CN103025035B - Resonant Capacitor Adjusting Element and Its Applicable Current Preheating Electronic Ballast - Google Patents

Abstract

The invention discloses a resonant capacitor adjusting element and a current preheating electronic stabilizer applied to the same, which are used for driving a lamp tube with a filament, and comprise: an AC-DC conversion circuit for converting an AC input voltage into a high-voltage DC voltage; a control unit; an auxiliary voltage generating circuit; and an inverter circuit for converting the high voltage DC voltage into an AC output voltage and outputting a resonant current and a filament current to the lamp tube, the inverter circuit comprising: the resonance circuit provides energy for preheating the lamp tube; and the resonant capacitor adjusting circuit is connected with the resonant circuit and the detection element, judges whether the inverter circuit starts to operate or not through the detection element, and correspondingly conducts or opens two high-voltage switch ends of the resonant capacitor adjusting circuit at the delay time after the inverter circuit starts to operate so as to change the equivalent resonant capacitance value of the resonant circuit.

Description

Resonant Capacitor Adjusting Element and Its Applicable Current Preheating Electronic Ballast

technical field

The invention relates to an electronic ballast, and in particular to a resonant capacitance adjustment element and a current preheating electronic ballast which is applicable to it, which can control the cross-voltage at both ends of the filament of the driven lamp tube.

Background technique

Lighting is the basic need of human beings. In recent years, with the frequent global economic, trade and commercial activities, and the improvement of the quality of home life, lighting power consumption has also risen. The overall lighting power demand is very considerable. Currently, the most widely used lamp body is A low-pressure gas discharge lamp is also called a fluorescent lamp or a fluorescent lamp. Therefore, if the energy saving of this low-pressure gas discharge lamp can be devoted to, considerable electric energy can be saved. In addition, with the evolution of the times and the improvement of social living standards, ordinary lighting drive circuits are no longer enough for use. Low electromagnetic interference, high efficiency, high power factor, no flicker and light weight, high-quality lighting, and power saving Electronic ballasts have become the mainstream of lighting equipment in recent years.

Existing electronic ballasts include current preheating electronic ballasts and voltage preheating electronic ballasts. The traditional current preheating electronic ballast can provide a good starting sequence for the fluorescent lamp. Through the control chip, such as STL6574, it can provide two operating frequencies of the fluorescent lamp. When the operating frequency is in a relatively high frequency state, it is used to preheat the fluorescent lamp. filament, where the energy to preheat the fluorescent lamp can be provided by a resonant circuit within the electronic ballast. And when the working frequency is in a relatively low frequency state, it is used to stably provide the working current required by the fluorescent lamp.

The current preheating electronic ballast will continue to output a stable constant current to maintain the brightness of the fluorescent lamp after the fluorescent lamp is working normally. However, when the operating current flows through the filament in the fluorescent lamp, a voltage across the filament will be formed. Therefore, when the current preheating ballast is used for general fluorescent lamps with low filament impedance (such as 2-5 ohms), the cross-voltage at both ends of the filament can be lower than a threshold voltage, such as 4V (volts), which will have a greater impact on the life of the filament. Not obvious. However, when the current preheating ballast is used for high-efficiency fluorescent lamps with high filament impedance (such as 8-15 ohms), since the filament is high impedance, the cross-voltage (such as 16V) at both ends of the filament will be higher than the threshold voltage at this time. In this way, excess energy will be wasted and the service life of fluorescent lamps will be shortened, and even high-efficiency fluorescent lamps will burn out.

Therefore, it is an urgent problem to be solved at present how to develop a kind of electronic ballast that can solve the problem that the existing current preheating type electronic ballast will cause the lifespan of the fluorescent lamp to be shortened or burnt out.

Contents of the invention

The object of the present invention is to provide a resonant capacitance adjustment element and a current preheating electronic ballast to which it is applied, which can change the equivalent resonant capacitance value of the resonant circuit through the resonant capacitance adjustment circuit (element), so as to achieve The purpose of adjusting the current value of the filament current before and after preheating and lighting is to change the cross-voltage at both ends of the filament in multiple sets of lamp tubes to increase the service life of the fluorescent lamp. Therefore, the current preheating electronic ballast of the present invention can At the same time, it is suitable for general fluorescent lamps with low filament impedance and high-efficiency fluorescent lamps with high filament impedance. The resonant capacitor adjustment element (circuit) provided by the present invention can operate normally in a high-frequency environment, so it is suitable for high-frequency current preheating electronic ballasts, and its delay characteristics can be used to stabilize current preheating electronic ballasts. The equivalent resonant capacitance value of the resonant circuit of the device is changed after the fluorescent lamp is ignited, so that the current value of the lamp filament current and the cross-voltage at both ends of the filament are reduced.

To achieve the above purpose, a broad embodiment of the present invention is to provide a current preheating electronic ballast to drive at least one set of lamp tubes. The current preheating electronic ballast includes: an AC-DC conversion circuit that converts the AC The input voltage is converted into a high-voltage DC voltage, which is connected to the DC bus and outputs a high-voltage DC voltage; the control unit controls the operation of the current preheating electronic ballast; the auxiliary voltage generating circuit generates auxiliary voltage; and the inverter circuit is connected to the DC bus Connected to convert the high-voltage DC voltage into an AC output voltage and output the resonant current and the filament current to the group of lamps. The inverter circuit includes: a resonant circuit connected to the group of lamps to provide the preheating of the group of lamps The required energy, including resonant inductance and multiple resonant capacitors; and a resonant capacitor adjustment circuit, connected to the resonant circuit and a detection element, the resonant capacitor adjustment circuit judges whether the inverter circuit starts to operate through the detection element, and in the reverse Change the delay time after the circuit starts to operate to turn on or open the two high-voltage switch terminals of the resonant capacitor adjustment circuit correspondingly, so as to change the equivalent resonant capacitor value of the resonant circuit, so as to change the cross-voltage at both ends of the filament in the group of lamp tubes.

