Novel synchronous rectification circuit and charger

Abstract

The utility model relates to the technical field of rectification circuits, in particular to a novel synchronous rectification circuit and a charger, which are characterized in that the input end of an input winding circuit is connected with an external bus; the output end of the input winding circuit is connected with the source electrode of the first switching tube; the grid electrode of the first switching tube is connected with the signal output end of the control chip; the drain of the first switching tube is connected with the first end of the output capacitor; the second end of the output capacitor is grounded; the first end of the output capacitor is connected with the output end of the novel synchronous rectification circuit. The control end of the input winding circuit is connected with the drain electrode of the second switch tube. The source electrode of the second switch tube is grounded; the grid electrode of the second switch tube is connected with the signal output end of the control chip. Aiming at the problem of large heating of a diode in the prior art, a first switch tube and a second switch tube are respectively arranged at the front stage and the rear stage of a winding and are controlled by a control chip, so that charge and discharge control of an output capacitor is realized, an existing diode rectification process is replaced, and heating is reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of rectifier circuits, in particular to a novel synchronous rectifier circuit and a charger. Background Art

[0002] Battery chargers organically combine high-frequency switching power supply technology with embedded microcomputer control technology, utilizing intelligent dynamic adjustment technology to optimize charging characteristics and effectively extend battery life. They utilize multiple charging stages, including constant current, constant voltage, and low constant current, and are characterized by high reliability, ease of operation, light weight, and compact size. To achieve constant current output, the charger typically incorporates a rectifier circuit to convert AC input into DC output.

[0003] In the prior art, corresponding rectifier circuits already exist. For example, Chinese patent CN200910135409.3 discloses a synchronous rectifier circuit suitable for a switching power converter, which includes a power transistor, a diode, a controller, and a phase-locked circuit. The power transistor and the diode are coupled to the output end of the transformer and the switching power converter to perform rectification. The controller generates a drive signal based on the on signal and the off signal to control the power transistor. The phase-locked circuit generates an off signal based on the on signal. Once the diode is forward biased, the on signal is enabled. The on signal is used to enable the drive signal to turn on the power transistor, and the off signal is used to disable the drive signal to turn off the power transistor.

[0004] However, during actual implementation, the inventors found that this type of technical solution usually uses Schottky diodes for rectification control, such as the above-mentioned diode bias enabling process, which leads to the problem of large diode heating during the control process. Utility Model Content

[0005] In view of the above problems existing in the prior art, a new synchronous rectification circuit is provided.

[0006] The specific technical solutions are as follows:

[0007] A novel synchronous rectification circuit includes an input winding circuit, a first switching tube, a second switching tube, an output capacitor and a control chip;

[0008] The input end of the input winding circuit is connected to an external bus;

[0009] The output end of the input winding circuit is connected to the source of the first switching tube;

[0010] The gate of the first switch tube is connected to the signal output terminal of the control chip;

[0011] The drain of the first switch tube is connected to the first end of the output capacitor;

[0012] The second end of the output capacitor is grounded;

[0013] The first end of the output capacitor is connected to the output end of the novel synchronous rectification circuit

[0014] The control end of the input winding circuit is connected to the drain of the second switch tube;

[0015] The source of the second switch tube is grounded;

[0016] The gate of the second switch tube is connected to the signal output terminal of the control chip.

[0017] In another aspect, the input winding circuit includes:

[0018] a transformer, wherein a first end of a first winding of the transformer is connected to an input end of the input winding circuit;

[0019] The second end of the first winding is connected to the control end of the input winding circuit;

[0020] A first end of the second winding of the transformer is connected to the output end of the input winding circuit, and a second end of the second winding is grounded;

[0021] The first winding and the second winding are coupled through an iron core.

[0022] On the other hand, the input winding circuit further includes:

[0023] a first capacitor, wherein a first end of the first capacitor is connected to an input end of the input winding circuit;

[0024] a first resistor, wherein a first end of the first resistor is connected to an input end of the input winding circuit;

[0025] a first diode, wherein a cathode of the first diode is connected to the second end of the first capacitor and the second end of the first resistor;

[0026] An anode of the first diode is connected to a control terminal of the input winding circuit.

