CN1783680A - Switching type controller - Google Patents

Abstract

This invention relates to a switch control device connected to the primary side of a transformer to control the switch of the transformer to provide a DC power output including: a switch power switch with its output connecting to one end of the primary side of the transformer and the other connected with the input voltage, a current sensing device connected with the other output end of the switch to sense current signals by the switch action of the switch, a controller connected with the control end of the switch and the current sensing device and connected with the assist winding by a bleeder to get the voltage signals and discharge time from the winding and get current signals from the sensing device and output switch signals to the control end.

Description

A kind of switching control device

Technical field

The present invention relates to a kind of switching control device, be used in the control circuit of power supply unit, especially relate to a kind of switching control device about the switch mode power supply supply.

Background technology

Various power supply units have used is widely providing stable voltage and the electric current of adjusting.Based on the consideration that meets security regulations (safety), the power supply unit of an off-line type (off-1ine) must it primary side and secondary side between electrical isolation (galvanic isolation) is provided.Since it is so, one switching control device is configured in the primary side of power supply unit, and an optical coupler (optical-coupler) is stablized adjuster (secondary-side regulator) with secondary side must be used for stablizing output voltage and/or the output current of adjusting this off-line type power supply unit.In order to save number of parts and the needs of removing the secondary side anti current feed circuit, the primary side control technology is suggested in succession, and for example No. the 4th, 302,803, the U.S. Patent bulletin of announcing on November 24th, 1981.Yet above-mentioned prior art can't satisfy precise output voltage and maximum output current simultaneously.

Summary of the invention

Technical problem to be solved by this invention is to provide a kind of switching control device at the primary side of power supply unit, not needing optical coupler and secondary side to stablize under the situation of adjuster, in order to obtain precise output voltage and maximum output current.And, the present invention further proposes the characteristic of frequency hopping (frequency hopping), reduce electromagnetic interference (electric and magnetic interference in order to the frequency spectrum (spectrum) of the switching frequency that prolongs switching signal, EMI), the volume of power supply unit and cost are reduced.

To achieve these goals, the invention provides a kind of switching control device, be applied to the power supply unit of transformer primary side control, comprise one and switch power switch by a current sensing device, in order to switch this transformer.Wherein this transformer side is connected to the input voltage of power supply unit.One controller, be connected to the control end of this power switch, an auxiliary winding (auxiliary winding) and this current sensing device of this transformer, output one is switched signal controlling and is switched this power switch, in order to stable output voltage and the maximum output current of adjusting power supply unit, and receive a voltage feedback signal and a current feedback signal.During this section of the deadline of this switching signal (off time), this controller should auxiliary winding by this transformer, by a discharge time of repeatedly take a sample a voltage signal and this transformer, is used for producing in inside a voltage feedback signal; During this section of the ON time (on time) of this switching signal, this controller by measuring a current signal of this transformer primary side, produces a current feedback signal by this current sensing device in inside.This controller produces this switching signal according to this voltage feedback signal and this current feedback signal.

This controller comprises a voltage-waveform detector, is connected to this transformer, and the auxiliary winding by this transformer receives this voltage signal, by this voltage signal of repeatedly taking a sample, in order to export this voltage feedback signal and a discharge time signal.This voltage-waveform detector is connected to the auxiliary winding of being somebody's turn to do of this transformer by ohmic voltage divider.The discharge time of this discharge time signal indication transformer, the while is also represented the discharge time of secondary side switch current.One current-waveform detector is connected to this current sensing device, receives this current signal of this transformer primary side by this current sensing device, produces a current waveform signal by measuring this current signal.Wherein this current waveform signal generates according to the primary side switch current of this transformer.One integrator is connected to this current-waveform detector and this voltage-waveform detector, receive this current waveform signal by this current-waveform detector, receive this discharge time signal by this voltage-waveform detector, export this current feedback signal by this current waveform signal of integration and this discharge time signal.One oscillator (oscillator) output one oscillator signal (oscillation signal) and a ramp signal (rampsignal), this oscillator signal is in order to determine the switching frequency of this controller output switching signal.One adder is connected to this current sensing device and this oscillator, receives this current signal by this current sensing device, and receives this ramp signal of this oscillator output, in order to produce a slope signal (slope signal).

One voltage circuit error amplifier is made up of first operational amplifier and first reference voltage, this voltage circuit error amplifier is connected to this voltage-waveform detector, receive this voltage feedback signal in order to amplify this voltage feedback signal and loop gain (loop gain) is provided, its objective is as output voltage and control.One current circuit error amplifier is made up of second operational amplifier and second reference voltage, this current circuit error amplifier is connected to this integrator, receive this current feedback signal in order to amplify this current feedback signal and loop gain is provided, its objective is as output current and control.One peak current limiter (peak-currentlimiter) is connected to this current sensing device, receives this current signal, is used for the maximum of limiting transformer primary side current signal.

One first comparator is connected to this adder and this voltage circuit error amplifier, and this voltage feedback signal after receiving this slope signal and amplifying is as voltage control.One second comparator is connected to this oscillator and current circuit error amplifier, and this current feedback signal after receiving this ramp signal and amplifying is as Current Control.One pulse duration demodulator is connected to this oscillator, this peak current limiter, this first comparator and this second comparator, and the pulse duration of this switching signal is controlled in the output that receives the output of output, this voltage circuit error amplifier of this oscillator signal, this peak current limiter and this current circuit error amplifier.One programmable current source (programmable current source) is connected to the input of this voltage-waveform detector, in order to do temperature-compensating.This programmable current source receives the temperature of this controller and exports a programmable electric current, in order to the variations in temperature (temperature deviation) of offset supply supply on output voltage.

One module generator (pattern generator) produces a digital module sign indicating number (digital patterncode).But one first program electric capacity (first programmable capacitor) is connected to this oscillator and this module generator, can be according to the output of this digital module sign indicating number in order to the demodulation switching frequency.The frequency spectrum of this switching frequency is prolonged, therefore the electromagnetic interference of supply capable of reducing power source.But the second program electric capacity (secondprogrammable capacitor) is connected to this integrator and this module generator, can be in order to adjust the time constant of this integrator, make the switching frequency of the switching signal of itself and this controller output produce the directly proportional relation, the current feedback signal of this integrator output thereby be proportional to the output current of power supply unit.But but this first program electric capacity and this second program electric capacity, its capacitance is controlled by this digital module sign indicating number.

Effect of the present invention, being is not needing optical coupler and secondary side to stablize under the situation of adjuster, in order to obtain precise output voltage and maximum output current, and the characteristic of proposition frequency hopping, reduce electromagnetic interference in order to the frequency spectrum of the switching frequency that prolongs switching signal, therefore can make the volume and cost reduction of power supply unit.

Describe the present invention below in conjunction with the drawings and specific embodiments, but not as a limitation of the invention.

Description of drawings

Fig. 1 has the circuit block diagram of switching control device for power supply unit;

Fig. 2 is the main waveform of power supply unit and switching control device among Fig. 1;

Fig. 3 is the controller of the preferred embodiment according to the present invention;

Fig. 4 is the voltage-waveform detector of the preferred embodiment according to the present invention;

Fig. 5 is the oscillator of preferred embodiment of the present invention;

Fig. 6 is the current-waveform detector of preferred embodiment of the present invention;

Fig. 7 is the integrator of preferred embodiment of the present invention;

Fig. 8 is the circuit diagram of pulse duration demodulator of the present invention;

Fig. 9 is the circuit diagram of adder among the present invention;

Figure 10 is the module generator of preferred embodiment of the present invention; And

Figure 11 is the programmable electric capacity of preferred embodiment of the present invention.

