KR20050107124A - Circuit making use of push/pull-type control chip to drive half bridge-type inverter circuit - Google Patents

Abstract

A circuit that uses a push / pull-type control chip to drive a half bridge-type inverter circuit connects the drive circuit to a half-bridge inverter circuit of the prior art. A push / pull control chip having two output terminals, a drive circuit having two input terminals and two output terminals, and a half bridge type switch assembly having two electronic switches. The two input terminals of the drive circuit are connected to the two output terminals of the push / pull control chip and are controlled by the push / pull control chip. Each of the two electronic switches of the half bridge type switch assembly has a control terminal, the control terminal is connected to one of the two output terminals of the drive circuit, and an AC power source (DC power source) sent to the primary side of the transformer ( Driven by a drive circuit that switches to an AC power source.

Description

CIRCUIT MAKING USE OF PUSH / PULL-TYPE CONTROL CHIP TO DRIVE HALF BRIDGE-TYPE INVERTER CIRCUIT}

The present invention relates to a circuit that uses a push / pull control chip to drive a half bridge type inverter circuit, and more particularly, to an inverter circuit that can use a push / pull type control chip to control a half bridge type inverter circuit.

The power supply for the backlight source of the TFT LCD panel uses an inverter circuit to turn on the cold cathode fluorescent lamp (CCFL) by making energy conversion. Prior art inverter circuits can be divided into half bridge-type, full bridge-type, and push / pull-type according to different circuit topologies. have. An inverter circuit is a circuit which converts DC power into AC power.

As shown in FIG. 1, the transformer T1 divides the circuit into a front-end circuit on the primary side 101 and a rear-end circuit on the secondary side 102. The front end circuit of the primary side 101 includes a DC voltage source Vcc, a first switch Q1, and a second switch Q2. The rear end circuit of the secondary side 102 has at least one capacitor C1, C2, C3, a load and at least one diode D1, D2. The push / pull control chip 103 is connected between the front end circuit of the primary side 101 and the rear end circuit of the secondary side 102. Reference is also made to FIG. 2. The push / pull control chip 103 outputs the first control signal a and the second control signal b to switch the switching operations of the two switches Q1 and Q2 on the primary side 101, respectively. The DC power supply Vcc is used to provide energy, and the transformer T1 converts the rear end circuit 102 to drive the load by raising the voltage of the DC power supply Vcc. The output voltage waveform c on the secondary side of the transformer T1 is the voltage waveform at point C. As shown in Fig. 2, the output voltage waveform c on the secondary side is an AC voltage waveform.

In the above description, the push / pull control chip 103 is an LX1686, LX1688 or LX1691 push / pull control chip, O2 Micro International Limited manufactured by Linfinity (Microsemi) Corporation. O2-9RR push / pull control chip, or BIT3494 push / pull control chip, manufactured by Beyond Innovation Technology.

As shown in FIG. 3, transformer T2 divides the circuit into a front end circuit on the primary side 201 and a rear end circuit on the secondary side 202. The front end circuit of the primary side 201 is a DC power supply (Vcc), two electronic switches (Q1, Q2), a half bridge type control chip (TL494), two capacitors (C1, C2) and an isolation transformer ( Tr). The rear end circuit of the secondary side 202 has a load. Reference is also made to FIG. 4. The half bridge control chip TL494 outputs the control signals D1-D2 via two output terminals D1 and D2. The control signals D1-D2 control the switching operations of the two electronic switches Q1 and Q2 via the isolation transformer Tr. The two electronic switches Q1 and Q2 are n-channel FETs or p-channel FETs. Through the switching operation of the two electronic switches Q1 and Q2, the electrical energy stored in the capacitors C1 and C2 is converted to 1 of the transformer T2 via the coupling capacitor C3 to form an AC power source ac. The vehicle may be transferred to the vehicle side terminal T21. The voltages of the capacitors C1 and C2 are half of the direct current voltage Vcc (Vcc / 2). AC power ac is used to provide energy to transformer T2, which switches to secondary side 202 to drive the load.

In the above description, if the inverter circuit used is half bridge type, the half bridge type control chip needs to be matched for normal operation, and if the inverter circuit used is push / pull type, the push / pull control chip is used for normal operation. Since they need to be matched, they have less flexibility and commonality in practical use. In other words, control chips cannot be used jointly, cannot be purchased together, or require more complex circuitry to be matched.

In addition, in the half bridge type inverter circuit of the prior art, the isolation transformer needs to control the switching operation of two electronic switches. Half-bridged control chips cannot drive two electronic switches directly. In addition, both electronic switches used in the half-bridge inverter circuit of the prior art are n-channel FETs or p-channel FETs.

