Full bridge inverter with push/pull control chip

A full bridge inverter with a push/pull control chip uses two similar drivers to connect to the prior art full bridge switch assembly, and controls the prior art full bridge switch assembly with the push/pull control chip. The full bridge inverter comprises a push/pull control chip with two output terminals. Two drivers both have an input terminal and an output terminal. The input terminal is connected to the output terminals of the push/pull control chip and a full bridge switch assembly with four electronic switches. Each electronic switch has a control terminal connected to the output terminal of the two drivers so as to convert DC power into AC power by the two drivers.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a full bridge inverter with a push/pull control chip, and more specifically relates to a push/pull control chip controlling the full bridge switch assembly for driving the load.

2. Description of the Related Art

The primary power supply of the cold cathode fluorescent lamp (CCFL) of the TFT LCD is used with the inverter circuit. The prior art inverter circuit converts DC power into AC power, and is discriminated into half bridge inverter, full bridge inverter and push/pull inverter, for example, by the topology of the different circuits.

Referring toFIG. 1, the transformer T1divides the whole circuit into a front circuit101and a back circuit102, and there is a push/pull control chip103connected between the front circuit101and the back circuit102. The front circuit101comprises a DC power, a first switch Q1, a second switch Q2etc. and the back circuit102comprises at least a capacitor (C1, C2, C3), a load, at least a diode (D1, D2) etc.

Referring toFIG. 2, the push/pull control chip103transmits a first control signal a and a second control signal b to the first switch Q1and the second switch Q2, respectively, for switching the two switches. Power is thus supplied to the load through the transformer T1according to the DC power. The voltage wave c of the secondary of the transformer T1is the wave of the ac voltage at point C inFIG. 2.

In the above description, the push/pull control chip103is chip LX1686 and the series LX1686, LX1688, LX1691 of the LINFINITY (MICROSEMI) Corp., the series of the chip O2-9RR of the O2 Micro International Limited Corp., and the series of the chip BIT3105, BIT3494 of the Beyond Innovation Technology Corp.

As shown inFIG. 3, the transformer T2divides the whole circuit into a front circuit201and a back circuit202. The front circuit201comprises four electronic switches (P1, P2, N1, N2), a full bridge control chip203and a capacitor C1. Moreover the back circuit202comprises a load. Referring toFIG. 4, the full bridge control chip203transmits four control signals (POUT1, POUT2, NOUT1, NOUT2) to the four electronic switches (P1, P2, N1, N2), respectively; by switching those switches, power is supplied to the load through the transformer T2according to the DC power. The full bridge control chip203is the BIT3105 of the Beyond Innovation Technology Corp.

In the above description, driving the full bridge switch assembly requires the full bridge control chip203and driving the push/pull inverter requires the push/pull control chip103, thus lacking practical flexibility. Furthermore, the control chip of the inverter circuit is limited in use so as to be hard to purchase together.

SUMMARY OF THE INVENTION

The primary object of the present invention uses two similar drivers to connect between the output terminal of the push/pull control chip and the control terminal of the full bridge switch assembly, and the push/pull control chip controls the full bridge switch assembly for switching.

The present invention is connected between the four electronic switches (P1, P2, N1, N2) of the full bridge switch assembly of the prior art and the push/pull control chip with the two similar drivers. Moreover, the push/pull control chip controls switching of the four electronic switches (P1, P2, N1, N2) of the full bridge switch assembly through two similar drivers.

In the above description, the driver comprises a first accelerated diode connected to the output terminal of the push/pull control chip with a negative pole terminal and connected to the control terminal of the electronic switch with a positive pole terminal for speedily cutting off the N-MOSFET, a first resistor parallel to the first accelerated diode for restraining the current via the control terminal of the N-MOSFET, a link capacitor connected to the negative pole terminal of the first accelerated diode and the positive pole terminal of a second accelerated diode and thereby the second accelerated diode connected to the control terminal of the P-MOSFET with a negative pole terminal for speedily cutting off the P-MOSFET, a second resistor parallel to the second accelerated diode for restraining the current via the control terminal of the P-MOSFET, a Zener diode connected to a positive pole terminal of the second accelerated diode with a positive pole terminal and connected to the DC power with a negative pole terminal for preventing excessive voltage. A third resistor is parallel to the Zener diode for producing a Zener voltage.

In the above description, the present invention receives the control signals transmitted from the push/pull control chip with two similar drivers for controlling the four electronic switches (P1, P2, N1, N2) of the full bridge switch assembly for switching.