Wherein, description of drawings:

The 10-transformer, 20-power switched switch

The 30-current sensing device, 31-electric capacity, 32-electric capacity

The 40-rectifier, 45-electric capacity

50,51-resistance 60-rectifier, 65-electric capacity

The 70-controller, 71-operational amplifier, 72-operational amplifier

The 73-comparator, the 74-comparator

The 75-comparator, 79-NAND gate logical circuit

The programmable current source of 80-, the 81-bipolar transistor

The 82-bipolar transistor, 83-resistance

84,85,86-p mirror transistor, 87,88-n mirror transistor

The 100-voltage-waveform detector, 110,111,115-electric capacity

121,122,123,124,125-switch

130,131-diode, the 135-current source

150,151-operational amplifier, the 155-comparator

The 156-critical voltage

The 161-inverter, the 162-inverter

163-NAND gate logical circuit, 164,165, the 166-AND door

170,171-D type flip-flop

The 180-current source, the 181-transistor

182-electric capacity, 190-sampling pulse generator

The 200-oscillator, the 201-operational amplifier

The 202-operational amplifier, the 205-comparator

210,211-resistance, 215,216-electric capacity

230,231,232,233,234-switch

250,251,252,253,254,255,259-transistor

The 260-inverter, the 300-current-waveform detector

The 310-comparator, the 320-current source

330,340, the 350-switch, 361,362-electric capacity

The 400-integrator, 410, the 411-operational amplifier

420,421,422,423,424,425-transistor

450,452-resistance, 460,461,462,464,466, the 468-switch

471,472,473,474-electric capacity

500-pulse duration demodulator, 511-NAND gate logical circuit

The 512-inverter, 515-D type flip-flop

The 518-inverter, 519-AND door, 520-blanking circuit

521,522-inverter, 523-NAND gate logical circuit

The 525-current source, 526-transistor, 527-electric capacity

The 600-adder, 610, the 611-operational amplifier

620,621, the 622-transistor, 650,651-resistance

900-module generator, the 910-first programmable electric capacity

The 930-second programmable electric capacity, the 951-clock pulse generator

The 952-XOR door, 971,972, the 975-buffer

Embodiment

Fig. 1 is a power supply unit among the present invention.Power supply unit comprises a transformer 10, and this transformer 10 has auxiliary winding NA, first side winding NP and secondary side winding NS.One switches power switch 20, flows through the electric current of this transformer 10 first side winding NP in order to switching, and this transformer 10 first side winding NP are connected to the input voltage VIN of this power supply unit.One current sensing device 30 is connected to this transformer 10 by this power switched switch 20, in order to the primary side current of this transformer 10 of sensing.One switches the control end that signal VPWM is connected to this power switched switch 20, in order to controlling the change action of this power switched switch 20, and obtain stable output voltage VO and the maximum output current IO that adjusts power supply unit at transformer 10 secondary side winding NS end.One controller 70 is connected to the control end of this power switched switch 20, auxiliary winding NA and this current sensing device 30 of this transformer 10, this current sensing device 30 as same current sensing resistor, and this controller 70 produces this switching signal VPWM.

In conjunction with Fig. 1,, be the various signal waveforms of power supply unit with reference to figure 2.When switching signal VPWM changes conducting (being high levle in logic) into, so produce primary side switch current IP.Primary side switch peak value electric current I P1 can be obtained by following formula:

$I_{P1}=\frac{V_{\mathrm{IN}}}{L_P}\×T_{\mathrm{ON}}...\left(1\right)$

Wherein LP is the inductance value of the first side winding NP of transformer 10; TON is the ON time (on time) of switching signal VPWM.

In case switching signal VPWM changes into by (being low level in logic), this moment, the energy storage of transformer 10 will be sent to the secondary side of transformer 10, and passed through the output VO of rectifier 40 to power supply unit, so produce secondary side switch current IS.Secondary side switch peak value current IS 1 can be expressed as:

$I_{S1}=\frac{(V_O+V_F)}{L_S}\×T_{\mathrm{DS}}...\left(2\right)$

Wherein VO is the output voltage of power supply unit; VF is the forward pressure drop (forwardvoltage drop) of rectifier 40; LS is the inductance value of the secondary side winding NS of transformer 10; TDS is the discharge time of transformer 10, also can be expressed as the discharge time of secondary side switch current IS.Simultaneously, produce voltage signal VAUX on the auxiliary winding NA of transformer 10, voltage signal VAUX1 is expressed as:

$V_{\mathrm{AUX}1}=\frac{T_{\mathrm{NA}}}{T_{\mathrm{NS}}}\×(V_O+V_F)...\left(3\right)$

Wherein TNA and TNS are respectively the auxiliary winding NA of transformer 10 and the umber of turn of secondary side winding NS.

When secondary side switch current IS dropped to zero, the voltage signal VAUX that auxiliary winding NA is produced began to reduce, this also the energy storage of indication transformer 10 fully discharge in this moment.Therefore, TDS can be measured to the corner (corner) that voltage signal VAUX begins to descend by the drop edge (falling edge) of switching signal VPWM in the discharge time of equation (2), as shown in Figure 2.The umber of turn of primary side switch peak value electric current I P1 and transformer 10 can be with deciding secondary side switch peak value current IS 1, and secondary side switch peak value current IS 1 can be expressed as:

$I_{S1}=\frac{T_{\mathrm{NP}}}{T_{\mathrm{NS}}}\×I_{P1}...\left(4\right)$

Wherein TNP is the umber of turn of the first side winding NP of transformer 10.

As shown in Figure 1, controller 70 comprises power source supply end (supply terminal) VCC, earth terminal (ground terminal) GND, test side (detection terminal) DET, output (outputterminal) OUT, sense terminals (sense terminal) CS, voltage compensation end (voltage-compensation terminal) COMV and current compensation end (current-compensation terminal) COMI.Power source supply end VCC and earth terminal GND are in order to provide power supply.One resistance 50 forms voltage divider (divider) with resistance 51 for being connected in series, the auxiliary winding NA that two resistance is connected to transformer 10 and earth terminal are with reference between accurate.The test side DET of controller 70 is connected to the junction of resistance 50 and resistance 51.Produce voltage VDET at test side DET, can obtain:

$V_{\mathrm{DET}}=\frac{R_{51}}{{\mathrm{<figure-callout\; id="50"\; label="R"\; filenames="A20041009552800261.png"\; state="\{\{state\}\}">R</figure-callout>}}_{50}+{\mathrm{<figure-callout\; id="51"\; label="R"\; filenames="A20041009552800261.png"\; state="\{\{state\}\}">R</figure-callout>}}_{51}}\&times;V_{\mathrm{AUX}}...\left(5\right)$

Wherein R50 and R51 are respectively the resistance value of resistance 50 and 51.