[0027] On the other hand, the power supply terminal of the control chip is connected to an external power supply circuit;

[0028] The transformer further includes a third winding, wherein the third winding is coupled to the first winding and the second winding through the iron core;

[0029] The external power supply circuit is connected to the cathode of the second diode;

[0030] An anode of the second diode is connected to a first end of a second resistor, and a second end of the second resistor is grounded.

[0031] On the other hand, between the signal output terminal of the control chip and the gate of the first switch tube is provided:

[0032] a third resistor, a first end of the third resistor being connected to the signal output end of the control chip;

[0033] an optocoupler, wherein a signal input end of the optocoupler is connected to the second end of the third resistor;

[0034] A fourth resistor, wherein a first end of the fourth resistor is connected to the signal output end of the optocoupler, and a second end of the fourth resistor is connected to the gate of the first switching tube.

[0035] On the other hand, a fifth resistor is provided between the gate of the first switching tube and the drain of the first switching tube.

[0036] On the other hand, a sixth resistor is further included, a first end of the sixth resistor is connected to the drain of the first switch tube, and a second end of the sixth resistor is grounded.

[0037] On the other hand, a seventh resistor is provided between the gate of the second switch tube and the signal output terminal of the control chip.

[0038] A charger comprises the novel synchronous rectification circuit mentioned above.

[0039] The above technical solution has the following advantages or beneficial effects:

[0040] In response to the problem of high heat generation of diodes in the existing technology, this solution provides a new synchronous rectification circuit. By setting a first switching tube and a second switching tube before and after the winding respectively, and controlling them by a control chip, the charging and discharging control of the output capacitor is realized, replacing the existing diode rectification process and reducing heat generation. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The embodiments of the present invention will be described more fully with reference to the accompanying drawings, which are for illustration and description only and are not intended to limit the scope of the present invention.

[0042] Figure 1 It is an overall schematic diagram of an embodiment of the utility model; DETAILED DESCRIPTION

[0043] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0044] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features therein can be combined with each other.

[0045] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

[0046] The utility model includes:

[0047] A new type of synchronous rectification circuit, such as Figure 1 As shown, it includes an input winding circuit A1, a first switch tube Q1, a second switch tube Q2, an output capacitor E1 and a control chip U1;

[0048] The input end of the input winding circuit A1 is connected to the external bus HV;

[0049] The output end of the input winding circuit A1 is connected to the source of the first switch tube Q1;

[0050] The gate of the first switch tube Q1 is connected to the signal output terminal DRV of the control chip U1;

[0051] The drain of the first switch tube Q1 is connected to the first end of the output capacitor E1;

[0052] The second end of the output capacitor E1 is grounded;

[0053] The first end of the output capacitor E1 is connected to the output terminal 12V of the new synchronous rectification circuit

[0054] The control end of the input winding circuit A1 is connected to the drain of the second switch tube Q2;

[0055] The source of the second switch tube Q2 is grounded;

[0056] The gate of the second switch tube Q2 is connected to the signal output terminal DRV of the control chip U1.

[0057] Specifically, to address the problem of high heat generation in the diode in the prior art, a new synchronous rectification circuit is provided in this embodiment. By respectively providing a first switching tube Q1 and a second switching tube Q2 before and after the input winding circuit A1 and controlling them by the control chip U1, the charging and discharging control of the output capacitor E1 is realized, replacing the existing diode rectification process and reducing heat generation.

[0058] Specifically, the novel synchronous rectifier circuit in this embodiment has an input connected to an external bus HV that receives high-voltage AC power, typically at 50 Hz. Input winding circuit A1 includes a transformer that steps down the high-voltage AC power to a target voltage, typically 12V or 24V, but other voltages are possible. The transformer windings are adjusted according to the target voltage.

[0059] To achieve the rectification process, in this embodiment, the charge and discharge control of the output capacitor E1 is mainly achieved by turning on and off the first switch tube Q1 and the second switch tube Q2.

[0060] Specifically, the signal output terminal DRV of the control chip U1 outputs a square wave signal of a specific frequency to the gates of the first switch tube Q1 and the second switch tube Q2 to change their gate voltages so that the first switch tube Q1 and the second switch tube Q2 are turned on at a high level and turned off at a low level.

