TW201212496A - Switching mode power supply with burst mode operation - Google Patents

Abstract

This invention discloses a control method and device of switch mode power supply (SMPS). When SMPS works on light load, a high frequency pulse signal is modulated by a low frequency modulation signal and switch driver signal is generated, thus, during signal modulation cycle, the switch is driven by a series of high frequency pulses or maintain off status to realize close loop regulation of SMPS output.

Description

201212496 VI. Description of the Invention: [Technical Field] [0001] The present invention relates to a switching power supply capable of entering biir<5+J, n~rst~m〇de (intermittent mode) under light load conditions, and more particularly The intermittent mode of the switching power supply is erected. [0002]

D 〇 099129547 [Prior Art] Today, more and more electronic products are powered by switching power supplies, which stems from the good characteristics of the switching power supply itself. The switching power is generally above several tens of kilohertz, and the semiconductor device is turned on and off to transfer energy. Therefore, it has a small size, light weight, and high conversion efficiency: advantages. In order to achieve energy conversion, the switching power supply can adopt various lifting structures to describe the principle of switching power supply by using a wide range of flyback topology structures as an example. In general, it can be used in the following functional modules: " input unit, energy blending unit, energy wheeling unit, feedback I疋 and off control single core AC voltage energy unit I, rectified and filtered The action plate is smooth and straight, and the switching control unit controls the conduction of the switch according to the feedback signal of the feedback unit, and the DC voltage is converted into a high frequency signal, and then the stabilized DC voltage is outputted by the change. The combination of 'final get = normal Μ situation' electronic products will also be servant in light-loaded machine-like "collectively referred to as light-load state". In light load and ^, the load requires a power supply knife after the year is small 'if the control unit is still The original frequency drives the switching tube, the frequency is very high, and the corresponding switching tube switching loss becomes remarkable, and the conversion efficiency is improved. For this reason, the 'returnable lie method. Simply starting from the table> the light load status requirement The switching frequency is lower than 20KHZ, the frequency form number is _ ^ 3 1/* 27 ! 0993444896-0 201212496 falls into the 曰 frequency dry perimeter 'this will cause noise problems again. For the 4 problem 'more f pass is to use intermittent Mode. The so-called intermittent plate type, that is, the control switch is driven by the high-frequency pulse signal for a period of time (set time length M〇n), and remains in the off state during the adjacent other time period (the duration is set) The two state loops alternate. Thus, the equivalent switching frequency is reduced, which can effectively improve the efficiency. However, in the prior art, the durations M〇n and Moff are automatically adjusted according to the power demand of the load, which causes Mon and M〇ff's shirt (that is, right The frequency of the modulated signal of the high-frequency pulse signal is not modulated. This uncertainty also introduces a noise problem. [0003] The technical problem to be solved by the present invention is a switching power supply. In the light load or standby & amp, the prior art intermittent mode exists because the frequency of the modulated signal is automatically adjusted according to the power demand of the load, resulting in uncertainty of the frequency of the modulated signal, which may cause noise problems. The invention adopts the following technical solutions. According to the invention, the switching power supply and the control circuit thereof are provided, and when the switching power supply enters the light load state, the control inductor-shooting 1 power supply operates in the intermittent mode. The switching power supply operates in the intermittent mode. During the mode, the frequency of both the high-frequency pulse signal that controls the switch to be turned on and off, and the low-frequency modulation signal that modulates the high-frequency pulse signal are adjusted to a set value, and the output of the switching power supply is realized by adjusting the duty ratio of the low-frequency modulated signal. Closed loop control 099129547 When the switching power supply operates in a non-light load state, the control circuit operates at p Any one of WM control mode, quasi-resonant control mode, and off-time control mode. Corresponding to off-time control mode, when the switching power supply operates in a non-light load state, the switching frequency decreases as the load becomes lighter; From the non-form number A0101, page 4/27 pages, 0993444896-0 201212496, the light load state enters the light load state, and the switching frequency is continuously unchanged. The switching power supply of the present invention includes a control circuit, and the control circuit includes: a feedback loop, the feedback loop Outputting a feedback signal to the control circuit according to the load state, the control circuit compares the feedback signal with the set threshold signal reflecting the light load; and according to the comparison result, the control circuit switches the switching power supply to operate in the normal mode in the intermittent mode or the non-light load state; a high frequency pulse signal generator, receiving the feedback signal and the current detection signal, and outputting a high frequency pulse signal; an intermittent mode generator receiving the feedback signal, outputting a control signal to the high frequency pulse signal generator, and controlling the output pulse signal thereof Frequency; the intermittent mode generator also outputs a low frequency modulated signal; The current detecting module detects a current flowing through the switch and outputs a current detecting signal. The modulating circuit receives the high frequency pulse signal and the low frequency modulation signal, and outputs a switch control signal to control the switch of the switching power supply. The low