JP2001267856A - Rf power amplifier and its improvement - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an improved RF power amplifier capable of directly driving a switching transistor(TR). SOLUTION: An RF oscillator 20' supplies an RF signal showing the RF period of fixed frequency and constituting each positive pulse of a train of an RF pulse of a rectangular wave having fixed size and fixed width. The RF pulse is supplied to a one-shot circuit 200 and supplied to a 2nd one-shot circuit 240 through an inverter 202. These RF pulses are converted into rectangular wave signals of bridge phase A, or B and supplied to plural power amplifiers PA1 to PAN. The signals of the bridge phase A or B have inter-pulse dead time DT and these phases are different from each other by 18 deg.. Each of the amplifiers PA1 to PAN has a MOSFET TR and a buffer amplifier of a driving circuit. Power is supplied from a synchronizing isolation RF driving power supply (SIPS) to each amplifier.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to AM radio broadcasting, and more particularly, to an A radio with synchronous RF drive and an improved power supply.
An RF power amplifier system of the type employed in M radio broadcasts.

[0002]

BACKGROUND OF THE INVENTION U.S. Pat. Nos. 4,580,111 and 4,949,050 disclose an amplitude modulator for use in AM radio broadcasting, and the modulator produces an amplitude modulation. To generate an amplitude modulated signal digitally, a plurality of RF amplifiers are selectively turned on and off. Each RF amplifier has a plurality of switching transistors, each transistor in the form of a MOSFET, connected to a bridge circuit. The bridge circuit provides an output signal to an output combiner. Each MOSFET transistor has a gate driven by an appropriately phased RF frequency signal that can turn on the appropriate MOSFET transistor at the correct time.

A driving system for driving an RF amplifier MOSFET switching transistor includes a MOSF
It has a secondary winding for driving the ET switching transistor. This provides a low impedance source of drive for each MOSFET switching transistor. This also provides the correct out-of-phase drive for the MOSFET switching transistor. Thus, the bridge arrangement has a MOSFET switching transistor for information and a MOSFET switching transistor below. Precise out-of-phase drive to the MOSFET transistors provides the proper gate voltage with respect to the source voltage.

[0004]

From the practice of digital radio, it is desired that the switching transistor be directly driven. Such a circuit is disclosed in U.S. Pat.
2,647.

[0005]

SUMMARY OF THE INVENTION The present invention is directed to a circuit for controlling an amplifier synchronously to ensure that the turn-on and turn-off of the amplifier coincide with the start and end of each RF period, respectively. . Such synchronous operation minimizes damage to the MOSFET. If the switching is not synchronized, the high dv / d of the transistor
The MOSFET is damaged by the breakdown at t2.

The present invention employs a buffer amplifier in the gate circuit of each MOSFET switching transistor,
And the power supply of the buffer amplifier has a DC to DC converter, and operates in synchronization with the employed carrier frequency such that the ripple voltage of the DC power supply of the buffer amplifier has a DC ripple voltage equal to the amplifier carrier frequency. It is directed to a direct drive RF power amplifier system.
This minimizes intermodulation products since the ripple frequency is locked to the carrier frequency.

The present invention comprises an RF source, each pulse having a fixed amplitude and duration, and providing a train of RF pulses exhibiting a fixed frequency RF period; a DC voltage source; And a first transistor switch connecting the DC voltage source across the load to cause a DC current to flow through the load in a second direction when the DC current flows through the load in a second direction. A bridge circuit having a second transistor switch connecting the DC voltage source across its load, and the first and second transistor switches at a frequency that, when enabled, depends on the frequency of the RF pulse. Sending the RF pulse to drive the switch on and off so that the current from the DC voltage source alternately flows in the first and second directions through the load. An RF power amplifier system having a Tchidoraiba, vital supply a turn-on signal,
A driver control circuit that selectively provides the switch driver with the switch driver to enable the switch driver to send the RF pulse to the transistor switch, the driver control circuit comprising first and second transistors The switch switches between the start of the RF period and the RF
An RF power amplifier system, comprising: an amplifier turn-on control signal and logic responsive to the RF pulse to enable the switch driver to be turned on and off in synchronization with the end of a cycle. .