Voltage signal VAUX further charges to electric capacity 65 by rectifier 60, in order to the power source supply end VCC of power supply to controller 70 to be provided.The source electrode of power switched switch 20 (source) is connected to earth terminal with reference to accurate position by current sensing device 30, and utilizes current sensing device 30 to become a current signal VCS in order to conversion primary side switch current IP.The sense terminals CS of controller 70 is connected to current sensing device 30, in order to detect this current signal VCS.

The output OUT of this controller 70 produces switching signal VPWM, in order to controlling the change action of this power switched switch 20, and then obtains stable output voltage VO and the maximum output current IO that adjusts power supply unit in transformer 10 secondary side winding NS end.Compensating network is connected to the voltage compensation end COMV of this controller 70, as the voltage circuit frequency compensation.This compensating network can use electric capacity such as electric capacity 31 to be connected to earth terminal with reference to accurate position.Another compensating network is connected to the current compensation end COMI of this controller 70, as the current circuit frequency compensation.This compensating network also can use electric capacity such as electric capacity 32 to be connected to earth terminal with reference to accurate position.

During this section of deadline of this switching signal VPWM, auxiliary winding NA many sampling one voltage signal VAUX of controller 70 by this transformer 10 and this transformer 10 one discharge time TDS, in internal circuit, export a voltage feedback signal VV; During this section of the ON time of this switching signal, controller 70 is measured a current signal VCS of this transformer by this current sensing device, and in internal circuit output one current feedback signal VI.Wherein this switching signal receives this voltage feedback signal VV and this current feedback signal VI and generates.

Cooperate Fig. 1, with reference to figure 3, Fig. 3 is the controller 70 of preferred embodiment of the present invention.At test side DET, this controller 70 comprises a voltage-waveform detector 100.This voltage-waveform detector 100 is connected to the auxiliary winding NA of being somebody's turn to do of this transformer 10 by ohmic voltage divider (50,51), and auxiliary winding NA receive this voltage signal VDET by being somebody's turn to do of this transformer 10.Voltage-waveform detector 100 produces this a voltage feedback signal VV and a discharge time signal SDS by this voltage signal VDET that repeatedly takes a sample, and this discharge time signal SDS represents TDS discharge time of secondary side switch current IS.At sense terminals CS, controller 70 comprises a current-waveform detector 300.This current-waveform detector 300 is connected to this current sensing device 30, receives this current signal VCS of these transformer 10 primary sides by this current sensing device 30.This current-waveform detector 300 is exported a current waveform signal VW by measuring this current signal VCS.That is to say that this current waveform signal VW generates according to the primary side switch current IP of this transformer 10.One integrator 400 is connected to this current-waveform detector 300 and this voltage-waveform detector 100, receive this current waveform signal VW by this current-waveform detector 300, receive this discharge time signal SDS by this voltage-waveform detector 100, this integrator 400 is by integration this current waveform signal VW and this discharge time signal SDS, in order to export this current feedback signal VI.One oscillator 200 is in order to export an oscillator signal PLS and a ramp signal (ramp signal) RMP, and this oscillator signal is in order to the switching frequency of decision switching signal VPWM.One voltage circuit error amplifier is made up of an operational amplifier 71 and a reference voltage VREF1, this voltage circuit error amplifier is connected to this voltage-waveform detector 100, receive this voltage feedback signal VV in order to amplify this voltage feedback signal VV and loop gain is provided, control in order to output voltage.One current circuit error amplifier is made up of an operational amplifier 72 and a reference voltage VREF2, this current circuit error amplifier is connected to this integrator 400, receive this current feedback signal VI in order to amplify this current feedback signal VI and loop gain is provided, control in order to output current.

One adder 600, be connected to this current sensing device 30 and this oscillator 200, receive this current signal VCS by this current sensing device 30, receive this ramp signal RMP by this oscillator 200, the addition of current signal VCS and ramp signal RMP by transformer 10 primary sides, in order to export a slope signal (slope signal) VSLP, the effect of this slope signal VSLP is that voltage circuit is formed slope-compensation (slope compensation).One peak current limiter is made up of a comparator 74 and a reference voltage VREF3, the anode input of this comparator 74 is provided by this reference voltage VREF3, the negative terminal input of this comparator 74 is connected to this sense terminals CS, receive this current signal VCS, in order to the maximum of this current signal VCS of limiting transformer 10 primary sides, and (cycle-by-cycle) electric current of property performance period restriction.One first comparator 73 is connected to this adder 600 and this voltage circuit error amplifier, this voltage feedback signal VV after receiving this slope signal VSLP and amplifying, and the output control signal is as voltage control.One second comparator 75 is connected to this oscillator 200 and this current circuit error amplifier, this current feedback signal VI after receiving this ramp signal RMP and amplifying, and the output control signal is as Current Control.

Refer again to Fig. 3, this operational amplifier 71,72 all has the characteristic of conduction (trans-conductance) output.The output of this operational amplifier 71 is connected to the anode input of voltage compensation end COMV and this first comparator 73.The output of this operational amplifier 72 is connected to the anode input of current compensation end COMI and this second comparator 75.The negative terminal input of this first comparator 73 is connected to the output of this adder 600.The negative terminal input of this second comparator 75 is provided by this ramp signal RMP, and this ramp signal RMP is produced by this oscillator 200.

One pulse duration demodulator 500 is connected to this oscillator 200, this peak current limiter, this first comparator 73 and this second comparator 75, receive this oscillator signal, and by a NAND gate logical circuit 79, the pulse duration of this switching signal VPWM is controlled in the output that receives the output of output, this voltage circuit error amplifier of this peak current limiter and this current circuit error amplifier.Wherein three of this NAND gate logical circuit 79 inputs are connected respectively to the output of this first comparator 73, this comparator 74 and this second comparator 75.The output of this NAND gate logical circuit 79 is exported a reset signal RST, and this reset signal RST is supplied to this pulse duration demodulator 500, adjusts the work period of the switching signal VPWM of these pulse duration demodulator 500 outputs in order to control.

With shown in Figure 3, form current control loop with reference to figure 1, control the amplitude (magnitude) of primary side switch current IP according to this reference voltage VREF2 by the pulse duration demodulation that detects this switching signal VPWM of transformer 10 primary side switch current IP.Relation on secondary side switch current IS and primary side switch current IP are proportional is shown in equation (4).According to signal waveform shown in Figure 2, the output current IO of power supply unit is a secondary side switch current IS mean value.Output current IO can be expressed as:

$I_O=I_S\&times;\frac{T_{\mathrm{DS}}}{2T}...\left(6\right)$

Wherein T is the switching cycle of this switching signal VPWM, with the directly proportional relation of the time constant of this oscillator 200.Therefore the output current IO of power supply unit can obtain stable the adjustment.