frequency modulated signal frequency is less than a lower limit of a frequency range to be excluded, the high frequency pulse signal frequency being greater than an upper limit of a frequency range to be excluded. The range of frequencies that need to be excluded includes the audio range. The present invention further provides a control method for a switching power supply that operates in a batch mode when the load of the switching power supply is in a light load state. When the switching power supply operates in the intermittent mode, the control method further includes the following steps: setting a frequency of the high frequency pulse signal for controlling the switch to be turned on and off in the switching power supply; setting a frequency of the low frequency modulation signal for modulating the high frequency pulse signal; Adjusting the duty cycle of the low frequency modulated signal enables closed loop control of the switching power supply 099129547 Form No. A0101 Page 5 / Total 27 Page 0993444896-0 201212496. The method of judging that the load is in the light load state is to compare the feedback signal from the output of the switching power supply with the set threshold signal reflecting the light load, and based on the comparison result, determine that the load is in the light load state. By adopting the technical solution proposed according to the inventive concept, when the switching power supply operates in the intermittent mode when its load is in the light load state, the frequency of the high frequency pulse signal and the frequency of the low frequency modulation signal can be kept within the set range. Thereby avoiding the audio range, reducing noise, and better solving the technical problem. In addition, the invention also has the advantages of simple circuit structure and low cost. [Embodiment] FIG. 1 is a specific embodiment according to the inventive concept, which is based on a flyback topology. The invention is equally applicable to other switching power supply topologies. This embodiment uses a flyback topology as an illustration, but for ease of explanation. In this embodiment, the voltage input signal Vin is adjusted to provide energy to the load. As shown in Fig. 1, first, the voltage input signal Vin is coupled to the energy transfer unit transformer T1, and the switch S1 is periodically turned on and off under the action of the control signal 101, so that the energy of the primary side of the transformer T1 is coupled to the pair. Then, through the rectification of the diode D1 and the filtering of the capacitor C1, a constant value signal ϋο is finally obtained, and the constant value signal may be the voltage signal Vo or the current signal 1〇. In a specific embodiment of the invention, the signal is a voltage signal Vo. The input signal of the control circuit 105 is all from the switch current detection signal 102, and various current detecting means can be applied, such as detecting the current I, the voltage drop across a resistor; the other is from the signal U to be sampled and fed back through the network. 103 processed feedback signal 104, 099129547 Form No. A0101 Page 6 of 27 0993444896-0 In response to the feedback signal 104, the control circuit 105 controls the conduction and closing of the switch S1 to achieve closed-loop adjustment of the amount to be adjusted Uo. The control circuit 105 may be an integrated circuit, a discrete device, or a combination of both. The feedback signal 104 can be any electrical signal that reacts to the load state, such as a voltage signal, a current signal, or a combination of a voltage signal and a current signal (e.g., a power signal). In a specific embodiment of the invention, the switch S1 is a MOSFET, the amount to be adjusted Uo is a voltage signal V 〇, and the feedback signal 104 is a voltage: signal. The control mode of the switching power supply includes a fixed frequency mode and a frequency conversion mode. The former is like an ordinary PWM control mode, and the latter is an off-time control mode and a quasi-vibration control mode. In the ordinary PWM control mode, the output is adjusted by controlling the on-time of the switch; in the off-tin] e control mode, the output is adjusted by controlling the switch off time; in the quasi-resonant control mode, the control switch is turned on. The duration adjusts the output. When the voltage drop across the switch reaches a minimum, the switch turns on. 2 is a flow chart of a method in accordance with the inventive concept. Module 202 detects the output power of the switching power supply, and module 203 determines a feedback signal based on the detected output power. In a specific implementation manner in which the control circuit 105 adopts a common PWM control mode or a quasi-resonant control mode, the magnitude of the feedback signal is related to the switch conduction time; and the control circuit 105 adopts the 〇ff-1I me control mode. The size of the feedback signal is related to the size of the switching frequency. Module 204 compares the feedback signal determined by module 203 with a light load threshold signal. Correspondingly, in a specific implementation manner in which the control circuit 105 adopts a normal PWM control mode or a quasi-resonant control mode, the size of the light load threshold signal is related to the switch conduction time. In a specific embodiment of the invention, the light load threshold signal is set to correspond to 25% of the switch on time of the full load form number A0101 page 7 / total 27 pages 201212496; the control circuit 105 adopts the 〇ff_time control mode In a specific implementation, the size of the light load threshold signal is related to the size of the switching frequency. In a specific embodiment of the invention, the light load threshold signal is set to correspond to 2% of the full load switching frequency. When the output power represented by the feedback signal is greater than the light load threshold power represented by the light load threshold signal, the switching power supply is in a non-light load state, enters the module 2 〇 5, and the control circuit operates in a normal working mode, such as the ordinary pWM mode and the standard Resonant control mode, of f-1 ime control mode; conversely, the switching power supply is in light load state 'Enter module 206, and the control circuit works in intermittent mode.