The present invention comprises an RF source, each pulse having a fixed amplitude and duration, and providing a train of RF pulses exhibiting a fixed frequency RF period, a DC voltage source, and a first voltage source when on. And a first transistor switch connecting the DC voltage source across the load to cause a DC current to flow through the load in a second direction when the DC current flows through the load in a second direction. A bridge circuit having a second transistor switch connecting the DC voltage source across its load, and the first and second transistor switches at a frequency that, when enabled, depends on the frequency of the RF pulse. Sending the RF pulse to drive the switch on and off so that the current from the DC voltage source alternately flows in the first and second directions through the load. An RF power amplifier system having a Tchidoraiba, vital supply a turn-on signal,
A driver control circuit that selectively provides the switch driver with the switch driver to enable the switch driver to send the RF pulse to the transistor switch, wherein the switch driver and each of the transistor in the bridge circuit D having a driver amplifier inserted between the switches and a second DC voltage source for providing a DC drive voltage to each of the driver amplifiers.
A transformer having a C to DC power supply, a primary winding and a plurality of secondary windings, and a ripple voltage of the DC power supply at the secondary winding having a ripple frequency equal to the frequency of the RF pulse; When turned on, the primary winding is connected to the second D
Also included is a system having a first switching transistor for connecting to a C voltage source and a control circuit for turning on and off the first switching transistor in synchronization with the frequency of the RF pulse.

Conventionally, RF power amplifier systems have been known in which each pulse has a fixed amplitude and duration and a fixed frequency R
An RF source is provided that provides a train of RF pulses indicative of the F period. A bridge circuit comprising: a first transistor switch connecting a DC voltage source across the load to cause a DC current to flow through the load in a first direction when on;
A second transistor switch connecting a DC voltage source across the load to cause a DC current to flow through the load in a second direction when on. The switch driver sends an RF pulse to drive the first and second transistor switches on and off at a frequency that depends on the frequency of the RF pulse when enabled, and the current from the DC voltage source passes through the load. It operates to flow alternately in the first and second directions. The driver control circuit provides a turn-on signal and selectively provides the switches to enable the switch drivers to send RF pulses to the transistor switches.

[0010] In accordance with a more limited aspect of the invention, the driver control circuit is configured to turn on and off the amplifier such that the first and second transistor switches are turned on and off synchronously with the start and end of the RF period. A logic circuit responsive to the control signal and the RF pulse for enabling the switch driver.

Suitably, the RF power amplifier system includes an RF power amplifier system wherein each pulse has a fixed amplitude and duration and provides a train of RF pulses indicative of a fixed frequency RF period.
Adopt source. The bridge circuit includes a first transistor switch connecting a DC voltage source across the load to cause a DC current to flow through the load in a first direction when on, and a second transistor switch in a second direction when on. A second transistor switch connecting a DC voltage source across the load to allow DC current to flow through the load. The switch driver sends an RF pulse to drive the first and second transistor switches on and off at a frequency that depends on the frequency of the RF pulse when enabled, and the current from the DC voltage source passes through the load. First and second
It operates to flow alternately in the direction of. The driver control circuit provides a turn-on signal and selectively provides them to the switch driver to enable the switch driver to send RF pulses to the transistor switches.

In accordance with the present invention, a driver amplifier is interposed between the switch driver and each transistor switch in the bridge circuit and is provided with a DC to DC power supply for providing a DC drive voltage to each driver amplifier, wherein the power supply is A second DC voltage source, wherein the transformer has a plurality of primary windings and a first switching transistor for connecting the primary winding to the second DC voltage source when turned on. It has a secondary winding. The switching transistor is adapted so that the ripple voltage of the DC power supply at the secondary winding has a ripple frequency equal to the frequency of the RF pulse.
It is turned on and off in synchronization with the pulse frequency.

[0013]

DETAILED DESCRIPTION One application of the present invention relates to an RF power amplifier employed in an AM broadcast transmitter. An example of such a transmitter is shown in FIG. 1 and takes the form of a digital amplitude modulator as disclosed in US Pat. No. 4,580,111.