This current-waveform detector 300 detects this current signal VCS, and produces this current waveform signal VW.This integrator 400 by integration this current waveform signal VW and this discharge time TDS further produce this current feedback signal VI.Therefore this current feedback signal VI can be designed to:

$V_I=\frac{V_W}{2}\&times;\frac{T_{\mathrm{DS}}}{T_I}...\left(7\right)$

Wherein this current waveform signal VW is expressed as:

$V_W=\frac{T_{\mathrm{NS}}}{T_{\mathrm{NP}}}\&times;R_S\&times;I_S...\left(8\right)$

Wherein TI is the time constant of integrator 400.By equation (6)-(8) as can be seen, this current feedback signal VI can be write as again:

$V_I=\frac{T}{T_I}\&times;\frac{T_{\mathrm{NS}}}{T_{\mathrm{NP}}}\&times;R_S\&times;I_O...\left(8\right)$

We can be found to, and this current feedback signal VI is proportional to the output current IO of power supply unit.When output current IO increased, this current feedback signal VI was increase, but the maximum of this current feedback signal VI is limited in the numerical value of reference voltage VREF2 by the stable adjustment of current control loop.Under the FEEDBACK CONTROL of current control loop, maximum output current IO (max) can be obtained by following formula:

$I_{O\left(\max \right)}=\frac{T_{\mathrm{NP}}}{T_{\mathrm{NS}}}\&times;\frac{G_A\&times;G_{\mathrm{SW}}\&times;V_{\mathrm{REF}2}}{1+(G_A\&times;G_{\mathrm{SW}}\&times;\frac{R_S}{K})}...\left(10\right)$

Wherein K is a constant, equals TI/T; GA is the gain (gain) of current circuit error amplifier; GSW is the gain of commutation circuit.When the loop gain very high (GA * GSW＞＞1) of current control loop, maximum output current IO (max) is reduced to:

$I_{O\left(\max \right)}=K\&times;\frac{T_{\mathrm{NP}}}{T_{\mathrm{NS}}}\&times;\frac{V_{\mathrm{REF}2}}{R_S}...\left(11\right)$

The maximum output current IO (max) of power supply unit is according to the numerical value of reference voltage VREF2, thereby obtains the stable fixed current that is adjusted to.

In addition, the pulse duration demodulation that is sampled to switching signal VPWM by voltage signal VAUX forms voltage control loop, and controls the amplitude of voltage signal VAUX according to the numerical value of reference voltage VREF1.Relation on voltage signal VAUX and output voltage VO are proportional is shown in equation (3).Voltage signal VAUX obtains voltage VDET through suitable decay again, shown in equation (5).More than 100 sampling voltage VDET of voltage-waveform detector be in order to producing voltage feedback signal VV, and the numerical value of this voltage feedback signal VV is by the stable adjustment of voltage control loop, and according to the numerical value of reference voltage VREF1 and controlled.Voltage circuit error amplifier and commutation circuit provide loop gain for voltage control loop.Therefore, output voltage VO can be reduced to:

$V_O=(\frac{{\mathrm{<figure-callout\; id="50"\; label="R"\; filenames="A20041009552800261.png"\; state="\{\{state\}\}">R</figure-callout>}}_{50}+R_{51}}{{\mathrm{<figure-callout\; id="51"\; label="R"\; filenames="A20041009552800261.png"\; state="\{\{state\}\}">R</figure-callout>}}_{51}}\&times;\frac{T_{\mathrm{NS}}}{T_{\mathrm{NA}}}\&times;V_{\mathrm{REF}1})-V_F....\left(12\right)$

Cooperate Fig. 1, refer again to Fig. 3, voltage signal VAUX reaches repeatedly sampling by voltage-waveform detector 100.Discharged into before zero at secondary side switch current IS, carry out voltage sampling and measurement immediately.Therefore, the change of secondary side switch current IS can't influence the numerical value of the forward pressure drop VF of rectifier 40.Yet when temperature changed, the forward pressure drop VF of rectifier 40 also changed thereupon.One programmable current source 80 is connected to the input of this voltage-waveform detector 100, as temperature-compensating.This programmable current source 80 receives the temperature of this controller 70, in order to export a programmable electric current I T.Programmable electric current I T produces voltage VT in conjunction with resistance 50 and 51, is used for compensating the forward variations in temperature of pressure drop VF.

$V_T=I_T\&times;\frac{{\mathrm{<figure-callout\; id="50"\; label="R"\; filenames="A20041009552800261.png"\; state="\{\{state\}\}">R</figure-callout>}}_{50}\&times;R_{51}}{{\mathrm{<figure-callout\; id="50"\; label="R"\; filenames="A20041009552800261.png"\; state="\{\{state\}\}">R</figure-callout>}}_{50}+{\mathrm{<figure-callout\; id="51"\; label="R"\; filenames="A20041009552800261.png"\; state="\{\{state\}\}">R</figure-callout>}}_{51}}...\left(13\right)$

Can find the ratio decision output voltage VO of resistance value R50 and R51 with reference to equation (12) and (13).Resistance R 50 determines temperature coefficient (temperature coefficient) with the resistance value of R51, in order to the forward pressure drop VF of compensation rectifier 40.Because programmable current source 80, equation (12) can be write as again:

$V_O=(\frac{{\mathrm{<figure-callout\; id="50"\; label="R"\; filenames="A20041009552800261.png"\; state="\{\{state\}\}">R</figure-callout>}}_{50}+R_{51}}{{\mathrm{<figure-callout\; id="51"\; label="R"\; filenames="A20041009552800261.png"\; state="\{\{state\}\}">R</figure-callout>}}_{51}}\&times;\frac{T_{\mathrm{NS}}}{T_{\mathrm{NA}}}\&times;V_{\mathrm{REF}1})-V_F+V_T...\left(14\right)$

For the characteristic that produces frequency hopping prolongs the frequency spectrum of the switching frequency of this switching signal VPWM, in order to reduce the electromagnetic interference of power supply unit, a module generator 900 is in order to produce a digital module sign indicating number PN ... P1.One first programmable electric capacity 910 is connected to this oscillator 200 and this module generator 900, receive this digital module sign indicating number PN ... P1 is as the frequency of oscillation of this oscillator 200 of demodulation, in order to the switching frequency of the switching signal VPWM that adjusts these pulse duration demodulator 500 outputs.One second programmable electric capacity 930 is connected to this integrator 400 and this module generator 900, uses so that the time constant of this integrator 400 and switching frequency produce the directly proportional relation.This digital module sign indicating number PN ... P1 controls the capacitance of this first programmable electric capacity 910 and this second programmable electric capacity 930.

Main purpose of the present invention provides a switching control device at the primary side of power supply unit, not needing optical coupler and secondary side to stablize under the situation of adjuster, in order to obtain precise output voltage and maximum output current.And the present invention further proposes the characteristic of frequency hopping, reduces electromagnetic interference in order to the frequency spectrum of the switching frequency that prolongs switching signal, therefore can make the volume and cost reduction of power supply unit.