Figure 3 is a block diagram showing a block diagram of a specific embodiment of the flow circle according to the method of Figure 2, which is based on a flyback topology and an off-time control mode. Corresponding to the mode_2〇5 in Fig. 2, that is, in the non-light load state, the intermittent mode generator 302 does not function, and the high frequency pulse signal generator 3 0 3 is in the feedback 彳g No. 1 〇4 and the switch current detecting module. 3 〇1 output current detection signal 102 under the control switch S1 'switching power supply works in 〇 ff_ time mode. Corresponding to the module 2〇6 in Fig. 2, that is, in the light load state, the intermittent mode generator 302 functions 'on the one hand, the output signal 305 controls the frequency of the output signal 307 of the high frequency pulse signal generator 303, and the other The low frequency modulation signal 306 is modulated by the AND gate 308 to the output signal 307 of the high frequency pulse signal generator 303. The modulated signal is applied to the drive circuit 309 to generate a signal 310 to control the switch si. In a specific embodiment of the invention, the detection of current J sl is achieved by detecting the voltage across resistor R1. Figure 4 is a detailed schematic diagram of the block diagram shown in Figure 3. The high frequency pulse signal generator 303 includes a high frequency pulse signal frequency control circuit 401, a circuit selection module 402, a third comparator 403, and an RS flip flop 404. High frequency pulse 099129547 Form number A0101 Page 8 of 27 0993444896-0 201212496 The signal frequency control circuit 401 is used to set the high frequency pulse signal generator

The frequency of the output signal 307, 303, can be achieved by adjusting the capacitance of the capacitor C2 and/or the current source 12. The circuit selection module 402 compares the size of the input signal' to select either a large signal or a small signal as the selected output signal. Corresponding to the non-light load state, the circuit selection module 402 selects the feedback signal 1〇4 output by the feedback network 103 as the input of the inverting terminal of the third comparator 403; and corresponding to the light load state, the circuit selection module 402 selects the intermittent mode generator 302. The output signal 305 serves as an input to the inverting terminal of the third comparator 403. The S terminal of the RS flip-flop 404 is connected to the output of the third comparator 403, the R terminal is connected to the output current detection signal 1〇2 of the switch current detecting module 301, and the output signal 307 is sent to the gate 308 via the intermittent mode generator 302. After the output signal 306 is modulated, the switch S1 is controlled. The output signal 307 of the RS flip-flop 404 is simultaneously supplied to the Tpulsel module to generate a pulse signal that controls the discharge of the capacitor C2.

The intermittent mode generator 302 includes a low frequency modulated signal frequency control module 410, a light load threshold setting module 411, a first subtractor 412, a second subtractor 413, a first comparator 414 and a second comparator 415. The low frequency modulation signal frequency control module 410 outputs the frequency of the low frequency modulation signal 306 by setting the intermittent mode generator 302. The frequency change can be adjusted by adjusting one or more of the voltage source V3 voltage value, the capacitance C3 capacitance value, and the resistance R3 resistance value. to realise. The light load threshold setting module 411 is configured to set when the switching power supply enters the light load state. The output thereof is connected to the inverting terminal of the comparator 415 and serves as an input of the subtractor 413. In a specific embodiment of the invention, the light load threshold corresponds to Load 20% of full load power. The first subtractor 412 performs logic processing on the feedback signal 1〇4 and inputs the same phase of the first comparator 414. The feedback signal 104 has a size of vfb, Vref is a preset signal, and the logic function is 099129547. Form No. A0101 Page 9 / Total 27 pages 0993444896-0 201212496

