Half-bridge flyback resonant circuit

Abstract

The present invention discloses a half-bridge flyback resonant circuit. The half-bridge flyback resonant circuit comprises a half-bridge circuit comprising an upper bridge arm and a lower bridge arm,wherein the upper bridge arm and the lower bridge arm are connected in series between an anode and a cathode of an input power, and the upper bridge arm and the lower bridge arm are respectively provided with switch elements which are used for switching on and off in turn; a primary input circuit being connected in parallel with the lower bridge arm and comprising an energy storage element and a primary winding of a flyback transformer, wherein a dotted terminal of the primary winding is connected between the upper bridge arm and the lower bridge arm, and a non-dotted terminal of the primary winding is connected with the cathode of the input power through the energy storage element; and a flyback secondary circuit configured to output an appropriate output voltage and comprising a secondary winding of the flyback transformer, wherein a non-dotted terminal of the secondary winding is taken as an anode outputting the output voltage, and a dotted terminal of the secondary winding is takenas a cathode outputting the output voltage. The half-bridge flyback resonant circuit improves the efficiency, reduces the cost, improves EMI, and is especially suitable for but not limited to a low-power source with high-voltage input and an auxiliary power source.

Description

Technical field [0001] The invention relates to the field of switching power supplies, in particular to a half-bridge flyback resonant circuit. Background technique [0002] With the development of science and technology, the use of switching power supplies has spread across various fields. When designing low-power switching power supplies, due to cost reasons, the topologies are preferred to choose the three topologies of flyback circuit, forward circuit or series resonant circuit. Figure 1-3 Three topological structures are illustrated in turn, all of which have their own defects. [0003] The flyback circuit has the following defects: the switch tube works in a hard-switching state, which generates more heat and is low in efficiency. A heat sink needs to be added to the switch tube; the EMI effect is poor; the switch tube Q1 bears high voltage stress, and the rated voltage is generally greater than 2 *Vin voltage switch tube. When the input voltage is high (for example, 1000V)...

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Problems solved by technology

[0003] The flyback circuit has the following defects: the switch tube works in a hard switching state, generates a lot of heat, and has low efficiency, so a radiator needs to be added to the switch tube; the EMI effect is poor; the voltage stress of the switch tube Q1 is high, and the rated voltage is generally selected to be greater than 2 *Vin voltage switching tube

When the input voltage is high (such as 1000V), it is difficult to find a suitable switch tube

[0004] The forward circuit has the following defects: the switching tube works in a hard switching state, generates a lot of heat, and has low efficiency, so a radiator needs to be added to the switching tube; the EMI effect is poor; additional reset windings or clamping circuits need to be added; the voltage borne by the switching tube Q1 High stress, generally choose a switch tube with a rated voltage greater than 2*Vin voltage

When the input voltage is high (for example, 1000V), it is difficult to find a suitable switch tube; when outputting multiple voltages, each channel must add a filter inductor, and the cross-regulation rate of each voltage is poor

[0005] The series resonant circuit has the following defects: a dedicated PWM chip is required, there are many power devices, and the cost is high. Even if a series resonant circuit integrated with a resonant inductor is used, such as Figure 4 , also requires more power devices, and the cost is higher; when outputting multiple voltages, the cross-regulation rate of each voltage is poor

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