Fig. 4 is the voltage-waveform detector 100 of preferred embodiment of the present invention.One sampling pulse generator (sample-pulse generator) 190 produces sample-pulse signal in order to repeatedly sampling.One critical voltage (threshold voltage) 156 adds voltage signal VAUX, thereby produces accurate Bit Shift reflected signal (level-shift reflected signal).First signal generator (first signal generator) comprises D type flip-flop 171, two AND doors 165,166, in order to produce first sampled signal (firstsample signal) VSPl and second sampled signal (second sample signal) VSP2.Secondary signal generator (second signal generator) comprises D type flip-flop 170, NAND gate logical circuit 163, AND door 164 and comparator 155, in order to produce discharge time signal SDS.One time delay circuit (time-delay circuit) comprises inverter 162, current source 180, transistor 181 and electric capacity 182, when switching signal VPWM is disabled state (disable) in order to produce Td time of delay.The input of inverter 161 is provided by switching signal VPWM, and the output of inverter 161 is connected to the input of inverter 162, also is connected to first end input of AND door 164 and the clock pulse input (clock-input) of D type flip-flop 170 simultaneously.But the output conducting of inverter 162 or by (on/off) transistor 181.Electric capacity 182 is connected in parallel with transistor 181,182 chargings of 180 pairs of electric capacity of this current source.Therefore, Td time of delay of the capacitance of the electric current of current source 180 and electric capacity 182 decision time delay circuit, and electric capacity 182 is the output of time delay circuit.Draw (pull high) to supply voltage VCC in the D input of D type flip-flop 170.The output of D type flip-flop 170 is connected in second end input of AND door 164.This AND door 164 output discharge time signal SDS.When switching signal VPWM is a disabled state, therefore discharge time signal SDS is enabled status (enable).The output of this NAND gate logical circuit 163 is connected in the replacement input (reset-input) of D type flip-flop 170.The input of NAND gate logical circuit 163 is connected to the output of time delay circuit and the output of comparator 155.The negative terminal input of comparator 155 is provided by accurate Bit Shift reflected signal.The anode input of comparator 155 is provided by voltage feedback signal VV.Therefore, after time of delay Td, in case accurate Bit Shift reflected signal is lower than voltage feedback signal VV, discharge time signal SDS is a disabled state.In addition, as long as switching signal VPWM is an enabled status, discharge time signal SDS also is a disabled state.

The sample-pulse signal that sampling pulse generator 190 produces puts on clock pulse input, the AND door 165 of D type flip-flop 171 and imports with 166 the 3rd end.The D input of D type flip-flop 171 links together with inverse output terminal and forms except that 2 counters (divide-by-two counter).The output of D type flip-flop 171 is imported with second end that reverse output is connected to AND door 165,166.First end input of AND door 165,166 is provided by discharge time signal SDS.The 4th end input of AND door 165,166 is connected to the output of time delay circuit.Therefore, the output according to sample-pulse signal produces the first sampled signal VSP1 and the second sampled signal VSP2.In addition, during this section in enabled status cycle of discharge time signal SDS, the first sampled signal VSP1 and the second sampled signal VSP2 are for alternately generating.Yet,, be used for forbidding producing the first sampled signal VSP1 and the second sampled signal VSP2 at Td time of delay of insertion at the beginning of discharge time signal SDS.Time of delay Td this section during, the first sampled signal VSP1 and the second sampled signal VSP2 so be disabled state.

The first sampled signal VSP1 and the second sampled signal VSP2 by test side DET and resistive voltage divider in order to sampling voltage signal VAUX alternately.The first sampled signal VSP1 and the second sampled signal VSP2 control switch 121 and switch 122 are kept voltage (second hold voltage) in order to obtain keeping voltage (first hold voltage) and second across first of first electric capacity 110 and second electric capacity 111 respectively.The switch 123 and first electric capacity 110 are connected in parallel, and are used for 110 discharges of first electric capacity.The switch 124 and second electric capacity 111 are connected in parallel, and are used for 111 discharges of second electric capacity.One buffer amplifier (bufferamplifier) comprises operational amplifier 150 and 151, diode 130, diode 131 and current source 135, keeps voltage in order to generation.Operational amplifier 150 and the input of 151 anode are connected to first electric capacity 110 and second electric capacity 111 respectively, and operational amplifier 150 and 151 negative terminal input are connected to the output of buffer amplifier.The output that outputs to buffer amplifier that diode 130 connects by operational amplifier 150.Diode 131 is connected to the output of buffer amplifier by the output of operational amplifier 151.Therefore, keep voltage by first and second high voltage of keeping voltage obtains keeping voltage.This current source 135 is used for tenth skill.Switch 125 periodically is conducting to the voltage of keeping of first output capacitance 115, in order to produce voltage feedback signal VV.The change action that switch 125 produces conducting or ends by oscillator signal PLS.After time of delay Td, the first sampled signal VSP1 and the second sampled signal VSP2 begin to produce first to be kept voltage and second and keeps voltage, and the surging that so can eliminate voltage signal VAUX disturbs (spikeinterference).When switching signal VPWM is a disabled state, and power switched switch 20 ends, and will produce the abrupt voltage wave of voltage signal VAUX this moment.

With reference to figure 1, Fig. 2 and Fig. 4, when secondary side switch current IS discharges into zero, voltage signal VAUX begins to descend, and it is disabled state that the detection by comparator 155 makes discharge time signal SDS.The pulse duration of discharge time signal SDS thus with the directly proportional relation of TDS discharge time of secondary side switch current IS.Simultaneously, be disabled state according to discharge time signal SDS, and the first sampled signal VSP1 and the second sampled signal VSP2 are disabled state, and repeatedly sampling stop.At this moment, keep voltage in the output generation of buffer amplifier, expression final voltage (end voltage).Final voltage thus with the directly proportional relation of voltage signal VAUX, dropped to before zero at secondary side switch current IS, voltage signal VAUX is sampled.The acquisition of keeping voltage is to get first to keep the high voltage that voltage and second is kept voltage, and when voltage signal VAUX begins to reduce, will ignore sampled voltage.

Fig. 5 is the oscillator 200 of preferred embodiment of the present invention.Operational amplifier 201, resistance 210 are formed first voltage commentaries on classics current converter (first V-to-I converter) with transistor 250.This first voltage changes current converter and produces reference current I250 according to reference voltage VREF.A plurality of transistors form current mirrors (current mirror) as 251,252,253,254 and 255, according to reference current I250 in order to produce vibration charging current (oscillator charge current) I253 and oscillating discharge electric current (oscillator discharge current) I255.The drain electrode of transistor 253 produces this vibration charging current I253.The drain electrode of transistor 255 produces this oscillating discharge electric current I 255.First oscillation switch 230 is connected between the drain electrode and oscillating capacitance 215 of transistor 253, and second oscillation switch 231 is connected between the drain electrode and oscillating capacitance 215 of transistor 255.Ramp signal RMP is obtained by oscillating capacitance 215.The anode input of vibration comparator 205 is connected to oscillating capacitance 215.Vibration comparator 205 outputting oscillation signal PLS, this oscillator signal PLS determines switching frequency.First end points of the 3rd oscillation switch 232 is provided by high critical value voltage (high threshold voltage) VH.First end points of the 4th oscillation switch 233 is provided by low critical value voltage (low threshold voltage) VL.Second end points of second end points of the 3rd oscillation switch 232 and the 4th oscillation switch 233 all is connected in the negative terminal input of vibration comparator 205.The input of vibration inverter 260 is connected in the output of vibration comparator 205, in order to produce oscillator signal/PLS, vibration inverter 260 output inverse oscillation signal/PLS.Oscillator signal PLS is used for conducting or by second oscillation switch 231 and the 4th oscillation switch 233.Inverse oscillation signal/PLS controls the conducting of first oscillation switch 230 and the 3rd oscillation switch 232 and ends.With reference to shown in Figure 3, the first programmable electric capacity 910 is connected in parallel with oscillating capacitance 215, according to digital module PN ... the signal of P1 is in order to the demodulation switching frequency.The switching cycle T of the capacitance C910 decision switching frequency of the capacitance C215 of the resistance value R210 of resistance 210, oscillating capacitance 215 and the first programmable electric capacity 910, switching cycle T can be obtained by following formula:

