FEATURES

? Built-in Smart Auto PID Control – the World’s

First

? Power Supply Voltage: 50V

? High Output Voltage: ±40V

? High Output Current: 20A

? High Efficiency: > 92

@VVPS = 50V & VTEC = 25V & ITEC = 20A

? High Temperature Stability: < ±0.001°C

? Low Thermistor Injection Current: < 1μA

? Continuous Bi-directional Output

? Programmable Output Current and Voltage Limits

? Real Time Temperature, Current and Voltage

Signals

? Selectable Temperature Sensor Types: thermistor,

RTD, or temperature sensor IC

? High Reliability and Zero EMI

? Compact Size: 63(L) × 61(W)× 16.7(H) (mm)

100 Lead (Pb)-free and RoHS Compliant

APPLICATIONS

Driving high power TEC modules at high efficiency.

DESCRIPTION

TEC (Thermo-Electric Cooler) is a semiconductor

device which can cool down or heat up the temperature

of an object by injecting an electrical current in one or

the other direction. This TEC controller, TEC50V20ACH,

is designed to drive a TEC at high efficiency for

regulating the object temperature precisely by

controlling the direction and magnitude of the current

going through the TEC. It is powered by a DC voltage

between 10V to 50V and the output current can go up

to 20A without using a heat sink. Figure 1 is the photo

of the TEC controller TEC50V20ACH, Pin 1 to pin 18

shows the signal pins, and the others are power pins.

See Figure 2.

The controller TEC50V20ACH allows setting the setpoint

temperature, maximum output voltage magnitude,

and the maximum output current magnitude

respectively. These three settings are the input

parameters for the three control loops: constant

temperature, constant current, and constant voltage.

Before hitting the maximum output voltage magnitude

or the maximum output current magnitude, the

temperature loop is in control. When hitting the

maximum output voltage magnitude, either outputting a

positive or negative value across the TEC, the voltage

loop takes over the control, the controller will be

outputting a constant voltage to the TEC; when hitting

the maximum output current magnitude, the current

loop takes over the control, the controller will be

outputting a constant output current to the TEC. The

highest output voltage magnitude is limited by the

maximum power supply voltage, and the maximum

output current magnitude is 20A.

The temperature signal can be obtained by using one

of these 3 temperature sensors: thermistor, RTD or

temperature sensor IC. When using a thermistor, the

set-point temperature range is determined by an

external temperature network formed by 3 resistors. In

order to reduce the injection current to the thermistor to

reduce the errors caused by the self-heating effect, the

injection current is provided in pulse mode, reducing the

current by 10 times as opposed to a continuous current.

One advanced feature of this TEC controller is that it

comes with a smart auto PID control micro-processor, it

continuously senses and compensates for the thermal

load automatically. No need to use any external

components for forming a compensation network, nor

requires tuning.*

*Firmware PID control – currently not available.

Conservative users can still select the conventional

analog compensation network. The same as in the past,

it requires a onetime pre-tuning network to match the

thermal load, but provides reliable and high accuracy

control. For fixed thermal load applications,

conventional analog compensation can be selected;

while for applications with variable or multiple different

thermal loads – one type at a time, the automatic PID

control is more suitable.

Figure 2 is the top view of the controller, showing the

pin names and the locations. There are a total of 22 pins.

Pins No.1 to No.18 are control input or indicator output

signals; the rest of the pins are power inputs or outputs.

The pin function details are given in Table 1.

At the thermistor input, there is a linearization circuit for

the thermistor, to make the temperature output voltage

be more linearly proportional to the actual thermistor

temperature. There is a voltage inverter circuit, and it

makes the temperature output voltage be positively

proportional to the temperature, since the thermistor

has a negative temperature coefficient. These 2 circuits

together are called temperature measurement circuit.

See Figure 6.

The set-point temperature voltage and the voltage

representing the actual temperature are sent to an error

amplifier. There is a compensation network inserted in

the loop, to stop the oscillation of the controller caused

by phase delay effects of the thermal load. Therefore,

the compensation network must match the need for

driving a particular thermal load. To simplify the tuning,

a tunable compensation network is provided by the

evaluation board for this TEC controller. Of course,

users can also use an external compensation network

if they need it. A detailed guidance about how to tune

the compensation network with a thermal load is given

in the evaluation board application note.