The following description is a background of the description of the present invention with respect to the embodiment shown in FIG. 3, followed by a description of the operation of the circuit shown in FIG. 1 and a detailed description of the power amplifier shown in FIG. .

Referring to FIG. 1, an amplitude modulator 10 is shown receiving an input signal from an input source 12, which may be an audio signal source. The modulator 10 includes a source 12
R, amplitude modulated as a function of the amplitude of the input signal from
Generate an F carrier signal. The amplitude-modulated carrier signal is supplied to an output line connected to a load 14, which may take the form of an RF transmitting antenna. This output line has an output network 11 having an inductor 13 and a capacitor 15.
Having. The digitizer 16 supplies a plurality of digital control signals D1 to DN. The control signal is a binary signal having a binary 1 or binary 0 level. The number of signals having a binary 1 or binary 0 level depends on the instantaneous value of the input signal.

[0016] From each of the output control signal D1 DN is supplied to the RF power amplifier _PA 1 -PA _N of N. The control signal turns the associated power amplifier either on or off. Thus, if the control signal has a binary 0 level, its associated amplifier is deactivated and no signal is provided at its output. However, if the control signal has a binary one level, its associated amplifier is activated and the amplified carrier signal is provided at the output. Each power amplifier has a single common R
It has an input connected to the F source 20. RF source 2
0 acts as a single source of RF carrier signals, the RF carrier signal, as the amplifiers PA ₁ -PA _N receives signals similar amplitude and phase and frequency, supplied by RF splitter 22 You. The carrier signal is amplitude modulated according to the control signals D1-DN, and the amplitude modulated carrier signal has a similar output and phase. These signals are transmitted to a plurality of transformers T ₁ , T ₂ ,. . . , T _N , respectively. The secondary windings operate as independent signal sources, whereby the signals provided from the various transformers are additively combined with each other to provide a combined signal, and the combined signal is applied to the load 14. Supplied to This combined signal has the same frequency as the RF signal provided from RF source 20, but
The amplitude of the combined signal is modulated according to the input signal provided by input source 12.

As is customary in such systems,
RF source 20 includes an RF oscillator 21 having a frequency on the order of 60 to 1600 kHz. This oscillator supplies a signal to the RF driver 23, the output of which is supplied to the power amplifier _PA 1 -PA _N. The RF driver power-amplifies the RF signal obtained from the oscillator 21 before the signal is supplied to the power amplifier where the modulation occurs. RF driver 23 includes several amplifiers stages and configured similarly to the power amplifier _PA 1 -PA _N.

[0018] Figure 2 illustrates one form of the power amplifier PA ₁ of FIG. 1, the same applies to other power amplifier _PA 2 -PA _N. The illustrated power amplifier comprises four MOSFET transistors 70, 72, 74 connected together in a bridge configuration across a DC supply voltage B + on the order of 250 volts.
And 76. Primary winding 4 of the associated transformer T1
4 is connected across bridge connections J1 and J2.

In particular, the semiconductor amplifier element is a metal oxide field effect transistor (MOSFET), typically identified as a gate, a drain, and a source.
With two electrodes. The drain-source paths of the MOSFET transistors 70 and 72 representing the primary current path are DC
It is connected in series across the power supply, as is the drain-source current path of MOSFET transistors 74 and 76. The primary winding 44 of the corresponding coupler transformer T1 is D
M across common connections J1 and J2 to C blocking capacitor 78
It is connected between OSFET transistors 70, 72 and 74, 76.

Transistors 70, 72, 74 and 76
Operates effectively as a switch connecting the two sides of the primary winding 44 to either a DC voltage source or ground. Proper operation of these transistors allows the transformer winding 44 to be connected in either direction across the DC power supply.

Referring to FIG. 2, MOSFET transistors 70, 72, 74 and 76 are controlled by signals applied to their gate electrodes. The gate signals for all four transistors are derived from the individual secondary transformer windings. This transformer has a toroidal ferrite core around which a primary winding 82 and four secondary windings 84, 86, 88 and 90 are wound. The transformer turns ratio is 1: 1 so that the same signal appearing in the primary is applied to each circuit connected to the four secondary windings.

