Installation and Operation

DS51612A-page 9

2.3.1.2

APPLYING LOAD TO MCP1630 COUPLED INDUCTOR BOOST

CONVERTER DEMO BOARD

A variable resistive load can be used to verify the line and load regulation. The load

resistance is connected between the TP3 and TP4 test points. To measure the output

voltage, connect the common lead of the multi meter to TP4 and the positive terminal

to TP3. By varying the load, the load regulation can be verified by measuring the output

voltage over the entire load range of 0 mA to 30 mA. Similarly, by varying the line

voltage from 3V to 5.5V and checking the output voltage, the line regulation can be

calculated.

Evaluating the Application

The best way to evaluate the MCP1630 Coupled Inductor Boost Converter Demo

Board is to dig into the circuit. Measure voltages and currents with a Digital Volt Meter

(DVM) and probe the board with an oscilloscope.

The voltage on the switching node can be calculated below.

Firmware

The PIC12F683 device comes preprogrammed with firmware to operate the system as

described above. The firmware flow diagram is shown in Appendix C. “Demo Board

Firmware”.

The program is fairly simple and straight forward. There is an initialization routine at the

beginning of the program.

The internal oscillator clock is set to 8 MHz.The TRISIO is configured to set GP2

port and GP3 (Push button S1) as Input Port.The OPTION register is configured to

wake-up on Port pin change of GP3.

The TMR0 is initialized with a value which causes TMR0 to overflow after 10 ms The

TMR0 overflow interrupt is also enabled. Initialize registers TEMP and TEMP2 for 2

seconds time measurement.

The PWM duty cycle is specified by writing to the CCPR1L register and to the

CCP1CON <5:4> bits. The CCPR1L contains the eight MSbs and the CCP1CON <5:4>

contains the two LSbs. This 10-bit value is represented by CCPR1L:CCP1CON <5:4>.

The switching frequency is set to 100 kHz.

(

–

+

)

+

--------------------

+

=

Where:

TMR0 overflow occurs for every 10 ms.

TEMP and TEMP2 counts for 2 seconds (TEMP2 = 10, TEMP = 20)

Hence 10 * 20 * 10 ms = 2 Seconds)