Printer power supply with high overcurrent point

Abstract

The utility model discloses a printer power supply with a high overcurrent point, which comprises an EMI filtering and rectifying circuit, a PFC control circuit, an LLC control circuit, an output rectifying and filtering circuit and a feedback circuit, and the PFC control circuit is used for boosting to improve the power factor of the power supply. By adopting LLC control, over three times of overcurrent points can be realized, the efficiency is relatively high, the voltage spike of the MOS tube and the diode is relatively small, and the safety is relatively high. Compared with a traditional flyback topology scheme power supply, the size of the whole power supply can be smaller; and the working characteristic of LLC control serving as a soft switch also enables the circuit to have better anti-electromagnetic interference performance. In the EMI filtering and rectifying circuit, the lightning stroke and surge protection effect is achieved through a fuse, a piezoresistor and a thermistor, and the electromagnetic infection resistance is further improved after filtering.

Description

Technical Field

[0001] The utility model relates to the technical field of power supply, in particular to a printer power supply with a high overcurrent point. Background Art

[0002] Printers are inductive loads, and the instantaneous startup power will reach more than 3 times the rated power. For label printers, when the printer prints out all-black label paper, the power supply output overcurrent point needs to reach more than 15A, and the output voltage cannot be lower than 22V, that is, the peak power must be more than 330W. Traditional power supplies generally use flyback topology solutions. When the overcurrent point is large, the peak voltage of the primary MOS and the secondary Schottky will be large, which can easily exceed its withstand voltage value, and the only way is to increase the absorption of the peak. In order to prevent the flyback transformer from saturating the core at a higher power output, a transformer with lower inductance will be used, resulting in lower efficiency. And in order to meet the overall heat dissipation requirements, the power supply volume can only be increased. Utility Model Content

[0003] In view of the above-mentioned deficiencies in the prior art, the technical problem to be solved by the present invention is to provide a printer power supply with a high overcurrent point, high efficiency and small size.

[0004] In order to solve the above technical problems, the technical solution adopted by the utility model is:

[0005] A printer power supply with a high overcurrent point includes an EMI filter rectifier circuit, a PFC control circuit, an LLC control circuit, an output rectifier filter circuit and a feedback circuit.

[0006] The EMI filter rectifier circuit comprises a fuse, a varistor, a thermistor, a safety capacitor, a first inductor, a second inductor and a bridge stack, one end of the fuse is respectively connected to one end of the varistor, one end of the safety capacitor and one end of the primary winding of the first inductor, the other end of the primary winding of the first inductor is connected to one end of the primary winding of the second inductor via the thermistor, the other end of the varistor and the other end of the safety capacitor are connected to one end of the secondary winding of the first inductor, the other end of the secondary winding of the first inductor is connected to one end of the secondary winding of the second inductor, the other end of the primary winding of the second inductor and the other end of the secondary winding are respectively connected to two input ends of the bridge stack; the other end of the fuse and the other end of the varistor are externally connected to an AC power supply;

[0007] The PFC control circuit includes a first control chip, a first MOS tube, a first diode and a third inductor, one end of the primary winding of the third inductor is connected to the output end of the bridge stack, the other end of the primary winding of the third inductor is respectively connected to the anode of the first diode and the drain of the first MOS tube, the source of the first MOS tube is connected to the first input end of the first control chip, the gate of the first MOS tube is connected to the driving end of the first control chip, the cathode of the first diode is connected to the second input end of the first control chip, and the secondary winding of the third inductor is connected to the third input end of the first control chip;

[0008] The LLC control circuit includes a second control chip, a second MOS tube, a third MOS tube, a first capacitor and a transformer, the drain of the second MOS tube is connected to the cathode of the first diode, the source of the second MOS tube is respectively connected to the drain of the third MOS tube and one end of the primary winding of the transformer, the other end of the primary winding of the transformer is grounded through the first capacitor, the source of the third MOS tube is grounded, the gate of the second MOS tube and the gate of the third MOS tube are respectively connected to the first driving end and the second driving end of the first control chip, the secondary winding of the transformer is connected to the input end of the output rectifier and filter circuit, and the output end of the output rectifier and filter circuit is used to connect the device to be powered;

[0009] The output end of the output rectifier and filter circuit is connected to the input end of the feedback circuit, and the output end of the feedback circuit is connected to the input end of the second control chip.