Each of the four secondary windings is
0-76 is connected between the associated one of the gate and source electrodes. The secondary 84 is connected directly between the gate of the MOSFET 70 and the connection J1, while the secondary 88
Is also directly connected between the gate of MOSFET 74 and connection J2. Secondary windings 86 and 90 are similarly
It is connected between the gate and source electrodes of SFETs 72 and 76.

The primary winding 82 of the toroidal transformer is RF
Connected to the output of source 20, the power amplifier has a sine wave R
Supply F drive voltage. Each MOSFET is "ON" when the RF signal applied to the gate is in its positive half cycle.
And when each signal is in its negative half cycle, each M
The OSFET is "off". Therefore, MOSFET
Turns on and off periodically at the frequency and phase of a given RF gate signal. Secondary windings 84 and 90 are connected across MOSFET transistors 70 and 76 in a similar direction, so that the signals appearing at the gates of these transistors are in phase with one another. Therefore, MOSF
The ET transistors 70 and 76 are turned on and off at the same time. On the other hand, windings 86 and 88 are connected across MOSFET transistors 72 and 74 in a direction opposite to the connection direction of windings 84 and 90. MOSFET transistors 70 and 7
6 is therefore 180 ° relative to the signal applied to the gates of transistors 72 and 74.
° The phases are different. Therefore, transistors 70 and 76
Is "on", transistors 72 and 74 are "on"
Off ".

From the above description, each PA ₁ with a secondary winding associated with the gate of each MOSFET transistor
-PA _N it can be seen that require a transformer. As shown in FIG. 2, the secondary windings 84, 86, 88 and 90 are MOSF
Sine wave RF is applied to the gate electrode of the ET transistor switch.
Supply drive signal. When the transistors 70 and 76 are "ON", the driving voltage is reversed.
Is required to have the proper phase to be "off". In addition to the proper phase of these RF signals,
RF driver 23 (see FIG. 1) includes several stages of amplification. Each of these stages is a loss in the amplifier, tuner circuit, and coupling circuit.

In addition to the foregoing, the bridge amplifier of FIG.
A tuning circuit having a buffer amplifier 100, a capacitor 102, and an inductor 104 is employed. The drive signals are tuned and form a sinusoidal drive signal having gradual rise and fall times during the transition. Such an amplifier has a narrow band and needs to be tuned to each operating frequency. Also, the drive method shown in FIG. 2 requires higher drive power because the signal is a binary level, and the drive signal is an AC signal that varies between positive and negative levels. Such a sinusoidal drive signal has a gentle dv
/ Dt. Switching such RF drives on and off at high switching rates is difficult because of the increased switching losses due to the slow dv / dt from using a sinusoidal drive signal. Thus, during each on-off transition, the RF drive tuning circuit is detuned due to dynamic load fluctuations, which can cause undesirable phase modulation at the transmitter output.

In accordance with the present invention, a direct MOSFET transistor drive, described in detail with reference to FIG. 4, is provided. One application of the present invention is illustrated by the circuit of FIG. 3 and employs a circuit similar to that of FIG. 1 and, therefore, like reference numbers indicate like components. But,
In this embodiment, the RF oscillator 20 'represents a fixed frequency RF period, and each positive pulse outputs an RF signal comprising a train of square wave RF pulses of fixed magnitude and fixed width. Supply. The RF pulse is supplied to a set of one-shot circuits including the one-shot circuit 200, and is supplied to the second one-shot circuit 2 by the inverter 202.
04. These transmit the bridge phase A or bridge phase B square wave signal or pulse to the power amplifier PA ₁ −
Supplied to the supply to the PA _N, bridge phase A or bridge phase B signal, the dead time D between pulses as shown in FIG. 9
It has T and its phase is different by 180 °.