Vsubl = Vref - Vfb, Vsubl is the size of the output signal 421 of the first subtractor 412. The second subtractor 41 3 performs logic processing on the output of the load threshold setting module 411 and outputs the result to the circuit selection module 4〇2, the logic function is Vsub2 = Vref-Vth, and Vth is the value of the output threshold value of the load threshold setting module 411. The second subtractor 413 outputs a signal 305 having a size of "pi?". The in-phase terminal of the first comparator 414 is connected to the output of the first subtractor 412, and the inverting terminal is connected to the output of the low-frequency modulation signal frequency control module 41? The low frequency withering code 306 is sent to the gate 308, and the output signal 307 of the high frequency pulse signal generator 3〇3 is modulated. The inverting terminal of the second comparator 415 is connected to the low frequency modulation signal frequency control module 41 o. The anti-袓 terminal is connected to the load threshold undetermined module 411, and the output signal 1420 is sent to the Tpuise2 module to generate a pulse signal for discharging the control capacitor C3. A sawtooth signal is obtained at the non-phase of the comparator 415, and the sawtooth signal frequency is obtained. The frequency is the same as the frequency of the low-frequency modulation signal 3〇6. The specific working principle of the embodiment shown in Fig. 4 will be described below with reference to the waveform diagram 5. The 5A diagram corresponds to the non-light load, and the 5B diagram corresponds to the light load. Work situation In a specific embodiment of the present invention, the value Vfb of the return signal 1〇4 becomes larger as the load becomes lighter. When Vfb is smaller than the value Vsub2 of the second subtractor 413 rounding signal 305, the switching power supply operates. In the non-light load state, the circuit selection module 402 selects the feedback signal 1〇4 as the input of the inverting terminal of the third comparator 4〇3. In FIG. 5A, VC2 is the voltage waveform across the capacitor C2, and VR1 is the end of the resistor R1. The voltage waveform, ^ is the signal of the 4th s terminal of the flip-flop, VR is the signal of the R terminal of the flip-flop, and the waveform of the output signal 307 of the high-frequency pulse signal generator 303 is in the non-light load state, and the switch driving signal 310 is The waveform is the same as the Vn waveform. With a high frequency pulse signal period (0993444896-0 099129547 Form No. A0101 Page 10 / Total 27 Page 201212496

TsO to Ts2) will be described as an example. At Ts〇, the voltage across capacitor C2 rises to Vfb, and the third comparator 4〇3 outputs a high level, which on the one hand sets flip-flop 404, outputs a high level, switch S1 turns on, and switch current isi increases. Large, the voltage vri rises accordingly. On the other hand touch aTpulsei

). During the period from TsO to Tsl, the voltage continues to rise. When the preset voltage value Vimax of Vsense is reached, the comparator 416 outputs a high level, the flip-flop 404 is reset, the low level is turned on, the switch is turned off, and the voltage is v R1. One thousand is 0, and it will remain until the next cycle begins. At time Ts2, capacitor C2 voltage VC2 rises again to Vfb. Thereafter, each physical quantity repeats the waveform between Ts and Ts2.

The module produces a pulse signal having a width Tpl that causes the voltage across capacitor C2 to be fully discharged during the pulse time. After the Tp丨 period, the capacitor C2 is again charged by the current source 12 until the next cycle begins (the VC2 waveform period is Ts at the time Ts2, that is, the Vn period is Ts, which includes two parts of time, Tpl and Tchrs-n. In this implementation In the example, Tpl is a fixed duration 'Tchrs-n is determined by the size of the capacitor Μ, the current source u, and the feedback signal kl 〇 4. The capacitance of the capacitor C2 is Cs, and the current of the current source 12 is s. The formula is 'hrs-n. Ϊ;, the change of the size of the feedback signal 104, or by adjusting one or both of the capacitance value of the capacitor C2 and the current value of the current source 12, the size of the Tchrs_n can be adjusted, thereby changing the period Ts. That is, the frequency of the switch drive signal 31〇 is adjusted. On the other hand, under the condition of non-light load, as the load becomes lighter, the feedback signal 104 becomes larger 'Tchrs-n becomes larger, TS becomes larger, and the frequency of the switch drive signal decreases accordingly. 099129547 Form No. A0101 Page 11 / Total 27 Page 0993444896-0 201212496 When Vfb is less than Vsub2, that is, Vfb < Vref - Vth, equivalent to Vref - Vfb &gt; Vth, that is, the output of the first comparator 414 is always at a high level. In the non-light load state, intermittent mode The generator 302 does not modulate the output signal 307 of the high frequency pulse signal generator 303. When Vfb is greater than Vsub2, the switching power supply operates in a light load state, and the circuit selection module 402 selects Vsub2 as the input of the inverting terminal of the third comparator 403. In Fig. 5B, V" is the voltage waveform of the capacitor C3. Taking TmO to Tm2 as the modulation period as an example, at the time of ΤιηΟ, Ve3 rises to Vth, the second comparator 415 outputs a high level, and a width is generated by Tpulse2. Is the pulse signal of Tp2, the pulse signal causes the voltage across the capacitor C3 to be discharged. After the pulse signal is applied, the voltage across the capacitor C3 is charged again until Τm2. Vb is the output of the first comparator 414, that is, the intermittent mode occurs. The waveform of the output signal 306 of the device 302. After the time Tm2, the respective physical quantities repeat the waveform between Tm0 and Tm2.