Then the present invention uses two similar drivers to connect to the prior art full bridge switch assembly, and the prior art full bridge switch assembly controlled by the push/pull control chip. The present invention also can use the push/pull control chip to control the push/pull inverter and control the full bridge switch assembly through the two drivers so as to increase the flexibility and the practical worth thereof.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring toFIG. 5, the present invention connects to the primary winding of a transformer T2through a full bridge switch assembly302for converting DC power VCC into AC power, and supplies power to the load through the transformer T2. In the above description, the peak to peak of the AC power is a voltage of 2VCC.

Referring toFIG. 5, the present invention comprises a push/pull control chip103, two drivers304and a full bridge switch assembly302. The push/pull control chip103transmits two control signals through two output terminals A and B. The input terminals of the two drivers304are connected to the two output terminals A and B of the push/pull control chip103, respectively, and are controlled by the push/pull control chip103. The full bridge switch assembly includes four electronic switches (P1, P2, N1, N2), and connects to the output terminal of the two drivers304with control terminal G of each electronic switch. Moreover, the present invention converts DC power into AC power with the two drivers304, and transmits the AC power to the primary winding of the transformer T2. In the above description, the electronic switches P1, P2are P-MOSFET switches and the electronic switches N1, N2are N-MOSFET switches.

Referring toFIG. 5, the sources of the electronic switch P1, P2are connected to the DC power, and the sources of the electronic switch N1, N2are connected to a reference terminal. The drains of the electronic switches P1, N1are connected to one terminal of the primary winding of the transformer T2, and the drains of the electronic switches P2, N2are connected to other terminals of the primary winding of the transformer T2. Moreover, the control terminal of the electronic switches P1, P2, N1, N2are connected to the output terminal of the driver304, respectively. In the above description, the electronic switch P1, P2, N1, N2constitute the full bridge switch assembly, and the electronic switch P1, N2constitute a positive half cycle driver, while the electronic switches N1and P2constitute a negative half cycle driver so as to form the AC power.

Referring toFIG. 5, a driver304comprises a first accelerated diode D3connected to a output terminal A of the push/pull control chip103with a negative pole terminal and connected to the control terminal G of the electronic switch N1with a positive pole terminal, while a first resistor R3is connected in parallel with the first accelerated diode D3. A second accelerated diode D2is connected to the control terminal G of the electronic switch P1with a negative pole terminal and is connected to the output terminal A of the push/pull control chip103through a link capacitor C2with a positive pole terminal; a second resistor R2is connected in parallel with the second accelerated diode D2. Moreover, a Zener diode D1is connected to a positive pole terminal of the second accelerated diode D2with a positive pole terminal and connected to the DC power with a negative pole terminal, and a third resistor R1is connected in parallel with the Zener diode D1. The driver304mentioned above is used to drive the electronic switch P1and electronic switch N1.

Referring toFIG. 5, in the above description, the other driver304comprises a first accelerated diode D6connected to an output terminal B of the push/pull control chip103with a negative pole terminal and connected to the control terminal G of the electronic switch N2with a positive pole terminal; a first resistor R6is connected in parallel with the first accelerated diode D6. A second accelerated diode D5is connected to the control terminal G of the electronic switch P2with a negative pole terminal and connected to the output terminal B of the push/pull control chip103through a link capacitor C3with a positive pole terminal; a second resistor R5is connected in parallel with the second accelerated diode D5. Moreover, a Zener diode D4is connected to a positive pole terminal of the second accelerated diode D5with a positive pole terminal and connected to the DC power with a negative pole terminal; a third resistor R4is connected in parallel with the Zener diode D4. The driver304mentioned above is used to drive the electronic switch P2and electronic switch N2.

In the above description, the two drivers304are controlled by the push/pull control chip103for driving the four electronic switches (N1, N2, P1, P2) of the full bridge switch assembly302so as to convert the DC power into the AC power, and the AC power is transmitted to the primary winding of the transformer T2. A capacitor C1is connected to the primary winding of the transformer T2and the full bridge switch assembly302for disconnecting the DC component in the AC power.

Referring also toFIG. 5, inFIG. 6, the push/pull control chip103is the chip LX1686 and the series LX1686, LX1688, LX1691 of the LINFINITY (MICROSEMI) Corp., and the series of the chip O2-9RR of the O2 Micro International Limited Corp., and the series of the chip BIT3105, BIT3494 of the Beyond Innovation Technology Corp.

