TWI389437B - A power supply with improved light load efficiency - Google Patents

Description

Power supply for improving light load efficiency

The invention relates to a resonant converter, in particular to a converter which uses an output voltage of a power factor corrector to dynamically follow an input voltage and has a switch for automatically switching a power factor corrector to reduce a switching frequency.

As shown in the first figure, the conventional two-stage power supply is to add a first-order resonant converter 2 after the power factor corrector 1 of the preceding stage, and the power factor corrector 1 can be realized in order to have a wide-area input. The power factor correction function, even when operating at low voltage input, is still higher than the peak value of the input maximum AC voltage. The switching frequency of the power factor corrector implemented by the peak current control method is proportional to the output voltage. If the output voltage of the power factor corrector is set to a high voltage, in addition to the increase of the switching frequency of the power factor corrector itself, the switching frequency of the subsequent series resonant converter must also be increased to maintain the function of the post-stage voltage regulation. Under the condition that the output load is insufficient to make the converter of the latter converter switch to zero, the loss caused by the high switching frequency reduces the overall efficiency.

Since the current sampling signal of the power factor corrector is not good under high voltage input conditions, the power factor corrector cannot correct the current waveform correctly. To improve this condition, the boost inductor or the current sampling resistor must be increased, but all must pay more. Loss and improvement are not effective.

The technical problem to be solved by the present invention is to provide a power supply device for improving light load efficiency, which solves the problem of switching loss caused by excessive switching frequency at a light load. Therefore, the object of the present invention is to reduce the switching frequency of the series resonant converter at light load, and to facilitate flexible switching, and to turn off the power factor corrector when the light load does not need to consider the power factor (PF) value to improve the light load. effectiveness.

In view of this, the present invention provides a power supply device for improving light load efficiency, which is combined with a power factor corrector (PFC) and a series resonant converter (SRC), and is designed in a circuit by a control circuit to achieve a power factor corrector. The output voltage dynamically follows the input voltage, making the post-stage series resonant converter flexible switching characteristics to improve the conversion efficiency of the power factor corrector and the series resonant converter.

In order to solve the above technical problem, one technical solution of the present invention provides a power supply device for improving light load efficiency, which comprises a first rectifying circuit, a power factor corrector, a series resonant converter, a control circuit and a a driving circuit, wherein the first rectifying circuit is used for full-wave rectifying the input AC power; wherein the power factor corrector is coupled to the first rectifying circuit to provide a stable DC voltage; wherein the series resonant converter The power factor corrector is coupled to provide a DC/DC conversion; wherein the control circuit is coupled to the power factor corrector for determining an input voltage of the power factor corrector and an output current of the series resonant converter The size of the switching signal is generated, and the output voltage of the power factor corrector is adjusted according to the input voltage of the control circuit; wherein the driving circuit is coupled to the control circuit for receiving the switching signal and controlling the power factor correction Switch.

When the AC power supply high voltage input (230V) of the mains and the output load is less than 75W, the power factor corrector is turned off to reduce the switching frequency of the series resonant converter and improve the overall efficiency.

Thereby, the switching of the power factor corrector is switched by the control circuit according to the input voltage of the power factor corrector and the output current of the series resonant converter to reduce the switching frequency of the switching of the SRC converter of the latter stage, and the SRC conversion of the subsequent stage Because the input voltage is only the peak voltage of the input voltage, there is no action of boosting the voltage. In order to maintain the power supply, the input current of the SRC increases, so that the switch can achieve flexible switching. Therefore, the purpose of improving light load efficiency is achieved.

The above summary and the following detailed description are exemplary in order to further illustrate the scope of the claims. Other objects and advantages of the present invention will be described in the following description and drawings.

The invention is designed with a control circuit between a power factor corrector and a series resonant converter, providing a switch for switching the power factor corrector action, and changing the output voltage of the power factor corrector with the input voltage of the alternating current power source. The series resonant converter reduces the switching frequency of the switching converter of the latter stage under the condition of low voltage input, and increases the input current amount of the latter stage, so that the switch can achieve the flexible switching effect and improve the light load efficiency. The present invention will be described with reference to the accompanying drawings and drawings, in order to illustrate the embodiments of the invention The effect that can be achieved.