The Vu waveform period is Tm, that is, the period of the low frequency modulation signal 306 is Tm, and the period includes two parts of time, Τρ2 and Tchrnl·. In the present embodiment, Τρ2 is a fixed duration, and Tchrm is determined by the magnitudes of voltage source V3, capacitor C3, resistor R3, and light load threshold setting module output signal 422. The voltage value of the voltage source V3 is Vm, the capacitance value of the capacitor C3 is Cm, and the resistance of the resistor R3 is Rm. The calculation formula is: by adjusting the voltage of Vth, the voltage source V3, the capacitance of the capacitor C3, and the resistance R3. One or more of the resistance values can adjust Tchrm, which in turn changes the frequency of the low frequency modulated signal 306. 099129547 Form No. A0101 Page 12/Total 27 Page 0993444896-0 201212496 During the entire light load operation, the circuit selection module 402 selects the signal 3〇5 as the input of the inverting terminal of the comparator, and the high frequency pulse signal generator 303 outputs the signal. The frequency of 307 is not affected by load changes. During light load, a high frequency pulse signal period also contains two parts of time, Tpl and Tchrs-b,

Tchrs-b is the charging duration of capacitor C2 in one cycle during light load, and its expression is chrs-b.

Cs (Kef ~ Vth) Ο The size of the Tchrs-b can be adjusted by adjusting the size of the signal 305, the capacitance of the capacitor C2, and the current value of the current source 12 to change the period of the high-frequency pulse signal. :, corresponding to the non-light load state, Vfb &lt; Vref-Vth, corresponding to the light load state, Vfb &gt; Vref - Vth, so there is a critical point of two state switching, satisfying Vfb = Vref - Vth. At this critical point, when Tchrs-n = Tchrs-b is satisfied, that is, when two states are switched, the frequency of the output signal 307 of the high-frequency pulse signal generator 303 does not abruptly change.