In the present invention, the direct MOSFET shown in FIG.
A transistor drive is also provided. One application of the present invention is illustrated by the circuit of FIG. 3 and employs a circuit similar to that of FIG. 1 and, therefore, like reference numbers indicate like components. However, in this embodiment, the RF oscillator 20 'exhibits a fixed frequency RF period and each positive pulse comprises a train of square wave RF pulses of fixed magnitude and fixed width. Supply signal. The RF pulse is supplied to a set of one-shot circuits including the one-shot circuit 200, and is supplied to a second one-shot circuit 204 by the inverter 202. These bridges the phase A or bridge phase B square wave signals or pulses supplied to the supply to the power amplifier PA ₁ -PA _N, bridge phase A or bridge phase B signal, the dead time between pulses as shown in FIG. 9 18 phase with each other with DT
0 ° different.

[0028] Each power amplifier _PA 1 -PA _N in FIG. 3 is a further form of the power amplifier PA ₁ shown in detail in FIG.
In FIG. 4, four MOSFET transistors 70, 7
2, 74 and 76 are shown as shown in FIG. 2, with the drains of transistors 70 and 74 connected to a B + voltage source. Direct drive is obtained with the circuit shown in FIG.
As a result, only the logic level signal is employed and no bipolar signal is employed.

Various MOSFET transistors 70 and 7
Each of the 2, 74 and 76 drive circuits has a MOSFET drive amplifier acting as a buffer amplifier, and
These have buffer amplifiers 210, 212, 214 and 216. Each is a synchronous separation RF drive power supply (S
IPS) 220. This power supply is a DC to DC power supply and provides a low voltage output to operate the MOSFET buffer amplifier;
The power supply exhibits a ripple voltage whose ripple (such as from the output of RF oscillator 20 'in FIG. 3) is a ripple of the same frequency as the carrier frequency Fc. Power supply 220 of FIG.
Is shown in more detail in FIG. 5 and described below.

In FIG. 5, an input signal is obtained at the frequency Fc from the output of the one-shot circuit 204 (FIG. 3), inverted by an inverter 222, and a rectangular pulse train is supplied to a divide-by-2 circuit 224 to be Q When

[0031]

[Outside 2] A flip-flop having an output is configured. These outputs are 180 ° out of phase and each has a frequency Fc / 2. The pulse obtained from the Q output of the divide-by-2 circuit 224 is supplied to the one-shot circuit 226,

[0032]

[Outside 3] The pulse obtained from the output is supplied to the one-shot circuit 228. The output pulses obtained from the one-shot circuit are 180 ° out of phase with each other and are applied to MOSFET transistors 230 and 232, respectively. The pulses obtained from the one-shot circuits 226 and 228 also have a dead band that ensures that the transistors 230 and 232 are not turned on at the same time. These transistors each have a plurality of secondary windings 242,
Primary winding 2 of transformer T10 having 244 and 246
40 and connected in series. When transistor 230 is on, the upper end of winding 240 is connected to DC power supply V1, while when transistor 232 is on, winding 24
The upper end of 0 is connected to ground. As shown,
Each secondary winding is provided with a full-wave diode bridge to provide DC power to the associated MOSFET buffer amplifier. Rectified DC from secondary winding 244
The voltage is provided via buffer amplifier 210, while via secondary winding 246 and through amplifier 214. The amplifier is floating with respect to ground. The full-wave diode bridge connected across winding 242 is referenced to ground, so that a single output from the top of this full-wave diode bridge is provided to amplifiers 212 and 216. This is a half-bridge switching power supply that operates at half the carrier frequency (Fc / 2) of the transmitter. The DC ripple voltage obtained from each of the full-wave diode bridge circuits of the secondary windings 242, 244 and 246 exhibits a ripple frequency equal to the carrier frequency (Fc) of the amplifier, and therefore no intermodulation products are generated. . When the power supplies operate at different frequencies, mixing between the amplifier carrier frequency and the switching power supply frequency will result in undesirable intermodulation products. As shown in FIG. 4, an inductive steering drive (ISD) circuit includes a buffer amplifier associated with each buffer amplifier.
It is provided between OSFET transistors. in this way,
Inductive operation drive circuits 250, 252, 254 and 25
6 are transistors 70, 72, 74 and
76 gate drive circuits. Each of these circuits takes the form of the inductive actuation drive circuit 250 shown in FIG. 6 and is described below.