Please refer to the second figure, which is a circuit diagram of an embodiment of a power supply for improving light load efficiency provided by the present invention. As shown in the second figure, the converter for improving light load efficiency of the present invention comprises a first rectifying circuit 10, a power factor corrector 20, a series resonant converter 40, a control circuit 50 and a driving circuit 30. . The first rectifier circuit 10 is coupled to an AC power source; the power factor modifier 20 is coupled to the first rectifier circuit 10; and the series resonant converter 40 is coupled to the power factor modifier 20; and the control circuit 50 is coupled to the power The input terminal x of the factor corrector 20, the output terminal y of the power factor corrector 20, and the output terminals p, q of the series resonant converter 40 are coupled; and the ZCD terminal of the driving circuit 30 is coupled to the control circuit 50, and the other One end z is coupled to the power factor corrector 20.

The first rectifier circuit 10 includes a plurality of diodes D _a , D _b , D _c , D _d , and is used for full-wave rectified input AC power; wherein the power factor corrector 20 includes a first energy storage circuit 201 , The first switching circuit 202 is coupled to the first rectifying circuit 10 for storing or releasing energy, and the first switching circuit 202 is coupled to the first energy storage circuit 201 for switching current. Turning on or off; wherein the series resonant converter 40 includes a second switch circuit 401, a resonant circuit 402, a transformer 403, a second rectifier circuit 404, and a second tank circuit 405, and the second switch circuit 401 and The power factor corrector 20 is coupled to switch the current on or off, and the resonant circuit 402 is coupled to the second switch circuit 401 for generating a resonance, and the second switch circuit 401 is mutually turned on to achieve a zero voltage switching condition. The transformer 403 is coupled to the resonant circuit 402 for sensing the current of the resonant circuit 402 to the next stage circuit, and the second rectifying circuit 404 is coupled to the transformer 403 for rectifying the current induced by the transformer 403, and the second storage Energy 405 and 404 is coupled to second rectifier circuit, to store or release energy.

The first energy storage circuit 201 includes a capacitor C _in and an inductor L ₁ , and the first switch circuit 202 includes a power switch transistor SW ₁ and a diode D _e .

The second switch circuit 401 includes power switch transistors SW ₂ and SW ₃ ; and the resonant circuit 402 includes an inductor L ₂ , a capacitor C _b and a magnetizing inductance L _m ; and the transformer 403 includes a primary side coil N _p and a second The side coil N _s ; and the second rectifying circuit 404 is a synchronous rectifying circuit including power switching transistors SW ₄ , SW ₅ for ensuring that the series resonant converter 40 avoids the secondary side coil of the transformer 403 during the dead time. The energy of N _s is reversed back to the primary side coil N _p ; and the second tank circuit 405 includes a capacitor C _o .

In addition, the output of the series resonant converter 40 further includes a sense resistor R _o for providing current detection of the load.

Please refer to the third figure, which is a block diagram of an embodiment of a control circuit for a converter for improving light load efficiency. As shown in the third figure, the control circuit 50 of the present invention for improving light load efficiency includes a filter circuit 501, a voltage follower 502, an adjustment feedback voltage dividing circuit 503, and a first comparator. 504, an error amplifier 505, a second comparator 506, a signal isolation circuit 507, a logic circuit 508, a bounce circuit 509 and a signal switch circuit 510.

Please refer to the second figure, wherein the filter circuit 501 is coupled to the input terminal x of the power factor corrector 20, and the voltage follower 502 is coupled to the filter circuit 501, and the feedback feedback voltage divider 503 is respectively associated with the voltage. The coupler 502 and the output terminal y of the power factor corrector 20 are coupled, and the first comparator 504 is coupled to the regulated feedback voltage divider circuit 503, and the error amplifier 505 and the output of the series resonant converter 40 are coupled. both ends of the resistor R _o p, q coupling, and the second comparator 506 is coupled to the error amplifier 505, the signal isolation circuit 507 is coupled to a second comparator 506, and the logic circuit 508, respectively, the first comparator 504 and the signal The isolation circuit 507 is coupled, and the bounce circuit 509 is coupled to the logic circuit 508, and the signal switch circuit 510 is coupled to the bounce circuit 509.

