CN2660780Y

CN2660780Y - Electronic transformer

Info

Publication number: CN2660780Y
Application number: CN 200320103527
Authority: CN
Inventors: 郑清吉
Original assignee: Individual
Current assignee: Individual
Priority date: 2003-11-24
Filing date: 2003-11-24
Publication date: 2004-12-01
Anticipated expiration: 2013-11-24

Abstract

The utility model relates to an electronic transformer, including an EMI filter which consists of a capacitor C1, a transformer T1 and a capacitor C2. The EMI filter is connected with a bridge rectifier circuit D1-D4 and is characterized in that the EMI filter also includes a voltage feed half-bridge inverter circuit connected with the output terminal of the bridge rectifier circuit. The electronic transformer provided by the utility model has unique structure and rational design. By adopting the voltage feed half-bridge inverter circuit, the utility model can effectively realize rectifier function without the filter capacitor, therefore reducing power consumption of product. The utility model is also provided with a unique switch crystal wafer protective circuit and an output short circuit protective circuit, and the simplified structure make usage and maintenance more convenient and reliable.

Description

Electronic transformer

Technical field

The utility model relates to a kind of electronic transformer.

Background technology

Existing electronic transformer is provided with filter capacitor mostly behind bridge rectifier, both increased the cost and the space of transformer, also consumes extra electric energy, has reduced the power of transformer.In addition; the electronic transformer in past is in order to guarantee the operating state of switching transistor Q1, Q2; protect it not breakdown; need increase many protection components at base stage or other positions of this switching transistor Q1, Q2; and; existing output short circuit protection circuit is to increase a winding in order to sampling on transformer coil T3, and complicated circuit such as configuration controllable silicon could realize this function, and these all can cause the raising of transformer cost.

The utility model content

The purpose of this utility model is to overcome the prior art defective, and a kind of simple in structure, superior performance, safe and reliable electronic transformer are provided.This transformer can be exported the high-frequency alternating current of different voltages.

The purpose of this utility model is achieved in that a kind of electronic transformer, it comprises the electromagnetic interface filter of being made up of capacitor C 1, transformer T1 and capacitor C 2, this electromagnetic interface filter connects bridge rectifier D1-D4, and it is characterized in that: it also comprises a voltage feed half bridge inverter circuit that is connected with bridge rectifier D1-D4 output.In addition, in described voltage feed half bridge inverter circuit, switching transistor Q1, Q2 are positioned at the source that has of this bridge circuit, form passive leg by capacitor C 3, C4, and transformer T3 then is connected between two intermediate points of active leg and passive leg in the bridge circuit; The start-up circuit of forming half bridge inverter circuit by resistance R 1, capacitor C 5 and bidirectional diode DB3; The base stage of switching transistor Q1, Q2 connects two secondary winding T2b and the T2c of pulse transformer T2 respectively, and the elementary winding T2a of pulse transformer T2 connects the elementary of transformer T3; The secondary of transformer T3 is output.

Electronic transformer structure uniqueness of the present utility model, reasonable in design, adopt the voltage feed half bridge inverter circuit need not use filter capacitor promptly can realize rectification function effectively, thereby reduced the product power consumption, the simplification of structure also makes using and keeping in repair more reliably and makes things convenient for.For the protection of switching transistor Q1, Q2, the utility model makes switching transistor Q1, Q2 be operated in optimum state by the number of turn and the inductance value of adjusting each winding of transformer T2, need not can make switching transistor Q1, Q2 stablize lasting work by protection component.The utility model also is provided with output short circuit protection circuit, only can finish short-circuit protection function with simple elements.At cross-over connection two series capacitance C6, C7 at the beginning of the transformer T3, between the inferior utmost point, thereby promote the EMI effect, satisfied the EMI test request.

Description of drawings

Accompanying drawing is the circuit diagram of the utility model electronic transformer

Embodiment

Below in conjunction with drawings and Examples the utility model is described further.

Circuit of the present utility model sees also accompanying drawing: among the figure, by capacitor C 1, the electromagnetic interface filter that transformer T1 and capacitor C 2 are formed, this electromagnetic interface filter connects bridge rectifier D1-D4, this electronic transformer comprises a voltage feed half bridge inverter circuit (frame of broken lines is interior among the figure), switching transistor Q1 wherein, Q2 is positioned at the source that has of this bridge circuit, by capacitor C 3, C4 forms passive leg, transformer T3 then is connected between two intermediate points of active leg and passive leg in the bridge circuit, by resistance R 1, capacitor C 5 and bidirectional diode DB3 form the start-up circuit of half bridge inverter circuit.Wherein switching transistor Q1, Q2 are the critical elements in the oscillating circuit, and the while is the double as power switch again.

The electromagnetic interface filter of AC power by being made up of capacitor C 1, transformer T1 and capacitor C 2 produces inhibition to radio frequency interference, provides DC power supply through bridge rectifier D1-D4 for described voltage feed half bridge inverter circuit again.