A typical MOSFET starts to turn on at 2Vdc and turns on completely at 4Vdc.
The turn-off threshold starts in the opposite direction at 4 Vdc and turns off completely at 2 Vdc.

To achieve the best efficiency as a class D amplifier, a fast turn-off is essential. On the other hand, the turn-on slope is less important, since the current through the MOSFET at each turn-on period is zero and therefore consumes no power. During turn-off, the current still flows through the bridge amplifier, and if the fall time is slow, interruption of the current causes power consumption and overall low efficiency.

The input drive signal "x" is an ideal rectangular wave as shown by a waveform 260 in FIG. The input capacitance of the MOSFET and the output impedance of the MOSFET driver limit the rising and falling slope of the signal.

To explain the drive function of the circuit, reference is made to the prior art circuit 251 of FIG. The output impedance of the MOSFET driver is Ro.
The input gate capacitance of 0, as shown in FIG.
ss. The standard drive circuit has two element circuits, Ro and Ci.
ss, the transient response waveform 26
2 is shown in FIG. 8 and has the properties of a log function. The rise time is relatively fast, but the fall time is relatively gradual with a trailing slope and the MOSFET current is not zero during the 4V to 2V switch-off period, so the power of the MOSFET is not zero. Increase consumption. On the other hand, an ISD circuit 2 having components L1, R1, CR1, R3
50 (FIG. 7) has a trapezoidal drive signal with linear rise and fall times, as can be seen from the waveform 264 shown in FIG. As the input drive signal "x" goes from low to high, the voltage is delayed at the gate of the MOSFET and energy is stored in the series inductor L1. The gate voltage waveform overshoots due to energy returning from the inductor. Similarly, the transient response is a turn-off condition.

The correct inductor L1 value is to minimize transient switching losses when the rise and fall times are tested (largest dv / dt). Some overshoot and undershoot are needed to provide overdamped transients to ensure a linear ramp of rise and fall times. When the negative undershoot is greater than the diode drop voltage of CR1, only the snubber circuit including CR1 and R3 is activated. The two components are conducting in the overshoot state.

In such a fast fall time, MOSF
ET consumption is minimized, and therefore, maximum power efficiency is achieved, allowing the bridge amplifier to operate at very high frequencies suitable for use in digital radio operation. Using this inductive drive circuit, a capacitor C1, a resistor R2, a diode CR1 and a resistor R1 are used to prevent oscillations formed by a series inductor coupled with the gate capacitance of the MOSFET.
A diode snubber circuit having 3 is added. This operational drive allows for the elimination of an RF drive tuning circuit having capacitors 102 and 104 (FIG. 2).

The switch driver arrangement is such that the MOSFET transistors 70 and 76 are turned on and off by the bridge phase B pulse as a pair and the MOSF
A bridge phase B pulse or to drive the MOSFET transistors so that the ET transistors 72 and 74 are turned on by the bridge phase A pulse
Provided for sending a bridge phase A pulse. Phase B
The pulse is sent by the logic switch driver AND gate 300 when enabled from the Q output of the D flip-flop 302. The phase B pulse sent by AND gate 300 is provided to a pulse transformer.
The output of pulse transformer 304 is rectified by diode 306 and buffered by buffer amplifier 210.

Similarly, a switch driver logic gate in the form of an AND gate 310
When enabled by 2, the bridge phase A pulse is sent to the gate of transistor 74 by pulse transformer 312 and diode 314 and is buffered by buffer amplifier 214.

Whenever transistor 70 is turned on, a phase B pulse is also sent by OR gate 320 to turn on transistor 76 by buffer amplifier 216 and inductive steering drive circuit 256. Similarly,
Whenever transistor 74 is turned on, phase A
The pulse is sent by the OR gate 330, the buffer amplifier 212 and the inductive operation drive circuit 252 to the gate electrode of the transistor 72 to turn on the transistor 72.