[0061] In one embodiment, the input winding circuit A1 includes:

[0062] A transformer T1, wherein a first end of a first winding of the transformer T1 is connected to an input end of an input winding circuit A1;

[0063] The second end of the first winding is connected to the control end of the input winding circuit A1;

[0064] A first end of the second winding of the transformer T1 is connected to the output end of the input winding circuit A1, and a second end of the second winding is grounded;

[0065] The first winding and the second winding are coupled through the core.

[0066] The transformer T1 includes two mutually coupled windings with different numbers of turns to achieve a voltage transformation process.

[0067] The first end of the first winding of the front stage is connected to the AC high voltage, and the second end is grounded by the second switch tube Q2. When the second switch tube Q2 is turned off, the path to ground is closed.

[0068] The second end of the second winding of the subsequent stage is grounded, and the first end is controlled by the first switch tube Q1 to be connected to the output capacitor E1. When the first switch tube Q1 is turned off, charging of the output capacitor E1 stops.

[0069] During the voltage transformation process, when the square wave signal is at a high level, the second switch Q2 turns on, connecting the first winding's path to ground and forming a positive voltage at the top and a negative voltage at the bottom. Correspondingly, an induced voltage forms on the coupled second winding, with a positive voltage at the top and a negative voltage at the bottom. Simultaneously, the first switch Q1 turns on, rectifying the output high-level voltage and charging the output capacitor E1.

[0070] When the square wave signal is at a low level, the first and second switches Q1 and Q2 are turned off, and the output capacitor E1 discharges the load. DC output is achieved by controlling the square wave signal output by the control chip U1 to match the frequency of the AC signal, such as 50Hz, and aligning the phase.

[0071] In one embodiment, the input winding circuit A1 further includes:

[0072] A first capacitor C1, wherein a first end of the first capacitor C1 is connected to an input end of the input winding circuit A1;

[0073] a first resistor R1, wherein a first end of the first resistor R1 is connected to an input end of the input winding circuit A1;

[0074] a first diode D1, wherein a cathode of the first diode D1 is connected to a second end of the first capacitor C1 and a second end of the first resistor R1;

[0075] An anode of the first diode D1 is connected to the control terminal of the input winding circuit A1.

[0076] Specifically, to achieve better rectification and avoid output voltage ripple, in this embodiment, the aforementioned filter circuit is also provided within input winding circuit A1. A first capacitor C1 and a first resistor R1 are connected in parallel to form a filter network. When the first switch Q1 is turned off, this filter network absorbs the voltage across the first winding and compensates for the phase, preventing a zero point. Furthermore, a first reverse-direction diode D1 is provided to control the current direction and the voltage across the first winding, ensuring that the first winding forms a path to ground.

[0077] In one embodiment, the power supply terminal of the control chip U1 is connected to the external power supply circuit VCC;

[0078] The transformer T1 further includes a third winding, which is coupled to the first winding and the second winding through an iron core;

[0079] The external power supply circuit VCC is connected to the cathode of the second diode D2;

[0080] An anode of the second diode D2 is connected to a first end of the second resistor R2 , and a second end of the second resistor R2 is grounded.

[0081] Specifically, when the control chip U1 outputs a square wave signal of a specific frequency, it requires power from the external power supply circuit VCC. However, this external power supply circuit VCC may contain a certain amount of ripple. To eliminate this ripple, in this embodiment, the induced voltage signal on the tertiary winding is introduced into the power supply circuit of the control chip U1 via a second resistor R2 and a second diode D2. This eliminates the ripple component and improves the accuracy of the square wave signal.

[0082] In one embodiment, the following is provided between the signal output terminal of the control chip U1 and the gate of the first switch tube Q1:

[0083] A third resistor R3, a first end of the third resistor R3 is connected to the signal output terminal DRV of the control chip U1;

[0084] Optocoupler U2, where the signal input end of the optocoupler U2 is connected to the second end of the third resistor R3;

[0085] A fourth resistor R4 , wherein a first end of the fourth resistor R4 is connected to the signal output end of the optocoupler U2 , and a second end of the fourth resistor R4 is connected to the gate of the first switch tube Q1 .

[0086] Specifically, to achieve more accurate control, in this embodiment, an optocoupler U2 is provided for the circuitry following the winding. The signal input of optocoupler U2 is connected to the second end of the third resistor R3 to receive the output signal of control chip U1. The signal input is also connected to the light-emitting diode in optocoupler U2, which only responds to output signals above a specific voltage to filter out noise. By providing optocoupler U2, a better isolation effect is achieved, improving the accuracy of gate voltage control.

