LED Driver Circuit Using CAT3603

CAT3603 is a three channel charge pump LED driver IC from Catalyst Semiconductors that can be operated in either LDO mode or fractional mode. The IC can deliver 30mA per channel and can be operated from an input voltage range of 3 to 5.5V DC. CAT3063 has a quiescent current as low as 0.1uA and this makes it suitable for battery powered applications. The operating frequency is 1Mhz which makes it possible to use small capacitors.

LED Driver Circuit Diagram Using CAT3603

Another features are soft start, current limiting, high efficiency (90%) and short circuit protection. Applications of this IC are hand held devices, LCD back lights , LED lighting gadgets etc. The output current can be programmed using an external resistor connected between the RSET (pin 4) and ground.

Charge pump:

Charge pump is a DC to DC converter circuit that uses capacitors as the energy storage component for creating an output voltage that is either higher or lower than the input voltage. A switching circuit (using BJTs or MOSFETs) is used for connecting and disconnecting the voltages from the storage capacitor.

The switching frequency is usually in the kilo or MHz range. The output voltage will be a pulsed one and it is smoothed using an output filter capacitor. Charge pump circuits can double, triple, quadruple, multiply or scale any given voltage. In theory, a charge pump can generate any desired voltage.

CAT3063 LED driver circuit.

The circuit diagram of a three channel LED driver circuit using CAT3063 is shown below (Fig 1). C4 is an input filter capacitor. R1 is the resistor used for programming the output current. C3 is the output filter capacitor. C1 and C2 are the storage capacitors of the internal charge pump circuit. A logic high at pin 5 will enable the IC and a logic low on the same pin will drive the IC into shutdown mode.

In the shutdown mode, the quiescent current is almost equal to zero. With the used value of R1, the LED current per channel will be 25mA. When powered up the CAT6063 operates in 1X mode i.e, the output voltage will be equal to the input voltage. If this output voltage is enough to regulate the current through all LEDs, the IC remains 1X mode.

If the output voltage is not sufficient enough to regulate the desired current through the LEDs, the device automatically switches to the 1.5X mode where the output voltage is 1.5 times the input voltage. This process is repeated when ever the IC is powered up or awaken from shutdown mode.

Selection of R1 is shown in the table below.

LED current (mA)	R1 (kilo ohm)
1	649
5	287
10	102
15	49.9
20	32.4
25	23.7
30	15.4

Notes.

CAT6063 is not suitable for resistive loads.
Unused LED output channels must be connected to Vout pin. They cannot be left floating.
All capacitors are ceramic capacitors.
Dimming of the LEds can be achieved by using a DC voltage for setting the pin4 (RSET) current or by driving the pin5 (EN) using a PWM signal.
There is an exposed pad beneath the IC and it should soldered to the ground plane of the PCB for improved thermal performance.
Supply voltage should not exceed 6V DC.
Total output current should not exceed 120mA.

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Build a 12v to 5v DC high efficiency SMPS buck converter using 34063 IC

This project converts 12v DC to a regulated 5v DC at up to 1.8 amps, suitable for driving a tablet computer from a 12v car battery in a power blackout etc.

The circuit for this buck converter is nothing original, basically it is the circuit from the 34063 IC datasheet, and all I did was to use an external PFET instead of the external PNP transistor shown in the datasheet. The external PFET allows currents up to a few amps at good efficiency, however I have used hard current limiting at 1.8A for safety and good performance in this prototype.

Energy conversion efficiency is very high due mainly to the choice of external components used with the cheap 34063 SMPS IC.

 PCB layout.
The prototype was tested in hardware, please excuse the messiness. The layout is far from ideal, I did it this way to allow easy swapping of parts and just to be lazy, to save the effort of making a PCB. However it still works pretty good, and a proper PCB would improve performance a little bit.

PFET choice.
I did not have a lot of PFETs in my parts box so I used a 100v 8A rated part. This was an SMD PFET so I just tacked it on the bottom of the PCB. It is efficient enough to not need a heatsink even at 5v 1.5A continuous output. The PFET I used was not ideal, its "Rds on" value is about 0.3v at 1.5A (0.2 ohms) which is too high and costs efficiency. Going to a 50v >20A PFET with an RDS <0.1 ohms or <0.05 ohms would give a noticable increase in efficiency.

