CN103683949B - Switching power unit - Google Patents
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- CN103683949B CN103683949B CN201310421540.2A CN201310421540A CN103683949B CN 103683949 B CN103683949 B CN 103683949B CN 201310421540 A CN201310421540 A CN 201310421540A CN 103683949 B CN103683949 B CN 103683949B
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Abstract
The invention provides switching power unit, it can power consumption when not making usual action when increasing, and is used in the transient recovery voltage electric discharge of the level and smooth electrolytic capacitor after the rectification of AC power.This switching power unit has: rectification circuit, and it carries out rectification to alternating voltage; Electrolytic capacitor, it is smoothing to the alternating voltage being carried out rectification by rectification circuit; Transformer, the voltage after its applying is level and smooth by electrolytic capacitor; Switch element, it is connected with transformer (T); Control circuit (Z1), it makes switch element carry out ON-OFF action, control circuit (Z1) has: starting circuit (Z10), and the voltage of electrolytic capacitor, when the starting to starting the action of switch element, is supplied to (Vcc) terminal of control circuit (Z1) by it; Discharge circuit (Z14), it is connected with (Vcc) terminal, discharges via the transient recovery voltage of starting circuit (Z10) to the electrolytic capacitor produced after AC power is cut off.
Description
Technical field
The present invention relates to the switching power unit being carried out output voltage control by switch motion.
Background technology
In switching power unit, the electrolytic capacitor smoothly waited when the rectification for AC power is after by charged tension discharge, when being positioned between terminal with high impedance, produce the transient state recovery phenomenon (with reference to patent documentation 1) that voltage between terminals is recovered at leisure.Such as after LCD-TV etc. pulls up from AC socket, although the voltage of electrolytic capacitor is discharged and stops action, afterwards because transient state recovers phenomenon, although substrate is pulled up from AC socket, in electrolytic capacitor, produce transient recovery voltage.So exist due to this transient recovery voltage, power supply to carry out in a flash action and situation about disconnecting immediately.Thus, the LED moment bright light of power supply opening, or transformer sends ring.In addition, also there is the situation that secondary side microcomputer carries out misoperation, user is misunderstood.
Therefore, in the past, as shown in Figure 4, between the terminal of the electrolytic capacitor C1 of the rectifier smoothing circuit by rectification circuit DB formation AC power AC, connect high resistance R20, make the transient recovery voltage electric discharge produced in electrolytic capacitor C1.In addition, also high resistance is connected providing to control circuit Z20 between the terminal of the electrolytic capacitor C3 of supply voltage.
Patent documentation 1: Japanese Unexamined Patent Publication 2004-119886 publication
But, there are the following problems in the prior art: owing to must connect high resistance R20 between the terminal for the level and smooth electrolytic capacitor C1 after AC power rectification, because this increasing components number, and, owing to also carrying out the electric discharge based on high resistance R20 when usual action, therefore also add power consumption during usual action.
Summary of the invention
The present invention puts the problems referred to above solving prior art in view of the above problems, its object is to provide a kind of switching power unit, when its power consumption when not increasing usual action, the transient recovery voltage electric discharge of the level and smooth electrolytic capacitor after AC power rectification can be used in.
Switching power unit of the present invention, it has: rectification circuit, and it carries out rectification to the alternating voltage inputted from AC power, electrolytic capacitor, it is smoothing to being carried out the described alternating voltage after rectification by this rectification circuit, transformer, the voltage after it is smoothing by described electrolytic capacitor to 1 winding applying, switch element, 1 winding switching of itself and this transformer, control circuit, it makes this switch element carry out ON-OFF action, and secondary side rectifier smoothing circuit, it is level and smooth that its pulse voltage induced in the secondary winding of described transformer the ON-OFF action due to described switch element carries out rectification, the feature of this switching power unit is, described control circuit has: starting circuit, the voltage of described electrolytic capacitor, when the starting to starting the action of described switch element, is supplied to the power supply terminal of described control circuit by it, and discharge circuit, it is connected with described power supply terminal, discharge via the transient recovery voltage of described starting circuit to the described electrolytic capacitor produced after described AC power is cut off, described discharge circuit has commutation circuit, when the action of described switch element stops, this commutation circuit makes the impedance of described power supply terminal reduce, described control circuit has comparison circuit, this comparison circuit is by the voltage of described power supply terminal and comparing of reference voltage, the described commutation circuit of described discharge circuit is switched, described discharge circuit has power supply holding circuit, this power supply holding circuit is under the state being made the impedance of described power supply terminal reduce by described commutation circuit, the voltage of described power supply terminal is made to maintain more than the operation voltage of described comparison circuit.