[0087] In one embodiment, a fifth resistor R5 is provided between the gate of the first switch tube Q1 and the drain of the first switch tube Q1 .

[0088] Specifically, in order to control the gate-drain voltage, in this embodiment, a fifth resistor R5 is further provided between the gate of the first switch tube Q1 and the drain of the first switch tube Q1 to control the voltage.

[0089] In one embodiment, a sixth resistor R6 is further included, a first end of the sixth resistor R6 is connected to the drain of the first switch tube Q1 , and a second end of the sixth resistor R6 is grounded.

[0090] Specifically, in order to control the drain voltage of the first switch tube Q1 , in this embodiment, a sixth resistor R6 is further provided as a pull-down resistor, which forms a pull-down resistor when the first switch tube Q6 is not turned on.

[0091] In one embodiment, a seventh resistor R7 is provided between the gate of the second switch tube Q2 and the signal output terminal DRV of the control chip U1 .

[0092] A charger includes the novel synchronous rectification circuit mentioned above.

[0093] The above are only preferred embodiments of the present invention and do not limit the implementation methods and protection scope of the present invention. Those skilled in the art should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the description and illustrations of the present invention should be included in the protection scope of the present invention.

Claims

1. A novel synchronous rectification circuit, characterized in that: It includes an input winding circuit, a first switch tube, a second switch tube, an output capacitor and a control chip; The input end of the input winding circuit is connected to an external bus; The output end of the input winding circuit is connected to the source of the first switching tube; The gate of the first switch tube is connected to the signal output terminal of the control chip; The drain of the first switch tube is connected to the first end of the output capacitor; The second end of the output capacitor is grounded; The first end of the output capacitor is connected to the output end of the novel synchronous rectification circuit The control end of the input winding circuit is connected to the drain of the second switch tube; The source of the second switch tube is grounded; The gate of the second switch tube is connected to the signal output terminal of the control chip.

2. The novel synchronous rectification circuit according to claim 1, characterized in that: The input winding circuit comprises: a transformer, wherein a first end of a first winding of the transformer is connected to an input end of the input winding circuit; The second end of the first winding is connected to the control end of the input winding circuit; A first end of the second winding of the transformer is connected to the output end of the input winding circuit, and a second end of the second winding is grounded; The first winding and the second winding are coupled through an iron core.

3. The novel synchronous rectification circuit according to claim 2, characterized in that: The input winding circuit further includes: a first capacitor, wherein a first end of the first capacitor is connected to an input end of the input winding circuit; a first resistor, wherein a first end of the first resistor is connected to an input end of the input winding circuit; a first diode, wherein a cathode of the first diode is connected to the second end of the first capacitor and the second end of the first resistor; An anode of the first diode is connected to a control terminal of the input winding circuit.

4. The novel synchronous rectification circuit according to claim 2, characterized in that: The power supply end of the control chip is connected to an external power supply circuit; The transformer further includes a third winding, wherein the third winding is coupled to the first winding and the second winding through the iron core; The external power supply circuit is connected to the cathode of the second diode; An anode of the second diode is connected to a first end of a second resistor, and a second end of the second resistor is grounded.

5. The novel synchronous rectification circuit according to claim 1, characterized in that: Between the signal output terminal of the control chip and the gate of the first switch tube is provided: a third resistor, a first end of the third resistor being connected to the signal output end of the control chip; an optocoupler, wherein a signal input end of the optocoupler is connected to the second end of the third resistor; A fourth resistor, wherein a first end of the fourth resistor is connected to the signal output end of the optocoupler, and a second end of the fourth resistor is connected to the gate of the first switching tube.

6. The novel synchronous rectification circuit according to claim 1, characterized in that: A fifth resistor is provided between the gate of the first switching tube and the drain of the first switching tube.

7. The novel synchronous rectification circuit according to claim 1, characterized in that: A sixth resistor is also included, wherein a first end of the sixth resistor is connected to the drain of the first switch tube, and a second end of the sixth resistor is grounded.

8. The novel synchronous rectification circuit according to claim 1, characterized in that: A seventh resistor is provided between the gate of the second switch tube and the signal output terminal of the control chip.

9. A charger, characterized in that: The charger includes the novel synchronous rectification circuit according to any one of claims 1 to 8.

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