KR0162382B1 - Power controlling circuit for half-bridge inverter - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power control circuit of a half-bridge inverter. In the related art, each freewheel diode detects a current through two separate current transformers (CT) in order to detect an energized current of two freewheel diodes. Since it must be connected in series, two current transformers, which are relatively expensive and large in size, are required, which makes it difficult to increase the price and reduce the size. Therefore, the present invention detects the conduction current of two freewheel diodes with only one current transformer (CT) in setting the on-time by detecting the conduction current of the freewheel diode for the zero voltage switch operation (ZVS) of the inverter. By enabling the zero voltage switching turn-on of the switching elements connected in parallel to each other, it is possible to stably detect the current of the two free wheel diodes and to prevent the cost increase.

Description

Power Control Circuit of Half-Bridge Inverter

1 is a power control circuit diagram of a conventional half bridge inverter.

2 is an exemplary view showing a connection relationship between a free wheel diode and a capacitor in FIG.

3 is an exemplary view showing a current path at a dead time.

4 is a circuit diagram of a conventional embodiment.

5 is a waveform diagram of each part with respect to FIG.

6 is an exemplary view showing another example of the current sensing unit in FIG.

7 is a power control circuit diagram of the half-bridge inverter of the present invention.

FIG. 8 is a detailed circuit diagram of the driving controller in FIG.

FIG. 9 is an explanatory diagram showing a loop state at the time of turning on transistors Q1 and Q2 which are switching elements in FIG.

FIG. 10 is another embodiment of the current transformer CT in FIG.

* Explanation of symbols for main parts of the drawings

110: inverter unit 120, 130: first and second drive unit

140,150: first and second drive control unit 160: current sensing unit

170: starting pulse generator Q1, Q2: switching device

FWD1, FWD2: Freewheel Diode CT: Current Transformer

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power control circuit of a half bridge inverter. In particular, the present invention relates to a power control circuit of a half bridge inverter. The present invention relates to a power control circuit of a half bridge inverter capable of stably detecting a current of a free wheel diode.

FIG. 1 is a power control circuit diagram of a conventional half-bridge inverter. As shown therein, freewheel diodes and capacitors FWD1 and C11 (FWD2 and C12) are respectively connected to transistors Q1 and Q2 which are serially connected switching elements. An inverter 11 connected in parallel and a working coil HL1 and a resonant capacitor C2 are sequentially connected to a connection point of the transistors Q1 and Q2 to generate a high frequency current; and the free wheel diode FWD1 and FWD2. The drive control unit 10 detects an energized current of the drive current and generates a drive signal by setting an on time and generates the drive signal, and the inverter according to the drive signals DR1 and DR2 of the drive control unit 10. The first and second drivers 12 and 13 turn the transistors Q1 and Q2 of the transistor 11 to turn on or off, respectively.

In addition, the driving control unit 10 detects the energizing current of the freewheel diode FWD1 or FWD2 of the inverter 11 with the current transformer CT to rectify and smooth the rectification current, and detects the current. A comparator 17 for comparing the output of the unit 14 with a reference voltage Vref, a latch unit 18 for latching the output of the comparator 17, the latch unit 18 and the current sensing An adder 16 that sums the outputs of the unit 14 and outputs them to the comparator 17, and compares the outputs of the comparator 17 with the outputs of the power control unit 21 to convert the transistors in the inverter 11 ( On-time setting unit 19 for setting on-times of Q1 and Q2, and driving signals DR1 (1) to first and second driving units 12 and 13 in accordance with the output of this on-time setting unit 19. A drive signal generator 20 for generating DR2 and a start pulse generator 15 for initially supplying a start pulse to the adder 16 for driving the transistor Q1 of the inverter 11 are constituted.

The prior art thus constructed will be described in detail with reference to FIGS. 1 to 5 as follows.

The prior art detects the moment when the freewheel diode FWD2 is energized as shown in FIG. 3b to drive the transistor Q2 which is a switching element, and switches at the moment when the freewheel diode FWD1 is energized as shown in FIG. 3d. Driving the transistor Q1, which is an element, enables continuous self-oscillation.

The technical operation described above will be described with reference to FIG. 1.

Assuming that the current inverter 11 state is after the transistor Q2 is off after the continuous operation state, the energy accumulated in the LC tank composed of the working coil HL1 and the resonant capacitor C2 as shown in 3c and d. The current generates the conduction current of the free wheel diode FWD1 after charging the resonance capacitor C12.