According to the present invention, discharge circuit is configured to, and discharges via the transient recovery voltage of starting circuit to electrolytic capacitor, and therefore when usual action, the voltage of electrolytic capacitor can not be discharged due to discharge circuit.Therefore there is following effect: can power consumption when not making usual action when increasing, being used in the transient recovery voltage electric discharge of the level and smooth electrolytic capacitor after the rectification of AC power.
Accompanying drawing explanation
Fig. 1 is the circuit structure diagram of the circuit structure of the execution mode that switching power unit of the present invention is shown.
Fig. 2 is the circuit structure diagram of the circuit structure that the control circuit shown in Fig. 1 is shown.
Fig. 3 is the signal waveform in each portion and the oscillogram of action waveforms that Fig. 2 is shown.
Fig. 4 is the circuit structure diagram of the circuit structure of the switching power unit illustrated in the past.
Label declaration
AC: AC power
AND1: with circuit
C1, C2, C3: electrolytic capacitor
C4, C5, C6, C7: capacitor
COMP1: low-voltage misoperation prevents (UVLO) circuit
COMP2: constant-voltage control circuit
COMP3: overcurrent limiting circuit
D1, D2: rectifier diode:
D3, D4: diode
DB: rectification circuit
EA: error amplifier
FF1: trigger
OR1: or circuit
PC: optical coupler
Q1: switch element
Q2, Q3, Q4: switch element
R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12: resistance
T: transformer
TR1, TR2: transistor
VR: variable voltage
Vref: reference voltage
Z1: control circuit
Z2: buffer circuit
Z3: feedback circuit
Z10: starting circuit
Z11: constant voltage circuit
Z12: oscillating circuit
Z13: drive circuit
Z14: discharge circuit
ZD1: zener diode array
ZD2: Zener diode
Embodiment
With reference to Fig. 1, the switching power unit of present embodiment has rectification circuit DB, electrolytic capacitor C1, C2, C3, switch element Q1, transformer T, rectifier diode D1, D2, resistance R1, R2, capacitor C4, C5, control circuit Z1, buffer circuit Z2, feedback circuit Z3.
AC input terminal ACin1, ACin2 of rectification circuit DB that bridge diode is formed is connected with AC power AC, and the alternating voltage inputted from AC power AC by full-wave rectification, and is output from rectification circuit DB.Electrolytic capacitor C1 is connected with between the rectification output cathode terminal and rectification output negative pole terminal of rectification circuit DB.Thereby, it is possible to obtain having carried out the DC power supply after rectification smoothly by rectification circuit DB and electrolytic capacitor C1 to AC power AC.
Between the positive terminal and negative terminal of electrolytic capacitor C1, be connected in series with a winding P1, switch element Q1, the resistance R1 of transformer T.Switch element Q1 is made up of the power MOSFET (MetalOxideSemiconductorFieldEffectTransistor: mos field effect transistor) of N-type, the drain terminal of switch element Q1 is connected with a winding P1 of transformer T, and the source terminal of switch element Q1 is connected with resistance R1, the gate terminal of switch element Q1 is connected with driver output (DRIVE) terminal of control circuit Z1.In addition, the positive terminal of electrolytic capacitor C1 and the starting voltage of control circuit Z1 input (START) terminal and are connected, and the negative terminal of electrolytic capacitor C1 is connected with ground connection (GND) terminal of control circuit Z1.
Control circuit Z1 is the circuit for carrying out the switch control rule making switch element Q1 vibration (ON-OFF) action, by rectification circuit DB and electrolytic capacitor C1, the DC power supply after rectification is smoothly carried out to AC power AC, the ON-OFF action of the switch element Q1 connected by 1 winding P1 via transformer T, is output to the secondary winding S1 of transformer T within the off period.Between the two-terminal of the secondary side winding S1 of transformer T, electrolytic capacitor C2 is connected via rectifier diode D1, the pulse voltage induced in the secondary side winding S1 of transformer T is rectified smoothly by the secondary side rectifier smoothing circuit be made up of rectifier diode D1 and electrolytic capacitor C2, provides the output voltage of direct current to the not shown load be connected between positive output terminals OUT+ and ground connection lead-out terminal OUT-.In addition, the line be connected with positive output terminals OUT+ is power line, and the line connecting ground connection lead-out terminal OUT-is GND line.In addition, the capacitor C4 for making common-mode noise reduce is connected with between the negative terminal of the electrolytic capacitor C1 1 side and the GND line of secondary side.