Schottky diode choice.
I used a TO-220 60v dual 10A schottky diode pack (total 20A). This is a no-brainer, although this is overkill these diodes are only $1-$2 and can also be pulled for free from any old PC PSU and most commercial SMPS supplies. Besides the safety of being very large and over-rated, the main benefit is these diodes have a very low forward voltage drop of <0.3v at 1.5A or 2A and this equates to reduced losses (more efficiency).

Inductor choice.
This is just a commercial "3 amp" 24mm total diameter inductor/choke available from hobby suppliers like Altronics Australia. I think it is a 220uH or 330uH value, but sorry I lost the paperwork.  A few other powdered-iron toroid inductors were tried and it is not that critical. It has 51 turns of 1.0mm diameter wire if that helps. The inductor measured 0.32mV at exactly 1A DC, so DC resitance was measured at 32 milliohms.

Schematic and operation.
Sorry for the hand-drawn schematic! As you can see the circuit is minimum parts. It uses just two resitors to drive the PFET from the IC (same as the datasheet), this is not ideal but was done to test the concept and see if a PFET can be driven as easily as the PNP transistor normally is. PFET turnon is good at 0.07uS, but turnoff is not great taking 0.8uS. This costs about 1-2% efficiency. The 560 ohm resistor could be reduced to speed up the turnoff, but this would increase losses in that resistor so it is a tradeoff.

34063 SMPS IC.
The 34063 IC does all the clever stuff, mainly it regulates voltage at 1.25v on VFB pin5. Because of the 6k8:2k2 voltage divider on the output, this gives very close to 5v, I actually saw about 5.01v-4.99v Vout in testing, very nice.

Max current limit resistor.
The resistor between Vin and pin7 sets the max inductor current limiting, this was set by me to roughly 0.18 ohms to give 1.8A current limiting. (Imax = 0.32v / R = 0.32v/0.18 = 1.78A). The current limit is best at slightly above the max required current. This gives better safety and also helps stabilise oscillation.

Caps etc.
CT used the datasheet value of 1nF. That gave oscillator value of 26.2kHz measured on pin3 (with no load), however the whole circuit usually operated at 29-33kHz because of the way the regulation works in the IC. The filter caps; 680uF on the input and 1000uF on the output were chosen to be "good enough". Output ripple was approx 25-30mV which is fine.

Measured efficiency!

Vin    Iin   Pin        Vout  Iout   Pout      Eff %    
12.5v  670mA  8.375W     4.99  1.53A  7.63W     91.1%
12.5v  430mA  5.375W     5.00  1.00A  5.00W     93.0%
12.5v  210mA  2.625W     5.00  0.50A  2.50W     95.2%

Note! Readings were taken from meters with only 2 decimal point resolution and were not lab grade accuracy, so there may be a couple of percent error in readings.

Calculating efficiency (at 1.5A output).
The static power losses were seen on the scope and can be calculated;

PFET Rds on period loss = 0.3v / 12.5v = 2.4% loss

DIODE Vf off period loss = 0.28v * 1.53A * 0.56 offduty = 240mW = 2.8% loss

Inductor resistance loss = 1.53A squared * 0.032 ohms = 75mW = 0.9% loss

560 ohm resistor loss = 10.5v squared / 560 * 44% onduty = 87mW = 1.0% loss

Total static losses at 1.53A output = 7.1%
Calculated other (switching) losses = 100% - 91.1% - 7.1% = 1.8%



Scope current L1 inductor (on period) at 5v 1.5 amps.
Above is the on period current through the PFET and L1 inductor. As it is a PFET this is inverted so the pointy bit at the bottom is the max current, the top is zero current. At 1.5A and 32kHz the SMPS is very stable, as switching period is reduced becuase the peaks just hit the 0.32v max current limit set by my choice of 0.18 ohm resistor. (However voltage regulation is still the main regulation).

Duty cycle is about 44%, and current ripple in the inductor is nice and low with inductor current averaging 1.5A (ripple of 0.56A, between 1.22A and 1.78A). The noise spikes I suspect are from from my messy PCB with power and load wires everywhere and scope leads laying around next to the PCB and wiring.

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Scope current L1 inductor at 5v 1.0 amps.
Same thing but at 1A. Frequency dropped a bit, closer to the 34063 oscillator freq of 26.2kHz, but still (just) triggering on the max current peaks. Current ripple now larger from approx 0.5A to 1.6A (average output 1A). Timing is still 20uS/hdiv but says 40uS on the screen as I had zoomed my h-axis (sorry).