Accordingly, one object of the present invention is to provide a circuit that uses a push / pull control chip to drive a half bridge inverter circuit. The circuit uses a drive circuit connecting the output terminal of the push / pull control chip and the control terminal of the half bridge type switch assembly composed of two electronic switches. The circuit is controlled by a push / pull control chip that drives the switching operation of the half bridge type switch assembly.

In a circuit using a push / pull control chip to drive the half bridge inverter circuit of the present invention, the drive circuit is connected between the control chip and two electronic switches of the half bridge inverter circuit of the prior art. The control chip is replaced with a push / pull control chip to switch the switching operation of the two electronic switches.

The drive circuit has a first acceleration diode, a second resistor, a second acceleration diode, and a third resistor. The negative terminal N of the first acceleration diode is connected to the output terminal of the push / pull control chip, and the positive terminal P of the first acceleration diode is connected to the base of the transistor switch. The first acceleration diode is used to speed up the cutoff operation of the transistor switch. The emitter of the transistor switch is connected to a reference terminal, and the collector of the transistor switch is connected to the DC power supply via the control terminal of the second electronic switch and the first resistor. . The second resistor is in shunt with the first acceleration diode to limit the base current of the transistor switch. The negative terminal N of the second acceleration diode is connected to the other output terminal of the push / pull control chip, and the positive terminal P of the second acceleration diode is connected to the control terminal of the first electronic switch via the coupling capacitor. do. The second acceleration diode is used to speed up the conduction operation of the first electronic switch. The third resistor is in parallel with the second acceleration diode for limiting the current of the control terminal of the first electronic switch.

The drive circuit further includes a Zener diode and a fourth resistor. The positive terminal P of the zener diode is connected to the control terminal of the first electronic switch, and the negative terminal of the zener diode is connected to the DC power supply. Zener diodes are used to avoid sudden, very large spike voltages that burn out the first electronic switch. The fourth resistor is in parallel with the zener diode to provide a zener voltage.

The present invention provides a circuit that uses a push / pull control chip to drive a half bridge inverter circuit. The circuit uses the drive circuit to receive the control signal of the push / pull control chip to switch the switching operation of the half bridge type switch assembly consisting of two electronic switches.

The circuit of the present invention connects the driving circuit to the half-bridge inverter circuit of the prior art by fitting the push / pull control chip to control, and thus has very high flexibility in practical use without limitation by the control chip. In addition, it is only necessary to use a push / pull control chip for simultaneous control of the push / pull inverter circuit and the half bridge inverter circuit.

As shown in FIG. 5, the present invention provides a circuit that uses a push / pull control chip to drive a half bridge inverter circuit. The circuit is connected to the primary side of the transformer T2 to convert the DC power source into the AC power source ac. AC power supply ac provides energy for operation of the load via transformer T2. The peak-to-peak value of the AC power source ac is the voltage Vcc of the DC power source.

Reference is again made to FIG. 5. The circuit using the push / pull control chip to drive the half-bridge type inverter circuit of the present invention includes a push / pull control chip 103, a driving circuit 304, a half bridge type switch assembly 302, and two capacitors ( C2, C3). The push / pull control chip 103 has two output terminals A and B for outputting two control signals. The drive circuit 304 has two input terminals and two output terminals. The two input terminals are connected to the two output terminals A and B of the push / pull control chip 103 and controlled by the push / pull control chip 103. The half bridge type switch assembly 302 is composed of two electronic switches Q1 and Q2 each having a control terminal G. The two control terminals G are connected to the two output terminals of the drive circuit 304 and by the drive circuit 304 to switch the DC power supply Vcc with an AC power supply sent to the primary side of the transformer T2. Are driven respectively. Electronic switch Q1 is a p-channel FET, while electronic switch Q2 is an n-channel FET.

Reference is again made to FIG. 5. The source S of the electronic switch Q1 is connected to the DC power supply Vcc. The source S of the electronic switch Q2 is connected to a reference terminal Gnd. The drain D of the electronic switches Q1 and Q2 is connected to one terminal of the primary side of the transformer T2. The other terminal on the primary side of the transformer T2 is connected to the reference terminal Gnd via the capacitor C3 and to the DC power supply Vcc via the capacitor C2. The control terminals G of the electronic switches Q1 and Q2 are connected to two output terminals of the drive circuit 304, respectively. The two electronic switches Q1 and Q2 are connected to form a half bridge type switch assembly. The two electronic switches Q1 and Q2 are connected in a positive half cycle or a negative half cycle to form an AC power source ac at the terminal T21 on the primary side of the transformer T2. Driven.

