Application of the principle uPC1237H

  
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1237H-circuit principle shown in Figure 2-122. Its interior has four separate detectors can finish respectively to their inspection tasks. When the circuit is abnormal, it can
Application of the principle uPC1237H - schematic

immediately drive the relay, disconnect the output circuit, speaker protection and associated circuitry from damage. Relay output drive current rvPC1237H up 80rnA, wherein the overload protection circuit, the midpoint voltage offset circuit protection reset in two ways, one is automatically reset method, namely 3 feet by a 0 - 02t.eF capacitance ground when the circuit failure relay, the relay is automatically released after troubleshooting. Another species is shutdown reset method, namely 3 feet directly to ground, then self-locking function within the circuit, the relay pull once, even if it will not release when the fault disappears after the shutdown circuit must be reset. Two methods has its advantages. When should each use flexibly select oLePC1237H single-supply operation, the operating voltage range is very wide, 25V - 60V between can work reliably. Power protection circuit consists Rzo, R2l, Cll composition (Fig 2-122 R12.Ri l and island), 7 feet for power protection input into the terminal. Vc by, R2l charge to cll after power. Since the time of action C5, the relay in the boot after the delay time remains active until the pre-stage amplifier stage and push into a stable state after the end of the time delay relay release, connected speakers, thus avoiding power impact. Delay time from equation Cii-Rzl-ln [(V8 - V7)/V8] decision, according to the figure number, the delay time of 1.7 seconds. Midpoint offset by the protection circuit Rj4, islands (Fig. 2-122 in people, Q), 2 feet for protection midpoint voltage offset input. Its a positive level detection threshold voltage is 0 - 62V, the negative threshold voltage level detection is a 0.17V. Such a high index, in practical applications can cause frequent movement of the relay, the impact sound effect, so in practice the protection of the electrical circuit path has expanded o overload protection circuit consists Vr5, VT4, Rio, Rl l and R etc. (Figure 2-122 for VTs, VT7, Ri, R2 and Ro), 1 pin overload protection input. When the output overload, the voltage drop across R6 increases, and this will trigger VT4 conducting a VTs conduction, thereby triggering a foot so that relay. Adjusted odds of Rio and can be changed to protect sensitive Rl1 degrees. Shutdown protection circuit from anti- f, RL9 and C12 (Figure 2-122 for f wind, R10, C4), 4 feet for the shutdown protection input into the terminal. Working through the power supply circuit VD7 rectified when the buck by R19, to establish a stable straight 4 feet after filtering C4 stream level. Just 4 feet a loss of power, the relay immediately pull. Since the C12 is much smaller than the capacity of the power supply filter capacitor, so if a shutdown pin 4 immediate loss of power, effectively preventing the shutdown impact o




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