Scope current L1 inductor at 5v 0.5 amps.
Here the L1 current has gone "discontinuous" meaning the L1 current is reduced to zero during the end of the off period, and has to start from 0 amps again during every on period. Typical of the regulation system used in a 34063 IC, the timing will "stutter" as needed to maintain Vout regulation at a steady 5.0v. This does not matter and the 34063 can be quite energy efficiency when "stuttering" in discontinuous mode like this. At less than 0.5 amps the stuttering can become very erratic looking, but this is all normal.



PFET drain/source voltage (main switching waveform).
(The PFET on period is the top of the waveform). Above you can see the PFET turnon (through a 10 ohm resistor) is nice and fast, It was about 0.07uS turnon time. However the turnoff is poor, because the turnoff is from a 560 ohm resistor and is slow at 0.8uS. This costs significant efficiency.

Using an external digital driver (like a 12v CMOS digital buffer/inverter chip?) to drive the PFET would improve turnoff time a lot and increase efficiency, but this was a test of using the simple datasheet example circuit with an external PFET (instead of the suggested external PNP) and as proof of concept it still works well enough.



5v DC output showing voltage ripple.
Because it is a switching regulator there will always be some ripple on the DC output voltage. This is shown when running at 5v 1.5A and the ripple is typical and acceptable enough at 30-35mV.

Improving efficiency.
This circuit was thrown together very quickly to show how to use a cheap common 34063 IC to get a high efficiency supply from 12v->5v DC at 0-1.5A or so. If you want to invest some effort it can be improved further;

1. My PFET is not a good choice, using a better PFET will give an easy 1% more efficiency, and would be the first choice.

2. The inductor is just an ordinary "off the shelf" type. A properly selected inductor or a good core hand wound for best performance could allow lower operating frequency and less current ripple, and maybe less DC ohms, and maybe pick up another 0.5% efficiency or so. (For lower operating freq CT should also be increased to 1.2nF or 1.5nF etc).

3. The PFET turnoff is too slow. Adding a cheap digital buffer IC could pick up 0.8-1.2% efficiency there from reduced switching losses and reduced loss from the 560 ohm resistor.

4. My PCB has very thin long tracks. Using a well designed PCB with thick short tracks for the main current paths might save 30 milliohms and give maybe 0.5% or more efficiency.

Bill of materials.
* 34063 SMPS 8pin IC (Fairchild/ON Semi/AIS etc, ie MC34063A or NCV34063A).
* 8pin IC socket (optional).
* PFET, rated more than double the input voltage and a few times the desired output current, preferably well under 0.1 ohm Rds on.
* Inductor L1 is a powdered iron toroid of 20-30 mm diameter, with thick wire >1.0mm preferred, 3A rated for a 1.5A capable supply. Value in the 150-470uH range, you may need to try a couple of different types. Ideally current ripple will be <50% at full output current.
* Schottky TO-220 dual 10A or dual 16A diode pack. Choose for low forward voltage, most brands are very good, parts can be found in any old PC PSU.
* 470-1000uF 35v electro cap.
* 1000uF 16-25v electro cap (25v will be larger and generally have a longer life).
* CT 1nF 25-50v ceramic or greencap.
* some 1/4W resistors; 560 ohm, 10 ohm, 6k8, 2k2.
* If you need a test load then a large 10W 4.7 ohm resistor will do.

Modifying the circuit for 12v car operation.
This circuit was designed for a car battery, generally 13.8v to 12.0v when running. If used in a car the circuit needs more protection as the Vin might be >15v at times. I would use a 100 ohm resistor instead of the 10 ohm resistor. Also a 13v zener diode across the 560 ohm resistor will add safety for the PFET. A 12v line filter might also be advised, they can be bought from auto stores.

Modifying the circuit for 24v operation.
Use 560 ohms instead of 10 ohms, so it now has two 560 ohm resistors. And again a 13v zener from PFET gate to source pin. With a 24v Vin you should use a higher inductor value and larger inductor core, 470uH and up are recommended.

[b]Modifying the circuit for high output currents.[b]
The circuit is meant for 5v out, 0-1.8A. It will do ok up to 2.5A just by changing the current limit resistor (at 2.5A the resitor should be 0.12 ohms or so).

Currents up to 5 amps or more should be ok, but use a larger inductor core size rated for more than the max amps you need, and again a larger inductor value helps >470uH is good. The diode pack will be fine, but the PFET should be rated for a few times more current than your max current. If needing 5A output I would use a 40-50v 60A TO-220 PFET which are a common size.