Please refer to the fourth figure, which is a circuit diagram of an embodiment of a control circuit for improving a light load efficiency power supply according to the present invention. As shown in the fourth figure, the converter for improving light load efficiency of the present invention, wherein the filter circuit 501 includes capacitors C _m1 , C _m2 for DC sampling of the full-wave rectified AC voltage V _m and obtaining a sampling The voltage follower 502 is an operational amplifier _Op1 , the non-inverting input is coupled to the filter circuit 501, and the inverting input is coupled to its output terminal so that the output voltage is the same as the input voltage. To provide isolation to prevent load effects; and adjust the feedback voltage dividing circuit 503 to include resistors R ₂ , R _adj1 , a voltage regulator TL431 and a transistor Q ₁ , wherein the resistors R ₂ , R _adj1 and the voltage follower 502 The output end is coupled to provide a reference voltage divider V _ref according to the sampling signal, and the voltage regulator TL431 receives the reference voltage divider V _{ref at} the reference terminal R thereof, and the positive terminal A _{thereof is} coupled to the resistor R _adj1 , and the negative terminal thereof is coupled to the resistor R _adj1 . terminal K to provide a sampled input voltage signal _V in_SG, the transistor Q ₁ and the negative terminal of the TL431 regulator is coupled to K, and receives a feedback voltage V _fb signal, the feedback voltage V _fb signal power factor corrector 20 output voltage divided by the regulator TL431 Sampling the voltage signal _V in_SG accord When the input voltage sampling signal V _{in_SG} rises, the equivalent resistance (Rds-on) of the transistor Q ₁ becomes smaller, and the feedback voltage signal V _fb decreases. Since the negative feedback mechanism must return the voltage signal V _fb The voltage is re-adjusted to 2.5V, so the output voltage of the power factor corrector 20 rises to the boost function, and vice versa, so the output voltage of the power factor corrector 20 follows the sampled signal.

The first comparator 504 is a hysteresis comparator system, which comprises an operational amplifier O _p2 and the resistor R _3, R _adj3, wherein the inverting terminal of the operational amplifier O _p2 input a reference voltage _V in_ref, its non-inverting input The terminal obtains the input voltage sampling signal V _{in_SG} via the resistor R ₃ , and the non-inverting input terminal thereof is coupled to the output terminal thereof via the resistor R _adj3 for the voltage magnitude (225V~230V) set according to the reference voltage V _{in_ref} and the input. After the voltage sampling signal V _{in_SG} is compared, an input voltage determination command V _{in_SGout is generated} .

Referring to FIG fourth complex, wherein the error amplifier 505 comprises an operational amplifier O _p3, its inverting input and the non-inverting input terminal, respectively, at both ends of the detection resistor R _o p, q are coupled to the two detection resistor R _o the differential pressure across the end of the amplification process for generating an output current sample signal _I o_SG; second comparator 506 is a hysteresis comparator system, which comprises an operational amplifier O _p4 and resistors _{R 8,} R adj4, wherein the operational amplifier O _p4 inverting input terminal of a reference input current _I o_ref, its non-inverting input terminal of the sample signal to obtain an output current _I o_SG via a resistor R ₈ and via the resistor _R adj4 its output coupled to the reference current I _o the The magnitude of the output current set by _-ref (4.2A~4.4A) is compared with the output current sampling signal _{Io_SG to} generate a first output current determination command _{Io_SGout} ; and the signal isolation circuit 507 is an optical coupler PC817. The method includes a light-emitting diode D ₁ and a dual-carrier junction transistor Q _p1 for isolating the first output current determination command I _{o_SGout} , and also converting the light load efficiency converter of the present invention. Output and input for electrical Isolate and generate a second output current determination command I _{o_SGout2} .

The logic circuit 508 is a gate, which includes diodes DA ₁ and DA ₂ , wherein the diode DA ₁ is coupled to the output end of the first comparator 504, and the diode DA ₂ and the signal isolation circuit 507 are coupled. The _bipolar junction transistor Q _{p1 is} coupled to logically AND the input voltage determination command V _{in_SGout} and the second output current determination command I _{o_SGout2} to generate a determination signal as a basis for turning off the power factor corrector 20; The bounce circuit 509 includes a dual carrier junction transistor Q _p2 and a capacitor C ₄ , wherein the base terminal of the bipolar junction transistor Q _p2 is coupled to the logic circuit 508 , and the capacitor C ₄ and the bicarrier The emitter of the junction transistor Q _p2 is coupled to the emitter, and the emitter pole is coupled to a certain voltage source V _cc1 for bounce processing of the determination signal to avoid circuit malfunction and generate a control signal V _c1 ; and the signal switch The circuit 510 includes a transistor Q ₂ having a gate terminal coupled to the bounce preventing circuit 509 for controlling the driving circuit 30 according to the control signal V _c1 to turn off or operate the power factor corrector 20 .