At this time, the current sensing unit 14 of the driving controller 10 receives the conduction current of the freewheel diode FWD1 through the current transformer CT1 and converts the converted voltage into a voltage, and rectifies and converts the converted voltage in the rectifying smoothing unit. Smooth and applied to the positive input terminal (+) of the comparator 17 through the adder (16). Accordingly, the comparator 17 compares the two voltages by receiving the output voltage of the rectifying detection unit 14 and the reference voltage Vref supplied to the negative input terminal − through the positive input terminal (+), respectively. As a result of comparison, when the voltage according to the conduction current of the freewheel diode FWD1 is greater than the reference voltage Vref, a positive signal is generated, and when the voltage is less than the reference voltage Vref, a negative signal is set on time. Provided by 19. Then, the on time setting unit 19 sets an on time proportional to the power control voltage provided by the power control unit 21 and outputs the on time to the driving signal generator 20. Accordingly, the driving signal generator 20 outputs the driving signal DR1 according to the on time to the first driver 12.

As a result, the first driver 12 conducts the transistor Q1 of the inverter 11 by the on time set by the on time setting unit 19 and then turns it off.

Thereafter, the energy supplied during the on time of the transistor Q1 immediately after the transistor Q1 is turned off is accumulated in the LC tank including the working coil HL1 and the resonant capacitor C2 as shown in FIGS. 3a and b. Since the on current flowing during the turn-on period of the transistor Q1 cannot be changed rapidly, the charging current is supplied to the capacitor C11, and the free wheel diode FWD2 is energized after the capacitor C11 is charged above the charging voltage. do.

Accordingly, the amount of current flowing through the freewheel diode FWD2 is detected by the current transformer CT2 of the current sensing unit 14 and converted into a voltage, and rectified and smoothed. The rectified smoothed voltage is a constant reference voltage Vref. If it is abnormal, the driving signal generator 20 is driven by the output of the comparator 17 during the on-time proportional to the power control voltage of the power control unit 21 set by the on-time setting unit 19. By enabling 13), the transistor Q2, which is a switching element of the inverter 11, is turned on for a set on time and then turned off.

On the other hand, since the start pulse is generated in the start pulse supply unit 15 of the drive control unit 10 and applied to the positive input terminal (+) of the comparator 17 through the adder 16 at the beginning of the drive, the comparator 17 On time is set and generated by the on time setting unit 19 according to the output of Accordingly, since the drive signal generator 20 generates a drive signal by the output of the on-time setting unit 19, the transistor Q1 of the inverter 11 is turned on during the on-time by the first driver 12. Lose.

And, based on Figure 4 with respect to the embodiment of the prior art as follows.

In FIG. 4, the driving control unit 10 of FIG. 1 is divided into first and second driving control units 100 and 200, and the first driving control unit 100 includes the free wheel diode FWD1. Current sensing unit 14 and rectifying and smoothing through the resistor R21, diode D1 and condenser C21, and the output of the current sensing unit 14 The voltage Vcc is applied to the negative input terminal (-) of the comparator OP1 applied to the positive input terminal (+) by applying the divided voltage Rref through the resistors R22 and R23 to compare the first voltage. A comparator 17 for outputting a drive signal to the driver 12 and the output of the comparator 17 to the positive input terminal + of the comparator OP1 via a resistor R24 and a diode D2. The latch unit 18 for forward feedback and the output of the comparison unit 17 are charged through the resistors R26 and R27 and the capacitor C22, and the charging voltage is supplied to the negative input terminal (-). ) Output (Vcon) An on-time setting unit 19 which controls the output of the comparing unit 17 to set on time by applying the positive input terminal + of the applied comparator OP2 to make a comparison, The driving control unit 200 detects the energizing current of the free wheel diode FWD2 and outputs a driving signal to the second driving unit 13 to control the driving of the transistor Q2. Configure in the same way.

