DC/AC inverter

Abstract

A DC/AC inverter for transforming a DC power source to an AC power, which drives a load. The DC/AC inverter comprises a full-bridge switch circuitry, a resonant tank, a frequency generator and a driver circuit. The full-bridge switch circuitry is electrically connected to the DC power source to convert the DC voltage to a pulse signal. The full-bridge switch circuitry comprises a first power switch, a second power switch, a third power switch, and a fourth power switch. The resonant tank is electrically connected between the full-bridge switch circuitry and a load for boosting and filtering the pulse signal to generate an AC power supplied to the load. The frequency generator generates a pulse signal at one of at least two predetermined operating frequencies based on an operation state of the DC/AC inverter. The driver circuit is coupled to the frequency generator and provides four driving signals based on the pulse signal of the frequency generator for turning on and off the first power switch, the second power switch, the third power switch, and the fourth power switch respectively. The four driving signals have the same frequency, wherein the duty cycle of two of the four driving signals is smaller than 50% and the duty cycle of the other two of the four driving signals is larger than 50%.

1 . A DC/AC inverter for transforming a DC power source to an AC power source, which drives a load, said DC/AC inverter comprising: 
 a full-bridge switch circuitry electrically connected to said DC power source for being operative to convert said DC voltage to a pulse signal, said full-bridge switch circuitry comprising a first power switch, a second power switch, a third power switch, and a fourth power switch;    a resonant tank electrically connected between said full-bridge switch circuitry and said load for being operative to boost and filter said pulse signal to generate an AC power supplied to said load;    a frequency generator for being operative to generate a pulse signal at one of at least two predetermined operating frequencies based on an operation state of said DC/AC inverter; and    a driver circuit coupling to said frequency generator and providing four driving signals based on said pulse signal of said frequency generator for turning on and off said first power switch, said second power switch, said third power switch, and said fourth power switch respectively, wherein said four driving signals have the same frequency, the duty cycle of two of said four driving signals is smaller than 50% and the duty cycle of the other two of said four driving signals is larger than 50%.    
   
   
       2 . The DC/AC inverter, as recited in  claim 1 , further comprising a protection circuit electrically connected to said driver circuit in which said protection circuit comprises at least two timers for being operative to selectively alter said driving signals depending on a conduction state of said load and an output of said timers.  
   
   
       3 . The DC/AC inverter, as recited in  claim 2 , further comprising a pulse width modulator electrically connected to said driver circuit for providing a pulse width modulation signal to said driver circuit to generate said four driving signals.  
   
   
       4 . The DC/AC inverter, as recited in  claim 3 , wherein said frequency generator is electrically connected to said pulse width modulator and said driver circuit and provides a triangular wave signal and a pulse signal, both of which have the same frequency, to said pulse width modulator and said driver circuit respectively such that said pulse width modulator generates said pulse width modulation signal depending on said triangular wave signal.  
   
   
       5 . The DC/AC inverter, as recited in  claim 3 , wherein said pulse width modulator comprises: 
 an error amplifier;    a resistor electrically connected an inverting input of said error amplifier;    a capacitor having one end electrically connected to said resistor and said inverting input of said error amplifier to form an inverting integrator;    a comparator having a non-inverting input electrically connected to an output terminal of said error amplifier and the other end of said capacitor;    a switch; and    a current controlled source electrically connected to said inverting input of said error amplifier through said switch.    
   
   
       6 . The DC/AC inverter, as recited in  claim 3 , further comprising a dimming control circuit electrically connected to said pulse width modulator for providing a dimming pulse signal to control whether said pulse width modulator provides said pulse width modulation signal.  
   
   
       7 . The DC/AC inverter, as recited in  claim 6 , wherein said dimming control circuit comprises: 
 a dimming frequency generator being operative of providing a triangular wave signal; and    a comparator having a non-inverting input electrically connected to said dimming frequency generator for receiving said triangular wave signal and an inverting input electrically connected a dimming control voltage such that said comparator compares said dimming control voltage with said triangular wave signal to generate said dimming pulse signal.    
   