Reference is again made to FIG. 5. The drive circuit 304 is used to drive two electronic switches Q1 and Q2. The driving circuit 304 includes a first acceleration diode D1, a second resistor R2, a second acceleration diode D2, and a third resistor R3. The negative terminal N of the first acceleration diode D1 is connected to the output terminal B of the push / pull control chip 103, and the positive terminal P of the first acceleration diode is the base of the transistor switch Q3. Is connected to. The emitter of the transistor switch Q3 is connected to the reference terminal, and the collector of the transistor switch is connected to the DC power supply via the control terminal G of the electronic switch Q2 and the first resistor R1. Connected. The second resistor R2 is in parallel with the first acceleration diode D1. The negative terminal N of the second acceleration diode D2 is connected to the output terminal A of the push / pull control chip 103, and the positive terminal P of the second acceleration diode D connects the coupling capacitor C1. It is connected to the control terminal G of the electronic switch Q1 via. The third resistor R3 is in parallel with the second acceleration diode D2.

The driving circuit further includes a Zener diode D3 and a fourth resistor R4. The positive terminal P of the zener diode D3 is connected to the control terminal G of the electronic switch Q1, and the negative terminal N of the zener diode is connected to the DC power supply Vcc. The fourth resistor is in parallel with the zener diode D3.

Reference is made to FIG. 6 as well as FIG. The output terminal A of the push / pull control chip 103 outputs the first control signal a, and the output terminal B of the push / pull control chip 103 outputs the second control signal b. The first control signal (a) and the second control signal (b) are 50% larger duty cycle, such as the clocks of POUT1 and POUT2 of the BIT3015 chip manufactured by Beyond Innovation Technology. cycle). The terminal T21 on the primary side of the transformer T2 can obtain the AC voltage waveform ac together with the peak-peak value Vcc of the DC power supply.

Reference is made to FIG. 6 as well as FIG. At times t1 to t2, the first control signal a is at a high level, while the second control signal b is at a low level. The first control signal a is sent to the control terminal G of the electronic switch Q1 via the third resistor R3 and the coupling capacitor C1 to turn off the electronic switch Q1. Since the second control signal b is sent to the base of the transistor switch Q3 via the first acceleration diode D1 and the second resistor R2 to turn off the transistor switch Q3, the DC power supply Vcc ) May be sent directly to the control terminal G of the electronic switch Q2 via the first transistor R1 to drive the electronic switch Q2. The first acceleration diode D1 is used to accelerate the cutoff operation of the transistor switch Q3 and the conduction operation of the electronic switch Q2. At this time, the electronic switch Q2 is turned on, while the electronic switch Q1 is turned off. Therefore, the electrical energy stored in the capacitor Q3 can be sent to the primary side of the transformer T2 to obtain the negative voltage -Vcc / 2 of the AC voltage waveform at the terminal T21. In the above description, the electronic switches Q1 and Q2 are driven in a negative half cycle.

Reference is made to FIG. 6 as well as FIG. In the time from t2 to t3, the first control signal a is still maintained at the high level, while the second control signal b is raised from the low level to the high level. As a result, the base of the transistor switch Q3 is turned on in response to a high level control signal. Therefore, the control terminal G of the electronic switch Q2 receives the low level signal of the reference terminal Gnd so that the electronic switch Q2 is turned off. Since the first control signal a is still kept at the high level, the electronic switch Q1 is still off. In other words, in the time from t2 to t3, both the electronic switches Q1 and Q2 are turned off. As a result, the primary side of the transformer T2 is open-circuited so that energy stored in the transformer T2 can be released. This is an energy release state. Therefore, the terminal T21 on the primary side of the transformer T2 receives the zero voltage of the AC voltage waveform ac.

Reference is made to FIG. 6 as well as FIG. In the time from t3 to t4, the first control signal a falls from the high level to the low level, while the second control signal b remains at the high level. The first control signal a is sent to the control terminal G of the electronic switch Q1 via the second acceleration diode D2 and the coupling capacitor C1 to turn on the electronic switch Q1. The second acceleration diode D2 is used to accelerate the conduction operation of the electronic switch Q1. Since the second control signal b is still kept at the high level, the electronic switch Q2 is still off. In other words, at a time from t3 to t4, the electronic switch Q1 is on, while the electronic switch Q2 is off, so that the electrical energy stored in the capacitor C2 is stored in the transformer T2. The positive voltage (+ Vcc / 2) of the alternating voltage waveform ac can be obtained at the terminal T21 by being sent to the primary side. In the above description, the electronic switches Q1 and Q2 are driven in a positive half cycle.

