Multi-output DC-DC converter with increased power efficiency and power density

• US 20060274559A1
• Filed: 06/01/2005
• Published: 12/07/2006
• Est. Priority Date: 06/01/2005
• Status: Active Grant

• Current Assignee: Delta Electronics Incorporated, Delta Electronics Thailand Public Company Limited (Delta Electronics Incorporated)
• Original Assignee: Delta Electronics Incorporated
• Inventors: Saeueng, Sakda, Xu, Mingchun, Hon, Weng Leong
• Granted Patent: US 7,501,715 B2
• Time in Patent Office: Days
• US Class Current: 363/21.60
• CPC Class Codes: H02M 3/33561 having more than one ouput with independent control
• CPC Class Codes: H02M 3/33592 having a synchronous rectifier circuit or a synchronous freewheeling circuit at the secondary side of an isolation transformer
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

A multi-output DC-DC converter is advantageous over the conventional multi-output DC-DC converter in terms of increased power efficiency and power density. The inventive multi-output DC-DC converter is characterized by that the rectifying circuit located at the output stage of the DC-DC converter is implemented by a pair of self-driven synchronous rectifier transistors that can prevent a reverse current from flowing through the switch elements of the DC-DC converter. Also, a plurality of post voltage regulators are tapped to a secondary winding of the DC-DC converter, in which each post voltage regulator includes a voltage level shifter circuit for allowing gate drivers to impose a small amount of dead time on the control pulse signals for driving the internal transistor switches to minimize the dead time loss occurred during power conversion operation.

Claims

1. A multi-output DC-DC converter comprising:

a power inverter including a switch circuit for transferring energy received from an input DC voltage;

a power transformer having a primary winding and a secondary winding, wherein the primary winding is coupled to the power inverter for receiving the energy therefrom and transferring the energy across the secondary winding according to the open and close of the switch circuit;

a rectifier transistor circuit coupled to the secondary winding for rectifying the energy transferred from the secondary winding into a rectified DC voltage;

an output filter coupled to the rectifier transistor circuit for smoothing the rectified DC voltage to generate a regulated DC voltage; and

a plurality of post voltage regulators tapped to the secondary winding for providing a plurality of regulated DC voltages.

2. The multi-output DC-DC converter according to claim 1 wherein the power inverter comprises a main pulse width modulator coupled to the switch circuit for generating control pulse signals to drive the switch circuit.

3. The multi-output DC-DC converter according to claim 2 wherein the rectifier transistor circuit comprises a first rectifier transistor and a second rectifier transistor, and wherein the multi-output DC-DC converter further comprises a pair of series capacitor coupled across the secondary winding and a gate terminal of the first rectifier transistor for providing control pulse signals to drive the first rectifier transistor.

4. The multi-output DC-DC converter according to claim 3 wherein a gate terminal of the second rectifier transistor is connected to the main pulse width modulator via an inverter.

5. The multi-output DC-DC converter according to claim 4 wherein the post voltage regulator comprises:

a current blocking device coupled to the secondary winding for blocking the transfer of a current from the secondary winding;

a synchronous rectifier coupled to the current blocking device for rectifying an AC voltage induced across the secondary winding into a rectified DC voltage;

an output filter coupled to the current blocking device and the synchronous rectifier for smoothing the rectified DC voltage and generating a regulated DC voltage;

a feedback circuit coupled to an output end of the output filter for comparing the regulated DC voltage with a reference voltage and generating a feedback signal accordingly; and

a blocking controller coupled to the feedback circuit and the main pulse width modulator for generating control pulse signals in accordance with the feedback signal to drive the current blocking device and the synchronous rectifier.

6. The multi-output DC-DC converter according to claim 4 wherein the post voltage regulator comprises:

a first transistor switch for rectifying an AC voltage induced across the secondary winding;

a second transistor switch for blocking the transfer of a current from the secondary winding;

a ramp signal generator coupled to the secondary winding for generating a raw ramp voltage;

a first gate driver coupled between the ramp signal generator and the first transistor switch for receiving the raw ramp voltage and generating control pulse signals in accordance with the raw ramp voltage to drive the first transistor switch;

a voltage level shifter circuit coupled to the ramp signal generator for subtracting a voltage level from the raw ramp voltage to generate a phase-shifted ramp voltage; and

a second gate driver coupled between the voltage level shifter circuit and the second transistor switch for receiving the phase-shifted ramp voltage and generating control pulse signals in accordance with the phase-shifted ramp voltage to drive the second transistor switch.

7. The multi-output DC-DC converter according to claim 6 wherein the ramp signal generator comprises:

a constant current source coupled to the secondary winding for providing a constant current;

a capacitor coupled to the constant current source for being charged by the constant current and generating the raw ramp voltage; and

a voltage-controlled current source coupled across the capacitor for changing a charging rate of the capacitor.

8. The multi-output DC-DC converter according to claim 6 wherein the post voltage regulator further comprises a bootstrap driver coupled between the second transistor switch and the second gate driver for boosting a voltage level of control pulse signals provided by second gate driver to the second transistor switch.