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Adding Intelligence to Lighting Applications
HB-LED - Simple Digital Solution
Some power supply applications require fast dynamic response to compensate for load changes. In these applications, a fast ADC and fast calculation performance are required. However, a LED provides a stable load for a constant-current power supply. Therefore, a fast ADC and fast processing power are not always required to implement a digital control loop for a LED driver application.
A low-cost device in the PIC12F or PIC16F family with a CCP peripheral and an ADC can be used to implement a LED driver using digital control. The CCP peripheral is used in PWM mode to control the power supply circuit. Operating from the internal 8 MHz device oscillator, the CCP can provide PWM frequencies above 100 kHz to keep power component sizes small. Since the LED provides a constant load, it is a sufficient to sample the output current and adjust the PWM duty cycle at a much lower rate. A simple rate of 1000 Hz is ideal for many applications. Figure shows a Buck LED driver with a simple digital control.
Figure: PIC12HV615 Buck LED Driver with Digital Control
The table below shows a list of devices that can be used for simple digital controllers.
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Recommended Low Cost 8-bit MCUs for Digital Control |
Device |
Pins |
Flash |
Ram |
ADC |
Comparator |
ECCP |
CCP |
RC Osc |
Vreg Option |
Comm. |
PIC10F202 |
6 |
0.75KW |
24 |
0 |
0 |
0 |
0 |
Yes |
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PIC10F206 |
6 |
0.75KW |
24 |
0 |
1 |
0 |
0 |
Yes |
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PIC10F220 |
6 |
0.375KW |
16 |
2CH,
8-bit |
0 |
0 |
0 |
Yes |
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PIC10F222 |
6 |
0.75KW |
23 |
2CH,
8-bit |
0 |
0 |
0 |
Yes |
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PIC12F615/
PIC12HV615 |
8 |
1KW |
64 |
4CH, 10-bit |
1 |
2-pin |
- |
Yes |
Yes |
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PIC16F616/
PIC16HV616 |
14 |
2KW |
128 |
8CH, 10-bit |
2 |
4-pin |
- |
Yes |
Yes |
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PIC16F716 |
14 |
2KW |
128 |
4CH, 8-bit |
- |
4-pin |
- |
- |
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PIC16F684 |
14 |
2KW |
128 |
4CH, 10-bit |
2 |
4-pin |
- |
Yes |
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PIC16F690 |
20 |
4KW |
256 |
12CH,
10-bit |
2 |
4-pin |
- |
Yes |
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I2C™, SPI, EUSART |
PIC16F685 |
20 |
4KW |
256 |
12CH, 10-bit |
2 |
4-pin |
- |
Yes |
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PIC16F883 |
28 |
4KW |
256 |
11CH, 10-bit |
2 |
4-pin |
1 |
Yes |
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I2C™, SPI, EUSART |
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