Changing output voltage.
Just change the 6k8 resistor, to change the output voltage to something other than 5.0v. Like most SMPS circuits it works best with roughly 2:1 Vin:Vout ratio, if using different ratios then again increasing the inductor value >470uH will help.

Source: http://forum.allaboutcircuits.com/showthread.php?t=7885 

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Battery Charger Using LTC4078

Using the LTC4078 standalone linear charger circuit you can design a very simple single-cell battery charger circuit for Li-Ion Li-Polymer battery . This LTC4078 battery charger circuit works from both wall adapter and USB inputs. This charger can detect power at the inputs and automatically select the appropriate power source for charging.

Battery Charger Using LTC4078 Circuit diagram

As you can see in the circuit diagram , this Li-Ion Li-Polymer charger requires few external components and you will need to apply just few equations ,to design a full work USB , wall adapter charger .
The charge current can be programmed up to 950mA from wall adapter input . IUSB pin is used for program the charge current for USB power that can be programmed by connecting a resistor to the ground.

The voltage on this pin can be used to measure the battery current delivered from the USB input using the following formula: IBAT = (VIUSB/RIUSB)*1000 . ITERM pin is the termination current threshold program that is set by connecting a resistor to ground. ITERMINATE is set by the following formula:
ITERMINATE =100V/RITERM ; RITERM =100V/ITERMINATE IDC pin is used for program the charge current for wall adapter power that is set by connecting a resistor to ground.The voltage on this pin can be used to measure the battery current delivered from the DC input using the following formula: IBAT = (VIDC/RIDC)*1000 .

The charge current delivered to the battery from the wall adapter or USB supply is programmed using a single resistor from the IDC or IUSB pin to ground and can be calculated using the following equations:
RIDC =1000V/ICHRG-DC , ICHRG-DC = 1000V/RIDC - Wall adapter
RIUSB =1000V/ICHRG-USB , ICHRG-USB =1000V/RIUSB – USB port.

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Digital Object Counter using LDR and digital IC 7490

This is the simple circuit on Hobby Electronics. In this circuit three modules are used in object counter. 555 timer are used as a monostable mode and astable mode. The other is counter module.

In this circuit 555 timer
configured as a monostable mode, is a simple automatic dark sensor
circuit that gives output when light falling is blocked on LDR. Pin 3 of
monostable circuit has been connected to pin 4 of astable timer. When
monostable circuit generates output, astable mode timer starts giving pulses to the counter module. Frequency for counter module is set up using R4, R3 and C2.

7490acts as a decade counter and 7447 uses the output of 7490
to display numbers on seven segment display. This circuit counts from 0
to 9. You can count 0 to 100 modifying counter module circuit. Just
adding few components as well as two counter ic, two display driver and two display. For count 0 to 100, comments on the comments box. You will get complete circuit.

The output will be: If you block light falling on LDR, the number on seven segment display will increase.

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10 Watt Stereo Amplifier Circuit Using TDA2009A

This is a design circuit for amplifier. This amplifier circuit has a power of 10 watts. This amplifier circuit is very suitable to apply to your car audio. This amplifier is using IC TDA2009A, as amplifier power. To avoid excessive heat in the IC using some heat sink compound between the heat sink & the IC. C1 & C2 is the input coupling capacitor and blocks DC, as well as C10 & C11 which is the output capacitor Kopel, and C6 & C7 which blocks the DC from the feedback loop. R1/R2 (and R3/R4) set the level of feedback. This is the figure of the circuit.

Get together with 1 (R1/R2) = 68 or 37 dB. C8/R5 (and C9/R6) provides high frequency stability where loudspeaker inductive reactance load can become excessive. C4 and C5 provide power decoupling or filtering. Absolute maximum supply voltage is 28V for the amplifier.

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14W CLASS A AMPLIFIER USING 2N3055 ELECTRONIC DIAGRAM

14W CLASS A AMPLIFIER USING 2N3055 ELECTRONIC DIAGRAM

Why Class A ? Because , when biased to class A, the transistors are always turned on, always ready to respond instantaneously to an input signal. Class B and Class AB output stages require a microsecond or more to turn on. The Class A operation permits cleaner operation under the high-current slewing conditions that occur when transient audio signal are fed difficult loads. His amplifier is basically simple, as can be seen from the block diagram.

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