In order to achieve the above-mentioned another purpose, a more general embodiment of the present invention provides a resonant capacitor adjustment element, which is an electronic element with four pins, which is applied to an inverter circuit of a current preheating electronic ballast, and includes: The first switch element; the control voltage generation circuit, connected to the detection element through the two detection terminals of the resonant capacitor adjustment element, which uses the detection element to determine whether the inverter circuit is in operation, and generates the first DC voltage corresponding to the state; and the time delay The circuit is connected to the control terminal of the first switch element and the control voltage generating circuit, and after delaying a delay time according to the state of the first DC voltage, generates a second DC voltage corresponding to the state to control the first switch element to be turned on or open. , so that the two high-voltage switch ends of the resonant capacitor adjustment element are turned on or opened.

Description of drawings

FIG. 1 is a schematic circuit diagram of a current preheating electronic ballast according to a preferred embodiment of the present invention.

FIG. 2 is a timing diagram of the voltage, current and state of the current preheating electronic ballast of the present invention.

FIG. 3 is a schematic circuit diagram of a current preheating electronic ballast according to another preferred embodiment of the present invention.

FIG. 4 is a schematic circuit diagram of a current preheating electronic ballast according to another preferred embodiment of the present invention.

Wherein, the reference signs are explained as follows:

Current preheating electronic ballast: 1, 1B, 1C

Lamp (group): 2, 2B

Filament: 21

AC-DC conversion circuit: 10

Electromagnetic interference filter unit: 100

First rectification circuit: 101

Power factor correction circuit: 102

Power factor correction control circuit: 1020

Inverter circuit: 11, 11B, 11C

Preheat circuit: 110

Resonant circuit: 111, 111B

Resonant capacitor adjustment circuit: 112

Control voltage generating circuit: 1120

Full bridge rectifier circuit: 1121

Clamp protection circuit: 1122

Delay circuit: 1123

Inverter control circuit: 113

Power switch circuit: 114

Voltage divider circuit: 115

Protection circuit: 116

Auxiliary voltage generating circuit: 12

DC bus: 13

Control Units: 14

AC input voltage: V _in

High voltage DC voltage: V _h

AC input current: I _in

AC output voltage: V _o

First DC voltage: V _dc1

Second DC voltage: V _dc2

Auxiliary voltage: V _cc

Modulation voltage: V _pwm

Filament voltage: V _d

Resonant current: I ₁

Lamp current: I ₂

Filament current: I ₃

Output frequency: f _o

First to second frequency values: f ₁ to f ₂

Resonant inductance: Lr

First inductance: L ₁

First~second auxiliary winding: Na~Nb

Resonant winding: Nr

Equivalent resonant capacitance value: C _t

The first resonant capacitor: C _r1 , C _ra

Second resonant capacitor: C _r2 , C _rb

Half bridge capacitance: C _h

First Diode: D ₁

_Second diode: D2

Third Diode: _D3

First protection diode: D _b1

Second protection diode: D _b2

_First resistor: R1

_Second resistor: R2

Third resistor: _R3

_Fourth resistor: R4

The first detection resistor: Rs

_First switching element: Q1

The control terminal of the first switching element: Q _1a

Current input of the first switching element: Q _1b

The current output terminal Q _1c of the first switching element

Second switching element: _Q2

The control terminal of the second switching element: Q _2a

Third switching element: Q ₃

Fourth switching element: Q ₄

First capacitor: C ₁

_Second capacitor: C2

_Third capacitor: C3

The first voltage dividing capacitor: C _b1

The second voltage dividing capacitor: C _b2

First Zener Diode: Z ₁

Second Zener Diode: Z ₂

_Third Zener diode: Z3

The first end (DC positive end): a

The second terminal (DC negative terminal): b

The third terminal (the first AC terminal): c

Fourth terminal (second AC terminal): d

First to fourth time: t ₁ to t ₄

Preheating time interval: T _pre

Lighting time interval: T _ign

Delay time: _Td

Thermistor (PTC): _Rh

Node: A

Detailed ways

Some typical embodiments embodying the features and advantages of the present invention will be described in detail in the description in the following paragraphs. It should be understood that the present invention can have various changes in different embodiments without departing from the scope of the present invention, and that the descriptions and drawings are illustrative in nature rather than limiting the present invention.

Please refer to FIG. 1 , which is a schematic circuit diagram of a current preheating electronic ballast according to a preferred embodiment of the present invention. As shown in Figure 1, the current preheating type electronic ballast 1 is connected to multiple (groups) of lamp tubes 2, and the multiple groups of lamp tubes 2 have at least one filament 21 inside, and the current preheating type electronic ballast 1 includes AC- DC conversion circuit 10 , inverter circuit 11 , auxiliary voltage generation circuit 12 , control unit 14 and bus capacitor C _b . In this embodiment, the lamp group 2 is composed of two (multiple) gas discharge lamps connected in series, but not limited thereto, it can also be composed of two (multiple) gas discharge lamps connected in parallel.