$T=\frac{({\mathrm{<figure-callout\; id="215"\; label="C"\; filenames="A20041009552800281.png"\; state="\{\{state\}\}">C</figure-callout>}}_{215}+C_{910})\&times;V_{\mathrm{OSC}}}{V_{\mathrm{REF}}/{\mathrm{<figure-callout\; id="210"\; label="R"\; filenames="A20041009552800281.png"\; state="\{\{state\}\}">R</figure-callout>}}_{210}}={\mathrm{<figure-callout\; id="210"\; label="R"\; filenames="A20041009552800281.png"\; state="\{\{state\}\}">R</figure-callout>}}_{210}\&times;({\mathrm{<figure-callout\; id="215"\; label="C"\; filenames="A20041009552800281.png"\; state="\{\{state\}\}">C</figure-callout>}}_{215}+C_{910})\&times;\frac{V_{\mathrm{OSC}}}{V_{\mathrm{REF}}}...\left(15\right)$

VOSC=VH-VL wherein.The capacitance C910 of the first programmable electric capacity 910 is according to digital module PN ... the variation of P1 and thereupon changing.

Fig. 6 is the current-waveform detector 300 of preferred embodiment of the present invention.One peak detector (peakdetector) comprises comparator 310, current source 320, switch 330, switch 340 and the 3rd electric capacity 361.The peak value of sampling current signal VCS is in order to produce peak-current signal (peak-current signal).The anode input of comparator 310 is provided by current signal VCS.The negative terminal input of comparator 310 is connected to the 3rd electric capacity 361.Switch 330 is connected between current source 320 and the 3rd electric capacity 361.The output of comparator 310 is used for conducting or cutoff switch 330.Switch 340 and the 3rd electric capacity 361 are connected in parallel, in order to the 3rd electric capacity 361 is discharged.Switch 350 periodically is conducting to the peak-current signal of second output capacitance 362, in order to produce current waveform signal VW.The action that switch 350 carries out conducting or ends by oscillator signal PLS.

Fig. 7 is the integrator 400 of preferred embodiment of the present invention.Second voltage changes current converter (secondV-to-I converter) and comprises operational amplifier 410, resistance 450, transistor 420,421 and 422.The anode input of operational amplifier 410 is provided by current waveform signal VW.The negative terminal input of operational amplifier 410 is connected to resistance 450.The grid of the output driving transistors 420 of operational amplifier 410.The source electrode of transistor 420 is connected to resistance 450.Second voltage changes current converter according to current waveform signal VW, by the drain electrode generation electric current I 420 of transistor 420.Transistor 421 and 422 forms has 2: 1 current mirror of ratio.Electric current I 420 is used for producing programmable charging current IPRG by the drain drives current mirror of transistor 422.This programmable charging current IPRG can be expressed as:

$I_{\mathrm{PRG}}=\frac{1}{R_{450}}\&times;\frac{V_W}{2}...\left(16\right)$

Wherein R450 is the resistance value of resistance 450.

Time electric capacity 471 is used for producing integrated signal (integrated signal).First switch 460 is connected between the drain electrode and time electric capacity 471 of transistor 422.This first switch 460 carries out conducting and the action that ends by discharge time signal SDS.Second switch 462 is connected in parallel with time electric capacity 471, in order to time electric capacity 471 is discharged.At the CX of integrator 400 end, the second programmable electric capacity 930 is connected in parallel with time electric capacity 471, can produce the directly proportional relation in order to time constant and the switching frequency with integrator 400.The capacitance C930 of the second programmable electric capacity 930 is according to digital module PN ... the variation of P1 also changes thereupon.The 3rd switch 461 periodically is conducting to the integrated signal of the 3rd output capacitance 472, in order to produce current feedback signal VI.Oscillator signal PLS controls the conducting of the 3rd switch 461 and ends.Across the current feedback signal VI at the 3rd output capacitance 472 two ends thereby can obtain:

$V_I=\frac{1}{R_{450}\&times;(C_{471}+C_{930})}\&times;\frac{V_W}{2}\&times;T_{\mathrm{DS}}...\left(17\right)$

According to equation (4)-(7), the secondary side switch current IS of current feedback signal VI and power supply unit and the directly proportional relation of output current IO.Therefore, equation (9) can be write as again:

$V_I=m\&times;\frac{T_{\mathrm{NS}}}{T_{\mathrm{NP}}}\&times;R_S\&times;I_O...\left(18\right)$

Wherein m is a fixed value, can be determined by following formula:

$m=\frac{{\mathrm{<figure-callout\; id="210"\; label="R"\; filenames="A20041009552800281.png"\; state="\{\{state\}\}">R</figure-callout>}}_{210}\&times;({\mathrm{<figure-callout\; id="215"\; label="C"\; filenames="A20041009552800281.png"\; state="\{\{state\}\}">C</figure-callout>}}_{215}+C_{910})}{R_{450}\&times;(C_{471}+C_{930})}\&times;\frac{V_{\mathrm{OSC}}}{V_{\mathrm{REF}}}...\left(19\right)$

The directly proportional relation of the resistance value R210 of the resistance value R450 of resistance 450 and resistance 210.The directly proportional relation of capacitance C910 of the capacitance C930 of the capacitance C471 of time electric capacity 471 and the second programmable electric capacity 930 and the capacitance C215 of oscillating capacitance 215 and the first programmable electric capacity 910.Therefore, current feedback signal VI is proportional to the output current IO of power supply unit.

Fig. 8 is the circuit diagram of pulse duration demodulator 500 of the present invention.Pulse duration demodulator 500 comprises NAND gate logical circuit 511, D type flip-flop 515, AND door 519, blanking circuit (blankingcircuit) 520 and inverter 512 and inverter 518.Move supply voltage VCC in the D input of D type flip-flop 515 to.Oscillator signal PLS drives the input of inverter 512.The output of inverter 512 is connected to the clock pulse input of D type flip-flop 515, with so that switching signal VPWM is an enabled status.The output of D type flip-flop 515 is connected to first end input of AND door 519.Second end input of AND door 519 is connected to the output of inverter 512.This switching signal of AND door 519 output VPWM are used for switching power supply.The replacement input of D type flip-flop 515 is connected to the output of NAND gate logical circuit 511.First end input of NAND gate logical circuit 511 is provided by reset signal (reset signal) RST, and making switching signal VPWM in order to another cycle of one-period is disabled state.Second end input of NAND gate logical circuit 511 is connected to the output of blanking circuit 520, in case switching signal VPWM is an enabled status, in order to the minimum ON time (minimum on-time) of guaranteeing switching signal VPWM.The minimum ON time of switching signal VPWM will be guaranteed minimum discharge time of TDS, and this will guarantee a suitable repeatedly sampling, in voltage-waveform detector 100 in order to sampling voltage signal VAUX.Discharge time TDS and switching signal VPWM the directly proportional relation of ON time.With reference to equation (1), (2), (4) and secondary side inductance value LS, shown in equation (20), discharge time, TDS can represent shown in equation (21):

$L_S={\left(\frac{T_{\mathrm{NS}}}{T_{\mathrm{NP}}}\right)}^2\&times;L_P...\left(20\right)$

$T_{\mathrm{DS}}=\left(\frac{V_{\mathrm{IN}}}{V_O+V_F}\right)\&times;\frac{T_{\mathrm{NS}}}{T_{\mathrm{NP}}}\&times;T_{\mathrm{ON}}...\left(21\right)$

Wherein TON is the ON time of switching signal VPWM.

