High-frequency and high-voltage power supply unit with internal protecting circuit

A high-frequency and high-voltage power supply unit with an internal protecting circuit comprising a first DC power supply means (1), a second DC power supply means (6), and converting circuit (2), a sensing/holding circuit (3), and an amplifying circuit (4):

• said first DC power supply means (1) for generating a DC voltage up to 300 volts comprising a bridge rectifier (10) and a voltage-increasing unit comprising capacitors (12, 13) and resistors (14, 15);
• said second DC power supply means (6) for generating a 9-volt DC voltage comprising a first transformer (61) connected to an AC power supply, a diode (62) for half-wave rectifying, and a capacitor (63) for filtering;
• said converting circuit (2) comprising a diac (25), two power transistors (23, 24), a first transformer (21), and a second transformer (22), said first transformer (21) having a primary coil (211) and two secondary coils (212, 213), said second transformer (22) having two primary coils (221, 222) and a secondary coil (223), said 300-volt DC bias is applied to said diac (25), said power transistor (24) is actuated ON which outputs a current to said primary coil (221) and through a core (224) a magnetic flux is induced in another primary coil (222) and a current is fed back to said primary coil (211) for said first transformer (21) and said current couples to said secondary coils (212 and 213) and actuates said power transistor (23) to be ON, cutting off said power transistor (24), said current from said power transistor (23) having opposite polarity as a current generated by said power transistor (24), thereby causing an oscillation between said coils (221 and 222), said oscillation of said coils (221 and 222) resulting a high-frequency and high-voltage AC voltage on said secondary coil (223), a pair of half-wave rectifiers being connected to two ends of said secondary coil (22) for obtaining a high frequency and high-voltage output on the output terminals (26);
• said sensing/holding circuit (3) comprising a series of resistors (31, 32) for dividing a signal from a wire (225) to a smaller amplitude, a charging capacitor (33), a SCR (35) with a gate connected to said charging capacitor (33) and an anode connected to a voltage of approximately nine volts, such that when a strong signal from the wire (225) charges the capacitor (33), the SCR (35) is triggered ON and further actuates said amplifier circuit (4);
• said amplifier circuit (4) comprising a pair of Darlington transistors (41, 42), said transistor (41) being actuated ON by a voltage passed from said SCR (35), which further actuates said transistor (42) to operate in a saturated status, a saturated voltage of said transistor (42) approximately equal to 0.3 volt further cutting off said transistor (24), terminating said oscillation between said coils (221 and 222) and cutting off said power supply unit, a core (224) of said secondary transformer (22) being connected with a wire (225) and further connected to said sensing/holding circuit (3), a pair of discharging tips (27) with air insulated therebetween disposed between said output terminals (26) and said wire (225) for discharging when both ends of said output terminals are disconnected from said load.