The AC-DC conversion circuit 10 is used to convert an AC input voltage V _in into a high voltage DC voltage V _h , which has an input side and an output side, the input side is used to receive the AC input voltage V _in , and the output side The side is connected to a DC bus 13 (DC bus) and outputs the high voltage DC voltage V _h , for example 450V. The input side of the inverter circuit 11 is connected to the DC bus 13, and converts the high-voltage DC voltage V _h into an AC output voltage V _o and outputs a resonant current I ₁ and a filament current I ₃ to the plurality of sets of lamp tubes 2, wherein The resonant current I ₁ is the sum of the lamp current I ₂ and the filament current I ₃ , that is, the resonant current I ₁ = lamp current I ₂ + filament current I ₃ .

In this embodiment, the inverter circuit 11 includes a preheating circuit 110, a resonant circuit 111 and a resonant capacitance adjustment circuit 112, wherein the preheating circuit 110 is connected to the filaments 21 on the series side of the plurality of lamp tubes 2, It is used for preheating the filaments 21 on the series side of the multiple groups of lamp tubes 2 . The resonant circuit 111 is used to provide the energy required for the multiple groups of lamp tubes 2 to preheat, light and emit light. In this embodiment, the resonant circuit 111 includes a resonant inductor Lr, a first resonant capacitor C _r1 and a second resonant capacitor C r1 The resonant capacitor C _r2 and the resonant inductance Lr are connected to the switch circuit 114 and one of the filaments 21 of the lamp tube 2, the first resonant capacitor C _r1 and the second resonant capacitor C _r2 are connected in series between the two filaments of the lamp tube 2, wherein the first The capacitance of the first resonant capacitor C _r1 is greater than the capacitance of the second resonant capacitor C _r2 . The two high-voltage switch terminals of the resonant capacitance adjustment circuit 112 are connected to the resonant circuit 111, and the two detection terminals of the resonant capacitance adjustment circuit 112 are connected to a detection element, for example, connected to the first auxiliary winding Na (winding) of the resonant inductor Lr , and includes a control voltage generation circuit 1120, a delay circuit 1123, a full-bridge rectifier circuit 1121 and a first switch element Q ₁ , wherein the resonant capacitance adjustment circuit 112 utilizes the first switch element Q ₁ to delay conduction To change the equivalent resonant capacitance C _t of the resonant circuit 111 connected to the two high-voltage switch terminals of the resonant capacitance adjustment circuit 112 . The auxiliary voltage generating circuit 12 is used to generate an auxiliary voltage V _cc , such as 5V, and provide the power required for the operation of the power factor correction control circuit 1020 (PFC control circuit) and the inverter control circuit 113 of the control unit 14 . The bus capacitor C _b is connected to the DC bus 13 to filter out the high frequency noise of the high voltage DC voltage V _h .

According to the idea of the present invention, the resonant capacitor circuit (C _r1 , C _r2 ) of the resonant circuit 111 is connected in series with the filament 21, and the two switch terminals of the resonant capacitor adjusting circuit 112 are connected in parallel with the second resonant capacitor C _r2 of the resonant circuit 111 connected, when the lamp tube 2 is lit, the inverter circuit 11 can change the equivalent resonant capacitance value C _t of the resonant circuit 111 through the operation of the resonant capacitance adjustment circuit 112, so that the current value of the filament current _I3 can be changed, That is to change the reactive power flowing through the filament 21 and the resonant circuit 111 , so that the amplitude of the voltage across the filament 21 (filament voltage V _d ) across the plurality of lamp tubes 2 can be changed.

Please refer to FIG. 1 again, the AC-DC power conversion circuit 10 includes an electromagnetic interference filter unit 100, a first rectifier circuit 101 and a power factor correction circuit 102, wherein the electromagnetic interference filter unit 100 is used to receive an AC input voltage V _in , and the first rectifier The AC side of the circuit 101 is connected to the EMI filtering unit 100 , the DC side of the first rectifier circuit 101 is connected to the input side of the power factor correction circuit 102 , and the output side of the power factor correction circuit 102 is connected to the DC bus 13 .

In this embodiment, the EMI filter unit 100 is constructed to block the high-frequency noise of the current preheating electronic ballast 1 itself and the external noise from the AC input voltage _Vin to avoid mutual interference. During operation, the AC-DC power conversion circuit 10 first rectifies the AC power into a full-wave DC power by the first rectifier circuit 101, and then the full-wave DC power is converted by the power factor correction circuit 102 through the conduction or cut-off of the second switching element _Q2 . The DC power source is boosted to a high voltage DC voltage V _h . The power factor correction circuit 102 includes a first inductor L ₁ , a third diode D ₃ , a detection resistor Rs and a second switch element Q ₂ , wherein one end of the first inductor L ₁ is connected to the DC side of the first rectifier circuit 101 The positive end is connected, the other end is connected with the anode end (anode) of the _third diode _D3 , and the cathode end (cathode) of the third diode D3 is connected with the DC bus 13, and the second switch element _Q2 is connected with the detection The resistor R _s , the first inductor L ₁ and the third diode D ₃ are connected. The power factor correction control circuit 1020 is connected to the control terminal _Q2a of the second switching element _Q2 , and by controlling the second switching element _Q2 to be turned on or off, the current distribution of the AC input current I _in is approximate to that of the AC input voltage _Vin Sine wave waveform to increase power factor.