Reference is made to the waveforms of FIG. 9 which provide a timing diagram illustrating the operation of the power amplifier shown in FIG. The module turn-on signal obtained from the D1 output of the digitizer 16 is the clock CLK of the flip-flop 302 in FIG.
Supplied to input. This flip-flop is MOSF
To send bridge B and bridge A phase pulses to drive ET transistors 70 and 74, A
To enable the ND gates 300 and 310, it acts as a driver control circuit for providing a turn-on or enable signal. As shown in FIG. 9, the falling edge of the bridge phase B signal causes the flip-flop 30
The Q output of 2 is raised, providing a binary "1" signal, which serves as an enable signal to enable AND gates 300 and 301. Flip-flop 3
The use of 02 for controlling the amplifier synchronously ensures that amplifier turn-on and turn-off occur at the beginning and end of the RF period. Waveforms 400 and 40 of FIG.
2,404,406,408 and 410 show timing diagrams of the complete operation of the amplifier over two complete clock periods. The amplifier output is Q and

[0043]

[Outside 4] Synchronize with output. This is an important factor in maintaining reliable operation. If the switching timings are not synchronized, damage to the MOSFET may occur and cause high dv / dt secondary breakdown of the transistor.

The pulse transformers 304 and 312 provide separated drive signals (bridge phase A and bridge phase B pulses).
With floating MOSFET transistors 70 and 7
Supply to 4. Rectified RF drive signals from the secondary of pulse transformers T1 and T2 are used to switch MOSFET transistors 210 and 21 on and off to turn floating transistors on and off to produce an amplified output signal.
4 buffered.

[0045]

According to the present invention, it is possible to provide an improved RF power amplifier capable of directly driving a switching transistor.

[Brief description of the drawings]

FIG. 1 is a diagram showing an outline of a conventional technology of one application to which the present invention can be applied.

FIG. 2 shows a schematic diagram of a prior art schematic of one power amplifier employed in FIG.

FIG. 3 is a schematic block diagram of one embodiment of the present invention.

FIG. 4 is a schematic block diagram of a power amplifier including a circuit according to a preferred embodiment of the present invention.

FIG. 5 is a schematic block diagram of an improved power supply.

FIG. 6 is a schematic block diagram of a conventional MOSFET drive circuit.

FIG. 7 is a diagram showing a schematic circuit of an inductive operation drive circuit.

FIG. 8 is a diagram illustrating voltage amplitude over time showing an RF drive waveform employing inductive operation.

FIG. 9 is a waveform shown as amplitude over time,
FIG. 5 is a diagram showing a plurality of waveforms showing a timing diagram of the amplifier.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Modulator 11 Output network 12 Input source 13 Inductor 14 Load 15 Capacitor 16 Digitizer 20 RF source 21 RF oscillator 22 RF divider 23 RF driver 24 Coupling circuit 44 Primary winding 70, 72, 74, 76 MOSFET transistor 82 Primary Windings 84, 86, 88, 90 Secondary winding 100 Buffer amplifier 102 Capacitor 104 Inductor 200 One shot circuit 202 Inverter 204 One shot circuit 210, 212, 214, 216 Buffer amplifier 220 Synchronous separation RF drive power supply 222 Inverter 224 Divide Circuit 226 One-shot circuit 228 One-shot circuit 230 Transistor 232 Transistor 240 Primary winding 242 Winding 244 Secondary winding 246 Secondary winding 250, 2 2,254,256 inductive operation driver circuit 300 the AND gate 302 D-type flip-flop 304 pulse transformer 306 diode 310 the AND gate 312 pulse transformer 314 a buffer amplifier 320 OR gate 330 OR gates

Claims (10)