Figure 6 is a schematic diagram of the switch drive signal during light load. Vn is a waveform of the output signal 307 of the high-frequency pulse signal generator 303, and the period is Ts. Vb is a waveform of the low-frequency modulation signal 3〇6 outputted by the intermittent mode generator 302, and the period is Tm. Vg is the waveform of the switch drive signal 310 generated after Vb is modulated by Vb. On the one hand, in a modulation period Tm, Vg has a smaller number of pulses of period Ts than Vn, which can effectively reduce switching loss at light load; on the other hand, by reasonably selecting relevant parameters, it can be light The Ts and Tm at the time of loading are set within a specific range to meet the requirements of noise reduction. After entering the light load state, if the load is further lowered, the value Vfb of the feedback signal 104 will become larger, and the value of the first subtractor 412 output signal 421 is Vsub1 099129547. Form number A0101 Page 13 / Total 27 pages 0993444896-0 201212496 small. It can be seen from FIG. 5B and FIG. 6 that the decrease of Vsub1 causes the duty ratio of the low-frequency modulation signal 306 to decrease, and within one modulation period, the number of high-frequency pulses included in the switch drive and the number 310 is reduced to reduce the load on the load. Energy supply for closed loop regulation of the output. Fig. 7 is a block diagram showing the construction of another embodiment of the flow chart according to the method shown in Fig. 2. This embodiment is based on a just-controlled mode or a quasi-spectral control mode. Corresponding to the PWM control mode, the trigger set bit circuit 7〇1 is the clock signal benefit, corresponding to the quasi-spectral control mode, and the trigger set bit circuit Μ is the valley bottom detection module. The flip-flop sets the bit circuit 7_out signal 702 to the set terminal of the flip-flop 404, and the circuit selection module right selects the -/# as the comparator from the feedback generator 104 and the intermittent mode generator 3Q2 output signal 5. The in-phase signal 704' of the inverting terminal of the 416 is compared with the reset terminal of the triggering current detecting signal 703 to the triggering device 404. The on-time of the switch S1 is determined by the size of the dimming of the comparator 416. After the switch S1 is turned off, for the PWM control mode, the &lt;^ reading 仏旒 occurs, and the clock is set to 099129547 cycles to set the trigger surface; for the quasi-resonant control mode, when the bottom detecting 杈 group detects the switch tube phantom When the drain-source voltage is at a minimum value, it is common knowledge for those skilled in the art to place the flip-flop 4 0 4 in the buffer clock signal generator and the valley-detecting module, and no specific one is made here. The description of the field section corresponds to the module 2〇5 in Fig. 2, that is, the non-light load state, and the intermittent mode occurs that H302 does not function. The circuit selection module 4〇2 outputs the feedback signal 104, and the switch current detection module 3〇 According to the size of the feedback signal 1〇4, that is, the conduction time of the switch S1, the switching power supply operates in the rigid mode or the quasi-resonant mode I. Based on the idea of the present invention, the size of the feedback nickname 104 varies with the load. Light and reduce. Corresponding to the module 206' in FIG. 2, that is, the light load state, the intermittent mode occurs (4), and the form number belongs to 1 UW 27 stomach 099344, 201212496 [0005] ❹ ❹ On the one hand, the circuit selection module 402 outputs a signal 305. The control switch is turned on for a corresponding determined value. On the other hand, the output signal 306 modulates the output signal 307 of the flip-flop 404 through the AND gate 308. The modulated signal is applied to the drive circuit 309 to generate a signal 310 to control the switch S1. . BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a specific embodiment based on a flyback topology in accordance with the teachings of the present invention. Fig. 2 is a flow chart showing a control method of a switching power supply according to the inventive concept. Figure 3 is a block diagram showing the structure of a specific embodiment of the flow chart according to the method of Figure 2. Fig. 4 is a detailed diagram corresponding to the block diagram of the structure shown in Fig. 3. Fig. 5 is a view showing the operation waveforms of the respective physical quantities corresponding to the embodiment shown in Fig. 4. The fifth map corresponds to the non-light load operation, and the fifth map corresponds to the light load operation. Fig. 6 is a view corresponding to the switch driving signal during the light load of the switching power supply of the embodiment shown in Fig. 4. Fig. 7 is a block diagram showing the construction of another embodiment of the flow chart according to the method shown in Fig. 2. [Major component symbol description] 101 control signal 102 current detection signal 103 feedback network 104 feedback signal 105 control circuit form number Α 0101 099129547 page 15 / total 27 page 0993444896-0 201212496 202 ' 203, 204, 205, 206 Module 099129547 301 Switch Current Detection Right Group 302 Intermittent Mode Generator 303 High Frequency Pulse Signal Generator 305, 306, 307, 421, 422, 702 306 Low Frequency Modulation Signal 308 Gate 309 Modulated Signal Via Drive Circuit 310 Switch Drive Signal 401 high frequency pulse signal frequency control circuit 402 circuit selection module 403 third comparator 404 RS flip flop 410 low frequency modulation signal frequency control module 411 light load threshold setting module 412 first subtractor 413 second subtractor 414 first Comparator 415 Second Comparator 416 Comparator 701 Trigger Set Bit Circuit 703 Output Current Detect Signal 704 Input Signal C1, C2, C3 Capacitor D1 Diode 12 Current Source Form No. A0101 Page 16 / Total 27 Page Output Signal 0993444896-0 201212496 Ιο Current signal I, current R1, R3 resistance SI switch T 1 transformer

Tchrs-η, Tchrm, Tpl, Τρ2 duration

Tm, Ts cycle

TsO, Tsl, Ts2 time V3 voltage source

Vb, Vg, V waveform n

VC2 ' vC3 voltage waveform Vfb value Vi max preset voltage value Vin voltage input signal Vo voltage signal V γ number VR1 voltage waveform, voltage. ί'Ά ? | | .v a ' Vsubl size Vth value Uo constant value signal, adjustment Signal, adjustment amount [0007] 099129547 Form No. A0101 Page 17 / Total 27 Page 0993444896-0

Claims (1)