In this embodiment, the inverter circuit 11 also includes a power switch circuit 114 and a voltage divider circuit 115, wherein the inverter control circuit 113 is connected to the power switch circuit 114 and the auxiliary voltage generating circuit 12 for controlling the power switch circuit 114 operation, so that the series terminal of the power switch circuit 114 generates a modulating voltage V _pwm . The voltage dividing circuit 115 is connected to the DC bus 13 for generating a divided voltage (V _h /2). The power switching circuit 114 includes a third switching element _Q3 and a fourth switching element _Q4 , the third switching element _Q3 and the fourth switching element _Q4 are connected in series, and the voltage dividing circuit 115 includes a first voltage dividing capacitor C _b1 and a second voltage dividing capacitor C b1. The voltage dividing capacitor C _b2 , the first voltage dividing capacitor C _b1 and the second voltage dividing capacitor C _b2 are connected in series, and the series terminal of the power switch circuit 114 and the series terminal of the voltage dividing circuit 115 are connected to the resonant circuit 111 and the plurality of lamp tubes 2. The inverter circuit 11 converts the high-voltage DC voltage V _h into a high-frequency AC output voltage V _o by alternately turning on or off the third switching element Q ₃ and the fourth switching element Q ₄ . In this embodiment, the preheating circuit 110 can be a second auxiliary winding N _b and a fourth capacitor C ₄ with the same magnetic core (Core) structure as the resonant inductor Lr, and the filaments on the series side of a plurality of lamp tubes 2 21 are connected in series with each other, but not limited thereto, and are used to preheat the filaments 21 on the series side of multiple lamp tubes 2 .

In this embodiment, the circuit connection relationship in the resonant capacitance adjustment circuit 112 is the control voltage generation circuit 1120, the delay circuit 1123, the _first switch element Q1 and the full-bridge rectification circuit 1121, wherein the control voltage generation circuit 1120 Whether the inverter circuit 11 starts to operate is determined through the first auxiliary winding Na (detection element) of the resonant inductor Lr, and _a first DC voltage V _dc1 corresponding to the state (potential) is generated. The delay circuit 1123 generates a second DC voltage V _dc2 corresponding to the state (potential) after delaying a delay time T _d according to the state (potential) of the first DC voltage V _dc1 to control whether the _first switching element Q1 is turned on or not. .

In this embodiment, the control voltage generating circuit 1120 includes a first capacitor C ₁ , a second capacitor C ₂ , a first resistor R ₁ , a second resistor R ₂ and a first Zener diode Z ₁ , and the delay circuit 1123 includes a second Two diodes D ₂ , a third capacitor C ₃ , a third resistor R ₃ and a fourth resistor R ₄ , wherein one end of the first auxiliary winding Na is connected to one end of the first capacitor C ₁ and the first node _A , The other end of the first capacitor _C1 is connected to _one end of the _first resistor R1, and the other end of the first resistor R1 is connected to the anode end of the _first diode D1 and the cathode end of the _first Zener diode Z1, The anode terminal of the _first Zener diode Z1 is connected to the first node A, the cathode terminal of the first diode D1 is connected to _one terminal of the _second capacitor C2, one terminal of the _second resistor R2 and the terminal of the _third capacitor C3 One end is connected, the other end of the _third capacitor C3, the other end of the _second resistor R2, the anode end of the _second diode D2 and one end of the _fourth resistor R4 are connected to the first node A, the second diode _The cathode end of the tube D2 is connected to the other end of the third capacitor C3 and one end of the third resistor _R3 , and the other end of the _third resistor _R3 is connected to the other end of the _fourth resistor R4.

In this embodiment, the _first switching element Q1 can be but not limited to a metal oxide semiconductor field effect transistor (MOSFET). The control terminal Q1a of the _first switching element Q1 is connected to the other end of the _third resistor _R3 and the second The other end of the _four resistors R4 is connected, the current input terminal _Q1b of the _first switching element Q1 is connected with the _first terminal a (DC positive terminal) of the full-bridge rectifier circuit 1121, and the current output terminal Q1 of the first switching element Q1 _1c is connected to the second terminal b (DC negative terminal) of the full-bridge rectifier circuit 1121, and the third terminal c and the fourth terminal d (two ends of the AC side) of the full-bridge rectifier circuit 1121 are respectively connected to the second resonant capacitor C _r2 Both ends are connected in parallel with the second resonant capacitor C _r2 .

Please refer to FIG. 2 together with FIG. 1 , wherein FIG. 2 is a timing diagram of the voltage, current and status of the current preheating electronic ballast of the present invention. As shown in FIG. 2 , at the first time t ₁ after the current preheating electronic ballast 1 receives the AC input voltage V _in and starts to operate, the control unit 14 controls the operation of the power switch circuit 114 to make the inverter circuit 11 Start to output the AC output voltage V _o and the resonant current I ₁ of the first frequency value f ₁ (for example, 65k Hz) with a higher frequency value (output frequency f _o ), and start to preheat multiple groups of lamp tubes 2, because of this At this time, the lamp 2 has not been turned on, so there is no lamp current I ₂ , the resonant current I ₁ will flow through the filament 21 and be transmitted to the first resonant capacitor C _r1 , so the resonant current I ₁ is equal to the filament current I ₃ at this time. In order to effectively preheat the filament 21 with the filament current I ₃ having a relatively large current value, in the preheating time interval T _pre , the two high-voltage switch terminals of the resonant capacitor adjustment circuit 112 will be correspondingly turned on, that is, the first switch element Q ₁ is turned on, so that the equivalent resonant capacitance C _t is the larger capacitance of the first resonant capacitor C _r1 (C _t =C _r1 ).

