Stabilized Power Supply Utilizing Resonance Circuit Driven by Carrier Modulated Both in Frequency And Amplitude

Abstract

With the stabilized direct-current power supply utilizing the resonance circuit driven by the carrier, the output of the resonance circuit is rectified and smoothed to produce the output voltage of the power supply. The output voltage of the power supply being fixed, the amplitude and the frequency of the carrier driving the resonance circuit is mutually related.

There is an optimal frequency of the carrier where the power supply becomes efficient. The optimal frequency depends on the magnitude of the load connected to the output of the power supply. So the power supply feeds the output current to the amplitude on the basis of the mutual relation so as to makes the frequency of the carrier follow the optimal frequency.

Implementation of the priactical PWM controller provided with both the frequency modulation input and the amplitude modulation input is configured. The error voltage, which is the voltage difference between the output voltage and the reference voltage of the power supply, is fed back to both the frequency and the amplitude of the carrier. Integral of the error voltage is fed back to the frequency through the frequency modulation input of the PWM controller, which stabilizes the feedback to the frequency. Proportional of the error voltage and the output current of the power supply is fed back to the amplitude through the amplitude modulation input. The output current, considered to be differential of the output voltage and then the error voltage, sets the base line of the amplitude which is modulated by the proportional of the error voltage. The mutual rekation control the base line of the amplitude so that the frequency of the carrier can track the optimal frequency.

Claims

1. A pulse width modulation (hereafter abbreviated to PWM) controller having 1. both frquency modulation input and amplitude modulation input, 2. a sawtooth voltage V.sub.T between a predetermined voltage V.sub.L and a predetermined voltage V.sub.H where V.sub.L i V.sub.H, and 3. a sample pulse: wherein 1. synchronized with the negation of a sample pulse, a sawtooth voltage begins to rise from V.sub.L to V.sub.H at a slope defined by the value of the frequency modulation input sampled by the sample pulse 2. the sample pulse is asserted when the sawtooth voltage reaches V.sub.H, and 3. the sawtooth voltage returns to V.sub.L while the sample pulse is asserted: generating the output of the PWM controller based on the pulses produced by comparing the amplitude modulation input and the sawtooth voltage V.sub.T together with the sample pulse.

2. A power supply including 1. a driver circuit, 2. a resonance circuit, 3. a rectification and smoothing circuit, 4. a reference voltage 5. an error amplifier, 6. a current detection circuit, 7. a frequency modulation circuit, and 8. an amplitude modulation circuit: wherein 1. the driver circuit including the PWM controller descrined in claim 1 generates a carrier which is supplied to the resonance circuit, the carrier being modulated in frequency and in amplitude, 2. the resonance circuit converts the frequency-modulated carrier at the input to an amplitude-modulated carrier at the output, 3. the rectification and smoothing circuit rectifies the amplitude-modulated carrier supplied by the resonance circuit to a direct-current output voltage of the power supply, 4. the reference voltage is externally supplied to set up the output voltage of the power supply 5. the error amplifier outputs the voltage difference between the output voltage and the reference voltage to both the frequency modulation circuit and the amplitude modulation circuit, the voltage difference being called an error voltage hereafter, 6. the current detection circuit measures the output current of the power supply and converts the output current so as to be supplied to the amplitude modulation circuit, 7. the frequency modulation circuit transforms the error voltage provided by the error amplifier so as to be supplied to the frequency modulation input of the PWM controller, and 8. the amplitude modulation circuit combines the output of the error amplifier and the current detection circuit so as to be supplied to the amplitude modulation input of the PWM controller: being stabilized by the frequency modulation circuit output of which includes the integral of the error voltage.

3. The power supply described in claim 2 including the current detection circuit supplying a current equivalent corresponding to the measured output current, where the amplitud modulation input of the PWM controller being provided with the current equivqlent, the driver circuit generates the carrier of such the amplitude that restores the output current if the carrier is at the predetermined frequency: making the power supply providing the output current by the carrier at the predetermined frequency corresponding to the output current.