Between the two-terminal of the auxiliary winding P2 of transformer T, be connected electrolytic capacitor C3 via rectifier diode D2 with resistance R2, rectifier diode D2 inputs (Vcc) terminal with the tie point of electrolytic capacitor C3 and the control circuit supply voltage of control circuit Z1 and is connected.Thus, the voltage produced in auxiliary winding P2, after being rectified diode D2 and electrolytic capacitor C3 rectification smoothly, is supplied to the Vcc terminal of control circuit Z1, as the control circuit power supply of control circuit Z1.
Buffer circuit Z2 is protective circuit, and it is connected between a winding P1 of transformer T, is absorbed in the high voltage of the transition produced when switch element Q1 interdicts.Buffer circuit Z2 is made up of diode D3, capacitor C6, resistance R3.The anode of diode D3 is connected to the tie point of the drain terminal of switch element Q1 and a winding P1 of transformer T.In addition, capacitor C6 and resistance R3 is connected in parallel between the tie point of a winding P1 of the negative electrode of diode D3 and the positive terminal of electrolytic capacitor C1 and transformer T.
Feedback circuit Z3 is by optical coupler PC, error amplifier EA, resistance R4, and R5, R6, R7, capacitor C7 are formed.Between power line and GND line, the emission side element (light-emitting diode) of resistance R4, optical coupler PC, error amplifier EA are connected in series, and resistance R5 is connected in parallel with the emission side element (light-emitting diode) of the resistance R4 be connected in series and optical coupler PC.In addition, between power line and GND line, be connected in series with resistance R6 and the resistance R7 of dividing potential drop, resistance R6 is connected with the control terminal a of error amplifier EA with the tie point of resistance R7.In addition, at the tie point of resistance R6 and resistance R7 and between the emission side element (light-emitting diode) of optical coupler PC and the tie point of error amplifier EA, capacitor C7 is connected with.Thus, be output to output voltage between positive output terminals OUT+ and ground connection lead-out terminal OUT-by resistance R6, R7 by dividing potential drop, be output to the control terminal a of error amplifier EA by the output voltage after dividing potential drop.Compare by the output voltage of dividing potential drop and the not shown reference voltage be built in error amplifier EA, the emission side element (light-emitting diode) of the optical coupler PC of this difference as feedback signal from secondary side is fed back to the sensitive side element (by optotransistor) of the optical coupler PC of 1 side.
Input between (FB) terminal and the negative terminal of electrolytic capacitor C1 in the feedback signal of control circuit Z1, sensitive side element (by optotransistor) and the capacitor C5 of optical coupler PC are connected in parallel, and feedback signal is imported into the FB terminal of control circuit Z1.In addition, the source terminal of switch element Q1 detects (OCP) terminal with the tie point of resistance R1 and the overcurrent of control circuit Z1 and is connected, the drain current flowing through switch element Q1 is detected as voltage signal by resistance R1, and detected voltage signal is imported into the OCP terminal of control circuit Z1.
With reference to Fig. 2, control circuit Z1 has: starting circuit Z10, low-voltage misoperation prevent (UVLO) circuit COMP1, constant voltage circuit Z11, the switch element Q2, the zener diode array ZD1 that are made up of N-type MOSFET, constant-voltage control circuit COMP2, overcurrent limiting circuit COMP3 or circuit OR1, oscillating circuit Z12, trigger FF1, with circuit AND1, drive circuit Z13, variable voltage VR, reference voltage V ref, resistance R8, discharge circuit Z14.
Starting circuit Z10 is connected between the START terminal be connected with the positive terminal of electrolytic capacitor C1 and the Vcc terminal be connected with the positive terminal of electrolytic capacitor C3, provides the constant-current circuit of constant current when starting to the electrolytic capacitor C3 be connected with Vcc terminal.Starting circuit Z10 is formed by with lower part: the switch element Q3 be made up of N-type MOSFET, the transistor TR1 of NPN type, resistance R9, R10 and diode D4.Between START terminal and Vcc terminal, be connected in series with switch element Q3, resistance R9, diode D4, and be connected with resistance R10 between START terminal and the gate terminal of switch element Q3.Resistance R10 is high-resistance biasing resistor.In addition, the collector terminal of transistor TR1 is connected with the gate terminal of switch element Q3, and base terminal is connected with the source terminal of switch element Q3, and emitter terminal is connected with the tie point of resistance R9 and diode D4.Thus, under the state that switch element Q3 is switched on, flow through base current in transistor TR1, constant current is provided to the electrolytic capacitor C3 be connected with Vcc terminal.