   
       8 . The DC/AC inverter, as recited in  claim 1 , further comprising a timer and a pulse width modulator in which said pulse width modulator is coupled to said timer and said driver circuit for providing a pulse width modulation signal to said driver circuit to generate said driving signals, said timer comprises: 
 a current source;    a capacitor electrically connected to said current source for being charged by said current source; and    a comparator electrically connected to said capacitor and a reference voltage, wherein said timer delivers a reset signal to reset said pulse width modulator when a voltage of said capacitor is lower than said reference voltage and said pulse width modulator starts to work when said voltage of said capacitor is high than said reference voltage.    
   
   
       9 . The DC/AC inverter, as recited in  claim 1 , further comprising a current detecting circuit electrically connected to said load for being operative to providing a signal indicative of a conduction state of said load and another signal indicative of a current passing through said load.  
   
   
       10 . The DC/AC inverter, as recited in  claim 9 , further comprising a voltage detecting circuit electrically connected to said load for providing a signal indicative of a terminal voltage of said load.  
   
   
       11 . The DC/AC inverter, as recited in  claim 10 , further comprising a protection circuit being capable of receiving said signal indicative of said conduction state of said load and said signal indicative of said terminal voltage of said load, in which said protection circuit comprises a control circuit having a timing control function, in which said protection circuit generates an indicative signal to said control circuit when said voltage or said current of said load is within a predetermined state and delivers a altering signal to said driver circuit wherein said driver circuit outputs a signal to alter an output of said driver circuit while said indicative signal remains for a predetermined period.  
   
   
       12 . The DC/AC inverter, as recited in  claim 11 , wherein said driver circuit receives said altering signal to control said full-bridge switch circuitry not to provide the power of said DC voltage to said resonant tank.  
   
   
       13 . The DC/AC inverter, as recited in  claim 11 , wherein said protection circuit further comprises a comparator which receives said signal indicative of said conduction state of said load to provide a control signal to said frequency generator such that said frequency generator determines said pulse signal operated at one of said predetermined operating frequencies depending on said control signal.  
   
   
       14 . A controller comprises: 
 a frequency generator for being operative to generate a pulse signal at one of least two predetermined operating frequencies depending on a control signal of said controller;    a pulse width modulator coupled to said frequency generator for providing a pulse width modulation signal based on said pulse signal;    a driver circuit coupled to said pulse width modulator for providing at least one driving signals based on said pulse width modulation signal;    a protection circuit electrically connected to said driver circuit comprising a timing circuit, wherein said protection circuit receives at least one external signals and a result of said timers to selectively alter said driving signals.    
   
   
       15 . The controller, as recited in  claim 14 , wherein said timing circuit has at least two timers to provide a reset signal and a time out signal in which said reset signal enables any circuit receiving said reset signal to reset said circuit and said time out signal enables any circuit receiving said time out signal to start said circuit.  
   
   
       16 . The controller, as recited in  claim 14 , wherein said driver circuit provides four driving signals having the same frequency in which the duty cycle of two of said four driving signals is smaller than 50% and the duty cycle of the other two of said four driving signals is larger than 50%.  
   
   
       17 . A timer applied to a power supply circuit comprising a driver circuit, a protection circuit, and a detection circuit, said timer comprises: 
 a voltage generator generating a voltage varying with time; and    at least two comparators, each of said two comparators electrically connected to a reference voltage and said voltage varying with time respectively to generate a comparative signal to at least one circuits of said power supply circuit, wherein a first comparative signal of said comparative signal is a reset signal such that any circuit receiving said reset signal is enabled to be reset.    
   
   
       18 . The timer, as recited in  claim 17 , wherein said power supply circuit further comprises a pulse width modulation circuit, a power switch circuitry, and a resonant tank in which said pulse width modulation circuit provides a pulse width modulation signal to said driver circuit to control said power switch circuitry and said power switch circuitry is electrically connected to said resonant tank.  
   
   
       19 . The timer, as recited in  claim 18 , wherein said at least one circuits receiving said reset signal is one of said protection circuit, said pulse width modulation circuit, and a combination thereof.  
   
   
       20 . The timer, as recited in  claim 17 , wherein a second comparative signal of said comparative signal is a time out signal such that any circuit receiving said time out signal is enabled to be started.  
   
   
       21 . The timer, as recited in  claim 20 , wherein said protection circuit receives said time out signal.  
   
   
       22 . The timer, as recited in  claim 17 , wherein said voltage generator comprises a capacitor and a current source in which a voltage across said capacitor is charged by said current source such that said voltage across said capacitor is varying with time.  
   