[0010] Furthermore, the output rectifier and filter circuit includes a second diode, a third diode, a second capacitor, a third capacitor, a fourth capacitor and a fourth inductor, the anode of the second diode and the anode of the third diode are connected to the secondary winding of the transformer, the cathode of the second diode and the cathode of the third diode are respectively connected to one end of the second capacitor, one end of the third capacitor and one end of the fourth inductor, the other end of the fourth inductor is connected to one end of the fourth capacitor, the other end of the second capacitor, the other end of the third capacitor and the other end of the fourth capacitor are grounded, and the other end of the fourth inductor is used as an output end for connecting the device to be powered.

[0011] Furthermore, the second diode and the third diode are composed of a diode group connected in parallel.

[0012] Furthermore, the feedback circuit includes a photocoupler and a voltage regulator chip, the input end of the photocoupler is connected to the output end of the output rectifier filter circuit, the output end of the photocoupler is connected to the input end of the voltage regulator chip, and the output end of the voltage regulator chip is connected to the input end of the second control chip.

[0013] Furthermore, it also includes a chip power supply circuit, the input end of the chip power supply circuit is externally connected to a DC power supply, and the output end is connected to the power supply end of the first control chip and the power supply end of the second control chip.

[0014] Furthermore, the chip power supply circuit includes a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a first triode, a second triode, a fourth diode, a fifth diode, a sixth diode and a fifth capacitor. The base of the first triode is connected to the DC power supply after being connected in series with the first resistor and the second resistor, the collector of the first triode is connected to the DC power supply after being connected in series with the third resistor and the fourth resistor, the emitter of the first triode is connected to the anode of the fourth diode, the cathode of the fourth diode is connected to the power supply end of the first control chip and the power supply end of the second control chip, the base of the first triode is also connected to the emitter of the second triode, the base of the second triode is connected to the cathode of the fifth diode, the anode of the fifth diode is grounded, the collector of the second triode is connected to the cathode of the sixth diode and one end of the fifth capacitor, the anode of the sixth diode is connected to the primary winding of the transformer, and the other end of the fifth capacitor is grounded.

[0015] The beneficial effects of the utility model are: using a PFC control circuit for boosting to improve the power factor of the power supply. Adopting LLC control can achieve more than three times the overcurrent point, with higher efficiency, smaller voltage spikes of the MOS tube and the diode, and higher safety. Compared with the traditional flyback topology power supply, the entire power supply volume can be made smaller; LLC control as a soft switch working characteristic also makes it have better anti-electromagnetic interference performance. In the EMI filter rectifier circuit, the fuse, varistor and thermistor play a role in anti-lightning surge protection, and the anti-electromagnetic infection performance is further improved after filtering. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Shown is a circuit diagram of a printer power supply with a high overcurrent point according to an embodiment of the utility model;

[0017] Figure 2 It is a schematic diagram of an EMI filter rectifier circuit 1 of a printer power supply with a high overcurrent point according to an embodiment of the utility model;

[0018] Figure 3 It is a schematic diagram of a PFC control circuit 2 of a printer power supply with a high overcurrent point according to an embodiment of the utility model;

[0019] Figure 4 It is a schematic diagram of the LLC control circuit 3 of the printer power supply with a high overcurrent point according to an embodiment of the utility model;

[0020] Figure 5 It is a schematic diagram of the output rectifier filter circuit 4 of the printer power supply with a high overcurrent point according to an embodiment of the utility model;

[0021] Figure 6It is a schematic diagram of a feedback circuit 5 of a printer power supply with a high overcurrent point according to an embodiment of the utility model;

[0022] Figure 7 It is a schematic diagram of a chip power supply circuit 6 of a printer power supply with a high overcurrent point according to an embodiment of the present utility model. DETAILED DESCRIPTION

[0023] In order to more clearly understand the technical content, achieved purposes and effects of the utility model, the utility model is described in detail below in combination with specific implementation methods and in conjunction with the accompanying drawings. It should be noted that the implementation methods of the utility model and the features in the implementation methods can be combined with each other without conflict. In the following description, many specific details are set forth in order to fully understand the utility model. The implementation methods described are only part of the implementation methods of the utility model, not all of the implementation methods. Based on the implementation methods in the utility model, all other implementation methods obtained by ordinary technicians in this field without making creative work are within the scope of protection of the utility model.

[0024] Please refer to Figure 1-Figure 7 As shown, an embodiment of the utility model discloses a printer power supply with a high overcurrent point, including an EMI filtering and rectifying circuit 1, a PFC control circuit 2, an LLC control circuit 3, an output rectifying and filtering circuit 4, a feedback circuit 5 and a chip power supply circuit 6.