UVLO circuit COMP1 is the comparison circuit compared voltage vcc and the variable voltage VR of electrolytic capacitor C3 (Vcc terminal).The non-inverting input terminal of UVLO circuit COMP1 is connected with Vcc terminal, reversed input terminal is connected with variable voltage VR, the output signal exported from the lead-out terminal of UVLO circuit COMP1 becomes Hi level when voltage vcc exceedes variable voltage VR, becomes Low level when voltage vcc is below variable voltage VR.Output signal from UVLO circuit COMP1 is imported into variable voltage VR, when the output signal from UVLO circuit COMP1 is Low level, variable voltage VR is set to the 1st reference voltage V a (such as, 15V), when the output signal from UVLO circuit COMP1 is Hi level, variable voltage VR is set to the 2nd reference voltage V b (such as, 10V) lower than the 1st reference voltage V a.Thus, the output signal of UVLO circuit COMP1 has hysteresis characteristic, when voltage vcc is more than the 1st reference voltage V a, becomes Hi level, when voltage vcc is below the 2nd reference voltage V b, becomes Low level.
In addition, the lead-out terminal of UVLO circuit COMP1 is connected with constant voltage circuit Z11.Constant voltage circuit Z11 carries out action when the output signal of UVLO circuit COMP1 is Hi level, and each portion being provided for control circuit Z1 respectively carries out the supply voltage of action.That is, the output signal of UVLO circuit COMP1 is the signal of the ON-OFF controlling control circuit Z1, and when control circuit Z1 operating stably the conducting of the switch motion (time), the output signal of UVLO circuit COMP1 is Hi level.Therefore, the 1st reference voltage V a of variable voltage VR is that the action of control circuit Z1 starts voltage, and the 2nd reference voltage V b of variable voltage VR is that the action of control circuit Z1 stops voltage.
In addition, the lead-out terminal of UVLO circuit COMP1 is connected with the gate terminal of switch element Q2.The source terminal of switch element Q2 is connected with the GND line being connected to GND terminal, the drain terminal of switch element Q2 is connected with the gate terminal of the switch element Q3 in starting circuit Z10, between the source terminal and drain terminal of switch element Q2, be connected with zener diode array ZD1.Switch element Q2 is switched on when the output signal of UVLO circuit COMP1 is Hi level, is cut off when the output signal of UVLO circuit COMP1 is Low level.When switch element Q2 is switched on, the gate terminal of switch element Q3 and GND line ground connection, switch element Q3 is cut off, and starting circuit Z10 stops, that is, the providing of constant current to the electrolytic capacitor C3 be connected with Vcc terminal is stopped.On the other hand, when switch element Q2 is cut off, via the gate terminal applying voltage of resistance R10 to switch element Q3, switch element Q3 is switched on, the electric current flowing through resistance R9 is detected between the base/emitter of transistor TR1, thus, starting circuit Z10 action starts, and makes the grid voltage of switch element Q3 flow through certain electric current in resistance R9.That is, the electrolytic capacitor C3 started to being connected with Vcc terminal provides constant current.
Constant-voltage control circuit COMP2 is the comparison circuit compared the voltage VFB of FB terminal and the voltage VOCP of OCP terminal.The non-inverting input terminal of constant-voltage control circuit COMP2 is connected with OCP terminal, reversed input terminal is connected with FB terminal, the output signal exported from the lead-out terminal of constant-voltage control circuit COMP2 becomes Hi level when voltage VOCP exceedes voltage VFB, becomes Low level when voltage VOCP is below voltage VFB.
Overcurrent limiting circuit COMP3 is the comparison circuit compared the voltage VOCP of reference voltage V ref and OCP terminal.The non-inverting input terminal of overcurrent limiting circuit COMP3 is connected with OCP terminal, reversed input terminal is connected with reference voltage V ref, the output signal exported from the lead-out terminal of overcurrent limiting circuit COMP3 becomes Hi level when voltage VOCP exceedes reference voltage V ref, becomes Low level when voltage VOCP is below reference voltage V ref.