   
       23 . The timer, as recited in  claim 22 , further comprises a switch in parallel with said capacitor such that said switch is turned on to discharges of said capacitor when a power source supplying power to said power supply circuit is lower than a predetermined value.  
   
   
       24 . A protection circuit applied to a power supply circuit comprising a timer, a driver circuit, and a detection circuit, comprises: 
 a logic control circuit being started after receiving a time out signal generated by said timer; and    at least one comparators, each of said comparators coupling to at least one circuits of said power supply circuit and a reference voltage for comparing a electrical signal of said at least one circuits with said reference voltage to generate a comparative signal to said logic control circuit, wherein said logic control circuit outputs a stopping output signal to said driver circuit to control a power switch circuitry stopping an output of a power source when said comparative signal is an indicative signal of a predetermined state.    
   
   
       25 . The protection circuit, as recited in  claim 24 , wherein said power supply circuit further comprises a resonant tank, a pulse width modulation circuit, a power switch circuitry, and a frequency generator in which said frequency generator generates a pulse signal to said pulse width modulator, said pulse width modulator provides a pulse width signal to said driver circuit to control said power switch circuitry, and said power switch circuitry is electrically connected to said resonant tank.  
   
   
       26 . The protection circuit, as recited in  claim 25 , wherein said frequency generator alters an operating frequency of said pulse signal after receiving said indicative signal to indicate a predetermined state.  
   
   
       27 . The protection circuit, as recited in  claim 24 , wherein said logic control circuit receives at lease one pulse signals generated by a frequency generator such that said logic control circuit delivers out said stopping output signal when said comparative signal is said indicative signal to indicate a predetermined state for a duration counted with operating frequency of said pulse signal for a predetermined period.  
   
   
       28 . The protection circuit, as recited in  claim 24 , wherein said timer further generates a rest signal such that said protection circuit receives said rest signal to be reset.  
   
   
       29 . A frequency generator applied to a power supply circuit, comprises: 
 a micro control unit being capable of generating at least one sets of a plurality of first pulse signals having the same frequency but different phases according to a frequency control signal and generating at least one adjustable pulse signals according to a pulse width modulation signal;    a direct digital synthesizer being capable of receiving said first pulse signals to generate corresponding signals; and    a switch electrically coupled to said micro control unit for controlling an output of said at least one adjustable pulse signals.    
   
   
       30 . The frequency generator as recited in  claim 29 , wherein said micro control unit further receives an external timing signal to generate said first pulse signals at a frequency that is a multiple of a frequency of said external timing signal.  
   
   
       31 . The frequency generator as recited in  claim 30 , wherein said signals generated by said direct digital synthesizer are one of triangular waves, ramp waves, and sawtooth waves.  
   
   
       32 . The frequency generator as recited in  claim 30 , wherein said signals generated by said direct digital synthesizer are provided to corresponding power supplies or pulse width modulators.  
   
   
       33 . The frequency generator as recited in  claim 29 , wherein said first pulse signals are provided to corresponding power supplies or driver circuits.  
   
   
       34 . The frequency generator as recited in  claim 29 , wherein said control signal is outputted from an output terminal of an OR gate, wherein an AND gate receives plural state signals and said OR gate receives an output signal of said AND gate and a time out signal.  
   
   
       35 . The frequency generator as recited in  claim 29 , wherein said micro control unit further generates at least one set of second pulse signals having the same operating frequency with a operating frequency of said adjustable pulse signals to be a frequency reference for a circuit which is electrically connected to said frequency generator.  
   
   
       36 . A DC/AC inverter for transforming a DC power source to a AC power source, which drives a load, said DC/AC inverter, comprising: 
 a half-bridge switch circuitry electrically connected to said DC power source for being operative to convert said DC voltage to a pulse signal;    a resonant tank electrically connected between said half-bridge switch circuitry and said load for transforming said pulse signal to said AC power supplied to said load;    a controller comprising a protection circuit having at least two timers and generating a pulse signal having at one of least two predetermined operating frequencies based on an operation state of said DC/AC inverter, and altering pulse wide of said pulse signal based on said timers, and    a driver circuit coupling to said controller for being operative to providing two driving signals for turning on and off said half-bridge switch circuitry in which the duty cycles of said two driving signals are varied based on said pulse signal provided by said controller.    
   
   
       37 . The DC/AC inverter as recited in  claim 36 , wherein two driving signals have the same duty cycle but 180° phase shift.  
   