A first control signal a is output via the output terminal A of the push/pull control chip103, and a second control signal b is output via the output terminal B of the push/pull control chip103. Moreover, a voltage wave ac of the AC power is in the terminal T21of the primary winding of the transformer T2, and the peak to peak of the AC power is 2 DC power.

Referring toFIG. 5, as well asFIG. 6, at time t1-t2, the potential of the first control signal a is high and the second control signal b is the low potential. The first control signal a is transmitted to the control terminal G of the electronic switch N1through the first resistor R3to turn on the electronic switch N1, and transmitted to the control terminal G of the electronic switch P1through the link capacitor C2, the second accelerated diode D2and the second resistor R2to turn off electronic switch P1. Moreover, the second accelerated diode D2accelerates turning off the electronic switch P1. The second control signal b is transmitted to the control terminal G of the electronic switch N2through the first accelerated diode D6to turn off the electronic switch N2, and transmitted to the control terminal G of the electronic switch P2through link capacitor C3and the second resistor R5to turn off the electronic switch P2.

At this time, the electronic switches N1and P2are on and the electronic switches N2, P1are off. DC power is then transmitted to the primary winding of the transformer T2by turning on the electronic switch N1, P2, and the AC power measured at the terminal T21of the transformer T2is the negative of the DC power.

Referring also toFIG. 5, as well asFIG. 6, at time t2-t3, the potential of the first control signal a is reduced to low from high and the second control signal b still at the low potential. At this time, the first accelerated diode D3accelerates turning the electronic switch N1. The first control signal a is transmitted to the control terminal G of the electronic switch P1through the link capacitor C2and the second resistor R2to turn on the electronic switch P1. Because the second control signal b is still at the low potential, the electronic switch P2is still on and the electronic switch N2is still off.

It is understood that, in the above description, when time is t2-t3, the electronic switches P1, P2are on and the electronic switches N1, N2are off. At this time, the energy stored in the transformer T2leaks according to the short of the primary winding of the transformer T2. The AC power measured at the terminal T21of the transformer T2is then at the zero potential.

Referring also toFIG. 5, as well asFIG. 6, at time t3-t4, the first control signal a still at the low potential and the potential of the second control signal b is reduced to low level from high level. The second control signal b is transmitted to the control terminal G of the electronic switch N2through the first resistor R6to turn on the electronic switch N2, and transmitted to the control terminal G of the electronic switch P2through the link capacitor C3, the second accelerated diode D5and the second resistor R5to turn off the electronic switch P2. Moreover, the second accelerated diode D5accelerates turning off the electronic switch P2. Because the first control signal a is still at a low potential, the electronic switch P1is still on and the electronic switch N1is still off.

At this time, the electronic switches N2, P1is on and the electronic switches N1, P2is off. The DC power is then transmitted to the primary winding of the transformer T2by turning on the electronic switches N2, P1, and the AC power measured at the terminal T21of the transformer T2is the positive of the DC power.

Referring also toFIG. 5, as well asFIG. 6, at time t4-t5, the first control signal a is still at the low potential and the potential of the second control signal b is increased to high level from low level. At this time, the first accelerated diode D6accelerates turning off the electronic switch N2. The second control signal b is transmitted to the control terminal G of the electronic switch P2through the link capacitor C3and the second resistor R5to turn on the electronic switch P2. Because the first control signal a is still at the low potential, the electronic switch P1is still on and the electronic switch N1is still off.

It is understood that, in the above description, when time is t4-t5, the electronic switches P1, P2are on and the electronic switches N1, N2are off. At this time, the energy stored in the transformer T2leaks according to the short of the primary winding of the transformer T2. The AC power measured at the terminal T21of the transformer T2is then at the zero potential.

Referring also toFIG. 5, as well asFIG. 6, the action of the present invention circuit and the voltage wave ac of the terminal T21of the transformer T2at time t5-t6are the same at time t1-t2. The rest may be deduced by analogy from the above description. The peak to peak of the AC power is double DC power, and converted to the secondary winding of the transformer T2for supplying the load with power.

Reference is made toFIG. 5, in which the Zener diodes D1and D4protect the electronic switches P1, P2for preventing the over-voltage. Moreover, the third resistors R3, R4are in parallel with the Zener diodes D1, D4, respectively, to provide a Zener voltage.

In the above description, the present invention uses two similar drivers to connect to the prior art full bridge switch assembly, and the prior art full bridge switch assembly is controlled by the push/pull control chip. The present invention uses the push/pull control chip to control the push/pull inverter and control the full bridge switch assembly through the two drivers so as to increase the flexibility and the practical value thereof.