4. The power supply described in claim 3 including the amplitude modulation circuit the output of which is supplied to the amplitude modulation input of the PWM controller: where the amplitude modulation circuit outputs the sum of the proportional of the error voltage provided by the error amplifier and the current equivalent supplied by the current detection circuit.

5. In the power supply described in claim 1 having 1. the resonance citcuit with plural resonances, 2. the frequency of the carrier without the feedback of frequency modulation being located at the bottom of the valley between the two resonances, and 3. the frequency range of the carrier being covered by one side of the correct slope of the valley: the amplitude of the carrier being reduced while the frequency of the carrier belongs to the other side of the false slope, which makes the frequency of the carrier moves to the correct slope, and protects the feedback against the accidental occurence that the turning on the power supply happens to make the frequency climb the false slope.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0076] [FIG. 1] Configuration of ideal PMM Controller

[0077] [FIG. 2] PLot of output voltage against amplitude of carrier

[0078] [FIG. 3] Frequency response of resonance and range of carrier frequency

[0079] [FIG. 4] Two resonance of resonance circuit

[0080] [FIG. 5] Transition of carrier frequency among resonances

[0081] [FIG. 6] Block diagram of stabilized direct-current power supply utilizing resonance circuit

[0082] [FIG. 7] Simulation circuit for stabilized direct-current power supply utilizing ideal PWM controller

[0083] [FIG. 8] Simulation for load of 50

[0084] [FIG. 9] Simulation for load of 5

[0085] [FIG. 10] Simulation for load of 1

[0086] [FIG. 11] Simulation circuit for stabilized direct-current power supply utilizing UCC3895

[0087] [FIG. 12] Simulation for load of 50

[0088] [FIG. 13] Simulation for load of 5

[0089] [FIG. 14] Simulation for load of 1

[0090] [FIG. 15] Simulation circuit for stabilized direct-current power supply utilizing LM5046

[0091] [FIG. 16] Simulation for load of 50

[0092] [FIG. 17] Simulation for load of 5

[0093] [FIG. 18] Simulation for load of 1

DESCRIPTION OF EMBODIMENTS

[0094] Stabilized Direct-Current Power Supply

[0095] A block diagram of a stabilized direct-current voltage power supply, using a resonance circuit and composed of a voltage generation circuit and a feedback circuit, is shown in FIG. 6. The voltage generation circuit contains a driver circuit, the resonance circuit, and a rectifying and smoothing circuit. The feedback circuit consists of an error amplifier, a current detection circuit, an amplitude modulation circuit, and a frequency modulation circuit. The driver circuit, supplied with an external direct current voltage supply, generates the high-frequency alternating current modulated both in frequency and amplitude, which is hereafter called carrier. The frequency modulation circuit regulates the frequency of the carrier. The amplitude modulation circuit controls the amplitude of the carrier. The carrier drives the resonance circuit.

[0096] The resonance circuit shows resonance. The amplitude of the carrier supplied by the resonance circuit depends on the frequency and amplitude of the carrier supplied to the resonance circuit. The rectifying and smoothing circuit rectifies and smooths the output of the resonance circuit, generating the output voltage of the power supply and supplying the output voltage to the load and to both the error amplifier and the current detection circuit.

[0097] The error amplifier compares the output voltage with the reference voltage supplied externally to set up the output voltage, detecting the voltage error and supplying the voltage error to the frequency modulation circuit and the amplitude modulation circuit. The current detection circuit monitors the output current, measuring the output current in magnitude and supplying the output current to the amplitude modulation circuit. Thus the voltage error and the output current is fed back to the frequency and the amplitude of the carrier.

[0098] Error Amplifier

[0099] The error amplifier detects the voltage error between the output voltage and the reference voltage, supplying the voltage error to the frequency modulation circuit and the amplitude modulation circuit.

[0100] Frequency Modulation Circuit

[0101] The frequency modulation circuit converts the voltage error for the FM input of the PWM controller. As Patent Documents one and three shows, transfer function providing the pole located in the neighborhood of the zero stabilizes feeding back the voltage error to the frequency. So the frequency modulation circuit converts the voltage error through the transfer function with the pole located in the neighborhood of the origin.