The input of blanking circuit 520 is provided by switching signal VPWM.When switching signal VPWM is an enabled status, blanking circuit 520 will produce the replacement that blanking signal (blanking signal) VBLK forbids D type flip-flop 515.Blanking circuit 520 comprises NAND gate logical circuit 523, current source 525, electric capacity 527, transistor 526 and inverter 521 and 522.The input of switching signal VPWM supply inverter 521 and first end input of NAND gate logical circuit 523.527 chargings of 525 pairs of electric capacity of current source.Transistor 526 and electric capacity 527 are for being connected in parallel.The conducting of the output control transistor 526 of inverter 521 with end.The input of inverter 522 is connected to electric capacity 527.The output of inverter 522 is connected to second end input of NAND gate logical circuit 523.The output output blanking signal VBLK of NAND gate logical circuit 523.The pulse duration of the capacitance decision blanking signal VBLK of the electric current of current source 525 and electric capacity 527.The input of inverter 518 is connected to the output of NAND gate logical circuit 523.The output of inverter 518 produces clear signal (clearsignal) CLR, be used for control switch 123, switch 124, switch 340 and second switch 462 conducting with end.

Fig. 9 is the circuit diagram of adder 600 of the present invention.One operational amplifier 610, transistor 620, transistor 621, transistor 622 formed the 3rd voltage with resistance 650 changes current converter (third V-to-Iconverter), according to the output of ramp signal RMP in order to produce electric current I 622.The anode input of operational amplifier 611 is provided by current signal VCS.The anti-phase input and the output of this operational amplifier 611 connect, and are used for setting up operational amplifier 611 as buffer (buffer).The drain electrode of transistor 622 is connected to the output of operational amplifier 611 by resistance 651, produces slope signal VSLP in the drain electrode of transistor 622, this slope signal VSLP thereby with ramp signal RMP and the directly proportional relation of current signal VCS.

Figure 10 shows the module generator 900 according to preferred embodiment of the present invention.One clock pulse generator (clock generator) 951 produces clock signal (clock signal) CK.A plurality of buffers 971,972 and 975, and XOR gate 952 forms linear displacement buffers (linear shift register), according to clock signal CK in order to produce linear code (linear code).The multinomial (polynomials) of the input decision linear displacement buffer of XOR gate 952, and the output of decision linear displacement buffer.This digital module sign indicating number (digital pattern code) PN ... P1 can adopt the part that stems from linear code to carry out optimized application.

Figure 11 is the programmable electric capacity of preferred embodiment of the present invention, for example first programmable electric capacity 910 and the second programmable electric capacity 930.Programmable electric capacity comprises the switching type capacitor device (switching-capacitor sets) that is connected in parallel with each other, capacitor C 1, C2 ..., CN and switch S 1, S2 ... SN forms the switching type capacitor device respectively.Switch S 1 and capacitor C 1 are for being connected in series, and switch S 2 and capacitor C 2 are for being connected in series, and switch S N and capacitor C N are for being connected in series.Digital module sign indicating number PN ... P1 control switch S1, S2 ... the conducting of SN with end, thereby change the capacitance of programmable electric capacity.

Main purpose of the present invention is to provide a switching control device at the primary side of power supply unit, not needing optical coupler and secondary side to stablize under the situation of adjuster, in order to obtain precise output voltage and maximum output current.And the present invention further proposes the characteristic of frequency hopping, reduces electromagnetic interference in order to the frequency spectrum of the switching frequency that prolongs switching signal, therefore the volume of power supply unit and cost can be reduced.

Certainly; the present invention also can have other various embodiments; under the situation that does not deviate from spirit of the present invention and essence thereof; those of ordinary skill in the art can make various corresponding changes and distortion according to the present invention, but these corresponding changes and distortion all should belong to the protection range of claim of the present invention.

Claims (17)

1, a kind of switching control device is connected in the primary side of a transformer, and control is switched this transformer so that direct current electric power output to be provided, and it is characterized in that, includes:

One switches power switch, and the one output is connected in an end of the primary side of this transformer, and the other end of the primary side of this transformer is connected in an input voltage;

One current sensing device is connected to another output of this power switched switch, by the change action of this power switched switch, in order to sensing one current signal;

One controller, be connected in a control end, this current sensing device of this power switched switch, and be connected in an auxiliary winding of this transformer by a voltage divider, obtain a discharge time of a voltage signal and this transformer and obtain this current signal from this auxiliary winding, and export a switching signal to this control end from this current sensing device;

This controller is between the off period of this switching signal, by repeatedly taking a sample this voltage signal and produce a voltage feedback signal this discharge time, and in conduction period of this switching signal, this current signal of integration, to produce a current feedback signal, carry out NAND gate this voltage feedback signal of logical operation and this current feedback signal, in order to adjust this switching signal.

2, switching control device according to claim 1 is characterized in that, this controller includes:

One voltage-waveform detector, be connected to the auxiliary winding of being somebody's turn to do of this transformer by ohmic voltage divider, receive this voltage signal by this auxiliary winding, produce this voltage feedback signal and a discharge time signal by this voltage signal of repeatedly taking a sample, this discharge time signal is represented the discharge time of this transformer;

One current-waveform detector is connected to this current sensing device, obtains this current signal by this current sensing device, by measuring this current signal in order to export a current waveform signal;

One integrator, be connected to this current-waveform detector and this voltage-waveform detector, receive this current waveform signal by this current-waveform detector, receive this discharge time signal by this voltage-waveform detector, this current waveform signal of integration and this discharge time signal are in order to export this current feedback signal;

One oscillator is in order to export an oscillator signal and a ramp signal, this oscillator signal switching frequency that decides this switching signal;

One voltage circuit error amplifier is connected to this voltage-waveform detector, receives this voltage feedback signal, in order to amplify this voltage feedback signal;

One current circuit error amplifier is connected to this integrator, receives this current feedback signal, in order to amplify this current feedback signal;

One adder is connected to this current sensing device and this oscillator, receives this current signal by this current sensing device, receives this ramp signal by this oscillator, in order to produce a slope signal;

One peak current limiter is connected to this current sensing device, receives this current signal, in order to limit the maximum of this current signal;

One first comparator is connected to this adder and this voltage circuit error amplifier, and this voltage feedback signal after receiving this slope signal and amplifying is as voltage control;

One second comparator is connected to this oscillator and this current circuit error amplifier, and this current feedback signal after receiving this ramp signal and amplifying is as Current Control; And

One pulse width demodulator, be connected to this oscillator and connect this peak current limiter, this first comparator and this second comparator by a NAND gate logical circuit, according to the output of this oscillator signal, this peak current limiter, the output of this first comparator and the output of this second comparator, control the pulse bandwidth of this switching signal.

3, switching control device according to claim 2 is characterized in that, this controller also includes a programmable current source, be connected in the input of this voltage-waveform detector, receive the temperature of this controller, in order to export a programmable electric current, as the temperature-compensating of this controller.