The input terminal of the lead-out terminal of constant-voltage control circuit COMP2 and the lead-out terminal difference AND circuit OR1 of overcurrent limiting circuit COMP3 is connected, or the lead-out terminal of circuit OR1 is connected with reset (R) terminal of trigger FF1.In addition, set (S) terminal of trigger FF1 is connected with oscillating circuit Z12, and output (Q) connecting terminals of trigger FF1 receives the input terminal with circuit AND1.In addition, be connected with the lead-out terminal of UVLO circuit COMP1 with another input terminal of circuit AND1.Thus, be Hi level, and trigger FF1 is set in the output of UVLO circuit COMP1, when the output signal of Q terminal is Hi level, becomes Hi level with the output signal of circuit AND1, by drive circuit Z13, switch element Q1 is switched on.
Discharge circuit Z14 be connected to be connected with the positive terminal of electrolytic capacitor C3 between Vcc terminal and GND terminal, via starting circuit Z10, the transient recovery voltage of electrolytic capacitor C1 is discharged.Discharge circuit Z14 is formed by with lower part: the switch element Q4, the NPN transistor TR2 that are made up of N-type MOSFET, resistance R11, R12, Zener diode ZD2.Between Vcc terminal and GND terminal, be connected in series with resistance R11 and switch element Q4, and be connected in series with resistance R12, Zener diode ZD2, NPN transistor TR2.That is, the drain terminal of switch element Q4 is connected with Vcc terminal via resistance R11, and the source terminal of switch element Q4 is connected with GND terminal.In addition, the collector terminal of transistor TR2 is connected with the anode of Zener diode ZD2, and the negative electrode of Zener diode ZD2 is connected with Vcc terminal via resistance R12, and the emitter terminal of transistor TR2 is connected with GND terminal.And the gate terminal of switch element Q4 is connected with the lead-out terminal of UVLO circuit COMP1, and the base terminal of transistor TR2 is connected with the drain terminal of switch element Q4.
When the operating stably of control circuit Z1, the output signal of UVLO circuit COMP1 becomes Hi level, and therefore switch element Q4 becomes state switched on.Under switch element Q4 is conducting state, the base terminal of transistor TR2 and GND terminal ground, transistor TR2 becomes the state be cut off.Under the state that transistor TR2 ends, Vcc terminal becomes the state be connected with GND terminal via resistance R11.Resistance R11 is set to the high impedances such as 5M Ω.On the other hand, when the output signal of UVLO circuit COMP1 becomes Low level, switch element Q4 is cut off.When switch element Q4 is cut off, the base terminal of transistor TR2 flows through electric current, and therefore transistor TR2 is switched on.Then, under the state that transistor TR2 is conducting, Vcc terminal becomes the state be connected with GND terminal with Zener diode ZD2 via resistance R12.Resistance R12, compared to resistance R11, is set to the Low ESRs such as 68k Ω.Like this, discharge circuit Z14 is the output signal according to UVLO circuit COMP1, the i.e. ON-OFF of switch motion, circuit low when making the conducting of the impedance of Vcc terminal when the cut-off of switch motion than in switch motion, switch element Q4 carries out work as the commutation circuit making the impedance of Vcc terminal reduce when switch motion ends.
Fig. 3 is the sequential chart of the signal in each portion that the control circuit Z1 shown in Fig. 2 is shown, a () represents the voltage of electrolytic capacitor C1, b () represents the voltage vcc of electrolytic capacitor C3, c () represents the output signal of UVLO circuit COMP1, d () represents the output signal from the DRIVE terminal of control circuit Z1, e () represents the ON-OFF state of switch element Q2, f () represents the ON-OFF state of switch element Q3, g () represents the ON-OFF state of switch element Q4, (g) represents the ON-OFF state of transistor TR2.
As shown in (a) of Fig. 3, at moment t1, when AC input terminal ACin1, ACin2 of rectification circuit DB are connected with AC power AC, the voltage rise of electrolytic capacitor C1.When the voltage rise of electrolytic capacitor C1, switch element Q2 ends, and the voltage of the gate terminal of the switch element Q3 therefore in starting circuit Z10 also rises.When the gate terminal of switch element Q3 voltage rise and when exceeding threshold voltage, as shown in (f) of Fig. 3, switch element Q3 becomes conducting state.Thus, starting circuit Z10 starts the action as constant-current circuit, provides constant current from starting circuit Z10 to electrolytic capacitor C3, and as shown in (b) of Fig. 3, the voltage vcc of electrolytic capacitor C3 rises.
In addition, when the voltage vcc of moment t1 electrolytic capacitor C3 starts to rise, the base current of the transistor TR2 in discharge circuit Z14 also begins to flow through, and transistor TR2 becomes conducting state.Thus, discharge circuit Z14 is switched to Low ESR, but owing to being provided sufficient starting current (constant current) from starting circuit Z10, even if therefore transistor TR2 becomes conducting state, as shown in (b) of Fig. 3, the voltage vcc of electrolytic capacitor C3 also rises.