Please refer to FIG. 5A and FIG. 5B respectively for the voltage operation diagram of an embodiment of the first comparator and the second comparator for improving the light load efficiency of the power supply provided by the present invention. As shown in the fifth and fifth B diagrams, when the input voltage sampling signal V in — _{SG is} greater than the high threshold voltage V _th , the input voltage determination command V in — _SGout is a high input voltage determination command V in — _h when the input voltage sampling signal V in — _{SG is} less than When the threshold voltage V _t1 is low, the input voltage determination command V _{in_SGout} is the low input voltage determination command V _{in_1} ; when the output current sampling signal I _{o — SG is} greater than the high threshold current I _th , the first output current determination command I _{o_SGout} is the high output The current determination command I _{o_h} , when the output current sampling signal I _{o_SG is} less than the low critical current I _t1 , the first input voltage determination command I _{o_SGout} is the low input voltage determination command I _{o_1} .

Referring to the sixth figure, a timing chart of the bounce prevention operation of the power supply for improving light load efficiency is provided. As shown in the sixth figure and in conjunction with the fourth figure, when the time is t ₁ , the input voltage determination command V in — _SGout is the high input voltage determination command V in — _h and the first output current determination command I _{o — SGout} is the high output current determination command I _{o — h} Then, the bipolar junction transistor Q _{p2 is turned} off and the capacitor C ₄ is charged by the constant voltage source V _cc , and the control signal V _c1 gradually rises until the capacitor C _{4 is} charged to the steady state, and the control signal V _c1 reaches a high level, that is, The Q ₂ gate of the transistor is extremely high, and the terminal of the transistor Q ₂ is extremely conductive with the source of the ground, that is, the ZCD signal is pulled, the driving circuit 30 turns off the power factor corrector 20; when the time is t ₂ , The input voltage determination command V _{in_SGout} is the low input voltage determination command V _{in_1} , and the first output current determination command I _{o_SGout is} still the high output current determination command I _{o — h} , then the _bipolar junction transistor Q _{p2 is} turned on and the capacitor C _{4 is} discharged. The control signal V _{c1 is} lowered to a low level, that is, the gate of the transistor Q ₂ is extremely low, and the terminal of the transistor Q ₂ is not electrically connected to the source terminal, the driving circuit 30 does not affect the power factor corrector 20, and the power factor correction is performed. 20 is normal Operation; similarly, when the first output current determination command I _{o_SGout} is the low input current determination command I _{o_1} and the input voltage determination command V _{in_SGout} is the low input voltage determination command V _{in_h} , then the _bipolar junction transistor Q _p2 When the capacitor C _{4 is} discharged and the control signal V _{c1 is} lowered to a low level, that is, the gate of the transistor Q ₂ is extremely low, and the terminal of the transistor Q ₂ is not conductive with the source terminal, the driving circuit 30 does not affect the power factor correction. The power factor corrector 20 operates normally.

In summary, the present invention is constructed by using a control circuit between a power factor corrector and a series resonant converter, which not only causes the output voltage of the power factor corrector to dynamically follow its input voltage, but also the power. After the input voltage of the factor corrector and the output current of the series resonant converter are logically judged, the power factor corrector is turned off under light load conditions, and the synchronous rectification series resonant converter is used to reduce the switching frequency of the light load and is easy to be flexible. Switching to achieve the purpose of improving light load efficiency. In this way, the converter for improving light load efficiency of the present invention can solve the problem of switching loss caused by the high switching frequency of the conventional converter and the light load.

The illustrations and descriptions disclosed above are only examples of the present invention, and are not intended to limit the present invention. Anyone skilled in the art can make various changes and retouching according to the above description, if other The spirit of the present invention and the technical means for not substantially changing the present invention are within the scope of protection covered by the present invention.

