Changhong DVB-2000 digital satellite receiver switching power supply circuit

The Changhong DVB-2000 digital satellite receiver features a switching power supply circuit. This circuit primarily comprises a power input section, an oscillation switching circuit, and a DC output section. The power input circuit receives 22V AC from a step-down transformer, which is then converted to DC using a bridge rectifier circuit consisting of diodes VD502 to VD505. The circuit is protected by a fuse (F502) and controlled by a power switch (K). Additionally, an external 12-24V DC power supply can be connected through F502 and switch K. The input circuit includes a series diode (VD501), which serves two main functions: it provides unidirectional conductivity and isolates abnormal voltage. This diode ensures that the AC 22V input is isolated from the external DC power supply, preventing simultaneous connection of both inputs. The oscillation switching circuit consists of a switching transistor (VD501), an oscillation switch integrated circuit (U1), and the switching transformer (T501).

The switching power supply circuit in the Changhong DVB-2000 is designed to efficiently convert AC voltage to a stable DC output suitable for powering the digital satellite receiver. The power input section begins with a step-down transformer that reduces the high voltage AC input to a manageable 22V AC. This voltage is then rectified by the bridge rectifier formed by diodes VD502 to VD505, which converts the AC voltage to pulsating DC. The fuse (F502) acts as a protective element, preventing damage to the circuit from overcurrent conditions, while the power switch (K) allows for manual control of the power supply.

The inclusion of diode VD501 in the input circuit is critical for ensuring the reliability of the power supply. Its unidirectional conductivity prevents backflow of current, which could potentially damage the circuit components. Furthermore, it isolates the AC input from the external DC power supply, ensuring that only one source of power is active at any given time. This isolation is essential for maintaining circuit integrity and preventing cross-interference between the two power sources.

The oscillation circuit is pivotal for the operation of the switching power supply. It utilizes a switching transistor (VD501) that rapidly turns on and off, creating a pulsed output that is transformed by the switching transformer (T501). This oscillation is controlled by an integrated circuit (U1), which regulates the switching frequency and ensures that the output voltage remains stable under varying load conditions. The design of the oscillation circuit contributes to the overall efficiency of the power supply, allowing it to deliver the necessary voltage and current to the digital satellite receiver while minimizing energy loss.

In summary, the power supply circuit of the Changhong DVB-2000 digital satellite receiver is a well-engineered system that incorporates essential components for voltage regulation, protection, and efficient power conversion. The careful arrangement of the input circuit, rectification process, and oscillation control ensures reliable performance and longevity of the device. Changhong DVB-2000 digital satellite receiver switching power supply circuit Rainbow DVB -2000 top box digital satellite receiver switching power supply circuit mainly by the p ower input circuit, an oscillation circuit switch, the DC output circuit is constituted, as shown in FIG. (1) power input circuit shown in FIG circuit, 22V AC B after step-down transformer and a bridge rectifier circuit VD502-VD505 rectifier, the fuse F502 and the power switch K is supplied to the switching power supply circuit.

External input 12-2V DC power supply is also supplied through F502 and K switching power supply circuit, the input circuit of a whole series diode VD501. Rectifier diode VD501 mainly serves two functions: O diodes with unidirectional conductivity. Abnormal voltage isolation. AC 22V input isolation and external input DC power supply, AC 220V input, external DC input voltage can not afford the role to prevent the two inputs simultaneously.

(2) switch oscillation circuit switching oscillation circuit is composed of a switching transistor VD501, oscillation switch integrated circuit Ul and the like of the switching transformer T501.