 78K0/IY2 block diagram

• STOP mode: 0.58μA (typ) (operating at fIL = 30kHz)

• High-speed system clock, selectable from the following four clock sources

– Ceramic/Crystal Oscillator: 1MHz to 10MHz

– External clock: 1MHz to 10MHz

– Internal high-speed oscillator: 4MHz ±2 % (–20°C to +70°C) or 8MHz ±5% (–40°C to +85°C)

– Clock for 16-bit timers X0 and X1: 40MHz (typ.) (when using PLL)

• Internal low-speed oscillator 30kHz±10%, watchdog timer, timer clock timer in intermittent operation

• 16-bit timer X: PWM output (40MHz (maximum) clock operation), linked with external signals, synchronous output of up to four channels, triggering A/D conversion

• 16-bit timer/event counter: PPG output, capture input, external event counter input

• 8-bit timer H1: PWM output, can work on the internal low-speed oscillation clock

• 8-bit timer/event counter 51: External event counter input

• Watchdog timer: can operate with internal low-speed oscillation clock

serial interface

• UART6 –– asynchronous 2-wire serial interface

• DALI–– 2-wire serial interface for lighting control (slave mode)

• IICA –– Clock synchronous 2-wire serial interface, supports multi-master communication, and can release standby mode by address matching in slave mode

• CSI11 –– Clock synchronous 3-wire serial interface, operates as SPI in slave mode

Figure 2 Flyback converter for LED constant current control

Multiplier (8 bits × 8 bits = 16 bits, 16 bits × 16 bits = 32 bits, 1 clock operation)

• 78K0/IY2: 5 channels

• 78K0/IA2: 6 channels

• 78K0/IB2: 9 channels

• Operational amplifier (only for products with built-in operational amplifier): 1 channel

• Comparator: 3 channels

• Power-on-clear circuit (POC)

• Low Voltage Detection Circuit (LVI) (Generate interrupt/reset when detection voltage is reached (selectable))

• Detection voltage: Selectable from ten levels from 2.84V to 4.22V After setting the LVI default start, 1.91 V is used only when the power is turned on.

Single-Supply Flash Memory

• Allows Flash self-programming

• Software protection function: prevent external copying (no Flash read command) security function

• The watchdog timer operates independently of the CPU clock to detect even when the system clock is stopped


• Use LVI to detect supply voltage drops and take appropriate action before the supply voltage drops below the operating voltage.

• With option byte function, important system operations are set in hardware.

• On-chip debug function: used for target device control and reference memory.

• Supports assembly language and C language

• Improve development environment (under development)

• Supports full-featured emulator (IECUBE) and simple emulator (MINICUBE2)

• Power supply voltage: VDD = 2.7V~5.5V

• Operating ambient temperature: TA = –40℃~+105℃

78K0/IB2 PFC LED Lighting Evaluation Board

Lighting accounts for about 16% of the power consumption of household appliances. Due to the need to reduce CO2 emissions and save energy, the application of LEDs in lighting has become more and more common in recent years, because LED lighting has higher luminous efficiency and longer service life than traditional incandescent or fluorescent lamps. In order to save system energy, there is a growing need for optimal on/off control and dimming control, requiring the use of microcontrollers for lighting system control. On the other hand, there is an increasing need to cut costs in order to promote LED lighting. There are many examples of using a board platform to reduce development man-hours or to incorporate the functions of an analog control IC into a microcontroller.

In response to these needs, this application note introduces the features, system configuration, and control methods of an LED lighting system using a 78K0/Ix2 microcontroller by taking the LED lighting evaluation board using the PFC control EZ-0011 as an example.

Figure 3 Outline drawing of LED lighting system using 78K0/Ix2 MCU

Main Features of 78K0/Ix2 LED Lighting Control System

Using the timer output function of 16-bit timers X0, X1 and 00 and 8-bit timer H1, LED constant current/dimming control is realized for 6 channels (maximum value). This eliminates the need for an LED constant current control IC, thereby cutting costs.

Power factor correction (PFC) control is implemented using the timer restart function and the comparator of the 16-bit timer X0. This eliminates the need for a PFC control IC, cutting costs.

A protection function capable of emergency stop of PWM output (without CPU) is implemented immediately by using the high impedance output function and the comparators of 16-bit timers X0 and X1 when an overcurrent or overvoltage condition is detected within the LED or PFC control element . This eliminates the need for dedicated protection circuits using external comparators, cutting costs.

And the operation after emergency stop can be controlled by software to realize the flexible protection function that meets the system requirements.

By using the DALI communication function of the serial interface UART6/DALI, using built-in hardware to transmit and receive Manchester codes (transmit: 11 bits; receive: 19 bits) conforming to the DALI communication standard, the CPU load during data transmission and reception is reduced .

The receive pin RxD6 of the serial interface UART6/DALI can be connected to the external interrupt pin INTP0 and the input pin TI000 of the 16-bit timer 00 in the microcontroller. Can cancel standby mode and measure pulse width during off cycle reception (low level, 88μs~1s) of DMX512 communication.

During infrared remote control signal reception, the CPU load during data reception is reduced by using the pulse width measurement function of the 16-bit timer 00 and using hardware to measure the pulse width.

During sensor detection, time management and control are flexibly implemented using the software processing capabilities of the microcontroller.

For details, see:



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