[Claims] An RF source providing a train of RF pulses each pulse having a fixed amplitude and duration and exhibiting a fixed frequency RF period, a DC voltage source, and a first direction when on. A first transistor switch connecting the DC voltage source across the load to allow a DC current to flow through the load; and to allow the DC current to flow through the load in a second direction when on. A bridge circuit having a second transistor switch connecting the DC voltage source across its load;
Sending the RF pulse to drive the first and second transistor switches on and off at a frequency that depends on the frequency of the pulse, and allowing current from the DC voltage source to pass through the load to the first and second transistors. An RF power amplifier system comprising: a switch driver for alternating flow in a direction; and a switch driver for providing a turn-on signal and enabling the switch driver to send the RF pulse to the transistor switch. And a driver control circuit that supplies them to the switch driver. The driver control circuit turns on and off the first and second transistor switches in synchronization with the start of the RF cycle and the end of the RF cycle. In order to enable the switch driver, an amplifier turn-on control signal and the RF pulse RF power amplifier system, characterized in that it comprises a logic circuit responsive to. 2. A pulse forming circuit for supplying said train of RF pulses as a phase A pulse and providing a second train of RF pulses as a phase B pulse, said phase B pulse having a phase of said phase A pulse And the switch driver sends the phase A pulse and the phase B pulse respectively to drive the first and second transistors when enabled, respectively. The system of claim 1, comprising a logic gate. 3. The phase A and the phase B to ensure that the first and second transistors do not turn on at the same time.
3. The system of claim 2, further comprising a pulse shaping circuit for shaping the phase A and phase B pulses such that there is a dead time between the pulses. 4. The logic circuit includes a D input, a CLK input, and a Q input.
Output and 4. The system according to claim 2, further comprising a D-type flip-flop having an output. 5. The phase B pulse is provided to the D input, and the amplifier turn-on signal is provided to the CLK input, whereby the flip-flop causes the phase A pulse and the phase B pulse to be applied. The system of claim 4, wherein the operation of the amplifier is controlled synchronously by enabling the first and second logic gates for transmission. 6. The bridge circuit has third and fourth transistor switches, wherein the first and third transistor switches are connected in series in the first bridge circuit across the load, and The second and fourth transistors are connected in series in a second bridge circuit across the load, and drive the phase A and B pulses to drive the third and fourth transistor switches. The system of claim 5, further comprising third and fourth logic gates for sending each. 7. An RF source, wherein each pulse has a fixed amplitude and duration and provides a train of RF pulses indicative of a fixed frequency RF period, a DC voltage source, and a first direction when on. A first transistor switch connecting the DC voltage source across the load to allow a DC current to flow through the load; and to allow the DC current to flow through the load in a second direction when on. A bridge circuit having a second transistor switch connecting the DC voltage source across its load;
Sending the RF pulse to drive the first and second transistor switches on and off at a frequency that depends on the frequency of the pulse, and allowing current from the DC voltage source to pass through the load to the first and second transistors. An RF power amplifier system comprising: a switch driver for alternating flow in a direction; and a switch driver for providing a turn-on signal and enabling the switch driver to send the RF pulse to the transistor switch. A driver control circuit that supplies the switch driver and the transistor driver to the switch driver in the bridge circuit, and supplies a DC drive voltage to each of the driver amplifiers in the bridge circuit. DC with a second DC voltage source for DC to DC
A power supply, a transformer having a primary winding and a plurality of secondary windings, and a ripple voltage of a DC power supply at the secondary winding is equal to R
A first switching transistor for connecting the primary winding to the second DC voltage source when turned on so as to have a ripple frequency equal to the frequency of the F pulse; And a control circuit for turning on and off the first switching transistor. 8. A transistor switch drive circuit for periodically turning on said switching transistor at a rate equal to half the frequency of said RF pulse, and each said transistor switch driving circuit for supplying said DC power supply ripple voltage.
The system of claim 7, wherein all connected across the next winding have a rectifier. 9. The system of claim 1, wherein said power supply is a half-bridge circuit having a second switching transistor, wherein each of said first and second switching transistors is a MOSFET. 10. A transistor switch drive circuit for periodically turning on said switching transistor at a rate equal to half the frequency of said RF pulse, and each said secondary winding for supplying said DC power supply ripple voltage. The system of claim 7, wherein all connected across the line have a rectifier, and wherein the power supply is a half-bridge circuit having a second switching transistor.