   
       38 . The DC/AC inverter as recited in  claim 36 , wherein a power switch of said half-bridge switch circuitry which is electrically connected to said DC power source is a PMOS power switch and another power switch of said half-bridge switch circuitry is a NMOS power switch.  
   
   
       39 . The DC/AC inverter as recited in  claim 38 , further comprising a protection circuit electrically connected to said driver circuit in which said protection circuit comprises at least two timers for being operative to alter said driving signals depending on a conduction state of said load and an output of said timers.  
   
   
       40 . The DC/AC inverter as recited in  claim 39 , further comprising a pulse width modulator electrically connected to said driver circuit for providing a pulse width modulation signal and said driver circuit generating said driving signals according to said pulse width modulation signal.  
   
   
       41 . The DC/AC inverter as recited in  claim 40 , wherein said frequency generator electrically connected to said pulse width modulator and said driver circuit for providing a triangular wave signal and a pulse signal to said pulse width modulator and said driver circuit respectively such that said pulse width modulator generates said pulse width modulation signal depending on said triangular wave signal.  
   
   
       42 . The DC/AC inverter, as recited in  claim 40 , wherein said pulse width modulator comprises: 
 an error amplifier;    a resistor electrically connected an inverting input of said error amplifier;    a capacitor having one end electrically connected to said resistor and said inverting input of said error amplifier to form an inverting integrator;    a comparator having a non-inverting input electrically connected to an output terminal of said error amplifier and the other end of said capacitor;    a switch; and    a current controlled source electrically connected to said inverting input of said error amplifier through said switch.    
   
   
       43 . The DC/AC inverter, as recited in  claim 40 , further comprising a dimming control circuit electrically connected to said frequency generator for providing a dimming pulse signal to control whether said pulse width modulator provides said pulse width modulation signal.  
   
   
       44 . The DC/AC inverter, as recited in  claim 43 , wherein said dimming control circuit comprises: 
 a dimming frequency generator being operative of providing a triangular wave signal; and    a comparator having a non-inverting input electrically connected to said dimming frequency generator for receiving said triangular wave signal and an inverting input electrically connected a dimming control voltage such that said comparator compares said dimming control voltage with said triangular wave signal to generate said dimming pulse signal.    
   
   
       45 . The DC/AC inverter, as recited in  claim 44 , further comprising a timer and a pulse width modulator in which said pulse width modulator is coupled to said timer and said driver circuit for providing a pulse width modulation signal to said driver circuit to generate said driving signals, said timer comprises: 
 a current source;    a capacitor electrically connected to said current source for being charged by said current source; and    a comparator electrically connected to said capacitor and a first reference voltage, wherein said timer delivers a reset signal to reset said pulse width modulator when a voltage of said capacitor is lower than said first reference voltage and said pulse width modulator starts to work when said voltage of said capacitor is high than said first reference voltage.    
   
   
       46 . The DC/AC inverter, as recited in  claim 36 , further comprising a current detecting circuit electrically connected to said load for being operative to providing a signal indicative of a conduction state of said load and another signal indicative of a current passing through said load.  
   
   
       47 . The DC/AC inverter, as recited in  claim 46 , further comprising a voltage detecting circuit electrically connected to said load for providing a signal indicative of a terminal voltage of said load.  
   
   
       48 . The DC/AC inverter, as recited in  claim 47 , further comprising a protection circuit being capable of receiving said signal indicative of said conduction state of said load and said signal indicative of said terminal voltage of said load, in which said protection circuit comprises a control circuit having a timing control function, in which said protection circuit generates an indicative signal to said control circuit when said voltage or said current of said load is within a predetermined state and delivers a altering signal to said driver circuit wherein said driver circuit outputs a signal to alter an output of said driver circuit when said indicative signal remains for a predetermined period.  
   
   
       49 . The DC/AC inverter, as recited in  claim 48 , wherein said driver circuit receives said altering signal to control said half-bridge switch circuitry not to provide the power of said DC voltage to said resonant tank.  
   
   
       50 . The DC/AC inverter, as recited in  claim 48 , wherein said protection ircuit further comprises a comparator which receives said signal indicative of said conduction state of said load to provide a control signal to said frequency generator such that said frequency generator determines said pulse signal operated at which one of said predetermined operating frequencies depending on said control signal.