The first driving control unit 100 applies a start pulse supply unit 15 for applying a start pulse Ps to the positive input terminal + of the comparator 17 to initially drive the transistor Q1 of the inverter 11. ), Including

On the other hand, if the conduction current of the free wheel diode FWD1 occurs in the same way as the hatched portion of FIG. 5, the first driving control unit 100 detects the current transformer CT1 and the resistor R21 of the current sensing unit 14. Is converted into a voltage by the rectifier and rectified and smoothed by the diode D1 and the capacitor C21, and then output to the comparator OP1 of the comparator 17 and the rectified smoothed voltage is input to the positive input terminal (+). The comparator OP1 is compared with the reference voltage Vref, which is the power supply voltage divided by the resistors R22 and R23 applied to the negative input terminal (−).

Vref = R ₂₃ ㆍ Vcc / (R ₂₂ + R ₂₃ )

At this time, when a current corresponding to a voltage greater than the reference voltage Vref flows to the freewheel diode FWD1, the comparator OP1 outputs a positive signal, and the positive signal is applied to the latch unit 18. Since the feedback is made through the resistor R24 and the diode D2, the output of the comparator OP1 maintains a positive signal.

Accordingly, when the positive signal output of the comparator OP1 operates the on-time setting unit 19, the charging circuit composed of the resistor R26 and the condenser C22 starts to be charged, and this charging voltage becomes the power. The comparator OP2 continuously outputs a positive (+) signal for a period of time less than the control voltage from the control unit 21, so that the diodes D3 and D4 remain open.

Therefore, during this period, the latch output of the comparator OP1 supplies the conduction signal to the first driver 12 for driving the transistor Q1, which is the switching element of the inverter 11, and the resistor R26 which is the charging circuit. ) And the comparator OP2 outputs a low potential signal immediately after the charge voltage of the capacitor C12 and the capacitor C12 becomes higher than the control voltage from the power control unit 21, so that the diodes D3 and D4 are turned on to charge the charge voltage of the charging circuit. And the driving signal supplied from the comparator OP1 to the first driving unit 12 become low potential.

Here, the driving-on time of the transistor Q1 as the switching element is charged until the charging voltage Vc ₂ by the resistor R26 and the capacitor C22 is equal to the control signal Vcon of the power control unit 21. In the ideal case, the on time (t _ON ) is expressed as follows (where V _H is the high potential output voltage of OP1):

Vc ₂ = V _H (1-e- ^{(tON / R26C12)} ) = Vcon

R ₂₆ C ₁₂ In (V _H / (V _H -Vcon))

In order to perform the above operation, it is common to suppress the occurrence of noise such as ringing by placing the freewheel diodes FWD1 and FWD2 and the switching elements Q1 and Q2 closest to each other in parallel connection. If the current flowing through the transistor Q2 is i _s and the current flowing through the freewheel diode FWD2 is i _d , i _c = i _s + i _d , and i _L is applied to the working coil HL1. The flowing current, Vc, is the voltage of the resonant capacitor C2, Vs is the driving voltage of the transistor Q1, and the waveform of each part of the inverter 11 is as shown in FIG.

On the other hand, at the time of initial startup which is not a continuous operation state during normal operation, oscillation is not started because neither of the freewheel diodes FWD1 and FWD2 flows current.

Therefore, the start pulse supply unit 15 outputs an on-time pulse that is a control signal to the comparator OP1 in order to input a drive signal to the first driver 12 to drive the transistor Q1 for initial startup.

As another embodiment for sensing the conduction current of the freewheel diodes FWD1 and FWD2, as shown in FIG. 6A, the freewheel diode itself is applied to the phototriac, photoresist, photo The current of the free wheel diode can be detected using a photo element such as an interrupt. Also, as shown in FIG. 6B, a device that generates a drop potential difference such as two or more free wheel diodes in series or a resistor in series is connected to the free wheel diode in series, and then the potential difference between both ends is used. The conduction current of the freewheel diode can be detected by a transformer or the like.

As described in detail above, the conventional technology enables full oscillation by providing only a start pulse at initial startup, so that separate oscillation circuits are unnecessary, and an off time generator for preventing simultaneous turn-on of two switching elements is required. Implementation circuitry is simplified. In addition, since the minimum off time (Td) is automatically generated during operation, it is possible to adjust the maximum power (maximum duty ratio) up to the most ideal range in the case of fluctuations in the power supply voltage or the power, thereby minimizing the current stress of the switching element. In addition, it is possible to prevent the occurrence of short circuit current which may cause the transistor to be damaged due to the setting error of the dead time, and to switch at the minimum amount of the conduction current of the freewheel diode for zero voltage switching. It is possible to minimize the current stress of the freewheel diode under load.