At moment t2, when the action exceeded as control circuit Z1 of the voltage vcc of electrolytic capacitor C3 starts the reference voltage V a of voltage, as shown in (c) of Fig. 3, the output signal of UVLO circuit COMP1 becomes Hi level, as shown in (d) of Fig. 3, switch motion is switched on.
In addition, when the output signal of UVLO circuit COMP1 becomes Hi level, as shown in (e) of Fig. 3, switch element Q2 is switched on, the gate terminal of switch element Q3 is grounded, and therefore as shown in (f) of Fig. 3, switch element Q3 becomes cut-off state.Thus, the action as the constant-current circuit of starting circuit Z10 is stopped, and later when operating stably, is provided in the voltage produced in auxiliary winding P2 to electrolytic capacitor C3.
In addition, as shown in (g) of Fig. 3, when the output signal of UVLO circuit COMP1 becomes Hi level, switch element Q4 in discharge circuit Z14 is switched on, the base current of transistor TR2 no longer flows through, and therefore as shown in (h) of Fig. 3, transistor TR2 is cut off.Thus, discharge circuit Z14 is switched to the high impedance do not had an impact when operating stably.
Then, at moment t3, after AC power AC is cut-off, as shown in (a) of Fig. 3, the voltage of electrolytic capacitor C1 reduces, and no longer provide voltage from auxiliary winding P2 to electrolytic capacitor C3, therefore as shown in (b) of Fig. 3, the voltage vcc of electrolytic capacitor C3 reduces.
At moment t4, when the voltage vcc of electrolytic capacitor C3 becomes the reference voltage V b as the action stopping voltage of control circuit Z1, as shown in (c) of Fig. 3, the output signal of UVLO circuit COMP1 becomes Low level, as shown in (d) of Fig. 3, switch motion is cut off.
In addition, when the output signal of UVLO circuit COMP1 becomes Low level, as shown in (e) of Fig. 3, switch element Q2 is cut off.Under the state that switch element Q2 is cut-off, as shown in (a) of Fig. 3, when producing transient recovery voltage when recovering phenomenon due to transient state in electrolytic capacitor C1, due to the transient recovery voltage of electrolytic capacitor C1, the voltage of the gate terminal of the switch element Q3 in starting circuit Z10 also rises.When the gate terminal of switch element Q3 voltage rise and when exceeding threshold voltage, as shown in (f) of Fig. 3, switch element Q3 becomes conducting state.Thus, the transient recovery voltage produced due to the transient state recovery phenomenon in electrolytic capacitor C1 is provided to Vcc terminal by starting circuit Z10.In addition, when the voltage of the electrolytic capacitor C1 when being set to usual action is 320V, the constant current being supplied to Vcc terminal from starting circuit Z10 when usual action is about 2.5mA.On the other hand, the transient recovery voltage of electrolytic capacitor C1 is low compared with voltage during usual action, and therefore due to the transient recovery voltage of electrolytic capacitor C1, the electric current being supplied to Vcc terminal from starting circuit Z10 is reduced to a few μ A ~ several 100 μ about A.
In addition, when the output signal of UVLO circuit COMP1 becomes Low level, as shown in (g) of Fig. 3, the switch element Q4 in discharge circuit Z14 is cut off, and the base current of transistor TR2 flows through.So as shown in (h) of Fig. 3, transistor TR2 is switched on, and discharge circuit Z14 is switched to Low ESR.Thus, the electric current being supplied to Vcc terminal due to the transient recovery voltage of electrolytic capacitor C1 from starting circuit Z10 is discharged by discharge circuit Z14 (low-impedance resistance R12), prevents the voltage vcc action risen to as control circuit Z1 to start the reference voltage V a of voltage.