Convention:

1. . . Power factor corrector

2. . . Resonant converter

this invention:

10. . . First rectifier circuit

20. . . Power factor corrector

201. . . First energy storage circuit

202. . . First switching circuit

30. . . Drive circuit

40. . . Series resonant converter

401. . . Second switching circuit

402. . . Resonant circuit

403. . . transformer

404. . . Second rectifier circuit

405. . . Second energy storage circuit

50. . . Control circuit

501. . . Filter circuit

502. . . Voltage follower

503. . . Adjusting feedback voltage divider circuit

504. . . First comparator

505. . . Error amplifier

506. . . Second comparator

507. . . Signal isolation circuit

508. . . Logic circuit

509. . . Anti-bounce circuit

510. . . Signal switching circuit

D _a , D _b , D _c , D _d , D _e , DA ₁ , DA ₂ . . . Dipole

C _in , C _a , C _b , C _o , C _m1 , C _m2 , C ₄ . . . capacitance

L ₁ , L ₂ , L _m . . . inductance

R _o . . . Sense resistor

SW ₁ , SW ₂ , SW ₃ , SW ₄ , SW ₅ . . . Power switch transistor

N _p . . . Primary side coil

N _s . . . Secondary side coil

O _p1 , O _p2 , O _p3 , O _p4 . . . Operational Amplifier

R ₂ , R _adj1 , R ₃ , R _adj3 , R ₈ , R _adj4 . . . resistance

TL431. . . Stabilizer

Q ₁ , Q ₂ . . . Transistor

V _ref . . . Reference partial pressure

V _{in_SG} . . . Input voltage sampling signal

V _fb . . . Feedback voltage signal

V _{in_ref} . . . Reference voltage

V _{in_SGout} . . . Input voltage judgment command

I _{o_SG} . . . Output current sampling signal

I _{o_ref} . . . Reference current

I _{o_SGout} . . . Output current judgment command

V _cc1 , V _cc2 . . . power source

PC817. . . Optocoupler

D ₁ . . . Light-emitting diode

Q _p1 , Q _p2 . . . Double carrier junction transistor

V _c1 . . . Control signal

V _th , V _t1 . . . Threshold voltage

V _{in_h} . . . High input voltage judgment command

I _{o_h} . . . High output current judgment command

V _{in_1} . . . Low input voltage judgment command

I _{o_1} . . . Low output current judgment command

Schematic description:

The first figure is a block diagram of a conventional power converter;

The second figure is a circuit diagram of an embodiment of a power supply for improving light load efficiency of the present invention;

3 is a block diagram of an embodiment of a control circuit of a power supply for improving light load efficiency of the present invention;

The fourth figure is a circuit diagram of an embodiment of a control circuit for a power supply for improving light load efficiency of the present invention;

Figure 5A is a voltage operation diagram of an embodiment of the first comparator of the power supply for improving light load efficiency of the present invention;

5B is a voltage operation diagram of an embodiment of a second comparator of the power supply for improving light load efficiency of the present invention; and

The sixth figure is a timing chart of the bounce prevention operation of the power supply for improving light load efficiency of the present invention.

10‧‧‧First rectifier circuit

20‧‧‧Power Factor Corrector

201‧‧‧First energy storage circuit

202‧‧‧First switch circuit

30‧‧‧Drive circuit

40‧‧‧Series resonant converter

401‧‧‧Second switch circuit

402‧‧‧Resonance circuit

403‧‧‧Transformer

404‧‧‧Second rectifier circuit

405‧‧‧Second energy storage circuit

50‧‧‧Control circuit

R _o ‧‧‧Detection resistance

SW ₁ , SW ₂ , SW ₃ , SW ₄ , SW ₅ ‧‧‧ power switch transistor

N _p ‧‧‧ primary side coil

N _s ‧‧‧second side coil

Claims (20)

