Two stage boost converter topology
View Patent ↗A power converter having a two stage boost circuit and a small boost converter. The main power flow for the power converter is via the two stage booster circuit having a single switch. The voltage spike of the switch is clamped by a diode and a capacitor. The energy at the capacitor is transferred to the power converter's output terminals by the small boost converter. The two stage boost converter topology enables the use of much lower voltage and Rdson MOSFET switches so as to reduce cost, switch conduction loss and turn on loss.
1. A power converter having first and second input terminals where an input voltage is provided and two output terminals where the output DC voltage is provided comprising:
a two stage boost circuit comprising:
a first stage circuit comprising a first switch alternately switched on and off as a function of a first control signal for controlling current through a first winding of a magnetically coupled inductor said first winding having one end connected to the first input terminal, a first diode, and a first capacitor, the first switch coupled between the junction of the other end of the first winding and the first diode and the second input terminal, and
a second stage circuit comprising a second winding of said magnetically coupled inductor connected to the other end of said first winding and connected in series with a second diode between said first winding and the first output terminal, and a second capacitor connected across said output terminals; and
a second boost converter coupled between said first capacitor and said second capacitor comprising a second switch, an inductor, and a third diode; said second switch is connected between the junction of said inductor and third diode and the second input terminal and is alternately switched on and off as a function of a second control signal.
2. The converter of claim 1 , wherein said first control signal is provided by a first control circuit for controlling the duty cycle of said first switch.
3. The converter of claim 2 , wherein said second control signal is provided by a second control circuit for controlling the duty cycle of said second switch.
4. The converter of claim 3 , wherein said second control circuit has a pulse width modulation controller.
5. The converter of claim 3 , wherein said first and second control signals are synchronized.
6. The converter of claim 2 , wherein said first control circuit has a pulse width modulation controller.
7. The converter of claim 1 , wherein said first switch is a MOSFET.
8. The converter of claim 1 , wherein said second switch is a MOSFET.
9. The converter of claim 1 , further comprising a current sensor for sensing the current through said first switch, said current sensor including a current transformer formed by a primary winding and a secondary winding; said current transformer primary winding is connected in series between said first winding and the junction of said first switch and said first diode.
10. The converter of claim 9 , wherein said secondary winding of said current transformer is connected to a measurement resistor through a fourth diode.
11. A power converter having first and second input terminals where an input voltage is provided and two output terminals where the output DC voltage is provided comprising:
a two stage boost circuit comprising:
a first stage circuit comprising a first switch alternately switched on and off as a function of a first control signal for controlling current through a first winding of a magnetically coupled inductor said first winding having one end connected to the first input terminal, a first diode, and a first capacitor, and a primary winding of a current transformer connected in series between said first winding and the junction of said first switch and said first diode, said first switch coupled between the junction of said current transformer primary winding and said first diode and the second input terminal, and
a second stage circuit comprising a second winding of said magnetically coupled inductor connected to the other end of said first winding and connected in series with a second diode between said first winding and the first output terminal, and a second capacitor connected across said output terminals;
a second boost converter coupled between said first capacitor and said second capacitor comprising a second switch, an inductor, and a third diode; said second switch is connected between the junction of said inductor and third diode and the second input terminal and is alternately switched on and off as a function of a second control signal; and
a current sensor for sensing the current through said first switch, said current sensor including a current transformer formed by said primary winding and a secondary winding, wherein said current transformer secondary winding is connected to a measurement resistor through a fourth diode.
12. The power converter of claim 11 , wherein said first control signal is a function of the output voltage such that said first switch is operated using voltage mode control, and wherein said second control signal is a function of the current sensed by said current sensor such that said second switch is operated using current mode control.
13. The power converter of claim 11 , wherein said first and second control signals are a function of the output voltage such that said first and second switch are both operated using voltage mode control.
14. The power converter of claim 11 , wherein said first control signal is a function of the current sensed by said current sensor such that said first switch is operated using current mode control, and wherein said second control signal is a function of the output voltage such that said second switch is operated using voltage mode control.
15. The power converter of claim 11 , wherein said first and second control signals are a function of the current sensed by said current sensor such that said first and second switch are both operated using current mode control.