After powering up for electronic transformer of the present utility model, the electric current of the resistance R of flowing through 1 is to starting capacitor C 5 chargings, be elevated to breakover voltage (about 35V) value of bidirectional diode DB3 when capacitor C 5 both end voltage after, this bidirectional diode DB3 snowslide is walked to wear, 5 base-emitter network discharges of capacitor C by Q2, Q2 is because of the forward bias conducting, during the Q2 energising, current path be VDD → C3 → T3 elementary → T2a → Q2 → ground.The transient change of the collector current of Q2, produce an induced potential by T2a at two secondary winding T2b of T2 and T2c two ends, consequently make the base potential of Q2 raise, its base current and collector current further increase, the positive feedback of interlock type makes Q2 reach capacity and conducting state immediately, start-up circuit provides an outer triggering signal, and the foundation of vibration and keeping then by means of the coupling between the transformer T2 winding produces positive feedback and realizes.

After Q2 reaches capacity, induced potential in each winding is zero, the Q2 base potential is on a declining curve, like this, the Q2 base potential descends, and the Q1 base potential raises, the positive feedback of this interlock type makes Q2 withdraw from the saturated cut-off state that jumps to rapidly, Q1 is then by by jumping to saturation conduction, and when the Q1 saturation conduction, current path is: Q1 → T2a → T3 is elementary → and C4 → ground.When pulse transformer T2 magnetic core enter saturated after, the very fast Q2 saturation conduction once more that makes again of the positive feedback of interlock type, and Q1 by conducting transition for ending.So go round and begin again, and the conducting in turn of Q1 and Q2 constantly changes the elementary sense of current of transformer T3.The electric current that changes is coupled to secondary by transformer T3, drive the light fixture even load, by changing the primary turns ratio of transformer T3, can export the high-frequency alternating current of different voltages.

In addition; the utility model circuit is simple; the electronic transformer in past is in order to guarantee the operating state of switching transistor Q1, Q2; protect it not breakdown; need increase many protection components at base stage or other positions of this switching transistor Q1, Q2; the utility model then makes switching transistor Q1, Q2 be operated in optimum state by the number of turn and the inductance value of adjusting each winding of transformer T2, need not protection component.

The utlity model has the output short circuit protection function; the output short circuit protection circuit in past is to increase a winding in order to sampling on transformer coil T3; and complicated circuit such as configuration controllable silicon etc. could be realized this function; in the utility model; described electronic transformer also comprises a short-circuit protection circuit; promptly the emitter at switching transistor Q2 connects sampling resistor R3; the emitter of switching transistor Q2 also connects resistance R 4 by diode D5; R5; in resistance R 4; the R5 two ends also meet filter capacitor C8; the base stage of transistor Q3 and resistance R 4; contact between the R5 connects, and the emitter of transistor Q3 connects capacitor C 5.Described short-circuit protection circuit adopts from switching transistor Q2 emitter resistance sample mode, only can finish short-circuit protection function with simple elements.Its operation principle is: when transformer T3 output short-circuit, switching transistor Q2 emitter current increases rapidly, resistance R 3 two ends pressure drops increase, and A point current potential raises, after the conducting voltage that is elevated to diode D5, produce electric current among the diode D5, this electric current is added to the base stage of switching transistor Q3 after through diode D5 rectification and capacitor C 8 filtering, reach the conducting voltage of this switching transistor Q3 when voltage after, triode Q3 conducting, thereby, oscillating circuit is quit work with bidirectional diode DB3 ground connection.In addition, regulate the sensitivity of resistance R 4 and this short-circuit protection circuit of R5 scalable.

This electronic transformer has two series capacitance C6, C7 in the first interpolar cross-over connection of transformer coil T3, thereby has promoted the EMI effect, has satisfied the EMI test request, has improved requirement of withstand voltage.

Claims

1, a kind of electronic transformer, it comprises the electromagnetic interface filter of being made up of electric capacity (C1), transformer (T1) and electric capacity (C2), this electromagnetic interface filter connects bridge rectifier (D1-D4), and it is characterized in that: it also comprises a voltage feed half bridge inverter circuit that is connected with bridge rectifier (D1-D4) output.

2, electronic transformer according to claim 1, it is characterized in that: in described voltage feed half bridge inverter circuit, switching transistor (Q1, Q2) is positioned at the source that has of this bridge circuit, (C3, C4) forms passive leg by electric capacity, and transformer (T3) then is connected between two intermediate points of active leg and passive leg in the bridge circuit; The start-up circuit of forming half bridge inverter circuit by resistance (R1), electric capacity (C5) and bidirectional diode (DB3); The base stage of switching transistor (Q1, Q2) connects two secondary winding (T2b) of pulse transformer (T2) and (T2c) respectively, and the elementary winding (T2a) of pulse transformer (T2) connects the elementary of transformer (T3); The secondary of transformer (T3) is output.

3, electronic transformer according to claim 1 and 2; it is characterized in that: described electronic transformer also comprises a short-circuit protection circuit; promptly the emitter at switching transistor (Q2) connects sampling resistor (R3); the emitter of switching transistor (Q2) also connects resistance (R4, R5) by diode (D5); at resistance (R4, R5) two ends and connect filter capacitor (C8); the base stage of transistor (Q3) is connected with contact between the resistance (R4, R5), and the emitter of transistor (Q3) connects electric capacity (C5).

4, electronic transformer according to claim 1 and 2 is characterized in that: described electronic transformer has two series capacitances (C6, C7) in first, the inferior interpolar cross-over connection of transformer (T3).