However, in the prior art as described above, in order to detect the conduction currents of the two freewheel diodes, respectively, it is necessary to connect them in series to each freewheel diode detecting the current through two separate current transformers (CT). For this reason, two current transformers, which are relatively expensive and large in size, are required, which makes it difficult to increase the price and reduce the size.

Accordingly, an object of the present invention is a half bridge for stably detecting the current of two freewheel diodes in setting the on-time by detecting the energizing current of the freewheel diode for the zero voltage switch operation (ZVS) of the inverter. It is to provide a power control circuit of the inverter.

It is still another object of the present invention to provide a power control circuit of a half-bridge inverter that senses the energizing current of two free wheel diodes with only one current transformer (CT) to enable zero voltage switching turn-on of switching elements connected in parallel. In providing.

The present invention for achieving the above object is a current sensing means for sensing the conduction current of the free wheel diode connected in parallel to the switching element of the inverter, and through the current sensing means for detecting the current of the free wheel diode, the sensed current Is converted to a constant voltage to set the on-time when a predetermined level or more, and the switching according to the first and second drive control means for generating a drive signal according to the on time, and the output signal of the first and second drive control means First and second driving means for driving the element, and starting pulse generating means for initially generating a starting pulse.

Hereinafter, look at on the basis of the accompanying drawings as follows.

FIG. 7 is a power control circuit diagram of the half-bridge inverter of the present invention. As shown therein, capacitors C11 and C12 are connected in parallel to transistors Q1 and Q2 which are switching elements connected in series, and the transistor Q1 ( Working coil HL1 and resonant capacitor C2 are sequentially connected to each other when Q2) is connected to the inverter unit 110 to generate a high frequency current, and the freewheel diode FWD1 connected in parallel to the switching element of the inverter unit 110. ) Or first and second to turn on transistors Q1 and Q2 of the inverter unit 110 according to the current sensing unit 160 for detecting the energizing current of FWD2 and the driving signals DR1 and DR2. First and second driving controllers 140 for detecting the energizing currents of the driving units 120 and 130 and the freewheel diodes FWD1 and FWD2 and setting the on-time to generate a driving signal when the current is greater than a predetermined level. 150 and a start pulse generator 1 for generating a start pulse at an initial stage and outputting the start pulse to the first drive control unit 140. 70).

In addition, the first and second driving controllers 140 and 150 have the same configuration as the driving control unit 10 of FIG. 1.

When described in detail with respect to the operation and effect of the present invention configured as described above.

Assuming that the current inverter unit 110 is off after the transistor Q2 is in the continuous operation state, the energy current stored in the LC tank including the working coil HL1 and the resonant capacitor C2 is converted into a resonant capacitor C12. Is charged and the freewheel diode FWD1 is brought into a conductive state by the charged energy current.

Then, a loop as shown in FIG. 9A is formed, and a voltage proportional to the conduction current flowing through the freewheel diode FWD1 is induced on the ⓐ side of the current transformer coil of the current sensing unit 160, and rectified through the diode D1. And the first driving control unit 120 is transferred.

The current transformer coil in the current sensing unit 160 is connected to the ground terminal to one coil middle tap so that the current flows to the first driving control unit 140 or the second driving control unit 150 according to the direction of the current. Has

The voltage detected by the current sensing unit 160 and the diode D1 is positive (+) of the comparator 17 through the adder 16 of the first driving control unit 140 having the configuration as shown in FIG. ) Is input to the on-time setting unit 19 compared with a reference voltage Vref inputted to an input terminal thereof and a negative input terminal thereof, and at this time, the voltage according to the energizing current of the freewheel diode FWD1 is constant. If the level is greater than the reference voltage Vref, a positive signal is output.

The on-time setting unit 19 receiving the output of the comparator 17 sets an on time proportional to the power control voltage of the power control unit 21 and outputs the on-time to the driving signal generator 20. Then, as the driving signal generator 20 receives the on-time set by the on-time setting unit 19 and outputs the driving signal DR1, the first driving unit 120 performs the transistors of the inverter unit 110. Q1) is turned on after conduction for the set on time.

When the transistor Q1 is turned on after being turned on for a set on time, energy supplied during the set on time of the transistor Q1 is accumulated in an LC tank including a working coil HL1 and a resonant capacitor C2. The on-current flowing during the turn-on period of the transistor Q1 supplies the charging current to the resonant capacitor C11 and energizes the freewheel diode FWD2 after the resonant capacitor C11 is charged above the charging voltage.