A power supply for improving light load efficiency, comprising: a first rectifier circuit coupled to an AC power source; a power factor corrector coupled to the first rectifier circuit; a series resonant converter, and the power a factor corrector coupled to provide DC/DC conversion; a control circuit coupled to the power factor corrector and the series resonant converter for inputting a voltage according to the power factor corrector and the series resonant converter The magnitude of the output current, and the output voltage of the corrector is adjusted according to the input voltage of the control circuit; and a driving circuit coupled to the power factor corrector and the control circuit, controlled by the control circuit And controlling the switch of the power factor corrector; wherein the control circuit comprises: a filter circuit coupled to the first rectifier circuit for performing DC sampling on the AC voltage rectified by the first rectifier circuit, and obtaining a a sampling signal; an adjustment feedback voltage dividing circuit coupled to the power factor corrector for regulating the sampling signal and adjusting the power factor corrector The voltage is applied to change the output voltage of the power factor corrector, and an input voltage sampling signal is output; a first comparator is coupled to the adjusted feedback voltage dividing circuit for sampling the input voltage signal A reference voltage is compared to generate an input voltage determination command; An error amplifier coupled to the output of the series resonant converter for amplifying an output voltage across the series resonant converter and generating an output current sampling signal; a second comparator coupled to the error amplifier Comparing the output current sampling signal with a reference current to generate a first output current determination command; a signal isolation circuit coupled to the second comparator for isolating the first output current determination command And generating a second output current determination command; a logic circuit coupled to the first comparator and the signal isolation circuit for logically determining the input voltage determination command and the second output current determination command A decision signal is used as a basis for turning off the power factor corrector; a signal switching circuit is configured to control the driving circuit according to a signal generated by the logic circuit, thereby turning the power factor corrector off or operating normally. The power supply for improving light load efficiency as described in claim 1, wherein the first rectifier circuit comprises a plurality of diodes. The power supply device for improving light load efficiency according to claim 1, wherein the power factor corrector comprises: a first energy storage circuit coupled to the first rectifier circuit for storing or releasing energy; And a first switching circuit coupled to the first energy storage circuit for switching the current on or off. The power supply for improving light load efficiency according to claim 3, wherein the first energy storage circuit comprises a capacitor and an inductor. The power supply for improving light load efficiency according to claim 3, wherein the first switch circuit comprises a power switch transistor and a diode. The power supply for improving light load efficiency according to the first aspect of the invention, wherein the series resonant converter comprises: a second switching circuit coupled to the power factor corrector for switching the current on or off a resonant circuit coupled to the second switching circuit for generating a resonance to cause the second switching circuit to be electrically turned on to achieve a zero voltage switching condition; a transformer coupled to the resonant circuit for the resonant circuit The second current is coupled to the transformer for rectifying the current induced by the transformer; and a second energy storage circuit coupled to the second rectifier circuit for storing Or release energy. A power supply for improving light load efficiency as described in claim 6 wherein the second switching circuit comprises a plurality of power switching transistors. A power supply for improving light load efficiency as described in claim 6 wherein the resonant circuit comprises a capacitor and an inductor. The power supply for improving light load efficiency according to claim 6, wherein the second rectifier circuit is a synchronous rectifier circuit, and the second rectifier circuit includes a plurality of The power switching transistor is used to ensure that the series resonant converter avoids the energy of the secondary side coil of the transformer from being back into the primary side coil during the dead time. A power supply for improving light load efficiency as described in claim 6 wherein the second energy storage circuit comprises a capacitor. The power supply for improving light load efficiency according to claim 6, wherein the output of the series resonant converter further comprises a detecting resistor for providing current detection of the load. The power supply device for improving light load efficiency according to claim 11, wherein the control circuit further comprises: a voltage follower coupled between the filter circuit and the adjustment feedback voltage dividing circuit, The sampling signal is used as a decoupling process, so that the output voltage is the same as the input voltage, and the load effect is prevented; a bounce circuit is coupled between the logic circuit and the signal switch circuit for determining the The signal is bounce-proof, and a control signal is generated to the signal switch circuit to prevent the circuit of the power supply from malfunctioning. A power supply for improving light load efficiency as described in claim 1, wherein the filter circuit comprises a plurality of capacitors. The power supply for improving light load efficiency according to claim 1, wherein the adjustment feedback voltage dividing circuit comprises a voltage dividing circuit, a voltage regulator and a transistor. A power supply for improving light load efficiency as described in claim 1 of the patent scope, The first comparator is a hysteresis comparator. A power supply for improving light load efficiency as described in claim 1, wherein the second comparator is a hysteresis comparator. The power supply device for improving light load efficiency according to claim 1, wherein the signal isolation circuit is an optical coupler, and the optical coupler comprises a diode and a double carrier junction transistor. The power supply for improving light load efficiency as described in claim 1, wherein the logic circuit is a gate. The power supply for improving light load efficiency according to claim 12, wherein the bounce circuit comprises a double carrier junction transistor and a capacitor. The power supply for improving light load efficiency as described in claim 1, wherein the signal switching circuit comprises a transistor.