Implementation of Low Cost DC-DC Circuit Based on MC34063

One-piece inductor

Overview:
In the power supply circuit, DC-DC conversion is widely used due to temperature rise, efficiency and other factors. This paper introduces a low-cost DC-DC conversion implementation, which can realize buck, boost and voltage reversal. Applications, such as simple circuit, low cost, high efficiency, low temperature rise, these circuits are widely used.

The core component of the circuit is the MC34063, a monolithic bipolar linear integrated circuit dedicated to the DC-DC converter control section. The chip contains a temperature-compensated bandgap reference and a duty cycle control oscillator driver. And a large current output switch that can output 1.5A of switching current. It can form a switching boost converter, a buck converter and a power inverter with a minimum of external components.

The package form of MC34063 is plastic double-row 8-lead in-line type, and the internal circuit block diagram is shown in Figure 1.

1 Working principle Due to the built-in high-current power switch, the MC34063 can control the switching current to 1.5A. The internal circuit contains the reference voltage source, oscillator, converter, logic control circuit and switching transistor.

The reference voltage source is a temperature-compensated bandgap reference. The oscillation frequency of the oscillator is determined by the external timing capacitor of pin 3. The switching transistor is turned ON by the inverting input of the comparator and the logic control line connected to the oscillator. The next pulse synchronized with the oscillator output is turned OFF.

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