Reference is made to FIG. 6 as well as FIG. At the time from t4 to t5, the first control signal a rises from the low level to the high level, while the second control signal b remains at the high level. The states of the electronic switches Q1 and Q2 are the same as those in the time from t2 to t3. Therefore, the primary side of transformer T2 is open-circuited so that energy stored in transformer T2 can be released. This is an energy release state. Therefore, the terminal T21 on the primary side of the transformer T2 receives the zero voltage of the AC voltage waveform ac.

Reference is made to FIG. 5. Zener diode D3 is used to avoid the sudden, very large spike voltage that burns off the electronic switch Q1. The fourth resistor R4 is in parallel with the zener diode to provide a zener voltage.

Reference is made to FIG. 6 as well as FIG. In the time from t5 to t6, the operation of the half bridge inverter circuit of the present invention and the circuit using the push / pull control chip to drive the voltage waveform obtained at the terminal T21 on the primary side of the transformer T2 are t1. The circuit operation in the time from to t2 is repeated. As described above, the peak-peak value of the obtained AC power supply is the voltage Vcc of the DC power supply. The AC power source is also switched to the secondary side of transformer T2 to raise the voltage and provide energy for the load.

Reference is made to FIG. 7 as well as FIG. The difference between the circuit shown in FIG. 7 and the circuit shown in FIG. 5 will be described below. The negative terminal N of the second acceleration diode D2 is moved from the output terminal A of the push / pull control chip 103 to the output terminal B. FIG. The positive terminal P of the second acceleration diode D2 is moved to the control terminal G of the electronic switch Q2. In addition, the third resistor R3 is also moved in parallel with the second acceleration diode D2. The negative terminal N of the first acceleration diode D1 is moved from the output terminal B of the push / pull control chip 103 to the output terminal A. FIG. The positive terminal P of the first acceleration diode D1 is also connected to the base of the transistor switch Q3. The emitter of transistor switch Q3 is also connected to the reference terminal. The collector of transistor switch Q3 is moved from control terminal G of electronic switch Q2 to control terminal G of electronic switch Q1 via coupling capacitor C1 and coupling capacitor C1. . The collector of the transistor switch Q3 is also connected to the DC power supply Vcc via the first resistor R1. The other components shown in FIG. 7 are the same as those shown in FIG. 5.

Reference is made to FIG. 8 as well as FIG. The push / pull control chip 103 is a LX1686, LX1688 or LX1691 type chip manufactured by Linfinity (Microsemi) Corporation, an O2-manufactured by O2 Micro International Limited. 9RR chips or BIT3494 chips manufactured by Beyond Innovation Technology. As shown in FIG. 8, the output terminal A of the push / pull control chip 103 outputs the first control signal a, and the output terminal B of the push / pull control chip 103 is the second control signal. Output (b). The first control signal a and the second control signal b output by the push / pull control chip 103 are different from the signals shown in FIG. 6. The first control signal (a) and the second control signal (b) are 50% lower duty cycle, such as the clocks of NOUT1 and NOUT2 of the BIT3015 chip manufactured by Beyond Innovation Technology. cycle).

Since the circuit operation of the second embodiment is the same as the circuit operation of the first embodiment of the present invention, no further explanation is given. The terminal T21 on the primary side of the transformer T2 can obtain the voltage waveform ac of the AC power supply having the peak-peak value Vcc of the DC power supply. The AC power is then switched to the secondary side of transformer T2 to raise the voltage and provide energy for the load.

In summary, the present invention provides a circuit that uses a push / pull control chip to drive a half bridge inverter circuit. The circuit connects the drive circuit 304 to the conventional half bridge inverter circuit by fitting the push / pull control chip 103 to control, and thus has very high flexibility in practical use. In addition, it is only necessary to use the push / pull type control chip 103 for simultaneous control of the push / pull type inverter circuit and the half bridge type inverter circuit.

While the invention has been described with reference to preferred embodiments of the invention, it will be understood that it is not limited to the description of the invention. Various alternatives and modifications may be proposed in the foregoing description, and other examples may occur to those skilled in the art. Therefore, all such substitutions and variations are intended to be realized within the scope of the invention as defined in the appended claims.

According to the present invention, the circuit connects the driving circuit to the half-bridge inverter circuit of the prior art by fitting the push / pull control chip to the control, and thus has very high flexibility in actual use without limitation by the control chip, It is only necessary to use a push / pull control chip for simultaneous control of the full inverter circuit and the half bridge inverter circuit.

1 is a circuit diagram showing how a conventional push / pull inverter circuit drives a load.