In discharge circuit Z14, Zener diode ZD2 maintains (clamper) circuit as the voltage of the voltage vcc maintaining Vcc terminal when the action of discharge circuit Z14 and carries out work.The Zener voltage of Zener diode ZD2 is set to the operation voltage higher than UVLO circuit COMP1.Thus, even if be discharged by discharge circuit Z14 (resistance R12), recover in the process of phenomenon (several seconds ~ a few kilosecond) in the transient state of continued electrolysis capacitor C1, voltage vcc is also maintained the operation voltage higher than UVLO circuit COMP1.In addition, voltage vcc is provided directly to UVLO circuit COMP1 as operation voltage.Thus, recover in the lasting process of phenomenon (several seconds ~ a few kilosecond) in the transient state of electrolytic capacitor C1, the output signal of UVLO circuit COMP1 can not become unstable, and maintains Low level.In addition, the Zener voltage of Zener diode ZD2 is set at least lower than the 1st reference voltage V a (action of control circuit Z1 starts voltage) of UVLO circuit COMP1.In addition, in order to obtain sufficient discharge effect, also the Zener voltage of Zener diode ZD2 can be set as the 2nd reference voltage V b (action of control circuit Z1 stops voltage) lower than UVLO circuit COMP1.
As described above, according to the present embodiment, have: rectification circuit DB, it carries out rectification to the alternating voltage inputted from AC power AC; Electrolytic capacitor C1, after it carries out rectification by this rectification circuit DB, alternating voltage is smoothing; Transformer T, the voltage after it is smoothing by electrolytic capacitor C1 to 1 winding P1 applying; Switch element Q1, it is connected with 1 winding P1 of transformer T; Control circuit Z1, it makes switch element Q1 carry out ON-OFF action; Secondary side rectifier smoothing circuit (rectifier diode D1, electrolytic capacitor C2), it is level and smooth that it carries out rectification to the pulse voltage induced in the secondary winding S1 of transformer T owing to making switch element Q1 carry out ON-OFF action, control circuit Z1 has: starting circuit Z10, the voltage of electrolytic capacitor C1, when the starting to starting the action of switch element Q1, is supplied to the Vcc terminal of control circuit Z1 by it; And discharge circuit Z14, it is connected with Vcc terminal, discharges to the transient recovery voltage of the electrolytic capacitor C1 produced after AC power AC is cut off via starting circuit Z10.By this structure, when switch element Q1 action (during operating stably), the action of starting circuit Z10 stops, and therefore, the voltage of electrolytic capacitor C1 can not be discharged due to discharge circuit Z14.Therefore, it is possible to when power consumption when not increasing usual action, be used in the transient recovery voltage electric discharge of the level and smooth electrolytic capacitor after the rectification of AC power.In addition, when AC power AC cuts off, the voltage of electrolytic capacitor C1 is not necessarily reduced to 0V, and the voltage of the electrolytic capacitor C1 that midway is remaining also promptly can be discharged by discharge circuit Z14.In addition, can the discharge circuit Z14 (resistance) be used for the transient recovery voltage of electrolytic capacitor C1 discharges be taken in control circuit Z1, can components number be reduced.In addition, the discharge circuit Z14 be taken in control circuit Z1 is made up of resistance, transistor, MOSFET substantially, owing to not being the element of integrated difficulty, and therefore can also the rising of inhibitory control circuit Z1 chip cost.
In addition, according to the present embodiment, discharge circuit Z14 has commutation circuit (switch element Q4), and this commutation circuit (switch element Q4), when the action of switch element Q1 stops, making the impedance of Vcc terminal reduce.By this structure, the transient recovery voltage of electrolytic capacitor C1 can be reliably made rapidly to discharge, and power consumption when can suppress operating stably.
In addition, according to the present embodiment, control circuit Z1 has UVLO circuit COMP1, this UVLO circuit COMP1 is by voltage vcc and reference voltage (the 1st reference voltage V a, 2nd reference voltage V b) comparison, the commutation circuit (switch element Q4) of discharge circuit Z14 is switched, discharge circuit Z14 has power supply holding circuit (Zener diode ZD2), under the state making the impedance of Vcc terminal reduce by commutation circuit (switch element Q4), voltage vcc is maintained more than the operation voltage of UVLO circuit COMP1 by power supply holding circuit (Zener diode ZD2).By this structure, recover the lasting process of phenomenon in (several seconds ~ a few kilosecond) in the transient state of electrolytic capacitor C1, the output signal controlling the UVLO circuit COMP1 of commutation circuit (switch element Q4) can be stablized, and maintains Low level.
Above, describe the present invention by specific embodiment, but above-mentioned execution mode is an example, certainly can carry out without departing from the spirit and scope of the invention changing and implementing.Such as, except the rectifier smoothing circuit be made up of rectification circuit DB and the electrolytic capacitor C1 of present embodiment, power-factor improvement (PFC) circuit can also be had.In addition, also half-wave rectifying circuit, full-wave rectifying circuit, full-wave voltage doubler etc. can be used, the rectification circuit DB replacing bridge diode to form.In addition, in the present embodiment, as shown in Figure 1, to using the example of kickback transformer to be illustrated, but forward type transformer or semibridge system transformer can also be used.Further there is illustrated the circuit example by feedback signal, output voltage controlled from secondary side, but also can use and indirectly carry out by the auxiliary winding voltage of 1 side the mode that controls.