At the first time t ₁ , the first auxiliary winding _Na (detection element) senses the electric energy generated by the resonant current I ₁ of the resonant winding Nr, and transmits the electric energy to the first two through the first capacitor C ₁ and the first resistor R ₁ The cathode end of the diode D ₂ generates a first DC voltage V _dc1 in an enabled state (high potential), which means that the inverter circuit 11 starts to operate. At this time, the first DC voltage V _dc1 in the enabled state (high potential) begins to charge the fifth capacitor _C5 . Since the fifth capacitor _C5 is approximately short-circuited at the initial stage of circuit operation, that is, the voltage value of the fifth capacitor _C5 is 0V. Therefore, the second DC voltage V _dc2 (V _dc2 >V _t ) obtained by dividing the first DC voltage V _dc1 through the third resistor R ₃ and the fourth resistor R ₄ will not immediately change to the disabled state (low potential ), the second DC voltage V _dc2 will maintain a high potential (enabled state) whose voltage value is greater than the first switch conduction voltage V _t , so that the _first switch element Q1 is turned on, so that the filament current _I3 will not Pass through the second resonant capacitor C _r2 , that is, bypass the second resonant capacitor C _r2 . At this time, the filament current I ₃ flows through the first resonant capacitor C _r1 , then flows into the full-bridge rectifier circuit 1121 from the third terminal c, flows out from the first terminal a, and passes through the conductive first switch Q ₁ and the second terminal b flows into the full-bridge rectifier circuit 1121, and then flows out from the fourth end d to the other end of the lamp tube 2 to form a loop. This is the positive half-cycle action of the current, and the negative half-cycle action is the filament current I ₃ from the fourth end Terminal d flows into the full-bridge rectifier circuit 1121, flows out from the first terminal a, flows out through the _first switch Q1 and the second terminal b into the full-bridge rectifier circuit 1121, flows out from the third terminal c, and then passes through the first The resonant capacitor C _r1 then flows into one end of the lamp tube 2 .

In the lighting time interval T _ign from the second time _t2 to the third time _t3 , the control unit 14 controls the operation of the power switch circuit 114 so that the frequency value f _o of the AC output voltage V _o and the resonant current I ₁ is determined by The higher-frequency first frequency value f ₁ (for example, 65k Hz) gradually decreases to a lower-frequency second frequency value f ₂ (for example, 40k Hz), so that the resonant circuit 111 operates at a higher frequency at the third time _t3 . The _second frequency value f2 has a high gain (gain), thereby generating an AC output voltage V _o with a higher voltage value (amplitude) to light the lamp tube 2 .

After the preheating and lighting procedures of the lamp tube 2 are completed, the first DC voltage V _dc1 will continue to charge the fifth capacitor _C5 to increase its voltage value. At this time, although the voltage value of the second DC voltage V _dc2 will correspondingly drops, but the second DC voltage V _dc2 (V _dc2 >V _t ) will maintain the enabled state (high potential), until the fourth time t ₄ , the voltage value of the second DC voltage V _dc2 will be less than the first switch on The voltage value V _t (V _dc2 <V _t ), that is, changes to the disabled state (low potential), and the energy is no longer transmitted to the control terminal Q _1a of the first switching element Q ₁ , so the first switching element Q ₁ is open and resonant The capacitor adjustment circuit 112 stops bypassing the second resonant capacitor C _r2 . At this time, the filament current _I3 flows through the first resonant capacitor C _r1 and the second resonant capacitor C _r2 and then flows to the other end of the lamp tube 2 to form a loop. However, the connection relationship of the equivalent resonant capacitor is the first The resonant capacitor C _r1 and the second resonant capacitor C _r2 are connected in series, and the resonant inductance Lr, the first resonant capacitor C _r1 and the second resonant capacitor C _r2 are connected in series, so the equivalent resonant capacitance C _t is smaller than the first resonant capacitor Capacitor C _r1 (C _t < C _r1 ), so that the current value of the filament current I ₃ can be reduced, thereby reducing the cross-voltage across the filament 21, increasing the life of the lamp tube, and reducing energy waste. It is applied to high filament impedance When using high-efficiency fluorescent lamps, it can also prevent high-efficiency fluorescent lamps from burning out. Since the filament current I ₃ flowing through the filament 21 is a virtual power, it will not affect the current value of the lamp current I ₂ , so the current value of the lamp current I ₂ can maintain a constant current value substantially.