[0025] The EMI filter rectifier circuit 1 includes a fuse F1, a varistor MOV1, a thermistor RT1, a safety capacitor CX1, a first inductor LF1, a second inductor LF2 and a bridge stack BDI. One end of the fuse F1 is respectively connected to one end of the varistor MOV1, one end of the safety capacitor CX1 and one end of the primary winding of the first inductor LF1, the other end of the primary winding of the first inductor LF1 is connected to one end of the primary winding of the second inductor LF2 through the thermistor RT1, the other end of the varistor MOV1 and the other end of the safety capacitor CX1 are connected to one end of the secondary winding of the first inductor LF1, the other end of the secondary winding of the first inductor LF1 is connected to one end of the secondary winding of the second inductor LF2, the other end of the primary winding of the second inductor LF2 and the other end of the secondary winding are respectively connected to two input ends of the bridge stack BDI; the other end of the fuse F1 and the other end of the varistor MOV1 are externally connected to two input ends of an AC power supply.

[0026] The PFC control circuit 2 includes a first control chip U1, a first MOS transistor Q1, a first diode D1 and a third inductor L3, one end of the primary winding of the third inductor L3 is connected to the output end of the bridge stack BDI, the other end of the primary winding of the third inductor L3 is respectively connected to the anode of the first diode D1 and the drain of the first MOS transistor Q1, the source of the first MOS transistor Q1 is connected to the first input end of the first control chip U1, the gate of the first MOS transistor Q1 is connected to the driving end of the first control chip U1, the cathode of the first diode D1 is connected to the second input end of the first control chip U1, and the secondary winding of the third inductor L3 is connected to the third input end of the first control chip U1. The first control chip U1 can be an L6562 chip.

[0027] The LLC control circuit 3 includes a second control chip U2, a second MOS transistor Q2, a third MOS transistor Q3, a first capacitor C7 and a transformer T1, the drain of the second MOS transistor Q2 is connected to the cathode of the first diode D1, the source of the second MOS transistor Q2 is respectively connected to the drain of the third MOS transistor Q3 and one end of the primary winding of the transformer T1, the other end of the primary winding of the transformer T1 is grounded through the first capacitor C7, the source of the third MOS transistor Q3 is grounded, the gate of the second MOS transistor Q2 and the gate of the third MOS transistor Q3 are respectively connected to the first driving end and the second driving end of the first control chip U1, the secondary winding of the transformer T1 is connected to the input end of the output rectifier filter circuit 4, and the output end of the output rectifier filter circuit 4 is used to connect the device to be powered. The second control chip U2 can be an L6599 chip.

[0028] The output end of the output rectifier and filter circuit 4 is connected to the input end of the feedback circuit 5, the output end of the feedback circuit 5 is connected to the input end of the second control chip U2, the input end of the chip power supply circuit 6 is externally connected to a DC power supply, and the output end is connected to the power supply end of the first control chip U1 and the power supply end of the second control chip U2.

[0029] In a specific embodiment, the output rectifier filter circuit 4 includes a second diode D12, a third diode D12A, a second capacitor C30, a third capacitor C32, a fourth capacitor C31 and a fourth inductor L1, the anode of the second diode D12 and the anode of the third diode D12A are connected to the secondary winding of the transformer T1, the cathode of the second diode D12 and the cathode of the third diode D12A are respectively connected to one end of the second capacitor C30, one end of the third capacitor C32 and one end of the fourth inductor L1, the other end of the fourth inductor L1 is connected to one end of the fourth capacitor C31, the other end of the second capacitor C30, the other end of the third capacitor C32 and the other end of the fourth capacitor C31 are grounded, and the other end of the fourth inductor L1 is used as an output end for connecting the device to be powered. The second diode D12 and the third diode D12A are composed of a parallel diode group.

[0030] In a specific embodiment, the feedback circuit 5 includes a photocoupler U3 and a voltage regulator chip U4, the input end of the photocoupler U3 is connected to the other end of the fourth inductor L1, the output end of the photocoupler U3 is connected to the input end of the voltage regulator chip U4, and the output end of the voltage regulator chip U4 is connected to the input end of the second control chip U2.