[0102] Amplitude Modulation Circuit

[0103] The amplitude modulation circuit merges the voltage error and the output current so as to fit the FM input of the PWM controller. The transfer function of the amplitude modulation circuit does not include such the substantial delay caused by an integral part in expression 1. So the feedback to the amplitude is much faster than the feedback to the frequency.

[0104] Driver Circuit

[0105] The driver circuit driving the resonance circuit includes a full bridge and the PWM controller generating gate pulses turning on and off four FETs in the full bridge. Two half bridges connected in parallel compose the full bridge where the half bridge comprises two FETs connected in a series. A pair of gate pulses drives two FETs in the half bridge, where the gate pulses ate approximately complementary. The full bridge operates in a phase-shift mode, where there is phase shift between the pairs, and the phase shift are under the external control.

[0106] The gate pulses turning on and off the FETs are of the same frequency, twice the frequency of the carrier. The FM input of the PWM controller controls the frequency of the gate pulses. There is the phase shift between one pair pf the gate pulses turning on and off one half bridge and the other pair of the gate pulses turning on and off the other half bridge, where the phase shift controls the amplitude of the carrier. The AM input of the PWM controller controls the phase shift of the pairs and then the amplitude of the carrier. The PWM controller generates the gate pulses following the output of the frequency modulation circuit and output of the amplitude modulation circuit.

[0107] Resonance Circuit

[0108] The resonance circuit shows frequency characteristic and load dependency. The resonance circuit is used in the voltage generation circuit. Let amplitude ratio of the resonance circuit be defined by the ratio of the input to the output in voltage where the output of the resonance circuit is connected to the resistor, the amplitude ratio shows resonance characteristics as a function of the frequency of the carrier. The resonance circuit has input capacitance. The sinusoidal carrier is indispensable to drive the input capacitance efficiently, An inductor resonating with the capacitance generating the approximate sinusoidal carrier, reduces dissipation where the inductor is in a series to the input. The resonance frequency of the inductor and the input capacitance is to be higher than the frequency of the carrier.

[0109] The resonance circuit used in the power supply has limitations that its electrical equivalent circuit can not represent. Selecting the range of the freuency for the carrier higher than the resonance circuit avoids the limitations. Then if the output voltage is higher than the reference voltage, the frequency increases moving away from the resonance frequency. In the opposite case, the frequency decreases, moving close to the resonance frequency.

[0110] Rectifying and Smoothing Circuit

[0111] The output of the resonance circuit modulated in amplitude varies with the frequency and the amplitude of the carrier at the input. The rectifying and smoothing circuit rectifies the output of the resonance circuit to be a direct current voltage by a diode bridge. The output of the diode bridge is buffered by a capacitance. The capacitance reduces the voltage ripples in the output voltage

[0112] Current Detection Circuit

[0113] The current detection circuit measures an output current, supplying the amplitude modulation circuit with the output current.

EXAMPLE 1

[0114] Simulation Circuit for Ideal PWM Controller

[0115] FIG. 1 shows a simulation circuit for the ideal PWM controller, where FM denotes the FM input, AM the AM input, and GA, GB, GC and GD the gate pulses. A circuit element called a behavior model, where a mathematical expression defines the relation between the input and the output of the model, is available for simulation. In the simulation circuit, there are many behavior models, which are identified by label ABM with a sequence number. ABM26, ABM13, ABM14 and ABM15 cooperate to generate rectangular pulses with the frequency specified by the FM input. ABM26 outputs integration of the FM input. ABM13 produces the output defined by [3]

10V*SIN(2**(150K*TIME20K*(V(%/N))))

[0116] Then ABM13 generates the sinusoidal wave with the frequency of the FM input. ABM14 and ABM15 digitize the sinusoidal wave with thresholds, generating rectangular pulses that are gate pulses GA and GB driving FETs M1 and M2 respectively in a half bridge.