In general, the control voltage generation circuit 1120 judges that the inverter circuit 11 starts to operate through the first auxiliary winding N _a (detection element) at the first time _t1 , and generates the first DC voltage V corresponding to the enable state (high potential) When _dc1 , the delay circuit ₁₁₂₃ will not immediately correspondingly change the enabled state (high potential ₎ of the second DC voltage V _dc2 , but will change to the disabled state ( Low potential) of the second direct current voltage V _dc2 to control the open circuit of the first switching element Q ₁ to reduce the filament current I ₃ and the filament voltage V _d . Since the delay time T _d is greater than (or equal to) the sum of the preheating time interval T _pre and the lighting time interval T _ign (T _d > T _pre + T _d ), therefore, in the preheating time interval T _pre and the lighting time interval T _ign , the equivalent resonant capacitance C _t (C _t =C _r1 ) of the resonant circuit 111 is relatively high, and the inverter circuit 11 has better operating characteristics. The resonant capacitance C _t (C _t <C _r1 ) is relatively low, so that the amplitude of the filament current I ₃ and the filament voltage V _d is relatively low. In some embodiments, the resonant capacitance adjustment circuit 112 can also be fabricated as a four-pin resonant capacitance adjustment element using semiconductor manufacturing technology, which includes two detection terminals and two high-voltage switch terminals, and is respectively connected to the detection Components and resonant circuits to reduce the number and volume of components in the realization of current preheating electronic ballasts.

In this embodiment, the resonant capacitor adjustment circuit 112 uses the first switching element Q1 with _a lower operating frequency and the full-bridge rectifier circuit 1121 to realize the switching characteristics of its two switch terminals, so the _first switching element Q1 is used for higher frequency The inverter circuit 11 with a high value (for example, above 40k Hz) can be turned on and off normally. If the resonant capacitor adjustment circuit 112 is applied to the inverter circuit 11 with a lower frequency value, the unidirectional _first switching element Q1 and the full-bridge rectifier circuit 1121 can be replaced by a bidirectional switching element (not shown), such as a three-pole AC switch (T _RIAC ), wherein the control end of the bidirectional switch element (not shown) is connected to the output end of the delay circuit 1123 (ie the serial connection end of the third resistor _R3 and the _fourth resistor R4), and the bidirectional switch element The two switch terminals are the two switch terminals of the resonant capacitor adjustment circuit 112 .

Please refer to FIG. 1 again. In this embodiment, the inverter circuit 11 further includes a protection circuit 116 for protecting the current preheating electronic ballast 1 when the lamp tube 2 fails. The protection circuit 116 includes a first protection diode D _b1 and a second protection diode D _b2 , which respectively correspond to the first voltage dividing capacitor C _b1 and the second voltage dividing capacitor C _b2 connected to the voltage dividing circuit 115 , when the lamp tube 2 fails , in the positive and negative half cycles of the AC output voltage V _o , the discharge of the lamp tube 2 is asymmetrical, for example, it is only discharged in the positive half cycle, and if the protection circuit 116 is not connected, it may cause the first voltage dividing capacitor C _b1 or One of the voltage values of the second voltage dividing capacitor C _{b2 is} too high, for example higher than the voltage value of the high voltage direct current voltage V _h . When the voltage value is higher than the voltage value of the high-voltage DC voltage V _h , the second protection diode D _b2 correspondingly connected to the second voltage dividing capacitor C _b2 will be turned on, so that the second voltage dividing capacitor C _b2 cannot continue to charge, preventing the second voltage dividing capacitor C b2 from charging. The voltage value of the two voltage dividing capacitors C _b2 is too high, resulting in damage to the first voltage dividing capacitor C _b1 or the second voltage dividing capacitor C _b2 .

In this embodiment, the resonant capacitance adjustment circuit 112 further includes a clamping protection circuit 1122, which is connected to the two switch terminals (Q _1c , Q _1c ) of the first switching element Q ₁ , which is connected by a second Zener diode Z ₂ and a third zener diode Z ₃ are connected in series to protect the first switching element Q ₁ and prevent the first switching element Q ₁ from being damaged by the high voltage generated at the moment when the preheating of the lamp tube 2 is completed. .

In this embodiment, the inverter circuit 11 is also connected in parallel with a thermistor (PTC) R _h between the two switch terminals of the resonant capacitance adjustment circuit 112, and when the current preheating electronic ballast 1 just starts to operate ( Before the first time _t1 ), since it takes a short time for the _first switching element Q1 to change from open circuit to conduction, the thermistor _Rh with a low temperature (for example, 25° C.) and a small resistance value can be used to temporarily replace the first switching element Q1. A switch element Q ₁ is to the bypass characteristic of the second resonant capacitor C _r2 , so that the equivalent resonant capacitance C _t is the larger capacitance value (C _t =C _r1 ) of the first resonant capacitor C _r1 , and the larger current The filament current I ₃ with a certain value preheats the filament 21 and at the same time prevents the lamp tube 2 from flickering briefly due to the small equivalent resonant capacitance C _t before the preheating is completed. After the lamp 2 is lit, the thermistor R _h is in a state of high temperature (for example, 100° C.) and a large resistance value, that is, an approximate open circuit state, so that it does not have a bypass characteristic, so it does not affect the characteristics of the resonant circuit 111 .