[0031] In a specific embodiment, the chip power supply circuit includes a first resistor R3, a second resistor R4, a third resistor R5, a fourth resistor R6, a fifth resistor R35, a first transistor Q4, a second transistor Q5, a fourth diode D9, a fifth diode DZ1, a sixth diode D6 and a fifth capacitor C6, the base of the first transistor Q4 is connected to the DC power supply after being connected in series with the first resistor R3 and the second resistor R4, the collector of the first transistor Q4 is connected to the DC power supply after being connected in series with the third resistor R5 and the fourth resistor R6, and the first transistor Q4 The emitter is connected to the anode of the fourth diode D9, the cathode of the fourth diode D9 is connected to the power supply end of the first control chip U1 and the power supply end of the second control chip U2, the base of the first transistor Q4 is also connected to the emitter of the second transistor Q5, the base of the second transistor Q5 is connected to the cathode of the fifth diode ZD1, the anode of the fifth diode ZD1 is grounded, the collector of the second transistor Q5 is connected to the cathode of the sixth diode D6 and one end of the fifth capacitor C6, the anode of the sixth diode D6 is connected to the primary winding of the transformer T1, and the other end of the fifth capacitor C6 is grounded.

[0032] The above embodiment has a printer power supply with a high overcurrent point. The primary MOS of the LLC control circuit works at ZVS (zero voltage) and the output diode is turned off at ZCS (zero current). There is no reverse recovery problem, the switching loss is small, and the loss of spike absorption is also small. Even when the peak power reaches 330W, the voltage spike of the MOS tube and the diode is small, thereby achieving a high overcurrent point. The specific principle is as follows.

[0033] 1. EMI filter rectifier circuit: After the AC power is input, it passes through the fuse F1, varistor MOV1 and thermistor RT1 to protect against lightning surges, and then is filtered by the safety capacitor CX1, the first inductor LF1 and the second inductor LF2 to improve the EMI performance, and finally is rectified into DC by the bridge stack BDI.

[0034] 2. PFC control circuit: The first control chip U1, the first MOS tube Q1, the first diode D1, and the third inductor L3 form a BOOST boost circuit, which is used to improve the power factor of the power supply.

[0035] 3. LLC control circuit: The second control chip U2, the second MOS tube Q2, the third MOS tube Q3, the first capacitor C7, and the transformer T1 form a half-bridge LLC resonant conversion circuit. Its operation can be divided into a charging stage and a discharging stage: in the charging stage, the third MOS tube Q3 is turned off and the second MOS tube Q2 is turned on. At this time, the power supply voltage charges the first capacitor C7 through the primary and secondary windings of the transformer T1. In the discharging stage, the third MOS tube Q3 is turned on and the second MOS tube Q2 is turned off. At this time, the first capacitor C7 and the secondary winding of the transformer T1 form an LLC resonant circuit, generating high-frequency oscillations, thereby transferring energy to the output load. Before the third MOS tube Q3 is turned on, the current first flows through the body diode (source D to drain S) of the switch MOS tube, and the voltage between the source D and the drain S of the MOS tube is clamped at close to 0V (diode voltage drop). At this time, the MOS tube is turned on to achieve zero voltage turn-on; before being turned off, since the capacitor voltage between the source D and the drain S is 0V and cannot change suddenly, it is also close to zero voltage turn-off. This soft switching characteristic makes the voltage spike of the MOS tube smaller and has higher efficiency.

[0036] 4. Chip power supply circuit: The first resistor R3, the second resistor R4, the third resistor R5, the fourth resistor R6, the first transistor Q4, and the fourth diode D9 constitute a high-voltage startup circuit. After the chip starts working, the transformer T1 winding is rectified through the sixth diode D6 and the fifth capacitor C6, and then the second transistor Q5, the fifth diode ZD1 and the fifth resistor R35 constitute a voltage stabilizing circuit, and output 15V to power the chips L6599 and L6562.

[0037] 5. Output rectification and filtering circuit: The second diode D12 and the third diode D12A form a full-wave rectification, which is then filtered by the second capacitor C30, the third capacitor C32, the fourth capacitor C31 and the fourth inductor L1 before output.

[0038] 6. Feedback circuit: The feedback loop composed of the optocoupler U3 and the voltage regulator chip U4 is used to stabilize the output voltage.

[0039] In summary, the printer power supply with a high overcurrent point of the utility model has more than three times the overcurrent point, and achieves more than three times the overcurrent point while ensuring a full load efficiency of more than 92%, and can achieve a peak power of more than 330W in a smaller volume.