[0117] The combination of ABM19, ABM17 and ABM18 generate the gate pulses driving FETs M3 and M4. ABM19 has input IN1 and IN2 where IN1 is for the FM input. ABM19 produces the output defined by [4]

10V*SIN(2**(180K*TIME20K*(V(%IN2)))+0.5**(1+V(%IN1))

where IN1 ranges between 1 and 1. Then the sinusoidal wave defined by expression 3 is delayed in phase against the wave defined by expression B11november15 by [5]

0.5**(1+V(%IN1))

Digitizing the sinusoidal wave defined by expression B11november15 with thresholds generates the rectangular pulses which are gate pulses GC and GD driving FETs M3 and M4 in the half bridge. The FM input controls the phase shift between the two pairs of the gate pulses driving the respective half bridges.

EXAMPLE 2

[0118] Simulation Circuit for Stabilized Direct-Current Power Supply

[0119] FIG. 7 shows simulation circuit of a direct-current stabilized power supply where the ideal PWM controller simulates an actual PWM controller. In other words, there is a sample & hold circuit. The sample & hold circuit supplied with the output of the frequency modulation circuit provides the output to the FM input, where the output is the output of the frequency modulation circuit sampled by a sample pulse. Digitizing the sinusoidal wave from ABM13 with thresholds generates the sample pulses. The circuit simulating the voltage generation circuit is the faithful reproduction of an actual circuit. Fundamentally in the feedback circuit, the output is linearly related to its input. So in the simulation circuit, the feedback circuit is replaced with simple circuits reproducing the relation between the input and the output. We show the simple simulation circuits for the error amplifier, the frequency modulation circuit, the amplitude modulation circuit, the current detection circuit and the driver circuit that constitutes the feedback circuit

[0120] Simulation Circuit for Error Amplifier

[0121] Provided with two input and one output terminals, ABM23 implements the error amplifier, where the output is equal to a voltage difference between the input. The output of ABM23 is the voltage error.

[0122] Simulation Circuit for Frequency Modulation Circuit

[0123] The combination of ABM24, GAIN17 and GAIN19 simulates the frequency modulation circuit where label GAIN with a sequence number identifies gain blocks. ABM24 functions as SDT(.Math.), the output being the integration of the input. GAIN19 provided with the output of ABM24 supplies the output to the FM input. Letting E be the gain of GAIN19, the transfer function of the frequency modulation circuit is given by

[00002]$\begin{array}{cc}\frac{E}{s}& \left[6\right]\end{array}$

[0124] Simulation Circuit for Current Detection Circuit

[0125] V6 and ABM27 simulate the current detection circuit, where label V with a sequence number identified voltage sources. The voltage source the output voltage of which is 0 V measures the current flowing through the voltage source. ABM27 outputs the current in voltage.

[0126] Simulation Circuit for Amplitude Modulation Circuit

[0127] The combination of E1, ABM31, GAIN22, SUM4 and LIMIT1 simulates the amplitude modulation circuit, where label E with a sequence number identifies a lookup table in voltage called ETABLE, label SUM with a sequence number does summing elements, and label LIMIT with a sequence number does limiting elements. The amplitude modulation circuit provided with the voltage error at the input of GAIN22 and the output current at IN+ of E1 supplies the output to the AM input of the PWM controller after the ABM31 stopping climbing the false slope on switching on the power supply outputs its input namely the output of E1 except the power supply being turned on.

[0128] A lookup table prepared in E1 converts the output current that the current detection circuit supplies at IN+ of E1, outputting the result to one input of SUM4. SUM4 receiving the output of GAIN22 at the other input combines the voltage error and the output current, summing the both of the input. LIMIT1 supplied with the output of SUM4 limits the range between 1 and 1, the output of LINIT1 meeting with the AM input of the PWM controller.

[0129] Simulation Circuit for Driver Circuit

[0130] The combination of M1, M2, M3, M4, ABM33, ABM34 and the PWM controller simulates the driver circuit. M1, M2, M3, and M4 simulates FETs constituting the full bridge. AMM33 and ABM34 simulate level converters for FETs at the high side.