Please refer to FIG. 3 together with FIG. 1 and FIG. 2 , wherein FIG. 3 is a schematic circuit diagram of a current preheating electronic ballast according to another preferred embodiment of the present invention. The lamp group 2B and resonant circuit 111B in FIG. 3 are different from FIG. 1. In this embodiment, the lamp group 2B is implemented with a single lamp, and the two high-voltage switch terminals of the resonant capacitor adjustment circuit 112 are connected to the second resonant capacitor C _rb is connected in series, and the resonant circuit 111B adjusts the conduction or open circuit of the two high-voltage switch ends of the resonant capacitor circuit 112, so that the first resonant capacitor C _ra and the second resonant capacitor C _rb are selected between the two filaments 21 of the lamp tube group 2B connected in parallel. Similarly, in the preheating time interval T _pre and the lighting time interval T _ign , the two high-voltage switch terminals of the resonant capacitor adjustment circuit 112 will be correspondingly turned on, that is, the _first switching element Q1 will be turned on, so that the equivalent resonant capacitor The value C _t is a larger capacitance value, that is, the equivalent resonant capacitance value C _t is the sum of the capacitance values of the first resonant capacitor C _ra and the second resonant capacitor C _rb . At the _fourth time t4 after the delay time _Td , the preheating of the lamp tube is completed and the light is turned on, and the two high-voltage switch terminals of the resonant capacitor adjustment circuit 112 will be correspondingly open, so that the equivalent resonant capacitor value C _t is smaller The capacitance value (C _t =C _ra ), that is, the equivalent resonant capacitance C _t is the capacitance value of the first resonant capacitor C _ra . Wherein, if the capacitance of the first resonant capacitor C _ra is smaller than the capacitance of the second resonant capacitor C _rb , the current preheating electronic ballast 1B can have better operating characteristics.

Please refer to FIG. 4 together with FIGS. 1-3 , wherein FIG. 4 is a schematic circuit diagram of a current preheating electronic ballast according to another preferred embodiment of the present invention. The inverter circuit 11C of FIG. 4 is different from that of FIG. 3. In this embodiment, since the duty cycle (duty cycle) of the power switch circuit 114 is 50% during operation, the voltage divider circuit 115 of FIG. 3 is simplified (or equivalent ) is a half-bridge capacitor C _h , and the half-bridge capacitor C _h is connected in series with the resonant circuit 111B, and the operation principle is the same as that described above, and will not be repeated here.

In summary, the current preheating electronic ballast of the present invention adjusts the equivalent resonant capacitance value in the resonant circuit through a resonant capacitance adjustment circuit (component), so that the equivalent resonant capacitance value can be reached after the lamp tube is preheated and lit. The front and rear are different and appropriate capacitance values, so that the filament current can be increased when the lamp is preheated and lit, and at the same time, the current value of the filament current can be reduced after the lamp is preheated and lit, so as to reduce the filament current. The purpose of cross-voltage (less than 4V) at the end, thereby avoiding energy waste and prolonging the service life of the lamp tube, so the current preheating electronic ballast of the present invention can be applied to both general fluorescent lamps with low filament impedance and high filament impedance High-efficiency fluorescent lamps. The resonant capacitor adjustment element (circuit) provided by the present invention can operate normally in a high-frequency environment, so it is suitable for high-frequency current preheating electronic ballasts, and its delay characteristics can also be used to stabilize current preheating electronic ballasts. The equivalent resonant capacitance value of the resonant circuit of the device is changed after the fluorescent lamp is lit, so that the current value of the filament current and the cross voltage at both ends of the filament are reduced (less than 4V).

The present invention can be modified in various ways by those who are familiar with this technology, but all are within the intended protection of the scope of the appended patent application.

Claims (19)

1. a current preheating type electric stabilizer, drives at least one group of fluorescent tube, it is characterized in that, this current preheating type electric stabilizer comprises:

One AC-DC change-over circuit, be that an AC-input voltage is converted to a high-voltage dc voltage, it is connected to a DC bus and exports this high-voltage dc voltage;

One control unit, controls the running of this current preheating type electric stabilizer;

One boost voltage produces circuit, produces a boost voltage; And

One inverter circuit, is connected with this DC bus, and for this high-voltage dc voltage being converted to an ac output voltage and exporting a resonance current and a heater current to this group fluorescent tube, this inverter circuit comprises:

One resonant circuit, is connected to this group fluorescent tube, energy required during to provide this group fluorescent tube preheating, and comprises a resonant inductance and multiple resonant capacitance; And

One resonant capacitance Circuit tuning, is connected to this resonant circuit and a detecting element, comprises:

One first switch element;

One control voltage produces circuit, is connected, judges whether this inverter circuit comes into operation by this detecting element, and produce one first direct voltage of corresponding states with this detecting element; And

One delay circuit, the control end and this control voltage that are connected to this first switch element produce circuit, according to the state of this first direct voltage after a time of delay of postponing, produce one second direct voltage of corresponding states, to control the whether conducting of this first switch element, to change the equivalent tank capacitance of this resonant circuit, to change the cross-pressure at the filament two ends in this group fluorescent tube.

2. current preheating type electric stabilizer as claimed in claim 1, it is characterized in that, this AC-DC change-over circuit comprises:

One EMI Filtering unit;

One first rectification circuit, is connected with this EMI Filtering unit; And

One circuit of power factor correction, is connected to this first rectification circuit and this DC bus.

3. current preheating type electric stabilizer as claimed in claim 1, it is characterized in that, this inverter circuit also comprises a bleeder circuit, is connected to this DC bus, to produce a branch pressure voltage, this bleeder circuit comprises one first derided capacitors and one second derided capacitors that are connected in series.

4. current preheating type electric stabilizer as claimed in claim 3; it is characterized in that; this inverter circuit also comprises a protective circuit; one first protection diode and the one second protection diode of this protective circuit are connected to this first derided capacitors and this second derided capacitors, to prevent the magnitude of voltage of this first derided capacitors and this second derided capacitors too high.