201212496 VII. Patent application scope: 1. A switching power supply, comprising a control circuit for controlling a switch in the power supply, wherein the control circuit comprises a feedback loop, and the feedback loop rotates a feedback signal to the control circuit according to the load state, and the control circuit Comparing the threshold signal reflected by the feedback signal disc to reflect the light load; according to the above comparison result, the control circuit switches the switching power supply to operate in the normal mode in the intermittent mode or the non-light load state. l The switching power supply according to claim i, wherein the switching power supply operates during the intermittent mode, and controls a frequency-frequency pulse signal that is turned on and off by the switch, and a low-frequency modulation signal that modulates a high-frequency pulse signal. The frequency of both is adjusted to the set value, and the closed-loop control of the output of the switching power supply is realized by adjusting the duty ratio of the low-frequency modulation signal. 3. The switching power supply according to claim 2, characterized in that the control circuit further comprises a high frequency pulse signal generator, receiving the feedback signal and the current detection signal 'outputting a high frequency pulse signal; intermittent mode The generator receives the feedback signal, and rotates the control signal to the high frequency pulse signal generator to control the frequency of the pulse signal; the intermittent mode generator also outputs a low frequency modulation signal; the switch current detection module detects the flow through The current of the switch, the current detection signal is rotated; the modulation circuit receives the high frequency pulse signal and the low frequency modulation signal, and outputs a switch control signal to control the switch of the switching power supply. 4. The switching power supply of claim 2, wherein the normal operating mode is a PWM control mode. 099129547 Form No. A0101 Page 18 of 27 0993444896-0 201212496 5. The switching power supply of claim 2, wherein the normal operating mode is a quasi-resonant control mode. The switching power supply of the second aspect, wherein the positive* working mode is the f-time control mode. 7. The switching power supply of claim 6, wherein the switching power supply operates. In the non-light load state, the switching frequency decreases as the load becomes lighter. When the switching power supply enters the light load state from the non-light load state, the switching frequency continues to change. 8. As in the second paragraph of the scope of the patent application The switching power supply is characterized in that the low frequency modulated signal has a frequency lower than a lower limit of a frequency range to be excluded - 9. The switching power according to the second aspect of the patent application, characterized in that The frequency-frequency pulse signal whose frequency is greater than the upper limit of the frequency range to be excluded 〇10. The switching power device according to claim 8 is characterized in that the frequency to be excluded is described in Q. The lower limit of the range is less than or equal to the lower limit of the audio. 11. The switching power supply of claim 9, wherein the upper limit of the frequency range to be excluded is greater than or equal to the upper limit of the audio. The switching power supply of the third aspect, wherein the intermittent mode generator comprises the following modules: a low frequency modulation frequency control module No. 6, the output of which is opposite to the first comparator and the second comparator The same phase is connected; the load light load threshold setting module has an output that is in phase with the second subtractor input end and the second comparator inverting end; the first subtractor, the input is connected to the feedback signal, and the output is coupled to the first comparator. Phase 099129547 Form No. A0101 Page 19 of 27 0993444896-0 201212496 ^Two Subtractor's Wheel Loader Light Loaded Value Set to find the group wheel to take control «Magic Road's high frequency pulse money generator __ The first: the comparator is connected in phase with the first subtractor output, the inverting terminal is connected to the low frequency withering frequency control module, and the output is modulated, and the second comparator is inverting the load. The threshold setting module is rotated, and the low frequency modulation signal frequency control module is connected to the low frequency modulation signal frequency control module in the same phase. The vehicle 13 . 14 . 15 is opened as described in item 3 of the patent scope. The power supply is characterized in that the control circuit (4) is connected to (4) _ (4) and the comparison result of the set value of the light-loaded value is considered to be negative, and the negative mode light cake, the intermittent mode generator output control signal and the difficult money (four) high-frequency pulse signal occur. And the modulation circuit' thereby controlling the switch; the load is considered to be non-light_, and the intermittent mode generator is inactive. The high frequency pulse signal generator controls the switch under the action of the feedback signal and the current detection signal. For example, applying for the special (4) surrounding the 12th Meng Wei, (4) is characterized in that the high frequency pulse signal generator includes a high frequency pulse signal frequency control circuit; the first comparator receives the high frequency pulse signal frequency control circuit at the same phase end The output signal outputs a set bit signal; the circuit selection module 'receives the feedback signal and the control signal from the intermittent mode generator, and outputs a selection signal to the inverting terminal of the third comparator; the flip-flop, the set bit The terminal receives the set bit signal, the reset terminal receives the current detection signal, and the output terminal