Then, a loop as shown in FIG. 9B is formed, and a voltage proportional to the conduction current flowing through the freewheel diode FWD2 is induced on the ⓑ side of the current transformer coil of the current sensing unit 160 and is driven through the diode D2. It is rectified and transmitted to the second driving controller 120.

Therefore, when the voltage rectified by the current sensing unit 160 is equal to or greater than a predetermined reference voltage, the on-time setting unit 19 is output by the output of the comparator 17 in the second driving controller 150 shown in FIG. 8. Is enabled and the driving signal generator 20 enables the second driver 130 to turn on the transistor Q2 which is the switching element of the inverter unit 110 for a set on time during the on time proportional to the power. Then turn it off.

On the other hand, since the start pulse generator 170 generates a start pulse and is applied to the positive input terminal of the comparator 17 through the adder 16 of the second drive controller 130, the comparison is performed. The driving control signal is generated by the on-time setting unit 19 according to the output of the unit 17.

Accordingly, since the driving signal generator 20 generates the driving signal by the output of the on-time setting unit 19, the transistor Q1 of the inverter unit 110 is turned on during the on-time by the first driving unit 12. .

During the initial startup, which is not in the continuous operation state during normal operation, oscillation is not started because neither of the freewheel diodes FWD1 and FWD2 flows current.

Therefore, the start pulse generator 170 controls the comparator 17 of the first drive controller 140 to input the drive signal to the first driver 12 to drive the transistor Q1 for initial startup. It outputs an on-time pulse that is a signal.

As another embodiment for detecting the conduction current of the freewheel diodes FWD1 and FWD2, as shown in FIG. 10A, two current transformer coils are provided and one coil of two bean foils is disposed depending on the direction of the current. In the case of using a lottery structure to be induced in the current and as shown in FIG. 10b, the forward and reverse diodes D30 (D40) and the first and second direction current sensing units 160a and 160b are formed in parallel with the current transformer coils. A single winding rectification method is used to detect current in the first direction or the second direction according to the direction of.

As described in detail above, the present invention enables full self-oscillation by providing only a start pulse at initial startup, and detects the conduction current of two freewheel diodes with only one current transformer, respectively. By enabling the voltage switching operation, there is an effect of reducing the cost and miniaturization.

Claims (3)

An inverter in which a free wheel diode and a capacitor are connected in parallel to each of the two switching elements of the inverter, and a working coil and a resonant capacitor are sequentially connected to the connection point of the switching element, and a current sensing unit for sensing the conduction current of the two free wheel diodes, respectively. And first and second driving controllers for setting on time and generating a driving signal when the voltage corresponding to the sensed current is equal to or greater than a predetermined level, and for driving the switching element according to the driving signal. In the power control circuit composed of two drive unit, the current sensing unit is configured to connect a single current transformer coil intermediate tap to the ground terminal so that the voltage induced according to the direction of the current is transmitted to the first drive control unit or the second drive control unit. A power control circuit for a half bridge inverter. A freewheel diode and a capacitor are connected in parallel to each of the two switching elements of the inverter, and a inverter coil and a resonant capacitor are sequentially connected to the connection point of the switching element, and current sensing for sensing the energizing currents of the two freewheel diodes, respectively. A first and second driving controllers configured to set on time and generate a driving signal when the voltage corresponding to the sensed current is equal to or greater than a predetermined level, and a first driving unit of the switching device according to the driving signal. And a power control circuit comprising two driving units, wherein the current sensing unit has a lottery structure using two current transformer coils. A freewheel diode and a capacitor are connected in parallel to each of the two switching elements of the inverter, and a working coil and an idle capacitor are sequentially connected to the connection point of the switching element, and current sensing for sensing the energizing current of the two freewheel diodes, respectively. A first and second driving controllers configured to set on time and generate a driving signal when the voltage corresponding to the sensed current is equal to or greater than a predetermined level, and a first driving unit of the switching device according to the driving signal. In the power control circuit composed of two driving units, the current sensing unit forms a forward and a reverse diode and a first and second directional current detectors in parallel with the current transformer coils, respectively, according to the direction of each current. A power control circuit of a half-bridge inverter, characterized in that the single winding structure configured to detect current in two directions.