SIMULATION EXAMPLES 1

[0131] The simulation circuit in FIG. 7 shows that the feedback implemented in the stabilized direct-current power supply is stable. FIG. 8, FIG. 9 and FIG. 10 shows simulation results for load of 50, 5 and 1 respectively. In the figure, a horizontal axis shows time, and vertical axes 1, 2 and 3 correspond to the output voltage, the output of the frequency modulation circuit and the output of the amplitude modulation circuit. the output current is added by 600 mA for 100 msec to the stationary output current of 1 A.

EXAMPLE 3

[0132] Simulation Circuit for Stabilized Direct-Current Power Supply Utilizing UCC3895

[0133] TEXAS INSTRUMENTS manufactures UCC3895 that is a PWM controller for the carrier of a fixed frequency. UCC3895 is capable of synchronizing with external reset pulses. Reset pulses and sawtooth pulses synchronized with the reset pulses make UCC3895 operate as a PWM controller for the variable frequency carrier. TEXAS INSTRUMENTS provides a spice model simulating UCC3895, where the spice model is ciphered, and details of the model are unknown. FIG. 11 shows the simulation circuit for a stabilized direct-current power supply where the spice model simulates UCC3895 with external synchronization. Comparing the simulation circuits in FIG. 7 and in FIG. 11, + the ideal PWM controller is replaced with UCC3895 and a resetsawtooth pulse circuit, which accompanies additional modifications to the amplitude modulation circuit. The amplitude modulation circuit supplies its output to the EAP terminal of UCC3895. The frequency modulation circuit provides its output to a frequency modulation input of the resetsawtooth pulse circuit.

[0134] ResetSawtooth Pulse Circuit

[0135] The resetsawtooth pulse circuit generates reset pulses and sawtooth pulses. As is shown in FIG. 11, the resetsawtooth pulse circuit includes the frequency modulation input and a sample & hold circuit. The sample & hold circuit samples and holds the frequency modulation input with the reset pulse until the next reset pulse. The output of the sample & hold circuit is converted to the current so as to charge a capacitor. Then the constant current charges the capacitor in each cycle. The voltage spanning capacitor reaching a predetermined voltage generates the reset pulse that in turn forces the capacitor to be discharged to the ground. The voltage spanning the capacitor is the sawtooth pulses synchronized with the reset pulses.

SIMULATION EAMPLES

[0136] The simulation circuit in FIG. 11 shows that the feedback implemented in the stabilized direct-current power supply is stable. FIG. 12, FIG. 13 and FIG. 14 shows simulation results for load of 50 , 5 and 1 respectively. In the figure, a horizontal axis shows time, and vertical axes 1, 2 and 3 correspond to the output voltage (ABM31:IN1), the output of the frequency modulation circuit (GAIN21:OUT) and the output of the amplitude modulation circuit (LIMIT1:IN).

EXAMPLE 4

[0137] Simulation Circuit for Stabilized Direct-Current Power Supply Utilizing LM5046

[0138] National Semiconductor manufactures LM5046 that is a PWM controller for the carrier of a fixed frequency. LM5046 is capable of synchronizing with external reset pulses. Reset pulses and sawtooth pulses synchronized with the reset pulses make LM5046 operate as a PWM controller for the variable frequency carrier.

[0139] National Semiconductor provides a spice model simulating LM5046. The spice model does not implement external synchronization. So we make a patch to the code of the spice model so as to simulate the external synchronization. The version of the spice model is;

TABLE-US-00001 * Model Number : LM5046 Phase-Shift Full Bridge PWM Controller with Integrated MOSFET Drivers * Last Revision Date : February 25, 2011 * Revision Number : 1.1

[0140] The patch is;