2 is a waveform diagram of a control signal output by a conventional push / pull control chip and an output voltage at the load end.

3 is a circuit diagram showing how a conventional half bridge inverter circuit drives a load.

Fig. 4 is a waveform diagram of the control signal output by the half bridge type control chip of the prior art and the output voltage at the load end.

5 is a circuit diagram of a first embodiment of the present invention.

6 is a waveform diagram of an output signal and an AC voltage of a push / pull control chip according to a first embodiment of the present invention.

7 is a circuit diagram of a second embodiment of the present invention.

8 is a waveform diagram of an output signal and an AC voltage of a push / pull control chip according to a second embodiment of the present invention.

<Explanation of symbols for main parts of drawing>

103: push / pull control chip 302: half bridge type switch assembly

304: drive circuit A, B: output terminal

a, b: control signal ac: AC power

C1, C2, C3: Capacitor D: Drain

D1, D2: Acceleration Diode D3: Zener Diode

G: control terminal Gnd: reference terminal

N: negative terminal P: positive terminal

Q1, Q2, Q3: electronic switch R1, R2, R3, R4: resistor

S: Source T2: Transformer

T21: Primary terminal Vcc: DC power

Claims (10)

A circuit using a push / pull-type control chip to drive a half bridge-type inverter circuit, the circuit comprising a DC power source for alternating current. Connected to the primary side of the transformer to switch to (AC power source), The circuit, Push / pull control chip with 2 output terminals, A driving circuit having two input terminals and two output terminals, the two input terminals being connected to the two output terminals of the push / pull control chip and controlled by the push / pull control chip, A half bridge type switch assembly composed of two electronic switches each having a control terminal, said control terminal being connected to two output terminals of said drive circuit, said alternating current power supplied to said primary of said transformer; And a push / pull control chip for driving a half bridge inverter circuit characterized in that it is driven by said drive circuit for switching to. 2. The circuit of claim 1 wherein the two electronic switches are p-channel FETs and n-channel FETs. 3. The method of claim 2, wherein the p-channel FET and the n-channel FET are driven in a positive half cycle or a negative half cycle. Circuit using push / pull control chip. 3. The circuit of claim 2 wherein a source of the p-channel FET is connected to a direct current power source. 3. The circuit of claim 2 wherein the source of the n-channel FET is connected to a reference terminal. The method of claim 1, wherein the driving circuit, A first acceleration diode, a negative terminal of the first acceleration diode, is connected to one side of the output terminal of the push / pull control chip, a positive terminal of the first acceleration diode is connected to a base of a transistor switch, and the transistor switch An emitter of is connected to a reference terminal, a collector of the transistor switch is connected to the DC power supply via the control terminal on one side of the electronic switch and a first resistor, A second resistor in parallel with the first acceleration diode, A second acceleration diode, the negative terminal of the second acceleration diode, is connected to another side of the output terminal of the push / pull control chip, and the positive terminal of the second acceleration diode is connected to the electronic switch via a coupling capacitor. Connected to the control terminal on the other side, And a push / pull control chip for driving a half bridge inverter circuit comprising a third resistor in parallel with the second acceleration diode. 7. The driving circuit of claim 6, wherein the driving circuit further comprises a Zener diode and a fourth resistor in parallel with the Zener diode, wherein the positive terminal of the Zener diode is the control terminal of another of the electronic switches. And a negative terminal of the zener diode is connected to the DC power supply. The method of claim 1, wherein the driving circuit, The first acceleration diode, the negative terminal of the first acceleration diode, is connected to one side of the output terminal of the push / pull control chip, the positive terminal of the first acceleration diode is connected to the base of the transistor switch, and the image of the transistor switch is An emitter is connected to a reference terminal, and a collector of the transistor switch is connected to the DC power supply via the control terminal on one side of the electronic switch and a first resistor via a coupling capacitor. Connected, A second resistor in parallel with the first acceleration diode, A second acceleration diode, the negative terminal of the second acceleration diode, is connected to another side of the output terminal of the push / pull control chip, and the positive terminal of the second acceleration diode is the control terminal of the other side of the electronic switch. Is connected to A push / pull control chip for driving a half bridge inverter circuit comprising a third resistor in parallel with the second acceleration diode. 9. The driving circuit of claim 8, wherein the driving circuit further comprises a Zener diode and a fourth resistor in parallel with the Zener diode, wherein the positive terminal of the Zener diode is connected to the control terminal on the other side of the electronic switch. And a negative terminal of the zener diode is connected to the DC power supply. 10. The method of claim 1, further comprising two capacitors connected between the primary side of the transformer and the half bridge switch assembly. Circuit.