5. current preheating type electric stabilizer as claimed in claim 2, it is characterized in that, this control unit comprises: a power factor correction control circuit and an inverter control circuit, controls this circuit of power factor correction and the running of this inverter circuit respectively.

6. current preheating type electric stabilizer as claimed in claim 1, it is characterized in that, this first switch element is bilateral switching element or unidirectional switch elements.

7. current preheating type electric stabilizer as claimed in claim 1, it is characterized in that, this first switch element is unidirectional switch elements, and this resonant capacitance Circuit tuning also comprises a full bridge rectifier, two of this full bridge rectifier exchange two high-voltage switch gear ends that end is connected to this resonant capacitance Circuit tuning, and two DC terminal of this full bridge rectifier are connected with two switch terminals of this first switch element.

8. current preheating type electric stabilizer as claimed in claim 7; it is characterized in that; this resonant capacitance Circuit tuning also comprises a clamp protection circuits; be connected to two switch terminals of this first switch element; framework is in this first switch element of protection, and this resonant capacitance Circuit tuning comprises at least one Zener diode.

9. current preheating type electric stabilizer as claimed in claim 1, it is characterized in that, this control voltage produces circuit and comprises: one first electric capacity, one second electric capacity, one first resistance, one second resistance and one first Zener diode, one end and a first node of this detecting element and this first electric capacity are connected, the other end of this first electric capacity is connected with one end of this first resistance, the other end of this first resistance is connected with the anode tap of one first diode and the cathode terminal of this first Zener diode, the anode tap of this first Zener diode is connected to this first node, the cathode terminal of this first diode is connected with one end of one end of this second electric capacity and this second resistance.

10. current preheating type electric stabilizer as claimed in claim 9, it is characterized in that, this delay circuit comprises: one second diode, one the 3rd electric capacity, one the 3rd resistance and one the 4th resistance, one end of 3rd electric capacity is connected to this first diode and this second electric capacity and this second resistance, the other end of the 3rd electric capacity, the other end of this second resistance, the anode tap of this second diode and one end of the 4th resistance are connected to this first node, the cathode terminal of this second diode is connected with one end of the other end of the 3rd electric capacity and the 3rd resistance, the other end of the 3rd resistance is connected with the other end of the 4th resistance.

11. current preheating type electric stabilizers as claimed in claim 1, it is characterized in that, this inverter circuit also comprises: a power switch circuit, is connected to this control unit, this DC bus and this resonant circuit, to produce a demodulating voltage to this resonant circuit.

12. current preheating type electric stabilizers as claimed in claim 11, it is characterized in that, this inverter circuit also comprises: a half-bridge capacitance, be connected in series with this resonant circuit, and the responsibility cycle during running of this power switch circuit is 50%, this inverter circuit is semibridge system, is equivalent to partial pressure properties by this half-bridge capacitance.

13. current preheating type electric stabilizers as claimed in claim 1, is characterized in that, this detecting element be one with the one first auxiliary winding of this resonant inductance with core structure.

14. current preheating type electric stabilizers as claimed in claim 1, it is characterized in that, this inverter circuit also comprises a preheat circuit, is connected with this group fluorescent tube, to carry out preheating to this group fluorescent tube.

15. current preheating type electric stabilizers as claimed in claim 1, wherein this inverter circuit comprises a thermistor, is connected to two high-voltage switch gear ends of this resonant capacitance Circuit tuning.

16. current preheating type electric stabilizers as claimed in claim 1, it is characterized in that, the resonant capacitance circuit of this resonant circuit is connected to the two ends of this group fluorescent tube, this resonant capacitance circuit comprises: one first resonant capacitance and one second resonant capacitance, and two high-voltage switch gear ends of this second resonant capacitance and this resonant capacitance Circuit tuning are connected in series or in parallel.

17. 1 kinds of resonant capacitance adjustment elements, for the electronic component of the multiple pin of tool, be applied to an inverter circuit of a current preheating type electric stabilizer, it is characterized in that, this inverter circuit comprises a resonant circuit, and this resonant circuit is connected to this resonant capacitance adjustment element and one group of fluorescent tube, energy required during to provide this group fluorescent tube preheating, and comprise a resonant inductance and multiple resonant capacitance, this resonant capacitance adjustment element comprises:

One first switch element;

One control voltage produces circuit, is connected with a detecting element by two test sides of this resonant capacitance adjustment element, its utilize this detecting element to judge whether this inverter circuit comes into operation, and produce one first direct voltage of corresponding states; And

One delay circuit, the control end and this control voltage that are connected to this first switch element produce circuit, according to the state of this first direct voltage after a time of delay of postponing, produce one second direct voltage of corresponding states, to control this first switching elements conductive or open circuit, and make this resonant capacitance adjust the conducting of two high-voltage switch gear ends or the open circuit of element, to change the equivalent tank capacitance of this resonant circuit, to change the cross-pressure at the filament two ends in this group fluorescent tube.

18. resonant capacitance adjustment elements as claimed in claim 17, it is characterized in that, this first switch element is bilateral switching element or unidirectional switch elements.

19. resonant capacitance adjustment elements as claimed in claim 17, it is characterized in that, also comprise a full bridge rectifier, two of this full bridge rectifier exchange two high-voltage switch gear ends that end is connected to this resonant capacitance adjustment element, and two DC terminal of this full bridge rectifier are connected with two switch terminals of this first switch element.