[0040] The above description is only an embodiment of the present invention, and does not limit the patent scope of the present invention. Therefore, any modification, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A printer power supply with a high overcurrent point, characterized in that: Including EMI filter rectifier circuit, PFC control circuit, LLC control circuit, output rectifier filter circuit and feedback circuit, The EMI filter rectifier circuit comprises a fuse, a varistor, a thermistor, a safety capacitor, a first inductor, a second inductor and a bridge stack, one end of the fuse is respectively connected to one end of the varistor, one end of the safety capacitor and one end of the primary winding of the first inductor, the other end of the primary winding of the first inductor is connected to one end of the primary winding of the second inductor via the thermistor, the other end of the varistor and the other end of the safety capacitor are connected to one end of the secondary winding of the first inductor, the other end of the secondary winding of the first inductor is connected to one end of the secondary winding of the second inductor, the other end of the primary winding of the second inductor and the other end of the secondary winding are respectively connected to two input ends of the bridge stack; the other end of the fuse and the other end of the varistor are externally connected to an AC power supply; The PFC control circuit includes a first control chip, a first MOS tube, a first diode and a third inductor, one end of the primary winding of the third inductor is connected to the output end of the bridge stack, the other end of the primary winding of the third inductor is respectively connected to the anode of the first diode and the drain of the first MOS tube, the source of the first MOS tube is connected to the first input end of the first control chip, the gate of the first MOS tube is connected to the driving end of the first control chip, the cathode of the first diode is connected to the second input end of the first control chip, and the secondary winding of the third inductor is connected to the third input end of the first control chip; The LLC control circuit includes a second control chip, a second MOS tube, a third MOS tube, a first capacitor and a transformer, the drain of the second MOS tube is connected to the cathode of the first diode, the source of the second MOS tube is respectively connected to the drain of the third MOS tube and one end of the primary winding of the transformer, the other end of the primary winding of the transformer is grounded through the first capacitor, the source of the third MOS tube is grounded, the gate of the second MOS tube and the gate of the third MOS tube are respectively connected to the first driving end and the second driving end of the first control chip, the secondary winding of the transformer is connected to the input end of the output rectifier and filter circuit, and the output end of the output rectifier and filter circuit is used to connect the device to be powered; The output end of the output rectifier and filter circuit is connected to the input end of the feedback circuit, and the output end of the feedback circuit is connected to the input end of the second control chip.

2. The printer power supply with a high overcurrent point according to claim 1, characterized in that: The output rectifier and filter circuit includes a second diode, a third diode, a second capacitor, a third capacitor, a fourth capacitor and a fourth inductor. The anode of the second diode and the anode of the third diode are connected to the secondary winding of the transformer, the cathode of the second diode and the cathode of the third diode are respectively connected to one end of the second capacitor, one end of the third capacitor and one end of the fourth inductor, the other end of the fourth inductor is connected to one end of the fourth capacitor, the other end of the second capacitor, the other end of the third capacitor and the other end of the fourth capacitor are grounded, and the other end of the fourth inductor is used as an output end for connecting the device to be powered.

3. The printer power supply with a high overcurrent point according to claim 2, characterized in that: The second diode and the third diode are formed by a diode group connected in parallel.

4. The printer power supply with a high overcurrent point according to claim 1, characterized in that: The feedback circuit includes a photocoupler and a voltage regulator chip, the input end of the photocoupler is connected to the output end of the output rectifier filter circuit, the output end of the photocoupler is connected to the input end of the voltage regulator chip, and the output end of the voltage regulator chip is connected to the input end of the second control chip.

5. The printer power supply with a high overcurrent point according to claim 1, characterized in that: It also includes a chip power supply circuit, the input end of the chip power supply circuit is externally connected to a DC power supply, and the output end is connected to the power supply end of the first control chip and the power supply end of the second control chip.

6. The printer power supply with a high overcurrent point according to claim 5, characterized in that: The chip power supply circuit includes a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a first triode, a second triode, a fourth diode, a fifth diode, a sixth diode and a fifth capacitor. The base of the first triode is connected to the DC power supply via the first resistor and the second resistor connected in series, the collector of the first triode is connected to the DC power supply via the third resistor and the fourth resistor connected in series, the emitter of the first triode is connected to the anode of the fourth diode, the cathode of the fourth diode is connected to the power supply end of the first control chip and the power supply end of the second control chip, the base of the first triode is also connected to the emitter of the second triode, the base of the second triode is connected to the cathode of the fifth diode, the anode of the fifth diode is grounded, the collector of the second triode is connected to the cathode of the sixth diode and one end of the fifth capacitor, the anode of the sixth diode is connected to the primary winding of the transformer, and the other end of the fifth capacitor is grounded.

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