Any device has a certain loss when it works, and most of the loss becomes heat. Low power devices have low loss and no heat dissipation device is required. However, high-power devices have large losses. If no heat dissipation measures are taken, the temperature of the die can reach or exceed the allowable junction temperature, and the device will be damaged. Therefore, it is necessary to add heat dissipation devices. The most common way is to install power devices on the radiator, and use the radiator to dissipate heat to the surrounding space. If necessary, add a cooling fan to strengthen cooling and heat dissipation at a certain wind speed. The flowing cold water cooling plate is also used on the power devices of some large-scale equipment, which has better heat dissipation effect. Heat dissipation calculation is to determine appropriate heat dissipation measures and radiators through calculation under certain working conditions. The power device is installed on the heat sink. Its main heat flow direction is from the die to the bottom of the device, and the heat is dissipated to the surrounding space through the radiator.
Small electronic radiators (or cooling fins) are made of aluminum alloy sheets through stamping process and surface treatment, while large electronic radiators are made of aluminum alloy extruded profiles and then processed and surface treated. They have various shapes and sizes for different device installation and different power consumption devices. Radiators are generally standard parts, and profiles can also be provided, which can be cut into a certain length by users according to requirements to make non-standard radiators. The surface treatment of the radiator is electrophoretic coating or black oxygen polarization treatment, which aims to improve the heat dissipation efficiency and insulation performance. It can be increased by 10.15% under natural cooling and 3% under ventilation cooling. The pressure resistance of electrophoretic coating can be 500 800V.
The electronic radiator manufacturer gives the thermal resistance values or relevant curves for different types of radiators, and gives different thermal resistance values under different heat dissipation conditions.
Calculation: a power operational amplifier pa02 is used as a low-frequency power amplifier. The device is packaged in 8-pin TO-3 metal shell. The operating conditions of the device are as follows: the operating voltage vs is 18V; The load impedance RL is 4, the working frequency can reach 5KHz under DC condition, the ambient temperature is set to 40 ℃, and natural cooling is adopted. According to pa02 device data, the typical value of static current IQ is 27ma, and the maximum value is 40mA; The typical value of RJC (from die to shell) of the device is 2.4 ℃ / W, and the maximum value is 2.6 ℃ / W.
