Japanese Patent JPS4226509

B1

1,051,310. Converting. PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd. Oct. 7, 1964 [Oct. 10, 1963; Feb. 13, 1964], No. 40887/64. Heading H2F. [Also in Division H3] Transistor circuits producing high direct voltage for television equipment and having a driver transistor 1 coupled to an output transistor 11, which feeds on L-C load including a deflection coil 19 and S-correction capacitor (shown only in Fig. 2), and boost diodes either in series with the H.T. transformer (Fig. 2) or in parallel with it (Fig. 3, not shown) or both (Fig. 4, not shown) is protected against short-circuits on the H.T. line due either to flashover in the picture tube or a service man's screwdriver. According-to the invention a limiting impedance is connected in series with the load on the output transistor and the voltage developed across the limiting impedance on short circuit is fed to the input of the driver transistor 1 to tend to cut it off. The input transistor 1 receives signals 7 so that it conducts only briefly in each cycle. The output transistor receives signals 12 and conducts for the greater part of each cycle, and the H.T. voltage is developed when it cuts off. The output transistor is protected in two ways by the invention: the short-circuit current is limited and the speed of switching off is reduced so that the H.T. voltage is reduced. In Fig. 2 the limiting impedance is resistor 29 and capacitor 30, which do not affect the normal operation of the circuit. At short circuit the voltage drop across the resistor 29 is applied to the input of transistor 1 to block it, which tends to switch on the output transistor 11. In Fig. 3 (not shown) the limiting impedance is capacitor 34 and the signal developed at short-circuit is fed through capacitor 35 and resistor 36 to the input of transistor 1. The drive pulses may be obtained from a Hartley oscillator (Fig. 6, not shown).

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JPS5989574	RUSH CURRENT LIMITING CIRCUIT FOR SWITCHING REGULATOR

JP5769664A

December 15, 1967

October 10, 1964

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H02H7/12; H02M3/335; H02M3/338; H02M7/539; H03K4/08; H03K4/64; H03K17/082; H04N3/18

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