Claims (1)
1. a switching power unit, it has: rectification circuit, and it carries out rectification to the alternating voltage inputted from AC power; Electrolytic capacitor, it is smoothing to being carried out the described alternating voltage after rectification by this rectification circuit; Transformer, the voltage after it is smoothing by described electrolytic capacitor to 1 winding applying; Switch element, 1 winding switching of itself and this transformer; Control circuit, it makes this switch element carry out ON-OFF action; And secondary side rectifier smoothing circuit, it is level and smooth that its pulse voltage induced in the secondary winding of described transformer the ON-OFF action due to described switch element carries out rectification, and the feature of this switching power unit is,
Described control circuit has:
Starting circuit, the voltage of described electrolytic capacitor, when the starting to starting the action of described switch element, is supplied to the power supply terminal of described control circuit by it; And
Discharge circuit, it is connected with described power supply terminal, discharges via the transient recovery voltage of described starting circuit to the described electrolytic capacitor produced after described AC power is cut off,
Described discharge circuit has commutation circuit, and when the action of described switch element stops, this commutation circuit makes the impedance of described power supply terminal reduce,
Described control circuit has comparison circuit, and this comparison circuit, by the voltage of described power supply terminal and comparing of reference voltage, switches the described commutation circuit of described discharge circuit,
Described discharge circuit has power supply holding circuit, and this power supply holding circuit, under the state being made the impedance of described power supply terminal reduce by described commutation circuit, makes the voltage of described power supply terminal maintain more than the operation voltage of described comparison circuit.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2012-208092 | 2012-09-21 | ||
| JPJP2012-208092 | 2012-09-21 | ||
| JP2012208092A JP6155586B2 (en) | 2012-09-21 | 2012-09-21 | Switching power supply |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN103683949A CN103683949A (en) | 2014-03-26 |
| CN103683949B true CN103683949B (en) | 2016-03-30 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201310421540.2A Active CN103683949B (en) | 2012-09-21 | 2013-09-16 | Switching power unit |
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| Country | Link |
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| JP (1) | JP6155586B2 (en) |
| CN (1) | CN103683949B (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2945270B1 (en) * | 2014-05-13 | 2018-01-31 | Nxp B.V. | Controller |
| JP6443120B2 (en) * | 2015-02-23 | 2018-12-26 | ミツミ電機株式会社 | Power supply control semiconductor device |
| CN107925351B (en) * | 2015-07-15 | 2020-05-15 | 三菱电机株式会社 | Control circuit |
| CN107181400B (en) * | 2017-05-27 | 2019-12-03 | 西安交通大学 | A kind of high position draw-out power supply self-start circuit and method |
| JP7087887B2 (en) * | 2018-09-27 | 2022-06-21 | Tdk株式会社 | Switching power supply |
| JP7318528B2 (en) * | 2019-12-27 | 2023-08-01 | 株式会社リコー | Power supply circuit and electronic equipment with power supply circuit |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1819032A1 (en) * | 2006-02-10 | 2007-08-15 | Thomson Licensing S.A. | Switched mode power supply comprising a discharging circuit |
| CN101027830A (en) * | 2004-08-18 | 2007-08-29 | 三垦电气株式会社 | Switching power supply apparatus |
| CN102545575A (en) * | 2010-12-24 | 2012-07-04 | 三垦电气株式会社 | Startup circuit, switching power source ic, and switching power source apparatus |
-
2012
- 2012-09-21 JP JP2012208092A patent/JP6155586B2/en active Active
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101027830A (en) * | 2004-08-18 | 2007-08-29 | 三垦电气株式会社 | Switching power supply apparatus |
| EP1819032A1 (en) * | 2006-02-10 | 2007-08-15 | Thomson Licensing S.A. | Switched mode power supply comprising a discharging circuit |
| CN102545575A (en) * | 2010-12-24 | 2012-07-04 | 三垦电气株式会社 | Startup circuit, switching power source ic, and switching power source apparatus |
Also Published As
| Publication number | Publication date |
|---|---|
| JP6155586B2 (en) | 2017-07-05 |
| CN103683949A (en) | 2014-03-26 |
| JP2014064391A (en) | 2014-04-10 |
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