4, switching control device according to claim 2 is characterized in that, this controller also comprises:

One module generator is in order to produce a digital module sign indicating number;

One first programmable electric capacity is connected to this oscillator and this module generator, adjusts capacitance according to this digital module sign indicating number, in order to the switching frequency of this switching signal of demodulation; And

One second programmable electric capacity is connected to this integrator and this module generator, adjusts capacitance according to this digital module sign indicating number, uses so that the switching frequency of the time constant of this integrator and this switching signal produces the directly proportional relation.

5, switching control device according to claim 2 is characterized in that, the time constant of this integrator and the switching cycle of this switching signal have directly proportional relation.

6, switching control device according to claim 2 is characterized in that, this voltage-waveform detector comprises:

One sampling pulse generator is in order to produce the sampling pulse wave signal;

One critical voltage, wherein this critical voltage adds that this voltage signal produces Bit Shift reflected signal surely;

One first signal generator, be connected to this sampling pulse generator, according to according to the sampling pulse wave signal in order to produce first sampled signal and second sampled signal, wherein this first sampled signal and this second sampled signal are to be used for control its switch alternately to move so that this voltage signal is taken a sample;

One time delay circuit receives this switching signal and produces a time of delay;

One secondary signal generator is connected in this time delay circuit, this critical voltage and this first signal generator, according to this time of delay, accurate Bit Shift reflected signal in order to produce this discharge time signal;

One first electric capacity and one second electric capacity by diverter switch alternating movement this voltage signal of taking a sample, are obtained one first respectively and are kept voltage and one second and keep voltage;

One buffer amplifier is connected in this first electric capacity and this second electric capacity, first keeps voltage and this second high voltage of keeping voltage is kept signal by this; And

One first output capacitance is connected in this buffer amplifier, and this keeps signal in order to export this voltage feedback signal by taking a sample.

7, switching control device according to claim 2, it is characterized in that, this voltage-waveform detector this voltage signal of repeatedly taking a sample produces final voltage, in order to produce this voltage feedback signal, wherein before the secondary side switch current of this transformer drops to zero, take a sample immediately and measure this final voltage.

8, switching control device according to claim 4 is characterized in that, this module generator comprises:

One clock pulse generator is in order to produce clock signal; And

One linear displacement buffer is connected in this clock pulse generator, according to this clock signal in order to produce this digital module sign indicating number.

9, switching control device according to claim 2 is characterized in that, this oscillator comprises:

One first voltage changes current converter, in order to produce vibration charging current and oscillating discharge electric current, comprises vibration operational amplifier, an oscillation resistance and an oscillistor;

One oscillating capacitance;

One first oscillation switch, wherein first end points of this first oscillation switch is provided by this vibration charging current, and second end points of this first oscillation switch is connected to this oscillating capacitance;

One second oscillation switch, wherein first end points of this second oscillation switch is connected to this oscillating capacitance, and second end points of this second oscillation switch is driven by this oscillating discharge electric current;

One vibration comparator has anode input and is connected to this oscillating capacitance, and wherein this vibration comparator produces this oscillator signal;

One the 3rd oscillation switch has first end points and is supplied with by high critical voltage, and second end points is connected to the negative terminal input of this vibration comparator;

One the 4th oscillation switch has first end points, be to be supplied with by low critical voltage, and second end points is connected to this negative terminal input of this vibration comparator; And

One vibration inverter has the output that an input is connected to this vibration comparator, in order to produce oscillator signal, this vibration inverter output inverse oscillation signal; Wherein this oscillator signal conducting or by this second oscillation switch and the 4th oscillation switch, wherein this inverse oscillation signal conducting or end this first oscillation switch and the 3rd oscillation switch.

10, switching control device according to claim 9, it is characterized in that, this oscillating capacitance and one first programmable electric capacity are for being connected in parallel, wherein this first programmable electric capacity comprises the vibration switch-capacitor, and wherein this vibration switch-capacitor carries out conducting by this digital module sign indicating number or ends.

11, switching control device according to claim 2 is characterized in that, this current-waveform detector comprises:

One peak detector, the peak value by measuring this current signal is in order to produce peak-current signal;

One the 3rd electric capacity is in order to keep this peak-current signal;

One second output capacitance is in order to produce this current waveform signal; And

One switch, to this second output capacitance, wherein this switch carries out conducting by this oscillator signal or ends in order to this peak-current signal of conducting.

12, switching control device according to claim 2 is characterized in that, this integrator comprises:

One second voltage changes current converter, produces a programmable charging current according to this current waveform signal;

One time electric capacity is in order to produce integrated signal;

One first switch, wherein first end points of this first switch is supplied with by this programmable charging current, and second end points of this first switch is connected to this time electric capacity, and wherein this first switch carries out conducting by this discharge time signal or ends;

One second switch is connected in parallel with this time electric capacity, in order to this time electric capacity that discharges;

One the 3rd output capacitance is in order to export this current feedback signal; And

One the 3rd switch, to the 3rd output capacitance, wherein the 3rd switch carries out conducting by this oscillator signal or ends in order to this integrated signal of conducting.

13, switching control device according to claim 1 is characterized in that, this switching signal has a minimum ON time, in case this switching signal is an enabled status, can further guarantee the minimum value of this discharge time, in order to this voltage signal of repeatedly taking a sample.

14, a kind of switching control device is connected in a transformer, and control is switched this transformer so that direct current electric power output to be provided, and it is characterized in that, includes:

One switches power switch, is connected in this transformer and drives transformer in order to switching;

One controller is connected in a control end of this power switched switch and an auxiliary winding of this transformer, obtains a discharge time of a voltage signal and this transformer from this auxiliary winding, and exports a switching signal to this control end;

This controller by repeatedly taking a sample this voltage signal and produce a voltage feedback signal this discharge time, and produces this switching signal according to this voltage feedback signal between the off period of this switching signal.

15, switching control device according to claim 14 is characterized in that, this controller comprises:

One voltage-waveform detector is connected to this auxiliary winding by ohmic voltage divider, receives this voltage signal by this auxiliary winding, produces this voltage feedback signal and a discharge time signal by this voltage signal of repeatedly taking a sample;

One oscillator is in order to export an oscillator signal and a ramp signal, this oscillator signal switching frequency that decides this switching signal;

One voltage circuit error amplifier is connected to this voltage-waveform detector, receives this voltage feedback signal in order to amplify this voltage feedback signal; And

One pulse width demodulator receives the output of this voltage circuit error amplifier, in order to produce a reset signal, is used for controlling the pulse bandwidth of this switching signal.

16, switching control device according to claim 14, it is characterized in that, this controller also includes a programmable current source, be connected in the input of this voltage-waveform detector, receive the temperature of this controller, in order to export a programmable electric current, as the temperature-compensating of this controller.

17, switching control device according to claim 14 is characterized in that, this controller also comprises:

One module generator is in order to produce a digital module sign indicating number;

One first programmable electric capacity is connected to this oscillator and this module generator, adjusts capacitance according to this digital module sign indicating number, in order to the switching frequency of this switching signal of demodulation; And

One second programmable electric capacity is connected to this integrator and this module generator, adjusts capacitance according to this digital module sign indicating number, uses so that the switching frequency of the time constant of this integrator and this switching signal produces the directly proportional relation.

Images