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.