Power overshoot protection circuit for digital television power amplifier

Abstract

The invention discloses a power overshoot protection circuit for a digital television power amplifier, which comprises a power detection circuit and an overshoot detection circuit, wherein the time constant of the power detection circuit is controlled by an external discrete device, and the power detection circuit is used for selecting the time constant to ensure that power overshoot of digital television signals of different modes can be detected; and the overshoot detection circuit comprises a see-saw amplifier with a high pass characteristic, a hysteresis comparator, a reference voltage source and a reset circuit. The power overshoot protection circuit has the beneficial effects that the time constant of the power detection circuit is optimally designed, the smooth function is taken on the random fluctuation of the signal amplitude, meanwhile, the characteristic of power overshoot is kept, so that the false operation due to the pseudorandomness of the digital television signal can be avoided, the detection of the power overshoot can be realized; the circuit is simple; the cost is low; and the power overshoot protection circuit can be conveniently suitable for an emitting system power amplifier adopting the China digital television standard.

Description

technical field [0001] The invention relates to a power overshoot protection circuit, more specifically, it relates to a power overshoot protection circuit for a digital TV power amplifier. Background technique [0002] In medium-power (hundred watts) and high-power (several kilowatts) digital TV wireless transmission systems, the RF power amplifier is in a high-energy, high-heat working state, and is one of the components with a high failure rate. Once the RF power amplifier fails, the transmission power will drop or even disappear, resulting in bad or off-broadcast accidents. In the RF power amplifier, the final high-power transistor is the most easily damaged part. The main causes of damage to high-power transistors include: overheating, overdrive, and overload. [0003] The overheating time of the transistor due to the failure of the heat dissipation system is generally on the order of seconds. By monitoring the working status of the heat dissipation system and the tem...

AI Technical Summary

Problems solved by technology

The above characteristics will affect the selection of the peak power protection threshold: if the level standard during the frame header period is used as the threshold, it is possible that the protection will not be activated until the average power during the frame body period increases by more than 3dB, and the meaning of protection will be lost

If the level during the frame body is used as the threshold, it is easy to trigger a false action when the frame header appears

Therefore, for digital TV broadcasting standards, it is difficult to achieve accurate and effective protection by using existing over-excitation or overload protection schemes.

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