TABLE-US-00002 Eleb2 LEB5 0 LEB6 0 1 Emsk1 MSK4 0 VALUE { if(V(CLK)<=2.5 & V(PWM)<=2.5,5,0) } Emsk2 MSK5 0 VALUE { if (V(PWM)>2.5 & V(CLK)<=2.5,5,0) } Eosc1 OSC1 0 VALUE { if(V(OSC2)>cos(2*3.14*50E9/(2/ (6.25E9*I(VRT))+110E9)),5,0) } Eosc2 OSC3 0 VALUE { if (V(VREFuv)<=2.5 & V(VCCuv)<=2.5 & V(FAULT)<=2.5,sin(2*3.141592*TIME*I(VRT)/100E12/2),0) } Eosc3 NCLK 0 VALUE { {5V(CLK)} } Eleb2 LEB5 0 LEB6 0 1 Emsk1 MSK4 0 VALUE { if(V(CLK)<=2.5 & V(PWM)<=2.5,5,0) } Emsk2 MSK5 0 VALUE { if(V(PWM)>2.5 & V(CLK)<=2.5,5,0) } ******************************************************************************* *Eosc1 OSC1 0 VALUE { if(V(OSC2)>cos(2*3.14*50E9/(2/ (6.25E9*I(VRT))+110E9)),5,0) } *Eosc2 OSC3 0 VALUE { if(V(VREFuv)<=2.5 & V(VCCuv)<=2.5 & V(FAULT)<=2.5,sin(2*3.141592*TIME*I(VRT)/100E12/2),0) } ******************************************************************************* Eosc1 OSC1 0 VALUE { if(I(VRT)>5e3V & V(OSC3)>=2.5,5,0) } Eosc2 OSC3 0 VALUE { if(V(VREFuv)<=2.5 & V(VCCuv)<=2.5 & V(FAULT)<=2.5,5,0) } Eosc3 NCLK 0 VALUE { {5V(CLK)} }

[0141] FIG. 15 shows a simulation circuit for a stabilized direct-current power supply where LM5046 with the patch is employed as a PWM controller for a variable frequency carrier. The simulation circuit utilizes a lookup table defined as follows.

TABLE-US-00003 * .SUBCKT imoEtable IN+ IN OUT+ OUT E1 OUT+ OUT TABLE {V(IN+,IN)}=( +(7.5m,660m) +(30m,650m) +(60m,645m) +(150m,610m) +(300m,600m) +(600m,550m) +(750m,520m) *(1.0,490m) +(1.5,400m) *(3.0,130m) *(3.333,95m) *(3.75,10m) *(4.28,90m) +(5.0,230m) +(6.0,450m) *(7.5,930m) +) .ENDS imoEtable *

[0142] Comparing the simulation circuits in FIG. 7 and in FIG. 15, + the ideal PWM controller is replaced with LM5046 and the reset sawtooth pulse circuit, which accompanies additional modifications to the amplitude modulation circuit. The amplitude modulation circuit supplies its output to the COMP terminal of LM5046. The frequency modulation circuit provides its output to the frequency modulation input of the reset sawtooth pulse circuit.

[0143] ResetSawtooth Pulse Circuit

[0144] The resetsawtooth pulse circuit is same with the one in FIG. 11.

SIMULATION EAMPLES

[0145] The simulation circuit in FIG. 15 shows that the feedback implemented in the stabilized direct-current power supply is stable. FIG. 16, FIG. 17 and FIG. 18 shows simulation results for load of 50 , 5 and 1 respectively. In the figure, a horizontal axis shows time, and vertical axes 1, 2 and 3 correspond to the output voltage (ABM31:IN1), the output of the frequency modulation circuit (GAIN21:OUT) and the output of the amplitude modulation circuit.

INDUSTRIAL APPLICABILITY

[0146] Rectifying and smoothing the output of a resonance circuit to produce the output1 of the power supply, the carrier driving the resonance circuit being modulated both in frequency and amplitude makes the resonance circuit driven with the carrier of such the frequency that is optimal for the output current namely the load. The modulation of the carrier also makes it possible to implement an efficient power supply with resonance circuits ranging from the widely employed resonance circuit of a low Q value to the resonance circuit of a high Q value where the resonance frequency is dependent on the load