outputs a high frequency pulse signal. The switching power supply of claim 12, wherein the high frequency pulse signal generator comprises 099129547 Form No. A0101 Page 20 / Total 27 Page 0993444896-0 201212496 Trigger Set Bit Circuit, Output a bit signal; triggering the second bit terminal to receive the set bit signal, the resetting end receiving the current detecting signal, the output end outputting a high frequency pulse signal; the circuit selecting module, receiving the feedback signal and coming from the intermittent mode generator The control 彳s number, the output signal to the switch current detection module. </ RTI> </ RTI> </ RTI> <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt; The bit circuit is a clock signal generator. The switching power supply according to claim 15 is characterized in that, in the control circuit corresponding to the normal operation mode being the quasi-resonant control mode, the trigger setting bit circuit is a valley detecting module. The switching power supply of claim 15, wherein the control circuit determines that the intermittent mode occurs when the load is a light load according to a comparison result between the received feedback signal and the set threshold signal reflecting the light load. The control signal that is rotated by the device is used as the selection signal by the circuit selection module to control the determined duration of the switch; the intermittent value generator does not function when the load is considered to be non-light load, the circuit The selection module transmits the output feedback signal to the open current detection mode 'Newly opened. The off current detection module controls the switch according to the feedback signal and the signal reflecting the switch current. A method of controlling a switching power supply, characterized in that when the load of the switching power supply is in a light load state, the switching power supply operates in an intermittent mode. The method for controlling a switching power supply according to claim 19, wherein when the switching power supply operates in the intermittent mode, the method further comprises the steps of: setting a high frequency for controlling the conduction and interception of the switch in the switching power supply; Pulse signal frequency; 099129547 Form number A0101 Page 21 of 27 0993444896-0 201212496 Set the frequency of the low frequency modulation signal modulating the high frequency pulse signal; realize the output of the switching power supply by adjusting the duty ratio of the low frequency modulation signal Closed-loop control. The control method of the switching power supply according to the second aspect of the invention is characterized in that the feedback signal from the output of the switching power supply and the set threshold signal reflecting the light load are compared, and the load is determined according to the comparison result. The light load state. The control method of the switching power supply according to claim 20, wherein when the load of the switching power supply is in a non-light load state, the switching power supply operates in a PWM control mode v . . . The control method of the switching power supply according to the second aspect of the invention is characterized in that, when the load of the switching power supply is not lightly loaded, the switching power supply operates in a quasi-resonant control mode. The control method of the switching power supply according to claim 20, wherein when the load of the switching power supply is in a non-light load state, the open source operates in an off-time control mode. 25. If the light foot switch is the control method of claim 20, it is preferable that the high frequency pulse signal _¥ is larger than the upper limit of the frequency range to be excluded. The control method of a switching power supply according to claim 20, wherein the low frequency modulation signal frequency is smaller than a lower limit of a frequency range to be excluded. The method of controlling a switching power supply according to claim 25 or 26, wherein the frequency range to be excluded includes an audio range. For example, the _ electric_control method described in Item 21 of the full-time application, the characteristic table 控制, according to the threshold signal, controls the frequency form number of the low-lying signal Α 010] page 22 / 27 pages 0993444896 - 0 201212496 rate, according to the feedback signal, controlling the duty ratio of the low frequency modulation signal; controlling the frequency of the high frequency pulse signal according to the threshold signal or the feedback signal. The control method of the switching power supply according to claim 28, wherein the controlling the frequency and the duty ratio of the low frequency modulation signal is implemented by: setting a frequency control module for the low frequency modulation signal, Comparing an output of the low frequency modulation signal frequency control module with a threshold signal to obtain a sawtooth wave signal 9, the sawtooth wave signal is compared with a signal based on a feedback signal by a first comparator, and the output frequency of the comparator output is A low frequency modulated signal with a controlled duty cycle. The control method of the switching power supply of claim 28, wherein the controlling the frequency of the high-frequency pulse signal is implemented by the following method: setting a frequency control circuit for the high-frequency pulse signal including the capacitor charging and discharging circuit, The signal outputted by the high frequency pulse signal frequency control circuit is compared with a signal based on a threshold signal or a feedback signal through a third comparator, and the output signal of the comparator is coupled to the set end of the RS flip-flop, and the RS triggers The output of the device controls the charging and discharging of the capacitor, thereby controlling the frequency of the high frequency pulse signal outputted from the output of the RS flip-flop. 099129547 Form No. A0101 Page 23 of 27 0993444896-0